Digital Communication - Study Mode

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[#161] The PSD of the Manchester line code

(A) may or may not have zero null depending on choice of pulse

(B) has the factor P(w)

(C) does not have dc null

(D) has a dc null

Correct Answer

(D) has a dc null

[#162] What is the required bandwidth of a PCM system for 256 quantization levels when 48 telephone channels, each band limited to 4 kHz, are to be time-division multiplexed by this PCM?

(A) 6.246 MHz

(B) 3.464 MHz

(C) 3.072 MHz

(D) 1.544 MHz

Correct Answer

(D) 1.544 MHz

[#163] The temperature at a particular place varies between 14°C and 34°C. For the purpose of transmitting the temperature record of that place using PCM, the record is sampled at an appropriate sampling rate and the samples are quantized. If the error in representation of the samples due to quantization is not to exceed ±1% of the dynamic range, what is the minimum number of quantization levels that can be used?

(A) 100

(B) 50

(C) 30

(D) 15

Correct Answer

(B) 50

[#164] 24 voice signals are sampled uniformly at 8 kHz and then sent using TDM scheme. The sampling process uses flat-top samples with 1 µs duration. An extra pulse of duration 1 µs is added for the purpose of synchronization. The spacing between two consecutive pulses is-

(A) 7.2 µs

(B) 5 µs

(C) 6 µs

(D) 4 µs

Correct Answer

(D) 4 µs

[#165] The quantization of a PCM system depends on

(A) Number of quantization levels

(B) Step-size

(C) Both step-size and number of quantization levels

(D) Sampling rate

Correct Answer

(C) Both step-size and number of quantization levels