US2353055A

US2353055A - Satellite communication system

Info

Publication number: US2353055A
Application number: US458979A
Authority: US
Inventors: Tola A Marshall
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1942-09-19
Filing date: 1942-09-19
Publication date: 1944-07-04
Anticipated expiration: 1961-07-04

Description

July 4 .1944. fr; A. MARSHALL SATELLITE COMMUICATION SYSTEM.

Filed Sept. 19, 1942 3 Sheets-Sheet 1 l rhs RLY lNVEA/TOR by f IAMARSHAQ.

ATTORNEY July 4, 1944- T. A. MARSHALL 2,353,055

` SATELLITE COMMUNICATION SYSTEM Filed sept. 19. 1942 s sheets-sheet 4 FOL A RIZED PQL AR/ZED ./Nl/ENTOR A7. MARSHALL BY I A 7- TURA/EY July 4 1944- T. A. MARSHALL 2,353,055

' SATELLITE COMMUNICATION SISTEM Filed epi. 19, 1942 3 sneetssheet s I als /N VEN TOR 77 A. MARSHALL JWM' Patented July 4, 1944 SATELLITE COMMUNICATION SYSTEM Tola A..Mar`shall, Floral-Parmi N. Y., assignorito:

Bell- Telephone Lab oratories, Incorporated,

New York, N. Y., a corporation of New York l Application september 19, 1942, serial No. 458,979'

16 Claims.

This invention. relates to communication systems and more particularly, tol teletypewriter eX- change systems wherein satellite arrangements provide for. a plurality of subscriber stations being connected through an automatically operated line concentrating unit switching center, to a central oi'lce.

. In. order to assist in understanding the invention. vit is desirable to briefly describe the present arrangement of the teletypewriter exchange central oice equipment and the method of operating and maintaining the trunk circuits extending to other central oflices and the terminating equipment at opposite ends' of each trunk.

.The operating and maintenance personnel may be divided roughly vintotwo groups:

A. A traic group which comprisesthe operators for establishing connections and the supervisory forcerouting and supervising the traffic; and

B. A plant group Whose duty it is tomaintain the circuits in proper operating condition, locate the causes of trouble when reported by the traffic group, and to clear the varioustroubles after the causes have been ascertained,

.The Various trunkv lines are multipled before several operators at, positions of the operator.

switchboard to permit the operators to estab-v lishconnections. Ifan operator nds a'particu-- lar line or trunk in trouble, she reports this fact.

to a. traffic control bureau which is usually located in some other part of the building and has l no direct access tothe `line ,or trunk. in trouble. Itis desirable. that thetrafc control bureau verify the fact that the. trouble exists before nol tifying the plant people vto clear it and in order to do this, the traic controlr bureau orders a.

trouble operator (whois located at oneof. the

positions of the toll switchboard)y to extend the line or trunk, in trouble, to ,the traffic control b ureau.r The troublehaving been veriiied, it is reported to a troubleclerk in the plant department who makes out a ticket and delivers it to the attendant at'a test board whose duty it isto determine. the cause of( the trouble. The test board is lso arrangedjthat each attendant thereat has access toa certain group oflines,and/or trunks andthe lines or trunks arenot multipled to other positions at the testboard.Y If at the time the trouble is reported .to thetrouble clerk theattendant at the. test `board should be busy testing another linear trunk, he would'not be able to take up the new trouble immediatel?,k and vlienc'e, the

necessity forL making outfaticket and delivering it 'to the attendant. As son as the te'st board attendant has determined trouble he instructs'theproper equipment man who has charge of the. partic 1,1la'1. eluipinrit` which is in trouble, to clear it. 'After the trouble vis cleared the equipment man notifies the test board attendant, who again `tests.to ,determine that the vlinel or trunk and apparatus associated therewithare inpropercondition; ,whereupon he notifies the trarne control bureau that the .une or trunk isagain ready for service.

When the traic control bureauorlginally vascertained that'the trouble'existed,. the trouble operator at e e the toll switchboard wasordered to render the The applicant has foiindvitv` desirable to,v ,sima plify'th'e operationof testing each trunkextending from a central oflice to a line concentrating unit switching center end each of the subscriber lines connected eitherdirectly 'tito the switching,

center erover any one of lthese trunks.

