US2416131A - Automatic telephone system - Google Patents

Description

Feb. 18, 1947. H .VQSS

AUTOMATIC TELEPHONE 'SYSTEM Filed Nov.' 10. 1944 6' Sheets-Sheet l mohomzzoo m0.

INVENTOR. JOHN H. VOSS l .BY

ATTORNEY A Fb 18 1947- J. H.. Voss AUTOMATIC TELEPHONE SYSTEM Filed Nov. 10, 1944 6 Sheets-Sheet 2 INVENIQR. norm u. yoss ATTORNE Y Feb. 1s, 1947. L H Voss AUTOMATI C TELE PHONE SYS Filed Nov. l0, 1944 6 Sheets-Sheet 3 Arron NEY Feb. 18, 1947. J H Voss AUTOMATI C TELEPHONE SYSTEM Filed Nov. 1o; 1944 e sheets-sheet 4 .N ms R m VV T A m. H N H O J Feb;- 18, 1947- J. H. -vcss AUTOMATIC TELEPHONE SYSTEM Filed Nov. l0, 1944 6 Sheets-Sheet 5 ATToRNEw( Feb. 18, 1947. 'J H V955 AUTOMATIC TELEPHONE SYSTEM Filed Nov; 1o. 1944.v

6 Sheets-Sheet 6 JOHN H. VOSS BY u' VArloRmsY Patented Feb. 18,- 1947 AUTOMATIC TELEPHONE SYSTEM John H. Voss, Downers Grove, Ill., assigner to Automatic Electric Laboratories, Inc., Chicago,l Ill., a corporation of Delaware Application November 10, 1944, Serial No. 562,797

This invention relates to automatic telephone 'systems ingeneral and is more particularly concerned with improvements in trunk selecting equipment for private branch automatic exchanges of the all relay type.

A private branch automatic exchange, usually located within a subscribers premises, provides intercommunicating service between a group of local telephone stations. In addition, the local stations usually serve as extension stations to the subscribers city exchange lines that provide the publie telephone system connections.

In private exchanges, where an attendant is not provided to supervise orextend connections between the public exchange trunks and local extension stations, the usual means for extending the local stations to the city exchange trunk lines is through the local link equipment. Only a small portion of a large unit of the local con- Anecting equipment is actually used for each trunk connection. To reduce the cost of trunk connecting equipment, various arrangements have been used, such as a multiple of all the trunk lines to key equipments at the local stations. However, except in very small establishments which use the conventional house telephone lwiring plans, a large multiple of trunk talking conductors is not desirable or practical from a transmission or cost point of view.

Further, the existing systems require special equipment to provide for additional trunk service facilities that are desired by many business establishments, such as, no unauthorized interference with an established connection, and the restriction of some of the local stations from originating outgoing trunk calls.

The object of the present invention is to pro- Ivide improved means whereby the minimum amount of switching equipment is required for a station to selectively connect a local line station to a city trunk line without sacrificing the desirable service facilitiesthat are usually provided in a more costly type of private exchange.

A feature of the improvement, relating to the rreduction in equipment requirements, is that the local exchange connecting link equipments are divided into two separate service groups, a local group and a trunk group which are directively connected to any local line by allotter equipment that is `common to all the link equipments in the local exchange.

Other features of the present invention relate to the novel circuit arrangements between station operated trunk select keys and the common ,.allotter to make anA operated key effective only 37 Claims. (Cl. 179-18) 2 1 at a station that corresponds to the line marked in the allotter. The allotter, being heldV only during the brief period required to directively extend a link to a calling line will successively extend a plurality of calling lines, therefore by these circuit arrangements false link assignment due to the simultaneous operation of keys at several stations is prevented.

Another feature of the present invention relates to the circuit arrangement for transferring trunk calls between local extension stations, whereby an answering extension station transfers the trunk circuit to a self locked trunk hold- .over the local links and permitting another station to seize the trunk link equipment to establish a telephone connection with the call on the held trunk.

Other features of the invention relate to the simplified circuit arrangements for special trunk services, such as restricting specified stations to local callsand incoming trunk calls, while other stations have an additional privilege of initiating trunk calls. In vconjunction with these stated trunk services, a tone signal, individual toeach line indicates to a calling line when the line is not being extended to a selected trunk.

Other features not specifically mentioned, together with the features and objects previously outlined, will be explained hereinafter. Reference will be made to the accompanying circuit diagrams, Figures 1 through '7, inclusive. These diagrams illustrate the features of the present invention as being incorporated in aV dial controlled local exchange, of the all relay type, having an ultimate capacity of lines, l0 local links, and 4 city trunk links. The drawings illustrate only sufficient apparatus and wiring details for the invention to be clearly described and understood. v 1

Fig. 1 illustrates the individual station equipment for two stations designated A and B connected to lines l1 and 10 respectively at the local exchanges. Station A is connected to illustrate a nonrestricted station and station Brillustrates the connections for a station restricted from originating outgoing calls to another exchange.

Fig. 2 illustrates a trunk nder link for extendinga trunk (Fig. 3) to any one of the local lines,

Fig. 3 illustrates a trunk circuit for e ,main exchange connection.

` calls.

Fig. 7 illustrates the incomplete connector on Fig. 4 illustrates the common allotter equipment for directively connecting a selected link to the calling line.

Fig. 5 illustrates a local nder link for extend-` ing the local connector (Fig. 7) to any of the local lines.

Fig. 6 illustrates the link distributor relays` wherein the locallinks (Figs. 5 and?) are preselectedand successively assigned to extend loca the local link. This circuit is well known, therefore the equipment shown covers Ythe seizure,

ring, busy test and control relays used to com, plete the operating description of the connecting equipment.

Referring to the drawings in -general,the system illustrated thereon has Va plurality of rfinder links which are dividedinto two groups, a trunk 1 group, Fig. 2, and a local group,Fig. 5. The trunk links are selected by :the manual operation of the substation set trunk keys shown in Fig. 1. The

localflinksiare automatically preselected bythe finder distributor relays shown in Fig. 6. The initial .Operation'of the finder link S, Fig. 2 or Fig. 5, is .controlled from the common lequipment.' Fig. 4, in conjunction with a line operated'relay equipment shown in Fig. `1. Theoperation of the link v the trunk link, Fig. 2, serves to connect the calling local line t0 an associated trunk line circuit, Fig.

3, leading to a city exchange of eithera manual or dial controlled type.

We will now proceed to give a more specic description of .the equipment `and wiring-'shown on drawings Figs. 1 to '7,inclusive. Fig. 1 illustrates two of the local . exchange lines 10 and 11 terminating, respectively, atstation 'B, a station that is restricted from making outgoing trunk calls, and at station lA that does not have re- The stations .designated stricted trunk service. Y A and Btogether .with ringers vl Il and IDI, re-

spectively, indicate conventional dial telephone 1 instrumentswherein a handset, when lifted from the cradle, closes switchhook springs, bridging the telephone transmission circuit across thelline talking conductors and which, in series Vwith normally closed dial springs will close adirect current control circuit over the stated talking conductors to the local exchange. Such telephones are so well known that detailed circuit and equipment are not shown. The combined station and 3 line equipments shown are given a general reference designation AI I` and BIO, respectively, The

key equipments are part of the telephone instrument and are of the .locking type .that are metions of the various conductors at the local ex- .I

change.

The line designations 10 and 11 are part of the exchange numbering plan as the 100 lines in the system are divided into 10 groupsof 10 lines each, for example, the rst group, lines 10 .to 19,

inclusive, includes lines 1 0 .a n d 11, and hence the 'ment havingV yconventional general functional designations L, CO and BY. For example, relay chanically interlocked with each other andwith the telephone switchhook lever similar to that disclosed in Patent No. 11,783,310, issued Decemberz, 1943. As illustrated, each stationhas a local key and a trunk hold key in addition to an l lindividual key for each trunk. Two of the indicated four trunk keys `shown are sufcient 1 equipment to illustrate the wiring between keys.

tween the station equipments vare in the termina- `It should be noted that the only differences be- [2i] (L) is a line operated relayand marks the callingline on the common allotter, Fig. 4, whichv starts the exchange equipment functioning to Yextenda link to line 11; relay I3@ (CO) is oper- 'is yoperated when the call is not extended, due to all local links or trunk links being busy or due to the calling station attempting to make anunauthorized outgoing .trunk lcall.AV lRelay 1 4!) (BY) operated, an audible `tone signal is connected to the associated line and the commonequipmen-t is released.

