blake chapter1 10

8/3/2019 Blake Chapter1 10

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Chapter 1: Introduction to

Communication SystemsMULTIPLE CHOICE

1. The theory of radio waves was originated by:

a. Marconi c. Maxwellb. Bell d. HertzANS: C

2. The person who sent the first radio signal

across the Atlantic ocean was:a. Marconi c. Maxwell

b. Bell d. HertzANS: A

3. The transmission of radio waves was firstdone by:

a. Marconi c. Maxwellb. Bell d. HertzANS: D

4. A complete communication system must

include:

a. a transmitter and receiverb. a transmitter, a receiver, and a channelc. a transmitter, a receiver, and a spectrum

analyzerd. a multiplexer, a demultiplexer, and a channel

ANS: B5. Radians per second is equal to:

a. 2Tvfc. the phase angle

b.fz2Td. none of the aboveANS: A6. The bandwidth required for a modulated

carrier depends on:

a. the carrier frequency c. the signal-plus-noise

to noise ratiob. the signal-to-noise ratio d. the baseband

frequency range

ANS: D7. When two or more signals share a common

channel, it is called:a. sub-channeling c. SINAD

b. signal switching d. multiplexingANS: D

8. TDM stands for:

a. Time-Division Multiplexing c. Time DomainMeasurement

b. Two-level Digital Modulation d. none of the

aboveANS: A

9. FDM stands for:a. Fast Digital Modulation c. Frequency-

Division Multiplexing

b. Frequency Domain Measurement d. none of

the aboveANS: C10. The wavelength of a radio signal is:

a. equal tofzc

b. equal to c zP

c. the distance a wave travels in one periodd. how far the signal can travel without

distortionANS: C11. Distortion is caused by:

a. creation of harmonics of baseband frequenciesb. baseband frequencies "mixing" with each

otherc. shift in phase relationships between basebandfrequencies

d. all of the above

ANS: D

12. The collection of sinusoidal frequenciespresent in a modulated carrier is called its:a. frequency-domain representation c. spectrum

b. Fourier series d. all of the aboveANS: D

13. The baseband bandwidth for a voice-grade

(telephone) signal is:a. approximately 3 kHz c. at least 5 kHz

b. 20 Hz to 15,000 Hz d. none of the above

ANS: A

14. Noise in a communication system originatesin:

a. the sender c. the channelb. the receiver d. all of the aboveANS: D

15. "Man-made" noise can come from:

a. equipment that sparks c. staticb. temperature d. all of the aboveANS: A

16. Thermal noise is generated in:

a. transistors and diodes c. copper wireb. resistors d. all of the aboveANS: D

17. Shot noise is generated in:

a. transistors and diodes c. copper wireb. resistors d. none of the above

ANS: A18. The power density of "flicker" noise is:a. the same at all frequencies c. greater at low

frequencies

b. greater at high frequencies d. the same as"white" noise

ANS: C


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19. So called "1/f" noise is also called:

a. random noise c. white noiseb. pink noise d. partition noiseANS: B

20. "Pink" noise has:

a. equal power per Hertz c. constant power

b. equal power per octave d. none of the aboveANS: B

21. When two noise voltages, V1 and V2, arecombined, the total voltage VTis:

a. VT= sqrt(V1vV1 + V2 vV2) c. VT= sqrt(V1

vV2)b. VT= (V1 + V2)/2 d. VT= V1 + V2

ANS: A22. Signal-to-Noise ratio is calculated as:a. signal voltage divided by noise voltage

b. signal power divided by noise power

c. first add the signal power to the noise power,

then divide by noise powerd. none of the aboveANS: B

23. SINAD is calculated as:a. signal voltage divided by noise voltage

b. signal power divided by noise power

c. first add the signal power to the noise power,then divide by noise power

d. none of the above

ANS: D

24. Noise Figure is a measure of:a. how much noise is in a communications

systemb. how much noise is in the channelc. how much noise an amplifier adds to a signal

d. signal-to-noise ratio in dB

ANS: C25. The part, or parts, of a sinusoidal carrier thatcan be modulated are:

a. its amplitude c. its amplitude, frequency, and

directionb. its amplitude and frequency d. its amplitude,frequency, and phase angle

ANS: D

COMPLETION1. The telephone was invented in the year

____________________.ANS: 18632. Radio signals first were sent across the

Atlantic in the year ____________________.

ANS: 1901

3. The frequency band used to modulate the

carrier is called the ____________________band.ANS: base

4. The job of the carrier is to get the information

through the ____________________.

ANS: channel5. The bandwidth of an unmodulated carrier is

____________________.ANS: zero

6. The 'B' in Hartley's Law stands for

____________________.ANS: bandwidth7. The more information per second you send,

the ____________________ the bandwidth

required.ANS:

greater

largerwider

8. In ____________________, you split the

bandwidth of a channel into sub-channels tocarry multiplesignals.

ANS: FDM

9. In ____________________, multiple signalstreams take turns using the channel.

ANS: TDM10. VHF stands for the ____________________frequency band.

ANS: very high11. The VHF band starts at

____________________ MHz.ANS: 30

12. The UHF band starts at

____________________ MHz.ANS: 300

13. A radio signal's ____________________ isthe distance it travels in one cycle of the carrier.ANS: wavelength

14. In free space, radio signals travel at

approximately ____________________ meters

per second.ANS: 300 million15. The equipment used to show signals in the

frequency domain is the_________________________.

ANS: spectrum analyzer16. Mathematically, a spectrum is represented

by a ____________________ series.

ANS: Fourier


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17. Disabling a receiver during a burst of

atmospheric noise is called____________________.ANS:

noise blanking

blanking

18. For satellite communications,____________________ noise can be a serious

problem.ANS: solar

19. Thermal noise is caused by the random

motions of ____________________ in aconductor.ANS: electronsSHORT ANSWER

1. Name the five elements in a block diagram ofa communications system.

ANS:

Source, Transmitter, Channel, Receiver,Destination

2. Name five types of internal noise.

ANS:Thermal, Shot, Partition, 1/f, transit-time3. Why is thermal noise called "white noise"?

ANS:

White light is composed of equal amounts oflight at all visible frequencies. Likewise, thermal

noise hasequal power density over a wide range offrequencies.

4. What is "pink noise"?ANS:

Light is pink when it contains more red than itdoes other colors, and red is at the low end of

the visible

spectrum. Likewise, pink noise has higher powerdensity at lower frequencies.

5. Suppose there is 30 QV from one noise source

that is combined with 40 QV from another noisesource.Calculate the total noise voltage.

ANS:

50 QV6. If you have 100 mV of signal and 10 mV ofnoise, both across the same 100-ohm load, what

is the signalto-noise ratio in dB?ANS:

20 dB

7. The input to an amplifier has a signal-to-noise

ratio of 100 dB and an output signal-to-noiseratio of 80dB. Find NF, both in dB and as a ratio.

ANS:

20 dB, NF = 100

8. A microwave receiver has a noise temperatureof 145 K. Find its noise figure.

ANS:1.5

9. Two cascaded amplifiers each have a noise

figure of 5 and a gain of 10. Find the total NFfor the pair.ANS:

5.4

10. Explain why you could use a diode as anoise source with a spectrum close to that of

pure thermal noise.

How would you control the amount of noisegenerated?

ANS:

When current flows through a diode, it generatesshot noise that can be represented as a currentsource,

the output of which is a noise current. The

equation for the noise current is very similar tothe equation for

thermal noise voltage. Since the power in theshot noise is proportional to the diode current,controlling

the diode current controls the noise power.

Chapter 2: Radio-Frequency CircuitsMULTIPLE CHOICE

1. The time it takes a charge carrier to crossfrom the emitter to the collector is called:

a. base time c. charge time

b. transit time d. Miller timeANS: B2. A real capacitor actually contains:

a. capacitance and resistance only c. capacitance,

inductance, and resistanceb. capacitance and inductance only d. reactance

onlyANS: C3. Bypass capacitors are used to:

a. remove RF from non-RF circuits c. neutralize

amplifiers


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b. couple RF around an amplifier d. reduce the

Miller effectANS: A4. A resonant circuit is:

a. a simple form of bandpass filter c. both a and

b

b. used in narrowband RF amplifiers d. none ofthe above

ANS: C5. Loading down a tuned-circuit amplifier will:

a. raise the Q of the tuned circuit c. "multiply"

the Qb. lower the Q of the tuned circuit d. have noeffect on Q

ANS: B

6. The "Miller Effect" can:a. cause an amplifier to oscillate c. reduce the

bandwidth of an amplifier

b. cause an amplifier to lose gain d. all of theabove

ANS: D

7. The Miller Effect can be avoided by:a. using a common-emitter amplifier c.increasing the Q of the tuned circuit

b. using a common-base amplifier d. it cannot be

avoidedANS: B

8. In a BJT, the Miller Effect is due to:a. inductance of collector lead c. base-to-emittercapacitance

b. collector-to-emitter capacitance d. base-to-collector capacitance

ANS: D9. In RF amplifiers, impedance matching is

usually done with:

a. RC coupling c. direct couplingb. transformer coupling d. lumped reactance

ANS: B10. Neutralization cancels unwanted feedback

by:

a. adding feedback out of phase with the

unwanted feedback

b. bypassing the feedback to the "neutral" orground planec. decoupling it

d. none of the aboveANS: A

11. For a "frequency multiplier" to work, itrequires:a. a nonlinear circuit

b. a linear amplifier

c. a signal containing harmonics

d. an input signal that is an integer multiple ofthe desired frequencyANS: A

12. A sinusoidal oscillation from an amplifier

requires:

a. loop gain equal to unityb. phase shift around loop equal to 0 degrees

c. both a and b, but at just one frequencyd. none of the above

ANS: C

13. The conditions for sinusoidal oscillationfrom an amplifier are called:a. the loop-gain criteria c. the Bode criteria

b. the Hartley criteria d. the Barkhausen criteria

ANS: D14. The Hartley oscillator uses:

