Exhibitors Herald and Moving Picture World (Apr-Jun 1930)

May 3, 1930 EXHIBITORS HERALD-WORLD 39 REPRODUCTION IN THE THEATRE By RCA Photophone System JOHN 0. AALBERG* FIGURE 1 Simplex projector equipped with RCA Photophone sound head and disc attachment FIGURE 2 RCA Photophone sound head attached Simplex Projector FIGURE 3 Diagram of RCA Photophone sound head showing film travel OERFECT sound in a theatre is evidence of a succession of operations excellently done. The first operations have to do with the making of the record and are described elsewhere. The reproduction of the record in the theatre is its presentation to the ultimate auditors and its importance should not be overlooked. Sound apparatus, which must be expertly operated and maintained, has suddenly been added to the projectionists’ cares. Some projectionists had the electrical and mechanical ability to cope with the problems that were of that nature but very few had the trained hearing which is necessary to adjust their reproducing systems as to the volume, balance, and allied problems that are essential to producing the real illusion of talking pictures. The training, or self-training, of these men presents a great problem to the industry. Reproduction divides itself into two factors, one pertaining to the physical equipment and the other to the operation of it and handling of the show. All the present producers of commercial sound equipment have standardized their equipment as to speed, position of sound track, and relation of picture aperture to sound aperture so that any record produced can be reproduced on any theatre equipment. Sound pickup from film is accomplished by adding a sound head to a standard projector (RCA Photophone System). See Figs. I, 2, and 3. Such a device has in it mainly the optical system, photocell, constant speed sprocket, and a gate for guiding the film past the reproducing light beam. This beam is located so that the film distance from the picture aperture to it in the direction of film travel is nineteen and a half frames, or pictures. The printing distance between any picture frame and its corresponding sound is made twenty frames in some laboratories, nineteen in others. The reason for such a spacing is that it would obviously be impossible to have the reproducing accessories at the projector picture aperture. The optical svstem is focussed so that the ^Reproduction Supervisor, R K O Studios. Eleventh paper in Technical Digest. reproducing light beam on the film is .085 in. x .001 in. The exciting lamp which illuminates the optical system is a small Mazda lamp, having a coiled filament suspended horizontally. Provisions for conveniently adjusting the position of this lamp are made because it is desirable that its position be such that the reproducing beam has the maximum amount of light possible in it. When a film is run through the light beam, a beam of varying intensity falls upon the active part of the photocell. These variations are to be converted into electrical impulses. The RCA photocell’s coating is caesium and a small amount of inert gas is added to the cell to increase sensitivity through ionization. The polarizing photoelectric cell voltage is supplied through the primary winding of a step-down transformer. The secondary of this transformer is connected through a fader to a step-up transformer at the amplifier. This arrangement eliminates the use of an amplifier on the projector and a source of possible trouble. For disc reproduction, a transfer switch is connected so that the photoelectric cell transformer is replaced by a magnetic pickup. This entire assembly is driven by a motor which will give constant 90 feet per minute film speed or 33-1/3 r.p.m. record speed independent of varying line voltages and condition of load within operating limits and satisfies the requirement of reproduction. MELLAPHONE TURN TABLE If you have not yet installed Mellaphone Equipment; or wish to replace your present equipment with Mellaphone Sound on Disc or Film, write today for full information and trade-in allowance. Special prices on Amplifiers, Speakers, and Tubes, Etc. MELLAPHONE FILM-pDISC SOUND ON Standard equipment for the medium sized house. Mellaphone Turn Tables are substantially built for continuous performance. Quiet, vibrationless, machined throghout with utmost precision. Connects to Main Shaft of All Makes of Projectors. Easily installed. Elec. Research Lab. or Audak Pick-Ups. Spring Suspension Filter. Change Over Fader with Monitor Control. Balanced Fly Wheels. Gleason Gears. Ball Bearings throughout. Record Lamp, Guard and Needle Cups. SOUND ON FILM, solidly constructed, compact, simplified in design. G. M. Photo Electric Cells. All Aluminum Film Head (Uses no chains). Latest Samson Head Amplifiers. Real Synchronous Z4 H. P. Motors. Finest Optical System Attainable. Gleason Gears. Immediate deliveries. Opportunity for Dealers. MELLAPHONE CORPORATION rn°ecwh?otrekr