# 3D152 Volume 1 UREs

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3D152 Volume 1 UREs

• 1.

### What is an example of analog-to-digital and digital-to-analog techniques?

• A.

Amplitude modulation (AM) and frequency modulation (FM).

• B.

Pulse code modulation (PCM) and frequency shift keying (FSK).

• C.

Phase modulation (PM) and quadrature phase shift keying (QPSK).

• D.

Pulse code modulation (PCM) and continuously variable slope delta (CVSD) modulation.

D. Pulse code modulation (PCM) and continuously variable slope delta (CVSD) modulation.
Explanation
"Finally, we have analog-to-digital and digital-to-analog conversions techniques like pulse code modulation (PCM) and continuous variable slope delta (CVSD) modulation." Page 1-2

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• 2.

### What converts analog signal information into an analog carrier signal?

• A.

Delta modulation (DM).

• B.

Digital modulation.

• C.

Analog modulation.

• D.

C. Analog modulation.
Explanation
"The definition of analog modulation is the conversion of an analog signal (the information) into another analog signal (the carrier). The type of modulation technique depends on the feature of the carrier signal that is used to represent the information." Page 1-2

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• 3.

### What converts analog signal information into a digital carrier signal?

• A.

Delta modulation (DM).

• B.

Analog modulation.

• C.

Digital modulation.

• D.

C. Digital modulation.
Explanation
"The definition of digital modulation is the conversion of an analog signal (the information) into a digital signal (the carrier)." Page 1-3

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• 4.

### The information-carrying components that occur on either side of a carrier are called

• A.

Sidebands.

• B.

Sine waves.

• C.

Frequency translators.

• D.

Modulating frequencies.

A. Sidebands.
Explanation
"The modulating signal is represented as a band of frequencies (sine waves of different frequencies) extending from some lower frequency, fL, to some upper or highest frequency, fH. Notice that the output signal includes two bands of frequencies: one at frequencies above the carrier, fc, and one below the carrier. These we call the upper sideband and lower sideband, respectively. The upper sideband (USB) has the same shape and orientation as the band of modulating signal frequencies. The lower sideband (LSB), however, is the mirror image of the original modulating signal." Page 1-8

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• 5.

### Amplitude modulation (AM) requires a bandwidth that is

• A.

Twice that of the modulating signal.

• B.

Half that of the modulating signal.

• C.

Twice that of the carrier signal.

• D.

Half that of the carrier signal.

A. Twice that of the modulating signal.
Explanation
"In general, AM requires twice the bandwidth to transmit as does the modulating signal alone." Page 1-8

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• 6.

### The upper sideband in a single-sideband suppressed carrier (SSBSC) modulation is eliminated by

• A.

Filtering.

• B.

Detection.

• C.

Compression.

• D.

Companding.

A. Filtering.
Explanation
"This process is shown in figure 1–5. Here, we use a filter that passes only the signal components in
the frequency range between fc – fH and fc – fL. Thus, the output of the filter contains only the lower
sideband. In particular, if we modulate a 27-MHz carrier frequency (in the Citizen’s Band frequency
range) with a voice signal band of 300 to 3400 Hz, the single-sideband suppressed carrier (SSBSC)
output is a band of frequencies between 26.9966 and 26.9997 MHz." Page 1-8

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• 7.

### We can express the 6-to–1 improvement of the single-sideband suppressed carrier (SSBSC) modulation over conventional amplitude modulation (AM) as

• A.

2 decibels (dB) of improvement.

• B.

4 dB of improvement.

• C.

6 dB of improvement.

• D.

8 dB of improvement.

D. 8 dB of improvement.
Explanation
"We can express the 6-to-1 improvement of SSBSC over DSBSC
as 8 decibels (dB) of improvement." Page 1-9

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• 8.

### The only basic waveform in nature is a

• A.

Carrier wave.

• B.

Pure sine wave.

• C.

Resultant wave.

• D.

Composite wave.

B. Pure sine wave.
Explanation
"The only basic waveform in nature is a pure sine wave; any other waveform is a “composite” or “resultant” wave." Page 1-9

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• 9.

