What it is and where it fits
The Siemens 3RK1903-0AK00 is a 65 mm terminal module for the ET200S High Feature DOL (Direct-On-Line) starter system. It provides the supply line connection and the physical interface between the ET200S backplane and the motor starter's power and control wiring. This module snaps onto a 35 mm DIN rail per DIN EN 50022, integrating directly into an ET200S distributed I/O station. It's the piece that carries the line-side power feed to the DOL starter, so if you're replacing one in a panel, verify the 65 mm width clears adjacent modules.
Lifecycle and compliance
RoHS compliance date is 05/01/2012, so the module meets EU substance restrictions from that date forward. Expect a CE declaration and material declaration to accompany the shipment.