US1102907A - Telephone central switching system. - Google Patents

Description

E. A. GRAY & E c. MOLINA. TELEPHONE CENTRAL SWITCHING SYSTEM.

APPLICATION FILED MAY17, 1907. Y Y Patented July 7, 1914.

a SHEETS-SHEET 1.

I Cir-cull.-

Office Selectdr;

J) j I p Z Con necfq rs Trunk Selector B. A. GRAY & E. '0. MOLINA. TELEPHONE CENTRAL SWITCHING SYSTEM.

APPLICATION FILED MAY 17, 1901. 1,102,907, Patented July 7, 1914, 'a SHEEN-SHEET 2.

Primary Selectors .1

Connector-s a JecandaT Seleccrs fittest.

E. A. GRAY & B. C. MOLINA.

TELEPHONE CENTRAL SWITCHING SYSTEM. APPLICATION FILED MAY 17, 1907.

g lgg gg y I Patented July ,7, 1914;.

65 WW 7* 4S2 if 0 b 7:? *MH Gffe'ce a Keys E. A. GRAY & E. G. MOLINA. TELEPHONE CENTRAL swrrcnme SYSTEM.

APPLICATION FILED MAY 17, 1907.

Patented July '7, 1914.

8 SHEETSSHBET 7.

Lwwm

Thousands- ]lundreals Controller and Translator Prima'ry Register fltest. 6 'Inmntom'.

E. A. GRAY '& E. O. MOLINA. TELEPHONE CENTRAL swrroame SYSTEM.

APPLIOATION FILED MAY 17, 1907.

Patented July 7, 191% Keys k 99 Keys.

Tens-Unitsdontwllen 1 curtain saaa' rarest UFFKQ;

ERNESTA. GRAY, OF BOSTON, AND EDWARD C. MOLINA, OF ARLINGTON, MASSACHU- SETTS, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A

CORPORATION OF NEW YORK.

TELEPHONE CENTRAL SWITCHING SYSTEM.

Specification of Letters Fatent.

Eatented July It, 1914.

Application filcd lllfllay 17, 1907. Serial No. 374-3291.

To all whom it may concern ,o It known that we, ERNEST A. (may and EDWARD C. lVloLiNA, residing'at Boston and Arlington, in the counties of Sufiolk 'or B-operator, depending upon whether the desired subscribers line terminates at the same or another oilice of thedistrict, tests the called line. If this is busy the operator so notifies the calling subscriber and disconnects the switchcord which has been employedifrom the answering jack, or, if

r the line is idle, completes the connection,

rings the called subscriber andsupervises and finally disconnects the lines. lnautomatic systems the operator is dispensed with, except, perhaps, in toll connections,

and all the above-mentioned operations taking place at the central office are performed by electromechanical apparatus controlled by a mechanism situated at each substation and manipulated by the calling subscriber. Both of these systems possess inherent diiiiculties. In manual practice the number of acts which the operator must perform for each connection greatly limits the lines the calls of which she can answer, and since a considerable percentage of these calls must be trunked to another office, the introduction of a second operator still further increases the amount which must be expended in salaries and cuts down the economy of operation. lhe efficiency of the service also suffers because of the added liability to error in the transfer of calls between the A and B operators,

and because of the assignment of trunks and n tall, that portion of the system including the the delay whichthis occasions. In automatic exchanges, not onl is the central otlicc apparatus comparatively costly, but the installing inthe substations of the somewhat complicated -'controlling apparatus having many spring contacts and moving parts seriouslyincreases this, while the maintenanee of these widely separated mechanisms still further swells the expense. Then the burden of performin the operationseontrolling selection is t. rown upon the subscriber, who not usually being skilled, and often laboring under the disadvantage of poor light upon the indicating numerals of the controller, is liable to error, wasting his own time and that-of the personv wrongly called, and uselessly tying up a portion of the central ofiice equipment.

The present invention has forits principal object the revision of a system combining the best .atures of manual and automatic practice, attaining thereby results excelling both in economy and efficiency. The subscriber may call as in central energy manual exchanges, by simply removing his receiver from its book and verbally communicating his order to an operator. This operator has merely to connect an element of the ofiee apparatus and her telephone.-

set to the calling line, receive the designw tion of the desired oflice and number of the, subscriber to be called and register these Thereafter upon a controlling apparatus. a l connecting Ste 78 are carried out by e180? trically controlle mechanisms without further effort upon the partof the answering. operator, who is free to make other con nections, and Without the introduction of a second or B-operator. The only additional attention iven to each call consists in the disconnection of the calling line from the central oiiice apparatus, afterthe operator has been notified of the termination of the conversation by a signal follcwing the hanging up of the receiver by the calling subscriber.

The invention consists in the various features and combinations hereinafter scribed and more particularly claimed.

In the accompanyingdrawings, Figures 1 and 2 show schematically the more important apparatus at two oliicea'arranged in accordance with our invention. r Fig. 3 illus-" trates diagrammatically, but in greater decord circuit and the oiiice and trunk selec tors. Figs. 4 and 5 are s milar views of the primary'and secondary selectors and the final selector, respectively; and Figs. 6, 7 and 8 show respectively the oflice, thousands hundreds and tens-units sections of the controller, the second pf these including the translator.

Similar characters designate like elements throughout the several figures.

The system will be here. considered as applied to an exchange having a plurality of central stations, and ten of these may be assumed, each of a capacity of ten thousand lines, so that in all one hundred thousand subscribers will be provided for.

In Figs. 1 and 2 the chief pieces of apparatus and intermediate conductors at the central stations or ofiices Afand' A p are shown, and since hereinafter, in describing the operation of the system, A will be taken as the station through which a call is originated and A the station completing the connection with the called subscriber, the call answering and connection completing apparatus have been given special prominence at stations A. and A respectively, and either omitted or barely indicated at the other station. Moreover, in these figures for the sake of clearness the various circuits have been represented by single lines, though there are provided complete metallic circuits which may include in port ons a third wire, as will be seen in Figs. 3 to 8, to which reference should be had for such minor mechanisms as relays and for details of the appa-v ratus and'circuits generally.

