The Siemens 3RV6921-1M is a SIRIUS short-circuit signalling switch designed to snap onto 3RV6 motor circuit breakers in sizes S00 and S0. It uses screw-type terminals for the auxiliary and control circuit connections and carries a rated insulation voltage of 690 V at pollution degree 3. The switch breaks the circuit in a maximum of 20 ms when a short-circuit trip occurs, giving you a discrete signal that the breaker has operated on a fault rather than an overload.
What it fits and how it mounts
This signalling switch snaps directly onto the side of a 3RV6 circuit breaker — no DIN rail footprint of its own, no extra panel space beyond the breaker's own width. It's sized for the S00 and S0 frame sizes, which covers the 3RV6 range from the smallest motor-protective breaker up through the 25 A class. The 19 mm width means it sits flush against the breaker body; you don't lose a DIN slot. Ambient operating range is -20 to +60 °C, storage from -50 to +80 °C, so it's fine inside a warm panel or a cold warehouse.