transponder
trran-SPON-der
/trænˈspɒn.dər/
An electronic device on an aircraft that transmits an identifying signal and altitude data in response to radar interrogation.
Refers specifically to the avionics unit that automatically broadcasts flight identity and altitude.
The story behind the word. Coined in the 1940s as a blend of 'transmitter' and 'responder'. It combined Latin 'trans-' (across) and 'respondere' (to answer) to describe a device that transmits automated answers back to radar.
Word relationships
- beacon transmitter: A generic term for an emitting beacon, whereas a transponder specifically responds to radar interrogation.
Commonly confused with
- radar: Radar emits ground pulses to detect objects; a transponder sits on the plane and replies to radar.
Word family
- transpond (verb): To respond automatically to a radio interrogation signal.
Collocations
- transponder code
- squawk transponder
- transponder failure
- mode C transponder
Example sentences
- "The pilot set the transponder code to 7700 to indicate an inflight emergency to ground controllers." Avionics Systems
- "Without a working transponder, the aircraft appeared only as a faint primary target on the controller screen." Air Traffic Monitoring
Memory hook
TRANSmitter + resPONDER = TRANSPONDER. The plane digital automated ID tag.
When not to use
Do not confuse with a basic radio transmitter used for pilot voice communications.
Fun facts
- Squawk codes like 7500 (hijack), 7600 (radio loss), and 7700 (emergency) are standardized worldwide.
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