'An pbject ofi the myentoin is to test attnecrf tial oice the oioeratiinalv eiectiveness of each of the circuits extending between the central oice and theline concentrating unit switching center, and each of thesubscribers lines connected directly to the switching center,

According to the present invention a testing position, in addition to a plurality of theusual operator positions, is provided at the operator switchboard at the central cnice.I At the testing position each of the trunks incoming lfrorn the line concentrating unit switchingmcenter is terminated, inv multiple appearance, at a jack. Also terminating at Athe testing positionoi'the operator Vswitchboard in'addition to a plurality of cord circuits, is another cord'circuit connected to a testing trunk circuit whicheitends Yto a test board located in a part of the building other than that wherein the operator switchboardis located. Therefore, a test board attendant may, at any desired time or'at regular intervalsl request. over an order Wire the operatorat the testingA posif tion of the operator switchboard to .connect the testing trunk plugnto the jackof any parti cular trunk extending to the line concentrating unit.

vswitching center, s o that the .tes t a bpard,attendm ant may originate a call to another 'test board the 'cause' of4 the troubled circuit busy andthe busy. conditionexisted during theperiod of making out the ticket,'testing and clearing the trouble.

attendant at the line concentrating unit switching center, or to any of the subscribers stations directly connected to the switching center or to any other subscribers station directly connected to the central office, and supervises such connections in the same manner as an operator at an operator switchboard.

A feature of the present invention is the provision for makingran over-all test on any one of the trunks extending to the line circuit switching center, with the supervisory signals coming from a subscriber station or attendant teletypewriter trunk circuit at the line concentrating unit switching center, or for making the tests locally with supervisory signals simulated at the jack associated with the particular line or trunk in the test board at the central oce.

Another feature is the direct means for testing trunks extending to the line concentrating unit switching center by requesting the operator at the test position of the operator switchboard to connect the testing trunk circuit to any one of the trunks through its multiple jack which appears at the test position.

Another feature is the provision of a high resistance sleeve conductor inthe testing trunk cord circuit which, when connected to a trunk,l operates a guard lamp at the test board but does not operate a sleeve relay in the particular trunk selected.

Another feature is the provision of a makebusy jack in the testing trunk circuit arranged to be patched with a cord circuit to the makebusy jack of the selected trunk wherebya busy lamp and an answer lamp are arranged to light over the sleeve and the tip conductors, respectively, of the testing trunk cord circuit, the answering lamp lighting one-half second later than the busy lamp. i

Another feature is the provision for extinguishing the answer lamp and the busy lamp at the test board successively when the call is abandoned before it is answered. Resumption ofthe call within four seconds relights the answer lamp. Resumption later than four seconds is like a new call. l i fr! Another feature is the provision for answering a call at the test board by restoring a locklng key to normal whereby the above-mentioned high resistance of the sleeve conductor of the testing trunk cord is reduced, to operate the sleeve relay of the selected trunk and circuits are closed to cause the guard lamp at the test board to light and extinguish the answer lamp.

Another feature is the provision when a recall signal is received at the test board, to furnish interrupted ground potential to a circuit for flashing a supervisory lamp. The lamp is extinguished by the momentary operation of a nonlocking restore key.

Another feature is the provision for originating a call at the test board after the selected trunk is made busy. by operating'the locking key connecting the testing trunk cord to the selected trunk and then restoring the locking key.V A supervisory lamp at the test board will light steadily after the key is released.

Another feature is the provision of a relay arranged to release when ground potential is removed from the ring conductor of the trunk. indicating that the line concentrating unit is ready to receive call directing pulses. The relay, polrli releasing, causes the supervisory lampto Another feature isthe provision of applying 75 a steady ground potential to the ring conductor of the testing trunk cord circuit when the connection of a subscribers line, in response to the call directing pulses, is completed at the line concentrating unit for causing the supervisory lamp to change from a flashing light condition to a steady light condition.

Another feature is the provision of applying ringing current tothe selected trunk by operating a key at the test board which current is transmitted to the line concentrating unit as 20-cycle dot signals.

Another feature is the provision of changing the supervisory lamp from a steady light conditionto a flashing light condition when the call to or through 'the line concentrating unit is answered, -A momentary operation of the restore key at the test board extinguishes the supervisory lamp.

