Digicom

C 1.) The knowledge or intelligence that is communicated between two or more points. A. Input B. Output C. Information D. Baseband

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C 2.) Digital modulation is sometimes called: A. Digital FM B. Digital AM C. Digital radio D. Digital transmission

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B 3.) If the information signal is digital and the amplitude of the carrier is varied proportional to the information signal, this is called A. Amplitude modulation B. Amplitude shift keying C. Frequency modulation D. Frequency shift keying

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B 4.) If the information signal is digital and the phase of the carrier is varied proportional to the information signal, this is called A. Phase modulation B. Phase shift keying C. Quadrature modulation D. Quadrature amplitude modulation

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D 5.) Which of the following is not an application of digital modulation? A. Relatively low-speed voice-band data communications modem B. High speed data transmission C. Digital microwave and satellite communications D. None of the choices

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A 6.) A measure of how much information can be propagated through a communications system and is a function of bandwidth and transmission time. A. Information capacity B. Information availability C. Information D. Information theory

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B 7.) The most basic digital symbol used to represent information is: A. Decimal digit B. Binary digit C. Hexadecimal digit D. Octal digit

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A 8.) The number of bits transmitted during one second A. bit rate B. dit C. baud D. bits per second

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A 9.) Information capacity is directly proportional to the transmission time and bandwidth. A. Hartley’s law B. Shannon-Hartley’s theorem C. Shannon limit for information capacity D. All of the above

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C 10.) In M-ary encoding, M indicates: A. The number of bits representing a symbol B. The number of symbols representing a bit C. The number of conditions D. The number of hamming bits

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D 11.) Baud is also referred as A. bits per second B. bits per symbol C. symbols per bits D. symbols per second

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A 12.) Baud and bits-per-symbol will be equal in: A. binary B. digital C. quaternary D. All of the above

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B 13.) The minimum theoretical bandwidth necessary to propagate a signal is called:

A. B. C. D.

Minimum bandwidth Minimum Nyquist bandwidth Hartley’s bandwidth Carson’s bandwidth

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A 14.) The simplest digital modulation technique is: A. Amplitude shift keying B. Frequency shift keying C. Phase shift keying D. Quadrature amplitude modulation

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A 15.) A binary information signal directly modulates the amplitude of an analog carrier.

A. B. C. D.

Amplitude shift keying Frequency shift keying Phase shift keying Quadrature amplitude modulation

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D 16.) Frequency shift keying is also called: A. Phase reversal keying B. Quadrature amplitude modulation C. Binary frequency modulation D. Binary frequency shift keying

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A 17.) In FSK, the frequency that represents logic 1 is:

A. B. C. D.

Mark

Space High frequency Low frequency

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C 18.) The most common circuit used for demodulating binary FSK signal is:

A. B. C. D.

Foster-Seeley discriminator Quadrature detector PLL Balanced-slope detector

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C 19.) An M-ary digital modulation scheme similar to conventional PM except that the input is a binary digital signal and there are limited numbers of output phases possible. A. Amplitude shift keying B. Frequency shift keying C. Phase shift keying D. Quadrature amplitude modulation

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B 20.) For M-ary encoding in BPSK, “M” is equal to: A. 1 B. 2 C. 3 D. 4

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D 21.) BPSK is also known as: A. Phase reversal keying B. Biphase modulation C. Continuous wave modulation D. A and B

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C 22.) Another term for a constellation diagram is: A. Signal celestial diagram B. Heavenly signal body diagram C. Signal state space diagram D. Extraterrestrial signal diagram

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B 23.) Digital modulation where four output phases are possible for a single carrier frequency.

A. B. C. D.

BPSK QPSK 8PSK 16PSK

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B 24.) For M-ary encoding in QPSK, “N” is equal to: A. 1 B. 2 C. 3 D. 4

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D 25.) For M-ary encoding in 8PSK, “M” is equal to: A. 3 B. 4 C. 16 D. 8

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B 26.) With 8PSK, the binary input data are combined into group of three bits called:

A. B. C. D.

Three bit Tribit Digit Bithree

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D 27.) For M-ary encoding in16PSK, “N” is equal to A. 1 B. 2 C. 3 D. 4

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D 28.) A form of digital modulation similar to PSK except the digital information is contained in both the amplitude and the phase of the transmitted carrier. A. Amplitude shift keying B. Frequency shift keying C. Phase shift keying D. Quadrature amplitude modulation

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C 29.) For M-ary encoding in 8QAM, “N” is equal to: A. 1 B. 2 C. 3 D. 4

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D 30.) For M-ary encoding in 16QAM, “N” is equal to:

A. B. C. D.

1

2 3 4

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D 31.) Bandwidth efficiency is also called: A. Information density B. Spectral efficiency C. Nyquist bandwidth D. Both A and B

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C 32.) A logic gate used in Differential BPSK transmitter is:

A. B. C. D.

OR NOR XOR XNOR

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B 33.) The empirical record of a system’s actual bit error performance.

