commuication qps

8/6/2019 commuication qps

1/13

InstrumentationFrom Wikipedia, the free encyclopediaJump to: navigation,searchFor other uses, seeInstrumentation (disambiguation).

This article may requirecleanup to meet Wikipedia'squality standards. (Considerusing more specific clean up instructions.) Please improve this articleif you can. Thetalk page may contain suggestions. (October 2010)

A control post of a steam turbine.

Pneumatic PID controller.

Instrumentation is defined as the art and science of measurement and control.[1]
http://en.wikipedia.org/wiki/Instrumentation_(disambiguation)http://en.wikipedia.org/wiki/Wikipedia:Cleanuphttp://en.wikipedia.org/wiki/Wikipedia:Cleanuphttp://en.wikipedia.org/wiki/Wikipedia:Manual_of_Stylehttp://en.wikipedia.org/wiki/Wikipedia:Manual_of_Stylehttp://en.wikipedia.org/wiki/Wikipedia:Template_messages/Cleanuphttp://en.wikipedia.org/w/index.php?title=Instrumentation&action=edithttp://en.wikipedia.org/w/index.php?title=Instrumentation&action=edithttp://en.wikipedia.org/wiki/Talk:Instrumentationhttp://en.wikipedia.org/wiki/File:Pneumatische_regelaar.jpghttp://en.wikipedia.org/wiki/File:Pneumatische_regelaar.jpghttp://en.wikipedia.org/wiki/File:Steuerstand01.jpghttp://en.wikipedia.org/wiki/File:Steuerstand01.jpghttp://en.wikipedia.org/wiki/Instrumentation_(disambiguation)http://en.wikipedia.org/wiki/Wikipedia:Cleanuphttp://en.wikipedia.org/wiki/Wikipedia:Manual_of_Stylehttp://en.wikipedia.org/wiki/Wikipedia:Template_messages/Cleanuphttp://en.wikipedia.org/w/index.php?title=Instrumentation&action=edithttp://en.wikipedia.org/wiki/Talk:Instrumentation


2/13


3/13

50ma, 0.25-1.25Volts, 0-10Volts, 1-5volts, and 4-20ma, causing only confusion until the 4-20mawas universally used as a standard electronic instrument signal for transmitters and valves.[unreliablesource?] The transformation of instrumentation from mechanical pneumatic transmitters, controllers,and valves to electronic instruments reduced maintenance costs as electronic instruments weremore dependable than mechanical instruments. This also increased efficiency and production dueto their increase in accuracy.

The next evolution of instrumentation came with the production of Distributed Control Systems(DCS). The pneumatic and electronic control rooms allowed control from a centralized room,DCS systems allowed control from more than one room or control stations. These stations couldbe next to each other or miles away. Now a process operator could sit in front of a screen and

monitor thousands of points throughout a large unit or complex.[vague]

[edit] MeasurementInstrumentation is used to measure many parameters (physical values). These parametersinclude:

Pressure, eitherdifferentialorstatic

Flow

Temperature

Levels of liquidsetc.

Density

Viscosity

Other mechanicalproperties ofmaterials

Properties of

ionising radiation Frequency

Current

Voltage

Inductance

Capacitance

Resistivity

Chemicalcomposition

Chemicalproperties

Properties

of light Vibration

Weight

[edit] Control

Control valve.

In addition to measuring field parameters, instrumentation is also responsible for providing theability to modify some field parameters.

[edit] Instrumentation engineering
http://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Vaguenesshttp://en.wikipedia.org/wiki/Wikipedia:Vaguenesshttp://en.wikipedia.org/wiki/Wikipedia:Vaguenesshttp://en.wikipedia.org/w/index.php?title=Instrumentation&action=edit&section=2http://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/w/index.php?title=Differential_pressure&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Differential_pressure&action=edit&redlink=1http://en.wikipedia.org/wiki/Static_pressurehttp://en.wikipedia.org/wiki/Rate_of_fluid_flowhttp://en.wikipedia.org/wiki/Temperature_measurementhttp://en.wikipedia.org/wiki/Level_Measurementhttp://en.wikipedia.org/wiki/Densityhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Current_(electricity)http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Resistivityhttp://en.wikipedia.org/wiki/Resistivityhttp://en.wikipedia.org/w/index.php?title=Instrumentation&action=edit&section=3http://en.wikipedia.org/w/index.php?title=Instrumentation&action=edit&section=4http://en.wikipedia.org/wiki/File:Pl_control_valve.jpghttp://en.wikipedia.org/wiki/File:Pl_control_valve.jpghttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Vaguenesshttp://en.wikipedia.org/w/index.php?title=Instrumentation&action=edit&section=2http://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/w/index.php?title=Differential_pressure&action=edit&redlink=1http://en.wikipedia.org/wiki/Static_pressurehttp://en.wikipedia.org/wiki/Rate_of_fluid_flowhttp://en.wikipedia.org/wiki/Temperature_measurementhttp://en.wikipedia.org/wiki/Level_Measurementhttp://en.wikipedia.org/wiki/Densityhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Current_(electricity)http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Resistivityhttp://en.wikipedia.org/wiki/Resistivityhttp://en.wikipedia.org/w/index.php?title=Instrumentation&action=edit&section=3http://en.wikipedia.org/w/index.php?title=Instrumentation&action=edit&section=4


