This is the Multiple Choice Questions in Chapter 8: Data Transmission from the book Electronic Communication Systems by Roy Blake
Start Practice Exam Test Questions
Choose the letter of the best answer in each questions.
MULTIPLE CHOICE
1. In practical terms, parallel data transmission is sent:
- a. over short distances only
- b. usually over long distances
- c. over any distance
- d. usually over a coaxial cable
ANS: A
2. The five-level teletype code was invented by:
- a. the Morkum Company
- b. the Teletype Company
- c. Western Union
- d. Emile Baudot
ANS: D
3. Data codes are also called:
- a. character codes
- b. character sets
- c. they do not have any other name
- d. both a and b
ANS: C
4. Digital data that is not being used to carry characters is called:
- a. FIGS data
- b. binary data
- c. numerical data
- d. all of the above
ANS: B
5. Character codes include:
- a. alphanumeric characters
- b. data link control characters
- c. graphic control characters
- d. all of the above
ANS: D
6. ASCII stands for:
- a. American Standard Character-set 2
- b. American Standard Code for Information Interchange
- c. American Standard Code 2
- d. Alphanumeric Standard Code for Information Interchange
ANS: B
7. BS, FF, and CR are examples of:
- a. nonstandard character codes
- b. escape characters
- c. control characters
- d. none of the above
ANS: C
8. LF stands for:
- a. Line Feed
- b. Link Feed
- c. Line Forward
- d. Link Forward
ANS: A
9. UART stands for:
- a. Universal Asynchronous Receiver-Transmitter
- b. Unidirectional Asynchronous Receiver-Transmitter
- c. Unaltered Received Text
- d. Universal Automatic Receiver for Text
ANS: A
10. In asynchronous transmission, the transmitter and receiver are:
- a. frame-by-frame synchronized using the data bits
- b. frame-by-frame synchronized using a common clock
- c. frame-by-frame synchronized using the start and stop bits
- d. not synchronized at all, hence the name "asynchronous"
ANS: C
11. In asynchronous transmission, the time between consecutive frames is:
- a. equal to zero
- b. equal to one bit-time
- c. equal to the start and stop bit-times
- d. not a set length
ANS: D
12. In synchronous transmission, the frames are:
- a. about the same length as ten asynchronous frames
- b. much longer than asynchronous frames
- c. 128 bytes long
- d. 1024 bytes long
ANS: B
13. Synchronous transmission is used because:
- a. no start and stop bits means higher efficiency
- b. it is cheaper than asynchronous since no UARTS are required
- c. it is easier to implement than asynchronous
- d. all of the above
ANS: A
14. In synchronous transmission, the receiver "syncs-up" with the transmitter by using:
- a. the clock bits
- b. the data bits
- c. the CRC bits
- d. a separate clock line
ANS: B
15. To maintain synchronization in synchronous transmission:
- a. long strings of 1s and 0s must not be allowed
- b. transmission must stop periodically for resynchronization
- c. the clock circuits must be precisely adjusted
- d. the channel must be noise-free
ANS: A
16. BISYNC:
- a. is an IBM product
- b. is a character-oriented protocol
- c. requires the use of DLE
- d. all of the above
ANS: D
17. HDLC:
- a. is an IBM product
- b. is a bit-oriented protocol
- c. is identical to SDLC
- d. all of the above
ANS: B
18. The use of flags in SDLC requires:
- a. "bit-stuffing"
- b. different flags at either end of a frame
- c. FEC
- d. ARQ
ANS: A
19. The initials ARQ are used to designate:
- a. automatic request for resynchronization
- b. automatic request for retransmission
- c. automatic receiver queue
- d. automatic request for queue
ANS: B
20. ARQ is used to:
- a. correct bit errors
- b. correct synchronization problems
- c. put data into a temporary buffer
- d. none of the above
ANS: A
21. FEC stands for:
- a. Fixed Error Control
- b. Forward Error Control
- c. Forward Error Correction
- d. False Error Condition
ANS: C
22. VRC is another name for:
- a. FEC
- b. ARQ
- c. LRC
- d. parity
ANS: D
23. CRC stands for:
- a. Control Receiver Code
- b. Correct Received Character
- c. Cyclic Redundancy Check
- d. Cycle Repeat Character
ANS: C
24. Huffman codes:
- a. allow errors to be detected but not corrected
- b. allow errors to be detected and corrected
- c. allow alphanumeric data to be corrected
- d. allow alphanumeric data to be compressed
ANS: D
25. Run-length encoding is used to:
- a. encrypt data
- b. compress data
- c. correct data
- d. none of the above
ANS: B
26. Public-key encryption:
- a. allows the use of digital signatures
- b. is used to convey symmetric keys
- c. avoids the "password problem"
