US1221166A

US1221166A - Telephone-exchange system.

Info

Publication number: US1221166A
Application number: US9363016A
Authority: US
Inventors: Charles L Goodrum
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1916-04-26
Filing date: 1916-04-26
Publication date: 1917-04-03
Anticipated expiration: 1934-04-03

Description

c. L. GoonRuM. `TELEPHONE EXCHANGE SYSTEM.

APPLICATION FLED APR. 26| ISIS.

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Patented Apr. 3, mi?.

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C. L. GO'DRUM.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FiLD APFLZ, 19H3.

Lila 21|.

operates :his V'sender to set s uc UNITED- sTATEs PATENT oiuiion.y

CHARLES Il. GOODRUM, NEW YORK, N. Y., ASSIGNOR- TO WESTERN ELECHTRIC COM- PANY, INOOREORATED, 0F NEW YORK, Y., A CORPORATION 0F NEW YORK.

TELEHONE-EXCHAN GE SYISTEM.

To all ywlw/fn t may concern:

lie it known that'I, CHARLES L.A Goomunvi, a citizen of tlie United States, residing at N ew York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telephone Exchange Systems, of which the following is a full, clear, concise, land'evact description.

This 'invention relates to telephone exchange systems employing machine switch ing with subscribers control. Its object is to provide a circuit arrangement Vwherein Vthe calling party iiiay set up a. connection with the called party over a train of automatic switches, and after talking with such party, may, by operating his sender, bring a third party into. the connection. Provision is also .iliade for introducing another party or parties intotlie talking circuit, if desired.

In accordance with this invention, a calling subscriber sets up a connection by means of la sender, overan automatic switch, or in the caseof, 'a large exchange, 4over a train of `such switches. When the called party responds, `a circuit change takes placein the connector which prepares a circuit for an electromagnetic responsive device, for example, a relay, which is operated if the calling party subsequently operates a switch,

which may bel-iis sender, to interrupt the,

line circuit. This relay, `in operating, connects a special connector, or in Vthe case of a large exchange, a special first selector, in parallelto the connecting circuit connected to the calling line. The callinfr partly now connector y or such. first'fselector and the 'succeeding switches to bring athirdparty iiitol the connection.V l 1 4 The invention will be more clearly under- 4 stood by reference to the accompanying `,drawings wherein Figure 1 illustrates a' lineV finder circuit; Fig. 2 a first and second selector circuit, and Fig. 3 a connector cir- 'cuit,'and a 'special first selector circuit arranged in accordance with .my invention. The invention `1will be best understood by describing in detail the operations involved in setting up a connection.

Upon the removal of tliereceiver at sub- V station A, the line relay is energized Specificationl of Letters Patent..

Patented Apr. 3, 191.7.

ing its right armature, connects a. source Ufaltemating current 10] through a relayY 102 to multiple finder terminals 103. ot the calling liiie to render the .saine calling, and by attracting i;s left armature, energizcs 'starting relay 101 over the following circuit: 'free pole of battery,l relay 104, left ai'- niature and backcoiitact of' slow relay 105, left armature aid bark contact oit relay 102, left armature and liront Contact: of relay 100, right armature and hack .contact of relay 102 to ground. I left armature, locks itself to ground at the right armature and back Contact of' relay 1,02, independently of relay 105. By attracting its right ariimture, it closes the circuit of primary step ping magnet 106 of the line 4finder as followf: free pole of battery, mag;`

group. Relay 105, by attracting its right armature, intenposes a break in the circuit of finder release magnet 109. Magnet 106 gives the finder brush. shaft 110 av primary inoveinent to position a set of brushes 111, 112 thereon, in operative relation. to multi-v ples of the calling group containing tb of the calling liiie 103, 113. Whenthe co i-i mutator brush 114 reachescalling coini'iiii4 tator lsegment 1.08, now grounded, finder side-switch 4escapeinent magnet 1151s ener-A gizeolv over the following'circuit' free pole of battery, magnet 115, aringfl and its iiifst contact, brush 114, segment 1.08, outer right Iarl'nature and front Contact o1' relay 104, and.

right armature of relay 102 and; its beck contact to ground. Escape magnet 115 is arranged to release the side switch from position 1 to position 2 upon its energization. Arm 4, in moving off its first contact, opens the circuit of :.nagnet v106,V atV which' time brushes 111, 11E: Vare in operative relationto Relay 10i, by attracting its YT .over the line circuit. lhis relay, by attract eef multiples oiy the callingv group containing -l those of the calling line l103, 113.

