US1193184A - Telephone-transmitter - Google Patents

Description

A. PLECHER.

TELEPHONE TRANSMITTER- APPLICATlON man APB. I9, 1912.

Patented Aug. 1, 1916.

2 SHEETS-SHEET I wmm ATTO R N EY wlmsssijd I A. PLECHER.

TELEPHONE TRANSMITTER.

APPLICATION FILED APR. I9. I9I2.

Patented Aug. 1, 1916.

2 SHEETS-SHEET 2.

ATTO R N EY ANDREW PLECI-IER, OF LAS ANIMAS, COLORADO.

TELEPHONE-TRANSMITTER.

Specification of Letters Patent.

Continuation of application Serial No. 633,461, filed June 16, 1911. This application filed April 19, 1912.

. Serial No. 691,892.

To all whom it may concern Be it known that 1, ANDREW PLECI-IER, a citizen of the United States, residing at Las Animas, in the county of Bent and State of Colorado, have invented a new and useful Telephone-Transmitter, of which the following is a specification.

This invention has reference to improvements in telephone transmitters, and its ob ject is to produce a transmitter in which is combined the clearness and distinct transmission of a Blake transmitter with the volume and wide range of the Hunnings transmitter with certain advantages possessed by neither.

In accordance with one form of the present invention the speech receiving diaphragm is not supported at the periphery after the common practice, but is free to vibrate at the periphery, being supported at thecentral portion, and in order that the diaphragm may respond vigorously to both the fundamentals of the tones of the human voice and also to the overtones or harmonies, the diaphragm is multi-tuned, so that different parts of it have different natu ral rates of vibration corresponding to the fundamentals and the overtones of speech and other sounds uttered against the dia phragm, wherefore the sound components are to a large extent individually strengthened as compared to sound or speech transmission through diaphragms as ordinarily constructed. The multi-tuning. of the diaphragm is advantageous when employed in connection with other features of the invention, but improved results may be obtained in speech or sound transmission when the diaphragm is not especially tuned, nor need the diaphragm be supported centrally and free peripherally, but the contrary may be true with good results. When the diaphragm is multi-tuned it is customary to employ a metallic diaphragm free tovibrate at the periphery and locally tuned about the marginal portion, while in the path of the peripheral portion of the diaphragm an electrical conducting medium is supported in a manner to be engaged by the diaphragm, the support being of a more or less elastic nature, but loose granules, such as are employed in connection with the Hunnings transmitter, are avoided, and the conducting medium opposed to the diaphragm. is customarily film-like either in the form of a metallic leaf, or in the form of fine powder,

or granules of metal or carbon caused to be strongly adherent to the carrying surface, which latter, however, need not be conductmg.

In another and important form of the invention the use of a metallic diaphragm is avoided, and in its place there is provided a membrane which may be stretched until sufficiently taut for the purposes of the invention, and this diaphragm membrane is provided on one face with a conducting film which may be quite thin, and yet, because of its large surface, will provide ample c0nducting capacity for heavier currents than are possible with the usual granular or Hunnings form of transmitter. Opposed to the conducting face of the membrance, which face is remote from that against which speech is uttered, there is provided a conducting plate which may be polished and then cross-hatched or otherwise treated to provide a multitude of points which not only prevent sticking of the electrodes made up of the plate and conducting film, but provide many points from which electrical discharges may readily pass. Y

By adjusting the back plate, as it may b called, into proper relation to the conducting surface of the membrane, no current will pass when the parts are at rest, but as soon as speech, which may be taken as typical of any sound to be transmitted, is uttered against the diaphragm, the latter is vibrated into and out of contact with. the back plate, thus establishing make-and-break transmis- Patented na i, was. i

sion with the great variation in resistance of such a type of telephonic transmission, but while there is mechanical make-and-break in the circuit, electric make-and-break is avoided, for the broad surface of the conducting film of the membrane and the broad surface of the back contact at once establish condenser conditions, the discharges of which maintain the continuity of the circuit electrically, thereby establishing in effect a variable contact transmitter wherein the variations of resistance is far in excess of the best form of commercial telephone transmitters, and the distant receiver is actuated with commensurate vigor.

The invention will be best understood. from a consideration of the following do i l l tailed description taken in connection with the accompanying drawings forming a part of this specification, with the understanding that while in the drawings different embodiments of the invention are disclosed, the invention is not confined to any strict conformity with the showing of the drawings, but may be embodied in any manner which does not mark a material departure from the I salient features of the invention.

