US2364796A

US2364796A - Trouble indicating system

Info

Publication number: US2364796A
Application number: US436457A
Authority: US
Inventors: Franklin A Korn
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1942-03-27
Filing date: 1942-03-27
Publication date: 1944-12-12
Anticipated expiration: 1961-12-12

Description

Dec. 12, 1944. F. A. KORN TROUBLE INDICATING SYSTEM Filed March 27, 1942 5 Sheets-Sheet l UJXUYH HJIM GJJVIJOSTV Sui/7.781.? 0i

mom muxmwx A TTORNEV .F. A. KORN TROUBLE INDICATING SYSTEM Filed March 27, 1942 Dec. 12, 1944.

W .v Ju w wt V \e? an BM 3m mmn m v2; 2 an N v R 92 \32 0 R M 22. M 0 W T E K T w A 4 mdfim WWW -3 \Qm NW NQQN w EWN b vm M Em: n z q q mvm \QQ mm? m: Rw n3 n3 Dec. 12, 1944. KORN 2,364,796

TROUBLE INDICATING SYSTEM F'ile'd March 27, 1942 '5 Sheets-Sheet 3 ATTORNEY Dec. 12, 1944. F. A. KORN I TROUBLE INDICATING SYSTEM Filed March 27, 1942 5 Sheets-Sheet 4 /NVENTO/-? F ,4. KORN s fivi l/igf/ Dec. 12, 1944. F. A. KORN TROUBLE INDICATING SYSTEM 5 Sheets-Sheet 5 Filed March 27, 1942 WWW QQNN

m9; vi m 6t 36w 6.5a 85 uqmaomh 33 v MEL w INVENT OR F A. KORN A TTORNEV tain Eonnection with the trouble indicator.

Patented Dec. 12, 1944 TROUBLE INDICATING SYSTEM Franklin A. Korn, Westfield, N. J., assignor to Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New york" Application March 27, 1942, Serial No. 436,457 I Claims. (c1. 179-1752) This invention relates to trouble indicating and recording circuits for telephone switching systems and particularly for such systems under the control of mechanical and electrical devices.

The object of the invention is to simplify the analyzation of recurring troubles in complicated switch controlling devices.

Devices of the character disclosed in the Patent 2,202,921 to A. C. Powell, June 4, 1940, are

used for indicating and recording troubles which occur in a telephone switching system as disclosed by W. W. Carpenter in his Patent 2,235,803, March 18, 1941, which employs a plurality, of markers for connecting switches between calling incoming lines. and outgoing lines selected according to registrations set up in the marker.

When a trouble occurs in completing a tele-.

phone connection. the marker, as shown in the above patent to Carpenter, seizes a trouble-indicating circuit and the trouble is analyzed from the combination of indicators associated with a plurality of circuit units connected with the marker. Upon analyzing the record as indicated in the trouble-indicating circuit, the trouble may be found to exist in any one of numerous circuits which are brought together and associated with the marker for completing a't'elephone connection. After this trouble is analyzed the unit of equipment which has caused unsatisfactory operation may be at once repaired or may be removed from service while the trouble is remedied. i

Troubles have, howeven'occurred whichcause repeated failures before an analysis can be made and which affect groups of equipment, such as switch trains, lines, senders .or markers, which give considerable trouble in a very short period of time; For example, a single fault in a line number indicating group to which all markers have access may cause a plurality of markers attempting to select a line in this group to ob- In telephone systems of'this character the equipment for completing a telephone connection operates so rapidlythat in many cases the same trouble is indicated by two or more markers which successively encounter this fault within'a very short period of time A feature of the present invention resides in a trouble-indicating circuit having means therein for automatically analyzing troubles which cause successive failures in completing telephone connections. i

Another and related feature. of the invention resides in ,atrouble-indicating circuit having an seizure. of said .trouble indicating circuit.

trouble indicator circuit;

auxiliary indicating device associated with each of a plurality of (indicating :devices which are operatively connectable with an equivalent plurality of circuits of diiferentlcharacters'to .indi- 'cate successive -failures in. the completionof .a

telephone connectioncaused by a fault in the same circuit connected in successive combinations of circuits of different characters for completing said telephone connections. Another and relatedfeature of the invention resides in a trouble-indicatingcircuit having 'a means to automatically release all ofl'aplurality of indicating devices iupon successive seizures of said trouble indicating circuit by markers having a plurality'ofother circuits connected thereto, excepting an indicating device connected with a circuit which indicates a. repeat of the same trouble indicated upon a precedin These and otherffeatureswill 'be, discussed more fully in the following description. r

To illustrate the features of the invention, ref erence may be made to the following drawings in which: g 1

Fig. 1 illustrates marker connecting relays in the left portion of the drawings and indicating devices in the remainder of the drawings;

Fig. 3 illustrates indicating devices individual to the markers and common equipment associated with repeated troubles indicated in the lead 483! as the marker starts functioning and energizes the timing circuit. If no trouble is encountered in completing the connection, this ground is removed from lead 483 l. by the energization of equipment in the marker. If thefunctioning of the marker is delayed beyond the time period allotted, a circuit is established 'for connecting the marker to the trouble indicator. The trouble indicator circuit is energized if it is not already connected to another marker. If

the trouble indicator is already connected to; a

marker, a lamp. is lighted'to identify the marker which attempted to associate its leads withthe trouble indicator but found it engaged.

Certain equipment in the trouble-indicator circuit is provided for each marker served by this indicator circuit. This comprises start relays,

= marker is connected thereto.

record is desired.

such as relay 420, individual to the marker equipment shown diagrammatically in Figs. 1 and 5, in a chain circuit with other start relays, such as 42I and 422 which are individual to other markers the same as the one shown. Relays, such as 4I0, 4II or 4I2 are also individual to the markers. These and associated lamps are energized to indicate a marker which attempts to seize the trouble indicator circuit when another can be connected to the trouble indicator for 1 recording a troubl and normally the trouble indicator is held busy to all markers until a per- Only one marker manent record has been made or the trouble analyzed. Under the repeat trouble recording arrangement disclosed herein, the trouble indicator is not held busy to other markers after the release of the marker which has made the record,

I thus as soon as this marker is disconnected from the trouble indicator another marker may seize it to make a record of a trouble which has caused a. failure to complete a telephone connection.

analyze the trouble and locate-the'circuit causing the failure. :The connecting relays, such as IOI I02, I03 and I04 are provided in each marker,

as shown in the Carpenter Patent 2,235,803, Figs.

