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Chapter 1: Introduction toCommunication SystemsMULTIPLE CHOICE1. The theory of radio waves was originatedby:a. Marconi c. Maxwellb. Bell d. Hertz

ANS: C2. The person who sent the first radio signalacross the Atlantic ocean was:a. Marconi c. Maxwellb. Bell d. Hertz

ANS: A3. The transmission of radio waves was firstdone by:a. Marconi c. Maxwellb. Bell d. Hertz ANS:D4. A complete communication system must

include:a. a transmitter and receiverb. a transmitter, a receiver, and a channelc. a transmitter, a receiver, and a spectrumanalyzerd. a multiplexer, a demultiplexer, and achannelANS: B5. Radians per second is equal to:

a. 2 fc. the phase angle

b. f 2 d. none of the above ANS:A

6. The bandwidth required for a modulatedcarrier depends on:a. the carrier frequency c. the signal-plus-noise to noise ratiob. the signal-to-noise ratio d. the basebandfrequency range

ANS: D7. When two or more signals share a commonchannel, it is called:a. sub-channeling c. SINADb. signal switching d. multiplexing ANS:D

8. TDM stands for:a. Time-Division Multiplexing c. Time DomainMeasurementb. Two-level Digital Modulation d. none of theaboveANS: A9. FDM stands for:a. Fast Digital Modulation c. Frequency-Division Multiplexing

b. Frequency Domain Measurement d. none ofthe above ANS:C10. The wavelength of a radio signal is:

a. equal to f c

b. equal to c c. the distance a wave travels in one period

d. how far the signal can travel withoutdistortionANS: C11. Distortion is caused by:a. creation of harmonics of basebandfrequenciesb. baseband frequencies "mixing" with eachotherc. shift in phase relationships betweenbaseband frequenciesd. all of the above ANS: D12. The collection of sinusoidal frequencies

present in a modulated carrier is called its:a. frequency-domain representation c.spectrumb. Fourier series d. all of the above

ANS: D13. The baseband bandwidth for a voice-grade (telephone) signal is:a. approximately 3 kHz c. at least 5 kHzb. 20 Hz to 15,000 Hz d. none of the above

ANS: A14. Noise in a communication systemoriginates in:

a. the sender c. the channelb. the receiver d. all of the above

ANS: D15. "Man-made" noise can come from:a. equipment that sparks c. staticb. temperature d. all of the above

ANS: A16. Thermal noise is generated in:a. transistors and diodes c. copper wireb. resistors d. all of the above

ANS: D17. 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 atlow frequenciesb. greater at high frequencies d. the same as"white" noise

ANS: C19. So called "1/f" noise is also called:


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a. random noise c. white noiseb. pink noise d. partition noise

ANS: B20. "Pink" noise has:a. equal power per Hertz c. constant powerb. equal power per octave d. none of theabove ANS: B21. When two noise voltages, V1 and V2, arecombined, the total voltage VTis:

a. VT= sqrt(V1 V1 + V2 V2) c. VT= sqrt(V1 V2)b. VT= (V1 + V2)/2 d. VT= V1 + V2 ANS:A22. Signal-to-Noise ratio is calculated as:a. signal voltage divided by noise voltageb. signal power divided by noise powerc. first add the signal power to the noisepower, then divide by noise powerd. none of the above

ANS: B23. SINAD is calculated as:a. signal voltage divided by noise voltageb. signal power divided by noise powerc. first add the signal power to the noisepower, then divide by noise powerd. none of the above

ANS: D24. Noise Figure is a measure of:a. how much noise is in a communicationssystemb. how much noise is in the channel

c. how much noise an amplifier adds to asignald. signal-to-noise ratio in dB

ANS: C25. The part, or parts, of a sinusoidal carrierthat can be modulated are:a. its amplitude c. its amplitude, frequency,and directionb. its amplitude and frequency d. itsamplitude, frequency, and phase angle

ANS: DCOMPLETION

1. The telephone was invented in the year____________________. ANS: 18632. Radio signals first were sent across theAtlantic in the year ____________________.

ANS: 19013. The frequency band used to modulate thecarrier is called the ____________________ band.ANS: base

4. The job of the carrier is to get theinformation through the ____________________.

ANS: channel5. The bandwidth of an unmodulated carrier is

____________________. ANS: zero6. The 'B' in Hartley's Law stands for

____________________. ANS: bandwidth7. The more information per second you send,the ____________________ the bandwidthrequired.ANS: greater/ larger/ wider8. In ____________________, you split thebandwidth of a channel into sub-channels tocarry multiplesignals. ANS:FDM9. In ____________________, multiple signalstreams take turns using the channel.

ANS: TDM

10. VHF stands for the ____________________frequency band. ANS: veryhigh11. The VHF band starts at

____________________ MHz.ANS: 30

12. The UHF band starts at____________________ MHz.

ANS: 30013. A radio signal's ____________________ is thedistance it travels in one cycle of the carrier.ANS: wavelength

14. In free space, radio signals travel atapproximately ____________________ meters persecond.ANS: 300 million15. The equipment used to show signals inthe frequency domain is the

_________________________.ANS: spectrum analyzer16. Mathematically, a spectrum isrepresented by a ____________________ series.

ANS: Fourier17. Disabling a receiver during a burst of

atmospheric noise is called____________________.ANS: noise blanking/blanking18. For satellite communications,

____________________ noise can be a seriousproblem.ANS: solar19. Thermal noise is caused by the randommotions of ____________________ in aconductor.ANS: electrons


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SHORT ANSWER1. Name the five elements in a block diagramof a communications system.ANS:Source, Transmitter, Channel, Receiver,Destination2. 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 it

does other colors, and red is at the low end ofthe visiblespectrum. Likewise, pink noise has higherpower density at lower frequencies.

5. Suppose there is 30 V from one noise

source that is combined with 40 V fromanother noise source.Calculate the total noise voltage.

ANS: 50 V6. 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 dB7. The input to an amplifier has a signal-to-noise ratio of 100 dB and an output signal-to-noise ratio of 80dB. Find NF, both in dB and as a ratio.ANS: 20 dB, NF = 1008. A microwave receiver has a noisetemperature of 145 K. Find its noise figure.ANS: 1.59. Two cascaded amplifiers each have a noisefigure of 5 and a gain of 10. Find the total NF

for the pair.ANS: 5.410. Explain why you could use a diode as anoise source with a spectrum close to that ofpure thermal noise.How would you control the amount of noisegenerated?ANS:

When current flows through a diode, itgenerates shot noise that can be representedas a current source,the output of which is a noise current. Theequation for the noise current is very similarto the equation forthermal noise voltage. Since the power in theshot noise is proportional to the diode current,controllingthe diode current controls the noise power.

Chapter 2: Radio-FrequencyCircuitsMULTIPLE CHOICE1. The time it takes a charge carrier to crossfrom the emitter to the collector is called:a. base time c. charge timeb. transit time d. Miller time

ANS: B

2. 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 amplifiersb. couple RF around an amplifier d. reduce theMiller effect ANS:A

4. A resonant circuit is:a. a simple form of bandpass filter c. both aand bb. used in narrowband RF amplifiers d. noneof the 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 QANS: B

6. The "Miller Effect" can:a. cause an amplifier to oscillate c. reduce thebandwidth of an amplifierb. cause an amplifier to lose gain d. all of theaboveANS: D7. The Miller Effect can be avoided by:a. using a common-emitter amplifier c.increasing the Q of the tuned circuit


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b. using a common-base amplifier d. it cannotbe avoided ANS:B8. In a BJT, the Miller Effect is due to:a. inductance of collector lead c. base-to-emitter capacitanceb. collector-to-emitter capacitance d. base-to-collector capacitance

ANS: D9. In RF amplifiers, impedance matching isusually done with:a. RC coupling c. direct couplingb. transformer coupling d. lumped reactanceANS: B10. Neutralization cancels unwanted feedbackby:a. adding feedback out of phase with theunwanted feedbackb. bypassing the feedback to the "neutral" or

ground planec. decoupling itd. none of the above ANS:A11. For a "frequency multiplier" to work, itrequires:a. a nonlinear circuitb. a linear amplifierc. a signal containing harmonicsd. an input signal that is an integer multiple ofthe desired frequency ANS:A

12. A sinusoidal oscillation from an amplifierrequires:a. loop gain equal to unityb. phase shift around loop equal to 0 degreesc. both a and b, but at just one frequencyd. none of the above

ANS: C13. The conditions for sinusoidal oscillationfrom an amplifier are called:a. the loop-gain criteria c. the Bode criteriab. the Hartley criteria d. the Barkhausencriteria

ANS: D14. The Hartley oscillator uses:a. a tapped inductor c. an RC time constantb. a two-capacitor divider d. a piezoelectriccrystalANS: A15. The Colpitts VFO uses:a. a tapped inductor c. an RC time constantb. a two-capacitor divider d. a piezoelectriccrystalANS: B

16. The Clapp oscillator is:a. a modified Hartley oscillator c. a type ofcrystal-controlled oscillatorb. a modified Colpitts oscillator d. only builtwith FETsANS: B17. A varactor is:a. a voltage-controlled capacitor c. used intuner circuitsb. a diode d. all of the above

ANS: D18. Crystal-Controlled oscillators are:a. used for a precise frequencyb. used for very low frequency drift (parts permillion)c. made by grinding quartz to exactdimensionsd. all of the above ANS: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

ANS: A20. In a balanced mixer, the output:a. contains equal (balanced) amounts of allinput frequenciesb. contains the input frequenciesc. 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 Oscillatorb. Variable-Frequency Oscillator d. Voltage-Feedback Oscillator

ANS: B22. A "frequency synthesizer" is:a. a VCO phase-locked to a referencefrequencyb. a VFO with selectable crystals to change

frequencyc. a fixed-frequency RF generatord. same as a mixer ANS:ACOMPLETION1. Generally, conductor lengths in RF circuitsshould be ____________________. ANS:short


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2. At UHF frequencies and above, elementsmust be considered as ____________________instead of asbeing "lumped". ANS:distributed3. When one side of a double-sided pc boardis used for ground, it is called a

____________________.ANS: ground-plane4. Interactions between parts of an RF circuitcan be reduced by using ____________________betweenthem. ANS: shielding5. In high-frequency RF circuits, theplacement 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 toshort unwanted RF to ground. ANS:bypass8. The bandwidth of a tuned-circuit amplifierdepends on the ____________________ of thetuned circuit.ANS: Q9. A value of ____________________ or more forQ is required for the approximate tunedcircuit equationsto be valid. ANS: 10

10. In a class C RF amplifier, the____________________ extracts one frequencyfrom all the harmonics contained in thedevice current (e.g. collector current).

