- Digicom & Datacom Which of the following is not an advantage of digital transmission? a. noise immunity b. ease of multiplexing c. bandwidth utilization d. ease of encryption ans: c _____ is the ratio of the the largest possible magnitude magnitude to the smallest possible possible magnitude that can be decoded by the DAC. a. resolution b. quantization c. dynamic range d. voltage ratio ans: c A process where the higher amplitude analog signals are compressed prior to tr ansmission then expanded at the receiver. a. compressing b. expanding c. encoding d. companding ans: d For a resolution of 0.01 V and analog sample voltage of 0.05 V, the 12-bit lin ear sign-magnitude code is a. 000000000101 b. 100000000101 c. 100010010011 d. 000001010001 ans: b _____ uses a single bit PCM code to achieve a digital digital transmission of analog analog s ignal. 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 is a. 64 kbps b. 3.152 Mbps c. 1.544 Mbps d. 6.312 Mbps ans: c How many channels does a T2 line carry? a. 24 b. 48 c. 96 d. 672 ans: c The capacity of the standard 4-kHz telephone channel with 30 dB S/N is a. 455225 bps b. 42525 bps c. 39846 bps d. 39840 bps
ans: c How many channels does a super group have? a. 60 b. 600 c. 1800 d. 10800 ans: a The output frequency at the channel combiner of channel 7 is a. 76-80 kHz b. 80-84 kHz c. 84-88 kHz d. 88-92 kHz ans: b The carrier frequency of the supergroup D25 is a. 2652 kHz b. 2900 kHz c. 2356 kHz d. 2108 kHz ans: a Which of the following is not a hybrid data? a. data in voice b. data under voice c. data above voice d. data in video ans: d _____ was the first fixed-length fixed-length 5-bit character code. a. EBCDIC b. ASCII c. Morse code d. baudot code ans: d CCITT V.26 modem has a modulation rate of _____. a. 1200 Hz b. 1200 bauds c. 1560 cps d. 9600 bauds ans: b What can a smart modem do? a. detect transmission errors and correct them automatically b. correct answer multiple choice quizzes c. accepts commands from the terminal via RS232 interface d. do a smart game ans: c One is an advantage of PTM over PAM. a. much better noise immunity b. low sampling rate required c. simpler to generate d. less costly ans: a When did ISO adapt the seven-layer OSI model? a. 1983
ans: c How many channels does a super group have? a. 60 b. 600 c. 1800 d. 10800 ans: a The output frequency at the channel combiner of channel 7 is a. 76-80 kHz b. 80-84 kHz c. 84-88 kHz d. 88-92 kHz ans: b The carrier frequency of the supergroup D25 is a. 2652 kHz b. 2900 kHz c. 2356 kHz d. 2108 kHz ans: a Which of the following is not a hybrid data? a. data in voice b. data under voice c. data above voice d. data in video ans: d _____ was the first fixed-length fixed-length 5-bit character code. a. EBCDIC b. ASCII c. Morse code d. baudot code ans: d CCITT V.26 modem has a modulation rate of _____. a. 1200 Hz b. 1200 bauds c. 1560 cps d. 9600 bauds ans: b What can a smart modem do? a. detect transmission errors and correct them automatically b. correct answer multiple choice quizzes c. accepts commands from the terminal via RS232 interface d. do a smart game ans: c One is an advantage of PTM over PAM. a. much better noise immunity b. low sampling rate required c. simpler to generate d. less costly ans: a When did ISO adapt the seven-layer OSI model? a. 1983
b. 1973 c. 1963 d. 1953 ans: a Amplitude shift keying is also known as _____. a. up/down keying b. on/off keying c. front/back keying d. I/O keying ans: b Which modulation system is used in telephony? a. FSK b. PCM c. Two-tone modulation d. single-tone modulation ans: a Modulation used by asynchronous data a. QPSK b. FSK c. PSK d. QAM ans: b PCM systems require _____. a. analog signals b. large bandwidth c. digital signals d. fiber optic cable ans: b Which theorem sets the limit on the maximum capacity of a channel with a given noise level? a. Nyquist theorem b. Hartley theorem c. Shannon-Hartley theorem d. Shannon theorem ans: c Quantizing noise is present in _____ system. a. PCM b. ATM c. TDM d. PAM ans: a _____ is the difference between the original and reconstructed signal a. quantizing noise b. fade margin c. noise margin d. noise figure ans: a What is the reason why companding is employed in PCM system? a. to solve quantizing noise problem b. to allow amplitude limits in the receivers c. to protect small signals in PCM from quantizing distortion d. to overcome impulse noise in PCM receivers
ans: c Band of frequencies in a transmission medium allotted to each communication ch annel on a continuous time basis. a. TDM b. FDM c. CDMA d. broadband ans: b Error control used in high frequency radio data transmission. a. FEC b. ARQ c. Hamming d. Parity ans: b What are the steps to follow to produce a PCM signal? a. sampling, coding and quantizing b. sampling, quantizing, and coding c. quantizing, sampling, and coding d. coding, quantizing, and sampling ans: b _____ identifies how the different stations in a multipoint system are interco nnected. a. network topology b. star network c. ring network d. bus network ans: a A transmission where data are inputted directly on the cable. a. broadband b. baseband c. digital d. analog ans: b A transmission where data are inputted inside the carrier wave. a. broadband b. baseband c. digital d. analog ans: a A transmission system for a multidrop network. a. token passing b. CSMA/CD c. polling d. CSMA/CA ans: c Before attempting to transmit data, each station has to listen to the channel. a. CSMA/CD b. token passing c. CSMA/CA d. polling ans: a
Synchronous modems cost more than asynchronous modems because a. they are larger b. they must contain clock recovery circuits c. the production volume is larger d. they must operate on a larger bandwidth ans: 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. polling c. CSMA/CD d. token passing ans: b The computer that initiates information transfer. a. master b. slave c. DCE d. DTE ans: a A store and forward switching. a. circuit switching b. packet switching c. message switching d. PSTN ans: c It is used to connected computers in the same building or in same area. a. LAN b. WAN c. MAN d. PBX ans: a Two or more LAN linked together over a wide geographical area. a. HAN b. MAN c. WAN d. RAN ans: c Which system allows different types of networks to be linked together? a. OSI b. CCITT c. Bell system d. AT & T ans: a OSI consists of how many layers of interconnection? a. 3 b. 5 c. 7 d. 9 ans: c Which network layer determines if the user can send or receive based on whethe r they can send and receive simultaneously or alternatively?
