A vehicular keyless entry system is formed of an in-vehicle device and a plurality of portable devices. The light shield comprises a structure formed above a point between a photo-sensitive element and adjacent circuitry. In this case, the gate electrode is formed in such a manner that an upper surface of the epitaxial layer becomes higher than that of a channel layer formed over the drain layer. A rule-based fault detection engine may be implemented by a low level building equipment controller.