US1778230A - Automatic telephone system - Google Patents

Description

Oct. 14, 1930. N; H. SAUNDERS AUTOMATIC TELEPHONE SYSTEM Original Filedsept. 17, 1927 6 Sheets-Sheet l -IWZFF Norman H.5aunclar'5 Oct. 14, 1930. N. H. SAUNDERS AUTOMATIC TELEPHONE SYSTEM 6 Sheets-Sheet Original Filed Sept. 17, 1927 N Eh EM mw Q QN Ihuen or Nur'man H.5'aundars I Oct; 14, 1930. N. H. SAUNDERS AUTOMATIC TELEPHONE SYSTEM 17, 1927 6 Sheets-Sheet 5 Original Filed Sept.

D J Inventor Nur'manf-IEraundars Oat; 14,1930; N. H. SAUNDERS AUTOMATIC TELEPHONE SYSTEM Original Filed Sept. 17, 1927. 6 Sheets-Sheet 4 lumen :31" Nurman H Saunders 6 Sheets-Sheet 5 N. "H/SKUNDERS Inuen or. Narman HSaundars flwm AUTOMATI C TELEPHONE SYS 'I'EM Original Filed Sept.

Oct. 14, 1930. N. H. SAUNDERS 7 AUTOMATIC TELEPHONE SYSTEM Original Filed Sept. 11,1927

. 6 Sheets-Sheet 6 NormafifiSaundarl Patented Oct 14, 1930 UNITED STATES A ENT OFFICE NORMAN H. SAUNDERS, HOMEWOOD, ILLINOIS, A SSIGNOR T RESERVE HOLDING GOMPANY,.OE KANSAS CITY MISSOURI, A CORPORATION OF DELAWARE ',AZU'TOMATIC TELEPHONE SYSTEM Application iiIedSepteniber 17, 1927, Serial No. 220,160. Renewed March 20, 1930.

The present invention relates in general to automatic telephone systems, more particularly to such systems in which line finders are employed to connect an idle selecting switch 5 with a calling line; and the principal object of the invention, briefly stated, is the production of a new and improved finder. switch system, the improvements tending to make the system morereliable, to give .uniform high quality service, and to make it cheaper to install and maintain.

i The present invention relates more specifically to a searching type finder system, in which'the' finder switches move under their own power and control in search of a calling line. In systems of this type, two basic groups of lines are grouped together and made first choice toione group of finders while 1 other subgroups are grouped together and make first choice to another group of finders.

' By this arrangement, a minimum travelof the finder switch is secured, and thereby the time required for the finder switch to pick up a calling line is materially reduced. In systems of this type, devised heretofore and of which I am aware, in case of an emergency, such as an all finder busy condition or trouble in one finder group, the preferential service was discontinued, that is, the remaining finder switches were called upon to pick up calls from, the two basic line groups irrespective 40 of the position of those lines in the banks of the finders, consequently a longer period of time was required onan average to pickup a calling line.

As a. further object of the present invention, I provide a new and improved distributor switch, which will maintain the.

preferential service arrangement even when the two groups of finders are thrown together as one large group and operated responsive to 9 calls from. either basic line group.

'- of the foregoing patent.

the needs of a. distributor switch and in ac- Further objects, not specifically mentioned here, will be best'understood from the detailed description and claims which follow.

The drawings comprising Figs. 1 to 6, inclusive, when arranged with Figs. 1, 2 and 3 from, left to right in a straight line, with Figs. 4, 5, and (5 right directly beneath, and withcorresponding lines in alignment, show suflicient details to enable a clear understandof Loniax and Saunders,'No; 1,688,588, issued -Oct.-23, 1928, I am using the finder and line equipment arrangement shown in that application. Thus it will be seen that Figs. 1, 2 and 3 are identical with Figs. 1, 2 and 3 In Fig. 1, I show a finder anda selector switch assumed to be in the group A, Fig. 2 I show two line equipments, the finder bank multiple and the 'vertical banks for controlling the finder switches of group A and group B, Fig. 3, I show a finder and a'selector switch assumed to be in the group B.

In Fig. 4, I show adistributor DA, through the operation of which the finders of group A are preselected and taken for use byfcalliiig lines. The distributor DA differs from the distributors in finder switch systems devised so heretofore, in that it employs a Strowger switch mechanism, instead of 'a rotary lineswitch mechanism, with the circuits of that Strowger switch mechanism modified to meet 35 cordance with the objects of the present invention. The distributor DA' is provided with two sets of wipers, one normally used, having: access to the finderswitches of the group A. The other group of wipers, whichare used under alternate circumstances, have access'to the finders of the group B, for a purpose which will be apparent hereinafter. Inasmuch as the groups A and B of finder switcheswill not exceed ten switches per group, it is not necessary to use the entire Strowger switch mechanism, but it is possible to simplify that mechanism by omitting the vertical magnet and mechanical arrangements associated therewith. The switch shaft through the operation of which the switch room attendant may throw thetwo. groups offinders Aand B into one group,thereby permitting thedistributor DA, for example, to have access to the finder. switches of both groups. In Fig. 6,;I showa distributorswitch DB which is identical in structure and circuits Ito that shown in Fig. 4, the switch DB hav- -ing normal access to the finders of the group r Theo'peration of the finder switch system shown in the present invention is identical vwith'that shown in the above mentlone'd copending application, with the exception of the operation of the distributor switches. Briefly, responsive to'the initiation of a call on the line, a preselected finder switch is started, in the. group having first choice access to thatline searching in a vertical direction for the level containingthe calling line, and when that level is found, switching over and searchingin a'horizontal" direction for the contacts otthe calling line. 'When the calling line is I'found, the finder is switched through to connect it with a selector switch, and a kick off ground is returned to the distributor switch.

