US1107136A - Telephone-exchange system. - Google Patents

Description

E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED AUG. 5, 1905.

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ED'WARD E. CLEMENT, OF WASHIITGTON, DISTRICT OF COLUMBIA, ASSIGNOR, BY ZVZESNE ASSIGNMENTS, TO FREDERICK G. STEVENS, OF ATTIOA, NEW YORK.

TELEPHQNErEXCHANGE SYSTEM.

mom as.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT, n citizen of the United States, residing at Washington, in the District of Columbia, have invented certain. new and useful Improvements in Telephone-Exchange Systems, of which the following is a specifica-' be employed with any type of system provided the necessary features are present, as will fully hereinafter appear.

My invention has for its object the simplification of the exchange switchboard and the uniform distribution of the load among the operators or among the connective circuits and apparatus.

its hereinafter described, the salient features of apparatus constructed in accordance with the invention are, a constantly rotating arm carrying a plug, a circle of contacts around the arm like jacks, and means operative when the plug comes opposite the coiltacts of a calling line to project the plug into the jack, stopping the arm and producing the same effect on the line cut-off relay and other pieces ot apparatus as when the ordinary plug is inserted in the ordinary jack. Instead of having a circuit connected through flexible conductors to the plug, I prefer to have a pair of bus conductors extend around the circle in proximity to all the contacts of the line jacks, so that when the plug is in any jack the 'contacts thereof will be closed on the bus-pain, This latter,

is connected to the cord or equivalent circuit associated with the plug. I am thus enabled to use platinum contacts and to produce absolute certainty in every connection. When a plug has become inserted in acalling jack as stated, and the subscribers have finished the ensuing conversation, they hang up their receivers as usual, severing the line circuits for battery currents, whereupon the super-- visory relays act to release the arm carryingthe plug, withdrawing the latter and again rotating it in search of a calling line My invention is illustrated in the panying drawing, wlierein Figurge 1 IS 'a diagram showing twosubaccom- Specification of Letters Patent. Patented Application filed August 5, 1905. Serial Io. 272,907.

scribers stations and a central station, with with the invention. Fig. 2 shows a modified arrangement of the contacts in the selector swltch. F g. 3- is a diagram showing the selector switches. i A

In the drawing, A and'A' are two subusual transmitter T, receiver R, switch-hook H, ringer Q, etc., suitable for 'a common battery system. As the apparatus at each station, and the line connections, are the same,

connections, only. Here the line Wires 1 3 and 4: leading respectively to the'line relay L and the ground. From relay L Wire 11 passes to the bus wire 12 of the main battery B. The relay controls a local circuit 13 terminal after the no other.

Each line has multiple terminals for calling, in thdbanks of the selectors, and multiboard panels. The multiple callingrtermi stated, andthey are connected to wire 13. They are accompanied by talking terminals, separate from the signalin switch 0, although they also appear in the switches 0' O In the diagram they are of clearness and simplicity. The multiple calling terminals of the line il-42 also appear in the vari o2 s selectors, being indicated by the letters 0 P, and their circult wire a connective circuit equipped in accordande distributionof the lines among the variousscribers stations veach'eq'uipped with the terminating at one contact in each of a the first selector of its set which reaches'its call. is initiatedfand by p p or calling cir-' cult, lettered 0 and-0 an shown only in.

