US 1818654 A
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Au@ 1l, 1931-' D.A S. s* sTEUARr v 1,818,654
MOUTHPIECE ARRANGEMENT FOR US WITH TELEPHONES AND THE LIKE Filed May 24,- 1930 4 sheets-sheer 1 Aug 11, 1931 D. s'. s. sTEuAR'r 1,818,654
MOUTHPIECE ARRANGEMENT FOR USE WITH TELEPHONES AND THE LIKE Filed May 24, 1950 4 Sheets-Sheet z li @ni Aug. ll, 1931. D. s. s. STI-:UART 1,818,654
MOUTHPIECE ARRANGEMENT FOR USE WITH TELEPHONES AND THE LIKE Filed May 24, 19:50. v 4 sheets-sheet s Aug. l1, 193.1'. n. ss. STEUART 1,818,654
MOUTHPIECE ARRANGEMENT FOIJ USE WITH TELEPHONES AND THE LIKE!Y Filed May-24', 1930 4 Sheets-Sheet 4 l f 1% 576. uw V" .in l`;
' l E) I L0 I l ff; if# l I f1' ma Patented Aug. 11, 1931 UNITED STATES Piiis'lafl vori-ics f MOUTHPIECE ARRANGEMENT FOR USE 71TH TELEPHONES ANDvTI-IE LIKE Application led May 24, 1930, Serial Noi/155,419, and iii Great Britain May 28, 1929.
The present invention concerns improvements in or relating to arrangements for use with telephone instruments and, more particularly, telephone instruments of the desk 0r wall types. The usual types of telephone instrument, as used in the public telephone service, are those known as the wall type and pillar type desk set and, while the invention will be described with relation to the pillar desk set, it will be understoodthat the features of the invention are equally applicable to other constructions of telephone of the type having a fixed transmitter. At present i it is usual in these types of telephone to bring the mouthpiece of the instrument very close to the lips of the user andas only a short mouthpiece is provided it is necessaryl to bring the instrument rightin front of the user.
The present invention has in view an arrangement to enable a user to speak into the telephonewithout.bringing the telephone ink front of him or bringing his lips to the mouthpiece, so that the mouthpiece can. be at a convenient distance away to enable him to write down messages received over the telephone or v to dictate messages over the telephone from papers on his desk.
A further object of the invention is to avoid the mouth of the user being brought near the mouthpiece `and to thereby reduce the danger of infection, while at the same time it ensures eflicient sound transmission so as not to interfere with the efficiency of the public telephone service. In fact, it isfound to increase the eiiiciency. u Y f l One of the features ofthe invention is that a tapering passage extends from an adaptor which fits into the mouthpiece of a pillar type telephone having a bell or cup-sliaped opening, said passage being formed with a number of straight yparts and having an inner surface which will not absorb sound to any marked extent. 4
Conveniently, the ,passage between the adaptor and the mouthpiece may be formed of a series of straight intermediate tubes provided `with sound reflecting :surfaces adapted to reflect sound ywaves whichv are received from onetube in longitudinal direction down the next tube. v
. A second feature of the invention is that the enlarged mouthpiece is arranged to have its open end facing upwards towards the mouth of the user, vand for this purpose the lower end is supportedv just above the base of the'telephone so that, whenplaced von a desk, the user need not lift up his hand when reading or writing, the mouthpiece being so situated as to emciently catch the sound waves proceeding from his mouth.
In using instruments with large mouthpieces according to the invention it is important that foreign noises should be cut out and it is found that this can be effected, according to a further feature of the invention, by providing adjustable meansffor exerting pressure on selected parts of the front and back of the transmitter casing.
According to a furtherfeature of the invention a stand mounted on a base is provided which carries the mouthpiece and the interconnecting tubes extending y to the adaptor, the mouthpiece being adapted to rotate' in a vertical direction with relation tothe tubes, while the stand gis adapted to rotate in ahorizonal direction so as to permit of the mouthpiece being adjusted to any desired position.
A furtherfeature of the invention consists in the provision. of adjustable means by which the adaptor which fits into the mouthpiece of a known type of telephone can be caused to connect therewith in anfafir-tight manner, withoutv necessarily being attached thereto. u Y
These andother features of the inventionl will be better understood by referring to the accompanying drawings in which: I
Figure l shows the front view ofthe novel mouthpiece and stand according to the iII` vention with the stand partlyv in section.k
Figure 2 showsa side view of the'mouthpiece ypartly insection.y
' Figure 3 shows a section on thel lineB--` .of Figure 2, looking in the direction of the arrows, which also illustrates oneformof side tone eliminator. f l
Figure '4 shows apart section on the line 'irregular surfaces.