A. B. C. D.

Probability of error Bit error rate Bit error performance Both A and B

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B 34.) The first to develop digital transmission system for the purpose of carrying digitally encoded analog signals over metallic wire cables between telephone offices is: A. Bell B. AT&T C. IBM D. Xerox

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D 35.) The processing of analog signals using digital methods and includes bandlimiting the signal with filters, amplitude equalization, and phase shifting. A. Digitizing B. Digital modulation C. Digital transmission D. Digital signal processing

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B 36.) It consist essentially of sampling analog information signals and then converting those samples into discrete pulses and transporting pulses from source to a destination over a physical transmission medium

A. B. C. D.

Digital transmission Pulse modulation Pulse transmission Digital modulation

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B 37.) A type of pulse modulation where the position of the constant width pulse within a prescribed time slots is varied according to the amplitude of the sample of the analog signal. A. PAM B. PPM C. PWM D. PCM

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D 38.) The analog signal is sampled and then converted to a serial n bit binary code for transmission.

A. B. C. D.

PAM PPM PWM PCM

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D 39.) A circuit in PCM system that periodically samples the analog input signal and converts those samples to a multilevel PAM signals. A. Analog to digital converter B. Digital to analog converter C. Serial to parallel converter D. Sample and hold circuit

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C 40.) In the receiver of a PCM system, the _____ converts the serial pulses received from the transmission line to parallel PCM codes. A. Analog to digital converter B. Digital to analog converter C. Serial to parallel converter D. Sample and hold circuit

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C 41.) An integrated circuit that performs the PCM encoding and decoding function is called:

A. B. C. D.

Compander LINCOMPLEX Codec Modem

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B 42.) A type of sampling where the input voltage is sampled with narrow pulse and then held relatively constant until the next sample is taken. A. Natural sampling B. Flat top sampling C. Organic sampling D. Hold sampling

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A 43.) An error that happens in a PCM system when the amplitude of the sampled signal changes during the sample pulse time. A. Aperture error B. Aperture distortion C. Overload distortion D. Peak limiting

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A 44.) Aperture time is sometimes called as: A. Acquisition time B. Droop C. Storage time D. Conversion time

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C 45.) To ensure that a minimum change occurs in the analog signal while it is being deposited across the capacitor in the sample and hold circuit in a PCM system, the acquisition time should be: A. Very long B. Long C. Very short D. Short

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B 46.) A type of sampling that introduces less aperture distortion:

A. B. C. D.

Natural sampling Flat top sampling Organic sampling Hold sampling

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B 47.) A theorem that establishes the minimum sampling rate that can be used for a given PCM system.

A. B. C. D.

Nyquist minimum bandwidth Nyquist sampling theorem Carson minimum bandwidth Carson sampling theorem

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C 48.) Foldover distortion is also called: A. Shadow B. Silhouette C. Aliasing D. Mirror

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C 49.) Another name for antifoldover filter is: A. Anti inflammatory B. Anti folding C. Anti aliasing D. Anti interfernce

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C 50.) The process of converting an infinite number of possibilities to a finite number of conditions.

A. B. C. D.

Filter Sampling Quantization Coding

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D 51.) The magnitude difference between adjacent steps is called:

A. B. C. D.

Quantum Quantization interval Quantization range Both A and B

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B 52.) Overload distortion is also called: A. Overload limiting B. Peak limiting C. Resolution D. Quantization range

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C 53.) The _____ is equal to the voltage of the minimum step size, which is equal to the voltage of the least significant bit of the PCM code. A. Overload limiting B. Peak limiting C. Resolution D. Quantization range

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C 54.) A range equal to + or – one half the magnitude of a quantum except the codes for +0 and -0.

A. B. C. D.

Quantum Quantization interval Quantization range Both A and B

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D 55.) Quantization error is also called: A. Aperture error B. Aperture distortion C. Peak limiting D. Quantization noise

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C 56.) A numerical indication of how efficiently a PCM code is utilized.

