US958868A - Telephone system. - Google Patents

Description

W. F. GRADO-LPH W. O. HAHNE.

TELEPHONE SYSTEM.

APPLICATION FILED FEB. 1, 1908.

latented May 'ZQ IQQO.

4 sEEE s-sHEET '1.

W. P. GRADOLPH & Wye; HAHNE.

TELEPHONE SYSTEM.

APPLICATION FILED FEB. 1, 1908.

Patented May 24, 1910.

4 SHEETS-SHEET 2 lJ EF.

j, A? m Wm. 61 be,

W. F. GRADOLPHKEWEG. HAHNE TELEPHONE SYSTEM.

APPLICATION FILED FEB. 1, 1908.

Patented May 24, 1910.

4 SHEETSSHEBT 3.

W. F. GRADOLPH & W. G. HAHNE.

TELEPHONE SYSTEM.

APPLICATION FILED FEB.1, 1908.

9 3 I Patented May 24, 1910.

4 SHEETS-SHEET wrLLIA'ni I;

once, ILLINOIS,

emoLrH, or .s'r. Lours,'mrssouar, AND WILLIAM o; IH KNE, or 0111* essrcuons 'ro GRADOLPH. ELECTRIC comrimy, or s'r. LouIs,

MISSOURI, A COBPORA'IlION OF MISSOURI.

l 4 Specification of Letters I atent.

TELEPHONE srs'rnm.

Originalapplication filed December 9-0, 1965, Serial No. 292,529. Divided and. this application filed February 1, 1908. Serial N0. 413,854.

To all whom it may concern:

Be-it known that we, \VILLIAM F.

none}; zens of u'set'ul Improvements in Telephone Systems,

variety of generating or for instance, thejtransmis'sionof speech, for .powe'r,

' that the sound waves of the .of which the taining'a full, clear dating currents,

.prises various and to a greater degree,

following is a'specification conande'xact description, reference being ha to the accompanying drawings frorming' a part hereof. r

Oiir invention-relates to the transmission of electrical energy by means of electrical waves of alternating, intermittent, or undu and particularly such waves as are employed in the electrlcal transmis sion of speech c1aimed. 4 I 7 Our. invention is applicable to a great translating devices;

and' for electric signaling. The-present application is a divisional application from the application filed by us December 20, 1905, Serial No. 292,529.

. It is well understood that the successful transmission of speech depends not only on of the sound proreceiver, but also,

the volume or loudness duced by the telephone current is essentinctness. The telephone tially alternating, but its waves or impulses were over an electrical conductor of great 1 are exceedingly complex, due to the fact human voice, not

which 1 'roduce the current waves, are

' simple waves but are composite, being the resultants of numerous waves, corresponding to overtones and harmonics, as well as of different amplitudes and may be quite accurately trical waves by the transmitter; and if the current waves be transmitted over the'line with their characteristics substantially unimpaired or. unmodified, the sound waves into'which they are translated by the receiv-' ing apparatus will besubstantially, identical,

at least as regards distinctness or clearness, with the sound Waves which affected the transmitter. Conse uently anything which disturbs the inter-re ation of the component or s'onorous sounds, and com features of novelty hereln-- after more; particularly described and causin on .clearness or dis- 1 active constants- Thcse composite sound wavesv translated into elecexisting waves, such waves of the resultant complex current waves causes loss of 'clcarness 1n the reproduced sound wavesywlnle anything that Patented May 24, 1910 4 causes a loss of current, as by dissipation,

eauses a loss of volume'or loudness. ,Thesedisturbing influences have, been largely overcome-as regards their effect in the transmit ting and receiving devices,.but the numerous 4 attempts to overcome them in theex'ternal circuithave' been, onlypartially'successful.. The disturbing influences which we here have more. particularly in mind are the self-inductive and SO 31 218 we are aware,

the electrostatic capacity of the line or ex-'.- I

ternal circuit; Both of these influences re- .duce the amplitude of the current waves an consequently cause a loss of volume; an

both also cause a loss of clearness or sharpuses; the effect of electrostatic capacity, or static induction, being to round off the crate of the waves, and the effect of both self and static induction being to retardation of base for vibrations (the component waves? of difierent periods, thus interference and a resultant deforme *waves It will therefore be seen that 'ifgood transmitting and receivingap eratus be employed, the successful telep 9111C.

roduce an unequal I transmission of speechdepends on the Selfinductive and the electrostatic capacity or condenser effect of the external circuit, and

hence it is desirable to reduce these characteristics of the line' to the minimum.