4-4 of Figure 2, with the mouthpiece parallel to the vertical tube.
Figures 5, 6 and 7 show alternative arrangements for eliminating side tone to that shown in Figures 2 and 3.
Figures 8 and 9 show an alternative arrangement which may be used either for amplifying speech sound waves or for eliminating side tones.
Referring to Figures 1 and 2, a pillar type telephone 10 of well known construction is shown resting on a stand 11 from which a pillar 12 is supported, the pillar 12 serving as a support for the mouthpiece 13 and a tubular arrangement which terminates at its upper end in an adaptor 14 for engaging with the usual mouthpiece of a pillar type telephone such as 10 without its being attached thereto.
The construction of the adaptor 14 and the manner effecting its engagement with the mouthpiece of a pillar type telephone will be better understood by referring to Figure 3. The adaptor 14 which is shown in section is made of metal, bakelite, ebonite or any similar material shaped on its outside so as to conform to the inside of the mouthpiece of a pillar type telephone so that when fitted inthe mouthpiece it fits snugly. Passing through the adaptor 14 is a hole 15 which tapers slightly so as to be slightly larger at the outside than at the transmitter end.
The adaptor on the outside of the mouthpiece is provided with an extension 16 which is threaded on the outside. On'this threaded yportion 16 a tubular member 17 is screwed. This tubular member has a cross section as shown in Figure 3, the wall 18 being inclined at an angle of approximately 45O to the axis of the hole 15 so that sound coming from the right of the tubular member 17 and striking against the wall 18 would be reflected in a direction parallel to the axis of the hole 13 ofthe adaptor 14 s0 as to affect the transmitter.
The inner surface of the hole 15 and the tubular member 17 are made substantially continuous so as to avoid any losses due to At the same time there is a gradual contraction of the cross sectional area as will be seen from the comparative diameters of the horizontal portion 17 and of the lower end of the hole 15.
The portion 19 of the tubular member 17 which is threaded on its inner portion to engage with the extension 16 is also threaded on its outer side as shown and on which is screwed aV milled edged washer 20. A casing 21 of aluminium or the like is provided with a cup-shaped portion 22 having a hole which passes over the outer thread 19, and in which is adapted to be placed a metal cup 23 containing a rubbermember 24 of cross section as shown.
Itwill be understood that the milledwasher 20, the Casin g 21, the metal cup 28 and the rubber 24 are placed over the outer thread 19 before the adaptor 14 is screwed by its extension 16 to the portion 19 of the tubular member 17. It will be readily appreciated that this amount of screwing can be varied as desired so as to permit of adjustment. This adjustment serves to ensure that when the adapter 14 is placed in the mouthpiece as will be described later, the adjustment of the milled washer 2O serves to render the contact between the adaptor and the mouthpiece, both sound-proof and air-tight, thus avoiding any loss in the etliciency of sound transmission which would ensue if there was a leak to the atmosphere.
It has been found that the ordinary telephone transmitter is most eflicient when inclined at an angle of 25 to the vertical with the mouthpiece facing upwards. The arrangei'nent ust described enables the adjustment of the adaptor to the mouthpiece to be readily made with the transmitter at this angle.
The horizontal portion of the tubular member 17 is provided with a flanged extension 25 over which lits a recessed portion 26 of a second tubular member 28. The tubular members fit fairly tightly together and a screw 27 prevents relative rotation after the requisite. adjustment has been made. rThis tubular member 28 has a section at its upper end as shown in Figure 3, the lower end 28 being shown in section in Figure 4, the outside view being clearly visible in Figure 1. This tubular member 28 is provided with a fiattencd surface 29 inclined substantially at an Vangle of 450 to the horizontal portion of the tubular member 17 so that sound transmitted `parallel to the aXis of the tubular member 28 will strike the surface 29 and be reflected in a horizontal direction along the tubular member 17 to the surface 18. The tubular member 28 is tapered as shown so that there is a contracting cross section for the sound waves and at its lower portion the tubular member is provided with a iianged extension 80, Figure 4, similar in general design to the flanged member 25.
The third tubular member 31 having a recessed portion 82 is arranged-to fit over the extension 30 in the manner shown and is secured against rotation by a screw 33. This tubular member 31 has another flat surface 34 arranged substantially atan angle of 45O to the axis of the tubular member 28 so as to reflect sound waves received from the right along the member 28 to the surface 29.
