Recent Developments in RCA Photophone Portable Recording Equipment
P. M. Robillard, E. B. Lyford · Journal of the Society of Motion Picture Engineers · 1931
This paper describes improvements made in the RCA Photophone Portable Recorder since the publication of the original paper describing this equipment. The new optical system and galvanometer, which require much less power for its operation, are described and illustrated. The new amplifier, considerably smaller and lighter than the previous one, is also described. Illustrations and electrical characteristics are given. This recorder is mounted upon a standard Mitchell camera and records by the Photophone variable-area method. The complete equipment weighs 450 pounds, including carrying cases and all accessories.