In the transmission of a simple electrical h characterized by high len' resistance electrostatic capacity and inductive leakages, the I energy lost or dissipated is proportional to and expressible in simple termsof there of the systems, and there is no distortion of the wave form. Such, however, is not the caseforja comp trical wave composed of a plurality of coin the telephonic transmission of the human voice or other sonorous sounds composed of aprime on fundamental In the latter case, each constituent wave of the-series is differently and independently affected, and hence the resultant wave form at the distant end or terminus of transmislex elecas the waves involved and an ascending series of partials correspondipg'to overtones ,or characteristics of articulat on and quality. I

sion is nolonger identical with the initial wave form impressed upon the conductbr.

This is due to the physical fact that each wave is oppositely as well as differently affected by the electro-magnetie'and electro'w static constantsjof the system, though both conspire" to discriminate in favor of thelower' while retarding or attenuating the upper harmonics directly as the frequency,

resulting in the loss of articulation and the natural characteristics of speech which are dependent .A pon .the transmission' of'. the upper harmonics or overtones, and while conceding that the greatest losses are prop 'erly chargeable to the dissipation'of the main line conductors, owi'n researches of" the subject -experimentally with commercial and artifieial circuit's'-have confirmed us in the opinionthat, so far as long aerial or cable lines are'concern'ed, operating under actual] conditions, which might' be called existing j meteorological conditions, little if anything of average or' permanent value is to be obtained by tuning or readjustment of the line constants, and,

so far as we are aware, there exists at the,

present time no. commercially successful method orsystemof transmission, telephone relay, or repeater,

Various attempts from time to time have been made to devise electromechanical apparatus capable of replenishingthe current 'at some intermediate point of the circuit,

or adapted to transfer the messages of one telephone circuit to another, and thereby either to increase the length of line that can be operatedsatisfactorily, or under other 'conditions to enable the receiver to 'rcpro duce the transmitted message with increased loudness. These 'eiforts,howevcr, have uniformly been unsuccessful and unproductive of practical result, and it is a fact -that nothing of the kind isjn practical oncommercial use at the present time iniconnection with telephonecircuits anywhere, for though in some instances the sounds repro duced by the receiver actuated by the replensociatecl conductors is a great hindrance toeconom c'fransrmssmn and a preventive of transmission through undergroundcables of anygreat length. The limit of distance to which speech can he telephonically transmitted, so as to be commercially intelligible is:

to their elec-- trical'characteristics, as outlined above, our.

