US1735575A - Automatic telephone system - Google Patents

Description

' AUTOMATIC TELEPHONE SYSTEM Original Filed Oct. 13, 1917 3 Shegts-Sheet 1 NOV-12,1929 EJACOBSEN 1,735,575

AUTOMATIC TELEPHONE SYSTEM Original Filed Oct. 1 1917 5 Sheets-Sheet 2 n 11- Ezm'Z Jasubssn v I Nov. 12, 19 29. I

E. JACOBSEN 'AUTOMAI IC TELEPHONE SYS TEM Original Filed Oct. 13, 1917 5 Sheets-Sheet s r tary or subsidiary to the main'exchange.

Patented Nov. 12, 1929 star EMIL JACOBSENhOF EEORT WASHINGTON, NEW Y0RK, ASSIG1\TOR, IBY MESNE ASSIGN- Mum's, TO AUTOMATIC DELAWARE a v ELECTRIC 'INQ, OF CHICAGO, ILLINOIS, A CORPORATION OF AUTOMATIC TELEPHONE SYSTEM Application filed October 13 1917, Serial No. 196,367. Renewed May 4, 1 923.

My invention relates in general to automatic telephone systems but is particularly serviceable in such systems as include aplurality of main exchanges and branch exchanges tribu- In such systems the main exchanges are interconnected by trunk lines and each main exchange is also connected :to its several branch exchanges by trunk lines, Connections arees- 1.1. tablished in the well known manner by automati'cswitches under the control-of calling devices at the subscrlbersv stations.

The branch exchanges may be'of any desired capacity but in the majority of cases E will notexceedone hundred lines. 'ConnecF tions :within a branch may-then be made throughthe medium ofeonnector switches whlch are responsive to two Cllgll'fi; this is only true of local connections, however, for

0 in connections from a main exchange to a eration is performed outside of it.

branch exchange generally at leastthree'digits and perhaps four or five, depend ng-upon the particular trunking arrangement in use, will have tobexcalled before the calling sub- 5 scriber obtains connection with a trunk line leading to the, desiredlbranch exchange, and if the calling'subscriber is located in another branch exchange thenumber of digits to be called may. be greater still. in any case,

.13. sinceonly the final 'con'nectors'are located at the branch"eXchange,-the entire trunking op- 1 This fact, when considered in connection with the large number of transferred calls 9 employees and matters handled bythe different departments: are not widely known outside of the particularconcern, w1l l render apparent the decided disadvantage in prior au tomatic operating methods, which it isthe 5 object of the present invention to overcome;

for it will bese'enthat if a main exchange subscriber calls a certa n ofliclal in a branch exchange and finds, when a response 1S secured,

thatth'e person wanted is temporarily in another department, or, if present, that he is not the proper person with whom to transact the business 1nhand,1t Wlll be necessary to release the entire connection and call the entire num bervover again-in orderto obtain connection with the proper local station. a The delay thus caused is a decided inconvenience andin addition may result in the loss of the trunk line during busy periods. I i I in manual systems transferred calls are handled readily by the operator at the branch exchange. The subscriber first called merely has to signal the operator by working his receiver hook up and down and when she re spends tell her to-whom the call is to be ex-v tended, whereupon the operator merely has to shift the plug in which the incoming trunk line terminates to a difierentjack;

In automatic systems, since there is no terminates in a dual or compound connector instead of the usual single connect-or switch. This dual connector comprises two separate and distinct switch mechanisms which, how ever, are permanently associated with one trunk and are mutually dependent so far as their circuits and operation are concerned.

when a call is received over a certain trunk line one ofthe two connectors associated therewith, which will be termed the main connector, is operated first toestablish connection with the desir'edline in the branch exchange. After a responseis had, if it is desired to transfer thecall to another station the called subscriber at the branch exchange operates his dial in accordance'with the number of the third station, (a two digit'num- 'ber), whereupon the other connector assoestablish connection with the line to which the call is to be transferred. .VVhen theparty thus called answers his telephoneitheparty main connector is released and restored to normal. That is, the main connector usually releases at this time althoughprovision is with the proper digits and operate the main connector again to connect with the desired 7 third line; and furthermore, the subscriber on the third line can extend the call to a fourth by agaiiroperating the auxiliary con hector rma this it will be understood that c the main and auxiliary connectors which constitute the dual or compound connector ofthis invention are operable alternately by lo'cal's'ubsc'r'ibers at the branch exchange to transfer calls as desired, andthat by this arrangement anincomingcall from a distant maine'xchange can be transferred or switched from one station to another at the branch without it becoming nece'ssary for the main exchange subscriber to replace his receiver I V andrelease the trunkconnection,

The above'is an outline of the operation orthe invention its simplest forrn. It has recently become the cornmon'p'ractice ifrhigh- 1y organized telephone systems to establish toll connections automatically by means of a separate trunking system which is inde' "pendent of the local trunking system, the two separatesystein's being required principally tin-"account of, the'fact that in toll or long distance work the signaling and busy test circuits required are different from those considered the best practice for local oper- V anon and on account of the necessity of providing better talking circuits. The embodiment'of the invention herein shown is designed for use in a: system of the above character and it has been considered best to show all the circuits which have to dowith the invention complete) although it will be understood that for straight. local service in systems where toll conuections'are established n'ial'i'ually" the circuits be considerably simplified. The apparatus and the circuit arrangements shown by which the foregoing and other usefulobjects' are att ained will be fully described and explained hereinafter, reference being had'to theaccompanying I drawings; Figs. 1,2 and 3, which form part ofthis specification. For a clear understand ing of the. drawings should be placed below Fig. 1, while hfig, 3 should be placed to the left of Fig.2, in such a manner that the lines a the m me-m edges will be in alignment. Whentlius arranged it will be seen'that I'Qhave shown an incoming' trunk line comprising conductors 146' and 148,

which extends from the repeater E (Fig. 3) in the main exchange and terminates in the dual or compound connector comprising main and auxiliary connectors F and H at the branch exchange. These main and auxiliary connectors are both ennanentlysssociated with the incoming trunk line and have access to the local lines in the branch exchange, two of which, the lines extending tqsubstat-ions hand A, are shown in Fig. 1. In 1 are also shown line switches C andQ which are associated, respectively, with the lines extending to substations A and A; and the connectorfD, which is one ofagroup of connectors used for establishing local connections.

Substation A maybe of any suitable'c'orn: mon battery type and as shown herein con-"- sistsessentially of the receiver 2, transmit" ter 3-, switch hook 4, ringerfi, and condenser 76. Being an automatic substation there is.

also provided a calling device represented herein by the impulse springs 7 and 8' and the impulse Wheel 9,. This calling device likei'vis'e may be of any suitableor' approved 7 type as, for example, one inwhicha calling dial is provided which maybe operated'by the subscriberto produce series of interruptions in the'line'circuit in accordance with the digits in a number whichit'is desired to call. A calling device of the above type and one which is suitable for the purpose is shownin the British patentto Dicken- Nog 2 9,654 of 1910'. v

The line conductors 12 and 13" terminate at the switch board of the branch exchange- I in the individual line or trunk selecting. switch C which is adapted tooperateflwhen'the re= ceiver is removed at'subst ation A to initiate l acall to extendconnectio'n to a trunk line extending to a local connector switch. The

line switch C may be-"br'iefly described as a 'rotary' line switch whose wipers have no normal position, or,- in other words, this line switch is of the type of line switch Whose Wipers remain on the contactso'f' the trunk lilo 7 line last used and when a call is initiated no trunk selecting operation Willtake place un-' less the trunkline on which the Wipers hap pen to be resting is busy A rotary line switch embodying these features is shown in the pat;

'ent to Lamb, No.- 1,193,160, granted'August 1, 1916. Each local line in the branchexchange is provided with a line switch similar to'the 'lineswitc'h C and the banks of all-these line switches are connected in multiple andform -terminals of trunk lines which extend to connector switches, one of which is the co'n nector D." h v The connector switch D is'niechanically cf the well known Strowger vertical and rotary type which is disclosed inthepatent to Keith, 7

Erickson and Erickson; No; 815,176, granted March 13,1906. Thecircuits are modifiedto a great extent, however, principally in order to permit the switch to be operated in accordance with the two wire system of control and also because of certain features desirable in a private branch exchange of the typeherein 7 described. The banks of all the local connectors are connected in multiple in the usual way and form terminals of normal conductorsover which access is had to the various local lines. Not all the levels are used for this purpose, however,- for where the branch exchange'is connected by trunk lines to a main exchange, as inthe present case, one or more levels must be reservedfor these trunk lines. Thus in Fig. 1 I have shown the first contactsets in certain levels, to-wit, the first, second, ninth, and tenth, and it will be seen that the normal conductors associated with substations A and A terminate in the first contact sets of the first and second levels, respectively, While in the first contact set of the ninth level there is terminated a trunk line comprising conductors 152, 153, and 154, which may be considered as normal "conductors associated with the conductors of the trunk line extending to the main exchange.