A. B. C. D.

Dynamic range Quantization range Coding efficiency Signal to noise ratio

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B 57.) Companding used in United States and Japan: A. A law companding B. µ law companding C. Analog companding D. Digital companding

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B 58.) Every function performed by a PCM encoder and decoder is now accomplished with a single integrated circuit chip called: A. Compander B. Codec C. Combo D. Vocoders

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D 59.) Special voice encoders/decoders are: A. Compander B. Codec C. Combo D. Vocoders

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B 60.) A type of PCM that uses a single bit PCM code to achieve digital transmission of analog signals.

A. B. C. D.

Differential PCM Delta PCM Adaptive Delta PCM Adaptive Deviation PCM

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B 61.) When the analog input signal changes at a faster rate than the DAC can maintain, _____ will happen.

A. B. C. D.

Granular noise Slope overload Peak limiting Thermal noise

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C 62.) A modulation system where the step size of the DAC is automatically varied, depending on the amplitude characteristics of the analog input signal. A. Differential PCM B. Delta PCM C. Adaptive Delta PCM D. Adaptive Deviation PCM

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D 63.) What do you call the number of amplitude, frequency, or phase changes that take place per second?

A. B. C. D.

Data rate in bits per second Frequency of operation Speed limit Baud rate

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A 64.) It is used by slow speed modems. A. FSK B. BPSK C. ASK D. QAM

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B 65.) These are the basic modulator and demodulator circuits in PSK

A. B. C. D.

PLLs Balanced modulators Shift registers Local oscillator

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D 66.) In which modulation can a 9600 baud rate signal pass over the voice grade telephone line?

A. B. C. D.

BPSK QPSK DPSK QAM

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A 67.) It is not used in a QAM modulator. A. XNOR B. Bit splitter C. Balanced modulator D. 2 – 4 level converter

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C 68.) In a digital communication system, it is the speed at which symbols are transmitted.

A. B. C. D.

Data rate Bit rate Baud rate Flow rate

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B 69.) A pattern showing all the possible combinations of amplitude and phase for a signal in digital communication. A. Eye pattern B. Constellation diagram C. Phasor diagram D. Fourier transform

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B 70.) Identify the terminal or computer that communications via a modem.

A. B. C. D.

Switches Data terminal equipment Servers Data communications equipment

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A 71.) Any digital modulation scheme that codes two bits of information per transmitted symbol.

A. B. C. D.

Dibit system Tribit system Quadbit system Bit system

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B 72.) It is a digital modulation scheme using two or more different frequencies.

A. B. C. D.

Amplitude shift keying Frequency shift keying Phase shift keying Quaternary phase shift keying

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C 73.) A logic one in digital communication. A. Negative voltage B. Positive voltage C. Mark D. Space

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A 74.) Cable used to make a direct connection between two devices using their serial ports. It is wired to simulate the presence of a link via modem between the devices. A. Null modem B. Virtual modem C. Imaginary modem D. J modem

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B 75.) Phase shift keying that employs four different phases and allows two bits of information to be transmitted simultaneously. A. Phase shift keying B. Quadrature phase shift keying C. Gaussian minimum shift keying D. Delta phase shift keying

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C 76.) In digital communications, a binary zero. A. Positive voltage B. Negative voltage C. Space D. Mark

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B 77.) Distortion created by using a too low sampling rate when coding an analog signal for digital transmission.

A. B. C. D.

Frequency distortion Aliasing Quantizing error Peak limiting

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A 78.) Device that converts sampled analog signal to and from its PCM or delta modulation equivalent.

A. B. C. D.

Codec Vocoder Modem Compander

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C 79.) Combination of compression at the transmitter and expansion at the receiver of a communication system.

A. B. C. D.

Codec Modem Companding Any of the choices

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A 80.) Conversion of a PCM or delta modulation bit stream to analog samples.

A. B. C. D.

Decoding Coding Compression Expansion

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B 81.) Filtering of signals by converting them to digital form, performing arithmetic operations on the data bit, then converting back to analog form. A. Pulse code modulation B. Digital signal processing C. Programmable logic control D. Quantizing

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B 82.) Bits added to a digital signal to help the receiver to detect the beginning and end of data frames.

A. B. C. D.

Sign bits Framing bits Stop bits Start bits

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A 83.) Sampling of an analog signal, so that the sample amplitude follows that of the original signal for the duration of the sample. A. Natural sampling B. Statistical sampling C. Universal sampling D. Flat topped sampling

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D 84.) A data line code in which the voltage or current does not necessarily return to zero between bits.

