The Siemens 3RH1911-1FB22 is a SIRIUS auxiliary switch block with 2 NO + 2 NC contacts, screw-type terminals, and a 10 A maximum rating. It snaps onto contactor relays and power contactors in the S00 frame size, following the EN 50005 contact arrangement. The block is rated for 10 million mechanical switching cycles, with contact reliability of one faulty switch per 100 million operations at 17 V, 1 mA — a solid figure for low-energy signal circuits where oxide film can be a problem.
Snap-on mounting to the contactor or contactor relay — no tools for the mechanical fit. The screw terminals accept 2x (0.5...1.5 mm²) or 2x (0.75...2.5 mm²) with core end processing, or 2x (20...16) and 2x (18...14) AWG. IP20 on the front means it's protected against finger contact but not washdown; keep it inside the panel. The 41.5 mm depth and 36.5 mm width fit the S00 contactor footprint — no extra DIN rail space beyond the contactor itself.
The contact ratings cover a wide voltage range. At 24 V AC-15 it's rated 10 A; at 230 V AC-15 it's 6 A; at 400 V AC-15 it's 3 A. For DC switching at 24 V it's 6 A, dropping to 0.3 A at 220 V. The surge voltage resistance is 6 kV, and the rated insulation voltage is 690 V at pollution degree 3. Storage temperature range is -55 to +80 °C; operating range is -25 to +60 °C.