US2358017A - Telephone system - Google Patents

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US2358017A
US2358017A US471683A US47168343A US2358017A US 2358017 A US2358017 A US 2358017A US 471683 A US471683 A US 471683A US 47168343 A US47168343 A US 47168343A US 2358017 A US2358017 A US 2358017A
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relay
line
contacts
subscriber
circuit
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US471683A
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Clarence E Lomax
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Automatic Electric Laboratories Inc
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Automatic Electric Laboratories Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/42—Systems providing special services or facilities to subscribers
    • H04M3/54—Arrangements for diverting calls for one subscriber to another predetermined subscriber

Definitions

  • the present invention relates to telephone systems and more particularly to such systems arranged to render secretarial service to certain subscriber substations served thereby.
  • agencies independent of the telephone operating company provide a type of service known as secretarial service, whereby certain subscribers, such as doctors, salesmen and others who do not have secretaries and whose duties require that they be absent from their ofiices for considerable periods of time, may have calls directed to their substations intercepted and forwarded to the agencies mentioned.
  • a call thus intercepted is answered by a secretary at the agency; and, after the secretary makes inquiry and learns the desired called subscriber, she gives the calling subscriber certain information in accordance with the prior instructions of the called subscriber.
  • Another object of the invention is to provide in a telephone system comprising a number of ofiices, an improved arrangement for rendering from an operator position in the central oflice secretarial service to certain subscriber substastitute and to discontinue interceptor service at certain subscriber substations served thereby,
  • a further object of the invention is to provide in a telephone system an improved intercepting arrangement, whereby calls extended both to and from subscriber substations at which ini type.
  • the telephone system there illustrated comprises'a central ofiice ID of any suitable type and a branch ofiice 20 of the automatic
  • the central ofiice l0 includes a secretary operator switchboard or position H of the manual type; and the branch oifice 20 serves a group of automatic subscriber substations, including the subscriber substations Tl, T2, T3 etc.
  • the subscriber substations in the branch oflice 20 are divided into a first subgroup, including the subscriber substation Tl, which is rendered ordinary automatic subscriber substation service, and a second subgroup, including the subscriber substations T2 and T3, which is rendered secretarial the subscriber.
  • , 22 and 23 respectively terceptor service is enforced are routed to ,an'"
  • each of the subscriber lines which is rendered secretarial service is providedrwith a secretary line circuit individual thereto, the secretary line circuits 32 and 3-3 being individual to the subscriber lines '22 and 23 extending to the" subscriber substations T2 and T3 which are rendered secretarial service,
  • the branch exchange 20 comprises local automatic switching apparatus including a number of local links, oneof thelocallinks, being illustrated as dered secretarial service.
  • branch ofiice 20 comprises a number of linefinders 4
  • a line finder' dis tributor 34 is operatively associated with the line finders 4
  • , 42 etc. for the purpose of assigning an idle line finder for the use of either a calling or called subscriber line extending vto a subscriber substation which is rendered'secretarial comprises a secretaryservice switch'll operatively connected to a trunk 12 extending between erator position II.
  • the secretary service switch II has access to the various secretary line circuits 32, ,33 etc. individually associated with the subscriber lines 22, 23 etc. extending to the subscriber substations T2, T3 etc. which are rendered secretarial service. 7
  • the central oflice I0 comprises, in addition to the secretary operator position II, anumber of secretary connectors 5I, 52 etc. respectively cor- V responding to the line finders M, 42 etc. and operatively connected thereto by means of a number of trunks 6
  • the actual number of-local finder-connector linksprovided inthe branch ofiice 20 is determined .by the amount of local traffic therein; while the actual number of line frisecretary connector links required between the branch oflice 20 and the central ofiice I0 is determined by the peak amount of secretarial trafiic between the branch office 20 andthe central office I 0. At this point it is noted that anysubscriber substation rendered ordinary. service may be converted,
  • each of the line is a line;
  • the secretary operator position II comprises, as shown in Fig. 3, in addition to the jacks J2, J3, JI I, JIZ etc., position apparatus not shown; whereby the operator thereat may answer calls on the trunks 62, 83
  • the trunk I5 may control, via the trunk 12 the secretary service switch II in the branch ofiice 20.
  • Also associated with the jacks J2 and JII aresignal lamps L382 and L38l, respectively, which are utilized for a purpose more fully explained hereinafter.
  • each of the secretary connectors in the central oilice I0 is identical to the secrek tary connector 5
  • theswitching mechanism 400 includes'a vertical magnet M405 ;for driving the I wiper setand the'vertical control wiper 404 step by step in the vertical direction away from their normal vertical positions; a rotary magnet M401" for driving the wiper set step by step-in the rotary merely by the provision of a secretary line circuit "direction away from its normal rotary Position,
  • a release magnet M409 for releasing the wiper set and the vertical control wiper 404- and for causing the wiper set to be returned to its normal rotary and vertical positions and for causing the vertical control wiper 404 to be returned to its normal vertical position;
  • Also associated with the switching mechanism 400 are two sets of switch springs S4l0 and S413 which are actuated when the wiper set is moved one step in the vertical direction away from its normal vertical position and a set of switch springs $414 which is actuated when the wiperset is moved eleven steps in the rotary direction away from its normal rotary position.
  • comprises a repeating coil 435; a relay group, including a pulse relay R420, an answer relay R430, a start relay R440, a cutoff relay R450 and a test relay'R460; and a control network connected and arranged in a manner more fully described hereinafter.
  • the line finder distributor 34 comprises, as shown in Fig. 2, a switching mechanism 200 of the rotary type, including five wipers to 205, inclusive, provided with individually associated contact banks, and a magnet M206 for driving the wipers noted in the clockwise direction; the switching mechanism 200 having access via the cable 410 to'the various line finders 4
  • the line finder distributor 34 comprises a relay group, including a start relay R2l0, a test relay R220, a step relay R230, a transfer relay R240, and a "cutoff relay R250; and a control network connected and arranged in a manner more fully described hereinafter.
  • each of the secretary line circuits in the branch office 20 is identical to the secretary line circuit 32 individually associated with the subscriber line 22 extending to the subscriber substation T2 which is rendered secretarial service.
  • the secretary line circuit 32 comprises, as shown in Fig. 5, a relay group, including a cutoff relay R560, a start relay R565 and a service relay R510; and a control network connected and arranged in a manner more fully described hereinafter.
  • the local line circuits 24, 25 etc. are of conventional connection and arrangement and are. of any suitable for'm.
  • the local links are of any suitable type; however, it is preferable that both the local finders and the local connectors thereof be of conventional Strowger types of standard connections and arrangements.
  • the local distributor 29 is of any suitable form and may be quite similar in connection and arrangement to the line finder distributor 34' illustrated.
  • the secretary service switch H comprises, as shown in Fig. 5, switching mechanism 500 of the Strowger type, icluding a wiper set provided with six wipers 50l to 506, inclusive, supported for both vertical and rotary movements, and an associated semicylindrical contact bank provided with ten vertically spaced-apart levels of contact sets arranged in circumferentially spaced-apart relation,
  • the switching mechanism 500 includes a vertical magnet M50!v for driving the wiper set step by step in the vertical direction away from its normal vertical position, a rotary magnet M508 for driving the wiper set step by step in the rotary direction away from its normal rotary position, and a release magnet M509 for releasing the wiper set and for causing it to be returned to its normal rotary and vertical positions.
  • the secretary service switch H comprises a select switch 520 of the minor type, including a single wiper 52L provided with an associated contact bank, a rotary magnet M522 for driving the wiper noted step by step in the counterclockwise direction away from its normal rotary position, and a release magnet M523 for releasing the wiper noted and for causing it to be returned in the clockwise direction back into its normal rotary position.
  • the secretary service switch H comprises a relay group, including a line relay R530, a hold relay R535, two transfer relays R540 and R545, a switch relay R550, and a control relay R555; and a control network connected and arranged in a manner more fully described hereinafter.
  • Institutirzg secretarial service at a subscriber substation in the branch office When a subscriber ata subscriber substation in the branch office 20 which is rendered secretarial service desires to utilize this service, he first extends a call to the secretary operator position It in the central office i0 and advises the operator thereat concerning any information which is to be givento other subscribers calling the subin his absence.
  • the subscriber thereat removes the receiver from its associated switchhook; whereby the local line circuit 25 is controlled over the subscriber line 22. More specifically, the local line circuit 25 controls thelocal distributor 29, whereby an idle local link, such, for example, as the local link illustrated is assigned and the local finder 21 thereof is operated to seize the subscriber line 22 extending to the calling subscriber substation T2. When the local finder 21 seizes the subscriber line 22,, the
  • subscriber line 22 is marked as busy via the control conductor C22B thereof to the local connectors having access thereto and the local connector 28 is conditioned to be operative in response to one or more digits received over the calling subscriber line 22.
  • the subscriber'at the calling subscriber substation T2 then dials one or more digits'over the subscriber line 22, whereby the local connector 28 is operated to select the trunk 15 extending to the secretary operator position H in the'central ofiice l0.
  • the local connector '28 tests the idle or busy condition of the selected trunk' 15 causing busy tone current to be returned over the subscriber line 22 to the calling subscriber substation T2 in the event the trunk 15 is busy at this; time.
  • the local connector '28 operates to seize the trunk 15, "whereby ground potential is applied tothe control conductor C15A thereof in order to mark the trunk 15 as busy to the other local connectors having access thereto and to complete an obvious circuit, including the contacts ofthe jack JII, for illuminating the signal lamp L38I.
  • the H lumination of the signal lamp L38I indicates the presence of'a call on thetrunk,15; 'whereby the operator at the secretary operator position I I answers the call by inserting the answer plugv of the cord circuit into the jack J II effecting the extinguishment of the signal lamp L3!
  • both the subscriber at the calling subscriber substation T2 replaces the receiver upon its associated switchhook and the operator at the secretary operator position II withdraws the answer plug of the cord circuit from the jack JI I
  • the local finder 21 and the local connector 28 are released, whereby both the subscriber line 22 extending to the subscriber substation T2 and the trunk 15 terminating in the jack JII at the secretary operator position II are rendered idle Vto'the local connector having access thereto.
  • the operator at the secretary'operator position 'I I then inserts the call plug of the cord circuit into thejack J I2 terminating the trunk 12 extending between the central office I and the branch office 20, whereby an obvious circuit is completed for energizing in series the upper and lower windings of the line relay R530 in thesec- :retary service switch H in the branch oflice 20.
  • the second and third digits are effective to operate 1 the switching mechanism 500, thereby to select the particular secretary line circuit associated 'With the subscriber line extending to the subscriber substation at which secretarial service is to be instituted or discontinued as the, case may be. More particularly, in the present example, in order to institute secretarial service at the subscriber substation T2, the three digits idialed are 1, 2 and 2; the first digit 1 indicating that secretarial service is to be instituted at the subscriber substation T2 and the second and third digits 2 and 2, respectively, identifying the secretary line circuit 32 individual to the sub- ,scriber line 22 extending to the subscriber substation T2. 7 V V i ,More particularly, the line relay R530 follows the single impulse of the'first digit 1 restoring and then reoperating. Upon restoring, the line relay R530 interrupts, at the contacts 53I, the
  • the transfer relay R540 restores, thereby to complete, at the contacts 54I, the'previ0us1y mentioned circuit including the contacts 536 and the set of switch springsS524, for energizing the winding of the transfer relay R545.
  • the transfer relay R545 operates to co'mplete, at the contacts 545, an obvious holding circuit, including the contacts 535, for energizing the winding thereof.
  • ⁇ Also the transfer'relay R545 interrupts,
  • the line'relay R530 then follows the second digit 2, thereby to complete, at the contacts 532; 'the first time it restores, the previously mentioned circuit, including the contacts 531, the contacts 5i I of the set of switch springs S5I0 and the contacts 541, for energizing the winding of the transfer relay R540 inrseries with'the vertical magnet M501; whereby the transfer relay R540 reoperates and the vertical magnet M501 operates wiper set of ,the switching mechanism 500 is driven one step in the vertical direction away from its normal vertical position, the sets of switch springs S5I0 and S5I3' are actuated More particularly, the set of switch springs S5I0 is actuated, thereby to interrupt, at the contacts 5Il thereof, a further point in the previously traced circuit'for energizing the winding of the transfer relay R540 in series with the vertical magnet M501 and to prepare, at the contacts'5l'2 thereof, an alternative circuit traced hereinafter for energizing the winding of
  • the set of switch springs vS5I3 is actuated into engagement, thereby to' prepare multiple circuits traced hereinafter for energizing the release magnets M523 and M509 of the select switch 520 and the switching mechanism 500, respectively.
  • the line, relay R530 follows the impulses of the second digit 2, where by the hold relay R535 and the transfer relay R540 remain operated during impulsing and the wiper set of the switching mechanism 500 is driven two steps in the vertical direction away from its normal vertical position.
  • the transfer relay R540 restores, thereby to interrupt, at the contacts 542, a further point in the previously traced alternative circuit for energizing in series thewinding of the transfer relay R540 and the vertical magnet M501;
  • the transfer relay R540 prepares, at the contacts 543, a circuit traced hereinafter for energizing in series the winding of the control relay R555 and the rotary magnet M508 .of the switching mechanism 500.
  • the line relay R530 then follows the impulses of the third digit 2, thereby to complete each time it restores, at the contacts 532, the previously mentioned circuit, including the contacts 531, the contacts 512 of the set of switch springs S5l0 and the contacts 543 and 553, for energizing the winding of the control relay R555 in series with the rotary magnet M508, whereby the control relay R555 operates and the rotary magnet M505 operates and restores twice in order to drive the wiper set of the switching mechanism 500 two steps in the rotary direction away from its normal rotary position.
  • the control relay R555 is of the slow-to-release type, whereby the latter relay and the hold relay R535 remain'operated during impulsing.
  • the line relay R530 remains operated and, shortly thereafter, the control relay R555 restores.
  • the wiper set of the switching mechanism 500 engages the 2 up 2 in contact set in the associated contact bank.
  • the control relay R555 completes, at the contacts 556, a circuit, including the contacts 536, the wiper 52I of the select switch 520 and the engaged first contact in the associated contack bank, the wiper 501 of the wiper set of the switching mechanism 500 and the engaged contact in the associated contact bank, the conductor C58!
  • the switch relay R550 operates to complete, at the contacts 552, an obvious holding circuit, including the contacts 536, for energizing the lower winding thereof. Also the switch relay R550 interrupts, at the contacts 553, a further point in the previously traced circuit for energizing the winding of the control relay R555 in series with the rotary magnet M508, thereby positively to prevent further operation of'the switching mechanism 500 at this time. Further the switch relay R550 completes, at the contacts 551, an obvious path for short-circuiting the upper winding thereof,
  • the service relay R510 When thus energized the service relay R510 operates to complete,-at the contacts 51!, an obvious holding circuit, including the resistor 513, for energizing the winding thereof. Also the service relay R510 completes, at the contacts 512, an obvious connection "between the winding of the start relay R5155 in the secretary line circuit 32 .and the control conductor C22B of the subscriber line 22 extending to the subscriber substation T2,1for-a purpose more fully explained hereinafter.
