This unit provides visual indication of the status of up to 30 lines or stations. If a line or station is in use (off-hook), the corresponding LED will light steady on the display. If line or station is ringing, the corresponding LED will flash. The LSM-30 consists of a control unit which mounts in the telephone equipment room and a display unit which connects to the control unit through simple two-pair modular connections. The LSM-10 is compatible with any Centrex and most PABX or Key Systems. It can also be used with Melco Services Observation Systems, allowing an observer to immediately identify the status of a line or station before accessing it observation. Mount the LSM-30 control unit in an apparatus cabinet, relay or on a wall.