US2022503A - Automatic telephone system - Google Patents

Description

Nov. 26, 1935. H, G, EVERS l AUTOMATIC TELEPHONE SYSTEM 6 SheecS-Sheetv l Filed May 7,I 1934 -A/ve/vro@ HARRY G. E VERS frr.'

Nov. 26, 19735. H, EVERS 2,022,503

AUTOMATIC TELEPHONE SYSTEM Filed May '7, 1954 6- sheets-sheet 2 -INvE/vroR- HARRY G. E vens Arrr;

Nov. :26,1935s H, G- EVERS 2,022,503

AUTOMATIC TELEPHONE SYSTEM l Filed May '7, 1954 6 sheets-sheet 3 INVENTOR- HARRY G. EvERs ATTY:

Nov. 26, 1935. H, G, EVERSS f AUTOMATIC TELEPHONE SYSTEM e sneejS-sheet 4 mmmu umm Filed May 7, 1954 www@ A rrr:

Nov. 26, 1935., G.l EVE-R5 ?,(')22,50.'ol

AUTOMATIC TELEPHONE SYSTEM Filed May '7, 1934 6 Sheets-Sheet 5 'INI/afvroe- HARRY G. Eve/vs rrr.

Nov. 26, i935., H. G. Evi-:Rs

' y AUTOMATIC TELEPHONE SYSTEM v Filed May 7, 1954 6 Sheets-Sheet 6 Patented ov. 1935 UNITED STA-Tes .PA-*TENT oFFIcEf f 2,022,503l AUToMATio 'TELEPHONE SYSTEM Application.May 7,11934, serial 16.224,274

20 Claims. (01.179-17'5? Thisinvention relates in-generalto automatic telephone systems, but more in particular to small systemssuited for installation in towns or vil1ages.'-- An automatic telephone system of this type is gen- `erally known as a community automaticexchange or C. A. X., and may have a capacitylofffty lines;- more or less. Usually the lines areparty lines having either bridged vory grounded-ringing l'circuits over whichl the subscribers are'signallediby" meansvotcode ringing. Provisionlis-lalsomadeu for trunkingy calls to and Yfrom distant exchanges? The objectof the presentinventionA-is to prof Vide a novel andl improved all relaycommunityHr automatic-exchange -of the `foregoing characten Oneof theffeaturesof the inventionirelatesto the novel circuit arrangement 'in-the al-lrelay finder connector link Vfor interconnecting'tlie'vari ouslines in this system.

Another feature of invention frelates to JanWim-' provedtalking .arrangement forreceiving the vinfill, pulses transmitted Vfrom a cal-lingline and forre'l" peating the impulses.`

Another feature ofthe invention relatesftolthe@ circuit arrangement for selectingt'andconnecting` vari-ous code rings to called subscriberslline's.'n

These andother features -of thel invention vwill 'l beapparent from the followingadeta'iled descripl tion of the invention.v

Referring now to the drawings, comprising Figs;

`l to 6, inclusive, there is shown by means of the usual circuit diagramone of theall-relay 'lnderll connector links, the dilierentilline circ'uitsfand.v

substation circuits by'means of which'ltheFinveni-"fv v tion maybe described and understoodi" Fig. 1 shows a party line, in :this case' linel"|'| T an-d its associated line circuit. The line conduce@ tors I4 and I5 and the incoming .test conductor@- lli `of this line, shown bracketed, extend to'itlie connecting end of the nder connector llink -inf Fig. 4 where'theconductors connectwithfcorrespondingly numbered conductors. 'I'he remainder of Fig. 1 shows thendin'g end of the nderf'connestor linkcomprising a set of ndergrou'p' relays FGR. and finder' units relays FUR. Each group of lines, such'asvthe teni group, has two lnder. group`A relays, such as relay -for iconnesting only theline conductors of line groupll) to `the link," and-'relayll whichffconriects' only` the test conductors of -linevgrcupL-l tof/the link." It is vassumed inlthis case that'thereare reight groups'of lines, each comprising sevenlines Yeach.- In order to simplify the-drawings? onlyf threevk groups of lines, namely th'e llllgroup, Q01-group, andf'll-group havefbeenshown- Each of the linesvr are connected to a line circuit in the samemariner as-f-illustratedrfor line The nder unit relays FUR'correspond in number to the number of lines'in each group, in thiscase, since there are seven lines ineachgroup there are seven finder unit relays. Only three of the finder unit relays, 5 however, have been shown in order to simplify the-*drawings K Figs. 2 and 3 show the control relays of this finder connector link.

Fig- 4 shows the connecting end of'this finder 10 connector link and two line circuits. In thesame manner as described for the finder group relays the connectingA end of the linkincludes two relays'Y y for each group of lines. The connector group relay 4||l forthe rst ortens vgroup connects only 15 the line conductors of the lines in thevlI-lgroup tothe link while the relay 4I| connects only the test Aconductors ofthe line in the Ill-groupto the linka Since there are eight groups of vlines then there are eight sets of vconnector group relays provided,` butonly four of such sets have been shown. The connector unit relays comprisea group of seven relays, one relay for each corre sponding line in a group. In this case only fourv ofthe.` connector unit relays are shown -in order 25 to reduce thedrawings. Each odd connector unit' relay prepares a 'circuit for the succeeding even connector unit relay, and each evenconnector unit relay prepares a circuit for the succeeding odd connector unit relay, as diagrammatically illustratedby the dotted lines. In a similar manner each odd connector group test relay, such as relay" 4| |,"prepares a circuit for the succeeding even'connector group rtest relay, such as relay 42|. In a similar manner each -even connector 35 group test relay such as relay 42| prepares a circuit for the succeeding` odd connector group test relay, such as relay 43|, not shown. In the upper righteha'nd corner is shown the line circuit for partyfline The subscribers ringers on'40 this line are'connected to both the negative and positive line conductors to provide the so-called divided ringing. In the lower right-hand corner of \Fig..4 is shown'the line circuit of a grounded twenty-party line.

45 Fig-5 in its upper portion diagrammatically illustratesthe'chain circuit arrangement between?" the various finder connector links'in this systeml while relays DYto 510, inclusive, comprise JKthe allotting and alarm relays. TS diagrammati- 50 callyillustrates-atime switch which is started in response Ato the operation of start reay -5||lfto close--springsf'UZ-and 503 at predetermined time intervals;V Relays V58|] and 590 and interrup-ter 593 -compriseatiming device forffreeing a nder v connector link in case the same is held by a permanent line.

Fig. 6 shows the code selecting relays CSR which are controlled by the impulse repeating relay in the link to selectively connect one of the code ringing conductors extending to a ringing interrupter, not shown. The ringing machine, not shown, is started in operation in response to the operation of a switching relay in any link circuit and periodically grounds the code ring conducto-rs shown to produce codes indicated by the numerals associated with such conductors.

Brieiiy, the operation of this system is as follows: When a calling subscriber initiates a, call the test conductor of the calling'line is marked with calling potential and the calling group is marked in al1 the nder group relays in all of the links. The start conductor is grounded and the finder group relays in the first idle link operate in sequence to nd the calling group. When the calling group is found the last operated nder group relay connects the test conductor of all the lines in the calling group to the finder unit relay, which now operates in sequence until the marked calling line is found.

When the calling line is found the transfer relay in the link is operated to prepare another idle link for use and the calling line is connected to the control circuit of the link in use. The rst digit transmitted by the calling subscriber operates an impulse repeating relay to successively operate the connector group relays. Only the last operated connector group relay is maintained energized to connect the test conductor of the called group to the connector units relays of the link. The second digit reoperates the impulse repeating relay to successively operate the corresponding connector unit relays. Only the last operated connector unit relay is maintained energized to connect the test conductor of the called line to the link control circuit. The third digit reoperates the impulse repeating relay to select the ringing code. If the called line is idle the ringing interrupter, not shown, grounds the selected code ringing conductor to cause the bells on the called line to be rung in accordance with the code selected.

In outgoing trunk calls the calling line is found in the same manner as just described and in response to dialling the two digits designating a trunk call the corresponding connector group and unit relays operate as before to connect with the trunk line. In this case the code selecting digit is not dialled as none is needed.

Local calls It will now be assumed that subscriber S in Fig. l desires to call a subscriber S4 shown in Fig. 4. When subscriber S removes his receiver a circuit is completed for energizing line relay I over the following circuit: from ground by way of armature I and resting contact, lower winding of line relay I, line conductor I5, through the substation loop over line conductor I4, armature 8 and through the upper winding of relay I to battery; at armature 5, relay I connects calling potential to the test conductor by way of armature II and the Winding of cut-ofi relay 2; at armature 6 and resting contact disconnects the cut-off relay. 2 from the incoming test conductor I6 and at its make contact grounds the test conductor I6 to make thisline busy to other subscribers attempting to call the same. At

armature 1 relay I grounds the start lead 6I common to the I0-line group to complete a circuit for energizing the common start relay 5I0 as follows: from ground by way of armature 1, armature I2 and resting contact, common start lead 6I, resistance 6| and through the winding of start relay 5I0 to battery. At armature 5|| relay 5|0 completes a circuit for energizing line relay 201; at armature 5|2 prepares the locking circuit for relays 540, 550 and 560; at armature 5I3 completes the circuit for energizing relay 52 0, and at armature 5|4 prepares a circuit for shunting relay 520 and for energizing relay 530. The circuit for energizing -relay 520 extends from ground through Winding of relay 520, armatures 5I3, 533, and 544, resistance 546 to battery. Relay 520, upon energizing, at armatures 52| prepares a circuit for energizing relay 530 and at armature 523 connects the winding of relay 560 to the time switch TS. Relay 530 is not energized at this time because this relay is shunted over the following circuit: from battery through the resistance 546, armatures 544, 533, 5I3, and 52| to the winding of relay 530 and battery.

