US2360291A

US2360291A - Telephone system

Info

Publication number: US2360291A
Application number: US384238A
Authority: US
Inventors: Paul W Wadsworth
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1941-03-20
Filing date: 1941-03-20
Publication date: 1944-10-10
Anticipated expiration: 1961-10-10

Description

Oct. 10, 1944 P. w. wADswoRTH TELEPHONE SYSTEM I A TTORA/EV Oct; l0, 1944. P. w. wADswoRTH l 2,360,291

-I TELEPHONE SYSTEM Fied Mazch 20, 1941 5 Sheets-Sheet 2 ATTORNEY APs Z Ja y w44?- P. W. wADsWom-H Zg TELEPHONE SYSTEM A Filed March 20, 1942!. -5 Shee'r,s-Shekj 5 en TELEPHONE i/ EN EVP. nf. wAoswo/P TH A NORA/5v @ct 944. P. W WADSWQRTH 2,369,29l

TELEPHONE SYSTEM Filed March 20, 1941 5 Sheets-Sheet 4 l@ v /M/E/v To@ Sr By P; W WDSWORTH A TOR/VE y Oct. 10, 1944. P. w. wADswoRrl-l TELEPHONE SYSTEM Filed March 20, 1941 I -5 Sheets-Sheet 5 m m W 5 M W W o...

Patented Oct. 10, 1944 TELEPHONE SYSTEM Paul W. Wadsworth, Garden City, N. Y., assigner' Q to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application March 20, 1941, Serial No. 384,238

6 Claims. This invention relates to telephone systems Yand particularly to systems in which dial impulse controlled switches are provided for completing connections between calling and called lines.

Objects of the invention are the provision of more efficient automatic switching equipment for establishing telephone connections between calling and called lines and an increase in theutility and efficiency of selectors in toll telephone systems.

According to this invention a selector in a toll olice having access to trunks to local dial oiiices and to trunks to other toll o'ices is arranged to absorb a rst train of directive impulses if the train consists of acertain number of impulses, to receive impulses in a simplex circuit and repeat the impulses in a loop circuit upon selection of a trunk to a local dial oice, to function as a toll transmission selector with a repeating coil in the talking connection upon selection of a trunk to a local dial ofce, and to connect the incoming conductors directly to the conductors of the selected trunk upon selection of an intertoll trunk or an intertoll selector.

According to a feature of the invention a combined intertoll and toll transmission selector is provided with two sets of independently actuated normal post springs, the actuation of one set alone being eiective to release the brushes to absorb the rst digit, the actuation of the other set alone being effective to Vcut out the repeating coil which is Vprovided Afor use upon selection of a trunk to a local dial oice, and the actuation of both sets of springs together being effective to indicate, to a preceding trunk circuit, selection of a group of intertoll trunks arranged for through supervision.

A clear and complete understanding of the invention will be facilitated by considering a system in which the invention is embodied, one such system being represented schematically in the drawings which form a part of this specification. The invention is not limited in its application to the particular system shown in the drawings but is generally applicable to toll and intertoll telephone systems,

Referring to the drawings:

Fig. 1 shows, in a rst toll office, an operators cord CDI, telephone and dial, a jack-ended outgoing trunk circuit OTI, and a signaling circuit CSi associated with a toll line TLI;

Fig. 2 shows, in a second toll "oiiice, a signaling circuit CS2, van outgoing trunk circuit T2, a two-way trunk circuit TWTZ and a toll selector TS2, all associated with the toll line TLI;

Fig. 3 shows, in the second toll oflice, an operators cord CD3, telephone and dial, a jack-ended incoming trunk circuit IT, and an associated intermediate dialing trunk circuit IDT connected to terminals in the bank of toll selector TS2 of Fig. 2;

Fig. 4 shows a lcombined intertoll and toll transmission selector circuit CS associated with the intermediate dialing trunk circuit shown in Fig. 3;

Fig. 5 shows a toll connector TC and a subscribers line L in a local dial oiice; and shows Aa two-way trunk circuit TWT5, outgoing trunk circuit OTS and signaling circuit CS associated with an intertoll trunk T; and

Fig. 6 shows the relative position in which Figs. 1 to 5 are to be placed to form an operative arrangement.

Reference may be had to the patent to R. E. King et al.'2,209,'777, granted July 30, 1940, for

Va detailed disclosure of the cord and operators position circuits provided in each of the two toll oices for interconnecting calling and called lines and trunks and for controlling the completion 'of toll calls. The outgoing trunk circuits OTI, 0T2 and OT5, signaling circuits CSi, CS2 and C55, and the intertoll selector TS2, are all similar to corresponding circuits disclosed in the aforementioned King et al. patent. The toll connector circuit TC is similar to the toll connector disclosed in the patent to E. D. Butz No. 2,021,285, granted November 19, 1935. Although not shown in the drawings, one or more intermediate selectors may be requiredfor selecting a. desired group of toll connectors. v

