US1678503A - Automatic telephone system - Google Patents

Description

July 24,1928.

' H. M. FRIENDLY AUTOMATIC TELEPHONE SYSTEM 5 Sheets-Sheet 5 sheets-sheet 2 H. M. FRIENDLY AUTOMATIC TELEPHONE SYSTEM Oriinal Fild Oct. 27. 1920 July 24, 192s.

July 24, 1928. 1,673,503

H. M. FRIENDLY AUTOMATI C TELEPHONE SYSTEM Original Filed Oct. 1920 5 SheetShe-et 5 Q; L N OQ N Q- N w lm" L *v i' @a w M- N Q@ N m. N L l Q *M fnl/@Eff MM Mbs July 24, 192s.

H. M. FRIENDLY AUTOMATIC TELEPHONE SYSTEM July 24, 192s. 4 1,678,503

' H. M.y FRIENDLY AUTOMATI C TELEPHONE SYSTE M Orl. nal Filed Oct. 27. 192C.)- 5 Sheetssheet 5 fill All

Patented July 24, 1928.

UNITED STATES HERBERT M. FRIENDLY, OF CHICAGO, ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed October 27, 1920, Serial No. 420,017.

'the present invention has for its broad objectf-s, the vimprovement of automatic and semi--autoniatic telephone systems, looking 'toward lowering maintenance costs and the all'ording of novel operative conveniences to users,

The invention in the specific form chosen for its illustration herein, contemplates a so called two-wire common batteryY automatic elcliihone system as has been widely used, the present invention necessitating novel de parturcs from equipments heretofore known, so lfar as I am aware, in attaining the novel objects, while retaining certain operative functions which are known.

ln overcoming limitations of present selector switches and (zo-operating or auxiliary iquipment elements as used in automatic teleplmne systems, the present invention con templates the following novel objects ai. Means, whereby in the event an open private conductor of a trunk or link leading to the succeeding switching element (leading directly or leading indirectly through a repeatr-nf iflevire) the selector (lirst selector, or succeeding selector) seizing the said trunk terminals, the seizing selector will be inca paritizteii against automatically releasingr contiqnent to the calling party hanging up the telephone reeeivi-ir to terminate the servire. er perhaps initiate a new call by again rif-.movingitthereafter. 'l` he selector will reniain ollnormal indicating` an abnormal condition and must be restored by the exchange stimulant.

(i. Means, whereby when a selector is in engagement with a trunk and the calling v has disronuectei'l from the service and selector is incapacitated against autori-storation as set forth in the foreo' paragraph, a, the line or trunk lead* ng to the selector is guarded against seizure, by its private beii'ig grounded, until. the selector Vis restored by the exchange attend ani.

c. Means, whereby when a selector functions-i as set forth in the foregoing paragrag'il'in nu and 7), the line or trunk en- L ed hv it is guarded against seizure by its private ronductor becoming` grounded until the selector is restored by the exchange attendant.

fj. Ttienne. whereby when a selector funci set forth in the foregoing paran, c and (2. a lamp will glow I'ot ier signal devicedisplay) indicative Renewed June 10, 1925.

that a selector has been incapacitated as set forth in the foregoing paragraphs.

e. Means, whereby when a selector functions as set forth in the foregoing paragraphs a, L and c, a lamp will glow (or other signal device display) indicative that a selector has stepped ofi-normal, and then extinguish, indicative that the selector has seized a trunk in nori'nal condition.

Means, whereby when a selector functions as set forth in paragraphs a, 5 and c, a continuous tone will be projected towards the calling telephone, idicative that the cali-selecting cannot progress, due to an inoperative link having been encountered] This application of a tone audible to the calling party applies only where the calling line remains connected to the selector as when no pre-selector is employed. i

g. Means, whereby when a selector has normally functioned and operatively seized a selected trunk link leading to a successive equipn'icnt element, a distinctive tone, audig ble to the calling party will be applied to the leading-in line conductors indicative thereof.

It. Means, whereby when a selector fails to .function normally and select and seize a disengaged trunk after its primary vertical operation, the specific selector will become incapacitated against releasing and will otherwise function as if an open trunk had been seized projecting a tone indicative of the condition towards the calling telephone; further, indicative that the call-selecting Cain not progress due to an inoperative link having been encountered. The reference to the application of a tone herein applies only when no pre-selector is employed.

It is a further object of the present invention to afford a trunk repeater, used primarily for translating from three-wire to two-wire operation (and perhaps also the further object of localizing the battery supply to the calling party where the called telephone is in a remote exchange district), so if a selector, (first or succeeding) of the present invention seizes it in gaining access to the trunk leading therefrom, the selector will adapt itself to the condition of the trunk leading from the remote side of the repeatern rlhat is to say, though the line conductors and a private conductor lead from the selector bank contact set seized, and they extend to the incoming side of the repeater' and that two line conductors only lead from the outgoing' side of the repeater, terminating in a ill) Il L

selector or a connector (or other equipment element) at a distant exchange. The selector seizing the trunk through the repeater will function (as set forth in the foregoing paragraphs a to 7i inclusive), as if the intervening repea'er were not present and the three-wire trunk were continued direct to the equipment element at the remote end of the trunk. l

The toregoing, and other novel objects of the aresent invention, and the invention itself will be understood from the following description thereof, together' with the accompanying drawings in which Fig. 1 shows a calling telephone leading to a preselector at the exchange, the preselector being in access to a first selector of my invention.

Fig. 2 which is joinable on the right of Fig. 1, so the lines extending towards the margins register, is a selector of my invention modified somewhat from the one shown in Fig'. 1.

Fig. 3 is a holding circuit adapted to be introduced between Figs. 2 and 5 (in lieu of Fig. l) so the lilies extending towards the margins register. It may also be similarly introduced between Figs. 1 and 2.

Fig. fi is a trunk repeater of my invention adapted to be introduced between Figs. 2 and 5 so the lines extending towa 1ds the niargins register. It may also be similarly introduced between Figs. 1 and 2.

Fig. 5 is a well known form of connector belonging to the general class as shown in U. S. Patent No. 13,901 reissued April 13, 1915 to Frank Newforth. A feature of the referred-to connector of Newforth and the connector shown in Fig. 5 is its function which causes the current supplied over the calling lineto be reversed in direction incident to the called party responding. It is shown herein for the purpose of elucidating the operation of Figs. 1 to 4 inclusive. It is adapted to attach to the right of either Figs. 1, 2, 3, or 4iso the lines running toward the margins register.

Figs. 6 to 11, inclusive, show how the various figures are to be assembled (the lines extending to adjacent margins registering), to display the various alternative equipmentrelationships as may occur in a comprehensive exchange system contemplated under the invention.

Heretofore in automatic telephone exchange operation a serious traffic phase has been the large number of complaints of failure to gain a response, when subsequent tests by exchange attendants would fail to discern a faulty condition of the calling line or the called line, the inference therefore being' that the failure was due to a faulty condition of a link or common switching element. Aside from the purely service pects this condition increases maintenance costs without commensurate results; in fact the large number of complaints untraceable to faulty conditions, retards the work of tracing actual faults and creates an element of doubt in all complaints, which condition operates psychologically against diligent search by the exchange attendants. l.Vhile in certain exchanges more or less complete tests are made of all trunks and apparatus elements periodically (usually at night when the traffic is light), such extensive routine testing of many trunks and apparatus elements in search for a few possible defective elements is costly, the costs of which will carry a substantial increased equipment cost, provided the necessity for routine testing can be obviated or if complaints can be reduced thereby. This is from the purely operating aspect, aside from the tral'lic phase as ccncerns the users directly. Even under conditions of rigid, periodic routine testing` the possibility occurs of defective equipment links remaining in service a. considerable time, vitiating many calls before the defective elements are discovered in the routine testing, or discovered in the process of their defective switchingoperation, by the exchange attendants.

Another objectional feature or limitation heretofore existing in exchanges of the class referred to is that should a defective selec tor or an open trunk, or open private companion thereto, be encountered in callselecting the call is vitiated. Further, the calling party has no means of knowing the condition ensuing, and, because of not gaining the response of the called party, is led to asF sume his (the calling) telephone or the called telepl'rone line is out of order. Even though the difficulty may be attributed to central otlice switching` equipment, the calling partyl is frequently powerless to switch througgh because of encountering the saine defective trunk in successive attempts.

