The Siemens 3RN1012-1CB00 is a SIRIUS thermistor motor protection relay designed for reliable monitoring and protection of motors against thermal overload. It operates by evaluating the resistance of a PTC thermistor sensor embedded in the motor windings. This compact unit is ideal for applications where direct current measurement is not feasible or as supplementary protection. It features a wide voltage range, auto/manual/remote reset capabilities, and a test function, ensuring versatile and secure motor operation in various industrial environments.