US1723209A

US1723209A - Automatic telephone system

Info

Publication number: US1723209A
Application number: US35280A
Authority: US
Inventors: Leonard L Ruggles
Original assignee: Automatic Electric Inc
Current assignee: Automatic Electric Inc
Priority date: 1925-06-06
Filing date: 1925-06-06
Publication date: 1929-08-06
Anticipated expiration: 1946-08-06

Description

A1184 5, 1929- L. L. RUGGLES I 1,723,209

' AUTOMATIC TELEPHONE SYSTEM Original Filed June'G, 192s s'sheets-sheet 1 In-Usn UP- Lsunard L. 51159155 T L. L. RUGGLES 1,723,209

AUTOMATIC TELEPHONE SYSTEM Original Filed June 6, 1925 6 Sheets-Sheet 2 T Y Q KR fi kvkwwih n 4 M was EWENME Q a T M T ENVMWKQA I a N a I. m

. filllllllll NQ M M I Tm Lennard LEuggZas m $355 A J E.

J E v m T T .NQQKQ v Aug. 6,.1929. RUGGLES AUTOMATIC TELEPHONE SYSTEM Original- Filed June 6, 1925 6 Sheets-Sheet HUT 1929- L. L. RUGGLES, 1,723,209

AUTOMATIC TELEPHONE SYSTEM Original Filed June 6, 1925 6 Sheets-Sheet 4 Man- Aug. 6, 1929. L. L. RUGGLES AUTOMATIC TELEPHONE sYsTEM Original Filed June 6, 1925 6 Sheets-Sheet 5 QMEQNWNEN .MQN

mam

[m rd L. Eu

Zea

HIT 5 Lanna g- 6, 1929- L. RUGGLES 1,723,209

AUTOMATIC TELEPHONE SYSTEM Original Filed June 6, 1925 6 Sheets-Sheet 6 M g, w a

K i I c I l I w A? U Q; A u L d h b s Q v 23L l I N l I LU T N m m w y w Inuen DI" Patented Aug. 6, 1929.

UNITED STATES PATENT OFFICE.

LEONARD L. RUGGLES, OF WHEATON, ILLINOIS, ASSIG-NOR, BY MESNE ASSIGNMENTS,

TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- \VARE.

AUTOMATIC rnnnrnonn SYSTEM.

Application filed June 6, 1925, Serial No. 32280. Renewed November 30, 1928.

The present invention rel ates to automatic telephone systems in g, eneral but is concerned more particularly with automatic telephone systems in which directors are einoioyeiil to translate the ottice digits of the telephone numbers into the codes necessary to eilcct the trunking ofthe various calls to the desire( oilices by way of the most suitable paths; and the principal object is the provision of novel circuit arrangements whereby, in case the group of trunk lines ordinarily used is found to be busy, the calls directed to a certain o1l"- lice may be re-routcd and sent to the desired o'lfice over a trunk line path not ordinarily used for trunking such calls.

The above statement of the main object of the invention, of course, sets that objcct iorth only broadly, and for a clearer undo ing of the scope of the invention reference may be had to the outlineof the system hereinatter given.

Referring now to the accompanying drawings, comprising Figs. 1-8, Figs. 1-6 show by means of the usual circuit diagrams a certain amount of apparatus employed in a telephone system embodying the principles of the inveii'ition; Fig. 7 sl'iows live 10,000 line (ultimate capacity) olliccs intcrcoimectcd by trunk lines, and it purports to show the relative geographical positions at the, ollices shown; and Fig. 8 is a trunking diagram showing how calls originated in chute A are completed in the. other others shown in Fig. 7. It. will be understood that the oilices shown in Fig. 7 may representonly a small part of a. large inulti-ottice net-work.

It will be noted that there are two wa to trunk calls to the oliice D from the oliice A, that calls may go from A to C and jtron'i C to l), or from A to B and from B to D. Calls from A to E go by way of C as ma be seen.

The outgoing trunk lines from A to C and from A to B are taken from the first selector bank as may be seen from Figs. 1 and The lirt, selectors of which the selector S, Fig. l, is typical are of the automatic vertical type, that is, two levels can be combined in such a way that, when the lower level is busy the wipers are automatically raised to the upper level and are then rotated to find an idle an A. to D tomatically sent to B and then when the next digit is transmitted the seized selector in B extends the call over to D just as though a selector in C had been seized, the trunks to C coming from. the same selector level in both o'tiiccs. On calls from A to C and from A to E, however, the situation is not the same because the call is not automatically trunked to the destination by merely permitting the sclector S, Fig. 1, to raise its wipers to the next higher level. Two methods of handling the calls destined for C and E from A, when the trunks from A to C are busy, are available.

In case the trunk group from B to C is asmall group intended merely to handle calls from B to C this group will probably not handle the extra amount of t-rafiic that wcaild be imposed by arranging the director to reroute the traiiic from A to C so that it goes from A through B and then to C over the B-to-(l trunks. hen this is the case, arrangements are provided so that not attempt is made to use the trunks from B to C to handie calls originating at A. Instead, the cnncction is denied at the director in these cases and the busy tone is given to the cal 1- ing subscriber. l-lowever,the arrangement of the directors is such that, in case the trunk group from B to C is large enough to handle extra. tratlic the calls may be rerouted to 0 through B when the trunks from A to C are all busy.

in order tor the drawings to be understood best. Figs. 1 and 2 should be placed together 'with Fig. 2 at the right of Fig. 1, and with the interconnecting lines in alignment, Figs.

8 and t should be placed with Fig. 4 to the right of Fig. 3 and with Fig. 4 under Fig. 1. Figs. 5 and 6 should be placed under Fi 3 and 4t, respectively. I

Fig. 1 shows the trunk circuit TC interposed in the trunk line extending from the line switch bank contacts 2-4l t0 the selector S, together with the director selector DS associated with the trunk circuit TC.

F lg. 2 shows the repeaters R and R accessihle from the third and fourth levels, respectively, of the selector S, Fig. l. The outgoing trunk associated with the repeater R extends to oflice C, while the outgoing trunk associated with the repeater R extends to office B. director shown in Figs. 3 6, 'rtion of the d the scan.

effect the switclit-l1i'ougli operation ut er and S, together with the relays 201 and 202. The function of the sequence switch S is to distribute the *arious series of impulses incoming from the trunk circuit TC to the various operating magnets of the director. The function of the sequence switch 5 is to ground the various register wipers, one after the other, as the digits are tra: sinitted, and to the last digit is transmitted.

