GB357687A - Improvements in or relating to television and like systems - Google Patents

Abstract

357,687. Sound reproduction associated with television. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London. - (Assignees of Smith, T. A. ; 20, Heights Road, Ridgewood, New Jersey, U.S.A.) July 21, 1930, No. 22013. Convention date, July 19, 1929. [Class 40 (ii).] In a transmission system for moving picture and sound films the number of picture frames scanned and transmitted in a given time is less than the number of frames passing a fixed point during that time, but the sound record is analysed at the normal rate. A film 4 having a sound record is moved at a uniform rate, for example twentyfour frames per second, in an upward direction by a sprocket 7 driven by bevel gearing 8 from a motor 5, which rotates, at, for example, twenty revolutions per second, a disc 2 with apertures or lenses arranged in five turns of a spiral such that the radial distance between the outermost and innermost holes corresponds to the length of a frame of the film 4. A shutter disc 6 with slots 6<1> slightly wider than the width of the individual apertures is rotated relative to the disc 2 so that a slot passes from the outer hole to the inner hole of the complete spiral during five revolutions of the disc 2. During the rotation of the discs 2, 6 an inverting lens system 9 causes the scanning beam from a light source 1 to move uniformly upwards until the innermost aperture is reached, and then to jump instantaneously in a downward direction a distance equal to the length of one picture frame, which is not scanned. In the present case, four jumps will occur per second so that only twenty picture frames will be scanned and transmitted per second. The scanning beam, modified by the film 4 passes through a lens 10 to a photo-electric cell 11. The sound record 17 is analysed at the normal rate corresponding to twenty-four frames per second by a constant' light 13 co-operating with lenses 14, 15 and a photo-electric cell 16. In a modified arrangement, Fig. 2 (not shown), the inverting lens system 9 together with the discs 2, 6 are located between the film and the photo-electric cell 11.