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22     The physical layer of a network

(a)    defines the electrical characteristics of signals passed between the computer and communication devices
(b)    control error detection and correction
(c)    constructs packet of data and sends them across the network
(d)    none of these

27. The application layer of a network

(a)    establishes ,maintains and terminates virtual circuits
(b)    defines user’s port into the network
(c)    consists of software being run on the computer
(d)    none of these

28.    A T-switch is used to

(a)    control how message are passed between computers
(b)    echo every character that is received
(c)    transmit characters one at a time
(d)    rearrange connections between computer equipments

29    which of the following divides the high speed signal into the frequency

(a)    T-switch
(b)    Modem
(c)    Frequency-division multiplexer
(d)    Time-division multiplexer

30     Bulletin board

(a)    is a public access message system
(b)    is a modem capable of accepting commands
(c)    converts analog signals into digital signals
(d)    converts digital signals into analog signals

31    A software that allows a personal computer to pretend it, as a terminal is

(a)   auto-dialing
(b)   bulletin board
(c)   modem
(d)   terminal emulation

32    A modem that is attached to the telephone system by jamming the phone’s hand-set into two flexible receptacles in the coupler is

(a)   gateway
(b)   bridge
(c)   acoustic coupler
(d)   time-division multiplexer

33    Modulation is the process

(a)    sending a file from one computer to another computer
(b)    converting digital signals to analog signals
(c)    converting analog signals to digital signals
(d)    echoing every character that is received

34     Demodulation is the process

(a)    converting digital signals to analog signals
(b)    converting analog signals to digital signals
(c)    combining many low speed channels into high speed channels
(d)    dividing the high speed signals into frequency

35    How many pairs of stations can simultaneously communicate on ETHERNET LAN?

(a)   1
(b)   2
(c)   3
(d)   Multiple

36    FDDI

(a)    ring network
(b)    star network
(c)    mesh network
(d)    bus based network

37    A distributed network configuration in which all data/information pass through a central computer
(a)    bus network
(b)    star network
(c)    duplex
(d)    multiplex

38    The communication mode that supports data in both directions at the same time
(a)   simplex
(b)   half duplex
(c)   duplex
(d)   multiply

39    A 6-MHZ channel is used by a digital signaling system utilizing 4-level signals. What is the maximum possible transmission rate?
(a) 1.5
(b) 6
(c) 12
(d) 24

40    Four bits are used for packet sequence numbering in a sliding window protocol used in a computer network. What is the maximum window size?

(a)    4
(b)    8
(c)    15
(d)    16

41    A station in a network forwards incoming packets by placing them on its shortest output queue. What routing algorithm is being used?

(a)    Hot potato routing
(b)    Flooding
(c)    Static routing
(d)    Delta routing

42    Two computers that communicate with each other use a simple parity check to detect errors for ASCII transmissions. Which of the following events will always lead to undetected errors?

(a)   one bit or any odd numbers of bits inverted in a block of data during transmission
(b)   Two bit or any even numbers of bits inverted in a block of data during transmission
(c)   one bit or any odd numbers of bits inverted in a byte of data during transmission
(d)   Two bit or any even numbers of bits inverted in a byte of data during transmission

43    RS-232-C

(a)   is an interface between two data circuit terminating equipment exemplified by a local and remote modem
(b)   is an interface standard between Data terminal Equipment and Data circuit Terminating Equipment
(c)   Specifies only the mechanical characteristics of an interface by providing 25-pin connector
(d)   Requires only 7 pin out of 25 in order to transmit digital data over public telephones

44    The probability that a single bit will be in error on a typical public telephone line using 4800 bps modem is 10-3. If no error detection mechanism is used, the residual error rate for a communication line using 9-bit frames is approximately equal to

(a)    0.003
(b)    0.009
(c)    0.991
(d)    0.999

45    The signal to noise ratio for a voice grade line is 30.1 db or a power ratio 0f 1023:1 The maximum achievable data rate on this line whose spectrum ranges from 300 Hz to 3400hz is

(a)   6200 bps
(b)   9600bps
(c)   34000bps
(d)   31000 bps

46    The residual error rate is the

(a)    number of bit errors per 24 hours of continuous operation on an asynchronous line
(b)    probability that one or more errors will be undetected when an error detection scheme is used
(c)    probability that one or more errors will be detected when an error detection mechanism is used
(d)    signal to noise ratio divided by the ratio of energy per to bit noise per hertz

47    Which layer of international standard organization OSI model is responsible for creating and recognizing frame boundaries?

(a)   physical layer
(b)   Data link layer
(c)   Transport layer
(d)   Network layer

48    If digital data rate of 9600 bps is encoded using 8-level phase shift keying (PSK) method, the modulation rate is
(a)   1200
(b)   3200
(c)   4800
(d)   9600

49. The path or channels over which information moves from one location to another make-up is called
(a)  Lines
(b) Remote computers
(c) Modems
(d) File transfers

50 Communications software package enable users to access services such as

(a)   electronic mail
(b)   electronic bulletin
(c)   video channels
(d)   both (a) and (b)


     26.A     27.C     28.D     29.C     30.A

31.D     32.C     33.B     34.B     35.A     36.A     37.B     38.C     39.C     40.C

41.A     42.D     43.B     44.B     45.D     46.B     47.B     48.B     49.A     50.D


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