# 3d1x2 5 Level CDC Vol. 1

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• 1.

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

• A.

Amplitude modulation(AM) and freqeuncy modulation (FM)

• B.

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

• C.

Phase modualtion (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
Pulse code modulation (PCM) is an example of analog-to-digital technique, where an analog signal is sampled and quantized into a digital representation. Continuously variable slope delta (CVSD) modulation, on the other hand, is an example of digital-to-analog technique, where a digital signal is converted back into an analog signal by varying the slope of a delta modulated waveform. Both PCM and CVSD modulation techniques involve the conversion between analog and digital signals, making them appropriate examples for the given question.

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• 2.

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

• A.

Delta modulation (DM)

• B.

Digital modulation

• C.

Analog modulation

• D.

C. Analog modulation
Explanation
Analog modulation is the process of converting analog signal information into an analog carrier signal. This involves varying the amplitude, frequency, or phase of the carrier signal in accordance with the input analog signal. By doing so, the information contained in the analog signal can be transmitted over long distances through the carrier signal. This method is commonly used in various communication systems, such as radio and television broadcasting, where the original analog signal needs to be converted into a format suitable for transmission.

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• 3.

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

• A.

Delta Modulation (DM)

• B.

Digital modulation

• C.

Analog modulation

• D.

B. Digital modulation
Explanation
Digital modulation is the process of converting analog signal information into a digital carrier signal. This is achieved by using techniques such as amplitude shift keying (ASK), frequency shift keying (FSK), or phase shift keying (PSK) to encode the analog signal into a digital format. These modulation techniques allow for efficient transmission and reception of the digital signal, ensuring accurate and reliable communication.

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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 fequencies.

A. Sidebands.
Explanation
The correct answer is sidebands. In a communication system, the carrier wave is modulated to carry information. The process of modulation creates two additional frequency components on either side of the carrier frequency, known as sidebands. These sidebands carry the actual information being transmitted. Therefore, sidebands are the information-carrying components that occur on either side of a carrier. Sine waves are simply the basic waveform used in communication systems. Frequency translators are devices that convert signals from one frequency to another. Modulating frequencies refer to the frequencies used to modulate the carrier wave.

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• 5.

### Amplitude modulation (AM) requires a bandwith 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 carrire signal.

A. Twice that of the modulating signal.
Explanation
Amplitude modulation (AM) requires a bandwidth that is twice that of the modulating signal because in AM, the modulating signal is multiplied by the carrier signal, resulting in sidebands that extend both above and below the carrier frequency. The sidebands contain information from the modulating signal, and to accurately transmit this information, the bandwidth must be able to accommodate both the positive and negative frequencies of the modulating signal. Therefore, the bandwidth required for AM is twice that of the modulating signal.

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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
In a single-sideband suppressed carrier (SSBSC) modulation, the upper sideband is eliminated by filtering. Filtering refers to the process of selectively allowing certain frequencies to pass through while attenuating or blocking others. In the case of SSBSC modulation, a filter is used to remove the upper sideband, leaving only the lower sideband. This is done to conserve bandwidth and improve spectral efficiency. By eliminating the upper sideband through filtering, the transmitted signal can be more efficiently transmitted and received.

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• 7.

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

• A.

2 decibels (dB) of improvement

• B.

4 decibels of improvement

• C.

6 decibels of improvement

• D.

8 decibels of improvement

D. 8 decibels of improvement
Explanation
The 6-to-1 improvement of SSBSC modulation over conventional AM means that the SSBSC modulation provides a signal-to-noise ratio (SNR) that is 6 times better than conventional AM. In terms of decibels, a 6-to-1 improvement corresponds to an improvement of 8 decibels. Decibels are a logarithmic unit used to express the ratio between two power levels, and an improvement of 6-to-1 corresponds to an increase of 8 decibels. Therefore, the correct answer is 8 decibels of improvement.

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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
A pure sine wave is the only basic waveform in nature because it represents a single frequency with no harmonics or distortion. It is a smooth, continuous waveform that oscillates between positive and negative values in a regular pattern. Other waveforms, such as a composite wave or resultant wave, are formed by combining multiple sine waves of different frequencies and amplitudes. Therefore, the pure sine wave is the most fundamental and natural waveform found in nature.

