IMPROVEMENTS IN TELEPHONE TRANSMITTERS
Year: 1884

page_text: I, HERBERT JOHN ALLISON, of the firm of Allison Brothers, Patent Agents, of
Chancery Lane, London, in the County of Middlesex, do hereby declare the nature
of the said invention for "IMPROVEMENTS IN TELEPHONE TRANSMITTERS " to be
as follows:-
My invention relates to telephone transmitters and more particularly to that
class of transmitters in which the current is modified and rendered undulatory in
form by passage between electrodes the pressure between which or area of surface
contact of which is varied by the movement of a diaphragm or diaphragms under
the influence of sound waves produced in air by the voice."
In all the forms of my instrument the electrodes are supported by a diaphragm
by the motions of which diaphragm either alone or in connection with another
diaphragm they act to modify the current as above stated.
In this instrument there is a back-board; a box or case; a front cover having a
mouth orifice; a rear cover, also having a central orifice; a front diaphragm and a
rear diaphragm; blocks of wood or other material, support the instrument at
a distance from the back-board. By this construction, sound waves impinge upon
the front diaphragm directly, and upon the rear diaphragm after a whole or partial
reflection from the back-board thus vibrating both diaphragms, relatively in
opposite directions, simultaneously.
The electrodes are arranged between the two diaphragms, one electrode being
fixed to the rear diaphragm, and having an inclined upper surface, and the other
one resting upon said inclined surface by gravity, and receiving motion from the
front diaphragm.
To the rear diaphragm and at about its centre I secure a block of wood or other
suitable material upon which I attach by a screw or in any convenient way, a
metal plate. This plate is covered or coated with what I designate as my electrode
compound, which I may prepare in the following way: I pulverize gas carbon
finely, and mix it with what is known as rubber varnish, that is to say, pure
rubber dissolved in bisulphide of carbon, so as to form a pasty mass, which I prefer
should not be so thick as to prevent its flowing from the brush. I do not limit
myself to any particular consistence of this mixture, because it may be desirable in
some cases to have it thick or viscid, and in others, thin and flowing. I have
found, however, that it is more convenient to make the compound not much
ו...D

page_text: thicker than ordinary varnish, so that it can be applied easily with the brush.
I do not limit myself to any particular binding material, such as rubber varnish,
because I may use other agglutinating mixtures in place thereof, such for example,
as shellac dissolved in alcohol, or even ordinary glue, or copal varnish, or Chinese
Japan varnish. All of these substances give good results, but I think in practice,
it is best to use a material which does not absorb moisture, as does glue, and which
will cause the compound to dry and harden quickly through the evaporation of a
volatile constituent, such for example, as alcohol or bisulphide of carbon.
A metal plate is partially or wholly covered with the electrode compound.
Another metal plate is also covered with my electrode compound used sub
stantially the same way. To the back of this plate is secured a projecting piece
also of metal, having a curved outer edge. On the front diaphragmn I secure two
pieces of wood, with a space between them, into which space, enters the curved
edge of the projecting piece. These pieces prevent lateral displacement of the
upper electrode which rests upon the lower electrode by gravity. I find it
preferable to make the angle of inclination of the electrode about 45 degrees.
The circuits in the instrument proceed as follows:-
From the battery to a binding post, by a wire to an induction coil, through the
prima y of said coil, by a wire to a plate through layers of electrode compound, to
another plate and projection, and thence by a wire connected to said projection,
and to a contact plate, thence to another spring and contact plate, and thence by a
wire to a binding post and back to the battery.
The secondary coil of the induction coil connects with the line and with a
receiving instrument, when a contact plate by the ring of a suspended receiving
instrument is raised the circuit in the instrument is broken. The vibrations of
the diaphragms are communicated to the electrodes, so that the latter cause
modifications of the current passing through them.
I do not limit myself to two electrodes provided with a coating of finely divided
conducting material mixed with an agglutinating substance, inasmuch as I have
used one electrode, consisting of a plate of metal or other conducting material
combined with a second electrode coated as described. The plates coated may be
either of conducting or non-conducting material.
In the latter case, electrical
circuit connection is established directly with the coating.
The instrument contains a back or base board a bar or ledge thereon and
brackets. Attached to the brackets and bar are cushions of felt. Surrounding the
diaphragm on its outer or front side, is a narrow spacing piece. Outside of this
piece outside of which is the cover having a mouth orifice.
When the diaphragm is in place, the upper part of its rear side bears against the
pads and two screws passing through said pads secure the diaphragm to the bar
and brackets.
The lower portion of the inner side of the diaphragm rests against one or more
pieces of rubber tubing which are slipped over pins on the back-board.
The instrument has no enclosing case or box, and the diaphragm is supported
and fixed only by the screws.
The electrodes which may consist of carbon, are supported upon the rear side of
the diaphragm ; said electrodes are three in number, two of them being fixed upon
said diaphragm and coincidently inclined and so arranged as not to be in electrical
contact with one another. The third electrode rests upon the two electrodes
aforesaid by gravity, and forms a bridge between them. The shape of these
electrodes is not material, nor is the manner of suspending the loose or bridge
electrode to keep it in position.
To the rear side of the diaphragm and at about its centre, is a bracket of
non-conducting material having an inclined upper surface. Upon said upper side
are secured two metal socket plates. Said plates are not in contact with each
other. Each plate receives one of the fixed electrodes which are made in segmental
form. In the bracket and protruding through an opening between the carbons is a
hook-shaped post of non-conducting material.

