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(1905) Sir John
Ambrose Fleming
made the first diode tube,
the Fleming valve. The device had three leads, two for the
heater/cathode and the other for the plate.
(1907) Lee De Forest
added a grid
electrode to Fleming’s’ valve and created a triode, later
improved and called the Audion.
(1921) Albert W. Hull,
an American engineer, invented a vacuum tube oscillator called
it a magnetron. The magnetron was the first device that could
efficiently produce microwaves. Radar, which was developed
gradually during the 1920's and 1930's, provided the first
widespread use of microwaves.
The introduction of Vacuum tubes at the beginning
of the 20th
century was the starting point of the rapid
growth of modern electronics. With vacuum tubes manipulation of
signals because possible, which could not be done with the early
telegraph and telephone circuit or with early transmitters using
high voltage sparks to create radio waves. For example, with
vacuum tubes weak radio and audio signals could be amplified,
and audio signals, such as music or voice, could be superimposed
on radio waves. The development of a large variety of tubes
designed for specialized functions made possible the swift
progress of radio communication technology before World War II.
The vacuum tube era reached its peak with the
completion of the first general purpose electronic digital
computer in 1945. This huge machine, called ENIAC (Electronic
Numerical Integrator and Computer) was built by the two
engineers at the University of Pennsylvania,
J. Presper Eckert, Jr.,
and John W.
Mauchly.
The computer contained about 18,000 vacuum tubes and occupied
about 1,800 square feet of floor space. ENIAC worked 1000 times
faster than the fastest non electronic computers then in use.
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