US1559138A - Automatic telephone system - Google Patents

Description

Oct; 27 1925.

4 Sheets-Sheet l //v VEN TOR H i H. G. WEBSTER AUTOMATIC TELEPHONE SYSTEM Filed July 26, 1907 Oct. 27, 2 1,559,138

- H. G. WEBSTER v AUTOMATIC TELEPHONE SYSTEF Filed July as, 1907 4 Sheets-Sheet 2 we; I I W??? Oct. 27, 1925.

H. G. WEBSTER AUTOLTATIC TELEPHONE SYSTEM 4 Sheets-Sheet 5 Filed July 26 1907 //VVE/VTDR 74 fl/ li/l'rn/ssss 5% 6? Oct. 27, 1925- 1,559,138

- H. G. WEBSTER AUTOMATIC; TELEPHONE SYSTEM Filed July 26, 1907 4 Sheets-Sheet 4 Iva/Euro)? Patented Oct. 27, 1925 UNITED. STATES PATENT OFFICE.

HARRY G. WEBSTER, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO KELLOGG SWITCHBOARD & SUPPLY COMPANY. 'A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed July 26, 1907. Serial No. 385,674.

To all whom it. may concern:

Be it known that I, HARRY G. WnBs'rER, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented new and useful Improvements in Automatic TelephoneSys terns, of which the following is a spec1fica-' tion.

My invention relates to automatic telephone systems wherein each connection is put up at the exchange by a plurality of successively operated selective swit hes, one of its objects being to secure an improved structure for returning the switches used in a connection to normal. Another feature of the invention consists in the manner in which a common return or grounded third conductor at the substations is employed in the control of the selective switches. Another feature consists in the provision made for trunking between exchanges employing but two conductors individual to each trunk. In systems heretofore proposed, a first selector has been employed to select an idle trunk leading to a distant exchange and there terminating in a second selector, a so-called repeater circuit being interposed at the originating exchange between the fixed contacts of the trunk circuit at the first selectors and the two trunk conductors proper. In accordance with the present invention, I do away with this repeater circuit and employ the relays used for controlling the first selector to repeat the impulses transmitted from the calling substation directlyjover the trunk wires to the electromagnets for controlling the second selector at the distant exchange. These, and other features of my invention will be at length explainedin the detailed descrip: tion wherein reference will be had to the accompanying drawings. Fig. 1 comprising parts 1, 2 and 3, to be placed in consecutive order, illustrate an organization of automatic exchange circuits constituting a preferred embodiment of my invention, all apparatus being shown at normal, the talking circuit to be established indicated by heavy lines, Fig. 2 shows diagrammatically a side elevation of a selective switch that may be employed in connection with the circuits of Fig. 1; Fig. 3 is a front elevation thereof;

Fig. 4 shows a detail view of the secondary magnet mechanism of said switch; Fig. 5

illustrates certain features of the release arrangement of the said switch; Figs. -6 and 7 are respectively top views of the primary off-normal and secondary off-normal switch combinations of the said selective switch.

In the organization of the system as a whole, the subscribers lines are preferably divided into groups of one hundred, both as calling and called lines. Each line of a group is provided with stationary multipled calling terminals appearing at the banksofa number of so-called line selectors having electrically adjustable contact wipers for selecting the contacts of the calling line whereby first selectors, one of which is preferably in permanent electrical connection with each line selector, are connected with calling lines, although I do not wish to be limited to this embodiment-of my invention. line groups above referred to, which number is chosen for the sake of example,'ten

line selectors for each line group, on the ordinary ten per cent. basis, would be adequate to take care of the calls originating from such group. At the line selectors, the lines of the calling subscribers have their multiple terminals preferably arranged in ten groups, each of which may be placed upon a different level of the line selector in the well known manner. To control the line selector in its travel to select the calling line, the lines having their contacts upon one level are preferably provided with a group contact multipled to each line selector of the group, a group wiper being provided for the line selector to wipe over the said group contacts to select the group in which a calling line is to be found, whereon the line selector moves its wipers over the individual contacts of the lines of that group to come to rest engaging the contacts of the calling line. I

' The line selectors are preferably not constantly operating devices,;but are normally at rest, a starting circuit common to a group of one hundredlines for starting the line selectors distributively being provided. Such starting circuit may have a selective. switch T atone end to select an' idle line'selector,

Assuming the one hundred line and starts an idle line selector as soon as a call is initiated over a line of the respective group.

The first selectors have contact wipers for which are provided multiple terminals of second selectors, which second selectors are common for connection to a limited group of subscribers lines, namely for a group of ten thousand lines in a one hundred thousand line system or for a group of one thousand lines in a ten thousand line system, in the well known manner. The second selectors have before them multiple terminals of third selectors (in the one hundred thousand line system) which are common for connection to a limited group of one thousand subscribers lines; and in this system, the third selectors would have before their wipers, multiple terminals of connectors, each common for connection to a one hundred line group of subscribers, the connectors having before their wipers, called multiple terminals of a one hundred line group of subscribers.

More specifically taking first the one hundred thousand line system on the usual ten per cent. trunking basis; each first selector would have ten levels of ten contact sets each, the sets of each level leading to second selectors of a different ten thousand group called subscriber group, the first selector being adjusted first to select the group wanted responsive to directive impulses, and then to select the first idle contact set of the group. The second selector would have ten levels of ten contact sets each, the sets of each level leading to ten third selectors of a different one thousand group, the second selector being adjusted to first select the group of contacls wanted responsive to directive impulses, and then to select an idle third selector of the group. The third selector would have ten cups of ten contact sets each, the contact sets of each group being on a different level and connected to connectors for a different one hundred of the thousand which the third selector serves, the third selector is selecting the group wanted responsive to directive impulses, and then the idle connector, in the well known manner. The connector has the contact sets of its one hundred lines arranged in ten groups of ten contact sets each, each group being on a different level, the wipers of the connector being first adjusted to select a group in which a calling line is found, and then directively adjusted over the contact sets of the individual lines until they engage the contact set of the called line. After this occurs, the called line is tested and a busy signal transmitted to the calling subscriber if the e be busy; otherwise a ring: ing generator is connected to the called line to signal the subscriber.

It will be understood that in the ten thousand line system, the second selectors assigned to the ten thousand line groups are omitted and the third selectors of the one hundred thousand line system have their terminal ends at the banks of first selectors, said third selectors being then employed as second selectors.

Before proceeding to the description of the circuit, I will first describe the mechanical features of the selective switch employed in connection therewith. The switch shown in Figs. 2 to 7 inclusive is specifically a line selector although the same structure may be employed as a first, second or third selector or connector; in the latter employments, however, the group contacts 31 and the group wiper 32 being superfluous. Fig. 3 shows ten levels or groups of contact sets 22232at, each level including ten sets. Each set of correspondingly placed contacts 2223-2 1 constitute calling terminals of an individual line. Each level of contact sets is provided withits group contact 31 as indicated at the right in Fig. 3. For engagement with the individual line contacts 22'23-24l, the wipers 262'728 are provided, normally resting as shown in Fig. 3, their ends being at the left of the contact banks, it being understood that from left to right, the contact banks are of the usual concave form. The shaft 178 is suitably journaled to the main frame of the switch at the axis of curvature and is first lifted step-by-step so as to bring the wipers 2G27-28 fastened thereto to positions horizontal with the different levels of contacts, the shaft being then rotated in a clockwise direction, the wipers engaging at each rotary step, a different line contact set. In the case of the line selector, the primary magnet pm which, by means of its arn'iaturedriven pawl 170, adapted to engage ratchet 171, effects the upward stepping of the shaft 178, controlled by the group wiper 32 m ving over the group contacts 31 to find a group contact whose electrical condition has been altered on account of initiation of a call. over a line having its individual con tact set in a corresponding level. The retaining pawl 172 engages successive teeth of ratchet 171 on each step of the line selec tor and holds the shaft against back movement. It will be understood that the two ratchets 171 and 177 are rigidly secured to the shaft. l or rotating the wipers 2G 27-72S over the contact sets of the selected level, secondary magnet am is provided, whose armaturedriven pawl 17 5 ,best shown in g. a, with each actuation of said magnet rm, drives shaft and wipers a rotary step, pawl 173 engaging the successive teeth of t e ratchet 177 and holding the shaft st back movement by the tension of restoring spring 179. It will be apparent on reference to Fig. 3 that on the first ron of tary step of shaft 17 8 and wipers 2627 28, the group wiper 32 is moved away from the group contacts 31, its continued engagement therewith being no longer necessary as will be understood from the description of the circuits.