From this'it appears that the contact sets of the first eightlevels of the local connectors'are assigned to the local lines, while the c onta ct'sets of the ninth level are reserved for trunk lines extending to the main exchange. The tenth level is also reserved for trunk lines which, however, extend to a different exchange; The provision of this last group of-trunk lines involves a somewhat novel operation in the connector D which will be explained fully hereinafter.

The main and auxiliary connectors F and H" are similar in mechanical construction to the connector D. The circuits, of course, are radically difierent and will be deseribedin detail in the description of the operation which is to follow. .The main exchange end of thetrunk line comprising conductors .146 and 148, has two branches, one of which terminates as before'mentioned in the repeater E (Fig. 3) and'the other of which terminates in the line switch C The repeater E comprises the eight relays 100 to 107, inclusive,

' whose functions will be described later; and

is accessible'to selectors of the toll trunking system and also to selectors of the regular main exchange trunking system,thus forming the means by which selectors of both kinds are given access to the trunk line. In the case of the toll selectors connection may be 1 ing on whether it is to be used by a local subscriber in the main exchange or a toll or long distance operator. At this time reference is had to the patent of WVinfred T. Powell, No. 1,356,010, granted October 19, 1920, which showsa similar arrangement. The line switch C affords means whereby connection from the branch exchange may be extended to subscribers in the'main' ex change by way of theregular main exchange trunking systems. The line switch C is similar to the line switch C, (Fig. 1), already described, and has access to selector switches over a group of trunk linesone of which is partially shown just tothe left of the line switch. v

For supplying current for operating and talking purposes I have shown throughout thedrawings a plurality ofbatteries, but it is to be understood thattliere is preferably but onebattery for each exchange, each of which has its positive terminal grounded. In order not ;to encumber the drawings'reference characters have been omitted from the various batteries therein shown, and to avoid any confusion on this account itis noted that when in the specification a'circuit 1s tracedfito battery it will be understood as extending to- -the ungrouncled or, livepole of a common exchange battery. The refer ence character IR inFig. 2 indicates an intermittent ringing machine of the usual type common to automatic telephone systems.

There is also provided :a busy signaling machine shown at several places in the drawing. and indicated by the reference char-'- acters Q and (4),. v

Having described briefly the general lay out ofthe system and the character'of apparatus employed, I will now proceed to explain in a more detailed manner the operation of the circuits. first be assumed that a subscriber in the main exchange desires to establish connection with a certain subscriber at the branch ex change who is ordinarily'to be reached at if the substation A, and will be further assumed that the calling subscriber has'operated a series of selector switches-of the regular main exchange trunking system in the usual way to establish connection at 1? .ductor135, bank contact 132 and the selector wiperin engagement therewith, through the For this purpose it will calling subscribers loop, and back to the selector. wiper in engagement with the bank contact 130, conductor 133, normally closed contacts controlled by the armature 108 of the bank contact 131, and thence by way of switches in the usual manner.

the test wiper of the last selector switch to holding magnets or relays in the various Conductor 134 being-grounded, a ground potential will be placed upon the multiples of contact 131 with the result that repeater E is made busy to otherselectors in the regular main exchange trunking system A branch of the above traced holding circuit extends from the junction of conductors 1 14c and 131t0 test, contact 139 and its multiples in the banks. ofthe idle toll selectors which have access to therepeaterE where, by a ground poten-v tial on these test contacts, the repeater E; is made busy to these selectors also.- A second branch may be traced by way of conductor 1 17 and the switching relay 150 of the line switch C to battery. By the energization of relay 150 the branch conductors 1 19 and 151 of trunk line are disconnected from their normal battery and ground connections in line switch C Anothercircuit closed by .the energization of relay 105 extends from ground G by wayof armature 11 8 and its workingvcontact and the upper winding of relay 107 to battery. Relay 107 is not operated, however, for its upper winding is merely a polarizing winding, being composed of German silver wire, and does not energize the core of the relay suiiiciently to enable it to attract its armature. Relay 105 also prepares a circuit for the relay 103 at its armature 119 whichwill. be traced later, and final- 1y at its armature 121 closes a bridge across the-trunk conductors 146 and 14:8, and thereby causes the energization of the double wound line relay 200 of the main connector I (Fig. 2) at the branch exchange. The energizing circuitof relay 200 may betraced as follows: ground at G, lower winding of relay 200, resting contact of armature 229 and thesa'id armature, conductor 159, armature 321 and its resting contact, conductor w 157,-trunk conductor 148, armature 121 and its working contact, armature 117' and its resting contact, armature 11 1 and its rest ing contact, spring .170 and its resting contact,upper and lower windings of relay 101 in parallel, conductors 1-71 and 172inparallel, lower winding ofelectropolarizedre: lay 107, armature 110 and its working cone. tact, resting contact of armature 112 and. the said armature, trunk conductor 1 16,0011- ductor 155, armature 319' and its resting contact, conductor 158 armature228 and its resting contact, and the'upper winding of he relay 200 to battery, 1 Upon energizing, the line relay 200 closes the usual energizing circuit for the slow acting releaserelay 201,

and this latter relay,up0n energizing inturn,

at its armatures 221 and 22d connects th'e in-.- coming trunk conductors 146 and-148 direct to the upper and lower Windingsof the line relay 200, respectively, by. wayofthe armatures 228 and 1229 of the relay 202. As

further result of its energization relay 201 V prepares at its armature 223?,- the usualop erating circuit for the rotary and vertical magnets 211 and212, and at its armature 222 connects ground Gr to conductor 153 with the result that ground potentialis placed upon the test contact97; and its multiples in the banks of the local connectors in order to renderthe trunk line busyJGr'oUnd G also extends by way of conductor 156' and the winding of the. cut-off"relay.302 toibattery; The cut-off relay 302 is --accordingly energized and its. armatures318and320 discQnnect the windings of the 'doublerwoundrelay 301 from thecondnctors of the incoming trunk line. At 'armatures 319 and 321 the original energizing circuit for the line rela];

200 is broken also, but this latter. operation is without efiect because; of the fact that another circuit 'for relay 200-fhas' already been closed by the relay 201 as explained It should be mentioned at this pointthat the relay 301. of the auxiliary connector His normally bridged across the conductors 146 and 148 in parallel with the line relay 20.0 of the main connector F. Relay301 does not energize when the bridge isclosed at the repeater E, however, because it is .diileren tially wound.

The foregoing operationshaveoccurred automatically upon the seizure of there peater E by the selector in the mainexchange. The calling subscriber may now call the last two digits in the number for the. purpose of ,7

this relay isacc ordingly deenergized a corresponding number of times'to produce at its armature 110 a seriesof interruptions in the circuit ofthe line relay 200 of the main connector F at the branch exchange. At' each deener ization relay 100 also completes a circuit forthe slow acting relay 1.03, which I and its resting contact, armature 223 and its Vc'uit extending as follows? ground on test contact 265, test wiper-261, side switch 711381 1;

extends as follows: groundat G armature 116 and its resting contact, armature 111 and its resting contact, working contact of armature'119 and the said armature, and the winding ofrelay 103 to battery. Relay 103 1 and its resting contact, working contact of armature 110 and the said armature, working' contact of armature 114 and thesaid' armature, resting contact of armature 11"- and the said armature, working contact of armature 121 and the said armature, to conductor 148. This direct bridge of course inchides the armature110 of the line relay 100, i and it will be understood that the principal function of the'relay 103 isto cut out the impedance of relaysl01and 107 while the line are produced at the repeater Ethe line relay 200 of the connector F is deenergized a number of times and at each deenergization transmits an impulse through the vertical magnet 211as follows: ground at G armature 225 working contact, winding of the lowresistance slow acting private control relay 203, winding of the vertical magnet 211', and the side switch wiper 215 in first position, to battery. In response to these impulses the vertical magnet is operated to raise the switch shaft step by step until the wipers 260 to 263, inclusive, arrive opp'osite the horizontal level of bank contacts inrwhich is located the contactset'assigned to the lineof substation A. The relay 203 energizes inseries with the vertical magnet andremains operated during the series of impulses to close at its armature 230 parallel energizing circuits for the-lowerwinding of relay 204 and; the left "hand winding of the private magnet 210.

