IMPROVEMENTS IN TRANSMITTERS FOR SPEAKING TELEPHONES
Year: 1882

page_text: "
LETTERS PATENT to William Phillips Thompson of the Agency for Foreign
Patent Solicitors 6 Lord Street Liverpool in the County of Lancaster and
of 323 High Holborn in the County. of Middlesex Civil Engineer, for an
Invention of "IMPROVEMENTS IN TRANSMITTERS FOR SPEAKING TELEPHONES
Communicated to him from abroad by George. F. Milliken James Wentworth
Brown and Henry D. Hyde all residing in the City of Boston County of Suffolk
and State of Massachusetts one of the United States of America.
-
PROVISIONAL SPECIFICATION left by the said William Phillips Thompson
at the Office of the Commissioners of Patents on the 19th September 1882.
WILLIAM PHILLIPS THOMPSON of the Agency for Foreign Patent Solicitors
6 Lord Street Liverpool in the county of Lancaster and of 323 High Holborn
in the County of Middlesex Civil Engineer "IMPROVEMENTS IN TRANSMITTERS FOR
SPEAKING TELEPHONES a communication to me from abroad from George F
Milliken, James Wentworth Brown, and Henry D. Hyde all residing in the City of
Boston, County of Suffolk and State of Massachusetts, one of the United States of
America
This invention relates to that class of telephone transmitters by means of which
variations are produced in the strength of an electric current proceding from a
generator of constant electro-motive force, which variations correspond in character
to the vibrations, undulations or waves, accompanying the sound which is to be
transmitted
It is well known that sounds of all kinds are produced by rhythmical vibrations,
and that when these vibrations are communicated to an elastic medium, as the
atmosphere, they cause alternate expansions and contractions of its particles which
may in turn be communicated to other elastic or resilient bodies upon which the
atmospheric vibrations impinge. It is also well known that when a normally
constant current of electricity is thus thrown into vibrations; undulations or

page_text: waves, by means of and corresponding to those accompanying a particular sound,
producing what is termed an undulatory electric current, that such sound may be
reproduced at a distance by the action of the undulatory current upon a suitable
receiving instrument.
4
Electrical variations of this character may be produced by varying the resistance
of a circuit of conductors which is traversed by an electric current due to the action
of a constant electro-motive force, and this has heretofore been effected either by
varying the pressure of one electrode upon another or otherwise by varying the
area of superficial contact between the electrodes.
In such apparatus the electrodes have, under all circumstances, been maintained
in constant physical contact with each other, and this condition of contact has
heretofore been regarded as an essential one for the successful transmission of
articulate sounds...
The experiments of Thomson, De la Rue and Muller have demonstrated that a
constant voltaic current may be made to overcome the resistance of and thus to
traverse an appreciable air-space intervening between two conducting electrodes
which are not in actual physical contact with each each other.
This discovery is availed of in carrying out this invention, which consists in an
improvement in the art of telegraphically transmitting sounds, by varying the
intervening distance between the surfaces of two separated electrodes which con-
stitute the opposite terminals of an otherwise uninterrupted circuit of electric
conductors, which is effected by imparting to one or both of said electrodes a form
of motion whereby the distance between them is varied by increments and
'decrements similar to those of the sonorous air-waves but of diminished
amplitude.
A transmitter of this nature possesses decided advantages over the forms now in
use, largely due to the fact that it may be equipped with non-fusible metallic
electrodes. The substances which have heretofore been most commonly employed
as electrodes have been either carbon in some of its various conditions, or some of
-the more fusible metals. Non-fusible metallic electrodes although capable of being
employed with advantage in transmitters in which the electric current is to be
broken at every vibration, the object being to transmit nothing more than the
pitch of a sound) have heretofore failed to reproduce articulate speech intelligibly.
The improved transmitter herein set forth is equipped with non fusible metallic
electrodes, preferably those of the harder kind such as iridium. Prominent among
the advantages arising from the use of such electrodes is that of durability. Fusible
metals are continually wearing away under the action of the current, and this
operates to throw the instrument which is equipped with them out of adjustment.
