US1345879A - Machine-switching telephone-exchange system - Google Patents

Description

L. POLINKOWSKY. MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR. 9,1918.

Patnted July 6, 1920.

8 SHEESw-SHEEI l.

L. PDLINKOWSKY. MAcHnNE sw|TcH|NG TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR. 9.19%8. y v 1,345,879. Patented July 6, 1920.

8 SHEETS-SHEEI www NNN

Rum.

ERF@ QN L. POLI'NKOWSKY.

MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION min MAR. 9. 191s,

1,345,879. Panted July 6, 1920.

L. POLINKOWSKY.

HACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

L. POLINKOWSKY.

MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

Patented July 6, 1920.

H wnu H 4% MNR Affy.

L. POLINKOWSKY. MACHINE swlTcHxNG TELEPHONE EXCHANGE SYSTEM.

APPLICAION FILED MAR. 9.1918.

L. POLINKOWSKY. MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAR. 9.1918. 1,345,879. Pa'nted July 6, 1920.

8 SHEElS-SHLEI I.

L. PULINKOWSKY. MACHINE swlTcHlNG TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED MAR. 9. I9l8.

1,345,879, Patented July 6, 1920.

IIIIII nlIll lulu mln Il l Il nu nu u un MII UNITED STATEYSATENT OFFICE.

LIPA POLINKOWSKY. OE LONDON, ENGLAND, AssIGNOR To WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 0F NEW YORK.

MACHIN-SWITCHING TELEPHONE-EXCHANGE SYSTEM.

Application led March 9,

To all whom t may concern Be it known that I, LIPA POLINKOWSKY, a citizen of Russia, residing at 70 W'estbourne Terrace, Hyde Park, London, lV., England, have invented certain new and useful Improvements in Machine-Switching Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to machine switching telephone exchange systems, and more particularlyr to systems of this character adapted for use in connection with toll or junction-line switchboards wherein incoming calls from outside of the exchange are answered by an operator and the desired connection is established by such operator, special facilities being given for controlling the establishment of the connection and the ringing of the desired subscriber.

A particular feature of the invention, therefore, involves arrangement of the circuits and apparatus so that the toll operator may with facility and accuracy establish the desired connection in accordance with the well-known principles of modern toll operation.

One of the broader features of the invention relates to the interrelation between a tol] switching system utilizing machine switching to extend the call to the desired line and the usual or local machine switching exchange or network (either full automatic or semi-automatic) in which such desired line appears, whereby maximum efficiency is achieved while utilizing the minimum apparatus.

Another of these more specific features involves a special form of group selector adapted to the special requirements of systems of this character.

Another particular feature of the invention, therefore, has to do with the correct and simple arrangement of the fundamental or selection controlling circuit from the controlling equipment of the toll operator to the trunk over which the connection is to be extended through a plug and jack.

A further feature involves that both the insertion of the plug of a connecting circuit or cord to which the call has been extended into the jack of the trunk line over which it is to be further extended and the depression of such assignment key individual to such call is a necessary prerequisite Specification of Letters Patent.

Patented July 6, 1920.

191s. serial No. 221.552.

of the association of such e uipment with such call thereby preventing false operation of the equipment and consequent loss of time due to the depression of the wrong assignment key.

Another feature of the invention has to do with the release of the operators controlling equipment after the completion of the selection controlling operations for extending a given call, such release being controlled and produced after a proper interval by a set of relays forming a part of said equipment.

Another feature of the invention relates to the provision in a system of the general character referred to of improved supervlsory means especially adapted for a toll switching operators position.

Still another feature of the invention-relates to the restoration of the selection controlling counting relays to normal after a selection controlling operation andprovides for an improved arrangement of circuits and apparatus whereby the cutting olf of the current of such counting relays to restore them is accomplished gradually rather than abruptly interrupted as heretofore.

lA further feature of the invention provides means whereby the controlling equipment is prevented from being held out of service on account of the inability of the call to be extended, as for example by the inability of a trunk hunting switchto find an idle trunk. Such means in the embodiment shown when it has been brought into association with a calling line s extended not only causes the controlling equipment to pass through its cycle of operations but also causes the signaling of the operator.

Another feature of the invention relates to the provision of circuits andapparatus whereby the extension of a call from a toll operators position may take place overa. two-wire or interoflice trunk while at the same time providingthe special zoperating features necessary and desirable in connection with a toll operators position.

Another feature of the invention relates to the arrangement of circuits and apparatus whereby premature disconnection may take place without tying up any of the apparatus involved or causing unduedelay in the restoration of such apparatus' to normal.

Still further features of the invention nos will suiiiciently appear from the description of the embodiment of the invention hereinafter described. Y

One embodiment of the invention is disclosed in the accompanying drzm'ings in which:

Figures l, 2, 3, 11, and 5 when taken together illustrate a complete toll operators Vswitching system for extending a call 'to aV desired line; i

Fig. 6 illustrates a two-wire or interoi'iice trunk leading from a toll operators position and the modified apparatus utilized in connection therewith.

And F ig. 7 together with 7 indicates diagrammatically a toll operators machine switching system in its relation to a usual local exchange or network.

For the proper showing of the system disclosed in Figs. l to 5, inclusive, Fig. 2 should be placed under Fig. 1 and Fig. 3 under Fig. 2; whereas Fig. e should be placed to the right of Fig. 1 and Fig. 5 to the right of Fig. 1. To illustrate the system as embodying-,1* a two-wire or interoiiice trunk from the toll operators position, Fig. 6 should be substituted 'for Fig. 111.7 l f Fig. 1 shows only so much of the connecting circuit or cord the toll operators position as is necessary. tor anY understanding of the invention. Preferably-the features shown in Fig. 1 would beY embodied in what is known as a universal Vcord circuit which, however, as it is well known. in the art, is not disclosed in detail. The set oi rcounting relays 306 shown iii Fig. 3 are precisely similar to counting relays as are well known in the art. The set of number keys shown is generallyv similar to 'those heretofore known and a suilicicnt description bothr ofthe counting relays and olf the number keys will appear in the description y of the. operation of the system hereinafter given. i

The group selector switches diagrammati- 1 cally 'shown in Figsgi'and G and also the linal selector switch diagrammatic-ally shown in Fig. 5 are wellknowii inthe art and details'of these switches as such are therefore not necessary herein. Furthermore, the sequence switches indicated respectively at 151, 551 and 651 on Figs. 4, 5 and 6, respectively are precisely similar to those wellknown in the art and will not be' described lin detail'it being understood that the se- T he exceptions yselector switches.

