US536382A - Telephone-exchange system - Google Patents

Description

BESTAVAILABLE COP;

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TELEPHONE EXCHANGE SYSTEM. I v No. 536,382. llatentedMa1u26, 1895.

BEST AVAILABLE COF" s. W. HOLMA N; TELEPHONE EXCHANGE SYSTEM.

9 Sheets-Sheet 2Q [No Model.)

No. 536,382. Patented Mar. 26, 1895.

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.S. W! HOLMAN.- I v TELEPHONE EXUHANG-ESYfiTBM. No. 536,382 Patented Mar. 26, 1895.

'BEST AVA!LABLE COP;

9 Sheets Sheet 4.

. s. HOLMA-NQ I TELEPHONE EXCHANGE SYSTEM.

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' Patented Mar. 26, 1895.

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SI WI TELEPHONE EXCHANGE SYSTEM.

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(No Model.)

Patented Mar. 26', 1895.

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(No Model.)

Patented Mar. 26,1895.

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BEST AVAILABLE COP.

S. W. HOLMAN. TELEPHONE EXCHANGE SYSTEM.

No. 536,382. Patented Mar. 26, 1895.

(No Model.)

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BEST AVAlLABLE CQP.

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- I"ELEPH 0NE E'XGHANGE SYSTEM.

No, 536,382. Patented Mar. 26, 1895*.

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may be placed I UNITED STATES BESTAVAILABLE com PAT NT- OFFICE.

SILAS W. HOLMAN, OF BOSTON, MASSACHUSETTS.

TELiEhHONE-EXCHANGE SYSTEM.

' srnomoarzorz forming part of Letters Patent messages, amem n 26, 1895.

4 Application filed March 24, 1894. Serial No. 504.965 (H model.)

To all whom it may concern.-

Be it known that I, SILAS W. HOLMAN, re-

siding at Boston, in the county of Suffolk and" State ;of Massachusetts, have invented cer- 'tain Improvements in Telephonic-Exchange Systems, of which the following is a specification. V 0

v The object of my present invention is to provide a simple, inexpensive, convenient, reliable, etficient and speedy mechanism and method y which any telephone subscriber in telephonic communication with anyot her'telephone subscriber, whether connected directly with the same central office or, with another central otlice.

iVhile telephone exchange systems are now in use by which' the'snbscribers connected with one central office may converse with each other with more orless facility, and by which some of the subscri ers connected with one central olficemay converse with some of the subscribers connected with another central office, i tis believed-thateven th esesystems are 'nnnecessarilybomplicated and.expensive in construction and unnecessarily cumbersome, unrel1able, inefiicient and slow in operation.

Someofthe salient features of my present system are:

The use attire subscribers stations of mag neto. telephone transmitters and receivers,

snchas are described in my Pat'entNo. 496,224,

though efficient battery transmitters may used, and I sometimesmake use of the liquid transmitter described in my Patent No. 505,917. I

\Vhen the distances separating any two subscribers is very great, orwhen particularly loud conversation is desired, my system contemplates the introduction into the circuit,

at one or more intervening central ofl'ices, of relay ieleplloneiwvliose purpose is to increase the loudness of the telephone conversation so that I, may give to each'subscriber the advantage of long distance lines without the expense and complication'of a long distance outfit. Two wires usually extend from each subscribers station to the central oiiice, one

of which is equipped with apparatusby means of which the subscriber may signal the central oilicc, while the other is equipped with apparatus by means of which'the central office may signal the subscriber and the two wires may be used together as a metallic circuit. By this device the signaling and switch.

ing apparatus is greatly simplified, the sub not, and everysubscriber has all of the advantages ot' a metallic-circuith Tiie line wires, so far as theyare not carried in cables,

are supported upon a peculiar insulator, by

means of which theyare protected from crosstalk and disturbing noises, and the cables are so constructed as to secure a minimum of electrostatic capacity, self induction and mutual induction, as described in m y Patent No. ;491,109, of February 7, 1893. Bythese devices loud, clearaand distinct transmission-of speech is attained and the telephonecircuits are protected .from cross-talkaud otherdistnrbing" noises. At the central office each circuit terminates in one or more'b'ranch torsignaling driest-- minals,to which connecting, I ing mechanism may be'conveniently attached either momentarily or during the life .of a conversation, as may be required. Annunciatorsby which the operator receives the signal from a subscriber are permanently connected from one wire of each 'subscribers'circuit through a battery to the earth, These annnnciators are so constructed as to be read- 1ly permeable to signaling currents, butimpermeable to telephone currents The cords orequivalent commntators use in connecting one subscribers'circuit to another are so constructed as to be readily permeable to-telephone currents lulel y impermeable to the signaling-currents. An advantage of thiskind of that there is no confusion"-between signals passing between the central ofiice and-one sub-- scriber, and those passing between the central oliioe and theother subscriber, in case the two subscribers be connected together. Other advantages of this arrangement will appear.

Attached to each operator and, as it were, made part of his person, is a simple piece'of mechanism by which he may signal any subscriber, converse with any subscriber, tell whether any subscriberis line is busy, or not, tell when a called subscriber has answered histelephone, tell whether a satisfactory couversation is being carried on, such assistance as is necessary, tell when the commutator is and vyet absoand if not, alford vertical wires may be arranged in several planes, and '1 am thus enabled tosec'ureina board now so generally in use,

conversation is finished and perform various other nsefnlservi'ces which will appear hereinafter.-

When the number of subscribers centering in one central office is not .very over one thousand besides the necessarytruuklinesto other-offices, each subscriberscircuit terminates in a pair of metallic pins ject from the face'of the switchboard. The operations of signaling, conversing andtest'- ing by the operator are performed by making momentarycontact between the apparatus at 'tached to his person and these pins. For-corn wersation between two pairs of pinsare connected together either by a peculiarly constructed flexible cord or by a are presently to be described.

When the number of subscribers centering in one central cities is very large, .I make use of two switchboards, one. of which, called in this specification theanirunciator-board) is equipped merely with an aununciator and a pair of pins foreach subscriber, while the other -board,.ca'lled the fconnecting-board, is equippedvrith a pair'of pins, for each subscriber, and as many of my flexible cords as there are con ersationsgoiug on through the, office-at any one time. Two operators or sets of operators are employed,- one of which an; swers calls at the annnriciator board, while the other makes con'nectionsat the connecting-board, and both are equipped with perpeculiar form of commutator, both'of which.

sonall y attached apparatus for performing thevarious other desired services; 'Meaus 'are provided forconveying orders mechanically from theannunciator-board to the connectingboard, as will be hereinafter fully described.

