The Siemens 3RH6131-1KF40 is a SIRIUS coupling relay — size S00, designed to switch auxiliary circuits from a 110 VDC control signal. It gives you 1 NC and 3 NO contacts (31 E switching element identification), rated for 6 A at 24 VDC and 10 A at 230 VAC. The built-in suppressor diode handles the DC coil flyback; no external snubber needed.
Snaps onto 35 mm standard DIN rail or screws directly to a panel backplate. At 45 mm wide and 57.5 mm tall, it occupies a single S00 footprint — no extra width for the auxiliary block. The screw terminals accept 2x 0.5 to 2.5 mm² solid/stranded or 2x 4 mm²; AWG equivalents are 2x 20–16, 2x 18–14, or 2x 12.
Contact ratings and switching duty
AC-12 operational current is 6 A; AC-15 at 230 V is 10 A, at 400 V it's 3 A, and at 690 V it's 1 A. DC-12 and DC-13 max operating frequency is 1 000 1/h. Mechanical life is 30 million switching cycles.