Which of the following device was used in early TDM/PAM telemetry systems?

DSP

Commuter

Logic gates

Linear switch

Correct Answer : Commuter

Explanation : Multiplexers in early TDM/PAM telemetry systems used a form of rotary switch known as a commutator. Multiple switch segments were attached to the various incoming signals while a high-speed brush rotated by a dc motor rapidly sampled the signals as it passed over the contacts.

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A special PCM system uses 16 channels of data, one whose purpose is an identification (ID) and synchronization. The sampling rate is 3.5 kHz. The word length is 6 bits. Find the serial data rate.

451kHz

336kHz

326kHz

152kHz

Correct Answer : Option (B) : 336kHz

Explaination : Serial data rate = sampling rate x no. bits/frame = 3.5 kHz x 96 = 336 kHz.

Which of the following is false with respect to PCM?

Reliable

Inexpensive

Resistant to noise

Not easily recoverable

Correct Answer : Option (D) : Not easily recoverable

Explanation : When signals have been degraded because of noise, attenuation, or distortion, all the receiver has to do is to determine whether a pulse was transmitted. Amplitude, width, frequency, phase shape, and so on do not affect reception. Thus PCM signals are easily recovered and rejuvenated, no matter what the circumstances.

Which of the following statements is true with respect to PCM?

Analog data is transmitted directly

Analog signal is amplified before transmission

The parallel binary data is converted into serial before transmission

The analog signal is converted into parallel binary data before transmission

Correct Answer : Option (C) : The parallel binary data is converted into serial before transmission

Explanation : The analog signal is converted into a digital signal. Since the converted digital signal is parallel bits of data, it has to be converted to serial before it can be multiplexed and transmitted.