79 and-80, for connecting a large plurality of leads from the marker to the trouble indicator circuit to give the troubl indicator a full record of the identification of the marker connected thereto and the other circuits connected 'to the marker which may have a fault thereinand which are of interest in tracing this fault "to a particular circuit as fully disclosed in the afore--' mentioned Patent 2,202,921 to A. C. Powell.

marker connecting relays are energized by the trouble indicator start relay, such as 420 after the trouble indicator circuit has been seized by,

the marker having these connecting relays therein. Relays 300, 30! and 302 are individual to the markers with relay 300 connected to the winding of the marker connecting relay I02 shown in the operating circuit of relay 420. These relays and associated lamps are energized to indicate the designation of the marker which has seized the 1 troubl indicator. Relays, such as II 5, H6, II I, I I20, I2I and I22 are individual to other units of equipment to which a marker associated with the trouble indicator may be connected. As disclosed I in the aforementioned Patent 2,235,083, to Carpenter, the marker is connectedwith a sender, different connectors, a district and oflice link frame equipment and trunk selecting equipment.

The different stages of operations in this equipment are also indicated by lamps individualthereto which may be energized to indicate thezlocation of trouble in this equipment connected to the'marker. Other types of recorders may be used successively and the trouble indicator is arranged to automatically analyze this troubl to indicate the particular circuit causing the failures. For example, the repeat relays 3I0 and 3| I and repeat lamp 3I2 are so connected to the individual

marker indicating relays

300, 3M and 302 that when the same marker is connected to the trouble indicator twice successively a circuit is established for repeat lamp 3I2. Relays I20, I2I and I22 may be individual to districts, and repeat relays I23 and I24 and repeat lamp I are so connected to the individual district indicating relays that when the same district indicates a trouble successively a circuit is established for repeat lamp I45. A quick 'analyzation of the trouble will follow the lighting of a repeat lamp as may be determined from the following. When two difierent markers are successively associated with the same district which had a fault therein, a registered telephone connection could not be completed because of the fault in this district. In this case the first marker'to seize the trouble indicator may operate individual marker relay 300 which lights individual marker lamp 305. The district having a fault therein may operate individual district relay I20 which lights individual district lamp I42.

relay 30I which lights individual marker lamp 306, but-the district Would again attempt to operate the same individual district relay I20. This, as explained later in detail, would operate the district repeat relay which lights district repeat lamp I45 and both marker lamps would be extinguished. Thus the trouble indicator points directly to the district giving the trouble and eliminates the markers from theinv'estigation.

Detail description The operation of the marker timing circuit and the manner in which it connects with the trouble indicator will first be described.

The timing circuit shown in Fig. 5 comprises relays 550I to 5501 and l0 to 55I3, inclusive,

together with the associated interrupter 5520.

The timing cycle, measured under the control of these relays and interrupter, is divided into two intervals which correspond to the decoding and marking stages of operation in the marker. The first interval covers the operation of the marker from its seizure until it has connected with the in place of the lamps shown when a permanent A It is particularly desirable to locate troubles which may disrupt telephone service which sometimes arise when a single trouble repeatedly assertsitself in a unit of equipment duringa busy period in the telephone exchange. According to the invention signaling circuits individual to each character of equipment are arranged to indicate when a trouble in aparticular circuit is repeated district and ofiice frame and the particular district junctor involvedin the call, while the second interval covers the-operation of the marker from the end of the first interval until the marker has been restored to normal.

The operation of the marker connector circuit in connecting the sender with the marker connects ground to conductor 483I. Assuming that the marker is not engaged on another call in the marker stage, as indicated by the'fact that relay 600I is not operated, relay 55I2 operates in a circuit from battery through its winding, conductor 5522, contact 3 of relay 600i, conductor 6049, back contacts of relays 55I3, 550I, 5505, 55 and 55I0 to the ground on conductor 483i. Relay 55I2 looks over its middle contact 3 to grounded conductor 483I and extends this ground The second marker to be associated with the faulty district may operate individual marker released, relay ssucso eiates in a circuit; from battery through itsfcontact 2'01" relay over its irmercontact 3 tov of interrupter 5520. When the interrupter closes; its

\ contact, relay 55.! operates in a circuit from battery through resistance 5518', winding and contact 12 of relay 55l0,.to ground over the interrupter 55.20.. Relay 5510, in operating, locks. over its contact 1. to ground on contact 1 of relay 551-2 and prepares. a circuit for relay 5511 from When; interrupter 5520 subsequently opens. its

contactsr this: shunt is. removed and relay 55 operates. Upon the. second closure of the con.- tacts of interrupter-5520, relay"55l0 releases, its winding being shunted. by the. ground over the interrupter contacts and over-contact 310i relay 55H. Relay 55, upon the release of re1ay55l0, holds. over the closed contact I of relay 5510'. to the ground supplied through theiinterrupter con tacts. Ebesecond opening". of the contacts. of interrupter 552E opens; the. holding circuit; for relay 551 which releases, thus completing the first cycle of operation and release. of relays 55l0 and. 55H. This: action. 01. relays 5510 and 5.5. continues as long: as relay 5512 remains opersited-and maintains, groundv on the armature of our, contacts. 1. of. relays 55M 5500, contact 1 on conductor [.1 Relay" 51503 of relay55tl, Contact an: 55m, to the ground contact-p2- ot relay 5500 next operation of relay 55M! completes a tor relay 5504 the next release ot? rel 55I10 closes a. circuit for relay 5505 and. the subsequent. operation of relay 55 operates relay 550i. Relays 5501,5505- and. 5500 all look: under the: control or relay 550 i- Within this interval the marker shouldc plete the reception and translato'ontof the office code and establish connectionswitlr'the omsce and district frame-sand district junctor. If it fails to dflrSD-EHCZ relay 60M remains cooperated, to permit relay tooperate, a. circuit is closed. from batterythrough the windin 01. relay 5432; conductor 5433 to groundat. the outer lower contact of relay 5505c Relay' 5432 causes the. trouble in dioatorto becalled in- Under normal conditions, when thernaflrer has tothe frames and district'junctor, re-

Upon the. operation. of relay 5501,, indicating the termination of the subsidiary timing inter-. val, acircuit is completed from battery through the winding of relay 5432,, over conductor 5433, and contact of relay 550i? to conductor 5523. Conductor 5523 is grounded as described in the Carpenter patent, untilqthe transfer of the incoming information to the decoder has been completed- If this transfer is unduly delayed until after the operation of relay 550i, relay 5032 is operated and causes: the trouble ind-iicator to be called in, as, will beset forth here.- inafter.

