US1126963A - Semi-automatic telephone system. - Google Patents

Description

A. H. DYSON.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLIGATION FILED FEB.12,1912.

1,126,963. Patented Feb. 2, 1915.

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A. H. DYSON.

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A. H. DYSON. SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED PEB.12, 1912. 1,126,963. Patented Feb. 2, 1915.

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APPLICATION FILED FEB. 12, 1912.

Patented Feb. 2, 1915.

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A. H. DYSON. SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLIOATION FILED 11313.12, 1912 1,126,963. Patented Feb. 2, 1915.

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m: unnnm DrTIB rn Il-lnwlnan ulltulmmu State of Illinois, have and more particularly UNITED STATES PATENT OFFICE.

ALFRED H. DYSON,

SUPPLY COMPANY,

OB CHICAGO, ILLINOIS, ASSIGNOB. TO KELLOGG SWITCHBOARD AND OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Yatent.

Patented Feb. 2, 1915.

Application flied February 12, 1912. Serial No. 677,012.

To all whom it may concern:

Be it known that I ALFRED H. Dyson, a citizen of the United States of America, residing in Chicago, county of Cook, and invented certain new and useful Improvements in Semi-Automatic Telephone Systems, of which the following is a specification.

My invention relates to telephone systems,

to the so-called semiautomatic systems in which automatic apparatus at the central ofiice is used for connecting callin and called substations, but is controlled y an operator at a central oiiice in establishing such connections, an object being to provide a system of the char actor described having improved circuit arrangements, the particular features thereof being more clearly brought out in the fol- 2o lowing specification and claims.

For a more complete understanding of my invention, reference is to be had to the accompanying drawings in which- Figure 1 comprising parts 1, 2, 3 and 4. illustrates diagrammatically the arrangement of the circuits of my invention. Fig. 2 illustrates diagrammatically the contact bank of the preferred type of selectors and connectors used in connection with the circuits illustrated. Fig. 3 is a side elevation of an impulse transmitter control key. 7 Fig. 4 is a ri ht end elevation of a l ey and portion of the containing box of Fig. 3. Fig. 5 is a left end elevation of the key of Fig. 3. Fig. 6 shows a portion of the key of Fig. 3 with its plunger depressed. Fig. 7 shows an arrangement of a plurality of keys of Fig. 3, as used by the operator. Fig. 8 is a side elevation of the transmitting mecha: nism of the impulse sender. Fig. 9 is a plan view oi the mechanism of Fig. 8. Fig. 10 is a sectional View along line 10 10 of Fig. 9 looking in the direction of the arrow in icated thereon. Fig. 11 illustrates a set of contact springs operated by the disks carried on the main shaft of the mechanism of Fig. 9. Fig. 12 illustrates the clutch disk of the mechanism of Fig. 8. Fig. 13 shows a portion of a holding plate for maintaining the mechanism of Fig. 8 at normal. Fig. 14: shows the four contact op erating disks carried on' the main shaft of the impulse transmitting mechanism.

Referring now in general to the circuits illustrated in Fig. 1, thesemay be more is located at the central ollice, a line selector E and first selector F which'are connected as a pair, a second selector J, c nnector switch I, a line circuit C and called substation L. For each paired line and first selectors E, F, an impulse sender selector switch G is provided. having access to a. pluralitv of impulse senders I which may be divided in groups and distributed before diflerent operators. An operntors telephone H is also provided for each onerat r, and is common t the gr up of impulse senders I controlled at the onern toi"s nositi n. Group c ntrol mechani m M is admited to control the selecti n of an idle one of such groups of irnnulse devices l. The substation telephone lines are divided into groims. and there are a nluralitv of a sociated line and imnulse device select rs E and G common t each such gr un of lines. and a master switch D is provided f each such group to c ntrol the start g of the electins! movement of an idle hair f such switches E and noon initiation of a call fr m an ass ciated line.

I have descr bed in general the circuits and aoparatus illustrated. and w l now refe mo e narticu a lv thereto. The s stem il ust ated is adapted for use in ser ng 10.000 s bstat on ,te enhone l nes 5--(i wh ch a e divided nto g ouns of one hund ed l nes. each ne te m na ng t the cent al o ce in a l ne circ t C. T e substat on te e hon s mav be o nnv s nda d common hottcrv design. and T ha e illustrated a well kno n substation telonhone inc d ng a.

sw ch hook I and receiver 9. wh ch nor-,

dance coil 7 and transmitter to the line terminals. Each line circuit C includes a line relay LR and a cut off relay CO. As previously stated, the lines and line circuits C are divided into groups of one hundred, and for each such group I provide preferably ten line selectors E having one hundred sets of bank contacts or line terminals 11, 12, 13, each line being multiply connected to its terminal sets 11, 12, 13 of the associated ten line selectors. These one hundred sets of contacts are further divided into ten sub groups or rows of ten contact sets each so that in the operation of switch E, its wipers l l, 15, 16 are first operated to select the row of contacts containing the terminal of the calling line, and are thereafter operated to select the desired terminals of the selected row. In order to control the selection of the group of terminals containing the termi: nals of the calling line, I provide a set or group terminals 17 and coiiperating wiper 18, there being as many group contacts 17 as there are rows or sub groups of contacts 11, 12, 13 of which of course there are ten. Therefore, it will be seen that each group of one hundred lines is further divided into ten sub groups of ten lines each. For each sub group of ten lines a group relay 19 is provided, being common to its ten line circuits C and connected by conductor 55 to its roup test contact 17.

or each group of one hundred lines a master switch D is provided, being adapted upon initiation of a call from any of its associated lines to start an idle line selector E and impulse sender selector G on a selecting operation. Master switch D is of a well known rotar r switch construction, being adapted to more its wipers 22-23 forward only. As switch D is common to one hundred lines and ten line selectors E, there are ten sets of bank contacts 20, 21, provided therefor, the coiiperating wipers 2-2, "23 being insulatingly mounted upon a shaft adapted to be ad anced bv a step by step movement effected by a well known ratchet and pawl arrangement controlled by the motor agnet 34, which is in turn controlled hv a relay 35. As previously stated, switch D being common to one hundred lines, its switch starting conductor 4-1 is connected to the line rclavs LR, LR, LR=, etc, of its one hundred lines, so that an; of the associated lines are adapted to eil'ect a starting operation of a pair of selectors 'EG by means of the common conductor 41.

Before proceeding further with the description of the circuits, it is believed that their operation will be more readily understood by referring to the tvpe of selector and connector switch mechanism preferably used.

For use with the selector and connector circuits of the system of Fig. 1 a switch such as is shown in an application of lVilliam Kaisling for automatic switch for telephone systems, Serial No. (500,664, filed January 3, 1911, may be used.

The switch referred to in the previous paragraph, in general comprises a. bank of contacts made up of 100 sets of contacts with three contacts to each set, and divided into ten sub groups of ten contact sets each as illustrated in Fig. 2. A set of wipers are provided, to coiiperate with the bank contacts, a primary magnet being adapted to primarily adjust the wipers to select a sub group of contacts, and a secondar magnet is provided to step the wipers in a. secondary direction in a. plane at right angles to the primary, to select a contact set of the selected sub group. The switch construction is such that the wipers are advanced against the tension of a pair of springs, one spring opposing each movement respectively. To release the wipers, that is, to restore them to normal, the secondary magnet is again actuated to step the wipers beyond the last contact of the sub group whercbv thev are automaticallv restored to normal bv the springs referred to, but over a. dillerent path than that taken bv the Wipers in the advance movement oi the switch in selecting a contact. Thus, in the operation of the switch the contact ng ends of the wipers trai el in a primary direction to select a sub group of contacts, then in a secondary direction to select a contact in the group. and in the release of the wipers this secondary direction is continued until the contacting ends have passed bevond the last contact in the group, followed bv the automatic release of the wipers. in which the contacting ends travel in a plane parallel to the p imary mo ement but in an or)- pos te direction until thei reach a po nt directlv abo e the sta t ng point when they are moved downward through a plane par a lel to the secondary movement. but in a direction opposite to the secondarv movement. until thev reach their normal sta t ing point. It is to he unders ood that for a more comnlete understand ng of this s itrh. reference s to be had to the above i dcnti fied mmlicn ti Fig. 2 illust ates cl an' 'amm t callv the contact bank and wine arrangements 0* the switch const ct on eferred to. but it is to be unde sto d that the group w uer 18 and its assoc ated g oup contacts 17 a e used oulv on the selector switches E and G.

