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1
Q

Shannon’s Limit for Information
Capacity

A. Any of these choices
B. It states that information capacity is
proportional to the bandwidth of the
system and the number of possible states
per symbol.
C. It states that information capacity is
directly proportional to bandwidth and
transmission time of the system.
D. It states that information capacity is a
function of bandwidth and signal-to-
noise ratio of the system.

A

D. It states that information capacity is a
function of bandwidth and signal-to-
noise ratio of the system.

Hartley’s Law (Ralph Hartley) - it states
that information capacity is directly
proportional to bandwidth and
transmission time of the system.
Shannon’s Limit for Information
Capacity (Claude E. Shannon) - it states
that information capacity is a function
of bandwidth and signal-to-noise ratio
of the system.
Shannon-Hartley Theorem - it states
that information capacity is proportional to the bandwidth of the system and the number of possible states per symbol.

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2
Q

The rate of change at the output of the
modulator:

A. Bit Rate
B. Baud Rate
C. Information Capacity
D. Nyquist Bandwidth

A

B. Baud Rate

Bit Rate (fb)- the rate of change at the input of the modulator and has a unit of bits per second (bps). Determines the
line speed.
Baud Rate (Baud) - the rate of change
at the output of the modulator.
Determines the line speed.

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3
Q

If a symbol is composed of 3 bits, there
are _____ data levels.

A. 16
B. 2
C. 4
D. 8

A

D. 8

M=2=2=8

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4
Q

A constant amplitude modulation
similar to conventional phase
modulation except that the input signal
is a binary digital signal:

A. PSK
B. FSK
C. QAM
D. ASK

A

A. PSK

Phase Shift Keying (PSK)- a constant
amplitude modulation similar to
conventional phase modulation (PM)
except that with PSK the input signal is
a binary digital signal.

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5
Q

If the bit rate for an ASK signal is 1200
bps, the baud rate is_

A. 600
B. 300
C. 1200
D. 400

A

C. 1200

Baud = fb = 1200 baud

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6
Q

It is the regeneration of clocks at the
receiver that are synchronous with
those at the transmitter for the precise
timing or clock synchronization
between transmit and receive circuitry.

A. Clock Recovery
B. Carrier Recovery
C. Any of these choices
D. Baseband Recovery

A

A. Clock Recovery

Carrier Recovery - the process of
extracting a phase-coherent reference
carrier from a receiver signal.
Sometimes called Phase Referencing.
Clock Recovery - it is the regeneration of clocks at the receiver that are
synchronous with those at the
transmitter for the precise timing or
clock synchronization between transmit
and receive circuitry.

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7
Q

It is a form of constant-amplitude angle modulation and similar to conventional frequency modulation except that the
modulating signal is a binary signal that
varies between two discrete voltage
levels:

A. PSK
B. FSK
C. ASK
D. QAM

A

B. FSK

Frequency Shift Keying (FSK)- also
known as Binary Frequency Shift Keying
(BFSK). Binary FSK is a form of
constant-amplitude angle modulation and similar to conventional frequency modulation (FM) except that the
modulating signal is a binary signal that
varies between two discrete voltage
levels.

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8
Q

It is determined after transmission is
done:

A. BER
B. SNR
C. P(e)
D. NF

A

A. BER

Bit Error Rate - an empirical record of a system’s actual error performance. It is determined after the transmission is done. Based on the previous (historical/ empirical).
Probability of Error, P(e) - it is a
theoretical expectation of the bit error
rate of the given system. It is
determined before transmission. Based on the future (expectation/theoretical/mathematical).

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9
Q

In 8PSK, if the C input is low, it indicates:

A. Positive Polarity
B. Negative Polarity
C. 0.541 V Magnitude
D. 1.307 V Magnitude

A

C. 0.541 V Magnitude

8 Phase Shift Keying:
The Q/1 bits both indicates the polarity
of the signal:
LOGIC 1 - Positive Polarity
LOGIC 0 - Negative Polarity
The C bit indicates the magnitude of the
signal:
LOGIC 1 -1.307V
LOGIC 0-0.541V

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10
Q

In ASK, if the binary input bit is high, the
output is:

A. there is no output
B. the space frequency
C. the carrier signal
D. the mark frequency

A

C. the carrier signal

Amplitude Shift Keying:
LOGIC 1 - the output is the carrier
signal.
LOGIC O - there is no output signal.

