US1497423A - Automatic telephone system - Google Patents

Description

lune 10 1924.,

B. D. WILLIS AUTOMATIC TELEPHONE SYSTEM Filed March 29. 1920 3 Sheets-Sheet 2 B i fi fizz E'FHEZ" 7.15.

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June 10 1924.

, B. D. WILLIS AUTOMATIC TELEPHONE SYSTEM 3 Sheets-Sheet s Filed March 29, 1920 Inuen UP Barnard D- JnfzZhs Patented June 10, 1924.

UNITED STATES BERNARD D. WILLIS, 01 OAK PARK, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY. OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed March 29, 1920. Serial No. 869.789.

To all whom it may concern Be it known that I, BERNARD D. VVInLrs, a citizen of the United States of America, and resident of Oak Park, in the county of ook, in the State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

My invention relates in general to automatic telephone systems, butmore especially to such automatic systems as include private automatic branch exchanges, commonly known as P. A. X.s; and the object of the invention is to provide new and improved main to P. A. X. trunk circuits which are well adapted for use in connection with private automatic exchanges of large size.

In accomplishing this object numerous new features have been developed and new circuits designed. resulting in a very efficient system characterized by the absence of all complicated equipment at the attendant operators positions. and having. nevertheless, all the principal operating features which have heretofore been considered desirable in a system of this kind. All of which will be explained fully in the detailed specification which is to follow, reference being had to the accompanying drawings forming a part thereof.

Referring to the drawings, comprising Figs. 1. 2, and 3, I have shown therein the complete circuits of a main to P. A. X. trunk, including all the apparatus at the private automatic exchange which is necessary in order to complete a connection from a calling subscriber in the main exchange to 11 called subscriber in the branch exchange. The localswitches and circuits in the main exchange have not been shown. as they have nothing in particular to do with the invention. It may be stated, however, that the main exchange may be of any standard two wire type such as is in common use today,

' and may be of any desired capacity. The

branch exchange may be of the same general type as the main exchange although of smaller capacity. As shown herein a branch exchange of 1000 lines capacity is contemplated, although the size may of course be increased or diminished to suit the circumstances of any particular case.

To proceed with the explanation. the trunk line comprising conductors 2 and 3 is one of a group of trunk lines which are accessible to selector switches in the main exchange and which extend by way of the usual repeaters to so called incoming selectors at the private automatic exchange. There are a number of attendant operators at the branch exchange or P. A. X., whose duty it is to handle general calls directed to the establishment in which the P. A. X. is located; and all of the main to P. A. X. trunks pass through the attendant operators positions before terminating in the incoming selectors. This is clearly shown in the drawing wherein the trunk line shown in Fig. 1 is connected to multiple jacks J J and J which are located at the first, second, and third operators positions, respectively, and extends to and terminates in the incoming selector E, Fig. 2.

The incoming selector E is a vertical and rotary switch of the well known Strowger type, as are the other numerical switches in the system, and functions as a first selector to pick out desired groups of connectors in the usual and well known manner. Theoretically, there may be ten such groups of connectors to which the incoming selector E groups, or 900 lines. A connector in one of these groups is indicated by the reference character H. Fig. 3. The connector H is a vertical and rotary switch of the Strowger type and is one of a group of similar connectors which have access to a group of 10!) local lines in the P. A; X., one of which lines is the line extending to the substation A. The reference character C indicates an individual line switch of the rotary type whose function it is to extend the line of substation A when calling to an idle local first selector (not shown).

