US1682100A - Telephone system - Google Patents

Description

Aug. 28, 192s.

J. WICKS TELEPHONE SYSTEM www @iw 3m HJ? IAvmuN Filed M arch 2. 1925. 5 Sheets-Sheet 3 NNN Imran U1" Jahn l/Llzclfs @wwhwww Patented Aug. 2d, 1.928.

UNITED STATES PATENT OFFICE- JOHN WIC-KS, OF OAX PARK, ILLINOIS, ASSIGNOB, BY MESNE ASSIGNMENTS TO AUTO- IATIC ELECTRIC INC., F CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE.

TELEPHONE SYSTEM.

Application led llarch', 1925. Serial No. 12,472.

The present invention relates to telephone systems in general, but is concerned more particularly with telephone systems employlng automatic switches for completing connections, and is concerned still more particularly with a telephone system covering an area which is more or less thickly populated and is served by means of a number of small automatic exchanges, one for each community, known as community automatic` exchanges, with a more or less centrally located manual exchange serving as a toll center through the medium of which the various community automatic exchanges are linked with each other and with trunk toll lines.

As is generally known, the ordinary twowire system of operation,v in which the automatic switches are controlled over the two sides of the line in series, is not applied unchanged to toll line'operation. There are a number of reasons for this, among which are the following: One reason for the change is on account of the fact that, since in a straight two wire system, the line relays of the automatic switches must be conas is so often done in case Morse telegra h systems are used in conjunction with te ephonelines.

The foregoing serves to illustrate whatis meant by the switch control circuit as distinct from the talking circuit and serves, therefore, to clarify the following statement 3f the objects and features of this invenion.

U One object of the invention is the production of. circuit arrangements enabling the control of the signalling (ringing) to be carried out in either direction over a toll l1ne through the medium of the switch control circuit rather than over the talking path itself.

Specifically, one object of the invention is the .provlsion of circuit arrangements whereby the ringing current itself is transmitted over the control circuit on calls from a community automat-ic exchange. (abbreviated as C. A. X.) to the toll center, together with the provision of circuit arrangements for cutting off the ringing current when the operator responds and for connecting the control ciiuit to the supervisory branch at the trolled through a resistance equal to the C A sum ofthe resistances of the separate conductors comprising the line and the associated telephone apparatus, and the toll lines (which are usuallylong as compared to the local lines and trunk lines to which two wire operation is applied) are too long for straight two-wire operation. Another reason for usino' some scheme other than the straight two-wire operation is found whenever the toll lines are associated in pairs for the purpose of forming phantom circuits.

According to the foregoing, in the case of a single toll line, arrangements are made for transmitting the talking current over the two sides of the line in series and for operating the automatic switches overl the two sides of the line in multiple with an earth return.

Similarly, in the case of a phantomed pair -of physical lignes,v the-three talking circuits thus secured are extended on the distant end by a like number of automatic switches which are controlled over' three'ofvthefour possible so-called Morse circuits, which are obtained by the well known method of using balancing coils and condensers,

Another object is the provision of circuit arrangements whereby on calls from vthe toll center to a C. A. X. the starting of the ringing operation (which is arranged. so as not to start automatically upon the completion of a toll connection) is placed under the control of the toll operator at the' toll center who controls the starting ofthe ringing operation over the control circuit.

Another object of the invention is the provision of greatly simplified circuit arrangements for controlling the rinv cut-off relay of a connector switch from-the selector repeater, which consists in an arrangement for utilizing the action of the-switching relay of the connector to obviate'the use .of anv added relay, togethen with suitable cooperating arrangements in the selectorl re peater. 1 Y l i The other objects and'the various features not here I mentioned will appear `from a perusal of the description. n'

Referring nowto the drawings comprising Figs. 1 3, they showv by means of the yusual circuit diagrams a sutic-ient amount-of apparatus in a system embodying the fea-tures of the invention to enable the invention to be understood and its utility to be appreciated.

The equipment shown in Fig. 1 is located in the toll center, i. e., the manual oiiee through which the toll calls are. closed, and Figs. 2 and 3 show apparatus in one of the community automatic exchanges.

Referring now particularly to Fig. 1, this drawing shows a cord circuit CC at an operators switchboard, together with the jack J associated with the two-way toll line TL leading to the communityA automatic exchange shown in Figs. 2 and 3. This drawing shows also the supervisory signal S and the drop signal D, together with the common calling device CD.

Fig. 2 shows the selector repeater SR,

Y through which calls coming in to the C. A. .X. over toll line TL are completed.

' Fi 3 shows the connector C, which is accessi le to the selector repeater SRL and which has access onV one level to the toll line Y TL and others, having access to the toll line TL through conductors 127-129. The connector C has accesson the other levels to the lines of local subscribers. The connector C is accessible to localselectors as may beseen in Fig. 2, Y I

Regarding'the mechanical constructzon of the selector repeater SR and the connector C, it may be pointed out that these swltches are ofthe usual vertical and rotary type and accordingly their lbank contactsare ar" 'ranged in horizontall rows or levels.

The booster battery BB, Fig. 1, is abattery of dry cells, which may be Aused economically on account of the slight 'current drain.

The apparatus having been described generally, it will nowppbe assumedthat the operator at the toll center is informed of a toll connection which is desired by the sub scriber at substation A, whose line terminates at'the (LA. X., shown in Figs. 2 and 3. That being the case,.th'e operator inserts a plug of an idle cord circuit, forl example,

the plug P of the cord circuit CC into the jack of an idle toll line. for example, the jack J ofthe tollline TL. When this occurs, the tip and ring conductors of the cord circuit CC are connected to the corresponding talking conductors of the j ack J.

