Quick Facts
- Type
- Avionics System
- Definition
- An electronic device that receives radar interrogations and transmits a coded...
- Used By
- Pilots, ATC
Definition#
A transponder is an airborne electronic device that receives an interrogation signal from ground-based radar and automatically transmits a reply containing identification (squawk code) and, in Mode C/S, pressure altitude.
Why It Matters Operationally#
Transponders enable secondary surveillance radar (SSR) and ADS-B, providing ATC with aircraft identity and altitude. They are required in most controlled airspace and for all IFR operations.