IMPROVEMENTS IN TELEPHONE TRANSMITTERS
Year: 1883

page_text: LETTERS PATENT to Charles Arthur Allison, of the firm of Allison Brothers,
Patent Agents, Southampton Buildings, London, for an Invention of
"IMPROVEMENTS IN TELEPHONE TRANSMITTERS," communicated to him from
abroad by Daniel Drawbaugh, of Eberly's Mills, in the County of Cumberland,
and State of Pennsylvania, one of the United States of America,
PROVISIONAL SPECIFICATION left by the said Charles Arthur Allison at
the Office of the Commissioners of Patents on the 4th September 1883.
CHARLES ARTHUR ALLISON, of the firm of Allison Brothers, Patent Agents,
Southampton Buildings, London, "IMPROVEMENTS IN TELEPHONE TRANSMITTERS,”
a communication to me from abroad by Daniel Drawbaugh, of Eberly's Mills, in
the County of Cumberland, and State of Pennsylvania, one of the United States of
America,
The invention consists:-
1 In a telephone transmitter having in combination with its diaphragm or
diaphragms, a series of blocks or pieces of low conducting material constructed and
arranged substantially as hereinafter described, the initial pressure between said
blocks being maintained by gravity.
2nd-In the construction whereby the box of the instrument is supported at a
distance from the back board so that a sound receiving chamber is formed between
said back board and the rear diaphragm and also in the sound reflector, and the
chamber thereby formed between the inner periphery of said reflector and the
exterior of the enclosing case, whereby the sound waves entering between the box
and the reflector are reflected into the space between the rear diaphragm and the
back board and concentrated upon said diaphragm.
3rd In the construction whereby the vibrations of the diaphragm simul-
taneously cause induced magnetic currents in an electro-magnet: and modifications
in a local circuit passing through electrodes of low conducting material, the modified
and induced currents uniting upon the line.
In all of these several constructions, there are three electrodes, namely:-
-a fixed
electrode attached to a diaphragm, a fixed electrode secured to the case or other
support, and a loose electrode resting upon and between the other two.

page_text: t
In carrying out the first part of the invention a base or back board is employed
to which is secured a box or receiver provided with a cover in which is formed a
mouth piece. A metal diaphragm is tightly held by its edges between the cover
and the box or case.
On the front side of the diaphragm or on that side against which speech is
uttered, and between said diaphragm and the rear side of the cover a layer of
cotton, felt or other similar elastic material is arranged which acts as a dampening
pad to destroy false or secondary vibrations in the diaphragm. To the rear side of
the diaphragm and at or near its centre a metal bracket is attached, by means of
solder or other suitable means. In the said metal bracket is arranged a block of
carbon or other low conducting material.
This block may be inclined or have an inclined side or face. Between the ends
of this block and the bracket a layer of rubber, paper or other suitable insulating
material is arranged.
To the back board or base, inside of the case a block of carbon or other low
conducting material is attached, which is by preference similar in form to the block
previously referred to, and supported in a similar bracket, the said bracket having
also a layer of insulating material.
The two blocks have, their inclined sides by preference arranged in relation to
each other so as to form a V.
The
The said blocks however should not be in contact with each other.
Upon the inclined faces of the blocks a third piece of low conducting material
rests. This third piece may be either of cylindrical, cubical or other suitable form.
The third block should be arranged in contact with both the other blocks.
third block is prevented from falling out of its place between the other blocks,
when the instrument is turned upon its side or reversed, by means of a bar, which
is attached by any suitable means to the base or back board.
The circuits in this instrument are by preference led as follows:-
From the battery to a binding post, then by a wire to the primary of the induction
coil, and by means of a wire to a bracket; thence through the fixed and loose
blocks to a bracket and diaphragm.
When the diaphragm is in its place, it comes in contact with a contact plate
The circuit continues from the diaphragm to this plate, and to a wire or conductor
and binding post, and thence back to the battery.