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11
Q

In 16QAM, if the Q’/l’ input is high, it
indicates:

A. Negative Polarity
B. Positive Polarity
C. 0.22 V Magnitude
D. 0.821 V Magnitude

A

D. 0.821 V Magnitude

16 Quadrature Amplitude Modulation:The Q/l bits both indicates the polarity of the signal:
LOGIC 1 - Positive Polarity
LOGIC 0 - Negative Polarity
The Q’/l’ bit indicates the magnitude of
the signal:
LOGIC 1-0.821V
LOGIC 0-0.22V

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12
Q

In FSK, which frequency is always lesser
in value?

A. Either Mark or Space Frequency
B. Mark and Space Frequency are equal
C. Space Frequency
D. Mark Frequency

A

A. Either Mark or Space Frequency

Mark frequency is logic 1. Space
frequency is logic 0. The mark and
space frequencies is separated from the carrier by the peak frequency deviation.Either of the mark or space can be
greater or lesser.

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13
Q

It is the ratio of the transmission rate to
the minimum bandwidth:

A. Spectral Efficiency
B. Modulation Efficiency
C. Any of these choices
D. Information Density

A

C. Any of these choices

Bandwidth Efficiency - also known as
the Information Density, Modulation
Efficiency and Spectral Efficiency. Used
to compare the performance of one
digital modulation technique to another.It is the ratio of the transmission rate in bps to the minimum bandwidth and has a unit of bps per Hertz (bps/Hz) or bits per cycle (bits/cycle).

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14
Q

16PSK has:

A. Tribit
B. Single Bit
C. Dibit
D. Quadbit

A

D. Quadbit

16 Phase Shift Keying (16PSK) - it is an
M-ary encoding technique where M =
16. There are sixteen different possible states. The incoming data in groups of four bits called Quadbits.

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15
Q

As the bit rate of an FSK signa
increases, the bandwidth _____

A. Remains the same
B. Decreases
C. Doubles
D. Increases

A

D. Increases

The bandwidth of FSK is computed
using Carson’s Rule:
B=2(△f+fh)

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16
Q

8PSK has:

A. Tribit
B. Dibit
C. Single Bit
D. Quadbit

A

A. Tribit

8 Phase Shift Keying (8PSK) - it is an M-ary encoding technique where M = 8 The incoming bits are considered in
groups of three bits called Tribit. The
input data is in the form of QIC, where Q means Quadrature Bit, I means In-Phase Bit and C means Control Bit.

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17
Q

In 8PSK, the outputs are separated by.

A. 22.5 degrees
B. 45 degrees
C. 90 degrees
D. 180 degrees

A

B. 45 degrees

8 Phase Shift Keying (8PSK) - it is an M-ary encoding technique where M = 8.The incoming bits are considered in
groups of three bits called Tribit. The
input data is in the form of QIC, where Q means Quadrature Bit, I means In-Phase Bit and C means Control Bit.

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18
Q

What is the unit for Bandwidth
Efficiency?

A. bits/cycle
B. unitless
C. Hz/bits
D. bits/second

A

A. bits/cycle

Bandwidth Efficiency - also known as
the Information Density, Modulation
Efficiency and Spectral Efficiency. Used
to compare the performance of one
digital modulation technique to another.It is the ratio of the transmission rate in bps to the minimum bandwidth and has a unit of bps per Hertz (bps/Hz) or bits per cycle (bits/cycle).

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19
Q

It is a form of digital modulation where the digital information is contained in both amplitude and phase of the transmitted carrier.

A. ASK
B. PSK
C. QAM
D. FSK

A

C. QAM

ASK - amplitude FSK- frequency PSK- phase
QAM - phase and amplitude

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20
Q

In ASK, if the binary input bit is low, the
output is:

A. the carrier signal
B. the mark frequency
C. the space frequency
D. there is no output

A

D. there is no output

Amplitude Shift Keying:
LOGIC 1 - the output is the carrier
signal.
LOGIC O - there is no output signal.