Assuming that: no such 'delay was encountered, relay 550i operates; but, since ground has been removed from. conductor 5523, relay 5432 does not. operate. As long as relay 6.001 remains released. and thereby indicates that the marker has not yet established connections tothe office and district frames and to the district junctor, relay 55l2 remains operated and relays 55 t0; and 55 continue to function; under the control of interrupter 5520 and the ground on conductor '48. When relay 55! operates for thesecond time at the start of the. second cycle, relay 5 502 operates in a circuit from battery through. its winding, contact 4 oitrelay 550i, back contacts; 1 of

relays

5503 and 5505,. contact 2 of relay 55! I, contact 2 of relay 55 t0, to the ground on conductor 3|. Relay 5502'. looks over its contact 2 to ground supplied over contact 2 of: relay 550T.

Relay 55H is operated by the opening of the interruptercontacts and. relay 55110 is released: by the subsequent closure of the interrupter con;-

tacts. With. relay 55| loperatedz and. relay 55l=0 lay is operated, opening the locking circuit for relay 5512. Relay H releases, opens the locking circuit for relay 5501: and opens the: cirfrom the grounded control conductor RB M to the armature of interrupter 5520,; thereby releasing. relays em: or 55I l, or: both, if they-are operated at the timer The release 'ofrelay 5501 in turn releases. which ever or the relays 5502.

cover the selection of a trunk' and the operation of switches 10: completing: the telephone connection. The operating circuit for relay 55l3 is traceable from battery through its over conductor 5524', contact 2 of: relay iwl; conductor $050, back contacts oi. relays 55123, 5501;, 5505i,.55tt,.9,m1

5510 to the ground the timing control can In operating, relay 5513 looks ductor 40M. through its winding, conductor 5524, front. contact of relay 0001, conductor 5050, and over its lower middle frontcontact to the ground on conductor 31-. Thisground -is alsoextended to the armature.- of interrupter 5520. Ground over contactof relay 55137 operates relay 55mm an obvious circuit. Relay5'5041, in operating, compl'etes a circuit from con-tact; I of relay 55H, over contact. 1 of relay 5506 and own contact 1 to the winding of relay 5505 so that the latter relay will operate, instead of relay 5501 as; before, upon the subsequent operationof-re1ay155Hundef control of interrupter 5520-. a, l 1 The next closure of the contacts of interrupter 5520 releases relay. 5540 but holds rela 55. Since relay 5500 is now' operated, relay 5505 is operated by; the release ofirelay 5510 while the subsequent reoperat'ion. "of" that. relay causes I relay 5505 to operate and injturrroperaterelay 54'3Zfor seizing the trouble indicator: Connecfionof marker to trouble indicator el -stance: 5435,, contact -'7 of relay 54 L3,, contact A 5 of. relay 5034, conductor-5438;; winding of. start relay 420.. of the trouble-indicator circuit to These start relaysarearranged inn locksto f preference chain' which allows but. one marker 1 f to connect to the trouble'indica'tor at any time.

.thev marker.

Relay 420operates over the above-traced cir multicontact connecting relay I03 which operates re1ay'I03 and connects ground to the windings of multicontact relays I I, I02 and I 04 thereby operating the latter multicontact relays. When the connecting relays of the marker have all 0perated, a chain. circuit is closed through numer- 3 ous conductors extending from various points in the marker to the recording equipment of the trouble indicator as fully explained in the aforementioned Carpenter patent.

Relay 4I2 individual to the marker equipment shown is also operated over an obvious circuit to ground on contact 6 of relay.54 I3. As hereinafter described, the circuit for lamp 4 I 5 is opened by the operation of relay 300. If, however, marker No. 2 attempts to seize the trouble indicator While it is busy with marker No.1, a circuit is established for relay 4 to light lamp 4! which gives the designation of the marker attempting to seize the trouble indicator. The circuit for lamp M4 is established through contact 3 of relay 30I which ;in this case would not be operated.

Operation of trouble indicator The operation of the connecting relays l0l, I02,

, I03, and I04 as herein stated connect a large plurality of trouble indicator circuit leads to the marker and through the marker to units of equip- :ment which have been associated therewith for completing a telephone connection; Thes units of equipment energize relays in the trouble indicator circuit to identify the. individual units of 1 equipment associated with the marker which has failed to complete the telephone connection because of a trouble in itself or a trouble in one of these unitsofequipment. Let it, therefore, be assumed that marker No. I is connected to the trouble indicator which operates relay 300. The connecting relays are individual to this marker,

and therefore, this relay is energized from ground on contact 4 of connecting relay I04 which extends through the winding of relay 300, winding of relay 3I0 to battery. Relay 3| 0 is marginal and does not operate at this time. Relay 300, in

operating, locksthroughits contact 1 to ground on contact 2 of relay 404.

Let it also be assumed that relays I2I, II5, II2, and I06 are energized over similar circuits from ground extended thereto from different units of equipment such as a district, sender, link, etc., associated with These relays are energized from .the above-mentioned ground circuits through their individual windings and through the windings of marginalrelays I23, H8, H3, and I08 to battery. None of the above marginal relays are I battery for operating relay 203;

energized at this time. Relays I2I, H5, H2 and I06 are held operated over the circuits traced and the trouble indicator is operated to later establish locking paths for the relays and energizing circuits for the indicating lamps. "335 is common to all markers'and operates lrom Relay ground on contact 5 of marker connecting relay I04 or a like relay when any marker seizes the trouble-indicating circuit for displaying a fault. Relay 335 looks through its contact 3, contact 6 ot-repeat controlrelay 2|0, contact 8' of relay 404toground. Nonerepect of indications The operation'of relay 335 establishes a circuit for relay 403 which may be traced from battery through thewinding of relay 403, contact v'7 of relay 201, lead 34I, contact. 4 of relay 335 to ground. Relay'403 establishes an obvious circuit for relay 40I through resistance 402. The operation of relay 40I establishes a circuit for operating relay 201 from ground on the inner spring of its contact 2, lead 342, winding of relay 201 to battery. Relay 201'locks throughits contact 5, lead 345, contact 2 ofrelay335, lead 333 to ground on contact-5 of repeat control relay 2I0. The latter relay, 2I0, may be either'normal or may beoperated by key 208 when it is desired that the trouble indicator show repeat connections for self-analyzing failures. 'It may be assumed for this first connection of a marker to the troubleindicating circuit that key 208 and relay 2I0 are normal. Returning to the operation of relay 40 I, this relay associates ground with its right-hand armature, lead 435, over the chain circuit through the start relays 422, 42I', and 420' which extends over conductor 430 through the winding of connecting relay I03 to battery before the ground forthis chain circuit is opened through contact 8 of relay 201 when the latter relay is operated by relay 40I.

