US1315444A - Plaihoorapii c - Google Patents

Description

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TELEPHONE SYSTEM.

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UNITED STATES PATENT OFFICE.

TOI-IN WICKS, OF CHICAGO, ILLINGIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, 0F CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Sept. 9, 1919.

To all whom it may concern ie ity known that I, Jenn7 lVicKs, a citizen o-IE the llnited States of America, and a resident of Chicago, county of (look, and State of Illinois, have invented certain new and useful In'iprovenients in Telephone Systems, of which the following is a specification.

My invention relates in general to telephone systems but is concerned more particularly with methods oi" handling toll or long distance connections in automatic telephone systems. The object oi the invention may be said to consist broadly in the production of a new and improved toll trunking system in which long distance connections are established automatically, together with the design of improved circuits and apparatus whereby such systems may be put into effective operation.

The above indicates in broad terms the scope of the invention. Various features are included in the working embodiment of the complete system which will not non1 be specitically mentioned, but which Will each be described in the specification. which is to follow and pointed out in tne claims.

Of the accompanying drawings, to which reference will be made in the specication, Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11, when arranged in order with corresponding lines at the ends thereof in alinenient, represont.` dia-granimatically a complete long distance connection between a calling substation A in one exchange and a called substation A3 in another exchange, in a system embodying the principles of my invention. Fig. 12 is a schematic diagram illustrating the general layout of the system, and Fig. 13 is a detail of the bank of the automatic switch shown in Fig. 6.

lcferring to Fig. 12, three automatic exchanges are shown which, beginning at the left. will he designated, respectively, as the No. l exchange, the No. 2 exchange, and the No. 3 exchange. These exchanges are assumed to be located in different cities and may each be of 10,000 lines capacity although the exact size is of no great consequence. On the assumption that the capacity is as noted above however, local connections in each exchange will be established through the medium of individual line switches or trunk selectors, first selectors, second selectors, and connectors. For example, in the No. 1 ex change, the subscriber at substation A is able to establish connection with the subscriber at substation A through the medium of the individual line switch C, the first selector switch E, the second selector switch F, and the connector switch H. This is the usual percentage trunking system and is thus briefiy mentioi'led because of the fact that a portion thereof. con'iprising the connector switches also forms a part of a second trunking system used only Afor the establishment of toll connections.

Each exchange is provided with a toll board presided over by operators who estab` lish all outgoing toll connections. The operators in any particular exchange have access to the local subscribers lirios over so called toll service trunks, cach of which terminates in a toll first selector. The toll first selectors have access to toll second selectors, which in turn have access to connector switches. These latter switches are the connectors previously mentioned forming part of the local trunking system. Referring to the drawing Fig. 12 again., the jack J is the terminal of a toll service trunk which extends to the toll first selector V. The toll selector V has access to toll second selectors, one of which is the `toll selector W', which in turn has access to connector swi ches, one of Which is the connector H. It will be seen therefore that the local trunking system and the toll service trnnking system are Finally blended together, in that the connector switches are common to both systems. The No. 2 and the No. 3 exchanges are both arranged in substantially the saine, manner as is exchange No. 1.

Proceeding now to the trunking between exchanges, the No. 1 exchange and the No. 2 exchange may be interconnected by a group of toll lines suiiieient in number to handle the traiic. One of these toll lines is the toll line X. Similarly, another group of toll lines, one of which is the toll line Z, connects the No. 2 exchange with the No. 3 exchange. There are no toll lines directly extending between the No. l and the No. 3 exchanges, therefore connections between these two oints must necessarily be established via tiie No. 2 exchange. This situation may arise in two Ways: Either or both of the No. l and No. 3 exchanges maybe of relatively small size and so located as to be subsidiary to exchange No. 2. In such case it would usually be uneconomical to provide a third group of toll lines extending directly between the N e. 1 and N o. 3 exchangis. The second case arises when the exchanges, which mayy all be of large size` are located in approximaicly a straight line or Where for topographical reasons the toll lines from exchange No. l to exchange N o. 3 pass through or near the city in which exchange No. 2 is located. Under these circumstances, and assumingthat toll connections are to be estab lished automatically, it has been found most efficient to cut the through toll lines at the intcrinediate exchange, thereby making each section available for short haul messages, and com )lete all the through calls by means of switc in apparatus at the intermediate or No. 2 exiI ange.

It will he perceived now that the toll lines and switching),` apparalusl comprise a third trunkinc' system, and it will he shown in the followingl that this third system is merged into the toll .servire trunlrinpr system at each exchange. The toll lines terminate at each end in the usual manual drops and jacks. Thus the toll liuc X extends fron'i jack J in the No. l exchange to jack J2 in the No. Q exchange and the toll line Z extends from jack J* in the No. 2 exchange to jack J in the No. 3 exchange. In addition there is provided for each toll line a toll selector repeater at cach end thereof, which in the ease of toll line X are the selector repeaters M and M', and in the case of toll line Z are the selector repeaters M2 and M3. Considering,r now the No. 2 or intermediate exchange, the banks of all the toll selector repeaters, includin repeaters M and M2, are Connected in niu tiple and the'first nine bank levels preferably (assumingthat the usual Strow- 2e'er type of switches are used) are multipled with the first nine bank levels of the toll first selectors. Thus in Fig. 12 it will be seen that the toll second selector W2 is accessible to toll first selector V2 and to tol] selector repeaters M and M2. The tenth bank level of the toll first selectors is dead beca-use the tenth level of the local first selectors is used for callingr recording toll operators and therefore does not correspond to a group of subscribers lines. Since the toll o erators are never required to eall the recor ing Operators there is thus left available for other purposes the tenth level of the toll first selectors and the same level of the toll selector repeaters. As previously mentioned no use is made of this level in the toll first selectors. In the toll selector repeeters, however, this tenth level is used for the through switching. To this end a roup of toll rotary connectors is provide one of which is. indicated by reference character N. These toll rotary connectors are accessible in common to all the toll selector repeaters in the No. 2 exchange and have common access to all the/groups of toll lines terminatin,r in the No. 2 exchange, it heiner understood, of course, that there may be a ninnher of such groups, extendlng each to a different city, in addition to the two groups indicated in Fig'. l2. No toll rotary conneclorsl are shown in the No. l or No. 'i exchanges. ln ease there should be a 'fourth exchange beyond the No. -l exchange, then the No. 3 exchange would take on the char- ;U-ter of an intermediate exchange and would be equipped in the saine manner exchange No. 2.

To further elucidate the general trunkinfr system, a call may be traced from the lsuistation A in the No. l exchange to sul)- station A2 in the No. 2 exchange. .The con nection is, of course, handled by the operai'or in the No. l exchange and is extended io the called line over the follo\ving n path: piet: d'. loll line toll selector repeater nl. toll .screed velerlei' ivi. and connector liz. The eonfurlion le llu` local :-;iili;-'criher A is srl up :is toilets: jack J. toll lint .we lector i", loll second selector W, and. rouoertor ll". fionnerii'au between jacks l and J is con'lpleed by a. rord circuit in the cus toniary manner. Assuming non' that the failed substation is substation A in the No. f3 exchange, the ecnncetion thereto may he extended over the followingr path: jack J', loll line X, toll selector repeater M', toll rotary connector N, toll line Z, toll selector repeater M, toll second selector W3, and connector H3.

It is thought that the foregoing will be suliicient lo make clear the general layout of the system. Reference will non' he had io the cirE uit drawings, Figs. l te l1, inclusive, for a brief description of the ap paratusinvolved. rlhesc drawings show diagramaiatically all the equipment necessary to establish the complete long:r distance corineetion between substations A and A3, previously referred to. The apparatus shown in. Figs. 1, 2, 3, and 4 is located in the No, 1 exchange; the apparatus shown in Figs. 5, (i, 7, and part of Fig. 8 is located in the N e. 2 exchange; While the apparatus shown in the remainder of Fig. 8 and in Figs. 9, 10, and 11 is located in the No. 3 exchange.

The su-bstations such as substation A (Fig. l) and substation A8 (Fig. 11) may be of the usual common battery type in which the transmitter and receiver are connected in series. In addition. each substation is provided with an impulse sender or callingr device which in the case of substau tion A includes the iin-pulse springs 2 andB which are controlled by the impulse wheel 4 through the medium of a finger hole dial (not shown). A calling device suitable. for the purpose is shown in British patent to S. G. S. Dicker, #29,654 of 1.910.

The individual line switches such as line fil lill) was# switches C and C may be of the general type of line switch described in the British patent to James, No. 26,301 of 1906; being, however, preferably of the particular type disclosed in U. S. Letters Patent No. 1,078,090, granted Jan. 17, 1912, to Frank Newforth. Line switches of the foregoing type are well known and therefore will not be described herein. It will be sufficient to say that through the medium of line switch C the line of substation A is given access to a plurali-ty of selector switches which form part of the local trunking system partially disclosed in Fig. 12. A three conductor trunk line which may be extended to one of these selector switches is indicated by reference characters 14, 15 and 16.

For the purpose of controlling a group of line switches such as the line switch C there is provided a master switch D, which 'is of the general type of master switch disclosed in British patent to James, #26,301 of 1006, above referred to; being, however, more nearly of the particular type disclosed in British patent to Martin, No. 1410 of 1010. The function of the master switch, as is well known, is to maintain all the idle line switches -of its associated group in operative relation with an idle trunk line.

The selector switches, amon which are included the toll selectors V, 73, W', and W, the toll selector repeaters M, M', M2, and M3, and also the local selectors E and F (shown only in Fig. 12) are mechanically of the general type of selector switch disclose-d in U. S. Letters Patent No. 815,321, granted March 13, 1906, to Keith, Erickson and Erickson; the side switch and private magnet, however, being in all cases omitted, and the circuits being modified to enable the switches to operate in accordance with the two wire system of control.

The connector switches, among which are included the connectors H and H3 and the toll rotary connectors N and N are mechanically of the general type of connector Vswitch disclosed in U. S. Letters Patent #815,176, granted, March 13, 1906, to Keith, Erickson and Erickson. The connector switches, like the selectors, also have their circuits revised in accordance with two wire practice. Reference is had to U. S. Letters Patent #13,901, reissued April 13, 1915, to Frank Newforth, for circuits of a modern two wire automatic telephone system.

A great many other circuit changes have been inade in order to enable the switches to operate in accordance with the general plan contemplated by my invention. For example, the connectors, such as connector H (Fig. 1) serve to complete both local and toll connections. On connections of the former type the ringing is preferably automatic and the called subscriber is supplied with talking battery from the usual back bridge relay of the connector. Uu toll connections, however', the ringing is operator controlled, While the called subscriber is supplied with talking battery from a bridge in the toll second selector. The busy test circuits operate differently also. Means is therefore provided in each connector which is effective to automatically switch its circuits Whenever such connector is seized by a toll second selector.

Details of the toll second selector to which particular attention is called are the means for supplying talking battery to a called subscriber, mentioned above, and the means for relaying ringing current, which means comprises a normally bridged relayA which is disconnected during conversation. The eircuits of the toll rotary connector N (Fig. 6) are also new to a great extent, an important feature being` the novel busy test circuits.

Attention is also particularly called to :i feature .of the toll selector repeaters. such :is the selector repeater M (Fig. 5). It will be observed that the line circuit through the selector repeater M (the heavy conductors) includes the repeating coil R. Then connection is completed from the toll line X (see Fig. 12) to a local line the repeating coil R is included in the circuit in accordance with standard practice. Suppose, however, that the connection is extended viaY the toll rotary connector N to the toll line Z. A reference to Fig. 7 will show that the line circuit will now include a repeating coil R2 in the selector repeater M2. lere it not for some special arrangement we would then have two repeating coils in the connection between the two toll lines at the No. 2 eX- change, resulting in an unnecessary transmission loss. Means is accordingly provided in the selector repeater M (and in all the other selector repeaters) whereby when connection is extended to another toll line the associated repeating coil is automatically cut out of circuit.

The above features of the automatic switches have been mentioned at this time in ordenthat they may be had in mind during the perusal of the detailed specification in which these features and many others will be fully described.

A brief mention should also be made of the switch operating or control circuit which is superimposed on the toll line Z. Referring to Fig. 8, it will be seen that toll line Z is equipped at each end with well known composite telegraph apparatus con'iprising the toroidal coils T, T', T2 and T3, together with the usual arrangement of condensers. Two 1ounded circuits are thus obtained in addition to the metallic talking circuit. The grounded circuit which includes the lower conductor of toll line Z is shown as a simple Morsetelegraph circuit, while the grounded circuit including the upper conductor of toll line Z is in use as a switch operating circuit, as will be further explained in the detailed specification. Since ringing currents ott ordinary frequency cannot be used on coinposite toll lilies without interference, I have indicated by reference characters U and U two composite ringers, one at each end of the toll line. The purpose and utility of a coinpositc ringer in this connection is well known and need no1A he explained in detail. Reference is had to ll. S. Letters Patent No. 'messi' granted sept.. 1c, 1902 r0.1. M. Feu

The opcrators cord circuits, one of which is shown in Fig. 3, are designed especially for automatic long distance work and include several features, thought to bfc new, which relate to control of supervision and other delails and which will be fully explained hereinafter. The reference character S indicates a callingl device or impulse .sonder which is similar to the substation calling devices.

Throughout the drawings I have shown a plurality of batteries B', B2, etc., for supplying` operating and talking current. It is to be understood, however, that in accordance with the usual practice there is preferably but one battery in each exchange, having its positive pole grounded. An exception to the above are the batteries for supplying current to the toll line switch control circuits. There is provided in each exchange in addition to the regular exchange battery a special battery or generator of approximately double the voltage of the exchange battery. These special batteries are the battery B5 (Fig. 4), batteries Ba and B15 (Figs. 5 and 7) and battery B22 (Fig. 9). Each exchange is also provided with a busy sig* nailing machine such as is indicated by ret erence character Q (Fig. 1) a ringing current generator such as generator Gen (Fig. 1) and intermittent ringing apparatus such as is indicated by reference characters I R (Fig. 1).

Having described bri'eiiy the general layout of the system and the character of the apparatus involved, 1 will now plbceed to exp-lain in a more detailed manner the operation of the circuits. For this purpose it will be assumed that the subscriber at substation A (Fig. 1) desires to obtain connection with the subscriber at substation A3 (Fig. 11), this being the complete circuit connections shown in the drawings and previously referred to. I Y y,

