USRE13534E - Electrical distbibsttiho system - Google Patents

Description

R'. 0. LEAKB.- ELECTRICAL DISTRIBUTING SYSTEM.

APPLICATION FILED MAY 12,1909.

Reissuea m1251913. 5 13,534.

R. C. LEAKE. ELECTRICAL DISTRBTING SYSTEM. APPLICATION PILE my 12, 1909.

11815511911 Feb. 25, 1913. 1 3,5 34.

z SHEETS-SHEET 2`.

M'nsses.

, a citizen of the United 'eledill distributing Um 'l @in was.

RICHARD C. LEAKE, OF AUBURN, NERIV YORK.

ELECTRICAL DISTBIBFTIG SYSTEM.

hun u. usgsss, .aim my i4, i901, serial no,

Bpcication of Reissued Letter Patent. Ressued Feb. 25, 281,711. Application for reissue :Med Icy 1i, 10W.

semi no. 49ans?.

To all whom it may concern Be it known that I, RICHARD C. LEAKE., States, residing at Auburn, in the county of Cayuga and State of New York, have invented a new and useful Improvement in-Electrical Distributing Systems, of which the following is a specificat-ion.- 4

- This invention relates to improvements in systems and involves one or more electrical transmission devices atoneor more local sending stations and a plurality of electrically'operated Vdevices at o `,or more remote or distant receiving stations, each electrically connected in asepare? circuit receiving currentfrom' the diercnt source `of electric energy, of 'which Aare controlled` individually orneceseively by fone'of the transmission substantial duplicates of eachother or may i differ in 'their function iii/performing the same or diercnt work, but each separate working circuit at -th'e"receiving stat-ion -incliides a coil' yor winding or some cquiyalent 'electrical appliance ycapable Qof operating some mechanical or electro mechanical apparatus, such as a signal, annunciator, counter-or similar mechanism, or may be 'used in -tel raphy, telephony and allied :the energizing systems, as or instance, for opening and closing the several circuits of an automatic telephonel exchange, and for pmany other purposes which cannot now be enumerated.

It may 'be stated here `that the invention resides -more 'particularly inthe means for making Aandbreaking any number of distant circuits, 'individually vor successively, so that :each circuit may "be made to perform some individual Work which may be or may not be associated withithe work performed by 'the'energiaing of 4the other circuits, and it is, therefore, quite immaterial what kind of a mechanism is brought into action by of either of the circuits. One of the primary objects of the invention is 'to minimize stlie number of line condoctors employed -in the #system from vthe lstation :may be' lcircuit tra-another circuit, and in order to `accomplish this I have introduced into the system, preferably at the receiving station, an automatic circuit changing device which yis controlled 4by ting station, an by which I am enabled'to cuits at the receiving stationyand to simulf working circuit.

The energizingA of -eachindividual working circuit at receiving station 4is effected by one or more comparatively quick current impulses corresponding to the dots of lthe Morse' telegraph system, circuit changing device is .'brou tion =by a prolongedclosing of t e'ciircuit at the sendin station, corresponding to the dash of sai Morse telegraph system, and in `order that the circuit changing device vIncjv not 'be brought into complete act-ion. c change from one working circuit to v:mother at the receiving station during such quick ,current impulses, I associate with the :electro fluence which may be of any suitable constructioncapable of retarding .the action of the circuit changer under quick current impulses but still havin-g the ability to `yield under a the sending station to. move,` changer one point-or step. f a

The general object, therefore-is'to -render it practicable of distant electric circuits .indivi nally -or successively over a minimum number of line conductors leading vfrom the sending to the sending to the receiving stations so that theI energizing of the entire series of distant cirstations may l station over the repeating of a certain mechanical ope'r-v` ation, and then to shiftor change 'from this' g Y :successively close the severa/l working cir` devices at,` the send-ing ation. These se'v` eral `devices atthe receiving ta-neously break :the previously energized? mechanical circuit-changer a retarding =inprolonged closingof the circuit at` the circuit,

the sender Iat the transmita.

receiving instruments by means of varying between current pulsations. l

Other morejspecifio objects and uses will be brought out in the tollowiii description.

