The sound track book of the theatre (undated)

DRIVE-IN THEATRES 409 the lot surface and looped up into each junction box, most nearly meets the requirements. Along the ramps No. 12 or No. 14 wire is adequate in size and these sizes are also adequate for the feed cables to the ramps. For unlighted junction boxes, both con respective two-conductor insulated parkway feed cable for each ramp circuit. Electrically there is little difference, but the availability and cost of the heavy single ground line with its spliced-on branches may be a determining factor. It is advisable to divide the total num A drive-in theatre, showing a typical screen tower, and ramp construction which permits a clear view of the screen to patrons of all cars ductors are used for the sound circuit. For the new lighted Motiograph junction boxes, an additional un-insulated bare copper cable extending to each box provides a lowresistance common grounded return wire for both the sound and the low voltage lighting circuits. It may consist of a single No. 8 or larger cable from the projection building out to the approximate center of each ramp, with smaller No. 12 bare wires spliced on to run along the ramps and loop up into the junction boxes along with the insulated cable, or the No. 12 bare wires may run all the way back to the projection building along with the ber of junction boxes installed into a number of separate groups, with a feed cable from each group running to the projection building. Electrical arrangements in the junction boxes protect other boxes on the same feed line from being affected by accidental short circuits in speaker connection cords, but it is only by dividing the boxes into groups with separate feed cables that a measure of protection against short circuits in the feed cables themselves can be obtained. Such cable faults might arise from the accidental knocking down of a junction box support post, or by actual failure of cable insulation from one cause