US1656300A - Telephone system - Google Patents

Description

1,656,300 R. F. STEHLIK TELEPHONE SYSTEM Filed May 19, 1924 5 Sheets-Sheet 1 led y 19. 1924 Inuen DI'--- .BudbEuh F S'ZEhhk Jan. 17, 1928.

R. F. STEHLIK TELEPHONE SYSTEM Jan. 17, 1928.

R. F. STEHLIK 'I'ELEPHOYNE SYSTEM uswm h HIT:

Filed May' 19, 1924 Buzzing uh F ETEhhk QM N Wm Jan. 17, 1928.

R- F. STEHLIK TELEPHONE SYSTEM wk wa 23* bin A, mlmtn 5 Sheets-Sheet 3 -Iws Budd h F. ETEFzZzk Filed May 19, 1924 Jan. 17, 1928. 1,656,300-

R. F. STEHLIK TELEPHONE SYSTEM Filed May 19, 1924 5 Sheets-Sheet 5 522E921 f. 525m Patented Jan. 17, 1928.

UNITED STATES PATENT OFFICE.

nunonrn r. srnnmx, or crir'caeo. mnnors, nssmnon, mr mnsrm nssmmms, 'ro AUTOMATIC ELECTRIC mc., or 'cmcaoo, rumors, a oonromnon or DELAWARE.

Application filed Kay 19,

' The present invention relates in general to telephone systems, but is concerned more particularly with telephone systems employing line finders, i. e., systems in WhlCll a finder switch individual to a trunk connects that trunk to a calling line when-a call is made.

One object of the invention is the production of new and improved circuit arrangements whereby the line finders are directed in their movements so that they do not need to test groups of lines during the primary movement and individual lines during the secondary movement, thereb permitting the finders to be made much simpler mechanically and electrically.

Another object is the production of new and improved circuit arrangements whereby the individual line relays are eliminated and their functions performed by a small number of common line-relays.

A further feature of the invention relates to the provision of a new and improved high speed sending switch which transmits two series of high speed impulses to a finder switch to set it upon the calling line under the control of the common line relays.

A further feature'of the invention resides in the arrangement whereby two finder -al 30 lotters are employed to enable a lar er number of finders than could be served by one allotter alone to be grouped together.'

A further feature has to do with new and improved circuit arrangements whereby the 5 setting up of a wrong combination on the common line relays when two lines in different tens groups are callin simultaneously is prevented by removing attery from all other tens groups when a line'in one tens do group is calling. This prevents the units designation of a second linefrom becoming confused with the units designation of the first line, as will hereinafter appear.

A special feature of this case resides in the arrangement whereby the wipers of the find ers are normally standing opposite the first level of bank contacts so as to eliminate the vertical movement of the shaft when a line terminating in the first level of the finders so is calling. In connection with this feature,

mnrnonn srsrmr.

1924. Serial I0. 714,188.

the necessary mechanical arrangements have been made to permit the ofi normal contacts to be operated whenever the shaft moves from its normal position, either vertically or in a rotary direction.

Another feature relates to the provision of circuit arrangements common to an entire group of finders for selecting one of two sets of WI ers on each finder.

A urther object relates to the production 00 of an improved and simplified cut-off relay, together with a mounting frame on which the cut-off relays of all .lines served by one group of finders maybe mounted, thereby permitting common units and tens bars to be 66 used 'as'the fixed contacts for the cut-ofi relays. There are a great many other objects and features, having to do for the most part with the circuit details, which, together with the foregoing, will be understood best from a further perusal of the-specification.

Referring now to the drawings comprising Figs. 1-1(), inclusive, Figs. 1-4, inclusive, show, by means o f.the usual circuit diagrams, a sufiicient amount of equipment in a system embodying the principles of the invention to enable the invention to be understood audits utilityappreciated; Fi 5-7, inclusive, show the mechanical details of the improved cut-olf relay and the frame in which it is to be mounted; and Figs. 8-10, inclusive, show such parts of a switch mechanism as are essential to enable the arran ement for maintaining the wipers of t switch opposite the first level of bank contacts and the new and improved arrangement for operating the off normal springs to be understood.

Fig. 1 shows the substations A and A whose lines terminate at the exchange in connector banks and also in the banks of the finder F, which is mechanically of the usual vertical and rotary type, having its bank contacts arranged in ten horizontal rows with ten sets of bank contacts in a row, making one hundred sets of bank contacts. The switch has two complete banks, each served by a separate set of wipers, making two hundred sets of contacts instead of one hundred 100 sets. Consequently, the finder F is enabled to connect with any one of a possible two hundred lines.

Fi 2 shows the seconda switch SS, whic is individual to the nder F, and which is connected with the latter through the intermediate distributing frame IDF. This switch'is operated simultaneously with the finder F to select a first selector such as the first selector S. Mechanically, the secondary switch SS is of the well known r0- tary type whose wipers move in a forward direction only and are advanced upon the back stroke of the stepping magnet rather than u on the front stroke. The selector S is simi ar to the finder F, but has only one set of wipers instead of two.

Fig. 3 shows the tens relays 201-210, inclusive, which are common to all of the two hundred lines in the group served by the finder F, together with the common units relays 211-220, inclusive, which are common to the first hundred lines of the two hundred line group, and the common units relays 221-230, inclusive, which are common to the second hundred lines of the two hundred line group. These relays operate to start the sender shown in Fig. 4 and to control the number of impulses transmitted by the sender.

Fig. 4 shows the two allotters FA-1 and FA-2 which are used to preselect finders in the two groups of finders having access to the lines of substations A and A. These finders are divided into two groups on account of the fact that there are more finders having access to the lines of substations A and A than there are sets of bank contacts on one allotter. Accordingly, the two allotters FA1 and FA2 are provided and they are arranged to operate as one allotter, the circuit arrangements being such that only one allotted finder can be operated in case a finder is allotted by each of the finder allotters when a call is made. The finder allotters FA1 and FA-2 are each mechanically similar to the secondary switch Fig. 4 shows also the sender which, upon a call being made, is controlled by the common line relays shown in Fig. 3 to transmit two series of directive impulses to the finder which is allotted by one of the allotters FA1 or FA--2. Mechanically, the sender is similar to either of the finder allotters FA-1 0r FA2.

Referring now particularly to Figs. 5-7, inclusive, Fig. 5 is a front View of a section of the improved cut-oil relay mounting frame; Fig. 6 is a view of the same section as seen from the right side of Fig. 5; and Fig. 7 is a top view of Fig. 5. This frame comprises essentially the mounting strips such as 401 and 402 on which the cut-off relays such as 405-408, inclusive, are mounted. The mounting stri s 401 and 402 are punched from soft iron stock, and the heel pieces or magnetic returns for the relays are a part of the mounting strips themselves. For example, the extension 416 of themounting strip 402, seen more clearly in Fig. 6, serves as a magnetic return for the cut-ofi relay 407 which is secured to the mounting strip 402 by the machine screw 417. The heel piece 416 serves also as a mounting strip for the jack springs 412 as well as a mountlng strip for the armature assembly.

he s ring carrying member 409 of the rela 40 is made of brass and is riveted to t e soft iron armature 410. There is a groove cut in the armature 410 so as to enable the ivot pin, secured in the ears of the mem er 413, to lie loosely between the armature and themember 409. The contact springs 411 and 418, which are connected respectively to the two conductors of a subscribers line, are suitably mounted on the member 409 and are insulated therefrom. The spring 418 normally makes contact with the associated tens bar 404 and the spring 411 normally makes cont-act with the units bar 421. The assembly is held in its normal position by the spring 415 which may be seen best in Fig. 7. This spring, together with the armature pivoting member 413, is secured to the heel piece 416 by the screw 414. Apparently the screw 414 clamps the member 409 also. However, this is not true on account of the fact that the hole in the member 409 is slightly larger than the head of the screw 414, as may be seen in Fig. 7. When the relay 407 is energized, the soft iron armature 410 is at tracted, pulling the springs 411 and 418 out of engagement with the common bars 421 and ,404.

