DISCLAIMER AND MEMORANDUM OF ALTERATION
Year: 1877

page_text: THE EDISON TELEPHONE COMPANY'S DISCLAIMER AND
MEMORANDUM OF ALTERATION.
Filed 10th February 1880.
TO ALL TO WHOM THESE PRESENTS SHALL COME, wc, the Edison
Telephone Company of London, Limited, of 11, Queen Victoria Street, in the
City of London, send greeting :-
WHEREAS Her Most Excellent Majesty, Queen Victoria, by Her Royal Letters
Patent, under the Great Scal of Great Britain and Ireland, bearing date at
Westminster, the Thirtieth day of July, in the Year of Our Lord, One thousand
eight hundred and seventy seven, in the Forty-first year of Her Reign, did for
Herself, Her heirs and successors, give and grant unto Thomas Alva Edison, of
Menlo Park, in the State of New Jersey, United States of America, his executors,
administrators, or assigns, or such others as he his executors, administrators, or
assigns should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend within the United Kingdon of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention of "IMPROVEMENTS IN
INSTRUMENTS FOR CONTROLLING BY SOUND THE TRANSMISSION OF ELECTRIC
CURRENTS AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT A DISTANCE,"
for and during the term of Fourteen years thence next ensuing: And whereas in
pursuance and performance of a proviso in the said Letters Patent contained the
said Thomas Alva Edison did within Six calendar months next after the date of
the said Letters Patent cause a Specification in writing under bis hand and seal
purporting to particularly describe the nature of the said Invention, and in what
manner the same was to be performed, to be duly filed in the Great Seal Patent
Office: And whereas by Indenture bearing date the Second day of August, One
thousand eight hundred and seventy nine, and made between the said Thomas
Alva Edison of the one part, and as the Edison Telephone Company of London,
Liraited, of the other part, the said Thomas Alva Edison assigned unto us the said
Edison Telephone Company of London, Limited (inter alia), the said herein before
recited Letters Patent, and all rights, powers, authorities, privileges, advantages,

page_text: profits, emoluments, and benefits to the said Letters Patent, appertaining or
belonging And whereas since the date of the said Assignment we have been
advised and have ascertained that the said Specification contains matters which are
of doubtful novelty, or which are not of sufficient practical value and utility to
justify their retention; and we are therefore desirous of striking out the whole of
the claiming clauses contained in the said Specification, with the exception of the
first, second, eighteenth and twentieth claiming clauses, and of striking out parts of
the description contained in the body of the said Specification; and also of otherwise
altering the said Specification, and correcting certain clerical errors contained in the
said Specification in manner more fully hereafter appearing,
S
"
"3
• NOW KNOW YE, that we the said Edison Telephone Company of London
Limited, by and with the leave of Her Majesty's Attorney General, and for the reasons
aforesaid do alter the said Specification, by striking out of the said Specification
printed by the Queen's Printers, and published at the Great Seal Patent Office in
One thousand eight hundred and seventy nine, the words "the same which
occur on page 4, at the end of line nine, and the beginning of line 10 respectively,
and substituting therefor the words "a corresponding"; we also strike out the
word "the" which occurs between the words "and" and "electro" on the said
page, line twenty two, and substitute therefor the word " an"; we also insert
between the words "the" and "instruments" which occur on the said page line
twenty five the word "transmitting" and we strike out the letter " at the end
of the said word "instruments"; we also strike out the word "are
"which occurs
on the same line and substitute therefor the word "is"; We also insert between
the words "in" and "Figs." (an abbreviation of the word Figures) which occur on
the same line, the words "section in" and we strike out the letter "s" in the said
word "Figs"; we also strike out the words commencing with "and" on the said
line twenty five and ending with the first word "instrument" on line 26 of the
said page four we also strike out the words "of the" which occur between the
Figure "2" and the word "receiving" on the said line twenty six and substitute
therefor the words "represents a"; we also add after the word "instrument" at
the end of the said line twenty six the words "which may be employed with it";
we also strike out the word "the" at the commencement of line twenty seven ou
the said page four and substitute therefor the words "referring to Figure 1 the ";
we also strike out that portion of the Specification commencing with the words
"in Fig" on page 5, line forty one, and ending with the word "sound" on page 6,
line three; we also strike out that portion of the Specification commencing with
the words "I also" at the end of line eight and ending with the words "the line "
on line eleven of the said page 6; we also strike out the whole of lines twenty four
to twenty eight inclusive on the said page 6; we also strike out the words " to
record" which are repeated on line thirty five of the said page 6 and add the letter
"s" to the word "rest" which occurs on line forty seven of the said page 6.
We also strike out of page 8, lines thirty seven to forty two inclusive, and lines
forty six to fifty three inclusive. We also strike out of page 9 lines eighteen to
twenty three inclusive, and lines thirty seven to forty one inclusive. We also
strike out of page 10 lines seventeen to thirty seven inclusive. We also strike out
of page 11 lines ten to thirteen inclusive, and lines forty four to fifty seven
inclusive, and we add at the end of line thirty seven of the said page eleven after
the word "named " the words following:-"I would observe in conclusion that I
do not claim generally the transmission and reproduction of sounds by increasing
and decreasing the resistance of the circuit, nor do I claim separately any of the
parts or arrangements hereinbefore described and illustrated in the accompanying
we also strike out the word "an," which occurs between the words "of "and "electric" on line 42 of the said page 11, and
we add the letter "a" to the word "regulator," which occurs on the same line 42, to make it read "regulators," and after
the said word "regulators" we insert the words "substantially as herein before described."
33
Drawings, except as hereinafter mentioned, but A.' We also strike out of page 12
lines one to thirty inclusive, lines thirty six and thirty seven, and lines forty two
to fifty six inclusive. We also strike out the word "eighteenth" which occurs at
the commencement of line thirty one on the said page 12, and substitute therefor

page_text: the word "third." We also strike out the word twentieth which occurs at the
commencement of line tuirty eight of the said page 12, and substitute therefor the
word "fourth." We also strike out the word "or" which occurs on line thirty
We also strike
nine of the said page 12, and substitute therefor the word "on."
out of page 13 lines one to fourteen inclusive.
And in order that the effect of the
said Disclaimer may be clearly understood we annex hereunto a copy of the said
Specification as it will appear when so amended, the preamble and testing clause
being omitted.
This Invention relates to that class of electrical instruments in which sound
becomes one of the elements in the transmission of the communication, and a
corresponding sound is produced at the receiving station so that oral communi-
cations can be sent by electricity and clearly distinguished at the receiving
station.
Musical tones may also be sent, but my present Invention is especially available
in transmitting and receiving oral communications.
In transmitting musical tones the respective notes each have a definite period for
each vibration, hence there is a response at the receiving end from the notes that
vibrate in time with the electric pulsations sent, but in speaking there is little
change in the musical tone but considerable in the modulations and inflections of
the voice.
In my present Invention I make use of the vibrations given to a diaphragm or
tyimpan by speaking into a resonant case to produce a rise and fall of electrical
tension upon the line with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation, and an electro
magnet at the receiving station will respond to the electric waves in such a manner
as to reproduce the articulation by acting upon a resonant plate.
The transmitting instrument in a complete form is represented in section in
Fig. 1, and Fig. 2 represents a receiving instrument which may be employed
with it.
Referring to Fig. 1, the resonant tube or box a is of a size and shape adapted to
being spoken into the same, having an opening at one end or side and a diaphragm
or diaphragms b, against which the sound waves from the human voice act, and
these and the motion that the diaphragm receives is the means of producing a riso
and fall of electric tension on the line by the devices hereafter set forth, so that the
battery B connected to the line will transmit a greater or less current to the
distant electro magnet m, Fig. 2, and increase or lessen the magnetism of the cores,
and in so doing act upon a resonant plate c and develop sound corresponding to the
articulation at the transmitting station.
The general features thus described pervade my entire Invention, but in developing
the same many useful and important inodifications and variations have been inade,
which I will proceed to set forth.
For convenience the speaking instrument Fig. 1 is provided with a handle a¹ and
flexible conductors to the battery and line respectively, so that it may be handled
and brought to the mouth, and in like manner it is preferable to place the hearing
instrument Fig. 2 in a movable handle b', so that it can be placed with the plate c
against the car; this brings the sound close to the organs of hearing, and the
resonant plate touching the ear increases the distinctness of the sound and prevents
any false or prolonged vibrations of the plate.
In some of the modifications I have shown the speaking instrument as a fixture,
and also the hearing instrument as a fixed resonant tube, these being variable to
suit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity of
the resonant tube for the voice. I have experienced great difficulty in reproducing
the sound of the hissing consonants, such as s; this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth, and does not act
distinctly upon the diaphragm. By providing an edge in the resonant tube below
the mouth upon which such consonant sounds are received the vibrations are given

page_text: either to the resonant tube or deflected to the diaphragın. 1 and I preferable to
employ a hole c at the lower part of the mouth piece against the edges of which the
downward sound waves are directed. The saine effect will be produced by a
vibrating edge placed in the lower part of the mouth piece, or the opening into the
resonant box may be contracted to about half an inch in diameter to effect the same
purpose. The next feature requiring consideration is the character of the diaphragm
in the speaking instrument.
Many materials have been employed by me such as metals, horn, vellum, celluloid,
ivory, &c., but almost all of these produce a prolonged or secondary vibration from
their own resonant character, hence the articulation is defective and the sound
vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
resonant action, and hence it will respond with the greatest accuracy to the sound
vibrations, and being of a laminated character can be employed of any desired
thickness, and when secured at its edges responds with the greatest accuracy to the
sound vibrations and does not require to be strained; furthermore, the changes of
temperature and atmospheric condition have little or no effect upon the mica
diaphragm or tympan.
I find that it is not practical to open and close the line circuits in instruments
for transmitting the human voice, the circuit to the line must be always closed and
the transmission be produced by a rise and fall of electric tension resulting from
more or less resistance in the line. This resistance may be produced in several
ways. I have shown several which will hereafter be named, but I find the most
delicate to be small bunches or tufts or disks of semi-conducting elastic fiber, such
as particles of silk and an intermediate conducting or semi-conducting material;
this device I call an electric tension regulator, it is more or less compressed
according to the vibrations of the diaphragm or tympan, and the electric current
rises in tension as it is compressed or lessens as the fiber expands. This fiber is
placed in a small roll t between the delicate diaphragın spring u, Fig. 9, and the
variable presser v adjustable by screw or otherwise in the electric circuit at this
point, or it may be within a cavity in said presser v, as in Fig. 1, there being a
delicate cork center piece w to the diaphragm b, with a piece of platina foil in
contact with the fiber; in all instances the telegraphic circuit at the diaphragm is
made by a thin strip of platina or similar material, extending to the center from
the line or battery connection.
The fiber is rendered semi-conductive by being rubbed with plumbago, soft metal,
or similar material, or by a deposit of metal upon its surface, or by fine particles of
conducting or semi-conducting material mixed with it, the conducting power
varying with the density of the tuft or bunch of fiber.
The delicate spring u, Fig. 9, upon the mica diaphragm bis easily secured by
solder passing into fine holes bored in the inica.
In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact such as would result from a disk covered with plumbago
placed adjacent to a diaphragm also covered with plumbago or other semi-conducting
material so that the proximity or extent of surface contact will produce rise and
fall of tension, the respective parts being in the telegraphic circuit. I sometimes
perforate the diaphragm 10, Fig. 18, and place a strip of elastic material 40 across
said diaphgram over the hole, and upon this a piece of fcil, so that the same
responds to very weak vibrations, and in some instances two or more diaphragins
are provided at different sides of the resonant box, each with its own tension
regulator, the diaphragms being either the same or of different sizes, characters, or
tensions so as to respond to varying sounds or acoustic condition, the various
tension regulators being all in the electric circuit, this will produce greater rise and
fall of tension for longer lines in consequence of the diaphragms acting simul-
taneously on the tension regulators. In some instances it is preferable to make
the mouth-piece of the speaking instrument sufficiently large or flaring to receive
all the sound vibrations, whether coming from the mouth, nose, or throat. The

page_text: tension regulator formed of fiber and conducting or semi-conducting material may
be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within a
case to form the tension regulator, the circuit passing through the same, and the
rise and fall of electric tension resulting from the compression of the same by the
movement of the diaphragin. I am enabled to record the sounds produced by
the human voice, or otherwise by causing the movements of the diaphragm to be
registered on paper or soft sheet metal, and then the paper may be used in an
instrument to reproduce the sound upon a delicate diaphragm by giving to the
same a vibration similar to that originally given by the voice.
h, Fig. 4, is the indenting transmitter, the diaphragin having a knife-edge point;
is the paper which has previously been passed through a machine to raise a V
shaped rib 6. The movement of the diaphragm of when the drum is in motion
causes the knife-edge point to indent the raised rib to varying depths according
to the amplitude of vibration of the diaphragm, thus these indentations represent
accurately all the tones and varying inflections of the human voice. The paper,
after being indented, is passed through a second apparatus n, Fig. 5, almost similar
to h. A spring 9 has a knife edge which rests upon the raised indented rib 6, the
spring being connected to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting
point, and either by direct action or through the vibration of a string conveys the
same motion to the diaphragm of n, and reproduces previous sounds. If these
sounds are to be transmitted over a telegraph line the diaphragm 10, see Fig 6, is
provided with a cork disk w and fibrous tension regulator t before described, to
produce the rise and fall of electric tension on the line. The sound may be
recorded in ink, as represented in Fig. 7. The diaphragm of h operates a very
flexible self feeding pen o, and causes the continuous line to be wide or narrow
according to the amplitude of vibration of the diaphragm. The ink used should
dry quickly and the strips may be passed at any time thereafter through the
instrument shown in Fig. 8 beneath the arm 12 having a point or points resting
on the paper, this arm is connected with a resonant diaphragm, and the ink marks
produce more or less friction according to the breadth and amount of ink deposited,
and this will set the diaphragm of n vibrating and reproduce the vibrations of the
diaphragm of h.
An obvious modification would be to coat the paper with a substance which
would cause considerable friction, or even rough unsized paper might be used and
a spring provided with a burnished point rather flat would cause the surface of
the paper to be made smooth more or less according to the vibration of the
diaphragm, and the differences in the surface of the paper would produce a response
in the receiving diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument,
as shown in Fig. 10.
h is the resonant chamber at the end of which is the diaphragm 10, and at each
side of this diaphragm there are springs c³, c³, having points made of compressed
blumbago mixed preferably with gum rubber, but any substance not liable to rapid
decomposition or the elastic or fibrous tension regulator aforesaid may be used.
These points face each other on opposite sides of the diaphragın, and make contact
vith platina foil disks secured to the diaphragm.
The spring c² passes through a hole or small slot in the side of the chamber h;
2, as, are the main batteries. The battery d has zinc to the line or spring c², and
he battery d³ has copper to the line or spring c³. When the springs of c² and care
djusted to make contact with the diaphragin equally no current passes to the line,
ut when the diaphragm is vibrated its movement to one side, say c², causes a
reater pressure upon the plumbago on that spring, and a lessening of the
ressure on the plumbago on c³, hence the balance of the batteries c² and
will be destroyed, c² having the advantage will send a negative current to
ne upon the return of the diaphragm, the battery currents will again

page_text: neutralize each other. The vibration of the diaphragın to the other side causes the
pressure to be reversed, and the battery d³ will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure, it follows that the strength
of the electric waves will be in proportion as the speaker's voice is strong or weak.
In Fig. 11 is shown the contact spring, which may be used adjacent to the
diaphragm at one or both sides thereof. e is a U shaped spring secured to the
screw e, which is adjusted back and forth by the thumb nut e; e is the pillar
holding such screw; is a piece of soft rubber or equivalent substance placed
between the prongs of the spring e³; e is a wire or band which serves to bind the
prongs tightly against the rubber 7 so as to prevent the prongs acting as a tuning
fork and transmitting harmonic vibrations not desirable; is the plumbago contact
point. The object of the spring and rubber is to present a semi-rigid point for
contact so as to prevent a rebound and allow of a slight yield when the plumbago
is pressed by the diaphragm. In Fig. 3 the diaphragm of the receiving instrument
is vibrated by a strip of paper chemically prepared that is in motion, the pulsations
of electricity passing over the line and producing more or less friction between the
paper and an arm upon the diaphragm.
The resonant box or chamber n is provided with a diaphragm as aforesaid, and
to said diaphragm an arm he is connected. At its outer end is an adjusting screw h³
that presses upon a platina faced spring that is secured to this arm, and said
spring rests upon the strip of paper that passes over the druin h³.
The paper is moved slowly by rotating the drum h³, and the waves of electricity
coming over the line pass through the arm h² to the platina-faced spring h³, thence
through the paper to the earth.
If a negative current passes in the opposite direction nearly all friction between
the platina plate and the paper ceases, and the diaphragm of the resonant box n
retains its normal position.
When the positive current passes through the same channel the normal friction
of the paper is augmented, and the chemical surface acting upon the platina spring
arm serves to give a forward movement to the diaphragm of the resonant box.
Thus the mechanical force applied to move the chemical paper or surface acts
with the electric current to produce the vibration of the diaphragm of the resonant
chamber, and these vibrations will correspond to those of the diaphragm b made by
speaking in the tube a.
The principle of this method of obtaining motion by electro-chemical decomposi-
tion is, that when a moving surface is in contact with a slightly yielding substance
the tendency is to move the latter by and with the former. If the circumstances
of contact are varied the adhesion of the surfaces will be sufficient to cause the
moving surface to move the yielding substance or else to cause the yielding surface
to slip more freely, and by its spring go in the opposite direction to the moving
surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion, making it more or less according to the substances employed. By
balancing the mechanical forces so that when the surfaces in contact are not
electrified the moving surface carries with it the yielding surface, and when
electrified the yielding surface slips back, over the moving surface a mechanical
movement is obtained that is dependent on the electrical condition of the surfaces
iu contact.
When it is requisite to obtain very perfect articulation, and when loudness is
not essential, I adopt a modification shewn in Fig. 12 of the device for compressing
and expanding the tuft of conducting fiber, which modification consists in placing
between the diaphragm 10 and the fiber t a vibrating tongue 21 of steel, perma-
nently magnetized, and arranging it to act in the same manner upon the tension
regulator t as if it was the diaphragm. I replace the cork upon the diaphragm by
a thim armature of iron 22, which is in close proximity to the magnetized tongue,
which tongue is secured at one end like an acoustic reed. In this position the

page_text: diaphragm is free to move, and at its approach to and recession from the magnetized
tongue causes said tongue to follow its inovements by magnetic attraction, and thus
the tongue is made to perform what the diaphragm previously performed in varying
the tension of the electricity on the line.
5 A plate supported eccentrically and free at its edges when placed in the speaking
tube responds advantageously to the tones of the voice. The circuit with this
plate is completed through one or more tension regulators placed around its edges.
In practice I combine with the speaking or telephonic apparatus signal bells so
arranged that when the telephone is not in use the line is thrown upon the bell by
0 a switch, which also acts as a call on the bell.
One feature about the bells is that the magnet which serves to actuate the bells
is made of very high resistance, using preferably German silver wire in the helix,
and thus serve to prevent a rapid consumption of battery power.
of telephonic wires may be worked from one battery if these bells are used. The
A large number
5 method I adopt for coating non-conducting substance with metallic substance is the
reduction to the metallic state of metals from their salts by exposing them to the
fumes which arise from the moist phosphide of a metal, such as phosphide of calcium,
or by placing the silk for instance in a sealed tube provided with metallic electrodes,
and volatilizing the electrodes by the passage of electric sparks. Such volatilized
metals settle upon and coat the silk.
When great loudness is desirable, as in factories, the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is stored
will
▲
under a regulated pressure. The air allowed to escape with act with great power
upon a local diaphragm. This diaphragm to obtain clear sounds requires a damper
to check prolonged vibrations. It must be dampened by holding the fingers against
it, or by a tightly stretched cord rubbing against it, or by a screw provided with a
rubber tip held against it.
In some instances I make a record of the sound by the movements of the
diaphragm, using for that purpose a strip of paper moved along regularly between
two rollers 25, 26, as in Figs. 14 and 15, and there is a smooth thread or fine wire
of soft metal 30 between the paper and the upper roller 25, and moving along with
it. The diaphragm 10 of the resonant box is connected by a delicate rod 28 with
this thread or wire as near to the bight of the roller as possible, there being a fork
or eye through which the thread passes; hence deflections or bends are made in
the thread or wire just before it is embedded into the paper by the pressure of the
rollers. This may be used to reproduce the sound by vibrating a resonant diaphragm
by the undulations of the groove made by the thread or cord.
By placing the fibrous-tension regulator within a small band of India rubber
the same is rendered more elastic and the fiber is allowed to expand by the heat
of the current without altering the electric tension.
In some instances the diaphragm should be free to vibrate without being checked
by contact with any stationary substance. I provide for this by placing upon the
diaphragm or tympan 10, Fig. 17, a small cylinder of hard rubber or non-
conducting material within which is the fibrous tension regulator tresting upon a
piece of platina foil connected to one pole of the battery, and within this cylinder
is a disc t¹º of iron or other metal loose but pressed towards the tension regulator
by a spring and screw cap to and the other electric conductor is connected wit
he said spring.
The inertia of the metal disk causes more or less compression of the tension
egulator as the diaphragm is vibrated and hence the electric pulsations are sent
ver the line in harmony with the vibrations.
y connecting the disk to to a yielding spring t" that extends across from one edge
Nearly the same effect is produced
f the diaphragm to the other as seen in Fig. 16. This construction of tension
egulating device is especially available with large diaphragms.
In some cases I use a soft rubber diaphragın immediately in contact with the
ansmitting or receiving diaphragm so as to check or dampen any prolonged or

page_text: false vibration and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable to use
lampblack mixed with pure plumbago, amorphous phosphorous, and a very small
amount of nonconducting material such as rubber dissolved in a solvent that will
entirely evaporate.
This
In Fig. 19 I have represented the circuit as passing through the diaphragm 10,
tension regulator t, and a Duluc's dry pile battery D, P, B, to the earth.
battery is composed of about 300 pairs of paper disks coated with silver aud
black oxyd of manganese.
Fig. 20 illustrates the device before mentioned for intensifying the sound; 10 is
the diaphragm vibrated by the sound; 42 is a valve moved by sucli diaphragm; 43 is a
reservoir containing air under a given pressure; b is the diaphragin against which
the air allowed to escape by the valve acts, and t is the tension regulator to transmit
the electric pulsations, or a hearing resonant case may be applied at the same place.
Fig. 24 represents the diaphragm 10, tension regulator t with its adjusting screw
and local circuit containing the battery B passing through a primary induction
coil 49, and there is a key 50 in the same circuit. A secondary induction coil 51
is in the line circuit and is influenced electrically by the change of tension in the
local circuit by the vibrations of the diaphragm 10. The secondary coil is some-
times required with many layers of fine wire to set up a current of high tension to
evercome the inductive effect from the line wires; being adjacent to each other I
place the receiving instrument at the distant station between the induction coil
and the earth as at R, and use an electro-magnet E, M, with polarized armature
to strike a bell; this will respond when the key 50 in the local circuit at the distant
station is opened and closed.
In Fig. 25 a similar induction coil 49 and local circuit is represented, but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes,
A shunt and rheostat
one on the diaphragm, the other on the adjusting screw.
at R' serves to prolong the magnetism in the induction coil, and thus ensure a
gradual rise and fall of electric tension in the line instead of a cessation of the same
when the platina surfaces separate, and at the receiving diaphragm c the rise and
fall of electric tension in the line and its helix acts upon the permanent magnet to
produce the vibrations of the diaphragmn c, and by connecting a shunt around the
helix, and placing therein the secondary battery S, B. composed of metallic plates
in acidulated water, the action is rendered more uniform and the sound distinct.
When the diaphragm is arranged as in Fig. 26 to act upon a spring 56 through
an intervening piece of soft rubber, said spring 56 produces rise and fall of electric
tension by employing a range of resistances 57 with spring tongues adjacent to 56.
The greater amplitude of vibration of the diaphragm the more direct will be the
electric circuit connections, and the less resistance, because the circuit will pass
along the spring instead of going through all the resistance coils.
When several line wires run near each other the wire used for the acoustic or
speaking telegraph is influenced by induction, and false sounds will be produced.
I counteract this tendency by placing one or more electro-magnets 59, Fig. 28, in
the circuit of the speaking telegraph, and one or more electro magnets 60 in the
circuit of the adjacent wires, and bringing the opposite cores of 60 at such a
distance from the cores of 59 that a certain magnetic action will be set up in 59 by
induction, in the opposite direction to the induction currents from the adjacent line
or lines.
By adjusting the distance between these magnets when the speaking telegraph is
not in use, until there is not any sound at the diaphragm from the induction
currents, then these currents will be neutralized whether strong or weak, and will
not produce any false sounds when the speaking telegraph is in use. I also employ
double coils of wire for the same purpose, one coil being in the acoustic wire, and
the other in the wire to be compensated.
A convenient form for the sound recorder or phonogragh is to employ a cylinder
61, see Fig. 29, having a helical groove in its surface covered with tin foil, and the

page_text: cylinder is resolved regularly by clockwork, and moved endwise by a screw on its
shaft so that the indenting point l' from the diaphragm 10 of h will be always in
line with such groove, hence the vibrations of the diaphragm will be recorded by
indenting the foil into the groove, and hence the same sound will be reproduced by
the point of the hearing instrument n, giving to the diaphragin of n, the
motions that result from the indentations of the foil moving in contact with such
point.
The foil may be on a flat grooved plate, and be indented and act as before
named.
I would observe in conclusion that I do not claim generally the transmission and
reproduction of sounds by increasing and decreasing the resistance of the circuit,
nor do I claim separately any of the parts or arrangements hereinbefore described
and illustrated in the accompanying Drawings, except as hereinafter mentioned, but
I claim as my Invention:-
First. In an Instrument for transmitting clectric impulses by sound, a diaphragm
or tympan of mica substantially as set forth.
Second. In an Instrument for transmitting electric impulses by sound, the com-
for
substantially as hereinbefore described
bination with a diaphragm or tympan of an electric tension regulators A
varying the resistance in a closed circuit, substantially as set forth.
Third. In a telegraphic apparatus operated by sound, a receiving instrument
provided with a resonant surface in combination with a frictional surface, moved
by power, and acting in connection with the electric current to vibrate such
resonant receiver, and produce tones corresponding to those at the transmitting
apparatus substantially as set forth.
.
Fourth. The method herein specified of recording the undulations of the diaphragm
on yielding material, and the reproduction of sound by such material acting upon
a diaphragm, to communicate to the same vibrations similar to the original ones,
substantially as set forth.
of London,
In witness whereof, the said Edison Telephone Company
caused their common seal to be hereunto affixed, the
November, One thousand eight hundred and seventy nine.
A
Limited, have
Twelfth day of
I hereby grant my fiat, giving leave to the above named Edison Telephone
Company, of London, Limited, the assignees of the said Letters Patent, to file in
the Great Patent Seal Office, with the Specification to which the same relates, the
above written Disclaimer and Memorandum of Alteration, upon condition that no
proceedings be taken in respect of any transmitters actually made and completed
prior to the date of the filing of the said Disclaimer and Memorandum of
Alteration.
Particulars of numbers, and identifying marks to be verified by Statutory
Declaration.

page_text: Filed 13th June 1881.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, THE
UNITED TELEPHONE COMPANY LIMITED, send greeting. WHEREAS Her most
Excellent Majesty Queen Victoria, by Her Royal Letters Patent under the Great
Seal of Great Britain and Ireland, bearing date at Westminster the Thirtieth day
of July, in the year of our Lord One thousand eight hundred and seventy seven,
in the forty first year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto Thomas Alva Edison, of Menlo Park, in the State of New
Jersey, United States of America, his executors, administrators, or assigns, Her
special license, full power, sole privilege and authority, that he, the said Thomas
Alva Edison, his executors, administrators, or assigns, or such others as he, his
executors, administrators, or assigns, should at any time agree with, and no others,
from time to time and at all times during the term therein expressed, should and
lawfully might make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention of
"IMPROVEMENTS IN INSTRUMENTS FOR CONTROLLING BY SOUND THE TRANSMISSION
OF ELECTRIC CURRENTS AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT
A DISTANCE," for and during the term of fourteen years thence next ensuing:
And whereas in pursuance and performance of a proviso in the said Letters Patent
contained, the said Thomas Alva Edison, did, within six calendar months next
after the date of the said Letters Patent, cause a Specification in writing under his
hand and seal, purporting to particularly describe the nature of the said Invention,
and in what manner the same was to be performed, to be duly filed in the Great
Seal Patent Office: And whereas by indenture bearing date the Second day of
August, One thousand eight hundred and seventy nine, and made between the said
Thomas Alva Edison, of the one part, and said Edison Telephone Company
of London, Limited, of the other part, the said Thomas Alva Edison, assigned
unto the said Edison Telephone Company of London, Limited (inter alia),
the said herein before recited Letters Patent, and all rights, powers, authorities,
[Price 1

page_text: privileges, advantages, profits, emoluments, and benefits to the said Letters
Patent appertaining or belonging: And whereas on the Thirteenth November,
One thousand eight hundred and seventy nine, the said Edison Telephone
Company of London, Limited, petitioned the Commissioners of Patents for leave
to amend certain parts of the said Specification of the said Letters Patent, which
petition was referred to Her Majesty's late Attorney General, Sir John Holker, and
leave was given to the said Edison Telephone Company of Loudon, Limited, to file
in the Great Seal Patent Office a Disclaimer and Memorandum of Alteration, as
appears by the fiat of the said Sir John Holker, dated the Ninth day of February,
One thousand eight hundred and eighty, and the said Disclaimer was duly filed in
the Great Seal Patent Office on the Tenth day of February, One thousand eight
hundred and eighty: And whereas by indenture bearing date the Twelfth day of
July, One thousand eight hundred and eighty, and made between the said Edison
Telephone Company of London, Limited, of the one part, and us, the said United
Telephone Company, Limited, of the other part, and duly registered in the Great
Seal Patent Office, the said Edison Telephone Company of London, Limited,
assigned to us, the said United Telephone Company, Limited, the said Letters
Patent, and the rights and privileges thereby granted, and the same thereby became
and are now vested in us, the said United Telephone Company, Limited: And
whereas, since the filing of the said Disclaimer and Memorandum of Alteration, and
very recently, that is to say, about the First March, One thousand eight hundred
and eighty one, your petitioners have ascertained that shortly prior to the applica-
tion for the said Letters Patent, a description of the Invention of the said Thomas
Alva Edison, in so far as it relates to the clectro chemical receiver as covered by
the third claim, was published in an American newspaper and afterwards copied
into an English paper, and we are advised that, although there was no Invention
by any one in England, or elsewhere, other than the said Thomas Alva Edison, of
the said part of his Invention, the aforesaid publication renders doubtful the
validity of the said third claim, and we are desirous of striking out the same, aud
of altering the numbering of the succeeding claim accordingly, in manner more fully
hereafter appearing. NOW KNOW YE, that we, the said United Telephone
Company, Limited, by and with the leave of Her Majesty's Attorney General,
and for the reasons aforesaid, do alter the said Specification by striking out of the
Specification as amended by the said Disclaimer, printed by the Queen's Printers,
and published at the Great Seal Patent Office, in One thousand eight hundred and
eighty, the whole of the third claim, comprising lines twenty to twenty four, both
inclusive, on page 9. We also strike out the word "Fourth" at the commencement
of line twenty five of the said page 9, and substitute therefor the word "Third."
We also desire to correct a clerical, occurring in the said amended Specification
by striking out the figure "2" which follows the reference letter "c" in line forty
seven of page 5 of the said printed copy of the said Specification, and of substituting
therefor the figure "3."
error
And in order that the effect of the said Disclaimer may be clearly understood,
we annex hereunto a copy of the said Specification, as it will appear when so
amended, the preamble and testing clause being omitted.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Royal Letters
Patent, under the Great Seal of Great Britain and Ireland, bearing date at
Westminster the Thirtieth day of July, in the year of our Lord One thousand
eight hundred and seventy seven, in the forty first year of Her reign, did, for
Herself, Her heirs and successors, give and grant unto Thomas Alva Edison, of
Menlo Park, in the State of New Jersey, United States of America, his executors,
administrators, or assigns, or such others as he, his executors, administrators, or
assigns, should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention of "IMPROVEMENTS IN

page_text: גי
CMENTS FOR CONTROLLING BY SOUND THE TRANSMISSION OF ELECTRIC
CURRENTS AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT A DISTANCE,"
for and during the term of fourteen years thence next ensuing: And whereas, in
pursuance and performance of a proviso in the said Letters Patent contained, the
5 said Thomas Alva Edison did, within six calendar months next after the date of
the said Letters Patent, cause a Specification in writing under his hand and seal,
purporting to particularly describe the nature of the said Invention, and in what
manner the same was to be performed, to be duly filed in the Great Seal Patent
Office: And whereas, by an indenture bearing date the second day of August,
10 One thousand eight hundred and seventy nine, and made between the said Thomas
Alva Edison of the one part, and us, the Edison Telephone Company of London,
Limited, of the other part, the said Thomas Alva Edison assigned unto us, the
said Edison Telephone Company of London, Limited (inter alia), the said herein-
before recited Letters Patent, and all rights, powers, authorities, privileges,
5 advantages, profits, emoluments, and benefits, to the said Letters Patent apper-
taining or belonging:
A
and correcting certain clerical errors contained in the said Specification
▲
"
"
And whereas, since the date of the said assignment, we have been advised and
have ascertained that the said Specification contains matters which are of doubtful
novelty, or which are not of sufficient practical value and utility to justify their
O retention, and we are therefore desirous of striking out the whole of the claiming
clauses contained in the said Specification, with the exception of the first, second,
eighteenth, and twentieth claiming clauses, and of striking out parts of the
description contained in the body of the said Specification, and also of otherwise
altering the said Specification in manner more fully hereafter appearing.
NOW KNOW YE, that we, the said Edison Telephone Company, of London,
Limited, by and with the leave of Her Majesty's Attorney General, and for the
reasons aforesaid, do alter the said Specification by striking out of the said
Specification printed by the Queen's Printers, and published at the Great Seal
Patent Office in One thousand eight hundred and seventy nine, the words "the
same," which occur on page four at the end of line nine and the beginning of line
ten respectively, and substituting therefor the words "a corresponding." We also
strike out the word "the," which occurs between the words "and" and "electro
on the said page, line twenty two, and substitute therefor the word "an."
insert between the words "the" and "instruments," which occur on the said page,
We also
line twenty five, the word "trans:nitting," and we strike out the letter"
end of the said word "instruments." We also strike out the word "are," which occurs
"§ "
at the
on the same line, and substitute therefor the word "is."
the words "in" and "Figs." (an abbreviation of the word Figures), which occur on
We also insert between
the same line, the words "section in," and we strike out the letter "s" in the said
word "Figs." We also strike out the words commencing with "and" on the said liue
twenty five, and ending with the first word "instrument" on line twenty six of the
said page four. We also strike out the words "of the," which occur between the
figure "2" and the word "receiving" on the said line twenty six, and substitute
therefor the words "represents a." We also add after the word "instrument" at the
end of the said line twenty six the words "which may be employed with it." We
Iso strike out the word "The" at the commencement of line twenty seven on the
aid page four, and substitute therefor the words "Referring to Figure 1 the."
Ve also strike out that portion of the Specification commencing with the words
In Fig." on page five, line forty one, and ending with the word "sound" on page
ix, line three, we also strike out that portion of the Specification commencing with
he words "I also" at the end of line eight, and ending with the words "the line
n line eleven of the said page 6. We also strike out the whole of lines twenty four
twenty eight inclusive on the said page 6. We also strike out the words "to
cord," which are repeated on line thirty five of the said page 6 and add the
tter "s" to the word "rest," which occurs on line of forty seven of the said page 6.
e also strike out of page 8 lines thirty seven to forty two inclusive and lines
"

page_text: forty six to fifty three inclusive. We also strike out of page 9 lines eighteen to
twenty three inclusive and lines thirty seven to forty one inclusive. We also strike
out of page 10 lines seventeen to thirty seven inclusive. We also strike out of
page 11 lines ten to thirteen inclusive and lines forty four to fifty seven inclusive,
and we add at the end of line thirty seven of the said page eleven after the word
"named" the words following:-"I would observe in conclusion that I do not claim
generally the transmission and reproduction of sound by increasing and decreasing
the resistance of the circuit, nor do I claim separately any of the parts or arrangements
herein before described and illustrated in the accompanying Drawings, except as
hereinafter mentioned; but we also strike out the word "an," which occurs between
the words "
of" and "electric" on line 42 of the said page 11; and we add the
letter "s" to the word "regulator," which occurs on the same line 42, to make it read
"regulators," and after the said word "regulators" we insert the words "sub-
stantially as hereinbefore described." We also strike out of page 12 lines one to
thirty inclusive, lines thirty six and thirty seven, and lines forty two to fifty six
inclusive. We also strike out the word "Eighteenth," which occurs at the com-
mencement of line thirty one on the said page 12, and substitute therefor the word
"Third." We also strike the word Twentieth, which occurs at the commencement of
line thirty eight of the said page 12, and substitute in therefor the word "Fourth."
We also strike the work "or," which occurs on line thirty nine of the said page 12,
and substitute therefor the word "on." We also strike out of page 13 lines
one to fourteen inclusive. And in order that the effect of the said Disclaimer
may be clearly understood, we annex hereunto a copy of the said Specification
as it will appear when so amended, the preamble and testing clause being
omitted.
This Invention relates to that class of electrical instruments in which sound
becomes one of the elements in the transmission of the communication, and a corre-
sponding sound is produced at the receiving station, so that oral communications
can be sent by electricity and clearly distinguished at the receiving station.
Musical tones may also be sent, but my present Invention is especially available
in transmitting and receiving oral communications.
In transmitting musical tones the respective notes each have a definite period
for each vibration, hence there is a response at the receiving end from the notes
that vibrate in time with the electric pulsations sent, but in speaking there
is little change in the musical tone, but considerable in the modulations and
inflections of the voice.
In my present Invention I make use of the vibrations given to a diaphragm or
tympan by speaking into a resonant case to produce a rise and fall of electrical
tension upon the line, with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation, and an electro
magnet at the receiving station will respond to the electric waves in such a manner
as to reproduce the articulation by acting upon a resonant plate.
The transmitting instrument in a complete form is represented in section in
Figure 1, and Figure 2 represents a receiving instrument which may be employed
with it.
Referring to Figure 1, the resonant tube or box a is of a size and shape adapted
to being spoken into, the same having an opening at one end or side, and a
diaphragm or diaphragms b against which the sound waves from the human
voice act, and these and the motion that the diaphragm receives is the means
of producing a rise and fall of electric tension on the line by the devices hereafter
set forth, so that the battery B connected to the line will transmit a greater or
less current to the distant electro magnet m, Figure 2, and increase or lessen the
magnetism of the cores, and in so doing act upon a resonant plate c and develop
sound corresponding to the articulation at the transmitting station.
The general features thus described pervade my entire Invention, but in
developing the same many useful and important modifications and variations have
been made, which I will proceed to set forth.

page_text: For convenience the speaking instrument, Figure 1, is provided with a handle a
and flexible conductors to the battery and line respectively, so that it may be
handled and brought to the mouth; and in like manuer it is preferable to place
the hearing instrument, Figure 2, in a moveable handle b' so that it can be placed
with the plate c against the ear; this brings the sound close to the organs of hearing,
and the resonant plate touching the car increases the distinction of the sound, and
prevents any false or prolonged vibrations of the plate.
In some of the modifications I have shown the speaking instrument as a fixture,
and also the hearing instrument as a fixed resonant tube, these being variable to
0 suit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity
of the resonant tube for the voice; I have experienced great difficulty in reproducing
the sound of the hissing consonants, such as S; this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth, and does not act
5 distinctly upon the diaphragm. By providing an edge in the resonant tube below
the mouth upon which such consonant sounds are received, the vibrations are given
either to the resonant tube or deflected to the diaphragm. I find it preferable to
employ a hole e at the lower part of the mouth piece, against the edges of which
the downward sound waves are directed. The same effect will be produced by a
vibrating edge placed in the lower part of the mouth piece, or the opening into the
resonant box may be contracted to about half an inch in diameter to effect the
same purpose. The next feature requiring consideration is the character of the
diaphragm in the speaking instrument.
Many materials have been employed by me, such as metals, horn, vellum,
celluloid, ivory, &c., but almost all of these produce a prolonged or secondary
vibration from their own resonant character, hence the articulation is defective
and the sound vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
resonant action, and hence it will respond with the greatest accuracy to the sound
vibrations, and being of a laminated character can be employed of any desired
thickness, and when secured at its edges responds with the greatest accuracy to the
sound vibrations, and does not require to be strained; furthermore, the changes of
temperature and atmospheric condition have little or no effect upon the mica
diagram or tympan.
I find that it is not practical to open and close the line circuits in instruments for
transmitting the human voice; the circuit to the line must be always closed, and the
transmission be produced by a rise and fall of electric tension resulting from more
or less resistance in the line. This resistance may be produced in several ways; I
have shown several which will hereafter be named, but I find the most delicate to
be small bunches or tufts or discs of some conducting elastic fiber, such as particles
of silk, and an intermediate conducting or semi-conducting material; this device I
call an electric tension regulator, it is more or less compressed according to the
vibrations of the diaphragm or tympan, and the electric current rises in tension as
it is compressed, or lessens as the fibre expands. This fiber is placed in a small
roll t between the delicate diaphragm spring u, Figure 9, and the variable presser v,
adjustable by screw or otherwise in the electric circuit at this point, or it may be
within a cavity in said presser v, as in Figure 1, there being a delicate cork centre
piece w to the diaphragm b with a piece of platina foil a in contact with the fibre.
In all instances the telegraphic circuit at the diaphragm is made by a thin strip
f platina or similar material, extending to the centre from the line or battery
onnection.
The fibre is rendered semi-conductive by being rubbed with plumbago, soft,
etal, or smilar material, or by a deposit of metal upon its surface, or by fine
articles of conducting or semi-conducting material mixed with it, the conducting
ower varying with the density of the tuft or branch of fiber.
The delicate spring u, Figure 9, upon the mica diaphragm 6 is easily secured by
older passing into fine holes bored in the mica.