### A modulated waveform that contains a carrier plus two sidebands for each modulation frequency is a description of

• A.

A phase modulation (PM).

• B.

A pulse modulation.

• C.

A frequency modulation (FM).

• D.

An amplitude modulation (AM).

D. An amplitude modulation (AM).
Explanation
An amplitude modulation (AM) is a modulated waveform that contains a carrier plus two sidebands for each modulation frequency. In AM, the amplitude of the carrier signal is varied in accordance with the modulating signal, resulting in the formation of sidebands around the carrier frequency. These sidebands carry the information of the modulating signal. Therefore, AM is the correct answer as it matches the given description.

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• 10.

### The amount of deviation in a frequency modulation (FM) signal is directly proportional to the modulating signal’s

• A.

Phase.

• B.

Amplitude.

• C.

Frequency.

• D.

Amplitude and frequency.

B. Amplitude.
Explanation
"Amount of deviation in FM is proportional to the amount (amplitude) of the modulating signal." Page 1-13

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• 11.

### If 100 percent modulation is exceeded and there is distortion in the modulating signal, additional sidebands are generated. We identify these sidebands as what?

• A.

Transmitted intelligence.

• B.

Intensity of speech.

• C.

Composite waves.

• D.

Splatter.

D. Splatter.
Explanation
"if 100-percent modulation is exceeded and/or there is
distortion in the modulating signal, additional sidebands are generated because of the harmonic
content of the distorted modulating signal. These additional sidebands, known as splatter, cause
unwanted bandwidth and distortion in the transmitted AM signal." Page 1-10

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• 12.

### What is the main advantage of differential phase shift keying (DPSK)?

• A.

Carrier presence is required to detect changes.

• B.

It requires a less complex receiver than a basic phase shift keying (PSK) signal.

• C.

It requires a more complex receiver than a basic PSK signal.

• D.

The demodulator needs to detect changes in absolute phase values.

B. It requires a less complex receiver than a basic pHase shift keying (PSK) signal.
Explanation
"DPSK encodes different digital values as changes in signal phase. DPSK is easier to implement and is more robust than PSK because DPSK looks for differences, rather than for specific values. This form of modulation can be found in local area network technologies." Page 1-3

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• 13.

### Which of the following is not considered an analog modulation techniques?

• A.

Pulse-amplitude modulation (PAM).

• B.

Pulse-duration modulation (PDM).

• C.

Pulse-position modulation (PPM).

• D.

Pulse-code modulation (PCM).

D. Pulse-code modulation (PCM).
Explanation
"PAM, PDM, and PPM are true analog pulse-modulation techniques. Although PCM and DM are called pulse-modulation techniques; they are really digital-coding techniques." Page 1-24

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• 14.

### The amount of phase shift in a phase modulation (PM) signal is directly proportional to the

• A.

Modulation index.

• B.

Rate of phase shift.

• C.

Frequency of the modulating signal.

• D.

Amplitude of the modulating signal.

D. Amplitude of the modulating signal.
Explanation
"The amount of phase shift is proportional to the amplitude of the modulating signal (that is, if a 10-volt signal causes a phase shift of 20 degrees, then a 20-volt signal causes a phase shift of 40 degrees)." Page 1-16

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• 15.

### What form of modulation is insensitive to signal variations?

• A.

Delta.

• B.

Frequency shift keying (FSK).

• C.

Pulse-amplitude modulation (PAM).

• D.

Binary-phase shift keying or bi-phase shift keying (BPSK).

D. Binary-pHase shift keying or bi-pHase shift keying (BPSK).
Explanation
"One distinct advantage of BPSK is its insensitivity to level variations." Page 1-18

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• 16.

### In quadrature-phase shift keying (QPSK) the radio frequency (RF) bandwidth for a quadriphase signal is what of that required by a bi-phase signal, given the same data rate.

• A.

Four times.

• B.

Double.

• C.

Half.

• D.

The same.

