Digital Communications Multiple Choice Questions on “Error detection and correction 1”.
1. In layering, n layers provide service to
A. n layer
B. n-1 layer
C. n+1 layer
D. none of the mentioned
Answer: C
Clarification: In layering n layer provides service to n+1 layer and use the service provided by n-1 layer.
2. Which can be used as an intermediate device in between transmitter entity and receiver entity?
A. IP router
B. Microwave router
C. Telephone switch
D. All of the mentioned
Answer: D
Clarification: IP router, microwave router and telephone switch can be used as an intermediate device between communication of two entities.
3. Which has comparatively high frequency component?
A. Sine wave
B. Cosine wave
C. Square wave
D. None of the mentioned
Answer: C
Clarification: Square wave has comparatively high frequency component in them.
4. Which has continuous transmission?
A. Asynchronous
B. Synchronous
C. Asynchronous & Synchronous
D. None of the mentioned
Answer: B
Clarification: Synchronous has continuous transmission where as asynchronous have sporadic transmission.
5. Which requires bit transitions?
A. Asynchronous
B. Synchronous
C. Asynchronous & Synchronous
D. None of the mentioned
Answer: B
Clarification: Synchronous transmission needs bit transition.
6. In synchronous transmission, receiver must stay synchronous for
A. 4 bits
B. 8 bits
C. 9 bits
D. 16 bits
Answer: C
Clarification: In synchronous transmission, receiver must stay synchronous for 9 bits.
7. How error detection and correction is done?
A. By passing it through equalizer
B. By passing it through filter
C. By amplifying it
D. By adding redundancy bits
Answer: D
Clarification: Error can be detected and corrected by adding additional information that is by adding redundancy bits.
8. Which is more efficient?
A. Parity check
B. Cyclic redundancy check
C. Parity & Cyclic redundancy check
D. None of the mentioned
Answer: B
Clarification: Cyclic redundancy check is more efficient than parity check.
9. Which can detect two bit errors?
A. Parity check
B. Cyclic redundancy check
C. Parity & Cyclic redundancy check
D. None of the mentioned
Answer: B
Clarification: CRC is more powerful and it can detect various kind of errors like 2 bit errors.
10. CRC uses
A. Multiplication
B. Binary division
C. Multiplication & Binary division
D. None of the mentioned
Answer: C
Clarification: CRC uses more math like multiplication and binary division.