Digital and Data Comunications

Digital and Data Comunications (C8 Past Board: Excel)ECE Board Exam April 2001

Determine from the following, the term used to described the ratio of transmission rate to its minimum bandwidth

which is also used to compare the performance of one digital modulation technique to another.

Information capacity

ECE Board Exam November 2000

A process of exchange of predetermined codes and signals to establishe a connection

Handshake

ECE Board Exam April 2000

These are rules in data communications intended for establishing data links and message interpretation.

Protocols


In telecommunication, what do we call the difference in the voltage levels between a driver and a terminator?

Noise Margin


A network interconnection facility, which is used to interconnect networks whose architecture are entirely different, is

called _________.

gateway


Main basic components of a data communications are composed of the following:

Transmitter, channel and receiver


A device that connects two dissimilar networks and performs the protocol conversion.

Gateway


Operating method in which the transmission is made alternately in each direction of a telecommunication channel.

Half-duplex operation


Transmission sent in both directions simultaneously.

Duplex


A system that performs parallel-to-serial and serial to parallel conversion of data link

DTE

ECE Board Exam March 1996

A word in telegraphy consist of __________ characters plus a word space.

7 and 1/2


Technique used in teleprinter terminal that utilizes chemically coated paper where characters are printed.

Electro thermal printing


Bit rate of a telecommunications carrier T2.

6.312 Mb/s


A process of sending data in computing technology by asking each remote computer terminal one ata a time if such

a computer terminal has data to send.

Polling


What do you call the definite time interval it takes to a key the slave station by the master in operating the long

range navigational equipment or loran?

Time delay


What does the elastic store referred to in the time division multiplex system used in fiber optic?

Holding memory


_________ is more prevalent in analog signals that have sleep slopes or whose amplitudes vary rapidly.

Slope overload


Is the total useful information processed or communicated over a specific amount of time.

Throughput


The series of periodically recurrent pulses is modulated in amplitued by the corresponding instantaneous samples.

PAM


Full duplex transmission means

Two way simultaneous transmission


The line control unit (LCU) operates on the data in digital form.

Data terminal equipment (DTE)


The number of voice band channels in a master group per CCITT standard is

300


Which of the following topology is normally used in system network architecture topology providing order of

structure?

Bus


Which of the following is referred to the SYN character of ASCII code?

16H


Why is parallel transfer method in data transmission faster that serial?

Bits are transferred simultaneously


In an open architecture concept of data communication, one of the following is not a function of a control layer.

Integrity of data


What is the function of the network layer in computer communications?

Congestion control


Which of the following term best described the overload distortion?

Peak Limiting


Which of the following refers to full duplex transmission?

Two way simultaneous transmission


A digital carrier facility used to transmit a DS1 - formatted signal at 1.544 Mbps.

T1


Transmission system for a multidrop network.

Polling


The line control unit (LCU) operates on the data in digital form.

Data terminal Equipment


The expander ina companding device provides _____________

less amplification for low signal levels


How would you determine if data transmission in computers and terminals is/are done in parallel transfer?

If group of bits move over several lines at the same time.


How are the variations of the transmitted photograph in terms of brightness and darkness converted into voltage

variations?

Through photodetector


In data transmission technology signals such as voice or radio are binary transmitted over a cable known as

____________.

baseband signal


Mode of communication system where both sides of the system wait for their turn to transmit at a time?

Half duplex


Why is it that almost all switching-type integrated data communication circuit are called digital?

They process digital information


__________ is the method encoding audio signals used in US standard 1,544 kbits/s 24 channel PCM system.

Mu-law


Which of the following described the very early standard that defines binary digits as space/mark line conditions and

voltage levels?

V.1


12 voice channels are sampled at 8000 sampling rate and encoded into 8-bit PCM word. Determine the rate of the

data stream.


Synchronous modems cost more than asynchronous modem because

they have clock recovery circuits


Codes must be

agreed upon in advance between sender and receiver.


One character or a sequence of characters forming a part, or the whole of a message with a specific meaning.

code


One of the data terminal devices that was invented to replace the Morse code telegraphy

Teleprinter


__________ is a group of bits that acts as a single unit of information such as a letter or numeral.

Byte


Transmission of information through a communication modem is intended to transmit digital information over which

of the following types of communication medium?

Analog


Which of the following refers to a network facility used to physically interconnect distinct networks in computer

technology?

Bridge


Communication through the use of a modem, is transmission of _______ data information in ______ medium.

digital, analog


Refers to an address that identifies a server on the network and a particular document on the server.