page_text: The loose electrode rests upon and thus forins a bridge between the fixed
electrodes. The fixed electrodes may be rectangular in shape, and the loose
electrodes may be of like form or the electrodes may be of other shapes. The
loose electrode may be suspended and maintained in place upon the fixed electrode
by an arm passing through it or by a thread or any flexible connection uniting it,
for example, to the diaphragm. The loose electrode is preferably inade thicker at
one edge than the other, so that it will tend to remain in position with its thickest
or heaviest side lowest. The under side of said loose electrode is preferably
provided with grooves.
The induction coil is inserted in a suitable socket in the base board and secured
in place in any suitable manner.
The circuits in the instrument proceed as follows:-
From the battery to a binding post, by a wire to a primary wire of the induction
coil to a contact piece, thence to another contact piece. These contact pieces have
holes through them, through which holes, screws pass, thus binding said pieces
closely together, thence by a wire to a metal socket plate; to a carbon; to another
carbon; to another carbon; to a socket plate; to a wire; to a contact plate; to
another contact plate; to a post and a wire and to a metal plate.
A bent metal plate secured by a rivet to a spring. This spring normally presses
a plate in contact with another plate, so that circuit continues from the plate to
the spring and thence by a wire to a binding post and so back to the battery.
The secondary circuit from the induction coil proceeds to the line and branch
wires therefrom go to a receiving telephone.
When the diaphragm is set in vibration by the voice, then the variation of
pressure between the electrodes will produce a modification of the current passing
through them, rendering said current undulatory and capable of reproducing the
speech or other sounds through the line and in the receiving instrument.
There is no box or enclosing case, such as is commonly used in carbon
transmitters, but the interior of the instrument is open and exposed to view on
three sides, thus affording easy inspection of the same.
The instrument contains a box or case an outer cover having a mouth-piece
orifice and a diaphragin to which is attached a metal bracket and to said bracket is
pivoted a metal cup.
Within said cup is inserted a hollow cylinder of carbon or other non-conducting
inaterial.
At the bottom of the cup and within the hollow of said cylinder, I place a piece
of rubber or other insulating material.
A cylinder of carbon or other low conducting material fits loosely within the
hollow cylinder. In the upper portion of said cylinder is secured a metal rod.
A cup is pivoted to the bracket by means of a shaft, which is rigidly secured to
the cup, but passes loosely through the hole in the bracket and is prevented
from coming out of said orifice by a nut. This shaft extends through the side
of the case.
When the cup is caused to stand vertically, the carbon cylinder will rest upon
the piece of insulating material at the bottom of the hollow of the cylinder, hence
the contact between the carbon cylinder and the cylinder will be a very light one,
and the instrument will then become a delicate microphone.
When, however, the cup is placed in an inclined position, then a portion of the
weight of the cylinder will rest upon the inner side of the cylinder, in which case
the contact will be less delicate and the apparatus will be adapted for use as a
speaking telephone.
This adjustment is effected by turning a lever, which is outside of the case of the
instrument and thus altering the inclination of the cup.
The circuits in the instrument proceed as follows:→
From a battery to a binding post, to the primary of the induction coil, by a wire,
to a rod, carbon, carbon, cup and bracket, by a wire to a spring, thence to a plate,
binding post and battery.

page_text: The secondary wires of the induction coil lead to line binding posts and to a
receiving instrument.
The instrument contains a diaphragm and an outer cover having a mouth piece
orifice. To the rear of the diaphragm, and at about its centre, is attached a brass
plate which supports a brass cup. In this cup is placed an annular cup shaped
piece of carbon or other low conducting material. In the hollow of the carbon a
ball of carbon or other low conducting material is adapted to rest; through this
ball passes a metal rod, the ball resting on a shoulder of the rod. The ball is rigidly
fastened to the rod. Said rod extends downwardly through a central opening in
the carbon and cup. Beneath its lower end is arranged a plate of metal having
paper or other insulating material on its upper surface; said plate is supported
by a stem rigidly secured to a flat spring, which is fastened to the bottom of
the case.
The rod extends slightly above the carbon ball.
The spring has a downward prolongation, which passes through the bottom of
the case and has a horizontal projection. To the bottom of the case is also attached
a ok to receive the ring of a receiving instrument or other object, which may be
hung thereon. To the side of the case is attached a flat spring which communicates
with a press button, the stem of which passes through the side of the case. When
this press button pushed in, the end of the spring is brought into contact with
the bent end of the spring.
When the ring of the receiving instrument is removed from the hook the spring
and plate assume their lowest position. In such case, the plate and rod are not in
contact. The ball then rests with its whole weight plus that of the rod upon the
carbon. The spring and the upper end of the rod are then out of contact.
instrument is then adapted for use for transmitting speech and the course of the
circuits is as follows:-
The
Proceeding from the battery to a binding post the current then passes by a wire
to the rod and ball, thence to the carbon cup, metal cup, plate, wire, to the primary
of the induction coil, thence by a wire to a binding post, and so to the battery
again. The secondary wires connect to the line.
In order to render the instrument very delicate, so that the carbon ball and cup
may be in very light contact, I support the carbon ball from below so that only
a small portion of its weight may fall upon the carbon cup beneath. This I do by
raising the plates, so that it shall come in contact with the end of the rod and lift
said rid slighty and as the rod has some play in its aperture in the carbon cup, it
moves slightly sidewise, so that the ball does not touch the cup around its whole
circumference. I find it convenient to raise this plate and hold it raised by
introducing the ring of a receiving instrument or any other object of suitable size
between a hook and horizontal projection of the spring. When the ring is intro-
duced between the hook and spring to a certain point, it will have raised the
spring and plate and consequently the rod sufficiently to bring the carbon ball into
the desired light contact with the carbon cup.
When the ring or other object is pushed in between the hook and the spring arm
all the way, then the plate and the ball are raised so that the carbons are wholly
out of contact; when the instrument is no longer operative for transmitting sound.
It is then, however, in a condition for signalling as follows.
The battery current entering at a binding post proceeds by a wire to a rod and
thence directly to the spring which is now in contact with the upper end of the
rod. When the press button is pushed in to close the circuit, the current continues
along the spring and thence passes by a wire to the line by a binding post.
The instrument contains a base or back board and an enclosing box or case made
entirely of metal, preferably of cast iron. It is provided with suitable recesses or
sockets on the front side to receive the electrodes, the induction coil and other
internal mechanism, and on its rear side are sockets to receive blocks of rubber
or other elastic material, the said blocks entering also into corresponding sockets
formed on the back board.

