3D152 Vol. 1 Unit Review Exercises

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3D152 Quizzes & Trivia

Questions and Answers
  • 1. 

    What is an examplel 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

    Correct Answer
    D. Pulse code modulation (PCM) and continuously variable slope delta (CVSD) modulation
    Explanation
    Pulse code modulation (PCM) and continuously variable slope delta (CVSD) modulation are examples of analog-to-digital and digital-to-analog techniques. PCM is a method of converting analog signals into digital signals by sampling the amplitude of the signal at regular intervals. CVSD modulation is a technique that converts analog signals into digital signals by encoding the changes in the slope of the signal. Both techniques involve the conversion of analog signals to digital signals and vice versa, making them examples of analog-to-digital and digital-to-analog techniques.

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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.

      Adaptive modulation

    Correct Answer
    C. Analog modulation
    Explanation
    Analog modulation is the process of converting analog signal information into an analog carrier signal. This is achieved by varying one or more of the characteristics of the carrier signal, such as amplitude, frequency, or phase, in accordance with the input analog signal. By doing so, the analog signal is superimposed onto the carrier signal, allowing for the transmission of the original analog information over a communication channel.

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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.

      Adaptive modulation

    Correct Answer
    C. Digital modulation
    Explanation
    Digital modulation is the process of converting analog signal information into a digital carrier signal. This involves 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 to achieve this conversion. These techniques allow for efficient and reliable transmission of digital data over long distances, and are widely used in modern communication systems.

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  • 4. 

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

    • A.

      Sidebands

    • B.

      Sine waves

    • C.

      Frequency translators

    • D.

      Modulating frequencies

    Correct Answer
    A. Sidebands
    Explanation
    Sidebands are the information-carrying components that occur on either side of a carrier. In a modulated signal, the carrier wave is modified by adding or subtracting frequencies, resulting in the creation of sidebands. These sidebands contain the actual information being transmitted, while the carrier wave simply serves as a reference for the transmission. Therefore, sidebands accurately describe the components that occur on either side of a carrier.

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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.

    Correct Answer
    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 used to vary the amplitude of the carrier signal. The modulating signal contains the information to be transmitted, and its bandwidth determines the range of frequencies needed to accurately represent that information. Since the modulating signal is used to modulate the carrier signal, the bandwidth of the AM signal must be able to accommodate the highest frequency components of the modulating signal, which requires a bandwidth that is twice as wide.

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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.

    Correct Answer
    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 blocking or attenuating others. In the case of SSBSC modulation, a filter is used to remove the upper sideband, leaving only the lower sideband and the carrier signal. This filtering process helps in reducing bandwidth requirements and improving the efficiency of transmission.

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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.

    Correct Answer
    D. 8 dB of improvement.
    Explanation
    The improvement of SSBSC modulation over AM can be expressed in terms of decibels (dB). Since the question states that the improvement is 6-to-1, it means that the power ratio of SSBSC to AM is 6:1. To convert this power ratio into decibels, we use the formula: dB = 10 * log10(power ratio). Plugging in the values, we get dB = 10 * log10(6/1) = 10 * log10(6) ≈ 7.78 dB. Since we are looking for the closest option, the correct answer is 8 dB 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.

    Correct Answer
    B. Pure sine wave.
    Explanation
    A pure sine wave is the only basic waveform in nature because it represents a single frequency without any harmonics or distortions. It is a smooth, continuous waveform that is commonly found in natural phenomena such as sound waves, electromagnetic waves, and vibrations. Other waveforms, such as composite waves, are made up of multiple frequencies and can be created by combining different sine waves. Therefore, a pure sine wave is the most fundamental and simplest waveform in nature.

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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).

    Correct Answer
    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 instantaneous amplitude of the modulating signal. This results in the creation of two sidebands, one above and one below the carrier frequency, each containing a copy of the modulating signal. Therefore, an AM waveform fits the given description.

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  • 10. 

