US2115320A - Automatic telephone system - Google Patents

Description

April 26, 1938. N SAUNDERS 2,115,320

AUTOMATIC TELEPHONE SYSTEM Filed June 14, 1955 5 Sheets-Sheet 1 FINDER I l TH vi VERTICAL GROUP A FIN INVENTOR. NORMAN H. SAUNDERS ATTORNEY.

TO CONN. BANKS April 26, 1938. N. H. SAUNDERS 2,115,320

AUTOMATIC TELEPHONE SYSTEM Filed June 14, 1935 5 Sheets-Sheet 2 INVENTOR.

ATTORNEY.

mB/F E E w 1 JSN 2N f 8N .i :5 :8 m H H Fi "m 5: 3% E. M I? g 1 & OH H. ew (1mg 5 (EN NORMAN H. SAUNDERS EOPUMZZOO CONNECTOR CONT.

April 26, 1938.

I N. H. SAUNDERS 2,1 15,320

AUTOMATI C TELEPHONE SYS TEM Filed Jun 14, 1935 5 Sheets-Sheet 5 BANK 352 LEVEL MINOR SWITCH INVENTOR.

NORMAN H. SAUNDERS ATTORNEY.

N. H. SAUNDERS AUTOMATIC TELEPHONE SYSTEM April 26, 1938.

Filed June 14, 1935 5 SHeetS-ShGGt 4 April 26, 1938. N. H. SAUNDERS AUTOMATIC TELEPHONE SYSTEM Filed June 14, 1935 5 Sheets-Sheet 5 s Y m 3: m m m E U 3: m m m U J) F b A W M. v H 3; S: H \Bmwl l V N {I m o A mm w 0E M. R o a: N m Now Q I: 5m

w M M x M MMMW h won I: ILIIQ l 1 mom 5 m 3 [mm w h 925 5%? G mm :m 3 E Ill o m m N m m w m N I m mmtbj 8m 5h 00min $2: :9: M23 :25 m 0E Patented Apr. 26, 1938 UNITED STATES PATENT OFFICE AUTOMATIC- TELEPHONE SYSTEM Application June 14, 1935, Serial No. 26,593

16 Claims.

The present invention relates in general to automatic telephone systems, but more especially to automatic systems of the Strowger step by step type, and the object of the invention is to 5 produce a better and cheaper system for use in giving service in an exchange comprising between about three-hundred and six-hundred lines.

In further explanation of the object of the invention, it may be pointed out that the standard Strowger switch has a capacity of one-hundred lines. By using finders and connectors linked together in pairs an automatic switchboard for one-hundred lines may readily be constructed, and such is the common practice for small exchanges of this size. It has also been found feasible to equip the finders and connectors with two sets of wipers and thus increase their capacity to two-hundred lines, which is the largest sized exchange heretofore built, so far as is known, using finder connector links of the stepby-step type.

In the range extending from about three-hum. dred lines to one-thousand lines it has been the practice to insert first selectors. A common arrangement is to use finders paired with the first selectors, and connectors arranged in groups accessible to the selectors, constituting what is commonly known as a one-thousand line system. This larger type of system is more expensive per line than the one-hundred line or two-hundred line system hereinbefore referred to, because it introduces an additional order of switches.

In view of the facts stated in the foregoing, it will be understood that the manufacturer is somewhat handicapped in selling automatic equipment for exchanges which are just a little too large for a simple finder connector link systerm. A system of the one-thousand line type has to be used, which results in a sudden rise in the cost per line, which although entirely justified by the equipment which has to be supplied,

ing equipment and by new and improved circuits which make it possible to use finders and connectors of much larger capacity than has heretofore been considered possible. In a representative system, such as will be described herein, the switching equipment comprisesfinder connector links, each finder and each connector having four sets of wipers, which gives them access to four-hundred lines. Thus a system is produced capable of giving service in an exchange of this size, and at the same time the necessity for providing first selectors is obviated. The system is arranged so that additional banks and wipers may readily be added to increase the capacity to six-hundred lines whenever the occasion should arise.

Further details of the system will be explained hereinafter in connection with the drawings, in the course of a full explanation of the equipment and circuits of which it is comprised.

Referring to the drawings, Figs. 1 to 5, inclusive, are circuit drawings which show the circuits which are necessary to enable the system to be explained; while Fig. 6 shows how the circuit drawings are put together. Of these circuit drawings, Fig. 1 shows a line circuit and a finder switch, Figs. 2 and 3 show a connector switch, while Figs. 4 and 5 show two allotters with the associated common start wires.

The general arrangement of the system will first be described briefly. There are four-hundred lines. The majority of these lines are subscribers lines, but a few of them may be trunk lines extending to another exchange. Each line is provided with a line circuit comprising two relays. Thus the line shown at the left of Fig. 1 comprising conductors |I and I02, is provided with line equipment consisting of relays I06 and I01. Relay I0! is a combined line and cut-off relay, while relay I06 is a lookout relay. From the line circuit conductors are extended to the multiple banks of the finder switches, There is also a branch for each line which extends to the banks of the connectors. Thus in the case of the line shown, the branch which extends to the connector banks comprises conductors I03, I04,

and I05.

All connections in the system are set up by means of finder connector links, each link comprising a finder switch and, a connector switch. These switches are of the well known Strowger vertical and rotary type. Each finder and each connector is provided with four sets of wipers so that it may have access to all four hundred lines of the system. There may be around thirty A, Fig. 4, as indicated by the cable, includingconlinks, more or less,

depending on the amount of factors which will be explained.

' provided for starting the finders. The lines are 'While the link circuits are allin one large group from thestandpoint of each line being able to serve all the linesin the system, these link circuits are nevertheless divided into two groups as regards the arrangements which are divided into groups A and B, the lines which have numbers in the even thousands constituting group A, and the lines which have numbers assigned inthe odd hundreds constituting group B. The finders'are divided into twocorrespond ing groups, the basis of the division being that the finders of group A normally servethe' lines in' groupA, while the finders in group B nor mally serve the linesin group B.; It will be understood, however, that. each finder has access ingroup B will be taken for use.

to all the lines, as stated hereinb efore, and if no finder in group A is available at the time that a line in that group makes acall, then a finder The same is true as regards lines in group B calling when no finders in the associated group are available.

The-starting of fin'ders is controlled by means oftwoallotters. Fig. e' showsallotter A which is'associated with the finders of group A, Fig. v

shows ,allotter B whichgis. associated with the finders of group BX? The finder switch which is shown in Fig. lis a-finder in group A, and consequently is accessible from the bank of allotter ductors 451, 458, etc. The allotter A may be a -point switch of the type which has a movemerit. in a forward "direction only. Only one set of contactsis shown, being the set of contacts whichisassigned to'the particular. finder which is'shown in Fig. l. The other sets of contacts are individual to and are wired tothe other finders of group A. Allotter B in Fig. 5 is similar to the allotter A, Fig. 4; Allotter B is associated with the finders of group B and the various sets of contacts in its bank are wired to the finders of that group, the same as the contact sets of allotter A are wired to' the finders of group A.

For each group of lines there are'ten common start .leadsq'lhe' common start leads for the I lines of group A are shown appropriately labeled at'the left of Fig; 4. 'There is one start lead for plained. l The individualstart lead for lines Ii to iii of the secondhundred and for lines H to H1 Q level of'the finder switches.

wires are accordingly numbered for convenience from 1 to 0. Each commonpstart lead is connected by way ofa resistance to a main start conductor M3, which extends to the allotter A.

each tens group of lines, corresponding to each Thecommon start Each line circuit is provided with an, individual startdead. The manner in which these individual start leads are connected will now be exof the fourthhundred are'connected to common start lead No. i of the A group, Fig. 4. The individual start leads 'for thelines 2| to 20 of the second and fourth hundreds' are connected I to common start lead No. 2, while the individual startleadsior lines ti. and of the second and fourth hundreds are connected to the common start lead No. 3, and so on. Thus it will be seen that as regards the line shown, which belongs to the fourth hundred, the individual start lead H5 is connected to the No. 3 common start lead.

The manner in which the other individual start wiresof group A are connected; upwill be clear from "the foregoing. As regards the individual start leads for the lines of group B, these are connected up tothe common start leads B shown in Fig. 5 in the same way that the connections are made in group A. V i a 1 The common start leads notonly function as a means 01 starting the finder switches through the medium of the allotters, but they also serve to mark the levels in the finder banks in which calling lines are located; Each finder switch is provided witha so-called vertical bank, the vertical bank of the finder switch, Fig. 1, being indicated at 28 'By reference to Figs. 1 and 4 it V will be seen that the energization of relay 4M 'associated'with the allotter A is effective to extend the common start leads I [to 9, inclusive, by

way of cable M4 to the vertical bank contacts'l to 9, respectively, of vertical bank 28. The cable 1 4i 4 is'common to all finders of group Aandthe conductors'thereof aremultipliedinto all the vertical banks such as 28 which are associated with such finders. 7

By reference to Fig. 5 it will be observed that relay 50! has the function of connecting all the common start leads of group B by way of cable.

414 to the vertical banks of the finders of group A. This relay SM is energized whenever a finder in group A is started up to ,find a calling line in group B. It should be pointed out also that there is a cable similar to cable 4I4 which extends to the vertical banksof the finders in group B. Relays .502 and 482, under control of allotter B, serve to connectthe common start leadsfof groups B and A to this cable. The conductors leading to the right from relay contacts of relays 402 and 502 are appropriately labeled to indicate the foregoing arrangement. a All of this will be more clearly understood from the detailed explana" tion of the operation of the system.

