US2337875A - Telephone system - Google Patents

Description

2s, 1943. D. SpEwnE 1 2,337,875

TELEPI'IONEl SYSTEM Filed April 28 ,.1942 4 Sheets-Sheet 1 ATTOR NEY Dec. 28, 1943. D. s. DEwlRE I' 2,337,875

TELEPHONE SYSTEM Filed'April 28, 1942 4 Sheets-Sheet Ely. 2

INVENTOR ATTQRNEY Dec. 28, 1943'.

D. s. Dl-:wml:l

TELEPHONE SYSTEM `4 sheets-sheet :s

`Filed April 28, 1942` www. WN

h mvENroR Beware 4 Sheets-Sheet 4 Dec. 28,1943. D. s. Dr-:wlRE

TELEPHONE SYSTEM Filed April 2a 1942 Patented Dec. 28, 1943 UNETE STS liia'iiNT OFFICE.

TELEPHONE SYSTEM application apra 28, 1942, serial No.' 440,795

9 Claims.

This invention relates to telephone systems and more particularly to arrangements for transferring telephone connections, whereby connections extended to one point may be routed to another point.

The prior art contains a number of disclosures of telephone systems in which incoming telephone calls may be transferred from one called subscriber to another called subscriber. Generally such facilities are provided by special private branch exchange systems. The present invention contemplates a plurality of private branch exchange installations and an object of the invention is to transfer a call which arrives at one such private branch exchange installation to another such; installation and especially where the two installations are in widely diiferent localities. The present invention differs considerably from prior arrangements in several essential aspects, as will be pointed out hereinafter.

In order to more clearly understandv this invention let it be assumed that a subscriber whose business is located in two widely different areas has two numbers published in the telephone directory, one for trunks terminated in an order table telephone installation in one of the areas and the other for a private branch exchange system located in the other area. An object of this invention is to provide means whereby incoming calls which are misrouted to the order table installation may be promptly transferred to the private branch exchange installation.

A primary object of this invention is to provide for the silent transfer of incoming calls received at one of the telephone installations to the other installation, whereby the calling party will be unaware that the transfer is being made and will be unable to hear any part of the conversation between the operators at the two installations.

Another object of this invention is to interconnect the order table installation with the privatebranch exchange or R B. X installation by means of a plurality of paths and provide apD paratus for automatically selecting one of the idle paths for completing the transfer of the in'- coming call. It is another object of this invention to employ relay apparatus to accomplish the autornatic transfer operations.

It is another object of this invention to provide means at the order table installation to indicate to the operator thereat that the selection of one of the various paths to the P. B. X has been accomplished. l

Another object of this invention is to provide apparatus for holding the calling partys line while the transfer operations are' being performed and then to release the hold -on the line 'aft-'er the transfer is completed;

Still another object of this invention is to prevent the simultaneous' seizure of two or more of the paths lto the P.`B. X'inst'allation by any one of the lines Vwhich'extend tothe order table installation.

And' it is a furtherobjectof this invention to prevent two telephone lines or trunks having in; coming calls from'bein'g simultaneously connected to any oneof the paths to the PyB. X;

These and otherobjects of uthis invention'will be `more clearlyv apparentV from the vmore 'cle-A ta'iled description hereinafter following, when read in connection With'the accompanying drawings in whichy Figures' 1 to 4 illustrate one embodiment of the vinvention merely for illustrative purposes. In'following the drawings'Figg 1 may' be placed above Fig. 2 and'lig. 3 above Fig. 4, and then Figsyl and 2 placed at the left of mss. 3 and 4, respectively.v

In the drawings threeofafplurality of telephone lines or trunks Nos. 1, 2 and 3 havingcon du'ctors TF1-R1, Tz-Rz and'T'a-'Ra respectively, are shown extending yfrom a central cnice (not shown) to the order table'only one of which is shown (but others may be multipled thereto). The order tableincludes, among other things, three (or more) keys KY1, KYz and KYs which correspond to the threel incoming' lines or trunks and are' used by the order tablel operator to answer'incor'ning calls or transfer them" to a P. B. X at a distant'point. The order' table and the P. B. X are connected to each other by a plurality of paths or lines R11;T11, R12-T12, R13-T13, etc'., one of which may be selected by the order table operator by operation of' anyoi the" keys such as KY1 to itsy transfer position. After' one of these paths' has been selected by the order table operator, she may then giveoral instructions' to the P.' `B. X operator concerning aninc'oming call intended for one ofthe parties available' through the' P. B; X. Theconversa# tion Ibetween operators will be inaudible tov the calling party. When the 'callingan'd calledparties are connected to eachother, `the order table operators telephone set will normally be disconnected from the parties talking' circuit, although the'operator may monitorth'e'connection if necessary.