Fig. 2 illustrates a `nder link having access to lines and is used for the purpose o f extending a city exchange trunk, FigfS, to one of thepossible 100 lines. One unit of link equipment is provided for each city trunk. The finder portion Vof each link comprises ten group relays, two o f which are shown as 2538 (group 1) and 2li! (group 0) Vand ve unit relays V22E-263 each 0f which extends the conductors of two lines from `each of the ten groups of-jlines. Ihus, Vior example, Arelay 2 2@ operated in conjunction with any one of the Agroup relays extends the lines Vhaving unit designations of 1 and 6 suchas lines 11,16, 01 land 06. Similarly the `relay 26D extends the conductors for the lines 5 and 0 suchas ' lines 15,10, 05 andUO. In order to connect only one of the two `lines .thus selected by the group and unit relays, there is provided a subgroup relay 21D which is Aenergized when thecalling line number ends in Vdigitslii to 0 inclusive and disconnects the .QQndllCtOl .QT 1111,35 ,1 .t9 5.- VFor SPHYFOSC ,0f as' spciating the Astated line and unity relays of the nder switch with the common equipment illustrated in Fig. 4, there are provided la pair of Vconnectrelays .280 and 290- l '1 Fig .3 trunk .circuit .illustrates tiierelav 01.1- irol equipment for a .local .extension stetige 0.0 @www connection .over V.eb-ilfulflk ,leading t0 ,a city exchange. More specifically, Stil is a series relay, .controllable over a loop circuit between the 10.0211 telephoe and City telepllgne exchange equipment. Relay '300 in conjunction With condenser S'll will provide a low impedance pathfor the .tiensmiesion Circuit and fer the operatn f the main exchange equipment. Relay 33| 0 is slow-to-release and Willremain in the'operated position if subsequent d ial p ulses 'should cause relay 3E3ll-to Iiutter. Relays 320, 33E), 340 are theV hold Vcontrol relays, and 356 is an A, C. relay responsive ,to the ringing current Vfrom vthe city exchange. Relay 35% is slow to operate vand will for each trunk having suihcient multiple appearances to be visible or audible at each local extension station, The signals for each trunk are distinguishable from the signalsV for the other trunks.

Fig, 4 allotter relays illustrate the equipment common to the links and comprise group relays, 10 auxiliary group relays, l0 unit relays and l slow-to-release trunk lockout relay. The first and last relays of each type are shown. The additional intervening relays,'consistlng of 8 additional tens group relays, 8 auxiliary group relays, 6 unit relays and the 8 additional sets of contacts on each of the group relays are not shown.

The tens group relays 400, 4I0and unit relays 420-460 are the common control relays for extending a marking corresponding to any of the calling lines, to corresponding relays in any of the links. Relays 400', 4I0 are the common control for making an operated calling station key effective only at the station of the particular line that is to be extended whereby a finder link, Fig. 2 or Fig. 5, depending on the service desired, can be connected to this allotter. The operated tens and units relays operate corresponding tens and units relays in the connected link to complete the connection. The unit relays 420-460 operated, when the calling station line numbers end in 6-0 also operate the subgroup relay 210 or 510.

The operating circuits for each group of tens and units relays are individually chained in a series circuit which prevents more than one tens relay and one units relay from operating at the same time, and which in conjunction with a continuaton of the stated chain through the trunk lockout relay 480 prevents establishing a local call when a trunk call is being connected. Y

Fig. 5, local iinder link, illustrates a group of line connecting relays having equipment similar to that described in Fig. 2 trunk link iinder except that it is used for local service and is associated with a local link connector, Fig. 7, of the all relay type.

Fig. 6, local finder distributor, illustrates a` group of link distributor relays which individually correspond to the local links and in conjunction with the slow-to-release reset relay 600, operate in a cyclic manner, marking idle local links and successively assigning the corresponding links to local calls. Relay 6|0 operates only when all trunks are busy or the call is blocked due to a restricted extension station attempting to make an outgoing call.

Fig. 7, local link connector, illustrates a partial group of relays that are dial controlled to extend a connection from one local station to another local station. pulses and controls relay '|20 which, being slow to release, holds during pulsing and is used as a master release control relay. Relay 130, for ring cut off, is responsive only to direct current closed when the call is answered, relay 'H40 for cut thru to an idle called line, relay '|50 forr busy test, and

is operated when the called line is busy. Relay- '|60 is operated during a series of dial pulses to prevent false operations on the busy test or cut thru during dialing. Relay 110 is one of the tens connecting relays. The units relays-the counting chain for selecting the tens, units relays are well known and are not shown in these drawings.

Having briefly described the purpose of the equipment shown on each ligure of the drawings, a detailed circuit description, of the illustrated system, will be given. For this purpose, the operation can vbe better understood if the description Relay |00 is responsive to dial Local connection Figures 1, 4, 5, 6, 7 y

For explanatory purposes, it Awill now be assumed that station A, line 11 is extending a, local connection to station B, line l0. The call is initiated by stationA lifting the .telephone handset from the support and then operating the local key. A line loop circuit is completed at contacts II4, between telephone set A and line conductors IIA and I IB, whereby relay I20'is energized as follows; from ground, relay contacts |3|, line conductor 11A, telephone instrument A, key contacts |I4, conductor IIB, contacts |32 and winding of relay |20 to battery. Relay |20 energizes and closes contacts I2I-I26 of which contacts |25 and |26 are the respective control points for energizing the associated allotter group relay 400 and unit relay 420. The primary energizing circuit for relay 400 is traceable las follows; from ground, contact |45, contacts |26, conductor |84, coil of relay 400, contacts 402, 48|, through a series of chain connected contacts that start at springs 404 and ends at 4|4,to resistance 49| and battery. Relay 400, in operating, will close a holding circuit through contacts 403 to battery at resistance 49| before the stated primary energizing circuit is opened at contacts 402 and 404. The primary energizing circuit is opened to all other group relaysl such as 4I0 at contacts 404 and 402, therefore an operating ground from other subsequently operated line relays will not be effective at this time.

Relay 400 energizes and closes contacts 405 to 406 of which contacts 406 complete a primary energizing circuit for relay 420 as follows; ground, contacts |44, contacts |25, conductor |82, contacts 406, coil of relay 420, contacts 425 and 482, through a series of chain connected contacts that starts at 423 and ends at contact 404', through the resistance 492 to battery. Relay 420 in operating closes a holding circuit at contact 424 to battery at resistance 402 before the stated primary circuit is opened at contacts 423 and 425. Any subsequent ground from other stations in the same group cannot operate other unit relays because battery thru the primary operating circuit is opened at contacts 423 and 425.

Before continuing with the circuit description for the operated relays 400 and 420 controlling the operation of the corresponding link relays 500 and 520, it will be necessary to briefly describe the circuit means for associating an idle link with the common allotter equipment. The local links are preselected by the well-known link relay distributor or allotter that operates in a cyclic manner and will be herein briey described. Each local connector link (Fig. 7) has an associated nder distributor relay in Fig. 6 such as B20, 630, or |540. A primary energizing circuit from a common operating ground at contacts 60| is closed when relay E00 is energized through a closed chain 4of series connected contacts starting at ground at contacts 643 and ending at contacts 623. Ground at 60| will energize all dirtributor relays 620-540 that are'associatedwith an idle link. For example, the circuit for 'energizing relay 620 is traceable as follows; ground contacts 60|, contacts B25, contacts "|22, coil of relay 620 to battery. Relay 620 operates and gift! 61513.!

and r58,63 in multiple to battery. ofthe other iinder distributor relaysf-fl operate in a like Vmanner Vand prepare acircuit .that Will extend the individual link start conductor such4 as 655 .to the common Start conductor ses througnback j oontactsof the preceding deenergizedfnderdistributor relay. Relay 52@ deenergizedwhenlthe link is connected to the cal-lingline and thecom- .mon .start conducto-r .435 is extended through .the distributor relays siii) and 53e When,de ener lgizedfurther extends the common start control conductor G55 vto thesucceeding preenergized relay. Whenthe last preenergized relay is deen- -ergized the chain ground at contacts 5573 Aisagain extended thru contacts .533, E23 to relay 5577 and :thecycle is repeated. The operation whichvtakes place When all links are `busy and the distributor relays ycannot reoperate will be fully described Vunder a separate heading Call blocked signal.

