US1708959A

US1708959A - Intercepting cord and trunk circuit

Info

Publication number: US1708959A
Application number: US51315A
Authority: US
Inventors: Ray L Stokely
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1925-08-20
Filing date: 1925-08-20
Publication date: 1929-04-16
Anticipated expiration: 1946-04-16

Description

April 16, 1929. R. 1.. STOKELY 1,708,959

INTERCEEPTING CORD AND TRUNK CIRGUIT Filed Aug. 20, 1925 4 Sheets-Sheet 1 W L S/0/re/y. by V ,4//j/.

April 16, 1929.

R. STOKELY INTERCEPTING CORD AND TRUNK CIRCUIT Filed'Aug. 20, 1925 4 Sheets-Sheet 2 April 16, 1929. R. L. STOKELY. 1,708,959

' INTERCEPTING CORD AND TRUNK CIRCUIT Filed Aug. 20, 1925 4 Sheets-Sheet 3 flay A. S/Me/y. by /4//3/.

April 16, 1929. R. L. STOKELY INTERCEPTING CORD AND TRUNK CIRCUIT Filed Aug. 20, 1925 4 Sheets-Sheet 4 M W w w a: mi KM b u 0 1 Q J m 3 WA m y p h h a H H h W I: m- MW- QNEQQ NQW kw H w A: i I Q? h M M \ww mm ull|\ M\% \M\ QM. R3

w mQ

Patented Apr. 16, 1929.

UNITED STATES RAY L. STOKELY, OF FLORAL PARK, NEW Ytlitll'l li, .4?

ssi

carrier oFFicE.

lOllt TO "W'EtlTlillitN ELECTRIC COMPANY, INCORPORATED, 013 NEW YORK, N. Y., A COltt'OlEtA'lION 0]? NEW YORK.

INTERCEZPTING CORD AND TRUNK GlTlEtO'UIT.

. Application filed August 20, 1925. Serial No. 51,315.

This invention relates to a telephone sys tem and more particularly to improvements in intercepting operators circuits for use in autmnatic telephone systems. i

It is tle object ol this invention to provide improved intercepting operators circuits for intercepting calls directed from various sources over automatic switches.

In an automatic telephone system the do.- tics of an intercepting operato' are particu larly to supervise calls from various sources that have been incorrectly directed to subscribers lines or lines on which the service has been discontinued. A call associated with an intercepting operators position does not reach a destination requiring a charge by the telephone company. Certain of such lines are equipped with call charging apparatus ordinarily operable when the line is connected to its destination. Other lines connected to the intercepting operators posi tion are associated at the initiating end with toll cord circuits or the like which require the operation of particular apparatus in the intercepting opcrators circuits to properly.

supervise the operator at the called position.

A feature of this invention is in the provision of means in intercepting operators circuits whereby the intercepting operatofls cord circuit may automatically discriminate between a local and a toll. call.

Another feature of this invention is in the provision of means whereby an intercepting operator receives a disconnect signal when a toll operator disconnects the cord circuit from the automatic switching apparatus.

A further feature of thisinvention is in the provision of bridged resistance operable in accordance withmeans for discriminating between calls from various sources to pre vent the operation of call charging apparatus when a call is initiated by a local subscriber and to properly signal the tool operator when i call is initiated from such a source.

These and other tleatures of the invention will be apparent from the iollowing description taken in connection with the accompanyinn; drawings. 1

Fig. 1 illustrates the incoming end of a toll line and a toll operators cord circuit arranged for completing a call from a toll line to automatic switching apparatus.

Fig. 2 illustrates a toll switching trunk and a toll selector circuit in an automatictelephone exchange system.

Fig. 3 illustrates a con'ibination local and toll connector circuit, arranged for opera tion from a toll selector, Fig. 2, or a local sub- A a more detailed description will now be given in connection with the accompanying drawings in which Fig. 1 a toll operatofs cord which is used with the incoming toll trunk and the toll switchingtrunk of Fig. 2. The toll cord is arranged for dialing; and supervision onec lls through the toll selector TS oil Fig. 2 and the connector G of Fig. 3. i

Fig. 3 also shows a local subscribe1"s station from which it is possible to select connector C in a -manner similar to that used by the toll operator and thus be connected to the intercepting operatofis trunlr IOT of Fig. L from which the call is completed to the intercepting operator by means of the cord cir cuit IOG.

