BE470530A - - Google Patents

Description

       

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  Telephone system.



   The present invention relates to telephone systems and more particularly relates to systems having a tandem exchange and a plurality of sub-exchanges associated therewith.



   In addition, the invention applies in particular to small exchanges using searcher-connector circuits and one of its aims is the realization of improved protection devices.



   As a result, in accordance with one of the features of the invention, the searcher switches to the sub-centers are rendered inoperative during the time during

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 which the switching device at the tandem exchange to which the sub-exchange has access is unavailable.



   With such a device, precautions must be taken to avoid lost calls due to a subscriber attempting to form a call when the switching device is inoperative.



   Hence, in accordance with another feature of the invention, if the switching apparatus of the tandem exchange to which the sub-exchange has access. becomes unavailable, the switching apparatus at the sub-exchange is rendered inoperative, the calls made to the sub-exchange being recorded during this period, for subsequent transmission to the exchange in tandem.



   This invention also applies to systems in which the. formation of calls by subscribers of the sub-exchanges is controlled by an operator, and, in accordance with yet another feature of the invention, when sending a call by a subscriber of a sub-central, a connection is established automatically through the tandem exchange to an attendant position, whereupon a tone is sent to the calling party, while, if the switching device of the tandem exchange is not available, the The switching device at the sub-office is disabled and no dial tone is transmitted to the calling party.



   The invention will be understood from the following description of an embodiment taken in combination with the accompanying drawings, among which:
Figure 1 schematically shows an automatic telephone system embodying the features of the present invention.



   The figure shows how the remaining figures of the drawings are assembled to form a system.

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 single and Figures 3 to 8 inclusive, taken together, show the details of the switching devices included in the system shown in Figure 1.



   With particular reference to FIG. 1, the system represented therein comprises a main exchange 9, a tandem exchange 10 and two satellite exchanges or sub-exchanges 11 and 12 interconnected by the emergency lines 13,14 and 17. more particularly, the first urban line
13 joins an operator position 15 provided in the main exchange 9 to the automatic switching devices provided in the tandem exchange 10;

   the second city line 14 extends between the automatic switching apparatus provided in the tandem exchange 10 and the automatic switching apparatus provided in the sub-central 11 and the third city line 17 extends between the automatic switching apparatus provided in the tandem exchange 10 and the automatic switching apparatus provided in the sub-central 12. The automatic switching apparatus provided in the tandem exchange 10 comprises a circuit connector finder switch 16 comprising a finder switch and a connector switch, each giving access to city lines 14 and 17 as well as to a plurality of additional lines, including two subscriber lines 18 and 19 respectively going to Tl and T2 telephone sets.

   More particularly, lines 14, 17, 18 and 19 terminate individually with line circuits which are schematically shown in a group at 20.



   The apparatus provided at sub-central 11 similarly comprises a finder-connector circuit 21 comprising a finder switch, and a connector switch, each providing access to a plurality of subscriber lines, comprising the two lines. indicated in 22 and 23, going / respectively to positions T3 and T4. Line circuits, 4

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 are individually associated with these lines and are represented schematically in a group in 24.

   The switching apparatus provided in sub-central 12 is identical to that provided in sub-central 11, and comprises a finder-connector circuit 25 comprising a finder switch and a connector switch, each providing access to a plurality of subscriber lines, two of which are shown at 26 and 27 as extending to stations T5 and T6, respectively. These lines terminate individually at exchange 12 in line circuits which are shown schematically as a group at 28.



   The subscriber lines going to the exchanges 10, 11 and 12 are of the well known magneto type, each subscriber station being equipped with a hand or magneto generator, to send the ringing current to the corresponding line, and to local batteries producing the supply current. these lines can be of the single part or the multiple part type if desired.



   By neglecting for the moment the details of the automatic switching apparatus provided at exchanges 10, 11 and 12, and considering the operation of the system in general, when a call is made on a line extending to n ' no matter which of the three exchanges 10, 11 or 12, the call progresses to the operator position 15 of the main exchange 9 and the automatic switching device provided in each of the three exchanges is muted to calls made up to until the device is released.



   For example, if a call to station T2 is made from station T1, the connector finder circuit finder switch 16 operates under the control of an individual line circuit at calling line 18 to seize the calling line. and to transmit a signal to the operator position 15 to indicate that there is a call.

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 pel on urban line 13 which must be answered. The control device included in the circuit of the finder-connector 16 also operates, when line 18. is input, to apply a determined potential, namely the negative potential of the battery, to one of the conductors of each. of the two urban lines 14 and 17.

   Some of the relays included in the tester of the finder-connector circuit 21, under the effect of the negative potential of the battery of the driver marked with the urban line 14, function to open in a point the actuating circuit of the actuating magnet of the seeker switch included in circuit 21 so that this switch can no longer answer calls made on lines going to sub-central 11. From a similarly, the circuit of the finder-connector 25 provided in the sub-central 12 is locked out of service for the duration of the call made by the set Tl on line 18.



   After having answered the call, and having checked with the calling subscriber of the number of the requested set, or of the name of the requested party, the operator on duty at position 15 dials the call number of the set. asked in the usual way. The calling party is supposed to hang up before the attendant has actuated the disk of her set and sent the inrush current. The "connector" part of circuit 16, under the effect of the pulses emitted by the disc, chooses the desired line, that is, in the case considered, line 19.



   After having maneuvered the disc from her set, the attendant activates the bell key provided in her circuit to send the ringing current to the calling and called lines, in order to thus activate the signaling mechanisms or ringing tones which are used. respectively filled the calling and called positions. Releasing the connection

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 established is entirely under the control of the operator on duty at. the operator position 15. More particularly, when the connection is no longer required, it is expected that either the calling party or the called party will operate its hand generator to transmit a disconnection signal to the operator control.

   On receiving this signal, the attendant releases the connection allowing the release of the circuit 16 of the finder-connector, in the working position, and of the line circuits associated with the calling and called lines 18, and 19, respectively. During the release of these devices, the battery potential is removed from the above-mentioned conductors of the city lines 14 and 17 respectively, which causes the operation of the relays included in the circuits 21 and 25 repeating thus the excitation circuits of the actuating magnets of the finder switches, respectively included in these circuits. In this way, the automatic switching device provided in the three exchanges 10, 11 and 12 is ready for its subsequent use.



   If the call sent to the Tl set, associated with line 18 and transmitted to the operator position 15, must be sent by a line terminating at one of the sub-exchanges 11 and 12, the operator, in s 'providing the telephone number of this desired extension, form two digits with its disk:

   the first digit being used so that the "connector" part of the circuit 16 chooses the urban line leading to the desired sub-central, ie, for example, the central 11 and the second digit being repeated through the circuit of the researcher-con - nector 16 in working position to the connector control device of the connector-finder circuit with which the selected central unit is provided. for example, if the call is to be routed to extension T4, it

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 associated with line 22, the operator first forms the number corresponding to urban line 14, which causes this urban line to be taken by the "connector" part of circuit 16.



  The pulses of the second digit formed at the operator position are repeated through the circuit tester 16 to the "connector" portion of circuit 21, thereby causing the switch to select the connector of the circuit. called line desired 22. After the called line ² a. selected, the attendant activates her ringing key to send ringing current through the connection established in order to energize the signaling devices with which the calling and called sets are respectively provided.



   Finally, the desired conversation circuit is fully established when the call is answered at the calling and called stations. Here again, the release of the connection is entirely under the control of the attendant on duty at position 15, the way in which the release of this device is effected being in substance similar to the release of the device. which has been described above. A call made on a line going to one of the sub-exchanges is first routed through the automatic switching device of the corresponding exchange and is then transmitted through circuit 16 of the finder-connector and, by the urban line 13, to the operator position 15.

   If, for example, a subscriber to set T4 sends a call at a time when the automatic switching device with which the three exchanges 10, 11 and 12 are provided is 3-available, the "seeker" part of circuit 21 will operate and look for the calling line 22, after which a current pulse marking the "tap" of this line is transmitted through the city line 14, to enter the circuit 16.



   The "finder" part of the circuit, which has just been mentioned, functions in turn to seize the calling street line 14 and to transmit a signal pulse.

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 signaling current in operator position 15.



  When the circuit 16 finder switch operates to take line 14, the circuit 16 tester operates to apply the negative potential of the battery to one of the city line conductors 17 and control apparatus of the circuit 25 existing in the exchange 12, under this action, makes the "seeker" part of the circuit 25 inoperative for calls made on the lines going to the exchange 12. The call signaling apparatus, provided for the operator position 15, under the effect of the signaling current pulse, operates and thus signals to the operator that a call coming through the city line 14 is awaiting an answer.

   After having answered the call and having conversed with the calling subscriber, to ascertain the call number of the requested set, the attendant can initiate the establishment of the desired connection by entering the appropriate selection digits. at the line, as described above. For example, if the call is to be routed to an extension via line 18, the attendant forms the single digit designating this line, so that the "connector" part of circuit 16 takes the called line.



   Alternatively, the call can be routed to another line terminating at the exchange 11 in which case, the operator forms the two digits of the call digit designating the called line. The "connector" part of circuit 18, under the effect of the pulses of the first digit, seizes the urban line 14 and establishes a pulse circuit comprising the conductors of this urban line through which the pulses of the second digit can be transmitted to the "connector" part of circuit 21. The pulses of the second digit are then repeated through the control device of circuit 16 and along the established pulse circuit, including the city line 14 to the switch

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 connector of circuit 21, and this switch responds by entering the desired called line.

   If the call routed to the operator position 15 from the calling line 22 is to be routed to a subscriber line terminating at the sub-central 12, the operator first forms the number designating the urban line 17, which causes the "connector" part of circuit 16 to operate so that it grasps line 17 and the "connector" part of circuit 25 is conditioned to operate under the effect of the pulses of the second digit designating the called station requested.



  In each case, after the transmission of digits is terminated, the attendant activates her call key in order to send an inrush current along the calling and called lines and the desired connection is fully realized, when the stations calling and called answer the call. Calls routed to the operator position 15 from lines going to the main exchange 9 can be routed :. under the control of the operator on duty at that position, along from the urban line 13, to any of the subscriber lines, ending at one of the exchanges 10, 11 and 12.



  To this end, the operator enters the urban line 13 and forms the number, calling the desired line, the connector switch of the circuits provided in one or more of the exchanges 10, II and. 12, responding to the pulses emitted by the disc, by establishing a connection comprising the city line 13, to the desired line, in the manner previously explained.



   When line 13 is initially taken, the finder switch of circuit 16 stops answering calls made on the subscriber lines going to exchange 10 and the control apparatus of circuit 16 operates and sets the negative potential of the network. battery on one of the conductors of each of the urban lines 14 and 17. The control device @

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 The control included in circuits 21 and 25 respectively, under the effect of this potential, operates so that the searcher switches of the two circuits mentioned above cease to answer calls sent on the lines to which they have access.



   As explained above, in all cases where a call is made on the city line 13, or on a line terminating at one of the three exchanges 10, 11 and 12, the automatic switchgear provided in the three exchanges ceases to answer other calls made on other lines before the automatic switching device has been released.

   In order to eliminate the need for a subscriber to restart several times to request a call, in order to have access to the automatic switching apparatus once it is released, precautions are taken so that a call, made at a time when the switching device is busy, or saved (put on reserve) until the automatic switching device is released and it is then automatically routed to the position of central operator 15 9.



   For example, if a call is made on line 22 at a time when the automatic switching device provided in the three exchanges 10, 11 and 12 is busy, the combined line, cut-off and registration relay of the line The call associated with line 22 operates and remains in the working position, even if the calling subscriber abandons the call.



   Thereafter, and when the automatic switching apparatus is released, the in-service line relay associated with line 22, in conjunction with some of the devices included in circuit 21, operates and initiates operation of the "part". seeks ur "of circuit 21, to take line 22. From this moment, the way in which the call is routed to the operator position 15 in the main exchange.

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 cipal 9 is exactly the same as described above.



   Similarly, calls made on lines going to exchanges 10 and 12 at times when the automatic switching device is. busy, are stored until the switching device is released, after which they are automatically routed to operator position 15. The attendant on duty at this position, by answering this call and if she does not receive an answer from the calling subscriber, can ring @@@ the station calling by the calling line and, therefore, he There is no need for the calling subscriber to remain at the device during the time that the automatic switching device is busy.



   Referring now in more detail to the switching apparatus included in the system and considering the apparatus provided in operator position 15, this apparatus comprises, as is, indicated on the right part of the FIG. 3: repeater transformer 370 having primary windings 373 and. 374 terminating the conductors of the urban line 13, and of the secondary windings 371 and 372, connected to the contacts of a call jack and. response 369, through which the urban line 13 is made accessible to the operator's cord circuit.