' The attendant operators do not handle all the incoming calls to the private automatic exchange but only those calls which are required to be distributed to the proper local parties. This may be made a little more .clear by a consideration of the numbering X.. trunks are accessible from the second level of the second thousand group of second selectors in the main exchange. 'With this arrangement, access to the main to P. A. X. trunks is had by calling the digit 2 twice, and after connection is established with one of these trunks any subscriber in the P. A. X. can be connected with by calling the digits in the local telephone number. Certain of the local exchange telephones may be given direct incoming service y listing their numbers in the telephone directory, the number 22being prefixed to the local numbers. For example local station number 345 would be listed in the directory as number 22345. In a great many cases, however, perhaps in a majority of cases, incoming calls will not be directed to an articular stations or individuals but wil e directed simply to the company or organization, and are answered by one of the attendant operators, who subsequently switches the calls to the proper stations after ascertaining the wants of the calling parties. To handle this class of calls the tenth level in the incoming selectors, corresponding to the digit 0, is reserved, and when this digit is called on one of the incoming selectors a line signal is lighted in front of an idle attendant operator. It will be evident then that the directory telephone number of the company or establishment which is served by the private automatic exchange will be number 220. It may be stated in this connection that the attendant operators may be reached by local subscribers also by calling the digit 0, there being a number of information trunks terminating in the tenth level of the local first selectors. Such arrangement is not shown in the drawings but is in accordance with standard practice and is mentioned here merely to assist in an understanding of the system as a whole. In order to distribute the general or miscellaneous company calls to idle operators each of the incoming selectors is provided with a rotary line switch which is operated, when the associated selector is raised to the tenth level, to select an idle operators position and light the line lamp thereat which is associated with the trunk line over which the call has been received. The rotary line switch which is associated with the selector E, Fig. 2, is shown just above, the said selector and is indicated by the reference character C.

The foregoing general remarks will serve to give a general idea of the purpose and scope of the invention. I will now explain more in detail the operation of the circuits themselves, with the object of pointing out the new improvements and explaining their utility. For this purpose it will be assumed first that a subscriber in the main exchange desires to call the subscriber at substation A in the private automatic exchange, whose telephone number as listed in the directory is number 22345. After explaining the operations which take place in setting up this type of connection, it will be assumed that a call directed to the company itself is received, and the manner in which this call is handled by an attendant operator and extended to the proper local station will then be explained in detail. To proceed, when the main exchange subscriber removes his receiver his line is extended by means of the usual line switch or trunk selector to an idle first selector switch, which is operated responsive to the calling .of the digit 2 to select an idle trunk line leading to an idle second selector in the second thousand group. The selected second selector is then operated responsive to the calling of the second digit 2, to select an idle trunk line leading to the private automatic exchange, and it will be assumed that the trunk line selected is the trunk line comprising conductors 2 and 3, Fig. 1. known practice, the two line conductors of the trunk line coming from the selector banks terminate in the line relay of a repeater which is inserted in the trunk line as previously mentioned. When the trunk line is seized, therefore, the line and release relays of the repeater will be energized and a bridge will be closed across the outgoing trunk conductors, these conductors being the conductors 2.and 3. When this bridge is closed at the repeater a circuit is completed for the double wound line relay 50 of the incoming selector E, and this relay is at once operated to close the circuit of the slow-acting release relay 51. Relay 51, upon energizing, prepares the selector for operation in its vertical movement in the usual manner.

The calling subscriber may now operate his calling device in accordance with the digit 3whichis the next digit in the telephone number. The resulting circuit interruptions are repeated by the line relay of the repeater which interrupts the bridge across trunk line conductors 2 and 3 each time its own circuit is interrupted, and causes the line relay 50 of the incoming selector E to deenergize a corresponding number of times and send a series of current impulses through the slow acting series relay 55 and the vertical magnet 59. Responsive to these impulses the vertical magnet 59 is operated to raise the switch shaft step by step until the wipers 8083, inclusive, stand opposite the third level of bank contacts. The slow acting relay 55 is energized in series with the vertical magnet, maintaining its armature attracted throughout the vertical movement of the switch, and at the first upward movement of the switch In accordance with well shaft closes an initial energizing circuit for the stepping relay 56. Upon energizing, re-

. ment of the switch the slow acting relay 55 deenergizes and closes the circuit of the ro-" tary magnet 57, which is accordingly operated to rotate the wipers 80-83, inclusive, into engagement with the first set of bank contacts in the levelr opposite which they were raised, the third level in this case.-

Near the end of its stroke, the rotary magnet opens the locking circuit of the stepping relay 56 which is deenergized therefore and opens the circuit of the rotary magnet. The rotary magnet then deenergizes also and again closes its interrupter contact. The operation now depends upon whether the trunk line with which the Wipers have connected is busy or idle. If thistrunk line is busy the test contact associated therewith will have a ground potential upon it and the stepping relay 56 will again be enerized by current fiow over a path which may e traced as follows: grounded test contact, test wiper 82, armature 67 and its resting contact, interrupter contact of the rotary magnet 57, off normal springs 63, and the winding of the stepping relay 56 to battery. Upon energizing, the stepping relay agaln closes the circuit of the rotary magnet which operates to rotate the switch wipers into engagement with the next set of bank contacts.

