Kinematograph Year Book 1942 (1942)

Film Exhibition and Kinema Technique 225 During this period, however, Westinghouse research engineers perfected the new " Westalite " rectifier. This does not, in general, supersede the copper-oxide type, but is better suited to the larger power applications, the D.C. supply to the kinema arc being a notable instance in which it can be used effectively. At a demonstration to the B.K.S. it was explained that the new rectifier made use of the properties of selenium ; but while other experimenters had used pure selenium, Westinghouse employed certain alloys. One failing of the copper-oxide rectifier is its limited working temperature, for it must not be worked at over 55 deg. C. total temperature. In contrast, the Westalite element can be worked satisfactorily up to a temperature limit of 85 deg. C. The efficiency is at least as high as copper-oxide. One considerable feature emphasised was the reduction in bulk of a rectifier made possible by this new development. Although the new equipment will not be on the market at present, as the full output of these rectifiers is absorbed in other directions, the new Westinghouse " Westalite " kinema arc rectifier, incorporating the well-known constant current feature, will be available when more stable conditions are secured. SECONDARY LIGHTING EQUIPMENT. THEATRE operation in war-time and especially under " blitz " conditions has proved a testing-time for the principle of secondary lighting, particularly when it is provided by the storage battery. Blast and bomb damage which have put electrical and gas mains out of action have not affected, in the majority of cases, the functioning of the battery installation which has demonstrated its reliability by immediately providing the necessary illumination to enable managements to deal with whatever circumstances may arise from enemy action. The advantages of the floatingbattery system have been proved under war conditions, and the wisdom of relying upon battery supplied secondary lighting is fully justified by events of the past year. Exhibitors possessing this equipment are unlikely to be interested in the suggestion made by the Birkenhead fire brigade of the desirability of kinemas installing storm-lamps in various parts of the theatre so that, in case of damage through enemy action to electric cables and gas mains, another form of lighting may be quickly available. Although it is well to prepare for every contingency, it does not seem that the battery installation is any more vulnerable than storm-lamp lighting unless a direct hit occurs on the battery-room, in which event the proposed tertiary lighting system would also probably be extinguished. British Thomson-Houston Co., Ltd. — The "Thyrect," a Thyratoncontrolled system, which automatically maintains battery and safety lights under all conditions, has for its main features automatic regulation and the provision of the " trickle " charge at constant rate, irrespective of variation in lamp load, supply voltage or condition of battery. It also affords " lump " charge at a constant rate after heavy discharge ; eliminates contactors between battery and lights and also increases indefinitely the life of the battery. Chloride Electrical Storage Co. Ltd. — The extensive range of stationary batteries and rectifier equipments handled by this firm are the result of continuous research into the requirements of exhibitors as regards secondary lighting. The batteries are of the sealed-in type incorporating robust plates of Plante design, such as are used in power station installations. The batteries can be delivered direct to site filled and fully charged ready for immediate use, so that the work of installation is an easy matter. The equipments provide an instant emergency lighting supply from the battery, and to maintain it in a fully charged condition so that it is ready for any demand. For this duty there are three types of equipments. Of the first, the well-known " Keepalite " equipment (Patent No. 313248), the important feature is the trickle charging of the battery, which H