   This equipment further comprises a signaling device in the form of a falling member 375 which is energized, via the urban line 13, for incoming calls to the operator position 15. it is also provided in the operator position 15 a call key 380 and a calling or pulse device 382, which operates in the usual way to send current pulses through the springs of the call key 380 and, through the town line 13, to the circuit tester

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 finder-connector 16 provided in the tandem control unit 10.



   As has been said previously, the subscriber lines terminating at the tandem exchange 10 are of the well-known magneto type and each of them can be associated with a set of stations with characteristics shown schematically at T1. and T2 (fig. 6). Each station is provided with a manually operated magneto or manual generator, which is used for sending out calls, the generators of this type provided at stations T1 and T2 being indicated respectively by 693 and 691.



   The line circuit associated with. line 18 has a relay 680 which is designed to perform all functions related to making and terminating calls of interest to line 18. more particularly, this relay functions as a combined line relay , cut-off and call recording. An identical line circuit, shown schematically at 690, is provided in connection with the subscriber line 19.



   The line circuits individually associated with the city lines 14 and 17 leading to the tandem exchange 10 are of a different arrangement from that of the line circuits individually associated with the subscriber lines. More particularly, the line circuit associated with the city line 14 comprises a line relay 630, a line switching relay 610 and a delayed-operation cut-off relay 620. The line circuit associated with the city line 17 similarly has line and cut-off switch relays 670,660 and 650 respectively. The two line circuits which have just been described are partially arranged to be controlled by a common locking relay 640.

   This relay has the effect of putting the negative potential of the battery to a line conductor of each of the two urban lines 14 and 17, when a call is made.

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 on urban line 13 or on one of the other lines going to central 10.



   The finder-connector circuit 16 included in the tandem exchange 10 includes a finder switch 500 and a connector switch 550, both of which are of the well-known ten-pin, stepping rotary type. More particularly, the rotary seeker switch 500 comprises four brush holders 501 to 504 and means comprising an operating magnet 530 and a ratchet mechanism, not shown, for bringing the brush holders in question onto the contacts of the switch. their respective associated contact benches.



   In order to control the operation of the seeker switch for picking up a calling line among those coming to the exchange 10, there is provided in the circuit control apparatus, a pulse relay 510 and a searcher start relay 520. The rotary connector switch 550 has four brush holders 551 to 554, an actuator 540 to bring the brush holders to the contacts of their associated contact banks and a set of non-normal springs 542, which are fed. to give contact when the brush holders in question are brought back to their first respective off-nominal positions.



   The circuit 16 control device comprises, in addition to the searcher start and pulse relays 520 and 510 respectively, a line relay 330, a delayed release hold relay, a pair of control relays 440 and 470 and a pair of transfer relays 460 and 465 obeying the pulses of the digits transmitted by disc.



   This apparatus further includes a line test relay 410, an ac control relay, a pendulum type time relay, a time-delayed circuit release relay 310 under control.

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 control of the pendulum relay 350 and two control and switching relays 420 and 430. In order to transmit a current pulse from the battery through the urban line 13 to the operator position 15, when the circuit 16 is entered, two additional relays 350 and 365 are provided in the control apparatus for this circuit, the first of the two being of the type with delayed operation and the second of slow action.

   In order to transmit a waiting tone to a calling subscriber, after the circuit 16 has been seized, a tone relay 340 has been provided, the function of which is to apply an alternating signaling voltage to the terminals of the secondary lines of the telephone. repeater 360. For the purpose of freeing the finder-connector circuit 16, in the event that a call routed through this route to the attendant position 15 does not receive a response, within a predetermined time interval, after the circuit has been taken, there is also provided a relay for releasing the circuit 387 of the thermal type.



   As has been said previously, the lines ending at the sub-central 11 are also of the magneto type, each substation being provided with a manual generator, adapted to be used during the sending of calls. . The manual generators with which the stations T4 and T5 are provided are indicated respectively at 775 and 814. The line cirduits associated with. these lines are made according to an arrangement identical to that adopted for the line circuits individually associated with the subscriber lines terminating at the tandem exchange 10.



  More specifically, the line circuit associated with line 22 has a combined line, cut-off and call recording relay 700, while the line circuit associated with line 23 has a similar relay.

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 810. The automatic switching apparatus provided at the sub-central 11 is, in general, similar to the apparatus existing in the tandem central 10. In this way, the connector finder circuit 21 comprises a finder switch 800 and an 8bO connector switch, both of the badly simple stepper rotary type.



   The switch 800 has four brush holders 801 to 804 and. devices comprising an operating magnet 816 and a snap-in mechanism, not shown, for bringing the different brush holders to the contacts of their respective associated contact banks. The switch connector 850 is of similar construction, but comprises only three brush holders 851 to 853 and a motor mechanism comprising an operating magnet 818 to bring the brush holders in question to the contacts of their contact banks. respective partners. This connector switch also includes a set of out-of-normal springs 827, which are caused to make contact when the switch brush holders are brought to their respective first out-of-normal positions.

   The circuit tester, group or more particularly / of relays therein comprises: a seeker start relay 825, a seeker switch pulse relay 820 and. a test relay: of line 720 whose mission is to stop the operation of the seeker switch 800 when the brush holders of this switch are moved to engage in the Contacts terminating a calling line. The control device further comprises a line relay 740, a slow acting mairtien relay 735, a delayed release control relay 710, an AC relay '130, and a release relay 830. delayed acting under the effect of pulses, for excitation in parallel with a maneuvering magnet. connector switch 818.

   In order to transmit a

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 current pulse from the battery through the city line 14 to the tandem exchange 10, in order to arrive in this way to seize the circuit t 16, when the searcher switch 800 operates to seize a calling line among the lines going to the exchange 11, two additional relays 755 and 760 are provided which are respectively of the type with delayed operation and delayed release.

   In the Lut to transmit a waiting tone to a calling subscriber, after the circuit 21 has been entered, the tester of this circuit further comprises a tone relay 745, which corresponds to the similar relay 340 included in circuit 16.



  Call made by a subscriber line terminating at the exchange in tandem.



   Returning now to the operation of the system in more detail and considering first a call made on one of the subscriber lines coming to the tandem exchange 10, if the call is sent by the set Tl associated with line 18, ' for example, the combined line, cut-off and call recording relay b80 will operate, more particularly, when the calling subscriber activates his hand generator (better: his magneto), 693, an alternating current is sent by the line 18 to energize the upper winding of relay b80.



  The circuit followed by this current can be followed from one of the tails of the magneto 693 via the springs 694, which are brought into contact when the armature of the magneto is rotated, the line conductor 567, the top winding of 680, 683 and 563 to the opposite terminal of magneto 693. When its top winding is energized by this circuit, relay 680 first operates to close the X contacts associated with 684, thereby closing a cir - fired including resistance 685 to excite its lower winding.

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   Thereafter, the relay 680, while continuing to function, opens., At b83, a breaking point in its primary operating circuit, as described above, and, to close, at 682, a circuit comprising the conductor b73, to indicate the calling line 18 in the seeker switch bank contacts 500. In 681, the ::: ,,, lais 680 closes a circuit to energize the searcher departure relay 520, this circuit starting from the ground at 457 (fig. 4), through the intermediary of 451, 485, the carrier- brushes 554 .. 'and its associated rest contact, 483, 442, 413 484, 681, 484 and the coil 520 to the battery.

   The relay 520 then operates to prepare, at 522, a break point in the circuit described below, to energize the line test relay 410, when the brush holders of the seeker switch 500 are brought into contact with the bank. of contacts terminating the conductors of the calling line 18.



  At 521, relay 520 closes a circuit to energize the actuator 530 of seeker switch 500.



  This circuit can be traced as starting from the ground at 411, through 486, 521, 511, and winding the magnet 530 to the battery.



   When energized by this circuit, the magnet 530 activates its associated ratchet mechanism to thereby condition this mechanism to advance the brush holder of the switch 500 by one step, when the operating magnet is subsequently de-energized.



   At armature 531, magnet 530 closes an easy circuit to follow in the diagram, to energize the upper winding of pulse relay 510. This latter relay, in turn, operates to open at bll, a breaking point. in the circuit indicated above to excite the magnet 530. When the magnet 530 is thus de-energized, the mechanism associated with ratchet and pawl latching advances the @

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 brush holder of the switch 500 and the armature 531 falls back to open the excitation circuit of the relay 510. The relay re 510 then drops to / close the operating circuit of the magnet 530; the magnet then attracts the armature 531 again, thus again closing the operating circuit of the relay 510.



  The alternating operation of the pulse relay 510 and of the magnet 530 continues until the brush holders of the switch 500 engage in the contacts terminating the conductors of the calling line 18. More in particular, when the brush holder 503 engages the contact terminating the test conductor 573, the circuit recalled above closes and energizes the upper winding of the line test relay 410, in series with the lower winding of the pulse relay 510.

   This circuit goes from ground to 682 through 573, brush holder 503, bottom winding 510, 522, 492 and top winding 410 to the battery. When the lower winding is energized by this circuit, pulse relay 510 is held in its operating position, independent of magnet 530, so that progress will not go. step of seeker switch 500 is turned off.



   Likewise, when this circuit closes, relay 410 operates its contacts in X and closes a clean holding circuit. This maintenance circuit starts from the ground at 441, via 415 and the lower winding from 410 to the battery. At 411, and its associated rest contact, the relay.) Delivers a key breaking point in the preceding circuit., Mentally described to energize the operating magnet of the seeker switch b30. At 413, and its associated rest contact, relay 410 opens a breaking point in the operating circuit previously traced for the starting relay of researcher b20.

   This last relay then falls and

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 opens at b22 a break point in the previously drawn circuit to energize the lower winding of pulse relay 510 and the upper winding of 410, in series.



  Relay b10 then drops out. At 414, relay 410 closes a circuit to short-circuit the lower winding of line relay 680, this circuit leaving the ground at 452, through 414.491, the brush holder 504, conductor 577, lower winding of 680 and 684 on the ground.



   When its lower winding is short-circuited by this circuit, relay 680 drops out and reconnects its upper winding via the conductors of line 18.



   At 411, and its associated make contact, relay 410 closes a circuit to energize latch relay 640, this circuit going from ground to 411, through 482 and the winding of 640, to the battery. While operating, the relay 640 closes circuits to put to the negative potential of the battery one of the line conductors of each of the two urban lines 14 and 17. In this way, at 643, and its associated working contact, relay 640 closes a circuit going, through resistor 646, to pre-cut contacts 621 associated with 612 to set conductor 767 of urban line 14 to the negative potential of the line.

   Similarly, at 642, relay 640 closes a circuit going through resistor 645, pre-cut contacts 661 associated with 642 to set a conductor 604 of the city line 17 to the negative potential of. battery.



   At 644, relay 640 opens a cutoff point in the hold circuit, described below, for line relay 630 and prepares a break point for the hold circuit, described below, of the hold relay. cut 620. In 641, the relay 640 opens, in a similar way, a

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 break point in the 670 line relay interlock circuit, and prepares a break point in the 660 cutoff relay hold relay.



   When the '/ 67 conductor of the urban line 14 is brought to the negative potential of the battery, the circuit 21 tester, shown in Figures 7 and 8, operates to open a breaking point in the switching circuit. .- glass of 1 '+ operating magnet 816 of the finder switch. more particularly, when the negative terminal of the battery provided in the tandem exchange 10 is connected to the urban line conductor 767, the line relay 740 is energized passing through a circuit comprising this line conductor 764 and the winding 752.

   When energized by this circuit, line relay 740 operates and closes, at 741, an easy-to-follow circuit, to energize delayed-action holding relay 735. The holding relay, in turn, operates to close. , at 736, a circuit to energize the delayed action relay 755 and, at 737, a circuit to energize the delayed release relay 710. The relay '/ 10, while operating, opens, at 711 and 712 respectively, breaking points in the operating circuits, described below, respectively for the relays' / 45 and 760.

   Relay 755, when operating, opens at 757, and its associated rest contact, a break point in the holding circuit of relay 760; andpreparing at 756 and 757 a breaking point in its own retaining circuit. At 758, relay 755 opens a break point in the circuit, described below, for energizing the respective lower windings of the test relay. from line 720 and from the relay to. 820 finder pulse in series.



   At 759, relay 755 opens a breaking point in the circuit, described below, for energizing the magnet

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 finder switch 800, to prevent this magnet from being energized by the operation of one of the line relays 700, 810, and so on. Thus, the seeker switch 800 ceases to respond to transmitting calls on the lines coming to the central 11, while the automatic switching apparatus provided in the tandem central is busy.



   Similarly, the finder-oonnector circuit loopback apparatus 25, provided in the sub-central 12, operates under the effect of the negative potential of the battery of the lead 604, of the line. urban 17, to make the "seeker" part of the circuit inoperative under the effect of calls sent on lines going to sub-central 12.



