IMPROVE- MENTS IN TELEPHONIC APPARATUS ور
Year: 1883

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
ور
PROVISIONAL SPECIFICATION left by the said Silvanus Phillips Thompson
at the Office of the Commissioners of Patents on the 7th March 1883.
SILVANUS PHILLIPS THOMPSON, of University College, Bristol, Professor of
Experimental Physics, "IMPROVEMENTS IN TELEPHONIC APPARATUS"
My present improvements relate to telephonic transmitters and receivers, and
chiefly to certain modifications in, and additions to, telephones of the kind invented
by Philipp Reis and described in the years 1862 and 1863 in Dingler's Polytechnic
Journal and in the journal of the Germano-Austrian Telegraph Union.
The first part of my improvements relates to transmitters of the above named
class or type which I modify in various ways so as to obtain an instrument less
liable to derangement of its parts, and more reliable in its articulation than the
said instruments in their original form. In some forms of Reis's transmitters the
mouth-piece was of wood, in others of tin. His tympanums were formed, some-
times of bladder, sometimes of collodion. His current-regulators or interruptors
consisted of pairs of contact points sometimes mounted on springs, sometimes kept
in contact by their own weight, sometimes consisting of curved levers pressed
against studs mounted on pins. In my improved instruments I, in some instances,
invert the position of these springs, and sometimes I change their form to render
them more certain than heretofore in their action, that is to say, I make them of
an S-shape or C-shape instead of simply straight, or nearly so.
In one form of Reis's transmitter in particular I have made several improve-
ments. This transmitter in its original form consisted of a conical tin mouthpiece
closed by a tympanum of collodion. The vibrations of the voice taken up by this
tympanum were caused to act upon a small curved lever of which, the material
was not prescribed, but concerning which two clear inferences might be drawn,
PD
037

page_text: from the context, firstly that it was to be a conductor of electric currents, secondly
that it should be non-metallic; it was also to be as light as possible. This lever
rested with one end against the tympanum, and its other end was caused, by means
of a delicate spring, to press against a contact-piece or stud mounted upon a vertical
spring and adjusted to the requisite degree of contact by a screw.
The function of
this lever was to open or close the circuit to a greater or less degree, in corre-
spondence with the vibrations impressed upon it, and by thus varying the contact
between the parts it would by these varying interruptions throw the current into
corresponding fluctuations, the object being to magnetise and demagnetise. the
magnet of the receiver.to make it increase and decrease the attraction it exercised
upon an armature in a manner corresponding to the original vibrations. The said
lever was made with its arms of unequal length, thereby sacrificing the range
of its motion in order to obtain a greater range of force or pressure between the
contact parts. The whole instrument was mounted on a stand.
This instrument I modify as follows. I enclose it within a box which can be
fixed to a wall, leaving only the mouth-piece exposed, and I make the mouth piece
in the form of a hollow cone and arrange the same so that it is screwed to the box
from the outside; the frame which holds the tympanum being affixed to the said
mouthpiece from the inner side of the box, I find that amongst tympanums of
collodion those which are made of the preparation of collodion known as celluloid
are the most satisfactory, and are least liable to become flaccid with the moisture
of the breath. But I sometimes use other substances such as indiarubber, ebonite,
'thin metal, or the like.
For the curved lever, since it is to be a non-metallic conductor of electricity and
as light as possible, I use by preference artificial coke carbon because this substance
is of its class the best conductor, and it does not fuse at the point of contact. For
the second contact-piece I employ a stud of silver, nickel, native amalgam ore, or
other good conductor of electricity and I mount the said stud on a vertical spring.
In some cases, and particularly for long-line work I combine with this trans-
mitter within the box a small induction-coil; the current from a local battery
passes through the contact pieces of the interruptor; and also through the primary
wire of the induction coil, the secondary wire being united with the line and with
the earth or return wire.
I also combine with this transmitter a separate call-bell, and a switch which
throws the cail-bell out of circuit when the line is wanted for talking.
In some instances I invert the aforesaid lever so that its own weight helps to
press it toward the tympanum, and sometimes I add a small weight for this purpose,
which I also attach to the lever, either directly or by a slight spring.
In some instances I mount the lever itself upon a spring for the same purpose,
and in some instances I support the contact-spring from above instead of below.
I also in some cases employ springs made of artificial carbon prepared in the
manner described in the specification of my former Letters Patent N° 8803,
A.D. 1882.