AWhen ringing current is received from any one ofthe many lines extending between the central office and 'the order .table installation as, `for example, when ringing` current is received over con-k ductors T1 and R1 of line No. 1, the relay RRi will be operated, the operating circuit including ture and make contact of relay RRi, conductor BK, the contacts of key KB and ground. The operation of the relay RRi will connect the lamp LBi to the conductor F for the purpose o f flashing the lamp LBi, as will now be described.

swer the call by operating her key KYi-which corresponds to the incoming line No. 1 conductors T1 and Ri-to the upper or answer position. This will connect the conductors T1 and Ri of the line No. 1 to the telephone set of operator No. 1, as will now be described.

Immediately upon the operation of the key KYi to the answer position, the relay CB (in Fig. 3) Will become operated, the interconnected circuit including the conductor Ri to which battery is connected at the central oilice, contacts I| and |02 of key KYi, contacts |03 and |04 of key KYZ, contacts |05 and |06 of key KY3, conductor R, contacts |01 and |08 of the key HY,

The operation of relay RRi causes relays EF and AF of the interrupter circuit to be operated, the interconnecting circuit including ground, lamp LB1, the contact and upper armature of relay RRi, conductor F, the armature of relay DF and its back contact, the winding of relay EF, the winding of relay AF, the armature and back contact of relay CF and battery. The operation of relay EF will cause this relay and relay AF to be held operated under control of relay CF through a circuit including ground, resistance |4, the upper armature, make contact and winding of relay EF, winding ofrelay AF, armature and back contact of relay CF and battery. The operation of relay EF will also cause relay DF to become operated by completing a circuit including ground, the winding of relay DF, the lower armature of relay EF and its make contact, the winding of relay AF, the 'armature and back contact of relay CF and battery. Relay DF will in turn cause lamp LBi vto become lighted over a circuit which includes ground, lamp LBi, the contact and upper armature of relay' RRi, conductor F and battery connected to the make contact of relay DF. The operation of relay AF will result in the operation of relay BF by the completion of the circuit from battery, through the winding of relay BF, through the armature and contact of relay AF to ground. Relay yBF in turn will cause relay CF to become'operated by completing a circuit from battery to the winding of relay CF through the make contact of relay BF to ground. The operation of relay CF will then cause relays AF, EF and DF to be released by opening the circuit of the windings of these relays, the latter circuit including the lower amature and make contact of relay EF. The release of relay DF will extinguish lamp LBi. The release of relay AF will break the circuit to the winding of relay BF-which is of the slow release type-and this relay will later release. Upon the release of relay BF the circuit to relay CF will be interrupted, relay CF-which is also of the slow release type--being released thereafter.

If, after the cycle of operations just described is completed, the lamp LBi is still connected to the conductor F through the upper armature of relay RRi-that is, if relay RRi remains operated-the cycle ofr operations already described will be repeated again and again until relay RR1 releases. It will `be observed that lamp LBi is lighted when relay DF is4 operated, and extinguished when relay DF is released. This ilashing lamp will attract the order table operators attention.

Upon observing Vthe flashing lamp LBi, the operator at the order table installation .(Who will be. referred to also. as operator No., 1) will anthe lower'inner armature and back Contact of relay S, the winding of relay CB, the upper inner armature and back contact of relay S, contacts ||0 and of key HY, conductor T, contacts ||2 and ||3 of key KYs, contacts ||4 and ||5 of key KYz, contacts IIE and ||1 of key KYi to conductor T1 which is grounded at the central office. Relays LR and K1 are also operated over a circuit which includes ground at the upper back contact of the relay HC, the winding of relay LR, conductor A, contacts |20 and |2| of key KYa, contacts |22 and |23 of key KYz, contacts |24 and |25 of key KYi, the winding of relay K1 and battery. The operation of relay LR causes relay RS to operate over a circuit which includes battery connected to the make contact of relay LR, the back contact of the upper inner armature of relay CT, the winding of relay RS and ground. Relay RS then causes relay CT to become operated, the interconnecting circuit including battery connected to the upper make contact of relay RS, the winding of relay CT, the make contact of relay CB, the back contact of the upper armature of relay HC and ground. Relay CT then locks in its operated position, the locking circuit being completed through the upper inner make contact of relay CT and the make contact of relay LR to battery which is connected to the latter contact.