   Now returning to the operation of the connector finder circuit 16, when the line test relay 410 operates as explained above, it connects, at its frames 416 and 417, the conductors of the loop lines 495 and 496 to the conductors. boiling lines 398 and 399, respectively, to thereby connect the conductors 563 and 567 of the calling line 18, through the line terminals of the repeater 360. En413, and its associated make contact, the relay 410 closes a circuit for energizing the upper winding of tone relay 340.



  This circuit extending from the ground, at 4b7, through the medial rest intcr- of 451.485, the brush holder 534 and its contact / partner, 483, 442, 413, 392, the upper winding of 340 and resistor 342, to the battery. An easy-to-follow branch of this circuit goes to the battery passing through heater 388 of thermal relay 387. When its top coil is energized following the circuit just described, relay 340 closes, in 341, an easy to follow circuit for shorting its top winding- /

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 laughter and, accordingly, immediately falls back and then functions again.

   As a result, relay 340 operates like a shaker, its upper winding being successively excited and de-energized under the effect of short-circuiting its armature 341.



   Consequently, a rippled induced voltage develops in the lower winding of 340 and this voltage is applied across the conductors 398 and 399 of the loop line, through a circuit including the capacitor 334, and the ar - Mature dropout 322 of the maintenance relay 320. This voltage is used to excite the receiver of the telephone device provided in the called station, thereby indicating to the calling subscriber that the automatic switching device provided at the exchange 10 is available and that the call is routed to the operator position of the exchange 9.



   Line test relay 410, while operating, also closes, at 412, a circuit to energize slow-acting relay 355, Se circuit going from ground at 441, through 412, 390, contacts made. before cut-off associated with 351 and the winding of 355, to the battery.



   Relay 355 then operates to close, at 356, an easy-to-follow circuit, in order to energize the delayed action relay 350. To its armatures 358 and 359 and their associated work contacts, relay 355 connects the line conductors 367 and 368 of the urban line 13 to the opposite terminals of the central bank with which 4.1 is provided the central 10, thus closing a circuit for exciting the falling member 375 provided at the operator position 15 of the central 9. More particularly, this organ or Signaling device is energized by a circuit going from earth through 359,368, winding 3'74, switch springs 377 and 376, falling member winding 375, winding 373,367, 358 and resistor 357 to the battery.

   This organ 375 functions

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 then starts to signal to the operator on duty at position 15 that a call coming in via urban line 13 must be answered. Closely following the operation of relay 355, delayed operation relay 350 operates to close, at 351, and its latch contact, a clean holding circuit. This hold circuit goes from the ground at 441, through 412,390,351 and the winding of 350, to the battery.

   At 351 and its break contact, relay 350 opens a breaking point for 355 in the switching circuit described above, causing the latter relay 355 to drop out, after a time interval to disconnect the line conductors from the urban line. 13 of the central battery terminals and to connect these line conductors to the line terminals of windings 361 and 362 of the repeater transformer. In this way, the desired speech connection between the Tl set and the equipment with which the operator position is provided.
15 is fully realized.



   As stated previously, if the attendant on duty at position 15 has not answered a call within a given time interval after connector finder circuit 16 has been seized, the thermal relay 387 operates and causes the release of the switching apparatus which i is in the working position. More particularly, when the heater element 388 of the relay 387 is energized as a result of the operation of the line test relay 410, the heating energy developed by this element causes the bending of the twin blade 389 towards the front. right.

   After a determined time interval, the free part of this twin blade has moved enough for contacts 389 to engage (or make contact) thus closing an easy to follow circuit for energizing line relay 330. This re-

  <Desc / Clms Page number 24>

 However, while operating, closes, at 331, an easy-to-follow circuit for energizing the long-acting holding relay 320. The holding relay, on operating, opens, at 322, a break point in the previously described circuit to set a voltage giving the waiting tone at the terminals of the conductors of the loop line 398 and 399, to thereby terminate the signal received by the calling subscriber.



  At 321, relay 320 closes an easy-to-follow circuit to energize control relay 470; this last relay, in turn, operates and closes, in% 475, an easy-to-follow circuit to energize the line control and switching relay 440. In 474, the relay 470, by falling, prepares a point of rupture in the circuit described below, to quote the delayed release rail 455, in parallel with the operating magnet of the connector switch 540.



   At 472, relay 470 closes a multiple hold circuit for relay 350, this hold circuit from ground at 472, through 391 and winding 350, to the battery.



   At 472, relay 470 also closes a multiple hold circuit for line test relay 410, this circuit starting from conductor 391 to ground, and going through 351, 390, 412, 415, and the lower winding of 410, to the battery. At 471, relay 470 prepares a holding circuit for latch relay 640.



  This holding circuit closes as a result of the subsequent operation of relay 440 and goes from the ground at 4QL, paz the intermediate of 471, 482 and the winding of 640, to the battery.



  At 441, and its associated normally closed contact, relay 440, when operating opens a breaking point in the initially closed holding circuit for relay 410, and a breaking point in the original holding circuit of relay 350. at 442 , relay 440 opens a breaking point in the @
 EMI24.1
 circuit previously described, to excite the winding stipéy

  <Desc / Clms Page number 25>

 inside the tone relay 340, in parallel with the heater 388, the thermal relay 387, to thereby stop the operation of the tone relay and de-energize the heater 388.



   At 444, relay 440 closes a clean hold circuit, this hold circuit going from ground at 311, through 396, 444 and winding 440, to the battery.



   When the heater element 388 drive circuit of thermal relay 387 is turned off, twin blade 389 begins to cool and curves to the left. After an interval of time, the contacts 389 'open and cut the operating circuit of the line relay 330.



   This relay then drops out and opens, at 331, and its associated working contact, the operating circuit of the holding relay 320, and it closes at 331, and its associated rest contact, the circuit mentioned above. to energize the relay 455, in parallel with the operating magnet of the connector switch 540, this circuit going from the ground, in 331, by 393 to 474, where it divides, one of the branches going to the battery to through winding 455, and the other branch going through 434 and 489, and magnet winding 540, to the battery. When energized by this circuit, relay 455 operates, and prepares, at 456, an operating circuit, described below, for relay 460, and opens, at 458, a break point in the circuit. operation of relay 430.

   Following shortly the closing of the circuit described above, to excite the magnet 540, the holding relay 320 drops out and opens, at 321, the operating circuit of the control relay 470, This last relay in turn drops out and opens, in 475, the operating circuit of control relay 440.



   In 472, relay 470 opens the holding circuit

  <Desc / Clms Page number 26>

 alternative previously described for the two relays 350 and 410, causing these two relays to drop out. At 471, and its associated work contact, relay 470, on falling, opens a cutoff point in the holding circuit previously described for latch relay 540, causing this relay to drop. At 471, and its associated normally closed contact, relay 470 closes an excitation circuit, of the pendulum relay 480, this circuit going from earth at 441, through 471 and the winding of 480 , to the battery. When the relay 480 is zero, cited by this circuit, a vibratory movement of the calibrated armature 481 begins, thus intermittently closing a circuit comprising the conductor 395 to energize the relay 310.

   Due to its delayed character of operation, relay 310 does not operate when energized intermittently by this circuit. At 474, the relay 470, on falling, cuts the circuit, described above, to excite the magnet 540, in parallel with the relay 455, causing the latter relay to drop.



   When magnet 540 is de-energized, it functions to advance one step from their home position the brush holders of connector switch 550 and to close off-normal springs 542, thereby closing a circuit to energize relay 430 This circuit can be followed from the earth by the intermediary of the springs 542, 490, 458, and the winding of 430, to the battery, When operating, the relay 430 closes, at 435, a holding circuit clean easy to follow and prepare cn 433 an AC circuit to repeatedly energize the magnet 540 in order to. return the connector switch 550 brush holder to normal.

     After an interval, the vibration of the calibrated armature 481 ceases and this armature, in its rest position, gives contact to its associated working contacts to keep the operating circuit of relay 310 closed. Relay 310 then operates.

  <Desc / Clms Page number 27>

 to cut, at 311, the holding circuit described above for the relay 440. On falling, the relay 440 opens, at 444, a new breaking point in its holding circuit and closes, at 443, the AC circuit at question above to excite the magnet 540. This circuit goes from the ground, through the springs 542, of 490, 443, 433, 488, of the armature 541, and of the winding of the magnet b40 , to the battery.

   As a result of the action of breaking the circuit of the springs associated with the frame 541, the magnet 540 operates like a shaker, to advance the brush holders of the switch bbO to their position. rest position or eleventh position. At this time, the non-standard springs 54 are open.



   When these springs are open, the holding circuit of relay 430 is cut and a cutoff point is opened in the circuit which has just been described, to excite the magnet 540. Following the fall of the relay 430, the circuit 16 tester is brought back to normal.



   When the latch relay 640 drops out as explained above, it operates to disconnect the negative battery terminal from leads 767 and 604 of city lines 14 and 17 respectively.



   When the negative potential of the battery is removed. of conductor 767, the line relay 740, existing in circuit 21, is de-energized and falls back to open, at 741, the operating circuit of the holding relay 735, thus obtaining the subsequent drop of the holding relay, of the 755 and the control relay 710? Before holding relay 735 drops out, a circuit momentarily closes to energize relay 830, in parallel with the operating magnet of connector switch 818, this circuit going from ground through 741, 738. , 849, and through the respective windings of magnet 818 and relay 830, to the battery.

   When energized by this circuit, relay 830

  <Desc / Clms Page number 28>

 works, but has no effect at this time. Little bit harsh, and when the holding relay drops out, the circuit just described is cut at 738, causing relay 830 to drop and magnet 818 in accordance with its ratchet and pawl mechanism, causes the switch 850 brush holders to their first non-normal positions.



   8277
When this is oroduit, the non-normal springs are, moved until they come into contact, to close an alternating circuit which excites the magnet 318 in parallel with the ree lais 830, this circuit starting from the ground on 736, and going through 847, springs 827, frame SI \ :? , and through the respective windings of magnet 818 and relay 330, to the battery. The resulting operation of relay 880 again has no effect at this time.

   Due to the cutting action of the springs associated with the frame 819? magnet 818 works, like a shaker, to bring the brush holders of switch 850 to. their respective resting positions through the contacta benches.



  At this time, the non-normal springs 827 are open.



  When these springs are released, a cutoff point is opened in the AC operating circuit or release circuit for the magnet 818. Following the release operation by the connector switch 850, the apparatus control of circuit 21 of the finder-connector returns completely to normal, and this circuit becomes available again for subsequent use.

   If the call routed to attendant position 15 is answered before thermal relay 387 operates; in the way just explained, the operation of relay 387 is stopped and the switching apparatus is kept in the working position.

   To answer to. call, the operator in service at position 15 inserts the plug terminating its cord circuit in jack 369 and activates the call key 380 to its position

  <Desc / Clms Page number 29>

 out.normal cut-off at rppos, when this key is actuated in its out-of-normal position, the springs 376 and 377 are released and open a new cut-off point in the circuit previously described to excite the falling member 375.

   The drop member 375 drops back to its normal position, and a simple circuit can be followed from the ground, through the windings of 330, and through the winding 36, of 369,368, of the coil 374, switching springs 377 and 378, and impulse springs 383, to the battery. The other branch of the simplex circuit shown goes, via winding 330, winding 361, 358, 367, winding 373, switching springs 379 and 381, and impulse springs 383, to the battery.

   When energized by this circuit, the line relay 330 operates to cause the subsequent operation of the holding relay 320 and the two control relays 470 and 440, in the order shown and in the manner described above. When the two relays 470 and 440 are operating, the circuit previously described for the locking relay 640 is closed to the armatures 441 and 471. At 472, the relay 4'70 closes the alternate control circuits described above for relays 350 and 410.

   The relay 440, while operating, closes its holding circuit and opens, at 442, a breaking point in the circuit described above, to energize the heating element 388 of the thermal rail C87, in parallel with the upper winding of the tone relay 340, in order to avoid a greater deformation of the twin-blade 389 and to stop the operation of the tone relay 340.



   At 441, and its associated break contact, the relay opens a breaking point in the holding circuit previously closed for the relay 410. The last relay is, however, kept in the working position, by its alternating mairtien circuits such as 'it is described above.



    @

  <Desc / Clms Page number 30>

 
 EMI30.1
 Mi 4 ": 13, relay 440 prepares a circuit, described below, to energize transfer relay 40J. Lin 445, and 446, relay 440 prepares a loop connection between calling line 18 and the called line. choose.
 EMI30.2
 van operation of the four relays; 3: 0. 320, 470 and 440, the circuit 16 tester is designed to. react to impulses - are transmitted to it by the urban line 13, from the operator position 15.



