Shown is the telephoto sender. The photographic negative is mounted over a cylindrical photo-electric cell and moved horizontally while being rotated. A tiny spot of light is thrown on the film and thus entirely traverses it in a long spiral. The light passing through the film naturally varies in intensity and the cell reacts by sending forth electrons in according variation. Thus the lights and shades are translated into electrical currents. Photo dated: December 2, 1926.
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