US1127467A - Telephone-exchange system. - Google Patents

Description

F. R. MGBERTY.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 3. 1911 Patented Feb 9, 1915.

7 sums-SHEET 1. I

m. W n v k a H r W W/fnesses F. R. MGBERTY.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED N013, 1911.

Patented Feb. 9, 1915.

7 SHEETS-SHEET 2.

4 Thou 0d P. R. MGBERTY.

TELEPHONE EXCHANGE SYSTEM.-

APPLICATION FILED N013 1911.

1,1??36? Patented Feb.9,1915.

7 SHEETS-SHEBT 34 WW Fran/r R. M- 54/1 y.

P. R. MCBERTY.

TELEPHONE EXCHANGE SYSTEM APPLICATION FILED NOV. 3. 1911.

Patented Feb. 9, 1915.

7 SHEETS-SHEET 4.

Fig. 5-

Fran/r //7 van/0r.-

A. M- emy F. R. MOBERTY.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 3,1911, V V .7 1,127,467.- Patented Feb. 9, 1915.

F. R. MOBBRTY. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 3,1911.

vi l Ms. W mm W A 9 i W Fm WM. m W m7 k m H m a r y b Wi/nesses:

P. R. MOBERTY- TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 3, 1911.

Patented Fb. 9, 1915.

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Mia/medial? P5} W/fnesses:

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To (ill whom it may concern mam: n MQBERTY, or new ROCHELLE, new loan, Assmnon r0 WESTERN ELECTRIC- oomranv or new roux, N. 2;, a conronarron or ILLINOIS,

TELEPHONE-EXCHANGE SYSTEM.

Be it known that LI'FRANK R. MCBERTY, citizen of the United States, residing at New Rochelle, in the county of lVestchester and State of New York, have invented a certain new and useful Improvement in Telephone-Exchange Systems, of which thefollowing is in full, clear, concise, and exact description.

represents a further development of the invention disclosed inimy application Serial No. 418,123, filed February 2-7, 1908, and

contains many features in common therewith, the present application being; filed as a continuation of and a substitute for my aforementioned application w1th respect to several of these common features.

In accordance with the embodiment of 'my invention which I have herein illustrated, and which I shall describe, the subsuch 'a manner that a call for connection operates a signal that attracts the attention of the operator. The operator is provided with switching means for putting herself into communication with the calling subscriber and ascertaining his wants; and also {with-connecting means through which the line of the calling subscriber may be entend ed'to a circuit over which his line-withoutanyffurther effort on his part, and without requiring the servlces of another operator maybe brought into connection with the par-ticul'a rline for which he is calling.

1 The circuit over which connection with the'called line establishedin accordance with my inventionfisprovided with an automatic switcher selector which has access to connection terminals of the line with we wh is which connection I is desired Specification of Letters Patent.

. Patented Feb.9,1915.

Application filed November 3, 1911. SerialNo, 658,291.-

under the control of a calling or sending 'de{ vice adapted to be manipulated by the operator who answers the subscribers call. Upon receivingthe call'ofthe callingaflsflbscriber the operator sets the'calling device with which she-isiprovidedgfand when she has completed connectiomwith the trunk line extending to the group in which the called line is included, the automatic switch at the other end of the trunk operates under,

the control oftheflcalling device to select and establish connection with the particu:

lar line with which connection is desired.

In the system. of this invention as preterablv organized, each subscribers line has multiple terminals upon each of a group of automatic'switches or final select0rs by which-connection is made to the line fromot-her lines; and connection switches are provided at the tientral oilice whereby. any line when callinsl may be united with one of a number of operators connecting air- .cuits by which the call may be answered. Each'..operator will have a number'of such connecting circuits, any oneof which may be united with any calling line of the group assignedlto that operator. I

So-far as manyv of the featuresof the present invention are concerned, any desired means may be employed for bringing a call ing line into connection with an operators connecting circuit, in order that-the operator may answer the call. In the particular system to be described, each subscribers line has an answeringspringiack and line signal as" in the manual system, appearing before one ,of the central-Iofiice operators and the operators connectingfcircuits' comprise fiexible cord conductors terminating eachin an answering'plug of theius uallfype, adapted for insertion in the sprin gjacks dfi calling lines.

.95 Likewise, there are prefer ably located at each of the operators posi-",

tions sprina'iacks. forming'the terminals of;

trunks to other ofiices, the flexible cord con: ductors being each also provided with a {callj ing or trunk plug of the usual type adapted for insertion in any of the-springi k f r extend the connecting circuit. Each trunk springiack at an operators position constitutes theterminal either; (1)

which is a final selectori or (2) of an o erw :trea

h of a direct; jtrunk extending to a direct trunk sw tch I entending to, an overflow,

' preferably a set of number keys, which may plugs into the jack of the calling subscriber be "similar in arrangement to the keys of an adding machine and which may be set in the combinations required to represent any line number of'the system. Thus the operator and throws the listening key as in standard practice. Obtaining the number of the 45 having direct accesstb the same five hun-.

party wanted, she presses the keys of the number as a received. She then takes the calling plug of the cord circuit which she has used for answering and inserts it in the jack is not already in use.

jack of the direct trunk which represents the group of selectors to which the line of theparty wanted is multiplied in case such If she cannot thusdirectly connect to the final selector, she will plug into the springjack of an overi flow trunk. The sending apparatus will in either case proceed automatically witha series of controlling operations, which will bring about the successive selections required toextend the circuit to the line represented by the keys depressed.

' to which it belongs.

In an exchangeof ten thousand lines capacity, the lines may be divided into, for example, twenty groups of five hundred lines each; so that the final selectors would be 500-line'machines, each line beingmulti- .plied to a. number of final selectors sufiicient to handle the incoming calls for the group Connection may thus be madeto' the line by any one of the group i of final selectors upon which the line is mu].-

tiplied, each final selector of a. given group dred' lines.

Referring to the accompanying drawings-Figure 1 isa schematic view illustrating my invention as particularly adapted for use in large cities where each exchange may comprise, for example, ten thousand lines, a large number of such exchanges" being connected by interoffice trunk lines. Fig. 2 shows my invention as applied to direct trunks connecting two exchanges only, the overflow selector inythis case being shown as located at the exchange at which the line of the calling subscriber terminates. Figs. 3 and 4 placed side by side form a complete diagram of the keys and sending or calling mechanism, Fig. 3.

together with a portion'of Fig. 3,.represent-. ing one form of sending or calling apparatus adapted to govern the various selecting operations under the. control of the keys shown in Fig. 3. Fig. 5 represents the callin subscribers line and the o erators cord circuit. Fig. 6 represents the overflow trunk and selector. Fig. 7 represents a direct trunk and its final selector to which the circuit may be extended by the overflow selector. Fig. 8 represents a number of subscribers lines to which the final selector may make direct connection. Figs. 5 to 8 when placed together edge to edge form a complete diagram, the lines which continue to the edge of .one sheet being continued on the next sheet, the-lines from the cord circuit of Fig. 5 leadingto the sender circuit of Fig. 3. Figs. 3 to 8 inclusive illustrate the circuits and apparatus involved in extending a connection from the calling line i to a line called for.