By thus providing the two radically difierent kin'ds'of work between two diflf'erent sets of oper ators, l attain an enormous advantage in simplicity and cheapness over the multiple few'er operators are necessary, that each operator is provided such mechanism as he needs. to it is well known that in the 111 each operator is necessarily cumbersome and expensive which he uses only a'v'ery small part at any one time, and much of which he never uses at'all, yet I retain the advantages of'the multiple board'and secure mauyothers which this and no other form of board in use ordescribed ppsseeses', after I As an alternative lorm'of connecting-board, I sometimes make used an uprightframe having stretched across it in a. horizontal direction as many pairsot wires as there are circuitslentering the cities and the same numberot wires stretched acrossi't direction. A pair of horizontal wires and a pair of vertical wires are legged'omto eachsubscrihers circu'it. Both the horizontal and and, second,

ulti-ple board, provided with large,.say not that'prosubscribers, the two P -must be telephonicallyconnected together, -the calling subscriber signaled that the con first, in that merely with use, whereasmechanism of i n a vertical EST AVAILABLE COP.-

sniall space and at small expense as appare tus in which every wire is, at somepoint, con-' tiguou's to every other wire, so-that by theinsertion of one peculiarly constructed piu,'I may connect any subscribers circuit to that of any other subscriber. By'touching the ap- 'p'aratus with which the person of the operator is equipped 'to proper terrni tntlsv provided at the head of the pin, the operator, may perforni all of the -.necessary acts of signaling, conversing, testing, &c., as aboveenumerated. AlthoughI have assumed the frame tobe upright, because this possesses advantages of accessibility from-both sides, the f rame could of con rse be placed in any position. Y

" The above are some of thesalient. features of my invention. These features and the methods and apparatus bywhich they are atspecitication.

tained will be fully described later in the It vWill 'be'convenient in describing my iu-" vention tofirst enumerate the successive steps whereby any-two persons at diiferent'subscribers stations are placed in speaking communication with each other for so longs-time. as they may wish to converse, and wherebythe connection is then dissolved. I will then,

with the aid of drawings, describe in detail the methods and apparatus I use for attain- Z .Thesncces sive steps whereby communicaanytwo subscribers stations. Joe

tion' between may be efiected andsubsequently,dissolved,-

are, first, the subscriber-signals the central oflice thathe'wish'es to communicat'e and, be iug answeredQtellsithe central oflice with what subscriber hew'ishes to communicate; second, the.ceutral oflice- 'rnust'- ascertain whether thesubscribertwanted is or is not using his telephone; third, if," r as"soon-as,-

the subscriber wanted is not u'singthis telethe circuits. from the two. subscribers nection is completed, and-the called sub scriber signaled that he is wanted at his told,

phone; fourth, wheuco'nversatioubetween these two-subscribers is concluded, the fact i should be inade apparent at'the central oflice', so that. the connection may be dissolved "fifth, in addition to these operations, the cent'ral ofl'ice operator should be able to determine whethe'ra party calledhas answered his signal, whether satisfactory conversation isas will fully appearihereiuscribers stations ,is considerable, or when particularly loud conversation is required,-it

is desirable that the centralEOfiice operator "shall hostile to connect into the line joining together two subscribcrsstations, a relay tele-- phone by ineans of which the loudness of the conversation is augmentedand-each subv scriber given the advantages of along distance telephone without'the expense and complication of alocal long distanceoutfit; seventh, the communication may bedissolved l removingthe commutator.

In he drawings: Fig'urel isa perspective view "of the apparatus at the-snbscribers stat-ion'; Fig. isa diagranisshowing the-mode of operatipnrdf -.Fi g.-: '-:Fig. 3 is adetailed View of -a 'sWitchbQaijd cord terminal-"shown connected to the central oflice terminals of a snhscribers line. -'Fig. 4 is a diagram of an exchange as arranged forza small number of a ,"subscribers,say one thousand-or under. Fig.

.5 is a. diagram of anexchange' as arranged for alargenumber of subscribers, say one thou-' sand to three thousand. Fig. 6 is a diagrammatic front view.of oneform of connecting board, by whichcordsarc dispensed with and any one line is connected to any other line by a single pin.

- sectionofhi'g. G at AB. Fig. 8 is a'vertical cross section o.Fig. 6 at XY. Fig. 9 is a de'-- 'tailed view of the pin used in connecting two wires'ot. the board shown in Figs. 6 to 8. Fig. .10 is aperspective view of the pin shown in Fig.9. Fig. 11- is a diagram illustratingthe 12 u iroduce at the central oflice into a circuit con,-

office's.

connections and method of operating the conuecting-boardshown in Figs. 6 to 10. Fig. 12 is a view ofa relay which I sometimes in necting together two subscribers, the object of the relay being to increase the strength of t he telephonic currents, and thus augment the mudness of the telephonic conversation. Fig. 12; is a View of an alternative form of relay. Fig. 14 is adiagram showing how two relays may beeonnected together to form a telephone repeater" capable of reinforcing telephonic conversation in both directions. Big. 15 is an alternative method of connecting together two relays for the same purpose.

Fig. 16 is a diagram fillustrating the method of connecting a subscribers line terminating in one central oilice with another su bserih'ers line terminat- .'ing in another-central office'by meaps of a trunkline joiningtogether the two central So far as' nxay be -lhe same letters refer in all the figures to likeinstruments,apparatns,

wires, &c.-, num rals being added to 1118.181?" ters to designate different parts of the same kind,and the letterssometimes being coupled. Thus, '1. in allcases designates aset t telephone apparatus, the transmitterof which is Fig. 7 is a horizontalcross BEST AVAILABLE cor.

ally to parts whichare particularly designated by the same letter with a numeral attached. To avoid confusion, so much of the apparatusoply is shown in the drawings as will enable the invention and its modeot operation tobe'u'nderstood.

Fig. 1 is aperspective view of the appara- --tus placed at each subscribers station, and Fig. 2 is a. diagram showing its connections I and modeof operation.

