De Forest, Lee (1873-1961), was an American inventor who pioneered in the technology of radio and television. In 1907, De Forest patented a three-electrode vacuum tube, which he called an audion (see Vacuum tube). The audion made it possible to amplify weak radio signals and transmit them over long distances. It was essential for later advances in broadcasting. In 1912, this tube was adapted as an amplifier for long-distance telephone calls.