This kick oflf ground releases the distributor switch from the finder that has just been opstated, and operates the motor magnet of the distributor to step the wipers overthe bank contacts in search of another idle finder in the same group. g V

In case the finder which has just operated happens to be the last idle finder of the group the distributor switch is not operated, since there are no other idle finders in the group for it to find. The all finder busy relay falls back, and the start circuit is connected through to the other'finder groups, operating totpick up calls in the first line group.

fi In case of a fault in the group B disthat group distributor to control its finders l j tributor, the despatcher may hold that equipment out of service by operating the key K t hereby'eXtending thestart circuit of both groups of lines to the distributor DA. The

distributor under this circumstance,'operates -to find" an idle finder in the A group responfisive as the initiation of a call on an A group riline,and' operates to find an idle finder in the thr'own that the distributor DA has access to tlie. -find er s ofthe'group B, and then ithas accessit'o' Lthose fi nders only in response to calls :i n, th'e-:grou p Blines. The distributor preelectmanidle finder in the'group A,"-and Bgroup responsive to the initiation of a call 4 "on a B group line. It is only when this key is call. At springs 463 cuit from ground over conductor 477, through when it is started responsive tothe initiation of a B call, it is a post selecting distributor, that is, it picks out an idle finder in the group Batter the call has been initiated.

Similarly, operating thekey in the op- 5 posite direction willdisconnect the distributor DA, and route all callsto the distributor I DB, giving that distributor access to the finders of group B responsiveto calls originating in thegroup B line, and'access to'findersof group A responsive to the'c'alls lnitlating 1n the group .Aline.

"Having thus" described my inventionin general, I will now proceedwvith a detailed description of its operation.

Line, swarms th am j Assuming now that the line S initiates a call, a circuit may be traced from ground at springs 211, conductor 254, through the hook- --switch, receiver. transmitter and calling device of the substation S, conductor 255,

springs 215,,through the righthandwinding of relayfZOl to battery, energizing relay 201'. At spring 213rand its break contact, relay 201 removes ground from the private conductor 256, associated with the line S and the banks of the finder switches, to render the line call ing. Relay 201. also'closes at spring'2l3and its make contact a circuit from ground;

through that spring and spring 214 to the start conductor '250,"thereby placing ground potential upon the second bank contact ofthe vertical bankVA, and upon the ninth bank 2 contact ofverticalflbank V B, for a purpose which will be brought out hereinafter. The ground conductor 250 completes a circuit through the resistance 251, conductor 260,

the spring 502and its break contact, conductor 475, through thewinding of start rela-y 409, through springs 460, to battery. Relay .409 energizesfoverthis circuit to start the preselected group A finder in search of the 1 calling line. The energization of relay 409,

'opensat spring 462a point in'the circuitof-a relay 408, to prevent the ener'gization' of that relay duringthe process of setting the instant relay 409 closes a cir springs 447 springs 457,through the winding of relay 406,springs 445, spring 443 and its break contact, springs 439, springs 435,

through the winding'of relay 401 to battery.

\ Relay 406 energizesiin this circuit, but be- 1 cause of the high" resistance ofthat relay,

relay 401 does not energize at this time. The

energization of relay 40G, closes a circuit from ground through spring 453, through the winding of all finders busy relay'405, to maintain that relay energized throughout the setting of the instant call even though the insta-nt call may use the last idle finder in the group A Belay 406, at s'pring 454 closes a circuit from ground on. spring 458 through thesupervisory lamp 412 and the slow alarmdevice, not shown, to battery. The lamp 412 lights to indicate a call is being set by the tinder control by distrilouiorv DA, and the slow alarm device is started operating. This dev which n ay be any well lniown slow C '='cuit of the slow alarm losed for longer than a s will operate, to call the s r s attention to the trouble, neiay 406 at springs opens a point in the all-iinders busy circuit of the group B, for a purpose which will'be explained hereinafter, At .spr 4.51, relay 406 opens a point in the circuit of wiper 427, to prevent the op ation of the distributor DA over circuits controlled through that wiper until the present call has been'set. At springs 450, relay 406 closes a circuit from ground th. augh resistance 4 is, springs 455, springs 450, wiper 425 new in engagement with the ntact to which conductor 163 is connect-ed, jiector 163, negative trunk conductor 150, spring 117 of the selector EA, tin "lgll the upper wig of line relay 1.02 of the selector EA to battery. Theline relay 102 energizes overthis circuit, and springs 116 K s the-obvious circuit tor l e release relay 101. .he release relay 101encrgizes, and at springs 113 places ground on release trunk conduc- 151, for a purposewhich ill be explained hereina :er. Relay 406 upon operating prn fi l-49 closes a circuit from ground thro ,i the wiper 424 now in engagement with the contact to which the conductor 162 is connected, tlj roughthe conductor, sp i 125 and its break contact, springs 121, sprin 120, through the windingof stepping relay 107 of the finder FA to battery. Relay 107 energizes over this circuit, to, start the f: er FA in operation.