Also the spring 2 of the jack J is operated to disconnect the operating conductor 13 from the drop D and to connect it to battery through contacts of the key K and the super visory signal S, whoseright hand terminal is connected to the exchang'evbattery EB throughl the jumper between terminals `10- and.12. Conductor 13 is' connected tothe junction of the right hand windings of the repeating coil on the toll-centerend of the trunk line TL.' The ljunction of the left hand windings of the repeating coil on the C. A. X. end of the toll line TL is normally level of bank contacts. gized in series with vertical magnet 121 and,l

grounded through the-operating conductor 101, armature 142 and its resting contact, armature 146 and its resting contact, marginal ringing-control relay 105, line relay ginally-adjusted ring-control relay 105 doesv Y not operate at this time. Upon operating,

line relay 107 closes at armature 150 a cirv cuit for the release relay 108, which energizes and at armature 152 opens a point in the circuit -of release magnet 126 and prepares a circuit for vertical magnet 121. At armature 151, release relay 108 places ground on conductorv 130, thereby preparing a subsequently closed circuit for switching relay 111 and closing a circuit for the polarizlng winding `01: the electro-polarized relay l102. This winding is composedo a comparatively small number of turns` of wire having a relatively high resistance. Accordingly, relay 102 does not operate at this time. l

As a further result of its operation, line relay 107 closes at armature 170 a circuit to ground through the right hand repeating coil windings for the dial tone current, `with the result that'the dial tone is heard by the calling operator. f f

In the toll center, the operator (assured by the' dial tone that the distant selector repeater is readyto be operated) now throws h the key K into dialling position, thereby connecting the calling -device CD, whose lower terminal is connected to jbattery, to the control conductor 13 in place of the signal,S. Accordingly, the supervisory signal lS restores.

The operator now manipulates her calling device CDA in accordance with the first digit in the desired number When she does so,v the control circuit is interrupted a corre'- sponding number of times with the result that line re'lav 107 of the selector repeater f SR, Fig.- 2, falls back each time the control 1circuit is interrupted.

Each time itfdeenergizes, line relay 107 closes at`armature`150 a circuit through armature 152 and its Workingcontact, series relay 109, and armature 158 audits rcstingcontact for vertical magnet 121. By the operation of Vertical magnet 121', the wipers 162--165 are raised step by step and come to rest olposite the'desired clay 109 is einer attracted throughout the vertical operation. As a result of the energization of relay 109, a circuit is closed at armature 154 from the grounded conductor 130 for stepping relay 110. Stepping relay 110 accordingly energizes; prepares a circuit at armature 155 for rotary magnet 124; and at armature closes a. point in its locking circuit, which is completed through the lnterru ter contacts 123 as soon as the oi norma contacts 122 close, as they do upon the first vertical ste of the switch.

Xt the end of the vertical movement, the slow acting series relay 109 falls back and closes the rotary magnet circuit, at the same time opening the initial'circuit of stepping relay 110, leaving stepping relay 110 energized through its locking circuit. The rotary ma et 124 now energizes from the grounde conductor 130 through the normally closed contacts controlled y armature 154 and through armature 155 and lts working contact, and advances the wipers of the switch into engagement with the first set of bank contacts in the called level. Near the end of its stroke, rotary magnet 124 opens the circuit of relay 110 at the interrupter contacts 123, whereupon relay 110 falls back and opens a further point in its locking circuit at armature 156 and at armature 155 opens the circuit of the rotary magnet 124 which deenergizes also. At contacts 123, the stepping relay 110 is again connected up through the resting contact and armature 159 tothe test wiper 154.

The further operation depends u on whether the trunk terminating in the rst set of bank contacts is busy or idle. lf it is idle, switching relay 111 isnot effected by the test wiper 164 on vaccount of the fact that the latter engages an ungrounded bank contact, and switchlng relay 111 energizes, seizing the trunk.

Assuming, on the .other hand, that the trunk is busy, test wiper 164 encounters ground on the busy test Contact and a circuit is closed through armature 159 and its resting contact, interrupter contacts 123, and off normal contacts 122 for the stepping relay 110 which energizes; closes a locking circuit .for itself at armature 156; and at armature 155 closes a circuit for rotary magnet 124 which thereupon energizes and advances the wipers into engagement with the next setof bank contacts.

This alternate operation of stepping relay 110 and rotary magnet 124 continues as dcscribed until an idle trunk is reached, which trunk, it will be assumed, is the one comprising conductors 166-169 and extending to the connector C, Fig. 3.

When this idle trunk is reached, switching relay 111, being no longer short circuited, energizes from the grounded conductor 130 in series with relay' 110. Stepping relay 110 does not operate at this time, however, on account of the relatively high resistance of switching relay 111. Upon energizing, switching relay 1 11 opens a point in the locking circuit of stepping relay 110 at armature 160 and grounds wiper 163 through relay 106, normally closed contacts controlled by armature 148, and the resting contact and armature 147. Relay 111 also opens the vertical and release magnet circuits at armature 158, and at armature 159 disconnects test wiper 164 from the test circuit and connects it to the grounded conductor 130, thereby placing ground on release trunk conductor 168 to make the seized trunk busy immediately. At armatures 157 and 161, relay 111 disconnects the right-hand repeating coil windings from ground and the dial tone lead and connects them to Wipers 162 and 165. Accordingly, line relay 202 of the connector` C, which is connected to conductors 166 and 169 through the normally closed contacts controlled by armatures 221 and 222 of back bridge relay 201, now

pulls up over the bridge including the lower winding of the electro-polarized relay 102 of the switch SR. The electro-polarized relay v102 of the selector repeater SR does not operate at this time, owing to the fact that the current flow in its lower Winding is in such a direction so as to oppose the eiect of the current flow in the upper winding.

In the connector C, release relay 203 energizes responsive to the closure of its circuit by line relay 202; prepares an energizing circuit for switching relay 210 and a locking circuit for busy relay 207 at armature 225; opens a point in the release magnet circuit and prepares a point in the operating circuit at armature 226; and at armature 224 places ground on release trunk conductor 168, so as to establish the usual holding circuit for the preceding switch and so as to maintain the connector busy. This, however, does not have any particular utility at this time. owing to the factthat the preceding switch is a selector repeater and not an ordinary selector. Accordingly, the release trunk conductor 168 is maintained gounded by the switch SR and the switch C a so.

Responsive to the above mentioned grounding of wiper 163 of the switch SR through the marginal relay 106, ground is extended over conductor 167 and armature 259 and resting contact to the upper Winding of relay 205, which energizes and locks up at armature 229 to conductor 168. The marginal relay 106 does not operate at this time on account of the fairly high resistance of the circuit.