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• 9.

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

• A.

A phase modulation (PM).

• B.

Pulse modulation.

• C.

A frequency modulation.

• 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 proportion to the waveform being modulated, resulting in the creation of sidebands. These sidebands are located above and below the carrier frequency and carry the information being transmitted. Therefore, an AM waveform with two sidebands for each modulation frequency accurately describes the characteristics of an amplitude modulation.

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• 10.

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

• A.

Transmitted intelligence

• B.

Intensity of speech

• C.

Composite waves

• D.

Splatter

D. Splatter
Explanation
When the modulating signal exceeds 100 percent modulation and distortion occurs, additional sidebands are generated. These sidebands are known as "splatter". Splatter refers to the unwanted and excessive sidebands that result from distortion in the modulating signal.

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• 11.

### The amount of deviation in a frquency modulation (FM) signal is directly proportinal to the modulating signal's

• A.

Phase.

• B.

Amplitude.

• C.

Frequency.

• D.

Apmlitude and frequency.

B. Amplitude.
Explanation
In frequency modulation (FM), the amount of deviation in the signal is directly proportional to the modulating signal's amplitude. This means that as the amplitude of the modulating signal increases, the frequency of the carrier signal will deviate more. Therefore, the correct answer is amplitude.

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• 12.

### 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
In phase modulation (PM), the amount of phase shift in the signal is directly proportional to the amplitude of the modulating signal. This means that as the amplitude of the modulating signal increases, the phase shift in the PM signal also increases. The modulation index, rate of phase shift, and frequency of the modulating signal do not have a direct relationship with the phase shift in PM.

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• 13.

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

• A.

Delta

• B.

Frequency shift keying (FSK)

• C.

Pulse-amplitude modulation (PAM)

• D.

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

D. Binary-pHaseshift keying or bi-pHase shift keying (BPSK)
Explanation
Binary-phaseshift keying or bi-phase shift keying (BPSK) is insensitive to signal variations because it uses two phases to represent the digital data. Each phase represents a different bit value, usually 0 or 1. The phase shift between the two states is 180 degrees, which means that even if there is noise or interference in the signal, the receiver can still distinguish between the two phases and accurately decode the data. This makes BPSK a robust modulation scheme that is commonly used in applications where signal variations are a concern, such as satellite communications and wireless data transmission.

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• 14.

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

• A.

Four times

• B.

Double

• C.

Half

• D.

The same

C. Half
Explanation
In quadrature-phase shift keying (QPSK), a quadriphase signal is used to transmit data. Compared to a bi-phase signal, a quadriphase signal requires half the radio frequency (RF) bandwidth to achieve the same data rate. This is because QPSK uses four different phase shifts to represent two bits of data, while bi-phase only uses two phase shifts for the same amount of data. Therefore, QPSK is more efficient in terms of bandwidth utilization, requiring only half the RF bandwidth.

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• 15.

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

• A.

Carrier presence is required to detect change

• 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 needds to detect changes in the absolute phase values

B. It requires a less complex receiver than a basic pHase shift keying (PSK) signal
Explanation
Differential phase shift keying (DPSK) has the main advantage of requiring a less complex receiver than a basic phase shift keying (PSK) signal. This means that the receiver in a DPSK system can be simpler and more cost-effective compared to a PSK system. In DPSK, the receiver only needs to detect changes in the relative phase values between consecutive symbols, rather than detecting changes in the absolute phase values. This simplifies the receiver design and reduces its complexity, making DPSK a more efficient modulation scheme in terms of receiver implementation.

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• 16.

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

• A.

Pulse-amplitude modulation (PAM)

• B.

Pulse-duration modulation (PDM)

• C.

Pulse-positon modulation (PPM)

• D.

