51. _______ encoding has a transition at the beginning of each 0 bit.
a. RZ
b. Manchester
c. Differential Manchester
d. All the above
Answer: (c).Differential Manchester

52. PCM is an example of _______ conversion.
a. digital-to-digital
b. digital-to-analog
c. analog-to-analog
d. analog-to-digital
Answer: (d).analog-to-digital

53. If the frequency spectrum of a signal has a bandwidth of 500 Hz with the highest frequency at 600 Hz, what should be the sampling rate, according to the Nyquist theorem?
a. 200 samples/s
b. 500 samples/s
c. 1000 samples/s
d. 1200 samples/s
Answer: (d).1200 samples/s

54. The Nyquist theorem specifies the minimum sampling rate to be_______.
a. equal to the lowest frequency of a signal
b. equal to the highest frequency of a signal
c. twice the bandwidth of a signal
d. twice the highest frequency of a signal
Answer: (d).twice the highest frequency of a signal

55. Which of the following encoding methods does not provide for synchronization?
a. NRZ-L
b. RZ
c. NRZ-I
d. Manchester
Answer: (a).NRZ-L

56. Which encoding method uses alternating positive and negative values for 1s?
a. NRZ-I
b. RZ
c. Manchester
d. AMI
Answer: (d).AMI

57. Which quantization level results in a more faithful reproduction of the signal?
a. 2
b. 8
c. 16
d. 32
Answer: (d).32

58. Block coding can help in _______ at the receiver.
a. Synchronization
b. Error detection
c. Attenuation
d. both (a) and (b)
Answer: (d).both (a) and (b)

59. In _______ transmission, a start bit and a stop bit frame a character byte.
a. asynchronous serial
b. synchronous serial
c. parallel
d. (a) and (b)
Answer: (a).asynchronous serial

60. In asynchronous transmission, the gap time between bytes is _______.
a. fixed
b. variable
c. a function of the data rate
d. zero
Answer: (b).variable

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