The Siemens 3RK1903-3AC00 is a 65 mm terminal module for the F-DS1E-X safety I/O block, integrating the supply line connection and coding for shutdown groups. This is the physical wiring interface that brings 24 VDC power and signal routing to the F-DS1E-X, with the coding feature ensuring that shutdown group assignments stay mechanically keyed — no mis-mating during a swap.
The 65 mm width occupies one standard module slot alongside the F-DS1E-X base unit. Wire the 24 VDC supply into the terminal module's supply line connection; the coding pins physically prevent plugging the wrong connector into a different shutdown group, which matters when you have multiple safety zones in the same cabinet and need to guarantee that a maintenance swap doesn't cross-connect zones.