For restoring the switch to normal, additional impulses are transmitted through the secondary magnet cm which will continue until the wipers 26-27-28 make their eleventh step, at which time they will be beyond the right edge of their. contact banks, and the shaft 178 will then be free to descend by gravity to its normal vertical level, carrying the wipers with it, because the vertical retaining pawl 172 is so disposed with respect to the vertically extending slot 176 of ratchet 171, that the eleventh step of the wipers brings said slot opposite the vertical retaining pawl 172, which then no longer supports the shaft. Then the shaft descending reaches its normal level, the rotary retaining pawl 173 no 1 longer engages the ratchet 177, the said ratchet having been brought by. the descent of the shaft below the pawl, as shown in Fig. 2,-and the shaft is then free to rotate, carrying with it wipers 26-2728 and 32 in a reverse clockwise direction back to the position shown in Fig. 3, this rotation being effected by the spring 179, shown in Fig. 5.

To the end of avoiding friction of the operating parts while the shaft 178 is being adjusted vertically, the spring 179 has one endattached to the spring case 180 which is rigidly attached to the shaft 178. The other end of the spring is fastened to the arm 184, having at each end an orifice, one of which fits loosely about the shaft 178 and the other about the post 185, these parts being best shown in Figs. 2 and 5. Upon the exterior of the spring casing is fastened the arm 182 which normally presses against arm 184 at an intermediate point so that there is no tension exerted by spring 179 to cause arm 184 to press against post 185 and shaft 178, this condition continuing while the shaft is being lifted under the influence of primary magnet pm. As soon, however, as the first' rotary step of the shaft is made, the arm 182 is carried free of the arm 184 and the tension of spring 179 tends to return the shaft, which return is prevented, as before described, by pawl 173. On the eleventh rotary step of the shaft, however, the downwardly extending portion of spring arm 183, carried by the spring case 180, passes over the top of the arm 184 to a position corresponding to that originally occupied by the arm 182. The tension of the spring is thereby again ineffective to exert pressure upon arm 184 and while the shaft descends by gravity, it has no friction to overcome. However, as it reaches its normal level, the horizontally extending end of arm 183 impacts upon the piece 181, the arm 183 is raised to clear arm 184 and the spring 179 is then efiective to rotate the shaft and wipers back to normal.

In Fig. 6 is shown the primary spring combination, the arm 186 being fastened to the shaft 178, normally holding the off-normal springs pan in the position shown. shaft, the arm 186 is raised so as to clear the spring engaged by it when the springs joined by the stud of insulating material shown move to the right to assume their alternate positions. The arm'187 controlling the secondary off-normal spring son fits loosely about the shaft 178 and is not raised therewith, the piece 187 fastened to the frame of the switch engaging a groove in the arm 187, as shown in Figs. 2 and 7, to hold it at its normal level. The said arm 187 is, however, keyed to shaft 178, and with the first rotary movement is moved to the right to free the secondary off-normal spring, which assumes its alternate position. It will be understood that both the primary and secondard off-normal springs are restored to normalonly when the shaft reaches its fully restored position at the conclusion of its back rotary travel. A tooth at 177 is omitted to render pawl 17 5 ineffective to further rotate the shaft after the eleventh step.

As before indicated, when the switch is used as a selector. or connector, the group wiper 32 is unnecessary, the switches for the selector and connector circuits being otherwise similar to the line selector except that the primary off-normal and secondary offoff-normal I On the first vertical step of the normal spring combinations will be altered to conform to the circuit diagrams. The relation of the off- normal arms 186 and 187 to the switch springs will be the same to the other switches, and mechanical illustrations of the various spring combinations are unnecessary. For a trunking first selector, a fourth wiper'and set of contacts may be provided as indicated in Fig. 1.

Referring now to Fig. 1, part 1, I. have there shown a subscribers substation including the usual transmitter, receiver, condenser and call-bell, the talking and ringing circuit being of character well known in the art and requiring no specific description, it being understood that hook-lever 1 upon the removal of the receiver, leaves its lower contacts and engages its upper contacts.

Contacts 5-6 and 78 unite the two line limbs 10 and 11 with the talking and signalling conductors of the substation. The grounded spring 9 is adapted to be actuated by the insulated teeth of diagrammatically indicated dial 3 which is rotated clockwise by the subscriber in transmitting the direc tive impulses until a number of teeth, corresponding to the digit to be transmitted,

have passed below the spring 9 whereon the dial being released on its return movement, connects limb 10, over contact 6:") through impedance 2, hook-lever 1, the transmitter and contact 7-9 to ground whereatter the tooth engaging spring 9 breaks the contact 7-8. When the tooth passes beyond the extremity of spring 9, the spring is retracted and contact 78 is again closed and contact 79 opened. This will be repeated as many times as teeth l ive been passed below the spring 9. It is apparent that an equal number of breaks in the circuit of limb 11 will be produced while the circuit of limb 10 will be alternately shifted to 'round through spring 9 and then reestablished at contact 78, the reestablished occurring before the opening of contact 'T9.

With the return of dial to normal, its tooth at the extreme left actuates spring a to engage spring 6 whereby circuit of limb 11 is shifted from limb 10 to ground through contact 4-6, whereatter contact is opened,v tnus opening the circuit of line limb 10. When the said tooth at the left of dial 3 passes below the extremity of spring l, said spring is retracted, contact 6 being closed before contact i 6 is opened, thus re-establishing the condu bridge between limbs and llthrough transmitter, hook-switch and the impedance coil of the talking circuit. he dial 3 employed in the usual manner to transmit the directive impulses to the electromagnets oi the selectiv switches, by making several sets of breaks in the circuit of line limb 11, as described, one set being produced for each digit of the called subscribers number, each set being followed by a single momentary opening of the circuit of the line limb 10.

The subscribers line is provided at the exchange with multiple called contacts 28 2930 with which a connector malzes connection when the line is used as a called line. The multiple calling contacts 22n3 Ql are also provided at the banks of the line selector assigned to the one hundred line group among which the calling line is included. At 12 is shown the line relay employed for initiating travel of an idle line selector, while at 15 is a cut-oft relay which, by its contact springs 16 and 17 control the talking connections of line limbs 10 and 11 to both the calling and called multiple contacts. The armature l t of line relay 12 controls the circuit oi group relay 21 which is common to the line relays of ten lines having their individual contacts on one level of the line selector banks. The said group relay controls by its armature the electrical condition of the multiple group contacts 31 and also has connection by its armature with the starting wire 21 eX tending to the upper armature of masterswitch relay R, and having branches tothe other group relays levels elected u l wiper engages the iilClM'lCllltil prii contact 22 or": the calling line. The primary oil-normal, 011, s rings 3l35, and the secondary oil-normal iings son are actuated by the mechanism of the line selector while the primary oilnormal springs, PON, and secondary oilnormal springs SQN to the right of the dotted line KY are actuated by the mechanism of the first selector E whose wipers are shown 7 at 63-6l'6566.

Th": first selector shown at E includes the impulse tr initting relays PE and SR, adapted when the line selector has selected the calling line, to be held energized over the metallic circuit of the line, the serially disposed batteries A and B having their common point grounded and being connected across the terminals of the two re lays. The said rlays jointly control the release relay lllt, while relay P t individually controls primary magnet PM, the secondary relay SR controlling the initial energizing circuit of busy relay BR which, when actuated, is operatively connected with private wiper oh the relay thereby being rendered sensitive to the grounded or ungrounded condition of the private contacts (58 engaged by the wiper The relay BR controls by its armature ('51, the circuit of secondary magnet SM and is thus effective to cause selection of the first idle contacts 68697O of a selected group in the well known manner. At F, l have shown the circuits of a trunking second selector including the wipers 101l0210ll, primary magnet Phi controlled by primary relay PR, being provided to adjust the wipers vertically while the secondary magnet SM is provided to adjust them rotarily under the influence of busy relay Eli initially operated by the secondary relay Slit and thereafter held energized by a circuit in cluding private wipr 101, in the well known manner, to select an idle third selector which is shown at L.

The third selector includes the wipers ll6-117ll8 and the primary magnet PM which is operable by current impulses transT mitted by primary relay PR after the second selector has completed its operation.