On the other hand the non-fusible metals are practically indestructible. There is
also no liability to rupture as in the case of the carbon electrodes; and again the
surfaces are capable of receiving an exceedingly high polish so that great nicety of
adjustment can be secured Further their conductivity being much greater than
that of carbon the electrodes may be made in the shape of slender wires, without
introducing any considerable resistance into the circuit. Owing to this the
principal resistance in the primary circuit may be brought to the working points of
the electrodes
;
The invention further consists in certain improved apparatus whereby the
necessary vibratory motion is imparted to the electrodes, which consists in the
combination with the said electrodes of a vibrating plate or diaphragm, and a
mechanical connection from said diaphragın to said electrodes, whereby the distance
between the same is varied strictly in proportion to the movements of the centre of
the diaphragm but in a diminished ratio. The invention also comprises certain
subsidiary mechanical devices and instrumentalities for more effectually carrying
out the object of the invention which will be hereafter more fully set forth.
An upright wooden standard having a conical mouth piece formed within it is
secured to a base upon which the several parts of the apparatus are mounted. An
elastic plate preferably of metal and of a circular form, is supported and secured at

page_text: its edge by suitable clamps leaving its central portion free to vibrate in a well
understood manner, This elastic plate is technically termed the diaphragm-An
upright standard preferably formed of non-conducting material, is fixed upon a
pedestal or foot and this is attached to the base in such a manner as to permit it
to have a horizontal movement. This attachment may be made by means of
screws passing through slots. The horizontal movement of the standard in each
direction is effected by means of an adjusting screw of the usual construction.
A lug is rigidly secured to the centre of the diaphragm by means of a screw or
otherwise. A slender but rigid metallic rod is pivoted to the lug and carries at its
opposite extremity a rocker of non-conducting material. Another similar rod is
pivoted to the adjustably fixed standard and carries a similar rocker The rods
are not situated parallel to a line passing through the axis of the diaphragm but
are inclined upward toward each other at an angle of about 20 degrees from a
horizontal plane. A metallic wire or rod preferably of platinum or iridium, is
inserted in each of the rockers passing horizontally through the same. These
metallic terminals form the electrodes of an otherwise uninterrupted electric circuit
as hereinafter explained. The ends of the respective electrodes which face each
other, are convex in form, the curve of their convexity corresponding with and
being a continuation of the curved faces of the rockers which serve to support
them. The curved faces of the respective electrodes must not be in actual contact
with each other, but must be separated by an exceedingly small space. The
rockers are linked together and firmly held in their proper relative positions, by
means of flexible wires. Thus one wire is secured at its upper end to a screw:
inserted in the top of the rocker. The lower end of this wire is secured to a screw
at the bottom of the rocker In like manner a second wire extends from the upper
screw of rocker to the lower screw of the rocker. The length of these wires is
capable of adjustment It will thus be understood that the position of the rockers
with reference to each other may be adjusted with such delicacy that the convex
faces of the respective electrodes may be brought and maintained in their required
relative positions without, actual contact. Hence if the diaphragm be caused to
vibrate to-and-fro as by the inpingement of air-waves thereupon the rockers will
be caused to move in a corresponding manner, but in a direction nearly vertical.
The curved faces of the electrodes are parts of circles which are eccentric to the
axes upon which they move, hence it necessarily follows that the relative motion,
of the two electrodes towards and from each other, must be similar in character to,
but of much less amplitude than the motions of the centre of the diaphragm. The
actual motion may be varied with reference to its ratio to that of the diaphragm
by varying the angles formed by the rods attached to the diaphragm and upright
standard The greater the angle of these rods above a horizontal plane, the less will.
the relative motion be. The rockers being linked together by the wires in the:
manner herein before described. It is evident that any motion, of whatever character
imparted to one, must necessarily be communicated to the other.
The electrodes are respectively connected to binding-screws by means of wires
which may for convenience and safety be wound spirally around the rods which
are pivoted to the diaphragm and to the standard.
The wires for connecting the transmitting instrument with the receiving*
telephone are attached to binding-screws. It is usually preferably to connect them:
in the primary circuit of an induction coil together with a battery of one or two
elements. The secondary wire of the induction coil in such case is connected to the
line and through the line with the receiving instrument at the distant station,

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Phillips Thompson in the Great Seal Patent Office on the
19th March 1883.