a. physical layer b. data link layer c. transport layer d. session layer ans: d A _____ that interconnects LAN having identical protocols at the physical and data link layers. a. bridge b. router c. gateway d. hub ans: a A _____ interconnects LAN having identical protocols at the physical data link and network layers. a. bridge b. router c. gateway d. node ans: b A _____ interconnects LAN that have totally different protocols and format. a. bridge b. router c. gateway d. WAN ans: c All bits in a character can be sent/received simultaneously. a. serial data b. parallel data c. full duplex d. duplex ans: b The bits in a character which are sent/received one at a time. a. parallel data b. serial data c. simplex d. half duplex ans: b A system that perform parallel-to-serial and serial-to-parallel conversion of a data link. a. DTE b. DCE c. modem d. FEP ans: a EIA stands for a. Electronic Institute Association b. Electronic Industry Association c. Electronic Improvement Ads d. Electrical Industrial Association ans: b An acoustic modem converts a complex digital signal into a. serial form
b. parallel form c. radio tones d. audio tones ans: d Which mode of transmission achieves less than full-duplex but more than half-d uplex? a. full\full duplex b. echoplex c. isochronous d. synchronous ans: b Rules governing the transmission of digital information. a. data communications standard b. line protocol c. isochronous d. digital communication ans: b Codecs must be a. eight bits per character b. eight seven or eight bits per character c. agreed upon in advance between sender and receiver d. the same in all modern computers ans: c The standard ASCII a. is version II of ASC b. has 132 characters including 32 control characters c. is subset of a 8-bit EBCDIC code d. is used only in US and Canada ans: b The Baudot code a. was invented by the Baudot brothers b. required the escape character to print numbers c. requires shift characters to provide sufficient combinations d. a descendant of Morse code ans: c The corrections and accuracy of the transmitted message control is a. verified by the modem b. determined by the sender and the receiver c. ensured by the used of digital techniques d. dependent on the communications system used ans: b Framing is a. concerned with the boundaries between characters b. referred to parallel-to-serial conversion c. concerned with synchronous system d. concerned with individual bits ans: a Asynchronous transmission is a. is less efficient but simpler b. is much faster than synchronous transmission c. is another name for synchronous transmission d. the most sought-after transmission
ans: a Digital transmission provides a higher level of signal quality than analog tra nsmission because a. repeaters regenerate digital pulses and remove distortion b. digital signals are smaller than analog signals and cannot easily be distor ted c. analog signals are continuous and are not easily distorted d. digital signals are easier to sample than analog signals ans: a Digital to analog converter in synchronous modems send signals to the a. modulator b. transmission lines c. terminal d. equalizer ans: d Binary codes are transformed in modems into a. hexadecimal b. Hullman code c. Gray code d. octal ans: c Synchronous modems cost more than asynchronous modem because a. they are larger b. they must contain clock recover circuits c. the production volume is larger d. they must operate on a larger bandwidth ans: b What is the best type of data communications test equipment? a. simulator b. protocol analyzer c. DTE d. breakout box ans: b What is the data rate of the ISDN Basic access B channel? a. 32 kbps b. 64 kbps c. 144 kbps d. 192 kbps ans: b What is the data rate of the ISDN basic access D channel? a. 64 kbps b. 16 kbps c. 8 kbps d. 144 kbps ans: b Baudot code uses how many bits per symbol? a. 9 b. 7 c. 5 d. 8 ans: c -
How many bits are there to present 8 combinations? a. 3 b. 4 c. 2 d. 5 ans: a How many number of equiprobable events are there for 8-bits of information? a. 256 b. 132 c. 2400 d. 512 ans: a Which computer terminal can be programmed to perform new functions? a. dumb terminal b. smart terminal c. intelligent terminal d. super terminal ans: c Which character code is used without parity bit? a. CCITT number 2 b. ASCCII c. CCITT number 5 d. EBCDIC ans: d Which hardware is used when the host computer and the terminal are in separate locations? a. LCU b. FEP c. Muldem d. Modem ans: d _____ is a data communications hardware that assist the host computer in handl ing input and output tasks. a. hub b. cluster controller c. front end processor d. concentrator ans: c ASCII means a. terminals using synchronous transmission in EBCDIC b. terminals using synchronous transmission in ASCII c. terminals using asynchronous transmission in ASCII d. any terminal having an American (dollar-sign) keyboard ans: c A unit of information used in data communications. a. dit b. bit c. byte d. baud ans: b Transmission of binary signals requires a. less bandwidth than analog