Operation of finder FA The operation of the finder in the present invention is the same as that described in detail inthe above mentioned patent, and for that reason will only be briefly described in the present specification. Responsive to the energization of relay'107, a circuit is closed from conductor 162 through springs 129, spring 124 and its break contact to the windingof the vertical magnet 125'to battery. The vertical magnet energizes over this circuit, elevates the shaft containing the wipers of the finder FA one step, and opens the springs 121, to open the previously circuit for the relay 107. Relay 107 falls back, and spring 129 opens the circuit just traced for the vertical magnet 105. This interaction of relay 107 and magnet 105 contin'ues as long as the vertical wiper 262 of the tinder FA fails to pick up ground poten tial, Since the Calling line S has a finder 250, the second bank contact of the vertical bank VA, wiper 262, conductor 158-, through the, upper winding of relay 106, springs 120,

through the winding relay 107 to battery. Re

lay 106 energizes over this circuit, and relay 107 which was in energized position when the circuit was closed, remains in its energized position. The energization of relay 106 transfers the impulsing circuit from the vertical to the rotary magnet, that circuit being closed through springs 129 andspring 124 and its make contact, through the winding of magnet 104 to battery. The rotary magnet 104 energizes, and moves the shaft containing the wipers of the finder FA one step in the rotary direction, and opens at springs 120 the above traced circuit forthe relay 1 07. Relay 107 falls back, opens the circuit for magnet 104, permitting that magnet to tall back and again close the circuit of relay 107. Assume now that the first contact in the sec- 0nd level is the contact of an uncalling line, the test wiper 234 will pick up ground potential, completing the circuit through conductor 157, spring 122, spring 132, through the wiper switching relay 109 to battery. Wiper switching relay 109 energizes overthis circuit, at spring 138 connects the test Wiper 231 through conductor 156, springs 138, springs 131, spring 125 and its make contact, spring 121, spring 120, through'the winding of relay 107 to battery. If the test wiper 231 is engaging an uncalling line, relay 107 energizes over this circuit, again closing a circuit for the rotary magnet 104 which energizes and advances the wipers another step. This interaction of relays 107, 109, and 104 continues until one of the other of the test wipers 231 and 234, engages an ungrounded contact associated with a calling line. During the stepping of the switch FA, the switch through relay 108v has been short circuited, ground being applied to the upper terminal from the release trunk conductor 151, and to the lower terminal from spring 127 when relay 107 is energized, and from conductor 156 through springs 138 and 131 when relay 107 is deenergized. Since the line'S appears in the banks to which Wipers 233 to 235, inclusive, have access, wiper 234 will lose ground potential when the contacts grounded contacts,

through the winding of the relay 108, spring 125 and its make contact, spring 121, spring 120, through the winding ofrelay 107 to battery. Because of the'high resistance of the Distributor DA searches forz'rtle finder The ground placed upon conductor 164 by springs 135 completes the circuit for relay 407, traceable through wipers 426, springs 442, through the winding of relay 407 to battery. Relay 407 energizes, and at spring 457 opens the circuit previously traced for relay 406. At springs 458, relay 407 opens the cir cuit previously traced through the alarm' lamp 412 and the slow alarm device, to deenergize those devices. The deenergization of relay 406, closes a circuit froiniground through off-normal springs 140 of the finder F A, conductor 165, wiper 427 of the distributor DA, springs 451, springs 445, spring 443 and its break contact,-springs 439', spring 435, through the winding of relay 401 to battery. Relay 401 energizes over this circuit, and at spring 431 prepares a locking circuit for itself, that circuit including the interrupter springs 435. At spring'430, relay 401 closes the obvious circuit for the rotary magnet 410,,

causing that magnet to energize and advance the wipers one step. If the next finder of the group A is busy, the wiper 427 will pick up ground potential, reclosing the previously traced circuit for relay 401, which again energizes, locksitself through the interrupter springs, and closes the circuit for the rotary magnet 410, energizing that magnet to cause the wipers of the switch DA to be moved on to the next contact set. This procedure will continue as longas the wiper 427 encounters finders. When an idle finder is encountered, the wiper 427 will fail to pick up ground, and the finder DA will come to rest upon the contacts associated with that finder, preselecting it in readiness for the nextcall.

