IMPROVEMENTS IN TELEPHONES AND APPARATUS EMPLOYED IN ELECTRIC CIRCUITS
Year: 1878

page_text: LETTERS PATENT to Thomas Alva Edison, of Menlo Park, in the State of New
Jersey, United States of America, for the Invention of "IMPROVEMENTS IN
TELEPHONES AND APPARATUS EMPLOYED IN ELECTRIC CIRCUITS."
Sealed the 29th November 1878, and dated the 15th June 1878.
PROVISIONAL SPECIFICATION left by the said Thomas Alva Edison at the
Office of the Commissioners of Patents on the 15th June 1878.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United
States of America. "IMPROVEMENT IN TELEPHONES AND APPARATUS EMPLOYED
IN ELECTRIC CIRCUITS."
In this apparatus I make use of a plate or body against which the sound waves
in the atmosphere act, and connected therewith is a button or buttons of carbon or
other semi-conducting material placed in the electric circuit. The pressure due to
the impact of the sound waves acts on the carbon, and produces the rise and fall of
electric tension in the circuit.
The circuits are arranged to bring into action one or more primary and secondary
currents, and an induction coil or coils, and switches and a call, so that signals can
be sent and messages transmitted in opposite directions over one line.
The receiving instrument is provided with an electro-magnet and an armature
formed of an iron plate diaphragm, and a hammer is attracted or repelled so as to
strike upon the diaphragm to form a call, and a stand is used to keep the telephone
instruments in proper position for the call to act.
Two or more vibrating instruments connected in the same circuit, and operated
by electro-magnets are thrown out of the circuit by a shunt, and act to give
signals in two distant instruments provided with diaphragms. I employ a con-
denser in the local or main line circuit to neutralize the static charge or discharge,
which condenser is preferably made of two strips of foil wound into a spiral form,
with non-conducting material intervening, and to which strips the respective
circuit wires are connected.

page_text: The carbon employed in the circuit is preferably the finest quality of selected
lamp-black, consolidated by heavy pressure, but plumbago and various forms of
carbon or iodide of copper, black oxide of manganese, finely divided metals, per-
oxide of lead, or similar semi-conducting materials reduced to a powder and moulded
in buttons or discs may be employed.
The induction coils serve to throw into the line a powerful induced current, and,
in some instances, I employ a battery connected with the line, and balanced so that
the sound waves acting on the carbon or other resistance, cause either the positive
or negative of the battery to preponderate on the line.
The condenser introduced in the same circuit gives both static and induction
currents. Fine wires may take the place of the strips of foil in the condensers.
Where the air waves strike upon a vibrating plate or disc, the change of pressure
upon the carbon may be obtained from a thin strata of air intervening between the
diaphragm and the platina plate of the carbon.
A magneto-electric. machine is sometimes used as the source of electric energy in
place of a battery, and the telephone instrument placed in the Wheatstone bridge,
and place resistances to balance the electric forces, so that variation of the resistance
in the telephone sends the current on the line.
Telephones in local circuits or shunts at way stations, with induction coils in the
main line, are used for operating local telephones on the main line.
The sound vibrations act by leverage upon the carbon or other resistance, to
increase or lessen the motion as circumstances require.
A secondary battery in some cases is employed in place of a condenser, and a
thermal battery can be employed as the source of electric energy.
Where the electric current is made to pass through water or an electrolytic
solution, the diaphragm acts upon a valve or cut-off to vary the volume of liquid
where the current passes, and effect a rise and fall of electric tension.
A Duluce dry pile is combined with a diaphragm at each terminal for transmitting
and receiving sound. An electrophorous similarly combined is sometimes employed
for the same purpose.
Calls are combined with the telephone so as to attract attention to the instru-
ment.
These calls are operated by pendulums, forks, or reeds, which set up magneto-
electric currents when vibrated, and from these the bell or other call receives its
movement from the distant station.
The receiving portions of the telephone are of a character adapted to respond to
the electric pulsations from the transinitting telephones aforesaid. Sometimes thero
are two or more receiving diaphragms to one air chamber to augment the sound.
It is important to use a damper upon the diaphragm to prevent false vibrations.
Mercury globules receiving motion from the electric action, are sometimes em-
ployed to actuate the receiving diaphragm, and the magnet of the receiving
diaphragm is polarized with a local battery and double coils.
A diaphragm connected directly upon the induction coil will respond to the
electric waves, and give audible sounds.
In place of flexible wires for the telephone connections, wires with universal
joints are preferable.
Long funnels are used with the telephonic receiver to increase the volume of
sound.
The expansion or contraction of gases and other materials by change of tempera-
ture or hygrometic condition are employed to vary pressure upon the carbon button
or disc between its two platina armatures, and a galvanometer in the circuit by its
movement indicates with the greatest and most absolutely certain accuracy the
extent of the disturbing cause that is exerted on the carbon.
The galvanometer may be wound differentially or placed in a Wheatstone bridge.