'This operation will continue as long as the test wiper 82 continues to engage grounded test contacts. When a nongrounded test contact is reached, which we will assume to be the test contact 86 associated with the trunk line comprising conductors 8891, inclusive, the stepping relay 56 is not again energized, but instead the switching relay 58, which heretofore has been short eircuited, is energized by current flow over a circuit which extends as follows: grounded conductor 71, winding of the switching relay 58, interrupter contact of the rotary magnet 57, off normal springs 63, and the winding of the switching relay 56 to battery. Owing to the high resistance of the switching relay 58 relay 56 is not'operated. Upon energizing, relay 58 connects the test wiper 82 with the grounded conductor 71 at its armature 67, and at its armatures 66 and 70 disconnects the trunk conductors 2 and 3 fromthe windings of the line relay 50 and extends them by way of the working con-- tacts of these armatures, line wipers and 83, bank contacts 84 and 87, trunk conductors 88 and 91, and normally closed contacts of the reversing relay 150 to the upper and lower windings of the double wound line relay 151 of the connector H, Fig. 3.

When the trunk line is extended to the connector as I above described, the line relay 151 IS energized and closes a circuit connector switch for operation in its vertical movement at its armature 165, and at its armature 166 completes a holding circuit extending back to the selector E over the following path: ground at G", working contact of armature 166, conductor 90, test contact 86, test wiper 82, and armature 67 and its working contact to conductor 71, whence the circuit extends as previously traced through the windings of the switching relay 58 and the stepping relay 56 in series to battery. By retaining its armature 68 in operated position the switching relay serves to prevent the release of the selector switch after the relays 50 and 51 have deenergized.

The holding circuit just described also serves to maintain ground potential on the multiplesiof test contact 86 in the banks of the other selector switches in order to make the trunk line extending to connector H busy.

The calling subscriber may now operate his calling device in accordance with the next digit in the desired number, with the result that a series of interruptions is produced in the bridge across trunk conductors 2 and 3' as before, thereby causing a series of deenergizations of the line relay 151 of the connector H. At each deenergization the line relay transmits a current lmpulse to the vertical magnet 159 over the following circuit: ground at G, armature 164 and its resting contact, armature 165 and its working contact, 01f normal springs 161 and 163, winding of the slow acting series relay 153, and the Winding of the vertical magnet 159 to battery. The above is the circuit over which the first impulse is transmitted. At the first upward movement of the shaft the ofl normal springs are shifted andthe circuit is completed over a new path as follows: armature 165 and its working contact, ofi' normal springs 161 and 162, armature 167 and its working contact (relay 153 being now energized) winding of relay 153, and the winding of the vertical magnet 159 to battery; By the operation of the vertical magnet the wipers 190192, inclusive, are raised step by step until they stand opposite the level of bank contacts in which is located the contacts associated with the line of substation A. The slow acting relay 153, which is energized in series with the vertical magnet, maintains its armature attracted during the vertical operation of the switch, and at the end of the vertical movement deenergizes and transfers the operating circuit from the vertical magnet 159 to the rotary magnet 158.

The calling subscriber may now operate his calling device in accordance with the next and final digit in the desired number.

for the slow acting release relay 152. Upon energizing in turn relay 152 prepares the As betore, a series of interruptions is produced at the repeater in the bridge across the trunk conductors 2 and 3, and the line relay 151 is again deenergized a number of times, transmitting impulses to the rotary magnet 158 over the following circuit: ground at G, armature 164 and its resting contact, armature 165 and its working contact, ofi' normal springs 161 and 162, armature 167 and its resting contact, resting contact of armature 171 and the said armature, armature 179 and its resting contact, and the winding of the rotary magnet 158 to battery. Responsive to these impulses the rotary magnet is operated to rotate the switch wipers into engagement with the particular set of bank contacts which is associated with the line of substation A, be-

