US628246A - Telephony. - Google Patents

Description

No. 628,246. Patented July 4, I899.

M. H'UTIN 81. M. LEBLANC.

TELEPHONY.

(Application filed Dec. 6, 1897.)

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No. 628,246. Patented July 4, I899. M. HUTIN & M. LEBLANC.

T E L E P H 0 N Y.

(Application filed Dec. 6, 1897.)

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No. 628,246. Patented July 4, I899. M. HUTIN & M. LEBLANC.

TELEPHONY.

(Application filed Dec. 6, 1897.)

:No Model.) 5 Sheets-Sheet 3.

No. 628,246. Patented July 4, I899. M. HUTIN & M. LEBLANG.

TELEPHONY.

(Application filed Dec. 6, 1897.) (No Model.) 5 Sheets-Sheet 4.

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No. 628,246. Patented July 4, I899.

. M. HUTlN 81. M. LEBLANC. v

TELEPHONY.

(Application filed Dec. 8, 1897.) rNo Model.) v 5 Sheets-Sheet 5.

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UNITED STATES PATENT OFFICE] MAURICEXH/HTIN ND MAURICE LEBLANC, or PARIS, FRANCE, ASSIGNORS 'ro THE soorErE ANONYME POUR LA TRANSMISSION DE LA FORCE PAR LELECTRICITE, OF SAME'PLACE;

TELEPHONY.

SPECIFICATION forming part of Letters Patent No. 628,246, dated July 4, 1899. Application filed December 6. 1897. Serial No. 660|9l1t (No model.)

September 18, 1895, No. 5,660; in Belgium 7 January 27, 1896, No. 119,552; in Switzerland January 31, 1896, No. 11,881; in Italy Febru: ary 6, 1896, No. 40,845/138; in England January 29, 1896, No. 2,107, and in Spain February 7, 1896,- No. 18,640,) of which the following is a specification." I

Our invention has referenceto a new method of and apparatus for telephonic transmission,

which is applicable to simplex telephony as well as to multiplex telephony and is in the nature of an improvement upon the system of simplex and multiplex telephony shown and described in our Patent No. 596,017, 1

:5 granted on December 21, 1897; In the said former application we have shown-thatit is practicable to obtain telephonic transmission between two or more stations by normally charging or exciting the line, and thereby the 0 transmitters and receivers, with alternating currents of a definite frequency and by modifying either the amplitude or the wave form of the normal currents by and in accordance with the sound-waves which are to be trans' 3 5 mitted.

Heretofore, before the invention of the system of telephony set forth in our aforesaid application, telephone-lines orthc transmitters associated therewith were either normally not 40 charged or excited at all or,- if normally excited, were soexcited by continuous current, so that the invention shown in the said application is distinguished from all former systems by the use of uormally-maintaineda1-, 5 ternating currents in the transmitters and receivers. -In the said alternating-current system of telephony, however, the normal alternating currents had to be of such frequency as not to produce by themselves sufiicient sound in the receivers to prevent the successful transmission of speech. F

One part of our present invention difiers from that set forth in our aforesaid patent in that the normal or exciting currents which are maintained are made to so act upon the receivers that no sound or, at least, no disturbing sound is produced by them whatever be the'frequency of the currents employed so long as they are not modified by the action of the transmitters. For attaining this end we employ multiphase currents acted upon by a multiphase transmitter and actuating a multiphase receiver.

It is well known that the amount of energy transferred by any symmetrical system of multiphase currents is normally constant from instant to instant. It follows from this that it is possible to so organize a receiver that no appreciable vibration of its diaphragm is caused by the passage of the exciting multiphase currents if the effective value remains constant, while at the same time any suitable variation in the magnitude of the excitingcurrents caused by creating voice-waves before a properly-arranged transmitter will set up vibrations in the receiver-diapliragln. \Ve

thus secure the advantages of the improved system of telephony disclosed in our abovementioned patent and avoid the limitations of the same or the objections that might be urged against the same.