Referring again to line selector E. for adiusting the wipers 1a. 15. 16 in a pr mary direction to select a sub group, a prima y magnet PM is provided. being adapted to act u on ratchet mechan sm and sha t P 3, thereby carrying wipers 14, 15 and 16 step by step to any of the sub groups of contacts 11, 12, 13-, its movement of course bein controlled through the group contacts I? and coiiperating wiper 18 which is carried around by shaft PS. For controlling magnet PM a group test-relay GT is provided, while a secondary magnet SM and associated test relay T is provided for controlling the secondary selecting movement-of Wipers Ll, l5 and 16. Primary ofi normal contacts PON are adapted to be moved to their alternatev position upon the first primary step of the wipers, while secondary of? nor mal contacts SON are adapted to be moved to their alternate position upon the first secondary step of the wipers.

Release relay RR controls the restorationof switch E and is adapted to be energized upon closing of the starting circuit for switch E and subsequently deenergized to effect a release of switch E. Main release relay MR3, which is energized by current over the calling line upon connection ther with, is adapted to control the release of certain of the switches, and relay 132 is cnergized to cut ed the talking conductors 93, 93' lead ng to the operators outfit, responsive to the transmission of the first primary impulse. The first selector F includes a release relay RR which is adapted to be ener-v gized responsive to the first impulse from the impulse sender I and remains energized until a release of the switch F is desired. Test relay T-"has a function similar to relay T of line selector E. Impulse relay IR is adapted to be energized over a circuit including the impulse device I, and is-open ated responsive to primary impulses trans mittcd from said impulse sender I to repeat these impulses to operate the diflercnt switches in extending connection to a called line. Relay 221 is operated responsive to energization of relay IR and is so constructed that its armature will not vibrate responsive to impulses from relay IR of a predetermined rate, so that While relay IR is vibrating responsive to the operating impulses transmitted from sender I, alternate contact 133 of relay 221 remains closed. Such operation of relay 221 may be secured in any well known manner, but I preferably employ a relay having a copper sleeve about itscore, thereby rendering its armature slow to retract upon the cessation of the circuit through its winding. Second selector J has magnets and relays with the functions corresponding to magnets and relays-of first selector F and have corresponding reference characters but with'a dilferent suflix.

Connector switch K includes a mechanical structure such as pre iously described, except that only two wipers are used. The magnets and relays oi'switch K having functions similar to magnets and relays of switch JQhave similar reference characters but with a differeut-sufiix. Release relay trol of relay RR is transferred to substation L. Switching relay SW is adapted to be energized responsive to the first secondarv impulse transmitted to switch K, thereby disconnecting magnet Plsl from conductor P and connecting in place thereof secondary magnet SM. Test relay TR is adapted to be energized responsive to the last secondary impulse transmitted to switch K, to test the terminals of the called line whereby if idle ringing relay RI and interrupter relay FF are operated to connect ringing current from encrator HG to the terminals of the called ine, but if said line is busy, relays RI and FF are not operated but busy relay BR is energized, thereby connecting a characteristic busy back signal from ma.- chine BB in circuit, to transmit a busy s gnal to the calling substation. Tip relay TP is adapted to be energized upon response of a called subscriber whereby closing relay CL'is also energized to close the circuit from the calling to the called substation. An interrupter 252 is provided preferably operated by a vibrating electromagnet, and is adapted to be connected to a secondary magnet SM" upon del lnergization of RR to effect the restoration of switch K.

Referring now to the, interrupter wheels 235, 239 of part 3, these are mounted upon a shaft in the rela'tive position shown, and are adapted to be rotated, from any source of power, in the direction of the arrow indicated in connection therewith. Interrupter wheel 235 is adopted to periodically close a circuit through interrupter relay FF and at the same time segment 239 is connecting ringing generator PG to alternate contact 2&0 of relay FF, and as rotation of said segment continues it will be noted that segment 239' is moved oil of its brush and grounded segment 239 is moved onto said brush previous to the interruption of the circuit through FF by the insulated portion .of 235, so that after each ringing period ground from segment is momentarily connected to the terminals of the called line to take care of any discharge, due to the ringing current having been applied, thereby stopping any tendency of tip relay T}? to kick up its armature responsive to such discharge. impulse sender selector G comprises switch construction similar to that of line selector E in that it has a group wiper 72 and three selecting wipers 73. 74:, 75. The magnets and relays of switch G which have functions similar to magnets and relays of line selector E have similar reference characters, but with a suliix prime added. Release relay Rid of selector G is not energized until the release of switch G, which is after the impulse sender I has operated to transmit the impulses.

As previously stated, the system is adapted for 10,000 lines and assuming a trunking capacity of ten per cent, which has been determined by practice to be suflicient although this may he changed to suit existing conditions, there would be one thousand line selectors E and therefore also 1000 connected impulse sender selectors G.

Impulse sender L-lrupulsc sender I comp"ises the impulse mechanism IM and control keys CK, diagrammatically illustrated in part 1. Impulse mechanism 1M coinp 'i.es the plurality of plates 120, 121, 122, 123 mounted upon a single shaft 119, also carrying a wiper 12% adapted to be advanced into connection with the contacts shown associated therewith. Shaft 119 is normally inert, but to rotate said shaft 1 preferably provide a constantly rotating source of power which is adapted to be opcratirely connected with shaft 119 by the operation of clutch magnet CM. In the operation or" impulse sender I, a plurality of primary impulses are first transmitted, which are caused by the operation of the teeth of plate 120, followed by a single secondary impulse eii'ected by plate 121. The prii'nar): imp as referred to are preferably interruptions of a previously established circuit through conductors 91, 91", which it will he noted are closed at impulse contacts 90 and also at contacts 89 of shunt relay 125. Thus when shaft 119 is rotated and the teeth of plate 120 act upon impulse contact 90 to interrupt it, these interruptions do not il'itui'llll'lii the circuit through conductors 91, 91 until shunt contact 89 is opened.

In the present system, I have preferably arranged ten sub groups ten contact sets each on the switches and therefore a maximum of ten primary impulses is su'ilicient to step the wipers of the switches to the farthest sub group, therefore ten impulse teeth 1 to inclusive are provided on plate 120. Thus for each revolution of shaft 119 one series of impulses are transmitted, meaning primary and a secondary impulse, and im pulse sender I is so arranged that as many revolutions of shaft 119 are made as there are digits in the called substations number. That is it the called substation number is 09, two revolutions of shaft 119 are eiiected, and by the cooperation of shunt relay 125, nine effective interruptions of impulse contacts 90 result from each revolution of shaft 119, of course followed by a secondary inipulse from contact 153 in each revolution. 1%. signal relay 88 is also provided which is adapted to be energized upon connection made with its associated impulse sender 1, thereby establishing an energizing circuitfor its associated signal lamp 104. A release relay BR is also provided, being adapted to be energized after the impulses have been transmitted, to effect the restoration of selector switch G.