In moving ir to position 2, arm .4 transl 5.5 phonic'iapparatus at substation A, line contery, magnet l116, its armature and back contact, armi 4 and its second contact, conduc tor 107, relay 105, inner right armature and ,front contact ot' relay 104, varmature and jlficlr contactot relay 104, armature and "back contact of relay 102 to ground. Arm 3 bridges its first and second contacts and escape magnet .11."3 is .n'mintained energized in position 2 in parallel with magnet 116. When brush 1.11 reaches terminal 103 of the calling line, .the following circuit 1s closed for relay 102? ground, generator 101, relay 1.02,.ri,g1ht` armature and front contact of relay 100, terminal 103, brush 111, arm 1 and its second contact, condenser 117, relay 118, fre pole of battery to ground. Relay' 102, in attracting its right armature, opens tlie circuit of magnet 110, thus stopfitig the finder with the brushes 111, 112 n tlicc-.illingline terminals 103,113. The cape magnet 115 is also denergized by c opening of this circuit, and releases the sir` switch into position 3, in which position, arm 2 closes the fol-lowing circuit to energize cut-'offjrelay 119 of the calling line: free pole of battery, relay 118, arm 2 and lts third contact, .brush 112, terminal 113, relay 11.9. to ground. Relay 119, in attractlng its armatures, connects` the calling line to the terminals 103 and 11.3 and denergizes'line relay `100, which, in retracting lts right' armature, removes the calling condition I tact from the multiples `103 'of the calling linev to render the same non-calling Vin the other finders in'which it appears.. Relay 102, by attracting its right armature, removes the calling condition from multiple segments 108 of the calling non-calling in the. other finders 1n Whichit appears, and .unlocks 'relay 104.. Relay 104, in retreating its inner right armature, reconnectsthe in-starter Wire l1 20 to conductor 121 which leads by -wa-y of arm 4 and its third contact tothe out-starterwire 122 leading to the next idle finder, Arms 1 and 2,. in moving 4into "position '3, Vclosethe following'circuit.: lfree pole of battery, relay 118, arm 2 and its third contact, brush 112, terminal 113,' left armature and front' contaotof relay- 119, line' conductor 123, tele'- 'ductor 124, right armature and front `convk'o f.1elay 119, terminal 103, brush 111, arm 1 and its third contact, conductor 125, conductor 200,', arm l201 and the first `contact of the first selector side switch, relay 202 to ground. Relay 202, in attracting its armature, energizes a slow relay203, which, in

'attracting' its left armature,- ,inte'rposes a break in the"cireuit ol the lirst selector release magnet 206, and connects primary stepgroup to. render the group the side switchI .msg provezithig1 ping magnet 204 and a'slow relay 207, in4

parallel to the back contact lay 202.

The calling party now operates. hls sender of stepping re 126 to transmit the first digit of tlle wanted number. Each time the .sender interrupts the line circuit, relay 202 denerizes, transmitting an impulse over the fo owing circuit to magnet`204: free pole of battery, magnet 204,

conductors

208, 209,l left armature and front contact of relay 203,.arma turc and back contact of relay' 202, armal ture and backl contact of relay 210 to' und. Slow relay 207 'energizes Aupon the retraction of the armature of relay 202,.- and remains energized as long as the sender is operating; At its amature and front con' tact, relay 207 closes a circuit to energize escape magnet 205. The escape ma 'et is constructed upon its denergization, to release the side switch fro -position 1 to 'p osition 2, in the Well-known 'mannen When the sender restores and maintains relay 202 energized, relay 207, tracts its armature, opening the .circuit of escape magnet 205, which, m denergizing,

releases the side Switchinto position 2. In.

position 2,'arm 211 closes the circuit of sec` .ondary stepping .magnet 212 to-

drive thebrushes

213, 214 over the multiples 215,216 of. the selected group of trunks. Slow relay 203, at its right arnature and front contact, connects ,escape magnet 205 to the front contact of a test relay 210. When brush 214 encounters the Afirst grounded multiple lcontact 2 16, relay210 energizes over the' follov`v- Ing circuit: free pole of battery, relay 210, brush 214, terminal 216, arm 221, 'inner left armature and-'back' contact of relay4 223, armatures and back 'cont-acts of relays 219, 228 to ground. At its armature and front contact, this relayj closes the circuit of escape 4magnet 205, whlch is constructed to release 3, upon its energizatlon.- Arm 211, 1n mov-4 mg out ofA position 2,* op'en's thecircuit of,

from position '2 to position after an interval, re-

magnet 212 to. stop elbrljxshes 213,214 upon massima trunk temine-1 5 '21a-"Q16, and.

