Half Duplex (HDX)

HDX uses a single path of communication for sending and receiving and is like a one-lane road, where only one car can move in one direction at a time, while a car at the opposite end of the lane must wait before driving. Similarly, HDX-based systems can send or receive in only one direction at a time and must wait for the completion of in-process communication before using the same channel to transmit in the opposite direction.

A Walkie Talkie is an example of a HDX device, where only one person at a time may talk or listen while using the device.