Improvements in Electric Telephone Transmitters.
Year: 1891

page_text: Date of Application, 19th Dec., 1891
Complete Specification Left, 19th Oct., 1892-Accepted, 19th Nov., 1892
PROVISIONAL SPECIFICATION.
Improvements in Electric Telephone Transmitters.
ALAN ARCHIBALD CAMPBELL SWINTON 66 Victoria Street Westminster
Engineer do hereby declare the nature of this invention to be as follows:-
The invention relates to improvements in electric telephone transmitters and
particularly to those species of transmitters in which granulated carbon or other
imilar material is employed.
As is well know the chief objection to transmitters of this type is the tendency
there is for the granules to become too tightly packed or wedged together, unless
they are from time to time shaken up.
According to my invention I obviate this injurious tendency by arranging the
electrodes with which the granules make contact side by side horizontally in the
same or approximately the same plane, the carbon or other granules being
distributed in a thin layer over the upper surfaces of the electrodes, so that the
granules rest on the electrodes, merely by reason of their own weight, and are not
otherwise compressed or wedged together.
The electrodes being caused to vibrate with the voice, the granules owing to
their inertia dance freely upon the electrodes, and owing to the varying intimacy of
contact thus occasioned, form a bridge of varying conductivity from electrode to
electrode.
In some cases I employ a horizontal diaphragm of thin wood, or metal, or of
mica, or other suitable material, & fix the electrodes of carbon, platinum, or other
suitable conducting material on the upper surface of the diaphragm, the granules
resting on the electrodes with a suitable receptacle or cover to preserve them from
dust, moisture, or displacement. Or I may vary this arrangement by using a
diaphragm of carbon, platinum, or other suitable conducting material, divided into
two or more portions insulated from one another, so that these portions of the
diaphragn itself form the electrodes.
Or in some cases I mount the electrodes in the bottom of a shallow box or
receptacle fixed to the horizontal diaphragm either above or beneath the latter, so
that the box & clectrodes vibrate with the diaphragm, the granules being contained
in the box. And in some cases when it is convenient for the diaphragm to be
inclined at an angle to the horizontal, the box may be so shaped, or so attached to
the diaphragm, that the electrodes and layer of granules are kept horizontal in
spite of the inclination of the diaphragm.
Or I sometimes fix the electrodes on the upper surface of a horizontal diaphragm,
or form them out of a horizontal diaphragm as above described, and place the layer
of granules over the electrodes keeping them in position by a ring or border of
suitable dimensions & shape; and in order to protect the granules, I employ a
second diaphragm parallel with the first and arranged sufficiently above it to give
the granules ample space to dance up and down. And in some cases I connect these
two diaphragms together at or about their centre, so that vibrations communicated to
the upper diaphragm by the voice are transmitted through the connection to the
lower diaphragmn and to the electrodes.
I may make my electrodes of various shapes, so as the line of discontinuity
a central
between them may be as long as possible. A convenient arrangement
disc forming one electrode with a concentric ring, outside of it, and insulated from
it, forming the other, the outer edge of this ring being preferably turned up all
round so as to form a rim to keep the granules in position.
I may employ only two electrodes or more than two, connected in parallel, or in
series, or in combinations of these arrangements as is well understood, the complete

