Historical Document · 1917
US 1,237,208 Automatic Telephone System
Keith system patent (filed 1908) on selector trunking.
Historical Document · 1917
Keith system patent (filed 1908) on selector trunking.
A. E. KEITH. AUTOMATIC TELEPHONE SYSTEM. APPLTCATIONTZLED run‘ 6. I908“ ‘1,237,208.. . . Patented Aug. 14,- 1917. _ 7 SHEETS-SHEET I. :53 W 6602/72 85 > A; E. KEITH.- _ AUTOMATIC TELEPHONE SYSTEM.’ ‘iii-337,208 YAPPIJCATIOAN man JuLY'_6, 190s. Patented Aug. ‘ 14, 1917. - T'SHEETS-SHEETQ .6% 'iioévieg ; , A. E.v KEITH. AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED MY 6. I908. - 1 , 2 3 7 . .2 0 ,8, mm H. m .m A J. s. ua,T .nh 4 Wu F-S H1 .l.T . 1 7.. . ;P ‘.E.l__l_l__l__l__=_l_Ii_,____=._i__=w;_m=__m=m=m?m\_1 .5 . .. __ .. 0/0 w . . 602672495535 _ Q.W, . l k - v , M a , AQ-ZRW/(ZLQTZTRCf? ' ’ I, '4.‘ _ A. E. KElTH. @UTOMATIC TELEPHONE SYSTEM. . APPLICATION FILED jULY 6, 1908. 1,237,908. PatgntedAuv. 14,1917. 7 SHEETS-SHEET 5 (a 5 91: APPLICATION FILED JULY 6. I908 1,287,208. Pa'tented Aug. 14, 1917 Q, I SHEETS-SHEET 6. Q Q S Qn w.. QQ. . Qb nW Hokmo.qmw M. UZ FmOIPEuJmw zemedwii?eim z’ a. ' ‘ _ .A. E. KEITH. AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED JULY 6,1906. 1,237,298. , ‘ ‘ Patented Aug. 14, 1917. . w I w” ////d iii” W” 217/; a!” fnusnfbr' HZEXE Z'TdEfE'KEll‘h @151 6.2). 7Z4”. ‘ I "UNITED ‘STATES PATENT oFEIoE; ‘ ALEXANDER E. KEITH, or I-iiINSDALE, ILLINOIS, .assIsuoze ‘T0 Aorom'mc- ELno'rnIc ’ oomrm, or omcnoo, ILLINOIS,‘ A CORPORATION or ILLINOIS.- - ' nu'rom'nc 'rntnrnoun sys'rum. speci?cation‘ of Letters Patent. 1,237,208, Patented Aug. 14, 19171 a Application ?led my c, 1908. ' Serial No. 442,124. a 'by each subscriber doesnot have 'acces to j To all whom it may concern! ' Be it known‘ that I, Annimnnnn E.'KE1TH, all of the groups of connectors and, there fore, doesnot have access to all of they" ' a citizen of the United Sta, ' of'AIn ' and'resident of 'Hinsdalle age‘county, - di?erent connectors of the exchange,. but . , simply to' as many ‘groups 'of connectors -60 H Illinois, have invented ‘ a‘ r as there -.are-| thousands, and .with ten 'per' useful Improvementin'Aut _ ‘ Systems, of which the follow s_}.a"speci?-v cent. ‘trunking: this means that each sub scriber has access to , as many connectors My invention relates ‘to automaticor semi as there are hundreds of subscribers to the cation. - ‘ 10 automatic telephone exchange systems‘ of 'ex'change—that is to say, if there are .ten that character _ in , which the automatic thousand subscribers to the exchange, then switches have vertical motion to select each subscriber will. have access to ten " , groups or-divisions' ofthe exchangepand. groups and-hence to one hundred connectors, rotary motion to connect with a, line in'the therebeing one thousand connectors In all, 15 selected group ‘or division, the, vertical mo. whereby the maximum number of subscrib tion of the switch being always under the ' ers calling at any one time are given proper 4 . direct control of the calling subscriber, or. trunking and connecting facilities. an operator, but the rotary motion being an \ It is also an object: to provide certain novel; tomatic if the switch is for _,the.;purpose of I details and combinations tending to increase " selecting‘idle trunks, .or_ undenithef control the. general e?iciency and se'rvice'ability of 75 of the calling subscriber lif ‘suchfrotary mo an automatic one thousand line connector I tion is for the purpose of making the ?nal switch’ and system therefor of this particu-' _ - ‘ connection directly“ with the ‘ line of the lar character. called subscriber, the vertical-motion, how ~25 ei'er, being in either case for the purpose of '- To the foregoing and'other useful ends, ; ‘ I my invention consists in: mattershereinafter 80; selecting a group of lines,‘ either trunk-lines set‘ forth and claimed. -- or subscribers’>lines,_dependingupon whether ' In the ‘accompanving drawings Figure-.1‘, ; ' the switch is a selector or- aconnector, and is a diagram of an automatic telephone sys--“ the rotary motion in either‘ case being for tem equipped with my improvediconnec-tor the purpose of connecting with a line in the switch‘ A'. At _€t.-therelis represented a first 85 selected group,‘ although for the broader‘. s'elector switch the", line of which leads to ’ ' '_ purposes of my invention, as will hereinafter substation D. ' more fully appear, all'of'the switches in the “Fig. 2 shows diagrammaticallya ?rst~' exchange need not. be characterized, by both ' selector switch-C1 allotted to-the subscrib ' ‘the vertical and rotary motion, as my in er’s- station D1. ‘Figs. 3,_-l and 5' show details of the'operw- ' - ventioncontemplates, in one res (act at leasty ' a novel form of connector switc for use in _ tive mechanism-_ of the connector switch > conjunctionwith other ‘switches of any-suit able, known or approved charactena 40 shaft. Y ' ' 9o ' ‘ Figs. cand- T'are, respectively, a side ele-. » I The principal object. of m“ invention is,‘ vation andplan ‘view of the wiper and hun: 95". therefore, ,the"-prov1s1on ,0 ._ a connector . dredsiselecting mechanism of the connector . - switch having a capacity of at leasts'one thousand subscribers?ines, and in which the ; Fig, 8-"isv a cross-section of :the’ wiperson . switch. > , ‘ ' » ‘wipers, although having both vertical and line 8-~8 in Fig‘.v 7. rotary motion, are soarranged that each line wiper takescare ofmore than one hun line 9——‘-9 in Fig. '7. _ ‘Fig. 9 is' across-section of the bank on '_ i , I00 \ dred ‘lines, preferably ?ve hundred lines, Fig.