a. a tapped inductor c. an RC time constant

b. a two-capacitor divider d. a piezoelectriccrystal

ANS: A

15. The Colpitts VFO uses:a. a tapped inductor c. an RC time constant

b. a two-capacitor divider d. a piezoelectric

crystal

ANS: B16. The Clapp oscillator is:

a. a modified Hartley oscillator c. a type ofcrystal-controlled oscillator

b. a modified Colpitts oscillator d. only built

with FETsANS: B

17. A varactor is:a. a voltage-controlled capacitor c. used in tuner

circuits

b. a diode d. all of the aboveANS: D

18. Crystal-Controlled oscillators are:a. used for a precise frequency

b. used for very low frequency drift (parts per

million)

c. made by grinding quartz to exact dimensions

d. all of the aboveANS: D

19. If two signals, Va = sin([at) and Vb=

sin([bt), are fed to a mixer, the output:

a. will contain [1 = [a + [b and [2 = [a[b

b. will contain[1 = [a / [b and [2 = [b / [a

c. will contain [= ([a + [b ) / 2d. none of the above


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ANS: A

20. In a balanced mixer, the output:a. contains equal (balanced) amounts of all inputfrequencies

b. contains the input frequencies

c. does not contain the input frequencies

d. is a linear mixture of the input signalsANS: C

21. "VFO" stands for:a. Voltage-Fed Oscillator c. Varactor-Frequency

Oscillator

b. Variable-Frequency Oscillator d. Voltage-Feedback OscillatorANS: B

22. A "frequency synthesizer" is:

a. a VCO phase-locked to a reference frequencyb. a VFO with selectable crystals to change

frequency

c. a fixed-frequency RF generatord. same as a mixer

ANS: ACOMPLETION

1. Generally, conductor lengths in RF circuitsshould be ____________________.

ANS: short

2. At UHF frequencies and above, elementsmust be considered as ____________________

instead of asbeing "lumped".ANS: distributed

3. When one side of a double-sided pc board isused for ground, it is called a

____________________.ANS: ground-plane

4. Interactions between parts of an RF circuit

can be reduced by using ____________________ between

them.ANS: shielding5. In high-frequency RF circuits, the placement

of wires and ____________________ can be

critical.

ANS: components6. A ____________________ circuit is used toremove RF from the DC voltage bus.

ANS: decoupling7. A ____________________ capacitor is used

to short unwanted RF to ground.ANS: bypass

8. The bandwidth of a tuned-circuit amplifier

depends on the ____________________ of thetuned circuit.ANS: Q

9. A value of ____________________ or more

for Q is required for the approximate tuned

circuit equationsto be valid.

ANS: 1010. In a class C RF amplifier, the

____________________ extracts one frequency

from all the harmonicscontained in the device current (e.g. collectorcurrent).

ANS: tuned circuit

11. Using additional feedback to compensate for"stray" feedback is called

____________________.

ANS: neutralization12. A Colpitts oscillator uses a

____________________ voltage divider to

provide feedback.ANS: capacitive13. Electrically, a piezoelectric crystal has both a

____________________ and a

____________________resonant frequency.

ANS: series, parallel14. To produce sum and difference frequencies,a mixer must be a non-____________________

circuit.ANS: linear

15. At some bias point, a diode or a transistorcan act as a ____________________-law mixer.

ANS: squareSHORT ANSWER

1. What inductance would you use with a 47-pF

capacitor to make a tuned circuit for 10 MHz?ANS:

5.4 QH

2. What value of Q is required for a 10-MHztuned circuit to have a bandwidth of 100 kHz?

ANS:1003. A tuned-circuit amplifier with a gain of 10 is

being used to make an oscillator. What should

be the value

of the feedback ratio to satisfy the Barkhausencriteria?

ANS:0.1


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4. What is the advantage of a Clapp oscillator

compared to a Colpitts oscillator?ANS:It is more stable because it "swamps" the device

capacitance with large value capacitors in the

feedback

divider.5. If a varactor has a capacitance of 90 pF at

zero volts, what will be the capacitance at 4volts?

ANS:

30 pF6. An oscillator has a frequency of 100 MHz at20C, and a tempco of +10 ppm per degree

Celsius. What

will be the shift in frequency at 70C? Whatpercentage is that?

ANS:

50 kHz, 0.05%7. Two sinusoidal signals, V1 and V2, are fed into

an ideal balanced mixer. V1 is a 20-MHz signal;

V2 is a 5-MHz signal. What frequencies would you expectat the output of the mixer?

ANS:

15 MHz and 25 MHz8. Suppose the phase-locked-loop frequency

synthesizer of Figure 2.39 has a referencefrequency of 1 MHzand a fixed-modulus divider of 10. What should

be the value of the programmable divider to getan output

frequency of 120 MHz?ANS:

12

Chapter 3: Amplitude ModulationMULTIPLE CHOICE

1. AM stands for:

a. Audio Modulation c. Angle Modulationb. Amplitude Modulation d. Antenna

ModulationANS: B

2. The "envelope" of an AM signal is due to:a. the baseband signal c. the amplitude signal

b. the carrier signal d. none of the aboveANS: A

3. If the audio Va sin([at) modulates the carrier

Vc sin([ct), then the modulation index, m, is:

a. m= [a / [c c. m= (Va / Vc)2

b. m= Va / Vc d. m= Va / [aANS: B

4. The equation for full-carrier AM is:

a. v(t) = (Ec +Em) vsin([ct) c. v(t) = (EcvEm)

vsin([mt) vsin([ct)

b. v(t) = (Ec +Em) vsin([mt) + sin([ct) d. v(t) =

(Ec +Emsin([mt)) vsin([ct)ANS: D5. Overmodulation causes:

a. distortion c. both a and bb. splatter d. none of the above

ANS: C6. The peak voltage of an AM signal goes from

Emax toEmin. The modulation index, m, is:a. m=Emin/Emax c. m= (EmaxEmin) / (Emax +

Emin)

b. m=Emax /Emind. m= (Emax +Emin) / (EmaxEmin)ANS: C

7. IfVa sin([at) amplitude modulates the carrier

Vc sin([ct), it will produce the frequencies:

a. [c + [a and [c[a c. [c + [a and 2[c + 2[a

b. ([c + [a)/2 and ([c[a)/2 d. none of theabove

ANS: A

8. At 100% modulation, the total sidebandpower is:a. equal to the carrier power c. half the carrier

powerb. twice the carrier power d. 1.414 vcarrierpowerANS: C

9. If a 5-kHz signal modulates a 1-MHz carrier,the bandwidth of the AM signal will be:

a. 5 kHz c. 1.005 MHzb. 10 kHz d. none of the above

ANS: B

10. If an AM radio station increases itsmodulation index, you would expect:a. the audio to get louder at the receiver c. the

signal-to-noise ratio to increaseb. the received RF signal to increase d. all of the

aboveANS: D

11. The modulation index can be derived from:a. the time-domain signal c. both a and b

b. the frequency-domain signal d. none of the

aboveANS: C


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12. The main problem in using quadrature AM

would be:a. requires too much bandwidth c.incompatibility with ordinary AM radios

b. requires too much power d. all of the above

ANS: C

13. As compared to plain AM, SSB AM:a. is more efficient

b. requires a more complex demodulator circuitc. requires less bandwidth

d. all of the above

ANS: D14. The SC in SSB SC stands for:a. single-carrier c. sideband-carrier

b. suppressed-carrier d. none of the above

ANS: B15. PEP stands for:

a. Peak Envelope Power c. Peak Envelope

Productb. Peak Efficiency Power d. none of the above

ANS: A

16. If an SSB transmitter radiates 1000 watts atpeak modulation, what will it radiate with nomodulation?

a. 1000 watts c. 250 watts

b. 500 watts d. 0 wattsANS: D

17. Music on AM radio stations is "low-fidelity"because:a. AM is susceptible to noise

b. commercial AM stations use low powerc. commercial AM stations have a narrow

bandwidthd. all of the above

ANS: C

18. The type of information that can be sentusing AM is:

a. audio c. digital datab. video d. all of the aboveANS: D

19. Two tones modulate an AM carrier. One

tone causes a modulation index ofm1 and the

other tone causes amodulation index ofm2. The total modulationindex is:

a. m1 + m2 c. sqrt(m1vm2 + m2vm1)

b. (m1 + m2) / 2 d. sqrt(m1vm1 + m2vm2)ANS: D

20. To demodulate a USB SSB signal, thereceiver must:

a. be set to USB mode c. both a and b

b. reinsert the carrier d. none of the above

ANS: CCOMPLETION

1. An advantage of AM is that the receiver can

be very ____________________.

ANS: simple

2. A disadvantage of AM is its____________________ use of power.

ANS: inefficient3. The ____________________ of an AM signal

resembles the shape of the baseband signal.

ANS: envelope4. In AM, modulating with a single audio tone

produces ____________________ sidebands.

ANS: two

5. Compared to the USB, the information in theLSB is ____________________.

ANS: the same

6. Compared to the USB, the power in the LSBis ____________________.

ANS: the same

7. In AM, total sideband power is always____________________ than the carrier power.ANS: less

8. In AM, as the modulation index increases, the

carrier power _________________________.ANS: remains constant

9. The power in an AM signal is maximumwhen the modulation index is

____________________.

ANS: one10. In AM, a voice-band signal of 300 Hz to

3000 Hz will require a bandwidth of____________________.

ANS: 6000 Hz

11. With a 1-MHz carrier, if the LSB extendsdown to 990 kHz, then the USB will extend up

to____________________.ANS: 1010 kHz

12. If an AM transmitter puts out 100 watts with

no modulation, it will put out

____________________ wattswith 100% modulation.ANS: 150SHORT ANSWER

1. An AM transmitter generates 100 watts with

0% modulation. How much power will itgenerate with 20%modulation?