The. operation of relay201 connects ground through its contact 3, winding of relay 203'to to ground through its contact 4, winding'of-relay 205 to battery; and assuming key 206 is operated, this ground extends through the'winding of relay 204 to battery. Key 206 is energized and locked when it is desired to immediately have the indicating lamps energized. Relay 203 connects ground with lead 223 which establishes a locking circuit for relays I06 and II 2 which were assumed to have -been operated. Relay 205' connects ground to lead 224 which establishesa locking circuit for relay 5 and relay I2I which were assumed to have been operated Relay 204 supplies battery to lead 225 which extendsto the indicating lamps for lighting the lamps associated with the operated indicating relays. This battery circuit will thusflextend through the filaments of lamp I3I, contact-1 of relay I06 to ground, lamp I36, contact 1 of relay 'Il2 to ground, lamp I38, through contact 1 of relay II5 to ground, lamp I43 through contact lof relay I2I to ground, and lamp 305 to ground'on contact 2 of relay 300. A' large pluralitywof indicating lamps are lightedin this manner to indicate the marker connected to the trouble indicator and also to indicate all of the various circuits which are associated with this marker.

The operationof relay 20! opens the energizing circuit-for relay 403 which is a slow-release relay. The release of relay 403 opens the energizing circuit 'for relay 40I which releases. Since relay 201- remains locked to ground "on contact 5 of -relay,2l0, the circuit for the connecting relays IOI, I02, I03, and I04 is opened by the disconating establishes alocking circuit ior itself over lead 355,. key 208. to ground on contact .1 of relay 203. Relay M6 establishes an obvious operating circuit for relay 405. The contacts of the latter relay are connected .to all of the markers in the office to-make the trouble indicator :busyto all of the markers until the trouble indications .in the trouble-eindicating circuit have been analyzed. Italso :releases the marker connected to the trouble indicating circuit by associating ground with lead 432 which extends throughthe upperwinding of :relay 5434 to battery, operating the latter. relay. The operationofrelay 543,4 Opens the cir-. cuit extending to startrelay 420. Relay 5434 also causes the release f, the marker and the circuits associated with the marker. Relay 5434 looks in a circuit from battery through its lower winding. contact }v to ground on contact. 2 of relay .54l3.. Relay 54-l3 is released by the release of the marker. causes the release of-relay 5434 if at this time the trouble indicator is not held busy against seizure by any marker. .As long as relay Ml5 .-re1;nains ope-rated ground over leads such as 440, Ml ,alnd 442 is connected to marker relays the same as-r-elay 5434 to prevent seizure of the trouble-indicator circuit. I

The foregoing operation of the troubleindicat: ing circuit thus leaves relays-D5, 406. and '20.! energized which maintains the ground and battery circuits established for-the indicating relays and lamps so thatthis record'may be analyzed before the trouble-indicator circuit is released.

The release of the trouble-indicating circuit is brought about by the energization "of release key 20.9 which establishes .an energizing circuit for relay 4B4. Relay 4- looks through its contact 4, lead 333 to ground on. contact 1 of relay 2t! and opens the locking circuits .for relays no; .335 and M2. The release of relay .335 opens the locking circuit for relay 201 which, releases to open the energizingmcirc'uits for relays 2 03', 204., and 2115 The release of relay 2B3 open's the locking circuit forrelay 406, which .relea'sesand causes there'lease of relay M5. The release of these relays .extinguishes all. lamps that were lighted and 'removes'the busy .ground from. all markers placed thereon by relay 4G5. and the mime-indicator. after repeat key 1031 is opertrouble indicator may again be seized by amarker which has failed to complete a. telephone connectior'i. v

' Repeat indication h h k The trouble indicator attendant recognizes normal operation the telephone exchange and unusual operation which cause rapid and re peated failures. Onsuch occasions the repeat key 208 is operated for quickly analyzing faiL ures which may be caused by trouble in a single unit of equipment or a single circuit. The .op-

eration of repeat 20B energizes relay 2-H! which remains operated under the control 0f the locking key- 2108.. Relay 2 associates 'ground from contacts 5 and 6 of release relay 404 through

contacts

2 and 3 of relay 21-0 :to contact 2 ofrelay 2'05 and contact 2 of relay. 203.150 establish locking circuits forfthese relays; locking circuit is also used for relay 204. Relay 320 .is connected in the repeat circuit, through contact 1 of relay IIO-an'd slow-release relay2 I2 is associated with thetrouble-zlndicating circuit through contact 4 of relay 210.. Contact 6 of relay 2m transfers the locking circuit .for relay 335 from 404. to; relay 40.5, For the sake of simplicity in the description, it may be assumedtha-t marker No. l the first marker to seize by this The operaizionmf-relay :4! establis'hes :an operating circuit. for .ltheconnect- .ingmelays ill-1,102,, Hi3 and ztfllc which associates this marker. with the. trouble-indicating circuit and associates a plurality. of other \oimuiis with: the trouble-indicating were J'rrlned together :for completing ,fihe I connec um. Theoperation of ithe ccrmecting relay 1 establishes :a circuit :for relay 3 which locks to gronndnn (contact-2 loftrelay 4104 as previously explained marginal relay .3'|:l:does not operatc tat time. time connecting relay. :IM

also establishes an operating. circuit for relay fiswhich this ense locks to mimic. eontacl; .ZDf relay niinstead at'contact '8 (cruelly "I. ",I'Relay 2335. establishes an-operatingcircuit torrelay 82D whichzmay be :tracedztrom battery through :its winding, contact .1 efrre'lay l lll to ground oncontact 1 nf re'layjli. The omentlon of relay. 328 establishes .a eimuitidrfmelay Miwldch may-he tracedlfrom battery of relay 321,,"loontedt #of relny 'illl to: on contact ii of relay 320. f Relay}!!! establishes a locking circuit ztar itself and am uperating for relay 122.2 iis el fecti e when marker..:discnnnects from the trouble indicatinglciruuit, as lice explained at the time that the marker is. disconnected. At this time relay 322 is shunted "by operating ground on relay "321. The-operatio'n'of relay 320 also energizes sre lay $2 5 over :an obvious circuit. Relay 325 energizes message. 324 over an obvious circuit and energizes switch magnet to:

tostep this switch forwardlone step as fully plained later. Thisiswitch steps io'rwardmpon each operation andreleaseof relay 32fl,. Y I,

The operation. proceeds as nreviously described and :for this first connection of {a *markerio, the

trouble-indicating circuit it may be assumed that relays IDS, Ill-2, Hiram! mlareroperatedwhich are the same relays as operated in. the previous description. Since this is assumed as the first connection to the trouble-indicator circuit after I the repeat .key is operated, none of marginal relays I08, H3, H8 or 123 are operated at this time. The operaticn of relay 3'35 establishes-a circuit for relay 403, aspreviously traced, through contact 7 of relay 2111,- contact 4, of relay 335 to ground. -.Re1ay 40! .now operates folconnecting ground on contact .1 of relay 405.. The lockingcircuit for .relay 201 is .difiierent from the one previously traced and extends through its contact '5 over lead 345, contact 2 of relay 3 35, lead 333,.

contact 5 of relay 2m ground o'n the contact of relay 2.12. Relay .201 establishes operating circuits for relays 203., 204,, and 205., as previously traced, from ground on contacts '3 and a of relay 201. Locking circuits are establishedror relays 33,1204, and .205 through contact and 3 of the repeat .relay2l-0 to ground ,on contacts 5 and Get relay 404'. vRelays2113,1104, anuns establish ground circuits for locking the indicating relays and battery circuits for theindicating lamps.