NVhen plug 100 of the toll operators cord circuit is inserted in jack 101 of a ringdown toll line in response to the lighting of a line lamp (not shown). relay 102 operates in an obvious circuit. The operation of relay 102 in turn operates relay 103, under control of relay 10d. lhe,o )eration of relay 1.03 prevents relay 105 from operating and lighting supervisory lamp 106. The toll. operator having received the number of the desired line througl'i her telephone set- 150, which is connected to the cord circuit by the operation of the dialing and, talking key 115, the tip of plug 10? is touched to the sleeve of jack 200 or likejaclcii as shown in Fi 2 to select an idle trunk line leaching to the machine switching oiliee in which the desired line terminates into which plug 107 may be inserted.

The insertion of the plug 10''!' in jack 200 of the trunk "l establishes an operating circuit for relays 109 and 202, over a circuit from battery,through the outer back contact of relay 116, left winding of relay 109, lowermost alternatecontacts of key 115, which the operator has now thrown fronrthe left-hand talking position to the right-hand dialing backcontacts of relay 201 and left w'ndiug of relay 202 to ground.

The operation of relays 109 and 202 com pletes a series circuit for the operatlon of relays 203 and 119 from battery, through the.

back contact of relay 120, winding of relay 119, right winding and contacts of relay 109, sleeve contacts of the plug 107 and ack 200, left contact of relay 202 andright winding of relay 203 to ground, The operation of relay 119 closes an obvious circuit for relay 116 which then operates, thereby closing the dialing loop'including the tip and ring of p ug 107, the left contacts of relay 109 and through the'contactsofdial 118. Relay 203, in oper ating, connects battery at its left front contact to the- Winding of relay 201 thereby causing its operation. 2 Relay 201, in operating, opens at its outer left back contacts the operating circuit for relay 202 and closes at contact214 a holding circuit for this same relay from battery, left front contact of relay 203, right Winding of relay 202, contact 214 of'relay 201 to ground through the left winding of relay 202. Relay 201, inoperating, also closes its innermost front contact thereby partially closing a bridge including relay 206 across the trunk conductors. The circuit is not completed, however, at this time as it is opened at the right-hand contacts of relay 203. Further, relay 201 in operating extends the trunk conductors to a distant office and locksithrough its contact 215 under control of relay 206.

The combinedoperation of relays 109, 116 and 201 closes the trunk circuit including the Winding of pulsing relay 204 in trunk sew lector TS at the machine switching ofiice. This circuit may be traced from battery, back contactof release magnet 208, righthand winding of pulsing relay 204, outer left back contacts of relay211, inner left back contactof relay 212, resistance 217, outer left back contact of relay 212, outer front contact of relay 201, ring contacts of thejack 200 and plug 107, outer lcft back contacts of relay 110, inner left front contact of relay 109, winding of polarized relay 120, contacts of the dial 118, inner front contact of relay 116, outer left front contact of relay 109, tip contacts of the plug 107' and jack 200, inner front contact of relay 201, outer right back contact ofrelay 212, resistance 216 and inner right back contact of relay 212 to ground. Relay 20 1 operates in this circuit but polarized relay 120 does not operate at this time due to its connection in. the circuit with respect to the polarity of the battery at the machine switchmg oflice.

The operation of relay 204 closes at its right front contact an obvious circuit for operating relay 222. Relay 222, in operating, closes its right front contact lhcrcby preparing the energizing circuit for the vertical or primary magnet 223. In this circuit is included relay 221 which operates in series with primary magnet 223 as described later. Relay in operating. also closes an energizing circuit for relay 257 which may be traced from ground, left front contact of relay 222, outer right back contact of relay 2,48. outermost right back contact of relay 21.1 and winding of relay 257 to battery. Relay 257 operates in this circuit for a purpose to be later described.

