US2249516A - Telephone system - Google Patents

Description

July l5, 1941. r. F. cRocKER. TELEPHONE SYSTEM Filed Dec. 29, 1939 'a sheets-sheet 1 July 15, 1941. 1'. F. cRocKER TELEPHONE SYSTEM Filed nec. 29, 1939 e Smets-sheet 2 INVENTOR T/'lomasj" Croc/(er.

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July l5, l1941.- r. F. cRocKER TELEPHONE SYSTEM y Filed Dec. 29,v 1939 8 Sheets-Sheet 5 lNVENTOl- Thomas/7. Croc/ref" BY @WLM ATTORNEYS July 1:5, 1941. r. F. cRocKER TELEPHONE SYSTEM Filed Dec. 29, 1939 8 Sheets--Sheel'I 4 lNvENToR Thomas F Croc/erf BY ,Gum/MW ,MM ATTORNEYS July l5, 1941. T. F. cRocKER' TELEPHONE SYSTEM Filed Dec. 29, 19759 8 Sheets-Sheet 5 July 15, 1941; T. F. cRocKER TELEPHONE SYSTEM Filed Dec. 29, 19:59

8 sheets-shea e July 15, 1941. T. F. cRocKER TELEPHONE SYSTEM Filed oec. 29, 1939 8 Sheets-Sheet '7 INVENTOR Thomosl Crocker BY 'om' T. F. CROCKER TELEPHONE SYSTEM July 1 5,- 1941.

Filed Deau 29, 1959 8 Sheets-Sheet 8 ATTORNEYS ltributingsystem. However, the traflic betweenA answered.

Patented July 15, 1941 UNITED STATES* aziasie TELEPHONE SYSTEM Thomas Frederick Crocker, Chicago, Ill., assigner to Associated Electric Laboratories, Inc.,`Chi cago, Ill., a corporation of Delaware Application December 29, 1939, Serial No. 311,552

38 Claims.

The present invention relates to telephone if: systems and more particularly to improved arrangements for distributing calls in telephone systems of the semi-automatic type.

In a, conventional telephone system of the semiautomatic type the various manual telephone@ lines terminate in jacks at the A and B operator positions; and an automatic switch trainprovided with a distributing system is interposed between the A operator positions and thevB `opert l ator positions. In a telephone system of this@ type, calls on the telephone lines are answered directly by the operators at the A operator positions and routed bythe switch train under the control of the distributing system to the B oper-u Y) ator positions to be completed.

Accordingly in telephone systems of thisY type, thetraflic between the A operator positions vand the B operator positions is governed by the disthe calling telephone lines andthe various A' operator positions is not governed but remains under the manual control of the operators at the A operator positions, rendering the number of calls on the telephone lines answered by an oper-M ator at a given A operatorposition and routed therefrom to the B operator positions to be completed entirely within the discretion of the operator at the given A operator position.

Accordingly, it is an object of the present in-f vention to provide in a telephone system of the type described, improved apparatus for distribut- .ing calls on telephone lines to a. number of A erator positions, an improved arrangement for `distributing and Vfor storing incoming calls on telephone lines to the operator positions to be Another object of the invention is to provide in a telephonesystem including a number of op- .erator positions provided with facilities for esvstoring recalls on the established connections to the operator positions to be answered.

A further object of the invention is to provide in a telephone system including an operator position, improved switching apparatus for routing va call to the operator position to be answered and for extending the call from the operator position after it has been answered.

A further object of the invention is to provide in a telephone system including an operator position, an improved switching link for establishing a connection between a calling line and a called line, which switching link is under the joint control of automatic apparatus and an operator at the operator position.

A further object of the invention is to provide in a telephone system including an operator position, an improved switching link selectively operative to establish al connection between a calling line and a called line including the operator position and to establish a direct connection between the calling line and the called line excluding the operator position, and apparatus under the controll of an operator at the operator position for selectively controlling the operation of the switching link.

YA further objectief the invention is to provide in atelephone system including an operator position, improved apparatus at the operator position 30 for supervising calling telephone lines in the system and established connections between telephone lines in the system and for performing servi-ce functions over the Vtelephone lines in the system. y

The features of the present invention are illustrated as being incorporated in a telephone-system comprising an exchange terminating a plurality of manual telephone lines and including arnumber of A operatorpositions, a numbel` of B operator positions Vanda number of switching links. The Vswitching links have access to the telephone lines, to the A operatorpositions and tothe B operator positions; while'the B operator positions have access to the telephone lines. The.

telephone lines comprise three classes which are rendered corresponding` classes of service consistingrof flat rate service, call register service and prepayservice.A

In accordance with one feature of the invention, the telephone system comprises a plurality of subscriber lines, a plurality of A operator positions, a B operator position, a plurality of storage units individually associated with the A operator positions, and means for assigning the'sto'rage units in a predeterminedorder. Also, thesystem comprises means for routing a call on any one of the subscriber lines to an idle one of the A operator positions to be answered when one of the A operator positions is idle, means for routing a call upon the one subscriber line to an assigned one of the storage units to be stored when all of the A operator positions are busy, and means for routing a call upon the one subscriber line stored in the assigned storage unit to the associated one of the A operator positions to be answered when the associated A operator position becomes idle. Also, the systemcomprises means for routing a call upon the one A operator position to the B operator position and vmeans for establishing a connection between the one subscriber line and the B operator position independent of the one A operator position, thereby to route a call from the one subscriber line to the B operator position. Further, the system com-- prises means-for routing a recall by an operator at the B operator position upon the established connection to an idle one ofthe A operator positions to be answered when one of the A operator positions is idle, means for routing a recall upon the established connection to an assigned one of the storage units to be stored when all of the A` operator positions are busy, and means for routing a recall upon the established connection stored vention, the system comprises, in addition to the storage units individually associated with the operator positions, a plurality of conservators individually associated with the storage units, wherein each of the storage units has a limited storage capacity and each of the conservators has an unlimited conservation capacity. The position distributor is operative to assign the storage units in a predetermined order when all of the operator positions are busy and to assign the conservators in a predetermined order when the storage capacities of the storage units are exhausted. The switching apparatus is operative to route the calls on the links to the operator positions to be answered when the operator positions are idle, to route the calls on the links to assigned ones of the storage units to be stored, to route the calls on the links stored in the assigned storage units to the associated ones of the operator positions to be answered when the associated operator positions become idle, to route the calls on the links to assigned ones' of the conservators to be conserved, and to route the calls on the links conserved in the assigned conserva- '25l tors to the'associated ones of the storage units in the assigned storage unit to the associated one of the A operator positions to be answered whenl the associated A operator position becomes idle.

In accordance with another feature of the invention, the arrangement for routing the calls and recalls from and to the A operator positions, y

the B operator position and the storage unit comprisesswitching apparatus including a plurality of switching links, wherein each ,switching link includes a rst branchprovided with an answer switch having access to-*calling lines and a second,V

.the finder switch of an assigned linkto seize acalling line; while a position distributor is provided for assigning idle ones ofthe operator positions for use in a predetermined order vand for assigning the storage units for use in a predeterto be stored whenthe storage capacities of the associated vstorage units are replenished. `Further, the switching apparatus is operative to route the calls on the links stored in the assigned storage units to thev associated ones of the operator positions to vbe answered and to route the calls on the'links conserved in the assigned conservators to the associated ones of the'storage units to be stored independently of the position distributor.

