US2203725A - Telephone system - Google Patents

Description

June 11, 1940. 1. GEITGEY TELEPHONE SYSTEM Filed Aug. 1a, 1938 5 Sheets-Sheet 1 NRN E3 5: EEEQ E IN VENTOR. 6

2,4 ATTORNEY? June 11, 1940. I. GEITGEY TELEPHONE SYSTEM Filed Aug. 16, 1938 5 Shets-Sheet 2 wk? TR IN VENTOR.

v GA w R M w 6E um. NQ am I TE M 8% Stu mfim IR VIN GE/TGEY W ZA l. GEITGEY TELEPHONE svsma Filed Aug. 16, 193s June 11, 1940,

5 Sheets-Sheet 3 INVENTOR.

IR VIN GE/TGEY- 1 Z] ATTORNEY.

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Jun; 11, 1940. LGEITGEY TELEPHONE SYSTEM F'iled Aug. 16, 1938 5 Sheets-Sheet 5 INVENTOR. IPVIN GE/TGEY I ATTORNEY;

Patented June 11, 1940 T OFFICE TELEPHONE SYSTEM sIrvin Geitgey, Elyria, Ohio, assignor to- Associated Electric Laboratories, Inc., Chicago, 111.,

a corporation of Delaware 1 o Application August 16, 1938; Serial No. 225,165

19 Claims. (01. 179-27) This invention relates to telephone systems in general, but is concerned more particularly with toll switching arrangements for handling toll or long distance traflic between two toll exchanges.

The object of the invention is the provision of circuit arrangements whereby the toll operator at either toll exchange may extend and complete connections to calledlinesin the other tollexchange without the assistance of the other toll operator. 1 l The presentinvention may be considered as an improvement to the circuit arrangements dis:

closed in the Crocker et a1. Patent 1,883,589, 'issued October 18,1932, in the method and appa-. ratus for extending and completing toll calls from one-toll exchangeto a second toll exchange. In

1 the present invention, when a toll call isreceived by a toll operator inone of the toll. exchanges for a subscribers line located in the second toll exchange; the toll operator directly completes the atoll connection overautomatic switchesin bothexchanges to the called line without the aid of the toll operator at the other. exchange. .The

circuits and apparatusalsojprovide the originating toll operators with complete supervision over the extended connection. One of the features relates to improved repeater circuits for extending calls to the distant toll exchange and for translating reverse battery supervision over the interexchange trunk line to high resistancesupervision. Another feature relates to the improved repeater circuit for controlling automatic ringing and manual re-ring of the called party. .1 The foregoing featurestogetherwith others no specifically mentioned will be described in connection with the description of the. operation of the invention, reference being had to the accompanying drawings, comprising Figs. 1 to6, inclusive. The drawings show by means of the usual circuit'diagrams when considered in conjunction with the Crockerfet a1. Patent 1,883,589 andthe WicksPatent 1,315,444; issued September 9,1919,

. the essential equipm ice switching system. n g o 3 .Fig. l correspond's topart of the inward toll operators position. and link circuit shown in Figs.

. 2 and 301: Patent 1,883,588,,the relays,1keys, conent for a complete toll servductors, and contacts having the same numerical characters as in that patent!" Onlysufficient circuit details of this patent areshown inthe draw .ingsto enablethe invention to be fullydescribed and understood, it being understood that thereon- 1 ductors 340 and 344 correspond to the conductors overwhichthe toll operator receives the incoming call.

connector Cl and a subscribers line Tl.

Fig. 2 shows theselector S, which corresponds to selector S shown in Fig. 4 of said patent, and

mally accessible overthe two-conductor trunk line from thedistant toll exchangeby way of normal connections in therepeater shown in Fig. 2, and is taken into use on calls originating from the distant toll'exchange. This selector repeater isv of the well known type of Strowger Vertical-and rotary switch which operates its shaft and wipers in a vertical direction to select a group and then automatically rotates the shaft and wipers u-ntil an idle switch in the selected group is reached; This selector repeater has access to toll transmission selectors such are are diagrammatically shown in Fig; land more fully shown in Fig. of Patent 1,883,589, and repeat impulses thereto. o Fig. 4 diagrammatically shows a toll transmis- I sion selector TTS and a toll connector T corresponding to the toll transmission selectorTTS and the toll connector C shown in Figs. '7 and 8 of Patent 1,883,589; Switch TTS has accessto groups of connectors such .as C and these connectors have access to subscribers lines such as '1'.

Fig.5 shows a toll selector repeaterin the distant toll exchange terminating the trunk line conductors 5'15 and 516. This toll select0r 1 repeater is also of the Well known Strowger vertical and rotary type and has access to selectors, such as selector SI shown in Fig. 6, by way o f itsj wipers. A portion of the circuits of this tollselector repeater terminate in the toll board, shown toathe right, and is usedby the toll operator in this distant toll exchange to. extend outgoing toll calls over conductors 515 and 516. Fig. 6 diagrammatically shows selectors SI and The selector Eil and connector Cl are similar to the selectors and connectors shown and described in the Wicks Patent 1,315,444, issued September-,9,

1919. Incoming calls to this distant toll exchange are extended over the trunk line conductors; to 50- the toll selector repeater of Fig. 5 which operates and repeats impulses to the selectors! and .con-

Outgoing calls from this distant exchange are 55 sumed that the toll operator has received and the toll selector repeater over the trunk line conductors 515 and 515 to the incoming selector repeater of Fig. 3 and through the toll transmission selector TTS and connector C to the called line- Having briefly. described the apparatus comprising the invention, the detailed description of the operation involved in setting up the various calls will now be given.

. Outgoing calls I Calls to the operators position of Fig. l are received and handled in the samemanner as described in the Crocker et al. Patent 1,383,589. In order to describe an outgoing call it will be asanswered a call and that the calling partyis now connected to the trunk comprising conductors 349 and 344. After the toll operator has ascertrained that the toll call is to be extended to subscriber Tl in the distant toll exchange, the key K3 is operated. I 1

I In response to the operation of key K3 in Fig. l relay 35! isenerg'ized over the following circuit: from ground by way of 'contact 234, spring contacts 389 of key K3, and through the upper winding of relay 35I to battery. Relay 3354!, upon energizing, at contacts 353 completes a locking cirv cuit for itself and an energizing circuitfor relays 352 and 203 as follows: from ground through the winding of relay 233, conductor 2H2, springs 3920f key K3, winding of relay 352, Contact 3st,

and the'lower winding of relay 35!, to battery. Atcontacts 358 and 363 relay 355 disconnects the incoming trunk conductors 343 and 344 and prepares a point in'the dialing circuit for extending the connection. Relay 352, upon energizing, at contact 366 prepares'a circuit for relay 354, and at contact 361 prepares a lockin circuit for relays 293, 35I, and 352 independent of key-K3. Relay 233, upon energizing, at contacts 230 and 23! connects up the operators headset and at contacts 234 opens the original energizing circuit of relay 35!, which relay, however, is'lo cked energized over its lower winding as previously described; The toll operator may now converse with the calling subscriberbyway of contacts 233, 23!, conductors 223 and 220., contacts 35'! and 355, and over conductors 343 and.

344 to the calling party. After receiving the telephone number of the desired called party, the toll operator will operate the calling device D and dial the digits of the called subscribers line.