The nefyt operation on the part o f the 0 )erator, after having inserted plug 107 into ]il(l( 200 is to rotate the dial. 118 to the first digit of the wanted number. As the dial returns to'normal, the loop dialing circuit is interrupted a number of times corresponding to the digit selected and thereby causes the synchronous release of relay 204. This relay in turn closes the prepared circuit for the vertical or primary magnet 223 which now operates a corresponding number of times and in series with relay It will be noted that relays 222 and 224 are slow to release and although the circuits for these relays are alternately opened. they will be held operated during the pulsing. The circuit for operating relay 221 and primary magnet 223 maybe traced from battery, winding of magnet 223, winding of relay 224. out crmost right back contact of relay 226, right front contact of relay 222 and right back contacts of relay 204 to ground.

The operation of relay 224 operates relay 238 over a circuit from ground on the left front contact of relay 222, front contact of relay 221 to battery through the winding of relay 238. Relay 238 looks over another circuit from ground on the left front contact of relay 222, middle right back contact of relay 226, inner right front contact and winding of relay 238 to battery.

When the selector takes its first step due to the energization of magnet 223, the oil'- normal switch 228 operates, thereby closing a circuit for the operation of relay 2 29 which may be traced from battery, back contacts of magnet 208, upper alternate contact of oil'- normal switch 228, winding of nmrginal relay 229, front contact of relay 224 to ground at the left front contact of relay 222. In attracting its right armature, relay 229 locks in a circuit including the back contact of rotary magnet 232 and its own right front contact. Relay 229, in operating, also closes a short circuit path around the winding of relay 226 which may be traced from ground, left front contact of relay'222, the winding of relay 226 to ground at the rightfront contact of relay 229 to preventthis relay from operating at this time.

With each interruption of the contacts of dial 118 during the transmission of. the first digit, the vertical magnet 223 will be energized and step the brushes to the desired level of the switch bank. Upon the cessationof the impulses and the release of relay 2 24;, which relay as stated held operated durlng which thus in turn breaks the energizing circuit of magnet 232. The switch will therefore, come to rest on

terminals

308, 309, 310

and 311 and if terminal 310 is not Cl1tt1't1C11G1- ized by a busy ground the switch brushes will remain 1 associated with these terminals.

Under these circumstances, the short circuit across the terminals of the winding of relay 226 will be opened when relay 229 releases and when the armature of magnet 232 restores to normal, relay 226 will operate in'the follow- 111g circuit: ground, left front contact of relay 222, winding of relay 226, normal contact of magnet 232, winding of relay 229, upper alternate contact of switch 228 and back con tact of magnet 208 to battery. Relay 226 opcrates in this circuit, but relay 229 which is marginal, will not operate at this time due to the high resistance introduced into the circuit by the winding of relay 226. Relay 226 in operating closes its left contacts thereby connecting the toll train through to the connectorC.

If the. first trunk upon which brushes 250,

' crate over a circuit frombattery through its winding, left front contact of relay 229, contact 233 of relay 224 to ground at the left front contact of relay 222. This series of operations will continue until an idle trunk has been found at which time busy ground is connected to the sleeve by the operation ofrel 226. It willbe noted that the operation of relay 226 transfers the holding circuit for relay 238 to brush 253, contact 311, inner right back contact of relay 302, contact 310 and thence to the busy ground.

When the trunk associated with

contacts

308, 309, 310, and 311 is seized an energizing circuit is completed for the relay 301 which may be traced as follows: ground through the left winding of relay 301, inner left back contact of relay 302, contact 309, brush 251, outer left front contact of relay 226, left front con tact of relay middle left back contact of relay 2&8, lower right winding of repeating coil 24l2, resistance 220, outer right front con tact of relay 238, upper right winding of repeating coil 24:2, inner left back contact of relay 2 13, inner left front contact of relay 226, brush 250, contact 303, outer left bach contact of relay 302, right winding of relay 305, to battery through the right winding of relay 301. i l