arms

201, 217,in l close .the foll relay 219 of lay 219,l arm 220 and its na.l '215, -brush 213, arm contact, conductors 200,125, arm 1 and-its third contact, brush 111, terminal [103",

owingfoircuit for the right armature and frontrcontect'of'rolay- @Premamtif- 119, conductor 124,01ephoni substation A, c ondmq moving into! positxonu, the x s e.con'd' selector: groin; te? irstcontachjterini# 2.01 land its the-test relay 22S is energized over 'the Jfollowing circuit: freepole of battery, relay 228, brush 225, terminal 227, conductor 300, left'armature and back contact of relay 301', conducto-r $502, armature and back 'contact ot' slow relay 303, armature and back contact of relay :l0-l to ground. Test relay 228, upon its energization, releases the vside switch into position *$13, as described vin con nection with the first selector operation. Arms 220, 221, in moving into position il, out olf relay 2li), and closethe following cir* cuit leading to the connector in which the seized trunk terminates: ground` relay 30st,

conductor 305, terminal 220, brush 221, arm 220 and its third Contact, terminal 215,4 brush 215i, arm 201 and its third contact,

conductors

200, 125, arm 1 and its third contact, brush I111, terminal 105l` right armature and front contact ol relay 119, conductor i12-l, through the Atelephonie apparatus at suhstation A, conductor 123, left armature and front contact of relay 11S),A terminal 1153, brush 1.12, arm 2 and itN thirdcontact, relay 118free pole otbattery. Relay lOi7 in attracting its armature, energizes a slow relay 303. Relay P103,4 in attracting its outer armature, interposes abreak in the circuit oi connector release magnet 308, and by attracting its inner armature, connects a slow relay- 300 tothe baclr contact ,of relay 304, The calling party now operates lnssenrler 1.26 to interrupt the line circuit a munberoftimes i equal to 'thetensdigit of the. wanted line,

plus one ture `of relay 301 energizes slow rela 300., Thisrelay, by attracting its left armature, connects the primary stepping magnet 307 of the connector to the front 'Contact of relay304,* and in attracting its4 inner right armature, .closes a circuit vto energize escape l 'magnet 311. .The sender 126, in restoring,

now causes the relay 304 to transmit imfpulseslover the following circuit tot magnet i. 307i kfreepole of battery, magnetSO', connector-side-switclr arm 309 and its first contact,.left armature andrback contact of relay u310 ,left armature and front Contact of relay A h position 4. `A;rms 325 -and'319, 1n moving 306, armature and Jfront contact of relay B04 `to ground. VV-hen the sender 'restores 'ing circuit: free pole of battery,y relay *terminal 316, towhich is connected vthe oli relayA or the calling line, as shown 1n Fig.

The'first retraction ofthe arma l terra), relay 300 deiinergizes, V llt retractiug its le'lt armature, this relay1 disconnects magnet 30T :from tie front contact of relay 230i, and in retract ng its inner right armature dcincrgizcs escape magnet F511, which in the \\'el'l-lrnl wn manner.I releases the sidiI switch into position 2. Arm 2300 iu position 2, connects the secondary stepping magnet 3,12' in the stepping ci cuit, 'l`hccalling party. now operates his seinler to interrupt the line circuit a nun'lber of times equal to the units digitof the ci lledmnnber, plus one. Upon the iirst rlcinergization ol' relay 304, relay 306 isenergized and connects magnol 312 to the front contact of relay BO-l, andat its inner right armature and front contact again energizes escape magnet 311. The sender, in restoring, now causes the relay 301 to transmit impulses over the following path, through nagnet B12/,to step the positioned brushes 313, 314 over the group of multiples contiining those of the wanted line 315, 316: tree pole ot hatte-ry, magnet 312, arni 809 and its second contact, left armature and hack contact of relay 310, lett armature and .iront contact of relay 300, ai mature and `flont contact of relay 301 to ground. The resto 'ation of th sender to normal position, and consequent maintained energiz/,ation ot relay 301, causes relay 300 to be denergized. This relay, in retracting its `inner right aiinature, de'energizes escape relay E318, outer armature and front Contact of relay 303:5 to ground. Arm 319, in 1noving into positirn 3, closes the following circuit to cnlrgize a relay 320 to close the ring-- 320, :514, c ut- 1, to grouml.V Relay 320, in attracting'ts armature, closes the ringing circuit as follows: ground, battery, ringing generator 317, relay 318, armature and front contact of relay 320, arm 325 and its third contact,

