US1798477A - Multioffice telephone system - Google Patents

Description

March 31, 1931. 7'

o. c. LEVY. ET AL 1,798,477

MULTIOFFICE TELEPHONE SYSTEM Filed May 51, 1929 '7 Sheets-Sheet 1 Inuln2nr|- scar 5'. Lin Clarence E. LEELZI-EX DTZTZEZL H Saundera March 31, 1931. i c, L V ET AL 1,798,477

MULTI OFFI CE TELEPHONE SYSTEM Filed May 31, 1929 7 Sheets-Sheet 2 Nmr'min H. Saunder s fl -i M rc sl, 1931. o. c. LEVY ET AL 1,1 8,417

MULTIOFFICE TELEPHONE SYSTEM Filed May 31, 1929 7 Sheets-Sheet 3 scar E..LEU Zaranca .ElLumax Nun an H.5aundsr's W March 31, 1931.

o. LEVY ET AL 7 7 MULTI OFF'I CE TELEPHONE SYSTEM F iled May 51, 1929 7 Sheets-Sheet 4 ZiT'i'LLBi E.Lmmax v Nur'man H. Saunder a March 31, 1931.

o. c. LEVY ET AL, 77

MULTIOFFICE TELEPHONE SYSTEM 7 Sheets-Sheet 6 Filed May 31, 1929 o a O O o o c InuEnlur's- Usnar E. s y larencnELumax r'man H.5i'L1TLdEPS- March 31, 1931. o. c. LEVY ET AL MULTIOFFICE TELEPHONE SYSTEM Filed May 51. 1929 7 Sheets-Sheet 7 Toy/"5247025 TELEPl-lflNE A r wmh LL 7 n" W mR M L. RQ s A 'l w w m 7 II M am r mm WQ. Mm [n B QT AWN awn 7 3 R J M; \Ml QB h MNN QR QR w w E R E z q z E w E a x m w flwfi 2 fi m \m B T WW J Mm J a w mm an W Eh fi A .QQ N 5 Qbm MR. 4 %\h h h r w 1 my 1 l 3 E db. w $.11 ER t mt @t as 7 5 LY QR mt m E BI KR kw a? Hit Patented Mar. 31, 1931 UNITED STATES PATENT OFFICE OSCAR C. LEVY, OF CHICAGO, CLARENCE E. LOMAX, 01 OAK PARK, AND NORMAN H. SAUNDERS, OF HOMEWOOD, ILLINOIS, ASSIGNORS TO RESERVE HOLDING COMPANY, 01' CHICAGO, ILLINOIS, A CORPORATION 01' DELAWARE mumrorrrca 'rnnnrnonn svsrnu Application filed Kay 81,

This invention relates to mult-i-oflice telephone systems in general, but is concerned more particularly with multi-office telephone systems in which calls are completed through the medium of automatic switches and in which certain classes of calls are extended by an operator. The main features of the invention relate to improved apparatus of the so-called universal switcher type and associated apparatus for use in multi-ofiice systems employing satellite or sub-exchanges and to improved; trunk circuits and operators circuits for use in systems of this kind.

The economic reasons for employing satellite or sub-exchanges are well known and will not be discussed here. Sub-exchanges usually have installed only originating and terminating apparatus such as lineswitches and connectors while the switches of the intermediate switching stages are located in the main exchange. All calls originatin in the sub-exchange are, therefore, trunke to the main exchange where office and group selection is made. This is the case in both local and outgoing calls, and obviously, trunking facilities are going to be tiedifup in local connections unless special provision is made to prevent it. A number of ways of releasing the trunking apparatus onlocal calls have been devised of which that employing the socalled universal switcher isqone of the most satisfactory. The main function of this apparatus is to register one or more digits of the called number as required to identify the call as local or outgoing and to perform the necessary switching operations to release the switches not absolutely required in the final connection. Universal switching apparatus is thoroughly described and its utility set forth in United States Patents Nos. 1,623,320 to Smith, and 1,682,158 to Willis. The features of this invention relating to the universal switcher may be considered as an improvement on the latter patent.

The provision of restricted service for certain classes of subscribers is also old and well known although as far as applicants are aware its application to sub-exchange systems employing universal switchers has never been entirely successful. This is due primarily to 1929. Serial N0. 867,168.

the fact that one or more digits must be dialled before the call can be identified as local or outgoing and in the case of calls from is desirable for various reasons that attempted trunk calls from restricted lines be intercepted by an operator who can then com lete the call as a toll call or inform the ca ling subscriber that service is denied.

The object of the invention, broadly stated, is to improve systems of the above general character by the rovision of new and improved; circuits an apparatus for performing the necessary switching operatlons efliciently and economically.

One feature of the invention relates to simple and efficient circuits for use in connection with universalswitcher type sub-exchanges in which both restricted service and non-restricted service is furnished. These circuits provide for the interception of attempted trunk calls from restricted lines and the automatic trunking of such calls to an operator.

Another feature of the invention relates to an improved universal switcher for sub-exmay be completed regardless of the busy or idle condition of the inter-ofii'ce trunks.

Another feature of the invention relates to highly efiicient trunk circuits over which toll change working arranged so that local calls the callingsubscriber meanwhile waiting on r the line.

Another feature of the invention relates to new connector circuits particularly adapted for small exchange use. These connectors are of the type whose wipers move only in one plane.

Still another feature relates to an improved trunk hunting switch of the rotary type adapted to connect with either of two classes of lines as required by the particular connection in which it is used.

The foregoing features together with inter-relation.

others not s cifically mentioned will be described in etail hereinafter, reference being had to the accompanying drawings comprising Figs. 1 to 8, inclusive. The drawings show by means of the usual circuit diagrams a suificient amount of the equipment in a multi-ofiice telephone system embodying the features of the invention to allow the invention to be readily understood.

In order to make the description as simple as possible, the application of the invention to a telephone system comprisingthree exchanges will be described. It is to be understood, however, that the application of the invention is not limited to this particular arrangement but that it may be used with other combinations of equipment and in systems comprising a different number of exchanges from that described herein.

The equipment located in the sub-exchange is shown in Figs. 1, 2, and 3. The equipment in the main exchange which is also an automatic exchange is shown in Figs. 4, 5, 6, and the left-hand portion of Fig. 7 The apparatus in the right-hand section of Fig. 7 is located in the third exchange which is as sumed to be a manual exchange or toll oifice. Fig. 8 is a layout diagram showing how the sheets on which l to 7, inclusive, are drawn should be placed together in order to be understood best.

Referring now l, T represents an ordinary automatic substation associated with a lineswitch which terminates in a group of line relays L1 5. at the sub-exchange. Start relays STE are common to all lines in the sub-exchange and initiate the operation of the finder switches such as switch F which has access to the subscribers lines. The finder switch F is associated with a switching repeater SR which is shown in detail. Gtl er switching repeaters SR, SR", SR' are shown as rectangles with only enough of their apparatus as is required to illustrate their it will be understood, of course, that there are a number of lines such as that extending to substation T and also a number of finder switches and repeaters in the exchange. In addition to its function as a trunk repeater, repeater SR is equipped with mechanism for recording the first two digits of a call. The purpose of this is to provide for certain switching operations in case the call is for a subscriber located in the subexchange.