B) is a. box] within which is an electric tap bell having two gongs land 2, a two point switch operated by the rod 3 and a press button circuit-closer operated by the presshutton 4.

i and r are magneto telephonessuch as aredescribed in my Patent No.406,224, one 0t which is intended to'be used as a transmitter and the' othe'r as a receiver. They are connected to the-box by .flexible cords as shown. The telephone.rhangs,wl1en not in use, upon the hook 5. This hook forms part of the rod "3 and when this roll is pushed in, slides within the bog: so that the telephone cannot be hung uponit. When the telephone is on the hook the rod cannot be pushed in/ When'the rod.

3 is pulled out the bell is in circuit, and when the rod is pushed in the telephones are in circult. The bell, cannot, therefore, be put out of circuit unless the telephone is off the hook, and the subscriber, having finished a conversation, cannot hang up his telephone un-' less he pulls out the rod and thus disconnects his telephone and puts the bell in circuit.

Two line wires to and w from the central office and an earth wire c',enter the top of the box.

Referring particularly to Fig. 2,6 is-a wooden frame in which slides the wooden block 7 by means of therod 3. 9 and 10 are metal plates secured to this block. 9 is connected through the telephones 'r and t to the wire to that extends to the central office. connects through the hell I) to he earth. The line'wire w terminates in a'metal spring 11, which re'sts on 10 and continues the circuit through the bell to earth when. the rod 3 is pulled out, but which rests on 9 and continues the. line w through the telephones andback to thecentral ofiice by the line 10 when the rod 3 is pushed in. The springpush-button 4 is connected to the earth and when operated connects the line 10 to' earth, and thus signalsthe central olfice-as will appear later.

Fig. 3 is a detailed viewof a switchboard cord terminal'shown'connected to the central office terminals of a subscribers line. k, k,

are the two conductors of the-cord which are joined to terminal springs s, s byscrews 12 and 13. p, p" are metal. pins projecting from the rubber face plate P of the switchboard and forming the terminals of the subscribers two line wires.

Fig. i is a'di'agram illustrating the connections and mode of operation of my system as applied to smaller ofiices of say one thousand subscribers or under. S is a subscribers sta- 4 ceases tion, to and theline wires, ending at the central oifice respectively in the pins 13 and 11 As shown, the line wire to is normally open at the central oihce and grounded 5 through the bell b at the subscribers station. Line .wire to is normally open at the subscribers station and grounded through the annuuciator a and battery B at the central office. S,- SYand S? are other similar suboffice switchboard. i

. An operator is shown at the switchboard -having'attached to his head atelephone TO. consisting of a transmitter to and receiver T0. 1.5 Each handof theoperator is equipped at the tip of the'thumb, first and second fingers of one or both hands with metallic thirn-bles f, z', n. [A wireextends from the thumbfo'f each hand, through the telephones and back to the 20. tip of the second finger 'n. A wire extends from the tip of the firstfinger i of each hand to the same pole of the grounded battery-B to which the annunciators are attached. The telephones attached to the head are wouudof very high resistance; in practice sometimes as much as five thousand ohms.

1o scribersimilarly connected to the, central 7:, t is a cord terminal connected by wires.

kw, kw through condensers 0', G with cord terminal 10 15.

c The operation of the system is as follows;

Suppose subscriber S wishes to telephone to central office. The central office operator,"

4o seeing the annunciator of fall, touches his thumb and second finger to the pins 19 and p He is thus in telephonic communication with subscriber S and can askforand receive the subscribers order to be connected with subscrtber S The operator then signals subscriber S, by touching the tip ofhis first finger ito pin 19?, thus allowing a current to pass from battery B through pin p", wire wl, bell b to earth and ringing hell I). He then connects the two lines together by placing cord terminal-7c)? between pins 19 and p'fiand cord terminal k t between pins' p and p. Theoperator then notifies subscriber S? that the connection is completed by touching the first ".55 or battery finger ofon'e hand to the pin 13 which makes a click in the subscribers telephone if he is listening, and rings his bell in case he has meanwhile hung up his telephone. -In practice, as soon as an operatorfgets an order for'aconnection, he placcsthe cord terminals in place, one with each hand, and simultaneously signals both subscribers, using the first finger of one hand to call the desired.

subscriber, and the'first finger of the other hand to notify the calling subscriber that con- BEST AVAILABLE com from each opemtors person to the grounded battery, I sometimes provide the operator with a pocket or local battery, one terminal of which runs to the first finger ot' the right hand, while the other terminal runs to the corresponding finger of the left hand. By

pins connecting with the subscribers lines, or by touching one hand to such a pin and the other to an earth plate, an y desired signals may be sent.

W'hen a subscriber has finished his conversation, he may send a disconnecting signal to in first calling. The operator may, however,

-ing on over any two connected lines by touch- "ing the pair of terminals of either line with his thumb and second finger. He may further tell whether or not either subscriber has hung'up his telephone for, when the telephone it is off the hook, the wire w will be at the same potential as the wire 10 since wires w' and ,w are connected together and to one terminal of the grounded battery B,but are otherwise insulated; and for the same reason if will boot the same potential. It, however, the telephone r is' on the hook, and consetogether, there will be a considerable ditferonce ofpotential between wires w and 10 which willmanit'est itself in a loud click at the operators telephone TO when contact is made with pine p, t The presence of a similar click when tfi e operator touches 19 101 shows telephone r to be on its hook. The very high resistance of the operators tele' phone TO doesnot allow of a snfificient short circuit between pins 11', p, or p, p to operate annunciators a','a" orbells b, b

the two. line wires becomes of great use in larger central oflices, as' will hereinafter app The objectof the: condensers C and (J is to prevent signal currents between the subscriber and operator of the other line. thecords are thus impermeable to signaling currents, they are of course readily permeable to telephone currents.

As manyoperators as are needed to take care-of the business may each be equipped with personally attached apparatus and all work simdltaneouslyat the switchboard.

When the number of subscribers centering in one central otfice becomes large, say over parts dififerent in kind; Qne -oi these,-called the annunciator-board, is used chiefly in receiving orders for connections, while the other,- jcalled the connecting-board, is used chieflyin connecting together thelines-aof subscribers.

Fig. 5 is adiagram illustrating the connectouching the two fingers simultaneously to' tell at any time whether conversation is notelephoue 'r is off the hook, wires to and w:

scriber and operator on one line, from oper-f vating the signaling apparatus of the sub While one thousand, 1 divide the board into two the central office by pressing the button 4 as quently wires to and w? are not connected use This similarity or ditference of potential between 'necting-board CB, and if desired.-

636382 BEIISTAVAILA'BLE COP. 5

ber of subscribers, say one thousand to three thousand.

