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— It requires neither darkroom nor special pro- tective lighting for location or processing, since the RCA Electrofax paper which is used does not become light sensitive until it is put into the printer. — It is believed to be the fastest automatic enlarger- printer ever developed, with an output rate of fifteen 17 x 22-inch drawings per minute. — It is equipped with a sight glass which allows an operator to check on the photographic process at all times. Operation of the device is handled by push-buttons and it has an automatic focus. Standard A-, B-, and C-size drawings are produced by the machine in full scale, and larger drawings in half-size. It can be pre-set to reproduce up to 500 microfilm originals at one loading, with up to 24 multiple copies of each. How the Eiilargev Operates The machine operates in this way: Loading is accomplished by placing up to 500 Film- sort cards in a rack above the lens system, or by insert- ing a 100-foot roll of 35-mm positive microfilm in much the same manner that a typewriter ribbon is installed. The press of a button starts the microfilm originals ■—either cards or roll — feeding automatically into the lens system at the rate of one frame every four seconds. The images are projected through the lens onto the special Electrofax printing paper, which feeds auto- matically into the machine from a roll approximately 3500 feet long. At this point, the operation becomes a mechanized version of the Electrofax printing process developed at RCA's David Sarnoff Research Center in Princeton, N. J. In the Electrofax process, light images are projected onto a special electrosensitive coating which can be applied to any solid surface — in this case, paper. The coating is made photosensitive by application of a charge of static electricity. During exposure, the charge is reduced or driven away in proportion to the amounts of light striking the different parts of the surface, leav- ing a latent electrical image. The image is made visible by brushing the surface with a magnetic brush carry- ing charged particles of pigmented resin powder. The powder particles cling to negatively charged areas of the surface, creating a visible print of the original pro- jected image. The image is fixed in place by brief application of heat, which causes the resin particles to fuse on the surface. In the new machine, all of these steps are carried out in sequence and automatically. The Electrofax paper, with a sensitivity several thousand times greater than that of blueprint paper, moves through the machine at a rate of 23 feet per minute. As it emerges, bearing the permanently printed reproductions, the paper is wound on an output roll from which the reproductions can be cut as needed. Finished reproductions of engineering drawings flow from Electrofax enlarger-printer as shown at rate of 15 per minute. Arthur L. Malcarney, right, General Manager, RCA Commercial Electronic Products, discusses new Electrofax machine with Dr. James Hillier, Chief Engineer. RADIO AGE 9