page_text: Passing through the back board and into the elastic blocks are screws. By this
arrangement, the box is attached to the back board by an elastic connection at the
same time said box has considerable weight. The consequence is that the vibrations
communicated from the wall, partition or other support to the back board are taken
up by the elastic blocks to such an extent that they are unable to overcome the
inertia of the heavy box.
In a ring groove on the front side of the box I place a gasket of elastic substance
against which rests the diaphragm. Outside of the diaphragm is a wooden cover
having a mouthpiece orifice.
To the rear side of the diaphragm is secured a metal cup-shaped bracket, which
receives an annular electrode preferably of carbon. On said annular piece of carbon
is placed a carbon ball to which is secured a metal rod, which passes down through
the annular carbon and bracket and through a tube of insulating material inserted
in the body of the case to prevent the rod from coming in contact therewith.
The lower end of the rod may be provided with a knob, a similar knob is formed
on the upper side of the spring, the end of which spring is secured to the side of
the case.
The hall normally rests upon the annular carbon:
The circuits in the instrument proceed as follows:-
From the battery to the binding post, by a wire to the primary of the induction
coil by a wire to the contact piece. This contact piece is fastened by a screw to a
The circuit then proceeds
plug of wood inserted in a suitable socket in the box.
by the contact piece to another contact piece on the diaphragm. These contact
pieces come together when the diaphragm is in place, thence by a wire to a bracket;
carbon, carbon, rod, and thence to a spring, wire, binding post and back to the
battery.
The secondary circuit in the coil proceeds to the line and to a receiving instrument.
When speech is uttered in front of the diaphragm, the latter in vibrating, cause
variations in pressure or contact between the electrodes, thus modifying the
current, and rendering the same undulatory in form, and capable of reproducing
sounds uttered through the line in a receiving instrument.
An important advantage of the metal case here described is that it is entirely
fire proof.
Dated this Second day of January 1884.

page_text: 1, HERBERT JOHN ALLISON, of the firm of Allison Brothers, Patent Agents, of
Chancery Lane, London, in the County of Middlesex, (A. communication to me
from abroad by Daniel Drawbaugh, of Eberly's Mills in the County of Cumber-
land and State of Pennsylvania, United States of America, Electrical Engineer,)
do hereby declare the nature of my invention for "IMPROVEMENTS IN TELEPHONE
TRANSMITTERS" and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
My invention relates to Telephone Transmitters and more particularly to that
class of Transmitters in which the current is modified and rendered undulatory in
form by passage between electrodes, the pressure between which or area of surface
contact of which is varied by the movement of a diaphragın or diaphragms under
the influence of sound waves produced in air by the voice.
In all the forms of my instrument represented in the drawings, it will be seen
that the electrodes are supported by a diaphragm by the motions of which diaphragm
either alone or in connection with another diaphragm they act to modify the current
as above stated.
Fig. 1. is a front view with diaphragm removed.
Fig. 2. is a vertical section on line xx of Fig 1.
Fig. 3. is a bottom view of one of the electrodes.
Fig. 4. shows the arrangement of two electrodes, and
Fig. 5. is a rear view of the diaphragm.
A is the back-board of the instrument; B is the box or case; C is the front
cover having a mouth orifice; D is the rear cover, also having a central orifice;
E is the front diaphragm; F is the rear diaphragm; G G are blocks of wood_or
other material supporting the instrument at a distance from the back-board A. By 1
this construction sound waves impinge upon the diaphragm E directly, and upon
the diaphragm F after a whole or partial reflection from the back-board A, thus
vibrating both diaphragms, relatively in opposite directions, simultaneously.
The electrodes are arranged between the two diaphragms, one electrode being
fixed to the rear diaphragm, and having an inclined upper surface, and the other
one resting upon_said inclined surface by gravity, and receiving motion from the
front diaphragm E.
To the rear diaphragm F and at about its centre, I secure a block of wood or
other suitable material H, upon which I attach by a screw, as shown in Fig. 4, or
in any other convenient way, a metal plate I. This plate is covered or coated
with what I have already designated as my electrode compound, which I may
prepare in the following way-I pulverize gas carbon finely, and mix it with
what is known as rubber varnish, that is to say :-pure rubber dissolved in
bisulphide of carbon, so as to form a pasty mass, which I prefer should not be so
thick as to prevent it flowing from the brush. I do not limit myself to any
particular consistence of this mixture, because it may be desirable in some cases to
have it thick or viscid, and in others thin and flowing. I have found, however,
that it is more convenient to make the compound not much thicker than ordinary
varnish, so that it can be applied easily with the brush. I do not limit myself to
any particular binding material, such as rubber varnish, because I may use other
agglutinating mixtures in place thereof, such for example, as shellac, dissolved in
alcohol, or even ordinary glue, or copal varnish, or Chinese Japan varnish. All of
these substances give good results, but I think in practice, it is best to use a
material which does not absorb moisture, as does glue, and which will cause the