Tn Fig. 2 is shown a double-hunting lineswitch DLS of the rotary lineswitch type. This lineswitch terminates a trunk from the repeater such as repeater SR shown in Fig. 1. The lineswitches such as switch DLS have access to local and outgoing trunks and to separate sets of contacts which are made available for selection in case all trunks of one class or the other are busy. The local trunks terminate in local connectors, such as LC, which has access to the lines in the sub-exchange. Connector LC is mechanically similar to the well known rotary lineswitch. The circuit is similar to that of the ordinary Strowger type connector with certain modifications which are a part of this invention and will be described in detail hereinafter.

Fig. 3 shows an incoming connector 10 through which is multipled an outgoing trunk extending from the banks of lineswitch DLS to the main exchange. Connector TC is simi lar to connector LC, except for certain modifications required due to its use as an incomin switch. One incoming connector is provi ed for each trunk from the main exchange. T1 represents another subscribers substation in the sub-exchange. The line from substation T1 will also terminate in a group of line relays such as LR, (not shown) accessible to line finders such as finder F.

In Fig. i is shown an incoming repeater DR associated with the trunk from the sub-, exchange. Associated with this repeater are a number of other trunks oi which one on tends to an incoming selector in the main office, another to the bani: of an intercepting trunk finder switch, and another extends to the banks of the local selectors in main ofiice.

In Fig. 5 is shown the regular equipment in the main ofiice. With the exception-of lineswitch LS the switches are shown only in skeleton form since they do not form part of the invention and may be of any lrnown type. It is assumed in this case, however, that these switches are of the well known Str wger type controlled over two sides of the line in series by what is commonly known as the two wire method of control. Two subscribers lines extending from substations T2 and T3 to lineswitches LS and LS1, respectively, are shown. These switches have access to first se lectors such as selector S. Selector S1 is an ordinary Strowger type selector and terminates a trunk extending from the operators osition in the third office to the main ofiice.

elector- S2, also an ordinary Strowger lector terminates a trunk extending from ropeater DR. These switches have access to the local switch train comprising selectors such as S3 and connectors such as C, through which calls are completed to the subscribers in the main exchange. Selector S3 also has access to the trunks extending from the main exchange to the sub-exchange by way of repeaters DR and to trunks extending to the operators position in the manual office.

In Fig. 6 is shown a link circuit FL comprising a finder switch and a lineswitch, both of which are of the rotary lineswitch type, and associated relays. The finder switch has access in its banks to intercepting trunks extending from repeaters such as repeater DR. The lineswitch has access to trunks extending to the operator in the manual exchange.

' causes the selector S2 to raise its wi mean? In Fig. 7, in the left-hand part of the'sheet is shown trunk apparatus TA associated with the main ofiice end of a trunk extending to the manual ofiice. This apparatus terminates a trunk from the banks of local selectors in the main ofiice, a trunk accessible to the link circuits such as link FL, and a trunk extending to an incoming selector in the main ofiice. The terminating equipment TM in the manual ofiice is equipped with two jacks, J and J, the former for calling and the latter for answering. The operators position is provided with two types of cords, a dialling cord DC for cooperating with jacks such as J, and an answeringcord AC for cooperating with jacks such as J.

To set up a connection in the sub-exchange, the calling subscriber first dials two dlgits whereupon switching repeater SR functions and causes lineswitch DLS to hunt for and connect with an idle local connector such as LC. The next two digits operate this connector in the usual way to extend the connection to the calling line. The first two diglts, in addition to operating switching mechanism in the repeater SR also operate apparatus in the main exchange. If the-call is from a non-restricted line the first digit ers to the called level and select an idle tru such asthe trunk to selector S3. The second digit then operates selector S3, which also raises its wipers to the called level, but immediately on the call being identified as a local one, the switches in the main exchange are released and restore to normal. If the call is for a subscriber in the main exchange, selector S3 hunts for and connects with an idle connector in the called group and that connector, such as connector C, operates in response to number to extend the connection to the called line and signal thatline in the usual way. If the calling station in the sub-office is restricted to local calls therein, repeater DR does not extend the connection to the incoming selector, but in response to the first two digits switches over and initiates the operation of the link circuit FL. -Thus, if the first two digits identify the-call as a local one, the trunk is released and the link circuit does not operate. However, if the number called is that of a subscriber at the main exchange the finder, switch associated with the link FL connects with the trunk by way of repeater DR and selects an idle operators trunk such as the trunk TA extending to the operators position TM. The remaining digits ,have no efiect. The operator then answers? the call and on determining the number of.the subscriber wanted, dials back over the trunk to operate selector S2 and other switches in the main exchange to set up a connection with the wanted line. The operator then causes the repeater DR to switch over the connecselectors.

' In case a non-restricted line of the sub-- exchange or'a subscriber in the main exchange desires to call the operator, the selector, such as S3 is operated to the tenth level, whereby the call is extended directly to the operator by Way of and position equipment, such as TM. The operator may also extend calls from either subor main exchanges to subscribers in some distant exchange by means of the answering cord circuit and the usual toll line equipment. The operator may'also extend'incoming calls to subscribers in the sub-exchange by way of trunks, such as trunk TA and selectors such as S1 and S3. In this case, selector S1 is dialled to a local level, such as the eighth.

level, where an idle selector such as S3 is connected with. Selector S3 is the'r'i operated to the tenth level Where it hunts for and connects with an idle trunk extending to the subexchange. On incoming calls connector IO operates and disconnects itself from the local trunk accessible to the lineswitch DLS. The next two digits .of the called number operate the incoming connector in the usual wa to establish the connection with the called line. On calls to a main exchange subscriber, selector S3 is operated to a local level and the call completed by way of a connector such as connector C.

Having explained the objects of the invention and the apparatus employed, the operations involved in setting up various connections in a system embodying the invention will now be described in detail.

