US1855598A - Telephone exchange system - Google Patents

Description

April w. w. CARPENTER ET AL 1,855,598

TELEPHONE EXCHANGE SYSTEM Filed Sept. 9, 1930 7 Sheets-Sheet l v at Nut Q5 but met fut INVENTORS W W CARPENTER R. E. C OLL/S April 26, 1932. w. w. CARPENTER ET AL 1,855,598

TELEPHONE EXCHANGE SYSTEM Filed Sept. 9, 1930 '7 Sheets-Sheet 2 all +16. E+2 m+ at m L WE hm:

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TELEPHONE EXCHANGE SYSTEM Filed Sept. 9. 1930 7 Sheets-Sheet 3 IHII INVEN TOPS WW CARPENTER RE COLL/S BY V A TTORNEI TELEPHONE EXCHANGE SYSTEM Filed Sept. 9, 1930 7 Sheets-Sheet 4 v 9 0'; LL 1 g \i Q INVENTORS W W CARPENTER By R. E. COLL/S A TTORNF v April 1932- w. w. CARPENTER ET AL 1,855,598

TELEPHONE EXCHANGE SYSTEM Filed Sept. 9, 1930 7 Sheets-Sheet 5 INVENTORS A W W CA RPENTE RE. COLL/S flaw ATTORNEY p 25, 1932- w. w. CARPENTER ET AL I 1,855,598-

TELEPHONE EXCHANGE SYSTEM Filed Sept. 9, 1930 7 Sheets-Sheet 6 Q 4" a I IF INVENTORS W W CARPENTER RE. COLL/S A fro/ME) A ril 26, 1932.

W. W. CARPENTER ET AL TELEPHONE EXCHANGE SYSTEM Filed Sept. 9, 1950 7 Sheets-Sheet 7' lNVENTORS W W. CARPENTER R. E. COLL/S fi-efmfl- W FE A TTORNEY Patented Apr. 26, 1932 UNITED STATES PATENT-OFFICE WARREN w. CARPENTER, OF QUEENS VILLAGE, NEW'YORK, AND RAYMOND E. corms,

OF EAST ORANGE, NEW JERSEY, ASSIGNORS TO BELL' INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW.YO RK TELEPHONE EXCHANGE SYSTEM Application filed September This invention relates to 'atelephone exchange system and more particularly to a system in which a charge is automatically made for a completed call. The object of the invention is the provision of means for controlling the call charging in such a manner as to more equitably recompense the operating company for the use of exchange equipment.

In large exchange areas having several oi iices some of which may be located at very distant points in the area, it is desirable that means be provided whereby a calling subscriber may be charged differently for calls to ofiices which are most remotely located from the office in which the calling line terminates than for calls to ofiices which are not so remotely located, since the remotely located ofiices must be reached over long interoflice trunks which are expensive to install and maintain and it is not equitable to the operating company to provide service to all points in the exchange area at the same basic rate.

\Vhere calls are handled on a manual basis, the rate of charge maybe very easily cared for bythe operator who is able to require the calling subscriber to deposit the required number of coins in his coin box before giving him a desired connectiomor to cause the proper operation of the subscribers message register. However, where calls are estab lished entirely by dial switching means, some provision must be made for automatically controlling the charging ofthe call in accordance with the zone of the exchange into which the call has been extended by the calling subscriber.

Furthermore, it is not equitable to the op erating company that for a basic charge the subscriber shall be enabled to hold an established connection indefinitely. In manual systems the operator is able to assess the charge in accordance with the number of unit periods durin which conversation is con tinued on any call. Where, however, calls are extended by means of a dial switching sys-.

tem, operator supervision is not desirable and from a standpointof economy, charging for overtime periods of conversation should be attained by automatic means 9, 1930. Serial No. 480,660.

TELEPHONE LABORATORIES,

Both automatic charging, in accordance with the zone of the exchange area into which a call is extended and in accordance with the elapsed conversational period have been heretofore accomplished. In accordance with the present invention, however, one specific embodiment of which is disclosed herein by way of example, provision is made whereby the charges for overtime periods of conversation may be .made in accordance with the zone into which the call has been extended and on a difierentbasis than the charges for the initial period ofconversation." This is accomplished by the provision of a timing switch individual to an interofiicetrunk accessible to a district selector or oifice selector which is started upon the response of the called subscriber and advances through a cycle to measure the prescribed unit period of conversation, the unit period having been chosen as that which, would be proper for a single unit charge, for exa1nple, five minutes. The

timing switch during the initial portion of its I cycle transmits reverse current'impulses to the district selector for controllin the calling subscribers, message register, the number of register operationsdependingupon the zone of the exchange 'intowhich the interoffice trunk extends.

During the latter portion of the first or initial cycle of the timing switch'the prescribed time for the initial period of conversation is counted. If the conversation continues after the timing switch has completed its initial cycle, for example, afterthe elapse of five minutes, the timing switch is started upon a second cycle. At this time, however through the provision of a relay the circuits of the timing switch are altered in such a manner that during the firstportion of the second cycle, the impulses which are transmitted to operate the calling subscribers message register are transmitted on a different basis than for theinitial period of conversation. i i

As thetiming switch advances through the latter part of its second or overtime cycle, it measures the prescribed time for the overtime period ofconversation. If the conversation continuesafter the completion of the second cycle of the timing switch, the timing switch will advance through additional overtime cycles as long as the conversation continues and will continue toloperate the subscribers message register for each such cycle. The district selector and, if necessary, the ofiice selector has access to a plurality of groups of trunks, may be usedfor local calls requiringibut a single charge for-theentire duration of .con-

versation and other groups of which extend as interoifice trunks to different zones of the erchange area. For example, one group of trunks extending to one zone of the exchange area may each ;.be equipped with a timing switch whereby oallsextendedthereover will bercharged at a ten cent, rate for the first five minutes of-conversation and thereafter five cents Eforeach additional five minutes, and another group of-trunks extending to a, more distant Zonemay each beequipped with a timing-switch wherebyjcalls extended thereoverlwill be charged at a fifteen cent rate, for the first five minutes of conversation and thereafter. five centslfor each additional five minutes. The trunks of each group over which local connections are established are notequipped with timing switches.

The controlof-the charging circuits at the districtselector is in accordance with the well known practice exercised by'a polarized supervisory relay which operates following the response ofthe called subscriber by a reversal of current over-the trunk circuit. On calls over-a local trunk but one current. reversal is produced when a called subscriber answers and in response thereto the polarized relay of the district selector respondsand prepares a charging circuit forithe. callingline messageregisterwhich becomes etl'ective to producea single operation of-the register upon the termination of. the conversation.

When, however, a connection is established y loveran interotfice trunk-equipped for causing multiple charges-for a'callin-accordancewith the elapsedtime. ofthe conversation, it becomes necessary to render: the changing circuits ofthe selector capable ofresponding to "the timing switch of the associated trunk to operate the register at intervals during the conversation. -Provision is therefore: made in .suchinteroflice trunk circuits for causing a momentary reversal ofthe current flowing from the trunk circuit through'th'e polarized relayofthe district selector following the .settingof the final selector upon the terminals of: the called line and before'thecalled subscriber responds which causes the charging cirouitsofthe districtselector to be so altered that. subsequentreversals of .current through vthe polarized relay of the jdistrictrs'elector controlled-by thetim-ing. switch of the trunk ciruit following-the responseof the-called subscriber, will cause the calling line message certain of which groups .of. two link circuits;

register to be operated upon each such reversal.