' brush 313, tern inal 315, conductor 324, condenser 323, bell 322,0onductor 321, to` ground 4 through the cutoff relay of the-called line. When the party at substation B removes his receiver, relay 31S becomes energized,

and in attractif. g its armature, opens' the circuit traced for` escape magnet 311, Wh1ch, 1n denergizing, releases the side switch lnto Arm 319, in position 4, maintains the circuit for relay 320 and the cutoff relay of the called line. In position 4 the following circuit is closed over the called line: free pole of batter relay 320- arm 3l9and its fourth contact, rush 314, rmlnal 316, conductor 321, telephonie apparatus at substation conductor 324, terminal 315, brush 313, arm

325 and its fourth contact, relay 301 to tery, relay 118 (Fig. 1), arm 2 and its third contact, brush 112, terminal 113, left armature and` front contact of relay' 119, conductor 123, telephonie apparatus at substation A, conductor 124, right armature and front contact of relay 119, terminal 103,

. brush 111, arm 1 and its 'third contact, conductor 125, conduct-or 200, arm 201 and its 'third contact, brush 213, terminal 215, arm

2204 and its third contact,brush 224, terminal. 226, conductor 305, relay 304.- to ground.

. The path for talking current to the called party has alreadyvbeentraced. Condensers 3,28,l 329' conductively separate but lnducvtively unite the calling and called ends of 4this circuit.

Assuming now that after the parties at substations A and B have conversed, it isdesired to bring the v party at substation` C into the "telephonic circult which has just been built up. The callingparty will now operate his sender 126 to interrupt the line circuit once. Relay 304, in denergizing, transmits an impulse to slow relay 306, and before this relay retracts its armatures, after its circuit is opened bythe attraction of the armature of relay 304;, animpulse is sent lover the following path to a relay 330:

ground, armature and front contact (if relay 5304, left armature and front contact of relay 306, left armature vand back contactof relay' 310, arm'309 and its fourthcontact, right winding of relay330, armature land back Contact of `relay 321, free [pole of' battery. Relay 330 energizes and locks itself over the following-circuit: free pole of battery, left- Winding .of -said relay, its armatureA and front contact, relay 332,

conductors

333, 334, outer' right armature and front contact of rela-y 30310 ground. Relay 332, in attractits armatures, connects the special rst sector 335 to talking conductors -305 and 327- in vmultiple with the connector circuit, Immediately' uponv the attraction of the armatures vof l'rela 332,' the folloyging. cir' cuitlis closed, inc udin the-sender 1 26 lat the-calling' substation: .reejpole of battery,

after relay. 303de11ergjizes, the circuittact, brush 112, terminal 113, left armature and front contact of relay 119, conductor 123, telephonie apparatus at substation A, sender 126, conductor 124, right armature and front contact'of relay 119, terminal 103, brush 111, arm' 1 and its third contact, conductor 125, conductor 200, arm 201 and its lthird contact, brush 213, terminal 215, arm

shown in Fig. 2 and the selectors are equiva' lent switches. The operations involved `in setting the

switches

335, 339 and 340 will not be described in detail, since they are.

identical with. that already described.

Upon the inclusion o1 the third substa` tion (l in the telephonie circuit, talking battery is supplied to said substation from-the connector 340 in a circuit similar to that described in connection with' the connector circuit shown in detail in Fig. 3. Relay 330, at its right armature and front contact,n' 1aintain relay 321 energized during conversation. Relay 321, in maintaining its armature attracted, prevents other regular connectors, to which conductor 341 is multiplied, from energizing-their relays 330, thus preventing' a relay 330 of any of such regular connectors from energizing and opertinga rela 332 thereof to connect the seized special se ector 335 to

conductors

305, 327 of such connector. Thus the selector 3.35 is rendered busy to other connectors to which it is normally, ac-

cessible.

If it is desired to bring a fourth party `into the telephonie circuit so builtu a relay of the connector 340, similar to relay 332 1s energized to connect a special first selector,

similar to 335, to

conductors

343, 344. From lng re ease of a given connector .is under theeontrol of the calling party and the particu;

lar called party to which Such connector is I connected.