The description of the system shown will best be given bya description of the operation thereof in connection with the extensionv of a call. It will be assumed that the toll operator has received a call over the cord 101 indicated generally in Fig. 1. The` operator thereupon inserts the plug 103 into thci'eby Yestablishing avr circuit which Vmay be traced froml battery, through the slow operating relay 202,1le'ft normal contact oi'f lthe. relay 201, conductor 251, conta-cts 108 and 100, of the key 102,'sleeve o'lf'tlie plug 103, sleeve of the jack 10% and slow-operating relay 101 to ground. This'circuit causes the energization ofthe relays'202 and L01.

YThe eiiergization Aoit the relay' 1-01 establishes a circuit over the sequence switch contact 453 -top to drive the sequence switchY 451 out of its normal position and such sequence switch will come`V to Vrest due to tne closure of the sequence switch contact only upon arriving in its fourth positioinin Vwhich position such sequence switch will remain until-the deiiergisation or the relay Zit01 as' will be hereinafter described.

Meanwhile, the relay 202 `by'its energizetion has established a circuit through the lower normal contact Vof the wipeout key '203, from'ground Aover the left `contact `and armature of the relay 202, conductor 391 to the holding magnets 45505 of the key set icck shown on Fig. 3. rlhe energizatioii of the Y relay 202 has also closed over its right contact and armature 'a circuit through the progresslamp 205, back contact and right armature of the relay 207,-back contact and*Y right Varmature of the relay v20S PforV the equipment busy lamp 206, which lamp will be lighted so long as the equipment( isbusy. y he operator then depresses the vnumber keys in accordance with the numerical designation or" the desired line, that is, she depresses the'appropriate'thousands key 301, thea-ppropriate hundreds keyY 302, the appiopriate'tenskey 303 and the appropriate iio units key 304.V 1t will be best understood that lthe Vnumerical designation of the desired line is recorded in accordance with the decimal system ofnotation.` In the embodiment of the invention as hereinafter dc- Yscribed, translation takes place and is necessary in View of the fact that the finalselector switches used are'assumed to have access to 200 lines and Vthe group selector switches used are assumed to have accessl to approximately 200 trunks leading to final The selection, therefore,

takes place in Vaccordance with some other system of notation than the Vdecimal system. This change from the decimal system to the non-decimal system is known in the art as translation.

If before the operator has depressed one key in each of the series of keys shown, she discovers that she has made a mistake, she may depress the Wipeout key 203, which by opening the circuit through its lower normal contact causes the denergization of the holding magnets 305 and the depressed keys are released. Then releasing the key 203 she may depress the proper keys in the respective key sets.

lVhen the operator has depressed one key in each of the sets of keys 301, 302, 303, 304 that is, has completed the recording of the numerical designation oiV the desired line, a circuit is established from the lower normal contacts of the key 203, left armature of the relay 202, left armature and back contact of the relay 204, right winding of the relay 201, conductor 394, right contact of the depressed key 301, right contact of the depressed key 303, right contact of the depressed key 302, conductor 309 or 310, alternatively, left or right contact of the depressed key 304, depending on whether the circuit is extended through the conductor 309 or 310, through the back contact and armature of the lower counting relay of the pair of counting relays individual to the contact of the depressed key 304, through the upper relay of the pair of counting relays of such key to battery. This causes the cnergization of the relay 201 and of the upper counting relay referred tto. The energization of the counting relay at this time is without effect as no circuit exists to ground over the conductor 399. The energization of the relay 201, however, has opened the circuit previously traced whereby the relays 202 and 401 were energized, and has closed a local locking circuit for its left winding over its left armature and front contact, the upper contacts of the key 203 and the back contact and armature of the relay 213, whereby the relay 202 is maintained energized after the relay 201 is locked up. The relay 401, however, is deenergized. The energization of the relay 201 has also closed a circuit over its right armature for the right winding of the relay 204 such circuit including the lower normal contacts of the key 203, and the left armature of the relay 202. rI`he energization of the relay 204 has over its right armature prepared the fundamental or selection controlling circuit at the opcrators quipmcnt. By the attraction of its lett armature it has opened the original energizing circuit for the relay 201 which, as will be recalled, included one of the counting relays, and while the relay 201 is maintained energized over its left winding the energized counting relay is de'energized. The attraction of its armature, however, has closed at its front contact a circuit for the slow operating relays 210 and 211, which circuit includes the lower normal contacts of the key 203 and the left armature of the relay 202. The energization of the relays 210 and 211 prepares the locking up circuit for the various counting relays 306, so that the operators equipment is now in condition to control the necessary selections for extending the call.

when the relay 401 was denergized oonscquent upon the energization of the relay 201 as above described it closed a circuit over its armature and back contact and Sequence switch contact 453 bottom to drive the sequence switch 451 out of its fourth position and into its sixth position. In the iifth and also sixth positions of the sequence switch 451 the fundamental or selection controlling circuit is completed at the group selector and since it has been' prepared in the operators equipment may be traced trom battery, through relay 402, sequence switch contact 404 bottom, ring contact ot' the jack 104, ring contact of the plug 103. contacts 113 and 114 of the key 102, conductor 252, conductor 397, back contact and armature of the cutoff relay 309, conductor 398, stepping relay 213, front contact and right armature of the relay 20,4, conductor 253 contacts 109 and 110 of the key V102. tip contact of the plug 103 and the jack 104, sequence switch contact 463 top to ground and back to battery. The closure ot this circuit has caused the energization ot he relays 402 and the relay 21.3. The cucrgization of the relay 402 Closes a circuit for the tripping spindle power magnet 405 over the sequence switch contact 462 bottom and the tripping spindle thereupon operates closing an intermittent circuit to ground over the top contact ot' the interrupter 422. and sequence switch contact 458 top to the fundamental circuit between the'relay 402 and the sequence switch contact 464 bottom. This intermittent circuit to ground, while it maintains the relay 402 energized, causes the intermittent denergization of the stepping relay 213 in the well known manner.

