US1737930A - Telephone system - Google Patents

Description

Dec. 3, l1929.l C, E, LOMA* 1,731,930

TELEPHONE SYSTEM Filed March 12, 1927 2 Sh'eets-Sheet 1 Inuen nr ElarencsELamax TELEPHONE SYSTEM l Filed March 12, 1927 2 sheets-Sheet 2 TRE.

[1m Clarence E Lnmax -15 lowed.

Patented Dec. 3, 1929 UNITED STATES PATENT. OFFICE CLARENCE E. LOMAX, or OAK FAn-x, ILLrNois, AssIeNoR .fro nnsnnvn HOLDING COMPANY, or KANSAS CITY, Missonnr, A ConPoRAfrmN or DELAWARE TELEPHONE `sYsfrrNr Application filed March 12, 1927. Serial No. 174,734.

yThis' invention relates .to telephone systems in general, but more particularly to toll switching systems in which all toll connections within a certain area are establish-ed and supervised from a main toll boar-d.

In telephone systems extending over an area incinding several more or less widely scattered communities er exchanges, inter-connected by toll or long distance lines, the practice ot completing and supervising` all connections between the exchanges ot the difieren-t communities, as well as all connections to outside points, 'from the main toll board located. in .one of the exchanges is oft-en advantageously iol- An-obvious advantage gained by this practice is that it obviates the necessity oi' employing a toll operator at 4each otthe separate exchanges. Furthermore, .the clerical work concerning the `charges for tollv connections'is concentrated at one .central oiiice. In large telephone systems of this kind for well know-n `economical reasons each exchange is not connected directly with everyother eX- change in the system, but is usual-ly connected 23 Aonly with one or two ot `the nearest exchanges.

For this reason special consideration must be given to the methods employed in carrying out Y above n'actice .in orderthat it may be done the most economical manner, both in regard o yto the amount ot equipment needed and in regard to the trunks used.

The main object of this invention consists in the provision ot improved circuits for use in a telephone system as described above Wherethe toll operator may be called from any one of the exchanges over one of the trunks extending to the exchange in which the toll board is located and whereby the toll operator may then control the establishment oi the dez tn 14o sired connection over the most direct .route and maintain supervision thereof over that saine trunk line.

The object of the invention and the various features thereof, will be described in detail '45 in the following specifications with the aid of the accompanying drawings which illustrate by means ot the usual schematic circuitdiagrams yand trunking diagrams a section of a telephone system embodying the ,principleso't' 5D the invention. lt is understood ol' course that the invention is in no Way limited to any particular system, the one show-n in part in the drawings having been chosen merely for illustration.

The drawings to be most easily understood 55 4should be placed with Fig. 2 to the right of Fig. l, and with the corresponding lines in alignment. The apparatusshown between they dotted vertical line in Fig. l and the dotted vertical line in Fig. 2 isl located in one eX- 60 change, which will be referred to as exchange A. The exchange A is an automatic exchange serving the subscribers of one commun-ity, and

'calls within this community are all established automatically without the aid of an operator. 65 The switches for setting up these local connections have been shown diagrammatically. For example, the local subscribers substation A terminates in the individual line switch LS, .which Ihas access together with other similar lineswitches to the local selectors, such as selector S. :lnthe banks of the 'loca-l selectors, access is had tolone or more groups of connectors, each group being accessible `in a separate level. Each group of connectors has access to a separate group of subscribers lines. The connector C shown is one oi the group having access to the group of subscribers lines including the line t-o subst-ations A2.

Exchange A is connected with the exchange ot another-community (which will be referred to as exchange B) by one or more toll trunk lines, such as the one comprising conductors 252 and 253. At this latter exchange, the main tol-l board is located from which all toll S5 connections :tor the system are completed. ln the exchange A, at the trunk relay group TEG, this trunk line is divided into two branches. The outgoing branch, that is, the branch over which connections to the toll board are extended, comprises conductors 22, 23, y2st, and together with the corresponding branches of ythe other `trunks to the exchange B is accessible in a particular level in the 95 banks of the local selectors. The incoming branch, lthat is, the branch over which the toll operator vsets up toll connections, comprises conductors 22', 23 and 24 and terminates in the incoming selectors. The corresponding me branches of the other trunks likewise terminate in similar incoming selectors.

Exchange A is alsovconnected with the exchange of another community (which will be referred to as exchange C) by one or more toll trunk lines, such as the one comprising conductors `2 and This trunk lineterminates at exchange A in the line switch LS by way ot' the impulse repeater R, and is Yaccessible with the lother similar trunks from exchange C in a particular` level in the banks or" the incoming selectors, such as selector S. In the banks oi the line switch LS access is also had to the outgoing branches of the trunk lines extending to exchange B.