b. more bandwidth than analog c. the same bandwidth as analog d. a license from the NTC ans: b What is the modulation rate of the CCITT V.26 modem? a. 56 kbps b. 1200 kbps c. 1560 kbps d. 9600 kbps ans: b The digital-to-analog converter in a synchronous modem sends signal to the ___ __. a. modulator b. transmission line c. terminal d. equalizer ans: d The number of bits that are zeros in each symbol when one is transmitting oddparity coded symbols. a. even b. odd c. unknown d. one ans: c A digital modulation technique that results in two difference frequencies repr esenting binary 1 and -. a. FSK b. QPSK c. ASK d. DPSK ans: a What is the input to the Digital-to-Analog Converter of a PCM decoder circuit? a. a b. a c. a d. a ans:
series of sampled amplitudes parallel binary word series of bits reconstructed intelligence signal c
The output of the DAC at a PCM decoder circuit is a _____. a. series of binary-coded digits b. parallel output of binary-coded digits c. fixed analog voltage d. reconstructed intelligence signal ans: b Serial printer a. are used to transmit grain prices b. faster than CRT terminals, and offers more flexibility c. prints one character at a time d. usually uses serial interfaces ans: c Delta modulation is a/an a. 5-bit modulation
b. integral PCM system c. 1-bit differential PCM system d. form of PDM ans: c Alternative way of digitizing analog signals. a. PCM b. Delta modulation c. PPM d. DPCM ans: b One dit is equal to _____ bits. a. 3 b. 3.5 c. 3.32 d. 4 ans: c Redundancy means the _____. a. transmission rate of the system b. symbols are to be repeated c. time between failures d. time between successes ans: b Which transmission media is not suitable to CSMA operation? a. Radio b. Optical fiber c. Coaxial cable d. Twisted pair ans: b _____ is a device used to convert a time varying electrical quantity to an app ropriate form. a. Codec b. Transducer c. ADC/DAC d. Modem ans: b The bandwidth of U600 mastergroup is a. 2250 kHz b. 2728 kHz c. 2520 kHz d. 2278 kHz ans: c Refers to the combination of digitally encoded signals transmitted with FDM si gnals as one composite baseband signal. a. composite data b. data under voice (DUV) c. hybrid data d. 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 systems b. A carrier systems
c. L carrier systems d. D carrier systems ans: c Level 5 a. 7680 b. 5760 c. 8064 d. 5670 ans: b
of VB VB VB VB
Japanese PCM multiplex hierarchy has channel capacity of channels channels channels channels
The line data rate (in Mbps) for level 4 of CEPT 30 + 2 PCM multiplex hierarch y a. 97.728 b. 400.352 c. 274.176 d. 139.264 ans: d The guardband between supergroup 18 and supergroup D25 is a. 12 kHz b. 56 kHz c. 128 kHz d. 8 kHz ans: b Supergroup 17 has a carrier frequency (in kHz) of a. 2108 b. 2356 c. 1860 d. 1612 ans: a A radio channel is composed of _____ VB channels. a. 1800 b. 900 c. 10800 d. 8064 ans: a What is the guardband between supergroup 1 and supergroup 2? a. 12 kHz b. 10 kHz c. 8 kHz d. 6 kHz ans: a CCITT's supermastergroup has how many voice band channels? a. 600 b. 1800 c. 10800 d. 900 ans: d The transparency mechanism used with SDLC is called a. zero-bit insertion b. modified link test c. beacon test d. invert-on-zero coding ans: a
What equation defines the composition of an ISDN basic access line? a. 2B + D b. B + D c. B + 2D d. 2B + 2D ans: 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. ISDN d. synchronous digital hierarchy (SDH) ans: d T-1 carrier service has _____ digital bit rate. a. 1.544 Mbps b. 2048 Mbps c. 1.644 Mbps d. 9600 Mbps ans: a Non-ISDN equivalent can be connected to ISDN line by the use of _____. a. terminal equipment b. terminal adapters c. modem d. network adaptors ans: b What is the baseband frequency of standard FDM basic supergroup? a. 312 to 552 kHz b. 60 to 2540 kHz c. 60 to 108 kHz d. 300 to 600 kHz ans: a What is the transmission signal coding for T1 carrier? a. binary b. NRZ c. bipolar d. Manchester ans: c The primary purpose of the data modem. a. interface analog terminal equipment to analog communications channel b. interface digital terminal equipment to digital communications channel c. interface analog terminal equipment to digital communications channel d. interface digital terminal equipment to analog communications channel ans: 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. modem d. UART ans: a SYN character of EBCDIC code. a. 32 H
b. 8 H c. 16 H d. 4 H ans: a _____ ensures that the transmitter and receiver agree on the prescribed time s lot for the occurrence of a bit. a. bit or clock synchronization b. modem or carrier synchronization c. character synchronization d. message synchronization ans: a Equation used to determine the number of Hamming bits in the Hamming code. a. 2^n = m + n + 1 b. 2^n >= m + n + 1 c. 2^n > m + n + 1 d. 2^n < m + n + 1 ans: b Data means a. digital information b. both digital and analog c. analog information d. neither digital or analog ans: a What determines which network configuration is most appropriate? a. application layer b. presentation layer c. network layer d. data link layer ans: c Ethernet is a baseband system using CSMA/CD operating at _____. a. 10 Mbps b. 20 Mbps c. 30 Mbps d. 40 Mbps ans: a Mechanism used by a station to gain access to local area network. a. channel multiplexing b. channel accessing c. CSMA/CD d. CSMA/CA ans: b What multiplexing scheme is used by baseband transmission? a. TDM b. space multiplexing c. FDM d. statistical multiplexing ans: a Use of coaxial cables in interconnecting networks is limited to an overall len gth of _____. a. 1500 ft b. 1500 m c. 1500 km
