US1615971A

US1615971A - Telephone-exchange system

Info

Publication number: US1615971A
Application number: US751235A
Authority: US
Inventors: Samuel B Williams; Earl S Gibson
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1924-11-21
Filing date: 1924-11-21
Publication date: 1927-02-01
Anticipated expiration: 1944-02-01

Description

Feb. '1 1927. 1,615,971

s. B. WILLIAMS ET AL TELEPHONE EXCHANGE SYSTEM Filed N v, 21. 1924 12 Sheets-Shet 1 by A7954 Feb. 1, 1927. l;6l5,97l 5. B. WILLIAMS ET AL TELEfHONE EXCHANGE SYSTEM FiIed Nov. 21, 1924 12 Sheets-Sheet 2 WW #5 8/ we w Feb. 1, 1927.

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S. B. WILLIAMS ET AL 1 TELEPHONE EXCHANGE SYSTEM Filed Nov. 2 1924 12 Sheets-Sheet 4 by Wmy Feb. 1,1927. 1 1,615,971

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S. B. WILLIAMS ET AL TELEPHONE EXCHANGE SYSTEM Feb. 1,1927. 1,615,971

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' S. B. WILLiAMS ET AL.

TELEPHONE EXCHANGE SYSTEM 7 Fil d N 21, 1924 -12 Sheets-Sheet 11 Patented Feb. 1, 1927.

STTE

SAMUEL B. "WILLIAMS, OF BROOKLYN, NEW YORK, AND- EARL GIBSON, OF RIDGE- woo'n, new JERSEY, AssrGnon-s T0- VJESTERN ELEUTRIG GOMBANY, INCORPQ- BATED,,O1E NEW YORK, N. Y., A GOR'PORdTION 0F YGBK.

rnnnrnonn-nxormnen system.

Application filed November 21', 192a; Serial No. 751,225.

This invention relates to telephone exchange systems and more particularly to systems employing machine switching apparatus controlled by operators for establishing connections.

The object of this invention is an improved method of routing conversational connections in a system comprising ofiices having automatic switching equipment un der the control of operators.

A feature of the invention relates to a system having switches controlled by senders and markers, the markers being arranged to receive variable settings from the senders in accordance with the manipulation of an oporators keyboard to determine the routing of a call through different tandem ofi'ices to a desired oflice.

Other features and advantages of the invention will become more thoroughly understood ironra consideration of the following detailed description and the appended claims.

Referring to the drawings: 7

Figs. 1 to 11 inclusive, arranged in the order illustrated in Fig. 13, disclose a sutticient amount of a telephone exchange system embodying features of this invention to euahle an understanding thereof.

Fig. 1 shows a trunk incoming to an operators positiontogether with one of a number oi cord circuits at said position.

Fig. 2 shows one of a numloer of district selector switches which hereinafter will he called semi-mechanical district selectors.

Fig. 3 shows the operators telephone set together with certain recording equipment at her position Fig. 4- illustrates an operators for setting up the records of calls.

Fig. 5 shows diagrammatically a sender selector switch, and alsoillustrates in detail an impulse controlling and sending equipment associated with the operators position and common to all trunks in such position.

Figs. 6 and 7 illustrate a portion of an operators recording sender. Fig. 6 shows the control relays of the sender while Fig. 7 shows the routing and code registers and illustrates diagrammatically the numerical register.

8 shows a sender connector for connecting the senders to the markers.

Figs. 9 and i0 illustrate one of? the marl:-

hey h o a rd ers serving to control the semi-mechanical switch and other similar switches.

Fig. 11 illustrates a frame and trunk connector for associating the marker with the district switches.

Fig. 12 shows a general layout oftlie sysstem with the various apparatus shown in simplified form. The purpose ofthis figure isto show the relation of the various apparatus to each other and to enable a general understandingot' the operation to be had.

The equipment illustrated in the drawing is designed especially for the A operators board in an automatic telephone system and serves to handle calls which for one reason or another are routed to the A operators position. The calls routed to this position are received on trunks, such as the trunk 100, w'hic'hmay leadfrom the terminalsot a regular district selecto'rswit'ch. The opera tor answers these calls by inserting the-plug into one of her trunk circuit jacksand converses with the calling subscriber. Having ascertained his wants she proceeds towrite up the number of thecalled line on her keyboard.

The above sending equipment shown in Fig. 5' is thereupon brought into action and transmits impulses t'h'roiigh the sender selec tor switch 500 to set the registers of the sender shown in Figs. 6 and The sender isthen' associated with an idle marker through the sender connector 800 and the routing and code record's transmitted into the marker. Thereupon the marker is associated wit-h the particular district selector 200 in which appears the trunkfli-EQ terminating in the cord circuit employed by the operator. The district selector 5200 is then controlled to select an idle trunlr leadingin the proper direction.