Induction coils are made of forms specially adapted to the telephone apparatus,
and the condensers are sometimes connected in a continuous metallic circuit.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Alva Edison in the Great Seal Patent Office on the 13th
December 1878.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United
States of America. "IMPROVEMENTS IN TELEPHONES AND APPARATUS EMPLOYED
IN ELECTRIC CIRCUITS."
In this apparatus I make use of a plate or body against which the sound waves
in the atmosphere act, and connected there with is a button or buttons of carbon or
other semi-conducting material placed in the electric circuit. The pressure due to
the impact of the sound waves acts on the carbon, and produces the rise and fall of
electric tension in the circuit.
Fig. 1 is a vertical section of the transmitting instrument, and Fig. 2 is a plan of
a portion of the same.
The body of the instrument is made of the two shells a and b, between which
the diaphragm c is clamped at its edge, and said diaphragm receives the impact of
the sound waves which enter through the opening or mouth-piece b'. e is a disk of
insulating material secured to the screw f, and in a cavity in this disk is the carbon
button between the platina disks 1 and 2; the disk 2 is secured to the screw f,
and the disk 1 is connected to the metallic ring 3 by a strip of platina at 4, in
order that said disk 1 may be free to move. The disk 1 is connected to the wire 5,
and the disk 2 to the wire 6.
As
Upon the diaphragm c there is a short tube i that rests upon the disk 1.
said diaphragm receives the impact of the sound waves, the carbon button is sub-
jected to different pressures, and varies the resistance to the passage of the electric
current through the same, consequently, the current passing in the circuit is varied
in its electric tension; this current acts in the distant receiver as hereafter ex-
plained, to give movement to a diaphragm, and produce sounds corresponding to
those which are received upon the diaphragm c.
The screw allows of the carbon button and disks 1 and 2 being raised or
lowered to adjust the initial pressure of the diaphragm on the carbon button.
The carbon employed for the button h is preferably the finest kind of selected
lamp-black consolidated by heavy pressure, but plumbago, carburet of iron, gas
retort carbon, or various compounds which are partial conductors in the dry state
may be used, such as iodide of copper, black oxide of manganese, peroxide of lead,
or similar semi-conducting materials, reduced to powder and moulded in buttons or
disks; also finely divided metals, such as platinum, black gold, or disks of metal
with a roughened surface having many points may be used.
The circuits are arranged to bring into action one or more primary and secondary
currents, and an induction coil or coils, and switches, and a call, so that signals can
be sent and messages transmitted in opposite directions over one line, as illustrated
in the diagram Fig. 3.
A at station 1 is the carbon transmitter, and said instrument is included within
the primary circuit of the induction coil D, E. D is the primary wire of the coil,
and is wound on the outside of the secondary coil E. C is a switch, which, when
moved to the right in contact with 15, places the transmitter A in the primary
circuit containing the battery K and coil D. When the switch is in the center the
primary circuit is open, and the apparatus is ready for the reception of a call signal.
When the switch is turned to the left at 16 the instrument A is thrown out of
circuit, and the battery only is connected to the primary coil D. The movement of
the switch from 16 several times serves to open and close the primary circuit, and
throw a powerful induced current into E, and then to the line.
The polarized relay F, coil E, and receiving instrument B, are all placed in the
main line wire at both stations. The powerful current thrown into the secondary
coil and line by the movement of the switch C from 16 works the tongues of both

page_text: polarized relays F in unison with the switch, the. tongues closing against their
contact points close a local circuit containing a call bell H. The same battery K
that is employed with the telephones is utilized to ring the bell.
The connections for the transmitter A are from the battery K by wire 20 to 21,
then through the telephone A to wire 22, and from 22 to 15, through the switch
lever C to the primary coil D, and to wire 23, back to battery. This is the con-
nection for transmitting and receiving telephonically. When not thus working the
switch C is placed in the central position between 15 and 16. When in this position,
if the switch of the distant station is moved to operate the call, the tongue of F
closes the local circuit at g, thence by wire 24 to battery K, and through K to wire 25,
thence through the magnets of the bell call to wire 26, and then through the tongue
of the polarized relay.
When the switch C is moved to work the distant call it is brought into contact
with 16, and the current passes from K by wire 20 to 16, thence through C to the
primary wire D, thence to 23, back to the battery K, and setting up a powerful
induced current in the coil E and line.
I will mention that it is not necessary to use a polarized relay, as an unpolarized
relay of the ordinary character may be used as the current due to the opening of
the primary circuit is much the strongest, but the lever of the unpolarized relay
should be light and the spools very short. It is not even necessary to use the call
bell H in may instances when the terminal is very quiet, as the sound given by the
polarized relay itself is sufficient, or a small bell may be worked by the tongue of
the relay itself.
The tongue of the polarized relay should be biased, so that it will always be
away from the point g, except when moved by the signalling currents, so as to pre-
vent short circuiting the battery K when transmitting telephonically.
By employing two cells and a considerable resistance in the magnets upon the
call bell, it is not essential to bias the tongue, but it may be made to respond to both
positive and negative, a shunt from one cell being used to furnish current to the
call bell.