In the present case, since there are two hundred lines served by one group of finders, there are twenty vertical units bars such as the units bars 421 and 422. The first ten units bars are associated with the first hundred lines and the second tens units bars are associated with the second hundred lines. The ten tens bars, such as 401 and 403, however. are common to the entire group of 200 lines.

It will be understood that the cut-off relay 4, Fig. 1, associated with the line of substation A, together with the cut-off relays'of the other lines of the system, is mechanically of the type shown in Figs. 5-7, inclusive, and that the common tens and units conductors, for example, the conductors 233, 243, and 253, Fig. 3, correspond to the common tens and units bars, the bars 403, 404, 421, and 422, for example, of the mounting frame shown in Figs. 5-7, inclusive.

Referring now particularly to Figs. 8-10,

inclusive, which show views of the vertical and rotary switch mechanism of the finder F, Fig. 1,'the new and improved arran ements shown therein will be described. 7 l e cam 460, Fig. 10, is secured to the shaft 452 in such a wa as to hold the shaft normally one step hig ier than its usual normal position so that the wipers remain opposite the first level of bank contacts.

The oil n rmal lever 457, Fig. 8, which controls the off normal springs 458 is bent obliquely at its right hand end so that the so-callcd normal lever 453, carried by the shaft 452 and best seen in Fig. 9, moves out of engagement with the lever 457 when the shaft is rotated one step, the lever being again engaged by the normal lever 453 when the shaft rotates back to normal. It goes without saying that the off normal lever 457 is disengaged by the normal lever 453 when the shaft is raised one step. Thus it will be seen that the oil normal springs 458 are allowed to operate as soon as the shaft 452 is rotated one step or moved vertically one step.

Referring now particularly to Figs. 1-4, inclusive, the detailed description of the operation will now be given. For this purpose it will be assumed that the subscriber at substation A, desiring to make a call, removes his receiver. When the receiver is removed at substation A, a bridge is placed across the line conductors 2 and 3. The positive line conductor 3 is, at this time, grounded through the resistance 11, armature 6 of the cut-off relay 4 and its resting contact, conductor 8, the common units conductor 243, and the resting contact and armature 246. Accordingly, a circuit is closed over the negative line conductor 2 and through armature 5 of cut-off relay 4 and its resting contact, conductor 7, common tens conductor 233, resting contact and armature 235, and the normally closed contacts controlled by armature 236 for the third tens relay 203, the line of substation A being number 33 in the first group from the standpoint of the finders. The tens relay 203, together with all the other tens relays, is connected to battery through the holding conductor 241, resting contact and armature 352, resting contact and armature 350, resting contact and armature 372, andresistance 310. Accordingly, the third tens relay 203 energizes over the calling line with results to be pointed out hereinafter.

Before proceeding further, it may be pointed out that the conductors 7-10, inclusive, are shown as independent conductors merely for the sake of convenience, and that, as a matter of fact, the resting contacts of the armatures such as 5 and 6 of the cutofi' relays such as 4 are common tens and units bais as shown in Figs. 5-7, inclusive.

Returning now to the operation of the system, relay 203, upon energizing, disconnects ground at armature237 from the third tens conductor 273, extending to the sender bank (thereby predetermining that the tens digit to be sent out subsequently will be the tens dlgit 2- which will raise the wipers of the allotted finder from their the first level to a position opposite the third level of bank contacts) places battery through the common impedance 280 on the common tens conductor 233 at armature 237; and at armature 236 opens the locking chain extending to the right of itself and closes a local locking circuit for itself at the same time opening its own initial circuit. Relay 234, which is included in the locking circuit of relay 203, now energizes and disconnects at its ten upper armatures the ten respective line relay branches from the associated common tens conductors, leaving all the common tens conductors 0 en with the exception of'conductor 233 whlcn, as above pointed out, is connected to battery at armature 237' of relay 203. Relay 234 also closes at armature 238 an energizing circuit for relays 244 and 254 in multiple. Relay 254, upon energizing, disconnects ground from each of the associated units conductors. However, since no line is calling in the second group this does not produce any further result at this time. Relay 244, upon energizing, disconnects ground from each of the associated units conductors at its ten upper armatures, and at armature 245 connects relay 249 to the chain locking circuit. Responsive to the removal of ground from conductor 243 at armature 246, the third units relay 213 energizes over the following circuit: From ground by way of the third units relay 213, normally closed contacts controlled by armature 247, contacts 250, units conductor 243, conductor 8, contacts 6, resistance 11, the calling line and substation, armature 5 and its resting contact, conductor 7 the third tens conductor 233, armature 237 and its working contact, and impedance 280 to battery. Relay 213, upon energizing, opens at armature 247 the locking chain circuit extending to the right of itself and closes a locking circuit for itself, at the same time opening its own ini' tial circuit. Relay 213 also disconnects ground from conductor 283 at armature 248, thereby predetermining that the units digit to be sent out subsequently will be the units digit 3. Relay 249 is included in the'locking circult of relay 213 and it accordingly energizes, disconnecting the units relays of the first group. Relay 249 also closes at armature 251 a circuit for relay 257 which thereupon energizes and disconnects the units relays of the second group. The number of the calling line is now completely registered and the common tens and units line relays positions opposite llll llll) are all disconnected from the subscribers lines, thereby preventin an 1nterference with the registered num er ue to further calls.

Relay 257 also places ground upon start conductor 263 at armature 258, thereby closing a circuit thIOU lI the resting contact and armature 337 of rela 315, Fig. 4, and armature 351 and its restlng contact for start relay 321. Start relay 321 thereupon energizes; locks itself to start conductcr 263 at armature 359 so as to prevent 1ts circuit being opened by relay 315 or by relay 318; places ground on the locking conductor 311 at armature 360; disconnects test wlpers 383 and 397 of the finder allotters FA-1 and F A2 at armatures 356 and 357 from the stepping magnets 381 and 396, respectively; and at armature 362 places ground on wiper 384 of the finder allotter FA1 through the resting contact and armature 386. ThlS ground potential is extended through the first contact in the bank of wiper 384 and over the associated conductor 69 to relay 26 of the finder F. Relay 26 accordingly energizes and prepares the finder F and the secondary switch SS for operation by connecting up the common conductors 61 and 62 and 64-67, inclusive.

As a further result of the energization of start relay 321, Fig. 4, the secondary switch SS, Fig. 2, is started due to the operation -of armatures 358 and 361 of the said start relay 321 in a manner to be pointed out hereinafter.

As a result of the above mentioned grounding of the locking conductor 311 by start relay 321, a circuit is closed through the resting contact and armature 348, and the first contact in the bank of wiper 303 and said wiper for the upper winding of relay 314 of the sender. Relay 314 thereupon energizes and closes at armature 334 a circuit through armature 341 and its resting contact for the lower winding of the two step relay 316. Relay 316 thereupon energizes part way only because of the fact that the lower winding is of a small number of turns of wire having a relatively high resistance. Accordingly, only the locking contacts (marked 1) close, but the remaining contacts (marked .2) are not operated. Upon the closure of the first step contacts by armature 340, a locking circuit is closed for the upper winding of the relay 316 in series with the lower winding. This locking circuit is not effective at this time, however,

owing to the fact that the initial circuit of the lower winding is still established. As a further result of the energization of relay 314, it prepares a locking circuit for itself and an impulsing circuit through the high speed interrupter 308 for the finder F at armature 333; opens a point in the normal restoring circuit of stepping magnet 305 at armature 332; and at armatures 330 and 331 connects u the high speed interrupter 307. According y, upon the first closure of the interrupter 307, a circuit is completed for stepping magnet 305, which thereupon energizes and moves the associated pawl into engagement with the next notch in the wiper driving ratchet wheel, but does not move the wipers themselves.

