21. 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
E. None of the above
22. 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 transmit the data with stop and start bits.
D. they operate with a larger bandwidth
E. None of the above
23. A distributed network configuration in which all data/information pass through a central computer is
A. bus network
B. star network
C. ring network
D. Point-to-point network
E. None of the above
24. Which of the following TCP/IP protocol allows an application program on one machine to send a datagram to an application program on another machine?
A. UDP
B. VMTP
C. X.25
D. SMTP
E. None of the above
25. A remote batch-processing operation in which data is solely input to a central computer would require a:
A. telegraph line
B. simplex lines
C. mixedband channel
D. All the above
E. None of the above