A. System Function
The system gives signals to the crew to help in the landing of the aircraft.
B. Sub-systems
(1) The Instrument Landing System (ILS) gives localizer and glideslope flight guidnace commands to the crew.
(2) The marker beacon system gives a signal to tell the crew when the aircraft is over a marker beacon. When over a beacon, the type of beacon (outer, middle or inner) is shown on the Electronic Flight Instrument System (EFIS). The audio system gives an audio identificaiton of the beacon.