The receiving instrument is provided with an electro-magnet, and an armature
formed of an iron plate diaphragm, and a hammer is attracted or repelled, so as to
strike upon the diaphragm to form a call, and a stand is used to keep the telephone
instruments in proper position for the call to act; these devices are shown in
Fig. 4.
A is the receiving instrument, provided with a diaphragm and a magnet for
giving notion to it, the same as shown in British Letters Patent No. 2909, of 1877,
granted to me. The magnet of the receiving instrument is included in the main
line a, a, a; C is the primary coil; D, the secondary coil, which latter is included
in the main line circuit; e is the sounder lever resting upon the diaphragm of A;
X is a rack or stand for holding both the receiving and transmitting instruments
when not in use. S is a switch; when it is turned to the point 1, the transmitter B
is included in the primary circuit with coil C and battery Q, and the transmitter
serves to increase and decrease its resistance when the diaphragm is vibrated by
sound. The transmitter is provided with a carbon button, through which the
current passes, and it produces more or less resistance, according to the strength of
the sound waves impinging on the diaphragm, as before described.
When the switch lever S is moved to the point 2 the secondary wire of the coil
is short circuited; it remains in this position for the reception of a call signal from
the distant station; were the coil D left in circuit it would tend to weaken the
signal call by its resistance to the passage of the current from the distant station.
When the switch lever is at the point 3, the current from the battery Q passes
only through the primary wire; by connecting and disconnecting the switch S
from the button 3 powerful induction waves are thrown into the line, and act upon
the distant receiver to attract and repell the lever e, and give the signal call. The
induction coil C, D, may be made as in Fig. 5, in which the large wire C forms the
primary coil, and the fine wire D wound round the same forms the secondary coil

page_text: aver being placed in the main circuit, and the former in the local circuit, as
heretofore explained.
Two or more vibrating instruments connected in the same circuit and operated
by electro-magnets are thrown out of the circuit by a shunt, and act to give signals
in two distant instruments provided with diaphragms.
This arrangement is shown in Fig. 6, in which the connections at one end of the
line are represented. Fig. 7 is a section of the resonant tube.
F and G are the vibrating reeds kept in continuous vibration by the electro-
magnets R and S in a local circuit, provided with a suitable contact spring operated
by the reed in the usual manner, but which are not shown here for clearness.
M and N are electrolytic cells arranged and operated similar to those shown in
aforesaid Patent, No. 2909. The armatures of the electro-magnets are harmonic
reeds.
The vibration of one of the electrodes serves to increase and decrease the resistance
of the electric current by causing the current to pass through a greater or less
amount of water between the electrodes. L is the main battery in the main line T,
in which are the cells M, N.
Hand K are keys used for the purpose of stopping and starting the waves over
the wire, which they accomplish by short circuiting the electrolytic cells N or M.
The reeds F and G are tuned to give different tones, and several reeds, substantially
the same as herein described, may be included in the same circuit, all being toned
differently. A and B are the receivers which are shown as resonant tubes. Upon
the ends of the resonant tubes are iron or steel diaphragms, which act as the arma-
tures of the electro-magnets E, E', which are facing them. X and X¹ are secondary
tubes which slide within the tubes A & B like the tubes of a telescope. The object
of the tubes is to allow of the lengthening or shortening of the column of air in the
resonant tube, so as to bring it in unison to the particular note or tone which it is
desired to hear.
The iron diaphragm responds to all the tones with equal power, and were not
some means provided for strengthening or reinforcing one particular tone it would
be very difficult for the operator to pick out the tone required, but by the use of the
resonant tubes this difficulty is overcome, because the tone is given distinct when
the armature is vibrated in harmony with the note of the tube.
The induction coils serve to throw into the line a powerful induced current, and
in some instances I employ a battery connected with the line, and balanced so that
the sound waves acting on the carbon or other resistance cause either the positive
or negative of the battery to preponderate on the line.
The induction coils and their arrangement in the electric circuits are shown in
Figs. 9, 10, 11, and 12.
In Fig. 9 the transmitter is provided with the diaphragm c and carbon button h,
as before described. 1, 2, and 3 are induction coils having their primary coils wound
on the outside, and all connected in the same circuit, in which also is included the
disks 1, 2, carbon button h, and local battery B.
The secondary or inner coils of 1, 2, and 3 are all connected together and are
included in the main line circuit with the receiver and call bell. The impact of the
sound waves upon the diaphragm c subjects the carbon button to more or less
pressure, according to their strength; hence the resistance of the circuit will be
varied owing to the small resistance of the local circuit and the power of the
battery; a very slight change in the resistance of the circuit throws a powerful
induction current into the secondary coils, which passing over the line sets the
distant receiver in vibration corresponding to the air vibrations striking the dia-
phragm of the transmitter.
The object of using more than one induction coil is to get a greater amount of
wire nearer the iron cores, which are bundles of iron wire.
In Fig. 10, the same kinds of coils are shown, but they are connected in the local
circuit slightly different, being connected in derived circuits, or for quantity.
