This type of modulation is different from all modulations learnt so far. It is clear from the block diagram given at the top that it is a type of digital modulation. That is the signals here are sampled and sent in pulse form. A common feature among other techniques is that pulse code modulation also uses sampling technique. In this case, instead of sending a pulse train which is capable of continuously varying parameters, this type of generator produces a series of numbers or digits. Each digit in it represents the appropriate length of the sample at a particular instant.

Basic block diagram of its realisation is given below:

Advantages of PCM

• It is mainly used in long distant communication.
• Transmitter efficiency is more.
• It has higher noise immunity when compared to other methods.

Disadvantages of PCM

• More bandwidth is required when compared to analogue systems.
• In this method encoding, decoding and quantisation of the circuit have to be done. This makes it more complex.

Applications of PCM

• It is used in the satellite transmission system.
• It is also used in space communication.
• Used in Telephony.
• One of the recent applications is the compact disc.