US1695043A - Telephone-exchange system - Google Patents

Description

W. T. HAINES ET AL TELEPHONE EXCHANGE SYSTEM Dec. l1, 1928. l1,695,043

Dec. 1l, 1928. 1,695,043. v w. T.. HAlNEs ET Al. TELEPHONE EXCHANGE sYsTEu Filed oct. 22. 1926 B'Sheet-s-Sheet 2 17 M Wfw Dec. l1, 1928. 1,695,043

w. T. HAlNEs ET AL TELEPHONE EXCHANGE SYSTEM Filed Oct. 22. 1926 8 Sheets-Sheet 3 Dec. 11, 1928.

w. T. HAINEs E1' AL TELEPHONE EXCHANGE SYSTEM y eu 4 .i w t w m, 4 N *e a j. fm m p .m 4/ e Qn M ,n Ns M w Filed Oo'rn 22, 1926 /fWe/i/U.-

Dec. l1, 1928. 1,695,043

. W. T. HAINES ET AL TELEPHONE EXCHANGE SYSTEMl Filed Oct. 22, 1 926 8 Sheets-Sheet 5 'ef/ WM- W Dec. 1l, 1928. 7 1,695,043

w. 'r. HAlNr-:s ET Al.

TELEPHONE EXCHANGE SYSTEM i Filed ow 22, 192e 8 Sheets-sheet e WMM A/fyf Dec. 11,1928. 1 1,695,043

W. T. HAINES ETAL TELEPHONE EXCHANGE SYSTEI Filed 00T'. 22. 1926 s Sheetssheet 7 Dec. ll, 1928. 1,695,043

w. T. HAlNEs ET Al.

TELEPHONE EXCHANGE SYSTEM Filed Oct. 22, 1926 B Sheets-Sheet 8 by W wm/y lateiiteclr Dec. 11, `1923.8.

unirse fsrrs WiLiirAM ai. irniirns.. on Meulan/iin onniien, New Jniisnrgsnin i-rari Tnnneiia'rri COMPANY, n.

, sienes 'ro if; nnnoritro correr conroisnfriori or NEW Yoan. Y

,TELEFOE-EXCHANGE iras, La

vii,as,04.3" perles.

assienon `ro .nianieronn 'riiiinriionn AND frio "on il' i Amacai-Oa and. ottenere-s, ieee.'y saliti iig.

This invention relates to telephone systems and has for its object to ieducethe number ot switching unitsfnecessary for the connec-v tion ot a particular manualoiiice with a given number of machine switching otlices. ,n

According to one aspect of the invention', there are provided a plurality of common equivalentli-nks, anyone of which is .associable inresponse to the operation oi any one of a plurality of keys with an 'operators position and isv controlled thereby to select a group of Ytrunks extending to one of apluallot a link circuit from a group serving the oiiice whose key has been operated. Thelink circuit then operates t f find the operators position. A relay 'operated under the control of the otlice key sets up conditions on conductors extending tothe link circuit' which operate a group ,of relays in a partie ular combination to initiate the operation of a trunk Ender having access to the trunks leading to the wanted office. lWhen an idle trunk has been selected, an indicationis sent back tothe operators position to inform her K of the number v l may insert the calling plug of her cord oiri' the trunk, ait'ter which she Y cuit'in the jack of the trunk. In theineantime, the link circuit has also associated a lsender withtheoperators position and the operator registers thenumbe'rfof the wanted line on the sender by means other numeri-A cal key set. After the completion of the registration her position is disconnected and she need pay .i'io'urther attention tothe connection unless signaled. y

The linkcircuit shown is arranged'to serve a maximumof eightoihces. If the number c of olces to which'access is desired exceeds eight, additional groups of links may be provided individual to other groups of oces.

the invention.v y Y y c `The operationof a system embodying the invention will bemore clearly understood"` y The operation of this key'` causes an .allot-ter switch to f Likewise, each link is preferably arranged to have access to a maximum ot twenty trunks to veach ot the eight oiicesjk 'Howeveigf since this total nuinbcrof trunks is a desir-f able maximum from atrailic standpoint, if Vthe average-number of trunks to a group fof otices exceeds twenty, less than eight oilices will usually be served by a particularv groupf of links. Similarly, it any one office requires approximately this maximum number 0i" trunks, a group of links will-be assigned to thatl one oiiice. It is, of course,fpo ssibleto" arrange link circuits of thistype toy disf criminate ybetween a larger number of oflicesl and to have accessto a larger number ofV trunks withouty departing from the spirit of from a consideration of thefollowingdetailed description in connection with the at-` f taoheddrawings in which,

Fig. 1 shows a manual operators lcord cir-ky cuit, a manual subscribers substation .and

a diagrammatic representation'of,switches` Fig. 3 vshows an allotter bymeans offwhich oneoi' a plurality of link circuits may be assigned 'for use;