the deenergiz'ation of the relay 203 at theze'nd V of the series of impulses, p'ermitsgtheside :switch wipers The operation cit-relay- 204 at this time is without function. The privatemagn'et, however, controls the side switch infthe usual manner, and upon 'deenergrzmg following toadvanceto their second The calling subscriber may now operate hisj dial 'inaccordance With-the finaldigit in Qthe-callednumbei, or, the digit'l, (the line i of substation A 'is connected to the first set of contactsin thesecondlevel) thereby producingle; singlefinterru tion .in the-circu t of the line relay l00 of t fe repeater E. -Accordingly 'it follows that the "line frelay-f100 energizes,- and the side switch wipers are relay 100 is transmitting impulses to the line relay 200 at thebranch exchange. In rer spouse to the interruptions in its circuit which will be deenergized once momentarily to in-' terrupt the circuit of the line relay 200 of the main connector F Now, however, the

being traceable over the iollowingpathz' ,line relay 200 transmits an impulse of cur- V I rent to the rotary magnet 212, the circuit;

ground at G, armature 225 -and its resting contact, armature 223 and its working contact, WlIlClll'lg of relay 203, resting contact of armature 236 and the saldarmature, wind ng of rotary magnet 212, and the sideswitclr wiper 215 in second position, to battery. By the operation of the rotary magnet in response to the impulse of current which it receives, the switch shaft is'rotated onestep and the wipers 260 to 263, inclusive, are brought into engagement, respectively, with bank contacts 264' to 267, inclusive, comprising the contact set assigned to the line of substation A. The relay 203 and the private a line of substation A, when called as above 2 It will be first assumed, however, thatthe described, was busy. In this case there would be a potential upon the test contacts 264 and 265withthe result that the private magnet; 210 would not deenergize when the circuit of its left handwindingv is broken at the relay 203, but is maintained over -a test cir- 216 in second position, contact springs I controlled by the arm'ature 235 of relay 205, right hand winding of theprivatelma-gnet 210, and

the side switch wiper 215'in second position to battery. Also relay 205 is energized over, the following circuit: ground on testcontact 264, test wiper 260, armature 231 and its resting contact, side switch wiper 217 in sec- 205, to battery. -,On energizingrelay205;

closes a locking circuit for itseli'and the private magnet independent of the test wiper 261 whichfex'tends from groundv G by way of the upper windingof the said relay 205,

the resting; contact; of spring 227' and the said spring, the upper winding'oi relay 204,

cluded in theabove locking circuit, isenergized and its armature 233,-- connects-a lead from the busy'sign'alingmachine Q to the conductor 148v ofthe trunk line. It is to be noted that by the attraction otarmature 236 of relay 2 05 the circuit ofjtherotary magnet 1.212 is opened tov prevent the calling subscriber from rotating the connector( on to another -1i ne.- The operation ot'arr natures 237 and 2340f relay 205 and 232 of relay 204 is .with

ond position, and the lower winding of relay 7 position, to battery. 1 Relay 204,lbeing 111-5 12 thcrew'it h' was attempted the line of substati,on-A" wasid1e. Under these-circumstances lwheii the slow acting relay 2 03 deenergizes at t-he-endof the :final impulse or series of impu lsesfthe privetemagnet 210 is deenergized also'aiid t he side switch Wipers aretadvanced 'to thei-rfit ldposition. the-advance of r the side s itch Wipers totheir *third position two circtiits are closed simtiltaneous'ly. The

of these extends from ground G through side switch wiper'QlG-in itsthird position, and hastwo branches, the first'branch being traceable by Way ofthe test Wiper26'1, test contact 265, private normal conductor "'284ythe winding of thecutcfi relay 15" of line sWitch GQhn d the wvi nd i-ng of:steppil g mageet 16f ',"-'t-0 battery. "The-current how n this-branch serves to energize t he-cut off relay 1 i hfl 'the ioWres'istfince s'teppirw' magnet 16 remaihih-g' deenergized; and the line vconduc- ""'30 ters '12": and 1 3" are thereby disconnected fl'Om their normal ba'ttery a' nd ground coni meet-ions in the line switch C? It should he *m'eritioned that when the relay 15' is ener- 'gi-ze'd a s above, itis' prevented'firorn completely-attracting its ai'r n atu re by reason of aminterloclringmechanismcontrolled hy jthe armazture'i of the line clay .1'4. Accordingly the wipers of the h ri'ef witch C :rem'aindisconnectec'l. This locking mechanism is :Etudly dc-- I 40 sc ibed in the pote'nt'to Lanih-previouslyrei izerr'ed to. Ground; at G oit course, also ex- 1 tends to rireltiples' of test contact 265 in order tofrender the Iineo'iE- SuhStaE-ion A busy to 'othei coiiiiector switches. f The secon'd hranch M ci-rctr' tezitends'from the =j1rncti0n=-of--$ide 'iper216 withthe test Wiper 261 'by to battery. Deferriiigfforamoment pla-nationfot' the effect produced by the --energizrng' of relay "QOQ the secondf circuit i 1 which as*hefore mentionedwas closed simulta- -iture-of-thecrihofi relay end the s'eid armaf i' ture; normal conthiotofi2 85, barik contact 266,

telry." "'Tli'ee boi ecircuit is broken an instant fterit? cozn'pletedhy the operatio'mof the R715 and also by thee'ner gization relay 209, everth-eless a momentary flow of ctutrent wili be prodeed in the lower inding of relay 205,=sri'tfic1ent to-enabiieth-is relay to attract its armature234.

"An energizing and iocking'circuitis thereupon completed as follows: ground at G 2 rmature 234 and its Working contact, right (hand armature of private magnet 210'and its restingcontact,side-switch Wiperf217 {in third-position, and-the lowerwmchrlg of relay 205, to battery. The "operation of-the a-r1riatu'res'235-ai1d 236- of relay'205is without i particular effect at this time but the QPera- 'tioli ef armature 237 "opens a circuit of the casemagnet 213 for a purposewhich will be red-1y described hereinafterb f Returning to the switching re1ay209, when this relay 'ei ergi zed a signaling circuit: is; ound atiG generator Gen. contact controlled by completed over the following pat-h the intermittent ringing eqriipment Iliynesti-ng contact ofiarmature' and the saidar: mat-ere, Working contact of armature 1248 and the saidarmature, ,vfiiper 263, harfllc'co-nitact 25?;nomnalconductor283, 1iiie conductor 12 throu-gh the r ngerandcOIideIrSer atzsrihstation A"-,'" l*ir1e conductor 13 norh1ai1 'condoctor 285;bank contact266, Wiper' QiiZar-rhaeture 247 and its workingficcntac t ar-mature 243 and its resting -contachupper W' IdiILgfOf the ringcut off rela y QOSQarid the exchange'; hattery to-ground atG BY theo er-at-iQn of the ringing apparatus-IR thea hovecircuit is closed interniitt'ently to operate the ringer at the called substation. ItW-i-H he" {observed "that Whenever the vgenerator Gen. is discone necte'd from-the circuit'a s iial l hooster hattery is substituted therefor inorder to enable the V silent periods. This relay 208 is so adjusted that itwill n'ot en'ergize as long as thereceiver TEIDR'IIISOIIfihQ hook at "the alled sub- :cutofi relay 208't0 "heenergi-zed during the 1* station. WV-hen the receiveris"remowedfhowever, the relay -298 is instantly enegized either by: current -from geherttorGezihhd the main exchange battery 1n seriesyor hyicu'rrent rain ex from the booster battery and the change hatteryin series, and-rqoon -a tracting its armature 244:, closes a] lockiryg circuit :for itself esffollows ground at :Gi f, norip'al 'contact219, closed atthe first upward move,

*ment of the' sw-itch sh'a ft) armature 244mm 7 .of the relay QU8- to "battery." The above cir-v ciiit also supplies groundfto th 'lowerjvincL- mg of the ha'cik bridge relay 207; -Fur t -herr siilts or the energization of relay 208 2rr closure of a contact in the release circuitat 7 arm ature' 245921 1101 t1'1e'e10sureof the talking circuit at the working 1 coiitact of arm atures 243 and 246, the upper Wir din-gi of re1 ay 28 and the lead to the ringing machine heing disconnected a :th'e' hack 'con'tactsfof these armatures,respectively; Uponthe closure of the talkingjcircuitf the hackibri'dge relay 207 which is bridged ac'ross 'ithetalking'gcoridnc-fl tors in series with the battery isjenergi'zed in the usual manner and completes a circuit for the slow acting relay 206. Relay 206 upon energizing prepares'at its armature 288 a circuit for the vertical'and rotary magnets 310 and 31 1 of the auxiliary connector H, opens a contact in the release circuit at its armature 240, and at ltsarma-ture 239'closes an energizing circuit for the upper winding of relay 202. Relay 202, upon energizing, reverses the incoming line'con'tluctors 1 10 and 148 as regards their connections to the windings of the line relay 200, thereby reversing the direction of current fiow inthe' conductors of the incoming trunk line. The operationioi "armature 226 of relay 202 iswithout function "at this time. By thereversal of the current in the line, the relay 107; whose lower winding is included in the bridge at the repeater and 'which-until now has remained inoperative because of the opposing magnetizing effects of its windings, is operatively energized, and upon attracting its armature, changes'the circuit-of the bridge at the repeater in such manner" that the two windings'of the relay 101 are connected in seriesrather than in parallel. This operatlon increases the impedance "and resistance of the bridge to prevent transmission loss,- and of course, also causesthe energizatlon of the relay 101. Upon attracting its'armatures 108 and 109, relay 101 con-- nects an additional pair ofcondensers in the talking circuit and also reverses the incom- 'ing'trunk conductors 133' and 135 as regards 'their connections to the windings oftheline relay 100. The d1rect1on of current flow 1n the calling line is accordingly reversedin the usual manner for the purpose of operating a meter or collecting a coin. r