A. B. C. D.

Unipolar code Return to zero code Bipolar code Non return to zero code

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B 85.) A series of pulses in which the amplitude of each pulse represents the amplitude of the information signal at a given time. A. Pulse code modulation B. Pulse amplitude modulation C. Pulse position modulation D. Pulse width modulation

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D 86.) A series of pulses in which the duration of each pulse represents the amplitude of the information signal at a given time. A. Pulse code modulation B. Pulse amplitude modulation C. Pulse position modulation D. Pulse width modulation

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C 87.) Representation of a continuously varying quantity as one of a number of discrete values.

A. B. C. D.

Sampling Filtering Quantizing Coding

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D 88.) Method of data compression by encoding the length if a string of ones or zeros instead of transmitting all the one or zero bits individually. A. Hybrid encoding B. Byphase encoding C. Manchester encoding D. Run length encoding

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B 89.) A device that detects the amplitude of an input signal at a particular time called the sampling time and maintains its output at or near that amplitude until the next sampling time. A. Quantizer B. Sample and hold circuit C. Coder D. Analog to digital converter

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A 90.) A line code in which the polarity of the voltage or the direction of the current remains the same at all times. A. Unipolar code B. Return to zero code C. Bipolar code D. Non return to zero code

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A 91.) One of the following is not a binary code: A. Morse B. Baudot C. CCITT - 2 D. Code 39

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A 92.) What is Hartley’s law? A. The maximum rate of information transmission depends on the

B. C. D.

channel bandwidth The maximum rate of information transmission depends on the depth of modulation The maximum rate of information transmission depends on the S/N of the system Only binary codes may be used

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A 93.) In telegraphy, what is the most commonly used modulation system?

A. B. C. D.

Frequency shift keying Two tone modulation Pulse code modulation CDMA

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B 94.) Which of the following system is digital? A. Pulse position modulation B. Pulse code modulation C. Pulse width modulation D. Indirect frequency modulation

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D 95.) Which is the most noise resistant modulation system in the following?

A. B. C. D.

Pulse amplitude modulation Frequency modulation Pulse position modulation Pulse code modulation

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B 96.) A limit on the _____ is set by Hartley-Shannon theorem. A. Maximum capacity of a channel with a given sampling frequency B. Maximum capacity of a channel with a given noise level C. Maximum number of coding levels in a channel with a given noise

D.

level Maximum number of quantizing levels in a channel with a given bandwidth

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C 97.) Companding is used _____ in PCM

A. To overcome quantizing noise B. To allow amplitude limiting in the receivers C. To protect small signals in PCM from quantizing distortion D. To overcome impulse noise at the receivers

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B 98.) What is used to connect the output of a data source to a telephone line?

A. B. C. D.

An FMVFT system A modem A lease for the line A router

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B 99.) Which is not a reason why an organization wishing to transmit large quantities of data will lease a line, instead of using the public switched network? A. Because it is cheaper B. To ensure privacy C. To ensure ready availability D. To allow equalization and hence higher data rates

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D 100.) Which is used in multiplexing Pulse Amplitude Modulation signals?

A. B. C. D.

Subcarriers D/A converters A/D converters FET switches

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B 101.) Keeping the multiplexer and DEMUX channels step with one another in a PAM/TDM system is done by a: A. Clock recovery circuit B. Sync pulse C. Sampling D. PSN generator

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A 102.) By sampling and _____, converting of analog signals to digital is done.

A. B. C. D.

Quantizing Companding Pre-emphasis Summing

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B 103.) It refers to emphasizing low level signals and compressing higher level signals.

A. B. C. D.

Decoding Companding Pre-emphasis Sampling

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C 104.) A telephone system using TDM and PCM A. TE1 B. RS-232 C. T-1 D. Bell 212

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B 105.) Pulse Code Modulation is preferred to PAM because of its

A. B. C. D.

Resistance to quantizing error Simplicity Lower cost Superior noise immunity

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D 1. OQPSK means: (A) Orthogonal QPSK (B) On-off QPSK (C) Out-of-phase QPSK (D) Offset QPSK

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C 2. A modified QPSK where the bit waveform on the I and Q channels are shifted in phase from each other by one-half of a bit time. (A)Shifted QPSK (B)Phase-shift QPSK (C)Offset QPSK (D) Both A and B

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B 3. OQPSK is sometimes called: (A) Offset-shift QPSK (B) Offset-keyed QPSK (C) Offset-phase QPSK (D) Offset-made QPSK

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A 4. A code used to reduce the number of transmission errors in 8PSK (A) Gray code (B) Black code (C) White code (D) Red code TIME’S