Line relay 201 energizes over the following circuit: ground by way of armature 50|, armature 5II, resistance 5|5, armature 53| and resting contact, in start lead 28|, armature 2I5 and resting contact, conductor |50, armature 246 and resting contact, upper left-hand winding of repeating coil RC, normally closed spring controlled by armature 233 and through the winding of line relay 201 to battery. At armature 230 relay 201 completes the circuit for energizing impulse repeating relay 303, and at armature 23| prepares the circuit for energizing relay 30|. The circuit for energizing impulse repeating relay 303 may be traced as follows: from ground by way of armature 249 and resting contact, conductor 262, armature 320 and resting contact, conductor 26|, armature 230, conductor 260, and through the Winding of impulse repeating relay 303. to battery. At armature 324 and working contact relay 303 completes a holding circuit for itself by way of resistance 329 and conductor 26|; at armature 325 completes an obvious circuit for energizing relay 30| and grounds conductor 264; at armature 326 opens a point in the circuit to relays 306, 301 and 309, and at armature 321 shunts armature 238. At armature 3I6 relay 30| prepares a high resistance circuit for line relay 201, at armature 3| 1 prepares a cir-- cuit for switch-through relay 2|3, and at armature 3|8 grounds conductor 21| to complete a circuit for energizing slow to release relay 302 as follows: from ground by way of armature 3|8, conductor 21|, through armatures 239 and 226 in multiple to conductor 212 and through the Winding of relay 302 to battery.

At armature 320 and resting contact relay 302 opens the original energizing circuit of relay 303 which is now held energized over its locking circuit from ground at armature 324. At armature 320 and working contact relay 302 grounds conductor 263 and closes a multiple ground circuit to relay 30| by Way of armature 23| and working contact and conductor 264. At armature 32| relay 302 grounds conductor 265 to prepare a circuit for the disconnect relay 206, at armature 322 connects grounded conductor 215 to iinder lock conductor |53 and completes a circuit for energizing the first nder group relay I||, and at Varmature 323 grounds the connector lock conductor 218 as well as lock conductor 210 by Way of armature 24|.

Theicircuit for energizing the rst finder group as follows: `from` grounded start lead 0|t arma relay-I extends from grounded conductor |53, armature 223 and resting contact, armature 220 and resting contact, conductor |56, resistance |90, armature |81 and resting contact, through the armatures and resting contacts of the iinder group relays, not shown, to armature |21, resting contact of armature |21, armature ||1 and resting contact, through the winding of relay to battery. At armature H6, relay com,- pletes its own locking circuit through the resting contacts of armatures such as armatures |25 and |85, on the finder group relays to grounded conductor |53; at armature H8 prepares the circuit for relay l l0; at armature i9 connects the grounded start lead 6| to the group test relay 203 by way of conductor |59 and armature 244; at armature ||1 and resting contact opens its original energizing circuit and at its working contact closes the circuit for the second nder group relay |2|. Relays such as relays |21 and IBI are slightly slow to operate on account of their slugs and the resistance |00. At the upper armatures of relay the test conductors of the |0 line group are connected to the test armatures of the finder units relays.

In order to= describe the operation of the finder group relays it will be assumed for the time being that the calling line is not in the first or the 0 line group. In this case, after an interval relay |2| energized over the following circuit: from grounded lock conductor |53, by Way of armatures 223 and 220 and their resting contacts, conductor |55, resistance |20, armatures and resting contacts of the nder group relays to armature |l1 and its working contact and through the winding of relay |2| to battery. In a manner similar to that described for relay relay |2| energizes and at armature |20 locks itself to grounded conductor |53. At armature |25 relay |2| lopens the locking circuit of relay whereupon the latter relay deenergizes after an interval, and at armature |21 opens a point in its original energizing circuit and at the working contact of armature |21 completes the circuit for the succeeding finder group relay associated with the .'iElLline group, not shown. At armature |28 relay |2| prepares the circuit for relay |20, at armature |20 connects the start lead 62 of the 20-line group to the group test relay 203, and at its upper armatures connects the test conductors of the 20-line group to the finder vunits relay. Relay l upon deenergizing, at its upper armatures disconnects the test conductors of the lil-line group, at armature I3 opens the prepared circuit to relay H0 and at armature H9 vdisconnects the start lead 6| from the group test relay 203. Finder group relays |3| to |1|, inclusive, not shown, and relay |8| operate in the manner just described, each succeeding relay opening the locking circuit to the preceding relay to deenergize the same, connecting the corresponding group start lead to the group test relay 203, preparing a circuit toits associated line connecting relay, completing its own locking circuit, and connecting the test conductors of its associated group to the nder units relay.

When the iinder group relay corresponding to the group in which the calling line is located is operated ground on the start lead completes the circuit for energizing the group test relay 203. For example, relay lll at armature ||9 completes the circuit for energizing group test relay 203 in case .a lineV in the lli-,line group yis calling,v

ture H9, conductor |59, armature 224 and through vthe lower winding of group test relay 203 tobattery. At armature 2|0 relay203 completes ashort circuit around its upper winding 5 to make this relay slow to release, atarmature 2|9 uopens a point in, the circuit to relay "202,1 at armature 220 disconnects grounded conductor |53 from conductor 55 to open the circuit to the succeeding. nder group relay before the same 10 can energize and close its locking circuit, and at armature 220 and Working contact connects the grounded conductor |53 to conductor |55 for energizing the rst nder unit relay |0| as follows:l from grounded conductor |53, armature l5 223 and resting contactarmature 220 and Working contact, conductor |55, armature |42 and resting contact, armature |and resting contact, 4through similar armatures on theA finder unit relays (not shown) to armature |48 and 20 resting Contact and throughthe winding of relay |0| to battery, At armature |4| relay |0| completes a locking circuit for itself by way of armatures |43 and |45 and the corresponding armatures on the other iinder unit relays (not 25 shown) to grounded conductor |53. At armature |42 relay |0| opens its original energizing circuit and completes the circuit for relay |02 and at its upper armatures connects the link line conductors and |5| to contacts on the nder 30 group rel-ay and at armature connects the test lead |52 to the test lead I9 of line to pre.v pare a circuit for the line test relay 204.

The finder unit relays, due to the copper slug on their upper ends, are fairly sloW to o-perate, 35 and therefore the second iinder unit relay only operates after a time suicient to permit the energization of the line test relay 204 in case a calling line is connected with. In case line is not a calling line, then the relay |02 energizes 40 after an interval by way of grounded conductor |55, armature |42 and Working contact. At ar mature |43 relay |42 opens the locking circuit of relay |0| Which accordingly deenergizes after an interval, at armature |44 completes a locking 45 circuit for itself from grounded conductor |53, at armature |45 and working contact prepares the circuit for the third nder unit relay (not shown) and at its upper armatures connects the line conductors |50 and |5| to the line inder group 50 contacts and at armature |24 connects the test conductor of line |2, since relay associated with the |0-line group is energized, to the test conductor |52.

Relay |0I, upon deenergizing, at its upper ar- 55 matures Idisconnects the test and line conductors, at armature |4| opens a point in its own locking circuit,l at armatures |42 and working contact opens the original energizing circuit of relay |02, and at the testing contact of `armature |42 con- 60 neots the third finder unit relay (not shown) to grounded conductor |55, by way of armature |45 and its working Contact. Finder unit relays |03 to |06, inclusive (not shown), and relay |01 operate in the manner just described, each relay at its upper armature connecting the test conductor of its corresponding line to line test relay 204, opening the locking circuit of the preceding operated relay, closing its own locking circuit, and preparing the energizing circuit to the succeeding relay which is completed when they preceding relay deenergizes.

Inthis case, since line |1 is calling, then when the finder unit relay |01 energizes this relay at armature |14 completes the circuit Afmenergiz-V 75 ing the line test relay 204 in series with the cutoffrelay 2 as follows: from ground at armature 3|8, conductor 21|, upper winding of line test relay 204, conductor |52, armature |14, armature I|4, armature 5, armature II and through the winding of cut-off relay 2 to battery. At armature 22| relay 204, upon energizing, completes a circuit for energizing relay 3|2 and for grounding conductor 259, at armature 222 short circuits its upper winding to render the relay slow to release and to connect direct ground to the test conductor, at armature V223 disconnects grounded conductor |53 from conductor I 55 to open the circuit to the succeeding nnder unit relay before the same can fully energize, at armature 223 and working contact completes a locking circuit to its lower winding and a circuit for energizing relay I|0, and at armature 224 opens the circuit to group test relay 203 to cause this relay to deenergize.

Cut-off relay 2, upon energizing, at armatures 8 and I0 opens the circuit of line relay I, at armature S completes a locking circuit for itself to grounded test conductor |52, and at armature I and its working contact completes the circuit for energizing lock-out relay 3. Relay I|0 is energized over the following circuit: from grounded conductor |-53 by way of armature 223 and work ing contact, armature 225, conductor |51, armature II8 and through the winding of relay IID to battery. At its upper armatures relay IIO connects the line conductors of the lines in the |0- line group to the contacts of the finder unit relays and in the case of armatures II2 and I|3 connects the calling line, or line I1, to conductors |50 and |5| by way of armatures |12 and |13, thereby completing a new energizing circuit for line relay 201 and for connecting dial tone to the calling subscribers line to notify such subscriber that he may now dial the called subscribers number. Lock-out relay 3, upon energizing, at armature II opens the original energizing circircuit of cut-on? relay 2, at armature I2 and resting contact, disconnects ground from the start conductor 6I to deenergize start relay 5| 0 if no other line is calling, and at armature I2 and its working contact completes a locking circuit for itself from grounded armature 1. Line relay I, upon deenergizing, at armature 6 disconnects direct ground fromincoming test conductor I6 at its working contact and at its resting Vcontact connects ground by way of armature 3|8, conductor 21|, armature 222, conductor |52, armatures |14 and I I4, and armature 9 to the incoming test conductor I6 to maintain this line busy at the called end of the link. At armature 1 relay I opens the locking circuit of lock-out relay 3.