The call may run to distant ofiice which may he reached through any one of a numher of tandem oiiices. Accordingly theopera'tors keyboard is equipped with a numher of tandem route keys in. order that she may determine a particular tandem oitice through which the call should be extended. These route keys L00 are shown in Fig. l. Moreover the operatofis position is equipped with three sets oi" code or office keys 401, 402. and 403, and also with numerical keys 4041- and station keys 405. Only a portion at each row of these keys'is illustrated.

The register senders accordingly are provided with a route register 700, oiiice or toll registers 701, 702, 703 and the numerical registers 7 04. Inasmuch as the numerical portion of the designation is not particularly concerned in this invention, the corresponding numerical registers have not been illus trated in detail.

In the marker there are provided four

registers

900, 901, 902 and 903 each corresponding respectively to the route and code registers of the senders. The marker is therefore equipped with a translator 905 which consists of three banks of multi-contact relays only a portion of each bank being shown. The first bank for instance, includes

relays

906, 907, etc., the second bank includes relays 908, 909, etc., and the third bank includes relays 910, 911, 912, etc. The purpose of this translator will be brought out in detail hereinafter.

Moreover the marker includes a testing relay set 1000, comprising a series of doubly wound test relays for testing the conditions of the idle links of the district selector switches 200 and the condition of the outgoing trunks in any desired group.

The selector switch 200 and the sender selector switch 500 are of the coordinate type such as shown and described in U. S. Patent No. 1,515,735 issued November 18, 1924, to O. L. Goodrum and J. N. Reynolds, and in U. S. Patent No 1,517,331 issued December 2, 1924, to S. B. Villiams.

The register senders and the markers are of the general type as shown and described in U. S. Patent N 0. 1,517,331 issued December 2, 1924, to S. B. Williams, and in U. S. Patent N 0. 1,543,967 issued June 30, 1925, to S. B. Williams and E. S. Gibson.

Before proceeding with a detailed description of the operation a general description of the system will be taken up in connection with the diagrammatic illustration in Fig. 12. This figure shows subscribers lines, such as line 1200, terminating in line switches 1201. The initiation of a call causes the operation of the line switch 1201 to select a trunk leading to a. subscribefis district selector switch 1202, and also causes the operation of the sender selector switch 1214 to associate an idle subscribei"s sender 1215 with the calling line. After the sub scriber has transn'iitted the record to the sender 1215 said sender is connected through the sender connector 1216 to an idle outgoing marker 1217.

In case the subscriber has dialed a wrong number or has dialed the operators number, the marker 1217 after having been associated with the district switch 1202 and with the proper group of trunks by means of the frame and trunk connectors 1218 and 1219 respectively, causes the operation of the district selector switch 1202 to select an idle trunk 1204 termii'iating in the jack 1205 at the A operatoi"s position. The A operators attention. is attracted and she rcsponds by inserting the plug of a cord circuit 1206 in the jack and obtains the number orally from the calling subscriber. The insertion of the plug in the jack initiates the operation of the sender selector 1231 and the cord circuit 1206 is automatically associated with the operators sender 1232.

Having obtained the number the operator recorns the same on her keyboard 1230. The keyboard 1230 is associated through a connecting device 1236 with the cord circuit 1206 and the record is transmitted through the sender selector 1231 and recorded in the operators sender 1232. After the record is recorded the sender 1232 is connected to the operators marker 1233 and a. portion of the record is trai'isferred from the sender to the marker.

If the wanted line is located in a distant otlice 1228 which may be reached through one or more tandem ofiices- 1226, 1227, etc., the operator must decide through which one of these tandem oiiices the connection should be reached. If it is desired to route the connection through the tandem oflice 1226 she depresses the proper route key which determines the corresponding setting 01 the route register in the operators marker 1233. Thereafter the marker is associated through the frame and

trunk connectors

1234 and 1235 with the semi-mechanical district switcs 1 07 and with. the group of trunks leading to the tandem point The switch 1207 is cont-rolled by the marker and the connection is extended over an idle trunk 1224 to the tandem office 1226.