In Fig 11, but one secondary coil is used, the primary circuit being divided into

page_text: several coils, arranged for quantity. This brings more current from the battery,
and a very slight change in the resistance in the carbon button of the transmitter
causes a powerful induced current to circulate in the secondary coil and line.
In Fig. 12 is shown another method of arranging the local batteries so that when
the diaphragm of the transmitter is in its normal position its resistance is equal to
R when no current passes in the primary coil of the inductorium, but the slightest
change in the resistance of the carbon button h destroys the balance between the
batteries, and a current passes to the primary.
In Fig. 8, a condensing induction coil is shown. The coil 1 is formed of two
long strips of metallic foil presenting a large surface to each other; the strips are
wound into a spiral with non-conducting material intervening, and to these strips
the respective circuit wires are connected. The current passes from end to end.
One coil of foil is connected in the main line circuit and forms part of it, while the
other is connected in the local circuit with the battery and carbon transmitter.
At
The induction coils and circuits are sometimes arranged as in Fig. 13.
station A the transmitter A is provided with the carbon button and disks afore-
inentioned. B is the receiver, provided with an iron diaphragm opposite the cores
of an electro-magnet, the same as in aforesaid Letters Patent, but an ear tube at the
end of a flexible tube connected to the body of the receiver is shown at 62. The
transmitter A is included within the primary circuit of an induction coil G. C is
a switch which when moved to the right in contact with D places transmitter A in
said primary circuit containing battery F and coil G. It also allows the line current
to pass through receiver B, secondary coil H, switch point C, and transmitter A to
ground. When the switch is placed to the left in contact with E the instrument A
is not in circuit, and the receiver B and coil H are short circuited, so that the line
is completed through the calling sounder J, switch point E, primary coil G,
battery F, to the ground. The batteries are so arranged at each end of the line that
when both switches are placed to left on E they will act together instead of against
each other, there being sufficient battery to work the calling sounders at each end
of the line. At station B the calling sounder is replaced by a relay J'; this device
I use when the line is too long for the sounder to operate distinctly, or when the
call bell K, which is worked by points of relay J', is required to be placed at a dis-
tance from the other instruments. The bell K is placed in a local circuit with
battery L.
Sometimes I employ a battery connected with the line and balanced so that the
sound waves acting on the carbon or other resistance cause either the positive or
negative of the battery to preponderate on the line.
In Fig. 14 the polarity of the iron core of the induction coil D, E, is reversed at
every vibration of the diaphragm c; h, h¹, are two carbon buttons, and the disks 1
and 2 are connected with the batteries B, B', and primary coil D. When the
diaphragm c moves forward h¹ sends a current in one direction, and when it goes
backward h sends a current in the contrary direction.
When the air waves strike upon a vibrating plate or disk the change of pressure
upon the carbon may be obtained from a thin strata of air intervening between the
diaphragm and the platina plate of the carbon.
Fig. 15 shows a transmitter and the carbon button h and disks 1, 2, arranged so
that the pressure on the carbon is obtained by the movement of the air between the
diaphragm c and disk 1 as said diaphragm is vibrated.
A magneto-electric machine is sometimes used as the source of electric energy in
place of a battery, and the telephone instrument placed in the Wheatstone bridge
and resistances placed to balance the electric forces so that variation in the
resistance in the telephone sends the current on the line.
Fig. 16 represents the transmitting instrument sectionally, and also shows the
circuit connections with the telephone in the Wheatstone bridge.
The transmitting instrument A contains the mouth-piece 6 and a diaphragm c
secured at its edges. The centre of the diaphragm is platinized, and upon this rests
the button h of carbon.

page_text: The metallic disk 2 is kept in contact with the button by the rod and spring e,
and e¹ is an adjusting screw to regulate the pressure of the plate 2 upon the carbon
button . Said screw passes through the metallic support that is secured to the
vulcanite ring g around the button. The diaphragm is connected to the wire 4 and
the plate 2 to the wire 5. Any atmospheric vibrations acting on the diaphragm c
produce a variation in the resistance of the carbon or similar button h in the electric
circuit in consequence of the difference in pressure upon such carbon button, result-
ing from the momentum of the parts and the inertia of the plate d. The trans-
mitter is in one branch of the Wheatstone bridge; R³ is a resistance equal to that
of A when not subjected to sonorous vibrations; R', R³, form the other sides of the
balance, and have equal resistances.
The bridge wire from M to N is contained in the telegraphic circuit that extends
from N by the line wire to the distant receiver H, thence to the earth, and returning
to the earth plate at the distant station and to M. The battery B of several cells
is between 5 and R¹, R³.
upon
When the resistance of A, R¹, is equal to that of R2, R³, no current circulates
the line. When sonorous vibrations vary the resistance of the carbon button / in A
the current will pass upon the line in one direction or the other. When the resist-
ance of A is increased the current passes in one direction. When it is lessened
the current passes in the other direction in consequence of the balance being
disturbed.
