The Siemens 3RT2936-1JL00 is a SIRIUS surge suppressor — a varistor with an integrated LED indicator — designed to clip directly onto the coil terminals of S2 and S3 frame contactors in the 3RT2 family. It accepts control supply voltages of 127–240 V AC at 50/60 Hz or 70–150 V DC, covering the common industrial control voltages across both AC and DC coil circuits. The clip-on fastening method means it snaps onto the contactor without tools or extra wiring — a panel-builder detail that saves a few seconds per unit when populating a row of contactors on a DIN rail.
The 14.5 mm depth and 30 mm width keep the suppressor flush with the contactor profile, so it doesn't steal extra DIN-rail space or push the enclosure fill factor over the limit. The LED on the varistor gives a visual confirmation that the suppressor is powered and the coil circuit is live — useful during commissioning or troubleshooting when you're scanning a row of contactors for a dropped control voltage. Rated for operation from -25 to +60 °C and storage from -40 to +80 °C, it handles the thermal range inside a standard IP54 control panel without derating concerns.