These three are the channels of signal transmission between two connected devices
1. Simplex – it is more of like a one-way street, the signal travels only in one direction. The sender can say anything they want and receiver can hear it but they cannot reply to it or send any message of their own. Simplex channel is used mostly in Fiber Optic Communication. The full bandwidth of the optic fiber cable is used in the transmission and the full capacity of the channel can be disposed of in the process. Some of the examples of Simplex are Radio, where a Radio Jockey can convey his thoughts to a very large audience and the audience can only listen not reply, Television, where 2D and even 3D images are transmitted through the channel. While these two are for entertainment purpose, simplex is also used between computer and printer and keyboard to a computer monitor.
2. Half Duplex – in half-duplex, both the sender and the receiver can communicate but both of them need to wait for their respective turns. Signals can travel in both directions but only one by one. The first sender sends a signal and the receiver receives it and then replies. The full capacity of the channel is used in this process as well while data transfers from one direction to another.
The easiest example to understand half duplex is to take the example of a walkie-talkie where a push-button is used to transfer the data. When pressed, the push button turns on the transmitter and the receiver is turned off. While the opposite happens when the button is released and the receiver on the other end is free to transmit the data which will be received by the previous sender.
3. Full Duplex – this channel is more advanced from the previous two. Both directions can send and receive data at the same time. The capacity of the channel is shared by both directions simultaneously. However, the other way to make it a success is to provide it with two physically separate transmission paths to send and to receive data separately.
The most known example of the full-duplex is a telephone where two-person can transmit data at the same time and talk as if they are sitting together. The data is transferred from both sides simultaneously and that’s the end of the purpose, nonetheless, how much these two understand each other while both speaking at the same time totally depends on their personal capabilities.