IMPROVEMENTS IN TELEPHONIC INSTRUMENTS.
Year: 1882

page_text: LETTERS PATENT to George Lee Anders of Queen Victoria Street, in the
City of London for an Invention of IMPROVEMENTS IN TELEPHONIC
INSTRUMENTS.
"
"
PROVISIONAL SPECIFICATION left by the said George Lee Anders at the
Office of the Commissioners of Patents on the 20th October 1882.
GEORGE LEE ANDERS, of Queen Victoria Street, in the City of London,
"IMPROVEMENTS IN TELEPHONIC INSTRUMENTS
"
My invention relates to telephonic transmitting and receiving instruments, and
comprises various improvements in such instruments as hereinafter set forth,
whereby I increase their sensitiveness while at the same time I prevent violent
vibrations of their contact surfaces and rupture of the circuit and the consequent
harshness of sound produced by these instruments when the voice is raised to a
high pitch.
According to one part of my invention I make use of a thin box or chamber
partially or wholly exhausted of air, in place of the diaphragm, tympan, or
sounding board heretofore used in certain forins of transmitting telephones, and I
thereby greatly increase the sensitiveness of the instruments, and am enabled to
successfully employ for the contact surfaces of such transmitters many materials
not hitherto practically available for this purpose. In one form of my said
instrument or apparatus I use a thin metal box (such as is used in a common form
of aneroid barometer) and exhaust it of air and mount it in a suitable frame so
that by means of screws attached to opposite sides of the said box I can strain
the sides apart in opposition to the atmospheric pressure. The box thus balanced.
between two opposing forces I find to be extremely sensitive to sound-vibrations
and yet incapable of excessive vibration a state of things which favours the
employment of good conductors, such as the metals, for the contact surfaces.
I attach to the end of one or both of the screws by which the box is strained, a
piece of platinum or other suitable conducting material and arrange another piece
of the saine or different conducting material so that it shall rest in contact with

page_text: that upon the screw. Connections are then made so that the current passes
through this contact, and the instrument is placed either in direct circuit with a
battery and receiving instrument, or in the primary circuit of an induction-coil, the
secondary eircuit being to line.
In other forms of my apparatus I make use of exhausted, or partially exhausted,
chambers of various forms not mechanically strained as above, but simply attached
to suitable supports or frames and provided with contact-surfaces such as are
commonly used in other transmitters and so arranged that the vibrations of the
walls of the chamber will be communicated to them.
I sometimes employ a closed chamber containing air at a slightly greater
pressure than the surrounding atmosphere instead of an exhausted chamber, the
action of the other parts being, in this case, simply the reverse of their action with
the exhausted chamber; that is to say-instead of screws straining the sides apart
as above described I use screws pressing the sides together, the other parts remaining
as above described.
According to another part of my invention I construct the telephonic receiver
by surrounding one pole or polar extension of a permanent magnet, with a wire
coil, and extending the other pole in the form of a fork, the two prongs of which
are on opposite sides of the coil and are of such length that a thin strip or plate of
iron or other magnetic metal stretched across the ends of the two prongs will be in
close proximity to, but not in contact with, the first named pole. The centre of
this strip or plate is connected to a diaphragm or sounding-board to increase the
volume of sound. In some instances, in this instrument, I dispense with the
permanent magnet and simply attach one end of a straight iron core passing
through a coil, to the centre of a U shaped piece of iron; a thin strip or plate is
stretched across the two extremities of the U-shaped piece in close proximity to
the other end of the iron core, and a diaphragm or sounding board is arranged as
above described.