- d. all of the above
ANS: D
27. SDLC stands for:
- a. Synchronous Data Link Control
- b. Synchronous Data Line Control
- c. Synchronous Data Link Character
- d. Synchronous Data Line Character
ANS: A
28. HDLC is:
- a. a bit-oriented protocol
- b. based on SDLC
- c. an ISO standard
- d. all of the above
ANS: D
COMPLETION
1. Parallel transmission can be used only for ____________________ distances.
ANS: short
2. The term "baud" was named after Emil ____________________.
ANS: Baudot
3. Data codes are also called ____________________ codes.
ANS: character
4. The ____________________ code is a 7-bit code commonly used in communication between personal computers.
ANS: ASCII
5. The two letters ____________________ designate the code character used to advance a printer to the next page.
ANS: FF
6. An asynchronous frame begins with the ____________________ bit.
ANS: start
7. An asynchronous frame ends with the ____________________ bit.
ANS: stop
8. At the end of an asynchronous frame, the line will be at the ____________________ level.
ANS:
mark
binary 1
9. An integrated circuit called a ____________________ is used in an asynchronous communication system to convert between parallel and serial data.
ANS: UART
10. When receiving digital data, ____________________ are used to hold data until they can be read.
ANS: buffers
11. Synchronous communication is more ____________________ than asynchronous since there are fewer "overhead" bits.
ANS: efficient
12. There must be sufficient 1-to-0 ____________________ to maintain synchronization in synchronous transmission.
ANS: transitions
13. Clock sync is derived from the stream of ____________________ bits in synchronous transmission.
ANS: data
14. In the ____________________ protocol, each frame begins with at least two SYN characters.
ANS: BISYNC
15. In HDLC, each frame starts with an 8-bit ____________________.
ANS: flag
16. The first eight bits of an SDLC frame are ____________________.
ANS: 01111110
17. BCC stands for ____________________ check character.
ANS: block
18. DLE stands for data link ____________________.
ANS: escape
19. HDLC uses bit-____________________ to prevent accidental flags.
ANS: stuffing
20. ____________________ errors cause many consecutive bits to be bad.
ANS: Burst
21. FEC stands for ____________________ error correction.
ANS: forward
22. An ____________________ scheme corrects errors by requiring the retransmission of bad blocks.
ANS: ARQ
23. Parity fails when an ____________________ number of bits are in error.
ANS: even
24. CRC codes are particularly good at detecting ____________________ errors.
ANS: burst
25. Huffman coding and run-length encoding are examples of data ____________________.
ANS: compression
26. A ____________________ is an encoding scheme that is not public in order to protect data.
ANS: cipher
27. A ____________________ is often used to generate an encryption key because it is easier to remember.
ANS: password
28. If the key is ____________________ enough, private-key encryption can be quite secure.
ANS: long
29. Messages cannot be ____________________ using a public key.
ANS: decrypted
30. Because it is ____________________-intensive, public-key encryption can be slow.
ANS: computation
SHORT ANSWER
1. How many different characters could be encoded using a six-bit code?
ANS:
64
2. What is the numerical difference between ASCII 'a' and ASCII 'A' if you treat them as hexadecimal (hex) numbers?
ANS:
20 hex (32 decimal)
3. The ASCII codes for the characters '0' through '9' are what hex numbers?
ANS:
30H to 39H
4. If an asynchronous frame is used to send ASCII characters in the form of bytes (8 bits), what is the shortest time it could take to send 1000 characters if each bit in a frame is 1 msec long?
ANS:
10 seconds
5. Suppose an asynchronous frame holds 8 bits of data, a parity bit, and two stop bits (it could happen). Calculate the efficiency of the communication system.
ANS:
66.7%
6. Suppose a synchronous frame has 16 bits of non-data in the front and a 16-bit BCC at the end. The frame carries 1024 bytes of actual data. Calculate the efficiency of the communication system.
ANS:
97.0%
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