My latest article, near end of this, WW2 proximity fuzes

https://myemail.constantcontact.com/Thursday-Tidings.html?soid=1102959880889&aid=Aek4_55BGhA

 

This required making vacuum tubes a little smaller than the one in your parlor radio

 

Yes that looks like one. The designers adopted then-common tiny vacuum tubes used in hearing aids and hardened them for shock forces where necessary. The fuzes used either four or five vacuum tubes each. The tubes and all other electronic components were “potted” in beeswax, and after much trial and error, were able to survive firing from a gun.