Q. Basic elements of a digital communication system?

Figure illustrates the basic elements of a digital communication system. For each function in the transmitting station, there is an inverse operation in the receiver. The analog input signal (such as an audio or video signal) must first be converted to a digital signal by an analog-to-digital (A/D) converter. If no analog message is involved, a digital signal (such as the output of a teletype machine, which is discrete in time and has a finite number of output characters) can be directly input.

Encoding is a critical function in all digital systems. The messages produced by the source are usually converted into a sequence of binary digits. The process of efficiently converting the output of either an analog or a digital source into a sequence of binary digits is called source encoding or data compression.