US1121666A - Automatic telephone-exchange. - Google Patents

Description

AUTOMATIC TELEPHONE EXCHANGE.

' 7 APPLICATION FILED JULY 5,1912. 1,121,666. Patented Dec. 22, 1914.

5 SHEETS-SHEET 2.

//7 V2/7/0/25. Frank N. Ree ves. A/ben EL unde/l. by

' Wi/nesses:

F. N. REEVES & A. E. LUNDELL.

AUTOMATICI TELEPHONE EXCHANGE.

APPLICATION FILED JULY 5,1912.

1,121,666, Patented Dec.22,1914.

5 SHEETSSHEET 3 LII I. A/fien f. LuHc/e/K E 527 Met my F. N. REEVES & A. E. LUNDELL. AUTOMATIC TELEPHONE EXCHANGE. APPLICATION FILED JULY 5, 1912.

1,1 21,666, Patented Dec. 22, 1914.

6 SHEETS-SHEET4.

{MW WWW/y.

F. N. REEVES 8; A. E. LUNDELL.

AUTOMATIC TELEPHONE EXCHANGE. APPLICATION FILED JULY 5. 1912.-

Patented Dec. 22, 1914.

5 SHEETS-SHEET 5.

//7 Vfl/O/S Frank N. Ree m. Alfie/7 EL unae/l. y 4%: V A/fy Wflnesses:

crime 1 FRANK n nnnvns, or u'nwanzgunw nnsnY; Ann ALBEN n. L NDEELL, on NEW YORK, N. Y., assreuons T0 wnsrnnn nr-ncrnrc .CQMPANY, on NEW- YORK,

N. Y., A CORPORATION OF ILLINOIS.

. Atacama.wem aouaaxcnasea'1:; 1 i

To all whom it may concern v Be at known that WE,-FRANK N. Rnnvns and ALBEN E. LUNDELL,- citizenshi the United States, residing, respectively, at

Newark, in the county of Essex and State of New Jersey, and at New York, in the county of New York and State of New York, have invented a certain new and useful Improvement in Automatic Telephone-Exchanges,

of which the following is a full, clear, concise, and ejxact description.

This inwyntion relates to automatic switching systems, and particularly to a telephone exchange system comprising one or more main oflices and one or more sub-ofiices or satellites associated and connected therewith-by trunk lines. Ina multi-oflice satellite system, there would be provided trunk lines leading from each main oflice to each other main ofiice of the'system, and other trunk lines leading from each main ofiice to its own satellites; and such a system may have, for example, ten' main ofllces, each,

with its satellites, having a capacity of 10,000- lines, making the capacity of the whole system 100,000 lines. The capacity of the satellites may be of, say, 500 subscribers lines, each, although the number may vary accord ing to requirements met in practice; and the subscribers lines may, terminate either in a satellite or directly in a main office.

Itis the objectof this inventionto-econo mize in the use of trunk lines betweenthe satellites and the main ofiices without rey' quiring' variable manipulation oh the calling devices to discriminate between calls local to a satellite and calls requiring connections through a main ofiice. To thisend automatic discriminating means is provided, preferably at eachsatellite, operating without the necessity 0f any knowledge on the r part of the party manipulating thecalling device whether the subscriber called for is connected to the same satellite as the calling subscriber or to a main office 'orsome other satellite of the exchange. The. calling device is manipulated in the same manner for all connections desired and strictly in accordance with the substation number of the subscriber wanted.

The characteristic feature of this invention is, therefore, that it provides in an-au tomatic satellite exchange system, means whereby a subscriber connected to a satellite Specification of Letters Yatcnt. I Dec; 22,1914. Applicetion filed July 5, 1912. Serial No. "707,815.

1 may be called Without any discriminating act at the calling device, wherever located 1n the exchange, to directthe connection, and without extendingthe connection through.

lite in the system of this invention one or, "more register senderseach adapted to be adjusted as by the impulses from the calling devices which-may belocated at the subscribers stations, and to: control the automatic switches or selectorsfor establishing the desired connection. Each register sender may comprise a plurality of switching devices .or registers correspondingtothe sev- 1 eral orders of digitsof the numbers of sub.- scribers. Certain of these devices are provided with automaticallyadjustable contacts so arrangedandconnected with other apjparatus thatif a subscriber iscalling for, an-

other connected to the same satellite these contacts: are concurrently operated whereby the connection is localized at the satellite, whereasif the call is for a subscriber connected to a main office orto. another satellite, one or another *of these contacts fails-to be operated whereby the connection will beautomatically extended through; a .trunk line to amain oilice, andfromthere extended in theusual 'way, 'under the controlof theregister -sender to: the .desired-subscribers line. J .Theinventicin-Will be more readily underdrawings wherein stood by; reference to the accompanying -a multi-oflice satellite telephone exchange system embodying the invention;-and Figs.

2, 3,4: and 5whenplaced'to gether from left to right in thevorde'r named represent the 'c1rcuits and apparatus involved in establish-.

ing connections between subscribers. Fig. 2 includes the apparatus associated with a calling subscriber of a satellite together with a portion of the register sender located at the satellite; Fig. 3 includes the remainder of the register sender; Fig. 4 represents a trunk selector at the satellite; and Fig. 5 represents a third and a final selector (or connector) also at the satellite and a called subscribers line and station apparatus; I

.In Fig. 1 of the drawings, represents a main office connected by trunk, lines .100 to other main offices A, B, O, D and I it being understood that similar trunk lines would extend in such an exchange from each of ,such main offices to each other main office.

Associated with main office E are sub-offices orsate'llites E and E Similarly the other main offices mayI have satellites such asA I IV, A for main jofiice'A B B, B for main office. B, et'cf" Subscribers lines are V.

eonnected some to the main offices directly, and others to the satelhtes; for example,

two subscribers" stations 6 e are connected 1 by lines 200 and 500 respectively .to satellite E and: other subscribers stations such as switches represented therein by a first selector 101, a secondselector 102, a third selector 103 and a connector 104. The apparatus at a satellite such as satellite E for example, may include suchapparatus as a trunk finder 202 terminating the line 200, a series of digit registers 203, 300, 301, 302 and 303, a trunk finder 402, a third selector 503, and connectors 504 and 105. The arrangement of apparatus thus diagrammaticallyfshown in Fig. 1 and to be more fully described with reference to the other figures of the drawings is such that the subscriber at station 6 for example may obtain a con- .nection to subscriber at station 6 over a local trunk line such as 403, or he may obtain a connection to any other subscriber of the exchange system whose line does not terminate at the satellite E through a trunk line such as 406 leading to the main office E, from whence the connection may be eX tended variously according to the particularlocation of the subscriber wanted. If any other subscriber than the one connected to the satellite E desires connection with a subscriber connected to said satellite E the circuit would be completed byway of selectors such as 101, "102 and 103 at the main exchange E through a trunk line such as 106 to a connector such .as 105 at the said satellite E. I

It will hereinafter be stated in detail the manner in which a connection is directed from a subscriber at a satellite so that it will. extend over a trunk line entirely local v to the satellite, or will be extended through an inter-office trunk line. At this point, it is sufficient to say that the trunk finder 402 is adapted to hunt for an idle trunk line in either of two series of trunk lines represented respectively by trunk litres403 and 406, and its operativezcondition with respect to these two series is determined by the automatically adjusted positions of the first three of the register sender switching devices 203, 300 and 301. And the adjusted positions of these devices are in turn determined and controlled by the first three movements of the substation calling device by which the subscriber indicates the tens of thousands, the thousands, and the hundreds digits of the number of the subscriber wanted.