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D 5. Gray code is sometimes called: (A) Minimum distance code (B) Minimum shifted code (C) Maximum shifted code (D) Maximum distance code

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D 6. In digital modulation schemes where n>1, less bandwidth is required to propagate a given bit rate, thus it achieved: (A) Bandwidth limiting (B) Companding (C) Compandoring (D) Bandwidth compression

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A 7. Bandwidth efficiency is normalized at _____ bandwidth. (A) 1 Hz (B) 10 Hz (C) 100 Hz (D) 1000 Hz

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c 8. A process of extracting the phase-coherent reference carrier from a receiver signal. (A) Carrier extraction (B) Demodulation (C) Carrier recovery (D) Discrimination TIME’S

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D 9. Carrier recovery is sometimes called: (A) Coherent recovery (B) Non-coherent recovery (C) Frequency referencing (D) Phase referencing

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C 10. When the binary data is encoded as a precise phase of the transmitter carrier, it is called: (A) Ultimate encoding (B) Manchester encoding (C) Absolute phase encoding (D) All of the choices

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B 11.A carrier recovery method that has the basic principle of filtering the received BPSK waveform and then squaring it. (A) Costas loop (B) Squaring loop (C) Remodulator (D) Balanced modulator

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A 12. A carrier recovery method that uses two parallel tracking loops (I and Q) simultaneously to derive the product of the I and Q components of the signal that drives the VCO (A)Costas loop (B)Squaring loop (C)Remodulator (D) Balanced modulator

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C 13. A carrier recovery method that produces a loop error voltage that is proportional to twice the phase error between the incoming signal and the VCO signal. (A)Costas loop (B)Squaring loop (C)Remodulator (D) Balanced modulator

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C 14. Data transmission rates in excess of 56 kbps can be achieved over telephone circuits using: (A) Absolute PSK (B) Differential PSK (C) Trellis code modulation (D) Adaptive PSK TIME’S

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B 15. Who developed trellis code modulation (TCM)? (A) Zuerich Rela (B) Dr. Ungerboeck (C) Takeshi Miro

(D) Isyana Rio

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D 16. The distance between symbols in a constellation diagram is called: (A) Plato’s distance (B) Pythagorean distance (C) Archimedean distance (D) Euclidean distance TIME’S

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C 17. The optimum signalling format that occurs only when two binary signal levels are allowed and when one signal is the exact negative of the other. (A)E and M signalling (B)Handshaking (C)Antipodal signalling (D) Selection

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B 18. An FSK where the transmitter and receiver are not frequency or phase synchronized. (A) Coherent FSK (B) Non-coherent FSK (C) Synchronous FSK (D) Asynchronous FSK TIME’S

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A 19.An FSK where the local receiver reference signals are in frequency and phase lock with the transmitted signals. (A) Coherent FSK (B) Non-coherent FSK (C) Synchronous FSK (D) Asynchronous FSK

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B 20. A code currently used for PCM is the _____, where the most significant bit (MSB) is the sign bit and the remaining bits are used for magnitude. (A)Folded-binary code (B)Sign-magnitude code (C)MSB coding (D) Both A and B

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B 21. The signal power-to-quantizing noise power ratio is called: (A) SINAD (B) Signal to distortion ratio (C) Noise factor (D) Noise temperature TIME’S

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B 22. An encoding in which the step size increases with the amplitude of the input signal. (A) Linear encoding (B) Non-linear encoding (C) Synchronous encoding (D) Asynchronous encoding TIME’S

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A 23. (A) (B) (C) (D)

Non-linear encoding is also called: Non-uniform encoding Asynchronous encoding Non-coherent encoding Active encoding

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C 24. The thermal noise when there is no analog input signal to the PAM sampler. (A) Random noise (B) Midrise noise (C) Idle channel noise (D) Midtread quantization TIME’S

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D 25. The first quantization interval is made larger in amplitude than the rest of the steps. (A) Random noise (B) Midrise noise (C) Idle channel noise (D) Midtread quantization TIME’S

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A 26. A type of coding that compares the PAM signal to a ramp waveform while a binary counter is being advanced at a uniform rate. (A)Level at a time coding (B)Digit at a time coding (C)Word at a time coding (D) All of the above

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B 27. The type of coding used to quantize PAM which determines each digit of the PCM code sequentially. (A) Level at a time coding (B) Digit at a time coding (C) Word at a time coding (D) All of the above TIME’S

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C 28. A digit-at-time coder that uses a successive approximation register. (A) Phase coder (B) Frequency coder (C) Feedback coder (D) Analog coder

