US1285278A - Special-service system for machine telephone switching-exchange. - Google Patents

Description

E. R. McBERTY III L; POLINKOWSKY. SPECIAL SERVICE SYSTEM FOR MACHINE TELEPHONE SWITCHING EXCHANGES.

APPLICATION FILED MAR. 19. I917- Patented Nov. 19, 1918.

2 SHEETS-SHEET I- Make/7mm.- Frank R Mcfieriy by: Pol/3'7 kowsky.

2 SHEET$-SHEET 2.

Patented Nov. 19, I918.v

APPLICATION FILED MAR. I9, I917- F. R. McBERTY (I; L'. POLINKOWSKY. SPECIAL SERVICE SYSTEM FOR MACHINE TELEPHONE SWITCHING EXCHANGES.

FRANK R. MoIBEBTY AND LIPA POLINKOWSKY, OF LONDON, ENGLAND, ASSIGNOBS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORA- TION OF NEW YORK.

SPECIAL-SERVICE SYSTEM FOR. MACHINE TELEPHONE SWITCHING-EXCHANGES.

apeoification of Letters Patent.

Patented Nov. 19, 918.

Application filed March 19, 1917. Serial No. 155,762.

To all whom it may concern:

Be it known that we, FRANK R. MGBERTY, a citizen of the United States, and LIPA POLINKOWSKY, a subject of the Emperor of Russia, both residing at- London, England,

have invented certain new and useful Improvements in Special-Service Systems for Machine Telephone Switching Exchanges, of which the following is a full, clear, conrise, and exact description.

This invention relates to a system for providing special service in telephone exchange systems utilizing automatic switches for extending the connection to a called subscriber and more particularly to circuits and apparatus whereby the repetition of busy calls may be provided for in systems of the type referred to in an etlicient and expeditious manner.

A principal feature of the invention provides that, when in response to the usual test by a selector switch having access to the desired line such line is found busy. the call is transferred to a special operator's position for attention, who, if the calling party so desires, may from time to time repeat the call until the desired line is found idle.

A more specific featureof the invention involves that, after a call has been transferred to a special operators position, such operator may maintain connection with the calling part "s line without interfering with the ability of such calling party to call and be. called in the usual manner until such time as such special operator repeats the call for the line originally found busy.

Subsidiary to this feature is the feature of the invention by which the initiation of the repetition of the call by the special operator is only possible when the calling subscriber is idle, and after the initiation of such repetition the calling subscribers line is maintained busy both as a calling and called line until the completion of the call, or, upon a repeated failure to obtain the desired line. until the breaking down of the attempted connection by the special opera Also subsidiary to this feature of the invention is the feature that the connection maintained from the special operators position to the line of the calling subscriber is independent of the breaking down of the original attempted connection and the restoration of the switches used therein, which breaking down and restoration may take place in the usual manner when the calling subscriber has restored his receiver to its switchhook after the first unsuccessful attempt to obtain the desired line.

A further and correlated feature of the invention involves that arepetition of the call will take place over automatic machine switches in a manner corresponding to the original attempted connection, and if the repetition of the call is successful, the conneotlon will be established between the calling and called subscribers over such line finder or call distributing automatic switches aswere used by the calling subscriber in the original attempted connection and automatic machine selector switches controlled by the special operator.

A further feature of the invention resides in the testing arrangement provided on the special operators position, and more particularly to the testing arrangement by which ringing current will be applied to the lines both of the calling and called sub scribers when, and only when, upon an attempted repetition of the call, the line of the called subscriber tests idle. Furthermore, this feature provides that, when once ringing has been initiated to both the calling and called subscribers, the control of the discontinuance of the ringing of such subscribers is independent, the discontinuance of the ringing of the calling subscriber taking effect when such calling subscriber removes his receiver from his switchhook and the discontinuance of the ringing of the called subscriber taking place when the called subscriber removes his receiver from its switchhook. provision being made for the special operator being connectible'to the circuit extending between the calling and called subscribers lines to explain to the subscriber who first answers the character of the call andrequest such subscriber to await the response of the other subscriber.

A further feature of the invention pro--.

ing subscribers meter and also or the disconnection of an unsuccessful repetition of the call without the operation of the calling subscribers meter, but provides that, upon a successful repetition of the call, the meter of the calling subscriber will be automatically operated upon the breaking down of the connection in the usual manner, provided always that not only is the called subscriber s line found idle, but that such called subscriber has responded.