Vat an automatic oice for completing a conY nection to a subscriber thereat;

Vrso i Figs. @and 7 showtheoperators'position equipment, ,Fien 6 showing the lamps an'dv' eontrolrelaysror indicatingthe number of v the selected trunk, and Fig. V2' showing a'plu.- p,

rality of oihce keys and the numerical keys ot the operatois position. A strap l(')rfb'ranch f line is connected to the left-hand contacts Vof 1 each oliice key in order to provide for a` second set of such office keys if required or a second Vgroup of common vlinks or switchvl ing devices. Likewisey the'straps or branchy lines associated with 'conductors extending from relay 730 yareincluded tor 'the same purpose. i lThe additional equipment required for operating a second set of common, links; is only the additional vset of office keys such.

as pllrto 718 inclusive and an additional re"- lay suohv'as 730. Thesecondv set-of keys is i60, same as the first set andthe, switching devices I arranged one. key per Vgroup ot trunks the orflinks are common to theseeond set of keys -W tionship of the parts of the system;

Fig. 9 shows the manner of arranging Figs. 1 to 7.

Referring firstto Fi r. 8, substation 800 appears at the central o ce in an answering jack before an operators position indicated at 801. Each operator is provided with a.

plurality of cord circuits and a plurality of outgoing trunk jacks leading to trunks Awhich extend to all ofthe ofiices to which the inanual office has direct connection. For use in establishing connections with machine switching oiices, her position is also pro vided with a trunk number indicator 802 and a key board 803 which includes both office and numerical keys. Each operator is served by a plurality of groups of link circuits three such groups being represented by links 804, 805 and806 respectively, each group having access to a particular group of distant ofiices. Eaclrgroup of links is reached through an allotter such as allotters 807, 808 and 809 which serves to insure the use of the links of the group in rotation and may be `controlled Y by a large number of operators. Each link circuit is provided with operators finder switches such as switch 810and a sender selector such as 811. If the number of operators exceeds the number accessible bythe finder of one link, the groups of links and operators positions are subdivided and an allotter provided for each subdivision. The link circuits are substantially Vot" the,` same arrangement, except formodifcations to care for the size of the trunk groups to which they have access. Link 801.1L for example, is represented as individual to a single office witha master switch 812 and trunk finders 813 and 814, both having'access to trunks leading to office 815. Link 805 is provided with a plurality of trunk finder switches 816 and 817 by means of which access may be had to offices 818 and 819 respectively. Link 806 is indicated as having access to a. plurality of offices, each oflice being served by a large number of trunks with master switches 820 and 821 to give access to a plurality of trunk finders 828 and 824, 825 and`826, which finders have access to trunks leading to oflices 827'and 829 respectively. The operation of an oflice key sets up a. registration in an associated link circuit which discriminates between trunk finders, such as finders 816 and 817 or between master switches such as switches 820 and 821-to cause `the selection of a trunk to the proper office. Each link circuit serves to interconnect the operators key set, a sender,

and the trunk outgoing to the wanted ofiice, to indicate to the operator the number of the trunk and to control selections over the trunk. rl"he talking circ-uit, however, is independent ofthe link, which reverts to common use.

Detailed description.

through lamp 105, resistance 111, sleeve con-r tacts of plug 100and jack 104, winding of cutoff relay 107 to ground. Relay` 107 operates in this circuit and opens the circuit of relay 101, extinguishing lamp 102.

As soon as plug 106 is inserted in jack 104, a circuit is closed from battery through the lower .left winding of repeating coil 108',

winding of supervisory relay 109, ring confacts ot' plug 10G and jack 104, over the subscribers line through the substation 100, back4 to the tip conductor of ack 104; and plug 106, upper left winding of repeating coil 108 to ground. Relay 109 operates in this circuit and connects battery Vover its front contact through resistances 110 and 111 to the sleeve contact of plug 106 shunt-ing lamp 105 and preventing its lighting.

The subscriber then informs the operator of the number of the wanted subscriber, whereupon the operator depresses a key at her position corresponding to the wanted office. l

Assuming that the wanted office is a machine switching oflice and is the one to which the key 711 corresponds, the operation of that key closes a. circuit from ground over the left contact of key 711, upper winding of relay 7 21, left back contact ot relay739, winding of relay "40 to battery. Relays 721 and 7 40 operate in this circuit. A circuit is also closed from battery over the back contact of relay 7 32, left winding of relay 741, right winding of relay 730, over the right contact oit key 711 l to ground atthe right back contact of relay Relays 7 41 and 730 operate in this circuit.