Upon the operation of relay CT the circuit extending to the winding of relay RS- is Opened, whereupon relay RS releases. It will be observed that before relay CT is operated, operators telephone set receiver RR is short-circuited by the lower armature and back Contact of relay CT so that no clicks will be heard by operator No. l while the ringing from the central ofce is being tripped. When relay RS operates, this short circuit is continued by the lower armature and make contact of relay RS. The short circuit around the receiver RR will be removed, however, as soon as relay CT operates and relay RS releases. The operators transmitter TR will receive current when relay CT is operated, current being supplied over a circuit which includes battery connected through retard coil RTa to the upper terminal of transmitter TR, the transmitter TR and ground connected to the lower inner make contact of relay CT. The ilow of current through the transmitter TR enables operator No. 1 to talk to the calling party connected to line No. l through the central oce. The transmitter TR is connected to the'repeating coil RP through a condenser I2, the other winding of the repeating coil being connected to line No. l through a condenser I3. The circuit interconnecting the latter winding of the repeating coil to the conductors Ti and R1 of line No. 1 includes contacts IID and of key HY, conductor T, contacts I |2 and |3 of key KYa, contacts ||4 and ||5 of key KYz, contacts IIS and ||1 of key KY1, conductors T1 and R1, contacts |01 and |02 of key KY1, contacts m3 and |04 of key KYz, contacts IE5 and |96 of key KYs, conductor R, contacts |61 and I 68 of key HY and the upper outer armature and make contact of relay CT. It will be observed that this talking circuit includes an armature of relay CT. This insures that the circuit of the calling subscriber will be completed only after relay CT has been operated.

Upon the operation of relay K1 pursuant to the closure of key KY1 to its answer position, the lamp LB1 will then be changed from a iiashing condition to a steadily lighted condition as a busy indication, the steady current being supplied to lamp LB1 from the battery connected to the lower armature and make contact of relay K1. The operation of relay K1 will also cause relay BB1 to release. It will be seen that relay K1 controls both the operating and locking circuits of relay RRi by means cf its upper and lower armature contacts, respectively. After the circuit between the calling subscriber connected to line No. 1 and operator No. 1 has been completed, operator No. l may then talk to the calling party and learn that the calling party desires to converse with some one who may be reached only through the P. B. X. In that case the operator will take steps to transfer the calling party to the P. B. X. which is, of course, located at a point distant from the order table.

Operator No. 1 will then operate her holding key HY, which is of the non-locking type, to its upper or hold position, at the same time leaving key KY1 in its answer position. This will cause relay RH1 to'become operated, the operating circuit for relay BH1 including battery connected to the upper left swinger of key HY, conductor H, the contacts |30 and ISI of key KYs, contacts |32 and |33 of key KYz, the contacts |34 and |5 of wey KY1, the winding of relay BH1 and ground. The operation of key HY to its hold position will further cause lamp LH1 to be lighted over the same circuit except that lamp LH1 may be substituted for the winding of relay BH1. The operation of key HY to its hold position will also cause relay HC to be operated, the operating circuit for relay HC including battery connected to the upper right swinger of key HY, the winding of relay HC, the contacts of the key KB and ground. The operation of relay I-IC will open the ground connection to the windings of relays CT, LR and K1 at the upper back contact of relay HC (the circuit to the winding of relay K1 was previously completed over contacts of keys KY1 to KYs and the upper armature and back contact of relay HC). The release of relay K1 causes relay BH1 to be locked in its operated position, the locking circuit for relay RH1 including the upper armature and make contact of relay RI-Ii, the make-before-break contact associated with the lower armature of relay K1 and battery. The operation Vof relay BH1 connects a resistance I5 across the conductors T1 and R1 of line No. 1 to hold the line No. 1 until it is completely transferred to the P. B. X. The operation of relay RH1 also causes lamp LH1 to be kept lighted, the circuit for lamp LH1 now including battery, the make-before-break contacts associated with the lower armature of relay K1,

the upper armature and make contact of relay RH1, the lamp LH1 and ground. The lamp LB1 is extinguished upon the release of relay K1. It will be observed therefore that the .hold lamp LH1 will be lighted to replace the previously lighted lamp LB1. Thus the operator No. 1 will be provided with positive indicating means to indicate to her that she is holding line No. 1.