ANS: tuned circuit11. Using additional feedback to compensatefor "stray" feedback is called

____________________.ANS: neutralization12. A Colpitts oscillator uses a

____________________ voltage divider to providefeedback.

ANS: capacitive13. Electrically, a piezoelectric crystal hasboth a ____________________ and a

____________________resonant frequency. ANS: series,parallel14. To produce sum and differencefrequencies, 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 ANSWER1. What inductance would you use with a 47-pF capacitor to make a tuned circuit for 10MHz?

ANS:5.4 H2. 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 isbeing used to make an oscillator. What shouldbe the valueof the feedback ratio to satisfy theBarkhausen criteria?ANS:0.14. What is the advantage of a Clapp oscillatorcompared to a Colpitts oscillator?

ANS:It is more stable because it "swamps" thedevice capacitance with large valuecapacitors in the feedbackdivider.5. If a varactor has a capacitance of 90 pF atzero 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 degreeCelsius. 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 fedinto an ideal balanced mixer. V1 is a 20-MHzsignal; V2 is a 5-MHz signal. What frequencies would youexpect at the output of the mixer?ANS:15 MHz and 25 MHz8. Suppose the phase-locked-loop frequencysynthesizer of Figure 2.39 has a referencefrequency of 1 MHz

and a fixed-modulus divider of 10. Whatshould be the value of the programmabledivider to get an outputfrequency of 120 MHz?ANS:12

Chapter 3: Amplitude ModulationMULTIPLE CHOICE1. AM stands for:a. Audio Modulation c. Angle Modulation


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b. Amplitude Modulation d. AntennaModulationANS: B2. The "envelope" of an AM signal is due to:a. the baseband signal c. the amplitude signalb. the carrier signal d. none of the above

ANS: A

3. If the audio Va

sin(a

t) modulates thecarrier 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) sin(ct) c. v(t) = (Ec

Em) sin(mt) sin(ct)

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

= (Ec + Em sin(mt)) sin(ct)ANS: D

5. 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 fromEmaxto Emin. The modulation index, m, is:a. m = Emin / Emaxc. m = (Emax Emin) / (Emax+Emin)b. m = Emax/ Emin d. m = (Emax+ Emin) / (EmaxEmin)ANS: C

7. IfVa sin(at) amplitude modulates the

carrier Vc sin(ct), it will produce thefrequencies:

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

b. (c + a)/2 and (c a)/2 d. none of theaboveANS: A8. At 100% modulation, the total sidebandpower is:a. equal to the carrier power c. half the carrierpower

b. twice the carrier power d. 1.414 carrier

powerANS: C9. 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:B10. 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 ofthe aboveANS: D11. The modulation index can be derivedfrom:a. the time-domain signal c. both a and bb. the frequency-domain signal d. none of theaboveANS: C12. The main problem in using quadrature AMwould be:a. requires too much bandwidth c.incompatibility with ordinary AM radiosb. requires too much power d. all of the aboveANS: C13. As compared to plain AM, SSB AM:a. is more efficient

b. requires a more complex demodulatorcircuitc. requires less bandwidthd. all of the above ANS: D14. The SC in SSB SC stands for:a. single-carrier c. sideband-carrierb. suppressed-carrier d. none of the aboveANS: B15. PEP stands for:a. Peak Envelope Power c. Peak EnvelopeProductb. Peak Efficiency Power d. none of the above

ANS: A16. If an SSB transmitter radiates 1000 wattsat peak modulation, what will it radiate withno modulation?a. 1000 watts c. 250 wattsb. 500 watts d. 0 watts ANS:D17. Music on AM radio stations is "low-fidelity"because:a. AM is susceptible to noiseb. commercial AM stations use low powerc. commercial AM stations have a narrow

bandwidthd. all of the above ANS: C18. The type of information that can be sentusing AM is:a. audio c. digital datab. video d. all of the above ANS:D19. Two tones modulate an AM carrier. Onetone causes a modulation index ofm1 and theother tone causes a


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modulation index ofm2. The total modulationindex is:

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

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

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

a. be set to USB mode c. both a and bb. reinsert the carrier d. none of the aboveANS: C

COMPLETION1. An advantage of AM is that the receiver canbe very ____________________. ANS:simple2. A disadvantage of AM is its

____________________ use of power.ANS: inefficient

3. The ____________________ of an AM signalresembles the shape of the baseband signal.

ANS: envelope4. In AM, modulating with a single audio toneproduces ____________________ sidebands.

ANS: two5. Compared to the USB, the information inthe LSB is ____________________. ANS:the same6. Compared to the USB, the power in the LSBis ____________________. ANS: thesame7. In AM, total sideband power is always

____________________ than the carrier power.

ANS: less8. In AM, as the modulation index increases,the carrier power ____________. ANS:remains constant9. The power in an AM signal is maximumwhen the modulation index is _____________.

ANS: one10. In AM, a voice-band signal of 300 Hz to3000 Hz will require a bandwidth of

____________________.ANS: 6000 Hz11. With a 1-MHz carrier, if the LSB extends

down to 990 kHz, then the USB will extend upto

____________________. ANS: 1010kHz12. If an AM transmitter puts out 100 wattswith no modulation, it will put out

____________________ watts with 100%modulation. ANS: 150SHORT ANSWER

1. An AM transmitter generates 100 wattswith 0% modulation. How much power will itgenerate with 20%modulation? ANS:102watts2. If the carrier power is 1000 watts, what isthe power in the USB at 70.7% modulation?

ANS:125 watts3. A carrier is modulated by three audiotones. If the modulation indexes for the tonesare 0.3, 0.4, and 0.5,then what is the total modulation index?

ANS: 0.7074. You look at an AM signal with anoscilloscope and see that the maximum Vpp is100 volts and theminimum Vpp is 25 volts. What is themodulation index?ANS: 0.6

5. A SSB transmitter is connected to a 50-ohmantenna. If the peak output voltage of thetransmitter is 20volts, what is the PEP? ANS:4watts

Chapter 4: Angle ModulationMULTIPLE CHOICE1. The FM modulation index:a. increases with both deviation andmodulation frequency

b. increases with deviation and decreaseswith modulation frequencyc. decreases with deviation and increaseswith modulation frequencyd. is equal to twice the deviation ANS:B2. One way to derive FM from PM is:a. integrate the modulating signal beforeapplying to the PM oscillatorb. integrate the signal out of the PM oscillatorc. differentiate the modulating signal beforeapplying to the PM oscillator

d. differentiate the signal out of the PMoscillatorANS: A3. The bandwidth of an FM signal isconsidered to be limited because:a. there can only be a finite number ofsidebandsb. it is equal to the frequency deviationc. it is band-limited at the receiver


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d. the power in the outer sidebands isnegligibleANS: D4. Mathematically, the calculation of FMbandwidth requires the use of:a. ordinary trigonometry and algebra c. Taylorseriesb. 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:C6. NBFM stands for:a. National Broadcast FM c. Near Band FMb. Non-Broadcast FM d. Narrowband FMANS: D7. When FM reception deteriorates abruptlydue to noise, it is called:

a. the capture effect c. the noise effectb. the threshold effect d. the limit effectANS: B8. An FM receiver switching suddenly betweentwo stations on nearby frequencies is called:a. the capture effect c. the "two-station"effectb. the threshold effect d. none of the aboveANS: A9. Pre-emphasis is used to:a. increase the signal to noise ratio for higheraudio frequencies

b. increase the signal to noise ratio for loweraudio frequenciesc. increase the signal to noise ratio for allaudio frequenciesd. allow stereo audio to be carried by FMstationsANS: A

10. A pre-emphasis of 75 s refers to:a. the time it takes for the circuit to workb. the "dead time" before de-emphasis occursc. the time delay between the L and Rchannels

d. the time-constant of the filter circuits usedANS: D11. FM stereo:a. uses DSBSC AM modulation c. has a higherS/N than mono FMb. is implemented using an SCA signal d. isnot compatible with mono FM

ANS: A12. An SCA signal:

a. can use amplitude modulation c. ismonauralb. can use FM modulation d. all of the above

ANS: D13. The modulation index of an FM signal canbe determined readily:a. using measurements at points whereJ0equals oneb. using measurements at points whereJ0equals zeroc. using measurements at points where thedeviation equals zerod. only by using Bessel functions ANS:BCOMPLETION1. FM and PM are two forms of

____________________ modulation. ANS: angle2. PM is extensively used in

____________________ communication.

ANS: data3. Compared to AM, the signal-to-noise ratioof FM is usually ____________________. ANS:better4. Compared to AM, the bandwidth of FM isusually ____________________.

