Digital Communication System MCQs

Question 1

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

Accepted Answer

64 Hz

Answer

16 Hz

Answer

32 Hz

Answer

96 hz

Question 2

Which of the following is the main advantage of PCM system?

Accepted Answer

Lower noise

Answer

Lower power

Answer

Lower band-width

Answer

None of the above

Question 3

By the use of which of the following low speed TDM is produced?

Accepted Answer

Rotating switches

Answer

Delay lines

Answer

Pulse oscillators

Answer

Electronic switching circuits

Question 4

The term noise temperature is used for which of the following?

Accepted Answer

All of the above

Answer

Thermal-noise source only

Answer

White-noise source only

Answer

Non-thermal-noise source only

Question 5

Which of the following measures cannot be used to reduce noise?

Accepted Answer

By increasing the channel bandwidth

Answer

By reducing the singnalling rate

Answer

By using redundancy

Answer

By increasing the transmitted power

Question 6

With reference to 'noise temperature' which of the following statements is correct?

Accepted Answer

It is a measure of the available noise power for non-thermal sources

Answer

It is a measure of noise figure of a receiver

Answer

It is the same as physical temperature of the body

Answer

None of the above

Question 7

The power-density spectrum is a function

Accepted Answer

even

Answer

square

Answer

linear

Answer

odd

Question 8

The power-density spectrum represents power per unit

Accepted Answer

bandwidth

Answer

wavelength

Answer

frequency

Answer

none of the above

Question 9

The energy-density spectrum of a signal represents

Accepted Answer

all of the above

Answer

energy per unit bandwidth

Answer

relative contribution of energy by positive components

Answer

relative contribution of energy by negative components