IMPROVEMENTS IN ELECTRIC TELEPHONES
Year: 1883

page_text: LETTERS PATENT to Herbert John Allison, of 41 Southampton Buildings,
Holborn, in the County of Middlesex for an Invention of "IMPROVEMENTS IN
ELECTRIC TELEPHONES" communicated to him from abroad by James Hart
Robertson of Brooklyn. New York. United States of America
PROVISIONAL SPECIFICATION left by the said Herbert John Allison at
the Office of the Commissioners of Patents on the 1st May 1883.
HERBERT JOHN ALLISON, of 41 Southampton Buildings, Holborn, in the County
of Middlesex, " IMPROVEMENTS IN ELECTRIC TELEPHONES" a communication to
me from abroad by James Hart Robertson, of Brooklyn, New York, United States
of America,
My invention relates to that class of electric telephone transmitters in which the
electric current passes through electrodes that are loosely in contact; and consists,
1. In the devices hereinafter described whereby magnetism is employed, instead
of a spring or gravity, to produce contact pressure of the electrodes and whereby
the magnetic force so employed may be adjusted at pleasure.
2nd. In the hereinafter described devices whereby the diaphragm is supported
and retained in its place in a telephone so that the utmost freedom of vibration of
the diaphragm shall be secured and :-
3. În placing the electrode loosely in contact with the diaphragm, and retaining
it in place by an elastic connection which will permit a variation of pressure
between the electrode and the diaphragm, at the point of contact, under the
vibrations of the diaphragm.
I will now proceed to describe these several improvements in the order named
above:
First Improvement.
The diaphragm is attached to the door of a case, which when closed, encloses
the mechanism. The mouth-piece is on the outer or opposite side of the door.
The diaphragm is attached to the door at its perimeter so as to leave it free to
vibrate. The fixed electrode, made preferably of carbon, is attached rigidly to the
centre of the diaphragm. The free electrode is also preferably of carbon. It may

page_text: be suspended from a bracket on points by wires so as to be free to vibrate. Any
other suitable mode of suspending it may be adopted. It is preferably so arranged
that by its own gravity it will hang in contact with the fixed electrode. Öne
circuit wire is connected to the diaphragm, through which the current from this
wire is conducted to the fixed electrode, and the other circuit wire is connected to
the bracket, thus establishing a circuit connection with the free electrode, through
the wires above mentioned and the pivotal points.
It is well known that in this class of instruments, a yielding pressure must be
exerted upon the free electrode to cause its contact with the fixed electrode on the
diaphragm; and that this pressure has to be made adjustable to meet the varying
conditions of the electric circuit and the varying force of vocalization employed in
using the telephone. This pressure has usually been supplied by a spring or by
gravity. But in the use of these agents for the purpose it is difficult to secure
that fineness and delicacy of action and adjustment necessary to produce the best
results. I have found that magnetism is a much better agent for the purpose. In
order to use the magnetic force conveniently and effectively, I arrange a fixed
magnet with its poles in such relation to the free electrode, which is attached to a
piece of iron or other metal susceptible to magnetic attraction, that it, the said
electrode, will be drawn and pressed by the magnet into contact with the fixed
electrode. Upon the magnet I place a keeper, whose adjustment to or from the
poles of the magnet will modify their magnetic force.
The magnet is fixed in its position by being rigidly attached to the door. The
piece of iron to which the free electrode is attached projects laterally beyond the
said electrode and acts as an armature to the magnet. The extremities of the poles
of the magnet are placed between the lower edge of the armature and the diaphragm.
The attraction exerted between the poles of the magnet and the armature will, as
is evident, draw the free electrode into contact with the fixed electrode with a
pressure due to the force of the magnet.
The keeper consists of a flat bar of iron or steel, placed upon the magnet, where
it will be held by magnetic attraction. According as the keeper is placed nearer
to or further from the poles of the magnet, is the magnetic force at the poles, less
or greater. By these means the contact pressure of the free electrode upon the
fixed electrode is increased or diminished at pleasure and adjusted to the variations
of the electric current or the vocalizing of the operator.
A rebate may be made in the side of the armature, and the shoulder of the
rebate arranged directly over the extremities of the poles of the magnet, whereby
the magnet will also act to draw the said armature, and the wires by which it is
suspended from the bracket downward, thus causing continuous and perfect metallic
contact at the pivotal points.
Second Improvement.
As already stated this consists in the method of supporting the diaphragm so as
to secure freedom of vibration.
The methods heretofore employed have been to support the diaphragm by its
rim, on a rigid or a yielding or elastic substance and in some suitable way secure it
on such support. With this arrangement the entire perimeter of the diaphragm is
supported by and in contact with the supporting substance which necessarily
suppresses or interferes somewhat with the vibrations of the diaphragm in response
to the impulses of the sound waves.
I have found that by supporting the diaphragm near its perimeter at several
separate points, its vibratory action is improved. The supports are made of rubber
in the form of small disks or studs, attached by cement preferably to the door.
Preferably three of these supports are used as that is the smallest number that will
properly support the diaphragm. They may be placed about equidistant from each
other, just within the the perimeter of the diaphragm, which is attached to them
by any suitable means, preferably cement.
Third Improvement.
Cd with the dienbracem.