‘ 10'is a plan View of the arrangement thus-obviating‘ thenecessity of- providing a .of the contacts inthe connector bank. . Fig. 11" is a cross-section of the bank and .separateiwip'erfor each‘ one hundred lines, 50 . notwithstanding ‘the- fact- that ‘said ' wipers ‘have both vertical‘ andxrotary' motion when shaft wiperstaken on line 11-11 in Fig. ‘10. ‘ Fig. 12 shows diagrammatically . the. ‘ever they are used to extend connection to a grouping of the different sets of contacts in the bank. . > , ' i called subscriber’s line’ Fig. 13 is a diagrammatic illustration of ' I also provide, .as will" hereinafter‘ more‘ *55. fully appear, a trunking arrangement where a section or portion of the trunking arrange- , 119 ' BEST AVAILABLE COP‘ 1,237,208 , ment'of a. ten thousand systemv embodying _ chanical details of the. ?rst-selector. switch "are, in general, well known, involving a V Fig. 14 is a diagrammatic illustration of p the ‘principles'of my invention. ' switch shaft (not shown) which carries the, ' a portion of the trunking arrangement of a" line 323ml 33 and the private wiper 100,000 system embodying the principles of, 3/1. wipers The side switch is controlled by the pri 70 my invention. , '. i vate magnet 35, and when the side switch is In Fig.1 a central battery B, for both in normal or ?rst position the side switch ' talking and operating purposes,'is shown wipers 36,37, 38 and 39 occupy the position having its positive terminal preferably shown by the dotted lines in Fig.1. In the 10 grounded at G. _ At E is shown a ringer gen~_ second position the wipers engage the mid erator, and at F is represented a busy-signal dle contact points, and when the side switch 75' ing machine. ‘ - . ' i _ _ ‘ The substations D and Dl'are of thegen passes to third position the wipers 36, 37, 38‘ and 39 engage the contact points shown by ‘ eral type disclosed in United States Letters full lines in Fig. 1. While the side switch is' .15 Patent No. 866,639, granted September 24, ‘ in ?rst and second position the calling sub 1907, to E. D. Fales, and are adapted for scriber controlsthe switch by means of ‘the V common battery work. . Substation D com vertical and rotary line relays 40 and Z11, prises a receiver 2, switch-hook 3, induc-' which latter are connected to the battery tion coil 4 which consists of the primary lead through the springs of the bridge-cut winding 5 and secondary winding 6, trans o? relay 1'2. ll'hile the Side switch is in ?rst mitter 7 , ringer'S and condenser 9. In ad position the calling subscriber controls the -.dition to the above-mentioned. parts there is' vertical magnet 413, which operates 'to give provided an impulse wheel 10 which-has the the switch sha ft‘ a vertical motion. - By means usual vertical_ impulse teeth 11 that‘ are of the rotary line relay 111. an-dlwhile the adapted to operate the vertical impulse . side switch is in ?rst or second position, the spring‘ 12. The impulse wheel also carries subscriber controls the private magnet 35 90 the rotary impulse tooth 13 which operates andytherefore, the side switch. YVhen the -' the rotary impulse spring 14. The said side switch is‘in secondposition the rotary 30 impulse wheel is, of course,_rigidly secured magi'ietilt is energized. and the switch shaft to a dial shaft. The switch-ho'ok-has radié ating from its body a numberof cam arms that carries the wipers 32, 33 and 31 is oper ated in a rotary direction. ,T he vertical and 15, 16 and 17 and is pivotally secured to the. rotary line relays,‘ acting conjointly, pro frame (not shown)‘ of the calling device. ' vide the means by which the release magnet ‘The cam arm15 controls the so-called lock 15 is operatedv by the subscriber- while the side switch ‘is in ?rst or second position. If 100 _ .operating ground Springs 19 and 20., - “Then the side switch passes to third position, how these ground springs engage, ground is ever,'s1nce ‘the selector C is of'the trunk-re - thereby provided to the ground post 21 from lease type the release magnet 45 is then con- . the substation ground G’. WVhen the switch 1 trolled through the connector A by way of 40 book is down the cam arm 16 maintains the ' the privatewiper 34: and by means of the 35 ing cam 18 which in turn controls the co springs 22 and 23 in contact, thereby bridg back-release relay - _ mg the ringer 8 in's'eries with ‘the condenser