The combined intertoll and toll transmission selector circuit CS comprises a repeating coil RC', a line relay 2L a release relay M2, a relay M0 for switching the repeating coil RC, a vertical stepping magnet 42T, a rotary stepping magnet 423, a release magnet 429, a set of

brushes

43H, 432, 433 and 13M, eleventh rotary step springs 43S, vertical off-normal springs 444], two sets of normal post springs Mi and M2, a test key TK, and various control relays. The normal post springs del are adjusted to be operated only when the brushes are on the tenth level and on any'of levels 2 to 9, inclusive, corresponding to digits which are to be absorbed. The normal post springs M2 are adjusted tc be `operated only when the brushes are on levels 1 and 10. The terminals of the rst and tenth levels are connected to intertoll trunks, these levels being represented by'terminals $35 and i538, respectively. The ter- -minals A36 represent a level in which the terminals are connected to trunks to a local dial ofce, neither of the sets of normal post springs being actuated on such a level if Selected in response to a rst train of impulses; and only springs 44| are actuated if this level is selected in response to a second digit after absorbing a like irst digit. If the first level is selected, normal post springs 442 are actuated to switch the repeating coil RC out of the talking connection. With either but not both of springs 44| and 442 actuated ground is connected to conductor 405 to effect the connection of a supervisory relay in the associated intermediate dialing trunk circuit for response to rering and disconnect signals fromY the calling operator. Upon selection of the tenth level, the actuation of both sets of normal postv springs disconnects ground potential from conductor 405 so that no supervisory signals will be given to the intermediate dialing operator, supervisory signals from the calling operator being transmitted through the intermediate dialing trunk circuit and through the selector CS to the selected intertoll trunk. y

Further explanation will be facilitated by describing in detail the circuit operations involved on calls originating in the first toll cnice and routed throughthe selector circuit CS. Assume i'lrst that the plug CPI of the cord CDI is inserted in jack J of the outgoing trunk circuitv OTI thereby closing a circuit for operating relay |04. Relay |04 effects the operation of relay ||0 as described in the aforementioned King et al. patent and closes a circuit for operatively energizing the upper Winding of signaling relay |40.

The operation of relay |40 connects signaling battery through conductor |64, retard coil |69, middle winding of composite signaling relay |10, upper winding of retard coil |66, upper conductor of toll line TLI, upper winding of retard coil 266 of signaling circuit CS2 in the second toll office,

to the windings of composite signaling relay 210. Relay 210 operates, closing a circuit through conductor 263, back contact of relay 2 |0 of outgoing trunk circuit T2, back contact of relay 214 of two-Way trunk circuit TWT2, back contact of relay 211, and the winding of relay 213. Relay 213 operates, connecting ground to conductor 253 to guard the toll line TL| from seizure in the second toll oce. Relay 213 closes a circuit, for operating relay 215, from ground through the front contact of signaling relay 210, conductor 263, back contact of relay 2|0, back contact of relay 214, winding of relay 215, a front contact of relay 213, thence in simplex through both windings of retard coil 260, back contacts of relay 230, conductors 21| and 212, inner front contacts of relay 213, conductors 28| and 282, back contacts of relay 290,

resistors

285, 266 and 281, and through the wind-ing of relay 288 to battery. The line relay 238 of toll selector TS2 is thereby operated in series with relay 215 of the two-Way trunk circuit TWTZ. Relay 215 closes a circuit through resistor 216 for holding relay 213 and closes a ci-rcuit for operating the sloW-to-release relay 211. Relay 211 also closes a holding circuit for relay ing a corresponding release and reoperation of relay 210 of signaling circuit CS2. Relay 210 repeats these dial impulses to relay 215 of two-way trunk circuit TWT2 and to relay 288 of selector TS2. Each release of relay 215 opens the operating circuit of relay 211; but, since this relay is slow in releasing, it maintains the connection of ground to conductor 283 during the response of relay 215 to dial impulses. The alternate release and reoperation of relay 288 causes the brushes of selector TS2 to be stepped up to the level corresponding to the digit dialed. At the end of the train of impulses the brushes 29|, 292, 293 and 294 are advanced step by step in the selected level to hunt for and seize a set of terminals connected to an idle trunk. When an ung-uarded l set of terminals is found, relay 290 is operated 213 and connects ground potential to conductor 283 to hold the selector TS2 and any succeeding switches or trunks through which a connection may be established. When the calling oper- Y and closes the circuit through conductor |64 causto disconnect relay 288 and connect toll line TLI, through brushes 29| and 292v and lthe engaged terminals to the next line, trunk or selector through which the desired connection is being established. For a detailed description of the operation of selector TS2 reference may be had to the aforementioned patent to King et al.

