Paper 3 questions bank
UNIT 1
1) In _______ the phase and amplitude of the carrier signal is
varied based on the information in a digital signal.
A. ASK
B. PSK
C. FSK
D. QAM
2) _______ rate is the number of bits per second; _______
rate is the number of signal units per second
A. Baud; bit
B. Bit; baud
C. Baud; base
D. Base; baud
3) ______ rate is always less than or equal to _______ rate
A. Baud; bit
B. Bit; baud
C. Baud; base
D. Base; baud
4) If the baud rate is 1200 and there are 4 bits for each signal
element, then the bit rate is _______
A. 4800
B. 1200
C. 400
D. 300
5) An 8-PSK modulated signal has a baud rate of 2000; the bit
rate is _______ bps
A. 8000
B. 6000
C. 2000
D. 1000
6) On a 16-QAM-constellation diagram, each constellation
point represents a _______
A. dibit
B. tribit
C. quadbit
D. pentabit
7) In which type of modulation can the bit rate be four times
the baud rate?
A. ASK
B. FSK
C. PSK
D. QAM
8) In _______ conversion we are representing analog
information as a series of 0s and 1s.
A. analog-to-analog
B. analog-to-digital
C. digital-to-analog
D. digital-to-digital
9) In a digital modulation system the _______ performs level conversion and
then encodes the incoming data into groups of bits
A. Precoder
B. Analog carrier
C. Modulator
D. Buffer
10) Hartley’s law is _______
A. I ∝ B t
B. I ∝ B/ t
C. I ∝ B +t
D. I ∝ B- t
11) The higher ______, the better the performance and the higher the
information capacity.
A. SN
B. S/N
C. S+N
D. S-N
12) The general expression for FSK is_________
A. vfsk(t)= Vc cos{2π[fc - vm(t) ∆ f ] t}
B. vfsk(t)= Vc sin{2π[fc+ vm(t) ∆ f ] t}
C. vfsk(t)= Vc sin{2π[fc - vm(t) ∆ f ] t}
D. vfsk(t)= Vc cos{2π[fc+ vm(t) ∆ f ] t}
13) The primary advantage of digital transmission over analog transmission
is__________
A. less susceptibility
B. more resistant
C. noise immunity
D. simpler to measure
14) With ______ the position of a constant-width pulse within a prescribed time
slot is varied according to the amplitude of the sample of the analog signal.
A. PWM
B. PPM
C. PAM
D. PCM
15) In PCM Transmitter,______ periodically samples the analog input signal and
converts those samples to a multilevel PAM signal.
A. Sample and hold circuit
B. Bandpass filter
C. Converter
D. Repeater
16) The minimum Nyquist sampling rate is
A. fs ≥ 2fa
B. fs ≤ 2fa
C. 2fs ≥ 2fa
D. 2fs ≤2fa
17) _______ is the process of converting an infinite number of possibilities to a
finite number of conditions.
A. Quantization
B. Resolution
C. Distortion
D. synchronization
18) For a PCM system with the Maximum decoded voltage at the receiver 2.55 V,
then resolution is_______.
A. 1V
B. 0.1V
C. 0.01V
D. 10V
19) If the frequency spectrum of a signal has a bandwidth of 500 Hz with the
highest frequency at 600 Hz, what should be the sampling rate, according to the
Nyquist theorem?
A. 200 samples/s
B. 500 samples/s
C. 1000 samples/s
D. 1200 samples/s
20) ________is the process of compressing and then expanding.
A. Processing
B. Modulating
C. Companding
D. Sampling
21) With delta modulation, each sample requires the transmission of ______ bit.
A. Two
B. One
C. Three
D. Four
22) The slope of the analog signal is ______ the delta modulator can maintain and
is called slope overload.
A. Greater than
B. Smaller than
C. Equal to
D. None of these
23) Granular noise in delta modulation is analogous to quantization noise in
conventional _______.
A. PWM
B. PPM
C. PAM
D. PCM
24) In _____________________,the step size of the DAC is automatically varied,
depending on the amplitude characteristics of the analog input signal.
A. Adaptive delta modulation
B. Amplitude modulation
C. Pulse modulation
D. Frequency modulation
25) For an 8-PSK system, operating with an information bit rate of 24 kbps, a
bandwidth efficiency is______ bits per second per cycle of bandwidth.
A. 6
B. 4
C. 8
D. 3
UNIT 1
Que. No. Answer
1 D
2 B
3 A
4 D
5 B
6 C
7 C
8 B
9 A
10 A
11 B
12 D
13 C
14 B
15 A
16 A
17 A
18 C
19 D
20 C
21 B
22 A
23 D
24 A
25 D
UNIT 2
1. PSTN stands for:
A. Public Switched Telephone Network
B. Private Switched Telephone Network
C. Primary Service Telephone Network
D. Primary Service Telephone Numbers
2. The pair of wires connecting a subscriber to the closest telephone office is
called the ________.