A clearer conception of the scope and purpose of the invention will be obtained from a consideration of the following description in connection with the attached drawings in which:

Fig. 1 showsg; a calling subscriberZs line; together with certainrelays-common toia= group of calling-lines I i Fig. 2 shows a start circuit and a portion Figs S and 6 show a line finder-district selectorlink circuit,"Fig. 3 showing the line finder and Fig. .6 the district selector;

Fig. 4; showsa link circuit'for associating a sender with the district selector;

Fig. 5 shows a 'skeletonized disclosure of a register sender;

,F g. shows a trunk circuit outgoing from the district selector of FigIG'terminating in a distant oflic-e andhaving individual thereto a t ming, swltch'for controlling the calling subscrlbers message register 'and schematiand schematically a trunk circuit and selector swatches for establishing a" local connection; an

cally other selector switches for extending the connection to a called subscribers line pFig. 18 shows the manner in whichFigs. 1

to 7 should be arranged to disclose the complete invention.

The invention has been embodied in a disclosure whichis substantially like that of U. S. ,Patent No. 1,690,206grante'd to A. Raynsford, on November 6, 1928, boththe present disclosure and that of the Raynsford patent showing ,a skeletonized sender of the character shown in the more complete disclosure of S. Patent No. 1,589,402

granted to O.H.'Kopp, June 22, 1926. Reference may be ;madc to thesepatents for op erations not completely disclosed herein. As in the casesof the'above-mentioned patents a,.,plurality of link circuits are arranged to .serveagroup of calling linesan'd are taken into service in rotation. Whena link circuit completes its function it hunts for and assoc ates. itself with a district selector which is readyfor use, and the.link and district-selector remain in a sub-allottedcondition,until the next linkinlthe scrieshas been put into service. The link circuit is then put into an allotted condition from which itwi-ll beadvanced by the initiation of a call by the action of the start circuitof Fig. 2. .The

' trip circuit of Fig. l and startcircuitof Fig.

2 are so arranged that only one line may be served at a time andso' that there may be cooperation between two groups of 'lines to each of which a group of link circuits is individual. The details of these functions are described in the aboveementioned Raynsford patent and sincethey form no partofthe present invention will be omitted from the following description.

Establishment of a connection 1 to ground at the outer contact of relay 102.-

Relay 101 in operating closes a circuit from battery, winding of relay 103, right back contact of relay 104 to ground at the outer front contact of relay 101. It also prepares a circuit from battery through resistance 111 and the left winding of marginal relay 109 in parallel, inner front contact of relay 101 to conductor 114 to identify the calling line to the line finder. Relay 103 in operating closes a circuitfrom battery over the back contact of relay 201, conductor 130, right winding of relay 108, inner back contact of relay 107, left back contact of relay 109, middle left contact of relay 103 to ground.

Relay 10 8 operates in this circuit and closes a locking circuit for itself from battery through the right winding of relay 201, conductor 129, over back contacts of relays S1111- ilar to relay 108, individual to other groups of lines appearing before the same line finder,

inner left front contact and left winding of relay 108, the right back contact of relay 109 to ground at the middle left front contacts of relay 103. Relay 108 prepares a circuit from ground at its outer right front contact through the winding of trip magnet 303 of the line finder to battery in preparation for tripping the proper set of brushes when the line finder is operated. Relay 201 operates in the locking circuit of relay 108 and in combination therewith closes a circuit from ground over its outer right contact, conductor 128, inner right contact ofre'lay 108, winding of relay 110 to battery. Relay 110 locks over its inner right contact, the left back contact of relay 109 to ground at the middle left contacts of relay 103. Relay 110 closes a circuit for starting the allotted line finder.

Assuming that the link and line finder shown are the ones to be used next, sequence switch 400 will be standing in position 1 and sequence switch 600 in position 2. The operation of relay 110 will therefore close a circuit from ground at its outer right contact, outer left front contact of relay 108,inne r left front contacts of relay 103, conductor 131, leftback contacts of relay 202, inner left back contacts of relay 203, conductor 206, upper left and lower right'contacts' of cam 403, brush 402 and terminal 401, conductor 378, left contacts of cam 601,'winding of brush 307.

relay 302to battery. Relay 302 upon operating closes a circuit from battery through the winding of updrive magnet 304 of the line finder, inner lower front contact of relay 302, right contact of cam of relay 302 to ground at the lower right contact of cam 603. Relay 302 also looks over its innerupper front contact, the-upper contacts of cam 604, the back contact of relay 305, commutator segment 306 to ground .on The line finder moves upwardly under the control of magnet 304 and with the trip magnet 303 operated the proper set of brushes is tripped. As soon as commutator closed thereover, the upper-contacts of cam 602, upper front contact brush 308 engages segment 309, a circuit is 605,conductor 404, contact230 of key 204 inner right front contact of relay 201 to conductor 129 and the right winding of relay 201. This circuit shunts the winding of relay 108 and causes that relay to release in turn releasing the trip magnet 303. When brush'308 leaves segment 309 the circuitof relay 201 is opened and that relay also re-' leases. 5

lVhen line finder brush 381 makes contact with terminal 380 which is connected over conductor 114 to battery, a circuit is completed over conductor 310, winding of relay 305, conductor 312, lower left and upper right contacts of cam 606 to ground at the right contacts of cam 607. Relay 305 operates in this circuit and closes a shunt around its winding from ground over commutator brush 307, segment 306, front contact of relay 305, resistance 311, conductor 310 and thence to battery in parallel through the left winding of relay 109 and resistance 111 over the circuit previously traced. This shunt circuit reduces the resistance in series with 305 also opens one foo become centered on the terminals of the callmg line, and commutator brush 314 engages an insulating 315. The release of relay 302 opens the circuit of the updrive magnet 304 to cause the hunting movement of the line finder to cease and connects battery through resistance 313 I the uppercontacts of cam 608,: lower back contact of relay 302, inner upper back contact of relay 316, brush 326, terminal 327, conductor 112 to ground through the winding of cut-oif relay 102. Relay 102 thereuponoperates disconnecting the line relay 101 of the calling'line which upon releasing in turn releases relay 109.

At the time relay 302 operatedit closed a ground at the lower right concircuit from tact of cam 603, upper front contact of relay portion of centering segment i11 In position 2 a circuit is closed from hattery-through the winding of relay 413, upper leftand lower right contacts of cam 414,

right back contact of relay 415,:to ground at theright contact of cam 416. Relay 4'13 operates closing a circuit from battery through the left winding of relay417, right front contact of relay 413 to ground at the left back contact of relay 415. Relay 417 in operating closes a circuit from battery through the winding of updrive magnet 418 of the sender finder 420, left contact of cam 479, outer right contact of relay 417, to ground at the left back contact of relay 409.

. The sender'finder moves upwardly under the control of magnet 418 to search for an idle sender.

