Keysight EXG and MXG X-Series Signal Generators User’s Guide 153Avionics VOR/ILS (Option 302)Using ILS Marker Beacon SoftkeysUsing ILS Marker Beacon SoftkeysAn ILS [Instrument Landing System] is a navigation system, used by aircraft toobtain guidance to a runway (performing a “runway approach”) and includesthe following three functions operating in tandem (working together):— ILS Localizer - ensures that the lateral/horizontal left-right approach of anaircraft is aligned with the center of a runway— ILS Glide Slope - ensures that the vertical descent path of an aircraft isaligned to the proper descent path (~ 3 degrees downwards slope) of arunway— ILS Marker Beacons - ensures the proper distance from a runway; thedistances are based on the Outer, Middle, and Inner ILS Marker BeaconsMarker Beacons are used to alert a pilot that an action is needed, such aschecking the aircraft altitude. Marker Beacon information is presented to pilotsby audio and visual information. The ILS Localizer may contain presentinformation on the Outer, Middle, and Inner ILS Marker Beacons. All ILS MarkerBeacons are broadcast at 75 MHz and are located at specific intervals along anILS approach. Each ILS Marker Beacon is identified by specific audio as well asvisual characteristics.Figure 5-16 ILS Marker Beacon SoftkeysILS Marker Beacon Code Color SoundOuter Marker _ _ _ Blue 400 Hztwo dashes per secondMiddle Marker ._._._ Amber 1300 Hzalternating dot and dashInner Marker . . . . White 3000 Hzdots only- Turns on and simulatesthe Inner Marker Beacon(3000 Hz modulation)- Turns on and simulatesthe Middle Marker Beacon(1300 Hz modulation)- Turns on and simulatesthe Outer Marker Beacon(400 Hz modulation)- Sets a Carrier Frequency by selecting an Index from 1 to 33.(Default: Index is 17 and corresponds to 75.000 MHz)- Sets the selected Marker Beacon, different from nominal:Inner=3000 Hz, Middle=1300 Hz, Outer=400 Hz(Range: 0 Hz to 10 MHz)- Sets the amplitude modulation depthon the Marker Beacon Carrier.(Range: 0 to 99%)- Turns off allMarker Beacon signals