In the drawings :Figure 1 is a more or less schematic representation, in most .part in section, of a transmitter wherein the make-and-break and the condenser effect is produced, but refinements "of construction are omitted. Fig. 2 is a face view of a back contact constructed in accordance with the present invention and wherein the showing may be considered as more or less exaggerated. Fig. 3 is a longitudinal section through a transmitter head with the invention applied, wherein the diaphragm is of the conductive-film membrane type. Fig. 4 is a plan view with parts omitted of a transmitter of the multi-tuned diaphragm type with one of the electrodes in the form of a conductive-film. Fig. 5 is a section on the line 5-5 of Fig. 4, with the supporting base omitted.

In the drawings two general types of transmitter are shown, in both of which a conducting film is provided as one of the electrodes.

In Figs. 4 and 5 is disclosed the multituned metal diaphragm type, while in Figs.

'1, 2 and 3 the disclosure is directed to the membranetype of diaphragm wherein the I circuit may be completely broken mechanically on the movement of the electrodes away one from the other, but wherein the condenser efi'ect maintains the electrical continuity ofthe circuit. transmitter have parts in common, but as the forms-of Figs. 1, 2 and 3 embody a greater departure from the ordinary telephone transmitter than the form of Figs. 4 and 5, the following description will be directed first to the forms of Figs. 1, 2 and 3.

Referring more particularly to Fig. 1, there is shown a support 1 carrying a foot member 2 on which is erected a post 3 in turn supporting a ring 4 engaging about a bead 5 surrounding one end of a mouthpiece 6 into which speech may be uttered, the word speech being .used for convenience of description to mean not only vocal, but other sounds, although customarily telephones are used in a great majority, of instances for speech.

Clamped between the ring 4 and head 5 is amembrane 7 of any suitable flexiblematerial, of which rubber may be taken as an example, but without confining the invention to the use of rubber alone. One side of the membrane 7 has applied thereto a Both forms of the '11 is shown, and these guides receive a foot 12 from which rises a post 13 terminating in a disk or plate 14 having a surface parallel with the film 8. The base 1 carries a screw 15 passing through the post 13 whereby the latter may be adjusted toward and from the i post 3 to bring the plate 14 into the desired relation with the film 8 of the diaphragm 7. Fast to the post 13 is a binding post 16 to which the other lead 17 of the circuit may be connected, and the circuit is customarily charged with a current of high amperage and low potential. That face of the plate 14 toward the film 8 is scored or cross-hatched, or suitably formed so as to present a multitude of points or projections of minute area toward the film 8, not only to prevent stick? ing between the film 8 and plate 14, but to provid a multitude of discharge points.

In Fig. l'the distance between the film 8 when at rest and the plate 14 is exaggerated, for in practice the distance is such that while when the diaphragm is at rest the circuit is broken between the film and plate, the vibratory movements of the diaphragm when toward the plate will cause contact between the film 8 and plate 14, thereby then establishing the circuit to be immediately afterward broken by the return movement of the diaphragm.

In order that the diaphragm may respond in a lively manner to sound waves, it is made more or less taut, so as to have a natural rate of vibration determined by the character of the sounds to be transmitted, and as this rate of vibration may be brought about not only by the tautness of the diaphragm,

but by its thickness and character and otherconditions, no special directions can be given as to this matter, but the mounting of the diaphragm to produce the natural rate of vibration is a matter well within the province of one well familiar with the principles of acoustics.

While the structure of Fig. 1 when properly adjusted will operate for the transmission of speech it lacks certain of the refinements of a commercial type, but will answer for an understanding of this part of the invention so far as the electrical actions are concerned.