In order to initiate a-lo distance call the subscriber at substation must get into communication with a so called recording operator at his exchange, which is the No. 1 exchange. Any approved method of `accomplishing this object will serve but since the substation A is an automatic substation it will be assumed that the subscriber calls the operator automatically as follows: Upon retrieving thc receiver at substation A, the line switch C is operated to extend the line conductors 12 and 13 throu fh to a selector switch, which may be the selector to which the trunk conductors 14, 15, and 16 extend. .-ifter the line switch has operated, the subscriber may manipulate the finger hole dial of his instrument in accordance with the digit O, thereby operating the selecto-r to scloct a group of trunks extending to a recording opcrators position; after which the selector rotates its Wipers automatically to connect with an idle one of these trunks, all in. a well known manner. The calling subscriber, upon hearing the operator respond, will give hcr the necessary ,information, such as the name and address of thrl person with whom convcrszition is desired. :1nd also his` own naine and telephone num ber; and will then replace his receiver, thereby restoring (hc line switch (l and the selector switch to normal position. The re cording operator in the meantime will write out the data received from the sul'iscriber on a ticket, which is passed to a toll operator whose duty it is to complete the required connection.

In theL case under consideration the wanted subscriber is located in the No. 3 exchange which must be reached via the No. 2 exchange. The toll operator, therefore, after first observing that the toll line X extending to the No. 2 exchange is idle, as indicated by the unlighted condition of bus)` lalnp L, inserts the calling )lug of the cord circuit shown in Fig. 3 in tlie jack J. By the insertion of the plug in the jack the following circuit is coinuletcd over the sleeve of the cord: ground at G2, armature 35 and resting contact, resting contact of ar1nature 31 and the said armature, Winding 2S of relay 27, contact springs 33 and 32 of key `K", sleeve otplug, sleeve of jack J', conductor 102, resting contact of armature 112 and the said armature, and Winding of relay 113 of the 4selector repeater M to battery B4. Relay 27 in the cord circuit is i'narginal and is not oaeratively ener ized by current flow in the a ove circuit. clay 113, however, is operated and by means of its armature 115 closes a circuit from ground G which includes the Winding of slow acting relay 114 and battery B4. Upon energizing, relay 114 by means of its armature 117 removes ground from the resting contact of armature 116 of relay 113, and by means of its armatures 118 and 119 closes circuits for the busy lamp L8 and the cut off relay 104. The first of these circuits may be traced as follows: Vground at G7, armature 118 and its Working contact, conductor 101 and .the busy lamp LS tov battery B2. Multi-ple busy lamps in other operators positions are also lighted in parallel With busy lamp L. A four conductor trunk line, which may be considered an extension of toll line X, is indi- Vated by reference character 140 (Fig. 3), and extends (when the No. 1 exchange is equipped as a switching exchange) to multiple. contacts in the banks of toll rotar;Y connectors such as the connector N (Fig. (S). lt will be seen that a branch of conductor 101 extends to test Contact 106 and its multiples where by a ground potential on these test contacts the toll line X is made busy. Returning to the relay 114, the circuit for the rut-ott relay extends as follows: ground at G18, Working contact of armature 119 and the said armature, conductor 105, and the Winding of cut off relay 101i to battery B3. By the operation of the cut,- otl relay the drop 103 is disconnected in the usual manner.

then the relay 113 was energized over the sleeve of the cord.y a switch control circuit cXteiuling to the No. 2 exchange was completed, which for convenience may be traced in reverse direction as follows: battery B5, resistance r, working contact of armature 116 and the said armature, winding of relay 120, windings 122 and 123 ot repeating coil R in parallel, contact springs of relay 124, line conductors of toll line X in parallel, contact springs 233 and 231i et relay 224 and their resting contacts, windings and 223 of repeating coil R in parallel, Winding of relay 220 armature 216 of relay 213 and its resting Contact, and armature 217 of relay 214 and its resting contact to ground at G1. Upon the closure of the above circuit relay 120 of the selector repeater M and relay7 220 of the selector repeater M are operated, The energization of relay 120 is Without effect for by the operation of relay 114 ground GT has been disconnected from the armature 121 of the said relay 120.

The relay 220 of selector repeater M, however, operates to corn lete the following circuit: ground at (111, armature 218 and its resting contact, armature 237 and its working contact, and the Winding of relay 226 to battery B6. Upon attracting its armature 254:, relay 226 shortcircuits the condenser 255. This operation is of no particular consequence in the connection now being established and may be for the present neglected. A further result of the energizaton of relay 226 1s the closure of a iii-cuit for slow acting release relay 227 as follows: ground at G1, armature 238 and its Working contact, and Winding of relay 227 to batter 7. Upon energizing, relay 227 prepares y means of its armature 941 Ia circuit for the vertical magnet 232 in the usual manner, and in .addition closes a busying circuit as Jollovvs: ground at G14, armature 240 and its Working Contact, conductor 201, and thebusy lamp L* (Fig. 6)

and its multiples at the toll board in the No. 2 exchange. A branch of conductor 201 extends by Way of a conductor of trunk 240 to test contact 206 and its multiples in the banks oi toll rotary connectors N and N f ud other similar connectors Where by a ground potential on these test contacts the toll line X is niade busy.