The induction coil H has its secondary coil included in the line circuit, and the
primary coil is connected with a transmitting instrument T constructed and
operating in a similar manner to the transmitter A, the local battery B' being in
the circuit through the carbon button and primary coil. The receiving instru-
ment L is provided with a diaphragm that is acted upon by the core of the
induction coil H, and hence the induction coil is utilized and serves for receiving
or transmitting telephonically.
In Fig. 17 the balance of the similar batteries B, B', with opposite poles to line is
obtained by the rheostat R³ that is of a resistance equal to that of the instrument A
when at rest, and when the resistance of the carbon button in A is increased or
decreased by the sonorous vibrations the current will pass upon the line either
positive or negative, according to the resistance in A.
In Fig. 18 a modification of the transmitter is shown. The plate c rests against
a disk of fibrous substance c', such as silk, with a finely divided material such as
plumbago worked into its fibers. There may be several such disks, and the plate 2
is at the opposite side of these disks. There are edges that are turned over to
receive the edges of the mouth-piece b, and a spring e presses the plate c towards
the disks of silk so as to hold them against 2. One conductor from an induction
coil passes to 2 and the other to c, and the slightest sonorous waves acting
against c varies the resistance according to the pressure upon the fibrous material.
Telephones in local circuits or shunts at way stations with induction coils in the
main line are used for operating local telephones on the main line, as shown in
Fig. 19. A and B are magnets placed at way stations; A¹, A³, are carbon trans-
mitters, which serve to short circuit the magnets more or less, according to the
vibrations of the diaphragms of said transmitters.
The sound vibrations act by leverage upon the carbon or other resistance to
increase or lessen the motion as circumstances require.
, and
In Fig. 20 the carbon his acted upon by the lever X upon the fulcrum
said button is placed between the fulcrum of said lever and the point where the
lever is acted upon by the diaphragm of the transmitter.
In Fig. 21 the carbon button is acted upon by the outer end of the lever X.
In Fig. 22 the carbon button h is secured to the outer end of the lever X, and
said button rests upon a button of carbon a secured to the diaphragm c of the
transmitter.
The lever is weighted at at, and there is a spring at a and adjusting rod by.
which the initial pressure of the carbon button h upon the button ¹ may he

page_text: adjusted. There is a plate k³ of mica or other light material secured to the lever A,
and upon this plate the sound waves strike.
The transmitter is shown as upon a resonant box with an opening in the top
of the box immediately beneath the diaphragm c.
The slighest vibration or jar given to the apparatus, such as that resulting from
walking about a room, or from the articulate speech or sound vibrations, vary the
pressure of hand a¹ upon each other, and in so doing the electric condition of a
circuit passing through X, h, a¹, and c, and wires 7 and 8, is varied, and a corre-
sponding response occurs in a distant receiving telephone.
A secondary battery is sometimes employed in place of condenser, as in Fig. 23;
this is used with a Walloston electrode. This arrangement allows the first part of
a wave to be strong, followed by a weakening, due to resistance placed in circuit
by polarization of the small point. This extra resistance allows more current to
pass to secondary coil.
A thermal battery similar to that shown in my Letters Patent aforesaid may be
used as the source of electric energy.
When the electric current is made to pass through water or an electrolytic
solution the diaphragm acts upon a valve or cut-off to vary the volume of liquid
where the current passes, and effect a rise and fall of electric tension. Fig. 24 is a
vertical longitudinal section of a transmitter fitted with this improvement; and
Fig. 25 is a cross section at the line x, x. B is a cylinder of insulating material
divided by a partition into two compartments or cells filled with a conducting
fluid. In each cell is an electrode of platina, carbon, or other conductor, one of
which is connected to the line wire, and the other to the battery and earth. The
top portion of the partition b¹ is slightly hollow, leaving a passageway 2 for the
fluid and current to circulate from one cell to the next.
Resting upon the face of the cylinder is a flexible head of mica, rubber, or other
non-conducting material e impervious to the fluid, and over this is a secured a cap c
provided with a slot. When the cap c is securely fastened to the cylinder the
diaphragm prevents any of the fluid circulating from one cell to the other, except
through the small aperture at 2 made by the curve on the end of the partition 1.
h is a box with a mouth-piece A, and at one side of the box is secured the dia-
phragm i, and upon the diaphragm is a piece of cork t, which extends outward
from it, and through the slot in the cap c on the head of the cylinder B, and comes
in contact with the mica or rubber flexible head e, to which it may be secured by
a cement, although this is not actually necessary.
The operation is as follows:-When the diaphragm i is properly adjusted to the
diaphragm in the cylinder B, the space for the circulation of the fluid from one
cell to the other is very narrow. If, now, the diaphragm is set in vibration by a
sound, the passageway is increased and decreased in size at every vibration, thus
increasing and decreasing the resistance to the passage of the current from one cell
to the other, owing to the alteration in the size of the liquid conductor.
If the amplitude of the diaphragın is very great, the space is nearly, if not
altogether, closed at the forward movement, and widened to its fullest extent by
the backward motion; and if the amplitude is small only a slight increase and
decrease in size of the aperture take place, according to the size of the opening,
so there will be more or less resistance to the current passing through the liquid
at this point, and there will be a corresponding rise and fall of electric tension on
the line at this point.
