US1237214A - Two-wire automatic telephone system. - Google Patents

Description

,e. awe-ma. TWO-WIRE AUTOMATK)TELEPHONEQSYSTEM.

rammin 14,1917;

l2 SNEET5-5NEET I APPLICATION FILED APBJ. I909.

a, is. MUELLER. I

TWO-WIRE AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED APR. 9. 1909.

Patented Aug. 14, 1917.

12 SHEETS-CHI -2.

G. E. MUELLER.

TWO-WIRE AUTOMATlC TELEPHONE SYSTEM.

APPLICATION FILED APILQ, I909. 1,237,214. Patented Aug. 14, 1917.

12 SHEETSSHEET 4.

TWO-WIRE AUTOMATIC TELEPHONE SYSTEM.

mwucmou FILED APR. 9. I909.

s. E. MUELLER.-

lililj LLLIII 1 12 SHEETSSHEET s.

Patented Aug. 14, 1917.

G. E. MUELLER.

TWO-WIRE AUTOMATIC TELEPHONE SYSTEM.

APPLICATION HLED APR- 9.1909. 1,237,214. Patented Aug. 14,1917.

2 SHEETS-SHEET 6.

G. E. MUELLER.

rwo-wms AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED APR, 9.1909- .1 ,237,214. Patented Aug. 14, 1917.

.l 2 SHEET$SHEET 1.

'G. E MUELLER.

TWO-WIRE AUTOMATIC TELEPHONE SYSTEM.

Ai'PucAnon min APR. 9'. I909.

1,237,214. Patented Aug. 14. 1917. I2 SHEETS-SHEET B.

G. MUELLER. TWO-WIRE nu ommc TELEPHONE SYSTEM.

APPLICATION FILED APBQQ. I909- 1,237,214. Patented Aug. 14, 1917.

I2 SHEETS-SHEET 9.

, G. E. MUELLER.

TWO-WlRE AUTOMATIC 115151 11011: "new. APPLICATION FILED APILQ, III

' 1,237,214. I PatentedAug. 14,1917.

G. E. MUELLER.

TWO-WIRE AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED APR. 9. I909. 0

Patented Aug. 14, 1917.

I2 SHEETS-SHEET ll.

G. E. MUELLER. L TWO-WIRE ALLTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED AHLQ. I909. L 1,237,214. Patented Aug. 14,1917.-

l2 SHEETS-SHEET I2- UNITED STATES OFFICE;

xnnnoec swrrcnnoann & SUPPLY COMPANY, A coarom'rron or minors.

To all whom/it mag concern r Be it known that I, GEORGE E. MUELLER, a residentof Aurora, county of Kane, State of Illinois, have invented. new "and useful Improvements in Two-Wire Automatic TelephoneSystems, of which the following is a I specification. g

' ing improved and simplified circuit arrangements,.wh ereby automatic selectors and connectors may be adjusted primarily to select desired f ups of contacts-rand thereafter secondarily' to select individual contact sets out of the pre-selected groups responsive to substation transmitters, which operate only to produjcefseries of rapid interruptions in the subscribers line circuits.

I am aware that systems of this general character, often referred to as two wire systems and so distinguished from systems wherein a common return conductor is employed together with; the usual pair of line .wires, have been heretofore proposed and the present invention "is directed to certain improved relations of parts and circuits.

In the arrangement now proposed, a socalled primary relay isconnected directly in a calling subscribers line and has its armature vibrated responsive to line c rcuit 1nterruptions to directive] of contacts. The usual first selectors are provided and each one has its individual primary relay, which, in additionto its directive impulse transmitting function, also controls two local circuits, each of which contains a so-called slow release relay,

namely a relay slow to release its armature when its circuit is interrupted, a feature of operation that may be secured in electromagnetic relays, in several well known ways,

as by placing copper shells about their cores,

The present invention is directed to secur adjust the auto} matic switches to select t e required groups- TWO-WIBE AUTOMA TIC TELEPHONE SYSTEM.