Thereafter the ofiice record may be trans ferred from the sender 1232 over the trunk 1224 by means of code impulses and received in a. corresponding sender in the tandem otlice 1226. This sender may control the switches in the tandem otlice to the sender connected in the desired otiice 1228 where the connection is completed to the calling subscribers line 1229. 7

Should the operator desire to extend the call through the tandem ottice 1227 she depresses the key represei'iting this tandem cities and the connection is now routed to trunk 122:; through the tandem otlis'e 1.227 to the desired line 1229 in the oiiice 1229. The manner in which records may he sent from a sender in one oiiice to a. sender in a different oiiice is illustrated and dcscril'icd in U. S. Patent No. 1,543,967, issued June 30, 1925, to S. B. Williams and E. S. Gibson.

It may iappen that the calling sul'iscriber wishes connection with a toll line. In this case the operator writes up the number on her keyboard causing the operation of the semi-mechanical district selector 1207 to seissued September 21, 1926, to

trunk 1211 to the called line 1213. The manner in which this connection is routed hrough the incoming and final switches is fully described in U. S. Patent No. 1,600, 1 1 13. W11- liams and E. 55. Gibson.

Detailed description of the operation.

It will be assumed that a connection has been extended to the A operators position and the operator upon answering ascertains that the called subscriber desires to converse with a. subscriber at a distant otlice which may be reached through a tandem o'flice.

The incoming connection is extended over the trunlr 1.00 from a preceding switch in the well known manner and a signal (not shown) is given to the A operator, advising her that a call is awaiting her attention. The operator seizes the plug 102 of an idle cord circuit 10?) and inserts it in the jack 101 ot the calling trunk. llhc insertion of the plug in the jack causes the operation of relay 127 in a circuit from battery. through the winding of said relay, the sleeve of. the plug 102, sleeve of the jack 101, over the sleeve. conductor 01 the incoming trunk to ground.

The relay 127 causes the operation of relays 130 and 131 individual to the cord circuit 103 in a circuit from ground, throngh the baclt contact o't' relay 126, outer right contact ot relay 127, inner right contact t relay 12S, windingz-s 0t relays 130 and 131, left contact of relay 111, resistance 301, to battery. Relay 130 completes a circuit from battery, above traced, through its winding and inner right trout contact, through the -inding oil relay 126, to ground. Relay 126. however, does not operate at this time, since its winding is shunted by the above traced circuit. The relays 130 and 131 serve to associate the operators key set with the trunk taken for use.

ltclay 131 causes the operation ct relays 105, and 115 in circuits leading from l'iattery, through the windings of these re lays in parallel, to grounc at the outer right :l'ront contact of relay 131. The relay 105 connects the operators telephone set (shown in Fig. 3) to the tip and ring conductors of the cord circuit 103, placingher set in conversational, connection with the calling subscribers line.

Relay 115- locks in a circuit from battery,

through its left front contact, contact ot relay 113, right tront contact and winding 01' relay 115, resistance 133, l at the to grounc lett contact of relay 127. it will: be noted that relay 113 was operated at this time in series with the left winding of the repeating coil 104., including the loop of the calling subscribers line. The locking circuit above traced'l'or relay 115 serves to shunt the supervisory lamp 129, preventing the same from illuminating.

Belay 128 locks in circuit from battery, through its left winding and inner left conact, le'lt back contact of relay 122, to ground at the lett contact of relay 127. lielay 128 opens the shunt around the winding of relay in series with relays 130 and 181.

At this stage ot the connection, green supervisory lamp 121 is illuminated in 'a circuit from battery, through said lamp, resist ance 120, left back contact of relay 119, cuter-most contact of relay 118, middle right back contact 0t relay 123, to groundat the contact 0t relay'127i.

The relay 131 also causes the operation of the relay 501 which is. associated withthe sender selector 500 and is individual torthe particular cord circuit 103' which the opertor has taken for use. This circuitinay be traced trom battery, through the winding of relay 501, thence through the inner uppercontact of relays 110' and 109, contact ct ielay 125, to groun at the contact ot'relay 124'. Relay 501 initiates the operation of the sender-selector switch 500 which serves to as sociate the cord circuit and operators kryl)O\1(l with. an idle register sender.

While the sender selector is operating, it places ground potential on the conductor 515, which results in the closure ot a circuit through the left contact ot relay 612, right contact of relay 61.7, outer leitt contact o't ielay 618, winding ot relay 610, to battory. Also during the operating period ot the sender selector 500, theverticalmagnet 516 com-- pletes a circuit for operating the relay 616. lhis circuit may be traced from battery, through the winding of relay 618, left contact of relay 619, conductor 620, to ground at tne contact of nragnet 516.

lhe frame test relay 618 causes the operation of the holding relay 606 in a circuit from battery, through the winding 0" the latter relay, inner left content of relay 618, and thence to ground over the circuit above traced. Relay .GOGlOClSS through its left contact, to ground. through the right Contact of relay 612. The relay 110m the operators cord circuit is now operated in series with the relay 607 in the sender. The circuit for this purpose may be traced from battery, through the winding of relay 110, right contact of relay 119, conductor 13 1, through the sender selector 500, conductor ,1 nine test 126, and this latter relay operates ii a 515, left contact of relay 612, winding of relay 607, conductor 621, to groiuid at the contact of relay 606.