Group test relay 203, upon deenergizing when its circuit is opened at armature 224, at armature 2|9 completes a circuit for energizing relay 202 through its upper winding by way of working contact of armature 223 and grounded conductor |53. At armature 2 I1 relay 282 completes an obvious circuit for the transfer relay 20|. At armature 2 I4 relay 20| prepares a locking circuit for itself, at armature 2| 5 opens the original energizing circuit of line relay 201 now held energized over the calling subscribers loop, and at the working contacts of armature 2| 5 connects the in start conductor 28| with the out conductor 282 so that a succeeding call may seize the next idle finder connector link. At armature 2| 6 relay 20| completes one point in the all link busy chain by connecting conductor 280 to conductor 283.

l The circuit forenergizing relay 3|2 may be traced as follows: from grounded armature 249 and resting contact, conductor 262, armature 22 I, conductor 259, armature 330 and resting contact and through the winding of relay 3|2 to battery. 5 At armature 362 relay 3|2 prepares a locking circuit for itself, at armature 363 prepares a circuit through the lower winding of relay 3| I, which relay does not energize at this time because the lower winding is short circuited by way of armature 363, armature 330 and resting contact, and the normally closed springs closed by armature 331. At armatures 364 to 361, inclusive, relay 3|2 prepares the pulsing circuit to the connector group relay. l5

Relay 5I0 deenergizes in case no other line is calling at this time, and at armature 5I disconnects ground from the start in lead 28|. At armature 5I3 relay 5|0 opens the shunt circuit of relay 530 which relay now energizes in series with relay 520 by Way of armature 52|. Relay 530, upon energizing, at armatures 53| transfers the start circuit from the beginning of the chain to the middle of the chain; at armature 532 prepares a short circuit for relay 520 and a circuit 25 for relay 530, at armature 533 opens a point in the low resistance shunt of relay 530, and at armature 534 disconnects the time switch from relay 560 before the time switch has had sufcient time to energize relay 560. 3o-

At this point it may be advisable to consider the operation of the allotter relays in response to a second call when relay 530 is energized. In this case start relay 5I!) is energized over the common start lead as before, and at armature 351 5|.I completes the start circuit and grounds the in start lead 28| as follows: ground by way of armature armature 5I|, resistance 5| 5, armature 53| and working contact to in start lead 28|','extending to the finder connector link near 4o the middle of the chain. At armature 5|4 relay 5|0 connects grounded armature 543 by way of armature 532 to the Winding of relays 52|) and 530 with the result that relay 520 is short circuit-V ed and Cleenergizes, while relay 530 is maintained 4a energized over this circuit. Relay 520, upon deenergizing, at armature 522 connects springs 503 of the time switch TS to the winding of relay 560. Relay 5|0 is deenergized and ground is removed from the in start lead 28| at armature 5I I. At 5o armature 5l4 relay 5|0 opens the circuit of relay 530 which accordingly deenergizes. At armature 53| relay 530 transfers the start circuit back to the beginning of the chain and at armature 543 disconnects the time switch TS from the winding 55 of relay 560.

A circuit for maintaining line relay 201 energized over the calling subscribers loop may be traced as follows: from ground by way of armature 236, resting contact and armature 241, conductor |5|, armatures |13 and II3, positive line conductor I5 through the substation loop to negative line conductor I4, armatures ||2 and |12, conductor |50, armature 246 and resting contact, upper left-hand winding of repeating coil RC, normally closed springs controlled by armature 233, and through the winding of line relay 201 to battery. Dial tone is also connected to the calling line at this time over the following circuit: from dial tone in Fig. 3, resting contact and armature 328, tone condenser TC, conductor 254, resting contact and armature 246, thence over the calling loop circuit just traced. The calling subscriber, after listening to the dial tone, dials the group and line digits followed by the code selecting digit. Line relay 201 deenergizes in response to each impulse. In response to the rst pulse relay 201 at armature 230 opens the circuit of impulse repeating relay 303 which accordingly deenergizes. At armature 23| and its resting contact relay 201 closes a high resistance priming circuit for itself which may be traced as follows: from grounded conductor 262, armature 320 andwcrking contact, conductor 263, armature 23| and resting contact, conductor 251, armature 3I6, resistance 3|9, conductor 254, upper left-hand winding of repeating coil RC, normally closed switch springs controlled by armature 233, and through the winding of line relay 201 to battery. This priming circuit while insuicient to energize line relay 201 due to resistance 329 greatly assists the energization of line relay 201 when the same is connected to a leaky calling line. At armature 23| and its make contact one of the multiple ground connections to relay 30| is opened but this relay due to its slow releasing characteristics remains energizing during the impulsing period.

Impulse repeating'relay 303, upon deenergizin'g, at armature 324 opens a point in its own holding circuit, at armature 325 opens a further circuit to'slow to release relay 30|, and at armay ing of repeating coil RC in order to improve the impulsing circuit, at armature 331 completes a lholding circuit for relay 3I2 by way of grounded conductor 259 and armatures 351 and 362, at armature y338 prepares an energizing circuit for relay 304 and the holding circuit extending to the lower windings of relays 308 and 309, at armature 339 prepares a point in the circuit for the busy relay 305, and at armature 340 disconnects grounded conductor 259 from conductors v269 and 394.

Slo-wto release relay 301, upon energizing, at armature 342 prepares a holding circuit for, relay 300, at armature 343 completes a locking circuit .from grounded armature 316 through the Vlower winding of relay 306, and at armature 345 pre pares a point in the circuit for the first connector group relay 4I I, Relay 301, due to its slowrelease characteristics, is maintained energized during the impulsingperiod and therefore deenergizes shortly after each series of impulses.Y

Impulse repeating relay 309, upon energizing, at armature 300 prepares a point in the energizing circuit of relaylfsiit and inthe holding circuit of relay 303, at armature 35,0 prepares a new energizing circuit for impulse're-peatingrelay r303 and-the circuit through the lower winding of relaysf308 and 300, at armature prepares a holding circuit for the lower windings of relays 30B and 300, at armature 352 disconnects ground at armature 316 from the even pulse conductor 380 and connects ground to the vodd pulse conductor 330, and at armature 353 completesa circuit. forV energizing connector group relay 4| |y as follows: from grounded lock conductor 210, through armatu'res`4fl2,-452 and 405 of the @01HHectorgroupre-- lays to conductor 389, working contact and armature 366, resting contact and armature 360, armatures 345 and 353, armature 36| and resting contact, armature 361 and working contact, conductor 39|, and through the winding of relay Y 4I I to battery. Relay 4I I at its upper armatures connects the test conductors of the lines in the lIll-group to the` connector unit relays; at armature 400 completes a locking circuit for itself to grounded lock conductor 218 by way or armatures 365, 452 and 442; and at armature 492 prepares the circuit for relay 4I0.

At the termination of the first impulse line relay 201 again energizes over the subscribers loop to complete a circuit at armature 230 for energizing impulse repeating relay 303 and a circuit through the lower winding of relays 309 and 308. At armature 23| relay 201 opens its priming .circuit and recloses the circuit for slow to release relay 30| to maintain .the same in energized position. The circuit for energizing relay 303 may be traced as follows: from ground at :armature 350 on the .energized repeating relay 309, resting contact and armature 341, conductor 26|, armature 230, conductor 260, and through the windrelays 306, 301 and 300, while at armature 326 and its working contact completes a circuit from grounded conductor 263 by way of armatures 338 forlenergizing relay 304 and 4for completing a circuit by way of armature V35| through the .lower windings-of `relays 308 and 309. Relay 309 lis maintained energized over this circuit while relay 308 is energized. At armature333 relay 308 opens a point in onerof itsenergizing circuits, at armature 341 opens the original energizing circuit of relay 303 which is now maintained energized over its own lockingvcircuit, at armature 348 and resting contact opens the original energizing circuit of .relay 309 and at its working contact prepares alocking circuit for itself. Relays 308 and 309 at this time .are maintained energized from,V

ground by-wayof conductor 263, working contact and armature 326,armature 333,armature 35| and through the lower-windings of relays308 and 300 -to battery. Relay 304, upon energizing, at armature 328 disconnects dial tone and prepares a circuitfor connecting'ring back tone to the calling subscriber, at armature 330 and its resting contact opens the `original energizing circuit of relay3|2 and its working contact closes alock- Yingoircuitfor itselfY from grounded conductor 259 as well as opening its original energizing circuit. At this time relay 3|2 is maintained energized over :the following circuit: from grounded conductor 250, working contact and armature 331, armature 351 and resting contact, armature 362 and the winding of relay 3|2 to battery.

.In rresponse to the second pulse of the first series, 'line relay 201 again deenergizes and at armature 230 opens the circuit to the impulse repeating .relay 303, while at armature 23| Vthe multiple circuit-to slow to release relay 30| is opened and the priming circuit for the line relay is again .,closed. Relay 303, upon deenergizing, at armature324 again opens itsrown holding circuit, all armature 325 again opens the circuit to slow to release relay 30|, at armature 326 recloses the circuit to slow to release relay 301 before such relay deenergizes, at armature 326 opens the holding circuit extending through the lower windings of relays 308 and 309, and at the normally closed springs controlled by armature 326 completes a locking circuit through the upper winding of relay 308 by way of armatures 333 and 348. Relay 309, upon deenergizing, at armature 350 prepares a circuit for reenergizing relay 303, at armature 35| opens a further point in the holding circuit through the lower windings of relays 308 and 309, at armature 352 connects ground at armature 316 to the even conductor 386 to complete an energizing circuit for the next connector group relay, in this case relay 42 and at armature 353 opens the original energizing circuit of relay 4| The circuit for energizing relay 42| may be traced as follows: from grounded armature 316 and resting contact, armature 343, armature 352 and resting contact, armature 359 and resting contact, armature 365 and working contact, conductor 380, armature 49|, and through the winding of relay 42| to battery. Relay 42|, upon energizing, at its upper armatures connects the test conductors of the lines in the 20-group to the connector unit relays, at armature 465 opens the locking circuit of relay 4|| which accordingly deenergizes, at armature 466 completes a locking circuit for itself from grounded lock conductor 218 by way of armatures, such as armatures 442 and 452, at armature 461 prepares a circuit for relay 428, at armature 468 connects the succeeding connector group relay 43| (not shown) to the odd pulse conductor 384, and at armature 469 prepares a point in the circuit for code switching relay 600. Relay 41|,v upon deenergizing, at its upper armatures opens the circuit to the test conductors of the line in the l-group, at armature 490 opens its own locking circuit, at armature 49| opens the circuit to relay 42| now locked energized, and at armature 492 opens the prepared circuit to relay 4 0.