"
WILLIAM PHILLIPS THOMPSON, of the Agency for Foreign Patent Solicitors
of 6 Lord Street Liverpool, in the county of Lancaster and 323 High Holborn in
the County of Middlesex Civil Engineer IMPROVEMENTS IN TRANSMITTERS FOR
SPEAKING TELEPHONES A. communication to me from abroad by George F.
Milliken James Wentworth Brown, and Henry D. Hyde, all residing in the City
of Boston, county of Suffolk and State of Massachusetts one of the United States
of America
:
This invention relates to that class of telephone transmitters by means of
which variations are produced in the strength of an electric current proceeding
from a generator of constant electro-motive force, which variations correspond in
character to the vibrations, undulations or waves accompanying the sound which
is to be transmitted.
It is well known that sounds of all kinds are produced by rhythmical vibrations,
and that when these vibrations are communicated to an elastic medium such as
the atmosphere, they cause alternate expansions and contractions of its particles
which may in turn be communicated to other elastic or resilient bodies upon which
the atmospheric vibrations impinge. It is also well known that when a normally
constant current of electricity is thus thrown into vibrations, undulations or
waves, by means of and corresponding to those accompanying a particular sound
producing what is termed an undulatory electric current, that such sound may be
reproduced at a distance by the action of the undulatory current upon a suitable
receiving instrument.
Electrical variations of this character may be produced by varying the resistance
of a circuit of conductors which is traversed by an electric current due to the action
of a constant electro-motive force, and this has heretofore been effected either by
varying the pressure of one electrode upon another or otherwise by varying the
area of superficial contact between the electrodes.
In such apparatus the electrodes have under all circumstances, been maintained
in constant physical contact with each other and this condition of contact has
heretofore been regarded as an essential one for the successful transmission of
articulate sounds.
The experiments of Thomson De La Rue and Muller, have demonstrated that
a constant voltaic current may be made to overcome the resistance of and thus to
traverse an appreciable air-space intervening between two conducting electrodes,
which are not in actual physical contact with each other.
This discovery is availed of in carrying out this invention, which consists in an
improvement in the art of telegraphically transmitting sounds, by varying the
intervening distance between the surfaces of two separated electrodes which
constitute the opposite terminals of an otherwise uninterrupted circuit of electric
conductors, which is effected by imparting to one or both of said electrodes
a form of motion whereby the distance between them is varied by increments
and decrements similar to those of the sonorous air-waves but of diminished
amplitude.
A transmitter of this nature possesses decided advantages over the forms now
in use, largely due to the fact that it may be equipped with non-fusible metallic
electrodes. The substances which have heretofore been most commonly employed
as electrodes have been either carbon in some of its various conditions, or some
of the more fusible metals. Non-fusible metallic electrodes (although capable

page_text: that of
of being employed with advantage in transmitters in which the electric current
is to be broken at every vibration, the object being to transmit nothing more
than the pitch of a sound) have heretofore failed to reproduce articulate speech
intelligibly. The improved transmitter herein set forth is equipped with non-
fusible metallic electrodes, preferably those of the harder kind such as iridium
Prominent among the advantages arising from the use of such electrodes
durability Fusible metals are continuously wearing away under the action of the
current, and this operates to throw the instrument which is equipped with them
out of adjustment. On the other hand the non-fusible metals are practically
indestructible. There is also no liability to rupture as in the case of the carbon
electrodes and again the surfaces are capable of receiving an exceedingly high
polish so that great nicety of adjustment can be secured. Further their con-
ductivity being much greater than that of carbon the electrodes may be made in
the shape of slender wires, without introducing any considerable resistance into
the circuit. Owing to this the principal resistance in the primary circuit may be
brought to the working points of the electrodes.
The invention further consists in certain improved apparatus whereby the
necessary vibratory motion is imparted to the electrodes, which consists in the
combination with the said electrodes of a vibrating plate or diaphragm, and a
mechanical connection from said diaphragm to said electrodes, whereby the distance
between the same is varied strictly in proportion to the movements of the centre
of the diaphragm but in a diminished ratio The invention also comprises
certain subsidiary mechanical devices and instrumentalities for more effectually
carrying out the object of the invention, which will be hereafter more fully set
forth.
