SIRIUS 3RH2 4- & 8-Pole Contactor Relays Siemens SIRIUS 3RH2 4- and 8-Pole Contactor Relays are available with screw or spring-loaded terminals. The basic unit contains four contacts with terminal designations according to EN 50011. Siemens 3RH2 Contactor Relays feature high contact stability at low voltages and currents. This performance is suitable for solid-state circuits with currents ≥1mA at a voltage of ≥17V. 3RH21 Coupling Contactor Relays for Switching Auxiliary Circuits are tailored to the special requirements of working with electronic controls.