ing the bank contacts indicated in the draw-' ing by reference characters 193195, inclusive. The slow acting relay 156 is energized in parallel with the rotary magnet and remains in operated position during the rotation of the switch. At its armautre 174 relay 156 connects the test wiper 191 with the test relay 155, and at its armature 17 5 relay 156 closes the operatin circuit over apath which is independent 0 the armature 171 controlled by the test relay 155 in order to guard against the possibility of the latter relay being momentarily energized while the test wiper 171 is passin over busy test contacts. Assuming first t at the line of substation A is busy when called as above described, when the test wiper 191 comes to rest in engagement with test contact 194, it will find a ground otential thereon and the test relay 155 will e energized. When the slow acting relay 156 deenergizes an instant later, a lockin circuit will be established for relay 155 y way of its armature 173 in an obvious manner. In energized position the test relay also opens the rotary magnet circuit at its armature 171 and at its armature 172 connects a lead from the busy signalling machine Q to the lower talking conductor. By this latter operation the calling subscriber is given an audible busy signal, and being advised thereby that the desired line is for the time being inaccessible, he will replace his receiver.

Having described the operations which take place when the called line is busy, it will now be assumed that the called line is idle. Under these circumstances, when the test wiper 191 comes to rest in engagement with test contact 194, it will find no ground potential and the test relay 155 will not be energized. Then when the slow acting relay 156 deenergizes the following circuit will be completed: grounded conductor 90. armature 173 and its resting contact. upper winding of the switching relay 157, resting contact of armature 174 and the said armature, test wiper 191, test contact 194, winding of the switching relay 196 of line switch C, and the windin of the stepping magnet 197 to battery. pon the closure of the above circuit relays 157 and 196 are energized in series and the latter relay operates to disconnect the line of substation A from its, normal battery and round connections in the line switch C. t is noted that the relay 196 is operated only about half way, due to the fact that the line relay of the line switch has not been energized, and the line conductors are not connected through to the line switch wipers. At the connector ll when the switching relay 157 is energized it establishes a locking circuit for itself at its armature 178, opens the rotary magnet circuit at its armature 179, connects direct ground to the test wiper 191 at its armature 177, and at its armatures 176 and 180 closes the talking conductors through to the line wipers of the connector,

The connection having been finally completed, ringing current from the generator en is projected intermittently out over the line of substation A in the usual manner to operate the bridged ringer at the substation. It will be noticed that the return path for the ringing current includes the upper winding of the ring cut-off relay 154, and when the called subscriber responds by removing his receiver the ring cut-off relay is energized and establishes a locking circuit for itself at its armature 168. The ring cut-oii relay also opens the ringing circuit at its armatures 169 and 170, and at the working contacts of these same armatures finally. completes the talking circuit. The calling subscriber is supplied with talking battery from the line relay in the repeater at the main exchange in the well known manner, while the called subscriber is supplied with talking battery through the windings of the double wound back, brid e relay 150. Relay 150 is energized while t e receiver at substation A remains off the hook and reverses the direction of current flow in the incoming trunk conductors 88 and 91. This operation is of no particular utility in connection with the present disclosure. but being a standard operation the circuits are shown in this manner.

Conversation-may now proceed over the established connection, which it will be noticed has been set up entirely automatically, and without any assistance from any of the attendant operators whose equipment is shown in Fig. 1. When the conversation is finished both subscribers will replace their receivers. The release of the automatic equipment is brought about by the replacement of the re'eiver at the calling substation which opens the circuit of the linerelay of the repeater at the main exchange. The release relay of the repeater is then deenergized causing the release of the main exchange automatic switches and the opening of the bridge across the trunk conductom 2 and 3. As a result, the line relay 151 of the connector H, Fig. 3, is permanently deenergized followed by the deenergization of the release relay 152. This latter relay closes the circuit of the release magnet 160 and the connector H is restored in the usual manner. Relay 152 also opens the holding circuit extending back to the selector E, whereupon the switching relay 58 is deenergized andthe selector is restored to normal through the medium of its release magnet 60.