In a small community near the community served by the exchange Ar` a manual paystation is located. The line from this paystation terminates at the exchange A in the line- 'switch LS2 via the ringing trunk circuit- RTC, and is also accessible in the i'irst set ot contacts in a particular level in the banks of the incoming selectors. The test contacts of the other sets in this same level are multiply connected to ground. In the bank of the line switch LS2 access is also had to the outgoing branches ot the trunk lines extending to the exchangelits banks being multipled with the banks of the line switches such as line switch LS.

Those `levels of banks of the local selectors in which access'is had to various groups ot connectors are multipled with the corresponding levels of the incoming selectors, so that the local selectors and incoming selectors have common accessto therconnectors for completing local connections. The other levels are not multipled between the two kinds of selectors.

The line switches LS,LS, and LS2 in the exchange A may be of any suitable type, s ch as the well known rotary type. The selectors, both the local selectors and the in coming selectors, and the connectors may be, tor example, of the well known Sti-owger vertical and rotary type. The repeater R may be like the two-way repeater shown and described in detail in the John Vicks Patent No. 1,643,797, granted Sept. 27, 1927. The trunk relay group TRG forms a particular part of this invention and will be described in detail subsequently. The ringing trunk circuit RTC will also be described in detail in the following descriptions.

At the exchange B, the trunk lines from the exchange A terminate at the main toll board in jacks, such as jack J. Individual to each trunk is a call lamp, such as the lamp L, a disconnect lamp, such as the lamp L', a dialling keyJ such as key K, for associating the dial I) with the trunk, and a group of relays for controlling the signalling, the dialling, and the supervisory circuits. The operator is also provided 'with cord circuits (not shown) which may be of any suitable type having ground potential connected to the sleeve conductor. The trunk lines extending between exchanges A and B are composited in the usual way by means of toroidal compositing coils, shown conventionally, to providea. dialling circuit over onev wire of ,the trunkline, and also another circuit over the other wire that may be used for telegsible in the banks of local seletcors via repeaters in the well known manner.

With the general object of the invention, the layoutoi' the system, and the apparatus shown, in mind, a further understanding and appreciation of the invention may be gained from a detailed description of the operation thereof. To describe the operation, it will lirst be assumed that a Vsubscriber served by the exchange C wishes to be connected with the manual pay station P.

To obtain this connection, the calling subscriber at the exchange C removes his receiver' and dials theV toll or long distance number, which causes automatic switches in the exchange C to connect with and extend the connection over one of the trunk lines extending to exchange A, such as, for example, the one comprising conductors 2 and 3. The extension of the connection to the exchange A over this trunk line causes the lineswitch LS to operate in the usual manner to select an idle trunk accessible in its banks. It may he assumed that the trunk selected by the lineswitch LS is the one Colnprising conductors 22, 23, and 24. In selecting this trunk, lineswitch LS extends the connection to the trunk relay group TRG and also connects ground potential to release conductor 24 and to release conductor 34 via conductor 14 thereby marking this trunk line engaged to all switches having access thereto.

By the extension of the connection to the trunk relay group TRG, a circuit is closed .for line relay 201i including the two trunk conductor in series. Relay 204:, in operating, closes the circuits for release relay 203 and an auxiliary relay 202 at armature 218, and also prepares a'circuit for control relay 201 at armature 212. Release relay 208 energizes and at armature 210 connects ground to release conductor 24 to maintain the lineswitch LS operated and maintain the trunk in question marked engaged. At armature 209 a point in the talking circuit is closed, and at armature 211 ground potential, which is normally connected to `conductor 255 by way of armature 228 and its resting contact and the winding of impulsing relay 221, is discon -ipeaeao Vdoes armature 203 come to rest in en0'affement with its Working contact and maintain the circuit of relay 261 closed. During this interval battery potential is connected to condnctor and closed circuit ina f be traced which extends from batterj7 through resistance 205, resting Contact and armature 206. working 'Contact and armature 211, conclue tor 255, through the upper right hand coil YT2, over the upper trunk conductor 252 vto the main toll board at exchange B, and there through the upper left hand coil T11, conductor 257, armature 272 and the resting contact, through the lower winding of signalling relay 265 to ground. Relay 265 energizes and closes a locking circuit for its upper Winding in series With the call lamp L at armature 273. The lamp L is lightedI and notifies the operator of the incoming call.