In accordance'with a further feature'of the invention, the switching apparatus comprises a plurality of relays, the relays being arranged in a plurality of rst groups individually Yassociated mined order when all of the operator positions -f are busy.Y Further, the system lcomprises calling means under the control of anoperator at any one of the oper-ator positions -to whichthe call ona link is routed for governing the operation of the call switch of the link, thereby to extend the call from Y.

first and the--second-branches of the link, and

means under thecontrol of an operator at any one ofthe operatorpositions for completing a communication connection between thefirst and the second branches of the link independent of v the oneoperator position. Also, the system corn--Y prises means under the jointY control of any one of the calling lines and an operator at anyone of the operator positions to which a call on the corresponding one of the links is routed for-re- .with thev operator positions and in a plurality'of second groups individually associated' with vthe links, whereby each relay is included in a particular rst group-and in a particular second thereby to extend the call on the assigned link to the operator position associated with the one relay to be answered, the one relay being included in a given first group and in a given second group. Also, the switching apparatus comprises means controlled by the operation of the one relay for preventing operation of the other relays in the given rst group and the other relays in the given second group.

In accordance with a further feature of the invention, the system comprises a plurality of groups of links, a plurality of groups of feeder trunks lindividually associated with the groups of links, a 'plurality ofigroups vof automatic vswitches individuallyassociatedwith the groups of links, a

leasing the connection prior'to operation of the calling means, vand means under the joint control of any one of the calling lines and the corresponding one of the called linesffor releasingthe conplurality of` operator positions, and a plurality of position trunksindividually associated with the operator positions, each of the position trunks being associated with corresponding feeder trunks in the groups of feeder trunks. Also, the system includes a position-distributor for selecting corresponding feeder trunks in the groups of' feeder trunks and corresponding switchesV in the groups Of. Switches in a predetermined order, means controlled by the presence of a call-on any one of the links in any one of the groups` of links for connecting the one link in the'one group of links to the selected feeder trunk inf the associated one of the groups of feeder trunks and for preventing the other linksin the one group of links from being connected to the selected feeder trunk in the one group of feeder trunks an'dfor operating the selected switch in thev associated one of the groups of switches. 'Furthenthe system comprises means controlled bythe voperation of the selected switch in the one vgroup of switches for connecting the selected feeder trunk in the one group of feeder trunkscto the associated one of the position trunks and for preventing the corresponding feeder trunks in the other groups of feeder trunks from being connected to the one position trunk, thereby to extend the call on the one link in the one group of links to the operator position associated with the one position trunk to lbe answered.

o telephone lines; and means controlled by the testing means for selectively controlling thev operation of the signals, whereby a signal corresponding to a particular class of telephone lines is operated when a connection is completed between any telephone line of the particular class and the operator position.

In accordance with a further feature of the invention, the system includesa groupof twoparty subscriber` lines, each of these lines having a line circuit associated therewithwhich includes first and second registers and a lockout relay, an operating circuit and a holding circuit being provided for the lockout relay. Means is provided at the operator position to which a call is routed from one of the subscriber lines for selectively operating the first and second registers;

and means is provided at the operator position for completing the operating circuit of the lockout relay in the line circuit associated with the two-party subscriber line, thereby to Vcause the lockout relay to operate and complete'the holding circuit therefor in the event there is a calling condition on the associated subscriberline. Further, the systemV comprises means controlled by the operation of the lockout relay fo-r causing restoration of the switching apparatus over which the call from the line to the operator position is routed, additional 'means controlled by the operation of the lockout relay for preventing reoperation of the switching apparatus, and means controlled when the calling `condition is removed from the subscriber line vfor interrupting the holding circuit for the lockout relay,k

thereby to cause the lockout relay to restore.

Further features of the invention pertain to the particular arrangement of the circuit elements thereof, whereby the above-outlined and additional operating features areA attained.

The novel features believed to be ,characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specificationtaken in .connection with the accompanying drawings in which Figure 1 illustrates the general arrangement of a telephone system including a local exchange and a distant exchange embodying the present invention; and Figs. 2 to 8, inelusive, taken together, illustrate the details of a system having incorporated therein the features of the invention, as briefly outlined above.

Description of the apparatus incorporated in the telephone system Referring now more particularly to Fig. 1 of the drawings the telephone system there illustrated comprises a local exchange 2U, a distant exchange 30 and a plurality of one-way trunk lines, including the trunk line 619, extending therebetween. The local exchange 20 and the distant'exchange 3U are of the manual type, each serving a number of groups of telephone stations towhich different classes of service are rendered. For example, the local exchange 2i) serves a group of subscriber substations, including the subscriber substation TI, which is rendered flat rate service; a group of party subscriber substations, including the yparty subscriber substations T2 and T3, which is rendered call register service; and a group of paystations, including the paystation Td, which is rendered prepay service'. A telephone line having a line circuit individually associated therewith extends to each telephone station in the local exchange; the telephone lines 225, 21D and 285 respectively extendingto the subscriber substation TI, the party subscriber substations T2 and T3, and the paystation T4. The flat rate line circuit 25 is individually' associated with the telephone line 225; the twoparty line register circuit 24B is individually associated with Vthe telephone line 215; and the prepay manual line circuit 288 is individually associated with the telephone line 285. Each of the subscriber su-bstations and paystations in the local exchange 2B is provided with station equipment, includinga telephone instrument and a ringer'.

Also', the local exchange 28 comprises a number of A operator positions, including the first A operator position 18D, the second A operator position 505 and the last A operator position LEDS; a number of B operator positions, including the rst B operator position 694 and a number of tolll operator positions, 'including lthe toll operator position 699. Each A operator position has a position trunk individually extending-thereto, the position trunks 479, 510 and L5M individually extending to the A operatorV positions'l, 505 and L5M, respectively; each B operator position has a group of trunks-individually extending thereto, the trunk 696 being included inthe group of trunks individually extending to the first B operator position V6M;V and each toll operator position' has a group of trunks individually extending thereto, the trunk 665 I being included in the group of' trunks individually extending to the toll operator position 699. Each trunk extending to each B operator position is provided with a trunk line circuit individual thereto, the trunk line circuit 580 being individual to the trunk 68S extending to the'rst B operator position 694; and each trunk extending to'each toll operator position is provided with a trunk -line circuit individual thereto,V the trunk line circuit 691 being individual tothe' `tion' 699. `tween the local exchange 20 and the distant VexchangeV 30 is provided with a trunk line cirtrunk 695 extending to the .toll` operatorposi- Also, each trunk line extending becuit individual thereto, the trunk line circuit 612 V` being individual to the trunk line 610 extending .between the -local exchange and the distant exchange i 3 0.

Further, the local exchange 20 comprises a number of groups of finder-selector` links com- ,w 1.0 V.

ciated .with the vgroups of links, including the-15. Vlink distributors and ||2 individually associated with the first and second groups of links, respectively. The link distributor 30| is opera- .tive to assign idle ones of the links in the first group oflinks in a predetermined order to these() use of the lines in a rst group of telephone lines; while the link distributor ||2 is operative to assign idle ones of the links in the second group of links in a predetermined order to the use of' the telephone lines in a second group of 25 telephone lines, the telephone lines being divided` into groups individually associated with the groups of links. Each link comprises a finder switch and a selector switch. For example, the first link |00 in the first group of linkscom-Bgo prises a finder switch 300 and a` selector switch 600; while the first link |03 in the second group of links comprises a finder switch |23 and a selector switch |33.