Line relay 201 reenergizes over the calling subscribers loop at the end of the second pulse, and at armature 230 closes a circuit for energizing relay 303 by way of resting contact of armature 350 and working Contact of armature 341, while at armature 23| the circuit to slow release relay 30| is .again reclosed. Relay 303, upon energizing, at armature 324 again closes its locking circuit, at armature 325 again closes the circuit for relay 30 and at armature 326 opens the holding circuit through the upper winding of relay 308 which accordingly deenergizes. Relay 308, upon deenergizing, .at armature 346 prepares a point in the original energizing circuit of relay 308, at armature 341 opens the energizing circuit of relay 303 which is now held energized over its locking circuit, and at Iarmature 348 opens a point in its own locking circuit and prepares a circuit for relay 309. From the foregoing it will be seen that relay 303 follows the pulses of line 201; that relays 308 and 309 are energized on the rst pulse, and for each odd pulse; that relays 309 and 308 are deenergized on the second pulse or on each even pulse; that relay 309 grounds the odd pulse conductor 384 on energization and grounds the even pulse conductor 386on deenergization to successively operate the connector group relay such as relaysl4| I, 42|, etc. The circuit for reoperating impulse repeating relay 303 is taken through armatures 341 and 350 so that the circuit to relay 303 cannot be closed until relays 308 and 30,9 have operated or released.

will very quickly fall back when its circuit is mof mentarily opened by line relay 201 at armature! When relay 303 is deenergized such relay' 230. cannot again energize until the repeating relays 308 or 308 have operated or released to close the circuit for relay 303, even though the line relay' is immediately reoperated. Relays 308 and 309? need not necessarily be fast operating relays in order to repeat the impulses received. In addition a primary circuit or articial leak is provided through resting contacts on the line relay 201 for facilitating its reoperation over long, clear' lines. This impulsing circuit in combination with the odd and even pulsing'circuits has proven to be a very satisfactory circuit arrangement on lines of varying electrical characteristics which here-- tofore have prevented automatic working.

In response to the third pulse relays 201 and 363 deenergize 4and relay 303 causes the energization of relay 309 as previously described for the first pulse. ductor 334 the third connector group relay 43| (not shown) is energized over the odd pulse conductor 384 at armature 468. In the same manner When relay 309 grounds the odd con-v as described for relay 42 relay 43| (not shown) 1 closes its upper armatures to connect the test leads of the 30-line group; opens the locking circuit of relay 42| which deenergizes; closes its own iccking circuit; prepares the circuit through its .associated line connecting relay (not shown) similar to relay 420; and connects the connector group test relay of the 40-line group (not shown) to the even conductor 386. At the end of the third pulse relays 201, 303 and 308 energize as previously described for the end of the first pulse.

In response to the fourth impulse relays 291, 303 and 309 deenergize as described for the second impulse. When relay 309 grounds the even conductor 386 the connector group test relay (not shown) for the 40-line group is energized in a .31.,

manner similar to that previously described. This connector group relay closes the test leads of the 40-line group; opens the locking circuit of the connector group relay of the'30-line group which deenergizes; closes its own locking circuit;

prepares a circuit through its own associated line connecting relay (not shown), and connects the connector group test relay of the fifth line group (not shown) to the odd conductor 384.

In the same manner as just described each odd il pulse grounds the cdd conductor 384 to energize the corresponding connector group relay, and each even pulse grounds the even conductor 383 to energize the corresponding connector group test relay. The connector group test relays 435 and 46| and the associated connector group line connecting relays 438 to 460 are not shown because their circuit operations are identical with the connector group relays shown. In response to the seventh pulse odd conductor 384 is grounded by relay 309 to energize the connector group test relay 41| of the 10-line group by way of armature 456 on the connector group test relay of the 60- line group. Relay 41| at its upper armatures connects the test leads of the lines in the 'l0-group 7 .5

:reozasoa rto' the connector unit relays,.= at#` armaturer452 :opens the locking circuit of theflast-A operated con- `Inectonfgroup test relay, .at armaturefl'453-Av closes its own locking circuit, at armature 454 connects the connector group test relay=48| -lof the180`line group toeven conductor 386, at armature'f455 prepares the circuit to line connectingr'elay 41 vof Ithe`10-line group and at armature 456 :prepares y a circuit for the ring reversing relay 3 I4.

Relaysl 201 andv 303 remain energized after the `last impulse-of the series andafter an interval slow to release relay 391 deenergizes. At'armature 343 relay 381 opens a pointin 'the pulsing circuit as Well as the holding circuit of relay 306 which accordingly deenergizes, andV at armature '345 opens a point in the yoriginal energizing circuit of relay 4H.

Relay 306, uponl deenergizing, at armature 335 removes the-short circuit from the repeating coil RC, atarmature 331 .opens the locking circuit of relay 3|2 and substitutes the circuit through the lower winding of rrelay 3| in series With the Winding of relay 3| 2, whereby relay 3|2 is maintained energized and relay 3|| is energized over the circuit from'grounded conductor-258 in series With' the'winding of relay 3 |2. At armature 338 relay308 opens the circuit' to relays 398 and 309 to deenergize the same if 'they should be energized at this time, at armature 339 opens a point in the circuit to the busy relay 305, and at armature 340 reconnects ground- Y ed conductor 259 to conductors 289 and 394. Re-

lay 3| upon energizing, in series With relay 3|2, at armature 351 .prepares a locking circuit for itself, at armatures 358 and 359 kprepares the pulsing circuit over the odd and even conductor 383 and 385 to the connector unit relays and Vat armatures 360 andl 36| .prepares a circuitfor connecting the grounded lock conductor 218 to conductor 399.

'The calling subscriber maynow dial the second digit of the desired called subscribers number. "In the same manner as previouslydescribed the line relay 201and repeating relay 3031deener'gize for each impulser and Vin response'to the iirst impulse completes the circuit for energizing relays`306, 301v and 309. 'Relay 396, upon energizing, at armature 331 opens the holding circuit of relay 3L! tocause; this relay to deenergize and likewise completes a locking circuit through the upper Winding of relay 3| for maintaining this relay :inl energized'po'sition. "Inresponse to the energization of relays-301 and 309 a circuit is completed `for energizing the first connector unit relay 40|. Relay`3l2, upon deenergizing, at armatures 384 'toi-331 prepares the pulsing circuit for the code selecting relay'CSR.

Relay 40| energizes over the following circuit: from grounded lock conductor "218, armatures `4|2, M5, 432, and similar armatures on the connector unit relays (not shown), conductor 381,

Working contact and armature 360, armatures 345 and 353, armature136| and working contact,

'through relay 2|3, and at armature 438 grounds with the odd conductor 383. yner -as just described the remaining connector is energizedl to connect the test conductor v"-34 of? lline 1| tothe link test conductor.

aconducto-rl392. 'QLine relay 201 energizes at the "end off eachc-pulsesand. again' completes the cir- -cuitforenergizing repeating relay 303 incase -relays-308 or-309-have operated or released, as

previcuslydescribed 5 In order vto'xdescribe the operation'ofthe connector unit relaysit Will be assumed that the second digit `being-ldialled Vis more thanthe digit 1. "T'Relays'201, 303 and 309 deenergize in the vsame mannerasi previously described for the lil second pulse. At `armature 353 relay 309 yopens the circuit to connector unit relay 49|, now held over its locking circuit, and at armature i352 `disconnects ground from the odd pulse conductor `383 and connects ground tothe evenl `pulse conductor-1385 to energize the second connector unit relay 432. vThis circuit may be traced as follows: ground by Way of armature 41B and resting contactarmature 343, armature 352`and resting contact, armature 359 and Working contact, even pulse conductor `385, armature -436 and through the Winding of relay 402 to battery.

fit-fits two uppermost armatures-relay 402 connects the link line conductors 252 and1255 to the contacts of the connector group relays, 'at the vthird uppermost contact connects the link test conductor .382 to the test conductor of line'12 by Way of the operated contacts on connector Agroup relay 41|. Atarmature'433 relay 492 completes a locking circuit: for itself from grounded 10 locking conductor 218 by Way of armatures 4|2 and 4|8 and similar armatures on other -connector units relays (not shown); at armature 432 opens the locking circuit ofrelay'40l which` 'Jnow deenergizes and .at .armature 434 connectsi the third connector relay1493 (not shown) tothe odd-pulse conductor 383. At the'end ofthe second pulse relays'201and 303 reenergizeand'relay 2.308 deenergizes, 1as 1previously described.

In response to the third'pulse relays2|l1Y andsc 303deenergize and relay 399 reenergizes tof ground the odd pulse conductor 383, asfpreviously described. 'The' third connector unitV relay 403 (not shown) is energizedl to connect up the test conductor of line 13; to unlock the second connectorfl relay 492fwhich accordingly fdeenergizes;` to` lock -itself to lock conductor 218; and to-'connect the `fourth connector unit relay (not shown) to the even-pulse conductor 335. Relays'f2il1, 303and `308-energizeat the end of the Vthird pulse,.1as 50 :previously described.

In'response to the fourth pulse'relays 201,303

Fand: BS-deenergize, as previously described. At armature 352 relay'ilY grounds the leven pulse conductor '385 to energize the fourth connectorr) unit relay. The fourth connector un'it relay connectsup the test conductor o'f 'line 114; unlocks the third connector unit relay which deenergizes; locks itself to lockzconductor 218; and connects the 'fth connectorunit` relay (shown dotted) U9 In the same manunit relaysareV energized and deenergized in response to succeedi-ng pulses to connect the test f conductors `ofthe' succeeding lines' inl the `group C5 A*to the f linktest conductor 382.