not caused by jan'y' losses due to capacity. itself, which .is a function of the medium surroundingthe conductor or pair of conduct0rs,-by which it is ca able of stormg up and certain amount of loss, known 'as dielectric ever, is trifling when compared tozthe other .Inore thoroug 1 y understood by considering that there are two componentsof current presentinj the conductor, one in phase with .the electro-motive force, and tending to do us'efulwork at the receiving end, and the advance oftheelectro-motive force, representin" a successive chargin and discharging 0 t e medium surroun mg the'conduc- -tor. This latter current may be, and is, in a tele hone cable, many'times greater than the use ul current. The '-resultant current at the transmitting end is therefore larger than the useful currenttransmitted tothe receivingegd. This roduces C R losses throughgreater than would occur if the current at thextransmitting-end were the same as that at the receiving end. It 'isobvious, therefore, that anything which will diminish the attenuation of the current flowing through medium, will increase the efficiency of the circuit. v It has been proposed for a number of years, .to obviate the excessive charging current existing in a circuit ofthis kind, by introducin -into the circuit, in various manners, reactance coils which should cause the current of equal and opposite effect to the capacity .current in the cable or circuit, and annul it. -None of these proved eflectual when tried in actual service until recently, when the theory of the design and placing of such loading coils was evolved, and it was found that if ductors .at roper "intervals, which are determinable y mathematics, the efficiency many disadvantages'of this arrangement, however, prominent among which is the expense' ofithe coils themselves, and in underground telephone cable work, the expense of the frequent building of vaults and boxes to contain these coils. To this we may add the 'difiiculty of access to these coils which are embedded. in an insulatingv compound, and cannot be repaired without removing the entire containingliox, and the difiiculty due to magnetic induction between different circuits due to the'overlapping magnetic fields of these reactive coils, and again circuits loaded with these coils are very diliicult to for 22 gage cabl'e'ii i l iihiles; 1 9' vgage-cable 25 miles; 16. gage cable 44 miles. This 1s restoring energy to t e circuit. There is a hysteresis-due to this process, which, howlosses of "ener .fin the'cable." This maybe other a capacity current, a quarter'period in out tlfiifsentire. ength of the conductor, far .i

the conductor, by lowering the .;amount of current necessary to charge the surrounding they were arranged in series with the con- I of transmission was increased. There are operate over, that is to say, when loaded ciredits are connected together, transmission of speech is poorer, due to the fact that the cir; cuits have different time constants and so cause a'reflex action to -the-voice currents.

The object of our invention is to avoid the objectionable. features of the aforesaid ar- .rangements, .and to secure the effective reactancein long conductors and cables, necessarytoneutralize the capacity thereof, in a simple, inexpensive, and practical manner.

The nature of our invention will be more readily comprehended in connection with the preferred type of apparatus, and thereforereference will now be made to they an:

.nexed' drawing wherein: such apparatus is illustrated diagrammatically.

1 g 1 ShOWS a system involvingthe application of our invention to telephonic transmission; Fig.2 is a diagrammatic view of a telephone system involving the application.of .our invention, and showing the transmitting and receiving appliances ateach end of the line; Fig. 3is'a diagram showing graphically thecurrent waves whenin phase; Fig. 4 is a diagram showing current waves as displaced in phase by our invention; Fig. 5 1s a diagram which shows graphically the. condition, of the current waves in the external circuit arising from the application of our invention; Fig. 6 shows diagrammatically a. system of two stations, each adapted to transmit or receive at will, the necessary changes in connections being made by a manually operated switch; -Fig. 7 shows diagrammatically a single station adapted to-transmit or receive at will, and equip ed with an automatic switch for effecting t c necessarychanges-in the conprimary windings, connected in multiple with each other and-in series with a telephone transmitter 5 'and a battery 6.-- I, and 8,arethe two wires of the external ciredit, and in series therewith is the second- .ary winding 9 of the transformer at the other cnd'of the circuit. 10 indicates the primary of the transformer, in series with the transmitter-l1 and battery- 12. The receivers at the two ends of thecircuit are in series with the transformer secondaries and are designated by 13 and 14. 15 is an impedancecoil of proper value, as will be fully explained presently, inserted in either line,

.and preferably close to the secondary 1 or 2', as the 'case'maybe.

16 isa.surging or buffer line, open or: grounded by preference open, and preferably Of '& ength greater than one wave length. This isurging'lin'e isconnected at the neutral point between.tho'

secondaries land V The operationof'this of our knowiledge and bel1ef,'as follows: The

w s the best currents produced the primaries 3 and 4by the sound waves entering the transmitter 5 are reproduce in the second try windings 1v and 2.. These induced currents are of course in phase, and would, in a simple sing e phase circuit; add up but the line 16 permits a surgeto take place in it, thus operating like a buffer,- i

as-it were, so that the independence of the- .two secondary currents is preserved. The

