CH8 - Digital and Data Communications

5/21/2018 CH8 - Digital and Data Communications

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- Digicom & Datacom- Which of the following is not an advantage of digital transmission?a. noise immunityb. ease of multiplexingc. bandwidth utilizationd. ease of encryptionans: c

-_____ is the ratio of the largest possible magnitude to the smallest possiblemagnitude that can be decoded by the DAC.

a. resolutionb. quantizationc. dynamic ranged. voltage ratioans: c

-A process where the higher amplitude analog signals are compressed prior to tr

ansmission then expanded at the receiver.a. compressingb. expandingc. encodingd. compandingans: d

- For a resolution of 0.01 V and analog sample voltage of 0.05 V, the 12-bit linear sign-magnitude code isa. 000000000101b. 100000000101c. 100010010011d. 000001010001ans: b

-_____ uses a single bit PCM code to achieve a digital transmission of analog signal.a. Quadrature Amplitude Modulation (QAM)b. Frequency Shift Keying (FSK)

c. Delta Modulation (DM)d. Phase Modulation (PM)ans: c

-The line speed of Bell System T1 carrier system isa. 64 kbpsb. 3.152 Mbpsc. 1.544 Mbpsd. 6.312 Mbpsans: c

-How many channels does a T2 line carry?a. 24

b. 48c. 96d. 672ans: c

-The capacity of the standard 4-kHz telephone channel with 30 dB S/N isa. 455225 bpsb. 42525 bpsc. 39846 bpsd. 39840 bps


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ans: c-How many channels does a super group have?a. 60b. 600c. 1800d. 10800ans: a

-The output frequency at the channel combiner of channel 7 isa. 76-80 kHz

b. 80-84 kHzc. 84-88 kHzd. 88-92 kHzans: b

-The carrier frequency of the supergroup D25 isa. 2652 kHzb. 2900 kHzc. 2356 kHzd. 2108 kHzans: a

-Which of the following is not a hybrid data?

a. data in voiceb. data under voicec. data above voiced. data in videoans: d

-_____ was the first fixed-length 5-bit character code.a. EBCDICb. ASCIIc. Morse coded. baudot codeans: d

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CCITT V.26 modem has a modulation rate of _____.a. 1200 Hzb. 1200 baudsc. 1560 cpsd. 9600 baudsans: b

-What can a smart modem do?a. detect transmission errors and correct them automaticallyb. correct answer multiple choice quizzesc. accepts commands from the terminal via RS232 interfaced. do a smart gameans: c

-One is an advantage of PTM over PAM.a. much better noise immunityb. low sampling rate requiredc. simpler to generated. less costlyans: a

-When did ISO adapt the seven-layer OSI model?a. 1983


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b. 1973c. 1963d. 1953ans: a

-Amplitude shift keying is also known as _____.a. up/down keyingb. on/off keyingc. front/back keyingd. I/O keyingans: b

- Which modulation system is used in telephony?a. FSKb. PCMc. Two-tone modulationd. single-tone modulationans: a

-Modulation used by asynchronous dataa. QPSKb. FSKc. PSKd. QAM

ans: b-PCM systems require _____.a. analog signalsb. large bandwidthc. digital signalsd. fiber optic cableans: b

-Which theorem sets the limit on the maximum capacity of a channel with a given

noise level?a. Nyquist theoremb. Hartley theorem

c. Shannon-Hartley theoremd. Shannon theoremans: c

-Quantizing noise is present in _____ system.a. PCMb. ATMc. TDMd. PAMans: a

-_____ is the difference between the original and reconstructed signala. quantizing noise

b. fade marginc. noise margind. noise figureans: a

-What is the reason why companding is employed in PCM system?a. to solve quantizing noise problemb. to allow amplitude limits in the receiversc. to protect small signals in PCM from quantizing distortiond. to overcome impulse noise in PCM receivers


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ans: c-Band of frequencies in a transmission medium allotted to each communication ch

annel on a continuous time basis.a. TDMb. FDMc. CDMAd. broadbandans: b

-Error control used in high frequency radio data transmission.

a. FECb. ARQc. Hammingd. Parityans: b

-What are the steps to follow to produce a PCM signal?a. sampling, coding and quantizingb. sampling, quantizing, and codingc. quantizing, sampling, and codingd. coding, quantizing, and samplingans: b

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_____ identifies how the different stations in a multipoint system are interconnected.a. network topologyb. star networkc. ring networkd. bus networkans: a

-A transmission where data are inputted directly on the cable.a. broadbandb. basebandc. digitald. analog

ans: b-A transmission where data are inputted inside the carrier wave.a. broadbandb. basebandc. digitald. analogans: a

-A transmission system for a multidrop network.a. token passingb. CSMA/CDc. polling

d. CSMA/CAans: c

-Before attempting to transmit data, each station has to listen to the channel.

a. CSMA/CDb. token passingc. CSMA/CAd. pollingans: a


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-Synchronous modems cost more than asynchronous modems becausea. they are largerb. they must contain clock recovery circuitsc. the production volume is largerd. they must operate on a larger bandwidthans: b

-When one station is designated as master and the rest of the stations are cons

idered slaves, message handling is _____.a. store and forward

b. pollingc. CSMA/CDd. token passingans: b

-The computer that initiates information transfer.a. masterb. slavec. DCEd. DTEans: a

-A store and forward switching.

a. circuit switchingb. packet switchingc. message switchingd. PSTNans: c

-It is used to connected computers in the same building or in same area.a. LANb. WANc. MANd. PBXans: a

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Two or more LAN linked together over a wide geographical area.a. HANb. MANc. WANd. RANans: c

-Which system allows different types of networks to be linked together?a. OSIb. CCITTc. Bell systemd. AT & Tans: a

-OSI consists of how many layers of interconnection?a. 3b. 5c. 7d. 9ans: c

-Which network layer determines if the user can send or receive based on whethe

r they can send and receive simultaneously or alternatively?


