The Festo SME-3-SL-LED-24-B is an electrical reed switch, the kind you clamp into a T-slot on a pneumatic cylinder to tell the controller where the piston is. It switches at 800 Hz with a 0.5 ms response time, which is fast enough for high-cycle pick-and-place or sorting stations where you need clean position feedback without missing a stroke. Runs on 12 to 24 V AC/DC and handles up to 500 mA with a 10 W switching capacity. IP66 means it stands up to washdown environments and dust — think food processing lines or outdoor conveyor sections where a lower-rated sensor would let moisture in and fail intermittently. The M8 3-pin connector makes for a quick swap when it does eventually wear out, which is the point: reed switches are mechanical, they have a finite life, and this one is built to be replaced without pulling cable.
Integration Note
Body dimensions are 18 x 19 x 13 mm, which is compact enough to fit into tight T-slot profiles on smaller cylinders. The -SL- in the code indicates the slot-style mounting — it clamps in, not bolts on, so you can adjust position along the slot without tools. That covers most indoor plant floors but if your application sees sustained heat above 60 °C you'll need to move the sensor outside the hot zone or use a different sensing principle.