The horizontal portion 85 is especially shaped having a grooved portion 39 which is adapted to lit into a half annular portion 40 integral with the pillar 12 and is secured therein by a half annular member 41, the two half annular portions being provided with flanges 42 and 43 through which screws 44 surface isk inclined approximately at right tions serve to embrace the steppedportion 49d and are secured by screws 52 to the leni larged portion 47 of the tubular member 31.
The arrangement issuch as to permit the tubular member 49 to rotate with a certa-in amount ofifriction relatively to the tubular member 31. The tubular member 49 is also provided with a flat'surface 53, which ,flat
angles to the surface 34 so as to reflect sound waves received parallel to the axis of the mouthpiece 13 in a horizontal direction to the surface 34. ,s The upper portion ofthe member 49 is provided with a flanged eXtension 54. Over this extension is fitted a rubber orcork ring 55 which can best be seen from the sectional view in Figure 2. On the outside of the rubber or'cork ring and stretched across the opening in the tubularv member 49 is an openly woven silk diaphragm 55a which is, rendered taut when the portion 56 of the mouthpiece 13 is forced over the outside.
The effect of the forcing of the member 56 over the rubber or cork ring and the silk is to ensure the mouthpiece sufficiently tightly in position on the yflanged extension v34 and it also serves to prevent undue resonance of the mouthpiece. The mouthpiece 13 isshaped as shown so that at its inner end `the cross sec* tion expands in a similar way. to the manner in which the cross section has `beenjexpandying from the transmitter itself. Ata distance along the mouthpiece thereis a change, however, so that at the actual outer end of the mouthpiece the taper is not as great as at the intermediate portion. v
For convenience such a shape of mouthpiece istermed bell shaped or cup'shaped Ifrom its somewhat resembling these articles at its outer end,` and it will be appreciated that this description only applies to the vouter partY of the mouthpiece and not to they whole of the mouthpiece. j
The mouthpiece is conveniently made of spun metal and, as shown, is provided with an outer lining 57 of cork or like sound-proof material, the object being to ensure that-there will not be blasting due to sound resonance j and side tone penetration aecting the metal mouthpiece 13.4 1
It might be desirable to have a still' further inner lining of cork so as to prevent anyposback stop for positioning the telephone when sible blasting7 due to speaking too loudlyr and `too close to the mouthpiece.
It' will be understood that while cork is mentioned any other suitablesound insulating lining could be provided. An alternative arrangement is that the aforesaid tubular members are made of bakelite, and the mouthpiece member 13 and the member 49 may then be moulded in one piece. v f
On the outer end of the tubular mouthpiece is provided a ring 58. The ring has a curved edge 59 and an inner cylindrical portion 60,
a diaphragm 61 of openly woven silk similar to thediaphragm 55a is secured in position on the ring by a second metal ring 62 which justts over the ring 60 and in being placed in position'draws the diaphragm 61 taut.
On the outer side of the ring 62 is a rubber or cork ring 63 which, being interposed between the outer side of the ring 62 and the inner surface of the mouthpiece 13 serves'to secure the ring 60 in position and prevents undue resonance of the mouthpiece. The purposes of the diaphragms 61 and 55a are to reduce echo and blasting. e
The pillar 12 extends into a socket 63 forming part of the casting of the stand 11. The arrangement is such that the height of the pillar 12 canbe adjusted, screws 64 being provided for securing the pillar 12 in the best g5 position.
Thestand 11 is providedwithtwo verticall extensions 65 and 66 provided ywith milled headed and rubber-tipped positioning screws 67 and 68ffrespectively and with a pivot arm 69 which is secured by ascrew 7 0 and is provided with a knob 71 to facilitate it being moved up and down as required. j
While the pillarV type telephone is being placed on the stand it is convenient to have the arm 69 lying fiat with the stand 11, but before positioning the pillar type telephone itr would be raised to the position shown in .Figure 2 of the drawings and would serve as a the'positioning screws 67 and 68 are in contact therewith. By this meansit will be appreciated that the pillar typetelephone will alwaystendto be maintained in one denite position on the-stand Without its being attached thereto. f
The stand 11 isalso provided witha downwardly depending wall 73 and with a Vcentral pivot 74. About this central pivot 74 a wheel shaped base 75, having spokes 76 and carryl ing on its outer rim elongated legs. 77, is adapted torotate. These legs 'are provided 'at their lower. extremities with rubber buffers 78 so as not to damage thefurniture and to give a friction tight grip on the table.l
In this construction asno ball race is prol' vided there is suflicient friction in the rela,-
tive movementof the stand 11 to the base 75 as ,to ensure that during dialling there will'be no movement of the instrurr'ient,` althoughit kthe back of the transmitter casing. A,found that when these are placed in a suitable is quite feasible to turn the instrument right round without any difficulty on its stand.