4/13

Instrumentation engineering is the engineering specialization focused on the principle andoperation of measuring instruments that are used in design and configuration of automatedsystems in electrical, pneumatic domains etc. They typically work for industries with automatedprocesses, such as chemicalormanufacturingplants, with the goal of improving systemproductivity, reliability, safety, optimization, and stability. To control the parameters in a processor in a particular system, devices such as microprocessors, microcontrollers or PLCs are used,but their ultimate aim is to control the parameters of a system.

[edit] Instrumentation technologists and mechanicsInstrumentation technologists, technicians and mechanics specialize in troubleshooting and

repairing and maintenance of instruments and instrumentation systems. This trade is sointertwined with electricians, pipefitters, power engineers, and engineering companies, that onecan find him/herself in extremely diverse working situations

Electronics interview questions on Communication SystemMonday, March 16, 2009, 11:40:26 AM | [email protected] (UGY)

Sample interview questions for ECE branch: (Communication Systems)

1. Expand ECE.

Electronics & Communication Engineering.

2. What is Electronic?

The study and use of electrical devices that operate by controlling the flow of electrons or otherelectrically charged particles.

3. What is communication?

Communication means transferring a signal from the transmitter which passes through a mediumthen the output is obtained at the receiver. (or)communication says as transferring of messagefrom one place to another place called communication.

4. Different types of communications? Explain.

Analog and digital communication.

As a technology, analog is the process of taking an audio or video signal (the human voice) andtranslating it into electronic pulses. Digital on the other hand is breaking the signal into a binaryformat where the audio or video data is represented by a series of "1"s and "0"s.

Digital signals are immune to noise, quality of transmission and reception is good, componentsused in digital communication can be produced with high precision and power consumption isalso very less when compared with analog signals.

5. What is engineering?

The application of science to the needs of humanity and a profession in which a knowledge ofthe mathematical and natural sciences gained by study, experience, and practice is applied with
http://en.wikipedia.org/wiki/Automatedhttp://en.wikipedia.org/wiki/Chemical_planthttp://en.wikipedia.org/wiki/Chemical_planthttp://en.wikipedia.org/wiki/Manufacturinghttp://en.wikipedia.org/wiki/Manufacturinghttp://en.wikipedia.org/wiki/Productivityhttp://en.wikipedia.org/w/index.php?title=Instrumentation&action=edit&section=5http://digin4placementpapers.blogspot.com/2008/07/electronics-interview-questions-on.htmlhttp://en.wikipedia.org/wiki/Automatedhttp://en.wikipedia.org/wiki/Chemical_planthttp://en.wikipedia.org/wiki/Manufacturinghttp://en.wikipedia.org/wiki/Productivityhttp://en.wikipedia.org/w/index.php?title=Instrumentation&action=edit&section=5http://digin4placementpapers.blogspot.com/2008/07/electronics-interview-questions-on.html


5/13

judgment to develop ways to use economically the materials and forces of nature for the benefitof mankind.

6. Difference between electronic and electrical.

Electronics work on DC and with a voltage range of -48vDC to +48vDC. If the electronic deviceis plugged into a standard wall outlet, there will be a transformer inside which will convert theAC voltage you are supplying to the required DC voltage needed by the device. Examples:Computer, radio, T.V, etc...

Electric devices use line voltage (120vAC, 240vAC, etc...). Electric devices can also be designedto operate on DC sources, but will be at DC voltages above 48v. Examples: are incandescentlights, heaters, fridge, stove, etc...

7. What is sampling?

The process of obtaining a set of samples from a continuous function of time x(t) is referred to assampling.

8. State sampling theorem.

It states that, while taking the samples of a continuous signal, it has to be taken care that thesampling rate is equal to or greater than twice the cut off frequency and the minimum samplingrate is known as the Nyquist rate.

