Mechanical and Optical Equipment for the Stereophonic Sound Film System Available to Purchase

The same mechanism employed for propelling the film in both recording and reproducing. To permit recording of the longer orchestral selections without interruption, the machines are designed to handle film in 2000‐foot lengths. Special features of the film‐propulsion system for obtaining great uniformity of speed at the translation points are described. The three signal‐ and one control‐channel currents are recorded by means of light valves of identical construction. All four tracks are exposed while the film is passing over a free‐running supporting roller, mounted on the same shaft with a new type of internally damped roller. In reproduction, each track is exposed, through an objective of high aperture, to light from an incandescent source. After passing through the film, the light from each track is carried by a glass rod to a photoelectric cell.