Assuming the calling 'party is the first to replace his receiver, relays 118, '304 become; de'e'nergized.

306 over the following circuit: armature and tracts 4its armatures andholdsithem attra ted Relay 304, in retracting` its armature, causes en impulse to'pass to relay o closes the following circuit for release `magthis .relay being opened when relay 304 re- 'tracts its armature. The denergized condilion of relays 301 and 303, and the energized condition of relay 300, cause -an in'ipulse to flow over the following e' nuit: outer armature :md back contact of relay 303, outer right armature and front contact of relay 300, .left arn'iature of relay 301 and its front contant, conductors 300, 32T, terminal .227, brush 225, relay 223,' free pole of battery. Relay 228, in attracting its armature, closes the circuit of second selector release magnet 230 as follows: free pole of battery, inag- .net 230, primary olnorinal contact 231, sidefswitcli arn'i 232 and its third contact, armature and back contact of relay 223, armature and front ront-act of relay V,255l to ground. Magnet 230` in attracting its arma ture, locks itself up over the prnnary offnornial contact 'which is opened when the brush sha-ft ooi'npletely restores, thus deenergizing magnet 230. In parallel. with the circuit just traced for relay 223, relay 210 ofthe first selector is energized. This relay, in attracting its armature, transmits an impulse to release magnet 200 of the first selector as follows: free pole of battery, nuagnet 20G, primary off-'normal contact arm audits third contact, armature and back contact of relay 203, and armature and front contact of relay 210 to ground. Magnet 200, in energiaing, locks itself to ground over primary off-norn'ial` contact which is opened when the selector brush shaft completely restores, thus denergizing ,magnet 200. Magnet 200, in. attracting .its armature, also grounds a. conductor 231V leading back to the fimlcr release magnet 109 over conductor 130. Th circuit is as follows: ground, armature and front Contact of magnet 20G,

conductors

231, 130` right armature and back contact of relay 105, conductor 131, magnet 100 to free pole of battery. l\l.`.f1gnet.10.0, in

attracting 'its armature, locks itself over ,These relays, in energizing,"release the asso elated switches, as described.

,i Then the called part-yv replaces his receiver, relays 320 and 301 aredeinergized. Relay 301in retracting its right armature,

net 303 of the connector: freepole of bat- 't'y release magnet 308, primary ollnormal' ture and back contact of'relay to ground.4

Magnet 308, in attracting its armature, locks itself over the prunary olinormal Contact 315, which is o1 cned when the connector brush shaft completely restores, thus deenergizing magnet 308. lVhcn the called party (i replaces his receiver.' a release mag net similar to 30S becomes energized and releases such connector, as already described.

(loing hack to that pointl in the operation where the callingparty sets the connector' upon the terminals of the wanted line, if such linc 'is busy as a called line, its multiple 310 will have potential iin )resscd thereon from battery diro-ugh a relay similar to relay 320 over sille-sivitch arm 310 and its fourth contact and brush 311i of another connector, or if busy as a calling line, from hat tory, through relay 118 (Fig. 1),'side-s\vitch arm 2 and its thir'l contact, brush 112. Consequently, upon the termination of the units impulses, the following circuit will be closed for a busy relay 310: ground, inner righty armature and back contact of slow relay 306, denergized Aipon the inaintained'energization of relay 304:4 upon the termination of the units impulses, armature and front contact of inafgne; 311, which is slow to release, and thus maintains its armature attracted for an irterval after its circuit is broken by the de niergization of slow relay 300, left winding of relay 310, conductor 351,

arm 319 and its second contact, brush 314 to terminal 316. Relay 310 locks itself over its right Winding, and inner armature and conductors 357, 333, 331 through the outer armature and front contact of relay 303, and

vholds the escape magnet 311 energized in parallel with itself over arm 326 4and its second Contact and conductor 359. Relay 310,4 at itsvonter right armature and front contact connects a'busy tone apparatus over conductors 1354.-, connected to the up per talking co1 doctor, thus indicating to the calling party` that the desired line is busy. When the calling party 'replaces his receiver, relay 30abeeoines denergized, and in retracting its armature, grounds the lower talking conductor .300. The relays 228 and. 210, branched off in parallel vat the second and first selectors, respectively, thereupon releasethe s\"\*itcl.ies hereinhefore described, the release nianjmt 200 of the .first selector, energizing the release magnet 109 of the finder. Relay 303, in retraeting its outer armature, closes a circuit for the release magnet 308 of the connector as follows: free. pole of battery, inagnnt 308, primary off-normal contact" 345, conductor 346, right armature).