Reverting to the .previous description wherein relays fill@ and 42e were operated in response to .the .operation of line relay IE5. Relay dell is .operted responsive to closure of contacts /yland this relay atcontacts .i758 ycompletes an energizing circuit for relays 755B and :5.9.5 that is traceable as follows; contacts 422,ei8, conductor 755, contacts 743, localkey contacts I i3, relay-con .tacts I2 I, local common start conductor i3 I, relay contacts 426, conductorli, contacts 22', con- Iductor 680 through coils of relays 539 and 58@ to battery. Contacts 5SH and 592 are closed responsive to relay 599 being energized and serveV the following purposes; contacts 592 close a multiple circuitover conductors 785, 787 to contacts 722 for holding'relay .E25 energized until the ,common equipment is released, as will be described vin a subsequent paragraph, and contacts 59| energize ,relay 750 through resistance 595 conductorsrli .and 784. Relay 755 operates and contacts 7M close an operating ground to relay 725. Relay 720 operates to controllthe individual 'linknolding relays` as follows; .contacts 72d prepare a ground circuit over conductor 75s for holdingthe ylink group and unit relays energized after a call is established, contacts 725 prepare a holdingcircuit for the subsequently operated connector .link

relays, such as 730, 7GB, 755, `775, etc., ycontacts 72I prepare a ground circuit over conductor 1755 for guarding the calling line, and contacts :.723 prepare a circuit to the dialcontrolled relays einbodied in the connector.

Relay 580 is operated in multiple With relay 590 and contacts 58 7 585 close circuits from the .common equipment conductors 38%, Mil to the tens group relays 5mi-5I@ and vfrom conductors.

the following circuit condition: conductor 'IIA contacts 5m, V52I, 57I, conductor 78I `lower coil of relay 708 to ground; conductor IIB contacts 5G72, 522, 573 conductor 784 upper coil Yof relay 79M@ battery; and .Coudurier I I C C Qntats der. .Y 5.2.3,f575-9911ductor 713.5 top ground at ClQSed contarts 12J,- ARelay 13.0 is-energized .by .way @if [email protected]. .72| @endurer 18.5, Contacts 23,115,03, andilconductor I I VCA. Relay 137)' at ts 731' and I ,2 .opens the `-circuit Vof, v.line I20 which deenergizes and opens contacts Ill relay .-72.17I2i5.. VContactslZI disconnectvgroundfrom .the 109111111011. ,Start .Qbnducwm .1.81. 485,681?. re.- flesing relays an and .5.9.0- .rhe 'holding @fait el'ay 62.5 is opened at contacts A5&2', nand in w njunction vvithtlre'ppen .contacts 722 relay ,izsfldeener'gized ltransf,erring the cornincn start .00; #91 yto .the next preselected link throughicqr: tact 62| y a ,r'ni63 ;2.' Relays .zland 420 are de- .energized When-their- Circiiits .arebrened at .Cn- .tacts L25 and |25 and restore all Icommon allotter .gritacs tfthlnormal position. ,The series @haie circuits batwee'narou .relays and the unitrelays reestahlishednd the'dmmw equipment Fig: .ailable 1for,extending the next call. Relays ed '52.0 remain eneieirefl .from `s201111@ .on conductor .7 8`8fromlcontacts.7?4,

Bday' 7 nitilli'herlereieed Qvergniats `59| 1S nov/hel .srftbelcallinesabsriberloaiheffore .when Clay .53.5 deenergizes'@miv contacts 59| open, vrelay .7.97.7 does not Vrelease asitiscontrollablepver/ t-lie .subscriber-line loop. rIhe operation .of an all relay -link connector in response to .dial raises Vis-.W f .11flgwr'rilarlgdthis. colnnect'r" link in Fig. v7, .in responsetothe receipt'of 'the vdialled .digits 1 and 0l dell energie@ relay 1710 .together witn the unit relaysmmotshown) to .connect with lin 10. L.Line 10 isnoW connected-through closed ` contacts 577,5', 75M, 775 to 'theY control .circuits for s ifaalling lire ',19 andxieriding th Qallad'lieeg drigrs fl .e aed 'UB to relay-710 and rendersene it?, 1.9.3 there 1213,@ voice ,cur-rem giilcontacts `76.3, closed contactson the operated 1111. trelarsand Contacts-:7.75am conductor liC.

If V the callediliriefis busy. the ground .circuit that holds the cut-off relay ISU energized, ,as ,previcusly described. iSXtended over cohdutor .lC to energize relay 7550- Relay 7510' operates and lccksfthrouehccmtacts 753,754 to ground at7255 v,aiterrelayi SYD returns to thenormal position and before contacts-753 are opened. A linesbusy tone signal is returned to the calling line by wayof coi-itactsI .and the circuitto relay 770 is opened at contacts -752 preventing connection with the called line if the line ybecomesfree before the l calling ,party disconnects. Y-llssurnethe line is free, the 4.terminal `IlC lwill' have a battery petentialextending from relay Ig'ftherefore lrelay 7550 is lnot operated and-after relay 750 releases, battery on It@ is extended .through contacts .775,y contacts on the operated units relays, contacts 752, y"E52, lower Winding of relay vlglltoground at. contacts 725. and ,fl Sil operate in series.

.andatcontactsd13I and Ai332 disconnects ground Relays 740 Relay i387 operates fromconductor I QA and battery through Acoil of lifting the telephone handset and operating the local key which completes a. circuit through the telephone instrument and local key contacts |04 which will close the loop from ground at the ringing supply source to battery atrelay 130.

Relay 130 operates and at contacts 135 completes a locking circuit through its upper winding before the ringing circuit is opened at contacts 133 and 13|. The line conductors |0A and |0B are further extended at contacts 132 and 134 to the talking condensers 192 and 193 and to the talking conductors 18|, 184, ||A and ||B and a voice current transmissioncircuit is completed between telephones A and B. v

The release of the established local connection `is controllable from relay 120, which is responsive to the calling subscriber controlled relay 100. When the handset at the calling station is restored to the cradle of the telephone instrument, the switchhook springs open the line loop in a well-known manner. and contacts 102 are opened, deenergizing relay 120 which opens contacts 12|, 124, and 125 and closes contacts 122. Contacts 125 open the holding ground to the connector relays 130, 140, etc., f.

and the operated connector relaysrelease. Contact 12| opens the holding ground to relay |30, and contact l|24 opens the holding circuit to relays 500 and 520, which, after deenergizingdisconnect the link from the line.

All trunk busy dall blocked signal In the preceding description, that related to the 'preselection of the local links, the operation of thender distributor relays Fig. 6 was described when idle links were available for reassignment. Briefly stated relays 'B20-B40 energized and allocated the links for successivejlocal calls. Each energized relay is deenergized when the associated link is seized. After all the stated relays are norman, a chain connected groundis closed to relay E08 and contacts 50| are closed.

Assume now that all links are busy and station A attempts to initiate a local call. The relays 620-540 cannot reenergize when contacts50| are closed because contacts 122 and correspondingV Acontacts in the other busy links are opened. The local common start conductor 485 is extended to relay 6|0 through contacts 62 I, 83|, 64|, etc. The operation of the equipment with station A ini- Relay 100 is deenergized tiating a call, has been previously describedv whereby key contacts ||3, |4 are closed, line relay |20 is energized and group relay 400, 400' and unit relay 420, together with contacts 408, 422 and 426, are operated. Ground 'at contacts. 422 is extended through contacts 408 to conductor and lower winding of relay |40`t conductor'l v to the open contacts 5| Ground on conductor |185 also energizes relay 6 0 as follows; ground on conductor |85, through contacts |43, key contacts |3,

relay contacts 2|, conductor 8|, contacts 426,'

conductor 485, contacts 52|, 63|, 64| to coil of relay `6|!) and battery. Relay 510 is energizedand battery'through resistance 650 and' closed. contacts 8| is extended to conductor lenergizingjl relay |40. i Relay |40 energizes and locks at contacts |42` toI ground at contacts |23. An audible tone signal is connected at contacts |4| to conductor IIB, and contacts |43, |44 and |45 are opened. Contacts |43 open the energizing circuit of relay 6|0 which deenergizes to disconnect battery from conductor 58|. |45 openthe circuits of relays 400 and 420 which now deenergize. The circuit for relay 400 is opened at contacts 401. All allotter relays Fig. 4 are now'inthe normal position, conductor |85 is open at contacts 408 and 422, and the common equipment is vnow available for a call from another station. Relay 40 remains locked to ground at contacts |23 until the line loop is opened and relay |20 is deenergized by station A restoring the handset or by restoring the local key. It is obvious that station A cannot initiate a new call unless relay |20 is rst deenergized to deenergize relay |40.