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a. physical layerb. data link layerc. transport layerd. session layerans: d

-A _____ that interconnects LAN having identical protocols at the physical and

data link layers.a. bridgeb. routerc. gateway

d. hubans: a-A _____ interconnects LAN having identical protocols at the physical data link

and network layers.a. bridgeb. routerc. gatewayd. nodeans: b

-A _____ interconnects LAN that have totally different protocols and format.a. bridge

b. routerc. gatewayd. WANans: c

-All bits in a character can be sent/received simultaneously.a. serial datab. parallel datac. full duplexd. duplexans: b

-The bits in a character which are sent/received one at a time.

a. parallel datab. serial datac. simplexd. half duplexans: b

-A system that perform parallel-to-serial and serial-to-parallel conversion of

a data link.a. DTEb. DCEc. modemd. FEPans: a

-EIA stands fora. Electronic Institute Associationb. Electronic Industry Associationc. Electronic Improvement Adsd. Electrical Industrial Associationans: b

-An acoustic modem converts a complex digital signal intoa. serial form


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b. parallel formc. radio tonesd. audio tonesans: d

-Which mode of transmission achieves less than full-duplex but more than half-d

uplex?a. full\full duplexb. echoplexc. isochronousd. synchronous

ans: b-Rules governing the transmission of digital information.a. data communications standardb. line protocolc. isochronousd. digital communicationans: b

-Codecs must bea. eight bits per characterb. eight seven or eight bits per characterc. agreed upon in advance between sender and receiver

d. the same in all modern computersans: c-The standard ASCIIa. is version II of ASCb. has 132 characters including 32 control charactersc. is subset of a 8-bit EBCDIC coded. is used only in US and Canadaans: b

-The Baudot codea. was invented by the Baudot brothersb. required the escape character to print numbers

c. requires shift characters to provide sufficient combinationsd. a descendant of Morse codeans: c

-The corrections and accuracy of the transmitted message control isa. verified by the modemb. determined by the sender and the receiverc. ensured by the used of digital techniquesd. dependent on the communications system usedans: b

-Framing isa. concerned with the boundaries between characters

b. referred to parallel-to-serial conversionc. concerned with synchronous systemd. concerned with individual bitsans: a

-Asynchronous transmission isa. is less efficient but simplerb. is much faster than synchronous transmissionc. is another name for synchronous transmissiond. the most sought-after transmission


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ans: a-Digital transmission provides a higher level of signal quality than analog tra

nsmission becausea. repeaters regenerate digital pulses and remove distortionb. digital signals are smaller than analog signals and cannot easily be distor

tedc. analog signals are continuous and are not easily distortedd. digital signals are easier to sample than analog signalsans: a

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Digital to analog converter in synchronous modems send signals to thea. modulatorb. transmission linesc. terminald. equalizerans: d

-Binary codes are transformed in modems intoa. hexadecimalb. Hullman codec. Gray coded. octalans: c

- Synchronous modems cost more than asynchronous modem becausea. they are largerb. they must contain clock recover circuitsc. the production volume is largerd. they must operate on a larger bandwidthans: b

-What is the best type of data communications test equipment?a. simulatorb. protocol analyzerc. DTEd. breakout box

ans: b-What is the data rate of the ISDN Basic access B channel?a. 32 kbpsb. 64 kbpsc. 144 kbpsd. 192 kbpsans: b

-What is the data rate of the ISDN basic access D channel?a. 64 kbpsb. 16 kbpsc. 8 kbps

d. 144 kbpsans: b

-Baudot code uses how many bits per symbol?a. 9b. 7c. 5d. 8ans: c

-


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How many bits are there to present 8 combinations?a. 3b. 4c. 2d. 5ans: a

-How many number of equiprobable events are there for 8-bits of information?a. 256b. 132c. 2400

d. 512ans: a-Which computer terminal can be programmed to perform new functions?a. dumb terminalb. smart terminalc. intelligent terminald. super terminalans: c

-Which character code is used without parity bit?a. CCITT number 2b. ASCCII

c. CCITT number 5d. EBCDICans: d

-Which hardware is used when the host computer and the terminal are in separate

locations?a. LCUb. FEPc. Muldemd. Modemans: d

-_____ is a data communications hardware that assist the host computer in handl

ing input and output tasks.a. hubb. cluster controllerc. front end processord. concentratorans: c

-ASCII meansa. terminals using synchronous transmission in EBCDICb. terminals using synchronous transmission in ASCIIc. terminals using asynchronous transmission in ASCIId. any terminal having an American (dollar-sign) keyboardans: c

-A unit of information used in data communications.a. ditb. bitc. byted. baudans: b

-Transmission of binary signals requiresa. less bandwidth than analog


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b. more bandwidth than analogc. the same bandwidth as analogd. a license from the NTCans: b

-What is the modulation rate of the CCITT V.26 modem?a. 56 kbpsb. 1200 kbpsc. 1560 kbpsd. 9600 kbpsans: b

- The digital-to-analog converter in a synchronous modem sends signal to the _____.

