US1799644A - Telephone system - Google Patents

Description

April 7, 1931. F. A. ROOME 1,799,644

TELEPHONE SYSTEM Filed Aug. 25, 1929 2 Sheets-Sheet l my lNl/ENTOR FA. Room:

9- r I 6 ATTORNEY April 7, 1931.

F. A. ROOME TELEPHONE SYSTEM Filed Aug. 23. 1929 2 Sheets-Sheet 2 C /NVEN7Z7R ATTORNEY f," A. Room:

m2: 3BR

Patented Apr. 7, 1931 "mt STATES PATENT OF E FRANK A. no'oivinor Anrrwnnr, BELGIUM, l ssre von ro ELECTRIC 'GOM- V i PANY, incqnrcnnrnn, or new; cnx,

Y, A c rce-Arron or" NEW YORK,

TELEPHONE sYsrEcM i Application filed August 23, 1929,6eria1No. 387,846, and in G'Ieajt Britain rumba 1e, 192s,

v ,Thisinvention relates to switching trunk circuits for at toll operators positions for selectively extending incoming toll lines to automatic and manual exchanges. I

An; Objectof the'invention is'to increase the number i of outgoing switching trunk groups, and the numberv of trunks in-each greupythat are directly'accessible at a single .tolloperators position andat the same time effect economies in the amount of apparatus and space required for carrying out the necessary function's.

In attaining this object the switching trunk circuits terminate in finder switches and the invention providesqfor continuous hunting by these switches at. the will of the toll operator. The finder switches are of the homing type, this rendering it possible to apply the principle ofgrading to the 'finder multiple and thus reduce the number of out. going trunks to aminirnumi The invention also permits the number-of directions and the number of trunksoutgoingin eachdirection to be unrestricted and governed only by, the

traific' conditions, and-moreover it permits the trunks of any or all of the groups to be dis tributed in any order. Consecutive or otherwise, around the finder banks.

' According to one feature of the invention veach swltchlng trunk circuit terminates in a finder switch having access to'a plurality of groups of outgoing trunks and means'is provided which, 1n response to an operation on the'part of the tolloperator, causes the finder switch to hunt until it engages an idletrunk in a wanted group of outgoing trunks,

According to a further feature a preparation swltching clrcuitis provided overiwhich a connection is adapted to be first made to an idle outgoing trunk extending to a wanted 4 exchange the connection being subsequently transferred to a regular switching trunk circuit under the operator7s control.

The accompanying drawings Show four embodiments of thepinvention but it will be understood by those versed inthe art, that various other changes may be made without departing from the spirit of the invention,

Fig. 1 shows a jack-ended'switching trunk circuit provided with direction keys,

"tion' keys DK DK etc.-

' corned, the number of directions andthe 1.1111 1- ,berof trunks outgoing in each direction are i unrestricted and determined only by thetrafto adistant exchange.

[,Fig; 1a shows a svs i teh-ingtrunk extending Fig. 2 shows a cordless' switching trunk circuit and preparationcircuit provided with direction keys.

Fig.- 3-shows a ack-ended switching trunk circuit provided with adial-eoperated coina dial operated marking switch. 7 v v Referring now to Fig, 1 this circuit shows a toll switching trunk circuit TST originating in an individual jack TJ at the toll board andterminating in the brushes a, b, c and d ofa trunk finder TF Three relays J hr, Clr,

Slr are associated with the trunkfinder TE and three relays PM", Sim Ogr are common to all the switching toll operators position.

The are of the finder runk circ'uits of a given trunk outgoing to a manual or automatic exchange. The a, b and cgterminals aremult pled th ughout agroup of fi ders at two or ator'has a strip of simple ush button directhese direction keys,after a toll plug TPhas been inserted in the jack TJ of a switchin trunk, the finderTF ofthatswitclling trunc hunts and-stops on the first free outgoing trunk OJ to the exchangein'dicated by the direction key which has been pressed.

The circuit. provides; for continuous huntting so long as the direction key remains pressed. I

' The finder has a'horne. position which makes it possible to apply the principle of grading y presslngl, one of to the finder multiple and thus reduce the number of outgoing; trunks to a. minimum. 7 So far as the operation of the circuits con fie conditions. Moreover the circuit does not demand that the trunks to a'p articular diIGC-r.