When the operator dials the next digit in the desired number, line relay 107 of the selector repeater SR deenergizes a correspondmg number of times as. before. .No

40 sired number, the resulting impulses of curcircuit, however, is closed for vertical magf net 121 of the switch at this time, on ac- "bank contacts.

count of the fact that this magnet is disconnected at armature 158 of switching relay 111. Responsive to each deenergization of relay 107, theV bridge across the conductors 166 and 169 of the trunk extending to the connector. C is opened -at armature 17,

whereupon line relay 202 of the connector C decnergizes. The result is vthat line relay 202- is deenergized once for each opening of the circuit Vat the operators calling device.

Each time line relay 202 of the connector C falls back, lit closes vat armature 223 a circuit for vertical magnet 214, the circuit at;v the time of the irst closure including' armature 226 and its working contact, contact of ofil normal spring 213 and said spring,

4and the slow acting series relay 204. By

the ,operation of vertical magnet 214, the -wipers 24(5 249 are raised step by step and cometo rest opposite the desired level of Relay 204 Vis energized in series with vertical magnet 214 upon the `lirst impulse of current being delivered to the latter, and, being slow acting, maintains its` armature 227 attracted throughout the vertical movement, thereby maintaining its own circuit and that of vertical magnet 214 closed through the normally open contacts controlled by off normal spring 213 and armature 227 and its working contact, after the off normal springs have shifted', as they do upon the first vertical step. .At the end of the veltcal movement, relay 204 falls back and transfers the operating circuit from the vertical l.magnet to the rotary magnet.

yWhen the operator turns her calling device for the next and last digit in the derent transmitted in response tothe deenersponds to these impulses and advances the wipers 246249 into engagement with the bank contacts in which the line of substation` A termina-tes;- It will be noted that the slow acting relay 209 is normally in multiple with magnet 215. Accordingly, re-

lays 208 and 209 both energize over the opf erating circuit upon the first impulse of current delivered to magnet 215. Relay 208 disconnects busyvrelay 207 at armature 237, so as to prevent its premature energization,

. and at armature 238" closes a local circuit for relay 209 and disconnects it from the operatingcircuit, so4 that relay 209 will4 not start to become deenergized until relay 208 has fallen back at the end of the rotary "inovementa Relay 209, upon energizing,

closes at armature 240, a point in the circuit of the stepping relay 206, and at armature 239 disconnects test wiper 247 from the test winding of relay 210 and prepares a path for connecting the test wiper 247 to busy relay 207 upon the subsequent deenergization of relay 208.

vAt the end oi' the rotary movement, relay 208 falls back and connects busy relay 207 to test wiper 247 at armature 237 through the Working contact and armature 239, and at armature 238 opens the local circuit of relay 209 and connects it to the operating circuit again. Relay 209, however, does not fallback immediately, on account of the fact that it is slow acting.

It may be pointed out here that the operator, having dialled thenumber, now restores her dialling key K, whereupon Vthe supervisory signal S becomes operated again.

The further operation depends upon Whether the called line is busy or idle. If it is busy, busy relay 207 is'energized from the ground potential encountered by -test Wiper 247 on the grounded testcontact. -At armature 235, relay 207 connects stepping relay 200 to the rotary test wiper 248. Relay 206, however, does notenergize atvthis time, even though the called line is busy, because the rotary test contact 253 is not jumpered to theregular test contact 252. These two contacts are not connected because the line oi -substation A is an ordinary line and not a line of a group having a common destination. At armature 233, relay 207 prepares a locking circuit for itself; 'at armature 234 it opens the operating circuit; and at armature 236 it connects up the common busy signalling lead to the lower heavy talking conductor.

After an interval which is sufficiently long to permit the automatic rotary movement to start, in case such movement is to take place, relay 209 falls back and disconnects relay 20G from the rotary test wiper 248 at armature 240, and at armature 239 it disconnects test wiper 247 from busy relay 207 and conncctsA it again to the upper winding of switching relay 210. The locking circuit of busy relay 207, which includes the work-- ing contact and armature 225 ot release relay 203, armature 233 and its working contact of busy relay 207, normally closed contactscontrolled by armature 239, and the resting cont-act and armature 237, is completed at the normally closed contacts controlled by armature 239. Accordingly, busy icl-ay 207 remains locked up over a local circuit and at armature 233 maintains the upper terminal of the test winding 210 dis connected from ground.

As a result of the connection of the comliion busysignalling conductor to the lower heavy talking conductor, a busy tone is transmitted back -to the calling operator to inform her that the desired line 1s, for the time being, inaccessible. In this case, the operator pulls down the connection and callsagain later. y

It will be. assumed now that the line of substation A is idle when called. In this case, test contact 252 is not grounded when the wipers of the connector C land upon the bank contacts of the called line, and busy relay 207 does not, therefore, energize when it is connected up to wiper 247 at armature 237. Under this condition, when relay 209 deenergizes, it completes at armature 239 a circuit for the test Winding of switching relay '210 as follows: From ground by vway of the working contact and armature 225, armature 233 and its resting Contact, upper winding of switching relay 210, resting contact and armature 239, wiper 247, bank contact 252, switching relay 261 of the line switch LS, and stepping magnet 263 to battery. Switching relays 210 and 261 enerrizc in series over this circuit. Relay 261, however, operates only about half lway on account of the usual interlocking device between its armatureproper and that ofthe associated line relay 262. Therefore, the wipers of the line switch are not connected In the connector C, switching relay 210, upon energizing, closes at armature 243 a locking circuit for its lower Winding; places direct ground on test wiper 247 at armature 242; disconnects rotary magnet 215 and re lay 209 from the operating circuit at armature 244; disconnects conductor 167 from the left hand terminal of the upper winding of ring cut-oif relay 205 at armature 259 and connects it to the right hand terminals ofthe same winding; and at armatures 241 and 245. connects up the line wipers 246 and 249.

The shifting of conductor 167 from the left-hand terminal to the right-hand terminal of the locking winding of relay 205 results in the operation of the marginal relay 106 of the `switch SR, Fig. 2, because the resistance of the locking winding of relay 205 is excluded from-the clrcuit of relay 106. Upon operating, relay 106 locks itself to battery, at armature 148, through the associated resistance and disconnects itself from wiper' 163. At armature 149, relay 106 connects the common lead from the battery interrupter 133 through the resting contact and armature141 to the operating circuit at the junction of the windings of relays 105. and 107. Accordingly, each time battery is placed on the associated common conductor by the'interrupter 133, current ceases to flow over the portion of the control circuit extending to the toll center and the signal S'falls down, to operate when the interrupter 133 opens a ain. action of the signal S informs t e operator that the line is seized.

