Year: 1882

page_text: I SILVANUS PHILLIPS THOMPSON, of University College, Bristol, Professor of
Experimental Physics seek leave to amend the specification of Letters Patent,
No. 3803 of 1882, as shown in red ink in the copy of the original specification
hereunto annexed :—
My reasons for making this amendment are as follows:-It has been suggested
that it might possibly be contended that the nature and scope of my Invention
were not described with sufficient clearness and that some portions of ny
Specification are open to a construction which could not safely be set up and I am
therefore desirous of explaining and limiting the nature and scope of my Invention
in the manner proposed, and of eliminating certain matters which are not of
sufficient value to be worth retaining.
Deputy
J. CLARK HALL,
Comptroller-General.

page_text: LETTERS PATENT to Silvanus Phillips Thompson, of University College,
Bristol, Professor of Experimental Physics, for an Inveution of "IMPROVE-
LETTERS PATENT to Silvanus Phillips Thompson, of University College,
Bristol, Professor of Experimental Physics, for an Invention of "IMPROVE-
MENTS IN TELEPHONIC APPARATUS
PROVISIONAL SPECIFICATION left by the said Silvanus Phillips Thompson
at the Office of the Commissioners of Patents on the 9th August 1882.
SILVANUS PHILLIPS THOMPSON of University College, Bristol, Professor of
Experimental Physics, "IMPROVEMENTS IN TELEPHONIC APPARATUS
"
My improvements relate to telephonic transmitters based upon the principle
discovered by Philipp Reis in 1861, namely that of employing current-regulators
actuated either directly or indirectly by the sound-waves produced by the voice. By
the term current-regulators I mean a device wherein a loose contact between two
parts of the circuit offers greater or less resistance to the flow of the electric
current, in which circuit a battery and a telephonic receiver are included; the degree
of intimacy of contact between the conducting pieces being altered by the
vibrations of the voice. In Reis's transmitter and in Edison's transmitter, and
other well known forms, of these instruments, the action is indirect; a tympanum
of stretched membrane, or other equivalent organ such as a diaphragm of mica
being used to collect, or magnify, or concentrate the vibrations of the voice and to
convey them to the point or points of loose contact that regulate the current. In
other forms of transmitters (for example some of Hughes's microphones) the mode
of action is direct, the air-waves beating directly upon the conductors or electrodes
which are in loose contact, without the intermediation of a tympanum or
diaphragm.
Of these two classes of telephone-transmitters, viz those in which the current-
regulator is combined with a tympanum or diaphragm, and those in which the
current regulator is acted upon directly by the air-waves of the voice, my improve-
ments relate to the latter only. I entirely dispense with the membrane tympanum
used in Reis's transmitter; I do not employ the tympanic diaphragm of mica used
in Edison's transmitter; I do not employ the non-tympanic diaphragm of foil used
in Hunning's transmitter; I do not even employ any diaphragm in the sense of a
partition between the current-regulator and the air-waves of the voice as in
Theiler's transmitter. In my improved transmitters the air-waves act directly
upon the current-regulator itself. By dispensing with tympanums, diaphragms,
and partitions, I obtain a more accurate correspondence between the vibrations of
the voice and the electrical undulations which they produce, than is practicable where
a tympanum, diaphragm, or partition is used. As a result, the articulation is clearer

page_text: for some of the consonantal sounds which are only imperfectly or difficultly
transmitted by telephones in which the current-regulator is affected indirectly
through a tympanum, diaphragm, or partition.
Transmitters of the class to which my improvements relate are ordinarily liable
to two defects. Firstly, they do not articulate so loudly as transmitters in which
there is a tympanum or diaphragm to collect or magnify the vibrations. Secondly,
when, to obviate this difficulty, the speaker speaks with his mouth very close to
the current-regulator, the moisture of his breath condenses upon the contact-points
or adjacent parts of the regulator, interfering with its action, and spoiling the
articulation. My improvements relate chiefly to means for remedying or obviating
these defects.
I propose to employ mirrors or sound-reflectors, or reverberators, consisting of
glass, metal, wood or other material, by which the sound-waves are turned aside
out of their straight path, or are made to converge upon the current-regulator,
precisely as rays of light may be turned aside or converged by a polished mirror.
If actual mirrors of polished metal or silvered glass are employed for this purpose,
they have the additional advantage of revealing to the speaker the presence of
moisture. But in any case the mirror, reflector, or reverberator serves to collect
the sound-waves as they come from the speaker's mouth, and to direct them on to
the current-regulator, while intercepting imoisture from the actual breath.
In some cases the reflector or reverberator has the form of an extended mouth-
piece; indeed in one sense the ordinary mouth-piece, such as used with magneto
telephones, and with various telephonic transmitters containing tympanums or
diaphragms, may be regarded as a reflector though it does not completely perform
the functions for which I have devised the improvements herein described. The
mouth-pieces hitherto used on ordinary transmitters are not intended to serve
either as reverberators or as protectors from moisture, I find that mouth-pieces for
this purpose must be deep and of conical or paraboloidal form. Any curved or
crooked mouth-piece contrived to retain, intercept, or dissipate the moisture of the
breath while reflecting the sound-waves on to the current-regulator is within the
scope of my improvements. Mouth-tubes consisting of a flexible tube have been
employed in combination with telephones of several kinds, for example the "Gower
Bell" magneto telephone. In all these, however, the air-waves do not act immediately
on the actual electrodes or conductors of the current-regulator, but on a tympanum,
diaphragm, or partition, the employment of such flexible mouth-tubes in com-
bination with a current regulator without any tympanum, diaphragm, or partition,
for the purpose of protecting the naked current-regulator from the deposition of
moisture by the breath is comprised in my improvements. In some cases I find it
advantageous to provide the mouth-piece with a flange at its inner end, such flange
not being in contact with the current-regulator.
Another part of my improvements consists in making such reflector, reverberator,
mouth-piece, or mouth-tube of such materials as will readily absorb moisture and
prevent its deposition upon the working parts of the current-regulator. Or such
absorbent or porous material may be used for the case of the instrument.
chemical substances capable of absorbing moisture may be placed in the case of the
instrument, or in the mouth-piece or mouth-tube.
Or
Another part of my improvements consists in employing such materials for the
current regulators as are at once neither hygroscopic, nor liable by their properties
with respect to heat, to condense films of moisture, while at the same time they are
good conductors of electricity. Polished metal is very liable to become covered
with a film of condensed moisture; coke-carbon, amorphous boron, spongy platinum,
and similar substances absorb moisture too readily, and commercial plumbago is
of too poor a conducting quality to be satisfactory. prefer to use as materials
for the current-regulator, either spongy platinum, carbide of platinum, boron, coke-
carbon, or elastic carbon specially prepared as hereinafter described, having first
deprived such materials of their hygroscopic properties by treatment with petroleum

