Elements of a Communication System

Elements of a Communication System

Every communication system - no matter what it carries or how - is built from three essential blocks, with noise capable of entering and degrading the signal at any point along the way.

• Transmitter - converts the message signal from the information source into a form that suits the transmission channel. If the source itself does not produce an electrical signal (for example, sound or speech), a transducer first converts it into an electrical signal before the transmitter processes it.
• Channel - the physical medium connecting transmitter and receiver. It may be a wired medium (wires, cables) or a wireless medium (free space), and in either case it can distort the signal or add noise to it as it travels.
• Receiver - operates on the received signal (which may have been weakened or corrupted) to reconstruct a recognisable, usable version of the original message for the end user.

Figure 15.1 (block diagram) shows this chain: an information source feeds a message signal into the transmitter; the transmitter outputs a transmitted signal into the channel; the channel (drawn as the box through which noise can enter) delivers a received signal to the receiver; and the receiver recovers the message signal for the user of information. …