a. modulatorb. transmission linec. terminald. equalizerans: d

-The number of bits that are zeros in each symbol when one is transmitting odd-

parity coded symbols.a. evenb. odd

c. unknownd. oneans: c

-A digital modulation technique that results in two difference frequencies repr

esenting binary 1 and -.a. FSKb. QPSKc. ASKd. DPSKans: a

-What is the input to the Digital-to-Analog Converter of a PCM decoder circuit?

a. a series of sampled amplitudesb. a parallel binary wordc. a series of bitsd. a reconstructed intelligence signalans: c

-The output of the DAC at a PCM decoder circuit is a _____.a. series of binary-coded digitsb. parallel output of binary-coded digitsc. fixed analog voltaged. reconstructed intelligence signalans: b

-Serial printera. are used to transmit grain pricesb. faster than CRT terminals, and offers more flexibilityc. prints one character at a timed. usually uses serial interfacesans: c

-Delta modulation is a/ana. 5-bit modulation


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b. integral PCM systemc. 1-bit differential PCM systemd. form of PDMans: c

-Alternative way of digitizing analog signals.a. PCMb. Delta modulationc. PPMd. DPCMans: b

- One dit is equal to _____ bits.a. 3b. 3.5c. 3.32d. 4ans: c

-Redundancy means the _____.a. transmission rate of the systemb. symbols are to be repeatedc. time between failuresd. time between successes

ans: b-Which transmission media is not suitable to CSMA operation?a. Radiob. Optical fiberc. Coaxial cabled. Twisted pairans: b

-_____ is a device used to convert a time varying electrical quantity to an appropriate form.a. Codecb. Transducer

c. ADC/DACd. Modemans: b

-The bandwidth of U600 mastergroup isa. 2250 kHzb. 2728 kHzc. 2520 kHzd. 2278 kHzans: c

-Refers to the combination of digitally encoded signals transmitted with FDM si

gnals as one composite baseband signal.

a. composite datab. data under voice (DUV)c. hybrid datad. Data In Voice (DIV)ans: c

-Transmit frequency-division-multiplexed voice band signals over a coaxial data

for distances up to 4000 miles.a. T carrier systemsb. A carrier systems


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c. L carrier systemsd. D carrier systemsans: c

-Level 5 of Japanese PCM multiplex hierarchy has channel capacity ofa. 7680 VB channelsb. 5760 VB channelsc. 8064 VB channelsd. 5670 VB channelsans: b

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The line data rate (in Mbps) for level 4 of CEPT 30 + 2 PCM multiplex hierarchya. 97.728b. 400.352c. 274.176d. 139.264ans: d

-The guardband between supergroup 18 and supergroup D25 isa. 12 kHzb. 56 kHzc. 128 kHzd. 8 kHz

ans: b-Supergroup 17 has a carrier frequency (in kHz) ofa. 2108b. 2356c. 1860d. 1612ans: a

-A radio channel is composed of _____ VB channels.a. 1800b. 900c. 10800

d. 8064ans: a

-What is the guardband between supergroup 1 and supergroup 2?a. 12 kHzb. 10 kHzc. 8 kHzd. 6 kHzans: a

-CCITT's supermastergroup has how many voice band channels?a. 600b. 1800

c. 10800d. 900ans: d

-The transparency mechanism used with SDLC is calleda. zero-bit insertionb. modified link testc. beacon testd. invert-on-zero codingans: a


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-What equation defines the composition of an ISDN basic access line?a. 2B + Db. B + Dc. B + 2Dd. 2B + 2Dans: a

-A digital network where voice, video, text and data are multiplexed into a sin

gle network for processing and are transmitted prior to use.a. frame relay

b. asynchronous transfer mode (ATM)c. ISDNd. synchronous digital hierarchy (SDH)ans: d

-T-1 carrier service has _____ digital bit rate.a. 1.544 Mbpsb. 2048 Mbpsc. 1.644 Mbpsd. 9600 Mbpsans: a

-Non-ISDN equivalent can be connected to ISDN line by the use of _____.

a. terminal equipmentb. terminal adaptersc. modemd. network adaptorsans: b

-What is the baseband frequency of standard FDM basic supergroup?a. 312 to 552 kHzb. 60 to 2540 kHzc. 60 to 108 kHzd. 300 to 600 kHzans: a

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What is the transmission signal coding for T1 carrier?a. binaryb. NRZc. bipolard. Manchesterans: c

-The primary purpose of the data modem.a. interface analog terminal equipment to analog communications channelb. interface digital terminal equipment to digital communications channelc. interface analog terminal equipment to digital communications channeld. interface digital terminal equipment to analog communications channelans: d

-The line control unit (LCU) that operates on the data in digital form.a. data terminal equipment (DTE)b. data communications equipment (DCE)c. modemd. UARTans: a

-SYN character of EBCDIC code.a. 32 H


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b. 8 Hc. 16 Hd. 4 Hans: a

-_____ ensures that the transmitter and receiver agree on the prescribed time slot for the occurrence of a bit.a. bit or clock synchronizationb. modem or carrier synchronizationc. character synchronizationd. message synchronization

ans: a-Equation used to determine the number of Hamming bits in the Hamming code.a. 2^n = m + n + 1b. 2^n >= m + n + 1c. 2^n > m + n + 1d. 2^n < m + n + 1ans: b

-Data meansa. digital informationb. both digital and analogc. analog information

d. neither digital or analogans: a-What determines which network configuration is most appropriate?a. application layerb. presentation layerc. network layerd. data link layerans: c

-Ethernet is a baseband system using CSMA/CD operating at _____.a. 10 Mbpsb. 20 Mbps

c. 30 Mbpsd. 40 Mbpsans: a

-Mechanism used by a station to gain access to local area network.a. channel multiplexingb. channel accessingc. CSMA/CDd. CSMA/CAans: b

