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16 November 1904. London, England. Beginning in the 1880s Professor John Ambrose Fleming of University College London investigated the Edison effect, electrical conduction within a glass bulb from an incandescent filament to a metal plate. In 1904 he constructed such a bulb and used it to rectify high frequency oscillations and thus detect wireless signals. The same year Fleming patented the device, later known as the 'Fleming valve.'