Improvements in Means for Preventing Induction in Telephones.
Year: 1891

page_text: Date of Application, 10th Mar., 1891-Accepted, 23rd May, 1891
COMPLETE SPECIFICATION.
Improvements in Means for Preventing Induction in Telephones.
We, THOMAS FRANKLIN WRIGHT and ED. GIBBONS WILSON both of
108 Dearborn Street Chicago, Illinois, United States of America Gentlemen, do
hereby declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
This invention relates to improvements in induction preventives for telephones,
but more especially to that class in which the device is attached to the receiver.
Prior to this invention numerous devices have been invented for preventing
induction in telephones, but so far as we are aware, none of the said devices have
been practically successful, when subjected to the ordinary conditions under which
they must operate, but our invention has been practically tested under all the usual
conditions, and has proved both operative and successful, the prime object thereof
being to prevent induction, without materially or injuriously reducing the strength
of the talking current.
"
Another object is to have the device of such a character that it is readily
attached to, and adapted for use in connection with the ordinary "hand phones or
receivers, now in use.
These objects are attained by the devices illustrated in the accompanying
drawing, in which:
Figure 1 represents a side elevation of an ordinary telephone receiver, of the Bell
pattern, having an induction device applied thereto embodying our invention.
Figure 2, a central longitudinal section thereof;
Figure 3, a face view of the induction device detached from the receiver;
and,
Figure 4 a side elevation thereof.
Similar letters of reference indicate the same parts in the several figures of the
drawing.
Referring by letter to the accompanying drawing, A indicates a casing preferably
composed of sheet metal, having the external appearance of a small cup or bowl, of
such dimensions and contour as to fit snugly within the concavity, or depression in
the end of the receiver, as more clearly illustrated in Figure 2, the face or interior
portion of the casing however having preferably an irregular shape, being concaved
around the outer portion or edges of the cup, and provided with a central projecting
portion or domb B, intended to fit against, and within the ear, which latter will be
practically covered by the casing, when applied thereto. The two walls of the
casing, that is the front and back thereof, are provided with central perfora-
tions C. D, between which a practically continuous passage is formed by the
insertion of the tube E, of any suitable material, but which is preferably composed
of a coil of small steel wire, which in practice has proven to produce the most
desirable results, although we are not prepared to state that other forms of tubes
and other material cannot be employed with equally good results.
Surrounding this tube, but enclosed within the casing is a spool F, preferably of
wood, of any suitable shape or dimensions, the most desirable being that conforming
to the interior of the casing.
This spool is grooved externally as shown, and has wound thereon a coil of fine
wire G, copper being found to produce the desired results, one end of which H, is
inserted or driven into the spool, while the other and free end I, terminates
immediately in front of, but preferably out of contact with the diaphragm J, of the
telephone receiver, which latter may, if desired, be perforated at the centre
immediately opposite the terminal of the coil, as shown at K, which we have found
DQ1

page_text: in some instances to promote the effectiveness of the device, while in others the
perforation could be dispensed with, sometimes without changing and sometimes
promoting the results.
This induction device may be attached to the receiver in any suitable manner,
either by the spring hook L, attached to the casing A, engaging the usual flange
upon the end of the receiver, or by any other device which will accomplish the
desired result.
In practice we have found it most desirable if not essential, that the wooden
spool F, be kept at all times in a perfectly dry condition, and to this end we have
usually dipped the spool in melted paraffin after the coil has been wound thereon,
thus effectually insulating the same against dampness, but other means may be
employed for accomplishing the same end, without departing from the spirit of this
invention.
It has also been our practice to have the wire forming the coil G, covered with
an insulating wrapping of some kind, so as to electrically insulate the coils from
each other, and from the casing, the extreme free ends H and I, only being
exposed, or without insulation.
So far as we are aware the shape of the dimensions of the casing, as well as of
the core, is immaterial, and may be made of any suitable form and size best adapted
for the intended uses; nor is it absolutely essential that the spool surround the tube,
or that the coil be wound upon a spool, so long as the inner end H, thereof, is
embedded in, or otherwise connected with a block of wood or other equivalent for
the coil, the arrangement herein shown however, being the most advantageous and
convenient known to us.
Nor are we prepared to state the theory of operation of this device, but simply
that it does operate to absolutely prevent induction, under all ordinary conditions
and that its operativeness has been practically tested and demonstrated.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is :-
First. An induction preventive for telephones, comprising a hollow casing having
perforations therein, a tube extending between said perforations, and a coil, one end
of which is embedded in a spool or block of wood or its equivalent, and the other
terminates opposite the centre of a perforation in the casing, opposing the
diaphragm, of a telephone receiver to which the casing is secured, substantially as
described.
Second. An induction preventive for telephones comprising a hollow casing pro-
vided with perforations, a tube consisting of a coil of metallic wire extending
between said perforations, and a coil one end of which is embedded in a spool or
block of wood or its equivalent, and the other terminates opposite the centre of a
perforation in the casing, opposing the diaphragm, of a telephone receiver to which
the casing is secured, substantially as described.
Third. An induction preventive for telephones comprising a hollow casing, pro-
vided with perforations, a tube extending between said perforations, a spool located
within said casing, and a coil of wire wound upon said spool, one end of which is
embedded in the spool, and the other terminates opposite the centre of a perforation
in the casing opposing the diaphragm of the receiver, to which the device is secured,
substantially as described.
Fourth. An induction preventive for telephones comprising a hollow casing,
provided with perforations, a tube consisting of a coil of metallic wire extending
between said perforations, a spool located within said casing, and a metallic coil
wound thereon, one end of which is embedded in the spool, and the other end
terminates opposite the centre of the perforation in the casing opposing the
diaphragm of the telephone receiver to which the device is secured, substantially
as described.
Fifth. The combination with a telephone receiver and the diaphragm thereof,

page_text: provided with a central perforation, of an induction preventive comprising a hollow
casing provided with perforations, a tube extending between said perforations, a
spool located within said casing, and a metallic coil wound upon said spool, one end
of which is embedded in the spool, and the other terminates opposite the centre of
the perforation in said diaphragm, substantially as described.
Dated this 10th day of March 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicants.