The Siemens 3RT2936-1CB00-ZX90 is a SIRIUS RC-type surge suppressor designed to clip directly onto size S2 contactors. It handles a control supply voltage of 24...48V AC at 50/60 Hz and 24...70V DC, making it suitable for mixed AC/DC control circuits common in panel builds. The RC element snubs the inductive kick from the contactor coil, protecting nearby PLC outputs and extending the life of the coil itself.
This suppressor clips onto the contactor without occupying additional DIN-rail space. The 14.5 mm depth and 30 mm width mean it stays within the envelope of the S2 contactor it mounts on, so no extra panel clearance is needed. Mounting position is any orientation.