Another feature is the provision for testing the functioning of the selected trunk circuit on a disconnect by the operator before a subscriber disconnects, by operating a locking key at the test board which opens the sleeve circuit of the testing trunk cord causing the trunk sleeve relay to release. 'Ihe release of the trunk sleeve relay causes the answer lamp at the test board to light If the subscriber disconnects before the locking key is restored the answer vlamp is extinguished and in five seconds is followed by the extinguishing of the busy lamp. Y

Another feature isthe provision of means for testing the functioning ofv the selected trunk circuit when the party at the opposite end of the trunk disconnects, whereby ground is applied to the ring conductor of the testing trunk cord to cause the supervisory lamp at the test board to light.

Another feature is the provision of means for testing the functioning of the selected trunk circuit when the operator disconnects after the party at the opposite end of the trunk circuit disconnects. This condition is simulated by operating the locking key to open the sleeve circuit of the testing trunk cord. The busy lamp at the test board is extinguished one and one-half seconds after the operation of the key. The guard lamp at the test board is maintained lighted and the trunk sleeve relay remains released removing the condition which has kept the busy lamp lighted.

'I'he drawings consist of three sheets. The first sheet contains Figs. 1 and 4, the second sheet Fig. 2, and the third sheet Fig. 3.

Fig. 1 is a diagrammatic showing of a subscriber station connected through a line concentrating unit switching center to a central office. Other subscriber stations, not shown, may likewise be connected to the line concentrating unit switching center. The equivalent of a subscriber loop is shown connected to a jack at the attendants test board at the line concentrating unit switchingcenter for the purpose of testing any one of the` trunks extending between the central office and the line concentrating unit switching center. The subscriber station may be similar to that shown in Fig. 3 of the copending application of C. W. Lucek,l Serial No. 431,854, filed February 21, 1942. Likewise, the subscriber line terminating circuit, the link circuit, the sequence circuit, the trunk circuit, the director circuit, alltrunks-busy circuit,.and the miscellaneous alarm circuit provided at the line concentrating unit switching center, represented by rectangle H4, may be similar to the corresponding circuits nating equipment shown in Fig. V2. Test plug 20|` ofv the testing trunk is inserted in'jack 203 which is a multiple appearance ofl the selected trunk at the test position of the operator switchboard. The test board attendants teletypewriter is inserted by means of its attached cord landY plug, into test jack 302. The automatic signaling.

trunk key SIS is used and its operation is hereinafter described. The test board attendants teletypewriter may also be inserted in looping jack 303 for testing outgoing trunks'or in jack 3I2 for calling theoperator at the test position of the operator switchboard, Y

When the trunk circuit shown in Figs. 1 and 2 is in the idle condition, both the inward andthe outward paths are in spacing condition. No relays or vacuum tubes are energized except receive supervisory relayl 2RS Whichis normally held in its spacing position by the'spacing 'condition of the outward path which extends through the upper winding of the relay. Relay 2RS will maintain condenser 224 discharged while thek trunk is in an idle condition.

Trunk busy atoperator switchboard If the automatic signaling trunk circuit is Abusy at the operator switchboard appearance while the make-busy jack 3I3 is patched to the makebusy jack 3|5 in the trunk circuit, busy lamp 3H will be lighted over a circuit traceable from grounded battery 225, say of 48 volts, resistance 226, say of 284 ohms, contact and middle lower armature of trunk-busy relay 2BY, sleeve con` ductors of jack 3|5, cord 3|4 and jack 3|3, through the lamp 3H to ground. .If a calling signal incoming over outward path R is awaiting answer at the operator switchboard, as indicated by the lighting of call, or line, lamp 205, busy lamp 3| 'l will light because busy relay 2BY is operated, and answer lamp 3H will light over the circuit traceable from grounded battery 221, say of 48 volts, resistance 228, say of 284 ohms, outer lower armature and contact of lamp relay 2L, tip conductors of jack 3|5, cord circuit 3|4 and jack 3|3, through the lamp 3| I to ground.