It will be assumed first that a subscriber at substation T in the sub-exchange is calling a subscriber at substation T3 in the main exstricted line. When a line is non-restricted, terminals 36- and 37 are connected by means of jumper 35, thereby placing a ground on contacts such as contact 57 in the banks of the finder switches which contacts are individual to the respective lines. On lifting the receiver at the substation, a circuit is closed which maybe traced from battery, winding of relay 12, armature 19, conductor 2, through the loop at the calling substation, conductor 3, armature 17 to ground. Belay 12 operates and at armature 20 marks the line as calling in the banks of the finder switches by disconnecting ground from the trunks such as trunk TA the last two digits of the called change and that the calling line is a non-retest conductor 33 and connecting that conmon starting lead 177, extending to repeaters such as repeater SR. Relay 14 operates and at armature 25 closes a part of the operating circuit for relay 15; this latter relay does not operate at this time, however, since its winding is shunted out by the ground through armature 23. Ground on the common starting lead, by way of contacts controlled by armature 135 causes the operation of relay 102. Relay 102 closes a clrcuit at armature 127 for relay 101 and stepping magnet 63 in series; at armature 126 test wiper 53 by way, of test conductor 61 is connected at a point between relay 101 and the stepping magnet; at armature 128 a locking circuit is closed for relay 102, including armatures 138 and 162; and at armature 129 a point in the discriminating circuit is closed. In case the test wiper of the finder switch is standing on a contact of a line that is not calling, the wiper will encounter a ground by way of a test conductor, such as conductor 33 and the normal ground connection thereto. This ground will cause the stepping magnet 63 to operate and at the same time shunt out relay-101. Magnet 63, on operating, opens its own circuit at interrupter spring 64 and on the wipers 51-54 ahead to the next set of contacts. As long as grounded test contacts are engaged the stepping operation is repeated until wiper 53 encounters the contact marked as calling, at which time battery through a cut-off relay, such as relay 11 will be encountered and the short circuit removed from relay 101. Relay 101 and the relay such as relay 11 will operate in series from ground on armature 127. Magnet 63, however, will not operate in series with relay 101. Relay 101- then switches the test conductor 61 from the circuit including relay 101 and connects a ground thereto to hold relay 11 in operated position. At armatures 120 and 125 the talking conductors of the trunk are closed through to line relay 103. At armature 123 the discriminating lead is connected up, and at armature 124 the timing device TD is connected through to relay 108. Relay 11, on operating, disconnects thenormal battery and ground connection from the calling line at armatures 17 and 19, respectively, and at armature 18 connects itself directly to test conductor 33. Ground from the finder switch by way of the test wiper and test conductor now holds relay 11 operated and also marks the line as busy in the connector banks by maintaining a ground on conductor 4. Relay 12 on being disconnected from the calling loop deenergizes and at armature 21 opens the circuit of relay 13. Relay 13 deenergizes, opens the original energizing circuit of relay 14 at armature 23, and at armature 24 disconnects the ground from the common starting conductor. Relay 14 now remains energlzed 1n deenergizing steps I 131 a point in the loop circuit to the switch ahead is closed. Relay 104 operates over the above-traced. circuit, and at armature 132 connects ground to the release trunk conductor to holdup relay 101 after relay 102 releases. This ground also extends b way of armatures 156 and 158 and conductor 174 to lineswitch DLS. At armature 133 a point -in the local impulsing circuit is closed; at armature 134 an operating circuit is closed for relay 105 independent of armature 130. The function of this latter circuit will be described in more detail later on. At armature 135 the initial energizing circuit of relay 102 is opened and the common starting conductor 177 is switched through to the next repeater of the group, namely repeater SR. The ground by way of armature 158 and conductor 174 causes the operation of relay 202. Relay 202 and also relay 201 are two-step relays and operate only in their first step initially, closing the contacts marked with the Roman numeral ,1 and under certain conditions 0 rate in their second step and close the a ditional contacts marked II. If the wipers of the lineswitch arestanding on contacts associated with an idle local trunk, nothing happens when relay 202 operates, as above, but if the w pers are standing on contacts associated with an outgoing trunk the operation of relay 202 closes a circuit for the stepping magnet which may be traced from ground on bank contacts associated with the trunk, wiper 224, armature 214 and its resting contact, armature 213 and its working contact, lnterrupter springs 269, winding of the stepping magnet 203 to battery. The stepping magnet energizes over this circuit and steps the wipers to the next set of contacts. Relay 113 will now operate from ground on the release trunk by way of armature 132, armature 152, winding of relay 113, resistance 119 to battery. This relay is made slow to operate in order that a preliminary ground impulse may be transmitted over conductor 174 on the seizure of the switch. The purpose of this ground impulse is to provide for stepping the'lineswitch ahead on each call so that in case of trouble on a trunk a subsequent call on the same line will not be held up indefinitely. Relay 113 -on operating closes a point in the loop circuit to the switch ahead at armature 157, at armature 158 disconnects the release trunk from lead 174 and connects it to lead 173, at armature 159 closes a path around armature 156, and at armature 161 closes a point in'its own releasing circuit. On. ground being-removed to the next set of contacts.

from conductor 174, relay 202 deenergizes, leaving the wipers of the'lineswitch standing on contacts associated with a local trunk. Ground on conductor 173 now causes relay 201 to operate in its first step. In operating in its first step, relay 201 actuates armatures 219 and 270 but not the other armatures. A circuit is closed thereby from ground on the test contact corresponding to the local trunk, wiper 221, armature 218 and its resting contact, armature 219 and its working contact, armature 213 and its resting contact, interrupter springs 269, stepping magnet 203 to battery. .The stepping magnet operates over the above circuit and at armature 269 interrupts its own circuit, and, on deenergizing, steps the wipers 221225 ahead If-the next set of contacts is engaged, the test contact such as contact 232 will be grounded, thereby causing the reoperation of thestepping magnet which again steps the wipers ahead to the next set of contacts. The hunting operation continues until the test wiper encounters the contacts associated with an idle trunk, such as the trunk comprising conductors 233-235. It will be noted that all contacts corresponding to local trunks with which wiper 221 engages, and contacts corresponding to outgoing trunks with which wiper 224 energizes are permanently grounded. 'Wiper 221 not encountering ground, relay 201 will operate in its second step from ground on conductor 173, upper Winding of relay 201, armature 270, armature 219, armature 213 and its resting contact, interrupter springs 269, winding of magnet 203 to battery. The stepping magnet 203, however, will not operate in serieswith the upper winding of relay 210. At armatures 217 and 220 the talk ing conductors of the trunk are switched through to the wi ers, and at armature 218 a ground is place on the release trunk conductor extending through wiper 221, bank contact 232, conductor 234, armature 321, contacts controlled by armature 357, relay 301, to battery. Relay 301 operates and at armatures 314 and 315 disconnects the talking conductors of the trunk from the incoming connector IC and switches them over to the talking conductors of the trunk leading to the main exchange. A loop circuit has now been extended to the repeater, such as DR, in the main exchange responsive to the lifting of the receiver at the calling station.

This circuit may be traced as follows: battery, upper winding of relay 406, upper winding of relay 405, armatures 422, 418, and 414, conductors 452, 450, and 352, armature 314 and its working contact, conductor 233, contact 230, Wiper 222, armature 217, conductor 171", armature 131, winding of relay 114, armature 157, contacts controlled by armature 136, armature 155, conductor 175, armature '220, 'wiper 223, contact 231,

conductor 235, armature 315, conductors 353, 449, and 451, armatures 415, 420, and 424, lower winding of relay 405, lower winding of relay 406, contacts controlled by armature 441, contacts controlled by armature 445, to ground by way of the induction coil DT' on which a dial 7 tone is superimposed. The dial tone informs the calling subscriber that the trunk has been seized andthat dialling may commence. Relay 114 operates in the above loop circuit and at armature 163 connects the discriminating lead to the positive trunk conductor 175, thereby shunting out the lower winding of relay 406 and unbalancing relay 405. Relay 405 is so constructed that its two windings oppose each other and prevent it from actuating its armatures when normally connected. When unbalanced by the ground on the positive side of the line relay 405 operates. Relay 114 also opens the circuit of relay 102 at armature 162, the latter relay deenergizes after a short interval and disconnects the discriminating lead from the trunk. Relay 102 opens the initial energizing circuit of relay 101 at armature 127; relay 101 now holding up from ground by way of armature 132 and armature 122.

