USRE13891E - Sidney hand browne - Google Patents

Description

1 3,89 l 2 SHEETS-SHEET 2.

/HVeH/off;

S. H.-BRGWNE,

TELEPHONE EXCEANGE SYSTEM.

APPLOATIoN ULEB so` 1914.

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UNITED sTATEs PATENT onirica.

SIDNEY HAND BROWNE, OF SHORT HILLS, NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONE AND 'JlllldlGrItAPIlI` COMPANY, A CORPORATION OF NEW YORK,

13,891."v 'l l Original No.j1,f073,5`89, datedy =September Vtelephone exchange systems, and has for its object av quickening of the telephone service and a lowering of the cost of producing the telephoneservice through a decrease in the number of operators, or in the number of hours of their Work, or both.

In telephone exchanges of the most general use, and recognized today to represent the` best practice in producing telephone service, the subscriber signies his desire to be connected with another line by removing hisl telephone receiver from its hook. AThis lights an incandescent lamp or sets some other form of visualsignal before a 'certain operator in the central office, notifying her that she must connect her telephone with his line, and' by conversation ascertain his de.- sire," then connecting him with the .line for Wh/ichr'he calls. It is usual/to provide each -op'erator with a certain number of lines,

from lwhich she'receives calls, and to give her access to all ofthe lines of the system directly, that she may connect the lines of `her group of vsubscribers with them, or by means of a trunking system to give lier similar access even though all the subscrib ers "lines do not appear before her. It is found that .to give each operator a certain number of subscribers lines which she shall answer, does not enable her to maintain an even rate of working, because some subscribers make many more callsin a day than do others; inventions have been made v enabling the number of lines terminating before'a given operator,- to be increased or vdiminished from time to time in order that the position of the switchboard served by one operator may not demand more of her than she can perform, or Vdemand so little as not to .keep hei' busy; Such an ability to Vredistribute the lines is given by the device zknown as the intermediate distributing bboard 3; but even thatrhas the disadvantage thatit is only useful to make relativ-ely perthe present systems.

Specification of Reissued Letters Patent. Regiss'oieii lltl'. 15, 1915.

23, 1913, Serial No. 222,645. Application for reissue filed September 30, 1914. Serial No. 864,359.

marient changes in the connections of the lines, and it has little usefulness unless the traine produced by the various lines, individually and in groups, be studied for a considei'able time so that it may be guessed whatl traflic Vthey will produce in the future, i

and redistribution made accordingly. The intermediate distributing board when used thus in the best way of which it is capable, will not even 'up the traliic in such a way' that each operator will be evenly busy throughout all the hours she is working, but will only prevent great inequalities among the operators at a given time. ForI example, during the busy hours of the day, the traffic of the office may be handled bv a certain number of operators, each worliing to full capacity, and with practically identical loads for each; but in the less busy hours of the day the operators may be reduced in number, one of them serving two or three or more of the groups of lines servedfbv aii operator each during the busy hours; but at the best she can give prompt service only by serving such a group of lines as she can easily reach with her answering cords and plugs from a fixed standing or sitting position; if the traiiic is so light that economy compels so small a number of operators as to give each of them a greater length of the switchboard to serve than she can handle without walking from one place to another to answer the calls, the quality of the service will suffer in that the calls will be answered less promptly. i

My invention accomplishes the result of automatically distributing the calls upon the switchboard so that as many calls come to an operator-s position as she can reason .ably well handle, and they come with a much greater steadiness than is true under This enables the total trailic to be handled by a minimum number of operators, insures that each call can be handled by an operator without her having to move from place to vplace to answeri it, and accomplishes both economy in the etim pense of furnishing and uniform excellence in the character of the service,

5l attain these objects by vthe circuits and Vmechanism illustrated in the accompanying drawings, in which- K Figure l is a plan view oi a switch; Fig.

2, an. elevation; Fig. 3, a horizontal section of that switch, and Fig. 4 is a scheme ofthe circuits. v

Similar letters refer Vto similar parts throughout the several views.