" The mechanical construction of the switchboard may be in accordance with the well known practice in the Strowger system, or it may be as disclosed in the copending application'of Mahoney, Serial No. 18,774, filed April 29, 1935.

The operation of the equipment in setting up Nil-I02, to another subscriber in the system whose number will be assumed to'be 3312. a

V 'Upon'removal of the receiver at station 4312, the subscribers talking equipment is' bridged across the line thereby closing a circuit over the a number'of representative connections will now, 7 be described. The first connection which will be considered is a call' from station 4312-, on line line conductors [OI-I02 for'the combined line 2' I and cut-off relay I01. "It will be observed that the three windings of relay I01 are connected across the line in series with the battery. Theupper winding of relay i0! is made of wire having high resistance, so that the relay is inefficient under these operatixg conditions and pulls up only part Way, closi ".g the contactsmarked' X and leaving the ,05%; of the other contacts unaltered.

V The closure of the upper contact X places battery potential through the middle winding of relay lflfl'on test contact 1 I8, thus marking the line as calling in thebanks of'the finders such as the finder shown in Fig. l. The closure of the lower 5 contact X places ground on the individual start wire II9.

Since the individual start wire H9 is connected to the No. 3 common start lead, Fig. 4, a circuit is completed which extends from the grounded common start lead by way of 410, M3, 428, and 425 to relay 404 of the allotter A, Fig. 4. Relay 404 accordingly energizes. At 422 relay 404 closes a circuit for relay 40I, and the latter relay upon operating connects all the common start leads by way of M4 to the vertical test banks of the finders in group A. Thus a ground is placed on the No. 3

, test contacts in these vertical test banks, including the No. 3 test contact in bank 28, Fig. 1.

The energization of relay 404 also opens the circuit of relay 405 at 42! and closes a circuit for relay 40'! at 420. Upon energizing, relay 401 closes a locking circuit for itself at 433. In addition, relay 401 closes a circuit for relay 409 at 434, and a circuit for relay 406 at 435. The latter circuit is to guard against release of relay 406 in the event that only one finder switch is available, as will be explained more fully later on. Relay 401 also shifts the circuit of wiper 450 at 430 for reasons to be presently explained, prepares the test circuit at 432 for test relay M0, and at 43I places ground on the wiper 45I. This latter operation grounds the individual start wire 456 extending to the finder shown in Fig. 1.

When the circuit of relay 409 is closed, this relay operates, at 431 prepares a locking circuit for relay M0, at 439 closes an impulsing circuit for the finder, Fig. 1, and at 438 attempts to close a circuit for relay 4| I. The contact engaged by spring 438, however, is weighted and upon the operation of relay 409 this contact is set into vibration with the result that the circuit to relay 4 is intermittently opened and closed. Relay 4II cannot operate under these conditions. As a matter of fact, this relay never does operate if the calling line is found in the normal manner. The function of relay 4II will be fully explained later on.

The efiect of grounding the individual start wire 456 is to operate the start relay I46 of the finder, Fig. 1.

Upon energizing, relay I46 prepares a circuit for rotary magnet I44 at I59, disconnects conductor I14 from the conductor 46I at I58, shifts the circuit of the guard wire 455 at I51 in order to prepare for energizing the stepping magnet 465 of the allotter, prepares a circuit for test relay I42 at I55, and at I56 closes circuits through the polarizing windings of test relays I4! and I42. These relays, however, do not operate at this time.

As already mentioned, the relay 409 of the allotter closes the impulsing circuit for the finder when it pulls up, so that the finder is started in its vertical movement by the time the so-called start relay I46 has pulled up. The circuit for the vertical magnet extends from ground by way of 448, 439, 436, 444, 454, and 459 to vertical magnet I45. On the closure of this circuit the vertical magnet of the finder energizes and advances all the sets of wipers into position opposite the first levels in their respective banks, at the same time shifting the off normal springs I60 and NH. It is understood that the vertical movement is in reality a horizontal movement in view of the way the switches are mounted, but it is thought that the explanation will be clearer if the familiar term vertical is retained. When the vertical magnet I45 energizes it also grounds conductor 460 at I5I, thereby operating the stepping relay 408 of the allotter. Upon energizing relay 408 opens the circuit of vertical magnet I45 at 436, whereupon the vertical magnet falls back and opens the circuit of relay 408. Relay 408 then falls back and again closes the circuit of vertical magnet I45, causing the magnet to advance the switch wipers another step. This operation in which the vertical magnet and relay 408 are alternately energized continues until upon the third step of the vertical magnet the vertical test wiper 29 arrives at the No. 3 test contact in the vertical bank 28.

The operation of stopping the vertical movement will now be explained. Upon the third step relay 408 of the allotter energizes by way of I5I and opens the vertical magnet circuit at 436. The vertical magnet accordingly falls back and breaks the circuit of relay 408 at I5I. Relay 408, however, does not fall back but remains held up over a circuit which extends from the grounded No. 3 test contact in the vertical bank 28 by way of 29, 458, 453, 440, upper winding of the test relay M0, 432, and winding of relay 408. Relay 4) energizes over the above circuit in series with relay 408, the latter relay holding up as stated prevents the circuit of the vertical magnet from again being closed.

Upon energizing, the test relay 4I0 locks itself at MI and also closes a circuit for relay M2. The

the initial energizing circuit of relay 40'! at 442, 7

but relay 40'! holds up over its locking contact 433. By opening contact 443 relay 4I0 prevents the energization of relay M I by way of the circuit previously closed at contact 438 of relay 409. At

444 relay 4I0 shifts the impulse or operating circuit from conductor 459 to conductor 462, thus accomplishing the changeover from vertical to rotary operation at the finder, Fig. 1. At 440, relay 4i0 grounds wiper 453 and also breaks the circuit which includes the upper winding of relay M0 and stepping relay 408. The latter relay now falls back in order to start the rotary movement of the finder switch, Fig. 1.

It will be understood now that all of the four sets of wipers with which the finder, Fig. l, is provided are standing opposite the third levels in their respective banks. Only two of these sets are connected up, however, because relay I40 has not been energized. The wiper sets which are connected up are the set which comprises test wiper I20 and line wipers I22 and I23, this set having access to lines in the second hundred, and the set comprising test wiper I26 and line wipers I28 and I129, this latter wiper set having access to lines in the fourth hundred. The calling line,

being a line in the fourth hundred, is accessible only to the latter set of wipers.

As mentioned hereinbefore, the rotary movement is started by the falling back of stepping relay 408, consequent upon the energization of test relay M0. The circuit for the rotary magnet extends from ground by way of 448, 439, 436, 444, 462, I59, I53, and I48 to the rotary magnet. I44. The rotary magnet controls the circuit of stepping relay 408 at I50 and consequently the stepping operation during the rotary movement is similar to that which takes place during the vertical movement. As the wipers are rotated step by step responsive to the operation of rotary magnet I44, the test wiper I20 searches for battery potential 40 V V is in calling condition. When relay 404 falls back on the test contacts in the third level of its bank,

and the test wiper I26 likewise tests for battery potential on the test contacts of the third level of its bank. 7 Test wiper I20 finds no battery potential, but as soon as test wiper l26 engages test contact I I8 of the calling line battery potential is found and a circuit is closed for energizing test'relay I4 I. Relay I4I operates over a circuit extending from'ground at the allotter, Fig. 4, by

Way of 440; 453, 458, upper winding of re1ayI4I,

wiper I26, H8, H3, and the middle winding of cut-01f relay I61 to battery,.this ci also'tofully energize relayl01.

By the 'energization of. relay 1, the. circuit 'ofrelease magnet I43 is opened at.I49, the rotary magnet cir'cuitis opened at I48, the relay locks rcuit servin itself at I 41, andat its two upper contacts the calling subscribers line is connectedthrough' to trunk conductors I10and I1I.- .The connecting through of the calling line to trunk conductors I10 and HI results in the energization ofline relay'204 of the connector, Fig. 2.

Upon energizing, relay 204 closes a circuit for the slow acting relay 206 at;234. Relay 206 accordingly energizes and at 238 places ground on holding' conductor I12. This operation comp-letes'a' I holding.circuitfor'relays MI and I01.

" When relay I01 pulls up in series with relay MI 7 7 of the finderit disconnects ground from the start 7 lead-I I9 at I I 4, and also disconnects its upper and lower-windings from the subscribers line at III start wire H9, relay 404lof'the-all otter falls back,

provided there is no other line in group A which it breaks the'cir'cuit of relay 40I which'falls back V also.

Returning now to theenergization of test relay I4I of the finder, when this relay pulls up it closes V at I48 a circuit which extends from the grounded impulse or operating conductor 462 byway of I59, I53, I48, I51, key 455, 450, and 430to the stepping magnet 465 of the allotter A, Fig. 4i Stepping magnet 465 accordingly energizes and opens its interrupter contact, thus breaking the circuit of relay 461. Relay 401 therefore falls back and'at 435 it removes ground from relay 406, but

. e g a the latter relay holds up over conductor 46 I. In

addition relay 401; breaks the circuit of relay 409 at 434,opens its own locking circuit; at 433, breaks I the circuit of start re1ay'I46 of the findertat 43l,

and at 430 alters the circuit which was formerly gtraced over wiper 450 to the stepping 'magnet 4 65 r so' that this circuit. includes the interrupter contact of the magnet. i This interrupter contact .being now'open, for-"magnet 465 is energized, the

foregoing shifting of the magnet circuit results in the opening of the circuit and the deenergizing of the magnet. 'When magnet465 deenergizes; the wipers of the allotter are advanced one step i'ntoassociation With'a set of contacts which is individual to the next finder, The allotter now proceeds to hunt for an idle finder under control of wiper 450. If the next finder is busy, there will begroundon the conductor corresponding to 455 and the stepping'magnet 465 will reoperate to advance thegwipers of theallotter into'association with the next finder, this operation con- ;tinuing until an idle finder is reached; It will be noted that relay 401 cannot pull up responsive to a new-call as long as the allotter is hunting for an idle finder, because the relay 401 will be short circuited by ground on contacts engaged by wiper 450.