It will be seen that ourimproved system of telephony as thus far indicated involves the production by the action of a suitable transmitter excited by multiphase currents of certain electrical variations corresponding to the sound to be transmitted. \Ve call such variations speech waves. These speechwaves in accordance with the above definition arein reality nothing but the variations of the effective value of the alternating exciting-currents of given frequency produced by the action of a transmitter upon these currents.

Ihw ill be shown more fully hereinafter that 5 it is necessary that the exciting-currents in the receiver should be of'the same frequency and of the same'phase as the exciting-curused at the origin for the excitation of v the transmitter. We have discovered that speech-waves generated by the action of a transmitter excited by a, current of a given frequency can be used to produce speech in a receiver only when the latter is excited by onrreutapfthe same frequency. If this condltion'jsfulfilled, proper telephonic transmissionresults; .bu'tit the frequencies of the exciting-currents -in transmitter and receiver, respectively, are different thereceiver will cease to reproduce the sounds acting upon the transmitterdiaphragm. When these free by alternating currents of a frequency COITQ" quencies are different, the sounds produced by the receiver will he urrintelligib le,and if the diderenceof these frequencies becomes sufficiently great the receiver ceases to produce sound. These principles are ntiliz'edin our improved system of multiplex'telephony. To

generate at various transmitting-stationsspending to the frequency of the exciting-cu 'rroute of the codrdinated'transmitter.

Suppose the frequency of the exciting-currents of a particular receiving-station to be to. It is obvious that when several of the transmitters are in operation the receiverof this station maybe exposed to the action of the speech-waves generated by an excitingcurrent of the frequency or and also totheaction of speech-waves generated by exciting currents of other frequencies.- It will here;

inafter appear that the speech-waves generated by the exciting-currentof the frequency mwill combine with the receiver exciting currents of-the same frequency to produce the proper sounds in the receiver,- while the s'peechwa'ves generated by exciting-currents of other frequencies will practically 'failto aifect the receiver-diaphragm; {It therefore appears that our in vention contemplates the generation of a number of speech-wavesby' frequencies, the transmission of the speechwaves over aset,

exciting-currents of different of line-wires, and. a combination; of. these speech-wavesin a plurality of receivers with exciting-currentsof frequencies so chosen.

that they will in each receiver I reinforce or bring out the-particular speech-waves to which it is desired that that particular receivershall respond. H

Our inventionalsocomprises animproved call system p'artichlarly adapted for'use in connection with. our multiplex system-just described, all ofwhich will moretullyap pear from the .followihgi detail description with reterence to' the annexed drawings, in p Figure-1 is aview, partly in section, of anv improved transmitter adapted for use in our cluding the calling devices. a I In Fig. 1 is shown a microphone-transmihmetrically opposite magnet-cores 6 6' are oon- I nected together, preferably in series, 'as'sre also the system. Fig. 2 is anend view of the receiver 7 with the mouthpieceand diaphragm removed.

Fig. 3 is a central vertical section of the same;

Fig. 4 is a diagram ot our improved system I .ofsimplex telephony. Fig. 5 is an illustrative diagram of arrangement of apparatus serving 7 asa'basis fortheoretical considerations. Fig. 1 75v 6 is a' general view-of .ourimproved system of multiplex telephony without. the calling devjces. Fig. 7 is a diagram of the complete,-

equipment of a single s'tatiom. Fig. Me a dia-' 4 gram of our improved multiplex system, in-

ter 24, which may be of any preferred type, but is-here shown as composed of a numberof carbon blocks 1 1., connected by carbon pencils 2 2., mounted on the sounding-board- 3 and arranged in two distinct circuits.

the form shown the blocks 1 and pencils it" constitute a' part of one circuit, having terminals at the binding-posts 4 5, while the blocks 1-' and pencils 2 constitute part of an-' other circuit, having terminals at the bind ing-posts4' 5. Any vibration of the soundiug-board will cause simultaneous and similar variations of the resistance of each ofthe two circuits. This structure represents, in effect, two microphones having a soundingboardcommon to both. his evident-that this-is the equivalent of two entirely independent microphones, which arose arranged that both are afiected by the same sounds simultaneously. 4

The construction of the receiver 23 is shown in Figs.,2 and 3. In' this structure 6 6' and It will be seen that the free ends ofthe cores are enlarged'to form pole-pieces. The cores,-

