Ranganathan Polytechnic College, CoimbatoreCOMMUNICATION ENGINEERING

QUESTION BANKPrepared by

A.Indhumathi, Lecturer/ECEUNIT -I

1. What are four terminal networks?Passive communication network shave two input terminalsand two output terminals.

2. Define balanced network.Balanced network is a network in which the correspondingseries impedance elements are identical and symmetricalwith respect to ground.

3. Define unbalanced network.4. Unbalanced network is a network in which the

corresponding series impedance are not identical &asymmetrical with respect to ground.

5. Define symmetrical network.A symmetrical network is a four terminal network in whichthe electrical properties are unaffected by interchanging theinput & output terminals.

6. Define asymmetrical network.An asymmetrical network is a four terminal network in whichthe electrical properties are affected by interchanging theinput & output terminals.

7. Define equalizers.

Equalizers are electrical networks designed to counteractthe attenuation or phase distortion occurring in any part ofthe circuit.

8. What are the types of equalizers? Amplitude or Attenuation equalizer Phase or Delay equalizers.

9. What is amplitude or attenuation equalizer?The network that counteracts the amplitude distortion iscalled amplitude or attenuation equalizer. Phase is notaffected.

10. What is phase or delay equalizer?The network that counteracts the phase distortion is calledphase or delay equalizer.

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What are the classifications of equalizers? Series equalizer, shunt equalizer, two terminal

equalizers & four terminal equalizers.

What are the applications of equalizers? It is used in PCM receiver Used in TV transmitter.

Define attenuator.An attenuator is a two port resistive network, used to reducethe signal level by a given amount. It can be the amount ofvoltage, power, current between its properly terminatedinput & output.

14. What are the types of attenuators?

Symmetrical attenuator & Asymmetrical attenuator.

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What are the applications of attenuators? Used for minimizing radiation Used in waveguides.

Define filter.A filter is a four terminal network. It allows passing a certainrange of frequencies & rejects other ranges.

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What are the types of filters? Low pass filters, high pass filters, Band pass filters, Band

elimination filters, band stop filters.Define LPF.

LPF: it passes all frequencies from zero up to cutofffrequency. It is termed as pass band or transmission band.

19. Define BPF.BPF: it passes frequency signals between two cutofffrequencies from f1 t of2. It attenuates all other frequencies.

20. Define HPF.HPF: it passes signals above the cutoff frequency &attenuates all the signals below the cutoff frequency.

21. Define antenna.An antenna is one or more electrical conductors of a specificlength that radiate radio waves generated by a transmitteror that collect radio waves at the receiver.

22. Define antenna polarization.The polarization of an antenna can be defined by the

direction of electric field radiated from it. In an antenna theelectric field & magnetic field are perpendicular to each

other & both are perpendicular to the direction ofpropagation.

23. Define directive gain.Directive gain is defined as the ratio of power density in aparticular direction at a given point by the antenna to thepower density that would be radiated by an isotropicantenna.

24. Define Directivity.Directivity is defined as the ratio of maximum radiationintensity of an antenna to the radiation intensity of anisotropic antenna radiating the same total power.

25. Define radiation pattern.Radiation pattern of an antenna is a graphical representationof the radiation of the antenna as a function of direction. It isexpressed as field per strength, E volts per meter.

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What are the classifications of radiation pattern? Radiation pattern classified into major lobes, minor

lobes, side lobes & back lobes.Define folded dipole.

The folded dipole is a single antenna, made up of twoelements. One element is continuous and other split at thecenter have been folded & joined together in parallel at theends.

28. Define antenna array.Antenna arrays are classified into broad side array, End firearray, Collinear array & Parasitic array

29. Define critical frequency.

Critical frequency for a given layer is the highest frequencyof the sky wave signal that will be returned back to earth byionosphere.

30. Define MUF.The maximum possible value of frequency for whichreflection takes place by the ionosphere for a given distanceof propagation is known as the maximum usable frequency.

