The vacuum tube,
used up to this time in
almost all the computers and
calculating machines, had been invented by
American physicist Lee De Forest in 1906.
The vacuum tube, which is about
the size of a human thumb,
worked by using large amounts
of electricity to heat a filament
inside the tube until it was
cherry red. One result of heating
this filament up was the release
of electrons into the tube, which
could be controlled by other
elements within the tube. De
Forest's original device was a
triode,