Outgoing trunk dall `For explanatory purposes we Will assume station A (line 11) will initiate a trunk call and that trunk #l is available for a call.

The handset at station A is lifted from vthe cradle and trunk key #l is operated, closing contacts ||5 and IIS. A loop is completedlbetween conductors ||A and ||B through key contacts H5 and telephone instrument, over which elay |20 is energized from ground at contacts |3| throughcontacts |32 to battery at relay |20, closing contacts |2|-|25. The operating circuits for Fig. 4 relays 400, 408 and 420 controllable from contacts |25 and |26 were fully described hereinbefore, and in a like manner contacts |28 operated extend a ground for energizing -400 from ground, contacts |45 and |26, conductor |84, coil of relay 400, contact 402, 48|, 404-4|4, and resistance 49| to battery. Relay 400 operates and locks at contacts 403. Relay 400' is energized at contacts 401. Relay 400 operates contacts 408 and an energizing circuit to relay 420 is closed from ground, contacts |44 and |25, conductor |82,.contact 406, coil of relay 420, contacts 425, 482, 423-464, and resistance l482 to battery. Relay 420 operates and extends a ground from contacts 422 to the trunk start conductor |A over which relays 280 and 290 are energized as' follows: ground, contacts 422, 408, conductor |85,'contacts |43, trunk key contacts H5, relay contacts |22, conductor IQUA, contacts 3|6, conductor 381, windings of relays 280 and 290 to battery. Group relays 208-2I0 and unit relays 220-260 operate in a like manner to corresponding relays in Fig. 5 as hereinbefore described. Brieiiy described relay 280 prepares operating circuits for the tens and units relays of which only relays 200 and 220 are energized. The operating circuit for relay 200 is from ground, contacts 40|, closed when 400 is operated, conductor 480, contacts 285 and relay 200 to battery. The operating circuit for 220 is traceable as follows: ground, contact 42|, con- Zduct'or. 482, contacts 283V and coil of` relay 220 to battery. 'Relay 200' operated, in' conjunction with relay- 22,0 operated,-'an'd.relay 210 normal, 4extends line conductors HA, IIB, ||C, ||D to conductors 38|, 382, 383,. andY 384, through oper- 'ated contacts ,20L-204, 22|-224, and closed contacts 21|.,.213', 215 andl 211 respectively. Relay 280 operates in ,multiple with relay 280 and contact`s` .292 close a circuiti for holding relays 200 .a'd".`2`20 energized thio'lgh operatedvv contacts S209 v and 229.','Contactsj2831close,and extend a Contacts |44 and no tn rcu'gii ecn-tects '2.15, 2' 's grcund dier' cen-ducten fuerte energien-'ie sien primary energizing-circuits yfor"gfd'ull relays MIU- die and unit relays 42e-4160'. 'v ceiitetctsw 29,5 eirtend a ground circuit over the line n conductor and 203,- t vrelay ist; Relay" |30 is energized 'td creenA cidritacts is r l and' |32'. At the open ce tactsj ist 'sind itz` f y ground and battery are renfved'- froth' tli'e" talkie' fueI conductors' HA end HB and relay mj is' deenergizedi and titel, centrer circuits' t'cj relays;

tno; 420, 28o' und' 29er are ctsscntdY et contacts restore the ecininen edu-inherit td the; ndrnieti condition eiicept that' relay 48e beine slew' te release' andccntrenebije frcrii new te' release relay 29u" vtm/remain in thev cpferated' pcs'iticn: fera fraction fV a1 Second, v'vli-iuliA WilIP'ri/'ent establisling" new calls' until all 'eviously' operated common relays have had sufcien't time to restore to a nornal Yposition'.- Before relay 23|! is t restored to the normal position, aftercontacts |122" are dpn'ed, relay s'i-'cj'is' enereidjas wiii'he described' hereinafter and al grind is closed from t contacts 3 |2 to c6nduti'V 383 and front 66ntats" 3M tooonductor', res'peetively, in rnultitle Witnjctaets" 295 and 292'. Relay am' is t energized the rfollowing r'nanner. When the Gdutfs" for' line 11 Wie e'Xteiided' t yCorlducters 38| and ,382, trie suhs'cribersiecp-circuit was extended tc the trunk circuitjleedihg through the coil 0f relay 353|), co1'1tact`s`332` and contacts i 334, to"r the city eichange line conductors 38`|A and'y B. Battery and ground i's su'pilied to colitHeF Citye'eh'ttng'e equipment) which in conjunction causes relay 330 to energize', closing con'- ta'cts 30|v and energizing 3I`G'. Relay 3 Hll 0515er# ates contacts 3M, 3|'2', and 3H'. Ground at conrelays 20e, 220 energized. ,Grcund' at contacts 3|? is extended to' conductor 383, contacts 215y `22's, 20's te heid' reIay ist dperated. Contacts sir operi the operating" circuit idr A. c; relay 35e `tcl iin'rve transmission and to lrevent' false hi'n ln' Signals; Relay 3|0` transfers the start ccnducter man to csnductdr site' at' ccnt'acts' 3"!5 leading` to the busyrelayv BID through contacts; 294 Aandconductor 682. The control f This lille'CirCllli',l tOgether with relay strurnent at the calling station. `The methodV of operation foi" extending' a call Within ay telephone ejicliange'i's Well known and is not included in this; description. It is 'Luldelsto'odv that the belt'- tje'ry az'r'dv ground supply to the' line i'sinaintaine'd froin' theA connecting' exchange and relay .330 jr'fe'ni'ainsin' the' energized D'sition. As previously described; relay'S' E?"controlled"r By relay 35D is also operated, holding the'v connection at the" local eX- ,cnange' by maintaining the neidgr'cund tcA the energizedV connect relays4V 200; 22u and une cut cfr 12 relay |30, andi as will' bef' `clescriled in a sub'see quent paragraph, relay 3m prevents other' lines fr'rn sei'zing'the busy trunk. I

The' connection is released when the line is pened by the callingA party disconnectingin the Well known marmer.A Relay 3BG' deenergizes. and the operatedl localexchange trunk is restcied to nerinal by relay 3|B discnnectng gro-und from conductors ses endless which releases relays 26D, 22e' and |3i. The connecting exchange is released when the above mentionedl line is' opened in the usual manner in response to a disconnect by'a calling'subscriber.

In a like manner,A a subsequent' trunkv start ground can be extended to "conduct/c1* were by other" s't'ations'ymaking a call on trunk #L but since the trunk is busy', contacts" |55` are; closed as previously' described, and the busy relay El@ is energized from ground` on conductor |9QA through closed contacts 3|5 conductor 339; conf tacts 294, cdndl'icter 652; Windingr of relay 6,5% to' battery. The operation of relay 6 -W'as fully described hereihheicre under tine headingAil trunk pusy blocked call signal. Relay' 6m' ex'- tends battery' thrdugh'A resistance tta, contacts 85| to the einrnor sidev relays 8e3, Mil etc., ci which, the pusyjrelay im* associated with the calling', line d10'crates` from the cdnirnon start eroundonjconductqr' |85. Relay |49 locks' itself et' cente'cts M2 and @pens the centrer ground at contactsjli; yMadrid uM3 extending the group rjeiey een, unit relay 42e and busy relayv` t'i. ite'- la'yYs/vd, '23 and Si@ vvdeener'g'izel and' restore the @emmen edu'ipm'enttc hvdrmei cehditien. 'The line lockoutjlljusy leklayuil) reinainsjin the enersized c'uditiqn until the dssgci'atedjiine relay igurcdntrciiahte freni the ceiiingfs'tntidn, is deenergized- It is obvious that e' restrictedstation such es BH] cannot originate an outgoing trunk call as the trunk key isconnected to' conductor i-SUB instead of IQQA. Conductor |933 (Fig. 3) is only Y ccnnecteu tc conductor! 381 and reiayslzec and zeiten inccming caus. c"endutitcrv i'scB is horhigtuy cennected thru contacts 36a, ses' to relay iai-c. Ir station 1.3' attempts to initiate an cutgoing' trunk call the' operation ofthe linel relays and umrhon equipment issirhuer' t'st'eticn Asi encept relays |25" and' tee are operated instead of relays |20" and 523 hthe start ground is connected to c'cnduct'cr' 90B et key contactsict and relay contacts" |22",Y yRelay 6|!3`1s Operated over the, above mentionedr circuit and extends battery' to relay |45. Relay M9 is operated in a like manner to relay Me; releases the common equipment and connects a tone signal to the calling party.

