US511882A - Tenths to charles e - Google Patents

Description

S. G. DREW. TELEPHONE ,TRANSMITTER.

No. 511,882. Patented Jan. 2, 1894.

UNITED STATES.

PATENT @EETCE.

STEPHEN C. DREW, OF BOSTON, MASSACHUSETTS, ASSIGNOR OF THREE- TENTHS TO CHARLES E. JACKSON, OF SAME PLACE.

TELEPHONE-TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 511,882, dated January 2, 1894.

Application filed January 23, 1898. Serial No. 459,317. (No model.)

To all whom it may concern:

Be it known that I, STEPHEN C. DREW, of Boston, county of Suffolk, State of Massachusetts, have invented an Improvement in Telephone-Transmitters, of which the following description, in connection with the accompanying drawings, is aspecification, like letters and figures on the drawings representing like parts.

In the telephone transmitters now in general use the diaphragm which receives the sound waves from the-voice, acts mechanically, either directly or through an interposed piece, upon one or more carbons, or other resistant buttons or electrodes included in the primary circuit of an induction coil, the secondary circuit of the induction coil constituting the line circuit extending to and including the distant receiver. The sound waves produced by talking cause the diaphragm to vibrate, the vibrations of the diaphragm, both as to number and amplitude being mechanically transmitted to the resistant electrodes to more or less vary the pressure upon or between the same, and thus cause them to interpose a greater or less resistance in the primary circuit of the induction coil to form an undulatory current therein corresponding to the undulations or variations in the sound waves. The undulations of the current in the primary circuit are reproduced by induction in the secondary circuit of the coil and in the receiver included in the secondary circuit, being made audible by the receiver. In transmitters of this class, the diaphragm is not free to vibrate to its fullest extent, the amplitude of its vibrations being limited, more or less, by the action of the resist-ant electrode or electrodes pressing constantly against it. To lessen this effect as much as possible it is necessary to mount the electrode or electrodes upon flexible or light springs, but by thus mounting the electrodes they are free to set up a counter vibration of their own independent of the diaphragm,whichinjuriously affects the transmission of sounds. The amplitude of the vibrations of a diaphragm is substantially the same at each side of its central position of rest, yet in transmitters of the class described wherein the electrodes press directly or indirectly against the diaphragm at one side, the only vibrations which act upon and affect the electrodes are those atthe side of the central position next to the electrodes, while the vibrations at the opposite side of the central position do not affect the electrode to any extent. One-half the full vibratory movement of the diaphragm is then practically unutilized in transmitting sound.

In my eiforts to improve the transmission of speech by means of the telephone, I have conducted experiments to discover, if possible, some means whereby the vibrations of the diaphragm might be transmitted to the resistant electrode or electrodes to vary the resistance offered by the latter to the passage of an electric current, andyet leave the diaphragm perfectly free to vibrate under the undulations of the sound waves, unobstructed and unhampered by any mechanical connections with electrodes or other devices. It is a known property of a magnet that any variation in the strength of its magnetism causes the magnet to lengthen or shorten, or otherwise change its form, for example,if the magnetism of a bar magnet be strengthened its length will be found to have increased somewhat, and vice versa, if the magnetism be lessened it will be found to have shortened. It is also a well known fact that when a piece of metal is moved toward and from a magnet it causes the magnetism of the magnet to be made either stronger or weaker, according as the piece of metal is moved toward or from the magnet; In the course of my experiments I have discovered that I may avail myself of this peculiar property of a magnet to transmit the vibrations of the diaphragm t0 the electrodes to vary the resistance of the latter without requiring any direct connection between the same. This I accomplish by placing a permanent or electro-inagnet behind, but preferably out of contact with the diaphragm, and placing the electrode or electrodes preferably in the form of buttons in such position with relation to the -magnet, that the pressure upon or between the button or buttons will be varied by and with the variations or changes in the form of the magnet due to the changes in its magnetism. The vibrations of the metallic diaphragm toward and from the end of the magnet cause the magnetism of the latter to be changed, and, therefore, its length or form to be also changed. These variations in length or form of the magnet are transmitted to and vary the resistance of the electrode or electrodes, said magnet, when the electrode or electrodes is or are in the form of a carbon or other button or buttons acting upon and varying the pressure upon or between the same. By such a construction the diaphragm is left entirely free to vibrate to its fullest extent under the influence of the sound waves produced by speaking; the contact between the electrode or electrodes may be made as firm and rigid as found necessary for the best results, Without, in any degree, limiting the amplitude of the vibrations of the diaphragm; and the vibrations of the diaphragm at each side of its central or stationary position, both toward and from the end of the magnet, exert an influence upon the magnet and thereby upon the electrodes. I am, therefore, enabled to obtain a much stronger and clearer transmission of speech than is possible in any transmitter now known to me.