ANS:


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102 watts

2. If the carrier power is 1000 watts, what is thepower in the USB at 70.7% modulation?ANS:

125 watts

3. A carrier is modulated by three audio tones. If

the modulation indexes for the tones are 0.3, 0.4,and 0.5,

then what is the total modulation index?ANS:

0.707

4. You look at an AM signal with anoscilloscope and see that the maximum Vpp is100 volts and the

minimum Vpp is 25 volts. What is the modulation

index?ANS:

0.6

5. A SSB transmitter is connected to a 50-ohmantenna. If the peak output voltage of the

transmitter is 20

volts, what is the PEP?ANS:4 watts

Chapter 4: Angle ModulationMULTIPLE CHOICE

1. The FM modulation index:a. increases with both deviation and modulation

frequency

b. increases with deviation and decreases withmodulation frequencyc. decreases with deviation and increases with

modulation frequency

d. is equal to twice the deviationANS: B

2. One way to derive FM from PM is:a. integrate the modulating signal beforeapplying to the PM oscillator

b. integrate the signal out of the PM oscillator

c. differentiate the modulating signal beforeapplying to the PM oscillator

d. differentiate the signal out of the PMoscillator

ANS: A3. The bandwidth of an FM signal is considered

to be limited because:a. there can only be a finite number of sidebands

b. it is equal to the frequency deviation

c. it is band-limited at the receiver

d. the power in the outer sidebands is negligible

ANS: D

4. Mathematically, the calculation of FMbandwidth requires the use of:a. ordinary trigonometry and algebra c. Taylor

series

b. Bessel functions d. fractals

ANS: B5. FM bandwidth can be approximated by:

a. Armstrong's Rule c. Carson's Ruleb. Bessel's Rule d. none of the above

ANS: C

6. NBFM stands for:a. National Broadcast FM c. Near Band FM

b. Non-Broadcast FM d. Narrowband FM

ANS: D

7. When FM reception deteriorates abruptly dueto noise, it is called:

a. the capture effect c. the noise effect

b. the threshold effect d. the limit effectANS: B

8. An FM receiver switching suddenly between

two stations on nearby frequencies is called:a. the capture effect c. the "two-station" effect

b. the threshold effect d. none of the above

ANS: A

9. Pre-emphasis is used to:a. increase the signal to noise ratio for higher

audio frequenciesb. increase the signal to noise ratio for loweraudio frequencies

c. increase the signal to noise ratio for all audiofrequencies

d. allow stereo audio to be carried by FMstations

ANS: A

10. A pre-emphasis of 75 Qs refers to:a. the time it takes for the circuit to work

b. the "dead time" before de-emphasis occurs

c. the time delay between the L and R channelsd. the time-constant of the filter circuits used

ANS: D11. FM stereo:

a. uses DSBSC AM modulation c. has a higherS/N than mono FM

b. is implemented using an SCA signal d. is notcompatible with mono FM

ANS: A

12. An SCA signal:a. can use amplitude modulation c. is monaural

b. can use FM modulation d. all of the aboveANS: D


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13. The modulation index of an FM signal can

be determined readily:a. using measurements at points whereJ0 equalsone

b. using measurements at points whereJ0 equals

zero

c. using measurements at points where thedeviation equals zero

d. only by using Bessel functionsANS: BCOMPLETION

1. FM and PM are two forms of ____________________ modulation.ANS: angle

2. PM is extensively used in

____________________ communication.ANS: data

3. Compared to AM, the signal-to-noise ratio of

FM is usually ____________________.ANS: better

4. Compared to AM, the bandwidth of FM is

usually ____________________.ANS:wider

greater

5. FM transmitters can use Class____________________ amplifiers since

amplitude linearity is notimportant.ANS: C

6. Both the power and amplitude of an FMsignal ____________________ as modulation is

applied.ANS: stay constant

7. In FM, the frequency deviation is proportional

to the instantaneous ____________________ ofthe

modulating signal.ANS: amplitude8. The frequency deviation of an FM signal

occurs at a rate equal to the

____________________ of the

modulating signal.ANS: frequency9. Mathematically, the number of sidebands in

an FM signal is ____________________.ANS: infinite

10. As FM sidebands get farther from the centerfrequency, their power ____________________.ANS: decreases

11. Mathematically, the value of an FM

modulation index can be as high as____________________.ANS: any number

12. In FM, as the modulating frequency

decreases, the modulation index

____________________.ANS: increases

13. In FM, as the frequency deviation decreases,the modulation index ____________________.

ANS: decreases

14. As the FM modulation index increases, thenumber of significant sidebands

____________________.

ANS: increases

15. For certain values ofmf, such as 2.4, theamplitude of the carrier frequency

____________________.

ANS:disappears

goes to zero

16. The bandwidth of an FM signal can beapproximated using ____________________rule.

ANS: Carson's

17. FM bandwidth can be calculated preciselyusing ____________________ functions.

ANS: Bessel18. The ____________________ effect ischaracteristic of FM reception in a noisy

environment.ANS: threshold

19. The ____________________ effect is seenwhen an FM receiver is exposed to two FM

signals that are

close to each other in frequency.ANS: capture

20. Rest frequency is another name for an FM ____________________ frequency.ANS: carrierSHORT ANSWER

1. If a 2-volt instantaneous value of modulating

signal amplitude causes a 10-kHz deviation incarrierfrequency, what is the deviation sensitivity of

the modulator?ANS:

5 kHz / volt2. If a 2-kHz audio tone causes a frequencydeviation of 4 kHz, what is the modulation

index?


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ANS: C

8. With low-level AM:a. the RF amplifiers must be Class A c. the RFamplifiers must be linear

b. the RF amplifiers must be Class B d. the RF

amplifiers must be low-power

ANS: C9. Power amplifiers must be linear for any signal

that:a. is complex c. has variable frequency

b. has variable amplitude d. all of the above

ANS: B10. In high-level AM, "high-level" refers to:a. the power level of the carrier c. the power

level of the final RF amplifier

b. the power level of the modulation d. none ofthe above

ANS: D

11. In high-level AM, the power in thesidebands comes from:

a. the modulating amplifier c. the driver stage

b. the RF amplifier d. the carrierANS: A12. In an AM transmitter with 100% modulation,

the voltage of the final RF stage will be:

a. approximately half the DC supply voltageb. approximately twice the DC supply voltage

c. approximately four times the DC supplyvoltaged. none of the above

ANS: C13. Practical transmitters are usually designed to

drive a load impedance of:a. 50 ohms resistive c. 300 ohms resistive

b. 75 ohms resistive d. 600 ohms resistive

ANS: A14. Which of the following can be used for

impedance matching?a. pi network c. both a and b

b. T network d. a bridge circuit

ANS: C

15. When a transmitter is connected to a resistor

instead of an antenna, the resistor is called:a. a heavy load c. a temporary load

b. a dummy load d. a test load

ANS: B16. When a transmitter is connected to a resistor

instead of an antenna, the resistor must be:a. wire-wound c. 1% tolerance or better

b. noninductive d. all of the above

ANS: B

17. A Class D amplifier is:

a. very efficient c. essentially pulse-durationmodulation

b. essentially pulse-width modulation d. all of

the above

ANS: D

18. To generate a SSB signal:a. start with full-carrier AM c. start with a

quadrature signalb. start with DSBSC d. all of the above

ANS: B

19. The carrier is suppressed in:a. a balanced modulator c. a frequency multiplier

b. a mixer d. none of the above

ANS: A

20. To remove one AM sideband and leave theother you could use:

a. a mechanical filter c. both a and b

b. a crystal filter d. none of the aboveANS: C

21. A direct FM modulator:

a. varies the frequency of the carrier oscillatorb. integrates the modulating signalc. both a and b


ANS: A22. An indirect FM modulator:

a. requires a varactor in the carrier oscillatorb. varies the phase of the carrier oscillatorc. both a and b

d. none of the aboveANS: B

23. AFC stands for:a. Amplitude to Frequency Conversion c.

Automatic Frequency Control

b. Automatic Frequency Centering d. AudioFrequency Control

ANS: C24. Frequency multipliers are:a. essentially balanced modulators c. essentially

mixers

b. essentially Class C amplifiers d. none of the

aboveANS: B25. With mixing:

a. the carrier frequency can be raisedb. the carrier frequency can be lowered

c. the carrier frequency can be changed to anyrequired valued. the deviation is altered

ANS: C


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12

COMPLETION

1. The accuracy and stability of a transmitterfrequency is fixed by the

____________________ oscillator.

ANS: carrier

2. In the USA, the ____________________ sets

requirements for accuracy and stability of atransmitter's

frequency.ANS: FCC

3. In Canada, _________________________

sets requirements for accuracy and stability of atransmitter'sfrequency.

ANS: Industry Canada

4. Frequency ____________________ is theability of a transmitter to change frequency

without a lot of

retuning.ANS: agility

5. Power output of SSB transmitters is rated by

____________________.ANS: PEP6. Reducing the dynamic range of a modulating

signal is called ____________________.

ANS: compression7. The opposite of compression is called

____________________.ANS: expansion8. ALC is a form of ____________________.

ANS: compression9. High-level modulation allows the RF

amplifiers to operate more____________________.

ANS: efficiently

10. Low-level modulation requires the RFamplifiers to be ____________________.

ANS: linear11. To isolate the oscillator from load changes, a

____________________ stage is used.

ANS: buffer

12. The peak collector voltage in a Class C RF

amplifier is ____________________ than theDC supplyvoltage.

ANS: higher13. Most practical transmitters are designed to

operate into a ____________________-ohmload.ANS: 50

14. Transmitters built with transistor RF

amplifiers often use a ____________________network forimpedance matching.

