US1617869A - Automatic exchange system - Google Patents

Description

Feb. 15, 1927.

I 1,617,869 F. M. SLOUGH AUTOMATIC EXCHANGE SYSTEM FIGJ Filed Dec. 24, 1917 6 Sheets-Sheet 1 INVENTOR Feb. 15, 1927.

F. M. SLOUGH 4 AUTOMATIC EXCHANGE SYSTEM Filed Dec. '24, 191? e Sheets-Sheet 2 C2 7 J 182 J 42 k 1 1 fl r al Ly Ha a: La up 42/ 56 36' v 31 [/VVENTUR Fab, 15,1927.

1,61 ,869 F. MLSLOUGH AUTOMATIC EXCHANGE SYSTEM Filed Dec. 24, 9 7

INVENTOR 6 Sheets-Sheet 3 1,617, 9 Feb. 15,1927. F. M SLOUGH 86 I AUTOMATIC EXCHANGE SYSTEM Filed Dec. 24.

6 Sheets-Sheet 4 HHHHH HHIHHI 1611869 Feb. 15,1927. RMSLOUGH AUTOMATIC EXCHANGE SYSTEM Filed Dc. 24. 1917 6 Sheets-Sheet 6 INVENTOR' //ZM/m% 7 lll Lil

Patented Fel 15, 1927.

' rinses Uhll'llED STATES PATENT @FFEQE.

FRANK Ii'i. SLO'UGH, OF ROCHESTER, IQ'E W YORK, ASSIGNOR TO THE STROltiBERG-CARL- SON TELEPHONE 00., OF ROCHESTER, NEW YORK,

YORK.

A CORPORATION OF NEXV AUTOMATIC EXCHANGE SYSTEM.

Application filed December 24, 1917. Serial No. 208,622.

My invention relates to automatic telephone systems, wherein the act of a subscriber in operating'a current con'miutating device at the substation is used to operate switch mechanisms at a central office where the telephone lines leading to the various telephone substation terminate, the said switch mechanisms operating to complete a telephonic connection between the said subscribers line and the line of a subscriber with whom it is desired to converse.

It is an object of my invention to accomplish the connection between the subs: "rs lines by the use of mechanism and elect ical circuits having positivcness of operation and simplicity of design, as well as to be capable of being inex aensively installed.

It is a further object or": my invention to accomplish the aforesaid object by the use of connection settingupuncchanism which will be common to a large number 01"- subscribers, and to furthermore provide means whereby the SQttl11g-1lP-1I1G0ll2tlll$l1l will be in use during but a small portion oi? the time in volved in the use of a. telephone from which a call originates.

It is another object of my in veution to providea plurality of the aforesaid setting-upmechanisms, and means whereby a calling subscriber secures tor a brief time the sole use oi? such mechanism, the said mechanism being thereafter discharged from the use of the said subscriber. and to provide means whereby the said setting-up-mechanism thereafter reverts to the common use.

It is a :turther object otniy invention to provide a novel means of completing the connection between connected subscribers lines by the use of a switch, pretcrahly non rotary in character, and upon which the connection can be made almostinstantly.

Other objects of my invention and the invention itself will be apparent to those skilled in theart to which it appertains from a description of the same which follows and which reference is had to the drawings forming a part of this specification and in which Fig. 1 shows several incoming telephone lines together with diagrammatic representations of the apparatus at the subscribers stations. and apparatus and circuits a connection switch involved in extending a telephonic connection from one subscribers station to another, the said connection switch being common to a large number of telephone lines, and having calling and called switching terminals together with co-operating switch terminals for interconnecting link circuits associated with the said connection switch. Controlling apparatus for the said connection'switch is also indicated in this figure.

Fig. 2 shows extensions from the line circuits illustrated in Fig. 1 connected to switch terminals of a connection switch whereby any of the lines initiating a call may be connected to a non-busy trunk circuit leading to an idle dialing or setting-upcircuit. The mechanical structure of the connection switch, the circuits of which are shown in Fig. 2 is much the same as the connection switch shown in Fig. l, and illustrated in Fig. 5. I

Figs. 3 and t together illust "ate the apparatus and circuits of a dialing or setting-upmechanism comprising as shown in Fig. 3 a step-by-step switch, controlling magnets therefor, and relay contacts for the said relays controlled by the said step-by-step switch. Relays and circuits associated with the relays and circuits of Fig. 3 are shown in Fig. 4.

Fig. 5 shows some of the mechanical structure of such aconnection switch, as has been referred to in connection with the drawings of Figs. 1 and 2, and Figs. 6, 7 and 8 show details in the various stages of operation of portions of the structure of the connection switch of Fig. 5.

The connection switch which is illustrated in the drawings and which I prefer to use, although other forms of switch may be used, is that illustrated and described in my Patent 1,363,364, granted December 28, 1920, and for a fuller description of the operation of the switch indicated in the drawings of the embodiment illustrated herein. reference may be had to the disclosure in the said patent.

The system of my invention will now be described in detail, the various apparatus and circuits involved in the setting up of a connection between two subscribers stations and the restoring of the apparatus and circuits involved in the said connection being so described.

Referring to Fig. 1, at A I show a telephone set comprising telephonic transmission apparatus, and a current commutator in the form of an automatic dial intenrupter at (Z, said substation apparatus extending by line conductors 13 and 14 from the substation to an exchange.

Assume now that the subscriber at A desires to make a call and to obtain connection with the subscribers set whose substation apparatus is shown at B he will take his receiver from the hook closing the contacts 15 thereof and completing a circuit including the contacts 15, the dial interrupter (5, line conductors 13 and 14, circuit conductors 16 and 17 thru normal contacts 18 and 19 of the relay 20, circuit conductors 21 and 22, the normal contacts 23 and 24 of the relay 25 to the ground pole at 26, and to the negative pole at 27 of the central station source of current 28, thru the line magnet 29, the said magnet and the said source of current being shown on an extension of the conductor 30 leading from the contacts 24 of the relay 25, the said extended conductor being shown in Fig. 2, leading to the relay 29 which is a high resistance relay, and to multiple contacts 31, 32 and 33 of the connection switch whose circuits are illustrated in Fig. 2, and which connection switch is of the cross-bar type similar to that described in my patent above referred to.

The relay 29 in this connection switch is used as a line bar magnet to displace a line bar associated with the calling line located on the said connection switch to condition the contacts 31, 32, or 33 to make connection with the co-operating contacts 34, 35, or 36, depending upon which trunk A B or C with which the said pairs of contacts are respectively associated, is capable of being seized for use by the calling line as will be now explained.

The line relay magnet 29 having operated, it will close its contacts 37, completing a circuit traced as follows: from the ground pole of the source of current, the contacts 37 of the relay 29, circuit conductor 38, and assuming that the first trunk which is C is not at the time in use and therefore selectable, the circuit will be continued thru the contacts 39 of the relay 40, the winding of the vertical magnet VM of the connection switch to the negative pole of the source of current 28, the vertical magnet corresponding to the trunk circuit C and the vertical bar V being thereby displaced and latched in its displaced condition by the co-operating latch members 41.

The line bar under the control of the mag net 29 having been operated, and the trunk bar V having now been operated, the switch contacts 33-36 and 42-43 will now be closed by the conjoint action of the said bars; the manner in which this is done will be apparent from the description of the operation of the connection switch described in my patent referred to above, and will be explaine'd however, later in connection with the disclosure of Fig. 5, showing parts of such a connection switch with slight modifications.

Sul'lice it to state however, for the time being, the switch contacts 42-43 and 33- 56 will remain closed for the entire connection regardless of the condition of the energization of the magnet 29, and the said contacts can only be restored to their normal opened position by the operation oi the restoring magnet RM, also the trunk bar can only be restored to normal by the operation of the release elcctromagnet N; these last-named magnets being inoperative for the time being.

