In article ,
says...

On Sat, 21 Jan 2017 20:11:57 -0000, Terry Casey
wrote:


I think I might have had a bit of trouble getting octal
valves into the bell push ...

Indeed, but there were some very small valves available to the public
in the early 1950's before transistors came along later in the decade.
I remember acorn valves, but there was also a little triode about 3 cm
long and the thickness of a pencil, IIRC. May have been gas-filled.
Both types were used in radio controlled model aircraft.
http://www.r-type.org/articles/art-151.htm

Ah - but my pocket money didn't run to anything fancy like
that and the octal types didn't cost me anything!

--

Terry