The embodiment of the invention shown in the drawings and her inafter described discloses the invention as applied to a semiautomatic machine switching exchange of a well-known type. The invention however, is not limited to semi-automatic systems, but is equally applicable to full automatic sys tems, particularly of the type in which a sequence switch associated with a trunlr or connecting circuit over which the call is extended, talres varying positions upon the test, ringing and response of the called subscriber, since it is obvious, as will hereinafter appear, that the control under which the call is originally extended might equally well have been exercised by the calling subscriber as by a semiautomatic operator, particularly in systems utilizing" registering" and w cont-rolling apparatus, well known to the art it will, of course, be understood that, in a full automatic system, the breaking down of the original attempted connection would place under the control of calling subscriber, the called subscriber not having responded.

In the drawings,

Figure 1 represents so much of a telephone efichange system of the well-known type referred to as is necessary for understanding of the invention, together certain additional circuits and apparatus used -for transferring calls to a special position.

Fig. 2 represents sutlicient oi the circuits and apparatus of such special position for a complete understanding of the invention.

The invention and the embodiment thereof shown on drawings will be best understood from the description of the oper ation of the system shown.

Referring to F l, 3 represents a t is phone line terminating in a group or first line finders, one or which is indicated i and having associated therewith the usual line relay 5, energised upon the initiation of a call to place selectable potential in the usual manner upon the terminal 6 of such line where it appears the first line tinder and energizing the pilot or starting relay 7 common to the group or lines in which it appears. T rgization of 1 h lay 1? closes which the relays 9 and 10 are deenergized. All or such idle first line finders thereupon start in motion to select and seize the calling" line in the usual manner. immediately that the brush ll of one of such line finders makes contact with the terminal 6, the relay 1:2 is energized, placing a busy guard upon such terminal 6 by the closure or the circuit to ground, through the low resistance righthand winding of such relay 12 and, when the usual interrupter (not shown} of such line finder is opened, as the brushes of such line tinder are centered upon the terminals of toe calling line, the relay 9 energizes, opening the circuit of the power magnet 8 and closing the circuit or the holding magnet 14 of such line tinder, and the line finder is brought positively to a stop with its brushes in contact with the terminals of the calling line. The energization of the relay 9 has furthermore closed a circuit in series with the circuit for the holding magnet 14 for a starting or pilot relay 15 common to the group of trunk lines terminating in a given set of second line finders, such as the one 16 shown.

Assuming that the operator to whose position the connecting circuit 17 is individual is idle, the contact 72 common to the starting circuits of the connecting circuits upon such operators position which have access to the trunks such as 22 is closed and the relay 18 is energized over a circuit including the back contact of the relay 19 and sequence switch contact 159.

Before proceeding turthe'r, it will be noted that sequence switch contacts shown within the several areas limited by the dotted lines on Fig" l are all controlled by the seouen'c'e switch diagrammatically indicated within such areas. Since such sequenceswitches are i" well-known construction and operation, they will not be described in detail herein Upon the energization of the relay 18, 0

the usual operations in systems of this type will take place, such as the automatic connection to an idle registering and controlling equipment and to the operators telephone the indication by the operator upon the usual set or" keys of the number of the desired line, the control or the several group selectors, such as indicated at and 21, and the control of the final selector, such as indicated at 22. Since these operations are well-known and not necessary to an under standing of the present invention, it will be assumed that the connection has been extended to the terminals of the desired line and the sequence switch 190., having been driven out of its position upon the completion of the selecting operations, has tested the desired line and moved into its poltion. It will be understood that s time the sequence switch 150 is in its fourteenth position, having been driven out of its twelfth position upon the completion of the selecting operation of the first group selector 20, and that the sequence switch 100 is in its seventh posltion, havlng been moved into such position upon the completion of the operation of the usual registering and controlling equipment, which has been'associated with the connecting circuit 17 for the purposes of this connection.