31. Define skip distance.The skip distance represents the minimum distance from thetransmitter at which a sky wave of a given frequency will bereturned to earth by the ionosphere.

UNIT – II1. Define modulation.

Modulation is the process by which the characteristics of acarrier signal is varied in accordance with instantaneous value ofthe modulating signal.

2. What is electromagnetic spectrum?Electromagnetic waves are the signals, in which it’s electric

& magnetic fields vary at a specific rate. These waves propagatein free space without using wires. The entire range of frequencyis referred to as the electromagnetic spectrum.

3. What are ELF and VF?

ELF: Extremely Low frequencies range of 30 to 300 Hzfrequency. These include AC power line frequency & lowend of human hearing range.VF: Voice Frequencies range of 300 to 3000Hz. This is thenormal range of human speech.

4. What are VLF & LF?

VLF: Very Low Frequencies range of 3 KHz to 30 KHz.These include the higher end of the human hearing range. Itis used in some government & military communications.LF: Low Frequencies range of 30 KHz to 300 KHz. This isused in aeronautical & marine navigation.

5. What are MF & HF?MF: Medium Frequencies range of 300 KHz to 3000 KHz. Itis used in AM radio broadcasting.HF: Higher Frequencies range of 3 KHz to 30 MHz. it is

known as short waves. Used in two way communication.6. What are VHF & UHF?

VHF: Very High Frequencies range of 30 MHz to 3000 MHz.It is used in mobile radio, marine, aeronauticalcommunications & FM broadcasting.UHF: Ultra High Frequencies range of 300 MHz to 3000MHz. it is used in land mobile communications & cellulartelephones.

7. What are SHF & EHF?SHF: Super High Frequencies range of 3 GHz to 30GHz. It isused in microwave frequencies, satellite & radarcommunications.EHF: Extremely High Frequencies range of 30 GHz to3000GHz. It is used in satellite communication andspecialized radar.

8. What is an infrared wave?These are frequency range higher than 300GHz. It is not

referred to as radio waves. It is used in astronomy to detectstars, TV remote control, guidance of airplanes and missiles.

9. What is visible spectrum?Just above the infrared region is visible spectrum. It isreferred to as light. Light is widely used in various kinds ofcommunications.

10. What is relation between wavelength & frequency?

It is mathematically expressed as𝐕𝐞𝐥𝐨𝐜𝐢𝐭𝐲 𝐂𝐟

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What is the need for modulation?To transmit information over long distances.To reduce the height of the antenna.For wireless communication, modulation is necessary.What are the types of modulation?Amplitude modulationFrequency modulationPhase modulation

Define amplitude modulation.Amplitude modulation is the process in which the amplitudeof the carrier signal is varied in accordance with theinstantaneous value of the modulating voltage, keepingfrequency and phase angle constant.

14. Define frequency modulation.Frequency modulation is the process in which the frequencyof the carrier signal is varied in accordance with theinstantaneous value of the modulating voltage, keepingamplitude and phase angle constant.

Wavelength =𝐟𝐫𝐞𝐪𝐮𝐞𝐧𝐜𝐲 ; λ =

15. Define phase modulation.

Phase modulation is the process in which the phase of thecarrier signal is varied in accordance with the instantaneousvalue of the modulating signal, keeping amplitude constant.

16. Define modulation index and give expression for AM

modulation index.Modulation index: it is defined as the ratio modulatingvoltage to carrier voltage.

Ma =Em

Ec ; ma =Emax −Emin

Emax +Emin

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What are the types of AM? Double side band full carrier (DSBFC) Double side band Suppressed carrier (DSBSC) Single side band full carrier (SSBFC) Single side band Suppressed carrier (SSBSC) Vestigial Side Band signal (VSB)

What are the types of AM modulator? Linear modulator

Transistor modulator and Switching modulator Non – linear modulator

Square law modulator Product modulator Balanced modulator

Define SSB.To save bandwidth, it is sufficient to transmit only onesideband and rejects other sideband and carrier. Thistechnique is known as SSB system.

20. What are the advantages & disadvantages of

SSB?

