US1851132A - Telephone system - Google Patents

Description

March 29,1932. N. H. sAuNDERs TELEPHONE SYSTEM Filed July i4. 195o 5 Sheets-Sheet l March 29, 1932. N. H. sAuNDl-:Rs

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N. H.l SAUNDERS TELEPHONE SYSTEM Filed July 14. 1930 Nurman H. Saunders Eff-5. Y

March 29, 1932.

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. .SQ .Sw di llllllllll R MWI IMM@ QlmxIlJu IJ SRP. .,I. all IIL www.. .QQ QW IIR@ l Patented Mar. 29, 1932 y 11er-11,1112?I Noni/renin SaUnnRs--or Iroiwrnwoon, ILLINOIS, ASSIGNOR, BY lMasiva ASSIGNMETS,

'rOASSOcIaIEn :insorgere LABORATORIES, ING., OI' CHICAGO, ILLINOIS, A CORPO- TELrIiOivE SYSTEM l application md July 14,l

The present invention relates in 'general to automatic telephone systems, butv more particularly to `such systems in which line linders are employed to. connect an idle ser lecting switch-with a calling line; and the tion the possibility ot a iind'er stopping on' a i busy line has been Jfurther guarded against by providing an improvedswitcliing 'through circuit which permits the iinder to pass over test contacts havingbooster battery potential connected thereto.' This improved Switching-through circuit also permits the use of a less expensive line circuit than has heretotore been used successfully in a system of thisv type.

As a further Obj ect- O the inventionan imr proved controlrequipment, comprising' relays, is provided common to a group of finders forcontrolling thevarious functions of the finders in that group.

@ne of the features of the invention relates to the means whereby the tinders' in a group are successively taken into use by the common cont-rolrelays and rendered unselectable on' release forv a succeeding call, although idle, until all the finders, which are selectable in the group, have been taken into use. y

Various objects andy Jfeatures not specifically mentioned here will best be understoody from reading thef'fdetailed description and claims Which follow; Y

The drawingsA comprising Figs. lto 5; in# elusive, when arranged WithFigs.` l, 2 andl 3 from left to rightl ina Straight line'or with Figs. a and 5substitut-ed for Figs.'v l and 3 with correspondingly' numbered' lines in' alignment, shotv sutlicierit details to enable a clear understanding ofl tlnsinvention.

Refer-rino' notv tolFig. l inmioredetaiil, theV selector S shown' on the left-hand side is of the old andfwell knovm'type` of;Strowvger` selector and is included in" af selector-finder 1930. Serial No. 467,661;

link. The finder switch FA is kof the Strow'- ger vertical and rotary type,'=havingy\vipers V230 to235, inclusive, which are' moved first in aV verticaly directionl and then inv a rotary direction to select the Contactv of a callingline. The Wipers of the nder are shown on the left-hand side of Fig. 2. Since in the present' embodiment ot this'invention alinderswitchf of 200 line capacity is beingy used,`thetnder FA is provided with two sets of Wipers,the Wipers E230 to'232inclusive, forming oney set of Wipers and the Wipersk 238 to 235, inclu#v sive, the second set. rlhe finder sWitch'Fl/#lsis` also equipped With avertical testvviper y2.62, shown iny the lower kleft-handV cornery of'v F 2. The finder comprises only" the operating inagnetsand two switching' relays. The two switching relays arejrelaysof the type disclosed' in Patent 1,673,884, issued' June 19, 1928 "to HIC. Pye.V The core of these switching relays are. provided With tvvo Wind'- ings which are separated by a magnetic spacl ing member, azproj'ectio'n of Whichieitends backA andforms a back stop againstwhich the armature of the relay rests. The Winding on the heel end' ofthe relay is'the magnetizfing coil,.a`nd the',4 iluX produced therebyr` traversing the path including this magnetic iron bacli stop, which is in' shunt of the air gap, and no amount efflux str'engthinthis inagnetizing coilV Will cause the armature to opera-te. A very 4small current in the `second operating 1 Winding of` the relay, Wlienin the' same f directionr as the inargnetizing Winding", Willcause'the relay to'operate,V The use/of these relaysas switching relays permits the calling lineto be markedin'thender blanks Vwith a Vpotential through relatively high resistance and impedance and preventsfune desired disturbances in" the searching circuit upon the' test wipero'fthe tinder encountering booster batteryv ypotential on a test contact before reachingjthetest' oontactof a`lca'lling line.; rllltherelaysjof this` type have` been l showv'vn the drawingsiwith lugsextending from their' centerportions.

In the lower haltet Fig. 1,' there is-shown the inderva'llotter' DA comprising thest-'ep 1 ping magnet'lvip'er's 1146 tov ll'il, inclusive', f

and a plurality of 'r'e-la'ys"'iior controllingthe various functions of the finders. The allotter DA is common to a plurality ot finderselector links, such as the finder-selector link FA and SA shown in the upper portion of Fig. 1. The allotter DA is mechanically similar to the well known rotary lineswitch while the circuit thereofv has been altered in accordance with the present invention.

In Fig. 2 is shown the subscribers lines S and S, it being assumed for the purpose of illustration that the subscriber S line number is 125, and that the subscriber S line nulnber is 295. Associated with each line are the usual line and cut-oil3 rela the circuits of which have been modilied accordance with one of the objects of the arescnt invention. The normal connections from connector banks are shown extending to the line and cut-off relays associated with the subscribers lines S and S. In the lower part of Fig. 2 is shown the vertical banks 7A and VB, which together with the wipers and 263 determine the vertical designations to which the finder switches are to be operated.

In Fig. 3, there is shown the iinder sv'i'c FB and selector SB, both switches bee' duplicates of these shown in F'j. l while in the lower half of Fig. 3 the alle 3 used for allotting calls to finder i Sor link this group. The allotb 'DB is mechanical y the same as the allotter shown in Fig. l but the circuits have been inodilied somewhat in accordance with the present invention. fhe allotter DB may be substituted 'for the allotter DA and vice versa without any circuit changes.

In Fig. 4f, there is shown a modification of the finder-selector link and the allotter which may be substituted for the finderselector link and allotter shown in Fig. l. The selector SAM is identical to the selector SA shown in Fig. 1, while the finder FAM has two additional relays, a transfer relay and a connecting relay. In the lower half of Fig. 4 is shown a group ot' common control relays which are common to the plurality of finder-selector links in this group, or the A group. This common relay equipment or a'llotter BDA is somewhat similar to the allotter DA shown in Fig. 1, and instead of having wipers for connecting the common control equipment with the linder a connecting relay is provided in each finder for connecting the common control equipment thereto. A transfer relay is also included in the finder for extending the start circuit to the next idle finder-selector link.

The finder-selector links F BM and SBM and the common control relay group BDB are identical to the equipment shown in Fig. 4 and may be substituted for the switches shown in Fig. 3. The common relays or relay allotter BDB is used for controlling the various functions of the finder-selector links in the B group, one of which is shown in the upper half of Fig. 5.

Throughout the drawings, I have shown a plurality oi batteries to avoid unnecessary complications, while in actual installations there would be but one battery, preferably with its positive pole grounded.

In order to enable a clear understanding of the invention it will now be assumed that the subscriber S initiates a call, and it will be further assumed that the finder FA has been preselected by the finder allotter DA in readiness to handle the call. Responsive to the removal of the receiver from the switchhook at substation S, line relay 201 associated with line S is energized to mark the line calling in the finder bank to render it selectable by placing a battery potential thereon through the winding of the cut-olf relay 202, and to place ground upon the start conductor 250. The grounding of start conductor 250 connects ground to the second contact in the bank VA and also closes a circuit or the start relay 163 in the inder allotter DA. In case both the selector SA and the inder FA are in normal position, test relay 161 in the iinder allotter DA is energized to complete the start circuit for the finder F A whereupon the finder is started in its vertical movement to hunt for the marking ground placed on the vertical bank VA. Since the calling line S has a iinder bank designation ot 125 and, since the present call assumed to be handled by the linder group to which that line is first choice,

it will be necessary for the finder to take two vertical steps to reach the level containing the calling line. The placing of ground on conductor 250 and the consequent marking of ground potential on the second bank contact of the bank VA, will cause the linder- FA to stop on the second level, at which time its wipers will be rotated into that level to pick out the contacts of the line S. I'Vhen the wipers are rotated into the level, tests will be made simultaneously by both sets of wipers, the lower set of wipers comprising wipers 233 to 235, inclusive, will test the line upon which they are resting, in this case line 121, and at the same time the upper set of wipers comprising wipers 23() to 232, inclusive, will test the line upon which they are restfng, in this caso line 221, and if neither one of these lines are calling both sets of wipers will be stepped on to the next contact where the test will be repeated. When the line S is encountered, the battery potential applied to the test contact associated with that line will render it selectable, thereby causing the finder FA to stop thereon and switch through so that the calling line will be connected through to the selector SA.