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C 29.These are flash encoders for quantizing PAM and are more complex and more suitable for high-speed application. (A) Level at a time coding (B) Digit at a time coding (C) Word at a time coding (D) All of the above

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C 30. (A) (B) (C) (D)

The first channel vocoder was developed by: Alex Reeves Alexander Reeves Homer Dudley Michael Moore

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B 31. A type of vocoder that takes advantage of the fact that the short-term spectral density of typical speech signal seldom distributes uniformly across the entire voice-band spectrum. (A)Channel vocoders (B)Formant vocoders (C)Linear predictive coders (D) Vocal tract coders

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A 32. The spectral peaks of the sound spectrum are called: (A) Formants (B) Peak envelope (C) Peaks (D) Vocal tract excitation

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C 33. A type of coder that extracts the most significant portions of speech information directly from the time waveform rather than from the frequency spectrum as with the other vocoders. (A)Channel vocoders (B)Formant vocoders (C)Linear predictive coders (D) Vocal tract coders

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B 34. In pulse transmission, bandlimiting a pulse causes the energy from the pulse to be spread over significantly longer time in the form of _____. (A)Primary lobes (B)Secondary lobes (C)Tertiary lobes (D) Quaternary lobes

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C 35. The secondary lobes in pulse transmission are also called: (A) Ringing trails (B) Ringing heads (C) Ringing tails (D) Ringing threads TIME’S

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C 36. An interference that is an important path to equalize the distortion for all frequencies, creating a uniform transmission medium and reducing transmission impairments. (A)Eye diagram (B)Tilt (C)Intersymbol interference (D) crosstalk

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B 37. A special filter inserted in the transmission path to equalize the distortion for all frequencies, creating a uniform transmission medium and reducing transmission impairments. (A)Bandpass filters (B)Equalizers (C)Ringing circuit (D) Overlapping circuit

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C 38. The following are primary causes of intersymbol interference except: (A) Timing inaccuracies (B) Insufficient bandwidth (C) Crosstalk (D) Amplitude distortion TIME’S

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D 39. A convenient technique for determining the effects if the degradations introduced into the pulses as they travel to the regenerator. (A)Eye pattern (B)Eye diagram (C)Constellation diagram (D) Both A and B

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A 40. The decision levels for the regenerator are represented by _____ in an eye pattern: (A) Crosshairs (B) Dot (C) Dash (D) Broken line

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C 41. An impairment due to the overlapping signal pattern which does not cross the horizontal zero line at exact integer multiples of the symbol click in an eye pattern. (A)Trajectories (B)Phase distortion (C)Data transition jitter (D) Granular noise

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D 42. It is a telephone local loop that combines analog telephone service with data communication. The downstream data rate is greater than the upstream rate. (A)DSL (B)Dial up (C)ISDN (D) ADSL

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A 43. To modulate a conventional analog transmitter for data transmission, audio tone of two or more different frequencies is used. (A)Audio frequency-shift keying (B)Video frequency-shift keying (C)Audio frequency-shift keying (D) Video phase-shift keying

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A 44. Which device allows data communications over cable-television wiring, as well as television signals? (A) Cable modem (B) Modem (C) V.21 (D) X.26 TIME’S

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C 45. It is a variant of QAM used with ADSL data communication systems. (A) Asynchronous quadrature phase modulation (B) Synchronous quadrature phase modulation (C) Carrierless amplitude phase modulation (D) Carrier amplitude phase modulation

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A 46. What modulation scheme for ADSL data communications systems uses many carriers at different frequencies each modulated using QAM? (A)Discrete multi-tone (DMT) modulation (B)Multi-tone (MT) modulation (C)Discrete tone (DT) modulation (D) All of the choices

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C 47. A transmission speed that is less than the maximum of which a modem is capable and that the modem resorts to when line conditions do not permit transmission at its maximum speed. (A)Roll off (B)Decay (C)Fallback (D) Actual

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C 48. Which device is used for the transmission and reception of facsimile documents? It may be used with a microcomputer or built into a stand-alone fax machine. (A)DCE (B)Cable modem (C)Fax modem (D) V.22

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A 49.Series of command transmitted to the modem whenever a communications software program is loaded. (A) Initialization string (B) Flowchart (C) Syntax (D) Password

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D 50.It refers to the series of tones transmitted by a modem to allow the automatic adjustment of line equalization (A) Fax tone (B) Signalling tone (C) Dial tone (D) Training sequence

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C 51. It is not a good idea to use a signalling system in which each letter of the alphabet is represented by a different symbol because: (A)It would be too difficult for an operator to memorize (B)It is redundant (C)Noise would introduce too many errors (D) It used in robotics only.