When the sequence switch 100 came into its seventh position, the circuit of the lamp 23 was closed by the sequence switch contact 104 through the flasher 24, 1nd1cat1ng to the operator that the extenslon of the call has been completed and that the test thereof has taken place. In systems of thls character, if the desired ,line 1s found ldle, the sequence switch 190 will move directly into its twelfth position, in which the ringing of the desired subscriber takes place. When such subscriber responds, the sequence switch 190 will be moved into its thirteenth position, which may be considered as the talking position for such sequence switch. On the other hand, if the desired l1ne 1s found busy, no circuit will at the time ex st to drive the sequence switch 190 out of 1ts tenth position, and the restoration to normal of the final selector-22 will take place, after which the sequence switch 190 will move into its eleventh position and there remain until the breaking down of the attempted connection by the operator under whose control it has been so far established. It will, therefore, be seen that, after the test of the desired line, the circuit of the connection as extended to the final selector will be closed by the sequence switch contacts 192 and 193 through the resistance 25, while the sequence switch 190 is in its eighth to eleventh positions. This causes the energization of the called supervisory relay 26 and the, consequent movement of the sequence switch 100 into its ninth position. If it is assumed that the desired line is idle, the closure of the energizing circuit for the supervisory relay 26 by the sequence switch contacts 192 and 193 will be maintained only for a brief interval or until the sequence switch 190 moves out of its eleventh position. This causes the deenergization of the relay 26 and the consequent movement of the sequence switch 100 from its ninth into its eleventh osition. In this position a circuit for the amp 23 is established over the sequence switch contact 103 bottom and the back con-' tact and armature of the relay 26 and such lamp now burns continuously, having up to this time been intermittently flashed, such continuous lighting of the lamp indicating to the operator that ringing is taking place. Upon the response of the called subscriber and the consequent movement of the sequence switch 190 into its thirteenth posi- 27botl1 being maintained energized. When Y such supervisory relays are deenergized by the hanging up of the receivers of the respective subscribers, the respective lamps 28 and 29 will be lighted over circuits-respectively including the sequence switch contacts 105 and 103 top. The operator then causes disconnection in the usual manner, by depressing the release key 30 individual to the connecting circuit 17, energizing the usual release relay 31 and causing the deenergization of the relays 32, 10 and 33, whichhave hitherto been energized to maintain the connection between the callin subscriber and the connecting circuit 17 1n the usual manner by a circuit including the back contact of the relay 31 and thesequence switch contacts 154 and 107 top. I

If on the other hand it is assumed that the final selector 13 found on its test that the called subscribers line was busy, the sequence switch contacts 192 and 193 were closed but were not subsequently opened, as the sequence switch 190 will not pass out of its eleventh position until the breaking down of the connection-by the operator. Relay 26, therefore, is maintained energized and, when the sequence switch 100 comes into its ninth position, a circuit is closed and maintalned closed including the sequence switch contact 106, left armature and back contact of the relay 34, conductor 35 and busy lam 231, situated adjacent the jack 232 individual to the connecting circuit 17 appearing upon the specialbusy operators position. The speclal busy operator, one of whose connectng circuits is indicated at 233 in Fig. 2. then inserts plug 234 of one of her idle connecting c rcuits in the jack 232 and depresses the listening key 235 individual to such connectmg circuit, thereby establishing talking connection between her telephone set 236 and the calling subscriber. This circuit may be traced from the left operating contact of the l stening key 235, over the back contact and rlght armature of the relay 237 ring contact of the plug 234. ring, spring of the jack 232, conductor 36, brush 37 of the second line finder 16, brush 38 of the first line finder 4 over the calling subscribers line 3, through brush 39 of th first line finder 4, brush 40 v of the second line finder 16, conductor 41, tip spring of the jack 232, tip contact of the plug 234, left armature and back contact of operator thereupon informs the calling subscriber that the line called for is busy and learns from him if he desires that the call shall be repeated until successful ifso, learning also from him the number of the desired line. During this conversation, the calling subscriber s transmitter is supplied with current from the battery shown associated with the repeating coil shown in connection with the connecting circuit 17. l fhen this conversation is finished, the calling" subscriber replaces his receiver upon its switchhoolr thereloy opening the circuit of the supervisory relay :2? and causing the illuminat tion of the supervisory lamp 28. Since at this time the sequence switch 100 is in its ninth position and the relay 3% is energized during the closure of the circuit therefor including the extra contact 238 of the jack 232 individual to this connectingcircuit, a circuit this time exists for the called supervisory lamp 29 including the front contact and left armature of the relay 3% and the sequence switch contact 1%. Since both the calling and called supervisory lamps are steadily illuminated, the operator is inorined the connection is no longer reuired and depresses her release lrey 3G to real: dew i the connection in the usual manner. So as the group selectors and 21 and the final selector i3 and their associated apparatus as well as the sequence switch 160 and 1511', are concerned, restoration takes place just as upon the conclusion of a norreal successful or unsucwssful call. Since, l'iowever call was unsuccessful, restoration is initiated the sequence switch 100 its ninth position, instead of with the sequence switch in its fourteenth position as would have nee the case if the call had been successful. Therefore the relation of the increment of the two sequence switches 100 and 150 in their restoring operations would have been in a manner well-known that metering; would not take place, the relay 42 being energized loclred up to open the circuit from the in t ring hattery d3 to th service meter l i- Lie calling su oscriloers line upon the deenergization of the relay 32,

The operation of the disconnecting key hy the cnerator the circumstances assumed although it caused the opening of the circuit hy which relay 33 is maintained energized and hy which the relay 10 is normally l e; ergized during the connection, althou it has thereby made the line 8 free to call and to he called by the dec er ization of the relay 33, has not caused lrcuits controllirn; the first line tinder e and the second line finder 16 to be restored to such condition that such line finders will appear as idle since the relays l 9 are now eneroised over a circuit rent contact and of the second line finder 16, right winding of the relay 10, bacl: contact and armature of the relay 12 and relay 9. Relay 9, in addition to relays 19 and 10, is now energi relay 9 preventing the closing of the circuit of the power magnet 8 of the first line finder a, the relay 10 by the opening of the back contact of its left armature opening the test circuit of such line finder 1, through the left winding of the relay 12, and the relay 19 opening the starting circuit for the second line finder 16 hereinbefore traced. Furthermore, the energization of the relay 34: opens at the back contact and right armature thereof the test-circuit of such second line finder 16 which would scriber s line, and such calling subscribers line has oeen rendered free to call and be called by the deenergization of its cut-01f relay 83, a connection is still established from the tip and ring conductors of the connecting circuit 283 of the special busy.

position to the terminals of the calling subscri ers line 3; which conductors, however. (since at this time they have no electrical potential impressed thereon and no ground connected thereto) interfere in no way with the use by the subscriber of the line 3, either for the sending or receipt of calls in the usual Th apparatus associated with the first line tinder l. second line finder 16. connect lug circuit 17 and the connecting circuit 233 remains in the condition described until the special busy operator initiates an attempted repetition of the call. To do this, the first act of such operator is to depress nioinentarily the assignment lrey 23. This causes a. test of the busy or idle condition of the inc 3 heretofore referred to as the calling This test is accomplished loy closing circuit from the sequence switch contact 0%, through left operating spring of the rey 28% left high resistance winding" of the 240, sleeve contact of the plop; 23 i sleeve of the jack 232, conductor 45, brush e second line finder 16. left winding elc 10 and brush 1-? of the first line f this time the line 3 is beingnsed either as a calling or called line, the relay 33 associated therewith will he energised and the potential normally upon the te minal of such line will be so reduced the relay 2 10 will not be ener 'ized over hi 'h resistance winding" thereof. if such case, nothing results in the apparatus i the special husy operators position from rue de; ression of the key 239 and the oper- -,ereby lrnows that the line 3 is lrsy. hand. if the line 3 was at this have een relay 2% would energized to close a circuit over the sequence switch contact 203, its armature and front contact and the sequence switch 204 top to drive the sequence switch 200 into its second position. In this position, the lamp 241 is lighted, to indicate to the operator the idle condition of the line to which the connecting circuit is now connected. Furthermore. the pilot relay 242 in serieswith such lamp is energized, to cause the energization of the lamp pilot 243. At the same time, a circuit was established over the sequence switch contact 203, armature and front contact of the relay 240, locking right-hand low resistance winding of the relay 240, sequence switch contact 205 bottom, and thence to the cut-off relay 33 of the line 3 to maintain such line busy both as a calling and a called line, in the usual manner. This circuit for maintaining the line 3 as a busy line will be maintained after the sequence switch 200 has left its third position over the extra contacts244 of the key 239 in substitution for the sequence switch contact 203, so long as the sequence switch contact 205 bottom is closed.

In the second position of the sequence switch 200, the selection of an idle registering and controlling equipment of the special 'busy. operators position will take place in the usual manner by the operation of the switch 245, a circuit for such switch being established over the sequence switch contact 206 bottom and the back contact and armature of the relay 246. The contacts of this switch 245 are included within the area limited by the dotted lines on the right-hand portion of Fig. 2. The operation of switches of this character and function being well known, and the'construction and operation of registering and controlling equipments, an idle one of which such switch 245 will connect to the connecting circuit 233 over the leads shown, being also well-known, will not be herein described. It is sufiicient to say that, upon the connection by the switch 245 of an idle registering and controlling equipment of the special busy operators position, the sequence switch 200 will be movedinto its third position, due to the energization of the relays 246 and 247, the circuit for such relays being closed from such equipment over the sequence switch contact 208. Furthermore, the energization of the relay 246 opens the power circuit established for the switch 245 in the second position of the sequence switch 200.