Uniform resource locator


One of the following stands for SONET acronym in telecommunication.

Synchronous Optical Network


The sinusoidal carrier is pulsed so that on of the binary states is represented by a carrier while the other is

represented by its absence.

ASK


What equation defines the composition of an ISDN basic access line?

2B + D


Quantization noise is caused by

the approximation of the quantized signal


Referred as a modem that is capable of sending and receiving fas as well as data transmission.

ARQ


An equipment in data communication which is referred to as a source of information to be transmitted at one end

and the sink which receives the information at the other end.

DTE


In computer communication the term RS-232C is referred to as ____________.

serial interface standard


Kinds of information transfer in digital communication where the bits comprising one character are sent in sequence

one at a time.

Serial transmission


Who is responsible in the correctness and accuracy of transmitted information content over a data communication?

The transmitter and receiver


Term for the transmission of printed pictures by radio?

Facsimilie


Determine the dynamic range for a 10-bit sign magnitude code.


Modem is referred to as _________

Data Communication Equipment


What is the principal difference between asynchronous and synchronous transmission?

The clocking is derived from the data in synchronous transmission


What is the IBM's asynchronous data link protocol designation?

83B


The term used to receive a data file from a remote computer is called __________.

downloading


Which of the following best described the primary source of errors in the transmission of data over telephone

networks?

Crosstalk


An IT network which interconnects local area network over a broad graphical area.

Wide are network


Refers to the PCM transcoder which translates voice-encoded signals between different digital formats.

XCBR


How do you transmit through multiplexing, a thousand of voice channel information over a single fiber optic using

one wavelength?

Time division


Known as the data transfer scheme that used handshaking principle.

Synchronous data transfer scheme


A coherent binary phase shift keyed BPSK transmitter operates at a bit rate of 20 Mbps with a carrier to noise ratio

C/N of 8.8 dB. Find Eb/No.


Which of the following modulation technique render the amplitude of any of its sidebands dependent on the

modulation index?

Frequency modulated


What do you call a system having a single communication channel that is shared by all machines on a network?

Broadcast system


What is the baseband frequency of standard FDM basic supergroup?

312 to 552 kHz


Refers to transmission of two sets of voice signals or other information through two different wavelengths.

Frequency division multiplex


Which of the following is not referred to as data equipment?

Modem


What is the reason why companding is employed in PCM systems?

To protect small signals in PCM from quantizing distortion


How would one squeeze more channels of communication into TDM frames of standard length?

Shorten the time delay for each channel


The standard that specifies a balanced interface cable that will operate for rates up to 10 Mbps with a span

distances up to 1200 m.

RS - 422A


Speed of data transmission is referred to baud rate which refers to changes in symbol per second as ________.

frequency and phase changes.

time


In facsimile, how are variations in picture brightness and darkness converted into voltage variations?

with a photodetector


Network protocol developed by US Defense Department which permits the exchange of traffic between two stations

without any prior call set-up.

Internet Protocol


Type of transmitting two or more channels of voice signal or other information in fiber optic communications in a

selected interval of micro or milliseconds, the data or channels being received at their own time slot.

Time-division multiplexing


The conversion of digital into analog for purposes of training into telephone line is done through ______.

Modem


Used for time division multiplexing

Pulse Modulation


What is framing?

Is concerned with the boundaries between characters


When one station is degnated as master and the rest of the stations are considered slaves message handling is

__________.

Polling


How would you differentiate timing and framing in data transmission?

Timing concerned with individuals bits while framing is to boundaries between characters.


One of the following refers to the standard procedure for asynchronous to synchronous conversion.

V.14


Which of the following refers to facsimile?

The transmission of printed pictures for permanent display on paper


Type of transmission in which each transmission is individually synchronized, this is normally done through the use

of start and stop elements.

Asynchronous transmission


In communications, the transmission of binary signals will require __________

more bandwidth that analog


Detrmine from the following the basic mode of transmission system in the public data network in which data are

transferred from the source to the network and from the network to the destination in the frame format.

Packet Mode


The difference between the original and reconstructed signal gives rise to

quantizing noise


The method of determining the bandwidth of any process system is _______.

Spectral Analysis


RS-232, RS-449, RS-530, V.24, and X.21 are examples of ________.

standards for interfaces between terminals and modems


One type of pulse communications systems uses pulse that appear as a group, and which vary in number according

to the loudness of the voice. This type of pulse modulation is called

pulse duration modulation


What kind of recording is used in facsimile?

