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(dated) A television set.

Watching a homemade mechanical-scan television receiver in 1928. The televisor (right) which produces the picture uses a spinning metal disk with a series of holes in it, called a Nipkow disk, in front of a neon lamp. Each hole in the disk passing in front of the lamp produces a scan line that makes up the image. The video signal from the television receiver unit (left) is applied to the neon lamp, causing its brightness to vary with the brightness of the image at each point. This system produced a dim orange image 1+1⁄2 inches (3.8 cm) square, with 48 scan lines, at a frame rate of 7.5 frames per second.