omitted from'the latter switches for the sake I will describe in detail the station A and its and 2 extend to the central oflice, where they terminate at the two contacts we and m of the cut-ofi relay M, which are normally in closed relation with terminals of the wiresple jacks for being called, on the switch nals of line 1-2are marked 0' as already a 4L4?) are by way of wires 89 and t0, cor-- responding to 3 and 4- of line l-2. The in- 1 terconnection of these lines is through acord circuit as vusual, and it is to be understood that I preserve the conditions nowrelied upon forbusy test and for supervision, at least of the called line. Nosupervision of the calling line in any particular connection is necessary, for the reason that the call ing subscriber of a connected air has it in his power toldisconnect himse f as soon as he is through talking. This will appear la ter from the description of the cord circuit apparatus, which I will now give. Broadly stated this-comprises four relays, two supervisory lamps, and a selector, the latter taking the place of the answering plug, for to this extent it is a single cord system. There is only one operators plug to a cord. There is another plug, but it is in the selector machine, and is automatically operated. The selector answers the call, putting the sub scriber on the cord circuit. The operator then gets the first signal through the lighting of the calling supervisory lamp, and comes on the line calling, thr0ugh the usual listening key, or through an automatic listoning device, to obtain the'number wanted. This obtained, she tests the line wanted and completes the connection by sticking a plug as in ordinary systems heretofore employed.

The selector I here present comprises a constantly driven shaft N, with collars carrying individual arms, carrying contacts 0 which are constantly sweeping over circularly arranged series of coiiperating line contacts 0". The shaft in the present case is shown as driven through a belt n and a pulley u, but it will be understood that, the driving means may be of any suitable description. The severab selectors are all driven by preference on or from the same shaft, so as to secure not only economy of power and transmission but perfect uniformity in speeds and synchronous movement of those selector arms which may sweep over multiples of same lines. An individual selector me: anism such as l have shown at in 1 comprises a, sleeve or collar 0 loosely mounted on the shaft between fixed collars e -0, and fitted with a projecting tubular arm carry- .ing the windings 0 upon it and combination core or plunger 0 ol"- within i' the arm thus constitutlng 1n ell'esizt asolenoid withv a plunger core. Qn the outer head or the magnet windings cap or casing 0 is provided to house a spring 0 by which the with aromas plunger is normally kept retracted toward the s aft, as shown in the gure. The function of this plun er is two-fold. In the normal or idle con ition of the arts it serves as a lockiugdetent or'clutc to hold the sleeve 0 fast on the shaft, its cnd project ing at such times into an opening or socket in the'shaft as indicated at 0 When the arm is opposite a calling line terminal the plunger is thrown forward and its outer end enters the jack ring 0 the inner end at the same time leaving its socket in the Shaft, thus stopping the sleeve and arm and spreading the jack springs to complete the cord and line connection. The inner end of the plunger, 0, is of soft iron, with a hard tip if necessary. Its outer end, 0 is of insulating material such as hard wood.

The winding 0 is double, consistingof an inner and outer layer, like the primary and secondary of an induction coil. The outer winding is connected on one side to the contact spring 0 through the wire 43, and on the other side by wire 50 to ground throu h the normally closed back contact of the re ay R and wires 48 and 44. The inner winding of the solenoid is connected on one side direct to ground and on the other by wire 14 to wire 15 and the front contact of the supervisory relay R. Of course these two windingsof the solenoid may be put on the tube in any desired fashion. They may be end-on instead of inner and outer, or in alternating layers, but the simplest method is that I have indicated. The only requirement is that the winding connected to contact 0 shall be able to pull in the core 0 when energized, and that the windin connected to wire 14 shall be able to hold t e core in when so attracted.

The cord circuit terminates at the answering end in the bus contacts o -o,- each a ring with its inner edge out into a comb, having a tooth for every line on the selector. These two combs, top and bottom, forming the two side terminals of the cord, may be spread to close on any pair of individual line contacts 0 0 by the plug or plunger 0*, the line contacts being arranged in a radial series, as indicated in the switches O and O lVhen the plunger arm is opposite a particular pair of line contacts, if the solenoid then gets current the plug will be thrown forward and between the two teeth of the combs o' -o at that point, spreading them against the line contacts. All these contacts are supposed to be fitted with platinum points at the ends, and each tooth of each comb corresponding platinum contacts. Mechanically, the structure comprising the combs and line contacts is built up by superposing the contacts upon each other with interposcd insulating rings in a manner well understood by those skilled in the art. This structure is not shown in detail in the drawings, except as to the arrangement of one F, it!