When the circuit of relay 409 isbroken by the deenergization of relay 401, the said relay 409 will fall back andbreak the circuits of relays 410- and 4 I 2. These relays accordingly fall back also. In the finder switch, Fig. 1, when ground is removed from'conductor 456 by the falling back of relay 461 in the allotter, relay I46 falls back.

At I58 relay I46 preparesa circuit for release v magnet I43, and at I51 ground from the off' normal springs of'the finder is extended to guard wire'455, thereby maintaining'the finder in busy condition with respect to the allotter in Fig. 4. e The equipment is nowready for the calling subscriber at station 4312 to dial the'number'of the called station,-but before proceeding with this allotter and;

finder circuits will be completed. 7

I Referring to the allotter A, Fig. 4, it will be seen that relay 406 is normally energized over common conductor 46% This conductor is com-,

operation, the explanation of the Thus in the case; of the. link shown. in the drawings, the branch of conductor 46I for, that link 1 circuit may betraced byway of off normal spring.

I66, key K, and spring I58 of relay I46, to conductor I14. 7 Conductor 'II4 in turnunay be traced byway of O-NZ; Fig. 2, 249, 244, and 291 T l to ground. Due to thefact that the connection i '35 between conductors I14 and 46! includes the serially related contacts of relay I46 and the off normal contact I60 (also contacts of busy key K),- it will be appreciated that whenever the" link'circuit is in use the connection between these conductors will be broken. and the conductor 46I will no longer be grounded at thelink circuit shown. If there are other idle link circuits in 7 group A, however, conductor 46I will still remain groundedi It will be assumed-now that all of the links except one are busy, and that the remaining idle link circuitisthe one shown in the drawings." The allotter. A will have its wipers associated with Y this link circuit, due to the fact that the guard wires such as 455 of all the other link circuits will be grounded. If a call comes in now from one of the lines in group A, relay 404 will'oper-f f ate over conductor 4I3 as previously explained;

finder, Fig.1, is operated to connect with the 'callfollowed by. theenergization of relay 461. The

ing line in the manner described, and at the beginning of the operation the last ground. is re moved from conductor 46Iby the energization of" start relay Hi6. fRelay 466 in the allotter does not fall back, however, because it is held up tem'- porarily at contact 435 of relay 401. As soon as the finder completes its operation, ground is placed on guard wire 455 as previously explained,

and the stepping magneti lfitiis energized to break the circuit of'r'elay 401. This relay then falls.

backasfin the case previously described, but now it breaks the circuit of relay 406, since conductor 46I is no longer grounded. Relay 406 thereupon falls back and at 421 breaks the automatic hunt-' ing circuit of the allotter stepping magnet 465.

Since all the link circuits are now busy all of the guard wires 455will be grounded and unless the a circuit of 465 were opened the allotter would con? tinue to hunt indefinitely. In addition to the .25 'mon to all of the link circuits'and has a branch 1 at each line circuit which isnormally grounded.

foregoing relay 406 transfers the starting circuits, as will now be explained.

Assuming now that another line in group A makes a call, a circuit will be completed over the main start conductor M3 by way of 428 (relay 406 deenergized) 513, 529, 525, and relay 505 of the allotter B, Fig. 5. Relay 505 accordingly pulls up and controls the allotter B through the medium of relay 501 to start up an idle finder in group B. The finders in group B are just like the group A finder which is shown in Fig. 1, and the allotter B is like the allotter A, so that the ensuing operation need not further be described. It should be noted, however, that relay 505 of allotter B closes a circuit for relay 402 instead of MI. By the energization of relay 402 the common start leads of group A lines are connected to the vertical banks of the group B finders. This is obviously essential because the calling line is starting a finder of group B rather than a finder of group A.

The handling of a call from a line in group B will now be explained briefly. When the receiver is removed from a line in group B, ground is placed on one of the common start leads shown at the left of Fig. 5 thereby closing a circuit over the associated resistance and main start wire 5I3, to relay 504 of the allotter B. Relay 504 controls the allotter B through the medium of relay 501 in order to start up an idle finder switch of group B. It will be observed that relay 504 also closes a circuit for relay 502, by means of which the common start leads of group B are connected up in the vertical banks of the group B finders.

Assuming now that all of the finders of group B become busy, ground will be removed from the common conductor 56l, which corresponds to conductor 46I of Fig. 4, and as the last finder completes its operation, relay 501 of the allotter will fall back and permit the release of relay 506. Upon relay 506 deenergizing, the main start wire 5I3 is transferred by way of 528, 51I, 429, and 42I to relay 405 of allotter A. Accordingly, another call coming in from a line in group B will cause the energization of relay 405 of allotter A, which will start up a finder switch in group A. Relay 405 closes a circuit for relay 50I which connects the common start leads of group B into the vertical banks of the finders of group A.

Attention is directed to the fact that whenever a line in group B makes a call, the finder which isstarted up to connect with the calling line must undergo a wiper switching operation, since the finder wipers which are normally connected are .those which serve the lines of group A. This wiper switching operation is performed by a relay such as relay I40, Fig. 1. Assume, for instance, that a calling line of group B starts up a finder in group A by means of relay 405 of the allotter, Fig. 4. When relay 405 energizes it grounds wiper 452 at 423, thereby closing a circuit over conductor 451 of the finder in use to relay I 40 of such finder. In a similar manner when a line in group B makes a call and starts a finder in group B by means of relay 564 of the allotter B, relay 504 will connect ground at its contact 523 to the conductor 551 of the finder in use, and will energize the relay of such finder which corresponds to relay I40 of the finder shown in Fig. 1.

In case all of the links of both groups A and B are in use, a circuit is completed for placing a busy tone on all the subscribers lines so that any subscriber upon removing the receiver will hear the busy signal. When all the links are in use relays 406 and 506 will both be deenergized. If another call comes in now from group A a circuit will be completed over conductor M3 by way of 428, 513, 529, and 512, to relay 403. This relay accordingly energizes and applies a busy tone to all the subscribers lines which are not engaged in conversation. Of course, any line which is actually involved in a connection will have its relay such as I01 energized so that the associated line will be clear. A similar circuit to the foregoing may be traced by way of the main start wire 5I3 to relay 403 and is eliective in a similar manner if a call should be made from a line in group B.

It will be recalled now that when the operation of the allotter A was being described it was explained that relay 4!! tried to operate at the initiation of the vertical movement of the finder and also at the initiation of the rotary movement, but was prevented from so doing because of the special construction of the contacts engaged by springs 438 and 440, which introduce a delay in the response of relay 4H. In the ordinary operation of the system relay 4i I never operates because its first circuit is opened at 443 upon the completion of the vertical movement of the finder, and its second circuit is opened at 449 by the falling back of relay 4I2 upon the completion of the rotary movement of the finder. In the event that something should go wrong, however, which will prevent the start ing of a finder, or the completion of its vertical or rotary movement, relay 4II will energize. When relay 4 operates it'disconnects at 441 the common ground conductor 46I from relay 406, owns the impulsing circuit at 448, at 440 looks the relay 409 to the branch conductor 516 of the common ground conductor 56I associated with the allotter B, and at 448 also closes an alarm circuit to call the attention of the attendant to the fact that trouble has occurred. Also at 445 relay 4II closes a circuit for stepping magnet 465, which energizes and breaks the circuit of relay 401. Relay 401 falls back and alters the stepping circuit of magnet 465 to include its interrupter contact, so that the magnet deenergizes and advances the allotter one step. Relay 401 falling back also opens the circuit of relay 406. After 401 falls back relay 409 remains held up by 516 and 56I, as stated. In this manner the allotter A is held out of service, and at the same time by the deenergization of relay 406 the main start wire M3 is transferred to allotter B, so that calls from group A may be handled by finders of group B. If the group B finders should all become busy, then ground is removed from conductors 56I and 516 with the result that relays 409 and 4 are deenergized and subsequent calls will try to get through by way of allotter A. In the meantime the trouble will no doubt have been fixed. At any rate, the next call will get a different finder due to the fact that the allotter has been advanced.

The key K, Fig. 1, is a link busy key pro vided for the purpose of rendering the associated link circuit busy. When this key is operated it disconnects conductor I14 from the common ground conductor 46I, and at the same time it connects conductor I14 to the guard wire 455 so as to make the associated link circuit test busy in the bank of the allotter.

Key K2, Fig. 4, is a busy key for the allotter A. When this key is operated it opens the branch 516 of conductor 56I so as to drop back relay 409 if energized, and it disconnects the common line was extended by means of the finder, Fig. 1," to the. connector, Figs; 2 and 3, it was described An additional result of the energization of relay ground conductor 46I from relay-406 so. as to release this relay and transfer the main start Wire M3 to allotter B. 'The allotter B, Fig. 5, is providedwith a similar busy key K3.

Returning now to the point where the calling how the line relay 20 1 was energized, followed by the energization of relay 205 for the purpose of placing ground on the holding conductor H2.

