A transceiver is a device that has both a transmitter and a receiver which are combined and share common circuitry or a single housing. If no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s. Technically, transceivers must combine a significant amount of the transmitter and receiver handling circuitry. Similar devices include transponders, transverters, and repeaters.
Transceivers are called Medium Attachment Units (MAUs) in IEEE 802.3 documents.
Reference:
http://en.wikipedia.org/wiki/Transceiver