Upon the original energization of the stepping relay 213. the circuit for the relay 201 over its leit winding is interrupted and such relay is denergized, the relay 202, however not being denergized since the original circuit therefor is restablished including the left normal contact of the relay 201 and the relay 401.

The energization oi the relay 213 .has closed a circuit over its front contact, left armature and back contact of the relay 219,v

the pair of counting relays appropriate to such thousands key,.w1nd1ng of the upper counting relay of such pair to battery. This Vcauses the energization of such upper counting relay which, by the attraction of its armature, prepares a circuit for the lower counting relay of such'pair, which includes 'the conductor 399, back Contact and armature of slow operating relay 212, and armature and front contaet'of the relay 211. The conductorY 399 it might be here noted is also connected through the resistance 220 to ground through the front contact and arma-` ture ofthe relay 210. The lower counting relay of the pair referred to is not at this time energized, however, as it is shunted by the direct path to ground through its back Contact and armature and the fronty lower counting relay of said pair, the arma- Y of counting relays will be locked up inthe ture of such upper counting relay and the conductor 399. The energization of such lower counting relay has extended a circuit from the left contact of the depressed thousands key 301 to the armature of the lower counting relay of the Vnext pair to the left of the pair which has been locked up. llpon such subsequent energization and deenergization of the relay 213, an additional pair well-known manner, until as the'tripping spindle of the group selector is about te move intothe position necessary for the given selection, the relay 307 having at thisl time been energized, the relay 213 is again denergized, whereupon the relays 309 and 308 are energized, the relay 309 opening the fundamental circuit at its back contact and thereupon causing, when the tripping spindle has moved into its next stopping position, the denergization of the relay a02.

'The energization of the relay 308 closes a circuit over itsy front contact including the conductor 396, slowjoperating low resistance relay 212, back Contact and armature of the relay 217, winding of the relay 207 to battery. The relays 212 and 207 arey energized. The'energization of the relay 212 opens the direct circuit-to ground from the Conductor 399 and reduces the amount of current by which the locked up counting relays maintained energized. lt also establishes a direct circuit to ground in shunt of the re- .lay 210 and such relay, slowly retracting its armatures, after an interval, opens the direct circuit from the conductor 399 thereby cutting off the current by which the countf Y relays 207 and Y217, 208 and 218, 209V and 219 form a set Yof'counting relays analogous to the'counting relays 306. kThese relays cause the change over of the control of the counting relays 306 from one set or combination of the number keys to another set or combination thereof. Vhen thel relay 207 was energized it prepared a circuit for the relay 217 but such relay was not energized at that time because it was shnnted by the low resistance path to ground over the conductor 395 and the front Contact and the relay 308A. Y

Vl/vhile this firstiselection 'controlling' operation has been going on the thousands progress lamp 205 has been lighted. ylhe energization of the relay 207 at the conclusion-of vthe thousands selection controlling operation armatureV of tracts its armature'andthe-circuits at theV operators equipment are now prepared,. the relay 309 havingV also been d'eenergize'd) for iooV the next or hundreds selection controlling equipment. Y Y

Upon the denergizationA of the relay a02 and the stopping of the tripping spindle in the desired position in the'well known manner, the sequence switch 451 was driven'out of the sixth position by a circuit including the back Contact and armature of the relay 4.02,'back contact and armature of the relay 4.07 and the sequence switch Contact V461.

Before this sequence switchlll reached vits Y ninth position, Vthe operation hereinbefore Y 1270 Vce to be should be reduced as far as possible. In

accordance with this Vfeatureof the invention,`therefore, the group selector shown on Fig. l is `arranged to select', first a large group and thenl a smaller vgroup in '.such

large group, both of such selections taking place under the control of the operators equipment and finally, to select an idle trunk line in such smaller group. As shown, the smaller groups referred to comprise only three trunk lines, each leading to final selector switches having access to the same lines. rl`he group selector, therefore, has access to liity groups, each bank or level of such group (there being ten banks or levels) comprising tive groups of three trunk lines and the busy back contacts individual to each such sub-group. lt will be understood of course, that the number of trunk lines in each subgroup and the number of subgroups in each bank or level may be altered as occasion or the traflic of the exchange may require. Also the switches utilized may have a capacity greater or less than 200 lines.

Upon the establishment of the fundamental circuit and the consequent energization ct' the relays 402 and 213, the relay 402 closes in the ninth position of the sequence switch a circuit over the sequence switch contact 455 for the switch carriage power magnet 403 and the switch carriage theret'ore is set in motion causing the intermittent connection to ground from the fundamental circuit over the sequence switch contact 458 top and the upper contact of the interrupter 421 in the well known manner. This causes the intermittent energization and deincrgization of the relay 213 in the manner well understood and the consequent hacking up of the various pair of the counting relays 306, beginning with the pair of ff-'uniting relays connected to the left contact ot the depressed hundred key 302. As thc final selector switches have a capacity of 200 lines the left contacts of the keys 302 are connected in pairs and as the various sets ot" trunk lines on the selected bank or level of the group selector comprise with busy back contacts tour sets of terminals,

the respective pairs of keys 302 are connected with the first or number naught, the ittli or number four, the ninth or number eight` the thirteenth or number twelve, the seref-nteentli or number sixteen pair of counting relays. lf the hundreds key depressed was the first or second key, that is the number naught or number one key, the group selector switch carriage will take one step under the control of the counting relays before the fundamental circuit is opened by such counting relays in the well known manner. causing the denergization of the relay 402. li the third or fourth hundreds key, that is the number two or three key, has been depressed, the group selector switch carriage will take live steps before the deencrgization of the relay 402 by the opening oi' the fundamental circuit, and so on. When, therefore, the group selector switch carriage has taken the requisite number of steps to bring its brushes 408, 409 and 410 on the first set of contacts of the selected sub-group, the relay 402 is denergized,