V i'lppamtus of the connecting circuit. Of the substations but a single one appears for each central station, these substations a and a being provided with the apparatus usual in central energy systems, the firstnamed being joined by line conductors Z and t to a manually operable switch. This switch may be furnished by a jack J (Fig. 3) to the tip and ring contacts of which the line conductors lead and with which co- 0" crates a plug P. With the line conducand with. a third conductor Z connected to the sleeve contact of the jack are associated the wellknown line and cutofi relays it and R the former of which has two windings, and the line signaling lamp 0. A suitable number of these answering jacks v J and their corresponding line, lamps are situated at each operators position, there being no multiple of said jacks.

The plug P furnishes one terminal of a connecting or cord circuit C, of which enough are assigned to each operator to permit the caring for the maximum number of simultaneous connections. As is customary, each cord has the main. conductors or talking leads L 1 united, respectively, to th tip' landring of the plug,-and a-third conductor L leading to the sleeve. It, includes a repeating coil obetween the h'alves ofjwhich is bridged the central station batteryli nzitlp its positive pole grounded. This battery may be common to all the conductors of the station, but to render the connection more clear others will be shown and referred to as independent.- The cord also contains the operators listening key K and the telephone set (1 supervisory signal lamps O and O with the supervisory relays R and R, the latter of which is marginal, together with the originating relay R controlling relay R and double wound guard relay R. The purposes of the relays and minor elements in the cord and throughout the system will be, made to appear more fully in the descrip' tion of operation, where mention will also be made of the many armatures, contacts and conductors, reference to which independentl of the circuits of which they are a part and the functions which they perform would convey but little information.

Ofiice aim! trunk selecting apparzfus.-The strands L L of the cord circuit are continued beyond the con'tactsof relay R- by main leads or conductors L and L terminating in a selecting apparatus D, whichserves in the present instance to pick out the office with whiclnconnection is desired. Additional conductors L and L also lead between the apparatus C and D. The office selecting apparatus includes an electromechanlcal switch S of which there are several well-known forms available, this being here shown as provided with a rotatable shaft 8 which carries insulated from it main contact members or arms s s and a test contact member .3 each of these arms cooperating with'a series of stationary con tacts s. The shaft also has fixed to it ratchet wheels 8 and s engaged by pawls m and m respectively, movable withthe armatures of motor magnets M and M to advance the contact arms in long and short steps over the fixed terminalsupon the energization of said motor magnets. A spring 8 exerts its tension to hold the arms normally in a position out of contact with an active terminal.

A pawl it, brought intoengagement with the ratchet wheel 8 by the attraction of a retaining magnet H temporarily holds the arms at the points to which theymay have been advanced by the motor magnets. An oii' normal contact device 8 operates to vary the circuit connections when the arms are stepped from their initial positions, as wilLbe hereinafter described. As illustrated, both in this device and those of the other switches of the system, the movable contact members are raised when the advance of the switch arms begins.

To allow the groups of trunk conductors which connect the oflice. A with others in the district to efficiently serve the maximum number-ofsubscribers, all the ofiice selectors are given access to any one of the trunks'in allgroups, and this is accomplished bv multi )l in heir ii 1d contacts to said trunks go ,.i i

But with as many oiiices as ten, which in;

this case have been assilmed as comprised within the. district, and with, the number of trunks necessary-to satisfactorily handle the calls of each office with the maximum elliciency and economy, it may be found. that using the switches S for the direct selection of oilice trunks requires more fixed. terminals for each switch than, is practical, both because of, structural considerations and speed of selection. For this reason we have shown associated with the otlice selectors groups of trunk selecting, apparatus E, the arrangement, being as follows, reference being had to Fig. l. :"lhe terminals 8 of each switch S are divided into ten successive groups 1/ corresponding to the total number of offices. The space covered by each sub-- tends the angle through which the selector arms are advanced upon each energization of. the motor mag-net M. The terminals 5 are themselves separated; by distances equal to the. short steps produced by the magnet M Similar contacts in each group a are multiplied together by conductors a leading to triple conductors L L L, which may be connected to the arms of one of a suitable number of switches S of the trunk selecting apparatusE, these being best shown in Fig. 3. The trunk selecting switches are of the same character as those of the office Selectors having revoluble con tact arms .9 5- s to which the main c0n.- ductors L? L and the third conductor L may be connected. The arms are mounted upon a shaftsand driven by a single motor magnet M, with a retaining magnet H both provided with armatures and pawls acting upon a ratchet Wheel 8 This Wheeloperates, an off normal contact device 8 There are three sets of fixed contacts 8 over which the arms are moved. The connection of the contacts of the arm 3 is local to the apparatus Pl, being. for test purposes as will later appear, but the contacts of the arms 5" and s are united to trunk conductors Lf and L, respectively, which lead to the distant office to, which the section of the associated oiticc selecting apparatus D corresponds. These trunks are arranged in groups of a magnitude suiiicient to satisfy traffic conditions, and similar contacts throughout the groups of switches S are multiplied to the trunks by means of pairs of conductors '0 (Fig. 1), so that any switch may have access to any one of the trunks. It will be seen, therefore, that under the influence of some appropriate controlling means, each apparatus D may first pick out a group of selecting apparatus E represent ing a particular oliice and then an idle trunk selector, which in turn may seal; an idle trunk couple terminating in such distant office. In. doing this the switch S of the iapparatus D is required to move its con tact ar is to the proper section a of the fined Etcrmina s, (2) advance said arms until they reach contacts 5 connected to nonousytrunk selecting apparatus E, and (3) sto the argms and establish the circuit through thetnunk selector. To vary the circuit connections. for. the accomplishmentof this, each. apparatus ll). includes three relays it 31 and It, the relay R having two windings. he first when energized puts the ap paratus. in condition for operation; condition (1) follows with l1 energized and B1 deenergizcd; for condition (2) R and R are both ei-iergized, and, finally, for condition (3), R 1s decnergized and l t- QHQIw gized. The trunk selecting apparatus E has only to advance its contact arms to an. idle trunk, and. to aid in this a single relay E. is provided. In addition the motor magnets Mi and M. and the retaining magnets H and H have other armatures than those actuatingv the pawls, these sharing in the control of the circuit.