When the finder switches through to the calling line the switching relay in the finder operates and connects ground to the common kick-ofil lead 136 extending lto the allotter, whereupon the allotterstepping mage net 164 is-operated vto prepare `the allotter to preselect i another yidle {finder-selector link.

, rEhe above general operation j ust described explains the normal operatiolfliof ythe finder and allotter. It may happen in some instances when a finder-selector link, suchr as that shownin Fig. l1, has been preselected by an allotter and a callis initiated lby a subscriber, such-as S, that the selector SA may may bein an o-normalcondit'ion or the finder-selector link may be faulty. In this case test relay'161 in the allotter is not energized and after atime interval relay 165 energizes to operate the stepping magnet of the allotterto cause the allotter to'fpreselect vanother finder-selector link.

In Vsome instancesdue to fault, the finderL Yin the B group become busy the allotter DA andthe finder-selector links in the Ay group are automatically restored for use.

Theallotter DA and the finder-selector links, lsuchas FA andvSA in the A group, normallyhandle all the calls from the subscribers inthe A group. In case all of the ndern-selector links in the'A groupbecome busy the ,busy commonrelay 162 in the allOtter is deenergized and the allotter `DB and the iinder-selector links, such asFB` and SB, han'dlethe callsfor the subscribers in the A group. rlhevoperation ofallotter DB and lay, suchas' relayr404,v transfers the call to the next idle linderin the chain injcase the finder AFAM isV busy at the time alcall is initiated. The transfer relay is maintained locked up after the Vfinder releases until the .busy commonrelay 461 deenergizes when all of the finders inthe chain have been Ataken into use. By this arrangement the finders of the groupare successivelytaken into use.

Having described the general-operation i of the systerma detaileddescription yof its operf ation willnow be given.. v

Assume now that the line S .wishes to Responsive tothe removal ofthe -reeivera circuit may be tra-ced from groundatspring 206, conductor 254, through theswitchhook, receiver, transmitter and calling device of substation S, conductor l255, contact209, and through the winding of line relay 201to battery. y Y v Linerelay v201, upon energizingover the above traced circuit, at armature 207 applies a battery potential to they finder test contact through the winding of cut-off1relay 202,l The application yof this battery to the test l.

contact of line 12,5 renders the. line S selectable to the finder. l lay201 connects ground. toconductor 250 to groundthe second vertical bank Contactiny the bank VA and to complete a circuit eX- tending from conductor 250 by yway of resistance 251, conductor 260, armature y179 and its. working Contact of normally 'energized busy common relay 162, winding of start Ifelay 163, working l. contact y of armature 178 and said armature, interrupter contact 183 ,of

At armature 205 line .reV

the stepping magnet 164, and throughthe winding of magnet 164 to battery. ,Duetto the high resistance of start relayV 163 the stepi ping magnet 164 is not energized over this circuit. Start relay 163, upon energizing, at armature 181 prepares a point inthekickfoff circu-itfor the stepping magnet; at armatures 182 -and 184 closes a circuitl for energizing relay 161 in case the finder-selector link iS in normal position or not faulty; and at arme ature l185 prepares the circuit for the changeover relay 165. i

, In case vthe nder selector link is in normal position a circuit may-be .traced for energizing test relayu161 as follows: from ground by way of spring 184, lower winding of relay 161, working Contact of armature 182 andsaid armature, guard wiper 147, conductor 141, vertical olf-normal springs 130 in theirnermal position, release ,trunk conductor 13,5, throughA the upper polarizing windings yof switching relays 104 and 105 to battery. The switching relays 104 and 105-are polarized over this circuit but` do not operate their armatures. At larmature 196 relay 161 opens a previously closed circuit for changeover relay 165 before the slow-acting changeover relay 165 has had time to fully operate. vAt armature'194 relay 161 closes a circuit over wiper 14 for energizing the line yrelay 102 ofthe selector SA, at armature 195 closesga circuit for energizing the vertice.- magnet 109 of the finder; yat armature 197 relay 161 com,-

pletes a locking circuit for itself; ata-rmature 198 anditsworking contact closes a circuit for maintaining the start relayv 16J energized n until' the finder switches through so lin Acase this iinderfswitch is the last! available 'idle finder'the'deenerezeten @f thejbusyf relay 163 and at springs 199 starts the weight attached thereto to vibrating. Relay 160 is a slow-to-operate relay and, therefore, during the vibration of springs 199 the relay not energized until a predetermined time after the springs 199 are maintained closed. At the resting contact of armature 198, relay 161 also opens a point in the kick-off circuit so that the operation of the changeover relay 165 will not operate the stepping magnet 164.

Line relay 102 of the selector SA energizes over the following circuit: ground through resistance 193, springs 194, wiper 146, conductor 140, conductor 134, armature 119 and its resting contact and through the upper Winding of line relay 102, to battery. At armature 124 relay 102 closes an obvious circuit for energizing the release relay 101 of t-he selector SA and the release relay at armature 120 grounds the release trunk conductor 135. At armature 121 release relay 101 opens a further point in the release circuit to the selector release magnet 106 and also opens a further point in the circuit to the busy common relay 162 which was previously opened at the resting conta ct of' armature 124. Busy common relay 162, however, is maintained energized over springs 168 and busy common conductor 138 extending to the other idle selectors in the A group.

The circuit for energizing the vertical mag net 109 of the finder may be traced as follows from ground by way of springs 195, springs 191, armature 186 and its resting contact, wiper 150, conductor 144, and through the winding of vertical magnet 109 to battery. By the operation of the vertical magnet the wipers ofthe finder are operated in a vertical direction, the wipers 230 to 235, inclusive, being operated opposite the first level of finder bank contacts and the vertical test wiper 262 being operated into engagement with the first vertical bank contact of the vertical bank VA. Since there is no ground potential on this vertical bank contact no circuit is completed for the changeover relay 165. Stepping relay 166 energizes from grounded springs 111 of the vertical magnet over conductor 139 and at armature 191 interrupts the circuit to the vertical magnet 109, whereupon the magnet releases and in turn at springs 111 opens the circuit of the stepping relay 166. Stepping relay 166, upon deenergizing, at armature 191 again completes the circuit for the vertical magnet, whereupon the vertical magnet raises the wipers another vertical step and at springs 111 again com pletes the circuit for the stepping relay 166. Since the second vertical bank contact has been grounded by the calling subscriber S, a circuit may be traced for energizing the changeover relay 165 as soon as the vertical magnet 109 releases responsive to the energization of the Steppin@ relay 166. The circuit for energizing the changeover relay may be' traced as follows: from ground by way of springs 205, conductor 250, second vertical bank contact, vertical test Wiper 262, conductor 174, conductor 145, wiper 151, armature 189 and its resting contact, springs 185, and through the lower winding of changeover relay 165 and the winding of stepping relay 166 to battery. The stepping relay 166 is held energized in series with the changeover relay 165 until such time as the changeover relay 165 is fully energized and has opened the original energizing circuit for itself at armature 189 after having first completed a locking circuit for itself at armature changeover relay 165, upon energizing, at armature 186 transfers the stepping circuit from the vertical magnet 109 to the ro tary magnet 108; at springs 187 prepares a circuit for the operating winding of switching relay 108; at armature 189 and its working contact prepares a circuit for the operating winding of switching relay 105; and at armature 190 closes a circuit for maintaining the start relay 163 in energized position independent of the busy common relay 162. Stepping relay 166, upon deenergizing responsive to the operation of the changeover relay 165, at armature 191 closes a circuit for energizing the rotary magnet 108 as follows: from ground by way of armature 195, armature 191, armature 186 and its working contact, wiper 149, conductor 143, armature 154 and its resting contact, armature 158 and its resting contact, and through the winding of rotary magnet 108 to battery. Rotary magnet 108, upon energizing advances the wipers 230 to 235, inclusive, into engagement with the lirst contact in the second level and also rotates the vertical test wiper 262 out of engagement with the contacts of the vertical bank VA. At interrupter springs 110 rotary magnet 108 completes a circuit for stepping relay 166, whereupon that relay energizes and opens the circuit of the rotary magnet. Further rotation of the wipers of the finder FA are dependent upon whether the test wipers 231 and 234 encounter a negative battery potential or not. In case negative battery potential is not on either of the test contacts with which the test Wipers 231 and 234 are now in engagement neither of the switch through or test relays 104 or 105 will energize. Therefore, when the rotary magnet 108 energizes the stepping relay 166 the stepping relay 166 in turn opens the circuit of the rotary magnet 108, the rotary magnet in turn will open the circuit of the stepping relay 166, whereupon the stepping relay deenergizes and again closes a circuit for the rotary magnet 108. This cycle of operation continues until one of the test wipers 231 or 234 encounters a negative battery potential.