Advantages: (1) it can transmit signals to long distances. (2)

Less noise (3) transmits good quality signals.Disadvantages: (1) High cost (2) transmitter & receiver is

complex (3) requires high performance.

21. What is VSB?Only a part of the lower (or upper) side band is filtered outbefore transmission is called vestigial side bandtransmission. In this system a part of lower side band issuppressed and the radiated signal consists of a full upperside band together with the carrier and a part of lower sideband signal.

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Give merits of AM VSB. Bandwidth is reduced. Power is reduced Low frequency component is not lost. VSB avoids the

phase distortion.Define demodulation.

The process of extracting modulating signal from themodulated signal is called detection or demodulation.

24. What are the types of diode detector?2 types: 1) Linear diode detector 2) Square Law detector.

25. What is linear diode detector?It is an amplitude demodulator; it recovers the originalmodulating signal from modulated carrier wave.

26. What are the classifications of transmitter based on

modulation? Amplitude Modulation transmitter Frequency Modulation transmitter Pulse Modulation transmitter

27. What is the classification of transmitter based onservice?

Radio broadcast transmitter Radio telegraph transmitter Radio telephone transmitter Television transmitter Radar transmitter navigation transmitter

28. What are the classifications of transmitter based on

frequency? Long wave transmitter &Medium wave transmitter Short wave transmitter VHF & UHF transmitter & Microwave transmitter

29. What are the classifications of transmitter based on

power level? Low level modulated transmitter High level modulated transmitter

30. What is the use of master oscillator?Master oscillator produces sub-harmonic of the carrierfrequency. The frequency generated should be stable. Itshould not change due to the variation of temperature,supply voltage and ageing of components.

31. What is isolating amplifier?

Master oscillator directly drives the harmonic generator; itmay draw input current from the master oscillator. Thisaction loads master oscillator. To avoid the loading effect ofmaster oscillator, buffer amplifier or isolating amplifier isplaced between the master oscillator and harmonicgenerator.

32. What is harmonic generator?Harmonic generators are class C tuned amplifiers which theRF voltage from master oscillator is distorted. The tunedcircuit of the amplifier selects the desired harmonicfrequency.

33. Differentiate between high level and low leveltransmitter.

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What are the functions of radio receiver?They separate a wanted radio signal from all other radiosignals & reject all the others.The separated RF signal is converted into IF signal.The IF signal is modulated to a usable level &demodulated to get the original signal.The modulating signal is amplified & fed to a speaker

S.No

.

High Level Modulation Low levelmodulation

1 Transmitter power is high Transmitter poweris low

2 Efficiency is high Efficiency is low

tohear the sound.

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What are the types of radio receiver? AM broadcast receiver & FM broadcast receiver Television receiver & Communication receiver Code receiver & Radar receiver Tuned receiver & Superhetrodyne receiver

What are the limitations of TRF receiver? Adjacent channel selectivity is poor Variation in bandwidth over tuning range High gain instability problem

What are the advantages of TRF receiver? High sensitivity Very simple to implement

What are the drawbacks of TRF receiver? Low stability Gain is not uniform Used only in single channel low frequency applications.

What is RF amplifier?It is a tuned amplifier. It amplifies the input RF signal. Itsoutput is given to mixer unit. This RF amplifier improves thesensitivity & selectivity of the receiver. It improves signal tonoise ratio.

40. What is IF?The input signal frequency fs , the local oscillator frequencyfo, the sum of these frequencies (fs+fo) and the differencefrequency of these two frequencies(fs-fo). Out of these, thedifference frequency alone is selected by the tuned circuitsin the output of the mixer. The difference frequency isintermediate frequency.

41. What are the advantages of Superhetrodynereceiver?

High selectivity High gain because IF amplifiers operates in low

frequency Frequency of IF signal is same, BW is same

42. What is image frequency?An image frequency is any frequency other than the selectedradio frequency carrier that is allowed to enter a receiver &mix with the local oscillator will produce a cross productfrequency that is equal to the intermediate frequency.