By the operation of the connection switch contacts just described, a pair of conductors including the conductor 30 in circuit with the subscribers telephone and the conductor 44 leading to the winding of the magnet relay 25 shown in Fig. 1 associated with the line circuit and connection switch of Fig. 1 are extended thru the said contacts to circuit connection with the conductors 45 and 46, respectively.

The conductors 45 and 46, as well as the conductor 47 leading to the restoring magnet RM of the switch and release magnet N thereof, and the conductor 48 leading to the magnet 40 for a purpose to be later describ d are shown extended in the disclosure of Fig. 4 to like referenced conductors 45, 46, 47 and 48 in Fig. 4 at the bottom of the sheet.

Referring now to the switch structure illustrated in Figs. 5, 6, T and 8, a brief description thereof will now be had to better understand the disclosures of Figs. 1 and 2 involving the use of such switch structure.

Fig. 5 shows portions of the switch structure in side elevation, portions of the supporting lrame being omitted for the sake of clearuess.

in Figs. 5 and T, at O, I showan operated plug carriage. This plug carriage consists in briel of a metal frame FR having slots at l? and R, the said slots being for the purpose of admitting the key-pin K oi a line bar H, whereby the said key-pin shown in 7 in the unlocked position 01" the plug carriage may lock and unlock the plug carriage. Also the slot R admits the ertical bar V carrying a key member F which member also shown in its unlocked position in Fig. 7, but which may in the locked position or? the plug carriage O enter the opening It thereof: to lock the same in normal position. Such a locked plug carriage is shown at l; in Fig. 5 and Fig. 6, the key-pin K being shown in its plug carriage locking position and the key member F also being shown in its plug carriage locking position in Fig. (i.

Propelling springs 8 shown in Fig. 5, prepel the plug carriages to the position of the plug carriage O in 5 and 7 whenever the said plug carriage is operath ely unlocked by the conjoint unlocking action of the two key members F and K, belonging to a trunk bar V and a line bar l-I, respectively.

When thus unlocked the metallic plugs 8, 9 and 10 will be carried to contact opera-ting position wherein the pairs of springs 23, 4-5, 6-7, are interconnected tor circuit operative purposes. When so operated the plug carriage, such as O, can thereafter be restored to IlOlll'ltll position by the operation of a restoring magnet RM shown in Figs. 5 to 8 inclusive, which restoring magnet being energized by suitable circuit connections will attract its armature Y, thus causing the re storing member M to force a previously operated plug carriage, such as 0, back to normal position by the cam surface 0 engaging the cam pin C carried on the plug carriage. The plug carriage being restored to normal position the key-pin K which is yieldingly carried on the line bar for the plug carriage 0, will take the position of the key-pin K of Fig. 6 tor the plug carriage L which is a restored plug carriage.

To unlock such a plug carriage as is shown in Figs. 5 and (3, at L, the line magnets as Llvl are energized and move the key-pin K from its normal position as shown in Fig. (3, to the position of K shown in Fig. 6 in dotted lines. Also the vertical magnet V will be displaced from its position of rest wherein the key member F of Figs. 5 and G rests in such a horizontal plane that it will obstruct the movement ot the plug carriage. and will take the position shown in Fig. 5 wherein the key member F is moved without the opening F and below the horizontal plane of the plug carriage frame, and the conjoint removal oi the key members F and K from their normal positions will allow the plugcarriage to be propelled under the power of the spring 8 to its operated position shown for the plug carriage O in Figs. 5 and 7 Any other plug carriage, such as the plug carriage 00, may be also operated simul taneously with the operation of the plug carriage 0, it its line bar HE is displaced by its own line magnet lilvi, at the same time as the line bar of the plug carriage O, and before the displacing ot the vertical bar V by the energization of the vertical magnet VM.

1 have described how the plug carriages are restored to normal position by the ener gization ot the restoring magnet RM, and in addition to the restoring function of the magnet RM. a restoring function isalso performed by the elcctromagnet N when enorgized, in that it will attract the armature latch member Z and withdraw it from its trunk bar latching position to a. position wherein the trunk bar will be restorm'l to normal position by the compression spring J propelling the said vertical bar u nvard.

Contact springs 252 and 184: are provided to control suitable circuits such as are described elsewhere in this specification.

Figs. 5 and 8 show an unoperated plug carriage Z which is locked from operation by the prior operation of the plug carriages O and ()G in the same vertical row and controlled by the same vertical trunk bar V. This locking is accomplished as will be seen by reference made to the Figs. 5 and 8, by the pin P carried by the member M entering a slot S oi tlierplug carriage. This locking by the members M associated with all of tht unoperated plug carriages in the same vertical row of the connection switch as an operated plug carriage is eflective until the final restoration of the operated plug carriages upon the energization of the electro-magnet RM associated therewith, at which time by the removal of the pin P -from the slot S, the plug carriages are again made available for use.

The disclosure oi? Fig. 4 and the disclosure of Fig. 3, are associated only with a particular trunk line as C it being understood that the other trunk lines, such as A and B are equipped in a like manner as the trunk line C with like controlling magnets, ap iaratus and circuit conductors as is illustrated in Figs. 2, 3 and a for the trunk circuit C the arrangement being such that it one trunk circuit as C is busy, a second line making a call will be connected to the next succeeding trunk circuit as B etc.

Continuing the narrative of operation, the operation of the connection switch of Fig. .2 having extended the calling line circuit to the conductor elf), the impulse relay IMP will be thereupon operated, being connected in multiple with the high resistance line magnet relay 29 of Fig. 2, and the relay IMP being of relatively low resistance practically all of the line current will traverse the winding oi the said relay; this shunting ot the high resistance magnet 29 will be ineii'ective to restore the connection switch contacts 33 36 and el2i3, even though such magnet is sui'liciently deenergized by such shunting to restore its contacts and its associated line bars to their normal positions, since at this time the control over the said switch contacts is exercised by the apparatus individual to the trunk circuit C The trunk circuit C having been thus selected, the apparatus of Figs. 3 and i which are individual to the trunk circuit C are now available to the use of the calling subscriber to facilitate under the subscribers control the setting-up of the connection to the called subscribers line including the automatic selection of the said line, and the automatic selection of a separate intercon necting link circuit by which the calling and called lines are united for conversational purposes. 7

The impulse relay IMP will be operated as before described almost instantly after the subscriber takes his receiver from the hook. It operates its contacts closing three pairs of contacts and opening one pair of contacts. The contacts 77 now being closed, the relay 78 which is of the slow releasing type will attract its armature breaking the contacts 49 in the circuit of the winding 50 of the relay 51.

At this time it may be stated that the relay 78 will remain energized when the contacts 77 in its energizing circuit are vibrated, and will keep the contacts 4.9 in the operating circuit of the relay 51 open until a definite period or" time after the circuit of the impulse relay IMP has been broken; which condition occurs only when the dialling or settingaip circuits of Figs. 3 and 4- have completed their functions, and the subscribers are in conversational circuit one with the other, or it the calling subscriber should replace his receiver upon the hook before the completion of the dialling operation, in which case the contacts +19 being closed a circuit will be completed for the energizing winding 50 ot the relay 51 including the source of current 28 and the contacts 52 of the relay 53 which will be closed by the operation of the relay 53 as will be later described.

The breaking down of the connection due to the subscriber hanging up his receiver prior to completing the dialling 'tunction will not now be described in detail, as it will be understood how this can be done by the operated relay 51 which is the relay controlling the breaking down of the connection oi the dialling circuit and the calling line; and the method in which this re lay is employed to break down an established connection will be described in detail in this narrative, since the same thing ocours in the same way when the subscriber has completed the dialling function and has been connected to the called subscribers line by the connection switch shown in F 1.

