A DS1 Interface Media Module raises a Red alarm when the framing pattern of the incoming DS1 bit stream has been lost. The Red Alarm Inquiry test checks the framing status of a DS1 board.

When the DS1 board detects a Red Alarm, it transmits a Yellow Alarm to the remote DS1 endpoint and sends a Red Alarm message to the system. After the Red Alarm is confirmed, the system places every trunk or port of the DS1 board into the out-of-service state. The inquiry test runs every 10 minutes until the Red Alarm is cleared.

When the Red Alarm is cleared, the DS1 board stops transmitting the Yellow alarm to the remote DS1 endpoint. The system restores all trunks or ports of the DS1 board to the service state they were in before the Red Alarm occurred.