On the casing 21 it will be noted that there is abracket member 80, see Figure 3, and secured at each end of the bracket there are milled headed screws 81 and'82 respectively. The milled headedv screw S2 has an extension 83 carrying an insert 84 at its lower end which is provided with a rubber buffer 85. The lower milled headed screw 81 is hollow at its 'lower end and in this hollow is fitted a spring 87 and a rod 8S having a cup-shaped eXtension 89 containing a rubber ball 90. These rubber members 85 and 90, as shown in Figure 2, are arranged to press on the front and 1t is :mission is increased considerably, particular'- ly when one endeavors to speak in noisy situations where there is traffic, moving machinery, or the like.
An alternative arrangement for bringing about this result is shown in Figure 5, which consists of a C or U shaped steel spring 100 having rubber pads 101 and 102 adapted tol press on the front and rear of the transmitter casing, the pressure of the springbeing normally such as to exert an excess of pressure on the transmitter casing.
The milled headed screws 103 and 104 are provided for permitting the adjustment of the pressure to that found most suitable according to the particular locality and the particular instrument employed. Such an adjustment would, of course, readily be made by simply listening to the side tone on the receiver when no conversation is proceeding. Itis found that in certain positions amplification of the side tone and of t-he actual speech may be effected and this may be of advantage in quiet locations. It will be understood, therefore, that the easiest adjustment for any 'location can best be determined inthe loca.- tion itselfby actual test of the different positions and pressures.
It has been found that a pair of springs ar ranged diametrically opposite to each other as shown vin Figure 5 produce enhanced effects.
An alternative device to that shown in Figure 5 is illustrated in Figures 6 and 7. This side tone eliminator consists of a pair of forked arms 110, 111, the ends of which are provided'with rubber pads 112, 113, the arms are hinged together by a spring 114 which exerts pressure so as to tend to bring the rubber padded ends 112 and 113 together. Handles 115 and 116 are `provided for opening the forked arms as normally held closed by the spring 114.v
The device is slipped on the transmitter casing, as shown, so that the pads 112 and 113 are at diametrically opposite points, the best position must, of course, be found by trial as before described.
An alternative device which may be used either for amplifying speech sound waves or for eliminating side tones is shown in Figures S and 9. The device comprises a flanged disc 121 having a central hole 122 and two pairs of arms 123 positioned at right angles to one another. Each arm 123 is bent at right angles and terminates with a screw-threaded boss 124, each boss is provided with a knurled headed screw 126, the terminal end of which i i is provided with a rotatable cup containing a rubber pad 127.
In use the device is fitted to the tubular member 17 by means of the milled washer 20 and the adaptor 14 in a similar manner to casing 21, see Figure 3.
lVhen the telephone mouthpiece 10 is placed in position over the adaptor 14 the rubber pads 127 of the screws 126 at the ends of the arm 123 are in position around the rim i 125 of the transmitter casing. The disc is now rotated until each pad 127 of a pair of diametrically disposed arms are adjacent the ends of the transmitter bridge in the casing 125, and the other two pads are positioned at i right angles thereto.
Vhen it is desired to amplify the speech sound waves, the pads at the ends of the transmitter bridge are tightened to exert the necessary pressure on t-he rim 125 of the casing at the point supporting the bridge, and when it is desired to eliminate extraneous noises, the pads at the ends of the bridge are screwed back and the remaining pair of pads are tightened instead, so as to eXert pressure N' at points at right angles to the former pair.
1n order to explain the operation and the method of using the instrument, it will be assumed in the first case that the pillar type telephone is noton the stand. LTo apply the 20 is then tightened up. It is assumedduring this time that the screws 81 and 82 are screwed well back so as not to interfere with the operations which have'been described.A
It is then possible t-o adjust the pressure of the members 85 and 90 on the transmitter casing by simply lifting the receiver, listening vto the side tone in the locality, and turning the screws 81 and 82 accordingly.A
It will be understood that the instrument The adaptor 14 is then placed in the il ilo To secure anV efficlientm sound-proof Contact the milled headed nutV asthebest distance, this will depend upon the according to the invention canbe applied to anyn pillar type telephone in any situation and each telephone and each situation will require its own adjustment.
