Synchronizer, Sound-Track

a device for synchronizing the operation of a motion-picture projector and a magnetic tape recorder when showing a sound film with a separate sound track; it provides synchronized reproduction of both picture and sound. The synchronizer makes it possible to control the speed of either the picture projection or the sound playback. For this purpose, the speed of the motion-picture film or the magnetic tape is altered by manual or automatic adjustment of the projector’s feed mechanism or the recorder’s tape transport, thereby maintaining the synchronization of picture and sound. Electromechanical synchronizers, which control the speed of the film in the projector, are the most widely used type. Closer synchronization of projector and tape recorder operation is achieved with automatic electronic devices that correct the motion of the feed mechanism and tape transport according to synchronizing signals recorded on the magnetic tape.