Bell Labs Mechanical Color System (1929)

In 1929  US Bell Labs demonstrated a color TV system, The Bell Labs system also used a scanning disk, but instead of three spirals with red, green, and blue filters, it used three banks of photocells with the appropriate filters. The receiver used three lights with filters and a system of mirrors to reconstruct the image. The Bell Labs system also suffered from the resolution and frame rate limitations of mechanical scanning schemes, and nothing further came of it. A 1930 booklet describes this system.

Modern Mechanix, November, 1929

Radio Engineering, August 1929

Popular Science, September 1929