IMPROVE- MENTS IN TELEPHONIC INSTRUMENTS "
Year: 1882

page_text: LETTERS PATENT to Silvanus Phillips Thompson, of University College,
Bristol, Professor of Experimental Physics, for an invention of "IMPROVE-
MENTS IN TELEPHONIC INSTRUMENTS
"
PROVISIONAL SPECIFICATION left by the said Silvanus Phillips Thompson
at the Office of the Commissioners of Patents on the 31st May 1882.
SILVANUS PHILLIPS THOMPSON of University College, Bristol, Professor of
Experimental Physics, "IMPROVEMENTS IN TELEPHONIC INSTRUMENTS
"
This invention relates to telephonic instruments and chiefly to improvements
in receivers of a well known form or type invented by Philip Reis wherein the
telephonic currents are received in a coil of wire surrounding a needle or rod of
iron or steel and mounted upon a suitable sounding-box of wood. In this instrument
the variations in the strength of the current produce variations in the degree of
magnetization of the needle, which in consequence of the molecular changes set
up by these variations in its magnetization emits sounds.
With this well known "Reis " instrument the sounds emitted are not loud, partly
because the mass of magnetic metal of the needle is too great to permit of very
considerable changes in its degree of magnetization being rapidly effected and
partly because the acoustic arrangement of the parts is defective and inconvenient.
The aforesaid needle is not so mounted as to affect the sounding box in the most
direct manner, and the shape of the instrument prevents its being so conveniently.
applied to the ear as the modern forms of telephone receiver.
In my improved instrument a rod or piece of very thin wire of iron, steel, nickel
or other magnetic material is employed in preference to the needle, bar, or rod used
in the "Reis instrument. One end of this wire is fixed to the centre of a
tympan or tympanum of mica, horn, ebonite, sheet metal or other appropriate
substance. Its other end is fixed to an adjusting screw or pin by means of which
the said wire and the tympan attached to it can be strained and retained at any
desired degree of tension. The said central wire rod is surrounded by a coil or
coils of covered copper wire which is wound upon a glass tube or other suitable
n

page_text: tube or bobbin care being specially taken that no part of the coils or of the tube
or bobbin on which the coils are wound comes into contact with the said central
wire so as to damp its vibrations. The combined coil, tympanum wire and
adjusting screw or pin are enclosed in an external case of convenient form having
an ear-piece.
In another form of my improved receiver I employ two or more wire pieces or
rods attached to the tympanum each of these rods or pieces passes through the
coil or coils and is attached to an adjusting screw or pin. In some instances each
of them has its own adjusting screw or pin. And in some instances each wire
passes through a separate coil. Flat ribbons of thin iron, steel nickel or other
magnetizable metal may also be used in the place of the thin wire.
This improved telephone receiver when connected with any suitable transmitter
reproduces sounds much more loudly than the original "Reis " needle instrument
herein before referred to and the articulation, especially of the sibilants and some
other consonants, is much clearer and more distinct than with the common
magnetic telephonic receivers.
I am aware of the Provisional Specification filed February 28th 1879 No 806
which describes an instrument having a bar subjected to a strain by loading it at
the end or pressed by a weight or spring in which instrument the said bar has its
end bearing against a sounding board or plate, or the curved end or ends of the
bar are put under strain by the pressure of a board or plate; but in my instrument
as above described the said bar is replaced by a thin piece of wire or ribbon,
attached to a tympan or tympanum at one end, and this wire or ribbon, is under
a longitudinal stress applied by the attachment of its other end to an adjusting
screw or pin which is rigidly attached to the case wherein the working parts of
the instrument are contained.
I sometimes modify the construction of my improved instrument as follows that
is to say I make use of a double coil composed partly of a few turns of thick wire,
and partly of many turns of thin wire, which coil may be either in one continuous
circuit with the line wire or may be separated into two distinct circuits the thick
wire being connected with a local battery, and the thin wire being joined in circuit
with the line wire and the distant transmitting apparatus.