page_text: or other oil, or with other suitable hydrocarbon, solid or liquid. And the essential
point of this part of my improvements is providing and applying in the manner
herein substantially as described, current-regulators that are not liable to become
bedewed with moisture. Where, however, by any of the means hereinbefore
described as part of my improvement, the breadth is already diverted effectually
from the current-regulator, the latter may be made of polished platinum, silver, or
other metal or even of some highly conducting form of carbon, the best conductor
being preferred, cæteris paribus, amongst those materials that neither rust nor fuse
together.
My improvements also partly consist in so arranging the conductors or electrodes
or other parts of the current regulator that the points of loose contact can be actuated
by the sound-waves whilst they are protected from the moisture of the breath, by
some portion of the conductors or electrodes projecting between the contact-points
and the breath of the speaker. Any microphone of the class to which my improve-
ments apply, if specially contrived so that the breath cannot get at the actual
points of contact is within the scope of my Invention.
The said improvements also relate to the forms to be given to the conductors or
electrodes combined together to form the current-regulator. The current-regulator
of Reis, consisting of one piece of platinum resting lightly against another is
imperfect; except when, as in some forms one or both the pieces of metal are fixed
upon springs or some equivalent elastic support; otherwise the current is liable to
too abrupt interruptions. I find that when there are many points of contact instead
of but a single pair, this result is less liable to happen. Multiple contacts therefore
are less liable to this objection. I attain this multiple contact in various ways.
A chain of metal links or of links of carbon, suitably hung, forms a suitable current-
regulator to combine with reverberators or reflectors as herein before set forth.
I also sometimes form the regulator of a number of narrow tongues of metal
capable of vibrating like the reeds of a harmonium, and arranged in series so as to
be in light contact in rows, or radially. Another of my improved forms of current
regulator consists of a grating or framework of prepared carbon, or metal tongues
so connected that the current cannot pass from one tongue to the next, except
through a piece or pieces of carbon or metal suspended or resting in loose contact
against the tongues; such regulators being combined with reverberators or mouth-
pieces or tubes in the manner set forth. Another form of regulator consists of
hook-shaped or cup-shaped conductors suspended or supported in loose-contact with
one another so as to be easily moved by the vibrations of the voice, whilst
protecting by their shape, from the direct action of the breath, the actual points
of contact. In the class of regulators in which I employ springs constructed of thin
strips or filaments of carbon, to vibrate as tongues by the direct impact of air-
waves, I sometimes render such carbon springs an-hygroscopic, as previously set
forth. Or I may use a solid ball or balls of carbon, in connection with springs or
tongues of carbon or of carburetted platinum; the whole being rendered an-
hygroscopic, if desired.
"
In some cases where a highly powerful action is desired propose to cause the
air-waves to act first on a vibrating tongue which then transfers the vibrations
indirectly to the current-regulator. This tongue may be itself an electrode, and
form part of the current-regulator, in which case it is formed of metal, carbon, or
other elastic conductor, whether an-hygroscopic or not. I sometimes arrange a
series of tongues radially in contact with each other either in pairs or in series
so that the current passes successively through all of them.
Another part of my Invention relates to improved materials suitable for current-
regulators of the last specified type. I may use for springs, platinum covered with
a film of carbide of platinum, which I form by heating strips of stiff sheet platinum
in a crucible in charcoal until the surface is strongly carburetted. Or I use springs
of platinum covered by electro deposit or otherwise with platinum black. Or I use
for springs carbon in elastic strips prepared by carbonizing in a crucible or furnace,

page_text: strips of animal or vegetable matter, natural or artificial, whether previously
parchmentised or not; and such strips may be made still harder by passing electric
currents through them whilst exposed to the vapor of a hydrocarbon, or in vacuo,
or in some gas in which carbon does not burn, and I may use material prepared in
5 any of these ways for making chains, strips, filaments, springs, or parts of any other
form suitable to be used in my current-regulators.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Silvanus Phillips Thompson in the Great Seal Patent Office on
the 9th February 1883.
SILVANUS PHILLIPS THOMPSON, of University College, Bristol, Professor of
Experimental Physics, "IMPROVEMENTS IN TELEPHONIC APPARATUS."
My improvements relate to telephonic transmitters based upon the principle
discovered by Philipp Reis in 1861, namely, that of employing current-regulators
actuated, either directly or indirectly, by the sound-waves produced by the voice.
By the term current-regulator I mean a device similar to that employed by Reis,
wherein a loose contact between two parts of a circuit (in which are included a
battery and a telephonic receiver) offers greater or less resistance to the flow of the
electric current, the degree of intimacy of contact between the conducting pieces
being altered by the vibrations of the voice. In Reis's transmitter, and in Edison's
transmitter, and other well known forms of these instruments, the action of the
sound waves upon the current regulator is indirect, a tympanum of stretched
membrane or other equivalent organ, such as a diaphragm of mica, being used to
collect or magnify, or concentrate, the vibrations of the voice, and to convey them
In other forms
to the point or points of loose contact that regulate the current.
of transmitters (for example, some of Hughes's 'microphones), the mode of action
is direct, the air-waves beating directly upon the conductors or electrodes which
are in loose contact, without the intermediation of a tympanum or diaphragın.
Of these two classes of telephone transmitters, viz:- those in which the current-
regulator is combined with a tympanum or diaphragm, and those in which the
current-regulator is acted upon directly by the air-waves of the voice, my
improvements relate to the latter only; I entirely dispense with the membrane
tympanum used in Reis's transmitter; I do not employ the tympanic diaphragın
of mica used in Edison's transmitter; I do not employ the non-tympanic diaphragm
of foil used in Hunning's transmitter; I do not even employ any diaphragm in the
sense of a partition between the current-regulator and the air-waves of the voice,
as in Theiler's transmitter. In my improved transmitters, the air-waves act
directly upon the current regulator itself; by dispensing with tympanums,

