Transponder

A receiver-transmitter that will generate a reply signal upon proper interrogation.

An automatic device that receives, amplifies, and retransmits a signal on a different frequency. 2. An automatic device that transmits a predetermined message in response to a predefined received signal. Note: An example of transponders is in identification-friend-or-foe systems and air-traffic-control secondary radar (beacon radar) systems. 3. A receiver-transmitter that will generate a reply signal upon proper interrogation. [JP1]