Relay 406, on operating, as previously described, closes an obvious circuit for relay 407 at armature 428. Relay 407 operates and at armature 429 closes a circuit for relay 402, at armature 430 closes a point in the circuit of relay 408, and at armature 431 closes a point in the circuit of relay 403 which will be described subsequently. Relay 405, on operating, completes the circuit of relay 403 by way of armature 427 and armature 431. Relay 403 operates and at armature 417 connects itself to release trunk conductor 448 of selector S2, atarmatures 418 and 420 the talking conductors are disconnected from Telay 406 and connected to conductors 446 and 447, extending to the line relay of selector S2, at armature 419 an additional ground is placed'on the holding circuit for relay 402, and at armature 421 an additional point is closed in the circuit of relay 403. The line relay of selector S2 operates over the previously traced loop circuit and the release relay which also operates in the usual way returns ground over release trunk conductor 448 to hold relay 403 in operated position. The selector also places a dial tone on the line in the usual manner to replace the dial tone originally supplied by repeater DR. Relays 405, 406, 407, deenergize and open the circuits previously closed by their respective operations, but this has no effect at this time. Relay 402, on operating, at armature 416 disconnects relay 401 from the release trunk conductor and connects the ground to that conductor to mark the trunk busy in the banks of the local selectors. The calling line has now been extended by way of repeater SR, lineswitch DLS, and repeater DR to incoming selector S2 in the main exchan At this point the further operation of t e apparatus depends on whether or not the calling subscriber dials within a certam predetermined time interval. A timing device or interrupter TD arranged to connect ground to a timing conductor at certa n predetermined intervals is associated with repeater SR. This device may be common to a numberof repeaters and may be so arranged that the timing operation is started responsive to the seizure of the associated switch, or if exact timing is not required, it ma be arranged to operate continuously an ground the timing conductor at regular intervals. The interval allowed before startin to dial will depend on local conditions an me? be any reasonable interval for instance, rom one and one-half to three minutes. It will be assumed in this case that the allowed interval is three minutes and that the timing device TD is adapted to start operating responsive to the seizing of repeater SR and to place ground impulses on the timing conductor at one and one-half minute intervals thereafter.

In case thecalling subscriber dials before the first ground impulse is transmitted the disconnect circuit does not function, since the timing conductor is opened at one or more points by armature 143, 147 or 150. However, if the calling subscriber does not dial within this interval, a circuit is closed from ground, timing device TD, armatures 124, 150, 147 and 143, winding of relay 108 to battery. Relay 108 operates and at armature 144 closes a holding circuit for itself in series with relay 107 to ground at armature 132. Relay 107 does not operate at this'time as its winding is shunted by the ground on the timing conductor. When ground is removed from the timing conductor at the end of the impulse, relay 107 operates and at armature 142 closes a point in the circuit of relay 112, and at armature 143 switches the timing conductor from relay 108 to the circuit of relay 112.

If the subscriber now dials before the second timing impulse is received, the timing conductor will be opened at armature 147 or 150 as will be described in detail hereinafter, and relay 112 consequently will not operate. Relays 107 and 108 will remain energized but will have no efiect on the connection. Assuming that the subscriber does not dial within the allowed interval, the second timing impulse will cause relay 112 to operate. The previously traced loop circuit to the main oflice is then opened at armature 155 and a busy tone from the tone enerator ET is connected to the upper talking conductor of the callin trunk. t armature 156 and contacts contro led thereby, tor is disconnected timing conductor is 112, and a holding the release trunk conducfrom conductor 173, the disconnected from relay circuit for that relay is closed including the release trunk conductor and ground at armature 132. Opening the loop allows the switches in main ofiice to release and the removal of ground from conductor 173 ermits the release of lineswitch DLS of which a more detailed description will be 'ven later. The busy tone on the line will inform the subscriber that it is necessary to hang up the receiver before attemptin to dial. a

o roceed with the call in the event that the su scriber dials within the allowed interval it will be assumed that the wanted subscriber is assi ned the number 8395. The calling subscri er now operates the calling device or dial in accordance with the first digit of the called-number, and the calling loop is interrupted as is well known in the art. As relay 103 responds to the first digit, the circuit of. relay 104 is momentarily opened and closed at armature 130. Eac time the circuit of relay 104 is opened its windin is short circuited at contacts controlled y armature 130, thus renderin the relay slow to release. The short circult of the winding of relay 104 permits relay 105 to operate from ground at armature 134. Relay 105 is also slow to deenergize since each time its operating circuit is opened, a high resistance circuit throu h relay 104 is closed. These two relays, there%ore, remain operated during the series of im ulses. At armature 136 and contacts contro led thereby relay 114 is cut out of the loop circuit extending to the main ofiice and a new loop circuit is closed to improve the impulsing over the trunk. Relay 114 deenergizes but this has no effect at this time. As armature 130 dro 5 back in response to the first impulse, a circuit is closed from ground, armature 130 and its resting contact, armature 133, armature 146 and thence by one branch connection throu h the winding of stepping magnet 116 to attery, and by wa of t e other branch and contacts controlled by armature 140 through the winding ofrelay 106 to battery. Relay 106 operates and at armature 139 closes an additional point in the impulsing circuit independent of armature 146, at armature 140 and contacts controlled thereby disconnects itself from the impulsin conductor and closes a locking circuit for itself to ground at armature 137, and at armature 141 disconnects ground from wiper 165. Stepping magnet 116 energizes and deenergizes responsive to each impulse and ste s the wiper ahead to the contact correspon ing to the digit dialled. As the wpers leave their normal or home position 0 -normal' contacts 164 close and relay 109 operates over an obvious circuit. Relay 109 on operating, at armature 145, closes a point in the circuitof release ma et 115, at armature 146 opens a point in t eimpulsing circuit which, however, .is now closed at armature 139, at armature 182 closes a oint in the circuit over which relay 110 wi l subsequently hold, at armature 147 opens a point in the previously described timing circuit, and at armature 179 disconnects conductor 181 from the dial tone enerator DT and connects it instead to the usy tone machine BT. Since the first digit dialled consists of eight impulses, wiper 165 will be advanced eight steps to contact 166.

Shortly after the last impulse of the series,

relay 105 deenergizes and at armature 136 and contacts controlled thereby reestablishes the original loop circuit including relay 114, and opens the locking circuit for relay 106 at armature 137. Relay 106 deenergizes, opens the auxiliary impulsing circuit at armature 139, at armature 140 and contacts controlled thereby opens a point in its own locking circuit and again connects its winding to the impulsing circuit, and at armature 141 closes a circuit from ground, armature 141, wiper 165, contact 166', contacts controlled b armature 149, windmg of relay 110 to attery. Relay 110 operates and at armature 148 closes a circuit for release magnet 115 including armatures 151 and 145, at armature 149 and contacts cont-rolled thereby disconnects itself from its operating circuit via contact 166 and closes a locking circuit for itself to ground by way of armatures 153 and 182 and in parallel therewith through the winding of relay 111 to ground at armature 132. Relay 111 does not operate at this time since its winding is shunted by the ground at armature 182. Release magnet 115 operates and restores wiper 165 to its normal or home position whereupon contacts 164 separate and open the circuit of relay 109. Relay 109 deenergizes, opens a point in the release magnet circuit, closes the original impulsing circuit, and by retracting its armature 182 removes the shunt from relay 111. Relay 110 now remains locked up in series with relay 111 and the latter relay also operates. Relay 111 on operating opens a point in the circuit of release magnet 115 at armature 151, at armature 152 opens one of the parallel paths over which relay 113 and the line-switch DLS are held operated, at armature 153 opens a point in the shunt circuit for its ownwinding so that the subsequent operation of relay 109 will have no eliect, and at armature 154 closes a point in a shunt circuit for relay 113 which is without effect at this time.

