Siemens SIRIUS 3RH2 Auxiliary Switch Block on the front for 3RH and 3RT screw terminal 73/74, 81/82 contactors. SIRIUS 3RH29 auxiliary switch for extending the auxiliary contacts in the control circuit. The 3RH29 front-side auxiliary switch can be mounted on the 3RT2 contactors and the 3RH2 contactor relays without any tools regardless of size. The 3RH19 / 3RH29 auxiliary switch blocks are available as front or side mountable variants, with up to four normally-open or up to two normally-open normally open and normally closed contacts. The auxiliary switch can be designed as positively driven contact elements in auxiliary contactors 3RH or as mirror contacts in power contactors 3RT.