opening the circuit for the power magnet 403 and causing the switch carria c to stop in the well-known manner` the hol in relay 404 being energized over a circuit inc uding the sequence switch contact 457, Seqeill switch Contact 461 bottom, back contact and armature of the relay 407 and back Contact and armature of the relay 402.` Thiedeenergization of the relay 402 has also caused" the sequence switch 451 to move out of its tact 571 and the resistance 519. This will cause the energization of the relay, 406I which by attracting its armature closes a' low resistance path through its right winding, its front contact and armature, the relay 407 and sequence switch contact 456. This low resistance path so reduces the potential upon the test terminal of the selected trunk line that no other group selector will be able to seize such trunk line. This method of testing and guarding the selected trunk line, since it is well known in the art, need not be further described. The relay 407 is now energized and drives the sequence switch 451 out of its tenth position by a circuit including the sequence switch contact 461 top and the back contact and amature of the relay 402. It will be noted that the fundamental circuit is entirely o en at the group selector in the tenth an eleventh positions of the sequence switch-451, the sequence switch contacts 463 and 464 having been opened as the sequence switch left its ninth position. The eleventh position of the sequence switch 451 is provided also as a testing position but the provision of two testing positions is already Well known 1n the art, the relay 40T when permanently energized. as has been described, drivin the sequence switch 451 into its twelfth position.

If when the sequence switch came into its tenth position and the brushes 408, 409 and 410 were resting on the terminals of the lirst trunk line and the sub-group of such trunk lines sufiicient current would not appear upon the test terminal thereof to energize the relay 406 over its left winding, the relay 407 would. therefore, not be energized and a circuit would he established .armature orn the relay spindle, is, therefore, set in motion and theV -interrupter thereof 522 intermittently shunts orthe power magnet 403 over the sequence switch Contact 455 bottom, back contact and armature ot the relay 407 and backcontact andarniature of the relay 402 to cause the v further movement of the brush carriage until an idle trunk line is found, when, owing to the energization of the relay 405 and the relay 407, as has been hereinbefore described, the movement of the brush carriage relays 212 and 208 are thereupon energized.

The energization of the relay 212 causes the restoration of thelocked up counting relays to normal in the manner hereinbefore described. rllhe energization'ofthe relay 208, bythe movement of its right armature has causedV the extinguishment of the hundreds progress lampA 220, and the lighting ot the tens progress lamp 221. 1t has also pref Vpared the circuit of the relay 218 which is energized when the relay 308 denergized, due to the operation ot the slow acting relays 212 and` 210. rllhe circuits are now prepared at the operators equipment for the tens selection controlling operation.

, When /upon the seizure ot an idle trunkl line bythe group selector the sequence switch 451 is; driven'into its twelfth position, the fundamental .circuit is extended from` the sequence switch Vcontact 463 bottom over the brush 40S and the sequence switch contact 554 top to Ground, and "from the sequence switch contact 464 top, over the brush 409 and over the sequence switch kContact, and the relay 502-to battery.

The establishment ot the 1undamental circuit in this manner causes the energization oi' the relays 502 and 213, and tens selection now takes place in the .nal selector under the control of the counting relays 306 in accordance with the depressed tens key 303. Relay 502 on energizing drives the sequence Vswitch 551 out of its first position over a circuit including the sequence switch contact r556. ln the second position o the sequence switchV a tripping spindle power magnet 505 is energized over the sequence switch contact 558 and front contact and The tripping the steppingV relay 213 over a circuit including the sequence switchcontact 559 top. As the tripping` spindle is coming into its proper position, the fundamental circuit is opened in the well known manner by the energization of the relay 309 and the relay 502 is denergized stopping the tripping spindle in its'proper position and driving the sequence switch 551 out of its second into its lifth position over a circuitincluding the sequence switch contact 557 top. ln the itth position of: the sequence switch 551 units selection takes place, the fundamental circuit having meanwhile been established at the operators equipment, the relay 209, 212 and 219 being energized in precisely the manner in which the relays 208,212 and 21S were energized as previously described. lt should be noted that the energization of the relay 209 has caused the extinguishment oit the tens progress lamp 221 and the lighting ot the units progress lamp 222. Relay 502 being again energized there is-'closed in the fifth position of the sequence switch 551 a circuit for the brush carriage power magnet 503 including sequence switch contact 561 bottom and the iront contact and armature of the relay 502. The brush carriage thereupon moves vcausing the intermittent oper4 tion of the interrupter 521v and the intermittent energization of the relay 213 by the closure of the shunt including the sequenceY switch contact 559 top and the top contact of the interruptor.

Depending onthe number of the desired line it may be that it will be necessary for the final selector to take twenty steps to reach such desired line. lt will be observed that the control of the counting relays in the units selection is determined both by the depression ot the units key 304 and the hundreds key 302. lf the hundreds digit is even it will only be necessary for the final selector to take ten or less steps to reach theV desired line with the given units digit, whereas it the hundreds digit ot the desired line is odd it will require from eleven to twenty steps for such Ylinal selector to reach the desired line of such units digit. The circuits orp Fig. 3 obviously disclose the method of translation for prochicingV this result. T he circuit for the first pair of counting relays to be energized `in this selection controlling operation may be traced, assuming the hun-V dreds digit is even, from the armature and front contact or" the relay 213 through the rarmature and front Contact of the relay-219,

conductor 394, right Contact ot the 'depressed thousands key 301, right contact of the depressed tcns key 303, right contact of the dcL pressed even hundreds key 302, conductor 309 and the left contact ot the depressed units key 304. On the other hand, it the depressed hundreds key was odd this circuit would include instead of the'conductor 309 and the'lett contact ot the key 304, the conductor 310 and the right contact of the key304. f l