After the lapse of the aforesaid interval, relay 201 iscon-tinuously energized and there,- e operates and prepares a circuit for relay 22.; at armature 207.A and at armature 20G again connects ground potential in series with iinpulsing relay 221 to conductor 255, dis-- connecting battery through resistance 205 therefrom. Thus it `is 'seen that relays 201, 212, and 203 have functioned to substitute battery potential for the ground potential on conductor for a short time in order to cause the lighting of lamp L by energizing relay 265. The reapplication of grof-unl potential to conductor 255 reconditions the circuits for dialling as Will be described presently. y

To answer the call, the toll operator at the toll board inserts the answering plug of an idle cord circuit into the jack J. A circuit is thereby closed for sleeve relay 264 from ground by Way ofthe sleeve ofthe plug of the cord circuit used, sleeve of jack J, holding conductor 277, through the Winding of relay 264 to battery. Relay 261i operates and vat armature ,271 opens the circuit of the upper winding `of relayT 265 and the lamp L thereby causing relay 265 to deenergize and the lamp L to be extinguished. At armature 272 a circuit is prepared for dialing and later for giving the disconnect signal, to be described later.

After inserting the plug of a cord in the j ack J, the operator will throw her listening key and inquire the Wants of the calling subscriber. After receiving this information including the name or the number of the Wanted subscriber, the tollA operator operates ling closed, for controlling the setting up of the desired connection. This circuit may be traced from battery in series with dial D, springs 275, Working contact and armature 269, Working -contactand armature 272, conductor 257, through the upper left hand coil T11, trunk conductor 252, through the upper right hand coil T2, conductor 255, armature 211 and Working Contact, armature 206 and the Working Contact, through the Winding of impulsing relay 221, resting Contact and armature 22S to ground. Impulsing relay 221 thereupon operates and closes a point in the talking circuit to be described later at armature 226, and at armature 227 closes a bridge across the trunk conductors 22 and 23', Which includes the left hand windings of repeating coil R3 and the upper Winding of the polarized relay 223. It should be noted that the louer polarizing Winding of relay 223 is energized from ground on conductor 24;. The

placing of a bridge across the conductor 22 and 23 closes the circuit for the line relay in the selector S thereby `causing the selector S to prepare itself for operation in the Well Vknown manner. The current iovv in the upper Winding of the polarized relay 223 at the time is in such a direction that this relay does not new operate. l

The toll operator nou7 dials the number of the paystation P, after which she again restores the key K to normal. As a result, springs y27 6 are closed and battery through the Winding of the supervisory relay 263 is substituted for the battery in series with the dial D. This causes relay 263 to operate and close a circuit for the supervisory lamp L at armature 27 O, causing the lighting of the lamp L.

In this example, the number of the paystation -P comprises only one digit. Responsive to the dialing thereof by the toll operator,

the selector S raises its Wipers opposite the level corresponding to the digit dialled, and then rotates its Wipers into engagement With the first set of bank contacts in this level.

1f the -paystation is -husy at this time, ground potential will be encountered by the test Wiper of the selector S', which Will canse the selector S to step to the next set of bank contacts. Since all the remaining sets have been artificially marked busy, the

selector S Will be stepped past the last set of contacts and give the operator the busy l i Zijl) signal, in the well known manner. It should be noted that connections to or tor the paystationP can only be completed from the main toll board, so if there is only one operator there, she will know beforehand whether the paystation P is busy or idle, and it busy, will notify the calling subscriber accordingly as soon she learns that such connection is desired. I y

It is assumed, however, that the paystalcion P is idle at this time. Then no ground potential will be present on the release conductor fiel, and the selector S will operate to extend the connection to the ringing trunk circuit RTC. As a result, ground potential is connected to release conductor 44 and 18 serially connected with conductors 24 and 24, thereby causing the cut-ott line relay in the line-switch LS2 to disconnect the normal ground and battery connections from the paystat-ion line. 'In extending the connection to the ringing trunlr circuit RTC, the circuit for relay 54: is also completed, this circuit including the bridge the trunk relay group TRG across conductors 22 and 23', now connected with conductors Ll2 and d3, respectively. Relay st operates and closes the circuit of relay 51. .Relay F1 operates and grounds conductor 44; at armature 56 so that the apparatus in exchange A associated with the connection may be maintained busy atter the called party answers until the operator releases the connection, as will be further described in later descriptions. At armatures and 57, the ringing circuit to signal the party at the paystation is closed, this circuit extending .from conductor 62, to which the grounded ringing generator G and direct ground are alternately connected,

resting contact and armature working contact and arma-ture 57, line! conductor 7, through. the ringer at the paystation P, line conductor', armature 55 and its working contact. armature 53 and its resting contact, through the upper winding of ring-cutotl relay 52 to battery. The ringer at the paystation is thus opera-ted intermittently until the call is answered.