page_text: The usual mode of fastening said electrode to the diaphragm is by a rigid
connection, as for example a metal pin or stud, rivetted to the centre, or a pin of
carbon rigidly attached thereto.
I have found that there is an advantage in making this connection slightly
elastic. The method in which this is accomplished is by an electrode with a collar
or flange on the same, and an electric disk, which, when the electrode is connected
to the diaphragm will be interposed between the diaphragm and the collar.
This electrode consists of a stud or pin of carbon or other suitable substance,
having a pointed end. The disk may be made of rubber or other suitable elastic
material. It has a central opening, through which the point of the electrode may
pass. The point of the electrode projects from the inner face of the flange through
the hole, a distance just equal to the thickness of the disk. The electrode thus
constructed is then placed on the centre of the diaphragm and there secured by
cementing the disk to it. It is evident that with this arrangement the point will
just touch the face of the diaphragm with a loose contact, and that the elasticity of
the disk will permit of varying pressure between the point and the diaphragm aş
the latter is vibrated.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Herbert John Allison in the Great Seal Patent Office on the
1st November 1883.
"
HERBERT JOHN ALLISON, of 41 Southampton Buildings, Holborn, in the County
of Middlesex, "IMPROVEMENTS IN ELECTRIC TELEPHONES a communication to
me from abroad by James Hart Robertson, of Brooklyn, New York, United States
of America,
Figure 1 is a face view of the mechanism, and a part of the case, of an ordinary
telephone transmitter, with my improvement N° 1 added.. Figure 2, is an edge
view of the same; and Figure 3 is a detached view of one of the electrodes.
Figure 4 is a face view of a common telephone, and a part of the case, embodying
my improvement N° 2; and Figure 5 is an edge view of the same. Figures 6, 7
and 8 are detached views of parts of a telephone mechanism embodying my
improvement N° 3.
My invention relates to that class of electric telephone transmitters in which the
electric current passes through electrodes that are loosely in contact; and consists,
1st In the devices hereinafter described and claimed whereby magnetism is employed,
instead of a spring or gravity, to produce contact pressure of the electrodes and
whereby the magnetic force so employed may be adjusted at pleasure.
2nd In the hereinafter described devices whereby the diaphragm is supported
and retained in its place in a telephone so that the utmost freedom of vibration of
the diaphragm shall be secured and :-
3rd In placing the electrode loosely in contact with the diaphragm, and retaining
it in place by an elastic connection which will permit a variation of pressure
between the electrode and the diaphragm, at the point of contact, under the
vibrations of the diaphragm.
I will now proceed to describe these several improvements in the order named
above :-
First Improvement.
This is shown in Figures 1, 2 and 3.
A, is the diaphragm. It is attached to the door B, of a case, which, when closed,
encloses the mechanism. The mouth-piece, not shown, is on the outer or opposite
side of the door. The diaphragm is attached to the door at its perimeter, so as to
leave it free to vibrate. C, is the fixed electrode, made preferably of carbon
attached rigidly to the centre of the diaphragm. D, is the free electrode, also
preferably of carbon. It may be suspended from the bracket E, on the points a, a',
by the wires f, f¹, as shown, so as to be free to vibrate. Any other suitable mode
of suspending it may be adopted. It is preferably so arranged that by its own.
gravity it will hang in contact with the fixed electrode C, as shown in Figure 2.
F, and F, are the circuit wires, one, F, being connected to the diaphragm A,
through which the current from the wire F, is conducted to the electrode C, and
the other, F', to the bracket E, thus establishing a circuit connection with the
electrode D, through the wires f, f¹, and pivotal points a, a¹.
It is well known that in this class of instruments, a yielding pressure must be
exerted upon the free electrode to cause its contact with the fixed electrode on the
diaphragm; and that this pressure has to be made adjustable to meet the varying
conditions of the electric circuit and the varying force of vocalization employed in
using the telephone. This pressure has usually been supplied by a spring or by
gravity. But in the use of these agents for the purpose it is difficult to secure
that fineness and delicacy of action and adjustment necessary to produce the best