Upon the next subsequent opening of the circuit at the interrupter 307, stepping mag-' net 305 deenergizes and advances the wipers 301304, inclusive, one step. Wiper 303 opens the circuit of the upper winding of relay 314, and wiper 301 closes a locking circuit from its locally grounded bank contact through the resting contact and armature 342 and armature 333 and its working contact for the lower winding of relay 314, thereby maintaining relay 314 energized. This looking ground is extended to the interrupter 308. However, the interrupter 308 is open at this time, being affixed to the shaft of the interrupter 307. As a further result of the advance of the wipers of the sender, wiper 304 closes a circuit for pick-up relay 315, whereupon relay 315 energizes; prepares a restoring circuit for the sender at armature 336'; and at armature 335 connects the interrupter 307 in multiple with interrupter 308, i. e., connects it to the same ground supply conductor, at the same time removing ground locally from interrupter 307. Since, as before stated, the interrupters 307 and 308 are being operated at a high speed so as to produce a given number of interruptionsin the shortest allowable time, the interrupters 307 and 308 again close at practically the same time that the Wipers 301304, inclusive, arrive upon the second set of bank contacts responsive to the above mentioned deenergization of the stepping magnet 305. Thereis not closed until wiper 304 arrives upon the second associated bank contact, pick-up relay 315 cannot start to energize until about the time the interrupters 307 and 308 close again. This does not cause any harm to result, however, owing to the fact that the circuit of the interrupter 307 is shifted by meansof the make-before-break combination controlled by armature 335, relay 315 having. energized completely before the closure of the interrupters is terminated. Accordingly, at the end of this closure of the interrupters 307 and 308, they, as well as the lower winding of the relay 314, are supplied with ground only through wiper 301.

Upon the second closure of interrupters 307 and 308, which interrupters close simultaneously, a circuit is closed through interrupter 307- for the stepping magnet 305 of the sender, which thereupon energizes but does not step the wipers, and a circuit is closed through interrupter 308, armature 339 fore, since the circuit of pick-up relay 315 gized to disconnect the interrupters.

and its resting contact, conductor 61, armature 49 and its working contact of relay 26, Fig. 1, for vertical magnet 31 of thc finder F. Vertical magnet 31 thereupon ener izes and raises the wipers 16-21, inclusive, ot the finder F from their position opposite the first level of bank contacts to a position opposite the second level of bank contacts.

Upon the next opening of the interrupter contacts 307 and 308, stepping magnet 305 of the sender deenergizes and advances, the wipers 301-304, inclusive, into engagement with the next set of bank contacts. Wiper 301 is moved out of'engagement with its locally grounded contact and into engagement with the contact in which conductor 272 terminates. The associated relay 202 is not energized and therefore conductor 272 is grounded, maintaining the lower winding of relay 314 energized.

Upon the next closure of the interru ters 307 and 308, stepping magnet 305 o the sender and vertical magnet 31 of the finder F are again energized and the wipers of the finder F are raised by vertical magnet 31 from their position opposite the second level of bank contacts to a position opposite the third level of bank contacts.

Upon the next opening of the interrupters 307 and 308, stepping magnet 305 of the sender deenergizes and advances the wipers 301-304, inclusive, into engagement wifih the next set of bank contacts. Wiper 301 at this time engages the bank contact in which conductor 273 terminates. Since the ground potential has been removed from conductor 273 by the third tens relay 203, as hereinbefore pointed out, this latter operation opens the circuit of the lower winding of relay 314 and removes ground from the interrupters 307 and 308.

Since, as before pointed out, the interrupters 307 and 308 are erated at the maximum allowable speed, t ey closeagain at about the same time that the wipers, 301-304, inclusive, arrive upon the set of rupters would operate magnet 305 of thesender and the vertical magnet of the finder F again before the stop relay could be ener- However, the next closure of these interrupters is ineffective owing to the fact that the wiper 301, which is supplying ground. to

these interrupters, engages an ungrounded minates, results also in the opening of the circuit of relay 314. Accordingly, relay 314, which is only very slightly slow to deenergize to enable it to hold up while the wiper 301 is passing from one contact to another, deenergizes and disconnects its own lower winding and the interrupters 307 and 308 from the wiper 301 at armature 333; disconnects interrupter 307 from in multiple with interrupter 308 at armature 331; and at armature 334 opens the initial circuit of the two step counting relay 316, whereupon the locking circuit for the two windings in series becomes effective and the relay energizes completely; disconnects, at armature 341, armature 334 of relay 314 from the junction of its own windings and connects it instead to the junction of the windings of relay 317; at armature 342 disconnects the lockin armature 333 of relay 314 from the tens igit test wiper 301 of the sender and connects it to the units digit test wiper 302, preparatory to the transmission of the units digit to the finder; and at armature 339 transfers the upper terminal of the interrupter 308 from the vertical magnet operating conductor 61 to the rotary magnet operating conductor 62. As a further result .of the deenergization of relay 314, it closes at armature 332a restoring circuit for magnet 305 in multiple with the pick-up relay 315, This circuit includes armature 336 of relay 315 and its working contact and the local interrupter contacts 306 of stepping magnet 305. Accordingly, stepping magnet 305 operates in a buzzer-like manner and advances the sender wipers to their normal position, at which point its circuit and the circuitof the pick-up relay 315 are opened due to wiper 304 passing off the last grounded bank contact.

Relay 315 now deenergizes responsive to the opening of its circuit; opens a furtlier point in the restoring circuit of the sender at armature 336; and at armature 335 prepares the interrupter circuits for the transmission of the next series of impulses.

As a further result of the return of the wipers 301-304, inclusive, to normal, the previously traced circuit for the upper winding of relay 314, which includes the resting contact and armature 348 of relay 317, and the first contact in its bank and wiper 303, is again established. Accordingly, relay 314 again energizes and closes a circuit at armature 334 through armature 341 and its working contact for the lower winding of the two step relay 317, whereupon relay 317, being similar to relay 316, operates through its first step only and closes a locking circuit for itself at armature 347. This looking circuit is not effective immediately, however, on account of the fact that the initial circuit for the lower winding of the said relay is still established. As a further reno I sult of the energization of relay 314 it prepares a locking circuit for itse f and an operating circuit for the interrupter 308 at armature 333, and at armatures 330 and 331 again connects up interrupter 307. Accordingly, step ing magnet 305 is energized-upon the next 0 osure of the interrupter 307 and is subsequently deenergized upon the following opening of the interrupter 307, thereby advancin the wipers 301-304, inclusive, one step. Viper 302 is now brou ht into engagement with its locally groun ed cor 1- tact, thereby completing the locking circuit of relay 314 and placing ground upon the lower terminal of the interrupter 308 through the working contact and armature 342 and armature 333 and its working contact. Wiper 304 of the sender also engages a grounded bank contact, closing a circuit for the pick-up relay 315, which accordingly energizes and at armature 335 transfers the lower terminal of the interrupter 307 from ground locally to ground comin from the units test wiper 302, as hereiribefore explained.

Upon each of the three following closures of the interrupters 307;and 308, a circuit is closed by interru ter 308 for rotary magnet 30 of the finder as follows: from ground by way of test wiper 302, working contact and armature 342, armature 333 and its working contact interrupter 308, armature 339 and its working contact, conductor 62, armature 48 and its working contact, and rotary magnet 30 to battery; Responsive to the three closures of this circuit, rotary magnet 30 advances the switch wipers 16-21, inclusive, into engagement with the third set of bank contacts in the third level, which was previously selected by the vertical magnet 31. The normally connected set of wipers (19-21, inclusive,) is now in engagement with the bank contacts associated with the line of substation A, and the alternate set of wipers (16-18, inclusive,) is in engagement with the bank contacts associated with the line of substation A.