l/Vhen the receiver at the paystation P is removed to answer the call, a directcurrent circuit is closed for relay 52 including the bridge at the paystation, whereupon relay 52 operates and closes a locking-circuit for itselt' at armature 59, at the same time connecting ground potential to the lower terminal of the upper winding oi relay 53. At armatures 53 and 60 and their working con tacts, the talkingl circuit is completed and at'the saine time a circuit for the reversing relay 53 is completed. Relay 53 operates and reverses the connections of relay V54e to the trunk conductors, thereby causing a reversal oi current in the upper winding of the polarized relav This causes relay 223 to op#V erate and close the circuit ot relay 222. Re-

lay 222 operates, shunting armature 226 at armature 229, shunting armature 227 at armature 230, and at armature 228 opening the circuit including impulsing relay 221 and supervisory relay 263 at the main Atoll board at its resting contact and closing the circuit of im pedance control relay 224 at its working contact. Relay 224i operates and closes a locking circuitv for itself at armature 234, prepares a circuit for controlling the disconnected signal, as will be described later, at armature 233, and at armatures 232 and 235 opens the shortcircuits around the windings of the impedance 225. Relay 221 deenergizes, but since its armaturesv 226 and 227 are shunted, the release of relay 221 produces no effect. Relay 263 at the toll board, in restoring, opens the circuit of the supervisory lamp L1, thereby causing the lamp L1 to be extinguished, which, notities the toll operator that the'called subscriber has answered. Y

The two subscribers may now hold conversation, the talking circuit Vextending from the exchange C over the trunk conductors 2 and 3, conductors 12 and 13 via the repeater R, through the lineswitch LS, conductors 22 and 23, through the repeating coil R2, conductors 222 and 232, through the repeating coil R2, conductor 22 and 23', through the incoming selector S', conductors l2 and 43, through the ringing trunk circuit RTC, line conductors 6 and 7 to the paystation P. The

toll operator also has supervision of a con-` nection over the trunk line comprising conductors 252 and 253 which are now connected via the winding oit' impedance 225 to the conductors 222 and 232. The inclusion of the windings of the impedance 225 in the circuit extending to the main toll board, prevents all but a very small amount of tall:- ing current from being shunted thereover, at the same time making it possible 'tor the toll operator to listen to the conversation.

At the termination oit the conversation, both subscriberswill replace their receivers. Then the calling subscriber replaces his receiver (assuming he is lirst to replace his receiver), the switches in the exchange C associated with the connection are released and the bridge across the trunk conductors 2 and 3 is opened. The opening olv the bridge across the line conductors 2 and 3 opens the circuit of the line relay 204e in the trunk relay group TRG. Y Relay 204 thereupon deenergizes and opens the circuit of relay 201 at armature 212, and opens the circuit oit relays 202 and 203 at armature 213. Relays 201 and 202 deenergize immediately and relay 203, being slow acting, deenergizes a short time thereafter. Due to the slow acting characteristic of Yrelay 203, battery through resistance 205 is again momentarily connected to conductor 255 but this has no utility in this particular type ot connection. Viith relays 201 to 204, inclusive, in a deenergized con- CTI Y sultn dition, ground potential is again applied to conductor 255 by Way ot armature 213 and the resting contact, Working contact and armature 233, through the Winding of relay 221, resting contact and armature 211, there byagain closing the circuit of relay 263 at the main toll board in series with relay 221. Relay 263, in operating, again closes the circuit of lamp L. The lighting of lamp L at this time indicates to the operator that the conversation has terminated and that one of the subscribers has hung up his receiver.

lVhen the called subscriber replaces his receiver, the bridge across the line conductors 6 and 7 is opened, thereby causing the deenergization of reversing relay 53. Re-

lay 5.3 in releasing its armatures again causes the current flow over the trunk conductors 42 and 43 connected to conductors 22 and 23 to be reversed back to normal, thereby causing the polarized relay 223 to restore its armature 231 to normal. The restoration or armature 231 opens the circuit of relay 222 which likewise restores its armatures to normal. Y