The operation of relay HC will also provide a locking circuit for that relay so that the LR and K1 relays will be prevented from operating when the key HY is restored to its normal position. The locking circuit for relay HC vincludes the lower armature and make contact of relay HC, conductor H, contacts |30 and |3| of key KYa, contacts |32 and |33 of key KYz, contacts |34 and |35 of key KY1, the upper armature and make contact of relay RH1, the make-before-break contact of relay K1 and battery.

In order to transfer the calling line No. 1 to the P. B. X, the operator No. 1 will first restore key KY1 to its normal position. This will cause relay HC to be released, will open the operating circuit for relays K1 and IR, and will disconnect the conductors T1 and R1 of line No. 1 from the telephone circuit of operator No. 1. Operator No. 1 will then operate key KY1 so as to close its lower or transfer contacts. The operation of the key KY1 to the transfer position will complete a connection from the order table to the P. B. X circuits, as will now be described.

The operation of key KY1 to the transfer position will `cause the windings of relays E1, PL and LR to be connected in series with each other. The series circuit will include battery connected to the winding of relay E1, the winding of relay E1, contacts |39 and |4| of key KY1, cond-uctor P, the winding of relay PL, conductor L, contacts |42 and |24 of key KY1, contacts |23 and |22 of key KYz, contacts |2| and |20 of key KYB, conductor A, the winding of relay LR, the upper armature and back contact of relay HC and ground. The operationof relay PL will cause the operation of relay S over a circuit including the winding of relay S and the battery connected thereto, the upper armature and make contact of relay PL and the upper armature and back contact of relay HC. The operation of relay LR will cause the operation of relay RS and CT and the subsequent locking of relay CT and release of relay RS as hereinbefore described, except that relay CT will operate and lock through the lower make contact of relay PL instead of through the make contact of relay CB. These operations prepare the telephone circuit for talking. The operation of relay E1 will connect battery to the conductor BB1 which extends to relay J1 to ground, whereupon relay J1` will become operated. The circuit for operating relay J1 includes battery connected to the lower outer armature and make contact of relay E1, conductor BB1, the make-before-break contacts associated with the upper outer armatures of relays A1, B1 and C1, the winding of relay J1 and ground. The operation of relay J1 will connect battery to the upper terminals of the lower or operating windings oi' relays A1, B1 and C1 by means of the the three upper armatures respectively of relay J1. One of the relays A1, B1 or C1 will then be operated, the particular relay operated depending upon the conditions of relays N1, N2 and N3 which are respectively associated with the three paths shown interconnecting the order table with the P. B. X. This will now be more fully explained.

If the relays N1, N2 and N3 are in their released positions, then the relay A1 will alone be operated in response to the operation of relay J1. This is because the lower terminal of the operating wind-y ing of relay A1 is then grounded over the conductor OP1 and 1the `backl 'contact' of if the armature Vof- K re1ay-N1.` The lower terminals'ofithe operatingof? the operatingr winding oi relay B1 being grounded over acircuit'including conductor CP2,N the back contact ofthe armature` of relayl N2 andthe make `contact of thev armature -of relay N1. In that case theerelay Brwill become operated.-

On the other hand, if relays N1 and N2 are b'oth'operated and relay N3 alone released, then the relay C1 will be operated because the lower terminal of its operating winding will become grounded over a circuit which includes conductor OPs., theback contact of the varmature of relay N2, the make contact of relay N2, and the make contact of relay N1.

Ii `all three relays N1, N2 and N3 are operated at the time when a call is received, over one of the incoming, lines, then in'that case no path will be available for transferring the call to the P. B. X.

After one of the relays ple, operates, asalready notedvhereinabove, it will then releaselrelay J1. This s accomplished by opening the circuit tothe Winding of relai7 J1 at the make-befo-re-break contact of the upper outer armature of the relay A1. Relay A1 willalso lock itself in its operated position over such as A1, for eXama circuit which includes battery connected to the lower outer armature of relay E1, the conductor BB1, the upper outer make contact of relay A1, the upper or locking winding of relay A1, the make contact ofthe inner upper armature of relay A1, the back contact of the upper inner armature of relay A2, the back contact of the upper inner armature of relay A3 and ground.