Assuming that fno vother' line inthe 'second level of the finder banlrfterrninals lare call-V ing, except subscriber S, then when v'test'wip- 'ers 281 fand 23a-are rotated into engagement with the fifth set of contacts the 'test Wiper 234 will encounter :a negative battery potential which is applied thereto through 'the "Winding 'ofrelay202- When test `wiper 234 encounters this battery potential, switching relay 105 energizes orverrthe '-tollowingfcil cult: from ground hyrway el the 'working c'ontactof armature 189 and said armature,v

wiper 151, flower winding'oi switching relay 105, conductor 173, testl wiperv 23%, the `test Contact engaged thereby, conductor 256, armature 207,A andy through the `winding of cut orf frelay1202 to battery; Testing relay 105 and cut-ott relay 202 energize in series over the above ltraced circuit. lt should possibly have been mentioned that when the re-V lease relay 101 Yofthe selectorI SA grounded the release trunk conductor 135,11, circuitfwas closed through the upper winding of both switching relays 104 and '105 to energize the polarizing windings vof such relays. The circuit just ltraced -through the lower Winding ofswitching relay 105 assists thecireuit throughnfthe polarizing winding with vthe f the calling potential has been encountered byy the test wiper 234.Atarinatures 156 and 159 switchingfrelay 105 ConnectsV up the lower setoic wipers 233 andi235. arma-ture 157 result that the switching lrelay 105 energizes yery'quiclrly to 4stop "thev rotation of the wipers.Y c f It might also be ymentioned at this time that in case either of the testwipers 231 or 2311 should encounter a'bcoster battery -nietering potential or y'a lhusy rground vpotential during their rotationbe'fore 'the Lcalling line is 'reached the booster battery potential or the busy ground potential encounteredwould naturallyclose a circuit fthrot1gl1'the`-lower' Winding 'of the switching relays 2but 'these ycircuits 'would vbein opposition to `thelcircuit through the polarizingwinding with theresult that the switching relay ywould vnot lbe operated. i

The cut-olf relay k202'at armatures 206 and 209 disconnects theline relay 201 and the normal battery and groundconnections from the subscribers line conductors; and at armature 208 completesV a lockingcircuitffork itself and also prepares a circuit for guardingjthe line from intrusion lb y'Way ot' the connector banks. Line relay 201, upon den energizing', at .armature 205 Jremoves ground from the rconductor 250. l

Returninglnow to the iinder FA and when switching relay '105 energizes inseries 'with the cut-off relay 202,!it should be stated that armature 158 operatesvery quickly'and' opens the rcuit to the rotary magnet so that there is no possibilit-y of the rotary magnet oper` ating to step the wipers ank eXtra stepafter -rel'ay 105 connects the groundedrelease trunk Yconductor1135Vtotest Wiper 1234 V'by Way 'fof `conductor '173 to ground the test contacts in both the finder and'connector banks s'o that the same will test lousy to other finders land to' connectors, respectzvely, having accessthereto. The 'closure ot springs 157 tempof rarily short-circuits the lower winding' of;y

relay l105 butthis has no eii'ect on a relay'of this type because :after itis onceop'er'ated the relay is maintainedenergized by .i'tspolar-` izing"winding until ground 1is removed `from the release trunlrconnector 135. At thevworlr- 4ing 'contact of `armature 158 relayf105 connects'the ground vat armature 195 'to the com# mon kick-'off conductor 1'36ffor energizingithe stepping magnet r164 'ofthe 'allotter DA.

lVhen the switching relay 105 connectsthe line conductors ofthe calling'line S -to conductorsfll and 1737 dialftone is connected over these conductors to the callingline `in 'the well llrnownlmannerfan'd when the vcalling su'bscriberS hears the dial tone thesubscriber willlrnowthat the iinder has found and con nected with his'line, and ythat he may proceed to se't up kthe desired connectionto the called party. Sincetheloperation ofthe selector SSA fand 'the remaining aswit'ches in :the

:switch train to th'e called flineisold and'well" knownit is,therefore,'` notln'ecessary to describe Q for show their foperation. By' means vof the `vertical off-'normal springs f129`fon 'the 'finder and falso the 'switching relay i103 of the selector one :of the grounded multiple circuits of the common busy relay 162 K4is opened. Y In ca-sezallof'the selectors in the A group or all 'o'fthe :nders in Ethe Agroup are busy-erin an olf-'normal iconditi'on allot' the 'multiple grounds 15o-'conductor' 138 would be removed andthe circuit for the busy common relay 162 would 'be opened.

Returning nowto the allotter DAand at a rio disconnects ground' from conductor "134 sol Y 'that the impulses transmitted by the calling subscriherscallingdevice may be eifective for operating the line 'relay of the selector-yat armature 195 disconnects ground trom-fthe stepping and kick-oli circuit; at 4armature 197 opens `another point in its own locking circuit; at armature 198 opensja point in the n circuit for the start relay 163; and at vibratf ingsprings 1-99Vopens the energzingfcii-rcuitof relay 160 4betore therslow-acting'relay 160 hask had time to iully operate; {A'tarmature 1195 'relay' lllalsoopens the locking 'circuitfof changeover relay 165 whereupon the latter relay is deenergized. Relay 165, upon deenergizing at armatures 187 and 189 disconnects ground from the lower operating windings of the switching relays 104 and 105 and at armatures 190 opens another point in the circuit for maintaining the start relay 163 in operated position. The switching relay 105 is maintained in operated position by itsI upper polarizing winding.

Stepping magnet 164, upon deenergizing, advances its wipers 146 to 151, inclusive, into engagement with the next set of bank contacts leading to the succeeding finder-selector link in the A group. In case such finder-selector link is in an off-normal position and is busy the vertical off-normal springs correspond ing to vertical off-normal springs 130 are operated to connect ground to guard conductor, such as guard conductor 141, which in this case will extend to the succeeding bank contact with which the wiper 147 is now in engagement. This ground connection will extend by way of wiper 147, armature 182 and its resting contact, armature 178, interrupter springs 183 of the stepping magnet 164, and through the winding of the stepping magnet 164, to battery. Magnet 164 operates in a buzzer-like manner as long as Wiper 147 encounters busy ground potential and as soon as wiper 147 encounters a guard conductor leading to an idle finder-selector link the wipers of the allotter come to rest in such position to preselect this idle finden selector link for the next calling party. The finder allotter DA, therefore, preselects another idle finder-selector link as soon as the finder with which it is associated has switched through and established connection with the calling line.