In some forms of my said instrument I provide for augmenting the sound by
attaching one end of the wire or ribbon to the tympanum and its other end to one
pole or end of an electro magnet so that the vibration of the iron of the electro-
magnet and themselves to the vibrations of the wire or ribbon. It is convenient in
this modification to have one pole of the electro magnet made of thinner material
than the other pole so as to be more readily capable of vibrating. Moreover in
some instances I wind the two limbs of the electro magnet with coils of thick or
thin wire in the manner hereinbefore specified, according to the conditions of the
circuit in which the receiving instrument is to be used.
With respect to the use of mica as a material for the tympanum I observe that
in the Specification of Letters Patent of Thomas Alva Edison dated July 30th
1877 No 2909 a claim is made for the use of mica as a tympan or diaphragm in an
instrument for transmitting electric impulses by sound the function of the said mica
tympan being to collect the vibrations from the speakers voice and to cause them
to vary the pressure upon a so-called tension regulator beneath, but in my improved
receiver the function of the tympanum is to cominunicate the vibrations of a
strained wire to the ear of a listener or to the intervening air.

page_text: 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 30th November 1882.
SILVANUS PHILLIPS THOMPSON, of University College, Bristol, Professor of
Experimental Physics "IMPROVEMENTS IN TELEPHONIC INSTRUMENTS"
This invention relates to telephonic instruments and chiefly to improvements in
receivers of a well-known form or type invented by Phillip Reis. In this instru-
ment, which is now commonly known as the Reis receiver, the telephonic currents
are received in a coil of wire surrounding a needle or rod of iron or steel mounted
upon a suitable sounding box of wood. In the said instrument the variations in
the strength of the current produce variations in the degree of magnetization of
the needle, which, in consequence of the molecular changes set up by- these
variations in its magnetization, emits sounds. The final result of such molecular
changes, is in general, to produce either an expansion or a contraction of the said
rod, bar or needle. It is known, for instance, that the effect of increasing the
degree of magnetization of a rod of iron, steel or cobalt is to make it expand in
the direction of its magnetization, and that an increase in the degree of
magnetization of a rod of nickel causes it to contract in the direction of its
magnetization.
In this well-known needle instrument of Reis the sounds emitted are not loud,
partly because the mass of magnetic metal is too great to permit the required
changes in its degree of magnetization to be rapidly effected, and partly because
the acoustic arrangement of the parts is defective and inconvenient. The aforesaid
needle is not so mounted as to affect the sounding box in the most direct manner
and the shape of the instrument prevents its being so conveniently applied as the
modern forms of telephone receiver to the ear.
My improved instruments are all based upon the same principle of utilizing the
expansion and contraction arising from the molecular changes set up by the
varying degree of magnetization due to the telephonic currents, and the improve-
ments hereinafter set forth relate to various methods of obviating or avoiding
the defects of the said Reis instrument whilst preserving and developing its
fundamental principle.
In carrying my invention into practice the said improvements are embodied in
various forms of instruments which are illustrated in the accompanying drawings
Figure 1 represents a central longitudinal section of an instrument constructed
according to my invention.
Figures 2 to 3d are elevations illustrating different modifications of my invention
Figures 4, 7 and 8 represent central longitudinal sections and
Figures 5 and 6 and 9 to 26 are views of parts of different instruments
constructed according to my said invention.
Like letters indicate the same or corresponding parts throughout the drawings
In the form of my improved instrument shown in Figure 1, a thin rod or piece
of very thin wire W, of iron, steel, nickel, cobalt or other magnetic material is
fixed by one end to the centre of a tympanum T of mica, horn, ebonite, sheet
metal or other appropriate substance. Its other end is fixed to an adjusting
screw or pin S by means of which the said thin rod or wire can be strained and
retained at any desired degree of tension. In some instances I use flat ribbons or
strips of thin iron, steel, nickel, cobalt or other magnetizable metal in place of the
thin rod or wire, and I employ strips of various forms as hereinafter described.