and back Contact of relay 301, outer arma ture and back Contact of relay to ground. The retraction of the outer ari'nature of relay 303 opens the circuit of escape magnet 311 and bus relay 310.. The apparatus is now restore' connection.

to normal, ready for another What is claimed is:

1, In. a` telephonev exchange system, the combination ,with a calling and a called line, automatic selector and connector switches for establishing a connection between said line, and a third line, of an additional automatic switch, an electromagnetic responsive device 'associated with the last switch to said connection for operatively associating said additional switch with vsaid calling line,

means operated by the response of the called party for preparing a circuit for said device,'

and means controlled by the calling party for closin said circuit and for settin said additiona switch to bring said thir line into the connection.

2, In -a telephone exchange system, the combination with a calling and a called line, automatic selector and connector switches, a

slender associated with said calling line 3. In a 'telephone exchange system, the' combination with av calling and a called line,

automatic selector and connector switches, a

sender associated with said calling. line adapted tocontrol said switches to' establish a connection including said lines, and a third line, of an additional automatic switch, a,

relay associated with the last switchof the connectionf for operatively Vassociatii -ig',. vsaid additional switch withvsaid sender, ain elecltriiiagnetic switch operated when the called 4party answers and adapted to prepare a circuit for said relay, andmeans including said sender for completing said circuit, Wlereby said' additional switch may be set by said sender tobring said third party into the connection.v .v

4. In a' telephone exchange' system, the combinationwith a calling und a. called line, automatic selector and connector switches, a sender associated with lsaid calling line adapted to control said switches to interconnect said lines, side switches therefor, and a third. line, of an additional antomatic'switch, an electromagnetic responsive device associated with the'iast switch to said connection for operatively associating said additional switch with said sender, a circuit adapted to beV ,closed 'to advance the connector 'side Switch'whel the. culled `-party answers to prepare a circuit for said device, means for closing said circuit controlled by said sender, and a relay operated by the closure of said circuit for removing the control of said addi tional switch from the remaining lines.

5. In a telephone exchange system, the combination with a calling and a called line, automatic selector and connector switches, side switches therefor, and a third line, oi an additional automatic switch, an electromagnetic i-esl'ionsive device associatedv with the last switch to said connection for connecting said additional switch to said ea]l ing line, a circuit adapted to be closed to advance the connector side switch when the' called party answers to prepare a circuit for said device, and means for closing said cirenit controlled by the calling party.

6. In a telephone exchange system, the combination with a calling andv a called line, automatic selector and connector switches, a sender associated with Said calling line adapted to control said switches to establish i connection including said lines, of a third line, :in additional train of automatic switches, an electromagnetic responsive device associated with tiie last switch in the established connection for associating the first switch of the additional train of switches with said calling line, nieans'oper ated by the response ofthe called party for preparing the circuit of said device, and means including the calling partys sender for completing said circuit whereby said additi-onal switches may be set by said sender.

7. In a telephone exchange system, the

combination -with a calling and a 'called line,

automatic selector and connector switches, a sender associated with said calling line adapted to control said switches to establish :i ,connection including said lines, a release circuit for said connector, fast and slow relays associated with Said connector, the -former responding to the line circuit interruptions caused by said sender, and the latter holding open said release circuit, and a third line, of an additional automatic -switch,`an'

electromagnetic responsive Vdevice associated with the last switch to Vsalti connection for operatively associating said additional switch with said sender, means operated upon the response of the called party for Vpreparing a circuit for said device, and means including said sender and said fast Aand slow relays for completing said circuit while the -established'-connection is maintained, w'hereupon said additional switch maybe set by'saidsenderto bring said third pnrty'intothe connection.' l

8; In' a telephone exchange system, the

establish a connctioni'iiicluding said lines,

nd a third lino, of anadditionnl automatic Suid circuit, whereby s'aid vmgltliisiolml switch switch, un electromagnetic responsive device may be set by said sender to b1 fing said third associiltzod with the lust switch ,to said conline into the connection. 1o nection for operativelyassociating said addi- In witness whereof, I here into subscribe 5 `tionl switch with Suid culling line2 meims my nume `this 25th day April A. D., 1916.

`for preparing a, circuit for said device, and means mcl'ldlng said sender for completing CHARLES L. GOODRUM.