US2258980A - Telephone system - Google Patents

Description

0a. 14, 1941. L. L. EAGON ETAL- 2,25s;9s0

TELEPHONE SYSTEM Filed April 18, 1940 4 Sheets-Sheet l L.L.EAGON lNVEA/TORS J a MC KIM A T TORNEY SMT/ON DIST/INT OFF/CE FIG 5 FIG. FIG. 2 FIG. 3

0a. 14, 1941. L, A QN ETAL 2,258,980.

TELEPHONE SYSTEM Filed April 18, 1940 4 Sheets-Sheet 2 L.L. EAGON lNl/ENTORS JR MC KIM MVF/WHCMJ? A 7'7'ORNEV Oct. 14, 1941.

L. L. EAGON ET 1.

TELEPHONE SYSTEM Filed April 18, 1940 4 Sheets-Sheet 3 uwm M 2m N2 3? L] h n 5 K SEC k WE 2 M: Ohm Ga, 2d 7 VL 2H 052B 5 mmktvi $15K. 55.0 E vwm M Em a m @E L. L. EAGON uvvewrms 53 MC /M 4 7' TORNEV Oct. 14, 1941. L, EA ON ET AL 2,258,980

TELEPHONE SYSTEM Filed April 18, 1940 4 Sheets-Sheet 4 w 15s r BOA Pp TRAFFIC DISPLAY \POS/ T/ 0 N C/RCU/ 7' KE YSE T POSITION SENDER WllllllI-lh L.L.EAGON INVENTORS J5 Mex/M A T TORNE V POSITION L/NA AND CONNEC' Patented Oct. 14, 1941 V UETED STATES PATENT OFFICE TELEPHONE SYSTEM This invention relates to telephone systems and more particularly to systems in which idle units of equipment are automaticallyselected for use in telephone connections.

In automatic switching telephone systems using line switching equipment and particularly those systems which automatically select anidle trunk from a group of trunks, no record is made or signal given to indicate the number or location of the trunks selected for telephone connections. Under circumstances, when for example, a faulty trunk circuit is encountered during the completion of a telephone connection the equipment involved ,in the connection may be held awaiting an alarm and the tracing of the fault by a test and repair man. 'This sometimes delays the completion oi'a telephone connection and maintains ctherequipm'entjin an operated condition beside the unit of equipment 2b marker; overflow circuits and testing and trunk having a fault therein; If an automatically se lected trunk circuit having a fault is disco'n nected before a recordis made of its number or location it is thereafter d'ifiicult to locate and could be again selected for a telephone connection.

According to the present invention, a'device is included in automatically selectable circuits which may be operated by an observing telephone operator to immediately remove a faulty circuit I v I oifice. When usedas :an incoming trunk circuit from service and actuate'a signal individual to the faulty circuit so that its location is given. The associated equipment maybe released 'or a circuit of the same character may immediately be selected for replacing the faulty circuit in the telephone connection. The procedure in completing the telephone connection after the faulty circuit is removed from service may vary 'to some extent depending upon the character of the circuit having the fault therein but-in any case the faulty circuit may be immediately disconnected from other equipment and connected with a testing device so that it cannot be again selected until the fault has been corrected.

A feature of the present invention is therefore an arrangement for increasing the effi'ciency of an automatic switching telephone systemby' diverting faulty circuits from a telephone connection for which they were automatically selected to a display and test board.

Another and related feature is a system in which trunk circuits having a fault therein may be made non-selectable and removed from service by means available to one operator not cognizant of the number or location of thetrunk circuit,

' 'The'se'andother features will be discussed more "fully in" the following description.

"To illustrate the features of the invention, reference may be had to the accompanying drawings in which:

ii) 7 Figs. 1 to 4;inclusive, when arranged 'as indicated in Fig; 5' show the operating advantages of equipment arranged according to this "invention-,1 i g 1 and 2 iliustrate'a distant oiiice, an interlii toll trunk circuit andautomatic switches for intercomiecting this trunk circuit to other trunk circuits; g

i Fig; 3gshows another intertoll trunk circuit, a distant ofiice, a trunk assignment connector, a

display switchboard equipment individual to the intertoll trunk circuit;

Fig.4 illustrates a cordless operators position circuit, a link circuit and testing. and display 2 switchboard equipment individual to the intertoll trunk, Figs. 1 and 2.