Linecelecing appomzua.-Fron the fixed terminals, with which the arms a s of each trunk selecting switch cooperate, the two -i':onductor trunks Li L extend to apparatus for selecting and connecting with the called line, which may, of course, belong either to the originating or to a distant oilice. In either case at their incoming ends each pair of trunk conductors is equipped with an apparatus h (l ig', for furnish ing ener y to this portion of the circuit and for controlling the-connection. This includes a repeating coil f, having one winding bridged across the trunk and the other winding" joined to conductors 1 and l f which lead through relay contacts to the conductors L and L and extend the talking circuit. Condensers f f are inserted between the sections of each winding of the R and R each have two windings, which in the relay It are of relatively high and low resistance, said windings being designated by the characters 1 and r respcct-ively. The functions of these relays and also those forming a part of the line selecting apparatus will be better understood after themechanism composing said selectin; apparatus have been enumerated.

It bcing'rememl'iered that ten-thousandline. oillces were assumed, the called line may group i leads or conductors L be conveniently arrived at by passing through three successive sections of apparatus: the first selecting the thousands in which said line is. located, the second the hundreds or an allied group and the third the tens group and the particular unit therein. These three assemblages of apparatus may be termed, respectively, the primary selectors I, the secondary selectors I and the final selectors or connectors 1 To the conductors' L and L of each trunkis permanently assigned a primary selecting apparatus which also has a thirdconductor L connecting it to the apparatus F. This primary apparatus 1 may be much the same as the oliice selecting apparatus D, the shaft 8 of its switch S carrying main contact arms 8 and s and a test arm 8, movable in long and short steps over terminals .9 by

successively acting ratchet mechanisms under the influence of motor magnets M and M and temporarily tionto which it is driven, by detent mechanism associated with a retaining magnet H. An ofi normal contact device a, double wound relay R and a marginal relay R and relay contacts upon the motor magnet M and retaining magnet H are features of the primary selector. The same general considerations of machine and trunk efliciency and economy obtain throughout the line selecting apparatus as in the office selectors, and it. may be that it is found expedient-,'-for example, to employ selecting switcheshaving in all 200 fixed terminals.

Itwill be assumed that such are to be used. In the primary switches these terminals are divided into ten groups to (Fig. 2) corresponding; to the thousands of the total numbeitfof lines in the ofiice, each of which groups may include twenty terminals. Similar terminals of each group in all the primary' selectors are multiplied by conductors to, to inter-apparatus trunks having main L and a third conductorL (Fig. 4). Each of the conductors U terminates in a contact device of secondary selecting apparatus 1, while leads L and L extend to the contact arms s 862, respectively, of switches S belonging to said secondary selecting apparatus. This enables onset the primary selectors to appropriate for the continuation of the connection the first idle secondary selector. The motor magnets M and M retaining magnet H h voii normal contact a and relays R and-R the'latter being marginal, are hereasin the primaryselecting apparatus.

The fixed terminals 8 of the switches S? are'divided into'secondary or hundreds groups (Figf 2),,isomewhat as are those sands groups, and 'foijsimilain reasons are multiplied by coaducttrsa a; trunk con} '1 leadin held at the posifinal selectors I, but as already pointed out, the switches are of two hundred points each,

so that the secondary groups will comprise two hundred instead of one hundred units, and there will be five of such groups to each thousand and five sections containing forty contacts 8' in the switches S The final selectors I have connecting switches S to the main arms a s of which the trunk conductors from the second ary selectors may be tensions L and L the test arm 3" is local to the apparatus 1 The fixed term'inals s of these switches H are in twenty sections y (Fig. 2), representing the tens of the-full group of two hunis joined through ex The connectionof dred; each section having ten unit terminals to which the substation lines, one of which is shown at Z, Z", with thetbird conductor to the answering jack J are multiplie by conductors 1 ,1 and Z as shown in Figs. 3 and 5 but indicated collectively at y in Figs. 1 and 2. Connected i with this substation line are its line and cut; oil relays R and R and a line lamp O. motor magnet M in this switch moves the contact arms in long steps from one tens section to another, while motor magnet M carries them by short steps over successive unitterminals until the line sought is reached. A retaining magnet H acts in the usual manner. Having in mind of the three kinds of line selecting switches, the functions of the relays at the incoming curl of the trunk and included in the primary and secondary apparatus may be stated. Relay R? assists in controlling the supervisory signal 0 The remaining trunk relays affect three groups of results-first, to establish and maintain connection between battery and the conductor L this rendering possiblethe succeeding operations of the primary selector, it applies current to the retaining magnet. H of said primary selector, which in turn does the same for one winding of the primary selector relay the purpose and relation R, then to the test arm 8 and relay R; I second, to receive and repeat locally into i the line selecting apparatus impulses transmitted from the calling oiiit i; third, to establish the talking circuit. These are brought about as follows: First, relay R momentarily establishes the desired connection with conductor L, which is then temporarily retained byrelay P tand ultimately relay R second, relay R receives and repeats into motor magnet-s M M and M of the primary, secondary and iinal selecting switches, respectively, the series of impulses which correspond to .the

thousands, two-hundreds, and hundreds and tens of the,desiredl number; relay R receives and} repeats into relays it and R and motor magnet M of the final selector arcane? the two single pulses and one series of pulses which are sent out from the calling" ofice to start the primary and secondary selector arms seeking for non-busy inter-apparatus trunks and to move the final selector arms to the unit terminals of the desired number; third, as soon as all the selectin impulses have been received and the talking circuit is established in thecord by the deenerg'iaation of relay it, relay R is energized. This relay JR shunts itself by relay R, which in turn energizes relay R. The lastsramed relay establishes the talking circuit, maintains the'circuit of relay it, opens the circuits of relays R and R, and substitutes a direct connection between the conductorl} and battery for the previous connection through the winding of relay R The ends attained by the relays of the primary and secondary selectors are closely analogous to those accomplished by the relays of the oflice selecting apparatus D. That is, in the primary selector 1, to cause the arms of the switch S under the in flue-cc of the calling oiiicc to (1) seek the section 10 of its contacts from which conductors lead to the multiplied secondary selectors l representing the thousand of the called line; (2) to continue the movement by shorter steps within said section to reach an idle trunk, and (3) to stop the arms and The relays of the complete connection. secondary apparatus l eflect the same result with respect to the finalselecting ap-' paratus l. The operations follow one another in the order given with (1) relays R and R ener 'ized. and R and R deenergized; (2) R R" and R R all energized, and '(3) with It and R deenergized and R and l energlzed.

