The Siemens 3RK1400-0BG00-0AA2 is a SlimLine S22.5 AS-Interface standard slave module offering two PNP digital inputs and two PNP digital outputs in a 22.5 mm wide housing for IP20 control cabinet mounting. It snaps onto 35 mm standard DIN rail or mounts to a panel wall using push-in lugs, which keeps the footprint tight for high-density I/O layouts inside a cabinet. The module requires an external 20 to 30 V DC auxiliary power supply (AUX POWER) for the output circuits, separate from the AS-Interface bus power, and that supply must comply with VDE 0106 (PELV), protection class III.
Signal integrity and wiring notes
Inputs are PNP transistor type, so you're switching a positive signal — common for Siemens and most European sensor families. The input voltage range is 20 to 30 V DC, which covers the standard 24 V control supply with margin for drop. Outputs are also PNP, rated for a maximum aggregate current of 4 A across both channels. Each output delivers 22 to 24 V DC at 24 V nominal. Minimum switching load per output is 5 mA; off-state leakage stays under 1.5 mA — worth checking if you're driving a high-impedance PLC input or an LED pilot light that might glow when off. Terminals accept 2 x (0.25 to 1.5) mm² solid or stranded, or 2 x (0.25 to 1) mm² with end sleeves. AWG equivalent is 2 x (24 to 16). A detachment tool is needed for the spring-loaded connections — keep one in the panel bag.