page_text: compound to dry and harden quickly through the evaporation of a volatile
constituent, such for example, as alcohol or bisulphide of carbon.
Referring now to the drawings:-
Fig. 3, shows the metal plate I, partially covered with the electrode compound.
The plate may be wholly covered, but I think the results are a little better when
it is partially covered, substantially as here shown.
J is another metal plate covered with my electrode compound used substantially
the same way. To the back of this plate is secured a projecting piece L, also of
metal having a curved outer edge. On the diaphragm E, I secure two pieces of
wood M, with a space between them, into which space, enters the curved edge
of the projecting piece L, as shown in Fig. 2. These pieces M. prevent lateral
displacement of the upper electrode J, L which rests upon the lower electrode by
gravity. I find it preferable to make the angle of inclination of the electrode I
about 45 degrees.
The circuits in the instrument proceed as follows:-
From the battery to the binding post 1., by the wire a to the induction coil N,
through the primary of said coil, by the wire b to the plate I, through layers of
electrode compound to the plate J, projection L, and thence by the wire C,
connected to said projection, and to the contact plate P, thence to the spring and
contact plate Q, and thence by the wire b, to the binding post 2 and back to the
battery.
The secondary coil of the induction N connects by wires e e to the line binding
posts 3 and 4, and from said wires e e branch wires ff extend to the binding
posts 5 and 6, to which a receiving instrument may be attached. The spring
contact piece overlaps the plate P, and has a rectangular downward projection,
so that when the ring of a receiving instrument is placed over the arm R, said
contact plate Q is raised and the circuits between the parts P and Q is broken.
S is a bar for holding the induction coil N in place, said induction coil passes
through an opening in the rear diaphragm F, and is secured to the back-board A.
The vibrations of the diaphragms are communicated to the electrodes, so that the
latter cause modifications of the current passing through them.
I do not limit myself to two electrodes provided with a coating of finely divided
conducting material mixed with an agglutinating substance, inasmuch as I have
used one electrode, consisting of a plate of metal or other conducting material
combined with a second electrode coated as described. The plates coated may be
either of conducting or non-conducting material. In the latter case, electrical
circuit connection is established directly with the coating.
Fig. 6, represents the instrument with the diaphragm removed.
Fig. 7, is a vertical section or line x x of Fig. 6.
Fig. 8, is a rear view of the diaphragm.
Fig. 9, shows the underside of the loose electrode, and
Fig. 10 the upper side of the fixed electrode.
A, Fig. 6, is the back or base-board of the instrument, B is a bar or ledge thereon
and CC are brackets. Attached to the brackets C and bar B are cushions of felt
or similar yielding material D. E is the diaphragm here shown of wood or other
non-conducting material. Surrounding the diaphragm on its outer or front side, is
a narrow spacing piece G. Outside of this piece G and connected to it is the
cover H, preferably of wood, having a mouth orifice I. The spacing rim G may
be a mere bead or a raised rim integral with the diaphragm E or cover H or with
both.
When the diaphragm is in place, the upper part of its rear side bears against
the pads or cushions D, and two screws J passing through said pads secure the
diaphragm to the bar B and brackets C.
The lower portion of the inner side of the diaphragm rests against one or more
pieces of rubber tubing K, which are slipped over pins L on the back-board A.
It will be apparent from the foregoing that the instrument has no enclosing case
or box, and that the diaphragm is supported and fixed only by the screws J.

page_text: The electrodes which may consist of carbon, are supported upon the rear side of
the diaphragm; said electrodes are three in number two of them being fixed upon
said diaphragm and coincidently inclined and so arranged as not to be in electrical
contact with one another. The third electrode rests upon the two electrodes
aforesaid by gravity, and forms a bridge between them. The shape of these
electrodes is not material, nor is the manner of suspending the loose or bridge
electrode to keep it in position. I consider the weight of the loose or bridge
electrode to be of importance, inasmuch as I have obtained the best results with a
loose electrode weighing about half an ounce. I also find that the apparatus
works most satisfactorily when the fixed electrodes are so secured to th diaphragm
as to stand at an inclination of about 45 degrees. The particular construction
and mode of arranging the electrodes shown in the drawings, which is the best
means I now know of carrying the invention into practical effect, is as follows:-
To the rear side of the diaphragm and at about its center, is a bracket M of
wood or other non-conducting material having an inclined upper surface. Upon
said upper side are secured two metal socket plates 0 0¹. Said plates are not in
contact with each other. Each plate receives one of the fixed electrodes P P¹
which are made in segmental form. In the bracket M. and protruding through an
opening between the carbons P P' is a hook-shaped post Q, preferably of hard
rubber or other non-conducting material.
R, Fig. 7, is the loose electrode, which rests upon and thus forms a bridge
between the fixed electrodes P P¹. This electrode is here shown as an annular
piece of carbon suspended or held in place by the arm passing through its central
aperture. It should be understood that I do not limit myself to two fixed
electrodes of segmental form, nor to a loose electrode of annular form; thus for
example, the fixed electrodes. may be rectangular in shape, and the loose electrodes
may be of like form. Nor do I limit myself to a loose electrode having a central
aperture to receive the arm Q, nor to a loose electrode necessarily supported by an
arm or post passing through an aperture in it, inasmuch as said electrode may be
suspended and maintained in place upon the fixed electrode by a thread or any
flexible connection uniting it, for example, to the diaphragm.
The loose electrode is preferably made thicker at one edge than the other, so
that it will tend to remain in position with its thickest or heavest side lowest ; and
if necessary, the board A may be slightly recessed to accomodate it.
The under
side of said loose electrode is preferably provided with grooves, in order to admit
air between the surfaces as much as possible to avoid the effect of atmospheric
pressure, which tends to press the electrodes uniformly together, and to resist the
movement of the loose electrode.
T is the induction coil inserted in a suitable socket in the base-board and
secured in place in any suitable manner, as for example, by the metal bar U
attached to the bar B.
The circuits in the instrument proceed as follows:-
From the battery to the binding post 1, by the wire a (dotted lines), to post b to
the primary wire of the induction coil T, to contact piece c, Fig. 1, thence to
contact piece d Fig. 3. These contact pieces have holes through them, through
which holes, the screws J pass, thus binding said pieces closely together. Thence
by wire e to the metal socket plate O; to carbon P'; to socket plate O'; to
wire e'; to contact plate &; to contact plate c'; to post b' and wire a' and to the
metal plate V.
W is a bent metal plate secured by a rivet to the spring X. This spring
normally presses the plate W in contact with the plate V, so that circuit continues
from the plate V to the spring X and thence by the wire f to the binding post 2,
and so back to the battery.
The secondary circuit from the induction coil T proceeds by the wires g g' to
the posts hh' and thence by wires i to the binding posts 3 4, and thence to the
line.