:Relay 413 also closes a circuitfrom battery-the right winding of relay 415, left contacts ofcam 421, middle winding of relay 415 to ground at the inner left contact of relay 413. The current in this circuit however, is not sufiicient to operate relay 415 but does create a flux in its magnetic circuit so that it becomes quick to operate when the test circuit is later closed. The test circuit extends from .brush 422 over the lower contacts of cam 419, right back contact of relay 409, left winding of relay 415, upper right and lower left contacts of cam 421, middle winding of relay 415 to ground at the left contact of relay 413. An idle sender is characterized by battery connected to conductor 502. When therefore brush 432 engages terminal 423, corresponding to the sender of Fig. 5 which is assumed to be idle, the test circuit above traced is completed over terminal 423 to battery and relay 415 operates quickly. Relay 415 in operating closes a locking circuit for itself from battery through its right winding, left contacts of cam 421, to ground at the left front contact of relay 415. It also opens the circuit of relay 417 which releases in turn releasing magnet418 and bringing the sender finder to rest on the terminals of the idle sender. The release of relay 417 in turn releases relay 413. With relay413 released and relay 415 operated a circuit is closedfrom battery through the winding of sequence switch mag-net 400, upper left contact of cam 476, contact 427 of jack 428, left back contact of relay 413, right front contact of relay 415, to ground at the 316, brush 334,

right contact of cam 416,advancingsequence switch 400 to position 3.

When the link circuit advances into position 2 for 'huntingfor an idle sender, a circuit is closed for relay 318 extending from batterythrough the upper winding of this relay, lower left contact of cam 610, upper left contact of cam 611, conductor 375, terminal 477 and brush 478 of district finder 410 to ground at the right contact of cam 429. lVith relay 302 released and relay 318 energized a circuit is closed for advancing sequence switch 600 into position 3 which may betraced from battery through magnet 600, the lower-right contact of cam 612,the lower front contact of relay 318, the upper back contact of relay 302 to ground at the lower right contact of cam603. As sequence switch 600 advances from positions 2to 3, relay 318 releases. in position 3 busy battery is applied to the "sleeve conductor 112 over line finder brush 326, theinner upper back contact of relay 316, theleftcontacts of cam 608 through resistance 313 to battery.

W hen sequence switch 400 reaches position 3 a circuit is closed from ground through the left and middle winding of relay 503, back contacts ofrelays 504 and 505, conductor 506, terminal 430, brush 431, upper contact of cam 434, brush 432, terminal 433, conductor 320, lower contacts of cam 648, to battery through the winding of relay 351 and in parallel over the upper right contact of cam 648 to battery through the upper winding of relay 316. Relay 316 is marginal and does not operate. Relay 351 operates but'is ineffective at this time. Relay503 also operates and closes an obvious circuit for relay 507 which in turn closes a circuit for relay 509. Relay 509 closes a circuit for relay 510.

As soon as sequence switch 400 arrived in position 2% it prepared the pulsing circuit fori'receiving dial pulses. This circuit may be'traced from battery through the left winding of relay 500, conductor 537, terminal 440, brush 441, lower contact of dam 429, -brush With sequence switch 600 478, terminal 477, conductor 375, left contacts'of cam 615, upper back contact of relay terminal 333, conductor 117, through the subscribers' substation, conductor 116, terminal 332, brush 331, lower back contact of relay 316, winding of relay 616, left contacts of cam 617, conductor 382, terminal brush 443, upper right and lower left contacts of cam, 403, brush 444, and terminal 445 to ground at the back contact of relay 513. Relay 500 operates in turn operating relay 518 in the well known manner. Relay 518 in turn operating relay 519. A circuit is thereupon closed from the source of tone cur-rent 516 through the right winding of relay 500, switch 520 in its normal position, front contact of relay 519, contact of cam 514, to ground at the front contact of relay 509. This tone'is transmitted to the calling subscriber to inform him'that the sender is ready to receive impulses, which he may then send by manipulating his dial.

When relay 510- operated it removed battery from conductor 502'releasing relay 415. With relay 415 released a circuit is closed from battery through the winding of sequence switch magnet 400, lower left contact of cam 47 6, right back contact of relay 415 to ground at the right contact of cam 416. Sequence switch 400 advances to position 5 over this circuit and remains in thls position throughout the further operation of the sender.

The calling subscriber now proceeds to dial the desired line number for setting the registers (not shown) and translator of the sender in the well known manner. After dialing the first digit the switch, one wiper of which is shown at 520, advances from normal closing a circuit extending to battery through the winding of relay 517 ,terminals and wiper 520, contact of relay 519, contact of cam 514, to ground at the outer right contact of relay 509. Relay 517 closes an obvious circuit for relay 521. As soon as the code registers of the sender have been set in accordance with the first two digits dialed by' the calling subscriber, the translator is set in a manner described in the afore-mentioned patent to O. H. Kopp and after the setting of the translator the class switch 540 is advanced into a position for making a full mechanical'call. ith sequence switch 600 in position 3, relay 318 is now energized over a circuit extending from battery through its upper winding, the lower left contact of cam 610, the lower right contact of cam 611, conductor 378, terminal 401 and brush 402 of district finder 410, the lower right and upper contacts of cam 435, brush 436 and terminal 437 of sender finder 420, thecontact of relay 521, the back contact of relay 504, the left contact of cam 526, winding of sender stepping relay 522, back contact of counting relay 525, left winding of overflow relay 523, left contact of cam 527. resistance 530 to ground. Relay 522 and 318' operate in this circuit, relays 318 looking over its inner lower front contact, upper left contact of cam 610, thence over the circuit traced whereby it remains energized as the sequence switch 600 advances into position 4. Relay 318 also closes a circuit to advance sequence switch 600 into position 4 extendingfroin battery through the winding of magnet 600, lower right contact of cam 612, lower front contact of relay 318, upper back contact'of relay 302, and thence to ground over the lower right contact of cam 603.

With relay 318 operated and sequence switch 600 in position 4, a circuit is closed for the updrive magnet 619 extending from battery, winding of magnet 619, lower right and upper left contact of cam 606, lower front tact ofcam 603. Theupdrive magnet 619v causes the district selector switch shaft to move upwardly in a brush selecting movement. Each time that brush 626 engages a conducting segment of commutator strip 627 a holding circuit for rela Y 318- is established from ground at the right contact of cam 607, brush 626, segment-627, upper right contact of cam 611, upper left contact of cam 610, inner lower front contact and upper winding of relay 318 to battery. This holding ground intermittently shunts the sender stepping relay 522 and in the well known manner causes the successive operation of counting relays in the sender until the sender is satisfied in accordance with the distinct brush setting registered inthe sender when counting relay 525 operates opening the fundamental circuit at the sender. Sequence switch550is thereupon advanced to position 3. 7

At the district selector upon the opening of the fundamental circuit and when the brush 626 engages the next insulating segment of commutator strip 627, relay 318 releases opening the circuitofiupdrive magnet 619 and closing a circuit for advancing sequence switch 600 to position 5, which circuit may be traced from battery, winding ofmagnet 600, upper left and lower right contact of cam .613, lower back contact of relay 318,- upper back contact. of relay 302 to ground at the lower right contact of cam 603. From positions 5 to of sequence switch 600, a circuit is established for trip magnet 614 over the upper right contact of cam 603 to ground for of brushes when the district selector. switch shaft is next advanced in a group selecting movement. I I

With sequence switch 600 in position 5 and sequence switch 550 in position 3 the fundamental circuit previously traced is again closed, and relays 522 and 318 operate as before. Relay 318 looks as previously described and closes the previously traced circuit for advancing sequence switch 600 to position 6. When sequence switch 600 arrives in position 6, updrive magnet 619 is again energized and the district selector shaft is moved upwardly to trip the selected brush set and then in a group selecting movement. As in the case of brush selection a holding circuit for relay 318 is prepared extending from ground at the right contact of cam 607, brush 628, commutator strip 629, the upper con tacts of cam 610, the innerlower front con-; tact and upper winding of relay 318 to battery, in shunt of the winding stepping relay 522. As the district selector shaft moves upwardly stepping relay 522 will be intermittently shunted operating counting relays until the sender is satisfied with respect to its district group registration, when counting preparing to trip the proper set relay525" will operate to open the funda As soon" as brush 628 en-- mental 7 circuit. gages theneXt insulating segment of strip 629,- relay' 318 releases thereby opening the circuit of u'pdrive magnet 619' advancing sequence switch 600 into-position 7" over the circuit previously traced for advancing it' into-position 5".

