The Siemens SIRIUS 3RH2911-1FA22-ZW97 is an auxiliary switch block that snaps onto the front of contactor relays and power contactors in sizes S00, S0, S2, and S3. It carries 2 normally-open instantaneous contacts, rated for AC-15 pilot duty at 690 V at 1 A, and is designed to signal or interlock the main contactor's state in a control panel.
The 6 kV surge voltage resistance means this switch block can handle transient spikes common in industrial motor circuits without welding or failing — important when it's wired into the same panel as a contactor switching inductive loads. It's a mirror contact per IEC 60947-4-1 when used with a 3RT2 contactor, meaning the NO contact's position positively reflects the main contactor's welded or open state. That's a safety-relevant feature for applications where you need a reliable feedback signal to a safety circuit or PLC input. The AC-15 rating at 690 V at 1 A covers the typical control-circuit voltage for a 400 V motor drive panel. At lower voltages the switch can handle more current: 10 A at 24 V, 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, and 0.5 A at 440 V.
Snaps onto the front of the contactor — no tools needed, no DIN-rail space consumed beyond the contactor itself. The block is 36 mm wide, 37.5 mm tall, and 43.7 mm deep, so it adds minimal depth to the contactor assembly. Terminals accept 2x (0.5 to 1.5 mm²) solid or stranded, or 2x (0.75 to 2.5 mm²) with ferrules, and the AWG equivalents are 2x (20 to 16) and 2x (18 to 14).