The operationwof relay 741 closes a locking circuit for relay 740 which extends tliirough the winding of relay 739 over the front con tactof' relay 740 to ground at the inner right front cont-act of' relay 741. Relay 739 does not operate as long as key 711is held operatedbut as soon as the operator releases the key, it operates, removing the operating battery from relay 721 and the operating ground `from relays 730 and 741. However. relay 741alse closes a locking circuit for relay 721 extending from battery through the lower winding and lower front contact of relay 721 to ground at the inner right front contact of relay 741. In addition `it closes a locking circuit for itself and relay 7 30extending as previously traced through the windings of these relays, over the inner right frontcontact of relayA 730, right back contact of relay 731 to ground at 1the outer right front contact of relay 741.

Relay 741 also closes a. circuit from battery over its left Contact, back contact of relay 744,

through lamp 745to ground at the left back contact of relayy 746. l rIhis lamp p remains lighted steadily until a sender is ready to re-V ceive the number of `the called subscriber.' Relay 741 likewise closes a circuit from battery over its left contact, through lamp k636v to ground at the outer leftback contact ot' relay 620. This lamp remains lighted until an idle trunk has been foundleading to the wanted oiice. v

Theoperation of rela-y730 removes ground from conductor 419 tomark this position as ances 309 and 310 form two arms, so as to' cause relay 308'to operate.

The operation yof relay 308 I'closes a circuit from battery over its vfronticontact-through the right winding of relay 311 to ground at the 4back contact of relay 312. Relay 311 operates and .closes a circuit. from ground through the winding of relay 312, yinner left front contact, left lwinding andouter left front contact of relay 311tobattery at the inner right back ,contactof relay 313. Relay 312 operates in this circuit opening'the ground at its back contact to preventthe. operation of other relays similar to relay 311 and the use of the allotter until the allotted link circuit has been started intooperation. l The `operation of relay 312 also closes 'a circuit from ground overv its front contact, left back contact oi relay 313, outer right iront contact of relay 311, brush 306 and itsassociated i Contact, winding of relay 408 in the link circuity to battery. Fora more complete descrip'- tion of the allotting arrangement reference is made to U. S. Patent 1,513,362, granted to L. M. Allen, October 28, 1924.

Relay 408 operates and locks over its outer l right front contact to ground at the back contact oirelay 413 to .initiate the operation of the link circuit.' It also connects battery'over" right back contact of relay 414, leftback contact of relay 415, resistance 416, contact j417l of jack 418,` conductor 457, contact 508 of jack 509, conductor 5.29 inner left front contact of relay 408 to `ground through resistance 310 and through windingot relay 30,8and resistance 309. This circuit balances thecircuitv previously traced through to the opposite side oi' relay 308 and causes that relay to .release. lRelay 311, however, does not release, since it is lheld operated in the locking circuit previously traced. f f

Relay 408 in operating also closes `a circuit from battery through the 'winding of relay 409,v andfin parallel therewith from battery through the right winding ot relay 510, lett backcontact of relay 410,.inner right front contact of relay 408 topground. Relay 409 operates and locks over its inner right Jfront contact, right back contact of relay 516, inner right back contact of relay 517 to ground at the left back contact of relay 414. Relayf 510 locks through its leftwinding and vinner' left contacts to ground at the inner left back 1 Contact of relay'516'. 'l

Relay 409 in operating closes a circuit vfrom ground over its middle rightfront contact through the winding of relay 410 to battery.V Relay 410 operates opening the energizing ycircuit of relay 409 and locking over ritsinner lefti'front contact to ground at the inner right v front contact of relay 408. The operationoi relay410 connects` ground over its outer right frontcon'tact, conductor 5 13, contact 511 of jack 512, .conductor 317 brush301 of the aly' lotter switch, left back contact ofrrelay 314,1.

to the winding of relay 313 and battery. Relay 313 operates, opening the' Vholding circuit of relay 311. It also closes a circuit from battery through winding and back contact oi magnet 307, left rontcontact ofree lay 313 to its energizing ground Magnet 307 operates in this circuit and steps the brushes of the allotter switch tothe next set of terv minals. As soon as brush 301 leaves the terminal vconnected to conductor 317, relay 313 releases. The allotter circuit is now ready to allot another link circuit for subsequent calls. Relays 314, 315v and 316'and interruptor 322 provide timed operating means for relay 313, to advance the allotter-.it the link fails toldoso. When relays7 31 andj415L operate as will be `described hereinafter, the battery arms of the lheatstone bridgeare opened in the same order as they are closed.

the right winding of relay 411', leftback con` tact of relay-412`to ground at the inner right front Contact of relay 410.v Relay 411 oper` ates and closes a circuit from battery through the winding of relay 412, inner right front .Contact oil" relay 411 5to ground. VRelay 412" operates after an interval and closes a hold-V ing circuit for itself overits left frontlclom .tact to ground attheinner righty front con-f tact kof relay-410 and opens the energizing circuit of relay 411. VThis relay, however,cl`oses Since relay-308 is polarized this momentary a holding circuit for itself extending through its left Winding and left front contact, outer left front contact of relay 408 to brush 401.

