The Loss of Signal Alarm Inquiry Test verifies the synchronization status, echo cancellation, and continuity of the DS1 link.

A Loss of Signal Alarm indicates that the board is unable to derive the synchronization clock from the DS1 facility. If the board is administered as a timing source and it detects a Loss of Signal alarm, the board will stop providing the synchronization clock for the system and will transmit a Yellow alarm to the remote DS1 endpoint.

When the Loss of Signal alarm is confirmed, every trunk or port of the board is put into the out-of-service state. The inquiry test will run every 10 minutes until the loss of signal has been restored.