The same reference letters indicate corresponding parts wherever shown.

General plan of system-When any one of the operators connecting circuits is put into service to answer a call, the sending apparatus is automatically appropriated to the i use of that connecting circuit; anda controlling or stepping circuit is established between a controlling relay at the selector and a magnet at the sender which is adapted to operate a step-by-step mechanism. Means Y are provided for transmitting electrical impulses over this stepping circuit, and for operating the selector and the stepping mechanism at the sender in unisonthere with. The-advance of the stepping mechanism at the sender in unison with the impulses transmitted over the stepping circuit furnishesa means for measuring off at the sender the exact extent of operation of the distant selector; and when a predetermined number of impulses have been transmitted, as indicated by the advance of the sender stepping mechanism to apredetermined point, the stepping circuit may be automatically opened, bringing that particular selecting operation to an end, after which another selection may be made in the same way. In case the operator plugs into a direct trunk jack, the connection to the called line is eiiected through a single or final selector. .In'case she plugs into an overflow trunk, the connection is established through both an overflowswitch, which is a first selector, and then through a final selector. In the former case, the final selector, and the latter case each-selector in the train through which the circuit is successively-ex- \12' tended,-is, asi it is reached, brought under" control of the sending apparatus by the establishment of the selecting circuit, which includes a controlling relay ormagnet at the. selector and a relay or magnet at the 130 Lil-whee? machanism, the particular pair of terminals required for determining the successive selecting operations being chosen by keys which are depressed by the operator. In the particular system shown, there are four rows of ten keys each, numbered from 0 to 9 inclusive, the first row representing thousands, the second row hundreds, the third tens and the fourth units digits. A thousands key in combination with a hundreds key determines the level selection of an overflow switch; a hundreds key in combination with a tens key determines the level selection of a final switch; and a tens key in combination with a units key determines the line range selection of a final switch.

The sender or calling device comprises an arm having two brushes, an inner and :an outer brush, arranged to be advanced over a series ofinner and outer terminals by the stepping mechanism or escapement operated by the, stepping magnet which responds in" unisrn with the stepping impulses The terminals are in three divisions. Those in the first division determine the level selection of an overflow selector; those in the second division, the level selection of a final switch; and those in the third division the line range selection of a final switch. Each combination of keys, above set forth, is adapted when depressed to select a correksponding pair of terminalsin the present case by connecting one terminal of the pair to ground and the other to battery-and the finder brush upon reaching the pair of terminals so selected will complete a circuit for a stop relay. Thls relay in itsresponse breaks the circuit over which the stepping impulses are transmitted, so bringing the selecting operation to an end. The response of the stop relay also brings switching mechanism into action to prepare the sender for the next selection, and so on until the last selection has been made, whereupon the stop relay in its response causes switching mechanism to be actuated which will disconnect the sending apparatus from the circuit which has been established, leaving the calling line united through the operators connecting circuit and the selector or selectors, as the case may be, to, the line which has been selected. In the system shown, the impulses for measuring each selection are derived from a battery associated with the selector under control, and are produced by the action of interrupter contacts closed periodically in the advance of such selector,

which intermittently short-circuit the line.

Power is applied to the movable element the selector under control of a line relay,

which is in a portion of the stepping circuit nct shunted by the interrupter, and which is released when the circuit is opened by the stop relay at the sender.

The local controlling circuits at each selector and at the sending apparatus, which must be established in definite order at successive stzfes of the operation to bring into service d1 erent devices or parts as required, are

in the present system established by automatic switching appliances which I term sequence-switches.- switch for eachselector, and one for the sending or ealling'apparatus. The sequenceswitch consists in its elements of a movable switch-operating member, a number of circuit-changers or switches actuated in se-' quence 'as said member is moved from one position to another, an electromagnet, and motor mechanism operated or controlled by said magnet for advancing said movable, member. v

The sequence-switch may control any desired sequence of operations, whether of the same or of different devices. In each posi-r tion' to which its movable member is ad-. vanced a circuit is established whereby a given operation of the device under control There is a sequenceis made possible, and at the same time another circuit is established, whereby the moj.

tor magnet of the sequence-switch may be actuated automatically when such operation of the device under control has been coinpleted; so that as each operation takes place, the sequence-switch .will be automatically advanced to a succeeding position, in which a new'operation or another stage of the same operation will be brought about, and so on. Fmally, the sequence-switchestablishes a condition whereby the apparatus under control is returned to its normal con- Y dition, and also establishes a circuit whereby the sequence-switch itself will be returned to normal.

Referring to Fig. 1 attention is directed i to the fact that in the particular system shown, the operations performed intransmitting a call received from the subscriber U may be: first, the operator plugs into the jack w of a direct trunk 17 leading to a final selector at the distant oliice; and, second, the selection by the chosen final selector of the subscrlbers line U wanted. r as an alternative, the operations required in transmitting a call may be: first, the operator plugs into the jack 7 of an overflow trunk y leading to an overflow selector 7 second, the selection by the overflow selector of an idle trunk of a group of direct trunks m each terminating at one end in a final switch" p at the distantoiiice and at the other end in a spring ack m at still another distant office, said trunks 29 being also multiplied to terminals of the overflow selector; and third, the selection, by the final selector m of tlje fdire'ct trunk chosen, of the subscribers line U wanted.

f In Fig. 2, an embodiment of the invention is schematically shown in which two exchanges are connected by a number of interoflice trunks w, m? terminating in springjacks 21: before two different operators in one exchange and in final selectors at the other exchange, the called for subscribers line U at the latter exchange being multipled to final selectors which are represented before .both operators at .the former exfinal switch representing the called for subscriber to be busy, she will plug into an 'overflow jack in order to take for use some other trunk leading to a final switch representing the same subscriber.

While I have thus shown interoifice trunks terminating at one otfice in a springjack and at the other olfice in a final selector or switch, it is not to be understood that my invention is so limited with respect tocertain of its features, the overflow trunkfeature being applicable to trunks of telephone systems in general with a view to trunk economy. Thus, to handle the maximum traffic, ordinarily several times the number of trunks are provided that would suffice to handle the average tralfic. According to" my present invention it is necessary to provide only the number of regular trunks required to handle the average traffic, and in addition thereto a few extra or overflowtrunks to take care of the excess trafiic,

such arrangement" obviously reducing the 'total number of trunks required to handle the maximum traffic.