In the drawings Il`igure il isa diagrammatic view of Aan electrical distributingsystem embodying the various features` of my invention. Fig. 2 is a face view of the detached ,electromechanical circuit changing devicefincliiding the means for i'etarding its action under quick current impulses. Fig. 3 is a sectional View taken on line 3 3, Fig. 1. Fig. 4 is an enlarged elevation of one of the electrically operated counters at tl'ieiece-ivin'g station Seen iii Fig. 1;` showing also the means for resto-ring said counter to its normal starting position. F ig. 5 is a diagrammatic view of a portion ofthe electrical distributing vsystem seen inFig. 1, sho-Winge modified/form of rctarding mechanisni for preventing the 'action 'of the circuit changing device under quick cui-rentimpulses;7 and effecting suoliv act-ion by a prolonged closing of the circuit through the sending instrument at the' transmission sta-A tion. Fig. G is a still further modified form of .retarding deyice adapted to be. substituted.'

for that shown in F ig. l, and by which the circuit .changer is caused to act by a long pause intorveningibetween the -intermittent current impulses.

In order toclearly demonstrate the practicability otl my invention I have shown in Fig. 1, somewhat diagrammatically:anelectrical distributing system, including a transmission station A and a distant receiv ing station B f, which stations are connected by a-minimum number of line conductors, consisting in-tliis instance, of a main feed Wire 1 a return .conductor Q wliieli'may be either a wire or ground,

suoli conductors constituting the main line circuit vreceivingcurrent from a source of electric energy, as a battery 3 in which is connected at the transmission suitable electric switch lt whereby eurrent impulses may be transmitted over the line' conductors to tlierecei'ving stationu At tliereceiviug station I have vshown a plurality of, in tliis instanoethree, electro magnets, 5, Gand 7 ,each havingy its winding connected ina separate circuit, butfor ythe purpose of simplifying the drawing, I-

have' shown all of these circuits capable of deriving currentrfrom the samesource of electric energy, as the battery.; 3 of, the main line circuit. Each of these' electromagiiets 5, 6 and 7 are adaptedto. perform eertainwork which may be similar or entirely different", `one from. tlieother, and

while .I havefshown a series of similar mechanical-'countingidevices 5', 6. arid each adapteiflV to ber brought-into action `by its par= by insulating material, oi VAn additional contact terminal 18 is station, a, mounted to rotate about said axis to contact .v 18 is movedl into contactwithbth by 'solenoids or other electrically operatedv instruments and 'I have only shown these electro magnets 5, G and 7 andthe counters Gvand 7 as a means for clearly demonstrating the practicability andoperation of my invention.

The important part of my invention, as associated with the several distinctI circults at the receiving station, consists `in providing `the receiving station with a suitable circuit changer, such as a multi-pole switch, which is only brought into action by the prolonged closing of the circuitll at the sending station through the medium of the switch 4 and an electro `magnet 8 having its winding connected in the-main line circuit, the action of ythe circuit changer being pre vented by some retarding influence, as a dash-pot Q having a piston 10 which is connected to the armature as.` l1 of the electro magnet -8 One end of cach ofithe wiiidiiigs" 5, 6

, and 7 is electrically connected by Wires 12, 13 and M respectively to the main feed Wire 1 of the line circuit 1 and 2 andthe other ends of each of saidr windings ofv the magnets 5,6 and,`7 are connected respectively by wires 1,2, 13

and 14 to metal contact'terminals 15, 16

and 17 respectively. These latter termil nais or pole-.pieces 15 16 and l7 preferably consist of circular` metal segments arranged about `a .common axis and insu lated at their ends, onefromtheotlier, either an air gap. V

successively with the segmental terminals 15,

16 and 1.7 and is actuatedgkstepfby's'tep from one segmental terminal, to *another by the armature 11e-through the medium of a pawl l9 ratchet 2Q- and a connect-- ing link 2l connecting the. freeiend'of the armature mounted, said armature being nected by a wire 24 to'thesanie source of.- electric energy.y as'- t-he battery 3 in lwhich the winding'sot the electro magnets M -to a 1 swinging ylever 22 upon which`I theI .pa'wl 19- held ,away i' from the adjacentpole of Vthe electro magnet f by means of aspring 23 The contact arm .18 .is electrically coniis i broken.

, 17 is etl'ected through the prolonged ener- (i ll 'ment -'-16-' the circuit through the electro magnet sis closed by breaking the cirfrom theI segment net --l'd will be closed, and that thiought the suitable means, as a countcrureight -37 ibut. it is clearly apparent that the coun rs may be used in other relations, and that he cuit through the electro magnet -5--, and in likemanner as the arm -18'- is shifted 16- to the segment -l-.fthe circuit through the electro imagnumbers which may be registered are prac tically unlimited-so'far as'vtheory or principle of the device is concerned.

