An electronic control device for controlling electric units of motor vehicle doors which have different equipment. A media travels along a transport path past the media-guiding roller with a first side of the media facing the exterior surface of the web-guiding roller. File headers are stored in the volume for each file, and the file headers included references to a table sector or sectors associated with the file. A processor extracts data relating to the scattered light to determine the density of particles in the beam, to determine the level of smoke in the region.