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1.INTRODUCTION
DEFINITION OF COMMUNICATION:
Communication, at its simplest level, involves the symbolic representation
of thoughts, ideas, quantities and events we wish to record for later retrieval or transmit for
reception at a distant point. Operationally, this involves the transformation of one set of quantities
into others that are somehow more suited for transmission or recording over a degrading medium
and the recording of estimates of the original quantities at the receiving point. The goal of
communication is to achieve the maximum information through across a channel with fixed
capacity.
In its basic electrical sense, the term communication refers to the
sending, receiving and processing of information by electrical means. As such, it started with wire
telegraphy in the1840’s, developing with telephony some decades later and radio at the beginning
of this century. More recently, the use of satellites and fiber optics has made communications even
more wide spread with an increasing emphasis on computer and other data communications.
BASIC COMMUNICATION SYSTEM:
The communication system exists to communicate a
message. This message comes from the information source, which originates it, in the sense of
selecting one message from a group of messages. Although this applies more to telegraphy than to
entertainment broadcasting, for example, it may nevertheless be shown to apply to all forms of
communications. Information itself is that which is conveyed. The amount of information
contained in any given message is measured in bits or digits. The greater the total number of
possible selections, the larger the amount of information conveyed.
Unless the message that comes from the information source
is electrical in nature, it will be unsuitable for immediate sending.
Eventually in transmitter, the
information modules the carrier i.e. is impressed on a high frequency sine wave. The actual method
of modulation varies from one system level to another, thus modulation may be high level low
level, and the system itself may be amplitude modulation, frequency modulation, pulse modulation
or any variation or combination of these, depending on the requirements.
Fig 1.1 BLOCK DIAGRAM OF COMMUNICATION SYSTEM
The transmission channel is the electrical medium that bridges the distance from the source to
destination. It may be a thin wire, a coaxial cable or a radio wave or a laser beam. Every channel
introduces some amount of transmission loss or attenuation. So the signal power progressively
Decreases with increasing distance. Various unwanted undesired effects crop up in the course of
signal transmission.
Noise refers to random and unpredictable electrical signals produced by natural
processes both internal and external to the system. These constitutes are the fundamental system
limitations.
Distortion is waveform perturbation caused by imperfect response of the system to
the desired signal itself.
Interference is caused by extraneous signals from human sources-other transmitter,
power lines and machinery, switching circuits etc.
The receiver operates on the output signal from the channel in preparation for
Noise Source
InformationTransmitter Source
Channel
Receiver Destination
delivery to the destination. Receiver operations include obtained amplification to compensate for
transmission loss, demodulation and decoding to obtain the original signal. Filtering is another
important function at the receiver.
2.ELECTRONIC EXCHANGE
INTRODUCTION :
At the outset this topic covers different types of exchanges, its functions, working
principle, applications in various fields and advantages over conventional electromechanical
exchanges. Basically electronic exchanges are termed as “Electronic Private Automatic Branch
Exchange (EPABX)”. This is small telephone system run by an organization for private use.
“Public Switching Telecom Network (PSTN)” which are also a group electronic exchanges of
higher capacity (having more no of lines) which are linked to each other by a vast network spread
out all over state/country and used for general public. PABX’s are linked to PSTN through
different types of trunk/tie lines.
TYPES OF EXCHANGES:(a) ELECTRO MECHANICAL EXCHANGES:
In olden days, when communication systems were just
being introduced, these electromechanical exchanges were in vogue for a period of 80 to 100 years.
In those days exchange of communication through voice was only the need for the society. So
voice switching/connectivity was done by the help of manual operator connecting between two
subscriber are in later days by the help of cross-bar exchanges and further by STROWGER
exchanges using relays, coils, keys, springs, etc.
(b) ELECTRONIC EXCHANGES: As technology advanced the same switching principle
for voice communication were developing in electronic version using semiconductor devices. This
electronic exchange came into picture in late 70’s using the basic principle of PCM/TDM
technology and 8 bit microprocessors. They were also used mainly for voice switching only. But
presently the technology is so advanced that the electronic exchange use minimum of 32-bit/64-bit
processor and support voice, data, video, text i.e. different multimedia communications.
These exchanges have the following basic components:
POWER PLANT AND BATTERY
M.D.F. AND TELEPHINE INSTRUMENT.
SWITCHING SYSTEM.
3.POWER PLANT
AND
BATTERY
POWER PLANT Majority of exchanges work on –48V DC. This –48V
DC is delivered from a float-cum-boost-charger (FCBC), which converts 230V AC, to DC. In this
positive terminal is grounded. A separate earth pit is constructed for communication equipment,
and +ve of FCBC, terminals in the switch are clubbed and connected to earth so that the resistance
between earth and +ve terminal should be less than 1 ohm. Then –ve terminal will be floating.
FCBC’s are thyristor controlled SMPS types. Switch mode
power plant is the latest versions using transistor switching and also microprocessor-controlled
versions are also available depending on need. They switch from float to charge mode depending
on the condition of the battery.
Battery charger is a completely solid state D.C. power supply,
capable of operating in both constant voltage and constant current modes. It uses thyristors, silicon
diodes, integrated circuits and silicon transistor for high reliability. Meters are provided for
monitoring the D.C. voltage, load current.