Secondary magnet SM of the second se lector is controlled by the busy relay BB which is initially operatedrrsponsive to a current impulse transmitted by the secondary relay SR, the circuits of the said busy relay being thereafter controlled over a connection extending to the private wiper 101 to select the first idle connector.

The connector, H, shown in Fig. 1, part 3, comprises the primary magnet PM? and a secondary magnet Sh both of which are operable responsive to directive impulses transmitted by the relay PR, the locking relays BB and LE being employed to shift at the proper time the upper strand of the talking circuit of the connector indicated by the heavy line, from connection wit-h magnet PM and to connection with second ary magnet SM Associated with the connector is provided an auxiliary switch including the wiper 156 which has access to four contacts 157, each being connected to a generator of different frequency to the end that the subscribers on a party line'may be selectively signaled by means of call-bells attuned to the different frequencies'of the genitrators, .n the well known manner. The magnet MM controls the wiper 156, the said magnet being arranged to be connected with the upper limb of the talking circuit by locking relay LE in order that the last set of impulses transmitted from the substation may operate upon magnet MM to cause Wiper 156 to select the generator of the required frequency to ring the bell of the particular subscriber wanted.

The locking relay LR is actuated by an impulse transmitted by the relay SR immediately following the selection of the proper ringing generator, and is effective to connect the test relay TR, previously actuated in a manner hereinafter to be described, with the private wiper 194 to render the test relay sensitive to the electrical con dition of the private contact 28 of the called line, the test relay TR then determining the transmission of a busy signal from busy back machine BB to the calling subscriber, or the operative connection of the-selected gcnerator to the called-for line.

A novel feature of the invention consists in this that if two subscribers have completed their conversation, the act. of the called-for subscriber in replacing his receiver, while ineffective to produce the restoration to normal of any switch employed in the connection, is however, effective to actuate the mechanism of the connector in such a way that his line is free from the busy potential placid upon its contact by the connector and is available for further use as either a calling or called line whether the calling subscriber hangs up his receiver to release theoswitches used in the connection, or not, The busy potential upon the private contact 28 of the called line is placed there by private Wiper 194 of the connector via the normal contact of armature 147 of test relay TR. The relay l38 which is provided in the path of current over the called-for line, is of course, deenergized when the called subscriber replaces his receiver and is effective to actuate the called release ixlay CRR,whose circuithas previously been closed at the alternate contact of armature 123 of locking relay LE when relay 138 was first energized on the removal of the receivtr at the called substat-ion. The-energizati'on of relay CRRby attracting its armature stablishes a circuit including the test relay TR and itself, whereby armature 147 is attracted and also armatures 146 and 150 of test relay TB in order to remove the busy potential from wiper 194 and to place theline wipers 195 desires his line to be connected with the subscribers line indicated at K by the multiple called terminals 28-2930 at connector H, and whose line circuit and substation connections are omitted from thedrawing, it being understood that they will be connected to the called terminals in the same manner as those of the subscriber C,'the subscriber at C after removing his receiver, operates his dial 3 to cause sets of breaks in the circuit of line limb 11, one set being produced corresponding in number to the units of each digit of the called subscribers line number which is assumed to be 23456, a sixth set being produced to correspond with the posi-. tion of the contact 157 of the generator G: of the proper frequency to ring the tuned bell of the called subscriber; This sixth set will consist of four breaks, the wiper 156 being required to make four steps to select the generator G Then the subscriber C removes his receiver, a circuit is closed from the active side of battery A through normal contact 17, over line limb 10, contact 65, coil 2, through the alternate hook-lever contacts, the substation transmitter, contact 7-8, returning over limb 11, normal contact 16, the winding of line relay 12 to ground, operating the said relay 12 whose armature 13 engages its alternate contact to connect the active side of battery A to the private or testcalled' multiple contacts 28 at the connectors to protect the line of the'calling subscriber against in-coming calls. The attraction of armature 14 closes a circuit for the group relay 21 from battery A which relay attracts its armature to remove the ground from the group multiple contacts 31 at the line selectors of the group which includes the calling line the said armature engaging its alternate contact and completing a circuit as follows: from ground over starting conductor 21 normal contact of armature of relay R of the masterswitch T through wiper 190 of the master-switch, contact 192 of the idle line selector D, the master-switch wipers 190 and 191 normally resting engaging contacts of an idle line selector (it being understood that each line selector of a one hundred line group has its individual contacts 192, 193 before the wipers of the master-switch T of said line group) the circuit being further traced through contact 4L5, off-normal contact 35, primary relay p1" of the line selector, to battery A Relay pr attracts its armature 36 to close a circuit from ground through secondary off-normal spring son, secondary relay 5? to battery A operating the said secondary relay whose armatures 39 and 42 are attracted disengag ing their normal contacts springs whereby a circuit is completed from the positive pole of battery B, through primary relay PR of the first selector E, through normal contact 48, alternate contact at 39, alternate contact at 42, contact 49, secondary relay SL to the negative pole of battery A, the said batteries A and B being serially connected and having their intermediate point grounded as shown. The relays PR and SR are operated to close a circuit through release relay RR of the first selector before the relay pr of line selector D can cause the line selector to make a step and have its armature 36 thereafter retracted whereby a premature operation of release relay 1')" of line selector D over armature 5d of relay ER is effectively prevented. When relay pr was energized, its armature 38 was attracted to close the circuit of primary magnet pm, which magnet, under the influence of impulses transmitted by generator G, steps the shaft and wipers 'E--26-27 of line selector D upward as long as relay pr remains operated. The said relay pr in attracting its armature 37, connected the relays winding with the group wiper 32, thereby rendering the said relay sensitive to the grounded or ungrounded conditions of the group contacts 31. I have shown in Fig. 1, the group contact 81 of the line of subscriber C as adjacent to the normally grounded rest contact of wiper 82 so that but one step of the line selector is required to bring the wipers 2526-27 adjacent to the levels having line contacts of subscriber C. The first movement of the linevselector shifts the primary oil-normal springs pow 3334l35, whereby the relay 37 at spring is disconnected from the starting wiper 190 and is solely dependent for continuance of its energization upon group wiper 32. Thus, on the first step eiiected by primar magnet pm, the

wiper engages the ungrounded group contact 31, relay pr is de-energized and further actuations of primary magnet pm, prevented at retracted armature 38 of the said relay n".

The relay, s7" operated as before described, has its circuit continued through secondary oil-normal spring son to the shifted primary on normal spring and remains energized when the armatures of relay pr are retract d. Hence a circuit is completed thro 'h generator G", secondary magnet 8172-, contact 41, normal contact 38 to ground over which circuit current impulses flow through secondary magnet cm, which steps the wipers 2526-27 rotarily over the contact sets of the selected level. With the first rotary step, secondary off-normal spring a diseng ges its contact whereby secondary relay 87" is dependent for its continued energization solely upon a circuit extending through normal contact 4L3, alternate contact ll), through private wiper now engaging successively the individual private contacts 22 of the lines of the selected group. Noncalling l nes will have their contacts .22 grounded at normal contacts 1 of their respective line relays 12. Thus, while wiper 25 is passing over contacts 22 ot such lines, the relay s?" will continue energized and successive pulsations will flow through secondary magnet sin. soon, however, as wiper 25 engages contact 22 of the line of C said contact will be opened or ungroui'ided at armature 14-, relay s? will have its circuit opened at said armature and the relay will be tie-energized, armature 4-1 opening the circuit of secondary magnet 8m whereby additional movements of the secondary switch are prevented and wipers 2526-27 rest in engagement with contacts 22 232 l or the calling line. Armature 42 is retracted, effecting closure of a substitute circuit for relay Silt oi switch E before the original circuit broken, the said substitute circuit extending from batter A through normal contact of armature 42, contact 272l, contact 19-20, cut-ofi' relay 15 of the call-- ing line to ground. Said relay 15 by attracting its armature 18 completes a locking cir cuit for itself extending through said contact, contact 2 25, normal contact 4-0 to the active side of battery A In attracting its armature 17, a substitute circuit for relays PR and SR is completed, extending from battery B through relay PR, normal contact as, normal contact 39, contact 26-23, over limb 11 of the line, contact 87, through transmitter and impedance coil, re turning over contact 5--6, limb 10, contact- 17-19 now closed, contact 24.27, normal contact -12, contact 49, secondary relay SE to battery A. By the make-before-break arrangement of armature 42. this substitute ircuit is completed before their relays PR iii and SR are deenergized and their armatures retracted. I 1

