The Siemens 3RN1010-1CG00 is a thermistor motor protection evaluation unit — a standalone device that monitors PTC thermistor sensors embedded in motor windings and trips the contactor coil when overtemperature is detected. It is a phased-out product; the preferred successor is the 3RN2010-1CW30, which offers the same AUTO evaluation mode and contact arrangement (1 NO + 1 NC) but with updated electronics. The 1 NO + 1 NC contact set provides a normally-open run-permissive and a normally-closed alarm output, standard for fail-safe motor protection schemes.
IP20 rated, so it belongs inside a closed cabinet.