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Electronics and Communication Engineering - Communication Systems

Exercise : Communication Systems - Section 3
41.
Which of the following microphones works on the principle of Faraday's law?
Carbon
Condenser
Moving coil
Electret
Answer: Option
Explanation:

In moving coil microphone variations of sound pressure cause an emf to be induced in the moving coil.

42.
In a CE amplifier connection, the emitter is at ground potential for
AC quantities
DC quantities
all quantities
none of the quantities
Answer: Option
Explanation:

XC for ac frequencies is very low and therefore emitter is nearly at ground potential.

43.
In an AM wave with m = 1, the carrier is suppressed. The resulting power saving will be
Answer: Option
Explanation:

.

44.
Directive gain is
a power ratio
a voltage ratio
a current ratio
a distance ratio
Answer: Option
Explanation:

Directive gain is the ratio of power density radiated in a particular direction by the antenna to the power density that would be radiated by isotropic antenna.

45.
Which of the following sampling frequencies is considered adequate in voice telephony?
4 kHz
8 kHz
16 kHz
32 kHz
Answer: Option
Explanation:

Generally bandwidth of voice telephony is 4 kHz.

Sampling frequency should be twice this value.

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