I Specification. of Letters Patent P t t d A 14, 1917 Application filed April 9, 1909. Serial No. 488,857. I

lays have to depend for their, currents upon the telephone lines directly, whichmay ob- VlOllSlY be of widely varying resistances. Those points of novelty formin the present invention will be more particu arly pointed out when the drawings are described and in I the a pended claims. I I

Re erring to the accompanying drawings forming a partof this application, Parts 1,

2, 3, 4 and 5 of'Figure 1, whenarranged in COIISQCUMVE' order, show circuits of a telephone system embody ng the present invention; Fig. 2 is a plan view of' a selector for the circuits of Fig.1, and Fig.3 a side elevation thereof partly in section ,Fig. 4 shows j causes a. MUELLER, or aonomannmois. Assmiioa, iaY imsnn Assmimnnre ab.-

a detail of the connection between the drivv ing pawl" of said selector and its actuatin member; Figs. 5, 6, 7 and 8 show details 0% the wiper and contact arrangements of Said selector; Farts 1, 2, and 3 of Fig. 9, when arranged 1n consecutive order, illustrate a modified automatic telephone system circuit embodyingthe invention; Figs. 10, .11 and 12 are, respectively, left, front and side elevations of a selector for use with the circults of Fig. 9; Fig. 13 shows its primary off-normal switch; Fig. 14 is a detail of the primary magnet and its associated parts;

and Fig. 15 illustrates a modification of the circuit of Fig. 9, Part 2.

Referring first for a moment to Fig. 1, Part 3, the wires 120,121 are in the operationof the system extended to the left so as to reach the calling substation and be. there connected to ether. When this occurs, the relay PR wil obviously be held ener ,gized, its winding beingconnected to the wire 120 from one side of the battery B,

while the opposite side of said battery is connected through resistance r" andnormal contact 172 with wire 121. When relay PR 'first energizes, armature 131 opens a'contact in the circuit of relay IR and simul taneously armature 128 energizes relayCR, whose armature actuates secondary-relay SR. The latter, by armature 133, closes groundto normalv contact 130 preparatory to the prime adjusting'o erations of relay PR. As be ore indicated these are roducedby rapid interruptions in the cal ing line "at the substation, whereby wires 120,

121 are correspondingl rapidly interrupted and relay'PR' first dianergizes and thenenergizes with each'interru tion, its armature being thus vibrated. n the first deenergization of relay PR; relay IR operates by current through normal contact 131. On the succeeding operations of relay PR, the interruptions in their circuits are so brief that neither relay IR nor CR retracts its armatures, although each back stroke of armature 130 transmits an adjusting impulse over wire 120 to the right.

When at the conclusion/ of the interruptions between wires 120, 121, relay PR remains energized for a space, obviously the circuit of relay IR remains open correspondingly and its armature soon retracts to connect ground traced through contacts 173, 132, to the secondary impulse wire 121, whereby the secondary adjustment of the selector is initiated. At this time relays CR and SR will obviously remain operated, since they are not operatively affected by the vibrations of the armature of relay PR, nor b its continuing energized. A prolonge interruption in the circuit of wires 120, 121 will, however, result in their deenergizations and avail is made of this fact for restoring the apparatus to normal, as hereafter explained at length.

Referring now generally to Fig. 1 with its parts adjacently disposed in consecutive order, as the circuit arrangement of-Fig. 1 is drawn out, the system illustrated has a capacity of 1.611 thousand subscribers lines, first selectors F being provided for the purpose of selecting the thousands, second selectors G for selecting the hundreds, and connectors H for selecting the tens and units.

I preferably employ one hundred point switches having their contacts arranged in ten groups of ten contact sets each. Assuming ten thousand subscribers lines, as called lines, the lines would be divided into one hundred groups of one hundred lines each, and each such group on the usual tenper cent. trunking basis would be provided-with their multiple called contacts appearing in the banks of ten connectors. The roup to which any'line as a called line is assigned will be determined by the directory number which the line'bears', so that all the lines having their multiple called contacts at a group of ten connectors would, have directory numbers of the same hundreds value.

thousand, and the multiple contacts of the connectors for the first hundred of the first thousand will constitute the first group of ten contacts of each second sole-tor for that thousand; the contacts for the connectors for the second hundred of the first thousand will constitute the second group of contacts of the second selectors for that thousand, and so on forv the other groups for the first thousand. Corresponding connections will be made from the different groups of ten connectors of the hundreds of the other thousands to the second selectors assigned to those thousands. On the usual ten per cent. trunking basis, there will, of course,

be one hundred second selectors G for each thousand of the exchange and the contacts of the connectors will therefore, if uniform multipling be observed, be multipled one hundred times, 'once at each second selector for the respective thousand.

