SHEILA TERRY / SCIENCE PHOTO LIBRARY SHEILA TERRY / SCIENCE PHOTO LIBRARY
Early television system. Historical artwork of a proposed 19th century system to transmit an image by using optical and telephone technology. The original image (a woman's head) is at left. This is scanned by a Lissajous Generator, using a light source (far left) and a pair of tuning forks (centre right, U-shaped) arrayed at right-angles. Mirrors on the tuning forks reflect the light, which is projected by a lens onto a selenium cell. The voltage of the selenium cell varies with the amount of light. This encodes the image as an electrical signal. This is sent along telephone lines and the image is then recreated (right). From Physique Populaire (E. Desbeaux, 1891).
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