Tele-Communication (Telecom) Terms Glossary and Dictionary - A

A & B BitA & B Bit is used in digital environments to convey signaling information. A bit equal to one generally corresponds to loop current flowing in an analog environment; A bit value of zero corresponds to no loop Current, i.e. to no connection. Other signals are made by changing bit values: for example, a flash-hook is sent by briefly setting the A bit to zero.

A LinksA Links, also known as SS7 access links, connect an end office or signal point to a mated pair of signal transfer points. They may also connect signal transfer points and signal control points at the regional level with the A-links assigned in a quad arrangement.

A&B Bit SignalingA&B Bit Signaling, also called 24th channel signaling, is a procedure used in T1 transmission facilities in which each of the 24 T1 subchannels devotes 1 bit of every sixth frame to the carrying of supervisory signaling information. On T1 lines that use Extended SuperFrame(ESF) framing, the signaling bits are robbed from the 6th, 12th, 18th, and 24th frame, resulting in "ABCD" signaling bits.

ABAM cableABAM cable refers to a type of T1 cable. This cable was a 22 gauge, 100 ohm insulated, twisted pair. ABAM cable is no longer available, but you can easily find cable that meets the technical requirements.

Abandoned CallAbandoned Call is a call in which the call originator disconnects or cancels the call after a connection has been made, but before the call is established.

AbandonmentAbandonment refers to the network replacement of a connect signal with an on-hook signal (network) prior to receiving a CI (customer installation) answer signal. Abandonment is the only way to end an unanswered call attempt.

Abbreviated AddressAbbreviated Address is an address that has fewer characters than the full address, usually for special communications and other services or for certain users. Examples of abbreviated addresses are (A) a four-digit telephone number for a user calling another user connected to the same switching exchange, and (B) message addresses that have only the addressee name and station code or number.

Abbreviated Address CallingAbbreviated Address Calling is a calling that enables a user to employ an address having fewer characters than the full address when initiating a call. Communications network users may be

allowed to designate a given number of abbreviated address codes. The allocation of the abbreviated address codes to a destination or group of destinations may be changed as required, by means of a suitable procedure.

Abbreviated Dialing

Abbreviated Dialing is a telephone feature (synonym speed dialing ) that (A) permits the user to dial fewer digits to access a network than are required under the nominal numbering plan, and (B) is limited to a subscriber-selected set of frequently dialed numbers.

ABCD SignalingABCD signaling is a 4-bit telephony line signaling coding in which each letter represents 1 of the 4 bits. This often is associated with CAS or robbed-bit signaling on a T1 or E1 telephony trunk.

ABCD Signaling BitsABCD Signaling Bits, also refered as ABCD Bits, are 4-bits telephony line signaling coding in which each letter represents 1 of the 4 bits. The implementations of ABCD signaling are different in E1 and T1 digital trunks. On E1, ABCD bit values may be used to signal an incoming call, disconnect, seize and so on, They are closely analogous to the A and Bits commonly used on T-1 digital trunks. On E1, there are 32 channels (time-slots) in contrast to 24 channels on T-1, hence the faster bit rate of 2.048 MHz versus 1.544 MHz for T-1. On E1, channels 0 and 16 are used to carry the ABCD bits and synchronization (framing) bits; hence only 30 channels are available for audio conversations. On T-1 digital trunks, the ABCD Signaling Bits implements the robbed bit signaling.

ABCD TonesABCD Tones are simply additional DTMF tones that may be used in any way the standard (0-9) tones are used. The ABCD Tones are used in the U.S. Military telephone network (Aoto Von), in some Automatic Call Distributor (ACD) systems, for control messages in some PBX systems, and in some amateur radio auto-patches.

ABDN: Attendant Blocking of Directory NumberAttendant Blocking of Directory Number (ABDN) is a feature of telephone service enables the attendant to block a DN (Directory Number) for a telephone from receiving to making calls. This is particularly useful when a caller dials the attendant DN and requests an external (long distance) call. If the caller chooses to disconnect until the attendant successfully places the call, the requesting DN becomes idle and can receive or make calls. Therefore, the requesting DN could be busy when the attendant establishes the requested call.

Absent Subscriber ServiceAbsent Subscriber Service is a telephone service provided by local telephone carriers to customers who will be away for a period of time and want to stop the service without losing their telephone number . The calls to the subscriber will be intercepted by a live operator or a machine and a message will be delivered. When the customers come back, they will get their old number. But in the meantime, while they are away, they pay less money per month than they would for normal phone service.

Absolute DelayAbsolute delay refers to the following: 1. The time interval or phase difference between transmission and reception of a signal. 2. The total time between the instant a bit enters the network and the instant a corresponding bit exists the network

Absorption BandAbsorption Band is a range of wavelengths (or, equivalently, frequencies) in the electromagnetic spectrum within which electromagnetic energy is absorbed by a substance. When the absorbing substance is a polyatomic gas, an absorption band actually is composed of a group of discrete absorption lines which appear to overlap. Each line is associated with a particular mode of vibration or rotation induced in a gas molecule by the incident radiation.

Absorption CoefficientAbsorption coefficient is measure of the attenuation caused by absorption of energy that results from its passage through a medium. Absorption coefficients are usually expressed in units of reciprocal distance. The sum of the absorption coefficient and the scattering coefficient is the attenuation coefficient.

Absorption SpectrumAbsorption Spectrum is a diagram which shows the wavelengths of electromagnetic radiation absorbed by a material. The material could be a gas, a solute or a solid. An absorption spectrum is, in a sense, the inverse of an emission spectrum.

AC/DC RingingAC/DC Ringing refers to telephone ringing that use both ac and dc voltages and currents.

AC: Access CodeAccess Code (AC) refers to a set of digits or numbers besides regular telephone number dialed on the telephone in order to access some telephone related services. For instance, some phone needs to dial 9 to "access outside line", some long distance carrier needs a special set of code to be connected, etc.

ACA: Automatic Circuit AssuranceAutomatic Circuit Assurance (ACA) is a PBX feature that helps one to identify bad trunks. The PBX keeps records of calls of very short and very long duration. If these calls exceed a certain parameter, the attendant is notified. The logic is that a lot of very short calls or one very long call may snidest that a trunk is hung, broken or out of order, The attendant can then physically dial into that trunk and check it.

ACB: Automatic Call BackAutomatic Call Back (ACB) is a telephone feature that allows one to instruct the telephone system to retain the called and calling numbers, when encountering a busy situation, to reestablish the call when there is an available line.

Access AttemptAccess Attempt is the process by which one or more users interact with a telecommunications

system to enable initiation of user information transfer. An access attempt begins with an issuance of an access request by an access originator and ends either in successful access or in access failure.

Access ChargeAccess Charge is the charge or fees imposed by a communications service or telephone company for the use of its network.

Access FailureAccess Failure refers to an unsuccessful access in a telecommunications system that results in termination of an access attempt in any manner other than initiation of user information transfer between the intended source and destination (sink) within the specified maximum access time

Access GroupAccess Group refers to a set of phones or terminals that have the same permission to access the phone system, computers and networks.

Access LineAccess Line refers to a transmission path that continuously connects a subscriber's premises to a switching center, common carrier operating center, or teleprocessing system.

Access LinkAccess link is the local line connecting customer to the central office switch, giving access to a PSTN carrier who will provide the customer dial tone or private line communications services. The access link may be a T1 line, a DSL connection, a cable (CATV) network, a broadband wireless link, or a metro-Ethernet connection.

Access NumberAccess Number refers to "dial-up Numbers" to access to an local Internet Service Provider.

Access ProtectionAccess Protection refers to the process or means to protect a telephone system local loop against possible outages and failures.

Access RateAccess Rate refers to the maximum data transmission rate over the access link in a typical network like former AT&T hikes cable access rate.

Account CodeAccount Code is a numeric code that must be entered to dial long distance numbers in some companies to control telephone billing. Account code can protect against telephone abuse and is a way to track calls back to the person or project originating the calls.

Accunet Spectrum Digital ServiceAccunet spectrum digital service refers to a former AT&T's leased line digital service as 56 Kbps.

ACD Cal Back MassagingACD Call Back Massaging is one of the ACD (Automatic Call Distributor) capabilities. It allows callers to leave messages for agents instead of waiting for a live agent. It helps to balance workloads of an agent between peak and off-peak hours.

ACD Caller Directed Call RoutingACD Caller Directed Call Routing refers to as an auto attendant capability of ACD. It allows callers to direct themselves to the appropriate agent group without the intervention of an operator. By responding to prompts (like pressing certain number on telephone), a caller is automatically routed to the designated agent group.

ACD Central OfficeACD (Automatic Call Distributor) Central Office refers to an ACD usually located in a central office and supplied to the customer by the telephone company with tariffed pricing structures.

ACD Conditional RoutingACD (Automatic Call Distributor) Conditional Routing refers to an ability of ACD that monitors various parameters within the system and call center and to intelligently route calls based on that information conveyed in those parameters like volume levels of calls in queue, the number of agents available, and etc.

ACD Data Directed Call RoutingACD (Automatic Call Distributor) Data Directed Call Routing refers to an ACD capability that it can automatically process calls based on data provided by a database of information resident in a separate data system.

ACD Intelligent Call ProcessingACD (Automatic Call Distributor) Intelligent Call Processing refers to the features of the ACDs to intelligently route calls according to (1) information provided by the caller, (2) a database on callers and system parameters within the ACD.

ACD NumberACD (Automatic Call Distributor) Number is the telephone number dialed in order to access any of the multiple agents in an ACD group.

ACD: Automatic Call DistributorAutomatic Call Distributor (ACD) is a telephone facility that manages incoming calls and handles them based on the number called and an associated database of handling instructions. Many companies, offering sales and service support, use ACDs to validate callers, make outgoing responses or calls, forward calls to the right party, allow callers to record messages, gather usage statistics, balance the use of phone lines, and provide other services.

AC-DC RingingAC-DC Ringing is telephone ringing function/facility that makes use of both AC and DC voltages and currents. An AC may be used to operate a ringer and DC to aid the relay action that stops the ringing when the called telephone is answered.

ACELP: Algebraic Code Excited Linear PredictionAlgebraic Code Excited Linear Prediction (ACELP) is a process employed in analysis by synthesis codecs in order to predict the filter coefficients required to synthesize speech at the receiving party. This process is specified in the ITU-T G723.1 codec specification.

Acoustic ConnectionAcoustic Connection is a connection to a device or system made by sound waves. Any system that provides voice communication, such as a telephone set, is an example of Acoustic Connection.

ACSB: Amplitude Compandored SidebandAmplitude Compandored Sideband (ACSB) is a narrow-band modulation using a single sideband with a pilot tone, allowing an expander in the receiver to restore the amplitude that was severely compressed by the transmitter. (Note that most of the noise reduction circuits used in audio recording are also variations of companding.) This mode promised greater robustness and fade-resistance on HF than even SSB, but was pretty much leapfrogged in favor of spread spectrum, which solves the problem even better.

ACTA: America's Carriers Telecommunications AssociationAmerica's Carriers Telecommunications Association (ACTA) is a trade association of "competitive", long distance carriers. One of their purposes is to petition the Federal Communications Commission (FCC) to ban the selling of software and hardware products by some companies that enable use of the Internet to voice long distance services.

Active CallActive Call refers to a state of a call in a call processing used in call center which indicates a connection is in any state except "Hold, Null, or Queued".

Active CampaignActive Campaign refers to an out-band calling project that is currently active.

Active LineActive Line refers to telecommunication channel or logical communications circuit that is currently established for data or voice transmission.

Active Noise ControlActive Noise Control is a process to control, reduce or cancel unwanted noise during a call.

Active ParticipationActive Participation refers to a feature in a call center which allows intrusion into an agent call by a supervisor who can listen to or join the conversation.

ACTS: Advanced Communications Technologies and Services (Europe)Advanced Communications technologies and Services (Europe) (ACTS) refers to a programme under the European Community 4th Framework R &TD Programme, collaborative research and technology development in Europe. It is one of the biggest European R&TD investments with

around 120 projects in place. The DTI/EPSRC High Performance Interfaces & Protocols (HPIP) LINK programme is the complementary UK initiative.

ACTS: Automatic Coin Telephone ServiceAutomatic Coin Telephone Service (ACTS) is a public coin-operated telephone service that completes a variety of phone calls, times the calls, and collects payment without the aid of an operator.

ACU: Automatic Calling UnitAutomatic Calling Unit (ACU) is a device that enables equipment, such as computers and card dialers, to originate calls automatically over a telecommunications network.

ACX: Asynchronous Cross-ConnectAsynchronous Cross-connect (ACX) is an ATM specific switch that can connect different ATM-compatible services together.

ADA: Average Delay to AbandonAverage Delay to Abandon (ADA) refers to the time the average caller who abandoned waiting before being abandoned.

ADACC: Automatic Directory Assistance Call CompletionAutomatic Directory Assistance Call Completion (ADACC) is a switch feature/application that offers the caller the option of having the DA call automatically completed to the requested listing.

ADAD: Automatic Dialing and Announcing DeviceAutomatic Dialing and Announcing Device (ADAD) is a device that use a mechanism that sends an unsolicited recorded message to your home or workplace and could leave such a message on your answering machine

Adaptive Channel AllocationAdaptive Channel Allocation refers to a channel allocation scheme in communications system traffic flow control, channel allocation that information-handling capacities of channels are not predetermined but are assigned on demand. Adaptive channel allocation is usually accomplished by means of a multiplexing scheme.

ADAS: Automated Directory Assistance ServiceAutomated Directory Assistance Service (ADAS) is an application that automates the greeting-and-inquiry portion of the directory assistance call and plays the subscriber's responses to the operator for a savings of 2-4 seconds in worktime.

ADC: Analog-to-Digital ConverterAnalog-to-Digital Converter (ADC, A/D or A to D) is an electronic device that converts continuous signals to discrete digital numbers. The reverse operation is performed by a digital-to-analog converter (DAC). ADC can uniquely represents all analog input values within a specified total input range by a limited number of digital output codes.

Add-on ConferenceAdd-on Conference is a call feature that allows an additional party to be added to an established call without attendant assistance.

Add-on Data ModuleAdd-on Data Module is plug-in circuit card enabling a PBX to send and receive analog and digital signals.

Address Complete MessageAddress Complete Message, a CCS/SS7 term, refers to the signaling message that contains call-status information sent prior to the called party going off-hook.

Address MessageAddress Message is a signaling message sent in the forward direction that contains (a) address information, (b) the signaling information required to route and connect a call to the called line, (c) service-class information, (d) information relating to user and network facilities, and (e) call-originator identity or call-receiver identity.

Address SignalingAddress Signaling is a process in telecommunication system used to convey address information. There are two address signaling methods, dial pulse (DP) and dual tone multifrequency (DTMF)

Addressed Call ModeAddressed Call Mode permits control signals and commands to establish and terminate calls in V.25bis.

ADE: Adaptive Design EngineeringAdaptive Design Engineering (ADE) is the process of providing specialized design and development of switching, transmission, and customer-premises equipment, or modifications of standard products to meet the specific needs of a customer.

Adjacent Signaling PointsAdjacent Signaling Points refers to two signaling points that are directly interconnected by one or more signaling links.

ADM: Add-Drop MultiplexerAdd/Drop Multiplexer (ADM), the main building blocks of SONET/SDH networks, combines, or multiplexes, several lower-speed streams of data into a single beam of light. ADMs, upon receipt of an optical signal (OC-n/STM-n), are configured to drop off the whole incoming signal or drop-off only certain lower rate optical signals and/or lower rate PDH signals (T1,T3). The remaining signal passes through. At the same time, optical or PDH signals could be added to replace the dropped-off signal and complete the outgoing optical signal. ADMs can be used both in long-haul core networks and in shorter-distance metro networks. A recent shift in ADM technology has introduced so called multi-service SONET/SDH (also known as a multi-service provisioning platform, or MSPP) equipment which has all the capabilities of legacy ADMs, but can also include cross-connect functionality to manage multiple fiber rings in a single chassis. These new devices can replace multiple legacy

ADMs and also allow connections directly from Ethernet LANs to a service provider's optical backbone.

Administrative Trunk GroupAdministrative Trunk Group is a category of trunk groups that provide call status monitoring. The function may be one of revenue protection (i.e., coin overtime collection), protection of the message network from overloads (i.e., no-circuit announcements), and so on.

ADPCM: Adaptive Differential Pulse-Code ModulationAdaptive Differential Pulse Code Modulation(ADPCM) is the process by which analog voice samples are encoded into high-quality digital signals. The first ADPCM standardized by the CCITT is G.721 for 32 kbps. Later came the standards G.726 and G.727 for 40, 32, 24 and 16 kbps. ADPCM is used to send sound on fiber-optic long-distance lines as well as to store sound along with text, images, and code on a CD-ROM.

Advanced Branch ExchangeAdvanced Branch Exchange is an uncommon PBX term refers to a PBX with advanced features normally including the ability to handle both voice and data in some sort of integrated way.

Aerial CableAerial Cable is transmission facility physically strung between poles or similar over-head structures.

Aeronautical Emergency Communications System PlanAeronautical Emergency Communications System Plan is a process that provides for the operation of aeronautical communications stations, on a voluntary, organized basis, to provide the President and the Federal Government, as well as heads of state and local governments, or their designated representatives, and the aeronautical industry with an expeditious means of communications during an emergency situation.

Aggregation DeviceAggregation Device is a special ISDN terminal adapter. It can aggregate or bond the two B channels into a single higher-speed connection. Sometimes, aggregate device also includes bridges which is the data link layer device connecting two LANs.

AHT: Average Handle TimeAverage Handle Time (AHT) is the average time it takes for calls to a service or a skill group to be handled. Handle time includes talk time plus after-call work time.

AIC: Automatic Intercept CenterAutomatic Intercept Center (AIC) is a centrally located set of equipment that is a part of an Automatic Intercept System and provides arrangements, having stored program control, whereby the caller is automatically advised, by means of either recorded or electronically assembled announcements, of the situation that prevents the completion of connection to the called number.

AIDR: As-Is Data RateAs-Is Data Rate (AIDR) is a term primarily used by telephone companies to represent the level of available data throughput that can actually be provided to an end-user over copper wiring. AIDR, as opposed to MEDR ( Maximum Engineering Data Rate) is an actual measure of what an end-user can be provided measured in kilobytes per second—in other words, an AIDR of 3000 means that the end-user in question can receive up to 3000 kilobytes per second of download speed.

AIN: Advanced Intelligent NetworksAdvanced Intelligent Network(AIN) is a telephone network architecture that separates service logic from switching equipment, allowing new services to be added without having to redesign switches to support new services. It encourages competition among service providers since it makes it easier for a provider to add services and offers customers more service choices. Developed by Bell Communications Research(Bellcore, now Telcordia), AIN is recognized as a telecom industry standard in North America.

AIOD: Automatic Identified Outward DialingAutomatic Identified Outward Dialing (AIOD) refers to a service feature of some switching or terminal devices that provides the user with an itemized statement of usage on directly dialed calls. AIOD is facilitated by automatic number identification (ANI) equipment to provide automatic message accounting (AMA).

Air-Ground Worldwide Communications SystemAir-ground worldwide communications system is a worldwide military network of ground stations that (a) provides two-way communications links between aircraft and ground stations for navigation and control, including air route traffic control and (b) may also provide support for special functions, such as for civil aircraft providing assistance to military missions and for meeting communications requirements for aircraft flying distinguished visitors.

AIS: Alarm Indication SignalAlarm Indication Signal (AIS), in a T1 transmission, is an all-ones signal transmitted in lieu of the normal signal to maintain transmission continuity and to indicate to the receiving equipment that there is a transmission interruption located either at the equipment originating the AIS signal or upstream of that equipment. Alarm Indication Signal (AIS) may also refers to a signal transmitted in lieu of the normal signal to maintain transmission continuity and indicate to the receiving terminal that there is a transmission fault located either at the transmitting terminal or upstream of the transmitting terminal.

AIS: Automatic Intercept SystemAutomatic Intercept System (AIS) is a type of Traffic Service System consisting of one or more automatic intercept centers and a centralized intercept bureau for handling intercept calls.

A-LawA-Law is the standard codec (compression/decompression) algorithm for pulse code modulation (PCM) from the ITU-T (the Telecommunication Standardization Sector of the International

Telecommunications Union). A-Law is the type of PCM used in most of the world. The other type, mu-Law, is used in the United States and Japan.

Alerting SignalAlerting Signal is a signal used by the telephony network to indicate the presence of an incoming call. It consists of a ringing signal periodically interrupted by silent (no ringing signal) intervals.

Alerting ToneAlerting Tone is used to indicate that an operator has connected to the line for emergency interrupt on a busy line during a verification call. Alerting Tone is 440 Hz on for 2 seconds and then on again for 5 seconds every ten seconds.

A-Link: SS7 Access LinkA-link, short of SS7 Access Link, is a dedicated SS7 signaling link not physically associated with any particular link carrying traffic. An A-link connects a signaling end-point (e.g., an SCP or SSP) to an STP. Only messages originating from or destined to the signaling end point are transmitted on an A-link.

All Trunk BusyAll Trunk Busy refers an equipment condition in which all trunks (paths) in a given trunk group are busy. All-trunks-busy registers do not indicate subsequent attempts to reach trunk groups.

AllomorphismAllomorphism is the ability of object instances of a specific class to imitate the behavior of another object class, and allows proprietary extensions. This is a technique for managing the complexity introduced by multiple versions of models.

Alternate Access CarriersAlternate Access Carriers, also known as Competitive Local Exchange Carriers(CLEC), are local exchange carriers in direct competition with the RBOCs. They are normally found only in the larger metropolitan areas.

Alternate Mark Inversion SignalAlternate Mark Inversion Signal is a pseudoternary signal, representing binary digits, in which (a) successive "marks" are of alternately positive and negative polarity and the absolute values of their amplitudes are normally equal and (b) "spaces" are of zero amplitude.

Alternate PartyAlternate party, also referred as alternate party diversion, is an optional feature of telephone services, where a call may be routed to a different number based on time-out and precedence schemes set up by the customer.

AM: Administrative ModuleAdministrative Module (AM) is a component of the Lucent 5ESS switch that provides the system-level interfaces required to operate, administer and maintain a 5ESS switch. The functions of the AM are: (1) performs common operations that can be done globally and

economically such as resource allocation, maintenance, and control. (2) AM processor is fully duplicated to provide a highly reliable and stable system. (3) performs call-processing support functions (4) performs administrative functions, and provides software access to external data links and disk storage. (5) The call-processing functions of the AM consisted of data routing and recource allocation. Data routing involves determining the SM on which a terminating line or trunk appears and then selecting an available trunk in a trunk group to carrythe traffic. The AM allocates and releases global resources such as TMS time slots to insure efficient operation of the switch. (6) A duplicated disk memory provides mass storage for programs and data. (7) The AM is the only processor in this distributed processing architecture, that keeps an up-to-date picture of the entire system. (8) The master control center (MCC) provides the primary interface between the 5ESS equipment and the pernnel adminstering/maintaining the system.

AMA: Automatic Message AccountingAutomatic Message Accounting (AMA) is a switching feature that automatically records data regarding user-dialed calls. AMA handles the automatic collection, recording, and processing of information relating to calls for billing purposes.

Ambient Noise LevelAmbient Noise Level is as it implied the level of acoustic noise existing at a given location, such as in a room, in a compartment, or at a place out of doors. Ambient noise level is measured with a sound level meter. Ambient noise level is usually measured in dB above a reference pressure level of 0.00002 Pa, i.e., 20 Pa (micro-pascals) in SI units. A pascal (Pa) is a Newton per square meter.

American Wire GaugeAmerican Wire Gauge is a standard method of denoting wire diameter, especially for nonferrous, electrically conducting wire.

AmeritechAmeritech was one of the seven baby bells spuned off from the former AT&T. Ameritech became SBC and now merged with AT&T again.

AMI: Alternate Mark InversionAlternate Mark Inversion (AMI) is a synchronous clock encoding technique which uses bipolar pulses to represent logical 1 values. It is, therefore, a three level system. A logical 0 is represented by no symbol, and a logical 1 by pulses of alternating polarity. The alternating coding prevents the build-up of an o.k. voltage level down the cable. This is considered an advantage since the cable may be used to carry a small d.c. current to power intermediate equipment such as line repeaters.

Amplified HandsetAmplified Handset is the phone handset equipped with amplifier to increase the voice volume.

ANAC Number: Automatic Number Announcement Circuit NumberAutomatic Number Announcement Circuit (ANAC) Number is a telephone number that plays

back the number of the telephone that carries it. ANAX Numbers are convenient if you wants to know the telephone number of a pair of wires.

Analog BridgeAnalog Bridge refers to a circuit in telecommunication system like switch that has the capability to extend (bridge) a normal two-person voice conversation to include a third person without degrading the quality of the call

Analog Carrier SystemAnalog Carrier System is a transmission system that uses repeaters that compensate for analog medium impairments, and produce output signals that are linear-scaled versions of input signals. Analog carrier systems can carry speech, data, video and supervisory signals although they are best suited for speech signals.

Analog ChannelAnalog Channel is a channel capable of transmitting analog signals within the specified bandwidth of the facility. Voice channels are analog channels.

Analog DataAnalog Data refers to the data represented by a physical quantity that is considered to be continuously variable and has a magnitude directly proportional to the data or to a suitable function of the data.

Analog DecodingAnalog Decoding is a process, in the electronics context, of converting digital to analog that generates an analog signal value from the digital signal resulted from analog encoding.

Analog FacsimileAnalog Facsimile is a device that can transmit and receive grey shadings. It has the capability of transmitting continuous shades of grey. Analog Facsimile is usually transmitted digitally.

Analog Loop-BackAnalog Loop-back is a testing scheme of modem self-test in which data from the keyboard or an internal test pattern is sent to the modem's transmitter, turned into analog form, looped back to the receiver and converted back into digital form

Analog SignalAnalog Signal is a signal that has a continuous nature rather than a pulsed or discrete nature. Electrical or physical analogies, such as continuously varying voltages, frequencies, or phases, may be used as analog signals. A nominally continuous electrical signal that varies in some direct correlation with another signal impressed on a transducer. For example, an analog signal may vary in frequency, phase, or amplitude in response to changes in physical phenomena, such as sound, light, heat, position, or pressure.

Analog SwitchAnalog Switch refers to telephone switching equipment that switches the analog signal without

changing its analog nature such as converting the signal into digital signal. Circuit switching is a typical analog switching.

AND: Automatic Network DialingAutomatic Network Dialing (AND) refers to a feature that simplify on-network calling among multiple business locations by providing a single step dialing for private networks and a single numbering/dialing plan.

ANI: Automatic Number IdentificationAutomatic Number Identification (ANI) is a system utilized by telephone companies to identify the DN (Directory Number) of a calling subscriber. ANI serves a function similar to Caller-ID, but utilizes different underlying technology. In addition, although Caller-ID blocked by prefixing a call with *67, ANI is (usually) impossible to block. Though ANI is thought of as an ISDN feature, it is actually distinct from ISDN, and is a part of Signaling System 7.

AnisochronousAnisochronous refers to the characteristics of transmission in which the time interval separating any two significant instants in sequential signals is not necessarily related to the time interval separating any other two significant instants.

ANM: Answer MessageAnswer Message (ANM) is an off-hook signal sent in the reverse direction that indicates when the called party answers. Billing of a call starts when the answer message is received.

Announcement ServiceAnnouncement Service refers to the feature/service of telephone system that allows a caller to hear a recoding when they dial a certain phone number or extension.

Announcement SystemAnnouncement System refers to the system or service that provides information to a caller via recorded messages or announcements.

Annoyance Call BureauAnnoyance Call Bureau is the department in local phone company which handles complain or report about annoyance calls or harassing calls people might receive.

AnnunciatorAnnunciator is a visual or audible signaling device that indicates the condition and/or availability of associated circuit (s) or stations.

Anonymous Call RejectionAnonymous Call Rejection refers to a feature that allows you to reject calls from callers who have blocked the display of their telephone numbers. Anonymous Call Rejection discourages anonymous calls, since callers must allow their numbers to be displayed in order to reach you.

Anonymous Telephone NumberAnonymous Telephone Number refers to a phone number that switching systems will handle differently so that it shouldn't be displayed and voiced back to the called party.

ANSA: Alternate Network Service AgreementAlternate Network Service Agreement (ANSA) is a special arrangement for ISDN service. Under ANSA, customers who reside in areas where the central office switch does not support ISDN can be serviced from a neighboring central office at no additional charge. From the customer's perspective, ISDN is readily available and affordable, but the customer MUST agree to migrate to the local central office if and when service becomes available. In most cases, this will involve a change in phone number. This agreement pertains to former Bell South customers only.

Answer BackAnswer Back is a specific identifying code, automatically transmitted by an addressed station upon the receipt of a special request signal from the originating station (or system).

APON: ATM Passive Optic NetworkATM Passive Optic Network (APON), also known as Broadband PON (BPON), is the initial PON specification defined by the FSAN committee used ATM as their layer 2 signaling protocol. Use of the term APON led users to believe that only ATM services could be provided to end-users, so the FSAN decided to broaden the name to Broadband PON (BPON). BPON systems offer numerous broadband services including Ethernet access and video distribution.

APS: Automatic Protection SystemAutomatic Protection System (APS) is a switching architecture designed for SONET (Synchronous Optical Network ) to perform error protection and network management from any point of the signal path.

Area CodeArea Code is a three-digit number (the first three digits in the phone number xxx-xxx-xxxx) identifying one of the assigned geographic areas in the North American direct assistance dialing numbering plan.

Area ExchangeArea Exchange is a geopolitical area setup for the administration of local telephone service, usually a single metropolitan area or collection of towns and villages sharing a common area of community interest.

Arithmetic ShiftArithmetic Shift refers to a shift, applied to the representation of a number in a fixed-radix numeration system and in a fixed-point representation system, and in which only the characters representing the fixed-point part of the number are moved. An arithmetic shift is usually equivalent to multiplying the number by a positive or a negative integral power of the radix, except for the effect of any rounding; compare the logical shift with the arithmetic shift, especially in the case of floating-point representation.

ARQ: Automatic Repeat & RequestAutomatic Repeat-reQuest (ARQ) is an error control method for data transmission in which the receiver detects transmission errors in a message and automatically requests a retransmission from the transmitter. Usually, when the transmitter receives the ARQ, the transmitter retransmits the message until it is either correctly received or the error persists beyond a predetermined number of retransmissions. A few types of ARQ protocols are Stop-and-wait ARQ, Go-Back-N ARQ and Selective Repeat ARQ.

AS: Articulation ScoreArticulation Score (AS) is a subjective measure of the intelligibility of a voice system in terms of the percentage of words correctly understood over a channel perturbed by interference. Articulation scores have been experimentally obtained as functions of varying word content, bandwidth, audio signal-to-noise ratio and the experience of the talkers and listeners involved.

ASA: Average Speed of AnswerAverage Speed of Answer (ASA), also called Average Seconds to Answer or Average Time to Answer (ATA), is the average answer waiting time for all calls to a service in a given period (e.g. the last 15 minutes, today, this month). It is the total amount of time all calls waited to be answered divided by the total number of calls. It is often expressed in seconds.

ASC: Accredited Standards CommitteesAccredited Standards Committees (ASC) is an IEEE committee accredited to develop standards. The committee consists of members and a Secretariat. The membership is generally composed of organizations, companies, government agencies, individuals, etc. having a direct and material interest in the activities of the committee. A balance of the various interest groups must be maintained, i.e., no one interest group can dominate the committee. The Secretariat is an organization that has oversight responsibilities over the ASC. The Secretariat organizes the committee, applies for its accreditation, oversees the committees' compliance to procedures, maintains the roster, submits standards for approval, publishes the standards, etc.

ASE: Application Service ElementApplication Service Element (ASE) is the function that allows applications to communicate with one another in a SS7 system. Examples of an ASE include TCAP (Transaction Capabilities Application Part) and MAP (Mobile Application Part).

ASK: Amplitude Shift KeyingAmplitude Shift Keying (ASK) is a modulation process which imparts to a carrier wave (sinusoid) two or more discrete amplitude levels. These are related to the number of levels adopted by the digital message

ASN: AT&T Switched NetworkAT&T Switched Network (ASN) refers to the former AT&T Global Network which was the most sophisticated communications network in the world. On an average business day, it had delivered more combined data, voice and internet traffic to more locations, more reliably, than any other network. It had handled more than 3.8 Petabytes (Peta = Quadrillion) of data every 7.5 minutes-as well as 410 million voice calls.

ASP: Application Service ProviderApplication Service Provider (ASP) refers to the business which provides software service based on network especially over the Web. It's a new way to sell and distribute software services in the Internet age. The ASP model can be appealing to businesses -- especially small businesses and startups -- because it can drastically lower the costs of software and services.

Associated ModeAssociated Mode refers to one of the three common channel signaling modes. In the Associated Mode, messages for signaling functions (which involve adjacent signaling points) are transported over a direct interconnecting link.

Associative StorageAssociative Storage is a storage device or process that the storage locations are identified by their contents, or by a part of their contents, rather than by their names or positions. This is also known as content-addressable storage.

Asynchronous OperationAsynchronous Operation refers to operations which are executed in computer out of time coincidence with any event. An operation that occurs without a regular or predictable time relationship to a specified event; e.g., the calling of an error diagnostic routine that may receive control at any time during the execution of a computer program.

AT: Access TandemAccess Tandem (AT) refers to a telephone switch that interconnects with CO (Central Office) switches and other access tandem switches to form the PSTN (Public Switched Telephone Network). It is often called a "class 4" switch, a reference to the original AT&T hierarchal network structure.

ATA: Analog Terminal AdapterAnalog Terminal Adapter (ATA) is a device that allows a normal PSTN telephone to connect to the Internet in order to make or place telephone calls. An ATA device may work in conjunction with a computer, such as a USB ATA device, or it may be a stand-alone device that communicates with a service provider over the Internet. The latter types of devices are common with many broadband VoIP service providers.

ATA: Average Time to AnswerAverage Time to Answer (ATA), also called Average Speed of Answer (ASA) or Average Seconds to Answer is the average answer wait time for all calls to a service in a given period (e.g. the last 15 minutes, today, this month). It is the total amount of time all calls waited to be answered divided by the total number of calls. It is often expressed in seconds.

ATB: All Trunks BusyAll Trunks Busy (ATB) is the state of a trunk group when all trunks are in use. The trunk group cannot accept any new inbound or outbound calls in this state.

ATDM: Asynchronous Time-Division MultiplexingAsynchronous time-division multiplexing (ATDM) is a method of sending information that resembles normal TDM, except that time slots are allocated as needed dynamically rather than preassigned to specific transmitters. ATDM is more intelligent and has better bandwidth efficiency than TDM.

ATIS: Alliance for Telecom Industry SolutionsAlliance for Telecom Industry Solutions (ATIS) is a standards body that developing telecommunications standards, operating procedures and guidelines through its sponsored committees and forums. ATIS member companies are North American providers of telecommunications services, and including wireline and wireless service providers, competitive local carriers, inter-exchange companies, local exchange companies, manufacturers, software developers, resellers, enhanced service providers, and providers of operations support.

Attack TimeAttack Time is the time between (a) the instant that a signal at the input of a device or circuit exceeds the activation threshold of the device or circuit and (b) the instant that the device or circuit reacts in a specified manner, or to a specified degree, to the input. Attack time occurs in devices such as clippers, peak limiters, compressors, and voxes.

AttemptAttempt, in telecommunication context, refers to a call offered to a telecommunications system, whether or not it is completed.

Attenuation ConstantAttenuation Constant refers to the following definition:1. The real part of the propagation constant in any electromagnetic propagation medium. The attenuation constant is usually expressed as a numerical value per unit length and may be calculated or experimentally determined for each medium.2. For a particular propagation mode in an optical fiber, the real part of the axial propagation constant.

Attenuation to crosstalk ratioAttenuation to crosstalk ratio is the difference between attenuation and crosstalk at a given frequency along a cable. Measured in decibels, ACR is a calculation used in networking transmission to assure that a signal transmitted across a twisted-pair cable is stronger at the receiving end than any interference signals imposed on that same pair by crosstalk from adjacent pairs.

ATU-C: ADSL Transmission Unit-Central OfficeADSL Transmission Unit-Central Office (ATU-C) refers to the modem of the central office that is a component of the ADSL network. It terminates the ADSL (Asymmetric Digital Subscriber Line) local loop at the central office premises.

ATU-R: ADSL Transmission Unit-RemoteADSL Transmission Unit-Remote (ATU-R) refers to the modem at the customer premises which is a component of the ADSL network. It provides local loop termination on the customer side

AudibleBusy ToneAudible busy tone is one of the audible tones in telephone system to signal a busy status. The "Precise" busy signal (Real Audio) / "Precise" busy signal (WAV): 480 and 620 Hz at -24 dBm0/frequency, is generated at telephone exchange, interrupted at 60 interruptions per minute (0.5 sec. on, 0.5 sec. off).

Audible Ringing ToneAudible Ring Tone is a ringing indication which is intercepted by the calling party to mean that the called line has been reached and that the ringing has started. It is also used on calls to operators (special service, long distance, intercepting, etc) during the "awaiting-operator-answer" interval. Audible Ring Tone is 440 Hz and 480 Hz for 2 seconds on and 4 seconds off at -13 dBm0/frequency.

Audible TonesAudible tones refer to the audible signal used in the telephone system to indicate the progress or disposition of a call. These include dial tone, busy tone, reorder tone, ring back and call waiting. It could be generated by either the called-party servicing switch or by the calling-party servicing switch.

AuditAudit refers to the following actions in telecommunication system: 1. To conduct an independent review and examination of system records and activities in order to test the adequacy and effectiveness of data security and data integrity procedures, to ensure compliance with established policy and operational procedures, and to recommend any necessary changes.2. Independent review and examination of records and activities to assess the adequacy of system controls, to ensure compliance with established policies and operational procedures, and to recommend necessary changes in controls, policies, or procedures.

Automatic Call ReconnectAutomatic Call Reconnect is a feature permitting automatic call rerouting away from a failed trunk line.

Automatic SoundingAutomatic sounding is the testing of selected channels or paths by providing a very brief beacon-like identifying broadcast that may be used by other stations to evaluate connectivity, propagation, and availability, and to identify known working channels for possible later use for communications or calling. Automatic soundings are primarily intended to increase the efficiency of the automatic link establishment (ALE) function, thereby the system throughput. Sounding information is used for identifying the specific channel to be used for a particular ALE connectivity attempt.

Automatic Switching SystemAutomatic Switching System refers to: 1. a telephony system in which all the operations required to set up, supervise, and release connections required for calls are automatically performed in response to signals from a calling device. 2. a data communication switching system in which all the operations required to execute the three phases of information-transfer transactions are automatically executed in response to signals from a user-end instrument. In an automatic switching system, the information-transfer transaction is performed without human intervention, except for initiation of the access phase and the disengagement phase by a user.

Auxiliary Service Trunk GroupsAuxiliary Service Trunk Groups is a category of trunk groups that provide selected services for customers or operators and terminate at announcement systems, cord switch boards, or desks. Typical applications commonly employ the following types of trunk groups: Direct Assistance, Intercept, Official, Public Announcement, Rate-and-Route, Repair Service, Timeo Weather.

Available LineAvailable Line is a circuit between two points that is ready for service, but is in the idle state. In facsimile transmission, available Line is the portion of the scanning line that can be specifically used for image signals.

AVBO: Advanced Voice BusyoutAdvanced Voice Busyout(AVBO) is the local voice busy-out feature in a PBX or other Customer Premises Equipment (CPE). AVBO provides a way to busy out a voice port or a time slot if a state change is detected in a monitored network interface. When a monitored interface changes to a specified state, to out-of-service, or to in-service, the voice port presents a seized/busy-out condition to the attached PBX or other CPE. The PBX or other CPE can then attempt to select an alternate route. AVBO adds the following functionality to the local voice busy-out feature: 1) For Voice over IP (VoIP), monitoring of links to remote, IP-addressable interfaces by the use of a real time reporter (RTR). 2) Configuration by voice class to simplify and speed up the configuration of voice busy-out on multiple voice ports. 3) Local voice busy-out is supported on analog and digital voice ports using channel-associated signalling (CAS).

Average LoadAverage Load is the load obtained by averaging a series of hourly loads; may be further defined as average carried load, average offered load. This term is not to be confused with load, which is inherently an average of all the instantaneous loads over a basic time interval, such as an hour.

AXEAXE is an Ericsson’s communications platform, a system for computer-controlled digital exchanges in large public telecommunications networks. This is the basis for Ericsson't wireline and mobile systems.

Tele-Communication (Telecom) Terms Glossary and Dictionary - B

B3ZS: Bipolar 3 Zero SubstitutionBipolar 3 Zero Substitution (B3ZS) is a T-carrier line code in which bipolar violations are deliberately inserted if the stream of user data contains a string of 3 or more consecutive zeros.B3ZS is used to ensure a sufficient number of transitions to maintain system synchronization when the user data stream contains an insufficient number of "ones" to do so.

B6ZS: Bipolar 6 Zero SubstitutionBipolar 6 Zero Substitution (B6ZS) refers to a T-carrier Line Code in which bipolar violations are deliberately inserted if user data contains a string of 6 or more consecutive zeros. B6ZS is used to ensure a sufficient number of transitions to maintain system synchronization when the user data stream contains an insufficient number of "1s" to do so.

B8ZS: Bipolar 8 Zero SubstitutionBipolar 8 Zero Substitution (B8ZS) is a method of line coding used in the T-carrier system which allows full 64 Kbit/s per second per channel. On a T1, ones are sent by applying voltage to the wire, where a zero is sent by having no voltage on the wire. Sending eight zeros in a row could cause T1 equipment to lose synchronization with the sending equipment, it is important that that pattern is not sent.

BabbleBabble refers to noise or confusion, which is the aggregate crosstalk from interfering channels.

Backbone CablingBackbone Cabling refers to a portion of premises telecommunications cabling that provides connections between telecommunications closets, equipment rooms and entrance facilities. It consists of the transmission media (optical fiber cable), main and intermediate cross-connects, and terminations for the horizontal cross-connect, equipment rooms, and entrance facilities. Backbone cabling, sometimes called backbone wiring, can further be classified as inter-building backbone (cabling between buildings), or intrabuilding backbone (cabling within a building).

Back-ChannelBack-channel is, in an asymmetric telecommunications system, typically a low-speed or less-than-optimal transmission channel opposite to the main channel's direction. An example of this is in ADSL where "A" stands for "asymmetric", and the channel from the subscriber to the supplier is slower and may be of less capacity than the channel from the supplier to the subscriber.

Background NoiseBackground Noise is the random signals that can be attributed to the unpredictable movement of free elections in a communication channel.

Back-HaulBack-Haul is a communications path which takes traffic farther than the ultimate destination, then routes it back. This is done because the cost of transmission to the more remote location is much lower than a more direct route.

Back-to-Back ConnectionBack-to-back connection is: 1. A direct connection between the output of a transmitting device and the input of an associated receiving device. When used for equipment measurements or testing purposes, such a back-to-back connection eliminates the effects of the transmission channel or medium. 2 . A direct connection between the output of a receiving device and the input to a transmitting device. The term "direct," as used in both definitions, may be construed as permitting a passive device such as a pad (attenuator) to accommodate power level constraints.

Backward ChannelBackward Channel is the channel in a data circuit that passes data in a direction opposite to that of its associated forward channel. The backward channel is usually used for transmission of request, supervisory, acknowledgement, or error-control signals. The direction of flow of these signals is opposite to that in which user information is being transferred. The backward-channel bandwidth is usually less than that of the primary channel, that is, the forward (user information) channel. For example, ADSL's upstream channel, considered a backward channel for some types of analysis, typically has a bandwidth less than one-fourth of the downstream channel.In data transmission, it is a secondary channel in which the direction of transmission is constrained to be opposite to that of the primary, i.e., the forward (user-information) channel. The direction of transmission in the backward channel is restricted by the control interchange circuit that controls the direction of transmission in the primary channel.

Backward SignalBackward signal is a signal sent from the called to the calling station, i.e., from the original data sink to the original data source. Backward signals are usually sent via a backward channel and may consist of supervisory, acknowledgment, or control signals.

BAF: Bellcore AMA FormatBellcore AMA Format (BAF) is a system of abstract syntax and semantics that supports coding of Automatic Message Accounting (AMA) data into records.

Balance Return LossBalance Return Loss refers to the following two definitions in telecmmunication: (1) A measure of the degree of balance between two impedances connected to two conjugate sides of a hybrid set ( a functional unit in which more than two different technologies are combined to satisfy a given requirement ), coil, network, or junction. (2) A measure of the effectiveness with which a balancing network simulates the impedance of a two-wire circuit at a hybrid coil ( a single transformer that effectively has three windings, and which is designed to be configured as a circuit having four branches, e.g., ports, that are conjugare in pairs).

Balanced ImpedanceBalanced Impedance is the state of impedance on a two-wire line when the impedance to ground as measured from one wire is equal to the impedance to ground as measured from the other wire. A balancing network is a combination of electronic components which stimulate the impedance of a uniform cable or open-wire circuit over a band of frequencies.

Balanced LineBalanced Line is a transmission line consisting of two conductors in the presence of ground, capable of being operated in such a way that when the voltages of the two conductors at all transverse planes are equal in magnitude and opposite in polarity with respect to ground, the currents in the two conductors are equal in magnitude and opposite in direction.

BallotBallot, also know as a Letter Of Agency(LOA), is a release form in telecommunication system used to authorizes a customer's long-distance phone service to be switched to (another) long-distance carrier, or reseller.

BAN: Billing Account NumberBilling Account Number (BAN) is an account number used by telephone companies to designate a customer or customer location that will be billed. A single customer may have multiple billing accounts.

BandBand in telecommunication refers to the following definitions: 1. The range of frequencies between two defined limits which are used for a specific purpose. 2. One of the geopolitical boundaries established to define a WATS (wide-area telephone service) serving area.

Band Elimination FilterBand Elimination Filter is an electrical device which blinds a receiving unit from recognizing a specific range of frequencies.

Banded RatesBanded Rates is tariffed rates that may be changed by the telecom carrier within a specified range. Frequently, state commissions require notice to the commission prior to each change. Banded rates are being used less frequently today.

Bandwidth CapBandwidth Cap refers to a bandwidth limitation, which is administered by an Internet service provider (ISP), that limits the transfer of a specified amount of data over a period of time. If a user exceeds the bandwidth cap, the ISP restricts connection speed or other services. The ISP may offer the purchase of additional bandwidth. Another type of bandwidth cap, also administrated by an ISP, is one which limits the speed of data transfer on a broadband Internet connection. Though the term is used in some cases and not on others, a bandwidth cap is not correctly considered a limit of speed.

Bandwidth CompressionBandwidth Compression is: 1. the reduction of the bandwidth needed to transmit a given amount of data in a given time. 2. the reduction of the time needed to transmit a given amount of data in a given bandwidth.

Bandwidth Limited OperationBandwidth Limited Operation refers to the condition of telecommunication system under which

the limitation on performance is imposed by the system bandwidth. The condition is reached when modal dispersion distorts the shape of the waveform beyond specified limits.

Bandwidth ThrottlingBandwidth throttling is a method of ensuring a bandwidth intensive device, such as a server, to limit ("throttle") the number of requests it will respond to within a specified period of time. Bandwidth throttling helps providing quality of service (QoS) by limiting network congestion and server crashes.

Basic ServiceBasic Service refers to the minimum set of capabilities which are necessary for use of the public telecommunications network. Current basic service includes an access line, with access to local and long distance calling, to emergency calling (911), and to voice/non-voice relay service.

BCC: Block Check CharacterBlock Check Character (BCC) is a character added to a telecommunication transmission block to facilitate error detection. In longitudinal redundancy checking and cyclic redundancy checking, block check characters are computed for, and added to, each message block transmitted. This block check character is compared with a second block check character computed by the receiver to determine whether the transmission is error free

BCD: Binary Coded DecimalBinary Coded Decimal (BCD) refers to a binary equivalent of the decimal system which also occupies a nibble. In BCD, the binary patterns 1010 through 1111 do not represent valid BCD number, and cannot be used.