Suppose that the instrument of Fig. 1 is l lt) connected up in a telephone circuit in the usual manner of connecting a telephone transmitter, then when speech is uttered into the mouthpiece 6 the diaphragm 7 is set into vibration in accordance with the uttered sounds. The film 8 is moved against the plate 14 in one phase of its movement and out of contact and away from the plate 14 in the other phase of its movement, thus establishing make and break conditions, with the resultant great variation in resistance in the transmitter circuit with correspondingly great variations in the line and commensurate variations at the distant receiver. As is well known such conditions will not result in the intelligible transmission of speech. There are, however, two expanded conducting surfaces represented by the film 8 and plate It, which during the period of break are separated by a very thin air space, while the roughened surface of the plate 14 presented toward the film 8 provides a multitude of fine points from which the current will flow. (in the break of contact condenser conditions are estab-- lished, so that the electrical continuity of the "circuit is maintained by electrostatic induction. The result of this action is that there is produced upon the local circuit pulsating currents closely approaching in degree of variation currents produced by make-andbreak conditions, but still without any break in the circuit when considered electrically, while the sound produced at the receiver has all the characteristics of the original sound uttered against the transmitter and is reproduced with greater intensity and more clearly and naturally than is the case when transmitters as ordinarily constructed are emplo ed.

While the structure shown in Fig. 1 is capable of practical operation certain refinements of construction are advantageous for commercial transmitters, and in Fig. 3 there is illustrated a structure Well adapted for commercial uses. 1

Mounted on a stem 19 through the intermediary of a pivot joint 20 is a head 21, the stem 19 representing either the post of a desk set, or the arm of a wall set, or any other suitable support. The head 21,which may be of metal, or which may be made of other material, is usually approximately circular in outline, and is formed on one face with a recessv 22 of appropriate diameter communicating through an axial passage 23 with another recess 24 in that face of the head 21 remote from the recess 22, and of smaller diameter.

The recess 22 is bounded by an annular rib 25 having an outer rounded edge 26 and surrounding the rib 25 is an annular channel 27. The periphery of the head 21 exterior to the channel 27 is formed with screw, threads 28 adapted to receive the inner threaded wall of a flange 29 extending axially from one face of a cap 30 of a size to inclose the recess 22 and groove 27. The cap 30 is formed at the central portion with a mouthpiece 31 of the usual flaring type common in telephone instruments, and whether or not the head 21 be formed of metal it is customary to construct the cap 30 of hard rubber or some similar material.

The outer end of the recess 21 is covered by a membrane 32 of elastic rubber or other suitable material having that face toward the recess 22 covered with a film 33 of some suitable conducting material of which goldleaf is to be preferred, since it is inert to atmospheric and other like influences, and is a good electric conducting material. Instead of gold, silver or platinum may be used, or aluminum or graphite may be employed, while operative results may be obtained from other conducting materials capable of carrying the desired current, though the conductor be in the form of a film. The conducting film 33 is sutficiently extensive to engage the rounded portion of the rib 25 so as to make good electric contact therewith, it being understood that this bead is made of conducting material, whether or not the head 21 be so made, but for convenience of description it will be assumed that the head 21 is of metal and the rib 25 is also made of metal. The margin of the membrane diaphragm 32 is engaged between two clamping rings 34, 35 of any suitable material, say metal, and these rings may be double walled, as indicated, so that the engaging portions may be made slightly elastic to grip the membrane, and one of the rings, say the ring 34, is formed with a channel 36 in which may be lodged anti-friction inner face of the cap 30. When the parts are assembled, and after the margin of the membrane diaphragm 32 is clamped between the rings 34 and 37 the latter are introduced into the channel 27 and then the anti-friction balls 37 are lodged in the channel 36 which operates as a ball-race-way, and then the cap 30 is screwed on to the head engaging the balls 37 and forcingthe rings 3% and 35 into the channel 27, thus stretching the membrane diaphragm 32 over the rib 25 until the desired tension is established in the diaphragm, whereby the latter may be tuned to any desired degree.

Extending through the passage 23 is a rod 38 surrounded by a sleeve 39 of insulating material, since -the head 21 is made of metal. At one end the rod 38 carries a disk 14 like the disk lat of the structure shown in Fig. 1, and this disk 14 has the face remote from the rod 38 cross-hatched to form a multitude of closely associated projections 40, although these projections may be otherwise formed than by cross-hatching, such cross-hatching being in the form of grooves at appropriate angles to cause-the projections. The grooves may be quite fine and the. projections quite minute, "so that the free face of the disk 14 diameter has more or less the appearance of being roughened, but the points of the projections should lie in as nearly one plane as may be and this plane should be as nearly parallel with the plane of the film 33 as may be, and likewise the points or projections of the disk 14 should be as close as practicable to the film 33 without actual contact when the parts are at rest.

