Malayan Colleges Laguna  MITL ECE142

1)Which of the following is not an advantage of digital transmission?

1. 1. noise immunity
   2. ease of multiplexing
   3. bandwidth utilization
   4. ease of encryption

2.          is the ratio of the largest possible magnitude to the smallest possible

magnitude that can be decoded by the DAC.

1. resolution
2. quantization
3. dynamic range
4. voltage ratio

3. A process where the higher amplitude analog signals are compressed prior to

transmission then expanded at the receiver.

1. compressing
2. expanding
3. encoding
4. companding

4. For a resolution of 0.01 V and analog sample voltage of 0.05 V, the 12bit

linear signmagnitude code is a. 000000000101

b. 100000000101

c. 100010010011

d. 000001010001

5.          uses a single bit PCM code to achieve a digital transmission of analog

signal.

1. Quadrature Amplitude Modulation (QAM)
2. Frequency Shift Keying (FSK)
3. Delta Modulation (DM)
4. Phase Modulation (PM)

6. The line speed of Bell System T1 carrier system is

1. 64 kbps
2. 3.152 Mbps
3. 1.544 Mbps
4. 6.312 Mbps

7. How many channels does a T2 line carry?

1. 24
2. 48
3. 96

d. 672

8. The capacity of the standard 4kHz telephone channel with 30 dB S/N is a. 455225 bps

2. 42525 bps
3. 39846 bps
4. 39840 bps

9. How many channels does a super group have?

a. 60

b. 600

c. 1800

d. 10800

10. The output frequency at the channel combiner of channel 7 is

1. 7680 kHz
2. 8084 kHz
3. 8488 kHz
4. 8892 kHz

11. The carrier frequency of the supergroup D25 is

1. 2652 kHz
2. 2900 kHz
3. 2356 kHz
4. 2108 kHz

12. Which of the following is not a hybrid data?

1. data in voice
2. data under voice
3. data above voice
4. data in video

13.        was the first fixedlength 5bit character code.

1. EBCDIC
2. ASCII
3. Morse code
4. baudot code

14. CCITT V.26 modem has a modulation rate of                .

1. 1200 Hz
2. 1200 bauds
3. 1560 cps
4. 9600 bauds

15. What can a smart modem do?

1. detect transmission errors and correct them automatically
2. correct answer multiple choice quizzes
3. accepts commands from the terminal via RS232 interface
4. do a smart game

16. One is an advantage of PTM over PAM.

1. much better noise immunity
2. low sampling rate required
3. simpler to generate
4. less costly

17. When did ISO adapt the sevenlayer OSI model? a. 1983

b. 1973

c. 1963

d. 1953

18. Amplitude shift keying is also known as                     .

1. up/down keying
2. on/off keying

3. front/back keying
4. I/O keying

19. Which modulation system is used in telephony?

1. FSK
2. PCM
3. Twotone modulation
4. singletone modulation

20. Modulation used by asynchronous data

1. QPSK
2. FSK
3. PSK
4. QAM

21. PCM systems require          .

1. analog signals
2. large bandwidth
3. digital signals
4. fiber optic cable

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

noise level?

1. Nyquist theorem
2. Hartley theorem
3. ShannonHartley theorem
4. Shannon theorem

23. Quantizing noise is present in                   system.

1. PCM
2. ATM
3. TDM
4. PAM

24.        is the difference between the original and reconstructed signal

1. quantizing noise
2. fade margin
3. noise margin
4. noise figure

25. What is the reason why companding is employed in PCM system?

1. to solve quantizing noise problem
2. to allow amplitude limits in the receivers
3. to protect small signals in PCM from quantizing distortion
4. to overcome impulse noise in PCM receivers

26. Band of frequencies in a transmission medium allotted to each communication

channel on a continuous time basis.

1. TDM
2. FDM
3. CDMA
4. broadband

27. Error control used in high frequency radio data transmission.

1. FEC

2. ARQ
3. Hamming
4. Parity

28. What are the steps to follow to produce a PCM signal?

1. sampling, coding and quantizing
2. sampling, quantizing, and coding
3. quantizing, sampling, and coding
4. coding, quantizing, and sampling

29.        identifies how the different stations in a multipoint system are

interconnected.

