The Siemens SIRIUS 3RT1926-3AF31 is a mechanical latching block designed to hold a contactor closed without continuous coil power — a common requirement for safety hold circuits or applications where a maintained state must survive a control-voltage dip. It clips onto S0 and S2 frame contactors in the 3RT1.2 and 3RT1.3 series, accepting a 110 V AC/DC control supply through its screw-type terminals.
The latching block mounts via clip-on fastening to the contactor front, occupying no additional DIN-rail width — it adds depth only. Rated for any mounting position, it fits panels where the contactor is installed horizontally or inverted. Screw terminals accept 2x (0.5... 2.5 mm²) solid or 1x 4 mm² solid conductors, with equivalent AWG capacity of 2x 14 or 1x 12 for the auxiliary circuit. This matches the wire sizes typically run to contactor coils in control panels — no special crimping or ferruling required for solid wire, though the terminal also accepts stranded with core-end processing.