Cir

d their cooperating n" U The assembleo continuous ring, id contact eep or the asses of f sci. ei's who maybe connected through the cord. Relay ll has itslamp S connected .lirc-m. front contactto ground, and its armature connected by wire 16 to the trout cont; at oi the relay R. The inner winding the solenoid 0 is also connected to the contact of relay R. Relay R has its ground and its armature to the front contact relay Il This relay Rfhas a seconc armature .which. through itsnormally clo d hack contact 'eontrolathe continuity 1e ground wire ll;48 to the lamp S,

lay Ill and the'solenoid o wires 19-20 and QL-ZQ as bridges they were continuous, which in effect an s are used for convenience of alien. it is much easier to trace cirnd perceive differences of potential points in a diagram of this kind. re resents a listening key adapted the operatorls telephone circuit j l is-l across the answering end of thecorcl, and 2"F39 represents a ringingkey of the usual t-vpe adapted when actuated to connerater circuit -30' to the calllac-3r. These list ing and be replaced by automatic hich will at the proper tunes I'ln I understood. The shaft N is cc stautly rotating, carrying :t selectors. 'll contemplate (l lilr cait hut 'ihution 0.. lnisiness this number of cords can for each lamp connected from its back contact to llt will he understood that l have spoken practice they are. As shown ground o t 4/ recs may be combined into operators set and the- 'ation of my improved system.

instead of twelve pairs of cords and plugs there will only need to be ten, and perhaps less. For each operator, then, wemay assume there are ten of the selectors, which in an exchange of 5,000, would mean .500 selectors. Each selector preferably has 100 line contacts or pairs 0'-o, over which its arm sweeps. If the same lines were multiplied to the same contacts in all the ten selectors on one position of the boarrhthat is it all the lines were located just as they now are, with their answering terminals before the same operator for a given number, and that operator only, the gain would not be so great from my invention. Since each selector has 100 lines on its bank, however, selectors will afford one connection each for the entire 5,000 lines, and 500 selectors will enable the lines to have ten multiple terminals each. Instead of multiplying them on their own positions,- I distribute these multiples of each line among ten dillerent operators. In other Words, as in the figure, the wire 13 is carried to the contact 0 of selector 0, which we will assume is associated with position number 1, then to contact 0 of selector G which We will assume is associated With position number .2, and so on. This line will then have a multiple in each of ten selectors associated with each of ten positions or each. oi ten operators. Instead of carrying the multiples down to selectors 1, 2, etc, in order, the Wires may be multiplied from position 1 to position 3, thence to position 5, or to 2, l, 6, or in fact in anyorder that when all the lines are finally multiplied will give a fairly uniform distribution. The notches or sockets 0 of the various selector arms in the common. shaft are set helically to each other or if they are all set straight along the shaft the line contacts are connected helically, so that only one arm will make contact with the same line contact at the same instant. As a line is multipled ten 1.. I times, or to tenselector switches, it follows that the ten notches of these ten switches must be set around the shaft step b y step, so that the arms will project like the steps of a winding stairway, in a helix. Thus when a line calls only one selector will touch it at once. Otherwise several or all the ten might connect with the same line and interfere. If it he desired to have the selectors all one sided, that is with their notches all in a line, the line Wire 13 must be connected to contact number 1 in the first selector, to contact number 2yin the next selector, to contact number '3 in the neikt,and so on. This achieves the samezend, but it should'be observed that it is preferable to carry around the notches, because thenthe shaft is bal anced in its rotation, since the arms will for If thearinsare all on one line, the shaft.