In position-7' of sequence switch 600 relay 318- iss operated'in' a circuit from battery, lower winding of relay 318, upper right contact of cam 618, upper left contact'of'caln 604,- b'ack contact of relay 305, commutator strip 306, brush 307, to ground.- The operation-' of 'relay 318' closes-a circuit from battery through: the winding of sequence switch magnet" 600, the lower-right contact" of-cam 612, the lower f'rontcontact of i'elay318, up-

per-b'ackcontact ofrelay 302', to groundat 639 and ground over the sleeve terminal of:

thefirst trunk, of the selected group proyided that 'trunk isb'usy, The' energizing circuit of relay-318-isopened in position 8k- If the first; trunk" offthe group; is busy and relay 31'8"-is-held energized in-position8; a circuit is; completed for the updrive magnet 619',

extending from battery through the winding ofmagnet 6'19; lower 'right and upper left.

contacts of cam 606, lower front contact of relay; 318, upper back contact of relay' 302,

to ground at the lower right contact of cam' 603. The: updrive magnet 619 'is energized and causes-thedistrict selector switch shaft to move-upwardly in search of 'an idle-outgoing trunk. Relay 318 is held ope-rated betweentrunk terminals over auci'rcuit extending-from batter-ythro ugh its lower wind ing, right conta'etsof cam-618, commutatorse'gment 630, brush 638; upper-contacts of cam 6'0'6,lower frontcontact ofrelay 318,

upper-back contact of relay toground atthelower right-contactof earn 603 As soon as an idletrunk'isreaehed, characterized by the absence of 'ground on its sleeve terminal, the locking circuit of" relay' 318 is opened and the relay releases in turn releasing the updrive 'magnet therebybringing the selector to rest oir thefirst idle outgoing t'r-unk," wliich will be-assumed to hethetrunk disclosed in lfigrii Thereleaseof relay 318 closes acircuit from battery, windingof sequence switch magnet 600, upper left and lower 'rl'ght contacts of caln 613', lower backcontactsofrelay 318', upper back contactiof relay'302 to'gi'ound at" the lower-right contact ofcam 603 advancing sequence switch 606 to position 9;-

As soon as relay 3'18 releases ground is connected to"- sleeve terminal 6&0' 'of the seigsames lected trunk circuit over brush 639, the upper right and lower leftcontacts of cam 632, the inner lower back contact of relay 318 to ground at the upper-left contact of cam 607, to asthe sequence switch arrived in position 8% ground is connected over the right contacts-of cam 632 to sleeve terminal 6&0 inclependent of relay 318, whichground is'ma'intained until sequence switch 600 leaves position 15%.

VV-ith sequence switch 600 in position 9, .a circuit=is established for relay 318- extending from b'atterythrough its lower winding, upper left contact relay-351, lower contacts of cam 604:, com-mutator segment 335 and brush 336 to ground. Relay 318 operates 1 and closes a circuit extending from batterythrough the" winding of sequence-switchmagnet 660, lower'right contact' of cam 612'," lower front "contact" of relay 318, upper backicontact of relay 302, to ground-l at the lower 'righttcontact ofi cam 603 for advancing sequence switch 600: into the selection beyond positionilO. In position 10 relay; 318 remains energized? overithe cir cult ust:tr'aced.'

Since the call 1s assumed: to be to an: office accessible directly through a district selector without" passing through an office selector; relay 511" of'fthe sender: was=operated as soon as sequence switch 550 reached: position. 2. and advanced the sequence switch, cams- 0f which are shownon' the left'of the vertical dot and dash line ofFig; 5, intoi'position 7 T. I

inthe manner described" in the aforementioned' patent to OJH." Kopp whereupon relay 51'1freleases: When the counting relay operates at the termination of district group selection with relay'511 deenergized,sequence switch 55Ois advanced to position 4' over a circuit from battery, winding of magnet 550, upper" contact ofcanr 551, inner left bank contact of relay 531, front contact of relay 529', left backcontact -of- 'relay 511to ground; 1

normalcondition; The testcircuit may be traced-in part from battery at'the incoming selector, the brushes only of which have-been indicated, upper winding ofpolarized relay 701, upper back-contact of'relay'702, conductor 703, terminal 6&1, brush 621", upper contacts' of cam 622, upperbaclr contact of relay 321, conductor'378, terminal 401', brush 402, lower right and'upper'leftcontacts of cam 435", brush436', terminal l37, front contact of relay 621', rightlo'ack contact of relay 50d,

render'the selected trunk busy. As soon J of cam 633, front contact'of, w

contact of cam 534, upper contact of cam 535, upper contact of cam 539, resistance 538, left contact of cam 537, winding of test relay 536, left winding of relay 523, contact of cam 546, translator brush 544 compensating resistance 545, left back contact of relay 524, right front contact of relay 507, conductor 543, terminal 439, brush 438, right contacts of ca m 405, brush 406, terminal 407, conductor 379, upper left and lower right contacts of cam 624, brush 625, terminal 642, conductor 704, lower back contact of relay 702, contacts of cam 705, lower winding of polarized relay 701 to ground at the incoming selector.

The current flowing in this circuit operates test relay 536, in the sender but is not in the proper direction to operate relays 523 and 701. Relay 536 upon operating "closes an obvious circuit for relay .540 which in turn closes an obvious circuit for relay 541, re-

lay 541 looking over its right contact-to ground on cam 542, until sequence switch 550 leaves position 5. With relay 541 operated a circuit is established for advancing sequence switch 550 into position 6 which may be traced from battery, winding of sequence switch magnet 550, lower contact of cam 547, contact of class switch cam 548, left contact of relay 541 to ground at the left back contact of relay 511. With sequence switch 550 in position 6, and district sequence switch 600 in position 10, a fundamental circuit is closed for controlling the incoming selector which may be traced in part from battery at the incoming selector over the circuit previously traced to the up per contacts of cam 535 in the sender, contacts of cam 539, winding of stepping relay 522, back contact of counting relay 525, lower contacts of cam 527, contact of cam 546, thence as traced to ground at the incoming selector. The control relay of the incoming selector and relay 522 in the sender operate over this circuit but polarized relay 701 in the trunk circuit does not operate.