The present invention has for its salient, general object the elimination of the necessity for persistent routine testing by 1reason of providing functions in the links which will incapacitate the link or element thereof for subsequent use after it has become seized, provided it fails to complete the call normally, by reason of its defectiveness, or the de fectiveness of a co-operating link. The exchange attendant can forthwith re-instate the element in service, or at least pro Tide against its subsequent seizure until its defectiveness has been corrected. Thus, after a call has been vitlated due to a defective link, an object of the present invention to guard subsequent calls against a similar fate because oi" the link. lt also evidences the condition to the exchange attendants.

Referring' to the drawings z- The cal automatic telephone set l? leads over line conductors 2 and 3 to prei uiuilllttiiillllllilll selector K located at the exchange. The prot-selector K is in access to a plurality ot tirst selectors, one only, as shown in schematic detail in Fig. 1, is reached over line conductors 4 and 5 and private conductor (3. The lirst selector is Ain access over connnon trunks to a plurality et second selectora, one only ot' which is shown, over line conductors '7 and 8 and private conductor 0. The second selector is shown in schematic detail as 'Fig 2, and is in accessr to a pluralily olf connnon trunk equipments, one only oit' which is shown in schematic de tail in Fig. l, reached over line conductors 204- and 205 and private conductor 200. The trunk leadingtroni Fig. 3 over conductors 301 and 2104i terminates in the connector shown in schematic detail in Fig. 5 reached over conductors 512 and 513. The repeater Fig. Ll may be substituted for Fig. 8 as Will be discussed presently. rPhe called tele phone Q is reached by the connector Fig. 5, over conductors 501 and 502.

'he calling automatic telephone P is the usual service type having` a sending device 17 oif the general class, as shown in Bri t-ish Patent to Dicker, No. 29,6541 ot 1010. rllhe prc-selector K is of the general. class, as shown in U. S. Patent to Lamb No. 1,103,- 100. grant-ed August 1, 1010. The selectors Figs. 1 and 2 are ot the general class as shown in U. S. Patent to Keith & Erickson No. 815,821, granted March 13, 1005, o'l course inoditied in such mechanical and. circuit details so as to operate on the .so-called tivo-Wire principle, and urtheras contein plated in the present invention. The connector Fig. 5 is of the general class as shown in U. S. Patent to Keith & Erickson No. 815,176, granted March 13, 1006, of course inodilied in auch mechanical and circuit details asto operate on the Eso-called two-Wire in'inciple, the saidv connector being Well known in the art. The telephone Q .is siinilar to P and is shown as a called telephone on bank contact set twenty-two reached, as stated, over line conductors 501 and Conductor 503 leads to the cut-od relay 504e ot a preeselector similar to K, so When the set Q is called by the connector Wipers 505 and 500 seizing the bank contacts` 507 and 500 leadingl to line conductors 501 and 502 respectively and private Wiper 509 seizes and ,grounds bank Contact 510 leading over conductor 503 to the Winding of cut-oil relay 5011 the operative windings ot` the pre-- selector on the called line Will be disconnected. The conductors 501. 502 and 503 are common to other bank contacts before connectors. reachable by the sarne co-ordi nate operation of the conductor Wipers. The foregoing line bank Contact arrangement and line cut-ott relay arrangement relating to the called line is not new, the present invention being primarily directed to iniproveinents in the selectors, repeater and the alternative holding circuit; ot course, conteinplating use With connecting switches also.

In practice it is usual to employ a single battery source, and this battery has one ol its poles permanently grounded. Also it is usual to employ a single ground, the said battery and ground being;Y innltiplcd respectively to terminals ot the elements adapted to each respectively. 'lo siniplity the drawings and descriptions the battery and ground is shown as iiuilependent sources through out, wherever applied. In the deacriptions, when circuit is traced to a Winding, the opposite terminal oli' which is shown applied to grounded battery or to ground, the described circuit is to be considered traced to ground through the Winding,` or direct to ground as indicated.

Also, when a circuit is traced to the Winding|77 o1? a relay. resistance, or magnet, it is to be understood as traced to the tree windingterminal thereof, and through the Winding and beyond as indicated.

Tone sources are indicated, designated cut-in tone and busy tone7 respectively. The said respective tone sources are repre sented convcntionally as au inductoriuin, the priniary winding; ot which, has one terminal applied to grounded battery and the other terminal thereof applied. to ground through an interrupter device adjustalfile to the desired period. rl`l1e secondary Winding,` will apply induced potential troni ground to the receiving conductor leading to the switches shown and to other switchei in connnon therewith. The tones are thus indicated as ground seeking and the receiving,l conductors trein the respective tone sources will be referred to as it they constituted a tone source in themselves.

To aid in locating' designated elements re- Ytei-red to by nuinber, in all but Fig. 1, the iirst digit will correspond numerically with the figure number'.

In elueidation o'l the present invention the performance of the equipments will be detailed under different assinned operative conditions.

Assume a call troni telephone P to telephone Q in which Figs, 1, 2, 3 and 5 are included. Upon the receiver being removed 'troni the hoolcswitch to initiate the call, pre-selector K will seize the trunk leading to the tirst selector. lalking and receiverexciting battery will be supplied to telephone P over the following` traced circuit :--Upper Windingl ot relay A, conductor 10, restingl Contact 11, armature 12, conchictor 5, Wiper 13 ot pre-selector K, conductor 3, telephone P, conductor 2. wiper 14 of pre-selector K, conductor l, arinature 15, rest-ing contact 1G, conductor 17 to the Winding of relay A. Relay A Will actuate, applying ground on l it) its armature 18 to its Working contact 19 and over conductor 20, to the Winding of slow-releasing relay B, causing said B to actuate. Grounded contact 21 is engaged by armature 22, the said ground being applied over conductor 23 to conductor 6. Ground on the latter conductor serves to disassociate the attachments to the line conductors in the pre-selector K and also to guard the first selector against seizure by any other pre-selector. The first selector is now in readiness to receive the Control open impulses from the sending device l7 at telephone P.

Upon the calling party sending one open impulse, (constituting the digit 1) relay A will retract and again attract its armature one time consequent thereto, relay B sustaining over the current lapse. Ground on armature 18 Will be applied to resting contact 24, for the interval of retraction, and over conductors 25, armature 26, resting contact 27, conductor 28, armature 29, working contact 30, series Winding of sloW-releasing relay C, conductor 31 to the Winding of the vertical magnet (designated VERT. M.), causing the said magnet to actuate and step the shaft carrying Wipers 32, 33 and 34 one vertical step into registry With the first bank level. Relay C Will actuate (fo-incident with the energization of the vertical magnet and sustain for its period after the deenergization thereof. Consequent to the shaft stepping off-normal, springs 35 and 36, 37 and 38, 39 and 40, and 4l and 42 respectively engage. A circuit can now be traced from the Winding of relay E, conductor 43, conductor 44, spring 36, spring conductor 45, conductor 46, working contact 47, armature 48 to grounded conductor 6. The Winding of relay E is shunted by resistance 49, and, moreover, relay E is marginally ad- `iusted to not operate in series with the inside winding of relay D, but relay D will operate when its inside Winding is included in series with and deriving current through the Winding of relay E. Relay E ivill actuate under 'the energization of the traced circuit path.

Upon relay C dcactuating its period after the shaft has been stepped up the one level and a prolonged closure of the telephone path ensues because of the restoration of the sending device 17, an energizing circuit can be traced from grounded conductor 6, armature 48, resting contact 56, armature 5l, working contact 52, conductor 53 to the Winding of the rotary magnet (designated ROT. M.). A locking` circuit is established co-incident with the actuation of relay E, traced as follows z-grounded Working contact 54 on relay E, armature 55, conductor 56, conductor 57, resting contact 58, armature 59 (the contact 58 and armature 59 being auxiliarily mounted on the rotary magnet), conductor 45, spring 35, spring 36, conductor 44, conductor 43 to the Winding of relay E. Thus, When relay E actuates it Will lock itself until the last described path is opened at contact 58 incident to the actuation of the rotary magnet. The latter function willoccur resultant to the closure of armature 48 upon resting contact 50. The rotary magnet will therefore actuate the period of relay C after the shaft is caused to step vertically and stop, causing the shaft to rotate one step, its Wipers 32, 33 and 34 engaging the first set of bank contacts 60, 61 and 62 respectively, relay E unlocking incident to the attraction of rotary magnet armature 59 from resting contact 58.