The master-switch Wipers 190 and 191 are now caused'to move over contacts 192-193 of the ten line selectors such as D which the master-switch is assumed to serve, in search of an idle line selector, the relay R having been energized by a circuit extending from battery A, through said relay, contact 191193, normal contact 46 through normal. contact 40, contact 25-22, alternate contact 18 to ground through relay 15. The relay R thus attracts its armature to close circuit through magnet m which drives the Wipers by any approved mechanical connections. It is obvious that vas long as wiper 191 is wiping contacts 193 of line selectors in eugagement with the calling lines, the relay R will be energized over a succession of locking paths similar to that just described, but when the wiper 191 reaches a contact 193 belonging to a line selector at rest, the said contact 193 will be open at wiper 25, relay R ole-energized, and also magnet m of the master-switch whereafter the wipers 190 and 191 rest in engaging the contacts of the idle line selector ready to start the sameresponsive to the initiation of a-call. The conductor 21 is a common conductor, a branch thereof extending to each group relay 21 of the ten ten'line groups. v

VVhen-cut-off relay 15 was energized, its armature 16 opened the circuit of line relay 12 whose armature 14 falling back deener-r gized the group relay 21 so that as soon as the calling line was selected, the starting ground was removed from conductor 21 and the ground restoredto the group contact 31 so that the level of contacts at the line selectors including that of subscriber C will remain unselectable until another subscriber of that level initiates a call.

The first selector E is now operatively connected with the calling subscribers line and he proceeds to operate his calling device 3 actuating the same a first time to effect two breaks in the circuit of conductor 11 followed by one break in the circuit of conductor 10. As before explained, each tooth of dial 3 in the return of the actuated dial closes contact 97 before breaking contact 7-8. Thus relay SR is held energized over a circuit extending over limb 10, contact 6-5, the impedance coil, 2, the transmitter and contact 7 9 to ground, while the relay PR is de-energized by the breaking of contact 78, while with the return of spring 9 after a tooth of dial 3 passes beyond it, a metallic circuit through contact 7+8 is reestablished before contact 79 is broken. Two de-energizations of primary relay PR caused by the the first actuation of dial 3,

are effective to transmit two current impulses from ground through secondary off-normal PON are shifted to engage their alternate contacts.

Following the second de-energization of primary relay PR, secondary relay SR is de-energized by a break caused in the circuit of limb 10 of'the line of subscriber L) by the, last tooth of dial 3 in its return to normal, the said dial operating uponrspring 4 to first close contact 4-5 and then open contact 56 whereby relay PR is maintained energized while relay SR isfde-energized, as before explained. The de-energization of relay SR caused an impulse of current to flow from grounded secondary off-normal spring SON through attracted armature 55, retracted armature 53, secondary off-normal, SON, contact 58, busy relay BRto. battery A energizing the said relay, which attracts its armatures 59 and 62 to place line wipers -66 on open'circuit, armature 61 to close, a circuit from generator G" through secondary magnet SM to ground, which magnet is now effective to move the wipers 63-64 6566 step-by-step over the contacts of the selected level. Armature 60 of busy relay BR completed a circuit for said relay. from battery A extending through normal contact 47 attracted armature 60 to wiper 64 and to themultiple private contacts 68 engaged by said wiper. Such contacts 68 as pertain to busy second selectors F willbe grounded, and relay BR will be looked over a series of successive locking circuits until wiper 64 engages a contact 68 pertaining to an idle second selector, at which time relay BR will be Clo-energized, and its-armatures retracted; whereof 60 will place a busy ground upon wiper 64' then engaging multiple contacts 68 of the selected idle second selector, while armature 61 opens the circuit of secondary magnet SM, whereby wipers 63646566 rest engaging contacts 6768'6970 of the idle second se-i lectorassumed to be F. v

In the present description, it is assumed that the conductors T and T connected to the contacts 69 and 70 are connected to a trunking second selector F located at a dis-- tant exchange, under which circumstances of course, a two-conductor trunk is very desirable. The conductor shown as ex-' tending from the 'multiple contact 67 to ground at the second selector F in the distant exchange is not an individual conductor shifted on the first secondary movement of the first selector, the wiper 63, connected, on selection made, to the multiple contact 67 provided for the common return 100, is connected through armature 55 and the primary off-normal contact PON 7 2 to the back contacts of the armatures 51 and 53 so that the next impulses transmitted by said relays which will pass over conductors TT as hereinafter explained, will be from a ground local to the battery A by way of the com mon return 100 or from a ground having a potential within operating limits like that of the ground return of the distant exchange battery.

With the first secondary movement of the first selector E, the secondary off-normal springs 58 and 59 were shifted to disconnect magnet PM and the busy relay BR from the armatures 51 and 53, which armatures will then be connected over a clear circuit extending through contacts 65-69 and 6670 to the trunking conductors T-T.

The conductors 200 and 100 are for alternative employmentand in the present description, it will be understood that the conductor 200 is to be left disconnected. If, however, there was no operative difierence of ground potential between the two exchanges, the common return 100 would not be provided at all and the local ground conductor 200 would be used. I consider the use of a wiper as 63 employed in connection with a selector to pick out a special return conductor according to the exchange to be connected with, to be new in the art.

The calling subscriber 0 now actuates his calling device 3 to produce three breaks in the circuit of conductor 11 followed by a break in the circuit of conductor 10. Three de-energizations of primary relay PR are thereby caused, and each transmits a current impulse from ground over common return 100, contact 67-63, secondary off-normal switch SON, off-normal contact PON 72, normal contact 51, contact 59, contact 6569, trunk conductor T, contact 83, primary relay PR to battery A energizing and de energizing relay PR thrice whereby three current impulses are transmitted from ground through alternate contact 88, contact SON primary magnet PM, to batpulse of current from common return 100 over the before traced path, through normal contacts 53 and 52, contact 6670, over trunk conductor T through armature of relay 86, thence through normal contact 85, primary off-normal contact PON secondary relay SE, to battery A operating the said relay which through attracted armature 90 transmits a current impulse from ground through secondary off-normal contact SON primary off-normal contact FON now shifted, busy relay BR to battery A. The said relay BR attracts armatures 9699 to place line wipers 101-102 103 on open circuit while wiping over contacts 105 and 106 of busy third selectors L, while armature 98 completes a circuit for generator G through secondary magnet SM to ground; armature 97 completes a circuit for relay BR extending from battery A through normal contact 95, alternate contact 97, wiper 101 and to the multiple private contacts 104- engaged by said wiper, such contacts as pertain to busy third selectors such as L, being grounded at normal contacts 97 of the second selectors rendering them busy. Thus, relay BR will continue energized, holding its armature 98 attracted and causing successive actuations of magnet SM until the wiper 101 engages contact 104; which is ungrounded, that is, one pertaining to an idle third selector. When this occurs, relay BR will be de-energized, its armatures retracted, 97 placing ground upon multiple contacts 104 of the idle third selector L; and 98 opening the circuit of secondary magnet SM whereby wipers 101102103 remain engaging the contacts 104105106 of the selected third selector. On the first secondary movemnet of second selector F, the secondary off-normal springs SON and SON were shifted whereby magnet PM and busy relay PR" were cut-off from armatures 88 and 90 and said armatures provided with clear circuits extending through to contacts 102 and 103.