Subject to this novel arrangement for translation in the number keysthen the selection of the desired line by the iinal selecico tor takes place generally in the usual manner. When the brushes 508, 509, 510 of the final selector are coming into contact with the terminals 511, 512, 513 of the desired line, the operation of the relay 309 of the counting relays causes the opening of the fundamental circuit and the consequent deenergization of the relay 502. The denergization of this relay opens the circuit hereinbefore traced to the power magnet 503 and closes the circuit for the holding magnet 504 over the sequence switch contact 563 and the sequence switch contact 557 top. It also causes the movement of the sequence switch contact 551 out of its fifth position. Positions six and seven of the sequence 551 are reserved for private branch exchange trunk hunting but since private branch eX- change trunk hunting forms no part of the present invention the sequence switch contact 560 is provided and the sequence switch 551 continues in motion until it comes to rest in its tenth position. In passing through its eighth position the sequence switch contact 564 is closed and the calling line is tested in the usual manner. If the desired line is idle the relays 506 and 507 are energized placing a busy guard upon the 'test terminal 513 of the desired line by reducing the potential normally applied to such terminal through the cut-off relay 517 of such line and the sequence switch 551 is driven directly through its tenth and eleventh positions into its twelfth position by a circuit including the armature and front contact of the relay 507 and the sequence switch contact 566. In the twelfth position of the sequence switch 551 a circuit is established for the relay 514 from the 24 volt battery through the relay 514, sequence switch contact 555 bottom, brush 409 of the group selector, the sequence switch contact 464 top, ring contact of the jack 104 and the plug 103, contacts 113, 112 of the key 102, which has meanwhile been released as will be hereinafter described, lower normal contact of the ringing key 124, and right Winding of the relay 122 of 48 volt battery and ground. Relay 514 due to the relation of the two batteries in the circuit traced will be energized and by attracting its right armature opens the normally ringing circuit at such final selector, preventing the impression of ringing current on the desired line in the twelfth position of the sequence switch 551. By the attraction of its left armature the relay 514 drives the sequence switch 551 out of its twelfth position over a circuit including sequence switch contact 570, and the sequence switch moves into its thirteenth position which is the talking position of this sequence switch, and the sequence switch contacts 568 top and 569 bottom now being closed a complete circuit is established from the cord circuit 101 to the desired subscriber sub-station.

relay 212, right armature and front contact of relay 217 right armature and front contact of the relay 218 right armature and front contact of the relay 219 and 214 to battery. This causes the energization of the relays 214 and 212.

The energization of the relay 212 restores the counting relays 306 to normal in the well understood manner. The energization of the relay 214 causes the energization of the relay 215, said relay 215 by its eneI'giza-l tion establishing a locking circuit for the.

relays 212 and 214 over its left amature. At the time when the relay 212 was energized the shunt through the front conta-ct and armature of such relay and the front contact and arma-ture of the relay 211 was closed around the relay 210 as hereinbe'fore described and such relay, slowly falling oil", not only has caused the restoration to normal of the counting relays, but on reaching its back Contact has closed a circuit, after a proper timing interval, including the front contact and right armature of the relay 214, front contact and right armature of the relav 215, conductor 254, contacts 115, 116

of the key 102 and right winding of the relay 117 causing such relay to energize. The energization of the relay 117 closes a circuit by the attraction of its left armature for the releasing magnet 120 of the mechanically locking asslgnment key 102, the circuit for which includes as well the right armature and the normal contact of the relay 121, and the relay 401. The ke 102 is thereupon restored to its normal con ition and the circuits as hereinbefore traced over the conductors 251 and 254 are interrupted at the contacts 106, 108 and 115, 116 hereinbefore referred to. By the interruption of the circuit over the conductor 251 the relay 202 is denergized disconnecting the holding circuits for the relays 207, 208, 209, 217, 218 and 219 by the retraction of its right armature and the holding circuit for thev relay 204 by the retraction of its left armature. The relays 204. 207, w8, 209, 217, 218 and 219 are. therefore, restored to normal condition, the relay 219 opening by the retraction of its right armature the circuit of the relay 214` which by its denergization opens the circuit of the relay 215. The deenergization of the relay 215 and the relays 21T, 218, 219i'have interrupted the circuit of the relay 212 and the denergization of lthe relay 204 has interrupted the circuit of the relays 210, 211. Furthermore, the fun-` erators controlling equipment shown inA Figs. 2 and 3 has now been restored to normal. Y' Y This release of the equipment and the opening ofthe fundamental circuit is timed,

' however, Aby the slowY operating relays Vreferred to so that it will not take place prematurely and by the premature substitution of the circuit extending to .the repeating coil of the cord circuit 101 for the portion of the fundamentalcircuit extending to the operators equipment, cause a false operationen the final selector, while on the otherhand such release will take place before the sequence switch 551 has in any event reached rits tenth position., l/Vhen the sequence switch 551 arrived in its eighth position the sequence switch contacts 5541 bottom and 555,

top Vare closed including between the two talking branches of the circuit, as extended to the final selector, the resistance 518.

Upon the release of the key 102, therefore,

a circuit is established to energize the super; visory relay 122, which operates and completes an alternative path for current from battery and the left locking winding of the relay 117y which is now energized, over the left winding of the relay 121, front contact and armature of the relay 122, contactslO? and 106 of the key 102, sleeve contact of the plug 103 and jack l104, through relay 401 to ground. rEhe resistances of the va# rious windings and the resistance connected to the armature of the relay 122 are so adj usted that upon the closure of4 this circuit, the relay 121 is energized and the releasing magnet 120 is denergized.

A 1f the desired line hasv been found busy in the'eighth or testing` position of ythe sequence switch 551, such vsequence switch would not move out of its tenth position and the relay 122, being maintained energized, the relay 117 is also maintained energized and the lamp 118 is connected in ,circuit with the interrupter 119. over the .front contact and right armature ofth relay 117, and by vits consequent flashing indicates to the operator that the desired line is busy. 1f, howevenas has heen assumed, the desired line was found idle, `the sequence switch 551 has moved' into the thirteenth position thereof. @n leaving its eleventh position the bridge 'through the resistance 518 is opened and in leaving its twelfth position the circuit through the relay 5111 is opened. TWhen, as a result .of

