US1400590A - Selective telephone system - Google Patents

Description

A; H. DYSON. SELECTIVE TELEPHONE SYSTEM.

v v v APPLICATION FILED NOV- 29,1907. 1,430,590.

Patented Dec..20, 1921.

6 SHEETS-SHEET 1.

' -A.'H'. D'YSON.

- SELECTIVE TELEPHONESYSTEM.

APPLICATION FILED NIOV. 29.1907- 1,400,590. B d 1 20, 19 1-." V 6 SHEETS-SHEET 2-- x A. H. DYSON.

SELECTIVE TELEPHONE SYSTEM.

APPLICATION HLED NOV. 29, I907.

1,400,590 Patented Dem 20, 1921.

I 6 SHEETS-SHEET 3.

W5 1 w zaz A, H. DYSON. SELECTIVE TELEPHONE SYSTEM.

APPLICATION FILED NOV- 29. 1907- 4 Patented'Dec. 20, 1921.

6 SHEETS-SHEET 4-.

A. H. DYSON. SELECTIVE TELEPHONE SYSTEM.

. APPLICATION FILED NOV- 29. 1907- 1,4()0,59O, Patented Dec. 20, 1921.

6 SHEETS-SHEET 5- I A. HQDYSON. SELECTIVE TELEPHONE SYSTEM.

APPLICATION FILED NOV- 29,1907.

1 A00; 590, Patented Dec. 20, 192 1.

6 SHEETS-SHEET 6.

6 J7 @WM UNITED STATES PATENT OFFICE.

ALFRED H. DYSON, or onrcaeo, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, T KELLOGG swrrcnnormn & sUrrLY COMPANY, A CORPORATION OF ILLINOIS.

SELECTIVE TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Dec. 20, 1921.

To all to ham it may concern de it known that I, ALFRED H. DYsoN, residing in the city'of Chicago, county of Cook, and State of Illinois, have invented new and useful Improvements in Selective Telephone Systems, of which the following is a specification.

My invention relates to telephone systems in which a portion of the connections made in putting through a call are accomplished by means of automatically operated telephone apparatus, while the remainder of the connections are made with the assistance of operators.

The present invention is well adapted for what may be termed feeder service, and may be operated in connection with ordinary manual telephone switchboards, although its employment is in no way limited in this respect.

" It is generally accepted that, in commercial telephone practice, the supplyingof service to subscribers at a point distant from the main exchange, especially where the number of subscribers within reasonable limits of the local. point from which service is to be supplied, is relativelysmall, a relatively expensive ma ,ter. One of the factors entering into this situation is thatof the expenses '30 involved in maintaining service at an exchange where but a small number of telephone operators are employed. The factors oi supervision, management, etc., in such cases constitute an item of expense producing an expense load, which must be charged upon the cost of the labor of the operators who perform the actual work of connecting subscribers lines, greatly in excess proportionately to the load which exists where a 40 relatively great number of operators are employed. v l

The present invention is directed more specifically toward providing a system for outlying exchanges such that connection may be completed by means of mechanism at such outlying exchanges, avoiding however, the use of the usual automatic substation impulse transmitting mechanisms at the telephones whose lines are connected with such outlying exchanges.

.rssuming a telephone system including a main switchboard centrally located of the usual manual character, in which the greater part of the lines comprised in the system as terminate, in the manner usual in manual practice, and also includingsay, two smaller exchanges located at outlying points, the subscribers of each exchange will require connections with subscribers whose lines terminate in their own exchange and also toe considerable extent, connections with subscribers whose lines terminate in each: of the other exchanges. A system organized in accordance with the particular embodiment-of my invention given in the present application will comprise the following features. Calls between the manual subscribers'whose lines terminate in the main exchange will be put up by means ofcord-cir'cuit apparatus in the usual manner. A call: to be extended 7 from a subscriber of one of the local exchanges to a subscriber of the main exchange will be effected by means of automatic apparatus which will automatically connect the calling line with an operators' position at the main exchange by means of a two wire trunk of which there will be a plurality provided for connecting the lines of the calling subscribers of such local exchange with the main exchange. When a calling subscribers line is connected with such trunk, a signal will be displayed and the operator at that position will connect the answering end of a cord with a spring-jack associated with the signal, learn the want of the calling subscriber, and with the calling plug of the cord make the connection to the called-for subscribers line ringing his bell in the usual manner. An-

wering and calling supervisory signals are provided operating as usual which will be displayed when the two subscribers replace their receivers. The act of the calling subscriber will also restore the switching mechanism through which connection has been extended to his line at his'loc'al exchange to normal, and as soon as the operator withdraws the answering plug, the two-wire trunk referred to will become idle and available for further use.

If a calling subscriber at a local exchange desires a connection with a subscriber Whose line terminates in the same exchange, the process of connection is as follows: The removal of the receiver of the callingsubstation will connect his line by automatic means with a two-wire trunk leading to the main exchange where the operator will answer as before. Learning that the completed connection is to be between two lines at the same local exchange, the operator will actuate a calling device, associated with her answering cord mechanism, which will transmit directive impulsesback over the two-wire trunk circuit to connect the calling line with the Wanted called-for line, this being effected by step-by-step switches operating responsive to directive impulses. When her calling de vice is through operating, the operator will Withdraw the answering plug from thejack of the connected trunk which will thenbe automatically disconnected from operative relation with the calling and called subscribers switching mechanisms so that the said trunk will be available to other subscribers in the local exchange for makingconnections.

It'is thus seen that, for local connection between subscribers of one outlying extrunk, books the line of the calling subscriber to the line of the called subscriber and then releases the trunk, leaving the two hnes hooked together independent of, and without and connection to, the main exchange ofiice. -When the two subscribers thus connected have finished their conversation, the replacing of their receivers will restore the local. exchange apparatus to normal.

If a calling subscriber in the local ex change desires hisline to be connected with that of a called-for subscriber in the other local exchange, the removal of the receiver will extend the call over a two-wire trunk to the main exchange, the operator there will answer and, learning that the call is to be ex tended to-a subscriber of the other local exchange, will connect the calling plug of the cord used to a spring-jack forming a. terminalof a twowire trunk leading to the wanted exchange, whereupon automatic mechanism which the operator adJuSts by directive impulses transmitted-by a calling device associated with the calling end of her cord is operated to complete the connection to the called subscribers line. In this case also, thereplacing of the receiver at the substations of the calling and called subscribers will display the two supervisory signals of the cord.- at the main exchange employed in the connection, whereon the operator will withdraw the plugs, and the trunks will be thenidle.

II" a calling subscriber whose line terminates in the main, 0., manual exchange,

wishes to converse with the subscriber of one ofthe outlying exchanges, the operator, after answering hls call 1n the usual manner by means of an answering plug, will insert the calling plug into a spring-jack forming a terminal of a two-Wire trunk leading to the wantedexchange, andby means of her calling device, will transmit directive impulses to automatic mechanism. at the distant exchange, which will have been automatically connected to the trunk she plugged into, to complete the desired connection.

It is thus apparent that my invention realizes a system wherein all connections are put up with the aid of operators who may all be located at one main exchange although the subscribers lines may be divided among a number of exchanges; further, that for local calls between subscribers at the distant exchanges, the long and relatively expensive trunk lines leading to the main exchange are held busy for a minimum time, while for calls between subscribers of two dist-ant exchanges, the trunk lines are employed to sub stantiallythe same extent to which they are employed in ordinary manual telephone practice where a number of exchanges are interconnected. 7

Referring to the drawings, 1 show in Figure 1,'comprising Parts 1, 2, 3 and 4. circuits of a telephone system containing an en1bodiment of my invention. Figs. 2, 3 and a are respectively left, front and side elevations of a 'doublemotion switch adapted for employment in connection with circuits at D, E, and F in Fig. 1. Fig. 5 shows the (if-normal mechanisms of said switch, while Fig. 6 is a sectional view of Fig. 3 'on line X X.

