US1616182A

US1616182A - Telephone-exchange system

Info

Publication number: US1616182A
Application number: US671370A
Authority: US
Inventors: Owen C From
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1923-10-29
Filing date: 1923-10-29
Publication date: 1927-02-01
Anticipated expiration: 1944-02-01

Description

Feb.- 1,1921. 1,616;182

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Patented Feb. 1, 1927.

UNETED STATES PATET Emit.

OWEN C. FROM, OF NEW YORK, N. Y., ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED,OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed October 29. 1923.

The present invention relates to telephone exchange systems and more particularly to systems in which automatic switches are employed for establishing connections.

The object of the invention is to provide improved means for transferring records from one part of the system to another in systems where designations are recorded on controlling equipment.

In particular, the object of the invention is to provide an improved arrangement of relays whereby such designations may be transferred by means of code impulses transmitted over a loop circuit.

A feature of the invention lies in supplying potential to the conductors of the impulse circuit at all times, and in producing the impulses by either boosting or shortcircuiting said potential.

A further feature of the invention lies in an arrangement for feeding a series of impulses of alternate polarity to said loop circuit and modifying the impulses to produce the codes by means of parallel circuits controlled by the settings of the registers.

A further feature of the invention lies in the manner of preparing these parallel circuits in advance of the period at which they become effective.

A still further feature of the invention lies in discharging the circuit during periods when no impulses are sent out.

Other features contemplated by this invention will be more thoroughly understood from a consideration of the following description and also from the appended claims.

A more specific discussion of the above features will be given in connection with the detailed description of the operation of the portions of the circuits in which they are involved.

In the drawings, Figs. 1 to 9, when arranged in the order illustrated in the diagram of Fig. 10, disclose as much of a tele phone exchange system incorporating the features of the invention as is necessary for a thorough understanding thereof.

Fig. 1 illustrates in schematic manner a calling subscribers line and a line switch of the coordinate type for extending the lines to outgoing trunks. This figure also shows diagrammatically a sender selector switch of the coordinate type.

Fig. 2 shows a portion of the detailed cir- Serial No. 671,370.

cuits of one of the trunks outgoing from the line switch of Fig. 1 and also a diagram of a coordinate group selector switch in which said trunk terminates.

Figs. 4, 5, 8 and 9. taken together, show one of a number of register sender controlling mechanisms which are associable with the trunks by means of the sender selector switch illustrated in Fig. 1. 1

Fig. 4 illustrates the counting relays and other control relays of the sender. Fig. 8 shows the controlling relays and circuits for sending code impulses representing the recorded designations. Figs. 5 and 9 show relay registers on which designations are recorded under the control of the calling subscribers line.

Fig. 3 illustrates the incoming end of an interotiice trunk circuit. This trunk appears in a cord circuit at a manual operators position in the called oiiice. This figure also shows 3. called subscribers line terminating at a manual office.

Figs. 6 and 7 show a register circuit serving the purpose of a 'all indicator.

Fig. 11 shows a chart indicating the character of mpulses transmitted for the digits 0 to 9. inclusive.

The line switch 100. the group selector swit h 200. and the sender selector switch 110 are of the coordinate type such as shown and described in detail in the Patent No. 1507,1410. granted September 2, 1924 to J. N. Reynolds.

The calling sub criber on initiating a call has his line automatically extended by way of the line switch 100 to an idle trunk such as the trunk 103 terminating in the group selector or district selector switch 200. At the same time, the trunk 1023 is associated with an idle register sender by means of the sender selector switch 110. Following this, the subscriber dials a number of digits which are recorded on the several registers of the associated sender. Thereafter in any suitable manner, the register sender determines the selective operation of the district selector switch 200 and an idle trunk is selected leading to the distant manual office in which the wanted line appears. Inasmuch as the pres-. ent invention is not concerned with the detailed operation of the selector switches nor with the manner in which the register sender exercises its control over the switches, several elements have been illustrated in scheinatic fashion. For a more detailed explanation of the way in which the operating circuits of the various switches function and the manner in which the register senders control the selection of trunks, reference is made to the Patent 151K831, granted December 2, 192%. to S. B. Vi illiams.

After a trunk has been selected by the switch 200 in the mechanical office leading; to the distant manual oliice illustrated in Figs. 3. 6 and 7, it is next necessary to trans fer the record. establised in the register sendor over the trunk to the distant otiice to bring about the operation of the call indicator in orter that the operator may be advised of the called line number. This is accomplished by means of the equipment snown in Fig. 8 wherein the

relay device

807 and 808 controls operations which result in the creation of impulses which form codes according; to the record established on the registers and transmits these impulses over the line to the dhsant manual o'llice. T he record is established in the distant inanual otlicc onthe call indicator registers and causes the illumination of lamps before the operator. In case the distant called otilce is one involving; machine switching ap aratus for building; a connec on, code impulses will be transferred to a reg iter sender. which in turn, will control. switches in the called oltice.

A detailed description will now be given of the establishment of a connection between a calling line in a mechanical otiice such as line 101 and a called subscribers line 319 in a distant office involving the transferv of the record from the first oilice to the second ollice, assuming that the numerical part of the designation is 2531. The four digits of the numerical lesignation are recorded on. the foul. niui'icrical registers of the sender shown. in Figs. 5 and 9. l i hen the call involves the extension of a connection to a distant oilice, it would probably be necessary to employ otlice designations for controlling the selective switches in the first office to select trunks leading to the desired distant office. ,Vhere office designations are involved the register sender will have other registers similar to those snown for recording these designations a .d for controlling the local switches accordingly. For the purpose of simplifying the disclosure these rc lie'ss have been omitted.

hen the calling subscriber initiates a call his line 101 is extended automatically through the line switch 100 to the first idle one of a number of outgoing trunks 102 103., etc. If the trunk 10?) is the first one to be idle. it is selected and the ca line is extended thcreo er to the strict newer switch 200. At the same time that the calling line is extended to the district selector, the sender selector switch 110 is operated automatically and the trunk 103 is connected to the idle register sender shown in the drawing.