The portion of he director shown in Fig. 4 comprises the sender, vmade r p of the send ing switch SEll and relays and 80st; together with the special lay 301 and the release relay 302.

The portion of the director shewnin 5 comprises the otiice register G3, the intermediate distributing frame ll)? at which the control of the cod digits is ctliected and the spec'al relays l and 401 The portion of the dire 6 comprises the 1 tors Dlll DR-4, which are the registers that record the subscriber digits.

Call from ofiice A to office D.

The layout having been thus do cribeo.

C Hi h til cen-

- 0 n O orally, the detailed description of the operation Wlll now he given. For this purpose will be assumed that a subscriber in omce A desires to converse with a subscriber in oi'tice D. That being the case, the aforesaid subscriber in otiice A removes his receiver and dials the number of the subscri er in oiice D.

It will be assumed that, when the subscriber removes his receiver, his line switch selects the trunk line extending through the trunk circuit TC to the selector S at the

terminals

2, 3, and 4. Accordin 'ly, line relay 9 pulls up over conductors and 7 and over the calling line and closes at armature 12 a circuit for release relay 10. Release relay l0 energizes and places ground upon release trunk con ductor 6 at armature 1%. At armature relay 10 connects test wiper 35 of the d ector selector DS throng i armature 30 and its resting contact, to the stepping magnet 26 oil the director selector DS through the local interrupter contacts of the said stepping magnet. At armature 15 relay 10 places ground on the lower terminal of switching relay of the director select-or DS, thereby closing a circuit through switching relay and stepping magnet 26 in series.

The further operation depends upon whether or not the director upon which the wipers oil the director selector S are standing is idle. If this director is idle, the test cont-act on which the test wiper is standing is ungrounded and the stepping magnet 26 is not operated. l hat being the case, the circuit through relay 25 is etlective, and switching relay 25 energizes, seizing the director.

Assuming, on the other hand, that the direcial on y closing a f) noes L 1e wipers sez rch of an idle director.

hen an idle director is reached, for example, the one shown in Figs. 3-0. tcstwiper 35 encounters an ungrounded test contact vhereupon the operation of said magnet 26 cases. Accordingly, relay 25, being no onger short circuited, energizes in series wi '11 stepping magnet 26. Stepping magnet does notencrgize at this time on account or" the relatively high resistance of relay Upon energizing, relay 25 opens a point in the test circuit and places ground on test wiper 35, thereby melting the seized dire... r busy; at armature 97 relay 25 closes through the special control lead 21; it prepares the imnulse circuit at armature 31; and at armaures 28 and 29 it connects the conductors 5 7 of the selector 5 to a closed loop in the dir-ctor ov r vipers 33 and 3%. This closed loo includes

conductors

38 and 39, and the rest'ng contact and armature 316 of relay 303, in mutiplc with contacts 52% or" 505. Accordingly line relay 91 or t selector S pulls up over this closed loop and closes armature 52 a circuit for release relay M @141. Release relay 92 thereupon energizes and at armatures and 54: prepares the switch for operation in the usual manner.

In the seized director, release relay 30:1 pulls up over release trunk conductor 10 re sponsive to the grounding of test wiper 3: of the director selector as above pointed out. At armature 315 release relay 302 removes ground from relearc conductor so as to prevent the premature operation of the v rious release magnets oi the director; at armature 312 relay 302 removes ground from the restoring conductor of the sequuice switch S; armature 3H relay 302 grounds the locking conductor and at armature 313 it prepares a circuit for locking up relay 301.

The seizure of the director is now complete and, as the impulse circuit is closed through from the trunlr circuit TC to the oirect-or, th calling subscriber may now d'al the various digits in the desired number.

When the calling subscriber manipun' his calling device in accordance with the in office digit, line relay 9 of the trunk circuit TC falls back a corresponding number or times and, each time it falls back it rounds the impulse circuit at armature lire y closing a circuit through the working contact and armature 31, w"" r 36, i"' pulse conductor a l, armature 309 0;. relay 301 and its resting contact conductor 331, series relay sequence switch wiper 209 in its first position, conductor 281, and vertical magnet e09 of the ol'lice register OR to battery. Vertical magnet e00 operates over the above circuit to raise the wipers of the office register OR step by step until they come to rest opposite the desired level of bank contacts.

Relay 201, Fig. 3, is energized in series with the vertical inagnct of the oliice register and, being slow acting, iiiaintains its armature 203 atti'actci'l throughout theserics of impulses. Upon operating, relay 201 closes a circuit for relay 202, whereupon relay 202 pulls upand prepares a circuit for magnet 205 at armature 201i.

At the end'of the series of impulses, relay 20l. falls back and closes a circuit for niagi'ict 205, also opening the circuit of relay moment later relay 202 falls back and opens the circuit of magnet 205. By the operation oi magnet 205 the wipers 208 and 200 are advanced one step. Wiper 209 shittsthe iinpulsing circuit from the vertical magnet ductor 231 to the rotary magnet conductor 232.

i /hen the call subscriber dials the second o'llice digit, the resulting series oil? ini- .1 r, 1 11.1.! p arses is transmitted by the line reiay oi tr" trunk circuit TC, Fi 1, to the director the above traced path as far aswiper 20 9 of shifts the operating circuit from the rotary magnet conductor 32 of the oilice register OR to conductor 24H extending to stopping magnet 501 of the digit register Dl-t-l, Fig. 0. Wiper 208 of the sequence switch iii grounds wiper of the sequence switch S I and also grounds the conductor 233 through the interrupter 210, thereby starting the sending operation in a manner to be pointed out later.

Responsive to the dialling of the first subscriber digit in the number, a corresponding number of impulses transmitted over the impulse circuit as above traced to wiper 200 of the sequence switch S and thence by way of conductor 2&1, to magnet 501 of the digit register DR-1. Accordingly the wiper oi this digit register isadvanced a number of steps corresponding to the digit dialled,

thereby registering the digit.

Similarly the digit register DR-2 is operated by means of stepping magnet 502, re-

fi'or stop relay 304.

ceiving current over conductor 242 when the second sul'iscriber digit is dialled.

Accordingly, responsive to the third and fourth subscriber digits, the digit registers DR-3 and are operated by current transmitted over conductors 243 and 244:, respectively, and register the said third and fourth subscriber digits.

