US2279822A - Intercepting trunk - Google Patents

Description

April 14, 1942. l. H. HENRY ETAL INTERCEPTING TRUNK Filed Oct. 26, 1940 I'NTERRUPTER CICIJIb INCOM/NG L /NK CONTROL 5 Sheets-Sheet l A T TURA/5y April 14, 1942.

l. H. HENRY ETAL INTERCEPTING TRUNK Filed oct. 26, 194o mm E V, Y

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ATTORNEY April 14, 1942. l. H. HENRY ET AL 2,279,822

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I INTEREPTING TRUNK 5 sheets-sheet 5 Filed Oct. 26. 1940 A /A/l/ENTORS;

/. H. HENRY F. A. KORN B @aM Aj TURN/5V Patented Apr. 14, 1942 erica azvfszz INTEREPTING TRUNK Israel H. Henry, East Orange, and Franklin A.

Korn, Westfield N. J., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 26, 1940, Serial No. 362,982

11 Claims. (Cl. 179-27) transmits, a.v signal to the. sender to identifyv the This invention relates to telephone systems and has for its object to improve the functioning of the equipment used in intercepting calls which cannot be completed in the normal manner.

not assigned for use, or for any other reason calls involving that numberV may not be completed, the corresponding terminals on the `rnumber group frame pass this information to the terminating marker which thereupon extends the connection to an intereepting trunk. Such trunks appear in jacks before an operator who',

can explain the reason for the non-completion of the call. In some cases, the intercepting positions are grouped at a centralized office and the trunk is equipped with means for tripping the ringing applied by the incomingl junctor and lighting a lamp at the operatorsposition.. y

Inl previous intercepting trunks it has been possible for the operator to connect with the trunk before the ringing has been tripped and the talking circuit establishedrso that the'ringing current may enter the operatorstelephone to her great discomfort. On the other hand, if she plugs in during a silent interval, her opening phrase may not be heard by the subscriber, requiring repetition and consequent delay.

In accordance with the present invention,

special means is provided to ensure proper trip- 0 ping of the ringing by connecting the tripping means to the trunk circuit only at the beginning of a complete ringing period at which time the operator is also signaled. To this end means is. provided, responsive during the silentinterval that intervenes between successive periods of ringing current, which must function in order that the subsequent application of the ringing current may establish the tripping circuit.

The intercepting trunk of the present invention may be selected either as aY regular intercept trunk, when an unused number is dialed, or as a trouble intercept trunk, when the called line is out of service because of trouble. The trunk appears in two jacks at the operators position and the lamps associated with vthe ,jacks are lighted selectively according to the manner in which the trunk was selected.

This trunk, together with the sendersv and other control equipment serves a plurality of ciiices and appears at the operators position in a plurality of jacks over which the establishment of a connection With the desired line may be effected. These jacks are individual to the offices and the insertion of a plug in one of the jacks i In the crossbar system, when a numberis y cnice in which the wanted line is located.

The invention will be more clearly understood from a consideration of the followingdescription in connection with the drawings in which:v

Fig. 1 shows an incoming trunk circuit;.

Fig. 2 shows the outgoing end 0f the intercepting trunk;

Fig. 3 shows a completing trunk associated with Fig. 2;

Figs. 4 and 5 show the incoming end of the intercepting trunk; and

Fig. 6 shows the arrangement of Figs. l to 5.

In general when a subscriber dials a number which does not represent an available called line, a relay is operated in the marker which controls the `selection of a trunk leading to an intercepting operatorsposition. The incoming trunk to which the call was extended is then connected ywith the intercepting trunk over incoming and line switches as used in connecting with a called line. The manner in which the marker functions is disclosed in U. S. vPatent No. 2,089,921, granted August l0, 1939, to W. W. Carpenter.

The intercepting trunk of Figs. 2 to 5 consists of three parts, viz., the outgoing trunk of Fig. l2 which is located in the same oice as.A the incoming trunk of Fig. 1, the centralizedincomingtrunk' of Figs. 4 and 5, located at the centralized oice, and the completing trunk of Fig. 3,

" which is associated with and located at the same oice as the outgoing trunk.

Assuming that the subscriber at substation It!) in attempting to make a call dials a number which has not been assigned, the number will f be recorded at the originating oiiice and the connection extended to an incoming trunk at the called cnice. Relay It will be operated in a circuit extending from battery through the left winding thereof, contactl of relay |02, tip contacts of jack I 4EII over aloop circuit closed in the sender at the originating office over the ring contacts of jack IGI, contact 4 of relay |02, right winding of relay IE5 to ground.