'Ihe connection is now extended to the line of substation A and it merely remains for the operator-to bring about the deenergization of ring cut-off relay 205 (which relay is locked up to conductor 168 at armature 229) of the connector C, so as to project ringing current out over the called line to signal the called subscriber. Before doing this, the operator extends a connection to the desired line through the medium of the other plug (not shown) ofthe cord circuit CC,

1g. .1. When the desired subscriber answers, he is told that he is Wanted in a. toll connection and is told to waitgfor the calling party who will now be signalled. The operatorl now throws the key K into ringing position, thereby connecting the booster battery BB (in series with the regular exchange batteryEB) to the operating conductor 13 through the upper contact and springs 2,

instead of the exchange batte alone (through the supervisory .signal g). Ac,- cordingly, the current flow over the control circuit during the open periods of the interrupter 133, Fig'. 2, is very much increased. As a. result, the marginal ringing control relay 105 in the selector repeater SR energizes in series with line relay 107, and at armature 147 grounds wiper/163. When this occurs, the locking windingof relay 205, Fi 3, is short cireuitedand the relay falls bac. At armatures 228 and 230 relay 205 disconnects wipers 246y and 249 from the windings of back bridge relay201 and connects them instead to the ringing circuit.Y Ringing current is now intermittently projected through t'he common ringing "conductor, jumper 271, resting contact and armature 230, and the lower talking conductor to the substation A to operate the bridged bell thereat,'and it returns by Iway of the upper talking conductor to ground through the jumper 27 3, lower winding of relay 205, and jumpers 272 vand 217.

atti i After holding her-'ringing key K, Fig. 1,

'nal S resumes its up and down operation lnder the control of the When the ringing key is restored, relay 105 in the C. A. X. falls back and removes interrupter' 133,

ground from conductor 163, so as to permit the ring cut-oil' relay 205 to lock up as soon as the subscriber at substation A responds.

When the subscriber at substation A rei sponds to the ringing of his bell b removing his receiver, a direct current rid e is placed across the conductors of his e,

whereupon ring cut-olf rela 205 energizes over the ringing circuit. pon energizing relay 205 again locks itself to conductor'168 at armature 229, and at armatures 228 Vand 230 disconnects the wipers 246 and 249 from the ringing circuit and extends them to the windings of back bridge relay 201. `Back bridge 201 now energizes over the line of substation A and at armatures 221 and 222 reverses conductors 166 and 169 as regards their connection with the windings of line relay 202. Thisl results in a reversal in the direction of current iiow in conductors 166 and 169v and consequently in the lower y.winding of the electro-polarized relay 102, 'Fig. 2. Accordingly, relay 102 responds by attracting its armature 141, thereby disconl necting the interrupter'lead 119 from the operating conductor, whereupon the 'supervisor-y signal S again operates steadily.

When the o erator notes that the supervisorysignal @is no longer alternately displaying and restoring, she knows that the calling subscriber has responded, Aand she, therefore, throws her listening key and 1nforms the subscribers that the connection is now completed.

The two subscribers may'now `converse this occurs, the supervisory signal S at the voperators switchboard starts to .energizel and deenergize again under the intermittent short circuiting influence ofthe int-errupter` I inthe C. A. X.

The operator recognizes-this operation on the part of the supervisory signal S. as the disconnect signal `and she accordinglyremoves the plug P from the jack J, thereby disconnecting the operatingv conductor 13 from battery through the supervisory signal S andconnecting it up .to the drop D again, When this occurs, relay 107 in the C.' A. X.

I falls back assoon as the interrupter Iperv mits and opens the circuit'of release relay' 108 at armature 150 and opens the circuit of line relay 202 of the connector C at armature 170. Responsive to the opening of its circuit at armature 150, relay 108 deenergizes, it-being arranged,`of course, so that the interrupter I operates slowl enough to permit relay 108 to fall back be ore it again operates relayv 107.

Upon deenergizing, relay `108 removes ground from conductor 130 at armature 151, leaving the said conductor groundedby way of wiper 164 ,from the connector C provided the release relay thereof has not yet fallen back. At 'armature 152 relay 108 closes a. point in the release magnet circuit. Relay 108 also renders the trunk line accessible again at varmature 153 to the local connectors.

As soon as conductor 168 is ungrounded in the connector C, relay 111 of the switch SR deenergizes and opens at armature 160, the circuit of relay 106 which deenergizes and disconnects the interrupter lead 119 from the operating conductor 101 at armature 149. Release magnet 126 now energizes through armature 158 and restores theswitch to lts normal position, whereupon the circuit of the release magnet is opened at off normal contacts 125.

In the connector C, when release relay 203 falls back responsive `to the deenergization of line relay 202 and removes ground from conductor-168 at armature 224,`- relays 205 and 210 fall back. At armature '226, relay 203 closes a circuit through off normal contacts 212 for release magnet 211, with the result that the switch is restored to its nor- Vmal position in the usual manner.

The foregoing description sets forth the operation when the toll loperator recalls the subscriber at substation A on a call ori nated by him without describing how t e subscriber at substation A is able to get in touch with the toll operator in the irst place to inform her that he desires a toll connection. vSuch explanation will nowbe given.

When the subscriber at substation A desires to set up a toll connection, he removes his receiver and dials the three digits necessary to obtain connection with the toll operator... A

When the receiveris removed at the substation A, a circuit is closed over the conductors of his 'line for line relay 262 of the line switch LS. Relay 262 energizes and at armature 284 places ground on the private normal conductor extending to the connector C and the other connectors,thereby makin the calling line busy to these connectors an closing a circuit through relay 261 and stepping magnet 263 in series. At armature 285,

relay 262 connects test wiper 287 to the junc-` tion` of relay 261 and stepping magnet 263.

From this point, the operation depends upon Whether the trunk upon which the wipers of the line switch are standing is busy or idle. If this trunk is idle, switchino relay 261 is not affected by the operation o armature 285 and` it accordingly energizes right like manner and advances the wipers 286- 288 in search of an idle trunk.

