Digital Communication Test Question Set 1

1)   In uniform quantization process

a. The step size remains same
b. Step size varies according to the values of the input signal
c. The quantizer has linear characteristics
d. Both a and c are correct
Answer  Explanation  Related Ques

ANSWER: Both a and c are correct

Explanation:
No explanation is available for this question!


2)   The process of converting the analog sample into discrete form is called

a. Modulation
b. Multiplexing
c. Quantization
d. Sampling
Answer  Explanation  Related Ques

ANSWER: Quantization

Explanation:
No explanation is available for this question!


3)   The characteristics of compressor in μ-law companding are

a. Continuous in nature
b. Logarithmic in nature
c. Linear in nature
d. Discrete in nature
Answer  Explanation  Related Ques

ANSWER: Continuous in nature

Explanation:
No explanation is available for this question!


4)   The modulation techniques used to convert analog signal into digital signal are

a. Pulse code modulation
b. Delta modulation
c. Adaptive delta modulation
d. All of the above
Answer  Explanation  Related Ques

ANSWER: All of the above

Explanation:
No explanation is available for this question!


5)   The sequence of operations in which PCM is done is

a. Sampling, quantizing, encoding
b. Quantizing, encoding, sampling
c. Quantizing, sampling, encoding
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Sampling, quantizing, encoding

Explanation:
No explanation is available for this question!


6)   In PCM, the parameter varied in accordance with the amplitude of the modulating signal is

a. Amplitude
b. Frequency
c. Phase
d. None of the above
Answer  Explanation  Related Ques

ANSWER: None of the above

Explanation:
No explanation is available for this question!


7)   One of the disadvantages of PCM is

a. It requires large bandwidth
b. Very high noise
c. Cannot be decoded easily
d. All of the above
Answer  Explanation  Related Ques

ANSWER: It requires large bandwidth

Explanation:
No explanation is available for this question!


8)   The expression for bandwidth BW of a PCM system, where v is the number of bits per sample and fm is the modulating frequency, is given by

a. BW ≥ vfm
b. BW ≤ vfm
c. BW ≥ 2 vfm
d. BW ≥ 1/2 vfm
Answer  Explanation  Related Ques

ANSWER: BW ≥ vfm

Explanation:
No explanation is available for this question!


9)   The error probability of a PCM is

a. Calculated using noise and inter symbol interference
b. Gaussian noise + error component due to inter symbol interference
c. Calculated using power spectral density
d. All of the above
Answer  Explanation  Related Ques

ANSWER: All of the above

Explanation:
No explanation is available for this question!


10)   In Delta modulation,

a. One bit per sample is transmitted
b. All the coded bits used for sampling are transmitted
c. The step size is fixed
d. Both a and c are correct
Answer  Explanation  Related Ques

ANSWER: Both a and c are correct

Explanation:
No explanation is available for this question!


11)   In digital transmission, the modulation technique that requires minimum bandwidth is

a. Delta modulation
b. PCM
c. DPCM
d. PAM
Answer  Explanation  Related Ques

ANSWER: Delta modulation

Explanation:
No explanation is available for this question!


12)   In Delta Modulation, the bit rate is

a. N times the sampling frequency
b. N times the modulating frequency
c. N times the nyquist criteria
d. None of the above
Answer  Explanation  Related Ques

ANSWER: N times the sampling frequency

Explanation:
No explanation is available for this question!


13)   In Differential Pulse Code Modulation techniques, the decoding is performed by

a. Accumulator
b. Sampler
c. PLL
d. Quantizer
Answer  Explanation  Related Ques

ANSWER: Accumulator

Explanation:
No explanation is available for this question!


14)   DPCM is a technique

a. To convert analog signal into digital signal
b. Where difference between successive samples of the analog signals are encoded into n-bit data streams
c. Where digital codes are the quantized values of the predicted value
d. All of the above
Answer  Explanation  Related Ques

ANSWER: All of the above

Explanation:
No explanation is available for this question!


15)   DPCM suffers from

a. Slope over load distortion
b. Quantization noise
c. Both a & b
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Both a & b

Explanation:
No explanation is available for this question!


16)   The noise that affects PCM

a. Transmission noise
b. Quantizing noise
c. Transit noise
d. Both a and b are correct
Answer  Explanation  Related Ques

ANSWER: Both a and b are correct

Explanation:
No explanation is available for this question!


17)   The factors that cause quantizing error in delta modulation are

a. Slope overload distortion
b. Granular noise
c. White noise
d. Both a and b are correct
Answer  Explanation  Related Ques

ANSWER: Both a and b are correct

Explanation:
No explanation is available for this question!


18)   Granular noise occurs when

a. Step size is too small
b. Step size is too large
c. There is interference from the adjacent channel
d. Bandwidth is too large
Answer  Explanation  Related Ques

ANSWER: Step size is too large

Explanation:
No explanation is available for this question!


19)   The crest factor of a waveform is given as -

a. 2Peak value/ rms value
b. rms value / Peak value
c. Peak value/ rms value
d. Peak value/ 2rms value
Answer  Explanation  Related Ques

ANSWER: Peak value/ rms value

Explanation:
No explanation is available for this question!


20)   The digital modulation technique in which the step size is varied according to the variation in the slope of the input is called

a. Delta modulation
b. PCM
c. Adaptive delta modulation
d. PAM
Answer  Explanation  Related Ques

ANSWER: Adaptive delta modulation

Explanation:
No explanation is available for this question!


