Abstract: High voltage transients are effectively clamped by means of a spark gap, in parallel connection with a load to be protected, and having a capacitor in series with the parallelled load-spark gap combination. The series capacitor limits follow-through current through the spark gap to a level permitting survival of the spark gap. Where the load is an incandescent lamp, the spark gap is formed by shaping the lamp internal lead structure, such that an additional external spark gap component is not required.

Abstract: A high pressure metal (sodium) vapor lamp comprises an outer vitreous envelope and an inner ceramic arc tube supported within it. The arc tube contains vaporizable metal in excess of the quantity vaporized in operation and the heat balance determines a cold spot whereat excess metal collects. The temperature of the cold spot determines the vapor pressure and the voltage drop across the lamp which must lie between specified limits. A thermal link is provided to a metal member such as the exhaust tube, the heat loss from which influences significantly the temperature of the cold spot. In completed lamps measuring too low in voltage, such thermal link may be partly severed without breaking open the outer envelope in order to raise the voltage. One convenient way utilizes an auxiliary wire which is cut by aiming a laser beam at it. Another convenient way to reduce the conductive cross section of the thermal link is to use a laser to drill one or more holes through a metallic member comprising the thermal link.

Abstract: A pair of varistor disks, each having one face thereof coated substantially entirely with electrode material and another face thereof coated with spaced-apart electrode material, such as in two semicircular patches, are joined together so that said faces coated with a single electrode are coincident. This configuration reduces by a factor of two the over-all area required for equal current density as compared with certain prior varistor configurations. The varistor of the present invention also exhibits a lower diameter-to-thickness ratio and hence provides a significantly stronger mechanical structure. Additionally, the varistors of the present configuration may be readily provided with grooves between electrode surfaces so as to increase the interelectrode spacing, without significantly reducing the mechanical strength of the device. The invention of the present structure also permits flexible lead configurations.

Abstract: Reconstituted metal oxide varistors are formed by hot pressing powdered metal oxide varistor ceramic with plastic resin. Metal electrodes may be pressed directly into the ceramic-plastic composite to provide improved contact characteristics.