BCH Code: Bose, Ray-Chaudhuri, Hocquenghem CodeBose, Ray-Chaudhuri, Hocquenghem (BCH) Code is a multilevel, cyclic, error-correcting, variable-length digital code used to correct errors up to approximately 25% of the total number of digits. BCH codes are not limited to binary codes, but may be used with multilevel phase-shift keying whenever the number of levels is a prime number or a power of a prime number. A BCH code in 11 levels has been used to represent the 10 decimal digits plus a sign digit. BCH codes make use of field theory and polynomials over that field. The way the check polynomial is constructed provides the key to indicating that an error has occurred.

B-Channel BundlingB-Channel Bundling, also known as bearer channel bundling, refers to a technique used to squeeze more voice conversations onto a single line in ISDN. The B channel, one of the fundamental components of the ISDN interface, is circuit-switched and can carry 64,000 bps of voice or data in either direction. B-channel bundling is based on Digital Speed Interpolation (DSI), in which speech is sliced up so that bits are transmitted only when someone is speaking.

BDCS: Broadband Digital Cross-Connect SystemBroadband Digital Cross-Connect System (BDCS) is a SONET DCS capable of cross-connecting DS-3, STS-1 and STS-3c signals.

Bell Customer CodeBell Customer Code is a three-digit numeric code, appended to the end of the Main Billing Telephone Number, that is used by Local Exchange Carriers to provide unique identification of customers.

BellcoreBellcore, now called Telcodia, was established by the former AT&T divestiture, representing and funded by the Regional Bell Carriers RBOCs. The organization establishes telephone-network standards, training materials and quality procedures.

BER: Bit Error RateBit Error Rate (BER) is the ratio of received bits that contain errors. BER is usually expressed as ten to a negative power. For example, a transmission might have a BER of 10 to the minus 9, which indicates that, out of a billion bits transmitted, one bit was in error. Typically, the bits in error need to be re-transmitted, which may slow down communications.

BERT: Bit Error Rate TesterBit Error Rate Tester (BERT) is the device that determines the Bit Error Rate (BER) on a given communications channel.

Bent Pipe TechnologyBent Pipe Technology refers to satellite technology to transmit calls from one point on Earth to a satellite and back down to another point on Earth.

BHCA: Busy Hour Call AttemptBusy Hour call Attempt (BHCA) is the number of times a telephone call is attempted during the busiest hour of the day.

BIB: Backward Indicator BitBackward Indicator Bit (BIB), a one-bit field in the SS7 Message Signaling Unit (MSU), indicates a negative acknowledgment by the remote signaling point when toggled.

Bidirectional SwitchBidirectional Switch is a switch in which a moving contact level travels in two directions to connect to a desired fixed contact. While the most common combination is a vertical motion followed by an angular motion, other combinations are possible.

BifurcatedBifurcated, in a telecommunication network, refers to a two-pronged connector. A "bifurcated wire wrap" terminal block is one that has an "H" shape, which forms one electrical connection pair with two connection terminals.

Billboard AntennaBillboard Antenna is an array of parallel dipole antennas with flat reflectors, usually positioned in a line or plane. The spacing and dimensions of the dipoles depend on the wavelength. The

main lobe of a fixed billboard antenna may, within limits, be steered by appropriate phasing of the respective signals to individual elements of the array.

Bill-To-RoomBill-To-Room is a billing option associated with Operator Assisted calls that allows the calling party to bill a call to their hotel room. With this option, the carrier is required to notify the hotel, upon completion of the call, of the time and charges.

Binary Golay CodeBinary Golay Code refers to two so-called closely related error-correcting codes. One is called extended binary Golay code which is an error-correcting code that encodes 12 bits of data in a 24-bit word in such a way that any triple-bit error can be corrected and any quadruple-bit error can be detected. The other is called perfect binary Golay Code which has odewords of length 23 and is obtained from the extended binary Golay code by deleting one coordinate position. Conversely, the extended binary Golay code can be obtained from the perfect binary Golay Code by adding a parity bit.

Binary SignalBinary Signal is a signal that may assume either of two polarities, neither of which is zero. A bipolar signal may have a two-state non-return-to-zero (NRZ) or a three-state return-to-zero (RZ) binary coding scheme. A bipolar signal is usually symmetrical with respect to zero amplitude, i.e., the absolute values of the positive and negative signal states are nominally equal.

Binary SwitchBinary Switch is a switch that must exist in one of only two states: on/off, zero/one, etc.

Biphase Mark CodeBiphase Mark Code is a type of encoding for binary data streams. If a binary data stream is sent without any modification via any channel, if there are long series of logical ones or zeros without any change, this can cause problems in synchronization. Streams encoded in NRZ are affected by the same problem. Using Biphase Mark Code makes synchronization easier.

BipolarBipolar is a code or transmission scheme incorporating both negative and positive polarity pulses. In AT&T's DDS bipolar transmission scheme, a negative-positive pulse and the absence of pulses indicates a binary zero. In this code, bipolar violation occurs when the alternating negative-positive pulsating pattern of the bipolar code is not followed.

Bipolar EncodingBipolar encoding is a type of line code (a method of encoding digital information to make it resistant to certain forms of signal loss during transmission). A binary 0 is encoded as zero volts as in unipolar encoding. A binary 1 is encoded alternately as a positive voltage and a negative voltage. This prevents a significant build-up of DC, as the positive and negative pulses average to zero volts. Little or no DC-component is considered an advantage because the cable may then be used for longer distances and to carry power for intermediate equipment such as line

repeaters. The DC-component can be easily and cheaply removed before the signal reaches the decoding circuitry.

Bipolar SignalBipolar Signal is a baseband method of sending binary data over wire or cable. It is also called bipolar transmission. There are two logic states, low and high, represented by the digits 0 and 1 respectively.

Bipolar ViolationBipolar violation refers to an error occurred during the transmission of a T1 signal where two pulses of the same polarity take places without an intervening pulse of the opposite polarity.

BISYNC: Binary Synchronous CommunicationsBinary Synchronous Communications (BISYNC) is a character (byte)-oriented form of communication developed by IBM in the 1960s. It was originally designed for batch transmissions between the IBM S/360 mainframe family and IBM 2780 and 3780 terminals. It supports online and RJE (remote job entry) terminals in the CICS/VSE (Customer Information Control System/Virtual Storage Extended) environment.

Bit PairingBit Pairing refers to the practice of establishing, within a code set, a number of subsets that have an identical bit representation except for the state of a specified bit. An example of bit pairing takes place in the International Alphabet No. 5 and the American Standard Code for Information Interchange (ASCII), where the upper case letters are related to their respective lower case letters by the state of bit six.

Bit SlipBit Slip refers to the loss of a bit or bits caused by variations in the respective clock rates of the transmitting and receiving devices. One cause of bit slippage is overflow of a receive buffer that occurs when the transmitter's clock rate exceeds that of the receiver. This causes one or more bits to be dropped for lack of storage capacity.

Bit StuffingBit Stuffing refers to the the practice of inserting non-information of bits to a stream of data. Bit stuffing is required by many network and communications protocols for the following reasons:1. To prevent data being interpreted as control information. For instance, many frame-based protocols, such as X.25, signal the beginning and end of a frame with six consecutive 1 bits. Therefore, if the actual data being transmitted has six 1-bits in a row, a zero is inserted after the first 5 so that the dat is not interpreted as a frame delimiter. Of course, on the receiving end, the stuffed bits must be discarded.2. For protocols that require a fixed-size frame, bits are sometimes inserted to make the frame size equal to this set size.3. For protocols that required a continuous stream of data, zero bits are sometimes inserted to ensure that the stream is not broken.

Bit SynchronousBit Synchronous is a data transmission technique in which each bit is synchronized against an accurate clock. In asynchronous transmission, this synchronization is held for one character. In synchronous transmission, this synchronization is held for a block of characters.

Bit-Count IntegrityBit-count integrity, in telecommunication, has the following meanings: 2. In message communications, the preservation of the exact number of bits that are in the original message. 2. In connection-oriented services, preservation of the number of bits per unit time.

Biternary TransmissionBiternary Transmission refers to the digital transmission in which two binary pulse trains are combined for transmission over a channel in which the available bandwidth is sufficient for transmission of only one of the two pulse trains at a time if they remain in binary form.

BITS: Building Integrated Timing SupplyBuilding Integrated Timing Supply (BITS) is a clock in a central office that supplies DS1 and/or composite clock timing references to all synchronous network elements in that office.

Black NoiseBlack noise refers to noise that has a frequency spectrum of predominantly zero power level over all frequencies except for a few narrow bands or spikes. An example of black noise in a facsimile transmission system is the spectrum that might be obtained when scanning a black area in which there are a few random white spots. Thus, in the time domain, a few random pulses occur while scanning.

Black RecordingBlack recording refers to the following definition in facsimile system of telecommunication: 1. if it uses amplitude modulation, recording in which the maximum received power corresponds to the maximum density of the record medium. 2. if it uses frequency modulation, recording in which the lowest received frequency corresponds to the maximum density of the record medium.

Blind TransmissionBlind Transmission refers to the transmission without obtaining a receiving acknowledgement of reception from the intended receiving station. Blind transmission may occur or be necessary when security constraints, such as radio silence, are imposed, when technical difficulties with a sender's receiver or receiver's transmitter occur, or when lack of time precludes the delay caused by waiting for receipts.

B-Link: Bridge-LinkSS7 Bridge-link(B-link) connects a STP to another STP. Typically, a quad of B-links interconnect peer (or primary) STPs (e.g., the STPs from one network to the STPs of another network). The distinction between a "B" link and a "D" link is rather arbitrary. For this reason, such links may be referred to as "B/D" links.

Blocked AttemptBlocked Attempt refers to an attempt that cannot be further advanced toward its destination due to an equipment shortage or failure in the network.

BlockingBlocking in telecommunication refers to the inability of the calling party to be connected to the called party be cause either: 1. All permitted trunk paths are busy. 2. A path between a given inlet and any permitted free outlet of the switching network of a switching system is unavailable

Blocking ProbabilityBlocking probability is the statistical probability that a telephone connection cannot be established due to insufficient transmission resources in the network. Blocking probability is usually expressed as a percentage or decimal equivalent of calls blocked by network congestion during the busy hour.

BOC: Bell Operating CompanyBell Operating Company (BOC ) refers to any of the 22 original companies (or their successors) that were created when AT&T was broken up in 1983 and given the right to provide local telephone service in a given geographic area. The companies had previously existed as subsidiaries of AT&T and were called the "Bell System." The purpose of the breakup was to create competition at both the local and long-distance service levels. BOCs compete with other independent companies to sell local phone service. In certain areas, long-distance companies, including AT&T, can now compete for local service. Collectively, companies offering local phone service are referred to as local exchange carriers.

BPON: Broadband Passive Optic NetworkBroadband Passive Optic Network (BPON), originally called ATM Passive Optic Network (APON), is the initial PON specifications defined by the FSAN committee used ATM as their layer 2 signaling protocol. Use of the term APON led users to believe that only ATM services could be provided to end-users, so the FSAN decided to broaden the name to Broadband PON (BPON). BPON systems offer numerous broadband services including Ethernet access and video distribution.

BPV: Bipolar ViolationBipolar Violation (BPV) is a Error Event in the DS1/T1 interface for an AMI-coded signal is the occurrence of a pulse of the same polarity as the previous pulse. A BPV error event for a B8ZS- or HDB3-coded signal is the occurrence of a pulse of the same polarity as the previous pulse without being a part of the zero substitution code.

BRAS: Broadband Remote Access ServerBroadband Remote Access Server (BRAS) is the aggregation point for the subscriber traffic. It provides aggregation capabilities (e.g. IP, PPP, ATM) between the Regional/Access Network and the NSP or ASP. Beyond aggregation it is also the injection point for policy management and IP QoS in the Regional/Access Networks.

BRI: Basic Rate InterfaceBasic Rate Interface (BRI) is an ITU-T ISDN multipurpose user interface standard for simultaneous voice and data services provided over two 64-kb/s bearer channels and one 16-kb/s data channel (2B+D) access arrangement to each user location. The B channels are used for voice or user data, and the D channel is used for any combination of: data, control/signalling and X.25 packet networking. The two B channels can be bonded together giving a total data rate of 128 kbit/s. BRI is the kind of ISDN interface most likely to be found in residential service.

BR-ISDN: Basic Rate ISDNBasic Rate ISDN (BR-ISDN or BRI) refers to one of the two levels of services in ISDN called Basic Rate Interface which is intended for the home and small enterprise, while the other service is called Primary Rate Interface (PRI), for larger users. Both rates include a number of B-channels and a D-channel. Each B-channel carries data, voice, and other services. The D-channel carries control and signaling information. The Basic Rate Interface consists of two 64 Kbps B-channels and one 16 Kbps D-channel. Thus, a Basic Rate Interface user can have up to 128 Kbps service. The Primary Rate Interface consists of 23 B-channels and one 64 Kpbs D-channel in the United States or 30 B-channels and 1 D-channel in Europe.

Broadband Internet AccessBroadband Internet Access is a high data-transmission rate Internet connection. DSL, ADSL, Wireless WAN and cable modem, all popular consumer broadband technologies, are typically capable of transmitting 256 kilobits per second or more, starting at approximately four times the speed of a modem using a standard digital telephone line.

Broadband Open AccessBroadband open access refers to the policy in broadband Internet access, which means that the owner of a network must make it available to all users under the same terms and conditions. The network owner cannot interfere with the content that travels over the network. By contrast, in a closed network, the network owner can prevent anyone it wants to from using the network, can determine what traffic it will or won't carry, and can set priorities based on where the traffic comes from or to whom it's going (or for any other reason).The telephone network is an "open access" or "open" network. As a result of this openness the Internet grew and flourished. Any internet service provider (ISP) who wants to offer service can do so, despite the fact that the phone companies that own the lines offer competing services.The FCC itself has acknowledged the importance of an open network in the development and growth of Internet.

Broadband TelephonyBroadband Telephony refers to the utilization of broadband data connections to deliver voice calls. Typically, services are hosted that means customers enjoy traditional phone functionality without the need to purchase a phone system. Calls are transmitted as IP Packets to the host company, where they either 'break out' to the public networks, or continue as IP calls across the Internet.

BSE: Basic Service ElementBasic Service Element(BSE) refers to 1. an optional unbundled feature, generally associated with

the basic serving arrangement (BSA), that an enhanced-service provider (ESP) may require or find useful in configuring an enhanced service. 2. a fundamental communication network service; an optional network capability associated with a BSA. BSEs constitute optional capabilities to which the customer may subscribe or decline to subscribe.

BSN: Backward Sequence NumberBackward Sequence Number (BSN) is a 7 bits field in the SS7 Message Signaling Unit (MSU) that acknowledges the receipt of signal units by the remote signalling point. It contains the sequence number of the signal unit being acknowledged.

BT GroupBT Group refers to British Telecommunications pls which is the privatized UK state telecommunications operator. It is the dominant fixed line telecommunications provider in the UK.

Busy HourBusy Hour refers to a consecutive 6-minute interval with the highest levels of measurement or derived load used in traffic engineering. A busy hour may also be identified by the period of the day, the class of service of the traffic, and so on, e.g., morning busy hour, coin busy hour.

Busy SignalBusy Signal is a signal that is used in Public Switched Telephone Networks to indicate that the called party is already taking another call. In most switching systems, the busy signal will be emitted until the caller goes on-hook

Busy ToneBusy Tone is a single tone that is repeated at a 60ipm (impulse per minute) rate to indicate that a call's terminating location is already in use.

Busy Verification ToneBusy Verification Tone is a Centrex feature that allows the attendant to call and be connected to a busy Centrex station within the attendant's customer group. The busy verification tone is applied to both parties of the connection to inform them of the intrusion by the attendant. No tone is applied if the station called for busy verification is idle.

Bypass Trunk GroupBypass Trunk Group is a trunk group, in a hierarchical network, (usually high usage) that circumvents one or more tandems in its routing ladder. 

Tele-Communication (Telecom) Terms Glossary and Dictionary - C

Cabling AdministrationCabling Administration is a process in telecommunication system engineering for premise wiring

that includes all aspects of premise wiring related to documenting and managing, testing the system as well as the architectural plans for the system.

CAC: Connection (or Call) Admission ControlConnection Admission Control (CAC), also known as Call Admission Control, refers to the set of actions taken by the network during the call set-up phase (or during call re-negotiation phase) in order to determine whether a connection request can be accepted or should be rejected. In the voice over IP communications, the CACs prevent an IP network from becoming clogged with traffic to the point of being unusable. When a network's capacity is consumed, admissions control mechanisms prevent new traffic from being added to the network. When calls traverse the WAN, admissions control assumes paramount importance. Within the LAN in which bandwidth is not a problem, CAC is less critical. CAC could also be a set of actions taken by each ATM switch during connection setup to determine whether a connection's requested QoS will violate the QoS guarantees for established connections. CAC also is used when routing a connection request through an ATM network.

CALEA: Communications Assistance for Law Enforcement ActCommunications Assistance for Law Enforcement Act (CALEA) is a US law established in 1994 that defines obligations of telecommunications carriers to assist law enforcement in executing electronic surveillance (or wiretapping) pursuant to court order or other lawful authorization. The purpose of CALEA is to preserve the ability of law enforcement to conduct electronic surveillance in the face of rapid advances in telecommunications technology.

CallA call, also knowns as phone call in telecommunication, is the attemted connection to establish a voice conversation between two people.

Call Accounting SystemCall Accounting System is the software that is essential to telecom cost management typically for business or organizations. It usually provides services like phone call tracking, telephone usage monitoring, corporate bill back, telephone usage bulling to, and etc.

Call CenterCall Center is a functional area within an organization, business or an outsourced, separate facility that exists solely to answer inbound or place outbound telephone calls; usually a sophisticated voice operations center that provides a full range of high-volume, inbound or outbound call-handling services, including customer support, operator services, directory assistance, multilingual customer support, credit services, card services, inbound and outbound telemarketing, interactive voice response and web-based.

Call CollisionCall Collision is the contention that occurs when a terminal and data circuit-terminating equipment (DCE) specify the same channel at the same time to transfer a call request and handle an incoming call. When call collision occurs, the DCE proceeds with the call request and cancels the incoming call. Call collision also refers to the condition that occurs when a trunk or channel is seized at both ends simultaneously, thereby blocking a call.

Call DeflectionCall Deflection is a feature of voice over IP (VoIP) that automatically redirects a call from the called endpoint to another endpoint (usually a voice mailbox) when the called endpoint is busy. Call deflection is one of several forms of call diversion (also known as call forwarding) defined under the H.450.3 specification.

Call DurationCall Duration is 1. the time between (a) the instant a connection, i.e., off-hook condition at each end, is established between the call originator and the call receiver and (b) the instant the call originator or the call receiver terminates the call. 2. In data transmission, the duration of the information transfer phase of an information transfer transaction.

Call FiltersCall Filter is a feature in an ISDN moden that is performed by the port monitor to determine if the caller has authorization to run the type of service requested. The caller ID (telephone number of the calling system) must be listed in the Call Filter file, together with a list of service types which that caller is authorized to use.

Call ManagementCall Management refers to the following functions in telecommunication system: 1. In telegraphy, it's about route selection, signaling, and circuit usage and availability for a call. 2. In universal personal telecommunications, it is about the ability of a user to inform the network how to handle incoming calls in accord with certain parameters, such as the call originator, the time of day, and the nature of the call.

Call OriginatorCall Originator is an entity, such as a person, equipment, or program that originates a call.

Call PriorityCall Priority is the priority assigned to each origination port in circuit-switched systems. This priority defines the order in which calls are reconnected. Call priority also defines which calls can or cannot be placed during a bandwidth reservation.

Call Process SignalsCall Process Signals refer to signals for call processing. Examples of Call Process Signals are various audible tones (such as dial tone, ringing tone, audible ringing tone, audible busy tone, and congestion tones) or announcements that inform the subscriber of the call progress status.

Call Set-upCall Set-up is one of the many states of call processing. The call Set-up state establishes a communications path: (1) between the calling party and the called party, and (2) between the calling party and the network entities.

Call Setup TimeIn telecommunication world, Call Setup Time is the time required to establish a switched call between users. For data communication, Call Setup Time refers to the the overall length of time

required to establish a circuit-switched call between terminals, i.e., the time from the initiation of a call request to the beginning of the call message.

Call Waiting ToneCall Waiting Tone is a special service that allows a busy line to answer an incoming call by flashing the switch-hook. Audible ring (instead of line busy) is applied to the calling line, and the Call Waiting Tone is applied to the called line. (So that only the called party hears the tone, the connection is momentarily broken, and the other party to that connection experiences a moment of silence.) Flashing the switch-hook places the existing connection on hold and connects the customer to the waiting call. Call Waiting Tone is two bursts of 440 Hz at -13 dBm0/frequency for 0.3 seconds plus or minus ten percent every ten seconds.

Called PartyCalled Party refers to a end user (person or his device) that receives a telephone call initiated by a calling part.

Caller IDCaller ID is, also known as calling number delivery (CND), a telephone service intended for residential and small business customers. It allows the called Customer Premises Equipment (CPE) to receive a calling party's directory number and the date and time of the call during the first 4 second silent interval in the ringing cycle.

Calling CardCalling Card refers to a physical object, often in the form of a wallet-sized card made of plastic or paper, which contains contractual information as to using postpaid or prepaid long distance services from the calling card provider. Calling card based long distance phone call is a form of dial-around, which is a two-step method for selecting a long distance service provider on a call-by-call basis.

Calling Card Service Prompt ToneCalling Card Service Prompt Tone is used to inform the customer that his/her credit card information must be keyed in. The first 60 milliseconds of this composite tone is 941 Hz and 1477 Hz which is the DTMF '#'. This tone will release and DTMF to dial pulse converter in the connection. Calling Card Service Prompt Tone is 941 Hz and 1477 Hz at -10 dBm0/frequency at -3 Transmission Level Point for 60 milliseconds and then 440 Hz and 350 Hz at -7 dBm0 for 0.940 seconds exponentially decayed from -10 dBm per frequency at -3 Transmission Level Point at time constant of 0.2 seconds.

Calling PartyCalling Party is a user (person or his device) that initiates a telephone call over the public siwiched telephone network. It is also refered as Call Originator.

CAM: Carrierless Amplitude ModulationCarrierless Amplitude Modulation (CAM) refers to the original approach for modulation of a Digital Subscriber Line (DSL) signal. Currently, Discrete multitone (DMT) is the preferred modulation alternative over CAP

CAMA: Centralized Automatic Message AccountingCentralized Automatic Message Accounting (CAMA) refers to an automatic message accounting system that serves more than one switch from a central location. When using CAMA, human intervention may be required.

Camp-OnCamp-On, also referred as Called-party Camp-on, is a telecommunication system feature that enables the system to complete an access attempt in spite of issuance of a user blocking signal. The system constantly monitors the busy user until the user blocking signal ends, and then proceed to complete the requested access.

CAP: Carrierless Amplitude Phase ModulationCarrierless Amplitude Phase (CAP) modulation is a viable alternative for the Digital Subscriber Loop (DSL) systems such as the HDSL, ADSL and VDSL. The conventional two-dimensional CAP-16 line code is extended to a three-dimensional scheme. The three-dimensional system is designed so that the new overall transfer matrix maintains perfect reconstruction of the transmitted information. The system is designed by solving a minimax optimization problem by using the sequential

CAP: Competitive Access ProviderCompetitive Access Provider (CAP) is a type telecommunication service providers that provide local telecommunications services mainly to business customers in competition with a local Bell Operating Company (BOC). Teleport and MFS are the two major CAPs operating in major metropolitan areas in the United States.

CappingCapping refers to the activity of ISPs (Internet Service Provider) to limit (capping) the accessing speed of cable modem so that cable modem ISPs can easily distribute bandwidth among users. The upload cap in particular is intended to discourage users to run big servers. In general, these caps are also put in place to make the system more robust. At slower speeds, packet loss is usually lower and the system can handle worse signal quality.

CarrierCarrier refers to the following definitions: 1. in telecommunication service, it refers a company which provides physical media circuit for telecommunication service. 2. in telecommunication technology, it refers to an physical signal (optical, electrical, infrared and etc.) at a continuous frequency capable of being modulated to variation of physical format in order to carry information. 3. in networking, some physical media for transmitting signal like wideband circuits. T1 line for instance, is also called carrier which means that telecommunication signal is being carried and transmitted by them.

Carrier FrequencyCarrier Frequency refers to the nominal frequency of a carrier wave, the frequency of the unmodulated electrical wave at the output of an amplitude modulated, the center frequency of a frequency modulation signal, frequency modulated, or phase modulated transmitter of the output of a transmitter when the modulation is zero.

Carrier HotelCarrier Hotel refers to a type of data center where multiple telecommunications network or service providers, such as tacos or internet service providers, site their connections to one another's networks (points of presence).

Carrier Service ProviderCarrier service provider is a company offering telecommunication (voice or data) service between points in a state or in one or more countries. Examples of Carrier service provider are AT&T, British Telecom etc.

Carrier SystemCarrier system refers to, in the telecommunication system, a system utilizing a method of providing several communications channels over a single path by modulating the data, voice or video transmissions onto a higher frequency carrier wave for transmission between nodes of a network. Loosely, in the transmission context of telecommunication system, it is sometimes a synonym with carrier.

Carrier WaveCarrier wave is the wave form that transports the signal wave, and is a sinusoidal component of a complex wave form of much higher frequency than the modulating signal which contains the information.

Carson Bandwidth RuleCarson bandwidth rule refers to a rule that defines the approximate bandwidth requirements of communications system components for a carrier signal. The signal is frequency modulated by a continuous or broad spectrum of frequencies rather than a single frequency.

CAS: Channel Associated SignalingChannel Associated Signaling (CAS), one of two types of telecom signaling technologies, is the transmission of signaling information within the information band, or in-band signaling. This means that voice signals travel on the same circuits as line status, address, and alerting signals. As there are twenty-four DS0 channels on a full T1 line, CAS interleaves signaling packets within voice packets. Various types of CAS signaling are available in the T1 world. The most common forms of CAS signaling are loopstart, groundstart, and E&M signaling. The biggest disadvantage of CAS signaling is that the network uses bits from information IP packets, such as voice packets, to perform signaling functions. CAS signaling is often referred to as robbed-bit signaling. The other type of signaling is the common channel signaling (CCS), which is an out of band signaling technology. SS7/C7 and ISDN are based on the CCS.

Casual CallingCasual Calling is a feature that allows a customer to place a long distance call using an ANI (Automatic Number Identification) (including undefined ANIs) to access a given carrier, other than the default long distance provider. Customers can place casual calls by dialing a special access code (a "CIC" code) before the area code and telephone number. For example, if the originator is calling from a non-coin phone, they may dial 1010555+destination number and have the call routed through WorldCom and billed to the originating phone number.

Casual CustomerCasual Customer refers to any person or organization (not necessary to pre-subscribe to the carrier.) that dials any CIC (Carrier Identification Code) code to place a long distance call.

Cause CodesCause Codes indicate the reason for ISDN-call failure or completion. Typically, cause codes are ranged from 0 to 127. Cause code values of 128 and higher aren't sent over the network.

CC: Clear ChannelClear Channel (CC) refers to the following definitions in the telecommunications system: 1. Channel in which the full bandwidth (e.g., 64 kbps) is used for transmission; no portion of the channel is set aside for control, framing or signaling. 2. a channel through which non-encrypted traffic can flow. Clear channels place no security restrictions on transmitted data. 3.a line that connects two points which is wholly dedicated to traffic between those two points. This is in contrast with a shared line, such as a frame relay, in which a user must share the frame network with other subscribers.

CC: Country CodeCountry Code (CC), part of a telephony numbering plan, indicates the country for which the telephone number is serviced. For example, the country code of the US is 001 and for P. R. China, is it 086.

CCBS: Completion of Call to Busy SubscriberCompletion of Call to Busy Subscriber (CCBS) is a feature in telephony system. It works like this when a called party is busy, this supplementary service enables the calling party to be connected to a called party after they have completed their call.

CCH: Connections per Circuit HourConnections per Circuit Hour (CCH) refers to the following meanings: 1. A unit of traffic measurement expressed as the number of connections established per hour at a switching point. 2. A unit of traffic measurement represents the rate at which circuits are established at a switch.

CCITT: Consultative Committee for International Telegraph and TelephoneConsultative Committee for International Telegraph and Telephone (CCITT) was an international organization responsible for the development of communications standards. CCITT now became the International Telecommunications Union Telecommunication Standardization Sector (ITU-T).

CCITT: International Telegraph and Telephone Consultative CommitteeCCITT is the abreviation of the International Telegraph and Telephone Consultative Committee in France. CCITT is standards body based in Geneva that publishes "recommendations" on standards used throughout the world communication industry.

CCS: Centi Call SecondsCenti-Call Seconds is a unit used (in North America) to quantify the aggregate of traffic running in a network, which is one hundred call seconds or one hundred seconds of telephone

conversation. That means 1 CCS could be 2 calls of 50 seconds duration or 20 calls of 5 seconds duration.

CCS: Common Channel SignalingCommon Channel Signaling (CCS) is a signaling method used in telephone networks that separates signaling information from user data. In CCS, one channel of a communications link is exclusively used for the sole purpose of carrying signaling for establishment and teardown of calls. The remaining channels are used entirely for the transmission of voice or data. In most cases, a single 64kbit/s channel is sufficient to handle the call setup and teardown traffic for numerous voice and data channels. The most common CCS signalling methods in use today are ISDN and SS7.

CCSS7: Common Channel Signaling System 7Common Channel Signaling System 7, abreviated CCSS7 or CCS7, CCIS7, or C7, is the signaling method used in countries other than the North America where the signaling system is called Signaling System #7 (SS7). Both CCSS7 and SS7 are based on the same common channel signaling technology and are interoperable across the network.

CCT: Continuity Check TransceiverContinuity Check Transceiver (CCT) is a device in the switch system that verifies outgoing trunk continuity for a common-channel signaling call and reports the results as well.

CDB: Call Detail BlockCall Detail Block (CDB) consists of several Call Data Elements. The CDB is generated at a Certain Point in Call (PIC). For example, a CDB is generated when the call is answered, released, and so on.

CDE: Call Detail ElementCall Detail Element (CDE) is a data element that includes a basic information field within a billing record of telephone calls. Examples of a CDE are the calling number, the called number, and so on.

CDR: Call Detail RecordCall Detail Record (CDR), a term used in both PSTN and VOIP systems, is the telephone call record written to a database for use in post-processing activities. A typical CDR includes the origination and destination addresses of the call, the time the call started and ended, the duration of the call, the time of day the call was made and any toll charges that were added through the network or charges for operator services, among other details of the call. CDRs are primiarily used for billing and network analysis.

CDR: Call Detail ReportingCall Detail Reporting (CDR) is a feature in both PSTN and VOIP systems that provides a database of information about each call, including date, time, duration, called number, calling number, call direction, service type, and associated inverse multiplexing session and port. Because the network carrier bills for bandwidth on an as-used basis, and bills each connection in

an inverse multiplexed call independently, CDR is used to understand and manage bandwidth usage and the cost of each inverse multiplexed session.

CED: Caller-Entered DigitsCaller-entered Digits (CED) are the digits entered by a caller on a touch-tone phone in response to prompts. Either a peripheral (ACD, PBX, or VRU) or the carrier network can prompt for CEDs.

CELP: Code Excited Linear PredictionCode Excited Linear Prediction (CELP), also known as Code-Book Excited Linear Predictive, is a loss compression algorithm used for low bit rate (e.g.,4800 bps in U.S. Fed-Std-1016) speech coding. CELP coding, at 4800 bps, breaks the performance barrier of most Government standards, providing Consortium ratings of "very good" intelligibility and "excellent" quality, comparable to 32,000 bps (CVSD). CELP is used in ITU-T Recommendations G.728, G.729, G.723.1.

Center FrequencyCenter Frequency refers to the middle frequency of the bandwidth of a channel.

Central MemberCentral Member is the center component of a fiber cable. It serves as an anti-buckling element to resist temperature-induced stresses. Sometimes serving as a strength element, the central member is composed of steel, fiberglass, or glass-reinforced plastic.

Centralized Intercept Bureau Order ToneCentralized Intercept Bureau Order Tone is a 0.5 second burst of 1850 Hz at -17 dBm0/frequency that tells the centralized intercept bureau operator that a call has reached the position.

CentrexCentrex is central office exchange service, a type of PBX service in which switching occurs at a local telephone station instead of at the company premises. Typically, the telephone company owns and manages all the communications equipment necessary to implement the PBX and then sells various services to the company. With Centrex, there is no onsite switching at the customer premise and all customer connections go back to the Centrial Office of the service provider.

CEPT: Conference of European Posts and TelecommunicationsConference of European Posts and Telecommunications (CEPT), also known as Committee of European Posts & Telephones, is a collaborative organization for telecommunications regulators in 43 European countries. The organization deals with questions regarding harmonization and radio/telecommunications. For example, CEPT defines the 2.048Mbps European E1 signal made up of 32 voice-frequency DS0 channels.

CF: Call ForwardingCall Forwarding (CF) is a phone service feature that allows the customer to forward their phone

to another phone number (for example, you can forward your home phone number to your cell number if you know you are going to be away from home).

CFB: Call Forwarding BusyCall Forwarding Busy (CFB) is a service that enables your incoming calls that encounter a busy condition or are not answered, after a customer-designated interval, to be automatically forwarded to another local or long distance phone number where network facilities permit.

CFNR: Call Forward No ReplyCall Forward No Reply (CFNR) is a service feature that forwards all calls to another extension number or an outside number automatically if it is not answered after 6 rings:

CFU: Call Forward UnconditionalCall Forward Unconditional (CFU) is a service feature that always forwards all calls (or only outside calls) to another extension number (or an outside number).

Change-BackChange-back is the inverse function of change-over. It is the procedure for transferring signaling information (traffic) from one or more alternate signaling links to a signaling link that has become available.

Change-OverChange-over is the procedure for transferring signaling information from a signaling link (which is experiencing failure or is required to be cleared of traffic) to one or more alternate (different) signaling links.

ChannelChannel refers to a one-way telecommunications link or transmission medium through which information or signal is transmitted from a sender (or transmitter) to a receiver. They may be either physical or logical depending on the application. A Radio Frequency (RF) channel is a physical channel, whereas control and traffic channels within the RF channel would be considered logical channels.

Channel Associated SignalingChannel Associated Signaling is a form of digital communication signaling. As with most telecommunication signaling methods, it uses routing information to direct the payload of voice or data to its destination. With CAS signaling, this routing information is encoded and transmitted along the same link as the payload itself. This results in lower available bandwidth for the payload, normally reducing a 64 Kbit/s DS0 to 54 kbit/s.

Channel Noise LevelChannel Noise Level refers to the following definitions depending the context: 1. the ratio of the channel noise at any point in a transmission system to an arbitrary level chosen as a reference. 2. the noise power density spectrum in the frequency range of interest. 3. the average noise power in the frequency range of interest

ChannelizedChannelized, in a telecommunications environment, means that the line that communications have been transmitted over contains more than one message thread, separated in some fashion. Typical channelization methods include packetizing, frequency differentiation, time division multiplexing (TDM). For example, Channelized T1 sub-divides the 1.44 Mbps bandwidth into 24 channels of 64 Kbps each.

Channelized E1Channelized E1 refers to that an E1 access link of at 2.048 Mbps is subdivided into 30 B-channels and 1 D-channel of 64 Kbps each. Channelized T1 and channelized E1 can be configured for ISDN PRI, synchronous serial, and asynchronous serial communications.

Channelized T1Channelized T1, also known as fractional T1, refers to that an access link operating at 1.544 Mbps is subdivided into 24 channels (23 B-channels and 1D-channel) of 64 Kbps each. The individual channels or groups of channels connect to different destinations. Channelized T1 and channelized E1 can be configured for ISDN PRI, synchronous serial, and asynchronous serial communications.

Check BitCheck Bit refers to the following definitions: 1. A bit, such as a parity bit, derived from and appended to a bit string for later use in error detection and possibly error correction. 2. A data bit associated with a character or block for the purpose of checking the absence of error within the character or block.

Check DigitCheck Digit is a form of redundancy check used for error detection in telecommunication system. It's the decimal equivalent of a binary checksum. It consists of a single digit computed from the other digits in the message.

ChurnChurn refers to the situation that many subscriber additions and then un-subscription. If the churn ratio is high for a service provider, it is not good, because that the cost is typically high to get a customer to sign in a service and the service provider has a problem to keep customers.

CIC: Carrier Identification CodeCarrier Identification Code (CIC) refers to the following definitions: 1. a numeric code assigned by the North American Numbering Plan (NANP) Administrator for the provisioning of selected switched services. The numeric code is unique to each entity and is used by the telephone company to route the call to the trunk group designated by the entity to which the code was assigned. 2. a 4-digit code that controls the routing applied to a call by the originating switch.

CIC: Circuit Identification CodeCircuit Identification Code (CIC) is information identifying a circuit between a pair of exchanges, for which signaling is being performed (14 bits in the ISDN user part)

CIR: Committed Information RateCommitted Information Rate (CIR), one of parameters in a Service Level Agreement (SLA), is the data transfer rate for an individual virtual circuit (VC) in an ATM or Frame Relay network, for which the provider commits to deliver. The provider may send any data in excess of this rate for this VC if its network has capacity at the time. This choice typically affects the price of each VC.

CircuitA circuit is a communications path between two or more points among a network. A physical circuit is actually a wire or a part of a wire which connects two computer or network devices for permanently dedicated communications. A virtual circuit may be a temporarily established logic connection between two network devices for communications within certain time limit.

Circuit Noise LevelCircuit Noise Level is the ratio of the circuit noise at any point in a transmission media of telecommunications system to a nominal reference point; this ratio is either expressed in decibels (above the reference noise, dbrn) or in adjusted decibels (dba, which reflects a specified adjustment due to external interference).

Circuit SwitchingCircuit Switching is a technology in which a dedicated physical circuit path must exist between sender and receiver for the duration of the "call." Used heavily in the telephone company network, circuit switching can be contrasted with contention and token passing as a channel-access method, and with message switching and packet switching as a switching technique.

Circuit Transfer ModeCircuit Transfer Mode is an telecommunications term that refers to an ISDN transfer mode through permanent bandwidth allocation.

Circuit-level Inverse MultiplexingCircuit-level Inverse Multiplexing is a method of inverse multiplexing in which the inverse multiplexer slices the data stream into equal portions, and transmits each portion over an available circuit. The receiving end adjusts for network-induced delay and reassembles the data packets into their proper order. The AIM and BONDING protocols define how circuit-level inverse multiplexing works. Applications that require transparent digital circuits, such as videoconferencing, nailed-up backup and overflow, and bulk file transfer applications, use circuit-level multiplexing.

CirculatorA circulator is a passive device with three or more ports in which the ports can be accessed in such an order that when a signal is fed into any port it is transferred to the next port, the first port being counted as following the last in order. There are circulators both for electronic signals and for light, the latter being used in optical fiber networks.

City Wide Digital CentrexCity Wide Digital Centrex is a capability to serve multiple business locations within a single

NXX (exchange code as in xxx-xxx-xxxx telephone number), using multiple LEC central office Centrex switches. Outside callers are unaware that multiple business locations are involved.

CladdingCladding is the material, usually glass, that surrounds the core of the optical fiber. Light bounces off the interface between the cladding and fiber and returns to the fiber.

Class 4 SwitchClass 4 Switch, also called tandem switch, is used for long distance communications in the PSTN. A class switch 4 is an intermediate switch or connection between an originating telephone call or location and the final destination of the call.

Class 5 SwitchClass 5 Switches provide telecommunication services using TDM (Time Division Multiplex) technology from basic dial-tone to advanced voice services and data network access to subscribers within a defined locality or local loop. Class 5 switches are deployed at a central office (CO) by service providers for both local and long distance telephony services, vs. the Class 4 switches are only for long distance and trunking services.

Class of Service ToneClass of Service Tone is the Class of Service signal that is used at a toll board operating as an 'A" board to identify the class or service of the calling customer. The indication may be high, low, or no tone. Class of Service is a single burst of either High Tone or Low Tone for 0.05 to 1 seconds.

CLASS: Custom Local Area Signaling ServiceCustom Local Area Signaling Service (CLASS) is one of an identified group of network-provided enhanced services. A CLASS group for a given network usually includes several enhanced service offerings, such as incoming-call identification, call trace, call blocking, automatic return of the most recent incoming call, call redial, and selective forwarding and programming to permit distinctive ringing for incoming calls.

Clean PowerClean Power refers to electrical power which has been conditioned and/or regulated to remove electrical noise from the output power.

Clear-Back MessageClear-back Message is a signal (message) sent in the backward direction to indicate that the called party is no longer "off-hook".

Clear-Forward MessageClear-forward Message is a signal sent in the forward direction to terminate a call (or a call attempt) so that the associated circuits can be released. This signal is normally originated when the calling party hangs-up the phone.

CLEC: Competitive Local Exchange CarrierCompetitive Local Exchange Carrier (CLEC) is a company which provides local telephone

service - other than the incumbent Local Exchange Carrier (LEC). Much like a LEC, a CLEC provides telephone service within a LATA. To handle InterLATA long distance calls, the CLEC will connect to an IXC. Most CLEC's will use the local loop (UNE-L) belonging to the incumbent Local Exchange Carrier. The telecommunication act of 1996 forced the incumbent LEC's to lease access to their local loop (UNE-L) to CLEC's at wholesale prices. Between 1996 and 2004, the FCC also required LEX's to lease other network elements (UNE-P) to the CLEX's.

CLID: Calling Line IdentificationCalling Line Identification (CLID), also known as Caller ID, refers to the following definitions in the telecommunications system: 1. A service available on digital phone networks that tells the person being called which number is calling them. The central office equipment identifies the phone number of the caller, enabling information about the caller to be sent along with the call itself. Synonymous with ANI (Automatic Number Identification). 2. A facility provided by a switched network which can notify a called terminal of the telephone number of the line from which a call originated.

C-link: Cross LinkSS7 Cross Link (C-link) connects STPs performing identical functions into a mated pair. A C-link is used only when an STP has no other route available to a destination signaling point due to link failure(s). Note that SCPs may also be deployed in pairs to improve reliability; unlike STPs, however, mated SCPs are not interconnected by signaling links.

ClippingClipping is a distortion of voice signals in which the beginnings of final sounds are cut off.

CLLI Code: Common Language Location Identification CodeCommon Language Location Identification (CLLI) Code is an eleven character alphanumeric descriptor used to identify switches, points of interconnection, and other categories of telephone network elements and their locations. All CLLI Codes are stored in a national database maintained by Telcordia.

CM: Communications ModuleCommunications Module (CM) is a component of 5ESS switch by Lucent/AT&T which is the interface between the Administrative Module (AM) and Switching Modules (SMs). The main function of a CM is to provide a message interface between the AM and the SMs to control digital space switching. It has four main functional elements: 1. Message Switch (MS). 2. Communications Module Control Unit (CMCU). 3. Time Multiplex Switch (TMS). 4. Network, Control and Timing (NCT) links.

CMCU: Communications Module Control UnitCommunications Module Control Unit (CMCU) refers to one of the functional elements of the Communications Module of 5ESS switch (see "CM"). It contains the network clock, and the metallic interface to the Time Multiplex Switch (TMS) and the Network, Control and Timing (NCT) links. The CMCU controls the operation of the message switch by interfacing the MMPs and the TMS.

C-MessageC-message, also called C-curve or C-message wight, refers to the shape of the curve that represents the sensitivities to different tones to humans ear.

CMI: Coded Mark InversionCoded Mark Inversion (CMI) refers to an encoding algorithm specified for STS-3c transmissions and DS-1 systems which doubles the data rate. A zero [0] is sent as a low to high [1] transition, while a one is sent as wither a one [1] or zero [0] depending on the previous state. If the previous state was high the one is sent as zero [0], it sent as one [1] otherwise.

CMS: Call Management SystemCall Management System (CMS) is a reporting package used on ACDs and PBXs made by Avaya. Avaya CMS is an optional database, administration and reporting application designed for enterprises that receive a large volume of telephone calls and have complex contact center operations. Avaya CMS provides an administrative interface to the automatic call distribution (ACD) feature of the DEFINITY Server, enabling your contact center managers to generate reports, administer ACD parameters and monitor call activities to help determine the most efficient service possible for your customers.

CNM: Customer Network ManagementCustomer Network Management (CNM) refers to a feature of ATM network which allows customers of ATM public networks to monitor and manage their portion of the carrier's circuits by providing the function and ability in the user interface to monitor physical ports, virtual paths, usage parameters, and quality of service parameters.

CO: Central OfficeCentral Office (CO) is the local switching facility of a telephone company to which telephones are connected. Central Office is a common carrier switching center in which trunks and loops are terminated and switched. Synonyms exchange, local central office, local exchange, local office, switching center, telephone exchange.

Coin Collect ToneCoin Collect Tone is an audible tone of telephone system over a coin recording-completing trunk informs the originating toll operator that the local operator or coin control circuit has collected the charge. Coin Collect Tone is a steady Low Tone.

Coin Denomination ToneCoin Denomination tones is audible tone of telephone system which enables the operator to determine the amount deposited in coin telephones. Coin Denomination Tones for the old 3 slot payphones were: Nickel - One tap of 1050 Hz and 1100 Hz (bell) Dime - Two taps of 1050 Hz and 1100 Hz (bell) Quarter - One tap at 800 Hz (gong).

Coin PhoneCoin Phone is the public phone accepting coins from caller as payment.

Coin Return ToneCoin Return Tone is audible tone of telephone system over a coin recording-completing trunk informs the originating toll operator that the local operator or coin control circuit has returned the change when the connection is not completed (also called coin-refund tone). Coin Return Tone is a single 5 to 1 second burst of High Tone.

Common CarrierCommon Carrier is a licensed, private utility company that supplies local or long distance communication services to the public at regulated prices. The term differs from private carrier, which operates solely for the benefit of one entity and does not offer services to the general public.

Communication SecurityCommunication Security refers to measures and controls used in telecommunication systems for security purposes. It may include crypto security, transmission security, emission security, traffic-flow security and physical security of equipments.

Communication SourceCommunication Source refers to sources that encode message data and transmit the information via a telecommunication channel to one or more receivers.

Communication SubsystemCommunications Subsystem, a general term in telecommunications systems, describes a functional entity or operational assembly that is smaller than the larger assembly under consideration.

Communication SystemCommunications System refers to a set of all the individual telecommunications networks components including switches, transmission systems, relay stations, etc. to perform a telecommunications task.

Communications DeceptionCommunications Deception refers to a scheme in telecommunications system that can deliberately transmit, retransmit or alternate information of communications to mislead an adversary's interpretation of the communications.

Communications LineCommunications Line refers to the physical link (such as wire or a telephone circuit) that connects one or more devices to one or more other devices.

Communications ProtectionCommunications Protection refers to the application of communications security measures to telecommunications systems in order to: 1. deny unauthorized users access to sensitive unclassified information of value; 2. prevent disruptions of telecommunications services; 3. ensure the authenticity of information handled by telecommunications system.

CompandingCompanding, also known as compansion, comes from the combination of compressing and expanding, which is a method of reducing the effects of a channel with limited dynamic range. The use of companding allows signals with a large dynamic range to be transmitted over facilities that have a smaller dynamic range capability. Companding reduces the noise and crosstalk levels at the receiver.

CompandorCompandor is the combination of a compressor and expandor used in telecommunication channels to improve transmission performance. It reduces the dynamic range of the transmitted signal at the transmitter (compressor) and recover this signal to the original dynamic range at the receiver (expander).

Completed SignalingCompleted Signaling is one of several signaling methods. In Completed Signaling, after one signal message (or element) has been sent, a second signal message cannot be sent in the same direction until the first signal message has been acknowledged (by a response in the opposite direction).

CompressorCompressor conducts the process or function of amplifying small signals while extremely large signals are compressed (at the transmitter).

ConcentratorConcentrator, a type of multiplexor, combines multiple channels onto a single transmission channel. A concentrator usually provides communication capability between many low-speed, usually asynchronous channels and one or more high-speed, usually synchronous channels. Usually different speeds, codes, and protocols can be accommodated on the low-speed side.

Conducted InterferenceConducted Interference refers to interference resulting from noise or unwanted signals entering a device by conductive coupling in the circuit.

Conference OperationConference Operation refers to an operation in the telecommunications system that a telephone call can be established in such a way that three or more stations can communicate directly with all the other stations. A three way call is one of the example.