  • secretarial service has been instituted at the subscriber'substation T2 in the branch office 20 by the operator at the secretary operator position II in the centraloflic'e l0 over the trunk 12 by the operation of the -secre-,
  • the holdrelay R535 interrupts, at the contacts 536, the previously traced multiple holdjing circuits for energizing the winding of the transfer relay R545 and the lower winding of the switch relay R550, thereby to cause the relays mentioned to restore. Also the hold relay R535 completes, at the contacts 538, the previously mentioned multiple circuits, including the .contacts 532 and the set of switch springs S513, for en'- ergizing the release magnets M523 'andiM509. When thus energized the release magnet M523 operates, thereby to release the wiper 52l of the selectswitch 520 and'to cause it to be returned in the clockwise 'direction'back into its normal rotary position.
  • the release magnet M509 When thus energized the release magnet M509 operates, thereby to release the wiper set of the'switchingmechanism 500 and to cause it to be returned to its normal rotary and vertical positions.
  • the sets of switch springs S5l0 and S5I3 are actuated. More particularly, the set of switch springs S5l 3 is actuated into disengagement, thereby to interrupt the previously traced multipleicirouits for energizing the release magnets M523 and M509 in 'order to cause these release magnets to restore. At this time the secretary service switch 1lis completely released.
  • removes the receiver fromits associated switchhook; whereby the localline circuit 24 is con trolled over the subscriber line 2
  • the local line circuit 24- controls the local distributor 29, whereby an idle local link, such, forexample, as the local link illustrated, is assigned and the local finder 21 thereof is operated to seize the subscriber line 2
  • is marked as busy via the control conductor C2
  • the subscriberiat the calling subscriber substation Tl then 'dails two digits over the subscriber line 2
  • the local connector 28 tests the idle or busy con dition of the selected subscriber line 22, causing busytone current'to be 'returned over the subscriber line 2
  • the magnet M206 of the switching mechanism 200 incorporated in the line finder distributor 34 is normally connected via the contacts 201 and 222 to the wiper 202 of the rotary switching mechanism 200, which wiper normally engages a contact in the associ-- sociated line finder is respectively idle or busy.
  • the local connector 28 operates to seize the subscriber line 22, whereby ground potential is applied to the control conductor C22B thereof in order to mark the subscriber 'line 22 as busy to the other local connectorshaving access thereto and to cause ringing current to be "projected over the'line conductors of the subscriber line 22 extending to the called subscriber. substation T2, whereby the ringer thereat is operated.
  • ground potential 'applied to the wiper 202 of the switching mechanism 200 completes an-obvious circuit, including the contacts 222 and 201; for energizing'the magnet'M206, whereby the latter'mag'net operates to interrupt, at the contacts 201, the previously traced circuit for energizingthe magnet M206 and to condition the wipers noted of the switching mechanism 200 to be driven one step in the clockwise direction.
  • the magnet M206 then restores, whereby the wipers noted of the switching mechanism 200 are driven one step in the counterclockwise direction and the magnet M206 is reconnected, at the contacts 201, to the Wiper 202 of the switching mechanism 200; whereby .the next line finder 4
  • the switching mechanism 200'incorporated in the line finder distributor 34 has operated to select the conductors extending thereto, battery'potential is applied by way ofthe' lower winding'of Q the test relay R460 in the "line finder 4
  • start relay R210 Upon operating, the start relay R210 completes,
  • test relay R220 completes, at the contacts 221, an ob vious holding circuit substantially identical-to that previously traced for energizing the winding thereof. in series with the magnet 'M206.
  • test relay R220 interrupts, atthe contacts 222, the previously traced original connection between the magnet M206 and the wiper 202 of the switching mechanism 200, and completes, at the contacts 223, an obvious alternative connection between the magnet M206 and the wiper 202. Also the test relay R220 completes, at the contacts 221, an obvious path, including the pontacts 2H and the wiper 201 andthe engaged contact in the associated contact bank, for ap-' plying ground potential tothe start conductor C415 in the cable 410, thereby to completean obvious circuit for energizing the winding of the start relay R440 in the preselected line finder 4
  • test relay R220 completes, at the contacts 224, a path, including the contactsf23lv and 24! and the wiper 203 of the switching mechanism 200 and the engaged contact in the associated contact bank, for applying ground potentialto the vertical conductor C416 in the cable 410; and completes, at the contacts 226, a connection, including the-contacts 246, between the winding of the cutoff relay R250 and the winding of the step relay R230, the winding of thestep relay R230 being connected to the interrupter conductor C414 in the cable 410.
  • completes, at the contacts 44l, a circuit for energizing in series the windings of the answer relay R430 in the line finder 4]. and the windings of the. line relay R360 in the secretary connector 5! via the trunk 6
  • the above-mentioned circuit extends v from ground by way of the lower windingof the line relay R360, the contacts 314, one of the line conductors of the trunk 6!, the contacts 42'!
  • test relay R460 being of the polarized-type.
  • start relay R440 completesqat the contacts 441, an obvious path, including theco-ntacts 451, between the vertical magnet M405 of the switching mechanism 400 and the vertical conductor C416 in the cable 410,;wherebythe vertical magnet M405 is energized and operates.
  • the vertical magnet M405 drives the wiper set of the switchingimechan'ism400s16 one. step in the vertical direction away from its normal vertical position, and completes, atthe contacts 406, an obvious path for applying ground potential to the interrupter-conductor C414 in the cable 410.
  • the wiper set of the switching, mechanism 400 When the wiper set of the switching, mechanism 400 is driven one step in the vertical direction away from its normal vertical position, the sets of switch'springs S4l0 and S4
  • the step relay R230 When ground potential is removed from the interrupter conductor-C414 the previously traced circuits for energizingin multiple the windings of the step relayfiR230 and the cutoff relay R250 are interrupted,-whereby the step relay R230 restores. However, the cutoff relay R250 does not restore immediately as it is of the slow-to-releasetype Upon restoring, the step relay R230recomp'letes, at the contacts 23l, the previously traced circuit for energizing the vertical magnet M405, whereby the'latter magnet reoperates, thereby to drive the wiper set of the switching mechanism 400 an additional step in the vertical direction away from its normalvertical position.
  • the vertical magnet M405 recompletes, at the contacts 406, the previously traced circuits for energizing in multiple the windings of thestep' relay R230 and the cutoff relay R250, whereby the step relay R230 reoperates shortly thereafter and the cutoff relay R250 is retained in its operated position as it is of the slow-.to-release type. Accordingly, it
  • the vertical magnet M405 and the step relay R230 interact in the manner described above, whereby the cutoff relay R250 is retained in its operated position and thevertical magnet -M405 andthe step relay R230 operate and restore alternately; whereby the wiper set of the switching mechanism 400 is driven step by step in the verticaldirection away from its normal vertical position.
  • the wiper set and the vertical control wiper 404 of the switching mechanism 400 aredriven'step by step in the vertical direction two"'s'tepss, in the present example, whereupon the vertical control wiper 404 engages the second contact in the associated Vertical control contact bank terminating the markconductor C418 having ground potential thereon; whereby ground potential on'the mark conductor C418 is applied to the test conductor C41l in the cable 410.
  • a multiple holding circuit is completed for energizing the lower'winding of the a transfer relay R240 in series with the winding of the cutoff relay R250; the last-mentioned circuit including the contacts-246 and 245 and the wiper 204 of the switching mechanism 200 and the engaged contact in the associatedcontact bank and a the grounded test conductor C41l in the cable 410.
  • the transfer relay R240 When the lower winding of the transfer relay R240 is thus energized the latter relay op 'erates shortly thereafter, the transfer relay R240 being of the slow-to-operate type.
  • thetransfer relay R240 interrupts, at the contacts 245, the previously traced circuitsfor energizing the lower winding of the'transfer relay R240 in series multiple relation with respect to the windings of the step relay R2 and the cutoff relay R250,'interrupts, at the contacts 246, a further p'ointiin the previously plete an obvious circuit, including the contacts 446" and 465, for energizingthe rotary magnet M401.
  • the rotary magnet M401 When thus energized the rotary magnet M401operates, thereby to drive the wiper set of the switching mechanism'400 one step in the rotarydirection away from its normal rotary position; andcompletes, at the contacts 408, an
  • the step relay R230 Upon restoring, the step relay R230 recompletes, at the contacts 231, the previously traced circuit for energizing the rotary magnet M401, thereby to cause the latter magnet to reoperate and drive the wiper set of the switching mechanism 400 an additional step in the rotary direction away from its'normal rotary position.
  • the rotary magnet M401 and the step relay R230 interact in the manner described above, whereby the wiper set of the switching mechanism 400 is driven step by step in'the rotary direction away from its normal rotary position.
  • the wiper set of the switching mechanism 400 is driven two steps in the rotary direction away from its normal rotary position, whereupon the wipers noted thereof engage the contact set in the associated contact bank terminating the conducors of the subscriber line 22 extending to the called subscriber substation T2. 7 r
  • test relay R460 operates exceedingly fast, as
  • the cutoff relay R560 When thus energized the cutoff relay R560 operate to complete, at the contacts 562 and 563, a holding circuit, including the contacts 512 and the, grounded control conductor 0223 of the subscriber line 22, forenergizing the winding thereof; Also the cutoff relay R560 completes, at the contacts 563, an
  • cutofi relay R560 interrupts, at the contacts '56I, the previously traced path for applying ground potential to the mark conductor C418, thereby to interrupt .the previously traced circuit for energizing the winding of the start relay R2 l in the line finder distributor 34 in order to cause the latter relay to restore.
  • test relay R460 interrupts, at the contacts 465, a further point in the previously traced circuit for energizing the rotary magnet M401, thereby positively to prevent further operation of the latter magnet, whereby further operation of the wiper set of th switching mechanism 400 is positively prevented at this time.
  • the test relay R460 completes, at the contacts 46
  • test relay R460 completes, at the contacts 466, an obvious circuit for energizing the winding of the cutofi relay R450, thereby to cause the latter relay to operate and interrupt, at the contacts L .a further point in the previously traced-circuit for energizing the vertical magnet M405.
  • the test relay R220 Upon restoring, the test relay R220 interrupts, at the contacts 221, a point in the previously traced path for short-circuiting the winding thereof, and interrupts, at the contacts 221, the previously traced path for applying ground potential to the start aconductor C415 in the cable 4T0, thereby to interrupt the previously traced circuit 'for energizing the winding of the start relay R440 in the line finder 4
  • interrupts, at the contacts 442, the previously traced original circuit for energizing the lower winding of the test relay R460; however, the latter relay remains in its operated position due to the previously traced completed holding circuit for energizing thelower winding thereof, including the grounded control conductor 0220 of the subscriber line 22. Also the start relay R440 interrupts, at the contacts 44
  • the step relay R230 first-controls the vertical motion of the wiper set of the switching mechanism 400, whereby the wiper set is operated two steps in the vertical direction, in the 'the'present example, and'a corresponding numberof impulses comprising the digit 2 are transmitted by'lthe step'relay R230 to the pulse relay R420 and repeated thereby over the trunk 6
  • the line finder distributor 34 is operative to control the line finder 4! to select the called subscriber line 22 and torepeatover the trunk 6
  • follows the' first digit 2 in an obvious manner;
  • the line relay R360 operated it 'completed,'at the contacts 361, an obvious circuit for energizing the winding of the hold relay R350,
  • the line relay'R 360 restores and then reoperates twice, in .the present example, in response to the two impulses of the first digit 2 transmitted over the trunk filfwhereby the vertical magnet M304 is operated aridirestored twice in order to drive the wiper set of the switching mechanism 300 two steps in the verticaldirection.
  • the hold relay The line relay R360 then follows the two 1mpulses of the second digit 2.
  • each timethe line relay'R350 restores it interrupts, at the contacts 36!, the previously mentioned circuit for energizing the winding of the hold relay R350, and completes, at the contacts 362,'the previously mentioned circuit, including the contacts 35!, the contacts 3l0 of the set of switch springs S308, and the contacts 34
  • the series relay R330 operates; and the rotary magnet M305 operates, thereby to drive the wiper set of the switching mechanism 300 one step in the rotary direction away from its normal rotary position.
  • Each timethe line relay R360 reoperates it recompletes, at the contacts 361, the
  • the series relay R330 re- "stores.
  • theowipef'SBt of the switching mechanism 300 engages the 2 up 2 in contact set in the associated contact bankv terminating the trunk 82 which is terminated by the jack.J2 at the secretary operator position II,
  • the series relay R330 completes, at the contacts 33!, a circuit, including the wiper 303 of the wiperset of the switching mechanism 300 and the engaged contact Iinthe associated contact bank, the control conductorof thetrunk B2 and the contacts of the jack J2, for energizing in series the upperwinding of the switch relay R320 and the signal lamp L382.
  • the switch relay'R320 When thisserics circuit is completed the switch relay'R320operates to complete, at the: contacts 324, an obvious holdi ing circuit, including the :contacts 353, for energizing the lower winding thereof.
  • the switch relay R320 interrupts, at the contacts 325,*a f urther point in the previously tracedcircuit for energizing the Winding, of theseries relay R330 in serieswith the rotary magnet M305, and com pletes, at the contacts 323, an obvious path, including the contacts 33l,for short-circuiting the upper winding of the switch rela R320.
  • the switch re1ayR320 completes, at the contacts R350 and the transfer relay R340, being of the *slow-to-r'elease type, remain operated during impulsing.
  • the line relay R360 remains operated in order *to retain the hold relay R350 in its operated posi- 'tio'n, whereby-the transfer relayR340'restores shortly thereafter;
  • the transfer tacts 34l acircuittraced hereinafter'for ener gizing -the1windihg of the series relay R330 inseries with the rotary magnet M305.
  • - T s I V 323 an-obvious .path forrapplying direct ground potential 'to the wiper 303 of the wiper set of V the switching mechanism'300, thereby to com plete a low resistance circuit substantially identif cal 'to that previously traced for illuminatingthe signal lamp L382.
  • switch relay R320 completes, at the contacts 32I and '322, an obivious connection, including the fwipers 3M and 302 of the wiper set of theswitching mechanism 300, between the upper and lower windings of 7 the battery reverse relay R310 'andthe line conductors of the trunk terminating in' the jack 7 J2, with which the illuminated signal lamp L382 7 is associated.
  • the illumination of'the signal lamp L382 indicates .to the operator at the secretary operator position ll that'there is a call onthe V relay operates as it is of the polarized type.
  • the battery reverse relay R310 When thus energized the battery reverse relay R310 operates to interrupt, at the contac'ts312 and 314, the previously traced original loop circuit extending'be'tween the line relay R360 in the secretary selector 5
  • the answer relay R430 complete at the contacts 43
  • the calling subscrib r substation TI is operatively connected via the subscriber line 2
  • the local connector .28 and the subscriber line 22t the called subscriber substation T2; and the subscriber line 22 extending to the called subscriber substation T2 is operatively connected .Via the line finder 4
  • theoperator at the secretary operator position L l answers .the call on the trunk 82 and gives the subscriber at the calling subscriber substation Tl the information which is to be given to calling subscriber substations in the absence of thesubscriber at the called subscriber substation T2, which is rendered secretarial service at this time.
  • ground potential therein i "removed from the control conductor :CZZ'B of the subscriber line 22, thereby to interrupt the previously traced original circuit for energizin the winding of the start relay R565, the previously traced holding circuit for energizing the winding .of the cutoff relay R560 and the previously traced path for applying ground potential to the control conductor 02-20 of the subscriber 'line 22.