Returning now to the final selector, all: the apparatus of this class at the oli'ice would have associated with it a ringing" generator N and a busy signal mechanism N Each final selecting apparatus has as signed to it a group of relays. fOt these, negatively polarized relay E by means of a final impulse of current from the calling oiiice, closes the circuit of the test arm a,

and of the busy signal mechanism; double wound sluggish relay R is adapted to control the display of a busy signal to the oporator; R, which be termed the primary connecting relay, completes one side of the line, cuts oil the busy signal mechanism and closes the circuit of the relay R relays R and it, the latter having two' windings, apply ringing current to the called line, and relay R the secondary connecting relay, interrupts the ringing current and completes the talking circuit. In varying the circuit connections, relay con-. tacts upon the retaining magnet H and of normal contact devices a and a assist.

'ao aratus.

til"

the oflice, trunk and primary and secondary line selectors for an idle apparatus among the multiple of the succeeding class to which it has access takes place under the control of the previously mentioned relays without the direct intervention of an operator. The selection of the ,ofi'ice at which the called subscribers line terminates and of all the grou s of units making up the number by whic 1 said called subscriber is designated is under the control of the calling subscribcrs operator, therefore, to start the series of selective operatipns and to govern them, each operator is provided with a controlling apparatus T (Figs. 6, 7 and 8) which receives current from the ofllce battery through a main lead L Said current, in certain of the controlling circuits, is interrupted to furnish motive impulses by one or more pulsators of any convenient type. Like the battery, these pulsators have been shown in the drawings in a number of places and indicated by different characters of reference for convenience in description.

With such an exchange as that now under consideration the contyplling apparatus,

which is shown as connected with the apparatus of the cord circuit C by conductors L L and if, and with the office selector 1) by a conductor if, may have'three sections T and '1, corresponding, respectively, to the offices of the exchange, the

thousands and hundreds digits of the total numberof subscribers, ten thousand, which 'may be connected to each, and the tens and.

units digits of said number. Each section is provided with a set of keys equaling in lnumber the offices or digits, the selection of which it governs, there being ten office keys K in section T ten thousands keys l' and ten hundreds keys K in sectio1i."i and ten tens keys K on" ten units keys K in section 1, each being preferably designated in practice by the office or digit which it represents. The keys may be of any convenient form, and are each provided with twocontacts normally open but closed upon the depression of a key. Each set of keys has a locking member I; to maintain a depressed key in this position until released by the cnergization of an electro-magnet 72 Combined with each set of keys is one or more electromechanical switches, preferably organized in the same general way as those of the selecting apparatus, and these will be hereinafter referred to without describing" them in detail. Groups of relays are also associated with each set of keys and those will be more particularly mentioned and their functions stated after an enumeration of the major mechanisms of the controlling o affect the oilice selecting apparatus D y 1 1n accordance wlth the condition registered upon the keys K at the controlling appanew 'ratus, said keys (Fig. 6) are connected consecutively to one of ten fixed cpntacts-s of a sending sw1tchS which governs the number of selective impulses applied tothe factthat although the primary groups of the line. selecting apparatus are arranged by tens, that is, upon the decimal system, as naturally would also-bethe digit keys before the operators, the secondary groups in the thousands will all be of two hundred units each and therefore non-decimal. To

' cause the 'decimally designated keys to conmagnet M is connected consecutively to a A control the sending of selective impulsesd reds key. 1 The contact a trol selection non-decimally it becomes necessary to in some way change or translate the condition originated into a different condition actually transmitted. For this purpose the combined thousands and hundreds sect-ion is equipped both as a controlling and a translating apparatus. It has a switch mechanism S (Fig. 7) the shaft of which supports three contact arms 8 si 'and s revoluble in lon and short steps by motor magnets M and I, respectively, and temporarily held by a retaining magnet Each arm cooperates with a set of fixe d contacts designated, respectively, by the characters 8 8 and 8?, there being .100 in each set,and thus equalingthe possible combinations of ten thousands keys with ten hundreds keys. Every tenth point 8 of the set 8, or those separated by intervals equivalent to the long steps of the s rin of a thousands ke. K and serves to to the primary apparatus I. The intermediate points are spaced from one another in accordance. with the short steps produced by magnet M every tenth point being multipled together in sets of ten and connected to a spring in the corresponding hunultimately reached by the arm 8" determines the point at which the arms s and 8 shall. rest upon the contacts 8" and s and it ma be considered that upon these the original numeri- I cal condition initiated by the hundreds keys .being primary ands auxiliary. It is now desired to transmit impulses to the secondis registered. For this-reason these will hercun fter be termed register contacts, 8"

ary selectors 1 according to their non-decimal arrangement of five two-hundreds groups to the thousand. For this purpose the contacts 8 of the primary register are connected in pairs, thus giving the fivegroups in each of the ten thousands which the entire hundred contacts represent.

Then, as the only function of this portion magnet M and a retaining magnet H I'fthe' number sought fell within the first hundred of the two-hundred group, it would only be necessary to proceed with selection therein through the final connecting apparatus by tens and units. If, however, it is in 'be advanced over the first hundred before said selection begins. To accomplish this the first and every alternate contact 3 of the'auxiliary register is multipled to a conductor leading to relay mechanism which puts the controlling section '11 into action. The second. contact 8 and every other alternate point is similarly multipled and is joined to relay mechanism'to bring into play an auxiliarysending switch s,'the motor magnet M of which causes its arm 5 to take 'ten steps, and ten impulses to be transmitted to the motor magnet M of the connector I carrying it by tens over the first hundred'of its two hundred contacts. At the termination of its ten steps, during which the arm'is temporarily held 'under the influence of a retaining magnet H the arm 5 rests upon an active contact 8 completing a circuit which transfers the control to the tens and units section T".- l

The section T (Fig. 8) includes a combined tens and units sending switch S of which the arm 8 first travels from one tens contact 5 to another under the in fluence of a motor magnet M and then is moved from units contact 8 to units contact by motor magnet M To govern these movements and the impulses 'sent to is operating or idle. The remaining relays have three functions (1) to close a motor magnet circuit, (2) to open said circuit: when l the deslred impulses have been transmitted,

the second hundred the connector arms must- Ofthe relays of the controller Twhich hundreds sending switch S This switch is provided with a contact arm 8 a motor the connector each tens point is joined to a tery lead will show whether the contrbller flee to be brought into circuit, instead the second relay R disconnects the controller from the cord. in addition'to What have been mentioned, the controller has ofi'ice test relays R and R, a thousands test relay R and a hundreds test relay R Of the controller relays those numbered R R R R R R R and R are sluggish, while relays R R R R and R have each two windings.