Referring now to control key CK, as the system is adapted for 10,000 lines, and which would be numbered from 1111 to 0000 inclusive which is a well known practice, although of course other designating charecters may be used, four rows of control keys CK, (3K CK", CK", are provided, each row having ten plungeis and associated contact springs 100 and a common set of springs 10?", 108, although I have shown but three plungcrs in each row. The character of keys CK is clearly illustrated in Figs. 3 to 6, they being so arranged that when a plunger is depressed, it also actuates its common contacts 10?, 108, all of the contacts being locked in such an operated position and held there until released by the energization of the associated release magnet RM.

Referring now to 3 to 0, which illustrate the preferred mechanical structure of control key CK. it comprises four keys similar to CK, although out a portion of a single key is illustrated, each such cey CK comprising; ten plungers 300, each having a set cooperating springs 100 which are adapted to he closed when the pie; moved to its opera ,ed position as indie in Fig. 6, where it is locked by means of the sliding plate 9. To actuate the common set of contacts 107, 108, a second sliding plate 10 is provided, being; adapted to he moved to its alternate position and thereby operate said contact springs when plunger is depressed as indicated in l ig. 6. The release magnet Rli-l is adapted when energized to more the locking plate 0 toward the left and thereby release any of its associated actuated planners, allowing their restoration and also the restoration of common contacts 107, 108. 7 illustrates an arrangement of the control key CK before an operator, the numerals indicating; the digit value of the plunger in each of the rows.

Impulse mechanism TM is illustrated in Figs. 9 to 14- in which the parts already referred to Fig. 1, part 4, are indicated by like reference characters. In Fig. 1, part l, I have illustrated a wiper 12 and its cooperating contacts. this being only diagrammatic. but in Fine. 8. 9 and 10 I have illustrated the preferred mechanical arrangement of this portion of the mechanism. Instead of the wiper 124 acting directly upon its associated contacts, I provide an arm having a roller at its end adapted to engage a pivoted member 303 which 18 associated with ten contact sets 1274', 127-2, etc. The contacts 127 of these ten sets betil 1 having a p nuances ing connected in common and acting to connect any one of the contacts 1', 2, etc, to the conductor leading from contacts 127. In a like manner I provide the four sets of contacts 167, 168, 169, 170, each havin such an associated member 303 which is 1'1 ewise adapted to be actuated by the roller arm 12 1. These sets of contacts which are operated by arm 19A are mounted upon a drum 304: which is rigidly secured to bracket 305, thus preventing its rotation. To provide power for operating shaft 119 a constantly rotating shaft 306 is preferably provided and which may be operated by any desirable motor power, said shaft being suitably journaled, one portion thereof being shown in bearing 307 of plate 308. A clutch plate 309 is rigidly secured to shaft 306 while clutch mechanism 310 is loose upon said shaft 306, but normally held against rotation by means of a pin 311 carried by ear wheel 312 and engaging slot 308' of p ate 308. For controlling the clutch mechanism,

I preferably provide the clutch magnet CM ivoted armature 313 carrying a pair of re lers, 3141 upon its bifurcated end, said rollers riding in the central slotted portion of the hub of clutch member 310. A spring clutch member 310 in its normal or unoperated position. A in 316 carried by member 310 is adapts to engage an opening 309' in constantly rotating clutch plate 309, when member 310 is actuated responsive to the energization of magnet CM. Pins 311-310 are so related to their cotiperating ' members 308, 309 respectively that pin 311 disengages itself from plate 308 as pin 310 engages a hole 309' of plate 309. Gear 312 is in mesh with gear 317 which is rigidly secured to shaft 119, so that when clutch member 310 isv moved into operative en.

gagement with the constantly rotating shaft 306, due to the connection of gears 312, 317, power is transmitted to shaft 119 which is rotated in the direction of the arrow indicated in connection therewith. Uion de- -energization of clutch magnet C if, and

upon pin 311 reaching slot 308, clutch member 310 is restored to normal by the action of spring 315, whereby it is released from plate 309 and again held against rotation by the pin 311 engaging slot 308.

On the basis previously referred to, that is an exchange of 10,000 lines and 1000 switches F and G, I preferably provide one hundred impulse senders I which are believed to be suilicient to establish any number of connections which may be desired at one time, although of course I contemplate using a number of senders I suificicnt to take care of the calls, which may differ according to existing local conditions. These one hundred senders I are distributed among a plurality of operators, preferably ten. A common 315 tends to hold armature 313 and tion of tooth 121'. Thereafter idle sender I and then selects the first idle sender Iin the selected sub group. Each sub group of senders I and their terminals 77, 78.and 79 have a group contact 76 of switch G. When all of the senders I of a sub group are busy, the group contact 76 has a busy or grounded potential connected thereto to render the group unselectable, and for controlling this busy potential, group mechanism M is provided. Mechanism M comprises a plurality of magnets 102-102, 102", etc., there being as many such magnets 102 as there are senders I in the sub group, which we have assumed is bar 103 coiiperates with the armature of the ten magnets 102 in such a manner that when all of the magnets are energized, contact 80 is closed, thereby connecting ground or busy potential to the as sociated group contact 76. These magnets 102 are controlled from relay'88 which is energized as 'soon as its sender I is seized by a selector G, and maintained energized until the impulses have been transmitted or operators releases key RK depressed.

In eneral the operation of sender I is as fol ows: Assuming the operator desires to call line No. 7899, she proceeds to depress the plungers of the control key CK corresponding to the di its of the number of the wanted line, first depressing'the plunger in the thousands row followed by the plungers corresponding to the digit in the hundreds, tens and units rows. This operation closes springs 106, 110, 113 and 116 and also their common contact springs illustrated directly below, whereby a circuit for the clutch magnet CM is closed starting a rotation of shaft 119, and although the interruption of impulse contacts 90 is effected responsive to the 10, 9 8 shunt relay 125 not having been energized, the circuit through 91, 91' is not interrupted until relay 125 is energized, which occurs upon wiper 124 connecting with contact 7 and at this time roller 90 is resting upon tooth 7 interrupting contacts 90. Relay 125 then locks itself through the contact 129, whereby the following tceth on impulse wheel 120 effect six more interruptions of conductors 91, 91 thus transmitting a total of 7 impulses. After the primary impulses have been transmitted. a secondary impulse is transmitted from secondary contact 153 through the ac: the closing of contacts 170 by wiper 124;, establishes an energizing circuit for the release magnet RM, whereby the contacts actuated by the plunger of the thousands key CK are re stored. Thus it will be seen that shaft 119 by its first revolution has transmitted the first series of impulses corres ending to the thousands digit of the called number, and clutch magnet CM being maintained energized through contacts 111, 11 i and 117, shaft 119 makes three more revolutions operating the impulse springs each revolution and releasing upon each revolution the keys (3K CK and CK respectively, through cooperation of wiper 124 and contacts 169 168, 167, respectively. Upon restoration 0 the contact ll? of key CK which is responsive to the last revolution of wiper 124, magnet CM dencrgizes and upon shaft 119 reaching its normal position, the clutch mechanism disconnects shaft 119 from the constantly rotating shaft, thereby rendering impulse mechanism IM inert. Also upon the last revolution of shaft 119, release relay ER is energized by the branch circuit of the energizing circuit for RM whereby a release impulse is transmitted to switch G which is restored.