I further modify my invention by constructing the receivers as follows, that is
to say
I combine a contact piece or pieces with a magnet or magnets and a vibrating
diaphragm or armature of magnetic material so arranged that the varying
attraction of the magnet upon an armature attached to the contact piece or pieces
causes a corresponding variation in the pressure between the contact-surfaces
through which the current passes; the variations in the attractive force are
produced by drawing off a varying proportion of the total attractive force of the
magnet in another direction by means of the aforesaid vibrating diaphragm or
armature; the action is as follows:-when the vibrating diaphragm or armature
approaches the magnet the attraction between them increases and the attraction of
the magnet upon the armature which is attached to the contact-piece diminishes to
a corresponding degree; the reverse action taking place when the said vibrating
diaphragm or armature recedes from the magnet. I sometimes attach one or more
contact-pieces directly to the pole or poles of the magnet, relying upon a variation
in the attraction between the two poles of the magnet to produce the varying
pressure upon the contact-surfaces, such variation of attraction being produced, as
above described, by the action of a vibrating diaphragm or armature. I sometimes
further increase the effect of the instrument by surrounding the pole or poles of
the magnet with a coil or coils of wire through which the varying current from
the contact passes in such a direction as to increase the variations in the attraction
of the magnet upon the contact piece or pieces; or I produce a similar increased
effect by extending the pole or poles of the magnet in two directions, placing the
armature attached to the contact piece or pieces opposite the extension or
extensions in one direction and the vibrating diaphragm or armature opposite the
extension or extensions in the other direction, each extension being surrounded by
a coil of wire, and the coils being so connected that the currents induced in one set
by the approach of the diaphragm or armature will pass through the other set in

page_text: such a direction as to weaken the attraction of the polar extensions within; or
both of these arrangements may be used in the same instrument.
In some cases I use two magnets with poles of different name opposite each other,
placing between the two poles a quantity of magnetic conducting material such as
iron or nickel in a granulated or finely divided condition, the particles being beld
in place, and caused to cling together, by magnetic attraction, thus forming a
conducting chain extending between the two poles which are otherwise insulated
from each other. A current is passed through this chain of magnetic particles;
a diaphragm or armature of magnetic material is vibrated in front of the poles,
thus causing the particles of the chain to adhere with varying force or pressure.
This form or modification of my invention may be varied by using a single pole
placed opposite to a block of magnetic material, and arranging the granulated or
finely divided material between the pole and the said block, instead of between the
two poles, the other parts being as above described.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said George Lee Anders in the Great Seal Patent Office on the
20th April 1883.
GEORGE LEE ANDERS, of Queen Victoria Street, in the City of London,
" IMPROVEMENTS IN TELEPHONIC INSTRUMENTS
"
My invention relates to telephonic transinitting and receiving instruments and
comprises various improvements, as hereinafter setforth, whereby I increase their
sensitiveness while, at the same time; I prevent violent vibrations of the contact.
surfaces and rupture of the circuit in the transmitting instruments and the conse-
quent harshness of sound produced by these instruments when the voice is raised
to a high pitch.
According to one part of my invention I employ a thin box or chamber partially
or wholly exhausted of air, in place of the diaphragm, tympan, or sounding board
heretofore used in certain forms of telephone transmitters as a medium for taking
up the vibrations of the air and conveying them to the microphonic contact
surfaces; and I combine the said box or chamber, in some cases, with other parts.
By these means I ensure great sensitiveness and freedom of vibration and at the
same time confine the extent of the vibrations within very narrow limits. These
conditions are especially favorable to the use of good conductors, such as the
metals, for contact surfaces and I am thus enabled to use for this purpose many
materials which have not hitherto been practically available for this purpose on
account of the tendency of the contact surfaces to separate so suddenly and completely,
under the influence of comparatively slight vibrations of the air, as to make the
transinission of speech extremely discontinuous and uncertain.
In one form of my said instrument or apparatus I use a thin metal box (such as
is used in a common form of aneroid barometer) and I exhaust the said box of air
and mount it in a suitable frame so that by means of screws attached to opposite
sides of the said box.I can strain the sides apart in opposition to the atmospheric
pressure. The box thus balanced between two opposing forces I find to be.
extremely sensitive to sound vibrations and yet incapable of excessive vibration,
a state of things which favors the employment of good conductors as above
stated.
My said invention is illustrated in the accompanying drawings, in which
Figure 1 is a vertical central section of one form of my improved telephone
transmitter.
Figure 2 is a plan of the same with the cover removed.
Figure 3 is a vertical central section of a modified form of the said transmitter.