'tioll sha be, spaced, or grouped inany partic has sets of terminals to each of which is co-nnected a,

operate at this moment.

ular sequence. The only condition is that the d terminals of all the trunks in a given direction shall be strapped together. Signalling from the called exchange takes place over the a brush of the finder.

When the plug is withdrawn the whole circuit restores to normal.

Giro wit operation When the toll operator plugs into the switching trunk circuit jack TJ, the sensitive relay J h1- operates over both its windings in series with the cord circuit sleeve relay S1. The resistance of the windings of relay J ho" is such that the relay Sr in the cord does not 7 At its left-hand front contact J hr prepares a circuit for the powermagnet P of the finder and at its right-hand contact prepares a circuit for relay Clr.

' The operator now p esses one of the direction keys DK DK etc., according to the exchangeto which the toll switching connection'is to be extended. The left-hand contact of key DK completes the circuit for the power magnet P which starts hunting, and the righthand contact of the key connects the test relay Ptr to the d terminals of all trunks outgoing in the required direction. When the brush carriage arrives at the terminals of a free trunk, the test relay Ptr energizes having found potential over the right-hand con-' tact of keyDK, brush d of the finder, outer right backcontact of relay Clo", brush 0, and the sleeve relay Tar of the trunk circuit. At its front contactrelay Ptr closes a circuit for I its low resistance left-hand winding in series with the slow operating relay Sh'r thereby making the c terminal busy. Relay Shr operating energizes relay Cg?" which in turn energizes Clr via right-hand front contact of relay J hr. Relay CZr locks over its ownfront inner right-hand contact. Relay CZ?" permanently opens the circuit for the power magnet,-

connects the tip and ring from the jack through to the outgoing trunk, disconnects the d brush and common test relay PM" from the 0 brush, and connects the latter to the marginal relay Sh". The operation of Clo" releases relaysPtr, Sh? andQr r.

The equipment connected to the 0 terminal of the outgoing trunk may-vary according to the requirements of the circuits in the distant exchange.

In the case shown in Fig. 1a of the drawing, high resistance relay Tar, shunted by the lower resistance R, energizes in series with marginal relay SZr when the trunk is picked up by the finder TFL Marginal relay SZr also operates which in turn operates relay S1 of the toll cord circuit to light the supervisory lamp SL which indicates to the toll operato that an outgoing trunk has been connected to whereupon she may release the key DK.

Operation of relay Tar completes a circuit to operate relay 2 in the trunk circuit which can be traced from battery, right-hand winding of relay 2, inner normal contacts of relay 3, lower left-hand winding of repeating coil i, lower right-hand winding of repeating coil 5, winding of polarized relay 1, contacts of relay Tar, upper right-hand winding of repeating coil 5, upper left-hand winding of repeating coil l, outer normal contact of return operates relay 3 which reverses battery l and ground with respect to the terminals of polarized relay 1, which relay thereuponoperates to close an obvious energizing circuit of relay To? which relay in operating opens the low resistances-hunt around the high re-a sistan'ce relay T m, thereby increasing the re sistance of the circuit including marginal relay SZr to a point where it releases, thereby releasing relay Sr in the cord circuit and extinguishing the lamp SL as an indication that 1 thecalled subscriber has answered.

lVhen'the called subscriber hangs up relay 8 releases which in turn releases relay 3 to again reverse the current flowing through polarized relay 1,'which relay thereupon releases which releases relay T61". This again shunts relay Tar and lowers the resistance of the circuit including relay Slr which again operates to close the circuit ofrelay Sr and light the supervisory lamp SL in the toll cord 'as an indication that the called subscriber has hung up.

The release of the switching trunk circuit TST is effected by withdrawing the plug TP from the jack TJ thus releasing all relays of. the circuit. A circuit is then closed over the outer left-hand back contact of relay Ch", lefthand back contact of relay Jim and the oi normal contact INT of the finder for the pewer magnet P, to cause the finder to rotate until it reaches the home position which is marked y the opening of the oit-normal contact INT.

Referring'now to Fig. 2 this shows a cord less toll switching trunk circuit TST and preparation circuit PC. The preparation circuit is shown in the upper part of the drawing the toll operators position being equipped with one preparation circuit only. The switching trunk circuit proper occupies the lower part of the drawing and each switching trunk is permanently associated with a particular toll line TL to which it may be connected by means of the holding many switching trunks as toll lines.