When an idle trunk is reached, relay 261 is no longer short circuited and energizes. Stepping magnet 263 does not energize in series with rela 261 on account of the ,relatively high resistance of the latter. Upon energizing, relay 261 disconnects test w1per 287 from the test circuit and connects it to the grounded private normal conductor at armature 282, thereby making the seized trunk busyimmediately, and at armatures 281 and 283 disconnects the line conductors from relay 262 and ground and extends them by way of wipers 286 and 288 to the line conductors of the selector (not shown) on the seized trunk line. When this occurs, the line relay of the seized selector energizes and pulls up the associated release relay, with the result that the release trunk conductor is grounded to maintain the line switch LS operated and to maintain the trunk busy after the slow acting line relay 262 deenergizes.

The calling subscriber nowr operates his calling device in accordance with the first digit in the number necessary to obtain connection with the toll operator, whereupon the seized selector raises its wipers opposite the desired level of bank contacts and rotates them in Search of an idle trunk.. It will be assumed that the trunk comprising conductors 166, 168, and 169 and extending to the connector C is in the one seized by the selector in use. In this case, the operation of the connector C, as regards its seizure and its response in accordance to the two digits is substantially the same as hereinbefore described, with the difference that, as no connection is made with conductor 167, the preliminary pulling up of the ring cut-0H relay 205 does not take place in this case.

Owing to the fact that the subscriber is calling the number of the toll operator, the wipers of the connector C come to rest in engagement with the bank contacts leading to one of the toll lines and it will be 'assumed that the banksdcontacts` 255-258 are the first contacts-in tleggroup assigned to the toll lines. Therefore, cthese contacts are the ones upon which the wipers land at the end of the directive rotary movement.

In this case, as in the case preceding, the further operation of the connector C after the directive rotary movement depends upon whether the line terminating in the contacts on which the wipers are standing is busy.

test contact 256. Accordingly, a circuit is provided for stepping relay 206 which energizes and closes a locking circuit for itself at armature 232, and at armature 231 closes a circuit .for rotary magnet 215 which accordinglyenergizes and advances the, wipers 246-249 into engagement with the next set of bank contacts. Current alsov flows through relay 209, in multiple with magnet 215, thereby maintaining relay 209 energized throughout the rotary movement. Near the end of its stroke, rotary magnet 215 opens at contacts 216 the circuit of stepping relay 206, with the result that stepping relay 206 falls back and opens a polnt inits locking circuit at armature 232, and at armature 231 opens the circuit of rotary magnet 215. Rotary magnet 215 deenergizes and closes its interrupter contacts again, therebyagain connecting relay 206 to wiper 248. In case the trunk terminating in the second toll line is idle, the rotary movement now stops, but if it is busy, and if it is not the last trunk line in the group, relay 206 energizes again from wiper 248 and again closes the circuit of rotary magnet 215, with the result that the wipers are advanced another step.

This alternate operation of rela 206 and magnet 215 continues as describe until an idle trunk line is reached, or until the last trunk line of the group is reached. The automatic rotary movement stops in either case because no ground is then encountered by test wiper 248.

When an idle trunk is reached, busy relay 207 falls back, and as soon as relay 209 falls back responsive to the cessation of the auto matic rotary movement, relay 210 is connected to wiper 247 and (assuming for the sake of illustration that the idle trunk is the one comprising conductors 127-129) wiper247 encounters battery through -conductor 128, armature 153 and its resting contact, and relay 103. Accordingly, relay 103 energizes in series with switching relay 210 of the connector C and at armature 142 disconnects the control conductor 101 from line relay 107 and connects it instead to the negative conductor 129 through the lower Winding of ring cut-oil'l relay 104, the n'ormally closed contacts controlled by armature 144 and the jumper 140.

In the connector C', relay 210 energizes over the above traced circuit and, in addition to performing the other functions described hereinbefore, connects up the line wipers at armatures 241 and 245. Ringing current is now rojected out over the ringing lead throug the negative wiper 249 to the selector repeater SR by way of conductor 129, and from thence through jumper 140, the normally closed contacts controlled 142, to the control conductor 101. .This ringing current passes over the two sidesof the toll line in multiple and reaches the control conductor 13 in the toll center and then goes through spring 2 and its lower 'contact and by way of the condenser 3 to the drop D. The drop D responds tothe ringing current and releases its indicator, thereby informing the operator of the call.

When the operator notes the released condition of the drop D, she inserts the plug of an idle cord circuit, for example, the `lu0` P of the cord circuit CC into the jacc Je; whereupon the control conductor 13 is dis-- connectedfrom the drop D and is connected to the exchange battery EB through the supervisory signal S. When this occurs, direct current flows from the ringing lead associated with the connector C, Fig. 3, (either directl from ground or from ground througi the generator) and thence out over the ringingcircuit to battery in the toll center. Accordingly, relay 104 in the selector repeater SR responds to the direct current and closes a locking circuit for its two windings in series at armature 144, at the same time opening the ringing circuit. The locking circuit includes the common conductor 132, the upper winding of relay 104, armature 144 and its working contact, lower winding of relay 104working contact and armature 145, the operating conductor 101, and the remaining part of the circuit, as traced, to battery in the toll center through the lsupervisory signal S. As a further result of its energization, relay 104 disconnects the resting contact of the operated armature 142 (of relay 103) from line relay 107 and connects it insteadto the interrupter lead 119 for a purpose to be explained hereinafter; at armature 143 disconnects the upper talking conductor from ground and connects it instead to the negative incoming trunk conductor 127; and at armature 143 connects conductor 129 to the lower talking conductor of the switch SR, thereby". completing the talking circuit as regards the selector repeater S In the connector C, ring cut-olf relay 205 does not energize responsive to the insertion of the plug P into the jack J because it is not included n the ringing circuit in this case, but upon the operation of relay 104, relay 205 energizes over both wipers ofthe connector C in series, over conductors 127 land 129, and through Vthe rightlhand repeating coil windings and the lower winding of relay 102. Relay 205 dpens the ringing circuit and connects up back bridge relay 201 to the wipers of the connector, whereupon relay 201 pulls upand reverses the current iow in the calling line, but this reversal has no particular function in the present case.

The electro-polarized relay 102 of the switch SR, through which relay 201 operates,

does not operate at this time on account of the comparatively small number of turns on its lower winding.

The calling subscriber and the operator may now converse with each other in any desired manner and the voperator completes the toll connection according to local practiccs.

