A photo sensor is formed in a partial area of the principal surface of a substrate. Also provided are methods of lightening the skin comprising the step of applying to skin in need of skin lightening treatment an extract of Lilium siberia. The system test is for testing a program within an environment. A displacement sensor is provided on the spindle bearing in order to determine the axial displacement of the tool interface. The first signal and the second signal are transmitted. In order to provide a satellite communications system which enables communication with a mobile user terminal via conventional communication satellites on any area of interest on earth, a quasi-geostationary satellite is operated in an inclined orbit and sends a spread downlink signal s\u2032 to said area of interest on earth to be received and despreaded by a mobile user terminal.