During the operation of the sender selector switch 110 a circuit may be closed in any suitable manner for the relay 204. Relay 20-1 operates and applies ground potential to the holding or sleeve conductor 111. As soon the sender selector switch 110 is operated, it may complete a circuit in any suitable manner for relay 203. Relay 203 closes a substitute circuit for the slow releasing relay 20- The slow releasing charactor of relay 20th and other similar relays hroughout the drawings has been indicated by weighted arrows across the armatures of such relays. The application of arrows pointing in opposite directions as applied to relays such as 807 and 808 indicates that Sh'll relays are both slow to operate and slow to release. Relay 203 also extends the tip and ring conductors of the trunk through the sender selector 110 to the selector sender. An impulse circuit is now traceable from battery through right winding of relay L00 in the sender. inner normal contact of relay 101, conductor 41S, inner left contact of relay 411 through selector 110, conductor 220, inner lower contact of relay 203, conductor 105. through the line switch 100, over the loop of the calling line and returning through the line switch 100 to the conductor 10 1-. inner upper contact of relay 203. conductor 291., through the selector 110, outer left contact of relay 411, outer contact of relay 101, left winding of coil 102 to ground. Relay 400 closes a circuit for slow release relay 104; which in turn closes a circuit for relay 4-10. Relay 1:10 applies holding; ground to conductor 120 which provides holding; circuits for the sender selector switch 110 and for relay 20?) in the trunk circuit. lrlclay 400 also closes a circuit through the left winding; of relay 4-0;). wh ch relay operates and closes a circuit for relay d2) extending); {WW1 battery. resistauve 40 left contact of relay 406, right contact of relay 40s. conductor 107. outer left contact of relay 408 through the wind' of relay 1 in series to ground. 4.213 operat and locks in a circuit extending from grounded battery. ice 4-05. conductor 109. le" 4112. inner right contact or r k 195 to grou so closes a circuit. for relay n21. extendn r from grouiuled battery left winding: of relay 403 inner left Contact of r lay 40 outer left contact of relay 1212, outer right back contacts of relays 42 -3 and 424-, outer left front contact of relay throucgh both wii'idinn's of relay in series to ground. This circuit is iueffective at this time due to the direct connection from the left winding of relay 103 to ground through front contact of relay 400.

I. it

The apparatus is now in condition for receiving the first series of impulses. The operation of counting relays of this character forms the subject matter of. applicants Patent No. 1,563,738, issued December 1, 1925.

The calling subscriber now manipulates his dial or other impulse transmitter to send a series of two impulses or interruptions of the impulse circuit. In response to the first interruption of the circuit, relay 400 releases and permits the above traced circuit for relay 421 to become effective, whereupon relay 421 operates and locks in. a circuit from ground through its right winding, conductor 413. left contact of relay 412, conductor 409, resistance 405 to battery. Relay 421 also closes a circuit from conductor 413, inner right contact of relay 425, through the left winding of relay 425, inner left contact of relay 421 to ground through the right wind ing of relay 403, the current .in which circuit opposes that in the locking circuit for relay and releases relay difierentially. The locli'ing circuit for relay 421 is in shunt of the energizing circuit through the left winding of relay 403 and tends to release relay 403. The circuit through the right winding of relay 403 which releases relay 425, is differential to the circuit through the left winding of relay 403, so that with relay 400 released, relay 403 releases quickly upon the operation of relay 421.

At the time relay 400 falls back in response to the first impulse, a circuit is closed fromground through the back contact of relay 400, right contact of relay 404, winding of relay 406 to ground. Relay 406 operates and opens the initial energizing circuit for relay It also closes an obvious circuit for relay 408. Relay 408 operates and locks in a circuit from battery winding and inner left contact of relay 408. outer right contact of relay 412, outer left contact of relay 410 to ground. Relay 408 closes circuits, the purpose of which will be made clear hereinafter.

At the end of the first interruption, relay 400 attracts its armatures and relay 403 is operated and completes a circuit for relay by way of grounded battery, left winding and inner left contact of relay 403, outer right front contact of relay 421, outer right back contact of relays 423 and 424., outer left back contact of relay 425,

througl'i both windings of relay 422 in series to ground. Relay 422 does not operate, beiug slninted. Relay 406 being slow to release does not retract its armatures during this time.

At the next interruption of the ciigcuit, relay 400 falls back, permitting relay 422 to operate in series with the left Winding of relay 403. Relay 422 operates and locks to battery over conductor 413 and closes a differential releasing circuit for relay 421extending from ground through the right winding of relay 403, inner left contact of relay 422, left winding of relay 421, inner right contact of relay 421 to conductor 413. Relays 421 and 403 release.

At the close of the second impulse, relay 400 remains energized long enough to per mit relay 406 to deenergize and retract its armatures. Since relay 408 is operated, a 4

circuit is closed from ground, right normal Contact of relay 406, inner right contact of relay 408, inner right contact of relay 412, conductor 416, right back contact of relay 901, winding of relay 902 to battery. Relay 902 attracts its armatures and locks in a circuit including its inner upper contact, conductor 903, winding of relay 412, and thence over the above traced circuit to ground at the right normal contact of relay 406. Relay 412, being shunted by the orig-- inal circuit for relay 902, does not energize at this time. Relay 902 extends

conductors

419, 429, 439, 449 to the relays of thousands register 900. Since relay 422 is the only u counting relay operated, a circuit may be traced from ground at the outer left contact of relay 410, conductor 417, outer right contactrelay 412, conductor 415, outer right back contact of relay 425, outer left back contact of relays 424 and 421, conductor 429, next to the innermost lower contact of relay 902, winding of relay 904. winding of relay 905 to battery.

Relays

904 and 905 operate and lock in a circuit from battery, windings of the two relays, inner right con tact of relay 904, conductor 906, conductor 901 conductor 426, outer right contact of re lay 410 to ground. Relay 905 closes an obvious circuit for relay 901 from grounoed conductor 906 which relay operates and locks to grounded conductor 906. At its contact, relay 901 opens the shunt around the wind ing of relay 412 permitting that relay to energize in series with relay 902. Relay 412 at its left armature, opens the locking circuit of the counting relays and at its outer right contact the locking circuit of relay 408. The counting relays are restored to normal. Relay 408 releases and opens the circuit of relays 412 and 902, disconnecting register 900 from the counting relays. soon as relay 412 falls back, tl'ie original circuit for relay 425 is closed and that relay energizes and. prepares a circuit for relay 421 as before.

