PCM:

The analog speech waveform is sampled and converted directly into a multibit digital code by an A/D converter. The code is stored and subsequently recalled for playback.

DM:

Only a single bit is stored for each sample. This bit 1 or 0, represents a greater than or less than condition, respectively as compared to the previous sample. An integrator is then used on the output to convert the stored nit stream to an analog signal.

• Figure (a) shows Delta modulation transmitter and (b) shows Delta modulation receiver.

• Delta modulation refers to the procedure of encoding and thereby transmitting only the difference between consecutive samples instead of sending each of the samples themselves.

• This method is useful only when the variation in the amplitude of the signal is small, otherwise, it leads to a phenomenon called "slope overload".

• Pulse code modulation is the procedure where each of the levels of an analog signal is assigned a value closest to a quantizer level used to quantize the signal.

• Another method of PCM that can be confused with Delta Modulation is the D(differential)PCM. Here, the difference between the signals is encoded based on its magnitude.