8 Chapter 1
George A. Campbell
(1870–1954) of the Bell
Telephone Laboratories,
had by 1899 developed suc-
cessful “loading coils”
capable of extending the
range and quality of the, at
that time, unamplified tele-
phone circuits. Unfortu-
nately, Professor Michael
Pupin had also conceived
the idea and beat him to the
patent office. Bell Tele-
phone paid Pupin $435,000
for the patent and by 1925 the Campbell-designed load-
ing coils had saved Bell Telephone Co. $100,000,000 in
the cost of copper wire alone.
To sense the ability of loading coils to extend the
range of unamplified telephone circuits, Bell had
reached New York to Denver by their means alone.
Until Thomas B. Doolittle evolved a method in 1877 for
the manufacture of hard drawn copper, the metal had
been unusable for telephony due to its inability to sup-
port its own weight over usable distances. Copper wire
went from a tensile strength of 28,000 lbs/in^2 with an
elongation of 37% to a tensile strength of 65,000 lbs/in^2 ,
an elongation of 1%.
Campbell’s paper in 1922,
“Physical Theory of the Elec-
tric Wave Filter” is still worth-
while reading today. I
remember asking Dr. Thomas
Stockham, “Do digital filters
ring under transient condi-
tions?” Dr. Stockham, (his
wife, Martha, said that she
worshipped the air he walked
on), replied “Yes” and pointed
out that it’s the math and not
the hardware that determines
what filters do. Papers like
Campbell’s are pertinent to Quantum filters, when they
arrive, for the same reasons Dr. Stockham’s answer to
my question about digital filters was valid.
Bell Telephone Laboratories made an immense step
when H.D. Arnold designed the first successful elec-
tronic repeater amplifier in 1913.
H.D. Arnold at Bell Laboratories had taken DeFor-
est’s vacuum tube, discarded DeForest’s totally false
understanding of it, and, by establishing a true vacuum,
improved materials and a correct electrical analysis of
its properties enabled the electronic amplification of
voice signals. DeForest is credited with putting a “grid”
into a Fleming value.
Sir Ambrose J. Fleming
(1848–1945) is the English
engineer who invented the
two-electrode rectifier which
he called the thermionic
valve. It later achieved fame
as the Fleming valve and was
patented in 1904. DeForest
used the Fleming valve to
place a grid element in
between the filament and the
plate. DeForest didn’t under-
stand how a triode operated, but fortunately Armstrong,
Arnold, and Fleming did.
Another Fleming—Sir Arthur (1881–1960)—
invented the demountable high power thermionic valves
that helped make possible the installation of the first
radar stations in Great Britain just before the outbreak
of WWII.
The facts are that DeForest never understood what
he had done, and this remained true till his death.
DeForest was never able, in court or out, to correctly
describe how a triode operated. He did however; pro-
vide a way for large corporations to challenge in court
the patents of men who did know.
With the advent of cop-
per wire, loading coils, and
Harold D. Arnold’s vacuum
tube amplifier, transconti-
nental telephony was estab-
lished in 1915 using 130,000
telephone poles, 2500 tons of
copper wire, and three vac-
uum tube devices to
strengthen the signal.
The Panama Pacific
Exposition in San Francisco
had originally been planned
for 1914 to celebrate the completion of the Panama
Canal but the canal was not completed until 1915. Bell
provided not only the first transcontinental telephony,
but also a public address system at those ceremonies.
The advances in telephony led into recording tech-
nologies and by 1926–1928 talking motion pictures.
Almost in parallel was the development of radio. J.P.
Maxfield, H.C. Harrrison, A.C. Keller, D.G. Blattner
were the Western Electric Electrical recording pioneers.
Edward Wente’s 640A condenser microphone made that
component as uniform as the amplifiers, thus insuring
speech intelligibility and musical integrity.