page_text: In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact, such as would result from a disk covered with plumbago
placed adjacent to a diaphragm also covered with plumbago or other semi-conducting
material, so that the proximity or extent of surface contact will produce rise and
fall of tension, the respective parts being in the telegraphic circuit.
I sometimes perforate the diaphragm 10, Figure 18, and place a strip of elastic
material 40 across said diaphragin over the hole, and upon this a piece of foil, so
that the same responds to very weak vibrations, and in some instances two or
more diaphragms are provided at different sides of the resonant box, each with its
own tension regulator, the diaphragms being either the same or of different sizes,
characters, or tensions, so as to respond to varying sounds or acoustic condition,
the various tension regulators being all in the electric circuit; this will produce
greater rise and fall of tension for longer lines in consequence of the diaphragms
acting simultaneously on the tension regulators.
In some instances it is preferable to make the mouth piece of the speaking
instrument sufficiently large or flaring to receive all the sound vibrations, whether
coming from the mouth, nose, or throat.
.
The tension regulator formed of fiber and conducting or semi-conducting material
may be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within
a case to form the tension regulator, the circuit passing through the same, and the
rise and fall of electric tension resulting from the compression of the same by the
movement of the diaphragm.
I am enabled to record the sounds produced by the human voice or otherwise
by causing the movements of the diaphragm to be registered on paper or soft sheet
metal, and then the paper may be used in an instrument to reproduce the sound
upon a delicate diaphragm by giving to the same a vibration similar to that
originally given by the voice.
h, Figure 4, is the indenting transmitter, the diaphragm having a knife edge
point; is the paper which has previously been passed through a machine to raise
a V shaped rib 6. The movement of the diaphragm of h when the drum is in
motion causes the knife edge point to indent the raised rib to varying depths
according to the amplitude of vibration of the diaphragm, thus these indentations
represent accurately all the tones and varying inflections of the human voice. The
paper after being indented is passed through a second apparatus n, Figure 5, almost
similar to h. A spring 9 has a knife edge which rests upon the raised indented
rib 6 the spring being connected to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting poiut
and either by direct action or through the vibration of a string conveys the same
motion to the diaphragm of 1, and reproduces previous sounds. If these sounds
are to be transmitted over a telegraph line, the diaphragm 10, see Figure 6, is
provided with a cork disk w, and fibrous tension regulator t before described, to
The sound may be
produce the rise and fall of electric tension on the line.
recorded in ink, as represented in Figure 7. The diaphragm of h operates a very
flexible self feeding pen o, and causes the continuous line to be wide or narrow
according to the amplitude of vibration of the diaphragm. The ink used should
dry quickly, and the strip may be passed at any time thereafter through the
instrument shewn in Figure 8, beneath the arm 12, having a point or points resting
on the paper; this arm is connected with a resonant diaphragm, and the ink marks
produce more or less friction according to the breadth and amount of ink deposited,
and this will set the diaphragm of n vibrating and reproduce the vibrations of the
diaphragm of h.
An obvious modification would be to coat the paper with a substance which
would cause considerable friction, or even rough unsized paper might be used, and
a spring provided with a burnished point rather flat would cause the surface of the
paper to be made smooth more or less according to the vibration of the diaphragm,

page_text: and the difference in the surface of the paper would produce a response of the
receiving diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument,
as shewn in Figure 10.
5 h is the resonant chamber, at the end of which is the diaphragm 10, and at each
side of this diaphragm there are springs c², c³, having points made of compressed
plumbago mixed 'preferably, with guin rubber, but any substance not liable to
rapid decomposition, or the elastic or fibrous tension regulator aforesaid may be
used. These points face each other on opposite sides of the diaphragin and make
contact with platina foil disks secured to the diaphragm.
The spring c³ passes through a hole or small slot in the side of the chamber h;
d², d³ are the main batteries; the battery d² has zinc to the line or spring c², and the
battery has copper to the line or spring c³. When the springs c² and c³ are adjusted
to make contact with the diaphram equally no current passes to the line, but when
the diaphragm is vibrated its moveinent to one side, say, c², causes a greater
pressure upon the plumbago on that spring and a loosening of the pressure on the
plumbago on c³, hence the balance of the batteries c² and c³ will be destroyed, c³
having the advantage will send a negative current to line; upon the return of the
diaphragmn the battery currents will again neutralize each other. The vibration of
the diaphragm to the other side causes the pressure to be reversed, and the battery d³
will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure, it follows that the strength
of the electric waves will be in proportion as the speakers voice is strong or
weak.
In Figure 11 is shewn the contact spring, which may be used adjacent to the
diaphragm at one or both sides thereof; e³ is a U shaped spring secured to the
screw e, which is adjusted back and forth by the thumb nut c; c is the pillar
bolding such screw; is a piece of soft rubber or equivalent substance placed between
the prongs of the spring e³; e' is a wire or band which serves to bind the prongs
tightly against the rubber r, so as to prevent the prongs acting as a tuning fork and
transmitting harmonic vibrations not desirable; is the plumbago contact point.
The object of the U spring and rubber is to present a semi rigid point for contact
so as to prevent a rebound and allow of a slight yield when the plumbago is pressed
by the diaphragm.
In Figure 3 the diaphragm of the receiving instrument is vibrated by a strip of
paper chemically prepared, that is, in motion, the pulsations of electricity passing
over the line and producing more or less friction between the paper and an arm
upon the diaphragin.
The resonant box or chamber n is provided with a diaphragm as aforesaid, and to
said diaphragm an arm h² is connected. At its outer end is an adjusting screw h³
that presses upon a platina faced spring h¹ that is secured to this arin, and said
pring rests upon the strip of paper that passes over the drum .
The paper is moved slowly by rotating the drum h³, and the waves of electricity
coming over the line pass through the arm h² to the platina-faced spring h*, thence
hrough the paper to the earth.
If a negative current passes in the opposite direction nearly all friction between
he platina plate and the paper ceases, and the diaphragm of the resonant box n
etains its normal position.
When the positive current passes through the same channel the normal friction
f the paper is augmented, and the chemical surface acting upon the platina
oring arm serves to give a forward movement to the diaphragm of the resonant
0x.
Thus the mechanical force applied to move the chemical paper or surface acts
ith the electric current to produce the vibration of the diaphragm of the resonant
amber, and these vibrations will correspond to those of the diaphragm b made by
eaking in the tube a.

page_text: The principle of this method of obtaining motion by electro chemical decom-
position is that when a moving surface is in contact with a slightly yielding
substance the tendency is to move the latter by and with the former. If the
circumstances of contact are varied the adhession of the surfaces will be sufficient
to cause the moving surface to move the yielding substance or else to cause the
yielding surface to slip more freely, and by its spring go in the opposite direction
to the moving surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion, make it more or less, according to the substances employed. By balancing
the mechanical forces, so that when the surfaces in contact are not electrified the
moving surface carries with it the yielding surface, and when electrified the
yielding surface slips back over the moving surface a mechanical movement is
obtained that is dependent on the electrical condition of the surfaces in contact.
When it is requisite to obtain very perfect articulation, and when loudness is
not essential, I adopt a modification shewn in Figure 12 of the device for com-
pressing and expanding the tuft of conducting fiber, which modification consists in
placing between the diaphragm 10 and the fiber t a vibrating tongue 21 of steel
permanently magnetised, and arranging it to act in the same manner upon the
tension regulator t as if it was the diaphragmn; I replace the cork upon the
diaphragm by a thin armature of iron 22, which is in close proximity to the
magnetized tongue, which tongue is secured at one end like an acoustic reed. In
this position the diaphragm is free to move, and at its approach to and recession
from the magnetized tongue causes said tongue to follow its movements by
magnetic attraction, and thus the tongue is made to perform what the diaphragm
previously performed in varying the tension of the electricity on the line.
A. plate supported eccentrically and free at its edges when placed in the speaking
tube responds advantageously to the tones of the voice. The circuit with this plate
is completely through one or more tension regulators placed around its edges.
In practice I combine with the speaking or telephonic apparatus signal bells so
arranged that when the telephone is not in use the line is thrown upon the bell by
a switch which also acts as a call on the bell.
One feature about the bells is that the magnet which serves to actuate the bells
is made of very high resistance, using preferably German silver wire in the helix,
and thus serves to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from one battery if these bells are used.
The method I adopt for coating nonconducting substance with metallic substance
is the reduction to the metallic state of metals from their salts by exposing them to
the fumes which arise from the moist phosphide of a metal such as phosphide of
calcium; or by placing the silk, for instance, in a sealed tube provided with metellic
electrodes, and volatilizing the electrodes by the passage of electric sparks, such
volatilized metals settle upon and coat the silk.
When great loudness is desirable, as in factories, the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is stored
under a regulated pressure.
The air allowed to escape will act with great power upon a local diaphragm.
This diaphragm, to obtain clear sounds, requires a damper to check prolonged
vibrations. It must be damped by holding the fingers against it or by a tightly
stretched cord rubbing against it or by a screw provided with a rubber tip held
against it.
In some instances I make a record of the sound by the movements of the
diaphragm, using for that purpose a strip of paper moved along regularly between
two rollers 25, 26, as in Figures 14 and 15, and there is a smooth thread or
fine wire of soft metals 30 between the paper and the upper roller 25 and moving
along with it. The diaphragm. 10 of the resonant box is connected by a delicate
rod 28 with this thread or wire as near to the bight of the roller as possible, there
being a fork or eye through which the thread passes; hence deflections or bends are
made in the thread or wire just before it is embedded into the paper by the

page_text: pressure of the rollers. This may be used to reproduce the sound by vibrating a
resonant diaphragm by the undulations of the groove made by the thread or
cord.
By placing the fibrous tension regulator within a small band of india rubber the
5 same is rendered more clastic, and the fiber is allowed to expand by the heat of the
current without altering the electric tension.
In some instances the diaphragın should be free to vibrate without being checked
by contact with any stationary substance. I provide for this by placing upon the
diaphragm or tympan 10, Figure 17, a small cylinder t7, of hard rubber or non-
conducting material, within which is the fibrous tension regulator t resting upon
a piece of platina foil connected to one pole of the battery, and within this
cylinder t is a disc 10, of iron or other metal, loose, but pressed towards the tension
regulator by a spring 18 and screw cap t³, and the ctber electric conductor is
connected with said spring.
The inertia of the metal disk causes more or less compression of the tension
regulator as the diaphragm is vibrated, and hence the electric pulsations are sent
over the hine in harmony with the vibrations. Nearly the same effect
produced
by connecting the disk to to a yielding spring that extends across from one
edge of the diaphragm to the other, as seen in Figure 1C. This construction of
tension regulating device is especially available with large diaphragins.
In some cases I use a soft rubber diaphragm immediately in contact with the
transmitting or receiving diaphragm, so as to check or dampen any prolonged or
false vibration, and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable
to use lampblack mixed with pure lumbago, amorphous phosphorous, and a very
small amount of nonconducting material, such as rubber dissolved in a solvent that
will entirely evaporate.
In Figure 19 I have represented the circuit as passing through the diaphragm 10,
tension regulator t, and a Duluc's dry pile battery D, P, B, to the earth. This
battery is composed of about three hundred pairs of paper disks coated with silver
and black oxyd of manganese.
Figure 20 illustrates the device before mentioned for intensifying the sound;
10 is the diaphragm vibrated by the sound; 42 is a valve moved by such
diaphragm; 43 is a reservoir containing air under a given pressure; b is the
diaphragm against which the air allowed to escape by the valve acts, and t is the
tension regulator to transmit the electric pulsations, or a hearing resonant case
may be applied at the same place.
Figure 24 represents the diaphragm 10, tension regulator t, with its adjusting
screw and local circuit containing the battery B passing through a primary
induction coil 49, and there is a key 50 in the same circuit. A secondary induction
coil 51 is in the line circuit, and is influenced electrically by the change of tension
in the local circuit by the vibrations of the diaphragm 10.
The secondary coil is sometimes required with many layers of fine wire to set
up a current of high tension; to overcome the inductive effect from the line wires
being adjacent to each other, I place the receiving instrument at the distant station
between the induction coil and the earth as at R, and use an electro magnet E, M,
with polarized armature to strike a bell; this will respond when the key 50 in the
local circuit at the distant station is opened and closed.
In Figure 25 a similar induction coil 49 and local circuit is represented, but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes,
one on the diaphragm, the other on the adjusting screw. A shunt and rheostat
at R' serves to prolong the magnetism in the induction coil, and thus ensure a
gradual rise and fall of electric tension in the line instead of a cessation of the
ame when the platina surfaces separate, and at the receiving diaphragm c the
ise and fall of electric tension in the line and its helix acts upon the permanent
nagnet to produce the vibrations of the diaphragm c, and by connecting a shunt
round the helix and placing therein the secondary battery S, B, composed of

page_text: .
metallic plates in acidulated water the action is rendered more uniform and the
sound distinct.
When the diaphragm is arranged, as in Figure 26, to act upon a spring 50
through an intervening piece of soft rubber, said spring 56 produces rise and fall of
electric tension, by employing a range of resistance 57 with spring tongues adjacent
to 56. The greater amplitude of vibration of the diaphragm, the more direct will
be the electric circuit connections and the less resistance, because the circuit will
pass along the spring instead of going through all the resistance coils.
When several line wires run near each other the wire used for the acoustic or
speaking telegraph is influenced by induction, and false sounds will be produced.
I counteract this tendency by placing one or more electro magnets 59, Figure 28,
in the circuit of the speaking telegraph, and one or more electro-magnets 60 in the
circuit of the adjacent wires, and bringing the opposite cores of 60 at such a
distance from the cores of 59 that a certain magnetic action will be set up in 59
by induction in the opposite direction to the induction currents from the adjacent
line or lines.
By adjusting the distance between these magnets when the speaking telegraph
is not in use until there is not any sound at the diaphragm from the induction
currents, then these currents will be neutralized, whether strong or weak, and will
not produce any false sounds when the speaking telegraph is in use.
I also employ double coils of wire for the same purpose, one coil being in the
acoustic wire, and the other in the wire to be compensated.
A convenient form for the sound recorder or phonogragh is to employ a
cylinder 61, see Figure 29, having a helical groove in its surface covered with tin
foil, and the cylinder is revolved regularly by clockwork, and moved endwise by a
screw on its shaft, so that the indenting point from the diaphragın 10 of h will
be always in line with such groove; hence the vibrations of the diaphragm will be
recorded by indenting the foil into the groove, and hence the same sound will be
reproduced by the point of the hearing instrument n, giving to the diaphragm
of n the motions that result from the indentations of the foil moving in contact
with such point.
The foil may be on a flat grooved plate, and be indented and act as before
named.
I would observe in conclusion that I do not claim generally the transmission and
reproduction of sounds by increasing and decreasing the resistance of the circuit,
nor do I claim separately any of the parts or arrangements hereinbefore described
and illustrated in the accompanying Drawings, except as hereinafter mentioned,
but I claim as my Invention,--
First. In an instrument for transmitting electric impulses by sound, a diaphragm
or tympan of mica, substantially as set forth.
Second. In an instrument for transmitting electric impulses by sound, the
combination with a diaphragm or tympan of electric tension regulators, substantially
as hereinbefore described for varying the resistance in a closed circuit, substantially
as set forth.
Third. The method herein specified of recording the undulations of the diaphragm
on yielding material, and the reproduction of sound by such material acting upon a
diaphragm to communicate to the same vibrations similar to the original ones,
substantially as set forth.
In witness whereof, the said United Telephone Company, Limited, have
caused their common seal to be hereunto affixed, the Twenty third day of
March. One thousand eight hundred and eighty one.

page_text: August 100%.
TO ALL TO WHOM THESE PRESENTS SHALL COME WE THE UNITED
TELEPHONE COMPANY LIMITED send greeting WHEREAS Her most Excellent
Majesty Queen Victoria by Her Royal Letters Patent under the Great Seal
of Great Britain and Ireland bearing date at Westminster the Thirtieth day of
July in the year of our Lord One thousand eight hundred and seventy seven in
the forty first year of Her reign did for Herself Her heirs and successors give and
grant unto Thomas Alva Edison his executors administrators and assigns special
license full power sole privilege and authority that he the said Thomas Alva Edison
his executors administrators or assigns and every of them by himself and themselves
or by his and their deputy or deputies servants or agents or such others as he
his executors administrators or assigns should at any time agree with and no others
from time to time and at all times thereafter during the term therein expressed
should and lawfully might make use exercise and vend within the United
Kingdom of Great Britain and Ireland the Channel Islands and Isle of Man an
Invention of IMPROVEMENTS IN INSTRUMENTS FOR CONTROLLING BY SOUND THE
TRANSMISSION OF ELECTRIC CURRENTS AND THE REPRODUCTION OF CORRESPONDING.
SOUNDS AT A DISTANCE for and during the terin of fourteen years thence next
ensuing And whereas in pursuance and performance of a proviso in the said
Letters Patent contained the said Thomas Alva Edison did within six calendar
months next after the date of the said Letters Patent cause a Specification
in writing under his hand and seal purporting to particularly describe the nature
of the said Invention and in what manner the saine was to be performed to
be duly filed in the Great Seal Patent Office And whereas by indenture bearing
date the Second day of August One thousand eight hundred and seventy nine
and made between the said Thomas Alva Edison of the one part and the Edison
Telephone Company of London Limited of the other part the said Thomas Alva
Edison assigned unto the said Company (inter alia) the said hereinbefore recited

page_text: Letters Patent and all rights powers privileges advantages profits emoluments and
benefits to the said Letters Patent appertaining or belonging And whereas on the
Thirteenth day of November One thousand eight hundred and seventy nine the
said Edison Telephone Company of London Limited petitioned the Commissioners
of Patents for leave to amend certain parts of the said Specification of the said
Letters Patent which petition was referred to Her Majesty's late Attorney General
Sir John Holker and leave was given to the said Company to file in the Great
Seal Patent Office a Disclaimer and Memorandum of Alteration as appears by the
Fiat of the said Sir John Holker dated the Ninth day of February One thousand
eight hundred and eighty and the said Disclaimer was duly filed in the Great Seal
Patent Office on the Tenth day of February One thousand eight hundred and
cighty And whereas by indenture bearing date the Twelfth day of July One
thousand eight hundred and eighty and made between the said Edison Telephone
Company of London Limited of the one part and as the United Telephone
Company Limited of the other part aud duly registered in the Great Seal Patent
Office the said Edison Telephone Company of London Limited assigned to us the
said Letters Patent and the rights and privileges thereby granted and the same
thereby became and are now vested in 'us the said United Telephone Company
Limited And whereas on the Twenty fifth day of March One thousand eight
hundred and eighty one we the said United Telephone Company Limited
petitioned the Commissioners of Patents for leave to further amend certain
parts of the said Specification of the said Letters Patent which petition was
referred to Her Majestys Attorney General and leave was given to us the said
United Telephone Company Limited to file in the Great Seal Patent Office a
further Disclaimer and Memorandum of Alteration as appears by the Fiat of Her
Majesty's Attorney General Sir Henry James dated the Fourth day of June One
thousand eight hundred and eighty one and the said Disclaimer and Memorandum
of Alteration was duly filed in the Great Seal Patent Office on the Thirteenth day
And whereas since the
of June One Thousand eight hundred and eighty one
filing of the said last named Disclaimer and Memorandum of Alteration we the said
United Telephone Company Limited have been in litigation with various persons
and companies with respect to infringements of the said Letters Patent and we the
said United Telephone Company Limited have found that the retention of Claims 1
and 3 of the said Specification as amended by the said hereinbefore recited
Disclaimers having regard to the language of the Provisional Specification has
given rise to questions as to how far such claims are valid as a matter of law upon
the face of the Specifications And whereas the subject matter of the said Clains 1
and 3 is not of great commercial importance And we are therefor desirous of
striking out the said Claims 1 and 3 and of confining the claim of the said Letters
Patent to the second claim thereof NOW KNOW YE that we the United
Telephone Company Limited by and with the leave of Her Majestys Attorney
General and for the reasons aforesaid do alter the Specification by striking out o
the said Specification as amended by the said Disclaimer printed by the Queen
Printers and published at the Patent Office in One thousand eight hundred and eighty
one the first claim comprising lines 39 and 40 on page 10, We also strike out th
third claim comprising lines 45 to 43 both inclusive on the said page 10 We als
strike out the word "second" at the commencement of line 41 on the said page 1
And in order that the effect of the said Disclaimer may be clearly understood w
annex hereunto a copy of the said Specification as it will appear when so amende
the preamble and testing clause being omitted.
This Invention relates to that class of electrical instruments in which soun
becomes one of the elements in the transmission of the communication and
corresponding sound is produced at the receiving station so that oral commun
cations can be sent by electricity and clearly distinguished at the receivin
station.
Musical tones may also be sent but my present Invention is especially availab
in transmitting and receiving oral communications.

page_text: In transmitting musical tones the respective notes each have a definite perio
for each vibration hence there is a response at the receiving end from the notes
that vibrate in time with the electric pulsations sent but in speaking there is little
change in the musical tone but considerable in the modulations and inflections of
5 the voice.
)
In my present Invention I make use of the vibrations given to a diaphragin or
tympan by speaking into a resonant case to produce a rise and fall of electrical
tension upon the line with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation and an electro
magnet at the receiving station will respond to the electric waves in such a manner
as to reproduce the articulation by acting upon a resonant plate.
may
The transmitting instrument in a complete form is represented in section in
Figure 1 and Figure 2 represents a receiving instrument which
with it.
be employed.
Referring to Figure 1 the resonant tube or box a is of a size and shape adapted
to being spoken into the same having an opening at one end or side and a
diaphragm or diaphragms b against which the sound waves from the human voice
act and these and the motion that the diaphragm receives is the means of producing
a rise and fall of electric tension on the line by the devices hereafter set forth so
that the battery B connected to the line l will transmit a greater or less current to
the distant electro magnet m in Figure 2 and increase or lessen the magnetism of
the cores and in so doing act upon a resonant plate cand develop sound corre-
sponding to the articulation at the transmitting station.
The general features thus described pervade my entire Invention but in
developing the same many useful and important modifications and variations have
been made which I proceed to set forth.
For convenience the speaking instrument Figure 1, is provided with a handle a
and flexible conductors to the battery and line respectively so that it may be
handled and brought to the mouth, and in like manner it is preferable to place the
hearing instrument Figure 2 in a moveable handle b' so that it can be placed with
the plate c against the ear this brings the sound close to the organs of hearing and
the resonant plate touching the ear increases the distinction of the sound and
prevents any false or prolonged vibrations of the plate.
In some of the modifications I have shewn the speaking instrument as a fixture
and also the hearing instrument as a fixed resonant tube these being variable to
suit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity
of the resonant tube for the voice I have experienced great difficulty in reproducing
the sound of the hissing consonants such as S this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth and does not act
distinctly upon the diaphragm By providing an edge in the resonant tube below
the mouth upon which such consonant sounds are received the vibrations are given
either to the resonant tube or deflected to the diaphragm I find it preferable to
employ a hole e at the lower part of the mouth piece against the edges of which
the downward sound waves are directed. The same effect will be produced by a
vibrating edge placed in the lower part of the mouth piece or the opening into the
resonant box may be contracted to about half an inch in diameter to effect the
sanie purpose. The next feature requiring consideration is the character of the
diaphragm in the speaking instrument.
Many materials have been employed by me such as metals horn vellum celluloid
vory &c. but almost all of these produce a prolonged or secondary vibration for
heir own resonant character hence the articulation is defective and the sound
ibrations blend.
After extensive experiments I find that mica is almost entirely free from any
esonant action and lience it will respond with the greatest accuracy to the sound
ibrations and being of a laminated character can be employed of any desired
bickness and when secured at its edges responds with the greatest accuracy to the

page_text: sound vibrations and does not require to be strained furthermore the changes of
temperature and atmospheric condition have little or no effect upon the mica
diaphragın or tympan.
I find that it is not practical to open and close the line circuits in instruments
for transmitting the human voice the circuit to the line must be always closed and
the transmission be produced by a rise and fall of electric tension resulting from
more or less resistance in the line This resistance may be produced in several
ways. I have shewn several which will hereafter be named but I find the most
delicate to be small bunches or tufts or discs of some conducting elastic fibre such
as particles of silk and an intermediate conducting or semi-conducting material
this device I call an electric tension regulator it is more or less compressed according
to the vibrations of the diaphragm or tympan and the electric current rises in
tension as it is compressed or lessens as the fibre expands. This fibre is placed in
a small roll t between the delicate diaphragm spring u Figure 9 and the variable
presser v adjustable by screw or otherwise in the electric circuit at this point or it
may be within a cavity in said presser vas in Figure 1. there being a delicate cork
centre piece w to the diaphragm b with a piece of platina foil in contact with the
fibre. In all instances the telegraphic circuit at the diaphragm is made by a thin
strip of platina or similar material extending to the centre from the line or battery
connection.
The fibre is rendered semi conductive by being rubbed with plumbago soft metal
or similar material or by a deposit of metal upon its surface or by fine power
varying with the density of the tuft or branch of fibre.
particles of conducting or semi-conducting material mixed with it, the conducting
A
The delicate spring a Figure 9 upon the mica diaphragm b is easily secured by
solder passing into fine holes bored in the mica.
In some cases I make use of a variable resistance resulting froin greater or less
intimacy of surface contact such as would result from a disk covered with plumbago
placed adjacent to a diaphragm also covered with plumbago or other semi
conducting material so that the proximity or extent of surface contact will produce
rise and fall of tension the respective parts being in the telegraphic circuit.
I sometimes perforate the diaphragm 10 Figure 18 and place a strip of elastic
material 40 across said diaphragın over the hole and upon this a piece of foil so
that the same responds to very weak vibrations and in some instances two or
more diaphragms are provided at different rides of the resonant box each with its
own tension regulator the diaphragms being either the same or of different sizes
characters or tensions so as to respond to varying sounds or acoustic condition the
various tension regulators being all in the electric circuit this will produce greater
rise and fall of tension for longer lines in consequence of the diaphragms acting
simultaneously on the tension regulators.
In some instances it is preferable to make the mouth piece of the speaking
instrument sufficiently large or flaring to receive all the sound vibrations whether
coming from the mouth nose or throat.
The tension regulator formed of fibre and conducting or semi conducting material
may be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within
a case to form the tension regulator the circuit passing through the same and the
rise and fall of electric tension resulting from the compression of the same by the
movement of the diaphragın.
I am enabled to record the sounds produced by the human voice or otherwise by
causing the movements of the diaphragm to be registered on paper or soft shee
metal and then the paper may be used in an instrument to reproduce the sound
upon a delicate diaphragm by giving to the same a vibration similar to tha
originally given by the voice. h. Figure 4 is the indenting transmitter th
diaphragm having a knife edge point is the paper which has previously been
passed through a machine to raise a V shaped rib 6. The movement of th
diaphragm of h when the drum is in motion causes the knife edge point b' t

page_text: indent the raised rib to varying depths according to the amplitude of vibration of
the diaphragm thus these indentations represent accurately all the tones and
varying inflections of the human voice. The paper after being indented is passed
through a second apparatus n Figure 5 almost similar to h. A spring 9 has a
5 knife edge which rests upon the raised indented rib 6 the spring being connected
to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indentir
point and either by direct action or through the vibration of a string conveys t
saine motion to the diaphragm of n and reproduces previous sounds. If these souj
Care to be transmitted over a telegraph line the diaphragm 10 see Figure 6 is provide
with a cork disc w and fibrous tension regulator t before described to produce the
rise and fall of electric tension on the line. The sound may be recorded in ink as
represented in Figure 7. The diaphragm of h operates a very flexible self feeding
pen o and causes the continuous line to be wide or narrow according to the
5 amplitude of vibration of the diaphragm. The ink used should dry quickly and
the strip may be passed at any time thereafter through the instrument shewn in
Figure 8 beneath the arm 12 having a point or points resting on the paper this
arm is connected with a resonant diaphragm and the ink marks produce more or
less friction according to the breadth and amount of ink deposited and this will
set the diaphragm of n vibrating and reproduce the vibrations of the diaphragni
of h.
An obvious modification would be to coat the paper with a substance which
would cause considerable friction or even rough unsized paper might be used and
a spring provided with a burnished point rather flat would cause the surface of the
paper to be made smooth more or less according to the vibration of the diaphragm
and the difference in the surface of the paper would produce a response of the
receiving diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument
as shewn in Figure 10.
is the resonant chamber at the end of which is the diaphragm 10 and at cach
side of this diaphragm there are springs c² 3 having points made of compressed
plumbago mixed preferably with gum rubber but any substance not liable to
rapid decomposition or the elastic or fibrous tension regulator aforesaid may be
used. These points face each other on opposite sides of the diaphragm and
make contact with platina foil discs secured to the diaphragm.
The spring passes through a hole or small slot in the side of the chamber h;
ad³ are the main batteries the battery 2 has zine to the line or spring c² and the
battery has copper to the line or spring c³. When the springs c² and c³ are
adjusted to make contact with the diaphragm equally no current passes to the line
out when the diaphragm is vibrated its movement to one side say c² causes a
greater pressure upon the plumbago on that spring and a loosening of the pressure
on the plumbago on c³ hence the balance of the batteries c² and c³ will be destroyed
having the advantage will send a negative current to line upon the return of the
liaphragm the battery currents will again neutralize each other. The vibration of
he diaphragm to the other side causes the pressure to be reversed and the battery d³
ill send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
esistance enormously under slight changes of pressure it follows that the strength
the electric waves will be in proportion as the speakers voice is strong or weak.
In Figure 11 is shewn the contact spring which may be used adjacent to the
aphragm at one or both sides thereof is a U shaped spring secured to the
rew e which is adjusted back and forth by the thumb nut es e is the pillar
lding such screw is a piece of soft rubber or equivalent substance placed
tween the prongs of the spring e³ e' is a wire or band which serves to bind the
ongs tightly against the rubber r so as to prevent the prongs acting as a tuning
k and transmitting harmonic vibrations not desirable 2 is the plumbago contact
int. The object of the U spring and rubber is to present a semi rigid point for

page_text: contact so as to prevent.a rebound and allow of a slight yield when the plumbago
is pressed by the diaphragm.
In Figure 3 the diaphragmn of the receiving instrument is vibrated by a strip of
'paper chemically prepared that is in motion the pulsations of electricity passing
over the line and producing more or less friction between the paper and an arın
upon the diaphragm.
The resonant box or chamber n is provided with a diaphragm as aforesaid and
to said diaphragm an arm h² is connected. At its outer end is an adjusting screw h³
that presses upon a platina faced spring that is secured to this arm and said
spring rests upon the strip of paper that passes over the drum h³.
The paper is moved slowly by rotating the drum and the waves of electricity
coming over the line pass through the arm h³ to the platina faced spring / thence
through the paper to the earth.
If a negative current passes in the opposite direction nearly all friction between
the platina plate and the paper ceases and the diaphragmn of the resonant box n
retains its normal position.
When the positive current passes through the same channel the normal friction
of the paper is augmented and the chemical surface acting upon the platina
spring arm serves to give a forward movement to the diaphragin of the
resonant box.
Thus the mechanical force applied to move the chemical paper or surface acts
with the electric current to produce the vibration of the diaphragm of the resonant
chamber and these vibrations will correspond to those of the diaphragm b made
by speaking in the tube a.
The principle of this method of obtaining notion by electro chemical decom-
position is that when a moving surface is in contact with a slightly yielding
substance the tendency is to move the latter by and with the former. If the
circumstances of contact are varied the adhesion of the surfaces will be sufficient
to cause the moving surface to move the yielding substance or else to cause the
yielding surface to slip more freely and by its spring go in the opposite direction
to the moving surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion make it more or less according to the substances employed. By balancing
the mechanical forces so that when the surfaces in contact are not electrified the
moving surface carries with it the yielding surface and when electrified the yielding
surface slips back over the moving surface a mechanical movement is obtained that
is dependent on the electrical condition of the surfaces in contact.
When it is requisite to obtain very perfect articulation and when loudness is
not essential I adopt a modification shewn in Figure 12 of the device for com-
pressing and expanding the tuft of conducting fiber which modification consists
in placing between the diaphragm. 10 and the fiber´t a vibrating tongue 21 of
steel permanently magnetised and arranging it to act in the same manner upon
the tension regulator t as if it was the diaphragm I replace the cork upon the
diaphragm by a thin armature of iron 22 which is in close proximity to the
magnetised tongue which tongue is secured at one end like an acoustic reed. In
this position the diaphragm is free to move and at its approach to and recession
from the magnetised tongue causes said tongue to follow its movements by mgnetic
attraction and thus the tongue is made to perform what the diaphragın previously
performed in varying the tension of the electricity on the line.
A plate supported eccentrically and free at its edges when placed in the
speaking tube responds advantageously to the tones of the voice. The circuit with
this plate is completely through one or more tension regulators placed around its
edges.
In practice I combine with the speaking or telephonic apparatus signal bells so
arranged that when the telephone is not in use the line is thrown upon the bell
by a switch which also acts as a call on the bell.
One feature about the bells is that the magnet which serves to actuate the bells

page_text: que of very high resistance using preferably German silver wire in the helix
and thus serves to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from one battery if these bells are used.
The method I adopt for coating non-conducting substance with metallic
5 substance is the reduction to the metallic state of metals from their salts by
exposing them to the fumes which arise from the moist phosphide of a metal such
as phosphide of calcium or by placing the silk for instance in a sealed tube
provided with metallic electrodes and volatilizing the electrodes by the passage of
electric sparks such volatilized metals settle upon and coat the silk.
When great loudness is desirable as in factories the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is
stored under a regulated pressure.
The air allowed to escape will act with great power upon a local diaphragm.
This diaphragm to obtain clear sounds requires a damper to check prolonged
vibration. It must be damped by holding the fingers against it or by a tightly
stretched cord rubbing against it or by a screw provided with a rubber tip held.
against it.
In some instances I make a record of the sound by the movements of the
diaphragm using for that purpose a strip of paper moved along regularly between
two rollers 25, 26 as in Figures 14 and 15 and there is a smooth thread or fine
wire of soft metals 30 between the paper and the upper roller 25 and moving
along with it. The diaphragm 10 of the resonant box is connected by a delicate
rod 28 with this thread or wire as near to the bight of the roller as possible there
being a fork or eye through which the thread passes hence deflections or bends are
made in the thread or wire just before it is embedded into the paper by the
pressure of the rollers. This may be used to reproduce the sound by vibrating a
resonant diaphragm by the undulations of the groove made by the thread or cord..
By placing the fibrous tension regulator within a small band of india rubber the
same is rendered more elastic and the fiber is allowed to expand by the heat of the
current without altering the electric tension.
In some instances the diaphragm should be free to vibrate without being
checked by contact with any stationary substance I provide for this by placing
pon the diaphragm or tympau 10 Figure 17 a small cylinder of hard rubber or
on-conducting material within which is the fibrous tension regulator tresting
pon a platina foil connected to one pole of the battery and within this cylinder tỉ
3 & disc to of iron or other metal loose but pressed towards the tension regulator
y a spring and screw cap to and the other electric conductor is connected with
id spring.
I
The inertia of the metal disc causes more or less compression of the tension
gulator as the diaphragm is vibrated and hence the electric pulsations are sent
ver the line in harmony with the vibrations. Nearly the same effect is produced
y connecting the disc to to a yielding spring t" that extends across from one edge
the diaphragm to the other as seen in Figure 16.
gulating device is especially available with large diaphragms.
This construction of tension
In some cases I use a soft rubber diaphragm immediately in contact with the
ansmitting or receiving diaphragın so as to check or dampen any prolonged or
se vibration and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable to
e lamp black mixed with pure plumbago amorphous phosphorous and a very
all amount of non conducting material such as rubber dissolved in a solvent that
I entirely evaporate.
.
In Figure 19 I have represented the circuit as passing through the diaphragm 10
sion regulator t and a Dulue's dry pile battery DPB to the earth. This
tery is composed of about 300 pairs of paper discs coated with silver and black
d of manganese.
igure 20 illustrates the device before mentioned for intensifying the sound 10
e diaphragm vibrated by the sound 42 is a valve moved by such diaphragm

page_text: 43 is a reservoir containing air under a given pressure b is the diaphragm against
which the air allowed to escape by the valve acts and t is the tension regulator
to transmit the electric pulsations or a bearing resonant case may be applied at the
same place.
Figure 24 represents the diaphragm 10 tension regulator t with its adjusting
screw and local circuit containing the battery B passing through a primary
induction coil 49 and there is a key 50 in the same circuit. A secondary induction
coil 51 is in the line circuit and is influenced electrically by the change of tension
in the local circuit by the vibrations of the diaphragm 10:
The secondary coil is sometimes required with inany layers of fine wire to set
up a current of high tension to overcoine the inductive effect from the line wires
being adjacent to each other. I place the receiving instrument at the distant
station between the induction coil and the earth as at R and use an electro-
magnet E M with polarized armature to strike a bell this will respond when the
key 50 in the local circuit at the distant station is opened and closed.
In Figure 25 a similar induction coil 49 and local circuit is represented but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes
one on the diaphragm the other on the adjusting screw. A shunt and rheostat at R¹
serves to prolong the magnetism in the' induction coil and thus ensure a gradual
rise and fall of electric tension in the line instead of a cessation of the same when
the platina surfaces separate and at the receiving diaphragm c the rise and fall of
electric tension in the line and its helix acts upon the permanent magnet to produce
the vibrations of the diaphragm c and by connecting a shunt around the helix and
placing therein the secondary battery S B composed of metallic plates in acidu-
lated water the action is rendered more uniformi and the sound distinct.
When the diaphragm is arranged as in Figure 26 to act upon a spring 56
through an intervening piece of soft rubber said spring 56 produces rise and fall
of electric tension by employing a range of resistance 57 with spring tongues
adjacent to 56. The greater amplitude of vibration of the diaphragm the more
direct will be the electric circuit connections and the less resistance because the
circuit will pass along the spring instead of going through all the resistance
coils.
When several line wires run near each other the wire used for the acoustic or
speaking telegraph is influenced by induction and false sounds will be produced
I counteract this tendency by placing one or more electro magnets 59 Figure 28 in
the circuit of the speaking telegraph and one or more electro magnets 60 in the
circuit of the adjacent wires and bringing the opposite cores of 60 at such a
distance from the cores of 59 that a certain magnetic action will be set up in 59
by induction in the opposite direction to the induction currents from the adjacent
line or lines.
By adjusting the distance between these magnets when the speaking telegraph
is not in use until there is not any sound at the diaphragm from the induction
currents then these currents will be neutralized whether strong or weak and will
not produce any false sound when the speaking telegraph is in use.
I also employ double coils of wire for the same purpose one coil being in the
acoustic wire and the other in the wire to be compensated.
A convenient form for the sound recorder or phonograph is to employ a
cylinder 61 see Figure 29 having a helical groove in its surface covered with tin
foil and the cylinder is revolved regularly by clock work and moved endwise by a
screw on its shaft so that the indenting point from the diaphragm 10 of h will
be always in line with such groove hence the vibration of the diaphragm will be
recorded by indenting the foil into the groove and hence the same sound will be
reproduced by the point 2 of the hearing instrument n giving to the diaphragm
of n the motions that result from the indentations of the foil moving in contact
with such point.
The foil may be on a flat grooved plate and be indented and act as before
named

page_text: I would observe in conclusion that I do not claim generally the transmission
and reproduction of sounds by increasing and decreasing the resistance of the
circuit nor do I claim separately any of the parts or arrangements herein-before
described and illustrated in the accompanying Drawings except as hereinafter
mentioned but I claim as my Invention
In an instrument for transmitting electric impulses by sound the combination
with a diaphragm or tympan of electric tension regulators substantially as herein
before described for varying the resistance in a closed circuit substantially as set
forth.
In witness whereof the United Telephone Company Limited have caused
their Common Seal to be hereunto affixed the
One thousand eight hundred and eighty two.
day of
An the grianer of Letters Patent granted to THOMAS ALVA EDISON of
Menlo Park in the State of New Jersey United States of America
Dated 30th July 1877 No. 2009.
To the Commissioners of Patents for Inventions.
I hereby grant my Fiat giving leave to the United Telephone Company Limited
the assignees of the said Letters Patent to. file in the Office of the Commiss™
of Patents for Inventions with the Specification to which the same relates the
annexed Disclaimer and Memorandum of Alteration: but nevertheless upon
condition that no proceedings for infringement be taken against James Merrill
Ormes, or Horace Hamline Eldred both of 31 Queen Victoria Street in the City of
London, The London and Globe Telephone and Maintenance Company Limited,
Messrs. Harrison Cox Walker and Company of Darlington in the County of
Durham, Telegraph Engineers, John Tasker of Sheffield in the County of York
Electrician or William Johnson also of Sheffield in the County of York, Electrician,
(hereinafter called the Opponents) or against any person or persons using any such
instruments as are hereinafter referred to, that is to say, in respect of
1. Any instruments made, or in course of manufacture on the 29th July 1882,
by, or to the order of, the said opponents or any or either of them.
2. Any instruments manufactured after the 29th July 1882 under or in
pursuance of any contracts bona fide entered into previous to that date by the said
opponents or any or either of them for the supply of instruments.
3. Any instruments manufactured after the 29th July 1882 under or in
pursuance of any contracts bona fide entered into prior to the 29th July 1882 with
he said opponents or any or either of them by any other person for the supply of
uch instruments to the said opponents or any or either of them.
4. Particulars of all such instruments as have been or shall be subsequently to
be 2nd June 1882 manufactured or delivered, and of all contracts under which
uch last mentioned instruments have been or shall be delivered to be furnished to

page_text: the United Telephone Company Limited and verified by Statutory Declaration on
or before the 14th September 1882.
5. All such instruments as have not been delivered prior to 29th July 1882 to be
numbered and marked with proper identifying marks before delivery, and an
opportunity to be given to the United Telephone Company Limited or their
agents to verify the same.
6. Any question of bona fides to be referred to and determined by the Attorney
General.
1
1
Sun 1882
HENRY JAMES,
The
United
Telephone
Company,
Limited.
JAMES BRAND
JOHN W. BATTEN} Directors.
THOS. BLAIKIE,
Sec³.

