IMPROVEMENTS IN TELEPHONES
Year: 1879

page_text: LETTERS PATENT to Philip Syng Justice, of 14, Southampton Buildings, in the
County of Middlesex, Engineer, for the Invention of "IMPROVEMENTS IN
TELEPHONES." A communication from abroad by Sidney Howe Short, of the
County of Franklin, in the State of Ohio, in the United States of America.
PROVISIONAL SPECIFICATION left by the said Philip Syng Justice, at the
Office of the Commissioners of Patents on the 23rd August 1879.
PHILIP SYNG JUSTICE, of 14, Southampton Buildings, in the County of Middlesex,
Engineer. "IMPROVEMENTS IN TELEPHONES." A communication from abroad by
Sidney Howe Short, of the County of Franklin, in the State of Ohio, in the United
States of America.
This Invention relates to the transmitting instrument of an electric speaking
telephone, and more particularly to instruments of that class in which the electric
undulations conveying articulate speech are controlled or caused by the varying
resistance of an imperfectly conducting medium under pressure.
As these variations in the amount of pressure upon the conducting medium are
caused by the vibrations of a diaphragm set in motion by the slight impulses of the
sound-waves, and are themselves very slight and inadequate to produce the desired
effects in circuits where there is any considerable resistance, it has been deemed
necessary to seek some material for such conducting medium, so that the necessary
scope in the variations or rise and fall of the tension could be obtained without too
great resistance to the electric current.
The object of this Invention is to secure this result by increasing the amount of
pressure which is applied to the ordinary carbon used as a medium for the trans-
mission of the variable electric undulations, and by enlarging the scope or degree of
variation in the pressure applied through the agency of the ordinary vibrating
diaphragm, whereby the excessive resistance of the ordinary carbon medium may
be overcome, and a sufficient variation in the electrical undulations obtained.
Heretofore the pressure has been applied to the carbon or other imperfectly con-
ducting substances employed in the transmitting instrument directly from the
diaphragm, using for that purpose only the force and motion imparted to the said
diaphragm by the sound-wave.

page_text: This construction and mode of operation leaves the carbon medium ordinarily
free from pressure, and allows it to offer its full and natural amount of resistance to
the electrical current, while the variety in pressure and the consequent variation
in the electric undulations are only such as can be produced by the slight and
unassisted impulses of the diaphragm directly applied to the carbon or other
medium. My Invention consists first, in holding by mechanism the carbon or
other imperfectly conducting medium in the transmitting instrument regularly
under pressure, and in causing the action of the diaphragm under the impulses of
the sound waves to vary the pressure thus regularly, applied, whereby the resistance
of the carbon or other conductor can be regulated at will, and greater sensitiveness
and scope of the electrical undulations be produced.
It consists in the second place in causing the vibrations of the diaphragm to act
through intermediate mechanism, whereby the motion of the said diaphragm is
exaggerated and greater effect produced through the carbon or other medium
employed. Secured on the diaphragm and perpendicular to its plane I place two
standards, which support at their upper ends two cups facing each other; one cup
being made of metal containing a concave carbon disc in electrical counection with
the transmitting wire, the other cup is composed of hard rubber or other non
conducting material, similarly provided with a carbon disc, but having a platinum
plate between the carbon disc and the bottom of said cup; this platinum plate is
also in electrical connection with the transmitting wire. Between the concave
surfaces of these carbon discs is placed a carbon button, having two convex surfaces,
formed on a shorter radius than that of the concave surfaces of the discs themselves;
this button is held loosely between the said concave surfaces, but may be compressed
to any required degree by the motion of a threaded shank attached to the metal
cup. It is obvious that on the diaphragm being bent inwardly the inner upper ends
of the standards are caused to diverge from each other, whereby the carbon medium
is relieved from the pressure caused by the before mentioned threaded shank.
Manifestly the amount of motion for a given deflection of the diaphragm at the
inner upper ends of the standards will depend upon their length, so that by this
construction any desired amount of motion can be produced by the ordinary or
slight vibrations of the diaphragm. To prevent unnecessary vibrations of the
diaphragm after the first impulse is given to it I place a slender rod threaded where
it passes through the shell of the chamber of the telephone, on the lower end of
which I secure a soft rubber button or ball which barely touching the diaphragm
or the standard which is secured upon it accomplishes the desired purpose.
...
"