Confirmation ToneConfirmation Tone is one of the audible tones generated in the telephone system that is used to acknowledge receipt by automatic equipment of information necessary for special services. It is currently used for: • Speed Calling - dialed number has been recorded. • Call Forwarding - dialed number has been recorded and service is activated. • Call Forwarding - service is deactivated.

Confirmation Tone is 350 Hz and 440 Hz at -13 dBm0/frequency on for 0.1 second, off for 0.1 second and then on for 0.3 seconds.

Contract TariffsContract Tariffs refers to services and rates based on contracts negotiated with individual customers, but theoretically available to all customers. Former AT&T has filed several hundred contract tariffs.

Control PlaneControl refers to one of the three entities in the ATM reference model. The control plane addresses all signaling and control related issues such as session setup and tear-down, and for network parameter changes during a session. The other two entities are user plane for the actual data transmission and the management plane for network management issues. The concept and model of user plane, control plane and management plane has been extended to other telecommunication technology groups beyond the ATM technology.

Control SignalControl Signal refers to a signal in telecommunication used for auxiliary functions with equipment connections to the Point of Termination (POT) or to the demarcation point. Examples are the toll connection restriction and the party identification functions.

Controlled Re-RoutingControlled Re-routing is a scheme in signaling. Using a controlled methodology, the signaling information (traffic) is transferred from an alternate signaling route to the normal signaling route, when it becomes available.

CONUS: CONtiguous United StatesCONtiguous United States (CONUS) refers to the 48 contiguous U.S. states. It is used primarily to designate the operating range or authorization of a satellite or radio facility.

Convolutional CodeConvolutional code is a type of forward error correction code using a shift register containing a number of stages to shift the input bits one at a time to produce a coded output. With the convolutional code, (a) each m-bit information symbol (each m-bit string) to be encoded is transformed into an n-bit symbol, where m/n is the code rate (n >= m) and (b) the transformation is a function of the last k information symbols, where k is the constraint length of the code.

COT: Central Office TerminalCentral Office Terminal (COT) refers to one of the UDLCs (Universal Digital Loop Carrier) terminals (the other one is called remote terminal). Both remote terminal and central office terminal interface with analog signals, convert it to digital signals, and transport them to the other side where the reverse is performed.

Country CodeCountry Code refers to the two or three digit codes used for International calls outside of the

North American Numbering Plan area codes. Dial: 011 + country code + city code + local phone number) (e.g. in "011 + 86 + 10 + 1234- 5678", 86 = China, 10 = Beijing).

CPC: Calling Party CategoryCalling Party Category(CPC), defined in the SS7 ISUP by ITU-T, characterizes the station used to originate a call and carries other important state that can describe the originating party. Based on the CPC parameter from the calling network, the called network can do some special processes related to the calling party category, just like overriding the Do Not Disturb (DND) list and some other barring services.

CPE: Customer Premises EquipmentCustomer Premises Equipment (CPE) is a type of terminating equipment, such as terminals, telephones, and modems, supplied by the telephone company, installed at customer sites, and connected to the telephone company network. CPEs may also refer to any telephone equipment residing on the customer site regardless who supplied them.

CPG: Call ProGressCall ProGress (CPG) refers to the status of the telephone line. It can be busy, ringing, not ringing, etc

CPNIE: Called Party Number Information ElementCalled Party Number Information Element (CPNIE) is a type of Information Elements in the ISDN messages defined in ITU-T Q.931.

CPSIE: Called Party Subaddress Information ElementCalled Party Subaddress Information Element is a type of Information Element in the ISDN messages defined in ITU-T Q.931.

CrammingCramming refers to the unauthorized addition of services or features to your telephone service by service providers. These services may be such things as voice mail, caller ID, special service packages or fee-for-service charges such as 900 calls.

Cross ConnectCross Connect is a method of connecting the various elements in a cabling system.

Cross-ConnectionCross-Connection refers to a connection scheme between terminal blocks on the two sides of a distribution frame, or between terminals on a terminal block.

Cross-Office CheckCross-office Check refers to the activity in call processing procedure which is a check on the circuits between two or more exchanges to verify an acceptable transmission path exists.

CRP: Customer Routing PointCustomer Routing Point (CRP) is an AT&T's terminology for third-party processors that accept routing requests from the CCSS7 network.

CRV: Call Reference ValueCall Reference Value (CRV) is the number carried in all Q.931 (I.451) messages that provides an identifier for each ISDN call. Call Reference Value is a scheme to distinguish call-legs signaled between two entities.

CS: Controlled SlipControlled Slip (CS) is an Error Event in DS1/T1 interface, which is the replication or deletion of the payload bits of a DS1 frame. A Controlled Slip may be performed when there is a difference between the timing of a synchronous receiving terminal and the received signal. A Controlled Slip does not cause an Out of Frame defect.

CSA: Carrier Serving AreaCarrier Serving Area (CSA) is a geographic customer area that is consolidated into a single digital transmission by the telephone company. Each carrier serving area (CSA) is served by a digital loop carrier (DLC), which multiplexes hundreds of analog lines into one high-speed digital trunk. The physical size of a CSA is based on the number of lines the DLC supports and the population density

CS-ACELP: Conjugate Structure Algebraic Code Excited Linear PredictionConjugate Structure Algebraic Code Excited Linear Prediction (CS-ACELP) is the CELP voice compression algorithm providing 8 kbps, or 8:1 compression, standardized in ITU-T Recommendation G.729.

CSL: Component Sub-LayerComponent Sub-layer (CSL) is the upper layer of TCAP (Transaction Capabilities Application Part). The CSL defines the actual messages, or components, that are contained in the TSL (Transaction Sub-layer Messages).

CSU/DSU: Channel Service Unit/Data Service UnitChannel Service Unit (CSU)/Data Service Unit (DSU), two units often combined into one, is a digital interface device that connects end-user equipment to the local digital telephone loop. The Channel Service Unit (CSU) is a device that connects a terminal to a digital line. The DSU component is a device used in digital transmission that adapts the physical interface on a data terminal equipment (DTE) device to a transmission facility, such as T1 or E1.

CSU: Channel Service UnitChannel Service Unit (CSU) is a device that connects a terminal to a digital line. This is a digital interface device installed on end-user premises that directly connects end-user equipment (terminal) to the local digital telephone loop. Typically, Channel Service Unit (CSU) and the data service unit (DSU) devices are packaged as a single unit called CSU/DSU.

CT: Call TransferCall Transfer (CT) is a service feature of telecommunications which allows customers to transfer a call to any other number.

CTI: Computer Telephony IntegrationComputer Telephony Integration (CTI) is the technology that links the computer, telephone and other services such as voice messaging and fax. CTI improves the handling of the customer relationship. For example, customer details can be on screen while an agent answers the call.

CTS: Clear-to-SentClear To Send (CTS) is a signalling message transmitted from the data communications equipment (DCE) indicating to the data terminal equipment (DTE) that it may begin data transmission. For example, a networking equipment such as IEEE 802.11 wireless station may send a CTS in response to an RTS (Request to Send) message. The CTS message silences all wireless stations in its vicinity to avoid collision and enables the sender of the RTS message to begin data transfer.

Customer-Originated TraceCustomer-Originated Trace is one of group features made possible by Local Area Signaling Service. It lets the terminating party request an automatic trace of the last call received. The trace includes the calling line directory number and time and data of the call. This information is transmitted to a designated agency, such as the telephone company or law enforcement agency.

CutoverCutover is the physical switch of telephone lines from one telephone system to another, or a replacement of old telephone equipment like switches by a totally new switches, or the installation of a new system. It's usually performed over the weekend and midnight.

Cut-Through DialingCut-Through Dialing refers to a call that the number dialed is "10"+CIC+" #" followed by an Authorization Code for IntraLATA calls.

CW: Call WaitingCall Waiting (CW) is a feature that allows a user to be notified of another incoming call while a call is already in progress, and gives the user the ability to answer the second call while make the first call remains on hold.

Tele-Communication (Telecom) Terms Glossary and Dictionary - D

D ChannelD Channel, an ISDN term, refers to the channel that carries control and signaling information. (The "D" stands for "delta" channel.) The B-channel ("B" for "bearer") carries the main data. The D-channel carries control and signaling information.

D Type Channel BankD type Channel Bank refers to the terms used in T1 technology. Channel Bank defines the type of formatting that is required for transmission on T1 trunk. The purpose of a Channel Bank in the telephone company is to form the foundation of multiplexing and demultiplexing the 24 voice channels (DS0). D type Channel Bank is one of the type of Channel Bank which is used for digital signals. There are five kinds of Channel Banks that are used in the System: D1, D2, D3, D4, and DCT (Digital Carrier Trunk)

DA: Directory AssistanceDirectory Assistance (DA) is a telephone service in which a customer will be connected to an operator at a DA bureau by dialing the proper service code or number and shall be told the directory number of the customer whom he/she desired to call, provided that the customer's number is, or will be, published (listed) in the telephone directory.

DACS: Digital Access and Cross-Connect SystemDigital access and cross-connect system (DACS, DCS or DCCS) is a digital switching device in telecommunications for routing T1 lines. The DACS can cross-connect any T1 line in the system with any other T1 line also in the system. DACS is a simple form of channel switch which works at the DS0, DS1(T1/E1) and DS3(T3/E3), as well as STS-level.

DAL: Dedicated Access LineDedicated Access Line (DAL) refers to a direct connection between customer location and telecommunication service facility to eliminate all local switching aspects of interexchange calling to/from this specific customer location

Dark FiberDark fiber refers to unused fiber-optic cables that have been laid out in the field. Oftentimes companies lay more lines than what's needed in order to curb costs of having to do it again and again. The dark strands can be leased to others who want to establish optical connections among their own locations.

Data Set Answer Back ToneData Set Answer Back Tone is one of telephone system audible tones that it will be heard when manually initiating a data call. It normally occurs shortly after the start of audible ringing and means that the remote data set has answered. The data set at the calling end should then be put into the data mode. Data Set Answer Back Tone is 2025 Hz steady at -13 dBm/frequency.

Data Strobe EncodingData Strobe Encoding is a coding scheme for transmitting data in digital circuits which uses two signal lines, Data and Strobe. These have the property that either Data or Strobe changes its logical value in one clock cycle, but never both. This allows for easy clock recovery with a good jitter tolerance by XORing the two signal line values.

DatakitDatakit is proprietary packet switching system similar to X.25 widely deployed by the RBOCs.

Datakit supports host-to-host connections and EIA-232 connections for terminals, printers, and hosts.

DatacastingDatacasting is broadcast of digital information over networks to receivers and players. Datacasting is sometimes used as an alternative to traditional video broadcasting, because the receivers and player units can have the "intelligence" to customize their playback programming for the location and intended audience. The system of receivers set up to receive messages from a particular datacasting is known as Datacasting Networks, which are a venue for advertisers.

DATU: Direct Access Test UnitDirect Access Test Unit (DATU) is a loop conditioning system which is installed in the Metallic Facility Terminal (MFT) frame and connected through a No-Test trunk to a switching facility. DATU is then accessed by dialing a telephone number and following the voice prompts.

DCB: Digital Channel BankDigital Channel Bank (DCS) is a device at a telephone company central office (public exchange) that converts analog signals from home and business users into digital signals to be carried over higher-speed lines between the central office and other exchanges. The analog signal is converted into a digital signal that transmits at a rate of 64 thousand bits per second (Kbps). This 64 Kbps signal is a standard known as a DS0 signal. The signal is multiplexed with other DS0 signals on the same line using time-division multiplexing (TDM) . Usually, the digital information is put on each DS0 signal using pulse code modulation (PCM). The channel bank is the foundation for all digital telecommunication transmissions. It is the part of a carrier-multiplex terminal that multiplexes a group of channels into a higher bit-rate digital channel and demultiplexes these aggregates back into individual channels. A channel bank changes analog voice and data signals into a digital format. It is called a "bank" because it can contain enough processing power to convert a bank of up to 24/32 individual channels to a digital format, and then back to analog again.

DCE: Data Circuit-Terminating EquipmentData Circuit-terminating Equipment (DCE) is a device that establishes, maintains and terminates a session on a network. It may also convert signals for transmission. DCE is typically the modem, contrast with DTE which is a terminal or computer.

DCF: Dispersion Compensating FiberDispersion Compensating Fiber (DCF) is a type optical fiber installed in a network which is a good way to compensate for dispersion. What is not widely known, however, is that to achieve adequate results with DCF, highly precise dispersion test must be carried out several times, at various levels.

DCS: Digital Cross Connect SystemDigital Cross Connect System (DCS) is a digital system in which: (a) access is performed by T-1 hardware architecture in private and public networks with centralized switching, and (b) cross-connection is performed by D3/D4 framing for switching digital-signal-0 (DS-0) channels to

other DS-0 channels. Modern digital access and cross-connect systems are not limited to the T-carrier system, and may accommodate high data rates such as those of SONET.

DDD: Direct Distance DialingDirect Distance Dialing (DDD) is a telecommunications service feature in North American Numbering Plan, in which a call originator may call any other user outside the local calling area without any operator assistance. It requires more digits in the dialing than are required for calling within the local area. DDD also extends beyond the boundaries of national public telephone networks.

DDI: Direct Dialing InDirect Dialing In (DDI), also known as Direct Inward Dialing (DID), is the ability or service feature for a caller outside a company to call an internal extension without having to pass through an operator or attendant. In large PBX systems, the dialed digits are passed down the line from the CO (central office). The PBX then completes the call. Direct Inward Dialing is often proposed as Centrex's major feature. But automated attendants (a specialized form of interactive voice response systems) also provide a similar service.

DecodeDecode is the process of interpreting previously coded information back into the usable form in which it existed before the coding process.

DecoderDecoder, in telecommunication, refers to a device in some telephone switching for translating dial digits into control signals.

Dedicated LineDedicated Line is a communications cable in telecommunications that is dedicated to a specific application, in contrast with a shared resource such as the telephone network. Practically, Dedicated Line may not be implemented by using a single, discrete, end-to-end cable, but they do provide guarantees of constant bandwidth availability and near-constant latency, properties that cannot be guarantied for more public systems. Such properties add a considerable premium to the price charged.

Degree of Start-Stop DistortionDegree of start-stop distortion refers to the following definitions: 1. In asynchronous data transmission, the ratio of a) the absolute value of the maximum measured difference between the actual and theoretical intervals separating any significant instant of modulation or demodulation from the significant instant of the start element immediately preceding it to, b) the unit interval. 2. The highest absolute value of individual distortion affecting the significant instants of a start-stop modulation.The degree of distortion of a start-stop modulation (or demodulation) is usually expressed as a percentage.Distinction can be made between the degree of late ( positive) distortion and the degree of early ( negative) distortion.

Delay Dial SignalingDelay Dial Signaling is one of the Start Dial Supervision Protocol. The Originating switch and trunk circuit will go off-hook. After a timing interval (75 to 300 mS), the Originating switch will look at the status of the incoming signaling from the Remote switch. If the supervision is on-hook, the Originating office will output digits to the Remote switch. If the supervision is off-hook, the Originating office will wait for the supervision to return to an on-hook state, then output digits. There is no minimum time to wait for a delay-dial pulse from the Remote switch. In fact, if the remote switch was in an on-hook state, there is no waiting at all prior to output of digits. If the Remote switch was not ready to receive digits, improper call completions can result.

Delay DistortionDelay Distortion is the signal distortion caused by the differing transmission delays of signals of different frequencies to pass through a telecommunications transmission line.

Delay EqualizerDelay Equalizer is a device used to equalize the signal distortion caused by the differing frequency delay characteristics of a transmission line. The delay equalizer operates by adding delay to the faster transmitting frequencies.

Delta ModulationDelta Modulation is a method of sampling and converting analog signals such as voice to digital signals. It is based on encoding the direction of signal change, indicating the direction of signal change with a single bit.

DemodulationDemodulation is the process of recovering the original modulating signal from a modulated carrier. The original modulating signal is usually the information being transmitted, typically voice or data.

DemodulatorDemodulator is a device for assembling signals after they have been received by an antenna. A demodulator is typically the first major device downstream from an antenna receiving system. The corresponding device on the transmission side of a system is a modulator.

Deposit Coin ToneDeposit Coin Tone is one of the audible tone in telephone system. It is sent from a Community Dial Office to a post-pay coin telephone, informs the calling party that the called party has answered and that the coin should be deposited. Deposit Coin Tone is a steady Low Tone.

Dial AroundDial Around is a telephone service feature which allows customers to dial a toll-free number before entering the destination number for long-distance calling. Dial around is especially convenient for residential customers and cellular users who wish to bypass their primary long-distance provider and take advantage of discounted calling rates.

Dial Jack ToneDial Jack Tone is used as a start-dial signal to tell a DSA operator that the connection reached through a dial jack is ready to receive dialing. Dial Jack Tone is a steady Low Tone.

Dial Long LineDial Long Line is an equipment (usually located in a central office) that extends the dialing, supervision and other signaling range of a loop.

Dial Off-Normal ToneDial Off-Normal Tone is a steady Low Tone. It is returned to an operator after he/she has completed a call into a step-by-step office and after the calling party has answered to remind him/her to restore the dial key

Dial PulsesDial Pulse is regular, momentary interruption of signaling current used to transmit numerical information either into a register or to control a switch directly. There are different ways of generating Dial Pulses. When end-users pick up the receiver on a telephone, an electrical connection is made to the lines leading to the central office. When end-users replace the receiver on the cradle the connection is broken or interrupted. This applies to both push-button and rotary dial telephones. By periodically breaking the connections leading to the central office, a number can be dialed. The number of interruptions is equal to the digit dialed, with the exception that ten interruptions correspond to zero. These pulses may be generated at the rate of ten times per second and there should be a 1/2 second delay between each two digits. The rotary dial on the telephone is a mechanical device which periodically breaks the connection leading to the central office.

Dial PulsingDial Pulsing is a means of signaling consisting of regular momentary interruption of a direct or alternating current path at the sending end in which the number of interruptions corresponds to the value of a digit or character. The interruptions are usually produced by a rotary telephone dial, but may be produced by a sender in a switching system.

Dial ToneDial Tone is sent to a calling customer or operator to indicate that the receiving end is ready to receive dial pulses or DTMF signals. It is used in all types of dial offices when dial pulses are produced by the customer's or operator's dials. Normally dial tone means that the entire wanted number may be dialed; however, there are some cases where the calling party must await a second dial tone or where an operator, after dialing an initial group of digits, must wait for a second dial tone before the rest of the number can be dialed. Some dialing switchboards are arranged to permit listening for dial tone between certain digits. Dial Tone is 350 Hz and 440 Hz held steady at -13 dBm0/frequency.

Dial Tone DelayDial Tone Delay is a measure of time required to provide dial tone to customers. This measures one aspect of the performance of a switching system

Dial Tone MarkerDial Tone Marker is the common control equipment used to control call-operating operations in a Number 5 Crossbar System.

Dial TrainDial Train is the series of pulses or tones that is sent from the originating station and the switching equipment in order to specify the destination of the desired call.

Dialing ParityDialing Parity is equal dialing access provided to consumers. No additional codes or numbers are necessary to access a different telephone service provider.

Dial-Normal Transmission SignalDial-Normal Transmission Signal is a second dial tone returned to an operator between digits indicating that he/she may dial the remainder of the number. For example, when an operator reaches a link-type Community Dial Office via a step-by-step office after dialing a routing code, he/she must pause until an idle link at the Community Dial Office returns dial tone. This method of operation is not recommended or considered standard. Dial-Normal Transmission Signal is a steady Low Tone.

DialupDialup is the technique of initiating and routing a call by means of dial signals from the originating station.

Dial-up AccessDial-up Access refers to the method of accessing a telecommunications system via dialup.

Dial-up LineDial-up Line is a communications circuit that is established by a switched-circuit connection using the telephone company network.

DiaphragmDiaphragm is a thin, flexible sheet that can be vibrated by sound waves as in a microphone, or by magnetic waves as in a telephone receiver.

DIB: Directory Information BaseDirectory Information Base (DIB) is the complete set of information to which the directory provides access, and which includes all of the pieces of information which can be read or manipulated using the operations of the directory

DID/DNIS: Direct Inward Dialing/Dialed Number Identification ServiceDirect Inward Dialing/Dialed Number Identification Service (DID/DNIS) refers to a service when a call arrives at an ACD or PBX, the carrier sends a digital code on the trunk line. The switch can read this code to determine how it should dispatch the call. Typically, this value is the specific number dialed by the user. By mapping each possible code with an internal extension, the switch can provide direct inward dialing (DID).

DID: Direct-Inward-DialDirect-Inward-Dial (DID), also known as Direct Dialing In (DDI), is a service offered by telephone companies that enables callers to dial directly into an extension on a PBX and not use an auto-attendant. Direct-inward-dial (DID) is the call in which the gateway uses the number initially dialed (DNIS) to make the call, as opposed to a prompt to dial additional digits.

Differential SignalingDifferential Signaling is a method of digital data transmission using two wires for each electrical path for high immunity to noise and crosstalk. The signals are sent down one wire as positive and the other as negative, and the circuit at the receiving end derives the signal from the difference between the two. It is superior to single-ended signaling, where the reference voltage is ground and can vary over long distances. In differential signaling, the reference voltage is controlled. Typically, twisted pairs are used so that external radiation impacts both wires at the same place, and the noise can be detected more easily.

DigitalDigital refers to, in telecommunications system, a means for encoding information of communication signals through the use of bits (binary digits). Digital transmission is increasingly replacing analog transmission because it provides more efficiency and flexibility for networking.

Digital Carrier SystemDigital Carrier System is a carrier system for digital signals that uses regenerative versus linear repeaters and time division multiplexing.

Digital TransmissionDigital Transmission is the transmission of a digital signal between two or more points. The usual definition applies to the manner in which the transmission carrier is modified to carry the transmitted information. For example, in digital microwave systems, the radio frequency carrier is an analog signal, but its information modulation is derived from the digital signal.

DigitizeDigitize is the process of converting any information from its base states to a digital form; i.e., a form in which only a limited number of states exist. It should be noted that a digital form does not necessarily imply a character encoded form of information.

Direct Interlata Connecting Trunk GroupsDirect Interlata Connecting Trunk Groups refer to those trunk groups used for switched LATA access that interconnect an IC's POP directly with a BOC end office switching systems.

Direct Progressive SystemDirect Progressive System is a switching system in which the switches are at least partially under the direct control of a customer's dial and in which the path through the switching office is selected progressively one step at a time.

Directive GainDirective Gain, usually expressed in dB, refers to the following definitions: 1. Of an antenna, the ratio of (a) 4Ï€ times the radiance, i.e., power radiated per unit solid angle (watts per steradian), in a given direction to (b) the total power, i.e., the power radiated to 4Ï€ steradians. 2. Of an antenna, for a given direction, the ratio of the radiance produced in the given direction to the average value of the radiance in all directions. If the direction is not specified, the direction of maximum radiance is assumed.

Directory Assistance Trunk GroupDirectory Assistance Trunk Group is a trunk group that provides the means for customers or operators to obtain listed directory numbers and newly connected numbers. Applications commonly employ the following types of trunk groups: End Office to Trunk, Concentrator, End Office to Desk, Tandem to Trunk Concentrator, Tandem to Desk, Cord Switchboard to Trunk Concentrator, End Office to Automatic Call Distributor, and Tandem to Automatic Call Distributor.

Directory NumberDirectory Number is the telephone numbers assigned to subscribers' main stations, which is typically listed in the phone book or directory.

DisparityDisparity refers to the digital algebraic sum of set of signal elements in Pulse-code modulation (PCM). The disparity will be zero and there will be no cumulative or drifting polarization if there are many positive elements ("1s") as there are negative elements ("0s").

Dispersion-Limited OperationDispersion-limited operation is operation of a communications link in which signal waveform degradation attributable to the dispersive effects of the communications medium is the dominant mechanism that limits link performance. Dispersion is the filter-like effect that a link has on the signal, due to the different propagation speeds of the eigenmodes of the link. Practically, this means that the waveform at the input will be different from the waveform at the output of the link.

Distinctive Call Waiting ToneDistinctive Call Waiting Tone is a feature in telecommunication system that enable a customer who has call waiting feature to hear a distinctive call waiting tone for those incoming calls from a preselected number while they are talking. This feature is sometimes called VIP Alert or Call Selector.

Distribution CableDistribution Cable is a hierarchical level of cable plant usually referring to that cable which is installed between the trunk or feeder cable and the drop cable to a customer's premises.

DiversityDiversity, in telecommunications system, refers to the technique of using one, two, or more separate transmission channels. These channels may be along the same paths, in which case the

diversity is that of frequency or polarization. The channels may be along separate physical paths, in which case there is a space diversity.

DLC: Digital Loop CarrierDigital Loop Carrier (DLC) is an equipment that combines a number of individual phone line signals into a single multiplexed digital signal for local traffic between a central office (of a telephone company) and a business complex or other outlying service area. Typically, up to 24 analog voice calls are combined into a single signal and transmitted over a single copper T-carrier system or E-carrier line, an optical fiber cable, or a wireless connection. In a home, business, or other installations using digital loop carrier, the analog phone lines of individual users are connected to a local DLC box which then converts the analog signals into digital and combines (multiplexes) them into one signal that it sent to the phone company's central office on the single line. At the central office, the combined signal is separated back into the original signals. Digital loop carrier can carry traffic for regular phone calls (so-called plain old telephone service) and Integrated Services Digital Network (ISDN) service. Approaches have been developed for using DLC to handle the higher bandwidth of Digital Subscriber Line (DSL) service. Digital loop carrier is typically used as an efficient way to provide service to an office building or complex and to extend service to new areas outside the current local loop. DLC is also used to set up telephone services in emergency situations.

D-Link: Diagonal LinkSS7 Diagonal Link (D-Link) connects a secondary (e.g., local or regional) STP pair to a primary (e.g., inter-network gateway) STP pair in a quad-link configuration. Secondary STPs within the same network are connected via a quad of D-links. The distinction between a "B" link and a "D" link is rather arbitrary. For this reason, such links may be referred to as "B/D" links.

DLTU: Digital Line and Trunk UnitDigital Line and Trunk Unit (DLTU) is a Lucent term which refers to a telecommunication device or component of 5ESS switch that provides the interface to digital trunks and lines.

DM: Delta ModulationDelta Modulation (DM) is a method of sampling and converting analog signals to digital signals. It is based on encoding the direction of signal change, indicating the direction of signal change with a single bit.

DMS: Digital Multiplex SystemDigital Multiplex System (DMS) refers to a family of switching systems made by Nortel Networks that provides digital circuit-switched service for voice and data transmission, and packet switched service for data transmission. DMS is characterized by the use of pulse code modulation (PCM) and time division multiplexing (TDM) throughout the switched network. The system allows the direct switching of PCM signals used in transmission systems without their conversion to analogue format

DMS-10 Digital Switching SystemDMS-10 Digital Switching System is a family of time division multiplexed digital switching systems for local, tandem, and toll applications, by the Nortel Networks (formerly Northern

Telecom). DMS-lOE digital switching system is a small Class 5 digital switch that can satisfy the need as a Community Dial Office (CDO) replacement vehicle. This system can be expanded to 8000 subscriber lines. The DMS-lOE digital switching system offers Custom Calling Features, CAMA, LAMA (Local Automatic Message Accounting), Integrated Business Services (IBS), Equal Access, and Operations Support System (OSS) interfaces.

DMS-100 Digital Switching SystemDMS-100 Digital Switching System is a large local Class 5 digital switching system that can be expanded up to 100,000 subscriber lines. Major features offered include LAMA, Integrated Business Network (IBN), Equal Access and OSS interfaces. The DMS-100 digital switching system is manufactured by Northern Telecom Ltd., now called Nortel Networks.

DMS-200 Digital Switching SystemDMS-200 digital switching system is a large toll/tandem digital switching system that can be expanded up to 60,000 trunk circuits. Major features offered include CAMA, Traffic Operator Position Service (TOPS), CCIS, Equal Access, and OSS interfaces. The DMS-200 digital switching system is manufactured by Northern Telecom Ltd., now called Nortel Networks.

DMT: Discrete MultitoneDiscrete Multitone (DMT) is a method of separating a Digital Subscriber Line (DSL) signal so that the usable frequency range is separated into 256 frequency bands (or channels) of 4.3125 kHz each. Discrete multitone uses the fast Fourier transform algorithm for modulation and demodulation. Dividing the frequency spectrum into multiple channels allows DMT to work better when AM radio transmitters are present. Within each channel, modulation uses quadratude amplitude modulation (QAM). By varying the number of bits per symbol within a channel, the modem can be rate-adaptive.

DNIS: Dialed Number Identification ServiceDialed Number Identification Service (DNIS) is a telephone service that identifies for the receiver of a call the number that the caller dialed. It's a common feature of 800 and 900 lines. If you have multiple 800 or 900 numbers to the same destination, DNIS tells which number was called. DNIS works by passing the touch tone digits (dual tone multi-frequency or MF digits) to the destination where a special facility can read and display them or make them available for call center programming.

DOC: Dynamic Overload ControlDynamic Overload Control (DOC) is a control application that is automatically activated by switching systems to speed up call processing and limit attempts from connected offices.

DOD Communication SystemDOD communication system, the US Department Of Defense (DOD) communication system, is one of the most advanced communication systems in the world. DOD communication systems are used not only for the administration of the Department, but, most critically, for the command and control of force structures. To this end, the Defense Communications Agency (DCA) strives to ensure that the Department's missions are carried out with state-of-the-art communications systems.

DOD: Direct Outward DialingDirect Outward Dialing (DOD) is a service of a local exchange carrier that allows subscribers within a company's private branch exchange (PBX) system to connect to outside lines directly. Using DOD, a company can offer each person or workstation within the company the ability to dial numbers directly, without the need to go through an operator or dial other numbers first. DOD is often used together with Direct Inward Dialing (DID).

Double Order ToneDouble Order Tone is one of the Order Tones. For the double-order tone, the signal is two short spurts of High Tone in quick succession, and means that the operator should pass only the desired number.

Double-ended SynchronizationDouble-ended Synchronization is a synchronization control scheme used in two connected exchanges in a telecommunications network. In Double-ended synchronization, the phase error signals used to control the clock at one telephone exchange are derived by comparison with the phase of the incoming digital signal and phase of the internal clocks at both exchanges.

DP: Dial PulseDial Pulse (DP) is a short, direct current signal which is produced by, or simulated to look like, the opening and closing of contacts in a rotary-dial telephone when numbers are dialed. Dial pulses control the action of telephone switching equipment.

DPC: Destination Point CodeDestination Point Code (DPC) refers to the scheme in SS7 signaling to identify the receiving signaling point. In SS7 network, the point codes are numeric addresses which uniquely identify each signaling point.

DPCM: Differential Pulse-Code ModulationDifferential Pulse-Code Modulation (DPCM) is a PCM technique that codes the difference between sample points to compress the digital data. Because audio waves propagate in predictable patterns, DPCM predicts the next sample and codes the difference between the prediction and the actual point. The differences are smaller numbers than the numerical value of each sample on the full scale and thereby reduce the resulting bitstream

DPSK: Differential Phase Shift KeyingDifferential Phase Shift Keying (DPSK) is a digital modulation format where information is conveyed in phase difference of a carrier signal between consecutive symbols.

DRE: Directional Reservation Of EquipmentDirectional Reservation Of Equipment (DRE) is a control application that reserves trunk capacity for incoming traffic.

DriftDrift is a term in telecommunication system that is a comparatively long-term change in an attribute or value of a system or equipment operational parameter. Drift is usually undesirable

and unidirectional, but may be bidirectional, cyclic, or of such a long-term duration and low excursion rate as to be negligible. The drift can be characterized as "diurnal frequency drift" and "output level drift".

DropDrop refers to the following meanings in telecommunications: 1. the portion of a device directly connected to the internal station facilities, such as toward a switchboard or toward a switching center. 2. a wire or cable between a building and a pole or cable terminus. 3. test jacks on the central office side.

DS2: Digital Signal 2Digital Signal 2 (DS2) refers to a higher level digital frame made of four T1 frames and transmitted at 6.312 Mbps.

DSB-RC: Double-SideBand Reduced CarrierDouble-SideBand Reduced Carrier (DSB-RC) is a transmission scheme in which (a) the frequencies produced by amplitude modulation are symmetrically spaced above and below the carrier and (b) the carrier level is reduced for transmission at a fixed level below that which is provided to the modulator.

DSB-SC: Double-SideBand Suppressed CarrierDouble-SideBand Suppressed Carrier (DSB-SC) is a transmission scheme in which (a) frequencies produced by amplitude modulation are symmetrically spaced above and below the carrier frequency and (b) the carrier level is reduced to the lowest practical level, ideally completely suppressed.

DSF: Dispersion Shift FiberDispersion-shifted fiber (DSF) is a type of single-mode fiber designed to have zero dispersion near 1550 nm. Dispersion Shift Fiber (DSF) is specified in ITU-T G.653. It has had dopants added which shift the zero-dispersion wavelength from the natural 1300 nm in silica-glass fibers to the minimum-loss window at 1550 nm.

DSI: Digital Speech InterpolationDigital Speech Interpolation (DSI) is a technique of sharing voice communication paths among a larger number of users by means of allocating the silent periods inherent in human speech to active uses. An earlier technology was called Time Assignment Speech Interpolation or TASI. The technique is somewhat analogous to that of the statistical multiplexing of data transmission.

DSN: Defense Switched NetworkDefense Switched Network (DSN) is a worldwide private-line telephone network. Multilevel precedence and preemption (MLPP) capabilities on the DSN are utilized by command and control users to ensure that the highest-priority calls achieve connection quickly, especially during a crisis situation. The DSN also provides global data and video services using dial-up switched 56 kbps or 64 kbps Integrated Services Digital Network (ISDN) services.

DSR: Data Signaling RateData Signaling Rate (DSR) refers to the aggregate signaling rate at which data pass a point in the transmission path in a data transmission system.

DS-SMF: Dispersion-Shifted Single Mode FiberDispersion-Shifted Single Mode Fiber (DS-SMF) is a type of optical fiber in a telecommunications transmission system using single-mode fiber that is best designed for longer transmission distances, making it suitable for long-distance telephony and multichannel television broadcast systems.

DSU: Data Service UnitData Service Unit(DSU), often referred to together with CSU as CSU/DSU, is the device used in digital transmission that adapts the physical interface on a Data Terminal Equipment(DTE) device to a transmission facility, such as T1 or E1. The DSU also is responsible for such functions as signal timing.

DSX: Digital Signal Cross-ConnectDigital Signal Cross-connect (DSX) is a cross-connection point for DS-1 signals.

DSX-1Digital Signal Cross-connect Level 1(DSX-1) is a standard that defines the voltage, pulse width and plug and socket for connecting DS-1 (T1) signals.

DTMF: Dual Tone MultifrequencyDual Tone Multifrequency(DTMF), also known as Touch Tone or Tone Dialing, is used for telephone signaling over the line in the voice frequency band to the call-switching center. DTMF is the tones generated when a button is pressed on a telephone, primarily used in the U.S. and Canada. DTMF is an example of a multifrequency shift keying (MFSK) system and is standardised by ITU-T Recommendation Q.23.

DTP: Data Transfer ProcessData Transfer Process (DTP) refers to the process in telecommunications system that establishes and manages the data connection. The DTP can be passive or active.

Dual AccessDual Access refers to the following meanings in telecommunication system 1. The connection of a user to two switching centers by separate access lines using a single message routing indicator or telephone number. 2. In satellite communications, the transmission of two carriers simultaneously through a single communication satellite repeater.

Dual SeizureDual seizure refers to the condition when two exchanges attempt to seize the same circuit at approximately the same time (kin to a two-way operation mode).

DuplexDuplex refers to a channel or a device which can communicate in both directions simultaneously. There are varous forms of duplex such as full duplex and half duplex.

DX SignalingDX Signaling is a signaling process used on long metallic circuits. The process uses a bridge circuit to detect the small current signals. The term DX is an old term used to refer to distant transmission.

Tele-Communication (Telecom) Terms Glossary and Dictionary - E

E Channel: Echo ChannelEcho Channel (E Channel) refers to the 64-Kbps ISDN circuit-switching control channel. The E channel was dropped in the 1988 ITU-TISDN specification. Now ISDN has only B channel, D channel, and H channel.

E&M Leads SignalingE&M Leads Signaling is a type of signaling in telecommunications industry. It indicates the use of a handset that corresponds to the ear (receiving) and mouth (transmitting) component of a telephone.

E&M SignalingE&M Signaling is a signaling method on a DS0 timeslot such that the signaling bits are used to indicate call states, such as on-hook, off-hook, alerting, and dial pulsing.

E&M: recEive and transMitrecEive and transMit (E&M), also known as Ear and Mouth, is the trunking arrangement generally used for two-way switch-to-switch or switch-to-network connections. E&M also is available on E1 and T1 digital interfaces.

E.123E.123 refers to the ITU-R recommendation which is the notation for national and international telephone numbers recommendation. E.123 defines a standard way to write telephone numbers, email addresses, and web addresses.

E.164E.164 refers to an ITU- recommendation that defines the international telecommunication numbering plan and telephone number format used for the PSTN and some other data networks. E.164 numbers can have a maximum of 15 digits. It is an evolution of standard telephone numbers.

E-2E-2 refers to the European Digital Signal 2 which is the European standard for digital physical interface at 8.448 Mbps.

E-4E-4 refers to the European Digital Signal 4 which is the European standard for digital physical interface at 139.264 Mbps.

E911 ServiceE911 Service, short for Enhanced 911 Service, is a North American telephone network (NANP) feature of the 911 (or basic 911) emergency calling system which can automatically report the telephone number and location of 911 calls made from wireline phones.

EBAF: Extended Bellcore AMA FormatExtended Bellcore AMA Format (EBAF), also known as Enhanced BAF, is an update to the BAF, which is a system of abstract syntax and semantics that supports coding of Automatic Message Accounting (AMA) data into records. The main difference between the BAF and EBAF is that EBAF is more flexible and can be used easier, as the BAF uses a defined structure for storing data. The EBAF can append other information to the end of an AMA record, and this makes it more flexible.

EC: Echo CancelerEcho Canceler (EC) is a device in telephony system for connection to a two-way telephone circuit to attenuate echo signals in one direction caused by signals in the other direction.

Echo CancellationEcho Cancellation is a method for removing unwanted signals from the main transmitted telephone voice signal.

ECSA: Exchange Carriers Standards AssociationExchange Carriers Standards Association (ECSA), now called ATIS (Alliance for Telecommunications Industry Solutions), is a standards body that developing telecommunications standards, operating procedures and guidelines through its sponsored committees and forums.

EDFA: Erbium-Doped Fiber AmplifierErbium-Doped Fiber Amplifier (EDFA), also called optical amplifier or an erbium amplifier, is an optical or IR repeater that amplifies a modulated laser beam directly, without opto-electronic and electro-optical conversion. The device uses a short length of optical fiber doped with the rare-earth element erbium. When the signal-carrying laser beams pass through this fiber, external energy is applied, usually at IR wavelengths. This so-called pumping excites the atoms in the erbium-doped section of optical fiber, increasing the intensity of the laser beams passing through. The beams emerging from the EDFA retain all of their original modulation characteristics, but are brighter than the input beams.

EDP: Event Detection PointEvent Detection Point (EDP), a term in Intelligent Network (IN), is a dynamically armed detection point. This will be armed by the SCF (Service Control Function) within the context of an IN service. EDP has two modes: 1) EDP-N (Event Detection Point-Notification) - this is dynamically armed and when triggered, the event is reported, however, processing is not

suspended.2) EDP-R (Event Detection Point - Request) - this is dynamically armed and when triggered, will suspend call processing. The SSF then waits for instructions from the SCF.

Effective Input NoiseTemperatureEffective input noise temperature is the source noise temperature in a two-port network or amplifier that will result in the same output noise power, when connected to a noise-free network or amplifier, as that of the actual network of amplifier connected to a noise-free source.

EIA/TIA-232EIA/TIA-232, formerly called RS-232, is the common physical layer interface standard, developed by EIA and TIA. EIA/TIA-232 supports unbalanced circuits at signal speeds of up to 64 kbps, which closely resembles the V.24 specification.

EIA/TIA-449EIA/TIA-449, formerly called RS-449, is a popular physical layer interface developed by EIA and TIA. EIA/TIA-449, essentially, is a faster (up to 2 Mbps) version of EIA/TIA-232 capable of longer cable runs.

EIA/TIA-586EIA/TIA-586 is a standard developed by EIA and TIA that describes the characteristics and applications for various grades of UTP cabling.

EIA-232EIA-232, a popular physical layer interface also known as RS-232 or TIA-232, is a standard for serial binary data interconnection between a DTE (Data terminal equipment) and a DCE (Data communication equipment). It is commonly used in computer serial ports. A similar ITU-T standard is V.24.

EIA-422EIA-422, also known as RS-422 or TIA-422, is the balanced electrical implementation of EIA/TIA-449 for high-speed data transmission. Now referred to collectively with EIA-423 as EIA-530, it provides for data transmission, using balanced or differential signaling, with unidirectional/non-reversible, terminated or non-terminated transmission lines, point-to-point, or multi-drop.

EIA-423EIA-423, also known as RS-423 or TIA-423, is the unbalanced electrical implementation of EIA/TIA-449 for EIA/TIA-232 compatibility.

EIA-449EIA-449, also known as RS-449 or TIA-449, specifiecs the functional and mechanical characteristics of the interface between data terminal equipment and data communications equipment. The electrical signalling standards intended for use with RS 449 are RS-422 for balanced signals, and RS-423 for the unbalanced signals, with data rates up to 2,000,000 bits per

second. The standard specified two D-subminiature connectors with 37 and 9 pins for the primary and secondary data circuits.

EIA-485EIA-485, formerly known as RS-485 or RS485, is a physical layer electrical specification of a two-wire, half-duplex, multipoint serial connection. The standard specifies a differential form of signalling. The difference between the wires’ voltages is what conveys the data. One polarity of voltage indicates a logic 1 level, the reverse polarity indicates logic 0.

EIA-530EIA-530, also known as RS-530 or TIA-530, is a balanced serial interface standard that generally uses a 25-pin connector. The specification defines the cable between the DTE and DCE devices. It is a replacement for EIA-449, which uses 37-pin connector. EIA-530 refers to two electrical implementations of EIA/TIA-449: RS-422 for balanced transmission and RS-423 for unbalanced transmission.

E-ISUP: Extended-ISUPExtended-ISUP, originally a subset of Q.761 ISUP, is expanding in to a superset of ITU and ANSI ISUP. In addition, it supports the delivery of SDP parameters via generic digits. E-ISUP runs over IP and therefore uses IP addresses instead of point codes.

Eligible Telecommunications CarrierEligible telecommunications carrier refers to the company that provides telecommunication services in the United State.

E-Link: Extended LinkSS7 Extended link (E-link) connects an SSP to an alternate STP. E-links provide an alternate signaling path if an SSP's "home" STP cannot be reached via an "A" link. "E" links are not usually provisioned unless the benefit of a marginally higher degree of reliability justifies the added expense.

Embedded Operations ChannelEmbedded Operations Channel refers to a channel provided on telecommunications facilities to support administration and maintenance

En-Block SignalingEn-block Signaling is the method in which the address digits are encoded into blocks for onward transmission. Note that the blocks of code contain all the address information required to route the call to its destination.

End-of-Pulse SignalEnd-of-pulse Signal is an address signal sent in the forward direction to indicate there are no more address signals to follow.

End-of-Selection SignalEnd-of-selection signal is a signal sent in the backward direction to indicate the successful

completion of the call set-up process. It can also be used to indicate an unsuccessful termination of the call set-up process, and that may contain information on the called party's line condition.

EPON: Ethernet Passive Optical NetworkEthernet Passive Optical Network (EPON) is a point to multipoint network topology implemented with passive optical splitters, along with optical fiber PMDs that support this topology. EPON is based upon a mechanism named MPCP (Multi-Point Control Protocol), which uses messages, state machines, and timers, to control access to a P2MP topology. At the basis of the EPON/MPCP protocol lies the P2P Emulation Sublayer, which makes an underlying P2MP network appear as a collection of point to point links to the higher protocol layers (at and above the MAC Client). It achieves this by prepending a Logical Link Identification (LLID) to the beginning of each packet, replacing two octets of the preamble. In addition, a mechanism for network Operations, Administration and Maintenance (OAM) is included to facilitate network operation and troubleshooting.

Equal AccessEqual Access refers to the AT&T Divestiture - 1982 Modified Final Judgement (MFJ), which is the provision of one-plus capability to interLATA competitors of AT&T. The MFJ and the FCC require local exchange carriers to provide equal access and customers should be able to reach the carrier of their choice by dialing 1 + the long-distance number. Equal Access may also refer to a more generic concept under which the BOCs must provide access services to AT&T's competitors that are equivalent to those provided to AT&T.

Equipment RoomEquipment Room is the facility that houses building telecommunications systems such as Servers, PBXs, and mechanical terminations of the telecomm wiring system. In most of the cases, it is different than a wiring closet due to the complexity of the components it contains. But equipment Room nonetheless may take the place of a building's wiring closet or it may be a separate entity.

ERC: Easily Recognizable CodeEasily Recognizable Code (ERC) is a part of a North American telephone number in the area code position that has the pattern NXX, where N=2...9 and XX = 00, 22, 33, ... 88, For example, 800, 877, 900 and 700.

ErlangErlang is a measure of traffic load on a telephone line in 60 minutes blocks. The figure is calculated as a rate at which calls arrive divided by the rate at which they are completed.

Erlang UnitErlang Unit is a statistical measure of telecommunications traffic used in telephony. It is named after the Danish telephone engineer A. K. Erlang, the originator of queueing theory.

ESF: Extended Super-FrameExtended Super Frame (ESF), sometimes called D5 framing, is a T1 framing standard that consists of 24 frames of 192 bits each, with the 193rd bit providing timing and other functions.

Preferred over its predecessor, Super Frame, because it includes a Cyclic Redundancy Check and bandwidth for a data link channel (used to pass out-of-band data between equipment).

ESN: Electronic Switched NetworkElectronic Switched Network (ESN) refers to a network that uses electronic switches to direct telecommunications traffic.

ESS: Electronics Switching SystemElectronics Switching System (ESS), an AT&T/Lucent term, refers to switching systems using stored programs to electronically switch telecommunication information. A 5ESS is a digital central office for end office applications. A 4ESS is its digital central office for toll center applications.

ETB: End of Transmission Block CharacterEnd of Transmission Block Character (ETB) refers to a transmission control character used to indicate the end of a transmission block of data when data is divided into such blocks for transmission purposes.

EURESCOM: European Institute for Research and Strategic Studies in TelecommunicationsEuropean Institute for Research and Strategic Studies in Telecommunications (EURESCOM) is the leading organization for collaborative R&D in telecommunications. EURESCOM provides efficient management of research projects and programmes for member companies and other clients.

EutelsatEutelsat is inter-governmental organization founded in 1983 with the launch of Eutelsat 1. Eutelsat aims to provide and operate a space segment for public intra-European international telecommunications services. The segment is also used to meet domestic needs by offering leased capacity, primarily for television. UK and France are the main shareholders.

Even ParityEven Parity is one of the parity processes for error checking, which indicates that the total number of ones in the information data stream plus the parity bit equals to an even number.

ExchangeExchange refers to a component of telecommunications network that is equivalent to the following terms: "office", "Central Office", "telephone switch", "telephone exchange", or "wire center". An exchange can be used as (1) Local exchange, (2) toll (trunk) exchange, or (3) gateway exchange.

Exchange CarrierExchange Carrier, also known as local exchange carrier(LEC), refers to a local telephone company that provides the telephone services to residents and business. In the United States, as the result of 1984 divestiture of then regulated monopoly carrier AT&T, wireline telephone companies are divided into two categories: long distance, also called inter-exchange carrier, or

IXCs, and local carrier, also called local exchange carrier, or LECs. According to the Federal Communications Commission, local phone calls are defined as calls originating and terminating within a LATA (local access and transport area).

ExpandorExpandor is the function or process to perform the inverse function of a compressor ( at the receiver).

EXZ: Excessive ZerosExcessive Zeros (EXZ or EZ) is a type of error event in DS1(T1)/E1 and DS3(T3)/E3 interfaces when an AMI-coded signal is the occurrence of more than fifteen contiguous zeroes. For a B8ZS coded signal, the defect occurs when more than seven contiguous zeroes are detected.

