Science Fair Project Encyclopedia Instrument Landing System - 1.
Localiser (LOC) - Informs the pilot with the airplane’s lateral
position relative to runway centreline. Localiser signals are
transmitted from beyond the departure end of the runway with a
horizontal antenna array. Course width is adjusted to provide
full scale deflection left or right at 350 feet off centerline
when over the approach end of the runway. Course width thus
varies with runway length, but nominally is 2.5 degrees each
side. It operates on frequences 108.0 to 111.95 MHz with the
channel width of 50kHz. - 2. Glideslope (GS) - Informs the pilot
with the airplane’s vertical position relative to the ideal
approach path. Glideslope antenna is located off one side of the
runway, approximately abeam the touchdown point (typically 1000
feet past the approach end of the runway.) Typical glideslope
signal has a 3 degree slope. The operating frequences reach from
329.15 to 335.0 MHz with the channel width being 150 kHz. - 3.
Outer marker - Situ