The third set of breaks caused by subscriber C in limb 10 consisting of four, are effective to cause four de-energizations of primary relay PR which effects four energizations of relay PR in the manner before described. The said relay PR transmits third four impulses from ground through normal contact 96, contact 102 105, the vfirst current impulse transmitted then dividing, a

armature 97, the attraction of armature 107 opening contact 108 and disconnecting the 1 relay RR from contact 105. :The rest of the first impulse passes through magnet PM? which steps the shaft up one step; Thethree other impulses of the four pass through magnet PM only, the switch wipers being thus raised to positions horizontal with their fourth levels of contacts forming terminals of connector switches assigned for connection to lines numbered from 23,400 to 23,499. r v

A break in conductor 10, following the four breaks in the conductor 11', produced the de-energization of secondary relay SR which transmits an impulse to secondary relay SE. in the before described manner,

t which relay attractsa-rmature 90 to-t-ran'smit an impulse from ground through normal contact 99, contact 103106, secondary off- .normal contact SON primary off-normalcontactPON shifted with the first primary movement of third selector L and through busyrelay BR to battery A which relay attracts armatures 1l1l15 todisconnect .line wipers 1171 18, armature 114 to cut 9 in secondary magnet SM and armature 113 to complete alocking circuit for relay BR extending through the attracted armature 110, of release relay BB and alternate contact 113 to private wiper116- and multiple private contacts 119 of the connectors of the selected level. Contacts 119 of'b-usy connectorswill be grounded. and relay BB will continue energized until w1per'116 engage-s an ungrounded contact 119, one pertaining to an idle connector H, whereon-relay BR .will bade-energized and its armatures retracted, Wipers 116-117-118 being left resting in engagement with contacts 119- 120121 of the selected idle connector H. Viththe first secondary movement of the selector 'L, secondary off-normal springs SON and SON were shifted whereby primarymagnet PM and relay BB were disconnected from the armatures 88 and 90 of relays PR and SR and the said armatures, connected through by a clear circuit to wipers 117-118, as soon as armatures 111-7-115 of relay BB were retracted.v 'The fourth set of breaks caused in limb 11 of the line of subscriber C, consisting of five breaks, are effective to operate the relays PR and PR in the before-described manner to transmit five impulses from ground through armature 88, contact 96, 102105, 111, 117120, through normal contact 131,

itselfby its armature 143 from battery A over private contact 119, wiper 116, normal contact 113, contact-104-101, and the ground at 'normalcontact: 97, the busy ground for contact 119 being traced to said contact97.

pulses pass through said magnetonly, armature 143 of relay RR. having disconnected the relay windingfrom the normal contact of armature 131. Thus the Wipers 1-94195- 196, of the connector are stepped up to their fifth contact level, comprising contacts of lines numbering from 23,451 to 23,459 followed by contacts of line 24,450, it being understood that zero is'represented by ten impulses in automatic telephone systems.

The break in limb 10 of the line of C following the five breaks in ,limbll, de-energizes relay SR which energizes relaySR which transmits an impulse from ground through alternate contact 90, contact 99, contacts:103106, 115, 118-121, through primary off-normal contact 128 of the connector H, shifted on the first primary movement thereof, and through locking relay LE to battery A the said relay locking itself by armature 132 to ground at shifted off-normal contact 129. Attracted armature 133 of relay LR- completes a circuit from battery A through armature 133, through the normal contact at armature 152 of relay LR", through attracted armature 144, armature of relay CR-R, test relay TR to ground operating the said testrelay which continues energized until the transmission of the last subsequent impulse. The set of gizes relay PR six times, whereby six impulses pass through armature 88 over the before traced circuit, through contact 117- 120, through alternate contact 131 of the now energized relay LR through normal contact 140, through alternate contact 142 of the energized re-la BB and through secondary magnet S 3 to battery A whereby magnet SM is energized and deenergized six times, and causes wipers 194 195'196 to engage the contacts 28-2930 of the called subscribers line being line numbered 23,456, the'line Wipers 195 and 196 being on open circuit at contacts 146 and 150 while wiping over multiple contacts 29-30. of lines not wanted. The break in line limb 10 caused by dial 3-following the last of'the six impulses mentioned, is effective, by the de-energization of relay SR and the: consequent energization "of Irelay SR, to transmit; a cu'nrenti im'pulseairom ground through the winding of: locking" relay LE 1 .,to-;'batteryA the-said relay attracting its '10 arm-atures and locking itselfby-a1unature 139 to ground at 'p1'imai1'y Jeff-normal spring ::The next set of breaks caused by subscrib- -cr (liiiialinibell sent toi the purpos'e of selecting the; desired generator zGr which breaks will. beat'our' in number, by de-ener gizing rclay PR :and cnergizing relay PR, causes transmi'ssi on of four. current impulses from groiuid'at armature SS'oVer therbefore tracedyfpz-uth zthrough :contact "117- 120, the

impulses now passing through alternate contact 131," alternate Contact :140,:norin'al contact 151', motor magnet MM of theg'enerator switch to ebattery. ilk, said magnetMM 'be- .ing; energized four .times and being effectiye, byv a Well known nieohanical arrangement, to move gwip'e'r 156' four l steps to rest engaging contact 157 ot-generator Gf; Thisgeneratorga s beforewindieated, delivers current of c a -:frequency to ring the. bell" ofthe" particular subscriber Wanted on thecalled-for line, the party line system preferably operating on the Well :kn'oW-n'wtunecl'reed' princip'le: The foursubstationson the calledfor line Will: be connected in multiple, as indicated at; the line*o'.t'= lythe Wires G, G G indicating the itapsxto'tli'e other substations telepho11es.- T

i A. final v,brealcin line limb 10 causes the transmission; of an impulse,-a's* b'efioredscribed, traversing icontact -118- 121, thence through primary off-normal -;co ntact- 128, shifted; secondary oft-normal spring :SON elf-normal sp ring- ON of the generator switchiwhichmms shifted on the-firstmovement thereof and through thelocking relay Lltto'batteryrA the said relay by. armature 153 locking itself to ground Via-priinary off-normalspr-ing129L- Thesaid relay LR attracts its armatures:whereon 152 now connectstest relay TR With the test Wiper 194 over a circuit extending from relay TR through armature ofvcalled releaserelay CRR, alternate contact 144, attracted makebefore-break armature 152, the attracted armature147 and thence to said Wiper194. If the called line is busy; relay TR'remains energized; While it idle, the said' relay-becomes (lo-energized, because if-thei line is idle (it being remembered that'the line circuit of the calledoline'IQ is identical with that of the calling line of C), theprivate contact 28 Will 2130 connected" 'toground through normal Contact 13- and cutofl"irelay 15. I (See line circuit of C.)

It Will be assumed first that the called line is 'idle', thebusy line features being hereinaftereziplained. :The relay TRfhaying-thu's' the itwo ends "of its Winding grounded, "i'become's tle-ene'rgized and its armatures are retracted 'to engage their normal contacts, whereof 147' connects battery A through a" suitable resistance to" wipe- 194' and the private-"multipl's"28 of the caLledLIine rendering the linebusy by raiscausing the operation of "cu t-off relayf15 "of, the. called line which disconnects the line relay 1-2' so that it will remain 'inert when the called slibscriber' inswe'irs." Sa d relay ing'; the potentialat' s'aid contact, and also" 15' ot the called-line byarmaturefi co'ih- ,called subscribei s iline -to" the talking n'niltiple-contact 30, as will be understood by inspecting the line circuit of G5 Qiithe retraction of armature 149, grounde'd ingized and de-energize'd, =periodically ringing the c'alled' line, over the line limb and through' the substation, ringing thetal'l' bell, returning over limb 11' of the called line through contact 29-495 and to 'grounct at the attracted upperarmature of relayell.

f T1 The called subscriber" answ ring the call removes his receiver,festablishing condu ttive bridge of the line limbs "at-his substation whereon as'soon as -r'elay GR is de ener "'jzetl, a circuit is completed' from battei'y A through the upper Winding of "ini'p'danee 136,contaet- 146, upper armature Meatbatact 195 919, over limb 11""o'f the called line through transriiitteran'dimpedance c'dil at the substation,- en'ergizing the t'ransl'nitter for talking,returning-ova" limb 10, alternate contact l7,--c'ontact 30-196,-"lo er' armature of-GR, armature 150,-i-e1ay'1385af1fl its non-inductive shiint, to ground through the lower Windingot impedance 136. The attracted armature of relay"1 3 8 energizes locking 'relay L'R which islo'cked by armature "126 to ground at :contact'129, Where'oh the said relayattracts its 'armatures','1 24 disengaging =itscontact to prevent the further operation of e e-nerator 1"elay" GR whereby ringing 'current'is kept 'e'xcluded frfo'm the called line 'While 'armatures 122 and 127 complete the talking circuit of connector H, indicated by the heavy lines, by engaging their alternate contacts;v Current 110W 'fl'ows from battery A- through alternate contact contacts 120 1-17", 111 105 '102, 96,

normal Contact '88, through the lo ure'nw-ind ing of relay 82, armature 81 normal contact lay 79 across trunk conductorsTT whereby current is caused to flow from battery A", overlimb T, through cont-acts 66, G2, alternate contact 53, control relay CR, alternate contact 51., contacts 59, (55-439, trunk conductor T to ground through alternate contact 83 and relay 79. Control relay GB at switch E is thereby operated, its make-beforebreak armature, switches reversing the connections of batteries-A and B to the calling line, the-system being thereby' adapted for use in connection with polarized pay stations or call counters "connected with the talking conductors of the subscribers line, such structures being well" known in the art. Armature engaging itsalternate contact completes acircuit from battery A through release relay RR, alternate contact 80 andto ground through primary 011- normal contact PONfl the said relay locking itself at said'groundby armature 94c,