The dash-pot Q- is shown as provided at its botto-m with a valve opening inwardly to admit air beneath the piston electro .mganet will be `simultaneously As previously stated,ithis1nove ment ot' the contact arm 18- successively into contact with ythe segments 15, 1G and comparatively small bleed hole -41-, the dash-,pot being open to atmosphere above the piston so that the upward movement of said piston is practically unobstructed or unretarded ,by reason ot the opening-#10# gizing of the electro magnet -8, but is prevented from Aoperation during quick current impulses, as will be presently described more in detail. to equalizc'thc pressure at both ends of the rlrhe counters 5', G and 7 each consist piston, while on the other hand any tendof a Arotary disk, each having a normal ency to attract. or draw the armature starting point or space and al series of' suc- -llM downwardly, as by the current imcessively arranged numerals, numbering pulses passed through the electro magnet from O to 9 inclusive so that the starting ,-8-, would be opposed bythe air pressure point o-r space and consecutive numerals lbeneath the piston -10- caused by the auare successfully brought into registration tomatic closing of the valve 4G-n It, with a suitable slight vopening -25- of a therefore, follows that by providing a comsuppo-rting case or frame -2i3-. Any suitparatively small bleed hole -41- in the able lmeans may be `employed for rotating pistoma prolonged closing of the circuit each disk step by step so as to bring the at the transmission station --A-- by the numerals successively into registration with switch -4-, which. exerts a maonetic pull their respective openings #25, andY I upon the'armature -1*l-, would allow the havev shown the operating means foreach air to gradually escape through the bleed disk as' consisting essentially ol a swinging hole -41-, thus permitting the armature armature -2T- carryingl a pawl -28-, which latter engages and rotates a ratchetwheel 2D- to which one of the counterdisks is secured, each of the electro magncts -5, 6 and 7 having associated there with one ot the armatures *2T- whereby each successive energizing of one of thel electro magnets attracts its armature '27- nnd rotates its counter-disk one step or space from its normal o-r starting position, cach armature being returned to its normal position by a suitable spring S0-1 ln to be `drawn to the limit of its inward moveposition to engage the next tooth of the ratchet-'wheel 20- so that when the switch tis open, thereby denergizing. the electro magnet -8--, the spring Q3- .returnsthe armature one tooth space and advances the contact arm f lS-rone segmental-space, or from the segment l5-'- into Contact with the segment -1G-. In like manner the arm the counting device shown, it necessary -18-. is advancedl from cont-act with one t() restore each' counting disk to itsI normal -segment to electrical contact with the next or s1 arting position, and for ,this purpose adjacent segment untilret'urned to its startl associate with cach disk or -counter a secing position.

ond electro magnet b2- and an armature i ln Fig. 6 I have -3l3--, which, when attracted by its armathe retarding device seen in `Figs. 1 and vture engages and lifts the pawl -iS-f out 2 in which a piston -10- is movable is of cngagcmcnt with 'its ratchet-wheel a dash-pot -5)," but is retarded in its sib-j the electro u'lagnet -'l-- being conupward movement, or on the return of the nected in local circuit which derives curarmature -11, instead of durin its movereni 'from a battery as afaud is provided ment .toward the adjacent'pole o 'the magwiih a switch 3l-1 under the control ot' a 1 net -8-. In this latter retarding device,

.local attendant' at the receiving station so l theypiston is provided with a comparativelythat by closing the circuit through the small bleed-hole 4V-u and a larger vertiinagnci- L5Q- and thereby lifting the pawl y cal passage which is normally closed by a wie@ to release the counter disk, the latter l valvel -40-, the bottom ot' the dash-pot is returned to its noi-unil position by any i --9- being closedand the valve '-40* l adapted to `open upwardly to allow' the 'By means ot' theirv l armature --11-, which is connected to the or combination ci. l piston -1()-'- by a rod -21- to descend as best scen in Fig. Ll. counters. any number numbers from 0 to 999 fniay be registered. l readily under the magnetic influence of the -10-', and this piston is provided with a number of counters and combinations of l ment, thereby moving the pawl -l9- into l to its normal position, y i and thus rotates the ratchet-wheel 20- shown a modification of :alo

electro magnet *8*, but is retarded in return movement, which is effected by the This arrangement of the dash-pot*9* and piston *10*causes the armature to be drawn downwardly where it remains during the shortiimpulses transmitted over thc line lwires `--1* and *2* and slowly returns to its normal position under the action of the vspring *23'* under a comparatively long pause or interval between the current pulsations through the electro magnet *8*, thereby eiecting theshift or change of contact of the arm *18* ,from one segment,l as from *15 togl.