' Aiswerz'ngc trunk call fWhe'r' a subscriber' in the city exchange desires tov extend a call to' a subscrbers line in tl'leyprivate exchange, twenty cycle generator together with battery and ground is connected to the selected trunk` line. Assuming that the trunk line shown in' Fig. 3 is the trunk line taken into Yuse then relay 353 is energized in response to thev application of-f alternatingourrent to trunk line conductors 38|`A and 38`|Bby` wayvv of condenser 352 and contacts 3| Relay' 353' at contacts 35| completes the circuit for energizing relay 360. `Relay 366i operates andv locks through contacts" 352 to ground at contacts 3 3 and transfers" cenductcr" iseBf, leading' to restricted subsoribier'stati'o'ns, such" as BI f, from contacts 364 t6 Contacts' 353, C'Oidut0I'Y 33T t0 relaysy 2580,'21116,

rently. When line l() described hereinbeiore. Contacts j|25,a nd

299. Contacts 36| closeV aground circuit to the' visual and audible signals that are individual to each trunk but have a plurality of appearances at the local exchange. Any 'station may answer the trunk call. If the answering station is in the non-restricted group such as station A (line 11) the answering station is extended in an identical manner as previously describedfor station A making an outgoing call. In practice it is cus:- tomary to instruct a clerical station to answer trunk calls.

Restricted stations and call transfer For explanatory purposes we will briefly describe a restricted station B (line 10) as answering the trunk call, transferring it to the-hold condition, releasing the trunk link, extending a local call to A (line l1) and then have station A pick up the call on the held trunk. Station B answers the trunk call by lifting the handset and operating the associated trunk key which closes an operating loop circuit to relay |20'r from ground, contacts |3|, conductor |8A, subset A, trunk #l key contacts |88 and conductor IBB, contacts |32 coil of relay tended in a like manner to that previously de scribed for station A making an outgoing call except that relay 485 is responsive to ground at contacts |44' and |25', conductor |83, contacts 335 coil'of relay 460', chain contact-s to battery through resistance 492. A common start ground is closed at contacts 483 and 408', conductor |86, contact |43' to trunk #l key contacts |85, contacts |22', conductor |98B. Conductor |98B is further extended by the incoming signal relay 388, contacts 363, tol conductor 381 and relays 288 and 293 to battery. Relays 28D and 298 operate and extend the control circuits vfrom the common group and unit relays equipment to the link group and unit relays as previously described. Group and extends the associated line conductors to the unit relays. Unit relay 280 is responsive to ground at contacts 45| and further extends lines l0 and 16. Sub-group relay 218 is responsive to -ground at contacts 462' and contacts 21|, 213, 215,

main operated from a multiple holding ground at and 3M as will be explained 'preswas extended to the trunk, a local subscriber controlled loop was extended to conductors 38| and 382 and the city exchange. The city exchange equipment responsive to a closed subscriber loop disconnects the ringing signal dnd a transmission circuit with direct current supply is completed, wherein relay 383 is energized. Relay 380 energizes relay 3|!! and the contacts 3 I2 previously explained holding grounds at contacts 3|?. and 3|4 are extended to conductors 383 and 338. Contacts 3|3 open and deenergize relay 358 which opens the incoming signal circuit at contacts- 33| and transfers conductor |9913 back to contacts 364 leading to the busy relay BIO. It is obvious, that any other station attempting to seize a busy trunk will operate the busy relay 6|0 as '|25' |20 to battery. The line 10 is exrelay 280 is responsive to ground at contacts 39| 14T are opened" after relay |20' deenergized and the common allotter equipment relays 400, 469' and 400' are deenergized.` It is obvious that the common equipment operating grounds are open and the common equipment is now ready for another call. Transferring a trunk call Continuing the preceding explanation wherein station B has answered a city exchange call. We will assume that the station Wanted is A (line 1l) Station B first places a -hold condition on the trunk by operating the station key |92 and relay 328 is energized from ground, key contacts |92, conductor |3D, contacts 208, 264, 218, conductor 384 coil of relay 320 to battery. Relay 328 operates. and locks through contacts 322 to ground at contact-s 3M. The station hold key, when operated, mechanically released the trunk key and the local station line loop is opened at contacts |88. The city exchange is held in the answered condition from a bridge circuit at closed contacts 32| and relay 389 is deenergized. Relay 380 deenergizes, opening contacts 39|, and relay 3|!) is deenergized after a slight delay due to its slow` release characteristics. The holding ground for the nder link is opened at contact-s 3|3 and the link relay equipment is released, and holding ground is removed at contacts 3|2 to release relay |33. Contacts 324 of relay 320 prepare an energizing circuit for relay 330 which is completed when relay 3 i i) deenergizes, from ground. contacts BH3 and 324, conductor 386, closed contacts 29|, conductor 385 to battery through the coil of relay 333. Relay 343 is now bridged across the exchange line at contacts 33| and 333 before the line is further opened at contacts 332 and 334. Relay 333 energizes responsive to direct current from the city exchange, opening contacts 34| and com,- pleting a holding circuit for relay 33D from grounded contacts 3|3, contacts 342 and 336, conductor 383, contacts 29| and conductor 385. Relay 328 deenergizes when its locking circuit is opened at contacts 34|. Relay 330 at contacts 335 lights the hold lamp HL and at contacts 331 connects conductor iSiiB to conductor 381 by way of contacts 333 to enable a restricted subscriber vto answer and connect with this held trunk line.

The local -station B, desiring to have station A pick up the trunk call, operates the local station key. Station B extends a local call to station A in a like manner to that described hereinbefore under the heading "Local call. The deviations due to station B establishing a local call instead of A are obvious. Station A is requestedto pick up the call in trunk #l and station B disconnects releasing the local call. Station A picks up the held trunk by operating trunk key #l which releases the local key operated when the local call was answered and completes a circuit over which relays |23 and |38 are energized. Line ||.is extended to trunk #l in an identical manner to that described under the heading Outgoing trunk call. Relay 238 is operated as previously described and at contacts 29| opens the circuit of ,198B to conductor 389 to prepare .the circuit to relay 6 0. It is obvious that relays 308' and 3 0 are reenergized. Contacts 3|2 and 3|4 are closed to -extend ground over conductors 383 and 388 to hold -operated link relays and relay |30 until station A disconnects'o-r the' call is' again transferredto ana other station.

Itis obvions'th'at'thetrunk link equipment can beadap'ted to any convention'alv all relaylocal'ex-V 'change' by means of adding contactsl to existing line, line relay and allotter equipment and provid-r ing the station-key'equi'pment for such trunk lines. Further the number of trunks provided is controllable by the' key equipment and contacts' on the line' relays', therefore the number of linksv can be increased or decreased from the number of trunks` indicatedV by thev illustrations' andV herein described.

What' is thought te' be'new and novel and is de-v sired to have protected bry'Letters Patent will be pointed out in the appended claims.

What is claimed is: A

I. a telephone system, a plurality of lines', sbscribers VVstation on each line, a plurality of relay type linende'rs having common access to said lines for extending connections therefrom, a plurality of keys at each station,` n'leansl responsive to the operation ofr one of said keys atY a calling stationfor causing any onev of a plurality of said relay' type linenders to loev connected to the line of said calling sta-tion and means responsive to the operation of aother'of said keys for causing only a particular one of said relay type linenders to be connected' to the lineV of the calling station; Y 1 y .2..InY a telephone system,V an exchange, subsciiber lines therein, a preselected relay type local link linelnder for' extending local connections from said lines, a relai`7 type trunk link linefinder for extending' connections from said lines to another exchange, a control equipment common to i said-local and trunk link lineiinders controlled over any one of said' lines to directively operate either' olf said lineiinders to connect with said one line. Y y Y 3'. In' a telephone system, an exchange, subscribers local stations therein, a preselected relay type local link and lineinder circuit for extending connections fromv al local station to another local station. a relay type trunk'link and iinen'nder circuit for' extending'connections from said local stations to another exchange, a plurality of keys at each station including a local select key and a triirik select key, a' control circuit commo-n to said link circuits and responsive to the operation of any oneof said keys, means in said common control circuit for causing either the local or the trunklink and linennder circuit to be connected to the call-` in accordance with the key operated ingV station thereat'.