The operation of the relay 78 also closes contacts 65 in the circuit of the relay shown on Fig. 2, the circuit being traced as follows: from the negative pole of the source of current thru the winding of the relay 4:0, circuit conductor 48 which is shown extended on Fig. 4, the contacts 65 of the relay 78 to the ground pole of the source of current.

The contacts 65 after the dialling operation has commenced are shunted by the contacts 64 ot' the relay 53 which is thereupon operated as will be later described. and these two pairs of contacts n'iaint-ain the operative circuit of the relay 4-0 which is now operated until the dialling circuit reverts to common use as will be later described.

The relay being operated the circuit conductor 38 is extended by the contacts 66 thereof to the circuit conductor 67, the contacts 68 of the like relay 40 oi the next succeeding trunk or stepping-up circuit B and from thence by means of the circuit conductor 69 to the vertical magnet of the trunk circuit B not shown in the drawing. It is by this means that the selecting circuit con'iprising in part the conductor 38 which selected the trunk or setting-up circuit to be used in establishing a connection, is extended from the busy trunk to the next succeeding idle trunk.

The impulse relay 1MP also closes its tacts 51- in the circuit of the .idM of the rotary selector switch RS of F ig. 3, the circuit for the said motor magnet MM being traced from the negative pole of battery through the winding of said magnet, circuit conductor 55 which is continued on Fig. 4-, and leads thru the contacts 54 ot the relay IMF to the ground pole of battery. The motor magnet thereupon attracts its armature l it'ting th pawl attached thereto from one notch ot the notched wheel H to the next succeeding notch to the left thereof. At the same time the spring SP is extended and tends torestore the armature to its normal position against the power of the magnet MM, and to cause the pawl to propel the notched wheel lVI-I on the shaft 56, a portion of the revolution corresponding to the angular distance between the notches on the said wheel. But for the time being the wheel remains in its normal position as does the shaft 56, and the carried switch arms 57 and 58.

The switch arm 57 in its normal position rests on an idle contact to which no conductor is attached, and is therefore impotent to control an electrical circuit in this position.

The switch arm 58 however rests upon the normal contact N OR, and thereby connects its connected ground conductor to the circuit conductor 59 which is extended from Fig. 3 to Fig. 4-; and the connection to ground comprising this conductor 59 and the switch arm 58 for the time being produced a short circuit about the winding of the relay 53, so it cannot be operated even though the contacts (30 ot' the slow releasing relay 78 are closed as is now th case by the closure of the contacts 77 of the impulse relay IMP as just described.

The calling subscriber may now operate the dial (Z at his telephone instrument A causing the circuit of the impulse relay IMP which has been described to be interrupted a number of times. the number of interruptions corresponding to the numeral of the first digit of the called subscribers line number.

We will assume in this description that conmotor i'nagnet the called subscribers line number is No. 32.

The first numeral indicating the lOs digit of the line number being 3, the number of interruptions caused to be produced by the dial of the calling subscriberwill likewise be 8. The impulse relay IMP will thereupon be rapidly vibrated three times from its operated position at the end of which period it will again come to its fully operated position. During these interruptions and consequent vibrations of the impulse relay contacts, certain circuit changes are effected as follows:

At the instant of the first break in the line circuit the impulse relay breaking its contacts 54, 61 and 77 the motor magnet MM in circuit of the contacts 5 will be momentarily restored to its normal position causing the pawl attached to its armature to propel the notched wheel NH one notch, and thereby to rotate the shaft 56 thereof which carries the switch arms 57 and 58 one step. The switch arm 58 thereupon moves the normal contact NOR to the off-normalcontact ON of the said switch, producing circuit changes as follows:

The relay 78 will not be responsive to the rapid interruptions of the contacts 77 which will retain its armatures in their attracted position, this being the property of such a slow releasing relay. The contacts 60 thereof will remain closed, and since the contacts 58-NOR- are now opened the short circuit previously described as being placed about the winding 53 will be removed, and the relay 53 will be energized over a circuit traced as follows: from the ground pole of battery, the winding of the relay 53, the contacts 60 of the relay 7 8, the resistance 62,

to the negative pole of battery. The flow of current over this circuit will operate the relay 58, causing it to close its contacts; the contacts 52 being closed to condition the relay 51 for subsequent operation as will be later described. The contacts 63 form a locking circuit for the relay 53 to maintain its operated condition in circuit with the resistance 62 and the source of current; the contacts 64: being closed to shunt the contacts ()5 in the circuit of the relay L0 to in-v sure its continued operation during the complete connection setting-up period.

The switch arm 58 as has been stated now contacting with the off-normal contact ON of the switch, completes a circuit from the ground ole of battery thru the said switch arm and the said switch contact, and circuit conductor which is extended on Fig. f to the winding of the off-normal relay ONE, and from thence to the negative pole of the source of current. source being completed thru the relay winding, this relay will be operated closing three pairs of contacts 71, 72 and 73, completing circuits to be described.

The circuit for the said The circuit of the interval relay INT will now be closed the same being traced from the ground pole of battery thru the winding of the said relay, contacts 73 of the relay tently short circuited by the successive operations of the impulse relay IMP under the control of the calling subscribers dial, but

its adjustment and electromagnetic charac= teristics will be such that it will maintain its operative condition until it is short circuited by the contacts 61 of the relay IMP for a definite length of time which is longer than the interval intervening between successive interruptions of a chain of interruptions produced by a calling subscribers line. But as will be later related, between each chain of interruptions produced by the calling subscribers dial the contacts 61 will be closed long enough to cause a short circuit of the relay INT of sutficient duration to insure its restoring to its normal inoperative condition.

The switch arm 57 will be stepped from one contact to another of the row of cont-acts with which it is associated in unison with the interruptions of the calling subscribers dial under the propelling action of the spring SP of the selector switch. The circuit of the conductor 80 connected to the switch arm 57 and which conductor 80 is shown extended from Fig. 3 to Fig. 4, leads in Fig. 4

to the break contacts 7 6 of the relay INT which are maintained open during the opera tion of the calling subscribers dial, the circuit being previously continued thru the said contacts 76 to the normally opened contacts 79 of the relay IR over a-circuit including circuit conductor 81, the normal contacts 82 of the relay NB, the circuit conductor 83,

normal contacts 84 of the relay PD, circuit.

conductor 85 to the said contacts 79 of the relay IR.

The closure of the contacts 79 has been previously mentioned, but the circuit controlled thereby from the grounded pole. of

batteryat 86 to the switch arm 57, is'broken at the contact 7 6 of the relay INT prior to the closure of the cont-acts 79 of the relay TR. This insures that the switch arm 57 is not operatively connected to the ground pole of battery 86, and is therefore unable to produce any electrical effect upon the circuits connected to the row of contacts 87, 88, etc.,

over which it may pass, preceding and during the first series of impulses. The contacts 71 and 72 of the relay ONR are also inopertive during this period to produce any electrical effect by their closure, since the conductors leading therefrom lead onlv to contact-s open circuited' at this stage of the op eration of the system.

At the end of the chain of interruptions caused by the first o eration of the subscribers dial other circuit changes will be effected.

Assuming that the called-for subscribers number is as has been stated No. 32, the first chain of interruptions thereby being three in number, the selector switch arm 57 will be moved successively over the contacts 87 and 88 of the selector switch finally coming to rest on the contact 89 thereof. The impulse relav now holds its contacts 54, 61 and 77 securely closed for a sufiicient length of time to cause the release of the interval relay INT by its being short circuited by the contacts 61 of the relay IMP, whereupon the following circuit changes are effected.