- Referring to Figs. 2, 3, 4 and 5, wherein the circuits and apparatus required for the shown, two windings normally serially included in the subscribers line together with the battery 207' through back contacts of the cutoff relay 206. The cutofi relay has two windings, one, a high resistance winding, 208, included serially with the front contact 209 in the circuit of a conductor 210 leading to feed ring 211 of the trunk finder, and the other, alow resistance locking winding, 212, adapted to be included with its own front contact 218 in the circuit of the same conductor 210, 213 being closed before the back contacts of 206 are opened. When energized the cutoff relay will disconnect the windings of the'line relay and extend the circuitof line wires 200, 201 by Way of conductors214 and 215 respectively to other feed rings 216 and 217 of the trunk finder.

The trunk finder may comprise,'as shown,

a movable brush arm 218 carrying two sets of three brushes each, corresponding brushes of each set. being connected together. One set trails over feed rings while the other trails over sets .of trunk contacts such as 219, 220, 221. A ratchet wheel 222 driven by a pawl 223 attached to the armature of a stepping magnet 224 comprises the power mechanismfor moving the brush arm. The type of trunk finder here shown is one which moves in one rotary direction only and when a half revolution of the brush arm has been made from the position indicated, the two sets of brushes will exchange places, the upper one then resting on the feed rings and the lower one on the contacts.

The circuit of the stepping magnet 224 includes an intermittently operated: vibrator or interrupter 225, a battery 226, and a back contact 227 of cutofi relay 206; this circuit for'starting the trunk finder 202, or by way memes of a normally open contact 229 of the trunk finder for restoring it.

/ Branch conductors 230, 231 and 232 lead to terminals on connector switches, by which the subscriber at the station c may be called. Conductors 230 and 231 are the line condnctors. and 232 is the test conductor. The latter is connected, when the trunk finder is in normal position, by way of contact 233 to the winding 212 of the cut-oil relay 206, and, when'the trunk finder is in off-normal position, by way of contact 234, to ground.

One'of the trunk lines local to the satellite together with its associated register sender is shown in Figs. 2, 3 and 4 of the drawi gs. It is connected to the set of terminal 219, 220 and 221 of the trunk finder 202 and terminates in the trunk finder 400. The register sender comprises several switch- I 259. "When in position 6, the numeral 6 ing devices or registers, 203, 300, 301,

302 and 303-, one for each order of the dig its of subscribers numbers together with a similar switching device 240, the function i of which is .to-control the resetting of the apparatus in case of premature disconnect on' the part of the calling subscriber. There is also'associated with the register sender a timing device 241 and aplurality of controlling relays, the functions of which will be stated presently. These various switch ing devices may be of any'desired structure adaptable to perform the necessary switching operations, but as shown, eachfor example the ten-thousands :register 203- comprises a shaft 242 carrying a plurality 4 of cams controlling sets of contact springs; also a ratchet wheel 243 and driving pawl 244 attached to the armature of a stepping magnet .245 and an escapement 246 and controlling niagnet 247 therefor. Rigidly mounted on; the shaft 242v is a disk 262 carrying a retaining pawl248 which engages a second ratchet wheel 249 which together with a star wheel 252 is secured to a sleeve 250 loosely mounted on said shaft. At the lower end of the shaftis a restoring spring 251, and in the normal position of the de-' vice a pin on the ratchet wheel 243 engages a stop 254. An interrupter or calling device 204 is adapted through circuits to be traced hereinafter to cause intermittent operation of the stepping magnet 245 to adjust the register to any position corresponding to the ten-thousands digit of subscribers numbers. normal a certain number of steps, the register is retained in such position by the escapement 246 until the latter is oscillated by intermittent energization of its controlling magnet 247 whereupon the register is restored to normal. During the advance movement, the pawl 248 passes freely over the teeth of the ratchet wheel 249 without moving it, but upon the return of the switching device under the control of the escape- 'when the. register is 011' normal.

Vhen thus moved away from ment, the pawl engages a tooth of this ratchet wheel and carries the star wheel 252 with it. This results in a series of interruptions of a contact 253 corresponding in number to the number of steps the switching device had been advanced from its normal position by the stepping magnet 245. The several cams 235, 255,256, 257, 258 and 263 are each (except 258) provided with a notch in which a contact spring rests when the register is in normal position, the positions of the switching elements being altered Cam 258 is so shaped that in its normal position it allows the contact spring, which it controls, to rest midway between opposing contacts 259, 261, but when off-normal -in all positions except number 6 it maintains the .con-

tact spring closed against the left contact being the ten-thousands digit of the group of subscriber lines served by this satellite,

a raised portion 260 of the cam servesto 4 ranged. For example, the cam 350 of the thousands register 300 is of the same gen eral shape and performs the same function as cam 258 of the ten-thousands register,

but the raised portion 305 by which the spring is lifted to close the right contact 360 is located in this case at. position number 7 on the caminstead of position 6, 7 being the thousands digit of the group of lines of this satellite. In all other positions ofi' normal the left contact 364 is closed. The corresponding cam 380 of hundreds register 301 is of somewhat different shape. tion after leaving normal, including positions 0 to 4, the spring is lifted to close the right contact 370 whereas during the latter half of the revolution, including positions 5 to 9, it is allowed to retract and close the left contact 376. a I

The shapes of the cams 258, 350 and 380 are determined in the case of each satellite by the numerals representing the first two or three (varying according to the capacity of the satellite) digits of the particular group of subscribers lines included in the Such a group may be, for exsatellite. ample, lines 67,000 to I 67,499. Thus the raised portion 260 of the cam 258, conre' sponds to the ten-thousands digit of these numbers; the raised portion 305 of the cam 350 likewise corresponds to the thousands digit, and the raised portion of the cam 380 corresponds to digits 0 to 4 inclusive comprising all of the hundreds digits of the numbers 67,000 to 67,499. It will thus be During the first half revoluseen that the three cams 258, 350 and 380 will lift their springs to close the right con- I tacts 261, 360 and 370 simultaneously only when the ten-thousands, thousand- 1 m? fl ou andsv, register 203 of the register dreds registers are advanced seven steps;

eight steps and from 1 to '5 steps respectively h I has associated Twithit relays 287 and 288. which cooperate with thetiming dev ce 241 from normal, Such a condition}, asiwill be more freely explainedhereinafte'r, results in the establishment of-a circuit. by which the: I

" (with the'resetting device 240 for controlling trunk finder 400 will be started in search of an. idle trunk line local to thesatelh'te.

i If, however, any other combination of positime is obtained, such circuit will not be, closed and the trunk finder 400 will be caused to hunt instead for a trunk line ex-' tending to the main exchange. It will be understood that for all other cams of the registers than those mentioned, namely, 258,

w 350 and 380, the sets of spring contacts controlled thereby, are capable of assuming but two positions, one the normal as mdlcatedj and the other the oil normal. Uertain of these such as'those operated by cams 256' and 257 of the tensethou'sands register.