Relay 607 causes the operation of relay 608, which in turn locks to the grounded conductor 621. Relay 110 in the cord circuit opens the circuit of relay releases. Relay 110 also causes the illunination of to relay 123.

The apparatus is now ready for the operator to set up the designation of the wanted SUbSCI'llJQI' S line on. her keyboard.

If the call is to be routed to a given tandem office, the operator first depresses the route key 406 which is individual to this particular tandem. office. She then depresses the oflice code keys 407, 408 and 409 which represent the number of the called otfice containing the desired line. Furthermore, she depresses the proper, combination of numerical keys 404 representing the number of the wanted line, and, if the wanted on a party line, one of the stations key 405. If the wanted line is a direct line, however, she depresses the start key 410.

The start key 410 causes the operation of relay 504 in a circuit from battery, through the Winding of this relay, conductor 519, through the contact 412 wl' h is common any one of these keys 1s depressed, tor 413, to ground. elay 504 causes the operation of relay 124 in a circuit from battery, through the winding and contact of the latter relay, conductor 135, inner left contact of relay 131, conductor 136, to ground at the contact of relay 504. Relay 124 locks through its front contact to ground at the left contact of relay 127.

Relay 504 causes the operation of relay 07 in a circuit from battery, through the winding of relay 507, lower back contact of relay 508, conductor 520, back contact of relay 506, inner back contact of relay 505, inner back contact of relay 503, to ground at the contact of relay 500. Relay 507 operates and connects the route keys 400 to the conductors 415, which lead through the sender selector 500 to the register sender. The impulse generating relays 502 503 are now set in operation to measure in tervals of time for the purpose of creating codes of impulses in accordance with the condition of the operators keyboard. These relays are made slow to operate and to release. The relay 502 is first operated in circuit from battery, through resistance 521, Winding of said relay, right back contact of relay 503, left normal contact of relay 505, conductor 523, upper back conshunt circuit for relay 503.

tact of relay 508, front contactof relay 507, conductor 524, to ground at the back contact of relay 540. Relay 502 operates after an interval operation of re lay 503 in a circuit from battery, through resistance 522, winding of relay 503, right front contact of relay 502, conductor 525, to ground at the contact of relay 519. Relay 503 operates and closes a shunt circuit for relay 502 from battery, through resistauce 521, inner left front contact of relay 503, to the grounded conductor 525. Relay 502 after an interval releases and closes a This circuit may be traced from battery, through the resistance 522, outer right back contact of relay 502, to the grounded conductor 525. Relay 503 releases after an interval. In this manner, the

relays

502 and 503 are operated and released in succession to measure intervals of time for, the creation of code impulses.

Relay 507 on operating, completes a looking circuit for itself from battery, its winding and inner tor 526, winding of relay 506, left front contact of relay to the grounded conductor 525. owever, does not operate yet, since its Winding is shunted by the previously traced circuit for relay 507.

As soon as relay 503 operates as above described, slow-release relay 505 is energized in a circuit from battery, through the winding of the latter relay, outer left contact of relay 503, to the Relay 505 operates and another branch of the above traced locking circuit for relay 50 contact of relay 505. outer left front contact of relay 503, to the grounded conductor 525. Relay 506, however, still remains deenergized. Relay 505 causes the operation of relay 508 by means of a circuit from battery, through the right contact of relay 505, conductor 527, upper winding of relay 508, outer left contact of relay 507, to the grounded conductor 524. lay 508 operates and locks through its lower Winding to the grounded conductor 524. Relay 508 in op ating opens the shunt relay 506 and this latter relay now operates in series with relay 507. At the end of the cycle, relay 503 releases as above related and opens the circuit of relay 505, which becomes dcencrgized. Relay 503 in releasing at this ciation of another.

Since the routing key 406 is depressed, a circuit is completed for sending a code impulse to the send-er during the period that the impulse relays 502 and 503 are operating as above explained. This circuit may be t aced from ground, through the high resistance 411, right contacts of key 406, conductor 416, through the outer right front contact of relay 507, conductor 528, outer left contact of relay 131, conductor 529, through the sender selector 500, conductor 622, contact of relay 623, windings of relays 604 and 605, to battery. Relay 604 is marginal, and therefore does not operate in series with the high resistance 411. Relay 605, however, becomes energized in the circuit traced.

