Data-Communication

Question 1
A stable multivibrator are used as
A
comparator circuit
B
squaring circuit
C
frequency to voltage converter
D
voltage to frequency converter
       Data-Communication       stable-multivibrator       Nielit Scientist-C 2016 march
Question 1 Explanation: 
● A multivibrator is a one type of electronic circuit, that is used to implement a two state system like flip-flops, timers and oscillators.
● Multivibrators are classified into three types based on the circuit operation, namely Astable multivibrators, Bistable multivibrators and Monostable multivibrators.
● The astable multivibrator is not stable and it repeatedly switches from one state to the other. In monostable multivibrator, one state is stable and remaining state is unstable.
● When the power is turned ON consider the flip flop is cleared initially, then the o/p of the inverter will be high. The charging of the capacitor will be done using two resistors R1& R2. When the voltage of the capacitor goes above 2/3 Vcc, then the output of the higher comparator will be High, it changes the control flip flop
Question 2
The astable multivibrator has
A
two quasi stable states
B
two stable states
C
one stable and one quasi-stable state
D
none of these
       Data-Communication       stable-multivibrator       Nielit Scientist-C 2016 march
Question 2 Explanation: 
A multivibrator is an electronic circuit used to implement a variety of simple two-state devices such as relaxation oscillators, timers and flip-flops. It consists of two amplifying devices (transistors, vacuum tubes or other devices) cross-coupled by resistors or capacitors.
Question 3
The process of converting the analog sample into discrete form is called
A
Modulation
B
Multiplexing
C
Quantization
D
Sampling
       Data-Communication       Sampling-Types       Nielit Scientist-B CS 22-07-2017
Question 3 Explanation: 
Sampling is the process of recording an analog signal at regular discrete moments of time.
sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave (a continuous signal) to a sequence of samples (a discrete-time signal).
Quantization in digital signal processing, is the process of mapping input values from a large set (often a continuous set) to output values in a (countable) smaller set, often with a finite number of elements.
The sampling rate fs is the number of samples per second.
The time interval between samples is called the sampling interval Ts=1/fs
Question 4
Which of the following is not a transceiver function?
A
Transmission and receipt of data
B
Checking of line voltages
C
Addition and subtraction of headers
D
Collision detection
       Data-Communication       Transceiver       Nielit Scientist-B CS 2016 march
Question 4 Explanation: 
A transceiver is a device comprising both a transmitter and a receiver that are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter receiver.
Question 5
Vestigial sideband most commonly used in radio transmission
A
radio transmission
B
telephony
C
television transmission
D
all of the above
       Data-Communication       Radio-Transmission       NieLit STA 2016 March 2016
Question 5 Explanation: 
Limitation of single-sideband modulation being used for voice signals and not available for video/TV signals leads to the usage of vestigial sideband. A vestigial sideband (in radio communication) is a sideband that has been only partly cut off or suppressed. Television broadcasts (in analog video formats) use this method if the video is transmitted in AM, due to the large bandwidth used. It may also be used in digital transmission, such as the ATSC standardized 8VSB.
Vestigial sideband (VSB) is a type of amplitude modulation ( AM ) technique (sometimes called VSB-AM ) that encodes data by varying the amplitude of a single carrier frequency . Portions of one of the redundant sidebands are removed to form a vestigial sideband signal - so-called because a vestige of the sideband remains.
Question 6
T1 carrier system is used:
A
For delta modulation
B
Industrial moise
C
For frequency modulated signals
D
None of the above
       Data-Communication       Carrier-System       Nielit Scientist-B CS 4-12-2016
Question 6 Explanation: 
The T-carrier system, introduced by the Bell System in the U.S. in the 1960s, was the first successful system that supported digitized voice transmission. The original transmission rate (1.544 Mbps) in the T1 line is in common use today in​ Internet service provider (ISP) connections to the Internet. Another level, the T3 line, providing 44.736 Mbps, is also commonly used by Internet service providers.
The T-carrier system is entirely digital, using pulse code modulation (PCM) and time-division multiplexing (TDM). The system uses four wires and provides duplex capability (two wires for receiving and two for sending at the same time). The T1 digital stream consists of 24 64-Kbps channels that are multiplexed.
Question 7
A low pass filter is:
A
Passes the frequencies lower than the specified cutoff frequency
B
Used to recover signal from sampled signal
C
Rejects higher frequencies
D
All of the above
       Data-Communication       Pass-Filters       Nielit Scientist-B CS 4-12-2016
Question 7 Explanation: 
A low-pass filter (LPF) is a filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency. The exact frequency response of the filter depends on the filter design.
Question 8
The sequence of operation in which PCM is done :
A
Sampling, quantizing, encoding
B
Quantizing, sampling, encoding
C
Quantizing, encoding, sampling
D
None of the above
       Data-Communication       PCM       Nielit Scientist-B CS 4-12-2016
Question 8 Explanation: 
● Pulse code modulation (PCM) is a digital scheme for transmitting analog data. The signals in PCM are binary; that is, there are only two possible states, represented by logic 1 (high) and logic 0 (low). This is true no matter how complex the analog waveform happens to be. Using PCM, it is possible to digitize all forms of analog data, including full-motion video, voices, music, telemetry, and virtual reality (VR).
● sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave (a continuous signal) to a sequence of samples (a discrete-time signal).
● Quantization in digital signal processing, is the process of mapping input values from a large set (often a continuous set) to output values in a (countable) smaller set, often with a finite number of elements.
● The encoder encodes the quantized samples. Each quantized sample is encoded into an 8-bit code word by using A-law in the encoding process.
Question 9
ICA(in computational intelligence) stands for__
A
Intermediate Computational Algorithms
B
Immediate Computational and Analysis
C
Independent Component Analysis
D
Independent Computational Algorithms
       Data-Communication       Independent-Component-Analysis       Nielit Scientist-D 2016 march
Question 9 Explanation: 
In signal processing, independent component analysis is a computational method for separating a multivariate signal into additive subcomponents. This is done by assuming that the subcomponents are non-Gaussian signals and that they are statistically independent from each other.
Question 10
​ An ideal op-amp is an ideal
A
Voltage controlled current source
B
voltage controlled voltage source
C
current controlled current source
D
current controlled voltage source
       Data-Communication       ideal-op-amideal-op-amp       Nielit Scientific Assistance IT 15-10-2017
Question 10 Explanation: 
An ideal op-amp lead us to an op-amp with input resistance is infinite, so no current flows into either input terminal (the “current rule”) and that the differential input offset voltage is zero (the “voltage rule”).
Ideal operational amplification will have
➝ High input impedance ( R in = ∞ ) and low output impedance ( R out = 0 )