, The Strowger switch mechanisms, such as is used for the distributor DA have a normal capacity of ten contacts in each row, so when the wipers 420 to 427, inclusive, have been stepped ten steps it is necessary to release them and to return them to their normal positions before additional steps can be taken. F or this purpose the cam spring 437 is provided. and after the wipers have been stepped off of the last contact in-their banks, that is after the eleventh step, cam springs 437 close,

associated with busy closing a circuit for the relay 403. Relay403 energizes, and at springs 440 locks itself through off normal springs436, thereby 1nsuring that it will remain in its energized closes springs 441, thereby closing a circuit for the release magnet 411 to energize that magnet. The release magnet upon energizing withdraws the holding pawls from the shaft, containing the wipers 420 to 427, thereby releasing the distributor DA to normal in the well known manner. The wipers of the distributor DA are mounted on a shaft in such a position that when the shaft is in its normal position, the wipers will encounter the first contact set in the bank, rather than encounter no contacts as is customary in a V Strowger switch. The oii-normalspring 436 opens just before the switch reaches its normal position, to unlock the circuit of relay 403, to permit that relay to restore an'd open the'circuit of the release magnet and prepare the circuit of the stepping relay 401. If the first finder of the group, upon whose contacts the distributor wiper 427 will pick up aground potential, and the circuit of relay 401 will be completed, energizing that relay to step the distributor DA off of that conta'ct'set. The testing operation will continue until an idle finder is found, at which time wiper 427 will lose its DAis now resting, 1s busy,

ground potential and the distributor will i come to rest. I

Line 8 initiates a call ances, in this case resistance 253, to complete a circuit for relay- 601 of the distributor,

DB. Relay 601 energizes over this circuit. opening the circuit of'relay 602 at spring 630, and closing a circuit for the start relay 601 at spring 631 traceable from ground through those springs and spring 647 is make contact, springs 637, through the winding of relay 604, springs '645,'spring 615 and its break contact, interrupter springs 659, relay 609 to battery. Relay 604 energizes over this circuit, and, because of the resistance of that relay, relay 609 is prevented from opera ating. The energization of relay 604 c'loses the alarm circuit'at springs 644; closes a holding circuit for all finder busy relay 605 at springs 643; opens a point in the testing circuit at springs 641'; opens a point in the all finders busy-circuit of the group A at ing a circuit through springs 338, springs 350,- springs 349, conductor 370,.through the winding of relay'303ofthe finder FE to battery. Finder FBoperates, first in a vertical direction to find the -level containing the calling'line, and'then in'a horizontal direction to find the calling line, and at the end of that operation switch through relay 302 energizes to connect the calling line with the idle select-or. The energization of relay 302 closes springs 330,,thereby placing ground on conductor 374, that ground being picked by wipers 621 to complete a circuit through springs=649 and the winding of relay603=to'battery. Relay'603 energizes, and atsprings 635 opens the circuit over which relay 309 of the selector EB was initially energized, to prevent the resistance ground from interfering with the operation of that relay during impulsing. Belay 603, at springs 637 opens a point in-the circuit of relay 604, permitting that relay to deenergize. "t spring638, relay 603 opens the circuit thro'ugh the alarm lainpiand slow alarm device to prevent fu'rther operation of those devices at this time; 'Relay604, fallsback, and at springs 641 completes a circuit for the stepping relay' 609, that circuit being trace- I able fromqground through ofi norn al spring 303 of the finder FByconductor 37 3, wiper 620, springs 641, springs 645, springs 650, springs 652, interrupter springs 659, through the winding of relay 609 to battery. Relay 609 upon energizingycloses springs 662, therebyconipleting a locking circuit for-itself in series with interrupter springs 659. At springs 661 relay 609-closes the obvious circuit for the rotary magnet 610, energizing that magnet to advance the wiper-s 620 to 627 52. of tlie' distributor DB one step, The operatron ofithe rotary magnet opens the circuit of relay609, permittingthatrelay to deenergize to open the circuit of the rotarymagnet.

Iflthenext finder of the group is busy,.wiper 620 cagain finds ground potential and the sanie cycle of operations' is repeated, continuing-untilthe wiper-620 encounters an "ungrounded contact associated with an idle,

finder. VVhen eleven stepshave been taken 3 by theqrotary niagnet, cam springs-660 oper ate,zclosing a circuit for relay 607, which energizes. Relay 607 looks itself to springs 653 through off-normal spring 659, to insure that it=willreniain in-an energized position until" thedistributor DB returns-fto-its normalpo- Allfinders busy condition Assume now that all the finders in group A becoinebusy, when the lastfinder of the group goes oii norinal, ground is removed from the all-finders busy, conductor 161 at oft-normal springs 126 ofthat'finder, thereby opening the circuit for normally energized relay 4050f the distributor 'iDA. 'This relay falls baclgand at .springs 445 opens a point in the testing circuit through wiper 427 and relay 401,- to prevent aneedless operation of the distributor DA. At springs 447, relay 405 closes a point in the start circuit, icontrolled by relay'409, so that responsive to a call in'the A group of lines, aB finder will be started. When relay .409is energized responsive-to the initiationofacall on a group A line, it closes springs 4'63, thereby closing a circuit from ground over conductor 477 through spring 447 and its 'brealr contact,

conductor 478, springs'647 of the distributor DB, springs 637, through the Winding of relay 604, hence over the previously (traced circuit to relay 609 to battery. Relay 604 energizes over this circuit, to start .the finder 1 y switch preselected by the distributor DB to operating in the usual manner. Since the calling line S appears in the upper half of the bank ofthe finder switches of group B,

take niore than five steps, in'this case nine steps, to reach'the level containlngthe callingline. The operation of the finderiunder this circumstance'is identical to that already explained and will not be repeated at this time.

' Similarly if all the finders in the groupB become busy, all finder busy relay 605 is deenergized wheuthelast finder of ,thegroup is taken {for use and ground is removed from 1;=

itwill be necessary that theselectedfinder DA, s prings457, relay 406, thence overthe 446, conductor 47 3 to the all finder busy common 161, and the other from that commonthrough conductor 47 3 and the springs 642 of the relay 604 ofthe distributor DB,conductor 510, springs 501, thence through the conductor472' to the relay 405. Itwillbe noted thatwhen-the relay once falls back, the ,directilocking circuit to the all finders busy common is broken at springs 446 and that'the parallel path for the relay'405 is open whenever the relay 604 of the distributor DB is energized. It then, while the distributor is sending a callfrom a line in either group, a finder in the group Abecomes idle thereby placing ground on conductor 161, all finders busy relay 405willnot be ener gized immediately but rather will remain deenergized untilthe relay 604 of the distribus tor DB restores at the completion otthe setting of the call; By' this arrangement, the idle finder in thegr'oup A is prevented from stealing the call from a group B finder. If it werenot for this provision, if the group B finder were setting a call in one'of the lower levels of the A line group, which levels appear as the uppermost levels of the'group B finders, a finder in the A group becoming idle after the group B finder has beenstarted, might be started and connected with the calling line before the group B finder would reach the contacts o'fthe calling line, thereby causing an unnecessary operation of the" group Bfinder. By holding'the all finder busy relay 405 open until the distributor DB comes to rest at the end of a call, this steal- 7 Similarly the all finders relay 605 of the distributor DB} ing of a call is preventedl is maintained energized over twocircuits one ofwhich is broken when I by spring 452 of the relay'406, of the distendant may tributor DA, this similar arrangement piefrom I an A venting the stealing of a callgroup finder bya B group finder. v

The operation, 0/ 7063 K7 is It may happen that because of some trouble in one of the distributors, the switch room atfind it advisable to remove that distributor from service forrepairs To do this he operates the keyK which'alters the start circuits so 'thatcalls from both line present time. the relay fall's back at springs 646, and the other held open' anew . groups are handled by the'one remaining distributor,.which selectsan idle finder in accordance with the group containing the line which'originatedthe call. Thatis when one distributor, for example DA, is handling all of thetrafiic in the two line groups, calls originatingin-the A line group will be handled by a finder in the A group, if there is an idle finder inthat group, and calls originating in the B line group willbe handled by-a group ,Bffinder, ii there is an idle finder in that group. It will be noted that the bank contacts accessible to the wipers 424 to 427 of the distributor DA are'multiplied to the bank contacts accessibleto the wipers 624 tov 62? inclusive, of the distributor DB.- Similarly the contacts accessible to: the wipers 420 to 423, inclusive, ofthe distributor DA, are multipled with the contacts accessible to the wipers 620 to 623 of the distributor DB. Inthe normal course-of operation, wipers 424 to 427 of the distributor DA'are the wipers used,and;

have direct access to the finders of the group V the distributor DB are normally used and havedi rect access to the finders of the group, B. When the key is thrown, the wiper sets to be c A. Wipers 620. to 623, incliisive, of

used by thedistributors,depends upon the startrelay energized by the initiation of a call. That is each line group start wireterminates-ina dilierent startr'e'lay in the distributor, so that when the A group star-tree lay is energized, the distributor selects-'aniidle finder in'the'A group from its no'rmal set of wipers lVhen the B group start relay is energized the distributor selects a finder in the I B group through its alternatesetof wipers. 7 Assume" now that the attendant, operates key K tothe left to operate springs 501 and 502. This operation removes the distributor DA from service, and routes the' calls to the distributor DB. The operation of spring 501 away from its break contact, opens the group busy common-161 from the. all finder busy rclay 405 of the distributor DA, permitting said relay to restore to normal. The busy common conductor161 is now connected through spring 501 and its make contact, conductor 512, .to the spring 632 of theirelay 602 in the distributor DB, this spring being open at the 1 The operation of spr'ing502 disconnects thestart wire 260from the group A and connects it to conductor 514' leading,

I through springs630 to the relayv602 of the distributor DB, When a line in the'A group initiates a call and'places ground on the start conductor260,'relay 602isenergized; At

springs 632, relay 602 extends the alL-finder I busycommon ground. of group A through i those springs to, .thewinding of relay 606,1 completing a circuit forthat relay to energize.

it. 7 At springs 633, rel cuit of relay 601,so that a call originating in the'B' group will have to wait untilthe dis-' tributor DB has finished with the instant call.

ay 602 opens'the cir-* i V D springs 659 through the Winding of relay 609 to battery. It will be remembered that in the foregoing description of the operation of distributor DB the control of the distributor Ywhen searching for an idle. finder is through thewiper 620,which operated the distributor until that wipertound an ungrounded contact, associated with anidle finder in the B It may happen therefore that the wipers oi the distributor DB atthis time are standing upon the contacts of a busy finder in the A group, in which case wiper 627 will pickup a ground'potential, which is projected through springs 65Tto the upper terminal of relay 608. If this is the case, relay 608'will not energize immediately but will be short circuited, and relay 609 will energize from the direct ground picked up by wiper 627 and applied to the circuit of relay 609 at a point excluding the winding relay 608. Relay 609, upon operating, closes the circuit of the rotarymagnet as hereinbetore described, to step the Wipers of the distributor DB in search of an idle finder in the A group. ."When that finder is found, wiper 627 loses its ground potential and. the short circuit is thereby removed from relay 608. Relay 608 then energizes through relay 609. -Itelay 609 does not pull up to again close the circuit of the rotary magnet, because of the high resistance of the winding of relay 608'. Relay 608 upon pull ing up, opens at springs 65'? the testing circuit through wiper 627, so that the distributor DBWill not st-ep otf theselected finder when the guard conductor of that finder is grounded. At springs 658, relay 608, closes a circuit from ground through spring638 to the alarm lamp and slow alarm device, for the purpose which has been previously described. At springs 656, the relay 608 closes a circuit from ground through resistance 613, spring 635,

I spring 656, wiper 625, conductor 163, conductor 163, trunk conductor 150, spr ng 117,

through the upper winding of the line relay 102 of the selector EA, energizing that relay to seize the selector and finder in the manner hereinbetore pointed out. At springs 655, relay 608, closes a circuit from ground through wiper 624 to the start conductor 162 which is ,eonnected through "startconnector 162 of the finder FA, that ground operating the relay ql07 to start the finder in the nianner'hereinbefore pointedout. The finde'rFA now opcrates in the manner which has already been described,finally positioning its w pers upon the contacts of the calling line and energizing relay 108 through the establishedconnection therewith; At spring 135, the kick off ground is applied to conductor 164 as bet-ore, ground now being picked up by wiper 626, completes a circuit through spring 649 and its make contact, through the winding of relay 603 to battery. Relay 603 energizes, and at spring 638 opens the alarm and signal circuits to prevent further operations of those devices at this time. At springs 637, relay 603 opens a point e in the circuit of relay 604, however since that relay is not energized this operation serves no useful purpose. At spring 636, relay 603 opens a circuit of relay 608, permitting that relay to fall hack to normal. The restoration of relay 608 closes at springs a point in the circuit of the distributor DB through which that distributor seeks an idle finder in the A group. it another call is waiting in the A group, conductor 260 will be still grounded,

and sta t relay 602 will remain operated. Relay 606 will also remain operated if there is an idle finder in the group A, and the distributor DB will test through wiper 627 to connect with that idle finder. If however the instant call was the only call pending in the group A, relay 602 deenergizes when the cut oil relay 202 of the calling line is operated, because that relay removes ground from the start conductor 260. Relay 606 Will thereupon be deenergized, and the distributor DB will test for an idle finder in the B group under the control of the testing circuit through wiper 620, in the manner already pointed out.

Thus it will be seen that When the key K is operated, calls in the A line group are handled by an A group finder under the control of the distributor DB. Since the operation of the key K has no eil'ect upon the handling of a line call by a B finder under thecontrol of the B distributor that operation will not be repeated at this time. 7

If there are no idle finders in the A group at the time the key K is thrown, vconductor 512 will not be grounded, therefore when reoperated over a circuit through spring 631 of the start relay 601. The B finder will pick up the A line code, making more than five vertical steps to reach the level containing the calling line.

If the key K is thrown to the right to operate springs 504 and 505 the distributor D13 is removed from service and all vcalls are handled by the distributor DA. The operation of spring 504, opens the circuit from the busy common conductor 367 to permitthe relay 605 to tall back. The operationot springs 505 extends the groupB start conductor 261 through those springs to conductor 476, preparing a circuit through springs 462 and relay 408 tobattery. When a group '13 line operation ofspring 594 extends the all finder busy common. 367 through conductor 474 thereby preparing the ClTCUltWlllCll is com-- pleted when relay 408 energizes to energize 1 the relay 404. Relay 404 transfers the con trol of the control of the distributor DA from the normalset of wipers to the alternate wipers 420 to 423, inclusive. 7 If the wiper 420 is standing on the contacts of a busy finder, a circuit for relay 401 Will-be completed through that Wiper, springs 484, spring 443 and its make contact, spring 439, interrupter spring 435 to the winding relay 401 to battery. Relay v401 will energize, lock itself, and close a circuit to the rotary magnet 410. The rotary magnet willadvance the wipers and-open the circuit of relay 401, this interaction of the magnet and relay continuing until wiper 4 20 encounters an ungrounded contact. Relay 402' will then be energized from ground through springs 4610f the 408, spring 444 and its make contact, spring 456, through the Windin ofrelay'402, spring 443' and its make contact, springs 439, through the interrupter springs 435,through the winding of relay .401zto battery. Relay 402; at springs 438, closes a circuit for the signal alarm lamp and the slow alarm device;

at spring 434 opens a point inthe circuit of the wiper 420 to insure that the circuit of DA will not step-elf of the contacts of the preselected finder when that finder is made busy by the present call: At springs 433, re-

lay 402'closes a circuit from ground through resistance-414, springs 455, through the wiper 420 through the conductor 375,to seize the line relay of the selector EB in the manner hereinbefore pointed out; "Atspring 432, relay 402 applies ground through the wiper 423 and conductor 376 to the start conductor 876,

ofthe finder FB, to start that finder operating in search of the calling line. When the finder P13 is on the calling lineand relay802.