' while armatures 79 and 81 complete the circuits of theupper and lower talking conductors .of the switch F whereby a complete talking circuit between the calling and called station is produced which may be traced from the substation C over the line A limb's andthroughout the exchange by the heavily marked conductors talking, current being supplied to the transmitter of the subscriber G from the series batteries'A and B through the inductive resistances ofrelays PR and SR, and to the called subscribers line through the inductive resistances of the windings of impedance 136 from battery A It is to be understood, that the multiplicity 7 of batteries indicated througho'utthe drawings by the letter A with different exponents may be, and preferably are, in case all the apparatus is in one exchange, the same source of current, the plurality of symbols referring actually to but one instrumentality. The source B having'its opposite; pole grounded from that of source A is, of

course, a separate battery. In the just preceding description however, it being assumed that the trunk lines T T" yinterconnect two distant exchanges, there would:

to their releasing position, when they debe two sources of current A, these sources having their positive poles grounded, one In such case, the

being at each exchange. battery symbols A to the left of reference would refer to a second source.

It will, "of course, be observed that the "calling subscriber G has current supplied to his line' from a source including the seriesbatterle's A, B of double potential as compared with the single battery A supplying current to the called line, the distribution of the proper amounts of current to calling and portionings of resistances forrelays PR SR and for the windings of impedance 136.

called lines being effected by suitable proscribcr K does this first, relay 138 is de-energized and its armature retracted to close a circuit from ground through resistance- 201, alternate contact 123, called'release relay ORR to battery A, which relay by attracting its armature causes the energizationof test relay TR over a circuit extending through the attracted armature of ORR and to battery through said relay CRR, the resistance, 201 being provided to prevent the shunting of relay TR' at the grounded armature'pf relay 1 38; The energization of relay TR places wipers 195 7196 on open circuit and also the private wiper 194 whose circuit will be found open at the attracted armature of called release relayGRR. Battery isthus removed from the private contacts '28 ofthe called line and its cut-off relay 15 is tie-energized so ,that the called line is now in position to initiate a call-or becalled by some other subscriber although the wipers of connector H have not been disconnected from the contacts 282930 of said called line. The replacing by 'thejcalled subscriber of his re- -ceiver thus frees his line without causing the restoration of the connector to normal.

' energized, its armature 54 closing'acircuit from battery A release relay'W' of the line selector D to ground through primary offnormal contact 34 ofthe line selector and armature 36. Armature 4L3 energizes secondary relay .91 by connecting it to ground at contact 33, "which relay 8?" operatively connects in circuit secondary magnet; sm which rotates the-wipers of the line selector o ndary relay s2" de-energized by contact 33.

Release relay w", however, which by arma ture 44M51S locked to ground at spring 34 of the --li.ne selector 1) and spring-PO13 at the iirst'selector R, will remain energized By armatureir' release relay 1 completed a- 'circu it from grounded primary 'ottnormal "spring 1 through busy relay BR,

which relay attracting its arn-iature 61, brings secondar n-i'agnet Slit into play 'whi'chrotates the wipers 63 Wi 66 to their restoring positions whereon thefiiir'st selector E is restored and when it reaches zero, by opening contact PON d'e-energ-izes -release relay T7 in case the line selector is already restored. places aground upon contact 193 of the line selector, so that -itwill render-it busy tothe master-switch T while being restored.

Armature L6 oit'relay r1" -.Arii1-ature4 :l de-energizwl cut-elf relay 15 byjle'aving its normal contact. 1t will be understood that when the switches -D and Ereach normal, allthe oit-normal contacts are shifted back tothe positions shown at Fig. 1,-andthe-apparatus will then be at normal.

The restoration of the trunking second selector "F iseffected by the energization of busy relay BR'ot switch E opening the T which tie-energizes =pletes a circuit ztor busy relay BR extend- -ingthrough attractedarmature 95, normal contacttogroun'd through primary offnorm-al spring 'PONH armature 81 in fall- -in'g-back,-completes a circuit from battery -A through relay 86, '-normal contact 81, attracted armature 9 1 of relay RR, primary off-normal contact'PON to-grou-nd so that relay 86 will be -energize'd until the switch F reaches normal. The operation .of'relay BR operatively connects the secondary magnet SM, which rotates the 'S\V1tCl1 F until-thewipcrs reachtheirrestoring position when the shaft falls and is rotated to normal, at which time -the oftnorinal contacts-are restored and the switch is ready for further use.

The 'relay-86 just referred to, is'provid'ed for holding the multiple contact 68* at the distant "exchange busyywhil'e the switch F is being restored, co-operating' in so doing with the double-acting relay 74:. This relay 74 mayinclude thecircuit-changing springs -77 and-78-and"an angular armature having .two tulcrums 7 6 and 7 5. hen a-relatively .ed fiow through relay 74 crum 75 strikes the longitudinally extendslight flow of current passes through the winding of relay 7 i, it will 'be energized sufficiently to-rotate the armature about the fulcrum 7 6 and willthen causespring 7 8 to engage-its-contact springs, but the operating end of-thearniature will not beraised sufiiciently to shittthe spring 7'7 by'this limit- As soon as fulingheel iron, the etficiency of the armature lever is obviously very materially decreased gized, and switch L .is at normal.

by the increased"length of the-"load armand the armature stops-1n anint'ermediate 1pos1- until thefirst selector also reachesnormal.

caused through the r-clay 752, the armature will continue to be attractedafterfulcrum 75'strikesthe heeliron -and iii-addition to closin contact 78 thearmature-will be attractedsuiiiciently to open contact 7?. At

ter'thelirst selector has selectedthetrunle ing second selector and assoon as the tirst" current impulse is transmitted, responsive to a de-energizat1on otsecondary-relay SR,

through contact 6670,a portion of this current will pass throughcontact T7 and relay 7 1 to battery A whereby the relay will be energized-to close contact 76; wher'con a low resista nce circuit tromground at contact 60 and through contact 64-68 'will'im inediately come into play, tullyfoper ating relay-7% so thatcontact will be opened and the relay winding 74 disconnected from the; trunk-limb T. Vi *henrelay BR was"en =ergizedto release thefirst selector E, it not only deEenergiZed relay 79' of switch F," but by armature 60, (lo-energized relay As' soon however, as the relay 86 of switch'F attracted its-armature'as before described, 1t

connected "'{ljlOl-llld through resistance 202 with limb T andthrough contact '77 with the ground "at 202 renders the; multiple contact 68busy during release ofswith If.

Returning now; -when busy relay BR was energized, its armature 97 -opene'dthe circuit of wiper 101, since armature -was then attracted, andcaused the de-energization of releaserelay ltIt of hird selector L and of release relay En ct connector H, these relays having'been locked inparallel toground'at armatureQZ; both'rela'ys become file-energized, RR closing'a circuit for relay BB at retracted armature 109; relay 133 then operatively connects secondary magnet SM? which rotates the wipers 0t switch L to the restoring position-when they fall and are rotated back to normal shifting the primary cit-normal and secondary .05- normal springs to their positions-of rest as shown at L, whereby relay BB is de -enerlVhile switch L is restoring, armature 112 holds multiple contacts 104 busy.

Relay RE at switch H has its armatures retracted whereon 142 completes a circuit from battery A through secondary magnet SM and attracted armature 134: through constantly traveling interrupter I, *wlii'ch transmits impulses to secondary magnet 8M until the wipers 194-195-196:r.ach

' their restoring positions, when they descend and are rotated back to normal at which time the openingv of the primary off-normal springs PON and the secondary off-normal springs SON cause all the locking-relays and apparatus of the connector to assume their usual 'inert conditions, the circuit of relays CRR and TR being opened at armature 123. The retraction of armature 141: of relay RR operated relay 137 by curr-tntto ground at oil-normal spring 130, relay 137 attracting its armature to hold ground upon multiple contacts 119 to prevent selection of the connector -H until the switch reaches normal, -when relay 137 becomes de-energized. The retraction of armature 145 connected ground through off-normal spring ON of the generator switch through release magnet RM to battery A, the magnet RM withdrawing a retaining dog from association with the ratchet of wiper 156, when this wiper is restored to normal by a suitable restoring spring, in the well known manner, at which time off-normal springs ON and ON. will be shiftedzto normal.