The subscriber next dials the second digit of the called number, that is In response to the first interruption of the circuit, relay 406 is energized, in turn energizing relay 408 relay 421 is operated and relay 425 released. In response to the next interruption of the circuit, relay 422 operates and relay 421 releases. In response to the third interruption of the circuit, relay counting relays. interruption of the circuit, the circuit prearmatures and releases relays 422 and 403,

in a manner similar tothat for the other In response to the fourth pared for relay 424, extending from battery through theleft winding and inner left contact of relay 403, outer right back contact of relays 421 and outer right front con 1 tact of relay 423, through both windings of relay 424 in series to ground, becomes effective andrelay 424 attracts its armatures, releasing relays 423 and 403 and looking to conductor 413. The fifth interruption of this circuit causes the operation of relay 425 in a circuit from'batterythrough the left winding and inner left contact of relay 403, outer right armatures and back contacts of relays 421, 422 and 423 outer'right armature and front contact of relay 424, the two windings of relay 425 in series, to ground. elay 425 locks to conductor 413 through its right winding and releases relays 424 and 403. Relay 425 also completes a circuit from battery, winding of relay 427, right back contact of relay 428, outer right contact of relay 408, outer right front contact of relay 425, conductor 415, outer right contact of relay 412,conductor 417, outer left contact of relay 410 to-ground. Relay 427 attracts its'armatures and locks in a circu-it through the winding of relay 428 and the right contact of 427 to grounded conductor 415. Relay 428 cannot operate, being shunted by the energizing circuit of relay 427. When, now, at the close of this series of impulses, relay 400 remains energized; for a considerable period of time, relay 406 releases and completes a circuit from ground, right back contact of relay 406, inner right contact of relay 408, inner right contact of relay 412, conductor 416, right front contact of relay 901, right back contact of relay 927, winding of relay 908 to battery. Relay 908 operates and locks in a circuit including its inner upper armature, conductor 903, winding of relay 412, inner right contact of relay 408 to ground at the right back contact of relay 406. Relay 908 extends

conductors

419, 429, 439, 449 to register 909. Since relays 425 and 427 are operated, a circuit may be traced from ground .at the outer leftcontact of relay 410, outer right contact of relay 412, conductor 415, outer right front contact of relay 425, outer right contact of relay408, inner-left contact of relay 42?, inner left contact of relay 428,.conductor449, lowermost contact of relay 908, winding of relay 91.0 to battery. Relay-910operates and locks crates and locks to conductor 505.

by way of conductor 911 to grounded conductor 907. Relay 910 also connects ground from conductor 911, outer right contact of relay 910, winding of relay 927 to battery. Relay 927 operates and locks to conductor 911. The operation of relay 927 opens the energizing circuit for relay 908, which was in shunt of the windingof relay 412 and relay 412 operates. Belay 412 opens the locking circuit for the counting relays and that of relay 408. Relay 408 in releasing opens the circuits of relays 412 and 908 whereupon these relays also release and the circuits of Fig. 4 are ready to receive the next set of impulses.

Belay 400 being energized at the time, as soon as relay 408.closes its outer left back contact, the previously traced circuit for relay is closed and that relay prepares a circuit for relay 421 as before. The calling subscriber now manipulates his dial to send a series of three impulses. :Relays 406 and 408 are operated at the first interruption of the circuit and at the end of the third interruption of the circuit,.relay 423 is operated and the other counting relays deenergized. Relay 400 remaining energized for a considerable period permits relay-406 to release. A circuit is closed fromground at the right back contact of relay-406, inner right contact of relay 408, inner right contact of relay .412, conductor 416,.right front contacts of relays 901, and 927, right back contact of relay 501, winding of relay 502 to battery. Relay 502 operates and locks in a circuit through its inner upper contact, conductor 903, winding of relay 412, inner right contact of relay 408 to. ground atithe right back contact-of relay 406. Relay 502 extends conductors-419, 429, 439, 449 to the relays of register 500. Since relay 423 alone is energized, a circuit may be traced:from ground-at the outerleft contact of relay 410,- conductor 4.17,.outer right contact of relay 412, conductor 415, outer right back contact of relay 425, Outer left back contact of relay 424, outer left front contact of relay423 c0nductor419, innermost lower contact of relay 502, winding ofrelay 503 to cattery. A circuit may also be trace from grounded conductor 415, outer right back Contact of relay 425, outer left back contact of relay424, outer left -backcontact of re lay 421, conductor4429, next totheinnermost lower contact of relay 502, winding of these relays also extends ground .from

conductor 505 to relay 501 which relay-opt The operation of relay- 501 opensitheeenergizing circuit of relay502 permltting relayj412. to

energize andbring about therelease of. the 1 counting relays as before.

The calling subscriber next operates his dial to send a single impulse, which represents the fourth and last digit of the called number. In response to this impulse, relay 421 is operated and relay 425 released. At the completion of the impulse, relay 106 releases and a circuit is completed from ground, outer right back contact of relay d06, inner right contact of relay 408, inner right contact of relay 412, conductor L16, right front contacts of relays 901, 927 and 501, right back contact of relay 506, winding of relay 507 to battery. Relay 507 opcrates and locks bypvay of its inner upper contact, conductor 903, winding of relay 41-12 and thence over the previously traced circuit to ground. Due to the energization 01" relay 121, a circuit is closed from grounded conductor e15, outer right back contact of relay 425, outer left back contact of relay 4-24, outer left front contact of relay -1l2l, conductor 119, innermost lower contact of relay 507, winding of relay 508 to battery. Relay 508 operates and locks by way of conductor 509 to grounded conductor 907. in addition, relay 508 closes an obvious circuit for relay 506. Relay 506 operates and locks to conductor 509. Belay 506 in operating opens the circuit in shunt of the winding of relay 412 and this relay energizes and brings about the restoration of the counting relays and the disconnection of register 510 from the energizing leads.

