Definition
A ground-based secondary surveillance radar system that interrogates aircraft transponders and receives coded replies, providing air traffic controllers with the aircraft's identity (via a four-digit beacon code) and, when Mode C is active, its pressure altitude. ATCRBS works in conjunction with primary radar but does not rely on reflected energy — it depends on an active transponder reply from each aircraft.
Plain English
It's the radar system that talks to your transponder. The ground station sends a signal asking 'who are you and how high are you?' and your transponder answers automatically. That's how controllers see your code and altitude on their screen.
Context Anchor
Seen in radar, transponder, and air traffic control discussions, especially when describing how controllers identify aircraft on their radar display.
Derivation
The name describes the parts: 'Air Traffic Control' (who uses it), 'Radar' (the underlying technology), and 'Beacon' (the transponder reply, which acts like a signal beacon answering the interrogation). 'Beacon' here means a small, deliberate signal sent in response — not a steady light or marker.
Why Pilots Care
Allows controllers to positively identify aircraft and receive reliable altitude information, enabling safe separation in controlled airspace.
Intuition Check
ATCRBS radar is not just ordinary radar bouncing off the airplane. It depends on the aircraft’s transponder answering the ground radar’s signal.
Example Sentence 1
When the controller assigned us a discrete code and told us to 'squawk and ident,' our transponder reply was picked up by the ATCRBS site and our data block appeared on her scope.
Example Sentence 2
ATCRBS supplements primary radar by providing discrete identification that primary returns alone cannot supply.