If two incoming calls over, for example, lines Nos.' l and 2 are being transferred simultaneous- `ly by' two different order time when, for example, relays A1, B1 and C1 and table operators at a relays A2, B2 and C2 are in their released positions, a situation will be developed in which both relays A1 and A2 will 'be operated simultaneously. This is because both relays J1 and J2 become operated simultaneously in response to the operation of relays E1'and E2, respectively, all of which occurs pursuant to the operation of keys KY1 and'KYc to their transfer positions. But relays J1'and J2 releasedue circuits in series, respectively, with their windings at the make-lcefore-breakV contacts associated with the upper outer armatures of relays A1 and A2. In` that event'ionly the relay A2`can remain operated vbecause its locking circuit will be completedthrough the upper inner make contact of` the rela-y A2 and ther back contact of the upper innerarmature. of relay As. The locking circuit for relay A1', although closed at theupper inner make contact oflrelay A1, is opened at the upper inner back contact of ,relay A2. The operation of relay A2 thus prevents relay A1 from being locked in its operated position.- In other words,- relay Az will'remain operatedbecause its locking circuit is completed; ,relayfAil will become released because its; locking, circuit remains, open. dueto l to the P. B. X. Thus, when three operators atto the opening ofthe the operation of-relay A2. Thus a double connection vto a single path between the order table and the P. B.A X is definitely avoided. This is an importantfeature of this circuit. Positive means are `provided to -restrict each path to the P. B. X to a single line from the central ofce.

Underthe circumstances just noted, therelease of' relay A1 willrcause relay J1 to become reoperated over the circuit previously described. Then relay B1 or relay C1 may be operated upon the reoperation of relay J1 to connect the incoming line No. 1 to path No. 2 or path No. 3 extending the order table operate their keys KYi-KYa and cause relays A1 to A3 to become operated at the same time, only that relay will remain operated to complete a path to the P. B. X, which has the highest subscript, namely relay A3. The other lines will be shifted to paths Nos. 2 and 3 controlled by the B and C (and other like) relays. The relays A1 to A3 therefore provide a so-called horizontal lockout or allotter circuit. This horizontal lockout or allotter circuit is employed to prevent two or more incoming lines from being connected to a single path extending to the P. B. X. Relays B1 to B3 provide another horizontal lockout or allotter circuit, and so on.

After relay A1 operates and locks. (relays A2 and A3 being released) and relay J1 is released, then relay N1 becomes operated. The operating circuitfor relay N1 includes the winding .of relay N1 and the battery connectedthereto, conductor H11, the lower outer armature of relay A1 and its make Contact, the vlower armature and back contact of relay J 1 and ground. The operation of relay N1 removes ground from the `conductor O91. This. renders path No. ly to the l?.Y B. X busy to other incoming lines from the central ofiice. The operationof Vrelay N1 advances the ground connection to `conductor CP2 associated with path No. 2 extending'to the P. B.v X. The groundcircuit to conductor CP2 ynow includes the back'contact of the armature o-f relay N2 and the make contact and armature of relay N1. Itwill be understood; of course, that after relay N2 becomes operated -in responserto th'e'release ofrelay J2, path-No. 2 vlikewise. will be renderedV` busy to incoming telephone lines and the grounding circuit for conductor OP: associated with' path No.' 3 will be completed 'through the make `contacts of the armatures of relays N1 and N2. The arrangement of relays N1 to N3 therefore provides a vertical' lockoutr or allotter circuit which is employed to prevent the connection of more than one path'to a'single incoming telephone linesuch as linev No. 1.

The operation of relay A1 alsocloses a circuit to Ainterconnect i the operator Aat the order `table with theoperator at the P. B. X. The operation ofzrelay; A1 connects battery at the second upper make contact of that relay over the conductor L1 to the lamp I P1 in order to'light this lamp. This lamp is employed to indicate to the operator' No. l that a path vto the P.A B. X has been selected, if all 'pathsvr are busythe f lamp LP1` will not be lighted.` The lamps LP1LP3 are therefore employed to notify the variousV operators at' the order table that a path has been selected for interconnecting the calling party on line No. l with the P.v B. X;

Whenran operator at the order table observes that lamp LP1 is lighted she will then operate the key HY toits ash'andfring position. This' is ernployed'rto4 transmit :ringing current to the P. B: `X-as willV nowxbef pointedz out. i

The operation of the key HYy to the ash and ring-positioncauses ringing current `to now 1 from ringing generatorGR throughl lrelay R11.