ANS: T

15. Matching networks also act as filters to help

reduce ____________________ levels.ANS: harmonic

16. Severe impedance ____________________can destroy a transmitter's output stage.

ANS: mismatch

17. Transceivers combine a transmitter and a____________________ into one "box".ANS: receiver

18. To allow a high modulation percentage, it is

common to modulate the____________________ as well as

the power amplifier in transistor modulators.

ANS: driver19. Pulse-width modulation is the same as pulse-

____________________ modulation.

ANS: duration20. Switching amplifiers are sometimes calledClass ____________________ amplifiers.

ANS: D

21. Because the sideband filter in a SSBtransmitter is fixed, ____________________ is

used to operate atmore than one frequency.ANS: mixing

22. To generate a SSB signal, it is common tostart with a ____________________ signal.

ANS: DSBSC23. Indirect FM is derived from

____________________ modulation.

ANS: phase24. Using a varactor to generate FM is an

example of a ____________________modulator.ANS: reactance

25. The modern way to make a stable VFO is to

make it part of a ____________________ loop.

ANS: phase-lockedSHORT ANSWER

1. If a 50-MHz oscillator is accurate to within

0.001%, what is the range of possiblefrequencies?

ANS:

50 MHz s500 hertz


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13

2. What is the efficiency of a 100-watt mobile

transmitter if it draws 11 amps from a 12-voltcar battery?ANS:

75.8%

3. The power amplifier of an AM transmitter

draws 100 watts from the power supply with nomodulation.

Assuming high-level modulation, how muchpower does the modulation amplifier deliver for

100%

modulation?ANS:50 watts

4. If the final RF amplifier of an AM transmitter

is powered by 100 volts DC, what is themaximum

collector voltage at 100% modulation?

ANS:400 volts

5. Suppose the output of a balanced modulator

has a center frequency of 10 MHz. The audiomodulationfrequency range is 1 kHz to 10 kHz. To pass the

USB, what should be the center frequency of an

idealcrystal filter?

ANS:10.005 MHz6. Suppose you have generated a USB SSB

signal with a nominal carrier frequency of 10MHz. What is the

minimum frequency the SSB signal can bemixed with so that the output signal has a

nominal carrier

frequency of 50 MHz?ANS:

40 MHz7. Suppose you have an FM modulator that putsout 1 MHz carrier with a 100-hertz deviation. If

frequency

multiplication is used to increase the deviation to

400 hertz, what will be the new carrierfrequency?ANS:

4 MHz8. Suppose you had an FM signal with a carrier

of 10 MHz and a deviation of 10 kHz. Explainhow youcould use it to get an FM signal at 100 MHz

with a deviation of 20 kHz.

ANS:

First, put the signal through a frequency doublerto get a 20-MHz carrier with a 20-kHz deviation.Then

mix that signal with an 80-MHz carrier to

generate a 100-MHz carrier with 20-kHz

deviation.

Chapter 6: ReceiversMULTIPLE CHOICE

1. The two basic specifications for a receiverare:a. the sensitivity and the selectivity

b. the number of converters and the number ofIFs

c. the spurious response and the trackingd. the signal and the noise

ANS: A

2. The superheterodyne receiver was inventedby:

a. Foster c. Armstrongb. Seeley d. HertzANS: C

3. Trimmers and padders are:a. two types of adjusting tools c. small

adjustable inductors

b. small adjustable resistors d. small adjustablecapacitorsANS: D

4. "Skin effect" refers to:

a. the way radio signals travel across a flatsurface

b. the tissue-burning effect of a strong RF signal

c. the increase of wire resistance with frequency

d. none of the aboveANS: C

5. The "front end" of a receiver can include:a. the tuner c. the mixer

b. the RF amplifier d. all of the above

ANS: D

6. "IF" stands for:a. intermediate frequency c. indeterminate

frequencyb. intermodulation frequency d. image frequency

ANS: A7. AGC stands for:

a. Audio Gain Control c. Active Gain Controlb. Automatic Gain Control d. Active GainConversion

ANS: B

8. The frequency of the local oscillator:


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14

a. is above the RF frequency

b. is below the RF frequencyc. can be either above of below the RFfrequency

d. is fixed, typically at 455 kHz.

ANS: C

9. The local oscillator and mixer are combinedin one device because:

a. it gives a greater reduction of spuriousresponses

b. it increases sensitivity

c. it increases selectivityd. it is cheaperANS: D

10. Basically, sensitivity measures:

a. the weakest signal that can be usefullyreceived

b. the highest-frequency signal that can be

usefully receivedc. the dynamic range of the audio amplifier


ANS: A11. Basically, selectivity measures:a. the range of frequencies that the receiver can

select

b. with two signals close in frequency, theability to receive one and reject the other

c. how well adjacent frequencies are separatedby the demodulatord. how well the adjacent frequencies are

separated in the mixerANS: B

12. When comparing values for shape factor:a. a value of 1.414 dB is ideal c. a value of 1.0 is

ideal

b. a value of 0.707 is ideal d. there is no idealvalue

ANS: C13. When comparing values for shape factor:a. a value of 2 is better than a value of 4 c. both

values are basically equivalent

b. a value of 4 is better than a value of 2 d. none

of the aboveANS: A14. Distortion in a receiver can occur in:

a. the mixer c. the IF amplifiersb. the detector d. all of the above

ANS: D15. Phase distortion is important in:a. voice communications systems c.

monochrome video receivers

b. color video receivers d. all of the above

ANS: B16. The response of a receiver to weak signals isusually limited by:

a. the AGC c. the dynamic range of the receiver

b. noise generated in the receiver d. the type of

detector circuit being usedANS: B

17. Image frequencies occur when two signals:a. are transmitted on the same frequency

b. enter the mixer, with one being a reflected

signal equal to the IF frequencyc. enter the mixer, one below and one above thelocal oscillator by a difference equal to the

IF

d. enter the mixer, and the difference betweenthe two signals is equal to twice the IF

ANS: C

18. An image must be rejected:a. prior to mixing c. prior to detection

b. prior to IF amplification d. images cannot be

rejectedANS: A19. Image frequency problems would be reduced

by:

a. having an IF amplifier with the proper shapefactor

b. having a wideband RF amplifier after themixerc. having a narrowband RF amplifier before the

mixerd. none of the above

ANS: C20. A common AM detector is the:

a. PLL c. ratio detector

b. envelope detector d. all of the aboveANS: B

21. An FM detector is the:a. PLL c. quadrature detector

b. ratio detector d. all of the above

ANS: D

22. Germanium diodes are used in AM detectors

because:a. they are faster than silicon diodes

b. they are cheaper than silicon diodes

c. they minimize distortion from nonlinearityd. all of the above

ANS: C23. A common SSB detector is:a. a PLL c. a BFO

b. a diode d. a product detector


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15

ANS: D

24. BFO stands for:a. Beat Frequency Oscillator c. BipolarFrequency Oscillator

b. Barrier Frequency Oscillator d. Bistable

Frequency Oscillator

ANS: A25. To demodulate both SSB and DSBSC, you

need to:a. use a Foster-Seeley discriminator

b. reinject the carrier

c. use double conversiond. use one diode for SSB and two diodes forDSBSC

ANS: B

26. Which would be best for DSBSC:a. carrier detection c. envelope detection

b. coherent detection d. ratio detection

ANS: B27. An FM detector that is not sensitive to

amplitude variations is:

a. Foster-Seeley detector c. a PLL detectorb. a quadrature detector d. all of the aboveANS: C

28. The function of a limiter is:

a. to remove amplitude variations c. to limitdynamic range

b. to limit spurious responses d. to limit noiseresponseANS: A

29. Suppressing the audio when no signal ispresent is called:

a. AGC c. AFCb. squelch d. limiting

ANS: B

30. LNA stands for:a. Limited-Noise Amplifier c. Low-Noise Audio

b. Low-Noise Amplifier d. Logarithmic NoiseAmplificationANS: B

31. AFC stands for:

a. Audio Frequency Compensator c. Automatic

Frequency Controlb. Autodyne Frequency Compensation d.Autonomous Frequency Control

ANS: C32. The function of AFC is:

a. maintain a constant IF frequencyb. match the local oscillator to the receivedsignal

c. lock the discriminator to the IF frequency


ANS: B33. SAW stands for:a. Symmetrical Audio Wave c. Silicon-Activated

Wafer

b. Surface Acoustic Wave d. Software-Activated

WaveANS: B

34. The important property of a SAW is:a. it stabilizes the audio in a receiver c. it is a

stable bandpass filter

b. it allows software radios to be built d. none ofthe aboveANS: C

35. The main function of the AGC is to:

a. keep the gain of the receiver constantb. keep the gain of the IF amplifiers constant

c. keep the input to the detector at a constant

amplituded. all of the above

ANS: C

36. DSP stands for:a. Dynamic Signal Properties c. Distorted SignalPacket

b. Direct Signal Phase d. Digital Signal

ProcessorANS: D

37. SINAD stands for:a. Sinusoidal Amplitude Distortion

b. Signal and Noise Amplitude Distortion

c. Signal-plus-Noise-to-Noise Ratiod. Signal-plus-Noise and Distortion-to-Noise

and Distortion RatioANS: D

38. TRF stands for:

a. Tuned Radio Frequency c. Transmitted RadioFrequency

b. Tracking Radio Frequency d. Tuned ReceiverFunctionANS: ACOMPLETION

1. Almost all modern receivers use the

_________________________ principle.ANS: superheterodyne2. The first radio receiver of any kind was built

in the year ____________________.ANS: 1887

3. When two tuned circuits____________________ each other, it meansthat when the frequency of one is

adjusted, the other changes with it.


