British inventor John Logie Baird and his first publicly demonstrated television system, with which he transmitted moving pictures March 25, 1925 at the London department store Selfridges. This was one of the first demonstrations of television technology. The selenium photoelectric tubes he used had such low sensitivity that human faces could not be televised due to their low contrast. So Baird used the two articulated ventriloquist's dummies shown, "James" and "Stooky Bill" (right), whose painted faces had higher contrast, and televised them speaking and moving. The banks of bright light bulbs were required to illuminate the faces enough to produce an image. His mechanical televisor system had a large spinning disk with 30 lenses mounted in it. As each lens passed across the subject it generated a scan line of the image. At the receiver a similar spinning disk with holes recreated the image. The image thus had a resolution of 30 scan lines, just enough to recognize a face. By the next year Baird was televising real human faces.

Source: Wikipedia