A directory of Objective Type Questions covering all the Computer Science subjects. Here you can access and discuss Multiple choice questions and answers for various compitative exams and interviews.

141. Which of the following is used for modulation and demodulation?
a. modem
b. gateway
c. protocols
d. multiplexer
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Answer: (a).modem

142. Which of the following types of channels moves data relatively slowly?
a. wideband channel
b. voiceband channel
c. broadband channel
d. narrowband channel
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Answer: (d).narrowband channel

143. Which of the following device is used to connect two systems, especially if the systems use different protocols?
a. hub
b. bridge
c. gateway
d. repeater
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Answer: (c).gateway

144. The synchronous modems are more costly than the asynchronous modems because
a. they produce large volume of data
b. they contain clock recovery circuits
c. they operate with a larger bandwidth
d. they transmit the data with stop and start bits
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Answer: (b).they contain clock recovery circuits

145. The cheapest modems can transmit
a. 100 bits per second
b. 300 bits per second
c. 600 bits per second
d. 900 bits per second
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Answer: (b).300 bits per second

146. Computers cannot communicate with each other directly over telephone lines because they use digital pulses whereas telephone lines use analog sound frequencies. What is the name of the device which permits digital to analog conversion at the start of a long distance transmission?
a. Modem
b. Interface
c. Attenuation
d. Teleprocessor
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Answer: (a).Modem

147. Demodulation is a process of
a. performing data description
b. converting analog to digital signals
c. converting digital to analog signals
d. multiplexing various signals into one high speed line signals
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Answer: (b).converting analog to digital signals

148. Demodulation is the process of
a. converting digital signals to analog signals
b. converting analog signals to digital signals
c. dividing the high-speed signals into frequency bands
d. combining many low speed channels into one high speed channel
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Answer: (b).converting analog signals to digital signals

149. A devices that links two homogeneous packet-broadcast local networks, is
a. hub
b. bridge
c. repeater
d. gateway
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Answer: (b).bridge

150. The physical layer, in reference to the OSI model, defines
a. the virtual circuit interface to packet-switched service
b. the interface between the X.25 network and packet mode device
c. data link procedures that provide for the exchange of data via frames that can be sent and received
d. All of the above
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Answer: (b).the interface between the X.25 network and packet mode device