Thel interconnecting circuit Aincludes generator GR, the lamp LCg-the upper outer make Contact of relay S, the contacts |39' and |07 of key-HY, f

conductor R, contacts |96 and-|85 o1" key KYV, contacts IM and |133 of key KY2, contacts |92,

|32, |33 and |34 of key KY1, the lower inner make left armature of relay SL1, the left or operatingwinding of relay R11, the condenser il, the conductor T11, the third lower make contact of relay A1, conductor T1, the upper inner make contact of relay EF1, contacts |49, |43-, -lllll and IIS-df key KY1, contacts ||5 and ||i of key KY2, contacts ||3 and ||2 of KYa, conductor T, contacts and |45 of key HY, the lower outer armature and make contact of relay S, and ground. The operation of relay R11 in response to the ringing current from generator G1R-causes relay R11 to be locked in its operated position, the locking circuit including ground, the right or locking'A winding ofY relay R111, the inner make contact of relay R11, the right back contact of relay S111 and battery. The operation of relay R11 causes lamp L11 to be lighted to attract the attention -of--the P. B. Xv operator.

When the P. B. X operator observes that the lamp L11 is lighted she will then connect her cord to the jack J 11 immediately below the lamp L11.

This will cause relay S111 to become operated, the operating circuit including-the winding of relay SL1 and the battery-connected thereto, the sleeve contacts or jack J11, and plug P11 and resistance Hi to ground. The operation of relay S111 re-` ing circuit including the winding of relay RL1, the tip contacts of jack J11 and plug P11, the retardcoil RT2,-the ring-contacts of plug P11 and jack J11, conductor T11, the third lower make contact oli-relay A1, the conducto-r T1 which-is connected to ground, conductor R1 which is connected to battery, the second lower make contact-of relay' A1, conductor R11 to the winding of relay R111. Conductors T1 and R1 are connected to ground andA battery, respectively, through operated contacts of relay E1 and the transfer portion of key KY1, normal contacts of the answer portion of keys KY1, KY2 and KYs, normalcontacts of the flash and ring portion of key-HY, operated contacts of relay S and windings of retard coil-RTL The operation of relay RL1 operates relay M1, the circuit for operating relay M1 `including the battery connected to the winding of relay M1, the make contact of relayRL1an'd ground. The operation of relay M1 is employed to connect battery through its upper make contact Lto the conductor LK1 which is connected to the locking winding of relay A1, thereby holding relay A1operated after the key KY1 is restored to its normal or neutral position.

The P. B. X operator may then operate the key KYo connected to her cord circuit in order totalk to the operator 'at the ordertable.V` They calling subscriber on line No. 1 will be unable to hear thisl conversation between the two operators open at the inner make contacts of the relay E1. This 4is a `feature of this-arrangement. 'By-this arrangement f the calling partyV will -remain 'un aware that a-switch-ingoperation hasbeen performed andthat instructions have been :lpass'ed between operatorsv to establish*a--path-circuit a--part'y available through the yPQ-B. X.

-After receiving instructions'from the operator at the-order table, the P. BQ-X operator-will then connect the plug P21 at the-otherend `of her cord circuit' to the jackI J21 to addons ofthe P. B. VX stations to-the circuit. The ringing--circuitto the P.- B. X-statio-n is obvious tol those skilled in the art and 4is not shown herein. After plug P21 engages jack J21, lamp- L21 will be-lightedythe circuit for lamp L21 includingbatt'ery connected to lamp L21, the-back contactI of relay SV1,the sleeve contacts of--plug-Pn and `jack J21" vand ground. *When the P. B. `X station vhandset isl then lifted from its mounting, relay SV1 Vwill be operated,`thereby extinguishing-lamp L21.