-'I he itun'cti on of itheswiltohing trunk zcircu i't is to establish a connection fromzthe tol l I'line to a distant ananual or automatic exchange.

"ilrheifun'ction' of the preparation a'ciircuit isto prep arera *connection' to: a manual .01 .aiito- :rna'tic exchange and later 'lun'cler the control of the :tol'l operator ito iiiransfie'r this rcoiinec iti'on to the switching trunk and to'll dine for i which it Jhaskbeen iprepamecl, :as soon :as these latter have hecome :Eree fromitaheir ipre iious connection. effecting Ethis imans fer, the apnepazration switchnnaintaims the connection aoirertth'e idistanlt exchange-and 'rnarksthe 'terminal on which the preparation lfinder ,is standing I'm the rposition .inultiple. The switching :trimk' finder then hunts :for the markedrte'nininal takes over'athe iprepared iCQIJiEIBGtIlDll zaffter which the preparatiomcir- -cuit is mestoredtonomnal.

is The sw itchingg trunkcircuits and preparaztion circuitzterminate Finthe brushes-of -:trunk finders TF, PF having tlflfiisets zo ftenininals Ito 162Gb of "which is connected a trunk -ou tgozinglto n manualnorzantomaticexchange; :The

$ 40, I) iandvc, terminals are annltipled' throirghout .agroup of ifinders, butithe ail-rand .e tersminals zare :HlllltlPlBd only over the finders abelongingutoja given operatorskpositione switching trunk :circuit -.contains two Q irelays thin and AGE? which control the circuit and there is also associated with it'a Signal- :ling'melay S'Zr'awhich may ibe eqtiippedimthe :toll position cor at the switch mac The preparation e:rr. c111t conta ns 'at'WO Bypr-essing one df-thesediretion keys-after I a holding key J H K or PHK 'fhas been throw-n, the finder-of the switching 'trunk enq gagedhuntsmnd stops on the firs't tfiree-out- -'goi-ng trunk "to the distant exchange, ind-ireared Hey the dir'e'ction hey -which has 'be'en depressed; The circuit prov-ides for een- The restoring of a key PHK or re- 'turns theswitching-circuit tomorinal anclain (1; switching "Wmi7c;-Referring"to Fig. 2,'i f it is desired *t'o,at "once; connect a laysfiPhrcand PM and aisign alliirg relay 1 4W,

tinuous hunting so lon g a's the direction key toll line such .as TL With aftrunlk men-is et,

the-operator throws *the l'ocliin'gij-unction CZWand'U'h randthe off normal contact INT holding key J :of the switching trunkiand itoll iline the vground at the router con-tact :oif

this ;key operates relay 37m" which prepares at its left-hand contact the circuit for the power magnet PTF of the switching trunk circuit finder and at its 'right-hand-contact connects up the battery 'forkrel'ay iClr;

The operator now presses one of the direc- 'tion -keys ID-K DIK etc., according to fth'e exchange to which the toll switching connection is to :be extended. The left-hand contact of the key DK completes, the I-circuit ":for the power magnet PTF which starts hunt- The right handcontact connectsfithe t'e'st relay Ptr tothe -Z :terrninals of allntrunks operating relay SM and thereby =1narks the terminal busy. Relay SM operating en- -ergizes relay Ggr Which in turn energizes 'iGZr 'WhlCh W-lll rema n locked over its owninner right-hand front-contact. Relay G Zr permanently opens the circuit of the power *magnet PTR connects line contacts itrom the holding key JHK to the a and Z9 brushes 'of fthe finder T-F disconnects the (Z and e brus'hes "and the commontest relay PM "from the -0 bru'sh' and connects the latter to relay -S'Zr', which operates in series "With the low resistance at the e terminalof the-trunk. VVhen and C91", While the lighting of the lamp SL outgoing trunkmay vary according to the requirements in the distant exchange and for purposes of illustration will be understood to be thesaine as shown in Fig, Tia andlclescribed in "C0I1I16Gl3l0Il with Fig. 1. 'Slgnal- 'l'ng is produced hy the operation and releasing of relay T61" under the-control of the supervisory relay 8 at the clistant ex changeand issuch that when relay Tb? 'operate'sfand at its back contact rem'oves the -indicates to the-toll' operator that the -outggoing tru-n'k has been connected whereupon "she-may release thedirection'key D'K;

The equipment at the 0 terminal of the shunt circuit to the high resistance winding or relay Tar, relay *Slr releases and extingiiis'he'sthesignalling llainp SL.

f The release of "the circui t is made by re-f' storing the holding keyJ-HK "which releases relay Jim" and thereby permitsrelayfClwto release. The power 'magnet PTF t'hen finds =afcircuit'Closed over the back contacts ot.