The mechanical details of the selector and 9 across the line. The springs2~1 and 25 are connector switches, as is well-known, are‘ then disengaged, and the primary circuit is very much the same. The present connector ' interr‘uptedl The signaling device, whereby. switch is of the general type of connector 110 a subscriber may signal another aftercon switch disclosed in United States Letters .nection has been established, comprises a Patent Nos. 815,176, granted iMarch v13, push-button spring ‘26 which normally en 1906, to Keith, Erickson and Erickson, and gages the contact point ‘27; but when the 830,653 and 830,65'-l,'granted September 11, button is pressed the said spring leaves the 1906, to A. H. Dyson, with the addition of 115 contact point 27’ and engages the contact the wiper-selecting mechanism shown in point '18 which is connected to the substation _Figs. 6 and 7. Furthermore‘, vthe connector 7 ground G1. Means whereby a subscriber bank is designed to accommodate one-thou may release the central station switching‘ap sand lines, and the connecting and operat~, ' paratus broughtinto service comprises the _ ing mechanism is arranged to so operate the 120 s1 aft wipers that any one of the thousand lease springs~ which are so controlled by the lines may be selected, as will be explained, three springs 29. 30 and 31. known as the re cam arm 17 that when the‘ switch-hook de The connector switch shaft, like the shaft scends thethree'release springs are brought of the selector, carries the line and private 60 into contact. thereby grounding both of they Wipers," which I have arranged in two sets 125 subscriber’s line conductors simultaneously. - . The ?rst-selector switchcsC and C1 are of 4 i the type disclosed in United States‘ Letters 47, 4,8 >gi)n-d;r§%,l?apd,5(),'5l (Fig. 1‘). lsofcar'ries the and master wiper 80. The-shits Tlie ver ical'line relay-53 directly controls Patent No. 815.321._granted March 13, 1906, ,the vertical magnet 54, the shaft rotary . 5:; .to Keith, Erickson and Erickson. The Inc? magnet 55;,a11d also the wiper-selector 1'0 130 - a - 1,237,268 ' tary magnet 56. The rotary line relay 57 ~L'are the privatebanks' P corresponding to controls the private magnet 58' and the‘ - the line banks L; -.Above the banks P‘ are. » SWltClllIlg relay _59a. The- private magnet even-hundreds banks L1 and P1 (duplicates 58, under certain ' conditions, controls in of the banks L and?) with ‘ accommoda- __ turn the vertlcal and rotary magnets 54 and tions for another ?ve. hundred lines, making 55, the release magnet 59, and also the side a total-of one thousand line contacts in the 70 I switch wipers 60,61, 62 and 63.- The side whole bank (Fig. 12).‘ The wipers 47 and switch, of course, has a’ normal‘or ?rst posi 118 are adapted‘ to. make contacts‘ with the tlon, a second positionand a third position. banks L, and the-wiper 49 with the banks P; 10 The release magnet 59. is- also controlled by Mounted .upon the shaft 78 immediately ‘-j the vertical and. rotary .line relays 53 and above thisset of wipers 'is a second set 50, 75 57 conjointly. By the usefofthe condensers 51-and 52 (-Fig'..1)'- adapted, to engagethe , "'64 and 65theicircuit through the connector.‘ contacts of the'banks L1 and P1. The wiper is divided into'two sections.-- The connector 80, whlch is adapted toengage the contacts 15 is provided with adi?'erentially-wound re ofthe master level M, is rigidly secured to GG-whichis composed. of the two'wind-v the shaft (-78, as'are the line and _ ' private . ' Kings 67 and‘j68. ~The function of thisrelay wipers, so that when the shaft is raised or ' ‘ is to provide the calling subscriber - with. lowered the wiper 80 iscarriecl along. The. battery current ‘for talking-‘purposes when .f'function-of the master level M and the oper i 20 the back-bridge relay 69 energizes, and also ' ation of thewiper selector switch (Figs. '1 85 1n conjunction withthe vertical line'relay and ) are as follows: The master level M - I 53, to control the ringer relay 70 by means‘ in a way controls. the rotary magnet 55 _ of- which'the ringer generator E .is bridged‘ (Fig. 1), causing it to automatically rotate ' across the terminals of the called line to . the shaft wipers over grounded contacts. 25, signal the called subscriber. The back- ‘ In'Fig. 1 it will be seen that theinterrupter 90 bridge‘relay '39, comprising the windings 71 springs of the rotary magnet 55 lead to the '_;:and- 72, ‘provides the called subscriber with wiperv 80 of the level M. In the level M v“talking battery current when the ‘primary some of thecontacts are grounded at Cr7 and substation is bridged someat G3. The‘ ground Gl’provides ground ‘a, circuit,‘of'the_called across the line. The shaftwiper selecting for-the ?rst contact of each group, namely - mechanism of the "connector shown in Figs. . contacts 84, 85,86, etc-a,‘ but, as shown in Fig.’ 6 and 7 comprises a rotary’ magnet 56 and 1. this ground 'is, however, controlled by the armature 73 adapted to engage the ratchet wiper selector .switch. The other_ contacts * wheel/74.; wherebythe wipers (Fig. 8) may are permanently grounded at' G8. vAmong 8.5 . be. moved overthe contacts of the bank (Fig; the functions‘ of the wiper and. hundred 'or' 100 7 ._ The-switching relay 59‘? is mounted upon . 