will need strong and heavy bearings, particularly if it is to rotate with any speed, which is desirable in order to cut down the time of reaching a calling line. 5 way' of reaching a balance for the shaft is to make the arms double, that is extending out on each side of the shaft, with two solenoids, two contacts 0, etc., for each sleeve 0. The contact banks 01, instead of being circular may then be semi-circular, lying all on one side of the shaft as is shown in Fig.2. The sweep over the contacts will be continuous as before, because one arm of a pair will-be leaving the bank on one side on its rotation when the other arm is just coming on. The radius of the circle is increased by this arrangement, but an .advantage is that the shaft and its connections are exposed and any contact bank can be removed bodily. I

In addition to the helical arrangement of contacts or arms, I may practise various methods of distributing the line contacts to gain perfect equality of load on all the operators. It will be observed that the 100 lines that appear on the same selector in number 1 position according to the arrangement I have outlined heretofore might appear together at each position where they had multiples. An'operato'r would thus be limited to 1,000 lines for her selective portion of the entire number, and the ten operators who had a given thousand linesthus apportioned to them as their complement would assist each other but no operators beside. Their load would be averaged .among themselves, and if their 1000 lines all got busy at once the rest of the exchange might be idle and it would avail them nothin In order to avoid this, a further distri ution scheme which is shown in Fig. 3 is thisz-Assume lines to be connected on number one selector of number one position (1P of Fig. 3) in serial" order, that is 1 ,2, 3, and so on. Line number 1 would go to contact number 2 in selector number 2 on position number 2, to contact number 3, selector number 3,-position number 3, and so on. Line number 2 would go to contact number 2 in selector number 1 of position number 1, thence to contact number 3 in selector number 3 'of position number 2. Line number 3 would go to contact number 3 in selector number 1 of position number 1, thence to contact number 4 in selector num-v ber 4 of position number 2, and so on. By this means, or by means of any equivalent arrangement, the even multiplying of the first 100 lines is broken and the lines distributed operators but only two lines would go to Another as to their potential calls among practically the same operator more than once. In a ten thousand line exchange with this arrangement and. the same decimal provision, since there would be 100 operators, each operator would have 1000 lines on her selectors, but they would be compounded of groups of ten, one group from each other operator, or one from each selector in the exchange. Thus no two lines need to be associated on the same position more than once;

The multiple connection of the contacts and the armature closing circuit 1113, the

otential of the test contacts 0 of the line in all the selectors to which it is connected is raised. .The first selector whose arm con tact 0 comes on the live terminal 0' picks up the line. -As soon as contact 0 touches contact 0, current passes form battery by the following circuit: B, 12, 11, Z, 13, 0, o 43, 0, 50, 48, 44, ground, B. The solenoid being thus-energized, core 0 is at once pulled into the tube, withdrawing its end from the notch 0 and freeing the arm from the shaft which continues to rotate. At the same time the plug end o of the core is pushed forcibly into the jack opening in the sleeve ring 0 and between the spring teeth 00, spreading them apart against the line contacts 0 -0 of the calling line; The instant this occurs, current finds a new path from the battery as follows: B, 12, 18, 17, R 20, 10, 0, 0 8, 6, M, ground, B. This energizes the relay R and the cut-off relay M, which immediately pulls up its armatures and disconnects the line relay L, connecting the line wires 1 and 2 at the same time to the wires 5 and 6 whence they are connected through 7 and 8 to o -o to 0 -0, to 9-10. Current from battery B now flows to line through the conductors 9-10 and the relays R and R. The latter immediately pulls up, closing the battery circuit as follows: B, 18, 17,16, 15, 14, inner winding of o, 45, and ground to B. This holds up the core of the solenoid before it has time to withdraw, being rather sluggish in its action. The i'nagnet L is of course cut off as soon as plug 0 is in, and the potential of the contacts 0 is dropped to normal, so that mother arms will stop thereon. A branch.of the last circuit is from armature grounded through the wire 46 which'whcn pulled up will close upon acontact 47 connected to the winding andwill thereafter hold itself up as long as the plug circuit is in use and the plug in the 1ack. The operator, perceiving the signal, comes in on the cord through the key 31-32 and getsthe number wanted. She tests the line with the tip of plug P in theusual way," and. completes the connection, by inserting the plugin one of the multiple jacks JJ' which happens'to be within her reach. As

soon as this plug is in the jack the relay R gets current by the following path: B, 18,

