IMPROVEMENTS IN TELEPHONES, PARTS OF WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO OTHER ELECTRICAL PURPOSES
Year: 1880

page_text: LETTERS PATENT to Louis Davis, of Birmingham, in the County of Warwick,
for an Invention of "IMPROVEMENTS IN TELEPHONES, PARTS OF WHICH
IMPROVEMENTS ARE ALSO APPLICABLE TO OTHER ELECTRICAL PURPOSES."
A communication from abroad by Ernest Marx, F. Aklemm, and Julius
Kayser, all of New York, and Abner G. Tisdel, of Ilion, State of New York,
United States of America.
PROVISIONAL SPECIFICATION left by the said Louis Davis at the Office
of the Commissioners of Patents on the 27th January 1880.
LOUIS DAVIS, of Birmingham, in the County of Warwick.
"IMPROVEMENTS IN
TELEPHONES, PARTS OF WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO OTHER
ELECTRICAL PURPOSES." A communication from abroad by Ernest Marx, F. Aklemm,
and Julius Kayser, all of New York, and Abner G. Tisdel, of Ilion, State of New
York, United States of America.
This Invention relates, 1st, to the class of telephones using a permanent inagnet
and wire helix, whereby the magnetic vibration of the poles caused by the induced
current and variation in magnetic force produce the sound waves by action upon a
diaphragm, or reversely, the variation in magnetic force and vibration of the
magnet are produced by the sound waves acting on the diaphragm, and the
Invention relates, secondly, to what are known as the carbon transmitters of
telephones.
In carrying out the first part of the Invention the improved telephone consists
of a permanent magnet, the poles of which approach each other closely, one or both
poles being surrounded by a helix, and one pole terminating in a thin metallic
tongue to be vibrated by the induced magnetism of the helix or by the vibration
of a diaphragm of non-conducting material fitted in contact with the vibrating
pole.
The permanent magnet is of U form, having one pole surrounded by the wire
helix, and its other pole terminating in the thin metallic tongue. The wire helix
is upon a right angled extension of the pole which projects contiguous to the
tongue, so that both poles of the magnet are within the magnetic field. These
parts are fitted in a case having a mouthpiece, beneath which is clamped the
diaphragm of mica, wood, or other non-conducting material. Upon the tongue is a