is energized, kick off ground will be placed on conductor 37 4 by the springs 380, that ground being picked up by the wiper 421 to complete the circuit through spring 442 and its make contact through the relay. 407 to bat tery. Relay 407 energizes to restore the distributor DA tonormal and'to complete the circuit preparatory to selecting another idle finder. If there is another idle finder in the B group and another call waiting in the B line group, the selectionwill be through the wiper 420,- and will be ace manner/just pointed out The. operation of thekey K does not in any way elfect the control of the distributor omplished in the .DA by a call in the A group so that operation will notbe repeated atthis time.

Having thus described my invention, what; I conslder new and desire tohave protected by Letters Patent is pointed out in the appended claims.

What is claimed is 1. In a telephone system, subscribers lines a distributor switch having a plurality of 'wi ers a ou 'of contact sets accessible to each of sald wipers,a finder switch assooiated with eachof said contact sets, a trunk line individual to each finder, means in'the wipers have been stepped ofi, the last contact set of the group for releasing them and returning themto the first contactset, and

means for stopping said wiperswhen'an idle finder is found. T

2. In a telephone system, subscribers"li'nes,- a group, of finder switches,.a trunk line individual to each finder, means in the finder for connecting the individual trunkline to a calling one jof said subscribers lines, a distributor. switch-having a'plurality of positions'corresponding to said finders, meane for operating S2116]. distributor from posi tion'to position .to test. the busy or idle con- H dition of said finders one at a time, and means in said distributor, operated after the last finder of the" group has been tested,'for

releasing said distributor and returning, it

to the position from which it teststhe first V 10o 8. In a telephone system, subscribers lines,

finder of said group.

a, group of finder switches, a trunk line. in-

dividual to each finder, means in the finder for connectlng the individual trunk line to .a calling one of .said' subscribers lines, a

distributorswitch having a plurality of positions corresponding to said finders, means" for operating said distributor from position :to position to test the busy or idle condi tion of said finders one at atime, means in said distributor, operated after the last find-, er of the group has been tested, for releas ing said distributor and returning-it to the posltion from which it tests the first finder ofsaid group, and means for preventing the performance of said testlng while said dis-f tributor is returning to said latter position, f

Inga telephone system, a distributor switch havingwlpers, a group .of-fincler switches aceessiblethrough normal onesof said wipers; a second group of finders'accessible through alternate ones of said wlpers, means 1n sa d-distributor operated through said: normal wipe'rs'top'reselect an idle finder in the group. accessible through the normalwipers, a ke'y, means responsive tothe operationof said key for conditioning sa d first means for operation through said alternate wipers, and means responsive to a' callfor operating said first'means to select use the alternate Wipers.

5. In a telephone system,,a plurality of 'groups'of lines, a plurality of groups of finder switches having access to said lines, a distributorswitch for each of said finder groups and normally operated toselect idle finders in that group, means forgiving said distributors access to the finders ofthe other finder group, means 'lor combining said lines into one glOlltp byarcinoving one of said distributors from service and means then responsive to the initiation'of a call on one of said lines for'operating said other distributor to select and start a finder in the group having access to that line.

i 6. In a telephone system, a first and a second roup of lines, a first and a second 'roup of finders having access to said lines respectively, first and second distributor switches for allotting said finders for use, means responsive to the initiation 01" a call on a line of the first group for operating said first distributor to start, a preselected finder or the first group in search of said line, means for giving said first dis ributor access to said second group finders, means responsive to the initiation of a call on a line in said second group to start said first distributor in search of an idle finder in said second group, and means in said first distributor operated responsive to the finding of said second group finder for starting it in search of said calling line.

7. in a telephone system, a first and a second group of lines, a first and a second group of finders having access to said lines respectively, first and second distributor switches for allotting said finders for use, .icans rcsponsive to the initiationot a call on a line of the first group for operating said first distributor test-art a preselected finder oi": the first group in search of said line, means for giving said first distributor access to said secoud group findergmoans responsive to the initiation of a call on a line in said second groupto start said first distributor in search of an idle finder in said second group, means in said first distributor operated responsive to the findingof said second group finder for starting it in search of said calling line, and means in said firstdistributor responsive to the finding of said second group line for opcrating said distributor to preselcct an idle finder of said first group.