ら
The second part of my improvements relates to the receivers. The receiving
instrument described in the journals herein before mentioned, though complete from
an electrical point of view was very incomplete from an acoustical point of view.
My improvements relate chiefly to the acoustical part of the said apparatus.
The original "Reiss" apparatus consisted of an electro-magnet laid flat upon a
sounding-board or box, .having in front of its poles an armature consisting of a
moderately stout bar of iron of oval section attached to a thin flat lever which was
hung like a pendulum from a pivot or hinge but restrained in its motion by a
spiral spring and an adjusting screw. I modify this arrangement for the purpose
of obtaining a better acoustic effect. In order, that when using the instrument the
vibrating lever may be put near to the ear, I make the whole of the parts smaller.
and more compact than heretofore. In some cases I turn the support which holds
the armature-lever round so that it, and the adjusting screw and spiral spring lie on

page_text: the same side of the armature lever as the electro-magnet. In another modification
I lay the lever between, or parallel to, the limbs of the electro-magnet, and hinge it
to the yoke-piece of the same, the screw and spring lying between the limbs of
the said electro-magnet. I enclose the whole within a case suitable to be held in
the hand. This case is a cylindrical box of wood or other material closed at one
end, and open at the other end. Over the open end I fix a suitable ear-piece. The
case itself can be used to support the hinged lever which carries the armature bar.
I find that when thus boxed up the vibrations of the armature are communicated
to the ear with less loss than when the instrument is standing open upon a board.
In some instances 1 enclose the receiver within the same box as the transmitter
and listen by an ear-tube to the vibrations of the armature

page_text: 1.
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
7th September 1883.
SILVANUS PHILLIPS THOMPSON, of University College, Bristol, Professor of
Experimental Physics. "IMPROVEMENTS IN TELEPHONIC APPARATUS"
My improvements relate to telephonic transmitters and receivers, and chiefly to
modifications in, and additions to, telephones of the kind invented by Philipp Reiss
and described in the years 1862 and 1863 in the journal of the Austro-German
Telegraph Union and in Dingler's Polytechnic Journal; and also in 1866 in Kuhn's
Handbook of Applied Electricity.
My said improvements consist in various details of construction and arrangement
whereby I convert instruments which are practically useless for the present
applications of telephony into highly useful and serviceable instruments.
The first part of my improvements relates to the Transmitter, which I modify
in various ways to obtain an instrument less liable to derangement of its parts and
more reliable in its articulation than was the original instrument of Philipp Reiss,
to which I have referred. The person using that instrument spoke into a tin cone.
closed at one end by a tympanum of collodion, and the vibrations of the voice,
taken up by the tympanum, were caused to act upon a small curved lever of which
the material was not prescribed; it must have been a substance that will conduct
electricity, but it was to be as light as possible, and the plain inference from the
description given is that it should be non-metallic. This lever rested with one end
against the tympanum and at the other end was caused by means of a delicate
spring to press against a contact piece mounted upon a vertical spring, and adjusted
to the requisite degree of contact by a screw. The function of this lever was to.
open or close the circuit to a greater or less degree according to the vibrations
imparted to it, and, by thus varying the contact between the parts, to throw the
current into corresponding vibrations; the object being to magnetize and
demagnetize an electro-magnet at the receiving end of the line so as to make
it increase and decrease in the force with which it attracted its armature which
was consequently thrown into vibrations corresponding to the original vibrations.
The aforesaid lever was made with its arms of unequal length, thereby sacrificing
the range of its motion in order to obtain a greater range of force or pressure
between the contact parts. The whole instrument was mounted on a stand.
My improvements in the said transmitters are illustrated in Figures 1, 2, 3, 4, 5,
of the accompanying drawings which I will now proceed to describe.
Figure 1 shews my improved transmitter in side elevation, the telephonic
apparatus being enclosed in a box or case which is shewn in transverse section.
Figure 2 is an exterior front elevation of the same
Figures 3, 4 and 5, are sectional side elevations illustrating various modifications
hereinafter described.
The box A can be fixed to a wall, leaving only the mouth-piece exposed; this
mouth-piece is a hollow metal cone, a, b, so arranged that it may be screwed to the
box from the outside. The frame or ring which holds the tympanum o is affixed
by screws or clamps to the socket which holds the mouth piece as shewn. I find
that amongst tympanums of collodion variously prepared those which are made of
the preparation of collodion known as celluloid are the most satisfactory, and are
least liable to become flaccid with the moisture of the breath. But I sometimes
use other substances such as ebonite, glass, thin metal or the like. Or I may make
the tympanum by evaporating to dryness liquid collodion with which there has
heen mixed boiled linseed oil Canada balsam mastic varnish or similar material.