The foregoing operations have Iall occurred in response to the vinsertion of the plug in jack J at the No. l exchange. At this point it should be noted that while the toll line X has been made busy to the operators and to the toll rotary connectors in the No. 2 exchange, the cut olf relay 204 has not been operated to disconnect the drop 203.- It follows then that if she so desires, the operator at the No. l exchange may signal the distant operator manually by throwing her ringing key K2 to project generator current out over the toll line to actu-ato the drop 203.

W'e have assumed, however, that the connection under consideration is to be established automatically and, such being the case, the toll operator will proceed by operating her calling device key K3, whereby through. the shifting oi' Contact spring 32 from engagement with Contact spring 33 into engagement with contact spring 3G the calling device S is substituted for the relay 27 in the circuit of relay 113 of selector repeater M. At this time also the listening key K should be in operated position whereby the opera'- tors head set P is bridged across the tip and ring strands of the Calling end of the cord circuit. Since the talking circuit is independent of any operating circuit and is kept clear. section after section. as fast as established, a trained operator is able, while operating her calling device` to judge of the correct response ot thc switching apparatus by certain characteristic sounds in her receiver. lspecially is this true in the case of busy signals which are transmitted back to the sending operator from the various switching points in case all outgoing trunks or toll lines of a desired group are busy as Will be explained hereinafter. A further feature of the cord circuit which should be mentioned is the fact that the calling device key KS. when operated, disconnects the tip and ring conductors of the answering end of the cord circuit. It follows that a subscriber Whose'line may be connected with by the answering end ot' the cord is prevented from interfering with or hearing Whatever is taking place at the calling end.

To proceed with the operation, the first di git of the number to be called is the digit 0, for as previously mentioned the tenth bank level of the selector repeaters is the level which is assigned to the toll rotary connector trunks. Accordingly, the operator will now manipulate the dial of the call ing device S in accordance with the digit 0,

thereljiy interrn ning ten times the circuit; of relay 113 of t e selector repeater M (Fig. 4). In responseto these interruptions of its circuit, relay 113 is denergized a corrosponding number of times, interrupting at each denergizationthc previously described control circuit which includes the relay 220 of selector repeater M' (Fig. 5) at the distant exchange. It follows that relay 220 is likewise. denergized ten times to cause a seriesl of interruptions in the circuit of relay v226.

At each interruption of its circuit relay 226 inrturn is denergized momentarily and sentis an impulse from ground G13 through sprlng 238 and its back Contact, spring 241 and its front contact, spring 271 and its hach Contact` and ,the winding ot' slow acting relay 22S and the winding of the vertical magnet 232 in series. The vertical magnet, in response to these impulses, operates to step up the shaft of the selector repeater M' until thi'` wipers 245, 246, 247, and 246 arrive al the tenth horizontal level of bank contacts. llelay 22Sl is energized in series with the vertical magnet and being slow acting retains its armature attracted during the serie-s of impulses. At the first upward movement of the shalft a circuit for the cut olf relay 204 (Mig. 6) is closed as follows: ground at G15, oil' normal Contact 260, conductor 205, and :the winding of cut off relay 204 to battery B1". The operation of the cut off relay disconnects the drop 203 in the usualmanner. An additional circuit closed upon the first upward movement of the shaft, is an ener gizing circuit for the relay 230, which extends from ground G by way of the armature 240 and its working Contact, armature 263 and its working` contact, off normal contact 262, and the winding of relay 230 to battery B11. Upon energizing, relay 230 locks itself independent of relay 228 by means of its armature 264, and by means of itsI armature 265 prepares a circuit for the rotary magnet 23,1 which is held open by the relay 228 during the vertical operation of the switch. At this point it should be mentioned that by the closure of the off normal Contact 262 the line switching relay 243, whose lower termin al is connected to ground G, is connected in series with the relay 230, the circuit passing through interruptor Contact 266 of the rotary magnet. The junction point 267, however, has already been connected to ground as preyiously mentioned so that the relay 243 is shortecircuited and remains inoperative for the present.

When the slow-acting relay 228 denergizes at the end of the series of impulses, it completes at the resting contact'of its armature the previously mentioned circuit of the rotary magnet, extending from ground G1". 4Upon energizing, the rotary magnet operates to rotate the'wipers 245,

246, 247, and 248 into engagement with the first set of bank contacts in the horizontal level to which they have been raised. Near the end of its stroke the rotary magnet opens the interi-opter contact 266, thereby breaking the lockingl circuit of relay 230.