. 7 7 are symmetrically-arranged soft-iron cores I mounted on the soft-iron yoke-piece 8, which.

r95 is composed of nested ring-laminae, as shown.'

with their pole-pieces, are split to prevent i.

eddy-currents. .Each core is wound with a bobbin such as 9 'lo 10', &c., the leading-in. .wires being carried through the opening 11in the case 12, as shown in Fig. 2.- The dianary'receiver. The bobbins upon the diabobbins 1O 10', on the diametrically opposite cores 7 7', constituting parts of two independent circuits whose coeflicient of mutual induction is practicallyzeror, The con-- nections are somade'that a current which will create. a, north pole in 6 or in 7 willcreate a south pole in 6 or in-7.

' The arrangement ahd con'nections of our system in its simplest form will be underphragm 13 is similar to that used in an ordistood byreference to Fig. 4. In this figure 'the'trausmitter 24 may be similar in form to the transmitte'r'shown in Fig.1, but is here more simply indicated as consisting of a diaphragm 3, apair of contact-blocks 1 1', and a second pairot' vcontact-blocks2 '2'--,'bearing upon the contact-blocks 1'1. 23 shoulti'preferably be of the "form shown in The --receiver mitter-contacts 1 2 are connected in series with the receiver-bobbin 6 and with one of the circuits of thetwo-phase generator 14,

- and the attraction upon receiver will be constant; The diaphragm will be bent toward the cores to a certain ex:-

while the other pair of I transmitter-contacts 1 2 are connected in series with the receiverbobbin 7 and with the other circuit of the twophase generator 14. This two-phase genorator may be of anyordinary type and may have its field-magnets excited from a source of direct current 15. It is designed to maintain' upon the line and-in the bobbins of the receiver quarter-phase currents of constant frequency and constant potential, Suppose the currents passing in the two circuits thus constituted when the transmitter-diaphragm is as rest to be represented by the equations i=Isin. 2 1r cat.-

and

'i-=Icos.2 1: out Since these currents are in quadrature and the two sets of receiver-magnet coils are displaced by ninety degrees, (see Fig. 2,) a rotary field will be produced in the receiver, the diaphragm of the tent, but will not vibrate so long as the sum of the euergiesof the line-cu rrents is constant. The conductivities of the two circuits in which these currents z and i flow will be practically the same and will be. constant so long as the transmitter-diaphragm is at 'rest; When,

however, the diaphragm is caused to vibrate,

simultaneous and equal changes in the conductivities of the two circuits will be prodnced. Each of these conductivities will be equal to a constant plus a time function depending upon the sounds acting upon the transmitter or when K is the conductivity of each'of the circuits, including the microphone- OOIIIBGUS K C j (i). Designating the'electrotnotive forces generated by the alternator and acting upon these two circuits by e=Esin.21r ml and 'e',=Ecos.27rwt and supposing the self-induction to be .negligible in comparison with the resistance, the currents passing when sound is being transmitted will be The attraction developed on the plate will be H -re.k +tf where 79 is a'constant depending on the parand ticular receiver, or, substituting herein the values of i and 'i' and reducing,

F k 2 f0) +1". ll-

In an ordinary telephone-receiver with a permanent magnet-core the magnetic fluxes are the sum of the magnetic fluxesdeveloped by the permanent magnet and also by the telephonic current flowing in the coil. If g represents the first of these magnetic fluxes and q) (t) the second, the'attractive force actingon the diaphragm will be equal to [9+ 9" (01 [9 9 0 9 where 70 represents a constant. Of the terms of this equation g is constant and (p (t) is negligible, being the square of a small quantity, so that the term 2 g (p (t) is the expression of the only attraction which causes appreciable motion in the plate.