  • the start relay R565 and the cutoff relay R560 in the secretary line circuit 32 restore; and the service relay R510 therein remains in its operated position, whereby secretarial service is maintained incforce at the subscriber substation'T2.
  • the removal of ground potential from and the application of battery potential to the guard conductor C412 in the cable 410 marks the line finder 4
  • 3 is actuated into disengagement, thereby to interrupt the previously traced circuit for energizing the release magnet M409, whereby the latter magnet restores.
  • the test relay R460 interrupts, at the contact 46
  • interrupts, at the contacts 36I, the previously mentioned circuit for energizing the winding of the hold relay R350, thereby to cause the latter relay to restore shortly thereafter, the 7 hold relay R350 being of the slow-to-release type.
  • the hold relay'R350 interrupts, at the contact 46
  • interrupts, at the contacts 36I, the previously mentioned circuit for energizing the winding
  • wiper setof the switching mechanism 400 is driven eleven steps in the rotary direction away from its normal rotary position without efiecting operation ofthe test relay R460, in the manner previously explained.
  • the set of switch springs S4 l 4 isv actuated, whereby an obivous path, including the contacts 445, is completed for applying ground potential to the guardconductor C412 in the cable 410.
  • This applicationof ground potential to the guard conductor C412 in the cable 410 completes a circuit,-includin the wiper 2-02 of the switching mechanism 200'and the engaged contact in the, associated contact,
  • test relay R220 interrupts, at the contacts 223, the previously traced circuit for energizing the mag net M206, thereby to cause the latter magnet to restore and drive the wiper set of the switching mechanism 200 an additional steprin the clockwise direction.
  • the wiper set ofthe switching mechanism 200 is operated to disengage the contacts in the associated contact bank terminating theconductors extending to the line finder 4
  • and to engage contacts in the associated contact bank ,terminatingconductors extending to another line finder 42 etc, whereby operation of the last-mentioned line finder is initiated to hunt for the subscriber line 22- extending to the'called subscriber substation T2, in the manner previously explained, and the start relay R440 in the line finder 4
  • the'line finder distributor operates in orderto assign another idle line finder to hunt for the" called subscriber line mentioned, and the previously selected. line finder is released.
  • Discontimu'ng secretarial service at asubscriberv substation in the branch office substation T2 the subscriber thereat firstinitiates -a call by removing the receiver from its associated switchhook; whereby'the local line circuitj25 is More particularlyftheilocal line circuit 25 is controlled in orderto cause ground potential to be applied to the control conductor 022B of the subscriber line 22in order to mark the subscriber line 22 as busy to the local connectors having access thereto, as
  • then operates in order to find the sub scriber line 22 having a call thereon extending to the calling subscriber substation T2; whereby operation of the associated secretary connector 5i is controlled over the trunk 6
  • the operator at the secretary operator position H then answers the call on the trunk 82 and converses with the subscriber at the calling subscriber substation T2 in the branch office 20.
  • the subscriber at the calling subscriber substation T2 then advises the operator at the secretary operator position l l that the secretarial service being rendered the subscriber substation T2 is no longer required.
  • the subscriber at the calling subscriber substation T2 then replaces the receiver upon its associated switchhook; and the operator at the secretary operator position ll withdraws the answer plug of the cord circuit from the jack J2; whereby the established connection is released in the manner previously explained.
  • the operator at the secretary operator position ll then inserts the call plug of .the cord circuit into the jack J l2 terminating the trunk 12 extending between the central office l0 and the branch ofiice 20, the trunk 12 being terminated in the secretary service switch H, as previously explained.
  • the operator at the secretary operator position H then dials three digits over the trunk 12; the first digit being effective to operate. the select switch 520 in order to indicate that secretarial service is to be discontinued. and the second and third digits being effective to operate the switching mechanism 500, thereby to select the secretary line circuit 32 associated with the subscriber line 22 extending to the subscriber substation T2.
  • the three digits 2, 2 and 2 are dialed; the first digit 2 indicating that secretarial service is to be discontinued at a subscriber substation and the second and third digits 2 and 2, respectively, identifying thesecretary line circuit 32 individual to the subscriber line 22 extending to the subscriber substation T2.
  • the secretary service switch H operates in response to the three digits 2, 2 and 2, in the manner previously explained, and, at the conclusion of the operation thereof, the control relay R555 restores, thereby to effect operation of the switch relay R550 in .the manner previously explained.
  • the switch relay R550 completes, at the contacts 552, the previously traced holding circuit for energizing the lower winding thereof and completes, at the contacts 55!, the previously traced path for short-circuiting the upper winding thereof and for applying direct ground potential to the wiper 52l of the select switch 520, whereby ground potential is applied to the wiper 502 of the wiper set of the switching mechanism '500 and the engaged contact in the associated contact bank terminating the conductor C582.
  • the application of ground potential to the conductor C582 completes an obvious path, including the contacts 511, for short-cirouiting the winding of the service relay R510 in the secretary line circuit 32, thereby to cause the latter relay to restore.
  • the servicere lay R510 interrupts, at the contacts 5', a further point in the previously traced holding cire cuit for energizing the winding thereof, and in,- terrupts, at the contacts 512, the previously traced connection between the winding of the start relay R565 and the control conductor 0223 of the subscriber line 22.
  • the operator at the secretary operator position H has thus dis,- continued secretarial service at the subscriber substation T2
  • secretarial service at the subscriber substation T2 is discontinued and this subscriber substation is rendered ordinary subscriber sub,- station service at this time.
  • a telephone system which comprises a central office and a branch oilice; which system includes'improvedapparatus for rendering secretarial service to a relatively large group of subscriber substations in the'branch ofiice from a secretary operator position in the central voflice via a relatively small number of links ,or trunks extending between .the branch .ofiice .and the central ofiice.
  • a calling station a plurality of lines, means for extending lacall from said calling station to any called one .of said lines, a link, an operator position, .means controlled from said operator position for selecting any one of said lines and characterizing the selected line, line identity apparatus associated with said operator position, and means controlled by the extension of a call to any characterized one of said lines for setting up a connection .jrom said one characterized line by way of said link to said operator position and for selectively operating said line identity apparatus tojid entify said one characterized line.
  • a calling station a plurality of lines
  • automatic switching apparatus selectively'controllable from said calling station to extend a call therefrom to any called one of 7 said lines
  • an automatic switching link an operator position, means controlled from said operator position for selecting any one of said lines 7 and characterizing the selected line in either of two ways, line identity apparatus associated with said operator position, and means controlled by the extension of a call to any called one of said lines only if said called line is characterized in 'a particular one of said two Ways for selectively operating said switching link to set up a connection from said one called line to said operator position and for selectively operating said line identity apparatus to identify said one called line.
  • a calling station a plurality of lines, means for extending a call from said calling station to any called one of said lines, an operator switchboard, a plurality of trunks accessible 'to said operator switchboard and individually corresponding to said lines, an automatic switch having access to said trunks, means controlled by the extension of a call to any called one of said lines for selectively operating said switch to select the one of saidtrunks corresponding to said one called line, thereby to initiate a' call on said one trunk, means control- 7 lable from said operator switchboard for answering the call on said one trunk, and means for connecting said switch to said one called line.
  • a calling station In a telephone system, a calling station, a plurality of lines, means for extending a call from said calling station to any called one of said lines, an operator switchboard, a plurality of trunks accesible to said operator switchboard and individually corresponding to said lines, an autosaid second switch to select the one of said trunks corresponding to said one called line, thereby to initiate a .call on said one trunk, means controllable from said operator switchboard for answering the call on said one trunk, and means for connecting together said first and second switches.
  • a calling station a plurality of lines, means for extending a call from said calling station to any called one of said lines, a first automatic switch having access to said lines, an operator switchboard, a plurality of trunks accessible to said operator switchboard and individually corresponding to said lines, a
  • second automatic switch having access to said trunks, means controlled by the extensionof a call to any called one of said lines for selectively operating said first switch to select said one called line and for selectively operating said second switch to select the one of said trunks corresponding to said one called line, thereby to initiate a call on said trunk, means controllable from said operator switchboard for answering the call on said one trunk, and means controlled by theanswering of the call on said one trunk for connecting together said first and second switches.
  • a calling station a plurality of lines, means for extending a call said lines, a first automatic switch having access matic switch having access to said trunks, means 7 controlled by the extension of a call to any called one of said lines for selectively operating said switch to select the one of said trunks corresponding to said one called line, thereby to initiate a call on said one trunk, means controllable from said operator switchboard for answering the call on said one trunk, and means controlled by the answering of the call on said one trunk for connecting said switch to said one called line.
  • a calling station In a telephone system, a calling station, a plurality of' lines, means for extending a call from said calling station to any called one of said lines, a first automatic switch having access to said lines, an operator switchboard, a plurality of trunks accessible to said operator switchboard and individually corresponding to said lines, a second automatic switch having access to said trunks, means controlled by the extension of a call to any called one of said lines for selectively operating operating said first switch to select said one called line and for selectively operating 7 to said lines, an operator position, a second automatic switch, means controlled by the extension of a call to any called one of said lines for selec- V tively operating said first switch to select said 7 one called line and for selectively operating said second switch correspondingly, means controlled by the operation of said second switch for extending a call to said operator position and for identifying said one called line, means controllable from said operator position for answering the call extended thereto, and means for connecting together said first and second switches.
  • a calling station a plurality of lines, means for extending; a call from said calling station to any called one of said lines, a plurality of links, an operator position, means controlled by the extension of a call to any called one of said lines for extending a call from said one called line by way of an" idle one of said links to said operator position, means controlled by the extension of a call over said one link for rendering it busy, means controllable from said operator position for answering the call on said one link, and means controlled jointly by the performance of a release operation at said calling station and by the performance of a release operation at said operator position for rendering said one link again idle.
  • a calling station a plurality, of lines, means forextending a call from said calling station to any called one of said lines, a link, an operator position, line identity apparatus associated with said operator position, means controlled by the extension of a call to any called one of said lines for extending a call over said link to said operator position a trolled by the answering of the call on said link for connecting said link to said one called line.
  • a calling station a plurality of lines, means for extending a call from said calling station to any called one of said lines, a link, an operator position, line identity apparatus associated with said operator position, means controlled by the extension of a call to any called one of said lines for extending a call over said link to said operator position and for transmitting a signal over said link individual to said one called line, means controlled by the signal transmitted over said link for selectively operating said line identity apparatus to identify said one called line, means controllable from said operator position for answering the call on said link, and means controlled by the answering of the call on said link for connecting said link to said one called'line.
  • a calling station a plurality of lines, means for extending a call from said calling station to any called one of said lines and for initiating the projection of ringing current thereover, a link, an operator position, line identity apparatus associated with said operator position, means controlled by the .extension of a call to any called one of said lines for extending a call over said link to said operator position and for selectively operating said line identity apparatus to identify said one called line, means controllable from said operator position for answering the call on said link, means controlled by the answering of the call on said link for connecting said link to said one called line, and means controlled by the connection of said link to said one called line for arresting the projection of ringing current thereover.
  • I 13 In a telephone system, a calling station, a plurality of substations, automatic switching apparatus selectively controllable from said calling station to extend a call therefrom to any called one of said substations, an operator position provided with facilities for rendering secretarial service to said substations, apparatus temporarily operated under the control of said position to select any desired one of said substations, means controlled by said apparatus for characterizing the selected substation and maintaining it characterized after said apparatus has restored to normal at the end of its temporary operation, and means controlled by the extension of a call to any one of said substations so characterized for setting up a connection from said one characterized substation to said operator position.
  • a first ofiice including a calling station, a plurality of substations, and means for extending a call from said calling station to any called one of said substations; a second oflice including an operator position provided with facilities for rendering secretarial service to said substations; two trunks extending between said ofiices; means controllable over a particular one of said trunks but not over the other of said trunks for conditioning any one of said substations to receive secretarial service; and means controlled by the extension of a call to any one of said substations which is thus conditioned for setting up a connection from said one called substation by way of the other of said trunks to said operator position.
  • a first office including a calling station, a plurality of substations, and means for extending a call from said calling station to any called one of said substations; a second oiifice including an operator position provided with facilities for rendering secretarial service to said substations, and substation identity apparatus associated with said operator position; two trunks extending between said offices; means controllable over a particular one of said trunks but not over the other of said trunks for conditioning any one of said substatios to receive secretarial service; and means controlled by the extension of a call to any called one of said substations which has been thus conditioned for setting up a connection from said one called substation by way of the other of said trunks to said operator position and for selectively controlling said substation identity apparatus over said other trunk to identify said one called substation.
  • a calling station a plurality of lines, means for extending a call from said calling station to'any called one of said lines, an operator position, line identity apparatus associated with said operator position, a switch controllable from said operator position to select any one of said lines, means including said switch operated at times to institute interceptor service upon any selected one of said lines and operated at other times to discontinue interceptor service upon any selected one of said lines, and means controlled by the extension of a call to any called one of said lines upon which interceptor service is in force for setting up a connection from said one called line to said operator position and for selectively operating said line identity to identify said one called line.
  • a calling station a plurality of'llnes, means for extending a call from said calling station to any called one of said lines, a plurality of relays individually associated with said lines, each of said relays including an operated position and a restored position and being provided with an operating circuit and a stick circuit and a path for shorting its stick circuit, means for selectively completing the operating circuits and the paths of said relays, means controlled when any one of said relays occupies its two positions respectively to institute and to discontinue interceptor service upon the associated line, an operator position, and means controlled by the extension of a call to any called one of said lines upon which interceptor service is in force for setting up a connection from said one called line to said operator position.
  • a calling station a plurality of lines, means for extending a call from said calling. station to any called one of said lines, a plurality of relays individually associated with said lines, each of said relays including an operated position and a restored position and being provided with an operating circuit and a stick circuit and a path for shorting its stick circuit, an automatic switch operable selectively to complete the operating circuits and the paths of said relays, an operator position, means controllable from said operator position for selectively operating said switch, means controlled when any one of said relays occupies its two positions respectively to institute and to discontinue interceptor service upon the associated line, and means controlled by the extension of a call to any called one of said lines upon which interceptor service is in force for setting up a connection from said one called line to said operator position.
  • a substation means for extending a call to said substation, means for extending a call from said substation, means selectively controllable to institute and to discontinue interceptor service at said substation, an operator position, and means controlled by the extension of all calls either to or from said substation when interceptor service is in force there-

Description

P 1944- c. E. LOMAX 2,358,017
TELEPHONE SYSTEM I Filed Jan. 8, 1943 5 Sheets-Sheet 2 FIG. 2
LINE FINDER msTmBuToR 34 llfikmzoe :;1 047g v Q c474\ I R2202 R250 TesTfi T 232 CUTOFF C4 212 1 227 247W 205 HST. R 210 zu i INVENTOR. CLARENCE E. LOMAX BY m'm m Mam ATTORNEYS -30o J LANE L156, 33' W7? FIG. 3 I WERE]? Sept. 12, 1944. LCM- X 2,358,017
TELEPHONE 5 Y5 TEM Filed Jan. 8, 1943 5 Sheets-Sheet 3 R370 BATT SECRETARY CONNECTOR CENTRAL OFFICE l0 C: SECRETARY OPERATOR K72 dfiA POSITION. n
INVENTOR. CLARENCE E. LOMAXC BY 1 m wzm ,M m
ATTORNEYS.