Mechanism of" selectors or connector switches.The mechanism of the overflow switch or selector, shown diagrammatically in Fig. 6 and of the final selector shown diagrammatically in Fig. 7, may be, for example, in general substantially that of the selectors shown and described and shown in my British Patent No. 20,839 of Septemfmitting deviceof the selector forms the sub- .1

her 11,1908; and hence a detailed description of theconstruetion and mode of operation of the selector mechanism is deemed unnecessary. 'Moreover, the power trans- *j ect matter ,of-my United States Letters Pat cut No.922,802, granted May 25, 1909. Certain otherfeatures of the mechanism ofthe' selector form's'the subject matter of my copendingapplication for Letters Patent of the United States, Serial No; 418,126, filed Februaryf27, 1908. It should be noted,

however, that the overflow selector shown in Fig.- 6 1s provided with twov interrupter levers orcontact devices, 167 and 167", the

key below No. 5 is depressed, as will be morefully set forth hereinafter in connection with the .description of thecircuit arrangements employed.

' An overflow selector in the system shown and described can select one of twenty different groups of final selectors, each of the final selectors having-a capacity of 500 lines.

selector can assist in the selection of any one of the ten thousand subscribers lines which terminate in said twenty dilferent groups of final selectors.

In the final selector each'level represents fifty subscribers. Level No. 0, for example,

of the first group of selectors represents subscribers No. 0 to 49, level No. 9 of the same selectors subscribers No. 450 to 499, level No. 0 of the second group of selectors representing subscribers N o. 500 to 549, level No.

9 of these latter selectors representing subscribers No. 950 to 999, and so forth, there being, as before stated, twenty different groups of final switches for a 10,000 line exchange. I

In the overflow selector each level represents1000 subscribers, level No. 0 representing subscribers N0. 0 to 499, and subscribers No. 5000 to 5499; level No. 2 subscribers No.

500 to 999 and No. 5500 to 5999; and so forth, level No. 9 representing subscribers No. 4500 to 4999 and No. 9500 to 9999. In the overflow switch or selector the terminals of each level are'connected to final switches as follows: Terminals No. 1, 3, 5, 7 and 9 of a given level are connected to final switches serving the same 500 subscribers, and terminals No. 2, 4, 6, 8' and 10 of the same level are connected to other final selectors serving another group of 500 subscribers, each level thus, as before stated, representing a thousand subscribers. For example, in level No. 9 of the overflow switch, terminals 1, 3, 5,etc., are connected to final switches serving subscribers No. 4500 to 4999, and terminals No. 2, 4, etc., are connected to switches serving subscribers N0. 9500 to 9999.

Each final selector can thus select any one of 500-subscribers lines and each overflow.

As before stated, the overflow switch has meme? .the other for subscribers below No. 5000. The operation of these two interrupters may be understood by reference to Fig. 6. The lower toothed segment over which the lower interrupter lever 167 travels has as usual ten teeth which transmit impulses for the level selection of the final switch, the lever 167 being used for this purpose-irrespective of whether or not the number of the line wanted is below or above 5000. Then comes the usual long tooth, followed by teeth which are in staggered relation with corresponding teeth on the segment over which the upper interrupter lever 16'? travels. In short every other tooth for trunk hunting, all of which would ordinarily be in the path of the lever 167, is placed upon an upper segment in the path of the upper lever 167*. As before stated, which of these two levers is active for trunk hunting is determined by the level relay 170, for while a tripped brush contacts with all the terminals of the level over which it passes, every other one only of said terminals has at the time of contact a circuit therefor closed through the contacts of an active interrupter, the circuit through the contacts of the other interrupter being opened at the .contacts of the level relay. Thus in hunting for a final switch representing a subscribers number below 5000, the brushes will test only terminals No. 1, 3, 5, 7 and 9 and will pass over without testing or interfering with terminals No. 2, 4, 6, 8 and 10 which represent a different group of final selectors.

In the particular system shown in the drawings, each selector is intended thus to se ect any one of 500 sets of terminals, there being three terminals in each set, for the two lines and the test conductor, respectively, of a telephone circuit. Each selector will thereforebe considered to have thirty brushes, ten sets of three each, and five hundred sets of three stationary terminals each arranged in ten levels corresponding to the ten sets of brushes. For simplicity in the diagram, there are shown only two sets of brushes and a few of the contact terminals inthe two corresponding levels.

. Mechanism. of sender or calling dem'ce.-'- The mechanism of thesending or calling apparatus may be as shown diagrammatically in Figs. 3 and 4. A pair of contact brushes 201, 201 are mounted at the extremity of an arm 211 carried by a rotary shaft or spindle 202, said brushes being arranged to wipe over two concentric circular ranges of stationary contact terminals 203. 203, which are mounted one above the other, (shown dia grammatically in Fig. 4, and hereinafter referred to as one outside the other), in a suitable insulating support surrounding the shaft 202. The brushes 201, 201, are electrically united, so that they will serve to connect a terminal 203* of the outer range to the corresponding terminal 203 of-the inner range, at any point'around the circle. In other words, whenever the brush 201 is in contact with a'terminal 203 at any point in the outer range of terminals, the corresponding terminal 203 in the inner-range will be electrically connected to such outer terminal through the brushes 201, 201; The normal position of the rotary arm is indicated diagrammatically in Fig. 4that is at 8 one step back of the first pair of terminals in the division which is used for controlling selections of the trunk selector.

The electrical connections of the stationary terminals in the outer and inner ranges 203, 203, are indicated diagrammatica ly in Figs. 3, and 4. Said terminals are arranged in three divisions which are traversed successively by the finder brushes 201, 201 as the arm 211 makes a complete revolution, That is to say, beginning with the no mal position of thebrushes. there is first a division which may be called the overflow division, comprising ten. pairs of terminals which are used in controlling the brushthen a pair of dead terminals; then a pair of term nals represent ng a secondary start-- ing position 8 for the brushes, prelim nary to the direct trunk division: then the, direct trunk division compris ng ten pairs of terminals used for controlling the brush-choosing act on. of the final selector; then a pair of dead term nals: then a pair of terminals representing the starting, position a for the b ushes prelim nary to the line range selection that is the rotary selective action of the final selector. division there are dead term nals; and at the beginn ng of each division there is an extra pair of inner and outer term nals 8 s",- a respectively, representing a starting position for the brushes. prelim narv to their entrv upon such divis on. start ng pos t on 8 of the finder brushes 201, 201. and in the second and third starting positions 8 8 thereof the finder brushes The brush-carrier arm 211- 18 adapted to i be rotated step-by-step around the annular In the normal bank of stat onary terminals, bv the action of an escauement which controls a train of gears. the brushes being caused to step from term nal to term nal at each com lete vibration of the pallet 204. The motive power for rotating the brush-carrier shaft 202 may be furnished bv a co led spring 208 act ng upon a gear wheel 207 wh ch meshes with ano her gear wheel 206 fixed upon said shaft 202. The pallet 204 of the escapement is mounted upon an arbor which also carries t e armature 215 of an electromagnet 205. This step magnet 205 is in a local circuit controlled by a stepping relay 21 8, which g 55 1 trolled at a back contact 249 of a relav 250,

- responds to the selecting impulses transinitted over the controlling circuit by the action of the interrupter of the distant se-' lector under control.

