Kinematograph Year Book 1942 (1942)

226 The Kinematograph Year Book. requires the minimum of maintenance and helps to prolong the life of the battery. Keepalite "B," the invention of Basil Davis (Patent No. 377671), employs the floating-battery system, and is available in a wide range of outputs and voltages, and eminently satisfies the requirements of many local authorities. The equipment employs a rectifier, in which choke control of a special nature ensures a constant floating condition of the battery despite wide changes in the lighting load, occasioned by the switching on of additional secondary lighting at dusk, as is the practice in many kinemas. With this equipment the only attention necessary is to switch on the rectifier and the secondary lights. As an alternative to Keepalite " B " there is the standard floating-battery system employing a rectifier generally similar to that used in the last system, but without the refinement of the automatic choke control. D. P. Battery Co., Ltd. — The popular D. P. Katholite floating battery system of emergency lighting continues in demand, and the company is able to offer a wide range of automatic installations which meets the various regulations of local authorities. 1. All lighting circuits are supplied from private generating plant with a battery of ample capacity installed on the premises. 2. The main lighting circuits are taken from an outside supply, with the safety lighting taken from a battery, which must be fully charged every day by means of either a motor generator or indep2ndent plant. Its capacity must be equal to supplying the safety lighting load for the number of hours required by the regulations. 3. The main lighting circuits are supplied from outside, but the safety lighting is connected to a motor generator running off the mains with a battery " floating." Although this method is approved by authorities in the London area, some authorities require that in the event of a main supply failure the public shall be turned out of the building. 3a. Is similar in principle to scheme 3, but in this case the safety lights are fed by a rectifier instead of a motor generator. 4. This is a non-automatic method in which the safety lights are connected to an independent battery fitted with small pilot lamps connected up to the main lighting switch, which are always on when the main switch is closed, but are actually fed by the battery. The trickle charger is set, and to avoid any possibility of the " trickle charge " apparatus failing to function, and such a failure escaping notice, so as to allow the cells to run down, a battery voltage indicator is provided. Research is continually taking place, but in view of the satisfactory service already obtained from Kathanode sound batteries in use throughout the country, there appears little prospect at present of any radical change being made in their construction. Nife Batteries, Ltd., have always contended that all the essential emergency lights should be controlled by one master switch in order to conform to the requirements of the Home Office. Under war-time conditions, however, the position is somewhat different, owing to the fact that certain parts of the kinema may not now be in use. Consequently, it is now an advantage to install a floating battery system, whereby the emergency lighting load is automatically balanced by the rectifier without manual adjustment. Special attention has been given to the design of equipment which will meet the new conditions, and automatic sets are now available in a wide range of outputs and voltages. Complete control of the equipment is still effected by one master control switch (British Patent No. 492908), having three positions as follows : — (i) Equipment out of action ; (ii) Float ; (iii) Quick charge. In Scotland, however, an automatic switch is still permitted, and since the Nife battery has no open circuit losses, it is not necessary to trickle charge the battery to maintain it in a healthy condition. In view of the fact that adequate D.C. supply is available in the kinema for the kine. arcs