- The required connection has now been established, and assuming that the calling subscriber has obtained the desired party at substation A the conversation can proceed as desired. Current for the transmitter at the called substation A is supplied through the windings of the back bridge relay 207 ofthe main connector'F, while current for the transmitter at the calling substation may be'siipplied through the windings of the line relay 1100 of the repeater jtake the pathshown in heavy lines which The voice currents will be understood without further explanation.

hen theconversation is finished both subscribers will replace their'receivers. By the replacing of the receiver the calling substation the energizing circuit'e f the line relay 100 of the repeater E is broken and this relay deenergizes to'open the circuit of the slow acting relay 105. The deenergization of these two relays causes the bridge across the trunlciccnductors 146 and- 148 to be permaipened 'witlrthe'r suit that theline relay 00 or" the main connector Fisdeenergized- The resulting deene'rgizationof the slow'acting release relay 201 causes the closure of thefollowing circuit for the release magnet 213: groundG armature 225 and ing' contact, oil normal springs 218, and the;

winding of the release magnet 218, to battery. By the operation of the release magnet 213 the main connector F is restored to normal position in the usual manner, thecircuit of the release magnet being opened at ofi" nor- "mal springs when the shaft reaches its lowest position. the repeater E when the slowacting relay 105 was deenergized ground'was disconnected from conductors 144: and 147, 0 thereby permittmg the operated selector switches in the main exchange trunking system to be released and also permitting the cut off relay of the line switch C to. deenergize. The apparatus is thus all restored to normal position when the receiver is replaced at the -callingsubstation. v

It will now be assumed that when the sub-.

to wait a minutewhile he isbeing called. This is accomplished by operating the auxiliary connector H'to establish connection with the local line extending to the substation A.

It will be recalled that when the receiver was removed at substation A the relays 207 and 206 were energized, the latter relay preparing a circuit for the'operating magnets 310. and 311 of the auxiliaryconnector. VVhen now tne'dial at substation A is operated in accordance with the digit 1 the relay 207 is de'energized momentarily and transmits an impulse of current tothe vertical magnet 310 as follows groiind at G armature 241 and its resting contact, armature 238 and its "working 'contact,' winding of the low resist-. 'anceslow acting private control relay 304:,

winding of the vertical magnet 310, and the side switch wiper 313 in first position,tobattery.. By theoperation of the vertical magnet the shaft of the auxiliary connector; H is raised one step whereby the Wipers 350 to 353,

inclusive, are raised opposite the first horizontal level of bank contacts The slow acting relay 30sis energized in series with "the v i vertical magnet and closes the usual energizing circuit for the private magnet 309. Upon the deenergization of relay 80t and the private magnet the slde switch wipers are advanced to second position in the usual manjner. The dial at substation A is now operated in accordance with the finaldigit lot is accordin ly again moment'arily' dee'ner gized; New,.llowever the side switch "wiper '11 thenumber of s'ub'stationfl lgand the relay 2 07 313 being inits second position, the rotary magnet 31lis operated and the switch shaft is rotated to bringthe wipers 350 to353, in-

gized as-before, and assuming that the line of substation A isidle when the relay 304: decnergizes,the private magnet will deenergizeralso, and the side switch wipers will be advanced to third position.

' By the advance of the side switch wipers to their third position circuits are closed simul- .taneously :forthe relays 306 and 308 of the auxiliary connector H and for the cut-off re- ,lay l5 of the line switch C. These circuits are the same as corresponding circuits in the main connectorI-I and need not be described in detail. By the energization of thccnt ofi' relay 15 the line conductors 12 and 13 are disconnected fron their normal-battery and ground connections in line switch C. Relay 306, upon energizing,;eloses a locking circuit for itself at itsarmature 335andat it armature 337 opens a contact in the release circuit. Relay,

306 correspondsto the relay 205 in connector completed-will be explained fully later on.

.By tlie-energization of the switching relay 308 a signaling circuit is completed for actuating tl eringer at substation A. This circuit is similar toithej one already described in conhas n w t substati n A- ordertopermit of a full explanation of the release it will now be assumed that no response is secured from substation A. Un-

der-these circumstances the party at substation A may oiier to try another number, perhaps having in mind some station at which the desired party is likely to be. If this is agreeable to the calling subscriber at the.

,main connector'release:magnet whlch may be traced as follows: ground at G ,'.work1ng main exchange the party at substation A? will now hang up his receiver in order to release the connector H. preparatory to. call- 7 ing the new number.

By the replacement of the receiver on the'hook relays 207, and

2000f them-ain' connector F are deenergized vand a circuit is completed for the release magnet .312 of the'auxiliary connector H as followszground at G ,-armature 239 and its rest-ing .contact,armature 330-and its resting iGQntachai-maturc 340 and itsrestlngcontact, the oil normal springs 316, and the winding offthe release magnet 312,to battery.. By the lenergi zatien of the releasemagnet' 312 the auxiliary connector is restored to normal po- ,sition-in'the usuaL-manner, after-which it .n ay be again operatediby the party at subtai en FA t e con rol-0 the 1 M of the mainconnector to establish connec- ..t-ion swith another local station.

I Ha ne r i ed emceethe 1 iliary' connection junder the above circunr stances,it will now be, assumed that the party at substation A is present when the signal is received and that he answers the telephone.

When the-receiver is removed the ring cut 7, oil relay 307 is energized and at its arn1a-' ture 339 completes a locking circuit for-itself in a readily understood manner.

and at armatures 338 and 3&2 the line-wip ers are disconnected from the upper winding :1

of relay 3.07 and-from the generiator-ilead respectively, and are connected instead to the heavy talking conductors. Backbridge relay 300 is now energized over the called line circuit and upon-attracting its armature completes an energizing circuit for the slow acting relay 303 This latter relay, uponenergizing, prepares a circuit for the operatng magnets of the-main connector at its armatures 328, opens a release c1rcu1t contact at its armature .330, and. at its armature 32 e nn t g u fi -1t theupp Winding ofrelay 202 of the-main connector, thereby providing against the deenergiz ation. of

this relay, should the-relays 207 and'206 be deenergi-zed to release the main connector,

The call has now been transferred through the medium of the auxiliary connector Hfto substation A and since the talking conductors ofthe two connectors are connected in multiple, thecalling subscriber atthe main ex- Ground is change may now converse withthe wanted party at substation A as desired. The party at substation A who has just transferred the call, upon observingthat conversation is proceeding satisfactorily will now replace his own receiver. :Upon the resulting deenergization of relays 207 and 206 of the main-connector, a circuit is now completed for the contact of armature .329 and the. said armature, resting contact of armature 24:0 and the said armature, armature2 l5 anditsworki-ng contact, off normal contact 218, and the .w nding of the releasemagnet 213, to" battery. By the energization of the release magnet 213 the main connector is restored to normal 202 is also maintained energized,.as previously'explained, from ground G6 at the auxiliary connector. .When the conversation ls completed .and the relays 200 an'd201 are de- ..energized by the'replacement of the. receiver at the callingeubstation, relay 201 breaks the circuit .ofthe cut 'ioff relay 302. ,By the deenerg-ization ofthis latter relay 'a circuit for the release magnet 31 2 ,015 the auxiliary c,on j

nector is ;.closed as followsi ground at G, aramature322 and its resting contact, off

normal contact 316, and the winding of the I '1 scriber to someone else in the branch exchange. Perhaps it is foundthat the business in hand can best be transacted by some other department or that it requires the consideration ofsome other official before it can be definitely'disposed of. l-Iowever, we are not particularly concerned with the precise reasons for it will be understood that circumstances will arise where it is necessary to transfer a call two or more times before the calling subscriber finally completes-his business. lVe will assume then, that the party at substation A, after conversing with the calling subscriber for a moment, finds it necessary to transfer the call to a third station. The main connector F has already been released and is now operated by the subscriber at station A under the control of the relay 300 of the auxiliary connector H. Vhen the calling device at station A is operated in accordance with the first digitof the number, a series of impulses is transmitted to the Vertical magnet 211 of the main connector over the following pathrground at G armature 327 and its resting contact, armature 328 and its working contact, Winding of the slow acting relay 203, winding of the vertical magnet 211, and the side switch wiper 215, in first position, to battery. By the operation of the vertical magnet the switch shaft and the wipers are raised to the requiredlevel of bank contacts, and, as before exlained, the side switch wipers are advanced to their second position at the end of the vertical operation of the switch by the private magnet 210 which is controlled by the TWhen. the dial is operated in 'ac-"' relay 203. cordance with the next and final digit in the number, the rotary magnet 212 Will be operated in a mannerreadily understood, and the switch wipers will be rotated on to the contacts of the desired line. 'The main connector, of course, is operated at this time in precisely the same way that it was operated first when the connectionwas first extended to the branch exchange, with'the exception that its operation is controlled by the relay instead of case the party at substation A will doubtless: wish to try still another station and will accordingly; replace his'receiverto release the main connector. Upon the deenergization of relays 300 and 303 a circult for the release magnet 213 is completed as follows: ground at G armature 239 and its resting-contact, armature 330 and its resting contact, armature 340 and its working contact, off normal contact 218, andthe winding of release magnet 213, to battery. After the main connector has been restored to normal by the operation of the release magnet 213 it may be again operated by the part-yat substation A as before. Suppose, however, that av response is secured from the'station to whichthe call has been transferred by the party at substation A. In this case when the receiver at the called station is removed the relays 207 and 206 of the main connector are energized.