Fig. 7 is a front view of mechanism that may be employed for'the trunk selector at Fig. 8 shows a mechanism that may be associated with relay 181. V

It will be understood that Figs. 2 to 7 are to a certain extent diagrammatic.

Referring first to Fig. 1, Parts .1, 2, and 3 are'to be placed adjacent to one another, Part 1 being at the left and Part 3 at the right, whilePart 4 is to be placed above Part 2, it being understood that the wires M, N, O, P and Q of Part 4- are extensions of the respective wires M, N, O, P and Q shown in Fig. 1, Part 2; At A and W, I have shown two subscribers stations comprising a well known type of substation mechanism, hook switch'l being provided with its contacts to open the normally closed signaling circuit of the substation when the receiver is removed and to operativelyconnect the substation transmitter in bridge of the line limbs. At A and lV are shown the line circuits of the substations A and W and as they are alike, a description of, A will sufiice for both. Generally speaking, the line of A is provided at A with the multipled called terminals 21, 22, 23, which will appear in the banks of a suitable number of connectors, of one of which I illustrate a circuit at F, the arrangements for selection being similar in a general way to those well known in automatic telephone systems. At A the line is also provided with multiple calling terminals 24, 25, 26, appearing in the banks of a number of line selectors, one of which I have shown at D, the arrangement being such that when a subscribed as A initiates a call, an idle line selector D will be set into operation by means of master-switch mechanism C,the said line selector D then automatically seelc ing out and connecting with multiple contacts 24-, 25, 26, of the calling line by means of its wipers 27, 28, 29 and 27 Each line selector D has paired with it in permanent electrical association, a first selector E, and each pair of switches DE has a set of wires N, O, P, leading; to multiple contacts 129, 130, 131, 132, which contacts are multipled before a number of trunk switches H, one trunk switch being pr0- vided for each of the trunks extending from the local to the main exchange, one of which trunks is indicated by the wires T T in Fig. 1, Part 4,. For these trunk switches H a master-switch mechanism G is provided, which serves to control the starting of an idle trunk selector H when the circuit of a switch pair DE is to be extended to the main exchange. To this end, a common wire M is preferably connected with the mechanism at G which may have a number of branches M, one extending; to the mechanism of each switch pair DE.

It will be understood that all the mechanism shown in Fig. 1, Parts 1, 2 and 3 is to be located at one of the local exchanges as is also the mechanisms shownat H and G in Fig. 1, Part 4. The wires T T extend from this local eXchange to the main exchange where they terminate in a signaling circuit indicated as a whole at I, which circuit may comprise the spring-jack shown and the relays shown in relation with, and controllingthe call signal 180.

An o-perator7s cord-circuit at the manual exchange, indicated as a whole at K, may comprise answering plug S and calling plug 'l with suitable supervisory, testing and impulse transmitting devices. At L, I show a subscribers station outfit connected by its line with a well known form of manual line circuit mechanism including the usual multiple springacks together with the usual line and cut-oit relays controlling the usual line signal 197.

From the preceding it will be understood that a call initiated at substation A causes the line terminals as, 25, 26, to be selected by a line selector D, and that on such selection a trunk selector H is set in motion to automatically connect its two-wire trunk T T to the switch pair DE of which the line selector D has selected the calling line A. and thereon a signal 180 will be displayed responsive to current over the two-wire trunk, to the operator at the main oiiice, whereon connection will proceed, as before described, according to the exchange for which the called-for subscribers line terminates.

The trunk select-or H is capable of employment in a double capacity. Its circuit mechanism is such that it not only is capable of being set in motion responsive to the initiationof a call at a substation as A' at the local exchange, but when idle may be set into motion by the insertion of a plug S or T into the spring-jack of its associated trunk T T at I. "When thus set into motion, its selective mechanism operates in a manner quite different from that in which it operates when set in motion responsive to a call originatingat the local exchange. 'll'hus when set in motion responsive to the connection of a plug with its spring-jack, the trunk selector H will select only a" switch pair DE whose line selector D has not selected a calling line. This isprovidcd because when a trunk selector is set into motion, in the manner just referred to, it means that the called-for subscriber only has his line terminating in the local exchange to which the trunk T T 3 extends, and therefore no calling" subscriber in that exchange can have any concern in the connection to be established.

On the other hand, when the trunk selector H is set into travel responsive to the initiation of a call from the local exchange, it is capable of selecting only a switch pair whose line selector has selected a calling line: This employment of an automatic trunk selector H in the double capacity as indicated rendering the single trunk automatically available an incoming and outgoing trunk, is believed to be novel and will be broadly claimed.

In practising my invention, I preferably employ for the line selectors D, the first lectors E and the connectors F, double-mo tion switches having their contacts arranged in groups as is usual in automatic telephone practice, while the trunk selectors H may be single-motion switches having only a rotary direction of travel.

7 That portion of the telephone system shown in Fig. 1;, Parts 1, 2 and 3, as as as the processes of selecting the call'edior line are concerned, operates substantially as a one thousand line automatic trunking system. That is to say, the subscribers lines, of which there may be a thousand, will be divided as called lines into ten groups of one hundred lines each and the lines of each such group will have their multiple terminals 21, 22, 23 grouped together at the exchange and appearing in the banks of say ten connectors F, which connectors will be assigned for connections to the particular line group, there being thus only one hundred connectors. The connectors F will have their multiple contacts 96, 97 9S, multipled before the wipers 93, 94, 95, of the first selectors E. The contacts 96, 97,, 98, of the ten connectors assigned to each hundred called lines will appear at the first selectors grouped together thus forming a group or level of contact sets. @n the usual ten per cent. trunking basis there will be required for each one hundred line group as a calling line group, ten line selectors D, the lines as callinglines being preferably divided into groups of one hundred and having multiple called contacts 24, 25, 26, grouped together and multipled ten times, once to each line selector D serving the calling line group. As there would be ten calling line groups there will be a total of one hundred line selectors and consequently one hundred first selectors E.

It is obvious that the number of trunk lines T T extending from each local exchange to the main exchange will be determined by the amount of trailic between the main exchange and the respective local exchanges. It may be assumed, taking into 7 consideration that a large proportion of the calls originating in the sub-exchanges will be for local. connections that a number of trunks T T'flequal tofive per cent. of the number of lines terminating in the local exchanges will be sufiicient to handle the business. exchange of A includes one thousand subscribers, fifty trunks would be provided. These fifty trunks may have their switches H ar anged in a single group in which case each of the one hundred switch pairs DE would have their terminals 129 130, 131, 132, appearing at-each switch H, so that each switch H would have before its contacts 133, 134, 135, 136, one hundred sets of multiple contacts 129, 130, 131, 132. In such case, the master-"switch mechanism G would be capable of starting each of these fifty switches H, and its wipers 166, 167, would have before them fifty cont-acts 168, 169. Another arrangement would be to divide the fifty switches H into two groups of twentyfive each. In such case,one-half, i. 6., fifty of the switch pairs DE would have their contacts 129, 130, 131, 132, multipled before the wipers of the switches of one group, in which case the said switches H would, of course, become fifty point switches. Under this assumption there would be two masterswitch mechanisms G each having twentyfive contacts 168, 169, and the common conductor M would not have one hundred branches, one to each switch pair of the total one hundred as in the previous case, but there would be two such conductors M one or each of the two master-switch mechaln such case, assuming that they nisms. G and each would have fifty branches M, one branch extending to each of the fifty switch pairs DE which its associated switches H had contacts of. 4 V 7 From the above it is apparent that the trunk switches H may be divided into any desired number of groups, the switches of each group having contacts 129, 130, 131, 132, of a portion of the switch pairs DE, there being asmany master-switch mechanisms Gr as there are groups of switches H and groups of switch pairs DE, the system being entirely flexible in this regard.

