first side auxiliary switch 1 NO contact 1 NC contact, spring-loaded connection, for 3RT1 contactors SIRIUS 3RH19 auxiliary switch for extending the auxiliary contacts in the control circuit. This 3RH19 auxiliary switch can be mounted on the 3RT1 contactors of sizes S0-S12 without tools. The 3RH19/3RH29 auxiliary switches are available as front- or side-mountable versions, with up to four instantaneous switching or up to two leading switching NO contacts and NC contacts. The auxiliary switches can be designed as positively guided contact elements in 3RH contactor relays or as mirror contacts in 3RT power contactors. They are available with screw connections and spring-loaded connections. Simple, efficient, always up-to-date - the SIRIUS modular system.