In response to a callingV signal incoming'over outward path R relay 2RS follows all pulses of the calling signal. During the idle condition of the trunk relay 2RS will keep condenser 224 discharged. Marking pulses permit condenser 224 to charge and will energize the filament circuit of vacuum tubes 2|3 to 2|'|. When a marking pulse in excess of one-half second is received as the result of a call, condenser 224 will charge suiliciently to cause tube 2 I6 to draw plate current and operate relay 2C which, in turn, operates relay 2CT. Relay 2CT, upon operating, will open the spacing contact circuit of relay 2RS so that tube 2|6 will remain conductive. Relay 2CT, upon operating, will also condition relay 2R so as to follow the signal pulses from the outward path, and will operate relay 2TR. Relay 2'I'R, upon operating, will lock itself in an operated position and operate relay 2-ON. Relay 2-ON, upon operating, applies power to the repeater relays 2R, 2S and 2SS and operates-busy relay 2BY. Relay 2BY, upon operating, lights bfusy lamp 202, energizes the filament circuit of the vacuum tubes independently of the marking contact of relay 2RS and applies a busy potential` to the sleeve of jack 203. Meanwhile, the tube illaments being energized, tube 2 |5`becomes conductive and prior to theoperation of relay 2-ON operates relay A which, in turn, operates relay 2AI so that the 20-cycle current from source 233 will be transmitted over. the inward path T when armature of relay 2EI, and transfers condenser 229 from ground to a high resistance charging path including resistances 234 and' 209 and grounded positive battery 208. When condenser 229 has charged for a period of one-half second tube 2|4 becomes conductive and relay 2E oper-Y ates to operate, in turn, relay 2EI. Relay 2E|, upon operating, will close the operating pathof relay 2L, which, upon operating, will light call, orline, lamp 205 and operate night alarm 235. 'I'he circuit for operating relay 2L is traceable from grounded battery on the winding of relay 2L, conductor 230, middle upper armature and contact of relay 2EI, contact and inner upper armature of relay 2CT, contact and lower arma-v ture of relay 2A| to ground at the innermost lower armature and back contact of trunk sleeve relay 2SL.

If the trunk shown inFig. 2 is idle at the time jacks 3|3 and 3|5 are patched together, neither the busy lamp 3| 1 nor answer lamp 3| I will light. However, the trunk may be made busy by the attendant at the test board by inserting the plug of patching cord 3|4 in make-busy jack 3| 5 to connect ground to the ning spring of the jack and thereby close the circuit extending over. conductor 342, through the winding of relay 2TS, to grounded battery and relay 2TS operates to connect source 23| of alternating current to a circuit extending over the outer lower armature and contact of relay 2TS to the trunk-busy lamp 202 which lights indicating that the trunk is busy.

Connecting the testing trunk plug 201 at the test position of the operator switchboard If the trunk is found to be idle, plug 20| will be connected to the multiple appearance at the testing position of the operator switchboard after rst operating automatic signaling trunk test key 3|6. Operation of key 3|6 to its open condition provides a high resistance circuit extending from grounded battery, through a high resistance winding, say 20,000 ohms, of relay 3T, contact and lower armature of relay 3U,

conductors

353 and 323, sleeve conductors of plug 20| and jack 203,` through the winding of trunk sleeve relay 2-SL to ground, and relay 3T operates but relayv 2SL does not operate at this time. Relay 3T,

upon operating, closes at its armature and con# tact a circuit traceable from grounded battery g; 3|9, say of 48 volts,

conductors

343 and 344, contact and armature of relay 3T, conductor 345, through guard lamp 30|, to ground and guard lamp 30| lights to indicate that testing trunk cord 206 is connected to a main trunk.

Incoming call An incoming call from the distant'switching center H4, which originated at either the center itself or one of the subscriber stations connected f'r thereto, will cause busy lamp 3|? to light over the sleeve circuit as hereinbefore described and answer lamp 3|| to light over the tip circuit of jack 3|3, also as hereinbefore described. The answer lamp 3| I lights one-half second later than the busy lamp 3H.

answer lamp 3H will be extinguished and be followed by the extinction of busy lamp 3|1. Ref

"Disconnection while subscriber station is still connected for communication Atest for the functioning of the automatic sig- 'naling trunk-circuit shown in Fig. 2 on a dis- 'connect vby the operator before the subscriber disconnects may be made vby operating the autog, -matic signaling trunk key 3l which, when op- Yerated, opens the sleeve conductor 323 ofthe `testing cord 26. Relays 3SI and 3U release.V