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21
Q

In 16PSK, the outputs are separated by:

A. 45 degrees
B. 90 degrees
C. 180 degrees
D. 22.5 degrees

A

D. 22.5 degrees

16 Phase Shift Keying (16PSK) - it is an
M-ary encoding technique where M =
16. There are sixteen different possible states. The incoming data in groups of four bits called Quadbits.

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22
Q

It uses XNOR as its primary circuit:

A. QAM
B. BPSK
C. QPSK
D. DPSK

A

D. DPSK

Differential Phase Shift Keying (DPSK)-
primary advantage is simplicity with
which it can be implemented. No carrier
recovery is needed. Uses XNOR as its
primary circuit. Two input bits
determines the phase shift of the signal.

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23
Q

In QPSK, if the Q/l input is low, it
indicates:

A. Positive Polarity
B. 1.307 V Magnitude
C. Negative Polarity
D. 0.541 V Magnitude

A

C. Negative Polarity

Quaternary Phase Shift Keying:
The Q/l bits both indicates the polarity
of the signal:
LOGIC 1 - Positive Polarity
LOGIC 0 - Negative Polarity

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24
Q

Two output phases are possible for a
single carrier frequency.

A. Biphase Modulation
B. Any of these choices
C. Binary Phase Shift Keying
D. Phase Reversal Keying

A

B. Any of these choices

Binary Phase Shift Keying (BPSK) - also known as Phase Reversal Keying (PRK)and Biphase Modulation. Two output
phases are possible for a single carrier frequency. One output represents logic 1. Another output represents logic 0.

