Communication System: Physics of Electronic Communication Systems (Learn Physic)

The term communication refers to the transmitting, receiving and processing of information by electronic means.
Basic Communication System
A basic communication system consists of an information source, a transmitter, a link and a receiver.

(1) Information : The idea/message that is to be conveyed is information. The message may be individual one or a set of messages. The message may be a symbol, code, group of words or any pre decided unit.
(2) Transmitter : In radio transmission, the transmitter consists of a transducer, modulator, amplifier and transmitting anteena.
Transducer : Converts sound signals into electric signal.
Modulator : Mixing of audio electric signal with high frequency radio wave.
Amplifier :Boosting the power of modulated signal.

Anteena : Signal is radiated in the space with the aid of an anteena.
(3) Communication channel : The function of communication channel is to carry the modulated signal from transmitter to receiver. The communication channel is also called transmission medium or link.
The term channel refers to the frequency range allocated to a particular service or transmission.
Table 28.1 : Different channels
Type of communicationChannels or links
Radio communication Free space
Telephony and Telegraphy communication Transmission line
Optical communication Optical fibre

(4) Receiver : The receiver consists of
Pickup anteena : To pick the signal
Demodulator : To separate out the audio signal from the modulated signal
Amplifier : To boost up the weak audio signal
Transducer : To convert back audio signal in the form of electrical pulses into sound waves.


Types of Communication System
Communication systems can be classified according to the nature of information or mode of transmission or types of transmission channel.
(1) According to the nature of information source
(i) Speech transmission
(ii) Picture transmission
(iii) Facsimile transmission (FAX) : This involves exact reproduction of a document or picture which are static.
(2) According to the mode of transmission
(i) Analog communication : The communication system, which make use of analog signals are called analog communication system.