New Automatic Sound Slidefilm System
Wesley Palmer · Journal of the Society of Motion Picture Engineers · 1949
A new completely automatic sound slidefilm system has been devised which operates by virtue of low-frequency tones recorded on the disk along with the program material. The system permits an uninterrupted flow of sound without audible gongs or bells. It is positive in action and immune to record wear, scratches, or blunt needles. A tone generator is available to record the disks required for the system.