Each second selector G is provided with multiple contacts 161, 162, 163, appearing in the banks of first selectors F, which first selectors are, of course, common for connection with all subscribers in the exchange. On a ten. per cent. basis, there would be one thousand first selectors F, and each such first selector Would have before its wipers 158, 159, 160 ten groups of multiple contacts, the contacts of each group being connected to the second selectors G for a different thousand. There being one thousand first selectors F and one thousand second selectors G, there will be a total of one hundred thousand.multiple-contact sets 161, 162,

163 at the first selectors, so that each second selector G will have its contacts multipled,

, joined to it. a line selector E before whose wipers 2, 25, 26 appear multiple contact sets 18, 28, 29, of one hundred lines, which sets ofcontacts may be called multiple calling contacts. The lines of the exchange as calling lines are divided into groups of one hundred and on a ten per cent. basis, the multiple calling contacts of each one hundred line group will be multipled before the Wipers 2, 25, 26 of ten line selectors assigned to that group of lines as calling lines. Further, the multiple contact, sets of each one' hundred line group would be divided into ten sub-groups often contact sets each, and when any calling line initiates a call, a line selector E w1ll operate to select the group in which the calling line has its contact set,

included and then will pick out the individual multiple contacts of the calling line,

whereby the line selector E ;will have caused V itspaired first selector, F to be operatively connected with the calling line. After this,

change.

directive impulses will be transmitted from the calling line to cause the first selectorto pick out a group of second selectors for the wanted thousand andthen an idle selector out of such group; thereafter directive impulses will adjust the selected idleselector to 'pick outthe group of connectors wanted and then an idle connector out of such group; wh'ereafter the selected connector will be adjusted to pick out the required group oflines and then the requiredline out of such group.

In the diagram, Fig. 1, Part, 1, I have illustrated a calling substation A connected by the line conductors 66 and 67 with a suitable line, circuit arrangement at the ex- The substation at A includes the customary hook switch 59, normally holding the call-bell in an operative bridge of the line limbs and adapted, on the removal of the receiver, to be lifted, disconnectingthe call-bell and'operatively connecting the talking set with the line. A calling device or dial 65 is provided, said calling device being normally locked by a pivoted pawl 61 controlled by the magnet 60 whose Winding also 1 serves as the impedance coil for the talking set. When the coil of 60 is energized, its armature is attrabted and the pawl 61' withdrawn from engagement with the dial 65 so that the same may be rotated by hand inthe direction of the arrow. The dial 65 has attached to it suitable teeth of insulating material which control the connections of the impulse spring 63. t It is obvious that the rotation of dial 65 in the direction of the arrow has no operative effect upon the spring 63. When, however, it is released, the teeth of insulating material operate to momen tarily open contact 63 as .many times as there have been teeth brought below-said spring. a

It is thus apparent that by the operatlon of the dial 65, a calling subscriber can cause a number'of sets of openings of line limb 67 at contact 63, and by successive actuations of the dial 65, the calling subscriber is enabled to count out the digits comprising the number of the called subscriber.

As before indicated, the lines, as calling lines, are divided into groups of one hundred by having their multiple contacts grouped at the exchange before the line selectors. The ten line selectors E for each such group of one hundred lines are preferably not constantly operating devices, but a are normally at rest. their wipers having a For starting an idle line selector E when a call is initiated, a. master-switch mechanism. D is provided, one for the one hundred lines, including wipers 80, 81, 82, having before them contacts 83, 84, 85, one such set being provided for each line selector of a one hundred line oup. Each .line of a group has its line reay 43; and a common conductor 73 is pro vided, connected to the master-switch relay 73- and having branches, one to each of the the master-switch D to start an idle line selector. Each line, in addition to its line relay 43, individual to it, has its cutofi' relay 51, the latter being employed to render the line relay inoperative when the line is connected With.

As before indicated, the multiple contacts 18, 28, 29, of the one hundred lines of a group of calling lines, are divided into ten groups often contact sets each at the line selector banks, whereby the one hundred lines are divided into ten sub-groups of tenlines each. Each such sub-group has a sub-group relay 47, 17 or 47", etc., and a sub-group contact 31, 31 'or 31, etc., appearing before the group selecting wipers 27 of the line-selectors E. The group relay 47 of each sub-group has an armature 49 controlling the electrical condition of the group contact 31 and an armature 48 which cooperates with the constantly traveling interrupter I and with the master-switch mechanism D in starting an idle line selector E. Each such group relay 4:7 is connected by a common conductor 50 having ten branches, one extending to each line relay of its sub-group, so that the line relay of any line of a subgroup can control the respective group relay.

he common interrupter I is provided having two pairs of segments 69--69 and 7-1 71, and the grounded wiper 72 is constantly traveling over the segments at a rapid rate, successively, grounding them. The segments 69 and 69 are connected to a common conductor 38 which has branches extending to armatures 108 of the relays 104 of the different line selectors E, and the inter rupter is employed, among other uses, to transmit currents over the conductor 38 to operate the windings 10' of the driving magnets 10 to produce the long step travel of the switches E. In order. to prevent a winding 10 from being actuated by a partial impulse over a wire 38, whereby but a partial long step of a switch E might be produced, the circuit at each switch E is so arranged that its relay 104, which controls the contact 108 in the circuit of winding 10', can be actuated only by current through one of the segments 71 or 71 of the interrupter I. By this arrangement, no current can' be. passed through a winding 10' upon the energization of the line relay 43 of a line and the consequent energization of the respective group relay, until thewiper 72 engages a contact 69 or 69 after having first been in engagement with the contact 71 or 71 to operate the relay 104, since the line and group relays were operated, whereby such operation of the line and group relays, which may occur at a time when the wiper 72 is about to pass oil a segment 69 or 69 is ineffective to produce a Wrong operation of the line selector E by causing it to make a partial long step.