S .is a; subscribers station equipped as above described and having line wires w'end w? extending to the central otiice. a is'the annunciator whichis now ,more intimately associated with its pins p, 19*; The wires w and w not onlyeonnect to'the pins 1), p ,.but also branch to thepins p'c, 0 0 on the con- C'OA is acentral ofiice operator eijuippedwith personally attached apparetn's,,as previously shownin-connection with Fig. 3. For

convenience, onlyone hand is shown for each operator. COA is another similarly equippedoperatorat another section of the same ennun'ciator board, for in prectice several operstore are usually. required both at the annunciator boerd and at the connecting-board.

0'00 'and 0 06 are -personally equipped operators at the connecting-board. All of the operators, wheth er at the annunciatorboard' or the counecting-boardgare similarly per sonallyequipped.

The operation of the exchange is as follows: Suppose subscriber S wishes to talk with subscriber 8. He presses the. button 4 and the annunciator a" is operated. The operator (J'OA sees this signel'a'nd places his thumb f and secondxfinger 'n'upon the pins 19' and 19?, replacing theshutter of the aunuuciator with the same movement of the hand. The oper ato'r then asks the'subscriber with what other. subscriber he desires to converse. The subscriber tells him with No. 4. The operator COA then communicates the number of the two subscribers to the proper section of the connecting-board.- For instance, he may write upon a slip-ofpaper the number.(l') of the ceiling subscriber, the nun1ber'(4),i0[ the desired subscriber and sendsit to the'con-n'ecte ing-board by mechanism to be described later. The operator'OOC (or,- if he is busy, the operator 0 09), looks at the slip and notes. that N o. l 'desires to be connected with No. 4. He places his thumb fc and finger-no upon the pins 12%, p 0, and, if he hears a loud click in' his telephone T'OC he knows that the line connectingto subscriber S is not in use.

Thisloud click is due to the fact that'thewire" approximately the same potential. The opcmtors telephone T'OC is of very high reto other pairs of pins.

sistance,,as beforeexplained, snd hence does not operate drop a when shunted across p, It plays the part of a volt meter i ha.smuch as the operator soon learns to determine dilierences in strengthot click, and thus easily to separate the "busy test from acctdental differences of potential; f It will be noticed that the busytesthere provided tells the operator, not merely whether the line of a desired subscriber. is connected to' some other line, as does the busy test of the system now generallyin use,'but whether the desired subscriber has his telephone off the hook and therefore in use, or whether it is on the'hook and therefore clearly o'ut'of use. A subscriber mcy'have finished his conversation and many -test, a. faulttliat is productive oi much thischief in practice. Having found the circuit of subscriber S not busy, the operator then 19 0, and cord-terminal 10% with pins p 0 andconnects cord terminul'k't with pins pc and p 0, thereby estsb'lishlng'a telephonic circuitbetween subscribers stationSend snbscrib'-. ers station S. He next touches his signaling finger it: of onehandto the pin p 0, thereby ringing the bell b of subscriber Sf, and the corresponding finger of the other handto pin pc, thus signaling subscriber S, either'by ringing his hellor making a click in his telephone, that the connection is con leted.v

As before stated,slgnnls to orfrom the c'eu-' tral oflice and one subscriber are not operative'of the ap'ptiratus of the other subscriber .or operator, because of the oondensers'C', (3 in the cords k'Jc'. Thus, when theopcrator 0'00 touches-:hls signelingtln-gers to pin p'c, itdoeslnot actuatetheannndcietora of op- "erator C'OA, nor does the operation of the press button tbysubscriber Soperute the :annunciator a of operator COA, even thoughthe two lines are in telephonic communicatlon; yet either subscriber S'- or fl msy signal his own appropriate operator .,et the an-' nunciator-hoard at any time, whether; the lines are connected together'or'nou' When either" subscriber, e. g.', S"hss tin ished his conversation and desires to converse with any third subscriber, e. g.,S he hasoulytosigna-l thecentral oflice by pressing button 4 and the connection will follow as at first,

whether hehas beendisconnected from subscriber S or not. The. operetors at the connecting-board may, however, at any" moment of leisure, by simply touching the fingers and n to the proper pairot pins 'p,p,a.nd no ting the presenc'eor absence both of click and conversation, determine. whether subscribers '-so con'nectedare carrying on a conversation onhav-e' finished. or are simply waiting, end,

in case they are having tiny-difficulty in con:

vetting-may help them out; 'I sometimes make use of one operetor or set of operators to make connections,and another. operetorto. watch connections and dissolve 'them when conversation is finished.

- insertion of one peculiarly constructed pin, I

' iv h, and each plane has as many pairs of ffhousand siayhundred subscribers, I place the wires one-tenth of an inch apart and make placed similarly but one behind the other. In

' at the pins i'p, Pp.

side and parallel to the back of frames Fh, F 1), the. Outside the various frames and par The verygreat flexibilityof the-presentsys-' tcni thus far described, as well vas its simplieity, convenience, reliability,eificiency and speediness, are in marked contrast to systems generally in use, as will easily be perceived byany one skilled inthe art to which thisin= vention pertains.

As an alternative form of connecting board, I sometimes make use of an upright frame having stretched'across it in a horizontal direction as many pairs of wires as there are circuits entering theoffice and thesame number of wires stretched across it in a vertical direction. A pair'of horizontal wires and a pair of vertical wires are legged on to each subseribers circuit.- Both the horizontal and vertical wires may be arranged in several, planes, and I am thusenabled to secure in a small space and at a small expense, an appa; rains in which every wire is, at some point, contiguous to every-other wire, so that by the they connect any subscribers circuit to that of any other subscriber, Within the board, wires are stretched both horizontally and vertically as shown in Figs. 6, 7 and 8, of which Fig.6 is a front. view of a board with the easing removed. Fig. 7 isia horizontal cross-section of Fig. 6 on the line AB, and Fig. 8 is a vertical section of Fig. 6 on the line XY.

Fh is an iron frame, fanningout at eachend-as shown. .Along this 'frame,in a hori zontal direction. are stretched plated steel wires wh, 1027!, 0., each secured by. insulating pins ip, ip, at either end, to the iron frameF'h. The wires are sup ported, wherever necessary, in perforated insulating braces pl), 117), rte. They are everywhere insulated from the frame. Each frame has the, wires arranged in four parallel-planes, as shown particularly in Fig. 7, w'h, 'w h, 10 b, and

wires as may be desired, having due regard to convenience indistance apart of wires and sizeof frame. Ina connecting-board for three the frame Fh about five feet high and fifteen feet long. There: may be several similar frames, Fh, Fill. F 11, and more-if desired,

practice I find three thousand six hundred horizontal wires require three frames which aggregate a depth of three inches.

