# CDC 3D152 Ure Volume 1

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Questions and Answers
• 1.

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

• A.

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

• B.

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

• C.

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

• D.

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

Correct Answer
D. D. Pulse code modulation (PCM) and continuously variable slope delta (CVSD) modulation.
Explanation
Analog-to-digital (ADC) and digital-to-analog (DAC) techniques are used to convert signals between analog and digital formats. Pulse code modulation (PCM) is an example of ADC, where analog signals are sampled and quantized to discrete digital values. Continuously variable slope delta (CVSD) modulation is an example of DAC, where digital values are converted back to analog signals by varying the slope of a waveform. Therefore, option D is the correct answer as it includes examples of both ADC and DAC techniques.

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• 2.

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

• A.

A. Delta modulation (DM).

• B.

B. Digital modulation.

• C.

C. Analog modulation.

• D.

D. Adaptive modulation.

Correct Answer
C. C. Analog modulation.
Explanation
Analog modulation converts analog signal information into an analog carrier signal. This process involves varying the amplitude, frequency, or phase of the carrier signal in accordance with the analog signal to be transmitted. Delta modulation (DM) is a form of digital modulation, not analog modulation. Digital modulation involves converting analog signal information into a digital format before transmission. Adaptive modulation is a technique used to dynamically adjust the modulation scheme based on channel conditions, but it does not directly convert analog signal information into an analog carrier signal. Therefore, the correct answer is C. Analog modulation.

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• 3.

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

• A.

A. Delta modulation (DM).

• B.

B. Analog modulation.

• C.

C. Digital modulation.

• D.

D. Adaptive modulation.

Correct Answer
C. C. Digital modulation.
Explanation
Digital modulation is the process of converting analog signal information into a digital carrier signal. This is done by encoding the analog signal into a series of discrete digital symbols, which can then be transmitted over a digital communication system. Digital modulation techniques, such as amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK), are commonly used for this purpose. These techniques allow for efficient and reliable transmission of digital information over various types of communication channels.

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• 4.

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

• A.

A. sidebands.

• B.

B. sine waves.

• C.

C. frequency translators.

• D.

D. modulating frequencies.

Correct Answer
A. A. sidebands.
Explanation
The correct answer is A. sidebands. Sidebands are the information-carrying components that occur on either side of a carrier signal. In modulation, the carrier signal is modified by adding or subtracting frequencies to transmit information. These modified frequencies are known as sidebands, and they contain the actual data being transmitted.

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• 5.

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

• A.

A. twice that of the modulating signal.

• B.

B. half that of the modulating signal.

• C.

C. twice that of the carrier signal.

• D.

D. half that of the carrier signal.

Correct Answer
A. A. twice that of the modulating signal.
Explanation
In amplitude modulation (AM), the bandwidth required is twice that of the modulating signal. This is because in AM, the modulating signal is used to vary the amplitude of the carrier signal, resulting in the creation of two sidebands above and below the carrier frequency. These sidebands contain the information from the modulating signal, and together they occupy a bandwidth that is twice the frequency range of the modulating signal. Therefore, option A is the correct answer.

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• 6.

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

• A.

A. filtering.

• B.

B. detection.

• C.

C. compression.

• D.

D. companding.

Correct Answer
A. A. filtering.
Explanation
The upper sideband in a single-sideband suppressed carrier (SSBSC) modulation is eliminated by filtering. In SSBSC modulation, only one sideband is transmitted, while the carrier and the other sideband are suppressed. To achieve this, a filter is used to remove the unwanted sideband, allowing only the desired sideband to pass through. Filtering is an effective method to eliminate the upper sideband and ensure that only the necessary signal is transmitted.

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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.

A. 2 decibels (dB) of improvement.

• B.

B. 4 dB of improvement.

• C.

C. 6 dB of improvement.

• D.

D. 8 dB of improvement.

Correct Answer
D. D. 8 dB of improvement.
• 8.