'Tavframeof-the switch, and when said magnet .- is in .an energized position the pawl 75 falls over the end of the spring 76,.locking the group-selecting mechanism of the‘ connector are the following: F_irst,_and as already in dicated, to pick out'for the use of the con nector eitherv one of the sets of main shaft '40--relay ‘in an energized position. Figs. 3, 4 wipers allottedto the connector, the 'set'>be~ 105 ‘and 5 show details‘, of the shaft and ratchet \ ing- determined ‘by the'locat'ion. of the line operating mechanism. It will be seen that desired. Ifthe line is in the series of banks the teeth 7 8a engaged by the vertical arma~ L (Fig. 12), the wipers 47, ét8'a'nd 119 will be ture pawl are the-same as‘ usual, while the selected, and if the line is in the series banks _. usual rotary -teeth are replaced by _ the L1, the wipers 50, 51 and ‘52 will be selected. ratchet wheel 77 which is loosely mounted ' It becomes evidentthat the'arrangement of upon the shaft‘ 78, ,so that the ,‘shaft may be ~ the banks in Fig. 12- is to obviate the neces _ raised and lowered _without. moving‘ the ' sity ' of providing means for rotating the -wheeli77.v However, when'the rotary -mag-. shaft 78 through toogreat an are, or of'mak net-operates, the rotary; armature pawl 7 9a ing the bank contacts too‘ small, on the one 115 , ‘engages the ratchet ‘wheel vand rotates the, hand, and on the other hand to limit the Y shaft" through the vmedium of the memberv vertical movement {of'theishaft to ten steps. " I "79. {It will be-seen that'the spring which The next function 'of this connectoraux -.1 mcupies the shaft slot and engages the teeth iliary mechanism is to rotate the shaft and .50 ‘ 110 . . 55. 78*‘.Qwhe'h the shaft is rotated'is ?exible. In its wipers. adjacent to the proper hundred " "Figs. 10, 11 and 12 is shown the connector _ group .of the bank contacts in the series of 12d "bank’arrangem'ent. In Fig. 12 the level» M,‘ Io anks L and L1 (Fig. .12) before the im iwhich'may be called the masterv level, 1886i? pulses'correspondin'g to the last twodigits . .otfinto ‘?ve groups of ten contacts. each, are sentjin for carrying the wipers into ac 60 'making, ?fty in theleveL. ‘Just above the tual contact with the line .desired._ ‘It 1s, 125 levelM (Figsill and 12) gis'a row of groups ‘therefore, apparent that these functions of goddehundreds line banks L,.each group p the connector auxiliary mechanism‘arenper-l ‘comprising ten levels of ten contacts, mak ‘ formed by the ?rst set-of impulses that are ing ve groupsqof one hundred line contacts "transmitted to‘ the- connector switch -' after each. Immediately above the linefb'anks connection has. been" established with said’ 130 p 4 1,237,2os connector. This connector, unlike the ordi- . a), the number of which is 2120. The ‘dial at nary connector, requires three ‘dial opera--v the calling substation is operated in the_ tions to accomplish its full function._ The well-known manner forea'ch digit. When ?rst set of impulses thatare directed to the the dial is turned for the ?rst digit the ?rst- ~ connector v(in this case corresponding to the selector switch C is operated to select the 70 impulses of the second or hundreds digit) connector switch .A, and the'grounding of affect the connector switch and its auxiliary - the line conductors for the three remaining 7 as follows: The impulses to the vertical line digits is effective in operating the connector 10 operate the vertical line relay 53, which in switch. The ground impulses for the sec turn operates the rotary magnet 56 of the ond digit operate the'wiper selector device 75 auxiliary mechanism. Normally the wipers to pick out the proper main shaft wipers 47, 88, 89 and 90, 'orthe main wiper-selecting 48,‘ 49 or 50,51, 52, and also rotate the said wipers, are out of engagement with the main shaft wipers adjacent to the certain bank contacts to which the various sets of hundred-group determined by the second 15 main switch wipers are multipled; and ' digit. For the last two digits the connector 80 normally the insulation on the terminal of switch operates in the usual manner to se the wiper 81 maintains. the ?rst bank con» lect a certain line from said hundred-group. ' tact 8% of .the main level hi insulated from The calling subscriber suitably‘operates the ground G7; One verticalimpuise operates dial for the ?rst digit 2. On the return mo to carry the wipers 88, 89 and 90 into en tion of the dial the vertical-impulse spring 85 gagement with the main shaft wipers;47, 12 and the rotary impulse spring 14 come 4:8 and 49, but it is insu?icient to rotate the into contact with the groundpost 21 in the