Since, in this case subscriber S4 on line 1| is being called, the

- second digitftherefor'e comprises only 'one pulse and therefore thieiirst connector unit relay 48| After the last impulse'of the secondV digit relays 152011 and' 303 remain energized and relay 301 falls -*back after an interval. f'opensthe lockingcircuit of` relay 309 which there- 75 At armature 343 relay301 upon deenergizes. Relay 306, upon deenergizing, at armature 331 opens the locking circuit of relay 3|| which likewise deenergizes; at armature 338 opens the circuit extending through the lower windings of relays 308 and 309 to deenergize the same if they are energized; and at armature 340 grounds conductors 269 and 394. Relay 3| upon deenergizing, at armature 351 opens a point in its own locking circuit, and at armatures 358, 359, 360 and 36| prepares the impulsing circuit to the code selecting relays CSR shown in Fig. 6.

The calling subscriber now dials the third or code selecting digit of the desired called subscribers line. Line relay 201 follows the impulses transmitted by the calling subscriber again causing relay 303 to deenergize for each pulse. Relay 306, 301 and 309 energize in the same manner as previously described. At armature 339 relay 306 prepares the circuit for busy relay 305. At armature 343 relay 301 completes the locking circuit for relay 306, and at armature 345 prepares the circuit for relay 6|0. At armature 352 relay 309 grounds the cdd pulse conductor 398 in response to the first pulse and at armature 353 completes an energizing circuit for relay 6|0. This circuit may be traced as follows: from grounded armature 323, conductor 218, armature 24|, conductor 219, armatures 652, 642, 632 and 622, conductor 395, resting contact and armatures 361 and 36|, armatures 353 and 345, armatures 360 and 366 and their resting contacts, conductor 396, and through the winding of relay 6 0 to battery.

The rst code selecting relay 6 9 energizes over the above traced circuit, and at armature 6| closes the circuit for energizing the busy test relay 305 in its rst step in series with test relay 3 5 in case the called line is busy. At armature 6|3 relay 6|0 completes a locking circuit for itself through the armatures 622, 632, 642 and 652 to the grounded lock conductor 219, at armature 6 |4 connects the second code selectingrelay 620 to the even pulse conductor 391, and at armatures 6|5 and 6|6 prepares points in the code ringing circuit. At the end of the first pulse relays 201, 303 and 308 energize as before.

In response to the second pulse relays 201, 303 and 309 deenergize, as previously described. At armature 353 relay 309 opens the original energizing circuit of relay 6 0, which is now held energized overits locking circuit and at armature 352 grounds the even pulse conductor 391 to energize relay 620. This circuit may be traced as follows: from ground by Way of armature 316 and resting contact, armature 343, armature 352 and resting Contact, armatures 359 and 365 and their resting contacts, conductor 391, armature 6 I4, and v through the winding of relay 620 to battery. At armature 62| relay 620 connects the test relay 3 l 5 in series with the busy relay 305 to test the idle or busy condition of the called line, at armature 622 opens the locking circuit of relay 6|0 which now deenergizes, at armature 623 closes its own locking circuit to grounded lock conductor 219, at armature 624 connects the third code selecting relay 630 to the odd pulse conductor 398, and at armatures 625 4and. 626 prepares points in the code ringing circuit.

Code selecting relays 630, 640 and 650 energize in response to the third, fourth and fifth pulses as a result of relay 309 alternately grounding the odd and even pulse conductors 398 and 391. Each subsequently operated code selecting relay opens the locking circuit to the previously operated code selecting relay to cause its deenergization. In response to the sixth pulse-relay 660 energizes over the even pulse conductor 391. At armature 66| relay 660 again completes the busy test circuit, at armature 663 locks itself to grounded lock conduc tor 219, at armature 664 opens its original energizing circuit after completion of its locking circuit, at armature 665 switches from one set of code ringing contacts to the other set, and at armature 666 completes the circuit for energizing the ring reversing relay 3|4. This circuit may be traced as follows: from ground by way of armatures 456 and 438, conductor 392, armature 666, conductor 319, and through the winding of relay 3|4 to battery. At armatures 31| and 312 relay 3|4 reverses the ringing connection so that generator will now be connected with the positive line conductor instead of the negative line conductor.

In response to the seventh pulse relay 309 at armature 353 completes an energizing circuit for relay 6H! as follows: from grounded lock conductor 219; armature 663, armature 664, and working Contact, armatures 642, 632 and 622, conductor 395, resting contacts of armatures 361 and 36|, armatures 353-345, armatures 369 and 366 and their resting contacts, conductor 396 and through the winding of relay 6&3 to battery. Relay 6|0 ,operates its armature for the purpose previously stated and in addition at armature 6|2 opens the locking circuit of code selecting relay 650 to cause its deenergization. In response to the eighth, ninth, and tenth pulse code selecting relays 620, 630 and 640, respectively, energize and lock, and deenergize the previously energized code selecting relay in the same manner as previously described. From the foregoing it will be seen that the code selecting relays 6|0, 620, 630, 640 and 650 are energized in response to the first five impulses in the code selecting digit, that relays 650 and 660 are energized for the sixth pulse, that relays 6|0 and 660, relays 620 and 660, relays 630 and 660, and relays 649 and 660 are energized for the seventh, eighth, ninth and tenth pulses.

In case the called line is busy a circuit is completed for energizing the busy test relay 305 in its rst step in series with the marginal test relay 3|5 as follows: from ground on the test conductor 34 of the called line, armatures 414 and 494, conductor 382, through the upper winding of marginal test relay 3|5, conductor 36|, through the operated one of the multiple contacts 6|| to 66|, inclusive, conductor 394, resistance 34|, armature 339 and through the winding of busy test relay 305 to battery. Busy test relay 305, due to resistance 34| closes only its X contact at armature 334 to prepare a circuit for fully energizing itself when relay 306 later on deenergizes. After the last pulse of the code selecting digit relays 201 and 303 again energize, and relays 306, 301, 308 and 309 cleenergize, as previously described. Relay 306, upon deenergizing, at armature 339 completes the circuit for fully energizing the busy test relay 335 as follows: from grounded conductor 259, armature 334 and working contact, normally closed springs controlled by armature 339 and through the winding of busy relay 305 to battery.

Assuming, however, that the called line is idle, then busy relay 305 is not energized because no ground is connected to the test conductor 34 of the called line. Now, when relay 306 deenergizes after the code selecting digit a circuit is completed for-energizing the test relay 3|5 in series with the cut-off relay 22 of the called line as follows: from grounded conductor 259, armature 334 and resting contact, on the unoperated busy relay 305, armature 340, conductor 394, through the operated one of the armature 6H to 66|, in-

clusive, conductor 38|, through the'upper wind-v ing of test relay 3I5, conductor 382, armatures 494 and 414, conductor 34, armature 25and resting contact, and through the winding of cut-off relay 22 to battery. At armature 311 relay 3I5 completes its own locking circuit before operating its remaining armatures as follows: from ground at the normally closed springs controlled by armature 22S, conductor 215, armature 322, conductor I53, armature 311 and through the lower windingof test relay 3I5 to battery. At armature 313 relay 3 I 5 prepares a circuit for connecting ground to the negative link conductor 252 since ring reversing relay 3I4 is energized, at armature 314 prepares the circuit for connecting generator to the positive link conductor 255, at armature 315 connects direct ground to conductor 332 to maintain the called line busy; at armature 316 v grounds conductor 268 to energize the prepared connector group relay, in this case relay 410, and at armature 313 preparesthe circuit for energizing the pick-up relay 616.

The circuit for energizing connector group rei lay 413 may be traced as follows: from grounded armature 315, and working contact, conductor 253, armature 455 on the operated connector group relay 41E, and through the winding of relay 413 to battery. At armatures 412 and 413 relay 416 connects the line conductors 32. and 33 of the called line to the link conductors 252 and 255.. When cut-oit relay 22 energizes in series with relay 315 that relay at armatures 21 and 29 dis-v connects the line relay 2l from the line conductor 32 and ground, at armature 23 connects the grounded test conductor 34 to the nder test conductor 35 to mark this line as busy in the finder end of the link circuit, and at armature 29 completes an obvious circuit for energizing the lockout relay 23. Relay 23, at armature 3i opens a point in the start circuit to start conductor 61.

At the beginning of each code ringing cycle generated by the ringing machine (not shown) the ringing machine grounds the pick-up lead' and completes the circuit for energizing relay 619 as follows: from grounded pick-up leadextending from the ringing machine, normally closed springs controlled by armature 612, conductor 333, armature 318, conductor 216, arma-- ture 245, conductor 211, and through the wind-` ing of pick-up relay 619 to battery. At armature 511 relay 516 prepares a circuit for ringingY shortrings, tl'ien a pause, followed by four moreshort rings. ln this case, assuming that the codey ring conductor 2 2 has been selected, then ringing relay 353 is energized over the following circuit: from ground at the ringing machine over the conductor marked 2 2, resting. contact and armature 59S, armatures 645 and 513, working contact and armature 665, conductor 686, armature 61 i, conductor 399, and through the windingA of ringing relay 343 to battery.. The code ring` conductor 2 2 was selected because in this case it is assumed that the code selecting digit dialled was thedigt 0, in which case code selecting relays 640 and 66ll-have been operated and locked inl operated position. Each time ringing relay 3I3isenergized from the ringing machine said 5 relay at' armature 368` connects ground by way of armatures 31Iand-313 to the negative link conductor4 252 since relay 3M is energized,l at armature 369 connects generator to the-positive link conductor 255 by way of armatures 312 and 314 10 to code ring the called subscriber, and at armature 316 completes an obvious circuit for energizing condenser discharging relay 3I9. Relay @H3 follows the impulses transmitted by ringing relay 353, but due-to its slow release characteristios this relay lags behind ringing relay 3i3 and at armature 354r connects battery through resistance 3,55 to the negative link conductor 352 momentarily after each application of generator in order to discharge the condensers associated with the ringers on the called line. At armature 353 relayv 3 l 0 completes a circuit for transmitting ring back tone to the calling subscriber as follows: from generator through working contact andV armature 356working contact and armature 326, the tone condenser TC to conductory 254 and thence over the calling subscribers loop, as previously described.