All the parts are shown exaggerated both in size and position in Figs. 1, 2 and 3, this being rendered. necessary by the limits of illustration and the separation of the conducting face of the diaphragm and the face of the disk contiguous to the diaphragm is greater in the showing of the drawings than need be in practice, and the thickness of the film 33 and the size of the projections 40 are exaggerated.

While in the drawings the head '21 is shown as of considerable diameter, it is customarily in practice to make it of about the of telephone transmitters as usually employed in telephgne sets.

That end of the rod 38 remote from the disk 14 is threaded, as indicated at 41, and extends into the recess 24. The threaded end 41 of the rod 38 receives a nut 42 formed on a spring washer 43, which in turn bears against another washer 44. which may be made of some insulating material, such. as

mica, and this washer 44 engages the inner wall of the recess, 25. Surrounding the sleeve 39 between the disk 14 and the inner Wall of the recess 22 is a spring 45 resting at the end remote from the disk 14 against a disk 46 of mica or other suitable insulating material lodged against the inner wall of the recess 22.

' 21 by screws 50 or in any other appropriate manner, the conductor 48 being carried through a perforation 51 in the cap 49. The conductor 48 is included in one side of the usual local transmitter circuit, while the other side of this circuit includes a conductor 52 secured to the head 21 when this head is of metal or to the rib 25 when thehead is of some other material, the purpose being to include the film 33 in one side of the circuit and the disk 14 in the other side thereof, so that the film and disk constitute the terminals of the local transmitter circuit.

When the parts are at rest the film 33 and roughened face of the disk 14 are separated sound waves the film 33 is moved into contact with the many points 40, whereby on one phase of movement contact is made and increased to a maximum, and on the other phase of movement this contact is broken, so that on this respect the transmitter is a make-and-break transmitter with a variable contact agreeable to the extent of vibration of thediaphragm on the one phase of movement of the diaphragm. On thebreak of the circuit the extended surfaces of the disk 14 and film 43 separated by a minute air space become in effect a condenser establishing electrostatic induction, so that there is no actual break in the electrical conditions, the many fine points 40 contributing to the flow of current across the air gap without, however, the establishing of any minute arcs as often occur in the granular type of microphonic transmitter when heavy current is passing and which give rise to the flying effect.

Practice has demonstrated that a much larger current may be employed with the phragm 32 is established by turning the cap 30 to screw it on to or unscrew it from the head 21 to the requisite degree and the relation of the disk 14 to the conducting face of the diaphragm is readily established by means of the nut 42, the ball bearings 37 preventing any twisting of the rings 34 and 35 While the cap '30 is being turned to establish the desired adjustments.

Although the film 33 may be extremely thin it presents a large surface and extensive contact at the rib 25, while the diametric'extension of the disk 14 is also considerable, wherefore ample conducting capacity is provided for the heavy current which may be' employed, and this current as before statedmay exceed, without detrimental effect and with advantage, the current which it is possible to employ with prior commercial types of transmitters.

Some, though not all, of the features of the transmitters of Figs. 1, 2 and 3 are retained in the transmitter of Figs. 4 and 5 where the condenser effect is not realized and where great variation of contact may be brought about by causing the make-andbreak in part only and not throughout the sound responsive elements as occurs in Figs. 1 and 3.

Referring now more particularly to the structure shown in Figs. 4 and 5 there is a base 53 on which is erected a post 54 terminating in an upstanding yoke 55 having at g the free ends of the legs of the yoke bearings 56 for trunnions 57 on opposite sides of a hollow body 58, this hollow body being comparatively flat and rounded at the" edges with one side 59 extended in the form of a neck terminating in an expanded mouthpiece 60, the said mouthpiece communicating with an interior chamber 61 substantially coextensive with the body through the neck 59 by way of the passages 62, while diametrically opposite the neck 59. a passage 63 is formed through the edge wall of the body 58. @ne fiat wall of the body 58 is in the form of a disk 64, the edge of which is threaded to fit like threads in the body portion, so that the disk 6-1 may be applied to or removed from the body at will, whereby access may be had to thechamber 61 when desired.

The body 58 and mouthpiece as well as the removable member 64 may be made of metal or may be made of some material of an electrically insulating character. When the body member is made of metal there is secured to the center portion of the cover member 64 a block 65 of insulating material extending entirely through the member 64, while the opposite wall of the body member 58 has a like block 66 lodged therein.

