MCQ on Pulse Code Modulation (PCM)

MCQ on Pulse Code Modulation (PCM)

MCQ on Pulse Code Modulation, MCQ on PCM, Objective questions on PCM, Objectives on Pulse Code Modulation, Pulse Code Modulation MCQ with Answer, Multiple Choice Question on PCM, Pulse Code Modulation Objectives with answer, MCQ on PWM, MCQ on PAM

Multiple Choice Questions of PCM

1. Companding is used

• to overcome quantizing noise in PCM
• in PCM transmitters, to allow amplitude limiting in the receivers
• to protect small signals in PCM from quantizing distortion.
• in PCM receivers, to overcome impulse noise.

Answer: to overcome quantizing noise in PCM

2. The biggest disadvantages of PCM is

• its inability to handle analog signals
• the high error rate which its quantizing noise introduces
• its incompatibility with TDM
• the large bandwidths that are required for it.

Answer: the large bandwidths that are required for it.

3. Indicate which of the following pulse modulation systems is analog

• PCM
• Differential PCM
• PWM
• Delta modulation

Answer: PWM

4. Quantizing noise occurs in

• time-division multiplexing
• FDM
• PCM
• PWM

Answer: PCM

5. Quantizing noise can be reduced by increasing the number of samples per second. It is true,

• yes, it is
• no, it is not
• not necessarily
• none of these

Answer: none of these

6. In PCM a system, the quantization noise depends upon

• the number of quantization levels only
• the sampling rate only
• both the sampling rate and the number of quantization levels
• none of the above is correct

Answer: both the sampling rate and the number of quantization levels

7. The signal-to quantization noise ratio in PCM system depends upon

• sampling rate
• number of quantization levels
• message signal bandwidth
• none of the above

Answer: number of quantization levels

8. Indicate which of the following systems is digital?

• Pulse-position modulation
• Pulse-code modulation
• Pulse-width modulation
• Pulse-frequency modulation

Answer: Pulse-code modulation

9. Quantizing noise occurs in

• time-division multiplex
• frequency-division multiplex
• pulse-code modulation
• pulse-width modulation

Answer: Pulse-code modulation

10. In order to reduce quantizing noise, one must

• increase the number of standard amplitudes
• send pulses whose sides are more nearly vertical
• use an R.F. amplifier in the receiver
• increase the number of samples per second

Answer: increase the number of standard amplitudes

11. The biggest disadvantages of PCM is

• its inability to handle analog signals
• the high error rate which its quantizing noise reduces
• its incompatibility with TDM
• the large bandwidth that are required for it

Answer: the large bandwidth that are required for it

12. The main advantage of PCM system is

• a lower bandwidth
• a lower power
• lower noise
• None of the above

Answer: lower noise

13. Quantization noise is produced in

• all pulse modulation system
• PCM
• all modulation system
• none of the above

Answer: PCM

14. One of the following systems is analog –

• PCM
• delta
• differential PCM
• PAM

Answer: PAM

15. For an efficient communication in PCM system number of samples per second must at least be equal to twice the highest modulating frequency. Comment

• Not necessary
• A very important consideration
• Who cares
• 80- 50, true

Answer: A very important consideration

16. In PCM system, output S/N increases

• linearly with bandwidth
• exponentially with bandwidth
• inversely with bandwidth
• none of these

Answer: linearly with bandwidth

17. The transmitted pulse in PCM system usually occur at a uniform rate for minimum bandwidth

• true
• false

Answer: true

18. In a DM system, the granular (idling) noise occurs when the modulating signal

• increase rapidly
• remains constant
• decreases rapidly
• the nature of modulating signal has nothing to do with this noise

Answer: remains constant

19. Quantization noise is produced in

• all pulse modulation system
• PCM
• all modulation system
• none of these

Answer: PCM

20. The main advantage of PCM signal is

• lower bandwidth
• higher bandwidth
• lower noise
• none of these

Answer: lower noise

21.  For transmission of normal speech signal the PCM channel needs a bandwidth of

• 64 kHz
• 8 kHz
• 4 kHz
• none of these

Answer: 64 kHz

22. The non-uniform quantization leads to

• reduction in transmission bandwidth
• increase in maximum SNR
• increase in SNR for low level signals
• simplification of quantization process