A. Subscriber line
B. local loop
C. drop line
D. twisted pair
3. Originally it as an electromagnetic bell that is placed directly across the tip and
ring of the local loop.
A. Dialer
B. Transmitter
C. Ringer Circuit
D. on/off hook circuit
4. Another function of the hybrid network is to allow a small portion of the
transmit signal to be returned to the receiver in form of:
A. echo
B. singing
C. feedback
D. sidetone
5. ________Are used to transfer digits and control signals between switching
machines.
A. E and M signaling
B. multifrequency signaling
C. two-of-six signaling
D. dual tone signaling
6. Defined as any disturbance created in acommunications channel by Signals in
other communications channels.
A. Crosstalk
B. Fading
C. Noise
D. Interference
7. Dial tone frequencies:
A. 350Hz and 44OHz
B. 480Hz and 620Hz
C. 440Hz and 480Hz
D. 90Vrms, 20Hz
8. These are Simplex Wireless communications system designed to alert
subscriber of waiting message.
A. SMS Systems
B. Cellular systems
C. Personal mobile systems
D. Paging systems
9. _________signals provide call status information, such as busy or ring-back
signals.
A. Supervising
B. Alerting
C. Controlling
D. Addressing
10. Cordless telephones using the ______ band offer excellent sound quality.
A. 2.4 GHz
B. 1.4 GHz
C. 2.4 MHz
D. 1.4 MHz
11.__________ enables the destination station of a telephone call to display the
name and telephone number of the calling party before the telephone is
answered.
A. Call waiting
B. Caller lD
C. Answering machine
D. Voice mail
12. In electronic telephone, the tone _______ is activated by the reception of a
20-Hz ringing signal.
A. Dialer
B. Transmitter
C. Ringer Circuit
D. on/off hook circuit
13. _____________ is a term used to describe a telephone instrument that is
ready for use, with the handset removed from its cradle.
A. On hook
B. Hand up
C. Off hook
D. Busy
14. The effective channel bandwidth for a voice-band message signal is
approximately
A. 300 Hz to 3000 Hz
B. 250 Hz to 2000 Hz
C. 300 Hz to 1000 Hz
D. 100 Hz to 3000 Hz
15. In traditional local loop, __________is the largest cable used in a local loop,
usually 3600 pair of copper wire placed underground or in conduit.
A. Drop wire
B. Feeder cable
C. Aerial
D. Distribution cable
16. The dc loop resistance for copper conductors is approximated by
A. Rdc = d2/0.1095
B. Rdc = 0.1095 x d2
C. Rdc = 0.1095/ d2
D. Rdc = 0.1095/ d
17. In facility parameters, which following not included?
A. noise measurements
B. frequency distortion
C. phase distortion
D. attenuation distortion
18. _________ C-type conditioning used for access lines and trunk circuits
associated with private switched networks?
A. C1 and C2
B. C3
C. C4
D. C5
19. Attenuation distortion is simply the frequency response of a transmission
medium referenced to a _______test tone.
A. 1004-Hz
B. 1040-Hz
C. 1400-Hz
D. 4001-Hz
20. A 1004 Hz test tone is transmitted over a telephone circuit at 0 dBm and
received at 16 dBm. The 1004-Hz circuit gain is_______
A. 16dB
B. 8dB
C. -16dB
D. -8dB
21. envelope delay is the first derivative (slope) of phase with respect to _______.
A. Frequency
B. Amplitude
C. Current
D. Voltage
22. D-type conditioning is mandatory when the data transmission rate is
_________
A. 9600 bps
B. 9000 bps
C. 6900 bps
D. 6090 bps
23. In the interface parameters, Station equipment impedances should be
_______resistive over the usable voice band.
A. 700 Ω
B. 600 Ω
C. 800 Ω
D. 900 Ω
24. A dropout is a decrease in circuit gain (i.e., signal level) of more than 12 dB
lasting longer than _____
A. 4 ms
B. 3 ms
C. 2 ms
D. 6 ms
25. When a two-wire circuit is connected to a four-wire circuit, as in a long-
distance telephone call, an interface circuit called a ________
A. loading coils
B. echo canceller
C. hybrid
D. echo suppressors
UNIT 2
Que. No. Answer
1 A
2 B
3 C
4 D
5 B
6 A
7 A
8 D
9 A
10 A
11 B
12 C
13 C
14 A
15 B
16 C
17 D
18 B
19 A
20 C
21 A
22 A
23 B
24 A
25 C