The operator having now depressed the numerical keys, indicating the designation of the desired line, for controlling the associated registering and controlling 'equipment, the relay 248 is energized in the third position of the sequence switch 200 by the socalled fundamental circuit extending from the sequence switch contact 209 top to the registering and controlling equipment. The energization of the relay 248 drives sequence switch 200 into position four by the closure of the circuit including the sequence switch contact 207 bottom; In the fourth position of the sequence switch 200, relay 248 being energized, a circuit is closed for the usual trippingspindle power magnet 249 over a circuit including the sequence switch contact 216 bottom, front contact and armature of the relay248 and back contact and right armature of the relay 250. The tripping spindle, therefore, starts in rotation intermittently shunting over contact 251 of the interrupter thereof, all of the fundamental circuit except that including the relay 248, thereby causing the usual controlling operation of the registering and controlling equipment. When, as a result of this operation, the fundamental circuit is opened,'and subsequently the tripping spindle comes into its proper operating position, wherein the contact 251 is open, the relay 248 is deenergized, opening the circuit of the tripping spindle power magnet 249 and stopping the tripping spindle in the proper position to control the tripping of the proper set of brushes upon the group selector, generally indicated at 252, in the usual manner. The deenergization of the relay 248, in addition to stopping the tripping spindle in its proper position, drives the sequence switch 200 into its sixth position over a circuit including back contact and armature of the called supervisory relay 253 and the sequence switch contact 207 top. In this position and in position seven, a circuit is closed for the power magnet 254 of the brush carriage of the selector, and such brush carriage now moves to select and seize an idle trunk line of the group prede- I05 termined by the set position of the tripping spindle. The circuit for the power magnet 254 includes the sequence switch contact 206 top and the back contact and armature of the relay 246. Immediately that an' idle trunk line in this selected group (as determined by the tripping spindle in the wellknown manner) has been found, the relay 247 is energized over its right high resistance winding, such circuit including the sequence switch contact 210. The test guard is then applied to the selected line in the usual manner by the closure of the circuit through the left low resistance winding and armature of the relay 247 and when, the brushes. of the selector being centered upon the terminals of the seized line, the circuit through brush 225 is opened and the shunt around relay 246 is thereby removed in the usual manner, the re lay 246 is energized and drives the sequence switch 200 out of its sixth and seventh positions into its eighth position. In this position, the fundamental circuit is established in the well-known manner from the registering and controlling equipment to the second 13s Upon the completion of the selection controlling operations for the desired call, acircuit is opened from the registering and controlling equipment over sequence switch contact 209 bottom, deenergizin the relay 2% ane driving the sequence switch 200 out of its eighth and into its tenth position. In this position of the sequence switch 200, the testing of the d sired line is awaited and, if such line is found idle, the ringing thereof and the response of the called subscriber are awaited. These operations, since they talre place the final selector, such as shownin 1, a final selector equi'mlent thereto, involve operations of a sequence switch such as 190 and the sequence switch contacts 192., 198, 19 and 195, as hereinbefore described. Consequently, as the sequence switch 190 comes '0 its eighth position, and .while it is in its ninth, tenth and eleventh positions, a circuit is closed by the sequence switcl1 contacts and to energize the supervisory relay 253, which closes a circuit to drive the sequence switch 200 out of its tenth and into its eleventh position, such circuit including the right armature and back contact of the re lay 250, armature and back contact of the relay 2-l8 which was deenergized (by the opening of the fundamental circuit upon the completion of the selection) armature and front contact of the relay 253 and sequence snitch contact bottom. if the desired line tests busy, the final selector sequence switch 190 will, as has been described, remain in its tenth or eleventh position and maintain the relay 253 energized. The sequence switch 200 will, under these circumstances, remain in its eleventh position and the called supervisory lamp 255 will be intermittently lighted by the circuit including the sequence switch contact 220 bottom and the flasher 256, indicating to the operator that the called line is busy. it may be here noted that, while the selection controlling operations were taking place, the lamp was termittently 'lluminated by a circuit including the s ence switch contact 215 bottom and the flasher 258.

It will be assumed first, however. that the desired line is at this time idle. Therefore, the supervisory relay 253 .will only be maintained energized for the very brief interval in which the sequence switch 190 is passing through its eighth to its eleventh position.

The supervisory r lay 258, therefore. de'c'nere'iz'e, and drives th sequence switch 200 t A. 113 out or its eleventh into its twenth or rin ing position by the closure of a circuit including the sequence switch contact 20!' top. As the desired line has been found idle and ringing is about to take place at the final selector in the twelfth position of the sequence switch 190 associated therewith, the ringing of the calling subscriber, that is, the subscriber connected to the line 3, must be immediately initiated from the connecting circuit In the twelfth position of the sequence switch 200, a circuit is therefore closed over the sequence switch contact 221, back contact and armature of the relay 259 and the back contact and left armature of the relay 250, to energize the relay 287, or

