Radio Craft Magazine, August 1935 Television Number

     

Presenting the Multiple-Image Television Receiver

The August, 1935 issue of Radio Craft magazine shows a futuristic image of a triple-screen television. The purpose of this set, which was never manufactured, was to let a group of people view the picture from different angles.

Television of the 1930s was an exciting, but still largely experimental, technology. Although mechanical scanning-disk TVs had been superseded by all-electronic sets, electronic picture tubes were still very small. A television of the time might have had a five-inch picture tube, whose image was enlarged by reflection onto a mirror or projection onto a translucent screen.

The cover article was written by Hugo Gernsback, a prolific writer and the publisher of many magazines covering electronics and science fiction. His article describes possible methods for building a multi-screen TV. One method uses a single picture tube with three emitting guns, each one directed at a separate screen.

As with many visions of the future, this one was literally incorrect yet strangely prophetic. Nobody built the three-picture tube that Gernsback imagined, but his idea was realized in modern color TVs. Every color picture tube has three emitting guns, which create three identical images in the colors red, green, and blue.

Instead of pointing the images in three different directions, the color tube superimposes them exactly in one image. In this way, the combination of R, G, and B can create any color of the rainbow in each of the picture tube's thousands of phosphorescent dots.

In tube color TVs, convergence is the process of adjusting the three guns' images to coincide exactly. This is an exacting and delicate procedure, as I learned when starting to restore my RCA CTC-11 television.

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