Relay IIIG, in operating, grounds conductor i227. over contact I of relay ID3. This causes the terminating sender link to seize the trunk of Fig; 1 and to connect it with an idle terminating sender. When thisconnection has been completed,` a pulsing circuit is established, connecting the sender of the originating oiiice with the terminating sender over conductors III and II2. At the same timel conductor II 3 is grounded, operating relay |02 toremove the battery and ground supplied to the trunk' through relay er which now releases. With relay released, a ringing circuit is established from the machine rringing source over conductor |25, contact 6 of relay |04, winding of relay |09, contacts 6 and I, of relay |08, contact 9 of relay |04,.contact I2 of relay |05, ring conductors of switches |20, |2|, 200 and 20|, contact 9 of relay 202, contact 8 of relay 203, condenser` 2II, winding of relay 2|2,

' contact of relay 203, contact of relay 202, tip

which locks over its contact 6 under the control of relay |06. With relay |03 operated,- ground is connected over its contact 8 Vthrough resistance 1 ||5, contact I0 of relay |05 toconductor llt V to mark the trunk busy. i

This locking ground for relay |03 extends back over conductor I4 to the sender as a signal thatA` the trunkfhas been closed, whereupon the sender Y summons a` marker `and transmits the number thereto.l The markery then closes a vcircuit through the sender and link to conductor ||1 operating relay 05. With relay |05 operated, the

trunk` and the incoming switches are connected to the marker throughr the incoming link control circuit.

Assuming that the number registered in the sender and transmitted to the `marker is one which is not in use, the marker will operate switches |20, |2|, 200 and 20| to connect the trunk of Fig. 1 with the intercepting trunk of Figs. 2 to 5. It will also ground conductors ||8 and |I9 operating rel-ay ||0 over contact 6 of relay |05 to indicate that no charge is to be made and relay |04 over'contact 4 of relay |05 to prepare for ringing. `Relay H0, when operated, locks over its third contact to ground over con# tact 4 of relay |03, while relay '|04 locks over its third contact, back contact of relay |09 to ground ingmarker is arranged to .seize a trunk in any one of four different trunk groups depending on the vtype and condition of the line intercepted. Two. groups of trunks are provided forlocal calls adtwo for toll calls, one ofpthese groups handling calls intercepted because the number is vacant'or, for some similar reason and the other handling calls intercepted because thefline is in trouble. When it is desired, the same trunks may be used for regular and trouble intercept, the operator receiving an indication, as will be pointed out hereinafter, of the nature of the call. Under the previously assumed condition, namely that an unused number was dialed, the marker tests the intercepting trunk. over conductor 224. This conductor willw be grounded over rcontact 4 of relay 2|9 if in use or made busy artificially, and over contact 3 of relay 2|9 and contact I0 of. relay 201 if the trunk' has been seized for `use in .connection with a trouble intercept call.

If this trunk is idle and is selected for use, the marker grounds conductor 224, completing a circuit over contact 3 of relay 2|8, 'contact of contacts of switches 20|, 200, |2| and |20, contact of relay |05contact 2 of relay |04, contactl 8 of relay |08 to ground. A circuit exists in parallel with relay 2| 2 which extends from Contact 8r of relay 203, resistance 223, contact I of relay 208, back contact of relay 2|2, through the windingsof relay 2|3 in parallel to contact of relay 203. yRinging current is applied to these circuits at regular intervals by the ringing machine and a ringing tone is transmitted to the calling subscriber through condensers `|29 and r`Relay 2|2 operates in response to the first application of sufficient duration and opens the circuit of relay 2|3 to prevent the operation of the latter relay. yRelay 2|3 is prevented from operating in` response to ringing current before relay 2 |2 operates by its diiferential winding, the windings being oppositelyenergized by the ringing current. y

After an; interval, the ringing interrupter removes ringingcurrent from conductor |25, substituting battery therefor. When this occurs, relay 2|2 falls back, reclosing the circuit of relay 2 I3. The right winding of relay 2|3 is now effective ,pcondenser `2|4 rendering the leftwinding opaque to direct current. Relay 2 |3 closes a circuit-from battery through the winding of relay 2|5, front contact of relay 2|3, conductor 221, contact 6 `of relay 203, contact 5 of relay 202, conductor 23| to Vground at contact 2 of relay 2|8. Relayl 2I5 locksv over its right contact to conductor 221 independent of relay 2|3.