Having described in general the circuits and apparatus of my invention, its operation in establishing a connection from a cal1- ing to :1 called substation will now be described. Assuming that a subscriber at substation A desires connection with substation L, whose number we will assume is 7899, upon initiating a call by removing his receiver 2 from its switch hook, a circuit for line relay LR is established from battery, the winding of relay LR, normal contact 36, line conductor 6, substation A, returning over line conductor 5 to ground at normal contact 37, thereby energizing relay LR, and closing its alternate contacts 38 and 39. The closing of alternate contact 39 establishes an energizing circuit for group relay 19 which opens its normal contact 40, thus disconnecting ground from its group contact l7 rendering it selectable. The closing of alternate contact 88 is effective to establish a star-tin circuit fora line selector E and imuulse-sencler selector G. As the wipers of the master switch I) are always stopped upon the terminals leading to an idle set of said selectors, it will be seen that upon the closing of said alternate contact 38, ground is connected to conductor 41, normal contact 22, viper and contact 21, conductor -13, normal contact 44, and the Winding of :he group test relay GT to battery, thereby eil'ccting its energizaticn, and causing the starting of switch E as will be described. The said ground connection to conductor 43 is also extended thereorer to conductor 45. normal contact 4-6 and the winding of relay HR to battery efi'ecting its energization, whereby it establishes a locking circuit for itself through its alternate contact 4.8, resistance 49, conductor 50 to ground at normal contact 51. Furthermore, the ground connection to conductor 43 extends through normal contact 52, conductor 53, normal contact 5-l through the winding of group test relay GT to battery, effecting its ener ization and causing the starting of switch i as will be described. Thus it will be apparent that upon-the initial energization of the line relay LR, a starting circuit is closed for a line selector E and a paired impulse-sender selector G. Returning now to line selector E, it will be remembered that relays GT and RR are energized. The energization of GT closes alternate contact 54-, thereby establishing a circuit for alterna ing current from generator through primary magnet PM. he first current impulse through magnet PM effects a primary step of group test wiper 18 into connection with the first group contact 17, also stepping wipers I l, 15 and 16 to the first sub-group or row of contacts 11, 12 and 13. The calling line is connected to terminals ll, l2, 13 of the fifth sub-group, therefore its grou test conductor 55 is connected to the fifth group contact 17. N ow, assuming that there is no other line in the hundred group which includes the line of substation A making a call, said first encountered group contact 7 is connected to ground through its conductor 55 and rounded contact 40. Thus a maintaining circuit for relay GT is estab lished from said grounded contact 17 through Wiper 1S, alternate contact 56 and Y o the winding of GT, to battery, maintaining alternate contact (r-l closed and causing magnot PM to advance wiper 1S and wipers l-l, 15, 16 another step, and continuing to do so until the contact 17 leading to thcgroup relay 19 of the calling line is reached, which being ungrounded at normal contact l0, relay GT loses its maintaining circuit, and is therefore cleiinergized, interrupting the circuil; for magnet PM and rendering it inert. It will be noted that on the first primary step of the wipers normal contact 'l-l of switch PON is interrupted. thus interrupt ing the initial circuit for GT, but it will be remembered that a maintaining circuit from contacts 17 is substituted therefor.

Wipers 14-, 15, 16 having been ad anced ii"e steps, thus placing them opposite the fifth sub-group or row of contacts 11, 12. 13, which is the subgroup including the terminals oi the calling line, the next sten is to effect a secondar operation of switch E to cause wipe s 14. l5, 16 to select the temnals of the calling line. this be ng brought about m follows: Upon deiinergizat on of magirt G. as iust stated. a circuit for test re ay T is esta lished. being tra ed f'om ground at normal contact 54: of GT, alternate contact 58, conductor 59, normal contact 60, alternate contact 61 (relay RR being, energized as previously described), and the winding of relay T to battery causing its energizetion, whereby its alternate contact 62 is closed, establishing a circuit for secondary magnet SM from its connected alternating current generator. Responsive to the first impulse of current through magnet SM, it steps wipers 14-, 15,16 into engagement with the first set of contacts 11, 12, 13, and as we have assumed there is no other line calling, the test contact 11 connected to, is grounded throu h its associated conductor 63 and connected normal contact 39. This connection establishes a locking circuit for test relay T, being traced from said grounded contact 11, wiper 14:, alternate contact 6%, alternate contact 65, and the winding of relay T to battery, whereby the energizing circuit for SM is maintained, causing it to advance wipers 14, 15, 16, as long as wiper 14 is passing over grounded contacts 11. It will be noted that during :the secondary move-' meut of wipers 14, 15, 16, that the line wipers 15, 16 are disconnected at normal contacts 66, 6-7 of relay '1 so that they will not interfere with any existing connections. When the circuit for relay '1 is interrupted causing its deenergization and the interruption of the circuit for magnet SM, wipers I l, l5, 16 remain in connection with the ter minals of the calling line. Upon the said initial energization of relay due to the closing of its alternate contact 67, and upon the opening of normal contact 51 of switch SON, a circuit for main release relay MRR is established, being traced from ground through the windin of said relay, second ary conductor S, a ternate contact 67 alternate contact 48, andthe winding oi relay HR to battery, whereby said. two relays are connected in series, thus maintaining relay RP, energized (as its initial circuit was interrupted at normal contact 51). and causing the energization of relay MRRJ Linc selector E having connected with terminals of the calling line, and its relay T having deenergized as described, a circuit for out oli relay CO is established'by a circuit traced from ground through the winding of said relay CO conductor 5, contact 12, wiper 15, normal contact 66, and the winding of impedance coil 69 to battery, causing the energization of cut olf relay CO, whereby the initial energizing. circuit for line relay LR is interrupted by the opening of normal contact 36, causing its deenergization followed by the restoration of group relay 1), whereby-ground is restored to contact 17, unless some other line in the subgroupincluding line circuit C ismakingn call. In such case, of course, relay 19 would remain energized until the other calling line were selected, and its energizing circuit interrupted. Also upon restoration of relay T, due to the interruption of its alternate contact 67, the initial energizing circuit for relay MRR is interrupted, butv on the closing of normal contact 67 and the energization of cut oil relay CO, it will be apparent that a. path for current from battery-through impedance coil 69 and out over the calling line and back along conductors 6, 6' and S throu h the winding of MRR to round is provided, thus maintaining relay R onergized and controlled from substation A. Furthermore, it will be remembered that after the opening of normal contact 51 of- SON, relays LR and MRR are ener ized in series but upon the interruption of ,lternate contact 67, this series circuit was interru ted and another energizing path for re ay RR is provided from the grounded alternate contact 70 of relay MRR. The connection from substation A is now extended over the heavily marked conductors to the first selector F. Now as soon as the line of substation A is selected and relav T restores, master switch D advances its wipers to the first idle set of selectors E, F, G, this being brought about as follows: Uoon closure of normal contact 65 of relay T, a circuit for master switch relay 35 is established from battery through the winding of said relav 35, wiper 22,-contact 20, conductors 256, 255, normal contact 65, alternate contact 6%, wiper 14:, contacts 11, 39 to ground, energizing said relay 35 and closing a circuit for magnet 34 which operates to advance wipers 22, 23 as .long as wiper is engaging grounded or busy terminals 20-. Upon reaching such an idle contact 20, relay 35 restores, interrupting the circuit for magnet 34: whereby the wipers remain in engagement with the idle set of contacts 20, 21. The next call from the associated group, of course starts the switches F, G, connected with said selected contacts 20, 21. It is therefore apparent that but a single line selector is operating to select at any one period although more than one line be calling.

The operation of impulse-sender selectin switch G will now be described. It

will be remembered that the ground connec tion to conductor 43 extending from master switch D was extended to-conductor 53 and.

