It’s hard to isolate the invention of the thermionic valve, even who to thank for it. Do we lump it in with the electric filament bulb, so giving the credit to Swan in Britain and Edison in the US (and the others Edison never credited, such as Lewis Latimer)? Do we go forward to John Ambrose Fleming’s diode — patent granted then revoked — or Lee De Forest’s ‘Audion’ triode? Commercial manufacturing of valves ramped up under RCA starting in 1920 (although being American, of course, they called them ‘tubes’).
So in reality, valves were masters of the electronic world for a relatively short time before being superseded by transistors. The first transistor was successfully demonstrated in 1947 at Bell Laboratories, and by the 1950s it already felt like good old thermionic valves were in their twilight years.
There was one last-ditch attempt at fashioning an ultra-reliable vacuum valve, a design which would deliver the very best measured performance yet