Such switches as the generator switch comprising. a rotary shaft having a ratchet and wiper and a motor magnetto drive the ratchet and a release magnet controlling a restoring pawl, are well known and illustration of the mechanical features of such are unnecessary. The same is'tru'e of the mas-' ter-switch mechanism which may include a rotary shaft provided with ratchet and wipers driven by an armature actuated pawl of magnet m,,no retaining dog or release magnet being required as the switch is" not provided with a restoring-spring, the wipers always being rotated in one direction.

If, at the time test relay TR, by the operation of locking rela LR was connected to wiper 194, the called line was busy because some other subscriber has already es tablished connection thereto, the multiplecontact 28 engaged by connector H would have been connected to battery through retracted armature 147 of test relay TR of the connector already connected to the line. If the line of the called subscriber had been busy becauseit was a calling line, its multi ple contact 28 would have been connected through normal contact13 of line relay 12 ot' the called line through alternate contact 18, and contact 22-25 of the line selector connected with said line and normal contact 40 of said line selector with the active side of battery A, as will be understood from an inspection of Fig. 1, 'part '1. In either of the above cases, the multiple contact 28 would be at a potential other than ground, test relay TR would have continued energized owing to the development of the pocuit with said line.

tential u po-n the multiple. contact 28 engagedmby wiper 194 of connector H into current circulating through alternate contact 147, alternate contact 152, alternate con tact 144, armature of relay ORR andthrough relay TR 'to ground. .The armatures of said relay TR continuing attracted,

busy back machine BB would remain con nected inoperative relation with the calling subscribers line. over a circuit extending through alternate'contact 154, attracted armature 148, normal contact 122, contacts 120-117, 105-102, through condenser 87 over limb T, contacts 69'65, alternate contact 51, condenser 158, normal contact 48, contact 2623, T over line limb 11, and through the substation giving the busy signalinthe receiver,- returning over limb 10, contact 1719, 2427, normal contact 49 and to ground through relay SR and battery A-. The calling subscriber hearing the signal, replaces his receiver and the release of the apparatus employed in the connection,

proceeds, so far as lineselector D and the J firstselector E are concerned, in the manner as that before described/ The release of the second selector F, however, is accomplished in a different manner. It Wlll be observed that release relay RR of switch E is pro-.

vided with a non-inductive shunt which renders it slow torelease its armatures.= Therefore, after relays PR and SR are de-enermultaneously over the trunk conductor TT from ground at conductor 100 and through relays PR and SR over thebefore traced path, it being remembered that owing to the failure of a response at the called substation,

relays 7 9 and 82 have remainedinert. Re-

lays PR and SR being thus simultaneously energized, now f first close circuit from "ground through attracted armatures 89- 91 and release relay RR 'to battery A The release relay being now energizedand relay 79 being 'de-energized, circuit is closed through busy relay BR and the release of' second selector F, first selectonLj and connector H, proceeds as befo're described."

It will be remembered that. as soon as the line selector D hasselected the calling line, the relays PR and 'SR are connected in cir- If before the calling subscriber actuates his calling device 3, he

;replaces his receiver, the de-energization' of relays PR and SR will restore theline se-' lector D as will be understood from the preceding description. Similarly, if at any time during the processof putting up a con- 'nection, the callingsubscriber replaces his receiver, the de-energization of relays-PR and SR will cause whatever switch he may have. set from normal to be released and restored.

If the calling subscriber should remove and replace his receiver, thus transmittinga flash-.signalonly so that the group relay 21 was energized to start-:the selector D but did notremain energized until group wiper. 32 selected the. group contact 81, thenthe primary relay. p1 willscontinue energizedum til the switch hasmade aneleventh vertical. 1 movement, at which time, group wiper. 32 will pass beyond the topmost group cont. tact 31v and relay 3? will .be. Clo-energized Immediately thereafter, the. secondary magnetsm will be .operatively connected through retracted armatures .38 of :relay pr, and thelinev selectorD willibe, rotatedeelevcn steps; to its restoringa'otary. position and be automatically restored.

As before indicated, thegroundcconduce tors lOO ancbQOO- are not;for simultaneous use, but arealternatives, that zis to say, if the ground conductor 200 :is used; the wiper 63, contact: 67 a and the.:-.com-mon .return .100 are superfluous, as would. .also be the secondary olfenorma-lrcontact .SGN' at switcltE all impulses: whether for: thelecal or.- for-the distant exchangeworkv being then; trans-. m-itted' 1. from ground sfroma. local commonreturn 200.- Db'GliGVG-dt ta-benovel Iinautos m-atio telephone. systemsztouse .the wiper of a iswitchwto piclc up-a particularcommon return-.- cond-uctor. such: -.'as 1100' which,- of :course leads preferably to ia point-havingan earth potential about the same as: the earth \where the-batteryvof jitlre exchange: containiijig the nvitchll h is -.loca-teda: lnrcasethere 'were a-.= series, say 1 three or four distant: exchanges, each having second zselectors i l with 11111.14

tiple terminals eappearing; atid i'iferent levels: in the banksof the. first aSGlGClEOIi. Einoffl-the exchange of subscriber G, then the contacts 67. in :eaclr .lerel,-'. containing terminals of Ethe second selector ofrone. erfchange, may be connected a to the. particular common return for'that. exchange. sov that the nvip rel-v63. may; pick? out :a: returnc conductor of: a plurality. of predetermined I potentials, the. conductou picked 'outein any: caseibfeinguof a1, potential: especially suited for: efficient operation of? p the apparatus .1 of lithe exchange. to. which; it"

mayb assigned;

It is to be stated:that forrlocal 'work; the V seconda'selectoramay, ifdesirrcd; be: ofsithe same character as that. shown at 1?; that is: to say where: a veryxgreat amount ofitrunle ing is 1 expectedi'to-ibe done; it." 111315 4 be considered preferable for the purpose of? se.-. cu-ringg -con-formit-y:in apparatus, to. have. all second selectors:= off? the clraracteu; of that? shownat although forlocalcalls, the-v secondQ seleotors won l contain more ape. paratus: thaw would be: absolutely 116N381 sary.

Iu-case for local business such second :se l lectors as Fwerenotdesired, a duplicate of the structure. shown at L may be'employed as second selectors for local business, that isto say, theiirstselector structure ofE- issoarranged that the wipers .64.6566 and the other apparatus of'swit'chiE will work pref erably' in connection with contacts. 104+. 105 -10S ofthe third S6lCtOI3.L, no change whatever being required. Foirinstance, let 751/5 it'be assumed that theswitch F isomitted andthat L is a second. selectortol be selecteddirectly by the first selector-"E, the second selectorL selecting :theconnector H in th ebefore described manner. thousand line systeinwould ofcoursebehad, Thev de-energizations of primary relay PR would transmit impulses from ground at connector 200 and. through contacts 65105,

through primary magnet PM i, the first irnpulse energizing release. relay BB The de-. energization ofrelay. SR would transmit an: impulse, through contactr66-elO6 to; energize. busy relay BR 'OfS\Vl;t'C11fL- in .thebefore de scribed manner. The primary magnet Ph and busy relay-BR would .becut .oifinttlre described manner; Successive sets of? iin..-.. pulses would be transmitted by. armatures 51 and 53 'o relays BRrand SRrto the -.circu-it= of the connector operatingit, as before (le scribed. W'hen the called subscriberanswers the call, ZMCliCUltifOT tl'IB reversing control relay GR atrtirst:selector E wouldlbie Lcompleted directly fromzbattery A?" through.

contactx65, returning throughcontaet.

