IMPROVEMENTS IN "TELEPHONE RECEIVERS
Year: 1885

page_text: I HARRY PRESTON PRATT, residing at 762 Walnut Street in the City of
Chicago, County of Cook and State of Illinois, in the United States of America,
gentleman do hereby declare the nature of my invention for IMPROVEMENTS
IN "TELEPHONE RECEIVERS" and in what manner the same is to be performed
to be particularly described and ascertained in and by the following statement:-
The invention relates to that class of telephone instruments known as receivers
and consists in the construction and arrangement of parts which will be herein-
after more fully described and pointed out in the claims.
The object of the invention is, to produce an instrument which shall more
cheaply, perfectly, clearly and distinctly reproduce vocal and other sounds and
signals than has heretofore been accomplished by like instruments for a like
purpose.
This result I attain by the use in a suitable box or case provided with a
diaphragm or plate made of iron or other suitable substance, of a coil of wire,
made without a core, the wire being wound tightly and evenly each convolution
of which is glued or cemented to the other convolutions so as to present an even
or nearly even surface at both top and bottom.
This coil I place in a box or case the ends of the wire. being electrically connected
in the usual manner, and secure it firmly to the case, beneath a diaphragm or plate
of iron or other suitable substance.
Through this coil I pass a current of electricity which so acts upon the plate or
diaphragmn as to cause it to give forth, sounds, speech or telegraphic signals received
over the line from the transmitting instrument in response to the direct action of
the electric current in clear and distinct tones as uttered or delivered.
A core has heretofore been regarded as essential to the successful operation of a
coil in a receiving telephone instrument but I have discovered that such core may
be dispensed, with to, advantage and I therefore dispense with the same and
substitute therefor a solenoid or simple coil made without a core in. place of the
compound coil and core formerly used, I am aware that magnets have sometimes
been otherwise attached to, or connected with the receiving coil but I do not use
any such magnet in connection with the solenoid: By the said invention I over-
come the confusion of tones, found, in the use of other instruments and obtain a
clear and satisfactory reproduction of sounds speech.or signals, transmitted from

page_text: the other end of the line, and cheapen the cost of the instrument. The invention
is of especial advantage where underground wires are used.
In the accompanying drawings which form a part of this specification and in
which similar letters of reference refer to like parts I have shown and illustrated
the invention.
Fig 1 represents a cross sectional view of the telephone showing one half of the
case cut away the central coil being represented entire.
Fig 2 is a top view of the same with the upper casing and earpiece and top plate
removed so as to expose the central coil.
Fig 3 is an elevation of the upper plate or the one which is placed between the
coil and the ear piece.
Fig 4 shows a modification having two coils instead of one.
Fig 5 also shows a modification, two coils being used the same as in Fig 4 and
the diaphragm being divided into two plates instead of one.
Fig 6 represents the invention as the same may be applied for receiving
telegraphic signale.
A represents the outer case of the electrophone or telephone B represents the
ear piece upon one side of said case C indicates the coil D is the top plate
placed over the coil and under the car piece E is the lower plate. F is the
surrounding band by which the coil is secured or held in position g and h
are the binding posts with which the ends of the wire composing the coil are
connected.
Hand I indicate the two coils in the modified construction shown in Figs 4
and 5.
r and p represent the two upper plates used in the modification shown in Fig. 5.
The coil C should be wound tightly and evenly with each convolution glued or
cemented so as to present an even or nearly even surface at both top and bottom.
Over the coil C I place the suitable plate D preferably of iron and in the form
shown in Fig, 3.
Both of the plates D and E may however be made round, square or of such
shape as will answer the desired purpose.
I do not confine myself to the use of a single coil, nor of a single plate nor to
the precise construction of coils and plates shown in the drawings but desire
to secure the right to all forms and modifications of the instrument which come
within the principle of the invention.
For example I contemplate the use of a secondary plate or diaphragm on the
farther side of the solenoid or simple coil as shown in Fig 1, and instead of a
single coil such as I have described, two or more may be used in connection and
combination with such plate or plates.
The shape and thickness of the plates may be varied to suit the size and work
of the instrument all such variations being mechanical details.
The modifications shown in Figs 4 and 5 need but little explanation and consist in
using two coils instead of one, in the same case and held in position by surrounding
bands, a single plate being used over the same.
The telephone may also be attached to a wire over which telegraphic signals are
transmitted by the use of an ordinary telegraph key.
The person receiving the communication may by holding the telephone to the
ear readily read such signals and in this manner the noise and confusion which
exist in all telegraph offices may be overcome, and an unauthorized person be
prevented from securing information, as he can easily do when an ordinary relay
and sounder, are used.
Fig 6 is designed to show this application of the invention.
The plate or diaphragm, in the instrument is nonpolarized, I used the term
non-polarized in the application and in the claims to denote the condition of the
diaphragm when not in action and to distinguish the instrument from others in
which the diaphragm is in contact or connection with one or more magnets,

page_text: The operation of the instrument will be readily understood by those skilled in
the art.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is
1. In an instrument for receiving sound, speech, or signals a non-polarized plate
or diaphragm, made of iron or other suitable substance in combination with a coil
or coils of wire without a core substantially as described and for the purpose
specified.
2. In an instrument for receiving sounds, speech or signals, the combination of
the case A the ear-piece B, the coil C without a core, and the non-polarized plate D
made of iron or other suitable substance all arranged constructed and operated,
substantially as described for the purpose set forth.
3. In an instrument for receiving sounds or signals, the combination of the
case A. the ear piece B, the coil C without a core, the non-polarized plate D made
of iron or other suitable substance and the plate E constructed substantially as
described, and for the purpose set forth.
4. In a telephone, the combination of the case A the nonpolarized plate D made
of iron or other suitable substance and one or more coils without a core or cores
substantially as described and for the purpose specified.
5. In an instrument for receiving sounds speech or signals, a coil or coils without
a core or cores in combination with one or more non polarized plates or diaphragms
made of iron or other suitable substance placed between said coil or coils and the
ear-piece substantially as described and for the purpose set forth.
6. In a telephone receiving instrument the combination of the case A. ear
piece B. non-polarized diaphragms or plates, coil C support F binding posts g
and substantially as described and for the purpose set forth.