The circuit leading from the ground pole of battery thru the contacts 79 of the relay IR will now be completed over the circuit conductor 85, the normally closed contacts 84 of the relay PD, the circuit conductor 82, normal contacts 83 of the relay NB, circuit conductor 81, the now and normally closed contacts 76 of the relay INT, circuit conductor 80 which is extended on Fig. 3 to connect with the switch arm 57 and which at the time contacts with the contact 89 of the switch; the circuit being continued thru the said switch arm and said contact over circuit conductor 91, circuit conductor 92, the normally closed contacts 93 6f the relay BR,'circuitconductor 94 which being extend ed on Fig. 4 leads thru the winding of the digital relay DR to the negative pole of the source of current. This will cause the operation of the digital relay which will close its contacts 95 and 96. The contacts 95 being closed, condition for operation the relay BR of Fig. 3 over circuit conductors 97, also 98 and 592 on both Figs. 4-, and 3, the conductor 93 leading from the said relay BR thru now closed contacts 72 of the oft-normal relay ONR- to the ground pole of battery.

The circuit just traced from the contacts 95 to the the said contacts, will be impotent however to operate the relay BR in series with the relay DR and the source of current connected to the terminals of the said relay, be cause the said relay BB is at the time short circuited by the connection to ground over the circuit conductor 94; of both Figs. 4 and 3, the contacts 93 of the relay BR, the switch contact-s 57 and 89 of the selector switch, the conductor 80 of both Figs. 3 and at, and the other conductors and contacts leading therefrom to the ground pole of battery includground pole of battery including The subscriber now having caused the first chain of interruptions vibrating the impulse relay IMP, now again operates his interrupter to send the second chain of interruptions, which under the assumption that the called-for subscriber's number No. 32, consists of two interruptions of current in the circuit of the impulse relay IMP. At the moment of the first interruption of cur- ,rent by the second actuation of the subscribers dial, spring SP of the motor magnet MM will cause the switch arm 57 to advance breaking its connection with the contact 89 in the circuit of the relay DR of Fig. 4, and thus removing the short circuit which has been existing about the winding of the relay BR. The relay BR will now operate being placed in a locking circuit serially connected with the winding of the relay DR and the source of current, the said circuit including the contacts 95 of the relay DR and the contacts 72 of the relay ONE. The relay BR having operated, its contacts 99 will now be closed completing a circuit including the source of current and the winding of the relay Pl) on Fig i, the said circuit including circuit conductor 100 of Figs. 3 and 4:.

The relay PD now being operated will attract its armatures breaking the contacts 84: thereof which have previously been described as being in the circuit of the switch arm 57 of Fig. 3, and the contacts 101 being closed the winding of the busy test rclay BT will be conditioned to be placed in operative relation to the said switch arm 57.

As soon as the second chain of interruptions have ended, the contacts 76 of the interval relay INT will again be closed in the same manner as has been described at the end of the first chain of interruptions; these contacts 76 opening during any operation of the dial by the subscriber. During the dial operation the contacts 74 of the interval relay will be closed, and the contacts 102 of the relay PD now also being closed, the slow releasing relay 103 will be operated during the sair second dial operation slowly being restored to normal thereafter when the contacts T l of the interval relay are again opened upon the interval relay being restored to normal. The contacts 10-flof the relay 103 will therefore be opened and after a given interval following the dial operation will again be closed. During this interval the busy test function takes place as will later be describet. Before considering the busy test function the operation of other apparatus will be considered.

The relay DB and PD of Fig. 4 having been operated, a circuit will be completed including the contacts 105 of the relay PD and the contacts 96 of the relay DB comprising the source of current and the winding of the relay D11 which relay will be operated thru the said closed pairs of contacts. This relay being operated will connect to the contacts of the switch RS immediately following the first selected contact 89. The called-for line magnets of a group of ten lines controlled by the relay DIE, will be connected to the next contact of the switch RS succeeding the first selected contact 89. These next ten contacts are designated 100, 107, 108, 109, 110, 111, 112, 113 and 11 1 and are thereby associated in the use of the switch here described with the line magnets of the group of ten lines numbered 31 to 10.

It will be obvious from what has been said, the switch arm 57 need only advance one step from its first selective position to be connected with a. circuit conductor associated with a line magnet of line 81, and two steps for the line magnet of line 32, and so on.

" In the case here considered it being the line 82 which is being selected, the switch arm 57 Wlll come finally to rest on the contact 106.

It has not yet been stated, but it is the case that when the relay BR was operated all of the contacts, such as the contacts 93 and the other nineteen like contacts associated therewith are broken so that the switch contacts 87, 88, 89, 90, 106, 107, etc., herein illustrated as being twenty in number are electrically disconnected from their associated relay magnets, such as the relay magnets DB DB and Dlt shown on Fig. 1, which as shown in the drawing are connected to the contacts 87, 88, 89 and 90 of the switch RS, by circuit conductors leading thru break contacts of the relay BR 115, 116, 93 and 117. These contact-s being broken the connection between the contacts of the switch RS and the digital controlling relays DB DB DB DB etc. will be severed. The relay DB however will be maintained operative by the locking circuit before described including the winding of the relay BR.

It is to be noted that each of the relays DB D11 DB DR and others not shown, are like relays performing like functions, and control like digital relays DL DL D11 and DL". These last-named digital relays when operated by the switch arm 57 under the control of the subscribers dial by having come to rest upon the proper contact of the switch RS, serve to thereafter connect to the next succeeding contacts of the switch BS in numerical order the line magnets of the group of lines under the control of the particular digitalrelay first selected. In this way I am enabled by simply continuing the motion of the switch arm 57 of the switch RS under the control of the subscribers dial, to cause the said switch arm to pass over the line magnets of the particular group of lines selected in turn until the particular magnet of the called-for line may be selected and placed in operative circuit relation with the switch arm 57, as will be described in detail for the line magnet of the line 32.

Assumim now that the'subscriber as has been descrioed, causes the second actuation of his dial to propel the switch arm 57 to its second position of rest on contact 106, a circuit will be ther by completed including the switch arm and contact 106, said circuit being traced as follows: from the negative pole of the sourceof current thru the winding of the busy test relay BT shown on Fig. 4, contacts 101 of the relay PD which are now closed, normal contacts 82 of the relay NB, normal contacts 76 of the relay INT, circuit conductor which being extended on Fig. 8 leads to the switch arm 57 of the switch RS, the contact 106, circuit conductor 118, circuit conductor 119, the now closed contacts 120 of the digital relay D11 circuit conductor 121. which being extended on Fig. 4i. leads therefrom to the connector switch of Fig. 1 and is connected to one side of the winding of the line magnet 122, the other side of the said winding being connected to the negative pole of battery. This circuit being completed there will be no flow of current over the same if the called-for line is not busy.

In the consideration of the busy test function at this time it is necessary to state that when a line, such as that leading from the substation A or the substation B and terminating in the line apparatus of Fig. 1 is busy, one of the line magnets ferving as cut-off relays for the lines of which there are a pair for each of the lines will be energized. The particular magnet energized depends as will be later more clearly seen upon whether the line is a *alling or called line. In the en'ibodiment illustrated. we are describing the line from substation A as a calling line, and the line leading to substation B as a called line.

Faince each of these line magnets have one of their winding terminals permanently connccted to the negative pole of battery, the cnergization of such a magnet is only be caused by a connection leading from the opposite or ground pole of battery to the other winding terminal. It is the presence of a ground connection on the circuit side of these line nragnets that operates to produce a busy characteristic to the line to prevent it from being connected to by acalling line. For the present in this description we will assume that the called line 32 which is the and can tion line leading to the substation B is not busy; the operation of the circuits involved thereupon being as follows.