Since the finder FA is a 200-point finder and, therefore, has two sets of wipers it may so happen that test wiper 231 instead of test wiper 234 may encounter the negative battery calling potential of the calling line, while the test wiper 234 does not. In this case the finder is operated in the same manner as previously described and when wiper 231 encounters the negative battery calling potential on the test contact, associated with the calling line, a circuit will be completed for operating the switching relay 104 as follows: from ground by way of armature 187, wiper 147, conductor 142, through the lower operating winding of switching relay 104, conductor 172, test wiper 231 and associa-ed test contact to negative battery potential. Switching relay 104, upon energizing, at armatures 152 and 155 connects the upper set of wipers for use. At armature 153 relay 104 connects the grounded release trunk conductor to the test Contact of the calling line for guarding purposes and at armature 154 opens the circuit to the rotary magnet, and also completes the circuit to the kick-off conductor for kicking the allotter olf to preselect another idle selector-inder link.

In case the test wipers 231 and 234 should simultaneously encounter calling potentials both switching relays 104 and 105 will energize and the energization of the switching relay 105 will be ineifective because the switching relay 104 disconnects the lower set of wipers. The calling subscriber may now complete the connection to the desired called subscribed in the well known manner.

When the called subscriber answers, the slow-releasing meter relay in the connector is momentarily energized to momentarily connect booster battery over therelease trunk to operate the meter of the calling subscriber. A metering arrangement of this type is shown and described in Patent No. 1,186,823, issued J une 13, 1916 to F. Newforth, Jr.

After the conversation and responsive to the calling subscriber replacing the receiver, ground is removed from the holding conductor of the connector switch in the well known manner, whereupon the circuit of the switching relay 103 of the selector SA is opened. Switching relay 103, upon deenergizing, completes the release circuit for the release magnet 106 of the selector in the well known manner, whereupon the selector returns to its normal position. The release of switching relay 103 also closes the release circuit for the release magnet 107 of the finder FA by way of armature 126, armature 124, and test set springs 127 to the finder vertical offnormal springs 129. Release magnet 107 of the finder energizes and restores the finder FA to its normal position. IVhen ground was removed from the holding conductor in the connector switch, ground was also removed from release trunk conductor 135 whereby the circuit extending through the polarizing windings of switching relays 104 and 105 was opened to cause the dcenergization of such relays. IVhen the selector SA and finder FA reach their normal positions the circuit for their respective release magnets are opened at the off-normal springs and the switches are ready to be used in another call.

Referring again to allotter DA shown in Fig. 1, and at a time when the start relay 163 has been energized responsive to a call, it will now be assumed that negative battery is not connected to guard conductor 141 because the selector SA or finder FA is in an off-normal position or because of some fault. Under these conditions the circuit for relay 161 will not be ccmpleted and, therefore, the slow-toenergize changeover relay 165 will have had time to fully operate. The circuit for energizing changeover relay 165 extends by way of ground at armature 184, arlz'iature 196, and through the winding of changeover relay 165 to battery. At armature 190 relay 165 energizes and completes the circuit for energizing the steppinginagnet 164 which in turn atinsuch idle link is foundtlie call will be proceeded with in theSaineina-nner aspreviously described.

Another condition which may arise is that o the linder may not switch throughwithin a predetermined time due tosome fault. Consider now the case, in which the finder has been seized and operated rbut Vhas failed to switch through within a predetermined time and, therefore, the allotter has not kicked-of and has not opened the circuit to the slow-tooperate relay 160. Under these conditions the vibrating` spring 199y after ak predeter-y mined time stops vibrating and is maintained infcontact, whereupon the slow-to-operate ielay l160 is operated: Relay 16() at armature 192 completes a locking circuit'for,itselffrom ground by way of conductor 114, jack springs 169', armature 192, and through thelwinding ofA relay 166V to. battery. lllhen this occurs relays 161, 162,163y and165 arein energized position. At armature 168 yrelay 160 opensV a point in the circuit of the busy common relay 162 and at armature 16"?y completes a circuit for operatingfthe stepping magnet 164 follows: ground by way vof armature 195, armature 167, armature 181, and through the winding of stepping magnet 164 to. battery. Stepping rmagnet 164, yupon energizing,` at spr-ings 183 interrupts'the circuit of the start relay 163 whereupon the start relay deenergizes. At armature 131 relayr163 opens the circuit of the stepping magnet 164 to cause the wipers of the allotter to advanceto the next nder-selector link, and at armature182 and its resting contact-prepares the pre-selecting circuit ofthe allotter; at armatures 1S21and 183 opens the locking circuit of relay 163 which deenergizes. Relay 161, upon deenergizing, at armature195 opens the looling circuit of relay 165. whereupon the latter.

relaydenergizes and at the vibratory springs 199 opens theY original energizing circuit of slow-to-operate relay 160 which relay, however, is maintained overV the previoi traced locking circuit. All of therelays iii the al-V lotter DA except relay' 160are deenergized and the relay 160 is maintained energized to maintain the circuit to the busy common relay 162 open so that any calls originating from the A group will now be transferred to the -allotter DB Vand calls will be handled by the magnet 164 to prevent the operation ofthe magnet 164, and at armature 180 removes ground from kconductor k115 to open lalock-V ing circuit for the supervisory lock-out kin the allotter DB'in case this relay should bek energized at this time. f Before the attendant in the switch room corrects the fault the calls originating in the Aand B group are handled by the allotter DB: and thender selector- Vlinks of the B group. In case all of the A, circuit of relay 160 is opened and the relay deenergizes to againcoinplete the circuit for the busy common relay 162. After relay 162 energizes the calls are handled by the allotter and iinder-selector links inthe A group in the same lmanner as previously described.

Assume now that at the time the substation is connected with a call all of the finders in the group containing the linder FA are busy, in which case the call will be handledby the finder in the group containing the finder F B, y provided no call is in progress at this time in the B group. It will benoted that the placf ing of ground on conductor 25,0 and'cont'act 2 of the vertical bank VA also places ground upon contact'9 ofthe vertical bank VB. It will be noted that the banks of the finder are slipped between groupl A and group B so that kof group B. Responsive to thegrounding of conductor 250, and in case all of the finder selector links, such as FA and SA, are busy the busy common relay 162 will be deenergized position and, therefore, the start lrelay in the allotterDB is energized to start a finder in the B group, for example finder B, in operation in a vertical direction until'fthe vertical wiper y263 encounters the marked bank contact, in this case theninth bank con tact in the vertical bank VB. vThe Wipers of the finder kare stopped'at this level` and rotated in af horizontalY direction intofengagement with the bank contact of the calling line.

In a similar manner calls from the line S have as its first choice the finders in the B group and lare handled by theA B group switches in a manner somewhat similar to the manner described for the A group switches. lVhile the finder selector links in the A and B groups are identicalit will be noted that the ycircuits of the allotters DA and DB are diiferentand in order to describe the operation ofthe allotter DB it will be assrnied that the line S initiates a call.

Responsive to subscriber ,S remoying his i receiver line relayQOB is energizedover conductors 257 and 259 and the call-ed subscribers loop. `At armature 210 line relay 203 grounds the second bank Contact 2 in the verticalbank VB and alsoconnects groundlto start conductor 061 hv ivav of resistance J At armature 212 relay Q03 connects negative battery through 7 ling ot cut-on' 204tto the coi` r the calling line to l Resoonsive to the @rounding ot conductor i *ay of armature ie SSO, armature 384, armature 7 t ing' conta-ift.