"cup testing relay GT of switch G, causing llI-S energization. Therefore a circuit for primary magnetPM is established, whereby an impulse on the connected alternating current generator effects an operation of magnet PM and a primary step of wiper 72. Switch G being of the construction previously described and referred to, its wipers 73, 7st and are also advanced a single step bringing them opposite the first row or subgroup of contacts 77, 78 and 7 9. Assuming that the ten senders I connected to the first subgroup 0r row of contacts 77,

78 and 79 are busy, their associated grou control mechanism M has its contact 8 closed, grounding and making busy the first test contact 76, whereby a maintaining circut for relay GT is established from the said grounded contact'ib, through wiper 7'2, alternate contact 81, and relay GT to battery. Therefore another primary step of switch G is effected, and assuming the test contact 76 of the second group and also of the third and fourth groups are busy, due to the associated den-i I being; in use, relay GT remains energized until wiper 7:2 reaches the contact ('6 of the fifth group as illustrated, which we will assume is ungrounded, and has idle devices 1 in its asso ,iated group. Therefore the relay GT de- -cnergizcs, interrupting its alternate contact 82-, whereby the circuit for magnet PM is interrupted, rendering it inert and preventing any further primary movement of switch G. Thus it will be seen that the wipers of switch G received a primary operaticn and selected a subgroup of contacts having; one or more idle d ,rices I connected therewith. Therefore upon deenergization of relay GT, a secondary operation of switch G is effected, being brought about as follows: A circuit for test relay T is cstab-- lished from ground at normal contact 82,

alternate contact 83, which is now closed, normal contact as and the winding of relay T to battery, causing its energization whereby its alternate contact 85 is closed and a circuit for secondary magnet SM is established. The first impulse of alternating current from generator through magnet SM to grounded contact 85 causes the magnet SM to eiicct a secondary operation of wipers 73, T 5, 75, into mgagement with the first set of contacts 7?, 7S and T9 of the selected group, which we will assume lead to a busy device 1. Therefore, its contact 77 is grounded or in a busy condition, as will be pointed out later on, and therefore a maintaining circuit for test relay T is es tablished from the said grounded contact T7, wiper 73, normal contact 86, alternate contact 87, and the Winding of T to battery. The circuit for magnet Sid being main taincd it continues to advance wipers 73, 74, 75 as long as test wiper "Z3 is wiping over busy or grounded contacts 77, and assuming that the fifth set of contacts are the first set in the group, which lead to an idle device I, the test contact 77 is in a condition as illustrated, that is, without any busy potential, and tl'ierei'orc relay T losing; its maintaining circuit deiinergices and interrupts the circuit for magnet SM rendering' it inert and allowing wipers 73, 7-1 and T5 to remain in engagement with the contacts 77, '78 and 79 leading to the impulse device I illustrated. Although the initial energizing circuit for T is interrupted upon the first secondary step of the wipers, due to the opening of contacts SON, it will be noted that a substitute circuit for relay T is established from a grounded test contact 77, previous to the opening of the secondary oti' normal switch contact 84:. A. circuit has now been extended from calling substation A over the heavily marked conductors to the operator's telephone set H and impulse device 1. Upon the said doenergization of test relay T of switch G, following the selection of an idle sender I, a circuit for relay 88 is established from ground through left hand winding of 88, the parallel paths, through normal contacts 89 and 90 and conductors 91, 91, contact 78, wiper 7%, normal contact 92, conductor 93, alternate contact 9% of relay MRR, conductor 95, and the winding of impulse rclay IR, to battery, energizing said relays SS and IR in series. The eucrgization cl IR effects the closure of its alternate contact 130 to establish an operating circuit for slow relay 2528. Upon energization of 88 a locking circuit for itself is established through its right end winding, alternate contact 96, normal contact 97, protective resistance 98 to battery. T he closing of alternate contact 99 of relay 88 connects ground through normal contact 100 to test contacts 77, thereby placing a. busy potential upon said contacts and preventing; any other switch G from selecting device I. The closing cl alternate contact 101 of S8 establishes an energizing circuit for magnet 102 of .mechanism M which attracts its armature, thereby relieving its pressure upon the common bar 103, while an energizing circuit for signal lamp 104- is also established through alternate contact 101, thereby indicating to the operator that device I has been selected by a calling line. The operator in response to the signal received actuates listening lcey 105 to connect her telephone set to the heavily marl-ted conductors leading to the calling substation and finds that the calling subscriber desires to communicate with suliistution No. 7899, thereafter again restoring listening key 105. The operator now actuates the buttons corresponding to he digits of the called suhatations number, which means that button #7 in the thousands row is first depressed, followed by the dc rcssion of buttons #8, #9, and #9, in the liundreds, teas and units rows, respec tively. The operation of button #7 effects the closing of its contact 106, as well as the movement of contact springs 10?, 108 to their alternate positions. While the opera ticn of said buttons #8, #9, #9, in a like manner effects an operation of their associated springs 110 to 118, inclusive, as will be apparent from the previous description.

The closing of alternate contacts 10?, 111, 11c and 117 establishes an energizing circuit for clutch magnet CM,thereby allowing the constantly rotating mechanism to act upon the shaft 119, rotating members 120 20124 inclusive in a clockwise direction. Upon wiper 124 making connection with contact 7, which is the contact that controls the transmission of seven primary impulses, a, circuit for shunt relay 125 is established from battery through said relay 125, con ductor 126, common plate 127, contact 7 to ground at alternate contact 106, energizing said relay 125, which establishes a locking circuit for itself through alternate. contact 128 to the grounded alternate contact 129 which has been closed by the cam plate 122.

The energization of relay 125 occurs while roller 90' is engaging impulse tooth 7 holding its contact 90 open, thus interrupting the circuit extending through conductors 91, 91, which is the first impulse or current interruption of the series of seven impulses which are transmitted responsive to the actuation of key #7 in the thousands row. The continued rotation of shaft 119 causes the next six impulse teeth of disk 120 to effect six more interruptions 01 contacts 90, thus making seven interruptions of the circuit extendi'n through conductors-91, 91. Although the left winding of relay 88 had its circuit interrupted seven times, it will be rememebred that said relay 88 is maintained energized through its alternate contact 96. It will also be remembered that impulse relay IR of first selector F was included in circuit extending over conductors 91, 91' and the left winding of relay 88, therefore said relay IR has its circuit interrupted seven times responsive to the said seven interruptionsor impulses, each interrnption causing it to retract its armature to interrupt alternate contact 130 and close normal contact 130, these operations of IR being rapid enough to prevent denergization of the slow relay 221, which slow relay maintains its armature attracted during the transmission of the impulses. The first clo sure of normal contact 1230 establishes an energizing circuit for relay RR of switch F operators circuit disconnect relay 132 at switch E and primary magnet PM, of switch F, being traced over the following paths. The circuit for release relay RE is traced from ground at normal contact 130,

alternate contact 133, conductor 134, normal contact 135, the winding of RR to battery, causing its energization, whereby it establishes a locking circuit for itself through its alternate contact 136, conductor 137', to uround at alternate contact 70. The circuit for relay 132 is established fromground at said normal contact 130, alternate contact 133, normal contact 135, conductor 138, normal contact 139, and the winding, of said disconnect reluy 132 to battery, whereby it is energized disconnecting the talking conductors 93 and 93 from conductors P, S at its normal contacts 140, 111. Relay 132 also est'ablishes a locking circuit for itself through its alternate contact 139, to ground, at alternate contact 70. Thus it will be seen that upon the first impulse transmitted, rolay 132 is energized to disconnect the operators talking strands from the talking conductors of the connection which is bci established, and also energizes relay \R.

This first impulse also, of course, operates primary magnet PM of'selector F, being traced from said normal contact 130, alternate contact 133, conductor 145, normal contact 146, and the windingof magnet PM to battery, causing its energization and the advancement by a single primary step of wipers 1&7, 1&8 and 1 19. This first impulse just described is, of course, followed by six more impulses, due to the followin six deeuergizutions or operations of impu lse relay IR, but as primary ofi normal contact 135 was interrupted upon the first primary step of switch F, said six impulses, follow the previousl described path through primary magnet M effecting six more operations thereof, and consequently six more primary steps of wipers 147, 1 18, 149, thus bringing them to the seventh sub-group or row of contacts 150, 151 and 152.