Relay 605 operates the relay 721 in a circuit from battery, through the Winding of the latter relay, right back contact of relay 7 22, conductor 729, normal contact of relay 609, to ground at the contact of relay 605. Relay 721 operates and closes a holding circuit for itself from battery, through its winding and inner contact, thence through the winding of relay 609, to ground at the contact of relay 605. Relay 609, however, being shunted, does not operate. Relay 721 connects the conductors 730 which lead from the impulse receiving relays of the sender through to the relays of the route register o.

Since the route key 406 is operated, none of the relays 600, 601, 602, 603 or 604 is en ergized, and consequently none of the four relays 705, 706, 707 or 708 of the register 700 is operated. The relay 7 22 is now energized in a circuit from battery, through its winding, lower contact of relay 721, conductor 731, back contacts of relays 601, 603 and 602, conductor 625. to ground at the contact of relay 605. Relay 722 looks over conductor 7 32, to the grounded conductor 621. Relay 7 removes the shunt and permits relay 609 to operate in series with relay 721.

The

relays

502 and 503 perform another cycle, during which time the impulses are sent to the sender in accordance with the record. on the first set of code keys 401 of the operators keyboard. When the relay 503 releases, as above described, the relay 509 is operated in a circuit from battery, through its winding, lower contact of relay 510, lower front contact of relay 508, conductor 520, thence through back contacts of

relays

506, 505 and 503 to the grounded conductor 525. Relay 509 operates and closes a locking circuit in series with relay-506, as above described.

Relays

502, 503, 505 and 506 operate and release in the manner described, causing the operation of relay 510 and consequently the release of relay 509.

Durin the interval measured by the impulse relays, code impulses are sent to the sender to cause the operation of certain of the impulse receiving relays 600, 601,602, etc. it will he noted that relay 605, which was previously operated in connection with the routing digit, was released when relay 507 became deen-ergized. 'Il1e fact that the key 407 is depressed, results in the operation of relay 601 in a circuit from battery, tl'irough the winding of said relay, winding of relay 600, conductor 627, through the sender selector 500, conductor 530, through contacts of relay 131, conductor 418, inner right contact of relay 509, conductor 531, left contacts of key 407, high resistance 411, to ground. Due to the high resistance 411,

relay 600 does not operate in this circuit.

Still another circuit is closed for'operating relay 605, and may be traced from battery, through the Winding of said relay, winding of relay 604, and thence as above described to conductor 528 through contact of relay 509, conductor 532, right contacts of k'ejy 407, high resistance 411, toground. Relay 605 operates in this circuit, but relay 604 remains inert. I

The first code register 701 isnow set in accordance with the operated condition of impulse relay 601. In the manner just above described, the relay 723 is operated to extend the impulse conductor 730 through to the register 701. Relay 709 is operated in a circuit from battery, through its wind ing, contact of relay 723, thencethrough the right front contact of relay '601 and back contacts of relays 603 and 602, to ground over conductor 625. Relay 709 looks to the grounded conductor 732. Relay 724 is opertied and, removing the above described shunt, permits relay 609 to operate in series with relay 723.

Atthe end of the cycle measured by the impulse relays 502'and 503 relay 509 is released as above described and relays 601 and 605 become deenergized, causing the release of relay 722 and the preparation of the circuit for the receipt of the next digit.

In a similar manner, the impulse relays 502 and 503 perform repeated cycles and the succes ive relays 511, 513, etc., are'energized to associate each successive set of 'keys at the operators keyboard with the register sender, and code impulses are transmitted to the sender in accordance with the par- .ticular key depressed in each row. Marginal relays 600, 602 and 603 are operated or remain inert on each occasion according to whether a low or high resistance is in cluded in series therewith. These impulse receiving relays in the sender are associated with the successive registers 7 02'and 703 and with the numerical registers 7 04,.and these registers are operated in accordance with the changes involved. ltwill be found from inspection that, due to the fact. that code keys 403 and 409 are depressed, relay 733 of the register 702 and

relays

734 and 735 of register 705 are operated. Similarly, the numerical registers 704 are operated in accordance with the depressed condition'of the numerical keys 404. The manner in which the register relays shown in Fig. 7 operate to receive the digits as wanted numbers, is more fully described and illustrated in U. S. Patent No. 1,517,331, issued Dec. 2, 1924, to S. B. Williams. I