'Relay 3U, upon releasing-closes a circuit extending through the high resistance winding of relay 3T to grounded battery. During the open interval of the sleeve conductor 323 of cord 206 before relay 3T is connected, the trunk-sleeve relay ESL is given an opportunity to release onthe ybusy condition being maintained by the presence of the connection to the make-busy jack3l5 oi the trunk circuit. 'I'he release of the sleeve relay in the trunk circuit causes relay 2L to operate, which, upon operating, causes the lighting of answering lamp 3II. connects before the automatic signaling trunk key 343 is restored, the answer lamp 3H is eX- tinguished and in ve seconds is vfollowed by the extinction of the busy 'lamp 3H. v

Subscriber disconnects 'first Disconnection bi1 the operator at the central `olice after the subscriber disconnects This condition is simulated by operating the automatic signaling .trunk key BIB to open the v sleeve conductor 323. Busy lamp 3H is extinguished-one and one-half seconds after the operation of key 3I6. Relays 3S! and 3U release. Relay 3T operates to maintain guard lamp 30| lighted. During the open sleeve interval before relay 3T is connected tov the sleeve, the trunk sleeve relay isgiven an Opportunity to release. It remains released removing the condition which has kept the busy lamp 3|'Iy lighted.

What is claimed is: Y Y

1. In a telegraph exchange system, a central oiiice, comprising an operator switchboard, a test board, main trunks terminating at said central oflice each havingv an appearance-at a position of said switchboard and a position of said test board, a testing trunk at said test board, having means for connection at said switchboard to any one of said main trunks, and means at said test board for determining the condition of any one of said main trunks, said means comprising patching means for interconnecting at said test board said testing trunk and one of said main trunks, signal devices connected to said patching means, and operable meansV arranged, when operated, to cause said signal devices to indicate whether a selected trunk is busy, idle or in the condition wherein a call from a distant point is awaiting'an answer,

2. In a telegraph-exchange system, a central If the subscriber disil i) oce comprising an operator switchboard, a test board, main trunks terminating at said central office each having a three-conductor appearance at a position of said switchboard and a position of said test board, a three-conductor testing trunk at said test board and having means for connection at said switchboard to any one of said main trunks, a trunk sleeve relay connected to one of said conductors at each of the appearances at said switchboard and arranged for connection to one of the conductors of said testing trunk, a high resistance operable element connected inparallel to said one conductor of said testing trunk, a signal device for holding a main trunk busy against subsequent seizure after said testing trunk is connected to the particular main trunk, and operable means arranged when operated to cause the operation of said element to operate said signal device and to prevent the operation of the sleeve relay in said particular main trunk. A

3. In a telegraph exchange system, a central oflice, comprising an operator multiposition switchboard, a test board, main trunks terminating at said central loflice each having a threeconductor appearance at each position of said switchboard and a position of said test board, a three-conductor testing trunk at said test board and having means for connection at said switchboard to any one of said main trunks, two-conductor means at said test board for indicating a call incoming over any one of said main trunks, said means comprising two-conductor patching connector for associating at said test board the particular main trunk with said testing trunk, and signaling elements-arranged to successively operate in response to the incoming call, one of the conductors offsaid patching .connector being effective to operate one of said signaling elements at one time and another of the conductors of said patching connector being eiective to operate another of said signaling elements at another time. y

d. In a telegraph exchange system, a central office comprising an operator multiposition switchboard, a test board, main trunks terminating at said central cnice, each having a three'- conductor appearance at each position of said switchboard and a position of said test board, a three-conductor testingl trunk at said test board having means for connection at said lswitchboard to any one of said main trunks, and twoconductor means at said test board for indicating a call incoming over any vone of said main trunks and said testing trunk, signaling means successively operative in response to an incoming call arranged to successively returnto normal when the call is abandoned before. the call is answered, and .means controlling one of said signaling elements arranged to vreoperate said one element after being returnedto normal, if the call is renewed within four. seconds.. 5. In a telegraph system for answering incoming calls at a test board, a central oflice comprising an operator multiposition switchboard, a multiposition ltest board, main trunksterminating at said central oiice, each havingran appearance at each position of said switchboard and a position of said test board, a testingtrunk at said test board and having means for connection at said switchboard toanylone of said main trunks, patchingmeans at `vsaid test board ,for associating any one. ofV said main trunks with said testing trunk and sources of potential in said main trunk for energizing' said patching Ya call incoming Vmeans and Ameans.when:effectively associated with onecf ."tion betweensaidone maintrunk vand said testsaid-main trunks at -said testingtrunk, signaling elements -at said-"test board, voperable meansin said Ytesting trunk, a -teletypewriter -arranged-rior connection to said testing trunk, means for energizing two said signaling velements'inrespcnse l-to over. one of said main trunks Awhen said one main trunkis eiectivelyrassociated `with said testing trunk` by saidfpatching means, `high resistance means responsive totthe yoperation of said operable` means for operating v.the third of'said signaling elementsand other -means effective to deenergize said-third-signaling vnaling means f independently of said-high `resistance means for the durationvofv the connection established betweensaid teletypewriter and said -one main trunk through said testing V'trunk in response to the incoming calls when saidoperrablemeans is restoredto normal.