If bank contact 62 be assumed to have a Aground on same due to a busy condition,

as shall be clear presently, the said ground communicated to Wiper 34, conductor 63, Working contact 64, armature 65, conductor 66, conductor 67 (inside Winding of relay F being short circuited through contact 64 and armature 65), armature 68, resting contact 69, conductor 57, rest-ing contact 58, armature 59, conductor 45, spring 35, spring 36, conductoi` 44, conductor 43 to Winding of relay E, Will cause the latter to act-nate and again close the described energization circuit to the Winding of the: rotary magnet. This will cause the shaft to be driven a step fur ther rotarily, the relay E locking coincident with its actuation over the described path and then unlocking incident `to the actuation of the rotary magnet attracting its armature 59 from its resting contact 58. If the Wiper 34 again encounters a grounded bank contact the same cycle of operations incident to driving the shaft an additional step from the first bank setwill ensue. However, assuming that the bank contact 62 is ungrounded, then, when Wiper 34 engages said 62, no ground will be communicated from said 34 over the` circuit to the Winding of relay E, and therefore no energizing circuit to the Winding of the rotary magnet will be reestablished. The described pat-h from the Winding of relay E to conductor 57 and to grounded Wiper 34 may be. now traced through inside Winding of relay D to grounded conductor 6, causing relay D to actuate. The ground assumed as applied to Wiper 34 serves as a short circuit to the said inside Winding on relay D.

Consequent to the actuation of relay D, armature 68 Will engage Working contact 70, leading to conductor 7l, and to grounded conductor 6. The ground from conductor 6 will be communicated over conductor 67, conductor 66, armature 65, nf'orking Contact 64, conductor 63, Wiper 34, to bank contact 62. Armatures 12 and l5 will engage Working contacts 72 and 73, and disengage resting contacts 1i and 16 respectively. Leading-in line conductors 5 and 4 are now continued over conductors 74 and 75 to Wipers 33 and 32, baalt contacts 61 and 60, conductors 8 and 7 conductors 205 and 204, to armatures 212 and 215 on relay D2. conductors 210 and 217 to the upper and lower \\"indings ot relay A2 respectively.

Relay A will deactuate, followed by relay B its period thereafter, the latter relay thus holdingl a ground on conductor 6 an appreciw able period alter the telephone l? has been extended to receive talking battery and receiverexciting battery 'from relay'A2 in lieu ot relay A. Upon relay A2 actuating due to :its windings becoming energized over the traced path including telephone l), its grounded armature 218 will engage Working contact 219, applying ground over conductor 220 to the Winding o'l slow-releasing relay7 B2, causing said B2 to energize and actuate. Grounded Working contact 221. is engaged by arn'iature so ground is communicated to conductor 223, conductor 206, conductor 9, bank contact 62 and over the traced path to conductor 6. Bearing in mind the slow release characteristic ot' relay B the groundv described as from working contact 221 is ap` plied to conductor 6 before the relay B deactuates, so no ground lapse occurs With relation to conductor 6, relay D remaining actuated, derivin its energizing current through the unactuated n'iarginal relay E.

It is to be noted here that when relay B deactuates its period after the deactuation ot relay A armature 65 retracts from Working contact 64, thereby removing for an instant the shcutcircuit trom the louresistance in side winding ol relay F. Euergizing current ot relay D (and also the pre-selector cut-o`ll relay) being now derived through the inside winding oi relay F to the grounded working contact 221 in Fig. 2 relay F will actuan-l, its armature 76 engaging Working contact 77. A locking' circuit now exists trom grounded battery, restricting resistance l. working' contact 77, armature 76, outside Winding; of relay F` conductor 7 9, spring 39 to oft-normal `ground on spring 40. This will .insure the attraction ot' armature 80 from resting contact 81 and armature 82 'trom resting contact- 855. The object ot' relay F will be clear presently. However, sullice it to sav here, that it lground were not applied ahead so current from conductor 67 will not be derived through relay F as set forth, it, ot course, would not actuate and lock. At this juncture relays D, F, A2 and B2 are actuated.

Upon the calling party sending one open impulse (constituting the second digit of the called number) relay A2 will retract and again attract its armature one time consequent thereto, relay B2 sustaining over the current lapse. Ground on armature 21S Will 3e applied to resting contact 224 for the in terral el. retraction and over conductor l.

armature 226, resting Contact 227, conductor 228, armature 229, Working contact 230, series Winding ot slow-releasing relay C2, conductor 231, to the winding of the vertical magnet (designated VEtT. M), causing the. said magnet to actuate and step the shaft carrying Wipers 232, 233, and 234 one vertical step into registry with the lirst bank level. Relay C2 will actuate coincident with the energization ot the vertical magnet and sustain for its period after the deenergiza tion thereof. Cousequent to the shaft stepping` oi'i'-iiormal, springs 235 and 236, 237 and 23S, 239 and 240 and 241 and 242 respectively engage. A circuit can now be traced from the Winding of relay E2, conductor 243, conductor 244, spring 236, spring 235, conductor 245, conductor 246, Working contact 247, armature 248, to grounded conductor 206. The winding ol relay E2 is shunt ed by resistance 249, and moreover, relay E2 is marginally adjusted to not operate in series With the inside Winding of relay D2, but relay D2 will operate when its inside winding is included in series with and deriving current through the Winding ot relay E2. Relay E2 Will actuate under the energiza.- tion oit the traced circuit path.

Upon relay C2 deactuating its period after the shaft has been stepped up the one level and a prolonged closure of the telephone path ensuesbecause of the restoration ot the sending device 17 an energizing circuit can be traced trein grounded conductor 206, armature 248, resting contact 250, armature 251, Working contact 252, conductor 253, to the Winding of the rotary magnet (designated ROT. M) A locking circuit is established coincident with the actuation of relay E2, traced as Yfollows: grounded working contact 254 on relay E2, armature 255, conductor 256, conductor 257, resting contact 258, armature 259 (the contact 258 and armature 259 being auxiliary mounted on the rotary magnet), conductor 245, spring 235, spring 236, conductor 244, conductor 248, to Winding of relay E2. Thus, when relay E2 actuates it will loch itself until the last described path is opened at contact 258 consequent to the actuation ot' the rotary magnet. The latter function will occur resultant to the closure ot armature 248 upon resting contact- 250. rllhe rotary magnet will therefore actuate the period of relay C2 after the shatt is caused to step vertically and stop, causing the shaft to rotate one step, its Wipers 232, 283 and 234 engaging the :[irst set oit bank contacts 260, 261 and 262 respectively, relay E2 unlocking incident to the attraction ot rotary magnet arm ature 259 'from the resting Contact 258.

It bank contact 262 be assumed to have a ground on same due to a busy condition, as shall be clear presently, the said ground communicited to Wiper 234, conductor 263,

werking contact 26st. armature 265, conductor 266. conductor 267 (inside winding ot relay F2 being short-circuited through conta :g and armature 265), armature 268, `resting contact 260, conductor 257, resting contact 253, armature 25.9, conductor 245, spring 235, spring 236, conductor 2441, conductor to winding of relay E2, will cause the latter to actuatc and again close the described energiaation circuit to the free terminal ot the winding` o'i the rotary magnet. This will cause the shaft to be driven a step further rotarily, the relay E2 locking co-incident with its actuation over he described path and unlocll'ing incident to the actuation ot the rotary magnet attracting its armature 259 from its resting contact 258. If the wiper 231A again encounters a grounded bank Contact the same cycle oi operations incident to driving` the shait au additional step from the first bank set will ensue. However, assuming that the bank contact 262 is ungrounded. Then, when wiper 23% engages said 262 no ground will be communicated 'irom said 234V-v over the circuit to the windi oi? relay m2 and therefore no energizing circuit to the winding of the rotary magnet will be resestablished. The described path troni the winding of relay E2 to conductor and to grounded wiper 234i may now be traced through inside winding of relay D2 to grounded conductor 206, causing` relay D2 to actuate. The ground assumed applied to wiper 234i serves as a short-circuit to the said inside winding on relay D2.

