Before tubes came around, there was a man who was fascinated with the
buzzer. MORSE. He asked his assistant to make combinations of the short
and long buzz to be called dot and dash. The Morse Code! he probably
didn't realized that he had stumbled on BINARY since he also used two
symbols only, dot and dash, 0,1, not there and there. So, all over
America there was a pair of wires along the railroad tracks carrying the
Morse Code! Another man , BELL, wanted to send his own voice over a
pair of wire. He made a speaker, moving coil with a cone. Then he sent
electric current to it via a carbon tip touching a paper diaphram. When
he spoke on it, it vibrated and the current running through the wires
vibrated correspondingly. The TELEPHONE!
CONTROLLING ELECTRICITY
It was all because of Edison's light bulb! After Edison invented the
light bulb, other experimenters like Lee de Forest played around with
the bulb. The DIODE was discovered via an vacuum tube. Electrons flowed
from the heated element called the Cathode to a Plate but not the other
way around. Then when a thord element was put between the Cathode and
Plate, to be called the Grid, electron flow from the Cathode to the
Plate can be controlled by a tiny current on the grid. The TRIODE, an
amplifier!
MAN went to WAR in 1917 with internal
combustion engines on biplanes, with machine guns in front of the
pilot.. In 1938 when Germany invaded Poland, WW2 began and MAN had
vacuum tubes! The famous walkie talkie of the US army, backpacks with
long antennas. Vacuum tubes. The Germans used them in their V-1 rockets
send to England. There were Pentagrid tubes.
Then
Peace in 1945. The Americans at the Bell Labs in California discovered
SEMICONDUCTORS. The original material was the GERMANIUM. And they were
PNPs! It was developed in 1949 and by the early fifties, a Japanese
company called SONY corporation made the pocket radio, an AM BC radio
working on batteries!
Communications technologies
were developed during the tube era. Superhet for tube receivers, vacuum
tube analog computers. These technologies simply were applied using
semiconductors called transistors.
WHY WERE THEY CALLED VALVES?
It was because they were valves controlling the flow of electrons! The
transistors are still valves not requiring heaters. The
Emitter-Collection junction is controlled by teh Base Emitter junction.
Tickle the Base and electrons flow in the E-C junction!
Now, what is WIRELESS?
In Europe before tubes and transistors were around, they experimented
with SPARK GAPS. It was like lighting matches. The electric spark spewed
waves of many frequencies. It was NOISE! Electrical noise. The receiver
was a simple glass tube filled with iron filings. The filings aligned
themselves when a spark occurred. Contact was made and it was a simple
switch! Aha, WIRELESS. In the meantime, the mathematicians like MAXWELL
in England theorized that signals can travel in space and information
can be imbedded in it by changing the signal strength. Aha, AM!
RESONANCE
Get a pair of tuning forks of the same note, bang one and the other one RESONATES! PHYSICAL RESONANCE! The frequency was within the human hearing range.
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