6.V In atelegraph exchange system for recall- -ing-the test board attendant in acommunication connection, a central oicecomprisingan-operator multiposition switchboard, a multiposition testboard, main trunk vterminating -at said central ofice, yeach having .a three-conductor vappearance at each positionv of said switchboard and a position of `said test board, a three-conductor testing trunk at said test board and hav- :ing means for connection at said switchboardtc any-'one of said main trunks, an operable device Ain said testing trunk arranged to operate when aground potential is applied to one conductor of any one of said maintrunks .in engagement with said testing trunk, another operable device in said testing trunk arranged to operate .and

vlock in its'operatedpositon 'in response to the operation-of the first-mentioned operable device, a signaling element at said test boardarranged to operate intermittently during vthe time' that said other operable device is locked in its `operated position, and 'an` operable Velement located at said test board and arranged whenv operated momentarily vto deenergize said operable` devices and saidsignalingelement.

'Z-.`In a telegraph exchange system hfororigi: nating. aV call #at an attendants test boardvfor .a connection- `to a main trunk, a central office comprising `an .operator multiposition switchboard,

-a multi-position test board,.rnain trunksl terminating at saidlcentral office, each-having asthreeconductor appearance-'at each position of :said switchboard and a position of said test -boarda testing tru'nk at said test vboard and yhaving means for connection at said switchboard to any -one'of saidmain trunks, patching meansatsaid testr Vboard for associating any one fof rsaid .main trunks with said testing trunk and la source of potential in said main trunks for energizing said patching Ameans, when effectively associated with one of said main trunks and said testing trunk, operable means at said'test board, signaling elements at said test board and said switchboard, means responsive -when (1) said patching means iseiectively associated with said one mainv trunk and -said testing trunk, (2) said operable means is'` operated, and (3) said testing trunk is yconnectedto said onemain trunk, for operating one oiA the signaling elements located at-said switchboard-and associatedwith said one main trunk, and vmeans responsive vto the release of said operable means for (1) making said one main trunk busy to other calls, (2) for maintaining operated the'said onesignaling element v-at sa`id switchboard, '(3) 'for completingy an operative connec to maintain energized said third sigingztrunk, and (4) aforoperating a signalingele- `ment at: saidtestiboard to furnish supervision-for /theldurationof the connection originated at the -attendants .test board.

`8. In a .telegraphsystem for sending call directing signals from an attendants test 4board to .any-.one of a plurality of main trunks, a central cnice, comprising an operator multiposition switchboard, a multiposition test board, main sition :of `said switchboard and` one vposition fof -saicl test board, a three-iconductor testingtrunk atisaid .test boardv and arranged for connection atsaid? .switchboard to any one of saidmain trunkswa teletypewriter connected. at said test y-lcoardl.to,.,saidy testing trunk Ikfor sending` call directing signals oyerone of said conductors in said ,testing .trunk and one of said conductors insaid main: trunk in engagement 'with said testing trunk, an operable device at 'said test board, a high-resistance operable element in lsaid'testing trunk and arranged tooperate in response to the operationof-said operable device, a second and a third .operable elementin said testing trunk successively responsive tothe restoration to normal ofsaid operableidevice said-secondi operable element being ,eifective when operated, to connect said teletypewriter ythrough said testing `trunk to said engagedmaintrunk for transmission of-ca11 directing-signals. Y