9. What is cut-off frequency?

The frequency at which the response is -3dB with respect to the maximum response.

10. What is pass band?

Passband is the range of frequencies or wavelengths that can pass through a filter without beingattenuated.

11. What is stop band?

A stopband is a band of frequencies, between specified limits, in which a circuit, such as a filteror telephone circuit, does not let signals through, or the attenuation is above the requiredstopband attenuation level.

12. Difference between mobile and a cell phone.

There is no difference, just language use, which differs from country to country, so in Britain it is

called a mobile, and in USA and South Africa and other places a cell phone.Even in Europe the name differs. The Germans call it a "handy", which in English hascompletely another meaning as an adjective, meaning useful.In Italy it is called a telofonino or "little phone".This difference in British and American English is also evident in many other things we useevery day, like lifts and elevators, nappies and diapers, pickups and trucks. The list goes on andon, any student of English has to decide which he or she will use, as the default setting.

13. Explain RF?

Radio frequency (RF) is a frequency or rate of oscillation within the range of about 3 Hz to 300GHz. This range corresponds to frequency of alternating current electrical signals used toproduce and detect radio waves. Since most of this range is beyond the vibration rate that mostmechanical systems can respond to, RF usually refers to oscillations in electrical circuits orelectromagnetic radiation.

14. What is modulation? And where it is utilized?

Modulation is the process of varying some characteristic of a periodic wave with an externalsignals.

Radio communication superimposes this information bearing signal onto a carrier signal.


6/13

These high frequency carrier signals can be transmitted over the air easily and are capable oftravelling long distances.

The characteristics (amplitude, frequency, or phase) of the carrier signal are varied in accordancewith the information bearing signal.

Modulation is utilized to send an information bearing signal over long distances.

15. What is demodulation?

Demodulation is the act of removing the modulation from an analog signal to get the original baseband signal back. Demodulating is necessary because the receiver system receives amodulated signal with specific characteristics and it needs to turn it to base-band.

16. Name the modulation techniques.

For Analog modulation--AM, SSB, FM, PM and SM

Digital modulation--OOK, FSK, ASK, Psk, QAM, MSK, CPM, PPM, TCM, OFDM

17. Explain AM and FM.

AM-Amplitude modulation is a type ofmodulation where the amplitude of the carrier signal isvaried in accordance with the information bearing signal.

FM-Frequency modulation is a type ofmodulationwhere the frequency of the carrier signal isvaried in accordance with the information bearing signal.

18. Where do we use AM and FM?

AM is used for video signals for example TV. Ranges from 535 to 1705 kHz.

FM is used for audio signals for example Radio. Ranges from 88 to 108 MHz.

19. How does a mobile work?

When you talk into a mobile telephone it converts the sound of your voice to radiofrequencyenergy (radio waves). The radio waves are transmitted through the air to a nearby base station.The base station then sends the call through the telephone network until it reaches the person youare calling. When you receive a call on your mobile phone the message travels through thetelephone network until it reaches a base station near to you. The base station sends out radiowaves, which are detected by your telephone and converted back to speech. Depending on theequipment and the operator, the frequency that each operator utilises is 900MHz, 1800MHz or2100MHz.

The mobile phone network operates on the basis of a series of cells. Each cell requires a radiobase station to enable it to function.

There are three types of base station and each has a particular purpose:

1. The Macrocell is the largest type and provides the main coverage for mobile phonenetworks.

2. The Microcell is used to improve capacity in areas where demand to make calls is high,such as shopping centres.

3. The Picocell only has a range of a few hundred metres and may be used to boost weaksignals within large buildings.
http://www.tech-faq.com/modulation.shtmlhttp://www.tech-faq.com/modulation.shtmlhttp://www.tech-faq.com/modulation.shtmlhttp://www.tech-faq.com/modulation.shtmlhttp://www.tech-faq.com/modulation.shtmlhttp://www.tech-faq.com/modulation.shtml


7/13

Each base station can only cope with a certain number of calls at any one time. So if demandexceeds the capacity of a base station an additional base station is needed.

20. What is a base station?

Base station is a radio receiver/transmitter that serves as the hub of the local wireless network,and may also be the gateway between a wired network and the wireless network.

21. How many satellites are required to cover the earth?

3 satellites are required to cover the entire earth, which is placed at 120 degree to each other. Thelife span of the satellite is about 15 years.

22. What is a repeater?

A repeater is an electronic device that receives a signal and retransmits it at a higher level and/orhigher power, or onto the other side of an obstruction, so that the signal can cover longerdistances without degradation.