The secondary circuit from the induction coil leads by suitable wires or con
ductors to the line wire binding posts.
Branch wires lead from the binding posts to a second set of binding posts to
which the receiving instrument may be connected.
In operation the vibrations of a diaphragm under the influence of sound waves
produced by the voice or otherwise, are communicated to the blocks of low
conducting material, so as to cause variations in the resistance offered by said
blocks to the current passing through them, said variations being due to a greater
or less compression of the said blocks, or to a greater or less variation of contact
between the same; or to the current being obliged to traverse a greater or less
thickness of low conducting material; or to all these causes combined.
It will be apparent that no matter how great the amplitude of vibration of the
diaphragın, contact between the loose block and the fixed blocks cannot be broken;
for if the first fixed block is moved towards the second fixed block the result is, to
lift the loose block to a higher point in the groove or V, formed by their inclined
sides, while if the first fixed block is moved away from the second fixed block, the
loose block descends to a lower position by its own gravity.
The diaphragms employed in carrying out my invention may be formed of any
suitable material.
The diaphragm may in some cases be constructed of wood and form the cover of
the box or case.
The current instead of passing from a bracket along a diaphragm and thence
when the latter is in place to a contact plate, may proceed by a wire to a second
4

page_text: contact plate which meets the first contact plate, when the diaphragm is in place
in the box.
According to a slight modification the front diaphragm is formed of sheet metal.
The said diaphragm being in a recess in the case or frame.
In front of the diaphragm is arranged a layer of cork or other suitable yielding
material.
The device is provided with a cover having a large central aperture and secured
in position by screws or other suitable means.
The rear diaphragm is also formed of sheet metal and is placed in an annular
recess in the case and in the rear of it is arranged a layer of cork or other suitable
material,
Through the rear diaphragm a circular opening is formed through which passes
an induction coil which is by preference secured to the back board or base of the
device
The arrangement of the low conductors is substantially the same as described in
the first modification.
In this case two pieces of carbon are held in metal brackets, secured to the inner
sides of the diaphragms.
The two carbons are so arranged that they cannot meet, and upon their inclined
sides is supported a cylindrical carbon.
Above this cylindrical carbon, and serving to keep it in place when the
instrument is inverted, a metal or other suitable bar is arranged, by preference
secured to the case.
The underside of the said bar is by preference covered with paper or other
insulating material.
Between the annular rear cover and the back board or base, studs are arranged
which support the case at a distance from the back board or base.
Surrounding the box or case and attached to the back board or base, is an
annular sound reflector, having an inclined inner periphery, so that sound waves
entering the chamber between said reflector and the outer periphery of the case,
are reflected or concentrated into a space or chamber between the back board or
base and the rear diaphragm, and are thus enabled to act and be in some measure
concentrated upon the latter.
By this means both diaphragms of the instrument may be affected simultaneously,
the front diaphragm by sound waves, directly impinging upon it, and the rear
diaphragm, by waves reflected and concentrated into a space between it and the
back board or base.
The effect of this is that compression is applied to a series of carbons from both
ends of said series which renders the apparatus more sensitive in its operation.
The circuits in this modification are by preference conducted as follows:-
From one pole of a battery to a binding post by means of a wire or conductor,
thence to the primary of the induction coil by means of another wire or conductor
to the carbons and one of the diaphragms, and thence by means of a series of
contact pieces and a wire or conductor and suitable connections to the other pole of
the battery.
The device is provided with a post on which a receiving telephone may be hung
when not in use, the ring or holding means of said telephone being arranged to
push upwards a contact piece, and thus break the circuit.
The secondary wire of the induction coil connects by means of wires with posts
communicating with the line.
Branch wires from the wires connected with the binding posts, connect with
posts to which the receiving telephone is attached.
According to another slight modification, the device is provided with a base or
backboard, an enclosing box or case, and a diaphragm of wood or other non-
conducting material. It is also provided with a cover having a mouth-piece orifice,
and a gasket of yielding material interposed between the diaphragm and the cover.

