16 November 1904: John Ambrose Fleming patents the oscillation valve

On this day in 1914, John Ambrose Fleming patented his oscillation valve – a component which formed the basis of the electronics industry for half a century.

John Ambrose Fleming's thermionic diode or oscillation valve
Fleming's oscillation valve: astonishingly useful and oddly beautiful
(Image credit: © SSPL/Getty Images)

Perhaps the only contact many of us have with the sort of valves you get in electronics these days is if we have an ageing cathode-ray tube TV, or if we know a particularly boring audiophile who is prone to drone on at length about how his organically grown amp produces a much richer, more vibrant sound than your puny CDs or that new fangled streaming "music" that all the kids are listening to these days.

But valves (which our Americanly-challenged friends call vacuum tubes) were the backbone of the electronics industry for 50 years or so, until they were superseded by solid-state transistors.

And it's all thanks to the efforts of John Ambrose Fleming, the first professor of electrical engineering at London's University College, who also worked for both Marconi and Edison. He invented the oscillation valve, which he patented today in 1904. It was, without doubt, one of the most important developments in the history of electronics.

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Fleming's valve was the first practical application of the “Edison effect” – the phenomenon of “thermionic emission” whereby electrons flow from a heated element to a cool one – which Edison observed while creating his electrical light bulbs. Indeed, in many ways, Fleming's “thermionic” valve is little more than a modified light bulb.

By heating an electrode inside a glass bulb containing a vacuum, it is possible to “rectify” an electrical current and radio waves, and amplify them. And the later addition of a grid through which the electrons had to pass meant the current could be regulated.

The valve's invention led to the introduction of radio around the world, the discovery of radar, and eventually to the supercomputers and artificial intelligence of today.

Ben Judge

Ben studied modern languages at London University's Queen Mary College. After dabbling unhappily in local government finance for a while, he went to work for The Scotsman newspaper in Edinburgh. The launch of the paper's website, scotsman.com, in the early years of the dotcom craze, saw Ben move online to manage the Business and Motors channels before becoming deputy editor with responsibility for all aspects of online production for The Scotsman, Scotland on Sunday and the Edinburgh Evening News websites, along with the papers' Edinburgh Festivals website.

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