In PCM system, N number of binary digits are transmitted per quantized sample. Hence BW and signalling rate are very large.

• These disadvantages can be overcome by delta modulation.

Delta modulator Transmitter :

The block diagram of a delta modulation transmitter is as shown below:

The operation of the circuit is as follows:

• X(t) is the analog e/p signal and x’(t) is the quantized version of X(-1). Both these signals are applied to a comparator.

• The comparator o/p goes high and it goes low if x(t) < x’(+). Thus the o/p is wither 1 or 0. The s + H circuit will hold thus level (0 or 1)

DM Receiver:

The block diagram of DM receiver is shown below. DM Receiver is identical to the chain of blocks producing x’(+) i.e. approximate signal. The original can be recovered back by passing this signal through a LPF.