The rotary brush-carrier shaft 202 of the sender carries a cam 222 which is adapted to close contacts 223, 224 while the brushes 201,

201 are traversing the terminals of each division;.said contact being open when the brushes rest in thestarting positions prelim nary to the respective divisions.

The coiled spring 208 which drives the gear train to rotate the brush carrier under control of-the escapement may be automati- "tion of the brush carrier.

, up said spring 208. The driving roller 213 is continuouslv rotated by a power shaft 211; and a clutch magnet 214-is ada ted when excitedto magnetive said roller 213 to attract the iron plate 212 into'engagement with said roller. A pawl 216'is adapted to engage a notch in the edgeof the plate 212. I to hold the latter against reverse. rotation,

when the clutch magnet 214 is denergized. Said pawl 216 is arranged to close a contact 215 whenever the disk 212 has been rotated awav from its normal position; said contact 215 being emplo ed to close a local circuit for the clutch magnet 214. to maintain said magnet excited (when it has once been en-' e gized) until the disk 212 has made a-complete rotation.- The spring20'i thus starts when the cam Q of the sequence switch, in positions 2. 3-and 4. closes the circuit of clutch magnet .214, and it continues to wind for one revolut on under the power of the clutch-magnet 214, the circuit of which is continued bv the pawl 216 riding'on the c rcumference of the power driven plate 212.

Upon this plate com leting the revolution the pawl 216 dro s into a notch in the periphery of the plate and the circuit of the magnet 214 is opened. The electrical connections of the sending a aratus mav be as sho n in Figs. 3'and 4 of the circuit d'ag am. The step ing magnet 905 is included in a circuit which is conthe circuit of which is-controlled by the stop relay 219. and at a front contact 247 ofthe step ing relav 218. Sa d stepping relay 218 is ada ted .to be included in a ste ping cir cu'it which also includes the line relay of the distant selector to be controlled; and said f stepping circuit is controlled bv a contact 246 of the'stop relay 219' at the sender. Said stop relay 219' is included in acircuit which is arranged to be completed by the finder brushes 201, 201, when said brushes contact with the pair of terminals 203, 203, which the operator has selected in each division by means of her keys. The stop relay 219 is also adapted in its response toclose a local circuit for the relay 250 which controls a local circuit for the stepping magnet 20 5','including aninterrupter 221, whereby the point finder may be independently advanced from the point at which it found the terminal grounded by the corresponding key, to the starting point 8 or s, as the case may-be, at the beginning of the next division of terminals; and after the last selecting operation the local circuitfrom the interrupter 221 is completed until the brush finder has traveled clear around to its original starting point .9 l

' A cam 222 carried bythe point finder shaft 202 is adapted to operate the contacts 223 and 224. Contact 223, as is clearly in-' dicated on the. drawings, is closed in all positions except when the shaft'is resting in the normal or starting position in which the brushes are in contact with the contact point a. In all other positions of the point finder shaft 202, eyen when the contact lever rests in one of the other notches shown upon the cam, which notches correspond to the subnormal or startin oints s s the contact 223 is closed through the wire 37 and interrupter 221 to ground. On the other hand, contact 224 is so arranged that it Willonly be closed when the contact lever rests upon the periphery'of the cam 222 and will be open Whenever the contact lever rests in any one of the notches cut in the periphery of such cam. The contact 224 controls a loc'al circuit for the stepping magnet 205 through the interrupter 221, and by opening, When I the finder brush reaches the starting points 8 s or s respectively, causes the finder brush to be arrested in such starting positions in the ordinary or usual o eration of the apparatus. The contact 223 also controls a local circuit for the stepping magnet 205 when, in an intermediate stage of the operation of the apparatus, an abnormal or knock-down operation takes place, and its utility is to assure the entire return of the apparatus to its normal position in case of any such abnormal or knock-down operas t1fon.

There IS a sequence switch associated with the sender, by which the stop relay 219 is brought successively under control of the finder brushes and the selected pairs of terminals in the different divisions of. the senderasaid sequence switch also performing other necessary circuit changes from time to time, as will hereafter bedescribed in detail. i

The connections of the keys with the sender terminals-By reference to Fig. 3, it

of the first division of the sender apparause? sition's, in a well-known manner.

adapted when depressed to close two con- Each key of the several rows of keys is tacts. i The right-hand contact of each of the thousands keys controls thecircuit of the key magnets K", K, K K The righthand contact of each of the thousands keys Nos- 5', 6, 7,8 and 9 also controls the cirthe overflow selector becomes active.

cuit of a relay C, which in turn determines, as will hereinafter be more fully described, which of the two interruptersTfif e left-hand contacts of thousands keys No.

I 0 and 5'controls the application of a ground connection to the first two inner terminals tus; the left-hand contacts of the keys No. 1 and 6 controls the application of a ground connection to the next two successive terminals of the sender; and so forth with respect to the remaining keys.

- The right-hand contact of each of the hundreds keys No. 0 to 4 inclusive controls the application of battery to outer terminals Nos. 0, 2, 4, 6 and 8 of the first division of the'sender terminals; and the right-hand contact of each of the hundreds keys No. 5 to 9 inclusive controls the application of battery to the remaining outer terminals of the first division of the sender terminals.

' The left-hand contact of hundreds keys No.

0 and 5 control the application of battery to the first two outer terminals of the second division of the sender terminals; the lefthand contacts of the hundreds keys 1 and 6 control the application of battery to the next two outer terminals; and so forth.

"keys No; 0 and 5 control the application .of a ground connection to the inner terminals No. 0. to 9 inclusive of the third division of sender terminals; the left-hand contacts f the tens keys 1 and 6 control I the application of a ground connection to the, inner terminals No. 10 to 19 inclusive 1 tens key ofthe sender terminals; and so forth with respect to the left-hand. contacts of the other The right-hand contact of the units keys No. 0 controls the application of battery to the outer terminals Nos. 0, 10, 20, 30 and 40 of the third division of the sender ter- I minals; the right-hand contact of the units key No. 1 controls the application of battery to the outer terminals Nos. 1, 11, 21, 31 and 41 of the same division; and so forth.