page_text: diaphragms and partitions, I obtain a more accurate correspondence between the
vibrations of the voice and the electrical undulations which they produce, than is
practicable where a tympanum, diaphragm, or partition is used.
As a result, the articulation is clearer for some of the consonantal sounds, which
are only imperfectly or difficultly transmitted by telephones in which the current- 5
regulator is affected indirectly through a tympanum, diaphragm, or partition.
Prior to the date of my invention direct acting telephone transmitters were not
available for practical commercial use owing to the defects below referred to
which my Invention seeks to remedy. Hence the advantage arising from dis-
pensing with tympanums, diaphragms and partitions were not up to that time 1
practically attainable.
Transmitters of the class to which my improvements relate are ordinarily liable
to two defects. Firstly, they do not articulate so loudly as transmitters in which
there is a tympanum or diaphragm to collect or magnify the vibrations. Secondly,
when, to obviate this difficulty, the speaker speaks with his mouth very close to the 1
current-regulator, the moisture of his breath condenses upon the contact points or
adjacent parts of the regulator, interfering with its action and spoiling the
articulation. My improvements relate chiefly to means for remedying or obviating
these defects.
My improvements are illustrated in the accompanying drawing, in which
Figure 1 is a front view, and
Figure 2 a transverse section of an instrument constructed according to one part
of my invention.
Figure 3 is a transverse section of another form of instrument
Figure 4 is a sectional elevation, and
Figure 5 a side elevation illustrating modifications of my Invention
Figures 6, 7 and 8 are transverse sections of various other forms or modifications
of my instruments.
Figure 9 is a transverse section, and
Figure 10 an end view of another modification, and
Figure 11 is a transverse section illustrating a further modification of my
Invention
Like letters indicate the same parts throughout the drawing.
Instead of using a tympanum or diaphragm for the purpose of collecting or
magnifying or concentrating the vibration of the voice and conveying them to the
point or points of loose contact that regulate the current 1 propose to employ
mirrors, sound-reflectors or reverberators (one form of which is shown in Figures 1
and 2), consisting of glass, metal, wood or other material, by which the sound-
waves are turned aside from their straight or direct path and are made to converge
upon the current-regulator, precisely as rays of light may be turned aside or
converged by a polished mirror. If actual mirrors of polished metal or silvered
glass are employed for this purpose, they have the additional advantage of
revealing to the speaker the presence of moisture. But in any case the mirror,
reflector, or reverberator serves to collect the sound-waves as they come from the
speaker's mouth, and to direct them onto the current-regulator while intercepting
moisture from the speaker's breath. By the use of such reverberators the speaker
is enabled to speak at such a distance from or in such a position with regard to
the contact points that the volume of sound conveyed to the contact points is con-
centrated thereon in such a manner as to give a sufficiently loud articulation
without the deposition of moisture upon the contact points. M is the mouth-piece
or tube; C is the current regulator; R is the reverberator; J is an adjusting
screw; and E is an outlet-cock for the water which collects in the mouth-tube;
the remaining parts are hereinafter described.
In some cases, the reflector or reverberator has the form of an extended mouth-
piece; indeed, in one sense, the ordinary mouth-piece such as that used with
imagneto-telephones and with various telephonic transmitters containing tympanums
or diaphragms, may be regarded as a reflector, though it does not completely

page_text: perform the functions for which I have devised the improvements herein described.
The mouth-pieces hitherto used on ordinary transmitters are not intended to
serve either as reverberators or as protectors from moisture. I find that my mouth-
pieces for this purpose must, as shown in Figure 3 and Figure 9, be deep and
of conical or paraboloidal form. Any curved or crooked mouth-piece such as
those shewn in Figures 4 and 5, specially contrived to retain, intercept or dissipate
the moisture of the breath while reflecting the sound waves onto the current
regulator, is within the scope of my improvements, but is, as will be seen, only
claimed in combination with current regulators of the class hereinbefore described
as having no tympanum or diaphragm. Mouth-tubes consisting of a flexible tube
have been employed in combination with telephones of several kinds, for example,
the "Gower Bell" magneto-telephone. In all of these instruments, however, the
air-waves act, not immediately on the actual electrodes or conductors of the
current regulator, but on a tympanum, diaphragm or partition. In Figure 6,
I illustrate this part of my improvement by depicting a flexible speaking tube
used in conjunction with a current-regulator. The employment of such flexible
mouth-tubes, in combination with a current regulator without any tympanum,
diaphragm, or partition, for the purpose of protecting the naked current regulator
from the deposition of moisture by the breath, is comprised in my improvements,
and I wish it to be understood that the use of a mouth tube or mouth piece
otherwise than in such combinations is not within the scope of my improvements
and I make no claim thereto.
In some cases I find it advantageous to provide the mouth-piece at its inner end
with a flange, such as that shewn at F in Figures 4, 5, 6 and 7, the said flange not
being in contact with the current regulator.
Another part of my improvements consists in making the reflector, reverberator,
mouth-piece or mouth-tube of such materials as will readily absorb moisture and
prevent its deposition upon the working parts of the current-regulator. Or I use
such absorbent or porous material for the case of the instrument; or I place chemical
substances, capable of absorbing moisture, in the case of the instrument, or in the
mouth-piece or mouth-tube.
Another part of my improvements consists in employing, for the current-regulator,
such materials as are at once neither hygroscopic, nor liable, by their properties
with respect to heat, to condense films of moisture, while at the same time they
are good conductors of electricity. Polished metal is very liable to become covered
with a film of condensed moisture. Coke or carbon, amorphous boron, spongy
platinum, and similar substances, in their ordinary condition, absorb moisture too
readily, and commercial plumbago is of too poor a conducting quality to be
satisfactory. I prefer to use, as materials for the current-regulator, either spongy
platinum, carbide of platinum, boron, coke, carbon or elastic carbon specially
prepared as hereinafter described, having first deprived such materials of their
hygroscopic properties' by treatment, with petroleum, or other, oil, or with other
suitable hydrocarbon, solid or liquid. In some cases, and especially where the
contact surfaces of the current regulator are of platinum or other metal, I find it
convenient to keep their surfaces constantly moistened with petroleum or other
hydrocarbon or oil by supplying them through a cotton filament in communication
with a small lubricator or oil-vessel.
The essential point or feature of this part of my improvements is the providing
and applying, in manner substantially as herein described, of current-regulators
that are not liable to become bedewed with moisture; where, however, by any of
my improvements herein before described, the instrument is provided with means
whereby the breath is diverted effectually from the current-regulator, the latter
may be made of polished platinum, silver, or other metal, or even of some highly
conducting form of carbon, the best conductor being preferred cæteris paribus
amongst those materials, that neither rust nor fuze together. In some of my
instruments, the aforementioned current-regulator consists of two pieces of metal or
carbon or other conductor of electricity kept lightly in contact either by gravity