page_text: small block of rubber or other similar material, which is in mechanical contact
with the diaphragm.
The magnet extends into a recess of the space in which is a spring that tends to
press the magnet away from the diaphragm, and in the back of the case a screw is
fitted, being upon the magnet against the pressure of the spring, so that by turning
the screw the pressure of the block upon the diaphragm may be regulated.
The instrument is adapted for transmitting or receiving. In operation as a
transmitter the vibration of the diaphragm will cause the vibration of the tongue
to and from the other pole of the magnet, such vibrations being entirely within the
magnetic field; the magnetic force and induced current will vary with the extent
of vibration. These variations in the induced current act in the receiving instru-
ment to vary the magnetic force of the helix, and the tongue and diaphragm of
the receiver will be vibrated in harmony with the transmitter to produce articulate
sounds.
The vibrating tongue may be short, and the poles of the magnet brought
closely together; the tongue being also protected may be of the most delicate
construction.
In carrying out the second part of this Invention the diaphragm is suspended
upon an arm, or as a spring tongue, and an adjustable spring arm carrying the
carbon contact point is employed in combination therewith, and also an induction
coil of novel construction.
The diaphragm is attached to the underside of the mouth piece by a metal arm,
and the spring arm before referred to is fixed upon a post attached to the underside
of the mouth piece; an adjusting screw is provided sustained in an extension from
the post and bearing on the spring, the carbon holder being attached to the outer
end of the latter.
The connections to the local circuit with battery are from the metal arm to a
binding post at the side of the box and from the post to the primary of the coil, and
from thence to a second binding post. The secondary of the coil is connected to
the main line. The arm sustaining the diaphragm is constructed of spring metal,
and tends to press the diaphragm in contact with the mouthpiece; the diaphragm
is damped by a ring of rubber or other material attached upon its edges, and is
fitted at its centre with a point of platinum.
The spring arm carrying the carbon holder tends to separate the contact points,
and its position is regulated by the screw. It will be seen that this construction
is very simple. The diaphragm is substantially a spring tongue, its vibrations
being upon its support, and its movement vibrates the spring arm. The movements
of the diaphragm are naturally more sluggish than the movements of the spring
arm, and the change of resistance is due to that difference, regulated by the pressure
given by the screw. The induction coil instead of being wound in the usual
manner, that is, by first winding the primary coil to the extent required and then
winding the secondary coil upon the primary, is wound to bring the wires of the
primary and secondary intimately together throughout. The primary wire is first
wound upon the core in two layers, the secondary wire with the primary are then
wound together in two or more layers, and these layers covered with paper, the
primary is then wound as at first, and both wires then wound together, and so on
until the induction coil is completed. This construction gives a coil of great power,
as every part of the coil is utilized, and the required induced current obtained by a
comparatively small coil. This induction coil is of special advantage when used
with a telephone transmitter, and is also adapted for general use.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Louis Davis in the Great Seal Patent Office on the 26th July
1880.
LOUIS DAVIS, of Birmingham, in the County of Warwick. "IMPROVEMENTS IN
TELEPHONES, PARTS OF WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO OTHER
ELECTRICAL PURPOSES." A communication from abroad by Ernest Marx, F. Aklemm,
and Julius Kayser, all of New York, and Abner G. Tisdel, of Ilion, State of New
York, United States of America.
The said Invention relates, first, to the class of telephones using a permanent
magnet and wire helix, whereby the magnetic vibration of the poles caused by the
induced current and variation in magnetic force produce the sound waves by action
upon a diaphragm, or inversely, the variation in magnetic force and vibration of
the magnet are produced by the sound waves acting on the diaphragm.
In carrying out this part of the said Invention, the improved telephone consists
of a permanent magnet, the poles of which approach each other closely, one or both
poles being surrounded by a helix, and one pole terminating in a thin metallic
tongue to be vibrated by the induced magnetism of the helix, or by the vibration
of a diaphragm of non conducting material fitted in contact with the vibrating
pole.
The said Invention relates, secondly, to what are known as the carbon trans-
mitters of telephones.
The object of this part of the said Invention is to simplify the construction and
connections of transmitting instruments for telephone lines, and to obtain a more
perfect operation than heretofore; and the Invention consists in the employment in
combination of a diaphragni suspended upon an arm, or as a spring tongue and an
adjustable spring arm carrying the carbon contact point, and also in the employ-
ment of an induction coil of novel construction.
And in order that the said Invention may be fully understood I shall now
proceed more particularly to describe the same, and for that purpose shall refer to
the several Figures on the annexed Sheet of Drawings, the same letters of reference
indicating corresponding parts in all the corresponding Figures.
Figure 1 of the accompanying Drawings represents a front elevation of a tele-
phone constructed according to the first part of the said Invention, the mouth
piece being assumed to have been removed in the Figure.
Figure 2 is a cross section of the instrument taken along the line 1, 2, Figure 1.
Figure 3 represents a sectional elevation of a transmitter constructed according
to the second part of the said Invention.
Figure 4 is a back view of the mouth piece and diaphragm; Figure 5 represents
a plan of the induction coil partially broken open, and Figure 6 is a partial section
of the coil.
Referring to Figures 1 and 2, A is a permanent magnet of U form having one
pole surrounded by the wire helix B, and its other pole terminating in a thin
metallic tongue a.
The wire helix B is upon a right angled extension of the pole which projects
contiguous to the tongue a, so that both poles of the magnet are within the
magnetic field. These parts are fitted in a case C having a mouth piece b, beneath
which is clamped a diaphragm c of mica, wood, or other nonconducting material.
Upon the tongue a is a small block d of india rubber or other similar material,
which is in mechanical contact with the diaphragm c.
The magnet A extends into a recess B¹ of the case C in which is a spring f¹,
which tends to press the magnet away from the diaphragm c, and in the back of
the case a screw g is fitted and bearing upon the magnet against the pressure of

