Retroreflective sensor - Effective detection range: 0 ... 3.5 m in TEACH mode , Light source: LED. Polarization filter for clear object detection, Effective detection range 0 ... 3.5 m in TEACH mode, Ultra bright LEDs for power on, weak signal indication and switching state, Flashing power on LED in case of short-circuit, TEACH-IN, Automatic adjustment in case of soiling in contrast detection mode, Not sensitive to ambient light, even with switched energy saving lamps