page_text: The permanent magnet is provided with a pole-piece in the form of a flat bar
which is secured to the rear side of the diaphragm.
The magnet in this arrangement is by preference in the form of a bar, bent at
right angles and secured. to the back board or base through which it passes, and
is so arranged that when the diaphragm and cover are in place its front end shall
be in contact with a pole piece or connection.
To the lower end of the magnet is secured as a pole piece, the core of a coil.
The magnetic poles are therefore at the outer extremity of the core, and at the
lower end of the bar, the parts facing each other in such manner that the said bar
shall become the armature of the electro-magnet, when the diaphragm is in place.
Secured to the rear side of the diaphragm and on each side of the bar, pieces
of wood or other suitable material are arranged, upon which is secured a metal
bracket.
To the base board is attached a similar bracket.
In these brackets are placed blocks of carbon or other low conducting material,
having inclined sides facing each other.
The carbons are not in contact. Resting upon both carbons is a prismoidal piece
of carbon or other low conducting material. This carbon is held in place by
gravity. It is prevented from being displaced when the instrument is inverted by
means of a metal bar, the lower side of which is covered with paper or other
insulating material.
The electro-magnet has two coils, both wound in the same direction, one
communicating with the line and the other in local circuit with the electrodes and
battery. It rests in a socket in the back board or base and is secured in place by
means of a bent bar.
The magnet is secured to the core by a screw or other suitable means.
The circuits in this modification are by preference arranged as follows:-
From the battery to a binding post, thence by a wire to a second post and
thence by a wire to the primary of a coil or electro-magnet; thence by a wire to
a metal bracket; thence to the series of carbons, after which it passes to a bracket
and by means of a wire or conductor to the diaphragm, and from the diaphragmi
to a contact piece, and when the contact piece is in position to a contact piece
attached to the box or case:
The current then passes by a fixed contact piece to a spring connecting plate to
a wire or connection to a binding post and thence to the battery.
The secondary circuit proceeds from the coil by wires or connections to a post
or posts, and thence to the binding posts, from which it passes to the line.
Branch wires lead from the posts to the binding posts to which a receiving
instrument may be attached.
An arm is attached to the back board or base to receive the ring of the
receiving instrument when not in use, which ring then raises a spring-plate out of
contact with another plate, thereby breaking the local circuit of the instrument.
The operation of this modification is as follows :-
When speech is uttered or sounds are given in front of the diaphragm, the
armature is vibrated in front of the electro-magnet and magnetic currents are
thereby induced in the latter, which currents are conducted by secondary wires to
the line.
At the same time the movement of the diaphragm causes a carbon to move
towards or from a second carbon, the effect of which is to allow another carbon to
fall lower down into the space between the two first carbons, thereby reducing the
area of contact between the middle and the outer carbons.
Conversely when the diaphragm moves inward the carbons are brought nearer
together, the middle carbon is raised thereby and the area of contact between the
sides of the said carbon and the fixed carbons is increased.
The bar in this arrangement is a flat spring which rests with very light pressure
upon the upper angle of one of the carbons.

page_text: This spring yields easily when the carbon is raised by the inward movement of
the diaphram. The weight of this carbon is sufficient to cause its descent as
the fixed carbons are separated more widely by the outward movement of the
diaphragm.
In order to secure the ready movement of the loose carbon, according to this
arrangement it is preferable to form or arrange the upper inclined surfaces of the
fixed carbons at an angle of not less than forty-five degrees to the horizontal line,
and to form the said loose carbon so that two of its sides may stand to each other
at an angle of ninety degrees or more; said angle being the same as that included
between the inclined surfaces of the fixed blocks.
Variations of construction and arrangement may be made in the various
modifications of the invention and combinations of the same may be employed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Charles Arthur Allison in the Patent Office on the 3rd March
1884.