Relays

301 and 305 operate in series. 11elay 305 locks to ground over a circuit from battery tl'irough its left winding and left front contact, contact 3532 of relay 306, con tact 310, brush 252, inner right front contact of relay 226 to groiilud on the left front contact of relay 222. Relay 301 in energizing closes an obvious circuit for relay 3 3. i lay 303 operated connects ground from its right front contact over lead -1 thereby making the connector C test busy to all local selectors. The operation of relay 303 closes the pulsing circuit for the primary magnet ,316 which may be traced from ground on the back contact of relay 301 effective when this relay releases, left front contact of relay 303, conductor 312, normal contact of oifnbrmal switch 313, conductor 31:1, winding of relay 315 to battery through the vertical magnet- 316. Relay 315 and rertical magnet 316 do not operate at this time as relay 301 is operated.

The toll operator now manipulates the dial 118 in the toll cord TC in accordance with the tens and units digits of the desired sub-- scribers line. The dial interruptions release pulsiiig relay 20-1 as hereinbefore described which opens, at its left contact, the circuit for relay 301 which releases in syiuwhronism with relay 20 1. Each release of relay 301 establishes the circuit hereinbefore traccl to operate the vertical. magnet 316. Relay 315 is operated upon the initial release of relay 301 and remains operated throughout the units series of dial interi-uptions. After the first impulse has been sent, o1f-normal switch 313 operates closing a new circuit for the operation of vertical magnet 316. This new circuit may be traced from ground on th back contact of relay 301., left *ri ut c 1,. of relay 303, conductor 312, lowermt t alternate contact of oil"-ner1nal switch 313, right front contact and win din of relay 315 to battery through the winding of magnet 316. The operation of relay 315 establishes a circuit 'appar of oil-normal swi i allow rclay'320 to operate and open to operz-iterelayj 321 from battery through its left winding, left front cont ctof relay 315, le'l't *tront contact of relay 305', contact 352 of relay 306, contact 310 and thence to the busy ground at the selector Fig. 2. Relay 321 is held operated by this ground under control of laus responsive to the operation of the toll operatofls ringing key.

At the end of the series of tor the tens digit,'1el ay315 r leases thereby closing a circuit for the oper: ion of rotary magnet 317 from c ound on the back contact of relay 301,'le't ont contact oi relay 303, conductor 312, l-i .in'iest alternate contact 313, ri back contactinterruptions A of relay 315, outer left back contact of relay 320 'in parallel to ba tery over one circuit through the winding of rel; Y 319, over another circuit through lower nost bac contact of relay 318 to battery through me winding otrotary magnet 317. The circuit is now in condition to receive the units digit impulses. These impulses interrupt the circuit for relay 301 thereby opening and closing the impulse circuit hcrcinhctore tr Tl... 3n release of rcla 301 on 1 rear 31. and

rotary magnet 317. Brusies 328, 329 and 330 are new rotated in response to the dial interruptia .s, to the wanted S1ll)ECl'll)'cl"S line.

T Relay 319 does not follow the iinpulscs as it is slow to release and rei rains operated durin dial interruptions. A testing circuit is thus established from brush 330 through its right front contact, contact 362 to hi ttery through the winding ot' relay 320.

Busy called station.

It the dialed, station is busy, relay 319 will remain operated a sui'licient length of time to over a circuit from ground on the busy sleeve ter1ninal412, placed hereon by an associated connector. Upon the release of rela 319 relay 320 locks over a circuit from battery through its winding, contact'362 oi relay 31S contact 338 of relay 319, inner right front contact of relay 320, conductor 331, to ground on the right front contact oi relay 303. Relay now operates from ground on trunk contacc 31.0, contact oi relay 306, left front contact of relay 305, winding of relay 302, inner left front Contact oi relay 320, left back contact of relay 319, lower back contact of relay 318 to battery through winding of rotary .iagnet 317. The operation of relay 302 opens the circuit between

cond rs

350 and and 360 and (it'll and (5011110eah

conductors

360 and 301 to

contacts

308 and 309 respectively at its left contacts. This operation also disconnects "clay 301 from

contacts

308 and 309 the connection bcteween contacts 310 l 311 at its inner 'ht back contact. Relay 301 does not release it is held operated over a circuit "from ground on the sleeve contact 310. inner right front contact of relay 302, resistance 346, right winding of relay 305 to battery through the right winding of relay 301. As relay 301 is held operated, relay 303 is also held operated thereby keeping ground connected to the local sleeve conductor 304.