g The trunk circuit, Figs. 1 and 2, maybe used asan incoming trunk circuit from the distant 'oiii'c'e Hi0 or as an outgoing trunk circuit to this it is actuated by .calling equipment in the distant ofiice I00 for selecting a cordless operators position having" an operatorfor setting up a connection to" another call station as hereinafter de- 335 scribed. When used as an'outgoing trunk circuit it is'automatically selected by a marker 32! over test lead 240 and associated with a calling trunk -circuit through 'the actuation of switch 285 by this marker. This trunk circuit is energized for an 40 incoming call by ringing current from oii'ice l'flil transmitted over trunk conductors I45 and M5 through'trunkline equipment I41 to the trunk circuitfrelay I03. Ringing current may be applied automatically or manually depending upon the equipment in the distant office-I00 and is transmitted as a calling signal to actuate the trunk circuit equipment. The energization of relay I03 releases relay Hi4 which, as may be noted, isnormally energized from battery through its winding to ground on the contact of relaylBii.

The ireleaseof relay I04 establishes a circuit for operating the incoming trunk relay 202 over a circuitjfrom battery through the winding of relay 202', contact 2 of relay I'M, contact '1 of relay said means causing the connection of the trunk 55 H1, contact 6 of relay 203 to ground. Relay 202 in operating establishes a locking circuit for itself through its contact 3, contact I of relay I I1, contact of relay 203 to ground. When ringing current is disengaged from the trunk conductors I45 and I48 relay I03 releases, which reenergizes relay I04. A circuit is thus established for relay I I3 from battery through its winding, contact of relay II2, contact 2 of relay I04, contact 3 of relay 202, contact I of relay I I1, contact 6 of relay 203 to ground. Relay H3 is looked through contact 4 of relay 20I, contact 5 of relay I I3 through its operating ground on contact 6 of relay 203.

Cordless operators position coming trunk and the operator at office I00 with type of call coming into the position. Only one marginal relay 442 has been shown to diagrammatically illustrate this signal arrangement which is fully disclosed in the patent application Serial No. 312,468 to J. B. McKim, filed January 5, 1940. The operation of relays M3 and H2 establishes a signaling path from battery through resistance IIO, contact 2 of relay II2, contact I of relay 4I3, winding of marginal relays represented by relay 442 to ground. The circuit just 'traced is for a new call incoming from a distant operator which would light a lamp such as 443.

an idle cordless operators position shown in Fig.

4. This link start circuit may be traced from ground on contact I of relay II4 through contact 2 of relay II3, contact I of relay II2, lead I30, winding of start relay.40l tOIbatteryLI'The link circuit is shown diagrammatically and reference is made to the patent application of King et al., Serial No. 295,010, filed" September 15, 1939, issued as Patent 2,236,246, Marchf25, 1941, or the patent application to Busch et al., Serial No. 295,012, filed September 15, 1939, for complete disclosures of this link structure; There are ordinarily a plurality of tool operators positions, such as 4H1, with the plurality or channels entering each position to which incoming trunks may be connected when actuated by an incoming call. The structure of link 400 is such that the channels of a plurality of positions are tested to quickly find'an idle channel in'a 'position occupied by an operator. When.an idle channel has been selected, a relay, suchas' relay 444, is energized to engage this channel for the particular incoming call which has energized a trunk circuit. This position equipment and circuit may be the same as shown in the aforementioned Patent 2,236,246 to. King et al., or the patent application to J. 'B. McKim- Serial No. 312,468, filed January 5, 1940. Only sufiicient of the position circuit is shown to properly. illustrate the invention. Relay 444i lights. the position signal lamp 445 and establishes a circuit for relay II2 to signal the incoming trunk equipment, Figs. 1 and 2, that a cordless posi tion channel has been selected and is ready to receive the incoming call. The latter circuit may be traced from ground through contact 3 of relay 444, link 400, lead I44, conta'ct'2 of relay II'I, contact 3 of relay II2, winding of relay II2 to battery, causing the operation of relay H2. The latter relay in operating establishes a looking circuit for itself through its winding and contact 3, contact 4 of relay II3, contact 2 of relay I04, contact 3 of relay 202, contact I of scribed relay 444, in addition to operating relay II2, also establishes an energizing circuit for relay 4I3 which connects ground to keys 3 I2 and 4| I and the link switch hold magnet 402 and also completes a signaling circuit for indicating the Other signaling circuits for lighting other lamps include either incoming trunk circuit resistances 22I or 222 in multiple with resistance IIO for establishing a different margin for the position signaling apparatus, as explained in the aforementioned patent application to McKim. The operator in position 4I0 now challenges the calling operator at the distant ofiice I00 and receives the call designation or code of the wanted office or party. The operator in position 4I0 accordingly manipulates the key-set 440 which operates the registering apparatus of the position sender 44I, causes the selection of a marker, such as '32I and the operation of registers and trunk routing equipment in the selected marker. The operation of this key-set sender and marker is fully disclosed in the Patent 2,236,246 to King et al. and it is thus deemed unnecessary to encumber this disclosure with a detailed description of these units of equipment. 1

Outgoing trunlc Registers in the marker 32I are set-according to code digits representing a particular outgoing trunk group extending to the wanted ofiice and aroute relay is accordingly operated which-controls the test of the trunks-in this group, At this time a ground is supplied by the marker for operating. the incoming trunk switch select magnet 218. The marker is equipped with a group of testing relays 322 equivalent to the maximum number of trunks in a group to be tested, which applies a test to the trunk circuits of a group. The trunk circuits of a group have test leads connected to. thecontacts of assignment connector trunk group multicontact relays such as diagrammatically shown at 326 and the test is made at this point by the marker. When an idle trunk is found in the desiredgroup a ground is placed on the test lead of .this trunk circuit by themarker 32I to prevent other markers from seizing the trunk. .This ground applied to the trunk circuit, Fig. 3, energizes trunk relay 305 as traced from the marker through a contact on group relayv 326, over lead 310, contact 4 of relay 3I6, contact 2 of relay 3I2, winding of relay 305 to battery. The marker also operates select magnet 300 and makes a test of junctor channels extending between the calling incoming trunk switch .282 and the selectedoutgoing trunk switch 302 to.find a channel which may be used. for connectingthese two trunks together as fully described in the aforementioned patent to .King et a1. As soon as this channel has been found, the switching apparatus is operated which. includes the hold magnets, such as 3IJI and 215, and, hold magnets of intermediate switches associated with :the selected junctor channel which closes the, crosspcintsof the cross-bar switches and connectsthe conductors of the incoming trunk, Figs. 1 and 2, to the outgoing trunk, Fig. 3. The, hold magnets for maintaining the switch contacts in position originally energized by the marker haye a second acsaeeo circuit extending through the switch contacts from the incoming trunk circuit and an auxiliary circuit from the cordless position circuit, Fig. 4. This second circuit may be traced 'from ground on contact dot the calling trunk circuit relay 2&2, contact 9 of splitting relay 2%, conductor .2179, contact 3 of switch 282, windings of all hold magnets to battery. This circuit also extends through contact 3 of switch 302, winding of outgoing trunkrelay 305 to battery. An auxiliary circuit for the hold magnets is used whenever the operator in thetoll position M6 wishes to operate the splitting relay 20i This circuit may be traced from ground on key t or key 496 to conductor M2, conductor 2T9, thence to the hold magnets "andwinding of" relay 365. Key M4 or key 6%, when operated, establishes circuits for operating relay 2t! and at the same time placing ground on the'hold magnets and relay 365.