C. Half.
Explanation
"The RF bandwidth for a quadriphase signal is half that required by a bi-phase signal, given the same data rate. Alternatively, twice as much data might be transmitted in the same bandwidth with a quadriphase signal as with a bi-phase signal." Page 1-19

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• 17.

### The form of pulse modulation in which the pulse is varied within a set range of positions is known as

• A.

Pulse-amplitude modulation (PAM).

• B.

Pulse-duration modulation (PDM).

• C.

Pulse-position modulation (PPM).

• D.

Pulse-code modulation (PCM).

C. Pulse-position modulation (PPM).
Explanation
"Pulse-position modulation (PPM) is used in military TDM equipment. PPM uses a pulse time method that represents an analog signal by varying the positioning (the time displacement) of a discrete pulse within a bit interval. The position is varied according to the sampled value of an analog signal." Page 1-4

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• 18.

### Quantized analog modulation is actually

• A.

Pulse-amplitude modulation (PAM).

• B.

Pulse-duration modulation (PDM).

• C.

Less tolerant of noise than frequency modulation (FM).

• D.

Analog-to-digital conversion.

D. Analog-to-digital conversion.
Explanation
"Quantized analog modulation reduces the analog signals to discrete (digital) pulses that describe the analog signals according to various arbitrary rules. This process is actually analog-to-digital conversion rather than modulation" Page 1-29

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• 19.

### How many bits per character of a 16-step pulse-code modulation (PCM) system are used to describe the quantized analog sample?

• A.

3.

• B.

4.

• C.

5.

• D.

8.

B. 4.
Explanation
"The number of steps needed is equal to 2n, where (n) is the number of code bits needed for the largest character. Thus, the 16-step system requires 4 bits per character (24=16) and a 128-step system requires 7 bits per character (27=128) to describe the quantized analog samples." Page 1-31

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• 20.

### The process of coding pulse code modulation (PCM) quantized pulses to make them a constant duration and amplitude is

• A.

Encoding.

• B.

Companding.

• C.

Uniform quantizing.

• D.

Nonuniform quantizing.

A. Encoding.
Explanation
"The capability for regeneration of quantized pulses can be further enhanced by coding the pulses to make them of constant duration and amplitude before transmission" Page 1-32

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• 21.

### In Time Division Multiplexing (TDM), the transmitting multiplexer will put a bit or a byte from each of the incoming lines into a specifically allocated what?

• A.

Channel.

• B.

Trunk.

• C.

Time slot.

• D.

Port.

C. Time slot.
Explanation
"The transmitting multiplexer will put a bit or a byte from each of the incoming lines into a specifically allocated time slot" page 1-36

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• 22.

### The two major types of frame structures are

• A.

Low speed and high speed.

• B.

High speed and EBCDIC.

• C.

CCITT and low speed.

• D.

EBCDIC and CCITT.

C. CCITT and low speed.
Explanation
There are two major types of frame structures:
1. Low speed frame – used for rates below 384.2 kbps and is composed of a number of 8 bit slots with each slot holding one character
2. Consultative Committee for International Telephony and Telegraphy (CCITT) frame –used for data rates above 384.2 kilobytes per second (kb/s) and uses subframes (P1 and P2) to maintain sync during longer data frames.

Page 1-37

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• 23.

### The method of multiplexing the T1 multiplexer uses is

• A.

Frequency division.

• B.

Binary division.

• C.

Pulse division.

• D.

Time division.

D. Time division.
Explanation
"T1 uses the TDM process (fig. 1–38). These inputs can be a combination of digital, video, and audio signals." Page 1-38

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• 24.

### Wave-division multiplexing (WDM) creates the virtual channels for multiplexing them together for transmission by using different

• A.

Wavelengths or lambdas.

• B.

Wavelengths or gammas.

• C.

Frequencies or lambdas.

• D.

Frequencies or gammas.

A. Wavelengths or lambdas.
Explanation
"using an optical device, it sends light through to create the virtual channels using different wavelengths or lambdas then it multiplexes them together for transmission." Page 1-39

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• 25.

