1. What is the main difference between DDCMP and SDLC?
a) DDCMP does not need special hardware to final the beginning of a message
b) DDCMP has a message header
c) SDLC has a IP address
d) SDLC does not use CRC

2. What is the number of separate protocol layers at the serial interface gateway specified by the X.25 standard?
a) 4
b) 2
c) 6
d) 3
e) none of the above

3. Layer one of the OSI model is?
a) physical layer
b) link layer
c) transport layer
d) network layer
e) none of above

4. The x.25 standard specifies a?
a) technique for start-stop data
b) technique for dial access
c) DTE/DCE interface
d) data bit rate
e) none of above

5. Which of the following communications lines is best suited to interactive processing applications?
a) narrow band channel
b) simplex lines
c) full duplex lines
d) mixed band channels

6. A communications device that combines transmissions from several I/O devices into one line is a ?
a) concentrator
b) modifier
c) multiplexer
d) full-duplex line

7. What is the minimum number of wires needed to send data over a serial communication link layer?
a) 1
b) 2
c) 4
d) 6
e) none of above

8. While transmitting odd-parity coded symbols, the number of zeros in each symbol is?
a) odd
b) even
c) a and b both
d) unknown

9. Avalanche photodiode receivers can detect bits of transmitted data by receiving?
a) 100 photons
b) 200 photons
c) 2000 photons
d) 300 photons

10.The receive equilizer reduces delay distortions using a?
a) tapped delay lines
b) gearshift
c) descrambler
d) difference engine