   From the foregoing description, it appears that the subscriber calling the Tl set can make a call which is routed to the operator position lb by operating the hand generator 693, and without picking up the receiver. the telephone set, located at the calling set, from its hook. If the call is made in this way, the operator, while answering the call and trying the connection established, does not receive an answer from ', -' calling subscriber.

   If the calling subscriber does not answer when
 EMI30.3
 the operator tries the co.me:ic:; the operator can call back the calling subscriber by operating the call key provided by convention in its cordon circuit, this -, üi sends the 80dr: nt of ri, on the conductors of --nes, through the repeater transformer 370, passing through the urban line 13, through the repeater transformer 360, passing through the conductors of the loop line
 EMI30.4
 ge 398, 3Y9, ± ± W5 and 496, and by the calling line 18 to activate the signaling device with which the
 EMI30.5
 ringing post T7 ..



  Part of this current is diverted through the in-
 EMI30.6
 roulum-, nt of the alternating current relay 450. C: this relay operates and opens at 45 a cut-off point in the circuit previously described for terminating ::! .., coils: the lower side of the line relay b80. Another part of the neck-

  <Desc / Clms Page number 31>

 The ringing signal is routed through the upper coil of line relay 680, operating this relay which closes, at 684, the circuit previously described, to energize its lower coil. When its lower winding is energized, relay 680 operates fully to disconnect its upper winding 683 from between conductors 563 and 567 of the. calling line 18.

   In this way, the impedance of this winding is removed between the conductors of the calling line 18 and most of the ringing current is carried along the line to energize the signaling device at the calling station. the end of the ringing call, and when the attendant releases her ringing key to disconnect the ringing current source from the line conductors, the alternating current relay 450 is de-energized and drops back to close, in 4b2 , the circuit previously described, to short circuit the lower winding of the line relay 680.



   The consequence is that the line relay drops again to connect its upper winding between the line conductors of the calling line 18.



   When the subscriber calling the station T1 picks up his receiver, in response to the call operation which has just been described, the desired conversation circuit is completely closed between the calling station T1 and the telephone apparatus used. by the operator in position 15.



  From this point of view, it should be noted that a transmission current is supplied to the loop between the calling station T1 and the repeater 360 by the local battery, provided according to the convention at the station T1. The transmission current for the loop between the operator's telephone set and the repeater 370 is bypassed on the exchange battery provided at the main exchange 9. following the establishment of the conversation connection @

  <Desc / Clms Page number 32>

 between the plague calling T1 and the operator's telephone set, as described above, the operator can converse with the calling subscriber and make sure of the call number of the requested set or of the name of the requested party.



   If the call is to be routed to a station associated with a line terminating at central station 9, the attendant can perform the desired call in the manner conventionally employed in manual exchange practice.



  Routing Û 'a call to a subscriber line terminating at the exchange on tandem -
If the set requested by the calling subscriber is associated with a subscriber line terminating at the read tandem exchange, the operator in service at position 15 activates the call device 382, to dial the number. call of the called station. For example, if set T2 is the called set, the attendant forms a single digit of 4 pulses, thus causing the brush holders of connector switch 550 to advance until they come to a stop. '' engage in the contacts terminating the conductors of line 19 ..

   More particularly, when calling apparatus 382 is operating, the simplex operating circuit described above for line relay 330 is cut a number of times, at impulse springs 383, corresponding to the number of pulses. the number transmitted by the disc.



   Each time this circuit is open, the line relay 330 drops out and opens, at 331 and its associated working contact, the operating circuit for the holding relay 320 and closes, at 331, and its associated rest contact, the circuit described above for energizing relay 455, in parallel with the operating magnet of the connector switch 540.



   Relay 455 operates at the start of transmission of the digit and, due to its delayed release character,

  <Desc / Clms Page number 33>

 remains in working position until shortly after the digit has been issued. Since the holding relay 320 is also of the slow-acting type, this relay also remains in the working position during each pulse period.



  When relay 455 operates, it prepares, at 456, the circuit described above to energize transfer relay 460 and opens, at 45 ?, a break point in the circuit described below to short circuit the main winding. hold of the combined relay, line, cut and call recording, associated with the line to be chosen. At 458, relay 455 opens a break point in the circuit described above to energize control relay 430. Each time the operating magnet 540 of the connector switch operates, the brush holders move forward. one step, so that at the end of the transmission of the digit, these brush holders are engaged in the contacts terminating the called line.

   In the case that we assume here, where the call number designating the called line 19 has 4 pulses, the magnet 540 is excited and de-energized 4 times, so that at the end of the transmission of the digit , the brush holders bbl to 554, inclusive, engage respectively in their 4 associated contacts. When these brush holders are moved to their first respective out-of-normal positions, the out-of-normal springs b42 are closed to prepare the circuit described previously in order to energize the relay 430. At the end of the emission of the signal. figure, the simplex circuit described above and comprising the two conductors of the urban line 13 is closed, and the line relay 330 remains in its working position to keep open the circuit described above, to excite the magnet 540 and relay 455 in parallel.

   On falling, relay 455 closes at 458 the circuit described above to energize relay 430. At 456, relay 455 opens the operating circuit prepared for the operation.

  <Desc / Clms Page number 34>

 relay 460 and, in 4b7, prepares the circuit described above to short-circuit the holding winding of the line relay associated with the line called N 19. The relay 430, while operating, closes, at 435, its holding circuit pre- cédemment described and prepared, in 433; a breaking point in the alternating circuit previously described, to energize the magnet 540, during the time when the connector switch b50 is released. At 432, relay 430 prepares a circuit, described below, to energize the line switch relay 420. At 431, relay 430 prepares the operating circuit of relay 460.

   Finally, at 436 and 437, relay 430 closes a loop connection between calling line 18 and called line 19.



   Following the transmission of the digit by the disk, the operator controlling 1 "call activates her call key so that the ringing current is sent again along the urban line 13 and through the repeater. 360. From this point, the ringing current divides between the calling and called lines, part of this current being routed through the armatures 416 and 417 of the relay 410 and the brush holders 501 and 502 of the controller. seeker 500, then outside via the calling line 18, and another part of the current is routed through the armatures 445, 446, 436, 437, the contacts established before breaking associated with 421 and 424; and the brush holders 551 and 552 of the connector switch 550 taken externally by the conductors of the called line 19.



  Another part of the current is bypassed through the windings of the ac relay 450. This relay operates and opens, at 451 and 452, respectively, break points in the circuits previously described to short-circuit the holding windings. line relays associated respectively with lines 19 and 18. Part of the

  <Desc / Clms Page number 35>

 Ringing current transmitted by line 18 is bypassed through the upper winding of line relay 680 with the result that this relay operates to close the drive circuit of its lower series winding, and it then assumes its position of work completed to disconnect its upper winding from between the conductors of line 18.

   In a similar fashion, the line relay associated with line 19 operates under the effect of the operation of the AC relay 450 to disconnect its working coil from between the conductors of the called line 19.



   The ringing current sent along the calling and called lines 18 and 19 serves to excite the ringing tones or signaling devices provided respectively to the calling and called stations Tl and T2. In this vein, it should be noted that, if line 19 is of the multi-part type, such that a certain number of sets are connected to it, the attendant activates her ringing key in accordance with the code. designating the desired T2 station. Each time this key is released to disconnect the ringing current from the urban line 13, the relay 450 drops to @@@ close, at 451, the circuit described above to short-circuit the lower winding of the relay of line 680, associated with the calling line 18.

   Likewise, when relay 450 drops out, it closes the above-mentioned circuit to short circuit the line relay holding winding associated with calling line 19, this circuit going from ground, at 457, through of 451, 485, of the brush holder 554, of 594 and of the holding winding of the indicated line relay, on the ground. conversely, each time the bell key is actuated, to send the bell current along the city line 13, the relay 450 operates again

  <Desc / Clms Page number 36>

 to open the short-circuiting circuits described above, so that the line relays respectively associated with the calling and called lines can fully operate again.

   At the end of the ringing call, the native current gone relay 450 is de-energized, and remains in its tripped position. With this relay in its tripped position, the holding winding of the line relay 680 is short-circuited and the corresponding winding of the line relay associated with the called line 19 is also short-circuited. relays will fall.



   The desired conversation circuit between the calling and called stations is closed after the ringing operation operation and as soon as the calling party picks up the receiver from its telephone set and the called party answers the call. It should be noted that the conversion circuit thus established comprises the brush holders for the finder switch 501 and 502, the loop line conductors 495 and 496, the armature springs in the working position of the 3 relays 410 , 440 and 430, the armature springs in the tripped position of the relay 420, the loop line conductors 493 and 494, and the brush holders 551 and 552 of the connector switch 550.



   The transmission current is supplied to the conversation circuit by local satellite stations provided by convention at each of the two stations T1 and T2. It is obvious that the operator on duty at. position 15 can intervene in the conversation at any time if it wishes.



   Either way, the call key 380 is kept in its out-of-normal working position until the connection is ready to be released.



   The operator is expected to intervene from time to time in the connection, in order to make sure when the conversation

  <Desc / Clms Page number 37>

 versation is complete, so that she can begin releasing devices soon after the conversation has ended.



  Routing of the call to a subscriber line terminating at a sub-exchange -
As stated previously, calls made on lines terminating at tandem exchange 10 can be routed, under the control of the operator on duty at position 15, to any desired line terminating. to one of the two sub-exchanges Il and 12. In this case, the operator, by answering the call, and making sure of the set requested by the calling subscriber, forms the two digits of the telephone number. call designating the desired line,

   the pulses of the first digit being used for the connector switch 550 to place its brush holders on the contacts terminating the city line terminating at the determined exchange terminating the requested line and the pulses of the 2nd digit being routed through the monitoring device from circuit 16 to the control device of the circuit provided in the chosen central unit, so that the connector switch of the chosen central unit takes the desired line.



   For example, if the call sent to the Tl set and routed to the operator position 15 of the main exchange 9 is intended for the T4 set associated with line 12 ending at the sub-exchange 11, the operator forms the two digits of the call number designating line 22. In this case, accepted by hypothesis, the first digit transmitted by the attendant carries a single pulse so that, when it ends, it carries them The connector switch brushes 550 are in the position where they engage their respective respective first contacts.

   Shortly after the end of the transmission of this digit, and when the delayed release relay

  <Desc / Clms Page number 38>

 rée 455 drops out, as explained above, it closes, at 458, the operating circuit previously described for relay 43U, causing this latter relay to operate to perform the switching of the line and the control functions described above. . For a call of this kind; the re. lais 430 also closes a circuit to energize the line switching and control relay 420, in series with the line switching relay b10 included in the line circuit associated with the chosen urban line 14.

   This circuit can be described as going from earth, through the winding of 420, of 432, of the contacts made before break associated with the armature 457, of 487, of the brush holder 553 and its first associated contact 591, in the cable 560, and of the winding of 610, to the battery. Each of the relays 420 and 610 operates, when energized by this circuit. The relay 420, while functioning, prepares, by its armatures 421 and 424, a simplex impulse circuit which comprises the two conductors of the urban line 14, and / through the winding of the line relay 740, provided in circuit 21. This pulse circuit closes at armatures 612 and 615, when relay 610 operates.

   At 612, relay 610 opens the original excitation circuit of the line relay '/ 40, after closing the simplex pulse circuit just mentioned. At 611 and 615, relay 610 disconnects the city line conductors 14, line conductors 56b and 561 going to the contacts of seeker switch 500.

   The simplex pulse circuit mentioned above, which closes under the effect of the operation of the two relays 420 and 610, can be described as going from the battery through the resistor 333 and from 332 to 397, where it splits, a branch going through 421,493, the balais holder 552, of b85, 612, 767, 764, of the winding 752 and the winding of the line relay 740 to the ground, and the 'other bran-
 EMI38.1
 che going through 424, 494, brush holder

  <Desc / Clms Page number 39>

 551, 581, 615, 766 ', 763, winding 751, and winding 740, on the ground.



   Following the closing of this circuit, the control apparatus of the two circuits 16 and 21 is designed to react to the pulses of the second digit designating the particular line desired leading to the sub-central 11. At the start of the first pulse of the second digit, the operating circuit of relay 455 is closed again, noting however that this relay being at this moment energized, the operating circuit of the magnet due to the connector switch 540 is then opened at 434. When operating , relay 455 closes, at 456, the previously mentioned circuit, to energize the digit transfer relay 460, this circuit going from ground at 431, through 456, 466, and winding from 460, to battery-.

   Relay 460, when operating, closes a short circuit of the winding of relay 465, this circuit going from the ground, through the non-normal springs 542, of 490, 443, 461, of the winding of 465, 466, 456 and 431, on the ground. Due to its delayed release characteristic, relay 455 remains in the on position throughout the second series of pulses to keep this shorting circuit closed. During each pulse of the second digit, line rail 330 drops back and operates alternately, thereby opening and closing, at 332, a break point in the previously described simplex pulse circuit ', which goes through the winding of the line relay 740.