### The most common wave-division multiplexing (WDM) system uses how many wavelengths?

• A.

One wavelength.

• B.

Two wavelengths.

• C.

Three wavelengths.

• D.

Four wavelengths.

B. Two wavelengths.
Explanation
"The most common WDM system uses two wavelengths, although four or more-wavelength systems are available." Page 1-40

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• 26.

### Individual pulses within a digital signal are

• A.

Bits.

• B.

Bytes.

• C.

Codes.

• D.

Blocks.

A. Bits.
Explanation
"In digital signals, we call each condition, state, or pulse a binary digit. We shorten this term to “bit.”" Page 2-1

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• 27.

### What unit is most commonly used in data systems to express signaling speed?

• A.

Baud.

• B.

Baudot.

• C.

Sense interface.

• D.

Bits per second.

D. Bits per second.
Explanation
"When we express the term “bit” with regard to time, we have bits per second (b/s). This simply means that we can move a certain number of symbols, states, or conditions in 1 second. This method is commonly used in data systems to express signaling speed for equipment." Page 2-2

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• 28.

### Bit count integrity problems are primarily caused by

• A.

Impedance mismatch.

• B.

System timing faults.

• C.

Improper equipment settings.

• D.

Changes in atmospheric conditions.

B. System timing faults.
Explanation
"Bit count integrity problems are primarily caused by system delay or timing faults." Page 2-4

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• 29.

### Three categories of synchronization used in digital data circuits are

• A.

Synchronous, asynchronous, and isochronous.

• B.

Isochronous, asynchronous, and bisynchronous.

• C.

Nonsynchronous, bisynchronous, and synchronous.

• D.

Asynchronous, bisynchronous, and nonsynchronous.

A. Synchronous, asynchronous, and isochronous.
Explanation
"Timing for digital devices fall into three categories: synchronous, asynchronous, and isochronous. These terms characterize the methods used to synchronize the send and receive devices." Page 2-4

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• 30.

### Which option is a characteristic of synchronous data operation?

• A.

Timing pulses are transmitted within the signal stream.

• B.

Start and stop pulses control data transmission.

• C.

System timing is not of critical importance.

• D.

All data bits are the same length in time.

D. All data bits are the same length in time.
Explanation
"Synchronous operation requires no synchronizing pulses in the signal stream, and all bits are the same length in time." Page 2-4

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• 31.

### A digital signal that contains synchronizing bits within the signal stream describes

• A.

Synchronous operation.

• B.

Asynchronous operation.

• C.

Synchronous and/or isochronous operation.

• D.

Asynchronous and/or synchronous operation.

B. Asynchronous operation.
Explanation
"An asynchronous signal is any signal that contains synchronizing bits within its signal stream." Page 2-5

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• 32.

### In what type of signal is the information contained in the transition, and there is a transition from one state to the other only when a mark bit is sent?

• A.

Non-return-to-zero (NRZ) level.

• B.

Non-return-to-zero mark.

• C.

Non-return-to-zero space.

• D.

Return-to-zero level.

B. Non-return-to-zero mark.
Explanation
"NRZ-M (mark). The information is contained in the transition, and there’s a transition from one state to the other only when a mark bit is sent." page 2-8

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• 33.

### In what type of signal does the signal level move to one of the discrete signal levels, but returns to the zero level after a predetermined time?

• A.

Non-return-to-zero (NRZ) level.

• B.

Non-return-to-zero mark.

• C.

Non-return-to-zero space.

• D.

Return-to-zero.

D. Return-to-zero.
Explanation
"When a signal transition occurs, the signal level moves to one of the discrete signal levels, but after a predetermined time (normally 50 percent of a bit), it returns to zero voltage (RZ).Figure 2–5 shows the three most common signal formats in the DII." Page 2-8

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• 34.

### Which statement best describes an alternate mark inversion (AMI) signal?

• A.

The information is transmitted in three different voltage levels.

• B.

A logic one is transmitted as positive voltage if the previous logic one was negative.

• C.

The level always returns to zero for 50 percent of the bit cycle after every transition.