page_text: or by the pressure of a light spring S, or by both these agencies. Figures 3, 4, 6,
7, 8, 11 illustrate such current-regulators.
the-scope-of-my-invention.
My improvements also partly consist in so arranging the conductors or electrodes,
or other parts of the current regulator, that the points of loose contact can be
netunted-by-the sound waves, whilst they are protected from the moisture of the
breath-by--some-portion of the conductors or electrodes projecting between the
contact-points and-the-breath-of-the-speaker. An example of such-an-arrangement
is-given-in Figure-8 wherein-the-contact-points C are protected from the breath-by
making-one-of-the electrodes in the form of a cup, against the concave-or-hollow
face-of-which-the-contact point-on-the-other-electrode-is-directed. Any microphone
of the class to which my improvements apply, if specially contrived so-that-the
moisture-of the-breath-cannot-have-access-to-the-actual-points-of-contnet,-is-within
The said improvements relate further to the form of the conductors or electrodes
combined to serve as the current-regulator. The current-regulator of Reis, con-
sisting of one piece of platinum resting lightly against another, is imperfect, except
when, as in some forms of Reis's instrument, one or both the pieces of metal are
fixed upon springs or some equivalent elastic support; otherwise the current is
liable to very abrupt interruptions. In Figure 7 I have shewn one of my current-
regulators wherein the two contact pieces are held upon springs S, S,; one of these
springs is fixed to an adjusting frame B and the other is fixed to an insulating
block K. I find that when there are many points of contact instead of but a single
pair of such points, there is less liability to such abruptness. Multiple contacts
therefore are advantageous. I provide multiple contacts in various ways.
instance, a chain or series of metal links, or of links of carbon, or other good
conductor of electricity, suitably suspended will form a good current-regulator to
combine with reverberators or reflectors such as those hereinbefore set forth.
For
I also sometimes form the regulator of a number of narrow tongues of metal or
of carbon, or carbonized or carburretted platinum capable of vibrating like the reeds
of a harmonium and arranged in series so as to be in light-contact in rows or
otherwise. Such a current-regulator is shown in Figures 9 and 10 wherein the
tongues a, b, c, d, e, f, are arranged radially and attached to a rim of non-conducting
material so that the current must pass through all of them in order, from the first
to the last.
Another of my improved forms of current-regulator consists of a grating or
framework of prepared carbon, or metal tongues so connected that the current
cannot pass from one tongue to the next except through a piece or pieces of good
conducting carbon or metal suspended, or resting, in loose contact against the
tongues; such regulators being combined with reverberators, mouth-pieces or tubes
in the manner herein set forth. In the instrument shown in Figures 1 and 2 the
current-regulator C consists of an inclined grating of carbon strips, against which
the voice-waves are reflected by the reverberator R and upon which rest light
balls R¹ of carbon or of metal suspended from the hooks R or otherwise by silken
strings. Another form of regulator consists of hook-shaped or-cup-shaped co
ductors-suspended or supported-in-loose-contact-with-one-another-so-as-to-be-easily
moved by the vibrations of the voice, whilst protecting, by their shape, from the
direct action of the breath, the actual points of contact. In the class of regulators
in which I employ springs constructed of thin strips or filaments of carbon, to
vibrate as tongues by the direct impact of air-waves, I sometimes render such
carbon springs anhygroscopic, as previously set forth. Or I may use a solid ball or
balls of carbon, in connection with springs or tongues of carbon, carburetted
platinum or of any suitable metal, the whole being rendered anhygroscopic if
desired.
-HOO-
In some cases where a highly powerful action is desired I propose to cause the
air-waves to act first on a vibrating tongue which then transfers the vibrations
indirectly to the current regulator or contact points. C. Such a vibrating tongue
is shewn at V in Figure 11 where it is attached behind a flanged tube T, the

page_text: contact points or current regulator C being on the same face of the tongue V as
that against which the voice-waves impinge. This tongue may be itself an
electrode; and serve as part of the current regulator, in which case it is formed
of metal, carbon or elastic conductor whether anhygroscopic or not.
Another part of my invention relates to improved materials suitable for current
regulators of the last specified type. I use, for springs, platinum covered with a
film of carbide of platinum, which I form by heating strips of stiff sheet platinum
in a crucible in charcoal until the surface is strongly carburretted. Or I use springs
of platinum covered by electro-deposition or otherwise with platinum black; or I
use, for the springs, carbon in elastic strips prepared by carbonizing in a crucible
or furnace, strips of animal or vegetable matter, natural or artificial, whether
previously parchmentized or not, and such strips may be made still harder by
passing electric currents through them whilst exposed to the rarefied vapour of a
hydrocarbon, or in vacuo, or in some gas in which carbon does not burn. And I
may use material prepared in any of these ways for making chains, strips, filaments,
springs, tongues, or parts of any other form suitable to be used in my current
regulators.
Having thus fully described my said Invention and the manner of performing
the same I wish it understood that I Claim make no claim to any of the matters
hereinbefore described except as is expressed in the following claiming clauses, that
is to say, I claim
First. In a telephonic transmitters wherein there is no tympanum or diaphragm,
the combination of reverberators or sound reflectors, substantially such as those
above described, with electric current regulators acting upon the principle of
variable contact, and acted upon directly by the air waves as, and for the purpose,
set forth.
Second. In a telephonic transmitter wherein there is no tympanum or diaphragm,
and having a current regulator acting upon the principle of variable contact and
acted upon directly by the air waves the employment or-application in combi-
nation with such current regulator, substantially as set forth, of a mouth-tube or
mouth-piece suitable for intercepting the moisture of the breath.
Third. In a telephonic transmitter of the class above specified, the employment
or application, substantially as set forth, of materials for absorbing or destroying
the moisture of the breath and for rendering anhygroscopic the contact surfaces
or contact points.
Fourth. The combination, with an electric current regulator, in a telephonie
transmitter, of a flange attached to the posterior-or-inner end of the mouth-tube,
substantially-as, and for the purpose, set-forth.
Fifth.-The-modification wherein-the-contact-points are protected-from-the-breath
by-making one-of the-electrodes concave or-cup-shaped, substantially as set forth.
Sixth. In-a-telephonie-transmitter, the employment, substantially as set forth, of
either-of-the-above described improved-forms-of-current-regulatore-not-included-in
the-preceding claiming clauses.
Seventh. The improvements relating to the current regulators constructed of
springs-or-tongues of prepared carbon-or platinum carburretted-or-covered-with-a
film-of-carbide-of platinum-substantially-as-set-forth.
In witness whereof I the said Silvanus Phillips Thompson have hereunto
set my hand and seal this eighth day of February in the year of our Lord
One thousand eight hundred and eighty three.
SILVANUS PHILLIPS THOMPSON. (LS.)