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C 1.) The transmission of information from or more source to one or more destination over the same transmission medium.

A. Modulation B. Demodulation C. Multiplexing D. Demultiplexing

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B 2.) In multiplexing, the transmission medium is referred to as a:

A. Line B. Trench C. Hub D. Space

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A 3.) To separate channels in TDM receiver, it needs to use:

A. AND gates B. Bandpass filters C. Low pass filters D. Integration

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D 4.) Multiple signals __________ in TDM

A. Share a common bandwidth B. Modulate subcarriers C. Are represented by random codes D. Take turns transmsitting

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A 5.) The fundamental building block for most TDM systems in the United States begins with:

A. DS-0 B. DS-1 C. DS-1c D. DS-2

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C 6.) DS-0 channels use how many bit PCM code:

A. 32 B. 16 C. 8 D. 4

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D 7.) An electronically controlled digital switch with two inputs and one output

A. Demultiplexer B. Mux C. Demux D. Multiplexer

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B 8.) The time it takes to transmit one TDM frame is called:

A. TDM time B. Frame time C. TDM frequency D. Frame frequency

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D 9.) In TDM, the “fixed time slot” is referred as:

A. Block B. Slot C. Hole D. Epoch

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C 10.) A communication system that uses digital pulses rather than analog signals to encode information.

A. Analog carrier system B. Multiplexed carrier system C. Digital carrier system D. Both A and B

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B 11.) T1 has how many voice band channels

A. 2 B. 24 C. 4 D. 16

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A 12.) Sampling frequency of T1 is:

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

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B 13.) There are how many bits in a frame for T1:

A. 192 B. 193 C. 7 D. 8

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A 14.) Every frame in T1 has an additional _____ framing bit/s:

A. 1 B. 2 C. 8 D. 16

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C 15.) For North American digital hierarchy, to upgrade from one level in the hierarchy to the next higher level, a special device is required. This is called:

A. Modem B. Digital cross connects C. Muldem D. DSX

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D 16.) The transmission of binary data that involves the transmission of only a single non-zero voltage level, such as either a positive or negative voltage for a logic one and zero volt for a logic zero:

A. Bipolar B. Manchester C. Return to zero D. Unipolar

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C 17.) The transmission of binary data where the binary pulse is maintained for the entire bit time.

A. Unipolar B. Bipolar C. Non-return to zero D. Return to zero

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A 18.) A popular type of line encoding that produces a strong timing component for clock recovery and does not cause dc wandering.

A. Digital biphase B. PCM C. Delta PCM D. BPRZ

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B 19.) Used for the transmission of PCM encoded time division multiplexed digital signals:

A. S carriers B. T carriers C. C carriers D. R carriers

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D 20.) The data rate of T2 carriers is:

A. 1.536 Mbps B. 1.544 Mbps C. 3.152 Mbps D. 6.312 Mbps

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A 21.) The rate of T3 carriers is:

A. 44.736 Mbps B. 1.544 Mbps C. 3.152 Mbps D. 6.312 Mbps

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C 22.) In Europe, a different version of T carrier lines is used. It is called:

A. C lines B. D lines C. E lines D. F lines

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B 23.) An E1 frame is composed of how many voice band channels:

A. 12 B. 30 C. 24 D. 36

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D 24.) An efficient alternative to synchronous TDM that is not used for carrying standard telephone circuits but are used more often for the transmission of data.

A. Statistical TDM B. Asynchronous TDM C. Intelligent TDM D. Any of the choices

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C 25.) It allows full duplex transmission over a two wire circuit, as signal can propagate in both directions at the same time without interfering with each other because the frequencies for the two directions of propagation are different

A. B. C. D.

WDM TDM

FDM CDMA

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A 26.) A type of multiplexing in which several channels are interleaved and then transmitted together.

