  # Digital Communication MCQ's Questions with answers part 1

1. Which circuit is called as regenerative repeaters?
a) Analog circuits
b) Digital circuits
c) Amplifiers
d) A/D converters

Explanation: The main advantage of digital communication is that the signals can be
reproduced easily. Thus digital circuits are called as regenerative repeaters.

2. What are the advantages of digital circuits?
a) Less noise
b) Less interference
c) More flexible
d) All of the mentioned

Explanation: Digital circuits are less subject to noise, distortion and interference as it works
on digital pulses and also the pulses can be regenerated.

3. How many different combinations can be made from a n bit value?
a) 2(n+1)
b) 2(n)
c) 2(n)+1
d) None of the mentioned

Explanation: 2(n) different combinations can be made from n bit value. For example, from 2
bit value 22 different combinations-00,01,10,11 can be made.

4. How many bytes does a gigabyte have?
a) 1 million bytes
b) 10 million bytes
c) 1 billion bytes
d) 10 billion bytes

Explanation: One gigabyte has 1 billion bytes.

5. What is the ASCII value of space?
a) 32
b) 48
c) 96
d) 65

Explanation: The ASCII value of space is 32 and ASCII value of 0 is 48.

6. Which block or device does the data compression?
a) Channel encoder
b) Source encoder
c) Modulator
d) None of the mentioned

Explanation: Source encoder converts the digital or analog signal to a sequence of binary
digits. This process is called as source encoding or compression.

7. What is the code rate?
a) k/n
b) n/k
c) All of the mentioned
d) None of the mentioned

Explanation: Here n is the total bits of sequence and k bits are mapped. Amount of
redundancy introduced is given by n/k and its reciprocal is the code rate.

8. Pulse shaping is done by which block or system?
a) Encoder
b) Baseband modulator
c) Pulse code modulator
d) Demodulator

Explanation: Pulse code modulator does filtering process to build pulses that occupy more
than one bit time.

9. Equalizer is used for?
a) Filtering
b) Diminish distortion
c) All of the mentioned
d) None of the mentioned

Explanation: Equalizer is used as a filtering option and also diminishes or reduces the
distortion.

10. Source coding block is used for?
a) Compressing
b) Digitizing
c) A/D conversion
d) All of the mentioned

Explanation: Source encoding does all these processes-compression, digitizing the signal
and performs analog to digital conversion.

11. SQNR can be improved by _______ sampling rate.
a) Increasing
b) Decreasing
c) Does not depend
d) None of the mentioned

12. Which offers better SQNR?
a) Delta modulation
b) PCM
c) Delta modulation & PCM
d) None of the mentioned

Explanation: PCM offers better SQNR than delta modulation.

13. Two functions are called as orthogonal if on integrating the product we get
a) One
b) Zero
c) Infinity
d) None of the mentioned

Explanation: Two functions are called as orthogonal if the integral value of integrating the
product is zero.

14. Eigen functions are not orthogonal.
a) True
b) False

Explanation: An important property of eigen function is that they are orthogonal.

15. Shot noise is produced by
a) Electrons
b) Photons
c) Electrons & Photons
d) None of the mentioned

Explanation: Shot noise occurs due to particle like the behaviour of electron and photon.

16. Shot noise is avoidable when current is
a) Zero
b) One
c) Infinity
d) None of the mentioned

Explanation: Shot noise is avoidable only when the current is zero.

17. Shot noise is
a) Stochastic process
b) Poisson process
c) Stochastic & Poisson process
d) None of the mentioned

Explanation: Shot noise is a Poisson process.

18. Which occurs due to equilibrium fluctuations?
a) Thermal noise
b) Johnson noise
c) Thermal & Johnson noise
d) None of the mentioned

Explanation: Thermal noise occurs due to equilibrium fluctuations. This noise is also called
as Johnson noise.

19. Flicker noise is called as
a) White noise
b) Pink noise
c) Brown noise
d) None of the mentioned

Explanation: Flicker noise is called as pink noise.

10. Which has the same power spectral density?
a) White noise
b) Brown noise
c) White & Brown noise
d) None of the mentioned