Tele-Communication (Telecom) Terms Glossary and Dictionary - F

FAA: Facility AcceptedFacility Accepted (FAA) is one of the message type codes in BICC protocol. It indicates that the FAR is accepted and the use of the facility or operation towards the other side is accepted.

Facilities Based Private Switched Network ServicesFacilities Based Private Switched Network Services refers to the services provided by so called Facilities Based Carriers, a long-distance service provider that owns its own physical facilities as opposed to the bulk of the long-distance companies who are resellers.

Facility LoopbackFacility Loopback refers to signal looped back toward the incoming facility. This technique is often used in T1 testing.

Facility-Based CarriersFacility-based Carriers refers to a local or long-distance service provider that owns its own physical facilities.

Fax: Facsimile TransmissionFax, also called Facsimile Transmission, is a system of communication or delivery for paper documents or other graphics material in which a special digital image scanner scans the pages of the document, compresses the scanned image using CCITT Group Compression, and transmits the digital signals by wire or radio to a FAX receiver at a remote point.

FBG: Fiber Bragg GratingFiber Bragg Grating (FBG) is a short length of optical fiber that filters out a particular wavelength. Periodically spaced zones in the fiber core are altered to have different refractive indexes slightly higher than the core. This structure selectively reflects a very narrow range of wavelengths while transmitting others. Fiber Bragg gratings are used to stabilize the output of a laser and to filter out wavelengths in a WDM system.

FCC: Federal Communications CommissionFederal Communications Commission (FCC) is the regulatory body governing communications technologies in the US. established by the Communications Act of 1934, as amended, and regulates interstate communications (wire, radio, telephone, telegraph and telecommunications) originating in the United States.

FDL: Facility Data LinkFacility Data Link (FDL) is a 4-kbps channel provided by the Extended Superframe (ESF) T1 framing format. The FDL performs outside the payload capacity and allows a service provider to check error statistics on terminating equipment without intrusion.

Feature BoardsFeature Boards are modular system cards that perform specific functionality, for example, DSC cards or modem cards.

FEC: Forward Error CorrectionForward Error Correction (FEC) is a technique for controlling errors in a one-way communication system. FEC sends extra information along with the data, which can be used by the receiver to check and correct the data. Using FEC, a receiver can correct errors incurred in transmission over a communications channel without requiring retransmission of any information by the transmitter, which typically involves a convolution of the transmitted bits and the appending of extra bits by both the receiver and transmitter using a common algorithm.

FER: Frame Erasure/Error RateFrame Erasure/Error Rate is a measure of the number of frames of data that contained errors and could not be processed. FER is usually expressed as a percentage or exponent.

FEXT: Far-End CrosstalkFar-End Crosstalk (FEXT) refers to crosstalk that is measured at the opposite end of the cable from which it is being disturbed.

FG: Feature GroupsFeature Groups (FG), also called access feature groups, are the standard interconnections (paths) between telecommunications carriers (e.g., local exchange and inter-exchange carriers). Currently, there are four common feature categories: FGA, FGB, FGC, FGD.

FGA: Feature Group AFeature Group A (FGA) is the arrangement that the user has to dial a local telephone number, following by the desired long-distance number.

FGB: Feature Group BFeature Group B (FGB) is the arrangement that is associated with 950-xxxx calling; the user enters 950 and 4 additional digits, followed by the long-distance number.

FGC: Feature Group CFeature Group C (FGC) services, replaced by FGD (Feature Group D) now, allows the end user

to have the same dialing plan (1 plus the telephone number) to reach any predetermined long distance phone companies of their choice.

FGD: Feature Group DFeature Group D is a local exchange carrier network service that, among other things, lets public-safety dispatch offices receive a 10-digit data stream, including the full call-back number, alongside wireless 911 calls. FGD is offered as a way by which wireless carriers can meet FCC enhanced 911 rules and dispatch offices can overcome their current bandwidth limits. This access group is associated with equal access arrangements, which allows the end user to have the same dialing plan (1 plus the telephone number) to reach any predetermined long distance phone companies of their choice.

FGD-EANAFeature Group-D (FGD) of type Exchange Access North American (EANA) is a type signalling protocol that provides certain call services, such as emergency (USA-911) calls. The command calling number outbound is used only for FGD-EANA signalling to generate ANI digits for outgoing calls.

FiOS: Fiber Optic ServiceFiber Optic Service (FiOS) is a data communications service provided by Verizon that uses fiber optic cables to transfer data. FiOS is called a "Fiber to the Premises," or FTTP service, since it brings fiber optic data transmission to residential homes as well as businesses. Since fiber optic technology sends data via pulses of light, it is the fastest method of transferring data.

FISU: Fill-In Signal UnitFill-In Signal Unit (FISU) is an SS7 message that is sent in both directions whenever other signal units are not present. FISU provides a CRC checksum for use by both signalling endpoints.

Fixed AccessFixed access refers to a terminal access to the network in PCS ( personal communications service) that uses wired technology.

FLAG: Fiber Link Around the GlobeFiber Link Around the Globe (FLAG) refers to an undersea fiber optic cable which connects England, Japan, and many places in between.

F-link: Fully Associated LinkF-link refers to the SS7 fully associated link, which is an SS7 signaling link directly associated with a link carrying traffic. F-link connects two signaling end points (i.e., SSPs and SCPs). F-links are not usually used in networks with STPs. In networks without STPs, F-links directly connect signaling points.

Frame SynchronizationFrame synchronization is the process in the telecommunications transmission system to align the digital channel (time slot) at the receiving end with the corresponding time slot at the transmission end as it occurs.

FRJ: Facility ReJectFacility ReJect (FRJ) is one of the message type code in BICC (Bearer independent Call Control) protocol (which, in turn, is part of SS7 protocol suite). Facility ReJect message indicates that the request to use the facility (an operation) towards the other side is denied. An example of such operations or facilities could be coin phones.

FSAN Group: Full Service Access Network GroupThe Full Service Access Network (FSAN) Group is a forum for the world's leading telecommunications services providers and equipment suppliers to work towards a common goal of truly broadband access networks. The Mission of FSAN is to drive applicable standards, where they already exist, into the services and products in the industry, while simultaneously advanced its own specifications, such as Gigabit rate G-PON and ATM-based B-PON Passive Optical Networking, into the appropriate standards bodies to provide further definition to the Full Service Access Network.

FSN: Forward Sequence NumberForward Sequence Number (FSN) is part of an SS7 MSU that contains the sequence number of the signal unit.

FTTC: Fiber To The CurbFiber-To-The-Curb (FTTC) refers to the installation and use of optical fiber cables directly to the curbs near homes or any business environment as a replacement for "plain old telephone service" (POTS). Think of removing all the telephone lines you see in your neighborhood and replacing them with optical fiber lines. Such wiring would give us extremely high bandwidth and make possible movies-on-demand and online multimedia presentations arriving without noticeable delay.

FTTH: Fiber To The HomeFiber-To-The-Home (FTTH), also known as Fiber to the Premises (FTTP), refers to a broadband telecommunications system based on fiber-optic cables and associated optical electronics for delivery of multiple advanced services such as the triple play of telephone, broadband Internet and television to homes and businesses.

FTTN: Fiber to the NeighborhoodFiber-To-The-Neighborhood (FTTN) refers to installing optical fiber from the telephone company central office to all curbs or buildings in a neighborhood.

FTTO: Fiber to The OfficeFiber-To-The-Office (FTTO) refers to installing optical fiber from the telephone company central office to a specific office in a building such as a business or apartment house.

FTTP: Fiber to the PremisesFiber-To-The-Premises (FTTP), also known as Fiber-To-The-Home (FTTH), refers to a broadband telecommunications system based on fiber-optic cables and associated optical electronics for delivery of multiple advanced services such as the triple play of telephone, broadband Internet and television to homes and businesses.

FTTS: Fiber To The SubdivisionFiber-To-The-Subdivision (FTTS) refers to the installing optical fiber from the telephone company central office to a subdivision of residential area.

Fully Dedicated AccessFully Dedicated Access refers to an Internet access service that is fully owned and operated by a company providing and ensuring high reliability, low latency, flexible, robust, and more quality services.

FX: Foreign ExchangeForeign Exchange (FX), in telecommunication, refers to a service that provides local telephone service from a central office located outside the subscriber's exchange area ( "foreign to" this area). A sample scenario of such service is the following: a user pick up the phone in one area and the dial tone is provided from another area (so called foreign area).

Tele-Communication (Telecom) Terms Glossary and Dictionary - G

G.703G.703, a standard based on Pulse-code modulation (PCM) standard, specifies voice over digital networks. Voice to digital conversion according to PCM requires a bandwidth of 64 kbps (+/- 100 ppm), resulting in the basic unit for G.703. G.703 specifies the physical and electrical characteristics of hierarchical digital interfaces at a rate up to 140Mbit/s.

G.704G.704 defines the synchronous frame structure used at primary and secondary hierarchy levels on G.703 interfaces up to 45Mbit/s. The conventional use of G.704 on a 2Mbit/s primary rate circuit provides 30 discrete 64kbit/s channels, with a further 64kbit/s channel available for common channel signalling.

G.707G.707 defines the Synchronous Digital Hierarchy (SDH) Bit Rates.

G.708G.708 defines the Network Node Interface (NNI) for Synchronous Digital Hierarchy (SDH).

G.709G.709 defines the Synchronous Multiplexing Structure.

G.711G.711 is an ITU-T standard for audio companding released in 1972. It is primarily used in telephony. G.711 represents 8-bit compressed pulse code modulation (PCM) samples for signals of voice frequencies, sampled at the rate of 8000 samples/second. G.711 encoder will create a 64 kbit/s bitstream. There are two main algorithms defined in the standard: mu-law algorithm (used in North America & Japan) and a-law algorithm (used in Europe and other countries).

G.721G.721 is a 32 kbps Adaptive Differential Pulse Code Modulation (ADPCM) speech compression algorithm. The sampling rate is 8 KHz. G.721 produces toll quality speech. With transmission error rates higher than 10.4, the perceived quality of G.721 is better than G.711. G.721 is the first ADPCM standard. Later came the standards of G.726 and G.727 for 40, 32, 24 and 16 kbps.

G.722G.722 is a wideband speech coding algorithm supporting bit rates of 64, 56 and 48 kbps. In G.722, the speech signal is sampled at 16000 samples/second. G.722 can handle speech and audio signal bandwidth upto 7 kHz, compared with 3.6 kHz in narrow band speech coders. G.722 coder is based on the principle of Sub Band - Adaptive Differential Pulse Code Modulation (SB-ADPCM). The signal is split into two sub-bands and samples from both bands are coded using ADPCM techniques.

G.722.1G.722.1 is an ITU-T standard for speech codecs that compresses 50Hz -7KHz audio signals into one of two bit rates, 24 or 32 Kbps.

G.723 or G.723.1G.723, also known as G.723.1 in more precise terms, is a standard-based voice codec providing voice quality (300 Hz to 3400 Hz) at 5.3 / 6.3 kbps. It was designed for video conferencing/telephony over standard phone lines, and is optimized for real-time encoding & decoding. G.723.1 is part of the H.323 (IP) and H.324 (POTS) standards for video conferencing.

G.726G.726 is a ITU-T speech codec based on ADPCM operating at bit rates of 16-40 kbit/s. The most commonly used mode is 32 kbit/s, since this is half the rate of G.711, thus increasing the usable network capacity by 100%. G.726 specifies how a 64 kbps A-law or µ-law PCM signal can be converted to 40, 32, 24 or 16 kbps ADPCM channels where the 24 and 16 kbps channels are used for voice in Digital Circuit Multiplication Equiment (DCME) and the 40 kbps is for data modem signals (especially modems doing 4800 kbps or higher) in DCME.

G.727G.727 is an embedded Adaptive Differential Pulse Code Modulation (ADPCM) algorithms at rates of 40, 32, 24 and 16 kbit/s. G.727 defines the transcoding law when the source signal is a pulse-code modulation signal at a pulse rate of 64 kbit/s developed from voice frequency analog signals as fully specified by G.711.

G.728G.728, based on the Low-Delay Code Excited Linear Prediction (LD-CELP) compression principles, is a 16 kbps compression standard. G.728 has an algorithmic coding delay of 0.625 ms. G.728 normally compresses toll quality speech at 8000 samples/second. G.728 Annex G (G.728 G) is a fixed point specification of the coder working at a bit rate of 16000 bits/second. G.728 Annex I (G.728 I) is the packet loss concealment (PLC) technique used along with G.728 G. G.728 coders are widely used for applications of telephony over packet networks, especially voice over cable and VoIP, where low delay is required.

G.729G.729 is an audio data compression algorithm for voice that compresses voice audio in chunks of 10 milliseconds. G.729 does coding of speech at 8 kbit/s using Conjugate-Structure Algebraic-Code-Excited Linear-Prediction(CS-ACELP). G.729 is mostly used in Voice over IP (VoIP) applications for its low bandwidth requirement. Standard G.729 operates at 8 kbit/s, but there are extensions, which provide also 6.4 kbit/s and 11.8 kbit/s rates for marginally worse and better speech quality respectively. Also very common is G.729a which is compatible with G.729, but requires less computation.

G.729 A/BG.729 A/B is an ITU-T standard for speech codecs that provides near-toll quality audio at 8 Kbps. G.729 Annex A is a reduced complexity codec and G.729 Annex B supports silence suppression and comfort noise generation.

G.780G.780 defines the terms for SDH Networks and Equipment.

G.781G.781 defines the structure of Recommendations on Equipment for the Synchronous Digital Hierarchy (SDH).

G.782G.782 defines types and characteristics of Synchronous Digital Hierarchy (SDH) Equipment

G.783G.783 defines characteristics of Synchronous Digital Hierarchy (SDH) Equipment Functional Blocks.

G.7xxG.7xx is a suite of ITU-T standards for audio compressions and de-commpressions. It is primarily used in telephony. In telephony, there are 2 main algorithms defined in the standard, mu-law algorithm (used in America) and a-law algorithm (used in Europe and the rest of the world). Both are logarithmic, but the later a-law was specifically designed to be simpler for a computer to process. G.7xx codec suite includes G.712, G.721, G.722, G.723, G.726, G.727, G.728, G.729 etc.

G.803G.803: Architecture of Transport Networks Based on the Synchronous Digital Hierarchy (SDH)

G.804G.804 is the ITU-T framing standard that defines the mapping of ATM cells into the physical medium.

G.832G.832: Transport of SDH Elements on PDH Networks: Frame and Multiplexing Structures

G.DMTG.DMT, another name for ITU G.992.1, is an ITU standard for ADSL using discrete multitone modulation.

G.LiteG.Lite, also known as ADSL Lite and Splitterless ADSL, is one of the Digital Subscriber Line technologies that allows broadband data access over normal phone lines (twisted pair cables, also called POTS). G.Lite offers a maximum of 1.5 Mbit/s downstream and 512 kbit/s upstream and does not require the use of phone line splitters.

Gateway RedundancyGateway Redundancy refers to a feature that enables the Gatekeeper to request that other Gatekeepers search their zones to locate a Gateway when Line Hunting fails to find a suitable service provider. If there is no service provider available, the Gateway Redundancy policy reables the Gatekeeper to complete the call by referring the call to other Gatekeepers.

Gateway Supported PrefixesGateway Supported Prefixes refers to some features in standard of H.323 version 2. It enables a Gateway to specify prefixes that the user should dial before the WAN number in order to make a call using a certain medium.

Gateway Switched ExchangeGateway switched exchange is the exchange that on top of trunk exchanges for international calls. The international gateway switch provides connections between different countries that have a wide range of operating parameters. Specifically, a gateway switch must support conversions between different signaling formats. Another issue for international calls is voice quality and echo control.

GETS: Government Emergency Telecommunications ServiceGovernment Emergency Telecommunications Service (GETS) is a White House-directed emergency phone service provided by a division of the Department of Homeland Security. GETS uses enhancements based on existing commercial telecom technologies.

GIS: Geographical Information SystemGeographical Information System (GIS) refers to a computer system capable of capturing, storing, analyzing, and displaying geographically referenced information, that is, data identified according to location. Practitioners also define a GIS as including the procedures, operating personnel, and spatial data that go into the system.

GlobalstarGlobalstar is a low earth orbit satellite system that deploys a network of 48 satellites to create a global voice and data service. This system is backed by Qualcomm, Loral, and Alcatel.

GloBanDGloBanD is an European Switched Nx64 data service consisting of a single circuit whose bandwidth is a multiple of 64 kbps. This circuit consists of one or more B channels. For example,

if a caller requests 512 kbps service, the line uses 8 B channels to supply the requested bandwidth. This service is available over T1 PRI lines only, and follows the CCITT Q.931 recommendation. It differs from MultiRate in being an overlay network, rather than an integral part of the worldwide switched digital infrastructure.

GNE: Gateway Network ElementGateway Network Element (GNE) refers to a Network Element (NE) that provides connections to other Network Element in most telecommunication and network systems, such as SONET/SDH/DLC, etc. GNE has a list of nests connected to it and their TIDs in the form of a route table. Whenever an input message comes to the GNE, it will route it to the appropriate NE using the TID in the route table.

GOS: Grade Of ServiceGrade of Service (GOS) is a measure of the success a subscriber is expected to have in accessing a network to complete a call. The grade of service is usually expressed as percentage of calls attempted by the subscriber during the busy-hour that are blocked due to insufficient network resources. The other measures for service quality is called Quality of Service (QoS) for the quality of voice service.

GOSIP: Government Open System Interconnection ProfileGovernment Open System Interconnection Profile (GOSIP) is a subset of OSI standards specific to US Government procurements, designed to maximize interoperability in areas where plain OSI standards are ambiguous or allow options.

GPON: Gigabit PONGigabit PON (GPON) is a Passive Optic Network (PON) technology operating at bitrates of above 1 Gb/s. Apart from the need to support higher bitrates, the overall protocol has been opened for re-consideration and the sought solution should be the most optimal and efficient in terms of support for multiple services, OAM&P functionality and scalability.

Ground StartGround Start is a method of signaling used primarily on Central Office (CO) trunk lines to PBXs. A ground is placed on one side of the two-wire line to indicate that it is in use so the other side of the two-wire interface does not attempt to use the line.

Ground Start SignalingGround-start signaling is a type of analog voice grade access line signaling in the telephone system that requires the customer interface to provide a ground on the ring conductor at the network interface to initiate service requests.

Ground-Start TrunkGround-start Trunk is a phone line that uses a ground instead of a short (loop-start trunks use a short between tip and ring) to signal the central office for a dial tone.

Group 3Group 3 is an ITU-T standard relating to fax devices. A Group 3 fax device is a digital machine

containing a 14400 baud modem that can transmit an 8 1/2 by 11 inch page in approximately 20 seconds with a resolution of either 203 by 98 dots per inch (dpi) or 203 by 196 dpi (fine), using Huffman code to compress fax data. Group 3 faxes use a standard dial-up telephone line for transmission.

Group Busy ToneGroup Busy Tone is audible tone of telephone system that is indicated by low tone on the sleeve of trunk jacks at cord switchboards. Absence of the tone tells the operator that there is at least one idle trunk in a group. Group Busy Tone is a steady Low Tone.

GTT: Global Title TranslationGlobal Title Translation (GTT) is a function usually performed in a Signal Transfer Point (STP). GTT is the procedure by which the destination signaling point and the subsystem number (SSN) is determined from digits (that is, the global title) present in the signaling message.

Tele-Communication (Telecom) Terms Glossary and Dictionary - H

H.225H.225, a key protocol in the H.323 VOIP architecture defined by ITU-T, is a standard to cover narrow-band visual telephone services defined in H.200/AV.120-Series Recommendations. It specifically deals with those situations where the transmission path includes one or more packet-based networks, each of which is configured and managed to provide a non-guaranteed QoS, which is not equivalent to that of N-ISDN, such that additional protection or recovery mechanisms beyond those mandated by Rec.

H.225.0H.225.0 is the specific document number for RAS, use of Q.931, and use of RTP under the H.323 VOIP architecture. It is also called as H.225.

H.235H.235 is the security recommendation for the H.3xx series systems. In particular, H.235 provides security procedures for H.323-, H.225.0-, H.245- and H.460-based systems. H.235 is applicable to both simple point-to-point and multipoint conferences for any terminals which utilize H.245 as a control protocol.

H.245H.245, a control signaling protocol in the H.323 multimedia communication architecture, is for the exchange of end-to-end H.245 messages between communicating H.323 endpoints/terminals. The H.245 control messages are carried over H.245 control channels. The H.245 control channel is the logical channel 0 and is permanently open, unlike the media channels. The messages carried include messages to exchange capabilities of terminals and to open and close logical channels.

H.248H.248, also known as Media Gateway Control protocol (Megaco), is for the control of elements in a physically decomposed multimedia gateway, enabling the separation of call control from media conversion. Megaco is a result of joint efforts of the IETF and the ITU-T Study Group 16. Therefore, the IETF defined Megaco is the same as ITU-T Recommendation H.248.

H.261H.261 is the video coding standard of the ITU. It was designed for data rates which are multiples of 64Kbit/s and is sometimes called p x 64Kbit/s (p is in the range 1-30). These data rates suit ISDN lines, for which this video codec was originally designed. H.261 transports a video stream using the real-time transport protocol, RTP, with any of the underlying protocols that carry RTP.

H.263The H.263, by the International Telecommunications Union (ITU), supports video compression (coding) for video-conferencing and video-telephony applications. H.263 was developed to stream video at bandwidths as low as 20K to 24K bit/sec and was based on the H.261 codec. As a general rule, H.263 requires half the bandwidth to achieve the same video quality as in the H.261. As a result, H.263 has largely replaced H.261. H.263 uses RTP to transport video streams.

H.264The H.264, also named Advanced Video Coding (AVC), is the MPEG-4 Part 10. H.264 is jointly developed by ITU and ISO. H.264 supports video compression (coding) for video-conferencing and video-telephony applications. The H.264 video codec has a very broad rang of applications that covers all forms of digital compressed video from, low bit-rate Internet streaming applications to HDTV broadcast and Digital Cinema applications with nearly lossless coding. H.264 is designed as a simple and straightforward video coding with enhanced compression performance, to provide a “network-friendly†video representation.�

H.323H.323, a protocol suite defined by ITU-T, is for voice transmission over internet (Voice over IP or VOIP). In addition to voice applications, H.323 provides mechanisms for video communication and data collaboration, in combination with the ITU-T T.120 series standards. H.323 is one of the major VOIP standards, on a par with Megaco and SIP.

H.450.2H.450.2 is the call transfer supplementary service in the H.323 VOIP architecture.

H.450.3H.450.3 is the call diversion supplementary service in the H.323 VOIP architecture.

H Channel: High-Speed ChannelHigh-speed channel (H-Channel) is the full-duplex ISDN primary rate channel operating at 384 kbps.

Hagelbarger CodeHagelbarger code is a convolutional code that enables error bursts to be corrected as long as there are relatively long error-free intervals between the error bursts.

Halftone CharacteristicHalftone characteristic refers to the following definitions in telecommunication: (1) in facsimile system, the relationship between the density of the recorded copy and the density of the original. (2) in facsimile system, the relationship between the amplitude of the facsimile signal to either the density of the original or the density of the recorded copy when only a portion of the system is under consideration.

Hamming CodeHamming code, sometimes referred to as an Error Correction Code (ECC), is an algorithm that can be used to detect errors in individual bits of transmitted data, and sometimes (dependent on the exact code used) correct that error. Although not particularly powerful, they are one of the "perfect" codes in that its standard array has all of the error patterns that can exist for single errors.

HandsetHandset refers to any of the various forms of manual telephone instruments held in hands that can receive and send voice.

HardwiredHardwired refers to: (1) equipment which is wired together so that its function if fixed as compared to equipment in which plug-in components may be varied to change the function. (2) equipment units which are permanently cabled together as compared to those which may be flexibly interconnected at a distributing frame.

HCO: Hearing Carry OverHearing Carry Over (HCO) refers to a method for using TTYs (Teletypewriter). HCO allows a person with a speech disability to hear a response from their party directly. HCO is often used in conjucntion with a Relay Service.

HCS: Header Check SequenceHeader Check Sequence (HCS) is a 16-bit cyclic redundancy check (CRC) check sequence (CS) that is derived from bits from the first 8 octets (excluding flags) of a UIH format packet.

HD: High DefinitionHigh Definition (HD) is a video format consisting of withering 720p (active lines of progressive ) or 1080 which could be either active lines of progressive, 1080p, or interlaced, 1080i.

HDSL: High Data Bit Rate DSLHigh Data Bit Rate Digital Subscriber Line (HDSL), also known as High Speed DSL or High data-rate DSL, provides equal bandwidth for both downloads and uploads. HDSL is one of oldest DSL technologies. HDSL can carry as much on a single wire of twisted-pair cable as can be

carried on a T1 line (up to 1.544 Mbps) in North America or an E1 line (up to 2.048 Mbps) in Europe over a somewhat longer range and is considered an alternative to a T1 or E1 connection.

HDSL2: 2nd generation HDSLHDSL2, the 2nd generation HDSL (High Data Bit Rate Digital Subscriber Line), is a variant of HDSL which delivers 1.5 Mbps service each way, supporting voice, data, and video using either ATM (asynchronous transfer mode), private-line service or frame relay over a single copper pair. This ATIS standard (T1.418) for this symmetric service gives a fixed 1.5 Mbps rate both up and downstream. HDSL2 does not provide standard voice telephone service on the same wire pair. HSDL2 differs from HDSL in that HDSL2 uses one pair of wires to convey 1.5 Mbps whereas ANSI HDSL uses two wire pairs.

HDSL4: 4th generation HDSLHDSL4, the 4th generation HDSL (High Data Bit Rate Digital Subscriber Line), is an enhanced version of HDSL2 which achieves about 30% greater distance than HDSL or HDSL2 by using two pairs of wire (thus, 4 conductors), whereas HDSL2 uses one pair of wires.

HDB3: High Density Bipolar 3High Density Bipolar 3 (HDB3) refers to a bipolar signaling technique. It relies on the transmission of both positive and negative pulses. High Density Bipolar 3 is based on Alternate Mark Inversion (AMI), but extends this by inserting violation codes whenever there is a run of 4 or more 0's.

HDT: Host Digital TerminalHost Digital Terminal (HDT) is the interface between a cable distribution system and the telephony switch, where the HDT acts as a digital multiplexer. It provides T1/E1 links to the telephony switch at 1.544 Mb/s and accepts 64 kb/s digital signals from lines on the subscriber side, usually in a T1/E1 format. Most vendors have designed the HDTs with an open interface to the telephony switch, allowing the service provider to choose different vendors for the switch and the HDT. On the subscriber side, however, the connection to the Network Interface Unit (NIU) is proprietary, requiring the cable operator to purchase both the HDTs and NIUs from the same vendor. Having an open interface to the switch also enables a cable operator to obtain telephony switching from another company through alliances or leasing agreements, so the operator doesn't need its own digital switch in the early stages of telephony offerings.

HeadsetHeadset refers to a voice communicatins sending and receiving device worn on the head.

Hierarchical NetworkHierarchical Network is a network that includes two or more different classes of switching systems in a defined arrangement.

High ToneHigh Tone is a generic tone used with various interruption patterns for the specific tones. High Tone is 4800 Hz at - 17dBm0. On some systems manufactured before 1974, High Tone was 400 Hz or 500 Hz at 61 - 71 dBmC. The following are a list of some specific High Tones: Partial

Dial Tone, Permanent Signal, Coin Return (test) Tone, Coin Return Tone, Number Checking Tone, Interception Loopback Tone, Warning Tone, Order Tone, Station Ringer Test and Class of Service.

High Water MarkHigh Water Mark in telecom refers to a counter that reports the highest number of DS0s that were in use at one time.

High-Priority Emergency Service CallHigh-priority emergency service call is a call identified as receiving emergency service treatment, which has been marked as requiring special treatment by the emergency service administration. The call has an associated CESID and transfer number.

High-Usage GroupHigh-Usage Group refers to a trunk group that is the primary direct route between two switching systems. The group is provided with an alternate route for overflow traffic in order to provide an acceptable level of blocking.

HitHit, in telecommunication, refers to a random and momentary disturbance in a transmission path which could result in a transmission error.

Holding TimeHolding Time is the length of time an attempt, call, or message occupies a component of the network that is normally expressed in seconds or minutes.

Home TandemHome Tandem is a tandem of a higher office class to which another tandem of an end office has a final trunk group. It may exist for all or defined subsets of tandem switched traffic.

Homing ArrangementHoming Arrangement refers to the last-choice trunk group(s) between switching systems in a specific routing ladder.

HookflashHookflash, a type of signaling, is a brief interruption in the loop current on loopstart trunks that the attached system does not interpret as a call disconnect. Once the PBX or PSTN senses the hookflash, it generally puts the current call on hold and provides a secondary dial tone or access to other features such as transfer or call waiting access. A hookflash is done by momentarily pressing down the cradle on a telephone. Some telephone handsets have a button called 'flash' or 'recall' that sends a 'timed loop break', or 'calibrated flash' which is a hookflash that has a precise timing.

Hop OffIn traditional telecom, Hop Off refers to a point at which a signal or call leaves a network and moves to another network. For example, a call made on a phone set can hop off the local

telephone network to long distance network. Conversely, a call coming through a major network can hop off that network to a smaller local network or private branch exchange (PBX). In voice over IP (VoIP), Hop Off is a point or gateway at which a call moves from an H.323 network to a network that uses some other protocol, typically at a gateway.

Horizontal WiringHorizontal Wiring is the wiring scheme that encompasses all cables from a work-area wallplate or network connection to the telecommunications closet. The outlets, cable, and cross-connects in the closet are all part of the horizontal wiring, which gets its name because the cable typically runs horizontally above ceilings or along the floors.

Howler ToneHowler Tone is one of the telephone system audible tones that is used in older offices to inform a customer that their receiver is off-hook. It has been superseded by the Receiver Off-Hook Tone. The Howler Tone was a 480 Hz tone incremented in volume every second for ten seconds until it reaches +40 VU.

HPF: High Pass FilterHigh Pass Filter (HPF), sometimes called a low-cut filter, is a filter that high frequencies can be transmitted well and frequencies lower than the cutoff frequency are attenuated or reduced. The actual amount of attenuation for a particular frequency varies from filter to filter.

HPPI: High Performance Parallel InterfaceHigh Performance Parallel Interface (HPPI) is a standard point-to-point protocol for transmitting large amounts of data at up to billions of bits per second over relatively short distances, mainly on local area networks (LANs). The proponents of HIPPI believe that its use can make computers, interconnected storage devices, and other resources on a local area network function as though they were all within a single supercomputer.

Hundred Call SecondsHundred Call Seconds is a measure of traffic intensity. It is one traffic path occupied for 100 seconds per hour. 36 hundred call seconds equal to one Erlang.

HuntHunt is a term that describes the automatic process by which a switch progresses from contact to contact, usually seeking an idle path.

Hybrid BalanceHybrid balance is an expression of the degree of electrical symmetry between two impedances connected to two conjugate sides of a hybrid set or resistance hybrid. It is usually denoted in dB.

Hybrid CoilBybrid Coil is a transformer-like device which is designed to provide the interface between a two-wire and four-wire circuit. It has four ports designed such that a signal input to one port will be split evenly to the two adjacent ports with no signal coupled to the opposite port. One port is

connected to the two-wire line. The two adjacent ports are connected to the four-wire line. The opposite port is connected to a balanced network to cancel any stray signals.

Hybrid Fiber Coaxial NetworkHybrid Fiber Coaxial Network is a telecommunication technology using optical fiber cable and coaxial cable in different portions of a network to carry broadband content.

Tele-Communication (Telecom) Terms Glossary and Dictionary - I

I.N.: Intelligent NetworkThe Intelligent Network (I.N. or IN) is a network architecture for both fixed and mobile telecommunication networks. It allows operators to to differentiate themselves by providing value-added services in addition to the standard telecoms services such as GSM services on mobile phones. It can also be regarded as an overlay on the core network.

IAC: Initial Alignment ControlInitial Alignment Control (IAC) is an SS7 MTP 2 function that provides the link alignment processing.

IAD: Integrated Access DeviceAn Integrated Access Device (IAD) is an access device that can simultaneously deliver traditional PSTN voice services, packet voice services, and data services (via LAN ports) over a single WAN link. It aggregates multiple channels of information including voice and data across a single shared access link to a carrier or service provider PoP (Point of Presence). The access link may be a T1 line, a DSL connection, a cable (CATV) network, a broadband wireless link, or a metro-Ethernet connection.

IAM: Initial Address MessageInitial Address Message (IAM) is defined in SS7 (Signaling System No. 7). It is part of the ISUP (Integrated Services Digital Network User Part) call setup. The message is used to seize a circuit and transfer addressing and call handling or routing information. The IAM includes the address and other information relating to routing and handling a call.

ICPIF: Calculated Planning Impairment Factor loss/delay busyout thresholdCalculated Planning Impairment Factor loss/delay busyout threshold (ICPIF) is an ITU-T G.113 standard for measuring quality of service. ICPIF replaces the old QDU (Quantisation Distortion Units) which were a subjective measurement. ICPIF represents predefined combinations of loss and delay in a VOIP network call. Packet loss and delay determine the threshold for initiating the busyout state. Gateways generate ICPIF values for each VoIP call, and these calculations can be stored for each VoIP call record.

IDN: Integrated Digital NetworkIntegrated Digital Network (IDN) refers to a network that uses both digital transmission and digital switching.

IEC: International Electro-technical CommissionInternational Electro-technical Commission (IEC) is the authoritative worldwide body responsible for developing consensus global standards in the electrotechnical field. IEC is dedicated to the harmonization and voluntary adoption of these standards, supporting the transfer of electrotechnology, assisting certification and promoting international trade. Since 1906, IEC has served the world's electrical industry, developing international standards to promote quality, safety, performance, reproducibility, and environmental compatibility of materials, products, and systems. It has also published standards for the electronics and telecommunications industries. The IEC's present membership of 51 countries includes most major trading nations.

ILEC: Incumbent Local Exchange CarrierIncumbent Local Exchange Carrier (ILEC) is a telephone company that was providing local service when the Telecommunications Act of 1996 was enacted. Compare with CLEC, a company that competes with the already-established local telephone business. In most part of the world, ILECs are the Post, Telephone, and Telegraphs (PTTs), government-managed monopolies.

Immediate StartImmediate Start is a method of E&M (ear & mouth) signaling. When the signaling leads indicate a change to an off-hook state, the interface is immediately ready to send signaling information.

Immediate Start SignalingImmediate Start Signaling is the most basic of Start Dial Supervision. The originating side goes off-hook, waits for a finite period of time (200ms, for example), then sends the dial digits without regard to the far end. The Immediate Start Signaling method is less reliable than Wink Start. In Immediate Start, there is no wink from the end that receives the call to signify that that is ready to accept digits.

IMT: Inter-Machine TrunkInter-Machine Trunk (IMT) is a connecting circuit between two automatic switching centers, both owned by the same company. For example, the trunk between two 4ESS machines of the same ILEC is an IMT.

INB: Install BusyInstall Busy (INB) is a status of operation in many systems. For example, INB may indicate a maintenance operation of the signaling channel during which, apart from this channel not being available for signaling, the configuration parameters (mostly ds0 characteristics of this interface) can be changed. The implementor may chose to just use the busy state as a superset state instead of inB in which case this state will be rendered redundant.

In-Band SignalingInband (In-Band) Signalling, also known as robbed-bit signalling, is a type of signalling in which metadata and control information is sent in the same channel used for data. For example, a line uses 8 kbps of each 64 kbps channel for WAN synchronization and signalling. The remaining 56 kbps handle the transmission of user data. T1 access lines containing one or more switched channels, and Switched-56 lines use inband signalling.

Indication of Camp-OnIndication of Camp-On is an audible tone generated by the telephone system. Attendant camp-on service allows an electronic switching system Centrex attendant to hold incoming calls to busy lines. Each time the attendant releases his/her talking connection from the loop involved in the camped-on call, the indication of camp-on tone is heard by the called customer if the customer has subscribed to the indication of camp-on option. The customer may get this tone several times as the attendant reconnects and releases from the loop in response to timed reminders from the console. Indication of Camp On tone is at 440 Hz and -13 dBm0/frequency for one second every time the attendant releases from the loop.

INE: Intelligent Network ElementIntelligent Network Element (INE) is a network element that can be provisioned from a remote Operation Support System (OSS).

INE: Intermediate Network ElementIntermediate Network Element (INE) refers to a line-unit-line termination (LULT) or a line-unit-network termination (LUNT)

INI: Inter-Network InterfaceInter-Network Interface (INI) refers to the point of demarcation in the network where two sub-networks meet when service is provided across multiple sub-networks.

In-Slot SignalingIn-slot Signaling is a signaling information periodically sent (in a digital time slot) that is permanently allocated in the (voice or data) channel time slot.

Intensity ModulationIntensity modulation refers to the form of modulation in optical communications in which the optical power output of a source is varied in accordance with some characteristics of the modulating signal.

Interactive MediaInteractive media refers to a newly designed telecommunications systems that permit two-way communications between televisions or computers in one location with software stored on a central computer. It's also possible to allow individuals in distant location to communicate, teach, or learn from one another.

Intercepting Loopback ToneIntercepting Loopback Tone is a steady High Tone sent from an intercept operator to the 'A' board operator in manual offices indicates that an intercept operator has completed the call and that the 'A' should disconnect from the circuit. The completion of intercepted calls in this manner is no longer recommended.

Interchange CircuitInterchange circuit refers to the circuit that facilitates the exchange of data and signaling

information between DTE (data terminal equipment) and DCE (Data circuit-terminating equipment).

IntercomIntercom, short for intercommunicating telephone, refers to an in-building electronic communications system. This communication system links different rooms within a building or ship etc.

Inter-Exchange TrunkInter-exchange trunk is the trunk between IECs which typically contains a 4ESS toll switch.

Interface StandardInterface standard refers to a standard in telecommunications that defines one or more functional and/or physical characteristics necessary to allow the exchange of information between two or more systems or equipments. An interface standard may include operational specifications and acceptable levels of performance.

Inter-LATA ServicesInter-LATA Services refers to revenues, functions, etc. that relate to telecommunications originating in one LATA and terminating outside that LATA.

Intermediate Cross ConnectsIntermediate Cross Connects refers to cross-connects located telecommunications closets within a premises distribution system.

Interoffice CallInteroffice Call is the telephone call that involves only one switching system. The two parties connected to the same local central office is an example.

Interoffice ChannelInteroffice Channel refers to: (1) In LEC (Local Exchange Carrier) tariffs, the channel connecting two serving wire centers located in two serving COs (Central Office). (2) In IXC (Interexchange Carrier) tariff, the channel connecting two serving IXC POPs (Point of Presence), interoffice transmission facilities used to connect LEC switching systems.

Intersymbol InterferenceIntersymbol interference refers to following definitions: (1) Destortion of the received sIntersymbol interference refers to following definitions: (1) Destortion of the received signal in a digital transmission system which distortion is manifested in the temporal spreading and consequent overlap of individual pulses to the degree that the receiver can not reliably distinguish between changes of state (i.e. between individual signal elements). (2) Extraneous energy from the signal in one or more keying intervals that interferes with the reception of the signal in another keying interval. (3) The disturbance caused by extraneous energy from the signal in one or more keying interval that interferes with the reception of the signal in another keying interval.

IntraLATAIntraLATA refers to a telephone call or circuit which does not cross a LATA boundary. IntraLATA communications require the use of an LEC, but not an IXC (intereXchange Carrier). IntraLATA telephone calls can still be long distance calls. In fact, because intraLATA long distance in the US is not subject to the same competitive market forces as interLATA long distance, intraLATA long distance calls normally cost much more than interLATA long distance.

Intra-Office TrunkIntra-Office Trunk is the trunk between two pieces of equipments within the same telephone central office.

IntrastateIntrastate, in telecommunication, refers to a call that remains entirely within the boundaries of a single state so that it falls under the jurisdiction of that state's telephone regulatory procedures.

Inverse MultiplexingInverse multiplexing is one of the multiplexing scheme in telecommunications. Not like the ordinary multiplexing which combines multiple signals into a single signal, inverse multiplexing speeds up data transmission by dividing a data stream into multiple concurrent streams that are transmitted at the same time across separate channels (like a T1 or E1 lines) and are then reconstructed at the other end back into the original data stream.

Inward TrunkInward Trunk is a trunk that is only for incoming calls. In another words, these trunks cannot be used for dialing out. An example of this is 800 lines.

IN-WATS: Inward Wide Area Telephone ServiceInward Wide Area Telephone Service (IN-WATS), similar to the 800 services, refers to service of interexchange carriers, such as formal AT&T, Sprint, local exchange carriers, independent phone companies, and long distance resellers in North America which allows subscribers to receive calls from specified areas and being charged for the call and with no charge to the calling party.

IOC: Independent Operating CompanyIndependent Operating Company (IOC) refers to the independently-owned company providing local telephone services to residential and business customers in a geographic area not served by a Reginal Bell Operating Company (RBOC).

IP CentrexIP Centrex is the Central Office Exchange Services (Centrex) for enterprises based on the IP telephony technologies. The traditional Centrex is a telephone switch service used by enterprises in which switching occurs at a central (local) office. In IP telephony, voice conversations can be digitized and packetized for transmission across the network. IP Centrex refers to a number of IP telephony solutions where Centrex service is offered to a customer who transmits its voice calls to the network as packetized streams across a broadband access facility.

IP-PBXThe IP-PBX is a telephone switch based on the VoIP technologies which is used by enterprises and located at the premises of a company and offers easier user administration and advanced applications. With an IP-PBX, the Local Area Network is the platform for connecting IP phones over a packet network to the call manager. This unifies the data applications and the voice network, but places demands on the packet prioritization aspects of the LAN infrastructure to ensure user satisfaction with the quality of audio.

ISC: International Switching CarrierInternational Switching Carrier (ISC) is an exchange which has the function of switching telecommunications traffic between the national network and the networks of other countries.

ISDN BRIAn ISDN Basic Rate Interface (ISDN BRI) is a type of ISDN interfaces that uses two B channels for user data, and one 16-kbps D channel for ISDN D-channel signalling. Both B channels can be switched; both channels can be nailed up; or one channel can be switched and the other nailed up. A line of this type can connect to standard voice service, Switched-56 data service, or Switched-64 data service.

ISDN D-Channel SignallingISDN D-channel Signalling is a type of out-of-band signalling in which a D channel handles WAN synchronization and signalling, and the B channels carry the user data. T1 PRI, E1 PRI, and ISDN BRI lines use ISDN D-channel signalling.

ISDN H-ChannelISDN H-Channel is a special, high-speed clear channel. H channels, designed primarily for full-motion color video, are not yet in common use. There are currently three kinds of H channel: H0 ("H-zero"), H11 ("H-one-one"), and H12 ("H-one-two"). An H0 channel operates at 384 Kbps (roughly one fourth of the North American Primary Rate Access or one fifth of a European Primary Rate Access). An H1 channel operates at 1.536 Mbps and occupies the whole North American Primary Rate Access. An H12 channel occupies the entire European Primary Rate Access.

ISDN PRI: ISDN Primary Rate InterfaceISDN Primary Rate Interface (ISDN PRI) is the ISDN configuration used primarily by large organizations with intensive communications needs. An ISDN PRI connection supports 23 64 kbps B-channels and one 64 kbps D-channel (or 23B+D) over a high speed DS1 (or T-1) circuit. The European PRI configuration is slightly different, supporting 30B+D.

ISDN: Integrated Services Digital NetworkIntegrated Services Digital Network (ISDN) is a system with digitized phone connections. For decades, telephony has used purely analogue connections. This is the first protocol to define a digital communications line that allows for the transmission of voice, data, video and graphics, at high speeds, over standard communication lines. The various media are simultaneously carried by bearer channels (B channels) occupying a bandwidth of 64 kbits per second (some switches

limit bandwidth to 56 kb/s). A defined data channel (D channel) handles signaling at 16 kb/s or 64 kb/s, depending on the service type.

Isochronous SignalIsochronous Signal is periodic signals in which the time interval that separates any two corresponding significant occurrences or level transitions is always equal to some unit interval or a multiple of that unit interval. For example, in digitized voice signals, ideally voice samples occur isochronously at precisely the sampling interval or frame rate. Packet data signals are not isochronous.

ISUA: SS7 ISUP-User Adaptation LayerSS7 ISUP-User Adaptation Layer (ISUA), an integral part of the OpenSS7 SIGTRAN stack, is an SS7 Signalling User Adaptation Layer for providing ISUP-User signalling over SCTP. ISUA is intended to be used on a Provider/User basis where ISUP resides on a Signalling Gateway (SG) and ISUP call control applications reside on an Application Server (AS).

ISUP: ISDN User PartThe ISDN User Part (ISUP), a key protocol in the SS7/C7 signaling system, defines the protocol and procedures used to set-up, manage and release trunk circuits that carry voice and data calls over the public switched telephone network (PSTN) between different switches. ISUP is used for both ISDN and non-ISDN calls.

ITC: Independent Telephone CompanyIndependent Telephone Company (ITC) is a local exchange carrier that is not one of the divested Bell-operating companies (there were 22 such companies before). ITCs are not generally subject to the restrictions of the MFJ (Modification of Final Judgment), although some of the large ones are bound by separate consent decrees. Southern New England Telephone and Cincinnati Bell are generally considered ITCs from a regulatory point of view.

ITSP: Internet Telephone Service ProviderInternet Telephone Service Provider(ITSP) refers to the company who provides "voice Over IP" services.

ITU: International Telecommunication UnionInternational Telecommunication Union (ITU) is an organization established by the United Nations to set international telecommunications standards and to allocate frequencies for specific uses.

ITU-T: International Telecommunication Union Telecommunication Standardization SectorInternational Telecommunication Union Telecommunication Standardization Sector (ITU-T) is an international body under the International Telecommunication Union (ITU) that develops worldwide standards for telecommunications technologies. The ITU-T carries out the functions of the former CCITT.

IUA: ISDN Q.921-User Adaptation LayerISDN Q.921-User Adaptation Layer(IUA), a protocol in the SIGTRAN protocol suite, defines a method for backhauling of ISDN Q.921 User messages over IP using the Stream Control Transmission Protocol (SCTP). IUA is used between a Signaling Gateway (SG) and Media Gateway Controller (MGC). It is assumed that the SG receives ISDN signaling over a standard ISDN interface.

IVR: Interactive Voice ResponseInteractive Voice Response (IVR) is a feature in a telephone system that provides information in the form of recorded messages over telephone lines in response to user input in the form of spoken words or, more commonly, DTMF signaling. Examples include banks that allow customer to check their balance from any telephone, and an automated stock quote system.

IXC: Inter-Exchange CarrierInter-Exchange Carrier (IXC) is a long-distance telephone company. The task of an IXC is to connect Local Exchange Carrier (LECs) and allow customers to place interLATA telephone calls.

Tele-Communication (Telecom) Terms Glossary and Dictionary - J K

JackJack is a connecting device usually in the wall into which a plug can be plugged to from a connection such as the telephone jack

JumperJumper may refer to the following things: (1) a wire that connects equipment and cable on a distributing frame in a telephone system. (2) when called as a jumper wire, it is a wire or connector used to establish a circuit for testing. (3) a metal bridge that connects parts of an electrical circuit that can be used to configure expansion boards. (4) an electrical switch consisting of a number of pins and a connector that can be attached to the pins in a variety of ways.

JunctionA junction is a point in the telecommunications network that comprises a switching office or facility cross-connect and/or ADM hardware, a point of connectivity where multiple fiber links come together, and/or a source or destination for a wavelength path.

JunctorJunctor refers to a connection or circuit, within a switching system, between inlets and outlets of the same or different switching networks. An interoffice trunk is an example of junctor.

Junctor Trunk GroupJunctor Trunk Group is a special-purpose trunk group providing a particular feature such as coin control, billing supervision, etc.

JurisdictionJurisdiction refers to, in telecommunication, a geographic area presided over by the same regulatory body, within the boundary of a single state or an area in which a common carrier is authorized to provide telephony service.

Key PulsingKey Pulsing is a method of signaling by depressing keys on a line otherwise arranged for rotary pulse dialing.

Key Station LineKey Station Line refers to the circuit which extends from the key set to the key system common equipment.