current from secondary 1 is, by the impedance 15, caused to la approximately 90 behind the E. 'M. F., w ile the current in the other line, flowing fromthe secondary 2, is by the electrostatic ca acity or'condenser-efi'ect existing between inc 8 and the surging line 16 caused to lead the E. M. F. by approximately in the line8, until the impedance at the i'eceiving station is reached. .-.The result is an out of phase condition tothe extent of approximately 180 difference between two currentsin lines'i7 and 8. -This condition is indicatedgraphically -in Figs. 4-

and 5, Fig. 3 illustrates thephase' relation of the currents in an ordinary s'stem' and it will be noted that the polarity o the current wave in one line is always of contrary sign to the current wave in the other, and consequently theca acity efi'ec't between the two is maximum. n the other hand, it will-be seen that in Figs. t and 5 conditions of our method, the polarities in- '100 -wh1ch represent 'what would be the-ideal thetwo lines are always of the same sign;

and, consequently, if such ideal conditions could be attained in practice, the self-induction and capacity efiect between the lines 7 vould be zero. When the currents reach the secondary 9 of the transformer at the other end of the line, the impedance'of the secondary causesthe phase relation to be restored,

at least partially, to the original relation, so

that there is produced a difierence of potential across the receiving transformer, and the current waves are consequently translated into sound' waves.

more nearly the currents in the two lines are kept 180 out of phase,-and the more nearly "1 15 .It will be understood, of-course, that thethey are brought into phase at the receiving transformer, the better the speech transmission'; and it is therefore desirable to aproxirnate these conditions as far as possible.

- t is obvious for various reasons, chiefly the factthat the components of the waves are of different-.periodicities and aretherefore differently afit'ected by the impedance and by the electrostatic capacity or condenser effect between the surging line and the circuit, the current waves, which reach the receiver at the otherend of the line are never identical the impedanceand the condensereffectju st mentioned -that "a considerable -.phase d s placement may-bezproduced without'defornb;

&.

with" those produced in' the transmitter; but it'is possib e to so PIOPOl'tlOD the values of mg the current wavesto an impracticable extent. The periodicity of the'ielephone, current is usuallyassumed. to "be 750 ;-and: on

' this assumption, with a transmitter trans- 'former of ;6 ohmsresistance in its primary .and 175 ohms inits secondary, and apr current of .14 volts, extensive expenments and practical'tests have indicated -an impedance of 1100-0hms as the best value, :whatever he .the length I. of the 'e x;ternal orv transmission circuit; In general, :we prefer,

as already stated, .to .make the surging ling,

16, slightly longerthan a wave length, as

suming'the riodicity of the current to 'be 750,. but di erent conditions may make a different :Ien-gth iadvisable, either longer or shorter as vthe-caseimay 'be,'-or it may .even.

be extended and connected 'withthe distantstation. Fig. 1 is designe'djto re resent .m the simplest :way the operation 0 our invention,

and no provision is madeinthis figure for transmitting from the transmitter 11.- It

" ;-wi-11':be understood,:of'course that thisend of the'line must for that-purpose beequippedx like the other .end, as clearly shown in Fig.- 2.

' Under some circumstances itis found desirablethat when e'ithers'et of instruments is receiving, the impedance, as 15) at'thatend of'theilineshould he cutout. It-may be advisable-at times tocutout half 'ofzthe' trans- :formersecondary whe'nireceivingpA com- 1 Q plete system; for" transmitting and receiving from each end of the line is shownby'means of the simple diagram," Fig. 6.. It will be seen that each statiomis equipped-alike. At each there is a. double pole switch 17, in the neu- -tral line, and in the main line, by which the impedance, the neutral line, and half of the secondary w nding may be out out at will. '-When it.is desiredfto receive, this switch-is opened, as'atthe right otzF-ig'. 6;

and when transmitting, {the switch is closed,

' as at the #left. When the 'user is through .50 person at the other end desires to talk, he;

talking, he opens his switch 17, and if-the the other-branch.