d. 1500 kft ans: b What defines how the stations are interconnected in a network? a. topology b. architecture c. topology or architecture d. topology and architecture ans: c _____ is a data communications network designed to provide two-way communicati ons between a large variety of data communications terminal equipment within a r elatively small geographic area. a. private area network b. local area network c. wide area network d. Ethernet ans: b _____ is the mode of transmission in public data network in which data are tra nsferred from source to the network then to the destination in an asynchronous d ata format. a. synchronous mode b. start/stop mode c. packet mode d. circuit mode ans: b A seven-bit character represent one of _____ possibilities. a. 7 b. 14 c. 64 d. 128 ans: d _____ is defined to be the maximum rate at which information can be transmitte d through a channel. a. bit rate b. baud rate c. coding d. channel capacity ans: d Circuit that performs the inverse mapping and delivers to the user destination , a reproduction of the original data source output. a. source coding b. channel coding c. inverse coding d. demodulation ans: a Digital modulation technique used in modems. a. ASK b. FSK c. PSK d. MSK ans: c Who developed the fixed-length binary code for telegraphy? a. Samuel Morse
b. Emile Baudot c. Alexander Graham Bell d. Guglielmo Marconi ans: b Inventor of pulse-code modulation for the digital encoding of speech signals. a. R.V.L. Hartley b. J.R. Carson c. H. Nyquist d. Alex Reeves ans: d In what year did computers and terminals start communicating with each other o ver long distance? a. 1950's b. 1960's c. 1970's d. 1980's ans: a Store-and-forward multiple-access network. a. ARPANET b. ALOHA c. PRNET d. Packet switching ans: c A source code whose average word length approaches the fundamental limit set b y the entropy of a discrete memoryless source. a. prefix code b. source code c. entropy code d. Huffman code ans: d Who promulgates communications-related military standards (MIL-STD)? a. DOD b. DCA c. DOC-STD d. ANSI-MIL ans: b What is the class of probability in error detection techniques that is known a s residual error rate? a. P1 b. P2 c. P3 d. P4 ans: b RS 232 is normally an interface between DTE and DCE. What is its signal rate? a. 20 kbps b. 30 kbps c. 40 kbps d. 50 kbps ans: a Digital switching concepts that can handle more channels. a. SDS b. TSI
c. TDM d. TMS ans: d What is the most significant advantage of modular switch than time-and-space s witch? a. flexible size b. simplified control c. simplified manufacturing, testing, and maintenance d. the latter is more advantageous than the former ans: a Which of the following is the biggest disadvantage of PCM systems? a. inability to handle analog systems b. high error rate as a result of quantizing noise c. not compatible with TDM d. the large bandwidth required ans: d The reason why companding is employed in PCM systems is a. to solve quantizing noise problem b. to allow amplitude limiting in the receiver c. to protect small signals in PCM from quantizing distortion d. 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 frequency b. resonant frequency c. critical frequency d. natural frequency ans: a The overlapping of the original spectrum and the first translated component is known as a. dc wandering b. aliasing c. droop d. distortion ans: b Transmission sent in both directions simultaneously. a. full duplex b. half duplex c. simplex d. echoplex ans: a Multiplexing in a time division multiplexing occurs based upon a. the position of data within a frame b. the position of a frame within a group of frames c. the activity of connected device d. the priority assigned to a connected device ans: a What is multiplexing? a. the process of increasing bandwidth on a channel b. a technique that enables more than one data source to share the use of a co mmon line
c. mailing letter at the post office d. the ability to share frequency by time ans: b One of the reasons why FDM is being replaced by TDM. a. there is more time than frequency b. it is difficult to place channels side by side c. noise is amplified with voice when an FDM system is used d. most available frequencies have been used ans: c In _____ modulation the carrier is periodic train of pulses. a. amplitude b. analog c. digital d. pulse ans: 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 c arrier frequency is a. TDM b. FDM c. quadrature multiplexing d. duplexing ans: c Which of the following pulse modulation technique is a digital transmission sy stem? a. pulse duration modulation b. pulse position modulation c. pulse width modulation d. pulse code modulation ans: d Information theory was developed by _____. a. Shannon b. Nyquist c. Reeves d. Hartley ans: a Disadvantage of digital transmission. a. more bandwidth and precise timing are required b. requires ADC and DAC device c. incompatible with existing analog facilities d. all of these ans: d A quadratic signaling has _____ possible states. a. 16 b. 4 c. 8 d. 32 ans: b What is the smallest unit of information in binary transmission system? a. byte b. digit c. bit