' In response .to setting the-calling device 1') in accordance with the first digit of the cit-normal springs 270 and 21! close to complete the circuit for energizing relays 238, 243 and 205. The circuit for energizing relay 238 extends from ground through off-normal springs 213 and 2H,

and through the winding of relay 203, to battery. The circuit for energizing relays 233 and 2355 extend fromground through off-normal springs 210fthroug h the windings of relays 235 and 245 in series, to battery. Relay 2138, upon energizing, at contacts 253 short circuits relay 201, at

contact 254 connects an additional, ground for maintaining relays 205 and 205 energized, and at contact 2555 completed an obvious circuit for one ergizing relay 209. Relays 2B6'and 235, upon energizing, at contacts 231 and 243 opens the loop through the operators position and at contacts 248,238, 250 and 239 prepares a point in the impulsing circuit. At contact 249 relay 2% completes the circuit for energizing relays 334 and 355 as follows: from ground by way of springs extended from the toll board of Fig. 5 through 258 of key K, contact 249, spring contacts 388 of key K3, contact 366, upper winding of relay 354, and through the lower winding of relay 355 to battery. Relay 209, upon energizing, at contact 242 completes the circuit for lighting the dial pilot lamp L and at contact 251 completes the locking circuit of relays 203, 35!, and 352, which locking circuit is independent of springs 392 of key K3. Relay 354, upon energizing, at contacts 3' completes a locking circuit for relay 355, and I at contacts 312 completes a locking circuit through its lower winding to ground at key K4.

. Relay 355, upon energizing, at contacts 3T6 completes a locking circuit for itself through its upper winding from ground by way of springs 259 of key K, conductor 2I4, springs 393 of key K3, contacts 31!, contacts 316, and through the upper winding of relay 355, to battery. At contact 315 relay 355 grounds the holding conductor 38! extending to the selector S,at contact 3'l'l prepares a point in the circuit of the supervisory relay 356, and :at contacts 314 and 3'18 completes the circuit for the line relay 4ll2 in selector S, as follows: from ground, through the lower winding of line relay 432, contact 4E8, conductor 383,, 22-" contact 318, contact 364, contact 239, contact 253, to the dial impulse springs. 212, contact 253, contact 248, contact 233, conductor 222, contact 359, contact 314, conductor 3 33, contact 41 I, and

through the upper winding of line relay 492 to 1' battery. The operation of.-1ine relay 452 inselector S operates the release relay (not shown) and prepares this selector for operation as de} scribed in the Crocker et. al. patent. V v u During the return of the dial to normal the impulse springs 212 are interrupted a number of times corresponding to the digits dialled. Each time the impulse springs 212are opened the line relay'4ii2 deenergizes to cause the selector S to operate itsshaft and'wipers in a vertical direction opposite the desired group of bank contacts. After selecting the desired group of bank contacts the selector S automatically rotates its shaftand wipers to select an idle trunk in this I group. vention it will be assumed that the outgoing repeater in Fig. 2 is seized by the selector S.

When the dial is fully returned to its normal position the dial shunt springs 210 and 21! open, thereby opening the circuit of slow-to-release For the purpose of describing this inrelay 238. Due to its slow release characteristics indicated by the copper rectangle at the lower portion of relay 238, this relay releases after an interval. At contact 253 relay 298 momentarily bridges relay 20'! across the trunk conductors 533 and 536 before relays 206, 239, and 205 are released. Relay 291-is now operated in series with relays 524 and 53!! over the following sircuit: from ground through the lower winding of line relay 53il,'contact 5H, lower left-hand winding of repeating coil RC',.Tc onductor 503, bank contact and wiper of selector S, contact 4 IT, conjductor 383, contacts 318, 334, j 239, 250, 212, through the winding of relay 231, contacts 248,

238, 359, and 314, conductor 380, contact 412,... upper wiper and bank contact of selector S, con-- ductor 533, upper left-hand winding or repeating coil RC, contact 5| Land'through the windings of relays 520'and 539, to battery. At contact 52! relay 231 maintains relays 206 and 235 energized and at contact 252v maintains relay 209 energized by way of ground extending through springs 253 key K. 4 V Q When the selector S switches through in the well-known manner, upon the seizure of the .re-

Tisshort: circuited via contact 253 upon.energizing over the above-tracecl'circuit, at l contact 54! closes a multiple ground for maintaining relay 560 operated,,at 542prepares a The switching relay I,

S, contact M3, conductor 382, contact 311, and

; throughthe winding of relay 356 to battery. Relay 356, upon energizing, at contact 319 lights the supervisory lamp L4 at the operators position.

= :Line relay 530, upon energizing over the "above- "tracedcircuit, at contact 53l preparesa point in the talking circuit and impulse repeating circuit,

. and at contact 532 completes an obvious circuit .for energizing relay 560. Relay 520, being mar- :ginal, will not energize in series withthe high resistance winding of relay 2ll1, and therefore relay 520 only energizes at a time whe'n relayzlll Relay 550,

pointgin the circuit of relay 510, and at 543precontact562 relay 560 completes a circuit through the upperwinding ofelectropolarized relay 505 'to preparethat relay for operation. It shoiild possibly be mentioned at this time that a circuit is completed through the lower winding of electropolarized relay 550 as follows: from ground through the upper windingof differential ring-- ing relay 84!] in Fig. 5, upper winding of line relay 830, back contact 822, normally closed con- .tacts controlled by armature BIZ, lower left-hand winding of repeat coil RC,conductor 516, con}- tact 563, lower right-hand winding of repeat coil RC'in the outgoing repeater of Fig. 2, lowerwinding of electropolarized relay 5M, upper right- "hand winding of repeat coil RC, contact 53!, contact 55!, trunk conductor 515, upper left-hand winding of repeat coil RC in Fig. 5, normally closed contacts controlled by armature 8| I, back contacts 823, and through the lower windings of line relay .821] and differential ring relay 84B,

to battery. Electropolarized relay 506 will not operate over this circuit because the two windings oppose each other. i

When the dial is again operated oil normal preparatory to dialling the second digit, relay 258 is again energized by way of springs 21! and this relay at contact 253 short circuits relay zlll causing relay 251 to release as well as causing the operation of marginal relay'520 in the outg'oing repeater.

Relay 52!], upon energizing, t at 52l completes the circuit for operating relayf51ll by I way of contact 542. Relay 510, upon operating, at contact 51! preparesa point in the circuit for short-circuiting the right-hand windings of the repeating coil RC and the lower windingoi relay D, and at contact 512 completes the circuit for energizing relayll. The circuitfor energizing relay 550 may be traced as follows: from. ground by way of back contact'5l3,.front contact 512,

through the winding of relay 550, back contact 5|4, and through resistance 5H5. to battery. At

; .551 relay .550 opens a point in the circuit of the repeating coil R0, at 552 prepares a point in the energizing circuitof relay 510,.and at 553 com pletes the short circuitaround the right-hand windings of the repeating coil RC and the lower winding ofrelay 500 to improve the impulsing circuit extending over the trunk conductors 515 and 515 to the distant exchange. When the calling device D is returning. to its normal position,

the impulse springs 212 interrupt the circuit of relays52l and 535, and the latter relay at contact 53! interrupts the loop extending through the windings of the line relay "83D and ring relay S-lli, as previously described. The improved impulsing circuit instead of extending through the windings of repeating coil RC and the lower r winding of relay 505', extend byway of conductor 516, front contact 553; contact 553, front contact 51!, impulserepeating contact 53!, front contact 555, to conductor 515.

Line relay 83!] in the toll selector repeater 0 .Fig. 5 operates over the previouslytraced loop circuit over conductor 515 and 516 but ring relay 860, beingdifferential, will not operate. Line relay 835, upon energizing, at front contact. 83l completes an obvious circuit for the slow-to-release relay 850, .andat contact 832 prepares a point in the circuit for repeating impulses tothe subsequent switches. Relay 85%, upon energizing, at contact 851 and its bank contact opens a point in the circuit to the release magnetyll, and at its front contact prepares a point in the circuit forrelays 880 and 890. Atccontact 852 relay 855 prepares a point in the circuit for the upper winding of relay 8!!) for supervisory purposes, at contact 853 removes the short circuit from around the resistance RI, and at contact .854 prepares a point in the circuit for relay 800 and vertical magnet 891.