ANS:wider/greater5. FM transmitters can use Class

____________________ amplifiers sinceamplitude linearity is not important.

ANS: C6. Both the power and amplitude of an FM

signal ____________________ as modulation isapplied.ANS: stay constant7. In FM, the frequency deviation isproportional to the instantaneous

____________________ of the modulating signal.ANS: amplitude

8. The frequency deviation of an FM signaloccurs at a rate equal to the

____________________ of themodulating signal. ANS:frequency

9. Mathematically, the number of sidebands inan FM signal is ____________________. ANS:infinite10. As FM sidebands get farther from thecenter frequency, their power _________.

ANS: decreases11. Mathematically, the value of an FMmodulation index can be as high as ________.ANS: any number


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12. In FM, as the modulating frequencydecreases, the modulation index ___________.

ANS: increases13. In FM, as the frequency deviationdecreases, the modulation index _________.

ANS: decreases14. As the FM modulation index increases, thenumber of significant sidebands ______.

ANS: increases15. For certain values ofmf, such as 2.4, theamplitude of the carrier frequency

____________________.ANS: disappears/goes to zero16. The bandwidth of an FM signal can beapproximated using __________ rule.

ANS: Carson's17. FM bandwidth can be calculated preciselyusing ________ functions. ANS:Bessel

18. The _________ effect is characteristic of FMreception in a noisy environment. ANS:threshold19. The ____________________ effect is seenwhen an FM receiver is exposed to two FMsignals that areclose to each other in frequency. ANS:capture20. Rest frequency is another name for an FM

_____ frequency. ANS:carrierSHORT ANSWER

1. If a 2-volt instantaneous value ofmodulating signal amplitude causes a 10-kHzdeviation in carrierfrequency, what is the deviation sensitivity ofthe modulator? ANS: 5 kHz /volt2. If a 2-kHz audio tone causes a frequencydeviation of 4 kHz, what is the modulationindex?ANS:23. What will be the deviation caused by a 3-kHz tone if the modulation index is 3?

ANS:9 kHz

4. If the deviation sensitivity of an FMmodulator is 2 kHz /V, what will be themodulation index caused bya 1-volt, 1-kHz audio signal? ANS:25. At a modulation index of 2, how muchpower is in the carrier of a 1000-watt FMtransmitter? ANS:48.4 watts6. At a modulation index of 2, how muchpower is in the first pair of sidebands of a1000-watt FM

transmitter? ANS:673watts7. At a modulation index of 2, how muchpower is in the fifth pair of sidebands of a1000-watt FMtransmitter? ANS:200 mW (0.2watt)8. Using Carson's rule, what is theapproximate bandwidth of an FM signal with amodulation index of 2being modulated by a 5-kHz signal?

ANS:30 kHz9. Using the Bessel chart of Figure 4.1, what isthe bandwidth of an FM signal with amodulation index of 2being modulated by a 5-kHz signal if weignore sidebands containing less than 1% ofthe total power?ANS:30 kHz

10. How would you use the fact thatJ0

is zerofor certain known values ofmf(2.4, 5.5, etc)to measure thefrequency deviation of an FM modulator?ANS:Use an audio frequency generator tomodulate the FM carrier. Using a spectrumanalyzer, adjust the audiofrequency until the carrier amplitudevanishes. Record the audio frequency. Then

do the calculation: =

fm mfwhere mfwill have one of the known

values. For example, iffm is measured to be 2kHz when mfis

5.5, then is 11 kHz.

Chapter 5: TransmittersMULTIPLE CHOICE1. The ability to change operating frequencyrapidly without a lot of retuning is called:a. agility c. VFOb. expansion d. spread-spectrum

ANS: A2. The difference between the DC power into

a transmitter and the RF power coming out:a. is a measure of efficiency c. may requirewater coolingb. heats the transmitter d. all of the above

ANS: D3. Baseband compression produces:a. a smaller range of frequencies from low tohighb. a smaller range of amplitude from soft toloud


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c. a smaller number of signalsd. none of the above

ANS: B4. ALC stands for:a. Amplitude Level Control c. Accurate LevelControlb. Automatic Level Control d. none of theaboveANS: B5. In an AM transmitter, ALC is used to:a. keep the modulation close to 100% c.maximize transmitted powerb. keep the modulation below 100% d. all ofthe aboveANS: D6. With high-level AM:a. all RF amplifiers can be nonlinear c.minimum RF power is requiredb. minimum modulation power is required d.

all of the aboveANS: A7. With high-level AM:a. the RF amplifiers are typically Class A c. theRF amplifiers are typically Class Cb. the RF amplifiers are typically Class B d.the RF amplifiers are typically Class AB

ANS: C8. With low-level AM:a. the RF amplifiers must be Class A c. the RFamplifiers must be linearb. the RF amplifiers must be Class B d. the RF

amplifiers must be low-powerANS: C9. Power amplifiers must be linear for anysignal that:a. is complex c. has variable frequencyb. 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 powerlevel of the final RF amplifierb. the power level of the modulation d. noneof the above

ANS: D11. In high-level AM, the power in thesidebands comes from:a. the modulating amplifier c. the driver stageb. the RF amplifier d. the carrier

ANS: A12. In an AM transmitter with 100%modulation, the voltage of the final RF stagewill 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 designedto drive a load impedance of:a. 50 ohms resistive c. 300 ohms resistiveb. 75 ohms resistive d. 600 ohms resistive

ANS: A14. Which of the following can be used forimpedance matching?a. pi network c. both a and bb. T network d. a bridge circuit

ANS: C15. When a transmitter is connected to aresistor instead of an antenna, the resistor iscalled:a. a heavy load c. a temporary loadb. a dummy load d. a test load

ANS: B16. When a transmitter is connected to aresistor instead of an antenna, the resistormust be:a. wire-wound c. 1% tolerance or betterb. noninductive d. all of the above

ANS: B17. A Class D amplifier is:a. very efficient c. essentially pulse-durationmodulationb. essentially pulse-width modulation d. all ofthe above

ANS: D18. To generate a SSB signal:a. start with full-carrier AM c. start with aquadrature signalb. start with DSBSC d. all of the above

ANS: B19. The carrier is suppressed in:a. a balanced modulator c. a frequencymultiplierb. a mixer d. none of the above

ANS: A20. To remove one AM sideband and leave

the other you could use:a. a mechanical filter c. both a and bb. a crystal filter d. none of the above

ANS: C21. A direct FM modulator:a. varies the frequency of the carrier oscillatorb. integrates the modulating signalc. both a and bd. none of the above

ANS: A22. An indirect FM modulator:


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a. requires a varactor in the carrier oscillatorb. varies the phase of the carrier oscillatorc. both a and bd. none of the above

ANS: B23. AFC stands for:a. Amplitude to Frequency Conversion c.Automatic Frequency Controlb. Automatic Frequency Centering d. AudioFrequency Control

ANS: C24. Frequency multipliers are:a. essentially balanced modulators c.essentially mixersb. essentially Class C amplifiers d. none of theaboveANS: B25. With mixing:a. the carrier frequency can be raised

b. the carrier frequency can be loweredc. the carrier frequency can be changed toany required valued. the deviation is altered ANS:CCOMPLETION1. The accuracy and stability of a transmitterfrequency is fixed by the __________ oscillator.

ANS: carrier2. In the USA, the ____________________ setsrequirements for accuracy and stability of atransmitter's

frequency. ANS: FCC3. In Canada, _________________________ setsrequirements for accuracy and stability of atransmitter'sfrequency. ANS: IndustryCanada4. Frequency ____________________ is the abilityof a transmitter to change frequency withouta lot ofretuning. ANS: agility5. Power output of SSB transmitters is ratedby ____________________. ANS: PEP

6. Reducing the dynamic range of amodulating signal is called _____________.ANS: compression

7. The opposite of compression is called____________________. ANS: expansion8. ALC is a form of ______. ANS: compression9. High-level modulation allows the RFamplifiers to operate more ___________. ANS:efficiently

10. Low-level modulation requires the RFamplifiers to be ____________________. ANS:linear11. To isolate the oscillator from loadchanges, a ___________ stage is used. ANS:buffer12. The peak collector voltage in a Class C RFamplifier is ____________________ than the DCsupplyvoltage. ANS: higher13. Most practical transmitters are designedto operate into a ___________-ohm load.

ANS: 5014. Transmitters built with transistor RFamplifiers often use a ____________________network for impedance matching.

ANS: T15. Matching networks also act as filters tohelp reduce ____________________ levels.

ANS: harmonic16. Severe impedance ____________________can destroy a transmitter's output stage.

ANS: mismatch17. Transceivers combine a transmitter and a

_________ into one "box".ANS: receiver

18. To allow a high modulation percentage, itis common to modulate the

____________________ as well as the poweramplifier in transistor modulators.ANS: driver

19. Pulse-width modulation is the same aspulse-_________ modulation.ANS: duration

20. Switching amplifiers are sometimes calledClass _____________ amplifiers. ANS:D21. Because the sideband filter in a SSBtransmitter is fixed, ____________________ isused to operate atmore than one frequency. ANS: mixing22. 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 anexample of a _____________ modulator.

ANS: reactance25. The modern way to make a stable VFO isto make it part of a ____________________ loop.ANS: phase-lockedSHORT ANSWER


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1. If a 50-MHz oscillator is accurate to within0.001%, what is the range of possiblefrequencies?