4; In 4a telephone system, an exchange, a pluy ralityof stations therein including a communica- Y tion path for each station, a, plurality of trunks terminating in diiierent tran-lcvr areas and having means for establishing' a connection to each oi said communicating paths, a control path for each traiiic area common to all of said communication paths, keys atVv each station for each control path,

a settingcircuit on each communication path rel sponsive to the operation of any of rthe station keys at a calling stationwto extend said control paths thereto, means controlled by said setting .circuit responsive to theY operation of a particular key to'make oneof the control paths eiective' to cause atrunk to a particulartrailic area to be c'onnected to the communication path of the calling i station,.and means responsiveto saidl connection for controlling said' setting circuit t'o disconnect said` control paths from the calling station there- 16 by permitting other stations to establishconnestions toother trunks.

V5. In atelephone system, subscribers lines, a plurality of locall links each including local con--A necting means for completing localconnections between subscriber-s lines, trunk lines, a plurality of trunk links each including trunk connecting means for completing rconnections between said subscribers lines and' saidtrunk lines, a local-key individual tov each subscribers line, a tru-nk key for each trunk line at each subscribers line, an allotter common to both said local and trunk links, means for operating said allotter to control the operation of thelocal connecting means in an idle one ,of said local links 'to complete the connection between the calling line and said .one link in re'- sponse to the initiation of a call by one of said subscribers lines andthe actuation of the individual local kei and' said last means being eiTective to operate said allotter to control thev operation of the trunk connecting means in the trunk link corresponding to the actuated trunk key to complete the connection between the calling line and the `corresponding trunk line in response to the initiation ofy a call by one of said subscribers lines and the actuation of a trunk key.

6. In a telephone system, a local exchange including a two-way trunk to another exchange for extending connections thereto, subscriber lines in said local exchange, a' portion of Said said last mentioned means normally ineiect'ive' to complete outgoing trunkcalls from restricted lines and effective responsive to incoming calls for completing incoming trunk calls to restricted lines.

7. In a telephone system, a plurality of subscriber lines, a line circuit ind'ividualto each line including a relayY operated in response to the initiation of a call thereover, a plurality of trunks having access to each line, a setting means common to said trunks operated in response to said operated relay to cause a predetermined one of said trunks to be connected 'to the calling line, a first and second means insaid line circuit to release said operated setting means, said' rst means responsive to said connection and said second means effective if said predetermined trunk is busy.

8. In a telephone system, a distant exchange, a local exchange', a two-way trunk connecting said exchanges, non-restricted and restricted subscriber lines at said local exchange, a rst control :path common tov said restricted subscriber lines, a second control path'V common to said nonrestric'ted subscriber lines, a subscriber key controlle'd means associated With each of said lines to provide each rsubscriber with an individual control of one of said paths, and means common to' saldi subscriber lines controlled oversaid subscriber controlled paths for permitting connection of said tru-nk'l to non-restricted lines for both incoming and outgoing trunk calls and for permitting connection of said trunk' to said restricted subscriber lines vronly on incoming trunk calls.`

17 scriber lines therein, a line circuit individual to each line, a trunk accessible to said lines, a common control equipment `for controlling the connection of said trunk rto saidlines, means in said line circuit responsive to Vthe initiation of a call for operating said common control equipment to control the establishment of a connection from said trunk in an idle condition to the calling line, means responsive to the establishment of said connection to release said rst means, a relay in said line circuit, means effective on a call to a trunk in a busy condition to operate said relay, said relay operated to release said common control equipment, and means in said line circuit to hold said relay operated under control of the calling line to permit other lines to use said common control equipment.

10. A system as set forth in claim 9 including a source of audible signalling current, and means responsive to the operation of said relay for connecting said source to said calling line to audibly signal the calling subscriber.

11. In a telephone system, a plurality of subscribers lines; a line circuit for each subscriber's line including a line relay, a cut-off relay and a busy relay; a plurality of links having access y to said lines, means responsive to a calling line initiating a call for operating the line relay in the calling subscribers line circuit, a setting means common to said subscribers lines and said links responsive to the operation of said line relay for seizing one of said links in case said one link is idle or for causing the operation of the busy relay in the line circuit of said calling line in case said one link is busy, means in said f.

seized link operated by said setting means for extending a connection to said calling line, means for operating the cut-off relay of said calling line in response to said connection, means responsive to the operation of said cut-off relay for releasing said line relay to in turn release said setting means for common use, and means operative in case said busy relay is operated for releasing said setting means for common use.

12. In a telephone exchange, a plurality of subscriber stations, a trunk line terminating in an all relay trunk iinder, tens and units relays in said iinder common to all said subscriber stations, and subscriber controlled means for selectively operating said tens and units relays to connect said trunk line to said subscribers stations in response to said stations originating outgoing trunk calls to said trunk line and-in response to said stations answering trunk calls incoming over said trunk line.

13. In a telephone exchange, a plurality of subscribers stations, a plurality of all relay lccal finders for extending local calls from said stations, a plurality of all relay trunk finders for completing trunk calls from and to said stations, tens and units relays in each of said local and trunk iinders common to all of said subscribers stations, subscriber controlled means for selectively operating said tens and units relays in said local finders to connect such local finders with said subscribers stations in response to said stations originating outgoing local calls, and subscriber controlled means for selecting any one of said trunk nders and for selectively operating the tens and units relays in the selected trunk finder to connect such trunk finder with said subscribers stations in response to said stations originating outgoing trunk calls over such trunk nders and in response to said stations answering trunk calls incoming over such trunk nders.

14. In a telephone exchange, a plurality of suba scriber stations, a pluralityl of all relay trunk nders for completing trunk'calls from and to said stations, tens and units relays in said trunk finders common to all said stations, and subscriber controlled means for selecting any one of said trunk nders and for selectively operating the tens and units relays in the selected trunk nder to connect such trunk nder with said subscribers stations in response to said subscriber stations originating outgoing trunk ycalls over such trunk finders and in response to said subscriber stations answering trunk calls incoming over such trunk finders.

15. In an all relay exchange, groups of subscribers lines, each different group having a different tens designation and each line in any one group having the same tens designation, each line in any one group having a different unit designation and corresponding lines in different groups having the same units designation, an all relay trunk nder having access to saidA lines, tens and units relays in said nder corresponding to said tens and units designations, and means responsive to a subscriber on one of said 'lines initiating an outgoing trunk call over said finder or responsive to said one subscriber answering an incoming trunk call incoming over said nder for operating the tens relay corresponding to the group containing said one subscribers line and for operating the units relay corresponding to the units designation of' said one subscribers line to complete a connection between said onesubscribers line and said trunk finder.

16. In an all relay exchange, groups of subscribers lines each having a group and a units designation, an all relay trunk finder having access to said subscribers lines, group and units relays in s aid finder corresponding to `said group and junit designations, and means including individual subscriber controlled means for operating the group relay corresponding to the group containing such subscribers line and for operating the units relay corresponding to the unit designation of such subscribers line to complete a connection between such subscribers line and said trunk yfinder in case such subscriber either originates an outgoing trunk call to said nder or answers an incoming trunk call on said iinder.

17. In a telephone system, aplurality of subscribers lines, a busy relay individual to each line, local links for extending calling lines in local connections, trunk links for extending calling lines in trunk connections to different traiiic areas, a relay common to said lines and links for controlling the operation of said individual busy relays during the initiation of local and trunk calls, means for operating said common relay in response to the initiation of a local call in the event all said local links are busy, means for operating said common relay in response to the initiation of a trunk call in the event the desired trunk link is busy, means for operating the busy relay individual to the 'calling line in response to the operation of said common relay, and means responsive to the operation of said busy relay for transmitting a busy tone over the calling line.

18. InV a telephone system, a plurality of subscribers lines, a busy relay individual to each line, local links for extending calling lines in local connections, trunk links for extending calling lines in trunk connections to different traffic areas, means for operating the busy relay individual to the calling line in response to the initiation'of a local call in the event all said local links are" busy, means for 'andrei i9 Y operating the' busy relay individual Vto a line in the event a` subscriber attempts to connect such line to a busy trunk link, and means responsive to the operation of said busy relay Afor transmittingk a busy tone over the corresponding subscribers line.V`

V19. In a telephone system, a plurality of subscribers lines, a busy relay individual to each line, local links for extendingcalling lines in local connections, trunk links for extending calling ,linesy in trunk connections to diierent tranic areas, means for operating the busy relay individual to the calling line in'resp'onse to the initiation of a local call in the event all said local links are busy,y means for operating the busy relay individual to a subscribers' line in the event a subscriber attempts to connect such line to a busy trunk link, certain of said subscribers lines being restricted from initiating trunk calls over said trunk links, means vfor operating the busy relay individual to a restricted subscribers line in the event such restricted subscriber attempts a trunk call, and means responsive to the operation of said busy relay for transmitting a busy tone over the corresponding subscribers line.

