Wireless: From Marconi's Black-box to the Audion - Sungook Hong - Google Books

https://books.google.de/books?id=UjXGQSPXvIcC&pg=PA165#v=onepage

By 1897 Guglielmo Marconi had transformed James Clerk Maxwell's theory of electromagnetic waves into a workable wireless telegraphy system, and by 1907 Lee de Forest had invented the Audion, a feedback amplifier and oscillator that opened the way to…