As a further result of each of the three closures of the interrupters 307 and 308 last mentioned, the interrupter 307 closes a circuit for stepping magnet 305 three times and the wipers 301-304, inclusive, are, accordingly, advanced three more steps. These wipers, therefore, come into engagement with the fourth set of bank contacts at the end of this series of operations and the units digit test wiper 302 engages the ungrounded bank contact associated with conductor 283, from which ground was reviously removed by the common units ine relay 213, Fig. 1, at armature 248. That being the case, the interrupters 307 and 308 are again rendered inefiective and relay 314 again deenergizes, and at armature 334 opens the initial energizing circuit of the lower winding of relay 317. When this occurs, relay 317 operates through its second step owin to its previously established locking circuit including both windings in series; disconnects ground from the first contact in the bank of wiper 303 at armature 348 so as to prevent the ick-up circuit of the upper wmding of re ay 314 bein again closed when the wipers of the sen er are subsequently restored to normal the second time; and at armature 350 attempts to remove battery from holding conductor 241. However, relay 323 is now energized by relay 324 as will be explained more fully 1 and, assumin that the secondary switch SS has not yet ound an idle trunk, test relay 322 has not yet energized, and armature ereinafter 350 and its resting contact is shunted by v the working contact and armature 376 and the resting contact, and armature 375 in series. Asa further result of the energization of rela 317, it closes a point in the allotter kic -ofl circuit at armature 346; disconnects the lower windings of relays .385 and 390 at armatures 344 and 345 so as to prevent them from being operated when the kick-off circuit is finally established; and at armature 349 closes a point in the switch-through circuit.

As a further result of the deenergization of relay 314, it closes at armature 332 the previously traced restoring circuit through interrupter contacts 306 for the stepping magnet 305 of the sender, whereupon the wipers 301-304, inclusive, are again restored to their normal position, whereupon the circuit of pick-u relav 315 is opened by wiper 304 and the said pick-up relay 315 deenergizes. The sender has now completed its'operation and remains at rest.

Returning now to the point at which start an the common interrupter 102 to battery. 7

At the same time, armature 358 of start relay 321 connects the junction of the lower winding of test relay 322 and step ing magnet 101 of the secondary switch SS to test wiper 104 of the secondary switch SS throu h the resting contact and armature 365 0? test relay 322, conductor 64 working contact and armature 45, and conductor 55. The operation now depends upon whether the trunk terminating in the bank contacts upon which the wipers of the secondar switch SS are standin is busy or idle. 11 case it is idle, test re y 322, Fig. 4, ener- 1 grounded bank contact.

gizes immediately over its circuit traced above, but the ste ing magnet 101 of the secondary switch is not operated owing to the relatively high resistance of test relay 322, permitting the wipers 103-105, inclusive, to remain on the idle trunk. In the present case, however, it will be assumed that the trunk upon which the wipers of the secondary switch SS are standing is busy. In this case, test wiper 104 is in engagement with a grounded 'test contact, short circuiting the lower winding of test relay 322 and preventing it from energizing owing to the fact that the said test wiper 104 is connected to the circuit including the lower winding of test relay 322 and stepping relay 101 in series ata point between the two. Due to the ground potential encountered by test wiper 104, stepping magnet 101 is energized through the common interrupter 102 and advances the wipers 103-105, inclusive, step by step in search of an idle trunk.

When an idle trunk is reached, which trunk it will be assumed is the one comprising conductors 161-163, inclusive, and extending to the selector S, the wipers 103- 105, inclusive, of the secondary switch SS are rotated no further on account of the fact that the test wiper 104 engages an un- I Also test relay 322, Fig. 4, being no longer short circuited, energizes in series with stepping magnet 101 of the secondary switch SS upon the next closure of the common interrupter 102. Upon energizing, test relay 322 closes a looking circuit for its upper winding at armature 367; removes battery from the holding conductor 241 at armature 375, armature 350 having been operated previously by relay 317; disconnects the test wiper of the secondary switch SS from the junction of its own lower winding and the stepping magnet at armature 365 and connects the said test wiper to ground, thereby making the seized trunk busy immediately; and at armature 364 places groundon the negative line conductor 161 of the selector S through conductor 66, working contact and armature 43 of relay 26 of the finder F, conductor 53, and wiper 103, whereupon line relay 111 of the selector S, which is connected to conductor 161 at armature 127, energizes over conductor 161 and closes at armature 121 a circuit for release relay 112. Release relay 112 immediately energizes and places ground on conductor 162 at armature 122, thereby making the associated trunk busy locally and independent of the ground sent ahead from the finder F through test wiper 104. Relay 112 also prepares the switch for operation by operating armature 123.

As a further result of the energization of the said test relay 322, Fig. 4, a circuit is closed for the connecting relay 24 of the finder F as follows: From round by way of the working contact 211K? armature 340 of the relay 317, armature 368 and its work ing contact, resting contact and armature 389, wiper 383 of the finder allotter FA-l,

conductor 68, off normal contacts 27 of tho finder F, armature 46 and its working contact, connecting relay 24, and resistance to battery. Relay 24 thereupon energizes; locks itself to the grounded release trunk conductor at armature 38; connects up the line wipers 19 and 21 to the line conductors 53 and 56 at armatures 36 and 41, respectively; and at armature 39 places ground on test wiper 20 of the finder F, thereby closing a circuit for cut-ofi relay 4. When this occurs, cut-oil" relay 4 energizes and disconnects conductors 7 and 8 from the line conductors2 and 3 at armatures 5 and 6, respectively.

Returning now to the point at which test relay 322, ig. 4, energized, the said test relay 322 closes at armature 366 a circuit for stepping magnet 381 of the finder allotter FA-1 as follows: From ground by way of the working contact and armature 366, working contact and armature 346, resting contact and armature 388, and stepping magnet 381 to battery. Responsive to the closure ofthis circuit, stepping magnet 381 energizes and moves the associated pawl into engagement with the next notch in the wiper driving ratchet wheel but does not advance the wipers 383 and 384.

As pointed out above, battery is removed from the holding conductor 241 at armature 375 of relay 322 upon the energization thereof. Responsive to this, relays 234 and 203, Fig. 3, deenergize, and relay 234 opens the circuit ofrelays 244 and 254 at armature 238, whereupon the said relays 244 and 254 deenergize. Relay 244, upon deenergizing,

opens the circuit of relays 249 and 213 at armature 245, whereupon relays 249 and 213 deenergize, and relay 249 opens the circuit of relay 257 at armature 251. Accordingly, relay 257 deenergizes and removes ground from start conductor 263 at armature 258, whereupon start relay 321, Fig. 4, deenergizes. Before proceeding with the explanation of what occurs in response to the deenergization of start relay 321, it will be well to point out that the amount of time required for the said relay 321 to fall back responsive to. the removal of the battery from the holding conductor 241 as described above, is sufficiently long to permit the line and release relays of the selector S to encrgize and to permit the connecting'relay 24 of the finder F to energize and lock itself to the release trunk conductor 55, which is grounded by release relay 112 of the selector S over the associated release trunk conductor 162, all as hereinbefore described.