Sept. 12, 1944.
C. E. LOMAX TELEPHONE SYSTEM Filed Jan. 8, 1943 5 Sheets- Sheet 4 FIG. 4
LINE FINDER 4| J ,LOCAL 022B LINE CIR.
- LOCAL 29 ,622A 22 25/ DISTRIBUTOR 75 28 7 1 LOCAL FINDER LOCAL L 2 CONNECTOR 3:, 0
- INVENTOR. CLARENCE E. LOMAX ATTORNEYS Sept. 12, 1944. E, L MAX 2,358,017
' TELEP HONE SYSTEM Filed Jan. 8, 1943 5 Sheets-sheaf. 5 j
SECRETARY LINE CIRCUIT 32 31 /573 R560% R56 R570 CUT 0F SERVICE FIG. 5
' SELECT sw. 520 506 SECRETARY SERVICE fi g 582 SWITCH 7| 3524 l f I 536 LINE T HOLD l53l 537 532 x INVENTOR.
CLARENCE E. LOMAX BY mfim wm ATTORNEYS Patented Sept. 12, 1944 TELEPHONE-SYSTEM Clarence E. Lomax, Chicago, Ill., assignor to Automatic Electric Laboratories, Inc., a corpora-.-
tion of Delaware Application January 8, 1343, Serial No. 471,683
23 Claims.
The present invention relates to telephone systems and more particularly to such systems arranged to render secretarial service to certain subscriber substations served thereby.
In a conventional telephone system, agencies independent of the telephone operating company provide a type of service known as secretarial service, whereby certain subscribers, such as doctors, salesmen and others who do not have secretaries and whose duties require that they be absent from their ofiices for considerable periods of time, may have calls directed to their substations intercepted and forwarded to the agencies mentioned. A call thus intercepted is answered by a secretary at the agency; and, after the secretary makes inquiry and learns the desired called subscriber, she gives the calling subscriber certain information in accordance with the prior instructions of the called subscriber.
In a telephone system of the type noted the telephone operating company has no supervision over the agencies and the apparatus 'usually employed therein is not well designedto render highly satisfactory secretarial service.
Accordingly, it is an object of the present invention to provide a telephone system incorporating an improved arrangement including an operator switchboard under the supervision of the telephone operating company for rendering secretarial service to certain subscriber substations served thereby.
Another object of the invention is to provide in a telephone system comprising a number of ofiices, an improved arrangement for rendering from an operator position in the central oflice secretarial service to certain subscriber substastitute and to discontinue interceptor service at certain subscriber substations served thereby,
A further object of the invention is to provide in a telephone system an improved intercepting arrangement, whereby calls extended both to and from subscriber substations at which ini type.
lined and additional operating advantages are attained.
The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood'by reference to the following specification taken in connection with the accompanying drawings, in which Figure 1 illustrates the general arrangement of a telephone system embodying the presentinvention; and ,Figs. 2 to 5, inclusive, taken together, illustrate the details of a system having incorporated therein the fea-' tures of the invention as briefly outlined above.
Description of the apparatusincorporated in the system Referring now more particularly to Fig. 1 of the drawings, the telephone system there illustrated comprises'a central ofiice ID of any suitable type and a branch ofiice 20 of the automatic The central ofiice l0 includes a secretary operator switchboard or position H of the manual type; and the branch oifice 20 serves a group of automatic subscriber substations, including the subscriber substations Tl, T2, T3 etc. The subscriber substations in the branch oflice 20 are divided into a first subgroup, including the subscriber substation Tl, which is rendered ordinary automatic subscriber substation service, and a second subgroup, including the subscriber substations T2 and T3, which is rendered secretarial the subscriber. lines 2|, 22 and 23 respectively terceptor service is enforced are routed to ,an'"
operator position.
Further features of the invention pertain to the particular arrangement of the circuit elements of the system, whereby the abo've-outextending to the subscriber substations Tl, T2 and T3. Each of the-subscriber lines is provided with a local line circuit individual thereto, the local line circuits 24, 25 and 26 being individual to the respective subscriber lines 2I-, 22 and 23 respectively extending to the subscriber substations TI, T2 and T3. Also each of the subscriber lines which is rendered secretarial service is providedrwith a secretary line circuit individual thereto, the secretary line circuits 32 and 3-3 being individual to the subscriber lines '22 and 23 extending to the" subscriber substations T2 and T3 which are rendered secretarial service, Also the branch exchange 20 comprises local automatic switching apparatus including a number of local links, oneof thelocallinks, being illustrated as dered secretarial service.
. the branch oflice 20 and the central oflice I and terminating in a jack J I2 at thesecretary opaccess to the subscriber lines extending 'to the subscriber substations TI T2, T3 etc.; and the local connectors 28 etc. also have access to a trunk I5 extending between the branch office and" the central oflice I0 and terminating in 'a jack J II at the secretary operator position II.
Further the branch ofiice 20 comprises a number of linefinders 4|, 42 etc. having access to the subscriber lines 22, 23 etc. extending to the subscriber substations T2, T3 etc. which are ren- A line finder' dis tributor 34 is operatively associated with the line finders 4|, 42 etc. for the purpose of assigning an idle line finder for the use of either a calling or called subscriber line extending vto a subscriber substation which is rendered'secretarial comprises a secretaryservice switch'll operatively connected to a trunk 12 extending between erator position II. The secretary service switch II has access to the various secretary line circuits 32, ,33 etc. individually associated with the subscriber lines 22, 23 etc. extending to the subscriber substations T2, T3 etc. which are rendered secretarial service. 7
The central oflice I0 comprises, in addition to the secretary operator position II, anumber of secretary connectors 5I, 52 etc. respectively cor- V responding to the line finders M, 42 etc. and operatively connected thereto by means of a number of trunks 6|, 62 etc. extending between Accordingly, the line finder 4| disposed in the branch office 20 and the secretary connector 5I disposed in the central office I Dar interconnected by, the trunk Iil. extending therebetween and constitute a linkwhich is utilized for a pur- V pose more fully explained hereinafter. Similarly,
.noted that the trunks 82, 83 etc. respectively terminating in the jacks J2, J3 etc, at the scoretary operator position I I respectively correspond to the subscriber lines 22, 23 etc. in the branch office 20 respectively extending to the subscriber substationsTZ, T3 etc. which are rendered secretarial service.
The actual number of-local finder-connector linksprovided inthe branch ofiice 20 is determined .by the amount of local traffic therein; while the actual number of line findensecretary connector links required between the branch oflice 20 and the central ofiice I0 is determined by the peak amount of secretarial trafiic between the branch office 20 andthe central office I 0. At this point it is noted that anysubscriber substation rendered ordinary. service may be converted,
whereby it may be rendered secretarial service,
V. the central oflice I0 and. thebranch ofiice 20.; I
'scribed hereinafter. Preferably, each of the line;
individual thereto in conjunction with the necesary circuit changes rendering the secretary line circuit thus provided accessible to the line finders 4|, 42 etc. and the provision of an additional and corresponding trunk terminating in a corresponding jack at the secretary operator position I I and accessible to the secretaryconnectors 5I, 52 etc. In passing, it is noted that the actual number of linev finder-secretary connector links required between the branch office 20' and the central oifice I0 will be only a minor fraction of the number of subscriber substations in the branch oflice 20 rendered secretarial service. a
In the central ofiice I0, the secretary operator position II comprises, as shown in Fig. 3, in addition to the jacks J2, J3, JI I, JIZ etc., position apparatus not shown; whereby the operator thereat may answer calls on the trunks 62, 83
etc. and the trunk I5 and may control, via the trunk 12 the secretary service switch II in the branch ofiice 20. Also associated with the jacks J2 and JII aresignal lamps L382 and L38l, respectively, which are utilized for a purpose more fully explained hereinafter.
Preferably, each of the secretary connectors in the central oilice I0 is identical to the secrek tary connector 5| which comprises, as shown in Fig. 3, a switching mechanism 300 of the Strowger type, including a wiper set provided with three wipers 30I, 302 and 303 supported for both vertical and rotary movements, and an associated semi cylindrical contact bank provided with ten vertically spaced-apart levels of contact sets arranged in circumferentially spaced-apart relation. Also the switching mechanism 300 includes a vertical magnet M304 for driving the wiper set step by step in the vertical direction away from its normal vertical position, a rotary magnet M305 for driving the wiper set step by step in the rotary direction away from its normal rotary position, and a release magnet M306 for releasing the wiper set and for causing-it to be returned to its normal rotary and vertical relay R350, a line relay R360 and a battery reverse relay R310; and a control network connected and arranged in a manner more fully definders in the branch ofifice l0 is identical to the line finder M which comprises, as shown in Fig.4, a switching mechanism 400 of the Strowgertype, including a wiper set provided with three wipers 40I, 402' and 403supported for both vertical and rotary movements, and an associated -semicylindrical contact bank provided with ten vertically spacedapart levels of contact sets arranged in circumf ment,1 and an associated vertical control contact bank. Further theswitching mechanism 400 includes'a vertical magnet M405 ;for driving the I wiper setand the'vertical control wiper 404 step by step in the vertical direction away from their normal vertical positions; a rotary magnet M401" for driving the wiper set step by step-in the rotary merely by the provision of a secretary line circuit "direction away from its normal rotary Position,
and a release magnet M409 for releasing the wiper set and the vertical control wiper 404- and for causing the wiper set to be returned to its normal rotary and vertical positions and for causing the vertical control wiper 404 to be returned to its normal vertical position; Also associated with the switching mechanism 400 are two sets of switch springs S4l0 and S413 which are actuated when the wiper set is moved one step in the vertical direction away from its normal vertical position and a set of switch springs $414 which is actuated when the wiperset is moved eleven steps in the rotary direction away from its normal rotary position. Further the line finder 4| comprises a repeating coil 435; a relay group, including a pulse relay R420, an answer relay R430, a start relay R440, a cutoff relay R450 and a test relay'R460; and a control network connected and arranged in a manner more fully described hereinafter.
In the branch ofiice 20, the line finder distributor 34 comprises, as shown in Fig. 2, a switching mechanism 200 of the rotary type, including five wipers to 205, inclusive, provided with individually associated contact banks, and a magnet M206 for driving the wipers noted in the clockwise direction; the switching mechanism 200 having access via the cable 410 to'the various line finders 4|, 42 etc. Also the line finder distributor 34 comprises a relay group, including a start relay R2l0, a test relay R220, a step relay R230, a transfer relay R240, and a "cutoff relay R250; and a control network connected and arranged in a manner more fully described hereinafter.
Preferably, each of the secretary line circuits in the branch office 20 is identical to the secretary line circuit 32 individually associated with the subscriber line 22 extending to the subscriber substation T2 which is rendered secretarial service. The secretary line circuit 32 comprises, as shown in Fig. 5, a relay group, including a cutoff relay R560, a start relay R565 and a service relay R510; and a control network connected and arranged in a manner more fully described hereinafter. In the branch ofiice 20, the local line circuits 24, 25 etc. are of conventional connection and arrangement and are. of any suitable for'm. Also in the branch office 20 the local links are of any suitable type; however, it is preferable that both the local finders and the local connectors thereof be of conventional Strowger types of standard connections and arrangements. Moreover, in the branch oflice 20, the local distributor 29 is of any suitable form and may be quite similar in connection and arrangement to the line finder distributor 34' illustrated.
In the branch ofiice 20, the secretary service switch H comprises, as shown in Fig. 5, switching mechanism 500 of the Strowger type, icluding a wiper set provided with six wipers 50l to 506, inclusive, supported for both vertical and rotary movements, and an associated semicylindrical contact bank provided with ten vertically spaced-apart levels of contact sets arranged in circumferentially spaced-apart relation, Also the switching mechanism 500 includes a vertical magnet M50!v for driving the wiper set step by step in the vertical direction away from its normal vertical position, a rotary magnet M508 for driving the wiper set step by step in the rotary direction away from its normal rotary position, and a release magnet M509 for releasing the wiper set and for causing it to be returned to its normal rotary and vertical positions. Also asill sociated with the switching mechanism 500 are two sets of switch springs S5l0 and S5l3 which are actuated when the wiper set is driven in the vertical direction one step away from its normal vertical position. Also the secretary service switch H comprises a select switch 520 of the minor type, including a single wiper 52L provided with an associated contact bank, a rotary magnet M522 for driving the wiper noted step by step in the counterclockwise direction away from its normal rotary position, and a release magnet M523 for releasing the wiper noted and for causing it to be returned in the clockwise direction back into its normal rotary position. Also associated with the select switch 520 is a set of switch springs S524 which is actuated when the wiper noted is driven in the counterclockwise direction one step away from its normal rotary position. Further the secretary service switch H comprises a relay group, including a line relay R530, a hold relay R535, two transfer relays R540 and R545, a switch relay R550, and a control relay R555; and a control network connected and arranged in a manner more fully described hereinafter.
A better understanding of the connection and arrangement of the system will be facilitated from ,a consideration'of the detailed operation of the various pieces of apparatus incorporated therein incident to handling local traffic in the branch ofiice 20 and secretarial traffic between the branch ofiice 20 and the central office 10, as will appear hereinafter.
, Institutirzg secretarial service at a subscriber substation in the branch office When a subscriber ata subscriber substation in the branch office 20 which is rendered secretarial service desires to utilize this service, he first extends a call to the secretary operator position It in the central office i0 and advises the operator thereat concerning any information which is to be givento other subscribers calling the subin his absence.
ial service at the subscriber substation T2, the subscriber thereat removes the receiver from its associated switchhook; whereby the local line circuit 25 is controlled over the subscriber line 22. More specifically, the local line circuit 25 controls thelocal distributor 29, whereby an idle local link, such, for example, as the local link illustrated is assigned and the local finder 21 thereof is operated to seize the subscriber line 22 extending to the calling subscriber substation T2. When the local finder 21 seizes the subscriber line 22,, the
subscriber line 22 is marked as busy via the control conductor C22B thereof to the local connectors having access thereto and the local connector 28 is conditioned to be operative in response to one or more digits received over the calling subscriber line 22. The subscriber'at the calling subscriber substation T2 then dials one or more digits'over the subscriber line 22, whereby the local connector 28 is operated to select the trunk 15 extending to the secretary operator position H in the'central ofiice l0. The local connector '28 tests the idle or busy condition of the selected trunk' 15 causing busy tone current to be returned over the subscriber line 22 to the calling subscriber substation T2 in the event the trunk 15 is busy at this; time. On the other hand, in the event the trunk 15 is idle at this time, the local connector '28 operates to seize the trunk 15, "whereby ground potential is applied tothe control conductor C15A thereof in order to mark the trunk 15 as busy to the other local connectors having access thereto and to complete an obvious circuit, including the contacts ofthe jack JII, for illuminating the signal lamp L38I. The H lumination of the signal lamp L38I indicates the presence of'a call on thetrunk,15; 'whereby the operator at the secretary operator position I I answers the call by inserting the answer plugv of the cord circuit into the jack J II effecting the extinguishment of the signal lamp L3! and completing an obvious connection between the calling subscriber substation T2 and theteleph one instrument at the secretary operator position II. The subscriber at the calling subscriber substa tion T2 then passes to the operator at the secre tary operator position llthe information which is to be given to other subscribers callingthe subscriber substation T2 in his absence. Subsequently, when both the subscriber at the calling subscriber substation T2 replaces the receiver upon its associated switchhook and the operator at the secretary operator position II withdraws the answer plug of the cord circuit from the jack JI I, the local finder 21 and the local connector 28 are released, whereby both the subscriber line 22 extending to the subscriber substation T2 and the trunk 15 terminating in the jack JII at the secretary operator position II are rendered idle Vto'the local connector having access thereto.