The said central rod, wire, ribbon or strip is surrounded by a coil or coils C of
covered copper wire which is wound upon a glass tube or other suitable tube or

page_text: bobbin, the central rod, wire, ribbon or strip being left free to vibrate, undisturbed
or unimpeded by contact with the coil or bobbin. The combined tympanum, wire
or ribbon and adjusting screw or pin are enclosed in a case of convenient form
having an ear-piece. The general action of this instrument is as follows, that is
to say-If the current received in the coils C through the line from the trans-
mitter increases in strength it will change the molecular condition of the central
rod, wire, ribbon or strip causing it to elongate slightly if it be of iron, steel or
cobalt and causing it, if it be of nickel, to contract slightly. A decrease in the
strength of the current will be followed by a partial demagnetization of the
central rod, wire, ribbon or strip producing an inverse movement. Hence, as one
end of the said central rod, wire, ribbon or strip is tightly screwed up to the case
of the instrument, the varying or fluctuating currents entering the same will cause
corresponding vibrations of the tympanum. This telephonic receiver, when
connected up with any suitable transmitter, reproduces sounds much more loudly
than the original Reis-needle instrument hereinbefore referred to; and its articu-
lation, especially of the sibilants and of some other consonants, is much clearer and
more distinct than that of the common magneto-telephonic receivers.
In Figure 2 the same general arrangement of parts is preserved, but the central
rod, wire, ribbon or strip W imparts its motions to the tympanum through the
agency of an intermediate arm or lever L whose function is to multiply or increase
the extent of the movement, In another arrangement of the parts for attaining
the same result in my instrument, two wires, placed at an obtuse angle to one
another, are attached to the tympanum as in Figure 3 or to a rod or finger
projecting therefrom as in Figure 3ª, or one wire is attached by its middle-portion
to the tympanum T; or a straight wire as in Figure 3b or curved wire as in
Figure 3 or Figure 3d is used in combination with the coils and tympanum and
strained at an obtuse angle, the wire or wires, or their equivalent ribbon, strip or
rod, being in these modifications surrounded as above described by the wire coil or
coils In all or any of the forms of instruments herein described the adjusting
screw or pin may be placed at either end of the wire, rod, ribbon or strip.
In other forms of my improved receiver I employ two or more rods, wires,
ribbons, strips or pieces attached to the tympanum, or to levers or projections in
connection with the same.
-
These rods, wires, ribbons, strips or pieces pass through the coil or coils and are
attached to an adjusting pin or screw. In some instances I provide each of them
with an adjusting pin or screw, and if desirable each of them is arranged within a
separate coil.
In the form of instrument shewn in Figure 4 there are two wires or ribbons W
and w, attached to the tympanum T at different points, but terminating in a
common adjusting screw and surrounded by one coil c. These wires or ribbons
may both be of iron or steel, but the instrument works better if one of them is of
nickel and the other of iron so that whilst one of them is expanding the other is
contracting by the variations in their magnetization.
In the form of instrument shewn in Figure 5 there are also two wires or ribbons,
one of them W is of iron, the other wis of nickel, and they communicate their
resultant motion to the tympanum T by means of the lever L.
In the form of instrument depicted in Figure 6, there are three wires or strips, a
central one w of nickel, and two external ones W, W, of iron. There are also
separate coils for each of the three wires or strips. The iron strips expand whilst
the nickel contracts, and, as they are attached to different parts of the tympanum,
the vibrations of the latter are greater than if one strip only were employed.
Figure 7 shews a further modification of my instrument. In order the more
effectively to magnetize the wire, strip or ribbon w, its ends are embedded in two
lumps or masses M of magnetic metal such as soft iron. In this form of my
instrument the anterior end of the wire or strip is attached to the tympanum, the
posterior end is screwed to the closed end of an iron tube J, which serves as a case
for the instrument and encloses the central wire or strip and the coils C, C.

