Definition
An aircraft radio receiver tuned to 75 MHz that detects signals from ground-based marker beacons positioned along an instrument landing system (ILS) approach. When the aircraft passes over a marker, the receiver activates a colored light and an audio tone in the cockpit, indicating the aircraft's position relative to the runway.
Plain English
A small radio in the aircraft that listens for signal beams shooting straight up from the ground at fixed points along an approach path. When you fly over one of these points, the receiver flashes a light and plays a tone so you know exactly where you are on the approach.
Context Anchor
Seen in instrument flying and navigation equipment discussions, especially with approaches that use outer, middle, or inner marker indications.
Derivation
Marker' comes from the idea of marking a specific spot — these beacons mark fixed points along the approach path. 'Beacon' originally meant a signal fire used to guide travelers; here it's a radio signal that guides aircraft. The receiver is the cockpit equipment that picks up that signal.
Why Pilots Care
Provides precise position fixes during low-visibility approaches without depending on other navigation aids.
Intuition Check
A marker beacon receiver does not steer the airplane or show a full route. It only alerts the pilot when the aircraft passes over a specific marker location.
Example Sentence 1
As the aircraft crossed the outer marker, the marker beacon receiver triggered a blue light and a steady audio tone in the cockpit.
Example Sentence 2
Audio tones from the marker beacon receiver confirmed passage over the middle marker during the ILS.