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Philip Syng Justice in the Great Seal Patent Office on the 12th
February 1880.
i
PHILIP SYNG JUSTICE, of 14, Southampton Buildings, in the County of Middlesex;
Engineer. "IMPROVEMENTS IN TELEPHONES." A communication from abroad by
Sidney Howe Short, of the County of Franklin, in the State of Ohio, in the United
States of America.
This Invention relates to the transmitting instrument of an electric speaking
telephone, and more particularly to instruments of that class in which the electric,
undulations which convey articulate speech are controlled or caused by the varying
resistance of an imperfectly conducting medium under pressure. As these variations
in the amount of pressure upon the conducting medium are caused by the vibration
of a diaphragm set in motion by the slight impulses of the sound waves, and are
themselves very slight and inadequate to produce the desired effects in circuits
where there is any considerable resistance, it has been deemed necessary to seek
some material for such conducting medium, so that the necessary scope in the
variations or rise and fall of the tension could be obtained without too great
resistance to the electric current. The object of my Invention is to secure the same.
result by increasing the amount of pressure which is applied to the ordinary carbon
used as a medium for the transmission of the variable electrical undulations, and
by enlarging the scope or degree of variation in the pressure applied through the
agency of the ordinary vibrating diaphragm whereby the excessive resistance of the.
ordinary carbon medium may be overcome and a sufficient variation in the electrical
undulations obtained. Heretofore the pressure has been applied to the carbon
or other imperfectly conducting substances in the transmitting instrument directly
from the diaphragm, using for that purpose only the force and motion imparted to
the said diaphragm by the sound wave. This construction and mode of operation
leave the carbon medium ordinarily free from pressure and allow it to offer its full
and natural amount of resistance to the electrical current while the variety in
pressure and the consequent variety in the electrical undulations are only such as
can be produced by the slight and unassisted impulses of the diaphragm directly,
applied to the carbon or other medium.
My Invention consists, first, in holding by mechanism, substantially as described,
the carbon or other imperfectly conducting medium in the transmitting instrument
regularly under pressure, and in causing the action of the diaphragm under the
impulses of the sound waves to diminish the pressure thus regularly applied,
whereby the resistance of the carbon or other conductor can be reduced and
regulated at will and greater sensitiveness and scope of the electrical undulations.
produced. It consists in the second place in causing the vibrations of the diaphragm
to act through intermediate mechanism, whereby the motion of the said diaphragm
is exaggerated and greater effect produced upon the carbon or other medium.
.
The apparatus in which I have embodied my Invention is shown in the accom-.
panying Drawing, in which Figure I. is a perspective view, and Figure II. a central
longitudinal section of my improved transmitter. In these figures a is an ordinary.
mouth-piece attached to a plate b which clamps to the disc c an ordinary diaphragm
e of iron or other elastic substance. To this diaphragm are connected by small
rivets the standards k, k', each of which is located preferably about midway between
the centre and the edge of the diaphragm e. To the inner ends of these standards.
are connected the cups m and n. The cup m is of metal, and in electrical connection
with the wire o. It contains a disc of carbon fitted to the cavity, which disc is
formed with a concave face, as shown in Fig. 2. The cup is made of hard rubber
or other non-conducting material and is connected to the standard k. It is
provided with a carbon disc similar to that shown in the cup.m. Underneath the