The interior chamber 61 is sufliciently extensive to receive a disk 67 of insulating material, to the periphery .of which there is applied a tube 68 of some material such as elastic rubber. and may be so constructed as to present the characteristics of a pneumatic tire or the elasticity of the rubber alone may be depended upon for under some circumstances a simple ring of rubber will give good results. This rubber ring or tube is covered with a film 69 of some conducting material of whichgold leaf is to be preferred, although silver or platinum will give good results and even aluminum or graphite may be employed, but not with such advantage as gold. The diameter-of the rubber tube or ring 68 is greater than the thickness of the disk 67, so that the tube projects laterally beyond the plane of either face of the disk 67. Carried centrally by the disk 67 and projecting axially from opposite sides thereof are rods 70, 71, respectively, each secured to the disk 67 by an adjusting nut 7 2 next to the disk, and another nut 73 more distant from the disk, the nuts 7 2 and 7 3 clamping between them a diaphragm 7-1, there being such a diaphragm on each side of the -disk 67, while the diameter of the diaphragm, which is of metal, is such that its periphery engages the conducting film surface 69 of the tube or ring 68 throughout its circumference, the marginal portions of the two diaphragms being electrically connected when at rest by means of the film 69. The rods 70 and 71 are long enough to pass through the respective blocks 65 and 66, and exterior to these blocks the rods may receive This tube is an endless tubelook nuts and each terminates in a binding post 7 6 to receive respective conductors 77, 78 of the local transmitter circuit.

When the structure is assembled, the rods 70 and 71 are secured to the disk 67 in axial relation thereto and project from opposite sides thereof. The tube or ring 68 properly coated with conducting material is then sprung upon the disk where its elasticity will hold it in place, the periphery of the disk being shaped to receive and retain the rubber ring. The nuts 7 2 are applied to the respective rods 7 0 and 71, and then the diaphragms 74 are placed upon the rods and are locked in place by the nuts 73. The cover member 64 having been previously removed, the diaphragm holder so far assembled is introduced into the chamber 61 through the opening left by the removal of the cover member 64, such opening being of sufiicient size for the purpose. The rod 71 is passed through the block 66 and then the lock nut 75 is applied, after which the binding screw of the corresponding binding post 76 is inserted and the conductor 7 8 may be secured to the binding post either at this time or later. The cover 64 may now be screwed into place, the passage in the block 65 for the rod 70 being large enough for the purpose and then the corresponding clamp 9 nut 75 may be applied, after which the conductor 77 may be attached to the corresponding binding post 76, it being understoodthat the diaphragms 74% have been properly adjusted before the assembling of 10 the completed structure. The only rigid support for each diaphragm is at the center, while the peripheral portions of these diaphragms are slit toward the central portion of the diaphragm to form tongues 79 having different natural rates of vibration, and while each diaphragm may have more than one tongue tuned to respond to the same rate of vibration, a sufficient number of tongues are provided to practically .cover the range of vibration of the fundamentals and overtones of a suflicient number of the sounds within the range ofthe normal human voice to cause vigorous selective response of portions of the diaphragm to such tones and overtones whereby the over tones particularly are not choked oi, as occurs with the ordinary peripherally clamped diaphragm and the resultant. transmission closely approaches in naturalness and purity of tone the sounds uttered at the transmitting end of the system.

62 into the chamber 61 and finally emerge 13a at .the passage 63 without the liability of rebound or reflection.

In the structure shown in Figs. 4 and 5 the movements of the tongues 7 9 may be suflicient to cause a break of the circuit at together, and they move simultaneously away from such conducting film, so that there is produced a greater variation in resistance than occurs with the ordinary diaphragm, and this variation of resistance is augmented by the more violent movements of the atuned tongues which respond with increased amplitude to those sounds to which they are tuned. Moreover, the diaphragm being supported at the center only and free to vibrate at the margins is therefore more sensitive to the action of sound waves and .the vibrations are correspondingly more pronounced, wherefore the impulses produced upon the line are more intense and the distant receiver is more vigorously acted upon than is the case in telephone systems as customarily installed.

