Inner Marker
A marker beacon
used with an ILS (CAT II) precision approach located between the
middle marker and the end of the ILS runway, transmitting a
radiation pattern keyed at six dots per second and indicating to
the pilot, both aurally and visually, that he/she is at the
designated decision height (DH), normally 100 feet above the
touchdown zone elevation, on the ILS CAT II approach. It also marks
progress during a CAT III approach.