ANS:50 MHz 500 hertz2. What is the efficiency of a 100-watt mobiletransmitter if it draws 11 amps from a 12-voltcar battery?

ANS:75.8%3. The power amplifier of an AM transmitterdraws 100 watts from the power supply withno modulation.Assuming high-level modulation, how muchpower does the modulation amplifier deliverfor 100%modulation? ANS:50watts4. If the final RF amplifier of an AM transmitteris powered by 100 volts DC, what is themaximum

collector voltage at 100% modulation?ANS:400volts5. Suppose the output of a balancedmodulator has a center frequency of 10 MHz.

The audio modulationfrequency range is 1 kHz to 10 kHz. To passthe USB, what should be the center frequencyof an idealcrystal filter? ANS:10.005 MHz6. Suppose you have generated a USB SSBsignal with a nominal carrier frequency of 10

MHz. What is theminimum frequency the SSB signal can bemixed with so that the output signal has anominal carrierfrequency of 50 MHz?

ANS:40 MHz7. Suppose you have an FM modulator thatputs out 1 MHz carrier with a 100-hertzdeviation. If frequencymultiplication is used to increase thedeviation to 400 hertz, what will be the newcarrier frequency?

ANS:4 MHz8. Suppose you had an FM signal with acarrier of 10 MHz and a deviation of 10 kHz.Explain how youcould use it to get an FM signal at 100 MHzwith a deviation of 20 kHz.ANS:First, put the signal through a frequencydoubler to get a 20-MHz carrier with a 20-kHzdeviation. Then

mix that signal with an 80-MHz carrier togenerate a 100-MHz carrier with 20-kHzdeviation.

Chapter 6: ReceiversMULTIPLE CHOICE1. The two basic specifications for a receiverare:

a. the sensitivity and the selectivityb. the number of converters and the numberof IFsc. the spurious response and the trackingd. the signal and the noise ANS:A2. The superheterodyne receiver wasinvented by:a. Foster c. Armstrongb. Seeley d. Hertz ANS:C3. Trimmers and padders are:

a. two types of adjusting tools c. smalladjustable inductorsb. small adjustable resistors d. smalladjustable capacitors

ANS: D4. "Skin effect" refers to:a. the way radio signals travel across a flatsurfaceb. the tissue-burning effect of a strong RFsignalc. the increase of wire resistance withfrequency

d. none of the aboveANS: C

5. The "front end" of a receiver can include:a. the tuner c. the mixerb. the RF amplifier d. all of the above

ANS: D6. "IF" stands for:a. intermediate frequency c. indeterminatefrequencyb. intermodulation frequency d. imagefrequencyANS: A

7. AGC stands for:a. Audio Gain Control c. Active Gain Controlb. Automatic Gain Control d. Active GainConversionANS: B8. The frequency of the local oscillator:a. is above the RF frequencyb. is below the RF frequencyc. can be either above of below the RFfrequency


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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 spuriousresponsesb. it increases sensitivityc. it increases selectivityd. it is cheaper

ANS: D10. Basically, sensitivity measures:a. the weakest signal that can be usefullyreceivedb. the highest-frequency signal that can beusefully receivedc. the dynamic range of the audio amplifierd. none of the above

ANS: A11. Basically, selectivity measures:

a. the range of frequencies that the receivercan selectb. with two signals close in frequency, theability to receive one and reject the otherc. how well adjacent frequencies areseparated by the demodulatord. how well the adjacent frequencies areseparated in the mixer

ANS: B12. When comparing values for shape factor:a. a value of 1.414 dB is ideal c. a value of 1.0is ideal

b. a value of 0.707 is ideal d. there is no idealvalueANS: C13. When comparing values for shape factor:a. a value of 2 is better than a value of 4 c.both values are basically equivalentb. a value of 4 is better than a value of 2 d.none of the above

ANS: 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 receiversb. color video receivers d. all of the above

ANS: B16. The response of a receiver to weak signalsis usually limited by:a. the AGC c. the dynamic range of thereceiver

b. noise generated in the receiver d. the typeof detector circuit being used

ANS: B17. Image frequencies occur when twosignals:a. are transmitted on the same frequencyb. enter the mixer, with one being a reflectedsignal equal to the IF frequencyc. enter the mixer, one below and one abovethe local oscillator by a difference equal to theIFd. enter the mixer, and the differencebetween the two signals is equal to twice theIF ANS: C18. An image must be rejected:a. prior to mixing c. prior to detectionb. prior to IF amplification d. images cannotbe rejectedANS: A

19. Image frequency problems would bereduced by:a. having an IF amplifier with the propershape factorb. having a wideband RF amplifier after themixerc. having a narrowband RF amplifier beforethe 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 above ANS:B21. An FM detector is the:a. PLL c. quadrature detectorb. ratio detector d. all of the above ANS:D22. Germanium diodes are used in AMdetectors because:a. they are faster than silicon diodesb. they are cheaper than silicon diodesc. they minimize distortion from nonlinearityd. all of the above ANS: C

23. A common SSB detector is:a. a PLL c. a BFOb. a diode d. a product detector

ANS: D24. BFO stands for:a. Beat Frequency Oscillator c. BipolarFrequency Oscillatorb. Barrier Frequency Oscillator d. BistableFrequency Oscillator

ANS: A


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25. To demodulate both SSB and DSBSC, youneed to:a. use a Foster-Seeley discriminatorb. reinject the carrierc. use double conversiond. use one diode for SSB and two diodes forDSBSCANS: B26. Which would be best for DSBSC:a. carrier detection c. envelope detectionb. coherent detection d. ratio detection

ANS: B27. An FM detector that is not sensitive toamplitude variations is:a. Foster-Seeley detector c. a PLL detectorb. a quadrature detector d. all of the above

ANS: C28. The function of a limiter is:a. to remove amplitude variations c. to limit

dynamic rangeb. to limit spurious responses d. to limit noiseresponseANS: A29. Suppressing the audio when no signal ispresent is called:a. AGC c. AFCb. squelch d. limiting

ANS: B30. LNA stands for:a. Limited-Noise Amplifier c. Low-Noise Audiob. Low-Noise Amplifier d. Logarithmic Noise

Amplification ANS:B31. AFC stands for:a. Audio Frequency Compensator c. AutomaticFrequency 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 frequencyd. none of the aboveANS: B

33. SAW stands for:a. Symmetrical Audio Wave c. Silicon-Activated Waferb. Surface Acoustic Wave d. Software-Activated WaveANS: B34. The important property of a SAW is:

a. it stabilizes the audio in a receiver c. it is astable bandpass filterb. it allows software radios to be built d. noneof the above

ANS: C35. The main function of the AGC is to:a. keep the gain of the receiver constantb. keep the gain of the IF amplifiers constantc. keep the input to the detector at a constantamplituded. all of the above ANS: C36. DSP stands for:a. Dynamic Signal Properties c. DistortedSignal Packetb. Direct Signal Phase d. Digital SignalProcessorANS: D37. SINAD stands for:a. Sinusoidal Amplitude Distortion

b. Signal and Noise Amplitude Distortionc. Signal-plus-Noise-to-Noise Ratiod. Signal-plus-Noise and Distortion-to-Noiseand Distortion Ratio ANS:D38. TRF stands for:a. Tuned Radio Frequency c. TransmittedRadio Frequencyb. Tracking Radio Frequency d. TunedReceiver Function ANS:ACOMPLETION

1. Almost all modern receivers use the_________________________ principle.ANS: superheterodyne2. The first radio receiver of any kind was builtin the year ____________________. ANS:18873. When two tuned circuits

____________________ each other, it means thatwhen the frequency of one isadjusted, the other changes with it. ANS:track4. The __________effect causes the resistance

of wire to increase with frequency.ANS: skin5. The superhet was invented in the year

______________. ANS: 19186. In a receiver, the _______________ refers tothe input filter and RF stage.

ANS: front end7. In a superhet, the output of the ___________goes to the IF amplifiers. ANS:mixer


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8. In a superhet, the __________ frequency isthe difference between the local oscillatorfrequency and the received signal frequency.

ANS: intermediate IF9. The ______ circuit adjusts the gain of the IFamplifiers in response to signal strength.

ANS: AGC10. An ____________________ converter uses thesame transistor for both the local oscillatorand the mixer.ANS: autodyne11. In low-side injection, the local oscillator is

____________________ than the received signalfrequency. ANS: lower12. ____________________ is the ability of areceiver to separate two signals that are closeto each other infrequency. ANS: Selectivity13. ____________________ is the ability of a

receiver to receive and successfullydemodulate a very weaksignal. ANS: Sensitivity14. A receiver with two different IFfrequencies is called a double-________receiver. ANS: conversion15. A multiple-conversion receiver will havebetter rejection of _______ frequencies. ANS:image16. A demodulator is also called a

________________.ANS: detector

17. An ______________ detector uses a diode tohalf-wave rectify an AM signal. ANS:envelope18. A _______________ detector is used for SSBsignals. 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: S22. 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 theinput signal. ANS:amplitude

24. A dual-____________________ MOSFET isuseful for AGC. ANS:gate25. Diode mixers are too ____________________to be practical in most applications.