• D.

Bipolar violations are intentionally inserted into a data signal to break up long strings of zeros.

B. A logic one is transmitted as positive voltage if the previous logic one was negative.
Explanation
"In AMI, alternate marks (or logic ones) are inverted in polarity. If a logic one is transmitted, it is represented by a positive voltage if the previous logic one was negative. Conversely, it is represented by negative voltage if the previous one was positive. Logic zeros are represented by zero voltage. This results in a three-level digital signal." Page 2-9

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• 35.

### Digital coding techniques such as binary with eight-zero substitution (B8ZS) are becoming more popular because they are designed to

• A.

Provide error-free signaling.

• B.

Operate at higher data rates.

• C.

Eliminate bipolar violations.

• D.

Maintain ones density standards.

D. Maintain ones density standards.
Explanation
"Because of the ones density problem, coding techniques such as B8ZS are getting more popular." Page 2-9

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• 36.

### Which statement best describes a binary with eight-zero substitution (B8ZS) signal?

• A.

The information is transmitted in three different voltage levels.

• B.

A logic one is transmitted as positive voltage if the previous logic one was negative.

• C.

The level always returns to zero for 50 percent of the bit cycle after every transition.

• D.

Bipolar violations are intentionally inserted into a data signal to break up long strings of zeros.

D. Bipolar violations are intentionally inserted into a data signal to break up long strings of zeros.
Explanation
"B8ZS intentionally inserts bipolar violations (BPV) into a data signal to break up long strings of zeros." Page 2-9

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• 37.

### The major difference between conditioned di-phase (CDI) and other schemes is the

• A.

Lack of mid-bit transitions.

• B.

Use of mid-bit transitions for timing.

• C.

Data being encoded in the mid-bit transitions.

• D.

Voltage levels used for signaling the mid-bit transitions.

B. Use of mid-bit transitions for timing.
Explanation
"CDI is a binary, polar, state transition encoding scheme that is used almost exclusively in military tactical applications. One major difference in this scheme is the use of mid-bit transitions for timing." Page 2-10

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• 38.

### How many bits are in the D4 framing sequence?

• A.

8.

• B.

12.

• C.

24.

• D.

48.

B. 12.
Explanation
"One framing bit from 12 consecutive frames is added to create a 12-bit framing sequence. These 12 frames together are called a superframe." Page 2-10

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• 39.

### How many bits are in the extended superframe format (ESF) framing sequence?

• A.

8.

• B.

12.

• C.

24.

• D.

48.

C. 24.
Explanation
"The ESF frame is based on the D4 frame. The difference between ESF and D4 framing is that the ESF superframe consists of 24 frames to create a 24-bit framing sequence." Page 2-10

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• 40.

### What communications control signal uses a two-frequency dialing combination?

• A.

Pulse dialing.

• B.

Tone dialing.

• C.

Digit dialing.

• D.

B. Tone dialing.
Explanation
"Tone dialing uses a two-frequency combination that is associated with 12 push button keys. Each row and column of keys is associated with a predefined frequency." Page 2-12

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• 41.

### What communications information signal uses a continuous 350- and 440-Hz frequency pair?

• A.

Dial tone.

• B.

Ringback signal.

• C.

• D.

Call waiting.

A. Dial tone.
Explanation
"A dial tone is a frequency pair used to convey informational signaling. For example, the generation of a continuous 350- and 440-Hz frequency pair by the switch equipment." Page 2-12

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• 42.

### What communications information signal uses a signal cycled on and off for 0.5 second and contains the generation of a 480- and 620-Hz frequency pair?

• A.

Dial tone.

• B.

Busy signal.

• C.

• D.

Call waiting.

B. Busy signal.
Explanation
"The local switch equipment generates a busy signal to the sender when the receiver’s line is in use. For example, a signal cycled on and off for 0.5 second and contains the generation of a 480- and 620-Hz frequency pair." Page 2-12

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• 43.

### What communications supervisory signal uses a continuous application of direct current voltage for signaling?

• A.

Record warning.

• B.

Fast busy signal.