The arrangement of multiple terminals 24, 25, 26, of the calling subscribers lines at the banks'of the line selectors D is preferably one in which the said contacts are divided into ten groups of ten contact sets each, primary movements of wipers 27, 28, 29, being first efiectedto select a group, whereafter secondary movementsthereof will be produced to select the individual contact set 24, 25, 26, of the. calling line out of the selected group. For determining the selection of the group, the lines having their con tact sets 24, 25, 26, in a group will be provided with a group contact 24 normally grounded and with a group relay'll, controlling by its armature, the grounding of therespective group contact. Each group relay 11 has a common conductor 1.2 extending by branches, one to each line relay 2 of the ten lines of its group.

The master-switch mechanism C which serves to start an idle line selector D is ren dered common to the entire group of one hundred lines which its line selectors D serve by having its relay 14 connected to a common conductor 13 which has one hundred branches, one extending'to armature switch. 9 of each cut-off relay 6 of the one hundred lines.

In describing more specifically the circuit connections shown in Fig. 1, I shall assume first that the subscriber whose substation is shown atA, desires his line to be connected with that of the subscriber whose substation 1s shown at 1 V, both calling and called substations being thus assumed to be included in the same local exchange, this of course in yolving the features that the initiated call is manifested over a trunk line T T and that the selective impulses, to establish connection with the called line, are transmitted back over the same trunk line.

The subscriber at A removes his receiver whereon hook-lever 1 rises, closing a relatively low resistance circuit through the substation, current then flowing from battery B through normal contact 7, hook lever 1 ro turning through contact 10, linerelay 2 to ground actuating the said relay whose armature 5 attracts and locks the relay through normal contact 9, common conductor 13,

master-switch relay 14 to battery, relay 14 being also energized. Armature 4 grounds private multiple contacts 21 of the calling line at the connectors F rendering said contacts busy. Armature 3 disconnects ground from the private multiple contacts 24 at line selectors D rendering them selectable and said armature, by engaging its alternate contact, energizes the group relay 11 to attract its armature, removing ground from the group contact 24, rendering it selectable by group private wiper 27. attracted armature of relay 14 connects ground through contact 1719 (wipers 17, 18 of masterswitch C normally rest engaging contacts 19, 20' of an idle switch pair DE), primary off-normal contact 31 at switch D, primary relay PR to battery B. The said relay now attracts its armature 36, closing circuit from generator through magnet PM, which magnet is now energized by successive impulses, stepping Wipers 27, 29, 28, 27, in a primary direction, wiper 27 engaging the successive contacts 24 of the different groups, seeking a contact 24 from which ground has been disconnected by the operation of a group relay 11. Armature 37 of relay PR being attracted on the initial energization thereof, maintains the relay energized over successive locking circuits established by wiper 27 passing over grounded contacts 24 (those pertaining to groups among which there are no calling lines), but as soon wiper 27 engages the group contact 24 pertaining to the group among which A is included, the relay PR will be deenergized owing to the absence of ground upon said contact and armatures 36 and 37 will be retracted, primary magnet PM being thereby disconnected whereby the primary steps of the switch cease. It should be noted that the primary off-normal (PO) contacts 30, 31, are shifted with the first step of switch D so that the initial energizing circuit of relay PR extending through contact 17-19 was opened with the first step of the switch.

Retracted armature 36 now completes a circuit from ground through shifted contact 30, normal contact 32, secondary relay to battery energizing the said secondary relay whose armature 44 connects the re lays winding through normal contact of release magnet RM with the private wiper 27, while armature 45 engages its alternate contact to complete circuit from generator through secondary magnet SM, normal contact 39 to ground, the magnet SM being new energized and deenergized by impulses from generator, stepping wipers 27 28, 29, step-by-step over the contact sets 24, 25, 26, of the ten lines of the previously selected group until they reach the contact set of the calling line. It will be observed that multiuple contacts 24 of non-calling lines will be connected to ground through their normal contacts 3 so that wiper 27 in pass: ing over such contacts will establish suc cessive locking circuits for relay SR, through attracted armature 44, holding the relay energized and magnet SM in operative relation with the generator until the wiper 27 engages the contact 24 of the calling line. This contact will be disconnected from ground at armature 3, relay SR will be deenergized and its various armatures retracted' It may be stated that the group wiper 27 of the line selector D does'not partake of the secondary movements of the switch, but remains engaging group contact 24 opposite whose group of contacts 24, 25, 26, the said wiper 2" has caused the wipers 27, 28, 29, to be brought. The sec-v ondary off-normal (SO) contacts 32, 38, 34, and 35, were shifted to their alternate positions on the first secondary movement of the wipers.

On the deenergization of relay SR, retracted armature 43 closed circuit from ground through shifted contact 34 to con tact 20 of the switch pair at master-switch C whereupon relay 16 was energized to re move ground from wiper 17 and to operatively' connect motor magnet 15 to the generator. The master-switch mechanism C may comprise mechanically the circularly arranged contacts 19, 20, at whose center the wipers 17, 18, may be mounted upon a rotary shaft provided with a ratchet actuated in the usual manner by the motor magnet 15, the movement of the wipers 17, 18, being always in the same direction. Magnet 15 now receives impulses from generator moving the wipers 17, 18, stepbystep over the contacts 19, 20, which operation will of course continue until the wiper 18 engages a contact 20 pertaining to an idle switch pair DE (contacts 20 of idle switch pairs being characterized by the absence of a ground connection), when the relay 16 will be deenergized, magnet 15 operatively disconnected and the mechanisms at C will. be ready to start another line selector D on initiation of a call from a line of its group. Before the wipers 17, 18, can select contacts 19, 20, of an idle switch pair, the relay 14 will have been deenergized, as hereafter described.