.- As long as thestation is receivlng lthe relay remainsneutral .hutwhenevei' the user speaks into the transmitter, .the...pulsating current ythereby setup unhalanc'esthe branches, so that the .magnetnowdraws'over armature 25,.and th e con a springs am .27; a

wire 30, spring 26,- wire'3l secondary 32,

In the .position for receiving, as, shown-in Fig. "Z, the circuit is asffollows: ffrom the distant stationyto terminal 28, springa27,

wire 33, receiver 33*,and terminal .34, .back to thelother station.- -When the-switch is thrown, as above explained, the primary transmitting circuit is throu h transmitter 35, battery 36, wire- 37, .re lay coils and h branches, primary windings 3850f the transmitt-ing transformer, and wire 39 back -.to

the transmitter. .The secondary circuit is .then as-follo-ws: secondaries32 and 40, wire' I .41, impedance 42, wire 43, contact spring 27, xvii-e45, terminal 28 th'ro h the distant station to terminal 34, then-wire 33 back to thesecondary winding 32. As-soon as the user-ceases speaking into the transmitter 35, .the balance of the relay branches is restored,

' position shown in the figure.- It will be oh- 0 and the springs 26, 27 are; restored tothe servedthat when the switch .is in the transmitting position the wire 31, from. the neutral point between the secondary wind .ings, -is-.connected with the neutral or surging line extending from terminal .46, by

spring 26, and wire 47. When the switch I is thrown over,-;this path to terminal46 is 1brokenby spring 26 leaving the contact or wire 47.

Fig.8 is a diagram showing ;a station equipped with theswitch just described, and

also with a convenient arrangement of signaling devices, utilizi our invention in the .latter as well as irtt e telephone system. In'this figure, 48, designates ,a hand-open ated. magneto machine ofordinary type, in-

which turning .the crank to call the other station causes the crank shaft to actuatea 'switch at'the other end of the same, indicated by48. This method of operating the magneto switch is common and well finderstood. The hook on which the receiver hangs when :not in. use is indicated at 50.

The weight of the receiver depresses the "switch arm 51, thus changing the connection ,thereat 1n the usual manner.

station is connected by line wires to the terminals 28 and 34, and from terminal'46 extends the neutral or'surging line.

The distant- When the'systemis not in use, the receiver hangs on the hook 50, and the rela switch is in the normal,'or receiving position, as in Fig. 7.. If new the otherstation signals, the circuit is established as follows: terminal 28, wire 28, impedance 28",,bel1 coils 52, wire 53,'springs .54 and 55 at the hook switch, wire.56, springs.- 57 and 58 at the magneto switch, 56", to terminal 136 lishing the 1 following receiving circuits:

34, back to the signaling station. The person; ca-lled then removes his receiver, estab- --;trom the-other station to terminal 28, wire 4.4,.spring 2:7, wire130, spring 26, wire 31, secondary winding 32, wire 33, receiver 33*,

wire 58,,spring's 59 and 55 at the hook' "switch, wire 56, springs 57 and 58 at the the transmitter.

magneto switch, wire 56, and terminal 34 back to the other' 'station.

When the user at the station at this end of the linejdesires to reply, he speaks into. the transmltter, whereupon the relay is unbalanced and the armature drawn over, as

previously e xplained,.to the position shown in Fig. 8.

The primary, transmitting circuit is thus established through transm1tter3 5, battery 36, wire 60, springs 61 and 62 at the hook switch, wire 37, relay coils 22 and branches, primary windings 38, and wire 39'back -to The secondary transmitting circuit is -then as follows: secondary ' windin 32 and 40, wire 63, spring 64 at the hoo switch, arm '51, wire 65, impedance m, wire .43, spring 27 at the relay, wire 44,.

terminal 28 to the other station, then back through terminal 34, wire 56, spring 58 and 57 at the magneto switch, wire 56, spring erator or ma 55, spring 59,wire 58, receiver 33, and wire 33 back to the secondary winding 32.

