MLS Components RNAV
The MLSMLS —Microwave Landing System used a precision DMEDME —Distance Measuring Equipment (the latest version) to calculate distance and thereby obtain a 3D fix by combining the distance with azimuth and elevation data.
If the DMEDME —Distance Measuring Equipment is not available, then the MLSMLS —Microwave Landing System gives the aircraft guidance in azimuth and elevation only, making it, effectively, an ILSILS —Instrument Landing System, with the same approach constraints.
The last MLSMLS —Microwave Landing System was turned over over a year ago having been made obsolete by superior technology. After you have passed the Radio Navigation exam, it is exceptionally unlikely you will hear about this system again.