- Returning now to the equation for the force acting on the diaphragm in our improved sys: tem, in which the cores are of soft iron and have no permanent magnetism which we found to be v,

E= k E2 2 f +1 (0], we observe at once that it is of the same form as the equation just considered. The term 70 E 'C corresponds to the term k g in the equation of the ordinary receiver and represents the constant pull which is produced by the magnetism generated in the soft-iron core by the action of the two-phase currentswhen the volume of these currents is not varied by the transmitter. The second term 70 E 20 f (t) correspondsto the term It, 2 g (t) in the equation of the ordinary receiver and represents the pull which reproduces speech. That it does reproduce speech is evident f om the fact that it is a simple function of the vibrat'onal period of the transmitter-diaphragn1.. The" irdtei'ln It, Ef (1) corresponds to the third term k m (t) in-theequation of the ordinary receiver and is negligible, case. This demonstration shows that a system constructed asshown in Fig. 4 will reproduce'spech, andthat the original alternatingcurrents will not 'afiect the receiverdiaphragm, solong as their values remain constant. ble to provide. a practical and operative simplex system, which may be excited by alternating currents of any frequency whatever, though we prefer in practice, for various reasons, to so design the generatorsin all of the systems described in this application that the frequencies of the exciting cnrrents are lower than the frequencies corresponding to the lowest tones within the range of the average human voice, but well audibility. The system thus constructed is,

however, open to .mitting a single at least three as in that I We have thus shown how it is possiwithin the limits of 1 the objection that for transtelephonic message four or line-wires are required for a j complete metallic circtiit,and that even when a ground return-jsemployed two line-wires must be used; but this disadvantage disappears when the system is multiplexed, as will be'presently described; but before proceeding with this description it will be useful to consider what woultLbe the result if, in a system sucl as has been abovedescribed the alternating'jcu'rrent-s which excite the receiver had-a'frequency difierent from that of the alternating currents which excite the transmitter. To illustrate the effeets'which would .-be produced under these conditions, we have imagined the system shown in Fig; o rin which 1 2 1'-2'.are the microphone-contacts, as before, and 67 two of the coils of the receiver.

These coils arepled-with two-phase current of consta ntvolume and of the frequency w Ironi' the generator 14. Their terminals are also connected in multiple withthemicrophon'econtacts through the line and the condensers.

16. a The microphone-contactsarefed'with -two-phase currents'of the frequency or, from the generator 14'." Theconden's'e'rs 15.16 are 495' and higher frequencies supposed to be of such capacity as to strongly oppose the passage of currents of the frequencies m and on. without materially opposing the passage of the superposed .currents ofthe necessary forthe produc-.-

fiSuppose also that'the resistance of each of the microphones is Q 7 I 'R-= r-i-f' (t).

Thediflerenc'e of potential between the-inicrophone-contacts and therefore the electro- .m0ti\'e-force impressed upon each ofithe coils 50,

. selt-inductionof the-circuits to be negligible 6 and. 7 by the generator 11', supposing the incomparison with their resistance, will he 1 The electrol'notive fore-cs expressed by the first terms of each of these .equations.-that' is to'say, the elcctromotive forces produced- I ren by the mere passage of the multiphase curcrophone-co'ntacts will, have no eifect upon the receiver, owing to the presence of the condensers 15 16, whose capacities are too 5 small to permit the passage of such currents The electromotive forces represented by'the second terms, however-that is to say the 7 from the generator 14' through the -mi-' electromot-ivc. forces ofvariations of electromotive force produced by'the variations-of resistance =01 the microphones-will, being of isutiiciently high frequency, cause currents tolpass'thuo-ugh thecondensers to the receiver. There will therefore 'flow: from the transmitter'to the receiver currents whose volumes maybe expressed by the tormulas it f, sin; 2 arm i Xf'it) cos; 2 irro t, .l

. where X has constant depending on the conditions of the circuits, the elect-romotive force 0! the generator 14", &c'. ;btit the currents flowing in the receiver-coils when the transinitter is at-rest are, as we haveseen,

l and f when R is a constant depending, among other. thingspupo'n the relative positions of the pla'teiand the cores. If we compare this I expression with'those or the ordinary receiver andxof the receiver in the first-described eye-- from, both of which equations are developed abov'e, jwe see at once that the only pull which i can produce audible sound is that which is represented bytlre term- ;i we J X fl (1.) 60's, 2 fitgw'jt. It-will be seen that the intensity otthe sound l corresponding tosuch pulls will present two (0- m beatsper second. We find in practice i that it is sufficient to give to this 'frequency 1 m rda value much below the lowesttones'to be transmitted in'order that the forces tending-tomodify'these' sounds shall render them unintelligible. 'f'lhe" buzzing in'the-receiver,