The incoming selector 725 is controlled over this fundamental circuit in the well known manner following which the incoming selector hunts for an idle final selector The fundamental circuit is then extended to the final selector which is then con trolled by the sender to select the desired wanted line 751. After the completion of incoming and final selections a heavy positive impulse of potential is transmitted over the fundamental circuit from the sender thereby causing the operation of polarized relay 701.

Relay 701 upon operating establishes a circuit from ground at its front contact over the inner lower back contact of relay 702 to battery through the winding of relay 706. Relay 706 operates closing a circuit for relay 708 extending from battery, winding of relay 7 08, back contact of relay 707 to ground at the inner lower front contact of relay 706.

Relay 708 inturn closes a circuit for reversing relay 709 extending from battery, winding of relay 709, lower front'contact of relay $06 to ground at the front contact of relay 702, the inner upper front contact of relay 706, sleeve terminal 640, brush 639, to ground over the right contacts of cam 632, but as long as relay 701 remained energized relay 702 is shunted and does not operate in this locking circuit, ceases the shunt is removed and relay 702 operates, disconnecting the windings of relay 701 from the fundamental circuit and closing the fundamental circuit over trunk conductor 703, the upper front contact of relay 702, the upper left windingof repeating coil 710, retard coil 711, upper front contact of relay 709,. upper winding of relay 712, to ground and connects the trunk conductor 704 over the lower front contact of relay 702, lower left-winding of repeating coil 710, retard coil 713, lower front contact of relay 709. to battery through the lower winding of relay 712. The current flowing over the fundamental circuit to the sender is now in such a direction as to cause the operation of polarized overflow relay 523 in the sender, but is not of sufficient strength to operate relay 712 in the trunk circuit. With relay 523 operated relays 531, 524,-and 504 are operatedin the manner fully described in the aforementioned to O. H. Kopp. With relays 531, 524, and 504 operated the sender sequence switch 550 is advanced to position 18 for controlling talking selection. Relay 351 in the district selector is operated in parallel with the winding of relay 316 throughout selections. The operation of relay504 above-mentioned now opens a shunt around the right winding of relay 503 including that winding in the circuit of relays 351 and 316. Relay 351 thereupon releases in turn opening the circuit of relay 318 which also releases. Upon the release of relay 318 the district sequence switch 600 is advanced into position 11 over a circuit extendingfrom battery, winding of magnet 600, upper left and lower right contacts of cam 613, lower back contact of relay 318, upper baclz'co'ntact. of relay 302, to ground at the lower right contact of cam 603. As the sequence switch enters position 11, ground is connected to conductor 320 at the upper left contact of cam 603 and thence over terminal 433,brush 432, upper contacts of cam 446, left winding of relay 415, right back contact of relay 409, lower contact of cam 434, brush 431, terminal 430, conductor 506, left back contact of relay 505 to the windings of relay 503. Since these windings are also connected to ground, relay 503 now releases in turn releasing relay 507. The release of relay 507 does not release relay 509 since that relay is locked to its own front Relay 706 locks over the winding of relay When the heavy positive impulse left= contact ofcam 610.

. its middle left contact to conductor 506 and" to, ground asabove. traced. After leaving position 10, relays 351 and 316are'both disconnected fromconductor'320;

Talking selection winding of'relay 318, lower leftncontact of:

cam 610, lower right zcontactof cam.611, con:-, d'uctor 378, terminal 401, brush. 402, lower. right; and upper. left contacts of: cam2 435, brush=436, terminal 437 condi1ctor 532, the front'icontactof relay'521, the. front: contact ofrelay 504', the right=contact of cam 526, the. sender sequence switch being in position1-8 for talking selection, the winding of stepping. relay- 522, the back contact.- of counting relay? 525, the lower and upper right contacts of cam:5'27, therightzbacl contact ofrrelay 507, resistance 530 to ground. Relays 318 and 522 energize in tliisc-ircuit, relay 318' closing a circuit extending from battery through se-' quence switch magnet 600, lower right. contact'of cam 612, thelower front. contact of relay 318, the upper-left contact ofcam 635 to ground at the lower rightcontaot of cam 632. Relay 313- upon energizing locks'to the fundamental circuitLover' its upper winding and inner lowerfront'contact and the upper 7 As sequence 600 rotates out of position 12 toward position 16 ground is:intermittently connected to the fundamentalcircuit in shunt of-senderstepping=relay 522 over the lower contacts of cam 6321 When the send-er is satisfiedas to its talking selection setting, the fundamental circuit is opened at the senderthrough the operation of counting relay 525 and relay- 318 deenergizes arresting'the sequence switch 600 in itsnextstoppingposition. The sequence switch may be'arrested in any one of three positions. Position 13 which is a mul tiple charging positionfor all connections to offi'ces lying outside the local area, position 14 which is a single charge position for local callsand position 15 for connections to an operators'position. It will first be assumed that a call is established to a distant office for which a multiple charge must be made and-that the sequence switch of the district selector is thereforepositioned in position 13.

After; the disconnectionof'relay 351 from conductor 320, thisrelayisheld operate d over. a circuit" extendingzthrough its winding, the lower: contacts of cam: 648'to ground at the upper, left contact. of cam 603. This circuit is maintained until sequence switch 600' leaves position10%. WVhen sequence switch 600 enters position 11, relay. 351 is held energized over' resistance 634,.the contact of. relay 616 togroundtover the upper left and lower right contacts'ofcam 632.. When sequence switch 600 reaches position 11 the calling subscribers line isiextended from conductor 117 over terminal 333, brush-334', the upper back contact of relay 316,.the lower right contact of'cam 615, the uppenleft'winding of repeatingcoil 631, toground andoverconductor 116, termina-l 332, brush 331, the lower back contact of relay 316, winding of supervisory 616,.the' lower right. contact of cam 617, the lower left' winding. of repeatingycoil631, to battery; Relay'616 is maintained energized in this circuit and maintains the holding circuit'for relay 351. extendingthrough the windingof'relay "351, resistance 634, the front contact of relay 616 to ground over the upper left and lower right contacts-ofcam 632. Relay 351 is thus. maintainedioperated until the calling subscriber releasesthe connection.

Alftertalking. selectionis completed, .rel ay 515 operates connecting battery to conductor 506: in parallel with the relay 505. The cur rent over this circuitis now sufficient to operate relay 415, which closes a circuit from battery through the left winding. of relay 417, lower contactsof oam.421, to ground at the left front. contact ofv relay 415. Relay 417 closes a circuit from battery through the winding. ofsequence-switch magnet 400, upperv contact of cam 479, .outer right front contact ofrelay 417 leftback contact of rclav 409', toground thus advancing sequence switch 400 to position 6. In-this position all of the conductors extendingto the sender are opened and the sender is completely released. The link circuit of Fig. 4.now functions to restore the sender. finder 420 thereof to normal, to hunt for and allot another line finder-district selector link for use on. another call andto advance link sequenceswitch 400 to position 10, so that the-link is ready to operatev in response to the-next call-in the group of lines served thereby.

With the district selector sequence switch 600 in position 13, a. circuit is established which may be traced from ground. through the upper winding, of relay 712, the upper front contactof relay 709, retard coil 711, the upper leftwinding of repeating coil 710, the upper front contact of relay 702, conductor 703, terminal 641, brush 621, the upper right and lower left contactsof cam 622, the upper right winding of repeating coil 631, winding of polarized relay 361, the lower right winding of repeating coil 631,.lower' contacts of direction through the winding cam 624, brush 625, terminal 642, conductor 704, the lower front contact of relay 702, the lower left winding of repeating coil 710, retard coil 713, the lower front contact of relay 709 to battery through the lower winding of relay 71 Relays 30-1 and 712 operate in this circuit and perform functions which will be later described.