Upon finally deenergizing, start relay 321 disconnects ground at armature 362 from the wiper 384 of the finder allotter FA1 and accordingly from conductor 69 upon which the wiper is standing. When this occurs, relay 26 of the finder F deenergizes and disconnects the common conductors 61 and 62 and 64-67, inclusive, from the finder F at armatures 49, 48, 45, 44, 43, and 42, respectively. As a result of the common conductor 66 being disconnected from con.

ductor 53, the initial circuit of the upper winding of the line relay 111 of the selector S is opened, leavin the said line relay energized over the calling line, and, as a result of the common conductor 64 bein disconnected from the release trunk cond uctor 55, the common finder controlling equipment no longer sup lies ground to the said release trunk 'con uctor .55, leaving it grounded only from the release relay 112 of the selector S. Relay26 also disconnects the combined test and switching conductor 68, which is individual to the'finder F, from relay 24. and connects it to ground locally,

[whereby the conductor 68 is maintained [grounded in order to maintain the finder F non-selectable to the finder allotter FA1 until the said finder F has been restored to normal. r

As a further result of the deenergization of start relay 321, Fig. 4, it removes ground from the locking conductor 311 at armature 360, whereupon relays 316, 317, and 322 deenergize. Relay 317 upon deenergizing, closes at armature 344 a circuit for the lower winding of relay 385 as follows: From ground by way of the grounded test conductor 68, wiper 383, resting contact and armature 356, resting contact and armature 344, and the lower winding of relay 385 to battery. Consequently, relay 385 energizes;

disconnects wipe-r 384 at armature 386 from the holding conductor 326; disconnects wiper 383 from the switching conductor 327 at armature 389; disconnects stepping magnet 381 from the kick-off conductor 328 at armature 388; and at armature 387 opens the circuit of the upper winding of relay 390,

whereupon relay 390 deenergizes '(assuming that the allotter I A-2 is not hunting, but is standing on an idle finder) and closes at armature 392 a circuit for the upper winding of relay 385 so as to maintain that relay energized after the circuit of its lower winding is subsequently opened. Relay 390 also connects wiper 398 to the holding conductor 326 at armature 391; connects wiper 397 to the switching conductor 327 at armature 394; and at armature 393 connects stepping magnet 396 -to the kick-off conductor 328. Thus it will be seen that the finder allotter FA1 has been completely out out of service, except as regards its testing operation, which will be explained subsequently, and that the finder allotter FA2 is now in operating position so that the first finder in group #2 will be operated upon the initia tion of the next call.

As a further result of the deenergization of relay 317, it opens the circuit of stepping magnet 381 of the'finder allotter FA--1 by removing ground from the kick-off con ductor 328 at armature 346- to permit the allotter to kick off, whereupon stepping magnet 381 deenergizes and advances the wipers 383 and 384 into engagement with the next set of bank contacts.

The further operation depends upon whether the finder associated with the second bank contacts of the finder allotter FA--1 is busy or idle. If it is idle, nothing further happens and the wipers 383 and 384 remain upon the second set of bank contacts. However, assuming the second finder to be busy, a ground potential is encountered by .wiper 383 on its second bank contact,

and stepping magnet 381 ener izes againthrough the resting contact an armature 356, armature 354 and its resting contact,

and the interrupter contacts 382, and the wipers 383 and 384 are advanced step by step in search of an idle finder owing to the buzzer-like action of stepping magnet 381 wgiich interrupts its own circuit at contacts 3 2.

As a still further result of the deenergization of relay 317, battery is again placed upon the holding conductor 241 at armature 350. The next call may now be registered as soon as it is made.

Returning now to the connection which the subscriber at substation A desires to establish, the next operation on the part of the calling subscriber is the manipulation of his calling device in accordance with the first digit in the desired number. He is informed that he may now do this by the socalled dial tone which he hears when his line is connected through to the selector S. This dial tone, generated by the buzzer 175, is superimposed on the ground lead of line relay 111 by the associated transformer. When the calling subscriber dials the first digit, the circuit of line relay 111 of the selector S is o ened a corresponding number of times. pon each opening of its circuit, line relay 111 deenergizes and closes at armature 121 a circuit through armature 123 and the slow acting series relay 113 for vertical magnet 118. By the operation of vertical magnet 118, the wipers 131-133, inclusive, of the selector S are raised step by step until they stand opposite the desired level of bank contacts. Relay 113 is energized in series with vertical magnet 118 and, being slow acting, maintains its armature attracted throughout the vertical movement. Upon energizing, series relay 113 prepares at armature 124 a circuit for the ste ping relay 114, which is closed at ofi norm contacts 120 and through the interrupter contacts of rotary magnet 119 upon the first vertical step of the switch. Accordingl stepping relay 114 energizes; closes a 10ering circuit for itself at armature 125; and at armature 126 prepares a circuit for rotary magnet 119.

At the end of the vertical movement, slow acting series relay 1'13 deenergizes and completes at armature 124 the circuit of rotary magnet 119, whereupon rotary magnet 119 energizes and advances the wipers 131-133, inclusive, into engagement with the first set of bank contacts in the selected level. Near the end of its stroke, rotary magnet 119 opens the circuit of stepping relay 114, whereupon stepping relay 114 deenergizes and opens at armature126 the circuit of stepping magnet 119, permitting stepping magnet 119 to deenergize and again close its interrupter contacts.

The further operation depends upon whether the trunk terminating in the first set of bank contacts is busy or idle. In case it is idle, switching relay 115 energizes immediately, seizing the trunk. Assuming the trunk to be busy, however, switching relay 115 is short circuited by the ground potential encountered on the busy test contact by test wiper 132 and does not energize. This same ground potential operates step ping relay 114 to close the circuit of rotary magnet 119 at armature 126, whereupon rotary magnet 119 energizes again, advancing the wipers 131133, inclusive, into engagement wit-h the second set of bank contacts. This alternate operation of stepping relay 114 androtary magnet 119 continues in this manner until an idle trunk is reached, which trunk it will be assumed is the one comprising conductors 134-136, inclusive. When this idle trunk is reached, switching relay 115 is no longer short circuited and enerizes in series with stepping relay 114. gtepping relay 114, however, is not opera.- tively energized at this time on account of the relatively high resistance of switching relay 115. Upon energizing, relay 115 removes ground from armature 121 of the line relay 111 at armature 129, thereby opening the circiut of the slow acting release relay 112; opens the test circuit and prepares the holding circuit at armature 128; and at armatures 127 and 130 disconnects conductors 161 and 163 from the windings of line relay 111 and extends them by way of the wipers 131 and 133 and conductors 134 and 136 to the windings of the line relay associated with the seized trunk. This line reenergize and the latter places.

Responsive to the manipulation of the calling device at the calling substation in accordance with the remaining digits of the desired number, the connection is completed in any well known or desired manner, and upon the termination of the ensuing conversation, the subscriber at substation A re places his receiver with the result that the release trunk conductor 135 of the trunk seized by the selector S is ungrounded in the usual manner, removing ground from the release trunk conductor 162 of the selector S, whereupon relay 115 of the selector S and relay 24 of the finder F deenergize. Relay 24, upon deenergizing, opens the circuit of cut-ofl' relay 4 of the calling line at armature 39, whereupon relay 4 deenergizes, restoi'ing conditions at the calling line to norma As a further result of the deenergization of relay 24 of the finder F, a circuit is closed for release magnet 29 as follows: From ground by way of armature 142 and its resting contact of busying relay 141, Fig. 2, conductor 57, spring 51, spring 50, armature 47 and its resting contact, armature 40 and its resting contact, off normal spring 28 and its upper contact, and release magnet 29 to battery. Upon the energization of release magnet 29, the wipers 16-21, inclusive, of the finder F are restored to normal position in the usual manner, whereupon the circuit of release magnet 29 is opened at off normal spring 28. As a further result of the restoration of the finder F to normal, ground is removed from'test conductor 68 at oif normal contacts 27, rendering the finder F selectable again to the finder allotter FA1.

In the selector S, switching relay 115, upon deenergizing responsive to the above mentioned opening of its circuit, closes at armature 129 a. circuit for release magnet 116 which includes springs 107 and 108, armature 121 and its resting contact, armature 123 and its resting contact, and ofl:' normal spring 117 and its upper contact. Release magnet 116 thereupon energizes, restoring the wipers 131-133, inclusive, to normal in the usual manner, whereupon its own circuit is opened at ofl' normal spring 117.

The entire connection is now released and the apparatus involved therein is ready for use in another call.

In order to explain the feature having to do with the automatic selection of the wipers of the finders, such as F, it will be assumed that the subscriber at substation A makes a call. The line of substation A, it will be remembered, terminates in the upper bank of the finder F. Accordingly, when this subscriber calls, the normally connected wipers must be disconnected and the u per set connected up instead, the wipers o the finder F being brought into engagement with the same bank contacts when the subscribcr at substation A is calling as they are when the subscriber at substation is calling.