Further, the local exchange 20 comprisesi switching apparatus associated with the links in the various groups of links and including a plurality of groups of feeder trunks individually associated with the'groups of links. The first group of feeder trunks, including the feederfAO.

trunks 480 and 580, is individually associated with the first group of links; and the group of feeder trunks, including the feeder trunks and' |4I, is individually associated with the second group of links. Further, it is noted that..45 corresponding feeder trunks in the groups of feeder trunks are commonly associated with the position trunks extending to the A operator positions. For example, the first feeder trunk 400 in the first group of feeder trunks and the first-.50 feeder trunk |40 in the second group offeeder trunks are commonly associated with the position trunk 410 extending to the first A operator position while the'second feeder trunk 580 in thefirst group of feeder trunks and the sec-55 ond feeder trunk |4| inthe second group'of feeder trunks are commonly associated with the 'position trunk 510 extending tothe second A operator position 505. Further; the 'switching apparatus comprises a plurality of groups 02.60 sequence switches individually :associated with the groups of links, the first group of sequence switches, including thel sequence switches-M0 and 5|0, being individually 'associated 'with the first group of links; and the second group of se-,- quence switches, including the Vsequence switches ||0 and being individually associated with the second group of links. Finally, the` switching apparatus comprises av plurality of groups of switching units individually associated witlrf/O the position trunks, the first switching unit 400 and the second switching unit |50'in the-first group of switching units being commonly associated with the' position trunk 410 extending to the first A operator position'100; and-,Q75

the rst switching unit 500 and the second switching unit |5| in the second group of switching units being commonly associated with the position trunk 510 extending to the secondA operator position 505.

Further, the local exchange 20 comprises .a

.plurality of storage units individually associated with the A operator positions, the first and sec- -ond storage units 800 and 8|0 being respectively associated with the rst and second A operator positions '|00 and 505. Each storage unit has a markingtrunk extending thereto, the marking trunks 810 and 005 respectively extending to the first storage unit 800 and the second storage unit 8|0. Also, a plurality Vof control trunks are individually associatedy with the operator positions, the control trunksSll and 590 being respectively associatedwiththefirst A operator positionl andthe second A operator position 505. Finally, the local, exchange 20 comprises an A operator position distributor 830 for assigning in a predetermined order idle ones of theA operator. positions to receive calls and'. for assigning. the .storage units in a predetermined Vorder when all of the A operator positions are Y each ofthe trunk lines extending to the distant exchange 30. Each sequence switch in each group of sequence switches has access to the control trunk extending to the associated A operator position and to the storage unit associated with the associated A operator position. Also, it is noted that each B operator position in the local exchange 20 has access to each telephone. line of A operator positions, not shown, land a number nism 3|0 of the ZOO-point Strowger type including a carriage provided with a rst wiper set,

`including the wipers 3| |,4 3|2 and3|3, asecond wiper set, including the wipers 3M, 3|5, SIG and 3| 1, and a control wiper 3|8. It is noted that the wipers 3| 3|2 and 3|3 of the first wiper `set and the wipers 3|4, 3|5, 3|6 and 3|'| of the second wiper set are capable of both vertical and rotary movements; while the control wiper 3|3 is capable of vertical movement. Further the mechanism 3|0 comprises a circumferentially disposed main contact bank provided with two sections respectively associated with the rst and second wiper sets and a vertical control contact .bank associatedwith the control vwiper 3|8. Ac-

cordingly, in the mechanism 3|0, the first and second wiper sets respectively have access to first and second groups of one hundred lines each, respectively terminated by the firstand second sections of the main contact bank. Also, the mechanism 3|0 is provided with a vertical magnet M365 for moving the first and second wiper sets thereof in the vertical direction, a rotary magnet M361 for moving the first and second wiper sets thereof in the rotary direction and a release magnet M369 for releasing the rst and second wiper sets thereof and for causing these wiper sets to be returned to their normal positions. Finally the mechanism 3|0 has three sets of switch springs S310, S31| and S312 operatively associated'therewith which are controlled in accordance with the movements of the first and second wiper sets thereof, in a manner more fully described subsequently.

Also, the finder switch 300 'comprises a number of relays, including two switching relays R320 and R330 and a start relay R340 -connected and arranged in a manner more fully described subsequently.

The selector switch 600, as best shown in Fig. 6, comprises a switching mechanism 6| 0 of the 1D0-point Strowger type including a carriage provided with a wiper set including the wipers 6II, 6|2 and 6|3. It is noted that the wipers 6| I, 6|2 and 6|3 of the wiper set arecapable of both vertical and rotary movements. Further the mechanism 6|0 comprises a circumferentially disposed main contact bank associated with the wiper set. Accordingly, the wiper set has access to a group of one hundred lines terminated by the main contact bank. Also the mechanism 6|0 is provided with a vertical magnet M6 I4 for moving the wiper set thereof inthe vertical direction, a rotary magnet M6|6 for moving the wiper set thereof in the rotary direction and a release magnet M6|8 for releasing the wiper set thereof and for causing the wiper set to be returned to its normal position. Finally the mechanism 6|0 has a number of switch springs S6|9, S620, S62| and S622 operatively associated therewith movements of the wiper set thereof in a manner more fully described subsequently.

Also the selector switch 600 comprises a number of relays including a lockout relay R625, a

.45 which are controlled in accordance with the battery supply relay R630, a control relay R640, t

partially shown in Fig. 4, the rst sequence switch 4|0 in the first group of sequence switches,

a start relay R430, a stop relay R440, a number of feeder relays individually associated with the links in the rst group of links and commonly `associated with the first feeder trunk 480 in the l, rst group of feeder trunks, including the feeder relay R450 individually associated with the first link |00 in the first group of links and the first feeder trunk 480 in the first group of feeder 4trunks, and a position relay R460 commonly associated with the first feeder trunk 480 vin the rst group of feeder trunks and the position trunkl 410 extending to the iirst A operatorposition 100. The sequence switch 4|0 is of the rotary type and comprises four wipers 4| I, 4|3,

415 and 411 provided with individually associat-` ed rotary contact banks 4|2, 4|4, 4|6 and 4|8. Also, the sequence switch 4|0 is provided with a rotary magnet M4|9 for moving the wipers noted in th e rotary direction.

The first link distributor 30|, illustrated in Fig. 3, has access to each of the links in the rst group ol' links in the local exchange 20 and is operativeto assign an idle one of the links in the first group of links to the use of any one of the telephone lin-es in the first group of telephone lines in the local exchange 20. The details of the connection and arrangement of the link distributor 30| are not disclosed as they form no part of the present invention; however, for reference purpose, it is noted that the connection and arrangement of a distributor of the type of the distributor 36| is shown in the copending application of Edward S. Peterson, Serial No. 253,021, filed October 3, 1938. Also, a marking network 305, shown in Fig. 3, is individually associated with the distributor 36| in order to initiate operation thereof when a call is initiated on any one of the telephone lines in the rst group of telephone lines in the local exchange.

`Preferably, each ofthe flat rate line circuits is identical to the flat rate line circuit 200 individually associated with the telephone line 225 extending to the subscriber substation Tl, shown in Fig. 2, which comprises a line and cutoff relay R2|0 and a busy relay R220 connected and arranged in a manner more fully described subsequently. Further it is noted that a tone transformer 2id is commonly associated with each of the flat rate line circuits.

Preferably, each of the two-party line register circuits is identical to the two-party line register circuit 240 individually associated with the telephone line y1li extending to the party subscriber substations T2 and T3, shown in Fig. 2, which comprises a line and cutoff relay R260, a lockout relay R250, a control relay RMo and two registers respectively provided with register magnets M2M and M242, and connected and arranged in a'manner more fully described subsequently. Also a signal lamp L243 is individually associated with the two-party line register circuit 240.

Preferably each of the prepay manual line circuits is identical to the prepay manual line circuit 260 individually associated with the telephone line 285 extending to the pay station T4,

identical to the trunk Yline circuit 660 individually associated with the trunk 690 rextending to the first B operator position 604, shown in Fig. 6, which comprises a line relay R660 and a busy relay R685 connected and arranged in a manner l more fully described subsequently.

Preferably each of the B operator positions Vin the local exchange 20 is identical to the rst B operator position 694,1sl1own in Figs. 6 and 2. The first B operator position 694 comprises conventional answering equipment, not shown; con- Y ventional callingV equipment including a number of call jacks J20I, J202 and J203 respectively terminating the telephone lines 225, 210 and 285;

and a number of conventional cord circuits, not shown.