From Figs. 1, 2 and 3 have omitted the',

many wires which are attached to the variouselectrical parts of the switch when it is connected for operation. In Fig. 4 these connections are shown for a switch, and the' a number in each circular arc; in the form of switch which I .show in these figures, there the bolts, 33, and the screws, 95. This serves are twenty-five contact pieces in each arc, and each piece is brought out at the periphery of the circular portion of the switch so that a wire may be attached to it. Between each row of contact pieces and the neighboring row, between the upper row and the top plate, 24, and between the lower row and the bottom plate, 23, insulating material, 94, such as hard rubber or liber, is clamped by the double purpose of insulating the contact pieces from each other and from the framework, and holding all of them securely in position.

Plates, 24 and 23, have attached to them or formed from them respectively the bearing studs, 17 and 29. These guide and support the vertical shaft, 30, which carries on its upper end the ratchet wheel, 13, and which is` adapted to be held in or returned to normal position by the action of the'spiral spring, 14, attached to the shaft, 30, at one end, and to the pin, 15, at the other. rlhe pin, 15, is carried bythe top plate, 24. lW hen the ratchet wheel, 13, is in its normal position, the-pin, 22, engages the post 16; the pin, 22, also engages the contact spring 19,

\ bending it out of contact with the contact part of the switch structure, by the insulat piece, 18. The spring,'19, carries on its end an insulation to preventl electrical contact with the'pin, 22. Spring, 19, and the piece, 18,v arey separated from electrical contact with each other and with the conducting nig pieces, 20, 20a and 20h, of rubber or other suitable material; they are bound to place by a screw, 21, bushed from Contact withthe spring and contact piece in a familiar manner and entering the bracket, 12. The

bracket, 12, serves the double purpose 'of supporting the magnet coils, 3 and 8a, and

of forming a part of the magnetic circuit of those coils; one end'of this bracket forms a pivot wlth the arm, 10, adaptedto'fbrm va vretaining pawl for the ratchet wheel, 13. The helical spring, 11, isa retractile one,

holding the pawl, 10, in engagement with a tooth of the ratchet wheel, 13, unless the y iron armature, 9, is suiiiciently attracted by" 'the cores of the coils, 8 and 8a, when they are energized. Of similar structure isV the magnet formed of the coils, 1 and 1a', the bracket, 2,A the 'iron armature, 4, and the lever, 3, exceptthat the latter carries a further pivoted part, 5; a helical, retractile 1 spring, 7 tends not .only normally to hold the arm and armature,3 and 4 respectively, away from the cores ofthe coils, 1 and 1% but to `-keep the free Iend of the arm, 5, in i I engagement with the post, 6, carriedl by the top plate, 24. Unless the coils are energized, the free tip of the arm, 5, will be out'v'of engagement with `the teeth of the ratchet wheel, 13; but if the coils. are energized, at-

.- tracting the armature, 4, the motion of the arm, 5, will-enableit, while'still sliding in.

.contact with the post, y6, to engage a tooth of the ratchet wheel, 13, and advance it one step; the wheel will then lbe held by a new engagement -of the pawl, 10, against* a tooth. When the cores, 1 and 1a, are denergized, the tip of the arm, 5, will again pass out of engagement with the ratchet wheel, 13,` and successivev impulses of. current will advance the ratchet wheel step .by step, carrying with I it the shaft, 30. The Vrelation between the teeth of the ratchet wheel and the contact pieces, 25, 25a, 25X, and the similar contact pieces in the other three rows, is such that' for each advance of the ratchet Wheel one step, the contact wipers, 34 35, 36 and 37, will engage the dii'erent contact pieces of the rows successively; the contact wipers, 34 to 37 inclusive, are in pairs, the two members of each pair' being in electrical contact, but each pair being i-nsulatedfrom the shaft and other conducting parts of the structure by insulating bushings, 32, 33, adapted not only to bind and to space theA contact wipers, but to center them alsoi-n a well-known manner. The ends of the contact wipers which do not-engage the contact pieces, are adapted to receive flexible conductors making continual' connection with the contact wipers during a movement through the whole'arc.Y

