Transmission mode is used to define the direction of flow between two linked devices. There are three types of transmission modes;
Simplex :- The communication is unidirectional, as on a one-way street. Only one of the two station/device on link can transmit; the other can only receive.
Half-duplex:- each station/device can transmit and receive but not at the same time. When one device is sending the other can only receive, and vice versa.
Full-Duplex:- both stations/devices can transmit and receive simultaneously.