What it is and where it lands
The Siemens 3RK1903-3AC10 is a 65 mm terminal module for the F-DS1E-X safety I/O system, without a supply line connection and with coding for shutdown groups. It belongs to the SIRIUS family of safety-related automation components. This module is the physical interface between the F-DS1E-X safety module and the field wiring — it carries the screw terminals for the safety inputs and outputs, and the coding feature prevents mismating when multiple shutdown groups are used in the same cabinet.
Integration into a safety cabinet
This module snaps onto a 35 mm DIN rail per EN 50022 and occupies 65 mm of rail width. It connects to the F-DS1E-X safety module via a ribbon cable or backplane connector (not included) — the 'without supply line connection' designation means the module does not carry its own power feed; it draws 24 VDC from the safety module's backplane. The coding for shutdown groups uses mechanical keys or color-coded inserts to prevent inserting the wrong terminal module into a given safety slot, critical when multiple safety zones share a single F-DS1E-X rack. Panel builders should plan for the 65 mm width per module and allow clearance for the screw terminals on the top and bottom.