In both forms of the transmitter shown in the drawings the contact is by way of a conductor filmwh'ether of metal or carbon in some form. Considering the membrane of Figs. 1 and 3, or the tube or ring of Figs. 4 and 5 as being made of rubber or some such material, the film of gold or other metal may be applied by first covering the diaphragm or the tube with a suitable size and then applying a. metal either in the form of a thin foil or otherwise, or in the case of aluminum or graphite the conductive film may be produced by applying a substance mentioned in the form of a paint, or a solution of gun cotton may be applied to the rubber or other like surface in a manner similar to .the production of incandescent lamp films and the gun cotton surface may then be flashed. Experience has demonstrated,however, that the results obtained from forms of carbon for the conducting film are not equal to those obtained from metal, while goldleaf .appears to give the best results.

With the present transmitter packing is of course impossible irrespective of the position of thetransmitter, since there .are no loose particles present as in the granular microphonic element.

Moreover, in both forms of the transmitter as included in. this invention theweight of the parts to be moved by the sound waves is small as compared with the ordinary granular transmitter, wherefore the parts move more vigorously and the overtones or harmonics are not blotted out either actually or effectively.

With the transmitter of Fig. 3 the spring 45 may respond to the impact of the diaphragm, and in [the structure shown in Figs. 4 and 5 the rubber ring or tube will yield slightly, so that in each case there is a yielding back contact. WVhile in the structure of Figs. 1 and 3 there is a mechanical break of contact, electrical continuity of the circuit is maintained by electrostatic induction, and while in the structure of Figs. 4

and 5 there may be actual mechanical break I of contact between some of the tongues and the conducting film, there are always some tongues in actual mechanical contact with the conducting film, wherefore the electrical continuity of the circuit is maintained, but the variation of contact'may be very marked. Again, in the structure shown in Figs. 4 and 5 the selective capacity of the tongues cause the impress upon the transmission line of superposed polyphase currents customarily representing every component of the uttered sound, which in the vast majority of cases is the human voice.

In both forms of the transmitter the diaphragm may be extremely sensitive to the sound waves, while the conducting surface ijs of such large area that it is able to handle any desired amount of current which may be utilized to itsfull extent. Moreover, in the form of the transmitter shown in Figs. 4: and -5 the contact though actual may be exceedingly loose when the diaphragms are at rest, thus contributing to a great range in the variation of contact even to the actual breaking of the circuit at some of the tongues.

In the structure shown in Fig. 3 the parts moving under the impulse of the sound waves may be highly sensitive to sound waves and may be tuned. This admits of the provision of an instrument of the makeand-break electrostatic-induction type of transmitter with a plurality of diaphragms each'difi'erently tuned from the others and all associated, in sound receiving relation to a single mouthpiece, so that the same reinforcement of the components of sounds may be obtained as is present in the form of the invention shown in Figs. 4 and 5. It is feasible to provide as many as twelve diaphragms in conjunction with asinglemouthpiece.

It is not necessary that the free face of the disk presented toward the conducting side of the membrane diaphragm in the structures shown in Figs. land 3 should be cross-hatched or checkered or otherwise roughened in effect, but such formation of said free face prevents cohesion of the disk and diaphragm and is, therefore, to be preferred. It is also advisable that the free face of the disk be highly polished before being roughened, checkered or cross-hatched.

The membrane diaphragm need not be more than simply taut for the natural rate of vibration may be obtained by variations in thickness, diameter, tension or by the use of dampers. The checkering, cross-hatching or roughening of the plate or disk constituting the back electrode is not only effective with respect to preventing cohesion, but increases the electrostatic condition and striking distance of the current by presenting many sharp points to the opposite or movable electrode or cont-act.

Again, when the potential in the local transmitter circuit is considerable, as, for instance, when the source of current comprises quite a number of cells in series, the membrane is very slightly pulled toward the back contact, whereby there is produced an electroscopic balance condition, wherefore the action of the speech vibrations uttered against the diaphragm are correspondingly more effective because "of the condition of unstable equilibrium established.

The transmitter of the present invention differentiates from prior transmitters by several distinctive characteristics, among which may be named the mechanical or physical make andbreak without destroying the electrical continuity of the circuit whereby great variation of resistance is obtainable and at the same timesuch variation is gradual and not sudden as would occur where the mechanical or physical break of the circuit is accompanied by a like break in the electrical continuity of the circuit. The structure of the transmitter provides for an exceedingly great amplitude of vibration in a membranous diaphragm with a coextensive conducting film. The electrostatic pull on the diaphragm which exists causes a readiness for instantaneous action and return to inaction. The checkered or scored back electrode presents an enlarged surface with 1. A telephone transmitter provided with two electrodes in face to face relation and electrodes movable into and out of contact under the action of sound waves, one of said electrodes being in the form of a membrane covered, by a conductive film and the other electrode. being shaped to provide numerous points for contact with a film, said contact points being in fixed relation one to the other. I