23, R 22, 2%),27, p, j, 38, cut-0E relay and ground back to battery. The cut-ofi relay of the called line is thus energized and pulls up, put-tingthe linewires 4142 onto the jack wires 3'Y38, and the operator then I uses the calling key 2829 to ring the subscriloer A. The energization of relay R produces another and quite as important an I effect as that of supplying current through wire for the supervisory lamp S, which so'long as the called subscriber does not an-.

'swer remains illuminated. I refer/co the removal of the ground from wire 48. This is necesary for two reasons The lamp S having performed its only function when it called the operators attention to the call,

must now be removed from operative connection, and the ground must be t; ken oif the solenoid 0 to. prevent its coming back on the same line for a recall and before the operator has had time to remove the plug P of the original connection. This will appear in a moment'more clearly. The sub-' scriber A having answered and the subscribers having finished their conversation, suppose A hangs upfirst, and A keeps hisreceiver down for a recall. The operator pulls the plug" P, relay R loses current and lets go, the ground comes back on lamp S and it lights, whereupon the operator comes in on'the cord again bykey 3132 for instruction. As the operator does not receive a signal from A when he hangs up, he may.

the solenoid core.

again it starts to rotate as before. it will be observed that the heel of the lunger will ride on the surface of the shaft until the notch comes opposite. This always positions the sleeve and arm correctly. It should be here remarked that the notch '0 may be replaced by a projection or stud, which will push the arm around by catching the endof the plunger! In such case the sleeve 0 should have 'a groove to permit the free passage of the stud under the end of the tube carrying the solenoid. The selector will not again pick up a calling line after such disconnection as just noted, until the plug P has been again disengaged from the jack J. The reason for this is that the relay R3 letting go its armature only when the plug is pulled, the ground. is oil the solenoid until that happens. Even if by accident. however, the same or another line should come back on the selector, the relay R has also lost its ground and would not hold up This latter precaution is not a necessity, however, as the likelihood of the selector picking up a line without a ground on the solenoid is very little.

Suppose A hangs up first and A is care less and does not follow suit. lets go, and the selector is released as before, but it remains idly. rotating until A" ha hung up and the operator has pulled t plug P. A, in the meantime, can go aheao. and make other calls, getting on other selectors by so doing. When A finally l g" the operator can disconnect in I manner. If she notes a conne io 3 ing for too long a time she ca listen in or break it.- It is thus impossiole for sutscriber A. or the called subscriber of'a pair to hang up the calling subscriber."B15. my system, however, it is equally impossible for the called subscriber to be hung up. Suppose A fails to clear out. The moment A restores his receiver to the hook his supervisory lamp S lights and the operator knows she is to pull the plug. The instant she pulls the plug the lamp S will light if A has his receiver down, and she cah deal with him in the usual way.

Having thus described my inventiotc, what I claim and desire to secure by Letters Patent of the United States is:

1. In a telephone exchange system; a pluhaving its answering end terminating in an automatic selector switch and its calling and terminating in a plug, answering terminals fortwo or more of the subscribers lines iri said selector switch but normally disconnected from the cord circuit subscribers line, together with means associated with the said terminais or the selector switch adapted-to be brought under the The relay It terminals thereof, and a spring ackor acks for each .rality of subscribers? lines, a cord circuit inc-2.1. a

a calling line in the act of calling. to

thereu on initially effect connection of said line tirough the said switch with the cord circuit, and a signal becoming operative upon the completion of said connection, and remaining operative throughout the continuance of said connection, substantially as described.