   In this way, the pulses of the 2nd digit are repeated to line relay 740 of circuit 21, by the operation of the control device existing in circuit 16.



   Line relay 740 follows the pulses and causes the brush holders of connector switch 850 to be placed on the contacts terminating the conductors of

  <Desc / Clms Page number 40>

 the desired called line. More specifically, at the start of the first pulse, when the line relay 740 drops, it closes at 741 the circuit previously described to energize the delayed release relay 830, in parallel with the operating magnet of the connector switch 818. Relay 830 operates, when energized for the first time, and, due to its delayed release characteristics, remains energized throughout the pulse period.



   At 831, relay 830, when operating, opens a breaking point in the circuit, described below, for shorting the holding winding of line relay 700 associated with called line 22.



   At 832, relay 830 opens a breaking point in the connection between repeater transformer 750 and line brush holder 852 of connector switch 850, thereby avoiding interfering with conversations taking place on lines. of subscribers occupied by calls in the opposite direction. In the present case, the conductors of the called line terminate at the respective first contacts of the contact bank of the connector switch, and, consequently, the 2nd digit formed at the operator position 15 must necessarily include a single pulse. , so that, at the end of the figure, the brush holders of the switch 850 remain engaged in their first associated contacts.

   When these brush holders are moved to their out-of-normal positions, the out-of-normal springs 827 close to prepare the previously described circuit to energize the operating magnet 813, curbing the release of the connector switch.

   Shortly after the end of the transmission of the 2nd cipher, and the line relay 340 being in its working position, the delayed release relay 830 drops back and connects, at 832, the line brush holder 852, to the conductor of loop line 863, and prepare, in 831, the circuit described above to short-circuit the holding winding of the line relay 700

  <Desc / Clms Page number 41>

 
At the end of the 2nd digit, and the line relay 330 of circuit 16 being in its working position, the operating circuit of the delayed release rail 455 is kept open by the armature 331.



   The result is that relay 455 drops out shortly after the end of the transmission of the 2nd digit and opens, at 456, a break point in the previously traced circuit covering the winding of relay 465. The winding of this last relay is then energized in series with the coil of relay 460 by a circuit which goes from the ground through the intermediary of the non-normal springs - b42, of 490, 443, 461 -. and of the windings connected in series relays 465 and 460 to the battery. Relay 460 remains in its working position and relay 465 operates when the short circuit described above is cut, and the series circuit, which has just been described, is established.

   While operating, relay 465 opens, at 466, a new breaking point in the operating circuit of relay 460 as well as a new point in the circuit previously described, to short-circuit its own winding. Thus, at 467, relay 465 closes an AC circuit to energize switching relay 610, this AC circuit going from ground to 473, through 467, 487, brush holder 553, from 591, and from the 610 winding, to the battery. Thereafter, relay 465 opens at break (or cut) contacts associated with 467, a break point in the circuit previously described, to energize relays 420, and 610 in series.

   The relay 420 is then de-energized and drops again to close at the break contacts associated with 421 and 424, a simple AC circuit to keep the line relay 740 of the circuit 21 energized.



  One of the branches of the simplex AC circuit can be described as running from the battery, through winding of impedance 365, to winding 363, to

  <Desc / Clms Page number 42>

 398, 446, 437, breaking contacts associated with 424, 494, of the ball carrier 531, of 581, 615, 766, 763, of the winding 751 and of the winding of the relay 740, on the ground.

   The other branch of this circuit goes from the battery through the winding of impedance 365, and through the winding 364, of 399,445, 436, to the break contacts associated with 421, 493, brush holder 552, b85, 612, 767, 764, winding 752 and winding 740 to the battery. After this simplex circuit has been made, the original simplex circuit going through resistor 333 is cut to reinforcements 411 and 424, while releasing relay 420.

   Following the release of the relay 420, in the way which has just been described, the desired connection is completely made between the calling and called lines 18 and 22 respectively, and also between each of these 2 lines and the operator position. 15 to the main exchange 9. To signal himself to the calling and called subscribers, the operator hovering over the call to the attendant position 15 activates his ringing key to send the ringing current through the established connection and calling and called lines, to activate the signaling devices provided at the calling and called stations respectively. here er.core, if the called set is associated with a line of the multi-party type, you can use a ringing code to signal yourself to the desired set.

   Each time the ringing current source is connected through the line conductors, the ringing current is sent through the city line 13, and through the repeater 360 to that loop line 398-399. Part of the current is returned to the calling line to excite the signaling device provided for the calling station, thereby signaling to the calling subscriber that the called station is ringing.

   In or-

  <Desc / Clms Page number 43>

 tre, the alternating current relay 450 operates at the start of each ringing period and drops again at the end of each ringing period, to perform the control functions described above, referring to the call routed to station T2. During each ringing interval, another portion of the ringing current is transmitted through town line 14, through repeater 750, along loop line conductors. 863 and 865, and outward along of the called line 22, to excite the signaling device provided at station T4.

   A part of this ringing current is shunted by the winding of the alternating current relay, which causes the operation of this relay, and opens, at '/ 31, a breaking point in the circuit described above. - previously to bypass the holding winding of the line relay 700. During the initial part of each ringing period, a portion of the ringing current which is conducted along line 22 is bypassed by the ringing current. upper winding of line relay 700, causing this relay to operate which closes, at 702, a circuit including resistor 705, to energize its lower winding.

   In this way, during each ringing interval, the relay 700 operates fully, so that its upper / disconnected winding at 701 between the conductors of line 22. Consequently, this winding cannot be used. bypassing the ringing current with respect to the signaling device provided for the station called T4. At the end of each ringing period, the alternating current relay 730 is de-energized and drops again to close, at 731, the circuit described above, which bypasses the lower winding of the relay 700, this shorting circuit going from ground at 731, through 846.831, brush holder 853, 844, lower winding 700 and '/ 02, to ground.

   As a result, the relay 700 returns to reconnect, at 701, its upper winding through the conductors of the

  <Desc / Clms Page number 44>

 line 22. The desired conversation circuit between the calling and called stations closes following the dream call, and when the calling party picks up the receiver from its telephone device, from its support hook, and the station called T4 answers the call. In this regard, it should be noted that the transmission current is supplied to the loop existing between the station called T4 and the repeater 750 by the local battery provided by convention at the station indicated.

   The transmit current is supplied similarly to the loop extending between the calling station T1 and the repeater 750 by the local battery provided at the station T1. Here again, the operator on duty in the position of. operator 15 of the main exchange 9 can intervene at any time in the connection, if she wishes. alternatively, it can check the connection at intervals, to determine when the connection is ready to be released.



   In all cases, the call key 380 is kept in its out-of-normal position to hold the set of switches in the working position until the attendant is sure that the connection is no longer necessary. .



  Call forwarding via a line (Subscribes ending at the tandem exchange. If the call, as it was routed to operator position 15, from set T1, is intended for another set associated with the calling line 18, the only operation carried out by the operator is to operate his call key in accordance with the ringing code designating the desired set, in order to thus activate the signaling devices provided individually at the sets associated with that line.

   The ringing code character indicates to the called subscriber that his set is requested and to the calling subscriber that the ringing call operation is in progress. ¯ At the end of this ringing operation

  <Desc / Clms Page number 45>

 ringing, and when the calling and called subscribers operate their receivers to connect the telephone sets, respectively provided to the calling and called stations, of line 18, the desired conversation circuit is completely closed.



  For a call of this type, only the line extending between the 2 extensions is used for the connec t i o n. Consequently, the attendant on duty at position 15 can release the on-duty circuit 16 as soon as the ringing operation is completed, thereby rendering the automatic switching apparatus provided for in the instructions. three exchanges 10, 11 and 12 available for later use. In this regard, it should be noted that no precaution is taken to protect the line 18 against its use, while the conversation which takes place through it is in progress. However, this will not result in interference with the conversation in progress, if the operator of the exchange 9 monitors each connection established after having completed a transmission of digits by its disc and before starting the ringing operation.

   For a call of this kind, the calling and called subscribers should not ring to mark the end of the conversation since the operation of any of the two generators provided at the calling and called stations would have the effect of taking the circuit. 16 in the manner previously indicated.



   It will be noted that a call between two stations connected on the same subscriber line can be made without the assistance of the operator on duty at operator position 15, from the main exchange 9. For example, if the subscriber calling the station T1 wants a communication with a second station connected to line 18, the desired station can be called directly by activating the handheld tape recorder 693 in accordance with the ringing code designating the desired station. In such a case, however, the call is routed to operator position 15 of the

  <Desc / Clms Page number 46>

 previously explained, assuming that the automatic switching device provided for the three exchanges 10,11 and
12 is available when the call is made.

   If the automatic switching device is busy, the call is registered by line relay 660, and is subsequently routed to the operator position, as explained subsequently, when the device becomes. available. If a reverse call is made in this way, the attendant, by answering the call while it is routed to operator position 15, can release the switching device to the working position without executing the call. no service whatsoever.



    Switching device release, automatic -
When the conversation held on a connection comprising two of the subscriber lines going to centers 10, 11 and 12 is finished, one of the subscribers using the connection should normally ring to transmit a disconnection signal to the operator. in service at position 15.



   For example, the subscriber calling at set T1 can activate hand-held magneto 693 for a short period of time so that ringing current is sent to the connection established at operator position 15, to excite. thus terminate the receiver of the attendant's telephone set, so that the attendant is notified when the call is about to be cut off. When handheld generator 693 is actuated for this purpose, the top coil of line relay 680 is energized by the ringing current, and the ac relay 450 bridging the connection is also energized and operates. Further, part of the ringing current is conducted through the established connection and through the operating winding of the line relay associated with the called line.

  <Desc / Clms Page number 47>

 



   Thus, if the connection established extends between lines 18 and 19, the operating winding of the line relay made in line circuit 690 is energized by the ringing current and operates. When relay 450 operates, it opens, at its armatures 451 and 452, break points in the circuits serving to short-circuit the holding windings of the respective line relays associated with the calling and called lines.



   As a result, the holding windings of the two line relays individually associated with the calling and called lines are energized in series, and the respective operating windings of these relays are disconnected between the conductors of the respective associated lines.



   If the established connection extends between line 18 and line 22 terminating at sub-central 11, part of the ringing current is sent through the established connection, and splits between the ac relay 730, the in - upper or operating bearing of the line relay 700 and the signaling device provided for the station called. As a result, both relays 700 and 730 operate. Relay 730, when operating, opens at 731, a breaking point in the shorting circuit of the lower winding of relay 700., allowing the lower winding of this relay to be energized, in such a way. so that the top winding of the relay is disconnected between the conductors of line 22, during the period when magneto 693 is actuated.

   When the operation of the magneto, 693 ceases, the relay 450 drops out and short circuits the holding winding of the line relay 680, along the circuit described previously, causing the relay to drop. Likewise, if the established connection includes line 19, the line relay maintenance winding included in the circuit

  <Desc / Clms Page number 48>

 fired from line 690 is also shorted and falls back.

   Alternatively, if the connection joins lines 10 and 22, relay 730 drops off at the end of the ringing period marking the end of communication, to close, at 731, the circuit previously drawn to bypass the 700 lower winding, causing the latter relay to drop and reconnecting its upper winding through the conductors of line 22. The relay operations just described occur during and after the ringing period of end of communication, regardless of whether it is the calling or called party that actuates its hand-held tape recorder to transmit the end of communication or disconnection signal to the operator.



   When the attendant on duty at the operating position receives the disconnection signal or, again, verifying the connection established, when she notices that this connection is no longer in use, she can initiate the connection. release of the switching apparatus in the working position by returning the call key 380 to its normal position, the switching springs 376 and 377 being closed to reconnect the winding of the indicator 375 between the conductors 367 and 368 of city line 13. The simplex switching circuit previously described for line relay 330 is interrupted at switch springs 377, 3iS, 379 and 381.

   The line relay 330, on falling, opens, at 331, the operating circuit of the holding relay 320, thus causing the successive release of this relay and of the relay 470, in the given order. On falling, the line relay 330 closes, at 331, the operating circuit previously described for the delayed release relay 455. Shortly thereafter, and when relay 470 drops, this circuit is cut off at 474. Momentary operation of relay 455 again has no effect at this time.
 EMI48.1
 When relay 470 drops, it closes, in 4-? It shines

  <Desc / Clms Page number 49>

 previously described to energize the pendulum type relay 480. In this way, a vibration of the calibrated armature 481 is initiated.