` At the lend of the silent period relay 2|3 rel e leases and vimmediately after, at the beginning of relay 202 to one cathode of the tube and from the other cathode ofthe tube over contact 8 of relay208, contactg of relay 203 and contact 9 of relay 202.`

This arrangement insures the application of the tripping tube 2I0 to the trunk at the start of a ringing period. If the trunk is closed through` during the silent period, relay 2|3 may operate immediately, but unless it is held operated long enough for relay 2I5 to operate and lock, this `operation is ineifective,y relay 2|3 releases and isreoperated at the next silent period. With tube 2 I0r connected to the trunk at the beginning of a ringing period, the operation of relay |09 in the incoming trunk and the establishment of the talking circuit is assured before the operator completion of this circuit' isa signal to the mark- 75 connects her telephone with the jack at the centralized oiice as will be described hereinafter.

i With tube 2I0 across the trunk, ringing current breaks down the tube which then presents sufficiently ylowresistance to operate relay |09.`

Relay |09 opens the locking circuit of relay |04 which cuts olgthe; ringing current; andextendsi the. tip. conductor` ofgtloe.r trunkf over contagia li ofrelay, |05,l contact. ofgrelay.I |04, togroun through the left .,winding.- of;J relay.- |0|ri andi exe, tends. the.ring.- conductor, of. the .trunk over; conf. tact I2. of relay |05., contacti |of relay` |044?- to;v battery. through. the .right windingfof relay. |01;

The operation. of. relay 20.0.1 also. transmits.. a; signal to the intercepting. operaton by closing` a.-

circuit. from battery through the right-Winding i of. relay 2|0; contact 4 of.A relay 208x,` contact or4 relay 20.1, upper-lrightlwinding. offrepeatingcoil) 20.4.-, contactl of relayl200',` conductor229,offtliel interoice trunk,V contact |1= of. relay. 400.; con. ductor- 4| upper left, winding, of repeating coil: 50.4,' contact 3 ,of relay501'.;` windings. of. relays. 5 L4; and 5|.5', contact 0,:of relay 503; lowerlleftwinde. ing of repeatingcoil 50,4, conductor M2; contact. off relay 400, conductor 23.0; contact liofgrelay.1 200, lower right Winding. ofrepeating1coilf204; contact; l; of; relay 201, contact- 5. of relay 208; left'windingfof relay 2| 0. to ground.

Relay 515 operates in this circuit, but the .cur. rentow is in the wrong direction to operate polarized; relay 5| 4 andY of insuflicient strength. tol operate marginal relay 2|0. Relay 51|5f closes. a circuit from ground over. its contact, conductorl 52,0, back contactof. relay 4.05, conductor 52|, Winding ofrelay 5.!6. and battery. Relay.y 5|@ closes a circuit frombattery over. its front; con-' tact,- contact 4 of; relays; 5H and; 5|8, contact |i of relayI |2through lamp 508 to ground.

The, trunk terminatesin two jacks.501| and 509, with which are associated lamps- 508 and 510. When thetrunk is usedfor a regular.v intercepting-fA callL lamp 5001's lighted as above described: and. the operator responds: by inserting the plug of a cord circuit ather position inte jack 50i-f Jack 509fand lainp 5,10? are used whenthe trunk is used fora trouble intercept call, as will appear hereinafter.

Batter-y on` the sleeve of. the: cord. completes a circuit over the sleeve ofjack 501', winding of relay 5-.|.'|`y and ground. Relay5 |21 opens the cir cuit of larnp 500,7 extinguishing the lamp. Atr contact l.. ity connects. ground to the winding of,` relay 50,3. Relay 503; operates, disconnect-ing. relays 5|4 and 5|5 fr orn the circuiti ot relay 216. and.. connects the upper left winding of, coil: 504- oyer contact 4 ofA relay contact of. relay 5|3, contact 3` ofY relay: 5|2 throughy the upper winding o ff relay` 521|; and? resistance 5.22` to ground. Relay 50,3 also connects the lower left winding ofrepeating coil; 5,04; over Contact 5; of-I relay 5-03., Contact 4 of; relay 5h35, contact 6 of relay 5.|2 throughA the lower winding of relay 5,|| and resistance 5,23, to battery. Condenser 5.24. is. also connected:y between the left windings of coil 504 over contacts. 4; andy 5 of relay 503. In addition, relay 503,- closes a circuit from battery through the winding of relay 405', conductor M31., Contact.. |-y of relarl: to ground The dis.- connection of' relay 5|- 5 4 causes. that relay to; re.. lease, in turn. releasing. rel-ay. 54.6:

With relay 503 operated; glollnd through the upper winding. of. re y 5H .is connected, toA battery through the right winding. ofrelay: 2.1.6; over the circuitpreviously traced batterytlrrough the lower winding of relay 51| is connected to ground1 through theleft winding ofA relay 2|;6- Relay 215 operates in these circuits, but relay 5H does not.

Ther operation of relay-2 l5.. ellisse-a.i circuit from battery through the Winding: off relay 2,53, contact. of relay 246,l to ground over conductor23;|.