Preferably each of the A operatorpositions is identical tothe rst A operator position 100, shown in Figs. 7 and 8, which comprises a trunk. circuit provided with a Set of position keys including an error release key K150, a permanent lockoutrelease key K'l55, a reverting call key K110, a split key K115, a coin collect key X180, a coin return key X1857 a rst register key K195, a second register key K190, a transfer key K165 and a control key K150. Also the trunk circuit at the .first A operator position 100 comprises a telephone instrument including a transmitter 108 and. a.` receiver 101, a repeater 10|, an irnpedance element 1158, a key senderv K12!) and a number .of relays including three tone relays R1I5, R120 and R125, a rear split relay R130, a front split relay R135, an impulse relay R140, two signal relays R885 and R890, a control relay R1|0 and aV startrelay R110. with the rst A operator position 100 are a peg count meter .provided with a register magnet M141 andthree signal lamps including. a flat rate signalk lamp L880, a message register signal lamp LSSI and a prepay signal lamp L832. .The key sender X120 is cf a well-known type; accordingly, the details of the connection and arrangement thereof are not disclosed as they form no part of the present invention.

Also associated Preferably, each of the call storage units is ...Y

identical Ato the call storage unit 800 individually associated with the rst A operator position 100, which comprises, asshown in Fig. 8, six Vmarking relays. IM to 6M, inclusive, a control relay R8|0 and a release relay R820 connected and arranged in a manner more fully described subsequently. Also, six storage lamps L80I to L806, inclusive, are associated with the call storage unit .800 and individually associated with the rst A operator position 100.

The A operator position distributor 830, shown in Fig.A 8, comprises a number of position relays R850, R860, R810, etc., respectively corresponding to the A operator positions, a control relay R835 and a busy relay R830 connected and arranged ina manner more fully described subsequently.

A better understanding of the connection and arrangement of the apparatus incorporated in the telephone system will be facilitated from a consideration of the detailed operation of the various pieces of apparatus incorporated therein incident to the completion and the handling of the various calls at the first A operator position 100, as will appear hereinafter.

General operation of the system Considering now the general operation of the system, with reference to Fig. l of the drawings it is noted that when a call in initiated at any one of the subscriber substations. or at any one ofthe pay stations in the local exchange 20, the line circuit individually associated with the telephone line extending thereto is controlled, thereby to initiate operation of the link distibu'to-r Accordingly, .at

this time, the distributor 30| operates in order 7 300 seizes the calling .telephone` line inthe first group of .telephone linesthe distributor .30 I. Yis released and `operates .topreselect anotherlidle link in the first group, of links as 'previouslynoted-.

The .A operator position 'distributor 830.1 pre selects an idle .one of 'the .A Voperator positions for use, and when a preselected. one of ther-A operator positions is taken .for` use thel -A foperator position. distributor :|330v operates-to preselect anothercne of-tvhe--A operator positions for use.y Assuming that .the A operator .-posi,

tion. distributor .830A has .preselected the .rst -YA operator position for use at this time-operation of the firStsWitChing unit..400 :inthexfirstl group of switching units is initiated. `More -par. ticularly, the first lsvvitcl'iing unit. 110D-inthe first group of switching unitsoper-ates to '-connectthe rst'link |00'in thefirst groupof linksgto the rst feeder trunk 4'80`in'the` associatedgroupof feeder trunks, to prevent any of .the other links in the rst group of links from -being connected to the rst feeder trunk -M30,` to initiate .operation of the lfirst sequence switchlll inthe. rst group ofsequence switches and toeausethe' A operator position distributor -830'to preselect another A operatorposition. at th=isftinie.../The first sequence switch 4.-|0the'n operatesto cause the first switching unit I|00 'to operate Vfurther and connect the feeder' trunk '4`80Ito-.the`. position trunk 410, thereby to extend the call-ffrom...the calling telephone line in the rst.group.of ,telephone .lines to .the first A operatorposition 100, and toprevent any of the' other feeder .trunks-in the other grcups. of feeder trunksfrom. being connected to the position trunk 4010. The.. op erator at the rst .A operator position 10012.11'- swers the call and operates the keysenderat her position, thereby .to-control the operation ofthe selector switch. 600 'in-order to extend the callt'oits destination.

In this.. connection it is lnoted` that theselectr switch 600" may bei selectively -controlledwtofex- 'tend the call 'to-i any idle 'B operator position in tl'ielocal exchangeg' toany idle tolroperator position 'in the local exchange 20, or AtotlieB operator position. 598 in the distant exchange 30. 'Inthe'event 'the callis to'be routedV to 'a telephone'station in 'the local .exchange 20"the selector `switch"|00 is controlled in order.. V.to route 'the call than' idle B cperatorposition in the 'local' exchange *20; Y'I"l'i"el.operator at Ithe idlerB operator positionlinthe'- local exchange 2.0 answersl themallfand then extends 'the' call to the' called t-elephone station` .in the -local exchange '20; 'inthe' usuarzma'nner. In' the event the .call is to"b`eroutedito 5a. :telephone station'i in the '.distantjjexchange" 30 fj the' selector switch' 600" 'is fcontrolled in orderv` to' route thejcall"to 'thelB ,operator .positionBSB in the distanti exchange'j0fTl'ie operator'at'the `B operator position 4 08in .thedistantexchange 30 answers `the call andthenexterrds cthecallto the .'calledf telephone sta-tion@` in i the 'distant'` exchange130, jin` thel usual-manner; In the event 'the 'call is Yto 'be'routed toll theselector switch 600 is controlled in order to ioute the call to an idle one oi the toll operator positions in the local exchange 20. The operator at the idle toll operator position in the local exchange 20 answers thecall and then routes the call toll in the usual manner.

- After the call has been routed from the iirst A operator position 150 in the local exchange 20 to an idle one of the B operator positions in the local exchange 20, to an idle one of the toll operator positions in the local exchange 20, or to the B operator position 698 in the distant exchange 30 andthe iniormation concerning the extension of the call has been conveyed to the called operator, the operator at the first A operator position 109 releases the connection between her position and the first link |00, whereupon Va direct connection is completed between the finder switch 300 and the selector switch B excluding the first A operator position 100. It is noted that the called operator to which the call is routed by the selectorswitch 600 may recall the operator at an idle one of the A operator positions in the local exchange 20 by causing reoperation of the rst -switching unit in one of the groups of switching units under the control of the A operator position distributor 830 in the manner previously explained.

In the event all of the A operator positions in the local exchange 20 are busy when operation of the first switching unit in one of the groups of switching units is initiated, the particular operating rst switching unit, as determined by the A operator position distributor 830, operates to cause the call or recall on the rst link to be stored in an assigned one of the storage units. More particularly, when all of the A operator positions are busy, the A operator position distributor 830 operates to assign the storage units in a predetermined order. Assuming that Athe A operator position distributor 830 has ,operated to assign the first call storage unit 800 individually associated with the rst A operator position 100 at this time, due to the busy condition of all of the A operator positions, when operation of the rst switching unit 400 is initiated, the operating first switching unit 400 reconnects the first link |00 to the feeder trunk 480 and initiates operation of the .rlrst sequence switch 410, whereupon the rst selector switch M0 seizes the first call storage unit 800, thereby to cause the call or recall onthe first link |00 to be stored in the first call storage unit 800 at this time. At this time, when all of the A operator positions are busy, thecalls and recalls on theY links are stored in the successive storage positions of the storage units in a predetermined order. At this time, when a number of callsY and recalls -on a number Vof the links are stored in one .of the call storage units, such, for example, as the first call storage lunit 800, further operation of the rst call storage unit 800 is initiated when the associated first A operator position 100 becomes idle. More particularly, when the irst A -operator position 700 becomes idle, the iirst call storage unit 800 operates, thereby to cause reoperationv of the switching unit in the rst group ofswitching units associated with the link having a call or recall thereon stored in the rst storageposition of the first call storage unitll, thereby to cause the call or recall on the last- Vmentioned link to be routed to the first A oper- `ator position 100 to be answered. Further, the first call storage unit 800 causes reoperationrof each of the switching units` in the firstgroup of switching lunits associated with the links having calls .or recalls-thereon stored in the other storage positions of the first call storage unit thereby to cause the calls or recalls on the lastmentioned links to be restored insuccessive advanced storage positions in the rst call storage unit 800. Accordingly, the first call storage unit 800 operates to causecalls and recalls routed thereto to be stored in a predetermined order when all of the A operator positions in the local exchange 20 are busy; -and to cause the stored calls'and recalls. to be released to be answered at the first A operator position in the ,same predetermined order in .which they were stored in he first call storage unit 800.