➝ R in = ∞ , so zero input current
➝ Infinite voltage gain
➝ So, it is a voltage controlled voltage source device.
Question 11
A carrier A​ c​ Cos(w​ C​ )t is frequency modulated by a signal E​ m​ Cos(w​ m​ )t. The modulation index is m​ f​ . the expression for the resulting FM signal is
A
A​ c,​ Cos[w​ c​ t+ m​ f​ Sin(w​ m​ )t]
B
A​ c​ Cos[w​ c​ t+ m​ f​ Cos(w​ m​ )t]
C
A​ c​ Cos[w​ c​ t+ ​ π ​ m​ f​ Sin w​ m​ t]
D
A​ c​ Cos[w​ c​ t+ 2 ​ π ​ m​ f​ E​ m​ Cos(w​ m​ )t/w​ m​ ]
       Data-Communication       FM-Signal       Nielit Scientific Assistance IT 15-10-2017
Question 11 Explanation: 
Question 12
In MOSFET fabrication, the channel length is delayed during the process of
A
Isolation oxide growth
B
Channel stop implantation
C
Poly-Silicon gate patterning
D
Lithography step leading to the contact pad
       Data-Communication       MOSFET       Nielit Scientific Assistance CS 15-10-2017
Question 12 Explanation: 
In MOSFET fabrication channel length is defined during Poly-Silicon gate patterning process
Question 13
When the object making the sound is moving towards you, the frequency goes up due to he waves getting pushed more tightly together. The opposite happens when the object moves away from you and the pich goes down. This phenomenon is called
A
Band Width
B
Doppler effect
C
Sound refraction
D
Vibrations
       Data-Communication       Doppler-Effect       KVS DEC-2013
Question 13 Explanation: 
→ The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source.
→ The Doppler effect is observed whenever the source of waves is moving with respect to an observer.
→ The Doppler effect can be described as the effect produced by a moving source of waves in which there is an apparent upward shift in frequency for observers towards whom the source is approaching and an apparent downward shift in frequency for observers from whom the source is receding.
Question 14
The closeness of the recorded version to the original sound is called
A
Fidelity
B
Digitization
C
Sampling
D
Nyquist Theorem
       Data-Communication       Fidelity       KVS DEC-2013
Question 14 Explanation: 
→ Digitization is the process of converting information into a digital format . In this format, information is organized into discrete units of data (called bit s) that can be separately addressed (usually in multiple-bit groups called bytes).
→ sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave (a continuous signal) to a sequence of samples (a discrete-time signal).
→ "fidelity" denotes how accurately a copy reproduces its source
Question 15
The diagram below represents
A
Moore’s law
B
Newton raphson method
C
Boyle’s law
D
Gregor law
       Data-Communication       Moore’s-law       KVS DEC-2013
Question 15 Explanation: 
Moore's law is the observation that the number of transistors in a dense integrated circuit doubles about every two years.
Question 16
A___ multivibrator circuit is one in which both LOW and HIGH output states are stable
A
Monostable
B
Bistable
C
Multistable
D
Tristable
       Data-Communication       stable-multivibrator       KVS DEC-2013
Question 16 Explanation: 
● The Bistable Multivibrator is another type of two state device.
● Bistable Multivibrators have TWO stable states (hence the name: “Bi” meaning two) and maintain a given output state indefinitely unless an external trigger is applied forcing it to change state.
Question 17
Refer to the monostable multibrator circuit in the figure below.

