Monday, February 12, 2018

The TCP/IP Reference Model

TCP/IP means Transmission Control Protocol and Internet Protocol. It is the network model used in the current Internet architecture as well. Protocols are set of rules which govern every possible communication over a network. These protocols describe the movement of data between the source and destination or the internet. 
The TCP/IP model is a condensed version of the OSI reference model consisting of the following 4 layers:
  •  Application Layer
  • Transport Layer
  • Internet Layer
  • Network Access Layer































Sunday, February 11, 2018

Free download Signal and System Book by B.P. Lathi







































Signal and System Book by B.P. Lathi

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Wireless communications FAQ & MCQ

A duration of traffic path occupancy from a call, sometimes referred to as an average duration of occupancy of one or more path from calls.
Holding time

ECE Board Exam November 2000
Frequency band where Total Access Communication System (TACS) is allocated.
935-960 MHz; 890-915 MHz

ECE Board Exam April 2000
Referred as the forward link channel of the cellular duplex system
Cell to mobile unit

ECE Board Exam November 1999
This referred to a condition in a telephone network where the calling party cannot get connected to the party being called
Blocked call

Transmission Lines FAQ

An SWR reading which has a short circuit termination.
Infinity

ECE Board Exam November 2000
In an open wire transmission line, what is the normal separation between its two (2) conductors?
2 to 6 cm

ECE Board Exam April 2000
Which of the following term is used to describe the attenuation and phase shift per unit length of a transmission line?
Propagation constant

ECE Board Exam November 1999
An indication in radio communication when the voltage standing wave ratio is equal to zero.
No input power

ECE Board Exam April 1999
Refers to a connector that normally connects RG-213 coaxial. cable to an HF transceiver.
PL-259

THYRISTORS FAQ

THYRISTORS 

1. It is like the four-layer diode but with the added gate connection 
SCR 

2. This is the maximum continuous anode current that the device can withstand in the conduction state under specifies conditions. 
Average forward current 

3. What bilateral thyristor functions basically like two parallel SCRs turned in opposite directions with a common gate terminal? 
Triac 

4. ____________ does not belong to the thyristor family because it does not have a four-layer type of construction. 
UJT 

5. It can be used a trigger device for SCRs and triacs. 
UJT 

6. It is a type of three-terminal thyristor that is triggered into conduction when the voltage at the anode exceeds the voltage at the gate. 
PUT 

7. A region of forward bias in which the device has a very high forward resistance and is in the off state 
Forward-blocking region 

8. A method for turning-off the SCR that basically requires momentarily forcing current through the SCR in the direction opposite to the forward conduction 
Forced commutation 

9. The value of gate current necessary to switch the SCR from the forward-blocking region to the forward-conduction region under specified conditions. 
Gate Trigger Current 

10. A four-layer semiconductor device that operates essentially as does the conventional SCR except that it can also be light-triggered. 
LASCR 

11. Functions basically like two parallel 4- layer diodes turned in opposite directions. 
Diac 

12. A diac with gate terminal 
Triac 

13. A four-terminal thyristor that has two gate terminals that are used t trigger the device on and off 
Silicon Controlled Device (SCS) 

14. A type of three-terminal thyristor that is triggered into conduction when the voltage at the anode exceeds the voltage at the gate. 
Programmable Unijunction Transistor (PUT) 

15. The characteristic of a UJT that determines its turn-on point 
Standoff-ratio 

16. The four-layer diode is also called 
Shockley diode 

17. The region that corresponds to the on condition of the SCR where there is forward current from anode to cathode through the very low resistance of the SCR 
Forward_ conduction region 

18. The SCR can only be turned on using its _________ terminal 
Gate 

19. Acts as the trigger source in the LASCRs 
Light 

20. A thyristor that conducts when the voltage across its terminals exceeds the breakover potential 
4-layer diode 

21. Basic methods of for turning off an SCR 
Anode current interruption and forced commutation

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OSCILLATORS FAQ

OSCILLATORS 

1. A circuit that produces a periodic waveform on its output with only the dc supply voltage as an input 
Oscillator 

2. The two major classifications for oscillators are feedback oscillators and _______________. 
Relaxation oscillators 

3. Characterized by the condition wherein a portion of the output voltage of an amplifier is fed back to the input with no net phase shift resulting in a reinforcement of the output signal 
Positive signal 