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What are the applications of AM? Radio broadcasting Transceiver communications Ship to shore & shore to ship communications

How to minimize sensitivity of image frequency? A filter that precedes the mixer A more complex mixer circuit that suppresses the

image. In most receivers this is accomplished by BPF in RF front

end.What is AGC? Give its types.

In radio receivers, the AGC system is used to keep theoutput signal as constant irrespective variations of its inputsignal strength. When a receiver does not have an AGCsystem, the output may be severely distorted. It is used tovary overall gain of radio receiver. Two types are SimpleAGC & Delayed AGC.

S.No.

Simple AGC Delayed AGC1 The output is not

stableThe output is more stable

2 Signal to noise ratio islow

Signal to noise is better

3 Threshold level cannotbe varied

Threshold level can bevaried

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Compare simple and delayed AGC.

What is the output of balanced modulator?It is an AM modulator. It generates double side bandsuppressed carrier signals. The purpose is to produce sum &difference frequencies, but to cancel or balance out thecarrier. The output of balanced modulator is the modulatedupper & lower sidebands.

48. Draw diode detector waveforms.

49. Draw an AM VSB signal.

50. Draw the amplitude waveforms & Draw thespectrum of AM.

51. Draw electromagnetic spectrum.

UNIT – III1. Define frequency modulation.

The frequency of carrier wave is varied in accordance withthe instantaneous amplitude variations of the modulatingsignal.

2. Give the maximum frequency deviation & expression for

FM.

Maximum frequency deviation, ∆f =

e = Ec sin (𝜔𝑐 t +𝑚𝑓 sin 𝜔𝑚 t )

K.Em

2π

3. What are the effects of noise in FM?The strong noise pulse affects the information signalcompletely.Noise is essentially amplitude variations.The frequency of FM signal may be minutely affected bynoise.

4. What are the advantages of FM over AM?FM receivers are free from disturbances.In FM, Noise is reduced by increasing deviation.The efficiency of FM system is high.Power required is lesser than AM.

5. What are the disadvantages of FM?A much wider channel is required in FM.FM circuit is more complex than AM.

The area of reception of FM is smaller than AM.6. Give applications of FM.

Latest broadcasting systems are switching over FM. Stereo sound transmission involves FM. Sound signal of TV transmission in FM.

7. Define FM detector. What are the types of FM detector?

FM detection or demodulation is the process in which theoriginal modulating signal is recovered from the frequencymodulated wave. The types are:

Slope detector Phase Shift discriminator or Foster seeley discriminator Ratio detector

8. What are the drawbacks of slope detector?It requires three tuned circuitsAlignment of the three tuned circuits is difficult.Output is affected by AM & so it requires AM limiters.

9. What are the advantages of indirect FM transmitter?

Frequency deviation is small. Does not require AFC system because crystal oscillator

is used.10. What is FM receiver?

FM receivers are also superhetrodyne receivers employingdouble frequency conversion to detect the original outputsignal from the modulated FM signal.

11. What are the applications of PCM?PCM is used in multichannel telephone communication & It isused in space communications.

12. What is AFC?

AFC circuit is generally used in all receivers to stabilize theintermediate frequency. It is used to sense any error in the IFsignal and to stabilize it.

13. What is phase modulation?In phase modulation, the basic function of modulator is toproduce a phase shift. It means time separation between twosine waves of the same frequency.

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What are the types of continuous wave modulation?

Amplitude modulation Angle modulation

Frequency modulation Phase modulation

Define pulse modulation.Pulse modulation is used to transmit analog information suchas continuous speech or data. The continuous waveforms aresampled at regular intervals. It is transmitted only at thesampling times together with synchronizing pulses. Thus theoriginal signals obtained from samples at the receiver side.

16. What are the types of pulse modulation? Analog pulse modulation

Pulse amplitude modulation

Pulse time modulation

Digital pulse modulation

Pulse code modulationDelta modulation

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What are the types of pulse time modulation? Pulse width modulation Pulse position modulation Pulse frequency modulation

Define PAM.In Pulse Amplitude Modulation, the signal is sampled atregular intervals. Each sample is made proportional to theamplitude of the signal at the instant of sampling. The pulsesare sent by either wire or cable.