Operation of the system.

To show the operation of the system, the

manner of receiving a call will now be described, together with the completion of the desired connection with an idle line and the failure to so connect with a busy line; at the same time the circuits involved will be traced. It may be assumed that the subscriber at substation a, which has an answering jack and its signal at central station A, wishes to communicate with subscriber at 06 whose line belongs to central station A and whose number is 2132. The subscriber at substation a (Fig. 3) takes the receiver from its hook, completing a circuit from battery B through conductor 14, one winding of relay 1t, armature 11 and its back contact in cutoil' relay conductor 12, limb Z of the line, substation set a, limb Z of the line, back contact and armature 13 of relay Il and second winding of relay R to ground. Thisci'iergizes the line relay, thereby closing a local circuit 141 including armature 1 1, battery 13 and the line signal lamp 0, which is thus illuminated. In response to the signal, the operator before whom it is situated inserts the plug P of one of the cords G at her position in the answering jack J of the calling subscriber-"s line. This results in the energization oi. the cutoff relay R, originating relay i and supervisory relay R by the simultaneous clos ng of two circuits, one from battery B to g1 ound through the winding of the cutoli' relay, conductors Z and L and winding of relay It; the other from the negative pole of battery B, one winding 15 of the repeating coil 0, winding of supervisory relay 1 limb Z of the subscribers line, substation set, limb Z of the line, and winding 16 oi? the repeat ng coil. 'lhe energization of relay selector 1), conductors It disconnects relay It froni the subscribers line, resulting in the falling back of the armature 1st and the extinguishing the line lamp 0. The operation oi relay it", through its arn'iature 1-0 and its front contact, places battery B' on conductors 17 and 18 and lights supervisory lamp 0 which is connected to ground. The energization of relay R opens the contact of its armature 19 and prevents the lighting of the supervisory lamp The operator throws the key K in the cord employed into the listening position and connects her telephone a through the springs 20 20 with the talking strands U L of said cord, and'at the same time closes at the springs 21 21 of the key a circuit from the battery B (Fig. 8), through spring 22 of the controller connecting relay R conductor L, normally closed springs 52 52 of the contact device a of the office 3 and 23, back contact and armature 24 of ,cord relay It, winding of connecting relay R conductor L winding of relay R conductor 25 and back contact and armature 26 of units relay On. operating the relay R by its armature 22 disconnects battery B from the conductor L and connects it to the main battery lead L, which with its branches is shown in heavy broken lines so that it may be readily distinguished, and to thus avoid the necessity for tracing back to the battery 13 the many circuits of the controller. When battery is connected to this lead hold-- ing magnets H of the o-fiice switch S H of the thousands-hundreds switch S 1 of sending switch 8" and H of the tens units switch S are energized by current to ground. The path of the first is through conductor 27, armature 28 and its back contact in relay R and conductor 29; the second through otl' normal contact 8" of switch S and conductors 30 and 31; the third through spring 31 of relay It and conductor. 32, and the last by ofi' normal contact r of switch S and conductors 33 and 3t. At thesamc time the lamp is illuminated and so continues while the controller isin operation. The armature 35 of controller relay R closes contact with spring 36 before breaking the resting contact of the spring, with the result that by means of conductors 38, 39,- 4:0 and :41 the key releasing magnets Z1 of all the controlh-u sections are momentarilv energized by current from battery ll f The object of this is to free any key which mighthave been accidentally depressed before the operator is ready to register the desired number.

The operation of controller connecting relay R 'in the cord, which was energized simultaneously with the starter relay 1t, disconnects by its armatures 76 and 84: the talkiiig leads Lf L of theofiice selector D relay by the operatidn of keyjK but which is oplened by th" 8nrg1Zi}blOI1 of relay tion the other armature 48 of R. cpmpletes a circuit from battery B to from the cord strands L L and joins theformer to the controlling apparatus through conductors Ligand L. Armature. 42"of relay R closes a by-path by mr ductor through one winding ofcord relay R ,conductor 44, contact of. key'jK, conductor '18 and front contact and armature 16 01. R?- to battery 3*". This by-path' serves "the double pur'pose of energizing the guns zany R 4 and substitutin' a; path to attei'y for the circuit of relays Ff" and R in place "6f that to battery B through armature Qeibf relay R, which circuit was closed now R.

is prevents any subs'e'quent throwing of the key intothe listening position from interferiiig with the circuits, and the attracthis relay firoundthrough the armature 16 of relay complete p n of the limit of ,iconductor18,contact45 of key K, secondj winding of relay R, conductor L and windingof' oiiice selector relay It. This energizes" relay R and locks relayi-R making'git independent of the circuit established through its first-mentioned windin ()n'operati ng th ejrelayR clo'sest e front contacts of its three armatures 49, and 51. Armature -eiil'connects ground to the winding of relay It! Armature 50 prevents the "ductors'L and L, which would otherwise take place upon the separation ofithe springs 35;

52 and 52 of the-0d normal device a, when thefinotor hin'agnet of the oilioe selector ref'sp'onds'to'ithe impulses which it is to re- "ceive, Armature 51 closes a circuit through conductorf53 from ground to battery B 'thioughthe winding of retaining magnet H Then the office selector relay R is ehergizeil by "current in one winding from -batt'ery B to ground through the armature 5'4 and its front contact in the retaining magnet H conductors 55 and 56, spring 57 audits restin condiictor 58. i1

contact'in relay R and 'W disconnects its armatures 59, 60 and 61 from the arms '8' s and 8 of the office selecting switch and closes their front contacts. The

apparatus is now rea y for automatic select1on'to begin whent; e operator has reg stered the office and. number upon the con-j troller'keys. 1 v