3. A telephone transmitter provided with electrodes, one of which is in the form of a conductive film and the other of which is laterally extended and formed with numerous points presented toward the film for contact therewith, one of said electrodes being responsive to sound waves to vibrate under the action thereof and having a range of movement sutficient in one direction to cause contact between the film and more or less of the numerous contact points of the other electrode with varying pressure depending upon the sound waves acting thereon, and also having a range of movement in the other direction sufiicient to entirely I of contact with the other and to contact during its vibration toward the other to varying extents therewith.

5. In a telephone transmitter, a conducting film and a disk-shaped conducting memher in close proximity thereto, said members having the areas of their facing portions sufiiciently extensive to establish an electrostatic relation between them, the conducting film having a resilient backing, and one of said members being related to the other to vibrate under the action of sound waves into and out of contact with the other and to contact during its vibration toward the other to varying extents therewith.

6. In a telephone transmitter, a conducting member having a contact surface divided into a plurality of contacting parts 111 fixed relation one to the other, and a vibratile conductive film in close proximity to the conducting member and having a range of movement under the action of sound waves to engage varying numbers of the contacting parts when moved theretoward and wholly disengaged from the contacting parts when moved in the other direction,

7 A' telephone transmitter having electrodes in electrostatic inductive relation and out of mechanical contact when at rest and related to make physical electrical contact when vibrating under the action of the sound waves to be transmitted.

8. A telephone transmitter having electrodes provided with extended conducting surfaces in electrostatic inductive relation one to the other and also located one with referenc'e'to the other to make physical electrical contact when vibrated under the action of sounds to be'transmitted.

9. A telephone transmitter provided with a membrane diaphragm responsive to sound waves uttered against it and provided on the surface remote from that receiving the sound waves with a conducting film, and a back electrode in electrostatic inductive relation to the conducting film' on the diaphragm and within the range of movement of the conducting film under the action of sound waves to cause physical electric con-. tact between the film and back contact.

10. A telephone transmitter provided with a membrane diaphragm responsive to sound waves uttered against it and provided on the surface remote from that receiving the sound waves with a conducting film, and a back electrode in electrostatic inductive relation to the conducting film on the diaphragm and within the range of movement of the conducting film under the action of sound waves to cause varying physical electric contact between the film and back contact, the back contact having that face presented toward the conducting film provided with numerous contact'points in fixed relation one to the other.

11. A telephone transmitter provided with a non-conductive membrane diaphragm supported at the margin and provided on one face with a conducting film coextensive to the marginal support, and a back contact in operative relation to the conducting film and extended toward the marginal portion of the latter, said back contact having the face presented toward the conducting film formed into a multitude of fixed pointed projections constituting contact points, the diaphragm having a range of movement under the impact of sound waves to cause it to engage varying numbers of the projections when moved toward the back contact and to wholly disengage therefrom when moved away from the back contact.

13. A telephone transmitter provided with a membrane diaphragm having a conducting 80 film on one face, a back contact in operative relation to the conducting film, a marginal support for the diaphragm, concentric radially elastic clamping rings for gripping the marginal portion of the diaphragm, said rings being of greater diameter than the marginal support for the diaphragm, and a cap member for the transmitter movable into operative engagement with the clamping rings to force them axially with relation 90 to the diaphragm support to place the diaphragm under radial stress.

14. A telephone transmitter comprising a body member having a rib outstanding from one face with a channel exterior to and surrounding said rib, and said body member be- 'ing screw threaded exterior to the channel, a cap member having a threaded flange adapted to the screw threads of the body member and of a size to cover the rib and channel, a membrane diaphragm provided on one face with a conducting film and of a diameter to engage the rib and enter the channel exterior thereto, concentric clamp rings adapted to receive between them the .peripheral portion of the diaphragm and of a size to enter the channel outside the rib, said rings being adapted to be engaged by the cap to stretch the diaphragm over the rib, and a back contact carried by the head in operative relation to the film on the diaphragm.

