The Siemens 3RV1901-1EA00-0FQ0 is a transverse auxiliary switch with 1 normally-open and 1 normally-closed contact, designed to mount onto 3RV motor-protective circuit-breakers in frame sizes S00 through S3. It signals breaker state — tripped or reset — back to the control system, typically wired into a PLC digital input or a safety circuit.
Snaps onto the left or right side of the 3RV breaker housing. Transverse mounting means the switch body sits parallel to the breaker face, keeping the overall width within the same DIN-rail footprint — no extra panel space needed beyond the breaker itself.