The contact 104 having been momentarily opened and again closed as has been described to produce the busy test interval, a circuit will be completed for the not busy relay NB to operate the same, the circuit being traced as follows: from the negative pole of battery, the winding of the relay NB, contacts 131 of the relay ET, the contacts 104 of the relay 103, the normal contacts of the interval relay INT, the now closed contacts 102 of the relay PD, and therefrom to the ground pole of battery. This circuit being closed a locking circuit for the not busy relay NB is therefore traced as follows: from the negative pole of battery thru the winding of the relay NB, thru the contacts 132 of the said relay, the contacts 71 of the relay ONR which is the off-normal relay, to the ground pole of the source of current. This circuit operatively locks the relay NB for the remainder of the connecsetting-up period. The apparatus is now in condition to be operated, to perform the final act to initiate the connection by interconnecting switch contacts of both of the lines on the switch of Fig. 1 by means of an interposed link circuit which we will assume in this description is the link circuit LK. The link circuit in this description is assumed to be the first link circuit in order, that is, not at the time in use. Although there are a plurality of settingaip circuits such as illustrated in Fig. 3 and Fig. 4 and in part in Fig. 2, there are two sets of mechanisms FLO in Fig. 1, and at BTD in Fig 1, which are common to all of the settingup circuits and mechanisms being used b any of them; the apparatus at FLC being capable of use by one setting-up mechanism at a time, and when taken for use by a setting-up mechanism effectively prevents another-setting-up mechanism which may be immediately thereafter prepared to perform the final connection function from so doing until after the said function has been performed by a setting-up mechanism which has previously taken the apparatus of F LC for use to perform this final setting-up function.

The method by which this is accomplished will now be apparent from the following de scription of its operation in connection with the continued operation of the apparatus :in volved in completing the connection which is being described:

The relay NB being operated will if the common apparatus F LC is not at the time in use, complete a circuit for the winding of the relay SIR, the said circuit being traced as follows: from the ground pole of the source of current thru the contacts 133 of the relay NB, the winding of the relay SIR, conductor 229, the normallyclosed contacts 134: of the relay FLC of the common apparatus FLC, thru the protective resistance coil 135 to the negative pole of the source of current. This will cause a flow of current over the circuit just described, operating the relay SIR. The operation of this relay which may be called the selective interlocking relay determines the moment when the setting-up mechanism associated therewith is to perform its final function or setting up function of the switch of Fig. 1.

The relay SIR being operated will operate its contacts 130, 137, 138 and 139 to perform functions later to be described. The contacts 137 are closed to complete a circuit to operate the line magnets of the calling and called lines in parallel, the circuit of each being separately traced as fol lows; it being understood that the operation of both proceeds simultaneously.

The circuit of the line magnet which is the line magnet 122 of the called-for line which leads to the substation B is traced as follows: from the ground pole of the source of current, the now closed contacts 137 of the relay SIR, the normally closed contacts lstO of the relay HIS, the now closed contacts 141 of the relay NB, circuit conductor 81, now closed contacts 76 of the interval relay INT, the circuit conductor which being extended from Fig. at to Fig. 3 leads in Fig. 3 to the switch arm 57 of the switch SR, the now closed contacts 57, 106 of the said switch circuit, conductor 118, circuit conductor 110, the now closed contacts 120 of the relay DL", circuit conductor 121 which upon being extended to Fig. 4 leads across the said figure, and is thereafter extended to circuit conductor 121 of Fig. 1, the contacts 142 of the relay 123, and from thence thru the winding of the relay 122 to the negative pole of the source of current. The relay 122 will thereupon be operated and open its contacts which extend back to the calling conductors leading to dialling or setting-up selective mechanisms on Fig. 2. The relay magnet 122 being operated will also operate the called line bar of the line with which it is associated and which is assumed to be line N o. 32 in this description, thereby conditioning for operation the sets of contacts 143, 144 and other sets of contacts associated with the line not shown in Fig. 1, but which may be provided in accordance with the traffic requirements of the system and which depend upon the number of link circuits required to handle the said traffic.

Each of the said sets of contacts are associated with a like co-operating set of contacts belonging to a link circuit for interconnecting telephone lines, such as the link circuit LK and the link circuit LK in Fig. 1.

In the meantime the contacts 139 of the relay SIR having been closed, a circuit is completed including the winding of the relay -Xlt, thru the cont-acts 150 and includes the contacts 139 and. the source of current. Current-from the. said source, will operate the'relay XR/which will attract its armature closing 00111536139151, and opening contacts tlll'llggWlllCl'l contacts a connection tothe ground pole of battery is maintained for the V rlaylMP: 1 o x i i,

The' lrelay153 isconnected to the conduc tor 48 thru contacts .154 and is operated over the same circuit including the conductor 45, leading back over the line'of the calling subscriber-..thru contacts. 24 of the subscribers cut-ott relay 25 which is shown-in Fig. 1, and which circuit has been previously described astheoperating circuit of the impulse relay IMF; the relay 153 being substituted in the cil'cuit at thistinie for the relay IMP. Subsequent to the closure of the contacts 154 ottherelay XR and momentarily subsequent to the opening of the contacts 155 of the relay 153, the contacts156 of the relay Xltwill be closed. The sequence of contact operation beingp'rovidedgby the construction and adjustment of the relay.

The contacts 157 in the circuit of the calling line cut-cit relaymagnetwill now be closed. v

The circuit of the calling line relay magnet will now be traced. as follows: from the grounded pole of the source of current, the contacts 137 i of the relay SIR, the now closed contacts 140 tacts 145 of the relayNB, the contacts 157 of the relay XR, circuit conductor .46 which extendstrom Fig. 4 to Fig.2, and on Fig.2 leads to the now closed contacts 42 and 43 Oil the connection switch of Fig. 2, circuit, conductor 44 which is extended from Fig. 2 and which on Fig.1 leads thru the winding of the calling line magnet 25 to the negative pole of the source of current. Current flowing over this circuit will operate the line relay magnet 25 which will sever at 1 thecontacts 146 the circuit of the conductor 147 leading to the called line magnet 20 of the calling line, and the contacts 148 being closed will connect a busy groundpotential upon the conductor 147 leading to the dial ling or setting-up circuits so that the line will test busy to calling lines calling the number of the present calling line. i

The contacts 24 and 23 in thecircuit of the subscribers station and leading; by means of the conductor and other interposed contacts and conductorspreviously described to the conductor of Fig. 4 will now be opened. This will cause the release of the relay in Fig. 4 connected to the the interconnecting circuit of the relay RIS, the conl The release OT the relay'15'3 anindica tion that the line magnets have beenprop erly operated to condition the connection of to the lines, and the contacts 155 of the relay 153 now restored to theirnormal-closed condition, a circuit is.

completed vfor relay RX, the circuit being trace-d as followsztrom the grounded pole of the source of current, contacts 155 of, the relay 153., thenow closed contacts 156 of the relay XR, the Winding of the relay RX to the negative pole of battery. I

The relay RX will now be operated,- and I preferably make this relay a slow'op erating relay andpre'ferably of the type indi cated'in thedrawing, though any other type of slow operating relaymay be used.

