From: Patent Tactics, George Brock-Nannestad
Jack Theakston wrote:
> The turntable was mechanically driven by the projector, and the record
> played from the inside out.
----- I think we need to tell that there was a differential built-in (like in
old rear-wheel drive cars) that permitted acceleration of the record to catch
up with the film strip if one or several frames had been lost - this was a
must to maintain synchronism
Several safeguards were installed in case the
> needle jumped or there was any electrical interference. Never-the-less, by
> 1930, sound-on-disc was considered old hat and theaters installing sound
> almost entirely went to sound-on-film.
> The difference was amplification-- the key to motion picture sound. Before
> De Forest's Audion tube (and later triode) were in common use, acoustic
> recordings were not loud enough to fill 2,000+ seat auditoriums.
----- not entirely acccurate: Edison used Higham's friction amplifier (also
known from Columbia Graphophones) for his Kinetophone system, and Parson's
invention in England that was licensed to the Gramophone Company used
compressed air to amplify acoustic reproduction, called the Auxetophone. They
were plenty loud. Pathé who was even more in the film business than Edison
used very heavily modulated 20 inch records to drive large diaphragms and
horns. The amplification (as in all acoustic reproduction) was supplied by
the drive train for the turntable.
Amplification was the prerequisite for sound-on-film, not sound film (rather
film with dialogue instead of intertitles)