The charger cubical is made of rigid angle iron construction. The
panels on the three sides and the top cover are removable and are louvered to provide good
ventilation. The whole unit is made mobile with the use of cast iron wheels. Besides provision have
been made to fix them on foundation bolts, if necessary, on removing the wheels.
Heavier components like transformer and choke are
mounted on the bottom frame while the other components are suitably located to facilitate easy
manipulability and wiring.
The thyristor control circuit is modular construction with glass
epoxy printed circuit board. Control module, meters and other indications and controls are fixed on
the recessed front panel as shown in the drawing enclosed. The thyristor control circuit employs
feedback technique to achieve high degree of regulation.
SPECIFICATION
INPUT VOLTAGE : 185-265 V AC single phase 50 Hz
OUTPUT VOLTAGE: -FLOAT MODE : 48-53 V DCBOOST MODE : 44-66 V DCBATTERY CURRENT : 10 AMPSLOAD CURRENT : 6.5 AMPSTOTAL CURRENT : 16.5 AMPSREGULATION : +/- 1VRIPPLE : 500mv PEAK-PEAK
BATTERY
For meeting essentially and emergencies as –48V DC
batteries back up with necessary amp-hour capacity (standard is 10 hour back-up) is connected in
parallel to FCBC, so that in case of A.C. mains, failure, exchange still works on batteries and
communication does not collapse.
Different types of batteries used in Electronic Exchanges are:
Conventional tubular lead-acid type.
Ni -cadmium type.
Sealed maintenance free (SMF) type.
SMF-VRLA (valve regulated lead acid type).
The last one is the latest model in which no topping up electrolyte
(sulphuric acid) or distilled water is required. It has glass absorbent mat separators between the
electrodes in the cell, which absorbs the gaseous vapors generated during charging of cell. It works
on oxygen recombination principle where water is not
evaporated.
In this 128 port ISDN exchange we are using Triumph-HP batteries, manufactured
by HBLNIFE Power Systems Limited, are value Regulated Lead Acid Batteries. They are designed
to provide long, reliable service life with minimal maintenance
4.MAIN DISTRIBUTION FRAMEAND
TELEPHONE INSTRUMENT
MAIN DISTRIBUTION FRAME (M.D.F.)
M.D.F. is a main distribution frame where all the subscriber lines and
junction lines from exchange are terminated on one side and field cables are terminated on other
side. This facilitates jumpering of any number to any location as per requirement and also exchange
side and line side to identity a fault. Exchange side is provided with protection devices like PTC
and GD tubes. PTC is potential temperature coefficient i.e. it has a varistor where its resistance
increases and opens beyond certain current in order to protect the subscriber card from drawing
excess current. GD tube is a gas-discharge tube (3 pin), which is kept across ‘A’ to earth and ‘B’ to
earth. This protects the exchange against high voltages due to lightning, HT induction, foreign
potential, etc. by the action of gas ionization in GD tube beyond 100 to 110V and grounds the
external voltage.
5.SWITCHING SYSTEM
5.1 GENERAL FEATURES
OF
CORAL FLEXICOM
The switching system used in this 128 port exchange in
VISAKHAPATNAM STEEL PLANT is coral FlexiCom 400.
GENERAL DESCRIPTION:
The Coral FlexiCom digital communications switching system
employs the latest Advancements in telecommunications technology. The Coral FlexiCom system
Is computer controlled, and switches both voice and data signals using Time Division Multiplexing
(TDM). Voice signals, encoded using Pulse Coded Modulation (PCM) and both packet and
channelized data are transmitted through the system over common highways, ensuring an efficient
transfer of signals from one port to another.
The Coral FlexiCom circuitry is divided operationally into two
functions. Control and switching. The system also is divided physically into two sections. Common
Control and Peripheral. Control functions are performed throughout the system, while switching
functions are performed only in the Peripheral
section. While the Peripheral circuitry capacity varies substantially from one configuration to
another in the family, the Common Control circuitry is nearly identical in all systems.
Fig 5.1.1 BLOCK DIAGRAM OF CORAL FLEXICOM SYSTEM
5.2 SYSTEM CONTROL:
Control of the Coral FlexiCom system operation is distributed among processors
throughout a four-level hierarchy within the system. The modular control hierarchy ensures that
control resources grow with the system. The open architecture ensures Continued compatibility
with systems and features yet to be conceived.
The Master Controller (MEX, MCPsl, or MCP-ATS), located in the
Common (Coral Flex Set 80, Flex Set 120, Flex Set 120, etc.) and APA interface modules. Control
section, is responsible for the supervision of the configuration database and system-wide functions.
Card Controllers, located on each card in the Peripheral section (24SFT, 24SLS, 8TPF, etc.),
oversee the status of Shared Service and Peripheral Interface ports. Station Controllers located in
all voice station equipment devices, manage the voice and data functions of multi-button digital
telephone sets Application Processor link to the Master Controller through a proprietary data
communications protocol to provide non-telephony enhancements to the system. This design offers
significant advantages over other systems built around a single point of control.
The number of controllers in the Coral FlexiCom system is directly
proportional to the systems size. When new features or ports are added to the system, control
power is increased as well. As a result, the work load on each controller remains consistent,
regardless of the size of the system. And by evenly distributing control functions, the risk of
system failure is reduced dramatically.
The Card Controller handles the real-time functions of port status
management. Station Controllers manage all display, indicator , data switching and status functions
of multi-button electronic telephone sets. Dedicated Applications Processors integrate processor-
intensive database manipulation and statistical data processing capabilities. The Master Controller
performs less time-critical functions such as management of the system resources and
configuration database, and supervision of diagnostic routine.