### The only basic waveform in nature is a

• A.

A. carrier wave.

• B.

B. pure sine wave.

• C.

C. resultant wave.

• D.

D. composite wave.

Correct Answer
B. B. pure sine wave.
Explanation
The correct answer is B. pure sine wave. A pure sine wave is considered the only basic waveform in nature because it represents the simplest form of oscillation. It is a smooth, continuous waveform that has only one frequency and no harmonics. Other waveforms, such as square waves or sawtooth waves, can be created by combining multiple sine waves of different frequencies and amplitudes. However, a pure sine wave is the fundamental building block for all other waveforms and is commonly found in natural phenomena such as sound waves and electromagnetic waves.

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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. a phase modulation (PM).

• B.

B. a pulse modulation.

• C.

C. a frequency modulation (FM).

• D.

D. an amplitude modulation (AM).

Correct Answer
D. D. an amplitude modulation (AM).
Explanation
An amplitude modulation (AM) waveform consists of a carrier signal that is modulated by varying its amplitude according to the input signal. The modulation process creates two sidebands, one above and one below the carrier frequency, each containing a copy of the original input signal. Therefore, a modulated waveform that contains a carrier plus two sidebands for each modulation frequency is a description of an amplitude modulation (AM).

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• 10.

### 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.

A. Transmitted intelligence.

• B.

B. Intensity of speech.

• C.

C. Composite waves.

• D.

D. Splatter.

Correct Answer
D. D. Splatter.
Explanation
When the modulation exceeds 100 percent and there is distortion in the modulating signal, additional sidebands are generated. These additional sidebands are known as "splatter". Splatter refers to the unwanted and excessive sidebands that can cause interference and distortion in the transmitted signal.

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• 11.

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

• A.

A. phase.

• B.

B. amplitude.

• C.

C. frequency.

• D.

D. amplitude and frequency.

Correct Answer
C. C. frequency.
Explanation
The amount of deviation in a frequency modulation (FM) signal is directly proportional to the modulating signal's frequency. In FM, the frequency of the carrier signal is varied according to the amplitude of the modulating signal. The higher the frequency of the modulating signal, the greater the deviation in the carrier signal's frequency. Therefore, the correct answer is C. frequency.

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• 12.

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

• A.

A. modulation index.

• B.

B. rate of phase shift.

• C.

C. frequency of the modulating signal.

• D.

D. amplitude of the modulating signal.

Correct Answer
D. D. amplitude of the modulating signal.
Explanation
The amount of phase shift in a phase modulation (PM) signal is directly proportional to the amplitude of the modulating signal. In phase modulation, the phase of the carrier signal is varied according to the amplitude of the modulating signal. A larger amplitude of the modulating signal will result in a larger phase shift of the carrier signal. Therefore, the amplitude of the modulating signal directly affects the amount of phase shift in a PM signal.

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• 13.

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

• A.

A. Delta

• B.

B. Frequency shift keying (FSK).

• C.

C. Pulse-amplitude modulation (PAM).

• D.

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

Correct Answer
D. D. Binary-phase sift keying or bi-phase shift keying (BPSK).
Explanation
Binary-phase shift keying (BPSK) is insensitive to signal variations because it only has two phases, 0 and 180 degrees. This means that the signal can only have two possible values, which makes it less susceptible to variations in the signal. Other forms of modulation, such as delta modulation, FSK, and PAM, are more sensitive to signal variations as they have multiple possible values or levels for the signal. Therefore, BPSK is the modulation technique that is least affected by signal variations.

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• 14.

### 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.

A. four times.

• B.

B. double.

• C.

C. half.

• D.

D. the same.

Correct Answer
C. C. half.
Explanation
In quadrature-phase shift keying (QPSK), the quadriphase signal carries two bits of information per symbol, while the bi-phase signal carries only one bit of information per symbol. Therefore, the quadriphase signal can transmit the same amount of data in half the time compared to the bi-phase signal. As a result, the RF bandwidth required for the quadriphase signal is half of that required by the bi-phase signal.