Should the first digit be any other than the digit 8, the operation will be the same in general except that no circuit will be closed for relay 110 and consequently neither relay 110 nor relay 111 will operate. No circuit will be closed at this time for release magnet 115 and wiper 165 will remain on the contact on which it was set until the connection is released. Belay 109 will remain operated and maintain the impulsing circuit open so'that' subsequent impulses will have no effect at the repeater. The above also applies when the first digit is a 4, this being without effect due to the open circuit at armature 154. The operation of the equipment in the main oifice is not affected.

Each deenergization of relay 103 as it follows the dialled impulses opens the loo circuit to the main oflice at armature 131. hese interruptions cause the line relay of selector S to operate in the usual way and the selector raises its wipers opposite the eighth level and then selects an idle trunk in that level. It will be assumed that the trunk selected is the one comprising conductors 528-530 terminating in contacts 525527" and extending to selector S The first digit has now been dialled with the result that relays 110 and 111 of repeater SR are locked in operated position and selector S at the main exchange has extended the loop circuit to-the line relay of selector S The apparatus is now in condition to receive the next series of impulses corresponding to the second digit of the called number, that is, the digit 3. Relay 103 responds to the impulses and relays 105, 106, 109 and stepping magnet 116 operate as in the previous case.

Wiper 165 is stepped to the third contact which is left dead since it corresponds, to a main ofiice number. The loop .to the main ofiice is interrupted at armature 131 and the line relay of selector S responds in the usual way to cause the selector to advance its wipers opposite the third level. The selector then rotates automatically until its wipers 53l533 are set on an idle trunk which will be assumed to be the trunk extending from contacts 534536 to connector C. Returning now to repeater SR, shortly after the last impulse of the series, relays 105 and 106 deenergize as before but as wiper 165 is standing on a dead contact,'no circuit is closed.

Relay 109 remains operated during the remainder of the connection and at armature 146 maintains the local impulsing circuit open up and release the connection. If the called line is idle, the connector will switch through in the usual manner, operate the cut-off relay of the lineswitch LS1, and signal the called subscriber in the usual way. The calling subscriber will be given the usual ringback itone. when the called subscriber answers the conversation may take place, the connector feedin talkin battery to the called line throug the bac -bridge relay and to the trunk through the line relay. Battery for the calling line is fed through line relay 103 of repeater SR. The calling line and trunk are in uctively connected through condensers 117 and 118 through which the voice currents pass.

When through talkin both. subscribers hang up their receivers. y called subscriber has no effect except to deenergize the back-bridge relay of the connector. When the calling subscriber hangs u the loop over which relay 103 is held operate d is opened and that relay deenergizes. Shortly after this, relay 104 deenergizes and disconnects ground from the release trunk at armature 132. Relay 105 energizes momentarily but without effect. Relay 103 on deenergizing opens the loop to the main ofiice and the connector deenergizes in the usual manner, removing ground. from the release trunk to permit the release of selectors S and S as well as relay 403 of repeater DR. Ground bein removed from the release trunk of repeater SR, relay 201 of lineswitch DLS restores to normal as do relays 11, 101, 111 and 113. Relay 109 remains operated from ground on the off-normal contacts 164 and, on rela 111 deenergizing, a circuit is completed or release magnet 115 which restores wiper 165 to normal position.' The circuit of relay 109 is then opened at the ofi-normal springs and that relay restores. The apparatus is now in normal position and ready to receive the next call.

Consider now a connection between substations T and T,, as above described in which the calling substation is restricted to local calls in the sub-exchan e. In'this case there will be no connection etw een terminals 36 and 37, hence the discriminat in conductor 34 will not be' grounded. The c'alhng subscriber on lifting the receiver is connected with repeater SR by way of finder switch F, and a loop is extended to an incoming repeater DR in the main oflice by way of a lineswitch DLS exactly as described in the previous connection. However, since no ground is present on the discriminating conductor which is connected to the line on the operation of relay 114, differential relay 405 of repeater DR will not operate as in the previous case. Since relay 405 does not operate, the circuit of relay 403 will remain open and the loop will, therefore, not be switched over to incoming selector S Relays 406, 407 and 402 will operate as previously described and the calling subscriber will receive the dial tone by way of induction coil DT, The apparatus is now in condition to receive the dialled impulses. It will be remembered that the number 8395 anging up by the is assi ed torsubstation T. which number the ca 'ng subscriber now dials.

Relay 103 responds to the impulses of the first digit and repeater SR functions exactly as described in the previous connection. Relay 103 interru ts the loo circuit extending to repeater R and re ay 406 which is energized over the loop responds to these interruptions. As relay 406 responds to the impulses, the circuit of relay 407 is momentarily o ened and that of relay 408 is momentarily c osed at armature 428 at each impulse. Relay 408 energizes and remains operated during the series of impulses due to its slow releasing characteristic. Relay 407 also remains energized during impulsing when its circuit is momentarily opened at each impulse. Relay 408 on operating opens a point in the starting circuit at armature 432 and cloas a circuit from ground, armatures 438, 433 and 439, relay 412 to battery. Relay 412 operates and opens a point in the circuit of relay 410 at armature 442, opens another point in the starting circuit at armature 443, closes a circuit for itself and relay 411 in series at armature 444 and at armature 445 disconnects dial tone ground from the lower winding of relay 406 and substitutes an ordinary ground. Relay 411 does not operate at this time since its winding is shunted by the ound on armature 438. Shortly after the ast impulse of the series, the previously described operations take place in repeater SR and relay. 408 of repeater DR also deenergizes. Relay 408 on eener 'zing removes the shunt from relay 411 and t at relay operates in series with relay 412. Relay 411 on energizing closes a point in the circuit of relay 410 at armature 436, closes'a point in the starting circuit at armature 437, at armature 438 disconnects the ground from armature .433 and substitutes battery through resistance 413, closes a holding circuit for its own lower winding at armature 440 and at armature 441 connects another ground to the lower winding of rela 406 to prevent a subsequent connection of dial tone groundto that relay. The apparatus is now in condition toireceive the next series of impulses.

The calling subscriber now dials the digit 3 and relay 103 of repeater SR responds and repeats the impulses over the loop to relay 406 of repeater DR. Repeater SR functions in exactly the same manner as described in the previous connection. 'Relay 408 of repeater DR operates as previously and at armature 432 again opens a point in the starting circuit which is also 0 en at armature 442, and at armature 433 c oses a circuit from battery, resistance 413, armature 438, armature 433, armature 439 and its working contact (relay 411 havingpreviously operated), upper winding of relay 411 to ground at armature 431. Relay 412 which was held operated in serieswith the upper winding I of relaiy 411 is thereby shunted out and de energizes, closing a pomt in the circuit of relay ,410 at armature 442, closing a point in the starting circuit at armature 443, opening a point in its own holding circuit at armature 444, and switching back the normal dial tone" circuit at armature 445. The latter circuit is not efiective at thistime since it is 0 net contacts controlled b armature 441. hortly after the last impu se of the series, repeater SR functions exactl as described in the previous connection an relay 408 deenergizes as previously. Relay 408 on deenergizing at this time closes a circuit from round, armatures 423, 432, 443, 437, 436 am? 442, winding of relay 410 to battery, and in parallel there'- to, conductor 454, contacts controlled respectively by armatures 636 and 622, winding of relay 603 to battery. Relay 410 operates over the above circuit and at armature 455 closes a locking circuit for-itself independent of armature 432, and at armature 435 switches the guarding conductor 453 from ground at armature 425 to battery through the winding of rela 404 to mark the trunk as calling in the ban s of the finder switches of links FL. Proceeding now to the link FL, relay 603 energizes in parallel with relay 410 over the previously traced circuit. On operating, relay 603 closes a circuit for relay 602 and stepping magnet 663 in series at armature 628, and at armature 627 connects test wiper 655 between relay 602 and magnet 663.

