To detekt in close proximity the position and status of windows and doors is one main task of home security and home automation systems. It can guide home security, airconditions, heating and other functions of Smart Home systems. Low energy consumtion, save operation and easy to mount are the main requirements for such systems. Reflective optical sensors are suited for this task. The Light source is invisible and not daylight sensitive. Cost and constructions are effordable and the detecting range is inside centimeter ranges.