4. An amplifier gain of greater than ________ will cause the oscillator to limit both peaks of the waveform 
100 

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Satellite Communication FAQ & MCQ

ECE Board Exam April 2001
What balance the gravitational pull of the earth to allow the satellite to stay on its orbit?
Centripetal force

ECE Board Exam November 2000
Satellite that rotates around the earth in a low-altitude elliptical or circular pattern.
Nonsynchronous satellite

ECE Board Exam April 1999
In a transoceanic satellite conversation, how much is the typical delay before a reply is heard?
600 ms

ECE Board Exam November 1999
What are the repeaters inside communications satellite known for?
Transponders

ECE Board Exam April 2000
Under a circular satellite orbiy, how high is a certain satellite located above the surface of the earth if the total satellite height is 9869 miles?

ECE Board Exam November 1998
 Is a kind of satellite which has a period of revolution equivalent to the period if rotation of the earth about its axis.
 Geosynchronous satellite 

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Navigational Aids MCQ

1.        The phenomenon evidenced by the change in the observed frequency of a sound or a radio wave caused by the time rate of change in the magnitude of the radial component of relative velocity between the source and the point of observation.
  1. Tunnel effect
  2. Doppler effect
  3. Gunn effect
  4. End effect
2.        Power density is inversely proportional to the square of the distance from the source or transmitter to the destination or receiver. this is called
  1. Coulomb’s law
  2. Inverse square law
  3. Lenz,s law
  4. Maxwell’s law
3.        They are nondirectional transmitters and/or receivers that operate in the LF and MF bands.
  1. Radio Beacons
  2. DME
  3. ILS
  4. LORAN
4.        The ratio of the pulse width to the time between the beginning of two pulses is called
  1. Doppler shift
  2. Duty cycle
  3. Tracking error
  4. PRR

ACTIVE FILTERS FAQ

ACTIVE FILTERS 

1. The ___________ of a band-pass filter is the ratio of the center frequency to the bandwidth. 
Quality factor 

2. An active filter category that rejects the frequencies within a certain bandwidth and passes frequencies outside the bandwidth 
Band-stop filter 

3. A filter response characteristic that provides a very flat amplitude response in the passband and a roll-off rate of -20dB/decade/pole 
Butterworth characteristic 

4. Each filter in a cascaded arrangement is called ___________. 
Stage or section 

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Fiber Optics FAQ and MCQ

Which of the following refers to the relative refractive index difference of single mode fibers?
0.1 - 0.3 %

ECE Board Exam November 2000
A parameter of light beam that do not change the quality when it enters one medium from another.
Frequency

ECE Board Exam April 2000
Which of the following limits the top speed of transmitting information in fiber optic communication?
Detector speed

ECE Board Exam November 1999
Type of multi-channel signal transmission in the optic fiber communication that uses twisted pair coupler to transmit two signals of different wavelengths.
Frequency-division multiplexing 

ECE Board Exam April 1999
Best applies to an optical fiber core.
A higher refractive index than the cladding

ECE Board Exam November 1998
How many times bigger does the bandwidth of a fiber optic multimode have over cable?
100 times bigger

ECE Board Exam April 1998
What law does a light travelling in an optical fiber follow?
Snell's

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SPECIAL- PURPOSE DIODES FAQ & ELECTRINCS MCQ

SPECIAL- PURPOSE DIODES

1. Diodes that were designed to operate in reverse breakdown
Zener diode

2. A device that operates in reverse bias
photodiode

3. A zener diode operating in breakdown acts as a
Voltage regulator 
4. A positive temperature means that the zener voltage
Increases with an increase in temperature on decreases with decrease in temperature. 

5. A diode that always operates in reverse-bias and is doped to maximize the inherent capacitance of the depletion region is
Laser 

6. When the light-emitting diode (LED) is forward-biased, __________pass the pn junction and recombine with____________ in the _________material.
Electrons, holes, p-type 

Electronics and Communication Engineering MCQ part-9

 FSK stands for:
a.
Full-Shift Keying
c.
Full-Signal Keying
b.
Frequency-Shift Keying
d.
none of the above


ANS:   B

  2.   PSK stands for:
a.
Pulse-Signal Keying
c.
Phase-Signal Keying
b.
Pulse-Shift Keying
d.
Phase-Shift Keying


ANS:   D

  3.   QAM stands for:
a.
Quadrature Amplitude Modulation
c.
Quadrature Amplitude Marking
b.
Quadrature Amplitude Masking
d.
none of the above