The apparatus of the outgoing trunk, Fig.3, is

further energized to associate ringing current with the equipment of the distant ofiice 358 and to establish a connection between that distant office and the office Hill. Relay385 establishes a circuit for relay 3 from ground through the right winding of relay 3| I, contact 2 of relay 305, contact 3 of relay 312-, resistance M3 to battery. Relay-3i I, in operating, establishes a locking circuit for itself and connects ground through its contact 3,-winding of relay 333 to battery. The alternating current source 3|! is thus associated with trunk conductors 3H3 and 3!!! leading to the distant omce 398. This ringing current is associated with conductors 3 i8 and 31-9 for a timeperiod regulated by the slow operating relay 399. The locking circuit for relay 3]! may be traced from battery through resistance 3H), contact 1 and left winding of relay 3H to ground on contact 4 of relay 395. Anobvious energizing circuit for relay 309 is also established through contact 2 of relay 3! I. period for the association of ringing current with theequipment of the distant office 308 before it operates to cause the release of relay 3| I. When relay 3 89 operates, it associates a ground with the left winding of relay 3! l which places a shunt on this relay. During this time period, relay 312 has operated providing all circuit connections are properly established and, therefore, the original operating [circuit for relay 3 is opened and the latter relay releases. The energizing circuit for relay 3|2 may be traced from battery through its winding, contact 3 of relay 305, contact of relay 303, contact 4 of switch 302 and similar contacts of inter-mediate switches, contact 4 of switch 282, thence over lead l8 through the link circuit 400-, left winding and contact 2 of relay 408, contact of relay 499 to ground. Relay M2, in operating, disassociates battery through its contact 3 from the right winding of relay 3 and establishes a locking cincuit for itself from ground through its contact I, contact 3 of relay 335 through its winding to battery. Relay 3l-2 also associates direct ground through its contact 2, contact 4 of relay 3i 5, lead 3 H! through the trunk assignment connector 320 to the marker testing apparatus. This busy ground replaces a ground as previously traced which was applied by relay 20-2 to the hold magnets and relay 395 and is arranged to maintain ground on the apparatus of the trunk assignment connector until all of the outgoing trunk apparatus is later released. The trunk assignmen-t connector 329 has trunk block relays therein representeddiagrammatically as rectangles 32-5 and 32?. Each block relay has contacts for Relay 3E9 establishes the correct time.

each trunk of a group and consequently, aground placed thereon makes any particular trunk busy to all markers so that this trunk will not be selected for a telephone connection. Relay 498 also operates in the circuit traced establishing a lockingcircuit for itself through its right winding. This relay also closes the signal circuit for lamp 445 and establishes an operating circuit for relay 409. Relay 409 opens the original operating circuit for relays 498- and M2 leaving the lamp circuit free to function with trunk signaling circuits. Thelocking ground for the outgoing trunk relay 312 now extends through the contact of relay 3B3, contact 4 of the switches, thence over lead I48 through'the link 400, contact I of relay 488, resistance 466 to battery, which shunts lamp 345 to extinguish this lamp. This indicates to the cordless toll operator that an idle outgoing trunk has been selected for the connection and that the equipment of the outgoing trunk circuit has satisfactorily operated.

The marker 32! and the sender t ll may be released in the manner fully described in the Patent 2,236,246 'to King et a1. Relay has been shown diagrammatically associated with otherapparatus of the marker for releasing this marker.

In the trunk circuit, Figs. 1 and 2, as previously stated, equipment is included for both incoming trunk and outgoing trunk operations. When this circuit is used as an outgoing trunk, relay 2% operates in the manner described for outgoing trunk relay 395 and relay ill operates in the manner as described for relay 352. When this circuit is taken for use either as an incoming trunk or an outgoing trunk, a busy ground indication is immediately placed on lead 246 extending toa contact on the trunk block relay 321, shown in the trunk assignment circuit 329, so that this circuit will not be selected by another marker making a test for anou-tgoing trunk. It will be remembered that relay 202 is immediately operated by the initiation of a call from the distant operator at ofiice I36 when this circuit is taken. for use as an incoming trunk. The operation of relay 282 places ground on its contact 2 and the busy circuit extends through contact 6 of relay H1, contact 2 of relay 248, conductor 246 to a contact Onthe trunk block relay 32?. Assuming that this circuit is selected as an outgoing trunk circuit extending to ofiice 5%, a ground is placed on conductor 2-19 when this trunk is chosen by the marker. This ground extends through contact 6 of relay ill, contact 2 of relay 2H! over conductor M8 to a contact on the trunk block relay. This ground also extends through the-winding of relay 2533 which operates relay 20.3 in the same manner as described for the operation of relay 3135. When relay H1 is operated in the manner describ-edfor relay 3l2, ground is associated through its Contact 6 through contact 2 of relay 210, to conductor 2% and a contact on the trunk block relay 321. Thus, under all conditions a busy ground is placed on a conductor as soon as either an incoming trunk or an outgoing trunk is chosen for service so that any markers in the office will not attempt to select this trunk.