WVhen relay SR- was first energized, the attractions of its armatures 42, 46, which armatures make-before-brealr both on attractions and retractions, completed a circuit from ground at E through relay 50, alternate contact at 42, contact 41, alternate contact at 46, through relay 54 to battery B energizing relays 50 and 54, whereby armature 53 placed ground on conductor P and multiple contacts 131 at the trunk selectors H, thus rendering the switch pair DE, which has beenimade busy, unselectable by wiper 135 of any trunk selector which maybe operating as an outgoing trunk selector with respect to the main I olfice. When relay SR was de'n'ergized, as

described, a circuit was completed from ground through relay 50, normal contact 42, contact 2825, normal contact at armature 8 of cut-off relay 6 to battery, thus energizing cut-oil relay 6, which by armature 8 locked itself over a circuit extending through contact 24'27, to ground at armature 44. Cut-oil relay 6 now opens the circuit including'relays 2 and 14, dele'nergizing them, while armature closes a contact in theupper talking conductor of the linecircuit of A (talking conductors being indicated throughout by heavy lines) whereby a'maintaining' circuit for relays 50 and, 54 is completed. i I

Armature 45 at D, when relay SR was deenergized, closed circuit iron'r ground through contact 35, over conductor 48,1101:- mal contact 85, wire M, the conductor M at G, the master-switch relay 168, to battery, Bflenergihihg the said relay 163 whose attracted armature completes circuit from ground through wiper 166 (wipers 166,

167 or master switch G normally engaging contacts. 168, 169 of an idle trunk selector H), through the contact 168 01' trunk selector H contact 153 of said trunk elector operatin relay OR, to battery 13, whereby relay t is energized, its armature 139 operating relay 145, whereupon circuit is closed from generator through} operating magnet'OM of switch H, attracted armatures 140, 14?, to ground, As long as relay OR- remains energized, relay 145 remains so, and magnet GM will be successively actuated by generator, each actuation eifecting a rotary step of wipers 133, 134, 135, 136, a difierent set of contacts 129, 130, 131, 132 being engaged on each step. Attracted armature 138 of relay OR has con- 'nected said relay to the wiper 134, which,

as'it successively engages multiple contacts .130, establishes successive locking circuit,

holding relay OR energized until said wiper 134' finds an ungrounded contact 130. Contacts 130 of any switch pair DE, whose line selector D has not operated to select a calling line, will be grounded either at normal contact 138 of another switch H whose wiper 1.34 already engages a multiple or 130 or over conductor Q and through normal con tact 52 of such switch: pair. Therefore, the

. relay OR will continue energized as switch H steps along, keeping circuit closed through magnet OM until wiper 134 engages a multiple contact 130 connected to the conductor O of a switch pair DE whose relay '50 has been energized, as is the case with the pair shown at Fig. 1. When this occurs, no ground being upon the contact- 130 engaged by wiper 134, relaylEORis deenergized, its armatnres fall back, deenergizing relay 145 and preventing further actnation of magnet GM, whereby the wipers of switch H willremain engaging the multiple contacts of the switch pair whose line selector D has selected the calling line A.

Armature 138 in falling back, places ground through wiper 134 upon the multiple cci'itacts 130, so that no other trunk selector 1%.- will be able toselect the contact 130 pertaining to the switch pair DE.

The armatures of relay 145 havingfallen back, a circuit is now completed from battery B at the main exchange, 'hrough signal relay 179, operating it and displaying signalg 180, through normal contact of relay 181, over trunk conductor T contact 148, contact 136132, Q, relay PR, to ground, operating said relay, whose armature 68 is attracted, closing circuit from battery 4 through relay 83' operating it,

contact 68, over P, contacts 131-4135, 144, through relay 160, to ground, operating said relay, a branch of this circuit through armature 53 and its connected resistance also existing.

the initial step of switch H the otf-norshifted contact 152 while armature 156 places ground uponthe contact 169 of the operated switch H at master-switch G, whereby relay 164 is energized and its arinature attracted, to remove ground from the wiper 166 and to connect the rotating magnet 165 operatively in circuit with generator, which magnet will be successively actuated, driving wipers 166, 167' step-by-step long as relay 164 continues energized over successive locking circuits through t 7 :3 16?, and successively engaged contacts 169, thecontacts 169 of the'busy trunk selectors, H, being grounded at their respective arma'tures 156.

The operation of relay 83 occurring simultaneously with that of relay 160, by attracted armature 85 removes ground from the conductor '64, so that, so far as the switch pair DE controls it, conductor M is u unded and the relay 163 at G will be deenergized, unless there be some other branch lifl of conductor M grounded at another switch pair. 7

The operator at H,

observing the display of signal 180, inserts answering plug S with- 129, over N, through relay SR at E, alter-' 11 te contact 56, through battery B to ground, whereby relay SR is energized.

Recapitulating, the line at A has now been selected by the switch D of switch pair DE,

said switch pair has beenconnected by the.

operation of a trunk selector H with the main oiiice, the operator has made connection with the trunk line of the operated switch H, atwhich private contacts 130, 131 have been duly grounded, whereby the switch pair DE in connection with the line of A is protected from seizure by any other switch H, whether operating in its incoming trunk or its outgoing trunk capacity. Also the primary relay PR and the secondary relay SR, by whose deenergizations the primary and secondary switch impulses are to be transmitted to the directively operated first selector and connector to be used in completing the connection with a called line,

have been duly energized preparatory to their directive controlby the operatorat K.

The operator at K now actuates levers 186, connecting her talking set in operative relation with calling line A, the connection from plug S being traced over the heavily marked conductors, and learns the number of the called-for subscriber, which, for purpose of description, may be assumed to be local 333, the word Local indicating that the called line has its terminals in the same exchange as that wherein the line of the calling subscriber A terminates. Having ascertained the number, the operator at K actuates levers 172, 174,-thereby operatively connecting the impulse springs 192, 193 with conductors N and Q through the contacts of plug S. By the make-beforebreak arrangement of levers 172, 17 4, no de- I I energizations of relays PR and SR are produced by the connecting of the saidimpulse springs.

Qklthough I have illustrated and shall describe the said impulse springs as a'pair of ordinary keys, it will be understood that iii practice the operator will be provided with an automatic dial or other impulse-controlling device not requiring the amount of care and attention that the operation of the keys 192, 193 would involve. It will also be understood that the impulse mechanism is common to the operators position having branches eXtendingto-the levers 172, 174 and 187, 189 of each operators circuit at the position.

The operator now opens contact at 193 three times, --thus prod icin-g ,three denerg h zations of primary relay PRQ- whose armatures are retracted three-times, the opening of contact 68, however, producing no effect upon relay 83 since said relay, by armature 86, has locked itself to groundat alternate contact 52. Each retraction of armature 72 transmits a currentimpulse from ground therethrough, through attracted armature 69, secondary off-normal contact 82, primary magnet PM, to battery B, whereby said magnetis actuated three times and advances the wipers 93, 94:, 95 in a primary direction, to bring them adjacent to agroup of ten multiple contact sets 96, 97, 98, forming terminals of connectors F :assigned for connections tothe third hundreds group of lines o'f the local exchange. After having opened contact 193 three times as described, the operator willopen contact 192 once, whereby a single deenergization of secondary relay SR will be effected, and an impulse of current transmitted from ground through normal. contact 71, alternate contact 73, the shifted contacti80 '(the primary ,oihnormal contacts 78, 79, 80 having all been shifted with the first step of the first selector), through secondary voil-normal contact 81, busy relay BR, to battery, said relay BR, by its armature '91, connecting .the secondary magnet SM operatively with generator, whereby said magnet will be successively actuated, moving wipers 93, 9st, 95, over the multiple contaots96, 97,98, of the selected group in searchof a set pertaining to an idle connector F, By armature 90, relay BR now has its winding connected through attracted armature 84 with the private wiper 93, which, by engaging successive contacts 96 .(contacts 96 of busy connectors being grounded) will establish successive locking circuits for relay BR" until an ungrounded, i. 6., idle, contact 96 is reached, when relay BB will bedeenergized and its armature 91 will fallback, preventing vfurther actuation of magnet SM, whereby wipers 93, 9 1, 95, will rest engaging the contacts '96, 97, 98, of the idle connector, assumedto be that shown at F in Fig. 1, Part 3. The secondary ofit': normal SO contacts 81, 82 were shifted on the first secondary step of the first selector,

"To transmit the tens digit of the called number, the operator opens contact-193 three times, deenergizing relay PR three times, the resulting three current impulses being transmitted now through contact 89, contact 9%97, normal contact 99,-magnet PM, to battery B actuating said magnet three times, which moves wipers 126, 127, 128 to a position adjacentto a group of ten contact sets 21, 22, '23, forming terminals of subscribersflines numbered 331 to 339, inclusive, followed bythe terminals of line 330, zerov being represented by ten impulses, in automatic'telephone systems. "The first impulse of current 'throng-h :oontact 94- 97 -a's described, has passed in part through normal contact 100, relay 108, to battery, operating said relay 108, whichlocked itself by armature 109, through normal contact 128, contact 90-498, attracted armature 8 1 and through armature 90, to ground, whereby the shifting ofprimary oil-normal contact 102 on the first step of connector F did not operate release magnet RM since armature 110 was then attracted.