page_text: LETTERS PATENT to Silvanus Phillips Thompson, of University College,
Bristol, Professor of Experimental Physics, for an Invention of "Improve-
MENTS IN TELEPHONIC APPARATUS"
PROVISIONAL SPECIFICATION left by the said Silvanus Phillips Thompson
at the Office of the Commissioners of Patents on the 9th August 1882.
SILVANUS PHILLIPS THOMPSON, of University College, Bristol, Professor of
Experimental Physics, "IMPROVEMENTS IN TELEPHONIC APPARATUS
"
My improvements relate to telephonic transmitters based upon the principle
discovered by Philipp Reis in 1861, namely that of employing current-regulators
actuated either directly or indirectly by the sound-waves produced by the voice. By
the term current-regulators I mean a device wherein a loose contact between two
parts of the circuit offers greater or less resistance to the flow of the electric
current, in which circuit a battery and a telephonic receiver are included; the degree
of intimacy of contact between the conducting pieces being altered by the
vibrations of the voice. In Reis's transmitter and in Edison's transmitter, and
other well known forms, of these instruments, the action is indirect; a tympanum
of stretched membrane, or other equivalent organ such as a diaphragm of mica
being used to collect, or magnify, or concentrate the vibrations of the voice and to
convey them to the point or points of loose contact that regulate the current.
other forms of transmitters (for example some of Hughes's microphones) the mode
of action is direct, the air-waves beating directly upon the conductors or electrodes
which are in loose contact, without the intermediation of a tympanum or
diaphragm.
In
Of these two classes of telephone-transmitters, viz those in which the current-
regulator is combined with a tympanum or diaphragm, and those in which the
current regulator is acted upon directly by the air-waves of the voice, my improve-
ments relate to the latter only. I entirely dispense with the membrane tympanum
used in Reis's transmitter; I do not employ the tympanic diaphragm of mica used
in Edison's transmitter; I do not employ the non-tympanic diaphragm of foil used
Price 6da1

page_text: in Hunning's transmitter; I do not even employ any diaphragm in the sense of a
partition between the current-regulator and the air-waves of the voice as in
Theiler's transmitter. In my improved transmitters the air-waves act directly
upon the current-regulator itself. By dispensing with tympanums, diaphragms,
and partitions, I obtain a more accurate correspondence between the vibrations of
the voice and the electrical undulations which they produce, than is practicable where
a tympanum, diaphragm, or partition is used. As a result, the articulation is clearer
for some of the consonantal sounds which are only imperfectly or difficultly
transmitted by telphones in which the current-regulator is affected indirectly
through a tympanum, diaphragm, or partition.
Transmitters of the class to which my improvements relate are ordinarily liable
to two defects. Firstly, they do not articulate so loudly as transmitters in which
there is a tympanum or diaphragm to collect or magnify the vibrations. Secondly,
when, to obviate this difficulty, the speaker, speaks with his mouth very close to
the current-regulator, the moisture of his breath condenses upon the contact-points
or adjacent parts of the regulator, interfering with its action, and spoiling the
articulation. My improvements relate chiefly to means for remedying or obviating
these defects.
I propose to employ mirrors or sound-reflectors, or reverberators, consisting of
glass, metal, wood or other material, by which the sound-waves are turned aside
out of their straight path, or are made to converge upon the current-regulator,
precisely as rays of light may be turned aside or converged by a polished mirror.
If actual mirrors of polished metal or silvered glass are employed for this purpose,
they have the additional advantage of revealing to the speaker the presence of
moisture. But in any case the mirror, reflector, or reverberator serves to collect
the sound-waves as they come from the speaker's mouth, and to direct them on to
the current-regulator, while intercepting moisture from the actual breath.
In some cases the reflector or reverberator has the form of an extended mouth-
piece; indeed in one sense the ordinary mouth-piece, such as used with magneto
telephones, and with various telephonic transmitters containing tympanums or
diaphragms, may be regarded as a reflector though it does not completely perforin
the functions for which I have devised the improvements herein described. The
mouth-pieces hitherto used on ordinary transmitters are not intended to serve
either as reverberators or as protectors from moisture, I find that mouth-pieces for
this purpose must be deep and of conical or paraboloidal form. Any curved or
crooked mouth-piece contrived to retain, intercept, or dissipate the moisture of the
breath while reflecting the sound-waves on to the current-regulator is within the
scope of my improvements. Mouth-tubes consisting of a flexible tube have been
employed in combination with telephones of several kinds, for example the "Gower
Bell" magneto telephone. In all these, however, the air-waves do not act immediately
on the actual electrodes or conductors of the current-regulator, but on a tympanum,
diaphragm, or partition, the employment of such flexible mouth-tubes in com-
bination with a current regulator without any tympanum, diaphragm, or partition,
for the purpose of protecting the naked current-regulator from the deposition of
moisture by the breath is comprised in my improvements. In some cases I find it
advantageous to provide the mouth-piece with a flange at its inner end, such flange
not being in contact with the current-regulator.
Another part of my improvements consists in making such reflector, reverberator,
mouth-piece, or mouth-tube of such materials as will readily absorb moisture and
prevent its deposition upon the working parts of the current-regulator. Or such
Οι
absorbent or porous material may be used for the case of the instrument.
chemical substances capable of absorbing moisture may be placed in the case of the
instrument, or in the mouth-piece or mouth-tube.
Another part of my improvements consists in employing such materials for the
current-regulators as are at once neither hygroscopic, nor liable by their properties
with respect to heat, to condense films of moisture, while at the same time they are
good conductors of electricity. Polished metal is very liable to become covered

