Computer Science - Networking - Discussion

Full Duplex: A full duplex system can transmit data simultaneously in both directions on the transmission path. The full-duplex method is used to transmit the data over a serial communication link. Two wires needed to send data over a serial communication link layer. Full-duplex transmission, the channel capacity is shared by both communicating devices at all times. Both the connected devices can transmit and receive at the same time. Therefore it represents the truly bi-directional system. The link may contain two separate transmission paths one for sending and another for receiving.

Example of Full duplex mode:

Telephone networks operate in full duplex mode when two persons talk on the telephone line, both can listen and speak simultaneously.

A single line can be used for sending and receiving. So why two?

One is for sender and the other for receiver.

Can anyone explain?