' 2I4 at 278, and at 2'15 connects dial tone to the calling subscribers line. The latter operation gives the calling party an audible signal which notifies him that he can begin to dial the de-' sired station.

It will be assumed-however, that for some reason or other the calling subscriber fails to dial, and the operations which take place under this condition will be described. Fig. 2'of the drawings shows two cams 284 and Y285. These cams are mounted on a constantly rotating shaft,

and make about one revolution per minute. These cams and'the associated contact springs are common to all the link circuits. When relay 2l3 of the connector pulls up responsive to the seizure of the link,--it prepares a circuit for relay '205 at contact 282- as explained above, and if the subscriber fails to dial,cam 284-will presently close a circuit for relay 205, the circuit extending from ground by way of ONI, contacts controlled by, 237, 282, and upper Winding of relay 205' Upon energizing, relay 2ll5lccks itself at holding conductor I'IZ' by relay 206'.

231, and at 235 substitutes the ground which is associated with the springs of earn 285 for the ground which was formerly connected to the About one 1 minute later, cam 285 will operate-its associated contact springs, thereby inserting a booster battery. in the holding circuit including conductor I'l2 This operation raises the potential sufiicient to operate relay I05 in the subscribers line circuit. Upon energizing, relay I 96 locks itself across the line at contacts 58 and H0, disconnects the line conductor Ifilfrom the finderbank at I08, and disconnects the test V conductor I05 from relay I01 at I09, at the same time placing ground on this test conductor to "maintain the line busy.

subscribers line circuit to fall back also.

The opening of the line conductor Ii' causes the line relay 204 in the connector tofall back, followed by the deenergization of relays 206, 208, 2I3, H2, and

205. Relay 206 on falling back removes ground from the holding conductor H2, which permits relay I4I of the finder and relay IE2? of the MI upon deenergizing closes a circuit at I49 for the release magnet I43 of the finder. The operation of the release magnet restores the switch shaft to normal, andthe circuit of the magnet'is broken at off normal springs I50 when the shaft is completely restored.

It will be appreciated'th'at the purpose of the I arrangement described in the foregoing isto pre- 7 vent the link from'being tied up when it is not Upon energizing, relay Relay actually being usedin setting up a connection;-

The apparatus functions as described not only if:

a calling subscriber should delay dialling but also.

if the receiver should be accidentally displaced" from the hook; or if the line should be short cir cuited at any point. Any of these occurrences the link is very shortly freed an'dthe line is locked out by meansof the-associated relay l06.. "It will be'noted that the lockedrout' condition depends on the maintaining of a bridge across the line, so that whenever the trouble becomes clear the lock:

' will cause the link circuit'to be taken for usethe same as on a regular call, but if no dialling occurs;

out relay will automatically be released andthe line circuit will be restored to normal condition.-

' Attention is directed also to the fact that the 7 lower winding of relay 205,'Fig. 2, is connectedto' a conductor coming from the power panel whereit is connected to the individual fusealarm' ter-v minal for this particular link circuit. If the fuse whichis individual to the link circuit should be'.

come broken or blown out battery will be placed 7 on this conductor, resulting'in the energization of relay 205 over its lower'winding. If the link circuit is in use at-the time, the connection or partial connection will be released as described in the foregoing and the calling linewill be locked out,:

requiring the subscriber to replace his-receiver before he can call again. In any event, thelink is made busy at 235, where the guard wire 455.

Returning again to the point where the calling line was extended to the connector, Figs. 2'and-3',' it will be assumed that dialling begins; The num-f ber of the called station, it will be remembered," is

3312, and therefore the-first digit to be dialled is the digit 3. It will be assumed, however, that by some mischance the calling subscriber dials the digit 1 instead of the digit 3. This may happen by reason'of faulty manipulationof the dial.

A single impulseor interruption corresponding 7 to the digit 1 may also be produced by. an:a'cc'i= ground is applied to dental momentarydepression of theswitchh'ool'g;

When the single interruption corresponding to;

I the digit 1 occurs, the line relay 204 of the con-' nector, Fig. 2, falls back momentarily." Relay 206- 'is slow to release and remains operateddurifig the momentary interruption of its circuit:"Wh'en I relay 204 falls back it trans'mitsan impulse'over' a circuit which extends from ground by way of 234, 222, 24], 253, 258, and 2l0'to the vertical Responsive to this impulse; the-- magnet 2 I4.

vertical magnet 2M operates and advances the shaft of the connector one step. When the shaft moves off normaLthe various ofinormal springs are shifted, including 0N4, but relay 2I3 remains locked up by way of 245,'259,and 219. Themovement of the switch shaft also brings the vertical wiper 329, Fig.3, into engagement with the first contact in the vertical bank 328.

energized in parallel with the vertical 'magnet.-' Shortly after the vertical magnet has operated..- relay 302 falls back and closesa circuit for the connector release magnet 2I5, the circuit extend ing from ground by way of 246, 3I3, 258, 299;

Relay 302 is .65 1 wiper 329, andcontact engaged thereby, and 0N2 (no-w shifted), to the release'magnet 2I6'. 'Re-J sponsiveto the closure'of the above circuit the release magnet energizes and restores the switch shaft to normal. It will be noted that when the release magnet 2I5 energizes it breaks its own operating circuit at 299. These springs do not open, however, until the armature is nearly operated and do not prevent the effective operation of the release magnet, because only a momentary energization of the magnet is required to disengage the usual double-dog of the switch and lock it under the release link. This construction is well known and need not be further explained.

It will be seen from the foregoing that if the first digit dialled is the digit 1, the only result is to operate and then immediately release the switch, thus absorbing or cancelling the digit.

It will be assumed now that the dialling of the called number proceeds in the proper manner, the first digit dialled being the digit 3. When the digit 3 is dialled three momentary interruptions are produced in the circuit of the line relay 204, and this relay accordingly falls back momentarily three times, transmitting three impulses over the previously traced circuit to verticalmagnet 214 and relay 302 in parallel. Vertical magnet 214 operates three times and advances the switch shaft three steps. The vertical wiper'329 is thus positioned on the third contact in the vertical bank 328. Relay 302 is slow acting and holds up during the series of impulses.

When the series of impulses is finished, relay 302 very shortly deenergizes and completes a circuit for wiper selecting relay 303. This circuit extends from ground by way of 246, 313, 258, 29-9, and wiper 329 and contact engaged thereby, to relay 303. Upon energizing, relay 303 looks itself at 324, and at 348 closes a circuit for the release magnet 215. The release magnet circuit extends from ground by way of 246, 313, 258, 348, and 0N2 to the release magnet 215. Responsive to the closure of the foregoing circuit, release magnet 215 operates and disconnects wiper 329 at 299. Also at 290 the release magnet closes a circuit for off normal relay 210 which extends from ground by way of 246. 353, 258, 299,345, (relay 303 being now energized), upper winding of relay 210, and winding of release magnet 215 to battery. Relay 210 cannot operate over the above circuit just at this time because the winding of the relay is short circuit-ed by ground on the operating circuit which was formerly traced to the release magnet by way of 0N2. However, an instant later the switch shaft will be restored due to the operation of the release magnet and the off normal springs 0N2 will be shifted back to normal position, opening the operating circuit for the release magnet 215. This removes the short circuit from ,the upper winding of relay 210 and this relay accordingly operates over the circuit traced. Upon energizing, relay 210 looks itself at 261, and at 253 breaks the circuit which includes its upper winding and the-release magnet 215, thus permitting the release magnet to deenergize. The energization of relay 210 opens the dial tone circuit at 251, and also alters some other circuits which will be explained later.

It will be seen as a result of dialling the first digit 3 of the called number the connector switch is operated to the third level and immediately released again. Moreover, the operation of the switch results in the energization of the wiper selecting relay 303, which remains locked up after the switch releases. The energization of relay 303 selects and connects up the set of wipers which comprises test wiper 331 and the two line wipers 334 and 335. This set of wipers has access to lines in the third hundred, one of which is the line of the called subscriber.

The calling subscriber may now dial the next digit of the called number, which is also the digit 3. Accordingly the line relay 204 falls back momentarily three times, and at 234 again delivers three impulses to the vertical magnet 214 and to the slow acting relay 302 in parallel. The verti cal magnet 214 advances the switch shaft three steps as before. Relay 302 energizes in parallel with the vertical magnet and holds up during the series of impulses. At the first step of theswitch shaft the off normal springs are shifted, and the shifting of 0N4 opens the initial energizing circuit of relay 213. The previously described looking circuit for relay 213 is now open at 253, due to relay 210 having energized, but relay 213 holds up for the time being over another locking circuit which extends from ground by way of 246, 313, and 2'59 to relay 213. At the end of the series of impulses the slow acting relay 302 falls back in due time. The deenergization of this relay does not now ground the vertical wiper 329 nor close the circuit of the release magnet 215, because contact 258 of relay 210 is now open. However,

the falling back of relay 302 does break the circuit of relay 213, permitting this relay to deenergize. Upon deenergizing, relay 213 breaks the circuit of relay 212, which falls back also. The only result of the deenergization of relays 213 and 212, which needs to be noted at this time, is the transfer of the impulsing circuit at 218 of relay 212 from the vertical magnet 214 to the rotary magnet 343.