15. A telephone transmitter comprising a body member having a rib outstanding from one face with a channel exterior to and sur- 1 rounding said rib and said body member being screw threaded exterior to the channel, a

cap member having a threaded flange adapted to the screw threads on the body member and of a size to cover the rib and channel, a membrane diaphragm provided on one face with a conducting film and of a diameter to engage the rib and enter the channel exterior thereto, concentric clamp rings adapted to receive between them the peripheral portion of the diaphragm and of a size to enter the channel outside the rib, said rings being adapted to be engaged by the cap to stretch the diaphragm over the rib, and a back contact Carried by the head in operabody member having a rib outstanding from one face with a channel exterior to and surrounding said rib, and sald body member being screw threaded exterior to the channel, a cap member having a threaded flange adapted to the screw threads on the body member and of a size to cover the rib and channel, a membrane diaphragm provided on one face with a conducting film and of a diameter to engage the rib and enter the channel exterior thereto, concentric clamp rings adapted to receive between them the peripheral portion of the diaphragm and of Ali a size to enter the channel outside the rib, said rings being adapted to be engaged by the cap to stretch the diaphragm over the rib, and a back contact carried by the head in operative relation to the film of the diaphragm, said back contact having the face presented toward the film provided with numerous points, and said back contact having an adjustable mounting in the head for determining its relation to the film of the diaphragm.

17. A telephone transmitter provided with a suitable head, a screw cap adapted to the head and provided with a sound receiving mouthpiece, and a membrane diaphragm adapted to the head between the cap member and said head, the head member having a support for the marginal portion of the diaphragm, and holding means for the peripheral portion of the diaphragm outside the support in' the path of the cap member for engagement thereby to readily tension the diaphragm, said peripheral holding means for the diaphragm being provided with antifriction devices between it and the cap. 7

18. A telephone transmitter having normally separated electrodes constructed and associated to make variable contact under the action of sound waves and to maintain the electrical continuity of the circuit, when out of mechanical contact by electrostatic induction.

19. A telephone transmitter having normally separated electrodes constructed and associated to make variable contact under the action of sound wavesand to maintain the electrical continuity. of the circuit, when out of mechanical contact, by electrostatic induction, one of the electrodes having its active surface in the form of a conducting film and the other electrode in the form of a plate with a multi-pointed face presented toward the film.

20. A telephone transmitter having a vibratory sound responsive electrode and a back electrode constructed and arranged to cause a range of vibration of the sound responsive electrode, under the action of sound waves, into contact with the back electrode and out of contact therewith and in the latter case establish electrostatic inductive relations between the electrodes.

21. An instrument of the character described coi'nprising opposed condenser elements one of which is mounted for vibration into and out of physical or mechanical contact with the other, and said condenser ele ments being associated to constitute electrodes for an electric circuit.

22. An instrument of the character described comprising condenser elements one of which is in the form of a conducting film with a vibratile membranous support, and the other in the form of a conducting plate having the surface scored or checkered to present many points in fixed relation one to the other toward the conducting film of the other element, and said condenser elements being associated and the one with the vibratile support having a range of vibration to cause it to contact with the conducting plate, whereby the condenser elements constitute electrodes for an electric circuit.

23. An instrument of the character described comprising opposed condenser ele- "ments one of which is vibratile and movableinto and out of contact with the other and provided with an expanded conducting surface and the other of which is in the form of a conducting plate having a surface in operative relation to the conducting surface of the other element, which surface of the second named element is scored or checkered to present many pointed portions toward the conducting surface of the first named element.

24. A telephone transmitter having a diaphragm tuned to respond sympathetically to the sounds to be transmitted, and a laterally expanded back contact in electrostatic relation to the diaphragm and located within engaging distance of the diaphragm on vibrations of the latter under the action of sound waves in a direction toward the back contact.

25. A telephone transmitter having a diaphragm tuned to respond sympathetically to the sounds to be transmitted, and a lat- Wit.

erally expanded back contact in electro- .or roughened to present numerous conducting points toward the other.

26. An instrument of the character described having laterally expanded electrodes in opposed relation and normally separated as my own, I have hereto af'fixed my sigby an a1r space, sald electrodes belng of connature 1n the presence of two \vltnesses. ductlng matenal and one of the electrodes being vibratile and in closerelation to the ANDREW PLECHER' 5 other to cause the electrodes when charged Witnesses: I

to be in a state of electro-static balance. F. W. LORING,

In testimony, that I claim the foregoing M. Frrswonrn.

Images