The Master Controller executes a multi-tasking operating
system program, which in turn executes the Coral FlexiCom operating software program. The
operating software is divided into task modules, each responsible for a portion of the system
operation. Various modules include voice switching, VoIP, ISDN service, data Switching,
diagnostics, administrative, programming interface, etc. Communications between the Common
Control and Peripheral circuitry is established through the Group Controller is considered neither a
Common Control nor Peripheral function.
The Group controller uses High-Level Data Link
Control (HDLC) channels to provide a two-way, serial data communications link between the
Master Controller and each of the Card Controllers. Each Peripheral Shelf has access to two HDLC
channels. While communications normally occurs on the first channel, the system can use either or
both channels when necessary to ensure absolute system reliability. The Group Controller also
provides Peripheral services functions such as generation of system tones, Peripherals bus timing,
diagnostics testing, and time slot interchange. Each Card Controller executes a card-specific
program to continuously monitor the activity of ports residing on its card and act on instructions
from the Master Controller to change a port state.
The Card Controller is responsible for identifying changes in the status
of each of its ports, such as on-hook/off-hook, hook-switch flash, dialing, ringing, incoming call,
central office disconnect, etc., and reporting these events to the Master Controller. The Master
Controller examines the configuration database, and determines the appropriate response to the
event, such as assigning or releasing time slots, returning dial tone, ringing a telephone, or
releasing a trunk seizure. The Master Controller then instructs the associated Card Controllers to
take the necessary action in order to carry out the response.
The Station Controller identifies station status, such as on hook/off-hook,
incoming data, and key-press sequences; and passes this information via a control channel over
twisted pair wiring to the Card Controller. The Station Controller also interprets control and
display information from the Master Controller, such as speaker on/speaker off, display text,
illuminate indicator LED.s, enable data, etc., and acts on the information accordingly.
Applications Processors provide enhanced functions that are not directly related to
processing calls, such as directory management and statistical computation.
Fig 5.2.1CORAL FLEXICOM SYSTEM CONTROL HIERARCHY
5.3 CORAL SYSTEM CONFIGURATION
The major distinction between Coral system configurations is their number of card
slots, into which Shared Service and Peripheral Interface cards may be inserted.
The Coral I cabinet is a highly cost-effective configuration in a compact,
wall-mount design; with as few as 6 Peripheral Interface and 1 Shared Service card slots (Coral I-
S); or 10 Universal card slots. Both systems have identical cabinet dimensions, and environmental
and electrical requirements.
The Coral I and Coral I-S cabinets operate from a standard 115/230VAC
power source.
The Coral II cabinet shares the wall-mount design of the Coral I with
slightly larger dimensions. The Coral II offers the option of operating from either 115/230VAC, or
from a 48- volt direct current (DC) stationary battery plant for increased service reliability.
The switching system used in this 128 exchange in Visakhapatnam Steel
Plant is coral FlexiCom 400, which is nothing but coral II.
5.4 CORAL FLEXICOM 400:
The Coral Flexi COM 400 configuration offers greater capacity and flexibility than the
Coral FlexiCom 300 cabinet, yet the wall-mount system remains compact and low-cost. The system
is cost effective for applications of 40 to 300 stations.
The above figure shows the coral FlexiCom 400 cabinet and illustrates the card
slot assignment. Requiring only 35”x 22” of wall space, the coral FlexiCom 400 demands little
more space than the previous version coral FlexiCom 300, yet provides 50% additional port
capacity contains 16 cards slots for both peripheral interface and shared service cards. The Coral
FlexiCom 400 can operate directly from a 48VDC power source, opening up a host of options and
applications, including battery operation where continuous service and maximum reliability are
critical issues. Internal power supplies are available for operation from either 48VDC, allowing the
system to be operated from a standard, .48VDC telecommunications
battery plant, or 115/230VAC.
As mentioned in the figure, the coral FlexiCom 400 cabinets are mainly 3 different
card slots such as:
INTERNAL POWER SUPPLY CARDS (PPS & RPS).
CONTROL CARDS.
PERIPHERAL CARDS.
6.INTERNAL POWER SUPPLY
6.1 PERIPHERAL POWER SUPPLY UNIT (PPS)
GENERAL DESCRIPTION:
The Peripheral Power Supply (PPS) provides internal operating voltages for the
Coral II, Coral II-R and Coral III switching systems. The PPS operates from a nominal input of 48
volts direct current (DC), typically supplied by an external 48VDC rectifier or stationary battery
plant. Actual input may vary from 42 to 58 volts; allowing operation from a battery power source
while the batteries are charged at an equalize charge rate; and under power failure, until the
batteries are completely discharged.
The PPS contains three, pulse width modulated (PWM), switch-mode DC-DC
converters which convert the 48VDC input power to +5VDC, –5VDC, +12VDC, and –12VDC
operating voltages for the Coral internal circuitry. The PPS also further filters and current limits the
48VDC input to feed the peripheral card slots.
All outputs except the –48VDC output are regulated. Voltage and current level
monitoring circuitry check each output of the PPS and produce alarm signaling to the Coral system
main processor in the event of abnormality.
CIRCUIT DESCRIPTION:
Fig 6.1.1 PERIPHERAL POWER SUPPLY BLOCK DIAGRAM
Above Figure presents a block diagram of the PPS power supply.