In response to the lighting ol1 lamp L, the operatorA removes the plug of the cord ircuit used from the jack J, thereby opening the circuit of the sleeve relay 264, and also the locking circuit of relay 262. Relays 262 and264 restore their armatures to norma-, and in so doing disconnect the supervisory relay 2,63 from conductor 257, again connecting ground through the lower Winding oil relay 265 thereto. As a result, relay 263 deenergizes and opens the circuit or' lamp L. At the exchange A, the line relay 221 also deenergizes and opens the bridge across the conductors 22 and 23 at armature 227, and also opens a point in the talking circuit at armature 226. Opening the bridge across conductors 22 and 23 opens a circuit of line relay 54 in the ringing trunk circuit RTC. Relay 54 deenergizes, and opens the circuit of relay 51 at armature 61. Relay 51 deenergizes and at armatures 55 and 57 again connects the line conductors 6 and 7 to the lineswitch L52, and at armature 56 disconnects ground potentialfrom the release conductor 44 and release conductors 18, 24', 24, 14, and 34 serially connected thereto With the following results: lineswitc'h LS1 again places the normal ground and battery connections to conductors 16 and 17; the selector SVrestores to normal in the usual manner, 4the energizing circuit of relay 224 as well as the polarizing circuit of relay 223 in the trunk relay groups TRG is opened, relay 224 restoring its armatures to normal; and the va ions ltrunk branches used in the connection are again marked idle.

Should he Qlled subscriber be the first to ieplacehis receiver, Vhe same operations would result, except that the operations re- "i in the replacement ot the receiver at the called 'paystation'would then precede receiver at the calling station.

calling subscriber' replaces his receiver iirst.

hns it is seen that the toll operator receives the disconnect signal as soon as either one the subscribers replaces his receiver.

From the description ofthe foregoing connection, itis readily apparent that any one of the subscribers in the exchange A can also establish a connection to the paystation P. For instance, should the subscriber at substation A Wish to establish a connection With the paystation l?, he likewise removes his receiver and dials the long distance number, resulting in the extension of a connection to the toll operator by Way of the lineswitch LS and a local selector, such as selector S, and they outgoing branch of a trunk line extending to the toll board such as the one comprising conductors 252 and 253 the. outgoing branch than by Way or armature 213 oi vfhich is also accessible in the banks of the' local selectors. All operations` concerning such a connection are identical to those described above.

t is also evident thatr a calling party. atV

the paystat-ion P can also obtain connection with any oi the local subscribers in the exchange A, or any of the subscribers in the exchange B in a similar manner. To establish such a connection, the subscriber at thc paystation P merely removes lhis receiver Which causes a connection to bel extended to the main toll board via the line switch LS2 an outgoing branch oi one of the trunks extending to the main toll board, such as the one comprisingconductors 252 and 253, as previously described.v After learning the `name or number of the Wanted subscriber, the

toll operator then sets up vthe connection by Way of al selector such as selector S5, anda connector such as connector C, if the call lis for subscriber in exchange A, or by vWay of one of the branches oit one 'of the' trunk linesv extending to exchange C such as the branch comprising conductors 32, 33, and 34, connected to conductors 2 and 3 via the repeater R. The repeater R repeats the impulses dialed by the toll operator to the automatic exchange C to control the setting up connection tothe Wanted subscriber in that exchange; y

Should a party at the paystation l?, or any subscriber at exchange Aor exchange B, lWish to obtain a connection 'With some one outside of the system or some onein the system not served by either exchange A or exchange B,

the call 'also extended to the toll operator in isc leading to the exchange serving the called party.

In the establishment of such a connection the operation of relays 201 to 204, inclusive, of a trunk relay group 'IRG is indentical to vthat previously described. However, it is obivous, that none of the relays 221 to 224 come into play (assuming that the call is extended over the trunk comprising conductors 252 and 253). In this case the talking circuit extends over the conductors 22 and 23. through repeating coil R2, conductors 222 and 232, armatures 232 and 235 and their resting contacts, through repeating coil R4, over the trunk conductors 252, and 253, through repeating coil R5, tip and ring ot jack J, and through the cord circuit used to the exchange serving the calling subscriber.

In this type of connection, the operations for giving the toll operator the disconnect signal in response to the replacement ot the receiver by the calling subscriber are some- What diii'erent than those previously described. IVhen the calling subscriber replaces his receiver atthe termination of the call, as in the previously described connections, relay 204 deenergizes and opens the circuit ct' relays 201, 202, and 203, and due to the slow-acting characteristic of relay 203, battery through'resistance 205 is connected to conductor 255 during the time that relay 203 holds up its armatures after relay 201 has released its armatures. This operation had no utility in the previously described connections, butin this case, causes the momentary energization of relay 261 at the main toll board, noting that in the establishmentof this type ot connection neither relay 262 nor relay 263 is operated since the dial D is not used and key K is not operated. Relay 261 operttes responsive to this momentary energization and closes the locking circuit tor itself at armature 267, and at armature 266 closes a circuitV for the supervisory lamp yL". The lighting ot' the lamp L indicates to the toll iperator that the calling subscriber has replaced his receiver. The other operations concerning the release of theapparatus used are similar to those previously described.