. The normal position of the contact wipers is out of engagement withany contact piece; one step of .the ratchet wheel, 13, causes them to make contact respectively with the v first contact pieces in the4 rows, and successively, impulse by impulse, to the end of the arc. As shown most clearly in` Fig. 3

tact to another, will engage the next following contact before leaving the precedingV one. The actuation of the magnets','8 and 8a, at any time, will release the ratchet aoY ioii

each contact wiper, in moving from one conwheel, 13, unlessthe magnets, 1 andv 1, are: also energized; upon suchy releasefthefcontact Wipers return to normal position out of engagement with any contact pieces` and.

the connection between the spring, 19j, and

the contact piece, 18, is broken, although it: had been made during all the timeythe conf tact wipers were not in their normal' posi,-A tion.'

Referring to Fig.' 4i? the line. formed.A` of? conductors, l 41 and 42, connects the subscribers instrument, 43, with the-mechanism i,

of the central ofiice. The subscribersinstru:-` ment is of a type adapted for use. withzcen; tral energy systems, and is one in whichthe line circuit is open the receiver is oii be seen that the subscribers line,l in ther.cen

tral oiiice, is associatedy with aanumber" o?. and may be considered4 as a unit with the elements; of 'a circuits.

electrical devices,

broadly considered to terminate in the: con'- tact wipers, 34, 35, 36' and Another group of devices may be considered asa unit, andas beginning., in the Contact pieces, 25, 26, 27" a-nd ,l2-8,`v (the numbers, for clearness, in ingv located contiguous to wires. connecting: with those contact pieces), and extending-' to.y include the plug The` drawing shows; further at the right, a subscribers` instrument and line, slmilar to that. firstmens tioncd, but from which the detailsfnot esl-` sential to this specification have been;`

omitted.

Considering first the character Y andv fune-- `tions of the mechanismy associated'witlr the It Ais providedl with` mul line, al and 42: tiple jacks, three ofi which are shown in Fig. Ll, each having the elements oftwo, line springs and a testring, respectively 41,

Similar'springs, in each jack are'connected'to one side of the line, and this, is-.truey whatever` may be. the number of spring jacks;requiredI for each line in a. given system.. The: test rings oi' all the. jacksv of la line arewconnected together and to the winding of the cut-off? relay, 55, the. other end of thatwinding-bezing connected to ground. Undernorma-l.

conditions this relay 1s not'. energized,uso. 56, will make` contactzwith that its armature,l the grounded point, 5S, and 1.tsarmature, 557', will makecontact with the point, 5.9, estab@ lishing thence a circuit from:therlinefwire,

4:1, through thev relay, 61, and the battery, y which is grounded'. The. relayf,.555?, isfpres erred to be shunted by the no 53,v to;` anotherrelay@L the relayto margins of the non-inductive resistance: asf v yel to direct' current.-y unless; the switch hooln.' It will;

the drawing: ati

the` drawing', bel-A the remaining; pole o-;

resistance, 54, so4 proportioned' tozallowf be. operative through the; proper voltage and. liney resistance=,..and yet to enable voice; currents to. passtlirrugggltv r als? ing., A relay/64, has itswinding; in a. con-- closed contact' betu'feen` its armature, .65', and

point. 66, serves to maintain a circuit: such that` ifftherelfay', 61,l should be'. energized, closing its. armature, 62, upon the poi-nt, 63', the'- interrupter, v20.0, kept'. constantly rotating at; thevproperratewill serve to cause. impulses of current' through the. path described, andl thev switch winding, 1; the` switch-winding, 1',.is that which has been describedv with lreference to Figs.. 1, 2 and 3,. as: adapted'to rotate the Contact. wipers, 34A, 35% 36" andy 3?,.,aznd with the conditions. which ll have described, such. rotationl would".l be: causedto begin immediately upon the supscriberiseV removing hisl -telephonefgreceiver fronnthe, hookrtomahea call.. Itisvmy in, tentionthatx this shall. be'the. result, and that'y when such rotation beginsfi-t. shall con.;A tinue through. the: arc of thea. .subscribers rotary switch.1 until, in-makingy successive contactsf,.fafl position is ound; connecting-r the subscriber.s;:ll-ine.l with.. a set." oft.` four' 'contact piecesgleadi" cuitaupon wh1"clr,.. at that. moment,` no` other subscrihersf linei's; connected.3.4 I have shown that;` each subscribes switch has: sets of 'four' trunk contactseaclr;A and these are: as` many` points; of' access. to plug-'terminated trunks.,l

