Definition
A ground-and-air radar system in which a ground interrogator transmits coded signals that trigger a reply from an aircraft transponder. The reply provides controllers with a stronger, clearer radar return than primary (skin-paint) radar, along with the aircraft's assigned identification code and, when Mode C is active, its pressure altitude.
Plain English
A radar setup where the ground station asks a question and the aircraft's transponder answers back. The answer tells the controller which aircraft it is and how high it is flying, making the radar picture much easier to read.
Context Anchor
Pilots encounter ATCRBS when using a transponder, setting an assigned code from ATC, selecting altitude-reporting mode, or reading about radar services and controlled airspace requirements.
Derivation
A 'beacon' is a signal sent out to be seen or heard. In ATCRBS, the aircraft acts like a small beacon that lights up only when the ground radar asks it to, replying with information rather than just reflecting energy back.
Why Pilots Care
Positive identification through ATCRBS allows controllers to provide separation, traffic advisories, and routing services.
Analogy
Think of ATCRBS like ATC asking, “Which aircraft are you?” and your aircraft’s transponder automatically answering with your assigned code and altitude information.
Intuition Check
Don't confuse this with regular (primary) radar. Primary radar bounces signals off the aircraft's skin. ATCRBS works only because the aircraft actively replies — if the transponder is off or failed, ATCRBS sees nothing.
Example Sentence 1
Before departure the pilot set the assigned squawk code so the aircraft would show up correctly on ATCRBS once airborne.
Example Sentence 2
With ATCRBS active in Mode C, the pilot's altitude appeared on the radar scope.