The Siemens 3RH2122-2AD00 is a SIRIUS auxiliary contactor in size S00, carrying 2 NO instantaneous contacts. It's the part you add to a contactor or a contactor assembly when the main poles aren't enough for your control circuit — think feedback to a PLC, status to an HMI, or interlocking between starters. Rated for 10 A at 24 V and 230 V, with a mechanical life of 30,000,000 cycles typical. That kind of flexibility saves headaches when you're squeezing it into a crowded panel.
At 45 mm wide and 73 mm deep, this contactor fits the standard S00 footprint — same as the 3RT2 contactors it's meant to accompany. The 10 A rating at 24 V and 230 V covers most 24 VDC and 230 VAC control circuits you'll find in a panel. The 30,000,000 mechanical cycles tell you it's built for high-cycling applications like conveyor lines or packaging machines where the contactor might switch every few seconds.