page_text: For making the curved lever c, d, in order that it may be as light as possible, I
generally use either aluminium or artificial coke-carbon, these substances being the
lightest of good conductors available for the purpose. I prefer the artificial coke-
carbon. I find the action of this lever to be more certain when a pin or pivot is
inserted at e to attach it to the support s which is preferably formed to receive the
said lever; I insert into the substance of the lever a small metallic centre piece or
eye to receive the said pin. This metal piece or eye may be fitted to bear and
vibrate upon a fixed pin or pivot; or the said eye may be tightly fixed on a pin
which is fitted to vibrate in bearings in the support 8. I find that, by using this
metallic piece or eye and thereby increasing the surface of metal in contact with
the carbon at this part of the current regulator, I greatly improve the action of
the instrument. The spring n I make of brass or other conducting material. I
sometimes employ a spring of prepared carbon similar to that used in many forms
of incandescent electric lamps. For the contact-piece touching the lever at d I
employ a small stud d* of silver, nickel, native amalgam ore, or other good conductor
of electricity, or, in some cases, one of the good conducting kinds of carbon, such as
pure dense graphite, and I mount the stud d* on a slender vertical spring g. This
spring may, in some cases, be replaced by a spring made of prepared carbon, in
which case the stud d may be dispensed with. The spring ġ is carried upon a
metallic support f, and its pressure against the lever c, d is regulated by an adjusting-
screw provided with a locking-nut k. The above named parts arranged in
combination with the tympanum as described constitute what I term the current
regulator. The effect and importance of the changes or modifications which
distinguish this regulator from that in the original instrument will be understood
by those familiar with the working of telephones, and they are essential to the
efficiency of these instruments.
I sometimes, however, modify the above described parts of the instruments in
the manner indicated in Figures 3, 4 or 5.
In Figure 3, the principal modification consists in inverting the position of the
curved lever c, d. Its support s I prefer, in this case, to place below the said lever,
as this arrangement permits the spring 9 and the support f to be shortened as
shown.
In Figure 4 I have shown the support a hanging vertically from the top of the
case and provided with a spring at n; when this suspended support is adopted, I
may further simplify the mechanism by making the pivot at e very stiff, and the
support & thin and springy, the spring n being then no longer needed.
Figure 5 shows a modification of the instrument, in which the vertically hanging
spring support s is adopted, and in which the support fand the contact spring g
are inverted and depend from the upper part of the box. The two parts & and f
may both be screwed to one block m of ivory or other insulating material. In
some instances I find it advantageous to make the springs a and g of carbon
prepared by carbonizing vegetable matter, similarly to the carbons used in
incandescent electric lamps.
.
In some instances, particularly for long, line work, I combine with this
transmitter, within the box, a small induction-coil, the current from the local
battery will then pass through the contact pieces of the interruptor and also
through the primary wire of the induction-coil, the secondary wire being united
with the line wire and with the earth or return wire. I am thus enabled to work
with a current of less strength than would be necessary if an induction-coil were
not used.
I also combine with this transmitter a call-bell B, and a switch S which throws
the call-bell out of circuit when the line is wanted for talking. This switch may
be of any ordinary kind; for example, it may be arranged so that the weight of
the receiver, when hung on the hook-shaped end of the switch, throws the bell
into circuit. I prefer, however, to use my improved form of switch, that is to say,
the switch shewn in Figure 15 arranged to work automatically. This apparatus
has an electro-magnet m with a pivotted armature and lever,, an arm a pivotted-

page_text: at a, a spring & and two pins p, t, which for convenience are screwed into a
plate e of ebonite or other insulating material. The coils of the electro-magnet m
are arranged in circuit with the call-bell, so that, when the bell is rung by a
current through the line, the electro-magnet attracts its armature land by. lifting
the lever releases the arm or piece a, which drops like the annunciators some-
times used in telephone exchanges. This piece, as it drops, lifts the spring 8, which
is in communication with the line, from the lower pin p, which leads to the bell-
circuit, and presses it upward against the upper pin t which communicates with
the receiving instrument and with the transmitter. This device therefore
automatically switches on the telephone in place of the bell.
