Definition
A ground-based secondary surveillance radar system used by air traffic control to interrogate aircraft transponders and display the returned identification, altitude, and position information on a controller's radar scope.
Plain English
It's the radar equipment on the ground that 'pings' an aircraft's transponder and shows the controller who the aircraft is, where it is, and how high it's flying.
Context Anchor
Seen in older FAA acronym lists and in discussions of air traffic control radar and transponder-based tracking.
Derivation
Beacon' here refers to the aircraft transponder, which acts like a signaling beacon when triggered by a ground signal. The 'indicator' is the controller's display that shows the returned data. Together, the name describes a ground system that triggers and displays transponder replies.
Why Pilots Care
It enables controllers to identify and separate traffic accurately using transponder returns rather than primary radar alone.
Intuition Check
Do not read “beacon” here as a light or airport marker. In this term, it refers to the electronic signal exchange between ground equipment and an aircraft transponder.
Example Sentence 1
The controller's identification of the aircraft on radar relied on ATCBI returns from the transponder.
Example Sentence 2
Older radar facilities still rely on the ATCBI to track aircraft without primary radar contact.