203, are of the make before break type while; others such as those operated. by cam263 are of the break before make type. St1llothers such as that of the cam 255 have but a single l contact closed when the register is off normal. Single contact of cam 235 is closed at normal.

The resetting device 240 and the timing 7 device-241 are each adapted to move in but one rotary direction and when moved away from normal to make a complete cycle and return to normal. The several cams 267,

l 268, 269, 271, 272 and 273 of the resetting device 240, with the'exception of cam 269,

control sets of springcontacts in amanner similar to that of theregisters. Cain-269 however, is arranged'to close its contact 274 at .each. of several alternate steps, viz., -1, 3, 5, and 7 steps awayffromnormalw The tineing device 241 ;has ai s'inglecam 275-. con-- trolling a sin le' contact 276 which is closed 1 When the circ it of'thecalling subscriber e .is extended by the operation of the trunk finder .202 to the trunkllizline terminating in] -contacts 214), 220 and 221, the cut-01f relay? 206 will have been 'operated,'opening the a circuit of line relay 205, and the subscribers line'circuit will havebeen extended by way of conductors 277 and 278, and current Will be supplied from battery 279 over the coils of the register line relay 281. The cut-off relay 206 is during such time maintained energized'over a circuit completed by way of the third or local conductor 282 of the trunk line. The register line relay 281' is energized by current flowing in the line and is, therefore, responsive to the line interruptions which follow upon the movements of the subscribers calling device 204. This relay controls the circuits of slow release relays 283 and 284. Other relays 285 and 286 which are quick acting are also controlled by the register line relay and in turn control the advance movement of the tenender. The ten-thousands register also forfsending impulses to the selectors and In. Fig.- 3,irel ysrsos ad 307 for the thousandsW-register, r'elays 308 and 309 for the hundreds re ster, and relays 311 and 312mm the tens register correspond in function with the relays 287 and 288 (Fig. f

2) 1 for the ten-thousands register. Similarly, relays 313 and 314 for the thousands register,315 and 316 for the hundreds register, and 317 and 318 for the tens register correspond in function to relays 285 and 286 of the ten-thousands register. This-will more fully appearhere- .inafterin the detail description of the operation of the system.

Associated with he interrupter 304 is a pair ofrelays 319 and 321, the function of which, as will more fully appear hereinafter, is to. insure the closure ofthe impulse circuit forthe escapement magnet 247 of the register 203 in such a mannerthat the first impulse always will be a full one. .1

'It will be understood that'in completing I:

a connection local tdthe satellite, the Ftenthousands and the thousands ,sets of impulses will not be required, the first set needed in such a casebeing the hundreds set of impulses. Accordingly, a relay 322;,

is provided having two normally open con tacts 323 and-324. 'This relay will'be enf ergized on a local 'call, and by its contact 323 will shunt contac'ts 253 and 343 and thus;

battery Icircuit bywa of contact 325 of ,the units register for starting the sending impulses. upon allocal call. 1

' "Thelitr unk finder 40.0 is of the'same gen-.-

eral'constrnction' a s,'trunki finder 200. It

is provided; however; with four sets of feed of :t'our brushes. Th es e sets or brushes are mounted on opposite ends of a brush arm rings 409,411, 412 and 413,,and two sets 414 and are respectively crossconnected and are adapted to trail over the feed rings and sets of trunk contacts such as 415, 416, 417

and Contacts 415, 4 16 and 418 are connected .to local trunk line conductors, 403, 404, 405, while another set, in which 417 is used instead of 418, is connected totrunk line conductors 406, 407, 408, leading over trunks to the main office. Preferably the con nections with such trunk lines alternate, that is to say, sets Nos. I, III, V and'VII are for local trunks, and sets Nos. II, IV, VI and VIII are for outgoing trunks. The third or test conductors of the local trunks are connected to the inner row of terminals 418,- whereas such conductors for the outgoing trunks are connected to the next to the inner row of terminals 417. A stepping magnet 419, di-

rectly under the control of the interrupter 421, is adapted to advance the trunk finder over the terminals step-by-step when the proper circuits are established for causing it to hunt for an idle trunk in eitherseries. For the purposes of controlling the trunk finder in advancing and returning, there are provided several contacts, 422 which is normally open, and 423 and 424 which are normally closed. There are also provided two test relays 425 and 426, and a starting relay 427. Relay 425 or relay 426 becomes operative according as to whether the trunk finder is hunting for an outgoing trunk or a local trunk. Associated with the local test conductor 408 of the outgoing trunk is a resistance 428, battery 429, and the relay 431, the purpose of which will more fully appear hereinafter.

As hereinbefore stated, calls local to a satellite will be extended beyond the trunk finder'400 through and by means of a third selector 503 and a connector 504. Such apparatus is well known and need-not be fully described here. The selector may be of the two-movement type wherein a series of steps are taken to select the desired group of connectors and then automatically hunt for an idle connector in the group. Likewise, the connector may be of the twomovement type in which the line wanted is selected by two series of steps. There is shown in Fig. 5 the talking circuit conductor of such apparatus including the main switch contacts 505 and 506 of the selector 503, and 507 and 508 of the connector 504; also condensers 509 and 511, and impedance coil relays 512 and 513 connected in bridge of the talking circuit on either side of the condensers, and supplying current through their respective windings from battery 514 to the calling and called subscribers lines. Associated with the local testconductor 405 of the local trunk, shown in Fig. 4, are the resistance 515 and release magnet 516 corresponding in some of their functions with the resistance 428 and relay 431, as will more fully appear hereinafter. Associated with the selector and connector switches 503 and 504 there would preferably be local test and holding contacts 517 and 518 respectively. The brush o'f the latter is adapted to be connected to ground 519 when the connector is operated, the object of this being to create a busy test condition for other connector switches and for operating the cutoii relay 206 ofthe called line. It will a grou connected to the same satellite; and let it be further assumed that this satellite includes of 500 subscribers lines numbered from 6 ,000 to 67,499, andthat the number of the called subscribers lineis 67,321. The;

calling subscriber at statibn e removes hisi telephone thereby-closin the line circuit through line.relay 205, t e current flowing over. the following path :--207, 205, back contact of-206, 200, apparatus at station a,

204, 5201-, back contact of 206, 205, ground.

Line {relay 205Lcloses at contact 228'thecircuit of'the stepping magnet 224 including the interrupter 225 over the following path 22e, 225, 224., 227, 228, ground. The intermittent operation of the interrupter 225 causes thetrunk finder 202 to take one or more steps away from normal in search of an idle trunk line, and it is assumed here that two steps are taken, the first trunk line being busy. The busy condition of test terminals is caused by the altered potential due to current flowing from battery through the low resistance winding 212 of a test or cutofl' relay 206 associated with some other line.

