Definition
A ground-based radar system used by air traffic control that works together with an aircraft's transponder. The ground station sends out an interrogation signal; the aircraft's transponder receives it and replies with a coded signal containing the aircraft's identity (squawk code) and, if equipped with Mode C or Mode S, its pressure altitude. This reply gives controllers a stronger, clearer return on their radar scope than skin-paint radar alone, along with positive identification and altitude data.
Plain English
A radar setup where the ground station asks each aircraft 'who are you and how high are you?' and the aircraft's transponder answers automatically. This gives controllers a clean blip on their screen with the aircraft's ID number and altitude beside it.
Context Anchor
Seen in ATC radar services, transponder code assignments, altitude reporting, and equipment requirements for controlled airspace.
Derivation
Beacon' originally meant a signal fire or light used as a guide. Here, the aircraft's transponder acts as an electronic beacon — it lights up with a reply whenever the ground radar 'asks' it to, making the aircraft easy to spot and identify on the controller's screen.
Why Pilots Care
Provides positive identification and altitude data that primary radar alone cannot supply, enabling safe separation of traffic in controlled airspace.
Grounding Statement
A ground station sends a radio question, and the aircraft’s transponder sends back an automatic radio answer.
Intuition Check
Do not think of this as only a radar beam bouncing off the aircraft’s surface. This system depends on the aircraft’s transponder actively replying to ATC’s signal.
Example Sentence 1
Set your transponder to squawk 1200 with altitude reporting on so the Air Traffic Control Radar Beacon System can display your position and altitude to controllers.
Example Sentence 2
Primary radar showed a target, but the Air Traffic Control Radar Beacon System supplied the altitude needed for separation.