, When-the system is in its normal condition, that is, with the receiver on the hook,

and with the relay switch in the position shown in Fig. 7, the other station is signaled in the following'manner: The hand geneto machine 48 is operated,

which not 0 y supplies the signaling cur.-

.rent, but also 0 crates the switch 49, as

28, wire 28, .50

already explaine resulting in the following circuit being established: from the armature through wire 66, rimary windings -67 of the signaling trans orzneror repeat- 'ing coil, wire 68, springs 69 and 70, at the magneto switch, and back to the armature. The secondary signaling circuit is then as follows: secondary windings 71 and 72, wire 73, springs 74 and 75,'wire 76, impedance through terminal 28 to the distant station, then back to terminal. 34, wire 56, springs 58 and 77 at the ma eto' switch,-wire 78 back to the secondary 1.

VVlienthe relay switch is in theposition shown (Fig. 8,) that is, in the transmitting.

position, the neutral point between the sec ondary windings 32 and 40 is connected. by wire 31, spring 26 and wires 47 and 79 to the terminal 46, from which extends the neutral or surging line. When the system is not in use, that is, with the receiver on the hook 50, the surging line which extends from terminal" 46 is connected between the bell magnets by wires 7!), 80,31, springs 82 and- 83 at the magneto switch, wire 84, springs 85 and 86 at the hook switch, and wire 87.

Removing the receiver from the hook-breaks this connection by separating springs 85 and 86, so that the surging line extending from terminal 46 will not be effective through wire 28, one of the bell magnets-52, wire 87 etc.- The line losses in telephone transmission circuits, due-to self and static induction, are

of vital'importance; and, inasmuch as our mvention overcomes these effects to so considerable a degree, we are enabled to'deliver tothe translating device, whatever it may be, a larger roportionofthe generated current than as,-so far as we are aware,

been possible in the systems heretofore pro posed.

' While we have shown ually operated switches in connection with our' im rovement, it will'be readily underautomatic and manstoodt at, in so far as the tIfiIlSIIllSSlOIl and,

receiving of electrical energy is; concerned, the action, as contemplated by our invention, may be carried out with equal success'by the simple-arrangement of lines and connections,

: as shown in Figs. 1 and 2 wherein such ap- 90 pliances are not employe Inconclusion, it should be stated that while the line conductors may be in any inductive position relativeto each other, they must, in every case, be arranged in inductive relation to fthe surging line, because the action between this line and the transmission lines is, as already explained, essential to the invention.

ing line-extends to the receiving or translat- It is of course evident that where the surgin" devices, the line conductors, if in-inducta ive relat1on thereto, are also 1n inductive relation to each other. We cla1m:-

1. In a telephone system, the combination mitting and receiving apparatus,'of means at each station for a'l'teringnthephase rela- 'tion of the'currents, and means at each station for cutting saidphase-altering means in or out of the circuit at will.

3, In a telephone system, the combination with a circuit and a plurality of stations thereon, each provided with transmitting 'affd'receiving apparatus, a differential relay at each station, dependent for operation upon, actuation, of the transmitting apparatus by sound waves entering the same, for changing the station from receiving to transmitting condition,

3 t. In a telephone system, the combinationw th a metal iccircuit, and a-plurality of stations thereon, each provided with trans- 'mitting and re'ceivin apparatusyof means ateach station for a terlng thephase rela-- tion of the currents in the twhsides of the 7 said phase altering means in circuit.

v 5.' In 'a telephone system, the combinationof a metallic circuit the-sides of which are in inductive relation' to each other, a plu rality of stations thereon, transmitting and receiving apparatus at each station, and

means in series with the circuit cooperating with means=in inductive relation with both sides of-the circuit for producing in. bothsides of the circuitat the same time currents of like polarity, and for restoring saidfourrents to their original polarity;

6. In a telephone system, the combination with a circuit, a plurality of stations thereon iea ch provided with'a transmitting and re-. 'ceiving appliance, and means for producing in the opposite sides of said circuit-between connected stations of the circuit at the same time currents of like polarity. a

v 7. In a telephone system, the combination with a circuit, a plurality of stations thereon each provided with a transmitting and'receiving appliance, of means for producing in the opposite sides ofsaid circuit between connected stations at the same time currents of like polarity, and -means for restoring said currents to their original polarity at the reccivin station.