page_text: In Figure 8 I have shewn a form of instrument in which the iron tube J is made
wide and short and provided with a bent iron handle H which carries an iron
cup G to the centre of which the wire or strip W is screwed, the spring of the bent
handle H is serviceable in keeping the wire or strip in a proper condition of
mechanical tension.
I further modify the arrangement of the wire, strip or ribbon in my instrument
as follows:-The wire or strip is bent into the form of a cork screw or helix as
shewn in Figure 9, or a helix is formed by taking a tube of iron or steel of
suitable diameter and cutting it spirally from end to end (as shown in Figure 10)
the separate turns of the spiral being slightly separated by means of the adjusting
screw.
In another form shewn in Figure 11 I employ a strip or ribbon of iron or other
magnetic metal bent or folded in a sort of zig zag form, and I sometimes employ a
chain, as in Figure 12, whose links are made of magnetic metal, and which is
strained within the coils C in place of the wire or ribbon. In some cases I
substitute a number of wires twisted together, which wires may be all of one kind
or of different kinds.
In one form of my improved instrument depicted in Figures 13 and 14, there
are five rods or wires, four of which W, W, W, W, are of iron and act on the
tympanum near its periphery. The fifth wire w, is of nickel and acts on the
tympanum at its centre. These wires are all attached at their posterior end to a
thin stiff disc. The five rods or wires are surrounded by a suitable coil or coils.
I sometimes modify the construction of my improved instrument in the manner
indicated in Figure 16, that is to say-I use a double coil composed partly of a
few turns of thick wire, and partly of many turns of thin wire, this coil may be
either in one continuous circuit with the line or may be separated into two distinct
circuits, the thick wire being connected with a local battery at B, or at B¹, and the
thin wire being joined in circuit with the line wire and through it with the distant
transmitting apparatus.
In Figure 16 I have shewn another modification of my instrument wherein
there are a series of rods, needles or strips arranged parallel to each other. The
rods W are of iron and the rods w are of some other metal, such as nickel.
A further modification of my instrument is shewn in Figure 17 wherein two
strips W are employed, both being attached to the tympanum or to some part,
such as a lever, in connection with the tympanum, and both being tightened by
means of an adjusting screw or screws. In this case it is convenient to give the
strips a preliminary curvature; and in some cases surround each of them with a
separate magnetizing coil. .
I find it, in some cases, expedient to bring to bear a stronger magnetizing power
than that of tho surrounding coils of wire, and accordingly attach the wire, rod,
ribbon, strip or strips to the poles of an electro-magnet, the coils of which may be
traversed either by the line current or by currents from a local battery. In some
instances I use both the surrounding coils and the electro-magnet in one instrument.
The form of instrument shown in Figure 18 embodies this device, K K are the
coils of an electro magnet whose poles are attached to the ends of the strips W which
are surrounded by the coils C.
In Figure 19 the instrument is modified by the employment of an electro-
magnet to magnetize the wire more strongly than the external coil or coils C
alone.
In some cases I not only attach the wire, rod, ribbon or strip to the pole of an
electro-magnet for the purpose of more effectively magnetizing the said wire or
strip, but I utilize this arrangement for the purpose of causing the vibrations due
to expansions and contractions in the iron of the electro-magnet to add themselves
to the vibrations of the wire or strip. This arrangement is equivalent to employing
a Reis's needle considerably thickened or enlarged at one end, both thick and thin
points expanding and contracting under the varying degrees of magnetization.
One form of my instrument in which this arrangement is adopted is shewn in

page_text: Figure 20, wherein an iron ring R rigidly connected with the tympanum at its
edge, secured at one end to an iron rod P whose other end has extending from it
the wire W strained by means of an adjusting screw or pin, the wire W and the
rod P being both surrounded by coils to magnetize them.
Figures 21 and 22 depict a further modification wherein the iron ring R is
secured to two iron rods P P¹, to one of these rods the magnetizing coil C is
attached, and to the other of them one end of the wire W is attached as shewn;
coils are in some cases wound round either or both of the iron rods P. P¹.