The practice employed in completing the' toll calls, it will be understood, varies somewhat with different operating companies and also with different-local conditions. For example, in some cases where the desired connections may be quickly set up, the calling subscriber remains on the line and the operator completes the connection right awayA. In otherv cases where the connection desired may be one that is of such a nature as to require considerable time to complete, the calling subscriber is requested to hang up his receiver and wait until he is recalled, as de# scribed in the first part of this specification.

In any event, the subscriber at substation A finally hangs up his receiver, and when he does so, lthe connector C is released in the hereinbefore described manner and ground is removed from conductor 128, whereupon relay 103 of the selec-tor repeater ASR falls back and'at armature 142 connects the oper- /ating conductor 101 through armature 146 and vits working contact to the interrupter 133 which places battery at intervals upon conductor 101. Upon each application of battery, the supervisory s'gnal S, Fig. 1, deenergizes, as inthe previous case, and this operation attracts the attention of the toll operator, who pulls down the connection, with the result that the supervisory signal S restores and relay 104`of the selector repeater SR falls back.

Perhaps it may be desirable to point out briefly that local connections between subscribers in the C. A. X. are established in somewhat the same wayas the connections to the toll operator in that they involve the use of a selector and a connector for each call, as will be readily understood.

Certain details not particularly dwelt upon in the foregoing will now be taken up.

The first point to be taken up is the arrangement of the battery supply to the control circuit including conductors 13 and 101 at either terminal and the two conductors of the toll line TL in multiple. From the standpoint of operating the selector repeater SR, the control circuit includes the line relay 107 of the selector repeater SR and is connected to a ground return both at the toll center and at the C'. A. X. The only polnt to be considered is the position occupied by the battery in the controlcircuit, and possible leakage to ground along the toll l1ne TL 1s about the only factor that need be considered in locating the battery in the control circuit. The battery is shown in the drawings as located at the toll center and is the exchange battery EB. With the battery located at the calling device end of the control circuit, the toll line TL is electrically dead each time the contacts of the calling device CD open (except for slight inductive kicks from the toll line itself and from the line relay of the selector repeater) which would not be the case if the battery were located at the opposite end of the control circuit.

The above sets forth what is considered to be the best practice in locating the battery supply to the control circuit. However, it may happen that no exchange battery is available at the toll center. In this case, rather than to provide a battery along with the necessary charging apparatus, etc., arrangements are made for using the exchange battery at the C. A. X., which battery must be provided in any event to operate the C. A. X. switches. That being the case, the cont-rol circuit is connected to ground at the toll center by means of a jumper connected between the terminals 10 and 11, and the jumper between terminals 10 and 12 is omitted. At the C. A. X., the common return conductor v132 is disconnected from ground by cutting the jumper 131 and it is jum ered to the exchange battery instead.

Tlie foregoing changes take care of the control circuit as regards the operation of the C. A X. switches from the toll center, but, in order to secure t-he desired alternate display and restore action of the superyxsory signal S, Fig. 1, the interrupter 133 1s disconnected from battery by the cutting ofv jumper 130, and it is connected to ground instead.

Since the control circuit is connected to ground at the toll center and, the C. A. X. ringing current must now be superimposed on battery instead of on ground as before (so as to operate relay 104 when the operator responds). In this case the ringing return circuit of the connector C must be connected to ground in order to operate the ring cut-off relay 205 on local calls. Accordingly, the jumpers 217 and 218, Fig. 3, are both cut and new jumpers are inserted which connect conductor 219 to ground and connect conductor l 220 to battery. Also jumpersv272 and 273 are reversed at one end to maintain the same direction of current How through the lower winding of relay 205.

In case it is not necessary to keep the polarity of the wipers of the connector C the same at all times, the above changes are suiiicient, but, in case it is desired to keep the polarity of the wipers of the connector() straight, it is necessary to further rearrange the jumpers individual to the connector C so that the ringing current (which is now superimposed upon battery instead of upon ground) goes out over the negative wiper 246 and so that the ringing return lead (which is now connected to ground instead of to battery) is connected with the lower wiper 249. Accordingly, the jumpers 271, 272, and 273 are removed. A new jumper is placed between the terminal associated with the resting contact of armature 228 and the terminal in which the common ringing lead terminates so as to send the ringing current out over the upper wiper 246. Two other jumpers are run which connect the resting contact of armature 230 to the common return conductor 219 through the lower winding of ring cutoff relay 205. Specifically, the terminal associated with the resting contact of armature 230 is connected with the left-hand terminal of the lower winding of relay 205, and the righthand terminal of the lower winding of relay 205 is connected to the terminal in which the common return conductor 219 terminates. This apparent reversal in the connection to the lower windingof relay 205 is necessary on account of the fact that the direction of the current flow in the lower winding must agree with the direction of the current flow in the upper winding of the relay, which it would not do if this man ner of connecting were not followed.

Since the ringing current is now impressed upon the negative talking conductor 127 leading to the selector repeater SR instead of upon the positive conductor 129 as heretofore, the umper 140 connecting the lower winding of1 relay 104 of the switch SR with the lower talking conductor 129 is cut and a jumper is inserted between the two upper terminals, thereby connecting the lower winding of relay 104 with the upper talking conductor 127.

In the toll center the jumpers between terminals 6 and 8 and terminals 7 and 9, respectively, are cut and new jumpers are run between terminals 6 and `9 and terminals 7 and 8, respectively, so as to reverse the battery BB to agree in polarity with the current from the C. A. X. battery.

What is claimed is:

1. In a telephone system, an automatic exchange, an operators switchboard, a trunk line extending from said automatic exchange to said switchboard, a ringing current response device associated with said trunk line at said switchboard, means for operating one of the switches in the automatic exchange to complete a derived ringing circuit over the trunk line to operate the ringing response device at the operator's switchboard, and a ring cut-off relay included in said circuit lfor interrupting said circuit.