The trigger terminal(pin 2 of the IC) is driven by a symmetrical pulsed waveform of 10kHz. Determine the duty cycle of the output waveform.
A
0.56
B
0.55
C
0.57
D
0.58
       Data-Communication       stable-multivibrator       KVS DEC-2013
Question 17 Explanation: 
Question 18
The percentage resolution of an eight bit D/A converter is
A
0.39%
B
0.38%
C
0.50%
D
0.51%
       Data-Communication       A/D-Converter       KVS DEC-2013
Question 18 Explanation: 
→ An eight-bit D/A converter have 2​ 8​ -1 resolvable levels which is nothing but 255 levels.
→ Percentage resolution is (1/255)×100=0.39%
Question 19
The diagram below depicts:
A
Sound in waveform
B
Wind frequency
C
Line of sight
D
Compressions on a map
       Data-Communication       Waveform       KVS DEC-2013
Question 19 Explanation: 
●The generic term waveform means a graphical representation of the shape and form of a signal moving in a gaseous, liquid, or solid medium.
●For sound, the term describes a depiction of the pattern of sound pressure variation (or amplitude) in the time domain
● The temporal frequencies of sound waves are generally expressed in terms of cycles (or kilocycles) per second. The simplest waveform is the sine wave, since it has only one frequency associated with it. The sound waves associated with, say, music, are constantly varying.
Question 20
The diagram below represents
A
Resolution
B
Vibration
C
Reverberation
D
Frequency
       Data-Communication       Reverberation       KVS DEC-2013
Question 20 Explanation: 
● Reverberation, in psychoacoustics and acoustics, is a persistence of sound after the sound is produced.
● A reverberation, or reverb, is created when a sound or signal is reflected causing a large number of reflections to build up and then decay as the sound is absorbed by the surfaces of objects in the space – which could include furniture, people, and air.
Question 21
The process of taking a snapshot of the waveform at regular intervals and representing it as a binary number is known as
A
Sampling
B
Standard Assessment
C
Sequential Formatting
D
Sound Structure
       Data-Communication       Digital-sampling       KVS DEC-2013
Question 21 Explanation: 
Digital sampling is the recording of a sound using a string of numbers to represent the sound. 1s and 0s. These numbers are called samples.
Question 22
The _____ measures the relative strengths of two signals or a signal at two different points
A
frequency
B
decibel
C
Attenuation
D
throughput
       Data-Communication       Signal       KVS 30-12-2018 Part B
Question 22 Explanation: 
Decibel (dB), unit for expressing the ratio between two physical quantities, usually amounts of acoustic or electric power, or for measuring the relative loudness of sounds. One decibel (0.1 bel) equals 10 times the common logarithm of the power ratio
Question 23
ECL is the fastest of all logic families. High speed in ECL is possible because transistors are used in difference amplifier configuration, in which they are never driven into ____.
A
Race condition
B
Saturation
C
Delay
D
High impedance
       Data-Communication       ideal-op-amp       UGC NET CS 2017 Jan -paper-2
Question 23 Explanation: 
→ ECL is the fastest of all logic families. High speed in ECL is possible because transistors are used in difference amplifier configuration, in which they are never driven into Saturation.
→ Emitter-coupled logic (ECL) is a high-speed integrated circuit bipolar transistor logic family. ECL uses an overdriven BJT differential amplifier with single-ended input and limited emitter current to avoid the saturated (fully on) region of operation and its slow turn-off behavior.
→ As the current is steered between two legs of an emitter-coupled pair, ECL is sometimes called current-steering logic (CSL), current-mode logic (CML) or current-switch emitter-follower (CSEF) logic.[
Question 24
Which of the following is/are true w.r.t. applications of mobile computing ?
(A) Travelling of salesman
(B) Location awareness services
A
(A) true; (B) false.
B
Both (A) and (B) are true.
C
Both (A) and (B) are false.
D
(A) false; (B) true.
       Data-Communication       Mobile-Computing       UGC NET CS 2017 Jan -paper-2
Question 24 Explanation: 
Mobile computing main applications:
1.Portability
2. Connectivity
3.Social Interactivity
4. Individuality
Travelling of salesman applicable to mobility of application.
Question 25
Which of the following services is not provided by wireless access point in 802.11 WLAN ?
A
Association
B
Disassociation
C
Error correction
D
Integration
       Data-Communication       WLAN       UGC NET CS 2015 Dec- paper-2
Question 25 Explanation: 
→ Wireless LANs are use high frequency radio waves instead of cables for connecting the devices in LAN. Users connected by WLANs can move around within the area of network coverage. Most WLANs are based upon the standard IEEE 802.11 or WiFi.
→ A wireless access point (WAP), or more generally just access point (AP), is a networking hardware device that allows other Wi-Fi devices to connect to a wired network.
→ Wireless access point in 802.11 WLAN services are association, association and Integration.
Question 26
Four channels are multiplexed using TDM. If each channel sends 100 bytes/second and we multiplex 1 byte per channel, then the bit rate for the link is __________.
A
400 bps
B
800 bps
C
1600 bps
D
3200 bps
       Data-Communication       Multiplexing        UGC NET CS 2015 Dec- paper-2
Question 26 Explanation: 
Given data,
-- 4 channels are multiplexed using TDM
-- Multiplex 1 byte per channel. So, total 4 bytes=4 channels.
-- Each channel sends 100 bytes/sec
-- Bit rate=?
Bit rate= 100 * 4 bytes(1 byte=8 bits)
= 100 * 4 *8 (we are converting into bits because we are finding bit rate)
= 3200 bps
Question 27
In a typical mobile phone system with hexagonal cells, it is forbidden to reuse a frequency band in adjacent cells. If 840 frequencies are available, how many can be used in a given cell?
A
280
B
110
C
140
D
120
       Data-Communication       Frequency-Band       UGC NET CS 2015 Dec- paper-2
Question 27 Explanation: 
-- Mobile phone system with hexagonal( equals to 6) cells
-- 840 frequencies are available.
-- How many can be used in a cell?
In this we need maximum 3 unique cells are required.