The essential dierence in lprinciple between the device shown in Fig. G and that shown in ,Figs 1 yand 2*is that in the former, the change of circuit at the receiving station is effected during a, pause, or comparatively long interruption betweenthe current pulsations rather than by the prolonged closing of the circuit, as in the de vice shown in Figs. 1 and 2. ,4

In Fig. 5 I have shown astill further modified retarding device in which the electro magnet *8* is connected in`a separatey circuit *1'* and *2'* with 'an electric switch *45*, one ofthe members of the switchl being mounted upon `ra weighted lever *46*, which is fulcrumed at '-47* and is provided with Aa weight mallyv held open. Directly above the switchlever *4*is a vertically' rocking tube *5D-'- which is centrally pivoted at -51* and contains a rolling member, as a ball *52*. One end of this tube, at one side of' its pivot-\1f-.51*, lies directly over the switch end ot', he lever *'46*and its lower side is slotted lengthwise, but of lesswidth than the diameter of the ball to permit. said ball to ride along the slot within the tube and to project slightly` therethrough when this end of the .tube is `tilted to contact with the switch end of the lever -,-46-, the slot, as *53* serving to receive the adjacent end of the lever,*46*, and the weight of the ball riding upon this lever operating to close thel switch against the action of the counter weight.

*48*. The opposite end of the tube *50* 1s weighted suiiiciently t0 counter balance the weight of the ball when in thev slotted end of the tube; and when no other influence is brought to bear upon the action of the-tube *50*, its slotted end is tilted upwardly to allow the switch *4.5* to open and break` the circuit *1'* and *2'* through the electro magnet *8*, thereby causing the ball *52* to roll down the in clined tube from-the slotted end into the extreme'weighted end, or to the opposite side Vof the pivot *51*. In this modifica-a tion shown'in Fig. 5, I provide an auxl and tends to attract the weighted end f of the tube *50*, which constitutes an armature for saidy electro magnet. Under such quick current impulses, however, the weighted end of the tubular armature *50* is rocked from the point below to a point above the horizontal plane of the swinging axis of the tube, and the inertia of the ball *tE-,together with the centrifugal force acting upon it during such impulsive action of the tube tends to keep the ball in the weighted ,end of said tube, but upon a slightly prolonged closing of the circuit through the magnet *60* of the switch *4*- the weighted end of the armature *50* is held up by the electro magnet *G0*, thereby allowing. the ball *52* to` roll along the inclined bottom of the tube and into the slot- *53*, thereby depressing the underlying end of the lever -46* and closing the switch *45* and circuit *1*' and *2'* through the electro magnet *8*, which, in turn, operates the armature *11*and contact arm *18* to change the circuit by shifting said arm from one segment, as

*15* to the next segment, as *16*. As soon as the switch *4* is again opened, the magnet *60* is denergized and allows the tubular armature *50* to rock in the gravity, thus opposite direction by its own to be opened allowing the switch *45* by the weighted lever *46*. Y

In the operation f the device shown 1n Figs. 1 to 4 suppose it is desired to cause the disks 5, G and 7 to indicate the number *789* then by closing the switch *L1- eight times in quick succession, will `produ-ce eight current impulses through the electro .magnet *5*.-,y thereby moving the lcounter-disk *5'* step by step `trom its starting point until the numeral *7* is brought into registration with the opening *25* corresponding to the disk 5. Nhen the circuit is closed for the eighth time, it is held closed for a suiiicient period. to allow the armature *11* to be drawn downwardly the limit of its downward movement against the action of the spring *23*, thereby retracting the pawl *19* one tooth space around theratchet-wheel *20* so as to engage the next adjacent tooth, and when the circuit is broken at the sending station by means by the opening of the switch *4* the g,