Each time line relay 530 in the outgoing re peater interrupts the loop circuit over the trunk conductors 515 and 515, line relay 8% in the'toll selector repeater deenergizes to operate relay 300 and, vertical magnet 8591. The circuit for en ergizing relay 800 extends from ground by way of back contact 85!, contact 855, and through the winding of relay to battery. The circuit for operating the vertical magnet 891 extends from ground by way of back contact 83!, contact 854. back contact 324; contact 855, and through the winding of vertical magnet 891, to battery. Vertical magnet 891 follows the impulses and steps the shaft and wipers in a vertical direction opposite the group of bank contacts corresponding to the digit dialled. On the i first vertical step of the shaft the off-normal springs 84 3 close to prepare the circuit. for the release magnet 8M, and at vertical oil-normal springs B85 prepares a point in the circuit for stepping relay 880. Relay 850 is maintained energized during the impulsing, and at contacts 813! I and 803 completes the circuit for energizing stepping relay 88D, and short circuits switching rewinding of stepping relayBilEl to battery. The

short circuit for switching relay 890 may be traced from the left-hand terminal of this relay by way of interruptercontact 883 of rotary magnet 884, contact 892, contacts 80! and 888, to the right-hand terminal of relay 890. Relay 88!],

upon energizing'at contact 88l prepares a point in the circuit to the rotary magnet 884, and at contact 882 completes a locking circuit for itself by way of the rotary magnet interrupter contacts 883 and vertical elf-normal springs 885, as Well as completing a short circuit from ground at armature 882-, through relay890 to ground at front contact 85L Due to the slow release characteristic of relays 880 and 858, these relays are maintained in operated position during the dialing. After the impulsing period line relay 030 is maintained energized to maintain re1ay'050 in ener ized position and shortly thereafter slowto-release relay-800 deenergizes. At contacts 804 and 805 the short circuit from around the lefthand windings of the repeating coil RC is removed and at contact 802 rotary magnet 884 is energized over the following circuit: from ground,

by way-of front contact 85!, contact 802, contact 88l, and through the Winding of rotary magnet 884, to battery. The rotary magnet 884 energized and rotates the wipers one step and near the end of its stroke opens the interrupter contact 883 to open the locking circuit of relay 880 which accordingly releases. Relay 889, upon releasing, at contact 88! opens the circuit of rotary magnet 884 to cause its deenergization, and at contact 882 removes the short circuit from around switching relay 898. The wipers'of the selector repeater are now in engagement with the first set of bank contacts in the selected group and the operation of the toll selector repeater depends upon the idle condition of the first selector such as St in the group.

In case this selector is in use, then ground is encountered bytest wiper 883 and stepping relay 880 is energized as follows: from ground on the bank contact engaged by test wiper 888 back contact 893, interrupter contact 883 of rotary magnet 884, vertical elf-normal springs 885, and throughthe winding'of stepping relay 880 to battery. The ground connection engaged by test wiper 883 likewise maintains the switchingrclay 890 short circuited to prevent its operation on busy connections. The operation of stepping relay 888 again completes the circuit for rotary magnet 884 at contact 88L and again completes a locking circuit for itself at contact 882 as well as short circuiting switching relay 890. The rotary magnet 884 reoperates and rotates the wipers another step into engagement with the second bank contact and again at contact 888 releases relay 888. This interaction between rotary magnet 884 and stepping relay 880 continues until wiper 883 no longer engages a grounded bank contact, at which time the short circuit is removed from switching relay 890. 1 Assuming now that the selector SI, Fig, 6, is

, the first idle selector accessible in this ground in which case no ground connection will be connected to conductor M5 and the switching relay 888 will not be short circuited. Switching relay tact 5H opens the circuit for relay 510.

switches thetalking conductors through to conductors SM and 8|! terminating in the selector SI of Fig. 6. At contact 892 relay 890 opens a point in the initial energizing circuit of relay 880, at contact893 grounds test wiper 883 to make selector SI busy, at contact 894 opens the circuit to the vertical magnet 891, and at contact 885 completes the energizing circuit for the line relay (not shown) in selector Sl from grounded armature 852 by way of wiper 864 of conductor 8|6.

The subsequent digits transmitted by the repeater of Fig. 2 operate relays838 and 800 as before, causing relay 800 to short circuit the lefthand windings of the repeating coil RC, while at contact 832 repeats impulses to the line relay in the selector SI. The. selector SI and connector CI in Fig. 6 are somewhat similar to the selector and connector shown in the Wicks patent previously: referred to and are operated in the manner set forth therein to connect with the called line. 1

After the toll operator has completed dialling the called subscribers number, elf-normal dial springs 218 and 2' of the calling device D open and restore relay 808 after an interval, as previouslydescribed. Contact 253 again bridges relays 20! across the trunk conductors 380 and 383 before relays 208, 209 and 205 release. Due to the high resistance of relay 201', relay 520 in Fig. 2 is released. Relay 201, however, energizes as previously described, and at contact 252 maintains relay 209 energized and at contact 25l maintains relays'206 and 205 in operated position. In the outgoing repeater relay 520 deenergizes since it is marginal in series with the high resistance relay 201, but line relay 530 is maintained energized over the previously traced loop circuit. Relay-520, upon releasing, at con- Relay 510 has not released previously because the chain of relays, namely 208, 528 and 510 are slow releasingrelays and the interval between digits, when the dial is at normal, is of insufiicient duration to finally open the circuit of relay 579 long of time to cause relay 510 to release- ,After completion of dialling, however, the dial does remain in normal position and the circuit to relay 510 .is'heldop'en long enough to cause its release.

Relay 510, upon releasing at front contact 5H removes the short circuit'from around the righthand windings of repeating coil RC and the lower winding of relay 500, and at front contact 512 momentarily opens the circuit of slow-to-release relay 550, which, however, is maintained in ODBI', ated position for a short interval due to its slow release characteristics. At back contact 51! relay 518 completes a circuit for operating the differential ringing relay 840 in the toll selector repeater of Fig. 5 in order to initiate the ringing operation, and at contact 5'l2 completes acircuit for energizing relay 558. This circuit may be traced as follows: ground by way of back contact 513, back contact 512, contact 552, and through the winding of relay 5H! to battery. At contacts 5 and 5i] relay 5H1 opens the circuit of relays 201' and 588. Relay 201 deenergizes but relay 530 is maintained in operated position in series with moans relay-510 as'rouowsi from'g round through the lower winding of line re1ay530, spring 5l8, con tact 543, and through the Winding of relay 05m to battery. At contact 5l3 relay 5H] opens the orginal energizing circuit ofrelay 5H] and at 5M prepares a point in a new circuitfor relay550.

Relay 550 is now connected to make contacts relay 558 may be operatedin casethe operator desires to rering thecalled subscriber. 55U,however, deenergizes when its circuit is opened after an interval atoontacts 5|3 and 5M. Atcontact 55! relay 553 completes the circuit for the left-hand windingoi repeating coil RC in order to complete the talking circuit, at contact 552 opens the original energizing circuit of relay 5l0 now locked in series withrelay 530, and at contact 553 disconnects negative battery connected to resistance 554 from conductor 575.

Relay 257 deenergizes in response to the opera tion of relay Sit; and at contact 725i opens the circuit of relays .256 and 255 and at contact 252 opens the circuit of relay 239. Relay 206, upon deenergizing,at contact fi lfl and 255 disconnects the calling device from the trunk conductors 553 and 505 and at contact 249 opens a point in thecriginal energizing circuit ol" relay 355 and 354 which relays are, however, rnaintained in operated position over their locking circuits.

Slow-to-release relay Zlfia'upon deenergizing, at contact Z IZ extinguishes the dial pilot lamp L and at contact opens thelocking circuit of relays 203, L and 552. Relay 235 likewise deencrgizes after an interval and. at contacts 231 and 240 connect up the operators headset.