Upon deinergizing, the relay 230 breaks the energizing circuit of the rotary magnet, which magnet .accordingly retracts its armature to again close the interruptor contact 266. The operation new depends on whether the first toll rotary connector trunk line, the terminals of which are now engaged by the selector repeater wipers, busy `or not. Assuming that this trunk line is busy, the test contact upon which the test or private wiper 247 is resting will have ground potential upon it, which ground potential will serve to maintain the line switchingl relay 243 short-eireaiitrd and also to again energize the relay 23)A Y[t should be mentioned here that the` relay iii, whirl: is in series with the pri vate wiper 247, if. of very low resistance .in order that thirelay 243 may` be eliccthely short-rirruitefl, and is made slow to energize by means oi' a slug of copper in order that it may not energize from momentary impulses received during the testing of busy trunk lines, leturning to the relay 230, when this relay energized over the private wiper, as previously described, the energizing circuit oi the rotary magnet is again closed, whereby the saine cycle of operations is repeated. It will he seen then that the relay 230 will operate ai: an interruptor to step the ewitrh wipers around through the medium of the rotary magnet as long as the test wiper 247 engages busy or grounded test contacts. When an idle or ungrounded test contact is reached. and the rotary magnet retrace; its armature the relay 230 cannot again energize. The switching relay 243, however7 being no longer short-circuited, at once energizcs in series with the said relay 230. Relay 243 is of such high resistance that the relay 230 remains inoperative. Upon energizing, the switching relay 243 opens at its armature 270 the circuit for the vertical magnet 232; shifts by means of its armature 275 the private wiper 247 from its normal connection to junction point 267 into connection with the grounded conductor 201; disconnects at its armature 272 the con duetor 202 from the winding of relay 213; extends the heavy line conductors by way of its armatures 273 and 274, line wipers 245 and 248, and trunk conductors 301 and 304 to the toll connector N (Fig. 6); and finally, by means of armature 271, completes a control circuit including the line relay 307 of the toll rotary connector N (Fig. 6) which maybe traced as follows.' ground at G1", armature 239 and its working contact, the said armatune 271 and its working contact,

wiper 246 and the bank contact engaged thereby, conductor 302, armature 317 and its resting contact, and the Winding of line relay 307 to battery B12.

Upon the closure of the above circuit, relay 307 is energized and by means of its armature 326 completes a circuit for the slow-acting release relay 303. Relay 308, upon attracting its armature 320, prepares a circuit for the vertical magnet 318 in the usual manner. It .should be noted here that trunk conductor 303, extending from the test contact 352 is not grounded by the release relay 308 as is customary. Instead, the test contact 352 and its multiples are maintained at ground potential, or nearly so, over the path which extends from ground G14 by way of armature 21:0 of relay E227, conductor 201, working contact of armature 27.5 and the said armature, Winding of low resisting relay 2112 and the private wiper 247. The toll connector N is thus made busy to other selector repeaters. Since relay 242 is slow to energize, as already explalned, 1t will not be operated by momentary current impulses due to other selector repeaters passing over the now busy multiple terminals of the trunk line extending to the toll rotary connector N.

The operator is new ready to call the digits necessary to actuate the connector N, whereby an idle toll line extending to the No. 3 exchange may be selected. In Fig. 13 is shown the lower or first bank level of one of the toll rotary connectors, it being assumed that this is the level in which the toll lines extending to the No. 3 exchange terminale. As previously mentioned, each level may contain more than one group of toll lines, and the first three sets of contacts, therefore, may be terminals of toll lines extending to the No. 1 exchange. The next set o1 contacts is connected to a trunk line comprising the conductors 341, 342, and 343, which extend to the jack J7 at a toll op erators position. The wrt Jfour sets of contacts may be the terminals of the group of toll lines extending to the No. 3 exchange, the toll line Z being the second toll line in the group. The next contact set, as before, is connected to the trunk lineextending to the jack J7. It will be understood that other groups of toll lines may be terminated ia the remaining levels of the toll rotary connectors in a similar manner, the next contact set after each group being connected as already explained. From the foregoing, it will be understood that since the toll lines extending to tht` No. 3 exchange are terminatcd in the first level of the toll rotary connectors, and since the rst one of these toll lines terminates in the fifth contact set of this level, the proper digits to be called new are the digits 1 and 5.

The operator at the No. 1 exchange, therefore` will now operate her calling device in accordance with the digit 1, thereby causing as before a momentary deiinergization ot the relay 113 oit the repeater M. In response to this momentary deiinergization an interruption is produced in the control circuit extending to the relay 220 of the selector repeater M at the No. 2 exchange. Relay 220 thereupon denergizes momentarily to interrupt the circuit of relay 220, which relay7 in turn produces a momentary interruption of the circuit of the line relay 307 of the toll rotary connector N. Responsive to this interruption of its circuit, relay 307 denergizes momentarily and transmits an impulse from ground G1 to the sloivacting relay 300 and the vertical magnet 318 in series. side switch wiper 320 being in its first position. In response to this impulse the vertical magnet operates to step up the switch .shaft until the wipers 345` 340, 347, and 343 stand opposite the first horizontal level oiV bank contacts. Relay 300 is energized in series with the vertical magnet 313 and closes by means of itsl armature 32S a circuit which extends from ground G17 to the winding ot relay 310 and the winding 316 of the private magnet 314 in parallel. The resultant energization of relay 310 is of no consequence at this present time. The momentary operation of the private magnet 314, however, effects the movement of the side switch Wipers 320, 321, to their second position in the usual. and well understood manner.