As sequence switch 600 advanced during talking selection into position 12% a circuit was establish-ed for relay 317 extending from battery through the winding of relay 317 the upper left and lower right contacts of cam 620, to ground at the right contacts of cam 632. As sequence switch 600 advanced out of position 12% relay 317 started to release but being slow to release does not fully release until after the energization of polarized relay 301. in the circuit previously traced through the winding of relay 712 in the trunk circuit. When therefore relay 301 operates a circuit is established for relay 319 extending from battery through the winding of re lay 319, the front contact of relay 317, the front contact of relay 301, the lower left contact of cam635, to ground at the lower right contact of cam 632, relay 319 operates and locks over its lower front contact, the lower contacts of cam 620, to ground at the right contacts of cam 632. r

Relay 712 in the trunk circuit upon operating establishes an obvious circuit for relay 707 which upon operating opens the circuit of relay 708. Relay 708 in turn opens the circuit of reversing relay 709 which thereupon releases and reverses the connection of ground and battery through the windings of relay 712 and the left windings of repeating coil 710, so that current now flows in such'a of polarized relay 301 that relay 301 deenergizes. The reversed condition of battery connected to the winding of polarized relay 301 is therefore effective for only a short interval. When relay 707 operated it connected the winding of polarized relay 714 and the right windings of repeating coil 710 to the tip and ring trunk conductors extending to the incoming selector.

When the calling subscriber at substation 751 answers polarized relay 714 is operated and connects ground from the upper front contact of relay 706 over the contactsof relay 714 conductor 720 to the middle contact of interrupter 715. As soon as the interrupter 715 closes its upper contact a circuit is established from battery through the winding of relay 716, the upper contact of interrupter 715, thence as traced to ground at the upper front contact of relay 706. Relay 716 upon operating locks over its left contact to ground at the upper front contacts of relay 706 independent of the contact of interrupter 715 and at: its right contact establishes a circuit for relay 717 which may be traced relay 7 24, to

from battery through the winding of relay 717, the right back contact of relay 718, the right contact of relay '716,the lower contact of interrupter 715 and thence as traced to a ground atthe upper front contact ofrela-y 706. Relay 717 upon operating locks: in a circuit through its winding, the winding of relay 718, the front contact of relay 717, the left contacts of cam 719, thence to ground on conductor 720. Relay 718 is shunted inthis locking circuit until the interrupter 715 opens its lower contact whereupon relay 718 operates in the locking circuit of relay 717. Thus through the operation of interrupter 715 and relays 717 and 7l8, relay 718 does not operate for a minimum of five-tenths of a second and a maximum of one and five-one hundredths seconds after the calledsubscriber answers.

On the next closure of the bottom contact of interrupter 715'with relay. 718 operated a circuit is closed from ground on conductor 720, lower contact of interrupter 715, right front contact of relay 716 right front contact of relay 718, right back contact of'relay 721,

winding of relay722 to battery through the left winding of relay 721. Relay722 operates' in this circuit but relay-7 21 being marginal does not. ;Relay 722 upon operating looks from battery through the left winding 1 of relay 7 21,winding of relay 7 22,.right'winding of relay 721, front contact ofrel'ay 722, left contacts of cam 719' to ground on conductor 720 shunting the right winding of relay 721. 'Upon the next opening of the lower ,7

contact of interrupter715, this shunt is opened and relay721 operates. When interrupter 715 again closes its lower contactrelay 722 becomes shunted from ground on conductor 720, left contacts of cam 719, front contact of relay 722, right winding of relay 7721, winding of relay 722, right front contact of relay 7 21, right front contact of relay 718, right front contact of relay 716, lower contactv of interrupter 715 to ground on conductor 720 cam 726 to ground. Relay 724 operates in this circuit but relay 723 being marginal does not operate. Relay 724 looks over the'left winding of relay 723, Winding of relay 724,

right winding of relay 723, right contact" of ground as traced at the right contacts of cam 726. When relay 721 releases, the shunt around the right winding of relay 723, from the left contact of'relay and relay 722 releases. Relay 721 is, how-' tacts of relays being shunted 721, right back contact of relay 723, right winding of relay 723, right contact of relay 724, to the left contact of relay 721 is opened at the left contact of relay 721, and relay 723 operates. Relays 723 and 724 being both operated, a circuit is established for relay 727 extending from battery, windingof relay 727 left back contact of relay 7 28, left con- 7 23 and 7 24, outer left contact of relay 718 to ground at cam 726. Relay 727 operates and locks through the winding of relay 7 28 and its own front contact, the

outer left contact ofrelay 718, to ground at the right contacts of cam 726, but relay 728 does not operate.

When relay 721 releases, the circuit of relay 722 is again established and under the control of interrupter 715, relays 7 21 and 722 ,scriber of 2.15 to 2.75 seconds. arrangement is necessary in order to prevent both operate and release in a second cycle.

Relay 721 again operating causes the shunt- '728 operates. When relay 721 again releases in its second cycle the holding circuit of relay 7 23'is opened and relay 723 releases. Re-

lay 728 upon operating connects the middle spring of interrupter 715 over the outer right front contact of relay728directly to ground at 'the upper contact of ,ent of supervisory relay714. Thus through relay 706 independthe operation of relays 721 to 724 inclusive under'the control of-interrupter 715 a time interval of 1.65 seconds is measured from the time relay 718 operates to the time relay 7 28 operates. During this timing interval if the calling subscriber releases or flashes his "switchhook all relays of the trunk circuit which have been operated will release. Relay728 thus operates after a total interval following the response of the called sub- This circuit possible false operation of the subscribers 'message reglster in case of a release by the called subscriber during the first two seconds of the delay period.

I At the time relay 718 operated following the response of the called subscriber, it closed a circuit for reversing relay 7 09 extending through the winding of this relay, lower front contact of relay 706, inner left front contact of relay 718 to ground at the back contact of relay 729. Relay 709 reverses the direction of the current flowing through the polarized supervisory relay 301 of the district selector .to cause its operation. Relay 721 and 722 again operate and release in a third cycle under the controlof interrupter 715 again causing the operation of relays 723 and 724. With relay 728 operated when relays 723 of relay 728, left contacts of and 724 both become operated, a circuit is established for relay 730 over a circuit'extending from battery, winding of relay 730, back contact of relay 7 31, left front contact 724, outer left contact of relay 718 to ground at the right contacts of cam 726. Relay 730 operates and locks through the winding of relay 731 and its own front contact over the left front contact of relays 718, to ground at cam 726, but relay 721 does not operate in this locking circuit since its winding is shunted until relay 724 releases. Under the control of interrupter 715 relays 721 and 722 are again operated and released in a fourth cycle causing the release of relays 723 and 724 and the removal of the shunt from around the winding of relay 731, whereupon relay 731 operates.