When the receiver is removed at substation A, a bridge is closed across the associated line conductors and conse uently across the register relay control con uctors 9 and 10 which are connected to the line of substation A through the contacts of the associated cut-off relay. Conductor 9 is connected to the third tens conductor 233, which is the same conductor with which the corresponding conductor 7 of the line of substamen A is connected; and conductor 10 is, at

; this time, grounded through the resting contact and armature 2560f relay 254. Accordingly, the third tens relay 263 energizes with the results hereinbefore pointed out.

203, it may be pointed out, is that relay 234 energizes and closes -a circuit for relays 244 and 254 in multiple. Relay 254, upon ener-, gizing, disconnects ground from the associated common units conductors of the group to which the line of substation A. belongs, ground being removed from conductor 10 at armature 25fitAccordingly, the third units relay 223 energizes through the normally closed contacts controlled by armature 260, armature-'259fand its resting contact, and over the callingline; Belay 223, upon energizing, opens the locking chain circuit at armature 260 and closes a local locking circuit foritself, at the same time opening its initial circuit at the normally closed contacts controlled by the said armature 260. Relay 223 also disconnects ground from the third units conductor 283 at armature 261, which is the same units conductor from which ground was disconnected by the third units relay 213 in the previously described call made by the subscriber at substation A. As a still further result of the energization of relay 223 it grounds the wiper switching conductor 262, which is extended to and joined to the common wiper switching conductor 65. This is done preparatory to operating the wiper switching relay 23 of the finder F when the proper time arrives, as will be hereinafter pointed out. The locking circuit of relay 223 includes relay 249, which relay accordingly energizes and, among other things, closes a circuit for rela 257 at armature 251, whereupon relay 257 energizes, and, among other things, places ground upon the start conductor 263 at armature 258.

Responsible to the placing of ground upon the start conductor 263, start relay 321, Fig. 4, energizes with the hereinbefore pointed out results, one of which is that it grounds at'armature 362, wiper 384 of the finder allotter FA.1 through the resting contact and armature 386. Accordingly, wiper 384 extends ground through conductor 69 to re One. of the results of the energization of relaylay 26 of the finder F. Accordingly, relay 26 energizes and performs the functions hereinbefore described. One result of the energization of relay 26 is that it connects the common conductor 65 to relay 23 at armature 44. Since conductor 65 is now grounded through conductor 262 b the units relay 223, Fig. 3, as herein efore pointed out, relay 23 energizes and disconnects wipers 19, 20, and 21 and connects up wipers 16, 17, and 18 at armatures 32-35,

inclusive, respectively. Relay 23 also prepares a locking circuit for itself at armawhen the connecting relay 24 energizes, the

loclring circuit of the wiper switching relay 23 18 completed at armature 37 and the wipers-1648, inclusive, .are connected up; at armatures 36, 39, and 41, respectively; The

cut-pfl' relayasaociated with the line of substation .A isnowfenergized over wiper 17 and disconnects the conductors 9v and 10 'from the calling line. The calling line is now connected through to a selector such as S and the call may proceed in the usual manner.

Inorder to explain the feature having to do with the arrangement whereby the wipers of the finder F are not operated vertically but are immediately rotated into engagement with the calling line when the calling line terminates in the first level of the finder F, it will be assumed that a subscriber whose line (not shown) terminates in the first level of the finder F, makes a call. The conductor associated with this line which corresponds to the conductors 7 and 9 associated with the lines of substations A and A, respectively, is connected to the first tens conductor 231 instead of to the third tens conductor 233. The other conductor amiated with the line in question, which conductor corresponds to the conductors 8 and 10 of the lines of substations A and A, respectively, is connected with the one of the units (301K uctors, depending upon the set of bank contacts in which the line terminatos. Accordingly, when a call is made over this line, a circuit is closed over the tens conductor 231 for the first tens relay 201 which accordingly energizes and, among other things, laces ground on conductor 271, thereby c osing a circuit immediately for the two windin of the two steprela 316, Fig. 4, in series. Relay 316, whic otherwise does not energize until the vertical movement has been completed, now

energizes and disconnects the interrupter 308 from the vertical magnet operatmg com ductor 61 and connects it to the rotary magnet operating conductor 62 at'armature 339. Relay 316 also prepares a circuit for relay 317 at armature 341, and at armature 342 disconnects the tens wiper 301 of the sender and connects up the units wiper 302. Accordingly, when the sender is started, as it is in the usual manner responsive to the encrgization of relay 201, the correct number of impulses is transmitted to the rotary magnet 30 of the finder F to brin the wipers into engagement with the ca ling line. The oil normal springs of the finder F are operated at this time owing to the improved mechanical arrangement shown in Figs. 8 and 0, which permits the oil normal springs to be operated whenever the shaft is moved from its normal position, either raised or rotated, as hereinbefore explained.

With known systems of this general character, the numbers are likely to become mixed or scrambled, so to speak, when two subscribers are calling simultaneously. For

example, in certain systems, if calls are initiated simultaneously on lines 12- and 21, the lowest tens digit 1, and the lowest units digit 1 are transmitted, making the composite number 11 which is not the number of either calling line. The way in which this and similar occurrences are avoided in the present system will now be explained. Assuming that two subscribers in different tens groups removed their receivers simultaneously, or nearly so, two of the tens relays 201-210, inclusive, start to energize simultaneously. However, none of the units relays start to energize because they are all normally short circuited by the armatures of relays 244 and 254. Regarding the tens relays, only one can energize completely and lock itself up, owing to the fact that each tens relay opens the locking circuit of each of the following ones. The common cut-oft relay 234 energizes an instant later, and disconnects all the common tens conductors, leaving only one tens relay locked up. Accordingly, battery is now removed from all the tens conductors except the one associated with the locked up relay, battery being placed on such conductor through the" impedance 280 and an armature of the locked up tens relay.

As pointed out hereinbefore, relays 244.

and 254 energize as a result of the energization of relay 234 and remove ground from the common units conductors to permit any one of the common units relays to energize. Now if battery were not removed from all the common tens conductors except the one associated with the energized tens relay, the units relay corresponding to the lowest units digit of any calling line in any tens group Assuming that two subscribers in the same tens group are calling, two units relays attempt to energize. However, only one units relay can energize completely and close a locking circuit for itself owing to the fact that each units relay, upon energizing, opens the locking circuit of the remaining unlts relays ot a higher order than ltself.

A moment later, relay 249 energizes and disconnects the associated units conductors and closes a circuit fonrclay 257 which energizes and disconnects the associated units conductors, at the same time grounding the start conductor, as hereinbefore pointed out, to start the sender to transmit the correct registered number to the allotted finder.

The effect of an accidental ground on a line will now be considered. Considering first an accidental ground on the negative conductor 2 of the line. of substation A, which may be considered typical of a ground on any negative line conductor, a circuit is closed over the associated conductor 7 and through the common tens conductor 233 for the common tens relay 203 which thereupon energizes and locks itself in the hereinbefore described manner.

As a result, relay 234, which is included in the locking circuit of relay 203, energizes and places ground on the timing conduotor 240 at armature 239, thereby closing a circuit through armature 338 and its resting contact, the resting contact and armature 343, and the resting contact and armature 353 for the slow-to-pull-up relay 325. This relay is slow to pull up, in addition to being slow to fall back, owing to the fact that the copper collar is placed on the end of the core next to the armature instead of the more usual position on the opposite end of the core. By this arrangement, the lines of force generated by the flow of current through the winding of the relay must pass through thecopper collar before they reach the armature, which causes a delay in the operation of the armature. Upon finally energizing, relay 325 prepares a circuit for the alarm buzzer 309 at armature 373, and closes at armature 374 a circuit for the similar slow-to-pull-up relay 324, the two relays being provided primarily in order to give a longer delay. than can be provided for by one relay. Upon energizing, relay 324 completes at armature 370 a circuit for the buzzer 309 and at armature 372 removes battery from the holding conductor 241.

