Siemens 3RT1975-5PP31 Changeover operating mechanism for contactors 3RT107, 3RT147 AC (50...60 Hz) / DC operation. Siemens 3RT1975-5PP31 is the exact printed commercial reference for a contactor / contactor accessory accessory in the SIRIUS 3RT Contactors range. Siemens' official product description is: Changeover operating mechanism for contactors 3RT107, 3RT147 AC (50...60 Hz) / DC operation, 200 . 220 V Operating mechanism: electronic with PLC input 24 V DC and RLT signal.