2. In a telephone system, an operators switchboard, an automatic exchange, a trunk line extending from said exchange to said switchboard, a ringing response device associated with said trunk line at said switchboard, means for operating one of the switches in said automatic exchange to complete a ringing circuit over a line wiper of said switch and a talking conductor local to the automatic exchange and including a derived circuit of said toll line to operate the ringin response device at the operators switchoard, a ringing current switching relay in the automatic exchange, a ring cut-off relay in said switch having a winding included in a circuit with the other line wiper of the switch, and means operated upon the response of the operator at said switchboard for closing a direct current circuit over the derived portion of said trunk line to operate said ringing current switching relay to disconnect the local talking conductor from the derived circuit and to connect it instead to a conductor of said trunk line, the latter operation completing a circuit over the trunk line and including the two line wipers of the said switch in series for operating the said ring cut-off relay.

3. In a telephone system, an operators switchboard, an automatic exchange, a trunk line extending from said switchboard to said exchange, a switch control circuit extending from the said operators switchboard over the trunk line to the automatic exchange, means under the control of the operator for operating a train` of switches in the automatic exchange over the said control circuit to establish a connection with a called line, means at the operators switchboard for momentarily increasing the current flow over the control circuit, and means in the automatic exchange initially responsive to this momentary increase in current flow for applying ringing current to the called line, said means being operable thereafter independent of any flow of current over the control circuit.

4. In a telephone system, a connector switch, means for operating said switch to extend a connection to a desired line, a relay in said connector switch, a control conductor extending to said switch, means for operating said rela-y over said control conductor prior to the completion of the operation of said switch, means operated subsequent to the completion of the operation of said connector switch for altering the con-f nection between said control conductor and said relay, and means controlled from the calling switchboard to apply a potential to said control conductor to bring about the dcenergization of said relay to project ringing current out over the called line.

5. In a telephone system, a connector switch. means for operating said switch to extend a connection to a desired line, a ringing-current-control relay in said connector switch, a supervisory-control relay, a control conductor extending from said super-v visory-control relay to said ringing-currentcontrol relay, a circuit for operating said ringing-current-control relay over said control conductor prior to the operation of said switch, means operated responsive to the operation of said connector switch for altering the connection between said control conductor and said ringing-current-control relay, a circuit for operating said supervisorycontrol relay over said control conductor, said circuit rendered effective by said alteration, and means controlled from the calling switchboard to apply a potential to said control conductor to bring about the deenergization of said ringing-current-control relay to project ringing current out over the called line.

6. In a telephone system, an operators switchboard, an automatic exchange, a. trunk line extending from said switchboard to said exchange, a switch in said automatic exchange, means controlled over said trunk line from said switchboard for operating said switch to extend a connection to a called line` a. switching relay in said switch operated responsive to an idle condition on the ycalled line, a marginal relay associated with said trunk line, a circuit for said marginal relay excluding the talking conductors of said trunk line, means for setting up a current flow over said circuit insuiiicient to operate said relay, contacts on said switching relay for increasing the current iow over said circuit to operate said marginal relay, and circuit connections controlled by said ,marginal relay for giving the calling operator a distinctive indication of the idle condition of the called line.

7 In a telephone system, an operators switchboard, an automatic exchange, a two- Way trunk line between said switchboard and said exchange, switches in the automatic exchange whereby the operator may set up a connection over the trunk line to a called line in the automatic exchange and whereby a calling subscriber at the automatic exchange may set up a connection over the said trunk line to the operator, a supervisory signal at the operators switchboard operated steadily in either case when the connection is finally established, and means for operating said signal intermittently in either case. responsive to the subscriber in the automatic exchange replacing his receiver.

8. In a telephone system, a trunk line extending from an operators switchboard to a selector, a connector, a circuit superimposed on said trunk line for controlling said switches to extend the trunk line to a called line, a line relay in said circuit at the selector by means of which such control is effected. a marginal relay in series with said line relay, said marginal relay being nonresponsive to normal current flow in said circuit, operator controlled means for increasing the flow of current in said circuit after the connection'is established in order to operate said marginal relay, and ringing -equipment in said connector controlled by said marginal relay.

9. In an automatic switch having means for signalling over a connected line, a ring cut-off relay, a ringing control conductor incoming to said switch, and circuit connections such that if said conductor is connected to a source of current before the switch is o erated the relay will be energized while if) such connection is made after the switch is operated the relay will be deenergized.

10. In an automatic switch having means for signalling a connected line, a ring cutoff relay, a ringing control conductor incoming to said switch, and circuit arrangements in said switch such that said relay is energized and deenergized by successive applications of the same potential to said conductor.

11. In a telephone System, means including a selector and a connector for extending a connection to a called line, a ringing control conductor extending between said switches, means in said selector for automatically and momentarily grounding said conductor when the selector connects with the connector, and a locking ring cut-ofi' relay in said connector energized over said conductor when the same is grounded.

12. In a telephone system, means including a selector and a connector for extending a connection to a called line, a ringing control conductor extending between said switches. means in said selector for automatically and momentarily grounding said conductor when the selector connects with the connector, a locking ring cut-off relay in said connector energized over said conductor when the same is grounded, means in said selector subsequently controlled at the will of the calling party for again grounding said conductor, and circuit arrangements in said connector such that when said conductor is again grounded it will cause said relay to be deenergized.

13. In a telephone system, a trunk line comprising two sections, an automatic switch for connecting with said trunk line and for transmitting ringing current over the two sections thereof in serial relation, a ring cutoff' relay in said switch, a circuit for said relay including a conductor of only one of said sections, and a relay controlled over the other section for closing said circuit.

14. In a telephone system, a trunk line comprising two sections, an automatic switch for connecting with said trunk line and for transmitting ringing current over the two sections thereof in serial relation, a ring cutoff relay in said switch, controlled over one of said sections only, and a second ring cut- 'ofi'I relay at the junction of said sections con.-

trolled over both of said sections.

15. In a telephone system, a ringing circuit having two branches both normally open, means for closing the first branch and for applying ringing. current to said circuit, means for opening the first branch and for closing the second branch, and means in the second branch for stopping the application of' ringing current to said circuit.

16. In a telephone system, a ringing circuit having two branches both normally open, means for closing the firstbranch and for applying ringing current to said circuit, means in said first branch for opening said first branch and for closing said second branch, and means in said second branch for stopping the application of ringing current to said circuit.

17. In a telephone system, a ringing circuit having two branches both normally open, means for closing the rst branch and for applying ringing current to said circuit, a relay energized over said first branch for opening said first branch, contacts on said .relay for closing the second branch, and a ring cut-ofil relay in said second branch.