Under these circumstances when the receiver is removed at the called station the talking circuit will be completed as inthe first instance and conversation can proceed as de sired. The party at' substation A will now replace his receiver and upon the resulting deenergization of relays 300 and 303 an en:

ergizing circuit will be completed for the release magnet 312 as follows: ground at G, armature 239 and its working contact, armature 329 and its resting contact, armature 341' and its working contact, ofl' normal contact 316, and the winding of the release magnet 312, to battery. The release magnet 312 is accordingly operated to restore the auxiliary connector to normal. From the foregoing explanation of the release circuits it' Will be seen that when a call is transmitted to anstation he can remain in on the connection if he so desires, as the connector'which is standing on his line is not releasedfuntil'hereplaces his lGCGlVBI'. This may be ob]e'ct1onable n someins'tances, and in the ease of'a mercantile establishment, for example, it will perhaps be p found best to exclude all of the ordinary employee's from being third parties to connections, only the higher oiiicials ofcertain other designated persons being permitted to remain in on transferred calls. In order to accomplish. this thenormal conductors of all those lines whose subscribers are to be denied'the' privilege of listening on transferred calls are reversed. "In order to explain the release of the switches when calls are transferred by this class of subscribers, let us assume that the subscribers atsubstationsAand- A areto be i Y preventedpfrom staying inon transferred rcal'lis, the normal conductors being reversed so that conductors 35 and 285 terminate in the line relays of the respective 'lineswitches C.

and Q rather than in the'normal ground con; nections. connector Fisoperated from the main eX- chan-ge to establishconnection with the line of substation A, when the side switch has advanced to third position the relay 205 will not be energized as in the connectionpreviously described for the energization of thisrelay requires that the line wiper 262' shall find means of the auxiliary connector H to the sub-.

which it, comes in engagement.

ground potential upon the bank contact with therefore remains deenergized whenever a line is called whose normal conductors are rc versed. 3 This is also true of the relay 306 of the auxiliary connector 1-1. N ow supposethat the party at substation A transfers the call by station VJ hen the party at substation A responds by removing hisreceiverthe relay 300 of the auxiliary connector isenergized and a circuit is instantly completed for the release magnet 213 of the'main connector over 7 the following path: ground at G working contact of armature 326 and the said armature, armature 242 and its working contact, armature 249 and its resting contact, armature 237 and its resting contact, (relay 205 being e 'n re o normal Contact 218,-and the 250 of relay 214, and the Winding of the saidrelay, to battery, Upon energizing, relay .214

at its armature 24E) shifts the release circuit from the release magnet of the ma n connector to the release magnet of the auxiliary con;

nector, and at it s armature 250 establishes a locking circuit for itself as follows: ground at G off normal contact 317, armature 250 and its'working contact and the Winding of the said relay 214,,to battery. Now let us assume that the partyatsubstation A desires to 7 1 transfer the call to athird party by operating the main-connector E again. NVhenthe cons nection iscompleted and such third party're moves his receiver the relay 2010f the main I connector will be energized as isusual under these clrcumstances and will instantly closea circu t for therelease magnet 312 which 1s traceable as follows: ground at G 2, working contact of armature 326 and the said arma ture,{ armature 242 and itsworking contact,

- armature 249 and its working contact, resting contact of armature 337 and the said armature, off normal contact 31.6,. and thewinding of the release magnet 312 tolbattery. The

' auxiliary connector H is. accordingly released and restored to normal, and when thes-haft is at its lowest position thelocking circuit of Now, if we assume that the main Relay 205' wean-re relay 214 is broken and this relay is-permitt-ed to deenergizel It will be seen that whenever the two connectors are off norm'ala'nd their back bridge relays 207 and 30Qare energized simultaneously, a circuit will be closed either through the releasemagnet 312 of the auxiliary connector or the release magnet 2130f the main connector, depending upon whether or not the relay 214 is energized. Inregard to this relay 214, it of course, is energized every timethe main connector is released providing the auxiliary connector H is in oper-.

ated position regardless of how the release of the main connector is brought about. lVhen the release occurs in response to the replacing of the receiver, however,the operation'of relay 214 is of no utility, and hence was not described beforei It will be observed that the main connector F, (and also the auxiliary connector is provided with twotest wipers and with two associated banks of test contacts. This provision is made to enable the connector'to ope crate as a rotary connector. Certain depart ments may require more than one telephone line, and it is desirable that when one of these departments is called, the connector in use will be capable of selecting the first idle line extending to such department. Let us con sider a department served. by three telephones. The test contacts in theupper test banks which. are associated with the first two lines will then beleft, dead, onlythe upper test contact which is associated with the last lineof the three being connected to the associated lower test contact, T henun ber to be. called when connection with th s particular;

department is desiredwill be determined by the position in the bank of the cont-act set as sociated with the first line of the group. Or,

in other words, when the department is called the number of the first line extending thereto will always be called. Now, supposing that the main connector F is operated to es} tablish connection with the first line of the;

group, and let itbeassumedfurther that the first, two linesare busy. Under these 'ciruin te ee here w ll b e er d P t t upon the test contact with which the test i r wiper -2t31is .in. engagement, while there will be no ground potential upon thetest contact engaged by the wiper 260, for this latter. test contact, as previously explained, is disconnected. Itfollows that when the slow acting relay 203 deenergiz'es at the end of the final series of impulses directed tothe' main connector the privatemagnet 210 will not de energize, but willbe held up overt-he follow-: 1ng:circuit:.ground on busy test Contact engaged by the test wiper --261,the said wiper" 261,- side switch wiper 216 in second position,

contact springs contrelled by the armature 235 of relay 205, the right hand winding of the privatemagnct2lO. and the side'switch wiper 215 in second position, to battery, 7 Relay203 having deenergized, a circuitmay now be traced throughthe rotary magnet 212'as follows ground at-GQQ, armature 230 and its resting contact, working contact of theile fthand armature ofthe private magnet and the saidl armature, resting contact of armature 232 and the said armature, resting contact of arinature 236 and the said armature, winding of the rotary magnet 212, and side switch wiper 215 in secondposition, to battery. The rotary magnet 212 is therefore energized and V the wipers of-the connector are advanced one lower winding of relay 204 in parallel, The 0 private magnet is thus held energized independent of the'test wiper while such wiper is passing from one contact to another in the bank and at the same time the relay 2045 is e'nergized to break the circuit of the rotary magnet. The rotarymagnet is then deenergizcd' and in turn breaks the circuit through the left hand winding ot the private magnet and the relay 20a. The relay 20 1 is therefore deenergized andsince-the test contact upon which the testwiper 261 is now resting is busyalso, the privatemagnet ismaintained energized, and the rotary magnet circuit isagainconipleted. The second operation of the rotary magnet is effective to advance the connector 7 wipers into engagement with the third line of the desire d group, which it will be assumed is idle. The parallel energizing circuits through the left hand winding of the private I magnet and the upper winding of the relay 20 1 are closed as before, and the saidrelay 20 1 again opens the circuit of the rotary magnet. Now, when the rotary I magnet deenergizes and breaks the circuit of the private magnet and relay 204, since the test wiper 261 is now I resting upon the ungrounded test contact, the private magnet will be instantly deenergized and wi'll permit the side switch wiper215 to advance to its third position and interrupt the rotary magnet circuit, thereby stopping the rotation of the switch Fromthis point onthe. operation isthe same as has already been; described. It may be mentioned thatv the connector will stop upon the last trunkj line ofevery group whether it is busyor not, for since the two test contacts associated with the last trunk line of each group are tied to gether the connector will operate when it lands on the last trunk line, precisely the same- Thea ruiliary c'onnectorH is adapted to operate as a rotary connector also and its circuits are substantially like those o7": themain c onnectorR-henceit .will need no detailed description. i g v j The principal feature of the invention, the

ldual connector, having-been eigplained, it will now-be necessary to devote a little spaceto a;

that the cut oii relay of the line switch C will description of the operations which occur,

when therepeater Eis seized by a toll seleetor, rather than by selector of the regular trunking system, as under these conditions; the operation of establishing a connection with a stationin the branch exchange. is"

slightly different. Accordinglyit willbe as- I sinned that a long distance operator has eX-. tended a, connectionthrough the medium of toll first and second selectors to the trunk conductors terminating in thebank contacts 136 p to 1410', inclusive, these contacts being 10;-

cated in the bank of the toll second selector.) I i i to control the first switch ofthe series, or the first selector, and as soon as the operation of th s switch is completed it 1s extended to the controlling relay of the next switch. lVhen,