The selection of the oficaand' a trunk leading th ercta- -Ip accordance with the number A -2132, th

of the ofiice sending switch S tothe main and'63 of the key' anddonductor 64, and also closes a the pantr lead through en energized the relay R? e operator depresses j the qlficekey' AFuKiQQt'houSjathds key 2K, hundedskey lKf-"fl tensfliey 3K. and units" key 21 The 'depression of the olfice key connects "the "second lfixed contact point 8 ccnductor 62, key spring s63, 63 and c5,

conductors 66 and 67, winding of relay R and itsjspring 68 to an intermittent ground provided by pulsator P Since the puleater is in constant motion relay 1t will be energized at a time substantially coincident with the depression of the oflice key; On operating this relay locks itself to ground by its armature 69, disconnects itself from the intermittent ground of the pulsator, and closes the following path from the spring of the pulsator P which is connected to battery B to ground; armature 7 O, conductor 71, winding of motor magnet M back contact and armature 7 2 of relay R conductor 73, back contact and armature 74 of relay R3 conductors 75 and L, armature-7 6 and spring 76 of relay R talking lead L armature 59. and its front contact in relay R, conductor 77, winding of motor magnet M, conductor 77 a and spring 78 of relay R Since this circuit contains the windings of t wo motor magnets, either of which may be more sensitive, it is essential that the first pulse of current over the circuit-when it is closed by the operation of the controller relay R shall be complete and not fractional. This is accomplished by including in the initial circuit of the relay R the intermittent ground contact of the pulsator P, as has beenalready described, thus fully energizing it before the pulsator applies current to the motor magnets. Said mag' nets M and M'- now will drive forward simultaneously the contact arms of the oflice controller switch S and the selector switch S, the latter covering a section a at each step. When two pulses have been transmitted through the motor magnets the arm of the controlling switch will close 1 a path from the batterylead L to ground throu h conductor 62, springs-63 63 ofthe pressed key, conductor 64, switch armis conductor 79 and one winding of relay R This relay then operates. and breaksthe circuit of magnets M and M at itsarmature .7

72. The arms of the oflice selectorare now at rest on the first triple set of contacts of its second section. If the .trunk selectorE connectcd'with this set of contacts is not busy it is only necessary to release'relay R; if the trunk selector is busy the movement of the arms must be continue'd'until they are brought to rest'on contacts leading to a non-busy apparatus. 3

It will be noted that the previously. de-

scribed path through the winding of relay RS is only one of two which'run from'conductor 79 to ground. The other path consists of conductor 80, off normal contact dewice a, which is now closed, conductor 81,

back contact and armature 82 of relay R, conductors 83 and L, armature 84 and spring 84 of relay R, talking-;leadlf*,,

armature 60 and its front 'oontacti' inrelay" R conductor 85, winding of relay R and front contact and armature 49 of realy R Therefore, relay R of the office selector was energized simultaneously with relay R of the controller when the contact arm of the office sending switch reached its second point. On operating the armature 78 of relay l 22 disconnects ground from the motor magnet M and closes from ground to armature 61 of relay R, which armature is joined to the test arm 8 of the office selecting switch, a multiple circuit consisting of (1) conductors 86 and 87, one winding of relay R and conductors 90 and 88, and (2) ls 'conductor 86, the winding of the motor amagnet M its armature 89 and conductors 90 and 88. The operationcf the armature 91 of relay R opens the circuit of the winding of relay R connected to conductor 58, and locks relay R to the battery 13 by means of spring 57, conductors 56 and and armature 54 of retaining magnet H and its front contact. If the trunk selector with the leads of which the arms of the office selector are now in contact is busy, conductor L will be connected with the battery B of th'e office selector already associated with it. Therefore, although the circuit of one winding is open, relay R will be keptenergized by current passing from conductor L through the test arm 8 of the office selector, conductor 95, armature Gland its front. contact, conductors 88 and 90, second winding of relay conductors 87 and 86 and armature 78 and spring 78 of relay R, which is now energized. Current Will also flow through the other branch of this circuit which includes the winding of motor magnet M and hence the contact arm will be driven forward until the test arm comes to rest on a lead which is not connected to battery, that is, until a non-busy trunk se lector is attained. Then, since current no longer flows through either winding of relay R it is denergized, breaks at its front contacts all its circuits previously described, connects talking leads L L through the two upper arms to the talking leads L L and unites battery B to conductor L by means of the test arm. This readers the chosen trunk selector busy, to guard, as has just been outlined, against its appropriation by another office selector. When this occurs current will flow from the conductor L to ground by three paths: (1) through spring 96 of the 0H normal device 8, conductor 0/ and the winding of the retaining magnet H (2) springs 96 and 98, conductor 99, back contact and armature 100 of motor magnet M aird winding of said magnet, and springs 90 and 98,. conductor 00 and the winding of relay R The magnet H applies the retention pawl, and by its armature 101 closes a path through conductor 102 to conductor L, which makes the cir- 'cuit for the retaining magnet independent armatures 103 and 104, and connects at armature 104 the test arm a to conductor 99 through conductor 105. The'motor magnet M in response -to the current flowing through its winding, propels the arms from their normal position and opens contact springs 96 and 98. Although the opening at these springs disconnects condiictor L from relay R and magnet M, these will be supplied with current by means of the test arm from the battery B of an office selector associated with a busy trunk selector through the multiple of the test contacts, until said test arm and the main-contact arms come upon the terminals of a nonbusy trunk, then current no longer being found atthe test contact, relay R will be released, thereby re'r'stablishing the connection between the arms .9 and s and the talking leads L and L atthe armatures 103 and 104, disconnecting the test arm from conductor 105 and joining it to conductor L by conductor 106.. The conductor L being connected to battery B, the test arm establishes on the test terminal corresponding to the selected trunk the condition which will prevent its being taken by some other trunk selector. v v

The selection of the thousand g1'0up.'Returning to the consideration ofitlie controlling apparatus, relay R when energized not only opened the contact of armature T2 to stop the advance over the'sections u of the office selector arms, but also closed a circuit from ground to the main battery lead L through its second winding and the winding of relay R by way of the conductors 107 'and -108. This latter relay is designed to operate sluggishly, in order that its armature 82 will not open the back contact before office selctor relay R has had time to lock up. Upon operating the armature 74 of relay R opens its back and closes its front contact. l\'o further action occurs in the controlling apparatus until the office, selector has completed the finding of a nonbusy trunk selector, and subsequently the latter of a non-busy trunk. But when trunk selector relay R is det nergized and the connection between the lead L and arm 8 is reestablished, current flows from the battery lead L through conductors 27 and 109, spring 110 of relay R conductor 111, winding of relay R, conductor 112, front contact and armature 74E of relay R i conductors T and L, armature 76 and spring 76 of rblay It, talking lead L armature 50 and its back contact in relay R office selector arm .9, talking lead L, armature 103 and its back tontact in relay 13"", trunk selector arm a, talking lead L of the interoifice trunk, conductor 112, spring 113 of relay R conductor 114, winding of relay R, conductor 115, back contact and armature 116 of relay R, conductor 117, back contact and armature 118 of relay It, conductor 119,"spring 120 of relay It, talking lead L armature 140 and its back contact in rela R and primary selector arms a to groun at its resting contact. Controller relay R and trunk relay R are both energized by the closing of this circuit." The armature122 of relay R are both energized by the closing of this circuit. The armature lished by relay R by connecting its winding to the battery B, through the conductor 130 and .spring 131 ofrelay R. The arma-- ture 132' of relav R substitutes its contact with the spring 113 for the resting contact thereof, but this has no effect until relay R is deenergized and its armature 122 assumes its normal position. Armature 133 of bold ing magnet H ,'by closing at its front con-- tact a connection between conductors 127 and 134, prevents the separation of conductors L and 127 when the oil normal contact device s is opened upon the actuation of the switchS. The armature 135 closes a path from battery B to ground through conduc-1 vtors 136 and 193, spring 137 of, relay R", conductor 138 and one wlnding of relay R.