In such case the high resistancewinding 208 of the relay testing would be shunted by that low resistance winding and the former would receive insuflicient current for its energization. As the trunk finder leaves nor- I mal, contact 229 is closed in parallel with contact 228, thus insurin the continued operation of the trunk finder without regard to the continued energization of the line relay. At the same time a ground is placed on conductor 232 at contact 234 thus leaving a busy test condition at the terminals of the calling line located on connector switches, and also contact 233 is opened taking away the control of the cutofl' relay from other connecting switches which may be seeking this line. The closure of contact 209 by the line relay places the winding 208 of the cutolf relay 206 in condition to receive current when the trunk finder 202 finds an idle trunk, and under the assumption that 'the f connecting the line relay and extending the circuit of the calling subscribers line slow release relay 283, independent of that closedby relay 291. Relay-283 closes at its contact 296 a path leading to the second slow release relay 284, the circuit of the latter, however, being open at this moment at the back contact 297 of relay 281. Relay 283 alsoopens a ground connection at contact 298 which maintains, during the sending operation, the circuit of the stepping magnet 299 of the reset device 240 opened; it

also closes a ground connection at contact- 11 for the How of current subsequently through relays 285 and 288.

The apparatus is now in condition for the sending of impulses over the subscribers line to register the number of the line wanted, which according to the assumption is number 67,321. The calling device or impulse transmitter indicated as 204 at the calling substation 6 may be of any suitable construction for producing successively severalseries of line interruptions indicated by the digits of the number of a subscriber wanted. There will thus first be produced by this calling device a series of seven impulses, one additional impulse being sent because the first numeral is, in the system described, 0 instead of 1. Each interruption causes the deenergization of register line'relay 281, and therefore, a momentary release of its armature and closure of contact 297. Slow release relay 283 remains energized notwithstanding the momentary interruptions of its circuit at the front contact of the line relay 281 and, therefore, contact 296 remains closed, and each time contact 297 is closed current flows through the slow release relay 284. and the stepping magnet 245 of the ten-thousands register, the circuit being as follows: 12, 245, 10, 284, 296, 297, ground. This results in the stepping forward of the ten-thousands. register 203 seven steps and, therefore, in the closure of contact'261. The first impulse of current in slow release relay 284: results in its energization, and this relay remains energized continuously so long as the current impulses continue in its local circuit, that is to say, while the first series of line interruptions take place. Upon its energization relay closes a local. circuit of relay 286 by 313 and 285 were. previously. this, three interruptions occur resulting in the advance of the tens. register three" way of its front contact 13, back contact 1 1 of relay 285 and battery 15; and the energization. of 286 in turn closes a locking circuit for itself by way of its front contact 16. Relay 285 is not energized, however, because short-circuite'd by the path to ground through contacts 13 and 14.. When, however, the seven interruptionshave taken place the line circuit again becomes steadily closed and contact 297 remains open so that relay 284: releases its armature, opening contact 13, whereupon relay 285 becomes energized to prepare the apparatus for de livering the next series of impulses to the thousands register 300. The circuit for relay 285 is over the following path :15, 286, 16, 285, 11, ground, and these relays will remain energized over this path under the control of relay 283 until the-register line relay 281 shall become disconnected from the circuit.

The next series of line interruptiona eight in number corresponding to the second digit 7 of the called subscribers number, the additional interruption being for numeral 0 as before, results in a stepping forward of the thousands register 300 eight steps, at the end of which relay 313 becomes energized in the same way that relay 285 was I a previously, whereupon the local circuits co n' l trolled by the register line relay28l, aref shifted to the relays 315 and 316of-the hundreds register 301. Four internip 'tions now follow resulting in four impulses to the stepping magnet of this register, whereupon relay 315 is energized as relays Following steps, whereupon relay 317' is energized, and.

finally two impulses are received by the stepping magnet of the units register 303, 10 I resulting in its advance to position. 1. 'The several registers, comprising the register sender, are now set away from normal seven, eight, four, three and two steps, respec:

tively, thus indicating and registering the i number 67,321 of the subscriber Wanted.

When the last impulse is received by th tens register, the current in the sub I scribers line'becomes steadya'gain and slow I release relay 28 1'opens its contact 13 thus permitting the energization of relay 317 which had been, during the sending-of the tens. impulses, short-circuited in the same. I manner that relay 285 had been during the sending of the ten-thousands impulses. The circuit for relay 317 is then as follows :334;, 318, 335, 317, 18, 11, ground. The circuit for the last series of impulses for advancing the units register is as follows :-326, 327, 328, stepping magnet 329, 331, 332, 333, 17, 28 296, 297, ground.

ing made operative for this purpose by the "closure of contact 336. This completes the contact 11 of relay 283 for the starting relay ground connection through conductor 18 and 427, the circuit being as follows :battery i 1 430, 427,19, 336, 18, 11, ground. Previously, by reason of the particular set conditions of the and ten-thousands thousands hundreds registers, the call belng assumed to be one between subscribers of the same satellite, a circuit had been prepared for the local; test relay 426 by 'way of contacts 261,

path for its winding 360 and 370, and the closure of contact 336 provided the ground path by way of conductor 18 for this test circuit which is to be Completed, when the brushes of the trunk finder 400 rest upon the terminals of an idle ently. The trunk finder'is stepped ahead by' I the intermittent operation of stepping mag local trunk line as will be explained presnet 419, the circuit being as follows :bat

tery 430, 431, 432, 433, 434, 419, 421, ground.

This circuit leads through the baclccontacts 433 and 434 of test relays 425 and426, and therefore the continued operation of the trunk finder depends upon the continuity of these contacts. The circuit of the outgoing test relay 425 is open at this time at the contacts 259 of the ten-thousands register,

364 of the thousands register, and 376 of the hundreds register, so that the bus or idle condition of the outgoing trunk lineswill have no effect upon this-relay. As soon,

however, as an idle local. trunk is found, say

the trunk line connected to terminals 415,

416 and 418, a circuit will be established for the local test relay 426 as follows: battery 524, 515, 525, 405, 418, inner brushes of trunk finder 414, 413, 435, 341, 370, 360, 231, 19,