   During each vibration of this armature, the operating circuit of relay 310 is closed but, due to the delayed operating characteristic of this relay, it remains in its tripped position until after armature 481 has come. , in its rest position, engage in its associated contacts, grounded. The relay 470, on falling, also interrupts, at 472, a breaking point in the common part of the holding circuits previously described, for the two relays 410 and 350, causing each of these two relays to drop. At 473, the relay 470 opens a point in the holding circuit previously described for the switching relay 610 produced in the line circuit associated with the urban line 14, causing the latter relay to drop, if it is in the off position. job.



   At 471, and its associated make contact, relay 470 cuts the multiple holding circuit previously drawn for latching relay 640. At 475, relay 470 cuts the operating circuit of control and control relay 440. line mutation.



   Relay 350, on falling, opens, at 351, a new cut-off point in the alternating holding circuit previously traced for relay 410, and again prepares the operating circuit of relay 355. Relay 410, re-prepares it. - falling, opens, at 41b, a new breaking point in the common part of its two locking circuits, as indicated above and, at 414, a breaking point in the circuit previously described for short -circuiter the lower bearing of the line relay 680 associated with the calling line 18. n 413, and its associated rest contact, the re-maneuver lais 410 again prepares the circuit / previously drawn for the relay of start of finder switch 520.

   In 411, @

  <Desc / Clms Page number 50>

 and its associated normally closed contact, relay 410 again prepares the actuator circuit for the actuating magnet of seeker switch 530. Finally, at 416 and 417,
 EMI50.1
 relay 410, when falling, opens dew. break points in the established speech connection, and two points in the
 EMI50.2
 cooked t simplex previously traced 211an t, via the urban line 14, energize the line relay 740 of the circuit 21.



   When the vibratory movement of the armature of the pendulum relay 481 is completed, the delayed action relay 310 is continuously energized and operates to open, at 311, the hold circuit of the relay 440, causing the relay to drop out. relay and opening at 445 and 44b two additional break points in the loopback connection joining the calling and called stations. In 444, relay 440 opens
 EMI50.3
 a new breaking point in its proore key maintenance circuit. n 441, relay 440 trips the operating circuit described above for relay at. penrLllG 470, causing the fall of this relay and the a r.

   #] - <R 1 310 with delayed action, In 44, the ra.ais 440 prepares again a new breaking point in the circuit previously drawn for ex-
 EMI50.4
 c iterate the start relay ûu switch ue researcher b20. n 44, and its associated contact of t¯ v; i1, the relay 4: 0 C :) Ir) e the prececm - :. nt circuit described to energize the two relays 460 and 465 in series, making. fall each of these two re-
 EMI50.5
 lais, if they are in the working position. In 4't'j, and its rest contact R; - '1 relay 440 f86 the previous circuit described to energize the magnet to the operation b40 of the connector switch bbc, by the i11tern- ; .ediôirs clus cut-off contacts of the circuit: i associated with the armature 541.

   When the last circuit is closed, the magnet b40 works; in the manner of a t-re ", to bring the brush holders from the comrauta-

  <Desc / Clms Page number 51>

 tor 550 to their respective rest positions. At this time, the non-normal springs b42 are no longer engaged. when these springs are open, the holding circuit of relay 430 is cut, causing this relay to drop in order to cut, at 433, the release circuit of the operating magnet 540. The result is the stopping of the operation. step of connector switch 550. Following the drop of relay 430, circuit 16 is fully released.



   If the established connection extends between two subscriber lines terminating at the tandem exchange 10, the release of the apparatus included in circuits 21 and 5 from the finder connector, initiates when the relay of. lock 640 drops out. More particularly, when this relay drops out, it removes the negative potential of the battery of conductors 767 and 604, of city lines 14 and 17, respectively.



  When the negative potential of the battery is removed from lead 767, circuit 21 is released in the manner previously explained, with reference to the release operations initiated by the operation of thermal relay 387. Circuit 25 is, similarly. , released when the negative potential of the battery is removed from the conductor 604 of the urban line. If the connection established goes to a subscriber line terminating at the sub-central 11, the release of the switching device in the working position of this central is initiated under the effect of the circuit interruption. simplex connecting by urban line 14 the exchanges 10 and 11 and includes the winding of the line relay 740.



  When this circuit is open, the line relay 740 is de-energized and drops again to open, in '% il, the operating circuit of the holding relay 735, and to close the operating circuit previously described for the delayed action relay 830. Subsequently, and when the holding relay '/ 35 drops out, it opens, at 738, the closed circuit for excitation.

  <Desc / Clms Page number 52>

 
 EMI52.1
 of. 1 ':.) - a1S 830. The functioning again CE the latter rb- 1¯éi', C-L1-: P '-: 1 ur m0ffi' -.- LJ.t f '[4-. [' <1n8 f-'f) 'r't cp mornes ,.

   MIi) ltrt: ;; the magnet 818 of the connector E: st excites j ') ur doing: J.V - :;': 1C2T 1¯.: s n .J.; = t, <#: - '> #. l-? i s l: r), J ', 1J contact, t. f3UÍ -v: l: j ', i, <, 1 none C: Y1t-; r ',:. il n7IlVc '? r1 is not entered, at this nO: -I1 - ": Ylt, ouisquo; 31 and 365 Hont open, n rutOG :: ÎJ'11i ,, the relay (35 0 Jvre (= ët.LE' .ia: Tlt, in r37, the circuit of "': 3.:. 0euv1'e of x .lalS (10, and cut, in 733, and one associated working contact, the operating circuit of relay r'bb , making retor ::: xr each of these relays. At 738, and its associated rest contact, rtlais? 35 closes the circuit previously drawn to energize the operating magnet: i8 of the connector switch , by% '1-ntir.r <; üiiiaire of the frame 819.



   As a result of the action of breaking the circuit of the control springs by the armature 819, the magnet 318 works, like a shaker, to bring the ba-holders -
 EMI52.2
 leave the switch-.ur 350 to their respective rest positions; at this moment, the non-normal springs' 827 are open to stop the functionning of the magnet Es137. Following this last operation, the control device included in circuit 1 is completely carried out. it should be understood that in this case, the release of the circuit 25 provided in the sub-central 12 is initiated when the locking relay 640 drops to remove the negative potential of the battery of the conductor 604 of the urban line 17 and is accom - fold exactly as described above.
 EMI52.3
 



  Call. Issued on .one, 1 ± ¯% e to ± ¯ subscribed leading to a sub-center -
As has been said previously, calls sent on the subscriber lines terminating at the sub-exchanges are routed to the operator position 15. From
 EMI52.4
 this 'Ooin- ::', they can be routed to the requested station.

  <Desc / Clms Page number 53>

 dice under the control of the attendant on duty at this position. For example, if a subscriber of the T4 set activates the handheld magneto 775, to initiate a call at a time when the automatic switching device provided in the three exchanges 10, 11 and 12 is available, the line relay 700 operates to initiate the operation of the finder switch 800.

   Particularly when magnet 775 is actuated, the upper winding of relay 700 is energized by a circuit from one terminal of magneto 775, through springs 778, 841, of the winding. greater than 700, 701 and 842 at the opposite terminal of magneto 775.



  When energized by this circuit, relay 700 operates and closes the "X" contacts associated with 702, thereby closing an easy-to-follow circuit of energizing the lower winding of 700.



   Thereafter, the relay 700 opens, at 701, a breaking point in its primary operating circuit, and closes, at 703, a circuit going through 843 in order to indicate the calling line 22 in the contacts of the bank. finder switch 800.



   At 704, relay 700, after fully working, closes a circuit to energize seeker switch start relay 825, this circuit going from ground to 721, through 704, 848 and 1. winding of 825, from to the battery. The relay / start 82b, while operating, closes at 826 an energizing circuit of the operating magnet 816 of the finder switch 800. This circuit can be described as going from the ground at 721, through 759, 862, 826, 821 and from the winding of the magnet 816, to the battery.

   When energized by this circuit, the magnet 816 operates and prepares the ratchet mechanism and the associated ratchet, to advance by one step the brush holders of the switch 800 and closes, at its armature 817, a easy to follow route

  <Desc / Clms Page number 54>

 
 EMI54.1
 to excite it higher cu relay ¯'vni) t3.v¯ '; ¯7iis 82C.



  Ge dsrn;, r relay, in 3'onctioirant, cuvez in 8J "a point this rupture c'ans 10 'cireuru cas maneuvra de l'Aimanu 1 8? - 6, cc c .. L = uàsexcite this (l .; rr; .311t, and fc'it progress by -not the ç> Jrti; - oalais ru switch 5OC.: -l other, When de-energizing the: ¯; ¯nt 8JJ3, the c.z ' cui t cc rework âu rE: left 111 se S2J e: st cut off the armature 317, causing Ci to fall back. C ':. 7.Or ::? Eîn'.; -. N alternating with 1 ',: hiant 816 and r (:. L1'Ü,' of impulse 82u continues until cc bare the carriers calais of the switch CR cl18rcreur 800 are engaged in the contacts terminating the conductors of the calling line 22.

   More particularly, when the brush holder 303 engages in its first associated contact, a circuit closes to excite the windings.
 EMI54.2
 respective lower nients of the two relays 8eÔ and (20 in series, this circuit going, via the conductor marked- to earth 843, from the first contact associated with the loss-brush 803, from 861, 7b8, from the winding lower of 'r2u, of 860 and of the lower winding of 820 to the battery.When this circuit is closed, the relay 820 remains in the working position regardless of the condition of the magnet 816, and, therefore,

     the step-by-step operation of the finder switch 800 is
 EMI54.3
 The line test relay 20 operates, when its lower winding is energized by breaking by the test circuit just described, and, while operating, closes, by
 EMI54.4
 724, a clean, easy-to-follow interlock circuit. In f3,
720 the relay / prepares a clean AC holding circuit, and in doing so, closes a circuit to energize the slow release relay 760; this last circuit can be described as starting from the ground at 713 through the intermediary of 723, 757 and the winding of 760, to the battery.

  <Desc / Clms Page number 55>

 



   In 721, and its associated rest contact, the relay 720 opens a breaking point in the common part of the operating circuits of the magnet 816, and of the relay 825. The relay 82b then drops back to open, at 82b, a new one. breaking point in the operating circuit of the magnet 81b.



   At 722, relay 720 closes a circuit to bypass the lower winding of line relay 700 associated with calling line 22, this circuit going from ground to 731 through 722, 84b, brush holder. 804 and its associated first contact 844, from the lower winding of 700 and 702, to the ground. When this circuit is closed, relay 700 drops out to reconnect its top winding or operating winding between the conductors of line 22. At 721, and its associated make contact, relay 720 closes a circuit to energize the circuit. top winding of tone relay 745. This circuit can be described as running from ground at 721, through 711, top winding at 75 and resistor 747, to the battery.

   At its two bottom fittings' / 2b and 726, the line test relay 720 connects loop conductors 864 and 866 to the line terminals of repeater 750, thereby closing a connection between the calling station and the @@@ @@ repeater indicated.



   When the top winding of tone relay 745 is energized through the circuit described above, it operates to short, at 746, its top winding, and immediately drops out. In this way, this relay operates like a shaker, and, as a result of the alternate excitation and de-excitation of its upper winding, develops an induced voltage in its lower winding. This voltage is applied across capacitor 748, between the line conductors of the calling line.



  The result is a tone-on-hold signal which is transmitted to the calling subscriber to indicate that the automatic switching device is available and has been seized.

  <Desc / Clms Page number 56>

 



   The delayed release relay 760, in operation, connects the terminals of the battery provided at the central 11 to the line conductors of the urban line 14 and, in doing so, closes an energizing circuit of the lower winding. of the line relay 630 associated with the urban line 14, in the tandem exchange 10. more particularly, this circuit can be described as going from the ground through the intermediary of 764, 767, the associated contacts made before breaking at 612, 621, b43, the lower winding of 630, 766, 763 and resistor 762, to the battery. When its lower winding is energized by this circuit, the relay 630 operates to close at 633, a clean-keeping circuit, this circuit comprising the upper winding of 630 and starting from the ground at 644.

   Line relay 630, when operating, also initiates the operation of seeker switch 500, to seek calling line 14, as explained below.



   Relay 760, while operating, also closes, at 761, an easy to follow circuit, to energize relay 755; this latter relay, in turn, operates to close a clean holding circuit. This hold circuit can be described as going from the ground at 713, through 723, 757, 756 and winding at 755, to the battery.



  At 757, and its associated rest contact, relay 755 interrupts the operating circuit previously described for delayed action relay 760, causing the latter relay to drop after a certain time interval, to open, at 763 and 764, two break points in the switching circuit described above for line relay 630.