With position finder 400 normal, this circuit extends over the normal contact of brush 401 to ground at the middle right front contact of relay 408. All positions other than those seeking the use of a link circuit Will have ground connected to the conductor appearing in the terminals of brush 401. Therefore, relay 411 will be hel-d operated as brush 401 moves over its bank until the calling position is found. Relay 411 also closes a circuit from ground over its outer right 1 front contact, outer right front contact of relay 412, middle left front contact of relay 408, back contact and Winding of the position finder stepping magnet 407 to battery.

Magnet 407 operates interrupting its own circuit, and advances the brushes of the position finder in search of the calling position. Vhen that position is found, battery will be connected to the terminal of brush 401 from the back contact of relay 732, left Winding of rela 731, left front contact of relay 7 30, and condllctor 419. Therefore, relay 411 cannot remain energized and it releases :to extend the circuit just traced over the outer left front contact of relay 408, left 'back contact of relay 411, Winding of relay 431, inner left front contact of relay 409, inner right front contact of relay 412, to ground at the middle right front contact of relay 409. Relays 731 and 431 operate in this circuit, relay 731 locking in a circuit from battery through its right Winding and right front contact to ground at the outer rightfront contact of relay 741. The operation of relay 731 opens the original holdin g circuit for relays 741 and 730, but they are held operated in a circuit from battery over the back contact of relay 732, right winding of relay 741, left Winding and inner left front contact of relay 730 to ground over conductor 419.

The operation of relay 431 closes a circuit from battery through the Winding of relay 415, contact of relay 431, left back contact of relay 414 to ground. Relay 415 operates and closes a locking circuit for itself through the Winding of relay 414, right contact-of relay 415, left back contact of relay 517 to ground at the inner right front contact of relay 510. It also closes a circuit `from ground through the Winding of relay 432, left front contact of relay 415 to battery at the right back contact of relay 414. Relay 432 in operating extends a pair ofV conductors from the link circuit to the position circuit for the purpose of initiating the operat-ion of the proper trunk selector. Relay 432 also supplies battery for the operation of the recording relays. One of the recording relay circuits may be traced from battery over the inner left front contact of relay 432 through the winding of sensitive relay 427, Winding of marginal relay 428, left back contact of relay 435, outer right front contact of relay 432, conductor 434, to brush 402, conductor 734, left back contact of relay 720, conductor 736 and thence to contacts of certain of the office relays. The second circuit extends from battery over the left front Contact of re lay 432 through the Winding of sensitive re'- lay 429, Winding of marginal relay 430, right back contact of relay 435, middle right front contact of relay 432, conductor 433, to brush 403, over conductor 733 to the inner left back contact of relay 720, conductor 735 to other contacts of the oilice relays. The office relays 721 to 728 are arranged to connectl conductors 735 and 736 Vto ground through a low or a high resistance in various combinations to operate relays 427 to 430 in corresponding combinations. i

Since relay 721 is operated, conductor 7 36 is connected over the upper contact of relay 721 to ground through the low resistance right Winding of relay`7 29 and conductor 735 extended over the lower upper front contact of relay 721 to ground through high resistance 747. Ilherefore, relays 427, 428 and 429 will be operated. A circuit will thereupon be closed from battery at the left front contact of relay '432'over the outer left back Contact of relay 435, front contact ofv relay 429, left front contact of relay 427, right back contact of relay 430, left front contact of relay 428 to conductor 436 and thence through the right Winding of relay 230 to ground through the left Winding of relay 519. i Similar circuits may be traced for other operated combinations of relays 427 to 430 Which lead to other `trunk finder switches which have been indicated diagrammatically by the rectangles 450 to 456 inclusive.

Relay 519 operates in this circuit-and after an interval connects ground over its front contact to its left Winding and the circuit above traced, thus increasing the 'current flow in the right winding of relay 230 to operate that relay. As soon as relay 230operates, it closes a holding circuit for itself and `an operating circuit for relay 231 extending from battery through the Winding of relay 231 and from battery through the left Winding of relay 230, inner left front contact of relay 230, conductor 513 to ground at the inner right front contact of relay 510. y

Relay 729 operates in the circuit above traced through its right Winding and closesa circuit from ground over its right front contact through the Winding of relay 748, to battery at the left front contact of relay 7 41. Relay 748 operates and locks to ground at the inner rightfront contact of relay 741.

