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During
his lifetime, Lee de Forest received over 180 patents. His most significant
was the 3 element vacuum tube. |
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But de Forest is most known for his contributions and improvements to the basic invention of all radio and television, the vacuum tube. Earlier Thomas Edison's electric lamp had been modified by the Englishman, Ambrose Fleming, who added a second element, called a plate, and called it the Fleming Valve. By 1906 de Forest had modified Fleming's Valve by adding a grid to control and amplify signals, and called his device the Audion. At the right is the original Audion patent, dated January, 1907. The Audion was used as a detector of radio signals, an amplifier of audio and an oscillator for transmitting
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The
first use of the audion was as a detector of radio waves. A detector
converts radio frequency, RF, into audio frequency, AF, that can be
heard using headphones or amplified for a loudspeaker. |
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| Moving to California in 1910, he worked for Federal Telegraph Company at Palo Alto. While there, de Forest finally made his Audion tube perform as an amplifier and sold it to the telephone company as an amplifier of transcontinental wired phone calls. For this innovation he received $50,000. | By 1916, he had perfected his Audion for its most important task, that of an oscillator for the radiotelephone transmitter. By late 1916 de Forest had begun a series of experimental broadcasts in New York City. According to de Forest, "The radio telephone equipment consists of two large Oscillion tubes, used as generators of the high frequency current." |
Lee de Forest and 1948 Mechanical Color Television
