Communication Systems - Section 1 (4)

Directions to Solve

Communication Systems - Section 1

25.

The rate at which information can be carried through a communication channel depends on

A.	carrier frequency
B.	bandwidth
C.	transmission loss
D.	transmitted power

Answer: Option B

Explanation:

Rate of information depends on bandwidth.

26.

Degaussing in a picture tube means

A.	Adding magnetism in mask and mounting frame
B.	Removing residual magnetism in mask, shield etc...
C.	Increasing resistance of coils to decrease time constant
D.	Decreasing resistance of coils to increase time constant.

Answer: Option B

Explanation:

Since gauss is a unit of magnetic flux, degaussing means removal of magnetism.

27.

An earth mat for a communication tower consists of

A.	one or two radials extending from base of tower at a depth of about 5 cm below ground
B.	a large number of radials extending from base of tower at a depth of about 3 m
C.	a large number of radials extending from base of tower at a depth of about 30 cm
D.	none of the above

Answer: Option C

Explanation:

The number of radials is large and depth is about 30 cm.

28.

The range of a cordless telephone is about

A.	1000 m
B.	500 m
C.	100 m
D.	10 m

Answer: Option C

Explanation:

The range depends on quality of instrument and is about 100 m.

29.

The velocity of sound waves in air

A.	is constant at all temperatures
B.	varies directly as temperature
C.	varies directly as temperature
D.	varies directly as square root of absolute temperature

Answer: Option D

Explanation:

v ∝ √T

30.

As the frequency increases, the absorption of ground wave by earth's surface

A.	decreases
B.	increases
C.	remains the same
D.	either (a) or (c)

Answer: Option B

Explanation:

Because of this reason ground waves can be used for frequencies upto about 1600 kHz only.

31.

If C is capacity of noisy channel, (bits/s), δf is bandwidth Hz and S/N is signal to noise ratio, then

A.
B.
C.
D.

Answer: Option A

Explanation:

This is Shannon-Hartley theorem.

32.

A telephone exchange has 9000 subscribers. If the number of calls originating at peak time is 10, 000 in one hour, the calling rate is

A.	0.9
B.	10/9
C.	0.81
D.	0.1

Answer: Option B

Explanation:

Calling rate is the number of calls per subscriber.

Communication Systems - Section 1 (4)

Communication Systems - Section 1

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