Other features of this invention will be hereinafter described in the specification and I pointed out in the claims.

Referring to the drawings, Figure l represents in vertical section one form of transmitter embodying this invention; a single electrode being shown resting directly against the magnet. Fig. 2 shows an irregularly formed magnet. Fig. 3 shows my invention embodied in a construction, employing two electrodes which are pressed together, more or less, by the change in form of the magnet. Fig.4:showsthemagnet actingupon theflexible side of a chamber containing pulverized carbon or resistant material which constitutes the electrode or electrodes. Fig. 5 shows a horseshoe magnet, in which lateral movement of the legs of the magnet is caused by the changes in its magnetism, and Fig. 6 shows an electro-magnet instead of a permanent magnet as in the other constructions.

In the form of transmitter selected by me to illustrate this invention (1 represents any usual or suitable diaphragm placed back of a mouth-piece a, the same to receive the soundwaves set up by conversation, or speaking, directed toward it or in its vicinity. Back of this diaphragm, which will preferably be of metal, and which I denominate hereinafter in the claims as the magnet influencing member, but preferably out of actual contact therewith at all times, is placed a magnet 17, preferably a permanent magnet, though an electro-magnet may be used if desired, as will be hereinafter set forth, said magnet being of any desired form or shape, it being shown in Fig. 1 as a straight bar-magnet.

In the embodiment of myinvention herein shown, I employ an electrode 0 of carbon or other suitable or equivalent material, said electrode, as shown, being arranged adjacent to and preferably in direct contact with the magnet, the said electrode, as herein shown,

resting against that end of the magnet oppo site the end facing the diaphragm, said electrode being supported in suitable manner, preferably by a stifi arm 0', shown as turned at right angles at its upper end, and threaded to receive the adjusting nut c acting between two ears 0 rigidly supported within the box A of the transmitter, rotation of the nut in one or the-other direction varying the pressure with which the electrode is pressed against the magnet.

In the transmitter shown, the magnet and electrode are included in the primary circuit of an induction coil D, said circuit comprising a part of the transmitting circuit to convey the variations in resistance to the distant receiver, said primary circuit, as herein shown, consisting of a wire 1 leading from one end of the coil to a binding screw'2,by which the magnet is also secured in its position in the inclosing case A back of the diaphragm, the circuit passing thence through the magnet and electrode, through the arm a of the latter, binding-post and wire 4 to the opposite end of the primary coil of the induction coil and a battery 0 included in said circuit. The secondary circuit 5 of theinduction coil, the ends only of which are shown, completes the transmitting circuit and leads tothe distant receiver, and need not be herein shown in diagram or detail as it is the same as in the usual transmitters now in common use.

The operation of the transmitter is as follows, viz:Oonversation directed toward the diaphragm causes the diaphragm to vibrate toward and from the end of the magnet I), though the diaphragm preferably never comes into direct contact with the end of the magnet, for reasons hereinbefore stated. These vibratory movements of the diaphragm, alternately toward and from the magnet in proximity thereto, act to vary the strength or polarity of the magnetism in the magnet, and, in accordance with that peculiar property of magnets hereinbefore mentioned, also vary its form or length at each change in its magnetism however slight that change may be. The variations in the length or form of the magnet act upon the electrode 0, held at one end in contact therewith, to vary the pressure upon the same, and thereby interpose a greater or less resistance in the primary circuit of the induction coil. The variations in the resistance interposed in the primary circuit of the induction coil by the variations in pressure upon the electrode by the magnet, correspond both in number and degree to the number and amplitude of the vibrations of the diaphragm under the influence of the sound- Waves, so that the undulations in the primary. .circuit of the induction coil must correspond with or be the exact counterpart of the vibrations of the diaphragm and the undulations of the sound waves, the result being that a corresponding undulatory current is induced or set up in the secondary circuit of'the coil,

which is received and made audible at and by the distant receiver in usual manner.