The operation of relay 201g=opens theener gizing circuit for relay 40 3, and -the r l gm relay 403 causes-the. release otgrelsy 401.." The 1 201 remains locked and consequentlythe release of relay 40I establishes an energizing circuit for 203; 204,- 205 and 2"].

ductor .435 for energizing'the connecting relays Relay relay. 406 from battery through th winding of relay 406,- lead 346, contact 6 of relay 201 to 1 ground on contact 1 of relay 40I. circuit for relay. 406 under this condition extends 1 over 'lead'355,':right contact of key 208 toground on contact/2 of relay. 2I2.

Relay 406 energizes relay 405 over an obvious circuit, as previously 1 described. zRelay 405 energizes themarker relay 1 5434 in the associated-marker for releasing this markerand also energizes relays the same as relay5434 in all other markers to momentarily hold these markers busy until further release of thetrouble-indicating circuit. The operation of relay 405xopens the locking circuit for relay 335 causing its release and opens the'energizing cirlcuitl for-.re1ay2I2. Relay 2I2 is slow in releas- I ing in order to permit time for the release of the associated. marker. xThe release of relay 335 .opensathe lockingv circuit for relay 201 causing its releasej. When relay 2I2 releases, the'locking circuit 'for relay 406 is opened causing its release. 1 The release of relay 406 opens the energizing circuit; for relay405'permitting its release which will allow another marker or the same marke to seize the trouble-indicating circuit. jsuccees'ioe seizures of trouble indicator for au-j to'ma'ticallyandl yzing repeated failures 1 I Withthe repeatkey'and repeat relay operated,- the indicating" relays and lamps are, therefore, locked in position after the marker connecting relays have been released and after the marker has been released. from the trouble indicator. When the-markerzNo. I was released, the cir- 'cuitfor relay--320was opened which causes the releasexof this relay. This removes the shunt .from rela'yr322 which now energizes in series with relay 32I1over a circuit which may be traced frornbattery through the winding of relay 32I,

contact-l ef relay-32I, winding of relay 322, to

ground on contact 9 of relay 404. Therefore,

when the first-marker to seize the' trouble-indicatin'g'circuit'aiter the repeat relay 2I0 isoper- Bates; l'iasbeen'disconnected from the trouble i cui-t: it: is unnecessary to operate relay 404 in order topermit other markers to seize the trouble indicatingcircuit,'since

relays

335, 201, 406 and 405 are released independently of relay 404.

Let it now be assumed that under this condition a second marker seizes the trouble indicator while the indicating lamps are displayed. Let it further be assumed for the sake of simplicity in description that the timing ,jcircuit shown in Fig." is'in marker No. 2 and that marker No. 2 seizesthe' troubleindicator instead of marker No;- I5 previously described,'relay 5432 is :o emeu m the marker to cause the seizure of the trouble indicatingcir'cuit. Relay 5432 establishes an operating circuit for relay 54I3 which connects battery through resistance 5451, contact T-of relay'54l3, contact 5 of relay 5434, to conductor 5438; Now assuming that this conductor is' connected' with conductor 431 through the The locking 2 such as IOI-, I02, I03 and I04 establishes coni fore, extend from battery through the winding of a connecting relay the same as connecting re-- lay I03 over lead 436,- contact 1 of relay 42I operated, contact 1 of relay 422 normal, conductor 435,- conductor 431, contact 8 of relay-20'|,-c0nductor-350, contact 3 of relay 404 to ground. The

operation of the connecting relays in marker No.

nection with the same trouble-indicating relays which are shown in Fig. Land the operation of these relays will depend upon the circuits from units of equipment which are connected to marker No. 2 for attempting to complete a telephone connection. The connectingrelay for'markr No. 2 has ground associated with contact 4 of a. relay the'same as relay I04 extending through the winding of marker indicating relay I which is individual to marker No. 2 and ground from contact 5 for operating relay 335 which is common to all markers; The circuit for relay 30I may be traced from ground over lead 463, winding of relay 30 I, through the winding of marginal relay 3I0 to battery. g I v At this time marginal relay'3I0 operates since ground is also extended through the winding of relay 300 and the winding of relay 3I0 tobattery, relay 300 having remained locked to round on contact 2 of relay 404. a locking circuit for itself over lead I to ground on contact 4 of relay 405 and in so doing connects ground to both the winding of relay 300 and the Winding of relay 30! which shunts both these relays causing their release and extinguishing

lamps

305 and 306. I I

It may now be assumedthat one ofthe, circuits from the same unit of equipment which was connected to marker No. I is found also to be connected with marker No. 2. This may be assumed to be a district and is thus connected to indicating relay I2I which is'one of the same relays as connected to marker No. I. The other indi eating relays operated may be assumed as relays H1, H0 and I01. Relay II5 operated 'by marker No. I remains locked and relay I I1 is operated through marker No. 2. With both relays I I5 and II1' energized a circuit is established for marginal relay I IBsince the resistance in series with relay H8 is reduced. sufficiently to cause this relay to operate. The operation of marginal relay II8 establishes a locking circuit for itself over lead I50to-ground on contact 4 of relay 405. This ground'shunts both relays I I5 and I I1 causing them to release and extinguish lamps- I38 and I40. The same is true with relays-H0 and I I2, both having been operated to cause the operation of marginal-relay II3. Relay 1 I3flocks over lead I50 to ground on contact 4 of relay 405 and No. 2, ground connected with the winding of this relay maintainsthe relay operated to battery through the winding of marginal relay I23, but

Relay 3I0 establishes marginal relay vl2! does not operate and lamp" 143 is maintained lighted.