It is obvious that with a mobile fluid all the harmonical and other sounds incident
to articulation act to produce corresponding changes of electric tension.
In Fig. 30 the cylinder B is represented as standing vertically instead of hori
zontally, as in Fig. 24, which permits of the diaphragms e and c being dispensed
with,
In Fig. 26 I have represented several narrow slits in the partition b¹ between the
cells, and a thin strip of metal i, from the diaphragm i, running down at the side
of the partition, and also slotted, but the slots in the normal position do not

page_text: correspond; hence, by the vibration of the diaphragm, the openings are increased or
lessened, and the resistance to the electric current increased or decreased.
Fig. 27 shows the partition b' arranged horizontally, the passage way from one
cell to the other being controlled by a valve or plunger 1, arranged at an aperture
through the partition.
In Fig. 28 the passage way is between two independent cells by means of a
flexible tube m, and the opening is increased or lessened by the movement of the
diaphragm acting through a finger n that presses upon the flexible tube.
I will mention that mercury may be used instead of an electrolyte, or a porous
material, such as paper, may serve to connect the cells together. 8 represents a piece
of porous material, such as paper or muslin, and the ends pass into liquid in the.
cells, so as to be kept moist by capillary attraction; and adjacent to this is a
presser p, connected to the diaphragm or other vibrating body, so as to be moved
by the same, and press with more or less force upon the moistened strip, and
interrupt the passage of electricity more or less, according to the amplitude of
vibration.
A Duluce dry pile is combined with a diaphragm at each terminal for transmitting
and receiving sound; this is shown in Fig. 31. D is a tube containing a Duluce dry.
pile of many pairs; one end is connected to earth, the other to a disk d, facing a
metallic diaphragm c connected to the line and distant station, where it connects to.
a precisely similar apparatus. The movement of the diaphragm to and from the.
disk causes a rise and fall of electric tension on the line.
An electropherous, similarly combined, is sometimes employed for the same pur-
pose, as in Fig. 32. The base 1 of metal is connected to earth. Upon said disk
there is a disk of sulphur 2, charged with electricity that faces the metallic
diaphragm c, which latter is connected to the line. The rise and fall of tension
on the line is produced by the movement of the diaphragm to and from the sulphur
disk.
Calls are combined with the telephone, so as to attract attention to the instru-
ment. These calls are operated by pendulums, forks, or reeds, which set up magneto-
electric currents when vibrated, and from these a bell or call receives its movement
from the distant station.
In Fig. 33 the tuning fork X is vibrated by the electro-magnet x², by waves set
in motion by a similar fork at the distant station; when the fork has received
considerable vibration, it strikes the lever, which latter releases a clock movement
that gives the alarm.
.
In Fig. 34 the fork ✗ strikes the bell and gives the alarm.
In Fig. 35 the fork X closes a local circuit, and the bell is rung by a magnet and
local battery.
In Fig. 36 a polarized relay is used with its tongue centered by a tightly drawn
wire. This tongue closes the local circuit containing a magneto call-bell.
In Fig. 37 two magneto pendulums X serve to give the call; the signaller lowers
his bell and gives the pendulum a large swing by hand, which soon sets the pendulum
in motion at the distant station by the currents which it sets up in the magnets n, n',
which are polarized.
The receiving portions of the telephone are of a character adapted to respond to
the electric pulsations from the transmitting telephones aforesaid. Sometimes
there are two or more receiving diaphragms to one air chamber to augment the
sound.
Fig. 38 shows a receiver provided with two metallic diaphragms d and two electro-
magnets d¹ through which the line current passes.
Fig. 39 shows the armature diaphragms à arranged edgeways to the opening in
the mouth-piece, with magnets opposite said diaphragms.
This arrangement
permits of the reception of signals, but prevents the transmission of any by magneto
induction.
Fig. 40 shows several electro-magnets, each provided with a diaphragm, all

page_text: included in one case, and all in the main line circuit; the sounds received are
augmented.
Dampers may be employed upon the diaphragm of the receiving and transmitting
instruments to prevent false vibrations. These may be the same as those shown
and described in my British Letters Patent, No. 1644 of 1878.
A diaphragm connected directly upon the induction coil will respond to the
electric waves, and give audible sounds. This device is shown in Fig. 41.
In place of flexible wires for the telephone connections, wires with universal
joints are preferable.
Long funnels may be used with the telephonic receiver to increase the volume of
Bound.
The expansion or contraction of gases and other materials, by change of temper-
ature or hydrometric condition, are employed to vary pressure upon the carbon,
button, or disk, between its two platina armatures, and a galvanometer in the circuit
by its movement indicates with the greatest and most absolute accuracy the extent
of the disturbing cause that is exerted on the carbon.
In Fig. 42 is shown an instrument for measuring minute quantities of heat. his
the carbon button, and 1, 2, the platina disks connected to the battery B and galva-
nometer G. M is a strip of vulcanite or other material that expands by heat. X is
an adjusting screw which serves to force M against the disk and carbon, and bring
sufficient pressure upon the carbon to deflect the galvanometer to the point where
the carbon button is most sensitive to a slight pressure.