the callin subscribers ringing relay. This by energizing, closes at its front contacts the circuit of the ringing generator 260 to the ring side the connecting circuit and ground to the tip side of the connecting circuit. Ringing current is therefore impressed upon the line 3 over a circuit extending from the jack 232, precisely that, hereinbefore traced, over which conversation takes place between the special busy operator and the calling subscriber. The ringing is now taking place of both the calling and called subscriber. in the circuit of the ringing generator 260 is included the usual cut-03d relay 261, so that, whenever the subscriber connected to the line 3 responds by removing his receiver from its switchhook, the increased flow of current through the circuit causes the energization of such relay 261, and the consequent energization of the relay 259, which by opening the circuit of the relay 237, immediately cuts off the ringing current from the line 3 and the calling subscribcrs line is now connected directly through to the repeating coil associated with the connecting circuit 233, the sequence switch contacts 213 bottom and 214: top being closed at this time. The consequent energization of the calling supervisory relay 262 opens the circuit of the calling supervisory lamp 263, which has been illuminated since the fourth position of the sequence switch 200 over the sequence switch contact 212, so that the operator knows that the calling subscriber has responded and may, by the depression of herlistening key 235, converse with him and inform him that the desired line has been found idle and is being rung. it may be here noted that the relay .259 uponenergizing established for itself a locking circuit, including its front contact and armature and the back contact and armature of the relay 250.

hen the called subscriber responds by removing his receiver from its switchhook. the relay 258 will be again energized in the usual manner. This causes the sequence switch 200 to more from its twelfth to its thirteenth position. if at this time the subscriber connected to the line 3, that is, the

calling subscriber, has already responded,

between the subscribers. On the other hand,

if the calling subscriber has not yet responded, the movement of the sequence switch 200 into its thirteenth position does not affect the ringing of each subscriber, which goes on until his response, without annoyance to the called subscriber. The called subscriber, however, will be informed by the operator when the lamp 257 is extinguished, which lamp has burned steadily in the twelfth or called subscribers ringing position of the sequence switch 200, and, upon the depression of her listening key 235, that conversation is desired and that the party desiring such conversation is being rung.

Upon the termination of the conversation, the falling back of the armatures of the supervisory relays 262 and 253 causes the lighting of the supervisory lamps 263 and 255, the circuits of which include respectively the sequence switch contacts 212 and 220 top. The operator thereupon is aware that the call has been finished and causes the restoration of the apparatus over which the call has been established. Her first act to this end is to depress momentarily for a second time the key 239 of the connecting circuit used. This closes through the right operating spring of such key a circuit for the relay 250 including the sequence switch contact 212. The energization of the relay 250 immediately, by a circuit including the sequence switch contact 204 bottom, drives the sequence switch 200 out of its thirteenth position, from which position it will pass directly into its seventeenth position under the control of the local contact 201. The attractionof the left armature of relay 250 closes a locking circuit for such relay, which will be maintained until, as the se quence switch 200 leaves its sixteenth position, sequence switch contact 212 is opened. The opening of the circuit of the relay 259 by the attraction of the left arn'iature of the relay 250 does not cause the re-ringing of the calling subscriber. since the circuit for the relay 237 is opened both at the back contact of the relay 250 and by the opening of the contact 221 as the sequence switch 200 leaves its thirteenth position. As the sequence switch 200 is passing through its fourteenth to its sixteenth positions, metering battery 270 is connected to the sleeve contact of the plug 234 over a circuit including the left armature and back contact of 4 the relay 271 and the sequence switch contact 205 top, it being noted that the relay 271, although energized in the fourth to twelfth positions of the sequence switch 200, was deenergized in the thirteenth position thereof, as will be'hereinafter explained, the call having been successful. This metering current will be conducted over a circuit hereinbefore traced from the sleeve contact of the plug 284 to the calling subscribers service meter 44 and operates it, causing the call to be metered, since it was successful.

In the seventeenth position of the sequence switch 200, the sequence switch contact 206 top being closed, the brush carriage of the first group selector 252 is restored by the energization of the power magnet 254. Upon the brush carriage coming into its normal position, the interrupter brush 225 makes contact with its home contact and a circuit is closed for the holding magnet 254 maintained the key 239 depressed for some reason, including the extra contacts 244: of such key, back contact and armature of relay 20 and the sequence switch contact 20a bottom and the sequence switch 200 returns to its normal position. In the eighteenth and normal positions of the sequence'switch 200, a local circuit is closed for the tripping spindle power magnet 249, including the sequence switch contact 216 top, and the contact 280 of the interrupter of the tripping spindle, whichdrives the tripping spindle back into its normal position, where the operating' contact of such interrupter, dropping into the deeper depression upon the controlling cam disk, opens the circuit through such contact 280 stopping the -tripping spindle in its normal position. It will be understood, of course, that, as is usual with apparatus of this type, circuit will exist from the operating contact of the interrupter to the contact 280 thereof in all positions of the tripping spindle except its normal position, whereas circuit will exist from the operating contact of such interrupter to the contact-251 thereof only while the tripping spindle is passing from one of its stopping positions to its next stopping position.