3. In a telephone exchange system, a plurality of subscribers lines and a cord circuit for interconnecting them terminating at its calling end in a plug and at its answering end in an automatic selector switch com- 7 prising the following instrumentalities: a

constantly rotating shaft carrying an arm, a series of contacts each connected to a subscriber's line, an associated common contact for the cord adapted to be brought into con nection with any line contact by said arm, a calling contact in said switch for each line and associated. with its line contact, and means associated with the arm and shaft cooperating with the calling contacts to stop the arm and connect the terminals of a calling line to the cord terminal or terminals, substantially as described.

4. In a selector switch for cord circuits a constantly rotating shaft, a sleeve detachably connected to rotate therewith, a tubular arm on saidsleeve and carrying a solenoid winding, a movable core within the tube having its end controlling the engagement of the sleeve and shaft, and cont-acts in the switch cooperating with the tubular arm, substantially as described.

5. in a selector switch a constantly rotating shaft, a tubular arm carrying a solenoid .upon it and a reciprocating core therefor within it, a clutch between the arm and shaft at one end of thc core and a plug at the other end, and a series of contacts cooperating with said plug, described.

6. In a selector switch for telephone systems a constantly rotating shaft, a sleeve thereon, a tubular arm on said sleeve having a solenoid winding upon it and a reciprocating core within it, a clutch controlling the engagement of the sleeve and shaft at one end of the core and a plug at the other end,.a circular series of line contacts and a substantially as tel-connection calling contact associated with each, a sweeping switch contact connected with the sole noid and said contact to bring the solenoid successively under control of the several lines through the several calling contacts, substantially as described.

7. In a semi-automatic telephone exchange circuit, a line circuit, a relay therefor with a source of current supply, a constantly driven selector switch mechanism having :1 traveling plunger and being connected with a plug terminal, and means whereby said line relay may control the switch mechanism to stop the plunger and thus produce conneetion with the line when calling, substantially as described.

l 8. In a telephone exchange system, a plurality of line circuits each having a line rc lay, one or more connection jacks and a plurality of multiple answering jacks, together with plugs automatically controllcd by the line relays for making connection with said answering jacks in response to calls, suhstantially as described.

9. In a telephone exchange system, a plurality of line circuits terminating in multi- V ple answering jacks, a constantly d rivcn connective device provided with a plunger and arranged to force the latter into a jack of a calling line on the closing of the subscribers line circuit.

10. In a telephone exchange system, a plurality of line circuits provided with multiplcd answering jacks and having one or more connection terminals, an opcratofis cord circuit and a constantly driven conned tive device associated therewith and provided with a movable plunger adapted to be forced into the answering jack of a calling line on the closing of the Sll JSCIllJGI S line circuit.

11. In a telephone exchange system, a plurality of lines to be intcrconucctcd, a plurality of link circuits for effecting said inand including a line seeking switch at one end having test terminals for the lines and a test relay associated there with and adapted to stop the switch at any given line, a battery supply relay at the calling end of said link, an energizingcircuit therefor completcd upon connect u made to the called line, said test relay having lost circuits completed initially through said test terminals and through a contact under control of the said battery supply relay, whereby the circuit of said lest relay is opened vihen connection with the called line is made.

12. In a telephone exchange system, a plurality of lines to be intcrconncetcd, a corn nocting link therefor having a line seeking switch at one end thereof containing a plurality of line terminals together with to operating link terminals adapted to be con-- nected dir ctly therewith but normally con tinnously disconnected therefrom during" travel of the switch, and means responds to a call over any line to ct connection of the said link terminals with the answering terminals of the line when the calling line is IQ'z'LC-llifl. A telephone enchsnge s stern comprising a plurality of subscribers lines to he interconneeted, connecting link therefor havingfs line se -king switch at one end including p urality of line terminals together with. coofoeretin'g link terminals normally disconnected therefrom. in travel but adapt ed to be connected directly therewith, line t'ost terminals also in said switch, as Wiper therefor, and means controlled through said test terminals and Wiper and responsive to at call over any line to etlect the aforesaid connection of the link terminals with the answering terminals of the calling line, when said calling line isreeched.