Ringing current to the called subscriber may now be traced as follows: from generator, working contact and armature 312, working Contact and armature 369, armature 314, positive link conductor 255, armatures 493 and 413, conductor 33, through theringers connected to the positive line conductor of this line to ground. Incase the ringers of this line should be bridged instead of grounded, then the ground return circuit extends back by way of negative line conductor 32, armatures 412 and 492, conductor 252', armatures 313, 368,- and-31I to ground.. 40

When subscriber S4- answers his code ring during the silent period or when ringing relay 3I3 is in deenergized position back bridge relays 2H and 2l2` energize in case the called line is a metallic line, or in case the called line is a grounded line then relay 2II alone is energized. The circuit for energizing back bridge relays 2 I l and 2I2 in case of a metallic line may be traced as follows: from ground throughv the winding of relay 2I2, lower right-hand winding of repeating coil RC, conductor 256, resting contact and armature 359, armature 314, over the circuit to the called subscribers loop previously traced for ringing currentback to conductor 252, armatures 313 and 368, conductor 253, through-the upper right-hand winding of repeating coil RC over armatures 238 and 32,1 in multiple, through the winding of relay 2| I` toV battery. In case the called line is a grounded linerelay 2I2 is short circuited over the following path: from the grounded positive line conductor of thecalled lineover armatures 413 and 493, conductor 255, armatures 314 and 369, conductor 256, through right-hand winding of repeating coil- RC, and through the winding of relay 2 I2 to ground. 65

Relay 2H, upon energizing, at armature 242 and resting contact opens a point in the circuit to disconnect relay 206 and at its working contact completes a circuit for energizing relay 2I6. At armature 243.1'elay 2l I completes a circuit for 70 energizing the battery reversing relay 269 in case the calling line is such as to require reverse battery supervision. The circuit for energizing relay g 2H)Y may beA traced as follows: from ground at armature 321, conductor 265, armature 242 and working contact, normally closed springs controlled by armature 231, and through the winding of relay 2 I0 to battery. At armature 231 relay 2 I 0 completes its own locking circuit to grounded conductor 259 and opens its original energizing circuit, at armature 238 completes the talking circuit, at armature 236 removes the short circuit from around relay 208 to permit its energization in case the calling line is a metallic line, at armature 239 opens one of the multiple circuits to relay 302, at armature 240 opens the circuit to pick-up relay 610 which accordingly de-energizes and at armature 24| disconnects ground from lock conductor 219 to cause the deenergization of the operated 'code selecting relays. Relay 200 now operates in series with the calling subscribers loop and relay 201 in case the calling line is a metallic line as follows: from ground through the winding of relay 208, normally closed springs controlled by armature 234, lower left-hand winding of repeating coil RC, resting contact and armature 241, conductor |5|, armatures |13 and H3, positive line conductor I5 of line |1 and thence through the calling subscribers Vloop and over the previously traced circuit through the'winding of line relay 201 to battery, In case the calling line is a grounded line then the positive line conductor such as conductor I5 will be grounded and relay l208 is prevented from operating. Relay 208, upon energizing if the calling line is a metallic line, at armature 232 completes a circuit for energizing battery reversing relay 209 in case the calling line is in a group requiring reverse battery supervision, in which rcase conductor |58 is connected to contacts, such as contacts I8, to conductor |51 which is grounded thereby completing the circuit by way of armature 243 for energizing the battery reversing relay 209.

All the code selecting relays in Fig. 6 now restore and relay 660 at armature 666 opens the circuit to ring reversing relay 3|4 and relay 610 at armature 61| opens the circuit to ringing relay 3|3. Relay 209, upon energizing, at armatures 233 and 234 reverse battery to the calling line, and at armature 235 completes a locking circuit for itself independent of armature 232.

When the calling line is a metallic line, talking battery is supplied from the windings of relays 201 and 208 through the left-hand windings of the repeating coil RC over the resting contacts and armatures245 and 241 to conductors |50 and |5|, and thence over the calling loop. In case the calling line is a grounded line, then talking battery is supplied through the winding of line relay 201 and from the grounded positive line conductor of the calling line. When the called line is a metallic line talking battery is supplied through the windings of relays 2|| and 2|2 over the previously traced circuit to the called subscribers loop and in this case if relay 2 I0 is operated the circuit for relay 2|| extends from the winding of repeating coil through armature 321 and conductor 266. In case the called line is a grounded line then the battery is supplied through the winding of relay 2 and from ground on the grounded positive line conductor of the called line.

After conversation and responsive to the called party replacing his receiver relays 2I| and 2|2 deenergize. At armature 243 relay 2| opens the circuit of relay 209 in case it is energized, and at armature 242 prepares the circuit for the disconnect relay 206 so that this link will be automatically released aiter a predetermined interval if the calling subscriber fails to replace his receiver. Battery reversing relay 209, if energized, now deenergizes and reverses battery to the calling line for supervisory purposes. In response to the calling subscriber replacing his receiver line relay 201 deenergizes and likewise relay 200, if energized. At armature 230 line relay 201 opens the circuit of relay 303 which deenergizes and at armature 23| opens one of the multiple ground circuits to slow to release relay 30|. Relay 303, upon deenergizing, at armature 325 opens the circuit of slow to release relay 30|, at arma-turey 321 disconnects relay 2|| from conductor 253, and at armature 326 closes the circuit for relays 306, 301 and 309. Relay 30|, upon deenergizing, at armature 3|8 opens the circuitpf relay 302 and disconnects ground from test conductor |52 to open the circuit of the cut-off relay 2. Cut-off relay 2, upon deenergizing, at armature I0 opens the circuit of lock-out relay 3, and at armatures 8 and 9 operatively connects line relay I to the line. After an interval lock-out relay 3 deener' gizes and at armature |2 prepares the circuit for start lead 6I.

Slow to release relay 302, upon deenergizing, at armature 320 disconnects ground from relays 306, 30'! and 309 to cause their deenergization, at armature 32| disconnects ground from conductor 265 to open a point in the circuit of the disconnect relay 206, at armature 322 opens the locking circuit of relay 3|5 and disconnects ground from conductors |53 and |51 to unlock the operated nder group relays I0 and I, the operated finder unit relay |01, and relays 204 and 202. At armature 323 relay 302 disconnects ground from the lock conductor 210 to unlock the operated connector unit relay 40I and connector group relay 41|. Relay 40|, upon deenergizing, at armatures 402, 493 and 404, disconnects the conductors of line 1| from the control relays in the link. Relay 41 I, upon deenergizing, at armature 414 disconnects the test lead 34 from the link circuit thereby opening the circuit to cut-oil relay 22. At armature 455 relay 41| opens the circuit to relay 410 which accordingly deenergizes and disconnects the line conductors 32 and 33 from the link. Relay 3|5, upon deenergizing, at armature 315 disconnects ground from test conductor 382, at armature 316 disconnects ground from conductor 268 to open the circuit oi relay 410, and at armatures 313 and 314 opens a point in the talking circuit. Relay 204, upon deenergizing, at armature 22| opens the locking circuit from relays 2|0 and 304 to cause the latter relays to deenergize.

Relay |I0, upon deenergizing, at armatures ||2 and H3 disconnects the line conductors I4 and I5 from the repeating coil RC. Relay III, upon deenergizing, at armature ||4 disconnects the test lead of the line from test conductor |52. Relay |01, upon deenergizing, at armatures |12, |13 and |14, disconnects the control relays oi the link from the calling line. Relay 202, upon deenergizing, at armature 2I1 transfers the transfer relay 20| from direct ground to the in lead 28| of the start chain so that if the in lead 28| is grounded at this time the transfer relay 20| will not restore and interfere with the operation of a succeeding link. In case the in lead 28| is not grounded 20| deenergizes and at armature 2I6 opens a point in the all link busy chain. At armature 2I5 relay 20| disconnects the out lead 282 and connects up the in lead 23| to line relay 201. Relay 2 I0, upon deenergizing, at armature 236 short circuits relay 208 and grounds conductor |5|, at armature 231 opens a point in its Cil own locking circuit as well as preparing its own original energizing circuit, and at armature 238 separates the right-hand windings of repeating coil RC. Relay 334, upon deenergizing, at armature 328 restores the circuit for connecting dial tone to a calling line, and at armature 33) prepares a point in the circuit to relay 3|2 as well as a point in its own original energizing circuit. Cut-off relay 22, upon deenergizing at armatures 21 and 29 prepares the circuit for line relay 2| and at armature 29 opens the circuit to lock-out relay 23. Lock-out relay 23 restores and at armature 3| prepares the circuit to start lead |31. All relays are now in their normal position and the link circuit may be used in a subsequent call.

Assuming now that the called line was busy instead of idle, and returning to the operation at a time when busy relay 235 wasfully energized after the code selecting digit was dialled, busy relay 325, upon. energizing, at armature 33| connects the busy tone to the calling line as follows: from busy tone by way of armature 33|, resting contact and armature 356, working contact and armature 328, tone condenser TC, conductor 254, resting contact and armature 242, and thence over the calling subscribers loop, as previously described. At armature 332 relay 325 prepares a circuit for grounding' test lead 322, and at armature 323 opens the circuit to relays 336, 307 and 329 and likewise prepares a circuit for reoperating relay 303 in case relay 22'! is again operated. At armature 335 relay 325 prepares a point in the circuit to reverting call relay 225 and at armature 334 completes a locking circuit for itself as follows: from grounded conductor 252, armature 334 and working contact, normally closed springs controlled by armature 339, and through the winding of busy relay 325 to battery. After receipt of busy tone the calling subscriber replaces his receiver, thereby opening the circuit to line relay 291, which accordingly deenergizes and causes the release of the operated relays in the manner as described for the release from an idle line. In this case, since busy relay 335 is energized, the deenergization of relay 224 at armature 22| opens the circuit of busy relay 335 to cause its deenergization.