In the accompanying drawings Fig 1 is a vertical longitudinal section of an
apparatus embodying this invention. Fig 2 is a plan view of the same, partly
in section Figs 3. 4. and 5 are enlarged detached views of certain portions
of the apparatus whereby its construction and mode of operation are more clearly
exhibited.
In the Figs A represents the base upon which the several parts of the apparatus
are mounted. B is an upright wooden standard secured to the base A and having
a conical mouth-piece b formed within it.
An elastic plate C, preferably of metal and of a circular forni, is supported and
secured at its edge by suitable clamps c c, leaving its central portion free to vibrate
in a well understood manner. This elastic plate is technically termed the
diaphragm. D is an upright standard, preferably formed of non-conducting
material, which is fixed upon a pedestal or foot D¹ and this is attached to the
base A in such a manner as to permit it to have a horizontal movement. This
attachment may be made in the manner shown in the Figure by means of screws dd
passing through slots d' d¹. The horizontal movement of the standard D in each
direction is effected by means of an adjusting screw E of the usual construction.
A lug C¹ is rigidly secured to the centre of the diaphragm C by means of a
screw or otherwise. A slender but rigid metallic rod F is pivoted at f to the
lug C' and carries at its opposite extremity a rocker G of non-conducting material
Another similar rod F1 is pivoted at f¹ to the adjustably fixed standard, D and
carries a similar rocker G¹ The rods F and F¹ are not situated parallel to a line
passing through the axis of the diaphragm, but are inclined upward toward each
other at an angle of about 20 degrees from a horizontal plane. A metallic wire or
rod, preferably of platinum or iridium, is inserted in each of the rockers G and G¹
passing horizontally through the same, as best seen in Fig 3. These metallic
terminals form the electrodes of an otherwise uninterrupted electric circuit as
hereinafter explained. The ends of the respective electrodes which face each other,
are convex in form, the curve of their convexity corresponding with and being a
continuation of the curved faces of the rockers which serve to support them The
curved faces of the respective electrodes must not be in actual contact with each
other, but must be separated by an exceedingly small space.. The rockers are.

page_text: rocker G'
linked together and firmly held in their proper relative positions, by means of
flexible wires as best seen in Figs 4 and 5. Thus a wire k is secured at its upper
end to a screw h inserted in the top of the rocker G'. The lower end of the wire k
is secured to a screw h¹ at the bottom of the rocker G. In like manner a wire k¹
(see Fig 5) extends from the upper screw i of rocker G to the lower screw i¹ of.
The length of these wires is capable of adjustment, by turning the
screws h or i It will thus be understood that the position of the rockers G and G²,
with reference to each other may be adjusted with such delicacy that the convex
faces of the respective electrodes g and g₁ may be brought and maintained in their
required relative positions, without actual contact. Hence if the diaphragm C be
caused to vibrate to-and-fro as by the impingement of air-waves thereupon, the
rockers G & G¹ will be caused to move in a corresponding manner, but in a
direction nearly vertical. The curved faces of the electrodes g and g¹ are parts of.
circles which are eccentric to the axes f and f¹ upon which they move, hence it
necessarily follows that the relative motion of the two electrodes towards and from
each other, must be similar in character to but of much less amplitude than the
motions of the centre of the diaphragm C The actual motion may be varied with
reference to its ratio to that of the diaphragmn C, by varying the angles formed by
the rods F and F¹. The greater the angle of the rods F and F' above a horizontal
plane, the less will the relative motion be. The rockers G and G¹ being linked
together by the wires i and k in the manner hereinbefore described, it is evident
that any motion, of whatever character imparted to one, must necessarily be
communicated to the other
The electrodes g and g¹ are respectively connected to binding-screws N and P by
means of wires w w¹ which may for convenience and safety be wound spirally.
around the rods F and F' as shown in Fig 1.
The wires for connecting the transmitting instrument with the receiving
telephone are attached to the binding-screws P and N in a well known manner
It is usually preferable to connect them in the primary circuit of an induction coil
together with a battery of one or two elements. The secondary wire of the
induction coil in such case is connected to the line and through the line with the
receiving instrument at the distant station.