It is understood, oi course, that the sequence switch S moved. one contact after each oi? the above series of impulses so as to distribute the impulses to the various magnets concorned, and that the wipers 208 and 200 advance one more step at the termination of the fourth and last subscriber digit, and wiper 200 encounters adead contact. Accordingly, the wipers of" the sequence switch remain in. this position until the director subsequently freed, at which time the component switches thereof are released. Returning now to the operation of: the sender,

which started upon the connection of ground through the interringter 210 to the slim i; nductor 233 the end of the second. s lice digit, an impulse of current is trans- I mitted over conductor-.233 upon the first subsequent closure of the interrupter 210. This impulse oi current is transmitted through armature fill) and its r sting contact, and re ng contact and armature 320, to the stepi inagnet305 of the sending switch SEN. lVhen this occurs, magnet 305 pulls up and .HIOVOS the associated pawl into engagement with the next notch in the wiper driving ratchet wheel, but does not move the

wipers

306 and 307.

Upon the following opening of the inter ruptcr 2h), magnet 305 italic back and advances the

wipers

306 and 307 onestep. Pickup wiper 30G encounters a grounded contact with the result that pick-up relay 303 pulls up. At arn'iature 310, relay 303 removes the shunt from around the ding contacts 32% of the magnet 305; it grounds the release trunk conductor 10 at armature 317 so as to prevent the premature release of: the directi'ir in ca: the cal ing .lliifitfl'illifi should hang up while a digit is being transmitted; and at armature 318 it prepares a locking circuit The shunt has now been removed from around the s-endin contacts at armature Sit) as above pointed out. Consequently, upon each of the fol lowing energizations of magnct 305, the outgoing control circuit is opened at armature 232i, the wipers 300 and 3-07 being ad vanced as above pointed out upon each deciicrgization oi? magnet 305i.

The advance of the

wipers

306 and 307, and toe sending oi? impulses, continues until three interrul'itions have been produced in the outgoing control circuit. Vi hen magnet 305 falls back at the end of the third interruption and step, wiper 307 comes into engagement with the bank contact in which the third impulse stop conductor terminates, thereby closing a circuit for step relay 304; as follows: From the ground by way of the grounded stopconductor-control wiper 21% of the sequence switch S, the first cede-digit stop conductor 251, first wiper 421 of the otlice register OR, bank contact 4-25; the associated jumper on the intermediate distributing frame IDF, the sixth impulse conductor, stop wiper 307 of the sending switch SEN, and stop relay 304; to battery. Stop relay 30 i energizes over this circuit and at armature 321 closes a locking circuit for itself; places a shunt around the sending contacts 32d at armature 319 and at armature 326 completes the circuit of stepping magnet 211 of the sequence switch S. Stepping magnet 211 pulls up and moves the associated pawl into engagement with the next notch in the wiper driving ratchet wheel preparatory to advancing the wipers 213 and 521%. Ata-rmature 320 relay 30% disconnects magnet 305from the start wire and connects it through the interrupter contacts 323 to the combined pick-up and restoring wiper 306. Accordingly, magnet 305'is now operated un der the control of wiper 806 and its self-interrupting contacts 323 to bring the wipers 306 and 807 around to their normal position. When the normal position is reached the op eration of magnet 305 ceases and the circuit of the slow acting pick-up relay 303 is opened. This relay, however, does not fall back now on account of the fact that it is slow acting. In the selector S, Fig. 1 line relay 91 falls back responsive to each 01 the three above mentioned interruptions produced in its circuit by the sending apparatus of the director. Upon each deenergization, line relay 91 com pletes at armature 52 a circuit through armature 5 and its working contact, series relay 93, series relay 9%,and vertical magnet 75 to battery. By the operation of vertical magnet 75 the wipers 6567 are raised step by step until they come to rest opposite the third level of bank contacts, and the vertical test wiper 68 is raised and brought into engagement with the third level test contact Relays 93 and 9% are energized in series with each other and in series with the vertical mag net 7 5, and, being slow acting, they maintain their respective armatures attracted throughout the vertical operation. At armature 55 relay 93 opens a point in the auton'iatic stepping circuitof vertical magnet 75. Relay 94:, upon operating prepares a circuit for stepping relay 96 at armature 56, and at armature 57 opens a point in the circuit of rotary magnet 77.

Just before the vertical step of the switch shaftis completed, the 015

normal contacts

79 and 63 close, and contact 68 completes a circuit of the stepping relay 96 which includes and its working contact, 63, areal.

interrupter contacts 7%, oil normal contacts 63; and the rotary interrupter contacts 76-. Relay 96 energizes and locks lit at armature 59, and at armature prepares automatic stepping circuit.

At the end of the vertical movement, relays 93 and 94 fall back. Relay closes at armature 57 a point in the circuit of rotary magnet 77, and at armature 56 opens the initial circuitof stepping relay 96, leaving this relay energized through its locking circuit which includes armature 59 and its working contact. Relay 93, upon falling back, closes at armature 55 a point in the automatic vertical stepping circuit.

From this point the operation depends upon whether the trunk line group terminating in the third level of bank contacts of the selector S busy or idle. It the entire group of trunk lines is busy, there is a ground potential on the chain conductor 69 through contacts such as 106 and 106, Fig. 2, and this ground potential is extended through the ertical test wiper 68 to relay 9 5. Relay 95 is, accordingly, energized and the stepping circuit is shifted from the rotary magnet 77 to the vertical magnet 75 through the series relay 94,-. That being the case, vertical magnet 75 energizes from ground on the grounder release trunk conductor 6, through the workingcontact and armature 60, armature 5S and its working contact, and series relay 9%. The slow acting series relay 94 energizes again in series with vertical magnet 75 and closes at armature 56 a shunt around the look ing armature 59 and its working contact of the stepping relay 96, and at armature 57 opens a point in the circuit of rotary magnet 77 so as to prevent the premature operation of rotary magnet 77 at the end of the ver iiCfll stepping movement. By the operation of vertical magnet 75, the wipers 67 are raised from their position opposite the third level bank contacts to a position opposite the fourth level bank contacts. Near the end of its stroke vertical magnet oaens the circuit of stepping relay 96 at the interrupter contacts 74, whereupon stepping relay 96 falls back and opens the circuit of vertical magnet 75 and the slow acting relay 9i at armature ,When this occurs, vertical magnet 75 falls back and at contacts 7% again completes the circuit of relay 96 t'rom ground through armature56 and its working contact.

Relay 96, accordingly, energizes again hut it 1 does not close the vertical magnet circuit again at this time on account of the fact that the vertical test wiper 68 is now in engagement with an ungrounded test contact, namely the test contact associated with the fourth level, and relay 95 has, therefore, fallen back. Accordingly, the vertical stepping circuit is pened at armature 58 and the rotary steppin circuitis prepared. 7

Arte-r a slight interval the slew LllU ing contact at arnmture 56; and at armature co )letcs the cii'c of rotary magnet 7'7.

