What Does Transponder Mean?

A transponder (XPDR, XPNDR, TPDR or TP) is an automated and electronic monitoring device that receives, cross examines, amplifies and retransmits incoming signals. A transponder is also a transceiver that generates reply signals upon proper electronic examination.


The transponder term is a blend of the words transmitter and responder.

Techopedia Explains Transponder

A transponder receives an interrogator signal and automatically transmits a radio wave signal at a predetermined frequency. Broadcast frequency signals, which are different than received signals, use a special frequency converter component for broadcasting.

Each communication satellite channel is a transponder and has separate transceivers or repeaters. Numerous audio and video channels may pass through a single transponder on a single wideband carrier with digital video data compression and multiplexing.

The transponder was first used on aircraft during World War II as part of the Identification Friend or Foe (IFF) system. Transponders are still used in military and commercial aviation.


Related Terms

Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…