Synchronization and Speed Control of Synchronized Sound Pictures

The reproduction of the synchronized sound picture of today presents no serious problem of synchronization, for this factor has been practically eliminated by the perfection of electrical means for reproducing sound with equipment which may be coupled mechanically to the picture projector. The important problem of the present day, in connection with the reproduction of synchronized sound pictures, is the provision of suitable means for maintaining a constant speed of the sound reproducing mechanism in order that the pitch of the sound being reproduced may not suffer any sudden change which would be sensed by a good musical ear. Control circuits using vacuum tubes with a frequency bridge as a speed standard with provision for manual variable speed control are described and explained for use with both A.C. and D.C. motors. Remote synchronization permitting the recording of pictures and sound simultaneously on equipment located some distance apart is obtained by a modification of the Michalke electric gear system.