When in a state of rest the heat of the band acting upon M will expand it, and
the elongation causes the pressure upon the carbon button to be increased, hence
moro current will pass through it, and the galvanometer needle will be deflected.
In Fig. 43 is shown a mercurial barometer with a float at 60 to act upon the
carbon button. The galvanometer G may be wound differentially or placed in a
Wheatstone bridge, the button being placed in one side of the balance.
In Fig. 44 the diaphragm at 12 is provided with a pin valve that allows the
compressed air or other fluid in the pipe 13 to pass to the pipe 14 and diaphragm 15.
This diaphragm 15 is of iron and faces the core of a polarized magnet, and it
receives more movement from the compressed air than it would if acted upon by
the voice alone. The diaphragm 15 vibrates in harmony with the diaphragm 12,
when the latter is vibrated by the sound vibrations of the human voice or
otherwise.
In Fig. 45 the diaphragm d and mouth-piece is at the side of a closed box.
Within this box there is a continuously rotating cylinder of chalk d³, on the surface
of which rests the end of a spring arm d' secured to the diaphragm.
The chalk has combined with it an alkali or other conducting electrolyte, and is
kept moist by water. One wire is connected to the chalk cylinder and the other to
the spring or diaphragm.
When no current passes to the cylinder of chalk the friction of the spring upon
the chalk causes the diaphragm to be drawn inward, but when an electric wave
passes through such cylinder the friction between the chalk and spring is destroyed
and the diaphragm moves outwardly, to be again drawn inwardly when the current
ceases. By this means the diaphragm d will be vibrated in harmony with the
diaphragm of the distant transmitting instrument, and will reproduce the sounds
that acted upon the diaphragm of the transmitter.
A sponge and cell of water is placed within the box containing the chalk cylinder,
which box should be air-tight.
The use of a chalk cylinder is an improvement on the device shown at Figure 3
in my British Patent No. 2909, of 1877.
Fig. 46 shows a tube containing mercury, in which is a float in water above
the mercury; the float is connected to the diaphragm d. The diaphragm will be
vibrated by the movement of the mercury, caused by the heat of the current passing
through the same.

page_text: Fig. 47 shows a transmitter made as a small mica condenser formed of disks
secured to the diaphragm, and provided with an adjusting screw X for tightening the
disks 1. The impact of the sound waves upon the diaphragm varies the capacity
of the condenser and transmits corresponding waves.
What I claim as my Invention and desire to secure by Letters Patent is,-
First. An electric tension regulator made of carbon or other finely divided
conducting material consolidated by pressure, substantially as and for the purposes
set forth.
Second. The carbon button h between the platina disks 1 and 2 in combination
with the adjusting screw f, diaphragm c, and mouth-piece, substantially as specified.
Third. The combination of transmitter A, coils D, E, switch C, polarized relay F,
bell H, battery K, and circuits, arranged and operating substantially as herein set
forth and as shown in Fig. 3.
Fourth. In combination with a telephonic and the primary circuit of an induction
coil the button of lamp-black carbon, prepared as set forth and placed in the
primary circuit, substantially as and for the purposes set forth and as shown in
Fig. 3.
Fifth. In combination with a receiving telephone instrument, having a diaphragm
and electro-magnet, a swinging lever placed with its moving end in contact with
the receiving diaphragm, and a switch or key for increasing the electric current and
operating the lever as a sounder or call upon the diaphragm, substantially as set
forth and shown in Fig. 4.
Sixth. In combination with the telephone transmitter B and receiver A the
induction coil C, D, battery Q, local circuit, switch S, and circuit connections,
substantially as set forth and as shown in Figure 4.
Seventh. In combination with the main line circuit and local circuit and the
telephonic instrument the induction coil composed of two wires, the largest of which
is surrounded by a finer insulated wire wound helically, the two being then wound
into a helix to form the induction coil, substantially as shown, and described in
connection with Fig. 5.
Eighth. The combination with an electro-magnet of an iron or steel diaphragm
secured to a resonant case for rendering audible acoustic vibrations, substantially
as described, and shown in Fig. 7.
Ninth. The combination with a diaphragın vibrated by an electro-magnet of a
resonant tube variable in its length, so as to adjust the column of air to the tone
of the transmitting instrument, substantially as shown and described with reference
to Fig. 7.
Tenth. The combination with a vibrating reed and electrolytic cells placed in
the electric circuit of a key placed in a shunt circuit, substantially as shown in
Fig. 6.
Eleventh. The condensing coil 1, Fig. 8, arranged in the electric circuit, and
operating substantially as described.
Twelfth. The induction coils 1, 2, 3, Fig. 9, electric circuits, and carbon trans-
mitter, arranged and operating substantially as and for the purposes set forth.
Thirteenth. The induction coils and electric circuits and carbon transmitter,
arranged and operating as described, and shown in Fig. 10.