The functions of this relay are analogous to those of the oific'e selector relay R. It

' temporarilydisconnects leads L L from arms-8 and s and closes the front'contact s of its armatures 139 140 and 141; Considering again the controller relay R, which was energized simultaneously with the trunk relay R, itsarmature 142 closes the circuitofrelay R from the battery lead L through conductors 27 143 a and 144. This relay R by means of its armature 145 looks its winding to battery by way of'con-- ductors 27 and 1 09 andspringllO, and opens the resting contact of said spring-and the.-

energizing, circuit of relays R and R, thereby releasing them. 'The armature 28 of-relay R opens-at its back contact the circuit of the retaining magnet H of the ofiice sending switch S, the arm a of which is returned by its spring. to its initial position. Uponits front contact the arma-- 'ture 28 closes a path from'the main battery lead through conductors 27 and 146, armature 147 and its back contact in relay R and conductor 148 to the springs 149 of the thousands keys K Since the key of the digit 2 is depressed, current will flow on.

from conductor 148 through springs 150 and 151, conductor 152, winding of relay R and its spring 153 and conductor 154 to an intermittent ground at pulsator P. Then relay R attracts its armatures, locks itself to a permanent ground connected to the armature 155, opens the-contact leading to the pulsator, and closes the front contacts of its armature 156 and 157. There is now a closed circuit from the pulsator through the winding of motor magnet M conductor 158, front contact and armature 156 of relay R, conductor 159, back contact and armature 160 of relay R, conductors 161 and L, armature 76 and spring 76 of relay R which isstill energized, lead-L, armature 59 and its back contact in relay R arm 8 of the oflice selector,-lead L armature 103 of relay R a'i'm s of the trunk selector, lead L, conductor 112,

spring 113 and armature 132 of relay R conductor 162, back contact and armature 122 of relay R, conductor 163, winding of relay R conductors 164 and 115, back contact and armature'116 of relay. R, conduc-v tor 117, back contact and armature 118 of relay R conductor 119, spring 120 of. relay R, lead L armature 140 and its frtnt contact in relay R, conductor 165, and

spring 166 and winding of relay R to ground. The closing of the circuit allows pulsator P 'to send a series of impulses through the motor magnet M the relay B of the trunk and relay R of the ,primary selector. Relay R being marginal will not be energized by the series of pulses. passing through it, on account of the high resistance of relay R and motor magnet M The first pulse which passes through the motor magnet drives the arms of the thousands hundreds switch 8 from, their normal position to the zero member of'the doiiperating set of fixedgcontacts; the second pulse will drive the arms from the zero contact to the first tens contact .9? while the third willadvance them to the second tens contact 8".

As will appear shortly, not more than threev impulses will be sent through the circuit under consideration. 1 At the same time, by means oftrunk relay R*,the'following cirjcuit from battery B to ground through the. winding-of motor magnet M" of the primary selector will be closed three times-er mature 1670f relay R, conductor 1168,

spring 169; of relay R, lead L, armature 139 and its front contact in relay R condoctorv 170, winding of mag et M and spring-171' of relay R Thus it will be seen t at the: three impulses which the pulsator P transmits through motor magnet M and relay R not only propel the arms of the thousands-hundreds switch, but, by,

contacts.

When the arm .9 of the thousands-hun dreds switch S comes in contact with the twenty first point 8 or that corresponding to the numeral 20, current will flow from iead L to conductor 148, as previously traced, through springs 149 and 150 of the epressed thousands key K conductor 172, 1 a, conductor 173, armature 174 and back contact in relay R and conductor to ground through two pathsone -ough COIlClIlC'JOI' 176 and one Winding of relay R thereby energizing it; the other through conductor 177, armature 157 and its front contact in relay R conductor 178, back contact and armature 179 of the relay R conductors 180 and L, armature 84 and spring 84 of relay R lead L armature 60 and its back contact in relay R arm 8'? of the oflice selector, lead L armature 104 and its back contactin the relay R arm 8 of the trunk selector, lead L, one Winding -181 of the repeating coil f, conductors 182 and 183, spring 184 of relay R conductor 185, Winding of negatively polarized relay R, conductor 186 and Winding of positively polarized relay R energizing the latter but not the former because the current floWs from the positive pole of the battery B The operation of the armature 160 of the controller relay R breaks the circuit containing the motor magnet M" and relay R, and therefore the local circuit through the motor magnet M is also interrupted. The armature 110 of relay R opens its back contact and closes a circuit from battery 13 to ground through conductor 117, back contact and armature 118 ofrelay R conductor 119, spring 120 of relay R, lead L armature 140 and its front contact in relay R conductor 165 and spring 166 and winding of relay R thereby energizing said relay. The armature 187 of relay R before breaking the resting contact of spring 166, locks the relay to battery 13 through conductor 136and armature 135 of retaining magnet H The armature 188 of relay R makes con tact With its spring 137, Which at this time has no effect, and opens the resting contact of said spring, thus breaking the circuit containing a Winding of relay R. The armature 18,9 of relay It opens the resting contact of its spring 171, and therewith completes circuit from ground to the test arm 8 through armature 141 and its front contact in relay R and the parallel paths consisting of (1) conductors 190 191 and 192-with the second Winding of relay R,

and of (2) conductors 190 193 and 192 With the Winding of the motor enagnet M. In the same manner as described in connection WitlLthB ofiice selector, the test arm 8 of the primary selector will retain relay R energized and operate motor magnet M until the arms of the primary selector come into contact With leads to a non-busy secondary selector 1 then relay R is decnergized, armatures 139 and 140 connect leads L and L to arms 8 and 8 and a circuit is closed from battery B to ground through the armature 135 of holding magnet 1. conductors 136 and 193, spring 137 and armature 188 of relay R conductor 194, armature 141 and its back contact in relay R test arm a, lead D 011 normal contact device .9 conductors 195 and 196 and the Winding of the retaining magnet H Upon the energization of this magnet its armature 197 closes a contact between conductors 195 and 198,'Which short 'circuits the OE normal contact device. The armature 199 of magnet H" 'closes a path from battery B to ground hrough conductors 200 and 201, spring 202 of relay R conductor 203 and one Winding of relay R. Upon operating this relay discon nects its armatures 204 205 and 206 from the arms .9 a and 3 respectively and closes it front contacts.

