# 30+ important MCQ on Encoding in communication, Probability and Random process Encoding in communication

Cover Image Credit – NASA Goddard Space Flight Center from Greenbelt, MD, USA, Hubble Peers into the Storm (29563971405)CC BY 2.0

## 1. Sampling theorem is mostly used in

1. Amplitude modulation (AM)
2. Frequency modulation (FM)
3. PCM
4. none of these

Answer – (3)

## 2. What is effective to decrease cumulative error?

1. PCM
2. DPCM
3. Delta Sigma Modulation
4. ADM

Answer – (2)

1. 50Hz
2. 100Hz
3. 200Hz
4. 400Hz

Answer – (3)

## 4. How many bits are in need to characterize a 256-level quantization in Pulse Code Modulation ?

1. 7
2. 5
3. 6
4. 8

Answer – (4)

Critical MCQ Series on Electronics

1. 5 KHz
2. 36 KHz
3. 70 KHz
4. 85 KHz

Answer – (2)

## 6. In Pulse Code Modulation use Lpf

1. remove aliasing effect
2. remove quantization noise
3. remove decoding noise
4. none of these

Answer – (1)

## 7. Adaptive Delta Modulation >> delta modulation as

1. provides better noise performance
2. it utilize less number bits used for encoding in communication
3. it doesn’t suffer from slope overload and threshold effects
4. simple circuit architecture

Answer – (3)

## 8. The compander in a telecom system is utilized for

1. equalizing the SNR for both weak and strong PAM signals
2. increasing amplification of the signals
3. improving A/D conversion
4. improving multiplexing

Answer – (3)

## 9. Using non-uniform quantization leads to

1. decrease of transmission band-width
2. increase in maximum Signal to Noise Ratio
3. increase in Signal to Noise Ratio for low band signals
4. Generalization of quantization method

Answer – (3)

## 10. What should be the Nyquist sampling rate for the signal s(t) = 10cos (50πt)cos2(150πt) when t is in seconds?

1. 150 samples/second
2. 200 samples/second
3. 300 samples/second
4. 350 samples/second

Answer – (4)

1. 3 dB
2. 6 dB
3. 2n dB
4. n dB

Answer – (2)

## 12. We detect a PAM signal by using

1. an ADC
2. an integrator
3. a bandpass filter
4. a high pass filter

Answer – (2)

1. 7
2. 8
3. 5
4. 6

Answer – (2)

## 14. The key advantage of Pulse Code Modulation are

1. possibility of TDM
2. less channel bandwidth
3. less transmission powers
4. better noise performance

Answer – (4)

## 15. Regenerative repeater could be utilized in

1. Analog communication
2. Digital communication
3. Both
4. None of these

Answer – (2)

## 16. In digital communication, Companding is used to

1. Reduce the probability of errors
2. Reduce quantization noise
3. To increase signal strength
4. Improve signal to noise ratio for low level input signals

Answer – (4)

## 17. The granular noise ensues in the Delta Modulation when the modulating signal

1. When the modulating signal increases rapidly
2. When the modulating signal changes with the step size
3. When the modulating signal decreases rapidly
4. When the modulating signal has high frequency component

Answer – (2)

## 18. In which modulation technique, redundant bits should be reduced

1. ADM
2. DPCM
3. PCM
4. none of these

Answer – (2)

1. 64 kbps
2. 32 kbps
3. 16 kbps
4. 8 kbps

Answer – (3)

## 20. Flat top sampling refers to

1. an aperture effects
2. aliasing
3. loss of the signal
4. none of these

Answer – (1)

## 21. In the present day standard digital voice communication, the amplitude of the voice signal is sampled at a rate of around

1. 2000 samples/sec
2. 800 samples/sec
3. 16000 samples/sec
4. 8000 samples/sec

Answer – (4)

## 22. Choose the right option which is digital in nature

1. PAM
2. PPM
3. DM
4. none of these

Answer – (4)

## 23. Pulse suffering is used in

1. Synchronous TDM
2. Asynchronous TDM
3. Any TDM
4. none of these

Answer – (2)

## 24. The key benefit of Time Division Multiplexing over Frequency Division Multiplexing is that it

1. needs less power
2. needs less bandwidth
3. needs simple circuitry
4. gives better S/N ratio

Answer – (3)

## 25. The SNR in PCM system is reliable on

1. sampling rate
2. number of quantization levels
3. message signal bandwidth
4. none of these

Answer – (2)

## 26. A random variable is computed by no. of independent events having Gaussian probability distribution. It is

1. central limit theorem
2. superposition
3. convolution
4. correlation

Answer – (1)

1. Poisson
2. Gaussian
3. Rayleigh
4. Rician

Answer – (3)

## 28. Random process termed “ Ergodic” when

1. All Ensemble average is not variable
2. All Ensemble average is constant
3. All Ensemble average is substitutable

Answer – (2)

1. 6/35
2. 4/35
3. 3/35
4. 7/35

Answer – (1)

## 30. The power spectral density of white noise

1. Keeps changing as square root of frequency
2. Keeps changing as inverse of frequency
3. changes as square of frequency
4. stays constant with frequency

Answer – (4)

1. 1/9
2. 1/12
3. 1/36

Answer – (4)

1. Exponential
2. Uniform
3. Poisson
4. Gaussian

Answer – (2)

## 33. A rectangular pulse of duration T is used in a matched filter circuit. The output of filter is a

1. Rectangular pulse of duration T
2. Rectangular pulse of duration 2T
3. triangular pulse
4. impulse function

Answer – (3) Codes used in Encoding in communication, Image Credit – Jugandi, Binary Line Code Waveforms, CC BY-SA 4.0

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