insulating end of the wiper 81' away from order named, grounding the vertical and ro ' the ‘contact 82 to which the ?rst bank; con tary line conductors 91_and 92, respectively, tact 84 is connected, nor into engagement the former twice and the latter once. After with the contact 83. A second impulse over the ?rstdigit is called the ?rst-selector shaft the vertical line willcarry the wipers 88, wipers 32, 33~ and 34 are raised to the sec 89 and 90 into- en‘ agement with the main ond level of the line and- private banks as shaft wipers 50, l and ‘52 of the even vfollows: When the‘ spring 12 engages the ‘so hundreds, and will carry the insulation on ground post 21 an energizing circuit is es 95 the wiper 81 .forward so as to insulate the tablished through the vertical relay 40 of the ?rst-selector C. The current in this cir enough to permit the contact 82 to fall into cuit ?ows from ground G’ through the connection with the‘ ground G’. The next springs 19 and 20 to the ground post 21, impulse to the vertical line'w‘ill move the thence to the vertical impulse spring 12,‘ 100 wipers 88, 89 and 90 into engagement with vertical line conductor 91. side switch wiper the odd numbers main shaft wipers 47, 48 . 36, contact point 93, vertical line relay 40, and 49, and then for‘ the ?rst time the insu through the bridge-cut-o? springs 94 and 95 lation on the wiper 81 clears the contact 82, to the battery lead 96, thence'through bat~ the ?rst contact 84: of the ‘section a te'ry B to ground G. Each time that the 105 ‘ 40 whereby on the masterlevel M is grounded, with the vertical line relay 40 is energized the springs ' vresult that the rotary magnet of the connec~ 97 and 98 are pressed into engagement, and tor is energized; and since all of the remain an energizing circuit. is each time established ing contacts of the section a are always through the vertical‘ma'gnet 4:3. The circuit ‘grounded, the connector‘ will rotate until through the said magnet extends from 110 _ contact 83 from ground G7, but still not its wipers are carried to a position corre sponding to the contact 85 of the next sec ground G2 to the springs 98 and 97, private magnet springs 98a and, 99, vertical magnet tion. and so on. Upon referring to Fig. 1 43 to the battery lead 96, thence through it will be seen that the odd hank terminals battery‘B to ground G. The tertical mag of the wiper selector bank are- multipled, net being operated twice, theli?'rst-selector 115 likewise the even. Hence, when the ratchet switch shaft wipers 32, 33 and 34 are carried wheel is operated one, three, ?ve, seven‘ or opposite the ?rst contact of the second bank 7 nine steps, the wipers 88, 89 and 90 are levelthat comprises the contact points which connected with the shaft wipers 417, 4:8‘ and constitute the terminals of the trunk-lines ‘19, respectively, as shown in Fig. lg'and' leading to the connector A. Following the 120 when operated two, four, six, eight or ten vertical impulses the rotary impulse springv steps. the said wipers are connected with‘ - becomes into contact with the groundv post the shaft wipers 50, 51 and A respectively. ' 21, thereby ‘grounding the rotary line con A clearer understanding of the object of ductor 92 once and energizing the rotary this arrangemcm in my improved connector line relay 41 of the ?rst-selector once. T he 125 switch may be had from an explanation of path of the energizing circuitinay be traced. its operation when one subscriber calls an as follows: From the substation ground G’ other. ,Suppose. for example, that the sub through the springs 19 and 20 to the ground scriber~at substation D ( Fig. 1) desires to post 21, rotary impulse spring 11, rotary line 130 signal the subscriber at substation D1 (Fig. conductor 92, side switch wiper 3?,contact 8,65 1,237,208 point 100, rotary line relay 41, bridge-cut relay 53 ?ows over the following path: olfsprings 101, 94 and 95. to the batteryv lead‘ from‘ ground G’ through the vertical im 96, thence through battery Bto, ground Gr. pulse spring 12, vertical line conductor 91, The'rotary line relay 41, upon-energizing, side sw'itch’, wiper ‘36, ?rst-selector shaft 5 closes the springs 102, and 98 in contact, wiper 32, conductor 108 to the vertical line 70 thereby closing an, energizing circuit relay 53, through the winding 67 of the dif through the private 'magneti35 vwhich ex- _ ferential relay 66 to the-battery-lead96, and ,. tends from ground Gj‘fthrough the springs ' through battery-VB to ground G. Of course, _ 98 and 102, private magnet 35 to'the' battery the ‘relay 66 becomes energized, ‘since the ,_ - 10 lead 96, ~thence through battery ,B to ground winding 67 is in series with the vertical line 75_ _ G} The private magnet 35 being ‘energized . relay 55, ‘but the energization of the said. for amoment, the side switch of the ?rst~ di?'erential relay at this time ‘is without. ‘ selector C passes from ?rst to second posi ve?'ect. ‘ Each time that the'vertical relay 53' tion, thereby permitting the side switch is energized the line relay springs‘ 110 and‘ 15 wiper 39 to engage the contact point'l03, 111 ‘are pressed into contact, thereby 'clos~ 80' ~- thus closing a circuit; through the I rotary ing an energizing circuit through the rotary ' magnet '44; The ‘current-?ow -is from magnet 56 of ‘the wiper selector. PThis cir 'ground'Gr3~ to the contact point 103,. side ' cuit extends from ground, Gt through the. ‘switch wiper. 