The operator may now manipulate her calling device in accordance with the digit 5, thereby again producin a series of interruptions in the circuit eig relay 113 of the .selector repeater M. )is before these inter ruptions are repeated through the medium of relays 220 and 226 of the selector repeater M until they finally effect the circuit of line relay 307 of toll rotary connector N and cause ve denergizations of the Said relay. At each denergization, relay 307 sends an impulse from ground G1 to the slow-acting relay 309 and the rotary magnet 319 in series, side switch Wiper 320 being in its second position. In response to these impulses the rotary magnet operates to rotate the wipers 345, 340, 347, and 348 until they arrive at the 5th set of contacts of the first level. Relay 309 is energized in series with the rotary magnet 319 and being slow-acting, retains its armature durin the series of impulses to close the energizing circuits of the relay 310 and the private ma net 314. At the end of the series of impu ses, relays 309 and 310 and private magnet 314 denergize (it being assumed that the 5th contact set is idle), the private magnet controlling the side switch wipers 320 and 321 to advance them to their third position.

We will assume, however, that the 5th qolltact set is busy and that the 6th contact set, which is the contact set in which the toll line Z extendin to the No. 3 exchange terminates, is itle. Under these circumstances the test contact of the 5th Contact sei', with which the rivate wiper 347 is now in engagement, will) have ground potential upon 1t and the private magnet 314 will be maintained 'energized over the following circuit: ground on busy test contact, private wiper 347, side switch Wiper 321 in the second position, and winding 315 of private magnet 314 to 'battery B11. The private magnet being held energized and its armature 322 being in engagement with its Working contact, as soon as the relays 309 and 310 denergize a new energizing circuit is completed for the rotary magnet 319 which may be traced as follows: ground at G11, armature 323 and its resting contact` resting contact of armature 331 and the said armature, armature 332 and its Working Contact, armature 334 and its resting Contact, winding oi rotary magnet 319, and the side switch wiper 320 in second position to battery B11. Upon the closure oi the above circuit the rotary magnet 319 opcrates to step the wipers 345, 346, 347 and 348 into engagement with the 6th contact set. Near the end of its stroke the rotary magnet 319 closes by means of its armature 323 the circuit of relay 310, which relay upon energizing, breaks the last described energizing circuit of the rotary magnet by means of its armature 331. The rotary magnet accordingly retracts its armature 323 and breaks the circuit of relay 310, which relay, upon denergizing allows its armature 331 to again engage its resting Contact. The energizing circuit of the rotary magnet is not again closed, however, for the private magnet 314 has already deenergized, the test contact 406 of the 6th contact set being nngrounded, and opened the rotary magnet circuit at its armature 332. The Wipers of the toll rotary connector N have nonr been brought to rest in engagement with the 6th contact set, which contact set is a multi le terminal of the toll line Z extending to t e No. 3 exchange, and the side switch wipers of the toll rotary connector have been advanced to their third positions.

By the movement of side switch Wiper 321 to itsl third position, a circuit is closed for thebusy lam L5 (Fi 7 and its multiples, which exten s as fo lows: ground at G19, side switch Wiper 321 (in third position), Wi er 347, test Contact 406, conductor 401, an the lamp Ls to battery B2. A branch of the a'bov'e circuit (not shown) extends to multi le test contacts similar to test contact 406 in the banks of the other toll roterr conncwrsfwlnre by a reime vom' tial on the said test contacts, the total line Z is made busy.

By the advance of side switch Wiper 320 to its third position, a circuit is closed which includes the switching relay 312 and the relay 242 of the selector repeater M. This circuit may be traced as follows: ground. at G11, armature 240 and its working contact, conductor 201, Working contact of armature 275 and the said armature, winding of relay 242, private Wiper 247, bank contact 352, conductor 303, Winding of relay 312, and the side switch wiper 320, in third position, to battery B11. Relay 312 of the toll rotary connector N and relay 242 of the selector repeater M are therefore energizedin series.

Considering first the function et relay 242, this relay, upon energizing, closes a circuit for relay 224 as hillmvs: Ground at G12. armature 244 and its Working contact, and the Winding of relay 224 to battery B17. Upon energizing, relay 224 disconnects its armatures 235 and 236l from their respective resting contacts and brings them into cngagen'ient, respectively, with Contact springs 233 and 234, the said springs being thereby disengaged from their respective resting contacts. By this operation the heavy line conductors are connected straight through, the repeating coil R being eliminated from the line circuit. Two of the repeating coil windings, the windings 222 and 2,23 are left in bridge of the line circuit in order that the simplex control circuit including the relay 220 may be maintained. The retardation coil 225 is included in the bridge to increase its impedance and to there )y prevent excessive transmission loss.