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
INSTRUMENTS FOR CONTROLING BY SOUND THE TRANSMISSION OF ELECTRIC
CURRENTS, AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT A
Sealed the 20th October 1877, and dated the 30th July 1871.
PROVISIONAL SPECIFICATION left by the said Thomas Alva Edison at the
Office of the Commissioners of Patents on the 30th July 1877.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United States
of America. "IMPROVEMENTS IN INSTRUMENTS FOR CONTROLING BY SOUND THE
TRANSMISSION OF ELECTRIC CURRENTS, AND THE REPRODUCTION OF CORRESPONDING
SOUNDS AT A DISTANCE."
The vibrations of the atmosphere, which result from the human voice or from
any musical instrument or otherwise, are made to act in increasing or lessening the
electric force upon a line by opening or closing the circuit, or increasing or
lessening the intimacy of contact between conducting surfaces placed in the circuit
at the receiving station; the electric action in one or more electro-magnets causes
a vibration in a tympan, or other instrument similar to a drum, and produces a
sound, but this sound is greatly augmented by mechanical action.
I have discovered that the friction of a point or surface, that is in contact,
whether a properly prepared and slowly moving surface, is very much increased
or lessened by the strength of the electric wave passing at such point of contact,
and from this variation in the friction a greater or less vibration is given to
the mechanism or means that produce or develope the sound at the receiving
station, thereby rendering clear and distinct the sound received that otherwise
would not be audible.
To carry out the peculiarities of my Invention under the varying conditions of
use, I have devised several modifications of the transmitting, receiving, and
intensifying devises employed in this sound telegraph; portions of the apparatus

page_text: are interchangeably, available in transmitting or recording; others are adapted to
local use; some are only available in transmitting, and others are ouly for receiving;
and some portions of my improvement can be availed of to make a record of the
atinospheric sound waves, or of the electric waves, or pulsations corresponding thereto
or resulting therefrom.
.
In one form of my apparatus the sound passes into a resonant box having one,
two, or more tympans at its sides that are vibrated thereby, the tension of these
being various, so as to respond to different sound waves, and the electric connections
pass through all to one line or circuit, in which is a battery and the distant
receiving instrument. Circuit contact points are provided at one or both surfaces 1
of the tympan or tympans; the tympans are of parchment, foil, mica, sheet metal,
or similar material. I find platinum, foil, or mica to respond advantageously when
the waves from the mouth are made to pass through a slot resembling the larynx
placed within the resonant tube. The contact points or surfaces are sometimes
metallic, but plumbago, or similar semi-conducting material, into which the tympan or 1
diaphragm is brought more or less intermittently into contact, or a point or pin
thereon serves to lessen or increase the electricity passing at that point.
In the receiving portion of the instrument the tympan is acted upon directly by
an electro-magnet, or through an armature, or the tympan is provided with an arm
extending out over a slowly moving surface or cylinder, and the electric current,
passing at the point of contact, increases or lessens the friction, and produces the
vibration of the arm and tympan in proportion to the difference of friction
developed between the arm and moving surface by the passage and cessation of
the current through the chemically prepared paper, preferably moistened with a salt
of mercury and an alkali. This feature is capable of very extended developement
in telegraphy; the clearness and extent of sound produced by the receiving tympan
exceeds anything heretofore attained in acoustic telegraphs.
The frictional surface may be any material which absorbs liquids, such as chalk
or paper; the transmitting points in all instances should be a poor conductor of
electricity, such as cyanide of copper, peroxide of lead, or plumbago, which
substance may be moulded with non-conductors.
Where plumbago is used between the cores and armature of an electro-magnet,
and such plumbago is included in a local or relay circuit, the pulsations or rise and
fall of electric tension will correspond to that in the coils of the electro-magnet in
consequence of the varying compressing action on the plumbago or similar material,
which increases and decreases its resistance.
A polarized arm, near a soft iron plate upon the tympan, will receive a motion
from the vibration of the tympan, and make more or less intimate contact with the
plumbago point without arresting the motion of such tympan.
In the line the effect of the static charges and discharges are neutralized by
condensers or by helices in shunts.
Where a rapidly revolving wheel is contiguous to the transmitting tympan,
and there is a plate of platina on that tympan to which the circuit is connected, the
rise and fall of electric tension will result accurately from the movement of the
ty.npan, producing greater or less contact with the wheel; a spring may intervene
between the wheel and tympan.
A spring or reed, attached to a stud at one end, and to the tympan at the other,
is vibrated or undulated by the sound waves acting on the tympan, and produces
greater or less contact with pieces of tin foil surrounding it, which also are in the
electric circuit or plumbago; contact points near the side of such spring effect the
same object. A column formed of disks of tin foil in a glass tube, pressed upon by
the vibrations of the tympan, also are employed under some circumstances to
regulate the electric tension in the circuit.
upon the
passage
and
The moving surface, whose friction is increased or decreased
cessation of the current aforesaid, is employed in some instances to vibrate by the
electric and mechanical action a frame of strings of different pitch to produce
musical sounds, or to give motion to reeds. or resonant boxes.

page_text: The transmitting tympan is sometimes made of cloth, with plumbago pressed
its surfaces, and generally it is preferable to weight the centre of the tympan, and
take the motion a little one side of the centre to prevent a flase movement or
rebound. These sound transmitting and receiving instruments are applied in single
or multipleyd telegraphs; the connections through the Wheatstone bridge, or the
induction coils, being used in the well known ways, and the circuits being
either single or relays.
Where alluininium is introduced in the electric circuit in connection with a
material containing an electrolite, the vibration of the tympan, and an extension
from it to the material containing the electrolite, causes a depolarization at the
point of contact at every vibration, thus increasing and decreasing the strength of
the current by depolarization.
Where a slot is made in the diaphragm, and the airways impinge against the
same, the vibration of the hissing sounds is auginented.
The resonant chamber for convenience is made portable, so as to be presented to
the mouth.
In addition to the tympan for transmitting the vowel sounds, I employ another
opening in the speaking tube or chamber, which opening may be increased or
lessened; I stretch edgewise over this a thin reed of foil, which is set in vibration
by all hissing consonants, and make contact with a plumbago point, or with a
platina point, which is connected to the line through an adjustable resistance coil,
or a self-acting reed giving a hiss may be thrown in and out of circuit by the
movement of the foil reed.
For transmitting and receiving letter by letter, I employ a shaft with 30 wheels,
and contact springs resting upon them; the wheels are provided with teeth of such
number and character that they will cause the springs to be vibrated against a
plumbago point the necessary number of times, and with proper pressure to transmit
the letter, which is rendered audible at the distant station by the magnet or
frictional surface. Each wheel is controlled by a key of a key board.

page_text: [
SPECIFICATION in pursuance of the conditions of the Letters Patent filed b
the said Thomas Alva Edison in the Great Seal Patent Office on the 30t
January 1878.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United State
of America. "IMPROVEMENTS IN INSTRUMENTS FOR CONTROLING BY SOUND TH
TRANSMISSION OF ELECTRIC CURRENTS, AND THE REPRODUCTION OF CORRESPONDING
SOUNDS AT A DISTANCE."
This Invention relates to that class of electrical instruments in which soun
becomes one of the elements in the transmission of the communication, and th
same sound is produced at the receiving station, so that oral communications car
be sent by electricity and clearly distinguished at the receiving station.
Musical tones may also be sent, but my present Invention is especially available
in transmitting and receiving oral communications.
In transinitting musical tones, the respective notes each have a definite period for
each vibration, hence there is a response at the receiving end from the notes that
vibrate in time with the electric pulsations sent, but in speaking there is little
change in the musical tone, but considerable in the modulations and inflections of
the voice.
In my present Invention I make use of the vibrations given to a diaphragm or
tympan, by speaking into a resonant case, to produce a rise and fall of electrical
tension upon the line with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation, and the electro-
magnet at the receiving station will respond to the electric waves in such a manner
as to reproduce the articulation by acting upon a resonant plate.
The instruments in a complete form are represented in Figs. 1 and 2, Fig. 1 being
a section of the transmitting instrument, aud Fig. 2 of the receiving instrument.
The resonant tubo or box a is of a size and shape adapted to being spoken into,
the same having an opening at one end or side and a diaphragm or diaphragms b,
against which the sound waves from the human voice act, and these and the motion
that the diaphragm receives is the means of producing a rise and fall of electric
tension on the line by the devices hereafter set forth, so that the battery B connected
to the line will transmit a greater or less current to the distant electro-magnet m,
Fig. 2, and increase or lessen the magnetism of the cores, and in so doing act upon
a resonant plate c, and develop sound corresponding to the articulation at the trans-
.mitting station.
The general features thus described pervade my entire Invention, but in de-
veloping the same many useful and important modifications and variations have
been made, which I will proceed to set forth.
For convenience the speaking instrument, Fig. 1, is provided with a handle, a',
and flexible conductors to the battery and line respectively, so that it may be
handled and brought to the mouth; and in like manner it is preferable to place the
hearing instrument, Fig. 2, in a movable handle b', so that it can be placed with
the plate c against the car, this brings the sound close. to the organs of hearing, and
the resonant plate touching the ear increases the distinctness of the sound, and
prevents any false or prolonged vibrations of the plate.
In some of the modifications I have shown the speaking instrument as a fixture,
and also the hearing instrument as a fixed resonant tube, these being variable to
suit the persons or the places.
4
The first especial feature that requires separate consideration is the peculiarity of
the resonant tube for the voice. I have experienced great difficulty in reproducing 5
the sound of the hissing consonants, such as 8; this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth, and does not act
distinctly upon the diaphragm.
below the mouth, upon which such consonant sounds are received, the vibrations
By providing an edge in the resonant tube

page_text: e given either to the resonant tube or deflected to the diaphragm.
referable to employ a hole c at the lower part of the mouth-piece, against the edges
The same effect will be pro-
which the downward sound waves are directed.
uced by a vibrating edge placed in the lower part of the mouth-piece, or the
pening into the resonant box may be contracted to about half an inch in diameter
effect the same purpose. The next feature requiring consideration is the character
f the diaphragm in the speaking instrument.
Many materials have been employed by me, such as metals, horn, vellum, celluloid,
vory, &c., but almost all of these produce a prolonged or secondary vibration from
heir own resonant character, hence the articulation is defective, and the sound
vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
resonant action, and hence it will respond with the greatest accuracy to the sound
vibrations, and being of a laminated character can be employed of any desired thick-
ness, and when secured at its edges responds with the greatest accuracy to the sound
vibrations, and does not require to be strained; furtherinore, the changes of tempera-
ture and atmospheric condition have little or no effect upon the mica diaphragm or
tympan.
I find that it is not practical to open and close the line circuit in instruments
for transmitting the human voice; the circuit to the line must be always closed,
and the transmission be produced by a rise and fall of electric tension, resulting
This resistance may be produced in
from more or less resistance in the line.
several ways. I have shown several which will hereafter be named, but I find the
inost delicate to be small bunches or tufts, or disks of semi-conducting clastic fiber,
such as particles of silk, and an intermediate conducting or semi-conducting material;
this device call an electric tension regulator; it is more or less compressed, according
to the vibrations of the diaphragm or tympan, and the electric current rises in
placed in a
tension as it is compressed or lessens as the fiber expands. This fiber
small roll t, between the delicate diaphragm spring u, Fig. 9, and the variable
presser v, adjustable by a screw or otherwise in the electric circuit at this point, or
it may be within a cavity in said presser v, as in Fig. 1, there being a delicate cork
center piece w to the diaphragın b, with a piece of platina foil x in contact with the
fiber; in all instances the telegraphic circuit at the diaphragm is made by a thin
strip of platina or similar material extending to the center from the line or battery
5 connection.
The fiber is rendered semi-conductive by being rubbed with plumbago, soft
metal, or similar material, or by a deposit of metal upon its surface, or by fine
particles of conducting or semi-conducting material mixed with it, the conducting.
The delicate spring
power varying with the density of the tuft or bunch of fiber.
, Fig. 9, upon the nica diaphragm b is easily secured by solder passing into fine
holes bored in the mica. In Fig. 3 the tension regulator is made by water or other
The wires to the battery are led to
semi-conducting electrolytic fluid in a cup f.
the electrodes or conducting points 2, 3, in such cup that are opposite to points 4, 5,
upon the diaphragm b. The cup is adjustable to vary the distance between the
5 electrodes and the rise and fall of tension results from the varying distance between
the electrodes as moved by the vibrations of the diaphragm.
If there are several electrodes opposite to each other and insulated, except at
their ends, and the circuit led from one to the other so that the current passes
through all the electrodes in succession, the rise and fall of electric tension will be
50 promoted, because the smallest vibration of one set of electrodes is multiplied by
the number of places at which the metallic circuit is interrupted or varied.
In the receiving or hearing instrument the resonant plate c should be of tinned
iron, resting upon the edges of the case, and the magnet m, adjustable nearer to or
This plate will
further from the same, and connected loosely by slotted tongues.
55 respond to the electric pulsations by the attraction of the magnetized cores, and the
sound resulting will be audible when the plate is placed near or against the ear.
the plate, is pressed away from the magnet by a delicate spring or allowed to fall
I

page_text: "
-
$
away from the magnet, the instrument may be used as a call by using a key or
switch at the sending station to open and close the circuit, and thus move the plate
to give a loud sound.
In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact such as would result from a disk covered with plumbago
placed adjacent to a diaphragm, also covered with plumbago or other semi-con-
ducting material, so that the proximity or extent of surface contact will produce rise
and fall of tension, the respective parts being in the telegraphic circuit. I also
sometimes employ a shunt circuit in the line, or a branch circuit to the earth, in
which is placed an electro-magnet to neutralize any static charge or discharge in
the line.
I sometimes perforate the diaphragm 10, Fig. 18, and place a strip of elastic
material, 40, across said diaphragm over the hole, and upon this a piece of foil, so
that the same responds to very weak vibrations, and in some instances two or more
diaphragms are provided at different sides of the resonant box, each with its own
tension regulator, the diaphragms being either the same or of different sizes,
characters, or tensious, so as to respond to varying sounds or acoustic condition, the
various tension regulators being all in the electric circuit; this will produce greater
rise and fall of tension for longer lines in consequence of the diaphragms acting
simultaneously on the tension regulators.
In some instances it is preferable to make the mouth-piece of the speaking
instrument sufficiently large or flaring to receive all the sound vibrations, whether
coming from the mouth, nose, or throat.
Several contact points of platina, placed contiguous to the diaphragm, may be
used, the same acting to increase or lessen the surface contact, according to the
amplitude of vibration of the diaphragm, and a drop of liquid such as oil or
glycerine, between the contact point and diaphragm, will serve to maintain a closed
circuit, but the movement of the diaphragm produces rise and fall of tension.
The tension regulator, formed of fiber and conducting or semi-conducting material,
may be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within a
case to form the tension regulator, the circuit passing through the same, and the rise
and fall of electric tension resulting from the compression of the same by the move-
ment of the diaphragm.
I am enabled to record to record the sounds produced by the human voice or other-
wise by causing the movements of the diaphragin to be registered on paper or soft sheet
metal, and then the paper may be used in an instrument to reproduce the sound upon
a delicate diaphragm by giving to the same a vibration similar to that originally
given by the voice.
h, Fig. 4, is the indenting transmitter, the diaphragm having a knife-edge point.
i is the paper which has previously been passed through a machine to raise a V shaped
rib 6. The movement of the diaphragm of h, when the drum is in motion, causes
the knife-edge point to indent the raised rib to varying depths, according to the
amplitude of vibration of the diaphragm, thus these indentations represent accurately
all the tones and varying inflections of the human voice. The paper after being
indented is passed through a second apparatus n, Fig. 5, almost similar to h. A
spring 9 has a knife edge which rest upon the raised indented rib 6, the spring
being connected to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting point,
and either by direct action, or through the vibration of a string, conveys the same
motion to the diaphragm of n, and reproduces previous sounds. If these sounds
are to be transmitted over a telegraph line the diaphragm 10, see Fig. 6, is pro-
vided with a cork disk w, and fibrous tension regulator t, before described, to
produce the rise and fall of electric tension on the line. The sound may be recorded
in ink as represented in Fig. 7. The diaphragm of h operates a very flexible self-
feeding pen o, and causes the continuous line to be wide or narrow, according to
the amplitude of vibration of the diaphragm. The ink used should dry quickly,

page_text: and the strip may be passed at any time thereafter through the instrument shown
in Fig. 8, beneath the arm 12, having a point or points resting on the paper; this
arm is connected with a resonant diaphragm, and the ink marks produce more or
less friction, according to the breadth and amount of ink deposited, and this will
set the diaphragm of n vibrating, and reproduce the vibrations of the diaphragm
of 1.
An obvious modification would be to coat the paper with a substance which would
cause considerable friction, or even rough unsized paper might be used, and a spring
provided with a burnished point, rather flat, would cause the surface of the paper
to be made smooth more or less, according to the vibration of the diaphragm, and
the differences in the surface of the paper would produce a response in the receiving
diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument,
as shown in Fig. 10.
is the resonant chamber at the end of which is the diaphragm 10, and at each
side of this diaphragm there are springs c², c³, having points made of compressed
plumbago mixed preferably with gum rubber, but any substance not liable to
rapid decomposition, or the elastic or fibrous tension regulator aforesaid may be
used. These points face each other on opposite sides of the diaphragm, and make
contact with platina foil disks secured to the diaphragm.
The spring c passes through a hole or small slot in the side of the chamber h.
d², ds, are the main batteries. The battery d² has zinc to the line or spring c²,
and the battery d³ has copper to the line or spring c. When the springs c² and c³.
are adjusted to make contact with the diaphragm equally, no current passes to the
line; but when the diaphragm is vibrated, its movement to one side, say c², causes
a greater pressure upon the plumbago on that spring, and a lessening of the pressure
on the plumbago on c³; hence the balance of the batteries c² and c³ will be destroyed,
c², having the advantage, will send a negative current to line; upon the return of
the diaphragm the battery currents will again neutralize each other. The vibration
of the diaphragm to the other side causes the pressure to be reversed, and the
battery d³ will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure, it follows that the
strength of the electric waves will be in proportion as the speaker's voice is strong
5 or weak.
In Fig. 11 is shown the contact spring, which may be used adjacent to the
diaphragm at one or both sides thereof. e is a U shaped spring secured to the
screw e, which is adjusted back and forth by the thumb nut e³; e³ is the pillar
holding such screw; is a piece of soft rubber, or equivalent substance, placed
0 between the prongs of the spring es; e' is a wire or band which serves to bind the
prongs tightly against the rubber, so as to prevent the prongs acting as a tuning
fork, and transmitting harmonic vibrations not desirable; is the plumbago
contact point. The object of the U spring and rubber is to present a semi-rigid
point for contact, so as to prevent a rebound, and allow of a slight yield when the
5 plumbago is pressed by the diaphragm.
50
In Fig. 3 the diaphragm of the receiving instrument is vibrated by a strip of
paper chemically prepared that is in motion, the pulsations of electricity passing
over the line and producing more or less friction between the paper and an arm
upon the diaphragin.
The resonant box or chamber n is provided with a diaphragm as aforesaid, and
to said diaphragm an ann h² is connected; at its outer end is an adjusting screw h³,
that presses upon a platina-faced spring that is secured to this arm, and said
spring rests upon the strip of paper that passes over the drum h³.
The paper is moved slowly by rotating the drum h³, and the waves of electricity
55 coming over the line pass through the arm h² to the platina-faced spring h*, thence
through the paper to the earth.
If a negative current passes in the opposite direction, nearly all friction between

page_text: the plativa plate and the paper ceases, and the diaphragm of the resonant box n
regains its normal position.
When the positive current passes through the same channel, the normal friction
of the paper is augmented, and the chemical surface acting upon the platina
spring arm serves to give a forward movement to the diaphragm of the resonant
box.
Thus the mechanical force applied to move the chemical paper or surface acts with
the electric current to produce the vibration of the diaphragin of the resonant
chamber, and these vibrations will correspond to those of the diaphragm b, made by
speaking in the tube a.
The principle of this method of obtaining motion by electro-chemical decom-
position is, that when a moving surface is in contact with a slightly yielding
substance, the tendency is to move the latter by and with the former. If the
circumstances of contact are varied, the adhesion of the surfaces will be sufficient to
cause the moving surface to move the yielding substance, or else to cause the
yielding surface to slip inore freely, and by its spring go in the opposite direction to
the moving surface.
By
The passage of electricity at the surfaces in contact will change the frictional
adhesion, making it more or less, according to the substances employed.
balancing the mechanical forces, so that when the surfaces in contact are not
electrified, the moving surface carries with it the yielding surface; and, when
electrified, the yielding surface slips back over the moving surface, a mechanical
movement is obtained that is dependent on the electrical condition of the surfaces
in contact.
When it is requisite to obtain very perfect articulation, and when loudness is not
essential, I adopt a modification, shown in Fig. 12, of the device for compressing
and expanding the tuft of conducting fiber, which modification consists in placing
between the diaphragm 10 and the fiber ta vibrating tongue 21 of steel, permanently
magnetized, and arranging it to act in the same manner upon the tension regulator t
as if it was the diaphragm. I replace the cork upon the diaphragm by a thin
armature of iron 22 which is in close proximity to the magnetized tongue, which
tongue is secured at one end like an acoustic reed. In this position the diaphragm
is free to move, and at its approach to and recession from the magnetized tongue
causes said tongue to follow its movements by magnetic attraction, and thus the
tongue is made to perform what the diaphragm previously performed in varying
the tension of the electricity on the line..
A modification of the magnetic receiving instrument consists in an iron plate
fitted into the aperture of a resonant tube, and secured by a central support, leaving
its outer circumference free to vibrate when the metal is attracted by the poles of
the electro-magnet, which are of course on each side of its center; but it is
preferable to place the support slightly out of center, as some portions of the plate
will then be in tone for every sound.
A plate supported eccentrically and free at its edges when placed in the speaking
tube responds advantageously to the tones of the voice; the circuit with this plate
is completed through one or more tension regulators placed around its edges.
I have discovered that vulcanite or hard rubber produces cold and heat waves on
its surface by the slightest movement, and in some cases I employ the same for the
diaphragm of the resonant case h, Fig. 13, and place a therino-electric pile h' in
very close proximity to the rubber, so that the vibration of the diaphragm 10
producing changes of temperature will cause currents of electricity to be set up
within the thermo battery, and these passing over the line and acting upon a very
delicate electro-magnet and diaphragm will reproduce the sounds acting upon the
rubber diaphragm.
In practice I combine with the speaking or telephonic apparatus signal bells, so
arranged that when the telephone is not in use the line is thrown upon the bell by
a switch, which also acts as a call on the bell.
One feature about the bells is that the magnet which serves to actuate the bells

page_text: is made of very high resistance, using preferably German silver wire in the helix,
and thus serve to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from one battery if these bells are used.
The method I adopt for coating non-conducting substance with metallic substance
is the reduction to the metallic state of metals from their salts by exposing them to
the fumes which arise from the moist phosphide of a metal, such as phosphide of
calcium, or by placing the silk, for instance, in a sealed tube provided with metallic
electrodes, and volatilizing the electrodes by the passage of electric sparks; such
volatilized metals settle upon and coat the silk.
When great loudness is desirable, as in factories, the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is stored
under a regulated pressure.
The air allowed to escape will act with great power upon a local diaphragm.
This diaphragm, to obtain clear sounds, requires a damper to check prolonged
vibrations. It must be dampened by holding the fingers against it, or by a tightly-
stretched cord rubbing against it, or by a screw provided with a rubber tip held
against it.
For repeating from one circuit into another I use with the receiving diaphragın
the elastic tension regulator Fig. 1 in addition to the electro-magnet, and connect
the relay or second circuit through the same, so that waves received froin the distant
station cause the magnet to vibrate the diaphragm, and this acting upon the tension
regulator transmits the waves into the second circuit, and they are received at the
other end by an electro-inagnet and diaphragm.
In some instances I make a record of the sound by the movements of the
diaphragm, using for that purpose a strip of paper moved along regularly between
two rollers 25, 26, as in Figs. 14 and 15; and there is a smooth thread or fine wire
of soft metal 30 between the paper and the upper roller 25, and moving along with
it. The diaphragm 10 of the resonant box is connected by a delicate rod 28 with
this thread or wire as near to the bight of the roller as possible, there being a fork
or eye through which the thread passes, hence deflections or bends are made in the
thread or wire just before it is imbedded into the paper by the pressure of the
rollers; this may be used to reproduce the sound by vibrating a resonant diaphragın
by the undulations of the groove made by the thread or cord.
By placing the fibrous teusion regulator within a small band of india-rubber the
same is rendered more elastic, and the fiber is allowed to expand by the heat of the
current without altering the electric tension.
In cases where a strip of hard rubber or a cord of silk or other material coated
with plumbago or metallic foil is introduced between the diaphragm and a rigid
support, the expansion and contraction due to the passage of the electric currents
will produce a movement upon the diaphragm corresponding to the diaphragm
producing the electric pulsations.
In some instances the diaphragm should be free to vibrate without being checked
by contact with any stationary substance. I provide for this by placing upon the
diaphragm or tympan 10, Fig. 17, a small cylinder of hard rubber or non-
conducting material, within which is the fibrous tension regulator t resting upon a
piece of platina foil connected to one pole of the battery, and within this cylinder t
is a disk of iron or other metal, loose, but pressed towards the tension regulator
by a spring ts and screw cap to, and the other electric conductor is connected with
said spring.
The inertia of the metal disk causes more or less compression of the tension
regulator as the diaphragm is vibrated, and hence the electric pulsations are sent
over the line in harmony with the vibrations. Nearly the same effect is produced
by connecting the disk (10 to a yielding spring t" that extends across from one edge
of the diaphragm to the other, as seen in Fig. 16. This construction of tension
regulating device is especially available with large diaphragms.
In some cases I use a soft rubber diaphragm immediately in contact with the

page_text: transmitting or receiving diaphragm, so as to check or dampen any pronged or
false vibration, and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable to
use lampblack mixed with pure plumbago, amorphous phosphorous, and a very
small amount of non-conducting material, such as rubber dissolved in a solvent
that will entirely evaporate.
In Fig. 19, I have represented the circuit as passing through the diaphragm 10,
tension regulator t, and a Dulucs dry pile battery D, P, B, to the carth. This battery
is composed of about 300 pairs of paper disks coated with silver and black oxyd of
manganese.
Fig. 20 illustrates the device before mentioned for intensifying the sound; 10 is
the diaphragm vibrated by the sound; 42 is a valve moved by such diaphragm;
43, is a reservoir containing air under a given pressure; b is the diaphragm against
which the air, allowed to escape by the valve, acts, and t is the tension regulator to
transmit the electric pulsations, or a hearing resonant case may be applied at the
same place.
Many curious and useful features have been developed by my extended researches
in the transmission and reproduction of sound. Among these may be mentioned
the fact that a copper diaphragm, or a diaphragm of mica or other flexible material
containing copper, will act with the core of a polarized electro-magnet in trans..
nitting or receiving.
If a diaphragm with a metallic button upon it is so close to the core of a per-
mancut magnet, see Fig. 21, that the vibrations of the diaphragm by sound cause
such button to strike the core, a corresponding electric pulsation will be set up in
a helix around the magnet, and the same will act in an electro-magnet at the
distant instrument by molecular disturbance.
If the diaphragm 10 has a thin tube attached to the center, as seen in Fig. 22,
and this project into the helix around one pole of magnet 48, the current set up in
that helix by the vibration of the diaphragm and tube will be much greater than
that resulting from a flat armature on the diaphragin or the diaphragm itself.
The magnet 48 may be polarized by a helix and a local circuit and battery.
If one pole of the permanent magnet m³, Fig. 23, is connected with the plate c
so that the latter is polarized by induction, the current set up in the helix around
one pole of the said magnet is intensified. In this case I groove the end of the
helix pole, and insert a small piece of soft rubber or tubing that serves to dampen
the vibrations of the diaphragm, and prevent false or harmonic vibrations in
speaking.
Fig. 24 represents the diaphragm 10, tension regulator t with its adjusting screw
and local circuit containing the battery B, passing through a primary induction
coil 49, and there is a key 50 in the same circuit. A secondary induction coil 51 is
in the line circuit, and is influenced electrically by the change of tension in the
local circuit, by the vibrations of the diaphragın 10.
The secondary coil is sometimes required with many layers of fine wire to set
up a current of high tension to overcome the inductive effect from the line wires,
being adjacent to each other. I place the receiving instrument at the distant
station between the induction coil and the earth as at R, and use an electro-magnet
E, M, with polarized armature to strike a bell; this will respond when the key 50
in the local circuit at the distant station is opened and closed.
In Fig. 25 a similar induction coil 49 and local circuit is represented, but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes,
A shunt and rheostat
one on the diaphragm, the other on the adjusting screw.
at R¹ serves to prolong the magnetism in the induction coil, and thus ensure a
gradual rise and fall of electric tension in the line instead of a cessation of the
same when the platina surfaces separate, and at the receiving diaphragm c, the rise
and fall of electric tension in the line and its helix acts upon the permanent inagnet
to produce the vibrations of the diaphragm c, and by connecting a shunt around

page_text: e helix, and placing therein the secondary battery S, B, composed of metamic
lates in acidulated water, the action is rendered more uniform and the sound
istinct.
When the diaphragm is arranged as in Fig. 26 to act upon a spring 56, through
n intervening piece of soft rubber, said spring 56 produces rise and fall of electric
ension by employing a range of resistances 57 with spring tongues adjacent to 56.
The greater amplitude of vibration of the diaphragm the more direct will be the
electric circuit connections and the less resistance, because the circuit will pass
along the spring instead of going through all the resistance coils.
When there is an electro-phorous or resinous disk 58, immediately facing each
diaphragm 10, as in Fig. 27, and the line connections are made to the diaphragm,
and the earth connections are made to these electro-phorous disks 58, the diaphragms
will respond to each other in either speaking or hearing.
Where several line wires run near each other, the wire used for the acoustic or
speaking telegraph is influenced by induction, and false sounds will be produced. I
counteract this tendency by placing one or more electro-magnets 59, Fig. 28, in the
circuit of the speaking telegraph, and one or more electro-magnets 60 in the circuit
of the adjacent wires, and bringing the opposite cores of 60 at such a distance
from the cores of 59 that a certain magnetic action will be set up in 59, by
induction in the opposite direction to the induction currents from the adjacent line
or lines.
By adjusting the distance between these magnets when the speaking telegraph
is not in use, until there is not any sound at the diaphragm from the induction
currents, then these currents will be neutralized, whether strong or weak, and
will not produce any false sounds when the speaking telegraph is in use.
I also employ double coils of wire for the same purpose, one coil being in the
acoustic wire, and the other in the wire to be compensated.
A convenient form for the sound recorder or phonograph is to employ a cylinder
61, see Fig. 29, having a helical groove in its surface covered with tin foil, and the
cylinder is revolved regularly by clockwork and moved endwise by a screw on its
shaft, so that the indenting point from the diaphragm 10 of h will be always in
line with such groove, hence the vibrations of the diaphragin will be recorded by
indeuting the foil into the groove, and hence the same sound will be reproduced by
the point of the hearing instrument n, giving to the diaphragm of n the motions
that result from the indentations of the foil moving in contact with such point.
The foil may be on a flat grooved plate and be indented and act as before-
nained.
I claim as my Invention,-
First. In an instrument for transmitting electric impulses by sound, a diaphragm
0 or tympan of mica, substantially as set forth.
Second. In an instrument for transmitting electric impulses by sound, the com-
bination with a diaphragın or tympan of an electric tension regulator for varying
the resistance in a closed circuit, substantially as set forth.
Third. The combination in an electric instrument actuated by sound, of a
5 diaphragm or tympan, a conductor, and an electric tension regulator composed of
yielding material and electric conducting material.
Fourth. The combination with the diaphragm and electric conductor, of the cork
disk and tension regulator, substantially as set forth.
Fifth. In a telegraph operated by sound, the transmission and reproduction of
50 the human voice by increasing and descreasing the resistance of the circuit, sub-
stantially as set forth.
55
Sixth. The combination with a diaphragm or tympan, of electrolytic fluid and
electrodes, the latter being vibrated by the diaphragin and varying the resistance in
the electric circuit, substantially as set forth.
Seventh. In an instrument for transmitting sounds by electricity, a resonant
case having an opening or edge, against which the consonant sounds act, substan-
tially as set forth.

page_text: Eighth. In combination with the diaphragm or tympan and the electric tension
regulator, the adjusting screw or variable presser to regulate the resistance of the
tension regulator in the electric circuit, substantially as set forth.
Ninth. The combination with a diaphragm in a speaking telegraph instrument of
a moving surface, and a recording mechanism actuated by the diaphragm or tympan
substantially as set forth.
Tenth. The combination with a receiving diaphragm or tympan in a telegraph
.operated by sound, of a moving surface, a point, and a connection from the saine to
the diaphragm, substantially as set forth.
Eleventh. The combination in an instrument for receiving sounds electrically, of
an electro-magnet and armature plate, substantially as set forth.
Twelfth. The combination in the telegraphic circuit of two or more tympans, a
resonant box, and one or more circuit closers to each tympan, substantially as set
forth.
Thirteenth. The combination with the diaphragm of a resonant case, of circuit
connections at both sides of the diaphragm and a battery, substantially as shown
in Fig. 10.
Fourteenth. In a telegraph instrument operated by sound, a resonant box or
case, a diaphragm and flexible circuit connections, substantially as set forth,
whereby the instrument is made portable and can be placed to the mouth in
speaking.
Fifteenth. In a telegraphic instrument operated by sound, an electro-magnet and
resonant plate or diaphragm provided with a handle and flexible conductors, sub-
stantially as set forth.
Sixteenth. The receiving instrument consisting of an electro-magnet, a case, and
a loose metallic plate, arranged and operated substantially as set forth, to act as a
call or to receive the message.
Seventeenth. In a telegraphic apparatus operated by sound, one or more contact
points of yielding material that produce a rise and fall of tension proportioned to
the pressure exerted by the diaphragm, substantially as set forth.
Eighteenth. In a telegraphic apparatus operated by sound, a receiving instrument
provided with a resonant surface, in combination with a frictional surface moved
by power and acting in connection with the electric current to vibrate such resonant
receiver, and produce tones corresponding to those at the transmitting apparatus,
substantially as set forth,
Nineteenth. The combination with a thermo-clectric, pile of a vulcanite or hard
rubber diaphragm, substantially as set forth.
Twentieth. The method herein specified of recording the undulations of the
diaphragm or yielding material, and the reproduction of sound by such material
acting upon a diaphragm to communicate to the same vibrations similar to the
original ones, substantially as set forth.
Twenty-first. The combination with the diaphragm and tension regulator, of a
magnetized tongue and an iron plate upon the diaphragm, as set forth and shown
in Fig. 12.
Twenty-second. In combination with the diaphragm operated by sound, an
electro-magnet, a valve, and a chamber of compressed air or gases to reproduce
the sounds in louder tones.
Twenty-third. The method herein specified of preparing fiber for electric tension
regulators by conducting or semi-conducting material associated intimately with
such fiber, substantially as set forth.
Twenty-fourth. In an instrument for receiving sound telegraphically, a plate,
loose at its edges, and supported upon a post or standard, substantially as set
forth.
Twenty-fifth. The combination with the sending and receiving diaphragm of the
dry pile illustrated in Fig. 19.
Twenty-sixth. The combination in a telephonic instrument, of an iron diaphragm
E

page_text: and a magnet, one end of which is attached to the magnet, substantially as
specified.
Twenty-seventh. The combination with the electric circuit and a diaphragm of
an induction coil and magnet, substantially as set forth.
Twenty-eighth. The combination with the induction coil, diaphragin, and local
circuit of a key in said circuit, and a call or sounder at the distant station, sub-
stantially as set forth.
Twenty-ninth. The combination with a diaphragin of rheostats or resistances in
the line or local circuit, and means for short circuiting such resistances in proportion
to the movement of the diaphragm, substantially as set forth.
Thirtieth. In combination with an electric circuit containing instruments for
reproducing sound, one or more electro-magnets and one or more compensating
inagnets for neutralizing the inductive effect of adjacent telegraph wires, substan-
tially as set forth.
In witness whereof, I, the said Thomas Alva Edison, have hereunto set my
1977
THOMAS ALVA. EDISON. (L.S.)
Witnesses,
CHA. H. SMITH, 76, Chambers St., New York.
WILLIAM G. MOTT,
"
"
"

page_text: LETTERS PATENT to Thomas Alva Edison, of Menlo Park, in the State of New
"IMPROVEMENTS IN
Jersey, United States of America, for the Invention of
INSTRUMENTS FOR CONTROLING BY SOUND THE TRANSMISSION OF ELECTRIC
CURRENTS, AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT A
DISTANC"
Sealed the 20th October 1877, and dated the 30th July 1877.
PROVISIONAL SPECIFICATION left by the said Thomas Alva Edison at the
Office of the Commissioners of Patents on the 30th July 1877.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United States
of America. "IMPROVEMENTS IN INSTRUMENTS FOR CONTROLING BY SOUND THE
TRANSMISSION OF ELECTRIC CURRENTS, AND THE REPRODUCTION OF CORRESPONDING
SOUNDS AT A DISTANCE."
The vibrations of the atmosphere, which result from the human voice or from
any musical instrument or otherwise, are made to act in increasing or lessening the
electric force upon a line by opening or closing the circuit, or increasing or
lessening the intimacy of contact between conducting surfaces placed in the circuit
at the receiving station; the electric action in one or more electro-magnets causes
a vibration in a tympan, or other instrument similar to a drum, and produces a
sound, but this sound is greatly augmented by mechanical action.
I have discovered that the friction of a point or surface, that is in contact,
whether a properly prepared and slowly moving surface, is very much increased
or lessened by the strength of the electric wave passing at such point of contact,
and from this variation in the friction a greater or less vibration is given to
the mechanism or means that produce or develope the sound at the receiving
station, thereby rendering clear and distinct the sound received that otherwise
would not be audible.
To carry out the peculiarities of my Invention under the varying conditions of
use, I have devised several modifications of the transmitting, receiving, and
intensifying devises employed in this sound telegraph; portions of the apparatus

page_text: are interchangeably, available in transmitting or recording; others are adapted to
local use; some are only available in transmitting, and others are only for receiving;
and some portions of my improvement can be availed of to make a record of the
atmospheric sound waves, or of the electric waves, or pulsations corresponding thereto
or resulting therefrom.
In one form of my apparatus the sound passes into a resonant box having one,
two, or more tympans at its sides that are vibrated thereby, the tension of these
being various, so as to respond to different sound waves, and the electric connections
pass through all to one line or circuit, in which is a battery and the distant
receiving instrument. Circuit contact points are provided at one or both surfaces
of the tympan or tympans; the tympans are of parchment, foil, mica, sheet metal,
or similar material. I find platinum, foil, or mica to respond advantageously when
the waves from the mouth are made to pass through a slot resembling the larynx
placed within the resonant tube. The contact points or surfaces are sometimes
metallic, but plumbago, or similar semi-conducting material, into which the tympan or
diaphragm is brought more or less intermittently into contact, or a point or pin
thereon serves to lessen or increase the electricity passing at that point.
In the receiving portion of the instrument the tympan is acted upon directly by
an electro-magnet, or through an armature, or the tympan is provided with an arm
extending out over a slowly moving surface or cylinder, and the electric current,
passing at the point of contact, increases or lessens the friction, and produces the
vibration of the arm and tympan in proportion to the difference of friction
developed between the arm and moving surface by the passage and cessation of
the current through the chemically prepared paper, preferably moistened with a salt
of mercury and an alkali. This feature is capable of very extended developement
in telegraphy; the clearness and extent of sound produced by the receiving tympan
exceeds anything heretofore attained in acoustic telegraphs.
The frictional surface may be any material which absorbs liquids, such as chalk
or paper; the transmitting points in all instances should be a poor conductor of
electricity, such as cyanide of copper, peroxide of lead, or plumbago, which
substance may be moulded with non-conductors.
Where plumbago is used between the cores and armature of an electro-magnet,
and such plumbago is included in a local or relay circuit, the pulsations or rise and
fall of electric tension will correspond to that in the coils of the electro-magnet in
consequence of the varying compressing action on the plumbago or similar material,
which increases and decreases its resistance.
A polarized arm, near a soft iron plate upon the tympan, will receive a motion
from the vibration of the tympan, and make more or less intimate contact with the
plumbago point without arresting the motion of such tympan.
In the line the effect of the static charges and discharges are neutralized by
condensers or by helices in shunts.
Where a rapidly revolving wheel is contiguous to the transmitting tympan,
and there is a plate of platina on that tympan to which the circuit is connected, the
rise and fall of electric tension will result accurately from the movement of the
tympan, producing greater or less contact with the wheel; a spring may intervene
between the wheel and tympan.
A spring or reed, attached to a stud at one end, and to the tympan at the other,
is vibrated or undulated by the sound waves acting on the tympan, and produces
greater or less contact with pieces of tin foil surrounding it, which also are in the
electric circuit or plumbago; contact points near the side of such spring effect the
same object. A column formed of disks of tin foil in a glass tube, pressed upon by
the vibrations of the tympan, also are employed under some circumstances to
regulate the electric tension in the circuit.
The moving surface, whose friction is increased or decreased upon the passage and
cessation of the current aforesaid, is employed in some instances to vibrate by the
electric and mechanical action a frame of strings of different pitch to produce
musical sounds, or to give motion to reeds or resonant boxes.

page_text: The transmitting tympan is sometimes made of cloth, with plumbago pressed into
its surfaces, and generally it is preferable to weight the centre of the tympan, and
take the motion a little one side of the centre to prevent a flase movement or
rebound. These sound transmitting and receiving instruments are applied in single
or multipleyd telegraphs; the connections through the Wheatstone bridge, or the
induction coils, being used in the well known ways, and the circuits being
either single or relays.
Where alluminium is introduced in the electric circuit in connection with a
material containing an electrolite, the vibration of the tympan, and an extension
from it to the material containing the electrolite, causes a depolarization at the
point of contact at every vibration, thus increasing and decreasing the strength of
the current by depolarization.
Where a slot is made in the diaphragm, and the airways impinge against the
same, the vibration of the hissing sounds is augmented.
The resonant chamber for convenience is made portable, so as to be presented to
the mouth.
In addition to the tympan for transmitting the vowel sounds, I employ another
opening in the speaking tube or chamber, which opening may be increased or
lessened; I stretch edgewise over this a thin reed of foil, which is set in vibration
by all hissing consonants, and make contact with a plumbago point, or with a
platina point, which is connected to the line through an adjustable resistance coil,
or a self-acting reed giving a hiss may be thrown in and out of circuit by the
movement of the foil reed.
For transmitting and receiving letter by letter, I employ a shaft with 30 wheels,
and contact springs resting upon them; the wheels are provided with teeth of such
number and character that they will cause the springs to be vibrated against a
plumbago point the necessary number of times, and with proper pressure to transmit
the letter, which is rendered audible at the distant station by the magnet or
frictional surface. Each wheel is controlled by a key of a key board.

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 30th
January 1878.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United States
of America. "IMPROVEMENTS IN INSTRUMENTS FOR CONTROLING BY SOUND THE
TRANSMISSION OF ELECTRIC CURRENTS, AND THE REPRODUCTION OF CORRESPONDING
SOUNDS AT A DISTANCE."
This Invention relates to that class of electrical instruments in which sound
becomes one of the elements in the transmission of the communication, and the
same sound is produced at the receiving station, so that oral communications can
be sent by electricity and clearly distinguished at the receiving station.
Musical tones may also be sent, but my present Invention is especially available
in transmitting and receiving oral communications.
In transmitting musical tones, the respective notes each have a definite period for
each vibration, hence there is a response at the receiving end from the notes that
vibrate in time with the electric pulsations sent, but in speaking there is little
change in the musical tone, but considerable in the modulations and inflections of
the voice.
In my present Invention I make use of the vibrations given to a diaphragm or
tympan, by speaking into a resonant case, to produce a rise and fall of electrical
tension upon the line with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation, and the electro-
magnet at the receiving station will respond to the electric waves in such a manner
as to reproduce the articulation by acting upon a resonant plate.
The instruments in a complete form are represented in Figs. 1 and 2, Fig. 1 being
a section of the transmitting instrument, and Fig. 2 of the receiving instrument.
The resonant tube or box a is of a size and shape adapted to being spoken into,
the same having an opening at one end or side and a diaphragm or diaphragms b,
against which the sound waves from the human voice act, and these and the motion
that the diaphragm receives is the means of producing a rise and fall of electric
tension on the line by the devices hereafter set forth, so that the battery B connected
to the line will transmit a greater or less current to the distant electro-magnet m,
Fig. 2, and increase or lessen the magnetism of the cores, and in so doing act upon
a resonant plate c, and develop sound corresponding to the articulation at the trans-
mitting station.
The general features thus described pervade my entire Invention, but in de-
veloping the same many useful and important modifications and variations have
been made, which I will proceed to set forth.
For convenience the speaking instrument, Fig. 1, is provided with a handle, a',
and flexible conductors to the battery and line respectively, so that it may be
handled and brought to the mouth; and in like manner it is preferable to place the
hearing instrument, Fig. 2, in a movable handle b', so that it can be placed with
the plate c against the ear, this brings the sound close to the organs of hearing, and
the resonant plate touching the ear increases the distinctness of the sound, and
prevents any false or prolonged vibrations of the plate.
In some of the modifications I have shown the speaking instrument as a fixture,
and also the hearing instrument as a fixed resonant tube, these being variable to
suit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity of
the resonant tube for the voice. I have experienced great difficulty in reproducing
the sound of the hissing consonants, such as 8; this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth, and does not act
distinctly upon the diaphragm. By providing an edge in the resonant tube
below the mouth, upon which such consonant sounds are received, the vibrations

page_text: are given either to the resonant tube or deflected to the diaphragm. I find it
preferable to employ a hole e at the lower part of the mouth-piece, against the edges
of which the downward sound waves are directed. The same effect will be pro-
duced by a vibrating edge placed in the lower part of the mouth-piece, or the
opening into the resonant box may be contracted to about half an inch in diameter
to effect the same purpose. The next feature requiring consideration is the character
of the diaphragm in the speaking instrument.
Many materials have been employed by me, such as metals, horn, vellum, celluloid,
ivory, &c., but almost all of these produce a prolonged or secondary vibration from
their own resonant character, hence the articulation is defective, and the sound
vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
resonant action, and hence it will respond with the greatest accuracy to the sound
vibrations, and being of a laminated character can be employed of any desired thick-
ness, and when secured at its edges responds with the greatest accuracy to the sound
vibrations, and does not require to be strained; furthermore, the changes of tempera-
ture and atmospheric condition have little or no effect upon the mica diaphragm or
tympan.
I find that it is not practical to open and close the line circuit in instruments
for transmitting the human voice; the circuit to the line must be always closed,
and the transmission be produced by a rise and fall of electric tension, resulting
from more or less resistance in the line. This resistance may be produced in
several ways. I have shown several which will hereafter be nained, but I find the
most delicate to be small bunches or tufts, or disks of semi-conducting elastic fiber,
such as particles of silk, and an intermediate conducting or semi-conducting material;
this device call an electric tension regulator; it is more or less compressed, according
to the vibrations of the diaphragm or tympan, and the electric current rises in
tension as it is compressed or lessens as the fiber expands. This fiber is placed in a
small roll t, between the delicate diaphragm spring u, Fig. 9, and the variable
presser v, adjustable by a screw or otherwise in the electric circuit at this point, or
it may be within a cavity in said presser v, as in Fig. 1, there being a delicate cork
center piece w to the diaphragm b, with a piece of platina foil x in contact with the
fiber;
in all instances the telegraphic circuit at the diaphragm is made by a thin
strip of platina or similar material extending to the center from the line or battery
connection.
The fiber is rendered semi-conductive by being rubbed with plumbago, soft
metal, or similar material, or by a deposit of metal upon its surface, or by fine
particles of conducting or semi-conducting material mixed with it, the conducting.
power varying with the density of the tuft or bunch of fiber.
The delicate spring
u, Fig. 9, npon the mica diaphragm b is easily secured by solder passing into fine
holes bored in the mica. In Fig. 3 the tension regulator is made by water or other
semi-conducting electrolytic fluid in a cup f. The wires to the battery are led to
the electrodes or conducting points 2, 3, in such cup that are opposite to points 4, 5,
upon the diaphragm b. The cup is adjustable to vary the distance between the
electrodes and the rise and fall of tension results from the varying distance between
the electrodes as moved by the vibrations of the diaphragm.
If there are several electrodes opposite to each other and insulated, except at
their ends, and the circuit led from one to the other so that the current passes
through all the electrodes in succession, the rise and fall of electric tension will be
promoted, because the smallest vibration of one set of electrodes is multiplied by
the number of places at which the metallic circuit is interrupted or varied.
In the receiving or hearing instrument the resonant plate c should be of tinned
iron, resting upon the edges of the case, and the magnet m, adjustable nearer to or
further froin the same, and connected loosely by slotted tongues. This plate will
respond to the electric pulsations by the attraction of the magnetized cores, and the
sound resulting will be audible when the plate is placed near or against the ear. If
the plate, is pressed away from the magnet by a delicate spring or allowed to fall

page_text: away from the magnet, the instrument may be used as a call by using a key or
switch at the sending station to open and close the circuit, and thus move the plate
to give a loud sound.
In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact such as would result from a disk covered with plumbago
placed adjacent to a diaphragm, also covered with plumbago or other semi-con-
ducting material, so that the proximity or extent of surface contact will produce rise
I also
and fall of tension, the respective parts being in the telegraphic circuit.
sometimes employ a shunt circuit in the line, or a branch circuit to the earth, in
which is placed an electro-magnet to neutralize any static charge or discharge in
the line.
I sometimes perforate the diaphragm 10, Fig. 18, and place a strip of elastic
material, 40, across said diaphragm over the hole, and upon this a piece of foil, so
that the same responds to very weak vibrations, and in some instances two or more
diaphragms are provided at different sides of the resonant box, each with its own
tension regulator, the diaphragms being either the same or of different sizes,
characters, or tensions, so as to respond to varying sounds or acoustic condition, the
various tension regulators being all in the electric circuit; this will produce greater
rise and fall of tension for longer lines in consequence of the diaphragms acting
simultaneously on the tension regulators.
In some instances it is preferable to make the mouth-piece of the speaking
instrument sufficiently large or flaring to receive all the sound vibrations, whether
coming from the mouth, nose, or throat.
Several contact points of platina, placed contiguous to the diaphragm, may be
used, the same acting to increase or lessen the surface contact, according to the
amplitude of vibration of the diaphragm, and a drop of liquid such as oil or
glycerine, between the contact point and diaphragm, will serve to maintain a closed
circuit, but the movement of the diaphragm produces rise and fall of tension.
The tension regulator, formed of fiber and conducting or semi-conducting material,
may be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within a
case to form the tension regulator, the circuit passing through the same, and the rise
and fall of electric tension resulting from the compression of the same by the move-
ment of the diaphragm.
I am enabled to record to record the sounds produced by the human voice or other-
wise by causing the movements of the diaphragin to be registered on paper or soft sheet
metal, and then the paper may be used in an instrument to reproduce the sound upon
a delicate diaphragm by giving to the same a vibration similar to that originally
given by the voice.
h, Fig. 4, is the indenting transmitter, the diaphragm having a knife-edge point.
i is the paper which has previously been passed through a machine to raise a V shaped
rib 6. The movement of the diaphragm of h, when the drum is in motion, causes
the knife-edge point l' to indent the raised rib to varying depths, according to the
amplitude of vibration of the diaphragm, thus these indentations represent accurately
all the tones and varying inflections of the human voice. The paper after being
indented is passed through a second apparatus n, Fig. 5, almost similar to h. A
spring 9 has a knife edge which rest upon the raised indented rib 6, the spring
being connected to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting point,
and either by direct action, or through the vibration of a string, conveys the same
motion to the diaphragm of n, and reproduces previous sounds. If these sounds
are to be transmitted over a telegraph line the diaphragm 10, see Fig. 6, is pro-
vided with a cork disk w, and fibrous tension regulator t, before described, to
produce the rise and fall of electric tension on the line. The sound may be recorded
in ink as represented in Fig. 7. The diaphragm of h operates a very flexible self-
feeding pen o, and causes the continuous line to be wide or narrow, according to
the amplitude of vibration of the diaphragm. The ink used should dry quickly,

