Definition
On a radar display, the area lying between the two short parallel lines (control slashes) that bracket a Mode C altitude readout for a specific aircraft. Information appearing within this zone is the data the controller has associated with that target, such as altitude, computer-assigned data block content, and other tag information.
Plain English
It refers to the space on a radar screen between the two short marks the controller uses to frame an aircraft's data. Anything shown between those marks belongs to that aircraft.
Context Anchor
Seen in FAA glossary wording about how air traffic controllers judge whether two radar targets are visually separate on a radar display.
Derivation
A 'beacon' here is the transponder return on radar (from the Latin 'beacon', a signal). 'Control slashes' are the small slash-like marks framing the target's data. Knowing this makes the term self-explanatory: it's the area between the two slashes the controller uses to control which data belongs to which target.
Why Pilots Care
Enables exact location references when receiving taxi instructions or reporting position to ATC or ground control.
Analogy
It is like checking whether the ends of two short pencil lines on a page are touching or have clear space between them.
Intuition Check
This is not about the rotating airport beacon or a light on the field. Here, “beacon” means an aircraft transponder reply shown on an ATC radar display, and “slash” means the line-shaped mark on that display.
Example Sentence 1
The controller verified the aircraft's altitude by reading the value displayed between the ends of two beacon control slashes on the radar scope.
Example Sentence 2
We reported our position as between the ends of two beacon control slashes while waiting for the runway crossing clearance.