With relay. mtreleaeedih tip CQIldllCiOt-ZHJ or theinteroicetrueke @extended 031er Geel? F: I. of.; relay.y 2.0.9,;.upper rlslltavvfledieg-,foif wrestler; coil; 20.4,. Contact. l. Off relay; 2.0L geniet# 3 Qff relay.v 20.87 .llprlrlfrA Wlrldllgfoli 1199212691.;- 'f 223.1 leftlwindine Qffrelar 2.1.1; Contacta Offrant 2.23.( Contact: Off relay 2.08@ Contact l; Off: raler,v 2101 loyer; right winding.. 0i Coll. 204g. contact; 6, off relay 2519, to the. ring; Conductor 23.010f. ,.ilietlrlter office trunk ThlS.. i.rCuiti extends. at'. the other. encltof; the,A trunk. thwushI tllefrinding .0i relay -.H asprevlouslrtraceellvelarI 2411. falesiethlsf.- Clfultbut bleef Cllrilen 0i Current. ignoti $11.911-,-

tO. operate. polarlzedgre1ayf-f2i2. Relay.'

A. 2H;- closes .ang obvious circuit forrelays 223| which,

in turn operates relay 222. RelayJ 222 olpermates relay. 2l.9.f Which. locks Heller the.. control; 0f

Relay.I 5M also Operates in. the.. Circuliofi relay; 2U: and Closes al Circuit.; from battery. through.; the Winding. 0f relay; Ellie Conductor; 524i. con. tallo @.f relay 5.", contact. 5.. 0f. relay. 5.115,; to efr-.Gund Relay 5.419 Closesan Devious, Qircugltefot relay 5ml. With relay; SL81 operandi @loosing circuitis closed forj relay5|z9a under1 the. control; Qff relay. 5 |.Iy extending..- from. the. Contact of relayA 5U. Ore contee@ 2. 0f relay 5.,!.9 totetouridover. 009226.02 0f. relay 5.4.3.: CQnllaQlSi; MG12: 0f; relay@ 5, .|.8; overlap in operation so that relay. 514,9 is.held,

operated Relayj 5.15 wnnects. sroundatathe. tip

0f 129k 501110 indicate-*t0 the. operaipttliarthe. talking circuit is4 ready.

This talking' circuit which nowU existsbetween. the. calling subscriberand the intercepting .operator isrnade up of apluralityfQf sections. One section, not shownZ includes the callingline and a.A part of the equipment at the origiriai'dngr oice from which the subscriber receives talking bat; tery. The first section shown. in detail extends from battery through the leftywindllg of; relay. |06, contact of relay |02, tip contacts. of: jack- |,0..|, overa dry bridgevin the originating ofice, ring1 contactsof jack I0 I., Contact lI;Of.1eliy. 1.0.21 to ground through the rightjwinding of. relay. |06. This section islinked tothe next section by means of condensers`|23 and |24 to which it is connected over contacts 2 and l0,v of relay |03.

The neigt section may; be traced from(battery through the rig-,ht winding ofV relay L01, contact- |0 of relay |04, contact 2 of relay |105; ring contacts of switches |20, |2|, 20.0. and: 20|.; coni tact 0 of relay 202, contact 1 of relay 203|, lower left Winding. of repeating coil 204, resistances. 208A and 20,5, upper left winding ofv repeating coily 2.04, contact 2:of relay 203; contact. |4 of relay202, tipi. contacts of switches 20|, 202, |2| and- |20, Contact of relays |05; and |04 to g'lound: through theI left Winding of'relay |01:-

'l'he third section ist linked: tothe second' section through repeating. coil 204 and-1 may be traced from battery, through resistance 5232 lower Winding ofrelay 5|.|, contact` 6 of relay 5.|;2, contact 4 of relay 513, contact 5 of relay 503,;A lopverlefgt winding of repeatingfcol 5041', conductor 4-|2, contact ofl relay 400, conductor 230, contact G-'of relay 20,0, lower right windin ot repeating coil 204, contact l of relay 2llljc3r`1'i tact 6 of; relay 2.08, contact 4- of relay 203, left winding of. relay. 2.|"|, upper winding' of-rela`y 2 28-,V contact; 3 of relay 20,'8, contact 4 of relay 42101, upper `right winding of repeating coil 204',

of repeating coil 504, contact 4 of relay 503,v

contact I of relay 5|3, contact 3 of relay' 5|2, upper winding of relay 5||, resistance 522 to ground. "Ihe nal section ofthe talking circuit which links with that just traced through coil 504 extends from battery through resistance lamp 506, winding of relay 505, lower right winding of repeating coil 504, ring of jack 501, over a bridgefin the operators cord to the tip of jack 501, upper right winding ofcoil 504, to ground at contact 3 of relay 5|9. Relays |06, |01, 2|1 and 5H are operated in this talking circuit. I

