Q.71 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 an undetected error?
(A) one bit or any odd number of bits inverted in a block of data during transmission
(B) Two bits or any even number of bits inverted in a block during transmission
(C) one bit or any odd number of bits inverted in a byte during transmission.
(D) Two bits or any even number of bits inverted in a byte during transmission.
Q.72 RS-232-C.
(A) is an interface between two data circuit terminating equipment as exemplified by a local and remote modem.
(B) is an interface standard between Data Terminal Equipment and Data Circuit Terminating Equipment’s.
(C) specifies only the mechanical characteristics of an interface by providing a 25-pin connector.
(D) requires only 7 pins out of 25 in order to transmit digital data over public telephone lines.
Q.73 The probability that a single bit will be in error on a typical public tele-phone 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
Q.74 The signal to noise ratio for a voice grade line is 30.1 dB (Decibels) or a power ratio of 1023: 1. The maximum achievable data rate on this line whose spectrum ranges from 30 Hz to 3400 Hz is….
(A) 6200 bps
(B) 9600 bps
(C) 34000 bps
(D) 31000 bps
Q.75 The residual error rate is the…..
(A) number of bit errors per twenty-four 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 bit to noise per hertz.
Q.76 Which layer os 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
Q.77 If digital data rate of 9600 bps is encoded using 8-level phase shift keying (PSK) method, the modulation rate is….
(A) 1200 bauds
(B) 3200 bauds
(C) 4800 bauds
(D) 9600 bauds
Q.78 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 transfer
Q.79 Communications software package enable users to access services such as…
(A) electronic mail
(B) electronic bulletin boards
(C) video channels
(D) both (A) and (B)
Q.80 Which of the following are parameters that must be set in your software and modem before you can begin communications?
(A) speed
(B) character format
(C) duplex
(D) both (A) and (B)
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