After'a call 'from a calling telephone line in any one of the groups of telephone lines has been extended from any one of the A operator positions to one of thev B operator positions in either the `local exchange 20 or the distant exchange 30 or to one of the Vtoll operator positions inthe localrexchange 20 the release of the established connection is under the joint controlof the calling telephone line and the called one of the 'operator positions.

`Flat rate subsclriber4 substation call ergizing in series the windings of the line and cutoff relay R2I0. V- This circuit extends from groundrby, way ofthe lower winding of R2l0, the contacts 2l2, C221,V the bridge path between the line conductorsCZZ'I and C226, C225, the contacts 2Ik| and the upper and intermediate windings of R2l0 to battery. When energized over the above-traced circuit the line and cut-off relay R2I0 operates partially, thereby to complete, at the contacts 2l4, a path for applying ground potential to the start conductor C230 and to complete, at the contacts 213, an obvious connecti'on between the control conductors C228 and C229 ,of thetelephone line 225. ,The path for applying ground potential to the vstart conductor C230 extendsfrom ground by way of the contacts 22|2l5v and 2M to the start conductor C230. The'application of ground potential to the start conductor C230 completes an obvious path for applying ground potential by way of the resistor 304 of the marking network 305 to the start conductor C308 extending to the distributor 30|, and completes an obviousqpath for applying Adirect ground potential to the rst contacts in the vertical control contact banksof the finder switches. Theapplication of ground potential to the start conductor C308 initiates operation of the distributor 30|and the application of direct ground potentialto the rst contacts inthe vertical control contact; banks of the finder switches marks the telephone line 225 as terminating in the first level of the main contact banks of the finder switches having access thereto, Y f

, The distributor V357| is of the preselective type and operates/to select another. idle link in the rst group of links as soon as the nder'switch of a previously selected link in the -rst `'group of links operates tofind'a calling telephone'linei 30| operates to cause. ground-potential to be :ap-1

plied: tothe; start .conductor C302, thereby .to complete van obvoius circuit for energizing-the winding of the start relay R340. The start relay R34fthen operates to interrupt; at the:contacts 348, a point in a multiplepathgfor 'applying ground potential to the all-link-busy. conductor C309 and to complete, at .the contacts 342, 'an obvious path for applying ground potentialto the control conductor C363 of the trunk 360. The previously mentioned path' for applying ground potential to the all-link-busy conductor C369r in the finder switchv 300 .extendsywhen completed, from ground by way ofthe .contacts 343 and the set of switch springs S312 to the all-link-busy conductor C369. Also, the start relay R340 completes, at. the'contacts 343, obvious multiple circuitsfor energizing the.lower windings of the switching relays R32ll1and R330, thereby to render each of these. switching relays extremely fast to operate in the event the upper winding thereof is energized. Further-the Astart relayR340 preparesgat the contacts 341, a circuit tr-aced hereinafter for energizing the ver- .Y

tical magnet M365 and prepares, at -the contacts 346,-a circuit traced hereinafter for energizing the rotary magnet M361.

The distributor 30| 'then operates to Cause ground potential to be applied to the vertical conductor C365, thereby to complete the previously mentioned circuit for energizing the'vertical magnet M365, this circuit extending from the' grounded vertical conductor C305=y 'by' way of the contacts 341 and M365 to battery. When energized over the above-traced circuitthe vertical magnet M365v operates to driverthe' first and second wiper sets of the mechanism 3I0 one step inthe vertical direction and to complete, at the contacts 366, an obvious path for applying ground potential to the interrupter conductor-C306.f The application of ground potential to the-interrupter conductor C306 causes the distributor 30|=toin terrupt the application of ground potential to-the vertical condutcor C305;A whereupon the Vertical magnet M365 restores to interrupt, at the contacts 366, the previously mentioned path for applying-ground potential to the interrupter conductor C366. Accordingly, the vertical magnet M365 operates intermittently, thereby tov drive the first contact in the associated vertical control contact bank having groundpotential thereon. The' application-of ground potential to the test conductor C3D1lcauses th'edistributor 30| to voperate, thereby. to interrupt the application lof ground potential tothe-vertical :conductorvC3'05 `and to apply ground potential to the rotary conductor C304'.` yThe .applicationuof ground potential .'to 'the.rotary:c'onductor C304 completes-the 75 previously mentioned circuit for energizing the rotary magnet M361, this circuit extending from the grounded rotary conductor C304 by way of the ycon- tacts 346, 330 and 328 and M361 to battery. When energized over the .above-traced circuit the rotary magnet M361 operates to drive the rst and second wiper sets of the mechanism-3I0 one step in the rotary direction and to complete, atlthe contacts 368, an obvious path for applyingground potential to the interrupter conductor C306. This rapplication of ground potential to the: interrupter conductor C306 causes the distributor 30| to remove the application of ground potenti-al tothe rotary conductor C304, whereuponthe rotary magnet M361 restores to interrupt,` at the contacts 368, the previously mentioned pathv for applying ground potential to theinterrupter conductor C336. Accordingly the rotary. magnet M361 operates intermittently, thereby to drive the first and second wiper sets of the' mechanism 3I0 step -by step in the rotary direction .until either the control wiper 3|3 or the control :wiper 3|6 of the respective iirst and second wiper sets engages the control conductor of a calling telephone line having battery potential thereon. `,In the present example the telephone line-225 is `included in the iirst section of the main` contact bank of the mechanism 3I0.

Accordingly, whenv the control wiper 3|3 of the rst wiper set of the mechanism 3I0 engages the contact of the contact set in vthe rst section of the main contact bank 'of the mechanism 3I0 terminating the ycontrol conductor C228 of the telephone line 225, a circuit is completed for energizing theupperv winding of the switching relay R320; This circuit extends from ground by way of the contacts 22|, 2|5 and 2I4, the Start conductor C230, the control wiper 3I8, the upper winding ofvR320, the-control wiper 3|3, the control conductor C228v of the telephone line 225, the contacts A2|3 yand* the intermediate Winding of R210 to battery. When energized over the above-traced'v circuit the switching relay R326 operates exceedingly fast, thereby to complete, at the contacts 325, .a holding circuit .for energizing the intermediate Winding thereof, this circuit extending from thev grounded control conductor C363of theltrunk360'by'way of the contacts 3361A and 325 andthe intermediate winding of R323'5 tov battery. Also, upon operating, the switching relay R326 interrupts, at-the contacts 328,*'a pointin the previously. traced circuit for energizing the rotary magnet M361, thereby positively to arrest-further Yoperation of the mechanism 3I0. interrupts, at the contacts 326, a point in a circuit traced hereinafter for energizing the upper-winding of the switching relay R330, thereby positively to prevent operation of the' latter relay at 'thisl time. Also the switching relay R320 interrupts, at the contacts 32|, a point in a circuit traced hereinafter for 1 energizing the .release magnet M369 land completes, at the contacts 321; a. connection vbetween the rotary conductor C304 and the' guard conductor C303, this connection extendingfrom the rota-ry conductor C30'4f by way-fof the contacts 346, 330, 321 and 344 Lto the guard conductor C363. When the rotary conductor C304 is connected to the guard conductor C303 operation .of the distributor 30| to controly the iinder switch 300 is arrested, whereupon thedistributor 30| operates automatically toiselectffor use another idle one of the' linksin the rstgroup of links.