page_text: and the strip may be passed at any time thereafter through the instrument shown
in Fig. 8, beneath the arm 12, having a point or points resting on the paper; this
arm is connected with a resonant diaphragm, and the ink marks produce more or
less friction, according to the breadth and amount of ink deposited, and this will
set the diaphragm of n vibrating, and reproduce the vibrations of the diaphragm
of h.
An obvious modification would be to coat the paper with a substance which would
cause considerable friction, or even rough unsized paper might be used, and a spring
provided with a burnished point, rather flat, would cause the surface of the paper
to be made smooth more or less, according to the vibration of the diaphragm, and
the differences in the surface of the paper would produce a response in the receiving
diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument,
as shown in Fig. 10.
h is the resonant chamber at the end of which is the diaphragm 10, and at each
side of this diaphragm there are springs c², c³, having points made of compressed
plumbago mixed preferably with gum rubber, but any substance not liable to
rapid decomposition, or the elastic or fibrous tension regulator aforesaid may be
used. These points face each other on opposite sides of the diaphragm, and make
contact with platina foil disks secured to the diaphragm.
The spring c² passes through a hole or small slot in the side of the chamber h.
d2, ds, are the main batteries. The battery d² has zinc to the line or spring c²,
and the battery d³ has copper to the line or spring c³. When the springs c² and c³.
are adjusted to make contact with the diaphragm equally, no current passes to the
line; but when the diaphragm is vibrated, its movement to one side, say c², causes
a greater pressure upon the plumbago on that spring, and a lessening of the pressure
on the plumbago on c³; hence the balance of the batteries c² and c³ will be destroyed,
c², having the advantage, will send a negative current to line; upon the return of
the diaphragm the battery currents will again neutralize each other. The vibration
of the diaphragm to the other side causes the pressure to be reversed, and the
battery d³ will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure, it follows that the
strength of the electric waves will be in proportion as the speaker's voice is strong
or weak.
In Fig. 11 is shown the contact spring, which may be used adjacent to the
diaphragm at one or both sides thereof. e is a U shaped spring secured to the
screw e, which is adjusted back and forth by the thumb nut e; e is the pillar
holding such screw; r is a piece of soft rubber, or equivalent substance, placed
between the prongs of the spring e³; e7 is a wire or band which serves to bind the
prongs tightly against the rubber r, so as to prevent the prongs acting as a tuning
fork, and transmitting harmonic vibrations not desirable; 72 is the plumbago
contact point. The object of the U spring and rubber is to present a semi-rigid
point for contact, so as to prevent a rebound, and allow of a slight yield when the
plumbago is pressed by the diaphragm.
In Fig. 3 the diaphragm of the receiving instrument is vibrated by a strip of
paper chemically prepared that is in motion, the pulsations of electricity passing
over the line and producing more or less friction between the paper and an arm
upon the diaphragm.
The resonant box or chamber n is provided with a diaphragm as aforesaid, and
to said diaphragm an arm h² is connected; at its outer end is an adjusting screw h³,
that presses upon a platina-faced spring 4 that is secured to this arm, and said
spring rests upon the strip of paper that passes over the drum h³.
The paper is moved slowly by rotating the drum h³, and the waves of electricity
coming over the line pass through the arm h² to the platina-faced spring h*, thence
through the paper to the earth.
If a negative current passes in the opposite direction, nearly all friction between

page_text: the platina plate and the paper ceases, and the diaphragm of the resonant box n
regains its normal position.
When the positive current passes through the same channel, the normal friction
of the paper is augmented, and the chemical surface acting upon the platina
spring arm serves to give a forward movement to the diaphragm of the resonant
box.
Thus the mechanical force applied to move the chemical paper or surface acts with
the electric current to produce the vibration of the diaphragm of the resonant
chamber, and these vibrations will correspond to those of the diaphragm b, made by
speaking in the tube a.
The principle of this method of obtaining motion by electro-chemical decom-
position is, that when a moving surface is in contact with a slightly yielding
substance, the tendency is to move the latter by and with the former. If the
circumstances of contact are varied, the adhesion of the surfaces will be sufficient to
cause the moving surface to move the yielding substance, or else to cause the
yielding surface to slip more freely, and by its spring go in the opposite direction to
the moving surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion, making it more or less, according to the substances employed. By
balancing the mechanical forces, so that when the surfaces in contact are not
electrified, the moving surface carries with it the yielding surface; and, when
electrified, the yielding surface slips back over the moving surface, a mechanical
movement is obtained that is dependent on the electrical condition of the surfaces
in contact.
When it is requisite to obtain very perfect articulation, and when loudness is not
essential, I adopt a modification, shown in Fig. 12, of the device for compressing
and expanding the tuft of conducting fiber, which modification consists in placing
between the diaphragm 10 and the fiber t a vibrating tongue 21 of steel, permanently
magnetized, and arranging it to act in the same manner upon the tension regulator t
as if it was the diaphragm. I replace the cork upon the diaphragm by a thin
armature of iron 22 which is in close proximity to the magnetized tongue, which
tongue is secured at one end like an acoustic reed. In this position the diaphragm
is free to move, and at its approach to and recession from the magnetized tongue
causes said tongue to follow its movements by magnetic attraction, and thus the
tongue is made to perform what the diaphragm previously performed in varying
the tension of the electricity on the line.
A modification of the magnetic receiving instrument consists in an iron plate
fitted into the aperture of a resonant tube, and secured by a central support, leaving
its outer circumference free to vibrate when the metal is attracted by the poles of
the electro-magnet, which are of course on each side of its center; but it is
preferable to place the support slightly out of center, as some portions of the plate
will then be in tone for every sound.
A plate supported eccentrically and free at its edges when placed in the speaking
tube responds advantageously to the tones of the voice; the circuit with this plate
is completed through one or more tension regulators placed around its edges.
I have discovered that vulcanite or hard rubber produces cold and heat waves on
its surface by the slightest movement, and in some cases I employ the same for the
diaphragm of the resonant case h, Fig. 13, and place a thermo-electric pile h' in
very close proximity to the rubber, so that the vibration of the diaphragm 10
producing changes of temperature will cause currents of electricity to be set up
within the thermo battery, and these passing over the line and acting upon a very
delicate electro-magnet and diaphragm will reproduce the sounds acting upon the
rubber diaphragm.
In practice I combine with the speaking or telephonic apparatus signal bells, so
-arranged that when the telephone is not in use the line is thrown upon the bell by
a switch, which also acts as a call on the bell.
... One feature about the bells is that the magnet which serves to actuate the bells

page_text: is made of very high resistance, using preferably German silver wire in the helix,
and thus serve to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from one battery if these bells are used.
The method I adopt for coating non-conducting substance with metallic substance
is the reduction to the metallic state of metals from their salts by exposing them to
the fumes which arise from the moist phosphide of a metal, such as phosphide of
calcium, or by placing the silk, for instance, in a sealed tube provided with inetallic
electrodes, and volatilizing the electrodes by the passage of electric sparks; such
volatilized metals settle upon and coat the silk.
When great loudness is desirable, as in factories, the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is stored
under a regulated pressure.
The air allowed to escape will act with great power upon a local diaphragm.
This diaphragm, to obtain clear sounds, requires a damper to check prolonged
vibrations. It must be dampened by holding the fingers against it, or by a tightly-
stretched cord rubbing against it, or by a screw provided with a rubber tip held
against it.
For repeating from one circuit into another I use with the receiving diaphragm
the elastic tension regulator Fig. 1 in addition to the electro-magnet, and connect
the relay or second circuit through the same, so that waves received from the distant
station cause the magnet to vibrate the diaphragm, and this acting upon the tension
regulator transmits the waves into the second circuit, and they are received at the
other end by an electro-magnet and diaphragm.
In some instances I make a record of the sound by the movements of the
diaphragm, using for that purpose a strip of paper moved along regularly between
two rollers 25, 26, as in Figs. 14 and 15; and there is a smooth thread or fine wire
of soft metal 30 between the paper and the upper roller 25, and moving along with
it. The diaphragm 10 of the resonant box is connected by a delicate rod 28 with
this thread or wire as near to the bight of the roller as possible, there being a fork
or eye through which the thread passes, hence deflections or bends are made in the
thread or wire just before it is imbedded into the paper by the pressure of the
rollers; this may be used to reproduce the sound by vibrating a resonant diaphragm
by the undulations of the groove made by the thread or cord.
By placing the fibrous tension regulator within a small band of india-rubber the
same is rendered more elastic, and the fiber is allowed to expand by the heat of the
current without altering the electric tension.
In cases where a strip of hard rubber or a cord of silk or other material coated
with plumbago or metallic foil is introduced between the diaphragm and a rigid
support, the expansion and contraction due to the passage of the electric currents
will produce a movement upon the diaphragm corresponding to the diaphragm
producing the electric pulsations.
In some instances the diaphragm should be free to vibrate without being checked
by contact with any stationary substance. I provide for this by placing upon the
diaphragm or tympan 10, Fig. 17, a small cylinder of hard rubber or non-
conducting material, within which is the fibrous tension regulator t resting upon a
piece of platina foil connected to one pole of the battery, and within this cylinder t'
is a disk 10 of iron or other metal, loose, but pressed towards the tension regulator
by a spring to and screw cap t³, and the other electric conductor is connected with
said spring.
The inertia of the metal disk causes more or less compression of the tension
regulator as the diaphragm is vibrated, and hence the electric pulsations are sent
over the line in harmony with the vibrations. Nearly the same effect is produced
by connecting the disk to to a yielding spring t" that extends across from one edge
of the diaphragm to the other, as seen in Fig. 16. This construction of tension
regulating device is especially available with large diaphragms.
In some cases I use a soft rubber diaphragm immediately in contact with the

page_text: transmitting or receiving diaphragm, so as to check or dampen any prolonged or
false vibration, and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable to
use lampblack mixed with pure plumbago, amorphous phosphorous, and a very
small amount of non-conducting material, such as rubber dissolved in a solvent
that will entirely evaporate.
In Fig. 19, I have represented the circuit as passing through the diaphragm 10,
tension regulator t, and a Dulucs dry pile battery D, P, B, to the earth. This battery
is composed of about 300 pairs of paper disks coated with silver and black oxyd of
manganese.
Fig. 20 illustrates the device before mentioned for intensifying the sound; 10 is
the diaphragm vibrated by the sound; 42 is a valve moved by such diaphragm;
43, is a reservoir containing air under a given pressure; b is the diaphragm against
which the air, allowed to escape by the valve, acts, and t is the tension regulator to
transmit the electric pulsations, or a hearing resonant case may be applied at the
same place.
Many curious and useful features have been developed by my extended researches
in the transmission and reproduction of sound. Among these may be mentioned
the fact that a copper diaphragm, or a diaphragm of mica or other flexible material
containing copper, will act with the core of a polarized electro-magnet in trans-
mitting or receiving.
If a diaphragm with a metallic button upon it is so close to the core of a per-
manent magnet, see Fig. 21, that the vibrations of the diaphragm by sound cause
such button to strike the core, a corresponding electric pulsation will be set up in
a 'helix around the magnet, and the same will act in an electro-magnet at the
distant instrument by molecular disturbance.
If the diaphragm 10 has a thin tube attached to the center, as seen in Fig. 22,
and this project into the helix around one pole of magnet 48, the current set up in
that helix by the vibration of the diaphragm and tube, will be much greater than
that resulting from a flat armature on the diaphragm or the diaphragm itself.
The magnet 48 may be polarized by a helix and a local circuit and battery.
If one pole of the permanent magnet m³, Fig. 23, is connected with the plate c
so that the latter is polarized by induction, the current set up in the helix around
one pole of the said magnet is intensified. In this case I groove the end of the
helix pole, and insert a small piece of soft rubber or tubing that serves to dampen
the vibrations of the diaphragm, and prevent false or harmonic vibrations in
speaking.
Fig. 24 represents the diaphragm 10, tension regulator t with its adjusting screw
and local circuit containing the battery B, passing through a primary induction
coil 49, and there is a key 50 in the same circuit. A secondary induction coil 51 is
in the line circuit, and is influenced electrically by the change of tension in the
local circuit by the vibrations of the diaphragm 10.
The secondary coil is sometimes required with many layers of fine wire to set
up a current of high tension to overcome the inductive effect from the line wires,
being adjacent to each other. I place the receiving instrument at the distant
station between the induction coil and the earth as at R, and use an electro-magnet
E, M, with polarized armature to strike a bell; this will respond when the key 50
in the local circuit at the distant station is opened and closed.
In Fig. 25 a similar induction coil 49 and local circuit is represented, but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes,
A shunt and rheostat
one on the diaphragm, the other on the adjusting screw.
at R¹ serves to prolong the magnetism in the induction coil, and thus ensure a
gradual rise and fall of electric tension in the line instead of a cessation of the
same when the platina surfaces separate, and at the receiving diaphragm c, the rise
and fall of electric tension in the line and its helix acts upon the permanent magnet
to produce the vibrations of the diaphragm c, and by connecting a shunt around

page_text: the helix, and placing therein the secondary battery S, B, composed of metallic
plates in acidulated water, the action is rendered more uniform and the sound
distinct.
When the diaphragm is arranged as in Fig. 26 to act upon a spring 56, through
an intervening piece of soft rubber, said spring 56 produces rise and fall of electric
tension by employing a range of resistances 57 with spring tongues adjacent to 56.
The greater amplitude of vibration of the diaphragm the more direct will be the
electric circuit connections and the less resistance, because the circuit will pass
along the spring instead of going through all the resistance coils.
When there is an electro-phorous or resinous disk 58, immediately facing each
diaphragm 10, as in Fig. 27, and the line connections are made to the diaphragm,
and the earth connections are made to these electro-phorous disks 58, the diaphragms
will respond to each other in either speaking or hearing.
Where several line wires run near each other, the wire used for the acoustic or
speaking telegraph is influenced by induction, and false sounds will be produced. I
counteract this tendency by placing one or more electro-magnets 59, Fig. 28, in the
circuit of the speaking telegraph, and one or more electro-magnets 60 in the circuit
of the adjacent wires, and bringing the opposite cores of 60 at such a distance
from the cores of 59 that a certain magnetic action will be set up in 59, by
induction in the opposite direction to the induction currents from the adjacent line
or lines.
By adjusting the distance between these magnets when the speaking telegraph
is not in use, until there is not any sound at the diaphragm from the induction
currents, then these currents will be neutralized, whether strong or weak, and
will not produce any false sounds when the speaking telegraph is in use.
I also employ double coils of wire for the same purpose, one coil being in the
acoustic wire, and the other in the wire to be compensated.
A convenient form for the sound recorder or phonograph is to employ a cylinder
G1, see Fig. 29, having a helical groove in its surface covered with tin foil, and the
cylinder is revolved regularly by clockwork and moved endwise by a screw on its
shaft, so that the indenting point from the diaphragm 10 of h will be always in
line with such groove, hence the vibrations of the diaphragm will be recorded by
indenting the foil into the groove, and hence the same sound will be reproduced by
the point of the hearing instrument n, giving to the diaphragmn of n the motions
that result from the indentations of the foil moving in contact with such point.
The foil may be on a flat grooved plate and be indented and act as before-
named.
I claim as my Invention,―
First. In an instrument for transmitting electric impulses by sound, a diaphragm
or tympan of mica, substantially as set forth.
Second. In an instrument for transmitting electric impulses by sound, the com-
bination with a diaphragm or tympan of an electric tension regulator for varying
the resistance in a closed circuit, substantially as set forth.
Third. The combination in an electric instrument actuated by sound, of a
diaphragm or tympan, a conductor, and an electric tension regulator composed of
yielding material and electric conducting material.
Fourth. The combination with the diaphragm and electric conductor, of the cork
disk and tension regulator, substantially as set forth.
Fifth. In a telegraph operated by sound, the transmission and reproduction of
the human voice by increasing and descreasing the resistance of the circuit, sub-
stantially as set forth.
Sixth. The combination with a diaphragm or tympan, of electrolytic fluid and
electrodes, the latter being vibrated by the diaphragm and varying the resistance in
the electric circuit, substantially as set forth.
Seventh. In an instrument for transmitting sounds by electricity, a resonant
case having an opening or edge, against which the consonant sounds act, substan-
tially as set forth.

page_text: Eighth. In combination with the diaphragm or tympan and the electric tension
regulator, the adjusting screw or variable presser to regulate the resistance of the
tension regulator in the electric circuit, substantially as set forth.
Ninth. The combination with a diaphragm in a speaking telegraph instrument of
a moving surface, and a recording mechanism actuated by the diaphragm or tympan,
substantially as set forth.
Tenth. The combination with a receiving diaphragm or tympan in a telegraph
operated by sound, of a moving surface, a point, and a connection from the saine to
the diaphragm, substantially as set forth.
Eleventh. The combination in an instrument for receiving sounds electrically, of
an electro-magnet and armature plate, substantially as set forth.
Twelfth. The combination in the telegraphic circuit of two or more tympans, a
resonant box, and one or more circuit closers to each tympan, substantially as set
forth.
Thirteenth. The combination with the diaphragm of a resonant case, of circuit
connections at both sides of the diaphragm and a battery, substantially as shown
in Fig. 10.
Fourteenth. In a telegraph instrument operated by sound, a resonant box or
case, a diaphragm and flexible circuit connections, substantially as set forth,
whereby the instrument is made portable and can be placed to the mouth in
speaking.
Fifteenth. In a telegraphic instrument operated by sound, an electro-magnet and
resonant plate or diaphragm provided with a handle and flexible conductors, sub-
stantially as set forth.
Sixteenth. The receiving instrument consisting of an electro-magnet, a case, and
a loose metallic plate, arranged and operated substantially as set forth, to act as a
call or to receive the message.
Seventeenth. In a telegraphic apparatus operated by sound, one or more contact
points of yielding material that produce a rise and fall of tension proportioned to
the pressure exerted by the diaphragm, substantially as set forth.
Eighteenth. In a telegraphic apparatus operated by sound, a receiving instrument
provided with a resonant surface, in combination with a frictional surface moved
by power and acting in connection with the electric current to vibrate such resonant
receiver, and produce tones corresponding to those at the transmitting apparatus,
substantially as set forth,
Nineteenth. The combination with a thermo-electric, pile of a vulcanite or hard
rubber diaphragm, substantially as set forth.
Twentieth. The method herein specified of recording the undulations of the
diaphragm or yielding material, and the reproduction of sound by such material
acting upon a diaphragm to communicate to the same vibrations similar to the
original ones, substantially as set forth.
Twenty-first. The combination with the diaphragm and tension regulator, of a
magnetized tongue and an iron plate upon the diaphragm, as set forth and shown
in Fig. 12,
Twenty-second. In combination with the diaphragm operated by sound, an
electro-magnet, a valve, and a chamber of compressed air or gases to reproduce
the sounds in louder tones.
Twenty-third. The method herein specified of preparing fiber for electric tension
regulators by conducting or semi-conducting material associated intimately with
such fiber, substantially as set forth.
Twenty-fourth. In an instrument for receiving sound telegraphically, a plate,
loose at its edges, and supported upon a post or standard, substantially as set
forth.
Twenty-fifth. The combination with the sending and receiving diaphragm of the
dry pile illustrated in Fig. 19.
Twenty-sixth. The combination in a telephonic instrument, of an iron diaphragm

page_text: and a magnet, one end of which is attached to the magnet, substantially as
specified.
Twenty-seventh. The combination with the electric circuit and a diaphragm of
an induction coil and magnet, substantially as set forth.
Twenty-eighth. The combination with the induction coil, diaphragm, and local
circuit of a key in said circuit, and a call or sounder at the distant station, sub-
stantially as set forth.
Twenty-ninth. The combination with a diaphragm of rheostats or resistances in
the line or local circuit, and means for short circuiting such resistances in proportion
to the movement of the diaphragm, substantially as set forth.
Thirtieth. In combination with an electric circuit containing instruments for
reproducing sound, one or more electro-magnets and one or more compensating
inagnets for neutralizing the inductive effect of adjacent telegraph wires, substan-
tially as set forth.
In witness whereof, I, the said Thomas Alva Edison, have hereunto set my
hand and seal, this Twenty-fourth day of December, A.D. 1877.
THOMAS ALVA EDISON. (L.S.)
Witnesses,
CHA. H. SMITH, 76, Chambers St., New York.
WILLIAM G. MOTT,
"
"
"

page_text: Filed 10th February 1880.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, the Edison
Telephone Company of London, Limited, of 11, Queen Victoria Street, in the
City of London, send greeting:
WHEREAS Her Most Excellent Majesty, Queen Victoria, by Her Royal Letters
Patent, under the Great Seal of Great Britain and Ireland, bearing date at
Westminster, the Thirtieth day of July, in the Year of Our Lord, One thousand
eight hundred and seventy seven, in the Forty-first year of Her Reign, did for
Herself, Her heirs and successors, give and grant unto Thomas Alva Edison, of
Menlo Park, in the State of New Jersey, United States of America, his executors,
administrators, or assigns, or such others as he his executors, administrators, or
assigns should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention of "IMPROVEMENTS IN
INSTRUMENTS FOR CONTROLLING BY SOUND THE TRANSMISSION OF ELECTRIC
CURRENTS AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT A DISTANCE,"
for and during the term of Fourteen years thence next ensuing: And whereas in
pursuance and performance of a proviso in the said Letters Patent contained the
said Thomas Alva Edison did within Six calendar months next after the date of
the said Letters Patent cause a Specification in writing under his hand and seal
purporting to particularly describe the nature of the said Invention, and in what
manner the same was to be performed, to be duly filed in the Great Seal Patent
Office: And whereas by Indenture bearing date the Second day of August, One
thousand eight hundred and seventy nine, and made between the said Thomas
Alva Edison of the one part, and as the Edison Telephone Company of London,
Limited, of the other part, the said Thomas Alva Edison assigned unto us the said
Edison Telephone Company of London, Limited (inter alia), the said herein before
recited Letters Patent, and all rights, powers, authorities, privileges, advantages,

page_text: profits, emoluments, and benefits to the said Letters Patent, appertaining or
belonging And whereas since the date of the said Assignment we have been
advised and have ascertained that the said Specification contains matters which are
of doubtful novelty, or which are not of sufficient practical value and utility to
justify their retention; and we are therefore desirous of striking out the whole of
the claiming clauses contained in the said Specification, with the exception of the
first, second, eighteenth and twentieth claiming clauses, and of striking out parts of
the description contained in the body of the said Specification; and also of otherwise
altering the said Specification, and correcting certain clerical errors contained in the
said Specification in manner more fully hereafter appearing.
NOW KNOW YE, that we the said Edison Telephone Company of London
Limited, by and with the leave of Her Majesty's Attorney General, and for the reasons
aforesaid do alter the said Specification, by striking out of the said Specification
printed by the Queen's Printers, and published at the Great Seal Patent Office in
One thousand eight hundred and seventy nine, the words "the same" which
occur on page 4, at the end of line nine, and the beginning of line 10 respectively,
and substituting therefor the words "a corresponding"; we also strike out the
word "the" which occurs between the words "and" and "electro" on the said
page, line twenty two, and substitute therefor the word "an"; we also insert
between the words "the" and "instruments" which occur on the said page line
at the end
twenty five the word "transmitting" and we strike out the letter "s
of the said word "instruments"; we also strike out the word "are" which occurs
on the same line and substitute therefor the word "is"; We also insert between
the words "in" and "Figs." (an abbreviation of the word Figures) which occur on
the same line, the words "section in" and we strike out the letter "s" in the said
word "Figs"; we also strike out the words commencing with "and" on the said
line twenty five and ending with the first word "instrument" on line 26 of the
said page four we also strike out the words " of the " which occur between the
Figure "2" and the word "receiving" on the said line twenty six and substitute
therefor the words "represents a"; we also add after the word "instrument" at
the end of the said line twenty six the words "which may be employed with it";
we also strike out the word "the" at the commencement of line twenty seven on
the said page four and substitute therefor the words "referring to Figure 1 the ";
we also strike out that portion of the Specification commencing with the words
"in Fig" on page 5, line forty one, and ending with the word "sound" on page 6,
line three; we also strike out that portion of the Specification commencing with
the words "I also" at the end of line eight and ending with the words "the line
on line eleven of the said page 6; we also strike out the whole of lines twenty four
to twenty eight inclusive on the said page 6; we also strike out the words "to
record" which are repeated on line thirty five of the said page 6 and add the letter
"s" to the word "rest" which occurs on line forty seven of the said page 6.
We also strike out of page 8, lines thirty seven to forty two inclusive, and lines
forty six to fifty three inclusive. We also strike out of page 9 lines eighteen to
twenty three inclusive, and lines thirty seven to forty one inclusive. We also
strike out of page 10 lines seventeen to thirty seven inclusive. We also strike out
of page 11 lines ten to thirteen inclusive, and lines forty four to fifty seven
inclusive, and we add at the end of line thirty seven of the said page eleven after
the word "named" the words following: :-"I would observe in conclusion that ]
do not claim generally the transmission and reproduction of sounds by increasing
and decreasing the resistance of the circuit, nor do I claim separately any of the
parts or arrangements hereinbefore described and illustrated in the accompanying
we also strike out the word "an," which occurs between the words "of " and "electric" on line 42 of the said page 11, an
we add the letter "s" to the word "regulator," which occurs on the same line 42, to make it read "regulators," and afte
the said word "regulators " we insert the words "substantially as herein before described."
Drawings, except as hereinafter mentioned, but ." We also strike out of page 15
lines one to thirty inclusive, lines thirty six and thirty seven, and lines forty tw
to fifty six inclusive. We also strike out the word "eighteenth" which occurs a
the commencement of line thirty one on the said page 12, and substitute therefo
"

page_text: the word "third." We also strike out the word twentieth which occurs at the
commencement of.line thirty eight of the said page 12, and substitute therefor the
word "fourth." We also strike out the word "or" which occurs on line thirty
nine of the said page 12, and substitute therefor the word "on." We also strike
out of page 13 lines one to fourteen inclusive. And in order that the effect of the
said Disclaimer may be clearly understood we annex hereunto a copy of the said
Specification as it will appear when so amended, the preamble and testing clause
being omitted.
This Invention relates to that class of electrical instruments in which sound
becomes one of the elements in the transmission of the communication, and a
corresponding sound is produced at the receiving station so that oral communi-
cations can be sent by electricity and clearly distinguished at the receiving
station.
Musical tones may also be sent, but my present Invention is especially available
in transmitting and receiving oral communications.
In transmitting musical tones the respective notes each have a definite period for
each vibration, hence there is a response at the receiving end from the notes that
vibrate in time with the electric pulsations sent, but in speaking there is little
change in the musical tone but considerable in the modulations and inflections of
the voice.
In my present Invention I make use of the vibrations given to a diaphragm or
tympan by speaking into a resonant case to produce a rise and fall of electrical
tension upon the line with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation, and an electro
magnet at the receiving station will respond to the electric waves in such a manner
as to reproduce the articulation by acting upon a resonant plate.
The transmitting instrument in a complete form is represented in section in
Fig. 1, and Fig. 2 represents a receiving instrument which may be employed
with it.
Referring to Fig. 1, the resonant tube or box a is of a size and shape adapted to
being spoken into the same, having an opening at one end or side and a diaphragm
or diaphragms b, against which the sound waves from the human voice act, and
these and the motion that the diaphragm receives is the means of producing a rise
and fall of electric tension on the line by the devices hereafter set forth, so that the
battery B connected to the line will transmit a greater or less current to the
distant electro magnet m, Fig. 2, and increase or lessen the magnetism of the cores,
and in so doing act upon a resonant plate c and develop sound corresponding to the
articulation at the transmitting station.
The general features thus described pervade my entire Invention, but in developing
the same many useful and important modifications and variations have been made,
which I will proceed to set forth.
For convenience the speaking instrument Fig. 1 is provided with a handle a¹ and
flexible conductors to the battery and line respectively, so that it may be handled
and brought to the mouth, and in like manner it is preferable to place the hearing
nstrument Fig. 2 in a movable handle b', so that it can be placed with the plate c
gainst the ear; this brings the sound close to the organs of hearing, and the
esonant plate touching the ear increases the distinctness of the sound and prevents
ny false or prolonged vibrations of the plate.
In some of the modifications I have shown the speaking instrument as a fixture,
nd also the hearing instrument as a fixed resonant tube, these being variable to
uit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity of
he resonant tube for the voice. I have experienced great difficulty in reproducing
he sound of the hissing consonants, such as s; this appears to arise from the fact
hat this sound is deflected downwardly in leaving the mouth, and does not act
istinctly upon the diaphragm. By providing an edge in the resonant tube below
he mouth upon which such consonant sounds are received the vibrations are given

page_text: either to the resonant tube or deflected to the diaphragm. I find it preferable to
employ a hole e at the lower part of the mouth piece against the edges of which the
downward sound waves are directed. The same effect will be produced by a
vibrating edge placed in the lower part of the mouth piece, or the opening into the
resonant box may be contracted to about half an inch in diameter to effect the same 5
purpose. The next feature requiring consideration is the character of the diaphragm
in the speaking instrument.
Many materials have been employed by me such as metals, horn, vellum, celluloid,
ivory, &c., but almost all of these produce a prolonged or secondary vibration from
their own resonant character, hence the articulation is defective and the sound 1
vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
resonant action, and hence it will respond with the greatest accuracy to the sound
vibrations, and being of a laminated character can be employed of any desired
thickness, and when secured at its edges responds with the greatest accuracy to the
sound vibrations and does not require to be strained; furthermore, the changes of
temperature and atmospheric condition have little or no effect upon the mica
diaphragm or tympan.
I find that it is not practical to open and close the line circuits in instruments
for transmitting the human voice, the circuit to the line must be always closed and
the transmission be produced by a rise and fall of electric tension resulting from
more or less resistance in the line. This resistance may be produced in several
ways. I have shown several which will hereafter be named, but I find the most
delicate to be small bunches or tufts or disks of semi-conducting elastic fiber, such
as particles of silk and an intermediate conducting or semi-conducting material;
this device I call an electric tension regulator, it is more or less compressed
according to the vibrations of the diaphragm or tympan, and the electric current
rises in tension as it is compressed or lessens as the fiber expands. This fiber is
placed in a small roll t between the delicate diaphragm spring u, Fig. 9, and the
variable presser v adjustable by screw or otherwise in the electric circuit at this
point, or it may be within a cavity in said presser v, as in Fig. 1, there being a
delicate cork center piece w to the diaphragm b, with a piece of platina foil x in
contact with the fiber; in all instances the telegraphic circuit at the diaphragm is
made by a thin strip of platina or similar material, extending to the center from
the line or battery connection.
The fiber is rendered semi-conductive by being rubbed with plumbago, soft metal,
or similar material, or by a deposit of metal upon its surface, or by fine particles of
conducting or semi-conducting material mixed with it, the conducting power
varying with the density of the tuft or bunch of fiber.
The delicate spring u, Fig. 9, upon the mica diaphragm b is easily secured by
solder passing into fine holes bored in the inica.
In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact such as would result from a disk covered with plumbago
placed adjacent to a diaphragm also covered with plumbago or other semi-conducting
material so that the proximity or extent of surface contact will produce rise and
fall of tension, the respective parts being in the telegraphic circuit. I sometimes
perforate the diaphragm 10, Fig. 18, and place a strip of elastic material 40 across
said diaphgram over the hole, and upon this a piece of foil, so that the same
responds to very weak vibrations, and in some instances two or more diaphragins
are provided at different sides of the resonant box, each with its own tension
regulator, the diaphragms being either the same or of different sizes, characters, or
tensions so as to respond to varying sounds or acoustic condition, the various
tension regulators being all in the electric circuit, this will produce greater rise and
fall of tension for longer lines in consequence of the diaphragms acting simul-
taneously on the tension regulators. In some instances it is preferable to make
the mouth-piece of the speaking instrument sufficiently large or flaring to receive
all the sound vibrations, whether coming from the mouth, nose, or throat. The

page_text: tension regulator formed of fiber and conducting or semi-conducting material may
be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within a
case to form the tension regulator, the circuit passing through the same, and the
rise and fall of electric tension resulting from the compression of the same by the
movement of the diaphragin. I am enabled to record the sounds produced by
the human voice, or otherwise by causing the movements of the diaphragm to be
registered on paper or soft sheet metal, and then the paper may be used in an
instrument to reproduce the sound upon a delicate diaphragm by giving to the
same a vibration similar to that originally given by the voice.
h, Fig. 4, is the indenting transmitter, the diaphragm having a knife-edge point;
i is the paper which has previously been passed through a machine to raise a V
shaped rib 6. The movement of the diaphragm of h when the drum is in motion
causes the knife-edge point I to indent the raised rib to varying depths according
to the amplitude of vibration of the diaphragm, thus these indentations represent
accurately all the tones and varying inflections of the human voice. The paper,
after being indented, is passed through a second apparatus n, Fig. 5, almost similar
to h. A spring 9 has a knife edge which rests upon the raised indented rib 6, the
spring being connected to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting
point, and either by direct action or through the vibration of a string conveys the
same motion to the diaphragm of n, and reproduces previous sounds. If these
sounds are to be transmitted over a telegraph line the diaphragm 10, see Fig 6, is
provided with a cork disk w and fibrous tension regulator t before described, to
produce the rise and fall of electric tension on the line. The sound may be
recorded in ink, as represented in Fig. 7. The diaphragm of h operates a very
flexible self feeding pen o, and causes the continuous line to be wide or narrow
according to the amplitude of vibration of the diaphragm. The ink used should
dry quickly and the strips may be passed at any time thereafter through the
instrument shown in Fig. 8 beneath the arm 12 having a point or points resting
on the paper, this arm is connected with a resonant diaphragm, and the ink marks
produce more or less friction according to the breadth and amount of ink deposited,
and this will set the diaphragm of n vibrating and reproduce the vibrations of the
diaphragm of h.
An obvious modification would be to coat the paper with a substance which
would cause considerable friction, or even rough unsized paper might be used and
a spring provided with a burnished point rather flat would cause the surface of
the paper to be made smooth more or less according to the vibration of the
diaphragm, and the differences in the surface of the paper would produce a response
in the receiving diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument,
as shown in Fig. 10.
h is the resonant chamber at the end of which is the diaphragm 10, and at each
side of this diaphragm there are springs c², c³, having points made of compressed
plumbago mixed preferably with gum rubber, but any substance not liable to rapid
decomposition or the elastic or fibrous tension regulator aforesaid may be used.
These points face each other on opposite sides of the diaphragm, and make contact
with platina foil disks secured to the diaphragm.
The spring c² passes through a hole or small slot in the side of the chamber h;
a², as, are the main batteries. The battery d² has zinc to the line or spring c³, and
the battery ds has copper to the line or spring c. When the springs of c² and c³ are
adjusted to make contact with the diaphragm equally no current passes to the line,
but when the diaphragm is vibrated its movement to one side, say c², causes a
greater pressure upon the plumbago on that spring, and a lessening of the
pressure on the plumbago on c³, hence the balance of the batteries c² and
will be destroyed, c2 having the advantage will send a negative current to
line upon the return of the diaphragm, the battery currents will again

page_text: neutralize each other. The vibration of the diaphragm to the other side causes the
pressure to be reversed, and the battery ds will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure, it follows that the strength
of the electric waves will be in proportion as the speaker's voice is strong or weak.
In Fig. 11 is shown the contact spring, which may be used adjacent to the
diaphragm at one or both sides thereof. e³ is a U shaped spring secured to the
screw e, which is adjusted back and forth by the thumb nut e; e is the pillar
holding such screw; is a piece of soft rubber or equivalent substance placed
between the prongs of the spring e³; e' is a wire or band which serves to bind the
prongs tightly against the rubber r so as to prevent the prongs acting as a tuning
fork and transmitting harmonic vibrations not desirable; 7 is the plumbago contact
point. The object of the V spring and rubber is to present a semi-rigid point for
contact so as to prevent a rebound and allow of a slight yield when the plumbago
is pressed by the diaphragm. In Fig. 3 the diaphragm of the receiving instrument
is vibrated by a strip of paper chemically prepared that is in motion, the pulsations
of electricity passing over the line and producing more or less friction between the
paper and an arm upon the diaphragm.
The resonant box or chamber n is provided with a diaphragm as aforesaid, and
to said diaphragm an arm h³ is connected. At its outer end is an adjusting screw h³
that presses upon a platina faced spring h* that is secured to this arm, and said
spring rests upon the strip of paper that passes over the drum h³.
The paper is moved slowly by rotating the drum h³, and the waves of electricity
coming over the line pass through the arm h² to the platina-faced spring h¹, thence
through the paper to the earth.
If a negative current passes in the opposite direction nearly all friction between
the platina plate and the paper ceases, and the diaphragm of the resonant box n
retains its normal position.
When the positive current passes through the same channel the normal friction
of the paper is augmented, and the chemical surface acting upon the platina spring
arm serves to give a forward movement to the diaphragm of the resonant box.
Thus the mechanical force applied to move the chemical paper or surface acts
with the electric current to produce the vibration of the diaphragm of the resonant
chamber, and these vibrations will correspond to those of the diaphragm b made by
speaking in the tube a.
The principle of this method of obtaining motion by electro-chemical decomposi-
tion is, that when a moving surface is in contact with a slightly yielding substance
the tendency is to move the latter by and with the former. If the circumstances
of contact are varied the adhesion of the surfaces will be sufficient to cause the
moving surface to move the yielding substance or else to cause the yielding surface
to slip more freely, and by its spring go in the opposite direction to the moving
surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion, making it more or less according to the substances employed. By
balancing the mechanical forces so that when the surfaces in contact are not
electrified the moving surface carries with it the yielding surface, and when
electrified the yielding surface slips back, over the moving surface a mechanical
movement is obtained that is dependent on the electrical condition of the surfaces
in contact.
When it is requisite to obtain very perfect articulation, and when loudness is
not essential, I adopt a modification shewn in Fig. 12 of the device for compressing
and expanding the tuft of conducting fiber, which modification consists in placing
between the diaphragm 10 and the fiber ta vibrating tongue 21 of steel, perma-
nently magnetized, and arranging it to act in the same manner upon the tension
regulator t as if it was the diaphragm. I replace the cork upon the diaphragm by
a thim armature of iron 22, which is in close proximity to the magnetized tongue,
which tongue is secured at one end like an acoustic reed. In this position the

page_text: diaphragm is free to move, and at its approach to and recession from the magnetized
tongue causes said tongue to follow its movements by magnetic attraction, and thus
the tongue is made to perform what the diaphragm previously performed in varying
the tension of the electricity on the line.
A plate supported eccentrically and free at its edges when placed in the speaking
tube responds advantageously to the tones of the voice. The circuit with this
plate is completed through one or more tension regulators placed around its edges.
In practice I combine with the speaking or telephonic apparatus signal bells so
arranged that when the telephone is not in use the line is thrown upon the bell by
a switch, which also acts as a call on the bell.
One feature about the bells is that the magnet which serves to actuate the bells
is made of very high resistance, using preferably German silver wire in the helix,
and thus serve to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from one battery if these bells are used. The
method I adopt for coating non-conducting substance with metallic substance is the
reduction to the metallic state of metals from their salts by exposing them to the
fumes which arise from the moist phosphide of a metal, such as phosphide of calcium,
or by placing the silk for instance in a sealed tube provided with metallic electrodes,
and volatilizing the electrodes by the passage of electric sparks. Such volatilized
metals settle upon and coat the silk.
When great loudness is desirable, as in factories, the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is stored
will
under a regulated pressure. The air allowed to escape & with act with great power
upon a local diaphragm. This diaphragm to obtain clear sounds requires a damper
to check prolonged vibrations. It must be dampened by holding the fingers against
it, or by a tightly stretched cord rubbing against it, or by a screw provided with a
rubber tip held against it.
In some instances I make a record of the sound by the movements of the
diaphragm, using for that purpose a strip of paper moved along regularly between
two rollers 25, 26, as in Figs. 14 and 15, and there is a smooth thread or fine wire
of soft metal 30 between the paper and the upper roller 25, and moving along with
it. The diaphragm 10 of the resonant box is connected by a delicate rod 28 with
this thread or wire as near to the bight of the roller as possible, there being a fork
or eye through which the thread passes; hence deflections or bends are made in
the thread or wire just before it is embedded into the paper by the pressure of the
rollers. This may be used to reproduce the sound by vibrating a resonant diaphragm
by the undulations of the groove made by the thread or cord.
By placing the fibrous-tension regulator within a small band of India rubber
the same is rendered more elastic and the fiber is allowed to expand by the heat
of the current without altering the electric tension.
In some instances the diaphragm should be free to vibrate without being checked
by contact with any stationary substance. I provide for this by placing upon the
diaphragm or tympan 10, Fig. 17; a small cylinder t of hard rubber or non-
conducting material within which is the fibrous tension regulator & resting upon a
piece of platina foil connected to one pole of the battery, and within this cylinder
t is a disc to of iron or other metal loose but pressed towards the tension regulator
by a spring and screw cap to and the other electric conductor is connected wit
the said spring.
The inertia of the metal disk causes more or less compression of the tension
regulator as the diaphragm is vibrated and hence the electric pulsations are sent
over the line in harmony with the vibrations. Nearly the same effect is produced
by connecting the disk to to a yielding spring t" that extends across from one edge
of the diaphragm to the other as seen in Fig. 16. This construction of tension
regulating device is especially available with large diaphragms.
In some cases I use a soft rubber diaphragm immediately in contact with the
transmitting or receiving diaphragın so as to check or dampen any prolonged or

page_text: false vibration and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable to use
lampblack mixed with pure plumbago, amorphous phosphorous, and a very small
amount of nonconducting material such as rubber dissolved in a solvent that will
entirely evaporate.
This
In Fig. 19 I have represented the circuit as passing through the diaphragm 10,
tension regulator t, and a Duluc's dry pile battery D, P, B, to the earth.
battery is composed of about 300 pairs of paper disks coated with silver and
black oxyd of manganese.
Fig. 20 illustrates the device before mentioned for intensifying the sound; 10 is
the diaphragm vibrated by the sound; 42 is a valve moved by such diaphragm; 43 is a
reservoir containing air under a given pressure; b is the diaphragm against which
the air allowed to escape by the valve acts, and t is the tension regulator to transmit
the electric pulsations, or a hearing resonant case may be applied at the same place.
Fig. 24 represents the diaphragm 10, tension regulator t with its adjusting screw
and local circuit containing the battery B passing through a primary induction
coil 49, and there is a key 50 in the same circuit. A secondary induction coil 51
is in the line circuit and is influenced electrically by the change of tension in the
local circuit by the vibrations of the diaphragm 10. The secondary coil is some-
times required with many layers of fine wire to set up a current of high tension to
evercome the inductive effect from the line wires; being adjacent to each other I
place the receiving instrument at the distant station between the induction coil
and the earth as at R, and use an electro-magnet E, M, with polarized armature
to strike a bell; this will respond when the key 50 in the local circuit at the distant
station is opened and closed.
In Fig. 25 a similar induction coil 49 and local circuit is represented, but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes,
A shunt and rheostat
one on the diaphragm, the other on the adjusting screw.
at R' serves to prolong the magnetism in the induction coil, and thus ensure a
gradual rise and fall of electric tension in the line instead of a cessation of the same
when the platina surfaces separate, and at the receiving diaphragm c the rise and
fall of electric tension in the line and its helix acts upon the permanent magnet to
produce the vibrations of the diaphragın c, and by connecting a shunt around the
helix, and placing therein the secondary battery S, B, composed of metallic plates
in acidulated water, the action is rendered more uniform and the sound distinct.
When the diaphragm is arranged as in Fig. 26 to act upon a spring 56 through
an intervening piece of soft rubber, said spring 56 produces rise and fall of electric
tension by employing a range of resistances 57 with spring tongues adjacent to 56.
The greater amplitude of vibration of the diaphragm the more direct will be the
electric circuit connections, and the less resistance, because the circuit will pass
along the spring instead of going through all the resistance coils.
When several line wires run near each other the wire used for the acoustic or
speaking telegraph is influenced by induction, and false sounds will be produced.
I counteract this tendency by placing one or more electro-magnets 59, Fig. 28, in
the circuit of the speaking telegraph, and one or more electro magnets 60 in the
circuit of the adjacent wires, and bringing the opposite cores of 60 at such a
distance from the cores of 59 that a certain magnetic action will be set up in 50 by
induction, in the opposite direction to the induction currents from the adjacent line
or lines.
By adjusting the distance between these magnets when the speaking telegraph is
not in use, until there is not any sound at the diaphragm from the induction
currents, then these currents will be neutralized whether strong or weak, and will
not produce any false sounds when the speaking telegraph is in use. I also employ
double coils of wire for the same purpose, one coil being in the acoustic wire, and
the other in the wire to be compensated.
A convenient form for the sound recorder or phonogragh is to employ a cylinder
61, see Fig. 29, having a helical groove in its surface covered with tin foil, and the

page_text: cylinder is resolved regularly by clock work, and moved endwise by a screw on its
shaft so that the indenting point from the diaphragm 10 of h will be always in
line with such groove, hence the vibrations of the diaphragm will be recorded by
indenting the foil into the groove, and hence the same sound will be reproduced by
the point of the hearing instrument n, giving to the diaphragm of n, the
motions that result from the indentations of the foil moving in contact with such
point.
The foil may be on a flat grooved plate, and be indented and act as before
named.
I would observe in conclusion that I do not claim generally the transmission and
reproduction of sounds by increasing and decreasing the resistance of the circuit,
nor do I claim separately any of the parts or arrangements herein before described
and illustrated in the accompanying Drawings, except as hereinafter mentioned, but
I claim as my Invention:-
:-
First. In an Instrument for transmitting electric impulses by sound, a diaphragm
or tympan of mica substantially as set forth.
substantially as hereinbefore described
Second. In an Instrument for transmitting electric impulses by sound, the com-
bination with a diaphragm or tympan of an electric tension regulators
varying the resistance in a closed circuit, substantially as set forth.
4 for
Third. In a telegraphic apparatus operated by sound, a receiving instrument
provided with a resonant surface in combination with a frictional surface, moved
by power, and acting in connection with the electric current to vibrate such
resonant receiver, and produce tones corresponding to those at the transmitting
apparatus substantially as set forth.
Fourth. The method herein specified of recording the undulations of the diaphragm
on yielding material, and the reproduction of sound by such material acting upon
a diaphragm, to communicate to the same vibrations similar to the original ones,
substantially as set forth.
of London,
A
In witness whereof, the said Edison Telephone Company Limited, have
caused their common seal to be hereunto affixed, the Twelfth day of
November, One thousand eight hundred and seventy nine.
I hereby grant my fiat, giving leave to the above named Edison Telephone
Company, of London, Limited, the assignees of the said Letters Patent, to file in
the Great Patent Seal Office, with the Specification to which the same relates, the
above written Disclaimer and Memorandum of Alteration, upon condition that no
proceedings be taken in respect of any transmitters actually made and completed
prior to the date of the filing of the said Disclaimer and Memorandum of
Alteration.
Particulars of numbers, and identifying marks to be verified by Statutory
Declaration.
JOHN HOLKER.