The mode of operation of the apparatus is as follows
The terminal wires of an electric circuit, within which is included a voltaic
battery, preferably of one or two elements, having been connected to the binding-
screws P and N of the transmitter, the electrodes g and g¹ are first brought
together and then slightly separated by delicately adjusting the screws h and i and
the screw E in the manner herein before explained. When the electrodes have been
thus adjusted so that there is no actual physical contact between them a continuous
but feeble electric current will pass across the narrow intervening space from one
electrode to the other. The effect of such a current on a galvanometer included in
the circuit will be to produce a slight deflection of the needle, which is evidence of
the actual passage of a current: but said deflection, on account of the resistance of
the arc will be very much less than that which is produced by bringing the
electrodes into actual contact. By securing the proper intermediate deflection the
most advantageous working adjustment may be determined without difficulty
If, when the apparatus is thus adjusted, sounds be uttered or words be spoken in the
vicinity of the mouth-piece b the diaphragm C will be thrown into vibration and
this vibration will be mechanically communicated, in the manner hereinbefore.
described, to the electrodes g and g¹ which will alternately approach towards and
recede from each other, with a motion corresponding precisely to that of the
diaphragm C but of very much less amplitude. These variations in the distance
between the electrodes cause very wide variations in the strength of the current
passing from one to the other, and thus produce the necessary waves or undulations
for the transmission of articulate speech.
It is obvious that in order to ensure a continuous operation, the amplitude of
vibration between the respective electrodes must be confined within certain limits,

page_text: for if it becomes too great, the electrodes will be brought into actual contact at one
extremity of the vibration, or will be separated from each other at the opposite end of
the vibration to such an extent as to wholly interrupt the passage of the current.
The actual amplitude of the air-vibrations and the movement of the diaphragm
caused by articulate speech is much greater than the admissible amplitude of
vibration between the electrodes g and g', and hence it is found necessary in
practically carrying out the invention to make use of mechanical means,
substantially such as described, for imparting to the electrodes g and g¹ a motion
similar in character to that of the diaphragm, but of much less amplitude.
Having thus described the nature of this invention, and in what manner the
same is to be performed as communicated to me by my foreign correspondent
I would have it understood that I claim
1st The hereinbefore described improvement in the art of telegraphically trans-
mitting sounds, which consists in varying the intervening distance between the
surface of two electrodes which constitute the opposite terminals of an otherwise
uninterrupted circuit of electric conductors, and which are held in close proximity
to each other, by increments and decrements corresponding to the expansions and
condensations of the air-waves accompanying said sound, but of diminished
amplitude.
2nd The hereinbefore described improvement in the art of telegraphically trans-
mitting sounds, which consists in varying the intervening distance between the
surfaces of two non-fusible metallic electrodes which constitute the opposite
terminals of an otherwise uninterrupted circuit of electric conductors and which
are. held in close proximity to each other, by increments and decrements corre-
sponding to the expansions and condensations of the air-waves accompanying said
sound, but of diminished amplitude.
3rd The combination, substantially as bereinbefore set forth, of a vibrating plate
or diaphragm, two electrodes in close proximity, constituting the terminals of an
otherwise uninterrupted circuit of electric conductors, and a mechanical connection
substantially such as described, from said diaphragm to said electrodes whereby
the distance between the same is varied in accordance with the movements of the
centre of the diaphragm, but in a diminished ratio.
4th The combination, substantially as hereinbefore set forth, of the diaphragm,
the convex electrodes not in physical contact with each other, and the independent
arms carrying the respective electrodes one of said arms being pivoted to the
diaphragm and the other to a stationary support.
5th The combination, substantially as hereinbefore set forth, of the diaphragm,
the convex electrodes not in physical contact with each other, the independent
arms carrying the respective electrodes, one of said arms being pivoted to the
diaphragm, and the other to a stationary support, and means substantially such as
described for adjusting or regulating the distances between the diaphragm and the
stationary support.
6th The combination, substantially as hereinbefore set forth, of the convex
electrodes, not in physical contact with each other, the curved rockers for
supporting said electrodes, the pivoted arms for carrying said rockers and the
means substantially such as described for communicating motion from one rocker
to the other.
In witness whereof I, the said William Phillips Thompson have hereunto
set my hand and seal this fifteenth day of March in the year of our Lord
one thousand eight hundred and sight thro