    If 100 percen 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

    Correct Answer
    D. Splatter
    Explanation
    When the modulation signal exceeds 100 percent and distortion occurs, additional sidebands are generated. These additional sidebands are identified as "splatter." Splatter refers to 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.

      Phase.

    • B.

      Amplitude.

    • C.

      Frequency.

    • D.

      Amplitude and frequency.

    Correct Answer
    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 changes in the modulating signal. The greater the frequency of the modulating signal, the greater the deviation in the carrier signal's frequency. This means that the amplitude and phase of the modulating signal do not directly affect the amount of deviation in the FM signal.

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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.

    Correct Answer
    B. Rate of phase shift.
    Explanation
    In phase modulation (PM), the amount of phase shift in the signal is directly proportional to the rate of phase shift. This means that the rate at which the phase of the signal changes is directly related to the amount of phase shift in the PM signal. The modulation index, frequency of the modulating signal, and amplitude of the modulating signal do not directly determine the amount of phase shift in the PM signal. Therefore, the correct answer is the rate of phase shift.

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

    Correct Answer
    D. Binary-phase shift keying or bi-phase shift keying (BPSK)
    Explanation
    Binary-phase shift keying or bi-phase shift keying (BPSK) is insensitive to signal variations because it uses a single carrier frequency and shifts the phase of the carrier signal to represent the binary data. It does not rely on variations in signal frequency or amplitude to transmit information. Therefore, BPSK is not affected by signal variations such as changes in frequency or amplitude, making it a robust modulation technique.

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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.

      Four times

    • B.

      Double

    • C.

      Half

    • D.

      The same

    Correct Answer
    B. Double
    Explanation
    In quadrature-phase shift keying (QPSK), the quadriphase signal carries twice as much information as a bi-phase signal at the same data rate. This means that the quadriphase signal requires a larger bandwidth to transmit the same amount of data. Therefore, the RF bandwidth for a quadriphase signal is double that required by a bi-phase signal.

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  • 15. 

    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.

    Correct Answer
    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 compared to basic phase shift keying (PSK) signals. In DPSK, the receiver only needs to detect changes in the relative phase between consecutive symbols, rather than detecting absolute phase values. This simplifies the receiver design and reduces its complexity.

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  • 16. 

    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)

    Correct Answer
    D. Pulse-code modulation (PCM)
    Explanation
    PCM is not considered an analog modulation technique because it is a digital modulation technique. Analog modulation techniques involve encoding analog signals onto a carrier wave, while PCM involves digitizing the analog signal into a series of binary numbers. PCM is commonly used in digital communication systems for transmitting and storing analog signals in a digital format.

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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)

    Correct Answer
    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 amplitude and duration of the pulse remain constant, but the position of the pulse within a time slot is changed to represent different information. This allows for efficient use of the available bandwidth and enables the transmission of multiple signals simultaneously. PPM is commonly used in applications where timing accuracy is critical, such as in radar and communication systems.

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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

    Correct Answer
    C. Less tolerant of noise than frequency modulation (FM)
    Explanation
    Quantized analog modulation refers to the process of converting continuous analog signals into discrete levels. This type of modulation, such as pulse-amplitude modulation (PAM) or pulse-duration modulation (PDM), is known to be less tolerant of noise compared to frequency modulation (FM). This is because quantization introduces errors and distortions in the signal, making it more susceptible to noise interference. FM, on the other hand, varies the frequency of the carrier signal, allowing for better noise immunity and hence being more tolerant of noise.

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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

    Correct Answer
    B. 4
    Explanation
    In a 16-step PCM system, there are 16 possible quantized analog samples. To describe these samples, each sample needs to be represented using a certain number of bits. Since there are 16 possible samples, the number of bits needed to represent them can be determined by finding the smallest power of 2 that is greater than or equal to 16. In this case, the smallest power of 2 greater than or equal to 16 is 2^4, which is 16. Therefore, 4 bits per character are used to describe the quantized analog sample in a 16-step PCM system.