18. In a telephone system, a trunkline connecting two points, a signal normally connected to said trunk line at the first point and an automatic switch at the second, a circuit superimposed on the two talking conductors of said trunk line, means at the said first point for transmitting current im,- pulses over said circuit to operate said switch, means for transmitting ringing current over said circuit to operate said signal, and means for disconnecting said signal from said trunk line while current impulses are transmitted over said circuit.

19. In a telephone system, a ground return switch control circuit, means for transmitting switch operating impulses over said circuit in one direction, means for transmitting ringing current over said circuit in the other direction, and a ring-cut-off relay included in said circuit during the transmission of ringing current.

20. In a telephone system, a grounded signalling circuit comprising two sections, one section consisting of a talking conductor and the other section consisting of two talking conductors in parallel, a non-talking conductor connecting said sections, and means for transmitting ringing current over said circuit.

21. In a telephone system, a grounded signalling circuit comprising two section', one section consisting of' a talking conductor and the other section consisting of two talking conductors in parallel, al non-talking conductor connecting said sections, means for Cil ringing over said circuit, and a ring cut-olf relay included in said non-talking conductor.

22. In a telephone system, an automatic exchange, an operators switchboard, a trunk line extending from said automatic exchange to said switchboard` a ringing current re-.

sponse device associated with said trunk line at said switchboard` means for operating one oi" the switches in the automatic exchange to complete a derived ringing circuit over the trunk line to operate the ringing response device at the operators switchboard, means for automatically and intermittently opening and closing said circuit thereafter while the said switch is maintained operated, and means for automatically stopping the ringing operation when the call is answered.

24. In a. telephone system, means including a trunk line for establishing a connection between an operators position and a called line, said connection being maintained intact by reason of a continuous iow of current over the two conductors of said trunk line in parallel, and means responsive to an increased tlow of current in said conductors for signalling the called subscriber. 25. In a telephone system, a connector switch, means tor establishing a connection with said switch, a ring control relay in said switch` a, supervisory control relay, a ring control conductor, a circuit including said ring control relay, said supervisory control relay and said ring control conductor in series closed by the establishment of said connection for operating said ring control relay, means for operating said connector to connect with a called line, means responsive to the establishment of the connection with the called line for increasing the current iiow in said conductor to operate said supervisory control relay, means controlled by said supervisory control relay for interrupting said current flow` and means for reestablishing a current tlow in said conductor to deactuate said ring control relay to apply ringing current to the called line.

26. In a telephone system. a connector. a first selector` a second selector. means for establishing a connection via said tirst selector and said connector to a called line, means for establishing a connection via said irst connection to the cal ed line, means in second selector and said connector to the called line, means in said connector for automatically signalling the called party operative responsive to the com letion of the said said connector operative responsive to the seizure of said connector by said second selector for disabling said automatic signalling means, and means in said second selector for remlering said automatic signalling means effective operative at will upon completion of the said second connection.

27. In a telephone system, a trunk line, a connector for extending a call over said trunk line, signalling means in said connector effective when the call is extended to signal over said trunk line, a ringing current switching relay for said trunk operative when the call is answered to interrupt the signalling, and a ring cut-oil relay in said connector responsive to the operation of said ring'ng current switching relay for completing the talking connection.

28. In a telephone system, a trunk line, an incoming branch normally connected to said trunk line, an outgoing branch normally disconnected from said trunk line, a connector for extending a call over said trunk lne via said outgoing branch, a, switching relay for said trunk operative when the 'all is answered for disconnecting said incoming branch from said trunk line and for connecting said outgoing branch thereto, and a relay in said connector responsive to the operation of said switching relay for 1"" completing the talking connection.

29. In a telephone system in which connections to a called line are established by automatic switches controlled over the calling line by successively interrupting a nor- 105 mal fiow of current over the two talking conductors of the calling line in parallel, means for changing the value of said normal flow of current, and means responsive to said change of value of the normal ow of current for signalling over the called'line.

,80. In a telephone system, a line, a trunk comprising two talking conductors, means for establishing a current flow over said two talking conductors in parallel, a switch for extending a call to said line controlled over said trunk, means for changing the value of the said current flow, and means responsive to said change for signalling over said line.

31. In a telephone system, a line, means including a selector, a trunk, and a connector, terminating said trunk for extending a connection to said line, means for establishing a current flow over one ot the conductors 125 of said trunk, means in the connector operative providing the line is idle when connection thereto is extendedfor increasing the value of the flow of current over said conductor, a signal, and means in said selector 13( responsive to said increase in the value of said current flow for causing the operation of said signal.

32. In a telephone system, a line, means including atrunk comprising talking conductors and a non-talking conductor and a switch forextending a connection to said line, means for establishing a current flow over the non-talking conductor of said trunk, means operative providing the line is idle when connection thereto is extended. for changing the value ofthe flow of current over said non-talking conductor, a signal, and means in said switch responsive to said change in the value of said current flow for causin the operation of said signal.

33. In a telephone system, a line, an operators switchboard, means for extending a call from said switchboard to said line, a

signal at said switchboard, means for o eratmg said signal steadily when the ca is answered, and means for o rating said signal intermittently when t e call is terminated.

34. In a telephone system, a line, an operators switchboard, means for extending a call from said switchboard to said line, a signal at said switchboard, means for operating said signal intermittentlyv after the call is extended', for operating said signal steadily when the`call is answered, and gir o ra sai si intermitten wenm aeal'iiamim n y 35. In a telephone system, a line, means including a trunk for extending a connection to said line, signallin means for signalling over said line norma y effective as soon as connection to the line is completed, means for successively applying a potential to one of the conductors of said trunk, and means which vis responsive to one application for disabling said signalling means and is disabled by the next application so that said signalling means becomes effective after said next a plication.

36. a telephone system, a line, means including a selector, a trunk, and a connector terminating said trunk for extending a connection to said line, signalling means for signalling over said line normally effective when connection to theline is completed, means in said selector for successively ap plying a potential to one of the conductors of said'trunk, and means which is responsive to one application for disabling said signalling means to prevent signalling over the line from taking place when-connection thereto is completed, and is disabled by the succeed ing application so that said signalling means becomes effective after said succeeding application. t

In witness whereof, I hereunto subscribe my name this 27th day of February, A. D. 1925.

JOHN WIcKs

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