Total cells used with frequency is = 840/3
= 280 frequencies
Question 28
A data cube C, has n dimensions, and each dimension has exactly p distinct values in the base cuboid. Assume that there are no concept hierarchies associated with the dimensions. What is the maximum number of cells possible in the data cube, C?
A
p​ n
B
p
C
(2​ n​ - 1)p+1
D
(p + 1)​ n
       Data-Communication       Mobile-Computing       UGC NET CS 2015 Dec- paper-2
Question 28 Explanation: 
Option-A:​ This is the maximum number of distinct tuples that you can form with p distinct values per dimensions.
Option-B:​ You need at least p tuples to contain p distinct values per dimension. In this case no tuple shares any value on any dimension.
Option-C:​ The minimum number of cells is when each cuboid contains only p cells, except for the apex, which contains a single cell.
Option-D:​ We have p+1 because in addition to the p distinct values of each dimension we can also choose ∗.
Question 29
The mechanism with which several uses can share a medium without interference is :
A
Frequency modulation
B
Amplitude modulation
C
Multiplexing
D
None of these
       Data-Communication       Multiplexing        UGC NET CS 2005 Dec-Paper-2
Question 29 Explanation: 
Multiplexing is a method by which multiple analog or digital signals are combined into one signal over a shared medium. It can share a medium without interference.
Question 30
The frequency reuse plan is divided into cell grouping using how many cells, where the number of cells equals N ?
A
3
B
10
C
7
D
21
       Data-Communication       Cellular-Networks       UGC NET CS 2005 june-paper-2
Question 30 Explanation: 
The cluster size N = 7 and the frequency reuse factor is 1/7 since each cell contains one-seventh of the total number of available channels.
Total cells=7*3
=21
Frequency reuse concept, cells with the same letter use the same set of frequencies. A cell cluster is outline in blue color and replicated over the converge area.
Question 31
Which interim standard describes inter-switching networking ?
A
IS - 54
B
IS - 95
C
DS - 45
D
ANSI - 41
       Data-Communication       Cellular-Networks       UGC NET CS 2005 june-paper-2
Question 31 Explanation: 
→ Interim Standard 95 (IS-95) was the first ever CDMA-based digital cellular technology.
→ The IS-95 standards describe an air interface, a set of protocols used between mobile units and the network.
→ IS-95 is widely described as a three-layer stack, where L1 corresponds to the physical (PHY) layer, L2 refers to the Media Access Control (MAC) and Link-Access Control (LAC) sublayers, and L3 to the call-processing state machine.
Question 32
Theoretically, how many 1.25 MHz Carriers are there in a CDMA cell ?
A
18
B
22
C
9
D
64
       Data-Communication       Cellular-Networks       UGC NET CS 2005 june-paper-2
Question 32 Explanation: 
→ In CDMA, multiple users share a 1.25 MHz channel by using orthogonal spreading codes (Walsh codes)
→ IS-95a standard designed for AMPS cellular band
→ Each cellular provider is allocated 25 MHz spectrum and ten 1.25-MHz CDMA duplex channels if A AMPS Band provider, 9 if B band provider
Question 33
The frequency band allocated for the downlink in GSM is :
A
960 - 985 MHz
B
935 - 960 MHz
C
920 - 945 MHz
D
930 - 955 MHz
       Data-Communication       Cellular-Networks       UGC NET CS 2006 Dec-paper-2
Question 33 Explanation: 
There are 2 popular GSM methods.
1. GSM-900
2. GSM-1800
GSM-900 uses 890 - 915 MHz to send information from the Mobile Station to the Base
Transceiver Station (uplink) and 935 - 960 MHz for the other direction (downlink), providing 124 RF channels (channel numbers 1 to 124) spaced at 200 kHz. Duplex spacing of 45 MHz is used.
Question 34
What is the transmission signal coding method for a T1 carrier called ?
A
Binary
B
NRZ
C
Bipolar
D
Manchester
       Data-Communication       Transmission-method       UGC NET CS 2006 June-Paper-2
Question 34 Explanation: 
The transmission signal coding method of T1 carrier is called Bipolar. Bipolar encoding is a type of return-to-zero (RZ) line code, where two nonzero values are used, so that the three values are +, −, and zero. Such a signal is called a duobinary signal.
Question 35
How much bandwidth is required to send 132 voice - grade channels by FDM on an international satellite system ?
A
500 MHz
B
10 MHz
C
1320 MHz
D
50 MHz
       Data-Communication       Multiplexing        UGC NET CS 2006 June-Paper-2
Question 35 Explanation: 
In telecommunications, frequency-division multiplexing (FDM) is a technique by which the total bandwidth available in a communication medium is divided into a series of non-overlapping frequency bands, each of which is used to carry a separate signal. The most natural example of frequency-division multiplexing is radio and television broadcasting, in which multiple radio signals at different frequencies pass through the air at the same time.
Frequency Division Multiple Access(FDMA):
FDMA is simply another example of the familiar data and voice transmission technique called FDM. This technique is used to allocate small portions of a large bandwidth (500MHz for satellite transponders) to individual users. For instance, a telecommunications common carrier in a particular country like Brazil. It might want 132 voice grade channels for sending voice and analog coded data to various other countries. The bandwidth required on the current international satellite systems for this many channels is 10MHz. Because 1 transponder has a bandwidth of 500Mhz, it could accommodate 50 users, each requiring 132 channels. The Brazilian user might be allocated the frequency band between 5990 and 6000MHz for the uplink to the satellite and the corresponding downlink frequencies would be 3765 to 3775Mhz.
Question 36
Infrared signals can be used for short range communication in a closed area using _______ propagation.
A
ground
B
sky
C
line of sight
D
space
       Data-Communication       FM-Signal       UGC NET CS 2014 June-paper-2
Question 36 Explanation: 
Propagation methods are 3 types
1. Ground
2. Sky
3. Line of sight


Question 37
Match the following with respect to the mobile computing technologies :  
A
a-iii, b-iv, c-ii, d-i
B
a-iv, b-i, c-ii, d-iii
C
a-ii, b-iii, c-iv, d-i
D
a-ii, b-i, c-iv, d-iii
       Data-Communication       Mobile-Computing       UGC NET CS 2014 June-paper-2
Question 37 Explanation: 
GPRS → An emerging wireless service that offers a mobile data
GSM → An integrated digital radio standard
UMTS → The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing cdmaOne technology. UMTS uses wideband code division multiple access (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators.
EDGE → Enhanced GPRS or EGPRS. It is a data system used on top of GSM networks. It provides nearly 3 times faster speeds than the outdated GPRS system. Nine different schemes for modulation and error correction.
Question 38
The GSM network is divided into the following three major systems :
A
SS, BSS, OSS
B
BSS, BSC, MSC
C
CELL, BSC, OSS
D
SS, CELL, MSC
       Data-Communication       Cellular-Networks       UGC NET CS 2012 Dec-Paper-2
Question 38 Explanation: 
GSM Architecture:

Mobile Station (MS)
Mobile Equipment (ME)
Subscriber Identity Module (SIM)
Base Station Subsystem (BSS)
Base Transceiver Station (BTS)
Base Station Controller (BSC)
Network Switching Subsystem (NSS)
Mobile Switching Center (MSC)
Home Location Register (HLR)
Visitor Location Register (VLR)
Authentication Center (AUC)
Equipment Identity Register (EIR)
Question 39
The VLF and LF bauds use _______ propagation for communication.
A
Ground
B
Sky
C
Line of sight
D
Space
       Data-Communication       Propagation       UGC NET CS 2013 Dec-paper-2
Question 39 Explanation: 
The VLF and LF bauds use ground propagation for communication.
Propagation methods are 3 types
1. Ground
2. Sky
3. Line of sight

