The monitoring relay for monitoring the correct phase sequence L1-L2-L3 (clockwise rotation) and monitoring the individual phase voltages for total failure. The phase voltages to be monitored are connected to terminals L1-L2-L3, terminals 11, 14 or 21, 24 of the relay output contacts are connected in front of the excitation coil of the motor contactor. If the phase sequence is correct, the output relay switches on (green LED on). If a phase fails completely, the output relay returns to its rest position (green LED off). A special supply voltage for the monitoring relay is not required. The device should only be connected to N if the three phases to be monitored are connected to N via a circuit (e.g. temperature monitoring or similar).