, The left-hand contact of each of theunits keys controls a local circuit which includes the key magnets K, K K K and the magnets D and C, the function of which latter magnets will hereinafter be set forth.

For the purpose of conveniently tracing the connections between the key contacts and the terminals of the sender, the various wires connecting the same have eachbeen numbered at two or more places, the numbers employed being 1 to 29 inclusive, the same number referring to the same wire.

Mechanism of sequence switches.-The mechanism of the sequence switches of the sender, the overflow selector and the final selector, respectively, maybe for example,

in gene a1 substantially that of the sequence switch. described and shown in my British Patent No.-20,839 of Septemberll, 1908; and hence a detailed description of the construction and mode of operation of the mechanism is deemed unnecessary, similar mechanism forming, moreover, the subjectmatter of my copending application for Letters Patent-of the United States, Serial No. 51,868, filed September 5, 1908.

In the circuit diagram herein, Figs. 3 to -7 inclusive, the switch springs of the sequence switches and the. operating cams therefor are not shown in their actual arrangement, but are so located as to give the clearest arrangement of circuits. The various positions of the cams of each sequence switch are indicated by numbers placed on the peripheryof said cams. It will be understood, however, that the mechanism of each of these sequence switches is substantially that disclosed in my aforementioned British patent. Referring, for example, to Figs. 3 and 4, it will be understood that the cams lettered J, K, L, M, N, O, P, Q, R, S, V and W are the switch operating cams and are mounted on the vertical rotary shaft of the sender sequence switch, said shaft being arranged to. be driven by power applied through the agency of a motor magnet 225, the rotation of the shaft and the cams carried thereby continuing as long as the motor magnet remains excited. The said cams J K, etc, are arranged to control circuits through the medium of switch springs, ac cording to the positions of said cams. tain of the switch springs may control circuits for the motor magnet225. A special cam I is also provided to control a local circuit for said motor magnet, whereby after the initial energizing circuit is broken by v one of the other switches, the motor magnet may still be exicted by current in the local of these .cams areinsulated and certain system-Briefly stated. the system in which v others. not insulated from the rotary shaft,

. as is indicated by the absence or the presence, respectively, of a ground connection at the cam.

In the operation of the sender sequence switch, the circuit for the motor magnet 225 will first be closed through the cam K. Then as the motor magnet is excited and the shaft of the sequence switch begins to rotate, the circuit through the cam K isbroken, but a local circuit will be continued for the motor magnet through the contact 226 closed by the special cam I, and the rotary element will thus continue to advance to a position determined by said special cam.

Further and detailed description of the operation of the several sequence switches will be given hereinafter in connection with the description of the operation of the system.

Brief statement of the operation of the the embodiment of my invention illustrated and described herein-is particularly designed tobe employed operates as follows: The act of the calling subscriber in taking his telephone ,for use displays at a central station switchboard a signal which leads the answering operator to complete connection with the calling line by inserting one of the plugs of a pair of connecting cords into a springjack associated with said signal. Upon this act of the operator, as in standard construction, the cut-off relay of the calling line is energized and the signal device (the line lamp) individual to this subscribers line is rendered inoperative. As will be hereinafter pointed out, this same operation of the cut-off relay and the consequent rendering inoperative of the signal device individual to such line takes place when a line selector selects and seizes the desired line. When the operator,having made connection with the calling line as described, haslearned the number of the line with which the call ing subscriber desired connection, she sets her calling device to correspond to thenumber of the desired line, inserts the other plug of the pair of connecting cords into the springjack of a direct trunk line extending to the group of lines of which the called line .is one, or else she inserts the plug in the springjack of an overflow trunk, thereby in either case bringing the calling device into operative relation with theautomatic switch at the other end of the trunk line. As soon as the calling device and automaticswitch mama? The automatic switch has a number of rows of stationary terminals wire$to the lines that terminate on the springjacks in the switchboard, and a number of movable terminals or brushes that are caused to pass over the stationary terminals in the movement of the switch, each movable terminal being arranged to pass over a particular row of stationary terv minals. While all of the movable terminals are connected with the trunk line, none of them is normally in condition to engage the terminals of the row over which it moves,

but the selector or switch is provided with mechanism that acts under the control of the calling device to select a particular one or groupof the movable terminals, and bring it into position to engage the stationary terminals of. its associated row. The

particular movable terminal selected depends upon the degree to which the movable term'inals-which all move togetherhave been displaced from their normal or resting position when the selecting mechanism opcrates; so, inasmuch asthe automatic switch controls the movement of the calling device so that they both move together, the operator, by setting the calling device, to produce, after a predetermined movement, a

current change that actuates the selectingmechanism, is able to bring about the operation of the selecting mechanism of the automatic switch at any predetermined point in its movement, and is thus able to select and make active any desired one or group of the movable terminals. The movement of the automatic switch is stopped by the operation of mechanism associated with the switch and actuated by another current change controlled by the calling device; and, as the extent of movement of the selected movv able terminal of the switch at the moment it is stopped determines the particular stationary terminal with which the movable terminal of the trunk switch completes connection, the operator, by setting the calling device to produce this other current change after a predetermined movement of the calling device, is able to stop the correspondingly moving automatic switch with its selected movable terminal in engagement with any desired one of the stationary terminals.

selected line in case the latter is busy, and

to transmit a busy signal to the other end of the trunk. If the line is not busy, connection with it is completed and ringing current is applied by means of a circuit which is automatically disconnectedwhen the called subscriber answers the call. The talking circuit of the trunk is at the same time completed at this end, and, as the devices at the other end of the trunk line have operated in the meanwhile to disconnect the calling device and-complete the trunk circuit at that point, the calling subscriber and the called subscriber are now brought into communication. During the use of their telephone, both subscribers have control of the the usual supervisory signals before the operator. When they replace their telephones the operator disconnects, and the resultant change otcurrent flow in the circuit causes the return of the automatic switch to its normal position. I

In the system in which I have illustrated the switching apparatus of my invention as being employed, the reciprocal control over each otherof the calling device and the automatic switch, the control of the called subscribers supervisory signal,

' the-transmission of the busy signal if the line is engaged, and the telephonic communication between the subscribers are all eilected'over the usual single pair of conductors.- The control of the calling device over the automatic switch to cause it to perform its various operations of starting, se-

- lecting a particular movable terminal, se-

- tionary terminal and returning to normalv lecting and connecting with a particular staposition is effected through the medium of switching apparatus at the automatic switch end of the trunk, which operates at each change of current flow produced by the calling device to shift the control of the calling device from one to the other of the various {operating circuits and mechanisms of the automatic switch. 7

Detailed description of operation of sys- I t'em..The apparatus and circuits not already described will sufficiently appear from .i'aonsiderationof the diagram,'Figs. 3 to 8 inclusive. and the description of the mode of operation hereafter to be given. In the dia- "gram, devices of known tvpes are designated bv'the usual conventional symbols. Certain 'nections'and' manner of use are well understood by those skilledin the'art, and to show them in detail would unnecessarily complicate the diagram. For convenience in tracing the circuits, separate batteries are shown .Iatfvarious points; but it will be understood that where batteries of the same polarity and 'Qpotent ial arev indicated atthe same exchange,

these would in practice be replaced by a central battery common to the exchange, which would be connected as indicated by the separate symbols shown on the diagram.