The foregoing circuit descriptions are the circuit operations for ringing the subscribers, such as subscribers S4 and Sii, which have their ringers connected to the positive line conductor. As diagrammatically illustrated in Fig. 4 line has ten substations connected thereto, five of such substations having their ringers connected to the negative line conductor and the remaining lines having their ringers connected to the positive line conductor. In order to ring the subscribers having their ringers connected to the positive line conductor, the code ringing digit dialled is six or more so that the code selecting relay 660' will be energized to cause the energization of ring reversing relay 3|4, as previously described. In order to ring the sube scribers having their ringers connected to the negative line conductor the code ringing digit dialled is less than six, and therefore relays 660 and 3M are not energized. In this case the operation o-f ringing relay 3|3 connects generator f grounded line having twenty subscribers there second set.

on. As willbe noticed armatures 424 and 430 on connector group relay 42| are tied together and connected to the testk conductor 44 of this line. Armatures'422 and 421 and armatures 423 and 428 are tied together and connected respectively to the negative and positive line con- -ductors 42 and 43. From the foregoing description it will therefore be understood that this line may be connected with in response to dialling the digits 2-6 or 2-7. The rst ten subscribers on this line are signalled by dialling digits 2 and 6 and then a code selecting digit 1 to 0. In response tothe calling subscriber dialling the digits 2 and 6 the control relays operate in the same manner as lpreviously described to cause the energization of the connector unit and connector group relays 42| and 423. In response to dialling the code selecting digit the code selecting relays CSR are energized as previously described to select thevdesired code. Since in this case ring reversing relay 3|4 is not energized, ringing relay 363 always connects the generator to the negative line and since relay i) is not energized, the co-de selected by the code digit dialled is determined by the conductor selected over the resting contacts of the armatures of relay 600. The second ten subscribers on this lineare signalled by dialling the digits 2 and '7 and then a code selecting digit 1 to 0. In response to the calling subscriber dialling the digits 2 and 7 the control relays operate as previously described to cause the energization of the connector unit and connector group relays 42| and 401. When relay 401 operates its armature 4|4 a circuit is completed for energizing the code switching relay 600, as follows: from grounded conductor 219, armatures 469 and 4|4, co-nductor 393, and through the winding of code switching relay 500 to battery. Relay 620' at its resting contact disconnects the first ten code ring conductors and at the working contact of these armatures connects the second ten code ring conductors. In response to dialling the code selecting digit the code selectin-g relays are operated as before to select the desired code ring conductor in the Now when the ringing relay 3|3 is energized over the selected code ring conductor, generator is connected to the negative line conductor in accordance with the selected code ring conductor. The following chart shows the digits dialled and the code ring conductors selected in accordance therewith:

I0-party code ring mature 4-|4i thenY whenever the group selecting digit 2 is dialled the circuit for code switching relay 555 in Fig. 6 is completed over conductor 393. Relay 555, it will be remembered, switches from one set of code ring conductors to the other set whenever the same is energized. Therefore, in response to dialling group selecting digit 2 one group of the ten subscribers may be signalled. In order to code ring the other ten subscribers on the line some other group selecting digit will be dialled to cause corresponding connector relays to operate and extend the connection to this line. In this case the connector relay operated does not complete a circuit for relay S55 so that the rst set of code ring conductors are used to signal the other group of ten subscribers on this line.

Another modication is shown for reversing the application of ringing current to the called line by the energization of ring reversing relay 3M. In this modification the circuit for relay 3HE extends from ground at armature 456 over the dotted conductor 446 (inshunt of armature438) conductor 392, over the dotted conductor 392 (connected in shunt of arm'ature 365) conductor 319, and through the winding of ring reversing relay 3I4 to battery. In this case whenever connector group relay 41| is energized in response to the group digit '1, relay 354 is energized to reverse the application of ringing current to the called line so as to ring such subscribers which have their ringers connected to the positive line conductor and ground. In order to ring the subscribers having their ringers connected to the negative line conductor and ground of this same line some other group selecting digit will be dialled to cause corresponding connector relays to operate and extend the connection to this line. In this case the operated connector group relay does not complete a circuit for relay 3I4 with the result that ringing current is connected to the negative line conductor when the ringing relay 3I3 is operated.

Re'uelrting calls In order to describe a reverting call it will be assumed that substation S desires to call another subscriber on his own line, for example, subscriber SI. Subscriber S therefore removes his receiver and dials the line selecting digits 1 and 7 and then the code selecting digit assigned to subscriber SI. The nder group relays i I0 and I I and the nder unit relay |61 operate to connect the control relays of the link to line I1. The connector group relay 4I I, the connector unit relay 491, and the code selecting relays in Fig. 6 operate also in the same manner as previously described. Since the called subscriber, subscriber SI, is on the same line as the calling subscriber S, line I1 is marked busy and busy relay 355 energizes in the same manner as previously described to transmit the busy tone to the calling subscriber'. In response to the receipt of busy tone subscriber S now replaces his receiver, thereby opening the circuit of line relay 261 which accordingly deenergizes. At armature 235 relay 251 opens the circuit of the relay 353. Relay 353, upon deenergizing, at armature 325 opens the circuit of relay 30| and at armature 324 grounds the test conductor 382 to maintain the line busy and to hold the cutoff relay 2 and slow release relay 352 in energized position as follows: from grounded armature 324 and resting contact, armature 332, conductor 382, armature 418, armature l491, test conductor I6 of line I1, armature 6 and resting contact, one

branch extending to the winding of' relay 2 to hold said relay and the other branch extending by way of armature 9, armatures IIll and |14, conductor |52, armature 222, armature 233, conductor 212, and through the winding of relay 352 to battery for holding the latter relay.

Slow to release relay 30|, upon deenergizing, at armature 3I8 and working contact, opens the original energizing circuit of relay 332 now maintained energized over the previously traced circuit, and at the resting contact of armature 3I8 completes a circuit for energizing reverting call relay 205. This circuit may be traced as follows: from ground at the resting contact of armature 324 over the previously traced circuit for holding cut-off relay 2 and relay 302 energized to conductor |52, conductor 21 I, armature 3 I 8 and resting contact, armature 335, conductor 213 and through the winding of reverting call relay 235 to battery. At armature 225 relay 255 opens the circuit to iinder group relay H0 which deenergizes, at armature 226 opens one of the multiple circuits to relay 302, and at armature 221 completes a circuit for energizing test relay 3|5 as follows: from ground at the normally closed springs controlled by armature 228, conductor 215, armature 322, conductor |53, armature 221, conductor 214, and through the lower winding of relay 3I5 to battery. Relay IIE), upon deenergizing, at armatures II2 and II3 disconnects the line conductors I4 and I5 from the link conductors |50 and |5I thereby opening the circuit to line relay 251. At armature 311 relay 3 I 5 completes a locking circuit for itself, at armature 318 prepares a circuit for energizing pick-up relay 310, at armature 316 completes the circuit for energizing relay M3, at armature 315 grounds th-e test lead 382 to maintain this line busy, and at armatures 313 and 314 prepares points in the ringing circuit. The circuit for energizing relay 4I may be traced as follows: from grounded armature 316 and working contact, conductor 268, armature 492 and through the winding of relay 4I|l to battery. At armatures 495 and 455 relay 4|Il connects the line conductors I4 and I5 to the link conductors 252 and 255.

At the beginning of the code ringing cycle the pick-up conductor is grounded in the ringing machine to cause the energization of pick-up relay 619 as previously described. At armature 312 pick-up relay 61|) completes its own locking circuit, and at armature 61| prepares the circuit for ringing relay 3|3. When the selected code ring conductor is grounded by the ringing machine ringing relay 3 I3 is energized over the previously traced circuit in accordance with the number of times the code ringing conductor is grounded by the ringing machine in order to transmit ringing current to line I1. The ringing circuit may be traced as follows: from generator, resting contact of armature 31 I, working contact and armature 368, armature 313, conductor 252, armatures 415 and 495 to negative line conductor I 4 of the line I1 and thence through the ringers on line I1 to positive line conductor I5, armatures 436 and 41S, conductor 255, armature 314, armature 369, and working contact, armature 312 and resting contact, to ground.

At completion of the'code ring and in response to either the calling or called subscriber answering during the silent period relay 2II energizes in series with relay 2|2 over the following circuit: from ground through the winding of relay 2|2, lower right-hand winding of repeating coil RC, conductor 256, resting contact and armature '369, and'thenceover the previously traced ringingfcircuit through .the substation loop, back to armature 368 and'resting contact, conductor '253, upper right-hand winding of repeating coil RC, armature 238 and resting contact, and through the winding oi relay 2 I to battery. At armature 242 relay 2li completes the circuit for energizing relay 2|@ andopens apoint in the circuit to the disconnect relay 2.36. Relay 2|3, upon energizing, at .armature 231 closes its own locking circuit and opensits original .energizing circuit, atarmature .236 remo-ves the short circuit from varound relay I268, at armature "249 rdisconnects ground from conductor 213 Sto deenergize the code selecting relays, at armature 238 opens the circuit to relays 2| l and `2I2 which accordingly deenergize, and at armature 239 opens the circuit to relay 332 to cause its deenergization. After an interval slow'to release relay 362 deenergizes and at armature 323 opens the locking circuit of relays 461 and 4H; and at armature 322 opens the circuit to relays 3I5, i I I, |31, 234, and 232. Relay 481, upon deenergizing, at armatures 415, 41'6'and l418 disconnects the link conductors 252, 255 and 382 from line I1. Relay 4i I, upon deenergizing, opens at armature 431 the circuit to test conductor I6 and at armature 493 opens the circuit of relay 4|6 which accordingly deenergizes. Relay SI5, upon deenergizing, at armatures '313 and 314 opens further points in the talking and ringing circuits, at armature 315 disconnects ground from test con ductor 332, at armature 316 disconnects ground from conductor 268, at armature '311 opens a point in the locking circuit, and at armature 318 opens a point in the original energizing circuit of pick-up relay 616. Relay III, upon deenergizing, at armature IIS opens the circuit to relay I0 which accordingly deenergizes, and at armature ||4 disconnects the test lead of line I1 vfrom the link. Relay |01, upon deenergizing, at armatures I12, |13 and |14 opens further points in the link circuit. Relay 204, upon deenergizing, at armature 2.2i opens the locking circuit of relays 2m, 384 and 385. Relay 202, upon deenergizing, at armature 2|1 `transfers relay 20| from direct ground to the in start lead 28|. Reverting call relay 205, upon deenergizing, at armature 221 opens a point in the original energizing circuit oi relay 3|5.