Having placed the telephone intolposition without in any way affecting the public exchange instrument, it will 'now` be possible to use thelinstrument' The pillar type telephone 'may be placed with themouthpiece 13 aboutia foot away from the speaker and adjusted so as to face towards the mouth o f the speaker. While afoot is mentioned individual speaker and, furthermore, it should be noted that speech has been found uto be effectively transmitted from as far as the receiver cord will reach, if not further. It is possible, therefore, to have the telephone about a foot to 18 inches awayy from the user while leaving the desk in front of him quite free. The sound waves from the speakers voice which reach the mouthpiece'pass down the mouthpiece, resonance and blasting effects beingprevented by the cork lining and rubber or cork pressure rings, andthese sound waves strike against the surface 53 of the tubular member 49. As this surface is substantially at an angle of 15C to that of the sound waves, these will be reflected on to the surface 18 and thence down the opening 15 to the orifice of the telephone. l
This arrangement is found to transmit speech very efliciently and, therefore, enables the speaker to speak at a considerable distance from the telephone,
It will be noted that the arrangement of the surface 53 is such that whatever the relative positions of the mouthpiece 13 and the tubular member 28 it will always reflect the vsound waves received from the mouthpiece on to the surface 34 in such a direction that the Vsurface 341 will again reflectfthem along the tubular member 28. This secures the ymost eflicient and pure transmission of speech.
It is possible with the instrument to adjust the mouthpiece to any desired position. If
, adj ustment .is required iny a vertical plane, this Ycan be done simply by rotating the mouthpiece. 13 withthe tubular member 19 in a vertical plane, for instance, the mouthpiece 13 can be turned towards a speaker at the other side of the table or desk to the speaker usually using` the instrument. On'the other hand, if the one who is to use the telephone is at the side of the table, then it is possible to make the required adjustmentbyrotating the whole instrument onfthe stand 11.. n.
vIf a speaker who is at the side is also standing by a table, a double adjustment becomes necessary as will be readily understood,.this `ispossible bymeans of the invention in this case moving both the mouthpiece 13 and the stand 11.
It ispossible with an instrument such as has been described, tohave the instrument lo- It will'be understood that the invention Ahas .been described by way of example only, but
considerable modifications can be made in the constructional details without departing from the spirit of the invention.` Y
What I claim is: f
1. An arrangement for enabling a pillar or wall type telephone to be used eihciently while enabling the user to speak at a distance, comprising-'an adaptor for fitting into the mouthpiece of the telephone, an enlarged l.
mouthpiece having a bell or cup-shaped opening'and atube connected at one end to the adaptor and at the other'to the enlarged mouthpiece and having a non-sound absorbing inner surface forming atapering passage between the adaptor and the enlarged mouthpiece, said tube being formed of a niunber of straight parts. f
Q. An arrangementfor enabling a pillar or wall type telephone to be used efficiently *15 while enabling the user to speak ata distance comprising an adaptor for fitting into the mouthpiece' of the telephone', an enlarged mouthpiece having a bell or cup-shaped opening and a tube connected atone end to the adaptor and at the other tothe enlarged mouthpiece and having a metal inner surface forming a tapering vpassage between the adaptor'and the enlarged mouthpiece, said -`tube being formed of a number of straight parts.
3. An arrangement for enabling a pillar or wall type telephone to beused efficiently while enabling the useV to speak at a distance, comprising Van adaptor for fitting into the mouthpiece of the' telephone, an enlarged mouthpiece and a series of straight inter-connected tubes connecting the adaptor to the mouthpiece and provided with sound reflecting surfaces adapted to'reflectsound waves which kare received from one tube in a longitudinal direction down the next tube.
4. An arrangement for use with a'desk or table telephone transmitter comprising an enlarged mouthpiece, a tube connecting' Said mouthpiece to said transmitter and having a passage for efficiently transmitting sound and vmeans Afor supporting said mouthpiece so that its lower end is supported just above thebase of the telephone and itsopen end faces vupwardstowards the mouth of the user.