-What multiplexing scheme is used by baseband transmission?a. TDM

b. space multiplexingc. FDMd. statistical multiplexingans: a

-Use of coaxial cables in interconnecting networks is limited to an overall len

gth of _____.a. 1500 ftb. 1500 mc. 1500 km


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d. 1500 kftans: b

-What defines how the stations are interconnected in a network?a. topologyb. architecturec. topology or architectured. topology and architectureans: c

-_____ is a data communications network designed to provide two-way communicati

ons between a large variety of data communications terminal equipment within a relatively small geographic area.a. private area networkb. local area networkc. wide area networkd. Ethernetans: b

-_____ is the mode of transmission in public data network in which data are transferred from source to the network then to the destination in an asynchronous data format.a. synchronous modeb. start/stop mode

c. packet moded. circuit modeans: b

-A seven-bit character represent one of _____ possibilities.a. 7b. 14c. 64d. 128ans: d

-_____ is defined to be the maximum rate at which information can be transmitted through a channel.

a. bit rateb. baud ratec. codingd. channel capacityans: d

-Circuit that performs the inverse mapping and delivers to the user destination

, a reproduction of the original data source output.a. source codingb. channel codingc. inverse codingd. demodulationans: a

-Digital modulation technique used in modems.a. ASKb. FSKc. PSKd. MSKans: c

-Who developed the fixed-length binary code for telegraphy?a. Samuel Morse


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b. Emile Baudotc. Alexander Graham Belld. Guglielmo Marconians: b

-Inventor of pulse-code modulation for the digital encoding of speech signals.a. R.V.L. Hartleyb. J.R. Carsonc. H. Nyquistd. Alex Reevesans: d

- In what year did computers and terminals start communicating with each other over long distance?a. 1950'sb. 1960'sc. 1970'sd. 1980'sans: a

-Store-and-forward multiple-access network.a. ARPANETb. ALOHAc. PRNET

d. Packet switchingans: c-A source code whose average word length approaches the fundamental limit set b

y the entropy of a discrete memoryless source.a. prefix codeb. source codec. entropy coded. Huffman codeans: d

-Who promulgates communications-related military standards (MIL-STD)?a. DOD

b. DCAc. DOC-STDd. ANSI-MILans: b

-What is the class of probability in error detection techniques that is known a

s residual error rate?a. P1b. P2c. P3d. P4ans: b

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RS 232 is normally an interface between DTE and DCE. What is its signal rate?a. 20 kbpsb. 30 kbpsc. 40 kbpsd. 50 kbpsans: a

-Digital switching concepts that can handle more channels.a. SDSb. TSI


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c. TDMd. TMSans: d

-What is the most significant advantage of modular switch than time-and-space s

witch?a. flexible sizeb. simplified controlc. simplified manufacturing, testing, and maintenanced. the latter is more advantageous than the formerans: a

- Which of the following is the biggest disadvantage of PCM systems?a. inability to handle analog systemsb. high error rate as a result of quantizing noisec. not compatible with TDMd. the large bandwidth requiredans: d

-The reason why companding is employed in PCM systems isa. to solve quantizing noise problemb. to allow amplitude limiting in the receiverc. to protect small signals in PCM from quantizing distortiond. to overcome impulse noise in PCM receivers

ans: c-The highest theoretical frequency that can be processed at a sampling rate (fs

) without aliasing.a. folding frequencyb. resonant frequencyc. critical frequencyd. natural frequencyans: a

-The overlapping of the original spectrum and the first translated component is

known asa. dc wandering

b. aliasingc. droopd. distortionans: b

-Transmission sent in both directions simultaneously.a. full duplexb. half duplexc. simplexd. echoplexans: a

-Multiplexing in a time division multiplexing occurs based upon

a. the position of data within a frameb. the position of a frame within a group of framesc. the activity of connected deviced. the priority assigned to a connected deviceans: a

-What is multiplexing?a. the process of increasing bandwidth on a channelb. a technique that enables more than one data source to share the use of a co

mmon line


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c. mailing letter at the post officed. the ability to share frequency by timeans: b

-One of the reasons why FDM is being replaced by TDM.a. there is more time than frequencyb. it is difficult to place channels side by sidec. noise is amplified with voice when an FDM system is usedd. most available frequencies have been usedans: c

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In _____ modulation the carrier is periodic train of pulses.a. amplitudeb. analogc. digitald. pulseans: d

-The process that uses the orthogonality of sines and cosines that makes it pos

sible to transmit and receive two different signals simultaneously on the same carrier frequency isa. TDMb. FDMc. quadrature multiplexing

d. duplexingans: c-Which of the following pulse modulation technique is a digital transmission sy

stem?a. pulse duration modulationb. pulse position modulationc. pulse width modulationd. pulse code modulationans: d

-Information theory was developed by _____.a. Shannon

b. Nyquistc. Reevesd. Hartleyans: a

-Disadvantage of digital transmission.a. more bandwidth and precise timing are requiredb. requires ADC and DAC devicec. incompatible with existing analog facilitiesd. all of theseans: d

-A quadratic signaling has _____ possible states.

a. 16b. 4c. 8d. 32ans: b

-What is the smallest unit of information in binary transmission system?a. byteb. digitc. bit


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d. nibbleans: c

-The lowest layer in the ISO protocol hierarchy.a. network layerb. physical layerc. transport layerd. data link layerans: b

-Basic speed rate of digital system.