Assuming that master switch 200 is standing in its tirst operative position, that is, position 4, and hence is controlling trunk selector 210, the operation of relays 231 and 230 closes a circuit from battery through the Winding y ground connected to thetermina'l of thisl and back Contact yof stepping magnet 217 of selector 210, brush 202 in position 4, middle left contact of relay 231, inner vright back contact ot relay 520, left` front contact of relay 510, Windi ng of relay 521, to ground at the inner right .iront contact of relay 510. A circuit is also extended 1n shunt of the Winding ot relay 521,0ver the .bach contact oit 're-` lay 521, `outer leit back Contact of relay 520 outer left front contact of relay 230, through brush-203 in position 4, over the brush 2110i' trunk linder 210 to the trunk circuit connected to theterminal on Which thebrush 211 isv standing.

A busy 'trunk will be characterized by brush and Will cause the energization of stepping magnet 217, While shunting the Winding ot relay 521, and the advance of the trunk iinder to kthe' next trunk. JAssuming that none ot the trunks connected to vsvvitch210 are idle,brush 215 will be advanced to posi' f tion 21 Where a circuit will be closedk from switches.

battery through the Winding of magnet 217, brush 201 inposition 4,'brush 215 in position 21, middle right front contactot relay'231,

conductor 543 to ground at the outer left contact oi relay 437 Magnet 217 4will be held operated in this circuit. At the same time a circuit is closed from .battery through the Windingof lrelay 239, 4brush 204 in position 4, brush 216 in position 21, outer right front conta-ct of relay 231, 4conductor 544, to ground at the innerleft contact oit relay 437. Relay 239 operates and extends ground over its front contact to the back contact. andzvvinding of magnet 207 and battery, operating magnet 207 to advance the master selector' to position 5. .The grounded condenser oonnected to the lett contact vof relay 239 'serves to protect the terminals of brush` 201 While switch 200 is advancing.

As soon as switch 200 leaves position 4, the holding circuit ott magnet 217 is opened and lthe switch 210 advances toposition 22, Where it remains yuntil switch 200 reaches position 12 or returns to position 4, positions 4 and 12 being multipled together.V Vilith switch 200 in position 5, a circuitis closed yfrom battery through the Winding and back contact oit? magnet 227, brush 202 in position 5 and thence as previously traced through the Winding of relay 521, the shunt circuit non7 en`V tending through `brush 221.

Vhen Yan idle trunk is' found no ground will be connected to the terminal of brush 221 and relay 521 Will be able to operate in the 4circuit traced tor it, While magnet 227 does i not operate in seriesvvith tl atqrelay. r)The operation of relay 521`conneots ground over its right front contact to brush 221, marking the trunk y busy to other trunk hunting Under the conditions assumed in the drawing', the tiret idle trunk encountered was trunk No. 29, which is shown in full; The

trunk groups begin to number from 0,v hence ther irst trunk on switch 220 Will beNo. 20, and the tenth trunk No. 29. It now ybecomes vnecessary to give the operator 'an indication of the number of this trunk. For this purpose the operation of relay 521 closes a circuit y*from battery through the Winding ot relay 437,1eitt front contact of relay 432, inner leit front Contact ot relay'521 to ground oper-A ating relay. 437. With relay 437 operated, a

circuit isolosed rom'battery over the inner lett `front contact of relay 432, Winding of f relay 435 to ground at the outer left front 'contact of relay 437.k Relay 435 koperated transfers the circuit tracedover conductors 433 and 434from the windings'of'relays'427` to 430-to conductors 443 and 444 respectively. Conductor 443 is extended over the lett back contact ot relay522 to conductor 533, inner f lett front Contact ot relay 231, conductor 233 v to brush 205, and conductor 444. is extended over the right rback contact-ot relay 522, conductor 534, inner right front Contact of'relay' 231 to brush 206. r, ,y

- This transferfopens the circuity ot relay 729 permitting that relay to release and-close a l lcircuittrom ground at vits. back contact over back contact of relay 620, right Winding of sensitive relay 623, resistance 624 to battery'.

The circuit of these: relays is completed over brushes 205 and 206 to .ground through loW or high resistance in accordance With the position occupied by master selector ,200, The brushes being in Vposition 5,'under the` present assumption, the circuit of relays 622- and 621 extends over brush 205, conductor 236, lot-v resistance'le'tt Winding of relay.523

to groundand that for relay 623 extends over brush 206, through thehigh resistancef right.

ivindingot relay 523 to ground. Therefore relays 621, 622 and .623 are all operated.` These relays lock through their left windings;`

to ground at the right contact of relay 7 41. l

The operation of relay 623 also closes an obvious circuit 'for relay 625, which relay closes'a circuit tor relay 620, butrelay 620 is,

slow to operate to provide sui'iicient time fforf j relays 021 to 623 to establish their locking cir cuits. y Relay 620 in operating disconnects conductors 737 and 738 romrelays 621 to 623 andconuects there over the left front contact of relay 620, left back contact of relay 626, right Winding of sensitive relay 627, right Winding of marginal relay 628v to ground, and over the right front Contact ot relay 620, right back contact oit relay 626 to ground through the right Winding of sensitive relay 629 respectively. Relay 620 also extinguishes the no-trunk lamp 636, indicating that a trunk has been found and the indication of the trunk number is being prepared.