spring *23* will return the' armature *11* to its normal position, thereby actuating the pawl= *19* and its ratchetewheel l 'forwardly one tooth space to shift Atact of the switch, the counter -6- wi again closes it the contact arm -18- from the terminal segment ,-'15-' to the next terminal segment --16.v cuit is broken throu By this operation, the cirh the electro-magnet ,-5- and is establis ed through the electro-.magnet-(--f Now, by repeating the closing 'of thecircuit in quick succession 'nine times, through the medium of they switch -4-, 'and prolonging the last conbe advanced step lby step from its starting position until the numeral S is brought into registration with its' opening -'-25 and the contact arm -18-'will then be advanced `from contact with` the .segment 16 into contact with the segment -17-,

thereby breaking the circuit through the electro-magnet 6 and closing another circuit through the electro-magnet 7-. Now, by again repeating the operation ofA the switch -4- ten .times in quick succession, and rolonging, the last closing ofthe circuit' said switch, the counter 7 is advance step, by step until theA numeral -S-i is brought into registration with its opening Q5-f, at -Which time, the Contact arm '-18- is moved from the segment -17- to the first or starting position in contact with 'the segment -15-, which breaks the ciucuit through the electro-magnet -7- and through the first named electro magnet -5-, ready for arepetition of the operation just described, it being understood, of course, that each counter 6L-- and -7'- is provided with the saine operating means and restoring mechanism as that described for the counter -5-, and that each of said counters is restored to its starting position by a counter-weight'as ,-35--, after eachpawl leased from engagement with its ratchetwheel Z9-in the manner previously described...

1. Ina system of electrical distribution,

.a plurality of working circuits, an electri- ',cally operated circuit changing switch co-ntrolling said circuits, means operated. at will for impressing current'impulses on said circuits and for operating said switch, additional means to retard the action of=the switch under comparatively vshort current impulses and to permit its action under prolonged closing of any one of said circuits. 2. In a system of electrical distribution, a plurality of electric working circuits, each deriving current from a single line conductor, aicircuit changing switch common to said circuits in circuit with said line conductor, electrically controlled means for actuating the circuit changing switch, and vadditional means for retarding the movement'of the switch .actuating means in one kr'recton under comparatively short cur-v lly -28- has been retrolling thev operation of and a retarding device for the circuitwhereby said-v -by the prolonged I the operationof the circuit to change from one branch4 rent ulsations through said electrically 65 contro led means,fbut adapted to permit such action under prolonged closing ofthe circuit.

- 3. In a system of electrical distribution7 'a line conductor,a`nd a plurality of electric working circuits, each connectedto said conductor, a circuit changing switch, lcommon to all circuits, tro-magnet' means controlled by vsaid magnet Ifor lfoonthe circuit changer,

changer 'actuating means, actuating means is brought into action onlyv byI the prolonged closing of the circuit through the electro-magnet.

4. In a systemcf electrical distribution, a main line circuit comprising-a main fe Wire and return conductors, lincluding there in a vsending station and a receiving station,

a plurality of circuit closers connected 1n the main circuit at the sending station, a

plurality of branch circuits at the receiving' station, a circuit changin switch for opening one of the branch circuits and closing another'branch circuit, the closed branch circuit being energized by the current impulses produced by the circuit closers at the sending station `of the main circuit, and means brought into action by the prolonged closing of the circuit at the sending station for actuatingthe circuit-changing'switch.

5. In a system of electrical distribution, a

main line circuit includingsi sending-hud a receiving station, comprising a singley main feed wire and return conductor. a circuit closer inthe main line circuit at the sending station, a series ot branch circuits deriving current from' the main line circuit, a series of electrically operated devices at the receiving station, onefor each octl said branch circuits, electric means in each of the circuit changing switch common to all of said branch circuits, an electro magnet in the main line circuit energized by the'closin the circuit closer, an' armature for said e ectro magnet, means controlled by the arma` ture for controlling the operation ofthe circuit. changer, additional means for preventing lthe operation of the circuit changer under quick impulses produced by the circuit closer inthe main line circuit, whereby the device corresponding to the closed branch circuit at the receiving station is operated, said means for' preventing the action of the circuit closer under quick current impulses through the electro magnet being actuated energizing of the electro magnet to cause changing switch circuit to another. 1

