Lee De Forest Biography (1873-1961)


Like many inventors, Lee De Forest was a brilliant innovator but a poor businessman; he spent much of his life fighting lawsuits and lost as many fortunesas he made. A prolific inventor, De Forest had more than 300 patents to hiscredit. He worked in a host of areas including radar, diathermy (applicationof alternating current to the body in medicine), telephone, and color television. But his most important achievement was his audion, an electronic devicethat helped launch a century of innovation in electronics. De Forest was bornat Council Bluffs, Iowa, on August 26, 1873. His father was a minister whoseinterest in astronomy may have sparked his son's love for science. De Forestattended Yale University, studying under Josiah Willard Gibbs (1839-1903), apioneer in the disciplines of physical chemistry and advanced thermodynamics. De Forest's 1899 Ph.D. dissertation, on the reflection of "Hertzian" (or radio) waves, was possibly the first scholarly treatise in the United States todeal with Heinrich Hertz's (1857-1894) discovery. When he heard of GuglielmoMarconi's early success with wireless, or radio, De Forest began building his own wireless set ups. De Forest's first major invention was the responder,which he introduced in 1901. A device for detecting radio waves, the responder was superior to the coherer detectors then in use, in that it contained a liquid electrolyte instead of metal filings like the coherer did. These filings tended to stick together, impairing the coherer's sensitivity. De Forest found a financial backer and established the American De Forest Wireless Telegraph Company. Competing with Marconi, De Forest began selling equipment to theUnited States Army and Navy, and aggressively marketed his devices to the public by carrying out wireless demonstrations around the country. In 1903, DeForest created an improved version of his responder which was very similar toa design patented by Reginald Fessenden. Fessenden sued, and in 1905 court injunctions were issued to keep De Forest's company from manufacturing the detector. Disillusioned by the defeat and angered by the shady activities of hisboard of directors (who were embezzling funds), De Forest took his patents and quit the company in 1907. By this time, De Forest had already made a new invention of far greater importance than his responder. He had discovered thatby adding a third element (a wire grid) to the diode invented by John Ambrose Fleming, he could amplify weak signals far more effectively than availabledetectors could. He obtained a patent for his device, which he called an audion, in 1906. In order to make the first wireless voice transmission onChristmas Day, 1906, Reginald Fessenden had to have specialized equipment constructed, but De Forest's audion or triode soon made radio voice communication commonplace. The audion could perform three functions which would revolutionize electronics. First, it could amplify weak signals including radio waves, telephone signals, or any signal that required boosting. Second, it could modulate a signal--that is, it could impose voice, music or other sounds upon a radio "carrier" wave for broadcast. Finally, when overloaded with asignal, the audion became an oscillator with the ability to generateradio waves, though De Forest did not make this discovery until 1912. Until Walter H. Brattain, John Bardeen, and William B. Shockley invented the transistor in 1948, De Forest's triode would remain the most important component invirtually any electronic device. The success of the audion enabled De Forestto raise capital for another company he called the De Forest Radio TelephoneCompany, and again he began staging broadcasts around the country. On January20, 1910, in a spectacular demonstration, he used his broadcasting system totransmit the singing of Enrico Caruso to listeners on the east coast of theUnited States. He had won more Navy contracts and appeared to be flourishingat last. But once more, De Forest found himself in trouble when he and a number of company officials were arrested for mail fraud. Apparently, his backerswere again involved in fraudulent activity, and prosecutors, bent on puttinga stop to an epidemic of swindling in the radio industry, charged De Forestand his associates with trying to exploit "a strange device like an electriclamp (the audion), which... had proven to be useless. " While out on bail, adesperate De Forest offered to sell the broadcating rights to his audion to the American Telephone and Telegraph Company. Feigning disinterest, AT&T sent an anonymous agent to offer De Forest a paltry $50,000 for the device, swearing "on his word of honor as a gentleman" that he did not work for AT&T. De Forest accepted. Shortly after, he made up some of his losses when he sold AT&T the radio-signalling rights to the audion for a better price of$340,000. In 1913, De Forest was acquitted of fraud, but the president of hiscompany was found guilty and sentenced to prison. De Forest continued to find new ways to use the audion. In the 1910s, he discovered that he could increase the sensitivity of his audion detector by sending back some energy from the diode circuit into the grid, creating a feedback loop. When he applied fora patent for this "regenerative" circuit, he promptly embroiled himself in yet another lawsuit, this time with Edwin H. Armstrong , Irving Langmuir at General Electric, and Alexander Meissner in Germany. Armstrong had been issueda patent for such a circuit in 1914 and won initially, but after a 20 year battle, De Forest was victorious in his appeal to the Supreme Court, though most radio engineers believe that the idea belonged to Armstrong. This was enough for De Forest. In 1919 he stopped working on radio and took up the challenge of synchronizing sound to motion picture s. He devised an electrical-optical method of directly recording a sound track on film and, on April 12, 1923,gave a demonstration of a talking motion picture. Incredibly, movie executives expressed indifference to this innovation, thinking that public interest was lacking. When "talkies" became an instant sensation years later, De Forestgained nothing. De Forest died on June 30, 1961, in Hollywood, California. Hehad received his last patent, for an automatic telephone dialing device, atthe age of 84. Despite the misfortunes that De Forest's work in wireless brought him, he always expressed a special fondness for radio, which he considered his "child." Though his reputation as an originator seems to have diminished over time, his audion undoubtedly was more important in the development ofelectronics over the first half of the twentieth century than any other single invention.

User Contributions:

Comment about this article, ask questions, or add new information about this topic: