AIM Text
Source: FAA Aeronautical Information Manual · current edition · paragraph 1-1-14.
Research Notes
AIM 1-1-14 covers Microwave Landing System (MLS) — a higher-precision landing system that was developed but largely not deployed.
Status: MLS was an ICAO standard developed in the 1980s as an ILS successor. Mostly not deployed in the U.S. — GPS/RNAV/LPV approaches have largely filled the need. Some MLS deployments exist internationally.
Reference: AIM 1-1-14 (historical reference).