The operation of relay 302 opens the locking circuit for relay 238 to cause its release and further opens the locking circuit or relay 321. The latter relay however, is slower to release than relay 238 and a locking circuit for relay 321 is established through the normal contacts of relay 238, traced from ground on the left front contact of relay 222, conductor 207, left back contact of relay 257, inner left back contact of relay 211. inner right back contact of relay 238, middle right front contact of relay 226, brush 253, contact 311 to battery through the winding and inner left front contact of relay 321. The release of relay 238 closes an operating circuit for relay 212 from ground on the left back contact of relay 238, winding of relay 212, lower altcrnate contact of oil-normal spring 228 to battery on the back contact of magnet 208. The operation of relay 212 reverses battery and ground over the circuit traced, for the dial pulsing circuit associated with the windings of relay 204, thereby operating polarized relay 120 which opens the circuit for relay 119 in turn releasing relay 116 and opening the dialing circuit. The operation of relay 120 further opens theholding circuit for relay 109 to cause its release. The release of relay 109 establishes an operating circuit for relay 133 through the windings of relays 102 and 134,

right contact of relay 109 to the sleeve ground. Relay 134 is marginal and does not operate in series with the high resistance sleeve of the toll trunk shown in Fig. 2. The operation of relay 133 establishes an obvious operating circuit for relay 110 which operation associates the talking conductors with supervisory relay 124 bridged across said talking conductors. The release of relay 238 as previously traced, also closes a circuit for operating relay 241 from battery through its winding, middle right back contact of relay 238, lower right winding of repeat coil 242, middle left back contact of relay 248, left front contactof relay 204, outer left front contact of relay 226, brush 25]., contact 309, inner left front contact of relay 302, conductors 360 and 34!), enter right front cont-act of relay 320, outer right front contact of relay 302 to ground through interrupter 323. The interrupter 323 opens and closes the above traced circuit ing generator 327 through its inner right back contact and closes conductors 360 and '-361tl1roiigh to

conductors

340 and 341.

- Toll calls intercepted.

' i If thetoll operator has dialed a number 'which has not been assigned to a subscriber or a number'which has been changed, the conneetion is completed through to the intercepting operators trunk IOT, and the brushes 328, 329 and 330 will rest on

contacts

420, 421 and 422. The operation of Figs 1, 2 and 3 is thesame as described for a call to an idle subscribers station up to the point of seizing the subscribers station and associating a ringing source with the line conductors. A circuit is closed from ground on contact 332 of relay 318, sleeve brush 330, terminal 422, left back contact of relay 402 to battery through the winding of'relay 403 and also over the same circuit through terminal 422, through the left back contact of relay 401 to battery through '1 lampv426. Relay 402 now operates from the tery through the winding of relay 405. Re-

lays 405 and-401 operate in the circuit traced. Relay 405performs no useful function at this time. A locking circuit for relay 401 is established from battery through its left winding to ground associated with contact 422. The operation of relay 401 extinguishes lamp 426. .A circuit is now elosedfrom battery through the windingflof relay 241, middle-right-back contact of relay 238, lower right winding of the repeating coil'242, middle left back contactof relay 248, left front contact of relay 204, outerfleft front contact of relay 226,

brush 251, contact 309, inner left front coni tact of relay 302, conductor 360, outer right front contact of relay 321, conductor 340, contact 331 of relay .318, brush 328, contact 420, inner left back contact of relay 404, conductor 431, ring of jack 41.3 and plug 414, conductor 424, inner right back contact of relay 408 I to ground througlrthe winding of relay 406. c Relay 241 operatesand establishes an obvious operating circuit for relay 211 which establishes-a local holding circuit for relay 204.