n one or both of these operations theV relay y 122 is deenergized, the relay 117- dener-V gized and 'the y-lainp 118 is continuously lightedto indicate that the ringing thereofl may take place when desired. be noted that iii order to avoid the unnecessary energization of the release magnetf120', n the right armature of the relay ,121 is ar- 1t should ranged to" release more slowly than the left ygization closes a circuit froin the source of ringing Acurrent V125, armature and front contact of the relay 121,lower contacts of the key 124, contacts 112, 113 of the'key 102, ring contact of the plug 103 and jack 104, sequence switch contact e154 top, brush 4109, sequence switch contact 509 bottoni, brush 509, terminal 512, over the subscribers line, and the ringer at thel sub-,station thereof, and back over the terminal 511, brush 508, sequence switch contact 568 top, brush 408, sequence switch contact 163 bottom, tip contact of the jack 10e and plug 103, contacts 110, 111 of the key 102 and upper contact of the key 124i to ground. l

vWhen thedesired subscriber responds the circuit will be established during the usual intervals between ringing, that is, while the key 124; is4 not depressed to energize the supervisory relay 122, such circuit being'pie cisely the'ringing circuit traced except that it includes the normal contacts ofthe key 121,r and right hand side of the repeating coil in the cord 101 andthe windings of the relay 122. yllhe energization of the supervisory relay 122, opens the circuit for the superifisory lamp 118 causing the .extinguishment thereof since atV this time relay 117 is not energized. Conversation will now take place between lthe operator and the desired subscriber and the desired subscriber and the distant subscriber who e call has been received bythe ltoll operator upon the cord 101. The supervision onV the operators position takes place in the usual nianner, the supervisory relay 128 on the calling end of the cord 101 being shownv of the type which-maybe energized by 4either alternate ing or direct current to display the signal associated therewith, the supervision on the called side being of the type usual in any common battery exchange, that'is the lamp v118 being lighted upon the denergization thereof, such relay 122' being energized vwhenever the loop circuit to the desired sub-Y scribers substantion is closed and denergized whenever suoli circuit is open. i

. @n the hanging up of thedesired sub-V Htl scrileifs rei eii'er the operator may cause the breaking down o' the established connection s i gi., time l.) time witl'nlrawal of the plug Y'w fem the jack 104. This causes the deenergizalion of the relay 101 which drives the sequence switch 451 out ol its ti'fel'lth positioe o er it circuit including the sequence wie-l; intacts 452i bottom and such sequence swiich moves into its sixteenth position. Since the sequence switch 551 has passed out of its sixth position and the sequence switch contact 571 is open the relay 40T is deiinergized at this time (the relays 501 and -1-06 are still energized) and since the sequence switch has not yet reached its fourteenth position no circuit exists for the rela)v 402 and the sequence switch 451 is driven into its eighteenth position by a circuit including the back contacts of the relays 402 and 407 and the sequence switch contact 461 bottom. ln the eighteenth position the res toration of the brush carriage takes place in the usual manner. which being completed, the sequence switch 451 is driven into its first or normal position where the tripping spindle 105 is restored to its normal position in the usual manner. Since the restoration of the brush rarriage and tripping spindle iu systems of this character is well known in the arl they will not be described herein.

is the sequence switch "15.1 moved out otl irs sixteenth position the sequence switch .contacts 150 and 451' being opened, the restoration ol' the filial selector apparatus is initiated by the deinergization olf the relay 501. The retraction of the armature of such relay opens the original circuits of the relays 506 and i", freeing the line of the called subscriber and closes at its back contact the circuit over the sequence switch conta t 55? bottom to drive the sequence switch into its li liteenth position. Since the desired subscriber has restorei'l the receiver to its switchhook no circuit will exist in the fifteenth position of the sequence switch .G51 For the relay 502 and the sequence switch will be drii'en over a circuit including the bacl; contact of such relay and the sequence swit1h contact top into its sixteenth position from which position it willV be driven by a circuit including the back contact and armature of the relay 501 and the sequence switch contact 55.7. ln leaving its fifteenth position the sequence switch 551 opened the yontacts 504, and 5135 which since the relay 501 is deinergized opens the circuits of the relays 500 and 50T and frees the called subscriber`s line. ln the seventeenth position of the sequence switch .551 a circuit is again established therefor over the back contact and armature of the relay 502 and the Seduefce switch contact 557 top, (since the circuit -fer the sequen e switch contact 5511 is open :it the group selector and at the jack individual thereto) and the sequence switch 351 moves into its eighteenth position in which position the brush carriage is restored to and stops in its normal position in the usual manner. The tripping spindle has buen restored or may be now restoring since such restoration can take place in any of the positions of the sequence switch 551 from the twelfth to the tirst or normal position thereof.

All of the apparatus has now been restored to its normal condition and subsequent calls may be established thereover as desired. lt should be noted that so long as the sequence switch 451 is out of its normal position, that is, so long as the apparatus of the group selector is not ready to be used in the establishment of a subsequent call, the sequence switch Contact 454 being closed, the busy lamp 105 adjacent to the jack 104 is lighted indicating to the operator that the trunk line connected to such jack and the group selector associated therewith are not available for use. Multiples ot the busy lamp 105 and the circuit tlwrefor may be associated with multiples ol the jack 10al if suoli are used and since the sequence Switch contact 454 is closed at all times from the time that a plug is inserted in the jack 104, until thev roup selector apparatus is again in norma condition, the ilse of the 'trunk line leading t0 such group selector at one of the multiple jacks 10-1- will cause the lamp 105 to be lighted before all of the other multiples of the jack 104 so that such jack will not be taken for use by any other operator.

Assuming that the desired subscriber has been found busy, information with regard to which has been given to the operator by the [lashing of the lamp 118 as has been hereinbefore described, such operator will restore the connection as extended by removing the plug 103 from the jack 104. The restoration of the group selector on Fig. Yl will take place precisely as has been described as a result of disconnection after a call, .\t this time the sequence switch 551. is in its tenth position. The denergizaton of the relay 501 consequent upon the opening of the sequence switch contacts -150 and 450 drives the sequence switch 551 into its eleventh position, over the circuit includingr sequence switch contact 557 bot-A tom. The brush carriage is now restored to normal in the usual manner followed by the restoration of the sequence switch 551 to its tirst or normal position.

lt should be noted that when the Final selector shown in Fig. 5 is utilized for the extension of a call from an exchange of the ordinary local network, such final selector apparatus will operate in precisely the manner described in connection with the eX- tension of a toll call. except that Since the lll . relay 514 will not be energized, for reasons whichv will hereinafter ie described, the ringing to the desired subscriber takes place automatically from the source 516 when the sequence switch 551 comes into its twelfth.

position and the sequence switch contacts 568 bottom and `569 top are closed. the `desired subscriber responds under this source the ringing cutoff relay energized by the increased flow of current due to the closure of the circuit through the subscribers telephone set, by the attraction of its armature Vdrives the sequence switch 551 out of its twelfth position over a circuit including the sequence switch contactv 570 andinto its thirteenth or talking position. rlhe other operations ofthe final selector when used in a local call are well understood and need not be herein described.