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• 15.

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

• A.

A. Carrier presence is required to detect changes.

• B.

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

• C.

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

• D.

D. The demodulator needs to detect changes in absolute phase values.

Correct Answer
B. 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. Unlike PSK, DPSK does not require the receiver to detect changes in absolute phase values, which simplifies the receiver design. Instead, DPSK only requires the receiver to detect changes in the relative phase between consecutive symbols, making it more robust to phase variations caused by noise or channel impairments. This simplicity in receiver design makes DPSK a practical choice for communication systems where complexity and cost are important factors.

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• 16.

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

• A.

A. pulse-amplitude modulation (PAM).

• B.

B. pulse-duration modulation (PDM).

• C.

C. pulse-position modulation (PPM).

• D.

D. pulse-code modulation (PCM).

Correct Answer
D. D. pulse-code modulation (PCM).
Explanation
Pulse-code modulation (PCM) is not considered an analog modulation technique because it is a digital modulation technique. In PCM, the analog signal is sampled at regular intervals and each sample is quantized into a digital code. These digital codes represent the amplitude of the original analog signal at each sampling point. Therefore, PCM is a digital technique that converts analog signals into digital form for transmission or storage. On the other hand, pulse-amplitude modulation (PAM), pulse-duration modulation (PDM), and pulse-position modulation (PPM) are all analog modulation techniques where the amplitude, duration, or position of pulses are varied to represent the analog signal.

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• 17.

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

• A.

A. pulse-amplitude modulation (PAM).

• B.

B. pulse-duration modulation (PDM).

• C.

C. pulse-position modulation (PPM).

• D.

D. pulse-code modulation (PCM).

Correct Answer
C. C. pulse-position 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 of the pulse is used to encode information. The position of the pulse represents different values or symbols, allowing for the transmission of data. It is commonly used in communication systems to transmit analog or digital signals.

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• 18.

### Quantized analog modulation is actually

• A.

A. pulse-amplitude modulation (PAM).

• B.

B. pulse-duration modulation (PDM).

• C.

C. less tolerant of noise than frequency modulation (FM).

• D.

D. analog-to-digital conversion.

Correct Answer
A. A. pulse-amplitude modulation (PAM).
Explanation
Quantized analog modulation refers to the process of converting continuous analog signals into discrete pulses. Pulse-amplitude modulation (PAM) is a form of quantized analog modulation where the amplitude of the pulses represents the analog signal. Therefore, the correct answer is A. pulse-amplitude modulation (PAM).

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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.

A. 3.

• B.

B. 4.

• C.

C. 5.

• D.

D. 8.

Correct Answer
B. B. 4.
Explanation
In a 16-step pulse-code modulation (PCM) system, each quantized analog sample is described using 4 bits per character. This means that there are 16 possible quantized levels that can be represented by the 4 bits. Each bit can have two possible values (0 or 1), so with 4 bits, there are 2^4 = 16 possible combinations, allowing for the representation of 16 different levels. Therefore, the correct answer is B. 4.

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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.

A. encoding.

• B.

B. companding.

• C.

C. uniform quantizing.

• D.

D. nonuniform quantizing.

Correct Answer
A. A. encoding.
Explanation
The process described in the question involves taking the quantized pulses of pulse code modulation (PCM) and coding them to have a constant duration and amplitude. This process is known as encoding, which is the conversion of information into a specific format for transmission or storage. The other options, companding, uniform quantizing, and nonuniform quantizing, do not accurately describe the process of making the pulses a constant duration and amplitude.

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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.

A. channel.

• B.

B. trunk.

• C.

C. time slot.

• D.

D. port.

Correct Answer
C. C. time slot.
Explanation
In Time Division Multiplexing (TDM), the transmitting multiplexer allocates a specific time slot for each of the incoming lines. This means that each line gets a designated period of time during which its bit or byte is transmitted. This allows multiple signals to be transmitted over a single channel by dividing the available time into smaller slots. Therefore, the correct answer is C. time slot.

