A NEW CONSTRUCTION OF TELEPHONE TRANSMITTER
Year: 1881

page_text: I
LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for
an Invention of "A NEW CONSTRUCTION OF TELEPHONE TRANSMITTER." A
communication from abroad by Henri Machalski, of Lemberg, in the Empire
of Austria.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 19th September 1881.
SYDNEY PITT, of Sutton, in the County of Surrey. "A NEW CONSTRUCTION OF
TELEPHONE TRANSMITTER." [A communication from abroad by Henri Machalski,
of Lemberg, in the Empire of Austria.]
The construction of this transmitter is based upon a principle already known in
the construction of the microphone, namely, that graphite being an indifferent
conductor of electricity changes with its greater or less compression its degree of
conductability of the electric current.
If the graphite transmitting-apparatus be connected with a galvanic battery
and a telephone of any construction in a circuit so that the current passes by the
graphite, and so that with the undulations of the voice the compression of the
graphite becomes increased or diminished, a series of currents of electricity of
diverse intensities is formed, which by acting upon the telephone reproduces much
more strongly and distinctly than with other known apparatus the voice which
has struck the transmitter.
The construction of the said transmitter is represented by the annexed Drawings,
Figures 1 and 2. Figure 1 is to a scale of twice the actual size; and Figure 2 is
to a quadruple scale.
The construction is as follows:-The vibrating plate is formed of very thin
sheet metal, say tin plate or steel, it is marked a in the Figures. In the centre of
this plate there is attached by means of mastic or other adhesive material a small
tube b of elastic gum; it is enlarged at the point of attachment c, c; within this
tube a second small tube d is introduced, it is sufficiently small to be inserted with
facility. The interior capacity f is filled with very pure and well pulverised

page_text: graphite. The graphite should extend beyond the end of the tube d to g, and
should be moderately compressed.
Then the tube thus charged is closed by a metallic cork k; this cork has a
special form, and its diameter should be such that in entering the tube b it enlarges
it a little; in its upper end there is a conical hollow. Its base is also cylindrical,
but of smaller diameter, and contains a cylindrical cavity; upon this reduced end
a small piece of elastic gum tube is applied having an exterior diameter equal to
that of the cork.
The plate with its accessories being thus prepared is placed between the two
rings p and q, which are of hard rubber, wood, or other material. The tube should
coincide with the centre of the rings. The rings are clipped together by means of
screws. Upon one of the rings there may be applied concentrically upon the
surface s² a washer of soft rubber.
Between the plate and one or other of the rings a very thin conducting wire a
is placed, and the other end of it goes to the holder z.
The apparatus is mounted upon a foot with a conical base t forming the mouth
of the apparatus. Upon the surface u there is fixed by means of the screws 5 a
metal plate, upon which bears three spiral or other springs x, x.
The two rings p and q are fixed to the foot r by means of three screws 7; there
is also fixed upon the ring p the two arms d of the mechanism d, e, f, g, h; this
attachment is made by two screws 9, 10.
This mechanism, which does not require further description, is intended to
impart by means of the conical piston m which enters into the conical cavity in
the metallic cork k a micrometic to and fro movement to the cork k, and thus to
compress more or less the graphite f enclosed in the tube d.
By turning by means of a key the axis n, o, from right to left the piston m is
forced against the cork k which further compresses the graphite; by turning in the
contrary direction the pressure is diminished. To the mechanism there is attached
by means of the screw 11 a second conducting wire ẞ which passes to the
holder z¹.
The whole of the apparatus is enclosed in a box p, q, r, v, to which it is fixed by
screws 12.
Two other conducting wires y, d, attached to the holders z, z¹, pass out of the
box, and serve to connect the apparatus with the line conductors.
-Other-powders-which-aro-indifferent-conductors_of_electricity_may_be_mixed
with the graphite or substituted for it.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Sydney Pitt in the Great Seal Patent Office on the 18th
March 1882.
SYDNEY PITT, of Sutton, in the County of Surrey. "A NEW CONSTRUCTION
OF TELEPHONE TRANSMITTER." A communication from abroad by Henri
Machalski, of Lemberg, in the Empire of Austria.
This Invention has for its object a new construction of telephone transmitter.
The construction of this transmitter is based upon a principle already known in
the construction of the microphone, namely, that graphite being an indifferent
conductor of electricity changes with its greater or less compression its degree of
conductability of the electric current.
If the graphite transmitting apparatus be connected with a galvanic battery
and a telephone of any construction in a circuit so that the current passes by the
graphite, and so that with the undulations of the voice the compression of the
graphite becomes increased or diminished, a series of currents of electricity of
diverse intensities is formed, which by acting upon the telephone reproduces much
more strongly and distinctly than with other known apparatus the voice which
has struck the transmitter.
The construction of the said transmitter is represented by the annexed Drawings,
Figures 1, 2, 3, 4, 5, 6, 7, and 8. Figure 1 is to a scale of twice the actual size.
The Figures 2 to 7 are drawn to the actual size, and Figure 8 is to a quadruple
scale.
The construction is as follows:-The vibrating plate is formed of very thin
sheet metal, say tin plate, or iron or steel; it is marked a in the Figures. Its
diameter is about 44mm, and its thickness is about of a millimeter. In the
centre of this plate there is attached by means of mastic or other adhesive material
a small tube b, Figures 1 and 8, of elastic gum; it is enlarged at the point of
attachment c, c The dimensions of this tube are in height 0.017, outer
diameter 0.005.m., internal diameter 0.004... Within this tube a second small
tube d, Figure 8, is introduced; it is sufficiently small to be inserted with facility.
In height this tube is 0.005.m. to 0.007m.m., and its thickness is 0.0008. The
interior capacity f, Figure 8, is filled with very pure and well pulverised graphite.
The graphite should extend beyond the end of the tube d to g, g, say about 0.001m.m.,
and should be moderately compressed.
Then the tube thus charged is closed by a metallic cork or plug k, k, Figures 1
and 8. This cork has a special form, and its diameter should be such that in
entering the tube b, Figure 8, it enlarges it a little; in its upper end there is a
conical hollow. Its base for a length of 5 is also cylindrical, but of a diameter
of 0.0015 only, and contains a cylindrical cavity of a length of 0.002, and a diameter
of 0.0008, as seen at e, Figure 8. Upon this reduced end a small piece of elastic
gum tube n, n, Figure 8, is applied, having the same height 0.002 an exterior
diameter equal to that of the cork.
The plate with its accessories being thus prepared is placed between the two
rings p and q, Figure 1, which are of hard rubber, wood, or other material. The
tube should coincide with the centre of the rings. The rings are clipped together
by means of screws 1, 2, 3, 4, Figures 3 and 4.
The centre of the rings is cut out to the diameter 0.036 more or less according
to the diameter of the diaphragm a; if the diaphragm is thin the diameter may be
smaller, and vice versa.
Upon one of the rings there may be applied concentrically upon the surface 8º,
Figure 1, a washer of soft rubber of a thickness 0.0005.

