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Online Electronics and Communication Engineering Test - Communication Systems Test 2

Instruction:
  • This is a FREE online test. Beware of scammers who ask for money to attend this test.
  • Total number of questions: 20.
  • Time allotted: 30 minutes.
  • Each question carries 1 mark; there are no negative marks.
  • DO NOT refresh the page.
  • All the best!

Marks : 2/20

Total number of questions
20
Number of answered questions
0
Number of unanswered questions
20
Test Review : View answers and explanation for this test.
1.
A tweeter should be fed from the input through a
low pass filter
high pass filter
band pass filter
band stop filter
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Tweeter is high frequency loudspeaker covering the range above 5000 Hz.

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2.
A directional microphone gives an output of 0.5 mV whereas an omnidirectional one gives an output of 0.5 μV in the same position for the same sound pressure. The directivity of the directional microphone is
120 dB
90 dB
60 dB
30 dB
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Directivity =

= 60 dB.

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3.
In the equivalent circuit of a moving coil cone type loudspeaker, the mass of the moving system is represented by
a resistance
a capacitance
an inductance
a conductance
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Mass has inertia and is analogous to inductance.

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4.
The most commonly used transistor amplifier circuit is
CB
CC
CE
CE or CC
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Common emitter connection has high power gain, and good current and voltage gains.

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5.
Full duplex operation
requires modems at both ends of circuit
requires two pairs of cables
can transfer data in both directions simultaneously
all of the above
Your Answer: Option
(Not Answered)
Correct Answer: Option
Explanation:

Full duplex system has all these features.

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6.
Consider the following statements as regards DPSK and DEPSK
  1. DPSK demodulator requires a device which operates at carrier frequency and provides a delay of bit time Tb
  2. In DPSK, synchronous demodulation recovers the signal b(t) and the decoding of b(t) to generate d(t) is done at base band
  3. In both DPSK and DEPSK errors always occur in pairs
Which of the above statements are correct?
1 and 3
1 and 2
2 and 3
1, 2 and 3
Your Answer: Option
(Not Answered)
Correct Answer: Option
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7.
Consider the following statements about PCM
  1. PCM is not noise resistant
  2. PCM requires complex encoding and quantizing circuitry
  3. PCM requires large bandwidth
Which of the above are correct?
1 only
1, 2, 3
2, 3
1 and 3
Your Answer: Option
(Not Answered)
Correct Answer: Option
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8.
In a TV studio the illuminance is about
200 lux
1000 lux
10000 lux
10 lux
Your Answer: Option
(Not Answered)
Correct Answer: Option
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9.
In a radio receiver with simple AGC
the highest AGC voltage is produced between stations
an increase in signal strength produces more AGC
the audio stage gain is normally controlled by AGC
the faster the time constant of AGC, more accurate the output
Your Answer: Option
(Not Answered)
Correct Answer: Option
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10.
Bandwidth for practical PCM system is (where n is no. of channels, N length of PCM codes)
2n N fm Hz
4n fm Hz
2n fm
(N + 1)fm
Your Answer: Option
(Not Answered)
Correct Answer: Option
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11.
In radar PRF depends on maximum range.
True
False
Your Answer: Option
(Not Answered)
Correct Answer: Option
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12.
If B is channel bandwidth, S is signal power and N is the total noise within the channel bandwidth, the channel capacity C of a white band limited gaussian channel is
Your Answer: Option
(Not Answered)
Correct Answer: Option
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13.
Industrial noise has the frequency range of
1 to 100 Hz
200 to 5000 Hz
above 200 MHz
1 to 600 MHz
Your Answer: Option
(Not Answered)
Correct Answer: Option
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14.
In phase modulation, the phase deviation is
proportional to the amplitude of the signal and varies with frequency
remains constant while amplitude and frequency of signal varies
proportional to the amplitude of the signal and independent of the frequency
none of the above
Your Answer: Option
(Not Answered)
Correct Answer: Option
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15.
A lens has a hyperfocal distance of 7.5 m. It is focused at 7.5 m. Then
all objects from 7.5 m to infinity will appear in focus
all objects from 3.75 m to infinity will appear in focus
all objects from 0 to 7.5 m will appear in focus
all objects from 0 to 3.75 m will appear in focus
Your Answer: Option
(Not Answered)
Correct Answer: Option
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16.
The highest modulating frequency typically used in AM systems is
1 kHz
5 kHz
20 kHz
50 kHz
Your Answer: Option
(Not Answered)
Correct Answer: Option
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17.
BFO stands for
Beat Frequency Oscillator
Broad Frequency Oscillator
Blocking Frequency Oscillator
Ballistic Frequency Oscillator
Your Answer: Option
(Not Answered)
Correct Answer: Option
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18.
The number of spectral component of impulse wave is
1
0
2
∞
Your Answer: Option
(Not Answered)
Correct Answer: Option
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19.
In amplitude modulation
the amplitude of carrier varies in accordance with the amplitude of the modulating signal.
the modulating frequency lies in the audio range
the amplitude of the carrier remains constant
the amplitude of the carrier varies in accordance with the frequency of the modulating signal.
Your Answer: Option
(Not Answered)
Correct Answer: Option
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20.
If S represents the carrier synchronization at the receiver and r represents the bandwidth efficiency, then the correct statement for the coherent binary PSK is
r = 0.5, S is required
r = 1.0, S is required
r = 0.5, S is not required
r = 1.0, S is not required
Your Answer: Option
(Not Answered)
Correct Answer: Option
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