Answer: increase in SNR for low level signals

23. The equipment needed either at the transmitter or at the receiver is

• simpler
• more complicated
• of simple complexity, when delta modulation is used in the case of PCM
• none of these

Answer: of simple complexity, when delta modulation is used in the case of PCM

24. PCM systems use non-uniform quantization in order to

• raise SNR for low level signals
• cut down the required bandwidth of transmission
• increases the maximum SNR
• none of these

Answer: raise SNR for low level signals

25. The use of non-uniform quantization leads to

• reduction in transmission bandwidth
• increase in maximum SNR
• Increase in SNR for low level signals
• Simplification of quantizations process

Answer: Increase in SNR for low level signals

26. In QAM, both identities are varied.

• amplitude and phase
• frequency and phase
• bit rate and phase
• baud rate and phase

Answer: amplitude and phase

27. Signal-to-quantization noise ratio of a PCM system using 8-bit words for the analog signal that does not exceed its quantization boundary is

• 48 dB
• 54 dB
• 52.7 dB
• 64 dB

Answer: 48 dB

28. Granular noise is associated with

• PCM
• DPCM
• DM
• QAM

Answer: DM

29. The signal to quantization noise ratio in a PCM system depends upon

1. sampling rate
2. number of quantization levels
3. message signal bandwidth

• 1, 2 and 3
• 2 and 3 only
• 2 only
• 3 only

Answer: 2 only

30. In PCM, if the transmission path is very long

• repeater stations are used
• the pulse width may be increased
• pulse amplitude is increased
• pulse spacing is reduced

Answer: repeater stations are used

31. A signal having uniformly distributed amplitude in the interval (-V, + V) is to be encoded using PCM with uniform quanti-zation. The (SNR)q is determined by

• dynamic range of the signal
• sampling rate
• no. of quantizing levels
• power spectrum of a signal

Answer: no. of quantizing levels

32. In PCM the biggest disadvantage compared to analog modulation is

• large bandwidth
• larger noise
• inability to handle analog signals
• incompatibility with TDM system

Answer: large bandwidth

33. In an ADM system, the output signal amplitudes for l’s and 0’s are

• fixed and the repetition rate is also fixed
• fixed but the repetition rate is variable
• variable and the repetition rates is also variable
• variable but the repetition rate is fixed

Answer: fixed and the repetition rate is also fixed

34. The use of non-uniform quantization leads to

• reduction in transmission BW
• increase in max. SNR
• increase in SNR for low-level signals
• simplification of the quantization process

Answer: increase in SNR for low level signals

35. Consider the following statements comparing DM and PCM systems, DM requires

1. a lower sampling rate
2. a higher sampling rate
3. a larger BW
4. simple harware

Which of these statements are correct?

• 1, 2 and 4
• 1, 2 and 3
• 1, 3 and 4
• 2, 3 and 4

Answer: 1, 2 and 4

36. For uniform quantization with 32 levels, the qunantized output can be represented by n binary digits where n is

• 5
• 8
• 6
• 4

Answer: 5

37. In a PCM system, the number of quantization levels are 16 and the maximum signal frequency is 4 kHz, the bit transmission rate is

• 64 bps
• 16 kbps
• 32 kpbs
• 32 bps

Answer: 32 kpbs

38. PCM systems require regenerative repeaters over long distances. The correct sequence of the operations which such a repeater performs is

• Timing, equalization, and decision making
• Equalization timing and decision making
• Timing, thresholding, and equalization
• Thresholding, timing, and equalization

Answer: Equalization timing and decision making

39. In a DM system, the granular noise occurs when the

• modulating signal increases rapidly
• pulse rate decreases,
• modulating signal remains constant
• pulse amplitude increases

Answer: pulse amplitude increases

40. In a PCM system, the amplitude levels are transmitted in a 7 unit code. The sampling is done at the rate of 10 kHz. The BW should be

• 5 kHz
• 35 kHz
• 70 kHz
• 5 MHz

Answer: 35 kHz