The Loop Maintenance Operations System (LMOS) is a telephone company trouble ticketing system to coordinate repairs of local loops (telephone lines).
When a problem is reported by a subscriber, it is filed and relayed through the Cross Front End, which is a link from the CRSAB (Centralized Repair Service Answering Bureau) to the LMOS network.
As LMOS is responsible for trouble reports, analysis, and similar related functions, MLT does the actual testing of customer loops.
[3] The LMOS database is a proprietary file system, designed with 11 access methods (variable index, index, hash tree, fixed partition file, etc.
The first port of LMOS was to Digital Equipment Corporation's PDP 11/70 machines and was completed in 1981.