/hon this occurs *otary nnignet 77 pulls up and advances fie wiper. into engage ment with the this s I t contacts in the fourth level, and, n d oil its stroke, opens the circuit of g relay 96 at the interrupter contends (6. When this occurs,

relay 9%) falls ba -lr and opens a further point in its hiching circuit at in i: -rture ethanol at ernuiture (it) opens the circuitot rotary mag-- not Z7. Rotary magnet 77 thereupon falls back and closes its interrupter contacts (52 again.

From this point the operation depends upon whether the trunk terminating in the ot haul: contacts in the tourth level first set husy or idle. If it idle, the test contact ens aeed 1) Y Wine: (36 is unorounded and LD e i. 1

switching relay 9'? onengines seizing the trunk. Assuming, however that the first trrml: is busy, ground is encountered on the test contact thereof by test Wiper (36, short circuiting the switching relay 97 and again euergncir :tepping relay 9e. Relay 96 again completes its locking circuit at armature 5E), and at armature again completes the circuit 0t rotary magnet 7'7, whereupon the wipers (-67 are advanced another step. This or mate operation o'l relay 96 and magnet 7'? ci'int-inues as described until. en idle trunk is reached, which trunk, it will be as- Fllll'ltlll is the one comprising conductors Q: )6) Qt ue).

. 3:" ched switching circuited pulls ayllS. Stepii t iperate at this -h resistup in F03? re iy 96.

e on account or t reh tiveiy hi of switching relay Upon energiz 97 ren'ioves ground at he line relay armature i, (MIL A in switchiiw' u. armature 30 52; it open? tciri lit and prepares the l v circuit at ariur-iture (52, thereby "l'tllliltllilfi the lu t Wiper 36 to nialre the seized mm; busy innnedietely; and st arn1aturns (Bl l t it disconnects conductors 5 inc reiey 9i aiul extends them ioers and s7 and conductors lune relay l'ljl the repeater T511265 (Wer. conductors armature 113a circuit .felay 112, which thereupon nds he release trunk coni As a further re- Relay -3 and 83 and for the release i energizes and on doctor 8: at ainiatu suit ot its ener -i lion etiux lll bridge across .3 l v whereupon the distant sel lice B is prepared for opera in the usual manner.

. the dircctor t-he slow acting pick-up relay Z3 )3? tails hack after a slight ii'iterval responsive to the return to its normal posicontacts clay 111 closesat the outgoing tion of Wiper 306, as above pointed out. At

armature Z318 relay303 opens the loc ring cir cuit oi the slow acting stop relay 30 i, and at erznature 325 it opens the circuit of magnet Qllet the sequence switch S, whereupon the "v-iipors 21b and 214 are advanced one step.

Stop relay 304; falls back after a slight interval and again connects the stepping ignet 305 of the sending switch SEN to the dirt wir at armature 320. Accordingy, the second code digit 6 is transmitted in l l 1e seine manner as the first code digit In his case the transmission of impulses continues until the endott the s'xth interruption in the out ing control circuit at the sending z t oi magnet 305. At this time the wipers 306 and 2-307 advance another step and Wiper 307 encounters aground potential on the bank Contact in which the sixth inipulsesh p conductor terminates. The circuit tor stop relay 30d at this time is as follows: Fron ground by way of Wiper 21d of the sequence switch 5, the second bank contend; the second code digit stop conductor 252, the second wiper 4:22 of the oltice register (ll-t, bank contact 426, the associated juniper I on the intermediate distributing the c code d nor as the rust code digit 3 and the wipers 213 end 2h of the switch S are again advanced one step in the manner heretofore described. Wiper grounds the third code-digit stop condrrtor In the present case two code digits are enough. Accordingly, the third and fourth bank contacts in the ollice register OR associated with the oliice D are not wired to uny 01" the impulse stop conductors it ere instead juinpered over to the skip n .uctor 117. "llhat bein the case when e third Wiper 4:23 o the on, so register OR is i ded over conductor 25?, ground potentransn ii tted hy way ot brink contact 427, he self-interrupting contacts 212 to the 1 ing magnet 2L1 ot the sequence switch s op S. Stepping magnetQll. energizes and, be-

in self interrupting, again falls back, thereby advancing Wipers 213 and 21% another Viper 214 grounds thefourth code 7 stop conductor with the result that a circuit closed through the fourth wiper -il-2 l ot' the o'lliceregister OR, hank contact 428, th associated IDF jumper, and the skip conductor 4217 for stepping magnet 211 again. Accordi igly, the wipen 213 and 2A are autoniiticelly advanced another step, and wiper L14; shifts the ground potential from the fourth code-digit stop conductor 254; tothe first subsciioer-digit stop conductor 261.

In the oilice i lli 8, the selector S raises .te the sixth level rezmimsive izetion of stop relay 304 the second I is terminated 1n the same nlitlb by the director, as above pointed out, and selects an idle trunk extending to the otiice D, for example the trunk extending to the selector Returning now to the director, as the first subscriber-digit stop conductor 261, which leads to the wiper of the digit register DR1, Fig. 6, is now grounded, the next digit to be transmitted is the first subscriber digit. This digit is transmitted in the hereinbei ore described manner and is terminated upon the energization of stop relay 30 I over the particular impulse stop conductor on which the wiper ot' the digit register DR1 is standing. Upon the termination of this digit,

wipers

213 and 214 off the sequence switch S advance again with the result that ground potential is shifted from the first subscriber digit stop conductor to the second subscriber digit stop conductor 262. accordingly, the second subscriber digit, which is registered on the digit register DR-2 is transmitted in the usual manner. Similarly,.the third and fourth subscriber digits, which are registered on the digit registers DIR-3 and DR1 are transmitted in the hereinbetore described manner.

At the end of the transmission of the fourth subscriber digit,

wipers

213 and 214 of the sequence switch S are advanced another step with the result that wiper 21 i removes ground from the fourth subscriber-digit step conductor 26% and connects it instead to the switching branch 215 of the impulse conductor 331. The impulse conductor 331 is open at this time in the director on account of the fact that the wiper 209 or" the sequence switch S is standing on a dead contact. The impulse circuit is connected at its origin, however, to the switching relay 11 of the trunk circuit TC througharmature 13 and its working contact of line relay 9. Accordingly, switching relay 11 energizes over the impulse conductor and locks itself to the grounded release trunk conductor 6 at armature 19; it connects the release trunk conductor 6 with the release trunk conductor 6 at armature 1S, and at armatures 17 and 20 it disconnects conductors and 7 from line relay 9 and connects them to the conductors 5 and Tot' the selector S, at the same time disconnecting conductors 5' and 7 from the closed loop of the director. lhe established connection is now held up by the current flow over thecalling line through the line relay ot' the repeater E, Fig. 2.