Referring a ain to impulse device I, as the last tooth 2 of disk 120 leaves roller tooth 121 of disk 121 engages the roller of 153' of contact 153, thereby closing alternate contact 153 and transmitting a so-called secondary impulse to first selector Switch F to start its secondary movement, this secondary impulse being traced from grounded p ontact 153', conductor. 154, contact 79, wiper normal contact 158, alternatev contact 159, and the winding of test relay T to battery,

causing its energization whereby its alternote contact 160 is closed establishing an operating circuit for secondary magnet SM. The interruption of contacts 161, 162 of relay T disconnects the. talking conductors from the line wipers 148, 14:9 so that in wiping over the multiple contacts of any existmg connections they will not interfere therewith. Responsive to the first impulse of current from alternating current genera.- tor through magnet SM, wipers 14:7,148 and 119 receive a single secondary step advancing them into en ageme'nt with the first set ofcontacts 150, 1%1, 152, of the selected subgroup, and assuming that these contacts lead to a busy second selector J, test contact.

150 has a ground or busy potential connected thereto, whereby a maintaining circuit-for relay T is established from said grounded contact 150 through wiper 147, alternate contact 163, alternate contact 164:, and relay T to battery, whereby the operating; circuit for SM" being maintained it continues to conductor 93', conductors 156, S, 157,

advance wipers 147, 148, 119 as long as wiper 14-7 is passmg over busy contacts 150. Assuming the fifth set is the first idle one, its test contact is without a ground connection, and therefore relay T has its maintaining circuit interrupted, detinergizing and interrupting the circuit through magnet SM, whereby the wipers remain in en easement with the selected set of contacts,

Upon the first primary step of switch F, its primary oil normal contact is closed, thereby connecting ground to conductor 166 which extends back to the contact 20 of master switch D, maintaining a busy potential upon said contact 20 until first selector F is subsequently restored. Simultaneously with the cessation of the last primary impulse, contact 129 is interrupted restoring relay 1-25, and also wiper 12 lengages the first set of release contacts 167 but without establishing any circuit there through at this time. The continued to tation of shaft 119 brings wiper 12% into engagement with contacts 170, which are the release circuit contacts of magnet RM, whereby a circuit is established for said release magnet BM traced from battery through the windin thereof, contacts 170 which were crossed by Wiper 124:, to grounded alternate contact 108, energizing said magnet BM, whereby the contacts actuated in key CK are restored, the restoration to normal 01 contact 108 causing the interruption of the said circuit through magnet RM allowing it to deenergize. Thus it will be seen that the first series of impulses seven in number, having been transmitted, and the contacts actuated by the plunger of lrey CK have been restored, dlutch magnet (3M being maintained ener gized, as contacts 111, 111, 11? are still closed, the continued advancement of shaft 119 brings wiper 121 into en agement with contact 8' whereby a circuit tor a shunt relay 125 is established to remove the shunt from impulse contacts 90. This circuit for ielay 125 is established from battery through the winding of said relay 125, conductor 12G, plate 127, contact 8', alternate contact 110, at key #8 in the hundreds row, to ground at normal contact 107. At the time relay 125 is energized as just stated, roller 90 is resting upon tooth 8 interrupting contact 90, and the continued rotation of shaft 119, again closes contact 90, followed by seven interruptions thereof, due to the passing of the next seven impulse teeth of plate 120, making eight interruptions of the circuit through conductors 91, 91. This series of e ght interruptions of the circuit through conductors 91, 91 cause eight operations of impulse relay IR of first selector F as before, the said eight operations or de'nergizations of relay IR being efiective to transmit eight impulses through normal contact 130 thereof to the second selector J. The first closure of normal contact 130 establishes a circuit through primary magnet PM and release relay RR of switch J, being traced from ground at said normal contact 130, alternate contact 133, conductor P, normal contact 161, wiper 148, contact 151, conductor 171, normal contact 172, the winding of relay RR", to battery, the said impulse also flowing over conductor P conductor 173, normal contact 17-1, the winding of primary magnet PM to battery. The resulting energization of RR causes it to establish a locking circuit through its alternate contact 175, contact 150, wiper 1-17, alternate contact 163, and normal contact 16-1 to ground. The first impulse transmitted to primary magnet PM and the following seven impulses, causes said magnet PM" to step wipers 176, 177 and 178, to the eighth row or sub-group of contacts 179, and 181, respectively.

Following the last primary impulse. shunt relay 125 has its circuit interrupted due to the opening of contact 129 whereby it is restored, and at the same time a secondary impulse is closed through contact 103. this impulse being effective to start a secondary selecting operation of switch J and flowing over a path traced from said grounded contact 153. conductor 15-1, contact 79, wiper 75, conductor 93', conductor 156, secondary conductor S, wiper 149, contact 152, secondary conductor S conductor 182, normal contact 183, alternate contact 184, the winding of test relay T to battery, causing its energization and establishing an operating circuit for secondary magnet SM through alternate contact 185. The first impulse flowing from the alternating current generator through SM" causes it to step the wipers of switch J into engagement with the first set of bank contacts, which, assuming they are busy, have their test contact 179 grounded, whereby a maintaining circuit for test relay T is provided, being traced through wiper 176, alternate contact 186, alternate contact 187, and the winding of T" to bat tcry. The operation of switch J is similar to the operation of switch F as described, that is, is maintained energized and the wipers of switch J advanced until an idle set of contacts is reached, whereby T deenergizes interrupting the circuit of magnet SM" and preventing any further advance of the Wipers, which we will assume have stopped upon the fifth set of contacts leading to switch K illustrated. It will be noted that during the secondary travel of the wipers of switch J, line wipers 177, 178 have their circuit interrupted at normal contacts 188, 189, and upon denergization of relay T, a busy otential is placed upon test contacts 179 so ected, being traced from normal contact 187 of T, alternate contact 186, to Wiper 176 and contact'179.

Returning now to impulse device I, following the last secondary impulse as described, the continued rotation of shaft 119 brings wiper 12 1 into engagement with contacts 169 to efiect the release of the actuated contacts in the hundreds key OK, this being brought about by a circuit through release magnet RM, traced from battery through said magnet RM, contacts 169, which are now crossed by wiper 124 to ground at normal contact 108, resulting 1n the energization of RM, whereby the contacts 110, 111, 112, are restored. The continued rotation of shaft 119, clutch magnet CM .still being energized, starts the third revolution of shaft 119 and the mechanism carried thereby, to send the third series of impulses corresponding to the digit 9 in the tens unit, and upon wiper 124 making contact with contact 9, which is the contact for controlling the transmission of nine impulses, roller 90' at this time resting upon contact 9", a circuit for shunt relay 125 is established, whereby it is energized and locked up through its alternate contact 128. The said energizing circuit for relay 125 is traced from battery through the winding of said relay, conductor 1'26, plate 127, wiper 12 1, contact 9, to closed contact 113 of plunger #9 ground at normal contact 111. The impulse contacts 90 being open at the time shunt relay 125 energizes, the circuit throu h conductors 91 and 91 is interrupted and again closed as the roller rides oil tooth '9 followed by eight more interruptions due to the actuation of the following ei ht teeth of plate 120. These nine interruptions cause nine 0 erations of impulse relay IR, in the manner as previously described, thereby transmitting nine impulses from grounded impulse contact 130, over the primary conductor P, P, normal contact 188 of switch J, wiper 177, contact 180, conductor 1, the first one of the nine impulses di iding at point 190, part of the current flowingthrough conductor 191, normal contact 192, and the winding of release relay HR to battery energizing said relay whereby it establishes a locking circuit for itself through its alternate contact 193, conductor 194, normal contact 195 to the grounded test contact 179. As just stated, the first impulse dividing at contact 190 also follows a path along! conductor P, conductor 196, normal contacts 197, 198. and the winding of primary magnet PM, to battery causing its operation, whereby the wipers 199. 200. receive a single primary operation. thus moving primary ofi normal switch Pol to its alternate position and due to the opening of its contact 192 interrupting the initial circuit through release in the tens key CK to relay RR. Therefore, the following eight impulses traverse a path along the primary conductor P and through magnet PM causing eight more operations thereof, whereby the wipers are advanced eight more steps bringing them to the ninth sub-group of contacts 201, 202, which is the sub group includin the terminals of the called line. A secon ary impulse from secondary contact-153 of the impulse device I follows the ransmission of the primary impulses as beore, this secondary impulse flowing over the previously described path to the secondary conductor S, S of switches F and J, then through normal contact 189, wiper 178, contact 181, conductor S", conductor 203, alternate contact 204:, normal contact 205, and winding of switching relay SW to battery, causing its ener ization whereby it is locked up through its alternate contact 907, the grounded alternate contact 208 of relay RR. The energization of said switching relay disconnects the primary magnet PM from the primary conductor and con nects the secondary magnet SM thereto.

