middle marker

Aeronautics, Aerospace, Aviation, Business, Engineering, Natural sciences, Physical sciences A type of marker beacon placed to indicate the missed approach point of a Category I ILS or IGS approach (typically the point at which the glideslope descends through 200 feet AGL), triggering a continuous visual and aural sequence of alternating Morse code dots and dashes from the marker beacon receiver in the cockpit of an aircraft flying over the marker.