..9...In av telegraph exchange systemv having a 4satellite communication arrangement, afcentral oce,va `swift-ching center, a plurality of subvscrbersline's connected to said switching vcen-- ter, 'a plurality oi main trunks interconnecting said vcenter and said central cnice, -said central ofice comprising an koperator Vmultiposi-tion switchboardand-a multiposition test board-a .three-conductor appearance for each of said main trunksat each position of said switchboard and one .position of said test board, a three-conductor testing trunk atfsaidtest board and varranged for connection at said switchboard to any oneof said main trunks, a teletypewriter connected at said .'testrboard to said Ytesting-trunk for sending-call directing signalsfto said switching center, ancperable devicepl'ocated in said. testing trunk-and arranged to operate in `response to the initiation of a call at said test board tosaid switchingcenvter andztofrelease in responseA to the completion ofsaid call Vat said switchingcenter, a second operable device Varrangedto operate and .lockinan operatedpositionin response to the operationA of the first-mentioned operable device, a signaling element-arranged to operate to one condition -in response to the operation of the mst-*mentioned operabley device and to another condition when the first-mentioned device is released during `the time that saidsecond operable device is inits locked position, said signalingv element in said other condition, furnishing an indication that-the switching center is ready` to receive calldirecting signals for selecting the desired subscriber line'. t 10. In a telegraph exchange system having a satellitecommunication arrangement, av central cnice, a switching center, a plurality of subscriber lines connected to vsaid switching center, a .plurality of main trunks interconnecting said center and said central oice, said central oiiice'ccm#- prising an operator multiposition switchboard and a multiposition testboard-a three-conductor appearance ior each of said maintrunks atfeach A position of said switchboard and a positiongof said test board, a three-'conductor 4testing trunk'a't said test board arranged for connection at said switchboard to any one ofsaid main trunks, a teletypewriter removably connected at said test `board to4 said testing trunk for sending call-di- ,trunk and arranged in response to the operation of said operable device ,to a steady conditionuto -change from a varying .conditionto a steady condition to indicatetoa test board attendant that the"desired,subscriber line at rthe switching center has been selected and connectedto said one main trunk in responseA Ato the call directing .signals transmitted from rsaid teletypewriter.

y 11. In a telegraph exchange system having a satellite communication arrangement, va central oflice, a switching center, a. plurality of subscriber lines connected to said switching center, a plurali-ty of main trunks interconnecting said cen.- ter at said central olice, said central oliice com.- lprising an operator multiposition switchboard and a multiposition test board, a three-conductor appearance for each of said main trunks ateach position of said switchboard and a position of said test board, al three-conductor testing trunk at said test board arranged for connection at said switchboard to any one of said main trunks, a teletypewriter removably connected at said test board to said testing trunk for sending call directing signals to said switching center, means responsive to the call directing signals ,from said .teletypewriter for automatically connecting said one of said main trunks to one of said subscriber lines, a source of ringing current, switchingmeans in said testing trunk for applying ringing current from said source to said automatically established connection of said one subscriber line, and a signaling element at said test board arranged to operate when the ringing current from said source is applied to the automatically established connection.

Y 12. In a telegraph exchange system having a satellite communication arrangement, a central olflce, a switchin-g center, a plurality of ,subscriber lines connected to said switching center, a plu.- D

rality of main trunks interconnecting said center at said central oilce, said central oflce comprising an operator multiposition switchboard and a multiposition test board, a three-conductor appearance for each of said main trunks at each position of said switchboard and a position of said test board, la three-conductor testing Ytrunk at said test board arranged for connection at said switchboard to any one of said main trunks, a teletypewriter removably connected at said test board to said testing trunk for sending call directing signals to said switching center, to select a desired subscriber line, an operable device located at said testing trunk and arranged in response to a connection being automatically established between one of said main trunks and one of said plurality of subscriber lines by said call directing signals, to operate to a steady condition, a second operable device arranged to operate and lock in an operated position in response to the operation of the first-mentioned operable device, an indicating signal and a source of alternating current arranged to be connected to said indicating signal when said second operable device .Operates whereby a flashing signal is furnished to invdicate that s aidiautomatically, established connection is in a condition vfor telegraphic message communication, and a switching memberfor restoring said second operable device to normal.

