U.S.: A marker beacon used with an instrument landing system (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 ft above the touchdown zone elevation, on the ILS CAT II approach. It also marks progress during a CAT III approach.