After receiving oralacknowledgment-from the P. B. X operator that the call over -line No; 1V is being completed, the order table operator will then restore her key KY1 to its-normalor neutral position. This will `release relay E1 by opening the-circuit to its winding 1at the contact` 1390i key KY1. The release of relay E1 will break the talking circuit to the operator at "the order table at contacts |34 and Mil of key KY1. The calling subscriber can then talk to the desired party at the P. B. X station free from any control by the operator at the order table. The order table operator may, however, monitor on the circuit by operating the key KY1 to the answer position if she desires to do so-.Y The calling subscriberis now connected tothe P. AB. X station through the make-before-break-- 'contacts` of the upper and lower inner armaturesl of relay E1. The important function of relay E1 is to establish vconnections between'the calling party o-n line No. 1 and the desired P. B. X station and at the same time remove all control of the circuit from the order table operator when the Vconnections are-completed.

The release of relay E1 causes relay K1 to become operated, the "operating circuit-for relay K1 including battery connected to the winding of relay K1, the upper outer armature andback contact of relay E1, conductor AA1', the lower inner make Contact 'of-relay-A1,- conductor AA11, the lowermake contact-of relay M1 and ground. The operation of relay `K1 will open the locking circuit to relay BH1 at the make-before-break contact of the lower armature of relay K1, which will release relay 'HI-fand extinguish-the lamp LH1 which vpreviously indicated that the line No. 1 was being held by the order-table operator. The release of relay R11-I1 will also remove the shunt resistor l5' from the incoming line con'- I ductors T1 and R1. The operation-of relayK1 will also cause the lamp LB1 to light steadily as a busy indication, as hereinbefore described.

'-It will be observed-that lthe rcalling subscriber connected to the conductors- '1'1"and` R1 Ais now' connected -to-one'o'f `'the P. B. X stations over path No. 1 bet-Weenlv the ordertable' and the P1 B. X. This -circ'uit may now be traced from conductor T1 through -the make-before-break. contact of the inner upper armature of relay E1, conductor `T1-, l relay A1, conductor T11,- the ring contacts of jack J11 and plug P11, the ring contacts of plug P21 and jack J21, the -P. B. X station, Athe ring con'- because'the circuit `to the lcentral oirioewillbe 7o tQtS- took; Jvzlfand'plug P21-,- the-winding 'of relay the third lower make *contact of SVJgthe'tip contacts of plugPn andjack J 11, the f winding of relay RL1, conductor R11, the'second lower make contact ofy relay A1, to conductor 13.1 overfthe v-lower inner-make-before-break contact of relay E1. The .circuit between the calling subscriber and the desired P. B. X station is now therefore held by the flow of current through the winding of relay RL1 from the central office over the conductors `T1 and R1. In this circuit the retardation coil -RTz of the P. B. X operators cordcircuit is connected in parallel with the P. B. X station connected to the P. B. X operators cord circuit. Moreover, the key KYo enables'lthe P. B. X operator to monitor the circuit if shedesiresto do so. Y n

` After the conversation between the calling party and the'party at the P. B. X station is completed` and thewhandset of the P. B. X station is restored to its mounting, the relay SV1 will then release. The release ofvSV1 will light lamp L21 by completing the circuit to L21 at the back contact of relay Svi.

Upon observing this lighted lamp the P. B. X

operator will then disconnect the plugs P11 and P21 of her cord circuit from the jacks J11 and J21, respectively. When this happens the sleeve relay SE1 will be released and relay RL1 will also be released. AThe release of relay RL1-which, as previously noted, controlled the circuit between the calling party and the P. B. X station-will release relay M1 by opening the circuit of the winding of relay M1r at the make Contact of relay RL1. The release of relay M1 will then disconnect battery at its upper armature from the locking winding of relay A1 whereupon relay A1 will release, and will also cause relay K1 to be released by opening the circuitin series with the winding of relay K1 at the lower make contact of relay 'M1.r The release of relay K1 will then extinguish the lamp LB1 by breaking the circuit tothis lamp at the lower make contact oi relay K1. The release of relay A1 will release relay N1.

will be returned to their normal conditions bothv at the order table and at the P. B. X and the arrangement will be thereby prepared for another incoming call.

lWhile the arrangementhas been described for establishing connections between the line No. 1 and one of the P. B. X stations, similar circuits and methods of operation are involved in establishing connectionsbetween any of the other lines and vany of the other P. B. X stations.