23. What is attenuation?

Attenuation is the reduction in amplitude and intensity of a signal. Signals may attenuateexponentially by transmission through a medium, or by increments calculated in electroniccircuitry or set by variable controls. Attenuation is an important property in telecommunicationsand ultrasound applications because of its importance in determining signal strength as afunction of distance. Attenuation is usually measured in units of decibels per unit length ofmedium (dB/cm, dB/km, etc) and is represented by the attenuation coefficient of the medium in

question.24. What is multiplexing?

Multiplexing (known as muxing) is a term used to refer to a process where multiple analogmessage signals or digital data streams are combined into one signal over a shared medium. Theaim is to share an expensive resource. For example, in telecommunications, several phone callsmay be transferred using one wire.

25. What is CDMA, TDMA, FDMA?

Code division multiple access (CDMA) is a channel access method utilized by various radiocommunication technologies. CDMA employs spread-spectrum technology and a special codingscheme (where each transmitter is assigned a code) to allow multiple users to be multiplexed

over the same physical channel. By contrast, time division multiple access (TDMA) dividesaccess by time, while frequency-division multiple access (FDMA) divides it by frequency.

An analogy to the problem of multiple access is a room (channel) in which people wish tocommunicate with each other. To avoid confusion, people could take turns speaking (timedivision), speak at different pitches (frequency division), or speak in different directions (spatialdivision). In CDMA, they would speak different languages. People speaking the same languagecan understand each other, but not other people. Similarly, in radio CDMA, each group of usersis given a shared code. Many codes occupy the same channel, but only users associated with aparticular code can understand each other.

26. Difference between CDMA and GSM.

These are the two different means of mobile communication being presently used worldwide.The basic difference lies in the Multiplexing method used in the aerial communication i.e. fromMobile Tower to your mobile and vice versa.

CDMA uses Code Division Multiple Access as the name itself indicates, for example you are ina hall occupied with number of people speaking different language. You will find that the onelanguage you know will be heard by you and the others will be treated like noise. In the samemanner each CDMA mobile communication takes place with a "code" communicating betweenthem and the other end if one is knowing that code then only it can listen to the data being
http://en.wikipedia.org/wiki/Processhttp://en.wikipedia.org/wiki/Channel_access_methodhttp://en.wikipedia.org/wiki/Channel_access_methodhttp://en.wikipedia.org/wiki/Spread-spectrumhttp://en.wikipedia.org/wiki/Time_division_multiple_accesshttp://en.wikipedia.org/wiki/Timehttp://en.wikipedia.org/wiki/Frequency-division_multiple_accesshttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Processhttp://en.wikipedia.org/wiki/Channel_access_methodhttp://en.wikipedia.org/wiki/Spread-spectrumhttp://en.wikipedia.org/wiki/Time_division_multiple_accesshttp://en.wikipedia.org/wiki/Timehttp://en.wikipedia.org/wiki/Frequency-division_multiple_accesshttp://en.wikipedia.org/wiki/Frequency


8/13

transmitted i.e. the communication is in the coded form.

On the other hand GSM(Global System for Mobile Communications) uses narrowbandTDMA,which allows eight simultaneous calls on the same radio frequency. TDMA works by dividing aradio frequency into time slots and then allocating slots to multiple calls. In this way, a singlefrequency can support multiple, simultaneous data channels.

27. What is an Amplifier?

An electronic device or electrical circuit that is used to boost (amplify) the power, voltage orcurrent of an applied signal.

28. What is Barkhausen criteria?

Barkhausen criteria, without which you will not know which conditions, are to be satisfied foroscillations.

Oscillations will not be sustained if, at the oscillator frequency, the magnitude of the product ofthe transfer gain of the amplifier and the magnitude of the feedback factor of the feedbacknetwork ( the magnitude of the loop gain ) are less than unity.

The condition of unity loop gain -A = 1 is called the Barkhausen criterion. This conditionimplies that | A|= 1and that the phase of - A is zero.

29. Explain Full duplex and half duplex.

Full duplex refers to the transmission ofdata in two directions simultaneously. For example, a

telephone is a full-duplex device because both parties can talk at once. In contrast, a walkie-talkie is a half-duplexdevice because only one party can transmit at a time.

Most modems have a switch that lets you choose between full-duplex and half-duplex modes.The choice depends on whichcommunications program you are running.

In full-duplex mode, data you transmit does not appear on yourscreen until it has been receivedand sent back by the other party. This enables you to validate that the data has been accuratelytransmitted. If your display screen shows two of each character, it probably means that yourmodem is set to half-duplex mode when it should be in full-duplex mode.

