duplexer

A duplexer is an electronic device that allows a single radio antenna to both transmit and receive signals alternately. It functions as a switching device, enabling this dual capability without needing separate antennas for transmitting and receiving. The term "duplexer" was first used around 1932.1

A related device, the diplexer, is a combining network, often a filter circuit or impedance bridge. It permits diplex transmission, meaning two signals can be sent or received simultaneously using the same antenna. For example, a simple diplexer can combine picture and sound signals for transmission through a single antenna.2