Key SystemKey System refers to a group of associated key sets and common equipment located on a customer's premises and connected to provide various features accessible to a key set.

Key Telephone SetKey Telephone Set refers to a telephone instrument with keys or buttons which are used to select a specific line from several possible incoming lines. Those buttons usually have lamps and can provide features such as call holding, line status, signaling, conferencing and intercom.

Key Telephone SystemKey Telephone System refers to a multi-line telephone system that is typically adopted and installed in small business or office environments. Key telephone system is good for its expandability and the individual line selection buttons for each connected phone line.

Tele-Communication (Telecom) Terms Glossary and Dictionary - L

LabelLabel, in telecommunication, is one type of information contained in a signaling message that is used to identify the particular circuit, call, or management transaction to which the message is related.

LAMA: Local Automatic Message AccountingLocal Automatic Message Accounting (LAMA) refers to a set of automatic message accounting equipment and automatic number identification equipment in the central office of local telephone company used for the billing of local phone calls.

LAPB: Link Access Procedure, BalancedLink Access Procedure, Balanced (LAPB) is a data link layer protocol used to manage communication and packet framing between data terminal equipment (DTE) and the data circuit-terminating equipment (DCE) devices in the X.25 protocol stack. LAPB, a bit-oriented protocol

derived from HDLC, is actually the HDLC in BAC (Balanced Asynchronous Class) mode. LAPB makes sure that frames are error free and properly sequenced.

LAP-D: Link Access Procedure, D-ChannelLink Access Procedure, D-Channel (LAP-D), a Layer 2 protocol in the ISDN suite, is used to do call setup and other signaling over the D Channel. Data transmissions take place on B channels. LAP-D is almost identical to the X.25 LAP-B protocol. LAPD is defined in the ITU Q.921 protocol.

LAPF: Link Access Procedure for Frame Mode ServicesLink Access Procedure for Frame Mode Services (LAPF), as defined in ITU Q.922, is an enhanced LAPD (Q.921) with congestion control capabilities for Frame Mode Services in the Frame Relay network. LADF is used in the Frame Relay network for end-to-end signaling. LAPF conveys data link service data units between DL-service users in the User Plane for frame mode bearer services across the ISDN user-network interface on B-, D- or H-channels.

LAP-H: Link Access Procedure for H-ChannelLink Access Procedure for H-Channel (LAP-H) performs the same function as B-Channel (LAPB) but operates at rates exceeding DS-0 (64 Kbps). The H-Channel is good for fast facsimile, video, high-speed data, high-quality audio, and multiple info streams at lower data rates.

LAP-M: Link Access Procedure for ModemsLink Access Procedure for Modems (LAP-M) is the data link protocol used by V.32 error-correcting modems. When two LAPM modems establish a session, they transmit data in frames using bit-oriented synchronous techniques. An attached computer still sends data to the LAPM modems as standard asynchronous input, but the modem transmits it as frames.

LAPS: Link Access Procedure-SDHLink Access Procedure - SDH (LAPS), a variant of the original LAP protocol, is an encapsulation scheme for Ethernet over SONET/SDH. LAPS includes data link service and protocol specification used in transporting IP packets over SDH networks. LAPS provides a point-to-point unacknowledged connectionless service over SONET/SDH. LAPS enables the encapsulation of IPv6, IPv4, PPP, and other higher-layer protocols. X.86 Defines Ethernet over LAPS.

LASS Code: Local Area Signaling Services CodeLocal Area Signaling Services (LASS) Codes are numbers that customers enter on their telephone tough-pad to access special features of the telephone system. The most well-known LASS codes are *67 to toggle Caller-ID blocking and *69, for Last Call Return.

LASS: Local Area Signaling ServiceLocal Area Signaling Service (LASS) is a group features provided by virtually all switches of central offices that uses existing customer lines to provide some extra features to the end user or business user. Those features are based on delivery of calling party number via the local signaling network. Local CCS7 (Common Channel Signaling Seven) is required for all

configurations. Typical features of LASS are (1) Automatic Callback, (2) Automatic Recall, (3) Customer-Originated Trace.

Last Choice RouteLast Choice Route refers to the routing algorithm that is the last-choice group trunk group (or a series of last-choice trunk groups) between two switching systems.

Last MileLast Mile, also known as the first mile, refers to the final phase or construction to deliver or complete connectivity from a communications provider to an end customer. The last mile communications providers are usually the telecommunications and cable television service providers. "Last mile" is typically seen as an expensive challenge because that "fanning out" all the wires and cables is a considerable physical undertaking.

Last Mile TechnologyLast-mile technology refers to the telecommunications technologies that provide connection services to and from the home or business. The typical last-mile technologies include xDSL, Cable and cable modem access (DOCSIS), wireless access (802.16), and optic fiber and its transmission technologies.

LATA: Local Access And Transport AreaLocal Access And Transport Area (LATA) refers to the areas within which the Bell Operating and independent telephone companies can provide telephony services. Inter-LATA connections must be provided by Interexchange or long-distance carriers. This was created by the 1984 divestiture and defines a geographic area in which a local exchange carrier, or LEC provides services or connectivity. Traffic that crosses from one LATA to another is the exclusive domain of the IXC. The 358 LATA covers the Chicago area from roughly the Wisconsin state line to just South of Kankakee, and just West of Aurora and Ottawa to Lake Michigan and the Indiana state line.

LCV: Line Code ViolationLine Code Violation (LCV) is an error event in the occurrence of either a Bipolar Violation (BPV) or Excessive Zeroes (EXZ) Error Event on a DS1/T1 interface.

LDN: Listed Directory NumberListed Directory Number (LDN) is an organization's main telephone number that appears in the telephone book.

Leased LineLeased Line is a permanent telephone connection between two points set up by a telecommunications common carrier. Typically, leased lines are used by businesses to connect geographically distant offices. Unlike normal dial-up connections, a leased line is always active. The fee for the connection is a fixed monthly rate. The primary factors affecting the monthly fee are distance between end points and the speed of the circuit. Because the connection doesn't carry anybody else's communications, the carrier can assure a given level of quality. For example, a T-1 channel is a type of leased line that provides a maximum transmission speed of

1.544 Mbps. You can divide the connection into different lines for data and voice communication or use the channel for one high speed data circuit. Dividing the connection is called multiplexing. Increasingly, leased lines are being used by companies, and even individuals, for Internet access because they afford faster data transfer rates and are cost-effective if the Internet is used heavily.

LEC BillingLEC Billing is arrangement whereby the LEC (Local Exchange Carrier) invoices the customer for some of all telecommunications services.

LEC CardLEC Card (Local Exchange Carrier Card) is the billing arrangement which enables the caller to bill calls to an authorized calling card issued by a LEC (Local Exchange Carrier)

LEC ChargesLEC Charges refers to charges that are the responsibility of the LEC (Local Exchange Carrier).

LEC: Local Exchange CarrierLocal Exchange Carrier (LEC) is, as its name reveals, a telephone company providing local telephone service.

LERG: Local Exchange Routing GuideLocal Exchange Routing Guide (LERG) refers to a documents end of offices and their relationship to Tandem Offices produced by Bellcore Traffic Routing Admin (TRA)

LH: Line HuntingLine Hunting (LH) is a feature in telephony, also called multi-line hunting, that allows multiple telephone lines going into a business or promises to all act as a single group, called a hunting group (or multi-line hunting group). If the line called is busy, the call will be forwarded to the next available line. Only if all the lines in the group are busy, the calling party will get a busy signal.

Line Busy ToneThe Line Busy Tone indicates that the called customer's line has been reached but that it is busy or being rung or on permanent signal. When a line busy signal is applied by an operator, it is sometimes called a busy-back tone. Line Busy Tone is Low Tone on and off every 0.5 seconds.

Line CodeLine Code refers to a code in telecommunication that is chosen for use within a communications system for transmission purposes. A line code will typically reflect technical requirements of the transmission medium, such as optical fiber or shielded twisted pair. These requirements are unique for each medium, because each one has different behaviors related to interference, distortion, capacitance and loss of amplitude.

Line EquipmentLine Equipment refers to the telephony equipment located in a central office and associated with

a particular line. This includes a line relay or equivalent that is activated when the customer's telephone is off-hook.

Line FinderLine Finder is a component of a switch which locates an idle line and connects it to the line requesting service.

Line LinkLine Link refers to the input side of the switching network in the Number 5 Crossbar system.

Line Load ControlLine Load Control refers to a control process that limits the number of customers who can obtain dial tone in telephony system.

Line NoiseLine Noise refers to a noise originated in a transmission path of telephony system.

Line NumberLine Number refers the 4-digit XXXX number assigned to a North American telephone within a NXX exchange.

Line RelayLine Relay refers to relay equipment associated with a customer's line that is used to alter the switching of a demand for service for that line. It can also be used to deny incoming access to a line already in use.

Line SegmentLine Segment is the expanse of fiber-optic cable(s) between 2 network locations.

Line SignalingLine Signaling is a signaling method for transmitting signaling traffic between equipment to terminate and continuously monitor part or all of the traffic circuit. For example, supervisory signaling between exchanges provides the busy, idle, or out-or-service status of circuits.

Line SpeedLine Speed is the maximum rate of transmission at which signals may be transmitted over a given channel. It is usually measured in Baud or Bits per second.

Line TurnaroundLine Turnaround is the time required to change data transmission direction on a telephone line.

Linear DistortionLinear Distortion refers to, in the telecommunications system, the undesirable changes in the amplitude of a transmitted signal due to imperfections in the transmission path.

Link-by-Link SignalingLink-by-link Signaling is a signaling scheme, in which signaling messages are transmitted "one link at a time" in a multi-link connection. The network performs processing at each intermediate switching point for subsequent transmission. In the SS7 system, Link-by-link Signaling is the procedure used to exchange signaling messages between two Signaling Points (SPs) that are either directly connected to each other, or are connected via STPs (Signaling Transfer Point).

LLU: Local Loop UnbundlingLocal Loop Unbundling (LLU) is the process used in telecommunication to allow operators to use the twisted pair telephone connections from the central offices of telephone exchange to the customer premises. This local loop is owned by the incumbent local exchange carrier.

LNP: Local Number PortabilityLocal Number Portability(LNP) refers to the feature that was defined in the Telecommunications Act of 1996 as the "ability of users of telecommunications services to retain, at the same location, existing telecommunications numbers without impairment of quality, reliability, or convenience when switching from one telecommunications carrier to another." The Telecommunications Act mandates that all telecommunications service providers (wireline and wireless) provide, to the extent technically feasible, number portability in accordance with the requirements prescribed by the Commission.

LoadLoad refers to, in telecommunications system, a volume of traffic that equals the sum of the holding times for a number of calls or attempts. Loads are normally measured in CCS or ERLANGS. A statement of load is inherently an average of all of the instantaneous loads over a basic time interval such as an hour.

Load BalancingLoad Balancing generally refers to distributing processing and communications activity evenly across a computer network so that no single device is overwhelmed. In routing, it means the ability of a router to distribute traffic over all its network ports that are the same distance from the destination address. Load balancing increases the utilization of computers and network bandwidth. In Web services, load balancing scheme is also applied by employing two or more Web servers. If one server starts to get swamped, requests are forwarded to another server with more capacity.

Load CoilLoad Coil is an inductance coil installed at regular distances along a telecommunications transmission line to improve the transmission characteristics of the line over the range of voice frequencies. It's also called Loading Coil.

Loaded LinesLoaded Lines is a transmission line that has had load coils installed in series with each conductor, usually at definite spaced intervals. A common plan used in the U.S. is 88 millihenry coils installed at 6000 foot intervals.

Local Access MileageLocal Access Mileage refers to a recurring charge rate element for dedicated (non-switched) private lines that are based on mileage to the Central Office.

Local ChannelLocal Channel is: (1) in LEC (Local Exchange Carrier) tariff, the local loop that connects customer premises to serving LEC wire centers. (2) in tariff, the network components (transmission, switching, etc.) used to connect customer premises to serving IXC POPs (Point Of Presence).

Local Exchange LoopLocal Exchange Loop refers to the interconnection between customer premises equipment and telephone central office

Local LoopLocal Loop is the line from the premises of a telephone subscriber to the telephone company CO.

Long-Haul CommunicationsLong-haul communications refer to the following meanings: (1) Pertaining to circuits that span large distance, such as the circuits in interLATA, interstate, and international communications. (2) communications among users on a national or worldwide basis in the military community. Compared to tactical communication, Long-haul communications are characterized by higher levels of users, such as the National Command Authority, or more stringent performance requirements, such as higher quality circuits. etc.

Longitudinal VoltageLongitudinal voltage refers to a voltage in telecommunications system induced by or appearing along the length of a transmission medium.

LoopLoop, in telecommunications, is a pair of phone numbers, usually consecutive, like 836-9998 and 836-9999. They are used by the phone company for testing.

Loop LengthLoop Length is a complete electrical circuit. In telecommunication, it typically refers to the pair of wires that winds its way from the central office to the telephone set or system at the customer's premises.

Loop Start SignalingLoop Start Signaling, also known as loop signaling or loop start, is a method of signaling in telephony where a DC closure is applied to a phone line (loop), and the start of DC current flow indicates a change from on-hook to off-hook.

Loop Transmission FacilitiesLoop Transmission Facilities refer to telephony equipment that connects switching systems to customer premises equipment throughout the serving area.

Loop-Start TrunkLoop-start Trunk, also called POTS line and plain-service line, is a two-wire central-office trunk or dial-tone line that recognizes off-hook status when a telephone switch hook puts a 1000-ohm short across the tip and ring as the handset is lifted.

Low ToneLow Tone is a generic tone used with various interruption patterns for the specific tones. Low Tone is 4800 Hz and 620 Hz at -24 dBm0/frequency. On some systems manufactured before 1974, Low Tone was 600 Hz modulated at 120, 133, 140 or 160 Hz at 61-71 dBmc. The following are a list of specific Low Tones: Line Bust Tone, Reorder, Reverting Tone, No Circuit Tone, No Such Number, Vacant Code, Group Busy Tone, Deposit Coin Tone, Dial Off-Normal Tone, Trouble Tone, Dial Jack Tone, Dial Test Signal, Class of Service.

Low-Density Parity-Check CodeLow-density parity-check code is an error correcting code used in a method of transmitting information over a noisy transmission path. Low density parity check (LDPC) codes were introduced along with an iterative probability-based decoding algorithm by Gallager in the early 1960's. These codes were constructed using sparse random parity check matrices and showed promising distance properties. However, they went largely unnoticed until the advent of turbo codes, where they were “rediscovered†by MacKay, who showed that they perform almost �as close to capacity as turbo codes. More recently, Richardson and Urbanke have developed irregular LDPC codes that perform even better than turbo codes for very large block lengths (n>10^5) and can come within 0.1 dB of the Shannon capacity.

LPC: Linear Predictive CodingLinear Predictive Coding (LPC) is a speech encoding scheme that uses periodic pulses to excite a filter, similar to the way human voice is produced. The code is predictive in that it uses knowledge of past data (represented as vectors) to predict future values in a feed forward manner. It is a speech analysis technique as well as a method for encoding good quality speech at a low bit rate. It provides accurate estimates of speech parameters, and is relatively efficient for computation.

LPF: Low-Pass FilterLow-pass Filter (LPF) is a filter that low frequencies can be tranmited well and frequencies higher than the cutoff frequency is attenuated or reduced. It's sometimes called a high-cut filter for that reason.

LRC: Longitudinal Redundancy CheckLongitudinal Redundancy Check (LRC) is an error checking method that generates a parity bit from a specified string of bits on a longitudinal track. In a row and column format, such as on magnetic tape, LRC is often used with VRC, which creates a parity bit for each character.

LSRR: Loose Source and Record RouteLoose Source and Record Route (LSRR) is an option that provides a means for the source of an internet datagram to supply routing information to be used by the gateway in forwarding the datagram to the destination, and to record the route information.

LSSU: Link Status Signal UnitLink Status Signal Unit (LSSU) is an SS7 message that carries one or two octets (8-bit bytes) of link status information between signalling points at either end of a link. It is used to control link alignment and to provide the status of a signalling point (such as a local processor outage) to the remote signalling point.

LT: LATA TandemLATA Tandem (LT) is a BOC (Bell-operating Company) switching system that provides an intraLATA traffic concentration/distribution point for EO (End Office) switching systems or other tandems within a LATA.

LTB: Last Trunk BusyLast Trunk Busy (LTB) refers to a measurement of the number of times the last trunk in a trunk group was busy during measurement period.

LTCCS: Last Trunk CCSLast Trunk CCS (LTCCS) refers to the load in CCS carried on the last trunk in a high usage trunk group.

LTE: Line Terminating EquipmentLine Terminating Equipment (LTE) refers to a device in a telecommunication network system that originate and /or terminate line signals. LTEs can originate, access, modify, or terminate the transport overhead, or can perform any combination of these actions.

Tele-Communication (Telecom) Terms Glossary and Dictionary - M

M Plane: Management PlaneManagement Plane(M Plane) refers to one of the three entities in the ATM reference model. The M plane addresses the management functions of network elements such as switches for their Operation, Administration and Maintenance (OA&M). The other two entities are user plane for the actual data transmission and the control plane for signaling. The concept and model of user plane, control plane and management plane have been extended to other telecommunication technology groups beyond the ATM technology.

M2PA: MTP2 Peer-to-peer user AdaptationMTP2 Peer-to-peer user Adaptation layer (M2PA), a protocol in the SIGTRAN protocol suite, enables SS7 signaling messages over IP using Stream Control Transmission Protocol (SCTP). M2PA is intented to be used on a Peer-to-Peer basis and replace the functionality provided by a traditional SS7 link. M2PA is for an OpenSS7 Network Device.

M2UA: MTP2-User Adaptation layerMTP2-User Adaptation layer (M2UA), a protocol in the SIGTRAN protocol suite, is for backhauling of SS7 MTP2-User signaling messages over IP using Stream Control Transmission Protocol (SCTP). M2UA is intended to be used on a Provider/User basis where MTP Level 2

resides on a Signalling Gateway (SG) and MTP Level 3 resides on an Application Server (AS). It is not intended for peer-to-peer operation: that is, it is not intended to emulate a signalling link between two SCTP endpoints

M3UA: MTP3-User Adaptation layerMTP3-User Adaptation layer (M3UA), a protocol in the SIGTRAN protocol suite, supports transport of SS7 MTP3-User signaling over IP using Stream Control Transmission Protocol (SCTP). M3UA is intented to be used on a Provider/User basis where MTP Level 3 resides on a Signalling Gateway (SG) and MTP Users reside on an Application Server (AS).

Main FeederMain Feeder is the first facility cable coming from the central office. The feeder cable runs to cross connect points in the network where the second facility cable feeds are connected.

Main PBXMain PBX refers to the initial PBX that interfaces with the public telephone network via central office trunk lines.

Manual Ring-Down LineManuel Ring-Down Line is a number of phones connected together by a pair of wires and a talk battery.

MAP: Mobile Application PartThe Mobile Application Part (MAP), one of the protocols in the SS7 suite, allows for the implementation of the mobile network (GSM) signaling infrastructure. The premise behind MAP is to connect the distributed switching elements, called mobile switching centers (MSCs), with a master database, called the Home Location Register (HLR). The HLR dynamically stores the current location and profile of a mobile network subscriber. The HLR is consulted during the processing of an incoming call.

MAPOS: Multiple Access Protocol over SONET / SDHMultiple Access Protocol over SONET/SDH (MAPOS) is a protocol extension to SONET/SDH that has high performance, supports multiple access, broadcast and multicast transmission. MAPOS is connection-less, like IP, with simple design and seamless interconnectivity for LAN and WAN.

Marine TelephoneMarine Telephone is a radio telephone manufactured by Tellabs which the FCC gives certain frequencies. The marine telephone is not cellular; It will broadcast further and with greater power.

MasterMaster refers to the side in telecommunications that initiates and controls the session. The "slave" refers to the other end (side) that responds to the master's commands.

Maximal-Ratio CombinerMaximal-ratio Combiner is a diversity combiner in which: (a) the signals from each channel are added together, (b) the gain of each channel is made proportional to the rms signal level and inversely proportional to the mean square noise level in that channel, and (c) the same proportionality constant is used for all channels.

MCU: Multipoint Conferencing UnitMultipoint Conferencing Unit (MCU) is a device that menages a multipoint conference by connecting the multiple sites and stations in the same videoconference. The MCU can be used in conjunction with a Gateway to connect H.320 and H.324 videoconference end-points. The MCU combines video, audio and data streams from multiple conference end-points into one multi-location, interactive session.

MCU: Multipoint Control UnitMultipoint Control Unit (MCU) refers to a device in a telecommunication system that establishes conference calls between three or more people for converged voice, video and data conferences. Often referred to as a bridge, an MCU can provide audio-only services or any combination of audio, video and data, depending on the capabilities of each participant's terminal.

MD: Mediation DeviceMediation Device provides protocol translation and concentration of telemetry information originating from multiple network elements and transport to an Operations Support System (OSS).

MDC: Modification Detection CodeModification Detection Code (MDC) is synonym for manipulation detection code that is a bit string, in cryptosystems, that is a function of data to which it is attached for the purpose of manipulation detection. The resulting message (data plus MDC) may then be encrypted to achieve secrecy or data authentication. The function used to generate the MDC must be public.

Mechanical SpliceMechanical Splice refers to an alternative fiber-optic splice packaged as a kit, which connects the ends of fibers.

Mediation FunctionMediation function refers to a function in telecommunications network management, that routes or acts on information passing between network elements and network operations such as communication controls.

MEDR: Maximum Engineering Data RateMaximum Engineering Data Rate (MEDR) is a term primarily used by telephone companies to refer to the maximum data throughput supportable over targeted copper wire. MEDR is actually a theoretical measure of the amount of data throughput a line can handle, but does not necessarily refer to the amount of data available to the customer at the end of said copper wiring. The data throughput that can actually be presented to the end user is measured by AIDR or As Is Data Rate.

Mesochronous NetworkMesochronous network is a kind of telecommunication network in which the clocks of all nodes in the network run with the same frequency but unknown phases. Thus, all timing is exactly the same (truly synchronous).

MicrofilterMicrofilter is a device that prevents data noice from traveling over the telephone line and interfering with telephone calls. For example, a microfilter is a small device that plugs into the normal BT telephone socket and splits the line into both a standard BT telephone socket and a ADSL broadband socket. Failure to have a microfilter correctly installed on all BT socket you use may result in interference (buzzing noises etc.) on your telephone and/or reduced performance and possible loss of service on your broadband access. Also, in a burglar alarm that uses the telephone line, it is important to use a microfilter to reduce noice in the phone line.

MIC: Medium Interface ConnectorMedium Interface Connector (MIC) refers to the connector at the interface point between the bus interface unit and the terminal, i.e., the medium interface point.

MicronMicron is a unit of length measurement that is equal to 1/1000 of one millimeter or 1/25000 of an inch. Cladding and core of fiber optics are measured with this unit.

Mid-SpanMid-Span is a telephone service wire which runs from a pole to a hook attached to a cable strand, then to a house or building.

Mini ConnectorMini Connector refers to a physical connector utilized for PC and telecommunication hardware-interface applications.

Modal DispersionModal Dispersion refers to the behavior of individual light rays taking different paths as they travel down a fiber optic.

Modal LossModal Loss refers to the attenuation of a light signal as it moves through a fiber optic because of tight bends.

ModemModem, a word constructed from modulator and demodulator, is a device or program that enables a computer to transmit data over, for example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves. Modem translates information between analog and digital world.

Modular AdapterModular Adapter is a mechanism used to interconnect one wire/cable type to another, without using termination blocks.

Modular JackModular Jack is a kind of jack or connector which is equipped with a plug so that devices can be simply attached or detached.

MOS: Mean Opinion ScoreMean Opinion Score (MOS) is a method of providing a numerical measure of the quality of human speech at the destination end of the circuit typically in voice telecommunications particularly internet telephony. The scheme uses subjective tests (opinionated scores) that are mathematically averaged to obtain a quantitative indicator of the system performance.

MSLT Adjustment: Minimum Scan Line Time AdjustmentMinimum Scan Line Time (MSLT) Adjustment is an alternative to Scan Line Fix Up meant to eliminate fax failures caused by an excessive number of received page errors because of data loss. MSLT adjustment sets a minimum MSLT value that an ingress gateway communicates to a sending fax machine. This value overrides an MSLT of lesser value that is supplied by a receiving fax machine.

MSLT: Minimum Scan Line TimeMinimum Scan Line Time (MSLT) is the time set by the receiving fax machine and sent to the sending machine during the initial handshaking. MSLT defines how much time the receiving machine requires to print a single scan line.

MSDSL: Multi-Rate Symmetric DSLMulti-rate Symmetric DSL (MSDSL) refers to a DSL (Digital Subscriber Line) with a maximum distance of 8,800 m or 29,000 ft. It is capable of multiple transfer rates, as set by the internet service provider, typically based on the service and/or price. The maximum speed in both download and upload directions is 2 Mbit/s.

MSN: Multiple Subscriber NumberMultiple Subscriber Number (MSN) is an incoming call routing method in which a group of phone numbers is assigned to a particular PRI ISDN line by the telephone company. A PRI ISDN line is usually assigned multiple numbers in the US and in Europe.

MSO: Multiple Service OperatorMulti-Services Operator (MSO) is a service provider which provides multiple services such as voice (mobile and fixed line), data and video. Very often, a cable service provider is a MSO.

MSO: Multiple Systems OperatorMultiple Systems Operator (MSO) is a term used to describe cable operators that own more than one franchises.

MSTE: Multiplex Section Terminating EquipmentMultiplex Section Terminating Equipment (MSTE) refers to the element that terminates a SDH (Synchronous Digital Hierarchy) multiplex section.

MSU: Message Signal UnitMessage Signal Unit (MSU) is an SS7 signal unit that contains service information and signaling information fields and is retransmitted by the signaling link control if it is received in error. The value of a length indicator is always greater than 2.

MTIE: Maximum Time Interval ErrorMaximum Time Interval Error (MTIE) is the maximum error for all possible measurement intervals within the measurement period.

MTP: Message Transfer PartMessage Transfer Part (MTP), a protocol in the SS7/C7 protocol suite, transfers signal messages and performs associated functions, such as error control and signaling link security. Message Transfer Part (MTP) also provides reliable routing within a network. MTP has has three layers: Layers 1 (physical), 2 (data), and 3 (network).

MTP1: Message Transfer Part Level 1Message Transfer Part Level 1 (MTP1), a SS7 physical layer unit, defines the physical, electrical, and functional characteristics of the digital signaling link.

MTP2: Message Transfer Part Level 2Message Transfer Part Level 2 (MTP2) is the signalling protocol at the data link layer of SS7/C7 protocol suite. MTP2 provides error detection, sequence checking, and initiates retransmission in case of erroneous reception of messages. MTP Level 2 uses packets called signal units to transmit SS7 messages. There are three types of signal units: Fill-in Signal Unit (FISU), Link Status Signal Unit (LSSU), Message Signal Unit (MSU).

MTP3: Message Transfer Part Level 3Message Transfer Part level 3 (MTP3) is the signalling protocol at the network layer of SS7/C7 protocol suite. MTP3 provides routing functionality to transport signaling messages through the SS7 network to the requested endpoint. Each network element in the SS7 network has a unique address, the Signaling Point Code (SPC). Message routing is performed according to this address.

MTS: Message Telecommunications ServiceMessage Telecommunications Service (MTS) is a non-private-line intrastate and interstate long-distance service that uses, in whole or in part, the PSTN (public switched telephone network).

MTS: Message Toll ServiceMessage Toll Service (MTS) is switched service, also called message service, furnished to the general public (as distinguished from private line service). This includes exchange switched services and all switched services provided by inter-exchange carriers and completed by a local telephone company's access services.

Mu-Law (μ-law)Mu-Law(μ-law) is the standard codec (compression/decompression) algorithm for pulse code modulation (PCM) from the CCITT (Consultative Committee for International Telephone and Telegraph). A companding (compression/expanding) method, mud-Law makes it possible to improve the signal-to-noise ratio without requiring the addition of more data. Mu-Law, as a term, was derived from μ-Law, because the Greek letter μ is pronounced myoo. The term is sometimes seen as u-Law, although the pronunciation remains the same. Mu-Law is used in the United States and Japan. The other type of codec algorithm, A-Law, is the standard used in Europe and elsewhere.

Multichannel Multipoint Distribution ServiceMultichannel multipoint distribution service is a broadcasting and communications service that operates in the ultra-high frequency (UHF) portion of the radio spectrum between 2.1 and 2.7 GHz. Multichannel multipoint distribution service is also known as wireless cable. It was conceived as a substitute for conventional cable television (TV). However, it also has applications in telephone/fax and data communications.

Multifrequency SignalingMultifrequency Signaling is an in-band signaling method that uses multi-tone signals to represent the signaling traffic. A Multifrequency Signaling contains two or more frequencies out of an "n" pre-determined frequency set. Multifrequency Signaling is also called Multifrequency Code Signaling .

Multilevel Precedence and PreemptionMultilevel precedence and preemption is a feature or service of telephone system that allows properly validated users to place priority calls. If necessary, users can preempt lower-priority phone calls. Precedence designates the priority level that is associated with a call. Preemption designates the process of terminating lower-precedence calls that are currently using the target device, so a call of higher precedence can be extended to or through the device. An authenticated user can preempt calls either to targeted stations or through fully subscribed time division multiplexing (TDM) trunks. This capability assures high-ranking personnel of communication to critical organizations and personnel during network stress situations, such as a national emergency or degraded network situations.

Multi-Level SignalMulti-level Signal refers to a digital signal which has (2N+1) voltage levels (e.g., +Nv, +(N-1)v, +(N-2)v,….,+1v, 0v, -1v, ……-(N-1)v, and -Nv).

Multiline TelephoneMultiline Telephone is a telephone that incorporates visual displays and switches (keys) that permit the station user to access more than one central office or other line and to perform other desired functions. Typical functions include answering or originating a call on a selected line, putting a call on hold, operating an intercom feature, a buzzer, etc. Displays can indicate busy, ringing and message waiting status.

MultimediaMultimedia refers to communication applications that use graphics, video, and audio in addition to text.

Multiple AccessMultiple access refers to the following definitions: (1) The connection of a user to two or more switching centers by separate access lines using a single message routing indicator or telephone number. (2) In satellite communications, the capability of a communications satellite to function as a portion of a communications link between more than one pair of satellite terminals concurrently. (3) in computer networking, a scheme that allows temporary access to the network by individual users, on a demand basis, for the purpose of transmitting information.

Multiple HomingMultiple homing refers to the following definitions: (1) In telephone systems, the connection of a terminal facility which may use a single directory number so that it can be served by one or several switching centers. (2) In telephone systems, the connection of a terminal facility to more than one switching center by separate access lines. Separate directory numbers are applicable to each switching center accessed.

MultiplexerA multiplexer, also known as mux or muldex, is a device that encodes information from two or more data sources (usually a power of two) into a single channel. The multiplexer has a single output, which has the same value as the selected data input. They are used in situations where the cost of implementing separate channels for each data source is more expensive than the cost and inconvenience of providing the multiplexing/demultiplexing functions.

MultiplexingMultiplexing is a technique of combining multiple channels over a transmission path and then recovering or de-multiplexing the separate channels at the receiving end. Using multiplexing, multiple logical signals can be transmitted simultaneously across a single physical channel. The multiplexing process may following one of the principles such as TDM, FDM, CDM, or WDM, etc. Multiplexing may take placing in software, where multiple threads of information streams are delivered to a device or process at the same time.

Multipoint VideoconferenceMultipoint Videoconference is one of the videoconference with more that two sites. The sites must connect via a video bridge.

Must-CarryMust-Carry is a US cable regulation, also called Must-Carry rules. Must-Carry mandate that cable companies carry various local and public television stations within a cable provider's service area. It originated in 1972 and designed to insure that local television stations did not lose market share with increased competition from cable networks competing for a limited number of cable channels, must-carry rules have, over time, been ruled unconstitutional and gone through numerous changes.

MVL: Multiple Virtual LineMultiple Virtual Line (MVL), a technology pioneered by Paradyne, enables service provider a quick and easy way to offer multiple services over phone lines. It's low power, 768 kb/s symmetrical data rate and bandwidth utilization technique make it a variation of DSL technology at its most basic level. A low power DSL alternative, Multiple Virtual Line works over twisted copper pair, requires a one-to-one modem connection and supports voice and data transmissions simultaneously. But Multiple Virtual Line technology is unique in several ways. For one, it works over untwisted copper pair. That eliminates installation problems at customer locations with unpredictable wiring configurations, and helps service providers reach a wider scope of subscribers.

Tele-Communication (Telecom) Terms Glossary and Dictionary - N

NAA: Next Available AgentNext Available Agent (NAA) is a scheme for selecting an agent to handle a call. The strategy seeks to maintain an equal load across skill groups or services.

Naked CallNaked Call refers to an incoming call that receives no greeting message and no call menus/flexible routing before it is routed into an ACD (Automatic Call Distribution) queues.

Naked DSLNaked DSL is a digital subscriber line without a PSTN (Public Switched Telephone Network) service. In other words, only a standalone DSL internet service is provided on the local loop. In regular DSL, a wire runs from the telephone switch to a POTS (Plain Old Telephone Service) splitter. The POTS splitter separates the DSL and voice bands and then a wire carrying both services runs from the splitter to the cable head, where it continues on to the customer on an outside plant. But Naked DSL the portion of cable from the switch to the POTS splitter is removed, therefore removing dial tone from the line.

NANP: North American Numbering PlanNorth American Numbering Plan (NANP) is the North American telephone number arrangement or the process for assigning 10-digit (3+3+4) North American telephone numbers, NPA-NXX-XXXX. NPA is the Area Codes, NXX is the Exchanges and XXXX is the Line Numbers.

National Access FeeNational Access Fee is a Federal tax placed upon telecommunication services provided by telephone companies.

National Information InfrastructureNational Information Infrastructure is the foundation that supports the Information Superhighway by setting national standards that make networks and appliances compatible.

NATO Phonetic AlphabetNATO phonetic alphabet is a common name for the international radiotelephony spelling alphabet which assigns code words to the letters of the English alphabet so that critical combinations of letters (and numbers) can be pronounced and understood by those who transmit and receive voice messages by radio or telephone regardless of their native language, especially when the safety of navigation or persons is essential. It is used by many national and international organizations. It is a subset of the much older International Code of Signals (INTERCO), which originally included visual signals by flags or flashing light, sound signals by whistle, siren, foghorn, or bell, as well as one, two, or three letter codes for many phrases. The same alphabetic code words are used by all agencies, but each agency chooses one of two different sets of numeric code words. NATO uses the normal English numeric words (Zero, One, with some alternative pronunciations), whereas the IMO uses compound numeric words (Nadazero, Unaone). The name NATO phonetic alphabet became widespread because the signals used to facilitate the naval communications and tactics of the United States and NATO have become global.

NCAS: Non-Call Associated SignalingNon-Call Associated Signaling (NCAS) is a signaling that is independent of an end-to-end bearer connection, including support for the functions of registration, authentication, and validation

NCP: Network Control PointNetwork Control Point (NCP) may have different meanings depending on the context. 1) In IBM SNA, it refers to a host-generated network control program ( ran on an IBM 3704, 3705 or 3745) that controls the operation of a communications controller. 2) In Virtual Private Network (VPN), it is a centralized database that stores a subscriber's unique VPN definition. Highly sophisticated, this database screens every call and applies call processing control in accordance with customer-defined requirements. 3) Within the AT&T signaling network, NCP is the process that sends routing requests to a Customer Routing Point (CRP).

NCT: Network Control and TimingNetwork Control and Timing (NCT) is a control link between a switching module (SM) and the communications module (CM) in a Lucent 5ESS switching system.

NEBS Level 1"NEBS Level 1", the lowest level of NEBS standard developed by Bell Labs for RBOC central office equipment, addresses the personnel and equipment safety requirements of GR-63-CORE and GR-1089-CORE. This is useful for getting prototypes into a lab trial. It's also a requirement that is imposed on Competitive Local Exchange Carriers (CLECs) in order for them to deploy equipment into an RBOC's network.

NEBS Level 2"NEBS Level 2", the second level of NEBS standard developed by Bell Labs for RBOC central office equipment, addresses equipment operability, but in a controlled environment. For example, equipment could be used in a data center, however, if the equipment performs non-critical operations it could be used under environmental extremes. Note that this level is very rarely used because it is ambiguous.

NEBS Level 3"NEBS Level 3", the highest level of NEBS standard developed by Bell Labs for RBOC central office equipment, means the equipment is ready to be installed in the carier class operational network for the long haul. The equipment will operate under the environmental extremes found in a central office. In a nutshell, the equipment meets all of the requirements of GR-63-CORE and GR-1089-CORE.

NEBS: Network Equipment Building SystemsNetwork Equipment Building Systems (NEBS) is the Bellcore requirement for equipment deployed in a central office environment of PSTN in North America. NEBS covers spatial, hardware, crafts person interface, thermal, fire resistance, handling and transportation, earthquake and vibration, airborne contaminants, grounding, acoustical noise, illumination, EMC, and ESD requirements.

Negative-acknowledge characterNegative-acknowledge character is a transmission control character sent by a station as a negative response to the station with which the connection has been set up.

Network ConvergenceNetwork convergence refers to using packet network to conduct voice (telephony), video and data services, and phasing out the traditional circuit switched PSTN (Public-Switched Telephone Network) gradually. The migration process from two separate data and voice to finally a complete converged packet network carrying both voice and data services may take decades to finish. The driving forces behind such migration are cost saving, operation efficiency and new services deployment.

Network Element Function BlockNetwork Element Function Block is a functional block that communicates with a telecommunications management network (TMN) for the purpose of being monitored, or controlled, or both.

Network IndicatorNetwork Indicator (NI) is the Sub-Service Field in the Signalling Information Octet (SIO) of the message signal unit that permits discrimination between national and international messages, when NI is: 0 = international, 1 = reserved, 2= national, and 3 = national spare.

Network Management CenterNetwork Management Center is the location where large or public telephone networks are supervised, monitored and preserved.

Network ServicesNetwork Services, in a telecommunication network, are specified sets of information transfer capabilities furnished to users between telecommunications network points of termination. Network services categories include access and transport, public and private, and switched and non-switched.

NEXT: Near-End CrosstalkNear-End Crosstalk (NEXT) is an error condition that can occur when connectors are attached to twisted pair cabling. NEXT is usually caused by crossed or crushed wire pairs. The error condition does not require that the wires be crushed so much that the conductors inside become exposed. Two conductors only need to be close enough so that the radiating signal from one of the wires can interfere with the signal traveling on the other. Most medium- to high-end cable testers are capable of testing for NEXT errors.

NGN: Next Generation NetworkNext Generation Network (NGN) is a broad term for an integrated network that will offer voice, data, video services over both wireline and wireless infrastructure. The technologies required for the NGN is evolving.

Night ServiceNight Service is an telecommunication element that allows the lines ringing into a company to be handled differently during specific times of the day.

N-ISDN: Narrowband ISDNNarrowband ISDN (N-ISDN) is the communication standards developed by the ITU-T for baseband networks. N-ISDN is based on 64-kbps B channels and 16- or 64-kbps D channels.

NNXNNX refers to the first three numbers used in a North American local telephone number (NNX-NXX-XXXX) before the use of "1" in direct distance dialing. These numbers are now designated as NXX, allowing local central offices to have numbers that look like area codes.

No Such Number ToneThe No Such Number Tone is one of the audible tones in telephone system. It tells the calling party to hang up, check the called number, and dial again. In modern systems, calls to unassigned or discontinued numbers will also be routed to a machine announcement system, such as 6A or 7A, which verbally supplies the required message. In some older offices, you could be routed to an intercepting operator. In some offices, reorder tone is returned in this condition..

No-Answer TransferNo-Answer Transfer is a telecommunication service feature (provided by some cellular carriers in combination with call-waiting) that automatically transfers an incoming cellular call to another phone number if the cellular subscriber is unable to answer.

Noise-LikeNoise-Like is a distortion or unwanted signal that usually is electromagnetic interference or ambient noise.

Non-Associated Mode SignalingNon-associated Mode Signaling is one of many signaling schemes. In Non-associated Mode Signaling, signaling messages involving two non-adjacent signaling points are conveyed

(between those signaling points) over two or more signaling links in tandem that passes through one or more STPs (Signaling Transfer Part).

Non-Switched LineNon-Switched Line refers to: 1. a connection between computers or devices that do not have to be established by dialing. 2. a dedicated line.

NPA RoutingNPA Routing refers to the routing of calls based on the originating ANI (Automatic Number Identification) NPA (area code).

NPA SplitNPA Split refers to the telephone numbering scheme that subdivides an area code, with the creation of a new area code. This is necessary when the number of telephones in an area code (NPA) grows to an excessive number.

NPA: Numbering Plan AreaNumbering Plan Area (NPA) refers to North American "Area Codes." It is the first 3 digits of a phone number: 2-to-9, 0-to-9, 0-to-9.

NPA-NXX RoutingNPA-NXX Routing refers to Area Code / Exchange Routing. Route calls are based on the originating ANI NPA-NXX.

NRZ: Non-Return-to-ZeroNon-Return-to-Zero (NRZ) is a binary code in telecommunication system, in which "1s" are represented by one significant condition and "0s" are represented by another, with no neutral or rest condition, such as a zero amplitude in pulse amplitude modulation (PAM), zero phase shift in phase-shift keying (PSK), or mid-frequency in frequency-shift keying (FSK). The pulse has more energy than a RZ (Return-to-Zero) code, but it does not have arrest state, which means a synchronization signal must also be sent alongside the code.

NRZI: Nonreturn to Zero InvertedNonreturn to Zero Inverted (NRZI) is the signal that maintains constant voltage levels with no signal transitions (no return to a zero-voltage level) but interpret the presence of data at the beginning of a bit interval as a signal transition and the absence of data as no transition.

NS/EP TelecommunicationsNS/EP telecommunications, short for National Security or Emergency Preparedness telecommunications of the US, are the tlecommunications services that are used to maintain a state readiness or to respond to and manage any event or crisis (it could be local, national, or even international) that causes or could cause injury or harm to the population, damage to or loss of property, or degrade or threaten the national security or emergency preparedness posture of the United States. NS/EP telecommunications in the United States are managed and controlled by the National Communications System using Telecommunications Service Priority through both the Government Emergency Telecommunications Service and Wireless Priority Service.

NSAPI: Network Service Access Point IdentifierNetwork Service Access Point Identifier (NSAPI) is an index to the PDP (Packet Data Protocol) context that is using the services provided by the lower layer (SNDCP (Sub Network Dependent Convergence Protocol)). One PDP may have several PDP contexts and Network Service Access Point Identifiers.

NSP: Network Service ProviderNetwork Service Provider(NSP) is a company which provides telecommunication services with their own or leased equipment.

NT-1: Network Termination 1Network Termination 1 (NT-1) is a device based on ISDN that provides the interface between customer premise equipment and central office switching equipment.

Null ModemNull modem is a communication method to connect two DTEs (computer, terminal, printer etc.) directly using a RS-232 serial cable. The original RS-232 standard only defined the connection of DTEs with DCEs i.e. modems. With a null modem connection the transmit and receive lines are crosslinked. Depending on the purpose, sometimes also one or more handshake lines are crosslinked. Several wiring layouts are in use because the null modem connection is not covered by a standard. Null modems are commonly used for file transfer between computers, or remote operation.

Number Check ToneNumber Checking Tone is a steady High Tone. It is sometimes used at DSA switchboards in No. 1 crossbar and some step-by-step areas to verify the verbal identification of the calling line. On some older systems, Number Checking Tone was a steady 135 Hz tone.

NXXNXX refers to Exchanges in North American telephone numbering scheme that is the first 3 digits of a 7-digit phone number (2-to-9, 0-to-9, 0-to-9) and digits 4, 5 and 6 in a 10 digit NANP (North American Numbering Plan) telephone number - NPA-NXX-XXXX.

Tele-Communication (Telecom) Terms Glossary and Dictionary - Numbers

μ-law (Mu-Law)μ-law(Mu-Law) is the standard codec (compression/decompression) algorithm for pulse code modulation (PCM) from the CCITT (Consultative Committee for International Telephone and Telegraph). A companding (compression/expanding) method, mud-Law makes it possible to improve the signal-to-noise ratio without requiring the addition of more data. Mu-Law, as a term, was derived from μ-Law, because the Greek letter µ is pronounced myoo. The term is sometimes seen as u-Law, although the pronunciation remains the same. Mu-Law is used in the United States and Japan. The other type of codec algorithm, A-Law, is the standard used in Europe and elsewhere.

114 Service114 is the directory assistance service number in China. It is similar to the 411 service in the United States.

119 Service119 is the official national emergency number in China. It is similar to the 911 service in the US.

110 Block110 Block is a punch-down block used to connect wiring for telephone systems, data network wiring, and other low-voltage wiring applications. The 110 Block improves on the 66 Block by supporting higher frequencies and using space more efficiently.

1A1A is the first generation of standardized key telephony system developed and used by former AT&T.

1A-ESS1A-ESS refers to the Electronic Switching System of former AT&T that uses 1A processor. The 1A processor uses stored programs, and operates in a real time environment.

1PSS1PSS refers to the Packet Switching System of former AT&T using X.25 protocol.

2500 Set2500 Set refers to the single line desk telephone set using touchtone pad.

2B+D2B+D is a simple way to say ISDN's Basic Rate Interface. 2B means two bearer channels and D refers to  one data channel.

2B1Q: 2 Binary 1 Quaternary2 Binary 1 Quaternary (2B1Q)  is a full duplex physical layer encoding method used in ISDN and other digital communication technologies.  In 2B1Q, two binary bits are encoded into one quaternary signal, doubling the effectiveness of transmission.

2VSB: 2-level Vestigial SideBand modulation2-level Vestigial SideBand  modulation (2VSB) is a type of  modulation that is capable of transmitting one bit at a time.

2-wire Facility2-wire Facility refers to a telecommunication facility or equipment which supports transmission in two directions simultaneously. An ordinary telephone set is an example of 2-wire Facility.

411 Service411 service is for local directory assistance in the United States and Canada. In recent years, 4-1-1 has been used for long distance directory assistance in most areas of the United States. 

4B/3T4B/3T, also known as MMS43 code, is a type of line encoding method for ternary block encoding of binary signals, where four binary elements (binary block 4B) are represented as three ternary elements (ternary block 3T). 4B/3T encoding uses a matrix that maps each of the 16 bit patterns to 4 bits of the ternary signals. Four different ternary sequences are mapped to each 4 bit word. This encoding method is used by the ISDN Basic Rate Interface as a transmission method. 4B/3T encoding is also used in the exchange area between the ISDN exchange and the network terminator. The ternary representation of the data stream supports data rates of 160 kbit/s at a clock speed of 120 kbit/s. This allows for a maximum distance of 8 km between the network terminator and the ISDN exchange.

4ESS Switch4ESS Switch is the world€™s first digital electronic switch developed by Lucent Technologies (formerly AT&T). The first 4ESS Switch was installed in 1976 in Chicago. 4ESS was mainly used in toll offices in the former AT&T PSTN.

4-wire Facility4-wire Facility refers to a telecommunication facility or equipment which uses separate wiring for transmitting and receiving data. This means the transmission can only be carried in one direction. A lightwave carrier system is a four-wire Facility. 

4WL-WDM:  Four-Wavelength Wave Division Multiplexing Four-Wavelength Wave Division Multiplexing  (4WL-WDM) is  type of multiplexing introduced in 1996 by MCI Communications Corp, also known as Quad-WDM. It allows a single fiber to accommodate four light signals instead of one, by routing them at different wavelengths through the use of narrow-band wave division multiplexing equipment.

500 Service500 Service refers to the telephone service as 1-500-xxx-xxxx. The 500 in the dialing code 1-500-xxx-xxxx is a non-geographic area code. It is designed specifically for Personal Communication services (PCS). 500 Service provides for Follow-Me service by allowing you to specify which telephone facility you want the incoming call to be routed to depending where you are and some other criteria of your choice.

500 Set500 Set is the old rotary telephone set. 500 Set was the standard desk-top style telephone set used by former AT&T in North America from the late 1940s through the divestiture of AT&T in 1984.  There are many of such phones still in use today and supported by telephone systems.