Returning now to the outgoing repeater and at a time when relay 5') has'deenergized and beforerelay 555 is fullyrestored, negative battery extending by way of resistance 556, back contact 5H, and contact 553 is momentarily connected to trunkconductor 5% by way of front contact 563. Due to this momentary connection of negatential through resistance 5% to conductor 51B creates an unbalanced condition in the trunk loop with the resultthat the differential ringing relay 8 33 is momentarily operated. RelayBMl, upon operating, at contacts 85! and 842 connects generator across the trunk conductors BIQ and 8H to cause the operation of the ringing relay (not shown) in the selectorSi which ringing relayQin turn causes theringing of the called subscriber as described in the Wicks patent previously referred to. When the called party answers. relay 815 is energized. over the called subscribers loop by way of conductors 8M and Bit, wipers 562 and 855, contacts iifiband 5%, right-hand winding of the repeating coilRC, contact 852, and through the windings of relay all) to ground and battery. Relay Eilll, upon energizing, at contacts 8H and M2, reverses battery over the trunk conductors 515 and 515m cause the operation of electropolarized relay 500 in the outgoing repeater. i

"Relay 5llil, upon energizing, at contact removes the short circuit from around the high resistance lower winding of relay 543, thereby Relay tact 319 supervisory relay 355 extinguishes the supervisory lamp L4, thereby indicating to the toll operator that the called subscriber has responded. The toll operator maytalk-to either i the calling or the called party as described in the Crocker et a1. patent, and when satisfied that;

the proper toll connection hasubeen completed she may withdraw from the connection by re-' storing the key K3. Atspring 391 of key K3 9. new holding circuit is completed for relay 355 and at contact 352 the holding circuit of relays 352, and 352 is opened to cause the release of these relays. Relay 253, upon releasing, at contacts 335 and 225i disconnects theoperators headset and relay 535i, upon releasing, "at contacts 355 and 353 connects the called line to,

trunk conductors 3M) and 344 and the calling line connected thereto. i

Incase the called line were busy when called, then the busy relay in connector CI operates and connects interrupted ground to conductor 8M, thereby intermittently operating relay 813 over the following circuit: from ground through the interrupter and make contacts of the busy relay in connector Cl over the upper bank contact" and Wiper of selectorSl, conductor BM, wiper 852, contacts 89! "and 34!, upper right-hand winding of repeating'ooil RC, contact 852,and" through the upper winding of relay M5 to battery. Each operation of relay Bill at contacts till and fill! reverses' battery over the trunk conductors 515 and 575, thereby causing the intermittent operation of electropolarized relay 50B in. the outgoing repeater.

5m intermittently includes and excludes the high resistancelower winding of relay 548 in circuit with relay, 355 over conductor 555,thereby caus-z ing the intermittent operation of supervisory relay 356 at the toll positlon. Relay 356therefore intermittently operates to flash the supervisory lamp L l by Way-of contact 3'19 to indicate to the toll operator that the called line is busy.

After conversation and when the calledparty hangs up, relay 8H3 releases and restores the- Relay 553 at contact winding of relay "5483, thereby permitting the supervisory relay 355 in the toll position to char-- gice. Thesteady energization of supervisory re-. lay 355 causes the steady lighting of the supervisory lamp, thereby indicating to the toll operator that the calledsubscriber has replaced his receiver; i

In case the toll operator desires to re-ring the called party negative battery is through contacts 3'? and conductor 383 by Way of re-ring key RK to operate relay, 550 in the outgoing repeater. This circuit may betraced iromground at make contacts 5 l3 and 5M, wind: ingot relay B, contact 5I5, lower left-hand winding. of repeating coil RC, conductor 506, bank contact and wiper of selector S, frontcontact ill, conductor 383, contact 3'48, and through the ringing key RK and resistance to battery. At contact 553 relay 550 connects negative battery through resistance 564 and back contact 5H to conductor 515 by way of front contact 563 to cause the reoperation of difierential ringing relay M0 in the tollselector repeater of Fig. 5, in

connected ing generator across the conductors 8M and 8H to rering the called subscriber.

When 13116213011 operator receives the disconnect signal by the steady lighting of the supervisory lamp L4, the operator may release the established connection by releasing key K4 to open the locking circuit of relay 354. Relay 354,

from conductor 38!, and at contact 311i opens the circuit to the supervisory relay 356 and relay 540 in the outgoing repeater. The selector S is restored to normal in the same manner as described in the Crocker et a1. patent andrelay 548, upon deenergizing, at contact 54! opens the circuit for relay 566 and at contact 543 opens the circuit of relays 5H) and 536'. Relay 5m, upon deenergizing, at contacts 5H and 5H prepares the original circuits of relays 528 and 538, andat contacts M3 and 5M disconnects ground from relay 550 and substitutes a battery connection through resistance 5l6 therefor. Relay 536, upon deenergizing, atcontact 53! opensthe loop circuit extending over the trunk to the toll selector repeater of Fig. 5 to cause the deenergizaticn of line. relay 830 therein. After an interval slowto-release relay 560' deenergizes and at contacts Bill and 563 connects the trunk conductors 575 and 516 to the incoming selector repeater of Fig. 3.

' time, and at contact 832 disconnects ground from conductor 8|6 to release the line relay in selector and selector SI, at 853 reestablishes the short circuit around resistance RI, and at contact 854 SI. Release relay 856, upon deenergizing after an interval, at contact 85! opens the circuit of switching re1ay890, and removes ground from wiper 863 and from conductor 801. At back contact 85! relay 858 completes a circuit for energizing the release magnet 884 by way of vertical offnormal springs 843, at contact 852 disconnects the upper winding of relay 8 I 6 from the toll board opens the circuit to relay 860 which releases after an interval. Switching relay 890 likewise restores to normal. The release magnet 844 upon energizing releases the switch shaft and wiper and the vertical cit- normal springs 885 and 843 open, the latter off-normal springs opening the circuit to the release magnet 844, which-there-' upon deenergizes. The toll selector repeater of Fig. 5 is now in normal position, and may be used on subsequent calls. The succeeding switches such as selector SI and connector CI in Fig. 6 release in the'manner described in the Wicks patent previously referred to. The entire connection is now released and may be used on subsequent calls.

Incoming calls Having described a toll connection extending from the toll position in Fig. 1 over the trunk line to the distant exchange shown in Figs. 5 and 6, a description of a toll connection originating at the toll board of-the distant exchange, Fig. 6, over the trunk line conductors 515 and 516 ior relay 866.

v 840 at contacts 8 and842 again connects ring through the incoming selector repeater, the toll transmission selector T'IS, and connector C to a subscribers line such as Twill nowbe given. For this purpose, it will'be assumed that a call has come in to the operator's position in the toll board in Fig. 6, and that the toll connection is to be completed to the called subscribers line T in Fig. 4. ,The toll operator after ascertaining that subscriber T is the desired called. subscriber grounds conductor 888 extending from the toll board to the toll selector repeater. In response to grounding conductor 808 relay 8'"! is energized over the following circuit: from grounded conductor 868, contacts 86! and 853 and through the winding of relay 816 to battery. At contact 8H relay 818 connects the lower winding of relay 8H3 to conductor 866 extending to the toll board; at conductor 812 prepares a circuit for relay 866, and at contact 873 completes the circuit for operating relay 826. Relay 826, upon energizing, at contact 82! connects grounded armature 85l to conductor 86'! extending to the toll board.

Through back contacts 822 and 823 relay 820 disconnects the windings of line relay 830 and differential relay 840 from the trunk conductors 515 and 576, and at front contacts 822 and 823 connects the rectifier 863 in bridge acrossthese trunk conductors as well as preparing a circuit At front contact 824 relay 820 preparesthe circuit for; relay 800.