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25
Which modulation technique involves tribits, eight different phase shifts, and one amplitude? A. FSK B. ASK C. 4-PSK D. 8-PSK
D. 8-PSK 8 Phase Shift Keying (8PSK) - it is an M-ary encoding technique where M= 8.The incoming bits are considered in groups of three bits called Tribit. The input data is in the form of QlC, where Q means Quadrature Bit, I means In-Phase Bit and C means Control Bit.
26
In 8PSK, if the C input is high, it indicates: A. Positive Polarity B. 0.541 V Magnitude C. 1.307 V Magnitude D. Negative Polarity
C. 1.307 V Magnitude 8 Phase Shift Keying: The Q/l bits both indicates the polarity of the signal: LOGIC 1- Positive Polarity LOGIC 0 - Negative Polarity The C bit indicates the magnitude of the signal: LOGIC 1-1.307V LOGIC 0-0.541V
27
In FSK, if the binary input bit is low, the output is: A. the carrier signal B. there is no output C. the space frequency D. the mark frequency
C. the space frequency LOGIC 1 - the output frequency is the mark frequency. LOGIC O - the output frequency is the space frequency
28
The bit rate always equal the baud rate in which type of signal? A. FSK B. QAM C. 4-PSK D. All of these choices
A. FSK Frequency Shift Keying (FSK)- also known as Binary Frequency Shift Keying (BFSK). Binary FSK is a form of constant-amplitude angle modulation and similar to conventional frequency modulation (FM) except that the modulating signal is a binary signal that varies between two discrete voltage levels.
29
In PSK, as the level (M) increases, the transmission time: A. increases by 50% B. decreases C. decreases by 50% D. increases
D. increases As the level (M) of the PSK increases, the transmission time is faster. However, the signal's spacing is decreased and can cause interferences and errors.
30
The companding occurs before converting the signal to digital form: A. Level Companding B. Word Companding C. Digital Companding D. Analog Companding
D. Analog Companding Analog Companding - companding occurs before converting the signal to digital form. Digital Companding - companding occurs after converting the signal to digital for. Easier than analog companding.
31
For every one cycle there must be at least _____ samples. A. four B. three C. one D. two
D. two Sampling Rate - the minimum sampling rate is equal to twice the highest audio input frequency. Aliasing or Foldover Distortion will occur if the condition is not met. For every one cycle, there must be at least two samples. Also known as Nyquist Criterion.
32
The companding occurs after converting the signal to digital form: A. Analog Companding B. Digital Companding C. Level Companding D. Word Companding
B. Digital Companding Analog Companding - companding occurs before converting the signal to digital form. Digital Companding - companding occurs after converting the signal to digital form. Easier than analog companding.
33
The companding standard used by United States of America and Japan: A. u-Law Companding B. C-Law Companding C. D-Law Companding D. A-Law Companding
A. u-Law Companding u-Law Companding - companding standard used by United States of America and Japan. A-Law Companding - companding standard used by European countries.
34
The process of converting an infinite number of possibilities to a finite number of conditions: A. Coding B. Quantizing C. Companding D. Sampling
B. Quantizing Sampling - to sample periodically the continually changing analog signal and convert the samples to a series of constant amplitude PAM levels. The process of obtaining samples. Quantizing - the process of converting an infinite number of possibilities to a finite number of conditions. Rounding off the amplitudes of flat-top samples to a manageable number of levels. Assigning PCM codes to absolute magnitude. Coding - the quantized intervals are assigned to the individual PAM samples into binary signals.
35
The companding standard used by European countries: A. D-Law Companding B. u-Law Companding C. C-Law Companding D. A-Law Companding
D. A-Law Companding u-Law Companding - companding standard used by United States of America and Japan. A-Law Companding - companding standard used by European countries.
36
A pulse modulation technique in which the pulse width is proportional to the amplitude of the analog signal: A. PCM B. PAM C. PWM D. PPM
C. PWM Pulse Width Modulation (PWM)- a method sometimes called Pulse Duration Modulation (PDM) or Pulse Length Modulation (PLM). The pulse width is proportional to the amplitude of the analog signal.
37
It occurs when Nyquist Criterion is not met: A. Foldover Distortion B. Overload Distortion C. Aperture Distortion D. Quantization
A. Foldover Distortion Aperture Error (Aperture Distortion)- when the amplitude of the sampled signal changes during the sample pulse time. Aliasing (Foldover Distortion) - will occur if Nyquist Criterion is not met. Quantization Error (Quantization Noise) - the error produced by rounding off values. Peak Limiting (Overload Distortion) - if the magnitude of the sample exceeds the highest quantization interval.