page_text: THE UNITED TELEPHONE COMPANY'S DISCLAIMER AND
MEMORANDUM OF ALTERATION.
Filed 13th June 1881.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, THE
UNITED TELEPHONE COMPANY LIMITED, send greeting. WHEREAS Her most
Excellent Majesty Queen Victoria, by Her Royal Letters Patent under the Great
Seal of Great Britain and Ireland, bearing date at Westminster the Thirtieth day
of July, in the year of our Lord One thousand eight hundred and seventy seven,
in the forty first year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto Thomas Alva Edison, of Menlo Park, in the State of New
Jersey, United States of America, his executors, administrators, or assigns, Her
special license, full power, sole privilege and authority, that he, the said Thomas
Alva Edison, his executors, administrators, or assigns, or such others as he, his
executors, administrators, or assigns, should at any time agree with, and no others,
from time to time and at all times during the term therein expressed, should and
lawfully might make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention of
* IMPROVEMENTS IN INSTRUMENTS FOR CONTROLLING BY SOUND THE TRANSMISSION
OF ELECTRIC CURRENTS AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT
A DISTANCE," for and during the term of fourteen years thence next ensuing:
And whereas in pursuance and performance of a proviso in the said Letters Patent
contained, the said Thomas Alva Edison, did, within six calendar months next
after the date of the said Letters Patent, cause a Specification in writing_under his
hand and seal, purporting to particularly describe the nature of the said Invention,
and in what manner the same was to be performed, to be duly filed in the Great
Seal Patent Office: And whereas by indenture bearing date the Second day of
August, One thousand eight hundred and seventy nine, and made between the said
Thomas Alva Edison, of the one part, and said Edison Telephone Company
of London, Limited, of the other part, the said Thomas Alva Edison, assigned
unto the said Edison Telephone Company of London, Limited (inter alia),
the said herein before recited Letters Patent, and all rights, powers, authorities,
"

page_text: privileges, advantages, profits, emoluments, and benefits to the said Letters
Patent appertaining or belonging: And whereas on the Thirteenth November,
One thousand eight hundred and seventy nine, the said Edison Telephone
Company of London, Limited, petitioned the Commissioners of Patents for leave
to amend certain parts of the said Specification of the said Letters Patent, which
petition was referred to Her Majesty's late Attorney General, Sir John Holker, and
leave was given to the said Edison Telephone Company of London, Limited, to file
in the Great Seal Patent Office a Disclaimer and Memorandum of Alteration, as
appears by the fiat of the said Sir John Holker, dated the Ninth day of February,
One thousand eight hundred and eighty, and the said Disclaimer was duly filed in
the Great Seal Patent Office on the Tenth day of February, One thousand eight
hundred and eighty: And whereas by indenture bearing date the Twelfth day of
July, One thousand eight hundred and eighty, and made between the said Edison
Telephone Company of London, Limited, of the one part, and us, the said United
Telephone Company, Limited, of the other part, and duly registered in the Great
Seal Patent Office, the said Edison Telephone Company of London, Limited,
assigned to us, the said United Telephone Company, Limited, the said Letters
Patent, and the rights and privileges thereby granted, and the same thereby became
and are now vested in us, the said United Telephone Company, Limited: And
whereas, since the filing of the said Disclaimer and Memorandum of Alteration, and
very recently, that is to say, about the First March, One thousand eight hundred
and eighty one, your petitioners have ascertained that shortly prior to the applica-
tion for the said Letters Patent, a description of the Invention of the said Thomas
Alva Edison, in so far as it relates to [the electrochemical receiver as covered by
the third claim, was published in an American newspaper and afterwards copied
into an English paper, and we are advised that, although there was no Invention
by any one in England, or elsewhere, other than the said Thomas Alva Edison, of
the said part of his Invention, the aforesaid publication renders doubtful the
validity of the said third claim, and we are desirous of striking out the same, and
of altering the numbering of the succeeding claim accordingly, in manner more fully
hereafter appearing. NOW KNOW YE, that we, the said United Telephone
Company, Limited, by and with the leave of Her Majesty's Attorney General,
and for the reasons aforesaid, do alter the said Specification by striking out of the
Specification as amended by the said Disclaimer, printed by the Queen's Printers,
and published at the Great Seal Patent Office, in One thousand eight hundred and
eighty, the whole of the third claim, comprising lines twenty to twenty four, both
inclusive, on page 9. We also strike out the word "Fourth" at the commencement
of line twenty five of the said page 9, and substitute therefor the word "Third."
We also desire to correct a clerical occurring in the said amended Specification
by striking out the figure "2" which follows the reference letter "c" in line forty
seven of page 5 of the said printed copy of the said Specification, and of substituting
therefor the figure "3."
error
A
And in order that the effect of the said Disclaimer may be clearly understood,
we annex hereunto a copy of the said Specification, as it will appear when so
amended, the preamble and testing clause being omitted.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Royal Letters
Patent, under the Great Seal of Great Britain and Ireland, bearing date at
Westminster the Thirtieth day of July, in the year of our Lord One thousand
eight hundred and seventy seven, in the forty first year of Her reign, did, for
Herself, Her heirs and successors, give and grant unto Thomas Alva Edison, of
Menlo Park, in the State of New Jersey, United States of America, his executors,
administrators, or assigns, or such others as he, his executors, administrators, or
assigns, should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention of "IMPROVEMENTS IN

page_text: INSTRUMENTS FOR CONTROLLING BY SOUND THE TRANSMISSION OF ELECTRIC
CURRENTS AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT A DISTANCE,"
for and during the term of fourteen years thence next ensuing: And whereas, in
pursuance and performance of a proviso in the said Letters Patent contained, the
said Thomas Alva Edison did, within six calendar months next after the date of
the said Letters Patent, cause a Specification in writing under his hand and seal,
purporting to particularly describe the nature of the said Invention, and in what
manner the same was to be performed, to be duly filed in the Great Seal Patent
Office And whereas, by an indenture bearing date the second day of August,
One thousand eight hundred and seventy nine, and made between the said Thomas
Alva Edison of the one part, and us, the Edison Telephone Company of London,
Limited, of the other part, the said Thomas Alva Edison assigned unto us, the
said Edison Telephone Company of London, Limited (inter alia), the said herein-
before recited Letters Patent, and all rights, powers, authorities, privileges,
advantages, profits, emoluments, and benefits, to the said Letters Patent apper-
taining or belonging:
A
And whereas, since the date of the said assignment, we have been advised and
have ascertained that the said Specification contains matters which are of doubtful
novelty, or which are not of sufficient practical value and utility to justify their
retention, and we are therefore desirous of striking out the whole of the claiming
clauses contained in the said Specification, with the exception of the first, second,
eighteenth, and twentieth claiming clauses, and of striking out parts of the
description contained in the body of the said Specification, and also of otherwise
altering the said Specification in manner more fully hereafter 'appearing.
and correcting certain clerical errors contained in the said Specification
▲
NOW KNOW YE, that we, the said Edison Telephone Company, of London,
Limited, by and with the leave of Her Majesty's Attorney General, and for the
reasons aforesaid, do alter the said Specification by striking out of the said
Specification printed by the Queen's Printers, and published at the Great Seal
Patent Office in One thousand eight hundred and seventy nine, the words "the
same," which occur on page four at the end of line nine and the beginning of line
ten respectively, and substituting therefor the words "a corresponding." We also
strike out the word "the," which occurs between the words "and" and "electro"
on the said page, line twenty two, and substitute therefor the word "an." We also
insert between the words "the" and "instruments," which occur on the said page,
line twenty five, the word "transmitting," and we strike out the letter "s" at the
end of the said word "instruments." We also strike out the word "are," which occurs
on the same line, and substitute therefor the word "is." We also insert between
the words "in" and "Figs." (an abbreviation of the word Figures), which occur on
the same line, the words "section in," and we strike out the letter "s " in the said
word "Figs." We also strike out the words commencing with "and" on the said line
twenty five, and ending with the first word "instrument on line twenty six of the
said page four. We also strike out the words "of the," which occur between the
figure "2" and the word "receiving" on the said line twenty six, and substitute
therefor the words "represents a." We also add after the word "instrument" at the
end of the said line twenty six the words "which may be employed with it." We
also strike out the word "The" at the commencement of line twenty seven on the
said page four, and substitute therefor the words "Referring to Figure 1 the."
We also strike out that portion of the Specification commencing with the words
In Fig." on page five, line forty one, and ending with the word "sound" on page
six, line three, we also strike out that portion of the Specification commencing with
the words "I also "at the end of line eight, and ending with the words "the line
on line eleven of the said page 6. We also strike out the whole of lines twenty four
to twenty eight inclusive on the said page 6. We also strike out the words to
record," which are repeated on line thirty five of the said page 6 and add the
letter "s" to the word "rest," which occurs on line of forty seven of the said page 6.
We also strike out of page 8 lines thirty seven to forty two inclusive and lines
"
"
"
"

page_text: "
"
forty six to fifty three inclusive. We also strike out of page 9 lines eighteen to
twenty three inclusive and lines thirty seven to forty one inclusive. We also strike
out of page 10 lines seventeen to thirty seven inclusive. We also strike out of
page 11 lines ten to thirteen inclusive and lines forty four to fifty seven inclusive,
and we add at the end of line thirty seven of the said page eleven after the word
"named " the words following:-" I would observe in conclusion that I do not claim
generally the transmission and reproduction of sound by increasing and decreasing
the resistance of the circuit, nor do I claim separately any of the parts or arrangements
herein before described and illustrated in the accompanying Drawings, except as
hereinafter mentioned; but we also strike out the word "an," which occurs between
the words of" and "electric" on line 42 of the said page 11; and we add the
letter "
s" to the word "regulator," which occurs on the same line 42, to make it read
regulators," and after the said word “regulators" we insert the words "sub-
stantially as herein before described." We also strike out of page 12 lines one to
thirty inclusive, lines thirty six and thirty seven, and lines forty two to fifty six
inclusive. We also strike out the word "Eighteenth," which occurs at the com-
mencement of line thirty one on the said page 12, and substitute therefor the word
"Third." We also strike the word Twentieth, which occurs at the commencement of
line thirty eight of the said page 12, and substitute in therefor the word "Fourth."
We also strike the work "or," which occurs on line thirty nine of the said page 12,
and substitute therefor the word "
on. We also strike out of page 13 lines
one to fourteen inclusive. And in order that the effect of the said Disclaimer
may be clearly understood, we annex hereunto a copy of the said Specification
as it will appear when so amended, the preamble and testing clause being
omitted.
"
This Invention relates to that class of electrical instruments in which sound
becomes one of the elements in the transmission of the communication, and a corre-
sponding sound is produced at the receiving station, so that oral communications
can be sent by electricity and clearly distinguished at the receiving station.
Musical tones may also be sent, but my present Invention is especially available
in transmitting and receiving oral communications.
In transmitting musical tones the respective notes each have a definite period
for each vibration, hence there is a response at the receiving end from the notes
that vibrate in time with the electric pulsations sent, but in speaking there
is little change in the musical tone, but considerable in the modulations and
inflections of the voice.
In my present Invention I make use of the vibrations given to a diaphragm or
tympan by speaking into a resonant case to produce a rise and fall of electrical
tension upon the line, with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation, and an electro
magnet at the receiving station will respond to the electric waves in such a manner
as to reproduce the articulation by acting upon a resonant plate.
The transmitting instrument in a complete form is represented in section in
Figure 1, and Figure 2 represents a receiving instrument which may be employed
with it.
Referring to Figure 1, the resonant tube or box a is of a size and shape adapted
to being spoken into, the same having an opening at one end or side, and a
diaphragm or diaphragms 6 against which the sound waves from the human
voice act, and these and the motion that the diaphragm receives is the means
of producing a rise and fall of electric tension on the line by the devices hereafter
set forth, so that the battery B connected to the line will transmit a greater or
less current to the distant electro magnet m, Figure 2, and increase or lessen the
magnetism of the cores, and in so doing act upon a resonant plate c and develop
sound corresponding to the articulation at the transmitting station.
The general features thus described pervade my entire Invention, but in
developing the same many useful and important modifications and variations have
been made, which I will proceed to set forth.

page_text: For convenience the speaking instrument, Figure 1, is provided with a handle a¹
and flexible conductors to the battery and line respectively, so that it may be
handled and brought to the mouth; and in like manner it is preferable to place
the hearing instrument, Figure 2, in a moveable handle 6' so that it can be placed
with the plate c against the ear; this brings the sound close to the organs of hearing,
and the resonant plate touching the ear increases the distinction of the sound, and
prevents any false or prolonged vibrations of the plate.
In some of the modifications I have shown the speaking instrument as a fixture,
and also the hearing instrument as a fixed resonant tube, these being variable to
suit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity
of the resonant tube for the voice; I have experienced great difficulty in reproducing
the sound of the hissing consonants, such as S; this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth, and does not act
distinctly upon the diaphragm. By providing an edge in the resonant tube below
the mouth upon which such consonant sounds are received, the vibrations are given
either to the resonant tube or deflected to the diaphragm. I find it preferable to
employ a hole e at the lower part of the mouth piece, against the edges of which
the downward sound waves are directed. The same effect will be produced by a
vibrating edge placed in the lower part of the mouth piece, or the opening into the
resonant box may be contracted to about half an inch in diameter to effect the
same purpose. The next feature requiring consideration is the character of the
diaphragm in the speaking instrument.
Many materials have been employed by me, such as metals, horn, vellum,
celluloid, ivory, &c., but almost all of these produce a prolonged or secondary
vibration from their own resonant character, hence the articulation is defective
and the sound vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
resonant action, and hence it will respond with the greatest accuracy to the sound
vibrations, and being of a laminated character can be employed of any desired
thickness, and when secured at its edges responds with the greatest accuracy to the
sound vibrations, and does not require to be strained; furthermore, the changes of
temperature and atmospheric condition have little or no effect upon the mica
diagram or tympan.
I find that it is not practical to open and close the line circuits in instruments for
transmitting the human voice; the circuit to the line must be always closed, and the
transmission be produced by a rise and fall of electric tension resulting from more
or less resistance in the line. This resistance may be produced in several ways; I
have shown several which will hereafter be named, but I find the most delicate to
be small bunches or tufts or discs of some conducting elastic fiber, such as particles
of silk, and an intermediate conducting or semi-conducting material; this device I
call an electric tension regulator, it is more or less compressed according to the
vibrations of the diaphragm or tympan, and the electric current rises in tension as
it is compressed, or lessens as the fibre expands. This fiber is placed in a small
roll t between the delicate diaphragm spring u, Figure 9, and the variable presser v,
adjustable by screw or otherwise in the electric circuit at this point, or it may be
within a cavity in said presser v, as in Figure 1, there being a delicate cork centre
piece w to the diaphragm b with a piece of platina foil x in contact with the fibre.
In all instances the telegraphic circuit at the diaphragm is made by a thin strip
of platina or similar material, extending to the centre from the line or battery
connection.
The fibre is rendered semi-conductive by being rubbed with plumbago, soft
metal, or smilar material, or by a deposit of metal upon its surface, or by fine
particles of conducting or semi-conducting material mixed with it, the conducting
power varying with the density of the tuft or branch of fiber.
The delicate spring u, Figure 9, upon the mica diaphragm b is easily secured by
solder passing into fine holes bored in the mica.

page_text: In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact, such as would result from a disk covered with plumbago
placed adjacent to a diaphragm also covered with plumbago or other semi-conducting
material, so that the proximity or extent of surface contact will produce rise and
fall of tension, the respective parts being in the telegraphic circuit.
I sometimes perforate the diaphragm 10, Figure 18, and place a strip of elastic
material 40 across said diaphragm over the hole, and upon this a piece of foil, so
that the same responds to very weak vibrations, and in some instances two or
more diaphragms are provided at different sides of the resonant box, each with its
own tension regulator, the diaphragms being either the same or of different sizes,
characters, or tensions, so as to respond to varying sounds or acoustic condition,
the various tension regulators being all in the electric circuit; this will produce
greater rise and fall of tension for longer lines in consequence of the diaphragms
acting simultaneously on the tension regulators.
In some instances it is preferable to make the mouth piece of the speaking
instrument sufficiently large or flaring to receive all the sound vibrations, whether
coming from the mouth, nose, or throat.
The tension regulator formed of fiber and conducting or semi-conducting material
may be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within
a case to form the tension regulator, the circuit passing through the same, and the
rise and fall of electric tension resulting from the compression of the same by the
movement of the diaphragm.
I am enabled to record the sounds produced by the human voice or otherwise
by causing the movements of the diaphragm to be registered on paper or soft sheet
metal, and then the paper may be used in an instrument to reproduce the sound
upon a delicate diaphragm by giving to the same a vibration similar to that
originally given by the voice.
h, Figure 4, is the indenting transmitter, the diaphragm having a knife edge
point; is the paper which has previously been passed through a machine to raise
a V shaped rib 6. The movement of the diaphragm of h when the drum is in
motion causes the knife edge point to indent the raised rib to varying depths
according to the amplitude of vibration of the diaphragm, thus these indentations
represent accurately all the tones and varying inflections of the human voice. The
paper after being indented is passed through a second apparatus n, Figure 5, almost
similar to h. A spring 9 has a knife edge which rests upon the raised indented
rib 6 the spring being connected to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting point
and either by direct action or through the vibration of a string conveys the same
motion to the diaphragm of n, and reproduces previous sounds. If these sounds
are to be transmitted over a telegraph line, the diaphragm 10, see Figure 6, is
provided with a cork disk w, and fibrous tension regulator t before described, to
produce the rise and fall of electric tension on the line.
The sound may be
recorded in ink, as represented in Figure 7. The diaphragm of h operates a very
flexible self feeding pen o, and causes the continuous line to be wide or narrow
according to the amplitude of vibration of the diaphragm. The ink used should
dry quickly, and the strip may be passed at any time thereafter through the
instrument shewn in Figure 8, beneath the arm 12, having a point or points resting
on the paper; this arm is connected with a resonant diaphragm, and the ink marks
produce more or less friction according to the breadth and amount of ink deposited,
and this will set the diaphragm of n vibrating and reproduce the vibrations of the
diaphragm of h.
An obvious modification would be to coat the paper with a substance which
would cause considerable friction, or even rough unsized paper might be used, and
a spring provided with a burnished point rather flat would cause the surface of the
paper to be made smooth more or less according to the vibration of the diaphragm,

page_text: and the difference in the surface of the paper would produce a response of the
receiving diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument,
as shewn in Figure 10.
h is the resonant chamber, at the end of which is the diaphragm 10, and at each
side of this diapbragm there are springs c², c³, having points made of compressed
plumbago mixed 'preferably with gum rubber, but any substance not liable to
rapid decomposition, or the elastic or fibrous tension regulator aforesaid may be
used. These points face each other on opposite sides of the diaphragm and make
contact with platina foil disks secured to the diaphragm.
€3
The spring c³ passes through a hole or small slot in the side of the chamber h;
d², d³ are the main batteries; the battery d² has zinc to the line or spring c², and the
battery has copper to the line or spring c³. When the springs c² and c³ are adjusted
to make contact with the diaphram equally no current passes to the line, but when
the diaphragm is vibrated its movement to one side, say, c², causes a greater
pressure upon the plumbago on that spring and a loosening of the pressure on the
plumbago on c³, hence the balance of the batteries c² and c³ will be destroyed, c²
having the advantage will send a negative current to line; upon the return of the
diaphragm the battery currents will again neutralize each other. The vibration of
the diaphragm to the other side causes the pressure to be reversed, and the battery d³
will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure, it follows that the strength
of the electric waves will be in proportion as the speakers voice is strong or
weak.
In Figure 11 is shewn the contact spring, which may be used adjacent to the
diaphragm at one or both sides thereof; e³ is a U shaped spring secured to the
screw e, which is adjusted back and forth by the thumb nut e; e is the pillar
holding such screw;r is a piece of soft rubber or equivalent substance placed between
the prongs of the spring e³; e7 is a wire or band which serves to bind the prongs
tightly against the rubber r, so as to prevent the prongs acting as a tuning fork and
transmitting harmonic vibrations not desirable; 2 is the plumbago contact point.
The object of the U spring and rubber is to present a semi rigid point for contact
so as to prevent a rebound and allow of a slight yield when the plumbago is pressed
by the diaphragm.
In Figure 3 the diaphragm of the receiving instrument is vibrated by a strip of
paper chemically prepared, that is, in motion, the pulsations of electricity passing
over the line and producing more or less friction between the paper and an arm
upon the diaphragm.
The resonant box or chamber n is provided with a diaphragm as aforesaid, and to
said diaphragm an arm h² is connected. At its outer end is an adjusting screw h³
that presses upon a platina faced spring h' that is secured to this arm, and said
spring rests upon the strip of paper that passes over the drum h³.
The paper is moved slowly by rotating the drum h³, and the waves of electricity
coming over the line pass through the arm h² to the platina-faced spring h4, thence
through the paper to the earth.
If a negative current passes in the opposite direction nearly all friction between
the platina plate and the paper ceases, and the diaphragm of the resonant box n
retains its normal position.
When the positive current passes through the same channel the normal friction
of the paper is augmented, and the chemical surface acting upon the platina
spring arm serves to give a forward movement to the diaphragm of the resonant
box.
Thus the mechanical force applied to move the chemical paper or surface acts
with the electric current to produce the vibration of the diaphragm of the resonant
chamber, and these vibrations will correspond to those of the diaphragm 6 made by
speaking in the tube a.

page_text: The principle of this method of obtaining motion by electro chemical decom-
position is that when a moving surface is in contact with a slightly yielding
substance the tendency is to move the latter by and with the former. If the
circumstances of contact are varied the adhession of the surfaces will be sufficient
to cause the moving surface to move the yielding substance or else to cause the
yielding surface to slip more freely, and by its spring go in the opposite direction
to the moving surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion, make it more or less, according to the substances employed. By balancing
the mechanical forces, so that when the surfaces in contact are not electrified the
moving surface carries with it the yielding surface, and when electrified the
yielding surface slips back over the moving surface a mechanical movement is
obtained that is dependent on the electrical condition of the surfaces in contact.
When it is requisite to obtain very perfect articulation, and when loudness is
not essential, I adopt a modification shewn in Figure 12 of the device for com-
pressing and expanding the tuft of conducting fiber, which modification consists in
placing between the diaphragm 10 and the fiber t a vibrating tongue 21 of steel
permanently magnetised, and arranging it to act in the same manner upon the
tension regulator t as if it was the diaphragm; I replace the cork upon the
diaphragm by a thin armature of iron 22, which is in close proximity to the
magnetized tongue, which tongue is secured at one end like an acoustic reed. In
this position the diaphragm is free to move, and at its approach to and recession
from the magnetized tongue causes said tongue to follow its movements by
magnetic attraction, and thus the tongue is made to perform what the diaphragm
previously performed in varying the tension of the electricity on the line.
A plate supported eccentrically and free at its edges when placed in the speaking
tube responds advantageously to the tones of the voice. The circuit with this plate
is completely through one or more tension regulators placed around its edges.
In practice I combine with the speaking or telephonic apparatus signal bells so
arranged that when the telephone is not in use the line is thrown upon the bell by
a switch which also acts as a call on the bell.
One feature about the bells is that the magnet which serves to actuate the bells
is made of very high resistance, using preferably German silver wire in the helix,
and thus serves to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from one battery if these bells are used.
The method I adopt for coating nonconducting substance with metallic substance
is the reduction to the metallic state of metals from their salts by exposing them to
the fumes which arise from the moist phosphide of a metal such as phosphide of
calcium; or by placing the silk, for instance, in a sealed tube provided with metellic
electrodes, and volatilizing the electrodes by the passage of electric sparks, such
volatilized metals settle upon and coat the silk.
When great loudness is desirable, as in factories, the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is stored
under a regulated pressure.
The air allowed to escape will act with great power upon a local diaphragm.
This diaphragm, to obtain clear sounds, requires a damper to check prolonged
vibrations. It must be damped by holding the fingers against it or by a tightly
stretched cord rubbing against it or by a screw provided with a rubber tip held
against it.
In some instances I make a record of the sound by the movements of the
diaphragm, using for that purpose a strip of paper moved along regularly between
two rollers 25, 26, as in Figures 14 and 15, and there is a smooth thread or
fine wire of soft metals 30 between the paper and the upper roller 25 and moving
along with it. The diaphragm. 10 of the resonant box is connected by a delicate
rod 28 with this thread or wire as near to the bight of the roller as possible, there
being a fork or eye through which the thread passes; hence deflections or bends are
made in the thread or wire just before it is embedded into the paper by the

page_text: pressure of the rollers. This may be used to reproduce the sound by vibrating a
resonant diaphragm by the undulations of the groove made by the thread or
cord.
By placing the fibrous tension regulator within a small band of india rubber the
same is rendered more elastic, and the fiber is allowed to expand by the heat of the
current without altering the electric tension.
In some instances the diaphragm should be free to vibrate without being checked
by contact with any stationary substance. I provide for this by placing upon the
diaphragm or tympan 10, Figure 17, a small cylinder t7, of hard rubber or non-
conducting material, within which is the fibrous tension regulator t resting upon
a piece of platina foil connected to one pole of the battery, and within this
cylinder t is a disc 10, of iron or other metal, loose, but pressed towards the tension
regulator by a spring 8 and screw cap to, and the other electric conductor is
connected with said spring.
The inertia of the metal disk causes more or less compression of the tension
regulator as the diaphragm is vibrated, and hence the electric pulsations are sent
over the hine in harmony with the vibrations. Nearly the same effect is produced
by connecting the disk to to a yielding spring t" that extends across from one
edge of the diaphragm to the other, as seen in Figure 16. This construction of
tension regulating device is especially available with large diaphragms.
In some cases I use a soft rubber diaphragm immediately in contact with the
transmitting or receiving diaphragm, so as to check or dampen any prolonged or
false vibration, and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable
to use lampblack mixed with pure lumbago, amorphous phosphorous, and a very
small amount of nonconducting material, such as rubber dissolved in a solvent that
will entirely evaporate.
In Figure 19 I have represented the circuit as passing through the diaphragm 10,
tension regulator t, and a Duluc's dry pile battery D, P, B, to the earth. This
battery is composed of about three hundred pairs of paper disks coated with silver
and black oxyd of manganese.
Figure 20 illustrates the device before mentioned for intensifying the sound;
10 is the diaphragm vibrated by the sound; 42 is a valve moved by such
diaphragm; 43 is a reservoir containing air under a given pressure; b is the
diaphragm against which the air allowed to escape by the valve acts, and t is the
tension regulator to transmit the electric pulsations, or a hearing resonant case
may be applied at the same place.
Figure 24 represents the diaphragm 10, tension regulator t, with its adjusting
screw and local circuit containing the battery B passing through a primary
induction coil 49, and there is a key 50 in the same circuit. A secondary induction
coil 51 is in the line circuit, and is influenced electrically by the change of tension
in the local circuit by the vibrations of the diaphragm 10.
The secondary coil is sometimes required with many layers of fine wire to set
up a current of high tension; to overcome the inductive effect from the line wires
being adjacent to each other, I place the receiving instrument at the distant station
between the induction coil and the earth as at R, and use an electro magnet E, M,
with polarized armature to strike a bell; this will respond when the key 50 in the
local circuit at the distant station is opened and closed.
In Figure 25 a similar induction coil 49 and local circuit is represented, but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes,
one on the diaphragm, the other on the adjusting screw. A shunt and rheostat
at R' serves to prolong the magnetism in the induction coil, and thus ensure a
gradual rise and fall of electric tension in the line instead of a cessation of the
same when the platina surfaces separate, and at the receiving diaphragm c the
rise and fall of electric tension in the line and its helix. acts upon the permanent
magnet to produce the vibrations of the diaphragm c, and by connecting a shunt
around the helix and placing therein the secondary battery S, B, composed of

page_text: metallic plates in acidulated water the action is rendered more uniform and the
sound distinct.
When the diaphragm is arranged, as in Figure 26, to act upon a spring 56
through an intervening piece of soft rubber, said spring 56 produces rise and fall of
electric tension, by employing a range of resistance 57 with spring tongues adjacent
to 56. The greater amplitude of vibration of the diaphragm, the more direct will
be the electric circuit connections and the less resistance, because the circuit will
pass along the spring instead of going through all the resistance coils.
When several line wires run near each other the wire used for the acoustic or
speaking telegraph is influenced by induction, and false sounds will be produced.
I counteract this tendency by placing one or more electro magnets 59, Figure 28,
in the circuit of the speaking telegraph, and one or more electro-magnets 60 in the
circuit of the adjacent wires, and bringing the opposite cores of 60 at such a
distance from the cores of 59 that a certain magnetic action will be set up in 59
by induction in the opposite direction to the induction currents from the adjacent
line or lines.
By adjusting the distance between these magnets when the speaking telegraph
is not in use until there is not any sound at the diaphragm from the induction
currents, then these currents will be neutralized, whether strong or weak, and will
not produce any false sounds when the speaking telegraph is in use.
I also employ double coils of wire for the same purpose, one coil being in the
acoustic wire, and the other in the wire to be compensated.
A convenient form for the sound recorder or phonogragh is to employ a
cylinder 61, see Figure 29, having a helical groove in its surface covered with tin
foil, and the cylinder is revolved regularly by clockwork, and moved endwise by a
screw on its shaft, so that the indenting point from the diaphragm 10 of h will
be always in line with such groove; hence the vibrations of the diaphragm will be
recorded by indenting the foil into the groove, and hence the same sound will be
reproduced by the point of the hearing instrument n, giving to the diaphragni
of n the motions that result from the indentations of the foil moving in contact
with such point.
The foil may be on a flat grooved plate, and be indented and act as before
named.
I would observe in conclusion that I do not claim generally the transmission and
reproduction of sounds by increasing and decreasing the resistance of the circuit,
nor do I claim separately any of the parts or arrangements hereinbefore described
and illustrated in the accompanying Drawings, except as hereinafter mentioned,
but I claim as my Invention,
First. In an instrument for transmitting electric impulses by sound, a diaphragm
or tympan of mica, substantially as set forth.
Second. In an instrument for transmitting electric impulses by sound, the
combination with a diaphragm or tympan of electric tension regulators, substantially
as hereinbefore described for varying the resistance in a closed circuit, substantially
as set forth.
Third. The method herein specified of recording the undulations of the diaphragm
on yielding material, and the reproduction of sound by such material acting upon a
diaphragm to communicate to the same vibrations similar to the original ones,
substantially as set forth.
In witness whereof, the said United Telephone Company, Limited, have
caused their common seal to be hereunto affixed, the Twenty third day of
March, One thousand eight hundred and eighty one.

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME WE THE UNITED
TELEPHONE COMPANY LIMITED send greeting WHEREAS Her most Excellent
Majesty Queen Victoria by Her Royal Letters Patent under the Great Seal
of Great Britain and Ireland bearing date at Westminster the Thirtieth day of
July in the year of our Lord One thousand eight hundred and seventy seven in
the forty first year of Her reign did for Herself Her heirs and successors give and
grant unto Thomas Alva Edison his executors administrators and assigns special
license full power sole privilege and authority that he the said Thomas Alva Edison
his executors administrators or assigns and every of them by himself and themselves
or by his and their deputy or deputies servants or agents or such others as he
his executors administrators or assigns should at any time agree with and no others
from time to time and at all times thereafter during the term therein expressed
should and lawfully might make use exercise and vend within the United
Kingdom of Great Britain and Ireland the Channel Islands and Isle of Man an
Invention of IMPROVEMENTS IN INSTRUMENTS FOR CONTROLLING BY SOUND THE
TRANSMISSION OF ELECTRIC CURRENTS AND THE REPRODUCTION OF CORRESPONDING
SOUNDS AT A DISTANCE for and during the term of fourteen years thence next
ensuing And whereas in pursuance and performance of a proviso in the said
Letters Patent contained the said Thomas Alva Edison did within six calendar
months next after the date of the said Letters Patent cause a Specification
in writing under his hand and seal purporting to particularly describe the nature
of the said Invention and in what manner the same was to be performed to
be duly filed in the Great Seal Patent Office And whereas by indenture bearing
date the Second day of August One thousand eight hundred and seventy nine
and made between the said Thomas Alva Edison of the one part and the Edison
Telephone Company of London Limited of the other part the said Thomas Alva
Edison assigned unto the said Company (inter alia) the said hereinbefore recited

page_text: Letters Patent and all rights powers privileges advantages profits emoluments and
benefits to the said Letters Patent appertaining or belonging And whereas on the
Thirteenth day of November One thousand eight hundred and seventy nine the
said Edison Telephone Company of London Limited petitioned the Commissioners
of Patents for leave to amend certain parts of the said Specification of the said
Letters Patent which petition was referred to Her Majesty's late Attorney General
Sir John Holker and leave was given to the said Company to file in the Great
Seal Patent Office a Disclaimer and Memorandum of Alteration as appears by the
Fiat of the said Sir John Holker dated the Ninth day of February One thousand
eight hundred and eighty and the said Disclaimer was duly filed in the Great Seal
Patent Office on the Tenth day of February One thousand eight hundred and
eighty And whereas by indenture bearing date the Twelfth day of July One
thousand eight hundred and eighty and made between the said Edison Telephone
Company of London Limited of the one part and us the United Telephone
Company Limited of the other part and duly registered in the Great Seal Patent
Office the said Edison Telephone Company of London Limited assigned to us the
said Letters Patent and the rights and privileges thereby granted and the same
thereby became and are now vested in us the said United Telephone Company
Limited And whereas on the Twenty fifth day of March One thousand eight
hundred and eighty one we the said United Telephone Company Limited
petitioned the Commissioners of Patents for leave to further amend certain
parts of the said Specification of the said Letters Patent which petition was
referred to Her Majestys Attorney General and leave was given to us the said
United Telephone Company Limited to file in the Great Seal Patent Office a
further Disclaimer and Memorandum of Alteration as appears by the Fiat of Her
Majesty's Attorney General Sir Henry James dated the Fourth day of June One
thousand eight hundred and eighty one and the said Disclaimer and Memorandum
of Alteration was duly filed in the Great Seal Patent Office on the Thirteenth day
of June One Thousand eight hundred and eighty one And whereas since the
filing of the said last named Disclaimer and Memorandum of Alteration we the said
United Telephone Company Limited have been in litigation with various persons
and companies with respect to infringements of the said Letters Patent and we the
said United Telephone Company Limited have found that the retention of Claims 1
and 3 of the said Specification as amended by the said hereinbefore recited
Disclaimers having regard to the language of the Provisional Specification has
given rise to questions as to how far such claims are valid as a matter of law upon
the face of the Specifications And whereas the subject matter of the said Clains 1
and 3 is not of great commercial importance And we are therefor desirous of
striking out the said Claims 1 and 3 and of confining the claim of the said Letters
Patent to the second claim thereof NOW KNOW YE that we the United
Telephone Company Limited by and with the leave of Her Majestys Attorney
General and for the reasons aforesaid do alter the Specification by striking out of
the said Specification as amended by the said Disclaimer printed by the Queens
Printers and published at the Patent Office in One thousand eight hundred and eighty
one the first claim comprising lines 39 and 40 on page 10, We also strike out the
third claim comprising lines 45 to 48 both inclusive on the said page 10 We also
strike out the word "second" at the commencement of line 41 on the said page 10
And in order that the effect of the said Disclaimer may be clearly understood we
annex hereunto a copy of the said Specification as it will appear when so amended
the preamble and testing clause being omitted.
This Invention relates to that class of electrical instruments in which sound
becomes one of the elements in the transmission of the communication and a
corresponding sound is produced at the receiving station so that oral communi
cations can be sent by electricity and clearly distinguished at the receiving
station.
Musical tones may also be sent but my present Invention is especially available
in transmitting and receiving oral communications.