It will be observed that, as described, all of the apparatus of the special busy position has been returned to normal, and it only remains for the operator to remove the plug 234 from its jack 232, which may now be done, as the repeated call has been successful,

Assuming now that, when the final selector tested the desired line upon the repetition of the call by the special busy operator, such line was found busy. In this case, as has been described, sequence switch 190 of the final selector stops first in its tenth position and then, having restored the brush carriage of the switch in such position in the usual manner, moves into its eleventh position, where it remains under the control or the operator by which the call has been established up to this point. It will be recalled that, as the final selector was testing the desired line, the sequence switch 200 was moved into its tenth position. W' hen the circuit was closed at the final selector by the closure of the sequence switch contacts 192 and 193, in the eighth to eleventh positions or the -final selector sequence switch 190, the supervisory relay 253 was energized and the sequence switch 200 driven into its eleventh position. As the sequence switch contacts 192 and 193 are maintained closed, supervisory relay 253 is maintained in its eleventh position. The lanrp255 is now intermittently lighted by a circuit including the sequence switch contact 220 bottom and the tlasher 256. The special busy operator therefore learns "from the flashing of this lamp that the desired subscriber is busy and that the call is again unsuccessful. 'She will, therefore, restore the apparatus associated with the connecting circuit 233 and with the subsequent selectors over which the attempted call was extended. lt is, of course, desirable that such restoration should take place without afiecting the condition of the first and second line finders over which she has connected to the calling subscribers line, that is, the line 3, without the impression of any ringing current upon such line, and without causing the meterin of this second unsuccessful attempt to reach the desired subscriber upon the service meter or the callin line. These conditions are automatically rullilled in the embodiment of the inven ion shown, and all it is necessary for the special "busy operator to do is again to depress momentarily the key 239.

The depression of this hey at this time causes the energization of the relay 250 over a circuit including its right operating and the sequence switch contact 212 top. The euergization or this relay opens at the back contact of its left armature the circuit of the relay 237 which would otherwise be closed when the sequence switch 200 comes into its twelfth position and, since the relay 250 is locked up over such armature and the sequence switch contact 212 until the se quence switch reaches its sixteenth position, no ringing current can be connected to the calling subscribers line. The relay 250 by the attraction of its right armature closes a circuit over the sequence switch 2% bottom which will drive the sequence switch 200 out of its eleventh position, twelfth position and thirteenth position, and the sequence switch 200 will more under the control of its local contact 221 until reaches its seventeenth position. in the fourth to eleventh nositions or the sequence switch 200, both in the establishment of a successful call and in th attempted establishment of unsuccessful call, the relay 271 is energized over its right winding and the sequence switch contact 21% bottom. This ener ization by the attraction of the right armature of such relay closes a locking circuit for such relay including its right armature, the left winding thereof and the sequence switch contact 212. lln the operation taking place in the establishment of a successful call, when the sequence switch 200 moves into its thirteenth position, the sequence switch contact 222 top is closed. At this time, unless the desired subscriber has already answered, the armature of the relay 253 is in its retracted position, It being assumed that the desired subscriber responds, the relay 253 is energized, such relay having been energized either while the sequence switch-20G was in its twelfth position or being energized while the sequence switch 200 is standing in its thirteenth position. The energization or the relay 253 in the thirteenth position of the sequence switch 200 closes a circuit from the front contact and right armature or the relay 271, through the sequence switch contact 222 top, front Contact and armature of the relay253, back contact and armature of the relay 2&8 and back contact and right armature or the relay 250 to ground This low resistance direct to ground causes the deenergization of the relay 271 by shuntingthe left inding of such relay, tllB circuit or the right winding thereof being now opened at the sequence switch 21% bottom.

When, however, the key 289 is depressed in the eleventh position of the sequence switch 200, the attraction of the right armature thereof opens at its back contact the shunt circuit, which, with the attraction of the armature of the relay 253, would cause in a successful call the deenergization of the relay 271 as the sequence switch 201 passes through its thirteenth position. The relay 271 will, therefore, for an unsuccessful call be maintained over the circuit including its right armature, its left winding and the sequence switch contact 212, until the sequence switch 200 has left its sixteenth position. This being the case the circuit for the meering battery 270 is maintained open in the fourteenth to sixteenth positions of these quence switch 200 by the attraction of the leit armature oi the sequence switch 271 and the call will, therefore, not be charged to the calling subscriber.

V7 hen the sequence switch 200 comes into ts seventeenthposition, the restoration of he brush carriage of the group selector 252 takes place in the normal manner and consequent thereto, the sequence switch 200 is driven into its eighteenth position' From this position it is driven into its first or normal position over the circuit including the armature and baclr contact oi the relay 2&0 and the sequence switch contact 20% bottom as has been before described, the restoration of the trippin spindle taking place in the eighteenth an first or normal positions of the sequence switch 200.