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• 22.

### The two major types of frame structures are

• A.

A. low speed and high speed.

• B.

B. high speed and EBCDIC.

• C.

C. CCITT and low speed.

• D.

D. EBCDIC and CCITT.

Correct Answer
C. C. CCITT and low speed.
Explanation
The correct answer is C. CCITT and low speed. CCITT stands for International Telegraph and Telephone Consultative Committee, which is an organization that sets international standards for telecommunications. Low speed refers to slower data transmission rates. Therefore, the two major types of frame structures are CCITT, which represents the standard, and low speed, which represents the slower data transmission rates.

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• 23.

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

• A.

A. frequency division.

• B.

B. binary division.

• C.

C. pulse division.

• D.

D. time division.

Correct Answer
D. D. time division.
Explanation
The method of multiplexing used by the T1 multiplexer is time division. Time division multiplexing involves dividing the available bandwidth into time slots and assigning each input a specific time slot to transmit its data. In the case of T1 multiplexing, multiple T1 lines are combined into a single high-speed line by allocating each T1 line a specific time slot. This allows multiple signals to be transmitted simultaneously over a single transmission medium by taking turns using the available time slots.

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• 24.

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

• A.

A. wavelengths or lambdas.

• B.

B. wavelengths or gammas.

• C.

C. frequencies or lambdas.

• D.

D. frequencies or gammas.

Correct Answer
A. A. wavelengths or lambdas.
Explanation
Wave-division multiplexing (WDM) is a technique used in optical communication systems to combine multiple signals onto a single optical fiber. It works by using different wavelengths or lambdas to create virtual channels for multiplexing. Each signal is assigned a specific wavelength or lambda, and these signals are then combined and transmitted over the same fiber. Therefore, option A, wavelengths or lambdas, is the correct answer as it accurately describes the method used in WDM.

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• 25.

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

• A.

A. One wavelength.

• B.

B. Two wavelengths.

• C.

C. Three wavelengths.

• D.

D. Four wavelengths.

Correct Answer
B. B. Two wavelengths.
Explanation
The most common wave-division multiplexing (WDM) system uses two wavelengths. WDM is a technique used in optical fiber communication to increase the capacity of the network by transmitting multiple signals simultaneously using different wavelengths of light. By using two wavelengths, the system can transmit two separate signals over the same fiber optic cable, effectively doubling the capacity of the network.

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• 26.

### Individual pulses within a digital signal are

• A.

A. bits.

• B.

B. bytes.

• C.

C. codes.

• D.

D. blocks.

Correct Answer
A. A. bits.
Explanation
Individual pulses within a digital signal are represented as bits. In digital communication, a bit is the smallest unit of information and can have two possible values, either a 0 or a 1. These bits are used to encode and transmit data in a digital signal. Each pulse within the signal represents a single bit, allowing for the transmission and storage of binary information. Therefore, option A is the correct answer.

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• 27.

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

• A.

A. Baud.

• B.

B. Baudot.

• C.

C. Sense interface.

• D.

D. Bits per second.

Correct Answer
D. D. Bits per second.
Explanation
The most commonly used unit in data systems to express signaling speed is bits per second. This unit measures the number of bits that can be transmitted or processed in one second. Baud, Baudot, and sense interface are not units used to express signaling speed in data systems.

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• 28.

### Bit count integrity problems are primarily caused by

• A.

A. impedance mismatch.

• B.

B. system timing faults.

• C.

C. improper equipment settings.

• D.

D. changes in atmospheric conditions.

Correct Answer
B. B. system timing faults.
Explanation
Bit count integrity problems are primarily caused by system timing faults. This refers to issues with the synchronization and timing of signals within a system. When the timing is not accurate, it can lead to errors in counting or tracking the number of bits being transmitted or received. This can result in data corruption or loss, impacting the integrity of the bit count. Impedance mismatch, improper equipment settings, and changes in atmospheric conditions may cause other types of communication problems, but they are not directly related to bit count integrity.