The buzzer 309 now operates to give an audible signal to an attendant that trouble exists in this unit.

Responsive to the removal of battery from the holding conductor 241, the locked up tens relay 203 and relay 234 deenergize and the latterremoves ground from conductor 240 at armature 239, resulting in the subsequent deenergization of the slow acting relay 325 which opens the circuit of the buzzzer 309 at armature 373 and 0 ens the circuit of relay 324 at armature 3 4. After a slight interval, relay 324 deeuergizes also and again places battery on the holding conductor 241 at armature 372. In case the ground on the negative conductor of the line of substation A is still present, the above operations are repeated over and over and the buzzer 309 is intermittently operated to attract the attention of the attendant who proceedsto take the proper steps to remove the line of substation A from service in any well known or desired manner. On the other hand, if the ground on the negative conductor of the line of substation A was merely a so-called swinging or passing ground, the tens relay 203 and relay 234 are not again o rated after they are unlocked and are read for service.

It may be well to point out at this time that in the case of a regular call, battery is not prematurely removed from the locking conductor 241,-owing to the fact that the start relay-321, upon energizing, shunts armature 372 and its resting contact at armature 365 and its working contact before relay 324 has had time to energize.

Considerin now the effect; of a ground upon the positive conductor 3 %of the line of ground being accidentally substation A, which may be considered as typical of a ground on any positive line conductor, nothing happens responsive to the v laced on the positive line conductor 3 of t e line of substation A, but, if special provisions were not made, this ground would act as a shunt for "the corresponding units relay 213, Fig. 3,

to prevent its energization in case some other line having the same units designation makes a call. However, the resistance 11, Fig. 1, is interposed between the positive line conductor 3 and conductor 8 which connects to the third units conductor 243, thereby preventing the units relay 213 from being short circuited by the accidental ground, except as regards a call on the line of substation A itself. There is a resistance similar to 11 associated with eachline, thereby isolating each line in trouble due to ground on the positive conductor, leaving each unaffected line free to call regardless of the grounded condition on the other lines.

It may happen occasionally that one of the switches of any finder secondary link becomes defective through constant wear and fails to operate correctly. Assumin first that the finder F is out of order an does not find the calling line, the sender completes its operation in the usual manner and goes through the process of placing ground on the switching conductor to opertrunk when a call is made, this idle trunk is seized and the call goes through in the usual manner. Assuming, however, that the trunk is busy or that the circuit of the stepping magnet itself is open, the secondary test relay 322, Fig. 4, whose initial energizing circuit must include the steppin magnet 101, is unable to energize. There ore, the hereinbefore described switcl1-throughcircuit is not completed at armature 368 of the 0 test relay 322, and the connecting relay of the alloted finder does. notoperate. Also the usual kick-oil circuit for magnet 381 of the finder allotter FA--1 or magnet 396 or the finder allotter FA--2, as the case may be, is not completed at armature 366 of test relay 322. I Therefore, if special arrangements were not made to advance the finder allotter in use automatically and independent of test relay 322, that finder allotter would be tied up on the defective finder selector link. Accordin 1y, special arrangements have been made or automatically closing the kickoff circuit independent of test relay 322. Obviously, such auxiliary closing means must be timed so as to allow a suflicient amount of time for the secondaryswitch S S, or any are provided, as hereinbefore pointed out, for

the purpose of'intermittently operating the buzzer 309 and automatically unlocking the register relays when a ground occurs on a negative line conductor. These same relays are made use of in bringing about the automatic kick-off, as will now be explained. It will be apparent that the three relays 325,

deenergize and the circuit of relay 325 is find opened at armature 338 of the pick-up relay 315, which relay, it will be remembered, nerglzes at the end of the first step taken by the wipers of the sender at the beginning of' the first digit. When relay 315 pulls up relay 325 starts to fall back, and, at the end of the time for which theyv are adjusted, the three relays 325, 324, and 323 fall back one after the other, and relay 323 finally completes the kick off circuit at armature 369,

the other point in this circuit having been closed already at armature 346 of relay 317,

the adjustment of the relays 323-325, inelusive, being such that the sum of the time required for the three to fallback is greater than the longest time required for the finder F and the secondary switch SS to complete their operations under normal conditions.

A further oint that may be mentioned at this time is t at, since the pick-up relay-315 falls back at the end of the first digit, it is necessary to open the circuit of relay 325 at another point before relay.-315 falls back. Accordingly, the circuit of relay 325 is opened at armature 343 of relay 316 which energizes before relay 315 falls back and which remains energized throughout the remaining part of the operation.

It sometimes happens that a finder, the finder F for example, is operated by the common sender to bring its wipers into enga ement with the bank contacts of a particu ar line at a time when the test contact of such line (which contact is engaged by the test wiper 17 or the test wiper 20, depending upon which set of wipers is in use) is grounded. This may be due to the fact that the calling line was called by a connector switch after the receiver was removed and before the finder arrived, or it may be due in certain infrequent cases to the fact that the finder operated incorrectly and, therefore, landed on. a set of contacts belonging to a busy noncalling line. In any event, in case the test wiper in use of the finder F engages a grounded contact at the termination oflthe operation of the finder F ground is extended through the resting contact (or working contact, as the case may be) of armature 34 and said armature, and armature 39 and its resting contact to the junction of relay 24 and resistance 25. Accordingly, the relay 24 is short circuited and is not able to energize and connect up the line wipers of the finder F when the common mechanism attempts to close a circuit for the said relay 24 as it does in the hereinbefore explained manner after the finder F and the secondary switch SS. have both completed theiroperationsl Accordingly, no circuit is closed over the conductors 53 and 56 for the line relay of the selector switch seized switch SS'and no holdin on the release trunk 00nd by the secondary ground is placed uctor 55, and the er F is automatically released as soon as the finder allotter FA1 is advanced to the next set'of bank contacts as it is in the-hereinbefore described manner.

It sometimes happens during a busy part of the day that all trunks accessible to a particular group of secondary switches, for exam le, the switc SS is ocated' becomes busy.- When thls hap us, it is obviously undesirable to operate t e finder F and the secondary switch SS needlessly and is likewise desirable that the finder secondary link be made busy so that another link to which idle trunks are available may be operated to complete any call which may arise in this group. The way in which this is done will now be explamed. The make-busy relay 141, Fig. 2, 15 connected in a closed circuit in series with the res1stance144. However, relay 141 is normally short circuited by a ground potential applied to the common conductor 143 by each idle one of the selectors, such as S, accessible to the same group of secondar switches. For example, when the selector is idle, ground is supplied to the common conductor 143 by way of the spring 107, the spring 108, resting contact and armature 129, armature 121 and its resting contact, armature 123 and its resting contact, and oii normal spring 117 and its lower contact. Now when the selector S becomes busy (the same applies to each of the other selectors), ground is removed from the particular branch'of conductor 141 that extends to this selector at armature 121 of line relay 111, and again at armature 123 of release relay 112 when it energizes. Also when the 01f normal spring 117 shifts upon the first vertical step, a further point in this circuit is opened and remains open until the selector S again becomes idle and is restored to its normalposition. Accordingly, when all the selectors, such as S, are busy, ground is removed from conductor 143 at all points and relay 141, being no longer short circuited, energizes 1n series with the resistance 144. Upon energizing, relay 141, which has an armature and two contacts for each of the secondary switches, such as SS, in the same group, disconnects ground from conductor 57 and places ground on conductor 58, which is thetest conductor of the finder F and the secondary switch SS and which extends to the bank of test wiper 383 of the finder allotter FA-l. Accordingly, stepping magnet 381 of the finder allotter FA1 is operated in the usual manner to advance group in which the secondary the wipers 383 and 384 out of engagement It occasionally happens that all finders accessible to the finder allotter FA-1 or to the finder allotter FA'2, as the case may be, become busy. Arrangements are provided for preventing the unnecessary operation oi; such allotters when this occurs. Cons1dering the finder allotter FA1, the automatic stepping circuit of its stepping magnet 381 includes the resting contact andarmature 314 of the relay 319. Relay 319 is included in a closed circuit which includes the associated resistance 312. However, the normally grounded conductor 63, which is individual to the finder allotter FA1, is connected to the junction of resistance 312 and relay 319, normally preventing relay 319 from energizing. Conductor 63 is normally grounded in each of the finders. For example, it is normally grounded in the finder F through the lower contact of ofl? normal spring 28 and said spring, resting contact and armature 40, resting contact and armature 47, springs 50 and 51, conductor 57 and the resting contact and armature 142 of the make-busy relay 141. Now when the finder F becomes busy, the oil normal spring 28 is shifted and ground is removed from conductor 63 and is not replaced until the finder F is restored to normal position again. Also, if the make-busy relay 141 associated with the group to which the secondary switch SS belongs is energized, the circuit through which ground is supplied to conductor 63 by the finder F is opened. Accordingly, it

