WWII Tube Electronics Training Film
I love these old training films I'm still pretty green so these are very helpful.
This
WWII training film familiarizes radio operators with Vacuum Tubes. As
the film explains, these are the devices used in radios that control
electric current between electrodes in an evacuated container. Vacuum
tubes mostly rely on thermionic emission of electrons from a hot
filament or a cathode heated by the filament. The grid and filament
forming the tube are explained, as are some basic circuits, and a couple
of electronics packages are shown.