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• 29.

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

• A.

A. synchronous, asynchronous, and isochronous.

• B.

B. isochronous, asynchronous, bisynchronous.

• C.

C. nonsynchronous, bisynchronous, and synchronous.

• D.

D. asynchronous, bisynchronous, and nonsynchronous.

Correct Answer
A. A. synchronous, asynchronous, and isochronous.
Explanation
The correct answer is A. synchronous, asynchronous, and isochronous.

Synchronous synchronization refers to data transmission where the sender and receiver are synchronized with a common clock signal. Asynchronous synchronization refers to data transmission where the sender and receiver are not synchronized with a common clock signal, and instead, each data unit is accompanied by start and stop bits. Isochronous synchronization refers to data transmission where the sender and receiver are synchronized with a common clock signal, but the timing is not as strict as in synchronous synchronization.

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• 30.

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

• A.

A. Timing pulses are transmitted within the signal stream.

• B.

B. Start and stop pulses control data transmission.

• C.

C. System timing is not of critical importance.

• D.

D. All data bits are the same length in time.

Correct Answer
D. 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 in the data stream is transmitted for the same amount of time, ensuring that the receiver can accurately interpret the data. This is in contrast to asynchronous data operation, where the length of each bit can vary. By having all data bits the same length, synchronous data operation allows for more precise timing and synchronization between the sender and receiver.

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• 31.

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

• A.

A. synchronous operation.

• B.

B. asynchronous operation.

• C.

C. synchronous and/or isochronous operation.

• D.

D. asynchronous and/or synchronous operation.

Correct Answer
B. B. asynchronous operation.
Explanation
A digital signal that contains synchronizing bits within the signal stream describes asynchronous operation. Synchronizing bits are used to maintain timing and synchronization between the sender and receiver in asynchronous communication. Asynchronous operation does not rely on a fixed clock signal and allows for variable timing between data transmissions. This is in contrast to synchronous operation, where data is transmitted in a fixed and synchronized manner.

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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.

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

• B.

B. Non-return-to-zero mark.

• C.

C. Non-return-to-zero space.

• D.

D. Return-to-zero level.

Correct Answer
B. B. Non-return-to-zero mark.
Explanation
In a non-return-to-zero mark (NRZ-M) signal, the information is contained in the transition from one state to the other only when a mark bit is sent. In NRZ-M, a high level represents a mark (1) and a low level represents a space (0). The transition from a low level to a high level indicates the start of a mark bit, and this transition carries the information. The absence of a transition indicates a space bit. Therefore, the correct answer is B. Non-return-to-zero mark.

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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.

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

• B.

B. Non-return-to-zero mark.

• C.

C. Non-return-to-zero space.

• D.

D. Return-to-zero.

Correct Answer
D. 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 a high level and a low level, with the low level representing zero. This type of signal is commonly used in digital communication systems to represent binary data, where the high level represents a binary 1 and the low level represents a binary 0.

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• 34.

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

• A.

A. The information is transmitted in three different voltage levels.

• B.

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

• C.

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

• D.

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

Correct Answer
B. B. A logic one is transmitted as positive voltage if the previous logic one was negative.
Explanation
An alternate mark inversion (AMI) signal is a type of line code used in telecommunications to transmit digital data. In AMI, a logic one is transmitted as a positive voltage if the previous logic one was negative. This helps in ensuring that there is a balance between positive and negative voltages, preventing the loss of synchronization and allowing the receiver to accurately interpret the data. The other options are not accurate descriptions of AMI.

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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.

A. provide error-free signaling.

• B.

B. operate at higher data rates.

• C.

C. eliminate bipolar violations.

• D.