1 1101201 the subscriber has set up the record on the sender, the district selector switch 200 is operated to seize an idle trunk 207 outgoing to the distant called ofiice. During the operation of switch 200, relay 206 is operated and looks through its inner upper contact, conductor 210, upper contact of relay 208, to the grounded conductor 111. Upon the operation of relay 206, relay 205 is operated by the switch 200 in a suit able manner and looks through its left armature to conductor 210.

after the connection has been extended to the distant oll'ice, the apparatus is placed in condition to transmit code impulses over the trunk in accordance with the settings of the numerical registers in Figs. 5 and 9 to operate the call indicator in the distant oliice. When the apparatus is ready for this purpose a circuit is completed in any suitable manner for relay 800. The manner in which the above mentioned operations take place is shown and described n detail in the Patent No. 1,517,331, granted Decen'i ber 192% to S. B. Williams. Relay 800 closes a circuit from battery through the winding of relay 801., contact of relay 600, conductor 802, middle leit contact of. relay 506 to ground. delay 801 operates and locks through its inner left contact. conductor 4:30 to ground. at the inner it contact of relay 110. Relay S01 conn cts the relay 803 to the tip and ring conductors oi the line resulting in a c rcuit as follows: battery through the inner lower back contact of relay 300 (Fig. 3) conductor 301, right winding oi relay 502, winding of relay 303, inner normal contact of relay 504-, outer back contact of relay 805, thence over the tip side of trunk 207 through switch 200, uppermost lt'ront contact of relay 206, inner right contact 017' relay 205, conductor 211, through the selector switch 110, conductor 131, outer et't contact of relay 801, conductor 825, right normal contact of relay 81.2, conductor 832, outer right back contact of relay 805, winding contact of relay 805, middle leit't contact 0t relay 801, conductor through the switch 110, conductor 212, outer right contact of relay 205, lowermost front contact of relay 206 through the switch 200 thence over the ring side of the line, inner back contact of relay 305, outer normal contact of relay 004-, left winding of relay 302 to ground. llelays 303 and 302 operate and relay 302 closes a circuit for relay S06. Relay 306 operates and at its outer le'l t contact closes a circuit around relay 303 releasing this relay anc prerenting it from reoperattng in series witl the right winding of relay 302. ltelay 306 also closes a circuit from battery through the assignnientlamp 307, lower winding of relay 306, outer right back contact or" relay 309, upper inner contact of relay 308, right inner contact of relay 306 to ground. Lamp 307 lights to advise th operator that a call is awaiting attention on the incoming trunk 207. Due to the character of relay 308, however, it is not energized sufficiently to attract its armature.

The code impulses are sent to the receiving o'llice over a full metallic circuit comprising both tip and ring conductors of the line in series. Those impulses may be of either positive or negative polarity dependent upon the side of the line circuit to which the positive pole of battery is connected. They may also be weal; or dependent upon Wl'ltitllGl' battery is fed to the line through a high or low resistance. The ini pulses are received by the

relays

600, 601 and 602. Relay 600 is polarized in such a manner as to respond only to the current produced when the positive pole of battery is connected to the tip side of the line. lielay 601 is polarized in such a manner as to respond to current of the opposite polar ity. Both

relay

600 and 601 respond either to strong or weak impulses provided the polarity is in the proper direction. Relay 602 responds to strong impulses of either polarity but does not respond to weal: nupulses.

At the time the above traced circuit is closed, relay 603 in the mechanical ollice also of relay 803, left baclr 0 operates and closes a circuitincluding relays 302, 303 and 803 from battery through winding of relay 809, front contact of relay 803 to ground. trom battery, winding of relay 80 1, front contact of relay 809 to conductor 430 andground at the inner right contact of relay 110. ltelay 80 1 operates and locks throng. its inner right contact to conductor 30.

icturning to the called oilice, the operator observing the illumination of lamp 307 presses the individual assignment key 310 to associate the call indicator with the trunk 207. Key 310 closes a circu t from battery through the winding or relay 605,1ower contact of relay 308, right winding of relay 309, upper contact 01' key 310, contact 01' relay 606 to ground at the right back. contact of relay 607. A branch of this circuit also. extends through the winding of relay 626 to ground but the direct path to ground shunts this relay and prevents its operation at this time. Relay 309 operates and: locks in a circuit from battery through winding of relay 605, windings of, relay 309 to ground at its left contact. Relay 309 opens the original circuit of lamp 307 and connects this lamp in series with the interrupter 311. The lamp tlashes during the period that impulses are being received and until the operator later inserts the plug oi the cord circuit in the jack of the called line. Relay 309 also closes a circuit from battery through the winding of relay 305 and in parallel through the left winding of relay 312, inner right contact oi relay 309, winding of relay 606 to ground at the left back contact of relay 607. Relay 305 operates and extends the tip and ring conductors of the incoming trunk to conductors 60a and 603, respectively. When relay 305 operates it opens the circuit including relays 302 and 803. Relay 302 releases and opens the circuit of relay 306 which also deenergizes. Relay 803 in releasing, permits the release of relay 809 which relay completes a circuit from battery through the winding of relay 805, outer right contactof relay 80 1, back contact of relay 809 to grounded conductor 430 in which circuit relay 805 operates.

Relays

807 and 808 at the mechanical oiiice cooperate with each other to measure intervals of time during which the code impulses are produced and propagated over the line circuit to the distant oiiice. Due to the characteristics of these relays they operate and release slowly.