Three separate, switch-mode, DC-DC converters convert the 48VDC input power to +5VDC,
+12VDC, and –5VDC and –12VDC outputs. One DC-DC converter provides both the –5VDC and
–12VDC outputs. Filtering circuitry minimizes ripple and noise on the –48VDC feed to the
peripheral cards.
The filtering circuitry typically produces an output voltage about 1.5 volts lower than
the input to the PPS. Monitoring circuitry verifies that each voltage output is within tolerance.
Should any voltage fall out of tolerance, the monitoring circuitry produce an alarm signal to the
system processor, and shuts the PPS down. Note that the green power indicator of a PPS in shut
down condition is still illuminated.
Following a shutdown and when there is no clear reason for the voltage to drop
out of tolerance, the power ON/OFF switch must be turned to OFF and then to ON in order to
return the power supply to working order.
SPECIFICATIONS:
PPS (Peripheral Power Supply for Coral II, II-R, III and III-R)
Input:........................................... 42-58VDC, 20A Max.
Outputs:...................................... + 5VDC Nom. Regulated 15A Max.
……………………… ..……. – 5VDC Nom. Regulated 3A Max.
……………………… ........... +12VDC Nom. Regulated 8A Max.
.................................. …….......... –12VDC Nom. Regulated 0.15A Max.
.................................. …….......... –48VDC Unregulated 8A Max.
Indicators: .................................. Power On
............................. ………......Output Voltages Test Jacks
Fuses: .......................................... Input (Peripheral –48V, 15A)
............................. ................ Input (DC-DC Converters 8A)
Controls and Adjustments: Power on Switch
........ +5V Adjust
........ +12V Adjust
........ µV Adjust
6.2 RING GENERATOR POWER SUPPLY UNIT (RPS)
GENERAL DESCRIPTION:
T
The Ringer Power Supply (RPS) provides high voltage ring generator current
required by single-line telephone station ports of the 4SH/S, 8SH/S, 16SH/S, 4SH/S-LL, 8SH/S-
LL, 16SH/S-LL, 8SLS, 16SLS, 24SLS or 8SM cards installed in the Coral II, Coral II-R and Coral
III switching systems. The RPS operates from a nominal input of 48 volts direct current (DC),
typically supplied by an external 48VDC rectifier or stationary battery plant. Actual input may vary
from 42 to 58 volts; allowing operation from a battery power source while the batteries are charged
at an equalize charge rate; and under power failure, until the batteries are completely discharged.
In Coral II systems equipped with APS-2 power supplies; the RPS operates from -
48VDC supplied by the APS-2. The RPS contains a low frequency oscillator and power amplifier
which convert the 48VDC input power to 75, 85, or 105 volts (16, 20 or 25Hz) alternating current
(AC); for use as a ringing and message waiting signal on industry standard, single-line telephone
(SLT); and magneto telephone station ports. The output voltage is selected by choosing a tap on the
output transformer. The output voltage is regulated and adjustable from the front panel. Voltage
monitoring circuitry checks the output of the RPS and produces alarm signaling to the Coral
system main processor in the event of abnormality.
CIRCUIT DESCRIPTION:
Fig 6.2.1 RINGER POWER SUPPLY BLOCK DIAGRAM
Above figure presents a block diagram of the RPS power supply. The low
frequency oscillator produces an AC waveform, which is frequency-selectable via the front panel
mounted selector switch. The frequency selection options are 16Hz, 20Hz and 25Hz. The output of
the oscillator is fed to the power amplifier. A front panel mounted voltage adjust potentiometer
varies the gain of the amplifier, increasing or decreasing the output voltage. The output of the
power amplifier is fed to the output transformer. The output transformer has three taps to select the
nominal output voltage. The monitoring circuit verifies that the RPS is producing ring voltage. If
the monitoring circuit is satisfied; relay K1 is operated, passing the RPS output to BRV OUT, the
BRV bus of the first peripheral shelf. In Coral III cabinets, the RPS output also is
passed through the released contacts of relay K2 to BRV IN, which is
connected to the BRV bus of an adjacent peripheral shelf. If an RPS also is
installed in the adjacent shelf, relay K2 is operated. However, the BRV buses of
both shelves are still bridged together through the contacts of relay K1 in the
second RPS. If both RPS’s are functioning properly, relays K1 and K2 of both
RPS’s are operated, separating the peripheral shelf BRV busses and passing
the RPS outputs only to their respective
peripheral shelves.
SPECIFICATIONS:
RPS (Ringer Power Supply for Coral II, II-R, III and III-R)INPUT:........................................... 42-58VDC, 1A Max.OUTPUT:Voltage................................... Fasten Selectable 75, 85, or 105VACFrequency............................... Switch Selectable 16, 20, or 25HzCapacity.................................. 20VA Max.Indicators: ............................... Power On............................ …….........Output Voltage Test Jacks
FUSES:Input........................................ (-48V) 2A S.BOutput .................................... 1A S.B
CONTROLS AND ADJUSTMENTS:... Power on Switch...Output Voltage Adjust...Output Frequency...Output Voltage Select
7.CONTROL CARDS
GENERAL INFORMATION:
The Common Control portion of the Coral system provides the control mechanism
for establishing audio and data connections, or calls via the PCM bus between Peripheral I/O ports
in the system. Common Control is divided into five different functions:
Main Processor
Generic Feature Memory
Database Memory
Diskette Control
Peripheral Bus Interface or Group Controller.