→ Very low frequency or VLF is for radio frequencies (RF) in the range of 3 to 30 kilohertz (kHz), corresponding to wavelengths from 100 to 10 kilometers, respectively.
→ The low-frequency signals travel in all directions from the transmitting antenna.
Question 40
______ is a satellite based tracking system that enables the determination of person’s position.
A
Bluetooth
B
WAP
C
Short Message Service
D
Global Positioning System
       Data-Communication       GPS       UGC NET CS 2012 June-Paper2
Question 40 Explanation: 
Global Positioning System(GPS) is a satellite based tracking system that enables the determination of person’s position.
Question 41
The amount of uncertainty in a system of symbol is called
A
Bandwidth
B
Entropy
C
Loss
D
Quantum
       Data-Communication       Information-theory       UGC NET CS 2011 Dec-Paper-2
Question 41 Explanation: 
→ The amount of uncertainty in a system of symbol is called entropy. → Generally we can call entropy is disorder or uncertainty.
Question 42
The cellular frequency reuse factor for the cluster size N is
A
N
B
N2
C
1/N
D
1/N2
       Data-Communication       Cellular-Networks       UGC NET CS 2011 Dec-Paper-2
Question 42 Explanation: 
The frequency reuse factor is related to cluster size then the frequency reuse factor=1/N
Question 43
Handoff is the mechanism that
A
transfer an ongoing call from one base station to another
B
initiating a new call
C
dropping an ongoing call
D
none of above
       Data-Communication       Cellular-Networks       UGC NET CS 2011 Dec-Paper-2
Question 43 Explanation: 
Handoff is the mechanism that transfer an ongoing call from one base station to another.
Hard handover (or) Hard Handoff: Early systems used hard handoff. In a hard handoff, a mobile station only communicates with one base station. When the MS moves from one cell to another, communication must first be broken with the previous base station before communication can be established with the new one.
Soft handover (or) Soft Handoff: New systems use a soft Handoff. In this case, a mobile station can communicate with base stations at the same time. This means that, during handoff, a mobile station may continue with the new base station before breaking off from the old one.
Question 44
A telephone conference call is an example of which type of communications ?
A
same time / same place
B
same time / different place
C
different time / different place
D
different time / same place
       Data-Communication       Cellular-Networks       UGC NET CS 2011 Dec-Paper-2
Question 44 Explanation: 
A telephone conference call is an example of same time / different place type of communications.
Question 45
The diffusion current is proportional to
A
applied electric field
B
concentration gradient of charge carriers
C
square of electric field
D
cube of applied electric field
       Data-Communication       Diffusion-Current       NIELIT Junior Teachnical Assistant_2016_march
Question 46
For generating 1 MHμ frequency signal, the most suitable circuit is
A
phase shift oscillator
B
weinbridge oscillator
C
colpilt’s oscillator
D
audio oscillator
       Data-Communication       Colpitt’s-oscillator       NIELIT Junior Teachnical Assistant_2016_march
Question 47
In a two stage CE amplifier circuit, the ac collector resistance of the first stage depends on
A
the input impedance of first stage
B
the input impedance of second stage
C
load resistance only
D
none of the above
       Data-Communication       A/D-Converter       NIELIT Junior Teachnical Assistant_2016_march
Question 48
Class C amplifier is suitable for
A
a narrow frequency band
B
audio frequency
C
a wide frequency band
D
all the signals
       Data-Communication       amplifier       NIELIT Junior Teachnical Assistant_2016_march
Question 49
For a BJT, α and β are related to
A
β =α/(1−α)
B
β =α/(1+α)
C
β =1/(1+α)
D
α=β/(1+β)
       Data-Communication       BJT       NIELIT Junior Teachnical Assistant_2016_march
Question 50
Power spectral density of white noise
A
is constant with frequency
B
increases with frequency
C
decreases with frequency
D
varies exponentially with frequency
       Data-Communication       Power-Spectral-Density       NIELIT Junior Teachnical Assistant_2016_march
Question 51
The VHF frequency range is
A
30 to 300 KHμ
B
3 to 30 MHμ
C
30 to 300 MHμ
D
300 to 3000 MHμ
       Data-Communication       VHF       NIELIT Junior Teachnical Assistant_2016_march
Question 52
Vestigial sideband is most commonly used in
A
radio
B
telephony
C
television transmission
D
all of the above
       Data-Communication       Vestigial-sideband       NIELIT Junior Teachnical Assistant_2016_march
Question 53
In a uniform plane wave E and H are related by
A
E / H = 1
B
E/H =√ ∈/μ
C
E / H = π
D
E / H = √ μ / ∈
       Data-Communication       Waveform       NIELIT Junior Teachnical Assistant_2016_march
Question 54
The buffer amplifier should have
A
low output impedance and low input impedance
B
low output impedance and high input impedance
C
high output impedance and low input impedance
D
high output impedance and high input impedance
       Data-Communication       amplifier       NIELIT Junior Teachnical Assistant_2016_march
Question 55
When a reverse bias is applied to a P-n junction the width of the depletion layer:
A
Remains the same
B
Is increased
C
Is decreased
D
May increase or decrease
       Data-Communication       p-n-junction       NIELIT Junior Teachnical Assistant_2016_march
Question 56
The potential divides method of biasing is employed in amplifiers in order to
A
Reduce the cost of the circuit
B
Reduce the dc base circuit
C
Limit the input ac signal going to the base
D
Make the operating point almost independent of β
       Data-Communication       amplifier       NIELIT Junior Teachnical Assistant_2016_march
Question 57
The maximum efficiency of class B amplifier is
A
25%
B
50%
C
78.5%
D
88%
       Data-Communication       amplifier       NIELIT Junior Teachnical Assistant_2016_march
Question 58
In frequency modulation
A
The frequency of the carrier remains constant
B
The amplitude of the carrier remains constant
C
The amplitude of the carrier wave is varied
D
The frequency of the carrier is made equal to the signal frequency
       Data-Communication       amplifier       NIELIT Junior Teachnical Assistant_2016_march
Question 59
An 8-bit digital to analog converter has a maximum output voltage of 2v. If input voltage is 1.5v, the digital output at the end of conversion will be
A
0001 1111
B
0110 0001
C
1111 1000
D
1100 0000
       Data-Communication       A/D-Converter       NIELIT Junior Teachnical Assistant_2016_march
Question 60
An inductor
A
Allows a.c. to pass but blocks d.c.
B
Allows d.c. to pass but blocks a.c.
C
Allows a.c. and d.c. to pass
D
Blocks d.c. as well as a.c
       Data-Communication       A/D-Converter       NIELIT Junior Teachnical Assistant_2016_march
Question 61
Two resistors R1 = 60KΩ and R2 = 12KΩ are connected in parallel. Their effective resistance is
A
5 K Ω
B
60 Ω KΩ
C
12 K Ω
D
10 K Ω
       Data-Communication       Resisters       NIELIT Junior Teachnical Assistant_2016_march
Question 62
The demand factor for the electrical system is the ratio of
A
Max demand to connected load
B
Max demand to average load
C
Average power to max power
D
Reactive power to total power
       Data-Communication       Demand-Factors       NIELIT Junior Teachnical Assistant_2016_march
Question 63
Which of the following theorems is a manifestation of the law of conservation of energy
A
Tellegen’s theorem
B
Reciprocity theorem
C
Thevenin’s theorem
D
Norton theorem
       Data-Communication       Tellegen’s-Theorem       NIELIT Junior Teachnical Assistant_2016_march
Question 64
In wave connected windings, the number of poles is
A
A=2
B
A=4
C
A=6
D
A=8
       Data-Communication       Waveform       NIELIT Junior Teachnical Assistant_2016_march
Question 65
The _______ measures the number of lost or garbled messages as a fraction of the total sent in the sampling period.
A
Residual Error rate
B
Transfer failure probability