a. 1.44 kbpsb. 144 kbpsc. 64 kbpsd. 2,048 kbpsans: c

-A formal set of conventions governing the formatting and relative timing of me

ssage exchange between two communications system.a. simplexb. tail circuitc. queuingd. protocolans: d

- A device that connects 2 data terminal equipment (DTE) directly by emulating the physical connections of data communications equipment (DCE).a. short haul modemb. null modemc. X.25 modemd. smart modemans: b

-Impact printera. receives-only-printer with a keyboardb. includes ink-jet and terminal devicesc. rapidly becoming obsolete

d. strikes a ribbon against the paper to produce character image-Modem is referred to asa. universal asynchronous receiver transmitterb. universal synchronous receiver transmitterc. data terminal equipmentd. data communications equipmentans: d

-A signaling method relating to a multiplicity of circuits is conveyed over a s

ingle channel by labeled messages.a. code signalingb. synchronous

c. common channel signalingd. asynchronousans: c

-A data highway in LAN, this type of topology allows workstations to be connect

ed to a common line where all messages pass stations on the way to their destination.a. CSMA/CDb. busc. ring


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d. starans: c

-A packet format has an error detecting code ata. the start of the packet framing sequenceb. the destination addressc. the packet numberd. the end of packet framingans: d

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

a. X.75b. X.25c. X.50d. X.10ans: a

-_____ is a network operating system within several buildings in compound.a. internetb. Novell Netwarec. 10BASE-Td. intranetans: b

-

Used by Bell 103/113 series for full duplex, 2 transmission speeds of 0 to 300bps.a. FSKb. PSKc. BPSKd. ASKans: a

-What is the Nyquist sample rate for a voice input of 10kHz?a. 10kHzb. 20kHzc. 30kHzd. 40kHz

ans: b-What is the minimum number of bits required in PCM code for a range of 10,000?

a. 12b. 9c. 14d. 8ans: c

-How many levels can be represented in PCM transmission system if the binary nu

mbers 00000000 to 11111111 are used to represent signal levels?a. 256

b. 64c. 128d. 512ans: a

-Channel capacity is directly proportional toa. bandwidthb. noisec. number of bitsd. power


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ans: a-Which does not affect noise in a channel?a. bandwidthb. temperaturec. quantizing leveld. resistanceans: c

-_____ is a character oriented protocol.a. BOP

b. Bisyncc. ETXd. BCCans: b

-______ character signifies the start of the test for Bisynca. ETXb. STXc. SOHd. BCCans: b

-In _____ the clock pulse is used to time the sending and receiving of the char

acters.a. asynchronous datab. synchronous datac. bisynchronous datad. isochronous dataans: b

-All bits in a character are sent and received in _____ in serial port.a. one at a timeb. simultaneouslyc. in groups of 2 bitsd. in groups of 3 bitsans: a

-Bridge can only interconnect LANs having identical protocols at the _____ laye

rs.a. session and presentationb. network and transportc. physical and data linkd. presentation and sessionans: c

-OSI stands fora. Out-of-band Signaling Interconnectb. Organization for System Interconnectionc. Open System Interconnection

d. Organization System Interconnectionans: c

-ISO stands fora. International System Organizationb. International Standardization Organizationc. Interconnection for System Organizationd. International Subscribers Organizationans: b

-


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Message switching is ______ network.a. hold and forwardb. forwardc. holdd. store and forwardans: d

-Packet switching is _____ network.a. hold and forwardb. forwardc. hold

d. store and forwardans: a-Polling is an invitation of the primary to a secondary equipment to _____ a me

ssage.a. storeb. receivec. transmitd. readans: c

-Bit rate is _____.a. the rate of change at the output of the modulator.

b. the rate of change at the input of the modulatorc. the reciprocal of the time of one output signaling elementd. the reciprocal of the time of one input signaling elementans: b

-A code that uses three unequal length symbols, dot, dash, and space to encode

a character.a. Gray codeb. Baudot codec. Morse coded. Hollerith cableans: c

-

A 5-bit character codea. EBCDICb. BAUDOTc. ASCIId. HOLERITHans: b

-An 8-bit character code.a. EBCDICb. BAUDOTc. ASCIId. HOLERITHans: a

-An equipment that interfaces the data terminal equipment to the analog transmi

ssion line.a. modemb. muldemc. multiplexerd. codecans: a

-Set of rules governing the orderly exchange of data information.


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a. CCIR recommendationb. protocolc. CCITT recommendationd. standardans: b

-A communication network designed for transferring data from one point to anoth

er.a. Public Telephone Network (PTN)b. Public Data Network (PDN)c. Value Added Network (VAN)

d. Packet Switching Network (PSN)ans: b-Radio communications between points using a single share frequency.a. simplexb. full duplexc. half-duplexd. full/full duplexans: c

-The number of pins in the RS232C interfacea. 20b. 25

c. 39d. 30ans: b

-A modem is sometimes referred to as _____.a. Data Terminal Equipmentb. Data Communication Equipmentc. Universal Asynchronous Receiver Transmitterd. Universal synchronous Receiver Transmitterans: b

-Provide post equalization to the received analog signal.a. line equalizers

b. graphic equalizersc. adaptive equalizersd. post equalizersans: c

-The receive equalizer in a synchronous modem is calleda. a compromise equalizerb. a statistical equalizerc. an adaptive equalizerd. an impairment equalizerans: c

-Compromise equalizer settings typically affect

a. amplitude onlyb. amplitude delayc. delay onlyd. neither amplitude nor delayans: b

-Training sequence (a bit pattern used to synchronize the receive modem) accomp

lishes one of the following functions.a. activate RLSDb. enable any echo suppressors in the circuit