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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

    Correct Answer
    A. Encoding
    Explanation
    The process of coding pulse code modulation (PCM) quantized pulses to make them a constant duration and amplitude is encoding. This involves converting the analog signal into a digital format by assigning specific codes to each sample of the signal. The encoding process ensures that the quantized pulses maintain a consistent duration and amplitude, allowing for accurate transmission and reconstruction of the original signal.

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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

    Correct Answer
    C. Time slot
    Explanation
    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 time slot. This time slot is a designated portion of the overall transmission time that is assigned to each individual line. By allocating a specific time slot for each line, TDM ensures that multiple signals can be transmitted simultaneously over a single communication channel without interference.

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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

    Correct Answer
    C. CCITT and low speed
    Explanation
    The correct answer is CCITT and low speed. CCITT (International Telegraph and Telephone Consultative Committee) is a standard organization that develops recommendations for telecommunication systems. Low speed refers to slower data transmission rates. Therefore, the two major types of frame structures are CCITT, which represents a standard, and low speed, which represents the slower data transmission rate.

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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

    Correct Answer
    D. Time division
    Explanation
    The method of multiplexing used by the T1 multiplexer is time division. Time division multiplexing involves dividing the available transmission time into multiple time slots and assigning each slot to a different input signal. In the case of T1 multiplexing, the time slots are used to combine multiple voice or data channels into a single high-speed transmission line. This allows for efficient utilization of the available bandwidth and simultaneous transmission of multiple signals over a single line.

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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

    Correct Answer
    A. Wavelengths or lambdas
    Explanation
    Wavelength-division multiplexing (WDM) is a technology that combines multiple optical signals onto a single optical fiber by assigning each signal a different wavelength or lambda. This allows for the transmission of multiple channels of data simultaneously. The correct answer is "wavelengths or lambdas" because WDM uses different wavelengths or lambdas to create virtual channels and multiplex them together for transmission. Frequencies or gammas are not used in WDM.

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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

    Correct Answer
    B. Two wavelengths
    Explanation
    The most common wave-division multiplexing (WDM) system uses two wavelengths. WDM is a technique that allows multiple optical signals to be transmitted simultaneously over a single fiber optic cable. Each signal is assigned a different wavelength, and these wavelengths are combined and transmitted together. By using two wavelengths, the WDM system can effectively double the capacity of the fiber optic cable, allowing for more data to be transmitted at the same time.

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  • 26. 

    Individual pulses within a digital signal are

    • A.

      Bits

    • B.

      Bytes

    • C.

      Codes

    • D.

      Blocks

    Correct Answer
    A. Bits
    Explanation
    Individual pulses within a digital signal are referred to as bits. In digital communication, information is represented using binary digits or bits, which can have a value of either 0 or 1. These bits are used to encode and transmit data in the form of electrical or optical pulses. Each pulse represents a single bit, and the sequence of these bits forms the digital signal. Therefore, the correct answer is bits.

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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

    Correct Answer
    D. Bits per second
    Explanation
    The unit most commonly used in data systems to express signaling speed is "bits per second". Baud is a unit used to measure the number of signal changes per second, but it does not directly correspond to the number of bits transmitted. Baudot is a character encoding scheme used in telegraphy, not a unit of signaling speed. Sense interface is not a commonly used unit in data systems.

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  • 28. 

    Bit count integrity problems are primarily cause by

    • A.

      Impedance mismatch

    • B.

      System timing faults

    • C.

      Improper equipment settings

    • D.

      Changes in atmospheric conditions

    Correct Answer
    B. System timing faults
    Explanation
    Bit count integrity problems refer to issues with the accuracy and reliability of counting bits in a system. System timing faults can cause these problems by disrupting the synchronization and timing of the system, leading to errors in counting the bits accurately. This can result in data corruption, loss of information, or incorrect calculations. Impedance mismatch, improper equipment settings, and changes in atmospheric conditions may cause other types of system errors, but they are not directly related to 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

    Correct Answer
    A. Synchronous, asynchronous, and isochronous
    Explanation
    The correct answer is synchronous, asynchronous, and isochronous. Synchronous synchronization means that data is transmitted in fixed time intervals, with a clock signal ensuring that both the sender and receiver are synchronized. Asynchronous synchronization involves transmitting data without a clock signal, instead using start and stop bits to indicate the beginning and end of each data packet. Isochronous synchronization is used for real-time data transmission, where data is transmitted at a constant rate, ensuring that it arrives at the receiver in a timely manner.