23
CHARLES ARTHUR ALLISON, of the firm of Allison Brothers, Patent Agents,
Southampton Buildings, London, "IMPROVEMENTS IN TELEPHONE TRANSMITTERS
a communication to me from abroad by Daniel Drawbaugh, of Eberly's Mills, in
the County of Cumberland and State of Pennsylvania, one of the United States of
America,
The invention consists:-
1. In a telephone transmitter having in combination with its diaphragm or
diaphragms, a series of blocks or pieces of low conducting material constructed and
arranged substantially as hereinafter described, the initial pressure between said
blocks being maintained by gravity.
2. In the construction whereby the box of the instrument is supported at a
distance from the back board so that a sound receiving chamber is formed between
said back board and the rear diaphragm, and also in the sound reflector, and the
chamber thereby formed between the inner periphery of said reflector and the
exterior of the enclosing case, whereby sound waves entering between the box and
the reflector are reflected into the space between the rear diaphragm and the back
board and concentrated upon said diaphragm.
3. In the construction whereby the vibrations of the diaphragm simultaneously
cause induced magnetic currents in an electro magnet, and modifications in a local
circuit passing through electrodes of low conducting material, the modified and
induced currents uniting upon the line.
In all of these several constructions, there are three electrodes, namely a fixed
electrode attached to the diaphragm, a fixed electrode secured to the case or other
support, and a loose electrode resting upon and between the other two.
Referring to the drawings
:-
Fig. 1 is a front elevation of the instrument having a single diaphragm, said
diaphragm being removed to show the internal construction.
Fig. 2 is a vertical longitudinal section on line y―y of fig. 1.
Fig. 3 shows a loose carbon block in cylindrical form.
Fig. 4 is a perspective view of one of the inclined blocks of low conducting
material with its bracket or holder.
Fig. 5 is a rear view of a diaphragm formed of wood and constituting the cover
of the box or case.
In these figures 1 to 5 similar letters of reference indicate like parts.
A represents the base or back board to which is secured the box B having a
cover C in which is formed the mouth piece D. E is a metal diaphragm tightly
held by its edges between the cover C and the case B. On the front side of the
diaphragm E or on that side against which speech is uttered and between said
diaphragm and the rear side of the cover C, I place a layer F of cotton, felt, wool
or similar elastic material, which acts as a dampening pad to destroy false or
Becondary vibrations in the diaphragm. To the rear side of the diaphragm E and
at or near its centre I attach by solder or other suitable means a metal bracket H,
in which I place a block I of carbon or other low conducting material. This block
may be inclined or have an inclined side as shown in the drawings. Between the
ends of this block and the bracket H, I place a layer S of any suitable insulating
material such as rubber or paper.

page_text: To the back board A inside the case B, I attach a block J of carbon or other low
conducting material similar in form to the block I and held in a bracket K similar
to bracket H. Said bracket having also a layer S of insulating material. The two
blocks I and J have their inclined sides facing so as to form a V. The said blocks
are not however in contact with each other.
Upon the inclined sides of the blocks I and J rests a third piece of low
conducting material L. This may be in either cylindrical or cubical form, the
cylindrical form being represented in fig. 4. The loose block L is in contact with
both blocks I and J. It is prevented from falling out of its place between the
blocks I and J when the instrument is turned up on its side or reversed, by the
bar M which is suitably attached to the back board A.
The circuits in this instrument are led as follows:-
From the battery to the binding post N; by the wire a to the primary of the
induction coil O; by a wire to the bracket K; thence through the fixed block J,
loose block L and fixed block I, to the bracket H and diaphragm E.
When the diaphragm is in its place it comes in contact with a contact plate P.
The circuit continues from the diaphragm to this plate, to the wire e and binding
post N¹ and thence back to the battery.
The secondary circuit from the induction coil O leads by the wires d, d', to the
line wire binding posts Q, Q Branch wires e, e¹, lead from the binding
posts Q, Q, to the binding posts R, R', to which a receiving instrument may be
connected.