Returning to the operation oT relay 328 which 3 took place upon the operation of relay335 when marker No. 2 connected to this relay. This establi-sh-es a circuit for relay 323 which can-onlybe Relay 323 establishes .circuits for all of 'therepeat relays of which 109, 114, I19, 124 and 3 1-1 are shown. Since a different marker established connection and operated relay 31 0, the c'irouitior repeat relay 311 is opened at the contact of relay 310. This is true of the circuits in Fig. l, in which the marginal relays "108, I13 andfl1 8 were operated. Marginal relay 123, however, was not operated, since relay 121 is 'the only district relay operated. Repeat relay 124 'is, therefore, energized over a circuit "from battery through its winding, contact 1 of marginal relay 1'23," contact 2 of relay '3 to ground on contact 3 of relay '323. Relay 124 is looked through its contact, contact 1 of relay 424, to ground on contact 'I of 'relay 4'04. In'consequence of this operation only lamp 143 and lamp I remain lighted which indicates that this one unit .of equipment was associated with both markers and in 'all probability caused a failure in the telephone connections injwh'ich these markers were involved.

Release of --1narker No. 2

The operation of relay 335 establishes a circuit over lead 341 similar .to the one previously described for energizing relay 403. Relay 403 energizes relay 401 which nowestablishe's an obvious operating circuit over lead 342 for relay 2'01 and connects ground to lead 435 through the contacts of relaysv 4'22 and 421 extending over lead 436 to keep the connecting relays of marker No. 2 operated. Relay 212 is energized over a circuit from battery through its winding, contact 4 of relay 2 10, contact 9 of relay 201 to ground on contact 1 of relay 405. Relay 2'01 establishes a locking circuit for itself through its contact 5, lead 34!), contact 4 of relay'335, conductor 333, contact f relay 210, contact 1 of relay 212 to ground. The operation of relay 201 opens the operating circuit for relay 403 which is a slow-release relay. The release of relay 403 releases relay 401. The release of relay 401 opens ground extending over conductor 435 which opens the circuit for the marker connecting relays causing their release. A circuit is established through contact 1 of relay 401 for operating relay 406 marker relay-5434 which as herein described causes the release of the marker and associated circuit units but hold the trouble indicator busy against reseizure by this marker until the release of the relay 5434. Relay 405 also connects ground through leads 440,441, 442 and other like condoctors to all cfthe markers to prevent the seizure of the troubleimdicator during the time that this relay is operating. The locking circuit for relay .335 is opened through contact 2 of. relay 405 and the operatingwcircuit for relay 212 is opened through contact .1 of relay 405. The.locking circuit for the '

marginalr'elays

108, 1 13,. I 18., 12:3 and 31 0 is opened throughrcontact 4 of relay 40550 that all themarginal relays are released. The release of relay 335 opens the locking circuit for relay 120.1. The release of relay 212 opens the locking circuit for relay 406'Which releases relay The release of relay 335 also released relay 320 wfhichopened the operating circuit for relay 323 and also opened the operating circuit for relay 325. Release zof relay 325v disassociates ground from the circuit or register 324 and from the switch magnet 326; Each release of relay 320 causes'theswitch to make one step forward. A certain number. of successive operations mam: lamp 330 lighted. After that, lamp 329 "is lighted and if there areu'sufficient successive loperations 0f the trouble indicator, lampg328 sis lighted. Each lamp is of :a .difie'rent color to'ih di'cate its significance. and the attendant cc'an see quickly the approximate number :of recurring troublesencountered.

The trouble indicator has now been prepared tor .another seizure by :a marker since lie/1875734115 has released and n'o'longe'r holds the trouble :indi'cator busy tothe markers. From the'roregome, however, it is'apparent that one relay, r1121 remains locked to ground on the contact \of "relay operatedto permit the seizure :of the trouble indicator by the same or other markers successively to make :sure'that-the difficulty has been found. Under some conditions the above-described repeat signal maybe lighted upon'the third, fourth, fifth or subsequent successive seizures of the trouble-indicator circuit and does not necessarily occur upon the second successive seizure.

' It should "be apparent from the foregoing that after a repeat trouble has been encountered and the repeat control relay 2 10 remains operated, all of the trouble-indicating relays have been released'with the exception of thetroubledndicating relays which show repeat indications suchas relays I'2 'I- and1 24. v The operation of two' "indicating relays connected with the same, type o'fcircuits such as relays 11:5 and =11?! or relays-30,0 and 301 cause both relays to" be shunted and thus released. The bat-" ter-y and ground relays 2'03, 204 and 205 remain operated. Relays'3'21 -and322 'remain operated and the other relays of the trouble-indicating circuit are released. I

The subsequent seizure of -the trouble indicator I by a marker energizes a start relay such "as 420,2 4211 01- 422 the same as previously described which establishes a circuit for the marker connecting relays. associated. with the third marker torseize the trouble indicator after the repeat control relay.2I was operated. After the operation of the cations lighted in the troubleindicator.

? relays.

marker connecting relays the trouble-indicating relays are operated as previously described and the trouble indicator is again released as previously described. This continues as long as desired by the attendant observing the lamp indi- Each operation of. the trouble indicator as previously stated operates relay 335 from ground on the marker connecting relay. This lights lamp 336 1 to definitely indicate that the trouble indicator has been seized by a marker. Each successive seizure of the trouble indicator operates relay 320 which advances the A and B brushes of switch 326 as previously described and operates relay 323 to connect ground with'circuits'which may be established for repeat relays such as relays I09,

During the operation ofthetrouble-indicator circuit on a repeat basis the attendant may at any time operate key 425 so that if successive calls do not show a repeat circuit indication, the lamp designations associated with all of the indicating relays connected to the last circuit combination ;associated with the trouble indicator may be lighted until this key is restored to normal. For example, let it be assumed that lamp 336 is lighted showing that a marker has seized the trouble 1 indicator but that during this seizure no repeat lamp was lighted. Under this condition, all of the marginal relayswould be operated when this connection to the trouble-indicator circuit followed a previous connection to the trouble-indicator circuit with repeat control relay 2I0 operated. It will be remembered that when two relays such as relays H5 and II! are both operated one being locked by a previous connection of a marker to the trouble-indicator circuit, the resistance in series with the marginal relay is reduced causing the operation of the marginal relay. The operation of the marginal relay H8 would shunt both windings of relays H5 and H1 causing their release. cating relays would be released if no repeat 1 trouble was indicated. Consequently, if no re- In like manner all indipeat is recorded all of the indicating relays would be released upon the second connection of a imarker to the trouble indicatorl However, as long as the marker connecting relays remain operated from the last seizure, the circuits for certain indicating relays would remain established but not effective while the marginal relays I08, H3, H8 and I23 and 3I0 are operated to place I a shunt on the trouble indicator relays and prevent them from operating. Under this condition with all of the marginal relays operated and key 425 operated, a circuit is established from ground on contact 3 of marginal relay 3l0, contact 2 of marginal relay I23, contact 2 of marginal relay IIB, contact 2 of marginal relay l I3, contact 2 of marginal relay I08, contact of key 425, winding of relay 424 to battery. The operation of relay 424 opens the locking circuit for these marginal relays since it will be noted that contact 4 been recorded. .The release ofthe marginal re-- lays removes the shunt from the individual indicating relays and now permits these relays to be energized so that a complete record ofindications can be obtained where no repeat trouble is indicated. After a record of the indicating lamps has been made-key 425 may be released which removes the locking circuit for relay 424 causing its release. This restores the troubleindicating circuit so that it may function as herein described for releasing the associated marker and makerecords of repeat troublessuccessively associated by markers with the trouble-indicating circuit.