page_text: with a film of condensed moisture; coke-carbon, amorphous boron, spongy platinum,
and similar substances absorb moisture too readily, and commercial plumbago is
of too poor a conducting quality to be satisfactory. I prefer to use as materials
for the current-regulator, either spongy platinum, carbide of platinum, boron, coke-
carbon, or elastic carbon specially prepared as hereinafter described, having first
deprived such materials of their hygroscopic properties by treatment with petroleum
or other oil, or with other suitable hydrocarbon, solid or liquid. And the essential
point of this part of my improvements is providing and applying in the manner
herein substantially as described, current-regulators that are not liable to become
bedewed with moisture. Where, however, by any of the means herein before
described as part of my improvement, the breath is already diverted effectually
from the current-regulator, the latter may be made of polished platinum, silver, or
other metal or even of some highly conducting form of carbon, the best conductor
being preferred, cæteris paribus, amongst those materials that neither rust nor fuse
together.
My improvements also partly consist in so arranging the conductors or electrodes
or other parts of the current regulator that the points of loose contact can be actuated
by the sound-waves whilst they are protected from the moisture of the breath, by
some portion of the conductors or electrodes projecting between the contact-points
and the breath of the speaker. Any microphone of the class to which my improve-
ments apply, if specially contrived so that the breath cannot get at the actual
points of contact is within the scope of my Invention.
The said improvements also relate to the forms to be given to the conductors or
electrodes combined together to form the current-regulator. The current-regulator
of Reis, consisting of one piece of platinum resting lightly against another is
imperfect; except when, as in some forms one or both the pieces of metal are fixed
upon springs or some equivalent clastic support; otherwise the current is liable to
too abrupt interruptions. I find that when there are many points of contact instead
of but a single pair, this result is less liable to happen. Multiple contacts therefore
are less liable to this objection. I attain this multiple contact in various ways.
A chain of metal links or of links of carbon, suitably hung, forms a suitable current-
regulator to combine with reverberators or reflectors as hereinbefore set forth.
I also sometimes form the regulator of a number of narrow tongues of metal
capable of vibrating like the reeds of a harmonium, and arranged in series so as to
be in light contact in rows, or radially. Another of my improved forms of current
regulator consists of a grating or framework of prepared carbon, or metal tongues
so connected that the current cannot pass from one tongue to the next, except
through a piece or pieces of carbon or metal suspended or resting in loose contact
against the tongues; such regulators being combined with reverberators or mouth-
pieces or tubes in the manner set forth. Another form of regulator consists of
hook-shaped or cup-shaped conductors suspended or supported in loose-contact with
one another so as to be easily moved by the vibrations of the voice, whilst
protecting by their shape, from the direct action of the breath, the actual points
of contact. In the class of regulators in which I employ springs constructed of thin
strips or filaments of carbon, to vibrate as tongues by the direct impact of air-
waves, I sometimes render such carbon springs an-hygroscopic, as previously set
forth. Or I may use a solid ball or balls of carbon, in connection with springs or
tongues of carbon or of carburetted platinum; the whole being rendered an-
hygroscopic, if desired.
In some cases where a highly powerful action is desired I propose to cause the
air-waves to act first on a vibrating tongue which then transfers the vibrations
indirectly to the current-regulator. This tongue may be itself an electrode, and
form part of the current-regulator, in which case it is formed of metal, carbon, or
other elastic conductor, whether an-hygroscopic or not. I sometimes arrange &
series of tongues radially in contact with each other either in pairs or in series
so that the current passes successively through all of them.

page_text: Another part of my Invention relates to improved materials suitable for current-
regulators of the last specified type. I may use for springs, platinum covered with
a film of carbide of platinum, which I forin by heating strips of stiff sheet platinum
in a crucible in charcoal until the surface is strongly carburetted. Or I use springs
of platinum covered by electro deposit or otherwise with platinum black. Or I use
for springs carbon in elastic strips prepared by carbonizing in a crucible or furnace,
strips of animal or vegetable matter, natural or artificial, whether previously
parchmentised or not; and such strips may be made still harder by passing electric
currents through them whilst exposed to the vapor of a hydrocarbon, or in vacuo,
or in some gas in which carbon does not burn, and I may use material prepared in
any of these ways for making chains, strips, filaments, springs, or parts of any other
form suitable to be used in my current-regulators.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Silvanus Phillips Thompson in the Great Seal Patent Office on
the 9th February 1883.
SILVANUS PHILLIPS THOMPSON, of University College, Bristol, Professor of
Experimental Physics, "IMPROVEMENTS IN TELEPHONIC APPARATUS
"
My improvements relate to telephonic transmitters based upon the principle
discovered by Philipp Reis in 1861, namely, that of employing current-regulators
actuated, either directly or indirectly, by the sound-waves produced by the voice.
By the term current-regulator I mean a device similar to that employed by Reis,
wherein a loose contact between two parts of a circuit (in which are included a
battery and a telephonic receiver) offers greater or less resistance to the flow of the
electric current, the degree of intimacy of contact between the conducting pieces
being altered by the vibrations of the voice. In Reis's transmitter, and in Edison's
transmitter, and other well known forms of these instruments, the action is indirect,
a tympanum of stretched membrane or other equivalent organ, such as a diaphragm
of mica, being used to collect or magnify, or concentrate, the vibrations of the voice,
and to convey them to the point or points of loose contact that regulate the current.
In other forms of transmitters (for example, some of Hughes's microphones), the
mode of action is direct, the air-waves beating directly upon the conductors or
electrodes which are in loose contact, without the intermediation of a tympanum
or diaphragm.
Of these two classes of telephone transmitters, vis-those in which the current-
regulator is combined with a tympanum or diaphragm, and those in which the
current-regulator is acted upon directly by the air-waves of the voice, my
improvements relate to the latter only; I entirely dispense with the membrane
tympanum used in Reis's transmitter; I do not employ the tympanic diaphragm
of mica used in Edison's transmitter; I do not employ the non-tympanic diaphragm