Figures 4 and 5 represent respectively a sectional side elevation and a front
elevation, showing a further modification thereof
Figure 6 is a sectional side elevation showing a still further modification of the
same.
Figure 6 is a plan of an instrument wherein I employ a chamber filled with
compressed air or other fluid
Figure 6b is a vertical central section of the same.
The remaining Figures are hereinafter described.
Like letters indicate corresponding parts throughout the drawings
In Figures 1 and 2, A represents a circular box of thin metal, hermetically closed
and having its upper and lower faces corrugated to increase their elasticity; B, B'
are bolts fixed in the said upper and lower faces. The bolt B is passed through an
. aperture in the disc or sounding board C fixed in the case D and the said bolt is

page_text: secured therein by a washer a and a pin or cotter b. The bolt B' is passed through
an aperture in the case D and is adjustable therein by means of the screw nut c.
The disc C serves as a support for the loose contact piece E (similar to that used in
the well known "Reis" transmitter) which is fixed to one end of a rod E¹, the
other end of which is fixed to a block E' resting by means of two points or pins d
upon suitable bearings provided on the disc C. This contact piece bears upon the
extremity of the bolt B, which forms the other contact piece or surface. F is a
cover secured to the case D by screws to protect the said contact piece E.
The connections are made as shown so that the current passes through the contact
pieces B and E, and the instrument is placed either in direct circuit with a battery and
receiving instrument, or in the primary circuit of an induction coil, the secondary
circuit being to line.
On exhausting the air from the box A the upper and lower sides or faces are
caused to approach each other by the external pressure of the atmosphere, they
are then separated in opposition to the atmospheric pressure by turning the nut c
in the proper direction. The mouth-piece e leads into an air-space entirely
surrounding the vacuum box, so that the vibrations of the air impinge upon the
whole surface of the same.
A modified form of this instrument is shown in Figure 3, wherein the box A is
made of metal sufficiently thick to withstand the external pressure of the atmosphere
after the said box has been partially exhausted of air, so that no bolts are required
for effecting the adjustinent of the box as regards the approximation of its sides.
In this instance, the lower face of the box is fixed to one end of a stud. B², the other
end of which is firmly secured to the case D. A contact piece B³ is fixed to the
upper face of the box A. The contact piece E is fixed to one end of a rod or bar E¹
the other end of which is firmly secured to a post G fixed to the case D, and the
said piece E bears upon the contact piece B³.
A further modification of my improved telephone transmitter is shown in
Figures 4 and 5. In this instrument the vacuum box A has two pins or studs B, B¹
fixed in its sides and passing one through an aperture in the case D and the other
Both of the
through an aperture in a bridge-piece D¹ secured to the said case.
said pins or studs are held in place by nuts c, c', and can be adjusted thereby to
hold the sides of the-box-apart against the external atmospheric pressure. A
bushing fof cork, india-rubber or other suitable material is usually inserted below
the nut c, but this bushing is not essential and can be dispensed with, if desired.
This instrument is fixed in such position that the box A is vertical, and the contact
piece E is, in this instance, suspended by means of two rods E³, having points d'
which rest upon a plate D2 projecting from the bridge-piece D¹.
I further modify this instrument, in some instances, by suspending the elastic
box or chamber in any suitable manner from the case of the instrument and
employing a fixed, instead of a movable, contact piece.
In Figure 6 I have shown an instrument somewhat similar in construction to
that shown in Figures 4 and 5 but intended to be fixed with the box A horizontal.
The contact piece E in this instrument. is carried by a rod E' provided with an
adjustable weight H and resting by the point d upon a suitable bearing on the
bridge-piece D₁
Instead of employing an exhausted or partially exhausted chamber as above
described, I sometimes use an elastic box or chamber containing air or other fluid
at a slightly greater pressure than that of the surrounding atmosphere, the
adjustable bolts or their equivalents being then arranged in a manner simply the
reverse of that adopted with the exhausted chamber; for example, instead of screws
for straining the sides apart, I use screws for pressing the sides together, the other
parts remaining as above described.