page_text: results. I have found that magnetism is a much better agent for the purpose.
In order to use the magnetic force conveniently and effectively, I arrange a fixed
magnet with its poles in such relation to the free electrode D, which is attached to
a piece of iron or other metal susceptible to magnetic attraction, that it, the said
electrode, will be drawn and pressed by the magnet into contact with the electrode C.
Upon the magnet I place a keeper, whose adjustment to or from the poles of the
magnet will modify their magnetic force.
In the drawing O, is the magnet, which is fixed in its position by being rigidly
attached to the door B. H is the piece of iron to which the electrode D is attached.
It projects laterally beyond the said electrode as shown in the drawings and acts
as an armature to the magnet G. The extremities of the poles b, b¹, of the magnet
are placed between the lower edge of the said armature H, and the diaphragm A,
as shown plainly in Figure 2. The attraction exerted between the poles b, b', of
the magnet and the armature H, will, as is evident, draw the electrode D into
contact with the electrode C, with a pressure due to the force of the magnet.
I, is a keeper, consisting of a flat bar of iron or steel, placed upon the magnet,
where it will be held by magnetic attraction. According as the keeper is placed
hearer to or further from the poles of the magnet, is the magnetic force at the poles,
less or greater. By these means the contact pressure of the electrode D, upon the
electrode C, is increased or diminished at pleasure and adjusted to the variations of
the electric current or the vocalizing of the operator.
A rebate may be made in the side of the armature H, as shown in Figure 3, and
the shoulder of the rebate arranged directly over the extremities of the poles b, b',
of the magnet, whereby the magnet will also act to draw the said armature, and
the wires by which it is suspended from the bracket E, downward thus causing
continuous and perfect metallic contact at the points a, a¹.
Second Improvement.
As already stated this consists in the method shown in Figures 4 and 5 of
supporting the diaphragm so as to secure freedom of vibration.
The methods heretofore employed have been to support the diaphragm by its
rim, on a rigid or a yielding or elastic substance and in some suitable way secure
it on such support. With this arrangement the entire perimeter of the diaphragm
is supported by and in contact with the supporting substance which necessarily
suppresses or interferes somewhat with the vibrations of the diaphragm in response
to the impulses of the sound waves.
I have found that by supporting the diaphragm near its perimeter at several
separate points, its vibratory action is improved.
The circles c, c', c³, in dotted lines in Figure 4 show where I place the supports
and at e, c, Figure 5 are shown two of the supports. These are made of rubber,
in the form of small disks or studs, attached by cement preferably to the door B.
Preferably three of these supports are used as that is the smallest number that
will properly support the diaphragm. They may be placed about equidistant
from each other, just within the perimeter of the diaphragm which is attached to
them by any suitable means, preferably cement.
Third Improvement.
Relating to the connection of the fixed electrode with the diaphragm.
The usual mode of fastening said electrode to the diaphragm is by a rigid
connection, as for example a metal pin or stud, rivetted to the centre, or a pin of
carbon rigidly attached thereto.
I have found that there is an advantage in making this connection_slightly
elastic. The method in which this is accomplished is shown in Figures 6, 7 and 8;
Figure 6, showing a side view of an electrode d and an edge view of a collar or
flange d¹, on the same, also a central cross section of an electric disk e, which,
when the electrode is connected to the diaphragin, as shown in Figure 8, will be
interposed between the diaphragm and the collar d. In said Figure 8, is also
shown the free electrode D.
The electrode d consists of a stud or pin of carbon or other suitable substance,

page_text: having a pointed end h. d, is a flange on said pin. The disk e, may be made of
rubber or other suitable elastic material. It has a central opening i, through which
the point h, of the electrode d, may pass. The point h of the electrode projects
from the inner face of the flange d' through the hole i, a distance just equal to the
thickness of the disk. The electrode thus constructed is then placed on the centre
of the diaphragm A, and there secured by cementing the disk e, to it. It is
evident that with this arrangement the point h will just touch the face of the
diaphragm with a loose contact, and that the elasticity of the disk e, will permit
of varying pressure between the point and the diaphragm as the latter is
vibrated.
What I claim as my invention and desire to secure by Letters Patent is :-
1. The combination in an electric telephone transmitter of the diaphragm A, the
electrode C, fixed to the diaphragm, the swinging electrode D, to which is attached
the armature H, and a magnet G, the poles of which are between the said
diaphragm and armature, but not in contact with either, as described, whereby the
electrode D, is pressed into contact with the electrode C, as and for the purpose
specified.
2. The combination of the diaphragm A, to which is attached the electrode C,
the swinging electrode D, to which is attached the armature H, the magnet G,
the poles of which are between the said diaphragm and armature, but not in
contact with either, and the keeper I placed and held adjustably on said magnet
by magnetic attraction, as and for the purpose specified.
3. The combination of the diaphragm A, to which is attached the electrode C,
the swinging electrode D, to which is attached the armature H, and the magnet G,
the poles of which are between the said diaphragm and armature, the said
armature being constructed and arranged relatively to said magnet as described,
whereby the magnet acts to draw the armature downward as well as towards the
diaphragm as and for the purpose described.
4. The diaphragm A, supported and secured in its place in a telephone, at
separate points only, by means of the rubber disks or studs c, c, c, as and for the
purpose described.
5. The combination of the diaphragm A, the described electrode consisting of
the pin d, provided with the flange d', point h, projecting from the said flange;
and the elastic disk e, interposed between said diaphragm and flange, and attached
to both, and through an opening in which said disk, the said point extends as and
for the purpose described.
In witness whereof, I, the said Herbert John Allison, have hereunto set my
hand and seal, this first day of November in the year of our Lord one thousand
eight hundred and eighty-three.
T
YTTOON