The operator at the secretary'operator position 'I I then inserts the call plug of the cord circuit into thejack J I2 terminating the trunk 12 extending between the central office I and the branch office 20, whereby an obvious circuit is completed for energizing in series the upper and lower windings of the line relay R530 in thesec- :retary service switch H in the branch oflice 20.
as explained more fully hereinafter; while the second and third digits are effective to operate 1 the switching mechanism 500, thereby to select the particular secretary line circuit associated 'With the subscriber line extending to the subscriber substation at which secretarial service is to be instituted or discontinued as the, case may be. More particularly, in the present example, in order to institute secretarial service at the subscriber substation T2, the three digits idialed are 1, 2 and 2; the first digit 1 indicating that secretarial service is to be instituted at the subscriber substation T2 and the second and third digits 2 and 2, respectively, identifying the secretary line circuit 32 individual to the sub- ,scriber line 22 extending to the subscriber substation T2. 7 V V i ,More particularly, the line relay R530 follows the single impulse of the'first digit 1 restoring and then reoperating. Upon restoring, the line relay R530 interrupts, at the contacts 53I, the
previously mentioned circuit for energizing the windingof the hold relay R535, andcompletes, at the contacts 532, a circuit, including the contacts 531," the contacts 5 of the set of switch-springs "S5I0 and the contacts 548, for energizing the tracedcircuit'for energizing the winding of the transfer-relay R540 in series with the rotary magnet M522. Thehold relay R535 and the transfer relay R540 are of the sloW-to-release type; whereby the relays mentioned do not restore during impulsing. At this time the rotary magnet M522 restores and the wiper 52I of the selectswitch 520. engages the first contact in the associated contact hank connected to the wiper, I 50I of the wiper set of the switchingmechanism V 500,. for a purpose more fully explained hereinafter. Also when the wiper'52I of the select switch 520 is driven one step in the counterclock- Wise directionaway from itsnormal rotary position, the set of switch springs S524 is actuated into engagement, thereby to prepare. a circuit traced hereinafter for energizing the winding of the transfer relay R545. Shortly following the conclusion of the first digit 1 the transfer relay R540 restores, thereby to complete, at the contacts 54I, the'previ0us1y mentioned circuit including the contacts 536 and the set of switch springsS524, for energizing the winding of the transfer relay R545. When thus energized the transfer relay R545 operates to co'mplete, at the contacts 545, an obvious holding circuit, including the contacts 535, for energizing the winding thereof. {Also the transfer'relay R545 interrupts,
at the contacts 548,a further point in the previously traced circuit for energizing the winding of the transfer relay R540 in series with the rotary magnet M522 of the select switch 520, andrprepares, at the contacts 541, a circuit traced hereinafter for energizing the winding of the transfer relay R540 in series with the vertical magnet 'M501 of theswitching mechanism 500..
' The line'relay R530 then follows the second digit 2, thereby to complete, at the contacts 532; 'the first time it restores, the previously mentioned circuit, including the contacts 531, the contacts 5i I of the set of switch springs S5I0 and the contacts 541, for energizing the winding of the transfer relay R540 inrseries with'the vertical magnet M501; whereby the transfer relay R540 reoperates and the vertical magnet M501 operates wiper set of ,the switching mechanism 500 is driven one step in the vertical direction away from its normal vertical position, the sets of switch springs S5I0 and S5I3' are actuated More particularly, the set of switch springs S5I0 is actuated, thereby to interrupt, at the contacts 5Il thereof, a further point in the previously traced circuit'for energizing the winding of the transfer relay R540 in series with the vertical magnet M501 and to prepare, at the contacts'5l'2 thereof, an alternative circuit traced hereinafter for energizing the winding of the transfer relay R540 in series with the vertical magnetM501. The set of switch springs vS5I3 is actuated into engagement, thereby to' prepare multiple circuits traced hereinafter for energizing the release magnets M523 and M509 of the select switch 520 and the switching mechanism 500, respectively. The next time the line relay R530 restores it completes, at the contacts 532, the previously mentioned alternative circuit, including the contacts 531, the contacts 5I2 of the set of switch springs S5l0, the contacts 542 and the contacts 541, for energizing the winding of the transfer relay R540 in series with the vertical magnet M501. Accordingly, at this time, the line, relay R530 follows the impulses of the second digit 2, where by the hold relay R535 and the transfer relay R540 remain operated during impulsing and the wiper set of the switching mechanism 500 is driven two steps in the vertical direction away from its normal vertical position. Shortly following the conclusion of the second digit 2 the transfer relay R540 restores, thereby to interrupt, at the contacts 542, a further point in the previously traced alternative circuit for energizing in series thewinding of the transfer relay R540 and the vertical magnet M501; Also the transfer relay R540 prepares, at the contacts 543, a circuit traced hereinafter for energizing in series the winding of the control relay R555 and the rotary magnet M508 .of the switching mechanism 500.
- The line relay R530 then follows the impulses of the third digit 2, thereby to complete each time it restores, at the contacts 532, the previously mentioned circuit, including the contacts 531, the contacts 512 of the set of switch springs S5l0 and the contacts 543 and 553, for energizing the winding of the control relay R555 in series with the rotary magnet M508, whereby the control relay R555 operates and the rotary magnet M505 operates and restores twice in order to drive the wiper set of the switching mechanism 500 two steps in the rotary direction away from its normal rotary position. At this point it is noted that the control relay R555 is of the slow-to-release type, whereby the latter relay and the hold relay R535 remain'operated during impulsing. At the conclusion of the third digit 2, the line relay R530 remains operated and, shortly thereafter, the control relay R555 restores. At this time the wiper set of the switching mechanism 500 engages the 2 up 2 in contact set in the associated contact bank. Upon restoring, the control relay R555 completes, at the contacts 556, a circuit, including the contacts 536, the wiper 52I of the select switch 520 and the engaged first contact in the associated contack bank, the wiper 501 of the wiper set of the switching mechanism 500 and the engaged contact in the associated contact bank, the conductor C58! and the resistor 513, for energizing the upper winding of the switch relay R550 in series with the winding of the service relay R510, the service relay R510 being in the secretary line circuit 32 individual to the subscriber line 22 extending to the subscriber substation T2. When this series circuit is completed the switch relay R550 operates to complete, at the contacts 552, an obvious holding circuit, including the contacts 536, for energizing the lower winding thereof. Also the switch relay R550 interrupts, at the contacts 553, a further point in the previously traced circuit for energizing the winding of the control relay R555 in series with the rotary magnet M508, thereby positively to prevent further operation of'the switching mechanism 500 at this time. Further the switch relay R550 completes, at the contacts 551, an obvious path for short-circuiting the upper winding thereof,
whereby-a low resistance circuit substantially identical to that traced above is completed for energizing the winding of the service relay R510 in the secretary line circuit 32.
When thus energized the service relay R510 operates to complete,-at the contacts 51!, an obvious holding circuit, including the resistor 513, for energizing the winding thereof. Also the service relay R510 completes, at the contacts 512, an obvious connection "between the winding of the start relay R5155 in the secretary line circuit 32 .and the control conductor C22B of the subscriber line 22 extending to the subscriber substation T2,1for-a purpose more fully explained hereinafter. At this time, secretarial service has been instituted at the subscriber'substation T2 in the branch office 20 by the operator at the secretary operator position II in the centraloflic'e l0 over the trunk 12 by the operation of the -secre-,
.tary service switch 1| above described. After the operator at the secretary operator position H has thus instituted secretarialqservice at the subscriber substation T2 she withdraws the call plug of the cordcircuit from the jack J12, there'- by to interrupt the previously traced circuit for energizing in series the upper and lower windings of the line'relay R530 in the secretary service switch 11 over the trunk 12, whereby the latter relay restores. Upon restoring, the line relay R530 interrupts, at the contacts 53!, the previously'mentioned circuit for energizing the winding of the hold relay'R-535, thereby to cause'the latter relay to restore shortly thereafter. 'Upon restoring, the holdrelay R535 interrupts, at the contacts 536, the previously traced multiple holdjing circuits for energizing the winding of the transfer relay R545 and the lower winding of the switch relay R550, thereby to cause the relays mentioned to restore. Also the hold relay R535 completes, at the contacts 538, the previously mentioned multiple circuits, including the .contacts 532 and the set of switch springs S513, for en'- ergizing the release magnets M523 'andiM509. When thus energized the release magnet M523 operates, thereby to release the wiper 52l of the selectswitch 520 and'to cause it to be returned in the clockwise 'direction'back into its normal rotary position. When thus energized the release magnet M509 operates, thereby to release the wiper set of the'switchingmechanism 500 and to cause it to be returned to its normal rotary and vertical positions. When the switching mechanism500 is thus released the sets of switch springs S5l0 and S5I3 are actuated. More particularly, the set of switch springs S5l 3 is actuated into disengagement, thereby to interrupt the previously traced multipleicirouits for energizing the release magnets M523 and M509 in 'order to cause these release magnets to restore. At this time the secretary service switch 1lis completely released.
Rendering secretarial service to a subscriber substation in the branch o fice Considering now the manner in which secretaria'l service .is rendered a subscriber substation, such, for example, as the subscriber substation T2 in the branch office, 20,'afte'r secretarial service thereat has been instituted in the inanner previously explained, it is again noted that, in'the secretary line circuit 32 individual to the subscriber line 22 extending to the subscriber subscriber T2, the service'relay R510 occupies its operatedposition and the winding of the start relay R565 is connectedto the control conductor 6 0223 of the subscriber line 22. At thistime a call may be initiated at any'calling. subscriber substation in the branch office 20, such,'for example, as the subscriber substation T|,'and extended to the called subscriber substation T2;
whereby secretarial service is rendered, asexplained more fully'below. More particularly, the subscriber at the calling subscriber substation T| removes the receiver fromits associated switchhook; whereby the localline circuit 24 is con trolled over the subscriber line 2|. )MOrespecifically, the local line circuit 24- controls the local distributor 29, whereby an idle local link, such, forexample, as the local link illustrated, is assigned and the local finder 21 thereof is operated to seize the subscriber line 2| extending to the calling subscriber substation Tl. When the local finder 21 seizes the subscriber line 2|, the subscriberline 2| is marked as busy via the control conductor C2|B thereof to the local connectors having access thereto and the local connector 28 is conditioned to be operative in response to two'digits received over the calling subscriber line 2 The subscriberiat the calling subscriber substation Tl then 'dails two digits over the subscriber line 2|, whereby the local connector 28 is operated'toselect the subscriber line 22 extending to the called subscriber substation T2. The local connector 28 tests the idle or busy con dition of the selected subscriber line 22, causing busytone current'to be 'returned over the subscriber line 2| to the calling subscriber substaof' battery potential to the control conductor 0220 of the subscriber line 22 respectively mark the vertical and rotary positions of the various contact sets in the line finders 4|, 42, etc. terminating the subscriber line 22 extending to the called subscriber substation T2. Also the application of ground potential to the mark conductor C418'completes a circuit, including the resistor 208, for energizing the winding of the start relay R2 0 in the link finder distributor 34, thereby to causethe latter relay to operate? At this point it is noted that the magnet M206 of the switching mechanism 200 incorporated in the line finder distributor 34 is normally connected via the contacts 201 and 222 to the wiper 202 of the rotary switching mechanism 200, which wiper normally engages a contact in the associ-- sociated line finder is respectively idle or busy.
tion Tl in the event the called subscriber sub-- station T2 is busy at this time. On the other hand, in theevent the called subscriber substation T2'is idle at this time, the local connector 28 operates to seize the subscriber line 22, whereby ground potential is applied to the control conductor C22B thereof in order to mark the subscriber 'line 22 as busy to the other local connectorshaving access thereto and to cause ringing current to be "projected over the'line conductors of the subscriber line 22 extending to the called subscriber. substation T2, whereby the ringer thereat is operated. However, in the present example, 'thegsubscriber at the called subscribersubstation T2 is absent and the call there'- to'is not'answered at the called subscriber substation T2; rather, the call is answered at the secretary operator position H in the central of.-
fice I0, as explained more fully below.
The application of ground potential to the control conductor C2213 of the subscriber line.22 ex.-
tending to the called subscriber substation T2 also completes an -obvious circuit, including the contacts 512, for energizing the winding of the anobvious path'for applying battery potential by way of the winding of thecutofi'relayR560 in the secretary line circuit 32 to the control conof the line finder 4| in the cable 410. a This apductor C22Cof the subscriber line 22 appearing in the contact banks of the various line finders 4|, 42 etc. The application of ground'potential to the mark conductor C418 and'the application Thus it will be understood that, when a line finder 4| etc. is rendered busy, ground potential is applied to the associated guard conductor'C412 etc. and consequently to the wiper202 of the switching mechanism 200 in'th'e e'ventthe wiper'mentioned engages the contact in the associated contact bank terminating the guard conductor mentioned] In this event, ground potential 'applied to the wiper 202 of the switching mechanism 200 completes an-obvious circuit, including the contacts 222 and 201; for energizing'the magnet'M206, whereby the latter'mag'net operates to interrupt, at the contacts 201, the previously traced circuit for energizingthe magnet M206 and to condition the wipers noted of the switching mechanism 200 to be driven one step in the clockwise direction. The magnet M206 then restores, whereby the wipers noted of the switching mechanism 200 are driven one step in the counterclockwise direction and the magnet M206 is reconnected, at the contacts 201, to the Wiper 202 of the switching mechanism 200; whereby .the next line finder 4|,242 etc. selected by the switching mechanism 200 atthis time is tested in order to determine the-idle or busy condition the line finder" 4| is idle' atthis time and that,
the switching mechanism 200'incorporated in the line finder distributor 34 has operated to select the conductors extending thereto, battery'potential is applied by way ofthe' lower winding'of Q the test relay R460 in the "line finder 4|, the
contacts.4|| of the set of switch springs SM 0 and the contacts 444 to the guard conductor C412 plication of battery'potenti'al to theguard conductor C412 of the line finder 4| in thecable 410 completes a path substantially identical to that previously traced, including the contacts 201 and 222 and the wiper 202 of the switching mechanism'200I and the engaged contact in the associ ated contact bank, for shoIt-circuiting in series the line finder 4! is preselected thereby for use at this time. 1
Upon operating, the start relay R210 completes,
at the contacts 2 I2, an obvious circuit, including the contacts 241 and 201, for energizing the 'winding of the test relay R220 in series'with the mage net M206, whereby the test relay R220 operates. However, the magnet M206 does not operate due to the high series resistance of the winding of the test relay R220. Upon operating, thetest relay R220 completes, at the contacts 221, an ob vious holding circuit substantially identical-to that previously traced for energizing the winding thereof. in series with the magnet 'M206. Also the test relay R220 interrupts, atthe contacts 222, the previously traced original connection between the magnet M206 and the wiper 202 of the switching mechanism 200, and completes, at the contacts 223, an obvious alternative connection between the magnet M206 and the wiper 202. Also the test relay R220 completes, at the contacts 221, an obvious path, including the pontacts 2H and the wiper 201 andthe engaged contact in the associated contact bank, for ap-' plying ground potential tothe start conductor C415 in the cable 410, thereby to completean obvious circuit for energizing the winding of the start relay R440 in the preselected line finder 4|, whereupon the latter relay operates. Further the test relay R220 completes, at the contacts 224, a path, including the contactsf23lv and 24! and the wiper 203 of the switching mechanism 200 and the engaged contact in the associated contact bank, for applying ground potentialto the vertical conductor C416 in the cable 410; and completes, at the contacts 226, a connection, including the-contacts 246, between the winding of the cutoff relay R250 and the winding of the step relay R230, the winding of thestep relay R230 being connected to the interrupter conductor C414 in the cable 410. I
Upon operating, the start relay R440 in the line finder 4| completes, at the contacts 44l, a circuit for energizing in series the windings of the answer relay R430 in the line finder 4]. and the windings of the. line relay R360 in the secretary connector 5! via the trunk 6|. The above-mentioned circuit extends v from ground by way of the lower windingof the line relay R360, the contacts 314, one of the line conductors of the trunk 6!, the contacts 42'! and 441, the winding 431 of :the repeatingcoil 4135, the windings of the answer relay R430,, .the winding 436 of the repeating coil 435, the other line conductor of the trunk '61, the contacts 312 and the upper winding of the line relay R360 to bat tery; When this series loop circuitis completed the line relay R360 in the secretary connector 5| operates; however, the answer. relay R430-in 'the line finder 4| does not operateas-the latter Also the start relay is of the'polarized type. relay R440 completes, at the contacts 442, an obvious circuit for energizing the lower winding of the test relay R460, thereby to render the latter relay exceedingly fast to operate when -the upper winding thereof is subsequently energized,
. the test relay R460 being of the polarized-type.