5. An arrangement for use with a pillar type telephone comprisingffa stand, a pillar extending from said stand,: an enlarged mouthpiece, an arrangement of interconnected tubes terminating at one end in said mouthpiece and arranged to be supported by said pillar, an adaptor inwhich the other end of said tubes terminate and shaped so as to fit intothe mouthpiece of a pillar type telephone mounted on said stand and means for enabling said mouthpiece tobe rotated in a vertical plane. y
6. An arrangement for use with a pillar type telephone comprising a stand, means for positioning a pillar type telephone. on said stand, a support connected to said stand, an adaptor, an enlarged mouthpiece and an interconnecting tube having a passage for efficiently transmitting sound from said mouth- `piece to said adaptor, all carried by said support and adjustable means by which the adaptor can be caused to connectfwith the mouthpiece of the telephone in an air-tight manner. Y
7. An arrangement for enabling a pillar or Wall type telephone tobe used efficiently While enabling the user to speak at a distance, comprising an adaptor for fitting into the mouthpiece of the telephone, an enlarged mouthpiece having an elbow, a series of straight interconnected tubes connecting the adaptor to the mouthpiece and provided with sound reflecting surfaces adapted to reflect sound waves which are received from one tube in a longitudinal direction down the next tube, and means for rotatably mounting said elbow on horizontal tube of said series so as to permit of said mouthpiece being moved in a vertical plane.
8. An arrangement for use with a desk or table telephone transmitter comprising an enlarged mouthpiece having an elbow, a tube connecting said mouthpiece to said transmitter and having a passage for efficiently transmitting sound, means for supporting said mouthpiece so that its lower end is supported just above the base of the telephone and its open end faces upwards towards the mouth of the user, and means for rotatably mountingsaid elbow in a horizontal plane at the end of said tube so as to permit of the mouthpiece being moved in a vertical plane.
9. An arrangement for use with a pillar type telephone comprising a stand, a pillar extending from said stand, an enlarged mouthpiece, an arrangement of interconnected tubes terminating at one end in said mouthpiece and arranged to be supported by sa-idpillar, an adaptor in which the other end of said tubes terminate and shaped so as to fit into the mouthpiece of a pillar type telephone mounted on said stand, means for enabling said mouthpiece to be rotated in a vertical plane, a base for said stand and means j for rotatably supporting said stand on said or table telephone transmitter comprising an enlarged mouthpiece having an elbow and a tube connecting said mouthpiece to said transmitter and having a passage for eiiiciently transmitting sound, means for supporting said mouthpiece so that its lower end is supported just above the base ofthe telephone and its open end faces upwards towards the mouth of the user, means Jfor rotatably mounting said elbow in a horizontal plane at the end of said tube so as to permit of the mouthpiece being moved in a vertical plane, a stand for supporting said mouthpiece and tube and a base on which said stand is rotatably mounted.
1l. An arrangement for enabling a pillar or wall type telephone to be used eiiciently while enabling the user to speak at a dis, tance, comprising an adaptor for fitting into the mouthpiece of the telephone, an enlarged mouthpiece, a series of straight intermediate tubes connecting the adaptor to the mouthpiece and provided with sound reiiectingsurfaces adapted to reflect sound waves which are received from one tube in a longitudinal direction down the next tube, and a sound absorbing material such as cork lining inserted in said mouthpiece to prevent blasting and distortion.
l2. An arrangement for use with a desk or table telephone transmitter comprising an enlarged mouthpiece, a tube connecting said mouthpiece to said transmitter having a passage :tor efliciently transmitting sound, means for supporting said mouthpiece so that itsv lower end is supported just above the base of the 'telephone and its open end faces upwards towards the mouth of the user, and a sound absorbing material such as cork lining inserted in said mouthpiece to prevent blasting and distortion.
13. A telephone transmitter, a casing for said transmitter, means for exerting pressure on parts of said casing at opposite sides and means for exerting pressure on parts of saidy casing at right angles to the parts on which pressure is exerted by said first means.
14. An arrangement for use with a pillar type telephone comprising a stand, means for positioning a pillar type telephone on said stand, a support connected to said stand, an adaptor, an enlarged mouthpiece and an interconnecting tube having al passage for eiliciently transmitting sound from said mouthpiece to said adaptor, all carried by said support and adjustable means by which the adaptor can be caused to connect with the mouthpiece of the telephone in an air-tight manner, compriisng a cup of rubber fitting over the outside of the adaptor and a washer adapted to be rotated on a screw thread so .as to cause the cup to press against the mouthpiece of the telephone when the adoptor is in position in the mouthpiece.
15. An arrangement for enabling a wall or desk-type telephone to be used eliiciently vso While enabling the user to speak at a distance, comprising an .adaptor for fitting to the telephone and an enlarged mouthpiece having a long passage extending to the adaptor and including a number of sound deiecting surfaces suitably arranged and designed for transmitting sound eciently to the telephone.
In testimony whereof I aix my signature.
DOUGLAS STUART SPENS STEUART.