50-Pin Telco50-Pin Telco, also known as RJ21, is a connector very common in 10BASE-T wiring. As opposed to the RJ45 connector, the 50-pin Telco connector concentrates up to 12 UTP connections onto one connection. This concentration of UTP ports is then broken out for connection to a punch-down block inside a building's wiring closet. 50-pin Telco connections provide a very clean, uncluttered interface to the building's wiring. 50-Pin Telco is used to attach

25 pairs of telephone wires. It is also used for SCSI-1 connections and is the 50-pin version of the widely-used centronics connector found on the back of PC printers. 

56 kbps56 kbps is short for 56 kilobits per second. It is the data capacity of a normal single channel digital telephone channel in North America.

56 Kbps Modem56 Kbps Modem is also known as V.pcm Modem. It uses v.90, an ITU standard (1998) for a modem that communicates at 56 Kbps downstream and 33.6 Kbps upstream. It is intended for use only with ISPs and online services that are digitally attached to the telephone system. Most service providers are typically connected with high-speed digital T1 or T3 circuits.In practice, the downstream link isn't generally faster than 45 Kbps in these PCM modems, so called because they use pulse code modulation downstream and standard V.34 upstream. Initially, two incompatible technologies competed in this arena: x2 from U.S. Robotics and K56Flex from Rockwell and Lucent. Such modems can be upgraded to V.90 if they contain software-upgradable memory chips

5ESS Switch5ESS Switch is a telephone switching system first introduced in 1982 by Lucent Technologies ( formerly AT&T). It has evolved into a truly universal digital switch that meets all the telecommunications needs of the modern information age. Its versatility, flexibility, reliability, quality of service, and economic benefits are a direct result of using state-of-art designs and technologies for the system's hardware and software implementation. 5ESS has a wide variety of applications. It can serve as a local, toll or international gateway exchange, or a combination of these functions. It provides the following major applications: Local exchange, tandem exchange, Toll or transit exchange, Operator Services Position System (OSPS), Signal Transfer Point (STP) for a common channel signaling system, International gateway exchange, Wireless (cellular) switch (Mobile Switching Center/Mobile Telephone Switching Office; MSC/MTSO), Remote (switching) operations. 

5ESS-20005ESS-2000 is an improved version of the original 5ESS switching developed by Lucent Technologies (former AT&T). It is one of the most common switches used in the North American digital networks. It can be used for wireline and wireless network applications. 5ESS-2000 switching platform utilizes a common software and distributed hardware architecture simultaneously supporting both wireless and wireline applications. There are three sizes of 5ESS-2000 available: 1. Large switches called 5ESS-2000 Digital Cellular Switch (DCS).  2. Compact switch called 5ESS-2000 Compact Digital eXchange (CDX). 3. Very Compact Switch called 5ESS-2000 Very Compact Digital eXchange (VCDX).

64 Kbps64 Kbps is short for 64K bits per second. This is the standard speed for a phone line.

66 Block66 Block is a widely-used common type of connecting terminal board for terminating twisted-

pair cables. The 66  Block is designed for telephone systems, PBX systems and other low-speed or low-voltage terminal equipment. 

66-type Connecting Block66-type Connecting Block is the connecting block used to terminating twisted-pair cables. All the wires have to be cut manually with a special tool to connect to the terminating telephone equipment or to make connections between them.

66-type Cross Connect66-type Cross Connect is a cross connect system using 66-type connecting blocks and jumper wires. This is the most common cross connect systems in telephone system in North America.

700 Service700 Service refers to a telephone service that uses dialing plan pattern 1-700-xxx-xxxx. The 700 is a non-geographic area code which reserved just for the provisioning of special Inter-Exchange Carrier services. The 700 service was once deployed by former AT&T in the form of easy reach that allows your incoming calls to follow you in the same way as would 500 Service. 700 Service were also used for many different purposes and it is still evolving as the result of change of telecommunication regulations. Currently, it is commonly used in both voice and data VPNs (Virtual Private Networks).

711 Service711 refers to the Services Code on a nationwide basis (US) for accessing Telecommunications Relay Access (TRS).

800 Portability800 Portability refers to a requirement in the 800 service that allows customers to keep their 800 number with them when move to any other long distance carriers (service providers). As part of its efforts to promote competition, in 1991, the FCC endorsed the idea of phone number portability.

800 Service800 Service generally refers to the toll free services including 800, 888, 877, 866 number services that former AT&T, MCI, Sprint and the Bell operating companies used for so called IN-WATS service. Those 800, 888, 877, 866 numbers in the dialing plan are served as "area code" by analogy with normal telephone dialing plan. Dialing of 800 service is free to the person making the call.  However the call is billed to the person or company being called. 800 calls can terminate on any telephone or cell phone with their own normal telephone numbers. This is a way to charge the called parties who have their own "normal" phone number and subscribe to the 800 service so that the calling party can be free of charge. This 800 service is basically a database lookup and translation service for  incoming phone calls. The 800 service works like this: If a 800 number dialed, which means a 1-800 plus seven digits, the LEC (Local Exchange Carrier, i.e. the local phone company) central office sees the "1" and recognizes the call as long distance. It ships that call to a next level or a bigger central office depending on where the routing information is stored. The processing central office recognizes the 800 "area code" and examines the next seven digits. At this point, the LEC switch holds the call, while it queries a

centralized database, usually over a SS7 (Signaling System 7) link. That centralized database identified the LEX or IXC (Inter Exchange Carrier) providing the 800 number, as well as translating the 800 number into a "real telephone number". Based on that "real telephone number", the LEC switch will then route the call to the proper IXC (long distance company). Once the long distance company has the 800 call, there are many way it can send the call to the the phone it's intended for. 

800 Valuflex Service800 Valuflex Service is a service provided by former Nynex (NYNEX Corporation was acquired by Bell Atlantic Corporation (BNTR) on 8/14/1997). This service allows customer to make and receive regular phone calls and 800 number calls from local areas on their normal business phone lines. This allows customers to combine the regular business phone line (usually have regular non-800 phone number) with 800 number service to the same business phone without adding additional phone line. In the meantime, the 800 number calls can also share all the call features that the normal business phone line would have without subscribing them separately. 

877 Service877 Service is a toll-free service, the same as 888 and 800 services. 877 was introduced by NANP (North American Numbering Plan) in April 1998 as the result of running out of 888 numbers. 

888 Service888 Service is the toll-free service, the same as the 800 services. It was introduced by NANP (North American Numbering Plan) in April 1996 to include 888 numbers as part of the toll-free service. 

8B10BLF8B10BLF is short for 8-Byte/10-Byte Local Fiber. It refers to a multimode fiber optic channel that can support data rates up to 150mpbs.

900 Service900 service, also called a pay-per-call service, permits callers to place calls to 1-900 prefixed telephone numbers and connect to a program delivered by a third party called a 900 content provider. This is a tariffed network service provided by certain telephone companies to 900 content providers. Those program include live and pre-recorded services such as adult chat lines, vote casting, psychic consultations, horoscopes, games, donations processing, weather forecasts, translation, and medical, legal or government services, etc. 

905-928 MHz905-928 MHz is a frequency spectrum band segment that is mostly and commonly used by cordless phones (so called 900 MHz phone).

911 Service911 is the official national emergency number in the United States and Canada. Dialing 911 quickly connects caller to a Public Safety Answering Point (PSAP) dispatcher trained to route

your call to local emergency medical, fire, and law enforcement agencies. The 911 network is a vital part of emergency response and disaster preparedness system.

958 Number958 number is testing prefix number in the dialing plan structure NPA-NXX-XXXX where NPA stands for the area code and NXX stands for the Prefix. This means that the prefix number 958 is reserved only for testing purpose and will not be available for customers. 958 numbers (NPA-958-XXXX) are reserved for general testing, while 959 numbers (NPA-959-XXXX) are reserved for inter-exchange carrier testing.

959 Number959 number, similar to 958, is the prefix number (NPA-959-XXXX) reserved for inter-exchange carrier testing. The only way to reach a 959 numbers is being pre-subscribed to that inter-exchange carrier or using an access code 101xxxx as in dialing plan 101xxxx-1-NPA-959-XXXX. 

976 Service976 service, similar to 900 service, allows customers to place calls to 1-976 prefixed telephone numbers and connect to a pay-per-call program delivered by a third party. Rules of 976 is not exactly the same as for 900.

999 Service999 service is the phone number for emerfency services in Great Britain, which is equivalent to the 911 service in the US.

Tele-Communication (Telecom) Terms Glossary and Dictionary - O

OA&M: Operation, Administration and MaintenanceOperation, Administration and Maintenance (OA&M) is a group of management functions that provides system or network fault indication, performance monitoring, security management and diagnostic functions. Some systems require extensive end user provisioning functions, in this case, it is called Operation, Administration, Maintenance and Provisioning (OAM&P).

OADM: Optical Add-Drop MultiplexerOptical Add-Drop Multiplexer (OADM) is an optical multiplexing device used in wavelength-division multiplexing (WDM) systems for mixing and routing different channels of light into or out of a single mode fiber. It has the capability of adding one or more new wavelength channels to an existing muli-wavelength WDM signal, or removing (dropping) one or more channels, routing those signals to another network path.

OAM&P: Operation, Administration, Maintenance and ProvisioningOperation, Administration, Maintenance and Provisioning (OAM&P) refers to a group of management funcions that provides system or network fault indication, performance monitoring, security management, diagnostic functions, configuration and user provisioning. Operations

include coordinates actions between administration, maintenance, and provisioning. Administration includes designing the network, processing orders, assigning addresses, tracking usage, and accounting. Maintenance includes diagnosing and repairing problems that does not work as planned. Provisioning includes installing equipmet, setting parameters, verifying that the service is operational, updating, and de-installation.

OBC: Out-of-Band ControlOut-of-Band Control (OBC) refers to the standard method of issuing signaling commands on the special control channel, versus In-Band Control (IBC), on the in-band data channel.

OC: Optical CarrierOptical Carrier (OC) is a group of signal bandwidth in a SONET fiber optic network with many defined levels. It is typically denoted as OC-n, where n is the multiplexing factor of the basic rate of 51.8 Mbit/s. The current defined levels are:OC-1 - 51.8 Mbit/s OC-3 - 155.52 Mbit/s OC-12 - 622.08 Mbit/s OC-24 - 1.244 Gbit/s OC-48 - 2.488 Gbit/s OC-96 - 4.976 Gbit/sOC-192 - 9.953 Gbit/sOC-256 - about 13 Gbit/s OC-384 - about 20 Gbit/s OC-768 - about 40 Gbit/s OC-1536 - about 80 Gbit/s OC-3072 - about 160 Gbit/s

OC1: Optical Carrier OneOptical Carrier One (OC1 or OC-1) is a SONET line with a transmission speed of 51.84 Mbit/s (payload: 50.112 Mbit/s; overhead: 1.728 Mbit/s) using optical fiber. OC-1 is the basic rate for the SONET optical fiber lines and the other rate levels of SONET are multipled based on the OC-1 speed. OC-1 is equivalent to STS-1 (Electrical level) and STM-0 (SDH).

OC12: Optical Carrier 12Optical Carrier 12 (OC12 or OC-12) is a fiber optic network line with a SONET rate of 622.08 Mbit/s (payload: 601.344 Mbit/s; overhead: 20.736 Mbit/s) or 12 times the basic SONET signal transmitting rate of 51.84 Mbit/s (OC-1). OC-12 lines are commonly used by Service Providers as WAN connections. This connection speed is often used by mid-sized (below Tier 2) internet customers, such as web hosting companies or smaller ISPs buying service from larger ones. OC-12 is equivalent to STS-12 (Electrical level) and STM-4 (SDH).

OCC: Other Common CarrierOther Common Carrier (OCC) refers to telecommunications carriers in the US who were not part of the former original AT&T system.

OC192: Optical Carrier 192Optical Carrier 192 (OC192 or OC-192) is a SONET rate of 9953.28 Mbit/s (payload: 9621.504 Mbit/s; overhead: 331.776 Mbit/s) over optic fiber lines, or 192 times the basic 51.84 Mbit/s SONET signal (OC-1). The WAN version of 10 Gigabit Ethernet is designed to interoperate with OC-192. As of 2006, OC-192 connections are the most common for use on the backbones of large ISPs. OC-192 is equivalent to STS-192 (Electrical level) and STM-64 (SDH).

OC3: Optical Carrier 3Optical Carrier 3 (OC3 or OC-3) is a optic fiber line using SONET with a transmission speed of 155.52 Mbit/s (payload: 150.336 Mbit/s; overhead: 5.184 Mbit/s), or 3 times the basic 51.84 Mbit/s SONET signal (OC-1). OC-3 is equivalent to STS-3 (Electrical level)and STM-1 (SDH).

OC48: Optical Carrier 48Optical Carrier 48 (OC48 or OC-48) is a fiber optic line with a SONET rate of 2488.32 Mbit/s (payload: 2405.376 Mbit/s; overhead: 82.944 Mbit/s) or 48 times the basic SONET signal transmitting at 51.84 Mbit/s. OC-48 connections are used as the backbones of many regional ISPs. OC-1 is equivalent to STS-48 (Electrical level) and STM-16 (SDH).

OC768: Optical Carrier 768Optical Carrier 768 (OC768 or OC-768) is a fiber optic line with a SONET rate of 39,813.12 Mbit/s (payload: 38,486.016 Mbit/s; overhead: 1327.104 Mbit/s), or 768 times the basic SONET rate of 51.84 Mbit/s (OC-1). It's often referred to as "40 Gbit". OC-768 is equivalent to STS-768 (Electrical level) and STM-256 (SDH).

OC96: Optical Carrier 96Optical Carrier 96 (OC96 or OC-96) is a fiber optic line with a SONET rate of 4976 Mbit/s, or 96 times the basic SONET rate of 51.84 Mbit/s (OC-1). It's not used much in the real world.

OCC: Other Common CarrierOther Common Carrier (OCC) refers to telecommunications carriers in the US who were not part of the former original AT&T system.

OC-n: Optical Carrier level nOptical Carrier Level n (OC-n) is a group of signal bandwidth in a SONET fiber optic network with many defined levels, where n is the multiplexing factor of the basic rate of 51.8 Mbit/s. The current defined levels are:OC-1 - 51.8 Mbit/s OC-3 - 155.52 Mbit/s OC-12 - 622.08 Mbit/s OC-24 - 1.244 Gbit/s OC-48 - 2.488 Gbit/sOC-96 - 4.976 Gbit/sOC-192 - 9.953 Gbit/s OC-256 - about 13 Gbit/s OC-384 - about 20 Gbit/s OC-768 - about 40 Gbit/s

OC-1536 - about 80 Gbit/s OC-3072 - about 160 Gbit/s

Odd ParityOdd Parity, one of the parity processes, means that the total numbers of ones in the information data stream plus the parity bit (typically appended to the end of the data bitstream) is equal to an odd number of ones.

Offered LoadOffered Load is the total traffic load, including load that results from retries, submitted to a telecommunications system, group of servers, or the network over a circuit.

Offered TrafficOffered Traffic is a measurement in telecommunications that stands for the total attempts to seize a group of servers.

Off-HookOff-hook refers to the following meanings in telecommunications: (1) the signal that the telephone receiver has been lifted. Originating Off-hook activates a dial tone on switched networks. (2) the state of telephone that the receiver has been lifted.

Ones DensityOnes Density, also called pulse density, is a scheme that allows a CSU/DSU to recover the data clock reliably. The CSU/DSU derives the data clock from the data that passes through it. To recover the clock, the CSU/DSU hardware must receive at least one 1 bit value for every 8 bits of data that pass through it.

One-Way TrunkOne-way Trunk is the trunk circuit that can be seized at only one end.

On-HookOn-Hook is the normal inactive state of a telephone terminal. In this state, the switchhook contacts at the telephone instrument are open and no current signal is being sent to the central office.

ONI Order ToneONI Order Tone is a tone with 700 Hz and 1100 Hz at -25 dBm0/frequency for .095 to 0.25 seconds that tells the ONI (Operator Number Identification) operator that a call has reached the position.

Only-Route Trunk GroupOnly-route Trunk Group is a trunk group that is the one and only route for particular traffic items. It receives only first route traffic, does not receive overflow traffic, and has no alternate route.

OOS: Out-of-Service SignalingOut-of-Service signaling(OOS) is a call signaling indicating that the network or phone station is out of service.

OPC: Originating Point CodeOriginating Point Code (OPC) refers to numeric address in a SS7 network which uniquely identifies each signaling point. The OPC identifies the sending signaling point.

Open WireOpen Wire is a transmission path consisting of a pair of wires, spaced a parallel distance apart and mounted on insulators, usually on a pole line.

OPSM: Operator Position Switching ModuleOperator Position Switching Module(OPSM) refers to the operator services system for the AT&T 5ESS switch that gives phone companies and worldwide phone service administrators flexibility in deploying operators. The system is called the Operator Services Position System (OSPS), and its operation is based on the Integrated Services Digital Network (ISDN) capabilities of the 5ESS switch. These capabilities permit simultaneous data and voice communications between the switch and the operator's terminal equipment. OSPS allows the phone service providers to provide fully-featured North American and international operator service with operators located at a distance from the switching system.

Optical Power BudgetOptical power budget refers to the allocation (in a fiber-optic communication link), of available optical power launched into a given fiber by a given source among various loss-producing mechanisms such as launch coupling loss, fiber attenuation, splice looses, and connector losses, in order to ensure the adequate signal strength at the receiver.

Optical Power MarginOptical power margin refers to the difference between (1) the optical power that is launched by a given transmitter into the fiber, less transmission losses from all causes, and (2) the minimum optical power that is required by the receiver for a specified level of performance. Optical power margin is usually expressed in dB. At ease, several dB of optical power margin should be included in the optical power budget.

Optical ReceiverOptical Receiver is a device in a optical transmission system that detects an optical signal, converts it to an electrical signal, and processes the electrical signal as required for a further use.

Optical TransmitterOptical Transmitter is a device that accepts an electrical signal as its input, processes this signal, and uses it to modulate opto-electronic device and produce optical signals.

OPX: Off Premise ExtensionOff Premise Extension (OPX) is an extension telephone, PBX station, or key system station

located on property that is not contiguous with that on which the main telephone, PBX, or key system is located.

Order ToneOrder Tone is a high tone sent over interposition, local interoffice, or toll trunks. It indicates, 1) to the originating operator that the order should be passed; 2) to the receiving operator that an order is about to be passed. For Call Announcement and Automatic Display Call Indicator, the tone serves function two only.

Originating ResisterOriginating Resister is the equipment in a Number 5 Cross System that is connected to a subscriber initiating a call to receive the dial pulses or TOUCHTONE signals from the subscriber's telephone.

Originating UserOriginating User refers to the user who initiates a particular information transfer transaction. The originating user could be either the source user or the destination user.

OSC: Operator Service CallOperator Service Call (OSC) refers to a call that is placed through a human operator or an automated operator.

OSS: Operation Support SystemOperation Support System (OSS) performs management, inventory, engineering, planning, and repair functions for telecommunications service providers and their networks. Operations Support Systems (OSSs), typically based on the Telecommunications Management Network (TMN) model, are designed to support telephone company staff members to automate their daily jobs such as order processing, line assignment, line testing and billing, etc.

OTM: Optivity Telephony ManagerOptivity Telephony Manager (OTM) is an application that provides single-point analysis, configuration, and management of Telephony networks using a Web browser or graphical user interface (GUI). The OTM suite, which is offered by Nortel Networks, is designed for the management of Meridian 1 and Communication Server 1000 systems.

OutboundOutbound, in telecommunication, refers to outward sending, call originating, or dialing Out.

Outgoing Calls BarredOutgoing Calls Barred is a telecommunication facility that prevents a packet switch from accepting outgoing virtual calls from the data terminal equipment.

Outgoing SenderOutgoing Sender is an equipment in telecommunication network that transmits call completion information on an interoffice call.

Out-of-Band SignalingOut-of-band signaling is a signaling technique using frequencies or channels outside the frequencies or channels normally used for information transfer. Out-of-band signaling often is used for error reporting in situations in which in-band signaling can be affected by whatever problems the network might be experiencing.

Outside PlantOutside Plant has different meanings depending on where it is used: (1) In civilian telecommunications, it refers to all cables, conduits, ducts, poles, towers, repeaters, repeater huts, and other equipment located between a demarcation point in a switching facility and a demarcation point in another switching facility or customer premises. (2) In DOD (Department Of Defense) communications, it is the portion of intrabase communications equipment between the main distribution frame and a user and instrument to terminal connection for a user instrument.

Out-Slot SignalingOut-Slot Signaling is a signaling scheme in that the signaling associated with a (voice or data) channel is sent over the same transmission path (channel) or circuit, but in a different time slot (s). An example of this scheme is the ITU-T 2.048 Mbps digital carrier system.

Out-WATS LineOut-WATS Line refers to telephone lines used only for outgoing calls. Out-WATS Lines are, in effect, fixed-rate long distance subscriptions.

OverfillOverfill refers to the condition in telecommunications that prevails when the numerical aperture or the beam diameter of an optical source, such as a laser, light-emitting diode, or optical fiber, exceeds that of the driven element, e.g., an optical fiber core. In optical communications testing, overfill in both numerical aperture and mean diameter is usually required.

Overflow LoadOverflow Load refers to a part of the offered traffic of telecommunications that is not carried, i.e., overflow traffic equals offered traffic minus carried traffic.

Overhead InformationOverhead information is the signaling information of directing or controlling the transfer of user information or the detection and correction of errors. Overhead information transferred across the functional interface between end users and a telecommunications system, or between functional units within a telecommunications system. Overhead information originated by the user is not considered to be system overhead information. On the other hand, overhead information generated within the communications system and not delivered to the user is system overhead information. Thus, the user throughput is reduced by both overheads while system throughput is reduced only by system overhead.

OverlapOverlap is a mode where call control is waiting for possible additional call information from the

preceding PINX because it received acknowledgment that the subsequent PINX can receive additional call information.

Tele-Communication (Telecom) Terms Glossary and Dictionary - P

PABX: Private Automatic Branch ExchangePrivate Automatic Branch Exchange (PABX) is an automatic telephone switching system within a private enterprise. Originally, such systems - called private branch exchanges (PBX) - required the use of a live operator. Since almost all private branch exchanges today are automatic, the abbreviation "PBX" usually implies a "PABX."

PAD SwitchingPAD Switching refers to a technique of automatically cutting a transmission loss pad into and out of a transmission circuit for different operating conditions.

Pair CablePair Cable refers to a cable in which all of the conductors are arranged in the form of twisted pairs. This form of cable is, by far, the most common form of cable used for communications.

Pair GainPair Gain refers to the number of customers served by a communication system less the number of wire pairs used by that system. Pair gain can be achieved by multiplexing and by concentration.

Paired Disparity CodePaired disparity code is a code used in telecommunications in which some or all of the characters are represented by two sets of digits of opposite disparity that are used in sequence so as to minimize the total disparity of a longer sequence of digits.

PAM: Pulse Amplitude ModulationPulse Amplitude Modulation (PAM) is a form of signal modulation in which the data is encoded in the amplitude of a series, or train, of regularly recurrent signal pulses. PAM is used less frequently than PCM (Pulse-Code Modulation).

Parallel TransmissionParallel Transmission is a method of data transmission in which the bits of a data character are transmitted simultaneously over a number of channels/ports. In parallel transmission, coded information are transmitted via a system with multiple ports/channels. The port 1 is used to transport the first MSB (Most Significant Bit) and the second port carries the second MSBs, so on and so forth.

Parity BitParity bit is the additional bit inserted into the string of user information in the telecommunications data stream for the purpose of error correction and checking.

Partial Dial TonePartial Dial Tone is a steady high tone in telephone system that is used to notify the calling party that he/she has not commenced dialing within a pre-allotted time, measured after receipt of dial tones (permanent signal condition), or that he/she has not dialed enough digits (partial dial condition). This is a signal to hang up and dial again.

Partially Dedicated AccessPartially Dedicated Access is a long distance carrier access method in which a non-local call is carried by the long distance carrier via a dedicated trunk facility for either the first or last part of the call's journey, and on the carrier's network for the middle part of the journey. It is also called "dedicated to switched", "switched to dedicated", "on-net to off-net" and "off-net to on-net".

Party LineParty Line is a circuit assigned to serve two or more subscribers with discriminatory signaling for each station.

Pass Along MethodPass Along Method is a signaling scheme. In Pass Along Method, signaling traffic (information) is sent along the signaling path of a previously established physical connection.

Patch PanelPatch panel is a panel of network ports contained together, usually within a telecommunications closet, that connects incoming and outgoing lines of a LAN or other communication, electronic or electrical system. The patch panel allows easy access to all cable and ground line conductors. Conductor functions can be interchanged or checked rapidly for continuity, insulation, or quality of signal brought to the surface. Also, it provides easy access to output of surface panels.

PBX: Private Branch ExchangePrivate Branch Exchange (PBX) is a small telephone switch owned by a company or organization. These organizations purchase PBX's to reduce the total number of telephone lines they need to lease from the telephone company. Without a PBX, a company will need to lease one telephone line for every employee with a telephone. With a PBX system, the company only needs to lease as many lines from the telephone company as the maximum number of employees that will be making outside calls at one time. This is usually around 10% of the number of extensions. In a PBX system, every telephone is wired to the PBX. When an employee takes the receiver off-hook and dials the outside access code (usually 9), the PBX connects the employee to an outside line.

PC: Peg CountPeg Count (PC) refers to the measurement of the number of attempts to seize a server in a group of one or more servers.

PC: Point CodePoint Code (PC) refers a unique address code in telecommunication system that identifies a service provider within a signaling network.

PC: Protection ChannelProtection Channel(PC) is a standby, fully operational facility, providing diversity for one or several similar channels. When correctly implemented, it can result in improved availability or reliability of the channel, and of the circuits carried on each so protected channel.

ProvisioningProvisioning refers to the creation of an active subscriber account, or modification of parameters for an existing subscriber account. Provisioning of a subscriber account includes subscriber account registration and device activation.

PCM: Pulse-Code ModulationPulse-code Modulation (PCM) is a sampling technique for digitizing analog signals, especially voice/audio signals. It samples the analog signals 8000 times per second; each sample is represented by 8 bits for a total of 64 Kbps. There are two standards for coding the sample level. The Mu-law is used in North America and Japan while the A-law is used in Europe and most other countries.

PCS: Personal Communications ServicePersonal Communications Service (PCS) is a network that provides personal, terminal and service mobility. PCS includes broadband and narrowband in the United States.

PCV: Path Coding ViolationPath Coding Violation (PCV) is an Error Event in the DS1/T1 interface. PCV error event is a frame synchronization bit error in the D4 and E1-noCRC formats, or a CRC error in the ESF and E1-CRC formats.

PDH: Plesiochronous Digital HierarchyPlesiochronous Digital Hierarchy (PDH) refers to a protocol that consists of signals that have relatively the same bit rates and characteristics, but they are not synchronized to a common timing source.

Peak LoadPeak Load refers to the traffic volume at the highest level during a given time period. It is usually expressed as the traffic volume during the highest one-hour period of the day (Busy Hour).

Permanent CallsPermanent Calls are the private line calls used for fixed point-to-point calls, for connections between PBXs (E&M to E&M), or for remote telephone extensions (FXO to FXS).

Permanent SignalPermanent Signal is a high steady tone. Permanent Signal is used to inform an operator or other maintenance employees making a verification test that the line is temporarily out of service. An intermittent ground may also be applied to the ring of the telephone systems left in the hold condition.

PH: Protocol HandlerProtocol Handler refers to a device with programs that provides communications services that enables a device to send data to other devices by transmitting and receiving data as specified by the communications protocol.

Phantom CircuitPhantom Circuit is a third circuit derived from two physical circuits by means of repeating coils installed at the terminals of the physical (side) circuits.

Phase DistortionPhase Distortion, also known as as Delay Distortion, is an unwanted modification of a transmitted signal caused by the non-uniform transmission of the different frequency components of the signal.

Phase ShiftPhase Shift refers to the situation in which the relative position in time between the clock and data signals of a transmission becomes unsynchronized. In systems using long cables at higher transmission speeds, slight variances in cable construction, temperature, and other factors can cause a phase shift, result in high error rates.

PIC ChargesPIC Charges refers to a charge by Local Exchange Carrier(LEC) for a customer to change the PIC (Primary Interexchange Carrier). It is often paid by the new Inter Exchange Carrier (IEC). If a LEC sends a PIC charge to a customer, the new IEC will typically credit the customer's account.

PIC FreezePIC Freeze refers to an option that customers can choose to prevent unauthorized changes to their chosen Primary Long Distance Carrier

PIC RequestPIC Request is a request record sent to a Local Exchange Carrier (LEC) asking for an ANI (Automatic Number Identification) to be activated, deactivated or changed in some way.

PIC ResponsePIC Response is a response record sent by a Local Exchange Carrier (LEC), corresponding to a previous PIC Request, with a response code that indicates whether the request was performed.

PIC: Point In CallPoint In Call (PIC) refers to the phase or position within a call. Examples of PIC are Answered, Long Duration, Released, and so on.

PIC: Primary Interexchange CarrierPrimary Interexchange Carrier (PIC) refers to the long distance company that is automatically accessed when a customer dials 1+.

PICC: Pre-Subscribed Inter-Exchange Carrier ChargePre-subscribed Inter-exchange Carrier Charge is the charge that long distance companies pay to local telephone companies to help them recover the costs of providing the telephone wires, underground conduit, telephone poles, and other facilities that link each telephone customer to the telephone network. A long distance company pays this charge for each residential and business telephone line presubscribed to that long distance company. There is no tax due on PICC charges paid from one telecommunications vendor to another. However, if a retail consumer or business has not selected a long distance company, the local telephone company may bill the consumer or business for the Presubscribed Interexchange Carrier Charge. If the PICC charge is billed to the retail customer, it is subject to sales tax.

Pilot SignalPilot signal, in telecommunication, is a signal usually in single frequency, transmitted over a communications system for supervisory, control, equalization, continuity, synchronization, or reference purposes.

PINX: Private INtegrated Services Network eXchangePrivate INtegrated services network eXchange(PINX) is a PBX or key system which, in a BRI voice application, uses QSIG signaling.

PLAR: Private Line, Automatic RingdownPrivate Line, Automatic Ringdown (PLAR) is a leased voice circuit that connects two single endpoints together. When either telephone handset is taken off-hook, the remote telephone automatically rings.

Plar-OpxPlar-Opx specifies a PLAR Off-Premises eXtension connection. Using this option, the local voice port provides a local response before the remote voice port receives an answer. On FXO interfaces, the voice port will not answer until the remote side answers.

PlesiochronousPlesiochronous is the term used in telecommunication signal hierarchy. Plesiochronous comes from a combination of Greek words: (1) "Plesio" meaning "close", "near", or "almost the same"; and (2) "synchronous" meaning "happening at the same time", "occurring together", "simultaneous", or "having the same period between occurrences". In telecommunications, Plesiochronous is used to describe any two signals that have the same "nominal rate", but do not originate from the same (identical) timing (clock) source.

PNP: Private Numbering PlanPrivate Numbering Plan (PNP) is the telephone numbering plan that defines the format of telephone numbers to be used within a private telephone system. The Private Numbering Plan number normally consists of at least 3 digits, excluding "112".

POH: Path OverheadPath Overhead (POH) refers to overhead accessed, generated and processed by path-terminating

equipment; POH includes 9 bytes of STS POH and, when the frame is VT-structured, 5 bytes of VT (Virtual Tributary) POH.

PollingPolling is an access method in which a primary network device inquires, in an orderly fashion, whether secondaries have data to transmit. The inquiry occurs in the form of a message to each secondary that gives the secondary the right to transmit. In telecommunications, polling is a long distance carrier access method in which a non-local call is carried by the long distance carrier via a dedicated trunk facility for either the first or last part of the call's journey, and on the carrier's network for the middle part of the journey.

PON: Passive Optic NetworkPassive Optical Network (PON) refers to a group of ITU-T and IEEE standard technologies, which enable fiber as the first mile (or last mile) to the customer premises. A PON consists of a central office node Optical Line Termination (OLT) at the service providers office and a number of Optical Network Units (ONUs) near end users, and the fibers and splitters between them, called the optical distribution network (ODN). The OLT provides the interface between the PON and the backbone network, while the ONT provides the service interface to the end user. PON is a converged infrastructure that can carry multiple services such as voice (plain old telephony service or voice over IP), data, video, and/or telemetry, in that all of these services are converted and encapsulated in a single packet type for transmission over the PON fiber.

POP: Point Of PresencePoint Of Presence (POP) is the physical access location interface between a local exchange carrier and an Interexchange Carrier fiber network. The point to which the telephone company terminates a subscriber's circuit for long distance services or leased line communications.

Post-Dial DelayPost-dial Delay is the time interval between "end of dialing" by the customer and the reception (by the same customer) of the call progress signaling generated by the exchange serving this customer. The call progressing signals can be the dial tone, a recorded announcement, or the abandon of the call.

POTS Dial PeerPOTS Dial Peer refers to the dial peer connected via a traditional telephony network (POTS). POTS peers point to a particular voice port on a voice network device.

POTS: Plain Old Telephone ServicePlain Old Telephone Service (POTS) is the standard, analog telephone service which remains the basic form of residential and small business telephone service nearly everywhere in the world. Plain Old Telephone Service was originally known as the Post Office Telephone Service in many countries. It has been available almost since the introduction of the telephone system in the late 19th century, mostly unchanged to the normal user since then despite the introduction of electronic telephone exchanges into the public switched telephone network since the middle of the 20th century.

PPS: Pulses Per SecondPulses Per Second (PPS) refers to the number of pulses per second and the number of dial pulses per second. It is used as a type of measure in telecommunication and many other applications such as in clock oscillator discipline.

PRC: Primary Reference SourcePrimary Reference Source(PRC) refers to a telecommunication equipment that provides a timing signal whose long-term accuracy is maintained very well with verification to UTC (Coordinated Universal Time), and whose timing signal may be used as the basis of reference for the control of other clocks within a network. The Primary Reference Source may generate a timing signal completely autonomous of other references, in which case cesium beam technology is suitable. Alternatively, the primary reference source may not be a completely autonomous implementation, in which case it may employ direct control from normal UTC-derived frequency and time services.

Preemption TonePreemption Tone is one of the telephone system audible tones that provides to both parties of a connection that is preempted by a priority call from the AUTOVON network. Preemption Tone is 440 Hz and 620 Hz at -18 dBm0/frequency steady for anywhere from three to fifteen seconds.

PresubscriptionPresubscription refers to a BOC (Bell Operating Company) tariff service that permits each customer served from an equal access EO switching system to automatically route, without the use of access codes, all the customer's interLATA communications to one IC of the customer's choice. The customer may also gain access to other ICs using the appropriate carrier access code, e.g., 10XX.

PRI: Primary Rate InterfacePrimary Rate Interface (PRI) is an ISDN interface for primary rate access, which consists of a single 64-kbps D channel plus 23 (T1) or 30 (E1) B channels for voice or data. PRI intended for larger users, such as business users. The other ISDN interface is the Basic Rate Interface (BRI), which is for homes and small businesses.

Primary PathPrimary Path refers to the preferred route from one switched node to another.

Priority Audible RingPriority Audible Ring Tone is one of the telephone system audible tones that replaces normal audible ring for priority calls within the AUTOVON network. Priority Audible Ring is 440 Hz and 480 Hz at -16 dBm0/frequency on for 1.65 seconds and off for .35 seconds.

Private LinePrivate Line is a telecommunication service that involves dedicated circuits with private switching arrangements, and/or predefined transmission paths, whether virtual or physical. The purpose of Private Line is to provide communications between specific interested points.

Proceed To Send ToneProceed to Send Tone is a steady tone with 480 Hz at -22 dBm0/frequency. It informs the operator that an overseas sender has been seized and the address information (KP-CC-CC-ST) should be transmitted.

Proctor Test SetProctor Test Set is a tool used by Telco personnel to diagnose problems with phone lines.

Property SurchargeProperty Surcharge is a per-call or per-minute charge assessed on an Operator-Assisted call by the property owner from which the call was placed. This charge is separate from the Call Type Surcharge, and monies from this charge are usually assigned to the property owner as part of the compensation package.

Provisioning SoftwareProvisioning software refers to the software in telecommunication system which configures and records the hardware and software for specific telecommunication services when additions or changes are needed in the network and its elements. It optimizes the use of network elements and available network routes.

PSTN: Public Switched Telephone NetworkThe Public Switched Telephone Network (PSTN) is a circuit-switched network that is used primarily for voice communications worldwide, with hundreds of millions subscribers. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital and provides mobile as well as fixed telephone services.

PTE: Path Terminating EquipmentPath Terminating Equipment (PTE) refers to a SONET element that terminates a SONET/SDH (Synchronous Digital Hierarchy) path.

PTS: Public Telephone ServicePublic Telephone Service (PTS), sometimes called plain old telephone service (POTS), is the ordinary telephone service in which a customer has a connection to a central office and can be connected to any other customer of the service.

PTT: Post, Telephone, and TelegraphPost, Telephone, and Telegraph(PTT) are the government agency that provides telephone services. PTTs exist in most areas outside North America and provide both local and long-distance telephone services.

Pulse Link RepeaterPulse link repeater is a device in telecommunications that interface concatenated E&M (Ear & Mouth) signal paths.

PulsingPulsing is the part of signaling that forwards the destination code required to route a call. In

telephony, the transmission of address information to a switching office is via pulses (i.e., signals) that originate from the user's equipment. An examples of pulsing methods is DTMF (dual-tone multifrequency). Rotary dialing is another example in which DC (Direct Current) pulses are generated by a rotary dial.

Push Button DialingPush Button Dialing is the use of buttons on a telephone rather than a rotary dial to address a telephone message to a terminal point on the network. Push button dialing usually enlists two-tone signaling. In AT&T's terminology, the registered trademark "TouchTone" is used.

Push-to-Talk OperationPush-to-talk operation refers to the method of communication over a speech circuit in which the talker is required to keep a switch operated while talking. Push-to-talk operation can be found in a telephone system or two-way radio systems.

PVC: Permanent Virtual ConnectionPermanent Virtual Connection(PVC) is the term that describes that path data takes through a virtual network. PVCs are an integral component of many circuits and connections to the Internet.

Tele-Communication (Telecom) Terms Glossary and Dictionary - Q

Q.2931Q.2931, based on Q.931, is a signaling protocol, which specifies the procedures for the establishment, maintenance and clearing of network connections at the B-ISDN user network interface. The PNNI and the UNI specifications are based on Q.2931. The procedures are defined in terms of messages exchanged.

Q.700Q.700, an ITU-T specification, provides an introduction to CCITT Signalling System No. 7 (SS7).

Q.703Q.703, an ITU-T specification, defines the Signalling System No. 7 (SS7) - Message Transfer Part, Signalling Link.

Q.704Q.704, an ITU-T specification, defines the Signalling System No. 7 (SS7) - Message Transfer Part, Signalling System No. 7 - Signalling Network Functions and Messages.

Q.705Q.705, an ITU-T specification, defines the System No. 7 - Signalling network structure.

Q.706Q.706, an ITU-T specification, defines the Signalling System No. 7 - Message Transfer Part Signalling Performance.

Q.712Q.712, an ITU-T specification, defines the Signalling System No. 7 (SS7) - Definition and Function of SCCP Messages.

Q.713Q.713, an ITU-T specification, defines the Signalling System No. 7 - SCCP Formats and Codes.

Q.716Q.716, an ITU-T specification, defines the Signalling System No. 7 - Signalling connection control part (SCCP) performance.

Q.725Q.725, an ITU-T specification, defines Signalling System No. 7 - Signalling performance in the telephone application.

Q.731Q.732, an ITU-T specification, provides the Stage 3 description for numbering identification supplementary services using Signalling System No. 7 (SS7).

Q.732Q.733, an ITU-T specification, provides the Stage 3 description for call offering supplementary services using Signalling System No. 7(SS7)..

Q.733Q.734, an ITU-T specification, provides the Stage 3 description for call completion supplementary services using No. 7 Signalling System (SS7).

Q.734Q.734, an ITU-T specification, provides the Stage 3 description for multiparty supplementary services using Signalling System No. 7.

Q.735Q.735, an ITU-T specification, provides the Stage 3 description for community of interest supplementary services using SS7.

Q.736Q.736, an ITU-T specification, provides the Stage 3 description for charging supplementary services using Signalling System No. 7 (SS7).

Q.737Q.737, an ITU-T specification, provides the Stage 3 description for additional information transfer supplementary services using Signalling System No. 7 (SS7).

Q.761Q.761, an ITU-T specification, provides Signalling System No.7 (SS&) – ISDN user part (ISUP) functional description.

Q.762Q.762, an ITU-T specification, defines the general function of messages and Signals of the ISDN User Part (ISUP) of Signalling System No. 7 (SS7).

Q.763Q.763, an ITU-T specification, defines the formats and codes of the ISDN User Part (ISUP) of Signalling System No. 7 (SS7).

Q.764Q.763, an ITU-T specification, defines the Signalling System No. 7 - ISDN User Part (ISUP) Signalling Procedures.

Q.766Q.766, an ITU-T specification, defines the Signalling System No.7 - Performance Objectives in the Integrated Services Digital Network Application.

Q.772Q.772, an ITU-T specification, defines the Signalling System No. 7 (SS7) - Transaction Capabilities Information Element Definition

Q.773Q.773, an ITU-T specification, defines the Signalling System No. 7 (SS7) - Transaction Capabilities Formats and Encoding

Q.774Q.774, an ITU-T specification, defines the Signalling System No. 7 - Transaction Capabilities Procedures

Q.850Q.850, an ITU-T specification, defines the usage of cause and location in the Digital Subscriber Signalling System No. 1 and the Signalling System No. 7 ISDN User Part.

Q.920Q.920, an ITU-T specification, together with Q.921, defines the ISDN UNI data link layer.

Q.921Q.921, an ITU-T specification, together with Q.920, defines ISDN user-network interface - Data link layer - General aspects.

Q.922Q.922, an ITU-T specification, defines the Link Access Procedure/Protocol (LAPF), which is an enhanced LAPD (Q.921) with congestion control capabilities for Frame Mode Services in the

Frame Relay network. LADF is used in the Frame Relay network for end-to-end signaling. LAPF conveys data link service data units between DL-service users in the User Plane for frame mode bearer services across the ISDN user-network interface on B-, D- or H-channels.

Q.922AQ.922A is an ITU-T specification for Frame Relay encapsulation.

Q.930Q.930, an ITU-T specification, defines the Digital Subscriber Signalling System No 1 (DSS1) - ISDN user - network interface layer 3 - General aspects.

Q.931Q.931, the network layer protocol in the telecommunication architecture, is used in ISDN for call establishment and the maintenance and termination of logical network connections between two devices. Q.931 is one of the network layer (layer 3) protocols in the telecommunication architecture specified by the ITU Q series documents Q.930 through Q.931..

Q.932Q.932, an ITU-T specification, defines the generic procedures applicable for the control of supplementary services at the user-network interface. These procedures expand on the basic call-control functions defined in Q.931.

Q.933Q.933, an ITU-T specification, defines Digital subscriber Signalling System No.1 (DSS 1) - Signalling specification for frame mode basic call control.

Q.939Q.939, an ITU-T specification, defines service indicator coding examples.

Q.93BQ.93B, an evolution of ITU-T recommendation Q.931, is an ITU-T specification for signaling to establish, maintain, and clear BISDN network connections.

Q.950Q.950, an ITU-T specification, defines ISDN supplementary services.

Q.951Q.951, an ITU-T specification, provides stage 3 description for number identification supplementary services using DSS1, such as Calling line identification presentation (CLIP); Calling line identification restriction (CLIR); Connected line ID and Malicious Call Identification (MCID).

Q.952Q.952, an ITU-T specification, provides stage 3 description for additional information transfer supplementary services using DSS1 (Digital subscriber Signalling System No.1), including Diversion supplementary services and Explicit Call Transfer (ECT).

Q.953Q.953, an ITU-T specification, defines Stage 3 description for call completion supplementary services using DSS 1 such as Call waiting, Call hold, Completion of Calls to Busy Subscribers (CCBS), Terminal Portability (TP) and Call Completion on No Reply (CCNR).

Q.954Q.954, an ITU-T specification, provides the Stage 3 description for multiparty supplementary services using DSS 1, such as Conference calling and Three-party service.

Q.955Q.955, an ITU-T specification, provides Stage 3 description for community of interest supplementary services using DSS 1, such as Closed user group and Multi-level precedence and preemption.

Q.956Q.956, an ITU-T specification, defines Integrated services digital network (ISDN) - Stage 3 service description for charging supplementary services using DSS 1 such as Clause 2 - Advice of charge (AOC) and Clause 3 - Reverse charging.

Q.957Q.957, an ITU-T specification, provides Stage 3 description for additional information transfer supplementary services using DSS 1: User-to-User Signalling (UUS).

QDI: Quasi Delay Insensitive CircuitsQuasi Delay Insensitive (QDI) Circuits are those whose correct operation does not depend on the delays of operators or wires, except for certain wires that form isochronic forks.

QPSK: Quadrature Phase Shift KeyingQuadrature Phase Shift Keying (QPSK) is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (the carrier wave). Sometimes known as quaternary or quadriphase PSK or 4-PSK, QPSK uses four points on the constellation diagram, equispaced around a circle. With four phases, QPSK can encode two bits per symbol, shown in the diagram with Gray coding to minimize the BER.

QRSS: Quasi-Random Signal SequenceQuasi-Random Signal Sequence (QRSS) is a test pattern widely used to simulate voice signals.

QSIG: Q SignalingQ Signaling(QSING) is a common channel signaling protocol based on ISDN Q.931 standards and used by many digital PBXs.

Quad Lock ConduitQuad Lock Conduit is the conduit to protect telephone wires intended to be buried.

Quadruple Order ToneQuadruple Order Tone is one of the Order Tone (See Order Tone). This signal is four short

spurts in quick succession and means that the operator should pass the city name only and wait for another challenge. It is used in manual toll tandem (also called zip tones or trunk assignment tones). Quadruple-order tone is four short spurts of High Tone.

Quantizing DistortionQuantizing Distortion refers to a form of distortion that causes an irregular facsimile of the original audio. It is a result of a digital signal being corrupted to a degree which occurs in the digital-to-analog translation process.

Quantizing NoiseQuantizing Noise refers to signal errors which result from the process of digitizing (and therefore ascribing finite quantities to) a continuously variable signal (analog signal).

Quasi-Associated ModeQuasi-associated Mode is a special non-associated signaling operation. In Quasi-associated Mode, the signaling message route is determined (for each signaling message) by the signaling points between two or more signaling links (in tandem) passing through one or more STPs (Signaling Transfer Part).

Tele-Communication (Telecom) Terms Glossary and Dictionary - R

RADSL: Rate-Adaptive Asymmetric Digital Subscriber LineRate-Adaptive Asymmetric Digital Subscriber Line (RADSL) is a variation of ADSL which automatically adjusts the connection speed depanding on the quality and length of the telephone line. In RADSL, the broadband modem is configured at startup to test the phone line and adjust the data rate. RADSL typically operates at a lower date rate than regular ADSL. Like ADSL, RADSL provides relatively more bandwidth for downloads and less for uploads.

RAI: Remote Alarm IndicationRemote Alarm Indication (RAI), also known as yellow alarm signal, is a signal transmitted in the outgoing direction when a terminal determines that it has lost the incoming signal. Receiving remote alarm indication (RAI) means the far-end equipment over the T1 line has a problem with the signal it is receiving from the upstream equipment.

Rain Barrel EffectRain Barrel Effect refers to signal distortion of a voice telephone line caused by the under attenuated echo on the return path. The resultant distortion gives a near-singing effect like that of speaking into a rain barrel.

Range Extender With GainRange Extender With Gain is a unit that provides a range extension in a loop for both signaling and transmission.

RBHC: Regional Bell Holding CompanyRegional Bell Holding Company (RBHC), also known as Regional Bell Operating Companies (RBOC), refers to one of 7 regional companies created by the AT&T divestiture to assume ownership of the Bell operating companies. They are Ameritech, Bell Atlantic, Bell South, NYNEX, Pacific Telesis, Southwestern Bell and US West.