1. network topology
2. star network
3. ring network
4. bus network

30. A transmission where data are inputted directly on the cable.

1. broadband
2. baseband
3. digital
4. analog

31. A transmission where data are inputted inside the carrier wave.

1. broadband
2. baseband
3. digital
4. analog

32. A transmission system for a multidrop network.

1. token passing
2. CSMA/CD
3. polling
4. CSMA/CA

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

1. CSMA/CD
2. token passing
3. CSMA/CA
4. polling

34. Synchronous modems cost more than asynchronous modems because

1. they are larger
2. they must contain clock recovery circuits
3. the production volume is larger
4. they must operate on a larger bandwidth

35. When one station is designated as master and the rest of the stations are

considered slaves, message handling is                         .

1. store and forward
2. polling
3. CSMA/CD
4. token passing

36. The computer that initiates information transfer.

1. master
2. slave
3. DCE
4. DTE

37. A store and forward switching.

1. circuit switching
2. packet switching
3. message switching
4. PSTN

38. It is used to connected computers in the same building or in same area.

1. LAN
2. WAN
3. MAN
4. PBX

39. Two or more LAN linked together over a wide geographical area.

1. HAN
2. MAN
3. WAN
4. RAN

40. Which system allows different types of networks to be linked together?

1. OSI
2. CCITT
3. Bell system
4. AT & T

41. OSI consists of how many layers of interconnection?

1. 3
2. 5
3. 7
4. 9

42. Which network layer determines if the user can send or receive based on

whether they can send and receive simultaneously or alternatively?

1. physical layer
2. data link layer
3. transport layer
4. session layer

43. A       that interconnects LAN having identical protocols at the physical and

data link layers.

1. bridge
2. router
3. gateway
4. hub

44. A       interconnects LAN having identical protocols at the physical data link

and network layers.

1. bridge
2. router
3. gateway
4. node

45. A       interconnects LAN that have totally different protocols and format.

1. bridge
2. router
3. gateway
4. WAN

46. All bits in a character can be sent/received simultaneously.

1. serial data
2. parallel data
3. full duplex
4. duplex

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

1. parallel data
2. serial data
3. simplex
4. half duplex

48. A system that perform paralleltoserial and serialtoparallel conversion of

a data link.

1. DTE
2. DCE
3. modem
4. FEP

49. EIA stands for

1. Electronic Institute Association
2. Electronic Industry Association
3. Electronic Improvement Ads
4. Electrical Industrial Association

50. An acoustic modem converts a complex digital signal into

1. serial form
2. parallel form
3. radio tones
4. audio tones

51. Which mode of transmission achieves less than fullduplex but more than half

duplex?

1. full\full duplex
2. echoplex
3. isochronous
4. synchronous

52. Rules governing the transmission of digital information.

1. data communications standard
2. line protocol
3. isochronous
4. digital communication

53. Codecs must be

1. eight bits per character
2. eight seven or eight bits per character
3. agreed upon in advance between sender and receiver

4. the same in all modern computers

54. The standard ASCII

1. is version II of ASC
2. has 132 characters including 32 control characters
3. is subset of a 8bit EBCDIC code
4. is used only in US and Canada

55. The Baudot code

1. was invented by the Baudot brothers
2. required the escape character to print numbers
3. requires shift characters to provide sufficient combinations
4. a descendant of Morse code

56. The corrections and accuracy of the transmitted message control is

1. verified by the modem
2. determined by the sender and the receiver
3. ensured by the used of digital techniques
4. dependent on the communications system used

57. Framing is

1. concerned with the boundaries between characters
2. referred to paralleltoserial conversion
3. concerned with synchronous system
4. concerned with individual bits

58. Asynchronous transmission is

1. is less efficient but simpler
2. is much faster than synchronous transmission
3. is another name for synchronous transmission
4. the most soughtafter transmission

59. Digital transmission provides a higher level of signal quality than analog

transmission because

1. repeaters regenerate digital pulses and remove distortion
2. digital signals are smaller than analog signals and cannot easily be distorted
3. analog signals are continuous and are not easily distorted
4. digital signals are easier to sample than analog signals

60. Digital to analog converter in synchronous modems send signals to the

1. modulator
2. transmission lines
3. terminal
4. equalizer

61. Binary codes are transformed in modems into

1. hexadecimal
2. Hullman code
3. Gray code
4. octal

62. Synchronous modems cost more than asynchronous modem because

1. they are larger
2. they must contain clock recover circuits

3. the production volume is larger
4. they must operate on a larger bandwidth

63. What is the best type of data communications test equipment?

1. simulator
2. protocol analyzer
3. DTE
4. breakout box

64. What is the data rate of the ISDN Basic access B channel?

1. 32 kbps
2. 64 kbps
3. 144 kbps
4. 192 kbps

65. What is the data rate of the ISDN basic access D channel?

1. 64 kbps
2. 16 kbps
3. 8 kbps
4. 144 kbps

66. Baudot code uses how many bits per symbol?

1. 9
2. 7
3. 5
4. 8

67. How many bits are there to present 8 combinations?

1. 3
2. 4
3. 2
4. 5

68. How many number of equiprobable events are there for 8bits of information? a. 256

b. 132

c. 2400

d. 512

69. Which computer terminal can be programmed to perform new functions?

1. dumb terminal
2. smart terminal
3. intelligent terminal
4. super terminal

70. Which character code is used without parity bit?

1. CCITT number 2
2. ASCCII
3. CCITT number 5
4. EBCDIC

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

locations?