d. nibble ans: c The lowest layer in the ISO protocol hierarchy. a. network layer b. physical layer c. transport layer d. data link layer ans: b Basic speed rate of digital system. a. 1.44 kbps b. 144 kbps c. 64 kbps d. 2,048 kbps ans: c A formal set of conventions governing the formatting and relative timing of me ssage exchange between two communications system. a. simplex b. tail circuit c. queuing d. protocol ans: d A device that connects 2 data terminal equipment (DTE) directly by emulating t he physical connections of data communications equipment (DCE). a. short haul modem b. null modem c. X.25 modem d. smart modem ans: b Impact printer a. receives-only-printer with a keyboard b. includes ink-jet and terminal devices c. rapidly becoming obsolete d. strikes a ribbon against the paper to produce character image Modem is referred to as a. universal asynchronous receiver transmitter b. universal synchronous receiver transmitter c. data terminal equipment d. data communications equipment ans: d A signaling method relating to a multiplicity of circuits is conveyed over a s ingle channel by labeled messages. a. code signaling b. synchronous c. common channel signaling d. asynchronous ans: 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 destina tion. a. CSMA/CD b. bus c. ring
d. star ans: c A packet format has an error detecting code at a. the start of the packet framing sequence b. the destination address c. the packet number d. the end of packet framing ans: d It is a protocol used to connect the other packet switching network. a. X.75 b. X.25 c. X.50 d. X.10 ans: a _____ is a network operating system within several buildings in compound. a. internet b. Novell Netware c. 10BASE-T d. intranet ans: b Used by Bell 103/113 series for full duplex, 2 transmission speeds of 0 to 300 bps. a. FSK b. PSK c. BPSK d. ASK ans: a What is the Nyquist sample rate for a voice input of 10kHz? a. 10kHz b. 20kHz c. 30kHz d. 40kHz ans: b What is the minimum number of bits required in PCM code for a range of 10,000? a. 12 b. 9 c. 14 d. 8 ans: 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. 64 c. 128 d. 512 ans: a Channel capacity is directly proportional to a. bandwidth b. noise c. number of bits d. power
ans: a Which does not affect noise in a channel? a. bandwidth b. temperature c. quantizing level d. resistance ans: c _____ is a character oriented protocol. a. BOP b. Bisync c. ETX d. BCC ans: b ______ character signifies the start of the test for Bisync a. ETX b. STX c. SOH d. BCC ans: b In _____ the clock pulse is used to time the sending and receiving of the char acters. a. asynchronous data b. synchronous data c. bisynchronous data d. isochronous data ans: b All bits in a character are sent and received in _____ in serial port. a. one at a time b. simultaneously c. in groups of 2 bits d. in groups of 3 bits ans: a Bridge can only interconnect LANs having identical protocols at the _____ laye rs. a. session and presentation b. network and transport c. physical and data link d. presentation and session ans: c OSI stands for a. Out-of-band Signaling Interconnect b. Organization for System Interconnection c. Open System Interconnection d. Organization System Interconnection ans: c ISO stands for a. International System Organization b. International Standardization Organization c. Interconnection for System Organization d. International Subscribers Organization ans: b -
Message switching is ______ network. a. hold and forward b. forward c. hold d. store and forward ans: d Packet switching is _____ network. a. hold and forward b. forward c. hold d. store and forward ans: a Polling is an invitation of the primary to a secondary equipment to _____ a me ssage. a. store b. receive c. transmit d. read ans: 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 modulator c. the reciprocal of the time of one output signaling element d. the reciprocal of the time of one input signaling element ans: b A code that uses three unequal length symbols, dot, dash, and space to encode a character. a. Gray code b. Baudot code c. Morse code d. Hollerith cable ans: c A 5-bit character code a. EBCDIC b. BAUDOT c. ASCII d. HOLERITH ans: b An 8-bit character code. a. EBCDIC b. BAUDOT c. ASCII d. HOLERITH ans: a An equipment that interfaces the data terminal equipment to the analog transmi ssion line. a. modem b. muldem c. multiplexer d. codec ans: a Set of rules governing the orderly exchange of data information.