On the call being described, it'is assumed that the level selected by switch TS2 is a level in which the terminals are connected to intermediate dialing trunk circuits associated with combined intertoll and toll transmission selectors. The selected set of terminals is represented in the drawing by terminals 295 which are connected, through conductors 30|, 302, 303 and 304, to the intermediate dialing trunk circuit IDT of Fig. 3. Upon seizure Yof terminals 295, the line relay 325 of the incoming trunk circuit IT is operated, the circuit for operating relay 325 being traced from ground at the front contact of signaling relay 210, through conductor 263, back contacts of relays 2|0 and 214, winding of relay 215, a front contact of relay 213, thence in simplex through both windings of retard coil 260, conductors 26| and 262, back contacts of relay 230, conductors 21| and 212, front contacts of relay 213, conductors 28| and 282, front contacts of relay 290, brushes 29| and 292, conductors 30| and 302, back contacts of relay 310 of intermediate dialing trunk circuit IDT, conductors 32| and 322, both windings of retard coil 320, and through the winding of relay 325 to battery. Relay 325 closes a circuit for lighting the answeringlamp L3 associated with jack J3 of the incoming trunk circuit IT. When the call is answered by the insertion of the plug AP3 of a cord CD3 in jack J3, battery is connected through the'sleeve conductors of plug AP3 and jack J3 to conductor 3|3 to operate relay 3|4. Relay 3|4 closes a circuit for operating relay 3|6. Relay 3f 6 closes a circuit for operating relay 3|5, this circuit being traced from the Winding of relay 3|5, through front contacts of relays 3|6 and 325, a back contact of relay 310, conductor 303, brush 293, a front contact of relay 290, and through conductor 283 to ground at the lower front contact of relay 211 of two-way trunk circuit TWTZ. Relay 3|5 locks to conductor 303 under control of relay 3|6 but independent of relay 325, closes a circuit for operatively energizing the upper winding of relay 356 of intermediate dialing trunk circuit IDT, and extinguishes lamp L3. When the dial key at the calling operators position is restored to normal, relay |30 of outgoing trunk circuit OT! is operated and relay |40 is held under control of relay |94 in the manner described in the aforementioned King et al. patent. The talking circuit between the calling operator in the rst toll office and the answering Voperator in thesecond jtoll ofce includes conductors and |02, front contacts of Arelay |39, conductors |51 .and |62, repeating coil RCI, .condensers |65, toll line '-ILI., condensers 255, repeating coil RC2, conductors 26| and 252, back contacts of relay 23D, conductors 24| and 212, front contacts of relay 2.13,

conductors 28| and 282, front -contacts of relay 290, brushes 29| and 292, conductors 33.4 and 392, back contacts of relay 313, conductors '32| 4and 322, condensers 343, and conductors 3H and 31.2.

To complete the desired connectionfthe answering operator inserts the calling plug (JP3 of cord CD3 in the dial jack DJ of `the intermediate dialying trunk circuit IDT, Athereby causing'the operative energization of the left winding 'of relay 354. Relay 354 closes a circuit foroperating relay 355. Relay 355 closes a circuit through Athe right, low resistance winding of relay 354 and closes :a 4:locking circuit for relay 356. When the answering operator `actuates the dial key (not shown), bat#- .tery is connected through the impulse contacts ofthe dial, the ring conductor o plug CPB and conductor 352 to operate relay 351; and battery :is connected through the tip conductor of plug CPS and conductor to operate relay 358. Relay 358 closes a circuit for operating relay 359.

Relay 359 locks under the sole control of Yrelayv 3.55; Relay 351 closes a simplex circuit through .resistors 35| and 352, both windings of retard coil 1353, conductors 40| and, 452, back contacts of relay 4H), back contacts of relay 412, resistors `4|3 and 4|4, thence through resistor 4|5, back ,contacts Vof relays 409 and 430 in parallel, `Winding of relay 42 to battery at the back contact `of A y release magnet 429. Relay 42| closes a circuit for operating relay 422. Relay 422 connects 4ground through its inner lower front lcontact and va back contact of relay 433 to the winding of a common, permanent signal alarm relay 441 which operates to cause a maintenance alarm in usual manner in case no dial impulses are received within a predetermined interval of time.

When the intermediate, answering operator kdials the rst digit of the called route and subscribers number, relay 351 is alternately released and reoperated to repeat the dial impulses to relay 424. The release of relay 42|, in response to 4the first dial impulse, closes a circuit 4frornround at inner upper back contact of relay 4H), through the back Contact of relay 42|, upper front contact of relay 422, right contact of test key TK, `back contact of relay 430, winding of relay 4.23, and through the winding of the vertical stepping magnet 421 to battery. The stepping magnet 421 is thereby operated to step the brushes upto the rst level of the terminal bank. Vertical offnormal springs 440 are actuated when the brush shaft moves out of normal position. Relay l423 is loperated in series with magnet 421 and, when springs 443 are actuated, a circuit is closed from battery at the back contact of release magnet 429, through the upper contact of springs 445, winding of stepping relay 425, front contact of relay 423, conductor 4|9, to ground at a front contact of relay 422. Relay 425 locks through the back contact of rotary steppingr magnet 428, independent of relay 423. Relay 423 closes a circuit for operating relay 431; and relay 401 locks to conductor 4|9 under control of relays 439 `and 422, independent of relay 423. When relay 42| reoperates at the end of the first dial impulse, magnet 421 releases but relay 423 is slow in releasing and does not release until relay 42| remains operated for a predetermined interval after the last impulse inthe train. Relay l.422 is slow in releasing and .remains operated .during .the response Uof .relay 42| to dial impulses. lThe release :and reoperation of `relay 42|, in response -to each succeeding impulse inthe Vtrain created `by ithe dialing 4of `the rst rdigit by the answering operator, causes a corresponding operation and vrelease ofthe vertical stepping magnet 421, thereby advancing .the brushes to the level corresponding to the digit dialed. vWhen relay 423 releases vaft the end of the train of impulses, it opens the .operating circuit Loi relay 425 but relay 425 is held -opera'ted'un-der control .of springs '444 and magnet 428.