that of the ordina'ry sounds heard ln'thetelephone, doespnot' interfere with the perfect comprehension of; speech correctly reproduced. 'It' follows from these considerations "that in .our system (or-m) should be zero in order to reproduce speech with perfect clearness and that a m' must havea certain minimumvaluein order that the receiver may reproduce the 'sound in'an intelligible manner. This requirement may be formulated -in' the 'following rule: Whenever the receiver is excited-by currents'of the same frequ ency as the transmitter; speech will be reproduced; but when thereis a difference between the frequencies of the two exciting-currents and this difierence attains avalue aboveacertain minimum value,-but much smaller than the frequency-of the lowest. tonesof the human the intensity of whichnot being superior t'o voice, the receiver will .be practically silent. Our improved multiplexsystem is based upon the conclusion just-reached. In its essential elements it comprisesa number of transmitters and a nnmber ot receivers, preferably arranged in multiple upon one set of line-wires. Each transmitteris supplied with an exciting-current of a particular frequency and acts to send upon the line speech-waves produced by its action upon such current. The frequencies of these exciting-currents are so chosen as to bring the difference of their frequencies within the rule above enunciated. It is then arranged that each receiver is supplied with an exciting-current of a. frequency equal to that of the transmitter to which it is intended that it should respond and. with no other exciting-cu rrent. In such a receiver and in such a receiver only will the speech-waves produced-by theaction of this transmitter produce audible and articulate sound. Each receiver thus responds to the transmitter or transmitters excited by currents of the frequency of its own excitingcurrents and to no others.

Fig. 6 is a diagram of ourimproved multiplex system. .18 19 are the conductors, carrying sine and cosine currents, respectively. The generators 2O 21 supply, respectively, to th s line currents of. the frequencies a: co m. The telephone-stations A and A are designed for the frequency co, the stations l3 and B for the frequency to, and the sta-- tions C and '0" for the frequency to. The station A is provided with a two-phase receiver 23 and a two-phase transmitter 24,

whose circuits. are connected in series between the lines and the common return, which may be through the earth, as shown, or may be through a return-wire R. (Shown in dotted lines.) The transmitter and receiver are preferably similar to those shown in Figs. 1, 2, and 3. Interposed in these circuits are the electric resonators 25 26, composed of the 'selfi-ind-uction coils 27 28 and the condensers 29 30. These condensers and selfinduction coils are -so adjusted that the branches in which theyare located from line to earth are resonant for the frequency to. In multiple with these resonators are. placed the condensers 31 32, respectively, each of such capacity as to allow the speech-currents to pass, but to practically shut oif currents of the frequencies (93 o cs The arrange ment of the coordinate station A is the same as thatof rjt and the parts are correspond-' ingly lettered. The arrangements at B and B are similar; but the coils 27 28 27" 28. and the condensers 29" 30. 29" 30" are adjusted to respond to the frequency to. The corresponding parts of stations 0 and C respond to the frequency to".

In order to insure that the generators 21 22 shall furnish currents closely following the sine law, we prefer to place in each of their. circuits powerful resonators 33 33, each tuned to the frequency of its particular generator.

We also prefer to give to these gcneratorsa high internal im pedancc for reasons which will shortly appear. It will be seen that the normal effect'of these generators is to supply to tion, and thus vary the output, and consequently the terminal electromotive force of the corresponding generator 20, which, as stated above, should have a high internal impedance. The result will be to superpose on the currents alreadyflowing on the line those other currents, which we term speech-cur: rents, whose amplitude is a function of the time. These speech-currents will flow to earth through all of the condensers 31 32" 31"31, &c., and through all receivers. In the receiver 23 these waves, since they come from a microphone excited by currents of the frequency m, will combine with or be reinforced by the currents of the frequency to already flowing to earth. through the condensers 29" and coils 27 28 to produce speech, the action being essentially the same as in the form shown in Fig. 4 or as in the form shown in Fig. 5 in the special case where to: co; but these speech-currents flowing to earth through the other receivers 23", &c., will in these other receivers combine with the currents of the frequencies to and a) and will fail to produce speech in these receivers, as shown above in connection with Fig. 5, since the di-fierences (wco), (co- M), &c., fall within the values defined by the rule above enunciated. \Ve thus'arrive at a system in which n pairs of stations maybe served over a single pair of wires with an earth-return or over three wires with a complete metallic circuit, each station being in connection with be greater, and we do not limit ourselves toany particular numberof pairs of stations.