- This removes the battery and ground from the talking conductors, associated with the V toll cord to release'relay 124 and extinguish lamp 125. Relay 406 operates and closes an obvious'eircuit for relay 409 which operates and locks'to ground on the frontcontact of relay 405. Relay 409 operated closes a circuit for operating relay 408 from ground on the left front contact of relay 409, outer left back contact of relay 423 to battery through the winding of relay 408. The operation of relay 408 establishes an operating circuit for relay 407 from battery through the winding of relay 241 and thence to conductor 424 is traced for the operation of relay 406 through the inner right front contact of relay 408, right and left windings of rela 407, conductor 425, tip of plug 414 and jack 413, conductor 430, outer leftback contact of relay 404, contact 121, brush 329, contact 337 of relay 318, conductor 341, inner right front contact of relay 321, conductor 361, outer left front contact of relay 302, contact 308, brush 250, inner left front contact of relay 226, inner left back contact of relay 248, upper right winding of repeating coil 242 to ground through the right outer back contact of relay 238. Relay 408 further closes an obvious circuit for relay 423. The operation of relay 423 opens the operating circuit for relay 408 which is slow to release and remains operated until relay 407 operates at which time a holding circuit for relay 408 is established through its outer left front contact, front contact of relay 407, sleeve of plug 414 and jack 413 to ground through the winding of relay 401. The operation of relay 408 further opens the operating circuit for relay 406 to cause its release. Relays 418 and 419 do not operate when the intercepting operators cord circuit is associated with a toll call and will later he described in connection with a call from a local station. The resistance of the left winding of relay 407 is sufiicicntly high to cause the release of relay 241. The release of relay 241 releases relay 211 to reestablish the circuit for relay 124 through the windings of relay 204. Relay 124 operates and lights lamp 125 to signal the toll operator. \Vhen the intercepting operator actuates the talking key 416, a shunt is connected around the left winding of relay 407 which is of a high resistance thereby allowing relay 241 to operate and cause the toll operators lamp 125 to be extinguished. The intercepting operator now intermittently actuates and releases key 416 to flash lamp 125 until the toll operator responds.

The intercepting operator now requests information from the toll operator regarding the called station and furnishes whatever information is necessary under the service condition. The toll operator then removes the plug of cord TC from jack 200. The intercepting operator restores key 416 thereby releasing relays 241 and 211. Both operating circuits for relay 204 are thus opened to cause its release. The release of relav 204 opens the circuit hereinbefore traced for relay 407 to cause its release and the release of relay Relay 407 released opens the mousse locking circuit for relay 408Which releases and closes the circuit tor lighting disconnect lamp 415 thus giving; the intercepting operator a signal that the toll operator has disconnected. y

The release ot relay 20stalso closes a circuit to restorethe selector TS t'roni groiilnil on its right back contact, right back contact of relay 222, winding of release magnet 208 to battery throiio'h the middle alternate contact of oilnorn'ial spring 225%. The restoration ot sclector TS removes the busy around from contact 310 which causes the release of relay 318, also the holding; circuit for relay 301 is opened at the tip and. ring contacts 308 and The release of relays 30.1. and 318 closes a circuit for operatingrelease magnet 353. This circuit is traced from ground on the back contact of relay 301, lett back Contact of relay 2303, contact 336 or relay 31.8, niiildle alternate contact of ofii-norrnalxspring 311.3 to battery through the winding of magnet 353 and lamp 32 1i. 'lfhc operation of release magnet 353 restores connector U to normal. The release oi both these circuits may occur before the intercepting ope 'ator removes plug ll/l: from i M11413.

Local call interceptor An intercepted call trom a local subscriber Will now be considered. 1 he local subscriber is shown ll 300 in the upper left i] and corner oi Fig. 3. A circuit is extended by means Well known to the art tliirouggh the primary and secondary selectors PLl J and $1155 to tl'ie counectorC. and relay 301 operates'over a c lit from battery through its right Wl1'i(l inn, outer left back contact o't relay 306, ring similar to that described above for a toll call.

With three exceptions.