ANS:   A

ECE MCQ

 FDDI stands for:
a.
Fiber Digital Data Interface
c.
Fiber Distribution Delay Interface
b.
Fiber Distributed Data Interface
d.
Frequency-Division Data Interface


ANS:   B

  2.   FITL stands for:
a.
Fiber In The Loop
c.
Frequency Input to The Loop
b.
Fiber Input Timing Loss
d.
Fiber Input Timing Loop


ANS:   A

  3.   FTTC stands for:
a.
Fiber Transmission Timing Constraint
b.
Fiber Transmission Technology Committee
c.
Fiber Telephone Transmission Cable
d.
Fiber To The Curb


ANS:   D

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Electronics & Communication Engineering FAQ-12

SINGLE – SIDEBAND COMMUNICATIONS
SYSTEMS

1) A form of amplitude modulation in which the carrier is transmitted at full power but only one of the sidebands is transmitted.                       AM Single-sideband Full Carrier ( SSBFC )
2) A form of amplitude modulation in which the carrier is totally suppressed and one of the sidebands removed.                              AM Single-sideband Suppressed Carrier ( SSBSC ) 

3) A form of amplitude modulation in which one sideband is totally removed and the carrier voltage is reduced to approximately 10% of its unmodulated amplitude. Sometimes called single-sideband reinserted carrier.                               AM Single-sideband Reduced Carrier ( SSBRC )

4) It is the reinserted carrier in SSBRC for demodulation purposes.                           Pilot Carrier

5) A form of amplitude modulation in which a single carrier frequency is independently modulated by two different modulating signals.                         AM Independent Sideband ( ISB )

6) A form of amplitude modulation in which the carrier and one complete sideband are transmitted, but only part of the second sideband is transmitted.                               AM Vestigial Sideband ( VSB )

7) ________ is the picture portion of a commercial television broadcasting signal.                            VSB System



Electronics & Communication Engineering FAQ-11

TELEPHONE INSTRUMENTS AND SIGNALS
1)Process of conveying information from one place to another.
Communications

2)Is a long-distance communications
Telecommunications

3)One of the most remarkable devices ever invented.
Telephone

4)Anyone who uses a telephone or a data modem on a telephone circuit is part of a global communications network .
Public Telephone Network

5)The PTN is comprised of several very large corporations and hundreds of smaller independent companies jointly.
Telco

Electronics & Communication Engineering FAQ-10

CELLULAR TELEPHONE SYSTEM

1)Stands for Standard Cellular Telephone Service
CTS

2)An acronym for Personal Communications System.
PCS

3)Stands for Personal Communications Satellite System.
PCSS

4)An acronym for Advanced Mobile Telephone System.
AMPS

5)Proposed the cellular telephone concept in 1971.
Bell Telephone Laboratories

6)A standard cellular telephone service (CTS) initially placed into operation on Oct. 13, 1983.
AMPS

7)It was used by AMPS cellular telephones with a usable audio-frequency band from 300 Hz to 3 KHz and a maximum frequency deviation of + 12 KHz for 100% modulation.
Narrowband Frequency Modulation (NBFM)

Electronics & Communication Engineering FAQ-9

1)Information that is stored in digital form. Information that has been processed, organized and stored.
Data

2)Knowledge or intelligence.
Information

3)The transmission, reception, and processing of digital information.
Data Communications

4)It is to transfer digital information from one place to another.
Data Communications Circuit

5)A set of devices interconnected by media links.
Network

Electronics & Communication Engineering FAQ-8

Also called as Multiple Destination, It implies that more than one user has access to one or more radio channels within a satellite communications channel.
 Multiple Accessing
Multiple Accessing Arrangement:
 Frequency-division multiple accessing (FDMA)
 Time-division multiple accessing (TDMA)
 Code-division multiple accessing (CDMA)

2)A given number of the available voice-band channels from each earth station are assigned a dedicated destination.
Pre-assignment(dedicated)
 
3)Voice channels are assigned on an as-needed basis.
Demand Assignment
 
4)The method of assigning adjacent channels different electromagnetic polarizations and is possible by using orthogonal polarization and spacing adjacent channels 20 MHz apart.
Frequency Reuse