Air Traffic Control
Squawk Codes Explained: Deciphering Transponder Emergency Signals (7500, 7600, 7700)
A complete breakdown of 4-digit octal transponder squawk codes assigned by ATC, emergency squawk protocol triggers, and automated radar alert systems.
7 min read Published
1. What is a Transponder Squawk Code?
A Squawk Code is a 4-digit octal number (ranging from 0000 to 7777) assigned by Air Traffic Control (ATC) to an aircraft's transponder. This 12-bit octal code allows Secondary Surveillance Radar (SSR) computers to instantly correlate raw radar target blips with flight plans, callsigns, and altitude data.
2. Critical Emergency Squawk Codes
Pilots undergo extensive training to memorize three universal emergency squawk codes that immediately trigger flashing red alerts across air traffic controllers' screens worldwide:
3. Standard Conspicuity Squawk Codes
- 1200: Visual Flight Rules (VFR) standard in North American airspace.
- 7000: VFR standard in ICAO European airspace.
- 2000: Oceanic entry code or unassigned IFR flight in uncontrolled airspace.
- 0000: Reserved code used for military intercept testing or transponder calibration.
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