In another form of my instrument the wire or ribbon is a prolongation of the
core of an electro-magnet. An example of this form of instrument is given in
Figure 23 wherein the iron ring R bears two or more iron or steel rods P P which
on emerging from the coils which magnetize them are reduced or thinned down to
the condition of wires or ribbons and these are bent round and attached to the
tympanum as shown.
I find it convenient also to employ in this manner electro-magnets in which one
pole is made thinner than the other so as to be the more readily capable of
vibrating. An electromagnet having one pole thinner than the other and having
the thinner pole attached to a wire W is shewn in Figure 24 wherein I have also
shewn an arrangement of thick and thin coils similar to that hereinbefore
described and shewn in part in Figures 15 and 20. Figure 25 illustrates another
manner of arranging such a combination of electro-magnet, wire and coils.
Moreover, I sometimes use in my instruments ribbons or strips bent or folded
into a zigzag form and surrounded by coils wound upon the zigzags in the manner
illustrated in Figure 26, so that the wires pass backwards and forwards between
the folds of the ribbon or strip and magnetize them, thereby causing the individual
parts to expand and contract in the manner desired.
Having thus fully described my said Invention and the manner of performing
the same I wish it understood that all or any of the forms of wires, rods, ribbons,
strips or pieces whether straight, flat, tubular, curved, folded or twisted are, for
my purpose, equivalent devices provided that, by the expansions and contractions
they undergo when subjected to magnetizing forces, they communicate their own
vibrations to a tympanum.
I further wish it understood that I make no claim to, or in respect of, a telephonic
instrument constructed as described in the specification of Letters Patent No 806,
AD 1879 or any form of instrument in which a weight is suspended by an iron or
steel needle, rod or strip but I claim in a telephonic instrument:-
First The combination of a tympanum with a straight or other wire, rod,
ribbon, strip or piece (or two or more of the same) capable of magnetic expansion
or contraction fixed at one end to the case of the instrument and subjected
longitudinally to an elastic stress by means of an adjusting screw or other device,
substantially as set forth, so that its expansions or contractions will or may cause
vibrations of the said tympanum.
Second-The combination of two or more wires, rods, ribbons, strips or pieces
capable, in different degrees of magnetic expansion or contraction, (or of one or
more pieces that expand or contract with a piece or pieces that do not expand or
contract when magnetized) with a tympanum in such a manner that, by the
difference or opposition in their motions, the tympanum is acted on either directly
or indirectly and caused to vibrate.
X-
Thirdly The use in combination with the tympanum of a continuous coil of
wire composed partly of a few turns of thick wire and partly of a great number of
turns of thin wire for the purpose specified.
Fourth-The modification of my invention wherein the wire, strip or needle
such as is hereinbefore described is arranged in combination with an electro-
magnet, as in Figures 17, 18, 19 or 24 or in a substantially similar manner, for the
purpose specified.
:―
Fifth The combination of an electro-magnet one pole of which is thinner

page_text: than the other with a wire or strip such as is hereinabove specified, for the purpose
set forth.
Sixth-The modification of the said invention wherein the needle or strip is
formed by an extension or prolongation of the poles of the magnet substantially
as set forth,
Seventh-The modification of my invention wherein I provide for superadding
the effect of the expansion and contraction of the core of the electro-magnet to
that of the vibrations of the needle or strip substantially as set forth with reference
to Figures 20, 21 and 22 of the drawings.
Eighth-The modification of the said invention wherein the needle strip or
ribbon is made zig-zag and has the wire coils intertwined with or wound upon the
same substantially as described with reference to Figure 30.
In witness whereof I the said Silvanus Phillips Thompson have hereunto
set my hand and seal this twenty ninth day of November in the year
of our Lord One thousand eight hundred and eighty two.
SILVANUS PHILLIPS THOMPSON (L.S.)