C
Connection release failure probability
D
Connection establishment failure probability
       Data-Communication       Residual-Error-rate       NIELIT Junior Teachnical Assistant_2016_march
Question 66
If carrier modulated by a digital bit stream, has one one of the possible phase of 0, 90, 180 and 270 degrees, then modulation called
A
BPSK
B
QPSK
C
QAM
D
MSK
       Data-Communication       Quadrature-Amplitude-Modulation       UGC NET CS 2011 June-Paper-2
Question 66 Explanation: 
We can easily differentiate by using name itself
→ Binary phase-shift keying (BPSK) possible phases are 00 and 1800.
→ Quadrature phase-shift keying (QPSK) possible phases are 00, 900, 1800 and 2700.
→ Minimum Shift keying(QSM), the two carrier waves of the same frequency are out of phase with each other by 90°, a condition known as orthogonality and as quadrature.
→ Quadrature Amplitude Modulation(QAM) mapping changes in continuous phase. Each bit time, the carrier phase changes by ±90°
Question 67
A smart modem can dial, hangup and answer incoming calls automatically. Can you tell who provides the appropriate instructions to the modem for this purpose ?
A
Communication software
B
Error detection protocols
C
Link access procedure (LAP)
D
Telecommunications
       Data-Communication       Modem       UGC NET CS 2011 June-Paper-2
Question 67 Explanation: 
A smart modem can dial, hangup and answer incoming calls automatically. Communication software provides the appropriate instructions to the modem for this purpose.
Question 68
The thermionic emission current is given by
A
maxwell’s equation
B
Fermi-Dirac distribution
C
Langmuir child law
D
Richardson Dushman equation
       Data-Communication       Richardson-Dushman-equation       NIELIT Technical Assistant_2016_march
Question 69
Zener breakdown occurs
A
due to rupture of covalent bonds
B
due to thermally generated minority carriers
C
in lightly doped junctions
D
only in germanium diodes
       Data-Communication       Zener-breakdown       NIELIT Technical Assistant_2016_march
Question 70
Negative feedback in an amplifier
A
increase noise
B
reduce bandwidth
C
reduce gain
D
increase distortion
       Data-Communication       amplifier       NIELIT Technical Assistant_2016_march
Question 71
The gain of a bipolar transistor drops at high frequencies because of
A
early effect
B
parasitic inductive elements
C
high current in base
D
transistor capacitance
       Data-Communication       Bipolar-Transistor       NIELIT Technical Assistant_2016_march
Question 72
The main application of enhancement mode MOSFET is in
A
oscillator circuits
B
amplifier circuits
C
clipper circuit
D
switching circuits
       Data-Communication       MOSFET       NIELIT Technical Assistant_2016_march
Question 73
Transducer is a device which
A
amplifies a given electrical signal
B
transfer an electrical signal from one place to another
C
translates a physical parameter into suitable electrical quantity
D
changes the waveform of an electrical signal
       Data-Communication       Transducer       NIELIT Technical Assistant_2016_march
Question 74
N-channel FETs are considered better than p-channel FETs because
A
they consume less power
B
they have high switching time
C
mobility of electrons is greater than that of holes
D
they consume less power
       Data-Communication       N-channel/p-channel-FETs       NIELIT Technical Assistant_2016_march
Question 75
In a 4-bit weighted resistor D/A converter, resistor value corresponding to LSB is 16 k ohm. The resistor value corresponding to MSB is
A
32 k ohm
B
15 k ohm
C
64 k ohm
D
2 k ohm
       Data-Communication       A/D-Converter       NIELIT Technical Assistant_2016_march
Question 76
In a digital circuit, the clock is a
A
Flip-clop
B
Inverter
C
Monostable multivibrator
D
Free running multivibrator
       Data-Communication       Multivibrator       NIELIT Technical Assistant_2016_march
Question 77
In FM modulation pre-emphasis is done for
A
low frequency components
B
high frequency components
C
middle frequency components
D
all frequency components
       Data-Communication       FM-Signal       NIELIT Technical Assistant_2016_march
Question 78
When modulation index of AM wave is increased from 0.5 to 1, the transmitted power
A
increases by 25%
B
increases by 33.3%
C
increases by 50%
D
remains same
       Data-Communication       Waveform       NIELIT Technical Assistant_2016_march
Question 79
A waveguide behaves as
A
high pass filter
B
low pass filter
C
band pass filter
D
all pass filter
       Data-Communication       Waveform       NIELIT Technical Assistant_2016_march
Question 80
In a lossless RLC circuit the transient current is
A
sinusoidal
B
square wave
C
triangular wave
D
non-oscillating
       Data-Communication       Waveform       NIELIT Technical Assistant_2016_march
Question 81
In an ac circuit, the maximum and minimum values of power factor can be
A
10 and 1
B
1 and -1
C
1 and 0
D
Any positive value
       Data-Communication       A/D-Converter       NIELIT Technical Assistant_2016_march
Question 82
In an RC coupled amplifier, the voltage gain
A
Remains almost constant over a range of frequencies
B
Always increases with frequency
C
Always decreases with frequency
D
Is independent of frequency
       Data-Communication       amplifier       NIELIT Technical Assistant_2016_march
Question 83
To generate a 1 MHz signal, the most suitable oscillator is
A
Colpitt’s oscillator
B
Phase shift oscillator
C
Wien bridge oscillator
D
None of these
       Data-Communication       Colpitt’s-oscillator       NIELIT Technical Assistant_2016_march
Question 84
Kirchoff’s laws are applicable to
A
d.c. circuits only
B
a.c. circuits only
C
both a.c. and d.c. circuits
D
none of the above
       Data-Communication       Kirchoff’s-laws       NIELIT Technical Assistant_2016_march
Question 85
When a mobile telephone physically moves from one to another cell, the base station transfers ownership to the cell getting strongest signal. This process is known as _______.
A
handoff
B
mobile switching
C
mobile routing
D
cell switching
       Data-Communication       Cellular-Networks       UGC NET CS 2013 June-paper-2
Question 85 Explanation: 
→ When a mobile telephone physically moves from one to another cell, the base station transfers ownership to the cell getting strongest signal. This process is known as handoff.
Hard handover (or) Hard Handoff: Early systems used hard handoff. In a hard handoff, a mobile station only communicates with one base station. When the MS moves from one cell to another, communication must first be broken with the previous base station before communication can be established with the new one.
Soft handover (or) Soft Handoff: New systems use a soft Handoff. In this case, a mobile station can communicate with base stations at the same time. This means that, during handoff, a mobile station may continue with the new base station before breaking off from the old one.
Question 86
The materials having low retentivity are suitable for making
A
Temporary magnets
B
Permanent magnets
C
Weak magnets
D
None of these
       Data-Communication       magnets       NIELIT Technical Assistant_2016_march
Question 87
Which of the following is the fastest analog to digital converter
A
Flash ADC
B
Dual slope ADC
C
Successive approximation ADC
D
Counter type ADC
       Data-Communication       A/D-Converter       NIELIT Technical Assistant_2016_march
Question 88
Open circuit test on transformer is conducted to determine
A
Core losses
B
Copper Losses
C
Eddy Current losses
D
Hysteresis Losses
       Data-Communication       Transformer       NIELIT Technical Assistant_2016_march
Question 89
Which of the following is not a standard RS-232C signal ?
A
RTS
B
CTS
C
DSR
D
VDR
       Data-Communication       VDR       NIELIT Technical Assistant_2016_march
Question 90
An astable multivibrator has
A
one stable state
B
two stable states
C
no stable states
D
none of these
       Data-Communication       multivibrator       UGC NET CS 2010 Dec-Paper-2
Question 90 Explanation: 

