Draw a block diagram of a generalized communication system. Write the functions of each of the following:
(a) Transmitter
(b) Channel
(c) Receiver
 

Block diagram of a generalized communication system

(a) Transmitter: It modifies the input signal for efficient transmission. The signal must pass through an electronic circuit containing noise filter, analog-to-digital converter, encoder, modulator and signal amplifier. The signal is amplified for transmission and then released as electromagnetic waves at the end of the circuit.
(b) Channel: It is the medium through which the signal travels. There are two types of media, either guided or unguided. Guided media can be directed from transmitter to receiver by means of connecting cables. Examples include optical (glass-like) fiber, coaxial cables, telephone wire, twisted-pairs, etc. Unguided media refers to any communication channel that creates space between the transmitter and receiver. For radio or RF communication, the medium is air. In case of sonar, the medium is usually water as sound waves travel efficiently through certain liquid media. Communication channels also include vacuum of space and solid pieces of metal.
(c) Receiver: It captures and reconstructs the signal before it passes through the transmitter (i.e. the A/D converter, modulator and encoder). This is done by passing the received signal through another circuit containing noise filter, digital-to-analog converter, decoder, demodulator and signal amplifier.