What it is and what it does
The Siemens SIRIUS 3RT5956-1CC00 is an RC-element surge suppressor for contactor coils and relays. Rated for AC/DC control supply voltage, it covers 70 to 150 VDC and 48 to 127 VAC at 50 Hz, with the same AC range at 60 Hz.
Where it fits in the panel
This is a bolt-on accessory for SIRIUS contactors and relays — it mounts directly onto the coil terminals, typically snapping into the front of the device. No separate DIN-rail footprint is consumed, which matters when the panel is already tight on fill factor. The RC element is polarity-sensitive on DC circuits; verify the orientation against the coil's + and - before energizing. Operating temperature spans -25 to +60 °C, with storage from -40 to +80 °C.