Electrothermal recording


How would you isolate data communications faults in a basic error determination technique?

Carry out loop back test


Which of the following describes its system services control point, logical units and physical units as network

addressable units in a data network?

System network architecture


Where does harmonics in a square wave of a simple signal transmission belong?

Odd


In telecommunications when we call data communications it means the transmission of ________

Computer data


These are used to connect non-ISDN equipment to ISDN line.

Terminal adapters


Modulation in which no signal is present between pulses.

Pulse modulation


It is a protocol use to connect the other packet switching network.

X.75


What is the data rate of the ISDN BAsic access B channel?

64 kbps


According to the Nyquist theorem, the sampling rate that can be used in a PCM system is _____ the highest audio

frequency.

twice


_________ is one of the many electronic equipments referred to as a data terminal equipment.

Computer printer


Method of a telecommunications operation where transmission can be made simultaneously in both direction of a

channel.

Duplex operation


What refers to breaking up the data into blocks with some bounded size?

Segmentation


A device that is used to permit an equipment with non-ISDN interface to be connected to the digital network.

TA


Slowest communications hardware product.

Asynchronous


For a sample rate of 40 kHz, determine the maximum analog input frequency


Pulse carrier at the ratio of 8000 pulse/sec is amplitude modulated by an analog signal, this type of modulation is

PAM


What is one principal difference between synchronous and asynchronous transmission?

The clicking is derived from the data in synchronous transmission


This a fast computing machine with large amount of secondary storage to which other computer machine in the

network have access for data storage and retrieval purposes.

Mainframe


A connector that has the lowest loss at ultra high frequency

Type-N connector


A data communications network desiigned to provide two-way communications between a large variety of data

communications terminal equipment within a relatively small geographic area.

Local area network


Is individual signal for a handshake from the DCE to the DTE in response to an active condition for the request to

send a signal.

Clear to send


Highest theoretical frequency that can be processed at a sampling rate (fs) without aliasing.

Folding frequency


A seven-bit character can represent one of _______ possibilities.

128


What is the number of pins in the RS-232C interface?

25


Data is directly on transmission cable.

Baseband


Digital transmission provides a higher level of signal quality than analog transmission because

repeaters regenerate digital pulses and remove distortion.


What is the transmission rate of system for transmitting the output of a microcomputer to a line printer operating at a

speed of 30 lines/minute? Assume that the line printer has 8 bits of data per character and prints out 80

characters/line.


In what form does the information of data communications is transmitted between two points?

Binary form


A source code whose average word length approaches the fundamental limit set by the entropy of a discrete

memoryless source.

Huffman code


A ___________ interconnects LAN having identical protocols at the physical and data link layers.

Bridge


What is the system that process both digital and analog quantities?

Hybrid system


Communications code is __________.

agreed upon in advance between sender and receiver


Gateway can interconnect LANs that have _______ protocol and formats.

totally different


An invitation from the primary to a secondary to transmit a message.

Polling


Which of the following pulse modulation system is analog?

PWM


In spread spectrum transmission, which type of modulation is normally often used with direct-sequence?

PSK


Device that comply with the ISDN network interface and be connected directly to the digital network.

TE1


Two or more LANs linked together over a wide geographical area.

WAN


All bits in a character are sent and received ______ in serial port.

one at a time


Steps to follow to produce PCM signal.

Sampling, quantizing, and coding


The tranformer signal coding method for T1 carrier is

bipolar


In ______ transmission, a unique SYN character is transmitted at the beginning of each message.

synchronous


Transmission sent in both directions simultaneously.

Duplex


Binary communications systems are better because

the components are simpler, less costly and more reliable


Multiplexing scheme used by baseband transmission.

TDM


The correctness and accuracy of the transmitted message content is

determined by the sender and receiver.


Digital modulation technique used in modems.

PSK


Data switching systems

improve the efficiency of data transfer


Multiplexing in a time division multiplexer occurs based upon

the position of data within a frame


The process of assigning PCM codes to absolute magnitudes.

Quantizing


Ethernet is baseband system using CSMA/CD operating at

10 Mbps


Asynchronous protocol is

character oriented


The primary purpose of data modem is to

interface digital terminal equipment to analog communication channel


_________ is a device in data transmission to interface a data terminal equipment to an analog transmission line

Modem


A quadrature signaling have ______ possible states

4


Rules governing the transmission of digital information

line protocol


The standard ASCII

has 132 characters including 32 control characters.


Basic speed rate of digital system

64 kbps

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Digital and Data Comunications