By reference to Fig. 1 it will be seen that the diaphragm, being free from contact at either side with any device whatever, is absolutely free to vibrate under the influence of the sound waves, the amplitude of the vibrations beingldetermined solely by the sound waves and in no wise restrained by any device rest ing upon or against it. It will also be seen that, inasmuch as the movements of a piece of metal away from a magnet exert an equal thorough opposite influence upon the magnet from the movements of the same piece of metal toward the magnet, the vibratory movements of the diaphragm receding from the magnet exert an equally strong influence upon the magnet with the vibrations of the diaphragm toward the magnet, so that the full amplitude of the vibrations of the diaphragm is utilized to transmit the effect of the sound waves to the distant receiver. In this respect my improved transmitter differs, as hereinbefore stated, from the transmitters now in use, wherein the vibrations of the diaphragm are mechanically transmitted to the electrode, for, while in the mechanical transmission of the vibrations to the electrode the vibratory movements of the diaphragm at one side the central position alone are utilized, in my improved transmitter the vibratory movement of the diaphragm at each side the central position, both toward and from the magnet, are utilized. Again, it has been found that the electrode or electrodes when held firmly or rigidly respond more accurately to the vibrations of the diaphragm than when supported by yielding springs, yet a rigidly supported electrode if permitted to rest against the diaphragm, as in the transmitter referred to now in use, would practically prevent vibrations of the diaphragm. By referring to Fig. 1 however, it will be seen that in myimproved transmitter the electrode may, and

.preferably is firmly supported back of and in contact with the magnet, so that there can be no reactionary vibrations or movements of the electrode independent of those set up by the changes in form of the magnet due to the vibrations of the diaphragm. The undulatory current traversing the transmitting circuitmust, therefore, correspond exactly with the undulations in the sound waves produced by the speaking.

In Fig. 2, 1) represents an irregularly shaped magnet, in which the action is substantially the same as in Fig. 1, this figure showing that it is possible to carry the magnet to some point quite distant from the diaphragm, to thereby remove the delicate parts of the instrument from the vicinity of the diaphragm, when in such position they would be likely to receive injury.

Fig. 3 represents a construction corresponding somewhat to the construction of the well known Blake transmitter, in which two electrodes e, 6', independently supported upon stiff springs e e, are positioned directly back of the magnet b, the pressure between the electrodes being varied by changes in the form of the magnet due to the vibrations of the diaphragm.

Fig. at shows the magnet acting against the front wall f of a box or receptacle f containing powdered charcoal or resistant material which constitutes the electrode or electrodes, as in the Hunning transmitter, the changes in form of the magnet pressing the flexible wall of the chamber-in or out with greater or less force to vary the pressure upon or between the particles of resistant material within the chamber.

In Fig. 5, b is a horse-shoe magnet, the dia-- phragm being moved toward and from one pole of the magnet, the changes in the magnetism caused by the vibrations of the diaphragm manifesting themselves by a spreading movement of the legs of the magnet, so that the resistant electrode 0 may in this instance rest against the side of the magnet instead of against its end as in Fig. 1.

In Fig. 6 an electro-magnet is shown instead of a permanent magnet, the action of the two being substantially the same.

This invention is not limited to any particular shape, arrangement, or construction of the various parts, as the same manifestly may be varied in many ways and still come within the scope of this invention.

I consider myself to be the first to change the form of a magnet by moving an influencing member in proximity and with relation thereto, and utilizing the change in the form of the magnet thus produced to cause variations in the resistance in the electric transmitting circuit; and my invention therefore, broadly speaking, consists in changing the form of a magnet and thereby the resistance in an electric transmitting circuit by moving an influencing member in proximity to the magnet, the term electric transmitting circuit as herein used and as hereinafter employed in the claim, meaning any circuit which either directly, as when used for a line circuit, or indirectly, as for instance, when constitnting the primary circuit of an induction coil, the secondary circuit of p which constitutes the line, assists in the transmission of speech to a distant receiver.

The invention also includes certain details of construction whereby I am enabled to carry out the principles of this invention.

I claim 1. In a telephone transmitter,a diaphragm, and a resistant electrode adapted to be placed in an electric circuit, combined with a magnet arranged to be directly influenced by the vibrations of the diaphragm, and by its changes in form act upon and vary the resistance interposed by said electrode in said circuit, substantially as described.

2. In a telephone transmitter, a diaphragm and an electrode adapted to be placed in an electric circuit, combined with a magnet arranged to be directly influenced bythe vibrations of the diaphragm, and by its changes in form act upon and vary the pressure uppn the said electrode, substantially as described.

3. In a telephone transmitter, a diaphragm 'and' an electrode adapted to be included in an electric transmitting circuit, combined with a magnet rigidly held between the diaphragm and electrode, in contact with the latter and in position close to the former so as to be influenced and changed in form by the vibrations thereof, whereby the said changes in form of the magnet vary the pressure upon the electrode, substantially as described.

4:. In a telephone transmitter, a diaphragm and a fixed magnet arranged back of and close to the same and to be influenced and changed in form by the vibrations of the diaphragm, combined with an electrode adapted to be included in an electric transmitting circuit, and

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