The wires ""IL and tu'-'h form a pair of terminals for one circuit, which is brought to the frame by wires connecting to these terminals The other pairs are similarly connected.

F'v and .F-v are also iron frames in which vertical wires lr'z, w n, the, are stretched. Each frame has the wires stretched in two planes wr and u-""r. The frames supporting the vertical wires are placed one on either and 11 8, each pierced with square holes s'h, 3 &c.,- to allow the nsertion of pins to make contact with the horizontal and vertical wires.- The vertical wires wv and wu form a pair of terminals for' the same circuit; as do-the horizontal wires wh and will. In fact each circuit entering the office terminates in a pair of vertical wires and a pair of horizontal wires in thewire frames.

Fig. 9 is an enlarged view of the pin used. to connect any pair of vertical wires with any pair of horizontal wires. The same pin is shown in perspective in Fig. 10. As many such pins are provided as there are likely to be conversationscarriod on through the ofilcc at any one time. These pins may be inserted from either face of the board.

In Figs. 9 and 10 vs is the vulcanite faceplace. 1-1 is a square block of vulcanite through whichis a square hole of the same size as those in the face plate.- s'p and 8 1) are metal springs fixed to the inside of the block H and adapted to connect with vertical'wlres w'v and 10 2), when the block II is placed so that its square hole-shall matchasquare hole in the face plate. P is asqnare vulcanitepin that slides within the hole in H, Near the top of the pic at 2i and2 2 are ends oi. metal strips 23 and 24, which strips are adapted to connect at 25 and 26 with a pair'ot' horizontal wires. In the figure they are in contact with horizontal wires 'w h.- and w h: They would make contact with any pair of wires dependent upon the hole in which the pin was placed and the distance to which it was pushed in. The metal pin 21 has awire23 running along one face of the pin P and terminatingat 25.

It makes sliding contact with spring sp..

Similarly, pin 22 has a wire 24 running along the face of the pin P to the terminal 26 and making sliding contact with the spring s p. 27 is a bit of vulcanite attached to a spring s"p and intended to prevent contact between wire w-v and this spring. It will thus be seen that by movingthe pin in and out, metallic circuit contact may be made between the ver-' tical wires :u'o and w n, and any one of the pairs of horizontalwires, e. g., 'w h, -w h.

' By choosing the proper hole in which to insert the pin and by inserting it the proper distance, which is'determi ned in practice bythe feeling as the pins touch the various succe ssive horizontal pairs of wires, or which. r mightbe determined by a scale cut on the pm,

all l to them are the vulcanite face plates cs nectiug-board WCB, and his wire 10 branches its to vertical wire and' to horizontal wire 10 71 and, generally, each subscribers pair of wires branches to a pair of horizontal" wires' in the connectingboard. C,C ,&c.,.arecondensers-insertedbe= tween each annunciator-and the pair'of con-l meeting-board wire'sassociatedrwith its line wire.

by'to'nching his thumb and second finger to plug terminals and 26, and signals thetwo subscribers by touching his forefingertoplug' terminal 25. As an alternativearrangement;

f of the calling circuit of, the operator, Ihave,

'inf Fig. 31-1, shown aibatteryterniinatingz at 28, and a cord joining together the first 'finj gers'of both; blinds; It'is-evident that, by

touching' 28 with o'nehand and 25.with the other, a current will pass from batteryB over dines w'and 1 nd. ring the bell-s of subscribers' S andS Exactly the method ofcalling-fshown in Rig. 4 might,-however, b'e used.':-..-

loud conversationis desired, my systemcom templatefihefintrodnction into, theFicix-cuit;

at one 'ormo're intervening central offices, of

-'relaytelephones, whose purpose is to increase 3 5 the loudness-of the telephone conversationso vantage oflong distance lines without the p expense and complication of a long distance.

outfit.

tical use, have been found capable of. work ing only inonedir'ection, e. g.. if subscribers S is connectedrto subscriber ..S.?, the 'relay -fro or a ni'a'gn'et-o telephone transmitter,- very .65.- V i tw een them" than if both werelequipped with inay be made to nmgi'l-ifyeitherthetalking of S or of Sfibnt not oflhoth. Practical use, however,;,shows; thatmy herein described res.

; ay is equally operative ,in' either direction,

from subscriber S or subscriber-Sfiorfrom bothsimnltaneousiy The means whereby I accomplish this, as well as the details of con strnction of thy'relay, -form part of the pres-.

ent invention;

My relay, when'applied to a current arising greatly increases the loudnessof gtalking due to such current,iwhilepreserving all theclean phonesare proverbialk g ly inserting one of nay-relays in a cord used,

at the'central o-fii-ce,' t o connect-together the, circuits of two subscribers who are equipped;

with my .niagneto transmitters,- Linay insure 'as' loud and much; clearer conversation *b'epair of vertica'land a that I may give to, each subscriber the ad' 1. =e., -it-magriifiesfthe conversationiarising.

536.382 BEST AVAlLABLE COP;

so called longdistance battery transmitters.

By inserting a second relay telephone in series with the first, I maystill further increase 'the-loudness of the conversation, and in equippedwith a magnetotransmitter and connected with central oflicefCO' and subscriber S equi ppedwith amagneto transmitter and connected with central ofiice 00*, the two centralgofiices' being; connected 6 a line .five

V hundred miles in lengthgandboth central offices having relays in'se'rteil' in the line, is carried on with perfect ease.

Foe convenience in this specification, Iwi'll designate a pair of telephone 'relaysso connected together as to -magnify conversation in both directio'ns', asa telephone repeater.

