Abstract: Circuit protection devices comprise a PTC conductive polymer element and means for minimizing the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped. An enclosure encloses, but is spaced apart from, the PTC element. In one embodiment at least part of the interior surface of the enclosure is composed of polytetrafluoroethylene, a ceramic or another material which discourages the formation of permanent low resistance paths through carbonaceous material lying on its surface. In another embodiment the enclosure has a large internal surface area compared to the volume of the PTC element. In further embodiments, electrical leads are connected to and pass through the enclosure, and at least one of the leads is insulated along its length and/or the leads pass through opposite ends of the enclosure.

Abstract: A photosensitive semiconductor resistor has a monocrystalline semiconductor body of one conductivity type which, on two oppositely located surfaces, is provided with an anode contact and with a cathode contact, and is constructed so that the cathode contact is a highly doped zone of the same conductivity type as the semiconductor body. The semiconductor body can be exposed to photon radiation at its surface supporting the cathode contact and the area of the anode contact is at least 1000 times larger than the area of the cathode contact. Such a photosensitive semiconductor resistor is easy to manufacture and has both a low inertia and a good sensitivity.