The intercepting operator now converses with the calling subscriber. If the call cannot be completed she so informs the subscriber and withdraws her cord from jack 501, releasing relay 5|1 and opening the operating circuit of relay 503. Y K a The subscriber hangs up his receiver, releasing the equipment at the originating oiice, thereby opening the circuit of relay |08 in turn releasing relay |03. With relay |01 heldoperated over the trunk, ground is connected over the right contact of relay |01 to conductor |26 and through the timing Vcircuit to conductor |21 which extends through resistance ||5 and contact of relay |05 to conductor ||6 and the sleeve contacts ofthe switches, holding the connection. When relay |03 releases it connects ground from the left contact of relay 01 over contact I3 of relay |03 to conductor |28 leading to the timing circuit. After an interval the timing circuit responds to ground on conductor |28 by disconnecting conductors |26 and y |21, there by releasing switches |20, |2|,`200 and 20|.y

The opening of the switch contacts releases relay 2|8', in turn releasing relay 203. The'opening of contact 4 of relay 203 includes the rightr winding of relay 2|1 and the lower winding of relay 228 in the circuit of relay 5|| causing that relay to release, in turn releasing relays 5|9, 5|8 and 503. The release of relay 503 disconnects battery and ground from conductors 4|| and 4|2, thereby releasing relay 2| 1 which inturn releases relays 22| and 222 and the trunk is restored to normal.

Call completed If, after talking with the calling subscriber, it is possible and desirable for the operator to complete the connection, she does so by inserting the plug ofa cord at her position into one of the jacks of Fig. 4. l

The arrangement of Fig.`4 is for usewhere the intercepting trunks and the control equipment serve a plurality of oflices. Jack 4|5 is used` in completing calls inone oice and jack 4|6 in completing calls in a second oilice. The insertion of a plug in jack 4|5 'completes a "circuit from battery on the sleeve of the cord, sleeve of jack 4l5, contact of relay 409, winding of relay 4|0, conductor 4|1 to ground at contact 2 of relay 503. Relay 4|0'locks to ground at its inner upper contact and to battery over its lower front con-V tact and the sleeve of jack 4|5. For calls to the second oilice, the insertion of the plug in jack 4|6 closes a circuit from battery 'on the sleeve of the cord,'sleeve of jack 4|6, winding of relay 4|4 to ground over conductor 4|1. With relay 4| 4 operated, battery through resistance 4|8 is connected over the lower contact of relay 4|4 and contact of relay 409 to the winding of relay 4|0'so that both relays 4|0Aand 4|4` are operated for calls to the latter oflice.'` With relay 4|4 normal, ground through 100G-ohm resistance 4|9is connected over contact 3 of relay 401 to conductor 420 to indicatethat the call is to be completed in the rst omce. With relay 4|4 operated, direct ground is connected in shunt of resistance 4|9- as an indication that the connection is to be completed in the second oce.

Assuming that the plug has been inserted in jack 4|5, when the plug is seated a circuitlis closed from battery through the winding of relay 408, contact of. relay 401, contact 3 of relay 409, contact 2 of relay 404, tip of jack 4|5, over a loop in the cord circuit back to the ring of jack 4|5, contact 5 of relay 404, contact 8 of relay 409, contact 9 of relay 401, resistance 42| and ground. Relay 408 operates in this circuit,

closing a cicuit from ground at the upper con? tact of relay 4|0, contact of relay 408, contact 5 of relay 400, contact 9 of relay 409, conductor 422 to battery. The grounding of conductor 422 causes a key pulsing sender to be connected with the trunk. When the sender is attached and ready, ground is connected to conductor v423, operating relay 409. Relay 409 disconnects ground from start lead 422, and opens the circuitof relay 408 causing that relay to release. With relay 409 operated, the tip and ring of jack 4|5 are connected over contacts 2 and 5 of relay 404 and contacts 4 and 1 of relay 409 to conductors 424 and 425 leading to the sender.

. When conductors 42'4 and 425 are closed through from the sender to the position key-set, associated with the plug in jack 4|5, the operator is given a signal and she proceeds to set up the proper number on her key-set, thereby recording the number in the sender.

`When the number has been -set up in the sender, ground is connected to conductor 42B, operating relay 401 which locksover its contact 5 to ground over contact 5 of relay 409. With relay 401 operated the office identifying ground is removed from conductor 420. A circuit is closed from battery through the winding of relay 402, contact 1 of relay 401, contacts 6 and 5 of relay 409 to ground, operating relay 402 which closes an obvious circuit for relay 400. Relay 400 in operating disconnects conductors 229 and 230 from conductors 4|0 and 4|2, disconnecting the talking circuit from the jack 501.

With relays 400 and 401 operated the tip conductor 229 is extended over contact 2 of relay 400, through resistance 421, contact I0 of relay 401 to conductor 428 leading to the sender, while the ring conductor 230 is extended over contact 6 of relay 400, contact 4 of relay 401 to conductor 420. Conductors 420 and 428 extend to pulsing equipment in the key-pulsing sender.

Ihe opening of the talking circuit at contacts and 1 of relay 400 releases relay 5|| which opens the circuit of relay 5|9, but a substitute holding circuit is closed by relay 400 which may be traced from battery through the winding of relay 5|9, conductor 524, contact 3 of relay 400, conductor 429, to ground over contact 2 of relay 5|8, thereby maintaining the lamp 508 dark.