Line relay 9 at the trunk circuit TC now falls back and opens the circuit of release relay 10 at armature 12. Accordingly, release relay 10 falls back after an interval and removes ground from release trunk conductor 6 at armature 1 leaving this conductor grounded, however, from the release trunk conductor 6. At armature relay I0 opens the circuit of switching relay of the director selector DS, whereupon relay 25 falls back, freeing the director.

In the director, release relay 302 falls back responsive to the removal of the ground potential from release trunk conductor ell) when the director is freed. Upon falling back, relay 302 rounds at armature 312 the restoring conductor 332 of the sequence switch S. lVhen this takes place, a circuit is closed through wiper 213 and th interruptercontacts 212 for stepping magnet 211, with the result that thewipers 213 and are are advanced the remaining step to their normal iosition. At armature relay 302 grounds the release conductor 335, thereby closing parallel circuits through the various oil normal contacts of the home position switches of the director. For example, a circuit is closed through off normal contacts 112 for the release magnet 111 of the otfice register OR, and a circuit is closed through off normal contacts 20? for release magnet 206 of the sequence switch S, similar circuits being closed for the release magnets of the digit registers DE 1D1t4c. The result is that the various release magnets energize, and the respective wipers are restored to their normal positions, the circuits of the release magnets being then opened at the respective oli' normal contacts.

In the oliice D, the selector S is operated opposite the desired level in accordance with the transmission oi the first subscriber digitwhich was previously registered on the

digit register DR

1, 6 the hundreds selector seized by the selector is operated in accordance with the digit registered on the digit register Did-2 and transmitted as here inbetore pointed out; and the connector switch seized by the hundred selector in use is operated in accordance with the digits registered on and retransmitted. from digit registers DR-3 and DR-l to finally extend the connectionto the desired line in the o lice D.

lVhen the calling subscriber replaces his receiver at the termination of the conversation, the circuit of line relay 111 of the repeater R is opened. Line relay 111 falls back and at armature 11% opens the bridge across the outgoing trunk conductors with the result that the connection extending through the otiice D to the oliice B is released in the usual manner. Atarmature 1 13 relay 111 opens the circuit of the slow acting release relay 112, which deenergizes after an interval and removes ground from the release trunk conductor 82 at armature 115. When this occurs, switching relay 97 of the selector S and switching relay 11 of the trunk circuit TC fall back and the calling line switch i released in the usual manner. Upon the leenergization of relay 97 or" the selector S, a circuit is completed at armature through armatures 52 and 5st at the oil normal contacts 79 "for release nurgnet 78, whereupon release magnet 78 restores the wipers 67 to their normal position in the usual manner. The circuit of release magnet 7 8 is opened at ol'l' normal contacts 7 9.

'lhe foregoing example serves to illustrate how the calls which are normally trunlred from oilice A to oilicc D by way of the C o'ii'ice are autou'iaticallyrerouted through the oliice B by the group hunting selector S, Fig, 1. Itwill be ni'idcrstoml, oi course, that in case the entire group of trunk lines accessible tothe'third lovel of the selector S is not busy, then there no ground potential on the chain conductor (30 with the result that relay is not energized at the end of the vertical. movement. iiccordingly, no automatic vertical operation takes place, but, instead, the regular rotary magnet circuit is completed right away upon the falling back or: relays 93 and. 94. In this case the selector S selects an idle trunk in thethird level, leading to the oliice C. F example, the trunk leading to the selector S lirccording'ly, when the second code digit (3 is transmitted by the director as hereinhetore pointed out, the selector S raises its Wipers opposite the sixth level. and selects an idle trunk extending to the ol uce l), "for example the trunk extending to the selector S.

can from offi'ce A to 0773 06 0.

Assuming now that a calling subscriber in the o'l'iice A desires to converse with a subscriber whose line terminates in oilice C and that, upon the reniovalof the receiver at the calling substation, the connection is extended through to the selector S, hereinbefere described, and that the director selector DS seizes the director shown in Figs. 3-6, the calling subscriber now dials the ori ice digits assigned to the otfice C, followed by the four subscriber digits in the number, with the result that the oliice register UR, Fig. 5, brings its wipers 4l2l-l24; into engagement with the C ollice bank contacts 429 .432, andthat the digit registers DR1DR l are operated to register the subscriber digits of'the num ber. I

It willbe noted that the first bank contact 4-29 of the set allocated to the G ofiice is cross connected on the intermediate distributing frame IDF to the special conductor 455. Accordingly, when the stop-conductor-control wiper 2 A: oi the sequence switch S is grounded at the end of the rotary movement ot the oliice register OR, upon the sequence switch S passing into third position, a circuit isclosid over the iirstcode digit stop conductor S201, wiper 4121, bank contact 429, the associated jumper, special conductor Q55, and the norn'iaily closed contacts controlled by armature 40 lfor the special relay 401. This relay thereupon pulls up and loclzs itself inbe'forc a circuit for release relay 102 which "to the grounded conductor 3234; at armature 104i, at the same time opening its initial circuit so as to prevent the locking ground potential from remaining peri'nanently on the special conductor 455; OIiJQDilES the special conductor i553 at armature 4:05 through the jumper 4 51'; to the third impulse stop con ductor to control the sendii out oil? the first code digit 3; and a armature prepares a circuit for the special cut-oil i 2y 1301., Fig. 4, which latter circuit is closed only in case the selector S, Fig. l, is autouuii'icallyraised tolhc fourth level responsive to a busy condition of all the third lcrcl trunks as will hereinafter appear-L From the foregoing it may be seen that as the first code d' 'it stop conductor 525i is new t: A I connected. through the circuit above traced, incliu'ling the special conductor elfih and armature 405 and its working contact to the third. impulse stop conductor, the ii-st code digit to be l'ransn iited is the code digit Yfhen this transiuisison. takes place the selector S, Fig. l raises its wipers opposite the third level of contacts in the manner hcrcdescribed. Asi-xuining, nowthat there is at least one idle trunk in the third evel, the vertical test relay 95 of the selector S is not energized at the end of the vertical movement and the rotary movement commences as soon as relays 93 and. 9-4: {all back. Assuming that the trunk comprising); con: ductors 71-73 is the one select-ed, the conrcctiouv is extended through to the repeater 1% upon the enei' 'izatiou of swit hing relay 97 which takes place when the idle trunk is reached. 7 Accordingly, line relay 101 of the repeater R pulls up and closes a bridge across the outgoingtrunk conductors at armature 104, with the result that the selector S Fig;

8 1 repared for operation in the usual manner. At armature 103, linerclay 1,01 closes thereupon energizes and places around on the release trunk coruhu'ztor 72 at armature 105. At armature 10G, relay 102 closes a point in the chain circuit for supplying ground to the verticallest chain conductor 69.