Although there is nothing especially novel in the operations described in the preceding paragraphs, is has been considered advisable to include them in order to give a clear understanding of the operation of the system in handling strictly automatic connections; and in addition it will enable the rest of the explanation to be given in a more general manner as regards the operation of the switches themselves, thus permitting the explanation to be chiefly directed to the new features of operation. It will be supposed now that a main exchange subscriber is calling the company or establishment which is served by the private branch exchange equipment shown, using for this purpose the general call number 220. When the digits 2 and 2 are called the connection is extended by means of a first selector and a second selector to the repeater which is associated with an idle trunk line, the trunk line comprising conductors 2 and 3, for example, all as previously described. When the next digit is called, which is the digit 0, the wipers of the incoming selector E will be raised to the tenth level, after which the switch will automatically rotate in the usual manner to select an idle set of bank contacts in that level. With each set of bank contacts in the tenth level there is associated a pair of relays, such as relays 92 and 93, which are provided for the purpose of establishing a holding circuit for selectors which are raised to the tenth level. Assuming that the tenth level set of bank contacts shown in the drawing is the first idle set, the wipers of the selector E will come to rest in engagement therewith, the switching relay 58 will be energized, and the line conductors will be extended through to the relay 92.-Relay 92 is then energized, followed by the energization of relay 93, which relay establishes a holding circuit for the selector to maintain the same in operated position. i

.When the shaft of the selector E is raised to the tenth level, the upper set of oil normal springs, comprising off normal springs 64'and off normal springs 65, are closed, and by the closure of oflt normal springs 65 a circuit is completedfor the line relay 100 of tion now depends upon whether the test contact with which the test wiper 104 is in engagement is grounded or is not grounded, which in turn depends upon whether the operators position with which such contact is associated is busy or is not busy. It will be assumed that thefirst two operators positions are busy, and such being the case, the first two test contacts associated with the test wiper 104 will have a ground potential upon them. It follows that the switching relay 101 will be temporarily short circuited while the stepping magnet 102 is operated to rotate the switch wipers two steps until the test wiper 104 comes into engagement with the third test contact in its banks. Assuming that the third operators position is idle the third test contact will not be grounded and the rotation of the line switch will cease. lhe switching relay 101 is now energized and is of such high resistance that the stepping magnet 102 is not affected. Relay 101, upon energizing, connects ground G to the test wiper 104 as follows: ground at G", armature 107, working contact of armature 109 and the said armature, and armature 108 and its working contact to the test wiper 104. By this means the third test contact in the bank of the test wiper 104 is instantly grounded and the third position is made busy to other switches, it being understood of course that the banks of the line switch C are connected in multiple with the banks of the other line switches. A circuit may now be traced for the line lamp L as follows: ground at G working contact of armature 107 andthe said armature, working contact of armature 109 and the said armature, wiper 103, conductor 16, lamp L, common conductor 13, and the winding of the pilot relay 7 to battery. By current flow in the above circuit the lamp L is lighted and indicates to the operator that a call has been received over the trunk line associated therewith. Relay 7 is energized at; the same time, lights the pilot lamp L and also extends ground by way of conductor 10 to the multiple test contacts in the banks of the line switches- When the operator at position No. 3 observes the lighted lamp L she will respond by inserting the plug of her special cord circuit 0 in the jack J. By this operation the operators head set is connected across the trunk line conductors 2 and 3, and at the same time a circuit is completed by way 4 which includes the auxiliary line relay 52 of the incoming selector E. The line relay 52 is accordingly energized and closes the following circuit for relay 53: ground at G, armature 71 and its workin contact, the oli' normal springs 64, norma ly closed contacts controlled byarmature 72, and the winding of rela 53 to battery. -Relay 53 is energized an establishes a locking circuit for itself at its armature 72, at the same time breaking its original energizing circuit. In addition, relay 53 closes a circuit for the release magnet as follows: ground at G, armature 71 and its working contact, armature 73 and its working contact, off normal springs 61, and the winding of the release magnet 60 to" battery. By the operation of the release magnet the incoming selector E is restored to normal position,

and both upper and lower sets of oil normal springs are returned to' their original positions as shown in the drawing. By the openin of oil normalsprings the circuit of the me relay 100 of the line switch C is broken and relays 100 and 101 are therefore deenergized. Line switch 0 is thus restored to its normal condition, the wipers 103 and 104, however, remaining in connection with their respective third bank contacts. The relays 100 and 101 having deenergized, round is removed from both of the line switch wipers 103 and 104, and the line lamp L is extinguished. The pilot relay 7 then deenergizes, extinguishes the pilot lamp L, and removes ground from con doctor 10 thereby removing the bu condition from the third test contacts 1n the banks of the line switches, and rendering the third position accessible to other incomin calls. Y e I heturning' to ,theselector 11, when the selector is released as before described the locking circuit of relay 53 .is broken at ofi normal springs 62 and the said relay is therefore deenergized. Armature 73 of relay 53 now being in retracted sition, a circuit is etsablished for the s ow acting relay 54 which, upon energizing, prepares a circuit for the vertical magnet 59, which will be traced shortly. The attendant operator at the No. 3 position, whose cord circuit O has been connected with the trunkline by way. of jack J", will now inquire of the calling subscriber and ascertain the name of the local .partywith whom he desires to converse, Assuming that the wanted party is the party at the local station A,