RBOC : Regional Bell Operating CompaniesRegional Bell Operating Companies (RBOC) refers to those telephone carriers who were formed as a result of the breakup of AT&T and are based on a restructuring agreement that took effect in 1984. The RBOCs were organized into seven regional Bell holding companies called Ameritech, Bell Atlantic, Bell South, Nynex, Pacific Telesis, Southwestern Bell, and US West. Each RBOC was assigned a specific geographical area, and each geographical area was divided into service areas called LATAs (local access and transport areas). The RBOCs are also called the ILECs (incumbent local exchange carriers). In contrast, CAPs (Competitive Access Providers) and CLECs (competitive local exchange carriers) are companies that compete against the RBOCs in the local service areas. IXCs (interexchange carriers) are long-distance service providers such as AT&T, MCI, and Sprint. The Telecommunications Reform Act of 1996 changed the telecommunications landscape yet again. RBOCs were allowed to merge and the following mergers or acquisitions took place in the following years. The Act also attempted to increase competition by opening local markets. RBOCs were required to open their facilities to competitive providers and, if they complied according to the rules, were allowed to expand into long-distance markets.

RDI: Remote Defect IndicationRemote Defect Indication (RDI) is an indication in an ATM network that indicates a failure has occurred at the far end of the ATM network. The RDI alarm indication does not identify the specific circuit in a failure condition. When the physical layer detects loss of signal or cell synchronization, RDI cells are used to report a VPC/VCC failure. RDI cells are sent upstream by a VPC/VCC endpoint to notify the source VPC/VCC endpoint of the downstream failure.

Receive-After-Transmit Time DelayReceive-after-transmit time delay refers to the time interval between (1) the instant of keying off the local transmitter to stop transmitting and (2) the instant the local receiver output has increased to 90% of its steady-state value in response to a fro signal from a distant transmitter.

Received Noise PowerReceived noise power refers to the following different meanings: 1. The calculated or measured noise power, within the bandwidth being used, at the receive end of a circuit, channel, link, or system. 2. The absolute power of the noise measured or calculated at a receiving point. The related bandwidth and the noise weighting must also be specified. 3. The value of noise power, from all sources, measured at the line terminals of telephone set's receiver. Either flat weighting or some other specific amplitude-frequency characteristic or noise weighting characteristic must be associated with the measurement.

ReceiverReceiver is a device on a transmission path which converts the signals as received from the transmission system into the signals required by the destination equipment.

Receiver Off-Hook ToneReceiver Off-Hook Tone is one of the audible tones in telephone system, which is used to cause off-hook customers to replace the receiver on-hook on a permanent signal call and to signal a non-PBX off-hook line when ringing key is operated by a switchboard operator.

Recorder Connected ToneThe Recorder Connected Tone is used to inform the customer that his/her call is connected to a recording machine and that he/she should proceed to leave a message, dictate, etc. It is to be distinguished from the recorder warning tone, which warns the customer that his/her 2-way conversation is being recorded. Recorder Warning Tone is a .5 second burst at 440 Hz every 5 seconds.

Recorder Warning ToneRecorder Warning Tone is one of the audible tones in the telephone system. When recording equipment is used, the Recorder Warning Tone is connected to the line to inform the distant party that the conversation is being recorded. The tone source is located within the recording equipment and cannot be controlled by the party applying the recording equipment to the line. This tone is required by law and is recorded along with the speech. Recorder Warning Tone is a .5 second burst at 1400 Hz every 15 seconds.

RedialerRedialer is an interface hardware device that interconnects between a fax device and a Public Switched Telephone Network (PSTN). A redialer forwards a dialed number to another destination. Redialers contain a database of referral telephone numbers. When the user dials a specific number, the redialer collects the dialed digits and matches them to a listing in its database. If there is a match, the redialer dials the referral number (transparent to the user) and forwards the call to the referral number.

Reed-Solomon CodesReed-Solomon codes are block-based error correcting codes with a wide range of applications in digital communications and storage. Reed-Solomon codes are used to correct errors in many systems including: (1) Storage devices (including tape, Compact Disk, DVD, barcodes, etc) (2) Wireless or mobile communications (including cellular telephones, microwave links, etc) (3) Satellite communications. (4) Digital television / DVB. (5) High-speed modems such as ADSL, cDSL, etc.

Reference CircuitReference circuit is a hypothetical electric circuit of specified equivalent length and configuration, having a defined transmission characteristic or characteristics, used primarily as a reference for measuring the performance of other, i.e. real, circuits or as a guide for planning and engineering of circuits and networks.

Reference NoiseReference noise in telecommunication is the magnitude of circuit noise chosen as a reference for measurement. Many different levels with a number of different weightings are in current use, and care must be taken to ensure that the proper parameters are stated.

RegenerationRegeneration in telecommunication refers to the process of reshaping and amplifying received signals to their original form. This technique is usually applied to digital pulses.

Regenerative RepeaterRegenerative Repeater is a device which regenerates incoming digital signals and then retransmits these signals on an outgoing circuit.

RegisterRegister, in telecommunication, is a part of an automatic switching system that receives and stores signals from a calling device or other sources for interpretation and action, some of which is carried out by the register itself.

Register Progressive ControlRegister Progressive Control refers to a generic type of switching system in which the call progresses blindly one step at a time through the network under control of a translator and a register into which the originating subscriber has dialed the desired telephone number.

Registered EndpointRegistered Endpoint, a concept in a VOIP netowrk, is an endpoint that has informed the Gatekeeper that it is online, active and ready to receive calls, and has received confirmation from the Gatekeeper of its registration request.

Relative Transmission LevelRelative Transmission Level is the ratio of the test-tone power at one point to the test-tone power at some other point in the system chosen as a reference point. The ratio is expressed in decibels. The transmission level at the transmitting switch board is frequently taken as a zero level reference point.

RelayRelay refers to the following meanings: (1). A device, usually electromechanical, by which the variation in current in one circuit causes the opening or closing of contacts controlling the current flow in one or more other circuits. (2). A process of retransmitting signals or messages through an intermediate point or repeater.

Relay LogicRelay Logic refers to the equipment function in which algorithmic decision-making is performed by relay operations. The usual contrast is electronic logic in which the algorithm is carried out by two-state devices, such as flip-flops.

Release-GuardRelease-guard refers to a message sent by an exchange in the backward direction after receiving a "forward-clear" message and when a circuit is placed in the idle condition.

Reorder ToneReorder Tone is a low tone indicating that the local or toll switching or transmission paths to the office or equipment serving the called customer is busy. This signal may indicate a condition such as a timed-out sender or unassigned code dialed. It is interpreted by either a customer or an operator as a reorder signal. Reorder on a local call is a low tone for 0.3 seconds on and 0.2 seconds off. Reorder on a toll call is a low tone for 0.2 seconds on and 0.3 seconds off.

ReroutingRerouting, in telecommunications, refers to the recommencement of route selection from the first point of routing control in the switching system routing process. It takes place when congestion is encountered at some intermediate switching point in the connection that is to be established.

Resistance DesignResistance Design is a design method for subscriber loop circuits design in a telecom service provider. The key point of this method is to employ wire with the smallest diameter (least amount of copper) to ensure a loop resistance less than the signaling limit of the central office equipment serving the loop.

Responsible OrganizationResponsible Organization refers to, in telecommunications with 800 Portability, those organizations to whom the Number Administration Service Center (NASC) allows to make changes such as carrier, termination, 800 call routing (by time of day, location). A letter Of Agency (LOA) must be on file to change the Responsible Organization each customer/account.

RetrialRetrial refers to any subsequent attempt by a customer, operator, or a switching system to complete a call within a measurement period.

Return LossReturn Loss refers to a measure of the dissimilarity of the impedance of a transmission line and the impedance at its termination. It is a ratio, expressed in decibels, of the power of the outgoing signal to the power of the signal reflected back from an impedance discontinuity. If the terminating impedance exactly matches the characteristic impedance of the line, there is no reflection and the return loss is finite.

Reverse Battery SupervisionReverse Battery Supervision is a form of call supervision in which the signals are furnished from the terminating end of a loop to the originating office by reversing the direction of current flow.

Reverse ChannelReverse Channel refers to the telecommunicating path in the dialing up network from the called party to the calling party. This is the opposite of a forward channel.

Reverting ToneReverting Tone is the same type of signal as a line busy tone. In No. 5 crossbar systems, a second dial tone is sometimes also used when a calling party identification digit is required. The Reverting Tone informs the calling subscriber that the called party is on the same line and that he/she should hang up while the line is being rung. Reverting Tone is Low Tone on and off every 0.5 second at -24 dBm0/frequency.

RingRing refers to the following meanings in telecommunications 1. An audible signal. 2. The process of generating a signal to a subscriber's telephone set. 3. In a 3-conductor switchboard plug, the ring-shaped contact between the tip and the sleeve. 4. Ring topology in data networking.

Ring ConductorRing Conductor is one of two wires of a cable pair used in the subscriber loop that carries the battery power from the central office to the phone system at the customer premise.

Ring ToneRing Tone refers to the audible signal generated in telephone system and sent to a subscriber's telephone set

Ring TripRing Trip is the process of removing the ringing signal from the line at the central office when the called station is taken off-hook.

RingdownRingdown is a method of signaling which employs a ringing signal to operate a device such as a lamp in order to alert an operator. The term originates from the manual ringdown operation of a magneto telephone set.

RingerRinger is the device at a subscriber's telephone set which responds to a ring signal to produce an audible alert.

Rotary Dial TelephoneRotary Dial Telephone is a (old) telephone set at which the dial signaling is entered from a rotary dial as opposed to a TouchTone dial.

Rotary GroupsRotary Groups, also known as hunt group, refers to a series of telephone lines that are programmed to find the next “free line†when a call is received.�

Route AdvanceRoute Advance refers to the routing within a telecom switching system to an alternate route trunk group (or trunk subgroup) when all trunks in a prior trunk group (or trunk subgroup) are busy.

Routing AlternateRouting Alternate refers to the assignment of a substitute or an alternate path through a network for a call when the primary route is not available for immediate use.

Routing CodeRouting Code is the combination of characters or digits required internally by the routing process of a telecom switching system to route a transmission to the desired destination.

Routing IndicatorRouting Indicator is the address or routing code in the message header which indicates to the network as routing instructions for the transmission of the message to its final circuit or destination.

RS-232RS-232, a popular physical layer interface also known as EIA-232 or TIA-232, is a standard for serial binary data interconnection between a DTE (Data terminal equipment) and a DCE (Data communication equipment). It is commonly used in computer serial ports. A similar ITU-T standard is V.24.

RS-422RS-422, also known as EIA-422 or TIA-422, is the balanced electrical implementation of EIA/TIA-449 for high-speed data transmission. Now referred to collectively with RS-423 as EIA-530, it provides for data transmission, using balanced or differential signaling, with unidirectional/non-reversible, terminated or non-terminated transmission lines, point to point, or multi-drop.

RS-423RS-423, also known as EIA-423 or TIA-423, is the unbalanced electrical implementation of EIA/TIA-449 for EIA/TIA-232 compatibility.

RS-449RS-449, also known as EIA-449 or TIA-449, specifiecs the functional and mechanical characteristics of the interface between data terminal equipment and data communications equipment. The electrical signalling standards intended for use with RS 449 are RS-422 for balanced signals, and RS-423 for the unbalanced signals, with data rates up to 2,000,000 bits per second. The standard specified two D-subminiature connectors with 37 and 9 pins for the primary and secondary data circuits.

RS-530RS-530, also known as EIA-530 or TIA-530, is a balanced serial interface standard that generally uses a 25 pin connector. The specification defines the cable between the DTE and DCE devices. It is a replacement for EIA-449, which uses 37-pin connector. It is to be used in conjunction with EIA-422 and EIA-423.

RSS: Remote Switching SystemRemote Switching System(RSS) refers to an electronic switching system that is remote from its

host or control office. All or most of the central control equipment for the RSS is located in the host switching system.

RTP RedundancyRTP Redundancy is a method of overcoming packet loss by doubling packet payload without increasing the number of packets sent.

RTS: Request To SendRequest To Send (RTS) is the EIA/TIA-232 control signal that requests a data transmission on a communications line.

Tele-Communication (Telecom) Terms Glossary and Dictionary - S

SAC: Service Access CodeService Access Code (SAC) refers to a code of the form "NO/lX" that takes the place of an NPA in the dialing sequence in order to access a particular service provided by an IC, BOC, or independent company. SACs currently in use include 700 (IC Services), 800 (800 Service), and 900 (National DIAL-IT* network communications service). SACs are associated with supplementary features that may be ordered by an IC as part of the access charge tariff. A BOC may screen calls and route to an IC-specified point of presence based upon a SAC dialed. There is no requirement that SACs be of the Form N00 nor that all N00 codes be SACs.

SAM: Subsequent Address MessageSubsequent Address Message (SAM) refers to a SS7 (Signaling System No. 7) signaling message which carried further dial numbers after the initial address message has been sent.

SAS: Switched Access ServiceSwitched Access Service (SAS) refers to the services provided by telecommunication carriers to their customers for their use in furnishing their services to end users. It provides a two-point electrical communications path to a customer's facilities from an end user's premises. It provides for the use of common terminating switching and transport facilities and common subscriber plant of the Telephone Company. Switched Access Service provides for the ability to originate calls from an end user's premises to a customer's facilities, and to terminate calls from a customer's facilities to an end user's premises in the LATA where it is provided. There are 4 types of Switched Access Services: (1) Feature Group A: Switched Access provides line-side interconnection to Verizon's end office switches through an end user seven-digit access code (NXX-XXXX) for the long distance customer's use in originating and terminating calls to end users. (2) Feature Group B: Switched Access provides trunk-side interconnection to Verizon's end office switches through a uniform seven digit access code (950-XXXX) for the long distance customer's use in originating and terminating calls to end users. (3) Feature Group C: Switched Access provides trunk-side interconnection to Verizon's end office switches for providers of MTS and WATS for originating and terminating communications. (4) Feature Group D: Switched Access provides trunk-side interconnection to Verizon's end office switches through

either a 101XXXX arrangement or on a pre-subscribed basis for the long distance customer's use in originating and terminating calls to end users.

Satellite Operated PBXSatellite Operated PBX is a PBX system which is operating at a remote location and is tied into the primary PBX by means of tie lines. The satellite does not have its own unique incoming central office trunks. All incoming calls are extended to the stations by means of the tie lines.

SCA: Selective Call AcceptanceSelective Call Acceptance (SCA) is a telecommunication feature that allows customers to create a list of phone numbers from which they are willing to accept calls. Callers with phone numbers not on your list hear an announcement informing them that you are not receiving calls at this time.

ScannerScanner, in a telecommunication network, refers to a device in an electronic switching office that scans various parts of the switching network to determine when some change in operations is occurring. Information about the change is passed from the scanner to temporary memory in the controlling computer.

SCF: Selective Call ForwardingSelective Call Forwarding (SCF) is a feature in telecommunications system. Not every call is important. With Selective Call Forwarding, customers can forward callers from a select group of numbers to another number. Customer's list of acceptable numbers can be changed at any time from your phone. Selective Call Forwarding reserves customer's time for only the most important calls.

SCN: Service Control NodeService Control Node (SCN) is an intelligent network function in a communication network which collects traffic data for call services without requiring alteration of, or addition to, programs in all of the service switching nodes in the communication network even if a new call service is introduced as an intelligent network service. A service control node (SCN) has a unit assigning a call service identification (ID) to a new call service and the service switching node provides a registration table receiving the identification (ID) and registering the same in it. If a call service requested by the calling party is in the registration table, the traffic data is collected for the call service.

SCR: Selective Call RejectionSelective Call Rejection (SCR) is a feature in telecommunication system that enable customer to reject incoming calls they don't want to take. Selective Call Rejection screens every call against a "do not accept" list of numbers customers create and rejects those calls on the list. Selective Call Rejection assures you of avoiding calls, freeing customer's line for the calls you want to make and receive!

Screen PhoneScreen phone is a device that looks similar to a standard desk telephone, but is equipped with a

screen (LCD screen) to display communication information such as caller ID. It may also include a small keyboard for the Internet access.

SDA: Selective Distinct AlertingSelective Distinct Alerting (SDA) is a feature in telecommunication system that enables customer's telephone to identify special or important calls. Selective Distinctive Alert easily allows customer to create and update a list of telephone numbers from which calls will ring differently than other calls. The service alerts customer to calls from numbers on your list by providing a distinctive ringing pattern or a distinctive Call Waiting tone.

SDH: Synchronous Data Link HierarchySynchronous Data Link Hierarchy (SDH) is an European standard for data transmission over optical fiber network equivalent to SONET of North America. SDH's basic unit, the STM-1 (Synchronous Transport Module-level 1), operates at 155.52 Mbit/s. Transmission rates of up to 10 Gbit/s can be achieved in today's SDH systems and the 40 Gbit/s systems are possible. SDH systems are fully compatiable to SONET systems.

SDMT: Synchronized Discrete MultitoneSynchronized Discrete Multitone is a modulation technique for point-to-point transmission on a channel whose SNR (Signal to Noise Ratio) is highly frequency-dependent, and it has been adopted by ANSI as the standard for ADSL [up to 7 Mbit/s on unshielded twisted-pair (UTP)]. Synchronized DMT (SDMT), a variation of DMT for multiple point-to-point transmission, will be proposed to the ATIS committee T1E1.4 for VDSL (up to 51.8 Mbit/s on hybrid fiber/UTP), and to the IEEE committee 802.14 for the upstream channel of an HFC system.

SDN: Software Defined NetworkSoftware Defined Network (SDN) is a network that provides customers with the ability to achieve a corporate virtual private network (VPN) while using the facilities of the switched Network. The former AT&T's SDN, for example, is a customer's VPN that resides in the 4ESS-based switched Worldwide Intelligent Network and provides networked-based features and management capabilities that are usually not found in private networks. Some of the networked-based features are customized routing, advance numbering plans, call screening, authorization codes, remote access, security codes and customized billing. SDN is compatible with most private networks and PBXs and, as such, protects these existing investments. Since SDN does not require a sophisticated PBX base, businesses can choose tariffed access or dial-up. The service fully supports analog data transmission at up to 28.8 Kbps and end-to-end digital data transmission at 56/64 Kbps.

SDS: Switched Digital ServiceSwitched Digital Service (SDS) is a data application service providing a digital access line, by means of digital central offices, where facilities permit, to a customer's premises enabling the customer to transmit simultaneously two-way digital signals at a speed of 56 Kbps on a dial-up basis where both the originating and terminating stations are suitably equipped for SDS.

SDSL: Single-line Digital Subscriber LineSingle-line Digital Subscriber Line, also known as Symmetric Digital Subscriber Line (SDSL), is

one variaton of DSL technologies that provides equal bandwidth for both uploads and downloads. SDSL delivers 1.544 Mbps both downstream and upstream over a single copper twisted pair. The use of a single twisted pair limits the operating range of SDSL to 10,000 feet (3048.8 meters).

SDSU: SMDS DSUSMDS DSU is a type of Data Service Unit (DSU) for access to Switched Multimegabit Data Service (SMDS) via High-Speed Serial Interfaces (HSSIs) and other serial interfaces.

Secure TelephoneSecure telephone is a telephone that provides voice security in the form of end-to-end encryption for the telephone call, and in some cases also the mutual authentication of the call parties, protecting them against a man in the middle attack.

SeizeSeize is an action of a switching system in selecting an outgoing trunk or other components for a particular call.

Selector SwitchSelector Switch is the intermediate distributing switch in a step-by-step system. It is directly controlled by the customer dial in its vertical motion and hunts for an idle path in its angular motion.

SenderSender refers to an equipment in a switching system used to transmit and/or receive the called number to or from a distant office; a sender is usually arranged to transmit on a multi-frequency or dial-pulse basis. Under certain conditions of trouble, a sender may remain connected to a trunk without performing its intended function; this is know as a stuck sender.

Serial TransmissionSerial Transmission is a method of data transmission in which the bits of a data character are transmitted sequentially over a single channel.

Service IndicatorService Indicator is part of the information contained in a signaling message that is used to identify the user to whom the message belongs.

Service Observing ToneService Observing Tone is a steady 135 Hz audible tone. It indicates that the trunk to which it is applied is being service-observed. .

SF: Super FrameSuper Frame (SF), also called D4 framing, is a common framing type used on T1 circuits. SF consists of 12 frames of 192 bits each, with the 193rd bit providing error checking and other functions. SF is superseded by Extended Super Frame (ESF) but is still widely used.

SHDSL: Single-Pair High-Speed Digital Subscriber LineSingle-pair high-speed digital subscriber line (SHDSL) is a form of Digital Subscriber Line similar to HDSL but providing T1 or E1 connections over a single twisted-pair copper line.

SIF: Signaling Information FieldSignaling Information Field (SIF) is the bits of a message signal unit that carry information particular to a certain user transaction and always contain a label.

Signal PathSignal Path is the route of a signal channel that carries signaling data.

Signal UnitSignal Unit refers to the group of bit streams of a signaling message that functions as a transferable entities used to convey information over a signaling link.

SignalingSignalling refers to the process of setting-up communications links between two systems such as between a user system and a service provider system. Signaling is used in both traditional telephony and in packet-based communications. SS7/C7 is the most famous signaling system in telephony, while in data communication, the various VOIP signaling methods such as SIP and H.323 are introduced..

Signaling Data LinkSignaling Data Link refers to a type of signaling link that consists of two data channels that operate in opposite directions at the same data rate, and function as a single signaling system.

Signaling GroupSignaling Group is several signaling links that directly connect two signaling points together and have the same physical characteristics (e.g., bit rate and propagation delay).

Signaling LinkSignaling Link refers to: (1) a transmission facility in signaling network that consists of a signaling data link and its transfer control functions, used for reliable transfer of a signaling message between signaling points as an entity. (2) an assembly of signaling information that pertains to a call management transaction, and the like and that is transferred as an entity.

Signaling MessageSignaling Message refers to an assembly of signaling information pertaining to a call that includes, but not limited to, management transactions, that is transferred as an entity.

Signaling Message RouteSignaling Message Route refers to a signaling link (or consecutive signaling links connected in tandem) that is used to convey a signaling message from an originating point to its destination.

Signaling PointSignaling Point is a node in a signaling network (such as SS7/C7 signaling network) that either

originates and receives signaling messages, or transfers signaling messages from one signaling point to another.

Signaling Point CodeSignaling Point Code (SPC) is a binary code uniquely identifying a signaling point in a signaling network. This code is used, according to its position in the label, either as destination point code or as originating point code.

Signaling Point Numbering PlanSignaling Point Numbering Plan is a formal (standardized) description of the method (numbering plan) for converting "end-user-provided" address information into an address understood by the signaling network.

Signaling RelationSignaling Relation refers to a relation formed by two signaling points that involve the possibility of information interchange between corresponding user part functions.

Signaling RouteSignaling Route is predetermined path, described by a succession of signaling points, that can be traversed by signaling messages (directed by a signaling point) toward a specific destination point.

Signaling SystemSignaling System is a language or protocol that enables two switching equipment (element) to converse for the purpose of setting up calls. It possesses a vocabulary of varying size and varying precision, i.e., a list of signals which may also vary in size and a syntax in the form of a more or less complex set of rules governing the assembly of these signals.

Signaling Time SlotSignaling Time Slot refers to a time slot starting in a particular phase of each frame that is allocated for transmitting signaling messages.

Signaling Traffic Management FunctionsSignaling Traffic Management Functions is a control function of routing information used by message routing function. These functions insure the transfer of signaling traffic is performed in a manner that prevents irregularities in message flow.

SIGTRAN: Signaling TransportSignaling Transport (SIGTRAN) refers to a protocol stack for the transport of Switched Circuit Network (SCN) signaling protocols (such as SS7/C7 an Q.931) over an IP network. SIGTRAN, an evolution of the PSTN signaling, defines adaptors and a core transport capabilities that blend SS7 and packet protocols to provide users with the best both technologies have to offer. Applications of SIGTRAN include: Internet dial-up remote access, IP telephony interworking with PSTN and other services as identified.

SimplexSimplex refers to the capability for transmission in only one direction between a sending station and a receiving station. Broadcast television is an example of a simplex technology.

Simplex CircuitSimplex Circuit is a transmission path which is capable of transmitting in only one direction. The ITU definition differs from this more common definition. ITU simplex is a path which can operate in either direction, but only one direction at a time. This is commonly called half-duplex.

Single Frequency SignalingSingle Frequency Signaling is a method of conveying dial-pulse and supervisory signals from one end of a trunk or line to the other, using the presence or absence of a single specified frequency.

Single Order ToneSingle Order Tone is one of the Order Tones. This is a relatively long (0.5 second) signal which means that the originating operator should pass the office name and number. Single-order tone is one 0.5 spurt of High Tone.

SinkSink refers to the end point in telecommunications model which is also called receiver. In this model, a message flows from the "Source" via media (transmission path) to a "Sink".

SIP: Session Initiation ProtocolSession Initiation Protocol (SIP) is an application layer control protocol that can establish, modify and terminate multimedia sessions such as Internet telephony calls. SIP can also invite participants to already existing sessions, such as multicast conferences. Media can be added to (and removed from) an existing session. SIP transparently supports name mapping and redirection services, which supports personal mobility; users can maintain a single externally visible identifier regardless of their network location.

SIP: SMDS Interface ProtocolSMDS Interface Protocol(SIP) is used for communications between CPE and SMDS carrier equipment. SIP provides connectionless service across the subscriber network interface (SNI), allowing the CPE to access the SMDS network. SIP is based on the IEEE 802.6 Distributed Queue Dual Bus (DQDB) standard for cell relay across metropolitan-area networks (MANs). SIP consists of three levels. SIP Level 3 operates at the Media Access Control (MAC) sublayer of the data link layer of the OSI reference model. SIP Level 2 operates at the MAC sublayer of the data link layer. SIP Level 1 operates at the physical layer of the OSI reference model.

SIP-T: SIP for TelephonesSession Initiation Protocol (SIP) for Telephones (SIP-T), previously known as SIP-BCP-T, is a mechanism that uses SIP to facilitate the interconnection of the PSTN with IP. SIP-T allows traditional IN-type services to be seamlessly handled in the Internet environment. It is essential that SS7 information be available at the points of PSTN interconnection to ensure transparency of features not otherwise supported in SIP. SS7 information should be available in its entirety

and without any loss to the SIP network across the PSTN-IP interface. SIP-T defines SIP functions that map to ISUP interconnection requirements.

Skip RouteSkip Route is a control application that causes traffic to bypass a specific route and advance to the following rate selection.

SlaveSlave, in a telecommunication network, refers to the end or side of communications which responds to the master's commands. Master refers to the side in telecommunications that initiates and controls the session.

SLC: Signaling Link CodeSignaling Link Code (SLC) is a field with certain signaling network management messages regarding T1 connections. SLC indicates the particular signaling link to which the message refers among those interconnecting the two involved signaling points.

SM: Switching ModuleSwitching Module (SM) is a component of 5ESS switch of Lucent Technologies which terminates subscriber loops (lines) and inter-exchange trunks interfacing the 5ESS switch. The SM is the basic "growth module" of the 5ESS switch, which service providers can add more when subscriber increases.

Sneak CurrentSneak Current is an unwanted but steady current which seeps into a communication circuit. It is usually too weak to cause immediate damage, but if unchecked could potentially create harmful heating effects.

SNI: Subscriber Network InterfaceSubscriber Network Interface (SNI) refers to the TDM access links such as DS0, DS1/T1, DS3/T3, E1, E3 that connects CPE and an SMDS switch of the PSTN network.

SoftswitchSoftswitch is the next generation voice and multimedia switch based on the IP technologies. It is design to replace the Class 5 and Class 4 switches based on the circuit switching technologies. Softswitch gets its name because typically it is a software based solution implemented on general purpose computers/servers, while the traditional Class 5 and Class 4 switches are rely on dedicated facilities for inter-connection and are designed primarily for voice communications. Sometimes Call Agent or Media Gateway Controller, a key component in the VOIP solution, is also called Softswith, though the definition of Softswith is often extend to the whole solution.

SONET Line Terminating EquipmentSONET Line Terminating Equipment refers to the element that terminates a SONET line.

SONET MultiplexingSONET multiplexing is the process of transfering low speed traffic to high speed traffic in a

SONET network. It involves generation of the STS-1 signal for each tributary. The STS-1 signal contains the payload traffic plus transport overhead allowing for a variety of tributary types to be accommodated. An STS-n signal is created by interleaving bytes from n STS-1 signals that are mutually synchronized, so there is no timing adjustment required when going to higher level multiplex formats. Drop Module Interfaces (DMI) provide SONET/SDH formatting and multiplexing/demultiplexing of the STS-1 signal; ports for low-speed DS1/E1, DS3/E3, STS-1, OC-1 lines; and termination and framing services for tributaries.

SONET/SDH: Synchronous Optical Network (SONET) and Synchronous Digital Hierarchy (SDH)The Synchronous Optical Network (SONET) and Synchronous Digital Hierarchy (SDH), often combined as SONET/SDH, are a set of related standards for synchronous data transmission over fiber optic networks that are often used for framing and synchronization at the physical layer. SONET is the United States version of the standard published by the American National Standards Institutue (ANSI). SDH is the international version of the standard published by the International Telecommunications Union (ITU). Transmission rates of up to 10 Gbit/s can be achieved in today's SONET/SDH systems and the 40 Gbit/s systems are possible. SONET/SDH systems are fully compatiable with each other.

SONET: Synchronous Optical NetworkThe Synchronous Optical Network (SONET), the US version of the standard published by the American National Standards Institutue (ANSI), is a set of standards for synchronous data transmission over fiber optic networks that are often used for framing and synchronization at the physical layer. SONET is based on transmission at speeds of multiples of 51.840 Mbps, or STS-1. SDH is the international version of the standard published by the International Telecommunications Union (ITU). Transmission rates of up to 10 Gbit/s can be achieved in today's SONET systems and the 40 Gbit/s systems are possible. SONET systems are fully compatiable to SDH systems.

SourceSource refers to the starting point in telecommunications model which is also called sender. In this model, a message flows from the "Source" via media (transmission path) to a "Sink".

Source UserSource User refers to the user who provides the information to be transferred to a destination user during a particular information transfer transaction.

Space Division SwitchingSpace Division Switching is a switching in which single transmission-path routing determination is accomplished in a switch by using a physically separated set of matrix contacts or cross-points.

SPC: Signaling Point CodeSignaling Point Code is a binary code uniquely identifying a signaling point in a signaling network. This code is used, according to its position in the label, either as destination point code or as originating point code.

Special Dial ToneSpecial Dial Tone is used with Three-Way Calling, Centrex station dial transfer, and Centrex conference (station or attendant) services. The user on an existing connection flashes the switch-hook, receives special dial tone, and dials number of the third party to be added to the connection. Special Dial Tone is 350 Hz and 440 Hz at -13 dBm0/frequency for 0.1 second on, 0.1 second off, 0.1 second on, 0.1 second off, 0.1 second on, 0.1 second off, and then on steady.

Special LATA AccessSpecial LATA Access refers to a BOC-tariffed service offering that provides for a non-switched communications path (access link) between an IC Point of Presence (POP) and the premises of its end users, or to a BOC central office for Centrex services. It includes all LATA access services that do not use a BOC switching system.

Speech Digit SignalingSpeech Digit Signaling is a type of channel-associated signaling where time slots (primarily used to transport of encoded speech) are periodically used to carry signaling messages.

Speed CallingSpeed Calling is an optional feature of a telephone system which allows the placing of calls to frequently called numbers through the use of an abbreviated number of dial digits. It is also called abbreviated dialing.

Spelled FiberSpelled fiber is a transparent thin fiber, usually made of glass or plastic, for transmitting light. Optical fiber is a cylindrical structure that transmits light along its axis. The fiber consists of a core surrounded by a cladding layer.

SPID: Service Profile IdentifierService Profile Identifier(SPID) is a number that some service providers use to define the services to which an ISDN device subscribes. The ISDN device uses the SPID when accessing the switch that initializes the connection to a service provider.

Spill-Forward FeatureSpill-forward feature is a service feature in telecommunications that is in the operation of an intermediate office, that, acting on incoming trunk service treatment indications, assumes routing control of the call from the originating office. This increases the chances of completion by offering the call to more trunk groups than are available in the originating office.

SplitterSplitter is an electronic low pass filter that separates the analogue voice or ISDN signal from ADSL data frequencies when they get to the subscriber premises. For outgoing traffic, when they are transmitted from the subscriber premises, it combines the voice and the data frequencies onto one line. This allows a POTS phone connection to operate at the same time as ADSL digital data is transmitted or received on the same line. One splitter is located at the central office and another at the subscriber premises. The splitter at the central office can be separate device or may be incorporated into the DSLAM.

SplittingSplitting refers to a switching function used for several purposes including: (1) disconnection (isolation) of a channel that precedes the point where signaling frequencies are injected, and (2) disconnection (isolation) of a channel that succeeds the point where the signal receiver is connected. Splitting can be used to prevent false operation of signaling equipment (caused by signal reflections and spillover) when signaling information is being received. Splitting can also prevent interference from a preceding circuit or nearby equipment (terminal, or device) when a signaling point is receiving a signaling message.

SPM: Subscriber Pulse MeteringSubscriber Pulse Metering (SPM) is a set of functions that are employed by an analogue telephone system primarily to enable call-charge recording and billing. In order to achieve this, the relevant telephone equipment must be able to accurately determine several factors, amongst which is the ability to measure the duration of the call.

SSN: Subsystem NumberSubsystem Number (SSN), a term in the SS7 network, is the identification number that is used by the SCCP (Signalling Connection Control Part) to determine the local subsystem.

SSP: Service Switching PointService Switching Point(SSP) is an element of a SS7-based Intelligent Network that performs call origination, termination, or tandem switching. A SSP can be a combination voice switch and SS7 switch, or an adjunct computer connected to the local exchange's voice switch. The SSP provides the functionality of communicating with the voice switch via the use of primitives and creating the packets, or signal units, needed for transmission in the SS7 network. The Service Switching Point (SSP) must convert signaling from the voice switch into SS7 signaling messages, which can then be sent to other exchanges through the SS7 network. The exchange will typically send messages related to its voice circuits to the exchanges with a direct connection to it. In the case of database access, the SSP will be sending database queries through the SS7 network to computer systems located centrally to the network. This was the first usage of the SS7 network, as the need for 800 number lookup became necessary.

Start Dial SupervisionStart Dial Supervision is the line protocol that defines how the equipment seizes the E&M trunk and passes the address signaling information (sends dual tone multifrequency (DTMF) digits). The three main start dial supervision protocols used on E&M circuits are Immediate Start, Wink Start, and Delay Dial.

Station CodeStation Code is the final four digits of a standard seven- or ten-digit address. These digits define a connection to a specific customer's telephone(s) within the larger context of an NPA and central office code. The term "main station code" is an equivalent expression. In the past, a line number and a party letter often were combined to provide station identification. With the discontinuance of party letters, the four numerics have assumed the role of station identification.

Step-by-Step Switch (SXS) Switching EquipmentStep-by-Step Switch (SXS) Switching Equipment is a two-wire or four-wire progressive control switching system with a space division network. The two-wire version is used for local, local tandem, toll tandem, and private line switching. It can have ANI, CAMA, CENTREX, and private line switching features. The four-wire version is used as a local tandem or toll tandem.

STM: Synchronous Transmission ModuleSynchronous Transmission Module (STM), also known as Synchronous Transfer Mode, is the basic rate of transmission of the SDH ITU-T fiber optic network transmission standard. It has a bit rate of 155.52 Mbit/s and is the SDH equivalent of an OC-3 (SONET).

STM-0: Synchronous Transmission Module level zeroSynchronous Transmission Module level zero (STM-0) is the SDH ITU-T fiber optic network transmission standard. It has a bit rate of 51.84 Mbit/s and is the SDH equivalent of an OC-1 (SONET).

STM-1: Synchronous Transmission Module level oneSynchronous Transmission Module level one (STM-1) is the basic rate of transmission of the SDH ITU-T fiber optic network transmission standard. It has a bit rate of 155.52 Mbit/s and is the SDH equivalent of an OC-3 (SONET).

STM-4: Synchronous Transmission Module level 4Synchronous Transmission Module level 4 (STM-4) is one of the transmission mode of the SDH ITU-T fiber optic network transmission standard. It has a bit rate of 622.08 Mbit/s and is the SDH equivalent of an OC-12 (SONET).

STM-n: Synchronous Transmission Module level nSynchronous Transmission Module n (STM-n), also known as Synchronous Transfer Mode n, refers to a group of the transmission modes of the SDH ITU-T fiber optic network transmission standard, which is the multiplexing "n" of the STM-1 frames.

Stored Program ControlStored Program Control refers to a control of a telephone switch network by means of programmable operating instructions, resident in a semipermanent memory. The main purpose for introducing stored program control is to provide flexible systems where additions and changes can be introduced primarily through program modification rather than through changes in hardware.

STP: Signal Transfer PointSignal Transfer Point(STP) is an element of a SS7-based Intelligent Network that performs routing of the SS7 signaling.

StratumStratum is a hierarchical clock reference in the PSTN network, where 1 represents the highest possible quality of clocking.

Stratum 3Stratum 3 is a precision timing reference that provides a free-run accuracy of plus or minus 4.6 parts per million (PPM), pull-in capability of 4.6 PPM, and holdover stability of fewer than 255 slips during the first day.

STS-1: Synchronous Transport Signal level 1Synchronous Transport Signal level 1(STS-1) is the basic building block signal of SONET, operating at 51.84 Mbps. Faster SONET rates are defined as STS-n, where n is a multiple of 51.84 Mbps.

STS-3c: Synchronous Transport Signal level 3, concatenatedSynchronous Transport Signal level 3, concatenated(STS-3c) is the SONET format that specifies the frame structure for the 155.52-Mbps lines used to carry ATM cells.

STS-N: Synchronous Transport Signal Level NSynchronous Transport Signal Level N (STS-N) refers the basic logical building block signal of synchronous optical networks (SONET) data rate. There are 5 different data rates currently available and denoted as STS-N where N = 1,2,12,48, and 192). The STS-1 signal is known as the SONET basic rate (data rate of 51.84 Mbps) and is designed to carry one DS-3 Signal (the most popular long-haul digital signal in North America).

SU: Signal UnitSignal Unit(SU) is an element in the SS7 network in which signaling information is passed over the signaling links in messages. Signal units are continuously transmitted in both directions on any link that is in service. SS7 uses three different types of signal units: Message Signal Units (MSUs); Link Status Signal Units (LSSUs); and Fill-In Signal Units (FISUs).

Submarine Communications CableSubmarine Communications Cable is a cable laid beneath the sea to carry telecommunications between countries. The first submarine communications cables carried telegraphy traffic. Subsequent generations of cables carried first telephony traffic, then data communications traffic. All modern cables use fiber optic technology to carry digital payloads, which are then used to carry telephone traffic as well as Internet and private data traffic.

Subscriber LoopSubscriber Loop is a communication channel between a subscriber station and a carrier's central office. Usually this is a pair of wires.

Subscriber Loop CarrierSubscriber Loop Carrier is a system that allows one pair of wires, that would normally provide one phone line, to carry multiple conversations. Various models are available, with a capacity ranging from 2 to 96 lines. It is used between phone company central offices and areas where there are too many customers for the cable that is in place.

Subsequent Address MessageSubsequent Address Message is a SS7 (Signalling System No. 7) signalling message which carries further dial numbers after the initial address message has been sent.

Sub-Voice GradeSub-voice Grade is a communications channel with a bandwidth less than that of a voice grade channel. Usually it is derived from a voice grade channel by some form of multiplexing.

Supervisory SignalsSupervisory Signals refer to Signals used to indicate or control the states of circuits involved in a particular connection. A supervisory signal indicates to equipment, to an operator, or to a customer that a particular state in a call has been reached and may signify the need for action to be taken.

SwitchA switch is a networking device that connects network segments. There are two categories of switches: packet switch and circuit switch. Packet switch is for data networking operating typically at the layer 2 (Data Link Layer) of the OSI model. It is capable of inspecting the data packets as they are received, determining the source and destination device of that packet, and forwarding that packet appropriately. On the other hand, the circuit switch that establishes connections on demand and permits exclusive use of those connections until they are released. A circuit-switched network is a type of network in which a physical path is obtained for, and dedicated to, a single connection between two end-points in the network during the connection. The traditional voice phone service using PSTN (not the voice over IP) is circuit-switched.

Switch HookSwitch Hook, also called hook switch, is a plunger or switch where a telephone handset sits when the telephone is on hook, or hung up. When the handset is lifted, the switch hook goes up and the telephone is off hook.

Switch MatricesSwitch Matrices are the ratio of the number of input terminals to the number of output terminals of a switch.

Switch TrainSwitch Train refers to the sequence of switches which are involved in the completion of a circuit path from an originating station to a destination station.

Switched AccessSwitched Access is a service or feature that provides the transport of switched traffic between end-user and carriers. Switched Access connects end-users to Interexchange Carriers (IXCs), wireless carriers, and competitive local exchange Carriers (CLECs). Long distance calls and calls to cellular phones both rely upon switched access services to connect end-users to the networks of the called carrier. Switched Access is composed of the following fundamental elements: Physical Transport, Switching and Associated Options, and Carrier Common Line (Local Loop).

Switched CallsSwitched Calls refer to the traditional telephone calls in which a user picks up a phone, hears a dial tone, and enters the destination phone number to reach the other phone. Switched calls also can be private line auto-ringdown (PLAR) calls, or tie-line calls for fixed point-to-point connections.

Switched-1536Switched-1536, also known as H11 data service, is a data service consisting of a single 1536 kbps circuit, called an H11 channel. The H11 channel is comprised of all 24 channels on the line. Two T1 PRI lines are required to access switched-1536. One line carries the user data, and the other line contains the D-channel. NFAS is required for this data service because the D channel must be on a separate line. This service is available over T1 PRI lines only.

Switched-384Switched-384, also known as H0 data service, is a data service consisting of a single 384 kbps circuit, called a H0 channel. The H0 channel is comprised of 6 B channels. This service is available over T1 PRI lines only.

Switched-56Switched-56 is a data service consisting of a single 56 kbps channel. This service is available over any type of line. It is the only service available to T1 access lines and Switched-56 lines. Because Switched-56 was the first available data service, both the service itself and the lines that accessed it were called Switched-56. However, any type of line can now access Switched-56 data service, and there are other new services in addition to Switched-56.

SwitchhookSwitchhook is a switch on a telephone set, associated with the structure supporting the receiver or handset. It is operated by the removal or replacement of the receiver or handset on the support.

Switchhook FlashSwitchhook Flash refers to a signaling technique whereby the signal is originated by momentarily depressing the switchhook. The technique is sensitive to variations in the time of depression. Too short a signal will not be recognized and too long a signal will be interpreted as a disconnected signal.

Switching FeeSwitching Fee is per-line fee imposed by the LEC (Local Exchange Carrier) to reprogram their switching system to change customer's default long distance carrier. Some long distance carrier will reimburse the subscribers for this fee.

Switching MatricesSwitching Matrices are the mechanism that provides signal paths between its input and output terminations. Modern matrices are electronic and involve either time or space division switching. A time division switch employs a TDM process, in a time-slot interchange (TSI) arrangement. In space division, a physical, electrical, spatial link is established through the switch matrix. Whereas older space division switches used electro-mechanical mechanisms with metallic

contacts, modern space-division switches are implemented electronically using integrated circuits.

Switchless ResellerSwitchless Reseller refers to a reseller who owns no communications facilities and buys long distance service in bulk from a long distance company and resells that service to smaller users.

SXS: Step-by-Step SwitchStep-by-Step Switch(SXS) refers a bidirectional, biselective switch (vertical and angular) in which the moving contact selects from among 100 fixed contacts arranged in a 10 x 10 array.

Symmetric Digital Subscriber LineSymmetric Digital Subscriber Line (SDSL), also known as Single-line Digital Subscriber Line, is one variaton of DSL technologies that provides equal bandwidth for both uploads and downloads. SDSL delivers 1.544 Mbps both downstream and upstream over a single copper twisted pair. The use of a single twisted pair limits the operating range of SDSL to 10,000 feet (3048.8 meters).

Synchronous NetworkSynchronous network is a telecommunication network in which clocks are controlled to run, ideally, at identical rates, or at the same mean rate with a fixed relative phase displacement, within specified limited range. Ideally, the clock is synchronous, but in practice, they may be mesochronous.

System XSystem X is the old name of the UK's first national digital telephone exchange system.

Tele-Communication (Telecom) Terms Glossary and Dictionary - T

T.120The T.120, an ITU-T standard, is made up of a suite of communication and application protocols. T.120 protocols are designed for multipoint Data Conferencing and real time communication, including multilayer protocols which considerably enhance multimedia, MCU and codec control capabilities. Depending on the type of T.120 implementations, the resulting product can make connections, transmit and receive data and collaborate using compatible data conferencing features, such as program sharing, whiteboard conferencing and file transfer.

T.30The T.30, an ITU-T standard, describes the overall procedure for establishing and managing communication between two fax machines.

T.38The T.38, an ITU-T standard, defines procedures for real-time Group 3 facsimile communication over IP networks.

T1T1 is a digital WAN carrier facility. T1 transmits DS-1-formatted data at 1.544 Mbps through the telephone-switching network, using AMI or B8ZS coding.

T1 Access LineT1 Access line is a 1.544 Mbps T1 line that provides twenty-four 64 Kbps data channels and uses in-band signaling. This type of line can contain all switched channels, all nailed-up channels, or a combination of switched and nailed-up channels.

T1 CableT1 Cable refers to a physical cable for T1 Line. T1 cable is two twisted pairs of 22 AWG, 100 ohm wire with the added characteristic that each pair is individually shielded.

T1 CarrierT1 Carrier is a dedicated phone connection, a time-division multiplexed digital transmission facility, supporting data rates of 1.544Mbits per second. A T-1 line actually consists of 24 individual channels, each of which supports 64Kbits per second. Each 64Kbit/second channel can be configured to carry voice or data traffic. Most telephone companies allow you to buy just some of these individual channels, known as fractional T-1 access. Developed in the 1960s, the T1 carrier is designed to operate full duplex over two pairs in unshielded twisted pair (UTP) cable.

T1 LineT1 Line is a general term for a digital carrier typically leased from a local or long-distance provider, capable of transmitting 1.544 Mbps of electronic information. A T1 line is point-to-point, as opposed to a dialable ISDN line. T1 lines may be used fractionally or at their full bandwidth. E1 is the approximate European equivalent, prevalent also in Mexico. E.g., the UT video network is composed primarily of leased T1 lines that carry compressed video and Internet data between UT components.

T1 PRI LineT1 PRI Line is a T1 line that uses 23 B channels for user data, and one 64 kbps D channel for ISDN D-channel signalling. The B channels can be all switched, all nailed up, or a combination of both. This type of PRI line is a standard in North America, Japan, and Korea.

T1/DS-1T1/DS-1 is trunk level 1 that is the equivalent of 24 multiplexed voice grade channels at 64 Kbps. It is a dedicated phone connection with a total speed of 1,544 Mbps.

T2/DS-2T2/DS-2, trunk level 2, is a facility that is equivalent of 4 multiplexed T1 Channels at a speed of 6.3 Mbps.

T3T3 is a digital WAN carrier facility. T3 transmits DS-3-formatted data at 44.736 Mbps through the telephone switching network.

T3 LineT3 Line is a high-speed connection capable of transmitting data at a rate of 45 Mbps. A T3 Line represents a bandwidth equal to about 672 regular voice-grade telephone lines. A T3 Line is typically installed as a major networking artery for corporations and universities with a high-volume network traffic.

T3/DS-3T3/DS-3, trunk level 3, is a facility that is equivalent of 28 multiplexed T1 channels at a speed of 45 Mbps.

T4/DS-4T4/DS-4, trunk level 4, is a facility that is equivalent of 6 multiplexed T3 channels at a speed of 274 Mbps.

TA: Terminal AdapterTerminal Adapter (TA) is a device used to connect ISDN BRI connections to existing interfaces, such as EIA/TIA-232. Essentially, Terminal Adapter is an ISDN modem.

TAB: Telephone Answering BureauTelephone Answering Bureau (TAB), also called Telephone Answering Service, is a supplementary feature of telephone services whereby incoming calls on central office, Centrex Service, Inward Wide Area Telecommunications Service, Airport Telephone Service, and Administrative Terminal Lines may be answered at a common point through the use of answering lines and equipment. The service is available only where selective ringing is used. Various Telephone Answering Services are provided based on equipment, line configuration, and types of equipment used.