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c. initialize the scrambler circuitd. deactivate RLSDans: a

-When asynchronous data are used with synchronous modems that is calleda. synchronous transmissionb. isochronous transmissionc. asynchronous transmissiond. bisynchronous transmissionans: b

-

_____ is defined as a figure of merit used to express the degree of modulationachieved in an FSK modulator.a. modulation indexb. modulation ratioc. deviation factord. h factorans: d

-What channel in the 103 modem occupies a passband from 300 to 1650 Hz?a. low-band channelb. voice band channelc. high-band channeld. message channel

ans: a-Low speed modems generally have bit rates ofa. 9600 bpsb. 2400 bpsc. 4800 bpsd. up to 2000 bpsans: b

-Medium speed modems have bit rates ofa. 9600 bpsb. 2400 bpsc. 4800 bps

d. 2400 - 4800 bpsans: d

-High speed modems have bit rates ofa. 9600 bpsb. 2400 bpsc. 4800 bpsd. 2000 bpsans: a

-A means of improving the quality of a private-line circuit by adding amplifier

s and equalizers to it.a. line equalizing

b. line amplifyingc. line conditioningd. line encodingans: c

-A voice-grade circuit using the PTN has an ideal passband froma. 0 to 4 Hzb. 0 to 4 MHzc. 0 to 4 kHzd. 0 to 4 GHz


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ans: c-The digital-to-analog converter in a synchronous modem is calleda. a post equalizerb. a statistical equalizerc. an adaptive equalizerd. a line equalizerans: c

-The minimum-quality circuit available using the PTN is calleda. basic voice grade (VG)

b. basic voice channel (VC)c. basic voice band (VB)d. basic telephone channelans: b

-Direct distance dialing (DDD) network is commonly calleda. private-line networkb. PR networkc. dial-up networkd. trunk networkans: c

-The line control unit (LCU) operates on the data when it is in digital form an

d is therefore calleda. data terminal equipment (DTE)b. data communications equipment (DCE)c. modemd. UARTans: a

-With _____, each character is framed between start and a stop bit.a. synchronous datab. isochronous datac. asynchronous datad. nonsynchronous dataans: c

-With _____, rather than frame each character independently with start and stop

bits, a unique synchronizing character called a SYN character is transmitted atthe beginning of each message.a. asynchronous datab. isochronous datac. synchronous datad. nonsynchronous dataans: c

-A logic _____ is used for the start bit.a. 0b. 0 or 1

c. 1d. 0 and 1ans: a

-All stop bits are logica. 0b. 0 or 1c. 1d. 0 and 1


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ans: c-_____ ensures that the transmitter and receiver agree on a prescribed time slot for the occurrence of a bit.a. bit or clock synchronizationb. modem or carrier synchronizationc. character synchronizationd. message synchronizationans: a

-Characters that must be transmitted other than the data are called

a. parityb. errorc. overheadd. hamming bitsans: c

-In the United States, the most common CRC code isa. CRC - 16b. CRC - 8c. CRC - 7d. CRC - 32ans: a

-

The generating power polynomial x^7 + x^5 + x^4 + x^2 + x^1 + x^0 is equivalent toa. 101101110b. 101101111c. 010010001d. 10110111ans: d

-Parallel transmission is also calleda. parallel-by-bitb. serial-by-bitc. serial-by-characterd. A and C above

ans: d-Data meansa. digital informationb. both digital and analogc. analog informationd. neither digital or analogans: a

-Go-ahead sequencea. 10111111b. 00000010c. 11111110

d. 01111111ans: d

-Used to achieve character synchronization in SDLC.a. address fieldb. control fieldc. flag fieldd. frame check fieldans: c

-


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A command that places a secondary station in the normal disconnect mode.a. RDb. DMc. DISCd. SIMans: c

-Character oriented protocol.a. asynchronousb. SDLCc. ISO HDLC

d. synchronousans: a-Determines which network configuration is most appropriate.a. applicationsb. network layerc. data link layerd. presentation layerans: b

-A standard that combines previous standards 6159 (E) (unbalanced) and 6256 (E)

(balanced) and outlines the class of operation necessary to establish the link-level protocol

a. ISO 7809b. ISO 3309c. ISO 4335d. ISO 2230ans: a

-Ethernet is a baseband system using CSMA/CD operating ata. 10 Mbpsb. 30 Mbpsc. 20 Mbpsd. 40 Mbpsans: a

-

A type of digital encoding technique used to detect collision in CSMA/CD.a. UPRZb. BPRZc. UPNRZd. Manchesterans: d

-With _____, a station monitors the line to determine if the line is busy.a. CSMA/CDb. CSMA/CAc. Token passingd. FDDIans: a

-Describes the mechanism used by a station to gain access to local area network

.a. Channel multiplexingb. CSMA/CDc. Channel accessingd. CSMA/CAans: c

-Broadband uses


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a. TDMb. Space multiplexingc. FDMd. Statistical multiplexingans: c

-A typical multiplexing scheme used by baseband transmission.a. TDMb. Space multiplexingc. FDMd. Statistical multiplexing

ans: a-_____ uses the connecting medium as a single-channel device.a. broadband transmissionb. digital transmissionc. baseband transmissiond. analog transmissionans: c