- the number of which is No. 345, the operator will proceedito call this number by means of her calling device S, which is included in the circuitof'the auxiliary line relav 52 of the incoming selector. When the calling device is o erated in accordance with the .digit 3 the inefrelay 52 is deenergized three times and at each deenergl ation transmits ream :1

.a current im ulse to the vertical magnet 59 trol of the line relay 52 to raise the switchshaft step by step until the wi rs 80-83 inclusive, stand opposite the third level oi bank contacts. At the end of the vertical movement the wipers are automatically rotated in search of an idle trunk line as has been previousl described, and it will be assumed that t 1e wipers are brought to rest in engagement with the bank contacts 84 -87, inclusive, in which contacts is terminated the trunk line extendin to the connector H, Fig. 3. Theswitchmg relay 58 is now energized, and at its armature 69 opens the circuit extending to the vertical magnet 59 of the incoming selector.

The operator may now call the next digit in the number, or the digit 4, thereby causing another series of deenergizations of the line relay 52 which now at each deenergization transmits a current impulse to the vertical magnet 159 of the connector H as follows: ground at G, armature 71 and its resting contact, armature 74 and its Working contact, wiper 81, bank contact 85. conductor 89, off normal springs 161 and 163, winding of the slow acting relay 153. and the winding of the vertical magnet 159 to battery. It will be seen that the above circuit is very similar so far as the wiring in the connector is concerned to the operating circuit described in the previous operation of the connector, the incoming trunk conductor 89 over which the impulses are received being simply tapped on to the regular operating circuit at the contact spring which forms the working contact of armature 165 of the relay 152. The connector is therefore operated in the same manner as was described in the previous case and the wipers are raised opposite the level in which 'is terminated the line of the desired called station. When the dial of the calling device S is operated in accordance with the last digit in the desired number, another series of impulses is transmitted to the connector H over conductor 89 and the switch wipers are rotated until they come to rest in engagement with bank contacts 1931 95, inclusive, thus completing the connection. The remaining operations by which the called subscriber is signalled, and son on, have already been explained and will not need to be referred to again.

It will be observed that when the operator energized whether the operator is enga talking conductors and no complicated devices are required in order to open the talking circuit while the operators callin device is bein operated to prevent the calling subscriber rom hearing the impulses. The operators head set is bridged across the trunk all the time,

quired number, or start to call, while still talking. Since the incoming trunk line conductors continue without interruptions through the attendant operators positions the line relay 50 of the selector is always in setting up the connection or not, and a ter the selector E has cut through and extended the connection to a connector switch the line relay of such connector will be energized. It follows that the release of the connection is at all times under the control of the callin subscriber, and after the operator has finished calling the required number she may remove her plug from the jack and give her attention to another call. When the plug is removed from the jack the auxiliary line relay 52 of the incoming selector E is deenergized, but without interfering in any way with the connection which has been established. The line relay 151 at the connector remains in energized position until the calling subscriber han s up his receiver, when the connection is released in the same manner as was previously described.

In order to enable the operator to release the established connection in case she has accidentallyv called the wrong number a release key is provided for each incoming trunk at each operators position. These keys are indicated by the reference characters K, K and K in Fig. 1. Assuming that the attendant operator at position No. 3 has established a connection through the medium of the switches shown and desires,

to release the connection for the purpose of calling another number, the operation is as follows: key K is actuated momentarily and closes the following circuit: ground at G, contacts of key K conductor 16, wiper 103 (normally stands on bank contact last connected with), armature 108 and its resting contact, normally closed contact springs controlled by armature 72, and the wmding oi relay 53 to battery. Relay 53 is accordingly energised, establishes a locking circuit for itself, and closes the circuit of the release magnet 60, all as was previously explained whenit was described how the incomin selector was released from the-tenth level y the insertion of the plug in the jack J". The selector having been released the connector II is of course released also, because the connection thereto is broken at the selector wipers, and all the switches are thus restored to normal and may be reoperated to set u a new connection.

