Etching of de Forest (1873-1961) who was principally known for his invention of the Audion, in 1906. This was a vacuum tube device that could take weak telegraph or radio signals and amplify them. Soon audions were being used in radios and and were installed to boost voice signals as they crosed the US continent. In 1921, De Forest also contributed to the film industry when he used electricity to improve sound recordings. This achievement led directly to the creation of motion picture with sound. Published by the International Telecommunication Union.
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