20v. In a telephone system, subscribers lines, local links for use inlocal connections, trunk links for use in trunk connections, an allotter common to said lines and links, local and trunk keys at each subscribers line, means responsive to a subscriber on one of said lines operating one of said keys and removing his receiver for transmitting line designation markings corresponding lto said one line to said allotter, means Vin said allotter responsive to the receipt of said line designation markings for retransmitting corresponding line markings to said links and for extending a local link marking or a trunk link marking dependent upon the key actuated during said call, and means vresponsive to the extension of said link marking for operating a corresponding one of said links in accordance with said retransmitted line markings to completeaconnection between said corresponding one link and said oneline.; s

21. In a telephone system, a plurality of subscribers lines, a plurality of local for extending local callsfrorn said subscribers lines, a plurality of links for extending trunk calls from said subscribers lines, line connecting means in said local and trunk links for completing connections to said subscribers lines, an allotter lcommon to said local andr Ytrunk links, aplurality of numerical markingleads extending from` s aid lallotter to said local and vtrunk links, link seizing means in said local and trunk links for connecting said numerical marking leads to said line connecting means, subscriber controlled means for extending calling line'marking designations and local link marking designations in case a calling one of said lines initiates a local vcall or for extending calling line marking designations and trunk link marking designations in case said calling line initiates a trunk call, and means in said allotter responsive to said line marking designations for operating said link seizing means of a local link or atrunk link dependent upon said'link marking designations and for energizing said numerical marking leads in accordance with said calling line designations to operate said line connecting means over said energized marking leads to extend said calling line toa local link or a trunk link. v V

22. In a telephone system, laplurality of vsubscribers lines, a plurality 'of local links having access to said lines `for completing local connections, a plurality ofy trunk lines extendingto dif ferent traffic areas, a trunk: link for each trunk line having access f to said subscribers lines, a distributor including means for assigning idle ones of' said local vlinks for use in completing local connections, a local key `and a line relay individual to each subscribers line, a Ytrunk key for each trunk line at each subscribers line, an allotter common to said local and trunk` links, means for operating the line relay individual to the calling y, line in response Vto tlie'calling sub-'- scriber initiating a local call by operating said local key or in response to the callingsubscriber initiating a trunk call by operating one of said trunk keys, and means in said allotter responsive to the cperationof said line relay for operating the assigned idle local link to complete a local connection Withsaid calling line in case said local key is operated or for operating the trunk link corresponding to the `operated trunk key to complete a trunk ccnnectionbetween the corresponding trunk line and said calling line in case one trunk key is operated. n Y

23. In a telephone system, a plurality of Subscribers lines, a plurality of local links having access to said lilies for completing local connections, a plurality of trunk lines extending to diierent traffic areas, a trunk link for each trunk line having access to said subscribers lines, a distributor including means for assigning idle ones of said local links for use in completing local connections, a local key and a line relay individual to each subscribers line, a trunk key for each trunk line at each subscribers line, an allotterl common to said local and trunk links, means for operating the line relay individual to the calling line in response to the calling subscriber initiating a local call by operating said local key or in response to the calling subscriber initiating a trunk call by operating one of Said trunk keys, means in said allotter responsive to the operating of said line relay for operating the assigned idle local link to complete a local connection with said calling line in case said local key is operated or for operating the trunk link corresponding to the operated trunk key to complete a trunk connection betvveen the corresponding trunk line and said calling line in case said one trunk key is operated, and a cut-ofi" relay individual toV saidv calling line operated in response to either said local or trunk connection for releasing said line relay whereby said allotter fmeans reverts to common use for extending other calls.

24. In a telephone system, a, plurality of subscribers lines, va plurality of local links having access to said lines for completing local connections, a Yplurality of trunk llines extending to different tralic areas, a trunk link for each trunk line having access "to said subscribers lines, `a distributor including means for assigning idle ones of said local links foruse in Vcompleting local connections, a local key 'and a lline relayindividual to each subscribers line, a trunk key for each trunk line at each subscribers line, an allotter common to saidv local and 4trunk links,

'means `for operating the line relay individual to 21 key is operated or for operating the trunk link corresponding to the operated trunk key to complete a trunk connection between the corresponding trunk line and said calling line in case said one trunk key is operated, a busy relay individual to each subscribers line, means for operating the busy relay individual-tothe calling line in rei sponse to the operation of said line relay in case all said local links are busy during the initiation of a local call by the calling subscriber and in case said corresponding trunk line is busy during the initiation of a trunk call to saidcorresponding trunk line by the calling subscriber, and means for transmitting a busy tone to said calling subscriber in response to the operation of said busy relay. i

25. In a telephone system, a plurality of subscribers lines, a plurality of local links having access to said lines for completing local connections, a plurality of'trunk lines extending to different traiiic areas, a trunk link for each trunk line having access to said subscribers lines, a distributor including means for assigning idle ones of said local links for use in completing local connections, a local key and a line relay lindividual to each subscribers line, a trunk key for each trunk line at each subscribers line, an allotter common to said local and trunk links, means for operating the line relay individual to the calling line in response to the calling subscriber initiating a local call by operating said local key or in response to the calling subscriber initiating a trunk call by operating one of said trunk keys, means in said allotter responsive to the operation of said -line relay for operating the assigned idle local link to complete a local connection with said calling line in case said local key is operated or for operatingl the trunk link corresponding to the operated trunk key to complete a trunk connection between the corresponding trunk line and said calling line in case said one trunk key is operated,-a busy relay individual to each subscribers line, means for operating the busy relay individual to the calling line in response to the operation of said line relay in case all said local linksrare busy during the initiation of a local call by the calling subscriber and in case said corresponding trunk line is busi` during the initiation oi a trunk call to said corresponding trunk line by the calling subscriber,

means for transmitting a busy tone to said calling subscriber in response to the operation of said busy relay, and means controlled by said busy relay for releasing said allotter for common use in extending other calls.

26. In a telephone system, a plurality of subscriber stations, a plurality of local links and trunk links for completing connections to any of said stations, a plurality of station marking leads common to all said links, a local link marking lead common to said stations and said local links,

a trunk link marking lead individual to eachl trunk link and common to said stations, station marking means at each station for selectively conditioning either said local link marking lead or a particular one of said trunk link marking leads, a relay individual to each station, means for operating one of said relays in response to the operation of said station marking means by a station initiating a call, means responsive to the operation of said relay for extending the said conditioned link marking lead in accordance with the selective operation of said station marking means and for extending station designation markings corresponding to said station, means responsive to the extension of said station designation markings for energizing corresponding ones of said common station marking leads and for energizing said conditioned link marking lead, connect means in the link corresponding to said conditioned link marking lead operated in response to said energization of said conditioned link marking lead, and connect relays in said corresponding link operated over said corresponding energized common station marking leads in'response to the operation of said connect means for connecting said corresponding link .to said station.

27. In a telephone system; a plurality of subscriber stations, a plurality of local links and trunk links each having a plurality of connect relays for completing connections to any of saidv stations, a plurality of marking leads common to all said links, connect means in each link common to said stations for extending said common marking leads to said connect relays, stationA marking means at each station for marking a local link or a particular trunk link for extending a call thereto, a relay individual to each station for extending said local link and said trunk link markings and for extending corresponding station designation markings, means for operating one of said individual station relays in response vto the operation of said station marking means by a calling station initiating a call to extend the link marking corresponding to the operated station marking means and lto extend said station designation markings, and means responsive to the operation of said one relay for energizing the said extended link marking and for energizing certain of said common marking leads corresponding to said extended station designation markings whereby the connect means in the corresponding link is operated over said energized link marking to thereby operate certain of said connect relays over said corresponding certain energized common marking leads to complete the connection between the corresponding link and said calling station.