ANS: noisy26. The IF amplifiers in an AM receiver mustbe Class ____________________. ANS:A27. A double-tuned IF transformer is usually

____________________ coupled for the responseto have a flat top and steep sides.

ANS: over28. Multiple IF stages can be

____________________-tuned to increase thebandwidth. ANS: stagger29. Compared to tuned circuits, ceramic andcrystal IF filters do not require _______. ANS:adjustment

30. Up-conversion is when the output of themixer is a ____________________ frequency thanthe incomingsignal. ANS: higher31. In a block converter, the frequency of thefirst local oscillator is __________. ANS: fixedconstant32. Typically, AGC reduces the gain of the

__________ amplifiers.ANS: IF

33. An ____________________-meter is designedto indicate signal strength in many

communicationsreceivers. ANS: S34. The effectiveness of FM ____________ ismeasured by a receivers quieting sensitivity.

ANS: limiting35. A ____________________ refers to any kind ofFM or PM detector. ANS:discriminatorSHORT ANSWER1. Suppose the bandwidth of a tuned circuit is10 kHz at 1 MHz. Approximately whatbandwidth would you

expect it to have at 4 MHz? ANS: 20 kHz2. Using high-side injection for a 1-MHz IF,what is the frequency of the local oscillatorwhen the receiveris tuned to 5 MHz? ANS:6 MHz3. An IF filter has a 60 dB bandwidth of 25kHz and a 6 dB bandwidth of 20 kHz. What isthe shapefactor value? ANS:1.25


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4. Suppose a receiver uses a 5-MHz IFfrequency. Assuming high-side injection, whatwould be the imagefrequency if the receiver was tuned to 50MHz?ANS:60 MHz5. Suppose a SSB receiver requires aninjected frequency of 1.5 MHz. What would bethe acceptablefrequency range of the BFO if the maximumacceptable baseband shift is 100 hertz?

ANS:1.5 MHz 100 hertz6. The transformer of a double-tuned IFamplifier has a Q of 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

couplingneed to get a bandwidth of 100 kHz?ANS:0.01

Chapter 7: DigitalCommunicationsMULTIPLE CHOICE1. The first digital code was the:a. ASCII code c. Morse codeb. Baudot code d. none of the above ANS:C2. In digital transmission, signal degradation

can be removed using:a. an amplifier c. a regenerative repeaterb. a filter d. all of the above ANS:C3. TDM stands for:a. Time-Division Multiplexing c. Ten-DigitalManchesterb. Time-Domain Multiplexing d. Ten Dual-ManchesterANS: A4. Hartley's Law is:a. I = ktB c. C = B log2(1 + S/N)

b. C = 2B log2M d. SR = 2fmax ANS:A5. The Shannon-Hartley theorem is:a. I = ktB c. C = B log2(1 + S/N)b. C = 2B log2M d. SR = 2fmax ANS:B6. The Shannon Limit is given by:a. I = ktB c. C = B log2(1 + S/N)b. C = 2B log2M d. SR = 2fmax ANS:C

7. The Nyquist Rate can be expressed as:a. I = ktB c. C = B log2(1 + S/N)b. C = 2B log2M d. SR = 2fmax ANS:D8. Natural Sampling does not use:a. a sample-and-hold circuit c. a fixed samplerateb. true binary numbers d. an analog-to-digitalconverterANS: A9. Which is true about aliasing and foldoverdistortion?a. They are two types of sampling error.b. You can have one or the other, but notboth.c. Aliasing is a technique to prevent foldoverdistortion.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 theaboveANS: C11. The immediate result of sampling is:a. a sample alias c. PCMb. PAM d. PDM ANS:B12. Which of these is not a pulse-modulationtechnique:a. PDM c. PPM

b. PWM d. PPSANS: D13. Quantizing noise (quantization noise):a. decreases as the sample rate increasesb. decreases as the sample rate decreasesc. decreases as the bits per sample increasesd. decreases as the bits per sample decreases

ANS: C14. The dynamic range of a system is theratio of:a. the strongest transmittable signal to theweakest discernible signal

b. the maximum rate of conversion to theminimum rate of conversionc. the maximum bits per sample to theminimum bits per sampled. none of the above

ANS: A15. Companding is used to:a. compress the range of base-bandfrequenciesb. reduce dynamic range at higher bit-rates


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c. preserve dynamic range while keeping bit-rate lowd. maximize the useable bandwidth in digitaltransmission ANS:C16. In North America, companding uses:

a. the Logarithmic Law c. the Law (alpha

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

17. In Europe, companding uses:

a. the Logarithmic Law c. the Law (alphalaw)

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

18. Codec stands for:a. Coder-Decoder c. Code-Compressionb. Coded-Carrier d. none of the above

ANS: A

19. A typical codec in a telephone systemsends and receives:a. 4-bit numbers c. 12-bit numbersb. 8-bit numbers d. 16-bit numbers

ANS: B20. Compared to PCM, delta modulation:a. transmits fewer bits per sample c. cansuffer slope overloadb. requires a much higher sampling rate d. allof the above

ANS: D21. In delta modulation, "granular noise" is

produced when:a. the signal changes too rapidly c. the bitrate is too highb. the signal does not change d. the sample istoo largeANS: B22. Compared to PCM, adaptive deltamodulation 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: B23. Which coding scheme requires DCcontinuity:a. AMI c. unipolar NRZb. Manchester d. bipolar RZ ANS:C24. Manchester coding:a. is a biphase codeb. has a level transition in the middle of everybit period

c. provides strong timing informationd. all of the above ANS: D25. 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 transmitterand receiverb. carry signaling d. all of the above ANS:C27. So-called "stolen" bits in DS-1 are used to:a. detect errors c. synchronize the transmitterand receiverb. carry signaling d. all of the above ANS:B28. The number of bits per sample in DS-1 is:a. 1 c. 4b. 2 d. 8 ANS:

D29. The number of samples per second in DS-1 is:a. 8 k c. 64 k

b. 56 k d. 1.544 106 ANS:A30. The bit rate for each channel in DS-1 is:a. 1.544 Mb/s c. 56 kb/sb. 64 kb/s d. 8 kb/s ANS: B31. In DS-1, bits are transmitted over a T-1cable 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 codingANS: B33. The number of frames in a superframe is:a. 6 c. 24b. 12 d. 48 ANS: B34. A typical T-1 line uses:a. twisted-pair wire c. fiber-optic cableb. coaxial cable d. microwave ANS:A

35. "Signaling" is used to indicate:a. on-hook/off-hook condition c. ringingb. busy signal d. all of the above ANS:D36. A vocoder implements compression by:a. constructing a model of the transmissionmediumb. constructing a model of the human vocalsystemc. finding redundancies in the digitized data


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d. using lossless techniques ANS:B37. Compared to standard PCM systems, thequality of the output of a vocoder is:a. much better c. about the sameb. somewhat better d. not as good

ANS: DCOMPLETION1. Digitizing a signal often results in

________________ transmission quality.ANS: improved better

2. To send it over an analog channel, a digitalsignal must be _______ onto a carrier. ANS:modulated3. To send it over a digital channel, an analogsignal must first be ____________________.

ANS: digitized4. In analog channels, the signal-to-noise ratioof an analog signal gradually __________ as the

length of the channel increases. ANS:decreases/gets worse5. The _______ value of a pulse is the onlyinformation it carries on a digital channel.

ANS: binary6. A _________ repeater is used to restore theshape of pulses on a digital cable. ANS:regenerative7. There are techniques to detect and

____________________ some errors in digitaltransmission. ANS:correct

8. Converting an analog signal to digital formis another source of ____________________ indigitaltransmission systems. ANS:error/noise9. ____________________-division multiplexing iseasily done in digital transmission. ANS:

Time10. All practical communications channels areband-____________________. ANS: limited11. ________ Law gives the relationshipbetween time, information capacity, and

bandwidth. ANS: Hartley's12. Ignoring noise, the_________________________ theorem gives themaximum rate of data transmissionfor a given bandwidth. ANS:Shannon-Hartley13. The ________________ limit gives themaximum rate of data transmission for agiven bandwidth and a given signal-to-noiseratio. ANS: Shannon

14. ____________________ sampling is donewithout a sample-and-hold circuit.

ANS: Natural15. The ____________________ Rate is theminimum sampling rate for converting analogsignals to digitalformat. ANS:Nyquist16. _______ distortion occurs when an analogsignal is sampled at too slow a rate.

ANS: Foldover17. ____________________ means that higherfrequency baseband signals from thetransmitter "assume the identity" of low-frequency baseband signals at the receiverwhen sent digitally. ANS: Aliasing18. The output of a sample-and-hold circuit isa pulse-______ modulated signal. ANS:amplitude

19. ________ modulation is the most commonlyused digital modulation scheme. ANS: Pulse-code20. ____________________ noise results from theprocess of converting an analog signal intodigital format. ANS:Quantizing21. _________ is used to preserve dynamicrange using a reasonable bandwidth.

ANS: Companding22. In North America, compression is doneusing the _______-law equation.

ANS:mu23. In Europe, compression is done using the

_________-law equation. ANS: A24. A ____________________ is an IC thatconverts a voice signal to PCM and vice versa.

ANS: codec25. In a PCM system, the samples of theanalog signal are first converted to

________________ bitsbefore being compressed to 8 bits. ANS:12

26. The number of bits per sampletransmitted in delta modulation is____________________. ANS:1/one27. Delta modulation requires a

____________________ sampling rate than PCMfor the same quality ofreproduction. ANS:higher


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28. _______ noise is produced by a deltamodulator if the analog signal doesn't change.

ANS: Granular29. In delta modulation, _________ overloadcan occur if the analog signal changes toofast. ANS: slope30. The ____________________ size varies inadaptive delta modulation.

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

____________________ the bit rateof PCM. ANS: half 32. Unipolar NRZ is not practical becausemost channels do not have ______ continuity.

ANS: DC33. In AMI, binary ones are represented by avoltage that alternates in ________.