336, 18, 1'1, ground. The energization of the 7 test relay 426 causes the closure of a shunt 435 by way of a low reslstance locking winding 436 and contact 437. The increased How of current due to the shunting effect of winding 436 causesa change in potential at the test terminal 418 of the trunk line whereby other trunk finders in testing for idle .trunk lines will find this one busy. It willv be understood that these terminals are connected in multiple with corresponding terminals on other trunk finders. At the same time contact-=434being opened stops the operation of the stepping magnet 419, and therefore the trunk finder stops with its brushes in contact with the trunk line terminals 415, 416, 418. Relay 426 when energized also closes contacts 438 and 439 in the talking circuit leading to feed rings 409 and 411 respectively, and contact 441' which closes a circuit for relay 322 as follows :- battery 430, 431, 432, 433, 4-41, 342, 322, 18, 11, ground. The energization of relay 322 causes the short-circuiting at contact 323 of the interrupter contacts 253 and 343 of the ten-thousands and thousands register respectively, and also closes at contact 324 a circuit for relay 321 which is preliminary to the sending of impulses for the return of the several registers, this circuit being as follows:-430, 431, 432, 345, 324, 346, 325, 347, 321,348, 349, 304, ground. This circuit includes the interrupter 304 which may or may not at that instant have its contact closed. The closure, however, will be almost immediate and result in the energization of relay 321 which, by'the closure of its contact 351, will prepare relay 319 for operation as soon as interrupter 304 opens its contact. The circuit previously traced for relay 321 will thereupon continue from its winding through 319, 18 and 11 to ground, instead of directly to ground through 348, 349 and 304. Relay 319 is thus energized whereupon a stepping. circuit for the escapement magnet 247 of the tenthousands register is established by way of the front contact 352 as follows :- battery 22, 247, 23, 38,24, 25, 352, 304, ground. A succession of impulses for the escapement magnet 247 'follows. These are equal in number to the number of steps-seven under the present assumptioncorrespo-nding to the number of advance steps made by this register under the control of the stepping magnet 245. The. ten-thousands register returns to normal whereupon contact 23 is opened and contact 26 is closed, a circuit being thereupon established for the operation of the timing device 241 as. follows :battery '27, stepping magnet-31, 32, 28, 26, 38, 24, 25, 352, 304, ground. As soon as the tim ing device leaves normal it closes contact 276 thereby energizing relay 287 in the following circuit :33, 287, 34,37, 276, ground. And relay 287 in energizing closes contact 35 which controls relay 288, now short-circuited in the circuit just traced, for subsequent energization when the timing device returns to normal, and thus opens the shortcircuit at contact 276. Relay 288 thereupon becomes energized and opens at contact 24 the circuit for the stepping magnet 31 of the timing device, and at the same'time opens contact 34 and maintains itself and relay 287 energized in the following circuit :- battery 33, 287, 35. 288, 36, 11, ground. Relay 288 also extends the circuits of'conductors 37 and 25 by way of front contacts 39 and 41 to conductors 42 and 43, respectively.

The function of the timing device 241 is' to delay the operation of the thousands reg- The thousands register is now operated in the same manner as the ten-thousands register had been, the timing device operating after its return to normal, and

relays 306 and 307 operating one after the other in the same manner as relay 287 and 288 of the ten-thousands register. The

succession of interruptions at contact 343 has no effect in the operation of a selector because as previously explained it and contact 253 of the ten-thousands register are now short-circuited by contact 323 of rela 322. Upon the energization of relay 307 the stepping circuit for escapement magnet 353 is closed over the following path z- battery 354, 353, 355, 356, 357, 43, 41, 25, 352, 304, ground. The hundreds register is given four impulses and returns to normal, whereupon its escapement magnet 353 is disconnected from the circuit at contact 355, and the timing device 240 is brought into operation with the interrupter 304 over the following circuit : battery 27, 31, 32, 28, 358, 356, 357, 43, 41, 25, 352, 304, ground. And while it is off normal a circuit is estab lished for relay 308 over the following cir- 61m; :- battery 359, 308, 361, 362,42, 39, 37,

276, ground. Relay 308 on being energized closes contact 363 controlling relay 309 for subsequent energization-it now being shortcircuitedwhen the timing device 241 returns to normal and opens contact 276. When energized relay 309 extends the control circuit for the operation of the tens register which received three impulses causing three interruptions of contact 365, whereupon it is returned to normal and starts the timing device 241 much in the manner before stated. 241 makes one cycle, and then causes the energization of relay 31.2 which brings the units register into operation, its escapement magnet 366 receiving two impulses in the circuit of the interrupter 304. This circuit is as follows battery 367, 366, 395, 368, 369, 357, 43, 41, 25, 352, 304, ground. The units register 303 in returning to normal opens its contact 371 twice. Thus the hundreds, tens and units registers in returning to normal deliver four, three and two impulses, respectively, in the circuit of the trunk line 403, 404, which at this time is in circuit with the trunk line 37 2, 373, through the trunk finder 400. It will be noted that as soon as the tens register left its normal position in being set a short circuit of the trunk line conductors 372, 373 wasestablished through contacts 374, 323, 375, 365 and 371; also that upon the operation of each of the registers in turn the main trunk line conductors 277 and 278 were interrupted as, for example, at contacts 44, 45, and closed through contacts 46 and 47' di- ,rectly to the register line relay 281. This shifting of the main trunk line conductors serves to open the circuit forward to the selectors while maintaining it closed back to the calling subscriber, and the paths to the register line relay take the place of the normal paths through contacts 423 and 424 of the trunk finder 400. The short-circuit of the trunk line conductors 372, 373, is maintained at contact 399 of the units register after being opened at contact 374 of the tens register when the latter has returned to normal. 7

Only so much of a third-selector and final selector or connector are shown in- Fig. 5 as is necessary to illustrate the principal signaling and talking circuits to 3. called subscribers station 6 When the trunk finder makes the connection with the trunk line conductors 403, 404,. 405, and when the tens register has left normal, a circuit is established, preparatory to the sending of the hundreds impulses, as follows battery 526, relay 527,403, 415, the outer brushes of the trunk finder 400, 409, 438,

for operation in a well-known manner by the impulses which subsequently occur upon the return of the hundreds register 301 to normal. After the passage of these impulses and the following automatic selection of a trunk linev to an idle final selector or connector during the time of the operation of the timing device 241,the next, or tens, series of impulses follow over the same cirr cuit extended, however, to battery 514 and relay 512 of the connector. Finally the last series of impulses occur when the units register returns to normal whereupon the connector is given a second movement to the" terminals of the line "wanted. Any well-. known method may be employed for signaling the called subscriber, and upon his response by lifting his telephone from its switch hook a complete talking circuit is established. This circuit is shown in heavy lines in the drawings and can be traced from the switchhook of the calling subscriber e as follows :200, 214, 216, outer brushes of 1 0 apparatus at substation e Current is supplied in this circuit from battery 514 by way of the windings of relay 512 to the calling line, and relay 513 to the called line, the talking circuit being interrupted to battery current between the connections of these relays by condensers 509. and 511.