page_text: In transmitting musical tones the respective notes each have a definite perio
for each vibration hence there is a response at the receiving end from the notes,
that vibrate in time with the electric pulsations sent but in speaking there is little
change in the musical tone but considerable in the modulations and inflections of
the voice.
In my present Invention I make use of the vibrations given to a diaphragm or
tympan by speaking into a resonant case to produce a rise and fall of electrical
tension upon the line with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation and an electro
magnet at the receiving station will respond to the electric waves in such a manner
as to reproduce the articulation by acting upon a resonant plate.
The transmitting instrument in a complete form is represented in section in
Figure 1 and Figure 2 represents a receiving instrument which may be employed
with it.
Referring to Figure 1 the resonant tube or box a is of a size and shape adapted
to being spoken into the same having an opening at one end or side and a
diaphragm or diaphragms b against which the sound waves from the human voice
act and these and the motion that the diaphragm receives is the means of producing
a rise and fall of electric tension on the line by the devices hereafter set forth so
that the battery B connected to the line will transmit a greater or less current to
the distant electro magnet m in Figure 2 and increase or lessen the magnetism of
the cores and in so doing act upon a resonant plate cand develop sound corre-
sponding to the articulation at the transmitting station.
The general features thus described pervade my entire Invention but in
developing the same many useful and important modificatious and variations have.
been made which I proceed to set forth.
For convenience the speaking instrument Figure 1, is provided with a handle a'
and flexible conductors to the battery and line respectively so that it may be,
handled and brought to the mouth, and in like manner it is preferable to place the
hearing instrument Figure in a moveable handle b¹ so that it can be placed with
the plate c against the ear this brings the sound close to the organs of hearing and
the resonant plate touching the ear increases the distinction of the sound and
prevents any false or prolonged vibrations of the plate.
In some of the modifications I have shewn the speaking instrument as a fixture
and also the hearing instrument as a fixed resonant tube these being variable to
suit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity
of the resonant tube for the voice I have experienced great difficulty in reproducing
the sound of the hissing consonants such as S this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth and does not, act
distinctly upon the diaphragm By providing an edge in the resonant tube below
the mouth upon which such consonant sounds are received the vibrations are given
either to the resonant tube or deflected to the diaphragm I find it preferable to
employ a hole e at the lower part of the mouth piece against the edges of which
the downward sound waves are directed. The same effect will be produced by a
vibrating edge placed in the lower part of the mouth piece or the opening into the
resonant box may be contracted to about half an inch in diameter to effect the
sanie purpose. The next feature requiring consideration is the character of the
diaphragm in the speaking instrument.
Many materials have been employed by me such as metals horn vellum celluloid
vory &c. but almost all of these produce a prolonged or secondary vibration for
heir own resonant character hence the articulation is defective and the sound
vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
esonant action and hence it will respond with the greatest accuracy to the sound
ibrations and being of a laminated character can be employed of any desired
hickness and when secured at its edges responds with the greatest accuracy to the

page_text: sound vibrations and does not require to be strained furthermore the changes of
temperature and atmospheric condition have little or no effect upon the mica
diaphragm or tympan.
I find that it is not practical to open and close the line circuits in instruments
for transmitting the human voice the circuit to the line must be always closed and
the transmission be produced by a rise and fall of electric tension resulting from
more or less resistance in the line This resistance may be produced in several
ways. I have shewn several which will hereafter be named but I find the most
delicate to be small bunches or tufts or discs of some conducting elastic fibre such
as particles of silk and an intermediate conducting or semi-conducting material
this device I call an electric tension regulator it is more or less compressed according
to the vibrations of the diaphragm or tympan and the electric current rises in
tension as it is compressed or lessens as the fibre expands. This fibre is placed in
a small roll t between the delicate diaphragm spring u Figure 9 and the variable
presser v adjustable by screw or otherwise in the electric circuit at this point or it
may be within a cavity in said presser vas in Figure 1. there being a delicate cork
centre piece w to the diaphragm b with a piece of platina foil x in contact with the
fibre. In all instances the telegraphic circuit at the diaphragm is made by a thin
strip of platina or similar material extending to the centre from the line or battery
connection.
The fibre is rendered semi conductive by being rubbed with plumbago soft metal
or similar material or by a deposit of metal upon its surface or by fine power
varying with the density of the tuft or branch of fibre.
particles of conducting or semi-conducting material mixed with it, the conducting
A
The delicate spring u Figure 9 upon the mica diaphragm 6 is easily secured by
solder passing into fine holes bored in the mica.
In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact such as would result from a disk covered with plumbago
placed adjacent to a diaphragm also covered with plumbago or other semi
conducting material so that the proximity or extent of surface contact will produce
rise and fall of tension the respective parts being in the telegraphic circuit.
I sometimes perforate the diaphragm 10 Figure 18 and place a strip of elastic
material 40 across said diaphragm over the hole and upon this a piece of foil so
that the same responds to very weak vibrations and in some instances two or
more diaphragms are provided at different rides of the resonant box each with its
own tension regulator the diaphragms being either the same or of different sizes
characters or tensions so as to respond to varying sounds or acoustic condition the
various tension regulators being all in the electric circuit this will produce greater
rise and fall of tension for longer lines in consequence of the diaphragms acting
simultaneously on the tension regulators.
1 In some instances it is preferable to make the mouth piece of the speaking
instrument sufficiently large or flaring to receive all the sound vibrations whether
coming from the mouth nose or throat.
The tension regulator formed of fibre and conducting or semi conducting material
may be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within
a case to form the tension regulator the circuit passing through the same and the
rise and fall of electric tension resulting from the compression of the same by the
movement of the diaphragın.
I am enabled to record the sounds produced by the human voice or otherwise by
causing the movements of the diaphragm to be registered on paper or soft sheet
metal and then the paper may be used in an instrument to reproduce the sound
upon a delicate diaphragm by giving to the same a vibration similar to that
originally given by the voice. h. Figure 4 is the indenting transmitter the
diaphragin having a knife edge point is the paper which has previously been
passed through a machine to raise a V shaped rib 6. The movement of the
diaphragm of h when the drum is in motion causes the knife edge point b' to

page_text: indent the raised rib to varying depths according to the amplitude of vibration of
the diaphragm thus these indentations represent accurately all the tones and
varying inflections of the human voice. The paper after being indented is passe
through a second apparatus n Figure 5 almost similar to h. A spring 9 has a
knife edge which rests upon the raised indented rib 6 the spring being connected
to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting
point and either by direct action or through the vibration of a string conveys the
same motion to the diaphragm of n and reproduces previous sounds. If these sounds
are to be transmitted over a telegraph line the diaphragm 10 see Figure 6 is provided
with a cork disc wand fibrous tension regulator t before described to produce the.
rise and fall of electric tension on the line. The sound may be recorded in ink as
represented in Figure 7. The diaphragm of h operates a very flexible self feeding
pen o and causes the continuous line to be wide or narrow according to the
amplitude of vibration of the diaphragm. The ink used should dry quickly and
the strip may be passed at any time thereafter through the instrument shewn in
Figure 8 beneath the arm 12 having a point or points resting on the paper this
arm is connected with a resonant diaphragm and the ink marks produce more or
less friction according to the breadth and amount of ink deposited and this will
set the diaphragm of n vibrating and reproduce the vibrations of the diaphragm
of h.
An obvious modification would be to coat the paper with a substance which
would cause considerable friction or even rough unsized paper might be used and
a spring provided with a burnished point rather flat would cause the surface of the
paper to be made smooth more or less according to the vibration of the diaphragm
and the difference in the surface of the paper would produce a response of the
receiving diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument
as shewn in Figure 10.
is the resonant chamber at the end of which is the diaphragm 10 and at each
side of this diaphragm there are springs c² c³ having points made of compressed
plumbago mixed preferably with gum rubber but any substance not liable to
rapid decomposition or the elastic or fibrous tension regulator aforesaid may be
used. These points face each other on opposite sides of the diaphragm and
make contact with platina foil discs secured to the diaphragm.
03
The spring passes through a hole or small slot in the side of the chamber h;
d² d³ are the main batteries the battery d² has zinc to the line or spring c² and the
battery d³ has copper to the line or spring c³. When the springs c² and c³ are
adjusted to make contact with the diaphragm equally no current passes to the line
but when the diaphragm is vibrated its movement to one side say c² causes a
greater pressure upon the plumbago on that spring and a loosening of the pressure
on the plumbago on c³ hence the balance of the batteries c² and c³ will be destroyed
having the advantage will send a negative current to line upon the return of the
diaphragm the battery currents will again neutralize each other. The vibration of
the diaphragm to the other side causes the pressure to be reversed and the battery d³
will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure it follows that the strength
of the electric waves will be in proportion as the speakers voice is strong or weak.
In Figure 11 is shewn the contact spring which may be used adjacent to the
diaphragm at one or both sides thereof e³ is a U shaped spring secured to the
screw e which is adjusted back and forth by the thumb nut es e is the pillar
holding such screw is a piece of soft rubber or equivalent substance placed
between the prongs of the spring es e' is a wire or band which serves to bind the
prongs tightly against the rubber r so as to prevent the prongs acting as a tuning
fork and transmitting harmonic vibrations not desirable ² is the plumbago contact
point. The object of the U spring and rubber is to present a semi rigid point for

page_text: contact so as to prevent a rebound and allow of a slight yield when the plumbago
is pressed by the diaphragm.
In Figure 3 the diaphragm of the receiving instrument is vibrated by a strip of
paper chemically prepared that is in motion the pulsations of electricity passing
over the line and producing more or less friction between the paper and an arm
upon the diaphragm.
The resonant box or chamber n is provided with a diaphragm as aforesaid and
to said diaphragm an arm 2 is connected. At its outer end is an adjusting screw h³
that presses upon a platina faced spring * that is secured to this arm and said
spring rests upon the strip of paper that passes over the drum 15.
The paper is moved slowly by rotating the drum h5 and the waves of electricity
coming over the line pass through the arm h² to the platina faced spring h4 thence
through the paper to the earth.
If a negative current passes in the opposite direction nearly all friction between
the platina plate and the paper ceases and the diaphragm of the resonant box n
retains its normal position.
When the positive current passes through the same channel the normal friction
of the paper is augmented and the chemical surface acting upon the platina
spring arm serves to give a forward movement to the diaphragm of the
resonant box.
Thus the mechanical force applied to move the chemical paper or surface acts
with the electric current to produce the vibration of the diaphragm of the resonant
chamber and these vibrations will correspond to those of the diaphragm b made
by speaking in the tube a.
The principle of this method of obtaining motion by electro chemical decom-
position is that when a moving surface is in contact with a slightly yielding
substance the tendency is to move the latter by and with the former. If the
circumstances of contact are varied the adhesion of the surfaces will be sufficient
to cause the moving surface to move the yielding substance or else to cause the
yielding surface to slip more freely and by its spring go in the opposite direction
to the moving surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion make it more or less according to the substances employed. By balancing
the mechanical forces so that when the surfaces in contact are not electrified the
moving surface carries with it the yielding surface and when electrified the yielding
surface slips back over the moving surface a mechanical movement is obtained that
is dependent on the electrical condition of the surfaces in contact.
When it is requisite to obtain very perfect articulation and when loudness is
not essential I adopt a modification shewn in Figure 12 of the device for com-
pressing and expanding the tuft of conducting fiber which modification consists
in placing between the diaphragm 10 and the fiber´t a vibrating tongue 21 of
steel permanently magnetised and arranging it to act in the same manner upon
the tension regulator t as if it was the diaphragm I replace the cork upon the
diaphragm by a thin armature of iron 22 which is in close proximity to the
magnetised tongue which tongue is secured at one end like an acoustic reed. In
this position the diaphragm is free to move and at its approach to and recession
from the magnetised tongue causes said tongue to follow its movements by mgnetic
attraction and thus the tongue is made to perform what the diaphragm previously
performed in varying the tension of the electricity on the line.
A plate supported eccentrically and free at its edges when placed in the
speaking tube responds advantageously to the tones of the voice. The circuit with
this plate is completely through one or more tension regulators placed around its
edges.
In practice I combine with the speaking or telephonic apparatus signal bells so
arranged that when the telephone is not in use the line is thrown upon the bell
by a switch which also acts as a call on the bell.
One feature about the bells is that the magnet which serves to actuate the bells

page_text: is made of very high resistance using preferably German silver wire in the helix
and thus serves to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from one battery if these bells are used.
The method I adopt for coating non-conducting substance with metallic
substance is the reduction to the metallic state of metals from their salts by
exposing them to the fumes which arise from the moist phosphide of a metal such
as phosphide of calcium or by placing the silk for instance in a sealed tube
provided with metallic electrodes and volatilizing the electrodes by the passage of
electric sparks such volatilized metals settle upon and coat the silk.
When great loudness is desirable as in factories the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is
stored under a regulated pressure.
The air allowed to escape will act with great power upon a local diaphragm.
This diaphragm to obtain clear sounds requires a damper to check prolonged
vibration. It must be damped by holding the fingers against it or by a tightly
stretched cord rubbing against it or by a screw provided with a rubber tip held
against it.
In some instances I make a record of the sound by the movements of the
diaphragm using for that purpose a strip of paper moved along regularly between
two rollers 25, 26 as in Figures 14 and 15 and there is a smooth thread or fine
wire of soft metals 30 between the paper and the upper roller 25 and moving
along with it. The diaphragm 10 of the resonant box is connected by a delicate
rod 28 with this thread or wire as near to the bight of the roller as possible there
being a fork or eye through which the thread passes hence deflections or bends are
made in the thread or wire just before it is embedded into the paper by the
pressure of the rollers. This may be used to reproduce the sound by vibrating a
resonant diaphragm by the undulations of the groove made by the thread or cord.
By placing the fibrous tension regulator within a small band of india rubber the
same is rendered more elastic and the fiber is allowed to expand by the heat of the
current without altering the electric tension.
In some instances the diaphragm should be free to vibrate without being
checked by contact with any stationary substance I provide for this by placing
upon the diaphragm or tympan 10 Figure 17 a small cylinder t of hard rubber or
non-conducting material within which is the fibrous tension regulator tresting
upon a platina foil connected to one pole of the battery and within this cylinder t
is a disc to of iron or other metal loose but pressed towards the tension regulator
by a spring t and screw cap to and the other electric conductor is connected with
said spring.
The inertia of the metal disc causes more or less compression of the tension
regulator as the diaphragm is vibrated and hence the electric pulsations are sent
over the line in harmony with the vibrations. Nearly the same effect is produced
by connecting the disc t10 to a yielding spring t that extends across from one edge
of the diaphragm to the other as seen in Figure 16. This construction of tension
regulating device is especially available with large diaphragms.
In some cases I use a soft rubber diaphragm immediately in contact with the
transmitting or receiving diaphragin so as to check or dampen any prolonged or
false vibration and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable to
use lamp black mixed with pure plumbago amorphous phosphorous and a very
small amount of non conducting material such as rubber dissolved in a solvent that
will entirely evaporate.
In Figure 19 I have represented the circuit as passing through the diaphragm 10
tension regulator t and a Duluc's dry pile battery D P B to the earth. This
battery is composed of about 300 pairs of paper discs coated with silver and black
oxyd of manganese.
Figure 20 illustrates the device before mentioned for intensifying the sound 10
is the diaphragm vibrated by the sound 42 is a valve moved by such diaphragm.

page_text: 43 is a reservoir containing air under a given pressure 6 is the diaphragm against
which the air allowed to escape by the valve acts and t is the tension regulator
to transmit the electric pulsations or a bearing resonant case may be applied at the
same place.
Figure 24 represents the diaphragm 10 tension regulator t with its adjusting
screw and local circuit containing the battery B passing through a primary
induction coil 49 and there is a key 50 in the same circuit. A secondary induction
coil 51 is in the line circuit and is influenced electrically by the change of tension
in the local circuit by the vibrations of the diaphragm 10.
The secondary coil is sometimes required with many layers of fine wire to set
up a current of high tension to overcome the inductive effect from the line wires
being adjacent to each other. I place the receiving instrument at the distant
station between the induction coil and the earth as at R and use an electro-
magnet E M with polarized armature to strike a bell this will respond when the
key 50 in the local circuit at the distant station is opened and closed.
In Figure 25 a similar induction coil 49 and local circuit is represented but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes
one on the diaphragm the other on the adjusting screw. A shunt and rheostat at R¹
serves to prolong the magnetism in the induction coil and thus ensure a gradual
rise and fall of electric tension in the line instead of a cessation of the saine when
the platina surfaces separate and at the receiving diaphragm c the rise and fall of
electric tension in the line and its helix acts upon the permanent magnet to produce
the vibrations of the diaphragm c and by connecting a shunt around the helix and
placing therein the secondary battery S B composed of metallic plates in acidu-
lated water the action is rendered more uniform and the sound distinct.
When the diaphragm is arranged as in Figure 26 to act upon a spring 56
through an intervening piece of soft rubber said spring 56 produces rise and fall
of electric tension by employing a range of resistance 57 with spring tongues
adjacent to 56. The greater amplitude of vibration of the diaphragm the more
direct will be the electric circuit connections and the less resistance because the
circuit will pass along the spring instead of going through all the resistance
coils.
When several line wires run near each other the wire used for the acoustic or
speaking telegraph is influenced by induction and false sounds will be produced
I counteract this tendency by placing one or more electro magnets 59 Figure 28 in
the circuit of the speaking telegraph and one or more electro magnets 60 in the
circuit of the adjacent wires and bringing the opposite cores of 60 at such a
distance from the cores of 50-hat a certain magnetic action will be set up in 59
by induction in the opposite airection to the induction currents from the adjacent
line or lines.
By adjusting the distance between these magnets when the speaking telegraph
is not in use until there is not any sound at the diaphragm from the induction
currents then these currents will be neutralized whether strong or weak and will
not produce any false sound when the speaking telegraph is in use.
I also employ double coils of wire for the same purpose one coil being in the
acoustic wire and the other in the wire to be compensated.
1
A convenient form for the sound recorder or phonograph is to employ a
cylinder 61 see Figure 29 having a helical groove in its surface covered with tin
foil and the cylinder is revolved regularly by clock work and moved endwise by a
screw on its shaft so that the indenting point from the diaphragm 10 of h will
be always in line with such groove hence the vibration of the diaphragm will be
recorded by indenting the foil into the groove and hence the same sound will be
reproduced by the point 12 of the hearing instrument n giving to the diaphragm
of n the motions that result from the indentations of the foil moving in contact
with such point.
The foil may be on a flat grooved plate and be indented and act as before
named.

page_text: I would observe in conclusion that I do not claim generally the transmission
and reproduction of sounds by increasing and decreasing the resistance of the
circuit nor do I claim separately any of the parts or arrangements herein-before
described and illustrated in the accompanying Drawings except as hereinafter
mentioned but I claim as my Invention:-
In an instrument for transmitting electric impulses by sound the combination
with a diaphragm or tympan of electric tension regulators substantially as herein
before described for varying the resistance in a closed circuit substantially as set
forth.
In witness whereof the United Telephone Company Limited have caused
their Common Seal to be hereunto affixed the
One thousand eight hundred and eighty two.
day of
To the Commissioners of Patents for Inventions.
I hereby grant my Fiat giving leave to the United Telephone Company Limited
the assignees of the said Letters Patent to file in the Office of the Commiss"
of Patents for Inventions with the Specification to which the same relates the
annexed Disclaimer and Memorandum of Alteration: but nevertheless upon
condition that no proceedings for infringement be taken against James Merrill
Ormes, or Horace Hamline Eldred both of 31 Queen Victoria Street in the City of
London, The London and Globe Telephone and Maintenance Company Limited,
Messrs. Harrison Cox Walker and Company of Darlington in the County of
Durham, Telegraph Engineers, John Tasker of Sheffield in the County of York
Electrician or William Johnson also of Sheffield in the County of York, Electrician,
(hereinafter called the Opponents) or against any person or persons using any such
instruments as are hereinafter referred to, that is to say, in respect of
1. Any instruments made, or in course of manufacture on the 29th July 1882,
by, or to the order of, the said opponents or any or either of them.
2. Any instruments manufactured after the 29th July 1882 under or in
pursuance of any contracts bona fide entered into previous to that date by the said
opponents or any or either of them for the supply of instruments.
3. Any instruments manufactured after the 29th July 1882 under or in
pursuance of any contracts bona fide entered into prior to the 29th July 1882 with
the said opponents or any or either of them by any other person for the supply of
such instruments to the said opponents or any or either of them.
4. Particulars of all such instruments as have been or shall be subsequently to
the 2nd June 1882 manufactured or delivered, and of all contracts under which
such last mentioned instruments have been or shall be delivered to be furnished to

page_text: e United Telephone Company Limited and verified by Statutory Declaration on
before the 14th September 1882.
5. All such instruments as have not been delivered prior to 29th July 1882 to be
numbered and marked with proper identifying marks before delivery, and an
opportunity to be given to the United Telephone Company Limited or their
agents to verify the same.
0
6. Any question of bona fides to be referred to and determined by the Attorney

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
INSTRUMENTS FOR CONTROLING BY SOUND THE TRANSMISSION OF ELECTRIC
CURRENTS, AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT A
DISTANCE."
Sealed the 20th October 1877, and dated the 30th July 1877.
PROVISIONAL SPECIFICATION left by the said Thomas Alva Edison at the
Office of the Commissioners of Patents on the 30th July 1877.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United States
of America. "IMPROVEMENTS IN INSTRUMENTS FOR CONTROLING BY SOUND THE
TRANSMISSION OF ELECTRIC CURRENTS, AND THE REPRODUCTION OF CORRESPONDING
SOUNDS AT A DISTANCE."
The vibrations of the atmosphere, which result from the human voice or from
any musical instrument or otherwise, are made to act in increasing or lessening the
electric force upon a line by opening or closing the circuit, or increasing or
lessening the intimacy of contact between conducting surfaces placed in the circuit
at the receiving station; the electric action in one or more electro-magnets causes
a vibration in a tympan, or other instrument similar to a drum, and produces a
sound, but this sound is greatly augmented by mechanical action.
I have discovered that the friction of a point or surface, that is in contact,
whether a properly prepared and slowly moving surface, is very much increased
or lessened by the strength of the electric wave passing at such point of contact,
and from this variation in the friction a greater or less vibration is given to
the mechanism or means that produce or develope the sound at the receiving
station, thereby rendering clear and distinct the sound received that otherwise
would not be audible.
To carry out the peculiarities of my Invention under the varying conditions of
use, I have devised several modifications of the transmitting, receiving, and
intensifying devises employed in this sound telegraph; portions of the apparatus

page_text: are interchangeably, available in transmitting or recording; others are adapted to
local use; some are only available in transmitting, and others are only for receiving;
and some portions of my improvement can be availed of to make a record of the
atmospheric sound waves, or of the electric waves, or pulsations corresponding thereto
or resulting therefrom.
In one form of my apparatus the sound passes into a resonant box having one,
two, or more tympans at its sides that are vibrated thereby, the tension of these
being various, so as to respond to different sound waves, and the electric connections
pass through all to one line or circuit, in which is a battery and the distant
receiving instrument. Circuit contact points are provided at one or both surfaces
of the tympan or tympans; the tympans are of parchment, foil, mica, sheet metal,
or similar material. I find platinum, foil, or mica to respond advantageously when
the waves from the mouth are made to pass through a slot resembling the larynx
placed within the resonant tube. The contact points or surfaces are sometimes
metallic, but plumbago, or similar semi-conducting material, into which the tympan or
diaphragm is brought more or less intermittently into contact, or a point or pin
thereon serves to lessen or increase the electricity passing at that point.
In the receiving portion of the instrument the tympan is acted upon directly by
an electro-magnet, or through an armature, or the tympan is provided with an arm
extending out over a slowly moving surface or cylinder, and the electric current,
passing at the point of contact, increases or lessens the friction, and produces the
vibration of the arm and tympan in proportion to the difference of friction
developed between the arm and moving surface by the passage and cessation of
the current through the chemically prepared paper, preferably moistened with a salt
of mercury and an alkali. This feature is capable of very extended developement
in telegraphy; the clearness and extent of sound produced by the receiving tympan
exceeds anything heretofore attained in acoustic telegraphs.
The frictional surface may be any material which absorbs liquids, such as chalk
or paper; the transmitting points in all instances should be a poor conductor of
electricity, such as cyanide of copper, peroxide of lead, or plumbago, which
substance may be moulded with non-conductors.
Where plumbago is used between the cores and armature of an electro-magnet,
and such plumbago is included in a local or relay circuit, the pulsations or rise and
fall of electric tension will correspond to that in the coils of the electro-magnet in
consequence of the varying compressing action on the plumbago or similar material,
which increases and decreases its resistance.
A polarized arm, near a soft iron plate upon the tympan, will receive a motion
from the vibration of the tympan, and make more or less intimate contact with the
plumbago point without arresting the motion of such tympan.
In the line the effect of the static charges and discharges are neutralized by
condensers or by helices in shunts.
Where a rapidly revolving wheel is contiguous to the transmitting tympan,
and there is a plate of platina on that tympan to which the circuit is connected, the
rise and fall of electric tension will result accurately from the movement of the
tympan, producing greater or less contact with the wheel; a spring may intervene
between the wheel and tympan.
A spring or reed, attached to a stud at one end, and to the tympan at the other,
is vibrated or undulated by the sound waves acting on the tympan, and produces
greater or less contact with pieces of tin foil surrounding it, which also are in the
electric circuit or plumbago; contact points near the side of such spring effect the
same object. A column formed of disks of tin foil in a glass tube, pressed upon by
the vibrations of the tympan, also are employed under some circumstances to
regulate the electric tension in the circuit.
The moving surface, whose friction is increased or decreased upon the passage and
cessation of the current aforesaid, is employed in some instances to vibrate by the
electric and mechanical action a frame of strings of different pitch to produce
musical sounds, or to give motion to reeds or resonant boxes.

page_text: The transmitting tympan is sometimes made of cloth, with plumbago pressed into
its surfaces, and generally it is preferable to weight the centre of the tympan, and
take the motion a little one side of the centre to prevent a flase movement or
rebound. These sound transmitting and receiving instruments are applied in single
or multipleyd telegraphs; the connections through the Wheatstone bridge, or the
induction coils, being used in the well known ways, and the circuits being
either single or relays.
Where alluminium is introduced in the electric circuit in connection with a
material containing an electrolite, the vibration of the tympan, and an extension
from it to the material containing the electrolite, causes a depolarization at the
point of contact at every vibration, thus increasing and decreasing the strength of
the current by depolarization.
Where a slot is made in the diaphragm, and the airways impinge against the
same, the vibration of the hissing sounds is augmented.
The resonant chamber for convenience is made portable, so as to be presented to
the mouth.
In addition to the tympan for transmitting the vowel sounds, I employ another
opening in the speaking tube, or chamber, which opening may be increased or
lessened; I stretch edgewise over this a thin reed of foil, which is set in vibration
by all hissing consonants, and make contact with a plumbago point, or with a
platina point, which is connected to the line through an adjustable resistance coil,
or a self-acting reed giving a biss may be thrown in and out of circuit by the
movement of the foil reed.
For transmitting and receiving letter by letter, I employ a shaft with 30 wheels,
and contact springs resting upon them; the wheels are provided with teeth of such
number and character that they will cause the springs to be vibrated against a
plumbago point the necessary number of times, and with proper pressure to transmit
the letter, which is rendered audible at the distant station by the magnet or
frictional surface. Each wheel is controlled by a key of a key board.

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 30th
January 1878.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United States
of America. "IMPROVEMENTS IN INSTRUMENTS FOR CONTROLING BY SOUND THE
TRANSMISSION OF ELECTRIC CURRENTS, AND THE REPRODUCTION OF CORRESPONDING
SOUNDS AT A DISTANCE."
This Invention relates to that class of electrical instruments in which sound
becomes one of the elements in the transmission of the communication, and the
same sound is produced at the receiving station, so that oral communications can
be sent by electricity and clearly distinguished at the receiving station.
Musical tones may also be sent, but my present Invention is especially available
in transmitting and receiving oral communications.
In transmitting musical tones, the respective notes each have a definite period for
each vibration, hence there is a response at the receiving end from the notes that
vibrate in time with the electric pulsations sent, but in speaking there is little
change in the musical tone, but considerable in the modulations and inflections of
the voice.
In my resent Invention I make use of the vibrations given to a diaphragm or
tympan, oy speaking into a resonant case, to produce a rise and fall of electrical
tension upon the line with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation, and the electro-
magnet at the receiving station will respond to the electric waves in such a manner
as to reproduce the articulation by acting upon a resonant plate.
The instruments in a complete form are represented in Figs. 1 and 2, Fig. 1 being
a section of the transmitting instrument, and Fig. 2 of the receiving instrument.
The resonant tube or box a is of a size and shape adapted to being spoken into,
the same having an opening at one end or side and a diaphragm or diaphragms b,
against which the sound waves from the human voice act, and these and the motion
that the diaphragın receives is the means of producing a rise and fall of electric
tension on the line by the devices hereafter set forth, so that the battery B connected
to the line will transmit a greater or less current to the distant electro-magnet m,
Fig. 2, and increase or lessen the magnetism of the cores, and in so doing act upon
a resonant plate c, and develop sound corresponding to the articulation at the trans-
mitting station.
The general features thus described pervade my entire Invention, but in de-
veloping the same many useful and important modifications and variations have
been made, which I will proceed to set forth.
For convenience the speaking instrument, Fig. 1, is provided with a handle, a',
and flexible conductors to the battery and line respectively, so that it may be
handled and brought to the mouth; and in like manner it is preferable to place the
hearing instrument, Fig. 2, in a movable handle b', so that it can be placed with
the plate c against the ear, this brings the sound close to the organs of hearing, and
the resonant plate touching the ear increases the distinctness of the sound, and
prevents any false or prolonged vibrations of the plate.
In some of the modifications I have shown the speaking instrument as a fixture,
and also the hearing instrument as a fixed resonant tube, these being variable to
suit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity of
the resonant tube for the voice. I have experienced great difficulty in reproducing
the sound of the hissing consonants, such as s; this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth, and does not act
distinctly upon the diaphragm. By providing an edge in the resonant tube
below the mouth, upon which such consonant sounds are received, the vibrations

page_text: are given either to the resonant tube or deflected to the diaphragm. I find it
preferable to employ a hole e at the lower part of the mouth-piece, against the edges
of which the downward sound waves are directed. The same effect will be pro-
duced by a vibrating edge placed in the lower part of the mouth-piece, or the
opening into the resonant box may be contracted to about half an inch in diameter
to effect the same purpose. The next feature requiring consideration is the character
of the diaphragm in the speaking instrument.
Many materials have been employed by me, such as metals, horn, vellum, celluloid,
ivory, &c., but almost all of these produce a prolonged or secondary vibration from
their own resonant character, hence the articulation is defective, and the sound
vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
resonant action, and hence it will respond with the greatest accuracy to the sound
vibrations, and being of a laminated character can be employed of any desired thick-
ness, and when secured at its edges responds with the greatest accuracy to the sound
vibrations, and does not require to be strained; furthermore, the changes of tempera-
ture and atmospheric condition have little or no effect upon the mica diaphragm or
tympan.
I find that it is not practical to open and close the line circuit in instruments
for transmitting the human voice; the circuit to the line must be always closed,
and the transmission be produced by a rise and fall of electric tension, resulting
from more or less resistance in the line. This resistance may be produced in
several ways. I have shown several which will hereafter be named, but I find the
most delicate to be small bunches or tufts, or disks of semi-conducting elastic fiber,
such as particles of silk, and an intermediate conducting or semi-conducting material;
this device call an electric tension regulator; it is more or less compressed, according
to the vibrations of the diaphragm or tympan, and the electric current rises in
tension as it is compressed or lessens as the fiber expands. This fiber is placed in a
small roll t, between the delicate diaphragm spring u, Fig. 9, and the variable
presser v, adjustable by a screw or otherwise in the electric circuit at this point, or
it may be within a cavity in said presser v, as in Fig. 1, there being a delicate cork
center piece w to the diaphragm b, with a piece of platina foil x in contact with the
fiber; in all instances the telegraphic circuit at the diaphragm is made by a thin
strip of platina or similar material extending to the center from the line or battery.
connection.
The fiber is rendered semi-conductive by being rubbed with plumbago, soft
metal, or similar material, or by a deposit of metal upon its surface, or by fine
particles of conducting or semi-conducting material mixed with it, the conducting.
power varying with the density of the tuft or bunch of fiber. The delicate spring
u, Fig. 9, npon the mica diaphragm 6 is easily secured by solder passing into fine
holes bored in the mica. In Fig. 3 the tension regulator is made by water or other
Bemi-conducting electrolytic fluid in a cup f. The wires to the battery are led to
the electrodes or conducting points 2, 3, in such cup that are opposite to points 4, 5,
upon the diaphragm b. The cup is adjustable to vary the distance between the
electrodes and the rise and fall of tension results from the varying distance between
the electrodes as moved by the vibrations of the diaphragm.
If there are several electrodes opposite to each other and insulated, except at
their ends, and the circuit led from one to the other so that the current passes
through all the electrodes in succession, the rise and fall of electric tension will be
promoted, because the smallest vibration of one set of electrodes is multiplied by
the number of places at which the metallic circuit is interrupted or varied.
In the receiving or hearing instrument the resonant plate c should be of tinned
iron, resting upon the edges of the case, and the magnet m, adjustable nearer to or
further froin the same, and connected loosely by slotted tongues. This plate will
respond to the electric pulsations by the attraction of the magnetized cores, and the
sound resulting will be audible when the plate is placed near or against the ear. If
the plate. is pressed away from the magnet by a delicate spring or allowed to fall

page_text: away from the magnet, the instrument may be used as a call by using a key or
switch at the sending station to open and close the circuit, and thus move the plate
to give a loud sound.
In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact such as would result from a disk covered with plumbago
placed adjacent to a diaphragm, also covered with plumbago or other semi-con-
ducting material, so that the proximity or extent of surface contact will produce rise
I also
and fall of tension, the respective parts being in the telegraphic circuit.
sometimes employ a shunt circuit in the line, or a branch circuit to the earth, in
which is placed an electro-magnet to neutralize any static charge or discharge in
the line.
I sometimes perforate the diaphragm 10, Fig. 18, and place a strip of elastic
material, 40, across said diaphragm over the hole, and upon this a piece of foil, so
that the same responds to very weak vibrations, and in some instances two or more
diaphragms are provided at different sides of the resonant box, each with its own
or of different sizes,
tension regulator, the diaphragms being either the same
characters, or tensions, so as to respond to varying sounds or acoustic condition, the
various tension regulators being all in the electric circuit; this will produce greater
rise and fall of tension for longer lines in consequence of the diaphragms acting
simultaneously on the tension regulators.
In some instances it is preferable to make the mouth-piece of the speaking
instrument sufficiently large or flaring to receive all the sound vibrations, whether
coming from the mouth, nose, or throat.
Several contact points of platina, placed contiguous to the diaphragm, may be
used, the same acting to increase or lessen the surface contact, according to the
amplitude of vibration of the diaphragm, and a drop of liquid such as oil or
glycerine, between the contact point and diaphragm, will serve to maintain a closed
circuit, but the movement of the diaphragm produces rise and fall of tension.
The tension regulator, formed of fiber and conducting or semi-conducting material,
may be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within a
case to form the tension regulator, the circuit passing through the same, and the rise
and fall of electric tension resulting from the compression of the same by the move-
ment of the diaphragm.
I am enabled to record to record the sounds produced by the human voice or other-
wise by causing the movements of the diaphragin to be registered on paper or soft sheet
metal, and then the paper may be used in an instrument to reproduce the sound upon
a delicate diaphragm by giving to the same a vibration similar to that originally
given by the voice.
h, Fig. 4, is the indenting transmitter, the diaphragm having a knife-edge point.
i is the paper which has previously been passed through a machine to raise a V shaped
rib 6. The movement of the diaphragm of h, when the drum is in motion, causes
the knife-edge point to indent the raised rib to varying depths, according to the
amplitude of vibration of the diaphragm, thus these indentations represent accurately
all the tones and varying inflections of the human voice. The paper after being
indented is passed through a second apparatus n, Fig. 5, almost similar to h. A
spring 9 has a knife edge which rest upon the raised indented rib 6, the spring
being connected to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting point
and either by direct action, or through the vibration of a string, conveys the same
motion to the diaphragm of n, and reproduces previous sounds. If these sounds
are to be transmitted over a telegraph line the diaphragm 10, see Fig. 6, is pro-
vided with a cork disk w, and fibrous tension regulator t, before described, to
produce the rise and fall of electric tension on the line. The sound may be recorded
in ink as represented in Fig. 7. The diaphragm of h operates a very flexible self
feeding pen o, and causes the continuous line to be wide or narrow, according to
the amplitude of vibration of the diaphragm. The ink used should dry quickly

page_text: and the strip may be passed at any time thereafter through the instrument shown
in Fig. 8, beneath the arm 12, having a point or points resting on the paper; this
arm is connected with a resonant diaphragm, and the ink marks produce more or
less friction, according to the breadth and amount of ink deposited, and this will
set the diaphragm of n vibrating, and reproduce the vibrations of the diaphragm
of h.
An obvious modification would be to coat the paper with a substance which would
cause considerable friction, or even rough unsized paper might be used, and a spring
provided with a burnished point, rather flat, would cause the surface of the paper
to be made smooth more or less, according to the vibration of the diaphragm, and
the differences in the surface of the paper would produce a response in the receiving
diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument,
as shown in Fig. 10.
h is the resonant chamber at the end of which is the diaphragm 10, and at each
side of this diaphragm there are springs c³, c³, having points made of compressed
plumbago mixed preferably with gum rubber, but any substance not liable to
rapid decomposition, or the elastic or fibrous tension regulator aforesaid may be
used. These points face each other on opposite sides of the diaphragm, and make
contact with platina foil disks secured to the diaphragm.
The spring c passes through a hole or small slot in the side of the chamber h.
d, d, are the main batteries. The battery d has zinc to the line or spring c³,
and the battery d³ has copper to the line or spring c. When the springs and c³.
are adjusted to make contact with the diaphragm equally, no current passes to the
line; but when the diaphragm is vibrated, its movement to one side, say c³, causes
a greater pressure upon the plumbago on that spring, and a lessening of the pressure
on the plumbago on c³; hence the balance of the batteries c³ and c³ will be destroyed,
c, having the advantage, will send a negative current to line; upon the return of
the diaphragm the battery currents will again neutralize each other. The vibration
of the diaphragm to the other side causes the pressure to be reversed, and the
battery d³ will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure, it follows that the
strength of the electric waves will be in proportion as the speaker's voice is strong
or weak.
In Fig. 11 is shown the contact spring, which may be used adjacent to the
diaphragm at one or both sides thereof. is a U shaped spring secured to the
screw, which is adjusted back and forth by the thumb nut ; e is the pillar
holding such screw; r is a piece of soft rubber, or equivalent substance, placed
between the prongs of the spring e³; e' is a wire or band which serves to bind the
prongs tightly against the rubber r, so as to prevent the prongs acting as a tuning
fork, and transmitting harmonic vibrations not desirable; is the plumbago
contact point. The object of the U spring and rubber is to present a semi-rigid
point for contact, so as to prevent a rebound, and allow of a slight yield when the
plumbago is pressed by the diaphragm.
In Fig. 3 the diaphragm of the receiving instrument is vibrated by a strip of
paper chemically prepared that is in motion, the pulsations of electricity passing
over the line and producing more or less friction between the paper and an arm
upon the diaphragin.
The resonant box or chamber n is provided with a diaphragm as aforesaid, and
to said diaphragm an arm h' is connected; at its outer end is an adjusting screw h³,
that presses upon a platina-faced spring h* that is secured to this arm, and said
spring rests upon the strip of paper that passes over the drum h³.
The paper is moved slowly by rotating the drum ho, and the waves of electricity
coming over the line pass through the arm h³ to the platina-faced spring h*, thence
through the paper to the earth.
If a negative current passes in the opposite direction, nearly all friction between

page_text: the platina plate and the paper ceases, and the diaphragm of the resonant box n
regains its normal position.
When the positive current passes through the same channel, the normal friction
of the paper is augmented, and the chemical surface acting upon the platina
spring arm serves to give a forward movement to the diaphragm of the resonant
box.
Thus the mechanical force applied to move the chemical paper or surface acts with
the electric current to produce the vibration of the diaphragm of the resonant
chamber, and these vibrations will correspond to those of the diaphragm b, made by
speaking in the tube a.
The principle of this method of obtaining motion by electro-chemical decom-
position is, that when a moving surface is in contact with a slightly yielding
substance, the tendency is to move the latter by and with the former. If the
circumstances of contact are varied, the adhesion of the surfaces will be sufficient to
cause the moving surface to move the yielding substance, or else to cause the
yielding surface to slip more freely, and by its spring go in the opposite direction to
the moving surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion, making it more or less, according to the substances employed. By
balancing the mechanical forces, so that when the surfaces in contact are not
electrified, the moving surface carries with it the yielding surface; and, when
electrified, the yielding surface slips back over the moving surface, a mechanical
movement is obtained that is dependent on the electrical condition of the surfaces
in contact.
When it is requisite to obtain very perfect articulation, and when loudness is not
essential, I adopt a modification, shown in Fig. 12, of the device for compressing
and expanding the tuft of conducting fiber, which modification consists in placing
between the diaphragm 10 and the fiber t a vibrating tongue 21 of steel, permanently
magnetized, and arranging it to act in the same manner upon the tension regulator t
as if it was the diaphragm. I replace the cork upon the diaphragm by a thin
armature of iron 22 which is in close proximity to the magnetized tongue, which
tongue is secured at one end like an acoustic reed. In this position the diaphragm
is free to move, and at its approach to and recession from the magnetized tongue
causes said tongue to follow its movements by magnetic attraction, and thus the
tongue is made to perform what the diaphragm previously performed in varying
the tension of the electricity on the line.
A modification of the magnetic receiving instrument consists in an iron plate
fitted into the aperture of a resonant tube, and secured by a central support, leaving
its outer circumference free to vibrate when the metal is attracted by the poles of
the electro-magnet, which are of course on each side of its center; but it is
preferable to place the support slightly out of center, as some portions of the plate
will then be in tone for every sound.
A plate supported eccentrically and free at its edges when placed in the speaking
tube responds advantageously to the tones of the voice; the circuit with this plate
is completed through one or more tension regulators placed around its edges.
I have discovered that vulcanite or hard rubber produces cold and heat waves on
its surface by the slightest movement, and in some cases I employ the same for the
diaphragm of the resonant case h, Fig. 13, and place a thermo-electric pile h' in
very close proximity to the rubber, so that the vibration of the diaphragm 10
producing changes of temperature will cause currents of electricity to be set up
within the thermo battery, and these passing over the line 7 and acting upon a very
delicate electro-magnet and diaphragm will reproduce the sounds acting upon the
rubber diaphragm.
In practice I combine with the speaking or telephonic apparatus signal bells, so
arranged that when the telephone is not in use the line is thrown upon the bell by
a switch, which also acts as a call on the bell.
.. One feature about the bells is that the magnet which serves to actuate the bells

page_text: is made of very high resistance, using preferably German silver wire in the helix,
and thus serve to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from one battery if these bells are used.
The method I adopt for coating non-conducting substance with metallic substance
is the reduction to the metallic state of metals from their salts by exposing them to
the fumes which arise from the moist phosphide of a metal, such as phosphide of
calcium, or by placing the silk, for instance, in a sealed tube provided with inetallic
electrodes, and volatilizing the electrodes by the passage of electric sparks; such
volatilized metals settle upon and coat the silk.
When great loudness is desirable, as in factories, the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is stored
under a regulated pressure.
The air allowed to escape will act with great power upon a local diaphragm.
This diaphragm, to obtain clear sounds, requires a damper to check prolonged
vibrations. It must be dampened by holding the fingers against it, or by a tightly-
stretched cord rubbing against it, or by a screw provided with a rubber tip held
against it.
For repeating from one circuit into another I use with the receiving diaphragm
the elastic tension regulator Fig. 1 in addition to the electro-magnet, and connect
the relay or second circuit through the same, so that waves received from the distant
station cause the magnet to vibrate the diaphragm, and this acting upon the tension
regulator transmits the waves into the second circuit, and they are received at the
other end by an electro-magnet and diaphragm.
In some instances I make a record of the sound by the movements of the
diaphragm, using for that purpose a strip of paper moved along regularly between
two rollers 25, 26, as in Figs. 14 and 15; and there is a smooth thread or fine wire
of soft metal 30 between the paper and the upper roller 25, and moving along with
it. The diaphragm 10 of the resonant box is connected by a delicate rod 28 with
this thread or wire as near to the bight of the roller as possible, there being a fork
or eye through which the thread passes, hence deflections or bends are made in the
thread or wire just before it is imbedded into the paper by the pressure of the
rollers; this may be used to reproduce the sound by vibrating a resonant diaphragm
by the undulations of the groove made by the thread or cord.
By placing the fibrous tension regulator within a small band of india-rubber the
same is rendered more elastic, and the fiber is allowed to expand by the heat of the
current without altering the electric tension.
In cases where a strip of hard rubber or a cord of silk or other material coated
with plumbago or metallic foil is introduced between the diaphragm and a rigid
support, the expansion and contraction due to the passage of the electric currents
will produce a movement upon the diaphragm corresponding to the diaphragm
producing the electric pulsations.
In some instances the diaphragm should be free to vibrate without being checked
by contact with any stationary substance. I provide for this by placing upon the
diaphragm or tympan 10, Fig. 17, a small cylinder 17 of hard rubber or non-
conducting material, within which is the fibrous tension regulator t resting upon a
piece of platina foil connected to one pole of the battery, and within this cylinder t
is a disk to of iron or other metal, loose, but pressed towards the tension regulator
by a spring to and screw cap to, and the other electric conductor is connected with
said spring.
The inertia of the metal disk causes more or less compression of the tension
regulator as the diaphragm is vibrated, and hence the electric pulsations are sent
over the line in harmony with the vibrations. Nearly the same effect is produced
by connecting the disk to to a yielding spring t" that extends across from one edge
of the diaphragm to the other, as seen in Fig. 16. This construction of tension
regulating device is especially available with large diaphragms.
In some cases I use a soft rubber diaphragm immediately in contact with the

page_text: transmitting or receiving diaphragm, so as to check or dampen any prolonged or
false vibration, and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable to
use lampblack mixed with pure plumbago, amorphous phosphorous, and a very
small amount of non-conducting material, such as rubber dissolved in a solvent
that will entirely evaporate.
In Fig. 19, I have represented the circuit as passing through the diaphragm 10,
tension regulator t, and a Dulucs dry pile battery D, P, B, to the earth. This battery
is composed of about 300 pairs of paper disks coated with silver and black oxyd of
manganese.
Fig. 20 illustrates the device before mentioned for intensifying the sound; 10 is
the diaphragm vibrated by the sound; 42 is a valve moved by such diaphragm ;
43, is a reservoir containing air under a given pressure; 6 is the diaphragm against
which the air, allowed to escape by the valve, acts, and t is the tension regulator to
transmit the electric pulsations, or a hearing resonant case may be applied at the
same place.
Many curious and useful features have been developed by my extended researches
in the transmission and reproduction of sound. Among these may be mentioned
the fact that a copper diaphragm, or a diaphragm of mica or other flexible material
containing copper, will act with the core of a polarized electro-magnet in trans-
mitting or receiving.
If a diaphragm with a metallic button upon it is so close to the core of a per-
manent magnet, see Fig. 21, that the vibrations of the diaphragm by sound cause
such button to strike the core, a corresponding electric pulsation will be set up in
a helix around the magnet, and the same will act in an electro-magnet at the
distant instrument by molecular disturbance.
If the diaphragm 10 has a thin tube attached to the center, as seen in Fig. 22,
and this project into the helix around one pole of magnet 48, the current set up in
that helix by the vibration of the diaphragm and tube, will be much greater than
that resulting from a flat armature on the diaphragm or the diaphragm itself.
The magnet 48 may be polarized by a helix and a local circuit and battery.
If one pole of the permanent magnet m³, Fig. 23, is connected with the plate c
so that the latter is polarized by induction, the current set up in the helix around
one pole of the said magnet is intensified. In this case I groove the end of the
helix pole, and insert a small piece of soft rubber or tubing that serves to dampen
the vibrations of the diaphragm, and prevent false or harmonic vibrations in
speaking.
Fig. 24 represents the diaphragm 10, tension regulator t with its adjusting screw
and local circuit containing the battery B, passing through a primary induction
coil 49, and there is a key 50 in the same circuit. A secondary induction coil 51 is
in the line circuit, and is influenced electrically by the change of tension in the
local circuit by the vibrations of the diaphragm 10.
The secondary coil is sometimes required with many layers of fine wire to set
up a current of high tension to overcome the inductive effect from the line wires,
being adjacent to each other. I place the receiving instrument at the distant
station between the induction coil and the earth as at R, and use an electro-magnet
E, M, with polarized armature to strike a bell; this will respond when the key 50
in the local circuit at the distant station is opened and closed.
In Fig. 25 a similar induction coil 49 and local circuit is represented, but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes,
A shunt and rheostat
one on the diaphragm, the other on the adjusting screw.
at R¹ serves to prolong the magnetism in the induction coil, and thus ensure a
gradual rise and fall of electric tension in the line instead of a cessation of the
same when the platina surfaces separate, and at the receiving diaphragm c, the rise
and fall of electric tension in the line and its helix acts upon the permanent magnet
to produce the vibrations of the diaphragm c, and by connecting a shunt around

page_text: the helix, and placing therein the secondary battery S, B, composed of metallic
plates in acidulated water, the action is rendered more uniform and the sound
distinct.
When the diaphragm is arranged as in Fig. 26 to act upon a spring 56, through
an intervening piece of soft rubber, said spring 56 produces rise and fall of electric
tension by employing a range of resistances 57 with spring tongues adjacent to 56.
The greater amplitude of vibration of the diaphragm the more direct will be the
electric circuit connections and the less resistance, because the circuit will pass
along the spring instead of going through all the resistance coils.
When there is an electro-phorous or resinous disk 58, immediately facing each
diaphragm 10, as in Fig. 27, and the line connections are made to the diaphragm,
and the earth connections are made to these electro-phorous disks 58, the diaphragms
will respond to each other in either speaking or hearing.
Where several line wires run near each other, the wire used for the acoustic or
speaking telegraph is influenced by induction, and false sounds will be produced. I
counteract this tendency by placing one or more electro-magnets 59, Fig. 28, in the
circuit of the speaking telegraph, and one or more electro-magnets 60 in the circuit
of the adjacent wires, and bringing the opposite cores of 60 at such a distance
from the cores of 59 that a certain magnetic action will be set up in 59, by
induction in the opposite direction to the induction currents from the adjacent line
or lines.
By adjusting the distance between these magnets when the speaking telegraph
is not in use, until there is not any sound at the diaphragm from the induction
currents, then these currents will be neutralized, whether strong or weak, and
will not produce any false sounds when the speaking telegraph is in use.
I also employ double coils of wire for the same purpose, one coil being in the
acoustic wire, and the other in the wire to be compensated.
A convenient form for the sound recorder or phonograph is to employ a cylinder
61, see Fig. 29, having a helical groove in its surface covered with tin foil, and the
cylinder is revolved regularly by clockwork and moved endwise by a screw on its
shaft, so that the indenting point from the diaphragm 10 of h will be always in
line with such groove, hence the vibrations of the diaphragm will be recorded by
indenting the foil into the groove, and hence the same sound will be reproduced by
the point of the hearing instrument n, giving to the diaphragm of n the motions
that result from the indentations of the foil moving in contact with such point.
The foil may be on a flat grooved plate and be indented and act as before-
named.
I claim as my Invention,-
First. In an instrument for transmitting electric impulses by sound, a diaphragm
or tympan of mica, substantially as set forth.
Second. In an instrument for transmitting electric impulses by sound, the com-
bination with a diaphragm or tympan of an electric tension regulator for varying
the resistance in a closed circuit, substantially as set forth.
.
Third. The combination in an electric instrument actuated by sound, of a
diaphragm or tympan, a conductor, and an electric tension regulator composed of
yielding material and electric conducting material.
Fourth. The combination with the diaphragm and electric conductor, of the cork
disk and tension regulator, substantially as set forth.
Fifth. In a telegraph operated by sound, the transmission and reproduction of
the human voice by increasing and descreasing the resistance of the circuit, sub-
stantially as set forth.
Sixth. The combination with a diaphragm or tympan, of electrolytic fluid and
electrodes, the latter being vibrated by the diaphragm and varying the resistance in
the electric circuit, substantially as set forth.
Seventh. In an instrument for transmitting sounds by electricity, a resonant
case having an opening or edge, against which the consonant sounds act, substan-
tially as set forth.

