3RH2122-1BW40 Siemens Contactor Relay, 2 No + 2 Nc, 48 V Dc, Size S00, Screw Terminal. ontactor relay, 2 NO + 2 NC, 48 V DC, Size S00, screw terminal Auxiliary contactor SIRIUS 3RH2 for switching the control signals in the control circuit.The SIRIUS 3RH2 contactor relays have standard-compliant terminal designations and a reliable and time-saving connection technology. Thanks to the multiplication of outputs, simultaneous switching of several auxiliary circuits is possible. All contacts are available with positively driven operation for safety applications as well as SUVA versions.