The Siemens SIRIUS 3RT1936-1CB00 is a surge suppressor with RC elements, designed for mounting onto Size S2 and S3 contactors. It handles control supply voltages of 24...48 V AC at 50 Hz and 48...24 V AC at 60 Hz, plus 24...70 V DC — so it covers mixed AC/DC control circuits in a single unit. The RC element snubs the coil's inductive kick, which keeps transients off the PLC output or control relay driving the contactor.
The 24...48 V AC range at 50 Hz and 48...24 V AC at 60 Hz means the suppressor is designed for the standard control transformer secondaries found across European and North American panels. The DC range extending to 70 V covers 24 VDC control buses plus the higher nominal voltages (48 V, 60 V) sometimes used in longer cable runs. Because the RC element is a passive snubber, it draws negligible current in steady state — no thermal derating to worry about inside a crowded enclosure. The S2/S3 contactor frame sizes are the medium and large SIRIUS power contactors (roughly 45–70 mm wide), so this suppressor clips onto the contactor's coil terminals directly, not onto a DIN rail.