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ILS is designed to provide an approach path for exact alignment and descent of an aircraft on final approach to a runway. The ground equipment consists of two highly directional transmitting systems along with three (or fewer) marker beacons. The directional transmitters are known as the localizer and glide path transmitters. The system may be divided functionally into three parts: Guidance information - localizer, glide path Range information - marker beacons, Visual information - approach lights, touchdown and centreline lights, runway lights 1) The localizer transmitter, operating on one of the twenty ILS channels within the frequency range of 108,1 MHz to 111,9 MHz, emits signals which provide the pilot with course guidance to the runway centreline. Identification is in International Morse Code and consists of a three letter identifier preceded to the letter!(..) transmitted on the localizer frequency. Example: I – DIA _____2) The UHF glide path transmitter, operating on one of the twenty ILS channels within the frequency range 329.3 MHz to 335,0 MHz radiates its signals principally in the direction of the final approach. ____The glide slope transmitter is located between 750 feet and 1250 feet from the approach end of the runway (down the runway) and offset 400-500 feet from the runway centreline. It transmits a glide path beam 1,4 degrees wide. The term «glide path» means the portion of the glide slope intersecting the localizer. _____The glide path projection angle is normally adjusted to 3 degrees above horizontal so that it intersects the middle marker at about 200 feet and the outer marker at about 1400 feet above the runway elevation. _____The glide path facilities provide a signal which flares from 18-27 feet above the runway. Therefore, the glide path should not be expected to provide guidance completely to a touchdown point of the runway. ______3) Ordinarily, there are two marker beacons associated with an instrument landing system; the outer marker and middle marker. However, some locations may employ a third marker beacon to indicate the point at which the decision height should occur when used with a Category II ILS. ______The outer marker (OM) normally indicates a position at which an aircraft at the appropriate altitude on the localizer course will intercept the ILS glide path. The OM is modulated at 400 Hz and identified with continuous dashes at the rate of two dashes per second. ______The middle marker (MM) indicates a position at which an aircraft is approximately 3500 feet from the landing threshold. This will also be the position at which an aircraft on the glide path will be.at an altitude of approximately 200 feet above the elevation of the touchdown zone. The MM is modulated at 1300 Hz and identified with alternate dots and dashes keyed at the rate of 95 dot/dash combination per minute. ______The inner marker (IM), where installed, will indicate a point at which an aircraft is at a designated decision height (DH) on the glide path between the middle marker and landing threshold. The IM is modulated at 3000 Hz and identified with continuous dots keyed at the rate of six dots per second