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3.1 Draw a block diagram of PCM clearly explaining how a basic frame structure is achieved in each block.

Bits/Time slot = 8
Total number of bits in the PCM frame = 8 * 32
Data rate of the frame = 256/125µs
  = 2.048Mbit/s
Time taken for one slot = 125/32
  = 3.9µs
Data rate of a slot = 8/3.9 µs
  = 64kBit/s

This gives a PCM frame of 32 time slots (each with 64Kbit/s rate) at a data rate of
2.048Mbit/s where time slot 0 is used for synchronizing while time slot 16 is used for

3.2 A PCM system will comprise of sampling, quantizing and encoding. Explain each block. clearly.

Sampling: Sampling a band limited analog signal at a frequency higher than twice the
maximum frequency of the analog signal

Quantizing: Non-linear quantizing of sampled values
Sampling Quantizing Encoding

Encoding: Assigning ‘0’s and ‘1’s for the quantized voltage levels

Sign: + or – (1-bit)
Segment No.: 3-bits
Level No.: 4-bits

3.3 Three consecutive voice samples in a 30 channel PCM system are identified as follows.
+50V, 0V, -68V
Draw the wave forms that you can observe in the transmission media, assuming HDB3 transcoding.
(Assuming A-Law compression for non-linear quantizing)