Also it .is .noted that when Vthe carrageofthe Further the-switching relay R320/ mechanism 3|0 is driven one step in the vertical direction the sets of switch springs S31.0, S31| and S312 are actuated. More particularly, the set of switch springs S310 is actuated into engagement, thereby to prepare a further point in the previously mentioned circuit for energizing the release magnet M360; while the set of switch springs S312 is actuated into disengagement, thereby to interrupt a further point in the pre- Viously traced path for applying ground potential to the all-link-busy conductor C309. Finally the contacts 312 of the set of switch springs S31| are actuated into engagement, thereby to prepare a path traced hereinafter for applying ground potential to the guard conductor C303. Finally, upon operating the switching relay R320 completes, at the contacts 322, 323 and 32,4, connections between the conductors of the trunk 360 extending between the nder switch 300 and the selector switch 600 in the rst wiper set of the mechanism 3|0. More particularly, a low resistance circuit is completed, at the contacts 324, for energizing the intermediate winding of the line and cutolc relay R2|, this circuit extending from the grounded control conductor C363 of the trunk 360 by way of the contacts 336 and 324, the wiper 3|3, the control conductor C228 of the telephone line 225, the contacts 2|3 and the intermediate winding of R2|0 to battery. When the intermediate winding of the line and cuto relay R2|0 is thus energized this relay operates completely, thereby to interrupt, at the contacts 2|5, the previously traced path for applying ground potential to the start conductor C230 extending to the marking network 305 in order to arrest operation of the distributor 30|. Further the line and cutoi relay R2|0 interrupts, at the contacts 2|| and 2|2, the previously traced circuit for energizing the windings thereof across the line conductors C226 and C221 of the telephone line 225, thereby to clear the telephone line 225 of impedance elements. At this timeY ground potential appearing upon the control conductor C228 of the telephone line 225 is applied to the control conductor C229 thereof, thereby to mark the telephone line 225 as busy to the B operator positions in the local exchange 20.

Further it is noted that the distributor 30| operates in order to select another idlelink in the first group of links for use only in the event ground potential appears upon the all-link-busy conductor C303 ,in at least one of the iinder switches of the links in the rst group of links, ground potential being removed from the alllink-busy conductor C309 in the finder switch 300 of the irst link in the iirst group of links at this time due to the operated condition of the set of switch springs S312, as previously noted. Also ground potential is applied to the guard conductor C303 in the finder switch 300, thereby to prevent the distributor 30| from preselecting the rst link |00 illustrated at this time due to the busy condition of the nder switch 300. The path for applying ground potential in the lnder switch 300 to the guard conductor C303 extends from from ground by way of the contacts 312 of the set of switch springs S31| and the contacts 345 to the guard conductor C303, the start relay R340 being restored at this time. Further it is noted that the start relay R340 is of the slow-torelease type and restores shortly after the distributor 30| is released. Upon restoring the start relay R340 interrupts, at the contacts 342, the previously traced path OI applying ground potential to the control conductor C363 of the tion, it being of the differential type. On the trunk 360, ground potential being applied to the control conductor C363 of the trunk 360 in the selector switch 600 at this time. Further the start relay R340 interrupts, at the contacts 333, the previously mentioned multiple circuit lfor energizing the lower windings of the switching Vrelays R320V and R330, the switching relay R320 being retained in its operated position at this time due to the completed holding circuit for energizing the intermediate winding thereof.

When the trunk is connectedto the telephone line 225 a loop circuit is completed for energizing in series the upper and lower windings of the error relay R650 and the upper and lower windings of the line relay R655 in the selector switch 600. This circuit extends from 'ground by way `of the lower winding of R555, the lower winding of R650, the line conductor C662 of the trunk 660, the contacts-M56, C502, the contacts 556, C4||, the contacts 456, the line conductor C362 of the trunk 360the contacts 334 and 323,

and the wiper 3|2 to the line 'conductor C221 of the telephone line 225; and from battery by way of the upper winding of R655, the upper winding of R650, the line conductors 066| of the trunk 660, the contacts L553, 050|, the contacts 553, C4I0, the contacts 453, the line conductor 036| of the trunk 360, the contacts 332 and 322and the wiper 3|| to the line conductor C226 of the telephone line 225; the line conductors C226 and C221 of the telephone line Y225 being connected together by way of the bridge path at the subscriber substation TI. When the upper and lowerwindings of the error relay R650 arethus energized, this relay remains in its restored posiother hand, when the upper and lower windings of the line relay R655 are thus energized, this relay operates to complete, at the contacts-656, a circuit for energizing the winding of the hold relay R660, this circuit extending from ground by way of the contacts 615 and 656 and the winding of R660 to battery. When thus energized, the hold relay R660 operates to complete, at the contacts 662, a multiplevpath for applying ground potential to the control conductor C363-of the trunk 360 as previously noted. The multiple path for applying ground potential to the control conductor C363 of the 4trunk 360 extends from ground by way of the contacts 662, 654 and 621 and the control conductor C563 of the. trunk 660 to the control conductor C363 of the trunk 360. Also, the hold relay R660 completes, at the contacts 663, an obvious circuit for energizing the lower winding of the switching relay R610, thereby to render the switching relay R610 eXceeding- Y ly fast to operate when the upper winding thereof is energized. Further, the hold relay R660 prepares, at the contacts 66|, a circuit traced hereinafter for energizing the upper winding of R665, this circuit extending from ground by wayr t of the contacts 662, the set of switch springs S620 and the upper winding of R665 to battery. When thus energized, the transfer relay operates to prepare, at the contacts 661, a further point in the previously mentioned multiplecircuit for energizing the lower winding thereofA control conductor CilillV of'the trunk 860.

and the vertical magnet VM614 and to interrupt, at the contacts 668', `a point-,in al circuit traced hereinafter for energizing the rotary magnet MNE. Finally, upon operating, the transfer relay R385 completes, at the contacts 658, anobvious path for applying ground potential to the The application of ground potential to the control conductor C884 of the trunk 668 initiates operation of the iirst switching unit in one of the groups of switching units as determined by the A operator position distributor 838 in a manner more fully described hereinafter.

Before continuing with the operation of the iirst switching unit in one of the groups of switching units it is noted that the A operator position distributor 839 is operative to preselect one of the groups of switching units corresponding to an idle one of the A operator positions. Assuming that the first group of switching units associated with the iirst A operator position `'Hill has been previously selected at this timeby the A operator position distributor 839 dueto the idle condition of the rst A operatorY position 198, a holding circuit isV completed for energizing in series the winding of the control relay R835 and the right-hand winding of the position relay R858', the position relay R850 corresponding tothe first group of switching unitsand to the first A operator position 'H58'. rThisY circuit eX- tendsrfrom ground b-y way of the winding of R835, the contacts 884 and 853 and the righthand winding of R858-to battery. The operated position relay RB58v retains interrupted, at the contacts 856, a holding circuit tracedhereinafter for energizing the winding of the control relay R885 in series with the rightfhand winding of the posi-tion relay R870 and retains prepared, at the contacts 8&2, a path for applying battery potential to the control conductorV C884' in the distributor trunk 88d. The path for applying battery potential to the control conductor C884 in the distributor trunk' extends from battery by way of the resistor 8&2` and the contacts 852 to the control conductor C884 in the distributor trunkv 880. Finally, the operated position relay Ri'all retains prepared, at the contacts SSI, a point in a circuit traced' hereinafter for energizing the left-hand' winding of the position relay RillV corresponding to theV second A operator position. The application of battery potential to the control* conductor C884 in the' dis.- tributor trunk 880 prepares multiple circuitsk for initiating operation of each switching' unit in thefirst group of switching units, thereby tosel'ect the first group of switching units andthe corresponding rst A operator position 188.