ANS: polarity

34. Long strings of ____________________ shouldbe avoided in AMI. ANS: zeros35. Manchester code has a level

______________ in the center of each bit period.ANS: transition

36. Manchester coding provides________________ information regardless of thepattern of ones andzeros. ANS: timing37. There are ____________________ channels ina DS-1 frame. ANS:24

38. DS-1 uses a _______________ bit tosynchronize the transmitter and receiver.ANS: framing

39. 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 10641. 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. ____________________ compressiontransmits all the data in the original signal butuses fewer bits to doit. ANS: LosslessSHORT ANSWER1. Use Hartley's Law to find how much time itwould take to send 100,000 bits over achannel with a

bandwidth of 2,000 hertz and a channelconstant ofk= 10.

ANS:5 seconds2. Use the Shannon-Hartley theorem to findthe bandwidth required to send 12,000 bitsper second if thenumber of levels transmitted is 8.

ANS:2000 hertz3. What is the Shannon Limit of a channel thathas a bandwidth of 4000 hertz and a signal-to-noise ratio of15? ANS:16 kbps4. What is the minimum required number ofsamples per second to digitize an analogsignal with frequencycomponents ranging from 300 hertz to 3300hertz?ANS:6600 samples/second5. What is the approximate dynamic range, in

dB, of a linear PCM system that uses 12 bitsper sample?ANS:74 dB6. What is the approximate data rate for asystem using 8 bits per sample and running at8000 samples persecond?

ANS:64 kbps7. If bits were "stolen" from every DS-1 frame,what would the useable data-rate be for eachchannel in theframe?

ANS:56 kbps8. Assuming maximum input and outputvoltages of 1 volt, what is the output voltage

of a -law compressorif the input voltage is 0.388 volt?ANS:0.833volt

Chapter 8: The Telephone SystemMULTIPLE CHOICE1. DTMF stands for:a. Digital Telephony Multiple Frequency c.Dual-Tone Multifrequency

b. Dial Tone Master Frequency d. Digital TrunkMaster Frequency

ANS: C2. PSTN stands for:a. Public Switched Telephone Network c.Primary Service Telephone Networkb. Private Switched Telephone Network d.Primary Service Telephone Numbers

ANS: A3. POTS stands for:


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a. Private Office Telephone System c. PrimaryOperational Test Systemb. Primary Office Telephone Service d. PlainOld Telephone Service

ANS: D4. LATA stands for:a. Local Access and Transport Area c. LocalArea Telephone Accessb. Local Access Telephone Area d. Local Area

Transport AccessANS: A

5. A LATA is a:a. a local calling area c. a way of accessing atandem officeb. a type of digital local network d. a way ofaccessing a central office

ANS: A6. Central offices are connected by:a. local loops c. both a and b

b. trunk lines d. none of the aboveANS: B7. Local loops terminate at:a. a tandem office c. a central officeb. a toll station d. an interexchange office

ANS: C8. Call blocking:a. cannot occur in the public telephonenetworkb. occurs on the local loop when there is anelectrical power failurec. occurs only on long-distance cables

d. occurs when the central office capacity isexceededANS: D9. In telephony, POP stands for:a. Post Office Protocol c. Power-On Protocolb. Point Of Presence d. none of the above

ANS: B10. The cable used for local loops is mainly:a. twisted-pair copper wire c. coaxial cableb. shielded twisted-pair copper wire d. fiber-opticANS: A

11. FITL stands for:a. Framing Information for Toll Loops c.Framing In The Loopb. Fiber In the Toll Loop d. Fiber-In-The-LoopANS: D12. Loading coils were used to:a. increase the speed of the local loop fordigital datab. reduce the attenuation of voice signalsc. reduce crosstalkd. provide C-type conditioning to a local loop

ANS: B13. DC current flows through a telephone:a. when it is on hook c. as long as it isattached to a local loopb. when it is off hook d. only when it is ringingANS: B14. The range of DC current that flowsthrough a telephone is:

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

b. 200 A to 800 A d. 20 mA to 80 mA ANS:D15. The separation of control functions fromsignal switching is known as:a. step-by-step switching control c. commoncontrolb. crossbar control d. ESS ANS:C16. The typical voltage across a telephonewhen on-hook is:

a. 48 volts DC c. 90 volts DCb. 48 volts, 20 hertz AC d. 90 volts, 20 hertzACANS: A17. The typical voltage needed to "ring" atelephone is:a. 48 volts DC c. 90 volts DCb. 48 volts, 20 hertz AC d. 90 volts, 20 hertzACANS: D18. The bandwidth of voice-grade signals on atelephone system is restricted in order to:

a. allow lines to be "conditioned" c. allowsignals to be multiplexedb. prevent "singing" d. all of the above

ANS: C19. VNL stands for:a. voltage net loss c. via net lossb. volume net loss d. voice noise level

ANS: C20. Signal loss is designed into a telephonesystem to:a. eliminate reflections c. improve signal-to-noise ratio

b. prevent oscillation d. reduce powerconsumptionANS: B21. 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 basicFDM group is:a. 6 c. 24


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b. 12 d. 60 ANS:B23. Basic FDM groups can be combined into:a. supergroups c. jumbogroupsb. mastergroups d. all of the above

ANS: D24. In telephone system FDM, voice is put ona carrier using:a. SSB c. PDMb. DSBSC d. PCM ANS:A25. PABX stands for:a. Power Amplification Before Transmissionb. Private Automatic Branch Exchangec. Public Automated Branch Exchanged. Public Access Branch Exchange

ANS: B26. SLIC stands for:a. Single-Line Interface Circuit c. Subscriber

Line Interface Cardb. Standard Line Interface Card d. StandardLocal Interface Circuit

ANS: C27. In DS-1, bits are "robbed" in order to:a. provide synchronization c. cancel echoesb. carry signaling d. check for errors

ANS: B28. "Bit-stuffing" is more formally called:a. compensation c. justificationb. rectification d. frame alignment

ANS: C

29. ISDN stands for:a. Integrated Services Digital Network c.Integrated Services Data Networkb. Information Services Digital Network d.Information Systems Digital Network

ANS: A30. Basic ISDN has not been widely adoptedbecause:a. it took to long to developb. it is too slowc. it has been surpassed by newertechnologies

d. all of the above ANS:D31. ADSL stands for:a. All-Digital Subscriber Line c. AllocatedDigital Service Lineb. Asymmetrical Digital Subscriber Line d.Access to Data Services Line

ANS: B32. Compared to ISDN, internet access usingADSL is typically:a. much faster c. much more expensive

b. about the same speed d. none of the aboveANS: ACOMPLETION1. A ____________________ is a local callingarea.ANS: LATA2. Central offices are connected together by

_______ lines. ANS:trunk3. One central office can be connected toanother through a _________ office.

ANS: tandem4. With 7-digit phone numbers,

_______________ thousand telephones canconnect to a centraloffice. ANS: ten5. Call ____________________ is when itbecomes impossible for a subscriber to placea call due to an

overload of lines being used. ANS:blocking6. New ____________________ switchingequipment 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

10. In a twisted-pair telephone cable, the redwire is called ____________________.

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

ANS: tip12. Of the red and green 'phone wires, the

____________________ wire is positive withrespect to the other.

ANS: green13. A telephone is said to have __________ theline when the central office sends it dial tone.ANS: seized14. The ____________________ functions areprovided by a SLIC. ANS:BORSCHT15. A ____________________ coil prevents loss ofsignal energy within a telephone whileallowing fullduplex operation over a singlepair of wires.


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ANS: hybrid16. In a crosspoint switch, not all

_______________ can be in use at the sametime. ANS: lines17. The old carbon transmitters generated arelatively _________ signal voltage.

ANS: large18. The generic term for Touch-Tonesignaling is ____________________. ANS:DTMF19. A ______________ line provides morebandwidth than a standard line. ANS:conditioned20. In the telephone system, amplifiers arecalled ____________________. ANS:repeaters21. An echo ______ converts a long-distanceline from full-duplex to half-duplex operation.ANS: suppressor

22. ____________________ weighting is anattempt to adjust the noise or signal level tothe response of atypical telephone receiver. ANS: C-message23. In FDM telephony, the modulation isusually ____________________.

ANS:SSB/SSBSC24. In FDM telephony, ____________________bands separate the channels in a group.

ANS: guard25. Because of "bit robbing", a channel in a

DS-1 frame allows only ____________________kbps whenused to send digital data. ANS: 5626. A ____________________ is a group of 12 DS-1 frames with signaling information in thesixth andtwelfth frames. ANS:superframe27. In DS-1C, ___________ bits are used tocompensate for differences between clockrates. ANS: stuff28. Busy and dial tone are referred to as

____________ signals because they use thesame pair of wires as the voice signal.ANS: in-channel

29. SS7 is the current version of__________________ signaling.

ANS: common-channel30. SS7 is a ____________________-switcheddata network. ANS: packet31. In ISDN, the ____________________ channelis used for common-channel signaling. ANS:D

32. In ISDN, the ____________________ channelsare used for voice or data. ANS:B33. Terminal equipment especially designedfor ISDN is designated ______ equipment.

ANS: TE134. The A in ADSL stands for

____________________.ANS: asymmetrical35. In ADSL, the speed from the network tothe subscriber is ____________________ than thespeed in the opposite direction. ANS:greater/fasterSHORT ANSWER1. For a certain telephone, the DC loopvoltage is 48 V on hook and 8 V off hook. Ifthe loop current is 40mA, what is the DC resistance of the localloop?