Should the operator withdraw the` plug 103 from the jack 104 in order to break down the connection so far as it may have been established before the key 102 had been released by the energization of the magnet 120, such key may be Vreleased thereafter by any preferred mechanical means. lt is assumed that this key is of any of the well known types wherein the key when depressed is held in such depressed position by a mechanical latch plate which may be either released electrically as by the magnet 120 or by a restoring button of any preferred form. In the case of a release under these conditions the restoration of the key 102 opens a circuit for the relay 202 and consequently, as has been hereinbefore described, such relays of the operators equipment as are now energized will be denergized and the circuits for such equipment restored to their normal condition. Y

If, when upon the completion of the siec-V ond selection which takes place in the group selector shown in Fig. 4, no one of the trunk lines appearing in the selected sub-group of trunk lines is found idle, the brushes 408, 409 and .410of thisgroup selector will continue in motion until they come in contact with the busy back terminals 411, 412, 413 associated with such subgroup of trunk lines. The busy back apparatus shown connected to such terminals may be common to any desired number of switches and subgroups therein, such busy back apparatus serving a double function, first, to initiate and produce the proper restoration of the operators controlling` equipment to normal by causing such equipment to pass through its cycle of operations as quickly as possible` consistent with the proper operation thereof, and second, to cause the operation ofV the supervisory signal before the operator in such a .manner as to indicate to her that the call has not been extended beyond the group selector. `When the brush 410 of the group W hen Y selector comes in contact with the terminal 413 of the busy back the relays 406 and 407 will be energized as the resistances 418 and 419V and the resistance of the windings of the relay 420 are adjusted to allow sufficient current to pass to energize the marginal relay 406 and subsequently theretothe relay 407.V

a circuit exists to. ground from the. test terminal 413 through the relays 406 and 407,

At the f the potential of such terminal will be sufiicient to energize the relays 406 and 407 of some ,other group selector the brushes of which, having found no trunk line idle in the selected sub-group of 'trunk lines, have passed on to the terminals of the .busy back. rllhe sequence switch 451 now being in its twelfth position the interrupters 416, 417

will intermittently connect battery `and ground to the ring contact of the jack 104 through the resistance 414, 415 respectively. So long as the operators equipment is associated with the cord 101 and the trunk lines leading to the group selector shown on, Fig. 4 the connection to ground through the interrupter 417 is without effect, but the intermittent connection of the battery will cause the counting relays to operate in the well known manner until the relays308 and 309 have operated, when the usual changeover takes place andV such counting relays will again operate dueto such intermittent connection to battery until upon the energization of the relays 308 and 309, a second time the equipment is restoredv to normal and the assignment key released in the nianner hereinbefore described with relation to the establishment of a normal connection.

. As soon as such release has taken place the intermittent'-connection of the battery willA be without effect but the intermittent connection to ground through the interrupter 417 will cause the intermittentv operation of the relay 122 thereby causing the lamp 118,

to flash in accordance with the operation of such interrupter 417, thereby indicating to the operator that an idletrunk line to a desired final selector'is not available'. Under these circumstances the operator may restore t the connection so far as it has been extended by the withdrawal of the plug 103 from the jack 104 and the group'selector shown on Fig. 4, andrits associated apparatus will'be restored as has been hereinbefore described.

Should the desired line be found idle and the subscriber thereat fail to respond, restoration will take place under the control of the operator precisely as though the called subscriber had responded since in either case the sequence switch 451 is in the twelfth position and lthe sequence switch 551 is in the thirteenth position.

Where it is desired that the trunk line leading from the toll operators switching section to the group selectors should be of the interoilice or two conductor type the circuits of the trunk line and sub-group selector may be modified as sh'own iu Fig. 6. The relay 601 corresponds in every particular to the relay 401. Upon its initial energization it establishes a circuit to energize the relay 696, which in turn establishes a circuit for lighting the multiple busy lamps 105 and 695 which appears before the multiple jacks 104 and 694. This relay 696 also establishes a circuit for the relay 698. Both the relays 696 and 698 are arranged'to release slowly in any preferred manner. It will be recalled that at the initiation of the operation of the operators controlling equipment the relay 201 was energized and caused the denergization of the relay 401. (lorrespondingly the denergization of the relay 601 is produced and closes at its back contact the circuit for the relay 69T which includes the front contact and armature of the relay 696. The relay 697, by its left armature` establishes a locking circuit for itself. which locking circuit will be maintained until the breaking down of the connection in view of the slow release character of the relays 601, 696 and 698 and the relatively brief periods for which the relay 201 is maintained energized. The relay 697 at Vits right armature also closes the trunk circuit through to the group selector apparatus.

lt will be understood that the apparatus indicated to the left of the dotted line in Fig. 6 is located at the toll operators switching exchange whereas that shown to the right of the dotted line is located at a distant exchange to which it is desired the two wire truuk shall extend. immediately that the relay 697 has been energized, which as may be noted is coincidentJ with the completion of the fundamental circuit at the operator"s controlling equipment, a circuit will be established including the relay 602, sequence switch 655 bottom and the sequence ,switch 654 top, completing such fundamental circuit at the group selector and causing the energization of the line relay 602 and the ,stepping relay 213 in the well-known Inanner. The operation of the group selector on Fig. 6 to select the main group, that is, the bank or level, and the subgroup therein, now takes place in the well-known manner. The relay 602 by energizing closes a circuit over sequence switch contact 653 to drive the Sequence switch 651 into its second position. in the second position the sequence switch contact 6o6 being closed the tripping spin- ,both long and short circuits.