While this invention has been shownl and described in certain particular arrangements merely forthe'purpose of illustration, it will be understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims. f

What is claimed is:

. 1. In a telephone systemthecombination of a central office, a group of lines extending from said central oflice to a subscribers premises at a first location, a plurality of circuits interconnecting said premises at saidrst location'with the subscribers premises at a second location remote.

assists' i switching apparatus including a relay havingl contacts arranged to open the circuitbetween the incoming line to which the calling party is con-y nected and the circuits to which the operators at said rst and second locations to prevent the calling party connected to the incoming line from hearing the conversation between the operators at. the two premises.

2. In a telephone system, the combination of an plurality of incoming lines extending from a. central oiiice to a subscribers premises at a first location, a plurality of paths interconnecting said premises at said iirst location with the subscribers premises at a second location which is: remote from the first location, means controlled. by the operator at the first location to connectrv automatically any one of said incoming lines to' one of said paths to the subscribers premises at. the second location without permitting the calling party connected to said incoming line from. hearing the conversation between the operators. at said first and second locations, said means in cluding means to select only one of said paths.

that is idle to the exclusion of all other paths.

3. In a telephone system, the combination of a:

plurality of incoming lines extending to a subhas been selected.

4. In a telephone system, the combination of an plurality of incoming lines, a plurality of receiving circuits at a subscribers rst premises, a. P. B. X at the subscribers second premises which. are located at a point remote from the rst premises, said P. B. X having a plurality of telephone stations, and means for transferring an incoming line connected to one of the receiving circuits at the rst premises to one of the P. B. X stations without the calling party hearing the conversation between the operators at both premises.

5. In a telephone system, the combination of a plurality of incoming telephone lines, a plurality of receiving circuits at a subscribers rst premises, a P. B. X having a plurality of stations located at the subscribers second premises which are remote from the rst premises, means for transferring an incoming line connected to one of the receiving circuits at the rst premises to the Pv. B. X without the calling party hearing the conversation between `the operators at both premises, and means to prevent more than one incoming line from being connected to any one I P. B. X station.

from the rst location, means controlled byl the.

operator at the subscribers premisesvh at said iirst'locationto connect any one of said incoming lines through one of said circuits vthat is idle to the subscribers premises at the second locationso that'thecalling party may talkfwith the called` party at the second location, said means including 6. In a telephone system,` the combination of a plurality of incoming telephone lines connected to a subscribers rst premises, a P. B. X having a plurality of stations located at the subscribers second premises which are remote fromthe rst premises, a plurality of paths interconnecting the first premises with said P. B. X, means controlled by the operator at the first premises for transferring an incoming line to one of said paths that is idle Ifor connection to one of the P. B. X stations' without the calling party hearing the conversation between the operators at the first premises and at the P. B. X.

7. In a telephone system, the combination of a plurality of incoming telephone lines connected to a subscribers iirst premises, a P. B. X located at the subscribers second premises which are re- 4mote from the first premises, a plurality of paths interconnecting the two premises, a single switch controlled by the operator at the rst premises, means responsive to the operation of said switch for selecting one of the idle paths between the premises for connecting an incoming line thereto, means controlled by said switch to prevent the calling party from hearing the conversation between the operators at the two premises over the selected path, and means for preventing a second incoming line from being connected to the same path to which the first incoming line is connected.

8. In a telephone system, the combination of a plurality of incoming telephone lines extending to a subscribers rst premises, a P. B. X located at the subscribers second premises which are remote from the first premises, a plurality of paths interconnecting both premises, a switch controlled by the operator at the rst premises, means responsive to the operation of said switch to select one of the idle paths for connecting an incoming line thereto and to prevent the party connected to the incoming line from hearing the conversation between the operators at said iirst and second premises, and means responsive to the selection of an idle path to indicate at the first premises that one of said paths has been made available for the transfer of an incoming line,

9. In a telephone system, the combination of a plurality of incoming telephone lines connected to a subscribers rst premises, a P. B. X located at the subscribers second premises which are remote from the rst premises, a plurality of paths interconnecting both premises to any one of which an incoming line may be connected under the control of the operator at the rst premises, means controlled by the operator at the first premises for selecting one of the idle paths and for indicating at the first premises that an idle path has been selected, means to prevent more than one incoming line from being connected to the selected path, means to prevent two paths from being simultaneously connected to a single incoming line, and means to prevent the party connected to an incoming line from hearing the conversation between the operators at said first and second premises.

DONALD S. DEWIREt

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