Fig. 7 shows a complete station in its preferred form with calling devices, while Fig. 8 shows a system consisting of three pairs of stations with generators, transmitters, receivers, callinggenerator, call-bells, calling- -'switches.,-&c. In these figures, .23 24 and 23* and 24, &'c., are the receivers and t'ransmitters, respectively, as before. 25 26 and 25 earth connections, for which a common metallic return may obviously be substituted, as in the system shown in Fig. 6. 21 22 are the three two-phase generators delivering, as before, currents of the frequencies m,

m, and co, respectively. Thus far the sys as that already described in tem is the same connection with Fig. 6; but it is necessary to provide some calling device,'which, as shown more clearly in Fig. 7, may consist of-a bell 34 of the well known Abdank Abakanowicz type, or any other bell capable of being operated by alternating currents. These 7 bells may be placed in branch circuits from one of the mains, as- 19, in series with-a resonator 35 and supplied with current from the amt. iliary generator 36, as shown in Fig 8. This auxiliary generator may be of the singlephase type,fnrnishing.currents of a frequency 3?, which frequency is. preferably lower than the frequencies to, m, and w. The resonant branch ciruits in which the bells '34 34" 34 34" 34 34] are included are all tuned to this frequency ll; but, as will appear below, these circuits all contain two interrupters or switches; and mm only when both of these .are closed at any particular station that the bell r'in'gs.

Referring more particularl which the parts are shown on a 37'38'are. hooks on which the receivers are hnng,1as we prefer to duplicate the receivers, as is well understood in the art. If a'single receiver is used, the necessary single changes in the arrangement will be obvious. To avoid complicating the diagram, we have only shown the electrical connections for one of to' Fig. 7, in larger scale,

the receivers, which may obviously be connected in series or in multiple. The hook 37 carries on its under surface theinsulated conducting-plate 39, and a contactpoint 40, electrically connected to the bell 34, is so adjusted that when the receiver is'on thehook the plate is in contact with the point. This plate 39 is electrically connected'to the contact-point'41, normally held away from the contact-plate 42 by the core 43 of a-solenoid. The contact-plate 42 is connected to earth. In order that the bell 34 may ring, it is evideitly necessary that the point 40 touch theplate 39 and that the contact 41 touch the contact 42. To accomplish these results, it is necessary that the receiver be on the hook 37 and that the solenoid be su'fliciently deenergized 'to allow the point 41 to bear upon the contact-plate 42. This solenoid iswonnd with two c'oils 44 45, connected, respectively, in series with the resonators 25 26 and with the transmitter and receivers. These coils are therefore normally energized at each station by the line-currents of quency; but the coils 44 and 45, as well as the transmitterand receivers, are shunted by the circuit 46, which is normally open,'but which can be closed by the switch 47.

