The Siemens Industrial Controls 3RH2911-1FA22 Auxiliary Switch is a versatile electrical accessory featuring two normally open (NO) and two normally closed (NC) contacts with screw terminals. It operates in conjunction with contactors and control devices in HVAC systems to provide additional feedback or interlocking functions by changing state when the primary device actuates. https://www.partshnc.com/aux-switch-2no2nc-screw