page_text: Eighth. In combination with the diaphragm or tympan and the electric tension
regulator, the adjusting screw or variable presser to regulate the resistance of the
tension regulator in the electric circuit, substantially as set forth.
Ninth. The combination with a diaphragm in a speaking telegraph instrument of
a moving surface, and a recording mechanism actuated by the diaphragm or tympan
substantially as set forth.
Tenth. The combination with a receiving diaphragm or tympan in a telegraph
operated by sound, of a moving surface, a point, and a connection from the saine to
the diaphragm, substantially as set forth.
Eleventh. The combination in an instrument for receiving sounds electrically, of
an electro-magnet and armature plate, substantially as set forth.
Twelfth. The combination in the telegraphic circuit of two or more tympans, a
resonant box, and one or more circuit closers to each tympan, substantially as set
forth.
Thirteenth. The combination with the diaphragm of a resonant case, of circuit
connections at both sides of the diaphragm and a battery, substantially as shown
in Fig. 10.
Fourteenth. In a telegraph instrument operated by sound, a resonant box or
case, a diaphragm and flexible circuit connections, substantially as set forth,
whereby the instrument is made portable and can be placed to the mouth in
speaking.
Fifteenth. In a telegraphic instrument operated by sound, an electro-magnet and
resonant plate or diaphragm provided with a handle and flexible conductors, sub-
stantially as set forth.
Sixteenth. The receiving instrument consisting of an electro-magnet, a case, and
a loose metallic plate, arranged and operated substantially as set forth, to act as a
call or to receive the message.
Seventeenth. In a telegraphic apparatus operated by sound, one or more contact
points of yielding material that produce a rise and fall of tension proportioned to
the pressure exerted by the diaphragm, substantially as set forth.
Eighteenth. In a telegraphic apparatus operated by sound, a receiving instrument
provided with a resonant surface, in combination with a frictional surface moved
by power and acting in connection with the electric current to vibrate such resonant
receiver, and produce tones corresponding to those at the transmitting apparatus,
substantially as set forth,
Nineteenth. The combination with a thermo-electric, pile of a vulcanite or hard
rubber diaphragm, substantially as set forth.
Twentieth. The method herein specified of recording the undulations of the
diaphragm or yielding material, and the reproduction of sound by such material
acting upon a diaphragm to communicate to the same vibrations similar to the
original ones, substantially as set forth.
Twenty-first. The combination with the diaphragm and tension regulator, of a
magnetized tongue and an iron plate upon the diaphragm, as set forth and shown
in Fig. 12. .
Twenty-second. In combination with the diaphragm operated by sound, an
electro-magnet, a valve, and a chamber of compressed air or gases to reproduce
the sounds in louder tones.
Twenty-third. The method herein specified of preparing fiber for electric tension
regulators by conducting or semi-conducting material associated intimately with
such fiber, substantially as set forth.
Twenty-fourth. In an instrument for receiving sound telegraphically, a plate,
loose at its edges, and supported upon a post or standard, substantially as set
forth.
Twenty-fifth. The combination with the sending and receiving diaphragm of the
dry pile illustrated in Fig. 19.
Twenty-sixth. The combination in a telephonic instrument, of an iron diaphragm
5
5

page_text: and a magnet, one end of which is attached to the magnet, substantially as
specified.
Twenty-seventh. The combination with the electric circuit and a diaphragm of
an induction coil and magnet, substantially as set forth.
Twenty-eighth. The combination with the induction coil, diaphragın, and local
circuit of a key in said circuit, and a call or sounder at the distant station, sub-
stantially as set forth.
Twenty-ninth. The combination with a diaphragm of rheostats or resistances in
the line or local circuit, and means for short circuiting such resistances in proportion
to the movement of the diaphragm, substantially as set forth.
Thirtieth. In combination with an electric circuit containing instruments for
reproducing sound, one or more electro-magnets and one or more compensating
inagnets for neutralizing the inductive effect of adjacent telegraph wires, substan-
tially as set forth.
In witness whereof, I, the said Thomas Alva Edison, have hereunto set my
hand and seal, this Twenty-fourth day of December, A.D. 1877.
THOMAS ALVA EDISON. (L.S.)
Witnesses,
CHA. H. SMITH, 76, Chambers St., New York.
WILLIAM G. MOTT,
"
"
"J

page_text: Filed February 1880.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, the Edison
Telephone Company of London, Limited, of 11, Queen Victoria Street, in the
City of London, send greeting :-
WHEREAS Her Most Excellent Majesty, Queen Victoria, by Her Royal Letters
Patent, under the Great Seal of Great Britain and Ireland, bearing date at
Westminster, the Thirtieth day of July, in the Year of Our Lord, One thousand
eight hundred and seventy seven, in the Forty-first year of Her Reign, did for
Herself, Her heirs and successors, give and grant unto Thomas Alva Edison, of
Menlo Park, in the State of New Jersey, United States of America, his executors,
administrators, or assigns, or such others as he his executors, administrators, or
assigns should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention of "IMPROVEMENTS IN
INSTRUMENTS FOR CONTROLLING BY SOUND THE TRANSMISSION OF ELECTRIC
CURRENTS AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT A DISTANCE,"
for and during the term of Fourteen years thence next ensuing: And whereas in
pursuance and performance of a proviso in the said Letters Patent contained the
said Thomas Alva Edison did within Six calendar months next after the date of
the said Letters Patent cause a Specification in writing under his hand and seal
purporting to particularly describe the nature of the said Invention, and in what
manner the same was to be performed, to be duly filed in the Great Seal Patent
Office: And whereas by Indenture bearing date the Second day of August, Onc
thousand eight hundred and seventy nine, and made between the said Thomas
Alva Edison of the one part, and as the Edison Telephone Company of London,
Limited, of the other part, the said Thomas Alva Edison assigned unto us the said
Edison Telephone Company of London, Limited (inter alia), the said herein before
recited Letters Patent, and all rights, powers, authorities, privileges, advantages,

page_text: profits, emoluments, and benefits to the said Letters Patent, appertaining or
belonging And whereas since the date of the said Assignment we have been
advised and have ascertained that the said Specification contains matters which are
of doubtful novelty, or which are not of sufficient practical value and utility to
justify their retention; and we are therefore desirous of striking out the whole of
the claiming clauses contained in the said Specification, with the exception of the
first, second, eighteenth and twentieth claiming clauses, and of striking out parts of
the description contained in the body of the said Specification; and also of otherwise
altering the said Specification, and correcting certain clerical errors contained in the
said Specification in manner more fully hereafter appearing.
"
NOW KNOW YE, that we the said Edison Telephone Company of London
Limited, by and with the leave of Her Majesty's Attorney General, and for the reasons
aforesaid do alter the said Specification, by striking out of the said Specification
printed by the Queen's Printers, and published at the Great Seal Patent Office in
One thousand eight hundred and seventy nine, the words "the same" which
occur on page 4, at the end of line nine, and the beginning of line 10 respectively,
and substituting therefor the words "a corresponding"; we also strike out the
word "the" which occurs between the words "and" and "electro" on the said
page, line twenty two, and substitute therefor the word "an"; we also insert
between the words "the" and "instruments" which occur on the said page line
twenty five the word "transmitting" and we strike out the letter
S at the end
of the said word "instruments"; we also strike out the word "are" which occurs
on the same line and substitute therefor the word "is"; We also insert between
the words "in" and "Figs." (an abbreviation of the word Figures) which occur on
1 the same line, the words "section in" and we st: 'ke out the letter "s" in the said
word "Figs"; we also strike out the words commencing with "and" on the said
line twenty five and ending with the first word "instrument" on line 26 of the
said page four we also strike out the words "of the " which occur between the
Figure "2" and the word "receiving" on the said line twenty six and substitute
therefor the words "represents a"; we also add after the word "instrument" at
the end of the said line twenty six the words "which may be employed with it";
we also strike out the word "the" at the commencement of line twenty seven on
the said page four and substitute therefor the words "referring to Figure 1 the";
we also strike out that portion of the Specification commencing with the words
"in Fig" on page 5, line forty one, and ending with the word "sound" on page 6,
line three; we also strike out that portion of the Specification commencing with
the words "I also at the end of line eight and ending with the words "the line "
on line eleven of the said page 6; we also strike out the whole of lines twenty four
to twenty eight inclusive on the said page 6; we also strike out the words "to
record" which are repeated on line thirty five of the said page 6 and add the letter
"B" to the word "rest" which occurs on line forty seven of the said page 6.
We also strike out of page 8, lines thirty seven to forty two inclusive, and lines
forty six to fifty three inclusive. We also strike out of page 9 lines eighteen to
twenty three inclusive, and lines thirty seven to forty one inclusive. We also
strike out of page 10 lines seventeen to thirty seven inclusive. We also strike out
of page 11 lines ten to thirteen inclusive, and lines forty four to fifty seven
inclusive, and we add at the end of line thirty seven of the said page eleven after
the word "named " the words following:-"I would observe in conclusion that I
do not claim generally the transmission and reproduction of sounds by increasing
and decreasing the resistance of the circuit, nor do I claim separately any of the
parts or arrangements hereinbefore described and illustrated in the accompanying
We also strike out the word "an," which occurs between the words "of " and "electric" on line 42 of the said page 11, and
we add the letter "" to the word "regulator," which occurs on the same line 42. to make it read "regulators," and after
the said word "regulators "we insert the words "substantially as hereinbefore described."
33
Drawings, except as hereinafter mentioned, but A. We also strike out of page. 12
lines one to thirty inclusive, lines thirty six and thirty seven, and lines forty two
to fifty six inclusive. We also strike out the word " eighteenth" which occurs at
the commencement of line thirty one on the said page 12, and substitute therefor

page_text: "
the word third." We also strike out the word twentieth which occurs at the
commencement of line thirty eight of the said page 12, and substitute therefor the
word "fourth." We also strike out the word "or" which occurs on line thirty
nine of the said page 12, and substitute therefor the word "on." We also strike
out of page 13 lines one to fourteen inclusive. And in order that the effect of the
said Disclaimer may be clearly understood we annex hereunto a copy of the said
Specification as it will appear when so amended, the preamble and testing clause
being omitted.
This Invention relates to that class of electrical instruments in which sound
becomes one of the elements in the transmission of the communication, and a
corresponding sound is produced at the receiving station so that oral communi-
cations can be sent by electricity and clearly distinguished at the receiving
station.
Musical tones may also be sent, but my present Invention is especially available
in transmitting and receiving oral communications.
In transmitting musical tones the respective notes each have a definite period for
each vibration, hence there is a response at the receiving end from the notes that
vibrate in time with the electric pulsations sent, but in speaking there is little
change in the musical tone but considerable in the modulations and inflections of
the voice.
In my present Invention I make use of the vibrations given to a diaphragm or
tympan by speaking into a resonant case to produce a rise and fall of electrical
tension upon the line with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by _rticulation, and an electro
magnet at the receiving station will respond to the electric waves in such a manner
as to reproduce the articulation by acting upon a resonant plate.
The transmitting instrument in a complete form is represented in section in
Fig. 1, and Fig. 2 represents a receiving instrument which may be employed
with it.
Referring to Fig. 1, the resonant tube or box a is of size and shape adapted to
being spoken into the same, having an opening at one end or side and a diaphragm
or diaphragms b, against which the sound waves from the human voice act, and
these and the notion that the diaphragm receives is the means of producing a rise
and fall of electric tension on the line by the devices hereafter set forth, so that the
battery B connected to the line will transmit a greater or less current to the
distant electro magnet m, Fig. 2, and increase or lessen the magnetism of the cores,
and in so doing act upon a resonant plate c and develop sound corresponding to the
articulation at the transmitting station.
The general features thus described pervade my entire Invention, but in developing
the same many useful and important modifications and variations have been made,
which I will proceed to set forth.
For convenience the speaking instrument Fig. 1 is provided with a handle a¹ and
flexible conductors to the battery and line respectively, so that it may be handled
and brought to the mouth, and in like manner it is preferable to place the hearing
instrument Fig. 2 in a movable handle b', so that it can be placed with the plate c
against the ear; this brings the sound close to the organs of hearing, and the
resonant plate touching the ear increases the distinctness of the sound and prevents
any false or prolonged vibrations of the plate.
In some of the modifications I have shown the speaking instrument as a fixture,
and also the hearing instrument as a fixed resonant tube, these being variable to
suit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity of
the resonant tube for the voice. I have experienced great difficulty in reproducing
the sound of the hissing consonants, such as s; this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth, and does not act
distinctly upon the diaphragm. By providing an edge in the resonant tube below
the mouth upon which such consonant sounds are received the vibrations are given

page_text: either to the resonant tube or deflected to the diaphragın. I find it preferable to
employ a hole e at the lower part of the mouth piece against the edges of which the
downward sound waves are directed. The same effect will be produced by a
vibrating edge placed in the lower part of the mouth piece, or the opening into the
resonant box may be contracted to about half an inch in diameter to effect the same
purpose. The next feature requiring consideration is the character of the diaphragm
in the speaking instrument.
Many materials have been employed by me such as metals, horn, vellum, celluloid,
ivory, &c., but almost all of these produce a prolonged or secondary vibration from
their own resonant character, hence the articulation is defective and the sound
vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
resonant action, and hence it will respond with the greatest accuracy to the sound
vibrations, and being of a laminated character can be employed of any desired
thickness, and when secured at its edges responds with the greatest accuracy to the
sound vibrations and does not require to be strained; furthermore, the changes of
temperature and atmospheric condition have little or no effect upon the mica
diaphragm or tympan.
I find that it is not practical to open and close the line circuits in instruments
for transmitting the human voice, the circuit to the line. must be always closed and
the transmission be produced by a rise and fall of electric tension resulting from
more or less resistance in the line. This resistance may be produced in several
ways. I have shown several which will hereafter be named, but I find the most
delicate to be small bunches or tufts or disks of semi-conducting elastic fiber, such
as particles of silk and an intermediate conducting or semi-conducting material;
this device I call an electric tension regulator, it is more or less compressed
according to the vibrations of the diaphragm or tympan, and the electric current
rises in tension as it is compressed or lessens as the fiber expands. This fiber is
placed in a small roll t between the delicate diaphragm spring u, Fig. 9, and the
variable presser v adjustable by screw or otherwise in the electric circuit at this
point, or it may be within a cavity in said presser v, as in Fig. 1, there being a
delicate cork center piece w to the diaphragm b, with a piece of platina foil x in
contact with the fiber; in all instances the telegraphic circuit at the diaphragm is
made by a thin strip of platina or similar material, extending to the center from
the line or battery connection.
The fiber is rendered semi-conductive by being rubbed with plumbago, soft metal,
or similar material, or by a deposit of metal upon its surface, or by fine particles of
conducting or semi-conducting material mixed with it, the conducting power
varying with the density of the tuft or bunch of fiber.
The delicate spring u, Fig. 9, upon the mica diaphragm 6 is easily secured by
solder passing into fine holes bored in the mica.
In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact such as would result from a disk covered with plumbago
placed adjacent to a diaphragm also covered with plumbago or other semi-conducting
material so that the proximity or extent of surface contact will produce rise and
fall of tension, the respective parts being in the telegraphic circuit. I sometimes
perforate the diaphragm 10, Fig. 18, and place a strip of elastic material +0 across
said diaphgram over the hole, and upon this a piece of foil, so that the same
responds to very weak vibrations, and in some instances two or more diaphragins
are provided at different sides of the resonant box, each with its own tension
regulator, the diaphragms being either the same or of different sizes, characters, or
tensions so as to respond to varying sounds or acoustic condition, the various
tension regulators being all in the electric circuit, this will produce greater rise and
fall of tension for longer lines in consequence of the diaphragms acting simul-
taneously on the tension regulators. In some instances it is preferable to make
the mouth-piece of the speaking instrument sufficiently large or flaring to receive
all the sound vibrations, whether coming from the mouth, nose, or throat. The

page_text: tension regulator formed of fiber and conducting or semi-conducting material may
be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within &
case to form the tension regulator, the circuit passing through the same, and the
5 rise and fall of electric tension resulting from the compression of the same by the
movement of the diaphragm. I am enabled to record the sounds produced by
the human voice, or otherwise by causing the movements of the diaphragm to be
registered on paper or soft sheet metal, and then the paper may be used in an
instrument to reproduce the sound upon a delicate diaphragm by giving to the
same a vibration similar to that originally given by the voice.
h, Fig. 4, is the indenting transmitter, the diaphragm having a knife-edge point;
i is the paper which has previously been passed through a machine to raise a V
shaped rib 6. The movement of the diaphragm of h when the drum is in motion
causes the knife-edge point to indent the raised rib to varying depths according
to the amplitude of vibration of the diaphragm, thus these indentations represent
accurately all the tones and varying inflections of the human voice. The paper,
after being indented, is passed through a second apparatus n, Fig. 5, almost similar
to h. A spring 9 has a knife edge which rests upon the raised indented rib 6, the
spring being connected to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting
point, and either by direct action or through the vibration of a string conveys the
same motion to the diaphragm of n, and reproduces previous sounds. If these
sounds are to be transmitted over a telegraph line the diaphragm 10, see Fig 6, is
provided with a cork disk w and fibrous tension regulator t before described, to
produce the rise and fall of electric tension on the line. The sound may be
recorded in ink, as represented in Fig. 7. The diaphragm of h operates a very
flexible self feeding pen o, and causes the continuous line to be wide or narrow
according to the amplitude of vibration of the diaphragm. The ink used should
dry quickly and the strips may be passed at any time thereafter through the
instrument shown in Fig. 8 beneath the arm 12 having a point or points resting
on the paper, this arm is connected with a resonant diaphragm, and the ink marks
produce more or less friction according to the breadth and amount of ink deposited,
and this will set the diaphragm of n vibrating and reproduce the vibrations of the
diaphragm of h.
An obvious modification would be to coat the paper with a substance which
would cause considerable friction, or even rough unsized paper might be used and
a spring provided with a burnished point rather flat would cause the surface of
the paper to be made smooth more or less according to the vibration of the
diaphragm, and the differences in the surface of the paper would produce a response
in the receiving diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument,
as shown in Fig. 10.
h is the resonant chamber at the end of which is the diaphragm 10, and at each
side of this diaphragm there are springs c³, c³, having points made of compressed
plumbago mixed preferably with gum rubber, but any substance not liable to rapid
decomposition or the elastic or fibrous tension regulator aforesaid may be used.
These points face each other on opposite sides of the diaphragm, and make contact
with platina foil disks secured to the diaphragm.
The spring c² passes through a hole or small slot in the side of the chamber h;
a², a³, are the main batteries. The battery d has zinc to the line or spring c², and
the battery has copper to the line or spring c³. When the springs of c² and c³ are
adjusted to make contact with the diaphragm equally no current passes to the line,
but when the diaphragm is vibrated its movement to one side, say c², causes a
greater pressure upon the plumbago on that spring, and a lessening of the
pressure on the plumbago on c³, hence the balance of the batteries c² and
will be destroyed, chaving the advantage will send a negative current to
line upon the return of the diaphragm, the battery currents will again

page_text: neutralize each other. The vibration of the diaphragm to the other side causes the
pressure to be reversed, and the battery d³ will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure, it follows that the strength
of the electric waves will be in proportion as the speaker's voice is strong or weak.
In Fig. 11 is shown the contact spring, which may be used adjacent to the
diaphragm at one or both sides thereof. e³ is a U shaped spring secured to the
screw e, which is adjusted back and forth by the thumb nut es; es is the pillar
holding such screw; is a piece of soft rubber or equivalent substance placed
between the prongs of the spring e³; e' is a wire or band which serves to bind the
prongs tightly against the rubber r so as to prevent the prongs acting as a tuning
fork and transmitting harmonic vibrations not desirable; r is the plumbago contact
point. The object of the V spring and rubber is to present a semi-rigid point for
contact so as to prevent a rebound and allow of a slight yield when the plumbago
is pressed by the diaphragm. In Fig. 3 the diaphragm of the receiving instrument
is vibrated by a strip of paper chemically prepared that is in motion, the pulsations
of electricity passing over the line and producing more or less friction between the
paper and an arm upon the diaphragm.
The resonant box or chamber n is provided with a diaphragm as aforesaid, and
to said diaphragm an arm h² is connected. At its outer end is an adjusting screw h³
that presses upon a platina faced spring h* that is secured to this arm, and said
spring rests upon the strip of paper that passes over the drum h³.
The paper
is moved slowly by rotating the drum h³, and the waves of electricity
coming over the line pass through the arm h² to the platina-faced spring h*, thence
through the paper to the earth.
If a negative current passes in the opposite direction nearly all friction between
the platina plate and the paper ceases, and the diaphragm of the resonant box n
retains its normal position.
When the positive current passes through the same channel the normal friction
of the paper is augmented, and the chemical surface acting upon the platina spring
arm serves to give a forward movement to the diaphragm of the resonant box.
Thus the mechanical force applied to move the chemical paper or surface acts
with the electric current to produce the vibration of the diaphragm of the resonant
chamber, and these vibrations will correspond to those of the diaphragm b made by
speaking in the tube a.
The principle of this method of obtaining motion by electro-chemical decomposi-
tion is, that when a moving surface is in contact with a slightly yielding substance
the tendency is to move the latter by and with the former. If the circumstances
of contact are varied the adhesion of the surfaces will be sufficient to cause the
moving surface to move the yielding substance or else to cause the yielding surface
to slip more freely, and by its spring go in the opposite direction to the moving
surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion, making it more or less according to the substances employed. By
balancing the mechanical forces so that when the surfaces in contact are not
electrified the moving surface carries with it the yielding surface, and when
electrified the yielding surface slips back, over the moving surface a mechanical
movement is obtained that is dependent on the electrical condition of the surfaces
in contact.
When it is requisite to obtain very perfect articulation, and when loudness is
not essential, I adopt a modification shewn in Fig. 12 of the device for compressing
and expanding the tuft of conducting fiber, which modification consists in placing
between the diaphragm 10 and the fiber t a vibrating tongue 21 of steel, perma-
nently magnetized, and arranging it to act in the same manner upon the tension
regulator as if it was the diaphragm. I replace the cork upon the diaphragm by
a thim armature of iron 22, which is in close proximity to the magnetized tongue,
which tongue is secured at one end like an acoustic reed. In this position the

page_text: vouers to and ren from, the ghelized
tongue causes said tongue to follow its movements by magnetic attraction, and thus
the tongue is made to perform what the diaphragm previously performed in varying
the tension of the electricity on the line.
A plate supported eccentrically and free at its edges when placed in the speaking
tube responds advantageously to the tones of the voice. The circuit with this
plate is completed through one or more tension regulators placed around its edges.
In practice I combine with the speaking or telephonic apparatus signal bells so
arranged that when the telephone is not in use the line is thrown upon the bell by
a switch, which also acts as a call on the bell.
One feature about the bells is that the magnet which serves to actuate the bells
is made of very high resistance, using preferably German silver. wire in the helix,
and thus serve to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from one battery if these bells are used. The
method I adopt for coating non-conducting substance with metallic substance is the
reduction to the metallic state of metals from their salts by exposing them to the
fumes which arise from the moist phosphide of a metal, such as phosphide of calcium,
or by placing the silk for instance in a sealed tube provided with metallic electrodes,
and volatilizing the electrodes by the passage of electric sparks. Such volatilized
metals settle upon and coat the silk.
When great loudness is desirable, as in factories, the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is stored
will
under a regulated pressure. The air allowed to escape with act with great power
upon a local diaphragm. This diaphragm to obtain clear sounds requires a damper
to check prolonged vibrations. It must be dampened by holding the fingers against
it, or by a tightly stretched cord rubbing against it, or by a screw provided with a
rubber tip held against it.
In some instances I make a record of the sound by the movements of the
diaphragm, using for that purpose a strip of paper moved along regularly between
two rollers 25, 26, as in Figs. 14 and 15, and there is a smooth thread or fine wire
of soft mal 30 between the paper and the upper roller 25, and moving along with
it. The diaphragm 10 of the resonant box is connected by a delicate rod 28 with
this thread or wire as near to the bight of the roller as possible, there being a fork
or eye through which the thread passes; hence deflections or bends are made in
the thread or wire just before it is embedded into the paper by the pressure of the
rollers. This may be used to reproduce the sound by vibrating a resonant diaphragm
by the undulations of the groove made by the thread or cord.
By placing the fibrous-tension regulator within a small band of India rubber
the same is rendered more elastic and the fiber is allowed to expand by the heat
of the current without altering the electric tension.
In some instances the diaphragm should be free to vibrate without being checked
by contact with any stationary substance. I provide for this by placing upon the
diaphragm or tympan 10, Fig. 17, a small cylinder of hard rubber or non-
conducting material within which is the fibrous tension regulator t resting upon a
picce of platina foil connected to one pole of the battery, and within this cylinder
t is a disc to of iron or other metal loose but pressed towards the tension regulator
by a spring to and screw cap to and the other electric conductor is connected wit
the said spring.
The inertia of the metal disk causes more or less compression of the tension
regulator as the diaphragm is vibrated and hence the electric pulsations are sent
over the line in harmony with the vibrations. Nearly the same effect is produced
by connecting the disk (0 to a yielding spring t" that extends across from one edge
of the diaphragm to the other as seen in Fig. 10.
regulating device is especially available with large diaphragms.
This construction of tension
In some cases I use a soft rubber diaphragm immediately in contact with the
transmitting or receiving diaphragin so as to check or dampen any prolonged or

page_text: false vibration and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable to usc
lampblack mixed with pure plumbago, amorphous phosphorous, and a very small
amount of nonconducting material such as rubber dissolved in a solvent that will
entirely evaporate.
In Fig. 19 I have represented the circuit as passing through the diaphragm 10,
tension regulator t, and a Duluc's dry pile battery D, P, B, to the earth.
This
battery is composed of about 300 pairs of paper disks coated with silver and
black oxyd of manganese.
Fig. 20 illustrates the device before mentioned for intensifying the sound; 10 is
the diaphragm vibrated by the sound; 42 is a valve moved by such diaphragm; 43 is a
reservoir containing air under a given pressure; b is the diaphragm against which
the air allowed to escape by the valve acts, and t is the tension regulator to transmit
the electric pulsations, or a hearing resonant case may be applied at the same place.
Fig. 24 represents the diaphragm 10, tension regulator t with its adjusting screw
and local circuit containing the battery B passing through a primary induction
coil 49, and there is a key 50 in the same circuit. A secondary induction coil 51
is in the line circuit and is influenced electrically by the change of tension in the
local circuit by the vibrations of the diaphragm 10. The secondary coil is some-
times required with many layers of fine wire to set up a current of high tension to
evercome the inductive effect from the line wires; being adjacent to each other I
place the receiving instrument at the distant station between the induction coil
and the earth as at R, and use an electro-maguet E, M, with polarized armature
to strike a bell; this will respond when the key 50 in the local circuit at the distant
station is opened and closed.
In Fig. 25 a similar induction coil 49 and local circuit is represented, but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes,
one on the diaphragm, the other on the adjusting screw. A shunt and rheostat
at R' serves to prolong the magnetism in the induction coil, and thus ensure a
gradual rise and fall of electric tension in the line instead of a cessation of the same
when the platina surfaces separate, and at the receiving diaphragm c the rise and
fall of electric tension in the line and its helix acts upon the permanent magnet to
produce the vibrations of the diaphragın c, and by connecting a shunt around the
helix, and placing therein the secondary battery S, B, composed of metallic plates
in acidulated water, the action is rendered more uniform and the sound distinct.
When the diaphragm is arranged as in Fig. 26 to act upon a spring 56 through
an intervening piece of soft rubber, said spring 56 produces rise and fall of electric
tension by employing a range of resistances 57 with spring tongues adjacent to 56.
The greater amplitude of vibration of the diaphragm the more direct will be the
electric circuit connections, and the less resistance, because the circuit will pass
along the spring instead of going through all the resistance coils.
When several line wires run near each other the wire used for the acoustic or
speaking telegraph is influenced by induction, and false sounds will be produced.
I counteract this tendency by placing one or more electro-magnets 59, Fig. 28, in
the circuit of the speaking telegraph, and one or more electro magnets 60 in the
circuit of the adjacent wires, and bringing the opposite cores of 60 at such a
distance from the cores of 59 that a certain magnetic action will be set up in 50 by
induction, in the opposite direction to the induction currents from the adjacent line
or lines.
By adjusting the distance between these magnets when the speaking telegraph is
not in use, until there is not any sound at the diaphragun from the induction
currents, then these currents will be neutralized whether strong or weak, and will
not produce any false sounds when the speaking telegraph is in use.
I also employ
double coils of wire for the same purpose, one coil being in the acoustic wire, and
the other in the wire to be compensated.
A convenient form for the sound recorder or phonogragh is to employ a cylinder
61, see Fig. 29, having a helical groove in its surface covered with tin foil, and the

page_text: cylinder is resolved regularly by clockwork,
wise by a screw on its
shaft so that the indenting point l' from the diaphragın 10 of h will be always in
line with such groove, hence the vibrations of the diaphragm will be recorded by
indenting the foil into the groove, and hence the same sound will be reproduced by
the point of the hearing instrument m, giving to the diaphragm of n, the
motions that result from the indentations of the foil moving in contact with such
point.
The foil may be on a flat grooved plate, and be indented and act as before
named.
I would observe in conclusion that I do not claim generally the transmission and
reproduction of sounds by increasing and decreasing the resistance of the circuit,
nor do I claim separately any of the parts or arrangements herein before described
and illustrated in the accompanying Drawings, except as hereinafter mentioned, but
I claim as my Invention:-
First. In an Instrument for transmitting electric impulses by sound, a diaphragm
or tympan of mica substantially as set forth.
substantially as herein before described
Second. In an Instrument for transmitting electric impulses by sound, the com-
bination with a diaphragm or tympan of an electric tension regulators
varying the resistance in a closed circuit, substantially as set forth.
A
for
Third. In a telegraphic apparatus operated by sound, a receiving instrument
provided with a resonant surface in combination with a frictional surface, moved
by power, and acting in connection with the electric current to vibrate such
resonant receiver, a id produce tones corresponding to those at the transmitting
apparatus substantially as set forth.
Fourth. The method herein specified of recording the unduiations of the diaphragm
on yielding material, and the reproduction of sound by such material acting upon
a diaphragm, to communicate to the same vibrations similar to the original ones,
substantially as set forth.
of London.
In witness whereof, the said Edison Telephone Company Limited, have
caused their common seal to be hereunto affird, the Twelfth day of
November, One thousand eight hundred and seventy nine.
I hereby grant my fiat, giving leave to the above named Edison Telephone
Company, of London, Limited, the assignees of the said Letters Patent, to file in
the Great Patent Seal Office, with the Specification to which the same relates, the
above written Disclaimer and Memorandum of Alteration, upon condition that no
proceedings be taken in respect of any transmitters actually made and completed
prior to the date of the filing of the said Disclaimer and Memorandum of
Alteration.
Particulars of numbers, and identifying marks to be verified by Statutory
Declaration.
TATT

page_text: THE UNITED TELEPHONE COMPANY'S DISCLAIMER AND
MEMORANDUM OF ALTERATION.
Filed 13th June 1881.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, THE
UNITED TELEPHONE COMPANY LIMITED, send greeting. WHEREAS Her most
Excellent Majesty Queen Victoria, by Her Royal Letters Patent under the Great
Seal of rat Britain and Ireland, bearing date at Westminster the Thirtieth day.
of July, in the year of our Lord One thousand eight hundred and seventy seven,
in the forty first year of Her reign, did, for Herself, Her beirs and successors,
give and grant unto Thomas Alva Edison, of Menlo Park, in the State of New
Jersey, United States of America, his executors, administrators, or assigns, Her
special license, full power, sole privilege and authority, that he, the said Thomas
Alva Edison, his executors, administrators, or assigns, or such others as he, his
executors, administrators, or assigns, should at any time agree with, and no others,
from time to time and at all times during the term therein expressed, should and
lawfully might make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention of
'IMPROVEMENTS IN INSTRUMENTS FOR CONTROLLING BY SOUND THE TRANSMISSION
OF ELECTRIC CURRENTS AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT
A DISTANCE," for aud during the term of fourteen years thence next ensuing:
And whereas in pursuance and performance of a proviso in the said Letters Patent
contained, the said Thomas Alva Edison, did, within six calendar months next
after the date of the said Letters Patent, cause a Specification in writing under his
hand and seal, purporting to particularly describe the nature of the said Invention,
and in what manner the same was to be performed, to be duly fled in the Grant
Seal Patent Oce: And whereas by indenture bearing date the Second day of
August, One thousand eight hundred and seventy nine, and made between the said
Thomas Alva Edison, of the one part, and said Edison Telephone Company
of London, Limited, of the other part, the said Thomas Alva Edison, assigned
unto the aid Edison Telephone Company of London, Limited (inter alia),
the said hereinbefore recited Letters Patent, and all rights, powers, authorities,
"

page_text: privileges, advantages, profits, emoluments, and benefits to the said Letters
Patent appertaining or belonging: And whereas on the Thirteenth November,
One thousand eight hundred and seventy nine, the said Edison Telephone
Company of London, Limited, petitioned the Commissioners of Patents for leave
to amend certain parts of the said Specification of the said Letters Patent, which
petition was referred to Her Majesty's late Attorney General, Sir John Holker, and
leave was given to the said Edison Telephone Company of London, Limited, to file
in the Great Seal Patent Office a Disclaimer and Memorandum of Alteration, as
appears by the fiat of the said Sir John Holker, dated the Ninth day of February,
One thousand eight hundred and eighty, and the said Disclaimer was duly filed in
the Great Seal Patent Office on the Tenth day of February, One thousand eight
hundred and eighty: And whereas by indenture bearing date the Twelfth day of
July, One thousand eight hundred and eighty, and made between the said Edison
Telephone Company of London, Limited, of the one part, and us, the said United
Telephone Company, Limited, of the other part, and duly registered in the Great
Seal Patent Office, the said Edison Telephone Company of London, Limited,
assigned to us, the said United Telephone Company, Limited, the said Letters
Patent, and the rights and privileges thereby granted, and the same thereby became
and are now vested in us, the said United Telephone Company, Limited: And
whereas, since the filing of the said Disclaimer and Memorandum of Alteration, and
very recently, t'at is to say, about the First March, One thousand eight hundred
and eighty one, your petitioners have ascertained that shortly prior to the applica-
tion for the said Letters Patent, a description of the Invention of the said Thomas
Alva Edison, in so far as it relates to the electro chemical receiver as covered by
the third claim, was published in an American newspaper and afterwards copied
into an English paper, and we are advised that, although there was no Invention
by any one in England, or elsewhere, other than the said Thomas Alva Edison, of
the said part of his Invention, the aforesaid publication renders doubtful the
validity of the said third claim, and we are desirous of striking out the same, and.
of altering the numbering of the succeeding claim accordingly, in manner more fully
hereafter appearing. NOW KNOW YE, that we, the said United Telephone
Company, Limited, by and with the leave of Her Majesty's Attorney General,
and for the reasons aforesaid, do alter the said Specification by striking out of the
Specification as amended by the said Disclaimer, printed by the Queen's Printers,
and published at the Great Seal Patent Office, in One thousand eight hundred and
eighty, the whole of the third claim, comprising lines twenty to twenty four, both
inclusive, on page 9. We also strike out the word "Fourth" at the commencement
of line twenty five of the said page 9, and substitute therefor the word "Third."
We also desire to correct a clerical, occurring in the said amended Specification
by striking out the figure "2" which follows the reference letter "c" in line forty
seven of page 5 of the said printed copy of the said Specification, and of substituting
therefor the figure "3."
error
And in order that the effect of the said Disclaimer may be clearly understood,
we annex hereunto a copy of the said Specification, as it will appear when so
amended, the preamble and testing clause being omitted.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Royal Letters
Patent, under the Great Seal of Great Britain and Ireland, bearing date at
Westminster the Thirtieth day of July, in the year of our Lord One thousand
eight hundred and seventy seven, in the forty first year of Her reign, did, for
Herself, Her heirs and successors, give and grant unto Thomas Alva Edison, of
Menlo Park, in the State of New Jersey, United States of America, his executors,
administrators, or assigns, or such others as he, his executors, adininistrators, or
assigns, should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention of "IMPROVEMENTS IN

page_text: INSTRUMENTS FOR CONTROLLING BY SOUND THE TRANSMISSION OF ELECTRIC
CURRENTS AND THE REPRODUCTION OF CORRESPONDING SOUNDS AT A DISTANCE,"
for and during the term of fourteen years thence next ensuing: And whereas, in
pursuance and performance of a proviso in the said Letters Patent contained, the
said Thomas Alva Edison did, within six calendar months next after the date of
the said Letters Patent, cause a Specification in writing under his hand and seal,
purporting to particularly describe the nature of the said Invention, and in what
manner the same was to be performed, to be duly filed in the Great Seal Patent
Office And whereas, by an indenture bearing date the second day of August,
One thousand eight hundred and sevenly nine, and made between the said Thomas
Alva Edison of the one part, and us, the Edison Telephone Coinpany of London,
Limited, of the other part, the said Thomas Alva Edison assigned unto us, the
said Edison Telephone Company of Loudon, Limited (inter alia), the said herein-
before recited Letters Patent, and all rights, powers, authorities, privileges,
advantages, profits, emoluments, and benefits, to the said Letters Patent apper-
taining or belonging:
and correcting certain clerical errors contained in the said Specification
A
"
And whereas, since the date of the said assignment, we have been advised and
have ascertained that the said Specification contains matters which are of doubtful
novelty, or which are not of sufficient practical value and utility to justify their
retention, and we are therefore desirous of striking out the whole of the claiming
clauses contained in the said Specification, with the exception of the first, second,
eighteenth, and twentieth claiming clauses, and of striking out parts of the
description contained in the body of the said Specification, and also of otherwise.
altering the said Specification in manner more fully hereafter appearing.
NOW KNOW YE, that we, the said Edison Telephone Company, of London,
Limited, by and with the leave of Her Majesty's Attorney General, and for the
reasons aforesaid, do alter the said Specification by striking out of the said
Specification printed by the Queen's Printers, and published at the Great Seal
Patent Office in One thousand eight hundred and seventy nine, the words "the
same," which occur on page four at the end of line nine and the beginning of line
ten respectively, and substituting therefor the words "a corresponding." We also
strike out the word "the," which occurs between the words "and" and "electro
or the said page, line twenty two, and substitute therefor the word "an." We also
inst between the words "the" and "instruments," which occur on the said page,
line twenty five, the word " transmitting," and we strike out the letter "s" at the
end of the said word "instruments." We also strike out the word "are," which occurs
on the same line, and substitute therefor the word "is." We also insert between
the words "in" and "Figs." (an abbreviation of the word Figures), which occur on
the same line, the words "section in," and we strike out the letter "s" in the said
word "Figs." We also strike out the words commencing with "and on the said line
twenty five, and ending with the first word "instrument on line twenty six of the
said page four. We also strike out the words "of the," which occur between the
figure "2" and the word "receiving" on the said line twenty six, and substitute
therefor the words "represents a." We also add after the word "instrument" at the
end of the said line twenty six the words "which may be employed with it." We
also strike out the word "The" at the commencement of line twenty seven on the
said page four, and substitute therefor the words "Referring to Figure 1 the."
We also strike out that portion of the Specification commencing with the words
"In Fig" on page five, line forty one, and ending with the word "sound" on page
six, line three, we also strike out that portion of the Specification commencing with
the words "I also" at the end of line eight, and ending with the words "the line'
on line eleven of the said page 6. We also strike out the whole of lines twenty four
to twenty eight inclusive on the said page 6. We also strike out the words "to
record," which are repeated on line thirty five of the said page 6 and add the
letter "s" to the word "rest," which occurs on line of forty seven of the said page 6.
We also strike out of page 8 lines thirty seven to forty two inclusive and lines
"
"

page_text: "
"
forty six to fifty three inclusive. We also strike out of page 9 lines eighteen to
twenty three inclusive and lines thirty seven to forty one inclusive. We also strike
out of page 10 lines seventeen to thirty seven inclusive. We also strike out of
page 11 lines ten to thirteen inclusive and lines forty four to fifty seven inclusive,
and we add at the end of line thirty seven of the said page eleven after the word
"named" the words following:-" I would observe.in conclusion that I do not claim
generally the transmission and reproduction of sound by increasing and decreasing
the resistance of the circuit, nor do I claim separately any of the parts or arrangements
herein before described and illustrated in the accompanying Drawings, except as
hereinafter mentioned; but we also strike out the word "an," which occurs between
the words of" and "electric" on line 42 of the said page 11; and we add the
letter "s" to the word "regulator," which occurs on the same line 42, to make it read
"regulators," and after the said word "regulators we insert the words "sub-
stantially as herein before described." We also strike out of page 12 lines one to
thirty inclusive, lines thirty six and thirty seven, and lines forty two to fifty six
inclusive. We also strike out the word "Eighteenth,' which occurs at the com-
mencement of line thirty one on the said page 12, and substitute therefor the word
"Third." We also strike the word Twentieth, which occurs at the commencement of
line thirty eight of the said page 12, and substitute in therefor the word "Fourth."
We also strike the work "or," which occurs on line thirty nine of the said page 12,
and substitute therefor the word "on." We also strike out of page 13 lines
one to fourteen inclusive. And in order that the effect of the said Disclaimer
may be clearly understood, we annex hereunto a copy of the said Specification
as it will appear when so amended, the preamble and testing clause being
omitted.
This Invention relates to that class of electrical instruments in which sound
becomes one of the elements in the transmission of the communication, and a corre-
sponding sound is produced at the receiving station, so that oral communications
can be sent by electricity and clearly distinguished at the receiving station.
Musical tones may also be sent, but my present Invention is especially available
in transmitting and ceiving oral communications.
In transmitting musical tones the respective notes each have a definite period
for each vibration, hence there is a response at the receiving end from the notes
that vibrate in time with the electric pulsations sent, but in speaking there
is little change in the musical tone, but considerable in the modulations and
inflections of the voice.
In my present Invention I make use of the vibrations given to a diaphragm or
tympan by speaking into a resonant case to produce a rise and fall of electrical
tension upon the line, with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation, and an electro
magnet at the receiving station will respond to the electric waves in such a manner.
as to reproduce the articulation by acting upon a resonant plate.
The transmitting instrument in a complete form is represented in section in
Figure 1, and Figure 2 represents a receiving instrument which may be employed
with it.
Referring to Figure 1, the resonant tube or box a is of a size and shape adapted
to being spoken into, the same having an opening at one end or side, and a
diaphragm or diaphragms b against which the sound waves from the human
voice act, and these and the motion that the diaphragm receives is the means
of producing a rise and fall of electric tension on the line by the devices hereafter
set forth, so that the battery B connected to the line will transmit a greater or
less current to the distaut electro maguet m, Figure 2, and increase or lessen the
magnetism of the cores, and in so doing act upon a resonant plate c and develop
sound corresponding to the articulation at the transmitting station.
The general features thus described pervade my entire Invention, but in
developing the same many useful and important modifications and variations have
been made, which I will proceed to set forth.