" SZroper-ates, i-t-li-ghts the signaling l-arnp 8L.

The operation oiCZr-releases relays PhgSh l of the finder so that the finder rotates until it reaches the home position which is marked byI the opening of the off-normal contact L T. T

' To set up a connection on the preparation circuit the operator depresses key PHK and a direction key DK. The preparation circuit operates to select an idle trunk in the desired direction in exactly the same manner as the toll switching trunk circuit the operation of which has been fully described, with the exception'that the connection from the 6 brush of thefinder PF to the 0 brush does not pass over a contact of relay Dbr. When an idle trunk is engaged the supervisory re lay Pp? energizes and lights the signalling lamp PL. 7

. 1 (2) Transfer of a connection from the preparation circuit to a toll switching trunk circuit-'As soon as the operator is ready to extend the calling toll line TL to the prepared trunk OJ she throws the key JHK of that switching trunk thereby energizing relay J hr, but does not again use the direction keys. Instead, the operator throws the transfer key TK which need not be a locking key as the transfer will take a maximum of 2 seconds to complete. The transfer key operates relays T1)? and Din". Relay DZ)? disconnects the 0 brush of all free switching trunk finders so that the finder which hunts for the preparation switch will not test the 0 terminal of, any free trunks. Relay T291 over its inner front contact connects the common test relay PM to the a brush of the preparation finder. At its left-hand front contact Tpr completes the circuit for the power .magnet PTF of .the toll switching trunk finder TF which had been prepared by the operation of relay Jhr. -At its right outer contact Tpr connects testpotential to the (Z terminal of the line on the position multiple.

.The switching trunk finder rotating finds this potential on its (Z brush when arriving at the marked terminal and passes this potential on to the narrow testing 6 brush which causes the finder to test and center in the regular way, the circuit to the test relay being closed over the 0 wire of the position multiple and the stationary e brush of the preparation circuitrand thence to relay Pt?" which operates. The operation of PM re sults in the opening of'the driving circuit and the operation and lockingof relay Clo" vof the toll switching trunk in the manner already described. \Vhen this occurs the connection is at onceestablished from the preparation circuit restores to normal as already described.

Referring now to Fig. 3 this shows a toll switching trunk circuit TST which is essentially the same as that illustrated in Fig. 1 except that the marking of a group of d terminals by the connection of the test relay PM is made by a step by step switch under the control of the dial at the toll position instead of by simple direction keys.

In the switching trunk circuit itself the only difference from Fig.1 is the addition of relay Gi which becomes necessary owing to the fact that the back contacts have to be provided for disconnecting the common stepping relay I87 from the switching trunk circuit. The relay CZr, now having less con tacts, can have a make before break contact for locking and a common wire from its resting contactto the front of relay Sh?" for operating, the multi-contact relay Cg?" thus becoming unnecessary.

The direction device in the present circuit comprises the step by step switch S and five relays Z67, Z01", Rm", I81, and P87, all of which are common to the position. A feature of the step by step switch circuit is that it permits without any change of connections the dialing of one or two digit numbers. If

only single digit numbers are used, the

switch permits the selection of 10 different directions, but if both 1 and 2 digit numbers are used, then there may be selected up to 19 directions, the numbers corresponding to these, directions being 1 to 9 and 01 to 00.

Circuit operation.

The operation of the switching trunk circuit itself will not he described in full as it is practicallythe same as. that of the arrangement illustrated in Fig. 1 which has been fully described.

When the toll operator has plugged into the switching trunk ack TJ, the listening key LK and the dialing key DK of the toll cord circuit are thrown. The dial D is directly connected with the common position stepping relay Is?" which operates .over he back contacts of relay Cl r and energizes the slow releasing relay Rm". A. dialing tone or signal is required to indicate the connection of the stepping relay because the stepping circuit,- being individual to the position, is always ready for service when the operator begins to set up a toll switching connection. The relay Rm" releases so slowly that it remains operated throughout the dialing of the digits. At the first impulse produced bythe dial, relay Isr makes its back contact and over the front of Rm" it energizes Zer and Zcr in series. Z01" is another slow releasing relay which will only release when relay Tswoperates for the last time at the end of each series of impulses.

