The Vacuum Tube is a Very Fast Switch
If you can turn "on" and "off" then you can count...
that is the essence of modern binary computers. So, the faster you can make
the switch, the faster the computer will be able to run. There are three
important versions of this idea, each one faster than the previous. They
are: the relay, the vacuum tube, and the transistor.
Electromagnetic relays have been around since the 1800's. When a current
is applied to the relay, it creates a magnetic force that pulls a metal
contact between two conductors.
The Vacuum tube was invented around 1920(?) and was much faster than the
relay because it had no moving parts. The flow of electricity is controlled
like a valve controls the flow of water.
Bell Labs invented the transistor in 1954. Like the tube, it has no moving
parts. But, instead of being made of glass and wire and plastic, the transistor
is made of silicon (like sand) mixed with a few impurities. This construction
made it possible to make transistors very, very small. Modern computer chips
pack millions of transistors into a single chip!
But, in 1946, the fastest way to switch electricity was with a vacuum tube.
So, the scientists at Penn proposed to the Army that they be granted money
to build a new machine out of vacuum tubes. This new device would be very
fast, and would be able to perform the calculations for the firing tables
much faster than the Differential Analyzer or hand calculators.
Continue on to Punched Cards...
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