The relay RX being operated will after-an interval close itscontacts 158, therebyclos v ing a. circuit comprising the following the central source of battery the winding otthc relay FLC shown on Fig. 1,'which relay is common to a plurality of settiiig iip circuits,

the circuit conductor 159 which is shown X, tended to conductor 228 in Fig. 4, the winding 1660f the relay SIR, armature and contact 136 of this relay, armature 160 andback contact oi relay BIS, contacts 158 and relay RX, circuit conductor 161, which is shown extended Fig. 1 thru the normal contacts 162 of the relay 163ofFig. 1, and the wind ing of the slow releasing relay 164.. and the winding of the vertical magnet 165 of the connection switch shown in Fig.1 associated with thelink circuit LK.

being comsource 0t current, oursource will operate the llU slow releasing relay 164 andthe common controlling relay FLC both-of which are shown. in Fig. 1. FLC'being operated will prevent any control over the connection switch of 1, or any part thereot'to be exercised by any other dialling circuit for a'given period wherein the dialling or setting-up circuit whose operation has been described itself controls the operation of the apparatus of said switch. 1

The conunon controlling relay T The breaking of the contacts 134 thus disabling the relay SIR of another dialling or setting-up circuit is the means employed to prevent the said control being exercised by another dialling or setting-up circuit during the operation of the relay FLC. The relay S113 of the described diallingor set ting-up circuit is maintained operated how- V i 1UO {In this description it is assumed that the LlinlrcirouitjLK the first idle link circuit,

and-the operation thereof is described-ac- 166 thereof, being included. in the circuit just described and which winding; n'iaintai ns the energization of the 'electro-niagnet of the relay SIR.

fl he relay 16% being operated closes contacts 167 which are placed in multiple with thecontacts 162 of the relay 163 tornaintain the circuit of the relay 164, the magnet 165, the relay FLC, and the relay SIR independent of the contacts 162 atter the relay 16-1 is operated, and until the contacts 167 themselves shall as will he later, described 'be broken. The contacts 168 of the relay 16 1. are nowbroken, and as they are included in the initial operating circuit of the next succeeding link circuit LIP, the breaking of these contactsprevented forthe time being, the next succeeding link circuit from being operated.

The vertical magnet 165 having Operated it will attract the vertical bar 169 of the connection switch, which vertical bar is associated with the link circuit LK, and the operation of this vertical bar will cause the interconnection of the linkcircuit, contacts 170, 171 and 172 of the said connection switch to the associated co-operating contacts 173, 17st and 175, respectively. Also the operation of the trunk bar 169 of the link circuit LK will cause the contacts 176, 177 and 178 associated with the said link circuit to be connected to the contacts 179, 180 and Bloc-operating and associated with the said link contacts.

The interconnecting offboth ends of the ever by the winding link circuit with the tivolin'esby the two sets lease the trunk of co opei'ating contacts accomplishes the interconnection of the said lines subject to the control of the apparatus in the said link circuit LK.

The description of the connection switch of Figs. 5,6,7 and-8 will not here be repeated indetail, as it has been previously described and its operation will beundersto'od.

The connect on switch contacts 1'( '0173 and 172-415 shown on F ig. 1 having been closed, a circuit is completed forthe calling iubscribefls battery feed relay 188 of the link circuit including the tandem windings of the relay 188 in series with the source of current, the same being connected 'thru the said switch contacts to the limbsof the telephonel nes 13 andl leading to the substation telephone apparatus at A The relay 188 will thereupon attract its arniatures, closing the contacts 187, 199 and 202, and opening the contacts 203.

The trunk bar 169 having accomplished theinterconnection0t the lines is latched in its operated position by c0operating latch nienibers 182. This latch is subject to the control of an electro-inagnet183, which however for the time being is inoperative to 'rebar 169.

The contacts 171174: of the connection circuit for the relay ina'gnet switch nowbeing'closed, a holding e'nergiz ing circuit tor the line magnet relay 25 of the calling line will be completed including the said contacts traced as follows: from the ground pole of battery, the windings .186 oftlie relay 163, the contacts 187 or the relay 188, thecircuit conductor 189, now closed contacts 17117et of the connection switch, circuit conductor 190 leading to one side of the winding of the relay 25, the other side of the Winding being connected to the negative pole of the source of current. In this way the winding 186 of the relay 163 is placed in series with the winding of the relay 25, and the source of current. But this winding being at the time short circuited by the conductor 14 of F ig. 1, leading thru the connection switch contacts of Fig. '2- and continued as conductor 46 to Fig. 1, leads on Fig. 4 to the groundpole of battery thru the contactsrlhlo'f the relay X'R, contacts 14-5 of the relay NB, contacts 140 of the relay RIS, and contacts 1370f the relay SIR. Thus until the circuit of the conductor 44 just described is broken, the relay 163 will not be operative.

The pair of connection switch contacts 177 18O shown on Fig. 1 having been-closed as before described, a holding circuit is completed for the called line relay magnet 122 traced as follows: from the negative pole of the source of current, the winding of the magnet 122, the contacts 177180 of the connection'switch which are now closed, circuit conductor 201 leading thru the winding of the relay 204, to the ground pole of battery. Thus in addition toestablishing a holding 2O controlling the line bar of the called line, a circuit is completed for the winding of the relay 204 otf'the link circuit which causes the operation of the said relay 204 to closeits contacts 205 for a purpose to be later described.

The relay 20 1, at this time being placed in multiple with the resistance coil 185 thru D0 which resistance coil theop'erative circuit of the magnet 122 had been completed, this previously completed circuit as before described comprises the contacts 14-6 of the relay 25 shown in Fig. 1, the conductor 121 leading tl'i'elfctr'oni, and which being extended on Fig. 1 led thru contacts of the relay DL thru cooperating switch contacts of the steppingswitch RS and circuit conductor 80 leading thru contacts 76 of the 120 relay INT of F jg. 1, also thru contacts 14-1 of the relay NB, and resistance coil 1'85t'o the ground pole of battery thru contacts of th'e'relay RIS and contacts 137 of'the rclay sin.

The relays 188 and 204 have been operated and a circuit is completed to initiate thedisch'arge of the setting-up dialling circuits of Figs. 2, 3 and 4, so that it can revert n to common use; the primary circuit to cause the said discharge is traced as follows: from the ground pole of battery, thru contacts 205 of the relay 204, contacts 202 oi the relay 188, normal contacts 206 of the relay 163, circuit conductor 207 which is at this time extended to the dialling circuit of Fig. 4 by conductor 207 of Fig. 4, and leads therefrom thru now closed contacts 138 of the relaySIR and the winding 208 of the relay R18 to the negative pole of the source of current. Current from the said source flowing over the traced circuit causes the operation of the relay BIS attracting its arma- 1-111'68 and breaking its contacts 140, 150 and 160,-and closing contacts 209 all for purposes to be described.

The contacts 209 being closed complete a looking circuit from the ground pole of battery to the negative pole thereof, thru the winding 210 of the relay BIS, the contacts 209 thereof, and now made contacts 211 of the relay NB. This locking circuit maintains the operation of the relay BIS independent of the contacts 138 just mentioned.

The contacts 140 being broken in the common circuit of the originating circuits leading to the two nected lines, the shunting effect of the ground connected to the contacts 140 by the relay SIR will be eliminated and the relay 163 will be operated.

The relay 163 now' being operated attracts its armatures and switching circuits (ill to be described. The contacts 162 will be broken, but this will be for the time without effect since the now closed contacts 167 oi": the relay 164, are as has been described connected in multiple therewith. The contacts 191 of the relay 163 being closed likewise will be without effect since the contacts 168 of the relay 164 in the circuit of the conductor leading from the contacts 191 are has been described, previously broken. The contacts 184 of the link circuit trunk bar 169 also having been closed will complete a lock-' ing circuit from the ground pole of battery thru the now closed contacts 184, contacts 192 oi the relay 163, and a locking winding 193 of the relay 163, to the negative pole of the source of current. This locking circuit for the relay 163 having been completed the said relay will remain operated until the end of the conversational period, when as will be described, the contacts 1.84 will be again opened restoring the relay 163 to its normal position.

The contacts 150 of the relay RIS of Fig. 4 being broken in the circuits of the relays XR and IMP will cause the armatures of these relays and the apparatus controlled thereby in the dialling circuit to be restored to normal. The contacts 212 of the relay IMP being now restored to their normal position and the contacts 7 7 in the circuit of the slow releasing relay 78 being opened,

line magnets of the two 0011- a circuit will be completed for thewinding 50 of the relay 51 traced as follows: from the ground pole of battery, contacts 212 of the relay IMP, contacts 49 of the relay 78, the still closed contacts 52 of the relay 53, the winding 50 of the relay 51, to the negative sourceof current. Current from the said sourceflowing'over the said circuit will operate relay 51, which will attract its armatures closing contacts 213 and 214 in the circuits of the restoring switch member for the dialling or setting-up circuit, for the-connectionswitch of Fig. 2, and EMS for the connection switch ofFig/3. These restoring magnets bein energized thru the said contacts the switches will be released and will immediately seek their restoredor normal positions.

