MCQ Comm-2

1
PPM is
a)digital modulation technique
c)linear modulation technique
2 The signal to quantisation noise ratio in a PCM system depends upon
a)samppling rate
c)message signal bandwidth
3 One can provide two or more voice circuits on the same career by using
a)DSB-SC
c)ISB system
4 Neper is _____ decibel
a) Equal to
c) Is larger than
5 _____ is a unit of loudness
a) Decibel
c) Phon
6 Inter symbol interference is a problem in _____ transmission.
a) PCM
c) FM
7 A SSB signal contains 3KW. The power containt of carrier is
a) 0KWatt
c) 2KWatt
8 In FM signal, the power ____ as the modulation index increases
a) Increases
c) Remains constant
9 If a signal band limited to FM is sampled at a rate less than 2 FM, the reconstructed signal wi
a) Be smaller in amplitude
c) Be distorted
10 The most common device is used for the detection in radio receiver is
a) Transistor
c) Amplifier
11 Detection in superhetrodyne radio receiver takes place
a) following audio amplifier
c) preceding audio amplifiers
12 Reciever having poor IF selectivity will have poor
a) Sensitivity
c) Diverse reception
13 _____ is the main advantage of PCM

a) lower noise
c) lower bandwidth
14 In case the carrier of 100% modulated AM wave is supressed, the percentage saving will be
a) 30
c) 75
15 In a PCM system the signal to quantisations noise ratio depends upon
a) Message signal bandwidth
c) No of quantisation level
16 For the transmission of normal speech, the PCM channel needs a bandwidth of _____ KHz.
a) 2
c) 16
17 Which of the following statements is correct regarding demodulation?
a) It removes sidebands
c) It is opposite of modulation
18 Which of the following statements is correct regarding a TDM system?
a) It uses simpler circuit as compared to FDM

systems
c) It gives low signal to noise ratio
19 The telegraph circuit in which two messages can be transmitted in the same direction is called
a) Half duplex
c) diplex
20 A phase modulation system gives _____ advantages as compared to the frequency modulation
a) More
c) No specific
21 Due to which of the following reasons the local oscillator of a broadcast receiver is tuned to a
a) to help the image frequency rejection
c) To allow adequate frequency coverage without
switching
22 Which of the following statements is incorrect regarding use of synchronise system in data tra
a) They do not require large number of extra bit for
code
c) they establish synchronism at the beginning of a

message
23 In a pilot carrier transmission
a) only one side band is trasmitted
c) one sideband and carrier are transmitted
24 PCM transmission requires _____ bandwidth than amplitude modulated transmission
a) Same
c) More
25 The channel capacity is exactly equal to which of the following?
a) noise rate in the channel
c) Amount of information per second
26 With reference to sampling theorm which of the statements is correct?
27
28
29
30
a) the signal should be sampled atleast twice each

cycle
its highest
c) the at
signal
shouldfrequency.
be sampled atleast twice each
cycle at its lowest frequency
Sampling theorem finds applications in.
a) Frequency modulation
c) PCM
If the value of resistor is double the thermal noise power generated
a) Gets half
c) Gets quadrapled
The auto correction function of the white noise is
a) impulse function
c) constant
In communication system, redundancy
a) Helps to correct error
c) reduces efficiency of communications

31 Frequency shift keying is used mostly in
a) Telephony
c) Radio Transmission
32 The capacity of channel is

a) Bandwidth require for information
c) volume of informations it can take
33 In order to get the original signal from the sample signal, which of the following filters should
a) bandstop filter
c) high pass filter
34 For fast communication, which of the following requirements must be met?
a) Large bandwidth
c) High channel capacity
35 Channel capacity is a basically measure of
a) maximum rate of information
c) Amount of information a channel can take
36 With reference to auto co-relation function which of the following statement is incorrect?
a) it is a measure of both time variation and
statistical dependence
c) it is defined only for the periodic signals
37 Quantization noise occurs in
a) TDM
c) FDM
38 With reference to telex which of the following statement is correct?
a) it is the telegraph service between various
subscribers
c) it is television services between various
subscriber
39 _____ pulses have the largest width
a) horizontal
c) equalising
40 Telephone traffic is measured
a) with echo cancellers
c) in erlangs
41 in communication receivers the fidelity is provided by
a) audio stage
c) mixer stage
42 Shape factor of the filter response

