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Publication numberUS447858 A
Publication typeGrant
Publication dateMar 10, 1891
Filing dateJul 28, 1890
Publication numberUS 447858 A, US 447858A, US-A-447858, US447858 A, US447858A
InventorsThomas F. Wright
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Induction-preventive for telephones
US 447858 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

(No Model.)


INDUGTION PREVENTIVE FOR TELEPHONES. N0.447,858. Patented Mar. 10,1891.



SPECIEICATION formng part of Letters Patent No. 447,858, dated March 10, 1891.

Application filed July 28, 1890.

:seria No. 880.165.V (No model.)

T all whom, it may conccrn:

Be it known that we, THOMAS F. WRIGHT and ED. G. WILSON, both of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Induction-Preventives for Telephones, of which the following is a specification.

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 such 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 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 attachable 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 drawings, in which- Figure 1 represents a side elevation of an ordinary telephone-receiver of the Bell pattern, having an induction device Aapplied thereto embodying my invention; Fig. 2, a central longitudinal section thereof; Fig. 3, a face view of the induction device detached from the receiver, and Fig. 4 a side elevation thereof.

Similar letters of reference indicate the same parts in the several figures of the drawmgs.

Referring by letter to the accompanying drawings, A indicates a casing preferably composed of sheet metal, having the external appearance of a small cup or bowl, of such di-- mensions and contour as to fit snugly within the concavity or depression in the end of the receiver, as more clearlyillustrated in Fig. 2, the face or interior portion of the casing, however, having preferably an irregular Shape, being concaved around the outer portion or cdges of the cup and provided with a central a projecting portion or dome B, intended to fit against and within the car, which latter Will be practically covered by the casing when applied thereto. The two walls of the casingthat is, the front and backthereof-are provided with central perforations C D, between which a practically-continuous passage is formed by the insertion of a 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 pre= pared to state that other forms of tubes and other material cannot be employed With equally good results. Surrounding this tube, but inclosed 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, asshown, 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 pref-- erably out of contact with, the diaphragm J of the telephone-receiver, which latter may, if desired, be perforated at the center immediately opposite the terminal of the coil, as shown at K, which we have found in some instances to promote the effectiveness of the device, while in others the perforation could be dispensed with,son1etimes 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 fiange 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 paraffiue 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 forrning,` the coil G covered with an in'- sulating-wrapping of some kind, so as to electrieally insulate the coils froln 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'or the di- Inensions of the casiug, 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 other- Wise 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 practieally tested and demonstrated.

Having described our invention, What we claiin, and desire to secure by Letters Patent, 18-- 1. An induction-preveutive for telephones, comprising a hollow casing having perforations therein, a tube extending' between said perforations, and a coil one end of which is elnbedded in a spool or block of wood or its equivalent and the other terminates opposite the center of a perfo-ration in the casing opposing the diaphragrn of a telephone-receiver to which the casing is secnred, substantially as described.

2. An induction-preventive for telephones7 comprising a hollow easing provided 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 center of a perforation in the easing opposlng the diaphragxn of a telephone-receiver to which the casing is secured, substantially as -ing, and a coil of Wire wound upon said spool,

one end of which is embedded in the spool and the other terminates opposite the center of a perforation in the easing' opposing the diaphragm of the receiver to which the device is secured, substantially as described.

4. An induetion-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 center of the perforation in the casing opposing the diaph ragm of the telephone-receiver to which the device is secured, snbstantially as described.

5. The combination, with a telephone-receiver and the diaphragm thereof provided with a central perforation, of an induetionpreventive comprising a hollow casing provided with perforations, a tube extending between said'perforations, a spoollocated within said casing, and a metallic coil wou'nd upon said spool, one end of which is embedded in the spool and theother terminates opposite the center of the perforation in said diaphragm, substantially as described.



Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6411722May 11, 2000Jun 25, 2002Dan WolfEarphone for an RF transmitting device
Cooperative ClassificationH04R1/083