Consequcnt to the actuation ol relay D2, armature will engage working Contact 27 0, leading to conductor 271., and to grounded conductor 206. The ground Yfrom conductor 206 will be communicated over conductor 267l connuctor 266, armature 265, working contact 264, conductor 263, wiper L to bank contact 262. Armatures 212 and 215 will enl e working contacts 272 and 273, and disengage resting contacts 211 and 216 resiiectively. Leading-in line conductors 205 and 204 are now continued over conductors 27t-A and 275 to wipers 33 and 232, bank contacts 261 and 260, conductors 203 and 207. conductors 302 and 301 of Eig. 3, 304: and 301 to leading-in line conductors 513 and 512 ot Fig. 5 respectively. Included between conductors 302 and 30-1 is the series 'inding ot slow-releasing relay .A2 shuntcd by non-inductive resistance 305. lbe object oit Fig. 3 will appear presently. However suiiice it to say at this time that the relay A2 and its shunt 305 are in the same exchange ottico as Eig'. 2 and that con ductors 304i` and 301 lead to a remote ez;- change silice wherein Fig. 5 is located.

The calling telephone P is now related telephonically to conductors 513 and 512 of Fig. Conductor 513 extends to resting Contact 515 engaged by inake-before-breal spring 516, conductor 517 of rela-y A5. Conductor contact 518 engaged by break spring 510, conductor winding olf relay A5.

Relay A2 vill deactuate. 'followed by relay B2 its period thereafter, the latter relay thus holding a ground on conductor 206 an appreciable period ai'fter the telephone P has been extended to receive talkin g battery and receiver-exciting battery trom relay A in lieu of relay A2. Upon relay fr actuating due to its windings becoming energized over the traced path including telephone P, its grounded armature 521 will engage working contact 522 applying ground over conductor 523 to the winding of slow-releasing relay B5, causing said Bs to energize and actuate. Grounded armature engages working contact 525 and applies ground to conductor 526 and to conductor 514.

The subsequent functioning ot the vertical magnet (designated VERT. W.) and the rotary magnet (designated BOT. M.) responsive to the calling party sending the third series of two open impulses and the fourth series of two open impulses constituting the third and iourth digits respectively, of the called telephone number, wherein wipers 505, 506 and 509 are caused to engage bank contacts 507, 506, and 510 refugectively, and the called telephone Q signaled, will not be detailed since the connector Fig. 5, as set forth at the outset is well known in the art, and that thereinre the present invention is not specifically directed to its functions beyond what have been detailed in relation to the application cil ground to conducto' 5141-, and the reversiire; of projected battery from the windings ol relay A5 as will be explained in'escntly.

then the described energiZinn` circuit including relay A is established the winding of relay A3 is included in series 'l' saine,

upper winding extends 'to 'restniakediiefore- 520 to lower Alli and it will actuate, and, due to its slo\.v-releasing characteristic will sustain all controlling impulses sent Yfrom sending dcvice 17 in telephone P. Thus, grounded armature 306 will engage working contact 307 and ground conductor and maintain the said 303 grounded u ntii a prolonged opening of the described enerp'i'fing path as would be caused by the receiver ot the calling telephone being placed upon the hookswitch for a brief' period; live seconds. for example. l

Bearing in mind the slow-release characterist-ic of relay B2, the ground described as from armature 306 is applied to conductor 209 and over the traced path to conductor 206, before the relay B2 deactuates. so no ground lapse occurs with relation to conductors 206 or 6, D and D2 remaining actuated, D deriving energizing cu;v rent as described and D2 deriving` its energizing current through the unactuated marginal rue lay t2, the holding ground for both Said D and D2 being derived from armature SOG.

It is to be noted here that when relay B2 deactnates, its period after the deactuat-ion of relay A2 arniature 265 retracts :troni Working contact 264, thereby removing for a brief period the short-circuit from the low-resistance inside Winding of relay F2. Energizing current of relay D (and also the pre-selector cut-oil relay) being now derived through the inside Winding of relay F2 to the grounded armature 306 in Fig. 3, relay F2 Will actuate, its armature 276 engaging Working contact 277. A locking1 circuit now exists from grounded battery, restricting resistance 278, Working contact 277, armature 276 outside Winding; of relay F2, conductor 279, Spring 2239 to ott-norinal ground on spring 240. This will insure. the attraction of armature 280 from resting; contact 281 and armature 282 troni resting` contact 283. The object of relay F2 will be clear presently. However, sntiice it to say here, that if Lgrouniil Were not applied ahead so current t'roin conductor 26T will not be derived through it, it, o'f course, Would not actuate and lock. At this juncture relays D, F, D2, F2, A3, A and B5 are actuated.

The :foregoing descriptions contemplated a normal call selecting,` function. 'llhat if", that the equipment and linlcible circuit path between the calling telephone l) and the called telephone Q, is normal and idle.

It will now be assumed, first, that when Wipers 32, 33 an( 34 seized bank contacts 60, (il and (i2 trunk conductor l leading;` to second selector Fig. 2 ie open a.. come point bet 7een. bank contact 60 and 'the ground pernianently applied to the lower `WindingY of rela-y A2. .ln such event neither relay A2 nor its dependent relay B2 Will actuate and `ground conductor 20G as set forth. Relay D Will actuate normally when the bank contacte 60, 61 and G2 are eized, dieassociating` relay A. Relay A. followed by its dependent. relay B Will new deaetuate. Then, when relay B deactuates, there` having been no supplemental ground applied troni conductor 206, no current will be derived through the inside Winding ot relay F in maintaining relay D and therefore relay F Will not actuate and lock as described. Relay F remaining' normal, when relay A deactuates incident to relay D actua-ting (relay E deactuating` consequent to the Wipers attainingr the first rotary position), a lockingv circuit for relay D can be traced from grounded armature i8, resting contact 24, conductor 25, armature 2G, working: contact 84, outside Windingof relay D, conductor 85, armature S2, resting` contact 83, conductor 86, oftl-norn'ial spring); 4l, sprinf,r 42, restricting resistance 87 to grounded battery. Armature 22 of relay B retracts 'troni t(grounded Working; contact 2l a saillb cient period betere armature 88 en resting contact S9 consequent to the deactuatiou to creato a lapse of ground on conductor o' of sutlicient period to allow the cutotli' relay in the pre-Selector l; to rcfstore before the path. 'tiran grounded oil-normal spring spring1 39, conductor 7S), armature S0, Contact. 8l, armature 88, reeling Contact conductiu- 28 to conductor (3 is eatablishcd. The latter regrounding of conductor G guards the selector in Fig'. l against seizure by a pre-selector (perlfiaps K in a newly ini tiated call 'troni telephone P), and due to relay D being' locked actuated the around ou conductor t3, attached conductor 7l applied to Workingr Contact 70, arniature (itl. conductor (i7, conductor (itl, armature (i5, resting Contact 90, conductor ('33, v-riper 34. Will be applied to engaged bank Contact Thus, bank contact (and its multiples) is lajuar-dVH ed against .faeizure as long` as the Wiper Bit is in engagement, and thus prevents a second call being vitiated due to cncountcringv the open t-runl. .lt is clear, now, that not only ie the selector which encountered the detectire trunk guarded against seizure but the trunk seized is so guarded, and, 'tui-ther, this guarded condition will exisat until the eelector is releafzed manually by the oliice attendant, ilfor the traced circuit including the release inaguet will be open due to armature 2li being attracted from resting' contact 27, relay D being; locked actuated.