"Relay Z09" at its right-hand front contact energizes the step by step switch magnet SM, andlocks over its left-hand front contact to the interrupter springs I of the switch magnet SM so as to ensure the completion or the step, no matter how short a time relay Isr remains on its back contact. As soon as the magnet SM is fully energized and has opened its interrupter springs I and relay 187* has also energized again, relay Zer falls off openingthe circuit for the magnet SM, which makes its first step. I This is repeated for each impulse of the digit.

When the last impulse has been sent, relay Isr remains operated, and permits relay. Z01" to, release. Relay Zcr provides at its; back contact a circuitfor relay P87", via the brush B of the step by step switch. Relay PST at its right-hand contact closesthe circuit for the power magnet I of the finder TF and at its left-hand Contact connects the common test relay Ptr over the brush C of the step by step switch to the group of (1 terminals belonging to the trunks of the direction required. I w The trunk finder then continues hunting until a tree trunk OJ in the required direction is. found, in the manner described in connection with Fig. -When this has happened, relays PM Shr, Clr and Clir energize and at its back contact-s relay 0Z disconnects relay 181" fromthe switching trunk circuit and switches thelatter through to the selected trunk. The operator receives the signal on lamp SL as previously describedand may now proceed immediatelyvto dial out to the distant exchange if that exchange is automatic, otherwise she will restore the,

dialing key and proceed further with the call in the regular manner.

. hen relay (ll gr released relay I871 the latter relay opened the circuit of relay R77" which at its back contact provides a circuit tor the step by step switch magnet SM over the arc A and the interrupter springs I of the magnet to restore the switch to itshome position. When single digit dialing is used,

terminal 10 can be used for a direction on the arc C while on the arc B is will be stra ped to terminal 9. V

W on two digit dialing is to be used, the wiring of the arcs B and C will be as shown onthe drawing. If thefirst digit: dialed is i to the relapse of relay Z01" will operate relay Psr and complete the connection as described above. If the digit is 0, the stepby step switch will stop with the brushes on terminallO and relayPsr'will not become energized, but the circuitv will wait for a second digit to be sent in; To this position in the arc B an optional waitinglamp WDL may be wired which lights to remind the operator that a further digit is being waited for. The second digit may be any digit frornl to O, thus givin a total of 19direct1ons. ,When relayZcr fa ls off after the second digit,it

finder hunting.

will. then operate relay; and start the Referring How e Fig) 1-, this shows a ton switching trunk circuit TST; and prepara tion circuit PG essentially the sameasthat shown in Fig. 2 except that the marking of a group or" e terminalsby' the connection of relay Ptr is madeby a stepby step switchS underthe control of the 'dial at the tollposition in the manner described with reference to Fig. 3 instead ofbysimple vdirection keys in th switching trunk and preparation'cir cui'tsf The only other difierence consists in the addition of relays C l r and Pl r respec-' tively which become necessary owing to the fact that the back contacts have to be pro vided for disconnecting the common 'stepping relay Isr'from the switching and prepa ration circuits. RelaysCZr and PZr now having these contactsv can havev a make. before break contact for locking and a common wire from the resting contact to the front contact becoming unnecessary;

of relay Shr for operating, relayCgT'thus Circuit operatz'ba The operation of this arrangement will not be described in detailsince it is thoughtthat the operation will be evident after a consider ation of the descri tion .ofthe operation of the arrangements s own in Figs. Q a nd 3.

" (1) Toll switching tmmk.+After.throw Y ing the junction holdin'g key 'JI-IK and thereby energizing relay- J M, thetoll operator throws her listening and dialing keys, 5

JIKan d DK, thereby closing a circuitfor the commonsteppingrelay In of the stepby I step switch S'over theJspringspf the dial D. One or two digits are now dialed into the switch S and on the cessation of the impulses acircuit is closed for relay r89 which com- Y pletes the circuit. for the driving magnet PTF of the finder TF. At the same time the common test relay Ptr is connected to the group of e terminals belonging to the trunks of the direction required, The trunk finder continues hunting until a free trunk OJ is found, and when this. happens relays PM, SimCZrand Gl r energize, thefinderis arrested, the switching trunk is connected to the 1 a and b brushes, and the switch S is restored, all in the manner already fully described with reference to Fig. 3-. I