ANS:1000 ohms2. For a certain telephone, the DC loopvoltage is 48 V on hook and 8 V off hook. Ifthe loop current is 40mA, what is the DC resistance of thetelephone?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 achannel with a 3 ms delay.

ANS:1 dB5. If a telephone voice signal has a level of 0dBm, what is its level in dBrn?

ANS:90 dBrn6. A telephone test-tone has a level of 80dBrn at a point where the level is +5dB TLP. IfC-weightingproduces a 10-dB loss, what would the signallevel be in dBrnc0? ANS:65dBrnc TLP

Chapter 9: Data Transmission

MULTIPLE CHOICE1. In practical terms, parallel datatransmission is sent:a. over short distances only c. over anydistanceb. usually over long distances d. usually overa coaxial cable

ANS: A2. The five-level teletype code was inventedby:


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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 anyother nameb. character sets d. both a and b

ANS: C4. Digital data that is not being used to carrycharacters is called:a. FIGS data c. numerical datab. binary data d. all of the above

ANS: B5. Character codes include:a. alphanumeric characters c. graphic controlcharactersb. data link control characters d. all of theaboveANS: D

6. ASCII stands for:a. American Standard Character-set 2b. American Standard Code for InformationInterchangec. American Standard Code 2d. Alphanumeric Standard Code forInformation Interchange

ANS: B7. BS, FF, and CR are examples of:a. nonstandard character codes c. controlcharactersb. escape characters d. none of the above

ANS: C8. LF stands for:a. Line Feed c. Line Forwardb. Link Feed d. Link Forward

ANS: A9. UART stands for:a. Universal Asynchronous Receiver-

Transmitterb. Unidirectional Asynchronous Receiver-

Transmitterc. Unaltered Received Textd. Universal Automatic Receiver for Text

ANS: A10. In asynchronous transmission, thetransmitter and receiver are:a. frame-by-frame synchronized using thedata bitsb. frame-by-frame synchronized using acommon clockc. frame-by-frame synchronized using thestart and stop bits

d. not synchronized at all, hence the name"asynchronous"

ANS: C11. In asynchronous transmission, the timebetween consecutive frames is:a. equal to zero c. equal to the start and stopbit-timesb. equal to one bit-time d. not a set length

ANS: D12. In synchronous transmission, the framesare:a. about the same length as ten asynchronousframesb. much longer than asynchronous framesc. 128 bytes longd. 1024 bytes long ANS:B13. Synchronous transmission is usedbecause:

a. no start and stop bits means higherefficiencyb. it is cheaper than asynchronous since noUARTS are requiredc. it is easier to implement than asynchronousd. all of the above ANS:A14. In synchronous transmission, the receiver"syncs-up" with the transmitter by using:a. the clock bits c. the CRC bitsb. the data bits d. a separate clock line

ANS: B

15. To maintain synchronization insynchronous transmission:a. long strings of 1s and 0s must not beallowedb. transmission must stop periodically forresynchronizationc. the clock circuits must be preciselyadjustedd. 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 theaboveANS: D17. HDLC:a. is an IBM product c. is identical to SDLCb. is a bit-oriented protocol d. all of the above

ANS: B18. The use of flags in SDLC requires:a. "bit-stuffing" c. FECb. different flags at either end of a frame d.ARQ


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ANS: A19. The initials ARQ are used to designate:a. automatic request for resynchronization c.automatic receiver queueb. automatic request for retransmission d.automatic request for queue

ANS: B20. ARQ is used to:a. correct bit errors c. put data into atemporary bufferb. correct synchronization problems d. noneof the aboveANS: A21. FEC stands for:a. Fixed Error Control c. Forward ErrorCorrectionb. Forward Error Control d. False ErrorConditionANS: C

22. VRC is another name for:a. FEC c. LRCb. ARQ d. parity ANS:D23. CRC stands for:a. Control Receiver Code c. CyclicRedundancy Checkb. Correct Received Character d. Cycle RepeatCharacterANS: C24. Huffman codes:a. allow errors to be detected but not

correctedb. allow errors to be detected and correctedc. allow alphanumeric data to be correctedd. allow alphanumeric data to be compressedANS: D25. Run-length encoding is used to:a. encrypt data c. correct datab. compress data d. none of the above

ANS: B26. Public-key encryption:a. allows the use of digital signatures c.avoids the "password problem"

b. is used to convey symmetric keys d. all ofthe aboveANS: D27. SDLC stands for:a. Synchronous Data Link Control c.Synchronous Data Link Characterb. Synchronous Data Line Control d.Synchronous Data Line Character

ANS: A28. HDLC is:a. a bit-oriented protocol c. an ISO standard

b. based on SDLC d. all of the aboveANS: D

COMPLETION1. Parallel transmission can be used only for

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

_______________. ANS: Baudot3. Data codes are also called

____________________ codes.ANS: character

4. The ____________________ code is a 7-bitcode commonly used in communicationbetween personalcomputers. ANS: ASCII5. The two letters ____________________designate the code character used to advancea printer to the nextpage. ANS: FF

6. An asynchronous frame begins with the____________________ bit. ANS: start7. An asynchronous frame ends with the

____________________ bit. ANS: stop8. At the end of an asynchronous frame, theline will be at the _______ level. ANS:mark/binary 19. An integrated circuit called a ___________ isused in an asynchronous communicationsystem to convert between parallel and serialdata. ANS: UART10. When receiving digital data, __________ are

used to hold data until they can be read.ANS: buffers11. Synchronous communication is more

____________ than asynchronous since thereare fewer "overhead" bits.ANS: efficient12. There must be sufficient 1-to-0

______________ to maintain synchronization insynchronous transmission.ANS: transitions13. Clock sync is derived from the stream of

____________________ bits in synchronous

transmission. ANS:data14. In the _______ protocol, each frame beginswith at least two SYN characters. ANS:BISYNC15. In HDLC, each frame starts with an 8-bit

____________________. ANS: flag16. The first eight bits of an SDLC frame are

____________________. ANS:01111110


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17. BCC stands for ____________________ checkcharacter. ANS: block18. DLE stands for data link

____________________.ANS: escape19. HDLC uses bit-____________________ toprevent accidental flags.

ANS: stuffing20. ____________________ errors cause manyconsecutive bits to be bad. ANS:Burst21. FEC stands for ____________________ errorcorrection. ANS: forward22. An __________ scheme corrects errors byrequiring the retransmission of bad blocks.

ANS: ARQ23. Parity fails when an ____________________number of bits are in error. ANS:even

24. CRC codes are particularly good atdetecting ____________________ errors.ANS: burst

25. Huffman coding and run-length encodingare examples of data _________. ANS:compression26. A ____________________ is an encodingscheme that is not public in order to protectdata. ANS: cipher27. A ________ is often used to generate anencryption key because it is easier toremember. ANS: password

28. If the key is ____________ enough, private-key encryption can be quite secure.ANS: long

29. Messages cannot be ____________________using a public key. ANS:decrypted30. Because it is ___________-intensive, public-key encryption can be slow. ANS:computationSHORT ANSWER1. How many different characters could beencoded using a six-bit code?

ANS:642. What is the numerical difference betweenASCII 'a' and ASCII 'A' if you treat them ashexadecimal (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 theshortest time it could take to send 1000characters if each bit in a frame is 1 mseclong? ANS:10 sec5. Suppose an asynchronous frame holds 8bits of data, a parity bit, and two stop bits (itcould happen). Calculate the efficiency of thecommunication system. ANS:66.7%6. Suppose a synchronous frame has 16 bitsof non-data in the front and a 16-bit BCC atthe end. The framecarries 1024 bytes of actual data. Calculatethe efficiency of the communication system.

ANS:97.0%

Chapter 10: Local Area NetworksMULTIPLE CHOICE

1. CSMA stands for:a. Client-Server Multi-Access c. Carrier ServerMaster Applicationb. Carrier Sense Multiple Access d. none ofthe aboveANS: B2. The CD in CSMA/CD stands for:a. Carrier Detection c. Collision Detectionb. Carrier Delay d. Collision Delay ANS:C3. The Internet is:a. a network of networks c. a very large

CSMA/CD networkb. a very large client-server network d. notreally 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:D5. Dumb terminals are still used:a. in token-passing networksb. in networks requiring central monitoringc. in networks that cannot provide central

monitoringd. none of the above ANS:B6. In a circuit-switched network:a. communication is half-duplex onlyb. each channel carries only one data streamc. connection is usually done using a bustopologyd. all of the above ANS: B7. Each computer on a network is called a:


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a. hub c. nodeb. token d. circuit ANS: C8. Compared to CSMA/CD systems, token-passing rings are:a. slower c. not as widely usedb. more expensive d. all of the above ANS:D9. The key feature of a star network is thatindividual workstations are connected to:a. a central ring c. a nodeb. a central bus d. none of the above ANS:D10. On networks, long messages are dividedinto "chunks" called:a. packets c. carriersb. nodes d. tokens ANS: A11. When two or more PCs try to access abaseband network cable at the same time, itis called:

a. a collision c. excess trafficb. contention d. multiple access ANS:B12. When two PCs send data over a basebandnetwork cable at the same time, it is called:a. a collision c. excess trafficb. contention d. multiple access ANS:A13. One type of network that never has acollision is:a. CSMA c. token-passingb. Ethernet d. all networks have collisions

ANS: C14. In an Ethernet-based network, a switchcan be used to reduce the number of:a. nodes c. packetsb. users d. collisions

ANS: D15. The effect of too many collisions is:a. the network goes down c. the cableoverheatsb. the network slows down d. data is lost