TABS: Telemetry Asynchronous Block SerialTelemetry Asynchronous Block Serial (TABS) refers to the former AT&T polled point-to-point or multipoint communication protocol that supports moderate data transfer rates over intra-office wire pairs.

Tactical DesignatorTactical Designator, also called Tactical Callsign, refers a system consisting of a letter of the police phonetic alphabet followed by one or two numbers. For example, "Mary One" might identify the head of a city's homicide division.

TALI: Tekelec's Transport Adapter Layer InterfaceTekelec's Transport Adapter Layer Interface (TALI), a protocol in the SIGTRAN suite, is the interface of a Signaling Gateway, which provides interworking between the Switched Circuit Network (SCN) and an IP network. Since the Gateway is the central point of signaling information, not only does it provide transportation of signaling from one network to another, but can also provide additional functions such as protocol translation, security screening, routing information and seamless access to Intelligent Network (IN) services on both networks.

Talk BatteryTalk Batter refers to a DC voltage supplied by the central office to the subscriber's loop so as to supply the power to voice conversation.

Tandem SwitchingTandem Switching, also called class 4 switching, refers to the switching of long distance calls in PSTN. Tandem is a telephony term meaning "to connect in series." Thus, a tandem switch connects one trunk to another. A tandem switch is an intermediate switch or connection between an originating telephone call and the final destination of the call.

Tandem Tie Trunk SwitchingTandem Tie Trunk Switching is a switched network configuration in which transmission can be routed through two consecutive tie trunks.

Tandem TrunkTandem Trunk is a trunk circuit which connects a tandem switch to another tandem switch or to a telephone company central office.

TASI: Time Assignment Speech InterpolationTime Assignment Speech Interpolation (TASI) is an analog technique used in telecommunications on certain long transmission links to increase voice-transmission capacity. Time Assignment Speech Interpolation works by switching additional users onto any channel temporarily idled because an original user has stopped speaking. While the original user resumes speaking, that user will, in turn, be switched to any cannel that happens to be idle.

TAT-12/13TAT-12 is former AT&T's 12th and 13th transatlantic telephone cables in a ring structure which has been in operation since 1996, initially carrying 2x5 Gbit/s. This was the first TAT cable to use a ring structure, involving two stretches of cable across the ocean floor, which explains why two numbers (12 and 13) were used. All later cables also use a ring structure, but only use one number, TAT-14 etc.

TAT-8TAT-8 is the 8th Transatlantic telephone transport cable. It initially carried 40,000 telephone circuits which means 40,000 simultaneous calls between USA, France, and UK. It was constructed in 1988 by a consortium of companies led by former AT&T, France Telecom, and British Telecom. It was able to serve the three countries with a single trans-Atlantic crossing with the use of an innovative branching unit located underwater on the continental shelf off the coast of Great Britain. The cable lands in Tuckerton, NJ, USA Widemouth, England, and Penmarch, France.

TBOS: Telemetry Byte Oriented Serial ProtocolTelemetry Byte Oriented Serial(TBOS) protocol is an open standard for network management, originally developed by Bellcore for AT&T. TBOS transmits alarm, status, and control points between NE and OSS. TBOS defines one physical interface for a direct connection between the telemetry equipment and the monitored equipment.

TCAP: Transaction Capabilities Application PartTransaction Capabilities Application Part (TCAP), a protocol in the SS7 protocol suite, enables the deployment of advanced intelligent network services by supporting non-circuit-related information exchange between signaling points, using the Signaling Connection Control Part (SCCP) connectionless service. TCAP also supports remote control—ability to invoke features in another remote network switch.

T-CarrierT-Carrier is a digital transmission system standardized by former AT&T for short and medium distance transmissions. T-Carrier is a PCM (Pulse Code Modulation) system using 64 Kbps for a voice channel.

T-CCS: Transparent Common Channel SignalingTransparent Common Channel Signaling(T-CCS) is a feature that allows the connection of two PBXs with digital interfaces that use a proprietary or unsupported CCS protocol without the need for interpretation of CCS signalling for call processing. T1/E1 traffic is transported transparently through the data network and the feature preserves proprietary signalling. From the PBX standpoint, this is accomplished through a point-to-point connection. Calls from the PBXs are not routed, but follow a pre-configured route to the destination.

TCM: Trellis Coded ModulationTrellis Coded Modulation (TCM) is one of the coded modulation techniques used in digital communications. It combines the choice of a modulation scheme with that of a convolutional code together for the purpose of gaining noise immunity over encoded transmission without expanding the signal bandwidth or increasing the transmitted power.

TDD: Telecommunications Device for the DeafTelecommunications Device for the Deaf (TDD) refers to a telephone service that is specially designed for people who have severe speech or hearing disabilities. As of January 26, 1992, all public entities were required by the ADA (Americans with Disabilities Act) to provide people who have severe speech or hearing disabilities equal access to emergency services. This means direct access to 9-1-1 using TTY/TDD's and computer modems. Telecommunicators must be able to effectively handle calls from the community with speech and hearing disadvantage. This involves dispatching these calls for assistance using the appropriate resources in a rational and timely manner. One of the most critical skills that a telecommunicator must possess is recognition of a TTY/TDD call. An entity may provide a separate seven-digit line for use exclusively by non-voice calls in addition to providing direct access for these calls on the 9-1-1 line. If 9-1-1 is not available, an entity can provide emergency service through a seven-digit number. It may provide two separate lines, one for voice calls and one for non-voice calls. If this is done, the entity must ensure that the services provided on the non-voice line are as effective in terms of time response and availability in hours as the voice line. Also this non-voice number must be publicized effectively as the voice number and displayed as prominently.

TDD: Time Division DuplexingTime Division Duplexing (TDD) refers to a transmission scheme that allows an asymmetric flow for uplink and downlink transmission which is more suited to data transmission. In a Time

Division Duplex system, a common carrier is shared between the uplink and downlink, the resource being switched in time. Users are allocated one or more timeslots for uplink and downlink transmission.

TDM Cross-ConnectTDM Cross-Connect allows DSO channels from one T1 or E1 facility to be cross-connected digitally to DS0 channels on another T1 or E1. By using this method, channel traffic is sent between a PBX and CO PSTN switch or other telephony device, so that some PBX channels are directed for a long-distance service through the PSTN while the router compresses others for interoffice VoIP calls. In addition, Drop and Insert can cross-connect a telephony switch (from the CO or PSTN) to a channel bank for external analog connectivity.

TDM: Time Division MultiplexingTime Division Multiplexing (TDM) refers to a transmission technique in which a single communications channel is subdivided into a number of time slots, each of which carries the information of a separate data stream. Bandwidth is allocated to each channel regardless of whether the station has data to transmit.

TelcoTelco means a local or regional telephone company that owns and operates lines to customer locations and Class 5 Central Office Switches. Telcos have connections to other Cos (Central Office), Tandem (Class 4 Toll) offices and may connect directly to long distance carriers such as IECs.

Telco-Return CMTelco-Return cable modem(CM) is a device which uses the cable network only for subscriber downstream traffic, and uses the PSTN for subscriber upstream traffic (which is necessary in older cable plants).

TelecommandTelecommand refers to the transmission of non-voice signals for the purpose of remotely controlling a device.

TelecommunicationTelecommunication refers to the transmission of signals over a distance for the purpose of communication. Telecommunication is widespread and devices that assist the process such as the television, radio and telephone are common in many parts of the world. There is also a vast array of networks that connect these devices, including computer networks, public telephone networks, radio networks and television networks. Computer communication across the Internet, such as e-mail and instant messaging, is just one of many examples of telecommunication.

Telecommunication CircuitTelecommunication circuit refers to a physical telephone and other communication path that is used to transmit information from one location to another. It is also called Telecommunication line.

Telecommunications Act of 1996Telecommunications Act of 1996 refers to a United States telecommunications law, which was the first major overhaul of United States telecommunications law in nearly 62 years, amending the Communications Act of 1934. The general intention of the Act was deregulation and promotion of competition. The Act removed barriers which had previously prevented telecoms from competing head-to-head. A new group of telephone companies, "Competitive Local Exchange Carriers" (CLECs), grew to compete with the incumbents ("ILECs" or Incumbent Local Exchange Carriers). Deregulation and the new entrants provided consumers and businesses with choices in local phone service. When the smaller CLECs faced financial problems, the trend toward competition slowed, turning in to a decade of reconsolidation. The 1996 has widely been regarded by some as a failure. As former FCC Chair Reed Hundt stated, the telecommunications companies chose consolidation over competition. Ten years later, there are fewer telecommunications carriers then there were at the time of enactment. The US Congress is currently considering legislation that would essentially replace the Telecommunications Act of 1996.

Telecommunications ClosetTelecommunications Closet (TC), also called Wiring Closet, is a room or closet that houses all the telecommunication equipment. The TC also serves as a termination point for the horizontal cabling system of a network, the point of circuit administration and contains the network's distribution panels, cross-connects and backbone. The TC may also house auxiliary power supplies for workstation equipment.

Telecommunications NetworkTelecommunications Network is a network of telecommunications paths arranged so that information may be passed from one part of the network to another over multiple paths. The following are some examples or Telecommunications Network: Computer network, the Internet, the public switched telephone network (PSTN). Telecommunications Network generally conceptually consists of three planes (so called because they can be thought of as being, and often are, separate overlay networks.): (1) The Control Plane is the part of the network that carries control information sometimes called signaling. (2) The Data Plane or User Plane is the part of the network that carries its user's traffic or messages. (3) The Management Plane is the part of the network that carries the operations and administration traffic required for network management.

Telecommunications ServiceTelecommunications Service refers to the transmission, emission, or reception of intelligence of any nature, by wire, cable, satellite, fiber optics, laser, radio visual or other electronic, electric, electromagnetic, or acoustically coupled means , or any combination thereof.

Telecommunications Service Priority (TSP) System UserTelecommunications Service Priority (TSP) system user refers to any individual, organization, or activity that interacts with the NS/EP TSP System.

Telecommunications TariffsTelecommunications tariffs refer to the prices charged to consumers by telecommunications service providers.

TelecommutersTelecommuters refers to those who are working remotely accessing the related resources by means of telecommunication. In today’s business climate, companies have become more distributed, and frequently work across time, space, and organizational boundaries. Telecommuters are increasing in the percentage of work force.

TeleconferenceTeleconference refers to holding a conference via a telephone or network connection. The most simple form of teleconferencing is using three-way calling to setup your own teleconference. More advanced PBX equipment can setup conference calls between more than three participants. Computers have given new meaning to the term because they allow groups to do much more than just talk. Once a teleconference is established, the group can share applications and mark up a common whiteboard. There are many teleconferencing applications that work over private networks.

TeledesicTeledesic is a global "Internet-in-the-Sky" that will provide broadband and Internet access, videoconferencing, high-quality voice and other digital data services through a constellation of 288 satellites. The Teledesic Network consists of terminals that interface between the satellite network and the terrestrial end-users, network gateways and network operations and control systems that perform network management functions, and a space segment that provides the communication links and switching among terminals. Teledesic's space-based network uses fast-packet switching to provide seamless, global coverage. Each satellite is a node in the fast-packet-switch network and communicates through crosslinks to other satellites in the same and adjacent orbital planes. Communications are treated within the network as streams of short, fixed-length packets. Each packet carries the network address of the destination terminal, and each node independently selects the least-delay route to that destination.

TeleflipTeleflip is a service that makes it possible for a customer to send short email messages to anyone's phone using only their phone number. The way it works is like this: Open any email program or webmail site, then in the To: field, put your friend's phone number (don't use any parentheses around the area code), followed by @teleflip.com. For instance, if your friend's number was 415-555-1212, you'd just enter: 415-555-1212@teleflip.com. In the body of the message, type a short message, up to 160 characters. You can put something in the subject line too, but it will count towards that 160-character limit, finally,hit Send. Your message will go to TeleFlip, and TeleFlip will convert it into a text message and deliver it to your friend's phone via SMS (Short Message Service).

TelehealthTelehealth is the use of electronic information and telecommunications technologies to support long-distance clinical health care, patient and professional health-related education, public health

and health administration. Technologies used for this purpose typically are: videoconferencing, the Internet, store-and-forward imaging, streaming media, and terrestrial and wireless communications.

TeleoperationTeleoperation refers to the operation of a machine at a distance. It is in analogy to the phrase "remote control". It's most commonly associated with robotics and mobile robots but can be applied to a whole range of circumstances in which a device or machine is operated by a person from a distance.

Telephone Number MappingTelephone Number Mapping, also referred to "E164 NUmber Mapping" or Electronic Numbering (ENUM), is a scheme for mapping telephone numbers to the Domain Name System (DNS) using Dynamic Delegation Discovery System(DDDS). ENUM includes a suite of protocols to unify the telephone numbering system E.164 with the Internet addressing system DNS by using an indirect lookup method, to obtain NAPTR records. The records are stored at a DNS database. ENUM is a DNS-based protocol that is best suited to offer services that not only help facilitate, but expand on ways to complete calls over VoIP networks. It provides a user with a domain name on an E.164 server in order to associate a common international telephone number with a URI and provide other DNS-related services. The server is maintained by the Service Provider and is expected to become a standard since it can successfully address locating URIs with nothing more than a common international telephone number.

TelephonyTelephony is a general term for the technologies behind voice communications, including traditional circuit switched telephone networks and the newer IP telephony technologies (VOIP) over the packet switched networks.

TeletextTeletext is a one-way, or non-interactive, system for transmission of text and graphics via broadcasting or cable for display on a television set. A decoder or microchip resident in the TV set is needed to extract the teletext information. Teletext can be transmitted over one-way cable or over-the-air broadcasting via radio or television.

TeleworkTelework, also called telecommuting, is the ability to do work at a location other than the "official duty station", using networking technologies. With portable computers, high speed telecommunications links, and ever-present pocket communications devices, many employees today can work almost anywhere.

TelexTelex is a teletypewriter service allowing subscribers to send messages over the PSTN.

Terminal EquipmentTerminal Equipment (TE) refers to any ISDN-compatible device that can be attached to the network, such as a telephone, a fax, or a computer.

Terminated LineTerminated Line is a transmission line with a resistance connected across the conductors at the far end. If this resistance matches the characteristic impedance of the line, no signals will be reflected from the far end to distort information transmissions.

Ternary SignalTernary Signal is a type of digital signal which has three voltage levels (e.g., +5v, 0v, and -5v).

Testing SignalTesting Signal is a signal in telephony system used for measuring telephone circuit performance, such as noise bit error rate via loopback arrangement, and also to "trouble shoot" circuit problem and/or equipment faults.

TGW: Trunking GatewayTrunking Gateway(TGW) is a gateway that supports only bearer traffic (no signaling traffic). For example, a gateway that terminates T1s (or greater) with no signaling control is a trunking gateway.

Third Party BillingThird Party Billing refers to the use of an outside service bureau for bill processing such as: call rating, customer invoicing, collections, etc.

TIA/EIA-568 StandardTIA/EIA-568 Standard refers to the complete electrical and physical guidelines for industry-standard premise wiring systems which were developed jointly by the Telecommunications Industries Association and the Electronic Industries Association. As specified by the TIA/EIA-568, a fully functional premise wiring system is the result of multiple subsystems working together as a single network.

TIA: Telecommunications Industry AllianceTelecommunications Industry Alliance(TIA) is an organization that develops standards relating to telecommunications technologies. Together, the TIA and the EIA have formalized standards, such as EIA/TIA-232, for the electrical characteristics of data transmission.

TIA-232TIA-232, a popular physical layer interface, also known as EIA-232 or RS-232, is a standard for serial binary data interconnection between a DTE (Data terminal equipment) and a DCE (Data communication equipment). It is commonly used in computer serial ports. A similar ITU-T standard is V.24.

TIA-422TIA-422, also known as EIA-422 or RS-422, is the balanced electrical implementation of EIA/TIA-449 for high-speed data transmission. Now referred to collectively with TIA-423 as EIA-530, it provides for data transmission, using balanced or differential signaling, with unidirectional/non-reversible, terminated or non-terminated transmission lines, point to point, or multi-drop.

TIA-423TIA-423, also known as EIA 423 or RS-423, is the unbalanced electrical implementation of EIA/TIA-449 for EIA/TIA-232 compatibility.

TIA-449TIA-449, also known as EIA-449 or RS-449, specifies the functional and mechanical characteristics of the interface between data terminal equipment and data communications equipment. The electrical signalling standards intended for use with RS 449 are TIA-422 for balanced signals, and TIA-423 for unbalanced signals, with a data rate up to 2,000,000 bits per second. The standard specified two D-subminiature connectors with 37 and 9 pins for the primary and secondary data circuits.

TIA-530TIA-530, also known as EIA-530 or RS-530, is a balanced serial interface standard that generally uses a 25-pin connector. The specification defines the cable between the DTE and DCE devices. It is a replacement for EIA-449, which uses 37-pin connector. It is to be used in conjunction with EIA-422 and EIA-423.

Tie TrunkTie Trunk is a special service circuit connecting two private branch exchanges (PBXs) or equivalent switching systems.

Tie-LineTie-Line specifies a connection that emulates a temporary tie-line trunk to a private branch exchange (PBX). A tie-line connection is set up automatically for each call and is torn down when the call ends.

Tie-Line TrunkTie-Line Trunk is a PBX trunk that is tied to a line, which leads to a remote PBX; typically used for private telephone networks, although the tie-line connection often is carried on telco-provided lines.

TIIAP: Telecommunications and Information Infrastructure Assistance ProgramTelecommunications and Information Infrastructure Assistance Program (TIIAP) is a grant program from the National Telecommunications and Information Administration of the United States Department of Commerce, established by Congress in 1994 to assist non-profit organizations and units of state and local government to undertake projects which contribute to the building of a national information infrastructure.

Time Consistent Busy HourTime Consistent Busy Hour refers to the identical hour each day over a number of days, during which the highest average traffic is measured.

Time DivisionTime Division refers to a method of serving a number of simultaneous channels over a common

transmission path by assigning the transmission path sequentially to various channels, each assignment being for a discrete time interval.

Time Division SwitchingTime Division Switching is switching of time-division multiplexed (TDM) channels by shifting bits between time slots in a TDM frame.

Time of Day RoutingTime of Day Routing is a routing scheme that routes calls to different locations based on the time of day when a call is made. For example, during business hours, calls can route to an office, and after hours, calls can go directly to a voice-messaging system or to a home number.

TINA: Telecommunications Information Networking ArchitectureTelecommunications Information Networking Architecture(TINA) is a telecom services architecture defined by TINA-C. The resulting architecture specifications were consolidated as "TINA v1.0 Deliverables and Specifications" in September, 2000.

TINA-C: Telecommunications Information Networking Architecture ConsortiumTelecommunications Information Networking Architecture Consortium(TINA-C) was an organization formed in 1993 by 46 of the world's leading Telco operators, vendors and IT industry with the mission to define a common software architecture for telecommunications. As a result, the "TINA architecture" was developed by a group of some one hundred engineers from its member companies, working together at one time under one roof in New Jersey, USA, as its core team. It was announced in September of 2000, that TINA-C had completed its mission and would be dissolved at the end of the year.

TipTip refers to the ball-shaped contact at the end of a two-conductor switchboard plug in an old telephone system.

Tip and RingTip and Ring are telephony slang for the two wires which make up the electrical circuit used for telephone wiring. Tip is the nickname for the electrically positive wire and Ring is the nickname for the electrically negative wire.

Tip CableTip Cable is a small (usually 100-pair) cable connecting terminals on a distributing frame to cable pairs in the cable vault.

Tip SideTip Side is the conductor of a circuit which is associated with the tip of a plug, or of a telephone circuit. It is also called Tip Wire.

TIRKS: Trunk Information Record Keeping SystemTrunk Information Record Keeping System(TIRKS) is a Bellcore OSS that provides records keeping for interoffice trunk facilities.

TL1: Transaction Language 1Transaction Language 1 (TL1) is an element management protocol used primarily in the telecommunication industry. TL1 was designed by Bellcore (now Telecordia) in 1984 for use with its OSS (Operations Support System), MNA. TL1 is an MML (Man Machine Language), which means that TL1 messages should be readable and writeable by humans as well as machines.

TMN Model: Telecommunications Management Network ModelTelecommunications Management Network (TMN) model was introduced by ITU-T Recommendation M.3000 in 1985 as a reference model for the Operation Support System (OSS) of telecommunications service providers. The TMN concept is an architectural framework for the interconnection of different types of OSS components and network elements. TMN also describes the standardized interfaces and protocols used for the exchange of information between OSS components and network elements, and the total functionality needed for network management.

TMN: Telecommunications Management NetworkTelecommunications Management Network(TMN) refers to the standard interfaces that would allow a network to be managed consistently across all network element suppliers. Telecommunications Management Network originated formally in 1988 under the auspices of the International Telecommunication Union (ITU-TS) as a strategic goal to create or identify such standard. The concept has fostered and tracked a series of interrelated efforts at developing standard ways to define and address network elements. Telecommunications Management Network uses the OSI Management Standards as its framework. Telecommunications Management Network applies to wireless communications and cable TV as well as to private and public wired networks.

TollToll refers to, in telecommunications system: (1) the charge for making calls outside the boundaries of an exchange. (2) a general term applied to the facilities and services of carriers used in conjunction with making toll calls.

Toll FraudToll Fraud refers to the fraudulent, illegal use of a company's telecommunications system by a third party from a remote location.

Toll Restriction PBXToll Restriction PBX refers to a PBX that permits a user to call within the local service area, but prevents toll calls to a toll operator without the assistance of an attendant. Toll restriction is available on an individual basis under either of the following options: (1) Battery Reversal: Provides a battery reversal signal from the central office on attempted toll calls which causes the PBX system to route the call to intercept tone. (2) 0/1: Screen calls from restricted lines, and routes calls in which the first or second digit following the access code is a 0 or a 1 to intercept tone. However, station users on 0/1 toll restriction lines can be allowed to make toll calls to up to ten preselected exchange or area codes.

Touch ToneTouch tone refers to Dual Tone Multi Frequency (DTMF) that uses two tones to represent each key on the touch pad. When any key is pressed, the tone of the column and the tone of the row are generated, hence dual tone. As an example, pressing the '5' button generates the tones 770 Hz and 1336 Hz.

Traffic CapacityTraffic Capacity refers to the total volume of traffic which a communications facility can handle within a specified time period.

Traffic GroomingTraffic Grooming refers to the process of taking telecommunications traffic and sorting it into the most efficient arrangement possible. It involves the consideration of network topology and the different routes in use. When dealing with mesh networks, it's especially helpful.

Traffic UsageTraffic Usage refers to the total occupancy of a network. This is calculated as the product of holding time and calling rate, and can be expressed as call-hours. Traffic usage may be made up of many short calls or a few long calls - it doesn't matter.

Traffic-Flow SecurityTraffic-flow security refers to the use of measures that conceal the presence of valid messages on a communications circuit to prevent traffic analysts, normally achieved by causing the circuit to appear busy at all times. Traffic-flow security can be done by the protection resulting from features inherent in some crypto-equipment or by operational procedures.

TransmissionTransmission refers to the act of transmitting electrical signals (messages) and the associated phenonomena of radiant energy that passes through media. Signals can be a series of data unit, such as binary digits, or groups of those, variously called frames, blocks. Transmission has two aspects: (1) the dispatching by a sender, for reception elsewhere, of a signal, message, or any form of information. (2) the propagation of a signal by any means, such as by telegraph, telephone, radio, television, or facsimile via any medium, such as wire, coaxial cable, microwave, optical fiber, or radio frequency.

Transmission BlockTransmission block refers to the following meanings: (1) A group of bits or characters transmitted as a unit and usually containing an encoding procedure for error control purposes. (2) In data transmission, a group of records is sent, processed, or recorded as a unit. Transmission block is usually terminated by an end-of-block character (EOB), end-of-transmission-block character (ETB), or end-of-text character (EOT).

Transmission CoefficientTransmission coefficient is the value of some quantity associated with the resultant field produced by incident and reflected waves at a given point in a transmission medium divided by the corresponding quantity in the incident wave. The ratio of the transmitted to incident energy

flux or flux of some other quantity at a discontinuity in a transmission medium; for sound waves, it is called the sound transmission coefficient. The ratio of the transmitted flux of some quantity to the incident flux for a substance of unit thickness.

Transmission ImpairmentsTransmission Impairments is a condition that causes information to be lost in a signal. The following are some aspects of transmission impairments: (1) Attenuation. Signals loose power in time. (2) Dispersion. Signals tend to spread as they travel, with the amount of spreading dependent on the frequency. (3) Delay distortion. Due to velocity of propagation that varies with frequency. Thus, various frequency components of a signal arrive at the receiver at different times. (4) Noise; sources from Thermal, Intermodulation, Crosstalk.

Transmission LevelTransmission Level refers to the power of a transmission signal at a point on a transmission facility. It may be measured in absolute terms (dbm) or in a ratio to its level at some reference point (db).

Transmission MediumTransmission medium refers to any material substance which can propagate waves or energy for telecommunications purposes. Transmission medium are classified as one of the following: (1) Guided (or bounded)- waves are guided along a solid medium such as a transmission line. (2) Wireless (or unguided) - Transmissions and receptions are achieved by means of an antenna.

Transmission ObjectivesTransmission Objectives refers to the electrical performance characteristics for communication circuits, systems, and equipment based on both economic and technical considerations of telephone facilities, and on reasonable estimates of the performance desired. Characteristics for which objectives are stated include loss, noise, echo, crosstalk, frequency shift, attenuation distortion, envelope delay distortion, etc.

Transmission SystemTransmission system consists of a set of hardware facilities and software that transits a signal from one place to another. The signal can be an electrical, optical or radio signal.

TRIP: Telephony Routing over IPTelephony Routing over IP (TRIP) is a policy-driven inter-administrative domain protocol for advertising the reachability of telephony destinations between location servers and for advertising attributes of the routes to those destinations. TRIP's operation is independent of any signaling protocol; hence TRIP can serve as the telephony routing protocol for any signaling protocol.

Triple Order ToneTriple Order Tone is one of the order tones that has three short spurts of high tone. This signal is three short spurts in quick succession and means that the operator should pass the office name only and wait for another order tone.

Trouble ToneTrouble Tone, also called plugging up code tone, is a steady low tone. It is applied by an operator or test person at a B position in a manual office to the jack sleeve of a line or trunk in a calling multiple, to tell other operators that the line or trunk is in trouble.

TRS: Telecommunications Relay ServiceTelecommunications Relay Service (TRS) is the service that provides a bridge for telephone calls between voice telephone users and people who are deaf, hard of hearing, or speech-disabled. TRS is mandated by the US gorvenment with Disabilities Act and is regulated by the Federal Communications Commission (FCC).

TrunkTrunk refers to physical and logical connections between two switches across which network traffic travels. A switched backbone is composed of a number of trunks.

Trunk MemberTrunk Member refers to a single circuit or trunk in a trunk group.

Trunk OccupancyTrunk occupancy refers to the percentage of time that trunks are in use. Trunk occupancy may also be expressed as the carried CCS per trunk.

TSAPI: Telephony Services Application Programming InterfaceTelephony Services Application Programming Interface (TSAPI) is a call control model developed by Lucent and Novell for NetWare servers.

TSI: Time Slot InterchangeTime Slot Interchange (TSI) is the device in a switching system that permits any received incoming byte from an input tributary to be mapped to any outgoing or transmiting byte, respectively, on the associated output tributary.

TSI: Transmitting Subscriber InformationTransmitting Subscriber Information(TSI) is a frame that can be sent by the caller with the caller's telephone number that can be used to screen calls.

TSP: Telecommunications Service Priority SystemTelecommunications Service Priority (TSP) system is a prioritizing service providing national security and emergency preparedness (NS/EP) that are vital to coordinating and responding to crises. As a result of hurricanes, floods, earthquakes, and other natural or man-made disasters, telecommunications service vendors may become overwhelmed with requests for new telecommunication services and requirements to restore existing telecommunications services. The TSP Program provides service vendors with a Federal Communications Commission (FCC) mandate for prioritizing service requests by identifying those services critical to NS/EP. A telecommunication service with a TSP assignment is assured of receiving full attention by the service vendor before a non-TSP service.

TSPS Busy Verification ToneTSPS Busy Verification Tone is a variation of "Busy Verification Tone" which is 440 Hz at - 13 dBm0/frequency for an initial of 2 seconds on and then on again for 0.5 second every 10 seconds.

TSPS: Traffic Service Position SystemTraffic Service Position System (TSPS) is former AT&T's 5ESS OSPS's ability to provide several applications simultaneously on one switching system. One switch with OSPS can serve up to 128 teams of operators handling different applications, such as directory, tool, and operator assistance.

TTY: TeletypewriterTeletypewriter (TTY) is a communication terminal which is capable of receiving coded character signals from a communications network and converting these signals into printed pages. This specific term is a trademark of the Teletype Corporation, a former AT&T subsidiary.

TUA: TCAP-User Adaptation LayerTeletypewriter (TTY) is a communication terminal which is capable of receiving coded character signals from a communications network and converting these signals into printed pages. This specific term is a trademark of the Teletype Corporation, a former AT&T subsidiary.

TUP: Telephone User PartThe Telephone User Part (TUP) provides the signaling backbone between switching elements for basic call establishment, supervision, and release of circuit switched network connections for telecommunications services. TUP supports analog and digital circuits, and limited call management signaling.

Two-Way TrunkTwo-Way Trunk is the trunk that can be seized at either end which means a traffic may be originated from both side of the trunk. Both sides of the trunk can be used as "outgoing trunk" as well as "incoming trunk".

Tele-Communication (Telecom) Terms Glossary and Dictionary - U

U InterfaceU Interface is the interface between the telco and the user, also known as the local digital subscriber line (DSL) loop.

UncappingUncapping refers to the activities performed to alter customer's ISP (Internet Service Provider) modem settings. One of the purposes of uncapping is to change the bandwidth limitation, such as altering a 512kbit/s access modem to 10Mbit/s. Uncapping is an illegal activity and many ISPs check modem configuration files nightly to detect uncapped modems.

UNE: Unbundled Network ElementsUnbundled Network Elements (UNE), a requirement mandated by the Telecommunications Act of 1996 of USA, are the parts of the network that the ILECs are required to offer on an unbundled basis. Together, these parts make up a loop that connects to a DSLAM or a voice switch (or both). The loop allows non-facilities-based telecommunications providers to deliver service without laying network infrastructure. On February 20, 2003, the FCC adopted new rules for network unbundling obligations of incumbent Local Phone Carrier.

UNE-L: Unbundled Network Elements LoopUnbundled Network Elements Loop (UNE-L), an alternative to the UNE-P, allows CLECs access to or operate their own local switch. The underlying copper (loop) that runs to customer's house is then leased by the CLEC, and cross-connected to the CLEC's switch. Both UNE-P and UNE-L have their own unique advantages and disadvantages. Other CLECs bypass the ILEC's network entirely, using their own facilities. These facility-based LECs include cable companies offering phone service over coaxial cable.

UNE-P: Unbundled Network Elements PlatformUnbundled Network Elements Platform (UNE-P) is a combination of UNEs that allows end-to-end service delivery by a CLEC without ANY facilities. Despite not involving any CLEC facilities, it still requires facilities-based certification from the PUC to deliver services via UNE-P.

Uniform Call DistributorUniform Call Distributor is the feature that accepts incoming calls and distributes them equally among agents in a call center.

Unipolar SignalUnipolar signal is a two-state signal where one of the states is represented by voltage or current ( the current flow can be in either direction ) and the other state is represented by no voltage or current.

Universal Digital CarrierUniversal Digital Carrier refers to one digital copper pair consisting of two analog telephone lines.

Universal ServiceUniversal Service refers to the Federal Universal Service with the goals as mandated by the 1996 Act of USA, to promote the availability of quality services at reasonable and affordable rates; increase access to advanced telecommunications services throughout the Nation; advance the availability of such services to all consumers, including those in low income, rural, insular, and high cost areas at rates that are reasonably comparable to those charged in urban areas. In addition, the 1996 Act states that all providers of telecommunications services should contribute to Federal universal service in some equitable and nondiscriminatory manner; there should be specific, predictable, and sufficient Federal and State mechanisms to preserve and advance universal service; all schools, classrooms, health care providers, and libraries should, generally, have access to advanced telecommunications services; and finally, that the Federal-State Joint

Board and the Commission should determine those other principles that, consistent with the 1996 Act, are necessary to protect the public interest.

UPT: Universal Personal TelecommunicationsUniversal Personal Telecommunications (UPT) are a special segment of the international telephone number space which has been set aside for universal personal telephone numbers. UPT has been allocated country code 878. This concept was introduced by International Telecommunication Union (ITU) in 2001, and referred to as "global number portability".

User Information BitUser information bit is a bit transferred from a source user to a telecommunications system for delivery to a destination user. User information bits do not include the overhead bits originated by, or having their primary functional effect within, the telecommunications system. User information bits are encoded to form channel bits.

User PartUser Part refers to a function in the common channel signaling system. It is used to transfer signaling messages via the message transfer part. There are different types of user parts for telephone, data, and ISDN services. Each user part is specific to a particular application in the signaling system.

User PlaneUser Plane refers to one of the three entities in the ATM reference model. The user plane includes a group of protocols to facilitate the actual data transmission. The other two entities are control plane for signaling and the management plane for network management issues. The concept and model of user plane, control plane and management plane has been extended to other telecommunication technology groups beyond the ATM technology.

UTC: Universal Time CoordinatorUniversal Time Coordinator(UTC), also known as Coordinated Universal Time, is the time standard in telecommunications system developed based on atomic clocks since the accuracy of it has been improved considerably. Before UTC, the time standard was called "mean solar time" which was based on the "rotation of the earth about its axis", with respect to the sun.

Utility-Based Communications Service ProvidersUtility-Based Communications Service Providers refer to utility companies, particularly electric power and gas companies entering the telecommunications market. In the case of the electric companies, there is some interest in providing high-speed internet access as well as traditional voice service over power lines.

UUIE: User-User Information ElementUser-User Information Element (UUIE) is a a type of Information Elements in the ISDN messages, which is used to send user name and other information for call setup.

Tele-Communication (Telecom) Terms Glossary and Dictionary - V

V.24V.24 is an ITU-T standard for a physical layer interface between DTE and DCE. V.24 is essentially the same as the EIA/TIA-232 standard.

V.25bisV.25bis is an ITU-T specification describing procedures for call setup and tear-down over the DTE-DCE interface in a PSDN.

V.32V.32 is an ITU-T standard serial line protocol for bidirectional data transmissions at speeds of 4.8 or 9.6 kbps.

V.32bisV.32bis is an ITU-T standard that extends V.32 to speeds up to 14.4 kbps.

V.34V.34 is an ITU-T standard that specifies a serial line protocol. V.34 offers improvements to the V.32 standard, including higher transmission rates (28.8 kbps) and enhanced data compression.

V.35V.35 is an ITU-T standard describing a synchronous, physical layer protocol used for communications between a network access device and a packet network. V.35 is most commonly used in the United States and in Europe, and is recommended for speeds of up to 48 kbps.

V.42V.42 is an ITU-T standard protocol for error correction using Link Access Procedure for Modems (LAPM).

V.xxV.xx refers to various types of ITU-T communication standard. Some are for simple serial line communication (e.g. V.24, otherwise known as RS232), others are for modem communication (e.g. V.21, V.22, V.23, V.32), and others are for special uses (e.g. V.42, an error correction protocol). Sometimes, these standards are up-dated, and changed slightly, then they have bis added to the end (e.g. V.42bis a data compression protocol).

V5UA: V5.2-User Adaptation LayerV5.2-User Adaptation Layer (V5UA) is a protocol in the SIGTRAN protocol stack for the backhauling of V5.2 messages over IP using the Stream Control Transmission Protocol (SCTP). This protocol may be used between a Signaling Gateway (SG) and a Media Gateway controller (MGC). It is assumed that the SG receives V5.2 signaling over a standard V5.2 interface.

Vacant Code ToneVacant Code Tone is used in crossbar systems to indicate that the dialed office code is unassigned. In step-by-step areas, this signal is called vacant level tone. For operator-originated calls, the verbal announcement is preceded by two flashes. In modern systems, recorded verbal announcements are used for this service. Vacant Code Tone is Low Tone for 0.5 seconds on, 0.5 seconds off, 0.5 seconds on and 1.5 seconds off.

Vacant Position ToneVacant Position Tone is a steady low tone. It is applied to all straightforward trunks terminating in a vacated position in manual offices.

VAD: Voice Activity DetectionVoice Activity Detection(VAD) is a function when enabled on a voice port or a dial peer, silence is not transmitted over the network, only audible speech. When VAD is enabled, the sound quality is slightly degraded but the connection monopolizes much less bandwidth.

VAD: Voice Activity DetectorVoice Activity Detector (VAD) is the device that detects voice activity and allows DTX to operate. In conjunction with DTX, VAD reduces power consumption in the mobile station and RF interference in the system by muting the transmitter when there is no voice to transmit.

Validity CheckValidity Check refers to any check that is designated to ensure the quality of a transmission in telecommunications system. A validity check compares a group of bits with the code being used to ensure that group of bits constitutes a valid character.

Variable Length BufferVariable length buffer is a buffer in telecommunication system. The characteristic of this buffer is that data may be entered at one rate and removed at another rate without the data sequence.

VAS: Value-Added ServiceValue-Added Service (VAS), in telecommunications industry, refers to the non-core services or all services beyond standard voice calls. Conceptually, value-added services add value to the standard service offered by the telecommunications carrier, encouraging the user to use their phone more and allowing the carrier to drive up their ARPU (Average Revenue Per User).

VCDX: Very Compact Digital eXchangeVery Compact Digital eXchange (VCDX) refers to the smallest configuration of the Lucent 5ESS family which is a compact, packet-ready switch that delivers a full range of services from a single platform, using the same hardware and software as the full-size 5ESS switch. The VCDX can easily evolve into a full-size switch or become an element in a packet network within our Circuit-to-Packet Networks architecture, a convergent architecture that provides both cost-saving packet functionality and high-quality voice functionality. It is the product for bridging the transition of circuit networks to Asynchronous Transfer Mode (ATM)/Internet Protocol (IP) networks.

VCO: Voice Carry OverVoice Carry Over (VCO) refers to a method for using TTYs (Teletypewriter). VCO allows people who are hard of hearing or oral deaf (deaf with intelligible speech) to use a TTY without typing. They only use the TTY for reading during the inbound direction of the call. They talk to their party by speaking into a microphone. VCO is often used in confunction with a Realy Service.

VCS: Virtual Circuit ServiceVirtual Circuit Service (VCS) refers to a service made possible by virtual circuit technologies. Virtual Circuit is created within a shared telecommunication network system between two network devices. There are two types of Virtual Circuits: switched virtual circuits (SVCs) and permanent virtual circuits (PVCs).

VDSL: Very-High-Data-Rate Digital Subscriber LineVirtual Circuit Service (VCS) refers to a service made possible by virtual circuit technologies. Virtual Circuit is created within a shared telecommunication network system between two network devices. There are two types of Virtual Circuits: switched virtual circuits (SVCs) and permanent virtual circuits (PVCs).

VDSL2: Second Generation VDSLVirtual Circuit Service (VCS) refers to a service made possible by virtual circuit technologies. Virtual Circuit is created within a shared telecommunication network system between two network devices. There are two types of Virtual Circuits: switched virtual circuits (SVCs) and permanent virtual circuits (PVCs).

Vertical Redundancy CheckVertical Redundancy Check is the scheme or process of checking errors in communication/modem transmissions by combining vertical error checking and longitudinal error checking.

VIC: Voice Interface CardVoice Interface Card(VIC) connects the system to either the PSTN or to the PBX.

Virtual Call CapabilityVirtual call capability, also called a virtual call facility, is a service feature in telecommunications. Virtual call capability has the following characteristics: (1) A call set-up procedure and a call disengagement procedure determine the period of communication between two data terminal equipments (DTEs) in which user data is transferred by the network in the packet mode of operation. (2) End-to-end transfer control of packets within the network is required. (3) Data may be delivered to the network by the call originator before the call access phase is completed, but the data is not delivered to the call receiver if the call attempt is unsuccessful. (4) The network delivers all the user data to the call receiver in the same sequence in which the data is received by the network. (5) Multi-access DTEs may have several virtual calls in progress at the same time.

Virtual CollocationVirtual Collocation may means the following: 1) an interconnection agreement where one telephone company owns, installs and maintains equipment to connect networks at another telephone company's request. 2) a logic connection between end users that has a defined route and endpoints in ATM network.

Virtual SwitchingThe Virtual Switching is a technology allowing multiple switching functions to happen in one physical device or single functional switching to happen in multiple physical devices across network, while in the situation of a real switch, switching is conducted in one physical switch. Virtual switching technology enables a single switch to be used for many different applications. Each different function may have its own discrete performance and security controls. Using virtual switching technology, Service providers can create a dynamic service mix, as desired, without requiring new hardware and enabling the gradual evolution to include new services or a common control plane. Virtual switching is a core concept in the Multiservice network switching architecture.

VMB: Voice Mail BoxVoice Mail Box (VMB), in a telephony network, is a service that provides answering machine services for hundreds or thousands of users. Each user will have their own Voice Mail Box on the system. Each mail box will have a box number and a pass code.

Voice FrequencyVoice Frequency refers to the frequency range for the average human voice, which, when applied to station carrier, is 300 to 3400 Hz.

Voice Grade ChannelVoice Grade Channel is a channel suitable for the transmission of speech, digital or analog data, or facsimile, generally having a frequency range of about 300 to 3400 Hz.

Voice MailVoice Mail is a centralized telecommunication system to manage telephone messages for a large group of subscribers. It replaces the function of traditional telephone answering machine, uses a standard telephone handset for the user interface with indication of voice messages waiting and access method. Voice Mail is more sophisticated than traditional answering machines with much more functions such as remotely accessing the voice mail box from different phones in different locations.

Voice PortVoice Port is an apparatus placed at the telephone subscribers premises that modulates and demodulates the DS0 voice upstream and downstream channels in cable-TV networks.

Voice Response UnitVoice Response Unit refers to a technology that, by using a phone line, interfaces a person to information held in a PC.

VoIP: Voice over IPVoice over IP (VOIP) refers to a group of technologies that use the Internet Protocol (IP) to transmit voice as packets over an IP network. Using VOIP protocols, voice communications can be achieved on any IP network regardless it is Internet, Intranets or Local Area Networks (LAN). In a VOIP enabled network, the voice signal is digitized, compressed and converted to IP packets and then transmitted over the IP network. VOIP signaling protocols are used to set up and tear down calls, carry information required to locate users and negotiate capabilities. The key benefits of Internet telephony (voice over IP) are the very low cost, the integration of data, voice and video on one network, the new services created on the converged network and simplified management of end user and terminals.

VT: Virtual TributaryVirtual Tributary (VT) is a signal designed for transport and switching of sub-STS-1 payloads.

VT-n: Virtual Tributary Level nVirtual Tributary Level n (VT-n) is a SONET format for mapping a lower-rate signal into a SONET payload. For example, VT-1.5 is used to transport a DS-1 signal.

Tele-Communication (Telecom) Terms Glossary and Dictionary - W

Warning ToneWarning Tone is a high steady tone which warns an operator that the circuit he/she is connected to is not in condition for normal operation. Examples: An operator at an Automatic Display Call Indicator puts a plug into wrong jack, or an operator at a sender monitor puts a plug into a sender supervisory jack while the sender is under a test.

WATS: Wide-Area Telephone ServiceWide-Area Telephone Service (WATS), also known as Wide Area Telecommunications Service, is a specialized form of fixed-rate long-distance telecommunication service. WATS lines are commonly used by businesses and government agencies. Some individuals and small corporations also have WATS subscriptions. There are three types of WATS lines: IN-WATS (for incoming calls), OUT-WATS (for outgoing calls), or a combination of both services. IN-WATS lines have telephone numbers with certain area codes reserved expressly for that purpose, such as 800, 888, or 877. People calling these numbers are not charged a long-distance toll. Instead, the recipient (subscriber) is charged a fixed monthly rate up to a certain number of hours of usage. Beyond the limit, an additional toll is imposed. OUT-WATS lines are, in effect, fixed-rate long-distance subscriptions.

Wink StartWink Start is a method of E&M signaling. When the signaling leads indicate a change to an off-hook state, the other side must send a momentary wink (on-hook to off-hook to on-hook transition) on the correct signaling lead before the call signaling information can be sent by the sending side. After the call signaling information is received, the side that sent wink goes off-hook again and stays that way for the duration of the call.

Wink Start SignalingWink Start Signaling is the most commonly used trunk signaling type. In Wink Start operation, the originating trunk circuit goes off-hook. The remote switch detects the off-hook signal, transmits an off-hook pulse that is between 140 and 290 mess in length, and returns to the idle (on-hook) state. The originating trunk detects the Wink Back, waits for at least 210 mess and outputs digits to the remote switch. When the call is answered, the terminating switch will indicate this by an off-hook condition.

Wire CenterWire Center is the building in which one or more local switching systems are installed and where the outside cable plant is connected to the central office equipment.

Wire Center Serving AreaWire Center Serving Area refers to the area of an exchange served by a single wire center.

Wire TapWire Tap is an apparatus which is utilized to monitor conversations over telephone lines or the Internet by a third party, often by government agents. Historically, the monitoring connection was applied to the wires of the telephone line of the person who was being monitored and drew off or tapped a small amount of the electrical signal carrying the conversation so it is also called Telephone Tapping.

Work AreaWork Area in telecommunication system is the collection of all cable components between a horizontal-wiring wallplate or LAN outlet and end-user telecomm devices, such as telephones, data terminals, computers, modems, etc.

Tele-Communication (Telecom) Terms Glossary and Dictionary - X Y Z

X.25 Packet SwitchingX.25 Packet Switching refers to the switching process between the data terminal equipment (DTE, a user machine) and the data circuit terminating equipment (DCE, a network component), using X.25 protocol. In a typical X.25 Packet Switching network, the major components are the customer premises equipment (CPE, e.g., user terminals or host computers), packet assemblers/Dis-assemblers (PADs), concentrators, and X.25 switches.

xDSL: Digital Subscriber LinexDSL refers to a collection of Digital Subscriber Line(DSL) technologies, which is a modem technology for broadband data access over ordinary copper telephone lines (POTS) from homes to businesses. xDSL refers collectively to all types of DSL, such as ADSL (and G.Lite), HDSL, SDSL, IDSL and VDSL etc. They are sometimes referred to as last mile (or first mile)

technologies because they are used only for connections from a telephone switching station to a home or office, not between switching stations.

Yellow AlarmYellow alarm, also known as Remote Alarm Indication (RAI), is an indication provided to a source device indicating a signal failure condition at a sink device. An incoming yellow alarm indicates that the T1 network element connected to the T1 interface has a problem with the signal it is receiving from the T1 interface.

ZBTSI: Zero Byte Time Slot InterchangeZero Byte Time Slot Interchange (ZBTSI) is a technique used to ensure pulse density for clear channel capability. ZBTSI is applied to a DS1 frame to ensure that pulse density requirements are met, where bits 2 through 193 of each frame are scrambled to minimize the occurrence of all-zero octets.

Zero-Dispersion SlopeZero-dispersion slope, in a single-mode optical fiber, refers to the rate of change of dispersion, with respect to wavelength, at the fiber's zero-dispersion wavelength.

Zimmermann TelegramThe Zimmermann Telegram was a telegram dispatched by the Foreign Secretary of the German Empire, Arthur Zimmermann, on January 16, 1917, to the German ambassador in Mexico, Heinrich von Eckardt, at the height of World War I. It instructed the ambassador to approach the Mexican government with a proposal to form an alliance against the United States. It was intercepted and decoded by the British and its contents hastened the entry of the United States into the war.

Zulu DateZulu Date refers to the date at Greenwich England. Zulu Date may be ahead of the date in some time zones such as the USA, or behind some other time zones such as Japan, etc.

Zulu TimeZulu Time, also known as Greenwich Mean Tme (GMT), is the time at the Longitude Zero - Greenwich (England). Zulu Time is 6 hours later than Central Standard Time (US) and 5 hours later than Central Daylight-Savings Time. Zulu Time (GMT) is always the same worldwide. Communication network switches are coordinated on Zulu Time.