Relay Bill in the incoming selector repeater of Fig. 5 is now energized over a loop circuit as follows: from ground, through the lower winding of relay 6H3, normally closed springs controlled by contact 683, conductor 514, back contact 563,

conductor 516, lowerleft-hand winding of repeating .coil R0 of the toll selector repeater of Fig.5, normally closed springs controlled by contact 8l2, front contact 822, rectifier 863, contact 812, front contact 823, normally closed springs controlled by contact 8| I, upper left-hand winding of repeating coil RC, conductor 515, back contact 56L conductor 573, normally closed contacts controlled by contact GUI, and through the upper winding of relaytlll to battery. It will be noted that the rectifier 862 and the Winding of relay 866 is also bridged across this loop circuit, but the rectifier 862 blocks current flow through the winding of relay 866. The blocking effect of rectifier. 862 is such that relay 860 will onlyoperate when the current is reversed from normal over the trunk conductors 515 and 516.

Relay 618 in the incoming selector repeater of Fig. 23 operates over this loop circuit including the rectifier 863 and at contact 6| l completes the circuit for sloW-to-release relay 626. At contact 6l2 relay 6lil prepares a point for repeating impulses to the toll transmission selector after the incoming selector repeater has switched through. Relay 626, upon energizing, at contact 62| grounds conductor 564 to make the outgoing repeater and inter-exchange trunk line busy to selectors such as selector S. At contact 622 prepares a point in a circuit for the vertical magnet 6I6, relay 638 and relay 668, at contact 623 relay 626 prepares the circuit for switching relay 688, for rotary magnet 643 and opens the circuit to the release magnet 6l5.

The tolloperator now dials the digits of the called subscribers line, thereby disconnecting ground from conductor 868 for each impulse to be transmitted. Relay 810 follows the impulses and at contact 872 opens the loop circuit extending over the trunk conductors to cause the line relay 6"! in the incoming selector repeater to operate acorresponding numberof times; T At the back contact 8'13 relay 8!!! completes the circuit for energizing relay 800 by way offront contact 824. It will bejunderstood that the slow-torelease relay 82!! is maintained in operated position during the dialling period. Relay'Bllfl, upon energizing; at contacts 804 and 805 short encuits the left-hand winding of the repeating 0011 R0 to improve the impulsing circuit over the trunk conductors 515 and 515. Relay 800 islikee wise slow to release and is maintained in operated position only during the dialling period.

After the dialling of each digit relay 820 is maintained in operated position, while relay 80!! releases after an interval to remove the short circuit from around the left-handflwinding of the repeating coilRC.

Line relay Bill in the incoming selector repeaterfollows the impulses transmitted by contact 812 and on each deenergization thereof completes a-circuit for operating the series relay 638i and vertical magnet 6i6as follows: from ground by way of back contact 6H; contact 622, back contact 684, winding of slow-to-release series relay.630, and through the winding of vertical magnet 616 to battery. The series relay 63B,-upon energizing, at contact 63I opens a point in the circuit to rotary magnet 643 and prepares a point in the circuit to stepping relay 5M1. Vertical,

magnet 6l6 operates the shaft and wipers one step in-avertica1 direction for each impulse received to position the wipers of the incoming selector repeater opposite the desired group of After the last impulsej of the digit just transmittedrelay fill] is maintained in operated posi i tion with theresult that theslow-to-release series.

relay 630 deenergizes after aninterval. Itshould also be mentioned at this time that the slow-toe release relay BZiLdue to its slow release charace teristics, is maintained in operated position dure ingthe dialling period, while the series relay- 630 ismaintained in operated position only during the. dialling period and deenergizes shortly after the last impulse of the digit. When series relay 1 controlled by contact 63L contact 64!, and

throughthe winding offirotarymagnet 643 to battery. Rotary magnet 643 energizes and roytates the wipers 693 to 696 into engagement with the first set of bankcontacts in the selected group. The rotary magnet near the end of its stroke opens the locking circuit of stepping relay 640 at interrupter contacts 654 to cause thestepe ping relay to deenergize. It should be mentioned that .theswitching relay 68B is short circuited by contacts 63! when the series relay 630 is operated byway of cam springs 686 and interrupter springs 654; and after deenergization of series relayj630.

switching relay 680 is likewise short circ'uited.

from ground by way of front contact 623, cam

springs 686, and contact642; of the energized:

. of relay 680, interrupter contact 654, vertical offstepping relay 640. These short circuits are provided to prevent the premature energization of switching relay 680. Stepping relay 640 deenergizes when the rotary magnet interrupts its look ing circuit at 654, thereby at contact 64! opening the circuit to the rotary magnet643, which like- At contact .642 the short cirwise deenergizes. cult from around switching relay 680 is removed and further operation of the stepping relay and rotary magnet is dependent upon the busy condition of the contact engaged by the test wiper If the toll transmission selector is busy then the bank contact engaged by test Wiper 694, will be grounded with a result that the stepping relay 640 is energized over the following circuit: from grounded bank contact, test wiper: 694, back contact 683, interrupter contact 654 of the rotary magnet 643, vertical oft-normal springs 632, and through the. winding of relay 640 to battery. Ground at the test wiper. 594 likewise short circuits the switching relay 630 to prevent its energization. Relay B40, upon reoperating, at contact 64! again operates the rotary magnet 643. and at contact 642 again short circuits the switching relay 88!] as well as completing a locking. circuit for itself.

The rotary magnet again rotates the wipers an additional step and at interrupter contacts 654 .againopens the circuit of stepping relay 640.

Stepping relay 640, upon deenergizing, at GM opens the circuit of rotary magnet 643 which accordingly deenergizes. Relay 640 at 642 opens the short circuit from around switching relay 680 .to enablethis relay to energize providing .the test wiper 694 is not in engagement with a grounded bank contact. This inter-action between the stepping: relay 64B and rotary magnet 64?. continues until the test wiper 694 no longer engages a grounded bank contact with the result that the short circuit is removed from around the switching relay can, whereupon relay 68B is energized in series with the switching relay 640. The circuit for energizing relay'l'iiill may be traced as follows: from ground by way of front contact 623, cam springs 586, Winding normal contacts 632, and through the winding of relay 640 to battery. Due to the high resistance of the switching relay 680, stepping relay 640 is not operated over this circuit. Switching relay .680, upon energizing, at contacts EBI and 685 completes a circuit for. energizing relay 650 and line relay .107 of the toll transmission selector T'IS as follows: from ground by Way of contact 123, resistance TH], lower left-hand winding of repeating. coil RC of toll switch TTS, conductor 435, wiper 696, conductor 689, contacts 6B5'and 6I2, lower right-hand winding of repeat-- ing coil RC of the incoming selector repeater, upper winding of relay G50, upper right-hand winding of repeating coil RC, contact 68!, con-L ductor 686, Wiper 693, conductor 438, upper lefthand winding of repeating coil RC of switch TTS,resistance 169, contact "H6; and through the upper winding of line relay 101 to battery. At contact 682 relay 6B0 prepares a circuit for relay 690, at back contact 683 opens the rotary test circuit and atvfront contact 583 connects grounded contact 623 to test wiper 69 to mark 67!) by way of resistance $55, at contact 652 prepares a locking circuit through its lower winding and at contact 653 completes a shunt around contact 613 for controlling the operation of relay i500. Relay 610, upon energizing, at contact 61! opens a point in the'repeating coil circuit, at contact 612 prepares a point in the circuit for connecting negative battery potential to the lower prove the impulsing circuit.

talking conductor for the purpose of starting the ringing operation, and separates the contacts-613 which is without. effect at this time, since contacts 653 are now closed. r

In response to the subsequent digits dialled by the toll operator line relay Sill follows the loop pulses transmitted by relay i318, and at contact EH2 repeats these impulses to line relay ill! in the toll transmission selector TS. Each time line relay 6H1 deenergizes, contacts Elli completes a circuit for slow-to-release relay $59 by way of contacts 622 and 684. .Relay'tlit ,is

maintained in operated position during the dial ling period and at contact 662' completes an obvious circuit formaintaining relay 618 in energized position independent of'relay 658. At con tact663 relay 660 completes an obvious locking circuit for relay 656 and at contact 66! shortcircuits the upper winding of relay 650 and the right-hand winding of repeating coil R to im- The impulse repeating circuit for line relay it? of the toll trans inission selector 'ITS now includes the following circuit: from ground by way of contact 123,

. winding of relay 650 at contact 651 and at conresistance Till, lower right-hand winding of repeating coil RC, conductor 635, wiper 5%, contacts B85 and BIZ, BM, 68!, wiper G83, conductor 438, upper 1eft-hand winding of repeating coil RC, resistancelSB, contact lit, and through the upper winding of line relay 101 to battery. After each series of impulses or after each digit, relay 6S0 deenergizes to remove the short-circuit from around the right-hand winding of repeating coil RC of the'incomingselector repeater and the tact 6B2 opens the substitute circuit for relay Bill which, however, is still maintained energized over its original energizing circuit.