page_text: of foil used in Hunning's transmitter; I do not even employ any diaphragm in the
sense of a partition between the current-regulator and the air-waves of the voice,
as in Theiler's transmitter. In my improved transmitters, the air-waves act
directly upon the current regulator itself; by dispensing with tympanums,
diaphragmns and partitions, I obtain a more accurate correspondence between the
vibrations of the voice and the electrical undulations which they produce, than is
practicable where a tympanum, diaphragm, or partition is used.
As a result, the articulation is clearer for some of the consonantal sounds,twhich
are only imperfectly or difficultly transmitted by telephones in which the current-
regulator is affected indirectly through a tympanum, diaphragm, or partition.
Transmitters of the class to which my improvements relate are ordinarily liable
to two defects. Firstly, they do not articulate so loudly as transmitters in which
there is a tympanum or diaphragm to collect or magnify the vibrations. Secondly,
when, to obviate this difficulty, the speaker speaks with his mouth very close to the
current-regulator, the moisture of his breath condenses upon the contact points or
adjacent parts of the regulator, interfering with its action and spoiling the
articulation. My improvements relate chiefly to means for remedying or obviating
these defects.
My improvements are illustrated in the accompanying drawing, in which
Figure 1 is a front view, and
Figure 2 a transverse section of an instrument constructed according to one part
of my invention.
Figure 3 is a transverse section of another form of instrument
Figure 4 is a sectional elevation, and
Figure a side elevation illustrating modifications of my Invention
Figures 6, 7 and 8 are transverse sections of various other forms or modifications
of my instruments.
Figure 9 is a transverse section, and
Figure 10 an end view of another modification, and
Figure 11 is a transverse section illustrating a further modification of my
Invention
Like letters indicate the same parts throughout the drawing.
I propose to employ mirrors, sound-reflectors or reverberators (one form of which
is shown in Figures 1 and 2), consisting of glass, metal, wood or other material, by
which the sound-waves are turned aside from their straight or direct path and are
made to converge upon the current-regulator, precisely as rays of light may be
turned aside or converged by a polished mirror. If actual mirrors of polished
metal or silvered glass are employed for this purpose, they have the additional
advantage of revealing to the speaker the presence of moisture. But in any case
the mirror, reflector, or reverberator serves to collect the sound-waves as they
come from the speaker's mouth, and to direct them onto the current-regulator
while intercepting moisture from the speaker's breath. M is the mouth-piece or
tube; C is the current regulator; R' is the reverberator; J is an a ljusting screw;
and E is an outlet-cock for the water which collects in the mouth-tube; the
remaining parts are hereinafter described.
In some cases, the reflector or reverberator has the form of an extended mouth-
piece; indeed, in one sense, the ordinary mouth-piece such as that used with
magneto-telephones and with various telephonic transmitters containing tympanums
or diaphragms, may be regarded as a reflector, though it does not completely
perform the functions for which I have devised the improvements herein described.
The mouth-pieces hitherto used on ordinary transmitters are not intended to
serve either as reverberatore or as protectors from moisture. I find that my mouth-
pieces for this purpose must, as shown in Figure 3 and Figure 9, be deep and
of conical or paraboloidal form. Any curved or crooked mouth-piece such as
hose shewn in Figures 4 and 5, specially contrived to retain, intercept or dissipate
he moisture of the breath while reflecting the sound waves onto the current
egulator, is within the scope of my improvements, but is, as will be seen, only

page_text: claimed in combination with current regulators of the class herein before described
as having no tympanum or diaphragm. Mouth-tubes consisting of a flexible tube
have been employed in combination with telephones of several kinds, for example,
the "Gower Bell" magneto-telephone. In all of these instruments, however, the
air-waves act, not immediately on the actual electrodes or conductors of the
current regulator, but on a tympanum, diaphragm or partition. In Figure 6,
I illustrate this part of my improvement by depicting a flexible speaking tube
used in conjunction with a current-regulator. The employment of such flexible
mouth-tubes in combination with a current regulator without any tympanum,
diaphragm, or partition, for the purpose of protecting the naked current regulator
from the deposition of moisture by the breath, is comprised in my improvements.
In some cases I find it advantageous to provide the mouth-piece at its inner end
with a flange, such as that shewn at F in Figures 4, 5, 6 and 7, the said flange not
being in contact with the current regulator.
Another part of my improvements consists in making the reflector, reverberator,
mouth-piece or mouth-tube of such materials as will readily absorb moisture and
prevent its deposition upon the working parts of the current-regulator. Or I use
such absorbent or porous material for the case of the instrument; or I place chemical
substances, capable of absorbing moisture, in the case of the instrument, or in the
mouth-piece or mouth-tube.
Another part of my improvements consists in employing, for the current-regulator,
such materials as are at once neither hygroscopic, nor liable, by their properties
with respect to heat, to condense filins of moisture, while at the same time they
are good conductors of electricity. Polished metal is very liable to become covered
with a film of condensed moisture. Coke or carbon, amorphous boron, spongy
platinum, and similar substances, in their ordinary condition, absorb moisture too
readily, and commercial plumbago is of too poor a conducting quality to be
satisfactory. I prefer to use, as materials for the current-regulator, either spongy
platinum, carbide of platinum, boron, coke, carbon or elastic carbon specially
prepared as hereinafter described, having first deprived such materials of their
hygroscopic properties by treatinent with petroleuin, or other, oil, or with other
suitable hydrocarbon, solid or liquid. In some cases, and especially where the
contact surfaces of the current regulator are of platinum or other metal, I find it
convenient to keep their surfaces constantly moistened with petroleum or other
hydrocarbon or oil by supplying them through a cotton filament in communication
with a small lubricator or oil-vessel.
The essential point or feature of this part of my improvements is the providing
and applying, in manner substantially as herein described, of current-regulators
that are not liable to become bedewed with moisture; where, however, by any of
my improvements herein before described, the instrument is provided with means
whereby the breath is diverted effectually from the current-regulator, the latter
may be made of polished platinum, silver, or other metal, or even of some highly
conducting form of carbon, the best conductor being preferred cæteris paribus
In some of my
amongst those materials, that neither rust nor fuze together.
instruments, the aforementioned current-regulator consists of two pieces of metal or
carbon or other conductor of electricity kept lightly in contact either by gravity
or by the pressure of a light spring S, or by both these agencies. Figures 3, 4, 6,
7, 8, 11 illustrate such current-regulators.
My improvements also partly consist in so arranging the conductors or electrodes,
or other parts of the current-regulator, that the points of loose contact can be
actuated by the sound-waves, whilst they are protected from the moisture of the
breath by some portion of the conductors or electrodes projecting between the
contact points and the breath of the speaker. An example of such an arrangement
is given in Figure 8 wherein the contact points C are protected from the breath by
making one of the electrodes in the form of a cup, against the concave or hollow
face of which the contact point on the other electrode is directed. Any microphone
of the class to which my improvements apply, if specially contrived so that the