Continuingv now with the operation of one of the switching units in the iirst group of switching units, it is noted that the first switching unit ll'v in` the iirst group of switching. unitsV is operated` at this time, this particular switching unit being operated at this time due to the facts that only the rst group of switching units is prepared to be operated and that therst switching unit 408 in the rst group of switching units is associated with the rst link |00' in the `first group of links. Accordingly, at this time, when ground potential is app-lied to the control conductor C654 of the trunk G80 a circuitv is completed for energizing the upper winding of the feeder relay R450, this circuit extending from the grounded control conductor C664 of the trunk 650 by way of the contacts L559, 559 and 459, the upper winding of R450-, C488 and the contacts 43l= to the control conductor C884 in thet distributor trunk 880, the control conductor C885v in the distributor trunk 888y having K battery potential thereon as previously noted. At

' this point it isnoted that the application of ground potential to the control conductorrCBM of the trunk prepares an obvious multiple circuit for energizingthe upper winding of the feeder relay Rincluded in tne iirst switching unit 5Min the second group of switching units, an obvious multiple circuit for energizing the upper winding of the feeder relay LR558-y includedinthe first switching unit L5M)v in the last group oi .switching units, etc. However,

only the feeder relay Rli'a'l included in the iirst switching unit 4t() the` rst group of switching units is operated at this time due to the fact that battery potentialby way of the resistor 8-l2 in the A operator position distributor 838 only appearsupon the control conductor C884 in the distributor trunk 888- at this time. Further, it is noted that the application of battery potential to the con-trol conductor C884 in the distributor trunk 888 prepares obvious multipleY circuitsl for energizing the' upper windings ofv the feeder relays` included inthe other switching units in the rst group of switching units. However, only the feeder relay R458- in the rst switching unit 4801 in the first group of switching units is operated due to the fact that the first link 88 isthe only link inthe rst group of links which is operating at this time.

Upon operating, the feeder relay R458 completes, at the` contacts 4581, a holding circuit for energizing` the lower winding thereof in series with the winding of the start relay RliBll, this circuit extending from ground by way of the lower winding oi R458; the contacts 458, C491 and the winding of R430 to battery. When this holding circuit iscompleted the feeder relay R458 remains in itsoperated position, while the start relay R438 operates'. Also, upon operating, the feeder relay R458 interrupts, at the contacts 459i, the previouslyv mentioned prepared multiple circuitsfor energizing the upper windings of the feeder relays included in the rst switching units in the other groups ofv switching' units. Similarly, upon operating, the start relay R430 interrupts, .at-the contacts 431, the previouslyv mentioned prepa-red'multiple circuits for energizing theupper windings of the feeder relays included in the first switching unit in the first group of switching units. Also, upon operating, the start relay RMB-completes, at the contacts 432', an obvious connection-between the control conductors G88!V and C8811 irr the distributor trunk880', theecontrolconductor C884 having battery potential thereon; as previously noted, andthe control conductor C88I- having ground potential thereon'by way ofthe contacts 831. Accordingly, when the con-trolv conductors C8815 and C884 in the distributor trunk 888 areconnected together, an obvious circuit'is' completed for loading the battery -in the A operator position distributor 838 by yway of; theresistory 812', thereby effectively tdremove battery potenti-al from the control conductor C884 in the distributor trunk 88B-, The eirectiverernoval of battery potential from the. control conductor (388| in the distributor trunkA 888A positively prevents operation of any ofthe other switching units in the first group of switching units at this time.

Also, upon operating, the start relay R438' completes, at the contacts 433, a path for applying ground potential to the control conductor' C888.,

in the distributor trunk 888, this path extending from ground by way of the contacts 44| and 433 to the control conductor C883 in the distributor trunk 888. The application of ground potential to the control conductor C883 in the distributor trunk 888 completes the previously mentioned circuit for energizing the left-hand winding of the position relay R888 in the A operator position distributor 838, this circuit extending from the grounded control conductor C883 in the distributor trunk 888 by way of the contacts 851 and the left-hand winding of R888 to battery. When thus energized, the position relay R888 operates to complete, at the contacts 883, a holding circuit for energizing in `series the Winding of the control relay R835 and the right-hand winding of R858, this holding circuit extending from ground by way of the winding of R835, the contacts 874 and 883 and the right-hand winding of R868 to battery. Also, uponV operating, the position relay R858 prepares, at the contacts 882, an obvious path for subsequently applying battery potential to the control conductor C888 in the distributor trunk 888 and prepares, at the contacts BSI, a circuit traced hereinafter for Yenergizing the left-hand winding of the position relay R8`l8. Finally, the position relay R858 interrupts, at the contacts 884, the previously traced holding circuit for energizing in series the Winding of the control relay R835 and the right-hand winding of the position relay R858, thereby to cause the position relay R858 to restore. Upon restoring, the position relay R858 interrupts, at the contacts 853, a further point in the previously traced series holding oircuit for energizing the right-hand winding thereof and the winding of the control relay R335, and interrupts, at the contacts 852, the previously traced connection between the control conductor CBSI in the distributor trunk 888 and battery in the A operator position distributor 838, thereby to cause effective battery potential to be applied by way of the resistor 8i2 and the contacts 862 to the control conductor C888 in the distributor trunk 888. Also, upon restoring, the position relay R858 interrupts, at the contacts 85|, the previously traced circuit for energizing the left-hand winding of the position relay R888 and prepares, at the contacts 854, a holding circuit traced hereinafter for energizing in series the winding of the control relay R835 and the right-hand winding of the position relay R818. Accordingly, at this time, effective battery potential is applied by way of the resistor 8i2 in the A operator position distributor 838 to the control conductor C888 in the distributor trunk 888. The application of battery potential to the control conductor C888 in the distributor trunk 888 prepares the switching units in the second group of switching units to be operative, thereby to select tne second A operator position to receive the next incoming call.

Also, upon operating, the start relay R488 completes, at the contacts 484, an obvious connection between the control conductors C882 and C898 in the distributor trunk 838, thereby to prepare a point in a chain circuit traced hereinafter for energizing the winding of the -busy relay R838 in the A operator position distributor 838 for a purpose more fully described hereinafter.

Also, upon operating, the feeder relay R458 completes, at the contacts 45I, 452, 454 and 455, an alternative connection between the finder switch 388 and the selector switch 888, including the feeder trunk 488, and interrupts, at the contacts 453 and 456, the previously traced direct connection between the finder switch 388 and the selector switch 888. More particularly, at this time, the line conductor 038| of the trunk 368 is connected by way of the contacts 452, the line conductor C482 of the feeder trunk 488, the contacts 483, the line conductor C48I of the feeder trunk 488 and the contacts 45|V tothe conductor C4I8, and therefrom by Way of the previously traced path to the line conductor C66I of the trunk 858; while the line conductor C362;

of the trunk 388 is connected by way of the contacts 455, the line conductor C484 of the feeder trunk 488, the contacts 488, the line conductor C483 of the feeder trunk 488 and the contacts 454 to the conductor C4I I, and therefromr b-y Way of the previously traced path to the line conductor C882 of the trunk 660.

Also, upon operating, the start relay R438 completes, at the contacts 435, a circuit for energizing the rotary magnet MMS of the sequence switch 4I8, this circuit extending from ground by way of the contacts 435, 442 and 428 and MMS to battery. When thus energized, the rotary magnet M4N operates to interrupt, at the contacts 428, the previously traced circuitnfor energizing the rotary magnet M4I8, thereby to cause the rotary magnet M4I8 to restore and recomplete, at the contacts 428, the previously traced circuit for energizing the rotary magnet MMS. Accordingly, the rotary magnet MMS operates intermittently, thereby to drive the wipers noted of the sequence switch H8 step by step inthe clockwise direction. Also, upon operating, the start relay R458 prepares, at the contacts 435, a circuit traced hereinafter for energizing the winding of the stop relay R448.

