This 3RH7122-1AF00 is a Siemens SIRIUS contactor relay in the S00 frame size — a compact switching block with 2 normally-open and 2 normally-closed auxiliary contacts. It's built to pilot larger contactors or handle signal-level switching in control circuits, with an AC coil that pulls in at 27 VA and holds at 5.4 VA. The contacts are rated for 6 A at 24 V, 230 V, and 400 V, and 1 A at 110 V and 690 V. That covers most control-voltage taps you'll find in a panel — 24 V for PLC outputs, 230 V for line-voltage interlocks, and 400 V for contactor coil pickups in 3-phase gear. Screw-type terminals accept 2x 0.5 to 2.5 mm² solid or stranded, or 2x 4 mm² solid. The contact reliability is specified for PLC-level signals — 17 V, 5 mA — so you can wire this directly to a digital input card without worrying about oxide films causing intermittent faults.
The S00 footprint is 45 mm wide, 57.5 mm tall, and 72 mm deep — tight enough to pack several relays across a single DIN-rail section. That means you can orient it to match gland-plate entries or cable duct runs without worrying about derating the contacts. IP20 on the front — finger-safe for open panels, but keep it inside an enclosure where washdown or dust isn't a concern.
This relay lives in control circuits — piloting SIRIUS contactors like the 3RT series, or switching signal loads from PLCs, pushbuttons, and sensors. The S00 size matches the smallest contactor frame in the SIRIUS family, so it shares the same DIN-rail footprint and terminal spacing. Operating temperature range is -10 to +55 °C during operation, storage from -25 to +70 °C. That's fine for most indoor panel environments — no special ventilation required unless you're packing it next to a heat source. Installation altitude is limited to 2 000 m above sea level. Above that, you'd need to derate the insulation or use a different variant — but for 95% of industrial sites, that's not a constraint.