Handbook of projection for theatre managers and motion picture projectionists ([1922])

100 HANDBOOK OF PROJECTION FOR installation. In small, strictly moving picture houses, in which light effects are not attempted, it is much better to have auditorium lights that are not used during the show extinguished all at one time, rather than by pulling several small switches. In large houses, however, where there are many incandescent lights and circuits, this is neither a practical nor a desirable thing to do. In such houses dimers should always be used. In figure 14 we have both a digrammatic and photographic Figure 14. representation of a small 3-wire switchboard, commonly known as a "panel board." In the diagram, A is the fuse contacts, B the main switch, C the house circuit fuse contacts and D the service switches governing individual circuits. All of this is seen photographically represented at the right, except that in the photographic representation the main switch and fuses are omitted, and there are five circuits on each "side," instead of three. Both in the photograph and the diagram the screw heads connecting the individual circuit feeder bars to the main circuit feeder bars form the key to the connection. Taking the diagram for example, it will be observed that the center or neutral bar has a screw head over the second and third individual circuit bars, which means that the neutral bar is electrically connected to these two bars, or in other words, to the upper bar of the lower circuit and the lower bar of the upper circuit. The right hand short bar is connected to the lower bar of the lower circuit and the left hand feeder bar is connected to the upper bar of the upper circuit. It will thus be seen that the lower circuit is con