38
Which quantization level results in a more faithful reproduction of the signal? A. 2 B. 16 C. 32 D. 8
C. 32 To reduce the quantization error, increase the number of levels thus increasing the quality however it will also increase the memory size of the data.
39
It is a numerical indication of how efficiently a PCM code is utilized. A. Bandwidth Efficiency B. Spectral Efficiency C. Nyquist Criterion D. Coding Efficiency
D. Coding Efficiency Coding Efficiency - it is a numerical indication of how efficiently a PCM code is utilized. It is the ratio of the minimum number of bits required to achieve a certain dynamic range to the actual PCM bits used.
40
The smallest possible magnitude that can be decoded by the DAC: A. Both Resolution & Minimum Voltage B. Quantum C. Minimum Voltage D. Resolution
D. Resolution Resolution - the smallest possible magnitude that can be decoded by the DAC. The magnitude of the quantum. It is equal to the minimum step-size which is equal to the voltage of the LSB of the PCM code.
41
The input analog waveform is sampled by a sampling pulse with an output sampled waveform that is flattened at the top: A. Natural Sampling B. Ideal Sampling C. Sample & Hold D. Any of these choices
C. Sample & Hold Natural Sampling - the input analog waveform is sampled by a sampling pulse with an output sampled waveform obtaining the shape of the input analog waveform. Flat Top Sampling - also known as Sample & Hold. The input analog waveform is sampled by a sampling pulse with an output sampled waveform that is flattened at the top (staircase waveform). Most commonly used.
42
It is used to protect the lower amplitude signals from noise: A. Encryption B. Companding C. De-emphasis D. Pre-emphasis
B. Companding Companding - it is the process of compressing then expanding. The higher-amplitude analog signals are compressed prior to transmission then expanded at the receiver. It is used to protect the lower amplitude signals from noise. Means of improving the dynamic range of a communications systems.
43
A pulse modulation technique in which the position of the constant-width pulse within a prescribed time slot is varied according to the amplitude of the analog signal: A. PPM B. PAM C. PCM D. PWM
A. PPM Pulse Position Modulation (PPM) - the position of the constant-width pulse within a prescribed time slot is varied according to the amplitude of the analog signal.
44
In order to reduce quantization error, the number of quantization level must be _____ A. increased B. increased by 50% C. decreased D. decreased by 50%
A. increased To reduce the quantization error, increase the number of levels thus increasing the quality however it will also increase the memory size of the data.
45
It is designed specifically to take advantage of bits: A. Adaptive Delta Modulation PCM B. Automatic Delta Modulation PCM C. Delta Modulation PCM D. Differential PCM
D. Differential PCM Differential PCM - the difference in amplitude of two successive samples is transmitted rather than the actual sample. Designed specifically to take advantage of bits.
46
A type of PCM code in which the first bit is the sign bit and the rest of the bits are magnitude bits. A. Magnitude PCM B. Linear PCM C. Sign-Magnitude PCM D. Linear Sign PCM
C. Sign-Magnitude PCM Linear PCM - all the bits are magnitude bits. Sign-Magnitude PCM - one bit is a sign bit and the rest of the bits are magnitude bits.
47
If the first bit of the sign-magnitude PCM code is low, then it is: A. Neither Positive nor Negative B. Positive C. Negative D. Either Positive or Negative
C. Negative Sign-Magnitude PCM (Sign Bit): LOGIC 1 - Positive LOGIC 0 - Negative
48
The Nyquist theorem specifies the minimum sampling rate to be _____ A. Twice the highest frequency of a signal B. Twice the bandwidth of a signal C. Equal to the highest frequency of a signal D. Equal to the lowest frequency of a signal
A. Twice the highest frequency of a signal Sampling Rate - the minimum sampling rate is equal to twice the highest audio input frequency. Aliasing or Foldover Distortion will occur if the condition is not met. For every one cycle, there must be at least two samples. Also known as Nyquist Criterion.
49
The error produced by rounding off values: A. Quantization Noise B. Aperture Distortion C. Overload Distortion D. Foldover Distortion
A. Quantization Noise Aperture Error (Aperture Distortion) - when the amplitude of the sampled signal changes during the sample pulse time. Aliasing (Foldover Distortion) - will occur if Nyquist Criterion is not met. Quantization Error (Quantization Noise)— the error produced by rounding off values. Peak Limiting (Overload Distortion) - if the magnitude of the sample exceeds the highest quantization interval.
50
In Delta Modulation PCM, it occurs when the input changes very fast: A. Aperture Error B. Granular Noise C. Slope Overload D. Aliasing