30. What is a feedback? And explain different types of feedback.

Feedback is a processwhereby some proportion of the output signal of a system is passed (fed

back) to the input. This is often used to control the dynamic behaviour of the system.Types of feedback:

Negative feedback: This tends to reduce output (but in amplifiers, stabilizes and linearizesoperation). Negative feedback feeds part of a system's output, inverted, into the system's input;generally with the result that fluctuations are attenuated.

Positive feedback: This tends to increase output. Positive feedback, sometimes referred to as"cumulative causation", is afeedback loop system in which the system responds to perturbation(A perturbation means a system, is an alteration of function, induced by external or internalmechanisms) in the same direction as the perturbation. In contrast, a system that responds to theperturbation in the opposite direction is called a negative feedbacksystem.

Bipolar feedback: which can either increase or decrease output.31. Advantages of negative feedback over positive feedback.

Much attention has been given by researchers to negative feedback processes, because negativefeedback processes lead systems towards equilibrium states. Positive feedback reinforces a giventendency of a system and can lead a system away from equilibrium states, possibly causing quiteunexpected results.

32. Example for negative feedback and positive feedback.
http://www.webopedia.com/TERM/G/TDMA.htmlhttp://www.webopedia.com/TERM/G/TDMA.htmlhttp://www.webopedia.com/TERM/f/data.htmlhttp://www.webopedia.com/TERM/f/device.htmlhttp://www.webopedia.com/TERM/f/half_duplex.htmlhttp://www.webopedia.com/TERM/f/half_duplex.htmlhttp://www.webopedia.com/TERM/f/modem.htmlhttp://www.webopedia.com/TERM/f/switch.htmlhttp://www.webopedia.com/TERM/f/mode.htmlhttp://www.webopedia.com/TERM/f/communications_software.htmlhttp://www.webopedia.com/TERM/f/communications_software.htmlhttp://www.webopedia.com/TERM/f/run.htmlhttp://www.webopedia.com/TERM/f/display_screen.htmlhttp://www.webopedia.com/TERM/f/character.htmlhttp://www.webopedia.com/TERM/f/character.htmlhttp://en.wikipedia.org/wiki/Processhttp://en.wikipedia.org/wiki/Processhttp://en.wikipedia.org/wiki/Inputhttp://en.wikipedia.org/wiki/Inputhttp://en.wikipedia.org/wiki/Systemhttp://en.wikipedia.org/wiki/Feedbackhttp://en.wikipedia.org/wiki/Systemhttp://en.wikipedia.org/wiki/Systemhttp://en.wikipedia.org/wiki/Positive_feedbackhttp://en.wikipedia.org/wiki/Feedbackhttp://en.wikipedia.org/wiki/Feedbackhttp://en.wikipedia.org/wiki/Perturbation_of_biological_system_(Biology)http://en.wikipedia.org/wiki/Negative_feedbackhttp://www.webopedia.com/TERM/G/TDMA.htmlhttp://www.webopedia.com/TERM/f/data.htmlhttp://www.webopedia.com/TERM/f/device.htmlhttp://www.webopedia.com/TERM/f/half_duplex.htmlhttp://www.webopedia.com/TERM/f/modem.htmlhttp://www.webopedia.com/TERM/f/switch.htmlhttp://www.webopedia.com/TERM/f/mode.htmlhttp://www.webopedia.com/TERM/f/communications_software.htmlhttp://www.webopedia.com/TERM/f/run.htmlhttp://www.webopedia.com/TERM/f/display_screen.htmlhttp://www.webopedia.com/TERM/f/character.htmlhttp://en.wikipedia.org/wiki/Processhttp://en.wikipedia.org/wiki/Inputhttp://en.wikipedia.org/wiki/Systemhttp://en.wikipedia.org/wiki/Feedbackhttp://en.wikipedia.org/wiki/Systemhttp://en.wikipedia.org/wiki/Positive_feedbackhttp://en.wikipedia.org/wiki/Feedbackhttp://en.wikipedia.org/wiki/Perturbation_of_biological_system_(Biology)http://en.wikipedia.org/wiki/Negative_feedback


9/13

Example for ve feedback is ---Amplifiers

And for +ve feedback is Oscillators

33. What is Oscillator?

An oscillator is a circuit that creates a waveform output from a direct current input. The twomain types of oscillator are harmonic and relaxation. The harmonic oscillators have smoothcurved waveforms, while relaxation oscillators have waveforms with sharp changes.