page_text: carbon disc and resting against the bottom of the cup is a platinum plate p, which
is in electrical connection with the wire o¹. Between the concave surfaces of the
two carbon discs is a carbon button q having two convex surfaces formed on a
shorter radius than that of the concave surfaces of the discs, as clearly shown in the
Figure. The cup'n is fixed rigidly to its standard k', but the cup m is adjustable
in its standard and is capable of being advanced or withdrawn by means of the
threaded shank, the end of which for accessibility is opposite the perforations & in
the case c.
The button q is held 'loosely between the concave surfaces of the carbon
discs and may be subjected to compression to any required degree by turning the
threaded shank r, the compression being applied alike to the carbon discs and to
the carbon button held between them. The standards k, k¹, are set perpendicular
to the plane of the diaphragm. Obviously when the diaphragm is bent inwardly
the inner upper ends of the standards are caused to diverge from each other,
whereby the carbon medium is relieved from the pressure applied by means of the
threaded shank and the amount of resistance of the said medium is increased,
such increase being in proportion to the spread of the standards and the deflection
of the diaphragm. Manifestly the amount of motion for a given deflection of the
diaphragm in the inner ends of the standards will depend upon their length, so that
by this construction any desired amount of motion can be produced by the ordinary
or slight vibrations of the diaphragm.
Further, as the divergence of the standards increases from the diaphragm inwardly,
and the surface of the button is formed on a smaller curve than that of the cups, it
is plain that divergence of the standards caused by a depression of the diaphragm
will tend to open the cups more upon that side farthest from the diaphragm, and
that the amount of surface of the button in contact with the cups on each side will
be diminished: This diminution of the surfaces in contact also increases the
resistance of the medium and tends to magnify in the variations of the electrical
current the effect of the vibrations imparted to the diaphragın caused by the sound
waves in contact therewith.
It will be observed therefor that the carbon conductor is in its normal condition
under pressure. The amount of this pressure may be varied at will, and applied to
any degree that may be desired by means of the screw, so that there is no possi-
bility of any difficulty arising from top great resistance in the imperfect conductor
in the amount of resistance and in consequent electrical currents caused by the
diminution of pressure and the resulting increased resistance so that the scope of
the instrument is almost indefinitely enlarged. The amount of motion and the
leverage being dependent on the length of the standards which support the cups
any desired degree of sensitiveness may also be obtained. I have found by actual
experiment that the results are highly satisfactory in this respect. In order to
prevent repeated vibrations of the diaphragm after the first impulse is given, which
itself is sufficient for the communication of the sound, I have provided a device to
check these vibrations of the diaphragm. It is shown at t. and consists of a slender
rod threaded where it passes through the shell and having on its inner end a soft
rubber head u which may be in contact, or nearly in contact, with the base of one
of the standards, or with the diapliragm itself. The head is sufficiently soft to yield
under the impulse of the sound wave, but it offers sufficient resistance to deaden
the subsequent vibrations. The shape of the shell which I have shown has been
found convenient, but it, may be varied without departing from the spirit of the
Invention. A modification of the standards is shown in Fig. 3, in which short
posts x, x, are used, to the bases of which are fixed the ends of light curved springs
3. 3. These springs carry the cups and are moved in and out to graduate the
pressure on the carbon by means of screws z, z, the heads of which, as in the form
first described, are accessible through holes in the shell.
Having thus described the nature of the Invention as communicated to me by
my foreign correspondent, what I claim as new and desire to secure by Letters
Patent is,-
.
First. A telephonic transmitter in which the imperfectly conducting medium is

page_text: held under pressure applied independently of the diaphragm, and the electrical
pulsations are caused by diminution of the normal pressure effected by the vibra-
tions of the diaphragm.
Second. In a telephonic transmitter, the combination of an elastic diaphragm
adapted to vibrate under the impulse of the sound waves, of standards connected
to said diaphragm of an imperfectly conducting medium held under constant
pressure on said standards, and an electrical connection with a battery and a
receiving instrument, said devices being adapted to operate to cause the electrical
pulsations by diminution of the constant pressure, as set forth.
Third. The combination of the elastic diaphragm, the standards attached thereto,
the carbon conductors and the set screw carrying one of the carbon conductors by
which the pressure on the carbon may be varied, as set forth.
Fourth. The combination of the elastic diaphragm, the standards fixed thereto,
carrying discs of carbon formed with concave faces, and the double convex carbon
button, said button being formed on a smaller curve than that of the cups, as
set forth.
Fifth. In a telephonic transmitter, a standard fixed to the diaphragm at some
point between its centre and edge, and acting in connection with another standard
to hold the carbon under pressure and to diminish said pressure by vibrations of
said diaphragm, said carbon being in electrical connection, as set forth.
In witness whereof, I, the said Philip Syng Justice, have hereunto set my
hand and seal, this Nineteenth day of January, 1880.