21)   The digital modulation scheme in which the step size is not fixed is

a. Delta modulation
b. Adaptive delta modulation
c. DPCM
d. PCM
Answer  Explanation  Related Ques

ANSWER: Adaptive delta modulation

Explanation:
No explanation is available for this question!


22)   In Adaptive Delta Modulation, the slope error reduces and

a. Quantization error decreases
b. Quantization error increases
c. Quantization error remains same
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Quantization error increases

Explanation:
No explanation is available for this question!


23)   The number of voice channels that can be accommodated for transmission in T1 carrier system is

a. 24
b. 32
c. 56
d. 64
Answer  Explanation  Related Ques

ANSWER: 24

Explanation:
No explanation is available for this question!


24)   The maximum data transmission rate in T1 carrier system is

a. 2.6 megabits per second
b. 1000 megabits per second
c. 1.544 megabits per second
d. 5.6 megabits per second
Answer  Explanation  Related Ques

ANSWER: 1.544 megabits per second

Explanation:
No explanation is available for this question!


25)   T1 carrier system is used

a. For PCM voice transmission
b. For delta modulation
c. For frequency modulated signals
d. None of the above
Answer  Explanation  Related Ques

ANSWER: For PCM voice transmission

Explanation:
No explanation is available for this question!


26)   Matched filter may be optimally used only for

a. Gaussian noise
b. Transit time noise
c. Flicker
d. All of the above
Answer  Explanation  Related Ques

ANSWER: Gaussian noise

Explanation:
No explanation is available for this question!


27)   Characteristics of Matched filter are

a. Matched filter is used to maximize Signal to noise ratio even for non Gaussian noise
b. It gives the output as signal energy in the absence of noise
c. They are used for signal detection
d. All of the above
Answer  Explanation  Related Ques

ANSWER: All of the above

Explanation:
No explanation is available for this question!


28)   Matched filters may be used

a. To estimate the frequency of the received signal
b. In parameter estimation problems
c. To estimate the distance of the object
d. All of the above
Answer  Explanation  Related Ques

ANSWER: All of the above

Explanation:
No explanation is available for this question!


29)   The process of coding multiplexer output into electrical pulses or waveforms for transmission is called

a. Line coding
b. Amplitude modulation
c. FSK
d. Filtering
Answer  Explanation  Related Ques

ANSWER: Line coding

Explanation:
No explanation is available for this question!


30)   For a line code, the transmission bandwidth must be

a. Maximum possible
b. As small as possible
c. Depends on the signal
d. None of the above
Answer  Explanation  Related Ques

ANSWER: As small as possible

Explanation:
No explanation is available for this question!


31)   Regenerative repeaters are used for

a. Eliminating noise
b. Reconstruction of signals
c. Transmission over long distances
d. All of the above
Answer  Explanation  Related Ques

ANSWER: All of the above

Explanation:
No explanation is available for this question!


32)   Scrambling of data is

a. Removing long strings of 1's and 0's
b. Exchanging of data
c. Transmission of digital data
d. All of the above
Answer  Explanation  Related Ques

ANSWER: Removing long strings of 1's and 0's

Explanation:
No explanation is available for this question!


33)   In polar RZ format for coding, symbol '0' is represented by

a. Zero voltage
b. Negative voltage
c. Pulse is transmitted for half the duration
d. Both b and c are correct
Answer  Explanation  Related Ques

ANSWER: Both b and c are correct

Explanation:
No explanation is available for this question!


34)   In a uni-polar RZ format,

a. The waveform has zero value for symbol '0'
b. The waveform has A volts for symbol '1'
c. The waveform has positive and negative values for '1' and '0' symbol respectively
d. Both a and b are correct
Answer  Explanation  Related Ques

ANSWER: Both a and b are correct

Explanation:
No explanation is available for this question!


35)   Polar coding is a technique in which

a. 1 is transmitted by a positive pulse and 0 is transmitted by negative pulse
b. 1 is transmitted by a positive pulse and 0 is transmitted by zero volts
c. Both a & b
d. None of the above
Answer  Explanation  Related Ques

ANSWER: 1 is transmitted by a positive pulse and 0 is transmitted by negative pulse

Explanation:
No explanation is available for this question!


36)   The polarities in NRZ format use

a. Complete pulse duration
b. Half duration
c. Both positive as well as negative value
d. Each pulse is used for twice the duration
Answer  Explanation  Related Ques

ANSWER: Complete pulse duration

Explanation:
No explanation is available for this question!


37)   The format in which the positive half interval pulse is followed by a negative half interval pulse for transmission of '1' is

a. Polar NRZ format
b. Bipolar NRZ format
c. Manchester format
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Manchester format

Explanation:
No explanation is available for this question!


38)   The maximum synchronizing capability in coding techniques is present in

a. Manchester format
b. Polar NRZ
c. Polar RZ
d. Polar quaternary NRZ
Answer  Explanation  Related Ques

ANSWER: Manchester format

Explanation:
No explanation is available for this question!


39)   The advantage of using Manchester format of coding is

a. Power saving
b. Polarity sense at the receiver
c. Noise immunity
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Power saving

Explanation:
No explanation is available for this question!


40)   Alternate Mark Inversion (AMI) is also known as

a. Pseudo ternary coding
b. Manchester coding
c. Polar NRZ format
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Pseudo ternary coding

Explanation:
No explanation is available for this question!