What is claimed is:

1. In a telephone switching system, lines, a

plurality of groups of circuits, each group having a plurality of the same character of individual circuits, the circuits of the difierent groups being dissimilar in character, means to combine circuits from a plurality of said groups byautomatic selection for completing telephone switching connections between lines, a trouble indicator having connecting means available to the individual circuits of all of said groups, means in any of said combinations of circuits which is unable to complete a telephone switching connection because of a fault ina circuit in said combination for connecting said combinations of circuits with said trouble indicator, means operable in said trouble indicator to identify each individual ciredit in a combination. connected thereto, means to retain said identifying means operated, means to release the circuits of said combination and enable the connection of another combination to said trouble indicator connecting means available to the individual circuits of all said groups, and an automatic fault analyzer comprising means automatically responsive to successive connections of different circuit combinations with said trouble indicator to identify a circuit of a particular character successively connected to different circuit combinations unable to complete telephone switching connections.

2. In a telephone switching system, lines, a plurality of groups of circuits, each group having a plurality of the same character of individual circuits, the circuits of the difierent groups being dissimilar in character, means to combine circuits from a plurality of said groups byautomatic selection for completing telephone switching connections between lines, a trouble' indicator having connecting means available to the individual circuits of all of said groups, means in any of said combinations of circuits which is unable to complete a telephone switching connection because of a fault in a'circuit in said combination for connecting said combinations of circuits with said trouble indicator, means in said trouble indicator for indicating all of the individual circuits in said combination, means to release said circuits and enable the connection of another circuit combination to said trouble indicator connecting means avail-- able to the individual'circuits' of all said groups, other signals, and an automatic fault analyzer insaid troubleindicator responsive to its successful connection with different circuit combinations having the same individual circuit in each combination: comprising means to actuate one of said other'designals to distinguish a circuit of a particular character as one successively connected to different circuit combinations unable to complete telephone switching connections.

..3. In a telephone switching system, lines, a

'tionconnected to said, trouble indicator, means plurality of groups of circuits, each group, having. a-plurality of the same character ofv inmeans in any of said combinations of circuits.

which is unableto complete a telephone switching connection because ofv a fault in a circuit in said combination for connecting said combinations of circuits with said trouble indicator, means operable in said trouble indicator for in dicating all of the individual circuits in said combination and for releasing said circuits, and means in said trouble indicator responsive to its successive connection with difierent circuit combinations having the same individual circuit in each combination to indicate only the one individual circuit which was successively connected to the trouble indicator in different circuit combinations and release all said other individual indicating means operated unable to complete telephone switching connections.

4. In a telephone switching system, lines, a plurality of groups of circuits, each group'having a plurality of the same character of individual circuits, the circuits of the different groups being dissimilar in character, means to combine circuits from a plurality of said groups by automatic selection for completing telephone switching connections between lines, a trouble indicator having connecting means available to the individual circuits of all of said groups, means in any of said combinations of circuits which is unable to complete a telephone switching connection because of a fault in a circuit in said combination for connecting said cornbinations of circuits with said trouble indicator,

electrically operable signals in said troubleindicator, means to operate certain of said electrically operable signals to identify each individual circuit in a combination connected to said trouble indicator, means to retain said identifying signals and release the circuits of said combination and an automatic fault analyzer in said trouble indicator responsive to its successive connection with different circuit combinations having the same individual circuit in each combination comprising means including another electrically operable signal to distinguish a circuit of a particular character successively connected to different circuit combinations unable to complete telephone switching connections.

5. In a telephone switching system, lines, a plurality of groups of circuits, each group having a plurality of the same character of individual circuits, the circuits of the difierent groups being dissimilar in character, means to combine circuits from a plurality of said groups by automatic selection for completing telephone switching connections between lines, a trouble dicator, means to operate certain of said signals to identify each individual circuit in a combinato retain said identifying signals operated, means to release thecircuits of said, combination and enable the connection of another circuit combination to said trouble indicator connecting means available to the individual circuits of all, said groups, and means responsive to successive connections of said trouble indicator with, diiferent circuit combinations for automatically releasing said electrically operated signals-when the same individual circuit is not included in said successive circuit combinations and for operating diiferent electrically operable signals corresponding to the individual circuits in each combination successively connected with said, trouble indicator. f

, 6; Ina telephoneswitchin system, lines, aplurality of groups of circuits, each group having a plurality of the same character of individual circuits, the circuits of the, different groups being dissimilar, in charactenmeansto combine circuits from a plurality of, saidgroups by automatic selection, for completing telephone switching con-' I .nections between lines, a trouble indicator having connecting means available to the individual circuitsof allof said groups, meansiin any ofsaid combinations of circuits which is unable to complete. a telephone switchingccnnection because of a fault in a circuit in said combination for connectins said combinations of circuits with said trouble indicator, electrically operable signals in said trouble indicator,,.m.eans to operate certain of said signals to identify each individual circuit ina combination connected to said troubleiIldi", cator, means. to retain said identifying signals operated, means to releasev the circuits of said combination and enable the connection of other circuit combinations to said trouble indicator connecting means availab ev to the individual circuits of all saidgroups, and means responsive to .suc-

a trouble indicator, meansin each marker circuit I for seizing said trouble indicator upon failure to complete a telephone connection because of a fault in any circuit of said combination, means responsive to. the, connection of a markercircuit with said trouble indicator for connectingleads from the circuits in said combination including the marker circuit to said trouble indicator, electrically operable indicators s id trouble ind cator individuallto each circuit in any. cir uit combination, means automatically responsive. to the connection of said leads from a circuit co-mbinationto said trouble indicator foroperating indicators individual to the circuits in said combinationifor identifying said circuits, means in said trouble indicator to enable successive connections to markers and circuits combined therewith and successive disconnections, each operating theindicating means individualto the marker circuits and circuits combined therewith and means automaticallyoperable upon the successive connection bination, for releasing all said individual circuit indicating means except the one operated by said same circuit in said circuit combinations.

