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In May 1932 British papers carried exciting news from Paris. "Historic Feat - Two men watch each other speaking". Correspondents in the Galleries Lafayette department store and offices of the newspaper Le Matin had seen the French Minister of Post and Telegraphs talking to them down an ordinary telephone line.
The ever-enterprising Scotsman John Logie Baird had teamed up with French entrepreneurs and demonstrated just enough of a working system to make headline news. Lafayette promised that in a few week's time there would be a public tv payphone link between their branches in Paris and Lyons.
The world's first videophone needed a transmitter, at each end of the line, built from a heavy metal disc with a spiral of 24 holes. It spun at 75 rpm, in front of a powerful lamp to trace a bright mosaic across the caller's face. A photoelectric cell gathered the reflected light and converted it into a fluctuating electric signal. This went down the phone line.
At the other end the electric signal controlled a neon lamp which shone on a spinning drum clad with 24 mirrors. Reflected light traced lines on a translucent screen which, if the distant wheel and drum were rotating at exactly the same speed, displayed a small coarse image of the caller's face.
The idea was soon forgotten. The wheels were fearsome and the scanning beam dazzled each caller, making it difficult for them to see who they were talking to.
Videophones were reinvented several times e.g. by BT in later years, but failed commercially. Videoconferencing took off when terrorism and high fuel prices encouraged busines people to say in the office. Home video calling took off when it it became free e.g. with Skype