An IMPROVEMENT OR IMPROVEMENTS IN OR CONNECTED WITH TELEPHONE TRANSMITTERS
Year: 1881

page_text: LETTERS PATENT to Edward Hibberd Johnson, of New York, in the United
States of America, but at present of Lombard Street, in the City of London,
for an Invention of "An IMPROVEMENT OR IMPROVEMENTS IN OR CONNECTED
WITH TELEPHONE TRANSMITTERS."
PROVISIONAL SPECIFICATION left by the said Edward Hibberd Johnson
at the Office of the Commissioners of Patents on the 7th December 1881.
EDWARD HIBBERD JOHNSON, of New York, in the United States of America, but
at present of Lombard Street, in the City of London. "AN IMPROVEMENT OR
IMPROVEMENTS IN OR CONNECTED WITH TELEPHONE TRANSMITTERS.”
According to my Invention I use an electrode made from a metal of high specific
resistance, such as tellurium, boron, or silicon in combination with a diaphragm,
the primary wires of an induction coil and a cell of battery or other source of
electric energy, which combination constitutes a telephone transmitter, possessing
certain important and valuable advantages over other telephone transmitters.
I have found by experiment that when the metal which I use forms part of a
low resistance circuit, a slight variation of pressure between it and an electrode of
similar or dissimilar metal will produce a corresponding variation of the resistance
of the circuit, and consequently a variable strength of electric energy sufficient to
actuate the diaphragm of a telephone receiver, and that a variation quite sufficient
for the purpose of transmission of speech so as render it distinctly audible in the
receiver may be had without producing an actual break of the circuit by a
separation of the electrodes.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edward Hibbert Johnson in the Great Seal Patent Office on the
7th June 1882.
EDWARD HIBBERD JOHNSON, of New York, in United States of America, but
at present of Lombard Street, in the City of London. AN IMPROVEMENT OR
IMPROVEMENTS IN OR CONNECTED WITH TELEPHONE TRANSMITTERS."
According to my Invention I use an electrode made from a metal of high
specific resistance, such as "tellurium," "boron," or "silicon ", in combination with
a diaphragm, the primary wires of an induction coil, and a cell of a battery or
other source of electric energy, which combination constitutes a telephone trans-
mitter, possessing certain important and valuable advantages over other telephone
transmitters. I have found by experiment that when the metal which I use
forms part of a low resistance circuit, a slight variation of pressure between it and
an electrode of similar or dissimilar metal will produce a corresponding variation
of the resistance of the circuit, and consequently a variable strength of electric
energy sufficient to actuate the diaphragm of a telephone receiver, and that a
variation quite sufficient for the purpose of transmission of speech so as to render it
distinctly audible in the receiver may be had without producing an actual break
of the circuit by a separation of the electrodes. This cannot be accomplished
practically by metal electrodes of low resistance such as have been heretofore used.
The advantages of my metal electrode over other metal electrodes are therefore
obvious, and the advantage over carbon electrodes consists in the fact that the
annoyance and loss from breakage requiring renewal and of variation of effec-
tiveness by reason of the variable resistance offered by carbon electrodes is
obviated; and again that the metal being more denso than carbon will respond to
a weaker vibration, thus effecting a greater variation of the pressure exerted by
sound waves, and consequently augmenting the variation of current strength with
a given strength of sound-wave.
Having now described the nature of my Invention and in what manner the
samo is to performed, I claim,-
In telephone transmitters and in combination with a diaphragm, induction coil,
and source of electrical energy, the application of an electrode made from a metal
of high specific resistance, such as tellurium, boron, or silicon, and as distinguished
from metals of low specific resistance, such as copper, platinum, brass, and other
such inetals, as and for the purposes set forth.
In witness whereof, I, the said Edward Hibberd Johnson, have hereunto set
my hand and seal, this Fifth day of June, in the year of our Lord One
thousand eight hundred and eighty two.