Further the start relay R440 completesqat the contacts 441, an obvious path, including theco-ntacts 451, between the vertical magnet M405 of the switching mechanism 400 and the vertical conductor C416 in the cable 410,;wherebythe vertical magnet M405 is energized and operates.
Upon operating, the vertical magnet M405 drives the wiper set of the switchingimechan'ism400s16 one. step in the vertical direction away from its normal vertical position, and completes, atthe contacts 406, an obvious path for applying ground potential to the interrupter-conductor C414 in the cable 410. When the wiper set of the switching, mechanism 400 is driven one step in the vertical direction away from its normal vertical position, the sets of switch'springs S4l0 and S4|3 are actuated for apurpose more fully erating, the ,step relay R230 interrupts, at the contacts 23!, the previously traced path for applying ground potential to the vertical conductor C416 in the cable 410, thereby to interrupt the previously traced circuitfor energizing the vertical magnet 'M405, whereupon the latter magnet restores, thereby to interrupt, at'the contacts 406, the previously mentioned path for applying ground potential to the interrupter conductor C414 in the cable 410. 'When ground potential is removed from the interrupter conductor-C414 the previously traced circuits for energizingin multiple the windings of the step relayfiR230 and the cutoff relay R250 are interrupted,-whereby the step relay R230 restores. However, the cutoff relay R250 does not restore immediately as it is of the slow-to-releasetype Upon restoring, the step relay R230recomp'letes, at the contacts 23l, the previously traced circuit for energizing the vertical magnet M405, whereby the'latter magnet reoperates, thereby to drive the wiper set of the switching mechanism 400 an additional step in the vertical direction away from its normalvertical position. Also, upon reoperating, the vertical magnet M405 recompletes, at the contacts 406, the previously traced circuits for energizing in multiple the windings of thestep' relay R230 and the cutoff relay R250, whereby the step relay R230 reoperates shortly thereafter and the cutoff relay R250 is retained in its operated position as it is of the slow-.to-release type. Accordingly, it
will be understood that the vertical magnet M405 and the step relay R230 interact in the manner described above, whereby the cutoff relay R250 is retained in its operated position and thevertical magnet -M405 andthe step relay R230 operate and restore alternately; whereby the wiper set of the switching mechanism 400 is driven step by step in the verticaldirection away from its normal vertical position.
More particularly, the wiper set and the vertical control wiper 404 of the switching mechanism 400 aredriven'step by step in the vertical direction two"'s'tepss, in the present example, whereupon the vertical control wiper 404 engages the second contact in the associated Vertical control contact bank terminating the markconductor C418 having ground potential thereon; whereby ground potential on'the mark conductor C418 is applied to the test conductor C41l in the cable 410. This application of ground potential to the test conductor C41l in thecable 410 completes a circuit, including the wiper204 of the switching and the grounded interrupter conductor C414 in the cable 410, for short-circuiting the lower winding of the transfer relay R240 prior to the complete restoration of the vertical magnet M405 to remove ground potential at the contacts 406 from the interrupter conductor C414. However, when the vertical magnet M405 restores to interrupt, at the contacts 406, the applicationof ground potential to the, interrupter conductor ,C414 in the cable 410, the above-traced path for short-circuiting the lower winding'of the transfer relay R240 is interrupted; whereupon a circuit 7 is completed for energizing the lower winding of the transfer relay R240 in series with the lower winding of the step relay R230. The above-mentioned circuit extends from the grounded test conductor C41! in the cable 410 by way of the wiper 204 of the switching mechanism 200 and the engaged contact in the associated contact bank, the contacts 245, the lower winding of R240,
the contacts 226 and the winding of R230 to battery. Also a multiple holding circuit is completed for energizing the lower'winding of the a transfer relay R240 in series with the winding of the cutoff relay R250; the last-mentioned circuit including the contacts-246 and 245 and the wiper 204 of the switching mechanism 200 and the engaged contact in the associatedcontact bank and a the grounded test conductor C41l in the cable 410. When the lower winding of the transfer relay R240 is thus energized the latter relay op 'erates shortly thereafter, the transfer relay R240 being of the slow-to-operate type. Upon operating, the transfer relay R240 completes, at the contacts 243, an obvious holding circuit, including'the contacts 225, for energizing the upper winding thereof. Also the transfer relay R240 interrupts, at the contacts 2, a further point 7 in the previously traced path for applying ground potential to the vertical conductor C416 in the cable 410, and prepares, at thecontacts242, a point in a path traced hereinafter for applying ground potential to the rotary' conductor C413 in the cable .410. Also thetransfer relay R240 interrupts, at the contacts 245, the previously traced circuitsfor energizing the lower winding of the'transfer relay R240 in series multiple relation with respect to the windings of the step relay R2 and the cutoff relay R250,'interrupts, at the contacts 246, a further p'ointiin the previously plete an obvious circuit, including the contacts 446" and 465, for energizingthe rotary magnet M401. When thus energized the rotary magnet M401operates, thereby to drive the wiper set of the switching mechanism'400 one step in the rotarydirection away from its normal rotary position; andcompletes, at the contacts 408, an
obvious alternative 'path for applying ground potential to the interrupter conductor C414in the cable 410. This application of ground potential to the interrupter conductor C414 completes the The step relay ing of the step relay R230, thereby to cause the latter relay to operate shortly thereafter; however, the previously traced circuit for energizing the winding of the cutoff relay R250 is not com- I pleted due to the operated position of the transfer relay R240. Upon operating, the step relay R230 in order to cause the latter relay to restore. Upon restoring, the step relay R230 recompletes, at the contacts 231, the previously traced circuit for energizing the rotary magnet M401, thereby to cause the latter magnet to reoperate and drive the wiper set of the switching mechanism 400 an additional step in the rotary direction away from its'normal rotary position. Thus it will be under- ,stood that the rotary magnet M401 and the step relay R230 interact in the manner described above, whereby the wiper set of the switching mechanism 400 is driven step by step in'the rotary direction away from its normal rotary position. In the present example, the wiper set of the switching mechanism 400 is driven two steps in the rotary direction away from its normal rotary position, whereupon the wipers noted thereof engage the contact set in the associated contact bank terminating the conducors of the subscriber line 22 extending to the called subscriber substation T2. 7 r
When the wiper set of the switching mechanism 400 engages the contact set in the associated contact bank terminating the conductors of the subscriber line 22, a series circuit isrcompleted for energizing the winding of the cutoff relay R560 in the secretary line circuit 32 individual to the subscriber line 22 and the upper winding of thetest relay R460 in the line finder This circuit extends fr0m the grounded test conductor C41l in the'cable 410 by way of the upper winding of R460, the wiper 403 of the wiper set of th switching mechanism 400 and the engaged contact in the associated contact bank,
the control conductor 0220 of the subscriber line 22, the contacts 561 and the winding of R560 to battery. When this series circuit is completed the test relay R460 operates exceedingly fast, as
it is of the polarized type, to complete, atthe' contacts 462, an obvious path, including the contacts 442 and the grounded test conductor C41! in the cable 410, for short-circuiting the upper ,.previously traced'circuitlfor energizing the wind- "15 winding thereof, and an obvious path; including the contact 442, for applying direct ground potential to the wiper 403 of the wiper set of the switching mechanism 400 and consequently to the control conductor C220 of the subscriber line 22, whereby a low resistance circuit substantially identical to that previously traced'is completed 7 for energizing the winding of the cutoff relay R560 in'the secretary line circuit 32. When thus energized the cutoff relay R560 operate to complete, at the contacts 562 and 563, a holding circuit, including the contacts 512 and the, grounded control conductor 0223 of the subscriber line 22, forenergizing the winding thereof; Also the cutoff relay R560 completes, at the contacts 563, an
obvious path, including the contacts 512, for connecting the grounded control conductor C22B of the subscriber line 22 to the contro1 conductor 022C of the subscriber line 22; thereby to comfinder -4 plete analternative holding'circuit, including the wiper 403 of the 'wiper-setof-the switchingmechanism 400 and the engaged contact in the associated contact bank .and the contacts 462, for energizing the lower winding of the test relay R460 in order to retain the latter relay in its operated position subsequent to the restoration of the start relay R440, as explained more fully hereinafter. Also the cutofi relay R560 interrupts, at the contacts '56I, the previously traced path for applying ground potential to the mark conductor C418, thereby to interrupt .the previously traced circuit for energizing the winding of the start relay R2 l in the line finder distributor 34 in order to cause the latter relay to restore.
AlsO, upon operating, the test relay R460 interrupts, at the contacts 465, a further point in the previously traced circuit for energizing the rotary magnet M401, thereby positively to prevent further operation of the latter magnet, whereby further operation of the wiper set of th switching mechanism 400 is positively prevented at this time. ,Also the test relay R460 completes, at the contacts 46|, anobvious multi- .ple point, around the contacts 442, in the previously traced loop circuit, including the trunk 6| and extending between the line finder 4| and the secretary connector 5|. Further the test relay R460 completes, at the contacts 466, an obvious circuit for energizing the winding of the cutofi relay R450, thereby to cause the latter relay to operate and interrupt, at the contacts L .a further point in the previously traced-circuit for energizing the vertical magnet M405. Finally, the test relay R460 completes, at the contacts 464, aconnection, including the contacts 445 and 446, between 'the guard conductor C412 and the rotary conductor C413 in the cable 410, thereby to complete .a circuit, including the contacts 224, 23|, .242, 25I and 223, and the wiper .202 of the switching mechanism 200 and the engaged contact in the associated contact'banlg-for energizing the magnet M206. When thus energized the magnet M206 operates, thereby to condition the wipers noted of the switching mechanism 200 to be driven an additional step in the clockwise direction.
Also when the grounded rotary conductor C413 is thus connected to the guard conductor C412 in the line finder 4| 'as explained above, 'a path, including the wiper 202 of the switching mechanism 200 and the engaged contact in theassociated contact bank, andthe contacts 223,201 and "221, is completed for short-circuiting the wind- 'ing of the test relay R220, thereby to cause the latter relay to restore. Upon restoring, the test relay R220 interrupts, at the contacts 221, a point in the previously traced path for short-circuiting the winding thereof, and interrupts, at the contacts 221, the previously traced path for applying ground potential to the start aconductor C415 in the cable 4T0, thereby to interrupt the previously traced circuit 'for energizing the winding of the start relay R440 in the line finder 4| in order to cause the latter relay to restore shortly thereafter, the start relay R440 being of the slow-to-release type. Also, .upon restoring, the test relay R220 interrupts, at the contacts 223, the previously traced circuit for energizing the ."magnet M206, thereby to causethe latter magnet to restoreand .drive the wipers notedof the switching mechanism 200 an additional step in the clockwise :direction in order "to disengage the conductors in itheca'ble 410 extending to the line Further thetest relay R220interrupts, at the contacts 225, the previously traced holding circuit for'energizing the upper Winding of thetransfer relay R240, thereby to cause the latter relay to restore. At this time the line finder distributor 34 is completely released and is available for further use.
Upon restoring, the start relay R440 in the line finder 4-| interrupts, at the contacts 442, the previously traced original circuit for energizing the lower winding of the test relay R460; however, the latter relay remains in its operated position due to the previously traced completed holding circuit for energizing thelower winding thereof, including the grounded control conductor 0220 of the subscriber line 22. Also the start relay R440 interrupts, at the contacts 44|, a
multiple point in the loop circuit extending bethe guard conductor C412 in the cable 410 marks the line finder 4| as busy to the line finder dis,-
tributor 34, as previously noted. Accordingly, at this time, the wiper set of the switching mechanism 400 in the line finder 4| occupies its 2 up 2 in position-engaging the'contact set in the associated contact bank terminating the subscriber line 22 extending to the .called subscriber substation T2. Further'it is noted that the 2 up 2-in position of the wiper set of the switching mechanism 200 corresponds to the digits 2 .and 2 representing the directory number of the :called subscriber substation T2.
Reconsidering now the operation of the line finder 4| in conjunction with the line finder distributor 34, it is noted that each time the step relay R230 in the line finder distributor 34 operates and then restores it completes and then interrupts, at-the contacts 232, an'obvious path, including the wiper 205 of the switching mechanism 200 and the engaged contact in the associated-contact bank, for applyingground potential to the pulse conductor C411 in the cable 410,
thereby to complete and then to interrupt an obvious circuit for energizing the winding of the pulse relay R420 in the line finder 4|, whereby the latter relay :operates :and then restores.
:Each time the pulse relay R420 in the line finder 4| operates and :thenrestores it interrupts and then recompletes, at the contacts 42l, the previously traced loop circuit extending "between the line finder 4| and the secretary connector 5|, including the trunk 6| whereby the line relay R360 in the secretary connector 5| follows the pulse relay R420 in the line finder 4|. In
view of the foregoing explanation of the mode of operation of the line finder 4| in conjunction with the line finder distributor 34, it will be understood that the step relay R230 first-controls the vertical motion of the wiper set of the switching mechanism 400, whereby the wiper set is operated two steps in the vertical direction, in the 'the'present example, and'a corresponding numberof impulses comprising the digit 2 are transmitted by'lthe step'relay R230 to the pulse relay R420 and repeated thereby over the trunk 6| to the line relay R360. Hence, the line finder distributor 34 is operative to control the line finder 4! to select the called subscriber line 22 and torepeatover the trunk 6| to the line relay R360 in the secretary connector the two digits 2 and 2 corresponding to the directory number of the called subscriber line 22.
