( ii ) Communication Channel The medium through which information propagate from transmitter to receiver 1S called communication channel .
( iii ) Receiver It receives and decode the signal .
Analog Signal
A signal in which current or voltage changes its magnitude continuously with time , is called an analog signal .
Digital Signal
A signal in which current or voltage have only two values , is called a digital signal .
Note An analog signal can be converted suitable Into a digital signal and vice-versa .
Modulation
The process of superimposing the audio signal over a high frequency carrier wave is called modulation .
In the process of modulation anyone characteristic of carrier wave is varied in accordance with the instantaneous value of audio signal ( modulating signal ).
Need of Modulation