therefore, thetollsecond selector has com pleted its operation the grounded operating conductor is extended byway of the selector wiper and the bank contact 138 to theconductor 143, and thence by wayofthewinding of line relay 1'04; and the winding of slow acting relay 103 connected in parallel therewith by way of the armature119 of relay 105, to 1 battery. Relays 104: and 103 are accordingly energized and the la ter relay, upon attracting its armature 113, connects ground to the;

conductor 1441 thereby establishing a ground 'potential on testicontacts 139fand 13 1-and* their multiples to render the trunk line busy. This ground potential also extends over conductor 1 17 to the line switch C? and operates I I the cut-oil relay 150. upon the energization o fj 'th e line relay 104 a circuit is completed for the islow acting relay 105 which, upon energizing, breaks the circuit of the slow actingrelayf103 at its armature llf), and at its armature 120 connects ground G? to the con ductor 1 14, in order to maintain this conductor grounded afterthe relay' 103 is deenergized. Relay.103,-is3operatedin parallelwithi I I the line'relay as describedinorder to insure Y be energized before the (operating or control main exchange. The relay 105 also completes,

as before, a circuit forthe polarizing winding ,7 of relay l07 at its armature 118, (the closure V f o'fr this circuit being merely incidental h'owas 1t, does when calling. an individual line. I

ever), and atthesame armature, the line*re- V lay 104 now being operated,' coinpletes an en- V erg zing c rcultover theconductor' 14:6 of the trunk line torthe relays 200 andQ301 of the racedlasi foll w groun -Git a u 118, and, its working contact, armature 139;: i-

and itsworkin'g contact, resting contact of armaturelll and the said armature tru'nl'z-v conductor 146, conductor, 155', arrnature 319 anditsi'esti'ng contact; contact springs coning of the said relay 200, to battery. Relays V ;trol1ed by the armature 318; and the u er winding of relay 301 to battery. The branch ofthe above circuit which includes relay 200 extends from the resting Contact of armature 319 by way of conductor 158, armature 228 and its resting contact, and the upper wind- 200 and 301 areenergiz'ed in parallel, and

I 'the' former relay closes the usual circhit for the slow acting release relay 201. Relay 201 upon energizing performs the same functions as weredescribed before, ineludiiig the closure ofa'n energizing circuit for the cut-off relay 302. By the operation" of the relay 302- a locking circuit is established for relay 301 as follows: ground at G armature 239 and its resting contact, working contact of armature gizlng circuit 6f relay 301 is broken'at arma 324 and the said armatureyarinature 318and its Working contact, and the upper winding of relay 301, to battery. This circuit is} of course, established before the original enerture 319. In its energized position relay 301 prepares at its armature 323' a circuit including both windings of the reversing relay 2 02 in the main connector and at its armature 325 closes a circuit for the ring cut off relay 208 of the main connector. It follows that the ring out off relay 208 is energized at once hefore the main connector is operated and be conies locked over the usual circuit asso nas the shaft of the main connector begins to rise. v

The apparatus is now operator operates her calling deyice in ac cordarrce with the first digit of the local mam:

her in the branch exchange the line relay 10 i is deenergi'zed a niihibe'r of tinies and at each deenergiz'ation interrupts the circuit of the line relay 200 o-f'the main connector F In response to these interruptions of its circuit the line relay 200-is deenergiz'ed a chrh' spohding number ofti'nies and operates to raise the shaft of the main connector F throngh the medium ofthe vertical magnet 2 1 1 in ,usual manner, the side switch Wipers; being advanced to the second'pos tio'n at-theeiid ofthe Verticalinoiyernent. \Vheh theshbhd digit is 'calledft'he connector rotates-genderthe control of the relay 104 of the repeater and its line relay 200, and the c nnection 'to thec alled line is completed. Assuming that the called line is idle, tliside-sWith; V {wipers willbe advanced to third positiongand the switchingfrelay "209' will energiie; No' automatic ringing operation takes place;

however, for the ring cut; ofi'.,rela-y' 208 has;

already, been energized; When: the eper'ator' V a desires to signal the called subscriber, which ':usually' isi-niniediately, she will thrm'it her v 1h commenter the, transmission of in1pulses When the I tell ringing key and thus project'alternating ca rent out over the two t alkingconductors of,

the trunk extendi'iig to the toll first selector. At the toll second selector there is an. alternating current relay bridged across thetalking conductors whieh responds to this ringring current and operates togroui'id the wiper V:

of the toll 'selectorwh'ich is in engagement with bank Contact 137. Thisfoperation'srves to complete a circuit over the conductor 142 for the rela 106 of the repeater E. Upon ener izing the relay 106 disconnects; the

trunlr' conductor 1 18 from the lower talking conductor extending through the repeater V T;

and connects it instead to one side of the grounded generator. Ringingcurrentis then across the line during the ringing operation V and whlle this is, of course, not an ideal con-- dition under which to perform-the signaling operation, it has been found to work satisfactorily, When the called subscriber answers relays 207 an'd206 atthe; mainconhector F are energized and the latter relay opens the locking cirfcLiit of relay 301 at its armature 2391 Relay 301 therfOr Cleenr-f giz'es and cannot: again beenergi'zed during the ;call now under consideration. It will be ieyideintitherefo re that any stations to which the call may be subsequently transferred either h t e operatibn' of the auxiliary cohnector or by th'ereo'pe'ration of the main cohhhetor' F will he signaled automatically iii the usual way; when the relay 20s ch61 giz'ed' upon, the has -thee of the called huh seriberit also closed at its hhmhhhr'e 239' the energizing circuit for the upper winding of the eversing relay 2'02. The operation of this relay dnrihg a toll eofinection controls the superyis'i'dtr to the operator; At the mu see-0nd seleetor'there'is a double wound super visory relay bridged across the talkingconductors in series with-the battery. The lower I I Winding of this" suphr'vis r rel'ay which is connected to the lower heavy talking conduc tor and the lower inding of the relay 200 are both cbnnectefd to the sariie 'pole of the batter (lohsquenuy, when the rela 200' is 1h normal condition them Will be he cur-1 rent flow over the line; However, wl're'irthe reversing relay 202 energizes, conductor, 14 8" 200 whereupon a flow ofcurr'ent will be set V is" connected to thef uppe winding of relay up from ground through the lowerfwind ifig of, the supervisory relay atvthe toll second selector, over" the hhe-wiph of the said he:

leetorl (now in engagement with the bafik v14-5, winding of low resistance relay 102, (and the non-inductive resistance in parallel therewith), resting contact of armature l22'and the said armature, truck .conductor"148, work'ng contact of armature 224i and the said armature, armature 229 and its-working contact, and the upper winding of the line relay 200 to battery; By current How in the above circuit the relay 102 is energized and connects conductor l t6 with conductor 14:1 thereby completing the talking circuit. The

supervisory relay at'the toll second selector 7 I upper winding of relay 204, armature235-and may control the'supervisory light at the toll operators position in any suitablemanner to advise her that the" called subscriber. has answered. In case theoalled subscriber at the branch desires totransfer the call f to another static-nit is done in'exactlythe same manner as has been already described. 5'

The apparatus is disconnected when the' toll operator takes down the connection. This operation ordinarily removes the ground from the operating conductor and permits a relay in the toll second selector and the line relay 104 in the repeater E, to:deenergize. By the deenergization of these relays the apparatus is restored to normal position in a manner which is'similar' to the disconnection of the apparatus in a local call and which will therefore require no detailed explanation. it It will now'be assumed that'a' connection is attempted to be set up by a toll operator as described in the foregoing, and that the called line is busy. In this case at the "end'of'the rotary operation of themain connector F the side switch is notpermitted to advance to third position, but'is held insecond'position by the private magnet 2l0-whichis maintained'energize'd temporarily over a circuit which includes "its right hand winding and the test wiper 261. Relay 205 is also enerigized via test wiper 260 and immediately changes the temporary energizing circuit of 'the private magnet into a locking circuit which'includes the upper winding'of relay 205, the upper winding of relay 204;, and the right hand winding of private magnet. Inasmuch as the connection now undercon'sid eration is a toll connection, however, the relay 301 of the auxiliary connector will be energized and since the relay 205 and private magnet 210 are now energized-also,-a circuit will be completed for the reversing relay 202 as follows: ground at G ,'armature234t and its working contact; 'right 'han'd armature of the private magnet and its working con"- tact, lower winding of relay 202, armature 323'and its working Contact; and the upper winding of relay 202, to'batte'ry. The lower winding of relay 202 is of such high resistance that the release magnet218 is not ener ized, although it is connected in paralle'l'wit Ithe upperwinding of relay 20.2. in theabovee cir cuit. Relay 202 is energized-and 'shiftsthe lowertrunkconductor 14:8 from ground to the live pole of battery to control the supervi sion to the operator as before. Also at its armature 226 the locking circuitover which the relay 204 and the'private magnet are being energized is altered so that it no longer includes the upper winding of relay-2'05, but instead includes the lower test wiper 261. After the operation of relay 202 this locking circuit-extends as followsz'grounded test contact, test wiper-261, side switchwiper 216 in second position armature 226, spring 227,