Fourteenth. Two or more primary coils wound upon one secondary coil, as in
Fig. 11, in combination with the electric circuits and carbon transmitter, sub-
stantially as specified.
Fifteenth. The induction coil 1, resistance R, batteries B, electric circuits, and
carbon transmitter, arranged and operating as described, and as shown in Fig. 12.
Sixteenth. The induction coils G, H, telephonic instruments A, B, switch C, key
and sounder, arranged and operating in the electric circuits, substantially as described,
and as shown in Fig. 13.
Seventeenth. The carbon transmitters h, h¹, and induction coil D, E, and
diaphragin c, Fig. 14, in combination with the batteries B, B, and electric circuits,
substantially as and for the purposes set forth.

page_text: "
Eighteenth. The carbon button h and disks 1, 2, in combination with the
diaphragm c of the speaking tube, arranged and operating as shown in and described
with reference to Fig. 15.
Nineteenth. The combination with an induction coil of a diaphragm that is acted
upon by such induction coil, and gives out sonorous vibrations, substantially as
described and shown in Fig. 16.
Twentieth. In combination with the balanced circuits shown in Fig. 16 a tele-
phonic instrument included in one circuit, and acting to vary the electric condition
of the line by the resistance that is controlled by the sound vibrations, substantially
as set forth.
• Twenty-first. A transmitting telephone containing a variable resistance in the
electric circuit and a body acting by inertia, to vary the resistance in proportion
to the sound vibrations, substantially as described in connection with Fig. 16.
Twenty-second. The induction coils in local circuits or shunts at way stations in
combination with the telephonic instruments, also in such circuits, substantially as
and for the purposes described in and as shown in Fig. 19.
Twenty-third. The carbon transmitter h, lever X, and diaphragm c, arranged as
shown in Figs. 20 and 21.
Twenty-fourth. The combination with a resonant case c4, Fig. 22, of the lever X,
diaphragm c, carbons h and x¹, disk k, and circuit connections, substantially as set
forth.
Twenty-fifth. The apparatus shown in Fig. 22, capable of receiving atmospheric
and other vibrations, and transmitting the same electrically to a receiving telephone
through a circuit wire and connections, substantially as set forth.
Twenty-sixth. The carbon transmitter in a local circuit, containing a secondary
battery, in combination with the induction coil D, E, connected in the main and
local circuits, as illustrated in Fig. 23.
Twenty-seventh. In an acoustic telegraph apparatus, the combination of two
stationary electrodes immersed in two cells, a conducting fluid in said cells, and a
fluid connection between such cells and mechanism actuated by a sound vibrated
body for varying the dimensions of such liquid connection and the conductivity of
the same, substantially as set forth.
Twenty-eighth. The Duluce dry pile battery, arranged in connection with the
telephonic instrument, as illustrated in Fig. 31.
Twenty-ninth. The electropherous arranged in connection with the telephonic
instruments, as illustrated in Fig. 32.
Thirtieth. A telephonic call consisting of a reed or tuning fork vibrated by an
electro-magnet, and acting to strike a bell, release mechanism that sounds an alarm,
or open and close a local círcuit, in which is an alarm or call, as illustrated in Figs.
33, 34, and 35.
Thirty-first. The polarized relay in a telephonic electric circuit, and acting to
open and close a local circuit in which is a magneto call bell.
Thirty-second. In a telephonic electric circuit, a pendulum vibrated by a
polarized electro-magnet, and striking a call or bell, as illustrated in Fig. 37.
Thirty-third. A telephonic receiving instrument containing two or more metal
diaphragms and two or more electro-magnets, as illustrated in Figs. 38, 39,
and 40.
Thirty-fourth. The induction coil, Fig. 41, with its core facing the diaphragm of
the telephone, substantially as and for the purposes set forth.
Thirty-fifth. The combination in an electric circuit of one or more disks or pieces
of carbon or equivalent material operated upon by pressure to vary the resistance
in the circuit, and indicate by a galvanometer or other scale, differences of weight,
pressure, or electric condition.
Thirty-sixth. The diaphragm 12, Fig. 44, controlling a source of compressed fluid,
which latter acts upon the diaphragm 15, to give greater vibration thereto than if
acted upon by the voice or sound waves alone, as specified.
Thirty-seventh. In combination with the diaphragin d and arm d*, Fig. 45, the

page_text: continuously rotating cylinder of chalk moistened with a delequescent salt, and
operating substantially as described.
Thirty-eighth. The diaphragm of the telephonic instrument connected to a float
in a tube containing mercury and water, said diaphragm being vibrated by the
motion of the mercury, substantially as described in connection with Fig. 46.
Thirty-ninth. The telephonic transmitter, Fig. 47, made with a mica condenser,
formed of discs, secured to the diaphragm, and provided with an adjusting screw for
tightening the disks, as specified.
In witness whereof, I, the said Thomas Alva Edison, have hereunto set my
hand and seal, this 27 of November, A.D. 1878.
THOMAS ALVA EDISON. (L.S.)
Witnesses,
CHAS, H. SMITH, 76, Chambers St., New York.
GEO. T. PINCKNEY,
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