The translation and selection of the 7mmd'r'cds gr0'up.--In the previous reference to the energization of the controller relay R the opening of the contact by means of its armature 160 only Was considered. Its armature 207 completes a circuit from ground to the main battery lead L through one of its windings, conductor 2.08 and Winding of relay It, which is designed to operate sluggi'shly in order that it will not open the resting contact of its armature 174 be fore relay R of the trunk had time to start the series of operations at the primary selector, as already described. The armature 147 of relay R, by opening its back contact and closing the front, disconnects the conductor 146, Which with the conductor 27 extends to the main battery lead from the thousands keys, and connects it to the hundreds keys through conductor 209. The hundreds rey 1K being depressed, current noW flows from conductor 209 through springs 210, 211 and 212, conductor 213 and Winding of relay R to ground. 7 This, by its armature 214. closes a circuit from ground to pulsator P throughv the armature 215 and its back contact in relay R conductors 216 and 217 and Winding of motor magnet M As soon as one impulse has been transmitted, and therefore the arms of the switch S have moved one short step from the fixed contact 8 num bered 20, Where they had been carried under the influence of the long step motor magnet M current will flow from conductor 209 through springs 210 and 211 of'the depressed hundreds key, conductors 218 and 219, the latter being connected to the point of the contacts a, numbered 21, arm-s conductor 173 armature 1.74 and its front contact in re ay R conductor 220 and winding of relay R to ground. Relay R then destroys the circuit of motor magnet M at its backcontact, and closes at its front contact a circuit from the main battery lead to ground and containing its second winding, conductor 221 and winding of relay R. The energization of relay It opens the contact of armature .17 9,

' which is no longer required, and by its 103 and its back contact in relay R arm a, lead L conductor 112, sprin 113 and armature 132 ofrelay R, con'uctor 162, back contact and armature 122 of relay. R conductor 163, winding of relay R, conductors 164 and 115, back contact and armature 116 of relay R, conductor 117, back contact and armature 118 of re-.

lay R, conductor 119, spring 120 of relay R, lead L armature 140 and its back contact in relay R arm a, lead L, armature 205 and its front contact in relay R conductor 225, spring 226 and winding of relay R to ground. This circuit only energizes relay R of the controller, since relay R in the trunk, being positively polarized, will'not operate on flow of current from the negative pole of the battery, while relay It, bein marginal, cannot operate in series with t e high resistance of relays R? and R. On operating controller relay R" locks itself to ground through its armature 227, opens at its spring 223 the circuitWvhich has just been described, and closes by its armature 228 a circuit from intermittent ground at 'pulsator P through conductors 229 and 230, spring 231 and winding of relay R to the battery lead I L 'Ifhis relay R locks itself ten perinanentground by its armature 232" and spring 231, disconnects itself from the intermittent ground at its spring, and closes thefront contacts of, its armature 233 and 234. We now have a path from the pul-- sator P to ground through conductor 235,

I armature-233 and its front contact in relay'R conductor 236, winding of motor magnet M belonging to the sending switch 8", conductor. 237 back contact and ar'ma ture v238 of; relay R conductor 239, lead L, and to ground at the seoondary'selector through the windings of relays B, and R "ac-5 bythe same course as that just traced in relay R, arm 8 tor 247, back contact a the negatively describing the energization of relay R As before relay R will remain quiescent, but

this time relayR will be energized, as pulsator P transmits positive current. Motor magnet M and relay R now operate simultaneously. The' former drives forward the arm 5 of the switch S while the latter closes a circuit from battery E3 to ground through its armature 167, conductor 168, spring 169 of relay R, lead L armature 139 p of switch S,'lead I), armature 204 and its R conductor 240, winding of'motor magnet M of the secondary selecting switch S and spring 241 of relay R and its back contact in front contact in relay When one impulse has been transmitted by the pulsator P and the arms of switch S have reached the first set of contacts a of the first group as, or that corresponding to the first final group of two hundred numhers, the arm 8 of the primary hundreds.

switch S closes a circuit fromthe 1 r h conductor 242,

sending main battery lead throu arm 8 of the thousandsundreds primary register of switch S, which it will be're-,

membered is resting upon its twenty-second point 8 (numbered- 21), conductors 243, 244 and 245, and then to ground by two paths, the other through conductor 246, front contact and armature 234 of relay R 9", conducand armature 248 of relay R conductor L armature 84 and spring 84 of relay It, lead B, armature 60 and its backcontact in relay R arm 8 lead L armature 104 and its back contact in relay Rt", arm s lead L, onewinding 181 of the repeating coil f, conductors-182' and 183, spring 184 of relay R conductor 185, winding of relay R conductor 186 and winding of relay B. These two paths one one through a winding of relay R ergize simultaneously relay R of the controller and relay B: of the trunk, but not polarized relay R. The armature 238 of relay R opens its back' contact, thereby destroying the circuit from the pulsator P Relay R opens the back contact of its armature 116 and. closes acircuit from battery B to ground through conductor 117, back contact and armature 118 of relay R conductor 119, spring 120 of relay R, lead L armature 140 and its;

back contact in relay R arm .9 of switch 8, lead L armature 205 and its front contact of relay R conductor 225 and spring 226 and the winding of relay R When attracted the armature 249 of relay R locks the winding of the relay to bat-.

tery- B through cnnductor 200 and the armature 199 of the retaining magnet H and also opens the resting contact of its,

spring 226. The armature 250 of the relay breaks the circuit 200, 201 and 203, contain ing one winding of relay R and makes

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