6. In a system of electrical distribution, u plurality of electric working' circuits, a

acircuit closer and snelwboth in the` main line circuit,

- cessivel'y, and means for retarding thc acswitch operating magnet. .45

Vlonged closing of 10l therein an electromagnet,

action of the switch under short current imating under prolonged Vclosing of the circuit 'to overcome the retarding means and to plurality of electric working circuits, each .means for simultaneously energizing the switch under Vshort current impulses butal- Loperating devices therefor, whereby each of .operating the switch, means for closing the multi-pole electricswitch rhaving separate contact terminals, one for each circuit, Aelectrically operated means in circuit with each of said Working circuits for shitting the switch to close the working circuits suc tiorigof said switch under short current impulses but allowing its operation under prothe circuit. l 7. In-asy'stem of electrical distribution, a `plurality of electric circuits, each including a multi-pole switch and its operating. electro-magnet, both electrically connected in circuit with .one or another of thefirst named electr-of magnets, means for closing said last named circuit, additional means for retarding the pulses, said switch operating magnet.- operbreak the circuit through one ofthe first namedveleetro-magnets and close the circuit kthrough a. differentv one of said first named magnets,I and -a plurality of"indicating devices, each actuated by one of the lirstinamed electro-magnets when energized.

8. In an electrical. distributing system, a

including therein an electro-magnet, a plurality of mechanical devices, eachl actuated by one of said magnets, a multi-pole switch for successively connecting said magnets with. the source of energy, an additional last named magnet andcne :of the `first nam. magnets which may bein electrical connection -with theswitch and` additional means 'for preventing the operation ot the lowing the operation of said switch under prolonged closing'A of the circuit through the 9. In combination with a series of` rotary mechanical elements andseparatc electrical theA former is rotatedv step bystep by successive closing of .the circuitthroughits operating device, `meansfor releasing the. rotary elements, separate devices for restoring the rotary elements to their starting positions, a, multipole switch in circuit with f said electrical devices, an electro-magnet for circuit, through ad magnet and the `electrical device which may be in electrical connection With thcswitch and means for retarding the action of the switch under short current impulses through said rmagnet but: permitting the operation of said switch under prolonged closing of the circuit through I said magnet.

l0. In an electrical distributing system, a l

plurality 'of mechanical movements, and a 65 corresponding number of electrical work- "ing circuits, each including therein an electro-magnet for operating-oncolsaid4 mechanical,movemeiits step by ustep at euch energizing of its magnet, an electric switch having-,contact terminals in circuit. with said magnets, a magnet to operate said switch, a circuit closer for simultaneously closing the circuit through the ylast named magnet and that oneof the first named magnets which may be in electrical connection with theswitch and means controlled 4by vthe last, named magnctfor operating 'said switch under prolonged closing of the circuit but 'preventingthe operation of said switch underj comparatively short currentimpulses therethrough.

1l. An electric 'selective system comprisa two-Wire mainline circuit having a multi-contact circuit-changing switch and an electro-magnetconnccted in series in said circuit, a series 'of electric ytra'nslating devices connected to the mainline circuit and to their yrespective contacts of the switch, means for impressing current impulses ofl the same strength and polarity upon4 the mainline circuit for energizing tlhe electro-magnet, additionalmeans controlled by the electro-magnet ir' operating Ithe switch, and further means vfor detaining the lswitch-operating'means under such cur- `rent impulses.

12. ln an electric selective system, a two wire main circuit having means therein op-,

erable voluntarily for impressing current impulses thereon, an electro-magnet connected in said circuit, a circuit-changing switch in series with the magnet, translatingudevices electrically connected to the contacts ot the switch and to the main line circuit, `switch-operating means controlled by the electro-magnet and separate means for defer-ring the` action of the switclrop- ,erating means until a pause in the impulses of the main line. I t

' 13. In an electric selective system, a two-Y wire main line circuit having an electromagnct, a` circuit-changing switch and a series of translating dcvicef' connected` to the main line circuit and to said switch, 'voluntarily operative means vfor impressing current impulses of the same strength and polarity upon said circuit, switch-operating means, controlled by the electro-magnet, and means for' deferring the action ofV said switch-.operating means under such impulses and tor'causing such action under a prolonged pause in the impulses.

14. ln an electric selective system, a two- Wirc main circuit having au electro-magnet, a c.ircuitchanging switch and an electric translating device connected in series thereimmcans for impressing current impulses of '1 "j detent iol' same strength and Apol-arity upon saidn iv tit, u self-retracting armature for the @leem-@ma net, connections between the a1'- 4imitumin switch for operating the latter,

menus for deferringthe action of the amm- 4 ture to operate the switch untii a panse ocrims in the impuisesi a 'movable seit-retreating member, actuated step by step at euch operation of the translating device', a

holding Said member in its ladvauced position and electrieaiy l`operated hereunto set 15

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