Question 91
Frequency shift keying is used mostly in
A
Radio transmission
B
Telegraphy
C
Telephone
D
None of the above
       Data-Communication       Transmission-method       UGC NET CS 2010 Dec-Paper-2
Question 91 Explanation: 
The technology is used for communication systems such as telemetry, weather balloon radiosondes, caller ID, garage door openers, and low frequency radio transmission in the VLF and ELF bands.
Question 92
The threshold effect in demodulator is
A
exhibited by all demodulator, when the input signal to noise ratio is low.
B
the rapid fall on output signal to noise ratio when the input signal to noise ratio fall below a particular value.
C
the property exhibited by all A.M. suppressed carrier coherent demodulator.
D
the property exhibited by correlation receiver.
       Data-Communication       Modem       UGC NET CS 2010 Dec-Paper-2
Question 92 Explanation: 
The threshold effect in demodulator is the rapid fall on output signal to noise ratio when the input signal to noise ratio fall below a particular value.
Question 93
A leased special high-speed connection from the local telephone carrier for business users that transmits at 1.544 mbps is known as________ carrier.
A
T1
B
T2
C
T3
D
T4
       Data-Communication       Cellular-Networks       UGC NET CS 2010 June-Paper-2
Question 93 Explanation: 

Question 94
To employ multi-access in GSM, users are given different :
A
time slots
B
bandpass filters
C
handsets
D
frequency bands
       Data-Communication       Cellular-Networks       UGC NET CS 2009-June-Paper-2
Question 94 Explanation: 
To employ multi-access in GSM, users are given different frequency bands.
Question 95
GSM/CDMA systems :
A
are limited to very low speed data
B
require no local loop wires
C
are predominantly used for voice
D
all of the above
E
Option A & C
       Data-Communication       Multiplexing        UGC NET CS 2009-June-Paper-2
Question 95 Explanation: 
→ GSM offers very low speed data service because mobility management in wide area network is the main focus in GSM.
→ GSM/CDMA systems are predominantly used for voice.
Question 96
Assertion (A) :  Cellular telephone systems can handle a multitude of users.
Reasoning (R) : Cellular telephone systems permit extensive frequency reuse in a small local area.
A
Both (A) and (R) are true and (R) is the correct explanation for (A)
B
Both (A) and (R) are true but (R) is not the correct explanation
C
(A) is true but (R) is false
D
(A) is false but (R) is true
       Data-Communication       Cellular-Networks       UGC NET CS 2008 Dec-Paper-2
Question 96 Explanation: 
Cellular telephone systems can handle a multitude of users because cellular telephone systems permit extensive frequency reuse in a small local area.
Question 97
In a mobile communication system, a geographic region is divided into cells. For each frequency set, there is a buffer __________ wide where that frequency is not used.
A
one-cell
B
two-cells
C
three-cells
D
four-cells
       Data-Communication       Cellular-Networks       UGC NET CS 2008-june-Paper-2
Question 97 Explanation: 
In a mobile communication system, a geographic region is divided into cells. For each frequency set, there is a buffer two cells wide where that frequency is not used.
Question 98
Consider a typical mobile communication system. If 840 frequencies are available, how many can be used in a given cell ?
A
140
B
120
C
84
D
60
       Data-Communication       Cellular-Networks       UGC NET CS 2007-Dec-Paper-2
Question 98 Explanation: 