Suppose now that the operator at station A (see Fig. 8) desires to call the coerdinate station A. He closes the switch 47, which immediately forms a short circuit for the linecurrent of the fr quency a). The terminal voltage of the generator 20 drops and the coils 4'4" at the station A, which can only be energized by the currents of the frequency w. from this generator, owing to the fact that they are in series with the resonators 25" 26", cease to' hold up the core 43'). The contactpoint 415' accordingly drops, onto the contact-plate 42". The branch circuit of the bell 34 is thus closed and the bell rings. 7 At the same time the coils 43 44' at station A are deenergized and Zhe bell 31 but at the stations B B C C, which are not but depend for their action uponcurrents'of the frequencies m and co, the c'oils f the solenoids are-still energized, as the wire 46" does not form a short circuit for currents of these last-named frequencies. In this way the conjugate stations only can call each other. The receivers are now takenfrom the books, which are retracted by any suitable device, a's'by the weights 48 49. The circuit of the-bell is thus opened and at the'same hooks and cutout the coils 44 45, whose im- The bells' then stop ringing and the line is that the essential feature of this calling apparatus is that a local circuit is closed at one station'by short-circuiting at another station use of a bell responsive to alternating currents in multiple with the lineand energized by a low-frequency generator is 'not essential, though it forms a convenient arrangement and obviates the necessity of local batteries, nor is, indeed, the use of any bell essential, as the solenoid-core 43 forms itself a visual signal, which may in some cases be sufficient. It will also be understood that while we have described and illustrated our invention as practiced with symmetrical two-phase snchcurrents. Nor are we restricted to the particular forms of'apparatus shown and described, since these can be variously changed without departing from our invention. Thus itis obvious thatin place ofv twin microphones other kinds of transmitters may be used and that any receiver capable of having a constant rotary field developed in it may be substituted, for the construction specifically shown. nd' described.

Having now fully'described ourinventio'n, we claim-v acted upon by currentsof thefrequency m,

pedance would render conversation diflieult.

ready for'conversation. It will be understod the proper -frealso rings;

time the points 50 51 make contact wlth'the the line-currents of agiven frequency. The

currents we are not restricted to the use of 1. The method oftransmitting sound by electricity whicn consists in producing upon a line alternating currents the sum of whose normal energyjs substantially constant from instant to instant, and varying such energy by and in accordance with sound-waves, substantially as described.

2. The method of telephonic transmission, which consists in supplyinga line-circuit with alternating currents :the sum of the normal energy of which is substantially constant from instant to instant, modifying said energy by and in accordance with sound-waves, and translating the modified energy into sound-waves at a distan as described.

3. The method of transmitting sound by 1 electricity which consists in generating a plurality of dephased alternating currents, the sum of whose normal energy is substantially constant from instant to instant, causing simultaneous variations in the said currents by and in accordance with the sound'to be transmitted, and translating the said variations into sound-waves, substantially as described.

4. The method of transmitting vocal and other sounds telegraphically, which consists in generating and supplying to a'line-circuit dephased alternating currents, the sum of whosenormalenergyissubstantially constant from instant to instant, modifying theamount of energy transferred by said currents by and in accordance with sound-waves, and trans lating the modified electrical energy into sound-waves at a distant point, substantially as described.

'5. -The method of transmitting local and other sounds telegraphically, which consists in producing, upon a line, currents by and in accordance with sound-waves, by the action of the latter upon alternating currents of a given frequency; combining the sound-currents thus produced, ata distant point, with alternating currents of the same given frequency, and translating the resultant current into sound-waves, substantiallyasdescribed.

6. The method ofmultiplex telephony, whichconsistsin producing upon a set of linewires a number of sets of speech-currents, each by and in accordance with independent sets of sound-waves, by the action of each of the latter upon alternating currents of a different frequency; combining ata distant point or points, each set of speech-currents, thus produced, with alternating currents of such frequency as will combine with the speech currents to reinforce the same, and translating the resultant currents into separate sets of sound-waves, substantially as described;

7. The method of multiplex telephony,. which consists in generating a plurality of altei'nating currents of different frequencies, producing speech-cu rrents from said alternating currents by and in accordance with independent sets of sound-waves, and combining the action. of these speech-currents, in a plut point, substantially i m ultiphase currents of frequency only,

substanti' lly as'described. j

with the action frequency as to receiver, the action of one set of speech-currents, substantially as described.

8. The method of multiplex telephony which consists in generating a plurality of different frequencies, impressing said currents upon line-wires, varying the impedance of a plurality of resonant shunt-circuits in accordance with the different sounds to be transmitted and there by creating on the lines speech-currents, delivering said speech-currents to a plurality of receivers, and delivering also to each of the saidreceivers multiphase currents of one corresponding in each to the frequency of the current in the shunt-circuitto which the particular receiver is to respond, substantially as described.