Having descri ed my invention, what I and she can call the're-.

consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims.

IV hat I claim as my invention is:

1. In a telephone system, an incoming trunk line terminating in a selector switch at a branch exchange, multiple terminals of said trunk line at a plurality of operators positions, and means associated with said switch and controllable after said switch has been operated for selecting and signalling an idle operator.

2. In a telephone system, an incoming trunk line terminating in a selector switch at a branch exchange, multiple terminals of said trunk line at a plurality of operators positions, an auxiliary switch associated with said selector, and means controlled over said trunk line for operating said auxiliary switch to select and signal an idle operator.

3. In a telephone system, an incoming trunk line terminating in a selector switch at a branch exchange, multiple terminals of said trunk line at a plurality of operators ositions, an auxiliary switch for selecting idle operators ositions, lines accessible to said selector switch, and means for o eratin said selector switch over saidtrun line cit er to select one of said lines or to start said auxiliary switch, at the option of a calling party.

4. In a telephone system, trunk lines extending from a main exchange to a branch exchange and terminating in automatic switches, multiple terminals for each of said trunk lines at a plurality of operators positions, means controllable by calling main exchange subscribers for connecting with said trunk lines, means for operating said switches under control of said calling subscribers or under control of the operators'at said ositions to extend connections to branc exchange subscribers, and means under the control of the said calling subscribers for testing-said operators. positions and for selecting and signaling idle operators.

5. In a telephone system, trunk lines extending from a main exchange to a branch exchange and terminating in automatic switches, multiple terminals for eachof said trunk lines at a plurality of operators positions, means controllable by calling main exchange subscribers for connecting with said trunk lines, means for operating said switches under control of said calling subscribers or under control of the operaators at said positions to extend connections to branch exchange subscribers, and an auxiliary switch associated with each of said first named switches, the said auxiliary switches being controllable by the calling.

subscribers to select and signal idle operators.

6, In a telephone system, trunk lines extending from a main exchange to a branch exchange and terminating in automatic switches, means whereby calling main excange subscribers can connect with said tions, andmeans associated witheach switch responsive to a predetermined operation thereof for automatically selecting and signalling an idle operator.

7. In a telephone system, trunk lines extending from a main exchange to a branch exchange and terminating in automatic switches, means whereby calling main exchange subscribers can connect with said trunk lines and operate said switches in setting up main to branch exchange con-' nections, multiple terminals ermanently connected to each of said trunr lines at a plurality of operators positions, a line signal for each trunk line at each position, and

means associated with each switch responsive to a predetermined operation thereof for actuatin the line signal at. an idle position'to noti y the operator that a, call has been received over the associated trunle.

8. In a telephone system, a trunk line extending from selector banks in an auto-' matic main exchange to an automatic switch in a branch exchange, said trunk line and automatic'switch being available for use in establishing main .tobranch exchange connections, multi le terminals .of said trunk line at a plura 1ty of o erators positions, a line signal at each 0 said positions, an auxiliary switch operable to select an idle one of said positions, and operate the signal thereat, and means whereby a calling main exchange subscriber, if he desired to signal an'operator, may start the operation of said auxi iary switch by operating the said first switch to a certain predetermined position.

9. In a telephone system, a trunk line extending from a main exchange to a branch exchange and terminating in an automatic switch, multiple terminals for said trunk line at a pluralityof operators positions, means whereby a calling main exchange subscriber can seize said trunk line and operate said switch, and means responsive to a certain predetermined operation of said switch for signalling an idle operator, said means comprising a second switch independently oper able'while said first switch is standing in operated position.

10. In a telephone system, a trunk line extending from a main exchange to a branch exchange and terminating in an automatic switch, multiple terminals for said trunk line at a plurality of operators positions, means whereby a calling main exchange subscriber can seize said trunk line and operate said switch, means responsive to a certain predeterminedoperation of said switch for signalling an idle operator, and means for automatically releasing said switch when the operator answers the call, the connection between the subscribers line and said switch being maintained intact while the switch is being released.