Referring again to relay E, armature GIS and its resti g' contact 90 is so adjusted that when said ret facts troni. Workinge contact (34; a lapse ot Short-circuit liround the insidey windingoit relay F Vwill. occur ot sutlicicnt duration to canse the relay F to attract its armature TG against ite working; contact 77, provided, of course, that wiper del rereives ground iroin bank contact (32 following; the seizure thereot. The inside Winiiling' oi relay F niuat be short circuited at all times, except at the instant the armature G5 is retractincj, otlierwiee, it a Celector 'Wiper corresponding to engages a bank Contact inultipled with the guarded bank contact 62 tl e battery potential carried on the private Wiper ot a normal selector While hunting; 'will traverse the inside WindingI oi relay F in reaching` conductor t3 over the path traced, causing said F to tuate and thereby upset the guarded condition of ite selector, leadinxyin, as vvell 'its selector engaged pri vate bzfinlr contact. This is assuming; the Celector has become primarily incapacitated due to (be Wiper failing` 'to receive `flrountl. rthe armature may be a double one to promote ease oif adjustment (allowingY one to retract, followed by the other, for example) to nrovide for the snort-circuit lapse. i

In a normal connection. wherein rele actnates and locks for the service, irl

p1 duration of the n its locking` circuit :is opened consequent to the shaft restoring' and offnormal springs i139 and i9 diseng ingr., relay D is not locked through its outsu' 1 oe. traced locking path. including the outside Winding` of relay D will become closed and Will therefore aid in attracting; the arn'iatures of said l). Then, if relay F act-uates bccause of a normal seizure and the said locking path is opened the inside energized winding Will support the said relay D actuated.

A normal release (as by calling party replacing' receiver on the hookswitch) before the Wipers have seized a bank contact and therefore under the condition of relay D being` normal and relays A and B restoring to normal Will occur over the following ener- `rif/,ed path causing the release magnet (designated RLSE. M.) to actuate to unlock the shaft for restoration; grounded armature 18, resting Contact 24, conductor 25, armature 26, resting contact 27, conductor 28, armature 29, resting contact 91, spring 37, spring 3S, to the Winding of the release magnet. lt is clear that since relay D Will alivays be actuated if relay A is actuated, and that the traced releasing circuit includes resting contacts on both relays B and D, both relays D and A must be normal before an automatic release can take place. Therefore, if relay D is locked as set forth, due to no ground being applied to Wiper 34; from ahead after seizure, an automatic release. cannot take place. The office attendant. upon observing` the condition of the selector in Fig. il will conclude what the condition is and look to correcting the abnormal condition and, thereafter, release the locked selector into service. Of course, the otlice attendant in lieu of correcting the defect can put a false busy on the defective trunk and then reinstate the engaging selector into service forthwith.

lt is clear, noiv, that. if a ground is not applied to bank contact 62 before the period of deactuation of relay B after its seizure hy Wiper 34, if disengaged, the selector will lock and guard against seiyure as set forth. It will also be clear that if the open condition assumed as on conductor 7 leading to conductor 291i Were on the conductor 8 leading` to conductor 205 in lieu thereof the saine operative condition would ensue because relay A2 could not then actuate, as before. Also, if conductor 9 leading` to conductor 296 Were open, in lieu of the conductor 7 or the conductor 8, no ground could be applied back to Wiper 34. engaging bank contact 62 before the period of deactuation of relay B after Wiper 34 engaged bank contact 62, and therefore the same operative condition would ensue as when the circuit including,r conductors 7 and 8 Were assumed open. That is to say, broadly, if a ground is not. projected back to bank contact 62 after it, unprounded, is seized by Wiper 3l the selector in Fig. l will be incapacitated against automatic release, and the said selector, as Well as the seized trunk vcill be guarded against seizure.

Incidental to the normal functioning of the selector Fig. l there is a brief period vfherein relays D and B are co-incidently in an actuated condition. This occurs after relay D actuates and before relay B has had time to deactuate consequent thereto. Then, a path can be traced from ground-seeking cut-in tone source (designated eut-in tone), conductor 92, arn'iature 93, Working contact. 94, conductor 95, armature 9o, Working contact 97, conductor 9S, conductor 75, Working' contact 7 8, armature l5, conductor s', pre-selector Wiper lll, conductor 2, telephone l, conductor 3, pre-selector Wiper lil, conductor 5, armature l2, Working contact 72, conductor 74, Wiper 33, bank contact Gl, conductor S, conductor 205, armature 212, resting` contact 211, conductor 210, upl per winding of relay A2 to grounded battery. The distinctive tone propagated by the said tone source will be audible to the calling party through the receiver until relay D deactuates and opens the path at working' contact 97. This tone cannot be applied unless the selector has cut-in, so the tone Will index the condition that the call progressed responsive to the sent impulses and that an inoperative` element has not viti ated the call, though, of course` the cut-in tone will be audible to the calling party if an open trunk is encountered. in like manner, the selector itself functioningY normally up to and including,` its seizure of a disengaged bank contact set.

Tt is clear 'that While a pre-selector K is shown in Fig. l between the calling telephone and the first selector', it is not necessary to employ a pre-selector, and that a first selector may be provided specilic to each line leadingto a telephone as P. Also, in place of providing` a line leading direct from the lirst selector to a telephone, the line may lead to a spring jack on a switchboard, and a switchingplug;l prorided to (2o-operate with the springjack. lt of course, not neuT to provide springjack ended trunks leading` directly to first selectors of types heretofore known.

Under the conditions outlined above, that is a springjack ended trunk leading; directly to a specific selector as in l, for example, if an open trunk is encountered, and therefore relay F remains normal, the tone apevent neither relay A nor plied to conductor 95 will be applied from armature 99 to resting contact lO() and to conductor 98, auiflible to the calling party (or the ollice attendant when listening-in) over the described cut-in tone path. The ap f. cutin tone will in the lat ter instance be continuous, thus indicating that a detective linlr has been encountered. Ot course, il" the lirst selector encounters a detective trunk under the condition of there being no pre-selector the calling party will not be able to call 'further until the ollice attendant restores the first selector, and he will lnow when this has been done, as the tone will be disconnected consequent to the restoration of the first selector. However, if thc open trunk condition. is encountered by the second (or a succeeding selector) this tone will not be heard due to the fact that when relay B2 deactuates it ii'itroduces a lapse of ground potential to conductor 206 which causes relay D to deactuate and rclease the lirst selector.

Assuming that the call progressed normally, as hereinbetore described, up to the point ot wipers 232, 233 and 2341 seizing bank contacts 260, 261 and 262, but that 'trunk conductor 20T leading to connector Fig. 5 through holding circuit Fig. 3, is open at some point between bank contact 26() and' the ground permanently applied to the lower winding oit relay Af'. ln such its dependent relay B5 will actuate and ground conductor 514i as set forth. Also, relay A2 will not have current, derived through it to attract armature 506 to ground conductor 303. Then, when relay B2 deactuates, there having been no supplemental ground applied Afrom conductor 30?) no current will be derived through the inside winding ot relay F2 in maintaining relay D2 and therefore relay F2 will not actuate and loclr as described. Relay F2 remaining normal, vwhen relay A2 deactuates consequent to relay D2 actuating (relay E2 deactuating incident to the wipers attainingl the lirst rotary posi tion), a locking circuit "tor relay D2 can be traced 'trom grounded armature 218, resting contact 2241, conductor 225, armature 226, working contact 2811-, outside winding of relay D2, conductor 265, armature 262, resting contact 263, conductor 286, otl-normalspring 24151, spring 242, restricting resistance 287 to grounded battery. Armature 222 of relay l2) rctracts itroi'n grounded working Contact 221 a sullicient period before armature 288 engages resting contact 289 incident to the deactuation to create a lapse oi ground on conductor 206 of sufficient period to allow the cut-olii' relay in the pre-selector K and also the relay D in the first selector Fig. l to deaetuate, the latter relay closing the traced release magnet circuit to release the 'tion will exist until the said first selector to normal. This deactua tion el relay D taking place before the slowpick-up relay G2 can actuate because ot the closed path trein its winding to resting contact 289, armature 226, resting contact 281, armature 280, conductor 279, spring 239, to oil-normal ground on spring 240, causing grounded armature 296 to engage working contact 291, applying the said ground to conductor 206. The latter grounding guards the selector Fig. 2 against sei are by a selec tor (perhaps the selector in Fig. l in a newly initiated call troni telephone P), and due to relay D2 beingl locked actuated the ground from armature 290 applied to conductor 206, attached conductor 271 applied to working Contact 270, armature 26S, conductor 267, conductor 266, armature 265, resting` contact 290, conductor 263, wiper 23a will be applied to engaged bank contact 262. Thus, bank contact 262 (and its multiples) is guarded against seizure so long' as the wiper 234e is in engagement, and prevents a second call being vitiated due to encountering the open trunk. It is clear, new, that not only is the selector which encountered the `detective trunk guarded against seizure, but the trunlr seized is so guarded, and further, this guarded condiselector is released manually by the oliice attendant, for the traced circuit including the release magnet will be open due to armature 226 being attracted troni resting contact 227, relay D2 being locked actuated.