As the interrupter 715 continues to close and open its lower contacts, relays 721 and 722 are operated and released through two more complete cycles causing the operation of relays 723 and 724 during the first of these cycles and their release during the second of these cycles. Upon the operation of relays 723 and 724, with relay 731 operated, a circuit is closed from battery through the winding of relay 729, the left front contacts of relays 7 31 and 7 28, the left front contacts of relays 723 and 724, the outer left contact of relay 718 to ground at the right contacts of cam 726. Relay 729 operates and looks over its right contact to ground at the right contacts of cam 726, at its left back contact opens the circuit of reversing relay 709 and at its left front contact establishes a circuit for advancing sequence switch 700 into position 2. This circuit may be traced from battery through the winding of magnet 7 00, lower left contact of can1'7 32, to ground at the left front contact of relay 729. When sequence switch 700 advances, all operated relays of the trunk circuit except relays 702, 706, 712 and 714 release. This ends the first charging period. Through the control of interrupter 715 relays 717, 718, 721, 722, 723, 724, 727, 7 28, 730 and 731 have thus been operated and a period is measured so that relay 729 is not operated for. 5.5 seconds after relay 718 operates. During this period the reversing relay 709 is held operated to operate relay 301 in the district selector to enable the district delay circuit to function.

Reverting now to the operation of the circuit of the district selector it will be recalled that relay 319 was operated and locked and that relay 317 released. When therefore the called subscriber answers and relay 301 operates a circuit is established for relay 302 extending from battery, winding of relay 302, lower contact of interrupter 322, left contacts of cam 618, normal contacts of relay 317, front contact of relay 301, lower left contact of cam 635, to ground at the lower relays 723 and' right contact of cam 632. Relay 302 operates and locks over its'inner upper front contact, the upper right contact of cam 604, the upper left contact of cam 618, normal contact of relay 317, front contact of relay 301 to ground at the lower right contact of cam 632 as traced independent of interrupter 322. As soon as interrupter 322 closes its upper contact a circuit is now established for relay 323, extending from battery, winding of relay 323, lower back contacts of relay 324, lower right contact of cam 602, upper front contact of relay 302, upper contact of interrupter 322, left contacts of cam 618, thence to ground at the lower right contact of cam 632 over the front contact of relay 301. Relay 323 operates and locks through the winding of relay 324 and its own front contacts to ground over the locking circuit of relay 302 but relay 324 does not operate since its winding is at the time shunted over the upper contact of interrupter 32 2. \V hen however interrupter 322 opens its upper contact, relay 324 operates and closes an obvious circuit for relay 321. e

The operation of relays 302,323 and 324 under the control of interrupter 322 has in-' troduced a delay from the time relay 301 operated following the response of the called subscriber before applying charging battery for operating the calling line message register to avoid a false charge should the called subscriber release or flash his switchhook. If the called subscriber does not release during this period and relay 301 remains operated until relay 324 becomes operated, charging battery isapplied through resistance 325, the lower front'contact of relay 321, the inner upper front contact of relay 324, the upper front contact of relay 319, the left contacts of cam 605, conductor 310, brush 381, terminal 380, conductor 114, back contact of relay 101 to ground through the calling line message 105. At the end of the first charging period when reversing relay 709 released through the operation of relay 729 and in turn released relay 301, the circuit for holding relays 302, 323, 324 and 321 is opened at the contacts of relay 301.

Returning now to .a consideration of the operation of the trunk circuit of Fig. 7, it will be recalled that sequence switch 700 Was advanced to position 2 thereby releasing the operated counting relays 717, 718, 721. 722, 723, 724, 727, 728, 730 and 731. With quence switch 700 in position 2, when the interrupter 715 closes its lower contact, a circuit is again established for relay 717 extending from battery, winding of relay 717,

"=7 right back contact of relay 718, lower contacts of cam 738, lower contact of interrupter 715 to ground over the front contact of relay 714 and the upper front contact of relay 706. Relay 717 operates and locks through the winding of relay 718,the front ill contact of relay 717, the left back contact of relay 739, the right contact of cam 719, the ground at the upper contacts of cam 726 but relay 718. does not operate in this circuit until the interrupter .715 opens its lower.

When relay 718 operates it again contact. closes the circuit of reversing relay 709, over a circuit extending from battery, winding of relay 709, lower front contact of relay 706,

inner left front contact of relay 718, to.

ground at the back contact of relay 729. Re

lay 301 in the district selector'now receives currentin the proper direction to cause its operation and in turn causes the operation of relays 302, 323, 324, and 321 in the manner previouslv described, to applycharging current for operating the calling subscribers message register 105 a second time; c

The counting relays of the test circuit are 715 in i the manner leases the polarized relay 301 in the district selector whereuponthe relays 302, 323, 324, t

and 321 are again released. When sequence switch 700 advances out of position 2 the counting relaysof the trunk circuit arereleased and relay-729 is also released. In a similar manner the counting relays of the trunk circuit again functionthrough another cycle causing a further reversal of current to t the district selector through. the operation and release of reversing relay 709 and the further transmission of an operating impulse tothe calling subscribers message reg-1 ister 105 through the operation of relay 301 and relays 302, 323, 324 and 321 of the district selector circuit. Following this, .sequence switch 700 is advanced from positions 3 to 4 under the operation of relay 729 and in position 4 all operated counting relays and relay 729 of the trunkcircuit become released. It will thus be apparent that the calling subscribers message register 105 has been operated three times for registering a fifteen cent charge. r

Returning now to a consideration of the operation of the trunk circuit of Fig. 7, when relay 728 operated the first time it closed a circuit for relay 733 extending from battery through the winding of relay 733, inner right front contact of relay 728, to ground at the upper front contact of relay 7 06. Re-

la 7 733 o erates in this circuit and locks overits right contacts to ground at the upper front contact of relay 7 06'independent of relay 728, so that when relay 728 released it remained operated. At its left front contact relay 733 closes a circuit from office timing circuit 734, left front contact of relay 733,

now operated under the control of interrupter v and advances seiiii left back contact of relay 735 to battery through the winding of relay 736. Relay 736 operates in this circuit and locks through the winding of relay 735, the front contact of relay 736, the contacts of cam 737 to ground at the upper front contact of relay 706, but relay 735 being shunted'by ground supplied from the office timing circuit does not operate in this locking circuit until the timing circuit after a thirty second interval has removed the ground.

lVith relay 735 operated, sequence switch 700 is advanced to position 5 over a circuit extending from battery, winding of magnet 700, upper left contact of cam 732 to ground at the front contact of relay 735 as soon as the charging impulses have'been sent. In leaving position 4 the locking circuit of relays 735 and 736 is opened at the right contact ofcam 737 and these relays release. Nith sequence switch 7 in position 5, relays 735 and 7 36 are again operated under the control of ofiice timing circuit 734 and sequence switch 700 is advanced into position 6 under'the control of relays 735 and736. In a similar manner sequence switch 700 is advanced from position to position into position 15'. The advance of sequence switch 7 00 from position 4 into position 15 under the control of timing circuit 7 34 and thirty second intervals has thus measured off a maximum of five and one half minutes or a minimum of five minutes for the first talking. period. Y

Vgith sequence switch 700 in position 15, a circuit is established for relay 739 extending from battery, winding of relay 7 39, to ground over the lower left contact of cam 726. Relay 739 operates and locks over its inner right front contact to ground at the upper contact of relay 706 and closes a circuit extending from ground at its left front contact, the

'lower right contact of cam 732, to battery through the winding of sequence switch magnet 700 for advancing sequence switch 700 from position 15 into its normal position 1. If at this time both the calling andcalled subscribers are still conversing and relays 702 and 706 controlled from the calling subscribers line and relay 71t controlled from the called subscribers line are energized, the counting relays of the trunk circuit again function as previously described to reoperate and release reversing relay 709 whereby relay 301 in the district selector again functions to cause the calling line message register 105 to again operate to charge'for an overtime period of conversation. As previously described, when relay 7 29 is operated to release reversing relay 709, the sequence switch 700 is advanced to position 2 whereupon the operated counting relays and relay 729 become released.