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What are the types of PAM? Double Polarity PAM & Single Polarity.Define sampling theorem.

It makes the relation between original signal & samplingfrequency. Sampling theorem states that if the sampling ratein any pulse modulation system exceeds twice the maximumsignal frequency, the original signal can be reconstructed inthe receiver with minimum distortion.

21. Define PTM. What are the types of PTM?In PTM, the sampled pulses have constant amplitude. Butone of their timing characteristics (width, position,frequency) of the pulses is varied in accordance with theamplitude of the signal at the instant of sampling.

22. What are the advantages & disadvantages of PWM?

Advantages: No need to synchronize between the transmitter &

receiver.Disadvantage:

The transmitting power changes with respect to pulsewidth.

The transmitter must be powerful to handle maximum

width pulses.23. Define PPM.

The amplitude & width of the pulses are kept constant. Butthe position of each pulse with respect to the position of areference pulse is varied in accordance with the amplitude ofthe signal at the instant of sampling.

24. What are the advantages & disadvantages of PPM?

Advantages: It requires constant transmitter power.Disadvantages:synchronization.

It depends on transmitter-receiver

25. Define PCM.PCM is a digital process, sending a pulse train capable ofcontinuously varying one of the parameter; the PCMproduces a series of numbers or digits. In PCM, the totalamplitude range occupied by the signal is divided into anumber of standard levels. In this a signal is continuouslysampled, quantized, coded and sent.

26. Define quantizing.It is a process of mapping (dividing) an analog (modulating)signal into several equivalent discrete levels (range orsteps). It is the process of converting continuous input values

to discrete output values i.e. to a standard level is known asquantizing.

27. Define DPCM.

In DPCM, the difference in the amplitude of two successivesamples is transmitted rather than the actual sample. Fewerbits are required for DPCM. It works on the principle ofprediction. The value of the present sample is predicted fromthe past samples.

28. Define Delta modulation.Delta modulation uses a single bit PCM code to achievedigital transmission of analog signals. It transmits only onebit per sample. The present sample is compared with theprevious sample value and the indication, whether theamplitude is increased or decreased. If current sample issmaller than the previous sample, logic ‘0’ is transmitted. Ifcurrent sample is larger than the previous sample, logic ‘1’ istransmitted.

29. What are the advantages & disadvantages of DPCM?

Advantages: DPCM requires less bandwidth compared toPCM.

Its signal to noise ratio is better than DM.Disadvantages: More sensitive to noise and it is morecomplex

Requires high sampling frequency.

30. What are the advantages & disadvantages of DM?

Advantages:DM transmitter & receiver require very simple &inexpensive hardware.

Smaller signaling rate & No need of ADC in deltamodulation.

Disadvantages: Granular noise & transmission channel noise is

produced Severe slope overload distortion is produced.

31. Define sampling.The information signal is sampled with a train of narrowrectangular pulses. The sampling rate must be greater thantwice the highest frequency component of the information torecover the original signal with minimum distortion at thereceiver.

32. What is slope overload?The slope of the analog signal is greater than the deltamodulator can maintain is called slope overload. Theprobability of slope overhead is reduced by increasing theclock frequency or by increasing the magnitude of theminimum step size.

33. What is granular noise?When the original analog input signal has relatively constantamplitude, the reconstructed signal has variations that werenot present in the original signal. This is called granularnoise.

34. What is quantizing noise?The quantizing process actually changes the amplitude ofmodulating signal. The error caused due to the difference of

actual and nearest standard level introducesdistortion. This is known as quantizing noise.

some

S.NO

FM PM

1 Frequency of carrier wave isvaried in accordance withamplitude of modulatingsignal

Phase angle of carrier waveis varied in accordance withthe amplitude of the2 Maximum deviation occurs

atpeak positive & negativeamplitudes of modulatingvoltage

Maximum amount of leadingor lagging phase shift occursat the zero crossing level3 Crystal oscillator cannot be

usedCrystal oscillator can drivethe phase modulator

4 Not simple to implement Simple to implement

35. What is companding?It is the process of signal compression and expansion. It isused to overcome the problems of quantizing error andnoise. It improves the quality of the signal being transmitted.

