Lots of special-purpose vacuum tubes were made, mostly between WWII and 1960.
Most of them aren't on Wikipedia, except (at most) as passing mentions in related articles.
All of these were historically significant, many were used in early digital computers or radar.
Phasitron (in the 1950s, most of the FM broadcast transmitters in America used one.)
Zahl Tube (very important in early development of radar)
Trochotron (only mentioned in the Nixie tube article because I put it there long ago....)
Pixie tube (ditto)
Orbital-beam tube (mentioned in the Secondary Emission article, only because I put it there. Three of them were in the
SCR-270 radar that gave early warning of the Japanese attack on Pearl Harbor in 1941. I would call that "historically significant".)
Radechon (used as memory in the
Rice R1 computer of 1959)
GrapheconScan converters (a variety of designs)
Alphechon (one of the world's rarest collectible tubes--used as memory in RCA's
Spectra 70 computer system display terminals, all of which were junked in 1970-72.)
Sheet-beam tubeSquare-law tube (extremely rare item, used only in tube analog computers)
There's an article about
Robert von Lieben, but it barely mentions the
amplifying tube he invented, at about the same time as deForest.
I'll probably think of others later.
Plus there were two monostable-multivibrator circuits often seen in early computers, that were tube-only: the sanatron and the phantastron.
This guy is using a phantastron circuit for musical sound effects.
This is a pathetic list. Lots of errors and thousands of omissions.
Why don't I add the articles? Why should I, when some teenage RPGer
will just go in and wreck them a few weeks later? You do it.
And
finally....... (IMG:
smilys0b23ax56/default/tongue.gif)