page_text: Branch wires jj' proceed from the posts h h' to the binding posts 5 6, to which
a receiving telephone may be connected.
The operation of this instrument is as follows:-
It is obvious that the initial pressure between the loose electrode R and fixed
electrodes P P' is maintained by gravity, and that it is varied in accordance with the
proportion of the weight of the electrode R supported by the electrodes P P', which
variation depends upon the movement of the diaphragm in vibration.
And when
the diaphragm is set in vibration by the voice then the variation of pressure
between the electrodes will produce a modification of the current passing through
them, rendering said current undulatory and capable of reproducing the speech or
other sounds through the line and in the receiving instrument.
It will also be observed that there is no box or enclosing case, such as is
commonly used in carbon transmitters, but that the interior of the instrument is
open and exposed to view on three sides, thus affording easy inspection of the
same. The pads D and the rubber blocks or tubes K act not only as dampening
pads to stop out false vibrations not due to the voice, but also to prevent in large
measure, jars or vibration of the partition or wall to which the instrument is
attached, being communicated to the diaphragm.
Y is an arm to receive the ring of the receiving telephone, for suspending the
latter when not in use. The ring on passing upon the arm Y raises the bar W
which is thus moved out of contact with the plate V, breaking the local circuit in
the instrument.
The diaphragm, when of wood, may be provided with a paper lining F, to prevent
splitting.
Fig. 11, shows the instrument with back removed exhibiting rear side of
diaphragm.
Fig. 12, is a partial vertical section on line x x of Fig. 11.
Fig. 13, is a transverse section on line y y of Fig. 11.
A is the box or case of the instrument. B is the outer cover having a mouth-
piece orifice C, and D is the diaphragm. I have shown this diaphragm with a
central perforation E covered by a piece of felt or similar inaterial F, but this
construction is not at all essential inasmuch as I may use a solid continuous
diaphragm without such perforation or felt cover.
I make said diaphragm preferably of wood or other non-conducting material, and
to its rear side, and at about the center, I attach a metal bracket G. To said
bracket I pivot a metal cup I.
Within said cup is inserted a hollow cylinder of carbon or other non-conducting
material J.
At the bottom of the cup and within the hollow of said cylinder, I place a piece
of rubber or other insulating material L.
M is a cylinder of carbon or other low conducting material fitting loosely within
the hollow cylinder I. In the upper portion of cylinder M is rigidly secured a
metal rod N.
The cup I is pivoted to the bracket G by means of a shaft O, which is rigidly
secured to the cup I, but passes loosely through the hole in the bracket G, and is
This shaft extends
prevented from coming out of said orifice by the nut H.
through the side of the case A as shown in partial section, Fig. 1, and has at its
outer end, a lever P.
It will be obvious that when the cup I is caused to stand vertically, the carbon
cylinder M will rest upon the piece of insulating material L at the bottom of the
hollow of the cylinder J, hence the contact between the carbon cylinder M. and
the cylinder J will be a very light one, and the instrument will then become a
delicate microphone.
When, however, the cup I is placed in an inclined position, as shown in Fig. 12,
5 then a portion of the weight of the cylinder M will rest upon the inner side of the
cylinder J, in which case the contact will be less delicate and the apparatus will
be adapted for use as a speaking telephone.