The Coral Common Control card set consists of an MEX Main Processor and
Database Memory, one or more FSX Generic Feature Memory piggy-back cards, optional DBX
Database Memory Expansion, optional CLA card; an FDC Diskette Drive and Control; and one of
the following: SVC, SVC-D, or SVC-DT Peripheral Bus Interface or SVC-24.
Three different cards are used in the control cards as follows:
IMC8
MEX
SVC 24
7.1 IMC8 (INSTEAD OF 3.5’ DISKETTE):
IMC8 is used for software and database saves and restore The IMC8 is an
integrated Memory Card with 8Mbytes flash memory capacity. It contains the generic software of
the coral. The IMC8 is used to store the system database. An IMC8 slot is mounted on the MEX
board.
MEX requires more memory; IMC8 is used during run-time .The memory
management on the MEX allows part of the code to use portions of the IMC8 memory for run-time.
Therefore, the card must not be removed from its slot during system operation. If removed, the
system may crash. The flash RAM contains two data buses DB0 and DB1.DB0 contains automatic
backup software. This process is being done on every midnight. DB1 is for manual backup.
FLOPPY DISK DRIVE AND CONTROL UNIT (FDC)GENERAL INFORMATION:
The FDC card provides a floppy diskette drive and control circuitry, which
allows software, and database information to be transferred to and from the Coral system memory.
The FDC is used to install and update the feature generic software that determines system
operation. The FDC also may be used to automatically save and restore the system configuration
database that defines the characteristics of each individual installation.\
The FDC assembly incorporates a single floppy diskette drive. Above figure illustrates the front
panel of the FDC card. The diskette drive includes a drive opening where diskettes are inserted into
the drive, a diskette release button used to remove a diskette from the drive, and a read/write status
indicator.
SPECIFICATIONS:
FDC
DISKETTE DRIVE:
Physical Form Factor............... 312“, 13 Height� �
Media Form Factor .................. 312”,� Double Sided, 80 Tracks/Side,
........................ 135TPI High Density 18 Sectors/Track
Modulation Type ......................MFM
Diskette Type: ............................ M2HD Double Sided, High Density
..............................(2MB unformatted, 1.44MB formatted)
Soft Sector Format: ................... Intel RMX formatted 1.44MB �
7.2 MEX
GENERAL INFORMATION:
The MEX card is the “heart” of the Coral system control. The MEX card
integrates, either directly, or through one or more baby cards: the Main Processor, memory
Management circuitry, local bus interface, programming and maintenance data port, real-time
clock, generic feature software memory, and database memory. The MEX supervises overall
system operation by executing system-wide processes. These processes include port connection
management, feature management, generic Feature software installation, feature authorization,
configuration database management, database backup and restoration, Program Interface
input/output, and diagnostic testing. To manage port connections and feature operation, the Main
Processor communicates through the SVC or 4GC card over the HDLC buses with Card Processors
on each peripheral card. The Main Processor receives status messages from the Card Processors
regarding port activity, and determines the appropriate response based on programming entries
contained in the system database.
The Main Processor then instructs the
appropriate Card Processor what action to take with each port. The MEX card also incorporates the
SAU port which accepts the Software Authorization Unit. The SAU provides unique system
identification for the installation site. During software installation, the SAU identification number
is compared with the features authorization data, to verify the authorized use of enhanced Coral
system features. During regular system operation, the SAU is checked to ensure it remains attached
to the MEX. However, if necessary the SAU can be removed for short periods without interrupting
system operation.
All system memory resides on the MEX card. Random access memory
(RAM) is located directly on the MEX card. The MEX also acts as a mother card to baby CLA and
memory cards containing read-only memory (ROM) and RAM expansion memory. ROM, located
on FSX cards, stores the generic feature software, which determines the operation of the system.
RAM, on the MEX, stores the system configuration database. Database memory and real-time
clock functions in the Coral system are protected against power loss through the use of long-life
lithium standby batteries.
A separate battery is installed on the MEX. A monitoring circuit on the card
constantly measures the voltage level of each battery and signals the Main Processor when the
remaining energy stored in any battery approaches the point that it can no longer provide sufficient
power to maintain the memory circuitry. The generic feature software and feature authorization
information is installed and updated from diskette into the CLA and FSX ROM using a diskette
drive located on the FDC card. Similarly, the system database is regularly backed up to, and may
be transferred andrestored from, a database diskette kept in the FDC diskette drive.
The Program Interface provides a text-based facility for reviewing and changing
the system database, and for performing and monitoring diagnostic routines, from a simple data
terminal or personal computer. The Program Interface may be accessed via an RS-232C data
terminal port provided on the MEX front panel, or via additional RS-232C ports and/or a modem
provided on an RMI card.
Fig 7.2.1 FRONT PANEL OF MEX CARD
FRONT PANEL FEATURES:
Above figure illustrates the front panel of the MEX card. The front panel contains
the serial RS-232C programming port interface (referred to as KB0), recessed CPU Interrupt and
Reset pushbuttons, a recessed bank of slide switches used primarily to determine power-up settings
of KB0, the lock device port, and a seven-segment numeric display.