Returnirg now to the relay 312 of the connector which relay it will be remem bered, Was energized in series with the relay 242, the following operations were performed as a result of its energization: At the resting contact of armature 339 a conductor extending to the release magnet 313 is opened to provide against the energization of said release magnet upon the denergization of line relay 307 and release relay 308 by the en agement of armatures 337 and 338 with t eir Working contacts the incoming line conductors are extended through to selector repeater M2 (Fig. 7) b Way of line Wipers 345 and 348; and final y, by means of armature 317, conductor 302 is disconnected from the Winding of the line relay 307 and is extended to the line relay 413 of the selector repeater M2 over the following path: conductor 302, armature 317 and its working contact, Wiper 346 and the contact engaged thereby, conductor 402, resting contact o armature 412 andthe said armature, and the Winding of relay 413 to battery B11. Upon energizing, relay 413 completes a -cirz'uit exten iA rom 'round G2 and including the winung, of s,i ivf-acting relay 414 and the battery B12. Upon energizing in turn, relay 414 disconnects ground G23 from the resting contact of armature 416 ot the line relay 413, and in addition, connects ground G21 to the conductor 401. The latter' operation, however, is of no particular consequence just now, since conductor 401 has already been grmmded by Way of the private wiper 347 of the rotary connector N. As a further result of the energization of relay 414, ground G22 is connected to the conductor 405, whereby the cut-off relay 404 is operated to disconnect the drop 403.

When the relay 413 Was operated a control circuit extending to the No. 3 exchange was completed, which may be traced from the negative pole of battery B15 as follows: battery B15, resistance fr", Working contact of armature 41,6 and the said armature, relay 420, conductor 480, winding 481 of toroidal coil' T', Winding 483 of the said coil, upper line conductor of toll line Z, winding 484 or' toroidal coil T2, winding 485 of the said coil, conductor 486, relay 520, armature 516 of relay 513 and its resting contact, armature 51T of relay 514- and its resting contact to ground at G24. Upon the closure of the above circuit relay 420 of the selector repeuter M2 and relay 520 of the selector repeater M3 are energized in series. The operation of relay 420 produces no eil'ect for ground G21 has been disconnected from the armature 421 by the operation of the slowacting relay 414.

The toll selector' repeater M3 is almost exactly like the toll selector repeater M and its operation will, therefore, be described in a somewhat cursory manner. When the relay 520 is energized over the control circuit from the No. 2 exchange, an energizing circuit is completed for the relay 526, which relay, upon its operation, completes an energizingl circuit for the slow-acting relay 527. By the attraction of its armature 54,1, relay 527 prepares a circuit for the vertical magnet 532 in the usual manner, and by the attraction of its armature 540 closes a circuit for the busy lamp Le as follows: ground at G54, armature 540 and its Working contact, conductor 501, and the lamp L6 to battery B21. A branch of the above circuit extends to the test contact 506 and its multiples in the banks of the toll rotary connectors in the No. 3 exchange (it being assumed that the No.` 3 exchange fis so equipped) Where by a ground potential on these test contacts the toll line Z is made busy. As in the case of selector repeater M', the cut-ofi' relay 504 is not o erated until after the selector repeater Ms as made its first movement.

The foregoing operations at the selector repeaters M2 and M2 have taken place in response to the seizure of the toll line Z by the toll rotary connector N. These operations, it will be observed, correspond eX- actly to the operations at selector repeaters M and M responsive to the insertion of the plug in jack J. The operator at the No. l exchange is new ready to dial the directory number of the Wanted subscriber in the No. 3 exchange, but before proceeding, it will be well to return to the toll rotary connector N and consider its operation in case all the toll lines extendin to the No. 3 exchange had been busy. mmediately after the rotation of the connector N responsive to the dialing of the third digit, the relay 309 having denergized, the test relay 311 is connected in bridge of the line wipers 345 and 348 as follows: Wiper 345, armature 370 and its resting contact, armature and its Working contact, armature 327 and its resting contact, Winding of relay 311, resting contact of armature 338 and the said armature, and the resting contact of armature 371 and the said armature to Wiper 348. lt Will be seen then that during the automatic rotation of the-connector Wipers in search of an idle toll line the relay 311 will be connected in bridge of the several lines in succession. Since the toll lines are clear of all bridged battery, however, relay 311 is not energized. But on the assumption that all the toll lines extending to the' No. exchange are busy, the Wi ers Will finally arrive at the contact set which is connected to the trunk 341, 342, 343. The Wipers 345 and 348 are now connected to opposite poles or' the battery B16 by Way of conductors 342 and 341 and the windings of relay 340. It follows that relay 311 is instantly energized in series with relay 240 to stop the rotation of the switch by opening the rotary magnet circuit at its armature 334. At the same time, relay 311 locks its own circuit independent of relays 307 and 309 at its armature' 333, and connects the secondary of the transformer of the busy signaling machine Q1 in bridge of the heavy line conductors extending back to the No. 1 exchange. Relay 340 is energized to close the circuit of the lamp L2, but ordinarily the operator at the No. 2 exchange does not get time to answer, for the No. 1 exchange opcrater, perceiving the busy signal, W1l1 release the connection at once. In case, however, the busy signal is received several times in succession the No. 1 exchange operator may Want to inquire as to the probable length of time the toll lines will be tied up, and Will therefore Wait on the line. Observing the continued lighting of lamp LT the No. 2 exchange operator will answer by plugging into jack J". By the insertion of the plug ound is removed from conductor 343, where y the rivate magnet 314 of the connector N is a lowed to dener ize to advance the side switch Wipers to thir position. Re-

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