.Fig. 12, and the method andmechani-sm used 4 a repeater, and the inethod of conpectingsnch repeater into the line are shown in Fig. 14. gln Fig. 13 is shown aiinultiple contact mof the relay shown in Fig. 12;}and in .Fig. 15

.an alternative "to' Fig. 14. g

"Referring, to Fig-.12,- Mtfiis'a magneto telephone such'a's is described in tny Patent No.- 496,224. Adistingnishingieaturalas-settorth inthe paten t referred"'.t-o',:i-s -the method ,of mounting the diaphragrn. dg' between two concentric ring-shaped knife edges kn kn of intozthe similar: magneto'telephone Mt 'isreposted in the vibrating ofithe'diaphragm' (Z'g To the diaph ragmdg' and piojectin g. upward as shown, is fixed the plumbago electrode 1pc; Ag is a silver ;-hutton suspended from one end of a lever L'v' which'is pivoted at pv'and counterbalanced bya weight wt. ,iiy-mov ;ing the weight wt to-Ior front the point of supthin filinof vaseline'vs', whosepnrpese-is-to;

prevent Qtheoxidzititin 6f the mercury. .B' 'alifttte'ifandifih primary 'in dnctimi' I The -whole, relay revolves about ;the axis-.kasshown,

' ncss of antienlatio'n forsvhich magneto-tetra;

whereby the pressu realis -ween the-two elec- "trodesmay be Eva'ried without varying their inertia; I

- Theoperation 'ofthe-relay is'as' follows; Talking-into the magneto'ftelephone MR sets the diaphragm do; of the telephoneliit into vibrations similar in forth-to those of the diaphragm of Mt though of somewhat'less anipractice, conversation between subscriber S .The. mechanism of" each relay-is shownxjin of ;Mt" with great acenracy and amplitude,

inconnectiug together two such relaysto form lay which may housed as an alternative form is shown a method otgcoauectingitogether two s e relays toform-a repeaterithat may bens'ed as Wh'en the distance separating any two sub- 1 scribers 1s very great, orwhen particularly different diameter, whereby talkinghttered' IIO portof the. lever, the pressure ofAg' upon while the inertia of thesystem-Ag Ln? wt'is sented toward I the elect-rode, pfa. .iscovered with -a thin film-of niercury llg' intofwhich- 58 2882 BEST AVAiLABLE COP;

' duced in the primary coil 1, which in-turn induces through the secondary coil II and upon the line wires w"; an undulating currentsimilar in form to that given out by the magneto-telephone M1 but enormouslyincreasedin strength. Thus, talking into telephone MF is heard in telephone Mt much louder than if the relay were not in circuit.

An alternative form of relay telephone is shown in Fig. .13, in which the diaphragm (lg carries a silver plate Ag whose face is covered with mercury H9 A second silver plate Ag whose-face is covered with mercury Hg? is adjustable to and from the plate Ag by means of the screw s. Between the two mercury faces are placed a number of plumbagoballs pl as shown. In this instrument the vibration of themercury surface Hg to and from the mercury surface Hg causes the piumbago balls to dip more or less deeply into both mercury surfaces, and thus vary the resistance of andconseqnently the strength of currentilownig' in the circuit B Ag, lIg 12b Hg", Ag IUB".

It is evident that while such a relay as is shown in Fig. 1:2 (or Fig. 13) is capable of magnifying the sound uttered in Mt and heard in .Mt, sound uttered in M6 cannot lie-h ard in M6 i. e., the relay will not work both vays.

It might at first be supposed (and indeed it has been proposed) that two relays might be connected in opposite directions, 2'. e., the secondary coil of each to the magneto telephone of the other, either in series orn1ulti- On so connecting two relays, however, I iind that the slightest ja; will start the diaphragm of one relay of a .pair in vibration, and thatthis will induce a current in the second relay, which will again induce a current. in the first relay, and so the cycle of mutual reinforcement is kept up with increasing strength of current until the respective diaphragms are forced to their elastic limits,

when both continue to vibrate and give out aloud musical sound determined by the normal time of vibration of the diaphragms, and in no way allowing of the repetition of con- ,versatioi...= I have discovered, however, that the mutual ction of each relay of a repeater upon its matr may be prevented, and yet each reinforce the conversation in the desired direction by so arranging the two relays of a gepeater that, while the currents arising from the respective line circuits, act each upon the magnet of one relay and cause this relay to impose a magnified current upon the other line circuit; the current given out by each relay shall act dilferentiall y upon the magnet. of the other relay. One method of accom plishing this is shown in Fig. 14, and an alternative method in Fig. 15.

Fig. 14 is a diagram of a repeatercomplete consisting of two relays Rland RP. The relay-RZ consists-of the 'magnetotelephon-e Mt, having a diaphragm dg', electrodes at E ,,Ib,attery B, a primary induction coil 1 and-sec"- ondary coil II. sists of the magneto telephone M6 diaphragm c19 electrodes E battery B, primary coil I Similarly the relay RZ con- I and secondary coil I1 to w are conductors of a. flexible cord connecting the relay Rl: with the cord terminal Kt, which cord terminal is adapted to connect with any subscribers or trunk line circuit, say S. Similarly 111 -10 are conductors of a flexible cord connecting the relay R1 with the cord terminal Kt, which cord terminal is adapted to connect with any subscribers circuit, or tru nk line circuit.say S One terminal of the secondary coil ll of relay Rl connects to the line wire w -at junction j. The other terminal of II,- connects in divided circuit; through a double and differentially wound impedance coil Ic and wires 10 and w, with both terminals of the magneto telephone Mt of relay R1 Rs is an adjustable resistance inserted in wire to between junctionj' and the magneto telephone M19 of relay R1 Similarly one terminal of the secondary coil 11 of relay R1 contracts to the linewire w at junction j while the other terminal of Iliconnectsin divided circuit through a double and diderentially wound impedance coil In and wires to and w, with both terminals of the magneto telephoneMt of relay RZ. resistance inserted in wire w between j unctionj and the magneto telephoneMt of relay RZ. I 1

The double wound impedance (coil Io (or .10") is fully described in a. patent for simultaneous telegraphy and telephony, issued to me on December 12, 1893, and numbered 510,508. Briefly it consists of a magnetic core and a wire branching into two equal wires, one of which is wound around the core in a right'-handed direction, while the other is wound aroundthe core in'a left-handed direction. In practice each wire should have a large number of turns so that; alone and without the other, it would present a consideruble impedanceto'a telephone current. IE it is desired that the ohmic resistance'of the coil shall not be large, wire of large sectional area should be used. In practice, also, the the core should consist of an annular bundle of soft iron wires to increase the impedance. The peculiar usefulness of this coilarises from the fact that it is practically impermeable to telephone currentstending to pass over the two windings in series, and yet readily permeable to' telephone currents passing over the two windings in multiple.

The operation of the telephone repeater Rs is an adj ustable" v to battery B, through E and primary coil-l.