Relays

810 and 811, 812 and 813, 81st and 815, andv 831 operate in a definite sequence and their function is to measure a sufficient number of periods of code impulses to represent each of the different digits.-

VVith relay 805 operated a circuit is closed from ground through the inner right contact of relay 805,"conductor 817, thence Relay 809 closes a circuit,

lower contact of relay 308,

through the outer left contact of relay 901 and the outer upper contact of relay 9 12 and in parallel through the corresponding contacts of

relays

927 and 913, 501 and 511, and 506 to conductor 513, through the right winding of relay 818 to battery. Relay 818' operates and locks in a circuit through its left winding, the outer left normal contact of relay 831 to ground at the left contact of relay 804. A second locking circuit also extends from the inner left contact of relay 818, through the normal contact oi relay 815, conductor 822, back contact of relay 810 to the left contactoi relay 804a, and a third locking circuit is prepared which would-extend through the right front contact of relay 813 and conductor 820 to the right contact'ot relay 818. These locking circuits have no function at this time since the energizing circuit is maintained, but at the release of the sender they serve to insure that relay 818' will not release until

relays

810, 813 and 815 have ai'loperated and released. i Vith relay 818' energized", a circuit is closed from battery through. resistance 821, winding of relay 807, right back contact of relay 811, right back contact of relay 813, conductor 820 to ground at the outer right contact of relay 818. Relay 807 energizes after an interval and closes a circuit from battery through resistance 819, winding of relay 808, outer right front con tact of relay 807 to grounded conductor 820; Relay 807 also closes a circuit from battery through the winding of relay 813, outer left back contact of relay 812. conductor 829, middle contact of relay 807, conductor 820 to ground at the right contact otrelay 818. Relay 813 operates and locks through the winding of relay 812, inner left contact oi? relay 813, conductor 822', back contact of relay 810, left contact of relay 804 to ground, and also through the inner left back contact of relay 815, conductor 840, outer left back contactof relay 831 to the ground at relay 1. These two circuits insure that

relays

812 and 813 will not release until after both

relays

815 and 810 have operated. Relay 812 does not operate at this time since it is shunted by the energizing circuit of relay 813'. Relay 808 in operating closes a circuit from battery through resistance 821, outer contact of relay 808, to the grounded conductor 820. This circuit shunts relay 807 which starts to release after an interval. Relay 807 becomes deenergized and a circuit is closed from battery through resistance 819, outer right back contact of relay 807' to grounded conductor 820. This circuit shunts relay 808 which, after an interval, releases its armatures.

As soon as relay 818 is operated. a circuit is closed for sending the first impulse of the code representing the first digit of the number of the wanted subscriber. This circuit may be traced from ground which represents the positive pole of battery, outer right contact of relay 805, conductor 882, right normal contact of relay 812, conductor 825,

outer left contact of relay 801, conductor 431, through selector switch 110, conductor 211, inner right contact of relay 205, upper front contact of relay 206 through the district selector switch 200, thence over the tip side of the line, outer front contact of relay 305, conductor 60 1, through the

relays

000, 601, and 602, conductor 603, inner front contact. of relay 305 over the ring side of the line, through the selector switch 200, lower front contact of relay 206, outer right contact of relay 205, conductor 212, through the selector switch 110, conductor 132, mid dle left contact of relay 801, left front contact of relay 805, conductor 8241, left normal contact of relay 812, conductor 833, outer left contact of relay 818, high resistance 838 to battery. The current in this circuit is in the direction to cause the operation of relay 600, but since relay 914 of the thousands register 900 is not operated, a cIrcuit is closed from ground, conductor 916, inner left contact of relay 914, inner upper back contact of relay 912, conductor 835, right back contact of relay 815 to conductor This ground shunts the battery through resistance 836 and no impulse is sent out over the line. As soon as both

relays

807 and 808 have deenergized, relay 812 operates in the locking circuit of relay 813, reversing the connection of battery and ground to the impulse circuit and preparing a circuit for relay 811.

It might be well at this time to indicate how a common battery and a common ground is connected to the impulse circuit. The connections from battery extend through resistance 836, the outer left contact of relay 818, conductor 888 and the left normal contact of relay 812 to thering side of the line and also through resistance 827 and conductor 826 to the inner right armature of relay 812, so that when relay 812 is operated, battery is connected through the right alternate contact of that relay to the tip side of the line. The connections from the common ground extend either by way of conductor 882 and the right normal contact of relay 812 to the tip side of the line or when relay 812 is operated by way of conductor 823 and the left alternate contact of relay 812 to the ring side of the line.

Relay 808 in releasing, opens the shunt around relay 807 which, after an interval, attracts its armatures and in turn closes the operating circuit of relay 808. Relay 808 operates after an interval of time. lVhile relays 807 and 808 are undergoing energization and deenergization, a circuit is closed as follows for transmitting a second code impulse over the line: From ground through outer right contact of relay 805,

conductors

832 and 823, left alternate con tact of relay 812, conductor 82%, left front contact of relay 805, middle left contact of relay 801, conductor 482 thence over the above traced impulse circuit back to con ductor 4:31, outer left contact of relay 801, conductor 825, right alternate contact relay 812, conductor 826, high resistance 827, to the negative pole of battery. The current in this circuit would produce a weal; impulse in the direction to operate relay (501. However, since relay 9041- is operated, a path in parallel with the high resistance 827 is closed which may be traced by way of the right back contact of relay 814, conductor 828, inner lower baclr contact of relay 912, inner left contact of relay low resistance 915 to battery. Due to this path from battery through low resistance 915, the impulse transmitted i heavy and marginal relay 602 is also operated. The operation of relay 601 closes a circuit from battery through left windings of relays (508 and 609, left back contact of relay 608, conductor 610, contact of relay 601, conductor 611., left contact of relay 805, outer left contact of relay 012 to ground. Relay 009 operates but relay 608 being marginal remains inert, Relay 009 completes a circuit from battery through the left windings of relays 608 and 609, right winding of relay 608, inner right contact of relay 009, conductor 618 to grounded conductor 611. Relay (508, however, does not operate since its right winding is shunted by the previously traced circuit, Relay 609 closes a circuit from grounded conductor 018, outer right contact of said relay, left back contact of relay 61 1, winding of relay 15 to battery. Relay 015 operates and closes a locking circuit from battery through its winding and the winding of relay 814, inner right contact of relay 815 to grounded conductor 61?). Relay 614, however, being shunted does not operate at this time. Another circuit is closed from grounded conductor 6.11, contact of relay 602, outer right back contact of relay 008, inner right back contact of relay 6141, conductor 016, le;.t winding of register relay 700 to battery Relay 700 locks in a circuit through its windings and inner right contact, conductors 701 and 702, right contact of relays 605 to ground at the right contact of relay 612.