Pulse-code modulation (PCM)

D. Pulse-code modulation (PCM)
Explanation
PCM is not considered an analog modulation technique because it is a digital modulation technique. In PCM, the analog signal is sampled and quantized into discrete values, and then encoded into binary code. This allows for accurate representation and transmission of the original analog signal, but it is not a continuous variation of the signal like analog modulation techniques. Instead, PCM represents the signal in discrete steps, making it a digital modulation technique.

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• 17.

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

• A.

Pulse-amplitude modulation (PAM).

• B.

Pulse-duration modulation (PDM).

• C.

Pulse-positon modulation (PPM).

• D.

Pulse-code modulation (PCM).

C. Pulse-positon modulation (PPM).
Explanation
Pulse-position modulation (PPM) is a form of pulse modulation where the position of the pulse within a set range is varied. In PPM, the timing or position of the pulse represents the information being transmitted. This modulation technique is commonly used in digital communication systems to transmit data over a channel. PAM, PDM, and PCM are different forms of pulse modulation where the amplitude, duration, and code of the pulse, respectively, are varied instead of the position. Therefore, PPM is the correct answer in this case.

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• 18.

### Quanitized analog modulation (QAM) 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
QAM, or Quanitized analog modulation, is a method of converting analog signals into digital signals. It involves dividing the analog signal into multiple levels or states, each representing a specific digital value. This allows for more efficient transmission and storage of the signal. Therefore, the correct answer is analog-to-digital conversion.

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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
A 16-step PCM system uses 4 bits per character to describe the quantized analog sample. In PCM, the analog signal is sampled and then quantized into a discrete set of levels. The number of bits per character determines the number of quantization levels that can be represented. In this case, with 4 bits per character, there are 2^4 = 16 quantization levels available, which matches the 16-step PCM system mentioned in the question.

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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 process described in the question, where quantized pulses are coded to have a constant duration and amplitude, is known as encoding. Encoding involves converting information into a specific format that can be easily transmitted or stored. In this case, the PCM quantized pulses are being encoded to ensure consistency in their duration and amplitude.

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• 21.

### In Time Division Multiplexing (TDM), the transmitting multiplexer will put  a bit or 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
In Time Division Multiplexing (TDM), the transmitting multiplexer will allocate a specific time slot for each bit or byte from the incoming lines. This time slot is where the data from each line is placed before being transmitted. Therefore, the correct answer is "time slot."

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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
The correct answer is CCITT and low speed. CCITT (ComitÃ© Consultatif International TÃ©lÃ©phonique et TÃ©lÃ©graphique) is a standardization body that focuses on telecommunications. Low speed refers to a type of frame structure that operates at a slower data transfer rate. Therefore, CCITT and low speed are the two major types of frame structures mentioned in the question.

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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
The T1 multiplexer uses the method of time division. Time division multiplexing (TDM) is a technique where multiple signals are combined into a single transmission channel by allocating specific time slots to each signal. In the case of T1 multiplexing, it combines multiple voice or data signals into a single T1 line by dividing the available time slots among the signals. This allows for efficient utilization of the transmission medium and enables multiple signals to be transmitted simultaneously.

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• 24.

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

• A.

Wavelengths or lambas.

• B.

Wavelengths or gammas.

• C.

Frequencies or lambdas.

• D.

Frequencies or gammas.

A. Wavelengths or lambas.
Explanation
Wave-division multiplexing (WDM) is a technology that combines multiple optical signals onto a single fiber by using different wavelengths or lambdas. Each wavelength represents a virtual channel, allowing for the transmission of multiple signals simultaneously. The use of different wavelengths ensures that the signals do not interfere with each other and can be easily separated at the receiving end. Therefore, the correct answer is wavelengths or lambdas.

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• 25.

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

• A.

1

• B.

2

• C.

3

• D.

4

B. 2
Explanation
The most common wave-division multiplexing (WDM) system uses 2 wavelengths. WDM is a technology that allows multiple optical signals to be transmitted simultaneously over a single optical fiber by using different wavelengths of light to carry each signal. This increases the capacity of the fiber and allows for more data to be transmitted. Using 2 wavelengths in a WDM system allows for efficient transmission of multiple signals without interference.

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• 26.