39, through the interrupter springs 111 and 110, conductor 112,.springs' .113 and 114, ‘through the rotary magnet 56 85 net to the battery lead 96, andthrough bat-' ‘to the battery lead 96, thence through bat-' ’ .tery B'to gr'dund G. The, rotary magnet is tery'B to ground ‘G. The vertical line relay _ 20 ' springs 104, thence through the rotary mag energized once, and the shaftwipers 32, 33 [being energized once for the‘ second digit, and 34 are carried into engagementwith they the rotary magnet 56 is energized once and ' 25 ‘bank contacts that constitute the terminals operatedtoattract its-armature 7 3, whereby '90 leading to the connector switch A,.-assumiiig the ratchet wheel 74 and the wipers8l, 88,89 that the trunk leading, to the said ,“connector ' and 90 are moved one step. Normally these _' I leads off from the ?rst vset of contacts of'the , wipers rest in the'position shown'in Fig. 7, second level. But if the ?rsttrunk-line is but after operating one step the ?berwiper .30 busy, the first private ‘bank contact‘ is 81 still separates the'contact 82 from vground 95 grounded in the well-known manner, and connection, and the wipers 88, ~89'and .90 an energizing circuit is established through . engage the ?rst bank contact which is con- ' the. private magnet 35 when the private ‘ nected th the shaft wipers 47, 48" and 49-, erare adapted to engage'the banks . . wiper 34 strikes the grounded ‘private bank which 35 contact, thereby retaining the side switchim L and .» '1: Fig. 12),; The wiper. 80 rests'on 100 second position and thus maintaining the the contact .84, and the wipers 47 ‘and 48 are ' energizing 'circuitthrough the rotary mag-. opposite the ?rst hundred-group of the bank net 44., The rotary magnet, by continuing vL, and the wiper. 49 isopposite the private ' ‘to .rotate the wipers, breaks the energizing bank P; also, the wipers 50, 51 ‘and 52 0c 40 circuit of the private magnet as 'soonas, an cupy the same relative position withv r'efer- 1'o5. idle line is found, and as soon as the private ence to the banks lal‘andPl. “Then the ro ‘magnet is deénergized the side switch is - tary impulse spring 14 is grounded at the - tripped intothird position; but if there are substation, the rotary‘ line relay 57' is ener-~v _ ._ no contacts to be passed over, assumed in 45 the ?rst instance, the rotary magnet 44, as is gized by current ?owing'froin ground G’. ' " ' through the ground springs .19 and 20, 4110 well known, trips the side switch to third p_o-._ ground 'post- Q1,;impulse spring 14, rotary sition, with the resultthattheside switch - line conductor 92, side'swi-tch wiper 37, con- wipers 36,37, 38 and 39 engage the contact tact point. 106,v shaft , wiper 33, conductor points 105, 106, 107. and 108", respectively, 109, rotary line relay 57, winding 68 of the’] -50 thus extending the subscriber’s line conduc differential relay 66, back-bridge relay 115 tors 9l-and 92 to the connector A.- Also, springsv 11,5 and 116 'to ‘the. battery lead 96,’ since the side switchwiper 38'engages the thence from‘ battery Bto-‘ground G. The ' grounded contact point 107, a guarding po Irotary line relay,‘ upon energizing, operates. ' I - tential is established ‘at the private wiper‘ 34 to place "the springs 117 andll'l'in contact, 155 ~for-protecting the seized trunk-line from be thereby closing an energizin circuit through 1.20 ‘ his circuit ex switching relay 59“.ing molested by any other switch. The sec ‘the, .tends' from-‘ground G‘ through the springs ond digit‘is called after, ‘the subscriber has established connection with'the connectorA Y, :111 and v p _ 117_ , switching‘ relay'springs 76'and ' by way of‘ the trunk-conductors 108 and 109.- 118,}sw1tching relay‘59t _ p to, the battery lead __ 00 The subscriber also rotates the'dia-l for the 9'6, thence-through battery B to lgro'undLG. 125 secondldigit 1, thereby grounding the 'verti- . This relay,’ upon‘ energizing, ,operates to’ ' shift the springs 76~and from engage: ‘ calm-and‘ rotary line'conductors 91 and 192, ment with-springs 118 and 114. into engage “which causes theenergiz'ation .ofthe connec tor vertical and rotary line relays 53 ‘and ‘yment with the. springs 119 and 120. -When/ I 57. _ The-current .for energizingthevertical ._._the relay 59“ thus energizes, the lockingpawl $30: v terminals ‘of the ringer generator E across - thereby pressingthe release springs 29, i‘ '0 the. called subscriber’s line. A signaling. and 31 into engagement for amoment- The - current‘ is, therefore, sent'from the generator contact of the said release springs grounds 'Eto the ringer relay'springs. 