A communication system consists of three basic parts
(i) transmitter
(ii) communication channel and
(iii) reciever.
The block diagram given below depicts the general form of a communication system.
In a communication system, the transmitter transmits the message signal. The purpose of the transmitter is to convert the message signal, produced by the source of information, into a form suitable for transmission through the relevant communication channel. This modification is often achieved by means of a process known as ‘modulation’.
The communication channel carriers the modulated wave, form, from the transmitter to the receiver. This ‘channel’ can be a transmission line (as in telephony), an optical fiber (as in optical communication) or merely ‘free space’ in which the signal is radiated as an electromagnetic wave (wireless communication).
The main purpose of a receiver is to reconstruct the original message from the ‘signal received by it, after propagation through the channel. This is accomplished by using a process known as ‘demodulation’; this process is the reverse of the ‘modulation’ process, used in the transmitter.
