What it is and where it lands
The Siemens 3RK1903-0AC00 is a terminal module for the ET 200S RS reversing starter, fitted with a supply line connection. It is the interface that brings power and control wiring into the reversing starter assembly inside a SIMATIC ET 200S distributed I/O station.
What the key ratings mean for fit
Because this is a terminal module — not a contactor or relay — it carries no current or voltage switching ratings of its own. Its job is to terminate the motor and supply cables onto the ET 200S backplane, routing the line supply through to the reversing contactor pair. The module determines the wiring topology inside the IP20 enclosure; the actual motor switching capability comes from the contactor modules you plug into it. The substance prohibitance date of 05/01/2012 confirms RoHS compliance for the EU market. That date marks when the part was certified free of restricted substances per the RoHS directive — a standard compliance milestone, not a phase-out signal.
Panel integration note
The module snaps onto a 35 mm DIN rail inside the ET 200S enclosure. It is not a standalone component — it mates with the ET 200S backplane bus and the reversing contactor modules above it. Verify the existing ET 200S station has an open slot for this terminal module before ordering; it does not mount in a standalone panel like a contactor relay would.