7.3 SVC 24
GENERAL DESCRIPTION:
Fig 7.3.1 SVC24 CARD LAYOUT
SPECIFICATIONS:
Microprocessor:......................... Intel80386SX��
CPU Clock Rate: ........................ 12.5 MHz
Memory Addressing: ................. 16 MB
Data Bus Structure: ................... 16 Bit; Shared with DBX, FSX, FDC,
CLA and SVC/4GC
RAM Storage Capacity:............. 786,432 Bytes (768kB)
Memory Device: ......................... 128kb X 8 bit SRAM
RAM Back-up Battery:............... LF1/2W, 2430, 2430B
Voltage.........................................3.0VDC Nom.
Capacity....................................... 250mAH
Dimensions:
Diameter ................................... 0.965 in. (24.5mm)
Width......................................... 0.118 in. (3mm)
NEDA Equivalent ......................... 5011L
8.PERIPHERAL CARDS
GENERAL INFORMATION:
The Coral system divides Peripheral Interface functions among several
different station and trunk card types. Each card contains 2, 4, 8, 16 or 24 similar circuits, except
for 8TPF and 8ALS cards, which contain four power fail trunk circuits and four standard trunk
circuits.
Each Peripheral card is described in detail in the following sections as
follows:
8DRCM CARD.
ANALOG TRUNK.
DIGITAL TRUNK.
VOICE SWITCHING.
8.1 8 DRCM CARD
This Card integrates various shared services. 8 DRCM Card a
substitute the following functions. RMI – Music, Modem, Page and Relays, The Card includes 2
music sources, one of them can be internal.
8DTD – Eight Dial and Progress tone Detector
8DTR – Eight DTMF Signaling receivers.
CNF – Configured as CONF – One meet me bridge for 6 users.
CNF – Configured as C3WAY – Six circuits of 3-way Conference
Calls.
8DRCM resource card provides:
One (1) Internal or external music interface for music-on-hold and
Coral Flex Set background music
One (1) External music interface for music-on-hold and Coral
Flex Set background music
One (1) External voice paging interface (Public Address) and relay
contacts
One (1) Auxiliary or Major/Minor Alarm relay contacts
One (1) UNA (Universal Night Answer) or Central Bell relay contact
Three (3) RS-232E programming/maintenance interfaces, support
any asynchronous serial data terminal or printer, 7/8 data bits, all
parity options, and data rates of 300 to 38,400 bps
One (1) Bell 103/212A or ITU V.21/V.22, 300/1200bps remote
maintenance modem
Six(6) 3-way call Interface Bridge for three parties Conference/Consultation/Broker service
and Silent monitoring Sessions
One (1) Meet me bridge conference for six parties 8DTD (Eight circuit Dial Tone Detector
and call progress tone analyzer)
8 DTR (Eight circuit DTMF signaling Receiver and decoders) Each of the RS-232E
interfaces and the modem may be used to enter or modify the Configuration database, conduct
diagnostic testing and/or receive station message detail records (SMDR); and provides interface for
the following applications PI,Coral CAP, Coral VIEW Traffic, Coral VIEW Sentry, Coral VIEW
Designer, Coral VIEW Administrator, Wake-Up report printer, PMS Enhanced Hotel/Motel
system, Malicious Call trace report, etc.
The modem may be accessed from any station or trunk port in the Coral
FlexiCom system and requires no other equipment to operate. Each music port provides a line level
(–15dBm), balanced, 600_ audio pair. A music input provides music-on-hold to stations and trunks
placed on hold and background music over Coral FlexSet telephone speakers. The external paging
interface, night bell relay and alarm/auxiliary relay each provides a separate, single pole, single
throw, normally open.
Fig 8.1.1 8 DRCM CARD LAYOUT AND FRONT PANEL
8.2 ANALOG TRUNK
GENERAL DESCRIPTION:
The 8T, 8TPF, 8T/S, and 8T/S-PF cards contain eight circuits which
provide a two-wire PABX trunk circuit. The circuits are intended to be connected to central office,
loop signaling (loop- or ground-start) trunks. The circuits appear to the central office roughly
similar in nature to a single line telephone set. Each circuit provides loop termination for initiating
outbound and answering inbound calls. Inbound call detection is accomplished by detecting high
voltage alternating current, monitoring the tip (ground) conductor for central office ground, or
both. Cards with the /S suffix are functionally identical to cards without.
On 8TPF and 8 T/S-PF cards, circuits 2, 3, 4, and 5 also contain a transfer
circuit to connect the central office (CO) trunk metallically to a specific station, in the event of a
power loss to the system. Two additional pairs are used to connect the station circuit through the
transfer circuit of the trunk. With the exception of the transfer circuitry, the 8 TPF and 8T/S-PF
cards are otherwise identical with the 8T and 8 T/S cards, respectively.
Telephone sets used for power failure must be industry standard,
single line telephone sets (SLT), or proprietary EKT-PF telephone sets. Standard key sets may not
be used for power fail stations. Each circuit may be individually strapped for loop or ground start
signaling, and 600 ohms or 900 ohms nominal impedance.
Note that on some card layouts, two straps must be positioned to select loop or
ground start operation. The impedance of circuits on 8T/S and 8T/S-PF cards is fixed at 600 ohms.
In order to determine the I/O connections for all possible Coral configurations and slot positions.