9. The method'of operating a signal or signal-controllingdevice upon a circuit on which alternating currents of different frequencies are maintained, which consists in normally maintaining said signal in one position by the action of currents of one of andselectively shunting the currents of the said frequency when it is desired'to operate the signal, substantially as described.

10. The method of multiplex signaling, which consists in maintaining upon a line alternating currents of diiferent. frequencies, maintaini n g each signal in one position by the action of currents of one of said frequencies, and selectively shunting the currentsof a particular frequency when it is desired to operate a particular-signal, substantially as described.

11. In a telephone system, the combination of a plurality of lines, with a multiphase receiver, a multiphase transmitter, anda generator of multiphase alternating currents, the sum of whose normal energy is substantially constant from instant to instant, all connected to the said lines, substantially as described.

12. In a telephone system, the combination with a source of alternating current the en-..

ergy of which is substantially constant from instant to instant, a transmitter adapted to modify said energy in accordance with the sound to be transmitted, a connection from said transmitter to a'set of line-wires, and a receiver connected to said line-wires, substantially as described.

13. A telephone receiving instrument, consisting essentially of a diaphragm and means for producing a rotary magnetic field in inductive proximity to the said diaphragm, substantially as described.

1-1. A telephone-receiver comprising a diasaid frequencies,

phragm', a plurality ofsoft-iron cores-wound with coils for the reception of multiphase" cprrents for the productiorrofafrotarly magnetic "field, and. a ring-yoke, common'to an the cores, and composed'ef' ne'sted lamina,

15. In a system of multiplex telephony, the combination with a set of line-wires, of means for-simultaneouslyimpressingthereon speechcurrents by the action of transmitters upon alternating currents of different frequencies, receivers connected to said line-wires, and means for supplying to each receiver an alternating current of a frequency correspondiug to that of the current acted upon by the particular transmitter to which it is to respond, substantially. as described. 1 I

16. In a system of multiplex telephony, the combination otline-wires with a plurality of multiphase alternatiu g generators connected thereto, transmitters and receivers,'connec--- station comprising a transmitter and a receiver, a resonant circuit so'adjusted as .to allow to pass to said transmitter and receiver unmodified alternating-currents of one fre-.

quency only, and another circuit so adjusted as to allow to pass to the said receiverspeechcurrent-s only, substantially as described.

19. In-a system of multiple! telephony, the combination with line-wires, ofa plurality of multiphase generators of difierent frequencies in multiple therewith, aplurality of transmitters and'receivers', each connected in m ultiple with the said lines through circuits a1- lowing currents of one only of the said fresaid switch,

que-ncies to pass,.and other circuits so ad- 45 .j usted andconnectcd as toallow speechecurrents to pass to the said receivers, substantially as described.

20. In asystem of multiplex telephony, two or more line-wires, multiphase generators of different frequencies in multiple branches, for charging. the line, and a plurality'of stations, each havin'ga set of branches resonant to one of said frequencies, each branch containing one winding of a multiphase receiver and one branch of a multiphase transmitter,

incombi ation with means for admitting on rrents 0 higher (nequencies than those of the line-currents to the receivers, substantially asdescribed. I

21. In atelephone system, the combination of a source of alternating current, anindieating device connectedin a resonant shuntcircuit, a second resonant shunt-circuit tuned to the same frequency, and a key for opening and closing the second resonant shuntcircuit, and thereby operating the indicating device, substantially as described;

22. In a system of multiplexftelephony, I

plurality of generators of different frequennected to line through a circuit resonant to one of said-frequencies and through a switch,

.cies connected to line, a calling device cona second circuit, including a coil'co'ntrollin'g resonant'to another or saidjfrequencies,--a third-circuit at "a distant stationresonant to 'the'second ot-saidfrequ'encies,

and means for closing said third circuit and be actuated,

thereby causing the signal to substantially as described. I V

In testimony hereofe have signed our names to'thissp %ification in'the presence or two subscribing 't nessee. a

- MAURICE HUTIN. MAURICE- LEBLANC. Witnesses: a EDWARD P. MACLIAN,

PAU'L Boss.

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