dle power magnet 605 receives current and the tripping spindle moves, producing the usual rever-tive impulses by its interrupter over the sequence switch contact 657 bottom. llpon the completion of the first selection in the group selector the relay 602 denergizes and the sequence switch 651 is driven out of its second position over a circuit including the sequence switch contact 653. Before the sequence switch 6.61 reaches its fifth position the fundamental circuit will be again oompleted at the operators equipment and the relay 602 being energized, the power 11mgnet 603 of the brush carriage will be energized to move such brush carriage by a circuit including the sequence switch coniact 656 bottoni. During such movement of the brush carriage impulses are produced in the fundamental circuit by the interrupter 621 over the sequence switch contact 657 bottom. (1n the opening of the fundamental circuit. the brush carriage will be stopped and the sequence switch driven into its seventh position over the back Contact of the relay 602 and the sequence switch contact 653 top. ln this position the first trunk line of the sub-group is tested in the` usual manner by the relays 606 and 607 over circuits including the sequence switch contacts 661 and 660 and such line Will be seized if it is idle. otherwise, the brush earriage will be further moved by the energization of the power magnet 603 over a circuit including the sequence switch contact 666 and the back contact and armature of the relay 60T. If none of the trunk lines of the subgroups are idle the brushes will pass on lo the busy back terminals as shown in Fig. Je. Otherwise` upon the seizure of the idle trunk line in the subgroup selected the relays 606 and 607 will be energized and the sequence switch 651 will be driven into its tenth position. In the tenth position of vthe sequence switch the fundamental circuit will be extended over the sequence switch contact 666 top to the brush 608 and over the sequence switch contact 667 bottom to the brush 609 and the fundamental circuit will, therefore, be completed to the final selector where the tens and units selection will take place precisely in the manner hereinbefore described.

This change over from the hundreds selection controlling operation to the tens selection controlling operation in the operators equiinnent and f rom the 'fundamental circuit as extended to the line relay 602 at the group selector to the line relay 502 at the linal selector involves certain intermediate steps which are rendered desirable due to the particular arrangement of the operators equipment and to the fact that the relay 213 thereat is designed to operate over In the first place since the change over at the opervposition as has been described.

ators controlling equipment takes place in a very shorttime and may be completed betore the group selector has found anidle trunk line to the desired final selector, it is desirable that the 'tuiulamcntal circuit should be closed at the group selector Atrom the time tl at it is egain closed at theoperators equipment until it is completely tended through to the line relay 502 at linal selector, so that the ste ping relay .dreds selection controlling)v operation, is not at' the group selector but is n ainopened tained through the ninth position by the sequence switch contacts (S5/el top and bottom. 'As soon, therefore, as the relay 2309 is deiinerejized at the operators equipment, the relay 21B Ais energized over such circuit iucliuling the sequence switch contacts (356i top and bottom.

lil'hen a 'iree trunk line to the desired iinal selector has been teun-d. and seized the scquence switch (ll. is driven into its tenth The relation of the sequence switch contacts (S58 top and '66T bottom to the sequence switch contacts (e top and G55 bottom, is such that both the sequence switch contacts G58 top and 567 bottom are closed beiore the sequence switch contacts top and G55 bot--Vy tonI are opened. Furthermore, the cams on thc sequence switches are so arranged that the sequence switch contact 658 top will close in advance ot the sequence switch contact G67 bottom. ily this arrangement a circuit is tirst established tor the reiay '802 including the resistance 6323, the sequence switch contact 658 top and the 'lront contact and armature oli the relay 502. The resistance 633 isnow in parallel to the stepping relay 213 and while the current through this resistance will be sutlicient to maintain the relay (302 energized when theV contact 655 bottoni opens, it does not suiiiciently'reduce the current through the relay 213 t cause it to deinergize. The next step is the closure ot the sequence switch Contact G67 bottom which extends the branch of the fundamental circuit connected to the relay (3()2 over the low non-inductive resistance 6132 and the low resistance winding oi' the relay G3i., in parallel therewith, and the sequence switch .Contact G67 bottom and brush 609 to the step- 'png relay 502 at the iinal selector. lt.

over the local Vcircuits traced and the se i quence switcn G51 remains in its tenth' position.

Upon the eompletionot the units selec tion at the final selector the sequence switch 551 passes out oi its lilith position through its sixth and into its tenth position and from there-on in the manner which is hereinbetore described. As the sequence switch 553i lett its sixth position Vthe sequence switch. contact 571 was opened, so reducing the current inthe test circuit of this trunk line that it cannot be seized by any other group selector and that therelay 607 becomes 'denergizeth it being noted, however, that the relays (306v and 501 remain energized. r)The denergization oit the relay S07 closes a circuit over' the sequence switch contact (363 top to drive the sequence switch out of its tenth positionand into its Y fourteenth' position. Un coming ,into its eleventh position the sequence switchk conti at 65e. Ibottom and top are closed eX- tending the trunlr line from the operators position to the repeating coil 629 and such sequence switch contacts are maintained closed through the fourteenth position or talking position ot' this sequence switch.l @n coming into the'thirteenth position the scipienceswitch contacts. (366 bottom and top are `closed, andremain-closed in the fourteenth position connecting theV repeat-v -ing coil 629 to the trunk line extending to the final selector. VlVhile the bridge includllO the'resistancc 51S Vexists across the trunk line at the iinal selector, the supervisory re-V lay G2G is energized, thereby-short circuiting and thereby permitting the supervisory relay A22 to energize precisely as such relay was energized directly bythe establishment ot the bridge including the resistance 51S, in the connection as described in connection with Figs. 4 and 5, and with precisely the same results. in which a trunk circuit and group selector', y as shown in Fig. 6 are utilized takes placeL `trom the group selector but is controlled by tne lrey 124v as is standard pra ctice in switch-' ing systems oi' this character. fit the timev when ringing takes place the relay 626 is deenergized since the sequence switch 551 is in The ringing in a connection 1 i5 the high resistance winding oli the relay 62,7

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