In the director, the advanced one step in the usual manner at the end oi the transmission of the first code digit 3, and wiper 214: removes ground from the first code digit stop conductor and extends it instead to the second code digit stop conductor 252. The second code digit stop conductor 252 is connected through the second wiper 422 of the other: ree'isi ,1: UR. bani: contact 4130, the associated Ir) umpcr, special conductor 454, armature ice and its resting contact, ind the associated jiunper to the ship conductor H7. T he result is that v the wipers oi the sequence switch S are automatically advanced in the licreinbc'i described manner and the ground potential sequence switch S is is removed from the second cod-o digit stop conductor and placed on too tlnrc cod ontr he L id th tor lo the oliicc C Fig.

tor S raises its wiper IGSPOElESlV-Q to the tra code digit 5 and sci sands selector.

In the director. when the wipers of the sequence switch S are anced one step the end or the transmission of the secon digit 5, the fourth code Lllg'l stop co; 253i is grounded whereupon a circuit it through wiper 42 lbanl: contact 432, the associated ll)? and the ship conductor all for the srepp magnet- 211 oi the sequence switch S5, the result that the wipers 213 and 21 1- are automatically advanced one step and ground is extended to tie first subscriber digit stop conductor 261.

d code F )in his L o1 t 0 h ope 10 1 o h paratus is the same as ClQcCIllJQd hereinberore.

i iccording v, the director transmits t-ie suoscriber dig in the number in t ual inanner after which 1t switches through and 1S m 1*, n you; .fl

released 1 1o es-raoiis 10( taming cOIHlCCUOH is released in the usual manner when the calling subscriber replaces h s receiver.

the selccto r to raise the wipers from Lll'cll operated position opposite the third level of contacts to a, posi ion opposit he itiurtn level of bank contacts in the he icinbetore de- ,;1 1,. T 11: ."l L SCLL lBC manner. 1n LHZS case, as oeioie, the m 0 L 4', t. 1 4-. SQl-QCLUT Q staits IGLEtnlfl; and sole Us HLG trunk in "he fourth level.

hen. the i'ourth erel of bank contacts is reached the fourth level shaft springs place ground on the special conductor 21, and since the special relay e01 1n the director, Fig. 5, 1S operated i. circuit is closed tor th special cut-oil relay 301, Fig. la follows: firoin s the ground by way or the fourth level shaft springs of selector S, 1, conduct r 21, working contact and armature 2?. wiper 32 conductor 3?, working contact and armature 41'? of relay 401, Fig. 5, the jumper connected etween terminals P53 and 1-51, conductor 218, and the special cut-oil relay 301 to battery. Responsive to the closure of this circuit, relay 301 operates and locks itself t groun'; at armature 311 through the w rliing cont; and armature 313 of release relay 302. At armature 3110 relay 301 opens the start conductor so as to prevent fur her sending operations from taking place; it opens the outgoing; control circuit at armature 303, thereby releasin the partly .stablished connection including the selector S and the selector on the distant end or" the trunk line seizedby the selector S and a armature 309 relay 301 disconnects the impulse conductor 41 .ulll the branch leading to the wiper 209 or the quencc switch S and connects it through the small condenser 322 to the common busy signalling lead associated with the busy machine. Accordingly, )usy tone current is t r fed back over conductor ll to armat *e 13 and its working contact of the trunk ci 'cuit TC and is there placed on the calling l throu 'h the small condenser 8 and the t and armature 20. When the I subscriber hears this busy tone he is d to replace his receiver, whereupon and release relays of the trunk circuit bacl; ith the result that the seizing switch isfreed and the switching; relay :ie director selector DS falls ha 1: and the director with the hereinbetore 'de l results that the component parts of i or are restored to normal in the eating cc;

1 when the A to C trunks are busy in case the group of trunks from the B o'llice to the e is relatively small group of trunks, cannot therefore carry any appreciable It will now be assumed,

l oiral loa d.

d 1' I .ly large group or trunKs and 1t can warry, in adidtion to the regular B to C trailic, extra trafiic directed to the C otlice from the A thee at such tnnes as all the trunks running directly from the A ofiice to the C ofiicc are all busy. This situation may arise in case extra trunks are actually installed bctween the B and C oliices to take care of the above contingency or it may be, as is often the case that the peak load from oltice to the C office occurs at a time c trunks from B to C (which at the their peak load are all in use) are carrying a light load and that the trunks can carry some extra load on this account. In y event, in case the B to C trunk group, can ndle A to C traiiic, the jumper between the a rls and 453, 5, is out and a --ew juniner is run between the terminals 2 i-iccordingly, when the C oaice is called from the A ofiice when the A a however tha the group of trunks is a 0111- to C trunks are busy, the partially estab lished connection is not released by the special cut-0H relay 301, Fig. 4, in this case as in the one described. Instead oi? this, when the selector, S, Fin. 1 is automatically raised from the third level to the fourth level in rcspon" to the condition of all trunks busy on tl iaird level, a circuit is closed by the fourth level shaft springs which extends as previously traced. as far as contact 4153, Fig. 5 from which point it now extends through the new jumper between terminals 453 and 452 to battery through the special code con trol. relay 4-02. Relay i032 nowpulls up and disconnects conductor @434 from the skip conductor and connects it ins cad through the working.- contact of armature lOS to the fourth impulse stop conductor. I Aocordingly, when the sequence switch S advances responsive to the falling back of the slow acting pick-up relay 303, (which it does'in the manner pointed out hercinbefore) and places around on the second code digit con din-tor .52, the second code digit position is not shipped as in the n'eceding case, but instead the fourth impulse stop conductor is grounded. to preiilctermine that the'next cor e di is transmitted, that is, when, after the sending operations have again started, the wiper $307 of the sendingswitch SEN lands on the bank contact in which the fourth impulse stop conductor terminates, stop relay 304: energizes over the following circuit: From ground by way of the grounded wiper 214; of the sequence switch S, the second bank contact, the second code digit stop conductor 252, wiper 422 of the ollice register OR, bank contact 430, the associated 'IDF jumper, special conductor 45d, armature 403 and its working contact, the associated IDF jumper, the fourth impulse stop conductor, and thence by way of wiper 307 of the sending switch SEN and stop relay 304 to battery. This energization of the stop relay results in the termination of the digit being transmitted. After the usual time interval, the sequence switch S is again advanced and shortly thereafter the sending of the next digit commences.