Before going more specifically into the description of the circuit diagram, the preferred. mechanical arrangement of the switch will be referred to. As indicated in Fig. 2, ten groups of ten contacts 18, 18 18*, etc., to 18' are provided arranged in a circle, making one hundred of such contacts, while between the groups of contacts, contacts 19, (86), 19, 19", etc., to 19are located. A rotary shaft 1 is provided suitably journaled, as indicated in Fig. 3, to the circular base plate 8 and to the bridge 8 upon which shaft are mounted the wipers m, n, 0, p, 8, and the ratchet-wheel 20 which of course has one hundred and ten ratchet teeth. The magnet 10, whose spools are mounted upon. the bridge 8, has a; pole-piece 24 con necting the upper extremities of the cores, and through this pole-piece extends a slot ted stud 23 with which is associated the friction piece 23 and the screw 25 threaded to the piece 23, the whole furnishing a convenient means for adjusting the tension of the spiral spring 21, one end of which is attached to the end of the armature 3 and the,

other to the stud 23. The armature 3 is supported by the auxiliary shaft 1 which is journaled to the wiper shaft 1 and to the stud 23. The spring 21 serves of course as a retracting spring for the armature after each actuation of the magnet 10, being adjustable as described. The core of each spool of magnet 10 has, at its end adjacent to bridge 8, a pole-piece of the shape indicated at 9, the transversely disposed armature 3 havin the projections shown best in Fig. 2 exten ing'to proximitywith the respective concave surfaces of the pole-pieces 9, the whole producing an arrangement well calculated to give a strong initial pull upon the armature 3 when magnet 10 is operated,

permitting, along with this, a relatively' great movement of the said armature. An adjustable stop 4 is provided to limit the back stroke of the armature away from the pole-piece. The arm 6 carrying the driving pawl. 6 which is provided with a suitable spring to hold it in engagement with the ratchet as indicated in Fig. 4, is fastened to the armature shaft 1 so as to partake of the rocking movements of the armature, the pawl 6 being by them effective to drive the ratchet-wheel 20 step by step. The adjustable stop 12 is provided, threaded to aprojection of the piece 13 which is fastened by the bolts 15, 16 to the circular bank of the switch, and the said stop serves to limit the length of the stroke of the pawl 6 and of the armature 3 when the switch is performing its long step travel. The piece 13 also has a projection to which is suitably pivoted the pawl 7 which engages the teeth of the ratchet 20 and serves to prevent back movement of the ratchet which might otherwise occasionally occur from the jar occasioned by the armature 3 when forcibly retracted by the spring 21 at the conclusion of one of its long strokes. The pawl 7 carries a pin engaged by the arm 6 so that, when the latter is fully retracted, the two interlock and the pawl 7 is forcibly held in engagement with the ratchet 20. A further important function of this arrangement is to render impossible a between-contact posi tion of the wipers. Thus, if the pawl 7 is, at the time pawl 6 is retracted, not engaging a full tooth of ratchet 20, the impact of arm 6 will force the pawl 7 to fill the tooth upon whose surface it rests, whereby the wipers will be carried back to one of their definite operative positions. Upon the piece 13 is mounted the stop magnet 14, controlling, by its armature, the stop pawl 5 which, in the line selector, Fig. 3, is shown as below the pawl G being therefore normally out of engaging relation therewith. The said stop pawl 5 abuts upon the projection 17 of the piece 13 and, when the magnet 14 is energized, is brought forward so that its upper extremity is in the path of the pawl 6, thus limiting the stroke of armature 3, piece 6 and pawl 6.

It is now apparent that when magnet 14' is. denergized, actuations of the magnet 10 will, by awl 6, produce long steps. of the switch .wlpers, and for eachsuch long step, it wi],1 be understood that the wipers will be moved from a position engaging a betweengroup contact 19 over an entire group of contacts 18 to engagement with the next between-group contact 19. Thus, to select the group of contacts 18, for instance, three actuations of the magnet 10 will be produced while magnet 14 remains inert and the wiper m and the others will then have advanced three long steps to rest in a position where wiper m engages the contact 19. When, now, magnet 14 is energized, the movable stop 5 is substituted for the stationary stop 12 as the member limiting the stroke of the armature of the magnet 10, and successive actuations of magnet 10 will now obviously produce short steps of the wipers, each step i moving them the space from one contact 18? to another. When the switch of Fig. 3 is to be restored to normal, this is efi'ected by short step travel of the switch around in the initial direction of travel to the normal point to complete a circle of travel.