a) Can not be apply to crystal filters
c) is the same as the peak to valley ratio
43 In telephons, dial tone has a frequency of
a) 5Hz
c) 33Hz
44 In morse code the spacing between the element is
a) 1 dot
c) 6 dots
45 By the use of which of the following the PPM can be converted to PWM?
a) Astable multivibrator
c) Monostable multivibrator
46 Autocorrelation, for a gaussian process, also implies
a)ergodic process
c)statistical independence
47 The pilot carrier in SSB is used for
a) Lower power consumption
c) frequency stability purpose
48 The bit is a unit of
a) information
c) entropy
49 with reference to amplitude limiter which of the following statements is incorrect?
a) by virtue of the leak type bias, the circuit is
always biased in class c
c) leak type bias must be used
50 With reference to Time division complex which of the following statements is correct?
a) it interleaves pulses belonging to different
trasmissions
c) it stacks several channels in adjecent frequency
slots
b)analog modulation technique

d)not a modulation technique
PCM system depends upon
b)no. of quantisation levels
d)none of the above
s on the same career by using
b)SSB with pilot career
d)SSB- BC system
b) Smaller than
d) Any of the above
b) Mel
d) Sone
_____ transmission.
b) AM
d) All of the above
ontaint of carrier is
b) 1KWatt
d) 3KWatt
lation index increases
b) Decreases
d) None of the above
at a rate less than 2 FM, the reconstructed signal will
b) have higher frequencies supressed
etection in radio receiver is
b) Diode
d) Triode
r takes place
b) preceding IF amplifier
d) in the aerial itself
b) Blocking
d) All of the above
b) lower power
M wave is supressed, the percentage saving will be
b) 66.66
d) 125
ns noise ratio depends upon
b) sampling rate
e PCM channel needs a bandwidth of _____ KHz.
b) 4
d) 64
ect regarding demodulation?
b) It rectifies modulated signals
d) It is performed at the transmitting stations

ect regarding a TDM system?
b) It needs lower bandwidth

es can be transmitted in the same direction is called
b) duplex
d) quadruplex
dvantages as compared to the frequency modulation system for analog systems
b) Less
local oscillator of a broadcast receiver is tuned to a frequency higher than the incoming frequency?
b) to permit easier tracking
rrect regarding use of synchronise system in data transmission?

b) they are ideal for coping with data sources
which are sporadic in nature such as a human
being generating data on a tele type writer
d) they are widely used for high data rates

where data is in the form of a continuous
stream
b) only two sidebands are transmitted
d)Two sidebands as well as a track of carrier

are transmitted
dth than amplitude modulated transmission
b) Less
hich of the following?
b) Bandwidth of demand
of the statements is correct?

b) the guard time should be as large as possible
d) nyquist rate should be as slow as possible
b) Amplitude modulation
al noise power generated
b) Gets double
d) Remains unchanged
b) step function
b) helps to detect error
d) All of the above
b) Telegraphy
b) number of digits used in coding
d) maximum rate of information transmission

sample signal, which of the following filters should be necessarily used?
b) low pass filter
d) Band pass filter
owing requirements must be met?
b) High S/N ratio
b) entropy rate
n which of the following statement is incorrect?

b) it is an average function
b) PCM
wing statement is correct?
b) it is telephon services between various
subscriber
d) it is teleprinter services between various
subscriber
b) vertical
b) in terms of grade of service

provided by
b) detector range
d) All of the above
b) determines adjacent channel selectivity of

the filter
d) is equal to the 60dB bandwidth of
mechanical filter
b) 15Hz
d)233Hz
b) 3 dots
d) 9 dots
PM can be converted to PWM?
b) integrater
d) Bistable multivibrator
so implies
b) statistical dependence
b) providing better noise inmmunity
b) Rate of information
d) channel capacity
of the following statements is incorrect?
b) The output must be tuned

which of the following statements is correct?
b) it can be used with PCM only
d) it combines five groups into a single super
group
ming frequency?

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1

13 _____ is the main advantage of PCM

a) It uses simpler circuit as compared to FDM

c) they establish synchronism at the beginning of a

a) the signal should be sampled atleast twice each

c) reduces efficiency of communications

32 The capacity of channel is

42 Shape factor of the filter response

b)analog modulation technique

d) It is performed at the transmitting stations

d) None of the above

rrect regarding use of synchronise system in data transmission?

d) they are widely used for high data rates

b) only two sidebands are transmitted

d)Two sidebands as well as a track of carrier

of the statements is correct?

d) nyquist rate should be as slow as possible

b) number of digits used in coding

d) maximum rate of information transmission

n which of the following statement is incorrect?

b) in terms of grade of service

b) determines adjacent channel selectivity of

d) None of the above

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