The Siemens SIRIUS 3RH2122-4LB40 is a coupling relay for switching auxiliary circuits, sized for the S00 contactor frame.
The coil is rated 24 V DC with a closing and holding power of 2.8 W — a steady-state draw that a standard 24 VDC power supply handles without issue. The built-in varistor surge suppressor means you don't need to add an external flyback diode across the coil; the suppression is already inside the relay package. The contact block provides 2 instantaneous NO contacts. The continuous current rating varies by voltage: at 24 V it carries 10 A, at 230 V it also carries 10 A, but at 400 V it drops to 3 A, and at 690 V to 1 A. For a 24 VDC control circuit, the full 10 A is available; for higher-voltage auxiliary loads, use the voltage-specific derating curve. For DC loads, the switching frequency is given as 7 to 20 ms — this is the contact bounce/arcing window, not a cycles-per-hour figure.
Dimensions are 73 mm deep, 45 mm wide, and 57.5 mm high.