In operation the vibrations of the diaphragm E under the influence of sound
waves produced by the voice or otherwise are communicated to the blocks I, J, K,
of low conducting material, so as to cause variations in the resistance offered by
said blocks.to the current passing through them, said variations being due to a
greater or less compression of said blocks, or to a greater or less area of contact
between the same; or to the current being obliged to traverse a greater or less
thickness of low conducting material, or to all these causes combined.
It will be apparent that no matter how great the amplitude of vibration of the
diaphragm, contact between the loose block L and the fixed blocks I and J cannot
be broken; for if the block I be moved towards the block J, the result is to lift the
block L to a higher point in the V formed by their inclined sides, while if the
block I be moved away from the block J, the block L descends to a lower position
by its own gravity.
I do not restrict myself to the use of a metallic diaphragm in this instrument,
nor to a diaphragm necessarily of conductive material. Thus the diaphragm may
be of wood and form the cover of the box or case. Fig. 5 represents a rear view
of such a diaphragm. The current instead of passing from the bracket H along
the diaphragm itself, and thence when the latter is in place to the contact
plate P, proceeds by a wire g to a contact plate T and this plate meets the contact
plate P when the diaphragm is screwed to the box.
Referring now to the construction of the instrument shown in Figs 6, 7 and 8.
Fig. 6 is a front view of the instrument with the outer diaphragm removed; the
dotted lines show the lead of the circuit wires. Fig. 7 is a sectional view of the
same on line x, x. Fig. 8 is a rear view of the front diaphragm.
Similar letters of reference in these figures indicate like parts.
A is the back board, B is the box or case, D is the front diaphragm of sheet
metal. Said diaphragm sits in a recess in the case as shown. In front of it is a
layer of cork C or similar yielding material. E is the cover having a large central
aperture and secured in place by screws or other suitable means.
The rear diaphragm G is also of sheet metal and is placed in an annular recess
in the case, and in rear of it is a layer of cork C¹.
Through the rear diaphragm G is made a circular opening through which passes
the induction coil J which is secured to the base board A.

page_text: The arrangement of the low conductors is substantially the same as already set
forth with reference to Figs 1 to 6.
K and L are pieces of carbon shaped as shown and held in metal brackets N, N,
which brackets are secured to the inner sides of the diaphragms G and D.
The pieces K and L do not meet. Upon their proximate inclined sides rests a
cylindrical carbon O. Above this carbon and serving to keep it in place when the
instrument is inverted is a metal bar P secured to the case as shown in Fig. 6.
The under side of said bar is covered with paper or other insulating material V.
Between the annular rear cover and the backboard A are studs which support
the case at a distance from the back board.
Surrounding the case B and attached to the back board A, is an annular sound
reflector R, having an inclined inner periphery so that sound waves entering the
chamber between said reflector and the outer periphery of the cylindrical case B,
are reflected or concentrated into the space or chamber between the back board A,
and the rear diaphragm G, and are thus enabled to act and be in some measure
concentrated upon the latter.
In this way both diaphragms of the instrument may be affected simultaneously,
the front diaphragm D by sound waves directly impinging upon it, and the rear
diaphragm G, by waves reflected and concentrated into the space between it and
the back board.
This results in compression being applied to the series of carbons from both ends
of said series, which renders the apparatus more sensitive in its operation.
The circuits in the instrument lead as follows:-
From one pole of the battery to the binding post 1; by wire a (dotted lines), to
the primary of the induction coil J; by wire b to the carbon K; thence to
carbon O, carbon L and diaphragm D; on the latter to contact piece F; to contact
piece T; to contact piece S, when said contact pieces S and T are in contact; to
the wire c (dotted lines) and binding post 2 and then to the other pole of the
battery.
U is a post on which a receiving telephone may be hung when out of use, the
ring on said telephone pushing upward the contact piece S and thus breaking the
circuit.