The operation of relay 400 also opens the circuit of relay`2`|1 causing that relay to release, in turn releasing relays 22| and 222. These relays each release Slowly so that a circuit is closed after relay 22| releases and before relay 222 releases from ground at the back contactjof relay 2|1, back contact oi" relay 22|, left contact of relay 222 to the winding of relay 209 and battery.

Relay 200 connects conductor22`0 over contact 2 of relay 200, contact 3 of relay 202, conductor 232, contact 6 of relay 305 to ground through the right winding of relay 306 and in shunt Yof the winding of relay 306 to ground at contact 1 of relay 308. Conductor 230 is connected over contact of relay 209, contact 1 of relay 202, conductor 233, contact 3 of relay 305 to battery through the left winding of relay 306 and in parallel with the winding of relay 306 over contact I of relay 308 and through resistance 3I3.

'Relay 306 operates through its left winding and closes an obvious circuit for relay 301. At its inner left contact relay 301 connects ground over contact 3 of relay 308 and contact I of relay 305 to conductor 3M, thereby causing the terminating sender link circuit to connect a terminating sender with this trunk. At its outer left contact, relay 301 connects ground over conductor 3|5 to the winding of relay 222 preventing its release and thereby holding relay 2 I 9 operated to hold the trunk.

When the sender is ready for use, battery and ground are connected to conductors 233 and 232 by the sender in parallel with that supplied by relay k300. Ground is also connected to conductor 3|6, operating relay V305. Relay 3,05 opens the link start circuit at contact I, connects ground over contact 2 to conductor 3|5 to hold the trunk circuit and disconnects relay 306 from conductors 232 and 233, thereby releasing relays 306 and 301.

'I'he terminating sender proceeds to register the number transmitted to it by the key pulsing sender and when all the digits have been recorded transmits a signal to the key pulsing sender, discharges the trunk conductors and then connects low resistance battery to conductor 3|6 in place of ground, thereby releasing relay 305.

With relay 305 released, relay 306 is again connected to conductors 232 and 233 so that relay 306 reoperates, in turn operating relay 301.

At the same time that relay 305 is released, .ground is connected to conductor 311, operating relay 308 which locks Aunder the control of relay v301. This locking circuit is a signal tothe sender fwhich now seizes a marker after which the marker extends ground to conductor 3|8, `operating relay 304. Relay 304 operates and connects the outgoing tip, ringand sleeve conductors 3|9,

320 and 32| to the marker for test and connects 'the ringing control conductors to . relays 300, 302

iand 303 to determine the ringing to be used,

these relays functioning in a manner similar to relays |04, H0 and |08 of the incoming junctor. Assuming that relay 300 .is operated alone to ring an individual line, it locks over the back Contact of relay 309 to ground at contact 8 of relay 308.

vWhen the marker has selected the wanted line and operated the switches connecting the trunk of Fig. 3 to that line, relay 304 is released and a `ringing circuit is closed from ringing ground on conductor'322, contact 2 of relay 300, contact I of relay 303, contact 2 of relay 304, conductor 3|9,

over the switches and the called line back to tion, with relay 304 released and relay 300 operated a circuit is closed from battery through the winding of relay 30|, contact 5 of relay 300, contact I3 of ,n relay 304 to ground at contact 8 of relay 308. Relay 30| locks over its inner upper kcontact to ground over contact 8 of relay 308, independent of relay 300.

When the key pulsing sender receives a sigvvnal from the terminating sender that the designation has Abeen received, the former sender extends ground to conductor 430 operating relay 404'which locks over contact 6 to ground at the .outer upper contact of relay 4|0. Relay 4.04 disconnects the tip and ring of jack 4|5'from the key pulsing sender and connects them through the windings of relay 403 and contacts 6 and 2 `of relay 400 to conductors 230 and ,229'. With relay 209 operated, conductor 2,30 extends over contact 5 of relay 200, contact 1 of relay 202,`

.conductor 233, contact 3 of relay 305 tobattery through the left winding of relay 3 06, 'while conductor 2,29 extends over contact 2 of relay 209, contact 3 of relay 202, conductor 232, contact 6 of relay 305, to ground through the lright winding of relay 308. Relay 403 operates in this circuit and closes a holding circuit for relay 4.02,. After an interval, the key pulsing sender releases in turn releasing relay 409 which unlocks relay :401 and lpermits that vrelay to release. Relay 403 is held operated to transmit to the operator supervisory signals from the outgoing connection.

When Vthe called subscriber answers relay 30.9

' operates, opening the locking circuit of relay 30.0

,and permitting that relay -to release.