The contacts 160 of the relay BIS also being opened will open the circuit of the energizing windings of the relays SIR of Fig. 4, and FLU and 164 of Fig. 1, as well as the energizing winding of the vertical magnet 165 of the link circuit, and the armaturcs of the said relays SIR, FLU and 164 will berestored to their normal positions. The relay 164 being of the slow-releasingtype'will momentarily retain its armatures for a function now to be described.

he contacts 194 of the relay 1'64 and the contacts 195 of the relay 163 now being closed, a circuit will be completed from the ground pole of battery, thru the saidcontacts, thru the winding .otthe relay 196, the normal contacts 197 of the relay 198, thru the-now closed contact 199 ofthe relay 188, and the resistancecoil 200 to the negative pole of the source of current. The closing of this circuit will cause a flow from the said source of current thru the winding of the relay 196, operating the relay 196, and the said relay beingoperated'a locking circuit will he eompleted'tor the same independent oi the contacts 195 of the relay 163, and the-contacts 194 of the relay 164. This locking circuit traced as follows: from the ground pole of battery, the contacts 215 m the i-clay 196, the winding of the said relay, the normal contacts 19"! of the called subscribefis battery teed relay 198, and the now closed contacts 199 of the calling subscribers. battery ieed relay-188 thru the resistance coil 200', to tlie'negative pole of the source of current. This circuit including the said source of current will hold the relay 196, which is the ringing relay, operative to cause the ringing of the called subscribers telephone bell. vhich bell will continue ringing until the response of the called-tor subscriber. In the meantime the relay 164 will have restored its armatures and their controlled apparatus to their normal positions of rest.

The apparatus out Figs. 2, 3 and 4 concerned in the establishment of the just (lescribed function will'now be restored to normal, the operation of the apparatus involved being briefly described as follows: The releasing .1'elay51 having been operated as previously described, a locking cir cuit' tor the said relay is thereby formed which may be traced from the ground pole or" battery, thru the contacts 213 of the said relay, the locking winding 216 thereo'l, circuit conductor 47 of Fig. 4, leading there from to circuit conductor 47 ot'Fig. 2, the now closed contacts 217 of the vertical trunk bar V of the connection switch of Fig. 2, which trunk bar is associated with the setting-up circuit whose operationis being described, the circuit continued thru the said contacts 217 thru the winding of the release magnet RM, and the normally closed contacts 218 thereof to the negative pole of the source of current.

Connected in multiple with the said contact 218, is the winding of the vertical bar release magnet N, which will be operatively connected in the said circuit upon the subsequent breaking of the contacts 218, which occurs only when the release magnet has fully operated its releasing bar, together with all of the associated restoring members N for the line bar of the switch of Fig. 2, which operation insures the full restoration to the latched position of the ope-rated plug carriage which was originally displaced to contact operating position by the conjoint operation of the magnets 29 and VM previously described.

The operated plug carriage having been restored to normal position by the actuation of the restoring magnet RM, the contacts 218 will thereupon be opened to include the release magnet N in the operative circuit, so that it will un-latch the latching members 41, and the vertical trunk bar will thereupon be restored to its normal position. After it has practically acquired its normal position of rest, it opens the contacts 217, thus breaking the operative circuit of the electroonagnets RM and N of the connection switch, and also breaking the circuit of the locking winding 216 of the relay 51 of Fig. 1. The relay 51 is of the slow-1e leasing type and upon its having been opened, the connection switch of Fig. 3Will have also been restored to normal position.

This release occurs upon the closing of the contacts 214:, completing a circuit from the ground pole of battery, thru the said contacts and over conductor 219 which is extended on Fig.3, and leads thru the switch releasing magnet HMS, to the negative pole of the source of current. This causes the slow releasing magnet to attract its armature removing the retaining pawl from the teeth of the stepping wheel H, and also causes the closure 01 the contacts 220 in the circuit of the electromagnet MM of the switch which will attract its armature, and wh ch will withdraw its propelling pawl from the tooth oi the stepping wheel \VH, so that the shaft upon which the said Stepping wheel is nmunted together with the switch arm members 57 and 58 is rotated back to such a position that the switch rm 58 is removed from the ell-normal contact ON and crmtacts with too normal contact NOR for a purpose to be lescribed, and the switch arm member 57 takes the ultimate position where it malgescontact with the contact 221 oi the switch. The switch arm 58 engaging its normal contact NOR short circuits the winding oi: the relay 53, which relay thereupon slowly releases its armatures for opening their controlled circuits to restore the contained electroresponsive apparatus to normal.

The ground connection of the member 58 being removed from the oil-normal contact ON, the circuit oi the oil-normal relay ONE of Fig. {will be opened, and it will allow its armatures to be restored to their norn'ial positions.

The. rotation of the shaft 56 oi the switch of 3 to normal position is accomplished by a spring member SM in a way which is clear from the drawing.

The contacts 71, 72 and 73 of the off-normal relay control the circuits of all oi the operated apparatus ol Figs. 2, 3 and 4 now in operated position, and when these contacts are opened all of this operated apparatus will be immediately restored to normal by the opening of the circuits described in conne tion therewith.

The setting-up or dialling circuits illustrated in Figs. 2, 3 and i will now revert to the use of another calling line to which it may be now auton'urtically connected in the manner described tor the connection just d scribed, only instead oi the link circuit LK being seized .lor use by the operation at apparatus in the said setting-up circuit by the extending oi the conductors 1G1 and 207 leading from the said setting-up circuits to the said link circuit. thru contacts 191 and 222 oi the relay 163 to conductors 223 and 224; leading to the apparatus ol the next succeeding link circuit LE the said next succee iling link circuit will be instead seized for use, or if in the meantime it has been seized ior us by another dialling circuit connccted to the said condu-zi'tors 131 and 207 at the points 225 and 226, the next succeeding idle link circuit may be taken for use.

At this time it may be pointed out, although it should be apparent from the foregoing description that the conductors 161, 207, 227, 228, 229, 147 and 121 of Fig. 1, may be connected to by any of the setting-up or dialling circuits of the exchange, the connection being made at the points 225, 226, 230, 231, 232, 233 and 234C.

llll

'65 tion, the contacts'187, 199 and 202 thereof for a: condition wherein the called line was The setting-up circuits and mechanisms will'be opened, and the contacts 203 of the having been discharged from the connection, said relay will. be closed completing a cirthe connection functions performed by the cuit for the release magnet RM which is link circuit Lli continue as follows: better illustrated in Figs. to 8 inclusive; 1