The secondary wire of the induction coil J connects with the binding posts 3
and 4, by wires d, d (dotted lines), which posts communicate with the line.
Branch wires e, e¹ (dotted lines), from the wires d, d, connect with binding
posts 5 and 6, to which posts the receiving telephone is attached.
Referring to the instrument shown in Figs. 9 to 12:―
Fig. 9 is a front view of the instrument with the diaphragm and its attachments
removed.
Fig. 10 is a vertical section on the line x, x, of fig. 9.
Fig. 11 is a transverse section on the line y, y, of fig. 9.
Fig. 12 is a rear view of the diaphragm.
Similar letters of reference indicate like parts.
A is the base or back board, B is the enclosing box or case, C is the diaphragm
of wood or other non conducting material, D is the cover having a mouth piece
orifice, and E is a gasket of yielding material interposed between the diaphragm
and cover.
The permanent magnet G has a pole piece F in the form of a flat bar, which is
secured to the rear side of the diaphragm. The magnet G is in the form of a bar
bent at right angles, and is secured to the back board A, passes through said back
board and has its front end in contact with the pole piece F when the diaphragm
and cover are in place.
To the lower end of the magnet G is secured as a pole piece the core H of the
coil I. The magnetic poles are therefore at the outer extremity of the core H, and
at the lower end of the bar F, these parts facing each other as shown, and the

page_text: bar F thus becoming the armature of the electro magnet H, I, when the diaphragm
is in place.
Secured to the rear side of the diaphragm and on each side of the bar F are
pieces of wood J, Fig. 12, upon which is secured a metal bracket K. To the base
board is attached a similar bracket L. In these brackets are placed blocks of
carbon M, N, or other low conducting material having inclined sides facing each
other.
These carbons are not in contact. Resting upon both carbons M, N, is a
prismoidial piece of carbon or other low conducting material. This carbon is
held in place by gravity only. It is prevented from being displaced when the
instrument is inverted by means of the metal bar P, the lower side of which bar is
covered with paper or other insulating material.
The electro magnet H, I, has two coils, both wound in the same direction, one
communicating with the line, and the other in local circuit with the electrodes and
battery. It rests in a socket in the back board A. and is secured in place by means
of the bent bar Q.
The magnet G is secured to the core H by the screw R.
The circuits in the instrument proceed as follows:-
From the battery to the binding post 1; by the wire a to the post b, and thence
to the primary of the induction coil or electro magnet H, I; thence by the wire c
to the metal bracket L; thence to the carbon N; to the carbon O, to the carbon M,
to the metal bracket K; thence by the wire d on the back of the diaphragm to
the contact piece S; thence when the diaphragm is in place to the contact piece T
attached to the box B; thence by the fixed contact plate U, to the spring contact
plate V and thence by the wire e to the binding post 2, and thence to the battery.
The secondary circuit proceeds from the coil H, I, by the wires f,ƒ³, to the
post g, gl, and thence to the binding posts 3, 4, then to the line.
Branch wires h, h¹, lead from the posts g, g¹, to the binding posts 5, 6, to which
a receiving instrument may be attached.
W is an arm attached to the back board to receive the ring of the receiving
instrument when not in use, which ring then raises the spring plate V out of
contact with the plate U, and so breaking local circuit in the instrument.
The operation of the instrument is as follows:-
When speech is uttered in front of the diaphragm the armature F is vibrated in
front of the electro magnet H, I, and magneto currents are thereby induced in the
latter, which currents by the secondary wires f. f, proceed to the line.
At the same time the movement of said diaphragm causes the carbon M to move
toward or from the carbon N. The effect of moving the carbon M away from the
carbon N is to allow the carbon O to fall lower down in the space between
M and N, thus reducing the area of contact between the middle carbon O and the
outer carbons N and M.
Conversely when the diaphragm moves inward the carbons N and M are brought
nearer together, the carbon O is raised thereby and the area of contact between
the sides of said carbon and the fixed carbons N and M is increased.