CIRCUIT DESCRIPTION:
Fig 8.2.1 8 T, 8TPF, 8T/S, AND 8T/S-PF CARDS, CIRCUIT
Above figure is a simplified circuit diagram of one of the eight trunk circuits. The major
components are relays K1, K2, and K3; a polarity sensing, loop current detection circuit; an
electronic inductor (also known as a gyrator) and dialing circuit; and the audio coupling
transformer.
LOOP-START:
When strapped and programmed For loop-start operation, K2 is operated while
the trunk circuit is idle, and is released when the trunk is seized or answered. The loop current
detector is capacitively coupled to the trunk, and functions as an alternating current (A.C.)
detection circuit. The gyrator is turned off while the trunk is idle, thus there is no path for loop
current to flow. To signal an incoming call, the CO places a high voltage, A.C. ring generator
across the trunk; which is sensed by the loop current detector. When the trunk is seized, K2 is
released, and the gyrator is turned on. After a short delay, relay K1 is operated, passing the audio
signal from the trunk to the coupling transformer.
GROUND-START:
When strapped and programmed for ground-start operation, relay K2 is
released while the trunk is idle. The loop current detector is resistively coupled to the trunk through
the gyrator circuitry; however series resistance is sufficiently high to
prevent the trunk from being falsely seized. The gyrator is turned off while the trunk is idle, thus
there is no path for loop current to flow. If the ground-start trunk is idle from the central office, the
tip conductor is open circuit, while the ring conductor is fed –48 volts. To signal an incoming call,
the CO first places the tip conductor at CO ground. When this occurs, the loop current detector
senses current flow from the ring conductor, through the gyrator, to the tip conductor. When the
CO places ring generator across the trunk, the loop detector distinguishes its presence by sensing
that the current flow alternates. To answer an incoming call, the gyrator is turned on, passing
sufficient loop current to trip ringing.
After a short delay, relay K1 is operated, passing the audio signal from the
trunk to the coupling transformer. To seize the trunk for outbound calling, relay K2 is operated,
placing a local resistive ground on the ring conductor, and simultaneously places resistive –48 volts
in series with the loop current detector and the tip conductor. The grounded ring conductor passes
sufficient current to signal the CO, which in turn places CO ground through a talk path on the tip
conductor. The loop current detector senses current flow from resistive –48 volts to the tip
conductor. The gyrator is turned on and relay K2 is released.
After a short delay, relay K1 is operated, passing the audio signal from
the trunk to the coupling transformer. Dialing may be performed using DTMF, rotary pulses, or a
combination of the two. During DTMF dialing, tones generated either by the connected port or the
systems are passed through the switching system to the trunk. Rotary pulse dialing is performed by
the 8TPF trunk card itself, by releasing relay K1 to mute the trunk while dialing, then pulsing the
gyrator on and off at a specific rate. Answer and disconnect supervisory signaling is
detected by the loop current detector, which can sense loop current reversal and/or interruption.
The signaling type (loop-start or ground-start) is defined by the
A-LS/GS field in the 4T/8T Card Database (Route: TKDB), and by the LS/GS field in the LGS
Trunk Definition (Route: TRK, 2) branches of the system database.
SPECIFICATIONS: — 8T, 8TPF, 8T/S, 8T/S-PF
Number of Circuits:........................... 8
8 TPF Power Fail Circuits ............. 2, 3, 4, and 5
8 TPF Standard Circuits ............... 0, 1, 6, and 7
Impedance:
8T, 8TPF...................................... Selectable 600 ohms or 900 ohms nom.�
8T/S, 8T/S-PF.............................. 600 ohms
Loop Circuit: ......................................Electronic current sink (gyrator)
Ringer Equivalence:
Loop Start .................................... 0.4B
Ground Start ................................ 4.7B
U.S.A. Facility Interface Codes:
Loop Start .................................... 02LS2
Ground Start ................................ 02GS2
Dialing Modes:
Tone............................................. DTMF
Pulse............................................ Decadic Rotary Pulse (per RS-464)
8.3 DIGITAL TRUNK
GENERAL INFORMATION:
The 4TBR, 4TBRP, 8TBR and 8TBRP (TBR cards) are Coral I/O
peripheral cards that provide 4-wire digital trunks. These lines use Basic Rate Interface (BRI) logic
and conform to the CCITT international standards of Integrated Services Digital Network (ISDN).
TBR cards allow the Coral to support ISDN applications (Terminal Equipment, also called TE)
such as: Video Conference, Routers, Data Transfer and Fax Group 4. 4TBR and 4TBRP cards
provide four BRI lines. 8TBR and 8TBRP cards provide eight BRI lines. 4TBRP and 8TBRP cards
provide similar functions to the 4TBR and 8TBR cards.
In addition, these cards are used to supply power to ISDN applications, if
required. Each BRI line can be connected to its destination independently of the other lines on the
card. Each BRI line uses one pair of the four wires to transmit data and one pair to receive data.
The bit rate of each pair of wires is 192 Kbps. This bit rate supports two 64 Kbps “B” type
channels, and one 16 Kbps “D” type channel, conforming together a 2B+D line. The rest of the bits
are used for synchronization and maintenance purposes.
ISDN applications require 4-wire connections, while Public Switched
Telephone Network (PSTNs) provides 2-wire connections. Therefore, a 2 to 4-wire converter must
be used as an interface. An external device, BRI NT-1, is used for this purpose.
The TBR card interfaces between ISDN applications (TE) and the NT-1
as follows:
The Coral to NT-1 BRI line is defined as the User Side.