The calling subscriber may now dial the next digit of the called number, which is the digit 1. The line relay 204 therefore falls back once momentarily and transmits an impulse to the rotary magnet 343 in parallel with the slow-acting relay 302. The rotary magnet responds to this impulse and rotates the switch shaft and wipers one step, so that the various sets of wipers are brought into engagement with the first contacts of the third levels of their respective banks. Relay 302 operates in parallel with the rotary magnet 343. Relay 212 being now deenergized, when relay 302 operates it closes a circuit for the slow acting relay 305, said circuit extending from ground by way of 240, 313, 200, and 2'1'1 to relay 305. Upon energizing, relay 305 closes a circuit for relay 306 which extends from ground by way of 240, 280, 261, winding of relay 305, and 316 to relay 305.

Relay 300 cannot energize over this circuit because it is short circuited for the time being by the previously described to ground for energizing relay 305.

Upon energizing, relay 305 looks itself at 322 and also breaks the circuit of relay 305, which accordingly deenergizes. In addition to the foregoing, at 323 relay 300 transfers the impulsing circuit from the rotary magnet 343 of the connector to the stepping magnet 32! of the minor switch.

Summing up the operations which have taken place so far, as a result of the dialling of the first three digits, 3, 3, and 1, a particular set of wipers in the connector has been selectedand these wipers have been operated first by the vertical magnet 212 and then by the rotary magnet 34-3 and thereby brought into engagement with the terminals of the called line. The wiper set selected is the set comprising wipers 331, 334, and 335. By the operations referred to, this wiper set is now in engagement with the terminal set to which test conductor 353 and line conductors 35 i and 355 of the called line are connected. Although the called line has been selected the line is not tested at this time, as the testing operation 8 isdeferred until after the operation of the minor switch has been completed.

The calling subscriber now dials the last digit of the called number, which is the digit 2. Ac-

' Wiper 33 l V cordingly, the line relay 204will fall back twice 'momentarily and will transmit two impulses to stepping magnet 321 of the minor switch in parallel with the slow actingrelay 302. Responsive to these impulses, stepping mag-net 321 will advance the wipers 350, 35|, and 352 of the minor switch two steps, so that each wiper engages the second contact in its associated bank. Relay 302 operates in parallel with the stepping magnet 321 'andupon energizing closes a circuit for relay 305.

Relay 305 accordingly energizes also. At the end of the series of impul'seswhich operates the step--.

ping magnet 321, slow acting relay 302 falls back and thereby'connects test relay 209 to the test The test circuit may be traced from the test contact towhich test conductor 353 of the .calledline is connected, by way of test wiper33 contacts of relays 304 and 303, wiper 352 of the 'minor switch, 3|4, 3|8,"(re1ay 305 being still energizedhwinding of test relay 209, to battery.

Relay 209 accordingly tests the called line for the presence or absence of ground potential on its associated test contacts.

" Assuming that the called line is busy, there a will be a ground potential on the test contact with which wiper 33l'is-in engagement and test relay 209 will energize. Shortly after this occurs, the slow acting relay 305 will fall back, as

a the deenergization of relays 200 and 208.

latter'relay opens holding circuits for the various and contacts controlled by 3|8, "to relay 209.

its circuit was broken by the deenergization of relay 302. -When relay 305 'deenergizesj a looking circuit is completed for the test relay 209 which" extends from ground by Way of 202, 256, In energized position, relay 200 opens the impulsing circuit at 253 and closes the busy signalling circuit at 250. The latter operation gives the calling subscriber an audible busy signal to notify him that the called line is busy. 4

On finding the called line busy, the calling subscriber will hang up his receiver. This results in the deenergization of line relay 204, followed by The other relays in-the connector that have been energized and relay 206 takes ground off the holding conductor |1'2. Asa result of the ungrounding of conductor I12 relays Ml and l? are deenergized. The switches are released by their respective release magnets in the well understood manner. The circuit of the release magnet of the'connector may be traced from groundby way of 291, 244, 240, and 0N2 to'the'co'nnector release magnet 2|5. 'In parallel with the release magnet 2| 5 is 'therelease magnet .344 of the minor switch, the circuit of which extends from ground by way of 231, 244, 249, and the minor switch off normal springs MSQN to release mag- As soon as the connector is restored by.

" impulses which operated the minor switch, it will beassumed that the called line is idle.

Under these circumstances there will be no groundon the test contact engaged by test wiper 33| and test relay 209 will not pull up. Shortly after relay 302 falls back the slow acting relay 305-will fall back, and now since the test relay 209 is not energized a circuit will be. completed for the switching relay 2| ground by way of 262,258,255, lower winding of relay 2| 3! 0, 3|4, 352, contacts of relays 303 and 304, relay 303 being energized, test wiper 33| and contact engaged thereby, test conductor 353 and the winding of the cut-01f relay of the called line to battery. 'The line circuit of the called line is This circuit extends from;

not shown in the drawings but is similar to the line circuit which is shown in Fig. 1. On the closure of the above circuit the switching relay 2| of the connector and the cut-off relay of the called line operate in series, the operation of thelatter relay serving to clear the called line in the usual manner. V

When relay 2|| energizes'itlocks'itself at'212.

Relay 2 also cuts in the upper winding of line' relay 204 at 233, and at 261 opens the circuit of relay 306. Since the minor switch has. beenadvanced only two steps, relay 306 has no circuit' through wiper |,and therefore it dee-nergizes. Relay 2| l also closes'points in'the talking circuit at 264 and 265, and at 2.10 closes a circuit for the piok up relay 30! in order to start the ringing operation. The latter circuit extends 'from ground by way of 298, 210, contacts'controlled by 3|2, 281, and interrupter contacts of ro'tary magnet 343, to relay '30l. locks itself at 3|2,

The results of the energization of relay 30| are the closure of the ringing circuit at 301 and'308,

and the closing of'a circuit at 309. for transmitting ring back tone tothe calling subscriber.

Relay 30| energizes and V The ringing circuit may be traced from ground by way of generator GEN, interrupter I, ringing conductor label-ed FREQ.2, wiper 350 of the minor switches, 32| 308, 215, 265, 22 and contacts of relays'303 and 304 to'line wiper 335. Fromthis point the circuit extends out overconductor355 of the called line and to ground orto the other side of the line, depending on how' the ringer at the called station is connected. is bridged across the line, the return path, of the,

If the ringer ringer current will be by way. of the other line conductor 352, line wiper 334, contacts ofv relays 304 and 303, 220, 264, 214, 301, 320, and lower winding of ring cut-off relay 2|3 to battery andground.

When the called subscriber removes his 're ceiver, relay 2| 3 pulls up in the usual mannerand locks itself at 219. Relay 2| is now energized for relay 2|2 at 283. Upon energizing,re'lay 2|2 so that this locking circuit can'be established by way of ground, 246, 266, and 219. At 20|fre1ay 2|3 breaks the circuit of relay 30!, and the latter relay falls back. Relay2|3 also closes a circuit completes the'talking. circuit at 214 and 215.

The talking .circuit is shown in heavy. lines and need not be. traced in detail. Upon the closure of the talking circuit the back bridge relay 203:

Upon energizing will pull up overthe called line.

relay 203 reverses the direction of current flow 7 in the'calling lineat 23|-and 232.. Thisisa standard operation which is introduced in order to give supervision to an operater if the calling line is a trunk from an operators position. In the connection under discussion the, reversal of current has no particular function. V

The required connection having been established; the calling and called. subscribers may converse as desired. 7 When the conversation is 7 5-1 7 finished, the subscribers will replace their receivers. The release of the connection is controlled by the hanging up of the receiver at the calling station, which causes line relay 204 to fall back. This breaks the circuit of relay 200 which falls back and breaks the circuit of relay 208. The connection is accordingly released in the manner previously described.

In the foregoing explanation it was not specified if the called line was an individual line or a party line. The fact is that it could be either, as the operation is the same. This means that individual and party lines may be arranged indiscriminately, and have similar four digit numbers assigned. In case of an individual line the last digit, of course, would preferably be assigned in .accordance with the frequency of ringing current which is used to ring the individual lines, this being usually the No. 2 frequency. In case of-party lines the last digit of the number determines the ringing current or party selection. There may be as many as ten stations on a party line. At five of the stations the ringers would be connected between one side of the line and ground, while at the other five stations the ringers would be connected between the other side of the line and ground. In accordance with this arrangement, the circuit of relay 305 is arranged so that when the switching relay 2|! pulls up relay 306 will drop back if wiper 35I of the minor switch is standing on any position from 1 to 5, inclusive. Thus the ringing current frequency selected by the wiper 350 is projected out over the lower side of the subscribers line. However, if wiper 35I has been positioned on any contact from 6 to 0, inclusive, relay 305 will hold up by way of said wiper 35I after the relay 2|I has energized, with the result that the ringing circuit. connections to the line are reversed at 320 and 32I,. so that ringing current is projected out over the other side of the line.

The lines of the fourth and fifth hundreds are called in the same way as the lines in the third hundred, except, of course, that a different set of wipers is selected at the connector in use. In selecting a line in the fourth hundred the first digit dialled is the digit 4 and it follows that the vertical wiper 329 will be set on the fourth contact in its bank when the first digit is dialled, resulting in the energization of relay 304 instead of relay 303. The operation of relay 304 connects up the set of wipers which comprises test wiper 336 and line wipers 338 and 339. In calling a line in the fifth hundred, the first digit dialled will be the digit 5. Since the vertical wiper 329 is set on the fifth contact in its bank responsive to this digit, both relays 303 and 304 will be energized. By the operation of both these relays simultaneously the set of wipers which comprises test wiper 33? and line wipers 340 and MI is connected up. Otherwise the operations are the same as the operations which have already been described. The lines in the second hundred are called by means of the normally connected set 'of wipers which comprises test wiper 330 and Before taking up the establishment of trunk connections an additional feature of the regular exchange operation will be described. This featureis the handling of revertive calls on party lines. A revertive call is a call from one subscriber on a party line to another subscriber on the same line, and is made by dialling the regular directory number of the called subscriber. In order to explain the operations which take place in this type of call it will be assumed that the subscriber at station 4312, Fig. l, desires to call the subscriber at station 4317 on the same line.