C. Slope Overload Slope Overload - it happens when the input changes very fast. Solution to this problem is to increase the step-size. Granular Noise - it happens when the input does not change. Solution to this problem is to decrease the step-size.
51
The maximum quantization noise equal to _____ the resolution. A. half B. twice C. one-thirds D. thrice
A. half Quantization Error (Quantization Noise) - the error produced by rounding off values.
52
In Delta Modulation PCM, it occurs when the input does not change: A. Slope Overload B. Granular Noise C. Aliasing D. Aperture Error
B. Granular Noise Slope Overload - it happens when the input changes very fast. Solution to this problem is to increase the step-size. Granular Noise - it happens when the input does not change. Solution to this problem is to decrease the step-size.
53
A pulse modulation technique in which the analog signal is sampled and converted to a fixed-length, serial binary number for transmission: A. PPM B. PAM C. PWM D. PCM
D. PCM Pulse Code Modulation (PCM) - the analog signal is sampled and converted to a fixed-length, serial binary number for transmission. The binary number varies according to the amplitude of the analog signal. It was invented by Alex H.Reeves.
54
To sample periodically the continually changing analog signal and convert the samples to a series of constant amplitude PAM levels: A. Coding B. Sampling C. Quantizing D. Companding
B. Sampling Sampling - to sample periodically the continually changing analog signal and convert the samples to a series of constant amplitude PAM levels. The process of obtaining samples. Quantizing - the process of converting an infinite number of possibilities to a finite number of conditions. Rounding off the amplitudes of flat-top samples to a manageable number of levels. Assigning PCM codes to absolute magnitude. Coding - the quantized intervals are assigned to the individual PAM samples into binary signals.
55
What is the solution for slope overload in Delta Modulation PCM? A. Increase the step-size B. Increase the input signal C. Decrease the step size D. Decrease the input signal
A. Increase the step-size Slope Overload - it happens when the input changes very fast. Solution to this problem is to increase the step-size. Granular Noise - it happens when the input does not change. Solution to this problem is to decrease the step-size.
56
It is the ratio of the largest possible magnitude to the smallest possible magnitude that can be decoded by the DAC. A. Nyquist Criterion B. Quantum Interval C. Dynamic Range D. Resolution
C. Dynamic Range Dynamic Range - abbreviated DR, DNR or DYR is the ratio between the largest and smallest values that a certain quantity can assume.
57
To form a mastergroup, it needs to have how many supergroups? A. 17 B. 10 C. 13 D. 15
B. 10 AT&T FDM Hierarchy: (Group)- 12 voice-band channels (Supergroup) - 5 groups (60 VC) (Mastergroup) - 10 supergroups (600 VC) (Jumbogroup) - 6 mastergroups (3600 VC) (Superjumbogroup) - 3 jumbogroups (10800 VC)
58
The process of simultaneously transmitting two or more individual signals over a single communications channel: A. Emphasizing B. Demultiplexing C. Companding D. Multiplexing
D. Multiplexing Multiplexing - the process of simultaneously transmitting two or more individual signals over a single communications channel. MUX and DEMUX are kept on step by a sync pulse.
59
The data rate of T1 carriers is: A. 1.544 Mbps B. 1.536 Mbps C. 3.152 Mbps D. 6.312 Mbps
A. 1.544 Mbps North American Digital Hierarchy: T1 (DS-1) - 24 voice channels, 1.544 Mbps T1C(DS-1C)- 48 voice channels, 3.152 Mbps T2(DS-2) - 96 voice channels, 6.312 Mbps T3(DS-3)-672 voice channels, 44.736 Mbps T4(DS-4)- 4032 voice channels, 274.176 Mbps T5(DS-5) - 8064 voice channels, 560.16 Mbps
60
To form a jumbogroup, it needs to have how many mastergroups? A. 10 B. 6 C. 12 D. 5
B. 6 AT&T FDM Hierarchy: (Group)- 12 voice-band channels (Supergroup) -5 groups (60 VC) (Mastergroup) - 10 supergroups (600 VC) (Jumbogroup) - 6 mastergroups (3600 VC) (Superjumbogroup) - 3 jumbogroups (10800 VC)
61
A multiplexing technique in which multiple sources that originally occupied the same frequency spectrum are each converted to a different frequency band and transmitted simultaneously over a single transmission medium: A. PDM B. WDM C. TDM D. FDM
D. FDM Frequency Division Multiplexing (FDM) - multiple sources that originally occupied the same frequency spectrum are each converted to a different frequency band and transmitted simultaneously over a single transmission medium.
62
How many voice-band channels are there in a supergroup? A. 3600 B. 60 C. 600 D. 10800
B. 60 AT&T FDM Hierarchy: (Group)- 12 voice-band channels (Supergroup) -5 groups (60 VC) (Mastergroup) - 10 supergroups (600 VC) (Jumbogroup) - 6 mastergroups (3600 VC) (Superjumbogroup) - 3 jumbogroups (10800 VC)
63
The data rate of T3 carriers is: A. 274.176 Mbps B. 560.16 Mbps C. 6.312 Mbps D. 44.736 Mbps