Cut-ofi relay 2, upon deenergizing, at armature I3 opens the circuit of lock-out relay 3, and at armatures 8 and I6 reconnects line relay to the conductors of line I1. Line relay I now energizes over -the subscribers 'loop as follows: ground by way of armature I0 and resting contact, lower winding of line relay l, conductor I5, the substation loop conductor I4, armature 8, and through the upper winding .of relay I to battery. At armature 6 line relay I grounds the test conductor I6 to busy this line in the connector end of the link circuit, and at armature 1 completes the locking circuit for look-out relay 3. Lock-out relay 3 is maintained energized to prevent grounding of the start lead 3d. Relays 305, 213 and 384 now deenergize. Relay 26I deenergizes in case the in lead 28| is not grounded, as previously described. The entire link is now released and talking battery is furnished through line relay I to the subscribers on line I1. After conversation and in response to both parties replacing their receivers line relay I restores and opens the circuit oi lock-out relay 3 which is likewise deenergized and restores the line circuit to normal.

Call to switchthrough trunk It will now be assumed that subscriber S desired to call a subscriber in a distant automatic exchange, and in order to do so dials the digit 8 and 1 to connect with the trunk line extending to this automatic exchange. In response to subscriber S removing his receiver and dialling the digits 8 and 1 the finder relays, the control relays and the connector relays are operated as previously described to complete a connection with the called trunk line. In this case, since the digits 8 4and lV have been dialled, connector relays 48| and 40| are energized. At armatures 484 and 494 relays 48| and 40| connect the test lead of the trunk line 3| to test lead 382. At armatures 431 and 445 busy relay 305 is connected in series with the upper winding of switchthrough relay 2| 3 to the test conductor 382 to test 'the busy or idle condition of this trunk line. In case the trunk line 8| is busy, ground on the test conductor 481 of trunk line 8| completes a circuit for energizing ybusy relay 305 to close lits X contacts, thereby preparing a circuit for fully energizing itself then relay 306 deenergizes shortly after the impulsing period. This circuit may be traced as follows: from grounded test conductor 431, armatures :484 and 434, conductor 332, armatures 431 and 445, conductor 216, upper winding of switch-through relay 2|3, conductor "269, armature 3|1, resistance 34|, armature 33S, and through the winding of busy relay 305 to battery. Due to resistance 34| in the circuit relay '2|3 is not energized over the above traced circuit and the busy relay 305 operates to close only its X contact at armature 334. When relay 306 deenergizes shortly after the second impulsing period, as previously described, said relay at armature 339 closes the circuit for fully energizing busy relay 305 from grounded conductor 259. Busy `relay 365 now operates as previously Adescribed and connects busy tone to the vcalling line. The calling subscriber then hangs up to restore the link.

In case the trunk line 8| is idle when called, then there is no ground on test conductor 481 and busy relay 335 is not energized. Now when relay 335 deenergizes shortly after the second impulsing period a circuit is completed for energizing switchthrough relay 2| 3 in series with the cut-off relay of trunk line 8| as follows: from 'grounded conductor 259, armature 334 and resting contact, armature 340, armature 3|1, conductor 266, upper winding of switch-through relay 243, conductor 216, armatures 445 and 431, conductor 331, armatures 494 and 484, conductor 431, and through the cut-off relay associated with this trunk line to battery. At armature 250 relay 213 closes its own locking circuit to ground at armature 3|8 and at armatures '246 and 241 disconnects the calling line from the left-hand windings of the repeating coil and connects the calling line to conductors 252 and 255 direct. At armature 248 relay 2I3 opens a lpoint in 'the circuit to disconnect relay 206, at armature 249 disconnects ground from conductor 262 to open one of the multiple grounds to relay 36| and to open the locking circuit of relay 304. At armature 243 and working contact relay 2|3 grounds conductor 263 to complete an energizing circuit for relay 488 by way of armature 444, and at armature 25! connects grounded conductor 21| totest conductor 382 by way of armatures 445 and 431 to maintain the test conductor 481 grounded. Line relay 201 deenergizes when its Lik circuit is opened at armatures 246 and 241 and at armature 230 opens the circuit to relay 303. Relay 480, upon energizing, at armatures 482 and 483 connects the trunk conductors 485 and 486 to the link conductors 252 and 255. Relay 303, upon deenergizing, at armature 325 opens the circuit of slow release relay 30| which deenergizes after an interval. The trunk equipment operates and connects ground to test conduct-or 381 to hold relays 2 I3, 302 and cut-off relay 2 energized. The circuit for holding relay 2I3 energized extends from grounded conductor 481, armatures 484 and 494, conductor 382, armatures 431 and 445, conductor 210, armatures 25| and 250, through the lower winding of cutthrough relay 2I3 to battery. The circuit for maintaining relay 302 in energized position extends from grounded conductor 481 over the previously traced circuit to armature 25| and thence over armatures 239 and 226 in multiple to conductor 212 and through the winding oi relay 302 to battery. The circuit for maintaining cut-off relay 2 in energized position is the same as that previously traced and extends from armature 25| by way of conductor 21|, armature 222, conductor |52, armatures |14 and I|4, armature 9, and through the winding of cut-off relay 2 to battery. The calling line conductors I4 and |5 are now both connected directly to the trunk conductors 485 and 486 whereby the calling subscriber may now dial the digits of the desired subscriber at the automatic exchange to operate the automatic switches therein to complete the desired connection in the well known manner. Talking battery to both the calling and called subscriber is furnished from the automatic exchange.

After conversation and in response to the calling subscriber replacing his receiver, the switches in the automatic exchange release and disconnect ground from test conductor 481, thereby opening the holding circuit of relays 2 I3, 302 and cut-ofi relay 2. Relay 2|3, upon deenergizing, at armature 249 opens the circuit of relay 480. Cut-off relay 2 deenergizes and opens the circuit to lock-out relay 3 and connects the line relay I to the line conductors of line |1. Slow to release relay 302 deenergizes and at armature 322 opens the circuit to the nder relays |I0, III and |01' and relays 204 and 202. At armature 323 relay 302 opens the circuit to connector relays 40| and 48|. Relay 480, upon deenergizing, at armatures 482 and 483 disconnects the talking conductors of the link from the trunk line. The lock-out relay 3, the finder relays |I0, ||I, and deenergize as previously described. Relays 204 and 292 deenergize and the latter relay connects the transfer relay 20| to the in lead 28|. Connector relays 40| and 48| likewise deenergize. In case the in lead 28| is grounded transfer relay 20| is maintained energized, otherwise relay 20| deenergizes and the link may be used on subsequent calls.

Incoming trunk callsoperate the link circuit the same as previously described for a local subscriber calling another local subscriber. In this case, however, reverse battery supervision is needed and when the local called subscriber answers relay 2|| energizes and at armature 243 closes the circuit for battery reversing relay 209 to reverse battery over the calling trunk line.

Calls to ring-down trunks are made in the same manner as described for calls between local subscribers lines. On disconnect, however, it is necessary to transmit a disconnect signal over cuit for relay 590.

the ring-down trunk to signal the distant 'operator. After the completion of conversation over a ring-down trunk the calling subscriber replaces his receiver to cause the deenergization of relay 201. At armature 230 relay 201 opens the circuit of relay 303 which deenergizes and at armature 321 disconnects battery through the winding of relay 2| I from the negative conductor 252 whereby battery is disconnected from the negative ring-down trunk conductor to cause the distant operator to receive a disconnect supervision. Relay 2| upon deenergizing, at armature 243 opens the circuit to reversing relay 209 which deenergizes if operated and at armature 242 closes a holding circuit for slow to release relay 30| before the same deenergizes in response to the deenergization of relay 303. This circuit may be traced from ground at armature 32 conductor 265, armature 242 and resting contact, armature 245 and working contact, conductor 264, and through the winding of relay 30| to battery. The restoration of the link circuit is now controlled by the operator over the ring-down trunk. When the operator at the distant end disconnects the circuit to relay 2|2 is opened and said relay deenergizes to open the circuit of relay 30| at armature 245 to cause the deenergization of relay 30| and the release of the link as previously described.

Permanents The link circuit is considered held by a permanent if it remains in non-talking position for a minimum'of two minutes after seizure or after the called subscriber disconnects. Relays 589 and 590 and interrupter 593 in Fig. 5 comprise a timing device for causing the operation of disconnect relay 206 if a fault, such as a permanent, appears. At two minute intervals interrupter contacts 593 are closed to complete a cir- At armature 592 relay 590 disconnects ground from conductor 284 and at the Working contact of armature 592 completes an obvious circuit for energizing relay 580. At

armature 58| relay 580 prepares the circuit for connecting battery to conductor 285 to energize the disconnect relay 206 if a permanent exists. When interrupter spring 593 opens relay 599 deenergizes and at armature 59| momentarily connects battery to conductor 285 to energize disconnect relay 206 if a permanent exists. At armature 592 and its working contact relay 599 opens the circuit of relay 580 which deenergizes after an interval and at the resting contact of armature 592 grounds conductor 284. Relay 580, upon deenergizing, at armature 58| disconnects battery from conductor 285. Y

In case the link is held by a permanent condition and the same is not in talking position, that is in case relays 2| 2 |2 or 2 |3 are not energized, a circuit is completed for disconnect relay 295 when relay 580 is energized and relay 590 deenergizes as follows: from grounded armature 32|,

conductor 265, armature 242, 245 and 248 and their resting contacts, winding of disconnect relay 206, normally closed springs controlled by armature 229, conductor 285, armatures 53| and 59|, resistance 594 to battery. Relay 208 at armature 228 disconnects the ground at the norn mally closed springs controlled by armature 228 and connects the ground on conductor 284 extending from the resting contact of armature 592 to conductor 215 to maintain a holding condition on conductor 215 until the relay 599 is again operated. At armature 229 relay 208 opens 75

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