Definition of Transponder
A transponder is an electronic device carried in aircraft that responds to ground-based radar interrogation with a specific four-digit code that identifies the aircraft. In addition to this code, some transponders can also automatically transmit the altitude of the aircraft. This device uses radio frequencies to identify the aircraft on air traffic control radars, making it the airborne portion of the ATC radar beacon system.
The term “transponder” is a combination of “transmitter” and “responder”. It emits a radio signal in response to an interrogation from an external source, typically air traffic controllers or other aircraft. Whenever a pilot receives instructions from the air traffic controller, he will set a specific code on their transponder to “squawk” a code. For instance, “Speedbird 115 squawk 4552.”
Overall, a transponder is a vital component of the aircraft system as it allows air traffic control to identify and track the aircraft’s position in real-time.
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