Referring again to relay B2, armature 265 and its resting Contact 290 is so adjusted that when said 265 retracts from. working contact 264i a lapse of short-circuit around the inside winding of relay F2 will occur ot suliicient duration to cause the relay F2 to attract its armature 276 against its worlring contact 277, provided, of course, that wiper 234, receives ground from bank contact 262 following the seizure thereof. The inside winding of relay F2 must be shortcircuited at all times, except at the instant the armature 265 is retracting, otherwise if selector wiper corresponding` to 264iengages a bank Contact multipled with the guarded bank contact 222 the battery potential, carried on the private wiper of a normal selector while hunting will traverse the inside winding of relay F2 in reaching conductor 206 over the path traced, causing said F2 to actuatc and thereby upset the guarded condition of its selector leading-in, as well as its selector engaged private banlr contact, 62 and 262 respectively. This is assuming` the selector has become primarily incapacitated due to the wiper 234 failing to receive ground from ahead. The armature 265 may be a double one to promote ease of adjustment (allowing one to retract. tol

lowed by the other for example) to provide for the short-circuited lapse to the inside windingl of relay F2.

.ln a normal connection, wherein relay F 2 actuates, and locks for the duration of the service, when the locking circuit is opened consequent to the shaft restoring, and offnernial springs 289 and 2Ll0 disengage, relay D2 is not locked through i ts outside Winding and therefore held actuated by the energization of its inside Winding as described hereiobefore.

In view of the fact relay F2 in any event is short-circuitef'l for a period after relay D2 energizes and closes its arinature 226 into eue nement withv working' contact 281, the tracce lock'ip,v path includingl the outside winding' of relay .i222 will become closed and will therefore aid in attracting the arinatures of said D2. Then, if relay F2 actuates because ol a normal seizure and the said lockinp )ath is opened the inside energized winding of D2 will support the said relay D2 actuated.

A normal release (as by calling; party replacing receiver on the hookswitch) before :he wipers have seized a bank contact and therefore under the condition of rela-ys D2 beingnormal and relays A2 and B2 restoringto normal Will occur over the following,l ener k:Zed path causing the release magnet (designated ELSE. M.) to actuate to unlock the shaft for restoration z-grounded armature 218, resting` contact 224.-, conductor 225, armature 220, resting` contact 227, conductor 228, arn'iature 229, restinp` Contact 291, spring' 237, springl to the winding` of the release magnet. Vlt clear that since relay l? will always be actuated if relay A2 is actuated, and that the traced releasing circuit includes restino,` contacts on both relays l? and lf, both relays D2 and A2 must be normal before, au automatic release can take place. lherefore, if relay D2 is locked as set forth, due to no ground being,r applied to wiper 2.* from ahead after seizure, an aut-oic release cannot take place. The office :ff-.ttendant upon observing' the condition of he selector' in Fig. 1 will conclude what e condition is, and look to correcting the lmerinal condition. and thereafter', release locked selector into service. Of course, the oli'iee attendant in lieu of correcting the defect can put a false busy on the defective trunk and then reinstate the enj ag,'ingv seleetor into service forthwith.

Tt is clear, new, that if a ground is not ed to bank contact 262 before the period n of relay B2 after its seizure wiper 234i-, if disengaged, the selector will lock and guard against seizure as set forth. It will also be clear that if the open condition assumed as on conductor 207 leading to conductor 301 Were on the conductor 208 leading to conductor 302 in lieu thereof the saine operative condition would ensue be cause relay A2 could not then actuate, as before. Also, if conductor 209 leading to conductor 303 were open in lieu of the conductor 207 or the conductor 208, no ground could be applied back to wiper 234 engaging bank contact 262 before the period of deactuation of relay B2 after wiper engaged bank contact 262, and therefore the saine operative condition would ensue as when the circuit including conductors 207 and 208 were assumed open. That is to say, broadly, if a ground is not projected back to bank Contact after it, ungrounded, is seized by wiper the second selector F ig. 2 will be incapacitated against automatic release, and the said second selector, as Well as the seized trunk, will be guarded againstseizure.

Incidental to the normal functioning of the second selector Fig. 2 there is a brief period wherein relays V 2 and B2 are coincidently in an actuated condition. This occurs after relay D2 actuates and before relay B2 has had time to deactuate consequent thereto. Then, a path can be traced from groundseeking cut-in tone source (designated eut-in tone) conductor 292, arinature 293, working contact 2911, conductor 295, armature 296, Working contact 297, conductor 298, conductor 275, Workingcontact 273, armature 215, conductor 204, conductor 7, bank contact (30, Wiper 32, conductor 75, Working` contact 73, armature 15, conductor 4, pre-selector Wiper 14, conductor 2, telephone l, conductor 3, pre-selector Wiper 13, conductor 5, arn'iature 12, working Contact 72, conductor 74, Wiper 33, bank contact G1, conductor 8, conductor 205, arniature 212, Working` contact 272, conductor 271i, wiper 233, bank contact 2Gl, conductor 208, een ductor 302, series winding of relay A, conductor 304, conductor 513, resting contact 515, 1nako-before-break spring 510, conductor 517, upper winding of relay A. to grounded battery. The distinctive tone propagated by the said tone source will be audible to the calling,y party through the reeeiver until relay B2 deactuates and opens the path at Working' contact 297. This tone cannot be applied unless the second selector Fig'. 2 has cut-in, so the tone will indicate the condition that the call progressed responsive to the sent impulses an d that an inoperative selector element has not vitiated the call, though, of course, the cut-in tone Will be audible to the calling party if an open trunk is encountered, in like manner, the selector itself functioning` normally up to and including its seizing a disengaged bank contact set. Further, if an open trunk is encountered, and therefore relay F2 remains normal, the tone applied to conductor 295 will be applied from armature 299 to resting Contact 200 and to conductor 298,

audible to the attendant should he listen in on the trunk, over the described outin tone path. f course, due to the described ground lapse occurringl to conductor 206, the lirst selector Will be released, and also the pre-selector if one is employed as shown in Fig. 1.

Referring again to relay G2, an oilice of which is to delay the eiiective application of the traced `cround `liroin oil-normal sprint;` 240 through armature 28S and resting con tact 289 to conductor 206. That is to say, in lieu of applying the conductor leading from resting contact 289 to conductor 206 it is applied to the winding' of the slow-piel'- up relay G2, and then the ground on its (G2) armature 290 is s iecondarily applied 'to Workingl contact 291 and to conductor 200. Therefore, the delay occasioned by adjusting armature 288 to e'z'igage resting' contact 289 after armature 222`disengiaged Working contact 221 is augmented by the actuation period of relay (i2. This augnnented delay simplifies the adjustments oll arn'iature 28S and its resting contact 289 and insures that a ground lapse ot suliicient duration exists vtroni the ungg'roundingl consequent to armature 222 retracting and the re-application oit `ground by the attracting of armature 290 to deenergize relay D of the rst selector, causing the said first selector to release to nornial as described, and in turn release the pre-selector from it.

Consequent to the actuation et relay G2, which only occurs it. Wiper 234i does not receive Aground troni ahead after seizure as set forth, and relay B2 deactuates consequent to the actuation and .locking` of relay D5, grounded armature 292 engages Working' contact 293 causing;1 lamp L2 to glow.