page_text: transmitters being connected with a battery, and either directly with the line wires
and receiving telephones or through the agency of an induction coil in the usual or
any suitable manner.
It will be understood that the voice or sounds to be transmitted are in each case
directed on to the diaphragm, and the sound may be caused to impinge on either
the upper or lower surface of the said diaphragm through a mouthpiece of curved
or other suitable form.
Data
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COMPLETE SPECIFICATION.
Improvements in Electric Telephone Transmitters.
ALAN ARCHIBALD CAMPBELL SWINTON 66 Victoria Street Westminster
Engineer do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in
and by the following statement :-
Improvements in Electric Telephone Transmitters.
This invention relates to improvements in electric telephone transmitters, and
particularly to those species of transmitters in which granulated carbon or other
similar material is employed.
As is well known, the chief objection to transmitters of this type is the tendency
there is for the granules to become too tightly packed or wedged together, unless
they are from time to time shaken up.
According to my invention, I obviate this injurious tendency by arranging the
electrodes with which the granules make contact, side by side horizontally, in the
same or approximately the same plane; the carbon or other granules being
distributed in a thin layer over the upper surface of the electrodes, so as that the
granules rest on the electrodes merely by reason of their own weight, and are not
otherwise compressed or wedged together. The electrodes being caused to vibrate
with the voice, the granules, owing to their inertia, dance freely upon the electrodes,
and, owing to the varying intimacy of contact thus occasioned, form a bridge of
varying conductivity from electrode to electrode.
In some cases, as shown in section in Figure 1, and in plan in Figure 2, I employ
a horizontal diaphragm, D, of thin wood, or metal, or of mica, or other suitable
material, and fix the electrodes, E, E', consisting of plates of carbon, platinum, or
other suitable conducting material, on the upper surface of this diaphragm, so as to
be insulated from one another, the granules, G, resting on the electrodes with a
suitable recepticle or cover, C, to preserve them from dust, moisture, or displace-
ment. The whole may be conveniently mounted in a suitable box, B, the diaphragm
being held between rings of india rubber, felt, or other suitable material, R, R',
clamped between the box and the lid, L, which supports the curved mouthpiece, M.
T, T', are the terminals connected to the two electrodes, E, E'.
In some cases, as shown in section in Fig. 3, I mount the electrodes, E, E' in the
bottom of a holder, H, fixed to the diaphragm, D, either above or beneath the
latter, so that the holder and electrodes vibrate with the diaphragm, the granules, G,
being contained in the holder. And in some cases, when it is convenient for the
diaphragm to be inclined at an angle to the horizontal, the holder may be so
shaped or so attached to the diaphragm, that the electrodes and layer of granules
are kept horizontal in spite of the inclination of the diaphragm, this being the
arrangement shown in Fig. 3.
Or I sometimes fix the electrodes on the upper surface of a diaphragm, D, as
shown in section in Fig. 4, and place the layer of granules, G, over these electrodes.
keeping them in position by a suitable cover, C; or this arrangement may be
modified as shown in section in Fig. 5, by employing, to protect the granules from
moisture and dust, a second diaphragm, D', parallel with the first, and arranged

page_text: sufficiently above it to give the granules ample space to dance freely up and down;
and in some cases I connect these two diaphragms together at or about their centre,
by means of a pin, P, so that vibrations communicated to the upper diaphragm by
the voice coming through the mouthpiece, M, are transmitted through the pin to.
the lower diaphragm and to the electrodes.
I may make my electrodes of various shapes, so as the line of discontinuity
between them may be as long as possible, this being, I find, advantageous. A con-
venient arrangement is that shown in Fig. 5, a central disc, E, forming one electrode,
with a concentric ring outside of it, E, forming the other, the outer edge of this
ring being preferably turned up all round, so as to form a rim to keep the
granules in position, and the pin, P, above mentioned, being of carbon moulded on
the central disc.
Or any of the arrangements shown in Figs. 6 to 12 may be employed. In Figs. 6
and 7 the diaphragm itself forms the two electrodes, E, E', being formed preferably
of carbon divided into two or more portions fastened together but insulated from
one another by means of a suitable cement, such as fused shellac. Or, as shown in
Figs. 8, 9, 10 & 12, the electrodes, E, E', may be of carbon, platinum or other
suitable material, cemented or otherwise attached to a diaphragm of metal, mica,
thin wood, or other convenient substance, so as to be insulated from one another.
Or, as shown in Fig. 11, the two electrodes may be concentrically arranged.
Connection with the electrodes is preferably obtained my means of strips of metal
foil cemented onto the diaphragm, and attached at one end to the electrodes,
and at the other end clamped with the edge of the diaphragm in contact with
conductors leading to the terminals as shown in Figs. 1 & 2.
I may employ only two electrodes, or more than two, connected in parallel or in
series, or in combinations of these arrangements, as is well understood, the complete
transmitter being connected with a battery, and either directly with the line wires
and receiving telephones, or through the agency of an induction coil in the usual or
any suitable manner.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, 1 declare that what I
claim is:
(1) In an electric telephone transmitter, the combination of a layer of conducting
granules with a diaphragm and two or more electrodes placed horizontally and in
the same plane, with the granules resting upon them so as to form a bridge between
them of varying conductivity, substantially as set forth.
(2) In combination with the above, the several special forms of electrodes,
substantially as described and illustrated.
(3) The several arrangements of telephonic transmitters, substantially as described
and illustrated.
A. A. C. SWINTON.