In the ofiice B, Fig. 8, the selector S responds to the second'code digit 4 to raise its wipers opposite the fourth level and to select an idle trunk therein. For example, the

trunk extending to the C oilice and terminating in the selector S In the director, the next code digit 5 is now transmitted in the manner hereinbefore described as the sequence switch S is now in.

Obviously the transmission of the regis-- .igits is required in this case when the O oliicc is called. It will be noted that rue only dillcrence between the codes of the {l ol'lice and the E oilicc is that whereas the L'inal code digit on calls to the C office is the digit the linal code digit when the E oflice is called is the code digit 2. It will be seen further that since the calls from the A oflice to the E cllice are all ha udled through the C office and that the thousands selectors in the lid .1"" e are aoco: iblc to the ame ofiice selectorso and SQto which thethousandsselectors in the C oilice are accessible, the special arrangement hereinbciore described with refer-' ence to handling calls to theC oil'ice are applicable tothe E ol'licc. For example, when the director transmits the first digit 3 in the code 32 necessary to trunk the call to the ollice E, the selector El raises its wipers opposite the third level of bankcontacts and completes I the connection to a selector in the C oflice, such rcnce to Fig. 8 that the same to the G ofiice, the connection must be denied in case the trunk lines from B to C cannot be used. On the other hand. an extra digit must be introduced to trunk the call from the Ii to C oliice in case it is permissibleto use the B to C trunk for calls directed to C from A.

It may be seen troni the diagram,:Figs. 7 and S, that the oiiice E is more or less an outlyingoliice. Accordingly it may be readily supposed that this is a relatively new office and. one in which the traflic is increasing at a fairly rapid rate owing: to the building up of the territorywhich it serves. That being the case, it is desirable to have a ready means for ascertaining the traflic directed to the E other, in order that the trunking; facilities may be changed from time toftime as the traffic conditions change. This situation'has been taken careoit' by providing; in the director shown in Figs. 34% suitable metering arrangements, later described, for registering the number of calls directed to the E ofiice. It will be understood, of course, that the other di-' rectors are similarly equipped.

Referring now to Fig. 5, it will be noted,

that the first bank contact 433 associated with the E ofiice position of the oflice register OR is cross connected on the intermediate distributingframe IDF to the same special conductor 455 towhich the first bank contact 429 of the set belonging to the C ofiice is cross connected. Therefore, on calls to the E ofiice relay 401 pulls up and operates armature 417 just as described hereinbeiore on calls to the C ofiice. It Will be noted further that the second bank contact 424 of the set belonging to the E office is cross connected on the intermediate distributing frame in the same man ner as the second bank contact 430 of the set belonging to the C ofiice. Accordingly, the second code digitposition on calls to the E office is skipped or is used to transmitthe extra digit 4 necessary to trunk from B to'C, subject to the same conditions as described in connection with calls irom the A otfice to the B oflice.

- From the above it may be seen that the same special arrangements provided to take care of one office may be used to take care of as many offices as desired that are reached through the first mentioned ofiice.

It Will be noted that Fig. 5 shows a meter M. This meter is used to register the number of calls directed to the E oliice. It is for this purpose associated with the special terminals 441 and 442'. It Will be noted that the third contact 435 in the group assigned to the oflice E is jumpered on the intermediate distributing frame IDE to the special termi- Ind 441. Accordingly When the third Wiper 423 ofthe oifice register OR- is grounded by the sequence switch S on a call to the E office, the ground potential is extended over conductor 445 to energize the magnet 443 of the meter M. hen magnet 443 energizes it operates the associated armature 446 to turn the number-Wheel registering mechanism to register the call, and it also places ground on conductor 444, which is extended to the special terminal442 and from then by Way of the associated IDF jumper to the second impulse stop conductor so as to terminate the last digit 2 in the usual manner.

hat is claimed is:

1. In a multioflice telephone system, four offices, trunk lines from the first office to the second ofiice, trunk lines from the second oifice to the third office, trunk lines from the first office to the fourth oilice, trunk lines from the fourth ofiice tothe third oilice, switching mechanism in the first office responsive to a predetermined digit for extending a connection over one of said trunk lines to the second oflice, switching mechanism in the second ofiiee responsive to a second predetermined dig-it for extending the connection by Way of one of said trrmlr lines from the second oifice to the third oflice, means associated with the-said switching mechanism in the first 01"- fice, operative responsive to a busy condition or the said trunk lines from the first ofiiee to the second otlicc to extend the said connection to the fourth oliice by Way of one of said trunk lines instead of to the second oliice, switching mechanism in the fourth oilicc responsive to said second predetern'iined digit for further extending the said connection from the fourth office to the thiru olfice by Way of one of said trunk lines, and a register sender in the first ofice for transmitting the digits to operate said switching mechanism.

2. In a telephone system, a plurality oliices, trunk lines interconnectii said ofiices, switching mechanism in the first of said otfices responsive to a predetermined digit for extending a connection from the first oz'iice to the second ofiice by Way of one of aid trunk lines in case one is idle, means associ red with said mechanism responsive to a busy condition of the trunk lines connecting the first ofiice with the second olfice for extending the said connection by way of one of said trunk lines to the third ofiice, and a register sender in said first oiiice for controlling said switching mechanism. a

3. In a telephone system, a plurality fices, trunk lines interconnecting said switching mechanism in the ii omce ltni; sive to a predetermined digit to extend a c neetion to the second ofice, means, assoc with said mechanism, responsive to condition of the trunlr lines connect. first olfice with the second oilice to extend said connection by way of a trunk line to third ofiice, and means responsive to the oper ation of the last named means, controlled in accordance with the final destination of the call, operative to give the calling subscriber a busy signal and to release the connection to said third office.

4. In a multi-olfice telephone system, a registcr-trans-mitter for registering a telephone number and for transmitt ng digits to trunk the call to its destination, and means in said re'g'ister-transmitter responsive to a busy condition of one of the inter-oiiice trunk groups encountered for altering the untransmitted part of the digit combination to route the call to its destination over a new inter-ofiice trunl: path by Way of a different intermediate office.