Thefline relay R360 in the secretary connector 5| follows the' first digit 2 in an obvious manner; When the line relay R360 operated it 'completed,'at the contacts 361, an obvious circuit for energizing the winding of the hold relay R350,
whereby the latter relay operated; The first time the line relay R360 restores it interrupts, at the contacts 36 I the previously mentioned circuit for energizing the windingof the hold relay R350,
7 and completes, at the contacts 362, a circuit, in-
V cludingthe contacts and the contacts 309 of the set of switchsprings S308, for energizing the winding of the transfer relay R340 in series'with the vertical magnet M304, whereby the transfer relay R340 and the vertical magnet M304 the contacts 309 thereof, the previously'traced original circuit for energizing the winding of the "transfer relay R340 in Series with the vertical magnet M304 and there is completed, atv the con-,
tacts 3l0 thereof, an alternative circuit, including the contacts 362, 35land 342, for energizingthe winding of the transfer relay R340 in series with the v'ertical'magnet M304. The first time the line relay R360 reoperates it recompletes,
V at the contacts 36I, the previously mentioned circuit foren'ergi'zing' the winding of the hold relay R350,and interrupts, at the contacts 362, the previously traced alternative circuit for energiz ing thelwin'ding of the transfer relay R340'in series with the vertical magnet .M304. The line relay'R 360 restores and then reoperates twice, in .the present example, in response to the two impulses of the first digit 2 transmitted over the trunk filfwhereby the vertical magnet M304 is operated aridirestored twice in order to drive the wiper set of the switching mechanism 300 two steps in the verticaldirection. The hold relay The line relay R360 then follows the two 1mpulses of the second digit 2. 'Each timethe line relay'R350 restores it interrupts, at the contacts 36!, the previously mentioned circuit for energizing the winding of the hold relay R350, and completes, at the contacts 362,'the previously mentioned circuit, including the contacts 35!, the contacts 3l0 of the set of switch springs S308, and the contacts 34| and 325, for energizing the winding of the series relay R330 in series with the rotary magnet M305. When thus energized the series relay R330 operates; and the rotary magnet M305 operates, thereby to drive the wiper set of the switching mechanism 300 one step in the rotary direction away from its normal rotary position. Each timethe line relay R360 reoperates it recompletes, at the contacts 361, the
previously mentioned circuit for energizing the winding of the hold relayRj350, and interrupts, at the contacts 362, the previously traced circuit 7 for energizing in series the winding of the series relay R330 and the rotary magnet M305.- The hold relay R350 andthe series relay R330 are of the slow-to-release type and remain operated 'during impulsin-g. At the conclusion of the second digit 2 transmitted over the trunk 6! the line relayR3'60 remains in its operated position,
thereby to retain operated the hold relay R350;
and, shortly thereafter, the series relay R330 re- "stores. At this time theowipef'SBt of the switching mechanism 300 engages the 2 up 2 in contact set in the associated contact bankv terminating the trunk 82 which is terminated by the jack.J2 at the secretary operator position II,
the trunk 82 and the terminating jack J2 corresponding to the subscriber line 22 extendingto thecalled subscriber substation T2 in the branch ofiice 20, as previously noted. Upon restoring, the series relay R330 :completes, at the contacts 33!, a circuit, including the wiper 303 of the wiperset of the switching mechanism 300 and the engaged contact Iinthe associated contact bank, the control conductorof thetrunk B2 and the contacts of the jack J2, for energizing in series the upperwinding of the switch relay R320 and the signal lamp L382.. When thisserics circuit is completed the switch relay'R320operates to complete, at the: contacts 324, an obvious holdi ing circuit, including the :contacts 353, for energizing the lower winding thereof. 'Also the switch relay R320 interrupts, at the contacts 325,*a f urther point in the previously tracedcircuit for energizing the Winding, of theseries relay R330 in serieswith the rotary magnet M305, and com pletes, at the contacts 323, an obvious path, including the contacts 33l,for short-circuiting the upper winding of the switch rela R320., Also i the switch re1ayR320 completes, at the contacts R350 and the transfer relay R340, being of the *slow-to-r'elease type, remain operated during impulsing. At theconclusionof the first digit 2, the line relay R360 remains operated in order *to retain the hold relay R350 in its operated posi- 'tio'n, whereby-the transfer relayR340'restores shortly thereafter; Upon restoring, the transfer tacts 34l, acircuittraced hereinafter'for ener gizing -the1windihg of the series relay R330 inseries with the rotary magnet M305.- T s I V 323,"an-obvious .path forrapplying direct ground potential 'to the wiper 303 of the wiper set of V the switching mechanism'300, thereby to com plete a low resistance circuit substantially identif cal 'to that previously traced for illuminatingthe signal lamp L382. Finally the switch relay R320 completes, at the contacts 32I and '322, an obivious connection, including the fwipers 3M and 302 of the wiper set of theswitching mechanism 300, between the upper and lower windings of 7 the battery reverse relay R310 'andthe line conductors of the trunk terminating in' the jack 7 J2, with which the illuminated signal lamp L382 7 is associated. The illumination of'the signal lamp L382 indicates .to the operator at the secretary operator position ll that'there is a call onthe V relay operates as it is of the polarized type.
trunk 82 waiting to be answered and. that, consequently, a call has'been extended to or initiated,
at the called subscriber substation T2 in the branch oflice 20.
The operator at the secretary operator position answers the call by inserting the answer plug of the cord circuit into the jack J 2, whereby the contacts of the jack J2 are operated in order to interrupt the previously traced circuit for illuminating the signal lamp L382, whereby the last-mentioned lamp is extinguished. Also an operative connection is completed between the telephone instrument in the cord circuit at the secretary operator position H and the line conductors of the trunk-'82, whereby an obvious loop circuit is completed for energizing in Series the upper and lower windings of the battery reverse relay R310. When thus energized the battery reverse relay R310 operates to interrupt, at the contac'ts312 and 314, the previously traced original loop circuit extending'be'tween the line relay R360 in the secretary selector 5| and the answer relay R430 in the line finder 4| and to complete, at the contacts 3H and 313, an obvious alternative loop circuit between the line relay R360 and the answer relay R430; whereby the direction of current flow over the loop circuit mentioned is reversed. When the direction of current flow through the windings of the answer relay R430 in the 'line finder 4| is thus reversed th latter Upon operating, the answer relay R430 complete at the contacts 43|, a connection including the windings 438 and 439 of the repeating coil 43.5
between the wipers 40| and 4020f the wiper set of the switching mechanism 400, whereby the windings 438 and 439 are operatively connect d to the line conductors of the subscriber lin 22 extending to the called subscriber substation T2. Accordingly, at this time, the calling subscrib r substation TI is operatively connected via the subscriber line 2|, the local finder. 21, the local connector .28 and the subscriber line 22t the called subscriber substation T2; and the subscriber line 22 extending to the called subscriber substation T2 is operatively connected .Via the line finder 4|, the trunk 6|, the secretary con nector 5|, the trunk 82, the jack J2 and thecord circuit ,to the telephone instrument at thesecrfi taryoperator position I, whereby the subscriber at the calling subscriber substation Tl in the branch ofiice 20 may converse with the operator at the secretary operator position in .the central oflice ID. More particularly, theoperator at the secretary operator position L l answers .the call on the trunk 82 and gives the subscriber at the calling subscriber substation Tl the information which is to be given to calling subscriber substations in the absence of thesubscriber at the called subscriber substation T2, which is rendered secretarial service at this time. a
After the subscriber at the calling subscriber substation TI in the branch oflice .20 has received the information mentioned from the operator .at the secertary operator position H in the :central oflice l0, he replaces the receiver upon its associated switchhook; however, the local finder 21 and the local connector 28 remain in their'operated positions due to the operated position of the switching mechanism 400. The operator at the secretary operator position then withdraws the answer plug of the cord circuit ,from the jack J2, thereby to interrupt the previously traced. loop circuit for energizing in series the upper and lower winding .of the battery reverse relay R310 in thesecretary connector 5|, whereby the latter relay restores. Upon restoring, the battery greverse relay R310 in the secretary co-nnector 5| interrupts, at the contacts 315, apreviously completed multiple holding circuit for energizing the winding of the hold relay R350, interrupts, at the contacts 311 and 313, the prezviously traced alternativ loop circuit extending between the answer relay R430 in the line finder 4| and the line relay R360 in the secretary connector 5|, and completes, at the contacts 312 and 314, the previously traced original loop circuit between the answer relay R430 and the line re.- lay R360. Accordingly, the direction of current fiow over the trunk 6| between the answer relay R430 in the line gfinder 41 and the line relay R360 in the secretary connector 5| i -reversed, whereby the answer relay R430 restores as it is of the po, larized type. Upon restoring, the answer relay R430 interrupts, at the contacts .43|, the previously traced "loop circuit between the windings 43a and 43a of the repeating coil 435 and the local connector 28, whereby the local finder 2-1 and the local connector 28 are released.
When the local finder. 21 is thus =reelased the subscriber line 2| extending to the subscriber substation TI is marked as idle to the local connectors having access thereto; and when the'local connector 28 is thus released the subscriber line 22 extending to :the subscriber. substation T2 is marked as idle to the local connectors having access thereto. More particularly, when the local connector :28 is thus released, ground potential therein i "removed from the control conductor :CZZ'B of the subscriber line 22, thereby to interrupt the previously traced original circuit for energizin the winding of the start relay R565, the previously traced holding circuit for energizing the winding .of the cutoff relay R560 and the previously traced path for applying ground potential to the control conductor 02-20 of the subscriber 'line 22. The start relay R565 and the cutoff relay R560 in the secretary line circuit 32 restore; and the service relay R510 therein remains in its operated position, whereby secretarial service is maintained incforce at the subscriber substation'T2. When ground potential is removed from the control conductor 022C or the subscriber line 22 the previously traced holding circuit for energizing the lower winding of the'test relay R460 in the line finder 4| is interrupted, thereby to cause the latter relay to restore. Upon restoring, the test relay R460-completes, at the contacts 463, a circuit, including. the contacts 443 and the set of switch springs S4'l3, for energizing the release magnet M409, whereby the latter magnet operate in order to release the wiper set and the vertical control wiper 404 of the switching mechanism 400, wherebythe wiper set is returned to its normal rotary and vertical positions and the vertical control wiper 4:04 is returned to its normal vertical position. When the wiper set of the switching mechanism 400 is thus released the sets of switch springs SM 0 and S4|3 are actuated; -More particularly, the set of switch springs S4 |0-is actuated, whereby there is interrupted,
at ,thE-gCOlltaQts 4|2 thereof, the previously traced path for. applying ground potential to the guard conductor C412 inthe cable 410 and thereis completed, at the contacts 4 thereof, the previously traced path for applying battery potential by way of the lower winding of the test relay R460 to the guard. conductor C412 in the cable4'l0.
- The removal of ground potential from and the application of battery potential to the guard conductor C412 in the cable 410 marks the line finder 4| as idle to the line finder distributor 34, whereby the line finder 4| may be preselected at this time by the line finder distributor 34 for furtheruse. The set of switch'springs S4|3 is actuated into disengagement, thereby to interrupt the previously traced circuit for energizing the release magnet M409, whereby the latter magnet restores.
Also, upon restoring, the test relay R460 interrupts, at the contact 46|,the previously traced loop circuit extending between the answer relay R430 in the line finder. 4| and the line relay R360 in the secretary connector 5|, whereby the line relay, R360 restores, the answer relay R430 already occupying its restored position. Upon restoring, the line relay R360 in the secretary connector 5| interrupts, at the contacts 36I, the previously mentioned circuit for energizing the winding of the hold relay R350, thereby to cause the latter relay to restore shortly thereafter, the 7 hold relay R350 being of the slow-to-release type. Upon restoring, the hold relay'R350 interrupts, at
the contacts 353, the previously traced holding circuit for energizingthe lower winding of the switch relay R320, thereby to cause the latter relay'to restore. Also the hold relay R350 completes, at the contacts 352, a circuit, including the'contacts 362 and the set of switch springs $301, for energizing the release magnet M306, 7 thereby to cause the latter magnet to operate and release the Wiper set of the switching mechanism 300, whereby the wiper set mentioned is returned 7 V to its normal rotary and vertical positions. -When the 'wiper set ofthe switchingmechanism'300 is thus released the set of switch springs S301 is actuated into disengagement, thereby to' 'interrupt the previously traced circuit'for energizing the release magnet C306 in order to cause the latter magnet to restore. At this time the secretary connector 5| is completely released and available for further use. 7
In view of the foregoing explanation it will be understood that the release of the local connector 28 is eifected jointly by the subscriber at the calling subscriber substation T| in the branch office 7 20 and by the operator at the answering secretary operator position I in the central ofilce l0,
whereby the local connector" 28 is not released until both the subscriber at the calling subscriber substation Tl replaces the receiver upon its asso- 'ciated switchhook and the operator at the an swering secretary operator position I I withdraws the answer plug of the cord circuit from the jack J 2. When the local connector 28 is thus released the line finder. 2| and the secretary connector 5|,
' connected together via the trunk 6| to form' the link mentioned, are released, whereby the line finder 4| is marked aslidle to the switching mechanism 200 in the line finder distributor 34.
In the foregoing explanation of the mode of operation ofthe line finder 4| to 'find the subscriber line 22 extending to the called subscriber substatidn T2 in response to the extension of the 'callthereto from thecallin'g subscriber substati onT l, itwas assumed that the .line 'finder 4| operated under the control of the lin finderdis tributor 34, whereby the wiper set of the switchcontrolled over the subscriber line 22.
ing mechanism 400 found the contact set in :the associated contact bank terminating the subscriber line 22. some reason the Wiper set of the switching mechanism 400 in the line finder 4| fails to find the contact set in the associated contact bank'terminating the subscriber line 22 extending to the calledsubscriber substation T2 during itsoperation in the'rotary direction. In this case, the
wiper setof the switching mechanism 400 is driven eleven steps in the rotary direction away from its normal rotary position without efiecting operation ofthe test relay R460, in the manner previously explained. In this case; the set of switch springs S4 l 4 isv actuated, whereby an obivous path, including the contacts 445, is completed for applying ground potential to the guardconductor C412 in the cable 410. This applicationof ground potential to the guard conductor C412 in the cable 410 completes a circuit,-includin the wiper 2-02 of the switching mechanism 200'and the engaged contact in the, associated contact,
bank and the contacts 223, for energizing the magnet M206 and an obvious multiple path, including the contacts 201 and 221, for shortcircuiting the winding of the test relay-R220; whereby the magnet M206 operates and the test relay R220 restores. Upon restoring, the test relay R220 interrupts, at the contacts 223, the previously traced circuit for energizing the mag net M206, thereby to cause the latter magnet to restore and drive the wiper set of the switching mechanism 200 an additional steprin the clockwise direction. Thus the wiper set ofthe switching mechanism 200 is operated to disengage the contacts in the associated contact bank terminating theconductors extending to the line finder 4| and to engage contacts in the associated contact bank ,terminatingconductors extending to another line finder 42 etc, whereby operation of the last-mentioned line finder is initiated to hunt for the subscriber line 22- extending to the'called subscriber substation T2,=in the manner previously explained, and the start relay R440 in the line finder 4| restores in order to effect the release of this line finder in the manner previously explained. Thus it will be understood that, in the event any line finder preselected for use by the line finder distributor 34 is first operated to hunt for thesubscriber line extending toa called subscriber substation rendered secretarial service and fails to find thesubscriber linementione'd,
the'line finder distributor operates in orderto assign another idle line finder to hunt for the" called subscriber line mentioned, and the previously selected. line finder is released.