Since the attempted call by the special busy operator has been unsuccessful and is to be repeated a second time, the plug 234 will not be removed from the jack 232 and the connection from the conductors of the connecting circuit 233 to the line 3, referred to.

as the calling line, will be maintained as heretofore by the extra contacts 238 of the jack 232.

In caseof the attempted repetition of a call in which the desired line is found'idle but the desired subscriber does not respond, both the calling and the called lines will be rung from the special busy position, as has been described in the operation of the apparatus for a successful call the sequence switch 200 being in its twelfth position. The calling subscriber, that is, the subscriber whose line is indicated at 3, will be assumed to respond and the operator, having depresssed her listening key 235, will inform him that the desired line is idle and is being rung. Meanwhile, the lamp 257 is being constantly illuminated over circuits hereinbefore traced. The operator observing the prolonged lighting of this lamp (which would be immediately extinguished upon the called subscriber responding) will again converse with the calling subscriber, again depressing the key 235 if it has been released, and will inform such calling subscriber that the desired subscriber does not respond, inquiring from such calling subscriber, if the service requires, whether he desires that the call shall be again repeated. If the calling subscriber requests the call shall be repeated, the restoration of the apparatus of the connecting circuit 233 and of the subsequent selectors over which the call has been extended will take place, as has been descr bed in an attempted call in which the desired subscriber is found busy, by the momentary depression of the key 239. If the subscriber informs the operator that it is not necessary to repeat the call again restoration will take place by the depression of the key 239, followed by the withdrawal of the plug'23 t from the jack 232, and all of the apparatus utilized in the call, including the first line finder 4 and the second line finder 16 will be restored to normal condition. In the event of either restoration referred to, that is, after the desired subscriber has been rung but does not respond, the depression ofthe key 239, while the sequence switch 200 is in its twelfth position, will prevent the charging of the call to the calling subscriber, by the energization and locking up of the relay 250, as has been described, and the consequent opening at the back contact of the right armature of such relay of the circuit, which would otherwise be established, as has been described, for deenergizing the relay 271. The relay 271, therefore, will be maintained energized in the fourteenth to sixteenth positions of the sequence switch 200 and no meter operating current will be transmitted over the sequence switch contact 205 top to operate the service meter 44 of the calling line.

When, under any circumstances, the ser' ices of the special busy operator are no longer required by the calling subscriber, and the key 239 a second time momentarily depressed to restore her apparatus, the operator withdraws the plug 234 from the jack 232. The consequent opening of the contacts 238 causes the deenergization of the relay 34, which, by the, retraction of its armatures, opens the circuit which has maintained the relays 19,

10 and 9 energized, and restores the testcircuit of the second line finder 16, which circuit includes the test relay 45, to its normal sive to the busy condition of a called line I when a calling line has been extended thereto to extend such calling line to said special operators position.

2. In a telephone exchange system a calling line, an operators position, a connecting circuit between said calling line and said operators position, means for normally placing a busy guard on said line when connected to said circuit, a called line, switch ing apparatus for extending said calling line to said called line if idle, a busy signal on such position, means responsive to the busy condition of a called lme when said calling line has been extended thereto adapted to display said signal and means forremovingsaid'busy guard.

3. In a telephone exchange system a calling line, switching apparatus for extending said calling line to an operators position and placing a busy guard thereon While so extended, means for removing saitl busy guard, an operators equipment at such position, automatic selector switches operating under the control of said equipment for extending the connection from said position to a desired line and means on said position responsive to the busy or idle condition of operative said equipment.

l. in a telephone exchange system a calling line, special operaiors position, a connecting circuit extending said. calling line to said position, a called line, switching apparatus adapted to extend said calling line to said called line, rin ing means for ringing said calling line, ringing means for ringing said called line and means responsive to she busy or idle condition of said called line when said calling line is eat-ended thereto controlling the application of ringing current to both said calling and called lines.

In a telephone exchange system a calling line, a connecting circuit serving to exiend said line when calling, a called line, automatic seleclor switches to further eniend said calling line to said called ll e if idle a special operalor s position, an alternative connecting circuit extending to said special operaiors posit-101i and means responsive to the busy condition of said called line when the calling line is extended thereto for signaling said special operators posilion over said alternaeive connecting circuit.

In a telephone system, subscribers lines, means for interconnecting said lines, a special service line, and means responsive to the finding of a called line busy by said interconnecting means for automatically extending a calling line to said special service line. V

In 'WllBIlGSS whereof, We hereunto subscribe our names this 15th day of February A. ii, 191?.

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