by Dinesh Thakur Category: Switching

Duplex is a telecommunications term for communication channels that can be between two devices simplex, half-duplex, or full-duplex.

Simplex mode the communication channels is unidirectional, Only one of the devices can transmit; the other devices  only can receive.

In half-duplex, both devices transmit and receive, but one at a time. : When one station can transmit, the other can only listen, and vice versa.
Half-duplex indicates that when you type a character on your keyboard, the character is displayed on your screen by your computer or terminal as it is sent to the remote computer or terminal. The half-duplex is used where no need for communication in both directions at the given time;

Full-duplex (also called duplex), both devices transmit and receive simultaneously, means that the character is sent to the remote computer, which then sends it back to display it on your screen. If your modem software is set for half-duplex, but the remote computer thinks you are full-duplex, each character you type will appear as two characters on your screen. Full-duplex is like the telephone network.