The Siemens 3RV1901-1AA00-0FQ0 is an auxiliary switch that mounts laterally on a circuit-breaker of size S00, S0, S2, or S3, providing one normally-open and one normally-closed contact pair for remote status indication or interlocking.
Deployment context
The lateral mounting design clips directly onto the side of the circuit-breaker without occupying additional DIN-rail space — useful for panel builders who need to pack auxiliary contacts into a crowded enclosure without re-laying the rail.