lVhen relay 807 operates as above explain ed. it closes a circuit from battery, winding of relay 811. outer left front contact of relay 812. conductor 829, middle contact of relay 807 to grounded conductor 820, Relay 811 operates and locks through winding of relay 810, inner left contact of relay 811 to ground at the outer left contact of relay 813. Relay 810 does not operate in this circuit as it shunted. Relay 811 in operating, closes a circuit from grounded battery, Winding of relay 815, outer left back contact of relay 814, conductor 830, outer left contact of relay 811, outer left contact of relay 813 to ground. Relay 815 operates and locks in a circuit through the Winding of relay 814, inner left front contact of relay 815, outer left back contact of relay 831 to ground at the left contact relay 804. Relay 814 does not operate this time, being shunted.

Relays

807 and 808 are next deenergized in succession in the manner above explained. As soon as relay 808 is deenergized, the shunt around relay 810 is removed and that relay energizes in the locking circuit of relay 811. Relay 810 in operating opens the looking circuit for

relays

818 and 812 which release, in turn opening the locking circuit for relays 810' and 811 which also release, The release of relay 811 opens the energizing circuit for relay 815 and permits relay 814 to energize in the locking circuit of relay 815. The operation of relay 814 closes a circuit from grounded battery, winding of relay 912, outer upper contact of relay 918, conductor 838 to ground at the inner right contact of relay 814. Relay 912 energizes and locks in a circuit through the winding of relay 918, the lowermost contact of relay 912, conductor 839 to ground at the right contact of relay 801. Relay 918 does not operate at this time, being shunted.

The release of relay 812 reverses the direction of current in the impulse circuit and permits relay 601 to release. The energizing circuit of relay 609 is opened and relay of at 608 operates in the locking circuit which was previously traced.

During the next energization and deenergization of

relays

807 and 808, the impulse circuit is closed from ground at the outer right front contact of relay 805, conductor 832, normal contact of relay 812, conductor 825, outer left contact of relay 801 to conductor 431 and thence as above traced back to conductor 432, middle left contact of relay 801, left front contact of relay 805, conductor 824, left normal contact of relay 812, conductor 838, outer left contact of relay 818, resistance 886 to battery. Since relay 917 is not operated a shunt to ground is completed from conductor 833 by way of the right front contact of relay 815, conductor 837, inner upper back contact of relay 918, inner left back contact of relay 917 to ground. Therefore. no impulse may pass out over the line. Meanwhile, the energization of relay 807 has caused the energization of relay 813 which relay locks as before. lVhen now relays 807 and 808 d'eenergiZe, relay 812 energizes in the locking circuit of relay 813.

During the next energization and deener gization of

relays

807 and 808 the fourth and last impulse of the code of the first digit is 824, left front contact of relay 805, middle Y! contact of relay 801, conductor 482, thence through

relays

600, 601 and 602 and back to conductor 431, outer left contact of relay 801, conductor 825, right alternate contact of relay 812, conductor 826, resistance 827 F to grounded battery. ince resistance 827 is a l'iigh resistance and, due to the deenergized condition of relay 924, no parallel path is closed to battery through low resistance 915, the impulse sent out over the line is weak and of such a direction that relay 601 is operated; Relay 601 applies ground potential to conductor 610 whereby relay 609 is shunted and releases while relay 608 remains locked through its left winding. Relay 609 removes the shunt from relay 614 but that relay remains shunted at the inner. right contact of relay 608.

As soon as relay 811 operates, relay 814 being operated, a circuit is closed for relay 831 extending from battery through the left winding of that relay, left front contact of relay 814, conductor 880, outer left contact of relay 811 to ground at the outer left contact of relay 813. Relay 831 operates and locks in a circuit through its left winding, inner left contact to ground at the outer left contact of relay 818. Relay 881 opens the lockingcircuit for relays 814 and 815 but they are held operated as long as relay 818 remains operated. lVith relays 807 and 808 deenergized, the energizing circuit of relay 811 is opened and relay 810 is energized in series with relay 811.

Relays

815 and 810 both being operated, no locking circuit may be found for

relays

813 and 812 and these relays release, in turn releasing relays 810 and 811 and relays 814 and 815. The deenergization of relay 814 opens the energizing circuit for relay 912 and permits relay 918 to operate in the locking circuit of that relay. VVhen relay 912 energized, two of the leads connecting the impulse mechanism with the register 900 were transferred to register 909 and now that relay 918 is operated, the second pair is transferred. The release of relay 812 again reverses the direction of current in the impulse circuit so that relay 601 releases opening circuitof relay 608; Relay 608 deenergizes and opens the shunt around relay 614, which relay operates in the locking circuit of relay 615. The apparatus is now ready to transmit the second digit to the distant office.

A consideration of the foregoing operations will show that the impulse circuit is the same for all pulses from one armature contact of relay 812 to the distant office and back to the other contact of that relay. Battery, through a high resistance, and

ground are fed to the contacts of this relay in such a manner that the positive pole of battery, represented by ground, is connected to the tip of the impulse circuit through a normal contact ofthat relay and to the ring of the inunilse circuit through an alternate contact of the relay. It is therefore apparent that the function of relay 812 is to reverse the direction of the current in the impulse circuit. The contacts of this relay make their alternate arrangement before breaking their normal arrangement so that for a very brief interval ground is connected to bothsides of theimpulse circuit, tending to clear it of any residual charge. At no time is the impulse circuit open at the contacts of relay 812. As far as the operation of relay 812 is concerned, alternate weak impulses of positive and i'iegative polarity would be produced, separated by a brief grounded interval.

