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The triode valve is a switch device and an amplifier of electrical signals. It became a key component of radio, television, radar and computer systems before the development of the transistor in 1947.
The first triode valve was patented in 1907 by American wireless pioneer Lee De Forest and was called the Audion. It was initially used as a radio detector, like Fleming's diode valve of 1904, but its true potential was not realised until 1912 when it was incorporated into a circuit which could amplify audio and radio signals. For 50 years, valves were a fundamental component in all radio equipment, until being generally replaced by the transistor. In the USA, De Forest is known as 'the father of radio'.