In order to establish the above connection, the subscriber at station 4312 will remove his receiver and dial the number of the called station. The removal of the receiver takes an idle link into use and the finder thereof connects with the calling line. The subscriber then dials the four digits of the called number and the connector of the link is operated the same as has been previously described. Assuming that the link which is used is the one shown in the drawings, relay 304 of the connector, Fi s. 2 and 3, will be operated so as to select the set of wipers comprising 330, 338, and 339, which are then positioned on the first set of contacts in the third level of their associated banks. This set'of bank contacts is the set to which normal conductors I05, I03, and I04, extending back to the line circuit, Fig. l, are connected. It will be noted also that the minor switch is operated responsive to the last digit to position its various wipers on the seventh contacts in their respective banks. Aside from these differences, the operation of the connector is the same as it was before.

Taking up the detailed description at this point, when relay 302 falls back at the end of the impulses for the last digit, a circuit is completed over which the test relay 209 is connected to the test wiper 336, which is now in engagement with the test contact of the called line;

Since the called line is also the calling line, there will be a ground potential on conductor I05 and the test relay 209 will pull up. Relay 209 remains locked up after relay 305 falls back and at 250 connects a busy tone to the calling line. So far, therefore, the operation corresponds to the normal operation in calling a busy line.

In this case, however, the calling subscriber expects to hear the busy signal, as he knows that he is calling another subscriber on his own line, so he merely replaces his receiver for a short interval, long enough to signal the called party. When the receiver is hung up at the calling station, the line relay 204 falls back and breaks the circuit of the slow acting relay 200. Line relay 204 also places ground on the test wiper 336 in order to provide a holding circuit for maintaining the connection after relay 206 falls back, this holding circuit extending from ground by way of 234, 222, 241, 253, (busy relay 209 being now energized), wiper 352, contacts of relays 303 and 300, test wiper 333, conductor I05, I09, Fig. 1, H3, H3, wiper I26, I41, and I52 to holding conductor H2. Ground on the holding conductor I'IZ will hold up relays-MI and I01, Fig. 1. Also a branch may be traced from conductor I12 by way of 223, 243, and 248 to relay 208, which serves to hold up relay 208 after relay 206 has deenergized. When relay 206 falls back, it closes a circuit for relay 202 at 238, said circuit including the contacts 254 of the now energized busy relay 209. Upon energizing, relay 202 locks itself at 229.

Relay 202 also disconnects ground fromline relay 204 at. 225, and opens the trunk "conductors [l and ill at 2267and'221, Finally, at 230 relay 202 closes a, circuit for relay 2]],

which energ'izes'and locks itself ati 212. Relay 2|.| uponenergizing .breaksone circuit of relay 300 at 26], but relay 3065holds"up,over another circuit including wiper 35| of the minor switch,

7 1 now settingjon its seventh contact. Relay 2 also closes at'2l0 a circuit forrelay 30|, which looks itself at. 3|2 and completes the ringing circuit' in the manner formerly described.

The bell at thecalled station now begins to ring intermittently in the usual manner. Aftera short interval the calling subscriber :will again remove his're'ceiver, and the'called'subscriber will also take off his receiverin orderto answer the call.

Abridge is accordingly'placed across theiline which operates the ring' cut-off relay 2|3. f Relay 2|3 locks itself at 219, breaks the circuit of relay 306 'at 280, and breaks'the circuit of relay '30] i at 28L Relays 306 and 30| accordingly fall back.'

7 Relay 2|3 alsojcloses the circuit of relay 2l2,

raga-inst the'deenergization of relay 208. 731i 7 circuits at 244, and at 286 places a shunt around {which accordinglyenergizes and closes the heavy talking conductors at-214 and, 215. ,Thislatter operation connects up the back bridge relay 203, which energizes over the line circuit through the connector wipers, feeding current for the transmittersat the calling and called stations; Upon energizing, relay 203 closes a circuit for relay 20'! Vat-233., Relay 20! operates when its circuit is closed'andilocks itself at 24l.

v At 240 and 242 relay 20'! supplies holding ground for various energized relaysin the connecton thus providing For a similar reason relay 20'! opens the release magnet contact 241 of relay 208. This latter is to main- 'tain ground on the testwipen The circuit of which controls relay 201. a a

The calling and called subscribers may now continued energization of back bridge relay 203,

' converse, and'when't hey get through theyfwill both replace their receivers.

:'- may beanynumber of trunksin the'g'roup up to 7 w This brings about the deenergization of back bridge relay 203. Relay, 203 falling back breaks the circuit of relay 201. .When relay. 20.1 deenergizes, the link cir-' cuit is released invthe' manner previously explained; I a

' The operations'involved in making certain'represen ative trunk. calls will .now be explained.

It will be assumed. that the exchange being described is connected with a distantmanual .exchangeover a groupof ring downtrunks. There asmany as ten. ,It will be assumed, however,

" that'the' group comprises five trunks which are terminated in the first five sets'of contacts in the third level of the second hundred. These trunks are therefore accessible to the Wiper set compris ing test wiper 330'and line' wipersl332 and 333.

" cult similar to 'the 'line' circuit shown in Fi 1,

andat the manual exchange may terminate in a. 'jack and drop, or similar well known ring down 'signallingequipment. From the location of the trunks in the connectorbanks' as explained,'t'he line selecting digits assigned will be 2, 3; and 1.

Adding" the digit 1 to operate the minor switch,

Assuming: that'the. subscriber at station, 4312 the complete number of the trunkgroup will be explained. Assuming that the link shownin the l drawingsis the one-which handles the call, the

finder, Fig. 1, will connect with the callinglline and extendit to the connector, Figs. 2 and 3.

The line relay 204 'willtherefore energizejfol lowed by the energization of "relays 206,, 208, 2|3,

and H2, all as previously explained.

1 The calling subscriber will now start to dial, the first signal dialled beingthe digit 2. Line relay 204 therefore fallsgback twice momentarily and sends/two impulses to the vertical magnet,

2|4 and to? the slow acting relay 302 in parallel;

therewith. Responsive tothese impulses, the r 1 vertical magnet advances the'switch shaft two steps, thereby bringing the vertical wiper 329.

into engagement with thesecond contact'in its bank. The slow'acting relay 302 holds'up during the impulses and .falls back after the. impulses.

Upon deenergizing, relay 302 closes a circult for relay 2|| by way of 246, 3|3, 258, 299,- 'wiper 329 and contact engaged thereby and" cease.

upper Winding of relay 2| I to battery.,, Upon energizing, relay '2|| locks itself, at 212. In;

addition, relay 2| closes-a circuit for the releasev magnet 2|5, this circuit extending from ground by way of 246, 3|3,j258, 2'13, and off normal con-: tact ON 2, to the release magnet 21 5. Upon energizing, the release magnet 2|5 restores the switch shaft in the usual manner. 'Also the 2 release magnet closes a circuit for operating relayg2l0,

which, extends from ground by wayof'246, 3| 3 2 58, 2 99, 2', upper winding of 2| 0, and release.

the locking circuit of relay 2| at 260, and breaks and release magnet 2|5 deenergize.

magnet2|5 to battery. Relay 2|;0 'operatesin" the above circuit as, soon asthe off normal'springs 0N2 shift back on the restoration of the shaft and locks itself at 26!. Relay 2| 0' also'breaks the circuit'including its own upper windingand the release magnet at258. lAccordi'ngly relay 2|i| It will be seen that as a result of the dialling 2 of the digit 2 the connector switch hasbeen g'" operated and released and that the ofi normal relay 2| D'has beenenergized and locked up. :It

will be appreciated that this has been *accom plished without energizing either of the wiper selecting relays 303. and 304. The. connector therefore now has access to all linesin the second;

hundred, whichare reached by Way of the nor-i mally connected set of wipers.

The calling subscriber may now dialithe next d git 3.: As a result, t switch shaft '7 vanced three steps by means, of the vertical magnet 2|4. At'the end of thisoperationjrelay 2|3 'is deenergized in, the mannerpreviously exef' plained, followed by the d-eenergization of relay 2|2; Thus the impulsing circuit is transferredto the rotary magnet 343. J 1 The first trunk of the group is indicated in'lthe V drawings, Fig. 3, and comprises conductors 350," 35-|,- and 352. Each trunk may have a line cirthird level of their respective banks.

Relay 3oz:

of course is operated in parallel withthe rotary I magnet 343 and operates relay 305, which'in turn,

bringsabout the energization of'relay 306 in the. manner previously explained. 'Relay' 306 trans;

fers the impulsing circuit to the stepping magnet 32'! of the minor switch.

