- A unit which combines a radio transmitter and a receiver in the same housing, usually sharing certain circuits and components.
- A device which combines the functions of transmitter and a receiver. For example, that which enables a computer to both transmit and receive signals to and from a communications network.
- A device which both transmits and receives, as opposed to just performing either function. For example, a two-way pager.
- noun a combined radio receiver and transmitter