The Coral to TE BRI line is defined as the Network Side.
4/8TBR cards can be used both towards the TE and NT-1. 4/8TBRP cards can be used towards the
TE only. (The lines provided by 4/8TBRP cards must be defined as Network Side only. They must
not be defined as User Side interface.
In ISDN terms, the BRI 4-wire connection between the Coral and the
NT-1 as well as the connection between the Coral and the TE are referred to as an S/T interface.
The 2-wire connection between the NT-1 and the PSTN is referred to as a U interface.
fig 8.3.1 CORAL INTERFACES ISDN APPLICATIONS
Above figure illustrates these connections.
The TBR cards can be used to connect the Coral to another PABX. When the 4/8TBR cards are
installed in the Coral peripheral card synchronization slots and one of the lines is connected to the
NT-1 (User Side) towards the PSTN, the Coral System can be synchronized to the “far end” clock
via this card.
SPECIFICATIONS: — 4TBR, 8TBR, 4TBRP, 8TBRPNo. of BRI lines (2B+D):4TBR, 4TBRP ............................. 48TBR, 8TBRP.............................. 8Line Bit Rate: ............................. 192 KbpsOutput termination:.................... 100 ohmsOutput Pulse:............................... 750 mV Zero to Peak over the 100 ohms terminationInput termination:.............................. 100 ohmsPower Feeding:4TBRP, 8TBRP ........................... 2.8 W per line on Power Source 14TBR, 8TBR ................................ No Power FeedingEurope ......................................... -42VDCNorth America.............................. -48VDCLoop back: .......................................... Loop back 3.............................. ............ As defined by CCITT I.430
8.4 VOICE SWITCHING:
The Coral FlexiCom voice switching circuitry may be further divided
into two functions.
Peripheral Interface
Shared Service.
Individual voice channels are established through the Coral FlexiCom system
between two or more ports, during one of 64 TDM time slots over a PCM highway. A port may be
a Shared Service resource such as a tone detector circuit or one of the input/output circuits of a
conference bridge, or it may be a Peripheral Interface such as a Coral Flex Set or single-line station
interface, a digital trunk interface, or a Music-on-Hold input. The Coral FlexiCom system’s
universal slot. Design allows any type of port card to be installed in any order, in any slot in the
system.
Fig 8.4.1 CARD-LEVEL VOICE SIGNALLING PROCESS
Above figure illustrates the processing of voice signals from the
source to the PCM highway. The analog voice signal at the port is first converted to a series of
binary numbers by a PCM Coder/Decoder circuit, commonly referred to as a codec. The codec
samples the voice signal 8,000 times a second, measuring the analog amplitude and translating the
amplitude to a binary number. This is the essence of the PCM process, the international standard
for digital conversion, or digitizing, of an analog signal. Once digitized, a voice signal may be
transmitted to any other point in a digital network, whether across the room or around the world,
without any signal distortion or degradation. At the same time, the codec receives a binary number
(a digitized sample) from the other port in the connection and translates this to an analog voltage.
These voltages, generated by the codec 8,000 times a second, reconstruct with near-perfect
accuracy, the original voice signal sampled by the other port in the connection.
The codec is used also for port status processing. Codec’s are used on most
Peripheral Interface and Shared Service cards, with the exception of the 8/16/24SFT, CNF, T1,
30T, 30T/x, Flexi Gate-BRI, Flexi Gate-E&M, PRI-23, and PRI-30 cards, which process signals
that already are in a digital form.
Proprietary digital station sets such as the Coral Flex Set incorporate a codec in the telephone
circuitry to digitize the voice signal within the telephone set.
]
The digitized voice signal from the codec is applied to a PCM highway
via the Peripheral Bus Controller (PBC) circuit, located on the Peripheral Interface or Shared
Service card. The PBC establishes connections between the codec’s and the PCM highways. Each
PCM highway consists of a transmit and receive bus.
The Master Controller assigns transmit and receive time slots to a port when
the port requires a voice channel. The PBC outputs a sample from the port’s codec onto the
transmit busm during the assigned transmit time slot period. The PBC stores each sample on the
receive bus during the assigned receive time slot and
passes the samples to the ports.
Each transmit and receive bus is multiplexed into 64 time slots, which allows 64
simultaneous, two-way voice channels per PCM highway. Each Peripheral Card has access to two
PCM highways, another example of how the Coral FlexiCom system design embraces reliability as
the fundamental concern. This enables up to 512 ports to be in use simultaneously in each
Peripheral Shelf.
9.CONCLUSION
The Coral FlexiCom 400 is competitive with similar- sized hybrid and private branch
exchange systems. The Coral FlexiCom 400 delivers more features, more capacity, and more
configuration flexibility than any other system in its size range cabinet.
This system is ideal for general business and industrial telephone switching
applications. When a small stationary battery plant is added, the system is an excellent choice for
hospitals, campus environments, municipal government facilities, and in Vintage central offices to
provide Centrex services.
Electronic Exchanges not only used for voice switching but also for data, video, text,
etc. The digital exchanges support digital connectivity between different exchanges through
network interfaces like E1, E&M, LD, BRI, PRI, etc. ISDN exchanges support special ISDN
phones which one can use for various simultaneous applications of voice, video, data on a single
pair, calling line identification on both internal/external call, TCP/IP protocol, video conferencing,
TM/FRAME relay protocols (heavy data switching) etc., which has revolutionized the whole
world.