  To these same armatures, and to their respective associated bank contacts, relay 760 again connects the line conductors of the urban line 14, to the line terminals of the re-

  <Desc / Clms Page number 57>

 petitor 750, in order to extend the connection from the calling line 22 to the automatic switching device provided at the tandem exchange 10. In 761, the relay 760, when falling, opens a breaking point in the circuit. operation of relay 755. The relay '/ 55, while operating, also opens, at' / 58, a breaking point in the series circuit comprising the respective lower windings of the line test relay 720, and of the pulse relay of seeker 820, releasing this last relay.

   At 759, relay '/ 55 opens a new point in the finder switch magnet actuator circuit 816.



   Line relay 630, operating as explained above, closes, at 632, a circuit to indicate calling line 14. in the contacts of the seeker switch bank 500, this circuit going from the ground. in 45'7, by means of 451, 485, of the brush holder 554 and its associated rest contact, of 483, 442, 413, 484, 632 and 5/1, at the first contact of the bench associated with the door -brush 503.



  At 631, relay 630 closes a circuit to energize finder start relay 520, this circuit going from ground at 631, through 484 'and winding 520, to. drums. While operating, relay 520 closes, at 521, the operating circuit previously described for operating magnet 530, thus initiating the alternating operation of this magnet and of the pulse relay 510 in the manner previously explained. Due to the alternating operation of magnet b30 and relay 510, the brush holders of seeker switch 500 advance over the contacts of their respective associated contact sets until calling line 14 is found.

   When the calling line is found, the line test relay 410 is energized as explained above and @@, when operating, performs the

  <Desc / Clms Page number 58>

 functions previously explained. In addition, this relay closes, at 414, a circuit for energizing the delayed-operation cut-off relay 620, this circuit going from the ground at 452, via 414, 41, the brush holder 504 and its first associated contact, of 575, and of the winding of b20 to the battery.

   While operating, relay 620 closes, in b22, a clean holding circuit, this circuit going from the ground to the armature 644 currently in the working position of the locking relay 640, via 622 and the winding of 620 , to the battery, In 621, the relay 620 disconnects the lower winding of the line relay 630, from between the line conductors of the urban line 14.

   With the same armature, the relay 620 opens a point c'e rupture in the circuit previously described, to energize the line relay 740 from the battery connected to the resistor 646. When the locking relay 640 operates, it opens, in 544, a cutoff point in the line relay 630 holding circuit, causing the latter relay to drop to cut, at 631, the operating circuit described above for the searcher switch 520 start relay. , the relay 520 opens, at 521, a new cutoff point in the operating circuit of the magnet 530 and opens, at b22, another point in the circuit described above to excite the lower winding of 510, in series with the upper coil of relay 410.

   The pulse relay 510 drops off at this time. From this moment on, the way in which the control apparatus of circuit 16 operates to route the call to the operating position of the main exchange 9 is exactly the same as that previously explained when it was mentioned. a call made by the Tl set.



   During the course of the operations which have just been described, and when the locking relay 640 @

  <Desc / Clms Page number 59>

 operates, the circuit previously drawn, comprising the resistor 646 is closed to energize the line relay 740 existing in the circuit 21. In addition, the negative voltage of the battery is applied to the line conductor b04 of the urban line 17, to cause the operation of the control apparatus of circuit 25, which makes the "seeker" part of this circuit passive for calls made on the subscriber lines terminating at the exchange 12.



   When the line test relay 410 operates, a simplex circuit is also closed to energize the dellgne relay 740, included in circuit 21, one of the branches of this circuit going from the ground through the / 40, winding 752, 764, 767, 611, 565, brush holder 502, 495, 416, 398, winding 363 and winding impedance 365, on the battery. The other branch of this simple circuit goes from the ground through the winding of 740, of the winding 751, of 763, 766, of the contacts made before breaking associated with 615, 561, of the door -brushes 501, 496, 417, 399, winding 364, and winding impedance 36b, to the battery.

   When energized through the circuits described above, line relay 740 operates, to cause the holding relay 735 and the delayed-release control relay 710 to operate in sequence. given. The hold relay 735, while operating, closes, at 736, alternative holding circuits for each of the two relays 720 and 755, the holding circuit of the relay 755 going from the ground, at 736, through the intermediary of the winding of 755, to the battery, and the relay holding circuit '/ 20 going from the ground at 736, through 756, 757, 723, 724, and the top winding at 720, to the battery.

   When the control relay 710 operates, it opens, at '/ 13, a breaking point in the

  <Desc / Clms Page number 60>

 common portion of the initially closed holding circuits of relay 720 and 755, and opens, at 711, a break point in the previously described circuit, to energize the upper winding of tone relay 745. From the. In this way, the operation of tone relay 745 is stopped. Following the operation of relay 710, no operation of the control device included in circuit 21 occurs before the call has received a response from the operator position 15, and that the attendant on duty at this position has not made a ringing call, or has dialed a number with her disk.

   In the event that the attendant on duty at position 15 does not answer the call within a reasonable length of time, thermal timing relay 387 operates to initiate release of circuit 16 as explained below. above when it was a question of a call made to extension T1. During the release of the circuit, the cut-off relay 620 is de-energized and drops again under the effect of the release of the locking relay 640 to open its operating circuit in 644. During the release of the circuit 16, the test relay of line 410 also falls to open, at its reinforcements 416 and 417, the simplex operating circuit of line relay 740 of circuit 21.



   -When this simplex circuit is cut, the line relay 740 is de-energized and drops again to cause the successive release of this relay and of the two relays 735 and 710, in the order given. As soon as the relay 740 drops again, it closes, in 741, the circuit previously drawn to excite the relay 830 and the operating magnet 818, in parallel. This circuit is cut shortly after by the release of the holding relay 735. In this way, a pulse is sent to the operating magnet SIX, and the relay 830 will operate momentarily.

   Momentary operation or relay 830 has no effect but the excitation pulse sent to the magnet 818

  <Desc / Clms Page number 61>

 advances the connector switch brush holders 850 to their respective first non-normal positions, thereby closing the non-normal springs 827.

   When these spells are formed, the previously described circuit for energizing relay 830 and magnet 818, through the circuit break contacts controlled by armature 819, is closed. @
The result is -, the operation of the magnet 818, like a shaker, to bring the brush holders of the switch 850 to their respective rest positions, and at this time the out-of-normal springs 827 are open to cut off the drive circuit of relay 830 and magnet 818. In this way, the operation of the connector switch is stopped, and the relay 830 drops out.

   When the hold relay 735 drops again, it opens, at 736, a cutoff point in the common part of the alternative hold circuits described above for the two relays 720 and 755, causing each of these to drop. two relays. Shortly thereafter, relay 710 drops again to prepare again the original holding circuits of these two relays. Following the operation of the magnet 818, to return the brush holders of the connector switch to their normal position, the circuit 21 is fully released.



  Routing of a call to a subscriber line going to the tandem exchange .-
If the call, routed to the operator position 15, receives an answer, by activating the call key 380, to its out-of-normal position before the thermal shock operates, to initiate the release of the call. Switching device, the four relays 330, 320, 470, and 440 will operate successively, in the order given and in the manner which has been previously explained.

   Relay 440, in operation

  <Desc / Clms Page number 62>

 yet, opens, at 442, a breaking point in the circuit previously described to energize the upper winding of tone relay 340, in parallel with heating element 388 of thermal relay 387, thereby stopping the operation of the tone relay and to de-energize the heating element. The result is, 1, stopping the thermal relay 387 before the release of the automatic switching apparatus has taken place in the manner just explained, bi, by answering a call and checking the connection. i on, the operator does not receive a response,

   it can activate the bell key provided in its circuit. cords, to return the ringing current through the established connection, in order to energize the existing signaling device at the calling station T4. When ringing current is passed along the established connection, both AC relays / oU and 450 are energized and operate. However, the operation of relay 450 has no effect. When relay 730 operates, it operates to open, at 731, a break point in the circuit previously described to bypass the lower winding of the associated line relay 700 at calling line 22.

   From there, when the upper winding of the line relay 700 is energized by the ringing current transmitted to it through the ringing current source, provided at central 9, it operates to close the circuit previously described. to excite its lower winding. As a result, relay 700 remains in its full working position during the entire ringing call, so that its top winding is disconnected between the conductors of the calling line and ringing current is not diverted. by bypassing the signaling device provided at the calling station. Relays 450, 730 and 700 drop in an easy to terminate manner when the ringing call is terminated.

   When the calling subscriber answers the call, he can converse with the operator on duty at. position 15, and

  <Desc / Clms Page number 63>

 instruct the operator of the particular set requested. If the call is to be routed to a line terminating at the main exchange 9, the attendant can extend the communication to the desired station in the manner conventionally employed in manual office practice. On the other hand, if the connection is to be routed to an extension associated with a line terminating at tandem exchange 10, such as, for example, extension T2, the desired connection can be established under the control of the operator. operator of the central 9, exactly as described above, when there was a question of a call made by the telephone Tl.

   After the connection is completely established, the attendant maintains the call key 380 in its out-of-normal position to keep the automatic switching apparatus in its working position. At the end of the conversation, and when the disconnection signal has been received by the attendant, the latter can initiate the release of the apparatus by returning the call key 380 to its normal position. it should be noted that the two circuits 16 and 21 are released exactly as described previously. In this case, however, the release of the circuit 21 is initiated under the effect of the drop of the circuit test relay 410, to open the simplex circuit previously described, through which the line relay 140 of the circuit 21 is kept excited.



  Routing of a call to a subscriber line subscribing to the sub-central 12.



   If the call must be routed to a set, such as T5 set for example, connected to a line ending at sub-central 12, the attendant closes the two digits of the call number designating the set. longed for. In response to the pulses of the first digit, the connector switch 5bO operates to bring its brush holders to the contacts terminating the city line conductors 17 going to sounds - central 12. Shortly following the end of this digit. , the. relay to li-

  <Desc / Clms Page number 64>

 deferred beration 455 falls back to close the operating circuit previously described, for the control and switching relay 430.

   This latter relay, in turn, functions to close an excitation circuit of relay 420, in series with line switching relay 650, included in the line circuit associated with city line 17, this circuit going from the ground through the 420 winding, 432, the associated pre-break contacts at 467, 487, the brush ports b53, 592, and the 650 winding, to the battery, The two relays 650 and 420 then operate to close a simplex pulse circuit going from the battery and through resistor 333, to energize the line relay of the seeker-connector circuit 2b, provided in the sub-central 12.

   At 652, the relay 650 opens the circuit previously drawn to put the negative potential of the battery on the urban line conductor 604, as soon as the circuit simplex is closed which has just been mentioned. In this way, the circuit 25 control apparatus is conditioned to act under the effect of the pulses of the 2nd digit formed at the operator position 15.



  At the start of the 1st pulse of the 2nd digit, relay 455 is energized again and operates to close the switching circuit previously described for the digit transfer relay 460. This last relay, in turn, operates for close the circuit described above to bypass the winding of relay 465.

   During the pulses of the 2nd digit, the line relay 330 operates to repeat the pulses transmitted by the disk, by borrowing the previously mentioned simplex circuit, towards the line relay of circuit 25, which causes the positioning by the "connector" part of this switch of its brush holders on the contacts terminating the conductors of the line called 26. At the end of the second digit, and when the relay 455

  <Desc / Clms Page number 65>

 drops out, the circuit shorting the winding of relay 465 is cut, allowing this relay to be energized. in series with the winding of the relay 460. The relay 465 then operates to open, at 466, a point in the operating circuit of the relay 460, and to close, at 467, a holding circuit for the control relay. 650 line switching.



  * This holding circuit going from the ground in 473, through the intermediary of 467, 487, of the brush holder 553, and of sounds inond - associated contact 592, and of the winding of 650, to the battery .



  Relay 465 then operates to open, at the break contacts associated with 467, a break point in the series circuit previously described to energize the windings of the two relays 420 and 650 in series, which causes the drop to drop. relay 420. On de-energizing, relay 420 cuts, at 421 and 424, the previously described simplex circuit, through which pulses are sent to the line relay of the finder-connector circuit 25.



   By the break contacts associated with 421 and 424, the relay 420, on falling, closes a simplex AC circuit going, via an impedance 365, of the repeater windings 363 and 364, and of the conductors. 398 and 399 of the loopback line, to maintain the finder-connector circuit line relay 25 in its working position for the duration of a call. Following the fall of relay 420, in the manner just described, the desired connection is completely closed between the calling station T4 and the station called T5.

   To indicate to the called subscriber that his set is called, the operator activates his ringing key to send ringing current through the two branches of the connection established, thus to excite the signaling device provided both to the calling sets. and called. Finally, the desired speech circuit is closed when the calling and called parties activate the receivers provided at the calling stations.
 EMI65.1
 and called to connect the telephone devices provided rA-

  <Desc / Clms Page number 66>

 
 EMI66.1
 at these two stations on the calling lines, respectively 22 and 26.