Discontimu'ng secretarial service at asubscriberv substation in the branch office substation T2, the subscriber thereat firstinitiates -a call by removing the receiver from its associated switchhook; whereby'the local line circuitj25 is More particularlyftheilocal line circuit 25 is controlled in orderto cause ground potential to be applied to the control conductor 022B of the subscriber line 22in order to mark the subscriber line 22 as busy to the local connectors having access thereto, as
previously explained. This application of ground potential to'the'control' conductor C223 'o'fthe However, it may occur that for For example,'in order subscriber. line 22 completes the previously traced circuit for energizing the winding of the start relay R565 in the secretary line circuit 32, where,- by the latter relay operates. Upon operating, the start relay R565 initiates operation of the line finder distributor 34, whereby an idle line finder,
such, for example, as the line finder 4 I is assigned in the manner previously explained. The line finder 4| then operates in order to find the sub scriber line 22 having a call thereon extending to the calling subscriber substation T2; whereby operation of the associated secretary connector 5i is controlled over the trunk 6| to seize the trunk 82 terminating in the jack J2 at the secretary operator position I] in the central ofiice l0, all in the manner previously explained. The operator at the secretary operator position H then answers the call on the trunk 82 and converses with the subscriber at the calling subscriber substation T2 in the branch office 20. The subscriber at the calling subscriber substation T2 then advises the operator at the secretary operator position l l that the secretarial service being rendered the subscriber substation T2 is no longer required. The subscriber at the calling subscriber substation T2 then replaces the receiver upon its associated switchhook; and the operator at the secretary operator position ll withdraws the answer plug of the cord circuit from the jack J2; whereby the established connection is released in the manner previously explained.
The operator at the secretary operator position ll then inserts the call plug of .the cord circuit into the jack J l2 terminating the trunk 12 extending between the central office l0 and the branch ofiice 20, the trunk 12 being terminated in the secretary service switch H, as previously explained. The operator at the secretary operator position H then dials three digits over the trunk 12; the first digit being effective to operate. the select switch 520 in order to indicate that secretarial service is to be discontinued. and the second and third digits being effective to operate the switching mechanism 500, thereby to select the secretary line circuit 32 associated with the subscriber line 22 extending to the subscriber substation T2. More particularly, in the present example, in order to discontinue secretarial service at the subscriber substation T2, the three digits 2, 2 and 2 are dialed; the first digit 2 indicating that secretarial service is to be discontinued at a subscriber substation and the second and third digits 2 and 2, respectively, identifying thesecretary line circuit 32 individual to the subscriber line 22 extending to the subscriber substation T2. More particularly, the secretary service switch H operates in response to the three digits 2, 2 and 2, in the manner previously explained, and, at the conclusion of the operation thereof, the control relay R555 restores, thereby to effect operation of the switch relay R550 in .the manner previously explained. Upon operating, the switch relay R550 completes, at the contacts 552, the previously traced holding circuit for energizing the lower winding thereof and completes, at the contacts 55!, the previously traced path for short-circuiting the upper winding thereof and for applying direct ground potential to the wiper 52l of the select switch 520, whereby ground potential is applied to the wiper 502 of the wiper set of the switching mechanism '500 and the engaged contact in the associated contact bank terminating the conductor C582. The application of ground potential to the conductor C582 completes an obvious path, including the contacts 511, for short-cirouiting the winding of the service relay R510 in the secretary line circuit 32, thereby to cause the latter relay to restore. Upon restoring, the servicere lay R510 interrupts, at the contacts 5', a further point in the previously traced holding cire cuit for energizing the winding thereof, and in,- terrupts, at the contacts 512, the previously traced connection between the winding of the start relay R565 and the control conductor 0223 of the subscriber line 22. After the operator at the secretary operator position H has thus dis,- continued secretarial service at the subscriber substation T2, she withdraws the call plug oi the cord circuit from the jack J l2, thereby to eifect the release of the secretary service switch I l, in the manner previously explained. At this time, secretarial service at the subscriber substation T2 is discontinued and this subscriber substation is rendered ordinary subscriber sub,- station service at this time.
Local calls in the branch oflice .ciated secretary line circuit 32 the service relay R510 occupies its restored position, whereby the winding of the start relay R565 therein is disconnected from the control conductor C22B of the subscriber line 2-2 extending'to' the subscriber substation T2.
Conclusions In view of the foregoing it is apparent that a telephone system is provided which comprises a central office and a branch oilice; which system includes'improvedapparatus for rendering secretarial service to a relatively large group of subscriber substations in the'branch ofiice from a secretary operator position in the central voflice via a relatively small number of links ,or trunks extending between .the branch .ofiice .and the central ofiice.
While one embodiment of the invention has been disclosed, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention.
What is claimed is:
1. In a telephone system, a calling station, a plurality of lines, means for extending lacall from said calling station to any called one .of said lines, a link, an operator position, .means controlled from said operator position for selecting any one of said lines and characterizing the selected line, line identity apparatus associated with said operator position, and means controlled by the extension of a call to any characterized one of said lines for setting up a connection .jrom said one characterized line by way of said link to said operator position and for selectively operating said line identity apparatus tojid entify said one characterized line.
2. In .a .telephone system, a calling station, a
plurality of lines,- means 'for extending a call from said calling station to any called one of said lines, a plurality of links fewer in number than said lines, an operator position, a numerical switch, means at said position for operating said switch directively thereby to characterize any desired one of said. lines, line identity apparatus associated with said operator position, and means controlled :by the extension of a call to any characterized one of said lines for setting up a connection from said one characterized line by way of an idle one of said links to said operator position and for selectively operating said line identity apparatus to identify said one characterized line;
3. In a telephone system, a calling station, a plurality of lines, automatic switching apparatus selectively'controllable from said calling station to extend a call therefrom to any called one of 7 said lines, an automatic switching link, an operator position, means controlled from said operator position for selecting any one of said lines 7 and characterizing the selected line in either of two ways, line identity apparatus associated with said operator position, and means controlled by the extension of a call to any called one of said lines only if said called line is characterized in 'a particular one of said two Ways for selectively operating said switching link to set up a connection from said one called line to said operator position and for selectively operating said line identity apparatus to identify said one called line.
4. In'a telephone system, a calling station, a plurality of lines, means for extending a call from said calling station to any called one of said lines, an operator switchboard, a plurality of trunks accessible 'to said operator switchboard and individually corresponding to said lines, an automatic switch having access to said trunks, means controlled by the extension of a call to any called one of said lines for selectively operating said switch to select the one of saidtrunks corresponding to said one called line, thereby to initiate a' call on said one trunk, means control- 7 lable from said operator switchboard for answering the call on said one trunk, and means for connecting said switch to said one called line.
In a telephone system, a calling station, a plurality of lines, means for extending a call from said calling station to any called one of said lines, an operator switchboard, a plurality of trunks accesible to said operator switchboard and individually corresponding to said lines, an autosaid second switch to select the one of said trunks corresponding to said one called line, thereby to initiate a .call on said one trunk, means controllable from said operator switchboard for answering the call on said one trunk, and means for connecting together said first and second switches.
'7. In a telephone system, a calling station, a plurality of lines, means for extending a call from said calling station to any called one of said lines, a first automatic switch having access to said lines, an operator switchboard, a plurality of trunks accessible to said operator switchboard and individually corresponding to said lines, a
second automatic switch having access to said trunks, means controlled by the extensionof a call to any called one of said lines for selectively operating said first switch to select said one called line and for selectively operating said second switch to select the one of said trunks corresponding to said one called line, thereby to initiate a call on said trunk, means controllable from said operator switchboard for answering the call on said one trunk, and means controlled by theanswering of the call on said one trunk for connecting together said first and second switches.
8. In a telephone system, a calling station, a plurality of lines, means for extending a call said lines, a first automatic switch having access matic switch having access to said trunks, means 7 controlled by the extension of a call to any called one of said lines for selectively operating said switch to select the one of said trunks corresponding to said one called line, thereby to initiate a call on said one trunk, means controllable from said operator switchboard for answering the call on said one trunk, and means controlled by the answering of the call on said one trunk for connecting said switch to said one called line.
6; In a telephone system, a calling station, a plurality of' lines, means for extending a call from said calling station to any called one of said lines, a first automatic switch having access to said lines, an operator switchboard, a plurality of trunks accessible to said operator switchboard and individually corresponding to said lines, a second automatic switch having access to said trunks, means controlled by the extension of a call to any called one of said lines for selectively operating operating said first switch to select said one called line and for selectively operating 7 to said lines, an operator position, a second automatic switch, means controlled by the extension of a call to any called one of said lines for selec- V tively operating said first switch to select said 7 one called line and for selectively operating said second switch correspondingly, means controlled by the operation of said second switch for extending a call to said operator position and for identifying said one called line, means controllable from said operator position for answering the call extended thereto, and means for connecting together said first and second switches.
9. In a'telephone system,.a calling station, a plurality of lines, means for extending; a call from said calling station to any called one of said lines, a plurality of links, an operator position, means controlled by the extension of a call to any called one of said lines for extending a call from said one called line by way of an" idle one of said links to said operator position, means controlled by the extension of a call over said one link for rendering it busy, means controllable from said operator position for answering the call on said one link, and means controlled jointly by the performance of a release operation at said calling station and by the performance of a release operation at said operator position for rendering said one link again idle.
10. In a telephone system, a calling station, a plurality, of lines, means forextending a call from said calling station to any called one of said lines, a link, an operator position, line identity apparatus associated with said operator position, means controlled by the extension of a call to any called one of said lines for extending a call over said link to said operator position a trolled by the answering of the call on said link for connecting said link to said one called line.
11. In a telephone system, a calling station, a plurality of lines, means for extending a call from said calling station to any called one of said lines, a link, an operator position, line identity apparatus associated with said operator position, means controlled by the extension of a call to any called one of said lines for extending a call over said link to said operator position and for transmitting a signal over said link individual to said one called line, means controlled by the signal transmitted over said link for selectively operating said line identity apparatus to identify said one called line, means controllable from said operator position for answering the call on said link, and means controlled by the answering of the call on said link for connecting said link to said one called'line.
12. In a telephone system, a calling station, a plurality of lines, means for extending a call from said calling station to any called one of said lines and for initiating the projection of ringing current thereover, a link, an operator position, line identity apparatus associated with said operator position, means controlled by the .extension of a call to any called one of said lines for extending a call over said link to said operator position and for selectively operating said line identity apparatus to identify said one called line, means controllable from said operator position for answering the call on said link, means controlled by the answering of the call on said link for connecting said link to said one called line, and means controlled by the connection of said link to said one called line for arresting the projection of ringing current thereover.
I 13. In a telephone system, a calling station, a plurality of substations, automatic switching apparatus selectively controllable from said calling station to extend a call therefrom to any called one of said substations, an operator position provided with facilities for rendering secretarial service to said substations, apparatus temporarily operated under the control of said position to select any desired one of said substations, means controlled by said apparatus for characterizing the selected substation and maintaining it characterized after said apparatus has restored to normal at the end of its temporary operation, and means controlled by the extension of a call to any one of said substations so characterized for setting up a connection from said one characterized substation to said operator position.
14. In a telephone system, a first ofiice including a calling station, a plurality of substations, and means for extending a call from said calling station to any called one of said substations; a second oflice including an operator position provided with facilities for rendering secretarial service to said substations; two trunks extending between said ofiices; means controllable over a particular one of said trunks but not over the other of said trunks for conditioning any one of said substations to receive secretarial service; and means controlled by the extension of a call to any one of said substations which is thus conditioned for setting up a connection from said one called substation by way of the other of said trunks to said operator position.
15. In a telephone system, a first office including a calling station, a plurality of substations, and means for extending a call from said calling station to any called one of said substations; a second oiifice including an operator position provided with facilities for rendering secretarial service to said substations, and substation identity apparatus associated with said operator position; two trunks extending between said offices; means controllable over a particular one of said trunks but not over the other of said trunks for conditioning any one of said substatios to receive secretarial service; and means controlled by the extension of a call to any called one of said substations which has been thus conditioned for setting up a connection from said one called substation by way of the other of said trunks to said operator position and for selectively controlling said substation identity apparatus over said other trunk to identify said one called substation.
16. In a telephone system, a calling station, a plurality of lines, means for extending a call from said calling station to'any called one of said lines, an operator position, line identity apparatus associated with said operator position, a switch controllable from said operator position to select any one of said lines, means including said switch operated at times to institute interceptor service upon any selected one of said lines and operated at other times to discontinue interceptor service upon any selected one of said lines, and means controlled by the extension of a call to any called one of said lines upon which interceptor service is in force for setting up a connection from said one called line to said operator position and for selectively operating said line identity to identify said one called line.
17. In a telephone system, a calling station, a plurality of'llnes, means for extending a call from said calling station to any called one of said lines, a plurality of relays individually associated with said lines, each of said relays including an operated position and a restored position and being provided with an operating circuit and a stick circuit and a path for shorting its stick circuit, means for selectively completing the operating circuits and the paths of said relays, means controlled when any one of said relays occupies its two positions respectively to institute and to discontinue interceptor service upon the associated line, an operator position, and means controlled by the extension of a call to any called one of said lines upon which interceptor service is in force for setting up a connection from said one called line to said operator position.
18. In a telephone system, a calling station, a plurality of lines, means for extending a call from said calling. station to any called one of said lines, a plurality of relays individually associated with said lines, each of said relays including an operated position and a restored position and being provided with an operating circuit and a stick circuit and a path for shorting its stick circuit, an automatic switch operable selectively to complete the operating circuits and the paths of said relays, an operator position, means controllable from said operator position for selectively operating said switch, means controlled when any one of said relays occupies its two positions respectively to institute and to discontinue interceptor service upon the associated line, and means controlled by the extension of a call to any called one of said lines upon which interceptor service is in force for setting up a connection from said one called line to said operator position.
19. In a telephone, system, a substation, means for extending a call to said substation, means for extending a call from said substation, means selectively controllable to institute and to discontinue interceptor service at said substation, an operator position, and means controlled by the extension of all calls either to or from said substation when interceptor service is in force there-
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2866007A (en) * 1954-05-18 1958-12-23 Gen Telephone Lab Inc Answering service arrangements in telephone systems
US2908765A (en) * 1958-04-10 1959-10-13 Gen Dynamics Corp Concentrator for telephone answering service
US3009022A (en) * 1956-07-30 1961-11-14 William J Camp Automatic telephone intercept system
US3041405A (en) * 1958-12-08 1962-06-26 Automatic Elect Lab Line circuit with two-way transfer

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2866007A (en) * 1954-05-18 1958-12-23 Gen Telephone Lab Inc Answering service arrangements in telephone systems
US3009022A (en) * 1956-07-30 1961-11-14 William J Camp Automatic telephone intercept system
US2908765A (en) * 1958-04-10 1959-10-13 Gen Dynamics Corp Concentrator for telephone answering service
US3041405A (en) * 1958-12-08 1962-06-26 Automatic Elect Lab Line circuit with two-way transfer

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