Up to the present three series of impulses have been transmitted, whereby the subgroup of contacts, of connector switch K, including the terminals of the called line have been selected so that the final series of impulses, which are nine in number corresponding to the last digit of the number of the called line, are transmitted to cause the selection of the desired terminals. Returning now to impulse device I, following the transmission of the last secondary impulse, a continued rotation of shaft 119 brings wiper 121 in connection with terminals 168, whereby an energizing circuit for release magnet RM is established to effect the restoration of the operated contact springs 113, 114, 115 in the tens key CK. The sai cl circuit for Rh 2 is traced from battery through the winding thereof, contacts 168 to ground at normal contact 112, whereby said magnet is energized restoring its associated actuated contact springs, and upon wiper 124; leaving said contacts 168, the circuit for BM is interrupted, whereby it is restored. Shaft 119 now continues on its fourth revolution, magnet CM still being energized through alternate contact 117, and upon wiper 12a reaching contact 9, relay 125 is energized, and the transmission of nine primary impulses followed by a single secondary impulse, as last described is etl'iected. The final nine primary impulses traverse a path over the primary conductor P, P and P to conductor 196 of switch K as previously described, normal contact 197, and alternate contact 198, through the winding of secondary magnet SM* to battery, caus ng n ne operations thereof, and advancing wipers 199, 200 to the ninth set of terminals, which are the terminals of the called line. The final secondary impulse just referred to traverses the previously described path to secondary conductor S, S, S, conductor 20 alternate contact 210, normal contact 211 and the winding of line test relay TR to battery causing its energization. Up to this period in the operation of the system in establishing a connection, the operation is the same whether the wipers 199, 200 have connected to terminals of an idle or a busy line, but the 0 eration of connector K after this period dillers do ending upon whether the called line is i le or busy, and ii idle ringing current is connected to the terminals thereof, while if busy, a characteristic busy signal is transmitted to the calling substation.

Release of sender I and selector G.-Following the transmission of the final set of impulses, impulse sender I and impulse sender selector G are restored to normal,-

thus making sender I available for selection by another calling line for use in establishins;- other connections. Now as to the method of restoring impulse sender I to normal, as shaft 119 continues its rotation following the last secondary impulse, periphery 1:23 of com 123 engages roller 213 closing contacts 213 and at the same time wiper 11-1 is connecting contacts 167. The closing of contacts 167 establishes a circuit for release magnet Rll-l traced from battery through the winding of said magnet, conductor 214-, contacts 167, to grounded normal contact 115, energizing magnet RM and causing the restoration of its associated contact springs 116, 117, 118, but previously to the opening of contacts 118, the ground connection which caused the energization of RM also causes a {low of current through said contacts 118, conductor 215, and the winding of release relay RR to battery, causing its energizatiou, whereby it establishes a lockin circuit for itself through its alternate contact 217 to ground at said alternate contact 213, this locking circuit being the preferred method employed to energize relay HR for a suiiicicnt length of time to transmit a release impulse to switch G. Due to the opening of contact 117 of the units key CK", the circuit for clutch magnet- Ch'l'. is interrupted, whereby the rotation of shaft 119 is continued until it reaches the normal stopping point, where it remains due to the action of clutch mechanism disconnecting shaft 119 from the driving shaft as previously described. It will be noted that as wiper 1'2 leaves contacts 167. the circuit for release magnet RM is relay S8 restores and interrints the circuit through signal lamp 104: am magnet 102. Also due to the closing of alternate contact of relay RR, a circuit for release relay RE is established, being traced from batnormal contact 82, causing the energizution of RR whereby its alternate contact 218 is closed connecting the winding of test relay T in series with the winding of RR, thereby energizing T, RR and T now being energized over the said series circuit. The initial energizing circuit for RR being through its normal contacts 86, said contacts 88 are adjusted so they do not break until after looking contact 218 is closed. Al though alternate contact 219 is closed while relay ER is energized, this has no eflect upon the circuits at this time. As it will be noted, the conductor 220 leading therefrom is already connected directly to ground through conductor 166 and contact 165 of switch F. This ground from 219 is to maintain a ground or busy potential at contact 20 of master switch D during release of switch G, should a calling subscriber hang up before a connection to the called line is completed.

The restoration oi switch G is eficcted responsive to the energization of RR and T by an operating circuit established for magnet SM, through alternate contact 85 of relay T. It will be remembered that to restore switch G its wipers are advanced in a secondary direction until they have passed beyond the last contact in the group, this operation being cil'ected by magnet SM due to the closing of its circuit, as just described. As wipers 73, T l, 75, pass beyond the last Contact of the bank, a release pawl is ai'itomatically withdrawn allowing them and wiper 72 to restore, this restoring movement also causing restoration of the TJL'lmary and secondary ofl-normal switches. Upon the opening of contact 88 0'1 PON the series circuit including the windings of RR and T is interrupted allowing them to restore, the restoration of T interrupting the circuit through magnet SM. Switch G and impulse sender I having been restored, sender I is available for use in establishing other connections and may be selected by other selector switches G.

Referring now to the first selector F, its impulse relay IR having had its circuit interrupted by the restoration of switch G,

said relay IR denergizes, thereby interrupting the circuit for relay 29.1, which also deenergizcs closing its normal contacts 1.83, 222 and restoring the continuity of the primary and secondary talking conductors. A connection now extends from the calling 1&255963 substation A to called substation L, being traced over the heavily marked primary and secondary conductors and interrupted vonly at contacts 223., 224:, of connector K. The talking conductors 9.3, 9.3, leading back from switch G are disconnected from the griinary and secondary conductors P and respectively, at contacts 141 and 140 of relay 132.

Called Zine idle-Returning now to connector switch K, it will he remembered'that its relays SW, BB are energized followed by the energization of line test relay TR responsive to the last secondary impulse. Assuim'ng new that the line of substation L is idle, its terminals 20]., 202 are at normal as indicated in F ig. 1, Part 3. Relay TR upon its said energization closes itsrcontact 230 thereby connecting the winding of dis.- connect relay 231 to the grounded contact 208 of release relay RR, causing the energizaticn of said relay 231 which establishes a locking circuit for itself through its alternate contact 232 to ground at said contact 208. Relay 231 also by the interruption of its normal contact 197 disconnects the conductor leading to the operating magnets SM, PM, from the primary conductor P.