Toll connections to any of the subscrib- .n's .in the exchange A or exchange C or to the paystation P from distant points or from subscribers served by one of the other exchanges in the system may also be established. To establish such a call, the connection is .irst extended to the toll operator from the distant point or the calling substation in any Y Well knoivn manner. The toll operator, after learning the name or number ot' the Wanted subscriber, which 1t AWill be assumed 1s a subicriber in the exchange C, for example, in-

serts the calling` end of the cord used to an'fswer the call into the jack of anidle trunk extending to exchange B, for example Jack J. She then operates the dial key K and.. dials the number of the Wantedhsubscriber.'` The operations following are an identical to those previously described, except that no circuit is closed for relay 2211 when relay 222 isf' operated after the called party answers, since relay 201, as Well as relays 202,203 and 204, is

not operated. The talking connection in this case extends over trunk conductors 252 and 253, through repeating coil R4 through repeating coil R3, over conductors 22 and 23\ through the selector S to the exchange C and thc called subscriber by Way of a trunk suchV as the one comprising conductors 2 and 3.

This completes the description of the op-v exchange over said trunk line,vmeans at said irst exchange controlled over said trunk line for establishing a connection from said calling line tosaid called line, a signal at said second exchange, and means controlled by either party When he replaces his for operating said signal.

2. In Va telephone system,.a iirst and a second exchange, a trunk line connecting said exchanges, a calling and a called line, means at the lirst exchange for establishing a connection from said calling .line to said second exchange over said trunk line, means at said first exchange controlled over said trunk line for establishing a connection from said calling line to said called line, a signalat said second exchange, and means controlled by the called party when he removes his receiver and by either party when he replaces his receiver for operating said signal.

4 In a telephone system, alirst and a second exchange connected calling line in said lirst exchange, means for receiver .establishing a connection from said callingV by a trunk line, a

line to said second exchange oversaid trunk I line, a signal at said second exchange, means at said tirsU exchange for momentarily applying a certain potential to a conductor of said trunk line responsive to the extension or" said connection to operate said signal, a called` line, and means at said first'exchange controlled from said second exchange over said conductor for establishing atalking connection trom said calling line to said called line.

4. In a. telephone system, a first and a second exchange connected by a trunk line, a, calling hnemsa1d irst exchange, means fory ii iing a connection 'from said calling line to said second exchange over said trunk linev a signal at said second exchange, means at said first exchange for momentarily applying a certain potential to a conductor of said t i ik line responsive to the extension ot said Lotion to operate said signal, a. called line, means at said rst exchange controlled in said second exchange over said conf ctoif tor y `is ing a talking connection rroiii calling line to said called line While the iist connect-ion is intact.

' ln a telephone system, a irst and a seccxcliange connected by a trunk lino, a ine in said first exchange, means for ling a connection from said calling l y said second exchange over said trunk signal at said second exchange, means at sind ii s' excnange tor operating said signal over a. conductor ot said trunk line responsive to the extension of said connection, a called line, means at said iist exchange controlled over said conductor for establish- "nir a ta" 0* connection from said calling l e linac to said called line, a second signal at said second exchange individual to said trunk li* e, and means controlled by tno called party over said conductor When he removes his receiver to answer the call for operating said second signal.

6. lo a telephone system, a tirst and a Y second exchange connected by a trunk line,

line in said first exchange, means for ning a connection from said calling id second exchange over said trunk line, a sit ial said second exchange, means at said iii-st exchange for operating said nal over a conductor ot said'tiiink line respe-n l fe. to the extension ot said connection, i called line, and means at said iirst exchange controlled troni said second exchange over said conductor .tor cstablishil,2T a talking connection from said calling line to said all d line, a second signal at said second exchange, and. means controlled by either party over said conductor when he replaces his receiver at the termination ot the call for operating said signal.