page_text: Between the plate and one or other of the rings a very thin conducting wire a
is placed, and the other end of it goes to the holder z.
The apparatus is mounted upon a foot r, Figure 1, of wood or hard rubber with
a conical base t forming the mouth of the apparatus, as seen in Figure 1. Upon
the surface u there is fixed by means of the screws 5 a metal plate, upon which
bear three spiral or other springs x, x. The spirals should be capable of com-
pression each should have from 5 to 8 turns; the diameter is 0.005, and their
height in a state of repose is 8 to 9m.m.
;
The two rings p and q are fixed to the foot r by means of three screws 6, 7,
and 8, Figures 1, 2, 5. There is also fixed upon the ring p the two arms d, d,
Figures 1 and 7, of the mechanism d, e, f, g, h; this attachment is made by two
screws 9, 10, Figures 1, 4, 7. This mechanism, which is in no way peculiar and
does not require further description, is intended to impart by means of the conical
piston m, m, Figure 1 and 8, which enters into the conical cavity in the metallic
cork k, a micrometic to and fro movement to the cork k, and thus to compress
more or less the graphite f, Figures 1 and 8, enclosed in the tube d.
By turning by means of a key the axis n, o, Figures 1,6, and 7, from right to
left the piston m is forced against the cork kc, which further compresses the'
graphite; by turning in the contrary direction the piston m is drawn back, and
the pressure of the cork k upon the graphite is diminished. To the mechanism
there is attached by means of the screw 11, Figures 1 (and 7, a second conducting
wire which passes to the holder z'.
This mechanism for regulating at pleasure the compression of the graphite may
be varied and modified at will; it is necessary only to provide for the micrometric
movement of the cork to and fro.
The whole of the apparatus is enclosed in a box p, q, r, v, to which it is fixed by
screws 12, 13, and 14, Figures 1 and 5.
Two other conducting wires y, 6, attached to the holders z, z', pass out of the box,
and serve to connect the apparatus with the line conductors.
The details may be varied, especially in respect to the mounting, and the
mechanism for compressing the graphite and other accessories to the Invention.
Other powders which are indifferent conductors of electricity may be mixed
with the graphite or substituted for it.
The instrument may be used either with or without an induction bobbin..
But I claim as the Invention the construction of a microphonic transmitter,
consisting essentially of vibrating plate carrying at its centre a soft caoutchouc
flanged tube fixed against the said plate, and containing another tube also of soft
caoutchouc charged with graphite powder or other imperfectly conducting substance
compressed by a hollow cork or plug with thin walls, the said vibrating plate
being supported upon its other face by three or more coiled springs which balance
the pressure of the micrometric mechanism, substantially as described. I also
claim the microphonic transmitter, substantially as described and illustrated by
the annexed Drawings.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Eighteenth day of March, in the year of our Lord One
thousand eight hundred and eighty two.