For the first and'second selectors and for the connector, the stop magnet arrangement indicated in Fig. 2 is preferably employed,

withthe pawl 6. With this arrangement, in order to secure long step travel of the switch,

the magnet 14 must be energized to withpawls 6 and 5- be both made of magnetic material, there is a slight tendency to stick or freeze when the twovpawls are in engaging relation, ma ets 10 and 14 being simultaneously energized. Making one pawl of non-magnetic material, or providing air-gap ip acers of course obviates any such effect.

hile I have,in Fig. 1, at E, shown the circuit closers or wipers 2, 2, 25, 2 6 and 27 diagrammatically, as connected directly with the conductors of the line selector E, I have preferred, in the mechanical switch structure,to terminate the conductors, showrrconnected to the said wipers in Fig. 1, in stationary contacts while. the switch wipers themselves inthe mechanical structure have,

in themselves, no circuit connection, but act merely to close conductive bridges between bank contacts w1th which they are associated. The -electrical equivalency of the arrangement shown in Fig. l to those shown in Figs. 3, "5, 6, and 8 will be apparent. In 'Fi 3, five sets'or pairs of wipers m, n, o, 7) an e are indicated, mounted one pair above the other upon the main switch shaft 1. Referring now to Figs. 5 to 8 inclusive, when the wipers arein their normal positions, they will be engaging respectively they contacts 86, 87, 88 and 31 By referring now to Fig. 1, it will be apparent that when wipers m are in their normal position, they close the off-normal contact 86 to its associated contact, thus producing the normal 7 circuitcondition of contact 86 shown in Fig.

1. Similarly, when wipers n and o are in their normal positions, they close respectively the off- normal contacts 87 and 88 to their respective associated contacts, as indicated in Fig. 1. It is also apparent that when shaft 1 iscaused to make its first step, each of these off- normal contacts 86, 87, 88 will be opened, wiper nthen closing the offnormal contact'89 to ground, the said contact continuing closed to ground until the wiper has completed its revolution and is restored, whilet the other off-normal contacts remain open until' the line selector reaches normal.

I The private wiper 2 indicated in Fig. 1 is, in its mechanical embodiment as shown in Fig. 5, represented by the conductively ."wjoined segments 2, while the contacts 18 are those adjacent to the said segments. Thebetween-grou contacts 19, etc., are plainly findicated in ig, l5 andthe wiper 2 is represented by the contact 2 of Fig. 5, whereby the wiper m, in a between-group position,

ponductively bridges or closes a contact In Fig. ,7, the commonstrip 25, which extends circularly complete except for the break at the off-normal contact 88, represents the wiper 25, while its adjacent sets of contacts 28 represent the multiple contacts of Fig. 1 and the same arrangement as that shown in Fig. 7 is employed for the wiper 26 and the contacts 29 as indicated by the alternate reference characters given in Fig. 7. The ring 27 in Fig. Sis the equivalent of wiper 27 in Fig. 1. The wiper s has. a between-group position closing contacts 27-31, 2731" just indicated in Fig. 1, while the grounded segments of Fig. 1, Part 2, are plainly indicated in Fig. 8.

It will be understood that switches of the general character shown in the mechanical figures are used for -the first and second selectors and connectors, commons being. employed for the wiper contacts shown in Fig. 1, the switch wipers thus being, as in the case of the line selector, without circuit connections in themselves andbeing-nsed to cross the commons to the rivate contacts and the line contacts. he off-normal switch arrangements of the firstselector, second selector and connector will be secured in the manner obvious from the description given of the ofi'-normal arrangements of the line selector and need not be specifically referred to. a

' The detail of the circuit arrangements of Fig. 1 will best be understood when explained in connection with a description of the operation of the system and will now be described, it being assumed that A is a calling subscriber and desires his line to be com nected with that of the subscriber whose substation is indicated at C andwhose'numher will be assumed to be.-2222.

