List Of Telecommunications Objective Questions
1. Match List I with List II and select the correct answer using the codes given below the lists
List I
(Device)
A. LED
B. Zener
C.Varactor
D. SCR
List II
(Biasing mode)
1. Forward bias
2. Reverse bias
Codes:
A B C D
(a) 1 1 2 2
(b) 1 2 1 2
(c) 1 2 2,1
(d) 2 2 1 1
Ans:-C
2. A medium bandwidth high-gain multistage transistor amplifier can be economically realised, if the coupling technique used between different stages is
(a) DC
(b) RC
(c) Transformer
(d) LC
Ans:-C
3. If negative feedback is introduced in an amplifier let in a shunt current configuration, then the input resistance will
(a) Increase
(b) Remain the same
(c) Decrease
(d) Increase, decrease or remain the same depending upon input
Ans:-C
4. A differentiator is rarely used in analog computers, because it
(a) Reduces the gain
(b) Decreases the output of the amplifier
(c) Amplifies noise, drift and other unwanted disturbances
(a) May cause oscillation
Ans:-C
5. In a time base generator, a constant current source (I) is used to drive a capacitance (C). The Output voltage across the capacitance as a function of time (t) is given by
(a) (1/C)t
(b) (C/I)t
(c) I Ct
(d) t / IC
Ans:-A
6. A particular FM radio station is having frequency deviation equal to 75 kHz Taking the maximum audio frequency as 15KHz, the transmission bandwidth is approximately equal to
(a) 90 kHz
(b) 180 kHz
(c) 270 kHz
(d) 360 kHz
Ans:-B
7. The noise margin of a digital IC is the
(a) Maximum frequency of extraneous voltage that does not cause a gate to change its state
(b) Maximum extraneous voltage that does not cause a gate to change its state
(c) Thermal noise voltage which causes a gate to change its state
(d) Minimum frequency of extraneous voltage that causes a gate to change its state
Ans:-A
8. If it is desired to have a 64 × 8 memory and f the memories available are of 16 x 4 size, then the number of memories required will be
(a) 8
(b) 6
(c) 4
(d) 2
Ans:-A
9. The most economical manner in which a high- speed decade counter can be realised is by using
(a) Synchronous binary counter
(b) Ripple binary counter
(c) Ring counter
(d) Johnson counters
Ans:-A
10. Which one of the following statements is true of SP register in 8086 microprocessor?
(a) It can be used for reading instruction from memory
(b) The result of arithmetic operation always goes to SP
(c) It can be used for reversing the string
(d) The control command first goes to SP
Ans:-A
11. Match List I with List II and select the correct answer using the codes given blow the lists
List I
A. Immediate addressing
B. Implied addressing
C. Register addressing
D. Direct addressing
List II
1. LDA 30 SC
2. MOV A,B
3. Lx 1H, 2050
4. RRC
Codes:
A B C D
(a) 3 2 1 4
(b) 3 4 2 1
(c) 3 2 4 1
(d) 2 3 1 4
Ans:-B
12. For a periodic function the spectral density and the autocorrelation functions form
(a) Fourier transforms pair
(b) Laplace transforms pair
(c) Hubert’s transform pair
(d) Z-transform pair
Ans:-A
13. Delay distortion in transmission lines exists when
(a) Different frequency components have different attenuation
(b) Alpha is a constant
(c) Beta is proportional to frequency ‘
(d) Beta is a constant
Ans:-C
14. The capacity of a channel is the
(a) Number of digits used in coding
(b) Bandwidth required for information
(c) Volume of information it can take
(d) Maximum rate of information transmision
Ans:-D
15. Match List I with List II and select the correct answer using the codes given below the lists:
List I
A. Collector modulation
B. Phase shift method
C. Balanced modulator
D. Amplitude limiter
List II
1. FM generation
2. DSB generation
3. AM generation
4. SSB generation
Codes:
A B C D
(a) 3 4 1 2
(b) 4 3 1 2
(c) 3 4 2 1
(d) 4 3 2 1
Ans:-C
16. The frequency deviation of an FM signal is in creased from 25 kHz to 50 kHz For the same sinusoidal modulating signal of 10 kHz, the improvement In the demodulated signal to noise power ratio will be
(a) 2.0
(b) 2.5
(c) 4.0
(d) 5.0
Ans:-A
17. With a real-time constraint, the transmission bandwidth needed for a digital signal with r symbols per second is equal to or greater than
(a) 1/r
(b) r/2
(c) r
(d) 2r
Ans:-D
18. The round-trip distance for a satellite relay may be as great as
(a) 5000 km
(b) 50000 km
(c) 100000 km
(d) 500000km
Ans:-B
19. Serration pulses in composite video waveform serve the purpose of
(a) Equalising the change in the integrator before the start of the vertical retrace
(b) Helping vertical synchronisation
(c) Helping horizontal synchronisation
(d) Preventing ghost picture
Ans:-D
20. In radar engineering, in order to make use of narrow beam antennas for achieving accuracy in target direction Indication, it is preferable to use frequencies in the range of
(a) Lower VHF
(b) Upper VHF
(c) Lower UHF
(d) Upper UHF
Ans:-A
21. In navigational systems, the polar coordinates give Information of
(a) Range and azimuthally angle
(b) Range and elevation angle
(c) Range, height and velocity of descent
(d) Range, azimuth and elevation
Ans:-D
22. The principle of bridge duplex working involves
(a) Potential balance
(b) Current balance
(c) Resistance balance
(d) Impedance balance
Ans:-B
23. If the field winding of an unloaded dc shunts motor gets opened while running, it will
(a) Stop
(b) Run with reduced speed
(c) Run with increased speed
(d) Rach
Ans:-A
24. A dc cumulatively compounded motor delivers rated load torque at rated speed, If the series field is short-circuited, then the armature current and speed will
(a) Both decrease
(b) Both increase
(c) Increase and decrease respectively
(d) Decrease and increase respectively
Ans:-B
25. A separately excited dc machine, having an armature resistance of 2 ohms was working on a 220 V supply and drawing 10 A armature current from the source when the supply voltage suddenly dropped to 200 V. Assuming that the field circa it source voltage remained unaffected, how will the armature current of the machine react to the change?
(a) It will initially rise to 11 A and then settle down to 10A
(b) It will fall momentarily to 9.09 A and then slowly attain 10 A
(c) It will reduce to zero first and then settle back to 10A
(d) It will remain unaffected by the change and continue to be 10 A
Ans:-B