The operator now opens contact 192 once,

deenergizing relay SE armature 71 falling baclr to transmit an impulse, through alternate contact 73, contacts 92, 95-98, 101, and through magnet SM to battery, energizing said magnet, which efl ects av step of wipers 126, 127, 128 toward the previously selected group of contacts, not'moving them sufiiciently to engage the first contact set of the group, the position of the connector wipers after being brought to a'selected group being a space of .two steps distant from'the first contact set. I This first secondary step of connector F shifts the secondary oil-normal contacts 99 to engage its alternate contact, 100 to disengage its contact, and 101 to disengage its normal contact, but .not suliiciently to engage its alternate contact, the latter being effected only on the second secondary step of connector F. V .7 1 v The operator at K now. opens contact 193 three times, denergizing relay PR three times, three impulses being transmitted as before through contact 9 -1-97 the impulses now passing through alternate contact 99, contact 104, secondarymagnet SMito battery B actuating said magnetthree times,

"whereby wipers 126, 127,. 128 are advanced three secondary. steps to engage, on the third step, contacts 21, 22, 28, terminals of the called line, Local 338, assumed to be that indicated at W. The operator now opens contact 193 once, deenergizing relay SE, a current impulse being transmitted as before, through contact 95-98, the current then passing through alternate contact 101,

Before proceeding to a description of the testing, it may be observed that as soon as the operator has momentarily opened the contact 198 as last described, her work has ended and she will at oncerwithdraw the plug S from the spring aclrassociated with signal, 180, whereby. the trunk selector Wlll be instantly restored toner-males follac),

Idiscoimected from the battery B, its previous connections therewith having been either throu h armature 67 or 68 and the winding of relay 83. Relay 83 remains operated because its locking armature 86, but relay at G is deenergized, release magnet RM being thereby operated by current through contact 182, contact 159, to battery, which magnet withdraws the retaining pawl from the r tchet with which wipers 183, 13-1, 135,

136, are mechanically connected and the restoring spring of switch H turns the switch wipers back to normal, the talking wipers 136, during restoration being on open circuit at contacts 14:6, 148, relay 1 15 being energized by current through contact 161- 158, said relay 1415, to battery. As soon-as switch: ll reaches normal, the oil- normal ON contacts 152, 153, 15 1, are shiftedto the'position shown, whereby relay 155 is unlocked, its retracted armature deenergizing magnet Elli? and. relay 1455, and taking the ground contact 169 at master-switch G, whereby the switch H and the trunk circuit T T become idle and are available for further use for incoming or outgoing calls. The nultiple contacts 180, 131, of the switch pair DE still remain busy, 21-6., grounded, 130, by connection through-O, armature 85 and over conductor 48 to switch D, while '131, of course, continues grounded at armature 58 over P. -c

Returning now to switch F, test relay TR had just received an energizing impulse through its lower winding. If the callediiorline N is idle, as will now be assumed, itsacontact 21 will be connected only to the active side of battery B and since the test relay TR- has its windingconnected with the actiyeside or said battery, on the cessation of the impulse transmitted by relay SR, the relay TR will be deenergized and its armatur'es retracted. Before this occurs,

armature 116 will have closed circuit through relay 108, said relay, by armature 105, looking itselfto ground at armature 110. Armatures104 and 107 now disconnectrespectiv'ely'magnet SM" and the lower winding of-relay TE from contacts 97,, 98, while armature 106 completes a circuit effective, on the retraction of armature 117 of relay TR, to energizethe relay 111 and cut-ofi relay 6 of h -a W y cu en -J f om; QP-Ql through relay 111, closed contact 106, nor mal contact 117, contacts 12621, 1, relay 6, to battery. Armature'S of relay 6 is attracted, connecting the ground through relay 111 upon the multiple private calling contacts of the line circuit of V1 at the line selectors, armature 7 closing a contact in the talking circuit oi"; the line of 5V, while armature 10 opens the circuit of line relay 2 so that it cannot be operated. At relay 111 armature 113 now completes a circuit extending from ground through interrupter I, contact 122, contact 113, relay 125, to battery B, the said relay 125 now being energized and deenergized through the operation oi? interrupter l, alternately connecting and disconnecting ringing generator HG to and from the called subscribers line, current from said generator flowing, when armature oil relay 125 is attracted, through contact 12722, alternate contact 7, condenser and bell at substation W, returning through contact 23-128, and through the now attracted armature 114 O1: relay 111, to ground th ough battery B. The bell at the :alled substation 1V is thus rung, and when the called subscriber answers, a circuit will be completed from ground through release relay RR, attracted armature 112, back contact at relay 125, as soon as said relay is dei nergized, contact 127-22, through the substation at W and the now raised hook lover 1, returning through contact 23-12S, attracted armature 114, to battery 1%. Relay 1113. is new energized and its armature attracted to close circuit through relay 119, energizing the said relay, whose armatures 120-121 close contacts in the talking circult. Armature 121, locks said relay 119 to ground at armature 110, while armature 122 disconnects interrupter 1, so that relay continues inert. Armature 123 places an additional busy ground upon the private contact 96. It will he noted. that the attraction of armature 1223 opened the original locking circuit of relay 108, but before this occurred, relay 1111 completed an alternate circuit for said relay which thus remains ener ized, so that magnet 3M cannot opcrate.

Current also finds its way from ground through relay R151 over the line V1 as described, and through contact 121-, as soon as relay 119 is energized, current flowing thence through contact 98-95, contact 92, normal contacts 73- 10 and relay 74, to battery 13. liclay 7 1- is energized, and by its armature 7 5 opens the circuit, which had been closed with the first step of the first selector, extending from ground through primary oil-normal (PO) contact 78, normal contact 75, alternate contact 55, relay 66, to battery, the relay 66 having been held energized, and the lower talking conductor open at its armature, to the end that the, directive impulses transmitted over conductor Q, may not effect disturbances in the telephone receiver at substation A- which the subscriber will have at his ear. Thuswhen the called subscriber answers, the resulting operation of relay 7 1 by the attraction of armature75 deenergizes relay 66, so that itsarmatures are retracted and the complete talking circuit is closed tro a substation A to substation W, as indicated by the heavily marked conductors, condensers being interposed in the talking conductors as shown at E. The transmitter at substation A is energized by current from battery 13 through the impedance of relay 5 1, returning th rough the impedance of relay 50, to ground, while the transmitter at substation V1 is energized by current -from relay R11 flowing through the substation, returning to battery, through inductive resistance 115 and through relay 74; at E.

