Radio-Television Institute Photo Tube
This is a project that was part of the 1936 Radio-Television Institute course on television. It was built by a student, and demonstrated how a photo tube detected light and activated a relay, which then turned on a light bulb. The front of the photo tube is visible in the box. This tube is similar to the ones used in our 1930 RCA flying spot scanner camera . Inside the box are the photo tube and a 55 tube, a power transformer (center) and a relay (left).
Here is a similar unit made by the American Television Institute. The circuit is almost the same.