### Individual pulses within a digital signal are

• A.

Bits.

• B.

Bytes.

• C.

Codes.

• D.

Blocks.

A. Bits.
Explanation
Individual pulses within a digital signal are represented as bits. A bit is the basic unit of information in computing and digital communications. It can have a value of either 0 or 1, representing the two possible states of a digital signal. Bytes, codes, and blocks are larger units of data that are composed of multiple bits. Therefore, bits are the correct answer as they represent the individual pulses within a digital signal.

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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 (bps)

D. Bits per second (bps)
Explanation
The correct answer is bits per second (bps). Baud is a unit that measures the number of signal changes per second, which is not the same as the number of bits transmitted per second. Baudot is a character encoding scheme, not a unit of measurement. Sense interface is not a commonly used unit for signaling speed in data systems. Therefore, bits per second (bps) is the most commonly used unit to express signaling speed in data systems.

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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 occur when there are errors or discrepancies in the number of bits being transmitted or received. System timing faults refer to issues in the synchronization of the timing signals between different components or devices in a system. These faults can disrupt the proper timing of data transmission, leading to errors in counting the number of bits. Therefore, system timing faults can be the primary cause of bit count integrity problems.

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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
The correct answer is synchronous, asynchronous, and isochronous. These three categories of synchronization are commonly used in digital data circuits. Synchronous synchronization refers to a method where data is transmitted in a synchronized manner with a clock signal. Asynchronous synchronization, on the other hand, does not rely on a clock signal and instead uses start and stop bits to indicate the beginning and end of each data packet. Isochronous synchronization is used for real-time data transmission, ensuring a constant and predictable data rate.

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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
The characteristic of synchronous data operation is that all data bits are the same length in time. This means that each bit of data is transmitted for the same duration, ensuring that the receiver can accurately interpret the information being transmitted. This allows for reliable and efficient data transmission as the receiver can easily synchronize with the sender and decode the data correctly.

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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
A digital signal that contains synchronizing bits within the signal stream describes asynchronous operation. This means that the signal does not rely on a fixed timing mechanism to transmit data. Instead, it uses start and stop bits or other methods to indicate the beginning and end of each data unit. This allows for flexibility in the transmission process, as the sender and receiver do not need to be perfectly synchronized.

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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
In Non-return-to-zero mark (NRZ-M) encoding, the information is contained in the transition from one state to the other only when a mark bit is sent. In this type of signal, a transition from a high to low voltage level represents a mark bit, while the absence of a transition represents a space bit. This encoding scheme is commonly used in digital communication systems to transmit data.

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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
In a return-to-zero signal, the signal level moves to one of the discrete signal levels but returns to the zero level after a predetermined time. This means that the signal alternates between high and low levels, with each level being held for a specific duration before returning to zero. This type of signal is commonly used in digital communication systems to represent binary data, where the presence of a signal level represents a binary "1" and the absence of a signal represents a binary "0".

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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
AMI stands for Alternate Mark Inversion, which is a line code used for transmitting digital signals. In AMI, a logic one is represented by a positive voltage if the previous logic one was negative. This helps in maintaining a balanced signal and prevents the buildup of DC voltage on the line. By alternating the polarity of consecutive logic ones, AMI ensures that the average voltage over time remains close to zero. This technique is commonly used in telecommunications systems to transmit data efficiently and reliably.

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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
Digital coding techniques such as binary with eight-zero substitution (B8ZS) are used to maintain ones density standards. Ones density refers to the number of consecutive ones in a digital signal. Maintaining ones density is important because it helps to ensure that the signal remains balanced and prevents long runs of consecutive zeros, which can cause synchronization and timing issues. B8ZS is specifically designed to substitute certain patterns of consecutive zeros with specific patterns of ones and zeros, thereby maintaining ones density and ensuring the integrity of the signal.

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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, or binary with eight-zero substitution, is a line code used in telecommunications to ensure proper synchronization and prevent long strings of zeros. It intentionally inserts bipolar violations into the data signal, which means it alternates between positive and negative voltage levels, to break up consecutive zeros. This helps maintain the integrity of the signal and ensures accurate transmission.