The two subscribers A and \V are now in conversation over switchboard connections entirely local to their own exchange, the apparatus at the main office being entirely disconnected from the circuitnow existingand having no longer any function whatever to perform in connection therewith. WVhen the subscribers A and N have finished their conversation, they replace their receivers. When V does so, the connector F is restored to normal, while when A does so, the. line selector D and the first selector and other mechanism at E are restored to normal, at which time the busy grounds will be removed from conductors OP and also from contact 20 at the i'naster-switch C.

hen subscriber lV replaces his receiver, relay Bl t energized by current through hook lever 1, becomes deenergized, and its retracted armature causes relay 108 to be denergized whose re racted armature 110, closes circuit from ground, primary offnornial (PO) contact 102, release magnet R321 to ba tery B. Release magnet RM being thereby energized, withdraws the retaining pawls from the primary and secondary shafts of connector F and the connector wipers'and primary and secondary oil-normal contacts automatically brought back to their normal positions. Magnet 3M remains energized, until connector F finally reaches normal opening contact 102, whereby the arniatini'e of said release magnet RM continues attracted holding a busy ground on private contacts 96 until the connector is restoredand finally becomes idle and S0 available for further use. hen relay 108 was deenergized, it opened the locking circuits of relays 103 and 119, so that the conta ts at 120 and 124- were opened and wipers 127, 128 were on open circuit, while the connector was restoring. As soon as contact 106 was opened, cut-oil relay 6 of the line at W was de'e'nergized and its line circuit restored to its normal idle condition.

When the subscriber A replaces'his receiver, the act deenergizes relays 50 and 54 and their armatures are retracted, the retraction of armature 52' opening the looking circuit of relay 83, whose armatures fall back, armature 87,]closing circuit from ground, throughits normal contact, the shifted contact 79 and busy relay BR, to battery, operating the said busy relay, which attracts its armatures, whereof 91 closes thecircuit of release magnet RM, the circuit extending through normal Contact 88. Upon the operation of magnet RM, retaining pawls are withdrawnfromthe primary and secondary ratchets of the first selector and the switch restores to normal, at which time the primary and secondary offnormal switches will also be shifted back to their original condition. 7 a

The retracted armature 51 closes circuit from'ground overconductor 49, shifted contact 33, release relay RR at switch D, to battery, which relay, by armature 38, energizes secondaryrelay SR, and, by armature 40, locks itself to ground through primary olf-nor'malcontact 30 and contact 36. Circuit is now closed from ground through alternate contact so at relay SR, alternate contact 39, release magnet RM, to battery B, resulting in the energization of relay RM, restoring the first selector D to normal when the primary and secondary ofi-norinal switch springs will be shifted to their normal'positions. v

It will be seen that when relay SR was energized, thus removing the ground previously existing through contacts 43 and 34 upon contact 20 at the mastenswitch (I, a substitute ground will be immediately placed thereon, extending from said con tact 20 throughthe attracted armature of magnetltM, alternate contact 44, alternate contact 33, attracted armature 38 and its grounded contact. With the shifting to normal of the switch springs SO, (occurring when'wipers of switch D are restored as to their secondary movements) ground will still be maintained on said contact 20 through normal'contact 32, contacts 30, 36, untilswitch D finally reaches normal, when the opening of contact 30 will remove ground from said contact 20 and also open the locking circuit of release relay RE which I will be deenergized together with release magnet RM and secondary relay SR.

It will be observed that as soon as the re-' lease operations controlled from substation A are initiated, ground is placed on conductor O, at armature 52 so that the switch pair DE continues unselectable by any trunk selector H operating under control ofits wiper 134.

7 It will now be assumed that when the test relay TB of the connector F was operated by the impulse transmitted by secondary income o relay SR, the called line W was busy. In such case its multiple contacts 21 would be grounded, in case the line W was busy, because some other connector had connected therewith, by aconnection extending through normal contact 117 of said other connector, its attracted armature 106, to ground through its relay 111; or in case the line V] was busy as a calling line, its multiple contacts 21 would be connected to ground either at attracted armature 4 of its line relay '2, or over a connection extending through normal contact 4:, alternate contact 8, and through one of the multiple contactsQe at the line selectors, to ground at normal contact at of some line selector D that had selected the line (see Fig. 1, Part 1). In either case,.as soon as test 'relay TR was energized by the impulse before referred to, current would find its way from battery B through the upper winding of said relay TE, alternate contact 117, wiper 126, to ground through the engaged multiple contact 21, thus locking the relay TR, which, by armature 118, would hold connectedthe busy back machine I with the calling substation over a circuit extendingthrough said closed contact 118, to the left over the upper talking conductor, through the condensers at E, over the calling line and through the substation, producing the customary busy tone in the'receiver, returning over the lower talking conductor and through relay 5%, to battery B, the calling subscriber being thus advised that the called line was busy. Relay 103 would be energized and locked by the operation of relay TR as before described, but relay 111 would not be energized because of the continued attraction of armature 117. fhe calling subscriber replaces his receiver and the line selector D and the first selector E are restored to normal in the manner before described. The restoration or" the connector F is also effected by the calling subscriber, under these circumstances, since upon the deenergization of relay 83, the circuit of wiper 93 will be opened, whereby the locking circuit of relay 108 is opened and the relay deenergized to close circuit by its armature 110, through release magnet lath l whereby the conductor l? is restored to normal as before described. It is thus seen that until the called-for subscriber has answered the call to effect the energization of relay 119, the connector l is capable of being released by the calling subscriber.

It will also be seen that if the calling sub scriber were to replace his receiver while the operator was transmitting the impulses to make the connection with the called line, the automatic switching mechanisms will be restored t normal in due course. The line selector D will be restored as before described as soon as the subscriber replaces his receiver. The first selector E will, how ever, not be restored to normal until the operator has completed sending the directive impulses and has removed the plug S from the spring jack of the trunk. This will be apparent from consideration of the fact that the relay 83 of the first selector will, until the withdrawal of the plug as described, and the consequent simultaneous deenergization of relays PR and SR, be continued energized over a circuit extending through one of the attracted armatures 67 or 68 and over conductor P, through contact 131-435, and relay 160, to ground. As soon, however, as a plug is withdrawn, the resulting restoration before described of switch H opens this circuit of relay 88 and the relay is deenergized, whereupon the release of the first selector and 01": connector ll proceeds as before described.

It the calling subscriber A desires his line to be connected with that of a subscriber such as L, whose line terminates in the manual main oiiice, the removal of the receiver at substation A el'l'ects operations as before described, whereby the line at A is extended to the manual position K and the call inanitested upon the signal 180. The operator answering, inserts the answering plug 8, putting out signal 180 and establishingconditions before described, whereby the sleeve supervisory relay 177 is energized by current over conductor Q: and through relay PR, to ground, relay SR being also energized by current through supervisory relay 176 at K, the current through said relay 176 flowing in such a direction as to tilt the arinature of the said relay'upward so as to disengage its contact. The relay 66 during the process of this connection, is not employed, remaining inert, because the first se lcctor of the switch pair DE not used and therefore remains at normal, contact 78 re-- inaining open.