signal the cordless operator when all trunks of a group are busy. The overflow circuit diagram matically shown in Fig. 3 represents anoverflow trunk of the character fully disclosed in the Patent 2,236,246 to King et al. The overflow trunks 33B illustrate relay 33! associated with one group of trunks and relay 332 associated with another group of trunks. The individual trunks of the groups have leads, such as 242 and 372 extendingto these relays. One circuit, as shown, extends from battery through one winding of relay 33! over lead-242, contact of relay 203, contact I of relay 252 to ground on relay 2.!0. Circuits of this character maintain relay 33! operated until all of the trunks in the group are busy. Relay 33! releases when these ground circuits of all trunks in a group have been removed. When all the outgoing trunks in a group are found busy by a marker, the calling incoming trunk is routed to an overflow trunk associated with this group of outgoing trunks and apparatus is associated with the calling incoming trunk giving typical interrupted ground circuit. The interrupted ground circuit of the overflow interrupter is connected through contact 4 of switch 232 to lead I68 for flashing lamp 445 in the cordless position circuit. If a trunk becomes idle during this period of flash, relay 33! is again energized which changes the interruptions to a different period, thus changing the period of flash of lamp 455 to indicate to the cordless operator that an idle trunk is available in this group. It should be noted that the operating circuit for relay 33! extends through contact I of relay 203 which is energized when this circuit is selected as an outgoing trunk circuit and also through relay 232 which is energized when this circuit is used as an incoming trunk circuit. In each case the circuit is indicated as busy as hereinbefore described and, therefore, in either case the circuit to the overflow relay is opened. Relay 332 is associated with the trunk group having the outgoing trunk, Fig. 3, therein. This circuit extends from battery to the left winding of relay 332, over conductor 312, contact I of relay 385 to ground on contact I of relay 3H5. When the outgoing trunk is taken for use, relay 305 is operated and thus the circuit for relay 332 is opened. The multiple straps 338 and 339 indicate leads to the other trunks of each group. Leads 334 and 335, as well as 336 and 331, indicate the circuit for actuating the overflow interrupter.

Faulty circuits The cordless operator in position 4!!) is provided with means of supervising such telephone connections either through visual signaling means or by aural signaling means by monitoring or listening during conversation with the calling party. The operator may monitor on a telephone connection by operating key 439 to energize relay 426 which connects receiver 435 with the talking conductors by induction through high impedance coil 423. It is obvious that, when trouble occurs in equipment associated with a trunk circuit or in a trunk circuit, a telephone connection cannot be properly completed. Some troubles may develop unsatisfactory transmission, of which the operator is immediately aware when conversing with the calling party or monitoring upon a completed connection. Other faults may occur, such for example as a singing repeater or a faulty contact in an associated simplex or signaling circuit. Under any of the foregoing conditions, a connection must be immediately broken down and a new connection established in order to obtain satisfactory transmission between stations or a satisfactory connection. A trunk circuitv having a faulty condition may, be immediately removed from service so that it is not again selected by the marker for completing telephone connections and a different trunk circuit selected for the connection. To bring about this result, apparatus is included in each trunk circuit which is under the control of the cordless operator for immediately removing the faulty trunk from service and associating this trunk with a testing switchboard.

Faulty incoming trunk Returning now to the initiation of a call by the calling party or distant operator, such as the operator at telephone office I00, and the energization of the incoming trunk equipment and the equipment of the cordless toll operators position 4I3, during the operation required by the position operator, she may find that the incoming trunk, for one of the reasons herein presented, is not in a serviceable condition. When this is the trunk shown in Figs. 1 and 2, in use as an incoming trunk, the operator immediately advises the. calling operator at station I00 to extendher call tothe oflice over a different trunk and energizes key 4!! or key 405 to remove the trunk circuit from service. Key 4!! energizes relay 4I6 which associates battery through resistance 4!! with conductor I33. This establishes an operating circuit for relay 2!!) which may be traced from ground through its left winding, contact 7 of relay 202, lower winding of retardation coil 20!), conductor I33, resistance 4!! to battery. Relay 2I0, in operating, establishes a locking circuit for itself from ground through its right winding, contact 3, resistance 25!! to battery. This relay is locked in this manner in order that other operations in the incoming circuit will not cause its release until the trunk circuit has been tested and again placed in condition for service. The operation of relay 2H1 removes ground from conductor 24! which, as previously described, extends to conductor 242 and the overflow circuit. Contact 2 connects ground to the trunk block relay 32'! in order that all markers will find this trunk busy, which prevents the use of this trunk circuit until it is placed in serviceable condition. Contact 4 of relay 2!!) associates battery with conductor 456, filament of test board lamp 453 to ground. This circuit also extends through the contact of key 46!, filament of lamp 462 to ground. This illuminates a lamp in the test board 450 and in the trallic display board 46E], each switchboard having an attendant to maintain the equipment of the telephone office in a serviceable condition. Contact 5 of relay 2H1 connects ground from the test board jack 45! to the winding of relay I04 so that this relay cannot be released by a calling distant office. The operator in the cordless position 4H] may then energize key 4I5 if the connection has proceeded to the point of operating switches 282 to 302. This circuit extends a ground over conductor I32 through contact 4 of relay II2, winding of the splitting relay 2!!! to battery, operating relay 20!. It will be remembered that thehold magnets 215 and 30! of switches 282 and 302 were maintained operated from ground extending through contact 4 of relay 282, contact 9 of the splitting relay 20!, contact 3 of switch 282 to battery through hold magnet 215 and to battery through hold magnet 3IJI'. This ground also extends through con-1 tact 3 of switch 332 for maintaining the. outgoing trunk relay 3G5 operated. The energization .of relay .281, therefore, releases the switch hold magnets and the outgoing trunk relay 305, and disconnects the incoming trunk. from the switching connection. Key 4E5 may be used to simultaneously operate relay 2! and release the switches 282 to 3.02. The operator may now actuate the position release key 455 which releases relays 454 and. M3. .and the hold magnets of the link. switches 4%: which disconnects the incoming trunk from the cordless position equipment.