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Compare FM and PM.

Draw noise representation of quantized signal.

Draw slope overload distortion.

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Draw granular noise waveform.

Draw the waveforms of PWM & PAMa) PWM b)PAM

41. Draw the FM spectrum waves.

42. Draw the phasor diagrams for foster seelydiscriminator.

43. Draw the FM spectrograms

UNIT – IV1. State Acoustic principle.

The study about the changes in the sound waves are said tobe acoustic. In acoustical system, the oscillations in soundpressure are picked up by some form of receiving electroacoustic transducer called microphones.

2. What is a microphone? Give its types.Microphones are used for converting sound signals intoelectrical (audio) signals. It is operated only in air. Twotypes: Pressure microphones & Pressure gradientmicrophones.

3. What is a pressure microphone? Give examples.In pressure microphones, the acoustic pressure acts onlyone side of the moving element & the resulting output isproportional to the pressure applied to the moving element.Example: carbon microphone, condenser microphonepiezoelectric microphone & moving coil microphone.

4. What is a pressure gradient microphone? Giveexamples.In pressure microphones, the acoustic pressure acts onlyone side of the moving element & the resulting output isproportional to the difference between the pressure actingon the two sides of the moving element. Example: Velocityribbon microphone.

5. What are the advantages & disadvantages of carbon

microphone?Advantages: Electrical output is high, low cost. It is

robust.

Disadvantages: Frequency response is poor, Hissing soundis produced.

6. What is the application of carbon microphone?It is widely used in telephone & radio communication.

7. What are the advantages & disadvantages of condenser

microphone?Advantages: low distortion, small in size, high signal tonoise ratio.Disadvantages: high internal impedance requires voltageranging from 200 to 400 volts.

8. What is the application of condenser microphone?It is used in acoustic research for standard calibrationpurpose & for high fidelity recording of sound.

9. What are the advantages & disadvantages ofpiezoelectric microphone?Advantages: high sensitivity, small size, low cost, frequencyresponse is goodDisadvantages: not suitable for hot climates as the crystallooses the piezoelectric properties.

10. What is the application of piezoelectric microphone?

It is used in public address system & for hearing aids.11. What are the advantages o f moving coil

microphones? Light weight Requires no external voltage

Internal impedance is low12. What is velocity ribbon microphone?

S.No.

Carbon Microphone Condenser Microphone1 Stiffness Controlled

SystemMass Controlled System

2 High Electrical Output Low Electrical Output3 Operation depends upon

variation of resistance ofcarbon button

Operation depends uponvariation of Capacitance ofa capacitor

S.No.

Piezo Electric Microphone

Condenser Microphone1 Stiffness Controlled

SystemMass Controlled System

It works on the principle of pressure gradient which impliesthat driving force acting on a moving element is proportionalto the difference in pressures acting on its two sides.

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What is the use of velocity ribbon microphone? It is used particularly in studio work.

What are the advantages & disadvantages of velocity

ribbon microphone?Advantage: Response curve is better than moving coil type.Disadvantage: It requires a built in type transformer, itsinternal impedance is low.

15. Define loudspeaker.Loudspeaker is an electro acoustic transducer, whichconverts electrical signal into sound signal.

16. Compare carbon microphone & condensermicrophone.

17. Compare condenser microphone & piezoelectricmicrophone.

2 High Electrical Output Low Electrical Output3 Operation depends upon

piezoelectric effectOperation depends uponvariation of Capacitance ofa capacitor18.