Under the foregoing assumption that the subscriber calling and the subscriber called for were connected to the same satellite, it was pointed out that thelocal test relay 426 was made operative due to the particular setting of the ten-thousands, thousands and hundreds register and to the simultaneous closure of contacts 261, 360 and 370 in the circuit of that relay. In case, however, the subscriber called for is connected directly to a main oflice or to some other satellite than the one to which the calling subscriber is connected, the circuit to the local test relay 426 will notbe closed due to the failure of one or the other of said contacts 261, 360 and 370 of the tenthousands, thousands and hundreds registers being closed; and in such case the outgoing test relay 425 will be placed in operative condition instead, its circuit becoming closed at one or the other of the following alternative contacts 259, 364 and 376. Thus, if the call is for number 67,555, contacts 261 and 360 of the ten-thousands? and thousands register will be closed, but

contact 370 of the hundreds register will be opened, and instead contact 37 6 will be closed, the circuit of test relay 425 being over the following path :- battery 429, 428,

451, 408, 41.7, the next to the inner set of brushes of trunk finder 400, 412, 453, 389,

373, 360, 341, 261, 19, 33c, 18, 11, ground,

thus causing the outgoing test relay 425 to operate and close its low resistance winding 454 in shunt of its high resistance winding 453 by way of the locking contact 455. This relay in operating also opens contact 433 which stops the operation of the stepping magnet 419 of the trunk finder 400; and closes contact 465 thereby completing the following circuit for the operation of relay 321, which as before explained, is preliminary to the commencement of the impulses for returning the registers to normal Zl)1tte( y 430, 431, 432, 465, 391, 325, 347, 321, 348, 349, 304, ground. In this case the relay 322 is not operated, and the impulse-sending contacts 253 and 343 are therefore not short-circuited so that the sending of the ten-thousands and thousands impulses will result in the operation of first and second selector mechanisms, as

well as the third and final, suitablyarranged at the main or other offices to which the circuit is now extended. In either case, that is whether the circuit is extended to a third selector, such as 503 at the satellite, or to a first selector, such as 101, at a main office, the circuit formerly established through the register line relay 281 to the calling line will be broken at contacts 392, 393, when the units register returns to normal, and a through circuit established as before traced by way of contacts 381 and 382, current being supplied over this circuit to the calling line from a battery and the windings of a selector line relay at the switch to which the circuit is extended. -It will be noted that this. relay, such as relay 527- of the third selector'503, will *first receive current through the short circuit of line conductors 372, 373 over the following path :-372, 374 and 399 in parallel, 253, v343, 375, 365, 371, 37 3. This. will give ample time for the apparatus-at the selector to get into condition for receiving the impulses which follow.

When the subscribers hang up their telephones to disconn'ectthe apparatus of the selectors beyond, (or to the right in the dia-' gram) the trunk finder 400 may be restored according to any known method, it being assumed that the release magnet 516 will be energized upon the restoration of the third selector 503, whereupon the circuit previously traced for the local test relay 426 will be opened at contact 525 whereupon said relay. 426 will be denergized causing the closure of the following circuit :-battery 453, contact 422, 432, 433, 434, 419,421, to

the release relay 396, the circuit being as follows : battery 456, 422, 432, 433, 434,

457, 398, 396, ground. This relay thereupon opens its contact 397 in the circuit of the test conductor 282, thereby opening the circuit of the cutoff relay 206 which in turn closes contact 227 in the circuit of the stepping magnet 224, which circuit is as follows battery 226,225, 224, 227, 229, ground. The

. trunk finder 202 is thus restored to normal in the same manner as the trunk finder 400. All apparatus involved in the connection is now restored to normal, and is ready for service'on subsequent ca ls.

In the case of a connection over an outgoing trunk line the relay 431 would be energized in a manner similar to the energization of relay 516, whereupon the circuit of outgoing test relay 425. would be opened at normal as in the caseof a local connection.

' registers 203',

. relay 7 Should the calling subscriber ate hang u his receiver prematurely, that is after having started tosend a call, but before receiving a connection, 'any one or more of the 300, 301, 302 or 303 that may be olf normal actuated by stepping magnet 299, itscircuit being closed at contact 298 by the armature of slow release relay 283 whenthe circuit of register'line rela 2.81 is held iipen by the receiver hook. ake, for example, a case where the calling subscriber at e hangs up immediately after setting all the registers, but before the ten-thousands register 203 has been returned to normal. The circuit of ste ping magnet 299 will be closed at 298 an current will flow over the following path :- battery 280, 299, 73, 48, 298, ground. Switching device 240 is moved from nor: mal' to position 1. As soon, however, as 240 leaves normal, its cam 273 opens at contact 73 the circuit just traced, but cam 271 at the same time closes contact 71, thus preparing a new circuit for 299, Cam 272 opens at contact 290 the c rcuit of cut-ofi relay 206 whereupon contact 227 is closed and trunk finder 202 returns to normal. Cam 268 closes contact 68 thusenergizing 321 over the following path :battery 69, 68,270, 347, 321, sis, 349, 304, ground.

As is the case when register 203 is returned to normal, asv described in connection with a completed call, the closure of relay 321 will prepare relay 319 for operation as soon as interrupter 304 opens its contact. Relay 319 upon being energized closes a stepping circuit for escapement magnet 247 of the ten-thousands register 203 over the following path battery 22, 247, 23, 38, 24, 25,352, 304, ground. A number of impulses suflicient to return 203 to normal will be sent by means of interrupter 304. Upon 203 reaching normal, contact 23 is opened and 26 closed. But since 240 is in position ,1 instead of normal, and contact 32 is opened, timing device 241 will not be operated as described in connection with a normal return of 203. Instead, since contact 71 g is closed, acircuit for stepping magnet 299 to move 240 from position 1 to 2'will be closed over the following path :- battery 280, 299, 71,28, 26, as, 24, 25, 352, 304., ground- V In position .1 of 240, as when the timing device 241 is actuated in the normal operation of resetting the ten-thousands register 203, the relay 287 is energized but its circuit to ground is through contact 27 4 of 240 instead of 276 of 241. A circuit is also 241 is operatedit is short circuited until-275' returns to normal, it is likewise short cuited 1,121.,eee I will be returned to normal by meansof the resetting switching device 240 in position 1 of 240. When 240 reaches position 2, however, this short circuit is broken at 274 and relay 288 is energized opening :at contact24 the circuit for 299 In position 2 of 240 the thousands register 300 is returned to normal the same as was the ten-thousands register 203, the circuit of escapement magnet 320 being as follows: Battery 310, .320, 330, 338, 43, 41, 25, 352,304, ground. When 300 reaches normal, contact 330 is opened and contact.

337 is closed. Stepping magnet 299 then is energized over the following path Battery 280, 299, 71, 28, 337, 338, 43, 41, 25, 352, 304, ground. 240 thereupon is moved. from position 2 to 3 and relay 306 is energized as was relay 287, but the circuit 306 prepares for 307 is short circuited by the closure of contact 274 as was the circuit 287 prepared for 288. Since, however, the circuit of 299 is not openedin position 3, 240 continues into position 4 where the short circuit is broken at 274 and relay 307 is energized over the following path: Battery 339, 306, 344,307, 18, 36, 67, ground. This opens the circuit of 299 at contact 338 and 240 comes to rest in osition 4. Conductors 42 and 43 are eXten ed at contacts 362 and 357. At the latter contact the circuit of escapement magnet 353 of the hundreds register 301 is closed over a circuit very much the same as was 320 of thousands register 300, the path being as follows: battery 354, 353, 355, 356, 357, 45, 41, 25, 352, 304, ground. In the fourth position, therefore, the hundreds register 301 is returned to normal. When it arrives at normal, it opens at its contact 355 the circuit of its escapement magnet 353 and closes instead at its contact 358, the circuit of stepping magnet 299 of switching device 240, whereupon the latter is moved from position 4 through position 5 into position 6 where relay 309 is energized, as were relays 288 and 307, opening at its contact 356 the circuit of 299. In'position 6 of 240 capement magnet 366 of the units register 303 over the following path: battery 367, set, 395, 368, 369, 357, 4a, 41, 25, 362, 304.,

ground. Units register 303 then is returned to normal opening at its contact 395 the circuit of 366 and closing instead at its contact 394 the circuit of stepping magnet 299 which then continues to step along the switching device 240 until it arrives at normal and opens its contact 71, 68 and 67.