3U and through the tial relay 857 t start relay 2559 i relay 355 and cuit for energizing in case the relay 362 over the guard .vp-er E 357 energizes and starts the r-feighte` 377 and 37S vibrating f- DB and the iinder properly the difieren time performs no useil ln case the auila. short-circuited by Way t relay 362 energizesl over owing circuit: ground by Way oi t 382 armature 386, Winding' ot' relay S-(L, ari interrupter springs S76, and through the winding oi" the stepping' magnet oi the allotter 36S to battery. to 'the hic.l resistance of the auz-'liary ping magnet l is above traced circuit.

te.. i

energizes and at armature 397i closes a circuit for energizing the line relay la? of the selector SB: at armature closes a circuit for energizing the vertical magnet at armature 2396 prepares a locl 1 g circuit lor changeover relav 366: at aA the circuit circuit for energizing the nl d the differential relay it armacure 398 relay 362 pa f. circuit for the changeover rel E :it arme ire 399 closes a locln g circuit extending` from grounded armature to the u'indini ci" the busy common relay 'for temp rarily maintaining' the busy common rela. y locker in its energized position. Lin-e relay 36:2 in the selector SB energizee the 'following circuit: trom ground by Way ogt armature 394A, wiper 316, conductor 3ft-lb conductor 233i-, armature 319 and its rest' through the upper .vinf to battery. )it energizes the selector the latter relay. upon one" 320 grounds release trunk gir/.es the upper po` switching relays 304i and SB. At armature 326 line relay v efi c 1 do or the im connects one of the multiple ground connections connected to busy common conductor 338 for maintaining the busy common relay 358 in the allotter energized. Wvhen the circuit extending through the loner winding of diil'erential relay is opened by the operation of armature 397 and a circuit is closed through the upper windin oi: di'tlerential relay 357 by Way of grounded armature 237i. armature 380, armature 384, armature 397 and its working Contact, armature 390 and its resting contact, armature 393 and its resting contact, and through the upper winding to battery. magnetic flux is built up in opposition to the magnetic linx created by the lower Winding with the result that the differcntial relay 357 releases its armatures 377 and 378 and very shortly hereafter reoperates these armatures to start the weighted springs vibrating so as not to operate diil'erential relay 356. The relay 356 is a slow-tooperate relay and will not operate until the weighted springs 377 or 378 have stopped vibrating to maintain its circuit closed for a certain interval.

rhe circuit for energizing the vertical niet 309 may be traced as ff news: from ground by Way of armature 394 normally closed springs controlled by armature 392 ot the interruptor relay 3617 armature 388 and its resting contact. .viper 350, conductor 5314. and through the Winding of vertical nu gilet 309 to battery. By the operation of the vertical magnet 309 the Wipers 236 to 241, inclusive, and the vertical test Wiper 263 are operated vertically one step to position the vertical wiper :263 in engagement with the first vertical contact l. in the verti- :al bank V l, and to position the Wipers 236 ,o 241. inclusive, opposite the first level of ine bank contacts. The vertical olf-normal snrings 329 are operated responsive to this f :et vertical step to prepare a circuit for the release magnet 307 of the finder and to open one of the multiple ground connections conn'rted to busy common conductor 338. At ve ical ott-normal springs 380 ground is eeted to conductor 341 for preparing a further point in the locking circuit ol the changeover relay 360. At armature 311 vertical magnet 309 completes an energizing circuit for the stepping or pulse ending relay 36 as 'follows z from ground by Way of armature 311, conductor 339.y and through the winding of relay 361 to battery. At armature relay 361 opens the circuit extending throufgii the upper Winding of differential '.f 357 its resting contact and at its i j contact closes a circuit for energiz- 5 the lower windings o'l differential relay This results in the differential relay be ed and immediately reenergized vertical magnet 309 and the Vertical yniagggnet upon releasing at armature 311 opensy the,

- circuit tof the stepping yrelay 361.r This iiiter-action between thevertical magnet r`309 vand the interruptor relay 361 continues until thek Vertical ltest Wiper 263A encounters. a ground potential upon the test contact oi the vertical bank VB. In this case since the #2 Vertical test coiitact'is groundedthe tindeil `will have taken two steps to reach this Contact and as result thereon circuit may be Vt 'ed for energizing cut-od' relay 3:60 when ground is removed freni conductor 339. rliis vcircuit may be traced as follows: from grounded test contact 2,'wiper 263, conductor .3T/l, conductor 345, wiper 351, armature 391and its resting contact, armature 398, lower winding of cut-oli? relay 360, .and through the winding of steppingrelay 361 to battery. 1n thisA circuit the relay 361 is ined energized in series with the cut- 360 until the cnt-oit relay7 has conipletedits locking Vcircuit at armature 3,89 and has thereafter opened its original enera lgizing circnitat armature 391. At armature 390 changeover relay 360 completes acircuit for energizing the upper winding kor' the diferential relay 357 withfthe result that the dierential relays 357 again gives the weighted springs an additional kick to keep the 'ings Vibrating. yAt armature 38? change-V oi er relay 360 prepares a circuit for the opei-ating winding of polarized relay 304; andy at armature 391 and its working Contact pref pares a circuit fortlie'operating winding of switching relay 305 and at its resting contact opens its original energizing circuit and the circuit or" the stepping relay 361. At armature 388 lchangeover relay 350 changes the stepping circuit from the vertical magnet to the rotary magnet. The locking circuit for changeover relay 360 extends by way of Linder vertical oli-normal springs 330, conductor 341, rwiper 347, armature 396 and its werking contact, armature 389 and through the upper winding of changeoven relay 360 to battery. As soon as the stepping relay 36?l deenergizes, the ystepping circuit for the rc ary magnety 308 is completed by way of ground from armature 395, through the nor-. mally closed springs controlled by armature 392, armature 338 and its working contact,

IWiper 349. conductor'34'3, armature i354 and its resting Contact, armature 358 and its rest- -ing contact, and through the windhig of rotarymagnet 308 kto battery. By the operation of the rotary magnet the wipers of the finder are rotated onto the first rotary contact in this level, and at armature 310 the circuit for again energizing the stepping re-y 361 4is completedf The'stepping relay. 361 at armature 392 again opens the circuit tothe rotary magnet. `Further rotation yof.

the wipers are now dependent upon the test wipers encountering ,a calling potential. By

the .operation of relay 361 the stepping circuit to the rotaryinagnet is interrupted andy the rotary magnet interrupts the circuit of ythe stepping relay .361 with the result that this inter-action between the rotary magnet 308 and stepviiiiig relay 361 steps thewipers of the iin der step-by-step over the rotary contacts until a calling potential is encountered by one of the test wipers 237 or 240. yThen test wiper 237 encounters the calling potential appli 'l to the test contact of line Sa circuit may be traced for operating switching yrelay 304 as follows: from groundby Way of armature 387, wiper 348, conductor 3&2, lower operating winding of switching 30a connects the grounded `release trunk conductor 335 to the test contact of line S to guird the line against intrusion and at arinature 354 and its resting contact opens the ciri enteiicingto the rotary magnet 308 and ai. its Working contact connects the stepping circuit to common kicleori conductorN 336.

' rEhe calling subscriber S may now complete the remainder of the connection in the well known manner."

, Returning now to allotter DB .and at the time that the common hiclno conductor 336 was grounded, a circuit may be traced for operating the stepping magnet 363 of the alletter as follows: Oroundby way of armature 395, normally closed springs controlled by armature 392ai'mature 388 and its worlr-y ing contact, armature 354 andk its working contact, conductor 336, Aand through ythe winding of magnet 363, to battery. At interrupt-er springs 3716 magnet 363 opens the circuit of the auxiliary start relay 362 whereupon the latter relay deenergizes. Relay 362, upon deenergizing, at armature 394 removes ground :from the upper Winding ,of line relay 302 so that the line relay may be effective responsive to the impulses; at armature 395I disconnects ground from the stepping. andy kicleo circuits at armature 396 opens the locking circuit of changeover relay .360 at its working contact and at its resting-com tact prepares the stepping circuit for the allotterDB at armature 397 again reverses the circuit to the diierential relay 357 in case the start relay 359 is maintained energized ;l and at armaturev399, opens the locking cir-Y cuit extending through the winding of busyv rcommon relay 358, so that the latterrelay may release in case all of the finder-selector. K

iso'

links are busy. Since the stepping circuit through magnet is now opened at armature 395, the magnet deenergizes and steps the wipers 347 to 351 to the contacts of the next finder-selector link and in case this findervselector link is busy, wiper 347 will encounter a ground potential with the result that the stepping magnet is again energized and again interrupts its own circuit to step the wipers step-by-step in search of an idle fliuler-selector link. Magnet continues to operate in a buzzer-like manner stepping the wipers until wiper 347 no longer encounters a ground or ousy p -ntial whereupon the wipers stop in engagement with the next idle finder-selector link.

lThen the line relay 203 deenergizes, responsive to the energization of cut-off relay E204, line relay Q03 at armature 21() removes ground from start conductor to deenergize the start relay However, in case another subscriber in the B group were calling at this time the start relay 359 would be maintained. energized and the auxiliary start relay 362 would be maintained short-circuited from the ground potential encountered by wiper 347 until the alletter had preselected the next idle finder-selector link.