In. Figi/, indicate the existence oi' a plurality' off; 'possible trunks to be selected', by'showing,l not; only. the: contact pieces, 215., andfQS. as: one. trunk,` but 25a, 2.6?, 2LT?" and: 289 asa` illustriativefl ozt'V othe "tr-units. Burifngr the? period, therefore, ichA suc.g ceeds. thevy removalt of.' the: subscrrbes. re,. ceiver* from: its hook', the rotationwill. com ti'nuev as long.. asvthe. circuit-through the magnet, l, remains as. first't established@ When in' the, successive,` steps. the contact. wiper, 37,' engages a contact,` as: 25, which -is grounded lthrough the. back contact of' the armature, 69,; uponitsipoi-nt, 70, of. the. relay, 618,. further` rotation will be stoppledbecause" so.y indingiy ground, by the contact wiper, 3'?, ,will energizethe-z relay, (34,. oiv the line, causing its, armature to. breakl its, back contact.. As; this breaking prevents-further rotative` impulses, .he switch will remain upolrptlre contact; piecesy of) that: trunk, se.- lectilirg; itzaaseany extensi" of the subscriber-s linetort ,i operatoislposition1 upon which arefl'ocatedthez trunksignals and othery tr unl; mechaarismsyet4 toy he.` described. As a fur;- ther= result.,` ofI the'. ndng' oiv theV grounded Contact' piece, 2.52, the contact. wipe-r', 37,., the;relay;v 68,;will bea energized. and its 'armatul'eln, will make-contact. with the for'- wa-rd; poilrrt,v T1, andi afi'terward will break theybwckqcontact witlrthe point,` 70.A Simultaneousl .,also, the armature-r, 72', ofthe same willmakefcontact: with the point,` 73,

90 into-.1a. plu-g;terminated?L cirbreak the contact of its'armature, 56, from ground and apply it to the conductor leading immediately to the Contact wiper, 34; similarly it`will break the contact of its armature, 57, from the relay, 61, and apply` it to the contact, 60, leading directly to the contact wiper, 35. The effect is to extend the line immediately through the contact wipers mentioned to the line conductors of the trunk, terminating in an'operators position. yA further effect is to release the previously closed contactof the relay, 61, preventing a renewed rotation' of the subsoribers switch which would Otherwise occur.. A

lhe resistance 96 operates to reduce lthe current from battery 67 through the cut-oit' relay 55 to approximately such a volume as the cut-off relay 55 would receive from a plug inserted in one of the multiple jacks salvati-a6, and thus to give a busy test condition to the multiple jacks similarA to the 'condition placed upon those jacks Jbythe insertion of a connecting plug in one of them.

lt will be noted also that when theswitch of a vcalling line is connected' temporarily with a busy trunk while passing that trunk in its Search for an idle trunk, the cut-off relay associated with the seeking switch is' placed in shunt with the cut-olf` relay associated with the switch which is hplding that trunk busy; the resistance 96 in series with the two relays thus in shunt reduces the current through both of them to such a volume as will not actuate the relay 55 associated with the seeking switch yet will4 retain in its actuated condition the relay 55 associated with the switch which is holding the trunk busy, and .will also be. suficient to place a busy potential upon the multiple jacks of the calling line. It may be noted here that the action of shunting the cut-oit relay oi' the line holding the tested trunk is similar to the shunting of that relay when its multiple jacks are tested by the tip of a testing plug. The subscribers line now being eX- tended into the line conductors of the plugterminated trunk, the relay, 74, whose winding is bridged across the line conductors of the trunk, and in' 'series with the battery, will be operated.y One of the effects is to close the armature, 75, upon its contact 76,

connectingy the two windings of the relay, 68, in series with the battery and earth, thus holding it energized. The other armature,`

