The capacitive measuring principle detects an approaching human hand. The ifm touch sensors are dynamically bult to suppress interference like water or layers of ice to a large extent. While working in these varying conditions, it can still sense a gloved hand and trigger when near, even working through glass. Comparatively, static touch sensors detect hands and objects for as long as the sensing face is pressed. Since the touch sensors from ifm react to contact, no pressure is required for activation.  This feature makes them considerably easier to use and lowers the risk of failure due to use over time commonly associated with mechanical versions. The green LEDs can be controlled separately and used in many different situations, like to indicate the plant and machine condition or as start/stop indicators on machines.  In various industries, LEDs are commonly used in many situations, such as optical feedback signals that indicate when the sensor has been activated, as buttons on mobile machines or trailers, as stop buttons, or as door openers.