The organization and mode of operation of the system can best be understood by tracing the sucessive steps involved in extending the connection of a calling line through to the line called for, performing the requisite incidental operations, finally disconnecting the lines and restoring. the circuits and apparatus to normal condition.

Let it be assumed that the subscriber at station 500 (Fig. 5) wishes to talk to the subscriber No. 3249 (Fig. 8). The calling subscriber signals the central office operator in the usual way by removing his telephone receiver from its hook, thereby causing the line circuit to be closed, exciting the line relay at the central ofiice in the usual way, and causing the signal lamp 340 to be lighted. The operator'responds to the call in the usual Wayby inserting her answering plug into the answering jack of the calling line, and then by depressing her listening key brings her telephone set (not shown) into circuit, and inquires the number of'the subscriber-wanted. Nhile obtaining the number wanted she presses the keys of the number as received, which number, as assumed, is 32-l9. .A case will be assumed in which all of the springjacks of the direct trunk corresponding to such number are in use, and in which the operator, therefore, inserts the calling plug in the jack on an overflow trunk, thereby closing a circuit which includes the relay C (Fig. 3), which relay, upon being energized, results in the starting of the sequence switch. lhis circuit is as follows: from battery, winding of relay C (Fig. 6), wire 151, sleeve of the jack,

sleeve of the plug, wire 152, winding of the V relay C contact 153 of said relay, wire 127, winding of relay 0, wire 129, winding of polarized relay D, wire 130, left-hand con-' tact of No. 9 units key, wire 7%, right-hand contact of No. 3 thousands key, wire 131, and cam N to earth. Relay C energizes and lights the trunk busy light. Relay C doesv not energize, it being marginal. Relay D does-not energize, it being polarized, and

the current in this case being in the wrongv direction. Relay C energizes and closes ground through cam K of the sequence switch in its first position, front contact 128 of the relay C, winding of the motor magnet 225 of the sequence switch to battery. The sequence switch then starts from normal, whereupon contact 226 is closed by special cam I between the first and fifth position, thereby closing the local circuit for the motor magnet 225, and the sequence switch advances to the fifth position without stopping.

fifth position a circuit is closed for the step- With the sender sequence switch in thethe overflow sequence switch in the first position, wires 52, 54, tip of the overflow trunk jack, tip of the plug, wire 75, contact 155 of relay C wire 76,'cam V of the sender sequence switch in the fifth position, ire 71, winding of the stepping relay 218, wire 73. normally closed contact 246 of relay 219,

wire 72, contact 156 of the relay (1?, wire 77, ring of the plug and jack, wire. .-57, contact 157 closed by cam 2'- in-the first position of the overflow sequenceswitch toearth. The stepping relay 218 energizes and closes a circuitfrom earth through cam J of the sender sequence switch, in the fifth position,

from contact 247 of relay 218, wire 78, back' contact 249 of the relay250, wire 34,-winding of the sender stepping magnet 2(l5rlto battery. The'magnet 205thus' energized, attracts its armature-215, thereby operating the escapementmechanis'm of the sender so that the arm 2ll'advances one-half offa step and the brushes 201 and '201arebetween the terminals. 1 Upon the close iofthe' ,circ'uit just traced, line relay C also energizes and closing its front contact 158 closes the following circuit for the overflow sequence switch: from ground, through'contact 158,

'wire 51,contact 159, closed'bycam a in the first position of the overflow sequence switch, wires 50. 49. winding of the clutch magnet 160 of the sequence switch to battery. "The overflow' -sequence switch is carried to the second position under the control of the specialcam g. In the "second position of said overflow sequence switch, the motor magnet-161 of the overflow selector is ener-v gized by the following circuit: from ground,- through front contact 158 of line relayCf,

wire 51, contact162 closed in thesecond -po'- sition of cam a, wire 42, contact 163 closed in the second position of-cam 1,wire d5, winding of the motor magnet 161 to battery. The brush frame of the overflow selector now starts to rotate and upon th'e'r nachine cam 164 closing.contact465 'the circuit is closed from earth, through contact 165, wire 39, contact 166 closed by cam f in the second position, wire 49, winding of clutch magnet 160 of the sequence switch to battery. The sequence switch is thereupon. carried to the third position. v p

When the'interrupter lever 167 of the overflow selector reaches the first thoth, it closes a circuit from earth, contact 168 closed by the cam h, back contact 1690f the level relay 170, wire 64:, contact 339 closed by theinterrupter lever 167, wire 171,,back

contact 172 of the trip relay173, wire 62,

contact 174; closed bvthecam a, wire 53, to This circuit shunts' front contact 247. "This opens the circuit and 201 onto the pair of No. 0 terminals of the sender. When the interrupter .lever 167 opens contact 339 upon leaving the first tooth, the shunt is removed from the stepping relay 218 which thereupon again energizes and closes the circuit .of the magnet 205, thereupon allowing the sender arm 211 to take-another half step.' The contact 339 of the interrupter thus opens and closes in succession, energizing and deenergining the stepping relay and thereby causing the sender arm 211-to advance by steps untilthe sender brushes find the earth terminal from the thousands key and battery terminal from thehundreds key) This according to the number assumed will be the No. 6 pair of terminals in the first division of the sender terminals.

rUpon the brushes 201, 201 reaching the selected sender terminals No. 6, the polariz'ed stop relav 219 is energized by a circuit from earth, left-hand contact of No.3 thousands key, wire 2 inside terminal 6 of Ithesender, contact .lorush 201, wire 31, winding of the relay .219, wire 30, outside brush 2 0lf'o f-the sender arm, outside terminal 6,

wire 6', right-hand contact of No. 2 hundreds key, to battery. Relay 219, thus energized, closes a'locking'circuit for itself as followsfi from battery,-through the lefthand winding wire 135 and :front contact 245 of r'elay 219, wire 32,winding of relay 250,-wire 33, and cam J; now in the fifth.

position, [to earth. The resultant energization-o'ftherel-ay 250-closes a circuit for the clutch magnet 225 of the sender sequence switch as follows: from ground, through the cam O in its fifth position, front contact 175 of the relay 250,gwinding of the clutch magnet 225 ,to battery. The sender sequence switch is thereupon advanced from the fifth to the sixth position.