135 and136, the vertical and rotary .line conductors 91 side switch wiper ' 60, contact point 137,‘. and; 92 simultaneously‘ from ground G’ to 70 wiper 88 to the shaft wiper 47 , normal- con ‘:the - release spring 31, thence through the ductor 124,- vertical line conductor 138 (Fig. ' springs’30 and 29 to the vertical and rotary 2), condenser‘139, ringer 140,>springs-141' line conductors. The grounding of the ro . and 142.130 the rotary lineconductor 143, ro- '' tary line conductor 92 produces a short 1'0 tary normalconductor 125, shaft wiper 48, circuit ofv the rotary lin'e relay 57 in series wiper 89, contact point 144, side switch with the winding68 of; the differential re 15 ‘I . 'wiper 61, ringer relayspr'ings 132 and 134 lay. 66 extending from ground G5, to the ‘backto the generator; As soon as- the' contact point . 127, side vswitch wiper 62,. calling subscriber ceases to press the signal; springs 152' and 115, winding 68of the dif ferential relay66, rotary .line relay 57 to 830. " 1,5 ing button the ringer relay 70 becomes de energized, and the springs 132 and 133 re the rotary-‘line ‘conductor '92, to the release, sume their normal position. The subscriber at substation #2120, in response to the sig springs 30 and 31 and to ground G’. . There 'fo1‘e,‘since the winding 67_ of the diiferential nal,‘ removes the )receiver 145 from‘ the vrelay 66 alone carries current, the said relay ‘146, which allows the springs now becomes energized and attracts its ar 85 2.0~switch-hook v147 and 148 to engage and‘the springs 141 mature, which latter shifts the spring 131 and 142 to disengage, therebyremoving the from contactv with the spring 151 into con ringer 140 fromiacross his line.v The en v, gagement of the springs 14:7 and 148 closes 25' a tact withthe spring 130. The disengage inent of the springs 131 and 151 destroys the series energizing circuit through both energlzing circuit throughft-he relay 69, and windings of the relay 69 at the connector A,’ the spring 115 passes out of engagement said circuit extending" from ground G5 to with the spring 152 and into contact with _ "the. contact point 127, side switch wiper 62, the spring 116, , which removes the said ‘winding 72 of ‘the relay 69, through the short-circuit ‘of the rotaryline relay 57 and (so ringer springs 132 and 133, side 'switclr winding 68, and establishes instead an ener '95 wiper 61, contact‘ point» 144, wiper 89, shaft gizing circuit extending from the substation wiper 48, rotary line conductor 125, line'con-' ground G’ through the release" springs 31 ductor' 143,-’ thrOugh the primary winding vand 3O to_.the rotary line conductor 92, side 149, transmitter 150, through the springs switch wlper 37, shaft wiper 33, relay 57,‘ ‘as 1,47 and 148, vertical line conductor 138, nor winding 68 of the dili'erential relay 66,-v 100 - ma'l conductor 124,.sjhaft, wiper 47, wiper 88, through the springs 115 and ‘116 to the bat-I contact point 137 ,- through the winding 71 tery lead 96, thence-through battery B to _' of the relay '69, springs 151 and 131 to ‘the ground G. The rotary. relay 57 now oper - battery lead-96‘, thence through battery B ates, and the springs 153 and 154 come into The relay 69, upon energize .contact, whereby an energizing circuit is 105 40 vto ground G. tion, operates to shift the spring 115 from established through the release relay 46 of the, spring 116 (which latter is connected to the first-selector C in series with the release _ the battery lead 96) ‘to the spring 152, which . magnet 59 of. the connector A: However, ' is 111 turn connected with ground. This re i :45 versal ofvthe polarity of the spring 115 sets the current now in passing, as above stated, through the winding 68 aids the winding 67 110 up. an energizingcircuit which supplies the: in maintaining the springs 131 and 130 in , calling ‘subscriber with talking battery cur contact.- The energizing circuit through the The ‘circuit ‘may .be traced ' from release relay 46 andlrelease magnet 59 "8X ' rent; ~ground G5" to ‘the contact point 127, :slde tends fromgroundGrs to the contact point '50 "switch'wiper 62, through the sprlngs 152 107, side switch wiper 38, release relay 46, 115 _. and 115, winding 68 of the differential re shaft wiper 34, springs 154 and 1533, release lay 66,'rotary line relay 57, shaft wiper v33, magnet '59, springs 130'and 131 to'the bat-'f ' .side'switch wiper 37, ‘rotary line ‘conductor 'tery lead 96, and through battery B to _' 92, primary‘winding 5, transmitter 7, springs ground G. -When the connector release mag-g .55‘ 25. and'24 to the ‘vertical line conductor 91, net 59 is thus supplied with current vit en-‘ 120 side. switch wiper 36, vertical llne relay 53, ergiz'es, and as a result the switch ,shaft'and‘ ‘ winding 67 ofthe differential relay 66 to the slde switch .are restored to normal position, - battery lead 96, thence through battery ~B-to ‘thus, breaking the connection between ‘the ~ground G. The two substations are now‘ connector switch shaftwipers 47, 48 and 4:9 60 connected, and communication may be car» and the normal conductors 124, 125 and-126. 