After all the digits have been transmitted from the keyboard and relay 533 has been energized, and when relay 533 again releases, a circuit is closed for operating relay 5&0. This circuit may be traced from battery, through the winding of relay 54:0, thence through front contacts of relay and all preceding relays, over conductor 520, to ground as above traced. Relay 5 10 looks through its left front contact and thence through back contacts of

relays

507, 509, 511, 513, etc, through contact; of any operated key in the corresponding row, to ground. Relay 540 at its right contact, closes operating circuits for the key release magnets shown at the top of Fig. 4. These magnets cause the release of all depressed keys in their corresponding rows, and when all keys on the board have been released the key release relay 540 becomes deenergized. Thus the operators keyboard is restored to normal.

When the last digit of the ofice code has been recorded in the sender, the relay 728 operates and closes a start'circuit for the sender connector 800, which acts to connect the sender with an idle marker. The start circuit may be traced from the grounded conductor 782, through the contact of relay 728, conductor 7 36, outer left back contact of relay 611, right contact of relay 628, conductor 629, upper winding of relay 805, to battery at the back contact of relay 806. Relay 805 operates and closes a lockingcircuit through its lower winding and the winding of relay 806, the latter relay operating in this circuit.

Relay 806 causes the operation of the multicontact relay 801 individual to the sender in a circuit. from battery, through the winding of the latter relay, upper contact of relay 805, back contact of relay 807, to ground at the contact of relay 806. Re lay 806 also closes a start circuit for selecting the first idle marker. Assuming that the marker shown, which is individual. to the relay 1, is the first idle one, this start circuit leads from ground, through the contact of relay 806, conductor 811, contact of relay 807, front contact of relay 812 which is assumed to be operated, back contact of relay 813, upper back contact of relay 808, upper winding of relay 809, to battery at the contact of relay 810.

Relay 809 operates. and closes a locking circuit through its lower winding and the winding of relay 810, to ground over conductor 811. Relay 810 operates in this circuit and closes operating circuits for relays 808 and 804. The circuits for these relays leads from ground, through the contact of relay 810, thence in parallel through the lower winding of relay 808 and through the winding of relay 809 and the winding of relay 804, to battery. Relay 810 also places ground potential on conductor 814 to identify the marker as busy. The sender is now connected to the idle marker and is ready to transfer the record of the office code through to the

registers

900, 901, 902 and 903 of the marker.

In the manner described in U. S. Patent No. 1,600,399, issued September 21, 1926, to 1V. V. Carpenter, the record is transferred from the

registers

700, 701, 702 and 703 to the

corresponding registers

900, 901, 902 and 908 of the marker. All of the relays of the registers 900, 901, etc, are operated in circuits leading either through the front or back contacts of the corresponding relays of the sender registers, and a circuit is thereupon completed for relay 913. This circuit may be traced from battery, through the winding of said relay, thence through series contacts of all the marker relay registers, conductor 916, through the outer right back contact of relay 1006, to ground at the outer left contact of the holding relay 1001.

It will be noted that relay 1001 was operated at the time the sender connector 800 operated, by means of a circuit which may be traced as follows: Battery, through the winding of said relay, normal contacts thereof, conductor 1015, through the sender connector 800, to the grounded conductor 629. The relay 1001 is locked in a circuit from battery, through its winding and front contact, conductor 1016, back contact of relay 1017, conductor 1018, inner back contact of relay 1004, conductor 1019, to ground at the back contact of relay 1020.

hen relay 913 operates as above described, it locks through its inner right contact to ground on conductor 916. Relay 913 closes an obvious circuit for relay 915, which operates and locks to conductor 916. Relay 915 opens the locking circuit of relay 913. Relay 913 at its back contact opens the circuits of all register relays 900, 901, etc, and these relays all release with the exception of those relays which correspond to energized relays in the sender. From inspection it will he found that none of the re.- lays of register 900 are operated, whereas

relays

917, 918, 919 and 921 of the

registers

901, 902 and 903 are energized. Relay 913 now becomes released, since both its operating and locking circuits are opened.

The translator relay 906 is now operated in a circuit from battery, through the wind ing of this relay, back contacts of the register relays 900, conductor 920. contact of relay 915, to the grounded conductor 916. Relay 912 will also operate in a circuit from battery, through its winding, front contacts of relays- 919 and 921, back contacts of

relays

922 and 923, to the grounded conductor 920. Relay908 is operated in a circuit from battery, through its winding, contact of relay 912, back contact of relay 924, front contact of relay 918, back contacts of relays 925 and 926, to the grounded conductor 920. Relay 927 is also operated in a circuit from battery, through its winding, front contact of relay 917, back contacts of the remaining three relays of register 901, to the grounded conductor 920.