(Ed-106:v hen the calling; subscriber re placed his receiver, release relay .RR- of line selector L andR'R? of;connector H'wh'ich during conversation would have been looked.

over. contact. l0zel-r-ee6lnto. ground ;at normal 1053' on, .V 1. An automatic telephonesystem inclucb.

ing a: subscriberlsi line extending-- by its limbs. to the exchange, a pair of serially connected sources of electrical: energy at the exchange, a connection from one .poleofe eachsourceto one limb .of saidline, a relay for -eachsaid connection having its winding. in circuit with a-line limb, and the respec--. tive connection, athirollorreturn conduc.-.. tor :connected the junction pointota said sources, switching mechanism at the sub- In suchcase, a ten;- 80? switch responsive til-Said relays jointly servergiz ed over said metallic circuit, circuit changing members for sa d sw1tcl1 ng mech-' anlsm, an actuating device for said members,

included in said mechanism for operating said members to connect: one} of the line limbs to said third conductor, whereby'the relayjof, said limb is maintained operated, and thereafter opening the circuit of the other ,line limb whereby the second relay is 1de-energizedlinkscir'cuits, and a selective s with said telephoneline. I c v 2 ;,An automatic telephone system including asubscribers line extending by its limbs to the exchange, a pair of serially connected sources ofelectrica-lenergy at the exchange, a connectionfroin onegpoleof eachsource tofone limb, ofsaid line, a relay for each said connection ha ving its winding in circuit to connect an indifferent. idle link-circuit with a line limb, and the respective connec-I tion, a, third or return conductor connected atthe junction point of said sources, switching mechanism at the substation of said line including a, connection to isaid third or re-r turn conductor, means for closing the met-alk thereaftr lic circuit .of said line at the substation whereby said relays are energizedover said, metallic c1rcu1t,. circuit chang ng members for said switchingimechanism, an actuating device for said members includedinsaid mechanism for operating said members to connect oneof the line limbsto said third conductor, whereby the relay of said limb: ismaintained operated, and thereafter open-; ing the circuit of the other line limb whereby .the secondrrelay is de energized, ineansy tact members, aconnection ,from said device fo -subsequently re-establishing the metallic circuit ofsaidline, whereby saidsecond re- I lay is re-energized, :before disconnecting said third conductor,.said switchingmechanism also including means for efiectingthe complementary operation ,with' respect I to;

said line limbs and relays link-circuits at the exchange arranged in groups, a primary switch adjusting magnet responsive ,to deenergizations of one relay, the other re maining energized to select a desired group of link circuits, and a secondar'yswitch controlling electromagnet responsive to .de-encrgization of said other relay, the ,firstremaining energized to cause automatic selection of an idle link-circuit of the selected group. l I I 1 a: M

3. An automatic telephone system including a subscribers line extending byits limbs to the exchange, a pair of serially connected sources offelectrical energy at the exchange, a connection fromone pole ofeach source to a one. limb of said line, a relay foreach said connection} having its I windingfin circuit with a line limb, and the respective connection, a third or return conductor connected at v the junction point of said sources, switching mechanism-at the substation of'said line includingia connection to said third or return circuit, of said line at the substation Whereby said relays are energized over. said metal:

J conductor, means for closing the metallic lic circuit, circuit changing members-,for

said switching mechanism, an actuating de- :viceffor said-members included in said mechanism for operating said members tom connectone .ofthe line limbs tosaid thirdf;

conductor, Wherebyr'the; relay of said limb;

7 is maintained operated, and thereafter open;v

ing the circuit of theother, linef limbwhere-j I v for subsequently reestablishing the metallic;

lay is re-energized, before disconnecting- ,by the second. relay-is,daenergized, means;

complementary operation with respect to said line limbs and relays, a connector at; the exchange, a primaryconnector ad ust1ng magnet responsive to the first described op-. eration of sa d relays, a secondaryconnecton adpisting magnet,-and a circuit changer responsive to the complementary operation-of said relays to render said secondary magnet peration ofsaid'relaysji lgAtelephone systemcomprlsing a telee phone line having a pa ir;of conductors, asource of current at the exchange inseries tween each'pole of said source and one of saidconductors, aconnection at an intermediate point of said source to athird or common return conductor, a calling device at, the substation of said line including con- 'limbto said return conductor and thereafter open the circuitof the second line limb, said members On return movement re-establishmg the metallic circuit of the line and thereon breaking the connection tosaid return conductor link-circuits, and aselective switch responsive to said relays jointly serving to connect an indifferentidle link-circuit withsald telephone line. v

A. telephone system comprising a telesourcetof current-atvthe exchange in series with said conductors, a relay connected between each pole of said source and one of said conductors, aconnection at an interr responsive to the first described";

with said conductors, a relay connected be- ,c

. phone line having a pair of conductors, a

mediate point of said source to a third or common. return conductor, a calling device at the substation of said line including cons.

tact members, a connection from'said deviceto sai'd'return conductor; means for connect ing -said line-limbs at the substation to op crate saidrelays over the metallic circuit of the-line, actuating meansforsaid-icontact members for operation to connect one line limb to said return conductorandthereafter open the circuit of the second. line limb, saidmembers on return movement re-establi'shing the-metallic Circuit of'the line and thereon breaking' 'theconnection to said return conductor, mechanism included" in said actuating "means fO1- eifCti11g the coinpl'ementary operation, whereby 1n the operation of said calling'device said, relays, .after-de-energiza-tion, receive actuating cur.-

rent over the metallic circuit, said return conductor being employed to hold: an al-' ready: operated relay energized, link-circuits 21.135 the-exchangearranged in groups, apri% mary-s vitchadjusting-magnet responsive to de-energizations=-ofone relay, the other remainingenergized to select= a desired group of link circuits, and: a secondary switch controllingelectromagnet responsive. to doenergization of said other relay, the first remaining energized to cause automatic selection of anidle dink-circuit of the; selected group;

6. A telephone system comprising-a telephone line having'a pair offc'onductors; a source of current at the exchangein series; Witlr saidf conductors, a relay connected between" each pole-of saidsource and one of said"conductors, aconnection atan inter mediate point of said 'source to a third or common return conductor; a callingdevice atthe substation of saidline including-contact members," a connection-from said deviceto said return conductor means for connectin-g said line limbs at the substation-to operate said relays overth'e metallic circuit of the line, actuating means for said c0ntaetmembers-tor operation to connect one-line limb to said returnconductor and thereafteropen the circuit ofthe second line 'limb, said members on return movement re-establishing the metallic circuit of the line and thereon breakingthe connection to said returm conductor, mechanism included in sa-id' ac-- operation of sai'drelays:'

commonreturn conductor;- a calling device at the substation of said line; including;contact-members,- awconnect-ion from, said dc;- vice to said returrr conductor;- meanswfor'connecting'saiddine limbs at the substation toj operate ,saidrelays O-VQIftilB metalliccircuit" of the line, actuating means for said contact" members for? operation; to connect: one line limb to said-"return conductor andthereafter:

open the circuit of the second -linelimb; saidmembers on return movement-reestablishing the metallic. circuit of thehne-and thereon breaking the connection 'toasaid return conductor, mechanism includediin' said actuating means for effectingthe complementary operation, whereby in theoperatiomojf saidcalling device saidrelays, after de-energi zation, receive actuating currentoven the. metallic circuit, said return conductor being employed; to hold analready operatechrelay energized; othertelephone lines; link circuits at the exchange; a selectorw and f a-- connector; at the exchange and means; for-2' successively operating said selector andflconi nector responsive to said rela'ysto-connect' bya; link-cireuitsaidtelephone line and a- Wanted one of said other li'nesi 8'.- Anautomatic telephone systeminclud ing a:pairof-telephonelines, a; plurality of" stepby-step selective switches having individual motor driven means forlinki'ng said lines together; said switches including; a non-numericalswitch operable over thetW-o sides of one, of saidr'linesin" series forextendinga connection from saidzline,' a.re-. lease circuit extending" to aplurality" of switches linking said' lines, electromagnetic release mechanism for each of said plurality of-switch'es', andmeans for closing said;cir-' cuit long-priorto the time of-release and thereafter-niaintaining it continually; closed: and; foropening said circuit when." release is desiredtode energiz'esaid mechanism to cause restoration: of their respective switches.

9: Anautomatic telephone systen includ; ingpail" off-telephone lines a plurality of step=by step selective switches having in; div'i dual 'motor driven" meansfor" linking;

said lines together; said switches including;

a non-numerical step -bystep switch oper; ab'le overitlie two sides clique of thelines in: series for extending a connection there from; a release circuit extending; to a plu; rality; ofswitches linking said; linesr,. el'ectromagnet release mechanism. for eac said plnralityofswitches, contacts o sa switches included in said circuit servingto

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