The essential components of a communication system are information source, input transducer, transmitter, communication channel, receiver and destination.

1] Information source:

• The message or information originates in the information source.

• In general, there can be various messages in the form of words, group of words, code, symbols, sound signal, etc. however, out of these messages only the desired messages is selected and conveyed or communicated.

2] Input Transducer:

• A transducer is a device which converts one form of energy into another form.

• The message from the information source may or may not be electrical in nature. in a case when the message produced by the information source is not electrical in nature, an input transducer is used to convert it into a time varying electrical signal. for example, in case of radio-broadcasting, a microphone converts the information or message which is in the form of sound waves into corresponding electrical signal.

3] Transmitter:

• The function of the transmitter is to process the electrical signal from different aspects, for example in radio broad casting the electrical signal obtained from sound signals, is processed to restrict its range of audio frequencies and is often amplified.

• Modulation is the main function of the transmitter. In modulation, the message signal is super imposed upon the high frequency carrier signal.

• The channel and the noise:

• The term channel means the medium through which the message travels from the transmitter to the receiver, the function of the channel is to provide a physical connection between the transmitter and the receiver.

• There are two types of channels, namely point to point channels and broadcast channels, examples of point to point channel are wire lines, microwave links and optical fibers.

• The broadcast channels provide a capability where several receiving stations can be reached simultaneously from a single transmitter, an example from a single transmitter, an example of a broad cast channel is a satellite is geostationary which covers about one third of the earths surface.

5] Receiver:

• The main function of the receiver is to reproduce the message signal in electrical form from the distorted received signal.

• This reproduction of the original signal is accomplished by a process known as the demodulation or detection.

• Demodulation is the reverse process of modulation carried out in transmitter.

6] Destination:

• Destination is the final stage which is used to convert an electrical message signal into its original form. for example in radio broad casting,the destination is a loud speaker which works as a transducer i.e. it converts the electrical signal in the form of original sound signal.