34. What is a transducer and transponder?

A transducer is a device, usually electrical, electronic, electro-mechanical, electromagnetic,photonic, orphotovoltaic that converts one type ofenergy or physical attribute to another for

various purposes including measurement or information transfer.In telecommunication, the term transponder (short-forTransmitter-responderand sometimesabbreviated to XPDR, XPNDR, TPDR or TP) has the following meanings:

An automaticdevicethat receives,amplifies, andretransmits a signal on a differentfrequency (see alsobroadcast translator).

An automatic device that transmits a predetermined message in response to a predefinedreceived signal.

A receiver-transmitterthat will generate a reply signal upon properelectronicinterrogation.

A communications satellites channels are called transponders, because each is a separatetransceiverorrepeater.

35. What is an Integrated Circuit?

An integrated circuit (IC), also called a microchip, is an electronic circuit etched onto a siliconchip. Their main advantages are low cost, low power, high performance, and very small size.

36. What is crosstalk?

Crosstalk is a form of interference caused by signals in nearby conductors. The most commonexample is hearing an unwanted conversation on the telephone. Crosstalk can also occur inradios, televisions, networking equipment, and even electric guitars.

37. What is a rectifier?

A rectifier changes alternating current into direct current. This process is called rectification. Thethree main types of rectifier are the half-wave, full-wave, and bridge. A rectifier is the oppositeof an inverter, which changes direct current into alternating current.

HWR- The simplest type is the half-wave rectifier, which can be made with just one diode.When the voltage of the alternating current is positive, the diode becomes forward-biased andcurrent flows through it. When the voltage is negative, the diode is reverse-biased and the currentstops. The result is a clipped copy of the alternating current waveform with only positive voltage,and an average voltage that is one third of the peak input voltage. This pulsating direct current isadequate for some components, but others require a more steady current. This requires a full-wave rectifier that can convert both parts of the cycle to positive voltage.

FWR- The full-wave rectifier is essentially two half-wave rectifiers, and can be made with twodiodes and an earthed centre tap on the transformer. The positive voltage half of the cycle flowsthrough one diode, and the negative half flows through the other. The centre tap allows thecircuit to be completed because current cannot flow through the other diode. The result is still apulsating direct current but with just over half the input peak voltage, and double the frequency.

38. What is resistor?
http://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Electro-mechanicalhttp://en.wikipedia.org/wiki/Electromagnetichttp://en.wikipedia.org/wiki/Electromagnetichttp://en.wikipedia.org/wiki/Photonichttp://en.wikipedia.org/wiki/Photovoltaichttp://en.wikipedia.org/wiki/Photovoltaichttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Telecommunicationhttp://en.wikipedia.org/wiki/Automatichttp://en.wikipedia.org/wiki/Information_appliancehttp://en.wikipedia.org/wiki/Information_appliancehttp://en.wikipedia.org/wiki/Receiver_(radio)http://en.wikipedia.org/wiki/Amplifierhttp://en.wikipedia.org/wiki/Amplifierhttp://en.wikipedia.org/wiki/Amplifierhttp://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Signalling_(telecommunication)http://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Broadcast_translatorhttp://en.wikipedia.org/wiki/Messagehttp://en.wikipedia.org/wiki/Responsehttp://en.wikipedia.org/wiki/Transceiverhttp://en.wikipedia.org/wiki/Transceiverhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Interrogationhttp://en.wikipedia.org/wiki/Communications_satellitehttp://en.wikipedia.org/wiki/Channel_(communications)http://en.wikipedia.org/wiki/Transceiverhttp://en.wikipedia.org/wiki/Repeaterhttp://en.wikipedia.org/wiki/Repeaterhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Electro-mechanicalhttp://en.wikipedia.org/wiki/Electromagnetichttp://en.wikipedia.org/wiki/Photonichttp://en.wikipedia.org/wiki/Photovoltaichttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Telecommunicationhttp://en.wikipedia.org/wiki/Automatichttp://en.wikipedia.org/wiki/Information_appliancehttp://en.wikipedia.org/wiki/Receiver_(radio)http://en.wikipedia.org/wiki/Amplifierhttp://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Signalling_(telecommunication)http://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Broadcast_translatorhttp://en.wikipedia.org/wiki/Messagehttp://en.wikipedia.org/wiki/Responsehttp://en.wikipedia.org/wiki/Transceiverhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Interrogationhttp://en.wikipedia.org/wiki/Communications_satellitehttp://en.wikipedia.org/wiki/Channel_(communications)http://en.wikipedia.org/wiki/Transceiverhttp://en.wikipedia.org/wiki/Repeater


10/13

A resistor is a two-terminal electronic component that opposes an electric current by producing avoltage drop between its terminals in proportion to the current, that is, in accordance with Ohm'slaw: V=IR.