page_text: moisture of the breath cannot have access to the actual points of contact, is within
the scope of my invention.
The said improvements relate further to the form of the conductors or electrodes
combined to serve as the current-regulator. The current-regulator of Reis, con-
sisting of one piece of platinum resting lightly against another, is imperfect, except
when, as in some forms of Reis's instrument, one or both the pieces of metal are
fixed upon springs or some equivalent elastic support; otherwise the current is
liable to very abrupt interruptions. In Figure 7 I have shewn one of my current-
regulators wherein the two contact pieces are held upon springs S, S,; one of these
springs is fixed to an adjusting frame B and the other is fixed to an insulating
block K. I find that when there are many points of contact instead of but a single
pair of such points, there is less liability to such abruptness. Multiple contacts
therefore are advantageous. I provide multiple contacts in various ways. For
instance, a chain or series of metal links, or of links of carbon, or other good
conductor of electricity, suitably suspended will form a good current-regulator to
combine with reverberators or reflectors such as those herein before set forth.
I also sometimes form the regulator of a number of narrow tongues of metal or
of carbon, or carbonized or carburretted platinum capable of vibrating like the reeds
of a harmonium and arranged in series so as to be in light-contact in rows or
otherwise. Such a current-regulator is shown in Figures 9 and 10 wherein the
tongues a, b, c, d, e, f, are arranged radially and attached to a rim of non-conducting
material so that the current must pass through all of them in order, from the first
to the last.
Another of my improved forms of current-regulator consists of a grating or
framework of prepared carbon, or metal tongues so connected that the current
cannot pass from one tongue to the next except through a piece or pieces of good
conducting carbon or metal suspended, or resting, in loose contact against the
tongues; such regulators being combined with reverberators, mouth-pieces or tubes
in the manner herein set forth. In the instrument shown in Figures 1 and 2 the
current-regulator C consists of an inclined grating of carbon strips, against which
the voice-waves are reflected by the reverberator R and upon which rest light
balls R' of carbon or of metal suspended from the hooks R2 or otherwise by silken
strings. Another form of regulator consists of hook-shaped or cup-shaped con-
ductors suspended or supported in loose contact with one another so as to be easily
moved by the vibrations of the voice, whilst protecting, by their shape, from the
direct action of the breath, the actual points of contact. In the class of regulators
in which I employ springs constructed of thin strips or filaments of carbon, to
vibrate as tongues by the direct impact of air-waves, I sometimes render such
carbon springs anhygroscopic, as previously set forth. Or I may use a solid ball or
balls of carbon, in connection with springs or tongues of carbon, carburetted
platinum or of any suitable metal, the whole being rendered anhygroscopic if
desired.
In some cases where a highly powerful action is desired I propose to cause the
air-waves to act first on a vibrating tongue which then transfers the vibrations
indirectly to the current regulator or contact points C. Such a vibrating tongue
is shewn at V in Figure 11 where it is attached behind a flanged tube T, the
contact points or current regulator C being on the same face of the tongue V as
that against which the voice-waves impinge. This tongue may be itself an
electrode; and serve as part of the current regulator, in which case it is formed
of metal, carbon or elastic conductor whether anhygroscopic or not
Another part of my invention relates to improved materials suitable for current
regulators of the last specified type. I use, for springs, platinum covered with a
film of carbide of platinum, which I form by heating strips of stiff sheet platinum
in a crucible in charcoal until the surface is strongly carburretted. Or I use springs
of platinum covered by electro-deposition or otherwise with platinum black; or I
use, for the springs, carbon in elastic strips prepared by carbonizing in a crucible
or furnace, strips of animal or vegetable matter, natural or artificial, whether

page_text: previously parchmentized or not, and such strips may be made still harder by
passing electric currents through them whilst exposed to the rarefied vapour of a
hydrocarbon, or in vácuo, or in some gas in which carbon does not burn.
And I
may use material prepared in any of these ways for making chains, strips, filaments,
springs, tongues, or parts of any other form suitable to be used in my current
regulators
Having thus fully described my said Invention and the manner of performning
the same I wish it understood that I Claim
First. In a telephonic transmitter wherein there is no tympanum or diaphragm,
the combination of reverberators or sound reflectors, substantially such as those
above described, with electric current regulators acting upon the principle of
variable contact, as, and for the purpose, set forth.
Second. In a telephonic transmitter wherein there is no tympanum or diaphragm,
the employment or application, substantially as set forth, of a mouth-tube or mouth-
piece suitable for intercepting the moisture of the breath.
Third. In a telephonic transmitter of the class above specified, the employment
or application, substantially as set forth, of materials for absorbing or destroying
the moisture of the breath and for rendering anhygroscopic the contact surfaces
or contact points.
Fourth. The combination, with an electric current regulator, in a telephonic
transmitter, of a flange attached to the posterior or inner end of the mouth-tube,
substantially as, and for the purpose, set forth.
Fifth. The modification wherein the contact points are protected from the breath
by making one of the electrodes concave or cup-shaped, substantially as set forth.
Sixth. In a telephonic transmitter, the employment, substantially as set forth, of
either of the above described improved forms of current regulators not included in
the preceding claiming clauses
Seventh. The improvements relating to the current regulators constructed of
springs or tongues of prepared carbon or platinum carburretted or covered with a
film of carbide of platinum substantially as set forth
In witness whereof I the said Silvanus Phillips Thompson have hereunto
set my hand and seal this eighth day of February in the year of our Lord
One thousand eight hundred and eighty three.
SILVANUS PHILLIPS THOMPSON. (L.S.)