9.4 Line Configurations

A channel connecting a transmitter and a receiver can be of three types:

		Full duplex,
		half duplex and
		Simplex.

A full duplex channel allows for the simultaneous flow of data in both directions.

		Thus, two computers can simultaneously send and receive data from each other over a full duplex channel.
		This requires two transmission paths (e.g. two fiber optic cables).

A simplex channel supports communication in only one direction.

A channel that provides support in between full duplex and simplex channels is the half duplex channel which allows data to flow in either direction, but not in both directions at the same time.

Thus, when a half duplex channel between computer A and computer B is busy transferring data from A to B, computer B can send data to A only when the channel becomes idle.