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ANS: track

4. The ____________________ effect causesthe resistance of wire to increase with frequency.ANS: skin

5. The superhet was invented in the year

____________________.

ANS: 19186. In a receiver, the ____________________

refers to the input filter and RF stage.ANS: front end

7. In a superhet, the output of the

____________________ goes to the IFamplifiers.ANS: mixer

8. In a superhet, the ____________________

frequency is the difference between the localoscillator

frequency and the received signal frequency.

ANS:intermediate

IF

9. The ____________________ circuit adjuststhe gain of the IF amplifiers in response to signalstrength.

ANS: AGC

10. An ____________________ converter usesthe same transistor for both the local oscillator

and the mixer.ANS: autodyne11. In low-side injection, the local oscillator is

____________________ than the receivedsignal frequency.

ANS: lower12. ____________________ is the ability of a

receiver to separate two signals that are close to

each other infrequency.

ANS: Selectivity13. ____________________ is the ability of areceiver to receive and successfully demodulate

a very weak

signal.

ANS: Sensitivity14. A receiver with two different IF frequenciesis called a double-____________________

receiver.ANS: conversion

15. A multiple-conversion receiver will havebetter rejection of ____________________frequencies.

ANS: image

16. A demodulator is also called a

____________________.ANS: detector17. An ____________________ detector uses a

diode to half-wave rectify an AM signal.

ANS: envelope

18. A ____________________ detector is usedfor SSB signals.

ANS: product19. A BFO produces a locally generated

____________________.

ANS: carrier20. A DSBSC signal requires a

____________________ detection circuit.

ANS: coherent

21. FM detectors have a characteristic ____________________-shaped curve.

ANS: S

22. While still commonly found, the Foster-Seeley and ratio detectors are

____________________.

ANS: obsolescent23. Unlike the PLL detector, the quadraturedetector is sensitive to changes in

____________________ of the

input signal.ANS: amplitude

24. A dual-____________________ MOSFETis useful for AGC.ANS: gate

25. Diode mixers are too____________________ to be practical in most

applications.ANS: noisy

26. The IF amplifiers in an AM receiver must be

Class ____________________.ANS: A

27. A double-tuned IF transformer is usually____________________ coupled for theresponse to have a flat

top and steep sides.

ANS: over

28. Multiple IF stages can be____________________-tuned to increase thebandwidth.

ANS: stagger29. Compared to tuned circuits, ceramic and

crystal IF filters do not require____________________.ANS: adjustment


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17

30. Up-conversion is when the output of the

mixer is a ____________________ frequencythan the incomingsignal.

ANS: higher

31. In a block converter, the frequency of the

first local oscillator is ____________________.ANS:

fixedconstant

32. Typically, AGC reduces the gain of the

____________________ amplifiers.ANS: IF33. An ____________________-meter is

designed to indicate signal strength in many

communicationsreceivers.

ANS: S

34. The effectiveness of FM____________________ is measured by a

receivers quieting sensitivity.

ANS: limiting35. A ____________________ refers to anykind of FM or PM detector.

ANS: discriminatorSHORT ANSWER

1. Suppose the bandwidth of a tuned circuit is 10

kHz at 1 MHz. Approximately what bandwidthwould youexpect it to have at 4 MHz?

ANS:20 kHz

2. Using high-side injection for a 1-MHz IF,what is the frequency of the local oscillator

when the receiver

is tuned to 5 MHz?ANS:

6 MHz3. An IF filter has a60 dB bandwidth of 25kHz and a 6 dB bandwidth of 20 kHz. What is

the shape

factor value?

ANS:1.254. Suppose a receiver uses a 5-MHz IF

frequency. Assuming high-side injection, whatwould be the image

frequency if the receiver was tuned to 50 MHz?ANS:60 MHz

5. Suppose a SSB receiver requires an injected

frequency of 1.5 MHz. What would be theacceptablefrequency range of the BFO if the maximum

acceptable baseband shift is 100 hertz?

ANS:

1.5 MHz s100 hertz6. The transformer of a double-tuned IF

amplifier has a Qof 25 for both primary andsecondary. What valueofkc do you need to achieve optimal coupling?

ANS:

0.067. What value of transformer coupling would adouble-tuned 10-MHz IF amplifier with optimal

coupling

need to get a bandwidth of 100 kHz?ANS:

0.01

Chapter 7: Digital CommunicationsMULTIPLE CHOICE

1. The first digital code was the:a. ASCII code c. Morse code

b. Baudot code d. none of the above

ANS: C2. In digital transmission, signal degradation can

be removed using:a. an amplifier c. a regenerative repeater

b. a filter d. all of the above

ANS: C3. TDM stands for:

a. Time-Division Multiplexing c. Ten-DigitalManchester

b. Time-Domain Multiplexing d. Ten Dual-

ManchesterANS: A

4. Hartley's Law is:a. I= ktB c. C=B log2(1 + S/N)

b. C= 2B log2Md. SR = 2fmax

ANS: A

5. The Shannon-Hartley theorem is:

a. I= ktB c. C=B log2(1 + S/N)b. C= 2B log2Md. SR = 2fmax

ANS: B

6. The Shannon Limit is given by:a. I= ktB c. C=B log2(1 + S/N)

b. C= 2B log2Md. SR = 2fmaxANS: C

7. The Nyquist Rate can be expressed as:


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18

a. I= ktB c. C=B log2(1 + S/N)

b. C= 2B log2Md. SR = 2fmaxANS: D8. Natural Sampling does not use:

a. a sample-and-hold circuit c. a fixed sample

rate

b. true binary numbers d. an analog-to-digitalconverter

ANS: A9. Which is true about aliasing and foldover

distortion?

a. They are two types of sampling error.b. You can have one or the other, but not both.c. Aliasing is a technique to prevent foldover

distortion.

d. They are the same thing.ANS: D

10. Foldover distortion is caused by:

a. noise c. too few samples per secondb. too many samples per second d. all of the

above

ANS: C11. The immediate result of sampling is:a. a sample alias c. PCM

b. PAM d. PDM

ANS: B12. Which of these is not a pulse-modulation

technique:a. PDM c. PPM

b. PWM d. PPS

ANS: D13. Quantizing noise (quantization noise):

a. decreases as the sample rate increasesb. decreases as the sample rate decreases

c. decreases as the bits per sample increases

d. decreases as the bits per sample decreasesANS: C

14. The dynamic range of a system is the ratioof:a. the strongest transmittable signal to the

weakest discernible signal

b. the maximum rate of conversion to the

minimum rate of conversionc. the maximum bits per sample to the minimum

bits per sample

d. none of the aboveANS: A

15. Companding is used to:a. compress the range of base-band frequencies

b. reduce dynamic range at higher bit-rates

c. preserve dynamic range while keeping bit-rate

lowd. maximize the useable bandwidth in digitaltransmission

ANS: C

16. In North America, companding uses:

a. the Logarithmic Law c. the ELaw (alpha law)b. the A Law d. the QLaw (mu law)

ANS: D17. In Europe, companding uses:

a. the Logarithmic Law c. the ELaw (alpha law)

b. the A Law d. the QLaw (mu law)ANS: B

18. Codec stands for:

a. Coder-Decoder c. Code-Compressionb. Coded-Carrier d. none of the above

ANS: A19. A typical codec in a telephone system sends

and receives:a. 4-bit numbers c. 12-bit numbers

b. 8-bit numbers d. 16-bit numbersANS: B20. Compared to PCM, delta modulation:

a. transmits fewer bits per sample c. can suffer

slope overloadb. requires a much higher sampling rate d. all of

the aboveANS: D21. In delta modulation, "granular noise" is

produced when:

a. the signal changes too rapidly c. the bit rate istoo high

b. the signal does not change d. the sample is toolarge

ANS: B22. Compared to PCM, adaptive delta

modulation can transmit voice:a. with a lower bit rate but reduced quality c.

only over shorter distancesb. with a lower bit rate but the same quality d.

only if the voice is band-limited

ANS: B

23. Which coding scheme requires DCcontinuity:

a. AMI c. unipolar NRZb. Manchester d. bipolar RZ

ANS: C24. Manchester coding:

a. is a biphase code


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19

b. has a level transition in the middle of every bit

periodc. provides strong timing informationd. all of the above

ANS: D

25. The number of framing bits in DS-1 is:

a. 1 c. 4b. 2 d. 8

ANS: A26. Framing bits in DS-1 are used to:

a. detect errors c. synchronize the transmitter

and receiverb. carry signaling d. all of the aboveANS: C

27. So-called "stolen" bits in DS-1 are used to:

a. detect errors c. synchronize the transmitterand receiver

b. carry signaling d. all of the above

ANS: B28. The number of bits per sample in DS-1 is:

a. 1 c. 4

b. 2 d. 8ANS: D29. The number of samples per second in DS-1

is:

a. 8 k c. 64 k

b. 56 k d. 1.544 v106ANS: A

30. The bit rate for each channel in DS-1 is:a. 1.544 Mb/s c. 56 kb/s

b. 64 kb/s d. 8 kb/sANS: B

31. In DS-1, bits are transmitted over a T-1 cable

at:a. 1.544 MB/s c. 56 kb/s

b. 64 kb/s d. 8 kb/s

ANS: A32. A T-1 cable uses:

a. Manchester coding c. NRZ codingb. bipolar RZ AMI coding d. pulse-width coding

ANS: B33. The number of frames in a superframe is:

a. 6 c. 24b. 12 d. 48ANS: B34. A typical T-1 line uses:

a. twisted-pair wire c. fiber-optic cable

b. coaxial cable d. microwaveANS: A

35. "Signaling" is used to indicate:a. on-hook/off-hook condition c. ringing

b. busy signal d. all of the above

ANS: D36. A vocoder implements compression by:a. constructing a model of the transmission

medium

b. constructing a model of the human vocal

systemc. finding redundancies in the digitized data

d. using lossless techniquesANS: B

37. Compared to standard PCM systems, the

quality of the output of a vocoder is:a. much better c. about the same

b. somewhat better d. not as good

ANS: DCOMPLETION

1. Digitizing a signal often results in

____________________ transmission quality.

ANS:improved

better

2. To send it over an analog channel, a digitalsignal must be ____________________ onto acarrier.

ANS: modulated

3. To send it over a digital channel, an analogsignal must first be ____________________.

ANS: digitized4. In analog channels, the signal-to-noise ratio ofan analog signal gradually

____________________ as thelength of the channel increases.

ANS:decreases

gets worse

5. The ____________________ value of a pulseis the only information it carries on a digital

channel.ANS: binary6. A ____________________ repeater is used to

restore the shape of pulses on a digital cable.