In order to produce the code character of the impulses, parallel circuits are arranged under the control of the registers. There is a register for each digit and in each register there is one relay corresponding to each impulse of the code of the corresponding digit. The'relays corresponding to the positive impulses when deenergized, close a parallel or shunt circuit to ground, which short circuits the positive pulse. The relays corresponding to the negative pulses when ener ized, close a parallel path to ba tery through a low resistance, which supplements the battery through high resistance ordinarily connected to the impulse circuit and causes a heavy impulse. lVhen deenergized, this parallel path is open and only a weal: impulse reaches the impulse circuit. bus, when none of the relays of the register are operated, no positive pulses and only wear: negative pulses are sent, and according to which of the register relays are operated, weak positive impulses or heavy negative impulses are sent.

The connection of the shunt circuits with the main impulse circuit is under the control of the relay combinations 912 and 918, 913 and 928. etc., and the relay combination 814 and 815. Relay 81% also controls the relay combinations 912 and 918, etc. The leads for controlling the first two impulses of a code group extend through the back contacts of the first one of each pair of relays, i. e. 912, 918, etc. he leads for controlling the second two impulses extend through the back contacts of the second one of each pair of relays, i. e. 918, 928, etc. The front contacts of these relays connect to the correspondin arinatures of the next pair so that the onesat-ion of these relays serves to transfer the shunt loads from the control of one register to that of the next.

Furthermore, the lead for controlling the first positive impulse-extends through the back contact of relay 815 andthat for controlling the second positive impulse through the front contact of that relay. Similarly, the lead for controlling the first negative impulse extends through the back contact of relay 814: and the lead for controlling the second negative impulse extends through the front contact of that relay. The successive energizations of relay 814- cause the energization of the first relay of each successive pair of relays, namely 912, .913, 511 and 512, while the subsequent successive deenergizations of that relay permit the second relay of the corresponding pair, namely 918, 928, 516, and 520 to operate.

The cycle of operations, briefly, comprises the measurement of four intervals of time by the

relay combinations

807 and 808. An interrupter of any well known type would serve as well to measure these time intervals. At the beginning of the first interval, relay 813 operates and at the end relay 812 operates, reversing the impulse leads. At the beginning of the second interval, relay 811 operates, causing the operation of relay 815 which relay transfers the control of the positive impulse from the first to the third relay of the register involved. At the close .of the interval, relay 810 operates, releasing

relays

812 and 813, 811 and 810 and permitting relay 81 1 to operate. The release of relay 812 returns the impulse circuit to its first condition, ready to send a positive pulse. Relay 81 1 causes the operation of re lay 912 (or 913, etc.),'transferring the first two control leads to the next register. Relay 81l also transfers the control of the negative impulse from the second to the fourth relay of the register. At the beginning of the third interval, relay 813 again operates, the control of the positive impulse being at the front contact of relay 815. At the close of the interval, relay 812 operates again, reversing the impulse circuit, ready for a negative impulse which is controlled through the front contact of relay 81 1. At the beginning of the fourth interval, relay 811 operates, causing the operation of relay 831. At the close of the interval, relay 810 operates and all seven relays release ready for a new cycle. The release of relay 814; permits the energization of relay 918 (or 928, etc.), transferring the second pair of leads to the next register. It is thus clear that this relay combination results in an impulse sending arrangement in which the impulses are transmitted over an uninterrupted impulse circuit; that the code arrangement of the pulses is run der the control of registers; and that the control circuits are in all cases prepared in advance of the occasion on which they may be called upon to function.

Since the codes corresponding to the various digits in some cases involve only one or perhaps no positive pulse, it is quite possible that several negative pulses may occur in succession, tending to charge the line so that when the impulse circuit is opened, as has been the custom heretofore, a discharge may take place sufficient to erroneously opcrate in the receiving circuit and cause false registrations at the distant oflice. The arrangement of the present invention overcomes this difliculty by maintaining the impulse circuit closed throughout the sending of the impulses and by short circuiting the positive pulses when none is desired, instead of opening the line.

Returning now to the operation of the circuits for sending the second digit, relays 807 and 808 again undergo energization and deenergization in sucession and relay 813 energized. The impulse circuit is closed through the normal contacts of relay 813 and battery through resistance 836 is shunted by a circuit from ground, conductor 919, right back contact of relay 920, uppermost back contact of relay 913, inner upper front contact of relay 912, conductor 835, rightback contact of relay 815 to conductor When relays 807 and 808 deenergize, relay 812 energizes in the locking circuit of relay 813 and reverses the impulse leads.

Since the relay 921 is not energized, no circuit is closed through low resistance 915 and only a light impulse is transmitted over the impulse cicuit. This light negative impulse causes the operation of relay 601. Relay 601 places a ground potential on the conductor 610 and relay 609 operates in the manner above described. Relay 609 closes a circuit from ground over conductor 613, through the outer right contact of relay 608, left front contact of relay 614i, left back contact of relay 617, winding of relay 618 to battery. Relay 618 operates and closes a locking circuit for itself in series with relay 617 to grounded conductor 613. Relay 617 does not operate since it is shunted.

As soon as relay 807 is reenergized, relay 811 becomes energized and in turn causes the energization of relay 815. At the completion of the period, relay 810 energizes in the locking circuit of relay 811 and opens the locking circuit of

relays

812 and 813 which release, in turn releasing relays 810 and 811, permitting relay 814 to operate in series with relay 815 as before described. The operation of relay 814 closes a circuit for relay 913 from battery, Winding of relay 913, outer upper contact of relay 923, lower front contact of relay 918. conductor 838, inner right contact of relay 81a to ground. Relay 913 operates and. locks in a circuit including the winding of relay 923, lowermost contact of relay 913 to grounded conductor 839. Relay 913 transfers the first two leads from the impulse the operation of marginal relay 602.

gization of

relays

807 and 808, the impulse circuit is again closed through the normal contacts of relay 812 and due to the deenergized condition of relay 922, battery through resistance 836 is shunted by a circuit from grounded conductor 919, right contact of relay 922, inner upper back contact of relay 923, inner upper front, contact of relay 918, conductor 837, right front contact of relay 815 to conductor 833. In the meantime, relays 813 and 812 have been energized and locked in the manner previously described.

