As the white spot rotated, the cameraman hand-cranked the camera to keep it in sync with the recording.
The inclusion on the sound recorder of a second, parallel, sync or "Pilotone" track, has been the most common method in use until today.
In video recording, synchronism is electronically generated and generally called dual-system sound [3] On location, a camera is driven by a DC motor, with some sort of governor control to hold it fairly accurate at 24 fps, a sync pulse generator geared to the movement or motor shaft could be employed to provide the sync pulse output.
The sync pulse is typically a sine wave of 50 or 60 Hz with an RMS amplitude of approximately 1 volt.
[6] In 1972, Bell & Howell brought out a consumer version of a double-system Super-8 sound filmmaking system called "Filmosound".
In Hong Kong, sync sound was not widely used until the 1990s, as the generally noisy environment and lower production budgets made such a method impractical.
[9] The then popular Mitchell camera, which could be operated silently made it possible to shoot in sync sound.