The above described operation is the normal operation of the allotter DB and therefore the differential relay 356 controlled by vibrating springs 377 and 378 has not energized because the differential relay 357 has not been maintained closed by the vibrating springs 377 and 378. It will now be assumed, however, that through some fault the auxiliary start relay 362 has not functioned properly after the line relay 359 has energized responsive to a call. In this case the previously traced circuit for the differential relay is maintained closed for a sufiicient time interval to permit the vibrating springs 377 and 378 to be maintained in engagement and a circuit may, therefore, be traced for operating differential relay 356 as follows from ground by way of armature 374, armature 330. armature 384, armature 397 and its resting contact, vibrating springs 378 now closed. and through the lower Winding of differential relay 356 to battery. At armature 373 differential relay 356 completes a circuit for energizing the stepping magnet 363; at armature 374 opens its own energizingr circuit as well as the circuit extending to the lower winding of differential relay 357 and at armature 375 completes a circuit for energizing two-step relay A365 in its first step to close only springs 37 2. This latter circuit may be traced from grounded armature 385, armature 375. armature 371 and its resting contact, and through the upper winding of two step relay 355 to battery. Two step relay 265 operates only armature 37 2. After an interval of time, different relay 356 deenergizes and at armature 3T3 opens the circuit to stepping magnet 363, whereupon the wipers of the wipers of the allotter DB are advanced one step; at armature 374 again prepares a circuit for the differential relay 357; and at armature 375 removes the sliertcircuit from around the lower winding of two-step relay 355 with the result that relay 355 is operated by means of its two windings in series through its second step to operate armatures 370 and 371. At armature 370 two step relay closes a circuit for energizing the slow-to-operate alarm relay 353 and at armature 371 prepares a circuit for energizing the emergency alarm relay 354. At armature 355 relay closes a circuit for operating an alarm which indicates to the attendant a minor case of trouble, and at armature 366 completes a locking circuit for itself from grounded conductor by way of jack springs 364. New in case the auxiliary start relay 362 operates properly when the next finder-selector link has been preselected the differential relay 357 is operated in a manner previously described and the differential relay does not operate a second time and the switches operate in the same manner as previously described. However, in case relay 362 does not operate when the new selector-finder link is selected, then differential relay 356 is energized after a time to operate a second time, this time closing the circuit to relay 354 which energizes and locks up at armature 363 and at armature 369 sends in an emergency alarm. At armature 367 relay 354 opens the circuit of busy common 1elay 358 and the latter relay deenergizes and transfers the calls to the A group in the same manner as described for the transfer calls from the A group to the B group. ln the same manner as just described and in case stepping relay 361 or the changeover relay 360 do not function properly within a predetermined. time the differential relay 357 is maintained energized for a sufficient time to energize differential relay 356 to cause the allotter to send in an alarm, to step the allotter off this particular finder-selector link, and to bring in an emergency alarm in case the same fault occurs after the allotter h as selected another finder-selector link. The reasons for the two alarms is that if only the ordinary alarm is sounded then the trouble is of a minor nature, possibl.' in the finder-selector link. and if the attendant busy on other important work the trouble can be ignored for the present but when an emergency alarm sounded then the trouble is fairly serious and in all probability the trouble is in the allotter and, therefore, the whole B group is unavailable for handling calls. he attendant. therefore, when he hears the emergency alarm will immediately take whatever steps are necessary to correct the fault.

In order to describe the modifications shown in Figs. 4 and 5, Fig. 4 will be substituted for Fig. 1 and Fig. 5 will be substituted for Fig. 3. Responsive now to the reuit' .inoval ot the receiver'by calling subscriber 5S conductor 260 is grounded responsive to the operation ot the line rrelay 201 and thestart relay 464 is yenergized over theffollowing circuit: from grounded conductor 260, arma.- ture 471 and its working contact, armature 474, armature 487, and through the winding of startrelay 464 to battery. At armature 481 relay 464 connects negative battery-thru re- Ysistance 480, to conductor 451 andthence by way of normally closed springs controlled .by armature 429 through the winding of convnecting relay 405 toground. At armature 459 relay 464 prepares a lockingcircuit for relays 463 and 465 and also prepares the stepping circuit for the vertical and rotary magnets of the finder; and at armature 482 closes Va circuit for energizingthe slow-to-energize changeover relay 465 which circuit, however, is opened at armature 475 before the slowacting relay 465has had time to fully oper ate. Connecting relay 405, upon energizing over the Vabove traced circuit',atarmature 430 Vcloses a'circuit forenergizing testing relay'463 andffor energizing thepOlarizing windings of relays 406 and 407;,at armature 431 and its resting contact opens a point in one of the locking circuits of transfer relay 404; at armatuies432 and 433 prepares the circuits through the operating windings of the switching relay 406 and 407 armature 434 prepares the circuit for the rotary magnet 409; and at armature- 435 completes an energizing circuit for the vertical ymagnet 410. rl`he circuitfor energizing the test relay 463 may be traced as followsrfrom .ground byV way of .armature .47 7 lower winding of relay 463, conductor 454, armature 430, release .trunlr rconductor 415, and through the polarizing windings oi switching relays 406-and 406 to battery. At armature 476 relay 463 cernpletes a locking circuit for itself before it opens itsown original energizing circuit at armature 477. ,At armature 475 relay 463 opens the .circuit for slow-acting changeF .over relay l465 beforethe same has hadtime to fullyoperate, at armature 478 starts the springs 478 vibrating; and vat armature 479 .closes a shuntaround armature 487 toimainvtain ,ther start relay energized independent of changeover relay 465. IThe` circuit for venergizing vertical magnet 410 may be traced Aas follows z from ground by wayA of armature 459, normally closed springs controlled by armature' 488,- arrnature 433 and its resting Contact, common vertical conductor 456,ar-y

` .mature 435, and through thewinding of vertical magnet 410 to battery. By the operation et vertical magnet 410 the finder wipers 230 to 235, inclusive, and the vertical wiper 262 ,are operated one vertical step and theoinormal springs 412 and 413-operate to pre` pare circuits torthe finder releasermagnet 457 and to connect ground to armature 427 `or the transferireley 404 .to Prepare. a 100kbattery. grounds the common conductor 455 to cause ing circuit for the same. At armature vertical magnet connects ground to common conductor 455 for energizing the stepping relay 466. The inter-action between the vertical magnet y410 and stepping relay 466 is f' thesaine as described tor Fig. 1 and when the .verticalwiper 262 encounters the ground potential onithe second contact of the vertical bank VA a .circuit may be tracedfor'ener'- gizing the. changeover relay 465 as follows:

from grounded vertical test contact 2 of ver-l tical bank VA, wiper 262, conductor 174, armature 433, common conductor 452, armature 486 and its'resting contact, through the lower .winding n of changeover relay 465,l and lthrough ,the winding4 of stepping relayr 466 .to battery. This `circuit is eillective to energze the changeoverfrelaywhen the vertical magnet has deenergized and removed ground iro-in the commonconductor 455. Stepping relay 466-is maintained,energizedin series opens its own original energizing circuit at armaturev 486 after it has closed a locking "circuit forvitself througharniature v485 and with the changeover relay 465 until relay 465 its upper winding. At armature 483, relay 465 ldisconnects the stepping circuit from the common vertical stepping conductor 456 at its resting Contact and at its working Contact connects the `stepping' `circuit tothe common yrotary stepping cenductor 453 to prepare a cicuit for the rotary magnet 409. At armature 484, relay .465,prepares a locking circuit `for the kick-,olig relay and at ar-k mature 486 and its working contact prepares a circuit for the lower operating winding of switching relay 407; and at armature 487 opens the original energizing circuit of start relayp464 which circuit, however, is Ina-intained at armature 479. kSince the armature 486 opens the holding circuitof stepping relay 466, the latter relay releases and closes the circuitV :for energizing rotary'magnet 409 as follows: from ground byway of armature 459, normally closet springs controlled by .armature 488, armature 483 and its working contact, common rotary conductor 453,-ar-

kmature434, armature 439 and its resting conoli3 relay 202 testing relay 407 is operated by f way of conductor 173,' its lower winding,