A circuit is Anow Aclosed from battery through the wind- -ing of relay 202, conductor 234,*outer upper conytact Vof relay 30|, contact 3 of relay '300, to grounded conductor 23|. Relay 202 locks over contact 4 vto grounded conductor 23|. With relay -2-02 operated, the tip contact of switch 20| is yconnected over contact 2 of relay 202, conductor 235, contact |,of relays 300 and 30,3, contact'2 o f relay 30,4 to conductor 3|0, and ,the ring contact .of switch 20| is connected 4over contact j8 of relay 1.202, conductor 236, contact I2 of relay 300-c01ll7act ,8 of relay 3 03 and contact |12 o f relay 30,4 to conductor 3,20. A talking circuit is thereby established connecting the callingdand called subscriber over two sets lof incomingland Aline switches at the terminating orlice. n, c 'A-,lrfhe operation of relay |12`lisconnects,relay` A3,00 from the key-pulsing sender, releasing relay 3.00 .and in turn relays .301 and 303. With ,relay 3,08 released ground is disconnected imm, c011- ductor 32| at contact 15 of relay 308, but the outgoing switches are held operated byground over .contact 6 of relay 202 conductor 231, resistance 326, contact `8 of nrelay 3047,and conductor32l.

VRelay 308 in releasing opens the locking circuit causing that relay to release.

for relay 30| Throughout conversation no relays Vare operated 'in :the completingportion of the outgoing trunk which is shown in Fig. 3. `I ,telay |01 is held operated under the control of the called subscrber.

-The operation of relay '202 as above described, opens the circuitof relay 4,03 and that relay -releases, in turn releasing relays y402 and 400. v The release of relay 4,00 -gives a release signal at jack 415. f

The release of relay 301 also releasesrelay '220, in turn releasing relays 22|, 222 and I200. With relays 200 and-400 released, relay 5|| isre connected to relays 228 and 2-|1. However,` the |.9 released, ground is disconnected from the` tip oi the jack 501 andthe associated cord, vtherebyvlighting the lamp associated with that cord asa signal that the calledsubscriber has "answered, Relay 5|9 also releases relay 5|8.

"The operator maynow withdraw the plug from jack 4|5,releasing relay 4|0. Relay 4|0 in turn releases relay 404. When the operator withdraws the plug from jack 508, relay 5|1 is released Vin turn releasing relay 503.` The release of relay 503" disconnects relay 5H from relays 2|1 and 228; Relay 503 also, releases relay '405 which is madeslow to release to vprevent the operation of relay 5|6should relay5|5 oper- `ate momentarily followingl the release of relay 503.' With relay 405 released the trunk at the centralized oilice is restoredV to normal;

Trouble intercept -If the number called had been taken out of service lbecause of-trouble, the marker would have seized the intercepting trunk by grounding conductor 226, thereby-closing a circuit over contact of relay 2|9-contact 6 of relay 2|8, winding of relay 201 and battery. Rlelay 201 locks to conductor 225 when the connection is established through switches |20, |2|-, 200land In general, it functions in the same manner as relay 2|8but it reverseswthe connection of battery and ground through-the windings of relay- 2|B to conductors'ZZS and 230. At '.the centralized oicathis reversal causes polarized relay 5|4 to operate-as well as relay-5|5. Relay 5|4-in operating closes an obvious -circuit for relay 5|2 which -locks over contact 3 of A relay 5|1 and contact V3 of relay |i|8 in parallel to iii) ground at contact 1 of relay 5|2. Relay 5|2 rel verses-the connection Vof battery and ground through the. windings of relay 5|| to conductors f, `4|| andV 4|2 and therefore to conductors 229 andk 230 to compensate for the i reversal introduced by relay 201,so that polarized relay 228 'is normally not operated -Relay 5|2a1so transfers the lamp circuit closedby relay 5|6 from.

lamp 508 to lamp 5|0 to indicate 4to the operator lthat the call has beenintercepted because of trouble. Since jacks 501 and 509 are connected in parallel, v the result of the insertion of the plug -in yjack 509 associated with lamp 5|0 is thesame as previously described.

This intercepting trunk may also be seized over an incoming trimk from an operators posi- -tion' and in that case it may be desirable for the intercepting operator. to signal the operator at the originating cnice. i In that case, the operation .ofthe flashing key by the intercepting operator connects ground to the ring` of jack 501, operating relay505 in series with resistance lamp 506 and battery. Relay 505 closes a circuit from battery through the winding of relay 5|3, front contact of relay 505, back contact "20E, over the front contact of 'relay 228 tothe of relay5||,` to ground at contact 2 lof relay 5|1. Relay 5|3 reverses the connection of battery and ground tol conductors l4|| and- M2 through the windings of relay 5| I. y Polarized relay-220 operates in response to this reversed current and closes a circuit from the lower left winding of repeating coil204,t hrough resistance means to i. connect upper left winding of coil 204 in shuntof resistance 205, thereby decreasing the resistance in the circuit of a relay in the incoming trunk to signal the originating operator. H