Since at this time relay 739 is operated, the sequence switch 700 is advanced directrelays 735 and 736 at.

1y into position over a circuit extending from ground at the left front contact of relay 7 39, the lower right contact of cam 732 to battery through the winding of sequence switch magnet 700. Since the circuit previously traced for operating the counting relays under the control of interrupter 715 when sequence switch 7 00 is in positions 2 and 3, is opened at the left back contact of relay 739, consequently reversing relay 709 is not operated to cause further operation of the calling line message register. From position 5 sequence switch 700 is advanced in the manner previously described into position under the control of oflice timing circuit 734: and five minutes is thus measured off for the overtime period of conversation. From position 15 sequence switch 7 00 is advanced to normal under the control of relay 7 39. Thus for the overtime period of five minutes the calling line message register 105 is operated once. If conversation continues sequence switch 7 00 advances through similar cycles until the connection is released by the calling subscriber or the called subscriber hangs up and releases relay 714. A single charge is thus made for each overtime period of five minutes.

It will of course be obvious that by slight changes in the wiring and the cutting of sequence switch cams of sequence switch 7 00, other charges than fifteen cents can be arranged for and the length of the timing period changed to suit various plans of chargmg. V

Release of connection At the end of the conversation when the calling subscriber restores his receiver to the switchhook, relay 616 releases in turn opening the circuit of relay 351. Relay 351 re mains locked over a circuit extending through its winding, resistance 634, the right contact of cam 633, the front contact of relay 351 to ground at the lower contact of interrupter 328 until interrupter opens this contact. hen relay 351 finally releases a circuit is closed upon the next closure of the contacts of interrupter 328 extending from ground thereover, the back contact of relay 351, the upper contacts of cam 648, to battery through the upper winding of relay 316. Relay 316 operates and locks over its lower winding and inner lower front contact to ground at the lower left contact of cam 603, at its lower and upper back contacts disconnects the brushes 331 and 33st of the line finder from the left windings of repeating coil 631, at its inner upper back contact opens the holding circuit of the calling thereby causing its release, and at its outer lower front contact establishes a circuit extending from ground at the lower left contact of cam 603 over the front contacts of re-- lay 316, right contacts of cam 601 to battery line cut-off relay 102 ll through the winding of sequence switch magnet 600 thereby advancing sequence switch 600 into position 17. v

With sequence switch 600 in position 17 a circuit is established for relay 302, extend' ing from battery, winding of relay302, lower left contact of cam 601, upper left contact of cam 623, upper contacts of cam 648, back contact of relay 351 to ground atinterrupter 328. Relay 302 upon operating looks over its inner upper front contact, right contacts of cam 604, commutator segment 335, brush 336, to ground and establishes a circuit for advancing sequence switch 600 into position 18 which may be traced from battery through the winding of magnet 600, upper "right contact of cam 609, upper front contact of relay 302, .to ground at the lower righticontact of cam 603..

With sequence switch 600 in position-"18, a circuit is established for the downclrive magnet 329 of the line finder which may betraced from battery, winding of magnet 329,'uppe-r left contact .of cam 602, upper front contact of relay 302, to ground at the lower right con tact of cam 603. Magnet 329 operates to drive the line finder shaft-into normal position when ground is removed from commutator segment 335, thereby releasing relay 302 and arresting the line finder switch shaft in normal position. In position 18 of sequence switch 600, a circuit is also established from battery, winding of down drive magnet 636 of the district selector, lower right and upper left contacts of cam 610, low-er contacts of cam 632 to ground for driving the district selector shaft into normal position. hen the shaft reaches normal position a circuit 'is established from battery through the winding of sequence switch magnet 600, lower left contact of cam 612, normal commutator segment 637, brush 638 to ground at the right contacts of cam 607 for advancing sequence switch 600 into normal position.

Upon leaving position ground is removed at the lower right contact of cam 632 from sleeve brush 639 thereby opening the holding circuit of relays 702 and 706 of the trunk circuit. The circuit of relay 7'12isa1so opened at contacts of cams v622 and624 and relay 712 releases in turn releasing relay 707. Relay 707 upon releasing opensthe trunk circuit loop extending through the winding of relay 714 toward the incoming selector thereby initiating the release of the incoming selector and final selector employed in establishing the connection. Relay 706 upon releasing closes acircuit extending from ground at its lower back contact,the upper right contact of cam-7 32, to-battery through the winding of sequence switch magnet 700, for advancing this sequence switch from any position in which it may be standing into normal position. With sequence 700 in normal position and relays 702, 706, 712 and .714 released, all operated relays of the trunk circuit become released. All operated appa ratus employed in the extension of thecon nection has now been restored to normal condition in readiness for use on another call.

Gulls .to the local area i In the foregoing description it was assumed that the call initiated by the calling subscriber was to a subscribers line located outside the local areaand that therefore a multiple charge of more than five cents was made therefor and charges were made for overtime periods of conversation. Acall to a subscribers line in the local area will now be discussed. Calls of this character require but a single charge regardless of the duration of the conversation and are established directly from the district selector or oflice selector :toa local" incoming selector without the employment of the trunk circuit of the character disclosedin Fig. 6.

F or a call within the local area the district sequence switch 600 is set into talking selection position 14. As before described, when sequence switch- 600 advances from position 12 towards position 14 during its talking selection movement relay 317 operates When sequence switch 600 reaches position 14 the-circuit of polarized relay 301 is established from battery at the incoming selector 740, terminal 643, district selector brush 621, upper right and lower left contacts of cam 622, upper right winding of repeating coil 6'31, winding of relay 301, lower right winding of coil 631, lower contacts of cam 624, brush 625,:terminal 644, thence to ground at the incoming selector 740. The current flowing through the winding of relay 301 is not in this case in the proper direction tocause its operation. Therefore when relay 317 releases, after sequence switch 600 leaves position 12 4, no circuit is effective for relay 319 as before described. a

When the called subscriber answers the current flowing through the winding of polarized relay 301 is reversed at the incoming selector and relay 301 operates. With relay 301 operated a circuit is now established from ground at the lower right contact of 0211111632, lower left contact of cam 635, front contact of relay 301, normal contacts of relay 317, left contacts of cam-618, lower contactof interrupter 322 to battery through the winding of relay i302. Belay 302 upon opera-ting locks over its inner :upper front contact, the upper right contact of cam604, the upper left contact of cam 618, normal contacts of relay 317, front contact of relay 301, lower left contact of ca1n 635,;to ground atthe lower right contact of .cam 6312. As soon thereafter as interrupter r322closes its u'ppercontact relay 323 operates over a circuit extending from battery, through :its winding, the back contacts of relayr324, the flower ileft co ntact

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