What it is and where it fits
The Siemens 3RK1903-0AH00 is a 15 mm power bus jumper for the PE/N (protective earth / neutral) circuit in an ET 200S distributed I/O system. It bridges the power bus across modules, maintaining the PE/N continuity without separate wiring.
Integration note
Snaps onto the standard DIN rail within the ET 200S terminal assembly. The 15 mm width matches the module pitch, so it occupies one slot position and aligns with the adjacent bus connectors. No additional wiring is needed for the PE/N pass-through — the jumper handles the continuity internally.