" Consequently a strong telephone current is set up in secondary coil II; One terminal of this coil sends currents directly .into the line wire w as shown, while the other terminal I sends two equal and similar currents in multiple (hence without impedance), through thecoil and by wires 10. and wto both terminals of magneto telephone Mt. These two currents, being equal in potential when arriv;

so ing at the two terminals of Mthave no effect P on telephone Mt but one ofthem passes to line over wire w, while the other passes through the rheostat Rs to junction jf and thence back to coil 11'. Inorder' that the cur- .25 rents in w and w shall be equal, the electrical properties of the .rheostat Rs should be equalto those of the line circuit w w, but, since in practice it is not necessary to en--- gtirely prevent the action of coil 11' on telephone hitfi'no accurflib adjustment of such electrical properties necessary. It may be noted that these circuits form a Wheaistone bridge of which 11 is the actuating electro- 1 motive force, lhli' the galvanometer (or galyanoscope). 10 and w are two arms of the bridge, Rs the thirdarm and the subscribers circuit to w the fourth arm. Hence it follows that, so long as the well known proper proportions be attained between the wires w o and-w, the rheostat Rs and the line circuit ww, the coil II can-have no eifect on -the telephone Mt:-v

Having thus explained how a feeble telephone current in circuit 'w'w may, by means of relay RZ, inducea strongtelephone current on circuit ww, without aifecting relay RZ, it is easy to see by simple inspection of the diagram how, in a similar way, feeble currents in circuit w w may, by means of relay RP induce strong currents on circuit. 'w'w without afiecting relay RZ. Thus each relay magnifies the current in its own properdirection withoutaffecting the other. An alternative method of connecting together two relays to form a repeater in which each relay shall act diiferentially on the other "is shown in Fig. 15.

relays; dg, dgi diaphragms; E, E pairs of 6c electrodes; B, B batteries; 1', 1 primary coils; l1, 11', secondary coils; RS2, Rs, rheostats; Kt, K15 cord terminals, and w, w, &c.,

wires. The coil of magneto telephone Mtiis As before, RZ', Bl arel relays; Mt, M25 the magneto telephones of the Similarly the coil of magneto telephone M6 is wound in two halves a and b The operation is as follows: A telephone current arriving from'a subscriber's station (or trunk line) by'circu it ww ,passes through the telephone Mt in part by the circuit w, a, b, w",w,.and in part by the circuit 10', a, w, a but in both cases, around the magnet of Mt in the same direction. As previousl y described, a 'rei iforced telephone current is, through the action of the relay RZ, set up in the secondary coil 11. One terminal of the coil 11 sends a current to line via junction j and wire u, while the other terminal sends a ourpentvia wire w" through coils a, and b, around the magnet of MI? in opposite directions; hence producing no magnetizing effect on Mt. The current'th'rough bpasses to line over 19, while the current through a passes over wire w and thro'u h frheostat Ba, back to the coil I-I'. By-making the rheostat Rs electric all'yeq'ual to-the circuit w w, the coil II has nomagnetizing effect on the magneto telephone Mt of relay RP. Similarly telephonecurren tsarriving at magneto telephone Mt i re mcircuit w to, may, by means ofrelay RB induce i-einforced currents upon circuitjw. w? without affecting magneto telephone Mt of relay RZ. Thus proper direction without affecting-the other.

Numerous other methods of connecting together'the two relays so that 'each shall act only diife'rentially on the other, will readily occur to any one skilled "in the art to which this invention pertains. J

BESTAVAILABLE COP". 9

each relay may magnify thecur'rent in its own too The method of connecting a subscriber whose line terminates in one central office with a subscriber whose line terminatesi'n another central office is illustrated in diagram Fig. 16. The lineof subscriber s terminates f at central ofiice GO in-pins-p and p and an:

nunciator a? as previously described. Similarly the line of subscriber S i terminates at central ofiice C0 in pins 11- 9, p and annunciator 03.

Rp is a telepone repeater at central oifice CO with cord terminals k't, k t, and similarly R p-is a telephone repeater at central office COwith cord terminals kit and kt. ,Person;

ally equipped operators are. shown at both TL is a metallic circuit 'trunkline,.consisting of the two wires to and tw,' extending between the two central oflices and terminating at central office CO'in switchboard pins pt. and pr andannuncittor at. precisely as a subscribers line terminates. excepting. that the other terminal of tho annnnciator at counects directly to' earth instead'oi?v through a battery. Similarly the sametruul: line terminates at central office Coi in switchboard pins pt and t and annunci'ator at. I

1t will'be noticed .thatazrunkwire twis normally open at central office 00 and grounded through annunciator at; at central office 00*. Similarly trun-lcwire no? is normally open at the connection at one or both ofific'es.

central otfice CO and grounded thronghannunciator at at central office 00. It follows that when the personally equipped operator at' C0 touches his battery finger to pin pt, the annunciator (115 in central ofiice CO is operat'ed,-and when the personally equipped operator at C0 touches his battery finger to pin pi annnnciator at at central olitice CO! is'operated. The method of signaling to or receiving signals from a different central ofiice is thus exactly like signaling to or from a subscriber.

. Connections between a subscriber and atrunk line, at either central office, are made precisely as between two subscribers at one central oifice, excepting that, when theofiices are'widely separated, cords in which a telephone repeater is inserted, are used to make In many cases,- however, ordinary cords, as-above described, may be used at one or both oftices.' In operating the system, subscriber S may ask operator CO to connect him with operator CO and t-hcn ask operator C0 to connect him with subscriber S or subscriber S may tell operator CO' with whom be desires to communicate, and leave it to this op erator to make up the necessary through con- 'nection.

