Vitaphone projection system, an analog sound-on-disc system used for feature films in the 1920s.
https://s3-us-west-1.amazonaws.com/h...r_fullsize.jpg
Previously:
https://www.homemadetools.net/forum/...ment-gif-82077
https://www.homemadetools.net/forum/...748#post163494
https://www.homemadetools.net/forum/...450#post131750
https://www.homemadetools.net/forum/...181#post145706
https://www.homemadetools.net/forum/...549#post136091