The rotary magnet M458 continues to operate intermittently in order to drive the wipers noted of the sequence switch 418 step by step in the clockwise direction until the wiper 4 i 5 thereof engages the seventh Contact in the associated contact bank M8 terminating the marking conductor C881 in the marking trunk 878 extending to the rst call storage unit 888, whereupon a circuit is completed for energizing Yin series the winding of the stop relay R448 and the winding of the marking relay IM. This circuit extends from ground by way of the contacts 435, the winding of R448, the wiper M5 and engaged seventh contact in the associated contact bank M8 of the sequence switch 4I8, the marking conductor Cil'll in the marking trunk 818, the contacts 8II and the winding of iM to battery. When this series circuit is completed the stop relay R448 operates immediately and the marking relay IM operates shortly thereafter, the latter relay being of the slow-to-operate type. Upon operating, the stop relay R448 interrupts, at the contacts 442,-the previously traced circuit for energizing the rotary magnet M458 of the sequence switch 4I8, thereby to arrest further operation of the rotary magnet M4N at this time. Upcn'operating, the marking relay IM completes, at `the contacts IM2, an obvious circuit for energizing the lower winding of the control relay R8I8, thereby to cause the latter relay to operate and interrupt, at the contacts 8l i, the previously traced circuit for energizing `in series the winding of the stop relay R448 and the winding of the marking relay IM, whereupon the stop relay R448 and the marking relay IM restore. Upon restoring, the stop relay R448 recompletes, at the contacts 442, the previously traced circuit for energizing the rotary magnet M4I8 of the sequence switch 4I8, thereby to cause the rotary magnet M4 |9- to reoperate and drive the wipers noted of the sequence switch .an additionallsteplin the clockwise direction. Upon restoring, the marking relay 1M interrupts, at the contacts 1M?, the previouslymentioned circuit for energizing the lower Winding of the contrcl relay R810, thereby to cause the latter relay to restore and reprepare, at the contacts 8| i, the previously traced circuit for energizing the winding of the marking relay IM. When the wiper 4|5of the sequence switch 410 is driven an additional step in the clockwise direction into er1-- gagement with the eighth contact in the associated contact bank MI of the sequence switch 4i-0- a series circuit is completed for energizing the winding of the stop relay R440 and the Winding of the start relay R110, this .circuit extending from ground by way of the contacts 435, the winding of R449, the wiper 415 and engaged eighth Contact in the .associated contact bank 418 of the sequence switch 4|0, the control conductor C492 in the control trunk 490 and the winding of R110 to battery. When this series circuit is completed the stop relay R440 reoperates, thereby to arrest further operation of the rotary magnet M4|9 of the sequence switch 4|0, as previously noted, w-hile the startv relay R110 operates.

Upon operating, the start relay R110- completes, at the contacts RA11I, a circuit for energizing the winding of the position relay R460,

this circuit extending from ground by Way of the contacts RA11I, the control conductor C493 in the control trunk 490, the. Wiper 4|1 and engaged eighth contact in the associated contact bank 4|8 of `the sequence switch 410 and the winding of R460 to battery. When thus energized the position relay R460 operates to complete, at the contacts 461|, 482, 484 and 455, a connection between the nder switch 300 and the selector switch 600, including the position trunk 4101 extending to the iirst A operator position 100, and to interrupt, at the contacts 453 and 466, the previously traced alternative connection between the finder switch 300 and the selector switch 680. More particularly, the line conductor Cl of the trunk 380 is connected by way of the contacts 452, the line conductor C482 of the feeder trunk 480', the contacts 482, the line conductor C414 of the position trunk 410, the contacts 131, the retarder coil 130, .the contacts 133, the line conductor C415 of the position trunk 410, the contacts 455, the line conductor C484 of the feeder trunk 480, and the contacts 455 to the line conductor C362 of the trunk 360; while the conductor 04H1, connected by way of the previously traced path to the line conductor 055| of the trunk 650, is connected by Way of the contacts the line conductor C48| of the feeder trunk 480, the contacts 45|, the line conductor C413 of the position trunk 416, the contacts 136, the retarder coil 534, the contacts 138, the line conductor C412 of the position trunk 410, the contacts 454, the line conductor C483 of the feeder trunk 480, and the contacts 454 to the conductor C411, the conductor C4|| being' connected by way of the. previously traced path to the line conductor C562 of the trunk 560. Accordingly, at this time, the nder switch 300. is connected by way of the previously traced circuit including the rst A operator position 100 to the selector switch 600. Further, it is noted that the line conductors C413 and C414 of the position trunk 410 are connected by Way of the contacts 13S, 13|Y and 1|8, the windings 103 and 104 of the repeater 10|, the contacts 1| 8 and the contaets138 and 133 to the line conductors C412 and C415 of theposition trunk 410'..

Also, upon operating, the start relay R110 compietes, at the contacts RA114, anV obvious con-l nection between the control conductors C381 and C5813` in the distributor trunk 88d, thereby to prepare an obvious alternative circuit for energizing the left-hand winding of the position relay R860 so long as the busy relay R830 in the A operator position distributor 888 remains restored. Accordingly, so long as the busy relay R330 remains restored, operation of the position relay R850 is eiective to complete, at thev contacts 85|,

the previously mentioned alternative circuit for' energizing the left-hand winding of the position relay R860. Hence, the A operator position distributor 830 is not operative to select the first groupof switching units and, consequently, the first A operator position 10 so long as the rst A operator position is busy, the start relay R being operated while the first A operator position 1M is busy, unless all of the A operator positions are also busy, in which event the busy relay R330 in the A operator position distributor 830 is operated due to the completion of the previously mentioned chain circuit, as will be more fully explained subsequently.

Continuing now with the operation of the apparatus at the first A opera-tor position 100 incident to the seizure of the position trunk 410 extending thereto, it is notedthat when the start relay- R110 operates it also completes, at the'contacts RA113, an obvious path for applying ground potential to the control conductor C128. The

,Y application of ground potential to the controlconductor C128 completes a circuit for energizing the winding of' the tone relay R1 |'5', this circuit extending from the grounded control conductor C128- by wayof the contacts- 128 and the winding of R1|5 to battery. When the winding of the tone relay R1! 5` is thus energized this relay operates shortly thereafter, this relay being of the slow-to-operate type. Upon operating the tone relay R1|5 completes, at the contacts 1|6, an obvious circuit for energizing the winding of the tone relay R120, thereby to cause the latter relay to operate shortly thereafter, the latter relay being of the slow-to-operate type. Upon operating the tone relay Ry completes, at the contacts 123, an obvious circuit for energizing the winding of the tone relay R125, thereby to cause the latter relay tov operate shortly thereafter, the latter relay being of the slow-to-operate type. Upon operating the tone relay R completes, at the con- Atacts 121, an obvious holding circuit for energizing the winding thereof and interrupts, at the contacts 128, the previously traced circuit for energizing the winding of the tone relay R1l5, thereby to cause the latter relay to restore. Upon restoring the tone relay R1|5 interrupts, at the contacts H5', the previously mentioned circuit for energizing the winding of the tone relay R120, thereby to cause the latter relay to restore.

Assuming .that the plugs associated with the transmitter 108 and the receiver 101 are inserted into the` associated jacks J106 and J105 at this time, a circuit is completed for energizing in series the transmitter 108 and the control relay R1|0.. This circuit extends from ground by way of the winding 102' of the repeater 10|, the jack 105 and associated plug, the transmitter 108, the plug and associated jack J106 and the winding of R1|0 to battery. When the winding of the control relay R1||1 is thus energized it operates to interruptl at the contacts 1| an obvious path

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