A test circuit 363' is associated with the incoming trunk by the testing switchboard operator which associates testing equipment through the jack springs of jacks 45l and 452 with the trunk circuit. This removes the ground through the tip spring of jack 45! to place the trunk at the disposal of a test man in oii'ice Hill whose services may be required to complete the test of this trunk. The tip and ring springs of jack 452 are connected to the tip and ring conductors of the trunk. Other leads from the circuit, such as'45t, 455, 456 and 457, associate the equipment of test board see with the apparatus of the trunk in order that various tests of the trunk may be made directly from the testing switchboard. This testing circuit is diagrammatically shown in Fig. 3 and only the circuit and apparatus concerned with this invention is disclosed. This comprises key 35b for releasing relay 2M when the incoming trunk has been again placed in serviceable condition and key 363 for operating relay 2H3, if required. Key 356 associates ground through the sleeve of plug 352 which is inserted in jack 452 extending to lead 451 through the right winding of relay 2m and its contact 3, resistance 259 to battery. This places 'a shunt around the right winding 21 and'causes the release of this relay and places the incoming trunk in service. Key 353 is shown in the test circuit for enabling the test board operator to operate relay 2H), if necessary. This circuit extends from battery through resistance 364, key 353,

sleeve of plug 352, thence through the sleeve of jack 452, conductor 45?, right winding of relay 2!!) to ground. Relay 2H locks in the manner previously described and remains operated until key 366 is actuated to cause itsrelease.

Faulty outgoing trunk pleted. The cordless operator may be aware of this fault through her signaling apparatus or she may be aware of a fault by monitoring after the connection has been completed. Under this condition, relay 3H5 is energized immediately by the cordless operator to remove the outgoing trunk circuit from service. The cordless operator may actuate key M2 which operates relay M9 for associating battery with conductor MB. The operator in this instance also energizes key '414 for operating the splitting relay 2t". The circuit for energizing the splitting relay 2M may be traced from battery through its lower winding, contact 4 of relay H2, conductor l32 to ground on contact 2 of key 4M. In this instance, a ground is also associated withconductor I32 through contact! of key M4 for hold ing. the switches and the outgoin trunk energized. This circuit may be traced from ground through contact of key 4M, link 45%., conductor M2,. contact 3 of switch 282. to. battery through the switch hold magnet 2'55 and to battery through the switch hold magnet 3M, contact 3 of switch 392,, winding of relay 305 to battery. The energizing circuit for lock-out relay 3I6 may be traced. from battery through resistance 429, conductor Hi9, contact 2 of relay 2M, contactlpf switch .282, contact 2 of' switch 302, lower winding of retardation coil 3%, right winding of relay M6 to ground. Relay 3|6 looks through its left winding and contact 3, resistance on to battery. The operation; of relay SIB disconnects ground from the overflow circuit at its contact 1. This overflow circuit extends through contact I. of relay 38 5, conductor 312, left winding of, overfiowrelay-332 to battery. Contact 2 of relay 3H5 associates battery with the filament of lamp 343 to ground and through key fifiiL'fila ment of lamp 352 to ground, illuminating the lamp in the testing switchboard 3th and a lamp in the traffic display board 350.. Contact 4' of relay 315 removes the outgoing trunk from service and renders it noneselectable by opening the operating circuit for relay 3 and extending ground over conductorfow to the trunk block relay 325110 prevent -the markers of the telephone oiuce from selecting this trunk for service connections.

