A fastening assembly is for securing a heat sink to a heat generating electronic device located on a printed circuit board. The side edges of the upper surface of the cover particularly comprise one or more snap closures. The update frequency can also be made dependent on further factors such as: the motion of the mobile entity, the current environment of the mobile entity, and the progress of the location-sensitive application. A focal length of the first lens unit, a distance on an optical axis from a lens surface closest to an image side of the first lens sub unit to a rear principal point position of the first lens sub unit, and a focal length of the zoom lens at a telephoto end are appropriately set. A candidate text line classifier is applied to further screen out false-positive text identifications. At the back of the retroreflective layer an illuminator is disposed.