1. LCU
2. FEP

3. Muldem
4. Modem

72.        is a data communications hardware that assist the host computer in

handling input and output tasks.

1. hub
2. cluster controller
3. front end processor
4. concentrator

73. ASCII means

1. terminals using synchronous transmission in EBCDIC
2. terminals using synchronous transmission in ASCII
3. terminals using asynchronous transmission in ASCII
4. any terminal having an American (dollarsign) keyboard

74. A unit of information used in data communications.

1. dit
2. bit
3. byte
4. baud

75. Transmission of binary signals requires

1. less bandwidth than analog
2. more bandwidth than analog
3. the same bandwidth as analog
4. a license from the NTC

76. What is the modulation rate of the CCITT V.26 modem?

1. 56 kbps
2. 1200 kbps
3. 1560 kbps
4. 9600 kbps

77. The digitaltoanalog converter in a synchronous modem sends signal to the

          .

1. modulator
2. transmission line
3. terminal
4. equalizer

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

parity coded symbols.

1. even
2. odd
3. unknown
4. one

79. A digital modulation technique that results in two difference frequencies

representing binary 1 and .

1. FSK
2. QPSK
3. ASK
4. DPSK

80. What is the input to the DigitaltoAnalog Converter of a PCM decoder circuit?

1. a series of sampled amplitudes
2. a parallel binary word
3. a series of bits
4. a reconstructed intelligence signal

81. The output of the DAC at a PCM decoder circuit is a                        .

1. series of binarycoded digits
2. parallel output of binarycoded digits
3. fixed analog voltage
4. reconstructed intelligence signal

82. Serial printer

1. are used to transmit grain prices
2. faster than CRT terminals, and offers more flexibility
3. prints one character at a time
4. usually uses serial interfaces

83. Delta modulation is a/an

1. 5bit modulation
2. integral PCM system
3. 1bit differential PCM system
4. form of PDM

84. Alternative way of digitizing analog signals.

1. PCM
2. Delta modulation
3. PPM
4. DPCM

85. One dit is equal to               bits.

a. 3

b. 3.5

c. 3.32

d. 4

86. Redundancy means the        .

1. transmission rate of the system
2. symbols are to be repeated
3. time between failures
4. time between successes

87. Which transmission media is not suitable to CSMA operation?

1. Radio
2. Optical fiber
3. Coaxial cable
4. Twisted pair

88.        is a device used to convert a time varying electrical quantity to an

appropriate form.

1. Codec
2. Transducer
3. ADC/DAC
4. Modem

89. The bandwidth of U600 mastergroup is

1. 2250 kHz
2. 2728 kHz
3. 2520 kHz
4. 2278 kHz

90. Refers to the combination of digitally encoded signals transmitted with FDM

signals as one composite baseband signal.

1. composite data
2. data under voice (DUV)
3. hybrid data
4. Data In Voice (DIV)

91. Transmit frequencydivisionmultiplexed voice band signals over a coaxial data

for distances up to 4000 miles.

1. T carrier systems
2. A carrier systems
3. L carrier systems
4. D carrier systems

92. Level 5 of Japanese PCM multiplex hierarchy has channel capacity of

1. 7680 VB channels
2. 5760 VB channels
3. 8064 VB channels
4. 5670 VB channels

93. The line data rate (in Mbps) for level 4 of CEPT 30 + 2 PCM multiplex

hierarchy a. 97.728

b. 400.352

c. 274.176

d. 139.264

94. The guardband between supergroup 18 and supergroup D25 is

1. 12 kHz
2. 56 kHz
3. 128 kHz
4. 8 kHz

95. Supergroup 17 has a carrier frequency (in kHz) of a. 2108

b. 2356

c. 1860

d. 1612

96. A radio channel is composed of                VB channels. a. 1800

b. 900

c. 10800

d. 8064

97. What is the guardband between supergroup 1 and supergroup 2?

1. 12 kHz
2. 10 kHz
3. 8 kHz