page_text: It will be apparent that the delicacy of contact and initial pressure between the
carbons will depend upon the inclination of the cup I; also that said initial pressure
will be the less as the cup approaches a vertical position and greater as it more
nearly approximates a horizontal position. A very convenient means is therefore
afforded by this device of adjusting the telephone, so that it be as sensitive as may
be desired, this adjustment being effected by simply turning a lever P, which is
outside of the case of the instrument, and thus altering the inclination of the
cup I.
The circuits in the instrument proceed as follows:-
From the battery to the binding post 1, to the primary of the induction coil Q,
by the wire a, to the rod N, carbon M, carbon J, cup I, and bracket G; by the
wire to the spring R, thence to the plate S, binding post 2 and battery.
The secondary wires c d of the induction coil lead to the line binding posts 3
and 4; from said posts wires e f lead to the binding posts 5 and 6, to which a
receiving instrument may be attached.
T is a hook or bracket to support a receiving instrument, the ring of which,
when in place, pushes up the projection U of the spring R, and so breaks circuit
between the springs R and S.
Fig. 14, shows the instrument with back removed exhibiting the rear side of the
diaphragm.
Fig. 15, is a vertical section on line x x of Fig. 14.
Fig. 16, is a section on line y y of Fig. 16.
Fig. 17, shows the arrangement of the electrodes, there being represented
enlarged.
A is the case of the instrument. B is the diaphragm, which may be of wood,
C is the outer cover having a mouth piece orifice D. To the rear of the diaphragm,
and at about its centre, is attached a brass plate E, which supports a brass cup F.
In this cup is placed an annular cup-shaped piece of carbon or other low conducting
material G. In the hollow of carbon G, a ball H of carbon or other low con-
ducting material is adapted to rest; through this ball passes a metal rod I, the
ball resting on a shoulder of the rod as shown in Fig. 12. The ball is rigidly
fastened to the rod. Said rod extends downwardly through a central opening in
the carbon G and cup F. Beneath its lower end is arranged a plate of metal J
having paper or other insulating material on its upper surface; said plate is
supported by a stem K rigidly secured to a flat spring L, which is fastened to
the bottom of the case.
The rod I extends slightly above the carbon ball H.
The spring I has a downward prolongation N, which passes through the bottom
of the case and has a horizontal projection O. To the bottom of the case is also
attached a hook P, to receive the ring Q of a receiving instrument or other object,
which may be hung thereon. To the side of the case is attached a flat spring R,
which communicates with a press button S, the stem of which passes through the
side of the case. When this press button S is pushed in, the end of the spring R
is brought into contact with the bent end T of the spring M.
The operation of the instrument is as follows:―
When the ring Q of the receiving instrument is removed from the hook P, the
spring L and plate J assume their lowest position. In such case, the plate J and
rod I are not in contact. The ball H then rests with its whole weight plus that of
the rod I upon the carbon G. The spring M takes no part in pressing the carbon
ball down into the cup G as when the ball rests as above described in said cup the
spring M, and the upper end of rod I are out of contact. The instrument is
then adapted for use for transmitting speech and the course of the circuits is as
follows:
Proceeding from the battery to the binding post 1, the current then passes by
the wire a to the rod I and ball H, thence to the carbon cup G, metal cup F,
plate E, wire b, to the primary of the induction coil U, thence by the wire c to

page_text: the binding post 2, and so to the battery again. The secondary wires d and e
of the induction coil U lead to the posts 3 and 4, which connect to the line.
In order to render the instrument very delicate, so that the carbon ball and cup
may be in very light contact, I support the carbon ball from below so that only a
This I do by
small portion of its weight may fall upon the carbon cup beneath.
raising the plate J, so that it shall come in contact with the end of the rod I and
lift said rod slightly. As the rod I has some play in its aperture in the carbon
cup, it moves slightly sidewise, so that the ball does not touch the cup around its
whole circumference. I find it convenient to raise this plate J and hold it raised
by introducing the ring Q of the receiving instrument or any other object of
suitable size between the hook P and horizontal projection of the spring L. I cut
away or curve the under side of the projection O at V, so that when the ring Q
is introduced between the hook P and spring O to about this point V, it will have
raised the spring L and plate K and consequently the rod I sufficiently to bring
the carbon ball H into the desired light contact with the carbon cup G.
When the ring or other object is pushed in between the hook P, and the
spring arm all the way, or to the point indicated in the drawing, Fig. 15, then
the plate J and the ball H are raised to the positions indicated by dotted lines in
said Fig. and Fig. 17.
In such case, it will be seen that the carbons are wholly out of contact; when
the instrument is no longer operative for transmitting sound.
It is then, however, in a condition for signalling as follows:-
The battery current entering at binding post 1 proceeds by the wire a to the
rod I and thence directly to the spring M, which is now in contact with the upper
end of rod I. When the press button S is pushed in to close the circuit, the current
continues along the spring R, and thence passes by the wire f to the wire g, and
thence to the line by the binding post 4.
The other pole of the battery connects with the binding post 2 which by means
of the wire b communicates with the line binding post 3. The branch wires i
and g connect the secondary wire d-e and line binding posts 3 and 4 with the
binding posts 5 and 6, to which a receiving instrument may be attached.
Fig. 18, shows the instrument with diaphragm removed.
Fig. 19, is a vertical longitudinal section on line x x of Fig. 18.
Fig. 20, is a horizontal section on line y y of Fig. 18, and
Fig. 21, is a rear view of the diaphragm.
A is the base or back-board of the instrument, B is the enclosing box or case.
This box I make entirely of metal, preferably of cast iron. It is provided with
suitable recesses or sockets on the front side to receive the electrodes, the induction
coil and other internal mechanism, and on its rear side, I form preferably three
sockets to receive blocks C of rubber or other elastic material, the said blocks
entering also into corresponding sockets formed on the back-board A.
The blocks C should be inserted tightly in the sockets in the box B and may be
secured therein if desired, by any suitable cement or fastening.
Passing through the back-board A and into the elastic blocks C are screws D.
By this arrangement, the box B is attached to the back-board A by an elastic
connection; at the said time said box has considerable weight. The consequence
is that the vibrations communicated from the wall, partition or other support to
the back-board A are taken up by the elastic blocks Ċ to such an extent that they
are unable to overcome the inertia of the heavy box B. I have found that this
device is very efficacious in practice, especially where the telephone is attached to
a thin partition liable to be easily vibrated by persons moving in the building,
or in cases where the building itself is subject to the jar of machinery, or to the
passing of heavy vehicles.
Under these conditious, it very frequently happens with ordinary telephone
transmitters that the jarring and accidental vibrations affect the electrodes pro-
ducing disagreeable sounds in the receiving instrument and the blurring and
confusing of speech received thereby.