13. In a telegraph exchange system according to claim 10, wherein each ofsaid main trunks comprises a sleeve relay normally operated when its associated trunk is in a busy condition, interconnected make-busy jacks, an answer lamp signal, vandmeans for maintaining the trunk busy during a busy condition when the sleeve relay is given an opportunity to release, 'and said testing trunk comprises switching means, a plurality of relays,one relay of said plurality having a vrelatively high'resistancegvalue and certain other relays of said plurality being normally operated during an established connection between said testing trunk and any one of said main trunks, means cooperating with.- one of said certain relays for normally maintaining the sleeve relay of said one trunkA operated during the established connection between `said ,testing trunk and said one main trunk, circuit means responsive tothe operation of said switching means for releasing said certain re,- lays successively, other circuit means responsive to the release of said certain relays for operating said relay of relatively high resistance valuey and a sleeve conductor circuit in said testing trunk and said one main trunk connected thereto effective during its open condition interval created between the time of the operation` of said switching means and the `complete release of the last 'operated of said certain relays, to operate said relay of relatively high resistance value and to afford theopportunity to release to said trunk sleeve relay, said busy means of said one trunk including relays cooperating with said make-busy jacks in busy condition to operate said answer lamp signal;

14. In a telegraphexchange system according to .claim 10, wherein each of said main trunks comprises a make-busy jack, an answer lamp signal, a busy lamp signal, and means for maintaining theA trunk busy when said trunk is in a busy condition, and said testing trunk comprisesswitching means, a plurality of relays, one relay of said plurality having a relatively high resistance value, and'certain other relays of said plurality being normallysfoperated during an established connectionbetween said testing trunk and any one of said main trunks, means cooperatingwith one of said certain relays for maintaining the sleeve relay of said one trunk operated during the esta' lished connection between said testing trunk and said one main trunk, circuit means responsive to the operation of said switching means for releasing said certain relays successively, other circuit means responsive to the release of said certain relays for operating said relay of relatively high resistance value, and sleeve conductor means in said testing trunk and said one main trunk connected thereto eiective during the open condition interval created between the time of the operation of said switching means and the complete release of the last operated of said certain relays to operate said relay of high resistance value and to release said vtrunk sleeve relay, and means in said one main trunk cooperating with said make-busy jack in `busy condition, said busy means of said one trunk including relays cooperating with said make-busy jack in busy condition to operate said answer and said busy lamp signals, and restoring means responsive to the opening of the estabe lished connection at the subscriber line end for releasing, first, said answer lamp andthen, after a predetermined interval, said busy lamp.

15. I'n a telegraph exchange system according to claim 10, wherein said one of said main trunks comprises means for connecting ground potential to one of the conductor circuits of said testing trunk when said established connection is opened at the subscriber line end of the established connection, to reoperate, in turn, said operable device and said signaling element whereby the hashing condition of said signaling element is changed to a steady condition to indicate that the telegraphie message communication is concluded, and means responsive to the removal of said testing trunk from one said main trunk for restoring the testing trunk and said one main trunk to normal.

16. In a telegraph exchange system according to claim 10, wherein each of said main trunks comprises a sleeve relay normally operated when its associated trunk is in a busy condition, interconnected make-busy jacks, an answer lamp and a busy lamp signal controlled by said make-busy jacks when in busy condition, and means for maintaining the trunk busy during the busy condition when the sleeve relay is given an opportunity to release, and said testing trunk comprises switching means, a plurality of relays, one relay of said plurality having a relatively high resistance value, and certain other relays of said plurality being normally operated during an established connection between said testing trunk and any one of said main trunks, means cooperating with one of said certain relays for normally maintaining the associated sleeve relay of said one trunk operated during the estblished connection between said testing trunk and said one main trunk, circuit means responsive to the operation of said switching means for releasing said certain relays successively, other circuit means responsive to the release of said certain relays for operating said relay of high resistance value, a sleeve conductor circuit in said testing trunk and said one main trunk connected thereto effective during its open condition interval created between the time of operation of said switching means and the complete release of the last operated of said certain relays to operate said high resistance relay and to give an opportunity to release to said associated sleeve relay, a guard signaling element responsive to the operation of said high resistance relay, and circuit means in said one trunk responsive to the operation of said switching means for releasing said busy lamp signal said release being effected after a predetermined interval that said switching means remains in an operated position.

TOLA A. MARSHALL.