125 ried on over the circuit shown by heavy lines ’ The back~release relayl46, being ‘in the same circuit with. the release magnet, energizes in Figs. 1 and 2. ' ._ _ . . p _ ._ . , The release of the switching apparatus'is simultaneously with the latter and‘ operates bioughtabout when the calling subscriber tov closev a circuit through the selector re ‘restores the receiver to the switch-'hoolr3, lease magnet-45 by pressing the‘back-release 130 ' 1,2255? springs156 and 155. together. The circuit current sent to the calling substation 5on1 through the said release magnet extends the busy coil F through the springs 169 and from ground through the springs 15;‘) and 159 to the side switch Wiper 61,’ ringer_re 156 to the release magnet 45, thence to the lay springs 133 and 132 to the calling sub; battery lead 96, and through battery to scriber’s rotary line conductor 92, thence 70 groundv G. \Vhen the ground to the line conductors 91 and 92 is interrupted, all the magnets involved in the release are then de~ energized, and all of the switches are fully 10 restored. It will be understood, of course, that when the connector switch‘A is released through the primary winding 5, transmitter _ ' 7 to the vertical line conductor 91, and through the vertical line relay 53 of the con nector A andwinding 67 of the differential relay 66 to the battery lead 96, and to the 75 busy coil . When the subscriber hangs up and the wipers 47 and 4:8 disengage from his receiver after receiving the busy-signal, the normal conductors 124 and 125, the back he grounds the line conductors 91 and 92 bridge relay 69 of the connector A is vre~ simultaneously, energizing the line relays . _ ' stored, and the spring 115 returns into nor 53 and 57 of the connector A, as already ex 80 mal engagement with the non~grounded bat plained, and producing the release of the tery spring 116, thus cutting off talking switching apparatus as formerly. Further battery current from the calling line, and de more, when the connector release magnet energizing the bridge cuteoifrelay 128 of energizes, the wiper-selecting mechanism is . also. released. Referring to Fig. 3, it. will 85 If the called line #2120 is busy at the be seen that when the release 'armaturelGl . time that the calling subscriber #5000 at is attracted by the release magnet 59, the the selector C’. ~ tempts to establish connection, the connector link 162 is drawn forward, and when thus ' A is released by the last impulse to the ro-v moved (see Figs. 6 and 7 ) it rocks about the 25 vtary line conductor 92 as follows: The said pivot point 163, and the ?nger 164 imparts 90 impulse energizes the rotary line relay 57‘ an outward movement to the members 165 of the connector A, which relay in turn and 166. The locking link 75 then moves energizes the. private magnet 58, pressing about‘ the, pivot point 167, freeing the _ the private springs 157 and 158 into con springs 76' and 113. Also, when the pawl 30 tact after the private wiper 49 has been car 165 is moved about its pivot point 168 the 95 ried onto the grounded private bank con ratchet wheel '74 returns to normal position, tact. It is understood, of course, that when owing to the tension of the coil spring 169. ever a line is busy the connector private bankv Thus when the calling subscriber restores contacts connected with the private normal his receiver to the switch-hook, all of the. 35 126, shown at the selector 0, are all con central station switching apparatus which 100 nected to ground. Therefore, since the con he brought into use is fully released and re nector side switch is in second position when turned to normal position. the private springs 157 and 158 are brought In the foregoing it was shown how the into contact, an energizing circuit is estab connector switch was operated to select 40 lished through the release magnet 59 from a particular subscriber’s line from the ?rst 105 the said grounded private bank'contact to hundred-group; It will now be pointed out the private'wiper 4L9, wiper 90, thence to the how the connector operates to select any par- ‘ side switch wiper 62 (which is in second po ticular hundred-group from the ten groups sition) to the private magnet springs158 and in the connector bank. Assur a, forexam $5 157 to the release magnet 59, thence to bat- ' ,ple, that it is desired to select the line 25 tery B and to ground G. The connector 1n the N-group (Fig; 12) which, in this switch. shaft and side switch are thus re 110 case, occupies the position of the six After the ?rst-selector leased in the well-known manner,'and con- - hundred-group. nection is not established with the called switch has extended connection'to the con The busy signal is, of course, estab nector switch