77, of .the relay, 7st, leaves point, 78, and

engagespoint, 7 9lighting thefsignal lamp,

`86, because the back contact of the armature,

87, of the relay, 85, is closed. This lighting" is a signal to the operator in charge of that trunli, that a call requires to be i' answered; this she does, by actuating her listening key,

91, in the usual manner, after which, in cOn-.

versation with the subscriber, she determines his wants, lifts the trunk` plug, 92, tests the multiple jack of the called line, inserts the plug in the jack if the line proves not to be busy, and rings the called subscribers bell by means of the ringing key, 97, or other lequivalent mechanism, such as an automatic arrangement for establishin conditions to ring his bell until he respon s.

.The act of inserting the trunk plug, 92, in`

the jack of the line of a called subscriber, not only connects the calling and the called lines in readiness for talking 'when the called subscriber answers, but connects the battery through the winding of the relay, 85, and the sleeve, 92a, ofthe trunk plug through the test ring 4of the jack with the winding of the cut-off relay, 98, belonging to that line, and through that winding to ground. Thus the cut-oil' relay, 98, is operated, disconnecting the called line rom'connection with its own rotary switch and associated relays, so that the answering of the called subscriber will not cause any operation of those parts of the equipment of his line in the central oilice.

The relay, 85, also operates, breaking the -tion between the back contact, 82, and armature, 81, of the relay, 80. When the called subscriber answers, removing his receiver from its hook, the relay, 8.0, is energized. lts winding is bridged across the line at a point between the condensers, 84, 84, and the inner contacts ofthe ringing key, 97, and isY also in series with the battery. The armature, 81, thus loses contact 'with the point, .82; lamp, 83, is extinguished, notifying the operator that further ringing on her part is unnecessary. It is obvious that if the ringing key, 97, were an automatic one, ringing until the subscr ber should` answer, this function of the limp 83, would be unnecessary, and such a arrangement of my circuit might be made with advantage. Under ,the conditions-which l have described, conversationinay progress between the two subscribers. l, l

At the close of the conversation, the hang'- ing up of his receiver bythe calling subscriber, perinits the relay, 53, toy denergize,

between spring, 19, and point, 18, of the rojtaryswitch, had beenmade since .the first aattention, but because it stands the signal to mean that disconnection part of the called subscriber,

ways whereby step othemechanism, this falling away of the armature of the relay, 53, occurring for the rst time since the beginning of the entire cycle of events, will cause" the battery to energize the windings, v8, of the release magnets. The pawl, 10, drawing out of the ratchet wheel, 13, will allow the switch to return to its normal position, again breaking contact between' spring, 19, and contact, 1S'. It is thus evident that the hanging up of the telephone of the calling subscriber at the close `of the conversation, accomplishes' immediate disconnection, -and that upon again removing his receiver vfrom the hook, the rotation of the switch will be repeated.l

Because of the immediate release of the rotary switch and its return to a normal position, the relay, 74, will be denergized3 because the trunk plug is still in position and the contact made between armature, 87,

and point, 99, of the relay, 85, the falling back of the righthand armature of the re lay, 74, will make connection between its armature, 77, and the contact point, 7 S, relighting the lamp, S6. This is again a signal to the operator that the trunk requires is in use she.,under is desired, which act she then performs. The hanging up of the telephone onl the relay, 80,'closing its 4back-contact, and religh'ting the signal lamp, 83,l also serving as a disconnect signal to the operator in case she had not4 alreadey obeyed the' previous signal due to the disconnection of the rotary. switch.

rlhedescribed result of immediate discon-v nection upon pulling down the hook at the calling station, gives further clearness to my statement that the operation of my system accomplishes an improvement in -the quality of the service due to'speed. It is evident that a subscriber, concluding a conf versation, and desiring another connection, has only to hang up his receiver for an instant, or what isequivalent, pulldown the hook and let it up again, whereupon his rotary switch will immediately select another idle trunk. l v

Inasmuch as the equipment of each subscribers line includes in the central oiiice not only the mechanism of the rotary switch and the relays associated with it, but also a series of multiple jacks distributed before the operators, it is necessary that busy test Jfea-tures beprovided -for. I show in Fig.

