Cyril Frank Elwell

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Cyril Frank Elwell (August 20, 1884 – February 11, 1963) was an Australian-born American inventor who helped develop radio. He grew up in Australia with an American father and a German mother, then moved to the United States in 1902 to study electrical engineering at Stanford University. After helping repair the campus following the 1906 San Francisco earthquake, he graduated in 1907 and started the Poulsen Wireless Telephone and Telegraph Company, which later became Federal Telegraph.

Elwell initially worked on large electrical furnaces, but in 1908 he shifted to wireless radio after studying a spark-gap voice system. He believed the Poulsen arc converter could send continuous waves needed for voice radio. By 1910 he demonstrated voice transmission between Stockton and Sacramento, and Federal Telegraph pursued Navy radio contracts to Hawaii. He left the company in 1913 after a board dispute, then worked briefly with the Universal Radio Syndicate and served as a consulting radio engineer for France and Italy during World War I. From 1915 to 1923 he ran his own company, C. F. Elwell, Ltd.

In 1924 John Logie Baird bought from Elwell a thallium sulfide cell used in Phonofilm, an early talking-picture system. Elwell helped found Mullard, a major vacuum tube maker. After leaving Mullard, he returned to the United States in 1947 to work as a consulting engineer for Hewlett-Packard. He died in 1963 in Belmont, California and is buried in Palo Alto.