' (2) Prepamzf'z'mcircuitp il o set a connection on the preparation" circuit the toll operator depresses the preparation holding key PI-IK, the dialing keyDKand the preparation listening keyPLK, and then dials one or two digits characteristic of the wanted direction. The reparationjfinderPF opera ates under the control ofth'e switch Sto select an, idletrunk in the wanted direction inthe same 'manner as the trunk. finder TF Transfer 20; comi ectidn leesame operation which has been described with reference to Fig. 2. As soon as the toll line and switching trunk circuit to which a prepared connection has to be transferred become free, the toll operator throws the junction holding key J HK and the transfer key all free switching trunk finders so that the finderTF will not test the 0 terminal of any free trunks. Relay Tpr connects the common testrelay Ptr to the 6 brush of the preparation finder PF, connects test potential to the d brush of the preparation finder PF to mark the selected trunk in the d bank of the trunk finder TF, and completes the circuit for the power magnet PTF of the trunk finder TF which was prepared by relay Jim which operated when the key JHK was thrown. When the (1 brush of thefinder TF arrives on the marked terminal this test potential 7 passes over the centering brush 6 of the finder TF, the centering brush 6 of the finder. PF, and the inner right-hand front contacts of relay Tpr to the test relay PM", which operates and causes theresponse of relays Shr, Clr and Cl r. When this occurs,

the connection is at once established from the toll'line to the distant exchange, this being indicated by the lighting of lamp SL due to theoperation of relay SZr in parallel with relay Pp?" over the a wire of the engaged trunk. The toll operator on receiving this signal releases the transfer key TK and the key PHK, thereby initiating the restoration to normal of the preparation circuit.

What is claimed is:

1. A circuit arrangement for automatically setting up toll switching connections from an operators position to distant exchanges in which a toll operators position V is equipped with a plurality of switching trunkcircuitseach terminating in a finder switch having access to a plurality of groups of outgoingtrunks and in which means common to all said switching trunk circuits is provided which, in response to an operation on the part of the operator, sets in operation the'finder switch of a switching trunk circuit takenfor use by said operator and determines the group of outgoing trunks to be tested by said. finder switch, characterized by the provisionof a preparation switching circuit including a marking switch for making a connection is adapted to be first made to an idle outgoing trunk to a Wanted exchange, and also including means for subsequently transferring said connection, under control of the operator, to a particular switching trunk taken for use.

2. A circuit arrangement for a telephone system, as claimed in claim 1, in which said preparation circuit and said switching trunk on the part of said operator. TK. The transfer key operates relays DZM', Tpr. Relay Dbr disconnects the a brush of circuits each terminate in a finder switch having access to groups of outgoing trunks ex- 8. A circuit arrangement for telephone systems as claimed in claim 1, in which said preparation circuit and said switching trunk circuits each terminate in a finder switch having access to groups of outgoing trunks ex-. tending to said distant exchanges, and in which means common to said switching trunk circuit is provided for causing any one of said finder switches to hunt continuously until it engages an idle outgoing trunk in a group of trunks determined by an'operation on the part of said operator.

4. A circuit arrangement for a telephone system as claimed in claim 1, in which said preparation circuit and said switching trunk circuits each terminate in a finder switch having access to groups of outgoing trunks extending to said'distant exchanges, and in which means common tosaid switching trunk circuits is provided for causing any one of said finder switches to hunt continuously until it engages an idle outgoing trunk in a group of trunks determined by an operation on the part of said operator and in which said common means is adapted to close a test circuit common to a wanted group of outgoing trunks to restrict the finder switch to a hunting movement in that group. j

5. A circuit arrangement for a telephone system as claimed in claim 1, in which said preparation circuit and said switching trunk circuits each terminate in a finder switch having access to groups of outgoing trunks extending to said distant exchanges, and in which means common to said'switching trunk circuits is provided for causing any one of said finder switches to hunt continuously until it engages an idle outgoing trunk in a group of trunks determined by an operation on the part of said operator and in which said common means is adapted to close a test circuit common to a wanted group of outgoing trunks to restrict the finder switch to a hunting movement in that group, said test circuit extending over terminals of a fourth contact level, all of which are connected together in the same group.