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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

    Correct Answer
    D. All data bits are the same length in time
    Explanation
    In synchronous data operation, 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 and synchronize with the data stream. This characteristic allows for efficient and reliable data transmission, as it eliminates the need for complex timing mechanisms or adjustments.

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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

    Correct Answer
    B. Asynchronous operation
    Explanation
    A digital signal that contains synchronizing bits within the signal stream describes asynchronous operation. This means that the signal is not dependent on a common clock or timing mechanism to synchronize the transmission and reception of data. Instead, the synchronizing bits are used to indicate the start and end of each data packet, allowing the receiver to correctly interpret the information. Asynchronous operation is commonly used in serial communication protocols, such as UART, where data is transmitted bit by bit without a fixed clock signal.

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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

    Correct Answer
    A. Non-return-to-zero (NRZ) level
    Explanation
    In Non-return-to-zero (NRZ) level encoding, the information is contained in the transition from one state to another. A transition occurs only when a mark bit is sent. In NRZ level encoding, the signal remains at a constant level for the entire duration of the bit, either high or low, without any return to zero. This type of encoding is commonly used in digital communication systems to transmit binary 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

    Correct Answer
    D. Return-to-zero
    Explanation
    Return-to-zero is the type of signal in which the signal level moves to one of the discrete signal levels, but returns to the zero level after a predetermined time. In this type of signal, the absence of a signal is represented by the zero level, and the presence of a signal is represented by a non-zero level. This allows for easier synchronization and clock recovery, as the signal returns to zero at regular intervals.

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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

    Correct Answer
    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 for transmitting digital data. In this type of signal, a logic one is transmitted as a positive voltage if the previous logic one was negative. This helps in maintaining a balance between positive and negative voltage levels, preventing the accumulation of DC bias. By alternating the polarity of consecutive logic ones, it ensures that the level always returns to zero for 50 percent of the bit cycle after every transition. This helps in synchronization and error detection.

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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.

      Eliminated bipolar violations

    • D.

      Maintain ones density standards

    Correct Answer
    D. Maintain ones density standards
    Explanation
    Digital coding techniques such as binary with eight-zero substitution (B8ZS) are becoming more popular because they maintain ones density standards. Ones density refers to the requirement of having an equal number of positive and negative voltage levels in a digital signal. B8ZS ensures that this requirement is met by substituting a sequence of eight zeros with a special pattern that contains both positive and negative voltage levels. By maintaining ones density, B8ZS helps in reducing the occurrence of bipolar violations and ensures accurate transmission of data, making it an effective technique for high-speed and error-free signaling.

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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

    Correct Answer
    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 strings of zeros are not transmitted. It intentionally inserts bipolar violations into the data signal, which breaks up the long strings of zeros. This helps in maintaining synchronization and prevents loss of signal.

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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

    Correct Answer
    B. Use of mid-bit transitions for timing
    Explanation
    CDI differs from other schemes because it utilizes mid-bit transitions for timing. Unlike other schemes that rely on different factors for timing, CDI specifically uses the mid-bit transitions to determine the timing of the data. This means that the transitions between the two voltage levels during the middle of each bit are crucial for the timing synchronization in CDI.

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  • 38. 

    How many bits are in the D4 framing sequence?

    • A.

      8

    • B.

      12

    • C.

      24

    • D.

      48

    Correct Answer
    A. 8
    Explanation
    The D4 framing sequence consists of 8 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

    Correct Answer
    C. 24
    Explanation
    The extended superframe format (ESF) framing sequence consists of 24 bits. This framing sequence is used in telecommunications to synchronize and frame T1 digital transmission. It helps in the accurate transmission and reception of data by providing a structure for framing and synchronization.