The circuit of stepping magnet 299 is opened at 71, battery is removed from relays 321 and 319 at 68, while at 67 the circuit to ground of the locked up relays 287, 288, 306, 362, 308, 309, 311, 312,-is opened, after which all the apparatus is again in normal position and the trunks ready to be taken for another-call. Until 240 returns to normal and closes contact 290there will be no ground on the test conductor of this trunk,

4 described in shifting the circuit through interrupter 304 from stepping magnet 299 to the several register release magnets, are needed.

In the case of-a premature disconnect that occurs after the tens register 302 has been :movedofli' normal, such as the one abovedescribed, 01 one where 302 but not 303 has been moved off normal, the trunk finder 400 will be moved off normal and will connect with an idle trunk, since its release relay 427 is energized assoon as contact 336 of 302 'is closed. Further, this connection, as in a normal call, will be extended to a connector such as 504 upon the return to normal of the registers 203, 300, 301, 302 and 303 under the influence of switching device 240. 'Iherefore, even if impulses are not' sent from the units register 303, the relay 512 will be included in the talking circuit. In the normal sending of a call, the circuit of relav 512, upon the return to normal of units register 303, before being broken at its contact 399, would be closed at itscontacts 381 and 382 and extend over the talking circuit to the calling subscriber at e But in the case of a premature disconnect, such as referred to above, since the receiver is on the hook and the circuit through 6 broken, the circuit of relay 512 will be broken at 374 upon the return to normal of 302, or, if the units register 302 had been set, upon its return to normal and at its contact 399. When relay 512 is denergized, it opens at its contact 540 the circuit of slow-release relay 542, which in turn opens at its contact. 543 r the circuit of slow-release relay 533. Therefore, since 503 is off normal and its contact 530 closed, release magnet 516 will be energized upon the closing of contact 5340f slow-release relay 533,. current flowing as follows: battery 524, 516, 530, 534, 532, ground. Release magnet 516 thereupon opens at its contact 525 the circuit of test relay 425, or if 431 had been energized instead of 516, the circuit of outgoing test relay 426 would have been opened at 451. In either case, the circuit of stepping magnet 419 is closed as in a normal call over the following path: battery 456, 422, 432, 433, 434,

419, 421, ground, and the trunk finder 400 returned to normal where the circuit just traced is broken at contact 422. If, forexample, the calling subscriber at e hangs up his receiver after having set the ten-thousands register 203 and the thousands register 300, they will be returned to normal as previously described. After attending to the return of 203 and 300 the switching device will also be returned to normal. In this connection it' will be remembered that when the tl1ousands register 300 returns to normal it closes at its contact 337 the circuit of stepping magnet 299 which thereupon moves the switching device 240 from position 2 to 3 where relay 306 is energized, then to position4 where relay 307 is energized. The latter closes at its contact 357 the circuit of stepping magnet 299 over the following path, since the hundreds register 301 is at normal and its contact 358 closed: battery 280,299, 71 28, 35s, 356, 357, 43, 4.1, 25, 352, 304, ground. The switching device 240 thereupon will be stepped around from. position 4 to 6, relay and opens at its contact 71 the circuit of 299. I

All the apparatus is now at normal and the trunk ready for use in another call.

If the calling subscriber at 6 should hang up the receiver after the call has progressed to the point where several registers have returned to normal while others are still off normal, the latter will be returned as already described. Take, for example, the case where the registers203, 300 and 301 have been returned to normal while registers 302 and 303 have not yet sent their impulses to the final .connector and are there fore still off normal. The stepping magnet 299 of the switching device 240 is actuated over the circuit to ground closed as before at- 298, and in this instance at contact 388 of the tens register 302 instead of at contact "48 of 203 as it was in the previous instances.

Since registers 203, 300 and 301 are at normal,their contacts 26, 337 and 358 will be closed and switching device 240 instead of coming to rest inpositions 1, 2 and 4, will be moved on under the influence of its step- 'ping magnet 299 through circuits already described until it arrives at position 6. In

this position, since the tens register 302 reaches normal it opens its contact 387 andcloses 386 thus transferring the stepping circuit through interrupter 304 to stepping magnet 299. Switching device 240 thereupon is moved from position 6 through 7 to.

8 energizing in succession relays 311 and 312 after which units register 303 is returned to normal followed by a like return of switching device 240 as soonas contact 394 is closed. 1 Y

Inall these instances it will be remembered that as soon as the switching device 240 leaves normal, the circuit to ground through cut-ofi' relay 206 is broken at contact 290, whereupon the trunk finder 202 is returned to normal. When the trunk finder 400 has been moved off normal it will be returned when contact 399 of units register 303 is open upon the return of the latter to .normal, or Where the units register 303 hasnot been set up, upon the return. to normal of tens. register 302 and the opening of its. contact 37 4., Should the subscriber at e? hang up hisg receiver, immediately after removingitin preparation for a call, never'- theless he will have moved the trunk finder .202 off normal. But unless he held the receiveroff the hook fora suflici'enttime for the trunk finder 202 to connect with an idle trunk, it will return to'normalunder the influence of its steppiugimagnet 224, the

circuit being as follows: battery 226, interrupter, 225,224, 227, 229, ground. If the receiver is not returned until after an idle trunk has been found, relay 291 will be energized and an alternate circuit to ground for theslow-release relay 283 closed over the following pathaibattery, 283, 265, 266, conductor 236, 480, ground. Therefore, when register line relay 281 is .deenergized by hanging up the receiver, its contact 297 closes the circuit of stepping magnet 245 of the ten-thousands register 203 over the following path: battery 12, 245, 10, 284, 296, 297, ground. Register 203 is moved one step off normal and contact 265 is brokenthus openin the circuit of the slow-release relay 283. ontact 48 is closed and a circuit established for stepping magnet 299 of switching device 240 over the followm path: battery 280, 299, 73, 48, 298, groun Stepping magnet 299 moves 240 from normal to position lwhen register 203 is returned to normal under the. influence of. its stepping magnet 247, exactly the same as ,it is in the case of a premature disconnect occurring after the register 203 had been set. After register 203 has been returned to normal, switching device 240 also will be returned vto normal under the influence of its'steppmg magnet 299 in the manner heretofore .de-

scribed. That is, as soon'as contact 26 of register 203 is closed, the circuit of 299 will be closed, relays 288, 307, 309, and 312 will be energized in succession since the contacts 337, 358, 386 and 394 of the other registers are all closed, and'the circuit of stepping magnet 299 will remain closed through the interrupter 304 until switching device 240 returns to normal. We claim- I 1. In an automatic switching system the combination witha main oifice, a satellite ofhce, subscribers lines extending to said oiiices, and trunk lines between said ofiices,

of other trunk lines local to said satellite, automatic switches for controlling the connection between subscribers lines, calling devices for controlling said switches, means operating under the control of said calling devices adapted normally to select an inter-f oiiice trunk line, and means adapted upon the manipulation of a calling device in accordance with the number of a subscribers line connected to the same satellite as the one to which the calling subscribers line is 2 connected to prevent the selection of an inter-office trunk and to extend the connection instead through a local trunk line.