Assume now that the rst digit dialed by the intermediate voperator is one which is to be absorbed, the stepping of the .brushes to the correspending level being effective 4to -actuate normal Ipost springs 44| without actuating springs 442. .The actuationof spring's144l closes a circuit for operating relay 1445, this 4circuit including back contacts of relays 444 .and 443, .the front contact `of .springs 44|, lower back Contact of relay 459, front Vcontact of relay 42| and back contact of relay `4|l. The operation of relay 445 prevents the operation of the rotary stepping magnet 428 when relay 423 releases, and connects battery to the windings of relays 42| and 422, independent `of 'release lmagnet 429. When relay 423 releases, Yat the 'end of the train of impulses, a circuit is closed for loperating relay 444; this' circuit includes front contacts of

relays

445 and 425, the baclrccntact of relay 423, conductor 4|9, and a iront contact of relay 422. Relay 444 locks under control of relays 4|2 -a'nd 422, and closes a lock- 'ing circuit for relay 445 which is independent of relay 409 andV springs 44|. The aforementioned release of relay 423 at the end of the rst digit, closes a c'ircuitfor operating release mag- -net 429; this circuit "is traced from battery through the outer lower front contact of relay 445, middle contact of springs 440, winding of release magnet 429, front contacts of

relays

445 and 425, back contact of relay 423, conductor 4 I9,

f to ground at a front contact of relay 422. The

operation of release magnet 429 allows tlie brush shaft to be restored to normal in usual manner. When the shaft reaches normal position, the return of springs 440 to normal causes the release of magnet 429 and the release of relay 425. When the intermediate operator dials the next digit, the dial impulses are repeated by relay 351 to relay 42|. The release and reoperation of rezlay 42| in response to each impulse of the train vcauses a corresponding operation and release of the vertical stepping magnet 42.1 to step the brushes to the desired level. The release of relay 42I, in response to the rst impulse also causes the release of relay 445. Relay 423 operates in series with magnet 421 and remains operated until all of the impulses in the train have been received. When the shaft moves out of normal position, the actuation of springs 44|! closes the circuit for operating relay 425 and relay 425 locks under control of the rotary stepping magnet 428. Relay 444 being locked operated, relay 445 cannot be reoperated even though the level selected is one on which normal post springs 44| are actuated. When relay 423 releases at -the end of the second train of impulses, `or when relay 423 `releases at the end olf a rst train of impulses and relay 445 is not operated, a circuit is closed vfor operating the rotary stepping magnet 428 to step the brushes into engagement with the first Set 0f terminals in the selected level. .The circuit for operating magnet 428 includes the upper back contact of relay 445, upper front contact of relayV 425, backicontact of relay 423, conductor 4|9, and a front contact of relay 422. The operation of magnet 428 causes the release of stepping relay 425; and the release of relay 425 causes the release of magnet 428. The release of magnet 428 closes a testing cir-l cuit from battery at the back contact of release magnet 429, through the upper contact of springs 440, winding of relay 425, back contact of magnet 428, inner lower back contact of relay 430,

kthrough test brush 433 to the engaged test terminal. If the line, trunk or selector connected to the engaged set of terminals is busy, the test terminal has groundV potential connected thereto as a guarding potential, and stepping relay 425 reoperates, closing the circuit for operating rotary stepping magnet 428. Magnet 428 then steps the brushes into engagement with the next f set of terminals and causes the release of relayV 425; and the release of relay 425 causes the release of magnet 428. Relay 425 and stepping magnet 428 thus cooperate to advance the brushes step by step in the selected level to hunt for an unguarded set of terminals. When v,the test brush 433 engages a terminal which is not connected to ground, the release of magnet 428 closes a circuit for operating relay 430, from battery at the back contact of release magnet 429, upper contact of springs 440, Winding of relay 425. back contact of magnet 4'28, Winding of relay 430, conductor 4|0, to ground at a front contact of relay 422.v Being marginal, relay 425 does not operate in series with relay 430. Relay 430 connects ground at theV outer lower front contact of relay 422, through conductor 4|9, the inner lower front contact of relay 430, `brush 433 to .the engaged terminal as a busy, guarding potential and opens the circuit for operating alarm relay 441. y