ANS: regenerative

7. There are techniques to detect and____________________ some errors in digitaltransmission.

ANS: correct8. Converting an analog signal to digital form is

another source of ____________________ indigitaltransmission systems.

ANS:


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20

error

noise9. ____________________-divisionmultiplexing is easily done in digital

transmission.

ANS: Time

10. All practical communications channels areband-____________________.

ANS: limited11. ____________________ Law gives the

relationship between time, information capacity,

and bandwidth.ANS: Hartley's12. Ignoring noise, the

_________________________ theorem gives

the maximum rate of data transmissionfor a given bandwidth.

ANS: Shannon-Hartley

13. The ____________________ limit gives themaximum rate of data transmission for a given

bandwidth

and a given signal-to-noise ratio.ANS: Shannon14. ____________________ sampling is done

without a sample-and-hold circuit.

ANS: Natural15. The ____________________ Rate is the

minimum sampling rate for converting analogsignals to digitalformat.

ANS: Nyquist16. ____________________ distortion occurs

when an analog signal is sampled at too slow arate.

ANS: Foldover

17. ____________________ means that higherfrequency baseband signals from the transmitter

"assume theidentity" of low-frequency baseband signals atthe receiver when sent digitally.

ANS: Aliasing

18. The output of a sample-and-hold circuit is a

pulse-____________________ modulatedsignal.ANS: amplitude

19. ____________________ modulation is themost commonly used digital modulation

scheme.ANS: Pulse-code

20. ____________________ noise results from

the process of converting an analog signal intodigital format.ANS: Quantizing

21. ____________________ is used to preserve

dynamic range using a reasonable bandwidth.

ANS: Companding22. In North America, compression is done

using the ____________________-law equation.ANS:

Q

mu

23. In Europe, compression is done using the ____________________-law equation.ANS: A

24. A ____________________ is an IC that

converts a voice signal to PCM and vice versa.ANS: codec

25. In a PCM system, the samples of the analogsignal are first converted to

____________________ bitsbefore being compressed to 8 bits.

ANS: 1226. The number of bits per sample transmitted indelta modulation is ____________________.

ANS:

1one

27. Delta modulation requires a____________________ sampling rate than

PCM for the same quality ofreproduction.

ANS: higher

28. ____________________ noise is producedby a delta modulator if the analog signal doesn'tchange.

ANS: Granular29. In delta modulation,

____________________ overload can occur ifthe analog signal changes too fast.

ANS: slope30. The ____________________ size varies in

adaptive delta modulation.ANS: step31. Adaptive delta modulation can transmitPCM-quality voice at about

____________________ the bit rate

of PCM.ANS: half


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21

32. Unipolar NRZ is not practical because most

channels do not have ____________________continuity.ANS: DC

33. In AMI, binary ones are represented by a

voltage that alternates in

____________________.ANS: polarity

34. Long strings of ____________________should be avoided in AMI.

ANS: zeros

35. Manchester code has a level____________________ in the center of eachbit period.

ANS: transition

36. Manchester coding provides____________________ information regardless

of the pattern of ones and

zeros.ANS: timing

37. There are ____________________ channels

in a DS-1 frame.ANS: 2438. DS-1 uses a ____________________ bit to

synchronize the transmitter and receiver.

ANS: framing39. In DS-1, each channel is sampled

____________________ times per second.ANS: 800040. Data is carried over a T-1 line at a rate of

____________________ bits per second.ANS: 1.544 v10641. A group of 12 DS-1 frames is called a

____________________.ANS: superframe42. From a group of twelve frames, signaling

bits are "stolen" from every ____________________ frame.

ANS: sixth43. ____________________ compression

transmits all the data in the original signal butuses fewer bits to do

it.ANS: LosslessSHORT ANSWER

1. Use Hartley's Law to find how much time it

would take to send 100,000 bits over a channel

with abandwidth of 2,000 hertz and a channel constant

ofk= 10.ANS:

5 seconds

2. Use the Shannon-Hartley theorem to find thebandwidth required to send 12,000 bits persecond if the

number of levels transmitted is 8.

ANS:

2000 hertz3. What is the Shannon Limit of a channel that

has a bandwidth of 4000 hertz and a signal-to-noise ratio of

15?

ANS:16 kbps4. What is the minimum required number of

samples per second to digitize an analog signal

with frequencycomponents ranging from 300 hertz to 3300

hertz?

ANS:6600 samples/second

5. What is the approximate dynamic range, in

dB, of a linear PCM system that uses 12 bits persample?ANS:

74 dB

6. What is the approximate data rate for a systemusing 8 bits per sample and running at 8000

samples persecond?ANS:

64 kbps7. If bits were "stolen" from every DS-1 frame,

what would the useable data-rate be for eachchannel in the

frame?

ANS:56 kbps

8. Assuming maximum input and outputvoltages of 1 volt, what is the output voltage of a

Q-law compressor

if the input voltage is 0.388 volt?ANS:

0.833 volt

Chapter 8: The Telephone SystemMULTIPLE CHOICE

1. DTMF stands for:

a. Digital Telephony Multiple Frequency c.Dual-Tone Multifrequency


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b. Dial Tone Master Frequency d. Digital Trunk

Master FrequencyANS: C2. PSTN stands for:

a. Public Switched Telephone Network c.

Primary Service Telephone Network

b. Private Switched Telephone Network d.Primary Service Telephone Numbers

ANS: A3. POTS stands for:

a. Private Office Telephone System c. Primary

Operational Test Systemb. Primary Office Telephone Service d. PlainOld Telephone Service

ANS: D

4. LATA stands for:a. Local Access and Transport Area c. Local

Area Telephone Access

b. Local Access Telephone Area d. Local AreaTransport Access

ANS: A

5. A LATA is a:a. a local calling area c. a way of accessing atandem office

b. a type of digital local network d. a way of

accessing a central officeANS: A

6. Central offices are connected by:a. local loops c. both a and b

b. trunk lines d. none of the above

ANS: B7. Local loops terminate at:

a. a tandem office c. a central officeb. a toll station d. an interexchange office

ANS: C

8. Call blocking:a. cannot occur in the public telephone network

b. occurs on the local loop when there is anelectrical power failurec. occurs only on long-distance cables

d. occurs when the central office capacity is

exceeded

ANS: D9. In telephony, POP stands for:a. Post Office Protocol c. Power-On Protocol

b. Point Of Presence d. none of the aboveANS: B

10. The cable used for local loops is mainly:a. twisted-pair copper wire c. coaxial cable

b. shielded twisted-pair copper wire d. fiber-

optic

ANS: A

11. FITL stands for:a. Framing Information for Toll Loops c.Framing In The Loop

b. Fiber In the Toll Loop d. Fiber-In-The-Loop

ANS: D

12. Loading coils were used to:a. increase the speed of the local loop for digital

datab. reduce the attenuation of voice signals

c. reduce crosstalk

d. provide C-type conditioning to a local loopANS: B13. DC current flows through a telephone:

a. when it is on hook c. as long as it is attached

to a local loopb. when it is off hook d. only when it is ringing

ANS: B

14. The range of DC current that flows through atelephone is:

a. 20 QA to 80 QA c. 2 mA to 8 mA

b. 200 QA to 800 QA d. 20 mA to 80 mAANS: D

15. The separation of control functions from

signal switching is known as:a. step-by-step switching control c. common

control

b. crossbar control d. ESS

ANS: C16. The typical voltage across a telephone when

on-hook is:a. 48 volts DC c. 90 volts DC

b. 48 volts, 20 hertz AC d. 90 volts, 20 hertz AC

ANS: A

17. The typical voltage needed to "ring" atelephone is:a. 48 volts DC c. 90 volts DC

b. 48 volts, 20 hertz AC d. 90 volts, 20 hertz AC

ANS: D18. The bandwidth of voice-grade signals on atelephone system is restricted in order to:

a. allow lines to be "conditioned" c. allow

signals to be multiplexedb. prevent "singing" d. all of the above

ANS: C19. VNL stands for:a. voltage net loss c. via net loss

b. volume net loss d. voice noise level

ANS: C20. Signal loss is designed into a telephone

system to:


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a. eliminate reflections c. improve signal-to-

noise ratiob. prevent oscillation d. reduce powerconsumption

ANS: B

21. The reference noise level for telephony is:

a. 1 mW c. 1 pWb. 0 dBm d. 0 dBr

ANS: C22. The number of voice channels in a basic

FDM group is:

a. 6 c. 24b. 12 d. 60ANS: B

23. Basic FDM groups can be combined into:

a. supergroups c. jumbogroupsb. mastergroups d. all of the above

ANS: D

24. In telephone system FDM, voice is put on acarrier using:

a. SSB c. PDM

b. DSBSC d. PCMANS: A25. PABX stands for:

a. Power Amplification Before Transmission

b. Private Automatic Branch Exchangec. Public Automated Branch Exchange

d. Public Access Branch ExchangeANS: B26. SLIC stands for:

a. Single-Line Interface Circuit c. SubscriberLine Interface Card

b. Standard Line Interface Card d. StandardLocal Interface Circuit

ANS: C

27. In DS-1, bits are "robbed" in order to:a. provide synchronization c. cancel echoes

b. carry signaling d. check for errorsANS: B28. "Bit-stuffing" is more formally called:

a. compensation c. justification

b. rectification d. frame alignment

ANS: C29. ISDN stands for:a. Integrated Services Digital Network c.