One form of this instrument is shown in Figures 6ª and 6b, in which I represents
a chamber consisting of a hollow india-rubber ball compressed within the case D
of the instrument, so that the pressure of the air within the said chamber is greater
than that of the surrounding atmosphere. J, J are two metal terminal plates to

page_text: which the circuit wires are attached, the circuit being completed between the two
The air-waves
plates by pieces of carbon resting thereon in any suitable manner.
caused by the voice impinge upon the external surface of the chamber I and
thereby produce variations in the contact of the carbon with the plates J.
I further modify my invention by constructing transmitting instruments (which
may, if desired, be used as receiving instruments) as follows, that is to say, I
combine a movable armature and contact piece with a magnet or magnets and
a vibrating diaphragm or armature of magnetic material, and so arrange them
that the varying attraction of the magnet upon the said movable armature and
contact piece causes a corresponding variation in the pressure between the contact
surfaces through which the current passes.
In Figures 7 and 7a which represent a horizontal section and a transverse section
on the line xx Figure 7, of this form of instrument, g is an armature which is made
in the form of a spring and also serves as a contact piece; this spring armature and
contact piece is fixed to the case of the instrument. i is a horseshoe permanent
magnet between the limbs of which extends the adjustable contact piece j. which
is screwed into the case of the instrument. , is an ordinary diaphragm of iron or
other magnetic metal which is arranged in proximity to the poles of the magnet i.
The variations in the attractive force of the magnet i upon the armature 9 are
produced by drawing off a varying proportion of the total attractive force of the
magnet in another direction by means of the vibrating diaphragm k, which also acts
&S an armature; the action is as follows, that is to say, when the vibrating
diaphragm k approaches the magnet i the attraction between them increases and
the attruction of the magnet upon the.armature g diminishes to a corresponding
degree; the reverse action taking place when the said vibrating diaphragm recedes
from the magnet.
I sometimes attach one or more contact pieces directly to the pole or poles of the
magnet, relying upon a variation in the attraction between the two poles of the
magnet to produce the varying pressure upon the contact surfaces, such variation of
attraction being produced as above described by the action of a vibrating diaphragm
or armature.
In some cases I further increase the effect of the instrument by surrounding the
pole or poles of the magnet with a coil or coils of wire, through which the varying
current from the contact pieces passes in such a direction as to increase the
variations in the attraction of the magnet upon the contact piece; or I produce a
similar increased effect by extending the pole or poles of the magnet in two
directions as shown in Figure 8, which is a sectional elevation of the instrument;
the armature g carrying the contact piece j' is placed opposite one end of the
extension and the vibrating diaphragm k is placed opposite the other end thereof,
each end of the extension being surrounded by a coil of wire and the coils being
so connected that the currents induced in one set of coils by the approach of the
diaphragm or armature will pass through the other set of coils in such a direction
as to weaken the attraction of the polar extensions within; or both of these
arrangements may be used in the same instrument.
In some cases I use two magnets i, with poles of different name opposite each
other, as shown in Figure 9, and I place between the two poles a quantity of
magnetic conducting material 7 such as iron or nickel in a granulated or finely
divided condition, the particles being held in place and caused to cling together by
magnetic attraction, thus forming a conducting chain extending between the two
poles, which are otherwise insulated from each other; the current is passed through
this chain of magnetic particles; a diaphragm or armature k of magnetic material
is arranged in front of the poles, the vibrations of which diaphragm cause the
particles of the chain to adhere with varying force or pressure. This form or
modification of my invention may be varied by using a single pole, placed opposite
to a block of magnetic material, and arranging the granulated or finely divided
material between the pole and the said block instead of between the two poles,
the other parts being as above described
.