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What are the characteristics of loudspeaker? Efficiency approaches 100 percent Harmonic & inter modulations not present Input signal are produced faithfully

What are the types of loudspeaker? Dynamic cone type moving coil loud speaker. Horn Type moving coil loudspeaker Electrostatic type loudspeaker

What are the advantages & disadvantages ofdynamic cone type loudspeaker?Advantage: Compact in size, low cost & better response inaudio rangeDisadvantage:directivity

Low efficiency, low power, narrow

21. What is the application of dynamic cone typeloudspeaker?

It is used in all audio systems22.

23.

What are the advantages of horn type loudspeaker?

Sound effect of this speaker is very high & efficient Diaphragm is smaller in size Power handling capacity is more than 100 watts.

What is the use of electrostatic type loudspeaker?

S.No.

Cone Type LS Horn Type LS1 Sound effect of this

speaker is lessSound effect of this speaker isvery high & efficient

2 Diaphragm is larger insize

Diaphragm is smaller in size

3 Power handlingcapacity is from fewmilli watts to several100 watts

Power handling capacity is morethan 100 watts

S.No.

Woofer Tweeter1 It is used for the

reproduction of lowfrequencies

It is used for thereproduction of highfrequencies

2 It has large diameter cone

It has small diameter cone

This type of loud speakers used in high fidelityapplications.

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Compare cone type & horn type loudspeaker.

Give the speaker specifications. Diameter of the speaker frame Type & Wattage rating Voice coil impedance

Compare woofer & tweeter.

3 High wattage rating with Low wattage rating with lessmore cone depth cone depth

27. Define cross over network. To improve the quality & performance of amplifiers &

radio receivers, various control circuits are used. Thesecircuits are called cross over networks.

28. What is CD? Mention its layers.CD could store wide variety of data formats like text picture,video, software etc. It is 12cm or 5inch in diameter. It hasthree layers: Transparent substrate, thin metallic layer, outerlayer of protective acrylic.

29. What are the advantages of CD? High signal noise ratio Small size 7 low distortion Excellent Frequency range

30. What is MP3?MPEG-1 Audio Layer 3 commonly referred to as MP3. It is adigital encoding format using a form of lossy datacompression. MPEG stands for Moving Picture ExpertsGroup. It is for compressing moving picture. It is an audiospecific format.

31. What is DVD?DVD could store wide variety of data formats like textpicture, audio, video, software etc. It needs manufacturingprecision because of very fine encoding & extremely smalltrack thickness.

32. What are the characteristics of Hi-Fi systemprinciples?

Signal to noise ratio should be finite No frequency distortion No non linear distortion No spatial distortion

33. Expand DTS.Digital Track Sound

34. What is Hi-Fi system?When the sound reproduced with a degree of similarity tothe original or live sound, it can be said to be of high fidelityor simply Hi-Fi.

35. Define stereophonic system.A stereophonic system is a two channel system of soundrecording & reproduction, which gives the feeling of depth& direction to the reproduced sound.

36. What is bit rate?The bit rate is used to specify how many kilobits the file mayuse per second of audio as in when ripping a CD to MP3format.

37. What is surround sound system?Multichannel audio technique is used for enriching thequality of sound reproduction of a recorded source. It is for3D sphere of human hearing achieved with audio channels.

38. State the frequency bands of Dolby A system. Band 1 – below 80Hz Band 2 – 80Hz to 2999Hz Band 3 – 3000Hz and above

Band 4 – 9000Hz and above

UNIT-V1. What is TV?

TELEVISION means to see from distance. Its aim is to extendthe sense of sight beyond its normal limit along with thesound and scene being televised.

2. What is the use of camera tube?The camera tube converts light input to corresponding electrical

variations for the video signal.3. What is scanning?

Scanning is a process, in which it converts the charge imageproduced inside the TV camera Tube into a variableelectrical signal.

4. What is horizontal scanning? Give its frequency range.

The deflection of electron beam across the scene with acontinuous uniform motion for the trace from left to right.Frequency range is

5. What is vertical scanning? Give its frequency range.The saw tooth current applied to the vertical deflection coilsmoves the electron beam from top to bottom of raster at auniform speed, while the electron beam is being deflectedhorizontally.