,openstheline circuit of the stepping relay interrupter i221. wire 37, contacts 223, 224,

wire- 35,:wire 136. front contact 244 of relay 250, wire'34, winding of the sender stepping .magnet205 to battery. Thereupon the ma gnet-265,.acting under the influence of the inter r1'1pter 221, operates the sender escapcment and the sender arm 211 is advanced until the cam 222 IS in position so that the interrupter spring falls into the notch corresponding to poslt on s of the sender brushes 201, 201?.

The interrupter circuit is thereupon opened at contacts 223, 224, and the sender arm comes to rest with the contact brushes in their normal position .9 just preceding the division of the sender terminals of the level selection of the direct trunk.

WVhen the sender brushes 201, 201 reach position 8 the polarized relay 219 is reset, a circuit therefor being closed from ground, through outside terminal of position 8 wire 30, right-hand winding of the relay 219, wire 31, brush 201, inside terminal of position .9 to battery 243. The battery 243, it will be observed, is so grounded that the current flowing in this circuit is opposing the polarized relay 219, which is thus caused to reset to its normal condition. The relay.

219 upon being thus reset opens its front contact 245, thus opening the circuit of the relay 250, which latter relay is thereupon deenergized and closes its back contact 192. This closes a circuit from ground through cam P, now in the sixth position, contact 192, clutch magnet 225 of 1 the sequence switch to battery, and thereupon the sender sequence switch advances to the seventh position. The relay 219 upon being reset also closes its back contact 246 and thereby closes the circuit of the stepping relay 218. The sender is now in condition to receive pulsations of current for the level selection of the final switch.

When the energization of the polarized relay 219 opened the linecircuit which included the stepping relay 218, as hereinbefore described, it caused the overflow selector to become alocal device, so far as its own advancement was concerned. This selector was left with its motor magnet 161 energized and the brush frame revolving and transmitting pulsations of current for the level selection. The last closure of the contact 339 of interrupter caused, as described above, the sender arm to reach the selected sender terminals, thus energizing the stop relay 219, which thereupon opened the line circuit; but the line relay C continued to be energized so long as the contact 339 of interrupter was closed. Upon the interrupter contact opening, the line relay C is deenergized. The circuit of the motor magnet 161 continues to be closed even after the relay C opens its front contact 158, the circuit for the motor magnet then being from earth, contact 165 of machine cam 164, wires 39, 44, winding of the brush frame trip magnet 173, wires 40, 41 and 42, contact 163, closed in the third position of cam Z. wire 45, winding of the magnet 161, to battery. This circuit causes the trip magnet 173 to be energized, whereupon it opens its back contact 172 and prevents the closure of the contact 339 of the interrupter lever 167 from reenergizing relay C, which would otherwise shunt out the winding of the magover wires 43, 41, 42, contact 163, now ,closed in the third position of cam 1, wire 45, winding of the magnet 161 to battery. The motor magnet 161 is thus continued to be energized. The shunting of battery from the trip mag net 173 causes the trip magnet to become deenergized, thus resetting the brush tripper 338 and thereby preventing a second set of brushes from being tripped;

When the relay C was deenergized as above set forth, it closed a circuit for the clutch magnet 160 of the overflow sequence switch as follows: from ground, through the back contact 177 of the relay C contact 178 closed by the cam b in the third position, winding of the clutch magnet 160, to battery.

This causes the overflow sequence switch to advance to the fourth position, which position is the one for hunting an idle trunk.

It will be noted that the tip and ring selector brushes 337 are now open at the contacts 179 and 180, respectively, controlled by the cams e and 7c, and also that the battery cirwit to the tip is open at contact 1554 opened in the fourth position of the cam 03. I

The circuit last described for the motor magnet 161 gives battery to said magnet until the sleeve brush contacts with the first terminal, which if busy will have earth circuit, as will hereinafter be set' forth, and this being substituted for the earth rod can be traced over the same path. Contact 339 of the interrupter closes before the sleeve brush leaves this first terminal and thereby substitutes the following circuit for the en: ergization of the clutch magnet 161:from earth, contact 168, closed by the cam h in the fourth position, back contact 169 of the level relay 140, wire 64, contact 339 of the lower interrupter lever 167, wire 171, contact 172,

wire 62, contact 181, closed in the. fourth' position of cam 0, contact 163, now closed by the cam Z, wire 45, winding of the clutch magnet 161 to battery. The hunting continues until the sleeve brush finds the'terminal of an idle trunk, that is one having no earth circuit. When this happens, the clutch magnet 161 will be deenergized and the rotation of the brush frame will stop. Upon the overflow switch thus selecting a direct trunk, the operator before whom such direct trunk irminates in a springjack is notified that the trunk is busy by the lighting of the lamp 286. As will presently be described, as soon as a direct trunk is selected, the sequence switch thereof moves out of t 1e first position. Therenpon a circuit is closed from ground through contact 262, controlled by the cam 11,, wires 83, 285, winding of relay (J to battery, causing the relay to become energized andto close the circuit of the lamp 286.

During the time that the clutch magnet preventing it from becoming energized, .al-

though said holding magnet 183 has a circuit from ground through contact 18 1, closed by the cam in the fourth position,

. winding of magnet 183 to battery. The relay 182 becomin denergized at the time the circuit of tie motor magnet 161 is opened by finding an idle line, as just described, and opening its front contact 185 removes the shunt from the holdingmagnet 183, which magnet thereupon becomes energized and acts as a brake to prevent the brush frame from'stepping off of the terminal found idle. The denergization of relay 182 closes its back contact 186, thereby closing a circuit from ground over the wire'Gl, contact 187 closed by the cam 7' in its fourth position, wire 49, winding of the clutch magnet 160 of the sequence switch, to battery; The sequence switchis thus moved out of the fourth position. By reference to the numerals on the special cam g, it will be seen that the local circuit for the motor .niagnet 160 of the sequence switch remains closed at contact 335 of the oam g-between the fourth and ninth positions, so that the sequence switch advances to the ninth or talking position. The sequence switch isheld inthe ninth position by reason of a shunt of the magnet 160 closed over wire 46, contact 163 closedin the ninth position of cam Z, wires a2, 41 and 13, sleeve brush 337, wire 83, contact 262 closed in the second and third positions of cam a of the final sequence switch to ground.