The line relay 101 in the toll transmissionselector TTS and the relays (not shown) in the connector C operates in the same manner as described in the Crocker et a1. patent in response- .to the digits dialled to extend the connection tocalled line T.

' In' case the calledline T is busy, relay ml in the toll transmission selector TTS is operated, and relay M33 is intermittently operated there after to intermittently disconnect and connect ground to conductor lBt as described inthe Crocker et a1; patent. When relay 1m first energizes contact 124 closes the circuit to maintainrelay 101 in operated position, and tocomplete a circuit for energizing relay 690 as follows:

I from ground through the lower winding of line this relaydoes not operate due to the bridge circuit which does not permit sufficient current flow due to the balanced condition present in this bridge circuit; that is, the ground connection I from contact 692 through resistance 614 to one terminal of relay 60E! balances the ground connection from the lower winding of relaylfl'l, through resistance R to the other terminal of relay-600. condition, will not energize until the ground connection extending through the lower winding ofrelay 101 is openv Relay 6503, upon deenergizing, at front contact 65! opens the circuit to slow-to-release relay 610, and at back contact 65! momentarily connects negative battery potential through the resistance 655 to conductor 35 to operate ringingrelay 7M, which, however, is only effective if the called line is foundv idle. Relay 650' also at Contact 653 opens the circuit to supervisory relay 6M Relay 6'58, due to its slow release characteristics, releases after an interval, and at contact 61! closes a point in the circuit of the left-hand windings of therepeating coil .to permit transmission of busy tone, atcontact 612 disconnects the negative battery Relay 600, due to this balanced circuit potential from conductor 435 to release the ringing relay I04 and at contact 6'73 recloseswthe circuit to relay 600. When relay 103 in the toll transmission'selector TTS is operated, contact 'l29 disconnects ground extending through the lower winding of line relayllll from one terminal" of relay 600, thereby upsetting the balanced bridge circuit previously referred to. with the result that relay 6% now operates over the fol-,,

lowing circuit: from ground by way of contact 692, resistance 6M, through the windingxof relay Still, contacts 6H and 682, and through the winding of relay 590 to battery. Relay 693 is energizedover this circuit and relay 6% is maintained in operated position.

It may be advisable at this time to more fully. describe the balanced, circuit of relay 690 :in order to more fully understand its operation. Relay600 is connected in bridgeof the two upper legs of a so-called Wheatstone bridge. The i irst,,or upper leg of this Wheatstone bridge may be said to extend fromground through the lower. winding of line relay 'Hl'l, contacts 12$,resistance:

R, conductor 436, wiper 695, to conductor 688;

the corresponding other upper leg of this Wheat-' stone bridge may be said to extend from ground byway of contact 692 and'resistance fildto the center point of the bridge; the first lower legof this bridge may be said to extend from the center point at which the first lower leg terminating in conductor $88, and from thence to contact 682, and through the winding of relay 69!) to battery; and the remaining lower leg of this Wheatstone bridge includes the resistance GM to battery. 1

Relay 60G is bridged across the center point of this bridge circuit by way of the connection to.

conductor E588, contact 69!, and through thewinding of relay M10. The combined resistances of the lowerwinding of line relay 'llll and resistance R are equal to the resistance of M4 in the two upper legs, while resistance SM is equalto' the resistance of the winding of relay 690. Now, since relay 600 is bridged across the center points of this-bridge circuit, and since the resistances in thetwo upper legs from the ground connections.

are equal no current flows with the resultthat relay 600 does not operate until such. time; as

relay 103 energizes to disconnect the ground connection from the first upper leg. Therefore, on the first operation of relay 163 relay 680 is ener gized over the circuit previously traced.

'' Since it was assumed that the called line.

was busy,relay 103 is intermittently operated to.

cuit through the winding of relay 101, with the result that there is no current flow through relay 600 and relay 6B0 accordingly releases. From the foregoing description it will be seen that relay 600 is intermittently operated by the intermittent operation of relay 1.03. Each time relay 600 operates, said relay at contacts Bill and 603 reverses battery over the trunk conductors 515 and 516 to operate the supervisory relay 860 in the toll selector repeater of Fig. 5 through the rectifier 862. Since the rectifier 862 is poled'in the direction to permit operation of relay 860 when current is reversed over the trunk. Since relay Bllll is intermittently operated to intermittently reverse battery over the trunk, relay 860 likewise is intermittently operated. Each time supervisory relay. 860 operates said relay at contact 86! removes the shortcircuit from around resistance RI, thereby increasing current flow over conductor 8B8 extending to the toll board to cause the supervisory signal in the toll board to operator.

flash to indicate the busy condition to the toll Busy tone is also transmitted over the heavy talking conductors and repeating coils to the toll board. which also informs the toll operator that the called line is busy.

Assuming now that the called line T is idle instead of busy when called, then relay 10! is tact 6'12, back contact 65!, and resistance 655 to scribed in the Crocker etal. patent.

battery. Ringing relay TM operates and causes the ringing current tobe transmitted to the called line, after which relay m3 is steadily operated in response to the called party answering, as de- Relay m, upon steadily operating in response to the called party answering, at contact 128 maintains the line relay operated, and at contact I29 discon iiccts ground from one of the first upper legs of the bridge circuit previously described to cause the operation of relay 500., Relay 6M, accordingly energizes and at contacts 50! and 593 steadily reverses battery over the trunk to cause the steady operation of supervisory relay B60 in the toll selector repeater of Fig. 5. The steady operation of supervisory relay 866] at contact BEI removes the short circuit from around resistance RI, thereby causing a steady disconnect signal to indicate to the toll operator that the called party, has responded. For example, a relay similar to relay 356 of Fig. 1 may be connected to conductor 808 in the toll board to control a supervisory lamp such as L4. In response to the steady signal the toll operator will connect the calling and called parties after ascertaining that the correct party has answered the call.

After conversation and when the called party hangs up his receiver, relay 103 releases and connects ground through the winding of relay 101 and resistance R to the upper terminal of relay B00, thereby again establishing the balanced bridge circuit to cause the release of relay Elli]. Relay 600, upon restoring, at contacts 6M and 603 reverses battery over the trunk to normal, thereby releasing supervisory relay 860. Relay 86! upon deenergizing, at contact 85! short-circuits the resistance RI, thereby increasing the current flow over conductor 808 to bring in the disconnect signal to the toll position.