The operator learning the number of the called subscriber, inscrtsa calling plug T within a multiale springjack of the called line, assumed to be that shown L, whereupon current will flow from battery B through the sleeve supervisory relay 182, contacts 190, 191, 195-200, cut-off relay 198, to ground, operating said cut-o2? relay to attract its arniatures and relay 182' to close the circuit of calling supervisory signal 183 which is now displayed by current to ground through the armature of relay 1841. lhe operator will, of course, insert the plug '1 only fter having tested the calledlor line in the usual manner, the well-known arrangement including the high. wound test relay 185 being provided for this purpose. The operator now actuates levers 191 of her ringing key, to ring the bell of the called subscriber. When levers 191 are released, and the called subscriber answers the call,

current will flow from ground through relay 18%, through alternate contact 2041, contacts 188, 191, 194-199, attracted upper armature of relay 198, through transmitter and hook levhr 1 at the substation, returning through attractedlower armature of relay 198, contacts 200-495, 191, 190, relay 182, to battery. This current liow is in a direction to tilt the armature of polarized relay 18a upward, so that the calling supervisory signal 188 is unlighted during conversation. It will be understood that the talking circuit extends from substation :1 over conductors N and Q, trunk wires T T and the strands of operators circuit l to substation L, Under these circumstances, the first selector, which is paired with the line selector 1), is, of course, not available for use, although its mechanism takes no active part in the connection established.

W hen the subscribers finish their conversation, they replace their receivers, the act at substation L opening circuit through relay 184- which is deenergized and by the falling back of its armature, lights the all ing supervisory lamp 188.

When the calling subscriber A replaces his receiver, the line selector D is automatically restored in the manner before described. The trunk selector H is, however, not restored to normal, since the relays SR and PR continue energized, and, hence, the relay 83 associated with the first selectorj The replacing of the receiver at substation i deenergizes the relay 54:, of course, which relay, by now retracted armatru'e 5G, is effective to reverse the direction of the current flow through the polarized relay 17 6' oil the operators circuit K. It will be re menibered that the initial current through said relay 176 was from the negative or active side of battery l3 and alternate contact 56, relay SR and over wire N. By the falling back of armature 56, negative battery at B is disconnected from wire N and positive battery at substituted therefor, whereby the relay 1.76 will be energized by current in such a direction as to tend to throw its armature downward, which arniature engaging its Contact, will close the circuit ot the answering supervisory signal 178. The operator observing the two sig nals 178 and 183 displayed, will withdraw plugs S and T, the withdrawal of T restoring the line circuit of L andthe calling end or the cord-circuit to normal, while the withdrawal of S simultaneously deenergizes the relays SR and PR, whereby the trunlr selector H is restored to normal as before described. It will be seen that since the relay 83 is only dcnergized when the operator withdraws the plug S, its armature 87 continues to hold ground upon wire 417 con nected to the contact 20 oi the switch: pair DE used in the connection at the masterthe first selector will be produced by the. retraction of armature 71, since the CilCLl-ll'r or armature 73 through which the circuit would be closed from contact 71, is open at primary off-normal contact 8!), which is in its normal condition;

It will now be assumed that L is the calling subscriber and that W in the local ,e: change is the called-for subscriber. The removal of the receiver at substation L will operateline relay 196 to display line lamp 197 in the well-known manner, whereupon the operator inserting answering plug .8 to

engage tip and sleeve contacts 199, 200 of the answering jack of line L, will operate the sleeve supervisory relay 177 in series with cut-oft relay 198, deenergizmg the line relay and putting out the lamp bythe operation of relay 198, although supervisory signal 178 will not be displayed because relay 17 6 will open its contact when operated by currentover the calling line L. The operator having learned that the calling subscriber wishes to converse with a subscriber in a local exchangawill insert the calling plug '1 within a jack of one of her trunk lines T T leading to a selector H in the exchange wanted, having first thrown the levers 187,

189 to connect the impulse springs 192, 193

with the tipand sleeve contacts of the plug T respectively, and waits a moment before actuating the'impulse springs 193, 192 in order to give the switch H time to select the idle switch pair DE at the local exchange.

1 Cut-off relay 181 is of course operated when the plug is inserted.

Upon the insertion of plug '1, current flows from ground through spring192, contact 187,188, contact 194150, through normal contact 154, relay 141, to battery, operat ing the said relay, which, by armature 142, energizes relay 145 to place wipers 133-136 on open circuit. Circuit is also closed from generator through operating magnet OM, attracted armatures 143-147, to ground, whereby magnet OM is successively actuated to move'the wipers 133, 134, 135, 136 in search of multiple contacts forming terminals of an idle switch pair DE. This selection is effected by control of relay 141 exercised over it by the private wiper 135 engaging successive contacts 131 connected to wires P extending to the differentswitch pairs, the contacts 131 of a busy switch pair being grounded at armature 53 Ora pair whose line selector D has beenoperated from a calling substation, or the contacts 13101 a busy switch pair will be grounded through a relay 160 if some other trunk selector H has selected and is resting'with its wipers engaging the contacts of the switch pair, circuit in such latter case being traced through normalcontact 144 and'wiper 135 engaging a multiple contact 131. Relay 141 will, therefore, remain operated over successive locking circuits established by wiper 135 in its search for an idle contact 131, the said locking circuits extending to ground through busy contacts 131. As soon, however, as an idle contact 131 is reached, the said contact will be ungrounded, because conductor P will be' on open circuit at armatures 53, 67' and 68 of the idle switch pair. The armatures of relay 141 will then fall back, deenergizing relay 145, and opening the circuit of operating magnet OM.

- It will be understood, of course, that this automatic selection of an idle switch pair DE by the trunk selector H is completed in a very short space of time, it having been found feasible to operate rotary step-by-step switches at a rate of eighty steps per second. With the first step 01 switch H, the oflf-normal (ON) contacts 152, 153, 154 were shifted, 153 so that relay OR was disconnected from contact 168, master-switch mechanism G being then unable to aiiect the mechanism of switch H if its relay 163 should be operated.

.The multiple private contacts'130 of the selected switch pair DE, which is assumed to be that shown in Fig. 1, has a busy ground placed upon it by wiper 134, through normal contact 138, so that no other switch H operating under the influence of relay OR can select the now busy switch pair DE. Also the private contact 131 is rendered busy by ground placed upon it through relay 160 and normal contact 144.

As soon as relay 145 is dee'nergized as described, current flows from batte B through spring 193, contact 190189 contact 195151,136--132, over wire Q, through relay PR, to ground, operating the relay PR. The operation of relay PR energizesrelay 83 by current through attracted armature 68 over wire P, contact 131, 135, and through relay 160, to. ground, whereby relay 160 was also energized to operate and lock relay 155. Belay 155 now renders the contact 169 of the operated switch H at the master switch busy, so that if the wipers166, 167 are engaging the contacts 168, 169, they will be moved off from'them, or it they subsequently engage them, they will pass by them.

The operation of relay 83 by armature 87 will place ground on wire 47 and upon the contact 20 of the selected switch pair DE at master-switch C, so that it the wipers 17,18of said master-switch were engaging 13 the contacts-19, 20 of the selected s'witch pair, they would be moved off from them, the contact 20 remaining unselectable until the relay 83 was a in de'c'nergizied. Thus it will be impossible for the mas switch mechanism C, when it relay is; is ener Ed by any calling line, to start the l ne selector D, since whenever wiper 17 will eng the contact 19 of switch D, the armature of rela 18willbe attracted. I

lnder the. present circumstances, namely, those of a call being extended from a call ing manual. line to a called local exchange line, the line selector D of the switch pair DE to be used in the connection is not employed at all, as a calling subscribefis line at the local connection can have nothing to do with the connection be: m; put through.

Assuming that the number of the called subscriber was Local 833, as before the operator actuates lever 198 to produce three.

set of deenergizations of relay PR, each set consisting of three deenergizations and being followed by a single deenergization of relay SR produced by the opening of contact 192-. The various deenergizatious of relays PR and SR operate in the same man ner as before described to adjust the first selector at E and the connector F to establish connection with the called-for subscribefis line, assumed to be line W. The called-for line is tested in precisely the same manner as before described, and if found idle, the bell of the called subscriber is caused to be rung.