-_____ uses the connecting medium as a multi-channel device.a. broadband transmissionb. digital transmissionc. baseband transmission

d. analog transmissionans: a-The use of coaxial cables in interconnecting networks is limited to an overall

length of approximately.a. 1500 ftb. 1500 kmc. 1500 md. 1500 kftans: c

-Identifies how the stations are interconnected in a network.a. topology

b. topology or architecturec. architectured. topology and architectureans: b

-A data communications network that is designed to provide two-way communicatio

ns between a large variety of data communications terminal equipment within a relatively small geographic area.a. Private Area Networkb. Wide Area Networkc. Local Area Networkd. Ethernetans: c

-The type of encoding used in the transmission of data on an ISDN line between

a customer's premises and a carrier's central office.a. quadrature amplitudeb. 2B1Q encodingc. Manchesterd. UPRZans: b

-A mode of transmission in public data network in which data are transferred fr


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om source to the network to the destination in an asynchronous data format.a. synchronous modeb. packet modec. start/stop moded. circuit modeans: c

-IEEE 802.3 standard isa. CSMA/CDb. CSMA/CAc. token passing

d. FDDIans: a-IEEE 802.4 standard isa. CSMA/CDb. CSMA/CAc. token passing for bus topologyd. token passing for ring topologyans: c

-IEEE 802.5 standard isa. CSMA/CDb. CSMA/CA

c. token passing for bus topologyd. token passing for ring topologyans: d

-What is the data rate of the ISDN basic access B channel?a. 32 kbpsb. 64 kbpsc. 144 kbpsd. 192 kbpsans: b

-What is the data rate of the ISDN basic access D channel?a. 32 kbps

b. 64 kbpsc. 144 kbpsd. 192 kbpsans: b

-What equation defines the composition of an ISDN basic access line?a. 2B + Db. B + Dc. B + 2Dd. 2B + 2Dans: a

-What is the number of channels on which different operations can occur simulta

neously on one ISDN basic access line?a. 1b. 2c. 5d. 3ans: d

-Digital telephone and integrated voice-data workstations are examples of what

type of ISDN equipment?a. TE


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b. TAc. NT2d. TPans: a

-How many OSI layers are covered under the X.25 standard?a. 3b. 4c. 7d. 2ans: a

- An Open System Interconnection (OSI) layer has the responsibility for the physical transportation of the bits of data from one end of a point-to-point link tothe other.a. data link layerb. physical layerc. network layerd. session layerans: b

-A technique involving signaling by both ends of a link to ensure correct data

transfer.a. collision

b. burstc. handshakingd. stuffingans: c

-XON/XOFF isa. seldom usedb. always enabledc. a method of flow controld. a data compression functionans: c

-An example of outband signaling is

a. XON/XOFFb. RTSc. RS-232d. CTSans: d

-A recommendation which allows a synchronous modem to be used to transmit async

hronous characters, without error control.a. V.14b. V.13c. V.22d. V.23ans: a

-The scrambler in a synchronous modem is found in thea. modular sectionb. receiver sectionc. transmitter sectiond. demodulator sectionans: c

-A CCITT recommendation which gives the definition for the interchange circuits

between DTE's and DCE's.


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a. V.24b. V.25c. V.26d. V.27ans: a

-Binary codes are sometimes transformed in modems intoa. octal codesb. Huffman codesc. Gray coded. Hamming codes

ans: c-A Western Electric 2911 modem operates with a carrier frequency ofa. 1400 Hzb. 1200 Hzc. 1800 Hzd. 800 Hzans: c

-A special bit pattern used to denote the start and end of a data link layer fr

ame.a. EBCDICb. gateway

c. fibred. flagans: d

-A bipolar violationa. represents a zero followed by one bitb. occurs when two successive pulses have the same polarity and are separated

by a zero levelc. occurs when two successive pulses have the same polarity and are separated

by one leveld. represents as one bit followed by a zero bitans: b

-

What is a flow control?a. refers to opening and closing of flood control gatesb. the process wherby the modem matches the rate of the receiverc. the process of starting and stopping the terminal output to avoid loss of c

haracters by the receiving deviced. the process of switching "on" and "off".ans: c

-Buffering refers toa. the storage of data within the transmitting modem until the receiver is rea

dy to receiveb. a method of reducing the severity of communications headachesc. temporarily storing data to allow for small variations in device speeds

d. the process of isolating critical stages in a communications systemans: c

-What is the reason why many cables have RS-232 connectors with some wires cros

sed?a. RS-232 is the prevalent standardb. asynchronous modems reverse the direction of transmitted and received data

from the standardc. many computers and peripherals use RS-232 serial interface, but not as DTE

or DCE


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d. these connectors are readily available and cheaperans: b

-RS-232, RS-530, RS-449, V.21 and V.24 are examples ofa. standards for end-to-end performance of data communications systemsb. standards for interfaces between modems and transmission facilitiesc. standards for various types of transmission channelsd. standards for interfaces between terminals and modemsans: d

-Request To Send (RTS) / Clear To Send (CTS)

a. is the way the modem indicates ringing and the way the terminal indicates that it is ready for the call to be answeredb. is the way the DTE indicates that it is ready to transmit data, or the way

the DCE indicates that it is ready to accept datac. are the pins that represent received transmissions and carrier transmission

sd. is always activated prior to actual transmission/receptionans: b

-Extended command sets supported by modern modemsa. are prefixed with the letter Eb. can be counted on to provide a high-speed data transfer capability without

requiring flow control

c. are standardizedd. use different commands to control many advanced modem featuresans: d

-Which of the following can be done by a smart modem?a. detection and correction of transmission errorsb. correct answers in multiple choice quizzesc. accepts commands from the terminal via the RS-232 interfaced. converts digital signal to analog signalans: c