Integrated Services Data Networkb. Information Services Digital Network d.

Information Systems Digital NetworkANS: A30. Basic ISDN has not been widely adopted

because:

a. it took to long to develop

b. it is too slowc. it has been surpassed by newer technologiesd. all of the above

ANS: D

31. ADSL stands for:

a. All-Digital Subscriber Line c. AllocatedDigital Service Line

b. Asymmetrical Digital Subscriber Line d.Access to Data Services Line

ANS: B

32. Compared to ISDN, internet access usingADSL is typically:a. much faster c. much more expensive

b. about the same speed d. none of the above

ANS: ACOMPLETION

1. A ____________________ is a local calling

area.ANS: LATA

2. Central offices are connected together by

____________________ lines.ANS: trunk3. One central office can be connected to another

through a ____________________ office.

ANS: tandem4. With 7-digit phone numbers,

____________________ thousand telephonescan connect to a centraloffice.

ANS: ten5. Call ____________________ is when it

becomes impossible for a subscriber to place acall due to an

overload of lines being used.

ANS: blocking6. New ____________________ switching

equipment uses TDM to combine signals.ANS: digital7. Most local loops still use

____________________ copper wire.

ANS: twisted-pair

8. As compared to a hierarchical network, a____________________ network never needsmore than one

intermediate switch.ANS: flat

9. ____________________ coils were used toreduce the attenuation of voice frequencies.ANS: Loading


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10. In a twisted-pair telephone cable, the red

wire is called ____________________.ANS: ring11. In a twisted-pair telephone cable, the green

wire is called ____________________.

ANS: tip

12. Of the red and green 'phone wires, the____________________ wire is positive with

respect to the other.ANS: green

13. A telephone is said to have

____________________ the line when thecentral office sends it dial tone.ANS: seized

14. The ____________________ functions are

provided by a SLIC.ANS: BORSCHT

15. A ____________________ coil prevents

loss of signal energy within a telephone whileallowing fullduplex

operation over a single pair of wires.

ANS: hybrid16. In a crosspoint switch, not all

____________________ can be in use at the

same time.

ANS: lines17. The old carbon transmitters generated a

relatively ____________________ signalvoltage.ANS: large

18. The generic term for Touch-Tone signalingis ____________________.

ANS: DTMF19. A ____________________ line provides

more bandwidth than a standard line.

ANS: conditioned20. In the telephone system, amplifiers are called

____________________.ANS: repeaters21. An echo ____________________ converts a

long-distance line from full-duplex to half-

duplex operation.

ANS: suppressor22. ____________________ weighting is anattempt to adjust the noise or signal level to the

response of atypical telephone receiver.

ANS: C-message23. In FDM telephony, the modulation is usually

____________________.

ANS:

SSB

SSBSC24. In FDM telephony, ____________________

bands separate the channels in a group.

ANS: guard

25. Because of "bit robbing", a channel in a DS-

1 frame allows only ____________________kbps when

used to send digital data.ANS: 56

26. A ____________________ is a group of 12

DS-1 frames with signaling information in thesixth andtwelfth frames.

ANS: superframe

27. In DS-1C, ____________________ bits areused to compensate for differences between

clock rates.

ANS: stuff28. Busy and dial tone are referred to as

____________________ signals because they

use the same pair ofwires as the voice signal.ANS: in-channel

29. SS7 is the current version of

_________________________ signaling.ANS: common-channel

30. SS7 is a ____________________-switcheddata network.ANS: packet

31. In ISDN, the ____________________channel is used for common-channel signaling.

ANS: D32. In ISDN, the ____________________

channels are used for voice or data.

ANS: B33. Terminal equipment especially designed for

ISDN is designated ____________________equipment.ANS: TE1

34. The A in ADSL stands for

____________________.

ANS: asymmetrical35. In ADSL, the speed from the network to thesubscriber is ____________________ than the

speed in theopposite direction.

ANS:greaterfaster

SHORT ANSWER


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1. For a certain telephone, the DC loop voltage

is 48 V on hook and 8 V off hook. If the loopcurrent is 40mA, what is the DC resistance of the local loop?

ANS:

1000 ohms

2. For a certain telephone, the DC loop voltageis 48 V on hook and 8 V off hook. If the loop

current is 40mA, what is the DC resistance of the telephone?

ANS:

200 ohms3. Which two DTMF tones correspond to thedigit "1"? (Use the table in the text.)

ANS:

697 Hz and 1209 Hz4. Calculate the dB of VNL required for a

channel with a 3 ms delay.

ANS:1 dB

5. If a telephone voice signal has a level of 0

dBm, what is its level in dBrn?ANS:90 dBrn

6. A telephone test-tone has a level of 80 dBrn at

a point where the level is +5dB TLP. If C-weighting

produces a 10-dB loss, what would the signallevel be in dBrnc0?ANS:

65 dBrnc TLP

Chapter 9: Data TransmissionMULTIPLE CHOICE

1. In practical terms, parallel data transmission is

sent:a. over short distances only c. over any distance

b. usually over long distances d. usually over a

coaxial cable

ANS: A2. The five-level teletype code was invented by:

a. the Morkum Company c. Western Unionb. the Teletype Company d. Emile Baudot

ANS: D3. Data codes are also called:

a. character codes c. they do not have any othername

b. character sets d. both a and b

ANS: C

4. Digital data that is not being used to carry

characters is called:a. FIGS data c. numerical data

b. binary data d. all of the above

ANS: B

5. Character codes include:

a. alphanumeric characters c. graphic controlcharacters

b. data link control characters d. all of the aboveANS: D

6. ASCII stands for:

a. American Standard Character-set 2b. American Standard Code for InformationInterchange

c. American Standard Code 2

d. Alphanumeric Standard Code for InformationInterchange

ANS: B

7. BS, FF, and CR are examples of:a. nonstandard character codes c. control

characters

b. escape characters d. none of the aboveANS: C8. LF stands for:

a. Line Feed c. Line Forward

b. Link Feed d. Link ForwardANS: A

9. UART stands for:a. Universal Asynchronous Receiver-Transmitter

b. Unidirectional Asynchronous Receiver-Transmitter

c. Unaltered Received Textd. Universal Automatic Receiver for Text

ANS: A

10. In asynchronous transmission, thetransmitter and receiver are:

a. frame-by-frame synchronized using the databitsb. frame-by-frame synchronized using a

common clock

c. frame-by-frame synchronized using the start

and stop bitsd. not synchronized at all, hence the name"asynchronous"

ANS: C11. In asynchronous transmission, the time

between consecutive frames is:a. equal to zero c. equal to the start and stop bit-times

b. equal to one bit-time d. not a set length


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ANS: D

12. In synchronous transmission, the frames are:a. about the same length as ten asynchronousframes

b. much longer than asynchronous frames

c. 128 bytes long

d. 1024 bytes longANS: B

13. Synchronous transmission is used because:a. no start and stop bits means higher efficiency

b. it is cheaper than asynchronous since no

UARTS are requiredc. it is easier to implement than asynchronousd. all of the above

ANS: A

14. In synchronous transmission, the receiver"syncs-up" with the transmitter by using:

a. the clock bits c. the CRC bits

b. the data bits d. a separate clock lineANS: B

15. To maintain synchronization in synchronous

transmission:a. long strings of 1s and 0s must not be allowed

b. transmission must stop periodically for

resynchronization

c. the clock circuits must be precisely adjustedd. the channel must be noise-free

ANS: A16. BISYNC:a. is an IBM product c. requires the use of DLE

b. is a character-oriented protocol d. all of theabove

ANS: D17. HDLC:

a. is an IBM product c. is identical to SDLC

b. is a bit-oriented protocol d. all of the aboveANS: B

18. The use of flags in SDLC requires:a. "bit-stuffing" c. FEC

b. different flags at either end of a frame d. ARQ

ANS: A

19. The initials ARQ are used to designate:

a. automatic request for resynchronization c.automatic receiver queue

b. automatic request for retransmission d.

automatic request for queueANS: B

20. ARQ is used to:a. correct bit errors c. put data into a temporary

buffer

b. correct synchronization problems d. none of

the aboveANS: A21. FEC stands for:

a. Fixed Error Control c. Forward Error

Correction

b. Forward Error Control d. False ErrorCondition

ANS: C22. VRC is another name for:

a. FEC c. LRC

b. ARQ d. parityANS: D23. CRC stands for:

a. Control Receiver Code c. Cyclic Redundancy

Checkb. Correct Received Character d. Cycle Repeat

Character

ANS: C24. Huffman codes:

a. allow errors to be detected but not corrected

b. allow errors to be detected and correctedc. allow alphanumeric data to be correctedd. allow alphanumeric data to be compressed

ANS: D

25. Run-length encoding is used to:a. encrypt data c. correct data

b. compress data d. none of the aboveANS: B26. Public-key encryption:

a. allows the use of digital signatures c. avoidsthe "password problem"

b. is used to convey symmetric keys d. all of theabove

ANS: D

27. SDLC stands for:a. Synchronous Data Link Control c.

Synchronous Data Link Characterb. Synchronous Data Line Control d.Synchronous Data Line Character

ANS: A

28. HDLC is:

a. a bit-oriented protocol c. an ISO standardb. based on SDLC d. all of the aboveANS: DCOMPLETION

1. Parallel transmission can be used only for

____________________ distances.ANS: short2. The term "baud" was named after Emil

____________________.


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ANS: Baudot

3. Data codes are also called ____________________ codes.ANS: character

4. The ____________________ code is a 7-bit

code commonly used in communication between

personalcomputers.