The calling subscriber may now dial the last digit of the number, which is also the digit 1. From this point on somewhat different operations are involved, and the explanation will be given more in detail. Responsive to the dialling of the digit 1, relay 204 falls back once and sends one impulse to the stepping magnet 32'! and slow acting relay 302 inparallel, the stepping magnet 321 operating to advance the wipers of the minor switch one step. Relay 302 operates and closes a circuit for relay 305, which operates also. After the impulse ceases, relay 302 falls back and closes the usual test circuit, which in this case extends from the test wiper 330 by way of normally closed contacts of, relays 304 and'303, wiper 352 of the minor switch, 3M and 3l8, to test relay 209. Assuming now that the first trunk line is busy, conductor 350 will be grounded, test wiper 330 will encounter ground potential, and the busy relay 209 will energize. Upon energizing, relay 209 closes a circuit for relay 30l, which will now operate as a stepping relay for the rotary magnet 343. The circuit of relay 30I extends from ground by way of 349, 341, rotary control bank 26, the first pin in the third level, now engaged by wiper 326, wiper 326, 3", 254, contacts controlled by 3l2, 28l, interrupter contact of rotary magnet 343, and winding of relay 30! to battery. Upon the closure of the above circuit by the busy relay, relay 30I operates and closes a circuit for the rotary magnet 343 at 3. Relay 30! also closes a circuit for slow-acting relay 305 at 3l0, thus maintaining this relay energized in order to maintain the busy relay 209 connected to the test wiper. On the closure of its circuit by relay 30!, the rotary magnet 343 operates and rotates the connector wipers one step, at the same time opening the circuit of relay 30L Relay 30l accordingly falls back and breaks the circuit of. the rotary magnet. If the second trunk of the group is busy also the busy relay 209 will remain energized and the operation will continue, relay 30I and'the rotary magnet 343 operating alternately, the latter rotating the wipers step by step in search of an idle trunk line.

When an idle trunk line is found, relay 209 will fall back due to the absence of ground on the test contact engaged by wiper 330 and the circuit of relay 30l will be broken. This relay therefore cannot again energize and the rotation will cease. Slow-acting relay 305 falls back, as it will receive no more impulses from relay 3M, and the usual circuit is therefore completed for relay 2| 1. Relay 21 I now pulls up in series with the cut-off relay of the selected trunk line. The remaining operations, including the transmission of. ringing current over the trunk line, are the same as have been previously explained.

Some additional explanation will now be made in respect of the rotary control bank. This bank and the associated wiper 326 have been neglected so far because in any connection involving the operation of either relay 303 or relay 304 the ground connection to the rotary control bank is broken and the wiper 326 consequently can have no function. The rotary control bank therefore is in use only when a line in the second hundred is being called, or when the normally connected set of wipers is being used. The circuit drawing, Fig. 3, shows only the third level of this bank, as this is the level in which the group of trunks to the manual exchange is terminated. There being five trunks in this group, terminated in contacts I to 5 of the third level, as stated, there will be four pins inserted at positions 1 to 4, inclusive, of the third level of the rotary control bank, as indicated in the drawings. Wiper 326 therefore can maintain the circuit to the stepping relay 301 through successive pins as long as busy trunk lines are encountered and the busy relay 209 is held up. The fifth pin, corresponding to the last trunk line of the group, is omitted, so that when the wipers are advanced to the fifth set of contacts wiper 326 will find no pin to engage and the circuit of relay 30| will be broken, whether the fifth trunk line is busy or not. If the fifth trunk line is busy, relay 209 will hold up and will lock itself when relay 305 falls back, and the busy signal will be transmitted to the calling party in the usual manner.

In addition to the ring down trunks extend ing to the manual exchange, there may bevarious other groups of trunk lines, including a group of dial trunks extending to an automatic exchange. The operations involved in setting up a connection to an automatic exchange will therefore be described. It will be assumed that there is a group of five one way dialling trunks terminating in the first five contact sets of the ninth level of the banks of the second hundred. That is, these trunks terminate in the ninth level of the banks which are associated with the normally connected set of wipers comprising wipers 330, 332, and 333. These trunk lines differ from the ring down trunks in that they do not have line circuits such as is shown in Fig. 1, but the three trunk conductors of each trunk line extend directly from the connector banks to a. standard two-wire repeater. There will be accordingly five repeaters associated with the five trunk lines, respectively, and from the outgoing side of each repeater there will be a two conductor trunk line extending to the automatic exchange. At the automatic exchange these trunk lines may terminate in line switches or incoming selectors. Since the group of trunk lines terminates in the ninth level of the connector banks, and occupies the first five contact sets in that level, the number assigned to the group is the number 91.

Assuming now that the subscriber at station 4312 desires to extend a call to the distant automatic exchange, he will remove his receiver, whereupon an idle link circuit is taken for use. Assuming that the link circuit shown in the drawings is the one which is taken for use, the finder, Fig. 1, will connect with the calling line and extend it to the connector, Figs. 2 and 3. The connector line relay 204 and other relays will pull up responsive to the call in the manner previously described.

The calling subscriber will now dial the first digit of the number, which is the digit 9. The

line relay 204 accordingly falls back momentarily nine times and sends nine impulses to the vertical magnet 214 and the slow acting relay 302 in parallel. The vertical magnet 2I4 steps the connector shaft nine steps, advancing the various sets of wipers carried by the shaft until they stand opposite the ninth levels of their respective banks. The vertical wiper 329 is positioned in engagement with the ninth contact in the vertical bank 328.

Also the shaft springs 354 and 355 are operated,

throughout the series of impulses, falling'back after the impulses cease. On deenergizing, relay 302 closes a circuit'for the normal relay 2I0 which maybe traced from ground by way of 246,

313, 258, 299, vertical wiperf329andthe ninth contact engagedthereby; and thence through the V 'lowerwinding' of relay 2I0 to battery. Upon energizing, relay 2 I locks itself at 26 i1. additionsrelay 210 performs its usual-functions, It

1 cordingly fallsbackand permits relay 2l2'to dedigitof the numbeniwhich is the digit 1." V Accordenergize. Relay 2l2 transfers the irhpulsing chedit from thevertical magnet 214 tothe rotary,

magnet343. v I

-; The calling. subscriber may now dial thesecond ingly the line relay 204' falls back once rnomentarily and transmits an. impulse to the rotary magnet 343 in parallel with the slow-acting relay 302. The rotary magnet 343 responds byrotatmg the switch shaft one step, bringing the wipers 330, 332, and 333 into engagement with the first i trunkiline of=the group. Relay 302 operates in I 7 parallel with the rotary magnet 343, and now since relay 212 has fallen back a circuit is completed for slow acting relay 305, which operates also. "Upon energizingrelay 305' closes at 319 a ci'rcuitfor the lower winding'o-f switching relay 20!, the circuit extending from-ground byway of 349, 341, 355,

3 I 9, and the lower winding of relay 20 Lto battery; I

The'lowerwinding of relay 20! is an'inefiicient winding and consequently the relay operates only 7 far enough to close its contact marked X. The

V f closure of, contactX completes a circuit for the 7 upper winding of'relay 20l' which extends from ingot relay 20! is shortcircuited over the previously traced circuit for the lower winding and consequently. the relay remains only partly enground byway of 262,256, contact X, and the upperand lower windings of relay 20! in series to battery. It will be seen that the upper windergizedforthe'timebeing. r V

'Shortlyafter the ic'e'ssation of the impulse to the rotary magnet 343'; the slowacting relay 302 1 will fall back, ahdftherebyiacircuit is closed for connecting thebusy relay1209:to-the .test wiper 330; This circuit may be traced from test' wiper 330 by way of normally closed contacts of relays 3'04 and 303 to the minor. switch bank associated 'with wiper 352. Fromthis. point the circuit is completed-byway of 355, 346, 354, 3l4, 'and 3l8. toithe busy relay209 If the first trunk line of the group. is busy, relay209 will energize because ofthe groun'dion thecontact engaged by wiper 330Qcl'osing a' circuit for'relay 30l. In ex- '65 r-upt'er contacts of the rotary magnet343 to relay Relay 30! operates as formerly described, closilingfa circuitfor therotary rnagnet at' 3 H, and

3 "'.alsoclosing;ajcircuitfonthe slow acting relay planation 'of this circuit it should be stated that ground by -way of 349,- 341, rotary control bank 25, first piniof the ninth level, wiper 326,3",

254, contactscontrolled by 3l2, 28L and inter- 305 at'3l0i The switch wipers are accordingly rotated step by step until "an idle trunk.-line is s found, whereupon busy relay 209 will-fall back;

. breaking thecircuitof relay '30! at 254," and'the rotation i theswitchl will cease Relay'305now fans backalso; since it no longer? receives im- Upon deenergizing, v repulses from relay 30 l lay 305 'breaks'the circuit-of the lower winding of a relay 20l at 3l9, thus removing the short circuit from the upper winding of relayj20l; During the rotary operationg the groundconnection to the'up'per -winding' of'relay-20l through contact X was temporarily disconnected byfenergization V of relay 209; but'this connection has now-been reestablished by thefalling-back of relay 209, andf accordingly r'elay ZBI now energizes fully over the a circuit "which extends from ground by way of 252, 2%, contact X, and bothwindings of the relay in series tojbattery. Upon energizing relay EEH locks itself tothe holding conductor I12.

Relay 29! s also opens the release magnet circuit at Eel opens the iinpulsing circuitat 222,-and

at-223 it disconnectsthe-holding conductor H21 from the slow acting relay 208, and connects it instead to'the testwiper 330 In addition, re1ay' 20! connects the trunk conductors I10 and I'll direct to the wipers 332 and 333,"respectively,'at.

contacts 220 and 22-I,'atl the same time disconnectingthese trunk conductors fromfthe line relay 204-.- Relay 204 accordingly'falls back and breaks the circuit of relay 206;

V The two trunk conductors ill!" and Ill; and

the-holdingconductor I12 now extend viathe connectorwipers to} three conductors of the selected trunk. It follows that before the relay 255 of the connector can fall back, the line and so I release relays of the repeater associated with the selected trunk will energize-and the latter relay will place ground on the holding conductor I to maintain the connection.