-_____ always have a set of symbols.a. communications protocol

b. headersc. standardsd. codesans: a

-The Baudot code uses how many bits per symbol?a. 5b. 6c. 7d. 8ans: a

-Which protocol adjusts its block size based on the line error rate?

a. XMODEMb. YMODEMc. ZMODEMd. BOPans: c

-Which of the following is not a common DNA repeater?a. DESPRb. DEREP-AAc. DEREP-RA


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d. DEREP-RBans: d

-What is the number of bits that are zeros when transmitting odd-parity coded s

ymbols?a. oddb. evenc. unknownd. fourans: c

-

Standard for the 7-layer model for Open Systems Interconnectiona. X.75b. X.200c. X.400d. X.500ans: b

-One of the following options is a characteristic of a LAN.a. parallel transmissionb. low cost access for low bandwidth channelsc. application-independent interfacesd. serial transmissionans: c

- Not a common LAN medium.a. twin leadb. twisted pairc. fiber optic cabled. coaxans: a

-Not a local area network (LAN)?a. PBX systemb. Hospital systemc. Office building systemd. cable TV system

ans: d-CCITT standard concentrating on data communications over the telephone network

.a. V-seriesb. X-seriesc. I-seriesd. T-seriesans: a

-One of the following items cannot be provided in a broadband LAN.a. voice circuitsb. fiber optic transmission

c. CCTVd. frequency agile modemsans: b

-A small telephone switching system that can be used as a LAN./a. ringb. WANc. UARTd. PBXans: d


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-A LAN architecture that can be expanded to the greatest total system bandwidth

.a. digital PBXb. token passing networkc. broadband cable systemd. CSMA/CD baseband systemans: a

-Which is considered as the fastest LAN topology?a. ring

b. busc. stard. squareans: b

-Data communications refers to the transmission ofa. voiceb. videoc. computer datad. facsimile signalans: c

-______ is a procedure or rule that defines how data is to be transmitted.

a. standardb. protocolc. data specificationd. codeans: b

-Which of the following is a popular PC protocol?a. parityb. XMODEMc. CRCd. LRCans: b

-

What is the most widely used data communications code?a. Grayb. EBCDICc. Baudotd. ASCIIans: d

-The ASCII code has how many bits?a. 4b. 5c. 6d. 7ans: d

-What methods are used in data communications?a. analog methodsb. digital methodsc. both analog and digital methodsd. neither analog nor digital methodsans: c

-One of the following is not primarily a type of data communications.a. teletype


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b. telephonec. telegraphd. CWans: b

-Mark and space refer respectively toa. binary 1 and binary 0b. dot and dashc. message and intervald. on and offans: a

- A modem convertsa. analog signals to digitalb. digital signals to analogc. both of the aboved. none of the aboveans: c

-An I-series recommendation which describe what an ISDN is.a. I.112b. I.210c. I.120d. I.130

ans: c-Slow speed modems use _____ digital modulation method.a. BPSKb. QPSKc. QAMd. FSKans: d

-When the data signal is transmitted directly over the medium, this is called _

____ transmission.a. basebandb. broadband

c. analogd. digitalans: a

-_____ is the technique of using modulation and FDM to transmit multiple data channels of a common medium.a. basebandb. broadbandc. ringd. busans: b

-The cause of bit errors in data transmission.

a. noiseb. equipment failurec. Human encoderd. Poor S/N ratio at the receiverans: a

-What is the other name for parity?a. BCCb. LRCc. VRC


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d. CRCans: c

-QAM is the combination ofa. ASK and FSKb. ASK and QPSKc. ASK and MSKd. FSK and PSKans: b

-A CCITT standard that refers to various aspects of Integrated Service Digital

Network (ISDN)a. I-seriesb. V-seriesc. X-seriesd. D-seriesans: a

-Which of the following is not part of a QAM modulator?a. XNORb. bit splitterc. balanced modulatord. 2-to-4 level converterans: a

- Not a commonly used method of error detection.a. parityb. BCCc. CRCd. Redundancyans: d

-What is produced by a longitudinal redundancy check (LRC)?a. parity bitb. block check character (BCC)c. CRCd. Hamming code

ans: b-What is the basic modulator/demodulator circuit in PSK?a. PLLsb. Balanced modulatorsc. Linear summerd. VCOans: b

-What is the main reason why serial transmission is preferred over parallel tra

nsmission?a. it is fasterb. it is cheaper

c. it requires multiple channelsd. it requires only a single channelans: d

-Limitation of 10base-2 network.a. 30 stations per segmentb. 20 bytes per data fieldc. 50 feet of cabled. 40 segmentsans: a


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-A transmission media is not readily suitable to CSMA operation.a. microwave radiob. coaxial cablec. twisted paird. optical fiberans: d

-Which of the following refers to the measurement of an uncertainty?a. probabilityb. entropy

c. feasibilityd. all of theseans: b

-Not an important characteristic of the physical layer.a. electricalb. mechanicalc. logicald. all of theseans: c

-The bit rate of B-channel is _____ kbps.a. 16

b. 8c. 64d. 32ans: c

-Defines a 2400-bps, PSK, half-duplex modem operating at 1200 baud.a. V.26bisb. V.26terboc. V.27d. V.28ans: a

-Which of the following ITU standards describe the interconnection techniques b

etween PDNs and PSTNs?a. V.100b. V.200c. V.300d. V.400ans: a

-Is the progressive decrease of signal strength with increasing distance.a. radiationb. attenuationc. modulationd. propagationans: b

-The component most apt to break down in the radio circuit is thea. Crystalb. resistorc. transformerd. diodeans: b

Documents

CH8 - Digital and Data Communications