In case the toll operator desires to rering the called party she may do so by opening the circuit to relay 810 momentarily. The momentary release of relay lllii at contact 812 momentarily opens the loop circuit extending over the trunk conductor to line relay BIB which also momentarily releases. The momentary release of line relay 6H2 causes the operation of relay 6% over the circuit previously traced. Relay 8W reenergizes after the momentary opening of its circuit, and at contact 812 reclosesthe circuit over the trunk conductors to line relay 6H3 which accordingly reenergizes. The reenergization of line relay 6H] opens the circuit to relay 66!! which accordingly deenergizes after an interval. The, momentary operation of relay 560 in the ini coming toll selector repeater has caused the operation of slow-to-release relay iilil by way of con tact 622, and when relay 666 is deenergiz ed as just described, negative battery potential is again connected to conductor 435 during the release time of slow-to-release relay 610 as follows: from negative battery through resistance 555, back contact L contact 612, back contact iiiiLcontacts (H2 and 685, conductor 689, wiper (5%, conductor 435, lower left-hand winding of repeating coil RC, resistance TH], contact 722, and

through the winding of ringing relay EM to ground. Relay TM again operates and again initiates the ringing of the called party as described in the Crocker et al. patent.

The release of the connection is under control of the toll operator, who opens the circuit to relay 810 after receipt of the disconnect signa Relay 810, upon falling back, at contact 87! opens the circuit to relay 8M, at contact M2 opens the loop circuit extending over the trunk to release relay BID, at front contact 8'53 opens the circuit to relay 820, and at back contact 813 momentarily operates relay 800, which is without effect at this time. After an interval slow-to-release relay 82!) deenergizes and at contacts 822 and 823 opens the circuit to supervisory relay 8% and reconnects line relay 83B and differential relay 8M to the trunk conductor. At contact 824 relay 8% opens thecircuit to relay 800 which deenergizes after an interval.

Line relay 6H1 in the incoming selector repeater deenergizes and at contact 6 opens the circuit of slow-to-release relay 620 and also reoperates relay 660, causing the reoperation of relay 610, as previouslydescribed. After an interval slow-to-rlease relay 620 .deenergizes and at contact 62l disconnects ground from conductor 504 to remove the busy condition from the multiple banks accessible to the selector such as selector S. At contact 622 opens the circuit of relay 660 which deenergizes after an interval. At front contact 623 relay 620 opens the circuit of relay 680 which now deenergizes and also removes ground from wiper 694 and from holding conductor 431, and at back contact 623 completes an obvious energizing circuit for release magnet 6l5 through the vertioaloiT-normal springs 613. Switching relay 680 accordingly deenergizes and a contacts tea and at opens the circuit to wipers 593 and 695. At contact 682 relay 68E) opens ,the circuit to relay 5% which accordingly releases as well as opening the holding circuit of line relay ml in series with relay 695i], At contact $83 relay 6B0 opens a further point in the holding circuit and reestablishes the rotary test circuit and at contact @83 opens a point in the circuit to relay 5% and prepares the circuit for relay 6% and vertical magnet 5H6. Relay @963, upon deenergizing, at contacts 695 and 692 opens pointsin the circuit of relay tell. In re sponse to the disconnection of ground from the holding conductor 53? and the release of line relay m1, the toll transmission selector TTS and connector C release, as described in the Crocker et al. patent. As soon as the wiper shaft of the incoming selector repeater has restored to normal position the vertical ofi-normal springs 613 are opened to open the circuit of release magnet 615. All of the apparatus is now fully released and may be used on subsequent calls.

Having described the invention, what is considerednew and is desired to be protected by Letters Patent is set forth in the following claims: 1

What is claimed is:

1. In a telephone system, a first toll exchange, subscribers lines terminating in said exchange, an outgoing repeater and an incoming selector repeater in the first exchange, a second toll ex change, subscribers lines terminating in said second exchange, a two-way two-conductor trunk line interconnecting said exchanges, the two conductors of said trunk line normally connected to said incoming selector repeater by way of said outgoing repeater in the first exchange, a selector repeater terminating said trunk line in the second exchange, means including a toll operators position in the first exchange for operating said outgoing repeater to disconnect said two conductors of said trunk line from said incoming'selector repeater and to operate said selector repeater over said trunk linefor extending a toll call to a subscribers line in the second exchange, and means including a toll board in the second exchange for operating said selector repeater to operate said incoming selector repeater over said trunk line for extending a toll call to a subscribers line in the first exchange.

2. In a telephone system, a first toll exchange, subscribers lines terminating in said exchange, an outgoing repeater and an incoming selector repeater in the first exchange, a second toll exchange, subscribers lines terminating in said second exchange, a two-way two-conductor trunk line interconnecting said exchanges, the two conductors of said trunk line normally connected to said incoming selector repeater by way of said outgoing repeater in the first exchange, a selector repeater terminating said trunk line in the second exchange, means including a toll operators position in the first exchange for operating said outgoing repeater to disconnect said two in response to the operationof said incoming selector repeater over said trunk line.

3. In a telephone system, a first toll exchange, subscriberslines terminating in said exchange, an outgoing repeater and an incoming selector repeater in the first exchange, a second toll ex-' change, subscribers lines terminating in said second exchange, a'two-way two-conductor trunk line interconnecting said exchanges, the two conductors of said trunk line normally connected to said incoming selector repeater by way of said outgoing repeater in the first exchange, a selector repeater terminating said trunk line in the second exchange, means including a toll operators position in the first exchange for operating said outgoing repeater to disconnect said two conductors of said trunk line from said incoming selector repeater and to operate said selector repeater over'said trunk line for extending a toll call to a subscribers line in the second exchange, means including a toll board in the second exchange for operating said selector repeater to operate said incoming selector repeater over said trunk line for extending a toll call to a subscribers line in the first exchange, and means in said selector repeater for marking said selector repeater and saidtrunk line busy in said toll board in response to the operation of said selector repeater over said trunk line.

4. In a telephone system, a first toll exchange, subscribers lines terminating in said exchange, an outgoing repeater and an incoming selector repeater in the first exchange, a second toll exchange, subscribers lines terminating in said second exchange, a two-way two-conductor trunk lineinterconnecting said exchanges, the two conductors of said trunk line normally connected to said incoming selector repeater by way of said outgoing repeater in the first exchange, a selector repeater terminating said trunk line in the second exchange, means including a toll operators position in the first exchange for operating said outgoing repeater to disconnect said two conductors of said trunk line from said incoming selector repeater and to operate said selector repeater over said trunk line for extending a toll call to asubscribers line in the second exchange, means including a toll board in the second exchange for operating said selector repeater to operate said incoming selector repeater over said trunk line for extendinga toll call to a-subscribers line in the first exchange, means in said selector repeater for reversing battery over said trunk line in a toll call to a subscribers line in the second exchange, and means in said outgoing repeater responsive to said reversal of battery for transmitting high resistance supervision to said toll operators position.

5. In a telephone system, a first toll exchange, subscribers lines terminating in said exchange, an outgoing repeater and an incoming selector repeater in the first exchange, a second toll exchange, subscribers lines terminating in said second exchange, a two-Way two-conductor trunk line interconnecting said exchanges, the two conductors of said trunk line normally connected to said incoming selector repeater by way of said outgoing repeater in the first exchange, a selec tor repeater terminating said trunk line in the second exchange, means including a toll operators position in the first exchange for operating said outgoing repeater to disconnect said two conductors of said trunk line from said incoming selector repeater and to operate said selector repeater over said trunk line for extending a toll coming selector repeater for reversing battery over said trunk line in a toll call to a subscribers line in the first exchange, and means in said selector repeater responsive to said reversal of battery for transmitting high resistance supervision to said toll board in the second exchange.

6. In a telephone system, a firsttoll exchange an outgoing repeater and an incoming selector repeater in said exchange, a second toll exchange, subscribers lines terminating in said second exchange, automatic switches in said second exchange having access to said subscribers lines,

a two-way two-conductor trunk line interconnecting said exchanges, the two conductors of said trunk line normally connected to said incoming selector repeater to extend incoming toll calls received over said trunk line from the second exchange, means including a toll operators posi tion in said first exchange for seizing and operating said outgoing repeater to disconnect said incoming selector repeater from said two line conductors of said trunk line and tooperatively connect said trunk line to said outgoing repeater, means at said operator's position for operating said outgoing repeater to control said automatic switches over saidtrunk to complete a connection to a subscribers line in the second exchange,

and automatic means for giving the toll operator switchhook supervision over the established connectlon.