D. maintain ones density standards.

Correct Answer
D. D. maintain ones density standards.
Explanation
Digital coding techniques such as binary with eight-zero substitution (B8ZS) are becoming more popular because they are designed to maintain ones density standards. This means that they ensure a balanced number of ones and zeros in the data stream, which is important for efficient data transmission. By maintaining ones density standards, B8ZS helps to avoid long strings of consecutive zeros or ones, which can cause synchronization issues and reduce the accuracy of data transmission.

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• 36.

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

• A.

A. The information is transmitted in three different voltage levels.

• B.

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

• C.

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

• D.

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

Correct Answer
D. D. Bipolar violations are intentionally inserted into a data signal to break up long strings of zeros.
Explanation
B8ZS is a line code used in telecommunications to ensure that long sequences of zeros are not transmitted. It accomplishes this by intentionally inserting bipolar violations into the data signal. This means that instead of transmitting a string of zeros, the signal is modified to include alternating positive and negative voltage levels. By doing so, B8ZS prevents synchronization problems that can occur when a receiver encounters long sequences of zeros.

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• 37.

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

• A.

A. lack of mid-bit transitions.

• B.

B. use of mid-bit transitions for timing.

• C.

C. data being encoded in the mid-bit transitions.

• D.

D. voltage levels used for signaling the mid-bit transitions.

Correct Answer
B. B. use of mid-bit transitions for timing.
Explanation
Conditioned di-phase (CDI) is a scheme that uses 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 in the timing of these transitions rather than in the voltage levels used for signaling them. The lack of mid-bit transitions (option A) would not be a characteristic of CDI, as it relies on them for timing. Similarly, option C and D are incorrect as they do not accurately describe the major difference between CDI and other schemes.

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• 38.

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

• A.

A. 8.

• B.

B. 12.

• C.

C. 24.

• D.

D. 48

Correct Answer
B. B. 12.
Explanation
The D4 framing sequence is a specific pattern used in T1 digital transmission systems to maintain synchronization between the transmitter and receiver. It consists of 12 bits, which are used to identify the beginning of each frame. This allows the receiver to properly interpret the incoming data and ensure accurate transmission. Therefore, the correct answer is B. 12.

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• 39.

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

• A.

A. 8.

• B.

B. 12.

• C.

C. 24.

• D.

D. 48.

Correct Answer
C. 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.

A. Pulse dialing.

• B.

B. Tone dialing.

• C.

C. Digit dialing.

• D.

D. Address dialing.

Correct Answer
B. 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 is associated with a specific combination of two frequencies. When a number is dialed, the keypad generates these frequencies, which are then transmitted through the telephone line to the receiving end. 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 specific control signals and do not involve a two-frequency combination.

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• 41.

### What communications information signal uses a continuous 350-Hz and 44-Hz frequency pair?

• A.

A. Dial tone.

• B.

B. Ringback signal.

• C.

C. Off-hook alert.

• D.

D. Call waiting.

Correct Answer
A. A. Dial tone.
Explanation
A dial tone is a continuous signal that is used to indicate that a telephone line is active and ready to make a call. It is a specific frequency pair of 350 Hz and 440 Hz. When a person picks up the phone and hears a dial tone, it means they can start dialing a phone number. Therefore, the correct answer is A. Dial tone.

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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-Hz and 620-Hz frequency pair?

• A.

A. Dial tone.

• B.

B. Busy signal.

• C.

C. Off-hook alert.

• D.

D. Call waiting.

Correct Answer
B. B. Busy signal.
Explanation
A busy signal is a communication information signal that is cycled on and off for 0.5 second. It is used to indicate that the line is currently busy and cannot accept another call. The generation of a 480-Hz and 620-Hz frequency pair is characteristic of a busy signal.

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• 43.

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

• A.

A. Record warning.

• B.

B. Fast busy signal.

• C.

C. Loop-start.

• D.