ANS: ASCII5. The two letters ____________________

designate the code character used to advance a

printer to the nextpage.ANS: FF

6. An asynchronous frame begins with the

____________________ bit.ANS: start

7. An asynchronous frame ends with the

____________________ bit.ANS: stop

8. At the end of an asynchronous frame, the line

will be at the ____________________ level.ANS:mark

binary 1

9. An integrated circuit called a____________________ is used in an

asynchronous communication systemto convert between parallel and serial data.ANS: UART

10. When receiving digital data,____________________ are used to hold data

until they can be read.ANS: buffers

11. Synchronous communication is more

____________________ than asynchronoussince there are fewer

"overhead" bits.ANS: efficient12. There must be sufficient 1-to-0

____________________ to maintain

synchronization in synchronous

transmission.ANS: transitions13. Clock sync is derived from the stream of

____________________ bits in synchronoustransmission.

ANS: data14. In the ____________________ protocol,each frame begins with at least two SYN

characters.

ANS: BISYNC

15. In HDLC, each frame starts with an 8-bit____________________.ANS: flag

16. The first eight bits of an SDLC frame are

____________________.

ANS: 0111111017. BCC stands for ____________________

check character.ANS: block

18. DLE stands for data link

____________________.ANS: escape19. HDLC uses bit-____________________ to

prevent accidental flags.

ANS: stuffing20. ____________________ errors cause many

consecutive bits to be bad.

ANS: Burst21. FEC stands for ____________________

error correction.

ANS: forward22. An ____________________ scheme correctserrors by requiring the retransmission of bad

blocks.

ANS: ARQ23. Parity fails when an

____________________ number of bits are inerror.ANS: even

24. CRC codes are particularly good at detecting____________________ errors.

ANS: burst25. Huffman coding and run-length encoding are

examples of data ____________________.

ANS: compression26. A ____________________ is an encoding

scheme that is not public in order to protect data.ANS: cipher27. A ____________________ is often used to

generate an encryption key because it is easier to

remember.

ANS: password28. If the key is ____________________enough, private-key encryption can be quite

secure.ANS: long

29. Messages cannot be____________________ using a public key.ANS: decrypted


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30. Because it is ____________________-

intensive, public-key encryption can be slow.ANS: computationSHORT ANSWER

1. How many different characters could be

encoded using a six-bit code?

ANS:64

2. What is the numerical difference betweenASCII 'a' and ASCII 'A' if you treat them as

hexadecimal (hex)

numbers?ANS:20 hex (32 decimal)

3. The ASCII codes for the characters '0' through

'9' are what hex numbers?ANS:

30H to 39H

4. If an asynchronous frame is used to sendASCII characters in the form of bytes (8 bits),

what is the

shortest time it could take to send 1000characters if each bit in a frame is 1 msec long?ANS:

10 seconds

5. Suppose an asynchronous frame holds 8 bitsof data, a parity bit, and two stop bits (it could

happen).Calculate the efficiency of the communicationsystem.

ANS:66.7%

6. Suppose a synchronous frame has 16 bits ofnon-data in the front and a 16-bit BCC at the

end. The frame

carries 1024 bytes of actual data. Calculate theefficiency of the communication system.

ANS:97.0%

Chapter 10: Local Area NetworksMULTIPLE CHOICE

1. CSMA stands for:a. Client-Server Multi-Access c. Carrier Server

Master Applicationb. Carrier Sense Multiple Access d. none of the

aboveANS: B2. The CD in CSMA/CD stands for:

a. Carrier Detection c. Collision Detection

b. Carrier Delay d. Collision Delay

ANS: C

3. The Internet is:a. a network of networks c. a very largeCSMA/CD network

b. a very large client-server network d. not really

a network at all

ANS: A4. Most LANs:

a. are based on Ethernet c. use UTP cableb. use CSMA/CD d. all of the above

ANS: D

5. Dumb terminals are still used:a. in token-passing networks

b. in networks requiring central monitoring

c. in networks that cannot provide central

monitoringd. none of the above

ANS: B

6. In a circuit-switched network:a. communication is half-duplex only

b. each channel carries only one data stream

c. connection is usually done using a bustopologyd. all of the above

ANS: B

7. Each computer on a network is called a:a. hub c. node

b. token d. circuitANS: C8. Compared to CSMA/CD systems, token-

passing rings are:a. slower c. not as widely used

b. more expensive d. all of the aboveANS: D

9. The key feature of a star network is that

individual workstations are connected to:a. a central ring c. a node

b. a central bus d. none of the aboveANS: D10. On networks, long messages are divided into

"chunks" called:

a. packets c. carriers

b. nodes d. tokensANS: A11. When two or more PCs try to access a

baseband network cable at the same time, it iscalled:

a. a collision c. excess trafficb. contention d. multiple accessANS: B


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12. When two PCs send data over a baseband

network cable at the same time, it is called:a. a collision c. excess traffic

b. contention d. multiple access

ANS: A

13. One type of network that never has a

collision is:a. CSMA c. token-passing

b. Ethernet d. all networks have collisionsANS: C

14. In an Ethernet-based network, a switch can

be used to reduce the number of:a. nodes c. packets

b. users d. collisions

ANS: D

15. The effect of too many collisions is:a. the network goes down c. the cable overheats

b. the network slows down d. data is lost

ANS: B16. MAU stands for:

a. Multistation Access Unit c. Multiple

Auxiliary Unitsb. Multiple Access Unit d. none of the aboveANS: A

17. The standard that describes Ethernet-type

networks is:a. EIA 232 c. IEEE 802.3

b. IEEE 488.1 d. CCITT ITU-EANS: C18. Ethernet was invented by:

a. IBM c. Xeroxb. INTEL d. Digital Equipment Corporation

ANS: C19. An Ethernet running at 10 Mbits / second

uses:

a. Manchester encoding c. NRZ encodingb. Three-Level encoding d. AMI encoding

ANS: A20. A 100BaseT cable uses:a. fiber-optic cable c. RG-58U coaxial cable

b. twisted-pair copper wires d. 50-ohm coaxial

cable

ANS: B21. The word "Base" in 10BaseT means:a. the cable carries baseband signals

b. the cable has a base speed of 10 Mbpsc. it can be used as the base for a backbone cable

systemd. none of the aboveANS: A

22. The reason a CSMA/CD network has a

minimum length for packets is:a. to increase the data rate

b. to prevent packets from reaching all other

nodes during transmission

c. to make sure all other nodes hear a collision in

progressd. all of the above

ANS: C23. The reason a CSMA/CD network has a

maximum length for cables is:

a. to increase the data rateb. to prevent packets from reaching all othernodes during transmission

c. to make sure all other nodes hear a collision in

progressd. all of the above

ANS: C

24. NIC stands for:a. Network Interface Card c. Network Interface

Code

b. Network Interface Cable d. Network InternalCodeANS: A

25. 10BaseT cable typically uses:

a. a BNC connector c. an RJ45 connectorb. a T connector d. an RS11 connector

ANS: C26. UTP stands for:a. Untwisted-Pair copper wire c. Uninterruptible

Terminal Packetb. Unshielded Twisted-Pair copper wire d.

Unicode Text PacketANS: B

27. Compared to twisted-pair telephone cables,

CAT-5 cables:a. are cheaper c. allow faster bit rates

b. are easier to crimp connectors onto d. all ofthe aboveANS: C

28. A hub:

a. sends incoming packets out to all other

terminals connected to itb. sends incoming packets out to specific portsc. cannot be used in an Ethernet-type network

d. are more common in token-passing networksANS: A

29. A switch:a. sends incoming packets out to all otherterminals connected to it

b. sends incoming packets out to specific ports


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c. cannot be used in an Ethernet-type network

d. are more common in token-passing networksANS: B30. An advantage of using a switch instead of a

hub is:

a. it is cheaper when used in large networks

b. it is faster when used in large networksc. it reduces the number of collisions in large

networksd. all of the above

ANS: C

31. Broadband LANs:a. modulate the data onto a carrier

b. use coaxial cables

c. are provided by cable TV companies for

Internet accessd. all of the above

ANS: D

32. Using one node in the network to hold all theapplication software is done in:

a. peer-to-peer networks c. both a and b

b. client-server networks d. none of the aboveANS: B33. Record locking is used to:

a. store records securely on a server

b. prevent multiple users from looking at adocument simultaneously

c. prevent one user from reading a record thatanother user is writing tod. none of the above

ANS: C34. The software that runs a client-server

network must be:a. UNIX-based c. multitasking

b. WINDOWS-based d. Novell certified

ANS: C35. A "thin" client is:

a. basically, a PC with no disk drives c. same asa "dumb" terminal

b. a node that rarely sends data d. all of the

above

ANS: A

COMPLETION1. A LAN is a ____________________ Area

Network.

ANS: Local2. The Internet is a network of

____________________.ANS: networks3. In a ____________________ network, all

nodes are connected to a central computer.

ANS: star

4. In a ____________________-switchednetwork, users have a dedicated channel for theduration of

communications.

ANS: circuit

5. The ____________________ of a networkdescribes how it is physically connected

together.ANS: topology

6. Ring networks often use

____________________-passing.ANS: token7. A ____________________ is a short section

of a message in digital form.

ANS: packet8. ____________________ is when two nodes

try to seize the same cable at the same time.

ANS: Contention9. A ____________________ occurs when two

nodes transmit simultaneously on the same

baseband cable.ANS: collision10. In CSMA/CD networks, all collisions must

be ____________________.

ANS: detected11. Carrier-Sense means that a node "listens" for

the cable to be ____________________ beforeusing it.ANS:

quietfree

unusedavailable

12. A "____________________" cable links

clusters of computers together.ANS: backbone

13. 100BaseT cables can reliably carry up to____________________ bits per second.ANS: 100 mega

14. In CSMA/CD, packets must hav

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