Since the connection being extended is one which leads through a tandem office, the marker sends certain class information back to the sender at this time in order that the sender may be prepared to transmit the necessary designation impulses to the tandem office. This information consists in the operation of certain class relays in the sender from the translator 905; for instance, the class relay 610 in the sender is operated to indicate to the sender that the call is one leading through a tandem office. The circuit for operating this relay maybe traced from battery, through its winding, thence through the connector 800, conductor 816, contacts of relays 906 and 908, lower contact of relay 927, conductor 928, inner left contact of relay 1017, to the grounded conductor 1018. Also the class relay 635 is operated in a circuit from battery, through its winding, conductor 636, connector 800, conductor 822, to ground at the contact of relay 931. Furthermore, if it is assumed that the tandem office is equipped with full automatic switching apparatus, the class relay 616 in the sender is operated in a circuit from bat-- tery, through its winding, conductor 637, connector 800, conductor 823, to ground at the contact of relay 931. It will be noted that relay 931 is energized in a circuit leading through the translator 905 and contacts of relay 927. It will be understood that all class relays in the sender lock in order that they may remain energized after the marker is discharged. Other class relays may also be operated in the sender depending upon other factors concerned with the particular call in question. For a more complete description of the manner in which class indications are given to the sender, reference is made to U. S. Patent No. 1,517,381, issued Dec. 2, 192 1, to S. B. Williams.

With the translator 905 set, one of a num' ber of trunk group relays 1012, 1013, etc. is selected and operated to identify the particular group. of trunks which leads to thedesired tandem office. In this case, the relay 1012 is operated in a circuit from battery, through its winding, conductor 1022, through contacts of the translator 905, to the grounded conductor 928.

The frame connector 1100 is next operated to associate the marker with the particular semi-mechanical district frame in which the trunk 132 appears. F or this purpose, relay 1102 is operated in a circuit from battery, through its winding,conductor 1115, contact of relay 915, conductor 929, connector 800, conductor 817, contact of the frame test relay 618, conductor 631, conductor 737, connector 800, conductor 818 and thence to the grounded conductor 916. For a more com plete description of the manner in which the frame test is accoi'nplisl'ied, reference is made to U. S. Patent No. 1,600, 1 13, issued September 21, 1926, to S. B. Williams.

Belay 1102 completes a circuit from battery, through the right winding of relay 1103, contactof relay 1102, contact of relay 1116, back contact of relay 1106, to ground at the back contact of slow-release relay 1105. Relay 1103 operates and at its right contact closes an operating circuit for the relay 1105. Relay 1105 opens the circuit of relay 1103, but the latter relay being slightly slow to release does not deenergize at this time. lVhen relay 1105 closes its front contact, relay 1103 locks through its left winding and the winding of relay 1106, the latter relay operating in this circuit. Relay 1106 opens the circuit of relay 1105, and relay 1105 thereupon releases its armature. The multi-contact relay 110 1 is now energized in a circuit from battery, through its winding, contacts of relays 1103, and thenceto ground at the back contact of relay 1105.

With relay 1105 released, relays 1103 and 1106 remain locked ina circuit which leads through the lower front contact of relay 1106, front contact of relay 1103, conductor 1118, to the grounded conductor 916.

flhe vertical magnet 211 controlling the row of contacts 20 1- at the district switch 200, is operated in a circuit from battery, through its winding, thence through the lower back contact of relay 109, conductor 138, sender selector 500, conductor 535, conductor 632, thence through the connector 800, conductor 819, normal contact of relay 1007, conductor 1023, through contacts of the frame con nector 11.00, to the grounded conductor 1118. Magnet 211 rotates the bar 208 and prepares the contacts in vertical row 20 1. Magnet 211 at its inner lower contact also closes an energizing circuit for the multicontact relay 1107, which is individual to the district frame 200. With the frame connector 1100 operated, a circuit is closed for operating the relay 1007, traceable from battery, through the winding of said relay. conductor 102 1, thence through the frame connector 1100 to the grounded conductor 1118. Relay 1007 completes locking circuits for magnet 211 and relay 1107 traceable from battery, through the windings and contacts of said magnet and said relay, con ductor 1120, contact of relay 110 1, conductor 1121, front contact of relay 1007, to ground over conductor 1023 as above traced.