- the finder F is busy due to its being actually in use. or due to the fact that the associated secondary group is busy, it does not supply round to conductor 63, and when all the nders accessible to the finder allotter FA-1 are busy, ground is entirely removed from conductor 63, permitting relay 319, Fig. 4, to energize in series with resistance 312 and disconnect stepping magnet 381 from test wiper 383 at armature 354. In the same way relay 320 energizes when all finders accessible to the finder allotter FA-2 are busy and disconnects stepping magnet 396 at armature 355.

In case neither of the allotters FA1 and FA2 is standing on an idle finder, which condition may arise if all finders accessible to both allotters are busy or if both allotters are operating in search of idle finders, arrangements are effective to prevent the closure of the circuit of start relay 321. It will be noted that when test wiper 383 of the allotter FA--1 is in connection with a grounded contact, a circuit is closed through the resting contact and armature 356 of start relay 321 for the left hand winding of the shunt field relay 318. When either winding of relay 318 is energized alone, the armature of the relay is not attracted owing to the fact that the core of the other winding serves as a magnetic shunt for the core of the enerized winding. Therefore, when onl one finder allotter is standin on an idle nder, relay 318 is not energize However, when both finder allotters are standing on busy finders, both windings of relay 318 are energized and the said relay 318 operates; disconnects start relay 321 at armature 351; disconnects relay 325 at armature 353; and at armature 352 opens the holding circuit so as to unlock any register relays that might happen to be locked up at this time. As soon as one of the finder alloters FA-1 or FA2 finds an idle finder, either at the end of the hunting movement (if it is hunting) or as soon as one becomes available (if none were available at the time of the energization of relay 318), relay 318 falls back to permit calls to be put through.

It may be pointed out that the reason that the holding circuit of the register relays is opened at armature 352 of relay 318, as pointed out above, is to prevent the possible needless operation of a finder immediately following the termination of a busy condition on both allotters. For example, if both allotters are busy for some length of time, a calling subscriber might remove his receiver, wait for the dial tone, and, not hearing it, replace his receiver before a finder becomes available. In this case, if the register rela s were permitted to energize and lock up, t e registered number of such subscriber would be transmitted to the first finder to'become idle, which would be a needless operation on account of the fact that the subscriber has already replaced his receiver. Furthermore, a second subscriber might have his receiver off and his service would be delayed while the number of the first subscriber is being transmitted. However, as before pointed out, such an occurrence is prevented by the opening of the holding circuit at armature 352 of relay 318. k

In case an. attendant needs to make some minor adjustment on the finder F, and wishes to cut the finder F out of service while he is doing this, he removes the small pin that is lying between the spring 51 and the spring 50 and pushes the spring 51 into its alternate position with the tip of spring 52 in the slot (not shown) in the spring 51 at which point he inserts the pin between the springs 51 and 52 so as to hold ground on conductor 68 to cause the finder F to test busy to the finder allotter FA1. On spring 51, breaking contact with spring 50, ground is removed from the common conductor 63 at this point. Accordingly, the conditions which arise when the finder F is actually busy are simulated. Similarly, if

106 and 107 in the same manner as described in connection with springs 51 and 52 of the finder F.

It may be pointed out at this time that, as intimated hercinbcfore, the finders, of which F is one, and the secondary switches, of which SS is one, are split up into groups as determined b the lines and trunks, respectively, to which they have access. For example, the finder F has access to the lines of substation A andA, together with 198 other lines, making 200 lines in all. All the finders having access to these same 200 lines are considered as one group, although from the standpoint of the allotters they are split into two smaller groups as hereinbefore explained. This, however, has nothing. to do with the trunking arrangement now being described. In the same way, the finders hav-' ing access to the next 200 line group'of lines are another group of finders, etc.

The secondary switch SS has access to a number of first selector trunks, of which the trunk extending to the selector S is one. As ordinarily constructed the switch SS has access to twenty-five trunks, and all secondary switches having access to the same twenty-five trunks are considered one group. Similarly, the secondary switches having access to the second group of twenty-five first selector trunks are the second secondary group, etc. Now, in order to weave the finder switches and secondary switches in all groups into one unitary network, each finder switch of a given group is cross connected on the intermediate distributingframe IDF to a secondary switch in a different secondary group. For example, if there are thirty finders having access to the lines of substations A and A, and if there are thirty secondary groups, each finder is connected at the frame IDF to a secondary switch in a different one of the thirty secondary groups, but if there are thirty finders in the group as before, but only fifteen groups of secondary switches, two finders are connected to two secondary switches in each of the fifteen groups. This same arrangement is carried out for each of the primary groups.

The function of the intermediate distributing frame IDF, Fig. 1, will now be explained. It will be noted that the lines of substations A and A are connected to the connector banks independent of the intermediate distributing frame, but are connected to the cut-off relay and the finder banks through the intermediate distributing frame. Accordingly, the number of these lines remains the same in the connector banks, regardless of the connections at the intermediate distributing frame, but whenever it is desired, the outgoing trafiic imposed upon the various groups of finders may be regulated and readjusted at will, by merely shifting the heavy calling and 1i ht calling lines back and forth amongst t e various finder groups until the traflic on the various groups is equally balanced.

It may be well to point out at this time that although the system has been described as employing the special cut-olf relay and mounting frame shown in Figs. 57, inclusive, in case it is so desired, ordinary cut-off relays of any well known type may be employed, in which case their contacts may be multipled together in the usual manner. It may be well to point out also that in case it is not desired to use a special mechanical construction for the finders such as F, the 0rd] nary type of vertical and rotary switch may be employed instead, in which case the sender and the cooperating tens relays may be arranged to step the finder to the first level when a call is originated in that level, instead of merely rotating its wipers as described hereinbefore. Also it may be point-' ed out that applicant is well aware of the fact that numerous modifications of the system hereinbefore described may be made by those skilled in the art. Accordingly, applicant does not wish to be limited by any means to the exact details of the disclosure but wishes to be limited only by the appendedsaid lines, means for closing a circuit through said relays and said relays lncludlng a calling one of said lines in series to operate them to register the number thereof, and means for operating said switch under the control of said relays to establish connection with such line.

2. In a telephone system, lines, a switch having access thereto, registering means common to said lines, means for closing a circuit through said registering means and any calling one of said lines in series to register the number. thereof, a sender, and means for operating said sender under the control of said registering means to transmit the registered number to saidswitch to operate the same to establish a connection with the calling line.

3. In atelephone system, a link circuit comprising a directive finder and an automatic trunk hunting switch connected together, other similar link circuits, and a common apparatus comprising means for transmitting impulses to said finders and means for controlling the hunting movement of said hunting switches.

at. In a telephone system, a directive finder and an automatic trunk hunting switch paired together, other similar pairs, a common apparatus comprising means for trans mitting impulses to any one of said finders

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