A. FDM B. TDM C. CDMA D. A supergroup

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B 27.) In FDM system, each signal

A. Modulates the final carrier B. Modulates a channel C. Is mixed with all the others before modulation D. Is converted into a code

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D 28.) The following are typical FDM application,

A. Telemetry B. Stereo broadcasting C. Telephone D. Secure communcations

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B 29.) FDM telemetry systems mostly use:

A. AM B. FM C. QUAM D. PSK

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C 30.) In FDM telephone systems, the modulation used is:

A. AM B. FM C. SSB D. DSBFC

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A 31.) The L+R signal in FM stereo broadcasting:

A. Modulates the FM carrier B. Double-sideband modulates a carrier C. Frequency modulates a subcarrier D. Demodulates the subcarrier

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D 32.) In FM broadcasting, SCA signal is transmitted via

A. A 19 kHz subcarrier B. A 38 kHz subcarrier C. A 455 kHz subcarrier D. A 67 kHz subcarrier

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B 33.) The basic voice band channel in FDM that is actually bandlimited to approximately 300 Hz to 3 kHz frequency band:

A. Basic 200 channel B. Basic 3002 channel C. Basic 500 channel D. Basic 2005 channel

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A 34.) The next higher level after the basic message channel in FDM hierarchy is:

A. Group B. Voice channel C. Basic super group D. Basic master group

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C 35.) The bandwidth of a group in FDM is:

A. 12 kHz B. 24 kHz C. 48 kHz D. 96 kHz

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D 36.) To form a supergroup, it needs to have how many group/s?

A. 1 B. 3 C. 7 D. 5

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C 37.) A supergroup has how many message channel?

A. 10 B. 20 C. 60 D. 80

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A 38.) To form a mastergroup, it needs to have how many supergroups?

A. 10 B. 13 C. 15 D. 17

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D 39.) A mastergroup has how many message channels?

A. 100 B. 200 C. 800 D. 600

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B 40.) To form a jumbogroup, it needs to have how many mastergroups?

A. 10 B. 6 C. 15 D. 7

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C 41.) A jumbogroup has how many message channels?

A. 4100 B. 3200 C. 3600 D. 4800

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A 42.) A superjumbogroup has how many message channels?

A. 10800 B. 17200 C. 13600 D. 15800

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B 43.) In WDM, the wavelength spectrum used is in the region of:

A. 850 nm or 1300 nm B. 1300 nm or 1500 nm C. 390 nm or 770 nm D. 123 nm or 690 nm

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D 44.) In WDM, demultiplexers are also called:

A. Any of the choices B. Couplers C. Combiners D. Splitters

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B 45.) The initial SONET standard is:

A. OC-0 B. OC-1 C. OC-2 D. OC-3

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C 46.) STS-1 is made of how many DS-1 signals?

A. 12 B. 24 C. 28 D. 32

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D 47.) OC-48 has a data rate of:

A. 10.84 Gbps B. 103.68 Gbps C. 1.544 Gbps D. 2.48332 Gbps

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A 48.) A single optical fiber can carry _____ OC-48.

A. 16 B. 61 C. 32 D. 24

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D 49.) It is use of a single channel by more than one signal.

A. Multiband access B. Demultiplexing C. Multiple access D. Multiplexing

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A 50.) The combining of several signals into one communication signals into one communication channel by assigning each a different carrier frequency.

A. FDM B. TDM C. WDM D. CDM

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B 51.) A system to allow several transmission to use a signle channel by assigning time slots to each.

A. FDMA B. TDMA C. CDMA D. WDMA

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C 52.) It is a system that allows multiple access to use the same frequency with separate PN codes and a spread spectrum modulation scheme.

A. FDMA B. TDMA C. CDMA D. WDMA

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A 53.) Spread spectrum stations sharing a band are identified by and distinguished from one another by which of the following?

A. PSN code B. Frequency of operation C. Chipping rate D. Modulation type

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C 54.) In a PSN generator, the main circuit is a:

A. Multiplexer B. Shift register C. XOR D. XNOR

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B 55.) It is not a benefit of SS.

A. Jam proof B. Security C. Immunity to fading D. Noise proof

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D 56.) What do you call the extra bits used to spread the signal in a direct sequence spread spectrum system?

A. Bits B. Stuff C. PSN D. Chips

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B 57.) A form of spread spectrum communication in which the RF carrier continually moves from one frequency to another according to a prearranged pseudo-random pattern

A. CDMA B. Frequency hopping C. Direct sequence spread spectrum D. None of the choices

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C 58.) It is the method of reducing contention in a network, involving each station checking for interference before transmitting.

A. CSMA/CD B. Token passing C. CSMA/CS D. Token ring

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A 59.) Known as the attempt by two transmitters to use the same channel simultaneously.

A. Collision B. Polling C. Passing D. Token

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D 60.) A framing format recently developed for new designs of T1 carrier systems that consist of 24 193-bit frames

A. Superframe TDM format B. D type channel banks C. Fractional T carrier service D. Extended Superframe format

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