What is claimed is:

1.,'In a telephone system, anA operators position, a trunk terminating at said position, a signalassociated with'fsaid trunk, means for yestablishin'g a connectionoversaid trunk` to said position, means responsive to-the establishment of said connection for transmitting ringing cur- .rent over saidv trunkl in spaced periods and means responsiveto the iirst complete period of ringing current to simultaneously discontinue the transmission of said ringing current and to operate said signal.v i

2. In a telephone system, an operators position, a trunk terminating at said position, a signal-associated with said trunk, means for establishing a connection over said trunk to said position, means responsive to the establishment of said connection for transmitting ringing current over said trunk in spaced periods, means comprising a cold cathode tube responsive to the first complete period'of ringing 'current to discontinue the transmission of said ringing'v current and means simultaneously effective to operate said signal.'

3. In a-telephone system, a rst trunk, a second trunk, means for connecting said trunks .t0- gether,'a ringing machine associated with said rst trunk, means in said ringing machine for connecting ringing current and direct current to 'one conductor of said trunk vfor alternate periods, a relay in series with said conductor. and means vin said second trunk for operating said relay comprising a gas-filled tube and means forconnecting-said tube to said conductor'` at the beginning of a ringing period.

4." In a telephone system, a rst trunk, a second trunk, means for connecting said trunks together, a ringing machine associated with said `iirst trunk, means'in said ringing machine for connecting ringing current and direct current to rone conductor of. said trunk `for alternate periods, a relay in series with said' conductor,

and fmeans in said secondtrunk for operating operates afterv said .direct current responsive Asaid gas-lled tube to said conductor.

5. In a telephone system, a rsttrunk, a second trunk, means for connecting said trunks together, va ringingmachine associated with said .rst trunk, means'in said ringing machinefor connecting 'ringing current and direct current to one conductor of said trunk for alternate periods, a relay in seriesA with said conductor, and

means in said second trunk for operating said relay comprising a gas-lled tube, arelay responsive .tosaid ringing: current anda reiayrenect said .gas-filled tube to said conductor.

6; In a telephone system; a rst trunk, a second. trunk, means; for connecting said trunks togetherga ringing*A machine associated withsaid `rst trunk, means in'said ringing machine-for connecting ringingcurrent Aand direct` current to'l one` lconductor `of said" trunlrfor alternate pgriods, a relay in series with said conductor, and means in said second trunk for operating said relay comprising a gas-filled tube, a relay responsive to said ringing current and a relay responsive to said direct current connected in parallel, means responsive to the operation of said ringing current relay subsequent to the operation of said direct current relay to connect said gasiilled tube to said conductor, and means or rendering said direct current relay unresponsive to said ringing current.

7. In a telephone system, a rst trunk, a second trunk, a signal associated with said second trunk, means for connecting said trunks together, a ringing machine associated with said rst trunk, means in said ringing machine for connecting ringing current and direct current to one conductor of said trunk for alternate periods, a relay in series with said conductor, and means in said second trunk for operating said relay comprising a gas-filled tube, a relay responsive to said ringing current and a relay responsive to said direct current connected in parallel, means responsive to the operation of said ringing current relay subsequent to the operation of said direct current relay to connect said gaslled tube to said conductor, and means under the control of said responsive means to operate said signal.

8. In a telephone system, an intercepting trunk appearing in a plurality of jacks at an operators position, lamps associated Witn said jacks, means for seizing said trunk as a regular intercepting trunk, means for seizing said trunk as a trouble intercepting trunk,` and means to light the lamps at different jacks in accordance with said seizing means.

9. In a telephone system, an intercepting trunk serving a plurality of oii'ices, an operators position, answering jacks and completing jacks connected with said trunk at said operators position, means for establishing a connection over said trunk through one of said answering jacks, means effective while said connection with said answering jack is maintained to selze said trunk over one of said completing jacks to establish a connection with a line in one of said offices over a portion of said intercepting trunk circuit and means operated in accordance with the completing jack used for determining the oiiice in which said line is located.

10. In a telephone system, an operators position, a trunk terminating at said position, a signal associated with said trunk, means for establishing a connection over said trunk to said position, means responsive to the establishment of said connection for transmitting ringing current over said trunk in spaced periods,` means effective to discontinue the transmission of said ringing current and to operate said signal, and means to render said last-mentioned means responsive only to a complete ringing period.

11. In a telephone system, an operators position, a trunk terminating at said position, a signal associated With said trunk, means for establishing a connection over said trunk to said position, means responsive to the establishment of said connection for transmitting ringing current over said trunk in spaced periods, means effective to discontinue the transmission of said ringing current and to operate said signal, and means to render said last-mentioned means unresponsive to an incomplete ringing period.

ISRAEL H. HENRY. FRANKLIN A. KORN.

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