11. What does PCM stand for in digital-to-digital conversion?
a) Pulse Code Modulation
b) Parallel Code Modulation
c) Phase Code Modulation
d) Packetized Code Modulation

12. In uni-polar encoding, how is binary 0 represented?
a) Positive voltage
b) Negative voltage
c) No voltage
d) Alternating voltage

13. What does NRZ stand for in polar encoding?
a) Non-Return to Zero
b) Negative Return to Zero
c) Neutral Return to Zero
d) Non-Repeating Zeroes

14. What does RZ stand for in polar encoding?
a) Return to Zero
b) Reduced Zeroes
c) Residual Zeroes
d) Repeating Zeroes

15. Which encoding scheme combines RZ and NRZ-L?
a) Manchester
b) Differential Manchester
c) Bipolar
d) Polar NRZ

16. How many voltage levels does bipolar encoding use?

a) One
b) Two
c) Three
d) Four

17. In block coding, what does mB/nB notation represent?
a) Data compression ratio
b) Data storage capacity
c) Substitution ratio
d) Substitution type

18. Which step comes after division in block coding?
a) Substitution
b) Combination
c) Encoding
d) Quantization

19. What is the primary purpose of quantization in PCM?
a) Sampling rate adjustment
b) Noise reduction
c) Amplitude approximation
d) Encoding efficiency

20. What is the minimum sampling rate according to the Nyquist theorem?
a) Equal to the highest frequency
b) Half the highest frequency
c) Twice the highest frequency
d) One-third of the highest frequency