The Fail-Safe Alarm is designed to Alert in the event of Failure
The Fail-Safe System can indicate a Fault Conditions within Microseconds
The Fail-Safe Alarm can Monitor Single-Ended OR Differential Feedback devices
Din-Rail Mountes Failsafe Systems       EFD1002 Single Axis Failsafe Monitor       EFD1002 Failsafe Alarm Typical Mounting

Fault Detection Includes items such as . . .
Broken Wires : Shorts : Opens : Noise : Loss of Phase : Power Failure