, 8. In a telephone switching system, lines, a plu rality of marker circuits, a plurality of groups of other circuits, means automatically responsive to an incoming call over a line for assembling together. a marker circuit and a plurality of said other circuits selected from a plurality of said groups, into a combination of circuits for com- 5 .pleting a switching connection to a called line,

a trouble indicator, means in each marker circuit for seizing said trouble indicator upon failure to complete a telephone connection because of a fault in any circuit of said combination, means responsive to the connection of a marker circuit with said troubleindicator ,for connecting leads from the circuits in' said combination including operating the indicatingmeans individual to the marker circuits and circuits combined therewith, means automatically operableupon the successive connection to said trouble indicator of circuit combinations having the same circuit connected I 35 3 vidual circuit indicating means except the one opin each combination, for releasing all said indierated by said same circuit in said circuit combinations, repeat indicatorsin said trouble indicator, and means to operate a repeat indicator f to identify the group of circuits having a circuit thereiniconnected to more than one of said circuit combinations successively connected with said troubleindicator.

9. In a telephone switching system, lines, a plurality of groups of circuits, each group having a' plurality of the same character of individual cir- 'cuits,-the circuits of the different groups being dissimilar incharacter, means to combine circuits nections between, lines, a trouble indicator having cuits of all of said groups, means in any of said combinations of circuits which is unable to, comg 3 plete a telephone switching connection because of a fault in a circuit in said combination for 1 connecting said combination of circuits with said trouble indicator, electrically operable indicating devices in said trouble indicator individual to 5 the circuits in all of said, plurality of groups of circuits, said individual indicating devices being 7 dividedinto groups corresponding to the group of circuits of the same character, an auxiliary indicating device associated with each group ofin- 1 dividual indicating devices, means to operate in-' dividual indicating devicesiin different groups responsive to the connection of a circuit combination thereto to indicate'the circuits in said combination, means to retain said individual indicating devices operated, disconnect the circuits of I said combination from the, trouble indicator and enable the connection of another circuit combi- 1 nation to said trouble indicator connecting means lfrom a plurality of said groups by automatic selection for completing-telephone switching con- 3 connecting means available to the individual cirthe successive connection of different circuit combinations with said trouble indicator to cause the operation of an auxiliary indicating device connected with an individual indicating device successively energized by a circuit in more than one circuit combination.

10. In a telephone switching system, lines, a plurality of groups of circuits, each group having a plurality of the same character of individual circuits, the circuits of the different groups being 'dissimilar in character, means to combine circuits cuits, said individual indicating devices being divided into groups corresponding to the groups of circuits of the same character, an auxiliary indicating device associated with each group of individual indicating devices, meansto operate individual indicating devices in different groups responsive to the connection of a circuit combination thereto to indicate the circuits in said combination, means to retain said individual indicating devices operated, disconnect the circuits of said combination from the trouble indicator and enable the connection of another circuit combination to said trouble indicator connecting means available to the individual circuits of all said groups, and means'automatically responsive to the successive connection of different circuit combinations with said trouble indicator for operatively connecting said auxiliary indicating device with said individualindicating devices to cause the operation of an auxiliary indicating device connected with an individual indicating device successively energized by a circuit in more than one circuit combination;

11. In a telephone switching system, lines, a plurality of; groups of circuits, each group having a plurality of the samecharacter of individual circuits, the circuits of the difierent groups being dissimilar in character, means to combine circuits from a plurality of said groups by automatic selection 'for'completing telephone switching connections between lines, a trouble indicator having'connecting means available to the individual circuits of all of said groups, means in any of said combinations of circuits which is unable to comavailable to the individual circuits of all said roups, and means automatically resp nsive to cuits, said individual indicating devices being-divided into groups corresponding to the groups of circuits of the same character, an auxiliary'indicating device associated with each group of individual indicating devices; means to operate in-v dividual indicating devices in different groups responsive to the connection of a circuit combination thereto to indicate the circuits in said combination, means to retain said individual indicating devices operated, disconnect the circuits of said combination from the trouble indicatorand enable the connection of another circuit combination to said trouble indicator connecting means available to the individual circuits of all said groups, means automatically responsive to the successive connection of different circuit combinations with said trouble indicator to cause the operation of an auxiliary indicating device connected with an individual indicating device successively energized by a circuit in more than one circuit combination, means to release the individual indicating devices not connected with an operated auxiliary indicating device, and means to retain operated an individual indicating device successively energized by a circuit in more than one circuit combination.

12. In a telephone switching system, a plurality of switch controlling circuits, a trouble indicator, indicating devices in said trouble indicator individual to said controlling circuits, means in said switch controlling circuits responsive to a failure for causing the seizure of said trouble indicator and the operation of certain of said indicating devices to identify the individual controlling circuits connected thereto, means responsive to the operation of said indicating devices to disconnect said controlling circuits from said trouble indicator, and other means in said trouble indicatoroperably responsive to successive connections of the same controlling circuit with said trouble indicator to specifically identify said latter controlling circuit.

13. In a telephone switching system, a plurality of switch controlling circuits, a trouble indicator, indicating devices in said trouble indicator individual to said controlling circuits, means in said switch controlling circuits responsive to a failure for causing the seizure of said trouble indicator and the operation of certain of said indicating devices to identify the individual controlling circuits connected thereto, means responsive to the operation of said indicating devices to disconnect said controlling circuits from said trouble indicator, other indicating devices in said trouble indicator to identify controlling circuits repeatedly connected to said trouble indicator, and means to operate said other indicating devices responsive to successive connections of the same controllin circuit with said trouble indicator.

14. In a telephone switching system, a plurality of switch controlling circuits, a trouble indicator, indicating devices in said trouble indicator individual to said controlling circuits, means in said switch controlling circuits responsive to a failure for causing the seizure of said trouble indicator and the operation of certain of said indicating devices to identify the individual controlling circuits connected thereto, means responsive to the operation of said indicating devices to disconnect said controlling circuits from said trouble indicator and retain said indicating devices operated, other indicating devices in said trouble indicator to identify controlling circuits repeatedly connected to said trouble indicator, and means responsive to a subsequent seizure of said trouble indicator to release all operated indicating devices individual to controlling circuits excepting the indicating device individual to a control circuit re- 'peating its connection to said trouble indicator and to operate said other indicating device.

15. In a telephone switching system, a plurality of switch controlling circuits, a trouble indicator, indicating devices in said trouble indicator individual to said controlling circuits, means in said switch controlling circuits responsive to a failure for causing the seizure of said trouble indicator and the operation of certain of said indicating devices to identify the individual controlling circuits connected thereto, means responsive to the operation of said indicating devices to disconnect said controlling circuits from said trouble indicator and retain said indicating devices operated, and means responsive to a subsequent seizure of said trouble indicator by different controlling circuits to release all operated indicating devices and to operate indicating devices individual to the controlling circuits connected to the trouble indicator by said subsequent seizure.

FRANKLIN A. KORN.