When the operator at K finished transmit ting the impulses, she immediately released levers 187 and 189 of her calling device key, whereby, by the make-before-brcak ar rangement of springs 188 and 190, a maintaining circuit for relay PR including relay 182 was established and also a maintaining circuit for relay SR, which may be traced from ground through the tip supervisory relay 1841, attracted armature 204,-, normal contact 188, contact 194L15O, contact i8?-- 129, over N, through relay SR, normal contact 56, to positive battery at the tow ofthis current being in such direction that the relay 18 1 tends to tilt its armature down ward, the calling supervisory signal 183 therefore being energized. When the called subscriber answers the call, circuit changes as previously described are effected, resultin in the connecting of ground through relay R3 at switch F over the line of subscriber W, through contact 23-128, attracted armature 124, contact 98-95, through attracted armature 73 and 71 (which remain attractor because the plug T is left within the jack) and through relay 7 4-, to battery B. Relay 74 is, therefore operated, and by attracting its armature 76, disconnects positive battery from wire N, and, by armature 77 connects negative battery thereto over wire 59 andrelay SR. The direction of the flow of current through relay 18 1 is thereby reversed on the response of the called subscriber and the said relay tilts its armature upward, to open circuit through signal 183 which "is no longer lighted, the operator thus knowing that the called local subscriber has answered the call. Battery being supplied tothe called subscriber V7 for talking purposes as before, and also to the calling subscriber L, conversation can take place over a talking circuit extending from substation L,'tl1rough the answering jack of said line and the connected answering plug S, thence through calling plug T and the jack contacts of trunk wires F T" and over wires N and Q, to the talking concuctors of the first selector and through the connector andthe called line, to substation V7. W hen the subscribers finish their conversation, they replace their receivers. The act at substation L opened the circuit of relay 17 6 and its armature is retracted to light the answering supervisory signal 178. When the subscriber replaces his receiver, the connector F is restored as before described, and the circuit of relay 7 1 is openedand its armatures fall back, whereby the direction of current through calling supervisory relay 184i is reversed and the said relay tends to tilt its armature downward, said armature then closing circuit through calling supervisory signal 188. The two signals being now displayed, the operator withdraws plugs S and T, the wit. 1- draw-a1 of S restoring the line circuit at L and the answering end of the cord-circuit to normal; the withdrawal of plug T causes ground to be disconnected from tip contact 150 of the trunk spring-jack and battery from sleeve contact 151 thereof, relay 181 releasing slowly as before specified. Thus relays PR and SR are simultaneously deenergized,whereby the circuit through relay 83 at E, including serially the relay 160 at H, is opened and the two relays decnergized, the deenergization of 160 restoring trunk selector H to normal as before described. Relay 83 be ing deenergized, armature 87 falls back, closing the circuit of busy relay BR as before described, whereupon release magnet Rh is operated and the first selector at E is placed at normal, when all apparatus will be at normal.

Had the line W been busy, test relay TR would have been locked and the busy signal extended from the interrupter I over the upper talking conductor to the left, through a condenser 65, over wire N, over the upper talking conductor in Fig. 1 (Part 4:) and through substation L, returning to ground through cut-off relay 198, advising thecalling subscriber that the called line was busy. L would, therefore, replace his receiver and the two supervisory signals 178, 183, would then be displayed' The operator would withdraw the plugs, and upon the withdrawal of plug T from the sprmgqaclr of trunk line T T the first selector would be released, the deenergization of relay 83 opening the locking circuit of relay 108, said relay being then deenergized to energ ze relay RM and restoreconnector l If a calling subscriber, such as A, desires to be connected" with a called-for sub- 'scriber, such as W, whose line will now be I assumed to terminate in the other of the two local exchanges from that in which the'linc 1 of A terminates, the processes of connec- 7 jack connected with a trunk T T leading ating, with a calling plug.

to the distant exchange, and the connections from this pointon will proceed just as in the case in which the'calling subscriber L was connected with called subscriber TV. In such case, of course, the talking circuit finally completed will extend from substation A in the first exchange through the talking conductors of the line selector D of a switch pair (whose first selector will have no concern in the conversation), over the wires N and Q of such switch'pair, and wires T T whose switch H selects, over the cord-circuit at the manual exchange, out over another trunk T 2 T and wires NQ of a switch pair at the other local exchange, through the first selector connected to said wires and through a selected connector thereat, and over called subscribers line, to the substation. The

supervision of the cord-circuit as respects the calling line, is controlled in the same manner as that described where the calling line A was connected to the called line L, while the supervision at the cord-circuit as to the called-for subscriber, is controlled in the same manner as that described when the calling subscriber L has his line connected with that of subscriber W. The release of the mechanism employed at the distant oilices is effected on the withdrawal of plugs S and T in the same manner as described in those cases, respectively.

Itwill' bejobserved that while a switch H is operating under control of the private w per 13,4, 2'. 6., when started by the masterswitch mechanism G, thereis no busy potential upon the sleeve contacts 151 and it is barely conceivable that between the time the switch starts and the lamp signal 180 is dis played, the operator might plug into the Jack of the trunk,

whose switch H was open misconnection' would, of course, result and In such case. a

and the operator withdraw the plugs, thus restoring all apparatus to normal. V V

In view of the rapid ty of operat1on of the trunk selectors H, T have not deemed it advisable to unnecessarily complicatethe trung circuit by making special provision against the above mentioned contingency, as it would in practice-rarely, if ever occur, although it is, of course, within the scope of the invention that such means should be provided. V

The diagrammatically illustrated switch ofl igs. 2 to 6 is more specifically the line selector D.

As indicated in' Figs. 2 and 8, in which latter figure each line contact set24, 25, 26 is indicated by a single short line, the line contacts are arranged inten vertical rows, each row being a group, the said contact sets projecting as from the inner surface of a section of a sphere. The group contacts 24* are located immediately below their respective groups. j

The wipers 2?, 28, 29, and group wiper 27 are connected with the rotary primary shaft wiper 27* being rigidly con,- nected, while wipers 27, 28, 29 are pivotally connected at 300.

Primary movements of the wipers are effected by rotating shaft PS step-by-step rem left to right, a ratchet 305, Fig. 6, be ing fastened to said shaft and adapted tobe driven by armature actuated pawl 306 of magnet Phihthe retaining pawl 307 being provided to prevent-return movement under the influence of spring 302 against whose tension shaft PS is rotated. Each actuation of pawl 306 steps ratchet 805 and shaft PS to move wipers 27, 28, 29, opposite the next contact group, wiper 27 being correspondinglymoved to engage the next group contact 2d. i

Secondary movements of wipers 27', 28, 29, (wipe' 27 then remaining motionless) are elfected, after the primary adjustment is completed, by secondary magnet SM whose armature actuated pawl 809 engages the teeth of its associated ratchet cut in shaft Said shaft has fastened to it abroad iece 301 which en a 'es an anti-friction bearing'in the rearwardly extending support of wipers 2!, 28, 29, said piece be1ng broad so that however the wipers may be primarily adjusted, the bearing will still engage said plece 301.

Successive actuations of magnet SM, by'

pawl 809, step shaft SS downward, retaining pawl3l0 holding the shaft against back movement under the influence of spring 303,

whose tension is exerted against the downs ward movement of SS being linked thereto by the pivoted lever 30a loosely engaging a screw on shaft SS. Each downward step of haf SS y pie e 301 st ps the nta t

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