page_text: For convenience the speaking instrument, Figuro 1, is provided with a handle a¹
and flexible conductors to the battery and line respectively, so that it may be
handled and brought to the mouth; and in like manner it is preferable to place
the hearing instrument, Figure 2, in a moveable handle b' so that it can be placed
with the plate c against the ear; this brings the sound close to the organs of hearing,
and the resonant plate touching the ear increases the distinction of the sound, and
prevents any false or prolonged vibrations of the plate.
In some of the modifications I have shown the speaking instrument as a fixture,
and also the hearing instrument as a fixed resonant tube, these being variable to
suit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity
of the resonant tube for the voice; I have experienced great difficulty in reproducing
the sound of the hissing consonants, such as S; this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth, and does not act
distinctly upon the diaphragm. By providing an edge in the resonant tube below
the mouth upon which such consonant sounds are received, the vibrations are given
either to the resonant tube or deflected to the diaphragm. I find it preferable to
employ a hole e at the lower part of the mouth piece, against the edges of which
the downward sound waves are directed. The same effect will be produced by a
vibrating edge placed in the lower part of the mouth piece, or the opening into the
resonant 'box may be contracted to about half an inch in diameter to effect the
same purpose. The next feature requiring consideration is the character of the
diaphragm in the speaking instrument.
Many materials have been employed by me, such as metals, horn, vellum,
celluloid, ivory, &c., but almost all of these produce a prolonged or secondary
vibration from their own resonant character, hence the articulation is defective
and the sound vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
resonant action, and hence it will respond with the greatest accuracy to the sound
vibrations, and being of a laminated character can be employed of any desired
thickness, and when secured at its edges responds with the greatest accuracy to the
sound vibrations, and does not require to be strained; furthermore, the changes of
temperature and atmospheric condition have little or no effect upon the mica
dir ram or tympan.
find that it is not practical to open and close the line circuits in instruments for
transmitting the human voice; the circuit to the line must be always closed, and the
transmission be produced by a rise and fall of electric tension resulting from more
or less resistance in the line. This resistance may be produced in several ways; I
have shown several which will hereafter be named, but I find the most delicate to
be small bunches or tufts or discs of some conducting elastic fiber, such as particles
of silk, and an intermediate conducting or semi-conducting material; this device I
call an electric tension regulator, it is more or less compressed according to the
vibrations of the diaphragm or tympan, and the electric current rises in tension as
it is compressed, or lessens as the fibre expands. This fiber is placed in a small
rollt between the delicate diaphragm spring u, Figure 9, and the variable presser,
adjustable by screw or otherwise in the electric circuit at this point, or it may be
within a cavity in said presser e, as in Figure 1, there being a delicate cork centre
piece w to the diaphragin b with a piece of platina foil æ in contact with the fibre.
In all instances the telegraphic circuit at the diaphragm is made by a thin strip
of platina or similar material, extending to the centre from the line or battery
connection.
The fibre is rendered semi-conductive by being rubbed with plumbago, soft
metal, or smilar material, or by a deposit of metal upon its surface, or by fine
particles of conducting or semi-conducting material mixed with it, the conducting
power varying with the density of the tuft or branch of fiber.
The delicate spring u, Figure 9, upon the inica diaphragm b is easily secured by
solder passing into fine holes bored in the mica.

page_text: In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact, such as would result from a disk covered with plumbago
placed adjacent to a diaphragm also covered with plumbago or other semi-conducting
material, so that the proximity or extent of surface contact will produce rise and
fall of tension, the respective parts being in the telegraphic circuit.
I sometimes perforate the diaphragm 10, Figure 18, and place a strip of elastic
material 40 across said diaphragm over the hole, and upon this a piece of foil, so
that the same responds to very weak vibrations, and in some instances two or
more diaphragms are provided at different sides of the resonant box, each with its
own tension regulator, the diaphragms being either the same or of different sizes,
characters, or tensions, so as to respond to varying sounds or acoustic condition,
the various tension regulators being all in the electric circuit; this will produce
greater rise and fall of tension for longer lines in consequence of the diaphragms
acting simultaneously on the tension regulators.
In some instances it is preferable to make the mouth piece of the speaking
instrument sufficiently large or flaring to receive all the sound vibrations, whether
coming from the mouth, nose, or throat.
The tension regulator formed of fiber and conducting or semi-conducting material
may be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within
a case to form the tension regulator, the circuit passing through the same, and the
rise and fall of electric tension resulting from the compression of the same by the
movement of the diaphragm.
I am enabled to record the sounds produced by the human voice or otherwise
by causing the movements of the diaphragm to be registered on paper or soft sheet
netal, and then the paper may be used in an instrument to reproduce the sound
upon a delicate diaphragm by giving to the same a vibration similar to that
originally given by the voice.
h, Figure 4, is the indenting transmitter, the diaphragm having a knife edge
point; is the paper which has previously been passed through a machine to raise
a V shaped rib 6. The movement of the diaphragm of when the drum is in
motion causes the knife edge point to indent the raised rib to varying depths
according to the amplitude of vibration of the diaphragm, thus these indentations
represent accurately all the tones and varying inflections of the human voice. The
paper after being indented is passed through a second apparatus n, Figure 5, almost
similar to h. A spring 9 has a knife edge which rests upon the raised indented
rib 6 the spring being connected to a delicate diaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting point
and either by direct action or through the vibration of a string conveys the same
motion to the diaphragm of n, and reproduces previous sounds. If these sounds
are to be transmitted over a telegraph line, the diaphragm 10, see Figure 6, is
provided with a cork disk w, and fibrous tension regulator t before described, to
produce the rise and fall of electric tension on the line. The sound may be
recorded in ink, as represented in Figure 7. The diaphragm of h operates a very
flexible self feeding pen o, and causes the continuous line to be wide or narrow
according to the amplitude of vibration of the diaphragm. The ink used should
dry quickly, and the strip may be passed at any time thereafter through the
instrument shewn in Figure 8, beneath the arm 12, having a point or points resting
on the paper; this arm is connected with a resonant diaphragin, and the ink marks
produce more or less friction according to the breadth and amount of ink deposited,
and this will set the diaphragm of n vibrating and reproduce the vibrations of the
diaphragm of h.
An obvious modification would be to coat the paper with a substance which
would cause considerable friction, or even rough unsized paper might be used, and
a spring provided with a burnished point rather flat would cause the surface of the
paper to be made smooth more or less according to the vibration of the diaphragm,

page_text: and the querence in the surface of the paper would produce a response of the
receiving diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument,
as shewn in Figure 10.
h is the resonant chamber, at the end of which is the diaphragm 10, and at each
side of this diaphragm there are springs c³, c³, having points made of compressed
plumbago mixed 'preferably with gun rubber, but any substance not liable to
rapid decomposition, or the elastic or fibrous tension regulator aforesaid may be
used. These points face each other on opposite sides of the diaphragm and make
contact with platina foil disks secured to the diaphragm.
The spring c³ passes through a hole or small slot in the side of the chamber /;
d², d³ are the main batteries; the battery d² has zinc to the line or spring c³, and the
battery has copper to the line or spring c³. When the springs c² and care adjusted
to make contact with the diaphram equally no current passes to the line, but when
the diaphragm is vibrated its movement to one side, say, c², causes a greater
pressure upon the plumbago on that spring and a loosening of the pressure on the
plumbago on c³, hence the balance of the batteries c² and c³ will be destroyed, c³
having the advantage will send a negative current to line; upon the return of the
diaphragm the battery currents will again neutralize each other. The vibration of
the diaphragm to the other side causes the pressure to be reversed, and the battery d³
will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure, it follows that the strength
of the electric waves will be in proportion as the speakers voice is strong or
weak.
In Figure 11 is shewn the contact spring, which may be used adjacent to the
diaphragm at one or both sides thereof; e is a U shaped spring secured to the
screw e, which is adjusted back and forth by the thumb nut es; es is the pillar
holding such screw;r is a piece of soft rubber or equivalent substance placed between
the prongs
of the spring e; e' is a wire or band which serves to bind the prongs
tightly against the rubber r, so as to prevent the prongs acting as a tuning fork and
transitting harmonic vibrations not desirable; r is the plumbago contact point.
The Joject of the U spring and rubber is to present a semi rigid point for contact
so as to prevent a rebound and allow of a slight yield when the plumbago is pressed
by the diaphragm.
In Figure 3 the diaphragm of the receiving instrument is vibrated by a strip of
paper chemically prepared, that is, in motion, the pulsations of electricity passing
over the line and producing more or less friction between the paper and an arm
upon the diaphragm.
The resonant box or chamber n is provided with a diaphragm as aforesaid, and to
said diaphragm an arm h³ is connected. At its outer end is an adjusting screw h³
that presses upon a platina faced spring h* that is secured to this arm, and said
spring rests upon the strip of paper that passes over the drum h³.
The paper is moved slowly by rotating the drum h³, and the waves of electricity
coming over the line pass through the arm ² to the platina-faced spring h*, thence
through the paper to the earth.
If a negative current passes in the opposite direction nearly all friction between
the platina plate and the paper ceases, and the diaphragm of the resonant box n
retains its normal position.
When the positive current passes through the same channel the normal friction
of the paper is augmented, and the chemical surface acting upon the platina
spring arm serves to give a forward movement to the diaphragm of the resonant
box.
Thus the mechanical force applied to move the chemical paper or surface acts
with the electric current to produce the vibration of the diaphragm of the resonant
chamber, and these vibrations will correspond to those of the diaphragm b made by
speaking in the tube a.

page_text: The principle of this method of obtaining motion by electro chemical decom-
position is that when a moving surface is in contact with a slightly yielding
substance the tendency is to move the latter by and with the former. If the
circumstances of contact are varied the adhession of the surfaces will be sufficient
to cause the moving surface to move the yielding substance or else to cause the
yielding surface to slip more freely, and by its spring go in the opposite direction
to the moving surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion, make it more or less, according to the substances employed. By balancing
the mechanical forces, so that when the surfaces in contact are not electrified the
moving surface carries with it the yielding surface, and when electrified the
yielding surface slips back over the moving surface a mechanical movement is
obtained that is dependent on the electrical condition of the surfaces in contact.
When it is requisite to obtain very perfect articulation, and when loudness is
not essential, I adopt a modification shewn in Figure 12 of the device for com-
pressing and expanding the tuft of conducting fiber, which modification consists in
placing between the diaphragm 10 and the fiber t a vibrating tongue 21 of steel
permanently magnetised, and arranging it to act in the same manner upon the
tension regulator t as if it was the diaphragmn; I replace the cork upon the
diaphragm by a thin armature of iron 22, which is in close proximity to the
magnetized tongue, which tongue is secured at one end like an acoustic reed. In
this position the diaphragm is free to move, and at its approach to and recession
from the magnetized tongue causes said tongue to follow its movements by
magnetic attraction, and thus the tongue is made to perform what the diaphragm
previously performed in varying the tension of the electricity on the line.
A plate supported eccentrically and free at its edges when placed in the speaking
tube responds advantageously to the tones of the voice. The circuit with this plate
is completely through one or more tension regulators placed around its edges.
In practice I combine with the speaking or telephonic apparatus signal bells so
arranged that when the telephone is not in use the line is thrown upon the bell by
a switch which also acts as a call on the bell.
One feature about the bells is that the magnet which serves to actuate the bells
is made of very high resistance, using preferably German silver wire in the helix,
and thus serves to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from oue battery if these bells are used.
The method I adopt for coating nonconducting substance with metallic substance
is the reduction to the metallic state of metals from their salts by exposing them to
the fumes which arise from the moist phosphide of a metal such as phosphide of
calcium; or by placing the silk, for instance, in a sealed tube provided with metellic
electrodes, and volatilizing the electrodes by the passage of electric sparks, such
volatilized metals settle upon and coat the silk.
When great loudness is desirable, as in factories, the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is stored
under a regulated pressure.
The air allowed to escape will act with great power upon a local diaphragm.
This diaphragm, to obtain clear sounds, requires a damper to check prolonged
vibrations. It must be damped by holding the fingers against it or by a tightly
stretched cord rubbing against it or by a screw provided with a rubber tip held
against it.
In some instances I make a record of the sound by the movements of the
diaphragm, using for that purpose a strip of paper moved along regularly between
two rollers 25, 26, as in Figures 14 and 15, and there is a smooth thread or
fine wire of soft metais 30 between the paper and the upper roller 25 and moving
along with it. The diaphragm 10 of the resonant box is connected by a delicate
rod 28 with this thread or wire as near to the bight of the roller as possible, there
being a fork or eye through which the thread passes; hence deflections or bends are
made in the thread or wire just before it is embedded into the paper by the

page_text: pressure of the rollers. This may be used to reproduce the sound by vibrating a
resonant diaphragm by the undulations of the groove made by the thread or
cord.
By placing the fibrous tension regulator within a small band of india rubber the
same is rendered more elastic, and the fiber is allowed to expand by the heat of the
current without altering the electric tension.
In some instances the diaphragm should be free to vibrate without being checked
by contact with any stationary substance. I provide for this by placing upon the
diaphragm or tympan 10, Figure 17, a small cylinder t, of hard rubber or non-
conducting material, within which is the fibrous tension regulator t resting upon
a piece of platina foil connected to one pole of the battery, and within this
cylinder is a disc 10, of iron or other metal, loose, but pressed towards the tension
regulator by a spring ts and screw cap, and the other electric conductor is
connected with said spring.
The inertia of the metal disk causes more or less compression of the tension
regulator as the diaphragm is vibrated, and hence the electric pulsations are sent
over the hine in harmony with the vibrations. Nearly the same effect is produced
by connecting the disk to to a yielding spring t" that extends across from one
edge of the diaphragm to the other, as seen in Figure 16. This construction of
tension regulating device is especially available with large diaphragms.
In some cases I use a soft rubber diaphragm immediately in contact with the
transmitting or receiving diaphragm, so as to check or dampen any prolonged or
false vibration, and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable
to use lampblack mixed with pure lumbago, "morphous phosphorous, and a very
small amount of nonconducting material, such as rubber dissolved in a solvent that
will entirely evaporate.
In Figure 19 I have represented the circuit as passing through the diaphragm 10,
tension regulator t, and a Duluc's dry pile battery D, P, B, to the earth. This
battery is composed of about three hundred pairs of paper disks coated with silver
and black oxyd of manganese.
Figure 20 illustrates the device before mentioned for intensifying the sound;
10 is the diaphragm vibrated by the sound; 42 is a valve moved by such
diaphragm; 43 is a reservoir containing air under a given pressure; b is the
diaphragm against which the air allowed to escape by the valve acts, and t is the
tension regulator to transmit the electric pulsations, or a hearing resonant case
may be applied at the same place.
Figure 24 represents the diaphragm 10, tension regulator t, with its adjusting
screw and local circuit containing the battery B passing through a primary
induction coil 49, and there is a key 50 in the same circuit. A secondary induction
coil 51 is in the line circuit, and is influenced electrically by the change of tension
in the local circuit by the vibrations of the diaphragm 10.
The secondary coil-is sometimes required with many layers of fine wire to set.
up a current of high tension; to overcome the inductive effect from the line wires
being adjacent to each other, I place the receiving instrument at the distant station
between the induction coil and the earth as at R, and use an electro magnet E, M,
with polarized armature to strike a bell; this will respond when the key 50 in the
local circuit at the distant station is opened and closed.
In Figure 25 a similar induction coil 49 and local circuit is represented, but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes,
one on the diaphragio, the other on the adjusting screw. A shunt and rheostat
at R' serves to prolong the magnetism in the induction coil, and thus ensure a
gradual rise and fall of electric tension in the line instead of a cessation of the
same when the platina surfaces separate, and at the receiving diaphragm c the
rise and fall of electric tension in the line and its helix acts upon the permanent
magnet to produce the vibrations of the diaphragm c, and by connecting a shunt
around the helix and placing therein the secondary battery S, B, composed of

page_text: "
metallic plates in acidulated water the action is rendered more uniform and the
sound distinct.
When the diaphragm is arranged, as in Figure 26, to act upon a spring 56
through an intervening piece of soft rubber, said spring 56 produces rise and fall of
electric tension, by employing a range of resistance 57 with spring tongues adjacent
to 56. The greater amplitude of vibration of the diaphragin, the more direct will
be the electric circuit connections and the less resistance, because the circuit will
pass along the spring instead of going through all the resistance coils.
When several line wires run near each other the wire used for the acoustic or
speaking telegraph is influenced by induction, and false sounds will be produced.
I counteract this tendency by placing one or more electro magnets 59, Figure 28,
in the circuit of the speaking telegraph, and one or more electro-magnets 60 in the
circuit of the adjacent wires, and bringing the opposite cores of 60 at such a
distance from the cores of 59 that a certain magnetic action will be set up in 59
by induction in the opposite direction to the induction currents from the adjacent
line or lines.
By adjusting the distance between these magnets when the speaking telegraph
is not in use until there is not any sound at the diaphragm from the induction
currents, then these currents will be neutralized, whether strong or weak, and will
not produce any false sounds when the speaking telegraph is in use.
I also employ double coils of wire for the same purpose, one coil being in the
acoustic wire, and the other in the wire to be compensated.
A convenient form for the sound recorder or phonogragh is to employ a
cylinder 61, see Figure 29, having a helical groove in its surface covered with tin
foil, and the cylinder is revolved regularly by clockwork, and moved endwise by a
screw on its shaft, so that the indenting point from the diaphragm 10 of h will
be always in line with such groove; hence the vibrations of the diaphragm will be
recorded by indeuting the foil into the groove, and hence the same sound will be
reproduced by the point of the hearing instrument n, giving to the diaphragmu
of n the motions that result from the indentations of the foil moving in contact
with such rint.
The foi oay be on a flat grooved plate, and be indented and act as before
named.
I would observe in conclusion that I do not claim generally the transmission and
reproduction of sounds by increasing and decreasing the resistance of the circuit,
nor do I claim separately any of the parts or arrangements herein before described
and illustrated in the accompanying Drawings, except as hereinafter mentioned,
but I claim as my Invention,-
First. In an instrument for transmitting electric impulses by sound, a diaphragm
or tympan of mica, substantially as set forth.
Second. In an instrument for transmitting electric impulses by sound, the
combination with a diaphragm or tympan of electric tension regulators, substantially
as herein before described for varying the resistance in a closed circuit, substantially
as set forth.
Third. The method herein specified of recording the undulations of the diaphragm 4
on yielding material, and the reproduction of sound by such material acting upon a
diaphragm to communicate to the same vibrations similar to the original ones,
substantially as set forth.
In witness whereof, the said United Telephone Company, Limited, have
caused their common seal to be hereunto affixed, the Twenty third day of 5
March. One thousand eight hundred and night.

page_text: The
United
Telephone
Company,
Limited.
JAMES BRAND,
Chairman.
G. E. GOURAND,
Director.
R. H. KRAUSE,
Acting Secretary.

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME WE THE UNITED
TELEPHONE COMPANY LIMITED send greeting WHEREAS Her most Excellent
Majesty Queen Victoria by Her Royal Letters Patent under the Great Sea!
of Great Britain and Ireland bearing date at Westminster the Thirtieth day of
July in the year of our Lord One thousand eight hundred and seventy seven in
the forty first year of Her reign did for Herself Her heirs and successors give and
grant unto Thomas Alva Edison his executors administrators and assigns special
license full power sole privilege and authority that he the said Thomas Alva Edison
bis executors administrators or assigns and every of them by himself and themselves
or by his and their deputy or deputies servants or agents or such others as he
his executors administrators or assigns should at any time agree with and no others
from time to time and at all times thereafter during the term therein expressed
should and lawfully might make use exercise and vend within the United
Kingdom of Great Britain and Ireland the Channel Islands and Isle of Man an
Invention of IMPROVEMENTS IN INSTRUMENTS FOR CONTROLLING BY SOUND THE
TRANSMISSION OF ELECTRIC CURRENTS AND THE REPRODUCTION OF CORRESPONDING
SOUNDS AT A DISTANCE for and during the term of fourteen years thence next
ensuing And whereas in pursuance and performance of a proviso in the said
Letters Patent contained the said Thomas Alva Edison did within six calendar
months next after the date of the said Letters Patent cause a Specification
in writing under his hand and seal purporting to particularly describe the nature
of the said Invention and in what manner the same was to be performed to
be duly filed in the Great Seal Patent Office And whereas by indenture bearing
date the Second day of August One thousand eight hundred and seventy nine
and made between the said Thomas Alva Edison of the one part and the Edison
Telephone Company of London Limited of the other part the said Thomas Alva
Edison assigned unto the said Company (inter alia) the said hereinbefore recited

page_text: Letters Patent and all rights powers privileges advantages profits emoluments and
benefits to the said Letters Patent appertaining or belonging And whereas on the
Thirteenth day of November One thousand eight hundred and seventy nine the
said Edison Telephone Company of London Limited petitioned the Cominissioners
of Patents for leave to amend certain parts of the said Specification of the said
Letters Patent which petition was referred to Her Majesty's late Attorney General
Sir John Holker and leave was given to the said Company to file in the Great
Seal Patent Office a Disclaimer and Memorandum of Alteration as appears by the
Fiat of the said Sir John Holker dated the Ninth day of February One thousand
eight hundred and eighty and the said Disclaimer was duly filed in the Great Seal
Patent Office on the Tenth day of February One thousand eight hundred and
eighty And whereas by indenture bearing date the Twelfth day of July One
thousand eight hundred and eighty and made between the said Edison Telephone
Company of London Limited of the one part and us the United Telephone
Company Limited of the other part and duly registered in the Great Seal Patent
Office the said Edison Telephone Company of London Limited assigned to us the
said Letters Patent and the rights and privileges thereby granted and the same
thereby became and are now vested in us the said United Telephone Company
Limited And whereas on the Twenty fifth day of March One thousand eight
hundred and eighty one we the said United Telephone Company Limited
petitioned 'he Commissioners of Patents for leave to further amend certain
parts of the said Specification of the said Letters Patent which petition was
referred to Her Majestys Attorney General and leave was given to us the said
United Telephone Company Limited to file in the Great Seal Patent Office a
further Disclaimer and Memorandum of Alteration as appears by the Fiat of Her
Majesty's Attorney General Sir Henry James dated the Fourth day of June One
thousand eight hundred and eighty one and the said Disclaimer and Memorandum
of Alteration was duly filed in the Great Seal Patent Office on the Thirteenth day
of June One Thousand eight hundred and eighty one And whereas since the
filing of the said last named Disclaimer and Memorandum of Alteration we the said
United Telephone Company Limited have been in litigation with various persons
and companies with respect to infringements of the said Letters Patent and we the
said United Telephone Company Limited have found that the retention of Claims 1
and 3 of the said Specification as amended by the said bereinbefore recited
Disclaimers having regard to the language of the Provisional Specification has
given rise to questions as to how far such claims are valid as a matter of law upon
the face of the Specifications And whereas the subject matter of the said Clains 1
and 3 is not of great commercial importance And we are therefor desirous of
striking out the said Claims 1 and 3 and of confining the claim of the said Letters
Patent to the second claim thereof NOW KNOW YE that we the United
Telephone Company Limited by and with the leave of Her Majestys Attorney
General and for the reasons aforesaid do alter the Specification by striking out of
the said Specification as amended by the said Disclaimer printed by the Queens
Printers and published at the Patent Office in One thousand eight hundred and eighty
one the first claim comprising lines 39 and 40 on page 10, We also strike out the
third claim comprising lines 45 to 48 both inclusive on the said page 10 We also
strike out the word "second" at the commencement of line 41 on the said page 10
And in order that the effect of the said Disclaimer may be clearly understood we
annex hereunto a copy of the said Specification as it will appear when so amended
the preamble and testing clause being omitted.
This Invention relates to that class of electrical instruments in which sound
becomes one of the elements in the transmission of the communication and a
corresponding sound is produced at the receiving station so that oral communi-
cations can be sent by electricity and clearly distinguished at the receiving
station.
Musical tones may also be sent but my present Invention is especially available
in transmitting and receiving oral communications.

page_text: In transmitting musical tones the respective notes each have a definite period
for each vibration hence there is a response at the receiving end from the notes
that vibrate in time with the electric pulsations sent but in speaking there is little
change in the musical tone but considerable in the modulations and inflections of
the voice.
In my present Invention I make use of the vibrations given to a diaphragm or
tympan by speaking into a resonant case to produce a rise and fall of electrical
tension upon the line with such accuracy that the electric pulsations or waves will
represent the atmospheric sound waves produced by articulation and an electro
magnet at the receiving station will respond to the electric waves in such a manuer
as to reproduce the articulation by acting upon a resonant plate.
The transmitting instrument in a complete form is represented in section in
Figure 1 and Figure 2 represents a receiving instrument which may be employed
with it.
Referring to Figure 1 the resonant tube or box a is of a size and shape adapted
to being spoken into the same having an opening at one end or side and a
diaphragm or diaphragms b against which the sound waves from the human voice
act and these and the motion that the diaphragm receives is the ineans of producing
a rise and fall of electric tension on the line by the devices hereafter set forth so
that the battery B connected to the line will transmit a greater or less current to
the distant electro magnet m in Figure 2 and increase or lessen the magnetism of
the cores and in so doing act upon a resonant plate c and develop sound corre-
sponding to the articulation at the transmitting station.
The general features thus described pervade my entire Invention but in
developing the same many useful and important modificatious and variations have
been made which I proceed to set forth.
For convenience the speaking instrument Figure 1, is provided with a handle a'
and flexible conductors to the battery and line respectively so that it may be
handled and brought to the mouth, and in like manner it is preferable to place the
hearing instrument Figure 2 in a moveable handle 6' so that it can be placed with
the plate c against the ear this brings the sound close to the organs of hearing and
the resonant plate touching the ear increases the distinction of the sound and
prevents any false or prolonged vibrations of the plate.
. In some of the modifications I have shewn the speaking instrument as a fixture
and also the hearing instrument as a fixed resonant tube these being variable to
suit the persons or the places.
The first especial feature that requires separate consideration is the peculiarity
of the resonant tube for the voice I have experienced great difficulty in reproducing
the sound of the hissing consonants such as S this appears to arise from the fact
that this sound is deflected downwardly in leaving the mouth and does not act
distinctly upon the diaphragm By providing an edge in the resonant tube below
the mouth upon which such consonant sounds are received the vibrations are given
either to the resonant tube or deflected to the diaphragm I find it preferable to
employ a hole e at the lower part of the mouth piece against the edges of which
the downward sound waves are directed. The same effect will be produced by a
vibrating edge placed in the lower part of the mouth piece or the opening into the
resonant box may be contracted to about half an inch in diameter to effect the
same purpose. The next feature requiring consideration is the character of the
diaphragm in the speaking instrument.
Many materials have been employed by me such as metals horn vellum celluloid
ivory &c. but almost all of these produce a prolonged or secondary vibration for
their own resonant character hence the articulation is defective and the sound
vibrations blend.
After extensive experiments I find that mica is almost entirely free from any
resonant action and lience it will respond with the greatest accuracy to the sound
vibrations and being of a laminated character can be employed of any desired
thickness and when secured at its edges responds with the greatest accuracy to the

page_text: sound vibrations and does not require to be strained furthermore the changes of
temperature and atmospheric condition have little or no effect upon the mica
diaphragin or tympan.
I find that it is not practical to open and close the line circuits in instruments
for transmitting the human voice the circuit to the line must be always closed and
the transmission be produced by a rise and fall of electric tension resulting from
more or less resistance in the line This resistance may be produced in several
ways. I have shewn several which will hereafter be named but I find the most
delicate to be small bunches or tufts or discs of some conducting elastic fibre such
as particles of silk and an intermediate conducting or semi-conducting material
this device I call an electric tension regulator it is more or less compressed according
to the vibrations of the diaphragm or tympan and the electric current rises in
tension as it is compressed or lessens as the fibre expands. This fibre is placed in
a small roll t between the delicate diaphragm spring u Figure 9 and the variable
presser v adjustable by screw or otherwise in the electric circuit at this point or it
may be within a cavity in said presser vas in Figure 1. there being a delicate cork
centre piece w to the diaphragm b with a piece of platina foil x in contact with the
fibre. In all instances the telegraphic circuit at the diaphragin is made by a thin
strip of platina or similar material extending to the centre from the line or battery
connection.
The ɓbre is rendered semi conductive by being rubbed with plumbago soft metal
or similar material or by a deposit of metal upon its surface or by fine.
varying with the density of the tuft or branch of fibre.
particles of conducting or semi-conducting material mixed with it, the conducting
power
The delicate spring u Figure 9 upon the mica diaphragm b is easily secured by
solder passing into fine holes bored in the mica.
In some cases I make use of a variable resistance resulting from greater or less
intimacy of surface contact such as would result from a disk covered with plumbago
placed adjacent to a diaphragm also covered with plumbago or other semi
conducting material so that the proximity or extent of surface contact will produce
rise and fail of tension the respective parts being in the telegraphic circuit.
. I sometimes perforate the diaphragm 10 Figure 18 and place a strip of elastic
material 40 across said diaphragm over the hole and upon this a piece of foil so
that the same responds to very weak vibrations and in some instances two or
more diaphragms are provided at different rides of the resonant box each with its
own tension regulator the diaphragms being either the same or of different sizes
characters or tensions so as to respond to varying sounds or acoustic condition the
various tension regulators being all in the electric circuit this will produce greater
rise and fall of tension for longer lines in cousequence of the diaphragms acting
simultaneously on the tension regulators.
In some instances it is preferable to make the mouth piece of the speaking
instrument sufficiently large or Haring to receive all the sound vibrations whether
coming from the mouth nose or throat.
The tension regulator formed of fibre and conducting or semi conducting material
may be either dry or moistened with a liquid.
In some instances I make use of the best quality of lamp black retained within
a case to form the tension regulator the circuit passing through the same and the
rise and fall of electric tension resulting from the compression of the same by the
movement of the diaphragin.
I am enabled to record the sounds produced by the human voice or otherwise by
causing the movements of the diaphragm to be registered on paper or soft sheet
metal and then the paper may be used in an instrument to reproduce the sound
upon a delicate diaphragm by giving to the same a vibration similar to that
originally given by the voice. h. Figure is the indenting transmitter the
diaphragm having a knife edge point is the paper which has previously been
passed through a. machine to raise a V shaped rih 6. The movement of the
diaphragm of when the drum is in motion causes the knife edge point b' to

page_text: indent the raised rib to varying depthis according to the amplitude of vibration of
the diaphragm thusentations represent accurately all the tones and
varying inflections of the human voice. The paper after being
passed
through a second apparatus n Figure 5 almost similar to h. A spring 9 has a
knife edge which rests upon the raised indented rib 6 the spring being connected
to a delicate liaphragm 10 by a string or straw.
The indented rib reproduces in the spring 9 the movement of the indenting
point and either by direct action or through the vibration of a string conveys the
same motion to the diaphragm of n and reproduces previous sounds. If these sounds
are to be transmitted over a telegraph line the diaphragm 10 see Figure 6 is provided
with a cork disc w and fibrous tension regulator t before described to produce the
rise and fall of electric tension on the line. The sound may be recorded in ink as
represented in Figure 7. The diaphragm of h operates a very flexible self feeding
pen o and causes the continuous line to be wide or narrow according to the
amplitude of vibration of the diaphragm. The ink used should dry quickly and
the strip may be passed at any time thereafter through the instrument shewn in
Figure 8 beneath the arm 12 having a point or points resting on the paper this
arm is connected with a resonant diaphragmn and the ink marks produce more or
less friction according to the breadth and amount of ink deposited and this will
set the diaphraga of a vibrating and reproduce the vibrations of the diaphragm
of h.
An obvious modification would be to coat the paper with a substance which
would cause considerable friction or even rough unsized paper might be used and
a spring provided with a burnished point rather flat would cause the surface of the
paper to be made smooth more or less according the vibration of the diaphragm
and the difference in the surface of the paper would produce a response of the
receiving diaphragm.
I sometimes arrange the battery in connection with the transmitting instrument
as shewn in Figure 10.
is the resonant chamber at the end of which is the diaphragm 10 and at each
side of this diaphragm there are springs c² 3 having points made of compressed
plum go mixed preferably with gum rubber but any substance not liable to
rapid decomposition or the elastic or fibrous tension regulator aforesaid may be
used. These points face each other on opposite sides of the diaphragm and
make contact with platina foil discs secured to the diaphragm.
The spring passes through a hole or small slot in the side of the chamber h;
dds are the main batteries the battery 2 has zinc to the line or spring c² and the
battery has copper to the line or spring c³. When the springs c² and c³ are
adjusted to make contact with the diaphragm equally no current passes to the line
but when the diaphragm is vibrated its movement to one side say c² causes a
greater pressure upon the plumbago on that spring and a loosening of the pressure
on the plumbago on c³ hence the balance of the batteries c² and c³ will be destroyed
having the advantage will send a negative current to line upon the return of the
diaphragm the battery currents will again neutralize each other. The vibration of
the diaphragm to the other side causes the pressure to be reversed and the battery d
will send a positive current to the line.
As the tension regulator of fiber or of plumbago decreases and increases its
resistance enormously under slight changes of pressure it follows that the strength
of the electric waves will be in proportion as the speakers voice is strong or weak.
In Figure 11 is shewn the contact spring which may be used adjacent to the
diaphragm at one or both sides thereof e is a U shaped spring secured to the
screw which is adjusted back and forth by the thumb nut es e is the pillar
bolding such screw is a piece of soft rubber or equivalent substance placed
between the prongs of the spring e³ e' is a wire or band which serves to bind the
prongs tightly against the rubber so as to prevent the prongs acting as a tuning
fork and transmitting harmonic vibratious not desirable is the plumbago contact
point. The object of the U spring and rubber is to present a semi rigid point for

page_text: :
contact so as to prevent a rebound and allow of a slight yield when the plumbago
is pressed by the diaphragm.
In Figure 3 the diaphragm of the receiving instrument is vibrated by a strip of
paper chemically prepared that is in motion the pulsations of electricity passing
over the line and producing more or less friction between the paper and an arm
upon the diaphragm.
The resonant box or chamber n is provided with a diaphragm as aforesaid and
to said diaphragm an arm h² is connected. At its outer end is an adjusting screw h³
that presses upon a platina faced spring ht that is secured to this arm and said
spring rests upon the strip of paper that passes over the drum h³.
The paper is moved slowly by rotating the drum h and the waves of electricity
coming over the line pass through the arm to the platina faced spring h³ thence
through the paper to the earth.
If a negative current passes in the opposite direction nearly all friction between
the platina plate and the paper ceases and the diaphragm of the resonant box n
retains its normal position.
When the positive current passes through the same channel the normal friction
of the paper is augmented and the chemical surface acting upon the platina
spring arm serves to give a forward movement to the diaphragm of the
resonant box.
Thus the mechanical force applied to move the chemical paper or surface acts
with the electric current to produce the vibration of the diaphragm of the resonant
chamber and these vibrations will correspond to those of the diaphragm b made
by speaking in the tube a.
The principle of this method of obtaining motion by electro chemical decom-
position is that when a moving surface is in contact with a slightly yielding
substance the tendency is to move the latter by and with the former. If the
circumstances of contact are varied the adhesion of the surfaces will be sufficient
to cause the moving surface to move the yielding substance or else to cause the
yielding surface to slip more freely and by its spring go in the opposite direction
to the roving surface.
The passage of electricity at the surfaces in contact will change the frictional
adhesion make it more or less according to the substances employed. By balancing
the mechanical forces so that when the surfaces in contact are not electrified the
moving surface carries with it the yielding surface and when electrified the yielding
surface slips back over the moving surface a mechanical movement is obtained that
is dependent on the electrical condition of the surfaces in contact.
When it is requisite to obtain very perfect articulation and when loudness is
not essential I adopt a modification shewn in Figure 12 of the device for com-
pressing and expanding the tuft of conducting fiber which modification consists
in placing between the diaphragm 10 and the fiber ta vibrating tongue 21 of
steel permanently magnetised and arranging it to act in the same manner upon
the tension regulator t as if it was the diaphragm I replace the cork upon the
diaphragm by a thin armature of iron 22 which is in close proximity to the
magnetised tongue which tongue is secured at one end like an acoustic reed. In
this position the diaphragm is free to move and at its approach to and recession
from the magnetised tongue causes said tongue to follow its movements by mgnetic
attraction and thus the tongue is made to perform what the diaphragm previously
performed in varying the tension of the electricity on the line.
A plate supported eccentrically and free at its edges when placed in the
speaking tube responds advantageously to the tones of the voice. The circuit with
this plate is completely through one or more tension regulators placed around its
edges.
In practice I combine with the speaking or telephonic apparatus signal bells so
arranged that when the telephone is not in use the line is thrown upon the bell
by a switch which also acts as a call on the hell.
One feature about the bells is that the magnet which serves to actuate the bells

page_text: is made of very high resistance using preferably German silver wire in the helix
and thus serves to prevent a rapid consumption of battery power. A large number
of telephonic wires may be worked from one battery if these bells are used.
The method I adopt for coating non-conducting substance with metallic
substance is the reduction to the metallic state of metals from their salts by
exposing them to the fumes which arise from the moist phosphide of a metal such
as phosphide of calcium or by placing the silk for instance in a sealed tube
provided with metallic electrodes and volatilizing the electrodes by the passage of
electric sparks such volatilized metals settle upon and coat the silk.
When great loudness is desirable as in factories the tympan of the receiving
instrument may be made to control an air valve of a reservoir in which air is
stored under a regulated pressure.
The air allowed to escape will act with great power upon a local diaphragm.
This diaphragm to obtain clear sounds requires a damper to check prolonged
vibration. It must be damped by holding the fingers against it or by a tightly
stretched cord rubbing against it or by a screw provided with a rubber tip held
against it.
In some instances I make a record of the sound by the movements of the
diaphragm using for that purpose a strip of paper moved along regularly between
two rollers 25, 26 as in Figures 14 and 13 and there is a smooth thread or fine
wire of soft metals 30 between the paper and the upper roller 25 and moving
along with it. The diaphragm 10 of the resonant box is connected by a delicate
rod 28 with this thread or wire as near to the bight of the roller as possible there
being a fork or eye through which the thread passes hence deflections or bends are
made in the thread or wire just before it is embedded into the paper by the
pressure of the rollers. This may be used to reproduce the sound by vibrating a
resonant diaphragm by the undulations of the groove mide by the thread or cord.
By placing the fibrous tension regulator within a small band of india rubber the
sae is rendered more elastic and the fiber is allowed to expand by the heat of the
current without altering the electric tension.
In some instances the diaphragm should be free to vibrate without being
checked by contact with any stationary substance I provide for this by placing
upon the diaphragm or tympan 10 Figure 17 a small cylinder t' of hard rubber or
non-conducting material within which is the fibrous tension regulator t resting
upon a platina foil connected to one pole of the battery and within this cylinder t
is a dise to of iron or other metal loose but pressed towards the tension regulator
by a spring to and screw cap to and the other electric conductor is connected with
said spring.
The inertia of the metal disc causes more or less compression of the tension
regulator as the diaphragm is vibrated and hence the electric pulsations are sent
over the line in harmony with the vibrations. Nearly the same effect is produced
by connecting the disc to to a yielding spring t that extends across from one edge
of the diaphragm to the other as seen in Figure 16. This construction of tension
regulating device is especially available with large diaphragmns.
In some cases I use a soft rubber diaphragm immediately in contact with the
transmitting or receiving diaphragm so as to check or dampen any prolonged or
false vibration and render the sound more clear and free from prolonged tones.
In preparing the tension regulator I find in some cases that it is preferable to
use lamp black mixed with pure plumbago amorphous phosphorous and a very
small amount of non conducting material such as rubber dissolved in a solvent that
will entirely evaporate.
In Figure 19 I have represented the circuit as passing through the diaphragm 10
tension regulator t and a Duluc's dry pile battery D P B to the earth. This
battery is composed of about 300 pairs of paper discs coated with silver and black
oxyd of manganese.
Figure 20 illustrates the device before mentioned for intensifying the sound 10
is the diaphragm vibrated by the sound +2 is a valve moved by such diaphragm.

page_text: 43 is a reservoir containing air under a given pressure b is the diaphragm against
which the air allowed to escape by the valve acts and t is the tension regulator
to transmit the electric pulsations or a bearing resonant case may be applied at the
same place.
Figure 24 represents the diaphragm 10 tension regulator t with its adjusting
screw and local circuit containing the battery B passing through a primary
induction coil 49 and there is a key 50 in the same circuit. A secondary induction
coil 51 is in the line circuit and is influenced electrically by the change of tension
in the local circuit by the vibrations of the diaphragm 10.
The secondary coil is sometimes required with many layers of fine wire to set
up a current of high tension to overcome the inductive effect from the line wires
being adjacent to each other. I place the receiving instrument at the distant
station between the induction coil and the earth as at R and use an electro-
magnet E M with polarized armature to strike a bell this will respond when the
key 50 in the local circuit at the distant station is opened and closed.
In Figure 25 a similar induction coil 49 and local circuit is represented but the
tension regulator is made of platina foil upon the surface of two soft rubber tubes
one on the diaphragm the other on the adjusting screw. A shunt and rheostat at R¹
serves to prolong the magnetism in the induction coil and thus ensure a gradual
rise and fall of electric tension in the line instead of a cessation of the same when
the platina surfaces separate and at the receiving diaphragm c the rise and fall of
electric tension in the line and its helix acts upon the permanent magnet to produce
the vibrations of the diaphragm c and by connecting a shunt around the helix and
placing therein the secondary battery S B composed of metallic plates in acidu-
lated water the action is rendered more uniform and the sound distinct.
When the diaphragm is arranged as in Figure 26 to act upon a spring 56
through an intervening piece of soft rubber said spring 56 produces rise and fall
of electric tension by employing a range of resistance 57 with spring tongues
adjacent to 56. The greater amplitude of vibration of the diaphragin the unore
direct will be the electric circuit connections and the less resistance because the
circuit will pass along the spring instead of going through all the resistance
coils.
When several line wires run near each other the wire used for the acoustic or
speaking telegraph is influenced by induction and false sounds will be produced
I counteract this tendency by placing one or more electro magnets 59 Figure 28 in
the circuit of the speaking telegraph and one or more electro magnets 60 in the
circuit of the adjacent wires and bringing the opposite cores of 60 at such a
distance from the cores of 59 that a certain magnetic action will be set up in 59
by induction in the opposite direction to the induction currents from the adjacent
line or lines.
By adjusting the distance between these magnets when the speaking telegraph
is not in use until there is not any sound at the diaphragm from the induction
currents. then these currents will be neutralized whether strong or weak and will
not produce any false sound when the speaking telegraph is in use.
I also employ double coils of wire for the same purpose one coil being in the
acoustic wire and the other in the wire to be compensated.
A convenient form for the sound recorder or phonograph is to employ a
cylinder 61 see Figure 29 having a helical groove in its surface covered with tin
foil and the cylinder is revolved regularly by clock work and moved endwise by a
screw on its shaft so that the indenting point from the diaphragin 10 of h will
be always in line with such groove hence the vibration of the diaphragm will be
recorded by indenting the foil into the groove and hence the same sound will be
reproduced by the point 2 of the hearing instrument n giving to the diaphragm
of n the motions that result from the indentations of the foil moving in contact
with such point.
The foil may be on a flat grooved plate and be indented and act as before
named.

page_text: I would observe in conclusion that I do not claim generally the transmission
and reproduction of sounds by increasing and decreasing the resistance of the
circuit nor do I claim separately any of the parts or arrangements herein-before
described and illustrated in the accompanying Drawings except as hereinafter
mentioned but I claim as my Invention -
In an instrument for transmitting electric impulses by sound the combination
with a diaphragm or tympan of electric tension regulators substantially as herein
before described for varying the resistance in a closed circuit substantially as set
forth.
In witness whereof the United Telephone Company Limited have caused
their Common Seal to be hereunto affixed the
One thousand eight hundred and eighty two.
day of
I hereby grant my Fiat giving leave to the United Telephone Company Limited
the assignees of the said Letters Patent to file in the Office of the Commiss"
of Patents for Inventions with the Specification to which the same relates the
annexed Disclaimer and Memorandum of Alteration: but nevertheless upon
condition that no proceedings for infringement be taken against James Merrill
Ormes, or Horace Hamline Eldred both of 31 Queen Victoria Street in the City of
London, The London and Globe Telephone and Maintenance Company Limited,
Messrs. Harrison Cox Walker and Company of Darlington in the County of
Durham, Telegraph Engineers, Jobo Tasker of Sheffield in the County of York
Electrician or William Johnson also of Sheffield in the County of York, Electrician,
(hereinafter called the Opponents) or against any person or persons using any such
instruments as are hereinafter referred to, that is to say, in respect of
1. Any instruments made, or in course of manufacture on the 29th July 1882,
by, or to the order of, the said opponents or any or either of them.
2. Any instruments manufactured after the 20th July 1882 under or in
pursuance of any contracts bona fide entered into previous to that date by the said
opponents or any or either of them for the supply of instruments.
3. Any instruments manufactured after the 29th July 1882 under or in
pursuance of any contracts bona fide entered into prior to the 29th July 1882 with
the said opponents or any or either of them by any other person for the supply of
such instruments to the said opponents or any or either of them.
4. Particulars of all such instruments as have been or shall be subsequently to
the 2nd June 1882 manufactured or delivered, and of all contracts under which
such last mentioned instruments have been or shall be delivered to be furnished to

page_text: the United Telephone Company Limited and verified by Statutory Declaration on
or before the 14th September 1882.
5. All such instruments as have not been delivered prior to 29th July 1882 to be
numbered and marked with proper identifying marks before delivery, and an
opportunity to be given to the United Telephone Company Limited or their
agents to verify the same.
6. Any question of bona fides to be referred to and determined by the Attorney
General.
TAS