Basic Block Diagram of Communication System:
The Basic Block Diagram of Communication System is shown in Fig. 22.1. The essential components of a communication system are information source, input transducer, transmitter, communication channel, receiver and destination.
As already mentioned above, a communication system serves to communicate a message or information. This 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, pictures etc. However, out of these messages, only the desired message is selected and conveyed or communicated. It means that the function of information source is to produce required message which is to be transmitted.
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 required to convert it into a time-varying electrical signal. For instance, in case of radio broadcasting, a microphone converts the information or message which is in the form of sound waves into corresponding electrical signal. The transmitter processes the incoming information so as to make it suitable for transmission and subsequent reception. Transmitter is a collection of electronic circuits designed to convert the information into a signal suitable for transmission.
With reference to the basic block diagram of communication system given in Fig. 22.1, the term channel means the medium through which the message travels from the transmitter to the receiver. In other words, it can be said that the function of the channel is to provide a physical connection between the transmitter and the receiver. Noise may interfere with signal at any point in the communication system but its impact is most noticeable when it occurs in the channel or at the input of the receiver. When the noise is severe, it can make the information useless.
The function of a receiver is to receive the signal and perform a process which is reverse to what was done at transmitter stage. Destination is the final stage which is used to convert an electrical message signal into its original form. For example in radio broadcasting, the destination is a loudspeaker which operates as a transducer i.e., it converts the electrical signal in the form of original sound signal.