1.1. In a telephone system, a trunk line extending from a main exchange to a branch exchange and terminating in an automatic switch, multiple terminals for said trunk line at a plurality of operators positions, means whereby a calling main exchange sub scriber can seize said trunk line and operate said switch, a circuit over which said switch is controlled, means responsive to a certain redetermined operation of said switch or signalling an idle operator, means for automatically releasing said switch when the operator answers the call, and a second circuit independent of the circuit used by the subscriber over which the operator can control said switch and reoperate the same to extendthe connection in the direction of 2). called line in the branch exchange.

12. In a telephone system, a trunk line accessible to calling subscribers and terminating in an automatic switch, means for varia ly operating said switch in accordance with dlgits in called telephone numbers, a plurality of operators also having access to said trunk line, and means for signalling an idle operator when said switch is operated in accordance with a single particular digit.

13. In an automatic telephone system, a selector switch and an auxiliary switch permanently associated, the latter switch having access to lines extending to operators positions, means for variably operating said 105 selector switch under control of calling subscribers to establish connections, and means responsive to a certain predetermined operation of said selector switch for initiating the operation of said auxiliary switch to 110 select an idle one of said lines.

14. In a telephone system, serially related selector and connector switches for use in setting up a connection between two lines,

a motor magnet in the connector switch, and 115 relays in both switches which are operable independently to control said magnet.

15. In a telephone system, a pair of serially related selector and connector switches, means whereby said switches may be used either by subscribers or by operators in establishing connections, a motor magnet in said connector, a relay in said connector for controlling said magnet when the switch is' used by a subscriber, and a relay in said 195 selector for controlling said magnet when the switch is used by an operator.

16. In a telephone system, a trunk line extending to an automatic connector switch, said switch being for use in establishing two 1% nee-mes kinds of connections, a motor magnet in said switch, a circuit for said magnet including the winding thereof and a conductor of said trunk line for operating said magnet for establishing one kind of connection, a relay in said switch, and a second circuit s for operating said magnet controlled by said controlled by said relay for establishing the other kind of connection, another switch for completing connection to said trunk line when s connection or" either kind is to he estehlished, and e relsy inseid lost switch tor controlling seid first circuit.

18. in a telephone system, incens including on automatic selector switch for connecting e ceiling and celled line, two line relays in said switch for independently controlling the operation thereof, and rneens for operating first one reley end then the other to control said switch in establishing single connection '19. in a telephone system, means including an automatic selector switch for con meeting it calling and celled line, two line reloys in said switch for independently controlling the operation thereof, it circuit over which one of said rclcys is controlled by the subscriber on the ceiling line to pertielly extend a connection, end. at circuit over which the other reley is controlled by on operator to complete the some connection,

20. in a telephone system nieens including an sutonietic selector switch for connecting it calling end celled line, two line releys in seid switch for independently controllin the operation thereof, e circuit independent of the talking circuit for controlling one of ssid releys to opera e the seicl switch, end e circuit for Ineinteining the other relay energized to prevent the release of the switch while it is being operated.

21. In a telephone system, a, selector switch and a trunk line extending thereto, a line relay for controlling the operation of said switch, means for establishing c control circuit for said relay over two conductors of said trunk line in series, e sec- 0nd line relay for controlling the advancing operation of said switch, end means for establishing a, control circuit for said second relay over another conductor of said trunk line.

22. in a telephone system, c selector switch and e trunk line extending thereto, two line relays in said switch each of which is independently operable to control the entire selective movement of ssid switch, means for closing a circuit for one of said relays when the trunk line is seized, and nieansior closing e sepcrete circuit for the other oi said releys without opening the circuit of the seid first relay.

23, in e telephone system, a selector switch and a trunk. line extending thereto, two line relays in said switch eech of which is independently operable to control the entire selective movement of said switch, moons for closing seperete circuits for said relays over conductors of said trunk line, and meens for producing current impulses in one circuit to operate said switch while mcinteining the other circuit closed to prevent the release thereof.

lin en eutornetic telephone system, c selector switch, e, plurality of groups of other switches, at line relay in ssid selector operable to control the some to select e deiired group of seid other switches, o, second ins control the some to select a desired group of said other switches, automatic mee'ns for selecting en idle switch in the selected grow in either case, end it circuit over whi the selected idle switch may be controlled in its selective movement by said second relay,

Signed by nee ct Qhiccgro Coolr Gonnty, lllinois, this th day of torch,

reley in scid switch also operable to BERNARD W ELLES.

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