Richardson's handbook of projection (1930)

1148 HANDBOOK OF PROJECTION FOR on the projection room wall directly in front of the projectionist. RCA AMPLIFIERS.— In the matter of amplifiers I am using matter supplied by the RCA Photophone engineering department, just as written, as follows: RCA Photophone manufactures five types of amplifying equipment for the theatre installation, the type to be installed depending upon the size of the house and its acoustic properties. For the largest houses the equipment is known as Type "A," and for the smallest houses as Type "D," with the remaining types for intermediate size houses. There are two types of amplifying equipment known as the "B" equipment. These equipments are distinguished by the letters "MG" and "SPU." These two types of equipments have been designed for the same size houses. They differ only in the source of power, and for this reason have been given the same type letter. AMPLIFIERS— TYPES "A" AND "B" (MG).— RCA Photophone manufactures two types of equipment supplied by power from motor-generator sets. Type "A" equipment consists of either two RCA Photophone projectors or two standard motion picture projectors equipped with RCA Photophone sound attachments, two amplifier racks, one of which is a spare, two 4-unit motorgenerator sets, four storage batteries, twelve RCA Photophone electric-dynamic 12-inch cone type loud-speakers, and all necessary installation and operating accessories. The amplifiers, together wtih the 4-unit motor-generator sets and storage batteries, are furnished in duplicate. Only one amplifier is used for regular show operation. The other is kept in readiness as reserve equipment. In