From the start of the 20th Century, many methods of apparatus were used to try and synchronise film with sound, usually that of a singer or for sound effects. Until an infallible way became possible, most singers mimed their songs on screen to a phonograph or gramophone in a theatre, guarded by a speed control attendant with a good pair of eyes and ears.
By 1910, many systems including this Hepworth Vivaphone and the Gaumont Chronophone were installed throughout cinemas in Britain and the rest of Europe.
This example is missing the relay control box which sat between the sound and vision apparatus. It consisted of two wheels - one controlled by the projector and the other by the gramophone. Hinged pointers painted red and green respectively extended from both wheels upwards to create a marker for positioning and the nearer and more upright they were, the more accurate the result.
Both cogged wheels were then controlled by separate sprung electromagnets, so if synchronism is upset, the wheel to 'catch-up' is pushed along. Being automatic, to an extent, the small factor of slight changes in sound-to-vision synchronism was not normally spotted by audiance members, as the catch-up, or slow-down, was usually achieved within 50 frames of film.