Originally Posted by OzExpat
The LOC is often associated with an ILS as either the OM or MM, or both, which might be cheaper than installing marker beacons - though I could stand to be corrected on that point.
The OM is a 75 MHz Fan Marker modulated to 400 Hz. The MM is identical but modulated to 1300 Hz and the IM to 3000 Hz. A Fan Marker gives no useful azimuth cues but a fairly precise distance from touch down indication, with a wide spread either side of the Approach Centre Line. As
captjns mentions, CLs and NDBs are often collocated with OMs and MMs.
For what it's worth,
GBZ