page_text: In the ring groove on the front side of the box B, I place a gasket F of felt or
other elastic substance against which rests the diaphragm G, which may be as here
shown of wood or other non-conducting material or of metal with suitably changed
connections. Outside of the diaphragm is a wooden cover E having a mouthpiece
orifice as shown.
To the rear side of the diaphragm is secured a metal cup-shaped bracket H,
which receives an annular electrode preferably of carbon, I. On said annular
piece of carbon is placed a carbon ball J to which is secured a metal rod K, which
passes down through the annular carbon and bracket and through a tube L of
insulating material inserted in the body of the case to prevent the rod from coming
in contact therewith.
The lower end of the rod K may be provided with a knob M, a similar knob N
is formed on the upper side of the spring O, the end of which spring is secured to
the side of the case B at P.
The ball J normally rests upon the annular carbon I.
Qis the induction coil.
The circuits in the instrument proceed as follows:-
From the battery to the binding post 1, by the wire a to the primary of the
induction coil O, by the wire b to the contact-piece T. This contact-piece is
fastened by a screw to a plug of wood U, Fig. 20, inserted in a suitable socket
in the box B. The circuit then proceeds by the contact-piece T to the contact-
piece V on the diaphragm. These contact pieces T and V come together when
the diaphragm is in place. Thence by the wire c to the bracket H, carbon I,
carbon J, rod K, and thence to the spring O, wire d, binding post 2, and back to
the battery.
The secondary circuit in the coil Q proceeds by wires e e' to the line binding
posts 3, 4, from which posts extend wires ff' to the binding posts 5, 6, to which
posts, a receiving instrument may be attached.
The operation of the instrument is as follows:-
When speech is uttered in front of the diaphragm, the latter in vibrating, cause
variations in pressure or contact between the electrodes I and J, thus modifying
the current, and rendering the same undulatory in form, and capable of reproducing
sounds uttered through the line in a receiving instrument.
When the apparatus is intended not to be in operation, the ring of the receiving
instrument may be passed upon the arm W, thus raising the spring arm and
so lifting the ball J out of contact with the carbon H, thus breaking the local
circuit.
In Figs. 14 to 17, I have shown another telephone transmitter containing
electrodes in the shape of a ball and annular carbon operating in substantially
the same manner as above set forth.
An important advantage of the metal case here described is that it is entirely
fire proof. It is well known that powerful currents derived from electric light
wires and from lightning, have through various causes, been enabled to pass upon
telephone lines and the telephones. The effect of such currents is enorinously to
heat the wires of the connections and induction coil in the instrument and often
to set fire to the box or case of inflammable material, and to any adjacent
woodwork, thus producing a conflagration in the building. My improved case
being completely non-inflammable, effectually cuts off any danger of fire being
communicated from a burning telephone to other parts of a building, and limits
the destruction caused to the internal parts of the instrument itself.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed,
I declare that what I claim is: :-
1. In a telephone transmitter, electrodes consisting of flat plates having their
surfaces in contact, the said surfaces being covered with a hard thin coating of
finely divided conducting material combined with an agglutinating substance,
substantially as described.

page_text: 2. An electrode or resistance varying conductor for telephone transmitters
consisting of a thin stratum of finely divided conducting material combined with
an agglutinating substance, substantially as described.
3. A telephone electrode or resistance varying conductor for telephone transmitters,
consisting of a plate covered with a hard thin coating of finely divided conducting
material combined with an agglutinating substance, substantially as described.
4. In a telephone transmitter, electrodes consisting of metallic plates or surfaces,
provided with a hard thin coating of finely divided conducting material, combined
with an agglutinating substance, the said coated surfaces being in contact,
substantially as described.
5. In a telephone transmitter, electrodes consisting of metallic plates having their
surfaces partially covered with a hard thin coating of finely divided conducting
material, combined with an agglutinating substance, the coated portions of said
plates being in contact, substantially as described.
6. In a telephone transmitter, and rigidly attached to a support, an inclined plate
or surface coated with a mixture of finely divided material and agglutinating
substance in combination with a movable plate similarly coated and pressing by
gravity upon said inclined surface, and a diaphragm acting upon said novable
plate, substantially as described.
7. In a telephone transmitter, the combination of the diaphragm E, guides M,
plate J, coated with a mixture of finely divided conducting material and
agglutinating substance, and having a projection L, similarly coated plate I, and an
inclined support for said plate I, substantially as described.
8. In a telephone, the combination with the diaphragm and the fixed support
carrying the inclined electrode, of the loose plate having a surface of conducting
material resting upon the fixed electrode, and a projection in contact with the
diaphragm, substantially as described.
9. In a telephone, a diaphragm or sound receiving surface, two fixed electrodes
coincidently inclined or having their upper surfaces coincidently inclined, the said
electrodes not being in electrical contact with one another, a loose electrode resting
upon both of said fixed electrodes by gravity, and a means of maintaining said
loose electrode in position upon the fixed electrodes, substantially as described.
10. In a telephone, a diaphragm, two fixed electrodes supported upon said
diaphragm and not in electrical contact with one another, a loose electrode arranged
above and resting upon said fixed electrode by gravity, and a means of maintaining
said loose electrode in position upon the fixed electrodes, substantially as described.
11. In a telephone, a diaphragm, a support secured to the rear side of said
diaphragm and having an inclined upper surface, two fixed electrodes secured upon
the inclined side of said support and not in electrical contact with one another, a
loose electrode of light material resting upon said fixed electrodes and a post of
non-conducting material projecting from said support and passing loosely through
an aperture in said loose electrode, substantially as described.
12. In a telephone, a diaphragm rigidly fastened at one side and having the
greater part of its periphery free and unattached, two electrodes inclined or having
inclined upper surfaces supported upon said diaphragm and not in electrical contact
with one another, a loose electrode of like material resting upon said fixed electrodes
by gravity, and a means of supporting the loose electrode to prevent it from sliding
off the fixed electrodes, substantially as described.
13. In a telephone, a diaphragm, two fixed electrodes of semi-circular segmental
form, coincidently inclined, supported upon said diaphragm, and not in electrical
contact with one another, a loose electrode annular in form and resting by gravity
upon said fixed electrodes, and a post projecting above said fixed electrodes, and
passing loosely through the aperture in said loose electrode, substantially as
described.
D 14. In a telephone, two electrodes, one of said electrodes being loose of
substantially wedge shaped cross section or having one side made heavier than the
other, so that when said electrode is suspended, said weighted or thicker sido may