Assume now that Vthe levell in which trunk hunting occurs is one in which the terminals are connected to trunks leading to a local dial oice, suchv a level being represented by the terminals 425. In such a case, the normal post springs 442 are not actuated, relays 409 and 4|0 are not oper ated and the operation of relay 430 is ineffective to disconnect relay 42| from conductors 40| and 402. As shown in the drawings the terminals 436 connect directly to a toll connector TC, but intermediateV selectors may be provided if necessary to give access to all subscribers in the local dial oiiice, inV which case theterminals 436 would be connected to an intermediate selector. The ground potential connected through brush 433 to conductor 553 is further connected through a back contact of relay 506 of connector TC, conductor 554, brush 434, a back contact of. relay 409, outer lower front contact of relay 430, and through the upper frontV contact of Yrelay 401 to the winding of relay 401 to Yhold this relay operated under control of relay 506 of the toll connector. 430 disconnects the winding of relay 423 from the back contact of relay 42 I., and closes a circuit, for operating the line relay 50| of connector TC, from battery through the left winding of relay 50|, a back contact of relay 506, conductor 552, brush 432, a iront contact of relay 430, a back contact of relay 4|0, lower front Contact of relay 42|, lower right winding of repeating coil RC, resistor 406, lower front contact of relay 401, upper right winding of repeating coil RC, a back contact of relay M0, a front contact of relay 430, brush 43|,

Relay conductor 55|, a back contact of relay 506, and 75 Athrough the rightr winding of relay 50| to ground. RelayV 58 l' closes a circuit for operating relay 502 and relay 502 locks through its inner upper front contact and a back Vcontact of relay 506, through conductor 553, brush 433, inner lower front contact of relay 430, to ground at a front contact of relay 422. The trains of impulses created by the dialing of the last two digits of the called local subscribers number are repeated by relay 351 to relay 42|; and relay 42| repeats these impulses to relay 50|V to effect the selective operation of the toll connector TC to seize the called subscribers line. For a complete description of the operation of a toll connector reference may be had to the aforementioned patent to E. D. Butz. When the brushes of toll connector TC engage the terminals of the called line and the called line is idle, relay 506 is operated by the energization of its lower winding in series with test brush 593 and the, cut-,off relay-596 of the called subscribers line circuit. Relay 506 locks the conductor 553, disconnects relay 50! from conductors 55| and, 552,

and opens the connection between conductors 553 and 554, thereby causing the release of relays 50|, 502, and 401. The release of relay 401 opens the bridge through resistor 406 across brushes 43| and 432, connects the lower winding of relay 420 to brush 43|, and closes a circuit for operating relay 4| 2. Relay 4| 2 opens the short circuits across the left windings of repeating coil RC, connects talking condenser 4|| between these windings, and connects the upper winding of relay 42E) to brush 432. The release of relay 502 closes the ringing circuit for signaling the called station. If and when the call is answered, relay 502 is reoperated and locks through conductor 554, brush 434, a back contact of relay 409, a front contact of relay 430, and a back contact of relay 401, through conductor 4|9, to ground at a front contact of relay 422. With

relays

506 and 502 operated, conductors 55| and 552 are connected through brushes 59| and 592 to the line L, talking battery being supplied through the windings of relay 420. The operation of relay 420 connects ground to conductor 404 operating relay 315. Relay 315 opens the circuit through the low resistance, right winding of relay 354 to extinguish the supervisory lamp associated with plug CPS of cord CD3 `but does not connect ground to conductor 304 until the intermediate operator disconnects cord CD3 from both of jacks J3 and DJ. vWhen plug AP3 is disconnected from jack J3 relays 3| 4, 396 and 3|5 release in succession. When plug CP3 is disconnected from jack DJ, relays 354, 351 and 358 release. The release of relay 354 causes the release of

relays

355 and 356 in succession. The release of

relays

356 and 358 causes the release of relay 358. Relay 359 is slow in releasing; and before relay 359 releases, a circuit Vis closed from ground through the inner lower front contact of relay 359 and lower back contact of relay 356 for operating relay 310. Relay 310V locks to conductor 303, disconnects conductors 36| and 302 from the winding of relay 325, and connects these conductors to and through conductors 40| and 402 to the winding of relay 42|. Relay 42| is thereby held operated inY series with relay 215 under control of relay 210. Since normal post springs 442 are normal, ground at the inner upper back contact of relay 4| 0 is connected through the upper front contact of relay 42 lower back contact of relay 409, back contact of springs 442, conductor 405, and a front contact of relay 310 to the winding of relay 365 of the intermediate dialing trunk circuit IDT. Relay 365 operates, connecting, the winding of supervisory relay 366,

throughV resistors

363 and 364 and both windings of retard coil 360 to conductors 40| and 402, thence through front contacts of relay 310 to conductors 30| and 302 parallel with relay 42| of selector CS. After relay 356 has released, ground is connected through a front contact of relay 315, conductor 304, brush 29,4, and a front contact of relay 290, to conductor 284 to operate relay 219 of two-way trunk circuit TWT2. Relay 219 connects signaling battery through its front contact, back contacts of relays 218 and 240, retard coil 269, the middle winding of relay 210 and upper winding of retard coil 266 to the upper conductor of toll line TL| to cause the operation of composite signaling relay |10. Relay |10 closes a circuit including a front contact of relay ||0, for operating relay |05; and relay |05 opens the circuit through the lower, low resistance winding of relay |04 to extinguish the supervisory lamp associated with plug CPI of cord CDI. 'Ihe aforementioned operation of relay 310 also connects conductor 303 to conductor 403; but this is without effect since relay 409 of selector CS is not operated. Switchhook supervision is repeated by

relays

420, 315, 219, and |05 to the calling operator.