'7. In a supervisory bridge circuit comprising two normally open upper legs and two lower legs normally connected to one pole of battery, a relay included in the first lower leg, means for completing the first upper legfrom the other pole of, battery to operate said relay, contacts on said relay for connecting said other poleof battery to complete the second upper leg, a supervisory controlling trelay bridged between the junction of said upper and lower legs responsive to the operation ofsaid first relay, a balanced circuit including said first and second upper legs for preventing systems comprising a balancing supervisory bridge circuit including two normally open upper leg, means for completing the upper leg from the other pole of battery to operate said relay, contacts controlled by said relay for completing the second upper leg by connecting the other pole of battery thereto, equal resistances included in both 1 said upper legs, a second relay having one terminal of its winding connected to the midpoint of said second upper and said second lower legs,

other contacts controlled by said first relay for connecting the other terminal of. the second relay winding to the midpoint between the first lower leg and the first upper leg, said second relay energizing in response to the disconnection of said other pole of battery from said first upper leg and deenergizing in response the reconnection of the other pole of battery to said first upper leg, and supervisory means controlled by said second relay.

9. In a supervisory bridge circuit comprising two upper and two lower legs, means for closing the first upper leg, a relay included in said first lower leg operated responsive to the closure of said first upper leg, a bridge between the junctions of the upper and lower legs completed responsive to the operation of said relay, a supervisory controlling relay included in said bridge,

a balanced circuit comprising said first and secondupper legs for preventing the operation of said supervisory relay, said supervisory relay being operated in series with said second upper leg and said first relay in response to the opening of said first upper leg and released in response to the reclosure of said first upper leg.

10. In a supervisory bridge circuit comprising two upper and two lower legs, means foriclosing the first upper leg, a relay included in said first lower leg responsive to the closure of said first upper leg, a bridge between the junctions of the upper and lower legs completed responsive to the operation of said relay, a supervisory controlling means included in said bridge thereafter operative only in response to the opening of. said first leg, said relay being maintained operated responsive to the opening of said first upper leg, and said supervisory controlling means released responsive to the reclosure of said first upper leg. 11 In a supervisory circuit for use in telephone systems comprising a supervisory bridge circuit including two upper and two lower legs, means for closing the first upper leg, means in said first lower leg responsive to the closure of said first upper leg for closing the second upper leg and for completing a bridge between the junction of the upper and lower legs, and supervisory controlling means included in said bridge thereafter operated in, response toopening said first leg and released in response to reclosing said first leg.

12. In a telephone system, a first relay, a circuit forsaid relay, means for closing said circuit to operate said relay, a second relay, a circuit for said second relay prepared responsive to the operation of said first relay, means only responsive to the opening of said first circuit for operating said second relay over said second circuit, said first relay being maintained operated in said second circuit, said second relay released in response to reclosing of said first circuit, and supervisory controlling circuits controlled by the operation of said second relay;

13. In a telephone system, a first exchange and a second exchange, a two-conductor trunk line connecting said exchanges, a toll board in the second exchange having access to said trunk line, means including automatic switches in the first exchange controlled by the toll operator over said trunk line for completing a connection to a called subscribers line terminating in the first exchange, a pair of relays in one of said automatic switches, a circuit for operating the first of said relays completed by another of said automatic switches in response to the extension of the call to the called line, a circuit for the second of said relays prepared responsive to the operation of said first relay, means in said other automatic switch for intermittently opening and closing said first circuit in case the called subscribers line is busy, said second circuiteffective to operate said second relay only in response to the opening of said first circuit and eifective to release said second relay in response to each reclosure of said first circuit, said second relay thereby intermit tently operated-in response to the intermittent opening and closing of said first circuit, and means controlled by said second relay for intermittently reversing battery over said trunk line to give the toll operator at said toll board fiash supervision.

' 14. In a telephone system, a first exchange and a second exchange, a two conductor trunk line connecting said exchanges, a toll board in the second exchange having access to said trunk line, means including automatic switches in the first exchange controlled by the toll operator over said trunk line for completing a connection to a called subscribers line terminating in the first exchange, a pair of relays in one of said automatic switches, a circuit for operating the first of said relays completed by another of said autoreceivensaid second circuit effective to operate said second relay only in response to the opening 30 of said first circuit and effective to release said second relay in response to the reclosure of said first circuit, and means controlled by said second relay for reversing battery over said trunk line to give the toll operator at said toll board switchhook supervision,

l5.'ln a'telephone system, a first exchange and a second exchange, a two-way two-conductor trunl: line connecting said exchanges, a toll boardin the second exchange having access to said trunk line, means including automatic switches in the first exchange controlled by the toll operator over said trunk line for completing a connection-to a called subscribers lihetermihating in the first exchange, a pair of relays in one of said automatic switches, a circuit foroperating the first of said relays completed by another of said switches responsive to the extension of the call to the called line, a circuit for the second relay prepared responsive to the operation of said first relay, means in said other automatic switch for opening said first circuit in-response to the called subscriber answering, said second circuit effective to operate said second relay only in response to the opening of said first circuit, and means controlled by said second relay for reversing battery over said trunk line to give the toll operator at said toll board switchhock supervision.

16. In a telephone system, a first toll exchange, subscribers lines terminating in said exchange, automatic switchesin said exchange, an incoming selector repeater in said exchange, a second toll exchange including a toll board, a trunk line interconnecting said exchanges and operatively connected to said incoming selector repeater and to said toll board, means including said toll board for seizing said trunk line and for operating said incoming selector repeater to control said auto- 7 versing battery over matic switches to completela toll connection-to a called subscribers line, apair of relays'in said incoming selector repeater, a circuit for operating the first of said relays completed by one of said automatic switches, a. circuit for the second of said relays prepared responsive to the operation of said first relay, means in one of said automatic switches foropening said first circuit, said second circuit effective to operate said second relay only in response to the opening of said first circuit, and means controlled by said second relay for resaid trunk line for supervisory purposes. I

17. In a telephone system, a first exchange, a second exchange, a two-conductor trunk line connecting said exchanges, means including said trunk line for extendinga callfrom said first exchange to a called subscribers line terminating in the second exchange, means in said firstexchange for momentarily connecting a battery potential to only one of said trunk conductors, saidlast means being automatically operative after the extension of thecall to the called line, and ringingmeans in said second exchange respon sive to said momentary battery connection to said one trunk conductor for initiating the automatic ringing of the called subscriber. 18. In a telephone system, a first exchange,

second exchange, a two-conductor trunk line' connecting said exchanges, means including a toll operators position in the first exchange for extending a call from said first exchange over said trunk line to a called subscribers line terminating in the second exchange, means in said first exchange for connecting a battery potential to only one of said trunk conductors,vsaid last means being automatically and momentarily operated after the extension of the call to the called line and thereafter operated under manual control by the toll operator from said tollposition, and ringing means in said second exchange responsive to said automatic and momentary battery connection for initiating automatic ringing of the called line and thereafter responsive to said battery connection under control of the toll operator for reringing the called subscriber.

19. In a telephone system, a first exchange, a

second exchange, a two-conductor trunk line connecting said exchanges, means including a toll operators position in the first exchange for, extending a call from said first exchange over said trunk line to a called subscribers line terminating in the second exchange, means in said first exchange for connecting a battery potential to only one of said trunk conductors, said last means being automatically operated after the extension of the call to the called line, a differential relay in said second exchange having two windings, the first of said windings being connected to said onetrunk conductor and the sec 0nd winding being connected to the other conductor of said trunk line, said relay only operated in response to saidbattery connection to saidone trunk conductor, and means controlled by the operation of said relay for ringing the called subscriber.

IRVIN GEITGEY.

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