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The term "squitter" refers to a random broadcast of data occurring either intentionally or in response to noise.


Mode-S transponders automatically send periodic burst transmissions called "squitters". These transmissions are self generated and are not in response to interrogations from a secondary surveillance radar (SSR) system. The information sent in these burst transmission serves several purposes including:

  • Airborne Collision Avoidance System (ACAS) - Squitter information includes aircraft location and vertical speed. This information is used by ACAS systems on other aircraft to identify potential conflicts.
  • Automatic Dependent Surveillance Broadcast (ADS-B) - An extended squitter is a message or series of messages which broadcast an aircraft's identification, GPS position, projected aircraft trajectory and navigation system status to allow controllers to accurately track the aircraft.

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