2. In an automatic switching system the local to said satellite, automatic switches, calling devices therefor, an automatic trunk finder at-saidsatellite, and automatic discriminating means actuated under the concordance with the numbers of subscribers wanted adapted to render said trunk finder combinationwvith a main ofiice, a satellite oflice, subscribers lines extending to said offices, and a group of trunk lines between 1 said offices, ofanother group of trunk linesoperative with respect to said inter-office trunk lines or to said local trunk lines according as to whether the calling and called subscribers lines are connected to different offices or to one and the same satellite.

3. In an automatic switching system. the combination with. a main office, a satellite ofiice, subscribers lines extending tov said ofiices, and a group of trunk lines between said oilices another group of trunk lines local to said satellite, of means for finding an idle trunk line in either group, sub- 13 1.15- trol of calling devices when operatedin acscribers calling devices associated with said satellite, means controlled by said call ng devices for renderlng said trunk finding means operative with respect to the interoilicc trunk lines,-and automatic means op erating when the line of the subscriber wanted is connected with the same satellite as the one to which the subscriber calling is connected adapted to render said controlled means inoperative and to render said trunk finding means operative with respect to the group of'localtrunk lines.

4. In an automatic switching system the combination with a main oflice, a satellite ofi'ice, a group of trunk lines between said offices, of other trunk lines local to said satellite subscribers lines connected to said otlices, automatic switches, calling devices the satellite is calling a subscriber of the main ofiice for extending the connection through an inter-oilice trunk line, but adapted when the line of the subscriber wanted is connected to the same satellite as the one to which the line of the subscriber calling is connected, for extending the connection to a local trunk line.

5. In an automatic switching system the combination with a main ofiice, a satellite ofiice, and a group of trunk lines between said oflices, of other trunk lines local to said satellite, subscribers lines connected to said ofiices, automatic switches, calling devices therefor at the substations of said lines, a register sender atthe satellite adapted to be set under the control of said calling devices to indicate the number of a wanted subscribers line and totcontrol in turn the operation of said automatic switching apparatus to connect the calling subscribers line therewith, means associated with said register sender adapted when a subscriber of the satellite is calling; a subscriber of the main office for extending the connection through an inter-ofiice trunk line, but adapted when the subscriber wanted is connected to the same satellite as the one to which the subscriber calling is connected, forextending the connection to a local trunk line and means, made operative upon a premature disconnection by the calling subscriber for returning said register to normal.

, 6. Inan automatic switching system the combination with automatic switches for interconnecting any two subscribers lines, of a register sender adapted to be set under the control of a calling subscriber to indicate the numbers of wanted subscribers and to control in turn the operation of said automatic switches, and a switching device, operating automaticallv upon a premature dlsconnection by the calling subscriber,'to return tonormal any portion of said register sender and associated apparatus that may be ofi normal.

7. In an automatic switching system the combination with a main oflice, a satellite oflice, subscribers lines extending to said oflices, and trunk lines between said oflices, other trunk lines local to said satellite, automatic switches for controlling the connection between subscribers lines. calling de-' vices for controlling said switches, a finder switch, and automatic means operating under the control of the calling devices when manipulated in accordance with the number I, i

of the'subscriber wanted for ausing said finder switch to select an inter-oflice trunk line or a local trunk line according as to whether the calling andv called subscribers lines-are connected to different offices or to the one and the same satellite and means, made bperative upon a prematurezdiscon-l nection by the calling subscriber, adapted t we automatically return to normal any portion of said automatic discriminating means; that may at the time be ofl normal.

8. In a multi-oflice automatic switching system, the combination with several main ofiices interconnected by trunk lines, of satellite ofiices having groups of trunk lines connecting each satellite with a main office and another group of trunk lines local 'to each satellite, subscribers lines extending to said oflices, means for finding an idle trunk line in either group, subscribers calling devices associated with each satellite, means controlled by said calling devices for rendering said trunk finding means operative with respect to the inter-Oflice trunk lines. and automatic means operating when the line of the subscriber wanted is connected with the same satellite as the one to which the line of the subscriber calling is connected adapted to render said controlled means inoperative and to render said trunk finding means operative with respect to the group uf local trunk lines.

9. In a multi-officeautomatic switching system, the combination with several main ofiices interconnected by trunk lines, of satellite ofiices each connected to a main office by a group of trunks and having another group of trunks local to the satellite, subscribers lines connected to said offices, automatic switches, calling devices therefor at the substations of said lines, a register sender at the satellite adapted to be set under the control of said calling devices to indicate the numbers of wanted subscribers and to control in turn the operation of said automatic switching apparatus to connect the callin subscribers linet'herewith, means associate with said register sender adapted when a subscriber. of the satellite is calling a subscribenof the main oflice for extending the connection through an inter-office trunk line, but adapted when the line of the subscriber wanted isconnected to the same satellite as the one to which the line of the subscriber calling is connected, for extending the connection to a local trunk line.

' r 10. In an automatic switchin system, the

combination with .a plurality oi: central stations and substation lines extending thereto,

0f interofiice and intraoflice trunks for connecting the substation lines, trunk selecting apparatus, calling apparatus upon which the numbers of the substation lines may be registered, automatic means operating in accordance with the digit groups registered any portion of said calling apparatus thatv may at the time be ofi normal.

- coplel o this patent may be obtained for five cents each, by addressing the commissioner of intent:-

- 11. In an automatic switching system, the combination with a plurality 0 central stations and substation lines extending thereto, of interofiice and intraofiice trunks for connecting the substation lines, selector.

switches, trunk selecting apparatus, ap aratus upon which the numbers of a cal ed substation may be registered and subsequently automatically transmitted to selector switches, automatic means operating in accordance with the digit groups registered upon'said apparatus to determine the selection of interoflice or intraoflice trunks, and means made operative on a premature disconnection by the calling subscriber adapted to return to normal any portion of the call registering apparatus that may have been set.

In witness whereof we, FRANK N. Reeves and ALBEN E. LUNnnLL, hereunto subscribe our names this 3rd day of July, A. D. 1912.

FRANK N. REEVES. ALBEN E. LUNDELL. Witnesses:

WALTER F. Housman, O. D. M. Go'rma.

Washington, I). C."

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