Next the trunk connector 1101 is operated to associate the marker with the proper group of trunks outgoing from the district selector switch 200. For this purpose relay 1108 is operated in a circuit from battery, through its winding, contact of relay 1012,

conductor 1025, front contact of relay 1103,

front contact of relay 1106, to ground at the back contact of relay 1105. In the same manner as described in connection with the frame connector 1100, the relay 1108 causes the operation of relay 1109 and also relays 1111 and 1112, and consequently the operation of multi-contact relay 1110. Relay 1113, which is individual to the particular group of trunks to be used, is also operated in a circuit from battery, through its winding, thence through contact of the group relay 1012, conductor 1026, front contact of relay 1109, to ground at the back contact of relay 1111. The set of test relays 1000 is now connected to the group of trunks appearing in the vertical row 207 of the switch 200 and also to the horizontal test links for testing to select an idle cross-point through the switch.

At the time ground is placed on conductor 916, relays 1011, 1027, etc., are operated in parallel in a circuit traceable over conductor 1028, through the middle right contact of relay 1008, normal contact of relay 1005, to the grounded conductor 916. With

relays

1011 and 1027, etc., operated, all of the double

wound test relays

1029, 1030, 1031, etc., are operated in circuits which may be traced from battery, through the right front contact of relay 1017, thence through the left windings of relays 1029, 1030, etc., in parallel, thence through front contacts of

relays

1011 and 1027, conductor 1032, to ground at the normal contact of relay 1002. With all of the test relays operated, a circuit is closed for operating relay 1003, traceable from battery, through the winding of this relay, inner right back contact of relay 1008, thence through front contacts of

relays

1029, 1030, 1031, etc, conductor 1033, outer right back contact of relay 1008, middle right contact of relay 1008, to ground as above traced. Relay 1003 operates and closes an obvious circuit for relay 1002, which in turn opcrates and locks through its left contact to the grounded conductor 916. telay 1002 opens the original energizing circuits of the test relays but substitute circuits are provided which may be traced through the left hand windings and locking contacts of said test relays, front contacts of relays 10.11, 1027, etc., conductor 1034, to ground at the right front contact of relay 1002.

After both the frame and trunk connectors 1100 and 1101 have operated, a circuit is completed for operating the vertical magnet 212 of the selector 200, controlling the vertical row of contacts 207 in which appear

trunks

215, 216, and 217 of the group leading to the desired tandem oflice. The circuit for this purpose may be traced from battery, through the winding of said magnet, thence through the frame connector 1100, conductor 1123, contacts of relay 1012, conductor 1035, contacts of the trunk connector 1101, to the grounded conductor 1118.

l vith the vertical magnet 212 operated, a circuit is closed for the relay 1008 traceable from battery, through the winding of said relay, conductor 1036, frame connector 1100, thence to ground at the front contact of magnet 212. Belay 1008 releases relav 1003 and also all of the

relays

1011, 1027, etc. The test relays 1029, 1030 and 1031 corresponding to idle cross-points in the switch 200 will release, but all relays which correspond to busy

horizontal links

201, 202 and 203 or to busy

outgoing trunks

215, 216 and 217 will remain energized.

Assuming that the trunk 217 and the link 203 are both busy, the relay 1029 in the marker corresponding to this crosstpointwill remain energized in a circuit from battery, through the right winding and front contact of relay 1029, conductor 1037, trunk connector 1101, to the grounded sleeve conductor of the trunk 217. Furthermore, a holding circuit for relay 1029 leads from battery, through its left winding and locking contact, lower normal contact of relay 1011, conductor 1038, through the trunk con net-tor 1.100, conductor 218, to the grounded sleeve conductor of the busy horizontal link 203. Similarly, if the trunk 216 is busy, or it link 202 is busy, or both are busy, the relay 1030 remains operated.

Assuming, however, that the trunk 215 and the link 201 are both idle, relay 1031 releases.

Relays

1009 and 1039 are now operated in a circuit from battery, through the winding of relay 1009, thence through the winding of relay 1039, back contact of relay 1031, front contacts of relays 1030 and 1029, front contact of relay 1008, to ground upon the back contact of relay 1010. Relay 1039 closes a locking circuit for itself and relay 1009 traceable through the inner right front contact of relay 1039 to the grounded conductor 916. Relay 1039 also closes an obvious circuit for relay 1010.

The horizontal operating magnet 219 is now operated to complete the connection from the trunk 132 through the switch 200 to the idle trunk 215 leading to the distant tandem oflice. The circuit, may be traced from battery, through the right winding of magnet 219, conductor 220, frame connector 1100, thence through the middle left contact of relay 1039, to ground at the front Contact of relay 1010. lVhen the switch 200 has fully operated, relay 109 in the opera-