5'. In a telephone system, a plurality of ofiices interconnected by trunk lines, sending mechanisms, switching mechanism in the first ollice controlled by said sending mechai to extend a connection to the second in case there is an idle trunk, means associated With said mechanism responsive to a busy condition of the trunk lines from the first to the second oi'rice to extend the said connection by Way of a trunk line from the first office to the third office, and means r sponsive to the last named operation of said switching mechanism for causingsaid sending mechanism to transmit an extra digit to trunk the call from the third oliice to the second oifice.

6. In a call director, registering mechanism, sending mechanism controllable thereby to transmit a plurality of digits, means for canceling one of said digits, and a relay energized responsive to the transmission of a preceding digit tor rendering said canceling means ineil'ective to cancel said one digit.

7. In a telephone system, a selector having a group hunting movement eliective ii a selected group is busy, a director for controlling said selector and other selectors in accordance with a predetermined code, and means effective to "alter the code in case said group hunting movement takes place. i

8. In a telephone system, a selector having a group hunting movement effective if a selected group is busy, a director for controlling said selector and other selectors in accordance with a predetermined code, and meansfor automatically increasing the number of digits in the code in case s;iidg:'orip hunting movement takes place.

9. In a telephone system, an automatic switch for trunking a call from a lirst ofiice to a second olfice over a particular group oi trunks, a director for controlling said s ltCll and other switches in accordance with a pre determined code, means responsive it all trunks in said group are busy for causing said first switch to automatically select an other group of trunks, and means responsive only in case the said first switch selects the second group of trunks for causing the director to continue the trunking control in accordance with a revised code.

10. In a telephone system, an automatic switch for trunking a call from a first o'li'tice to a second olfice over a particular group of trunks, a director for controlling said switch and other switches in accordance with a predetermined code, means responsive if all trunks in said group are busy for causing said first switch to automatically select another group of trunks, and means responsive only in case the said first switch selects the second group of trunks for causing the director to insert an exaa digit in the code.

11. In a telephone system, a selector, a director for controlling said selector and other selectors in accordance with apredetermined code, and means for revising the code during transmission in case said selector is operated to select a busy group of trunks.

12. In a telephone system, a selector, a director for controlling said. selector and other selectors in accordance with a predetermined code, means in said selector for causing the same to select another group of trunks in case the code digit received corresponds to a busy group, and means effective in such case for revising the remaining portion of the code before transmission.

13. In a telephone system, a selector, a director for controlling said selector and other selectors in accordaz'ice with a predetermined code, means normally ell'cctive to cause said director to skip a possible code digit, a non skip relay, and means in said selector for coma-oiling said relay.

14-. In a telephone -'tcn1, a selector, a di rector l'or contrelling said select-(nand other selectors in accordance with a predetermined code, means normally effectiv to cause said director to skip a possible code digit, a nonskip relay, and means for operat' g said relay in case said selector is operated to select a busy group of trunks.

15. In a telephone system, a plurality of ofiices, trunklines interconnecting said oi fices, switching mechanisms in d o'lfices, a director for registering and. transmitting digits to trunk the call to its dest nation, the switching mechanism in the li 3t ofiice being responsive to a digit set up on said director for extending a connection trom the first to the second by way oi one of said trunk lines it one is idle, n'lcai'is associ ated with said first mechanism responsive to a busy condition of the trunk lines connecting the first oiiice with the second oiiice for extending the connection by way of one oi said trunk lines connecting the first oiiice with the third office, and means in said director for altering or not altering the un transmitted part of the digit coml nation dependent upon the destination of the call to control the switching mechanism in the third oiiice to route the call over the proper trunk lines to its destination.

16. In a telephone system, a first olIice, a second o'liice. two tandem 'olfices, means including a director normally effective for routing calls from the first oifice to the second oifice by way of the first of said tandem offices, but effective if all the trunks connecting the first office with the first tandem ofiice are busy for routing calls from the first olfice to the second oilice by way of said second tandem office, and equivalent trunking connections between the two tandem ofiices and said second office, whereby calls can be routed via either tandem oliice as set forth with the same setting in said director.

17. In a telephone system, groups of trunks, a director for registering and for transmitting digits to trunk the call to its destination, and discriminating means in said director responsive to a busy condition of one of the trunk groups for altering or for not altering the untransmitted part oil? the digit combination dependent upon the destination of the call.

18. In a telephone system, a selector, a director tor controlling said selector and other selectors in accordance with codes correspending to difierent QXC ianges, and means in said selector for causing said director to change one of said codes.

19. In atelephone system, a register sender for registering a designation and retransmitting in accordance therewith a predctcrininet digit combination, and means for altering said combination of digits after the transmission of the first digit.

20. Ina telephone system, a first ofiice, second or lice, a third otiice, trunks connecting each ofiice with the other t vo, a register sender in the first oii'ice normally effective for renting calls from the first office to they second office by way of the trunk connecting the two otlices, means cii'ectivc independentof control from said sender when all of the trunks connecting the first otiice with the second oiiice are found unavailable to route calls intended for the second otiice to the third chic-e, and means in the sender thereafter operable to control the routing of such calls from the third oflice to the second OifiCQ,

21. In a multi-oiiice telephone system, a register sender for registering a telephone number and for transmitting digit impulses to trunk the call to its destination, and means eii'ective when all the trunks leading directly to the desired otfice are busy for altering said sending apparatus after it has transmitted the first code digit so that it will transmit impulses to route the call to its destination over a different inter-ottice trunk by way of an intermediate otiice.

22. In a telephone system, a register sender, means for registering groups of digit impulses in said sender, means in the sender for transmit-ting groups of impulses corresponding to the impulses registered, and means in said sender effective responsive to the traitin' sion of the first registered digit under predetermined conditions for automatically changing the remaining number of digits to be transn'iitted.

23. In an anton at ic telephone system incl ding a number of exchanges interconnected by trunks, aregister sender, a device directively controlled by the sender, and means independent or" said sender for controlling said device after its operation by the sender to anton'iatically deviate calls between two exchanges through a third exchange in case all the trunks connecting the two exchanges are busy, means controlled by said device responsive to its automatic deviation for revising the remainder of thecode to be transmitted by the sender.

24, in telephone system, a register sender, for registering and retransmit-ting in accordance therewith a predetern'iincd digit combination, a selector directively controlled said sender to select a predetermined trunk group in accordance with the first digit of said combination, and means in said sender effective in case said selector automatically selects a different trunk group responsive to the transmission of the first digit of said combinat-ion for altering the said digit combination.

in witness whereof, I iereunto subscribe my name this third day of June, A. D.

Lnoniisn L. nUeoLns.