6. What is flicker?

The scanning rate of 25 frames per second in televisionpicture is not rapid enough to allow the brightness of one

picture of frame to blend smoothly into the next. Thisalternative bright & dark in a picture is known as flicker.

7. What is interlaced scanning?The total number of lines divided into two fields called odd &even field. Each field is scanned alternatively known asinterlaced scanning.

8. What is the purpose of blanking pulse?The purpose of blanking pulses is to make invisible theretraces required in scanning.

9. What is horizontal & vertical blanking pulse? Horizontal blanking pulses are used to blank out the

horizontal retrace from right to left for each line. Vertical blanking pulses are used to blank out the

vertical retrace from bottom to top for each field.10. What is synchronizing pulses?

The synchronizing pulses are transmitted as part of completepicture signal for the receiver, but they occur during theblanking time when no picture information is transmitted.

11. What is horizontal & vertical synchronizing pulses?

Horizontal synchronization at the end of each linedetermines the start of horizontal retrace.

Vertical synchronization at the end of each fielddetermines the start of vertical retrace.

12. Define aspect ratio.The width to height ratio of the picture frame is called theaspect ratio.

13. What is the average brightness?

Average brightness means, the average value of brightnessvariation of horizontal lines in one frame.

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What is pedestal height & DC level? The distance between average brightness & blanking

level is called pedestal height. The distance between zero level & the average

brightness is called DC level.What are the TV systems used in broadcasting?

FCC ( Federal Communication Commission) NTSC ( National Television Committee) CCIR ( International Television Consultativev

Committee) PAL ( Phase Alteration with Line) SECAM ( Sequential Couleures A Memory)

16. What is video processing unit?The video signal input of 1 Vpp is processed in a stabilizingamplifier & sync regenerator to minimize the effects of hum&noise, sync compression & other distortions, to correct it tothe standard forms.

17. What is audio processing unit?The audio signal is given a pre-emphasis by a high passnetwork with the time constant of 50us. The signal isamplified to make the signal at the standard level.

18. What is diplexer?It combines both the outputs of visual & aural transmitters. Itmaintains sufficient isolation between the visual & auralinputs.

19. What is sound trap circuit?

The video amplifier usually has a trap circuit, tuned to theinter carrier sound frequency of 5.5MHz to keep the signalout of picture signal. It removes the sound signal from thecarrier signal.

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Classify FM sound detectors. Foster seely discriminator Slope detector & Ratio detector Quadtrature detector Differential detector Phase locked loop detector

What is the use of color camera?The colour camera is used to develop signal voltagesproportional to the intensity of each primary color light.

22. What is the luminance signal?The luminance signal processing network recovers theluminance signal from the composite video signal.

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What are the features of LED display? Lower power consumption More balanced color saturation Thinner & better contrast Brighter display & more reliable

What are the advantages of plasma displays? Wider viewing angles & Less visible motion blur Fast response time & Capable of producing superior

contrast ratio.What are the disadvantages of plasma displays?

Consume more power

Does not work at high altitudes More expensive plasma compatible sensor must be

used.26. What is handycam?

Handycam is small model of camcorder, handle with singlehand. It is the combination of camera cum recorder.

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What are the features of handycam? Longer recording Offer 16 bit sound with higher resolution Easy to edit & archive.

What is CCTV?CCTV is used in large number of applications likeeducation, industry, machine, traffic control, business & soon.

29. What is cable TV?The cable television system is used for distributing highquality TV signals to a very large number of users. Thissystem feed increased TV programs to subscribers who paya fee for this service

30. What is burst blanking circuit?The circuit prevents the signal flow to the chrominance bandpass amplifier during color burst intervals

31. What is the use of chrominance band pass amplifier?

The chrominance band pass amplifier selects thechrominance signal & rejects other unwanted components ofthe signal.

32. What is the use of burst amplifier?

The burst gate amplifier separates the color burst signalfrom the chrominance signal & amplifies it to the requiredlevel. The frequency of this signal is 4.43MHz.