28. In a telephone system, a plurality subscribers lines, a local key individual to each` line for use in extending local connections, a"

plurality of trunk keys individual to each line for use in extending trunk connections to distantv one of said keys, normally open calling line marking contacts closed by the operated line relay `for marking the calling line with calling line desig' nations, normally openlocal connection mark` ing contacts closed by the operated line relay for marking the initiation of a local call in case the operated key on said calling line is a local key,

and normally open trunk connection marking contacts closed by the operated line relay for marking the initiation of a trunk call in case ther operated key on said calling line is one of said trunk keys. l Y

29. In a telephone system, a plurality of subscribers lines, a local key individual to each line for'use in extending local connections, a plurality of trunk keys individual to each line for use in extending trunk connections to distanti' areas, a line relay individual to each line, a line amenait clcuitlferfzeachfciSeidl egrlelays;includingnorf callingy subscribersline relay; inn response tothe` callingY subscriber initiatingav call and operating one o said keys, normally opengcalling line markb ingcontacts closed by the :operated linelrelay for marking lthe callingline-l with calling, Aline desigf nations, lnormally open local connection marking contacts closed by theA operated linelrelayv for" marking the, initiation of a local call vincase-fthe operated key on said calling line isa local key,

` normally open trunkl connection'markingr con-` tacts closed bythe operated line relaygfor marke ingtlieinitiation of a trunk; call in case the opere ated key .on said. calling 4line is one ofsaid1trunk keys, a busy relay individual toisaid calling line,r

means for operating saidbusy,` relay in case a busy condition is encounteredduring the initia tionY of a local or a trunk calland means con-2 trolled by theoperation .,-of said busy, relayl for erasing said markings. Y

30. In a telephone system, a pluralityof subscrbers lines, a local key individual to each line for use` in extending local connections, alplu;v rality` of trunk keys individual `to each line for` use .in `extending trunk connections. todistant areas, aline relay individual toveach line, a line,

circuit for each of saidy line relays includingnormally-open Ycontacts on the corresponding indi` vidual local vand trunk keys,A means for closing.;A

the line circuit of a calling line-to operate-the calling subscribers .linerelay in reSDQnse Vto the;

calling subscriber initiating a call andr operatingn one of said keys, normally open calling line marking contacts closed by the operatedlinev relayl forr marking Athe calling line` with callingv line designations, normally open local connection marking contacts closed bythe operated line re-l lay for marking the initiation of alocal callin,l case the operated key ony said calling.- line is a local key, normally open trunk connection mark- Y ingY contacts closed by .the operated line relayl for markingthe initiation of aztrunkcall incase the operated key on said calling line is one of said trunk keys, local links for extending calling linesf in' local connections, trunklinks for'fextendingi.,

calling linesfin trunk connections lto ydistant 31. In a telephone system, a. plurality of suba scribers lines, alocal key individual to eachline for use in extending local connections, a plural,

ityof trunk keys individual toveach lineitforiuse.I in` extending trunk connections kto distant, areas, aline ,relay individual to each line, a line circuitfor each of said line relays includingvnorrnally open contacts ,on the corresponding individual local and trunk keys, means for closing the line` circuit of a calling line to operate tne'calling subscribers vline rrelay in responseV to the calling subscriber initiating a call and operatinggone of said keys, normally open calling line Ymarking contacts closed by the operated Vline relay for'-v marking the calling-line Withicalling line desige nations, lnormally open local connection marking.:` contacts ,closed by the operated.linev-'relayfor;

markinggtheinitiation:of a lOal callin case ithef 245? operated-key; on said callingfline isy a; local rkey;A normally open'. trunk'. connection marking con.- tacts closedr by the-ffoperated` line-:relayv for 'markel ingthef initiation' ofA atrunkcall :in case the operatedkeyjon said calling line is one of said .trunkkeys, local linksfor extending calling lines -in local connections, trunk?, links for. extending;` calling linesin trunkconnections to distant areas; an al lutter: common'xto said localland trunk links,

I means 1 inn-said: allotter responsive .to said calling linedesignation l markings-,fior operating one of saidzlocal .links -to connect ,Witlfrsaid calling line in case3thecall -initiated; `,is aA local call or' for r operatingE oneV of said trunk links; .to connect with saidrcalling, linev in .z case the-:call initiated l is a trunk call, and means responsive to therconnec tion1of saidicalling line 'withleither. a local link ora trunkrlink for:erasing-saidmarkings.

32,.;.Inr aftelephone system; aa plurality of re'-, s-tricted subscriber nlinesg-azy plurality of. non-rea stricted subscriberflines; aptrunkline terminating inv analllrelaynder: arestrictedstart lead ,comi-f moni tosaid. .restrictedlines Jterminatingsin said trunkl line a nung-,restricted start ilead common i'tor, said non-restricted. lines;r terminating in rY said trunk; line; means.;in; saidgnder fcontrolled c over said ,starttleads :Linjresponse fto anyL of saidv ylines i. answeringfia: trunk cal-l incoming over saidetrunk line .for 4conditioningzsaidainder. tonconnect'.vvith the.V answering line, said finder: conditioning f meansi-A beingV- operative; over 1 said; non-restricted start .,leadgiir; responseitoaanyl of .said non-rav stricted. lines ,originating anz;outgoing vtrunk call over:saidtrunklineifor:conditioning said. iinden to connect witlnthe .calling ,21ine,. relays yin said nder .responsive t toatheooperati'onaof :said finder conditioning,:meansiafor connecting fsaid .trunk line to :said answeringrline :ain case` an.v incoming trunk callis answeredfand,y for. connecting said trunkrlinefto vsaidicallingline infcase an outgo-y inglcalliszoriginated bysaiol.'calling line, and-cir-A cuit'connections in saidwnderfand trunkrline for .preventing 'the operation ofl said finder .conditioningrmeansrover said restricted startv lead in* caseta restrictedlineattempts tol originate an outgoing trunk ,callzover said trunk.'line.

Y In. a telephonesystem,- aiplurality ofrestricted subscriber linesA a 'fpluralityflof -'nonrestrictedf-subscriberflines, a trunk? line terminating inan allrela'y Yinder, a restrictedl start lead com- --V rnonfzto :said :restricted lines Y terminating in said i to said fnonarestricted ilinesterminating in said trunkline, means in fsaid -indercontrolled overy said start leads in response-#td anyv of said 'lines answering. a trunkcall incoming over v saidtrunk line orfcondtioning Isaid finder to connect Witl'r the answeringr line,l saidiinder conditioning i means being operative-over said non-restricted` start lead in responseto any'of-f said non-"re-l stricted lines originating an outgoing trunk calli overisaid trunk line for conditioning-saidl linderto-Aconnect rivitn the ycallin?,f line, relays in said nder responsive'tc the Ioperation of'said. finder conditioning means: for connecting 'saidtrunkl 25 trunk line is busy in another established connection for preventing the operation of said finder conditioning means by subscribers attempting to complete connections thereto.

34. In a telephone system, subscribers lines, trunk lines, tens and units connecting relays associated with each trunk line, means controlled by one of said subscribers answering anv incoming trunk call over one of said trunk lines for directively operating certain of said tens and units connecting relays in said one trunk line to connect said one trunk line to the answering subscribers line, a holding key associated with each subscribers line, a holding circuitl in each trunk line, means responsive to the operation of the holding key at said answering subscribers line for completing the holding circuit in said one trunk line to hold 'said one trunk line and for releasing said operated tens and units connecting relays to disconnect said answering subscribers line from said one trunk line, and means controlled by another of said subscribers lines upon being informed of a trunk call on said held trunk line for directively operating predetermined ones of said tens and units relays in said held trunk line to connect said held trunk line to said othersubscribers line.

35. In a telephone system, subscribers lines, trunk lines, tens and units connecting relays associated with each trunk line, means controlled by o-ne of said subscribers lines for directively operating certain of said tens and units connecting relays associated with one of said trunk lines to connect said one trunk line with saidv one subscribers line, means controlled by said one subscribers line for holding said one trunk line and for releasing said operating tens and units relays to disconnect said one subscribers line from said one trunk line to thereby enable said one subscribers line to be connected to another subscribers line or another trunk line, said rst means reoperated by said one subscribers line in case such vsubscriber desires to be reconnected to said held trunk line for directively reeperating said certain tens and units connecting relays to reconnect vsaid held trunk line to said line and for releasing said operated tens andv units relays to disconnect said one subscribers line from said one trunk line, and means controlled by another oi said subscribers lines for directively operating predetermined ones of said tens and units relays in said associated held trunk line to connect said held trunk line with said other subscribers line.

37. In a telephone system, subscriber lines, kkeys for each line, a line relay for each line, a plurality of trunks each having a nder switch individual thereto and each having access to all of said lines, control'equipment common to said finder switches, the line relay of each line being operated in response to the initiation of a call over saidline and the operation of a key on said line to operate said control equipment, and circuits completed responsive to the operation of said key, said line relay and'said control equipment, for causing one of said iinder switches to be directively controlled tofextend a trunk to the calling line in accordance with the operation of said key.

JOHN H. VOSS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,568,039 Williams Dec, 29, 1925 2,020,816 Voss et al Nov. 12,1935 2,071,075 Koechling Feb. 16, 1937

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