page_text: the spring f, so that by turning the screw 9 the pressure of the block a upon the
diaphragm may be regulated.
The conducting wires h, h, from the helix B connect with the binding posts i, i¹,
respectively for connection with the circuit which is to contain a similar instrument
or other transmitter.
The instrument in the form shown is adapted for transmitting or receiving. In
operation as a transmitter the vibration of the diaphragm will cause the vibration
of the tongue a to and from the other pole of the magnet, such vibrations being
entirely within the magnetic field; the magnetic force and induced current will vary
with the extent of vibration.
These variations in the induced current act in the receiving instrument to vary
the magnetic force of the helix B, and the tongue a and diaphragm c of the
receiver will be vibrated in harmony with the transmitter to produce articulate
sounds.
I am aware that in telephones a permanent magnet has been used with one pole
fitted with a helix, and the other pole formed as a vibrating diaphragm. In such
instruments in order to obtain the required amplitude of vibration it is necessary
that the magnet bar should be shortened to admit a diaphragm of the size required,
while in the instrument which forms the subject of the first part of the present
Invention the vibrating tongue may be short and the poles of the magnet brought
closely together, the tongue being also protected may be of the most delicate
construction. By this construction the necessity for using a magnetically attracted
diaphragm is obviated, and it will be understood that one pole of the magnet is
formed as a thin tongue, so that the vibration will be made by the tongue entirely
as the natural effect with the poles of equal flexibility would be the vibration of
both poles equally.
Figures 3 and 4 represent a transmitter constructed according to the second part
of the said Invention.
A is the box of the instrument which may be of any desired form, and is fitted
at the top with the mouth piece a; B is the induction coil; b is the diaphragm
attached to the underside of the piece a by a metal arm; c, d, is a spring arm
fixed upon a post e, which is attached to the underside of the piece a; f is an
adjusting screw sustained in an extension from the post e and bearing on the
spring d; g is the carbon holder attached to the outer end of the spring d.
The connections to the local circuit with battery are from the arm c to a binding
post at the side of the box A, and from the post e to the primary of the coil B, and
thence to a second binding post. The secondary of the coil B is connected to the
main line.
The arm c sustaining the diaphragm b is constructed of spring metal and tends
to press the diaphragm in contact with the piece a; the diaphragm is damped by
a ring of india rubber or other suitable material attached upon its edges, and is
fitted at its centre with a point of platinum.
The spring arm d carrying the carbon holder tends to separate the contact
points, and its position is regulated by the screw f.
It will be seen that this construction is very simple. The diaphragm is sub-
stantially a spring tongue, its vibrations being upon its support c, and its move-
ment vibrates the arm d. The movements of the diaphgram are naturally more
sluggish than the movements of the spring arm d, and the change of resistance is
due to that difference regulated by the pressure given by the screw f.
The
induction coil B instead of being wound in the usual manner (that is to say), by
first winding the primary coil to the extent required, and then winding the
secondary coil upon the primary) is wound to bring the wires of the primary and
secondary intimately together throughout, as shown by Figures 5 and 6. The
primary wire g is first wound upon the core h in two layers; the secondary wire i
with the primary g are then wound together in two or more layers, and these
layers covered with paper; the primary is then wound as at first, and both wires
then wound together, and so on until the induction coil is completed. This con-

page_text: struction gives a coil of great power as every part of the coil is utilized, and the
required induction current obtained by a comparatively small coil. This induction
coil is of special advantage when used with a telephone transmitter, and is also
adapted for general use.
Having now described and particularly ascertained the nature of the said
Invention and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that what I consider to be novel and original
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is,-
.
Under the first part of the said Invention.
Firstly. In speaking telephones the non metallic diaphragm c in mechanical
contact with the vibrating pole of the magnet A in combination with a wire helix
surrounding the fixed pole of the magnet, substantially as herein before described.
Secondly. In speaking telephones the magnet A fitted with a wire helix "B"
and spring tongue a, and the diaphragm "c" having contact with a spring tongue
by an interposed block or piece of india-rubber or other similar material, the
whole combined for operating substantially as hereinbefore described.
Thirdly. In speaking telephones the spring fand adjusting screw "g" combined
with the magnet A; helix B; diaphragm C; block n; piece d, and case C,
substantially as and for the purpose hereinbefore described.
Under the second part of the said Invention.
Fourthly. In telephone transmitters the diaphragm b attached to the mouth
piece by the arm c and the adjustable spring arm d carrying the carbon holder,
the whole combined together for operation substantially as herein before described.
Fifthly. In telephone transmitters the spring carbon holder d and adjusting
screw combined with the diaphragm 6 hung as a spring tongue, substantially as
herein before described.
Sixthly. The induction coil B having its primary and secondary coils wound in
the intermediate or alternate layers, substantially as hereinbefore described.
In witness whereof, I, the said Louis Davis, have to this my Specification
set my hand and seal, this Ninth day of June, One thousand eight hundred
and eighty.
LOUIS DAVIS. (L.S.)

page_text: C
FIG. 4.