A CHECK or TRBL 974 indicates a supervision failure on Dialer 1, which is the primary telephone line for the FACP (Page 27) [1].
This Trouble condition means the system has detected a fault with the phone line or the dialer's connection to the network.
Steps to troubleshoot:
Verify the primary phone line is physically connected to the main PCB or the RJ31X jack (Page 103) [1].
Check for a dial tone on the line to ensure the service is active from the provider.
Inspect the telecommunication line cord for damage; it must be 26 AWG or larger (Page 103) [1].
Look for "Phone Line Cut" or "COMM. FAILURE" messages on the keypad, which often accompany this code (Page 62) [2].
Once the line is restored, enter your User Code + OFF (1) to clear the display (Page 62) [2].
Verify with current documentation before making changes.
