"The Tri-Ergon sound-on-film system was developed from around 1919 by three German inventors, Josef Engl (1893–1942), Joseph Massolle (1889–1957), and Hans Vogt (1890–1979).
The system used a photoelectric recording method and a non-standard film size (42mm) which incorporated the sound track with stock 35mm film. With a Swiss backer, the inventors formed Tri-Ergon AG in Zurich, and tried to interest the market with their invention.
Ufa acquired the German sound film rights for the Tri-Ergon process in 1925, but dropped the system when the public showing of their first sound film suffered technical failures." - (Wikipedia (en) 26.12.2019)
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