When the calling operator disconnects, relays |64, Ill), and |40 are released. The release of relay |46 causes the release of relay 210. The release of relay 210 causes the release of relays 215, 366 and 42|E The release of relay 42|' causes the release of relays Y50|', 422 and 365. The release of relay 2 15 causes the release of relay 211'. The release of relay 211 disconnects holding ground potential from conductor 283 there.-- by causing the return of selector TS2 to. normal in the manner described in the aforementioned King et al. patent and causing the release of` relay 310; The release of relay 42,2' causes the release of relay 430 andthe operation of release magnet 429 in series with the common relay 446 to cause the shaft and brushes 'of selector C S to be restored to normal. When the shaft reaches normal, springs 440 are restored to normal causing the release of magnet 429. The aforementioned release of relay 422 also disconnects. ground from

brushes

433 and 434, causing the release of

relays

502, 506 and 596.

yAssume next that the level in which trunk hunting occurs is the first level, in which level the terminals are connected to intertoll trunks. The terminals 435 representing this level are connected to a twofway trunk circuit TWT5 associated with an intertoll trunk or toll line TLS. The trunk circuit TWT5, and the associated outgoing trunk circuit OT.5 @mi Signaling circuit CS5 are all similar to the corresponding circuits associated with toll line TLI. Upon selection of the first level, the normal post springs 44| are not actuated but the normal post springs 442 are actuated, closing a circuit for operatively energizing the upper winding of relay 443. When relay 423 releases, it closes circuits inf cluding the middle contact of the eleventh` rotary step springs .4 39 for energizing the lower, locking winding of relay 443 and Afor operatively energizing the winding of relay 409. Relay 409 Econnects conductors 40| and.4 02 to contacts of relay 430, connects conductor 404 to brush 43,4, and connects ground directly to the middle contacts o f springs 44| and 4.42. Trunk hunting occurs in the manner hereinbefore described, relay 436 being operated. when an, ungualded 91? of terminals is found. The operation of relay 430 extends the connection from conductors 40| and, 442,. through front contacts 0f relays 409 and 4,30, brushes 43| and 4 32 and through selected terminals 435, to the line conductors and 452 of vtheY trunk circuit TWT5 connected to the; seized terminals. Since relay 409 is operated, the operationof relay 436 causes the releasegof` relays 42| and 422 insuccession. Holdiris ercundrebcntialat the front Contact Of relai/.f 2.11 off twg-Way trunk circuit TWT2 is Connested thrgugh; brush 293 0f Selector TS2. conductor 303 front contact of relay 359, conductor 433, front Contact of relay 409, condugtor M3' t@ the Winding Of relay 430 U0 hold relay 43,0 operated and from conductor 4|3. through the inner lower front Contact of relay 43.6 and brush 433- to conductor 453 to hold theintertoll trunk circuit connected to the seized terminals. The operation of relay 430 also causes the release of relay 461l and closes a circuit from the Winding of relay 4|0, through the inner upper frontrcontact of relay 409, the lower back contact of the eleventh rotary step springs 439 and front contacts of

relays

430 and 422, operating relay 4|0. Relay 4|0 locks in parallel with relay 409 and the lower Winding oi"` relay 443, through the middle contact of springsy 43,9 and back `contact of relay 423 to holding ground potential on conductor 4|9. Relay 4|0 disconnects ground from the armature of relay 42| to prevent the operation of release magnet 426 when relay 422 releases. Relay 4|0 also connects` conductors 46| and402 through talking metal contacts to brushes 43| and 432 in parallel with front contacts of relay 409. When the intermediate dialing operator dials the succeeding digits of the called route and subscribers number, relay 351 repeats these impulses in the simplex circuit through resistors 36| and 362, windings of retard coil 360, conductors 40| and 402, front contacts of relays 4| 0 and 430, through brushes 43| and 432, to the trunk circuit TWT5 to effect the transmission of correspending signals over the toll line TL5. When the intermediate dialing operator has completed dialing and disconnects cord CD3 from jacks J3 and DJ, relays 3|4, 3|5, 3|6, 354, 355, 356, 351, .358 and 359 are released and relay 310 is operated in the manner hereinbefore described. The operation of relay 310 releases relay 325, and completes the talking connection between toll lines TLI and TL5 by connecting conductors 30| and 302 to conductors 40| and 402. The repeating coil RC is not included in this connection and relay 420 is not used. Normal post springs 414| being normal, relay 365 of trunk circuit IDT is operated as hereinbefore described to connect relay 366 to conductors 40| and 402, thence through front contacts of relay 310 to conductors 30|l and 362, so that relay 366 is controlled by signaling relay 213. When the calling operator releases. the connection, all of the circuits are restored tonormal as hereinbefore described. V