7. ln a teleplio e system, a trunk line terminating at ono y an operators position and having tivo branches at the other end, a and a ce led line, nicans controlled :gy for extending a connec- 'ors position over one ive to said connection Y connecing a source ot po- Viai to one conductor ci said tiiinlr to sigpcrator, and ineens controlled by f reni arilv branches in series.

tcl lione system, trunk line tera-t an operators position, a calling Y 1ed line, means for connecting said like te slid trunk line, a battery,

means responsive to said connection for inoinentarily connecting one pole ot Said battery to a conductor of said trunk line to signaly iii telephone system, a trunk line tern'iinatng at an operators position, a calling a illcd line, means for connecting said ling line to said triinlr line, a battery, on.ns responsive to said connect-ion for moi `-ntarily connecting one pole of said battery to a conf1 ictor of said triinl; line t-o signal the operator, means controlled by the operator over said conductor 'tor establishing a conoii bets en sain calling and called lines, and means i sponsive to the replacement of tl e receiver on one of the lines for connectil `the other pole ot said battery to said conductor to give the operator the disconnect signet 10. in a telephone system, a trunk line. terminating at operators posit-ion, a calling and called line, means for connecting said. calling line to sail trunk line, means respon, 've to said connection for momentarily conncctig a characteristic potential to a conductor of said trunk line to signal the operator, means controlled by the operator for extending the connection to the called line, and means responsive to the replacenient ofiA the receiver on the calling line for again momentarily connecting said characteristic potential to said conductor to give. the operator the disconnect signal.

ll. in a telephone system, a trunk line extending from an exchato an operators pos. ion and having the same potential applied to both ends of a. conductor of said tiiinlr line, a calling line at said exchange and means for connecting it With said trunk line, means responsive to establishment of said connectiontor momentarily applying a dii'lferent potential to said conductor at the exchange to signal the operator at said position, a called line, an automatic switch connected to said trunk line at the exchange, and means controlled by the operator for intermittently applying a different potential to said conductor to control the operation of said switch to connect with said called line.

l2. ln a telephone system, a trunk line,

extending i[from an ,exchan 0e to an operators mitteilt-ly applying a different potential to said conductor to control the operation of said switch to connect with said called line, and means operative when the called party answers the call for disconnecting the first potential from said conductor at the exchange to signal the operator.

13. In a telephone system, a trunk line, extending from an exchange to an operators position and having the same potential applied to both ends of a conductor of said trunk line, a calling line at said exchange and means for connecting it with said trunk line, means responsive to establishment of said connection for momentarily applying a different potential to said conductor at the exchano'e to signal the operator at said position, a called line, an automatic switch connected to said trunk line at the exchange, means controlled by the operator for intermittently applying a different potential kto said conductor to control the operation of said switch to connect with said called line, means operative when the called party answers the call for disconnecting the first potential from said conductor at the exchange to signal the operator and for reapplying said first potential to said conductor when either party replaces his receiver at the end of the call to give the operator the disconnect signal.

14. In a telephone system, a iirst exchange, a first and a second switch at said exchange, a second exchange, a two-way trunk extending from said first exchange to said second exchange, an outgoing branch for said trunk accessible to said first switch, an incoming branch for said trunk terminating in said second switch, a third switch at said first exchange also having access to said outgoing branches, a third exchange, a second two-way trunk line extending from said third exchange to said first exchange and terminating thereat in said third switch and lbeing accessible to said second switch, and

subscribers lines at said first exchange having access to said first switch and being accessible to both said first switch and said second switch.

' 15. In a telephone system, an exchange, two lines terminating at said exchange, an operators switchboard, a trunk line extending from said switchboard to said exchange, means controlied over said trunk line for p1 1connecting said lines to establish a talking switchboard, means for controlling said signal over one conductor or" said trunk independent of the other conductor to notify the operator of said connection, and means controlled from said switchboard over said one conductor independent of the other for establishing a connection from the first line to the second line.

17. In a telephone system, an exchange, an operators switchboard, a trunk extending from the exchange to the switchboard, a battery at the exchange having one pole grounded, a second battery at the switchboard having one pole grounded, an impulsing relay at the exchange connected to the grounded pole of the first battery and to a conductor of said trunk, a call relay at said switchboard connected to the grounded pole f the second battery and to said conductor, means at the exchange for momentarily connecting the ungrounded pole of the first battery to said conductor to operate said call relay, and means at said switchboard for intermittently connecting the ungrounded pole oi' the second battery to said conductor to operate said impulsing relay.

18. In a telephone system, an exchange, an operators switchboard, a trunk extending from the exchange to the switchboard, a battery at the exchange having one pole grounded, a second battery at the switchboard having one pole grounded, an impulsing relay at the exchange connecte(VL to the grounded pole of the first battery and toV a conductor 0f said trunk, a call relay said switchboard connected to the grounded pole of the second battery and to said conductor, means at the exchange for momentarily connecting theungrounded pole of the first battery to said conductor to operate said call relay, means at said switchboard for intermittently connecting the unground ed pole of the second battery to said impulsing relay, an automatic switch at said exchange for extending a call controlled by said impulsing relay, an answering relay at said switchboard connected to the ungrounded pole of said second battery, means for connecting said answering relay to said conductor after said switch is operated to cause said answering relay to energize in series with said impulsing relay, and means 'for cisconnecting the ungrounded pole of the first battery from said impulsing relay when the call is answered. to cause said answering relay to deenergize.