itsworking contact, righthan-d winding of private magnet, and the S1Cl6'SWlt0l1 wiper V 215 insecond position, to battery. With the circuits in this condition'the private magnet and relay v204: are maintained energized via being held up by the busy lineand she is-not-iv fied when the line becomes idle by'the-lighting of the supervisory lamp whenthe reversing relay 202 deenergizes. The. foregoing operations occurring when calling a busy line only happen when the connector F is operated for the first time. On transferred calls both connectors lockion busy "in the Tusual manner whether the call is coming from a local subscriber in the main exchange or from .a toll operators-pos'ition; 1 i f Referring to Fig; 1 a brief description will new be given' of the operation of'thexconnector D in completing a localiconnection. Assuming thatit is desired to call substatlon A from the substation A, when the receiver is removed at the latter'substation an energizing circuit is completed for the line relay 14 of the line switch G as follows: ground at G, restingcontact of armature 19 and the said armature, lineconduc'tor 13, transmitter 3, recei'ver2, impulse springs 7 and 8,, switch hook springs,-lineconductor the'win'ding of line relay 14,- to battery. Upon energizing, the line relay 14: operates, a me chanical device whichin its normal'condition prevents the complete energization of the combined switching and cut-off relay 15 and its armature '22 completes a circuit for the said relay as follows: ground atG armae ture 22 and its working, contact, winding of the relay 15, and-the winding of thestepping magnet 16 to battery. At the same time that ion it completes the above traced circuit the line relay connects the test wiper 25 to the junc-' tionof the relay 15 and the steppingniagnet 1.6 asfollows: test wiper 2tig-arinaturel 0and 1115 12, armature 18and its resting contact, and

its restinglcontact, armature 2]. and its Workingcontact, to the junction of'the said relay and magnet. The operation now depends "upon whether the test contact with which 7 ping magnet 16 will he energized. Since the steppingmagnetlfi interrupts its .own circuit it will be operated intermittently to advance the wipers "23 to 26, inclusive, step by step as long as the test wiper 25 continues to en-- gageihusy or grounded test contacts. As soon as the test wiper 25 arrives at an nngrounded test contacnas for example the. test contact '29, the operation of the stepping magnet will cease, and the switching relay lfi being no longershort circu'ited, will immediately energize. Owingtoit he-high resistance of the switching relay the stepping magnet remains inoperative. It wil l'be understood, of course, thatiif the test wiper 2 5 isalready standing upon an idle orung-rounded test contact when the receiver is removed at substation A no rotation-oi the switch will take place, the switchin relay "being energised immediately. .p.on energizing, the relay1-5 shifts the connection of thetest wiper 25 from the line relay armature 21 to its own lower terminal andjat mmatures-l8 and 19 extends the incoming line conductors 12 and 13 by way the' line wipers 24 and 26,'bank[;eon'- tacts 28 vandffitlyandcontact springs 48 and 419.. to, the windings of the double wound 'line relay- 5.0. of the connector on energizing, the line relay 50 completes the usual energizing circuit for the slew acting release relay 52, which upon energizing in turn completes aholding circuit extending back to the line .switchC as follows: ground at G working contactof armature Q5 and the said-armature, :conductor, 32, bank contact 29, test wiper 25, armature 20 and itswonking contact, winding of switching relay 15, andthe winding of the stepping magnet 16, toib attery. It understood that the above circuit is .connoleted before the slow acting relay 14 hashad time to deenergize. Ground poten tial on multiples .of the test contact 29 ren- "ders the connector D busy to other line switches, and groundpotentia-l on its test contacts 91 and 269 and their multiples (by way of conductor 36). renders the'lin of substation Abusy to the local and incoming-con; nectors.

The dial of the calling device at substation A may now be operatedin accordance with the first digit in the number of substa tion A". A series of interruptions is thereby produced in the energizing circuit of the line relay 50 of the. connector D and at each resultingdeenergization ofthis relay an impulse istransmitted to the vertical magnet 59 as"follow-sz ground at G armature 64 and its resting contact, armature '63 and its resting contact, armature 6.6. and its working contadt,'side switch wiper 89 in first position,

low resistance slow acting private control relay 53, winding of the vertical magnet 59, and the side switch wiper 87 in first position,

to battery. By the operation of the vertical magnet the connector shaft is raised step, by step .until wipers 40, 4:1 and 42 stand opposite vthe required horizontal level of bank contacts.

and now, since the side switch wiper 87 is in second positiomflthe rotary magnet 60. is op.-

-.erated to rotate the wipers 40, .41 and 42 into engagement, respectively, with the bank conmots-93,414, and The relay 5,3 and the private. magnet are energized as before and at the end of the rotation of, the deenergizat n of the latter the side switch wipers are ad I Nanced to their third position. IA circuit is now completed for the lower winding of the switching relay 58 as follows: ground at G working contact of armatnrefi and the said armature, conductorBQ, shaft controlled contact springs 82, armature of the private mag;- net :57, loiversvniding .o'at switching Ir 1ay1 side-switch LwiperfiS in third position, test wiper 41, sbanik contact, 9 conductor 284, nindingni the cut relay 1.5. ofl ne w tch 0;, and the-winding of s epping magt l6,

' to battery. Simu tane u ly wit he cl sure .ofr'theaboue circuit a circuit is completed through he slow acting elay 5.3 a li rounded conductor :32,arma 7. 8 an its resting .cen a hsid swit h Wiper .8 i third position, Winding of the relay 5.3, resistance r 85., and the side switch wipersz, tobattery,

The opera ion new p nds. upon Wh t r the ine of subs ation. 'i busy .01? id If the in anathema-111 c groun p ten ial an t te t c ntac 9. a th lower i win ingie th -relay 5 will heshort ci cui d,

his. a ord ng y .b ins n p r i the relay .53 nergiz s t u a ir u iscemp et d for t e pr ate magne W' h upon energ zing disc nn ts the lo er Win ing at the sw tching l y 1 As fur e resu t at its en rs zat qn relay 53 n e s a lead ina thehusy s gna in ma e Q the lower f i the se ing line, an h y the ra lies subsc b ha e 1 sired line th tim b ng na s ibl The cak ingsubscriber il therefor p a e his receiver, and the switches 10 and D will berestored to normal in the usual and well understood manner.

"will: suppose, however, that the line of substation A was idle rather than busy when it was called. The switching relay 58 is so adjusted that it will energize slightly ahead of the slow acting relay 53 and when, therefore,-the circuits of these two relays are closed simultaneously, as already explained, the switching relay 58 willoperate in series with the cut 0E relay of the called line and will break the circuit of the slow acting relay 58 at the resting contact of armature 78 before the latter relay has had time to energize. In its energized position the switching relay 58 connects the grounded conductor 32 to its own upper winding at the right hand working contact of armature 78 and at the left hand working contact of the same armature connects this grounded conductor by way of theside switch wiper 88 in 7 third position to the test wiper 41, thereby placing direct ground upon the test contact- 94 and its multiples. As a further result'or' its energization relay 58 connects the line Wipers 4O ande42 at its armatures '7 7 and 79, thereby establishing the usual signaling circuit for actuating the ringer at the called substation. Upon the response of the called the calling subscriber atysubstation A replaces his receiverp Thisfact brings about the deenergization of the line relay 50 and the release relay 52 thereby completing a circuit for the release magnet 61 as follows: ground at G armature 64 and itsresting contact, armature 63 and its resting contact, armature 66 and its resting contact,- oil normal contact84, and the winding of release magnet,61,.to battery. By the operation of the release magnet 61 the connector is restored to normal-position, the release magnet circuit being then opened by the switchshaft at the oil normal contact 84. i The deenergization of relay 52 also removes ground from the conductor 32 thereby breaking the circuit of the switching relay 1-5 of'the line switch C. By the deenergization of the said switching relay the line conductors 12 and 13 are dis connected from the wipers of the lineswitch and the line isplaced in idle condition again ready for calling-or to be called.