During the next energization and deenergization of

relays

807 and 808, the impulse circuit is completed through the alternate contacts of relay 812, and due to the energized condition of relay 910, a path parallel. to that from battery through high resistance 827 is completed from grounded battery through low resistance 915, through right contact of 910, inner lower back contact of relay 923, inner lower front contact of relay 918, conductor 841, outer right front contact of relay 81d to the impulse circuit as previously described. Due to this parallel path, the impulse transmitted, which is of such polarity as to cause the operation of relay 601 is also a heavy impulse and causes Relay 601 shunts relay 609 which releases but the shunt around relay 617 is maintained at the inner right. contact of relay 608. Due to the energization of relay 602 a circuit is completed from grounded conductor 611, contact of relay 602, outer right front contact of relay 608, outer right front contact of relay 614-, outer right back contact of relay 617, conductor 619, left winding of re- 703 to battery. Relay 703 operates and locks to grounded conductor 701.

Meanwhile relay 811 is operated and locked as before described and relay 831 is energized through its left winding, left front contact of relay 81 1, outer left contactof relay 811 to ground at the outer left contact of relay 813. Relay 831 operates and locks direct to the outer left contact of relay 813. At. its outer left contact, relay 831 opens the locking circuit of relays 815 and 81-t but these relays are held operated through the right front contact of relay 813. lVhen relays 807 and 808 release, relay 810 energizes and opens the locking circuits for re- 813 812.

Relays

813 and 812 release, in turn releasing relays 810 and 811 and rclaya-a era and 815. As soon as relay 813 releases, relay 831 releases. On the release of relay n .il

814 the shunt is removed from the winding of relay 923 and that relay energizes in the locking circuit of relay 913. The release of relay 812 completes the impulse circuit through the normal contacts of that relay and relay 601 releases opening the circuit of relay 608 and permitting relay 617 to operate in the locking circuit of relay .618. The apparatus is now in condition for sending the impulses corresponding to the third or tens digit. V

Relays

807 and 808 again undergo energization and deenergization. During this period a circuit is closed from the positive pole of battery over conductor 832, right normal contact of relay 812, conductor 825, outer left contact of relay 801, thence over the tip side of the line, returning over the ring side of the line through the middle left contact of relay 801, left front contact of relay 805, conductor 824, left normal contact of relay 812, conductor 833, outer left contact of relay 818, resistance 836 to grounded battery. Since relay 503 is operated, there is no shunt path to ground and a weak impulse is transmitted over the line in such direction as to cause the operation of relay 600. Relay 600 closes a circuit from grounded conductor 611, contact of relay 600, left back contact of relay 609, left front contacts ofrelays 615 and 618, outer left back contact of relay 620, conductor 621, left winding of relay 704 to battery.

Relay 7041 operates and locks through its windings to grounded conductor 702. lVhen relay 807 operated, relay 813 operated and locked. lVhen now relays 807 and 808 deenergize. relay 812 operates reversing the impulse circuit and relay 600 deenergizes.

Next, relays 807 and 808 energize and deenergize again. During this period a circuit is closed from the positive pole of battery over conductors and 823, left alternate contact of relay 812, thence over the ring side of the line returning over the tip side of the line through the right alternate contact of relay 812 and in parallel through high resistance 827 to battery and throuu'h the back contact of relay 814, conductor 828, inner lower front contacts of relays 912 and 918. inner lower back contact of relay 511, left contact of relay 504C, conductor 5141 and low resistance 915 to the negative pole of battery. A heavy impulse is transmitted over the impulse circuit whereby relays 601 and 602 are operated. llelay 601 causes the operation of relay 609 whereupon a circuit is closed from around over conductor 613 through outer right contact of relay 609. left front contacts of relays 61 1 and 617, left back contact of relay 622, winding of relay 620 to battery. Relay 620 operates and prepares a circuit for relay 622 but this relay does not operate, being shunted. Another circuit is closed from grounded conductor 611, through contact of relay 602, outer right back contact of relay 608, inner right front contacts of relays 6M and 617, inner right bacl: contact of relay 622, conductor 623, left winding of relay 705 to battery. Relay 705 operates and. looks through its windings to grounded conductor 70.2. lVhen relay 807 energizes, relay 811 energizes and prepares a circuit for relay 810. Relay 811 also completes a circuit for relay 815 which operates and prepares a circuit for relay 8L1. \Vhen relays 807 and 808 deenergize, relays 810 and 814: operate in series with relays 811 and 815 respectively. Relay 810 opens the locking circuit for

relays

813 and 812 which relays de-energize. Relays 815 and 81 1 remain looked through the outer left contact of relay 831. The release of relay 812 reverses the impulse leads and permits the deenergization of

relays

601 and 602. Relay 601 released, permits relay 608 to operate in series with relay 609. The operation of relay 814 closes a circuit from grounded battery, winding of relay 511, outer upper contact of relay 516, i

lowermost front contacts of relays 923 and 918, conductor 838 to ground at the inner right contact of relay 814. Relay 511 operates and locks in series with relay 516 and the lowermost contact of relay 511 to grounded conductor 839. Relay 516 does not operate, being shunted. It is to be noted that at this time the first two leads from the impulse circuit tothe register have been transferred from the tens register to the units register.

Next, relays 807 and 808 energize and de energize. During this period the impulse circuit is closed from battery through high resistance 836 to the left normal contact of relay 812 and thence over the ring side of the line and back over the tip side of the line to the right normal contact-of relay 812 and to ground. Since relay 515 is not operated, a shunt circuit is completed from grounded conductor 916, left contact of relay 515. inner upper back contact of relay 516, inner upper front contact of relays 923 and 918, conductor 887, right front contact of relay 815 to conductor Therefore, no impulse is permitted to pass out to the line and since the two sides of the line are grounded. any charge which may have accumulated due to impulses passing thereover will bedischarged. hen relay 807 attracted its armature, relay 813 operated and prepared. a circuit for relay 812. When both relays 807 and 808 have deenergized, relay 81.2 operates in series with relay 818. Next. relays 807 and 808 energize and deenergize in succession. An impulse circuit is completed through the alternate contacts of relay 812 from battery through high resistance 827 and back to ground. Since relay 517 is not operated, no path is avail-