6. A circuit arrangement as claimed in claim 1 in which a testing relay set is provided common to all the finder switches of said operators position.

7 A circuit arrangement for a telephone system, as claimed in claim 1, in which said preparation circuit and said switching trunk circuits each terminate in a finder switch having access to groups of outgoing trunks extending to said distant exchange and in means:

. system, as claimed in claim 1, in which said preparation circuit and said switching trunk circuits each terminate in a finder switch having access to groups of outgoing trunks extending to saiddistant exchange and in which means including a direction key for each group of trunks accessible to the switch and common to the operators position is provided for causing any one of said finder switches to hunt continuously until it engages an idle outgoing trunk in a group of trunks determined by an operation on the part of said operator, said direction keys being adapted to close a test circuit common to a wanted group of outgoing trunksto restrict the finder switch to a hunting movement in that group, to close a circuit for the driving magnet of the switch taken for use and to connect a common test relay to the common test circuit 9. A circuit arrangement 'for atelephone system as claimed in claim 1, in which said preparation circuit and said switching trunk circuits each terminate in a finder switch having access to groups of outgoing trunks exsetting of said dial controlled switch.

10. A circuit arrangement for a telephone system as claimed in claim 1 in which said preparation circuit and said switching trunk circuits each terminate in a finder switch having access to groups of outgoing trunks ex tending to said distant exchanges and in which means comprising a dial and a switch controlled thereby and common to all the finder switches at said operators position is provided for causing any one of said finder switches to hunt continuously until it engages an idle outgoing trunk in a group of trunks 7 determined by an operation on the part of said operator.

11. A circuit arrangement for a telephone system as claimed in claim 1, characterized in this that said preparation circuit and saidswitching trunk circuit each terminate in a finder switch having access togroups of outgoing trunks eXt-endingto said distant exchanges, and by means comprising 'a dial and a switch controlled thereby for starting a selected finder switch andfor connecting a test relay common to the operators position to c-ontrolled'swvitch.

' V 12. A circuit arrangement for a telephone system as claimed in claim 1, in which said preparation circuit and said switching trunk circuits each terminates in a finder'switch having-accessto groups of outgoing tr mks extendi-nggto said distant exchanges and which means comprising a dial and a single motion switch controlled thereby by a single series of impulses or by the cumulative elieet oi? two or more series of impulses, is provided for causing anyone of said finder switches to hunt continuously until it engages an idle outgoing trunk in a group of trunks determined by the setting of said dial controlled switch. I i

13. In a switching system, an operators position, a finder switch associated with said position for connecting said position with an idle line in a particular one of a plurality the-"common test circuit of the group of trunks determined by the setting of said dial of groups terminating in said switch, means controlled by said operator for causing said switch to establish such a connection, a second finder switch for connecting said position with said lines, and operator controlled 1 means to cause said second switch to take a position determined by the setting or said first switch to transfer said connection from said first to said second switch.

14. In a switching system, an operators position,,a finder. switch associated with said 3 position for connecting said position with an idle line in a particular one of a lurality of groups terminating in said switci, means controlled by said operator for causingsaid switch to establish such a connection, a second finder switch for connecting said position with said lines, and operator controlled means to cause said second switch to take a position determined by the setting of said said second switch.

15. In a switching system, an operators position, a finder switch associated with said first switch to. establish said connection over 7 position for connecting said position-with an 1 idle line in a particular one of a plurality of groups terminating in said switch, means controlled by said operator for causing said switch to establish such a connection, a second finder switch for connecting said position with said lines, and operator controlled means to cause said second switch to take a positiondetermined by the setting of said first switch to establish a second connection therefor between said position and said line. 16.In a switching system, an operators position, a selector switch forconnecting said position with a particular one of a plurality .oflines terminating in said switch, a second switch, and means for operating it in accordance with the setting of said first switch to transfer the connection between saidposition and line to said second switch. i

17 In a switching system, an operators position, a plurality of finder switches, a plurality of groups of lines multipled in the banks of said switches and accessible to said position, means controlled by'the operator for determining the'particular group of lines 7 to be tested by one of said switches and to cause said switch to hunt in said group for and hold the first idle line of said group, and other means controlled by the operator for causing another of said switches to hunt for said seized line and stop thereon.

In witness whereof, I hereunto subscribe 7 my name this 22nd day of July, 1929.

FRANK A. ROOME.

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