Another part of my improvements, which is illustrated in Figures 6 to 14 of the
drawings, relates to the receiving instrument and chiefly to its acoustical
arrangements.
Figure 6 is a perspective view of one form or modification of my receiver, the
case being broken away at one side to permit the interior of the said instrument to
be seen.
Figure 7 shews the said instrument, with the case in longitudinal section and the
interior parts in side elevation.
Figure 8 is a front end view of the said instrument.
Figures 9, 10 and 11 are similar views_illustrating another form or modification
of the said receiver.
Figure 12 is a perspective view of a receiver constructed on the principle of the
Reiss needle telephone, the case being broken away at one side to permit the
interior of the said instrument to be seen.
Figure 13 shows this instrument with the case in longitudinal section and the
interior parts in side elevation, and:
Figure 14 is a longitudinal section showing a slightly modified form of the said
instrument.
The original apparatus of Reiss consisted of an electro-magnet laid flat upon a
sounding board or sounding box and having in front of its poles an armature
consisting of an iron bar of oval section attached to the end of a thin flat or
plank-like lever hung in the manner of a pendulum from a pivot or hinge, but
restrained by a spring and an adjusting screw from swinging freely like a pendulum.
According to my invention I modify this arrangement, for the purpose of getting
a better acoustic effect and a very convenient form of instrument, as follows,
viz-In order that the vibrating plank-formed lever may affect the ear more
satisfactorily, I make the whole of the parts smaller and more compact than in the
original instrument of Reiss, so that the instrument can be put directly to the ear,
the whole being enclosed within a case c suitable to be held in the hand, see
figures 6, 7, 8 or 9, 10, 11. This case c is a circular box of wood or other material
closed at one end, open at the other and provided at its wide end with a cover to
serve as an ear-piece or embouchure.
In the form shown in Figures 6, 7, 8, an electro-magnet m is placed with its
poles pointing toward the mouth of the case. In front of these poles, but not
touching them, the armature b (which is a bar or tube of iron of oval section) is
fixed on or near one end of the thin broad lever i, which should be made either of
wood or of brass or zinc. This lever is pivotted at p to a support k like a
pendulum. In some instances a steel spring, like that used for supporting clock
pendulums, is substituted for the pivot. The motion of the lever i is controlled by
the spiral spring o and the adjusting screw l. The latter passes through the
support and the cross-bar q, which may be of wood, brass, zinc, slate or mica, and
is screwed to the case at one of its ends. Another screw passing through the
cross-bar q is screwed into the end of the spiral spring o.
g
On the end of the box
or case containing the parts above enumerated there is screwed a cover f of wood
or other suitable material perforated with an aperture e as shewn in Figure 7.
This aperture serves as an embouchure for the sounds emitted by the apparatus.
I have shewn the aperture or cavity in the said cover ellipsoidal in form, the

page_text: curvature being such that the cross-bar or end support 7 of the apparatus and the
ear of the listener shall, when the instrument is pressed against the ear, occupy
the two focal points of this ellipsoidal cavity. The cross-bar or support q is, in
some instances, made broader than that shown in the drawing so that it will serve
as a sounding board.
Figures 9, 10, 11 shew a slight modification in the parts of my receiver, designed
to ensure still greater compactness of the same. The cross-bar is dispensed with
and the adjusting screw land spring o are turned round or reversed relatively to
the armature-lever i, so that the latter may be brought closer to the ear. As
before the armature b is an iron bar or tube of oval section, and the beam or
armature lever is pivotted at p to the support k. In this modification, the spring o
is fixed to a support s' which for convenience is of arched form.
In this instrument, the armature-lever is in close proximity to the orifice in the
cover and occupies the same position relatively to the focal points as the support
or cross-bar q in the instrument above described. When I dispense with the cross-
bar or support 9 I make the armature-lever i broader and lighter than when the
said support is present, and in some instances I make this lever broader than it is
shewn in the drawing so that it will serve as a sounding board.
I have thus modified the construction and arrangement of the older form of
Reiss receiver, I find that the apparatus, when mounted either as shown in
Figures 6, 7, 8 or in Figures 9, 10, 11, is more convenient and satisfactory in every
respect than the said older form of apparatus of Reiss. The articulate vibrations
set up (by the varying magnetization of the electro-magnet) in the armature and
in the Hat lever attached to it, are communicated to the ear with less loss when
the instrument is thus boxed up in a case than when it is standing in the open air
or on a sounding board.