\Vith the sender sequence switch in the] seventh position, the line circuit is closed as follows: from battery, line relay 193, (see' Fig. 7), wire 87, repeating coil, wires 79; '81, overflow selector brush 337, wire 55, contact179 closed in the ninth position of cam e, wire 54, tip of the overflow trunkjack and of the plug, .wire 75, contact 155 of re-- lay C wire 76, springs and cam V of the. sender sequence switch, wire 71, stepping relay 218, wire 73. back contact 246 of relay 219, wire 72, contact156 of relay C wire 77, ring of plug. overflow jack and trunk, wires '57, 56, contact 180 closed in the ninth position of cam is, overflow selector brush 337, wire 82, wire 80. repeat ng coil, wire 85.

cjontact194. closed in the first position of thezcam j of the sequence switch of the final selector, to earth. The stepping relay 218 is thus energized and closes a circuit for cuit: from ground, through front contact 195 of the line relay 193, Wire 90, contact 196, closed by'the cam a inthe first position, wire 109, winding of the sequence switch clutch magnet 197 to battery.

In the second position of the direct trunk sequence switch, the brush frame power magnet 200 has its circuitclosed as follows from ground, through front contact'195 of the line relay 193, wire 90, contact 198 closed by the cam a in the second position, wire 113, Winding of the magnet 200 to battery. The brush frame now starts to revolve, and upon the interrupter lever 199 reaching the first tooth and closing its con tact 227, a circuit is closed as follows: from ground, through contact 228, now closecLby the cam 2' of the sequence switch, wire 119, interrupter lever 199, contact. 227. wire 118, contact 229 of the brush frame trip magnet 230, wire 116, contact 231, closed in the second position of the cam d of the sequence switch. winding of the line relay 193 to battery. This shunts the battery from the stepping relav 218. and causes it to be denergized and-thereby to open the circuit to the magnet 205. This magnet thereupon releasesthe sender escapement, and the brusharm takes another half step, which places its brushes 201. 201 on the pair of sender terminals No. 0 of the second division.--;The selector interrupter closing and opening its contact 227 removes and places the shunt against the stepping relay 218. thereby operating the magnet 205 and advancing the sender arm 211 until sufficient pulsations have been transmitted to bring the sender brushes 201, 201 in contact with the inner and outer sender terminals No. 4; representing. in the case assumed, the comb nation of the No. 2 hundreds kev and the No. 4 tens kev. Thereunon the following c rcuit will be established from battery, left-hand contact of No. 2 hundreds kev. wire 10. outside terminal No. 4 of the second divis on of sender term nals. b ush 201*. wi e 30. wind ng of relav 219. w re 31, in-

s de b ush, 201. ins de te minal No. 4. wire 13. rightandcontact of No. 4 tens kev. to

earth. This causes the relav 2.19 to become Upon the opening of the line circuit and;

upon the interrupter lever 199 of the final selector opening contact 227, the line relay 193 is denergized and opens the last described circuit of the brush frame power magnet 200. This magnet is continued to be energized, however, by the following circuit: from ground, machine springs m and m wire 117, winding of the brush trip magnet 230, wire 115, winding of the magnet 200 to battery. The trip magnet 230 energized by this circuit places the trip lever 338 in the path of the rotating brush frame and a set of brushes is tripped. The magnet 230 also opens at its back contact 229 the interrupter circuit, thereby preventing the line relay 193 from again being energized by the operation of the interrupter. The sleeve brush when tripped closes the following circuit: from ground, contact 228,

then closed in the second position of cam 2', wire 122, machine springs m and m wire 123, sleeve brush, insulated rod 335, wire 89, Winding of the line relay 193 to battery. The line relay is thus energized and in 010s ing its front contact 195 recloses the earth circuit to the power magnet 200. The closure of this circuit continues the energization of the magnet 200, and also shunts from the sleeve brush at the battery from the trip magnet 230. The consequent deenergization of magnet 230 prevents another set of selector brushes from being tripped. When the interrupter is closed on the long tooth, the earth circuit is closed to the tip side of the line, and during this time the earth'circuit is opened 7 machine springs m and m It will therefore be seen that the interrupter has substituted earth circuit for the one that the sleeve brush has been supplying.

The locking circuit of the said relay 219 includes, as above set forth, the winding of the relay 250, which relay becoming energized closes its front contact 175 and causes the sender sequence switch to advance from the seventh to the eighth position, the circuit of the clutch magnet 225 thereof being closed in the seventhposition of cam O. The energization of the relay 250 also closes the circuit for the sender stepping magnet 205 through the interrupter contacts 223, 224, thus causing the sender brushes to advance to the position a where the said contacts' 223, 224 will be open, and the brushes will be in contact with the sender terminals of position 8 The inner terminal of position 8 has the same battery connection as the inside terminal of position 8 and hence the relay 219 is reset to its normal condition as heretofore described with respect to position s Thereupon the relay 250 is deenergized and upon closing its back contact 192, a circuit closed for the clutch magnet 225 through the cam P, in the eighth position, contact 192, winding of magnet 225,

to battery. This causes the sequence switch to advance from the eighth to the ninth position, which latter position is the one for receiving the line range pulsations. The relay 219 upon taking its normal position reclosed the line circuit.

Upon the interrupter lever 199 of the final selector passing from the long tooth and thereby opening contact 227, it removes the shunt it has had against the stepping relay 218 and the said relay is energized. Upon the interrupter rising on the next tooth, it again places the short circuit against the stepping relay, which is thereupon denergized; This action of the stepping relay is repeated under the influence of the interrupter lever 199 and the stepping relay opens and closes the circuit of the magnet 205 as hereinbefore described, and thereby causes the sender brush arm 211 to advance until a sufiicient number of pulsations of current have been received to advance the brush arm to the position where its brushes contact with the sender terminals No. 49, in the case assumed, whereupon the following circuit will be established: from ground,

left-hand contact of the No. 4 tens key, wire- 219 and it opens the line circuit and again closes its own locking circuit through the relay 250. The energization of relay 250 closes a circuit from ground, through cam O, in the ninth position, front contact 17 5 of relay 250, winding of magnet 225 to battery. This starts the sequence switch and it advances from position 9 to position 1, under control of the special cam I, which closes the contact 226 between the ninth and first positions of the sender sequence switch.

While the sender sequence switch ispassing the twelfth position, it shunts the relays C and D, a circuit to earth from the wire 132 being closed through the cam M of 'the sequence switch in the twelfth position. This elimination of the resistance of the relays C and causes the relay C of the cord to become energized, which thereupon closes a locking circuit for itself from ground through the supervisory lamp 270, contacts 234 of relay C to the winding of said relay C The relay C when energized opens, at its back contacts 155 and 156, the tip and ring of the trunk from the sender and closes said tip and ring to the repeating coil. This end of the circuit is now in talking position.

The sender starts to reset to its normal position under the influence of the sender interrupter 221 when the relay 250 is energized as hereinbefore described, but as the relay 2.39 is deenergized when the sequence switch leaves the eleventh position, another

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