In the light of the various above descriptions, further description of the system as a whole, whether composed of one or many-central oflices, becomes unnecessary.v

1. A metallic circuit telephone exchange system consisting of telephonic apparatus at each subscriber-s station, and a pair of wires, extending therefrom to the central office switchboard and there ending in pairs of open branch terminals, one of each or said pairs of line wires being normally open at the subscribers station and grounded at t'h'e'oentral oflice through a high impedance annular ciator and battery, the other wire being normally open at the central office and grounded through a bell at the subscribers station; switching mechanism at each subscribers station by means of which its two wires may be joined together through the s-ubscribers telephone and, at the central ofiice, a double conductor connecting cord provided with a condenser in each conductor and a donblecontnct terminal at each end,each of which contact terminals is adapted to make connectionw-ith any pair of said branch terminals on the switcln board; an operators switchboard commutator I comprising a transmitting and receiving telephone conveniently adjusted upon the person of the operator and having each terminal connected'by a flexible conductor with a metallic thimble placed upon a finger olf each hand, and signaling-apparatus consisting of a cond uctor connected toor adapted to be connected to an electric generator and connected by flexible conductors with other-metallic thimbles placed one upon a finger of each hand, i

whereby the operator may, by touching the proper combination of .metallically tipped fingers to the appropriate switchboard termi nals, send signals to and puthimself in tele- ST AVAILABLE COP;

phoni'c'commu'nicationiwith any desired subscriber or pair of subscribers;

2. A telephone operators switchboard commutator consisting of a transmitting and re ceiv-ing telephone conveniently adjusted upon the person oi the operator and having each terminal connected by a flexible conductor to a separate metallic thimble placed upon afinger of one or each hand, whereby the operator may, by touching the proper combinationof'metallically tipped fingers to the appropriateswitchboard terminals, place himself in telephonic communication with any desired subscriber or pair of subscribers.

3. Signalingapparatns for a switchboard operator consisting of a portable electric generator conveniently placed upon the person of the operator-and having each terminal connected by a flexible conductor to a separate metallic thimble placed upon a, finger of one or both hands, whereby the operator may by simultaneously touching the proper metallically tipped fingers, each to the appropriate subscribers or earth terminal upon the switchboard, 'signalanydesired subscriber or pair of subscribers. V

4. Signaling apparatus for a switchboard operator consisting of a flexible conductor conveniently placed upon the person of the operator and having one terminal connected to a metallic thimble placed upon a finger of one hand and the other terminal tea metallic thimbie placed upon a finger of the other hand, ;w-hereby the operator} niay,-. by simul-' taneously touching one metallicallyt tippedfin ger 'to the open terminal of a grounded electric generator and the othcrometallicaliy tipped finger to ,theayppropriate subscribers line terminal upon tie switchboard, send a calling signal to any desired subscriber.

5. A telephone metallic circuit interconnectiug board or commutator consisting pf two series of parallel'conductors, extending across said board at rightangles to each other,

the conductors in one or both series arranged in groups in ditferentplanes, a pair of immediately adjacent conductors in each series constituting the open branch terminals for each telephone circuit in combination with a'connecting plug consistingof two parts reciprocally movable, and resilient conductors, which electrically connect said parts, whereby, while one of said parts is in contact with a pair of circuit wiresin one plane, the other part is adapted'to be placed successively in contact with a pair of circuit wires in each of several other planes 6. A connecting plug foreleotric circuits,

oonsistingof two parts reciprocally movable,

and resilient MBdD'CtOPBy-Which electrically connectsaid parts, whereby, while one of said parts is in oontsctwith a pairot circuit wires a balanced elec thin film of mere opposing telephone relays,

1 magneto telephone of the other rel in one plane the other part is adapted to be placed successively in contact with a pair of circuit wires in each of several other planes.

7.' A telephone relay consisting'of a magneto telephone, a carbon electrode projecting from the diaphragm of the magneto telephone, trode consisting of a thin film of mercury held contiguous to the carbon electrode, at protecting film 0t non-oxidizable liquid covering the mercury electrode, a battery and an induction coil, the primary 0t said coil, the battery and the said electrodes be ing in circuit. I

8, A telephone relay composed of a mag-. neto telephone,

an electrode consisting of a ury attached to and vibrated by the diaphragm of the'magn'cto telephone, a second electrode consisting of a thin film of mercury supported independently of said diaphragm, carbon granules between the two mercury films and dipping slightlyinto both, protecting films of non-oxidizing liquid covering both mercury films, a battery and an induction coil, the primary of said coil, the battery and said electrodes being in circuit.

A telephone. repeater composed of two each relay consisting of a magneto telephone receiver, electrodes actuated by the diaphragm of said receiver, a battery and an induction coil; the magneto telephone of one relay being in circuit with the line wires extending in one direction, and the ay being in-circuit with the line wires extending in the other direction, and mechanism connected in the circuit of the secondary coil of'each relay to cause the current given out by each secondary coil to act differentially upon the magnet of the opposite relay.

10. A telephone repeater composed of two opposing relays, each relay consisting of a magneto telephonereceiver, electrodes actuated by the diaphragm of said receiver, a battery and an induction coil; the magneto telephone of one relay being in circuit with the line wires extending in one direction, while the magneto telephone of the other relay is in circuit with the line wires extending in the other direction, and a double and differentially wound impedance coilih the circuit of the secondary coil of each relay, through which, by a branching circuit, it is connected at-one or both terminals with the line wire of the other relay on opposite'sides of its magneto telephone, whereby the current given out by each relay acts only differentially on the magneto telephone of the. other relay.

11. A telephone repeater composed of two opposing relays, each relay consisting of a magneto telephone receiver,

ated by the diaphragm of said receiver, a bat- 'other relay.

. BEST AVAILABLE cos.

coil; the magneto telephone of one relay being in circuitwith the line' wires extending in one direction, while the magneto telephone of the other-relay is in circuit with the line wire extending in the other direction, and the circuit of the secondary coil of each relay is connected at one or both terminals to the middle of the coil of/the magneto telephone of the other relay, whereby the current given out by each relay acts only dilfer'entially on the magneto telephone of the tery and an induction P 12. A telephone exchange systenf consist-- electrodes actuing. of numerous subscribers stations, each equipped with telephones; wires extending from the various subscribers stations to the central oflice, and, at the centralofiice, a telephone repeatercomposed of two opposing'telephone relays, each relay consisting of amagneto telephon by the diaphragm of said rec and an induction coil; the magneto telephone of one relay being in circuit with theline wires extending in one direction, and the magneto telephone of the other relay being in circuit with the line wires extending in the other direction, and mechanism connected in the cirsuit of the secondary coil of each relay, by means of which the current given out by each secondary coil acts difierentially upon the magnet of the opposite relay. 13. A telephone exchange system consisting of two or more central offices; wires radiating from eachicentral office to subscribers stations, each equipped with telephonic apparatus; trunk lines extending between the central ofiices and, at one or more of the central offices, a telephone repeater composed of two opposing telephone relays, each relay consistdiaphragm'of said rehereof I have signed my fication, in the presence of witnesses, this 23d day of SILAS W. HOLMAN. Witnesses:

A. J. Buanow',

'1. J. CUNNINGHAM.

too

mg of a magneto telephone receiver, elec-

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