The bar P is a flat spring and rests with very light pressure upon the upper
angle of the carbon O. This spring yields easily when the carbon O is raised by
the inward movement of the diaphragm. The weight of the carbon O is sufficient
to cause its descent as the carbons N and M are separated more widely by the
outward movement of the diaphragm.
In order to secure the ready movement of the loose carbon, I have found it
preferable to form or arrange the upper inclined surfaces of the fixed carbons at an
angle of not less than forty five degrees to the horizontal, and to form said loose
carbon so that two of its sides may stand to each other at an angle of ninety
degrees or more; said angle being the same as that included between the inclined
surfaces of the fixed blocks.
,

page_text: I do not intend to claim herein the layers of cork or other elastic material with
which the diaphragm in the instruments shown in Figs 1 to 8 is covered.
I claim as my invention :-
1. In a telephone, the combination of a diaphragm with a block of low
conducting material closely applied to its rear or inner side and substantially at
its centre, and with a second block of low conducting material not in contact with
the first block, the said two blocks being inclined to one another or having inclined
faces placed relatively opposite each other, and with a loose block of low con-
ducting material which rests upon the opposite inclined sides or faces of the two
blocks aforesaid, and is held in place and in contact upon them by gravity,
substantially as described.
2. In a telephone, the combination of a diaphragm with a block of low
conducting material closely applied to the rear or inner side of said diaphragm and
substantially at its centre, and with a second block of low conducting material not
in contact with the first block, and with a loose block of low conducting material
which rests upon the two blocks aforesaid, and is held in place and in contact upon
them by gravity, substantially as described.
3.*In a telephone, the combination of the two supporting blocks I, J, of low
conducting material, cylinder of low conducting material resting on said blocks,
the partly insulated brackets H and K for holding the blocks, and the bar M. or
its equivalent for preventing the cylinder falling out of place, substantially as
described.
4. In a telephone, the combination of a diaphragm forming the cover of a box or
case, with a series of low conductors enclosed in said box or case and placed in
successive contact, one of the said conductors being closely attached to the rear or
inner side of the diaphragm, so as to vibrate therewith, a second conductor being
secured in the interior of the case and not in contact with the conductor first
mentioned, and a third conductor resting upon and in contact with the two
conductors aforesaid by gravity and forming electrical connection between them,
substantially as described.
5. A telephone containing a box or case within and between the opposite sides
of which, and in contact with said sides, are arranged a series of low conductors in
successive contact, which conductors are more or less compressed one upon the
other so as to modify their resistance to an electrical current passing through them,
by the vibrations of one of the aforesaid sides of the box caused by sound waves
impinging upon the exterior surface, substantially as described.
6. In a telephone, the combination of two diaphragms covering opposite sides of
the enclosing box or case of the instrument, and rigidly secured to said box or case,
a means of modifying an electric current so as to render it capable of transmitting
articulate speech, arranged between said diaphragms and influenced by the
vibrations of both of them, and a means of reflecting or concentrating sound
waves upon that one of the two diaphragms which does not face the source of
sound, substantially as described.
7. In a telephone, in combination with an enclosing box or case containing two
diaphragms on opposite sides thereof and a means of modifying an electric current
so as to render it capable of transmitting articulate speech, arranged between said
diaphragms and influenced by the vibrations of both of them, two communicating
sound receiving chambers, one chamber being formed annularly or substantially so
around the exterior of the enclosing case, and the other being formed in rear of
said case, substantially as described.
8. The combination of (1) a telephone containing an enclosing case, two
diaphragmns and means for modifying an electric current so as to render it capable
of transmitting articulate speech; (2) a back board or base; (3) supports arranged
between the rear side of said telephone and the back board; and (4) a sound
reflecting projection attached to said back board and surrounding the telephone
case, substantially as described.