Lamp L2 (which may be common to a` plurality ot selectors) is located observable to the exchange attendant, who Will understand 'lroin its glowing that a selector is in,- capacitated as set forth.

l'iainp L2 (which may be coininon to a plurality oit selectors) will glow upon the first oil-normal, movement of the shaft, ener gized from grounded battery. resistance 2ST, spring 242, spring' 241, conductor 286. resting contact 283, arinature 282, conductor 285 to 1ground through said L2. lt will extinguish only when relay F2 receives around Ylrorn a normal trunk seized. or when the attendant restores tho selector.

londenser-resistance sets 94l-95 and 963-97 and 9S 99 in Fig. l; 294l-295 and 296-297 and 298299 in Fig. 2 and 527-528, and 529-530 in Fig. 5 are ior the purpose of absorbing spark current at the instant of circuit opening and is a Well known device having no direct operative 'function in the switching elements.

Assumingy the normal condition oit the traced circuit from telephone P throughpmselector, first selector in Fig. l, second lector in Fig'. 2, holding circuit Fig'. 3, connector 5. The connector Fig. '5 will be assumed as seized and with the shaft thereof in norinal position; that is, relays i5 and B5 have actuated consequent to the seizure only. Under the assumed condition. .relays I) and F of Fig. l are actuatec relays D2 and F2 oi' 2 are actuated; relay A3 of Fig. |'is actuated and relays f5.5 and B5 ol Fig. 5 are actuated. As has been set forth, the circuit including the release magnet in Fig. l will become closed consequent to the dcaetuation oit relay l). Likewise the circuit including); the release magnet in 2 Will beconie closed consequent to the deactuation of relay D2. The actuated condition of .said D and D2 is dependent upon ground inaintained on conductor 303 in Fig. 3, which. lat'- teiD condition depends upon the actuated state oi relay A3, which in turn, depends upon the current supplied from relay A5 to the alling telephone l?. That is to say, the release nuie'net circuits ot the vlirst and the second selectors are held open by virtue ot the ground applied trono relay A5 ahead; the latter noiv controlled by the state of the path tlirorojh callingtelephone P. So if the reeen' r at said P is replaced `upon the hoolc switch relay A5 will deactuate, its period aitter its consequent deenergization, and ground Will thereby be reinoved from conductor 308, `followed by the deactuation ot relays D and D2 and the release to norinal oi" the selectors in Figs. l. and 2.

It is thus clear that the ollice ot relay A3 is to niaintain conductor 303 (which is joined to conductor 209) grounded While relay A5 (and its dependent relay is held actuated, and consequently held grounded under the condition ot conductor 514 beingr 2grounded.

Assume. now, that Fig'. 3 is reinoved and Fig, 5 is attached at the right of Fig. 2, conductors 207. 208 and 209 joining conductors 512, 513 and 5141.- respectively. ,This arrangement would be employed iiiithe second selector. Figi'. 2 is in the same exchange oliice as the connector or at least 'Where it is practicable to carry the private conductor 209 to the conductor 514 of the connector. The operation oilt Figs. l, 2 and 5 Will be the saine as when Fig'. 3 is employed bocaiise in lieu of conductor 209 receiving ground from conductor in Figi'. it will now receive it 'from conductor 5M in Fig. 5, it being clear from' the foregoing` that relays A5 and A5 inust operate coineidently? if eitheroperates, and relay B5 which controls the grounding of conductor 514;. is in a directly dependent secondary relation to relay A5. Fig. 3 is thus only an expedient to obviate carrying' conductor 209 in Fig. 2 conductively to conductor 514 in F ig. 5.

l/Vere the second selectorFig. 2 located in lili) a remote exchange oihce from Fig. 1, say in the saine exchange office with Fig. 5, and conductors 207, 208 and 209 connect di rectly with conductors 512, 5.13 and 514 respectively, as referred to in the preceding paragraph, Fig. 3 may be introduced in the trunk between Figs. 1 and 2, conductors 7, 8 and 9 connecting with conductors 301, 302 and 303 respectively and conductors 301 and 304 connecting with conductors 204 and 205 respectively. rllhen, in view of relay A3 being in series relation with relay A2, if a trunk conductor is open, neither relay A3 nor A2 can actuate. That is, if relay A3 cannot actuate relay B2 (dependent upon A2) cannet apply ground to conductor 206, and if relay A3 actuates relay A2 will actuate. The condition of conductor 303 will thus correspond to the condition of conductor 206, the operation of which with respect to the functioning of the selector in Fig. 1 has been fully discussed hereinbefore.

If, now, in lieu of the first exampled combination, that of Figs. 1, 2, 3 and 5, assume that the repeater Fig. 4 is substituted for Fig.. 3, (the lines extending to the left-hand margin of Fig. 4 registering with the lines extending to the right-hand margin of Fig. 2, and the lines extending to the right-hand margin of Fig. 4 registering with the lines extending to the left-hand margin of Fig. 5, bearing in mind the repeater Fig. 4 is in the same exchange office with Fig. 2, remote from the office in which Fig. 5 is), the object being to supply talking and receiver-exciting battery to the calling telephone P from the 'exchange office in which its line, terminating in pre-selector K extends, and, as before, the called telephone Q receives talking and receiver-exciting battery from the connector located in the office in which the called line terminates. lVhere the trunk between Fig. 2 and Fig. 5 is long and of high ohmic resistance the current supplied the calling telephone will be too attenuated for satisfactory service, hence the expedient of supplying the calling telephone locally from the repeater'. The broad idea of supplying battery from the trunk repeater (and also reversing the battery with relation to the flow through the calling telephone consequent to the current projected over the trunk from the connector being reversed) to the` calling telephone is not new, however, the novel repeater Fig. 4 of the presentinvention, in addition to the said functions, has the novel capability of rctlecting the condition of the out-going trunk circuit to the iii-coming conductors thereof. That is, if the trunk out-going from Fig. 4, or the circuit included thereby is open, the condition of the in-coming conductors to Fig. 4 will be changed because thereof consequent to the seizure of the repeater by the selector Fig. 2.

It will be assumed that the calling party has initiated the call, sent the first two digits and the first and second selectors functioned and the second selector Fig. 2 has engaged and seized bank contacts 260, 261 and 262, as before set forth. However, in the assumed instance the described telephonie path to said 260 and 261 will be continued from con 'ductor 207 to conductor 410, make-beforebreak spring 415, resting Contact 416, eonductor 417 through lower winding ot relay A4 to ground, and from conductor 208 to conductor 411, make-before-break spring 418, resting contact 419, conductor 420, through upper winding of relay A4 to grounded battery. Relay A4 will actuate from the current supplied through its windings and traced circuits back, including` the calling telephone. Grounded armature 421 engages working contact 422 which extends to the winding of slow-releasing relay Bt, causing it to actuate. A closed circuit path may be now traced from grounded lower winding of relay A5 of Fig. 5, conductor 520, spring 519, resting Contact 518, conductor 512, conductor 413, conductor 423, working contact 424, armature 425, conductor 426, winding 427 of slow-releasing relay E4, conductor 428, resting contact 429, make-before-break spring 430 of relay D, conductor 431, inside winding of relay F, conductor 432, resting contact 433, armature 434, conductor 435, working contact 436, armature 437, conductor 438-, conductor 414, conductor 513, resting contact 515, make-before-break spring 516, conductor 517 through upper winding of relay A5 to grounded battery; relay A actuating, followed by its dependent relay B5. Relay E4t will also actuate under the influence of energized winding 427. Grounded armature 439 engages working contact 440 attached to conductor 441, extending to working contact 442, armature 443, conductor 444, to conductor 412, con ductor209 leading to bank contact 262 vengaged by wiper 234. Thus, relays D2, D and the line cut-off relay in pre-selector K will be maintained as in the case of relay A3 actuating and accomplishing the same condition before described. Armature 443 applies the ground received from armature 439 to working Contact 445, conductor 446. through outside polarizing winding of relay F4 to grounded battery. At this liuncture relays At` B4 and Fr* are actuated, the relay F4 not being sutliciently energized to actuate.

