Aviation Glossary - Outer Marker

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Outer Marker

A marker beacon at or near the glideslope intercept altitude of an ILS approach. It is keyed to transmit two dashes per second on a 400 Hz tone, which is received aurally and visually by compatible airborne equipment. The OM is normally located four to seven miles from the runway threshold on the extended centerline of the runway. (See INSTRUMENT LANDING SYSTEM.) (See MARKER BEACON.)

source: FAA Pilot/Controller Glossary

A marker beacon at or near the glide slope intercept altitude of an ILS approach. It is normally located four to seven miles from the runway threshold on the extended centerline of the runway.

source: FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25A)

an ILS marker beacon usually on the runway centreline, often coinciding with the final approach fix, approximately 4 to 7 miles from the runway threshold

source: ICAO English Pro Aviation Glossary

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