D. 44.736 Mbps North American Digital Hierarchy: T1 (DS-1) - 24 voice channels, 1.544 Mbps T1C(DS-1C)- 48 voice channels, 3.152 Mbps T2(DS-2) - 96 voice channels, 6.312 Mbps T3(DS-3)-672 voice channels, 44.736 Mbps T4(DS-4)- 4032 voice channels, 274.176 Mbps T5(DS-5) - 8064 voice channels, 560.16 Mbps
64
An FDM hierarchy which is formed by frequency - division multiplexing five groups containing 12 channels each for a combined bandwidth of 240 kHz. A. Group B. Jumbogroup C. Mastergroup D. Supergroup
D. Supergroup AT&T FDM Hierarchy: (Group)- 12 voice-band channels (Supergroup) -5 groups (60 VC) (Mastergroup) - 10 supergroups (600 VC) (Jumbogroup) - 6 mastergroups (3600 VC) (Superjumbogroup) - 3 jumbogroups (10800 VC)
65
How many voice-band channels are there in a jumbogroup? A. 10800 B. 3600 C. 600 D. 60
B. 3600 AT&T FDM Hierarchy: (Group)- 12 voice-band channels (Supergroup) -5 groups (60 VC) (Mastergroup) - 10 supergroups (600 VC) (Jumbogroup) - 6 mastergroups (3600 VC) (Superjumbogroup) - 3 jumbogroups (10800 VC)
66
A multiplexing technique which constitutes propagating signals from different sources on different cables that are contained within the same trench: A. PDM B. TDM C. SDM D. WDM
C. SDM Space Division Multiplexing (SDM)-constitutes propagating signals from different sources on different cables that are contained within the same trench (transmission medium).
67
The Nyquist theorem specifies the minimum sampling rate to be _____ A. Twice the highest frequency of a signal B. Equal to the lowest frequency of a signal C. Equal to the highest frequency of a signal D. Twice the bandwidth of a signal
A. Twice the highest frequency of a signal Sampling Rate - the minimum sampling rate is equal to twice the highest audio input frequency. Aliasing or Foldover Distortion will occur if the condition is not met. For every one cycle, there must be at least two samples. Also known as Nyquist Criterion.
68
Generation of PCM in order: A. encoding, sampling, quantizing B. sampling, quantizing, decoding C. decoding, sampling, quantizing D. sampling, quantizing, encoding
D. sampling, quantizing, encoding Sampling - to sample periodically the continually changing analog signal and convert the samples to a series of constant amplitude PAM levels. The process of obtaining samples. Quantizing - the process of converting an infinite number of possibilities to a finite number of conditions. Rounding off the amplitudes of flat-top samples to a manageable number of levels. Assigning PCM codes to absolute magnitude. Coding - the quantized intervals are assigned to the individual PAM samples into binary signals.
69
The biggest disadvantage of PCM is A. the large bandwidths that are required for it B. its inability to handle analog signals C. the high error rate which is quantizing noise introduces D. its incompatibility with TDM
A. the large bandwidths that are required for it Pulse Code Modulation (PCM) - the analog signal is sampled and converted to a fixed-length, serial binary number for transmission. The binary number varies according to the amplitude of the analog signal. It was invented by Alex H.Reeves.
70
ASK, PSK, FSK and QAM are examples of ______ modulation. A. Analog-to-digital B. Digital-to-analog C. Analog-to-analog
B. Digital-to-analog Digital Radio (Digital Modulation)- it is the transmittal of digitally modulated analog carriers between two or more points in a communication system. An analog carrier is modulated by a digital signal. Digital information, analog carrier. The medium can be wired or wireless.
71
It is the distance between symbols on the constellation diagram: A. Skip Distance B. Euclidean Distance C. Laplacian Distance D. Any of these choices
B. Euclidean Distance Constellation Diagram - sometimes called Signal State-Space Diagram. A pattern showing all the possible combinations of amplitude and phase for a signal.
72
In FSK, the mark and space frequency are separated by. A. Carrier Swing B. Bandwidth C. Any of these choices D. Peak Frequency Deviation
D. Peak Frequency Deviation Mark frequency is logic 1. Space frequency is logic 0. The mark and space frequencies is separated from the carrier by the peak frequency deviation.Either of the mark or space can be greater or lesser.
73
In QPSK, the outputs are separated by. A. 180 degrees B. 22.5 degrees C. 90 degrees D. 45 degrees
C. 90 degrees Quaternary Phase Shift keying (QPSK)- also known as Quadrature Phase Shift Keying. It is a M-ary coding technique where M = 4. It has binary input data combined into group called Dibit. The input data is in the form of Ql, where Q means Quadrature Bit and I means InPhase Bit.
74
In PSK, if the signal's spacing is decreased further, it can cause: A. Attenuation B. Absorption C. Noise D. Interference
D. Interference As the level (M) of the PSK increases, the transmission time is faster. However, the signal's spacing is decreased and can cause interferences and errors.

EST (10 decks)

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