The Siemens 3RT1956-1CB00 is a SIRIUS surge suppressor — an RC element designed to clamp voltage spikes from the contactor coil when it de-energizes. It mounts directly onto the coil terminals of 3RT1 S6, S10, and S12 contactors via screw terminals, so it shares the same DIN-rail footprint as the contactor it protects. The voltage rating covers 24...48 V AC at both 50 Hz and 60 Hz, and a wider 24...70 V DC range — meaning it works across standard control voltages in North American (24 V, 48 V) and European (24 V, 48 V) panels without a separate DC-rated variant.
The DC range of 24...70 V is the one to watch if you are running a 48 V DC control bus — many suppressors top out at 60 V DC, but this one holds to 70 V, giving headroom for a 48 V nominal supply that can ride up to 56 V under float charge. The AC range of 24...48 V covers both 24 V and 48 V control transformers at line frequency. Because it is an RC element rather than a varistor or diode, it suppresses both positive and negative transients without polarity concerns — useful when the coil drive is bidirectional or when you are retrofitting into a panel where the original wiring polarity is unknown.