.il that the operators telephone is adapted to such a busy test, and that it will be received whenever there is existent at the test rings of the spring jacksra difference of potential with relation to the earth. There are .two

this busy test placed upon the test rings; one is the result of the presence 'of thetrunk plug in one of' 'tacts' are the last in will release the Y trunk lines through the potential is' the jacks of the line, and the other is a result of the engagement. of contact wiper 36 with trunk contact 26 of the iirst rtrunk reached by the line wipers in hunting for an idle'trunk. lf` this -.first trunk is idle the busy potential is placed uponthe test rings immediately trunk relay 68 pulls up its armature-72 and'closes,-at Contact 73, the cir,-

cuit including resistance 96. On the otherhand it the first trunk is already in use, its

relay G8 will of course be energized and, al-

though the progressively advancing line` wipers will4 not be arrested, busy potential will be placedvupon the test rings of the calling line during the short time wiper 36 remains in engagementwith contact 26 of said ltrunk and such busy potential will be` maintained without interruption as eachsucceeding contact 260i a busy trunk is engaged.` This follows since, as shown clearly.

in Fig. 3, the movable Aline wipers are of such width that they engage the next succeeding contact before breaking contact with the one preceding it. Thus it will be seen that even thoughv all the trunks in the system are busy,

the series to be reached by the movable wipers, nevertheless busy 90 except theone whose conpotential will be continuously applied to thel test rings of the calling line, from the time the first trunk is engaged until said idle one is found, and of course will be maintained duringthe time the calling lineare-- mains connected with said trunk, or in other words, until the calling subscriber hangs up- Consequently, there is prac- Y his receiver. tically no time during which a subscriber-s line, engaged either as ya calling or called line, is left unguarded.

In the practical arrangement of the various subscribers switches with relation to the -ioo trunks to the operators, I prefer to term1.l i

nate in each operators position such a num-V ber of trunks Vas when continuously cocupied by successive conversations, will furnish an can Just successfully perform. The number of these trunks per position Vdepends i amount of work which the operator' Y' upon the length Iof time of` the average'conv y versation, as well as upon the ability of the operators, but probably will be" approxi-y.

mately ten.

The rotary tacts, according tothe structure shqwn in Figs. l, 2 and 3. sets of contacts `forms a terminal for a trunk line,

access to the same trunk tionary contact points on in much the same manner asis followed in the ordinary multiple switchboard of .mod-v subscribers line is.

ern practice, wherein a switch for each subscribersv line has twenty-Eve, sets of stationary con,

Each of these twenty-five as shown clearly in Fig. 4; and in order to give a `number of subscribers lines line, I multiple the.

corresponding `stathe'rotary switches l ,'multipled-tova,separate 'ack on every secbelongs, access to twenty-live trunk lines, if

tle\switches are constructed' as here shown. Of course each switch maybe made-to afford access to a greater or less number of trunks if desired, by giving each rotary switch a greater or less number. of contacts.

Where' there is such a numberbf subscribers lines as would require, at' the time of maximum traffic, a greater number of trunk lines than there'ar'e contacts upon any switclnit would becomenecess'ary to divide the subscribers lines into groups', there bein l many lines in each group as would be li ely tokeep busy, at the time of maximum trailic ;v the' number of trunk lines Jfor which terminals are afforded on each switch. To make this clear, if the switches used have twentyfive seits of contacts each, and if there were centered in vtheoflice -as many subscribers lines as would require the use of say fifty trunks,'then the subscribers lines would be divided into two groups', each group being served by twenty-five trunks.

l corresponding contacts' on the switches of any one-grou would be multipled together l and connecte: to' the wires of one trunk line,

asvhas already been pointed out.