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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
Conditioned di-phase (CDI) is a scheme that differs from other schemes in terms of its use of mid-bit transitions for timing. In CDI, the timing of the data is determined by the presence or absence of mid-bit transitions. This means that the data is encoded by the timing of these transitions rather than by the voltage levels used for signaling them. This is in contrast to other schemes where timing may be determined by different factors such as the presence of transitions at specific points or the use of specific voltage levels.

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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
The D4 framing sequence consists of 12 bits.

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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 extended superframe format (ESF) framing sequence consists of 24 bits.

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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 is the correct answer because it uses a two-frequency dialing combination. In tone dialing, each number on the telephone keypad corresponds to a specific combination of two frequencies. When a number is dialed, the phone generates these tones, which are then transmitted to the telephone exchange to establish the call. This method is more efficient and faster than pulse dialing, where each digit is represented by a series of pulses. Digit dialing and address dialing are not commonly used terms in telecommunications.

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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 communications information signal that uses a continuous 350- and 440-Hz frequency pair. It is the sound heard when a telephone line is active and ready for dialing. When a user picks up the phone, they hear the dial tone indicating that they can start dialing a number. The specific frequency pair of 350- and 440-Hz is used to generate this distinct sound.

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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
A busy signal is a communications information signal that is cycled on and off for 0.5 seconds. It indicates that the line is currently busy and cannot accept another call. The generation of a 480- and 620-Hz frequency pair is a characteristic of the busy signal. This combination of frequencies is used to create the distinct sound of a busy signal.

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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
Loop-start is the correct answer because it is a communications supervisory signal that uses a continuous application of direct current voltage for signaling. This signaling method is commonly used in telecommunications systems to indicate the start of a call or to supervise the status of the telephone line. The loop-start signal is generated when a circuit loop is closed, allowing the flow of current to indicate the availability of the line for communication.

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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
Loop-start signaling is a method used in telecommunication systems to establish a connection between two devices. In loop-start signaling, the voltage is applied when the phone is in the off-hook condition. The off-hook condition refers to the state when the phone receiver is lifted or when a call is in progress. This voltage allows the signaling and communication to take place between the two devices. Therefore, the correct answer is off-hook condition.

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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
The seventh bit in frames 6 and 12 in common associated signaling (CAS) is used to convey signaling information known as "bit robbing." Bit robbing refers to the process of stealing one bit from each frame to carry signaling information. This technique allows for the transmission of additional information without requiring extra bits or frames.

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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
Associated mode is the correct answer because in this mode, the messages related to signaling between two points are conveyed directly through the interconnection of these signaling points. In other words, the signaling messages are sent directly from one point to another without any intermediate nodes or additional signaling paths. This mode is commonly used in common channel signaling (CCS) systems where a dedicated signaling channel is established between the two points for efficient and direct communication.

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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
CCITT psophometric and C-message are the two principle weighting characteristics used in telecommunication circuit noise. CCITT psophometric is a standardized measurement that evaluates the subjective annoyance caused by noise in telecommunication systems. C-message is a weighting characteristic that takes into account the frequency response of the human ear and is used to measure the overall loudness of speech signals. These weighting characteristics are important in assessing and quantifying the impact of noise in telecommunication circuits.

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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
Synchronization ensures that the receive equipment can find its place in the bit stream. This means that the timing of the receive equipment is properly aligned with the incoming bits so that it can accurately interpret and process the data. Without synchronization, the receive equipment may struggle to identify the start and end points of each bit, leading to errors in the data transmission.

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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
Latency is the term associated with the delay or lag introduced in the application of voltage from one section to the next. It refers to the time it takes for a signal to travel from its source to its destination. In the context of this question, latency is the most appropriate term as it directly relates to the delay in voltage application. The other options, phase delay, propagation constant, and phase delay distortion, are not as directly related to the delay in voltage application as latency is.

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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.

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• Current Version
• Mar 18, 2023
Quiz Edited by
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• Nov 03, 2011
Quiz Created by
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