   At the end of the conversation, and when the attendant on duty at position 15 receives the disconnection signal
 EMI66.2
 usual, it can activate the call key 0.51: $ 0 at its normal position, in order to initiate the release of the automatic switching device provided for the three exchanges.
 EMI66.3
 , ī¯, ai and 12. When Ir. key 380 is 1 ', - L.Cl1C: e at pOi: Ltj () r: normal, circuit 16 provided for central 10 and circuit 21 provided for central 11 are released exactly the way
 EMI66.4
 which was explained above.

   The way in which the circuit of the r: recte nr rechercheEUr25 provided at the central le is released is in all points of view similar to the mode of release of the circuit 21 located in the central 11., noting that the release of the circuit
 EMI66.5
 cooked 5 is initiated when both rF.:laisôda0. '. 640 râtom- b2nt 1) OUY 'open, respectively, the original operating circuit and the simplex holding circuit for the line relay included in this circuit.
 EMI66.6
 routing Q¯1.aJ2.pel ... r:} ge..ê;

   tr: 1.i.Gn. of subscriber subscribing to the exchange It hi the call routed to position ô.'o0eratrice 1-5 from the calling set T4 must be extended to a set associated with another line ending at sub-central
 EMI66.7
 11, the operator supervising the call forms the two digits of the call number designating the station called. for example, if the T3 set associated with line 23 is the called set, the attendant forms the two digits of the call number 12 designating the called line 23. n response to the single pulse of the first digit, the connector switch 550 brought its calais holders to the contacts corresponding to the urban line 14.

     At the end of the digit, relay 4bb drops out to close the operating circuit described above.

  <Desc / Clms Page number 67>

 cédeemment fear relay 43U. This last relay operates in turn, to close the circuit previously described in order to energize the winding of relay 420, in series with the winding of line switching relay 610, existing in the line circuit associated with the relay. city line 14. As a result, the conductors of the city line 14 are disconnected from the line brush holders of the finder switch 500 and are connected through the conductors 581 and 585 and the brush holders of the connectors. line 551 and 5b2 to loop line conductors 494 and 493 respectively.

   since the relay 420 is also in the working position, the simplex circuit described above, comprising the resistor 333 is closed to keep the line relay 740 of the circuit 25 in the working position.



  From this point, the way in which the pulses of the th digit are repeated by line relay 330, through the simplex pulse circuit, to line relay 740, to bring the brush holders of the switch connector 850 on the contacts terminating the conductors of called line 23, is exactly the same as that described previously, with regard to the call routed to the T4 set associated with line 22. At the end of the 2nd digit, and when the delayed release relay @@@@@@@@@@ 830, included in circuit 21 drops, a metallic connection closes between the calling and called lines, respectively 22 and 23.

   This connection includes searcher switch 800 line brush holders 801 and 802, loopback circuit conductors 864 and 866, loopback line conductors 863 and 865, and line loop holders 851 and 852 of the connector switch 850.



  After the end of the ringing operation, the desired voice circuit is closed by the intermediary of the connection when the called subscriber lifts his receiver from his hook.

  <Desc / Clms Page number 68>

 chet to answer the call, and that the calling subscriber
 EMI68.1
 coils its receiver from its hook so that its device is connected to Hgne 2. After the end of the conversation, the authentic switching device is released; GX8 ctHm6nt as previously described, when the operator on duty at position 15 returns her call key 390 to its normal position.
 EMI68.2
 



  Ù: a - ') 61 éHiis à la posilti :: JD d' op81'atl'Íce 1: 5. As mentioned above, calls routed to operator position 15 from subscriber lines terminating at the main exchange can be directed to a line terminating at any of the exchanges 10, 11 and 12. , under the control of the operator in service at position 15 For this purpose, the operator can
 EMI68.3
 8a if the automatic switching device one, nor, 18nl, where this device is available, by bringing the key 380,
 EMI68.4
 1 its out-of-normal position to close the simplex t circuit previously described in order to energize the line relay 3: 0.

   This relay, on functioning, initiates the operation of the three relays 20, 470 and 440, in the manner previously explained. When the relay 440 operates, it opens, at 442, a breaking point. in the maneuver circuit
 EMI68.5
 previously described, for the departure relay of the che :: cheur .b0, in order to prevent this relay from operating in response to calls made on subscriber lines going to the exchange in tandem 10.

   At 441, relay 40 closes the pre-circuit.
 EMI68.6
 2nd described, going through 471 and energizing latch relay 640. The relay 640, while operating, closes the circuits previously described to put the negative voltage of the battery on each of the con-
 EMI68.7
 urban line drivers (\) '(and C4, respectively li-

  <Desc / Clms Page number 69>

   urban fords 14 and 17. it follows that the control device, and more particularly, the relays 740, 735,
 EMI69.1
 lu and t55 included in the circuit ni operate in the order given.

   The last of these relays, when operating, opens, at 759, a point in the circuit previously described to energize the actuating magnet 816 of the finder switch. as a result, the seeker switch of circuit 21 remains passive to calls made on subscriber lines going to sub-central 11.

   Similarly, setting the negative battery of the conductor 604 of the urban line 17 to the potential causes the operation of the control device included in the circuit 25, to make the seeker switch passive to calls made. on the subscriber lines going to the exchange 12? Following the operation of the relays referred to above, the call can be routed to any extension associated with a line terminating at any of the three exchanges 10, 11 and 12, exactly from the manner previously described, with reference to the calls made by the Tl and T4 sets. Likewise, the manner in which the switching apparatus provided for in the three exchanges is released, when the operator returns the key 380 to its normal position, is the same as that previously described.

   
 EMI69.2
 



  The recording d) a-p-oels.-
As indicated above, if a call is made on a line going to one of the three exchanges 10, 11 and 12, at a time when the automatic switching device provided at the tandem exchange 1 U is busy . the call is held until the switching apparatus becomes available and is then routed to operator position 15, without any further involvement from the calling subscriber.

   In this way, if a call is made to the station

  <Desc / Clms Page number 70>

 At a time when the circuit 16 is occupied, the switching circuit previously described for the finder start relay 520 is cut at each of the two: armatures 413 and 442. As a result, the operation of the line relay 680, under the 'effect of the ringing current sent via line 18, under the action of the hand-held magneto
 EMI70.1
 693 has no effect to initiate the operation of the finder switch 500.

   In this case, however, since
 EMI70.2
 line 18 is not included in the previously re-established connection, routed through the intermediary or circuit25, the
 EMI70.3
 conductor b '? (' is cut off from the ground, so that the lower winding of relay 680 is e "quoted and the relay remains locked in its working position * Afterwards,
 EMI70.4
 s when the circuit 1 0 is released, the last operation that takes place is the operation of 7 ¯ operating magnet of the
 EMI70.5
 connector switch b40, to return the brush holders of connector switch 530 to their rest positions
 EMI70.6
 resDp-ctîves * During this operation, the brush holder b54 is earthed -because the circuit comprising 485 and the armatures 4bl and 4 fallout, it follows that.

   The lower anroulemb-.t of relay 080 in the working position may be momentarily short-circuited when brush holder 554 has crossed its 3rd associated contact. When, however, the lower end of bSO is c!? Tt-eircuit, the release of this relay is slightly slowed down and; since the brush holder 584 is moving at. high speed, the short circuit is cut before the 58G relay drops out. ar SIX 'te, it does not result from the operation CI :; 1 ib -: - ration of the connector switch 550, the release of water from the line relays associated with the subscriber lines leading to central 10 and which is'. in working position.



   When brush holder 554 has returned to its position
 EMI70.7
 de r.pos, -t while the line relay b80 is in position

  <Desc / Clms Page number 71>

 When working, the previously described circuit closes to energize seeker start relay 520. Hence, operation of seeker switch bOO to seek calling line 18 takes place as soon as circuit 16 is released. The way in which the calling line is found .., and the call is routed to operator position 15 is exactly the same as described above, referring to the call made by extension T1 at a time when the automatic switching device is available.

   Similarly, if a call is made on a line terminating at a sub-exchange, at a time when the automatic switching apparatus provided at the tandem exchange 10 is busy, the call is recorded. until the switching device in the working position is released; after which, it is automatically routed to the operator position 15 of the main exchange 9. Under the specified conditions, the four relays 740, 735, 710 and 755 of the connector finder circuit 21 are all in the working position. With relay 755 in its operating position, the actuator circuit of the actuating magnet 816 of the seeker switch is held open at 759.

   Hence, if a call is made on one of the lines going to the sub-central 11, such as for example line 22, the operation resulting from the line relay 700 is only effective to cause the operation. of the finder start relay 825.



  While operating, relay 825 operates to prepare, at 826, the operating circuit of magnet 81b, but this latter circuit is kept open at 759 until circuit 16 in the working position provided in the control unit. 10 is released to cause the Burst of the 4 relays 740, 735, 755 and 710 in the order given. When relay 755 drops, it closes the operating circuit of the magnet 816 and prepares the operating circuit of the pulse relay 820.

  <Desc / Clms Page number 72>

 



    In this way, the operation of the seeker switch 800, to capture the reign 22, is initiated. From this point on, the way in which the connection is routed to the operator spangle 15 is exactly the same as that described previously, referring to the call made to mate T4 at a time oL. The automatic switching device for the three exchanges 10, 11 and 12 is available.



   Claims.



  1.- Telephone system having a tandem exchange and a plurality of sub-exchanges associated with it, in which the paging operation which takes place during the sending of a call to connect the calling party to a selector switch is inhibited during the period when the tandem exchange switchgear is not available.



  2.- Telephone system, having an exchange in tandem and a plurality of sounds-exchanges associated with it, all provided with searcher-connectors circuits, in which the searcher switches of the sub-exchanges are rendered inoperative for the period during which the switching device of the tandem exchange to which the sub-exchanges have access is not available.

** ATTENTION ** end of DESC field can contain start of CLMS **.


    

Claims (1)

3. - Telephone system having a tandem exchange and a plurality of sub-exchanges associated with it, in which, if the switching apparatus of the tandem exchange to which the sub-exchanges have access, becomes unavailable, the switching device of the sub-office is disabled, and calls arriving at the sub-offices are registered for subsequent routing to the tandem exchange. <Desc / Clms Page number 73> 4.- Telephone system having a tandem exchange and a plurality of sub-exchanges which. are associated with it, and employing operators to follow up on communications sent by subscribers to sub-central offices, in which, when a call is sent by a subscriber to a sub-office, a connection is automatically established by passing through the tandem exchange, to an operator position where a sound is transmitted to the calling party, while if the switching device to the tandem exchange is unavailable, the switching device. switching of the sub-exchange is made inoperative, and no dial tone is transmitted to the calling party. 5. - Telephone system according to claims 1, 3 and 4, wherein the connections formed by subscribers of the sub-central and the tandem exchange are completed by operators placed at a main exchange associated with the tandem exchange. 6. A telephone system according to claims 1, 2, 3 or b, in which the connection originating from a subscriber calling from a sub-exchange or from a tandem exchange is automatically routed to a telephone. attendant position, from which a sound is transmitted to the calling party. 7. A telephone system according to claims 4 or b, wherein the searcher-connector circuits are employed in the sub-exchanges and the searcher switches are rendered inoperative, if the central switching apparatus. in tandem is unavailable. 8.- telephone system, according to claims 1 to 7, wherein, when the pager switches of the sub-exchanges are made inoperative, a call formed by a subscriber of a sub-exchange is recorded and auto-routed. <Desc / Clms Page number 74> EMI74.1 ...:. tà.que, îicnt à. through the exchange in tandem, when the switching device # 1.1 which.: 'is found becomes available. E '.- System known as tE :: lépjlO1G 01-'V9!}' The claims or the, in which the searcher switches are irrelevant oai 'the opening of the circuits of their magnets, causing the osriode will have which the COnil7îàtCi.lOia device at the central tandem and unavailable. llj.- teleohzne bystem according to claims 1,, 3, r or 8, in which, when the unit of cOYIL "l1utati () I1 of the tandem exchange becomes unavailable, a battery at EMI74.2 resistance is applied in the tandem exchange to a conductor of the city lines existing between the tandem exchange and the sound-exchanges to make the finder switches in the sub-exchanges inoperative. 11. The telephone system of claim 8, wherein when a subscriber of a sub-exchange forms a call, a relay operates to prepare a circuit for the finder switch magnet. 12. A telephone system according to claim 11, wherein the relay locks independently of the subscriber's circuit, so that it operates. EMI74.3 finder switch switch, as soon as the remote tandem switchgear becomes available. 13. A telephone byseme according to claims 1 to 12, wherein a single finder-connector circuit is provided at the tandem exchange and at each of the sub-exchanges. EMI74.4 The telephone system, substantially as described and illustrated in the accompanying drawings. EMI74.5 1 If / 1 Ir ..-