Relay 523 in operating closes an obvious circuit for relay 524 which locks over its right front contact to ground at the lett front contact of relay 437. lVhen relay 620 operates it extends conductors 737 and7 38 to ground instead of battery, thereby releasing relay 523 to close a circuit from ground over back contact of relay 523, front contact of relay 524, winding ot relay 522 to battery. The operation of rela 522 disconnects conductors 443 and 444 from brushes 205 and 206 and extends conductor 443 over its left front contact to conductor 543, middle right front contact of relay 231, to brush 225, and conductor 444 over its right front contact, conductor 544, outer right front contact of relay 231 to brush 226 respectively.

lith switchl 220in position 10, conductor 543 is extended to conductor 243, left Winding of relay 525, left normal contact of relay 526, right front contact of relay 522,1eft rontcontact of relay 521, to battery at the inner left front cont-act of relay 432. Conductor 544 is open in this position. The resistance of the left hand Winding of relay 525 being high only relay 627 of the indicator is operated. Relay 525 also operates in this circuit.

The operation of relay 627 closes a circuit for relay 630 Which in turn operates relay 631 and in turn operates relay 626, thus extending conductor 7 37 over the lett front contact of relays 620 and 626 to battery through the windings ot relays 632 and 633, and conductor 738 over the riglit trontcontacts o relays 620 and 626 to battery through the windings of relays 634 and 635.

The operation oit relay 525 closes a circuit from battery as previously traced to conductor 527 over the let't normal contact ot relay 526, lett trout contact of relay 525.` winding of relay 526 to ground at the lett front contact of relay 437. Relay 526 closes a holding circuit for itself, opens the circuit ot relay 525 and connects ground overits left front Contact to the left back contactof relay 536, right back contact of relay 525 to conductor 543 and thence to conductor 737 and the Wind ings of relays 631 and 632.

lith relays 631 and 632 operated the lighting circuits `for the indicator lamps are closed and these may be traced from battery over the left back contact ot relay 634 through the No. 2 tens lamp, right front conta-ct ot'rrelay 622, right front contact of relay 623 to ground at the left front contact of-relay 626, and

from battery over the inner left front contact o'tf relay 633, through the No. 9 units lamp, lett back contact of relay 628, right front contact of relay 627, right back contact of relay 629 to ground at the left front contact of relay 626 indicating to the operator that the trunk No. 29 was the one ot those outgoing to the Want-ed ottice which has been selected. The trunk indicating arrangement is substantially the same as that described and claimed in application of H. W. MacDougall, Serial No. 715,511 tiled May 24, 1924.

ln the meantime, the operation of relay 510 closes a circuit from ground over the left back Contact of. relay 516, inner left front contact ot relay 510, contact 514 of jack 515, lettnorinal contact of relay 421, lett Winding of relay 420 to battery. The operation ot relay 420 closes a circuit for relay 421 at the inner left front contact 'of rela-y 420. Re'- lay 421 is slow to operate but upon closing its inner lett front Contact `locks to ground over the front contact of relay 510 yand the inner lett back contact of relay 516. Relay 420 closes a circuit from battery through the winding and back contact of sender selector magnet 507, inner right front contact of relay 421 to ground at the left front contact of relay 420. Relay 420 closes a holding circuit for itself through its right Winding and inner right front contact, outer right front contact ot relay 510 to brush 506.

It the sender, to which switch 500 has access in the position it `then occupies, is busy, ground Will be connected to brush 506 and relay 420 held operated to cause magnet 507 to advance the sender selector to the next sendtr. ,its soon as an idle sender is reached` ground Will be removed :tromv the terminal of brush 506 andL battery will be connected thereto from the sender, in consequence of Which, relay L1.20 released and closes a circuit 'frein this battery over thebacl; contactof relay 420, through the winding ot relay 422, lelt front contact-ot relay 421, lett back contact ot relay 518 to ground.