page_text: by the action of gravity, assume a lower position than the unweighted or thinner
side, substantially as described.
15. In a telephone, an electrode having one side grooved, channeled, indented or
recessed, substantially as described.
16. In a telephone, the combination of the diaphragm E, support M, plates O O′,
fixed electrodes P P' post Q and loose electrode R, substantially as described.
17. In a telephone, a diaphragm rigidly fastened near one end and having the
greater part of its periphery unattached, and near its free end resting against a
piece or pieces of elastic material supported in contact with its inner side,
substantially as described.
18. In a telephone, a diaphragm rigidly secured at one end to a support, the
greater part of the periphery of said diaphragm being unattached, a piece or pieces
of elastic material being interposed between said diaphragm and the support, the
inner side of said diaphragm near the free end thereof resting against a piece or
pieces of elastic material supported in contact with said side, but not attached
thereto, substantially as described.
19. A telephone, having no enclosing box or case, the electrodes being supported
by the diaphragm, and the diaphragm being attached at one end to a support
secured to the back or base-board, substantially as described.
20. In a telephone, the combination of a diaphragm E, interposed frame or
piece G. and cover H having an orifice I, substantially as described.
21. In a telephone, the combination of the back or base-board A, the bar B,
brackets C, posts L and elastic tubes K with the diaphragm E, interposed frame or
piece G and cover H, substantially as described.
22. In a telephone, the combination of the contact plate V, bent contact plate W,
spring X, base-board A and arm Y, substantially as described.
23. In a telephone, the combination of the base-board A, bar B, brackets C,
posts L, elastic tubes K, diaphragm E, interposed piece G, cover H, bracket M,
Bocket plates 00', electrodes P P', electrode R, post Q, induction coil T, and circuit
connections, substantially as described.
24. In a telephone transmitter, the combination of two electrodes of low
conducting material, one loose, and the other annular in form attached to and upon
a movable support and surrounding the first electrode and means for varying the
inclination of the second electrode and support, so that said second electrode may
sustain more or less of the weight of the first electrode substantially as described.
25. In a telephone transmitter, the combination of an electrode of low conducting
material in the form of a hollow cylinder vertically disposed having a piece of
insulating material inserted in its lower end and sustained by a support and a
second electrode of low conducting material in the form of a solid cylinder adapted
to fit loosely in the first electrode and to rest on the said inserted piece of insulating
material and means for adjusting said first electrode and support at a desired
inclination so as to vary the proportion of weight of the second electrode
respectively sustained by the first electrode, substantially as described.
26. In a telephone transmitter, the combination of a diaphragm, a hollow
cylinder of low conducting material held in a support hinged or pivoted to said
diaphragm, a solid cylinder of low conducting material loosely fitting in said hollow
cylinder and a means for turning said hollow cylinder on its pivot or hinge,
substantially as described.
27. In a telephone transmitter, a diaphragm of non-conducting material, a metal
cup pivoted to said diaphragm, a hollow cylinder of low conducting material
contained in said cup, a solid cylinder of low-conducting material loosely fitting in
said hollow cylinder, a piece of insulating material arranged between the lower end
of said solid cylinder and the cup and means for turning said cup on its pivot or
hinge, substantially as described.
28. In a telephone transmitter, the combination of a diaphragm of non-conducting
material, bracket G, cup I, carbon J, carbon M, rod O and lever P, substantially as
described.

page_text: 29. In a telephone, the combination of two electrodes of low conducting material
respectively in the shape of an annular cup or socket, and of a ball adapted to be
received in said cup or socket, and means for raising and holding said ball out of
contact with said cup, substantially as described.
30. In a telephone, the combination of a diaphragın, an annular cup or socket of
low conducting material, supported by or upon said diaphragm, a ball of low
conducting material adapted to be received in said cup and a metallic rod fastened
to said ball and passing through the aperture in said cup, substantially as
described.
31. In a telephone, the combination of a non-conducting diaphragm, a conducting
support attached thereto, an annular cup or socket of low conducting material beld
in said support, a ball of low conducting material adapted to be received in said cup
and a metallic rod fastened to said ball and passing through the aperture in said
cup, substantially as described.
32. In a telephone, the combination of a non-conducting diaphragm, a conducting
support attached thereto, an annular cup or socket of low conducting material, a
ball of low conducting material adapted to be received in said cup, a rod attached to
said ball and extending downward through the aperture in said cup and a vertically
moveable support arranged beneath the lower end of said rod and capable of being
elevated to meet said rod and lift or sustain the same, substantially as described.
33. The combination in a telephone of the ball H, annular cup-shaped carbon G,
the support E F, rod I, plate J, spring L and hook or bracket P connected in circuit,
substantially as described.
34. The combination in a telephone of the rod I, support E F, spring M,
button S and spring R, substantially as described.
35. In a telephone, a containing box or case of metal having formed in the
substance thereof recesses and openings to receive the operating parts, supports and
circuit connections, substantially as described.
36. In a telephone, a back or base-board, a containing box or case of metal, and
case, substantially as
interposed elastic supports between said base-board and
described.
37. The method herein described of preventing the communication of jars or
shocks to a telephone from the support to which it is affixed, consisting in making
the enclosing case of the instrument of metal or other heavy material, and
sustaining the same by an elastic support or supports, the said supports serving to
take up or neutralize the vibrations and the heavy box or case to oppose the same
by its inertia, substantially as described.
38. In a telephone, the combination of the box B, elastic blocks C, back-board A
and screws D, substantially as described.
Dated this Second day of October 1884.