The calling subscriber will now dial the necessary remaining digitsto complete-the conn'ece tion' in the automatic exchange and thesedig'its are rep'eated by the repeater in the well known manner. Release of the connection is accomplished by hanging up the receiver at the calling station, whichdrops the'li'ne and release relays of'lthe'repeater. I The "release relay falling back removes g'roun'dfrom the holding circuit including conductor I ll-and the link circuit is restored j as previously described.

7 From the preceding explanation'it will'be clear that another group ofring-down trunks could be terminated in the 6th,"7th, 8th; or 10th level,

and could be reached by diallinga three digit Such a group of trunks might be a 7 group of toll trunks leading to the toll board inan adjacent exchange. Assuming these'trunks' are terminated in'the 10th level (of the second i number.

hundred), the number assigned would'be 01-1.

In calling the toll operator over one of these 1,

trunks, the first digit '0 will operate the connector, 7 shaft'to the'lOth level and at the same time will operate vrelay 2w by means -'of wiper '329. The

second digit 1 will rotate the connector shaft one step, whereby wipers 330; i332, andn333 are set on the first-trunk lineof the'group; Thejthird U digit 1 will operate the minor switch, whereupon autcmatic'trunk hunting willtake .place and'an idle trunk will be selected. The hunting'move ment is controlled through the rotaryrcontrolbank, whichhaspins inserted at the 10th levelf as explained in the case of the 3rd and Qthlevelsfi The "invention having been described, that,

which is considered to be new and for which the protection of Letters Patent is desired will 'be 5 1 pointed out in the appended claims.

What is claimedisf v 1. Ina finder system, a group of subscriber s:

lines comprising two sub-group's, a group of finders, each finder having access to all said lines, starting circuits whereby the lines of one subgroup normally use part of said finders and the lines of the other sub-group normally use the rest of said finders, whereby the finders are divided into two sub-groups, two groups of marking leads associated with said two sub-groups of lines, respectively, test banks in said finders, and means responsive to a call from any line for connecting the marking leads of the associated subgroup of lines to the test banks in the corresponding sub-group oi finders.

2. In a finder system, a group of subscribers lines comprising two sub-groups, a group of finders, each finder having access to all said lines, starting circuits whereby the lines of one subgroup normally use part of said finders and the lines of the other sub-group normally use the rest of said finders, whereby the finders are divided into two sub-groups, auxiliary start circuits whereby a calling line in one sub-group may use a finder in the non-corresponding sub-group if all the finders in the other sub-group are busy, two groups of marking leads associated with said two sub-groups of lines, respectively, test banks in said finders, and means responsive to a call on any line for starting a finder in one of said sub-groups, and for connecting the marking leads of the associated sub-group of lines to the test banks of the finders in the sub-group in which the started finder is located.

3. In a finder system, a group of lines, two groups of finders having access to said lines, means responsive to a call on one of said lines for normally starting a finder in one of said groups and for starting a finder in the other group if the finders of the first group are busy, a group of common marking leads associated with said lines, test banks in said finders, and means efiective when a finder is started for connecting said marking leads to the finder test banks in the group in which the started finder is located.

4. In a finder system, two groups of lines, a finder having access'to the two groups of lines through two sets of wipers, respectively, an allotter, means whereby said allotter may be used by a calling line in either group to start said finder, and a wiper selecting relay in said finder controlled by said allotter in accordance with the group in which the calling line is located.

5. In a finder system, two groups of lines, two allotters, means whereby a calling line in either group may use either allotter, finders having access to said lines and controlled by said allotters, each finder having a plurality of sets of wipers, and wiper selecting means in said finders controlled by the allotters.

6. In a finder system, two groups of lines, a first group of finders, each finder having two sets of wipers, one set having access to the first group of lines being normally connected and the other set having access to the second group of lines being normally disconnected, a second group of finders, each second group finder identical with said first group finders, means whereby a calling line in the first group normally starts a first group finder and whereby a calling line in the second group normally starts a second group finder, means whereby a calling line in the first group starts the second group finders only in case all the first group finders are busy and whereby a calling line in the second group starts a first group finder only in case all the second group finders are busy, and means for automatically switching wipers in the second group finder when the same is started by a calling line in the first group when all the first group finders are busy. I

'7. In a finder system, four groups of lines, a finder having access to said lines through four sets of wipers, there being a wiper set for each line group, means whereby any calling line can start said finder, means for selecting two of said four sets of wipers when the finder is started, and means whereby the two selected wiper sets search simultaneously for the calling line.

8. In a finder system, a finder having a plurality of sets of wipers, means controlled over a callingline for starting said finder to searchfor the calling line, means for eliminating part of said Wiper sets when the finder is started, and means for eliminating the remainder of said wiper sets except one as a result of the completion of the searching operation.

9. In a finder system, fourgroups of lines, a

finder having access to said lines through four setsof wipers, there being a wiper set for each group of lines, a group of common start leads for.

wipers before said finder is operated, and means whereby the two selected wiper sets search simultaneously for the calling line;

10. In a finder system, a first and a second group of lines, a first group of common start leads for said first group of lines, a corresponding second group of common start leads for said second group of lines, a first group and a second group of finders normally having access to said lines, a test bank in each finder, each bank comprising one bank contact for corresponding start leads in both groups of start leads and normally disconnected therefrom, a first relay for connecting said first group start leads to said test banks in response to a call on a line in the first group, and a second relay for connecting said second group start leads to said test banks in response to a call on a line in the second group.

11. In a finder system, a first and a second 'group of lines, a first group of common start leads for said first group of lines, a second group of common start leads for said second group of lines, a first and a second group of finders having access to said lines, a test bank in each finder, a first relay for connecting said first group start leads to the test banks of the first group finders in response to a call on a line in the first group, a second relay for connecting said first group start leads to the test banks of the second group finders in response to a call on a line in the first group in case all the first group finders are busy, a third relay for connecting said second group start leads to the test banks of the second group finders in response to a call on a line in the second group, and a fourth relay for connecting said second group start leads to the test banks of the first group finders in response to a call on a line in the second group in case all the second group finders are busy.

12. In a finder system, a first and a second group 01' lines, a first group of common start leads for said first group of lines, a second group of common start leads for said second group of lines, a first and a second group of finders, said first group finders normally having access to said first group of lines and having access to said second group of lines only when all the finders in "the second group arebusy, a test bank in each; 7

' ingsaid first group start leads to said test banks, 7 a second relay operated in response to a call on finder of the first group, a first relay for connect.-

a line in the first group i for operating said first relay, a third relayfor connectingsaid second group start leads to said test banks, and a fourth relayoperated in response to a call on a line in group of lines, a first group of common start ,leads for said first group of lines,-a second group 15 the second. group for operating said thirdrelay only in case allthe finderslin the second'group are'busy' 13. In .a finder system, a first and a s ec ond of common start leads for said second group of lines, a first and a second group of finders, said first group finders normallyhaving access to said 7 firstgroup lines and having access to saidsecond group lines only when all the second group finders V are busy, a plurality of sets ofwipersiin the. first group finders for access-to said lines wiperselecta ing means in eachfirstgroupfinder, a test bank in each firstgroup finder, a first relay for con-f jnecti'ng said first group startleads to said test banks, a secohdrelay operated in response to a,

, call on a linein the first group for'operating gsaid first relay, a third relay for connecting said second group start leads to'said'test banks, and" a'fourth relay operated'inrespon'se to a call on a linein the second group for operating saidthird relayandsaid wiper switching means in the first group finder takenflinto useonly in case all the second group finders are busy.

14. In a finder system, a-groupoflines,a group of finders for connecti ng:with any of said lines,

' I a group of common startleads; an allotter, a test bankcontact in each of said finders for each of ,said start leads, said start leads being normally disconnected from saidcontacta means controlled oyeraany' of said start leads for causing said allotter to start one of said finders, and means controlledbyl said allotter when it starts-one of said finders formarking the test bank contact of a calling line by connecting all ofsaid start leads to said test bankcontacts. V V ,7

15. In a finder system, a group, of-lines, a group offinders for connecting with any of said lines, a a

group ofcommonstart leads, a test bank contact in each of said finders for each of said start leads,

v said start leads being normally disconnected from.

said bank contacts, means includingsaid start} leads for starting one of saidfinders in response to a call on one of said lines, and means responsive thereto for marking the test bank contact of the calling line by connecting said start leadsto saidv :test bank contacts, a I

16. In a finder system, a first and a second groupf 01 lines, a corresponding first and second group of finders for connecting Withsaid lines in their respective groups',-. a test bank for ;each of said finders, a 'group of common start leads for each of said-groups of lines, a test contact on ea'ch'of said test banks for each of said start leads of a1;

group,,said start leads being. normally disconnected'fro'rn said testcontacts, means for starting oneof said finders responsive to a call on'one of said lines, means responsive thereto for marking thetest contactcorrespondingpto, the calling'line by connectingthe group ofs tart leads correspond? ing'totheline group in which the calling line is located to the 7 test: contacts of the associated finder group, aflplurality'of sets of Wipers having access tosaid lines for'each'of said finders, wiper selecting means in each of said finders, and means '7 for controlling said selecting'means in accordance withthe line group in' which the callingline is 7 located to accomplish wiper selection before the finder starts searching for the callingline- 7 :NORMAN H. SAUNDERS.

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