The procedure followed by a cordless operator when a faulty outgoing'trun-k has been discovered may be to operate key 4M energize the splitting relay and hold the connecting switches, operate key M2 to energize the self-locking lockout relay 6H3, release keys 4M and 4-52 and operate'key M5 to release the switches 382 to 352, by opening the hold magnet circuit. This operator then immediately resets the position sender i l! and the marker 32 in the same manner as before to cause the selection oi another trunk circuit in the same trunk group. Since the iaulty trunk has been madenonselectable to markers there is no danger that this trunk will again be selected There is therefore very little delay in completing the telephone connection between the calling station andthe wantedstation when a faulty trunk is encountered. In some instances, key-405'may be used in place of keys M4, M2 and M5 for removing a trunk fromservice and disconnectingthe switches therefrom. Contact I of key 49 6 operates the splitting relay 20]. Contact 2 connects ground through the contact of relay 661 to conductor I42 for maintainingthe switch hold magnets energized. Contact 3 establishes an energizing circuit for relay 4H) to operate the self-locking lock-out relay 353 as described. Contact 4 establishes an energizing circuit for theslow operating relay is? which allows sumci'ent time for the operation of the lookout relay 3H6 before it opens its contact. The opening of the contact on relay 4%? removes the ground supply for the switch hold magnets causing the release of the switches permitting the operator to proceed with theset'ting of the marker for the selection of another outgoing trunk for'cornpleting the t l phone connection for the calling station. g

Tests of the outgoing trunk by a test and maintenance man may be made by associating the testing circuit 366 through plugs Sti and 362 with jacks 33 I and 352. After the outgoing trunk circuit has been placed in a: serviceable condition,

key 386' is energized for connecting ground through plug 362 and jack 342 and the left winding of relay 3H3. This shunts the current from the left winding of relay 3H5 and causes its release which places the outgoing trunk circuit in service for selection by the markers of the telephone ofiice.

When the trunk circuit, Figs. 1 and 2, is selected as an outgoing trunk circuit, the lockout relay 2 l may be operated in the manner described for the operation of relay 3|6. In this instance, it is apparent that an incoming trunk circuit will be associated with the trunk circuit, Figs. 1 and 2, through switches, such as 282 and 302, and only the apparatus of the trunk circuit, Figs. 1 and 2, operated which is used for an outgoing trunk connection. When the trunk circuit, Figs. 1 and 2, is associated with the testing switchboard, all of its equipment and circuits may be tested regardless of whether it was in use as an outgoing trunk circuit or an incoming trunk circuit.

What is claimed is:

1. In an automatic switching telephone system, trunk circuits for incoming calls from call stations and outgoing calls to call stations, operators positions, means in a trunk circuit responsive to an incoming call for controlling the selection of an idle operators position and for actuating equipment in said position, signaling means in said operators position for indicating faulty operation of the equipment in an associated trunk circuit, lock-out means individual to each trunk circuit for removing said trunk circuit from service and rendering it non-selectable, and means in said operators position for operating the lockout means in a trunk circuit so connected with said position.

2. In an automatic switching telephone system, trunk circuits for incoming calls from call stations and outgoing calls to call stations, operators positions, means in a trunk circuit responsive to an incoming call for controlling the selection of an idle operators position and for actuating equipment in said position, signaling means in said operators position for indicating faulty operation of the equipment in an associated trunk circuit, lock-out means individual to each trunk circuit for removing said trunk circuit from service and rendering it non-selectable, connecting it to a testing device and operating a signal in said testing device, means in said operators position for operating the lock-out means in trunk circuits so connected, and means for disconnecting said trunk circuit from said position.

