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In 1906 Lee DeForest announced the development of the first three-element vacuum-tube detector in The Audion: A New Receiver for Wireless Telegraphy, from the Scientific American Supplement. The original Audion was capable of slightly amplifying received signals, but at this stage could not be used for more advanced applications, such as radio transmitters. The inefficient design of the original Audion meant it was initially of little value to radio, and due to its high cost and short life it was rarely used. In fact, in the 1909 edition of Operator's Wireless Telegraph and Telephone Hand-book, Victor H. Laughter's review of the Audion, while noting how sensitive the device was as a receiver, also stated "it is doubtful if it will ever come into wide use, owing to the difficulty in manufacture and short life". The Audion did have a strong allure for teenage experimenters, however. Its imperfect evacuation meant that, like a neon tube, it often glowed an enchanting blue or violet when in use, with the shade varying in response changes in signal strength. And then the filament would burn out. Years later, in the September, 1926 issue of Radio Broadcast magazine, Carl Dreher reminisced in Memoirs of a Radio Engineer about the enticing but frustrating early devices -- "Flung into deepest despair by the demise of a beloved tube, or the failure of a new one which never worked at all, the audion speculator would save up his pennies and plunge again."

Eventually vacuum-tube design was improved enough to make them more than novelties. Beginning in 1912, various researchers discovered that, properly constructed according to scientific and engineering principles, vacuum tubes could be employed in electrical circuits that made radio receivers and amplifiers thousands of times more powerful, and could also be used to make compact and efficient radio transmitters, which for the first time made radio broadcasting practical. Device for Receiving Wireless Time Signals from March 27, 1915 Electrical World magazine, announced that the DeForest Radio Telephone & Telegraph Company in New York City was now selling a vacuum-tube receiver designed to receive time signals from the navy's station, NAA, located at Arlington, Virginia. But as late as 1916 the Audion vacuum-tubes produced by the DeForest company were still plagued by quality control problems, and the company supplied usage tips, such as the March, 1916 QST magazine's Practical Pointers on the Audion by A. B. Cole, which actually revealed how little they understood about the operation of the device.

In 1914, the American Telephone & Telegraph Company purchased the U.S. commercial radio patent rights for the Audion from DeForest. However, the DeForest company retained the right to make sales for non-commercial use, although initially the procedures for purchasing Audions were restricted in an attempt to increase profits. Persons were supposed to first buy a unit which included an Audion vacuum tube -- perhaps a Type RJ9 DeForest Audion Detector "Licensed for amateur or private use only", as offered through the 1916 Manhattan Electrical Supply Company (MESCO) wireless catalog. And even after this initial, and expensive, purchase, replacement Audion tubes could only be obtained by exchanging the remnants of a burned-out Audion, as explained in the Renewal Audion Bulbs section of the catalog. Eventually this restrictive policy was relaxed somewhat, after the Elmer T. Cunningham's AudioTron Sales Company in Oakland, California began selling a cheaper bootleg vacuum tube, and the DeForest company responded with the Type "T" Tubular Audion Tube, recently added to the MESCO catalog, for experimenters "who do not wish to buy complete Audion Detectors with the necessary accessories, and for those whose limited means will not permit the complete instruments to be purchased".