Question 99
TDM is __________ .
A
A primary/secondary type protocol
B
A peer/peer protocol
C
A Non-priority peer/peer protocol
D
A priority type protocol
       Data-Communication       Multiplexing        UGC NET CS 2007 June-Paper-2
Question 99 Explanation: 
TDM:
1. TDM stands time division multiplexing.
2. Cross talk like problem not occurs in TDM.
3. TDM requires channel synchronization
4. TDM has greater noise immunity.
→ TDM is a non-priority peer/peer protocol.
Question 100
Which technical concept sets cellular apart from all preceding mobile/radio systems ?
A
FM-Transmission
B
Duplex Functionality
C
Frequency Reuse
D
TDMA Technology
       Data-Communication       Cellular-Networks       UGC NET CS 2007 June-Paper-2
Question 100 Explanation: 
→ TDMA sets cellular apart from all preceding mobile/radio systems.
TDM:
1. TDM stands time division multiplexing.
2. Cross talk like problem not occurs in TDM.
3. TDM requires channel synchronization
4. TDM has greater noise immunity.
→ TDM is a non-priority peer/peer protocol.
Question 101
The U-NII (Unlicensed National Information Infrastructure) band operates at the<__________ frequency :
A
2.4 GHz
B
33 MHz
C
5 GHz
D
16 GHz
       Data-Communication       Radio-Transmission       UGC NET CS 2007 June-Paper-2
Question 101 Explanation: 
The Unlicensed National Information Infrastructure (U-NII) radio band is part of the radio frequency spectrum used by IEEE 802.11a devices and by many wireless ISPs. It operates over following ranges:

Question 102
Which digital radio technology employs an N = 1 frequency-reuse plan ?
A
GSM
B
TDMA
C
D AMPS
D
CDMA
       Data-Communication       Cellular-Networks       UGC NET CS 2007 June-Paper-2
Question 102 Explanation: 
Cellular CDMA systems can use N=1(it means the same frequency is used in all cells)
Question 103
Quadrature Amplitude Modulation means changing both:
A
Frequency and phase of the carrier.
B
Frequency and Amplitude of the carrier.
C
Amplitude and phase of the carrier.
D
Amplitude and Wavelength of the carrier.
       Data-Communication       Quadrature-Amplitude-Modulation       UGC NET CS 2017 Nov- paper-3
Question 103 Explanation: 
Quadrature Amplitude Modulation means changing both amplitude and phase of the carrier.
Question 104
Match the following:

A
(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
B
(a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
C
(a)-(i), (b)-(iii), (c)-(ii), (iv)-(iv)
D
(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
       Data-Communication       PCM       UGC NET CS 2016 July- paper-3
Question 104 Explanation: 
Line coding→ Process of converting digital data to digital signal

Block coding→ Provide redundancy to ensure synchronization and inherits error detection

Scrambling→ Provides synchronization without increasing number of bits

Pulse code modulation→ A technique to change analog signal to digital data

Question 105
Consider a discrete memoryless channel and assume that H(x) is the amount of information per symbol at the input of the channel; H(y) is the amount of information per symbol at the output of the channel; H(x|y) is the amount of uncertainty remaining on x knowing y; and I (x; y) is the information transmission. Which of the following does not define the channel capacity of a discrete memoryless channel ?
A
max I(x; y)

p(x)

B
max [H(y) – H(y|x)]

p(x)

C
max [H(x) – H(x|y)]

p(x)

D
max H(x|y)

p(x)

       Data-Communication       Channel-Capacity       UGC NET CS 2016 July- paper-3
Question 105 Explanation: 
Transmission rate over a noisy channel:

→ H(X) is the amount of information per symbol at the input of the channel.

→ H(Y) is the amount of information per symbol at the output of the channel.

→ H(X|Y) is the amount of uncertainty remaining on X knowing Y.

The information transmission is given by:

I(X;Y) = H(X)−H(X|Y) bits/channel use

For an ideal channel X = Y, there is no uncertainty over X when we observe Y. So all the information is transmitted for each channel use: I(X;Y) = H(X) If the channel is too noisy, X and Y are independent. So the uncertainty over X remains the same knowing or not Y, i.e. no information passes through the channel: I(X;Y) = 0.

Capacity of a noisy channel:



Question 106
Which of the following is not a lossy compression technique?
A
JPEG
B
MPEG
C
FFT
D
Arithmetic coding
       Data-Communication       Arithmetic-Coding       UGC NET CS 2015 Dec - paper-3
Question 106 Explanation: 
JPEG( Joint Photographic Experts Group) is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality
MPEG (Moving Picture Experts Group): It is a method of lossy compression for coding audio-visual information (e.g., movies, video, music).
Arithmetic coding is a form of entropy encoding used in lossless data compression. Normally, a string of characters such as the words "hello there" is represented using a fixed number of bits per character, as in the ASCII code. When a string is converted to arithmetic encoding, frequently used characters will be stored with fewer bits and not-so-frequently occurring characters will be stored with more bits, resulting in fewer bits used in total.
Question 107
Which of the following steps is/are not required for analog to digital conversion?
(a)Sensing
(b)Conversion 
(c)Amplification
(d)Conditioning 
(e)Quantization
A
(a) and (b)
B
(c) and (d)
C
(a), (b) and (e)
D
None of the above
       Data-Communication       A/D-Converter       UGC NET CS 2015 Dec - paper-3
Question 107 Explanation: 

There are 107 questions to complete.
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