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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.

      Address dialing

    Correct Answer
    B. Tone dialing
    Explanation
    Tone dialing is the correct answer because it uses a two-frequency dialing combination to send signals over a telephone line. Unlike pulse dialing, which uses a series of intermittent pulses, tone dialing uses specific tones for each digit on the telephone keypad. These tones are generated by pressing the buttons on the keypad, and they are then transmitted as a two-frequency signal to the telephone exchange, enabling the call to be connected. This method of dialing is more efficient and accurate compared to pulse dialing.

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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.

      Off-hook alert

    • D.

      Call waiting

    Correct Answer
    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 ready for dialing a number. When a user picks up the phone, they hear the dial tone, indicating that they can start dialing a number. This signal is generated by the telephone company's central office and is used to indicate that the line is active and ready for use.

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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.

      Off-hook alert

    • D.

      Call waiting

    Correct Answer
    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 in use or unavailable. The busy signal also generates a frequency pair of 480 and 620 Hz, which is a characteristic feature of this 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

    Correct Answer
    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. In loop-start signaling, a continuous current is applied to the signaling loop to indicate that the line is in use or off-hook. This type of signaling is commonly used in analog telephone systems to establish and terminate calls.

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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

    Correct Answer
    C. Off-hook condition
    Explanation
    In loop-start signaling, the voltage is applied when the telephone receiver is off-hook. When the receiver is lifted off the hook, it indicates that the user wants to make a call, and the voltage is applied to establish the connection. The off-hook condition is necessary for the voltage to be applied in loop-start signaling.

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  • 45. 

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

    • A.

      Bit robbing

    • B.

      Bit stuffing

    • C.

      Frame correction

    • D.

      Frame enhancement

    Correct Answer
    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 practice of stealing one bit from each byte in a frame to be used for signaling purposes. This technique allows for the transmission of additional information without the need for additional bits or frames.

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  • 46. 

    In what common channel signaling (CSS) 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.

      Mulit-associated mode

    Correct Answer
    A. Associated mode
    Explanation
    In the associated mode of common channel signaling (CSS), the messages related to signaling between two points are conveyed directly through an interconnection between these signaling points. This means that the signaling messages are sent directly from one point to another without any intermediate nodes or routing. This mode is commonly used in telecommunication networks where a direct connection is established between the signaling points involved in the 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

    Correct Answer
    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 standard that measures the subjective annoyance caused by noise in telephone circuits, taking into account the frequency response of the human ear. C-message is a standardized weighting filter that simulates the frequency response of the average human ear. These weighting characteristics are important in analyzing and evaluating noise in telecommunication circuits, as they help to assess the impact of noise on the quality of communication.

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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

    Correct Answer
    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 set properly so that it can accurately detect and interpret the incoming bits. Without synchronization, the receive equipment may struggle to identify the correct starting point of the bit stream, leading to errors in data transmission. By synchronizing the receive equipment, it can effectively locate its position in the bit stream and accurately receive the transmitted data.

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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

    Correct Answer
    C. Propagation constant
    Explanation
    The term "propagation constant" is associated with the delay or lag introduced in the application of voltage from one section to the next. It refers to the rate at which a signal propagates through a medium, taking into account factors such as the speed of the medium and the wavelength of the signal. In the context of this question, the propagation constant represents the delay or lag in the application of voltage as it moves from one section to another.

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  • 50. 

    Attenuation distortion is caused by

    • A.

      A line loss for 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

    Correct Answer
    D. Differing attenuation rates for the various frequency components comprising a voice frequency transmission
    Explanation
    Attenuation distortion refers to the phenomenon where different frequency components of a voice transmission experience varying levels of attenuation. This means that some frequencies may be weakened or lost more than others during transmission. This can occur due to the inherent characteristics of the transmission medium, such as the materials used in the cables or the distance the signal has to travel. The answer choice correctly identifies that the distortion is caused by the differing attenuation rates for the various frequency components in a voice transmission.

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