Returning now to relay TR, itwill' he noted that although upon closure of its, al-

ternate contact 233 the, winding of busy relay BB is connected to the secondary conductor S and therefore through to the cut off relay CO',hcth of'the relays BR and 00 being connected to the same terminal of battery are not energized and further it will be noted that upon'energization of rela 231, due to the interruption of its norma contact 211, the secondary impulse through relay TR is interru )ted', causing the restoretirn thereof where y its normal contact 233 closed. Therefore ringing relay H1 is connected in series with relay CO, the circuit thereof being traced from battery through said relay R1, alternate contact 234, normal contact 233, conductor S, wiper 200, contact 202, and the winding of C0 to ground, energizing both said relays.- The energization of CO disconnects line relay LR, thereby removing the called substation control thereof.

Responsive to 'energization of ringing relay RI, the interrupter relay FF is energized by a circuit traced from battery through the live segment of interrupter wheel 235,

interrupter wheel 239-, alternate contact 240, conductor P, wiper 199, contact 201, conductor 6, the call hell and condenser of substation L, conductor 5, contact 202, wiper 200, conductors S, 241, normal c ntact 233, alternate contact 234-, conductor 242, alternate contact 2&3 and non inductive winding 244 to ground. During the revolution of the two interrupter wheels 235-239, it will be noted that due to their relative position upon their shaft, generator current from RG is disconnected by segment 239 previous to the interruption of the circuit through FF by live segment 235, so that ground from segment 239 is momentarily connected to alternate contact 240 and therefore to the terminal of the called line, taking care of any discharge of ringing current from said line which otherwise would have a tendencv to kick up relay TP. Due to the continued rotation of the interrupter wheels 235-239, ringing current is connected to the terminals of the called line upon each energization f FF. while upon each de'energ-ization of FF the tip relay TP is c nnected to a terminal of the called line so that upon. response of the called subsc 'iher and the following deenergizati n of relay FF a circuit for said relav T? is established from ground. through its windlug, alternate contact. 245. normal con-tact 24,0, wiper 199. contact 201, conductor 6, the upper switchhook contacts of substa: ti n L Wh se receiver has been removed, conductor 5, c"ntact 202, wiper 200. conductor 241,v normal contact 233. alternate contact 234 and the winding of RI to battery, causing the energization of tip relay TP which is now connected in series with relay RI. Responsive t the clsing of alternate contact 246 of T P. the c rc it closlug relav CL is energi'led by a circuit tracer} from batten through the winding o said relay CL, alternate contact 246. conductor 238-to ground at alternate c ntct 208. causing the, energimt'ion of (L whereb; its normal contact 236 is interrupted; disconnect ing relay FF and rendering it inert.

Due to the opening of normal contact 195 of CL, the control of release relay HR is removed from the calling subscriber. but as lip relay TP energi' ed before CL did. and due t the cl sing of alternate contact 2.48 of said tip relay TP, ground from alternate contact 208 through said contact 2.48. conductor 194 and locking contact 193 of RR- transfers the control of R'R" to the called substation. The closing of alternatecontactsv 223 an'd 224 of CL established the continuity of the talking circuit bet-Ween the substations A and L which is traced over the, heavily marked conductors connecting the two substations and which have. condensers 249, 250 interposed at. line selector E. Talking ba te y r t call sllb a s i Supplied through the windings of relays RI and TP, while the talking battery for the calling substation is supplied through windings of impedance coil 69 and relay MRR at line selector E. Thus the two substations are connected for comcrsation, the relays RI and '1? at connector K beins; connected in bridge of the called line while impedance coil 59 and relay MRR are connected in bridge of the calling line. Of course the two cut-oil relays CO and C0 are maintained energized over the paths previously clescribed.

Release-The subscribers having finished their conversation may now effect the restoration of the apparatus used in establishing the connection, the release of connector K and line circuit C being preferably controlled from the called substation L, while the release of line circuit C, line selector E, first selector F and second selector J is preferably controlled from the calling substation A. Assuming that the subscriber at L replaces his receiver first, the circuit for tip relay TP is interrupted due to the opening of the upper switchhook contacts, (RI remaining ener 'izcd by the circuit through CO) causing t 1e restoration of said relav TI and by the opcnin of its alternate contact 248 interrupting tie locking circuit for relay RR. Said relay RR therefore de'clnergizes interrupting its alternate contact 208, the ground from which it will be remembered maintains relays SlV,231 and CL energized, these relays now also restorin The restoration of CL disconnects wipers 199 and '200 from the talking strands to prevent interference with any existing conversations during release, while due to the closing of its normal contact 195, ground is connected to test conductor 251 from alternate contact 210' of switch SON thereby maintaining the multipled test contacts 179 busy during the release of switch K. Responsive to deenergization of relay 231 of switch K, its alternate contact 234 interrupts the series circuit through relays RI and CO whereby they are detinergized, thus all the relays of switch K are at normal. Returning now to release relay RR upon its said deenergization, a release circuit for the secondary magnet SM is established traced from ground through common interrupter 252, alternate contact 253, normal contact 254 and the winding of SM to battery, whereby said magnet is operated responsive to the interruptions of its circuit by interrupter 252, advancing wipers 199-200 in a secondary direction beyond the last contact in the sub-group, causing the automatic restoration of the wipers, as previously described.

Upon restoration of PON, its contact 253 is interrupted, interrupting the circuit through magnet- SM rendering it inert,

and upon restoration of switch SON, its alternate contact 210 is interrupted, thereby disconnecting ground from test conductor 9.51 and switch K being at normal is now available for selection for use in establishing other connections. The calling subscribe:- now replacing receiver 2 upon its switchhook, the circuit for main release relay MRR of line selector E is interrupted, causing its restoration, whereby its alternate contact is interrupted, thereby interruptin the circuit for relays 132 and RR of line so ector E, and release relay RR of first selector F, causing their restoration. Responsive to the restoration of relay RR a circuit for test relay '1 is established traced from battery through the winding of said relay '1, normal contact 61, conductor 59, alternate contact 58 and normal contact 54 to ground. Relay T therefore energizes, closing its alternate contact 62 establishing a release circuit for secondary magnet SM which is therefore operated to advance wipers 14:, 15, 16 beyond the last contact of the sub-group, whereby they and wiper 18 are automatically restored as previously described. It will be noted that during the restoring movement of wipers I l, 15, 16 over contacts 11, 12, 13, that wiper 14 has its circuit interrupted at alternate contact 64 of release relay RR, while wipers 15, 16 are disconnected at normal contacts 66, 67 of relay T. Furthermore, it will be noted that during the restoring movement of switch E and until its switch SON is restored, that ground from alternate contact 51 thereof is connected to test contact 20 of the master switch, being traced through normal contact 25 1-, conductors 255, 256 to terminal 20, thereby rendering switch E unselectable during its release movement. Upon restoration of switch TON, its alternate contact 58 is interrupted, therehv interrupting the circuit for relay T which is restored, opening the operating circuit for magnet SM. It will be remembered that cut-ofi" relay CO was energized over the primary conductor and through impedance coil 69 to battery, therefore, when contact 66 of relay T was interrupted, said relay CO was restored. Relay CO being restored the line of substation A is available for use in the establishment of other connections.

The restoration of switch E having been described, reference will now be made to the restoration of switch F. It will be remembered that release relay RR? decnergized and its circuit was interrupted by the restoration of relay MRR of switch E. therefore upon the closing of its normal con: tact 159 a circuit for relay is established from ground through alternate contact 257 of PON normal contact 159 and the wind ing of 'l to battery, whereby T is energized and due to the closing of its alternate

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