Definition
The four-digit transponder code (7600) that a pilot sets on the aircraft transponder to alert air traffic control to a two-way radio communications failure. When ATC sees 7600 on radar, they know the pilot can no longer communicate by radio and will adjust handling, clear other traffic, and provide assistance based on lost-communication procedures.
Plain English
A special code you dial into your transponder to tell controllers, without using the radio, that your radio has failed.
Context Anchor
Used during communication system malfunctions, especially when flying under air traffic control and normal radio contact is lost.
Derivation
Transponder comes from 'transmitter' + 'responder' — a device that responds with a coded signal when interrogated by ATC radar. The specific number 7600 is one of three reserved emergency codes (7500 hijack, 7600 lost comms, 7700 general emergency), chosen to be easy to remember and rarely set by accident.
Why Pilots Care
Squawking 7600 lets ATC provide radar vectors, altitude assignments, and approach clearances without waiting for radio acknowledgments.
Intuition Check
Do not read 7600 as a general emergency code. In aviation, transponder code 7600 specifically means lost radio communication.
Example Sentence 1
After both radios went silent, the pilot squawked 7600 and continued the flight using lost-communication procedures.
Example Sentence 2
The tower observed the 7600 code on radar and prepared light-gun signals for the arriving aircraft.