3. In an automatic switching telephone system, selectable trunk circuits for incoming calls from call stations and outgoing calls to said call stations, operators positions, automatic switches, means in a trunk circuit for controlling the selection of an idle operators position, means in said position for controlling the selection of another trunk circuit and the operation of said switches for connecting said two trunk circuits together for a telephone connection between call stations, magnetically operable self-locking means individual to each trunk circuit for removing a trunk circuit from service and rendering it non-selectable, and means in said operators position for operating said self-locking means.

4. In an automatic switching telephone system, selectable trunk circuits for incoming calls from call stations and outgoing calls to call stations, operators positions, automatic switches, means in a trunk circuit for controlling the selection 0! an idle operators position, means in said position for controlling the selection of another trunk circuit and the operation of said switches for connecting said two trunk circuits together for a telephone connection between call stations, signaling means in said operators position for indicating faulty operation of either trunk circuit so connected, magnetically operable selflocking means individual to each trunk circuit for removing a trunk circuit from service and rendering it non-selectable, and means in said operators position for operating said self-locking means in either trunk circuit so connected.

5. In an automatic switching telephone system, selectable trunk circuits for incoming calls from call stations and outgoing calls to call stations, operators positions, automatic switches, means in a trunk circuit for controlling the selection of an operators position, means in said'position for controlling the selection of another trunk circuit and the operation of said switches for connecting said two trunk circuits together for connection between call stations, magnetically operable self-locking means individual to each trunk circuit for removing said trunk circuit from service. rendering it non-selectable, connecting it to a testing device and operating a signal in said testing device, and means in said operators position for operating the self-locking means in either trunk circuit so connected and for disconnecting said trunk circuit.

6. In an automatic switching telephone system, groups of selectable trunk circuits for completing telephone connections from one call station to another, operators positions, automatic switches, markers, means in one of said trunk circuits responsive to an incoming call from a station for controlling the selection of an idle operators position, means in said position for setting one of said markers for the selection of a trunk in a particular trunk group, means in said marker for testing the trunks of said group, for selecting an idle trunk and for operating certain of said switches to connect the calling trunk with the selected idle trunk, signaling means in said operators position for indicating faulty operation of either trunk circuit so connected, lockout means individual to each trunk circuit for removing either trunk circuit so connected from service and rendering it non-selectable by markers, and means in said operators position for operating said lock-out means in either trunk circuit so connected.

7. In an automatic switching telephone system, selectable trunk circuits for incoming calls from call stations and outgoing calls to call stations, operators positions, automatic switches, means in a trunk circuit for controlling the selection of an idle operators position, means in said position for controlling the selection of another trunk circuit and the operation of said switches for connecting said two trunk circuits together for a telephone connection between call stations, magnetically operable self-locking means individual to each trunk circuit for removing said trunk circuit from service and rendering it non-selectable for telephone connections, and a single means in said operators position for operating said self-locking means in either trunk circuit and releasing said trunk circuit from said telephone connections.

8. In an automatic switching telephone system, groups of trunk circuits for incoming calls from call stations and outgoing calls to call stations,

operators positions, automatic switches, means in a trunk circuit responsive to an incoming call for controlling the selection of an idle operators position and for actuating equipment in said operators position, means in said position for controlling the selection of an idle trunk circuit of a group outgoing to a particular station and the operation of certain of said switches for connecting the calling incoming trunk circuit to the selected outgoing trunk circuit, signaling means in said operators position for indicating faulty operation of a trunk circuit, magnetically operable self-locking means individual to each trunk circuit for removing a trunk circuit from service, rendering it non-selectable and connecting it to a test switchboard, means in said operators position for operating the self-locking means in the outgoing trunk circuit and for disconnecting this trunk circuit from the telephone connection,

and means for selecting another outgoing trunk circuit for connection to said calling incoming trunk circuit.

9. In an automatic switching telephone system, trunk circuits for incoming calls from call stations and outgoing calls to call stations, operators positions, means in a trlmk circuit responsive to an incoming call for controlling the selection of an idle operators position and for actuating equipment in said position, signaling means in said operators position for indicating faulty operation of the equipment in an associated trunk circuit, lock-out means individual to each trunk circuit for removing said trunk circuit from service and rendering it non-selectable, connecting it to a testing device and operating a signal in said testing device, means in said operators position for operating the lock-out means in trunk circuits so connected, means for disconnecting said trunk circuit from said position, and means in said testing device for releasing said lock-out means for placing said trunk circuit in service.

LLOYD. L. EAGON. JAMES B. McKIM.

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