What is "duplexer"

duplexer \du"plex*er\, n. (Radio) a device which switches electronic circuitry so that a radio antenna can function as either a transmitting or receiving antenna.

n. (context lang=en electronics) A device that enables communication in two directions over a single path.

A duplexer is an electronic device that allows bi-directional ( duplex) communication over a single path. In radar and radio communications systems, it isolates the receiver from the transmitter while permitting them to share a common antenna. Most radio repeater systems include a duplexer. Duplexers can be based on frequency (often a waveguide filter), polarization (such as an orthomode transducer), or timing (as is typical in radar).