amature 433, 'Colnmonleeedtvf 45.2.5@1 ermature 486 and its working contact to ground. Since both the switching relays 406 and 407 had their upper windings or polarizing windings energized by way of armature 430 when relay 405 energized the switching relay 407 immediately operates and at armatures 441 and 445 connects the calling subscribers loop through to the line relay 402 of the selector SABI. At armature 442 relay 407 disconnects one of the multiple ground connections from busy common conductor 448; at armature 443 prepares a circuit for connecting release trunk ground to conductor 173 to guard the line against intrusion, it being remembered that after the switching relays rhave once been operated the circuit through their polarizing windings will maintain such relays in energized position; and at armature 444 connects ground by way of common kick-off conductor 450 to kick-ofir1 relay 462. At armature 444 and its resting contact, switch relay 407 opens the circuit of the rotary magnet 409 before the stepping circuit is again completed, so as to prevent the wipers from taking an additional rot ary step. When the stepping relay 466 deenergizes a circuit may be closed for energizing kick-olf relay 462 as follows: grounded armature 459, nor'- mally closed springs controlled by armature 488, armature 483 and its working contact, conductor 453, armature 434, armature 439 and its resting Contact, armature 444 and its working contact, common kick-olf conductor 450 and through the winding of kick-off relay 462- to battery. Relay 462 at armature 473 completes an obvious locking circuit for itself from grounded armature 484 and at armature 474 opens the circuit to the start relay 464, whereupon the latter relay releases. At armature 481 start relay 464 opens the shunt circuit around the upper winding of the transfer relay 404, thereby permitting the :transfer relay to energize in series with the v'connecting relay 405; and at armature 459 opens the original energizing circuit of the kick-off relay 462 and opens the locking circuit of relays 463 and 465. Relay 463 deenergizes before the slow-to-operate relay 460 has had time to fully operate and relay 465 after an interval of time for which it is adjusted deenergizes and opens the locking circuit of kick-oil relay 462 at armature 484.

lVhen the su 'tchiug relay "107 connects the calling suhscrla f oop in ..ri-cs with the line relay `402 of the selector the line relay energizes and at arniature 423 completes a circuit for the release relay 401 whereupon the latter relay prepares the selector for operation and at armature 419 grounds the release trunk cond ctor 415 for maintaining the switching relays energized after "he release of relay 405 as well as for guarding` he calling line against intrusion.

lV ien transfer relay 404 energizes in series with relay 405 as a result of the deenergization of the start relay 464, transfer relay 404 at the normally closed springs controlled by ari'nature 429 opens the circuit of connecting relay 405 whereupon the latter relay deenergizes. At armature 429 and its working contact, transfer relay 404 connects the start in conductor 451 to the start out conductor 414 extending to the next finder in the chain and at armatures 427 and 428 completes two locking circuits for itself. The upper locking circuit extending from grounded oit-normal springs by way of armature 427 and its upper winding maintains the transfer relay in energized position as long as the finder is in an off-normal position. The other locking circuit extends by way of armature 47 0, holding conductor 449, armature 428 and through the lower winding of transfer relay 404 to battery. This holding circuit is effective until each of the finders in the group have been taken into use and when the last finder in the chain, or A group, has been taken into use all of the multiple grounds are disconnected from the busy common conductor 448 at armatures, such as armature 426, and the busy common relay 461 will thereupon release and open all of the locking circuits extending to all of the transfer relays, such as 404, which at that time are locked up. This arrangement causes each finder in the chain to be taken into use in proper sequence, providing of course. such finders have been released before all of the finders in the cha-in have been used on preceding calls. At armature 426, transfer relay 404 prepares a point in the circuit of the finder release magnet 457 Connecting relay 405, upon deenergizing. at armatures 430, 433, 343 and disconnects the common control. relay group RDA from the finder switch. It can be seen, therefore. that on subsequent calls when the start relay 464 is energized that the start circuit will be completed for the connecting relay of the succeeding finder by way of conductor 414.

The calling subscriber may now complete the connection to the called subscriber in the well known manner and metering will take place as illustrated in Fig. 1. After conversation in response to the subscribers replacing their receivers ground ,is removed from the release trunk of the connector switch which in turn removes ground from release trunk conductor 415 whereupon the switching relays 403 and 407 are deenergized. At armature 442 switching relay 407 completes a circuit for energizing the finder release magnet as follows: from ground by way of armature 442, armature 437, armature 426 and its Working contact, vertical olf-normal springs 414 and through the winding of release magnet 457 to battery. .By the operation of the release magnet the finder switch wipers are restored to their normal position and the vertical off-normal springs are opened. The operation of the vertical off-normal springs 413 opens the upper locking circuit extending through the upper winding of transferrelay y armature 471 busy 'common relay 461'transfers the start circuit from the start conductor 260 of the A. group /tofstart conductor 261 of the B group and at armature 472 removes ground from conductory 115 Yfor unlocking relay `560 in case the same at thistimeymay be energized. At armature 470 lbusy common relay disconnects `ground from the corr-.mon hold conductor 449 with the result that ythe locking circuit through the lower windings relays, suchas relay 405. The finders-which their transfer relays in energized positiony at this time have not been released maintain throughout the next cycle of operation of the chain'fof finders.A At, armature 426 transfer relay Y404 and other similar transfer relays complete the `multiple groundr connection from armatures, such VVas armature 442, tothe common conductorVK 448 vwhereupon the busy common relay 461 is again energized to prercrate relay 465 is energized.

pare the locking circuitthrough' theylower ,windings of the 4transfer relays at armature V470; and at armature 471 prepares the rcircuit extending to the start relay-T464, so that subsequent calls in the group will operate the rstart relay 464.

In Vcase the upper set of wipers 230 to 232, inclusive, are operated into engagement with calling line the switching relay 406m the vfinder is energized in place of the switching relay 407 Vand in this case thelower set of kwipers are not connected up. The switchingv relav406 accomplishing similar functions to that described for switching relay 407.`

. Referring now to the common relay group RDA in Fig. V4, and at a. time when the start :relay 464 has been energized responsive to a call, it will. new he assumed that negative battery is not, connected to common conductor 454 by way of yarmature 430 and release trunk conductor n415v because of somefault.; Under these conditions/test relay 465%" will notk energize with the result that the slow-to'op- 4t armature y Y 48? relay`465 opensthe circuit of start relay 464 with the result that the start relay deenergizes and reniove'sthe shunt battery frein lay is lockedup and the call is transferred to the next finder inthe chain. Relay 465A deenergizes responsive to start relay 464 opening its lockingcircuitrat armature 459. v

. Another condition which may arise vis that the finder may not switchl through Awithin a predetermined time due to some faultu In this case the test relay 4631will be maintained energized foia. sufficient time interval to close the vibrating springs` 478 to cause the v energization of the sl'ow-to-operate relay 460.` Relay' 460,y upon energizing, at armature 467 opens the circuit of the vbnsy'coinmon relay 461 and at armature 468 closes a locking cir-l cuit Afor .itself over conductor 114. The deenergization of the busy common yrelay 461 connects the A'start conductor 260 tothe B start conductor 261, so that the calls now originating in the A group are handled by the YB group equipment until such timeas the fault is corrected or until .the locking circuit of relay460 is opened as a resultcf allthe i'inder-selector'linlrs inthe B group becoming busy. This operation lastl described is similar to the operation described for the A group apparatus shown in Fig. l.

. Since the apparatus Vshown in Fig. 5 is f identical with the apparatus shown in Fig'. 4 its operation is the same as describedffor Fig. 4 and it is,` therefore, thought the detailed description thereof may be omitted.

Having described the invention what is considered new` andqis desire tojhave pro tected by Letters Patent will beset forth in the following claims. f V

What is lclaimed is: y

1. In ak telephone system, an automatic switch,` a group of'V test contactsin the bankr potential, a busying potentiahasmetering p'o-y rtential, or no potential connected thereto, a switchingY relay in said switch, means for.`

seizing said switch, automatic Ameans respon-` tomatic operation.