The movable contacts on the selecting switch may properly be termed selecting v?. contacts since they arev actively involved in establishing a connection between a line and a trunk." Similarly the stationary contacts1 such as 25,A 2'6, 27 and '28', may be termed waiting contacts since they are passive and' remain in position to be engaged by the selecting contacts. These waiting contacts may also be termed multiple contacts, since the corresponding contacts on the switches of a group of lines are multipled together in a similar manner, to the multipling of the jack contacts in a multiple board.

The movable parts of the selecting switch form what may be termed a flexible termi--- nal for a line, and I do not wish to' be limited infall cases to any particular form 'of flexible terminal, as I believe that any form of mechanically actuated exible terminal,or selecting switch, whether moving in a kcircular or straight path, and whether moved a step at a time, or by steady and continuous movement will, if used for the purposes herein o'utlined,lie within the scope of my invention. Neitherdo I-wishto limit myself in all respects to the-exact construction of other apparatus, nor to the exact arrangement of circuits here shown, as many modifications mightbe made therein 'without departing from the spirit of my invention.

Having thus' dels-abeti my invention, what I desire to `claim and All of the secure by LettersPatent, is:

vl. In a telephone system, a substation, a y

telephone line extending in two limbs from Vsaid substation to a central olhce, a plurality of trunks, contacts therefor, a trunk lhunting selecting switchefor the line, wipers for said switchwhich successively engage\the contacts of said trunks, a relay having contacts for maintaining said wipers discon-` nected from said line limbs during trunk hunting and for connecting said line limbs to said wipers whenl an idle trunk is found.

-2. In a telephone system, a line, a source i of'xcurrent normally connected therewith for use in initiating a call, a trunk hunting line switch having trunk contacts and progres` sively advancing wipers which normally occupy a position out of engagement with said trunk contacts, a cut-off relay for the line for maintaining the line disconnectedfrom said wipers during trunk hunting, means for actuating said cut-oli' relay, when said line is y either a callingor a called line, to interrupt the normal connection of said line with its source of current and to connect the line with its wipers. y

3. In a call distributing system, a telephone line, a source of current normally connected therewith, a plurality of trunks, an automatic selecting' switch for connecting said line with an idle one of said trunks when a' call is initiated, contacts in said switch xfor said line, other contacts for said line, a terminal for each of said trunks for use in connecting with said other contacts when the line is to be called, and a 'cut-on' relay for maintaining the line disconnected from its switch contacts during the select the line from said source' when said line is connected with as a called linethrough one of its other contacts.

fl, In a telephone system, .a subscribers telephone, a line leading thereto, a cut-od i by the initial actuation of the line relay for f automatically advancing said wipers into successive engagementk with said trunks, means to stop said wipers upon Van idle trunk, and means to actuate said cut-oil relay to disconnect said source from the line and to connect the' line with said wipers after the latter have engaged the contacts of an idle trunk.

5. In a telephone system, a telephone line extending in two limbs to a central oiice, wipersassociated therewith, a plurality/J of stationary contacts, trunk lines ext-ending fromsaid contacts, means for automatically progressively advancing said wipers over said contacts until an idle trunk is found, a

source of current normally bridged between the limbs of said line but disconnected from said wipers, al current supply bridge betweenthe' limbs of each of said trunk lines,

a cut-oil relayoperated upon the selection of an idle trunk to interrupt the normal connections of said source with the limbs of the line and connect the line through its wipers with the current supply bridge in the selected trunk. l I

6. In a telephone system', a telephone line, a line relay therefor, a test` relay, a plurality of trunks, contacts therefor, wipers associated with said line, motor.means for progressively advancing saidl wipers overl said trunk contacts, a circuitl controlled by said line relay to cause the operation of said motor means and by said test relay to stop the operation of said motormeans when a wiper connects with an idle trunk, a cut-off relay operated upon connection with anidle trunk to open the normal connection of said line relay and complete circuit between said line, and idle trunk, and means for thereafter interrupting the circuit of the test relay.