page_text: 9. In a telephone, the combination of a diaphragm, a polarized armature attached
thereto, electrodes of low conducting material, one electrode being connected to
said diaphragm, an electro inagnet having two coils, one in circuit with the line,
the other in local circuit with the electrodes, a permanent magnet having for one
pole piece the core of the electro magnet and for the other the polarized armature,
and a local battery and circuit connections substantially as set forth, whereby the
movement of the diaphragm under the influence of sound waves inay simul-
taneously cause induced currents in the electro magnet by the vibration of the
armature, and also modifications in the local circuit by variations in contact of the
electrodes, the induced magneto current and modified battery.current uniting upon
the line, substantially as described.
10. In a telephone, the combination of the electro magnet H, I, having two coils,
one in circuit with the line and the other in local circuit with the electrodes, the
permanent magnet G having a pole piece F supported by the diaphragm, the
diaphragm C, the electrode M attached thereto, the electrodes O and N, and a local
battery and circuit connections, substantially as described.
11. In a telephone, the combination of an electro magnet, a permanent magnet
having for one pole piece the core of the other magnet, and a metal piece attached
to said diaphragm, which piece when the diaphragm is in place comes in contact
with the permanent magnet and become the other pole piece thereof and also the
armature of the electro magnet, substantially as described.
12. In a telephone, the combination of the electro magnet H, I, and the
permanent magnet G, with the diaphragm C and pole piece of said permanent
magnet, substantially as described.
13. In a telephone, the combination of a diaphragm, an electro magnet having
two coils, one in circuit with the line, the other in local circuit with a battery, and
a series of electrodes arranged in said local circuit and subjected to variations in
contact by the movement of the diaphragm, the said diaphragm by its motion
also inducing magneto currents in the electro magnet and line, substantially as
described.
14. In a telephone, the method of varying the resistance offered by electrodes of
low conducting material to the current in accordance with the vibrations of a
diaphragm due to sound waves, consisting in interposing between an electrode
attached to the diaphragm and a second electrode secured to a support, the said
electrodes not being in contact, a third electrode having two sides disposed at such
an angle that by the approach of the two fixed electrodes it will thereby be moved
upward between them so that a greater area of its surfaces comes in contact with
said electrodes, and which on the movement asunder of said fixed electrodes is free
to assume a lower position between them by gravity so that a less area of its
surface comes in contact with said fixed electrodes, substantially as described.
15. In a telephone, the combination of a diaphragm with a fixed block of low
conducting material closely applied to its rear or inner side, and with a second fixed
block of low conducting material not in contact with the first block, the said two
blocks being inclined to one another or having inclined faces placed relatively
opposite each other, and with a loose block of low conducting material of prismoidal
form having two faces placed relatively at substantially the same angle as the
inclined sides or faces of the fixed blocks and having said faces in contact with said
fixed blocks so that when said fixed blocks are moved together there shall be a
greater area of surface contact between the electrodes by reason of said loose block
being lifted by said movement, and when said fixed blocks are moved apart there
shall be a less area of such contact by reason of the descent of said loose block
by gravity, substantially as described.
16. In a telephone, the combination of a diaphragm with a fixed block of low
conducting material closely applied to its rear or inner side and with a second fixed
block of low conducting material not in contact with the first block, the said two
blocks being inclined to one another or having inclined faces placed relatively

page_text: opposite each other, and with a loose block of low conducting material of prismoidial
form having two faces placed relatively at substantially the same angle as the
inclined sides or faces of the fixed blocks and having said faces in contact with
said fixed blocks so that when one of said fixed blocks is caused by the movement
of the diaphragm to approach or recede from the other fixed block, the area of
surface contact between the loose block and said fixed blocks is varied, substantially
as described.
In witness whereof, I, the said Charles Arthur Allison have hereunto set my
hand and seal, this Third day of March, in the year of Our Lord One thousand
eight hundred and eighty-four
CHA³. A. ALLISON (L.S.)