The Siemens 3RN1000-1AB00 is a compact thermistor motor protection evaluation unit from the SIRIUS family, designed to monitor motor winding temperature via PTC thermistor sensors. The unit is housed in a 22.5 mm wide enclosure with IP20 protection, suitable for DIN-rail mounting in control panels.
Rated for 24 V AC/DC control voltage — the same supply that powers most PLCs and control transformers, so it drops into a standard 24 V panel without an extra power supply. The single CO contact handles the auxiliary signaling loop; if your BOM calls for two isolated contacts or a higher switching capacity, this unit won't cover that without an interposing relay.
An LED on the front provides local status indication of the trip condition — useful during commissioning or fault-finding without needing a multimeter.