ANS: B16. MAU stands for:

a. Multistation Access Unit c. MultipleAuxiliary Unitsb. Multiple Access Unit d. none of the above

ANS: A17. The standard that describes Ethernet-typenetworks is:a. EIA 232 c. IEEE 802.3b. IEEE 488.1 d. CCITT ITU-E

ANS: C18. Ethernet was invented by:a. IBM c. Xerox

b. INTEL d. Digital Equipment CorporationANS: C

19. An Ethernet running at 10 Mbits / seconduses: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 cableb. twisted-pair copper wires d. 50-ohm coaxialcableANS: B21. The word "Base" in 10BaseT means:a. the cable carries baseband signalsb. the cable has a base speed of 10 Mbpsc. it can be used as the base for a backbonecable systemd. none of the above

ANS: A

22. The reason a CSMA/CD network has aminimum length for packets is:a. to increase the data rateb. to prevent packets from reaching all othernodes during transmissionc. to make sure all other nodes hear acollision in progressd. all of the above ANS:C23. The reason a CSMA/CD network has amaximum length for cables is:a. to increase the data rate

b. to prevent packets from reaching all othernodes during transmissionc. to make sure all other nodes hear acollision in progressd. all of the above ANS:C24. NIC stands for:a. Network Interface Card c. Network InterfaceCodeb. 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 Packet

ANS: B


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27. Compared to twisted-pair telephonecables, CAT-5 cables:a. are cheaper c. allow faster bit ratesb. are easier to crimp connectors onto d. all ofthe aboveANS: C28. A hub:a. sends incoming packets out to all otherterminals connected to itb. sends incoming packets out to specificportsc. cannot be used in an Ethernet-type networkd. are more common in token-passingnetworksANS: A29. A switch:a. sends incoming packets out to all otherterminals connected to itb. sends incoming packets out to specific

portsc. cannot be used in an Ethernet-type networkd. are more common in token-passingnetworksANS: B30. An advantage of using a switch instead ofa hub is:a. it is cheaper when used in large networksb. it is faster when used in large networksc. it reduces the number of collisions in largenetworksd. all of the above ANS: C

31. Broadband LANs:a. modulate the data onto a carrierb. use coaxial cablesc. are provided by cable TV companies forInternet accessd. all of the above ANS: D32. Using one node in the network to hold allthe application software is done in:a. peer-to-peer networks c. both a and bb. client-server networks d. none of the aboveANS: B33. Record locking is used to:

a. store records securely on a serverb. prevent multiple users from looking at adocument simultaneouslyc. prevent one user from reading a recordthat another user is writing tod. none of the above ANS:C34. The software that runs a client-servernetwork 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. sameas a "dumb" terminalb. a node that rarely sends data d. all of theaboveANS: ACOMPLETION1. A LAN is a ________________ Area Network.ANS: Local2. The Internet is a network of

____________________.ANS: networks3. In a ____________________ network, all nodesare connected to a central computer.

ANS: star4. In a ____________-switched network, usershave a dedicated channel for the duration of

communications.ANS: circuit5. The __________ of a network describes howit is physically connected together.

ANS: topology6. Ring networks often use _______________-passing.ANS: token7. A ____________________ is a short section of amessage 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 nodestransmit simultaneously on the samebaseband cable.ANS: collision10. In CSMA/CD networks, all collisions mustbe ____________________. ANS:detected11. Carrier-Sense means that a node "listens"for the cable to be _________ before using it.ANS: quiet/free/unused/available

12. A "____________________" cable linksclusters of computers together.ANS: backbone

13. 100BaseT cables can reliably carry up to____________ bits per second. ANS:100 mega14. In CSMA/CD, packets must have a

____________________ length to ensure thatcollisions are detected.

ANS: minimum


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15. In CSMA/CD, the ___________ of a cable islimited to ensure that collisions are detected.

ANS: length16. A unique numerical address is provided toa node by its ____________________.

ANS: NIC17. A 100BaseTX cable is a

____________________ cable.ANS: fiber-optic

18. Hubs can be ____________________ to form,in effect, one big hub. ANS:stacked19. A switch looks at the ____________________of each incoming packet. ANS:address20. The effect of a switch is to greatly reduce

____________________. ANS: contentionSHORT ANSWER1. Explain how a network can be a physical

bus but a logical ring.ANS:A token-passing network sends the tokenfrom node to node in a prescribed order. So itdoesn't matterhow the physical connection is made. It stillworks like a token-passing ring.2. What is the key difference between a huband a switch?ANS:A hub sends incoming packets out to all otherports on the hub. A switch sends a packet to a

specific portbased on the address in the packet.3. What is the advantage of a CSMA/CDnetwork over a basic star network?ANS:If the central computer in a star network fails,the entire network is inoperative. If a nodefails in aCSMA/CD network, it can be disconnected andthe network still functions.4. Why do CSMA/CD packets have a minimumsize limit?

ANS:If a packet is too short, nodes at either end ofa cable could get on, send a packet, and getoff before thepackets travel far enough to collide. Thecollision would not be detected.5. What is a NIC address, and why is itunique?ANS:

The address is a long binary number "burned"into a NIC's memory chip at the factory. Eachfactory usesa different sequence of numbers, so thechances of two NICs on the same networkhaving the sameaddress is extremely small.

Chapter 11: Wide-Area Networksand the InternetMULTIPLE CHOICE1. MAN stands for:a. Manchester Access Network c.Metropolitan-Area Networkb. Multiple-Area Network d. Multiple AccessNetworkANS: C2. Packet switching is based on:a. store-and-forward c. real-time delivery

b. switched circuits d. all of the aboveANS: A

3. SNA stands for:a. Standard Network Access c. StandardNetwork Architectureb. Small Network Access d. Systems NetworkArchitecture ANS:D4. The number of layers in ISO OSI is:a. 3 c. 7b. 5 d. 8

ANS: C

5. The lowest-level layer in ISO OSI is calledthe:a. physical layer c. cable layerb. link layer d. transport layer

ANS: A6. Bad frames are usually detected by the:a. frame layer c. error-check layerb. physical layer d. link layer

ANS: D7. A virtual circuit is set up by the:a. user c. networkb. link layer d. frame

ANS: C8. Frame Relay:a. is faster than X.25 c. allows for variablelength packetsb. does less error checking than X.25 d. all ofthe aboveANS: D9. ATM stands for:a. Asynchronous Transfer Mode c.Asynchronous Transmission Model


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b. Asynchronous Transmission Mode d.Automatic Test Mode

ANS: A10. A bridge:a. separates a network into "collisiondomains"b. looks at the address of each packetc. operate at the data-link leveld. all of the above ANS:D11. IP stands for:a. Internet Process c. Interconnect Protocolb. Internet Protocol d. Interconnect Procedure

ANS: B12. TCP stands for:a. Transmission Control Process c. TransferConnection Protocolb. Transmission Control Protocol d. none ofthe above

ANS: B13. Together, TCP/IP consists of:a. 5 layers c. an application and a processb. 7 layers d. datagrams

ANS: A14. IP is a:a. connection-oriented protocol c.connectionless protocolb. virtual circuit d. non-robust protocol

ANS: C15. The "lifetime" of a packet in an IPnetwork:

a. is essentially foreverb. depends on elapsed time sincetransmissionc. depends on number of "hops" betweennodesd. is approximately 200 milliseconds

ANS: C16. UDP stands for:a. User Datagram Protocol c. User DataPacketb. User Data Protocol d. Universal Data Packet

ANS: A

17. HTTP stands for:a. High-speed Transmission Test Procedureb. High-Level Transfer Test Procedurec. Hypertext Transmission and TransportProcedured. Hypertext Transport Protocol

ANS: D18. HTTP allows the use of:a. dumb terminals c. browsersb. file transport d. none of the above

ANS: C

19. HTML stands for:a. Hypertext Markup Language c. Hypertext

Transfer-Mode Layerb. Hypertext Transfer-Mode Level d. High-speed Transfer-Mode Language

ANS: A20. HTML allows:a. telneting c. web page layoutb. high-speed file transfer d. all of the aboveANS: C21. FTP stands for:a. File Transfer Protocol c. File Test Procedureb. File Transport Protocol d. Fast TransportPacketANS: A22. FTP is used to:a. transfer files between a server on thenetwork and a userb. test files to see if their data has been

"corrupted"c. transport packets at maximum speedthrough the networkd. none of the above ANS:A23. SMTP stands for:a. Short Message Transport Protocol c. SimpleMail Transport Protocolb. Simple Message Transport Protocol d.Secondary Mail Transfer Procedure

ANS: C24. ISP stands for:

a. Internet Service Protocol c. Internet ServiceProcedureb. Internet Service Provider d. none of theaboveANS: B25. The standard Internet address (or URL) is:a. a 32-bit binary number c. running out ofavailable valuesb. four groups of base-ten numbers d. all ofthe aboveANS: D26. DNS stands for:

a. Domain Name Server c. Domain NumberingSystemb. Domain Name System d. Domain NamingSystemANS: A27. A DNS:a. has become obsolete on the Internetb. translates words to numbersc. stores all domain addressesd. describes the Internet address-namingprocedure


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ANS: B28. An intranet connected to the Internet isoften protected by:a. a DNS c. a "firewall"b. a "brick wall" d. the use of "spoofing"protocolsANS: C29. OSI stands for:a. Open Systems Interconnection c. OpenSystems Internetb. Open Standard Interconnection d. none ofthe aboveANS: ACOMPLETION1. A ____________________-Area Network wouldextend typically across a city. ANS

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