The connector D is capable of operating as a selector switch on the ninth and tenthlevels and in order to accomplish this is provided with a switching relay 51 and with contact springs 8-1 and-contact springs 82.1 These latter are controlled by a cam on the shaitin I such a manner that when the shaft is raised to either the ninth or tenth levelthe contact springs 81 will be closed, while if the shaft is raised to the tenth level the contact springs 82 will be separated. lVith this understand ing a brief explanation will now be madeof the operation of the connector D in selecting an idle trunk line such for example as the trunk line comprising conductors 146 and .148 which terminate in the first contact set of the ninth level. This trunk line, it will be understood, is one of a group of similar trunk lines which connect the branch with the main exchange. Since these trunk lines terminate in the ninth level, when a connection to the main exchange is desired, the first digit to be called will be the digit 9. When the receiver is removed at substation A line switch C is operated 1n the usual manner to extend the connection to an idle connector switch, which we will assume to be the'connector D. The

dial of the calling device being now actuated in accordance with the digit 9, the connector armature 7 5 prepares a test circuitincluding the private magnet 57, which :is held open temporarily by the slow acting relay 53, and at its armature 74 prepares va circuit forthe rotary magnet 60; l/Vhen therelay 53' deenergizes at the end of the vertical operation of the switch, the private magnet 57 is deenergizedalso and advances the side switch wipers to their 'secondposition. A circuit is immediately completed for the rotary-magnet 60 as followszground atGifl resting con tact of armature 69 and the said armature,

working contact of armature 74 and the said armature, winding of the rotary magnet 60,,and the side switch wiper v87 in second position, to battery. The rotary 'magnet V is accordingly operated and. the switch wipers are advanced into engagement with the first contact set of the ninth level. The rotary magnet also closes a circuit for the relay 54 which extends from groundGr by way or" contact springs 81 the armature of the said .rotary magnet, and the winding of'relay 54, to battery}; Relay 54 upon energizing opens the circuit of therotary magnet and permits it to deenergize thereby breaking-the circuit of the relay 54'. The test wiper 41 is now in engagement with the test'contact 97" and if we assume that the first trunk lineis busy there will be a ground potential upon test contact 97 with the result that the private magnet 57 will be energized over the following circuit:

groundedtest contact 97, test wiper l1, 'side switch wiper 88 in second position, working contact of armature 75 and the said armature, contact springs controlled by armature 67 of relay 53, and the winding of private magnet 57 to battery. By the energization of the private magnetover the above circuit the side switch-wipers are held in se'condposition and the switch will continue to rotate by the alternate energizations of the rotary magnet 60 and the interrupterrelay 54. As soon as the test wiper 41 arrives at an idlexor un-- grounded contact the circuit of the private magnet will be broken and the side switch wipers will be advanced to third position,

thereby breaking the circuit of the rotary magnet andstopping the rotation. If we as sume that the first trunk line, which is the one shown in the drawing, is idle, the rotary magnet will only be operated once and the side switch wipers will be advanced to their third position immediately. The switching relay 58is then energized in series with the cut'oti relay 302 (Fig. 2) with the usual results. The relay 56 being energized, a circuit is now completed for the switching relay 51 as followsz grounded conductor 32, armature 7' 8 and its right handw'vorking contact, .w'orkswitching relay 58 and thence to the line.

: 40 regardless of the fact that the contact springs to the conductor 32 to guard against the release of the switch upon the deenergization of relays and 52. I The dial of substation A ing contactofthe armature 7 6 and the said armature, armature73 and its resting contact, and the winding of the relay 51, to battery. By the operation of the armatures 62 and 63 of the switching relay 51 the incoming'line conductors are extended by a direct metallic connection to the armatures 77 and 79 of the wipers a0 and l2 which are now in engagementwith the conductors 152 and 154, respectively; The line switch C at the main 7 exchange is now operatedto extend the trunk line to an ldle selector switch in the main exchange The relay l of the connector'D, being in series with the upper line conductor, is energized at this time and connects ground may now be operated in accordancewith the digits in the number of the desired subscriber at the main exchange, thereby operating a series of switches in the main exchange trunking system to complete the connection. It should be notedthat the relay a l atthe connector D is slow acting and does not respond to impulses. It is also understood of course,

that the trunk will be clear of all connections in'the dual connector at this time owing to the fact thatthe cut ofi relay 302 has been operated as explained. The releaseofthe connection'occurs in the usualmanner when the callingsubscriber at substation A replaces his receiver and will require no detailed explanation. f

It has been mentioned before that there may be a second group of trunk lines accessible to the group of connectors of which the connector D is one, which trunk lines are. adapted to be called only by certain subscribers of the branchiexchange, the remaining subscribersbeing denied access thereto. These trunk lines may terminate in the tenth level and connection maybe extended ,to an idle one of them by calling the digit 0 in sub stantially the same way that connection is ex.- tended to a trunk line of the other group by callingthe digit 9. Special means are provided, comprisingshait controlled contact springs 82 which prevent theoper-ation of the switching relay 58, when certain subscribers are calling, thereby preventing such sub scribers from completlng connection with one of these trunk lines. 'These contact springs 82 are separate whenever the connector D is raised to the tenth level'and serve to disconnect the grounded conductor 32 from the lower winding ofthe said switching relay; however,all those lines. which are to'be given accessto the trunk lines terminating in the tenth level are provided with means in their respective individual line switchesfor closing an alternative circuit for the'switchingrelay of the connector in use. This means eom-' prises a fourth'wiper and a fourthsetof bank tenth level the relay 58 would be energized f 82 are separated, for its lower: terminal is connectedto ground by way of the conductor 31, bank contact 27, and the grounded wiper 23 of the line switch. Thus it will be seen that the subscriber at substation A having a line. switch wired liketheline-switch C would have accessto the trunks on both the ninth and tenth levels. Considering now the substation A and its associated lineswitch C it will be seen that the upper wiper 23 is disconnected. It will be readily seen that if the subscriberfat this lattersubstation should at tempt to obtain a connection with a trunk line in the tenth level the switching relay of the connector in use will be prevented from energizing and the connectionwould be pre-. vented.

Having describedmy inventionwhat-I conpointed out in the 1 I subscriber on the line last called, depending upon the class to which the said first line b.6- longs.

2. In a-telephone system, a pair ofautomatic switches, means for operating said switches alternately to connect with called lines, a release circuit comprising a conductor extending between said switches, two branches for said release circuit, a release magnet in one of said branches for one of said switches, a release magnet in the other branch for the other of said switches, a grounded battery having itsungrounded pole connected to said release magnets, and means for grounding said branches alternately over said conductor to energize said release magnets alternately.

3; In a telephone system, means includ- .ing a trunkline "for connecting a calling and'called subscribers line, apair or inductive windings connected in parallel across the said trunk line 'during'the establishment of the connection, and means'for connecting said windings in series across said trunk line duringconversation. I i

4. In a telephone system, a trunk lmem two sections, a re eater at which said sections are inductive y connected, means iior ex-- tending a calling lineto the first section, means responsive thereto'for completing a bridge across thesecond section, a differential relay having its two opposing windings connected in parallel in said bridge, means for interrupting said bridge and automatic switches respons ve to such interruptions for completing connection to a called line, and

means actuated upon-the response of the called subscriber for altering'the circuit ot said'bridge wherebyithe windingsof said relay are connected in series 551m "a telephone system, aotrun k line accessible from two different points and terminating in an automatic switch, a repeater in said trunk line, means for seizing said trunk line at either point and for transmitting impulses to" said'repeater, means in said repeater responsive to-impulses from one point-for repeating impulses over the two sides of said trunk'line in series to operate said switch, and means in said repeater responsive to impulses tromthe other polnt for repeating impulses to said switch over one conductor of said trunk line and groundi'eturn, independentof the other conductor,

16$In a telephone system, a trunk l ne III- 'c'ludinga repeater,a talking conductor normally'closed through saidrepeater and 1nof trunks.

eluding a relay winding, a second talking conductor extending through said repeater and normally open at contacts of said relay,

a third conductor overwhich impulses may be c transmitted to said repeater means in said repeater for repeating saidj impulses over one section of thenormally-xopen talking conduc tor to 'operate'an automatic switch to extend a connection to a called line, and means actuated upon the response of-the called subscriber to create aflowof current in thenormally closedtalking co'nduc'to'rto operate said relay and close the other talking conductor.

7. In a telephone. system, a branch exchange comprising a group of subscribers lines, local connectors-for connecting said) lines, two groups of trunk lines terminating in. said connectors and extending to different points, means whereby any subscriber in the branch may operate any idle oneof said connectors as a selector to selectand connect with an idle trunk line in one ofsaid' groups, and means for permitting certain ones only of said subscribers to "so' operate an idle connector to select andconnectwithan idle trunk line in the other group,.the remaining subscribers being denied accessto the said second group 8. In a. telephone system, a calling station,

automatic means for extending a talking con- 1 nection to acalledstation, automat c means operated from the 'calledstation over a portion of said first extended connection for then extending the conn'ection to a second called station, and means effective betorethe second called line is-found whereby apparatus used in extending an incomplete jcall toward such second called station maybe restored from said first called station whilesaid first extended connection is still maintained;

I 9. In a'telephone system, a calling station, automatic means for extending a talking connection to a called station,automaticmeans tending the connection to a second called staoperated from the called station for then ex 26110 tion, means effective before the connection is] established with the terminals of the second called station whereby" apparatus used in extending an incomplete call toward suchsec- 0nd called station'may be restored from said first called station without releasing its own connection, and means controlled from'the calling line for releasing both of said ex-, I

. tended connections. f 1 e V '10. In a telephonesystem, a callingline,a first automatic switch for extending a connection to a first called line, a second automatic" switch controlled from the first called line for then extending the connection. to a second called line, arelease circuit for said first automatic switch, a relay insaidsecond automatic switch for controlling said release circuit, and.

' a relay in said first switchcooperating with said first relay whereby: the first automatic i

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