8. In a telephone system, a first and a second group of lines, a first and asecond group of finders having access to said hnes respectively, first and second d1str1butor switches for allotting said finders for use, means responsive to'ithe initiation of a call on a line of the first group for operating said first distributor to start a preselected finder of the first group in search of said line, means for giving said first distributor access to sand second group finders, means responsive to the initiation of a call on a line in said second group to start said first distributor in search of an idle finder in said second group, means in said first distributor operated responsive starting it in search of said calling line, and means in said first distributor responsive to the finding of said second group line for operating said distributor to select another idle second group finder if another line in that group has initiated a call meanwhile.

9. in a telephone system, a first and a second group of lines, a first and, a second group of finders having access to said lines respectively, first and second distributor switches for allotting said finders foruse, means in said distributors for preselecting idle finders in their respective groups, means for giving said first distributor access to said second group lines, and means responsive to said last means for maintaining said distributor preselecting With respect to said first group finders and post selecting With respect to said second group lines and finders.

10. In a telephone system, a first and a second group of lines, a first and a second group of finders having access to said lines respectively, first and second distributor switches for allotting said finders for use, means in said distributors for preselecting idle finders in their respective groups, means for giving said first distributor access to said second group lines, and means responsive to said last means for maintaining said dis-- to the finding of said second group finder for i tributor preselecting with respect to said first group finders and for starting it in search of an idle finder in said second group responsive to the initiation of a call by a line of said second group. I I

' 11. Ina telephone system, two groups of telephone lines, group of finder switches for each of said line groups, a distributor switch for each finder group, each distributor having access to the finder of its corresponding group through normal wipers and to the l finders of the other group through alternate ipers, means in said distributors -for preselecting idle finders through the normal wipers, a relay in said distributors, a start Wire for each line group terminating in the relay of the respective distributor, means responsive to the initiation of a call on one of said lines for ener izing said relay over said start Wi e to st the preselected finder of the corresponding group, a key, a secono relay in said distributors. means responsive to the operation of said key for disconnecting one of said start wires from its relay and con necting it to the second relay oi the other distributor, means responsive to the initiation of a call on one otthe lines associated with said. one start Wire for energizing said second relay and means responsive to the venergization of said second relay for ope-rating said distributor to select and start a finder throu hits alternate Wipers.

12311 a telephone system, subscribers lines, agroupof finders having access to said lines, a-distributorswitch having a plurality of Wipers, a groupot contact sets accessible toeac'h ot said Wipers through which contats said distributor has access to said finders, means responsive to the initiation of a call on one of said lines for operating one of said finders to establish a connec tion with said line, means for making each of said finders busy-to said distributor, means responsive to the establishment of said conncction for stepping said Wipers over said contact sets in search of an idle finder, means operated-after the Wipers have been stepped off the last contact set of the group for releasing them and returning them to the first contact set, and means for I stopping said Wipers When an idle finder is found.

13. In a telephone system, a plurality of "choice access, means for removing one of said distributors from service, means then operated responsive to a call on one otsaid lines for operating'said remaining distributor to select and operate a finder of the group having first choice access to said line to establish a connection to that line.

14', In a telephonesystem in Which subscribers lines are arranged ingroups which are preferentially served by groups offin-ders each controlled by a. distributor individ ual to that group, means for removing one of said distributors from service and'tor thereby giving the other distributor access to all finders, and means in said distributor responsive to the initiation of a callon a line for selecting and operating a finder Which gives preference to the group containing that line to establish a connectionvvith that line.

15. 111 a telephone system, adistributor switch having a connected set and a disconnected set of Wipers, a' group of findersaccessible through said connected set of Wipers, a second group of finders accessible through said disconnected set of Wipers, means in said distributor for operating the normally-connected set of Wipersto preselect an idle finder in the first group, akey, means responsive to the operation of said key for preparing said 7 normallyrdisconnected set of Wipers for connection, and means responsive to the initiation of a call on one'ofsaid lines for comisaid lines to start such third finder pleting the prepared connection and for op erating said distributor to select another idle finder through said normally-disconnected Wipers and'to start such othe r'find'er to find the calling line. 7 Y a 16. In a telephonesystem, a group of lines, a group'of finders having access to said lines, a distributor having access I to said finders, means responsive to a call'on one of said lines for operating said distributor to start a preselected finder in search of the calling line, means insaid distributor responsive to'the finding of said line for operating said distributorto, preselect another idle finder, means for changing said distributor from a preselecting distributor to a post-selecting distributor whereby said distributor searches to the initiation ofa call on a second one of the second calling line. 17. In a telephone system,a group ofsubscribers lines, finders having access to said lines, a distributor having access to said find-' ers, means for operating said distributor to preselect an idle one of said finders, and

means responsive to the initiationofa call,

on one of said lines for operating said distributor to select another idle finder and to start such other finder to find the calling line.

' 18. In a telephone system, a group of subscribers lines, finders having access to said lines,- a distributor: having access to said finders, means for operating said distributor to preselect an idle one of said finders, and

means responsive to the initiation of a call on one of said lines for operating said distributor from connection With said preselected finder into connection With another idle one of said finders and to start said other finder to find the calling line.

In Witness whereof, I hereunto subscribe my name this 13th day of September, A, I).

NORMAN H. SAUNDERS.

'for a third idle one of saidfinders responsive lit)

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