D. E and M.

Correct Answer
C. C. Loop-start.
Explanation
Loop-start is a communications supervisory signal that uses a continuous application of direct current voltage for signaling. This signal is commonly used in telephone systems to indicate the start of a call. When a loop-start signal is applied, it signifies that the telephone line is in an idle state and ready to receive or initiate a call. This continuous direct current voltage is used to monitor the status of the line and initiate call setup procedures.

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• 44.

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

• A.

A. When dial tone is present.

• B.

B. On-hook condition.

• C.

C. Off-hook condition.

• D.

D. During the ringback signal.

Correct Answer
C. C. Off-hook condition.
Explanation
In loop-start signaling, the voltage is applied when the telephone handset is off-hook, meaning that the user has lifted the handset and is ready to make or receive a call. This is because when the handset is off-hook, the telephone line is connected and ready for communication. The voltage is used to signal the central office that the user wants to initiate a call or answer an incoming call.

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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.

A. Bit robbing.

• B.

B. Bit stuffing.

• C.

C. Frame correction.

• D.

D. Frame enhancement.

Correct Answer
A. 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 in order to transmit signaling information. This technique allows for the transmission of additional information without requiring additional 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.

A. Associated mode.

• B.

B. Nonassociated mode.

• C.

C. Quasi-associated mode.

• D.

D. Multi-associated mode.

Correct Answer
A. A. Associated mode.
Explanation
In associated mode of common channel signaling (CCS), the messages relating to signaling between two points are conveyed directly interconnecting these signaling points. This means that the signaling messages are sent directly from one signaling point to another without any intermediate signaling points or network elements involved. This mode is commonly used in scenarios where there is a direct connection between the signaling points, such as in a point-to-point communication setup.

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• 47.

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

• A.

A. Institute of Electronic and Electrical Engineers and CCITT psophometric.

• B.

B. Noise analysis and CCITT psophometric.

• C.

C. CCITT psophometric and C-message.

• D.

D. C-message and noise analysis.

Correct Answer
C. C. CCITT psophometric and C-message.
Explanation
The two principle weighting characteristics in use with telecommunication circuit noise are CCITT psophometric and C-message. CCITT psophometric is a standard that measures noise levels in telecommunication circuits, taking into account the human ear's sensitivity to different frequencies. C-message is a weighting characteristic that is used to measure noise levels in telecommunication circuits, specifically for speech transmission. Together, these two weighting characteristics help in accurately measuring and evaluating noise levels 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.

A. receive equipment timing is set properly.

• B.

B. transmit equipment timing is set properly.

• C.

C. receive equipment can find its place in the bit stream.

• D.

D. transmit equipment can find its place in the bit stream.

Correct Answer
C. 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 receive equipment is able to accurately determine the start and end of each bit, allowing it to properly decode and interpret the incoming data. Without synchronization, the receive equipment would not be able to correctly identify the boundaries between bits, 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.

A. Latency.

• B.

B. Phase delay.

• C.

C. Propagation constant.

• D.

D. Phase delay distortion.

Correct Answer
A. A. Latency.
Explanation
Latency refers to the delay or lag introduced in the application of voltage from one section to the next. It is commonly used in the context of data transmission or signal processing, where it represents the time it takes for a signal to travel from its source to its destination. In this case, latency is the most appropriate term associated with the delay or lag in voltage application.

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• 50.

### Attenuation distortion is caused by

• A.

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

• B.

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

• C.

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

• D.

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

Correct Answer
D. D. differing attenuation rates for the various frequency components comprising a voice frequency transmission.
Explanation
Attenuation distortion refers to the loss of signal strength as it travels through a transmission medium. The correct answer, D, states that attenuation distortion is caused by differing attenuation rates for the various frequency components comprising a voice frequency transmission. This means that different frequencies within a voice transmission experience different levels of signal loss, leading to distortion in the received signal. The other options (A, B, and C) mention factors such as line loss, distance of transmission lines, faults in transmission cables, and number of splices, but they do not specifically address the varying attenuation rates as the cause of attenuation distortion.

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