19. In atelephone system, a first exchange, a second exchange, a third exchange, a nonnumerical hunting switch and a numerical selector switch in said second exchange, a

Vtwo-way trunk line extending from said first exchange and terminating at said second exchange in said hunting switch and accessible to said selector switch, and a two-way trunk line extending from said third exchange and terminating at said second exchange in said selector switch and accessible to said hunting switch.

20. In a telephone system, a first exchange, a second exchange, a third exchange, a nonnumerical hunting switch and a numerical selector switch in said second exchange, a two-way trunk line extending from said first exchange and terminating at said second ex change in said hunting switch and accessible to said selector switch, a two-way trunk line extending from said third exchange and terminating at said second exchange in said selector switch and accessible to said hunting switch, a local selector switch having access to said second trunk line, and a connector also accessible to said local selector switch and to said first selector switch.

21. In a telephone system, an exchange, an operators switchboard, two-way trunk lines extending between the exchange and the switchboard, each having an incoming and an outgoing branch at said exchange, numerical selector switches terminating the incoming branches, a non-numerical switch at said exchange having access to said outgoing branches, and a paystation line terminating at said exchange and having a calling branch terminating in said non-numerical switch and having a called branch directly accessibleto said selector switches.

22. In a telephone system, an exchange, an operators switchboard, two-way trunk lilies extending between the exchange and the switchboard, each having an incoming and an outgoing branch at said exchange, numerical selector switches terminating the incoming branches, a non-numerical switch at said exchange, having access to said outgoing branches, a paystation line terminating at said exchange and having a calling branch terminating in said non-numerical switch and having a called branch directly accessible to said selector switches, and means individual to said called branch for signalling over said paystation line when a call is extended thereto and for interrupting the signalling when the party thereat answers.

23. In a telephone system, a trunk line connecting two exchanges and having two branches at one of the exchanges, means controlled over the trunk line for connecting said two branches to two lines, respectively to complete a talking connection excluding the undivided portion of said trunk line, an impedance coil, and means for inserting said coil in the undivided portion of said trunk line to reduce the shunting effect of a bridge at the distant end of said trunk line.

24. In a telephone system, a calling line and a called line, a trunk line having two branches, means for completing a talking connection between said calling line and said called line over said two branches excluding the undivided portion of said trunk line, an impedance coil, and means responsive to the called subscriber removing his receiver for inserting said coil in the undivided portion of said trunk line to reduce the shunting effect of a bridge in the undivided portion of said trunk line. y

25. In a telephone system, a first exchange, a second exchange, a calling and a called line, a trunk line connecting said exchanges and having two branches at said first exchange, means at said first exchange for establishing a. connection from said calling line to said second exchange over one branch of said trunk line, means at said first exchange controlled over said trunk line for connecting the other branch of said trunk line to said called line, means at said first exchange for completing a talking connection between said calling line and said called line over .said two branches excluding the undivided portion of' said trunk line, an impedance coil, and means Jfor inserting said coil in the undivided portion of said trunk line to reduce the shunting effect of a bridge in said trunk line at said second exchange.

26. In a telephone system, an exchange, two lines terminating at said exchange, an operators switchboard, a trunk line extending from said switchboard to said exchange and having two branches in said exchange, means controlled over said trunk line for connecting said lines to the two branches of said trunk line to establish a talking connection over said branches excluding the undivided portion of said trunk line, an impedance coil, and means for inserting said coil in the undivided portion of said trunk line to reduce the `shunting effect of a bridge in said trunk line at said operators switchboard.

27. In a telephone system, a first exchange, a second exchange, a calling and a called line, a trunk line connecting said exchanges and having two branches at said first exchange, subscriber controlled means at said first exchange for connecting said calling line to said second exchange over one branch of said trunk line, means at said first exchange controlled over said trunk line for connecting the other branch of said trunk line to said called line, a signal individual to said trunk line at said second exchange, means responsive to the called subscriber removing his receiver for controlling said signal over a conductor of said trunk line, and means at said first exchange for completing a talking connection over the two branches of said trunk line excluding the undivided portion of said trunk line. l

In witness whereof, I hereunto subscribe my name this 7 th day of March, A. D. 1927.

CLARENCE E. LOMAX.

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