- 'tion with stations, each provided with trans i C intothe circuit at will, of means arranged 8. In 'a te ephone system, the combination with stations, each provided with transmit-- ting and receivmgappliances, a circuit connecting said stations, of means interposed between the stations for altering'the phase relation of the currents during their trans- 45' mission over the lines of the circuit.

9. In a system of telephony, the combinawhich'are in inductive relation to each other,

of means in series with the circuit coiiperat:

mg with means in inductive relation with both sides of sald clrcuit for produc ng 1n said' currents to their on nal polarity. i

10. In a system of telep ony, the combination of a metallic telephone circ'uit,*the sides of whiclrarein.inductive relation to each pliances,

other, a plurality of stations thereon each.

provided with transmitting and receiving apfor retardingthe current in one hranclrof said circuit and correspondingly advancing the current in the other side of said circuit,

of means in series with said circuit' and means in inductive relation "to the cir- -cu1t -fo'r correspondingly advancing the rev tarded current and retarding the advanced current.-- v o 11. In a tele hone-system, the comhina-I {0 tion with anal metallic circuit the side's of which are ,in'indu'ctive relationto each'other, and a plurality of stations thereon each provide'dwith transmitting and receiving a plieirices, of an impedance coil .in each .si e 5' of said circuit, and a surging line in inductiverelation to both sides of said circuit.

12. In a telephone system, the combination with an all metallic 'circuit,the sides of 13.= In a telephone system, the combina- ,tion with a metalliccircuit and a station thereon provided with both telephone trans} 'mitting and receiving appliances, of means, arranged adjacent to the-saidstation, comprising an impedance in the circuit, and a sui'gin line in inductive-relation to both the lines, tc said means cooperating to change {he phase relations of the currents on the me. v a

14. In a telephone system, the combination with a metallic circuit andstations thereon each .provided with both telephone transmitting and receiving appliances, of

tion for. altering the normal phase relations of thecurrents passing over the line of the circuit, and other means located adjacent to a receiving station for restoring the norbeing delivered to the receiving appliances.

:15. In a telephone systenn-the combination with a circuit, a plurality 'of stations thereon, telephone transmitting and receivstation,- and means for bringing the said- --teleph0ne apparatus or .signaling devices adjacent to one station for altering'the normal phase relations the circuit, and means near another station for restoring the normal phase relations of the currents before theyare delivered to the receiving appliances. v 16. In a telephone system, tion with a circuit, a plurality of stations thereon, telephone transmitting and receiving apparatus, and signaling. devices at each station, the signaling devices being normadly in the circuit when the system is at 125 rest, and the telephone apparatus being arranged to be brought into the-circuit when "the system is in use, whereby any stat on -may become a sending station and anctner a receiving Statiom-of means arrangcd'adjaiso means arranged'adjacent to a sending star ma-l phase relations of the currents before ing apparatus and signaling devices at each of the currents sent over the combina- 1 20 cent to. a sending station for altering the ing the normal phase relations of the cur- 15 normal phase relations of the currents sent rents sent over the circuit, and other means over'the circuit, and means near a receiving also in permanent cooperative relation with station for restoring the phase relations hf, the circuit arranged near another station for the currents. restoring the normal phase relations of the 17. In a telephone system, the eombinacurrents. 20

*tion with a circuit, a plurality of stations In testimony whereof, we have signed our thereon, telephone transmitting and receivnames to this specification, in presence of ing apparatus and signaling devices at each two subscribing witnesses. station, and means for bringing the said WILLIAM F. GRADOLPH.

telephone apparatus or the signaling (1e- VILLIAM C. HAHNE. vices into the circuit at'will, of means in Witnesses:

ermanent cooperative relation with the cir- A. R. KELso,

wit arranged adjacent to a station for alter- HOUSTON BOND.

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