page_text: surrounding one pole or polar extension of a permanent magnet with a wire coil
and extending the other pole in the form of a fork, the two prongs of which are on
opposite sides of the coil and are of such length that a thin strip or plate of iron or
other magnetic metal stretched across the ends of the two prongs will be in close
proximity to, but not in contact with, the first named pole. This strip or plate is
connected to a sounding board to increase the volume of sound, and the diaphragm
ordinarily employed in instruments of this kind is not required. In this instrument
I sometimes dispense with the permanent magnet and simply attach one end of a
straight iron core, passing through a coil, to the centre of a U-shaped piece of iron;
a thin strip or plate is stretched across the two extremities of the U-shaped piece
in close proximity to the other end of the iron core, and a sounding board is
arranged as above described.
My improved receiver is illustrated in Figures 10 to 15 of the accompanying
drawings
Figure 10 is a side elévation of this instrument.
Figures 11, 12 and 13 are side elevations illustrating modifications thereof
Figure 14 is a vertical central section of a further modification of my improved
receiver, and
Figure 15, is a front elevation of a portion of the same.
K represents the magnet coil which surrounds the core L, to one end of which
is fixed the U-shaped polar extension L'.
In Figure 10 the strip or band M, of iron or other suitable metal, is attached to
the extremities of the U-shaped polar extension L' and is connected at its centre to
the sounding board N.
In the instrument shown in Figure 11, the strip or band M is not attached to the
polar extension L' but is in proximity to the extremities thereof and is fixed to a
forked arm or bow O secured to the sounding board N.
Figure 12 shows a further modification in which the polar extension is made
semi-circular and the sounding board is fixed to the centre thereof
Figure 13 shows a similar form of instrument with the exception_that_the
sounding board N is secured to an arm_or_post-P-fixed-to-the centre of the strip
or band M..
In the modification of my receiver shown in Figures 14 and 15, I employ a
permanent magnet Q one pole of which is fixed to the core L² which is surrounded
by the coil K; the other pole has fixed to it a forked piece R to the extremities of
which is secured the strip or band M. The centre of this strip or band is
connected to the sounding board N and also to a projection M' forming a core
within the coil K. If desired, however, the core L² may extend through the coil K.
and the projection or core M will then be dispensed with.
Having thus fully described my said invention and the manner of performing
the same I wish it understood that I claim,
First. In à telephone transmitter, the employment of an elastic box or chamber
exhausted or partially exhausted of air, or filled with air or other fluid at a higher
pressure than that of the surrounding atmosphere (with or without the means for
adjusting the sides of the said box relatively to each other), all substantially in the
manner above set forth and for the purposes specified.
Second. The modification of my telephone transmitter wherein I combine, with
the elastic box or chamber, a loose contact piece resting upon a suitable bearing or
bearings on the case of the instrument (with or without an adjustable counter-
weight), all substantially as described with reference to Figures 1 and 2, or to
Figure 6 of the drawings for the purposes specified.
Third. The modification of my telephone transmitter wherein I combine, with
the elastic box or chamber, a contact piece carried by an arm firmly secured at one
end to the case of the instrument, substantially as described with reference to
Figure 3 of the drawings for the purpose specified.
Fourth. The modification of my telephone transmitter wherein I combine, with

page_text: the elastic box or chamber, a loose contact piece suspended from the case of the
instrument, substantially as described with reference to Figures 4 and 5 of the
drawings for the purpose specified.
Fifth. In a telephone transmitter, the combination, with a diaphragm of iron or
other magnetic metal, of a permanent magnet (with or without the coils and
extensions) arranged to act upon a movable armature and contact piece, sub-
stantially as described with reference to Figures 7 and 8 of the drawings for the
purpose specified.
Sixth. The modification of my telephone transmitter wherein I employ the
granulated or finely divided magnetic material in combination with a diaphragm
and one or more permanent magnets, substantially as described with reference to
Figure 9 of the drawings for the purpose specified.
Seventh. In a telephone receiver, the combination, with a magnet and a coil or
coils as above described, of a strip or band of iron or other magnetic metal and
a sounding board, substantially as described with reference to either of the
modifications illustrated in Figures 10 to 15 of the drawings for the purpose
specified.
In Witness whereof I the said George Lee Anders have hereunto set my hand
and seal this Twentieth day of April in the year of our Lord One thousand
eight hundred and eighty three.
GEORGE LEE ANDERS (L.S.)