GB562081A - Improvements in or relating to reproducing apparatus for sound films - Google Patents

Abstract

562,081. Reproducing apparatus for sound films. WESTERN ELECTRIC CO., Inc. Feb. 24, 1943, No. 3026. Convention date, March 10, 1942. [Class 40 (ii)] [Also in Group XXXIX] Relates to reproducing apparatus for sound films 1, Fig. 1, in which the sound track 2 is divided longitudinally into two portions 3, 4, one 3 containing a complete record of all the sounds to be recorded and the other 4 containing a record of only those sounds which are above a predetermined volume level. According to the invention, the apparatus comprises means for simultaneously scanning the two portions of the sound track and deriving separate signal currents therefrom with unequal efficiencies, so that the gain imparted to the signals derived from the portion of the sound track which contains the complete sound record is less than the gain imparted to the signals derived from the other portion of the sound track, and means for combining the signal currents thus derived from the two portions of the sound track in additive phase relation and utilizing the combined signal currents to reproduce the recorded sound. Optical or electrical means may be used for deriving the signal currents from the two portions with unequal efficiencies. The sound may be recorded on the " squeeze track " system for noise 'reduction. In the reproducing apparatus shown in Fig. 2, the film 1 is scanned by an optical system 7, the light beams passing through the two portions 3, 4 of the sound track falling on the separate portions of a cell 6 having two separate anodes 9, 91, the signals from which are amplified in two separate channels by the double triode V1 and combined by the mixing tube V2. The gains are controlled by an optical filter 8 or by tappings 17, 18 or by both these means. If the amplification given by the tube V2 is not required, the mixing may be done by the circuit shown in Fig. 3. Specifications 362,915, 394,328 and 494,019 are referred to.