Upon the calling party sendingthe third digit 2 as before, relay Ar will deactuate twice and reactuate, opening the path described including relay A5 of Fig. 5 at working contact 424 two times. Grounded armature 421 retracts twice against resting contact 445, which communicates the ground to armature 446, working Contact 447 to winding of slow-releasing relay C", causing said G4 to actuate and so maintain until its period From the foregoing .it is clear that it the private wiper or oi a selectorh does not receive ground trom ahead after it en gages and seizes an ungreunded bank contact the said selector will be incapacitated. Therefore, it' because of any operative detect in the. said selector atteithe switching relay (l) or receives energizing battery from the interrupter relay (lt` or and the release relay (B or 132) deactuates the said selector will be incapacitated it its said private wiper does not receive ground alter the actuation oi' he switching relay (D or DE) and be'lore the release relay (B or B2) deactuates its period aitter the switching relay aetuates. So the selectors oi the present invention are not only adapted to become ineapacitatet and guarded against subsequent seizure when an open trunk conductor or private or other condition, such as a defective condition ahead which prevents normal operation ot applying ground back to the private wiper or a seizing selector, but the selectors are adapted to similarly function upon a said selector not l'unctiomng normally and completely. For example, it the selector alter ell'ecting a vertical movement and obtains a rotary movement fails to seize an operative trunk the selector will become incapacitated and guarded as set forth. ln this connection it may be stated that should the calling party replace the receiver on the hookswitch during the process et transmitting impulses Yfrom the sending device 17 the selector would not receive a rotary impulse incident to the line relay (A or A2) deactuating, because the slow-releasing period el the release relay (l or B2) will be shorter than that et the series relay (C or C2), and therefore, the selector would bev restored through the agency of the release magnet betere the rotary magnet ot the selector would receive an operative impulse consequent to the deactuation of the series relay, causing the wipers to engage the lirst set et bank contacts.

The alternative relations of the figures assumed may all occur in the same exciange system depending' upon the distance apart oit exchange oliices and the iouting ot a call; the latter referring to whether the call is destined to a telephone in the same exchange oiiice, or to a remote exchange ollice, or to a more remote exchange oilice. The assume-d alternate arrangen'ient seems the simplest and the most practical way oi setting forth the objects, operation and organization et the invention applied to a comprehensive ez;- change system.

It is clear from the foregoing that the number of numerical orders which the cX- change may employ may be increased or dccreased trom that described, and further, that the first selector in Fig. l may be interchanged with the second selector Fig. 2, or all selectors used may be of either type, or selectors ot well known type may be introduced. lilowevcr, the functioning of the latter, il en'iploycd, will be unchanged. linrther, the mene oi" controlling the switches, as by indirect automatic or manual control means is oll secondary inipor'aiice in carrying out the present invention to possible adaptations et it. l\loreoifer, the elements may be widely modilied mechanically and elet 'cally in applying the invention broadly by those skilled in the art, all with out departing` trom the scope ot the present invention as set lorth in the system chosen for its illustration herein in view oi the annexed claims.

I claim 2- l. In an automatic telephone system, a switch terminating a link consisting of telephonie conductors and a private conductor for inclusion in a temporary connection including a successive link between a calling and a called line, means l'or controlling the switch, and automatically applied means tor incapzuzitat-ing the switch against the control means il the link engaged by the switch has an open privatek path without restoring the switch from the engaged. line.

2. ln an automatic telephone system, a switch terminating a link consisting ol tele phonic. conductors and a pri *ate conductor ttor inclusion in a` temporary connection including a successive link between a calling and a. called line, means i'or controlling the switch, and automatically applied means for ineapacitating the switch against the control .nieans if the link engaged the switch has either an open telephonie` path, or an open private path without restoring the switch from the engaged line.

3. In an. automatic telephone system, a switch terminating a link consist-ing oi" telephonie conductors and` a private conductor for inclusion in a. temporary connection including a successive link between a calling and a called line, remote means tor ollierating and releasing the switch, and automatically applied means tor incapacitating the switch against releasing` when opel .'ted, by remote control it the link engaged by the switch has an. open private path while maintaining the switch ope ated.

l. ln an automatic telephone system, a switch terminating a link consisting et telephonie conductors and a private conductor for inclusion in a temporal-h,v connection including a successive link between a ci lling and a called line, remote means lor operating and releasing the switch, and automatically applied means for incaynicitating the switch against releasing when operated, by remote control it the link engaged by the switch lol) against the restoring means it the link en-v gaged by the switch has an open telephonie path while maintaining the switch operated.

(l. .ln a telephone system, a switch terminating a link consisting ottelphonic conductors and a. private conductor tor inclusion in a temporary connection including a successive link between a calling and a called line, meansk on the calling line to control movement ot the switch ineffecting the said connection and tor restoring the switch, and

ai'itomatically applied means for incapacitat-v ing the switch Aagainst the restoring means it the link engaged by the switch has an open private path while maintaining the switch operated. l

7. .ln a telephone system, a switch ter-` minating a link `consisting' ol telephonie con" ductors and a private conductor `for inclusion in a temporary connection including a successive link between a calling and a called line, means on the calling line to control movement ont' the switch in electing the said connection. and for restoring the switch, and automatically applied means vfor incapacitat ing the switch against therestoring means it the link engaged by the switch has either an open telephonie path, or an open privatel path whileinaint-aining the switch operated.

8. ln a telephone system, a calling line leading to a pre-selector,having access'to a first trunk leading to` a. switch, means on the calling line to initiate a functioning of the pre-selector which will causeit to seize the said trunk it idle, means on the calling line to ellect step-by-step control of the switch to eiliect a connection with an idle second trunk leading to a switch, means or" control on the calling line Jfor restoring the irst said switch, and automatically applied means to incapacitatc the lirst said switch aga-inst restoring under control ot the means on the calling line il' the second trunk has an open circuit condition to the lirst said switch while maintaining the switch operated.

9. In a telephone system, a calling line leading to a pre-selector having access to a lirst trunk leading to a switch, means on the calling linc to initiate the functioning ot the pref-selector which will cause-it to seize the said trunk it idle, means on the calling line toretl'ect stepbystep control of the switch to ellect a connection with an idle second trunk leading to la switch andto also effect step-by-step control of the second said switch in forming a connection between the calling line towards a called line, means ot control on the calling line for restoring the switches and the pre-selector, and automatically applied incansto incapacitate the first said switch against restoring under control ot the means on the calling line it thc second trunk presents an open circuit condition to the iirst said switch while maintaining the switch operated.

l0. In a telephone system, a calling line leading to a pre-selector having access to a lirst trunk leading to a switch, means on the calling line to initiate the functioning oi the preselector which will cause it to seize the said trunk if idle, other trunks each leading to a switch, means on the calling line to control the step-by-step movement ot the said switches including the first said switch to el'cct connection with the trunks succes`- sively, forming a train oit switch-terminating trunk links extending trom the pre-selector towards the called line, means of control on the calling line tor restoring the switches controlled and the pre-selector, and automatically applied means to incapacitatc against release under control ofthe calling line any said switch terminating a trunk which is in a seized relation to a succeeding trunk it the seized trunk presents Van open circuit condition while maintaining the switch operated.

ll. ln an automatic telephone system, a plurality ot lines, means tor establishing connection between two oi said lines, said means including a trunk line having a pair of leading-in line contacts and a leading-in private contact, and automatically applied means `for placing a permanent guarding potential on said private contact consequent to its seizure when one ot the conductors ot said trunk is abnormally open, to thereby prevent the said trunk being thereafter seized, whereby said potential cannot be removed except by local release of the line.,

l2. In a telephone system, a pluralityl ol'i trunk lines and an automatic switch tor seizing any one ot said trunk lines, a leading-in trunk line tor the switch, means Yfor propelling said switch to an idle trunk line, means for stopping the said switch on said idle trunk line, means controlled over the leading-in trunk for restoring the operated switch to normal, and a relay tor rendering the switch incai'iacitated against truiik-controlled restoring, and means automatically applied tor eti'ectively operating the relay it a conductor olf the idle trunk on which the switch stopped has an open conductor.

13. In an automatic telephone system, a switch terminating a link for cooperating with a successive link having leading-in conductors consisting of a pair of line conductors and a private conductor and outgoing

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