Assume noW that the selector CS selects the tenth level in which the terminals are connected ,to intertoll trunks which are similar to the inter-v toll trunks in level except that no supervision is to be given by the intermediate operator. Upon selection of the tenth level both ofthe sets of normal post springs 44| and 442 areactuated to disconnect ground from conductor 405 and thereby prevent the operation of relay 365 of the intermediate dialing trunk eircuitf IDT; and since relay 365 is not operated, relay 366 is not 'lonrlected to conductors 30| and 302. Answering Supervisory signals are transmitted from'the seized intertoll trunk, through brush 434 and a front contact of relay 405 to'relay 315 of the intermediate dialing trunk circuit IDT. Relay 315 repeats the answering supervisory signals through conductor 304, brush 294 and conductor 284 to relay 219 of two-way trunk circuit TWTZ; and relay 219 repeats these signals over toll line TLI to control the supervisory lamp'of the calling operators cord CDI in the manner hereinbefore described. When the calling operator disconnects, the outgoing trunk circuit is restored to normal, signaling relay 210 releases, two-way trunk circuit TWTZ is restored to normal, and a disconnect signal is transmitted over the intertoll dialing trunk. The release of relay 211 of two-way trunk' circuit TWTZ causes the release of relay 290 to restore selector TS2 to normal, the release of relay 310 to restore Vthe intermediate dialing trunk IDT to normal, and

the release of

relays

409, 4|0, 430 and 443 to restore selector'CS to normal.

If, when the brushes of selector CS are being advanced in a selected level to hunt for an unguarded set of terminals, all trunks connected to this level are busy, the brushesare advanced to the eleventh rotary position, actuating springs 439 to cause the release of relays409, 4I0Vand 443 if operated. Relay 430 is operated and relay 425 remains normal. The operation of relay 430 causes the release of relay 401. With relays 401 and`4 l 0 normal, relay 4|2 is operated. The operation of relay 4l2, with springs 439 actuated, connects interrupter 448 through resistor M8, iront contact of relay 424, lower right winding of repeating coil RC, and through the lowermost front contact of relay 4l2 to the upper winding of relay 420 causing the alternate operation and release of relay 420, The alternate operation and release of relay 420 causes like operations of relays 315, 219, H0 and 105 in succession to ash the supergincoming conductors through which said selector is seized, a set of brushes, a bank of terminals divided into levels, means controlled by digit impulses for selecting any desired one of Ysaid levels,rmeans for advancing the brushes into engagement with an unguarded set of terminals in `any selected level, and two sets of independently actuated normal post springs, a group of intertoll trunks connected to the terminals in one of said levels, a group of trunks to a local dial office connected to the terminals in another of said. levels, one of said sets of normal post springs adapted tobe actuated upon selection of a level giving access to said intertoll trunks, the other Vset vof normal post springs adapted to be actuated upon selection of a particular level, a repeating coil normally connected between said incoming conductors and the brushes of said selector upon selection oi a set of lterminals in a selected level, means rendered effective upon selection of a set of terminals in a level on which said one set of normal post springs are actuated for switching said repeating coil 'out of the connection between said incoming conductors and said brushes, and means comprising said other set of normal post springs for effecting the release of the brushes upon selection of said particular level to absorb the train of directive impulses effecting seizure of said particular level.

`3. In a telephone system, a trunk circuit, a selector individual to said trunk circuit, said selector comprising a terminal bank divided into levels, brushes for connecting with any set of terminals in said bank, means comprising an impulse relay in said trunk circuit for receiving trains of directive impulses, means controlled by said impulse relay in a simplex circuit vover the talking conductors between said trunk circuit and saidselector forfadvancing the brushes to select any desired level, means for automatically adf vancing theV brushes in a selected level to hunt visory lamp of the calling operators cord. When rthe calling operator disconnects cord CD4 from jack J the various circuit units are restored to normal as hereinbefore described. Y Y

The test key TKr enables the testing ofrelay 42! to insure satisfactory impulse repeating.

Various modiiications of each of the circuit units and of the trunking, switching and signaling arrangements may be made. 'I'he aforementioned King et al. patent is illustrative of a somewhat larger system to which this invention is applicable.

What is claimed is:

1. In a telephone system, a selector comprising incoming,Y talking and supervisory conductors, a bank of terminals divided into groups, brushes ior connecting with any set of terminals, means for advancing the brushes to select any desired gro-up, and means for advancing-the brushes to select an unguarded set of terminals in a selected group, a group of intertoll trunks connected to one of said groups of terminals, a group of trunks to a local dial oflice connected to another of said groups oi terminals, means includinga repeating. coil for completing a talking connection between said incoming conductors and the brushes of the selector on calls to a local dial oii'ice, and means comprising contact springs actuated responsive to selection of a group of intertoll trunks for eiecting the direct connectionof said incoming conductors to said brushes, said direct connection excluding said repeating coil.

. 2. In a telephone system, a selector comprising 15T for and seize an ung'fuardedY set of terminals, two independently actuated sets of normal Ypost springs for said selector, one of said sets of springs actuated upon selection of a particular level, means controlled by said one set of springs for effecting the return of the brushes to normal, a repeating coil normally included in'the connection between said trunk circuit and the brushes of saidselector upon selection of a set of terminals in a selected level, the other of said sets of normal post springs actuated upon selection of a certain level, and means controlled by said other set of springs for switching said repeating coil out of the talking connection between said trunk circuit and said brushes.