Subscriber A, by removing his receiver to initiate a cam-establishes a path for a flow of current from ground, through line relay 43, through contacts 52, 63, the substation transmitter, the raised hook-lever 59,- through magnet 60, over line limb 66, arma ture 55 to battery B, operating line relay 43, which, by armature 44, is locked to battery over'the common conductor 73 and relay 73 of master-switch D. The. flow of current through the substation may momen- It beseen that the multiple contacts 18 of the calling line are grounded over con- 'ductor ,32 and through normal contacts 53 l and 46'as long as the line circuit of A is at normal, the mid multiplecontacts 18 being thusnormally unselectable at the line selector. Attracted armature 46, however, re-. moves ground from the contacts 18, thus rendering them selectable,'and grounds the como mon conductor 50 energizing the group relay 47 which, byarmature 49, removes ground from the group contact 31'. As soon as wiper 72 engages one of the'segments 69 or 69, acircuit 1s completed from ground through attracted armature 48, over attracted armature 76, armature 79, wiper 82 of master switch D (wipers 80, 81, 82 of.

'master-sw tch D normally engaging contacts 83,- 84, 85 of an idle line selector E) through contact 85 of such idle line selector, over conductor 39, closed -10'fl'-normal contact 86, normal contact, 114, and the re'-.

lay 90 to battery B, energizing the said relay 90. Since, as indicated by the location of the multiple contact 31 normally engaged by the w1 er27, the callin line is included in the sub-group of ten, no long steps of the line selector E are required to be made to select the calling line in the present case, so that the winding 10. of magnet. 10 is not emplo ed, but the stop magnet 14 must be actuate at once and circuit must be closed through the short step winding 10 to initiate the short step travel of the switch. On the energization of relay 90, circuit is closed as. follows: from battery B', through' magnet 14, through relay 97, contact 109, attracted armature 95, wire 127, normal contact 87, conductor 39 and to ground at segment 69 or '69 through interrupter I. Attracted armature 93 has closed one break in the circuit of winding 10 and magnet 14 is now actuated to close the second break therein andt'o throw the stop pawl into operative relation with the mechanism of magnet 10. Circuit may now be traced from ground, through generator g, winding 10, attracted armature of relay 14, alternate contact 93 to ground and magnet 10 will now be actuated by successive impulses from generator 9 until the relay 90 1s deenergized, each actuation of winding 10 producing a short stop of wipers 2, 2, 25, 26' and 2 It will be noted that on the first step of the switch E, the off-normal, ON, contacts were shifted to alternate position whereby electromagnets 14 and 97 were locked to ground via contact 89 by means of the attracted armature 100. Armature 103 of relay 97 has now connected the winding of relay 90 through alternate contact 94 and normal contact 116 with the private wiper 2 of the line selector, and since on the first 'step of the line selector, contacts 86 and 87 are opened, the relay 90 nowdepends for its continued energization upon the grounded contacts 18 to be encountered by wiper 2 as thewipers progress in their short step travel. Contacts 18 of non-callin lines, will be unded at armature 46 0 their respective ine relays 43; and since wiper 2 engages a new contact 18 before leaving the previously enga (I one, relay 90 will cont nue energize until the switch wipers in their travel have reached a point where wiper 2 engages an 'ungrounded contact 18, such being one pertaining to the calling line. At this time, ci'rcuitthrough relay 90 will obviously be opened, the relay'will become deenergized and its armature 93 being retracted, will prevent further actuations of winding 10 of magnet 10 and the wipers of the line selector E will come to rest, the wipers 2, 25 and 26 engaging respectively the multiple contacts 18, 28 and 29 of the calling line, that of A. On he retraction of armature 93, ground is plac d, via normal contact 93, alternate contact 102 and contact 111, upon the conductor 40 extending to the private contact 84 atthe master-switch D, through its private wiper 81 and to battery through operating'relay '74, energizing said operating relay which opens contacts. 78 and 79 to prevent any possible ground upon wipers 80 or 82. The armature 77 closes circuit for generator 9 through motor magnet M of the master-switch. Wipers 80, 81, 82 being mounted upon a rotary shaft inoperative relation with the driving magnet M, are rotated step by step in search of contacts 83, 84, 85, pertaining to an idle line selector. The contacts 84 of line selectors in use will be connected to ground and relay 74 will continue energized, holding contact 77 closed until the master-switch wipers engage the contacts of an idle line selector, at which timethe circuit for relay 74 will be opened, the relay deenergized, its armature retracted, and wipers 80, 81, 82 will rest engaging the contacts 83, 84, 85 of such idle line selector and ready to start the same when another call is initiated from one of the lines of the group that the master-switch D serves.