5 The ringing relay 196 being operated, the the circuit being traced as follows: from the ringing generator 235 will be connected negative pole or the source of current, the thru the lamp 236 andv contacts 237 and 238 plug carriage restoring magnet RM, the ot'. the relay 196, to the line wires of the now closed contacts 252 associated therecalled line, the connection being extended with, and the winding of the vertical bar thereto by means of the closed contacts 178, release magnet 183 in multiple with the said 181, 176 and 179 oi" the connection switch contacts and short circuited thereby, the of Fig. 1, and circuit conductors which are contacts 254 of the relay 163, the normally directly connected to the line wires 24:1 and closed contacts 203 of the relay 188, the now 2&2 leading to the SIlbSCIibGI S substation closed contact 184 of thetrunk bar 169, to

telephone bell 2&3. the ground pole of battery. 6 i

The called subscriber responding to the This will cause the operation of the plug ringing of the bell by taking his receiver carriage restoring magnet RM, and it will from the hook, will cause a flow 01 current thereupon operate to restore the calling and superposed with the alternating ringingcun. called plug carriages of the connection 20 rent passing over the line from the source switch illustrated in Fig. 5 from their conof direct current 243, and the said source of tact closing positions to their normal posicurrent flowing thru the ringing trip relay tions, and the connection switch contacts 249 will cause it to operate to close its con 172-175, 17 117 1, 170-173, of the calling tacts 245 long enough to produce thedeline and the connection switch contacts energization of the relay 196, by short cir- 178 181, 177-180 and 176179, of the cuiting the relay, the deenergization of this called line will be opened. relay being accompanied by the opening of Upon the full restoring of the above Said the contacts 215 in the'locking circuit of the plug carriages to normal position, the con relay so that the relay will be unlocked and tact-s 252 associated with the electromagnet 30 restored to its normal position. The ringing RM will be opened, removing the short cirgenerator contacts 237 and 238 will also be cuit thereby placed about the winding of opened disconnecting the ringing generator the release magnet 183, and the release magtrom the line. net 183 will thereupon become operated to The contacts 2&6 and 2 1'? will now be reunl'atch the latch members 182 for the trunk 35 stored to their normally closed positions cozrbar 169, corresponding to the trunk bar V necting the talkingconductors 24:1 and 242 of Fig. 5, and the same will thereupon be thru the connection switch contacts to the lifted under the control of its propelling talking strands 248 and2 19 of the link cirspring to normal position. w cuit, the talking strands being thereby con- The vertical bar having practically atnected thru the said link circuit talking tained its normal position, will open'the strands, and the calling line connection contacts 18 1 controlled by the said vertical switch contacts to the line conductors 13 and bar, and the opening of these contacts will 1 1 of the calling line. The two subscribers release the relay 163 by opening the circuit are now united for conversational purposes of its holding winding 193. The opening of and the conversational period willnow be the contacts 184 will also open the energiz- 1 gin. ing circuit for the release and restoring When the contacts 247 and 246 of the relay magnets 183 and RM, and the connection 196 were closed, the called line battery feed switch link circuit LK will be restored to relay 198 was operated thru the said connormal position. I

50 tact; and over the called subscribcfs line The opening of the circuits of the calling and the-contacts in the circuit oi": the ringing and called line cutoff relay magnets 25 and relay 196 was openedso that this relay can 122 by the opening of the connection switch not again be operated during the conversacontacts 171 174, and 177180 will restore tional period regardless ot' the correct or inthese cut-oft relays to their normal position.

55 correct operation of other apparatus. The relays 163 being restored will restore The subscribers upon finishing their conthe apparatus controlled thereby, as will the vcrsation restore their receivers to the hook other released relays and magnets whose reto perform the disconnect function. Nhen lease has "been described, and thus all of the the calling subscribers receiver has been apparatus concerned in the connection will 60 stored to the hook, thus opening the line be restored to normal position and to a conconductors at the contacts 15 at the substadition where it may be again taken for use tion A, the battery teed relay 188' for the by a subsequent calling line. said substation will be dcenerc ized and its The operation of the circuits and appaarniatures will be restored to norn'ial posiratus oi. my invention has been described found not busy by the testing apparatus of the setting-up circuit-s shown in Fig. 1.

Now going back to that point of the description where the testing function was performed, we will assume that the called line is found to be busy by the apparatus provided for the testing function in the circuits of Figs. 3 and 4;. The operation oi the apparatus involved under such a condition will now be. described.

It has been described how a busy line is characterized by the presence of a. ground connection in the circuit side of one of the line magnets associated with the line. This ground connection would cause the operation as had been described of the line magnet, and it would therefore cause a ground connection to be placed on the conductor, such as the conductor 121 of the called line, such as the line 32 which in this description is assumed to be the called line; the ground being either placed on the conductor 121 by the contacts 274- ,of the line relay magnet 123 should the relay 123 be operated to cause the busy test or will be placed by the interconnecting link circuit, such as the link circuit LK associated with the called line to cause it to be busy, a conductor of the link circuit, such as the conductor 201 conveying the ground connection thru the relay 204, thru the said link circuit, thru contacts 177180 of the connection switch contacts of Fig. 1 in use by the said line'to the circuit side otthe winding of the line relay magnet 122 of the called line.

In any event the ground connection being made to conductor 121 characterizes the line associated with the raid conductor 121, which is the line 32 in this description as a busy line, and the busy test having been made the presence of this ground connection noses the said line to test busy; the testing function being described in detail as follows z- Referring back to the :toi'cgoii-ig description, a circuit was caused to be completed upon the second actuation of the f41ll)S(.llliQl' 5 dial including the switch arm 5? and the contact 108 of the switch of. Fig. 3, the said circuit being traced as follows: from the negative pole of the source oi" current thru the winding of the busy test relay B'l shown on Fig. 1. contacts 101 of the relay PD which are now closed, normal contacts 82 of the relay NB. normal contacts 76 oi the relay INT, circuit conductor 80 which being extended on Fig, 3 leads to the s ritch arm 57 of the switch RS, the contact 106, circuit conductor 118, circuit conductor 119, the now closed contacts 120 of the digital relay D11 circuit conductor 121 which being extended on Fig. 4- leads therefrom to the eonductor switch of Fig. 1 and is connected to one side of the winding of the line magnet 122, the other side of the said winding being connected to the negative pole of l This circuit being completed there no flow of current over the same ii the calledior line is not busy, the called-(tor lint: 32 however being busy there will be a flow of current from the ground connection to the circuit conductor 121, thru the busy test relay BT, operating the said busy test relay BT which will thereupon attract its armature. breaking contacts 131 in the circuit ot the relay NB to prevent its operation, clos ing contacts 257, and completing a circuit traced as tollows: from the ground pole of battery, thru the contacts 102 of the relay PD, contacts oi the relay INT, the contacts 104. of the relay 103, the contacts 257 of the relay ET, the winding of the relay HR, to the negative pole of the source oi current.

This circuit only completed atter the contacts 104; have been restored to normal and after an interval has elapsed. in which. as has been described. should the called line be available for use it may be taken. tor use. and the busy apparatus now being dcscribed disabled by the opening of the con tacts 82 of the relay NB. Should the dis" abling of the busy apparatus not occur prior to the closing of the contacts 104, this is be cause of the operation of the busy test re HT, indicating a busy condition of the line iattery. will to and the contacts 131 oi. the relay lil are opened in the circuit of the relay NB to prevent the relay 1 B l'unctioi'iing. as llO'fOlt described, to cause the connective operations 'The relay BB having operated it will close its contacts 281. and 282, the C().'lli'it(;i':-i 281 locking the relay BB in its operated condition, the locking circuit being traced from the negative pole of battery, thru the winding BB, thru the contacts 281, the contacts 71 of the relay ONR to the ground pole of battery. The contacts 282 beingop crated completes a circuit for the bus tone current generator, said circuit including the subscribcfis telephone to produce a characteristic tone in the said subscribcfs receiver to apprise the said subscriber or" the ljuiu. condition 0]" the callcd-itor line. The circuit of this busy tone is traced from the source of current. thru the usual bus apparatus ETD of 1 over the roiiduclor 227 of Fig. l which is (.filitll 'lftl tlicrcl'rom to the circuit conductor L32? oi Fig. l. thru contacts 282 of the relay HR to the couductor l5, which as has been described. leads thru the connection switch ot Fig. 2. over the subscrzbefis linc conductor 11 the subcribers telephone Al returning to ground at the central station by means (it line condoctor 13, shown in Fig. 1. The subscriber upon being apprised of the busy condition of the called-for line will re phone receiver to the hookswitch. feakinn the contacts 15 of the said. hool-tswiteh iii

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