• C.

Loop-start.

• D.

E and M.

C. Loop-start.
Explanation
"The loop-start or metallic loop signaling method uses a continuous application of direct current voltage." Page 2-13

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• 44.

### When is the voltage applied in loop-start signaling?

• A.

When dial tone is present.

• B.

On-hook condition.

• C.

Off-hook condition.

• D.

During the ringback signal.

C. Off-hook condition.
Explanation
"The voltage or 48-volt battery is not activated until the telephone handset is lifted, off-hook." Page 2-13

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• 45.

### In common associated signaling (CAS), what is the seventh bit in frames 6 and 12 used to convey signaling information known as?

• A.

Bit robbing.

• B.

Bit stuffing.

• C.

Frame correction.

• D.

Frame enhancement.

A. Bit robbing.
Explanation
"In CAS signaling, the seventh bit in frames 6 and 12 are “robbed” to convey signaling information. This is known as bit robbing. The pattern represented robbed bit is based on the type of signaling, such as loop-start, or E&M, and the signal being conveyed." Page 2-13

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• 46.

### In what common channel signaling (CCS) mode are the messages relating to signaling between two points conveyed directly interconnecting these signaling points?

• A.

Associated mode.

• B.

Nonassociated mode.

• C.

Quasi-associated mode.

• D.

Multi-associated mode.

A. Associated mode.
Explanation
1. Associated mode – The messages relating to signaling between two points are conveyed directly interconnecting these signaling points.
2. Nonassociated mode – The messages relating to signaling are conveyed over two or more links passing through one or more signaling points that are not the origin and the destination of the messages.
3. Quasi-associated mode – This is a subcase of the nonassociated mode. The path the messages take through the network is predetermined and fixed.

Page 2-14

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• 47.

### What are the two principle weighting characteristics in use with telecommunication circuit noise?

• A.

Institute of Electronic and Electrical Engineers and CCITT psophometric.

• B.

Noise analysis and CCITT psophometric.

• C.

CCITT psophometric and C-message.

• D.

C-message and noise analysis.

C. CCITT psopHometric and C-message.
Explanation
"The two principal weighting characteristics in current use are (1) CCITT (Consultative Committee for International Telephony and Telegraphy) psophometric, a noise weighting used in Europe with a noise (or level) meter called a psophometer, weighting and (2) C-message weighting." Page 3-2

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• 48.

### While timing makes sure the equipment is sending and receiving bits at the same time intervals, synchronization makes sure that the

• A.

Receive equipment timing is set properly.

• B.

Transmit equipment timing is set properly.

• C.

Receive equipment can find its place in the bit stream.

• D.

Transmit equipment can find its place in the bit stream.

C. Receive equipment can find its place in the bit stream.
Explanation
"While timing makes sure the equipment is sending and receiving bits at the same time intervals, synchronization makes sure that the receive equipment can find its place in the bit stream." Page 3-5

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• 49.

### What term is associated with the delay or lag introduced in the application of voltage from one section to the next?

• A.

Latency.

• B.

Phase delay.

• C.

Propagation constant.

• D.

Phase delay distortion.

A. Latency.
Explanation
"The transmission line presents a delay in each section, and the amount of delay is dependent upon the
frequency of the information signal. Thus, a delay, also known as latency or lag, is introduced in the application of voltage from one section to the next" Page 3-6

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• 50.

### Attenuation distortion is caused by

• A.

A line loss for the various frequency components comprising a voice transmission.

• B.

The line loss, the distance of transmission lines, and faults in the transmission cables.

• C.

Faults in the transmission cables and the number of splices in the line varying with the frequency.

• D.

Differing attenuation rates for the various frequency components comprising a voice frequency transmission.

D. Differing attenuation rates for the various frequency components comprising a voice frequency transmission.
Explanation
"Differing attenuation rates for the various frequency components comprising a voice frequency
transmission causes attenuation distortion" Page 3-6

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• Current Version
• Mar 21, 2023
Quiz Edited by
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• Dec 03, 2014
Quiz Created by
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