Belag' 422 closes a circuit from ground at its 'trent contact. lcl'tback contact ot relay 439, whirling et relay/423 to battery; Relay 423 locks in series with relay 43) over the outer right front Contact ot relay 423 to `jround at the inner right contact ot relayV 510, be' "clay 431) does jnot operate as liuig as relay 422 riufuains operated. Relay 423 closes` a circuit from battery thrinigh the winding ot relayl-BS. inner lett Jfront contact of relay 432, inner right front contact ol re lay 423 to ground at the outer right bach contact of relay r)17. Relay 438 extends three circuits lroin brushes 404, 405, and 406 of the position finder to brushes 503, 504, 505 respectively whence they are extended to the sender ters. Relay 423 also closes a circuit from battery through the winding of relay 232, outer `lef-t front contact of relay 231,

tact but ground is temporarily maintained on that conductor from the outer right front contact of rela 410, which is held operated to ground at t ie front contact of relay 408. Relay 411 is reoperated over the back Contact of relay 409 and the inner right contact of relay 412 to ground over the iront contact of relay 410 andthe inner right front contact of relay 408. y

The operation of relay 411 again Closes the operating circuit for stepping magnet 407 which now advances'position finder 400 to po sition 21. At this time a circuit is closed from ground through the winding of rela-y 413, Contact 441 of jack 418, 20th terminal of brush 401, outer left front contact of relay 408, left `front contact of relay 411 and winding of relay 411 to battery. Relay 413 now operates and removes the holding ground from relay 408 which releases in turn releasing vrelays 410 and 411 and 412. The release of relay 410 connects ground over its inner left back Contact to the winding of relay 413 causing that relay to release. This ground is also extended over brush 401 in position 21, and the back Contact of relay 408, to the back contact and winding of magnet 407 to step switch 400 back to normal. Y

The releaseofrelay 510 opens the locking circuits 'of relays 415,423 and 439, 517 and 518 and 232, which in turn permitthe release of relays 537, 435, 524, 526 and 432. The link circuit has new been completely restored to normal. i

If the operator depresses the wrong otlice key, she may correct it by operating the right key prior to the progress` of the link circuit tothe point where relay 230 locks. It will be remembered that the operation of an oilice key operated relays 740, 741 and 730. The release of the key permits relay 7 39 to operate in the locking circuit of relay 740. At this `time the depression of any other oice key will close a circuit from ground over thelett contact of that key through the upper wind-` ing of corresponding relay over the front contact of relay 7 39, to the Winding of relay" 732 and battery. Relay 732 in operatingr disconnects battery from relays 741 and 730, in turn removingr battery and ground from the remaining circuits ofthe position and releasing the oilice relays. Relays 740 and 789 also release` opening the circuit of relay 732 and restoring the position circuit to register the operation of the second otliee key. It the call is to be wiped-out altogether she may operate .key 719. operatingr relay 732 `toidestroy the registration.` Since no office key operated when relays 739 and 740 release, no registration is made. i

If the operator starts to operate the numerical keys before the sender has been attached to the link as indicated bythe operation of relay 744 and the extinguishing of lamp 745, the'corresponding digits will not beregiste'red. lith relays 744 and749 not opera-ted, the operation of any one of the numerical keys closes a circuit frombattery, through the left winding of relay 746, right back contacts of relay 749, overthe left contact of the key `to direct ground either at 756 or at the inner left back Contact ot' relay 749. Relay 746 locks through its right Winding to ground at the inner right front contact of relay 741. It also transfers the circuit of lamp 745 to ground through interrupter 757, causing lamp 745 toflash, to inform the operator that she has operated her numerical keys prematurely.- In addition, it opens the circuit of relay 744, preventing the establishment of the registering circuits from the key set710to the sender. In order to properly register the number, the operator must now operate an ofiiee key or Vthe release key 719, operating relay 732. This relay releases relay 431, permitting the operation of relay 414 in the locking circuitrof relay 418. Relay 414 operates relays 516 and 539 to completely release the link. Theoperated oiice key will cansethe allotment of another link.

Relays 540, 541, 542 and 548 provide means for automatically disconnecting a link circuit which fails to complete its operations in a given length of time;

The position of Fig. 7 is shown equipped with a set of keys permitting the selection of '8 ofiices. It will, of course, be' understood that it may also be provided with a second `set of keys for controlling the se- 100 lection of another-,group of eight offices and i it may likewise be provided `with arplurality of keys which havean entire group of link circuits individual thereto. The link ciry cuits serving trunks leading'to only a single 105 appear that the group of trunks correspond- U5 Y ing to key 711 numbers 80. The remaining trunk groups will, therefore, average ap# proximately 10trunksiper group, if the pre ferred number of trunks, namely 160, is served by these links. InV practice `trunk l2 groups differing so largely in size would probably not be employed. Instead 2 trunk groups of approximately 80 Atrunks each might be grouped together and two office keys with their corresponding relays employed to `discriminate between the two groups. There eight grous of trunks are served by one group of lin circuits, trunk groups approximating 20 trunks apiece would in all probability be selected. lThe 13 completeset of keysI and a-large-trunk group have beenshown in order to illustrate theu operation-more completely. The following table indicates the relationship between the ,oilice keys oit a group,the combination of resistances applied to conductors `735 and 736 7 relaysoil the group 427 to 430 and the ofiice switch corresponding to each other:

Indicator relays i Ground to conductor '.1'35-736 Keys. Relays. through Switch.