As soon as relay 90 was first operated, it closed alternate contact 91, whereby a flow of current was produced from the positive pole of battery 13*, Fig. 1, Part 3, through resistance 1' normal contact 172 of relay RV, link-circuit strand 121', conductor 122, closed contact 115 of relay 110, conductor 123, alternate contact 91 of relay 90, linkcircuit strand 120, normal contact 169 of relay RV, and primary relay PR to ground. By the closing of this circuit, primary relay PR is energized. The actuation of its contact 128 completes a circuit for control relay CR, which it may be noted is rendered slow to release by some suitable means as the copper shell shown. The actuation of relay rent will flow live pole of battery GR in turn closes a circuit through the lefthand winding of secondary grounded contact 128' of relay CH. The closing of this circuit in turn actuates secondaryrelay SR which opens its contact 129 and closes its contact 133. The connection from ground nate contact 130 to the link-circuit strand 120 will, upon the dei nergization of primary relay PR, apply ground to said strand at the right of condenser 173. When relay 90 is decnergized, as heretofore described, curfrom the live pole of battery B, Fig. 1, Part 1, through cut-ofl relay 51, normal contact 53, link-circuit strands 33 and 120, normal contact 169 of relay RV, through primary relay PR to ground.- In

this way, relay PR is maintained energized,

with the resulting energization of relays CR and SR, and the cut-ofl' relay 51 is operated and locks itself energized through contact 53-53, conductor 32, contact 18-2, closed contacts 103, 116, and normal contact 94 to ground. The operation of cut-ofi' relay 51 will also connect line limb 67 through alternate contact 52 to strand 33 and accordingly there will also be a path for current from the B Fig. 1, Part 3,through resistance 7', normal contact 17 2 of relay RV, to link-circuit strand 121, thence over the sleeve side of the circuit, through strand 34, line limb 66, locking magnet 60, the switch-hook-59, the transmitter, closed contact (33 of the calling device at the substation,.thence over the tip side of the circuit through line limb 67, strands 33and 120, to

round through relay PR and normal contact 169 of relay RV. Thus a circuit is provided under the control of the calling device at station A which will operaterelay PR, which is instrumental in" connecting strand 120 to ground through closed contact 133 of relay SR, to transmit impulses to operate the first selector F, second selector Q, and the'connector H.

The ground at contact 94 of relay 90, placed upon the multiple contacts 18 through the wiper 2, has made the contacts of the calling line unselectable to other selectors. Since the armature 54 of relay 51 opens the circuit of relays 43 and 73, normal contact 45 is again closed and the ground on conductor 32 is extended through said normal contact 45 to the multiple private contacts 56 of the calling line at the connectors, holding them grounded and unselectable. The said multiple contacts 56 were, on the initial operation of relay 43, grounded by attracted armature 45 so that the calling line was held busy against incoming calls during the travel of the line selector E.

It is now apparent" that the calling line has, by the operation of the line selector E, had connected to it the relays PR and SR of the first selector F, paired withthe line relay SR and throughcontact 133 and alter-- employed to cause the line selector that was operated, and the said relays are now controllable by means of, the dial 65 at the calling substation, which dial was unlocked as soon as cut-off relay 51 the line selector E is in order. The operation of this switch, when thecalling line is in a sub-group other than the first, differs from that heretofore described in that the long step winding 10' of themagn'et 10 is selectors wipers to-select the sub-group in which the calling line is included; whereafter the short step winding 10 is employed to select the individual contacts of the calling line out of the selected group. The wire 39, employed to start the line selector E when the calling line is in the first group as hereinbefore described, is not employed when the calling line is in any other su group than the first, the Wire 41 being the starting wire for all other sub-groups. i

I have shown at 47 a sub-group relay for the second sub-group and at 47 a subgroup relay for thethird sub-group. The common conductor 50 has branches to alternate contacts 46 of the ten line relays of the second sub-group, and the common conductor 50 has branches to the alternate contacts 46 of theten line relays of the third sub-group, and it will be understood that there will be other sub-group relays 47, 47, etc., for the fourth, fifth, etc, to the tenth sub-groups .with corresponding connections similar to 36 of Fig. 1, Part 2. connecting to the multiple sub-groupcontacts 31 of the second sub group; so the conductor 37, associatml with relay 47, connects to the conductor 37 of Fig. 1, Part 2, which is in comiection with the multiple sub-group contacts 31 of the third sub-group; a. fourth sub-groupcontact 3130f. Fig. 1, Part 2, of the fourth subgroup is shown and it will be of course understood that although but four sub-group contacts are shown associated with the wiper 27, there will in fact be ten such contacts, a corresponding number of sub grolilp relays 47 and a corresponding number of grounded segments for the wiper 27; also, that although but three contacts 19 are shown associated with the wiper 2 of Fig, 1, Part there will be nine such between-group contacts. I