Contacts with which wiper 655 engages are.

grounded by way of uarding conductors such as conductor 453 oraill trunks except those on which calls are being extended as just described, in which case the test contact will be marked by battery through a cut-ofi relay such as relay 404. f-Ajs long as wiper 655 encounters groundedicontacts relay 602 will be shunted out and magnet 663 will ener gize from ground on the test contact, armatur'es 618, 625, and 627, interrupter springs 664, stepping magnet 663toj-battery. The stepping magnet on energizing opens its own circuit at interrupter'springs 664 and on deenergizing steps wipers 653 -657 ahead to the next set of contacts. This operation is the same, as previously described for finder switch F and is repeated as long-as wiper 655 engages a grounded contact. 'When the wiper engages the contact marked as calling, the shunt is removed from relay 602 and that relay operates over the-previously traced circuit in series with the stepping magnet. The stepping magnet does not operate, however, due to the high resistance of relay 602. Relay 602 switches the test wiper from its previous connection between relay 602 and the stepping magnet to the opposite side of relay 602 at armature 625, switches the operating conductors through at armatures 619 and 620, connects ground to the local release trunk lead at armature 621, disconnects the through at armatures 626 and 675. To return now to repeater DR, the operation of the switching relay of the link circuit closed a circuit from ground armatures 628, 625 and 618, wiper 655, contact 660, conductor 453, contacts controlled by armature 426, armature 435, winding of relay 404 to battery. Re-

lay 404 operates, disconnects the calling loop from line relay 406 at armatures 422 and 424 closes an additional circuit for relay 402 and opens the circuit of relay 410 at armature 423, closes a circuit for relay 409 at armature 425 and at armature '426 connects itself directly to the guarding conductor independent of armature 435 of relay 410. Relays 406, 407, 410 and 411 now deenergize but have no further efi'ect on the connection. Relay 409 energizes and at armature 434 closes a point in the circuit of relay-403 which, however, is now open' at armature 425. The calling loop is now extended by way of conductors 352 and 353, contacts 661 and 662, wipers 656 and 657 v armatures 626 and 675, left-hand windings oi repeating coil R, upper and lower windings of impedance coil 616 to battery and ground, respectivel Further diallin by the calling subscriber will have no e ect either bei fore or after the operation of relay 404.

The operations of relays 602 and 603 and stepping magnet 663 have been described.

The finder switch has extended the calling trunk to thelink FL whose operation will now be considered. The operation of relay 602 closed a circuit from ground, armature 621, armature 635, relay 606 to battery, and in parallel thereto,- through armature 640, relay 611 to battery. Relay 606 operates and at armature 632 closes a locking circuit for itself including contacts controlled byarmature 630, closes an obvious circuit forrelay 604 at armature 633, and connects'zup a signalling circuit at armature 634whic'h will be described in detail hereinafter. Relay 611 also operates and at armature 6.41 closes a point in the circuit of relay 612 which has no effect at this time. Relay 604 operates, closes a point in its own circuit which will be effective at a later stage of the operation and closes a loop circuit for selector S2 at armature 676. Relay 602 also closed a circuit from supervisory ground, armatures 624 and 649, relay 613 to battery. Relay. 613 operates and at armatures 645 and 646 completes a hunting circuit similar to the previously described circuit of the finder switch. If the wipers ter a ground and stepping magnet 615 will operate in thewell known manner to advance the wipers to the next set of contacts. This operatlon is repeated until an idle is found 'whcreon relay 614 operates in senes with thestepping magnet, switches the test wiper over to its upper terminal, at armature 648, closes a holding circuit for itself at armature647, opens the circuit of relay 613 at armature 649, and at armatures 650 and 651 switches through a sim lex signalling and talkin circuit which will be considered in detail ater on. Relay 602 alsoprepares an operatin circuit for the incoming selector S2.

Consi ering now the trunk circuit TA, the operation of relay 614 (of link FL) closed a circuit from ground, armatures 621, 647, and 648, wiper 666, contact 669, conductor 672, armature 727, relay 701 to batter-7y. Relay 701 energizes and at armatures 20. and 721 connects the trunk circuit through to operators e uipment TM in the manual exchange. circuit may now be traced from battery, armature 634, relays 608 and 609 in series, right-hand windings of repeating coil R, thence in two parallel (paths by way of armatures 643 and 644 an their respective restin contacts, armatures 650 and 651, wipers 66 and 668, contacts 670 and 671, conductors 673 and 674, armatures 720 and 721 and their respective working contacts, trunk conductors 757 and 758, left-hand windings of fi repeating coil R4, conductor 750, contacts controlled respectively by armatures 744 and 745, relay 712 to ground at armature 740. Relays 608, 609 and 712 operate over the above circuit. Relay 608 opens a point in the circuit of relay 605 and closes a circuit for relay 607 at armature 638. Relay 609 opens a point in the circuit of relay 601 at armature 639. Relay 712 closes a circuit for the line lamp L1 at armature 743. Relay 607 operates and at armature 635 opens the original energizing circuit of relay 606, WhlCh, however, remains operated over a circuit including armature 632 and contacts controlled by armature 630. Relay 607 also closes another circuit at armature 636 for switching the starting conductor through to the next switch, and at armature 637 closes a point in the circuit of relay 605. Lam L1 lights to notify the operator that a cal is awaiting attention.

To answer the call, the operator inserts the plug of cord AC into jack J, closing a circuit for rela 711 by way of the sleeve of the plug, and ridging the left-hand windings of repeatin coil R5 across the trunk section inductive y coupled to the trunk by way of repeating coil R4. Relay'711 energizes and at armature 740 disconnects ground from the trunk and substitutes battery therefor, opens the circuit of lamp L1 and closes a circuit for lamp L2 at armature 741. Lamp L2 lights indicatin that the call is from a restricted line. Re ays 608, 609 and 712 deenergize when battery is connected to the energizing closes a circuit for relay 605 at armature 638. The circuit of relay 607 is opened but due toits slow releasing characteristic, that relay maintains its armatures in actuated position during the short interval of open circuit. Belay 605 energizes and at armature 630 and contacts controlled thereby opens the holding circuit of relay 606 and completes a circuit for relay 604 independent o armature 638. Relay 606 deenergizes and opens a point in its own holding circuit at armature 632, opens the circuit of relay 604 at armature 633 and at armature 634, disconnects batte from the trunk and substitutes the norma l ground connection. Relays 608, 609 and 712 again operate over the previousl traced simplex circuit from ground at the main ofiice to battery at the manual oflice. Relays 609 and 712 were without efiect on their momentary deenergization. Relay 608 on energizing again opens the circuit of relay 605 and closes the circuit of relay 607 which has not yet deenergized. A short time after its circuit is opened, relay 605'which is a slow-acting rela deenergizes and at armature 630 opens the olding circuit of relay 604. Relay 604 deenergizes and at armature 676 0 ns the rst loop circuit to the selector in t e main ofiice, the loop now being extended through armature 677 and ri ht-hand windings of repeating coil R1. lay 604 also prepares a circu1t for relay 612 at armature 629.