a. CCIR recommendation b. protocol c. CCITT recommendation d. standard ans: 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. simplex b. full duplex c. half-duplex d. full/full duplex ans: c The number of pins in the RS232C interface a. 20 b. 25 c. 39 d. 30 ans: b A modem is sometimes referred to as _____. a. Data Terminal Equipment b. Data Communication Equipment c. Universal Asynchronous Receiver Transmitter d. Universal synchronous Receiver Transmitter ans: b Provide post equalization to the received analog signal. a. line equalizers b. graphic equalizers c. adaptive equalizers d. post equalizers ans: c The receive equalizer in a synchronous modem is called a. a compromise equalizer b. a statistical equalizer c. an adaptive equalizer d. an impairment equalizer ans: c Compromise equalizer settings typically affect a. amplitude only b. amplitude delay c. delay only d. neither amplitude nor delay ans: b Training sequence (a bit pattern used to synchronize the receive modem) accomp lishes one of the following functions. a. activate RLSD b. enable any echo suppressors in the circuit
c. initialize the scrambler circuit d. deactivate RLSD ans: a When asynchronous data are used with synchronous modems that is called a. synchronous transmission b. isochronous transmission c. asynchronous transmission d. bisynchronous transmission ans: b _____ is defined as a figure of merit used to express the degree of modulation achieved in an FSK modulator. a. modulation index b. modulation ratio c. deviation factor d. h factor ans: d What channel in the 103 modem occupies a passband from 300 to 1650 Hz? a. low-band channel b. voice band channel c. high-band channel d. message channel ans: a Low speed modems generally have bit rates of a. 9600 bps b. 2400 bps c. 4800 bps d. up to 2000 bps ans: b Medium speed modems have bit rates of a. 9600 bps b. 2400 bps c. 4800 bps d. 2400 - 4800 bps ans: d High speed modems have bit rates of a. 9600 bps b. 2400 bps c. 4800 bps d. 2000 bps ans: 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 amplifying c. line conditioning d. line encoding ans: c A voice-grade circuit using the PTN has an ideal passband from a. 0 to 4 Hz b. 0 to 4 MHz c. 0 to 4 kHz d. 0 to 4 GHz
ans: c The digital-to-analog converter in a synchronous modem is called a. a post equalizer b. a statistical equalizer c. an adaptive equalizer d. a line equalizer ans: c The minimum-quality circuit available using the PTN is called a. basic voice grade (VG) b. basic voice channel (VC) c. basic voice band (VB) d. basic telephone channel ans: b Direct distance dialing (DDD) network is commonly called a. private-line network b. PR network c. dial-up network d. trunk network ans: c The line control unit (LCU) operates on the data when it is in digital form an d is therefore called a. data terminal equipment (DTE) b. data communications equipment (DCE) c. modem d. UART ans: a With _____, each character is framed between start and a stop bit. a. synchronous data b. isochronous data c. asynchronous data d. nonsynchronous data ans: c With _____, rather than frame each character independently with start and stop bits, a unique synchronizing character called a SYN character is transmitted at the beginning of each message. a. asynchronous data b. isochronous data c. synchronous data d. nonsynchronous data ans: c A logic _____ is used for the start bit. a. 0 b. 0 or 1 c. 1 d. 0 and 1 ans: a All stop bits are logic a. 0 b. 0 or 1 c. 1 d. 0 and 1
ans: c _____ ensures that the transmitter and receiver agree on a prescribed time slo t for the occurrence of a bit. a. bit or clock synchronization b. modem or carrier synchronization c. character synchronization d. message synchronization ans: a Characters that must be transmitted other than the data are called a. parity b. error c. overhead d. hamming bits ans: c In the United States, the most common CRC code is a. CRC - 16 b. CRC - 8 c. CRC - 7 d. CRC - 32 ans: a The generating power polynomial x^7 + x^5 + x^4 + x^2 + x^1 + x^0 is equivalen t to a. 101101110 b. 101101111 c. 010010001 d. 10110111 ans: d Parallel transmission is also called a. parallel-by-bit b. serial-by-bit c. serial-by-character d. A and C above ans: d Data means a. digital information b. both digital and analog c. analog information d. neither digital or analog ans: a Go-ahead sequence a. 10111111 b. 00000010 c. 11111110 d. 01111111 ans: d Used to achieve character synchronization in SDLC. a. address field b. control field c. flag field d. frame check field ans: c -
A command that places a secondary station in the normal disconnect mode. a. RD b. DM c. DISC d. SIM ans: c Character oriented protocol. a. asynchronous b. SDLC c. ISO HDLC d. synchronous ans: a Determines which network configuration is most appropriate. a. applications b. network layer c. data link layer d. presentation layer ans: b A standard that combines previous standards 6159 (E) (unbalanced) and 6256 (E) (balanced) and outlines the class of operation necessary to establish the linklevel protocol a. ISO 7809 b. ISO 3309 c. ISO 4335 d. ISO 2230 ans: a Ethernet is a baseband system using CSMA/CD operating at a. 10 Mbps b. 30 Mbps c. 20 Mbps d. 40 Mbps ans: a A type of digital encoding technique used to detect collision in CSMA/CD. a. UPRZ b. BPRZ c. UPNRZ d. Manchester ans: d With _____, a station monitors the line to determine if the line is busy. a. CSMA/CD b. CSMA/CA c. Token passing d. FDDI ans: a Describes the mechanism used by a station to gain access to local area network . a. Channel multiplexing b. CSMA/CD c. Channel accessing d. CSMA/CA ans: c Broadband uses