It being no assumed that the calling line is in the third sub-group, the one having the sub-group relay 47, the removal of the re ceiver at the substation will operate the line relay 43 of such calling line which pulses will flow over relay will lock in series with the master-switch relay 73, as before. The armature 46 of such line relay will remove the ground from the individual multiple contacts 18 of the calling line in the third sub-group at the line selectors, and will close circuit to operate the subgroup relay 4? by current over the common conductor 50*, while armature 45' will ground the multiple private contacts 56 at the connectors to render them busy. The operated sub-group relay47", by armature 49", removes ground from the conductor 37 and from the multiple sub-group contacts 31 at the line selectors E. Armature 48 closes a bridge between conductors and As soon as the interrupter wiper 72- is disconnected from one of the segments 69 or 09 and makes connection with one of the segments T1 or 71, circuit will be closed from ground over the conductor 70, closed contact 48, conductor 75", contacts 75, 78, 83, conductor 41 of the line selector engaged by wiper 80, through contacts 88, 98, and relay 104 to battery B, the relay 104 locking itself by armature 107 to ground via wiper 27, multiple contact 31 ofthe first subroup and contact 49, the relay 47 being unoperatcd because the call is not that of the line of the first sub-group. With the operation of relay 101. the relay 90 is energized by current through attracted armature 105. The stop magnet 14'and relay 97 are, however, not operated at this time, contact 109 being open. \Vhen now wiper 72 of interrupter I passes over contact 69 or 69*, current imthe conductor 38 through contacts 108, 101 and winding 10' of magnet 10 to battery and obviously, the continued travel of wiper 72 and successive actuations of winding'lO' will be produced as long as contacts 108, 101 remain closed. The first impulse through winding 10 effects a long step of the wipers 2, 2, 25, 26, and 27 (the stop magnet 14 not having been energized as mentioned), and at the end of this first step, of course, the wiper 2 will be engaging the grounded contact 19, the wipers 2. 25 and :26 will be between the first and second groups of their respective contacts 18, 28 and 20, and the wiper 27 will be engaging the multiple group contact 31" of the second sub-group. Since a line of the second sub-group is not calling, relay 47 will be inert, conductor 36 will be grounded at :ll'll'ltltlllt) 49 and the relay 104 will continue energized by current through attracted armature 107. contacts 27-31", conductor 36. contact 49 to ground. With the continued rotation of interrupter arm 72, another impulse will be caused to flow through the winding 10 of magnet 10 and a second long step of the which time wiper 2 wiper 21. will engage will engage contact 19", contact 31, and wipers '116, contact 103.

wiper will be efi'ected, at

2, 25 and :26 will be adjacent to the third group of multiple contact sets. Contact 31 having been ungrouuded by the operation of armature 4:9 of relay 7 of the third subgroup, circuit for relay 104 is opened and the relay is decnergized, its armature 108 preventing further actuations of winding 10 by interrupter I.

It will be of course understood that the off- normal contacts 86, 87, 88 and 80 were allshifted to their alternate circuit conditions 011 the initial step of the switch, the opening of contact 88 making relay 104 entirely dependent upon circuit through wiper 27 for its continued energization after the switch started.

On the deencrgization of relay 10+, relay 00 continued energized by current through normal contact 114, over conductor 125 and to ground through contact 2 10. The closing of contact 10!) will now complete an energizing circuit for stop magnet ll and relay 97 extending through attracted armature J5, over conductor 127, closed contacts 106 and 89 to ground, whereon armature 100 of relay 97 closes a locking circuit to ground at closed contact 89. As described in connection with the selection of the calling line in the first sub-group, magnet 14 has now thrown the stop into limiting position and has attracted its armature to close circuit from generator 9 through the shortstep winding 10 to ground through alternate contact 93. On the first actuation of winding 10 the resulting first short step of the wipers will open contact 210 so that the relay 90 will thereon depend for its continued energization upon circuits extending through alternate contact 01, contact through the private wiper .2 and to round 1])011 multi )le contacts 18 of non-calling lines. Relay 90 will therefore continue energized until wiper 2 engages the multiple contact 18 of the calling line, which contact will be ungrounded, due to the attracted condition of\ armature 46 of line relay 43 of such calling line, deenergizing the relay 90 and the armatures of said relay will be retracted whereof 03 will open the circuit of winding 10 and wipers 2, 25 and 26 will rest engaging the multiple contacts 18, 28, 29 of the calling line of the third subgroup. At this time, of course, the wiper :2 will be somewhere between contacts 19 and 19 and wiper 27 will be in engagement with the grounded contact segment between contacts 31 and 31, but since armature 107 was retracted'before wiper 27 engaged such grounded segment, the relay 104 is inert.

It will be observed that the alternate contact 91 of relay 90 caused the preliminary energizing circuit for relay PR to be closed during both the long and short step travel of the line selector E.

From the time the

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