The connection has now been extended to the operator at the manual exchan e. The talking circuit com rises fiv in uctively coupled sections as ollowsfFirst, the loop circuit extending from the calling substation to repeater SR to which battery and ground are fed throu h relay 103. Second the loop circuit exten in from repeater SR by we of lineswitch D S, connector IC, the trun extending from the sub-ofiice to the main office, repeater DR, link FL to the left hand winding of repeating coil R. Battery and ground are fed to thls 100 through impedance coil 616. Third, the simplex circuit extending from the rightlhand windin of repeatin'g coil R, the trunk extending rom the main office to the manual ofiice to the left hand windings of repeatin coll R4. Battery is fed to this circuit om the manual ofiice and ground from the main ofiice. Fourth, the dry-loop circuit extending from the right hand windings of repeating coil R4 through the operators answering ack to the left hand windings of repeatin coil R5 of the answering cord. Fifth, the loop extending from the right hand windings of repeating coil R5 to the operators telephone set which may be of any known type. These sections are all inductively coupled, the first and second through condensers 117 and 118, the second and third through repeatmanual and otth'e Relay 608 on de- 1 ing coil R, the'third and fourth through repeating coil R4 and'the fourth and fifth through; repeatin coil R5. The 0 erator talks with the cal ing subscriber an deter mines the identit of that subscriber and also the number of t e wanted subscriber. The calling subscriber is then instructed to-wait on the line while the o erator completes the call. The operator ma es out the usual toll ticketso that the proper charge may be made for the call.

As previousl mentioned, on the seizure of the link FL, a cop circuit is extended to the incoming selector S2 at the main exchange and when the call is answered the loop is placed under the control of the operator. This circuit may be traced from battery and ground through the line relay (not shown) of selector S2, conductors 446 and 447, contacts 658 and 659, wipers 653 and 1654 armatures 619 and 620 armature 677 ,and righthand windings of repeating coil R1. The

- line relay of the selector operates over the above circuit in the usual way. It will be noted that the primary windings of, the repeating coil are normally short circuited by armatures 643 and 644. This feature will be explained more in detail hereinafter.

The operator having determined the number of the wantedsubscriber, now inserts the plug of dialling cord DC injaqk J and dials the com lete number. I When the dial is turned 0 -normal, a circuit is closed from battery, contacts 754 of. the ofi-normal springs, over the rin contact of the 'plug, relay 713 to ground. elay 713 operates and at armature 744 and contacts controlled thereby, disconnects battery through relay 712 from the trunk and substitutesbattery through impulsing contacts 756 of the dial and the ti of the plug. As the dial returns to norma the impulsmg springs open the circuit in accordance with the particular digit dialled. Relays 608. and 609 respond to these interruptions by deenergizing and reenergizing. Relays 608 in deenergizing responsive to the first impulse closes a circuit for relay 605 as previously described. Relay 605 energizes and at armature 630 closes a circuit for relay 612. Relay 612energizes, closes a locking circuit for itself at armature 642 and at armatures 643 and 644 removes the short circuit from the left-hand windings of repeating coil R1 and short circuits the ri ht hand windings of repeating coil R. The eft-hand windings of repeating coil R1 are now included in the impulsing circuit. With each deenergization, relay 608 also opens the loop circuit to selector S2 at armature 677. Selector S2 operates in the usual way to step its wipers to the called level and then select an idle trunk. The three remaining digits are dialled and are repeated in-the same manner, operating a selector such as selector S3 and a connector such as connector C. Relay 605 energizes during impulsing and remainsoperated throughout each series of impulses, er functions however, after a It has no furt closing the circuit of relay 612 except to 0 en. the circuit of AG relay 610 to guard agalnst that relays operating due to the dialling impulses. The calling subscriber does not receive objectionable clicks when the 100 to the selector is interrupted due to the s ort circuit aroundthe windings of repeatin coil R. The dial on returning to its norma position opens the circuit of relay 713 which deenergizes and restores the trunk to its previous condition with rela 712 in the circuit.

The connector, having een set" on the contacts of the wanted line operates in the same manner as in the previously described connection. If the line is busy, the connector places a busy tone on the trunk which is andible to the operator but not to the calling subscriber since repeating coil R is short circuited. The operator then operates key K forward separating contacts 751 and closing contacts 752. Relay 710 operates from ground on contacts 752 and at armature 739 connects alternating current from enerator G to the trunk by way of conductor 50. The alternating current circuit extends through relay 610, armature 631, and condenser 678 to ground. Relay 610 energizes and at armature 640 opens the circuit of relay 611. Relay 611 deenergizes shortly afterward and at armature 641 opens a point in the circuit of relay 612 which also deenergizes. Relay 612 opens a point in its own locking circuit at armature 642, and at armatures 643 and 644 again short circuits the windings of repeating coil R1 and removes the short circuit from repeating coil R. The operator is again connected in a talking circuit with the calling subscriber and informs the subscriber that the wanted line is busy. The busy tone from the connector will not be heard at this time by either the operator or subscriber due to the short circuit on repeating coil R1.

If the called subscriber is idle, the connector switches through and signals the called subscriber in the usual manner. The operator will wait until the subscriber answers, thereby verifying the completion of the call and inform the subscriber that a toll call is waiting. The operator then actuates key K to the rear, closing a circuit from battery, contacts 753, sleeve of the plug and jack, relay 714 to ground. Relay 714 energizes and at armature 745 disconnects relay 712 from the trunk and substitutes resistance 759 therefor. Resistance 759 is of such a value that relay 608 will remain operated in series therewith, but relay 609 will release. 5 Relay 609 on falling back closes a circuit from ground,

holding circuit of relay 404 of repeater DR at armature 618. Relay 404 falls back immediately, opens the circuit of relay 409 and closes a circuit for relay 403 including armature 434 and its working contact relay 409 remaining 0 rated a short time a er its circuit is opene due to its slow releasing characteristic. Relay 403 operates and switches the incoming trunk through to selector S as in the previous connection. The connection set up by the operator via selector S is now held up by the calling loop and relay 403 is maintained in operated position by ground on release trunk conductor 448. The relays of repeater DR deenergize as in the previous case. Returning to link circuit FL, relay 602 deenergizes, o ens the operating loop to the selector an removes ground from the local release trunk. Relays 611 and 614 deenergize, the latter disconnecting the outgoing trunk. Relays 601, 607, and

608 then deenergize and the link circuit is ready to respond to the next call. Relay 701 deenergizes and transfers the operators trunk to its normal connection. I The operator then withdraws the plugs of cords AC and DC whereon all equipment in the manual office restores to normal.

In case the subscriber in the above describedcall had dialled the number assigned for calling the operator, that is the digits 80, the connection would be set up exactly as in the previous instance. If the call was for a subscriber in the main ofiice it would be completed as in the previous instance. In the case of a long distance call,;the operator being informed that the call is from a restricted line by the lighted condition of lamp L2 after answering the call, can handle the call as required by local conditions. If restricted lines are denied long-distance service the operator will so inform'jthe calling subscriber. If long distance calls are allowed, these may be handled in either of two ways; the operator will instruct the subscriber to hang up and will extend another connection over a dialling trunk when the long distance connection has been set up; or the operator will dial back as in the previous connection to extend the call by way of selectors S and a to another trunk to the manual board. The call will be switched over at repeater DR as in the previous case and will thenceforth be handled asa call from a non-restricted subscriber as will be described hereinafter.