a. TDM b. Space multiplexing c. FDM d. Statistical multiplexing ans: c A typical multiplexing scheme used by baseband transmission. a. TDM b. Space multiplexing c. FDM d. Statistical multiplexing ans: a _____ uses the connecting medium as a single-channel device. a. broadband transmission b. digital transmission c. baseband transmission d. analog transmission ans: c _____ uses the connecting medium as a multi-channel device. a. broadband transmission b. digital transmission c. baseband transmission d. analog transmission ans: a The use of coaxial cables in interconnecting networks is limited to an overall length of approximately. a. 1500 ft b. 1500 km c. 1500 m d. 1500 kft ans: c Identifies how the stations are interconnected in a network. a. topology b. topology or architecture c. architecture d. topology and architecture ans: 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 re latively small geographic area. a. Private Area Network b. Wide Area Network c. Local Area Network d. Ethernet ans: 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 amplitude b. 2B1Q encoding c. Manchester d. UPRZ ans: b A mode of transmission in public data network in which data are transferred fr
om source to the network to the destination in an asynchronous data format. a. synchronous mode b. packet mode c. start/stop mode d. circuit mode ans: c IEEE 802.3 standard is a. CSMA/CD b. CSMA/CA c. token passing d. FDDI ans: a IEEE 802.4 standard is a. CSMA/CD b. CSMA/CA c. token passing for bus topology d. token passing for ring topology ans: c IEEE 802.5 standard is a. CSMA/CD b. CSMA/CA c. token passing for bus topology d. token passing for ring topology ans: d What is the data rate of the ISDN basic access B channel? a. 32 kbps b. 64 kbps c. 144 kbps d. 192 kbps ans: b What is the data rate of the ISDN basic access D channel? a. 32 kbps b. 64 kbps c. 144 kbps d. 192 kbps ans: b What equation defines the composition of an ISDN basic access line? a. 2B + D b. B + D c. B + 2D d. 2B + 2D ans: a What is the number of channels on which different operations can occur simulta neously on one ISDN basic access line? a. 1 b. 2 c. 5 d. 3 ans: d Digital telephone and integrated voice-data workstations are examples of what type of ISDN equipment? a. TE
b. TA c. NT2 d. TP ans: a How many OSI layers are covered under the X.25 standard? a. 3 b. 4 c. 7 d. 2 ans: a An Open System Interconnection (OSI) layer has the responsibility for the phys ical transportation of the bits of data from one end of a point-to-point link to the other. a. data link layer b. physical layer c. network layer d. session layer ans: b A technique involving signaling by both ends of a link to ensure correct data transfer. a. collision b. burst c. handshaking d. stuffing ans: c XON/XOFF is a. seldom used b. always enabled c. a method of flow control d. a data compression function ans: c An example of outband signaling is a. XON/XOFF b. RTS c. RS-232 d. CTS ans: d A recommendation which allows a synchronous modem to be used to transmit async hronous characters, without error control. a. V.14 b. V.13 c. V.22 d. V.23 ans: a The scrambler in a synchronous modem is found in the a. modular section b. receiver section c. transmitter section d. demodulator section ans: c A CCITT recommendation which gives the definition for the interchange circuits between DTE's and DCE's.
a. V.24 b. V.25 c. V.26 d. V.27 ans: a Binary codes are sometimes transformed in modems into a. octal codes b. Huffman codes c. Gray code d. Hamming codes ans: c A Western Electric 2911 modem operates with a carrier frequency of a. 1400 Hz b. 1200 Hz c. 1800 Hz d. 800 Hz ans: c A special bit pattern used to denote the start and end of a data link layer fr ame. a. EBCDIC b. gateway c. fibre d. flag ans: d A bipolar violation a. represents a zero followed by one bit b. occurs when two successive pulses have the same polarity and are separated by a zero level c. occurs when two successive pulses have the same polarity and are separated by one level d. represents as one bit followed by a zero bit ans: b What is a flow control? a. refers to opening and closing of flood control gates b. the process wherby the modem matches the rate of the receiver c. the process of starting and stopping the terminal output to avoid loss of c haracters by the receiving device d. the process of switching "on" and "off". ans: c Buffering refers to a. the storage of data within the transmitting modem until the receiver is rea dy to receive b. a method of reducing the severity of communications headaches c. temporarily storing data to allow for small variations in device speeds d. the process of isolating critical stages in a communications system ans: c What is the reason why many cables have RS-232 connectors with some wires cros sed? a. RS-232 is the prevalent standard b. asynchronous modems reverse the direction of transmitted and received data from the standard c. many computers and peripherals use RS-232 serial interface, but not as DTE or DCE
