How this projector get synched with a gramaphone?

[Winbert Hutahaean]

Can someone explain to me how this projector can get synched with the gramaphone:

https://www.facebook.com/share/r/1CtnSY1Grz/

[Larry Arpin]

I remember seeing a picture of the projector and record player connected with a belt. But maybe they found another way to sync it up electronically.

[Steve Lee]

The original vitaphone system could be retrofitted to any motorized projector, as it used the projectors motor to power the turntable.
On the record there was a dot painted where the projectionist placed the needle. On the film leader there was also a sync frame that was needed to be placed into gate.
So once the projector was started up, in theory to two should stay in sync. As the films were being run on change over, there was also a control unit that switched between the pickups depending on which projector that was being run.

On the photo I should emagine both the projector and turntable are fitted with a interlock motor, in the same way as the cinerama system worked. Inch one projector over and the other two follow, or the practice of running a single print between multiple projectors at the same time.
It does exactly the same thing without the need of drive belts.