14:. in :1 telephone exchange system, rzility of subscribers lines to be. it i nested, a link circuit for ciiecting said int-en connection having a line seeking sv 'tch at one end thereof, means for actuating said switch, means associated with the link and controlled from any calling line to stop the switch in connection with any calling line, and a tip relay for the link, togetiier with holding means for said switch in its actu ated positions controlled by the said tip re: lay of the link independently of connection a plue conv "with culled lines.

15. in a telephone exchange s ystein, e. pln raf'y of: subscribers lines to be interconnected, link circuit for electing said interconnection having a. line seeking switch at one end thereof, means for actuating said snitch, moons nssociatetl with the link and controlled from any calling line to stop the switch in connection with any calling line, and a tip relay for the link, together with means governing the release of the line seeker from the calling line controlled by the said tip relay of the link independently of connection with czilledlincs. I

In a telephone exchange system, a nlurnlity of lines to be interconnected, a link containing an automatic line seeking switch for effecting said interconnection, nieans controlled from-celling lines to cause said switch to seek and make connection of the linlt with calling line, a tip battery supply relay on the answering end of said linlr energized through the line seeking switch, and retaining means for said switch in its ectnated positions cont-rolled exclusively said battery supply relay.

1?. in a telephone exchange system, a pinrality of lines to he interconnected, :1v connecting link containing an automatic switch, actuating {nee s for the switch, it tip hetsnpply relay energized from the sub lines through said automatic switch line controlled ilhu: the switch i ositio 5 controlled iii-xi oi lUSWSlV by sen lj'tiik relity to. interconnected, circuit for interconnecting the coi ing an entonmtic line IRA, g switch, battery supply relays at the answering and ceiling endsot said link respectively, sczuating means for said switch, means to c said switch connection with any over circuit including normally closed contacts of the s the calling id of said linli, i. L the flIISWQI'l' end or link, and i I in sctnat A b for retaining said s tions controlled through normally con-- tact-s of said ti; relay.

l9, Tn a telephone exchange system, a pin relityot lines to be interconnected, :1 link cil-:- cnit for interconnecting the same containing an automatic line seeking switch, sleeve oat tery sn ply relays at the answer calling ends of the said link respe actuating means for said switch, means to stop said switch in connection with any given line content 1 the circuit including normally closed contacts; on the sleeve relay of the calling end of-ssiid link, a, tip relay at the answering end of said link, and means to retain said switch in any actuated position controlled jointly by norm ally open contacts on said sleeve and tip relays of the answering end of said link,

20, in e telephone exclr rslity of lines to he in? containing an automatic switc connecting them, actuating n switch, means under control scrihers linesto bring said sv. it connection with any calling line, lain; remaining lighted (lifl of rest of said 'VltCl in connetton W line 4 21. in s telephone exch system, plurs-lit of lines to he interconnected, link containing an automatic switch for eilecting said interconnect-ion,actuating iii-eons for said switch, a battery supply relay If" gized through said switch from the s scribers line, together with retaining some for said switch in its actuated p s in, a pilot lamp remaining lighted dnrii no pe iod rest of said switch in corn? with any inc, controlled in common by seid battery snnply relay.

in atclephone exchang of subscribers lines, i an actor itllC switch for otter nec'tionbetween said lines. C1 prising e. i'iorriially co plug and plurali; I adaptedo he longit' l relay of I ing winding for said plug controlled from means controlled from the calling line to eflect association of said movable and fixed elements to. make connection of any line with said link, and means also controlled from the calling line to retain said elements in the aforesaid connective association during the continuance of any call.

In testimony whereof I aflix my signature in presence of two witnesses.

. EDXVARD E. CLEMENT. Witnesses:

ALEXANDER S. STEWART,

JAMES H. Mann.

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