d. these connectors are readily available and cheaper ans: b RS-232, RS-530, RS-449, V.21 and V.24 are examples of a. standards for end-to-end performance of data communications systems b. standards for interfaces between modems and transmission facilities c. standards for various types of transmission channels d. standards for interfaces between terminals and modems ans: d Request To Send (RTS) / Clear To Send (CTS) a. is the way the modem indicates ringing and the way the terminal indicates t hat it is ready for the call to be answered b. 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 data c. are the pins that represent received transmissions and carrier transmission s d. is always activated prior to actual transmission/reception ans: b Extended command sets supported by modern modems a. are prefixed with the letter E b. can be counted on to provide a high-speed data transfer capability without requiring flow control c. are standardized d. use different commands to control many advanced modem features ans: d Which of the following can be done by a smart modem? a. detection and correction of transmission errors b. correct answers in multiple choice quizzes c. accepts commands from the terminal via the RS-232 interface d. converts digital signal to analog signal ans: c _____ always have a set of symbols. a. communications protocol b. headers c. standards d. codes ans: a The Baudot code uses how many bits per symbol? a. 5 b. 6 c. 7 d. 8 ans: a Which protocol adjusts its block size based on the line error rate? a. XMODEM b. YMODEM c. ZMODEM d. BOP ans: c Which of the following is not a common DNA repeater? a. DESPR b. DEREP-AA c. DEREP-RA
d. DEREP-RB ans: d What is the number of bits that are zeros when transmitting odd-parity coded s ymbols? a. odd b. even c. unknown d. four ans: c Standard for the 7-layer model for Open Systems Interconnection a. X.75 b. X.200 c. X.400 d. X.500 ans: b One of the following options is a characteristic of a LAN. a. parallel transmission b. low cost access for low bandwidth channels c. application-independent interfaces d. serial transmission ans: c Not a common LAN medium. a. twin lead b. twisted pair c. fiber optic cable d. coax ans: a Not a local area network (LAN)? a. PBX system b. Hospital system c. Office building system d. cable TV system ans: d CCITT standard concentrating on data communications over the telephone network . a. V-series b. X-series c. I-series d. T-series ans: a One of the following items cannot be provided in a broadband LAN. a. voice circuits b. fiber optic transmission c. CCTV d. frequency agile modems ans: b A small telephone switching system that can be used as a LAN./ a. ring b. WAN c. UART d. PBX ans: d
A LAN architecture that can be expanded to the greatest total system bandwidth . a. digital PBX b. token passing network c. broadband cable system d. CSMA/CD baseband system ans: a Which is considered as the fastest LAN topology? a. ring b. bus c. star d. square ans: b Data communications refers to the transmission of a. voice b. video c. computer data d. facsimile signal ans: c ______ is a procedure or rule that defines how data is to be transmitted. a. standard b. protocol c. data specification d. code ans: b Which of the following is a popular PC protocol? a. parity b. XMODEM c. CRC d. LRC ans: b What is the most widely used data communications code? a. Gray b. EBCDIC c. Baudot d. ASCII ans: d The ASCII code has how many bits? a. 4 b. 5 c. 6 d. 7 ans: d What methods are used in data communications? a. analog methods b. digital methods c. both analog and digital methods d. neither analog nor digital methods ans: c One of the following is not primarily a type of data communications. a. teletype
b. telephone c. telegraph d. CW ans: b Mark and space refer respectively to a. binary 1 and binary 0 b. dot and dash c. message and interval d. on and off ans: a A modem converts a. analog signals to digital b. digital signals to analog c. both of the above d. none of the above ans: c An I-series recommendation which describe what an ISDN is. a. I.112 b. I.210 c. I.120 d. I.130 ans: c Slow speed modems use _____ digital modulation method. a. BPSK b. QPSK c. QAM d. FSK ans: d When the data signal is transmitted directly over the medium, this is called _ ____ transmission. a. baseband b. broadband c. analog d. digital ans: a _____ is the technique of using modulation and FDM to transmit multiple data c hannels of a common medium. a. baseband b. broadband c. ring d. bus ans: b The cause of bit errors in data transmission. a. noise b. equipment failure c. Human encoder d. Poor S/N ratio at the receiver ans: a What is the other name for parity? a. BCC b. LRC c. VRC
d. CRC ans: c QAM is a. ASK b. ASK c. ASK d. FSK ans: b
the and and and and
combination of FSK QPSK MSK PSK
A CCITT standard that refers to various aspects of Integrated Service Digital Network (ISDN) a. I-series b. V-series c. X-series d. D-series ans: a Which of the following is not part of a QAM modulator? a. XNOR b. bit splitter c. balanced modulator d. 2-to-4 level converter ans: a Not a commonly used method of error detection. a. parity b. BCC c. CRC d. Redundancy ans: d What is produced by a longitudinal redundancy check (LRC)? a. parity bit b. block check character (BCC) c. CRC d. Hamming code ans: b What is the basic modulator/demodulator circuit in PSK? a. PLLs b. Balanced modulators c. Linear summer d. VCO ans: b What is the main reason why serial transmission is preferred over parallel tra nsmission? a. it is faster b. it is cheaper c. it requires multiple channels d. it requires only a single channel ans: d Limitation of 10base-2 network. a. 30 stations per segment b. 20 bytes per data field c. 50 feet of cable d. 40 segments ans: a