In Figures 12 and 13, I have shewn another form of receiving instrument which,
like the preceding, is a modification of one of Philipp Reiss' receivers described in
the publications named above and particularly at page 1020 of Kuhn's Handbook.
That instrument, in its original form, consisted of a steel needle or wire surrounded
by a coil of wire and resting on two wooden supports or bridges over a sounding
board of pine wood. I now modify the said instrument in the following manner,
that is to say, I mount the spiral s³ on its bridges b, b, these parts being made of
such dimensions as will permit their enclosure within a case c of convenient size
and shape, in which I arrange them as shewn. In some instances I place a thin
sounding board, of pine-wood or other material capable of vibrating, against the
end of the needle, the same being clipped between the case and the cover, which
may be made and affixed in the same manner as the covers of the instruments in
Figures 7 and 10. In some instances, when the instruments are made large enough,
the sounding board is not required, the vibrations of the thin bridge of wood or
metal near the front of the case being sufficient to communicate sounds to the air.
I find that the sounds produced are louder when a mass of iron or steel is introduced
behind the needle; such mass appearing to augment the vibrations of the needle.
Accordingly I either make the back of the case of iron or steel, or I screw into it
an iron or steel screw; I find such a screw may conveniently serve at the same
time to hang up the instrument with, I, therefore, provide the screw with a hook
or loop at its posterior or outer end for this purpose. I have further discovered
that, since the vibrations of the steel or iron needle are due to mutual attractions
and repulsions between the molecules, which, occurring simultaneously, set up
attractions and repulsions and vibrations in the mass as a whole, their power is
increased by giving to the molecules of different parts of the needle a greater play
than is permitted by the mere elasticity of the needle itself. Accordingly I divide
the needle into two parts, each being mounted on its own bridge or support as
shown in Figure 14, wherein the two parts of the needle are marked n, n, the
bridges b, b and the spiral s².
Having thus fully described my said invention and shown how the same may
be conveniently and advantageously carried into practice I wish it understood that

page_text: am aware that switches have been previously devised for changing the com-
munications of telephones, such switches being usually, however, operated by the
action of hanging the receiving instrument on a hook or removing it therefrom.
I am also aware that automatic drop-switches have been devised which close a
local circuit for ringing a bell, not connected with the line-circuit, but I do not
regard these devices as any part of my invention, the object of my improved
automatic switch being to cut off the call-bell and put on the telephone without
the delay which bas heretofore been unavoidable. Moreover I wish it understood
that I do not claim irrespectively of, or apart from, my improvements any of the
apparatus described or illustrated in the publications hereinbefore mentioned as the
inventions of Philipp Reiss, such improvements consisting in, or involving, the
herein specified additions to, or re-arrangements of, the parts of the original
instruments of Reiss, whereby I am enabled to adapt them to the requirements
of practical telephony, that is to say, I claim :-
First. The improvements above set forth relating to the current regulator of the
Reiss transmitting telephone arranged within a box or case substantially as
described with reference to Figures 1 and 2 or either of the modifications thereof
illustrated in Figures 3, 4 or 5 of the drawings, for the purpose specified.
Second. In a lever forming part of the current regulator of a telephone and
made of carbon or similar material, the provision of a metallic centre piece or eye
to serve as the bearing on, or connection with, the pivot or fulcrum pin of the lever
for the purpose specified.
Third. The combination, with the said transmitting telephone, of a switch
arranged to enable the line-circuit to be joined either automatically or by hand
to the bell-circuit or to the telephone-circuit at will, as above set forth.
Fourth. The improved drop-switch constructed substantially as described with
reference to Figure 15 of the drawings and operating as, and for the purpose,
specified.
Fifth. The improvements above set forth relating to the Reiss telephone receiver
which has an electro-magnet arranged in combination with a suspended armature
within a case or box substantially as described with reference to Figures 6, 7, 8 or
Figures 9, 10, 11 of the drawings, for the purpose specified.
Sixth. The improvements above set forth relating to the Reiss needle telephone
provided with a case or box and having the parts of the instrument arranged
substantially as described with reference to Figures 12, 13, 14, for the purpose
specified.
In Witness whereof I the said Silvanus Phillips Thompson have hereunto
set my hand and seal this sixth day of July in the year of Our Lord One
thousand eight hundred and eighty three.
OTT UNITO
NUS PH
HILLIPS TH
THOMPSON. (L.S.)