2. In a telephone system,` an automatic'y switch, .a group of testcontacts in the bank of said switch,a test wiper in said switch having access to said contacts, a switching relay in ysaid switch having a polarizing.;

winding and an operating winding, means for seizing said switch, means responsive to said seizure for energizing the polarizing winding of said relay to prepare it for operation, automatic means responsive to said seizure for operating the test wiper of said switch step-by-step over said contacts, a circuit for operating said relay including said operating winding, said test wiper and one of said contacts in series, means for operating said relay over said circuit, and contacts operated by said relay for stopping the automatic step-by-step operation of said wiper on said one contact.

3. In a telephone system, an automatic switch, a group of test contacts in the bank of said switch, a test wiper in said switch having access to said contacts, a switching relay in said switch having a polarizing winding and an operating winding, means for seizing said switch, means responsive to said seizure for energizing the polarizing winding of said relay to prepare it for operation, automatic means responsive to said seizure for operating the test wiper of said switch step-by-step over said contacts, a circuit for operating said relay including said operating winding, said test wiper and one of said contacts in series, means for operating said relay over said circuit, contacts operated by said relay for stopping the automatic stepby-step operation of said wiper on said one contact, and said relay maintained in energized position solely over its polarizing winding.

4. In a telephone system, an automatic switch, a group of test contacts in the bank of said switch, means whereby each of said contacts have at certain times a zero potential, a potential of one value, or a potential of another value connected thereto, a test wiper in said switch having access to said contacts, a switching relay in said switch having an operating winding, means for connecting a potential of a further different value to one of said contacts, means for seizing said switch, automatic means for operating the test wiper of said switch stepby-step over said contacts, a circuit including the operating winding of said relay and said test wiper ineffective for operating said relay responsive to the wiper engaging test contacts having zero potential, a potential of said one value, or a potential of said other Vahle but effective tor operating said relay responsive to the test wiper engaging the contact having a potential ot' said further different value connected thereto, and means controlled by the operation of said relay for stopping the automatic step-by-step operation.

5. In a telephone system, a finder switch, a group of subscribers lines terminating in the bank contacts of said switch, the test Contact of an idle line normally having a potential of zero value, a test wiper in said switch for connecting one of a plurality of potentials of different value to the test contacts of busy lines, a switching relay in said switch having a polarizing winding and an operating winding, means responsive to a call on one of said lines for connecting a calling potential of a further different value to the test Contacts of a calling line, means responsive to said call for seizing said switch and for energizing the polarizing winding of the switching relay, automatic means for operating the test wiper of said switch step-bystep over the test contacts of idle and busy lines, a circuit including the operating winding of said relay and said test wiper ineffective responsive to said test wiper engaging test contacts having zero potential and said plurality of potentials of different value thereon but etl'ective for operating said relay responsive to said wiper engaging a calling potential, and means controlled by the operation of said relay for stopping the wiper of the switch on the contact of the calling line.

6. In a telephone system, a plurality of finder switches, a group of subscribers lines terminating in the bank contacts of said switches, the test contact of an idle line normally having no potential thereon. a test wiper in each switch for connecting a busy potential and a metering potential to the test contacts of busy lines, a switching relay in each switch having a polarizing winding and an operating winding, means responsive to a call on one of said lines for connecting a calling potential to the test contact of the calling line, means responsive to said call for seizing an idle one of said switches and for energizing the polarizing winding of the switching relay associated therewith, automatic means for operating the test wiper of said switch step-by-step over the test contacts of idle and busv lines, a circuit including the operating winding of the switching relay and said test wiper ineffective for operating said switching relay responsive to the test wiper engaging test contacts having no potential, busy potential` or metering potential thereon but effective for operating said relay responsive to said wiper engaging a calling potential. and n1 l,ans controlled by the operation of said switching relay for stopping the wiper of the switch on the Contact of a calling line.

7., In a telephone system, a finder switch, two sets of wipers in said switch, a pair ot talking conduct-ors in said switch normally disconnected from said wipers, a paid of` switching relays in said switch, means for energizing only the first switching relay to connect the first set of wipers to said couductors, and means for energizing only the second switching relay or both the iirst and second `relays to connect only vthe second set of wipers to said conductors.

8. VIn an automatic telephonesystem, a subscribers line comprising aline relayhaving onlya. single winding and only two-pairs of make springs and' aout-oli' relay having only a single winding, only two pairs ofl break springs, andV only a single pair of'make springs, means responsive to the initiation of completed through the windingof ,the cutoff relay andthe otherpair of springs of the line relayresponsive to the energization of the line relay for marking said line calling,

Y means responsive `thereto for establishing a "cut-ofi relay for maintaining it in energized conne'ctionwith said line and for completing an .energizingcircuit forisaid cut-off relayl including the said second circuit, and a hold-r .ing circuit including the winding of the cutoft relay and its pair of make contacts completed responsiveitoithe energization of the position. Y

Sl. In an automatic telephone system, a subscribers line comprising only a single wound line relay having only two pairs of make springs and a single wound cut-off relay having only two pairs of break springs and only a single pair of make springs, a linder having access to said line, a primary test contact associated with said line, a secondary test contact associated'with said line, means responsive to the initiation of a call on said line for energizing said line'relay over a? circuit including the two pairs ofbreak springs of the cut-off rela-y, a circuit completed through the first pair of make springs of the line relay and another circuitlcompleted through the winding of the cut-off relay and the other pair of make springs ofthe line relay responsive to the energization ofthe line relayfor marking said contacts as calling, wipers onV said finder having access to said contacts, means in the finder controlled through said wipers to select saidmarked contacts and to establish a connection to said line, means responsive to the establishment ot said connection 'for `energizing the cut-oli" relay over a circuit including a wiper of said finder, the marked secondary Contact, the ,saidA other pair of make springs of the line relay, and the winding ofthe cut-off relay, anda holding circuit for maintaining. the cut-off relay in energized position including its winding, its make springs,and the secondary test contact.

l0. Ina telephone system, a group of finder switches having vertical `and rotary move ments to find a calling line, a vertical magnet Y y in each nder for operating the inder in its vertical movement,ia rotary magnet Yineach finder forl operating the inder iny its rotary the calling line. Y

movement, means for closing a circuit to the vertical magnet of one ofsaid finders to ener-,- gizeV it, a pulse-ending relay common to said4 finders, means controlled by the vertical magnet in its energized position lfor energizing,

thek pulse-ending relay to vopen the circuit 'to the vertical magnet, a changeover relay common to saidlinders, means i'or energizing the changeovery relay in series with the pulseending relay, means controlled byv the energization of the changeover relay for deenergizing the pulse-ending relay and for chang,-

ing the circuit from Ythe vertical magnet to the rotary magnet ofthe operated inder to energize the rotary magnet, means controlled by the rotary magnet in its energized position v for energizing the pulse-ending relay to open the circuit to the rotary magnet, two test relays in the operated finder, means for energizing either one of said test relays, and means controlled by the energized test relay for opening the circuit of therotary'magnet to stopathe finder on the calling line.

ll. ln a telephone system, a group of finders having vertical and rotary movements to find a calling line, a verticalmagnet in each finder for controlling the vertical movement ofthe nder, a rotary magnet in. each nder for controlling the rotary movement of the finder, a common stepping circuit for operating said vertical and rotary magnetsV means common tosaid finders for first closing said circuit to the vertical magnet of one of said finders and then to rotary magnet thereof, and a pulse-ending relay common to all of saidmagnets renergized responsive y to eaclil energization of the vertical'and rotary magnets for opening said circuit tothe linder magnets to operate the finder step-bystep in its vertical and rotary movements to the calling line. n

12.111 a Ltelephone system, a group of finders having vertical and rotary movements to find a calling line, a vertical magnet in eachiinder for operating' the finder in its` verticall movement, a rotary magnet in each finder for operating the fin-der in its rotary movement, a common stepping `circuit for' operating the vertical and rotary magnets of said nders, a commonpulseending relayy for controllingsaid` circuit, means commonl ico to said finders for closing said circuit to the vertical magnet of one of said finders tol energize it, Ameans controlled by the vertical magnet mits energized position for energizing' the common pulse-ending relay touopen said circuit to the vertical magnet, means for changing said circuit from the vertical magnet' to the rotary'magnet of the op- L erated finder to energize it, means controlled by the rotary magnet in its energized position for energizing the pulse-ending relay to open Vsaid circuit to the rotarymagnet, and means for stopping the operated finderon

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