7. In a telephone system, a telephone line,

'a source of current normally bridged between the limbs of said line, a line relay, wipers associated with said line, a plurality of stationary contacts, trunk lines extending from said contacts, means for automatically progressively advancing said wipers l until an idle trunk line is found', anoperatingl circuit for said means controlled by said line relay to cause the advance. of said wipers, a test relay controlling said operating circuit to stop the advance of said wipers when an idle trunk is found, and a ycut-oil' relay operated upon the selection of lecting switches each set individual to a single subscribers line,a source of current, a rline relay, a cut-cil" relay for each lme having contacts normally serially included-in circuit with its associated line relay andv which maintains the limbs of the line d isconnected from its associated wipers during trunk hunting, an operating circuit for each selecting switch completed by the actuation of its line relay Zwhen the limbs ofits line are closed together at the substation, a test relay for each selecting switch responsive to 3' the idle condition. of a trunk line for opening the operating circuit of its selecting switch, a test circuit for each test relay including a wiper of its selecting switchv and a test Contact of a trunk, a relay associated -with each trunkvfor` removing, the idlecone.

dition from itsv test contacts/when said trunk is selected, a circuit vfor each cut-ofi relay includingy a wiper of its selecting switch anda contact of a trunk, closed upon y selection'of an idle-trunk by a calling line to energize the cut-oil relay thereof, thereby extending the limbs of that line through their lassociated. wipers to said idle 'trunk i line and opening the normal circuit of th line relay of said calling line, a branch from each cut-ofi` relay circuit,'multiple contacts of a subscribers line included in said branch, and means for completing Vthe circuit yof a cut-olf relay over its branch when a line lis connected with as a called l line at `one of its multiple contacts thereby opening "the normal circuit of its line relay-to prevent itfrom .starting its line selecting switch intooperation when'the limbs of the line are closed together in answering a call. 9. In a telephone system, a subscribers line extendingv iny 'two limbs to a central oiiice, multiple jacks for said line, a trunk huntingselecting switch for said line, wait- 'f ing contacts for said selecting switch pertaining to a plurality of trunk linesfleading.V

fromsaid switch, wipers for said switch, la

cut-cti' relay for Vsaid line, which, when energized, connects the limbs of said line with.' 1

wipers of said selecting switch,a circuit for the coil of saidv cut-off relay. including a wiper and having a branch extending to the test contacts of said multiple jacks, means to place a test potential upon said Amultiple jacks during the selective movement of said wiper insufficient for the operation of said cut-oll relay and to increase said test potential sufiicent for the operation of said cut-ofi" relay when said wiper l arrives upon the contact of an idle trunk, 10. In a telephone system.y a subscribers line, multipley jacks for said line. a trunk i hunting selecting switch1 orsaid line, vwaitf ing contacts for said selecting" switch perl taining-to a plurality of trunk lines leadingr Afrom said switch,lwipers for said switch, ka

cut-off relay for said line, a circuit .forthe coil of saidcut-orelay .including one of said wipers and having a branch 'extending to the-test contacts of said multiple jacks,

' ation of said cut-olf relay when said Wiper `means 4.to place a test potential upon said multiple jacks during the selective vInovement of said Wiper insuiiicient for thezoper- 'ation of said cut-oil relay and to increase said test potential suiicient for the operarries upon the contact of an idle trunk,

andanormal source of current disconnected froml said line by the operation 'of saidicut-` oi relay.` A y llgln a telephone system, a substation,

a telephone line extending in two limbs from i said substation to a central office, a source of current normally connected in bridge of said line, aline relay for said line, a plurality o f said trunks.

connecting circuits, `an automatic selecting vswitch for connecting said line with 'anidle one of said connecting circuits, means re" sponsive to the energization of the line relay f upon closing together the limbs of the line at the substation `for initiating the progressive advance of said 'automatic Selecting switch, and means :for placing a busy potential `upon the multiple jacks of said line.

during said .advance movement and [While said line is in circuit with a'selected one of gsinuiir HAND BROWNE.

yllitnesses:

GEQRGE W: MCRAE,

'WILLIAM C. IGaines.

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