7u n 72i nigh resLowresfgi. 200

715 725i Lowresr. Highres i 453 72o Highres. High res Low res v ;.Q f

High res i That is claimed is:

1. In a telephone exchange system, incoming lines, a plurality of groups of trunk lines, operators positions, a plurality of operators devices in each of said positions, one of said vdevices foreach group of trunk lines, a group of switching devices common to said loperators devices, Vmeans responsive to the actuation oi any one of said operators devices to cause an idle one of said switching devices to select a particulaigroup of trunks and an Vidle trunk line in said group, and means in-k said operatorspositions for connecting incoming lines to trunks selected by the actuation of said operators device.

ing lines, a plurality of groups of trunk lines,

f operators positions, a plurality of operators devices at eachk of said positions, one of said devices for each group of trunk lines, a group ofv equivalent switching devices common to said operators devices, means responsive to the actuation of any one of sai-d operators 'devices to associate an idle one of said switching devices with said operators devices, means to identify the group of trunk lines corresponding to said actuated operators device, means to cause said switching device to select an idle trunk line in the identified group, and means in said operators positions for connecting incoming lines to trunks selected by the actuation of said operators device. 3. In a telephone exchange system, a plurality of groups of trunk lines, operators positions, a plurality of operators devices at each of said positions, each device correspending 'to a groupof trunk lines, a group of equivalent link circuits, a plurality oit' switches each having access to one of said groups-ottieni; lines, meansresponsive to the actuation Vof one of said operators devices, to

associate van idle link circuit with saidfdevice,

means under the control of said actua-ted del vice to select a switch having access to the corlresponding group of trunk lines, and means toopei- .te said switch to select an idle trunk vline in said group.

4. In a telephone exchange system, a plurality of groups oi' trunk lines, operators positions, a plurality ofoperators keys at yeach of said positions,one of said keys for each group of trunk lines, a group` of equivalent switching devices common `to said operators keys, means responsive to the actuation of any7 one of said' keys to` associate an idle one of said switching devices with said keys, a pluiality of relays, means tooperate said relays in various combinations under the control of said` actuated keys to identify the group of; trunk lines corresponding to said actuated keys, and means-to cause said switchingV device to select an idletrunk line in the identitied group.

5. In a telephone exchange system, alplurality of groups oftrunklines, operators positions, a. plurality of operators devices in each'of said positions, one of said devices for each group of trunk lines, agroup of equivalent switchingdevices common to said operators devices, means responsive to the actuation of any one of said operatorsdevices to vices with said operators devices, a group of .f sensitive and marginal relays, means to op- .associate an idle one of said switching deerate said relays in various combinations under the control of said actuated devices'to identity the grou-p of trunk lines corresponding to said actuated operators device, and

means to cause 'said switching device to select l an' idle trunk line in the identified group.

2. In a tele hone exchange s stem incoin- V6. In a. telephone exchange system, a plurality oit groups of trunk lines, operator'spositions, a plurality of operators keys at each of said positions, each key corresponding to a group of trunk lines, a group of equivalent` link circuits, a plurality of switches each having access to one of said groups of -trunk lines, means responsiveto the actuationof one `of 'said operators keys to associate an V'idle `link circuit with said keys, a plurality of reot said groups of trunk lines, means responsive to the actuation of one of said operators devices to associate an idle link circuit with said devices, a group of sensitive and marginal relays in said link circuit, means to opcrate said relays invarious combinations under the control oft said actuated device to sclcct a switch having access to the corresponding group ot' trunk lines, and means to operate said switch to select an idle trunk line in said group.

8. In a telephone. exchange system, a plurality of groups oftrunks, operators positions.; one operat-oifis device for each group of trunks in each of'said positions, a group of switching devices common to said operators devices, groups of trunk selecting switches, and means responsive to the actuation of any one of said operators devices to select an idle i switching device, to select a trunkselecting 201 switch in a particular group and to select an idle trunk in saidv group.

9. In a telephone exchange system, incominglines, a plurality of groups oftfrunks, an operators position, one operators device for each group of trunks in said position, a group of switching devices, means responsive to the actuation of any one of said operators devices for select-ing an idle one of said switching' devices and to cause said switching device to select a particular group of trunks and an idle trunk in said group, avisual signal to' indicate the trunk selected, and meansto con- Vncct an incoming line to said indicated trunk.

trunk in said group, and means for having connected at the same time a plurality of lines to a plurality of trunks of the same group selectcd responsive to successive actuations of'V the same operators device.

In Witness whereof, We hereunto subscribe our names this 19th .day of October A. D.,

WILLIAM T. HAINES. ROBERT W. HARPER.

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