39. What is capacitor?

A capacitor is an electrical/electronic device that can storeenergyin the electric field between apair ofconductors(called "plates"). The process of storing energy in the capacitor is known as"charging", and involves electric charges of equal magnitude, but opposite polarity, building upon each plate.

Capacitors are often used in electricandelectronic circuits as energy-storage devices. They canalso be used to differentiate between high-frequency and low-frequency signals. This propertymakes them useful in electronic filters.

Capacitors are occasionally referred to as condensers. This term is considered archaic in English,but most other languages use acognate ofcondenserto refer to a capacitor.

40. What is inductor?

An inductor is a passive electrical device employed in electrical circuits for its property ofinductance. An inductor can take many forms.

41. What is conductor?

A substance, body, or device that readily conducts heat, electricity, sound, etc. Copper is a goodconductor of electricity.

42. What is a semi conductor?

A semiconductor is a solid material that has electrical conductivity in between that of aconductor and that of an insulator(An Insulator is a material that resists the flow of electriccurrent. It is an object intended to support or separate electrical conductors without passingcurrent through itself); it can vary over that wide range either permanently or dynamically.

43. What is diode?

In electronics, a diode is a two-terminal device. Diodes have two active electrodes betweenwhich the signal of interest may flow, and most are used for their unidirectional current property.

44. What is transistor?

In electronics, a transistor is a semiconductor device commonly used to amplify or switchelectronicsignals. The transistor is the fundamental building block of computers, and all othermodern electronic devices. Some transistors are packaged individually but most are found inintegrated circuits.

45. What is op-amp?

An operational amplifier, often called an op-amp , is a DC-coupled high-gain electronic voltageamplifierwith differential inputs[1] and, usually, a single output. Typically the output of the op-amp is controlled either by negative feedback, which largely determines the magnitude of itsoutput voltage gain, or bypositive feedback, which facilitates regenerative gain and oscillation.

TOPICS FOR EC TECHNICAL SECTION

communication system.

antenna & wave propagation.
http://en.wikipedia.org/wiki/Electronic_componenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Ohm's_lawhttp://en.wikipedia.org/wiki/Ohm's_lawhttp://en.wikipedia.org/wiki/Electrichttp://en.wikipedia.org/wiki/Electronichttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Electrical_circuithttp://en.wikipedia.org/wiki/Electrical_circuithttp://en.wikipedia.org/wiki/Electronichttp://en.wikipedia.org/wiki/Electronichttp://en.wikipedia.org/wiki/Energy_storagehttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Signal_(electrical_engineering)http://en.wikipedia.org/wiki/Electronic_filtershttp://en.wikipedia.org/wiki/Cognatehttp://en.wikipedia.org/wiki/Cognatehttp://en.wikipedia.org/wiki/Passive_componenthttp://en.wikipedia.org/wiki/Electrical_networkhttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Electrical_conductivityhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electrical_insulationhttp://en.wikipedia.org/wiki/Electrical_insulationhttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Semiconductor_devicehttp://en.wikipedia.org/wiki/Semiconductor_devicehttp://en.wikipedia.org/wiki/Semiconductor_devicehttp://en.wikipedia.org/wiki/Electronic_amplifierhttp://en.wikipedia.org/wiki/Electronic_amplifierhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Electronic_devicehttp://en.wikipedia.org/wiki/Electronic_devicehttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Direct_couplinghttp://en.wikipedia.org/wiki/Gainhttp://en.wikipedia.org/wiki/Electronic_amplifierhttp://en.wikipedia.org/wiki/Negative_feedbackhttp://en.wikipedia.org/wiki/Positive_feedbackhttp://en.wikipedia.org/wiki/Electronic_componenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Ohm's_lawhttp://en.wikipedia.org/wiki/Ohm's_lawhttp://en.wikipedia.org/wiki/Electrichttp://en.wikipedia.org/wiki/Electronichttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Electrical_circuithttp://en.wikipedia.org/wiki/Electronichttp://en.wikipedia.org/wiki/Energy_storagehttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Signal_(electrical_engineering)http://en.wikipedia.org/wiki/Electronic_filtershttp://en.wikipedia.org/wiki/Cognatehttp://en.wikipedia.org/wiki/Passive_componenthttp://en.wikipedia.org/wiki/Electrical_networkhttp://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Electrical_conductivityhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electrical_insulationhttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Semiconductor_devicehttp://en.wikipedia.org/wiki/Electronic_amplifierhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Electronic_devicehttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Direct_couplinghttp://en.wikipedia.org/wiki/Gainhttp://en.wikipedia.org/wiki/Electronic_amplifierhttp://en.wikipedia.org/wiki/Negative_feedbackhttp://en.wikipedia.org/wiki/Positive_feedback


11/13

microwave & radar.

control system.

digital electronics.

analog electronics.

network theory.

measurement.