A call from a non-restricted line in the sub-exchange to the operator will now be described. It will be assumed that the subscriber at substation T desires a long distance connection and calls the operator by dialling the code number 80. The calling line is extended to repeater SR by finder switch F and to selector S2 in the main office by way of lineswitch DLS and repeater DR in the same manner as for a call to a main ofiice subscriber. Repeater SR and selectors S2 and S3 respond as in the above-mentioned connection. Selector S3, however, is o rated to the tenth level where it selects an idle trunk such as the trunk comprising conductors 549-551 terminating on contacts 546- 548. Selector S3 on seizing the trunk completes a circuit from ground on the release trunk, through wiper 533, contact 548, conductor 551, contacts controlled by armature 716, relay 709 to battery.- Relay 709 energizes and at armature 734 com letes two parallel circuits, one for relay 7 02 y way of armatures 728 and 724, the other for the upper winding of rela 707 in series with resistance 717, and including armature 7 31. Relay 7 07 does not operate over its up er winding alone in series with resistance 17. Relay 709 also disconnects the out oing trunk and connects up the talking COIKfilClIOI'S of the in coming trunk at armatures 735 and 738, and

at armatures 736 and 737' disconnects the lower windin of relay 707 from the bridge across the rig t-hand windings of re eating coil R3 and substitutes the two wind ings of relay 705 therefor. Relay 7 02 energizes, closes a holding circuit for itself at armature 722 independent of armature 728, closes a holding circuit for relay 709 at armature 718, and at armature 723, substitutes battery for the normal ground connection on the trunk extending to the manual ofiice. A circuit may now be traced from battery, armature 723, lower winding of relay 708, contacts controlled by armature 732, conductor 749, thence in two parallel paths by way of left-hand windings of re eatin coil R3, armatures 720 and 721, le t-han windings of repeating coil R4, conductor 750, contacts controlled respectively by armatures 744 and 745, relay 712 to ground at armature 740. Relay 708 energizes, closes a circuit for relay 704 at armature 733, and at armature 755 closes the calling loop through to relay 705 by way of the right-hand windings of refieating coil R3 and armatures 736 and 737.

elay .704 energizes, connects a busying groundito release trunk conductor 748 at armature 725, closes a point in the circuit of relay 703 at armature 726, disconnects relay 709 from release trunk conductor 551 and places a holding ground on that conductor at armature 716 and contacts controlled there by, and at armature 728, opens the original circuit of relay 702 and places anadditional holding ground on the localrelease trunk. Relay 705 operates over the calling loop, closes a point in the circuit of relay 707 at armature 729, and at armature 7 30 closes an obvious circuit for relay 706. Relay 706 ener izes, closes a holding circuit at armature 60 for relay 7 09 which was held up by ground at armature 718 after being disconnected from conductor 551, and at armature 731 opens the previously traced circuit for the upper winding of relay 707' in series with resistance 717. It has taken considerable time as in the previously described connection and line lamp L1 lights to inform the operator that acall is awaiting attention.

The operator now inserts the plug of answering cord AG in jack J, op'eratin relay 711 as in the previous connection. Re ay 711 substitutes battery for the normal ground connection on the trunk at armature 7 40. Re-

lays 708 and 712 momentarily deenergize. Rela 7 08 on fallin back momentarily opens the circuit of relay 04 and closes a circuit for relay 703, armature 726 being actuated. The calling loop is also momentarily opened at armature 755. Relay 7 05 also deenergizes momentarily but this is without effect at this time. Relay 704 does not deenergize immediately due to its slow releasing characteristic. Relay 703 energizes and opens the holding circuit of relay 702 at armature 724. Relay 703 is also slow to release, and maintains its armature actuated long enough to insure the release of relay 702. Relay 702 on deenergizing again connects a ground to the trunk at armature 723 and relays 708 and 712 again operate. Rela 7 08 again closes the circuit of relay 704 whic has not deenergized and closes the calling loop through to relay 705. Relay 705 again operates and completes a circuit-for the upper winding of relay 707 b way of armatures 729 and 718. Relay operates .over this circuit and at armature 732 and. contacts controlled thereby, connects the upper and lower windings of relay 7 08 in series in the trunk. The upper winding of relay 708 is of. relatively high resistance and the current flow over the trunk is reduced so that relay 712 deenergizes. The interval during WlllCh relay 712 is energized after the insertion of the operators answering plug is too short to per- .mit lamp L to light, and the circuit of the lamp is again opened-when relay 712 falls back. The failure of lamp L to li ht informs the operator that the call is rom a non-restricted line. The operator is now connected with the calling subscriber by way of repeating coils R3, R4 and R5.

' Such calls to the operator will usually be made when along distance connection is required. The operator may complete the call while the subscriber waits on the line or may request the subscriber to hang up and wait until the operator calls back. Assuming that the call is to a near-by town and can be com pleted without undue delay, the operator will simplyextend the call by way of the answering cord AG in the usual manner in which toll calls are set up. Answering supervision will be provided by the cord circuit in known manner. When the conversation is completed and the calling subscriber hangs up, the calling loop will be opened at the switching repeater in the sub-office, and relay 705 will release. The circuit of relay 707 is opened at armature 7 29 and that relay also releases. Relay 707 on restoring a ain disconnects the upper winding of relay 08 from the trunk circuit and relay 712 o erates in series with the lower winding. T e. circuit lamp L2 is now closed at armature 743 and the lamp lights to give the operator disconnect supervision. Relays 705 and 709 also deenergize when the calling subscriber hangs up but have no eflect at this time. The switch train in the main oflice is held up by ground from the trunk apparatus TA controlled by relay 704. The equipment in the sub-oflice, however, releases as in thepreviously described connection between a sub-oflice and a main ofiice subscriber. .The operator now removes the answering plu from the jack and relays 711, 712, 7 08 and 04 restore. Ground is removed "from release trunk conductor 551 and selectors S and S and repeater DR restore to normal. The apparatus is now in condition to receive the next call. 7

A long distance connection from a restricted line in the sub-exchange would be completed in the same manner asthe above-de-- scribed connection, except that the intercepting operator would be required to set up the trunk switches in' the main viously mentioned.

A local connection in the sub-exchange will now be described. Local calls may be comexchange as prepleted automatically regardless of whether or not the calling line is restricted. It will be assumed that the subscriber at substation T is calling number 8425 which is the number assigned to substation T1 (Fig. 3). Gn lifting the receiver, the calling line is extended to repeater SR and by way of lineswitch DLS to repeater DR in the main exchange exactly as in the previous instances. The first digit dialled i. e. the digit 8 is registered in repeater SR and operates selector S or repeater DR (depending on whether or not the calling line is restricted) as previously described. It will be recalled that after the first series of impulses, wiper 165 restored to normal and relays 110 and 111 of repeater SR locked up to ground at armature 132. Repeater SR responds to the second series of impulses as do either selector S or repeater DR as previously described. However, since the second digit dialled is the digit 4, wiper 165 will be advanced four steps and engage contact 167.

the last impulseofthe series, a circuit is closed

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