4.v In a' telephone system, an operators -position including means for answering calls and an impulse sender forcontrolling selector switches, an intermediate dialing rtrunk circuit comprising incoming conductors through which said trunk circuit may be seized and conductors terminating at said operators position for answering a call upon seizure of said trunk circuit, a selector ,1 individual to said trunk circuit, said selector comprising a terminal bank divided into levels, brushes for connecting with any set of terminals in said bank, means controlledrby directive impulses for selecting any level, and means for'l automatically selecting an unguarded set of terminals in any selected level, means in said intermediate dialing trunk circuit including conductors terminating at vsaid'position responsive to the operation of said, impulse sender for controlling the'selectiveoperation of said selector,

said selector further comprising two independently actuated sets of normal post springs, one of said sets of springs adapted to be actuated upon selection of a particular level, means effective in response to the actuation of said one set of normal post springs to return the brushes to normal to absorb the impulses effecting seizure of said particular level, a repeating coil normally included in the talking connection between said trunk circuit and said brushes upon selection of a set of terminals in a selected level, the other of said sets of springs adapted to be actuated upon selection of another particular level, and means elective in response to the actuation of said other set of normal post springs for switching said repeating coil out of the talking connection between said trunk circuit and said brushes.

5. In a telephone system, an operators position including means for answering calls and an impulse sender for controlling selector switches, an intermediate dialing trunk circuit comprising incoming conductors through which said trunk circuit may be seized and conductors terminating at said operators position for answering a call upon seizure of said trunk circuit, a selector individual to said trunk circuit, said selector comprising a terminal bank divided into levels, brushes for connecting with any set of terminals in said bank, means controlled by directive impulses for selecting any level, and means for automatically selecting an unguarded set of terminals in any selected level, means in said intermediate dialing trunk circuit including conductors terminating at said position responsive to the operation of said impulse sender for controlling the selective operation of said selector, said selector further comprising two independently actuated sets of normal post springs, one of said sets of springs adapted to be actuated upon selection of certain levels including a particular level, means effective in response to the actuation of said one set of normal post springs upon selection of said particular level to return said brushes to normal to absorb the train ofv impulses eiecting seizure of said particular level, a repeating coil normally included in the talking connection between said trunk circuit and said brushes upon selection of a set of terminals in a selected level, the other of said sets of normal post springs adapted to be actuated upon selection of certain levels including a level on which said one set of springs are not actuated, means eiective in response to the actuation of said other set of springs for switching said repeating coil out of the connection between said trunk circuit and said brushes, means in said trunk circuit for connecting said incoming conductors to said selector, supervisory means in said trunk circuit, and means effective upon connection of said incoming conductors to said selector to connect said supervisory means to said incoming conductors, said last-mentioned means being rendered inoperative by said normal post springs upon selection of a level on which both of said sets of springs are actuated.

6. In a toll oince of a telephone system, a selector for use in completing desired telephone connections, talking conductors, a holding conductor, and two supervisory conductors leading to said selector, said selector comprising a bank of terminals divided into levels, a set of brushes for connecting with any set of terminals in said bank, means comprising an impulse relay connected to both of said incoming talking conductors in parallel for controlling the movement of said brushes to select any desired level, and means for advancing the brushes to select an unguarded set of terminals in any selected level, a first group of intertoll trunks connected to a rst level of said bank, a group of trunks leading to a local dial oftlce connected to a second level of said bank, a second group of intertoll trunks connected to a third level of said bank, two independently actuated sets of normal post springs for said selector, a first one of said sets of springs actuated upon selection of a particular level, means rendered effective by the actuation of said first set of springs upon selection of said particular level in response to a first train of impulses incoming to said impulse relay to return the brushes to normal t0 absorb the rst train or impulses, means including a repeating coil for completing a talking connection between said talking conductors and said brushes upon selection of a set of terminals in the level connected to trunks to a local dial olce, the second one of said sets of springs actuated upon selection of the level to which said iirst group of intertoll trunks are connected, means controlled by said second set of springs for connecting said incoming talking conductors directly to said brushes upon selection of a set of terminals in either of the levels connected to intertoll trunks, means including said holding conductor for maintaining the connection with a selected set of terminals in any level, a supervisory relay in said selector effective on a call to the local dial oince for transmitting supervisory signals over one of said two supervisory conductors, means including a brush of said selector for transmitting signals from a selected intertoll trunk over said one of the two supervisory conductors, means including a normally closed contact of said rst set of normal post springs for connecting ground potential to the other of said two supervisory conductors on a call to a trunk to a local dial office, and means including a normally closed contact of said second set of normal post springs for connecting ground potential to said other of the two supervisory conductors on a call to a trunk in said rst group of intertoll trunks, both of said sets of normal post springs being actuated to prevent the connection of ground potential to said other of the two supervisory conductors on a call to a trunk in said second group of intertoll trunks.

PAUL W. WADSWORTH.