In all these topics first three topics cover almost 65% questions of your technical part.

some of those question are:

which is digital technique

(1)PCM (2)PAM (3)AM (4)FM.

moving type radar is

(1) MTI (2) PHASED ARRAY RADAR (3) PULSED RADAR (4) N.O.T.

decibel is

(1)ratio of powers (2) voltege level (3)current level (4) N.O.T.

1.if impedence in delta n/w is purely inductive then impedence in star n/w will be

(1) purely capacitive (2) purely inductive (3) partially inductive (4) resistive.

2.if R & F are reference input & negative feedback signal then error signal at amplifier`sinput will be

(1)R+F (2)R-F (3)R/F (4)R.F

3.wave length of a wave travelling in wave guide is

(1)less than free space (2) more than free space (3) equal to free space (4)N.O.T.

5. Circuit of Astable multivibrator is given and asked to find which terminal(s) has to begrounged?

6. Ohms law?

Ans: J= E

7. Angstorm( )=?Ans: 10^-10m

8. Unit of conductivity?

Ans: -m.

9. How can an amplifier gives more o/p than i/p, dont u think its a violation of law conservationof energy?

Ans: dc supply used for active devices hence law is not violated.

10. A question based on IC-555?

11. Which junction is formed by recrystallization..?

12. Calculate Doppler Frequency?

13. By increasing PRF of the Radar, what is effect on error in unambiguous range?

14. 2 Questions based on Radar Classification..?

15. Which of the following is the analog modulation.?

a)PAM b) Delta c)PCM d).

16. Which of the following is digital modulation.?


12/13

a)PAM b) Delta c).

17. A FM broadcast station having Frequency deviation of 100MHz, CalculateModulation Index..?

18. A Question based on the definition of Geo-synchronous orbit..?

19. Howmany number of Geo-synchronous satellites are required to cover entire Globe..?

Ans: 3

20. Calculate cutoff frequency of TE10 mode wider dimension is given as 2.5cms..?

21. Directivity is same as..?

a) Same as Directive gain b) greater than directive gain c) smaller than directive gain d)None22. DB is expessed

a) Power ratio b)voltage level c) Current level d)None

23. The wave length of a wave travelling in wave guide is

a) less than free space b) more than free space c) equal to free space

24. Which of the following is not an omnidirectional antenna..?

25. Which antenna is used for TV broadcasting..?

Ans: Yagi-uda antenna..

26. The standard time taken to scan one Horizontal line in TV as per FMCC standard..?

Ans: 64sec.

27. A question based on the TV picture tube?

28. If impedance in delta n/w is purely inductive then impedance in star n/w will be

a) purely capacitive b) purely inductive c) resistive

d) Either capacitive or inductive depends on its magnitudes.

29. what is Laplace transform of integral of f(t)..?

30. Laplace transform of c1f(t)+c2f(t).?

31. Area under unit impulse signal is?

Ans: 1

32. The next nos of (777)8 & (1111)2 are.?

Ans: (1000)8 & (10000)2

33. In floating point representation, 853.29 can be represented as _____?

34. Shifting left and putting a zero in LSB is equivalent to..?

Ans. multiply by 2.

35. If we require o/p equal to i/p then which flip-flop has to be used .?

a) D-Flipflop b) D-Latch c)

36. Which of the following gate is used for making inverter..?Ans: NAND gate

37. In which technology the no. of gates are more than 12?

Ans: MSI.

38. For an n-bit microprocessor the value of n is based on?

a) Address bus b) Internal data bus c) External data bus d) None.


13/13

39. Address bus length of 80286 microprocessor is?

40. One more question based on microprocessor

41. Minimum RAM memory required in windows-95.?

42. which operating system is prefer for Servers?

a). Windows 98 b). Windows NT

43. A Qstn on Rise Time from Control systems

44. A Qstn based on stability from control systems..

45. In a feedback system the error signal is.?

Ans: a)r+s b) r-s c) rs d) None

Documents

commuication qps