When the called party is busy, relay Eli-Z0 operates as hereinbettore (lOSClllJQll bi a as there is no ground on the coruluctor connected to contact/310, relay 302 will not be operatiul and busy tone will hesent back to the calling); subscriber 300 over a circuit :lrombus-ay tone source 37.1., outer right back contact of re lay. llOiliouter right front contiuft or relay 3 30,

conduct rs 34 .5 and 360, contact 334i. oi relay 302.. conductor 850 to sul'iscriber 300.

l l l'ien. connector C is associated with anidle line or the intercepting operators trunk, relay 318 operates as previously (l6- scribed. Upon the operation Ofli relay 3 .8 the circuit tor ringing; relay 32 is established and ringing current is connected to the .versing battery to the calling; so

line or trunk through the contacts of relay 321. It the call is for subscribe such as l-OO and the receiver is removal from the switchhoolr in response to the ringing, a circuit is closed tor operating relay 321 as previously described to diiasconuect this ringing current source from the line. Relay 3(ltfoperates over the subscribers loop circuit, troui battery through its right Winding, conductor 350, contact 334 of relay i502, conductor {560,

outer right trout contact at relay 32h conductor 3&0, contact 333i. of relay 2318, brush 328, contact 4M0 though the subscribeM-m station 100, contact lll brush 3253, contact Sill o'l relay 3123 conductor S ll, inner right trout contact o't relay Eli/l coiuluctc" 236i contact 335, conductor 351, to rroui'id tl rah "helcit winding of relay e06. llclayi-lllti o pcr ates and reverses the circuit tor relay 301 thereby rell 1' 300 he opcu: i; tor

7 i 1 for operating polarized relay Sji'" orationv oi? relay 3753 establishes t the operation oi message regis 3 Un a. call which has been routed. to an iuoperator the operation. of the trunk circuit relays lllZ-i and 1 02 the same as on a toll call. it circuit is now OSl?lllJlll-lllll r the ope "ation oi. (ll'lljllfllltlltl31g relay ill i as relay 321i oi? coni'iector C is not opcrzlcil. 'ihis circuit n'iay be traced from battery on the right trout contact of relay 102, Wimlingr ct relay illi, lot" trout contact oil? relay llli-l, which is slow to release, ci'uiitact 4-520, brush 328 contact83l oil relay Elle, conductor 2340 to ground on the outer right back contact oil relay llelay ill-l; operated loclrs to ground on own right front contact and connects 4420 to c uiiductor 430 and contact 452 l to cmrductor 41-30. lit the intercepting ope'i -7- tor inserts thepluc, ll l of cord circuit 106 in jack 41:13 clear. 'ibcd under "loll call inter ceptcd the operation is the sonic i'vith the on; ception that polarized relay all; now operates. The circuit of relay 4:06 and ringing trip rclay 32], of connector C is closed as previously traced in connection with an intcrccptml toll call and relay ioperates to trip the ringin eurrent'but re ay lllli does not operate in series With relay i321. Gonseque tly relay illi) is not operated. The operating circuit For rclayll8 may be traced from battery through its \vincling, outer .'c'l1tl)a.ck cmitact o t relay 4:08 conductor 4-25 tip of pluir lls: a nil iacli: 41-13. conductor ii-l0, inner left trt at contact ot relay 4104i con tact .0, brush contact *l'l cond ctor 3 H) outer righttfiont contact i lay 32L, conductor 360, contact 334:, core motor 850 to battery through the Winding oi relay 306. The battery connected. to the Winding oi relay 306is ot a higher voltage than that in the interceptinp: operatofis cord circuit l'tlll connected to the Winding of relay 4-18 and thus the ditlerei'ico inv Volta re is impressed ipon the \VllKllllfl' o'li relay 41518 in the proper direction to cause its operation. Relay 118 3 operated closes an obvious circuit for operating relay .419 which looks to ground on the front contact of relay 405. Relay 419 operated operates relay 408 over a circuit from ground on the right front contact of relay 419,;outer'leit back contact o;t' relay 423 to battery through the winding of relay 408; Relay 408 in turn operates relay 423 over an obvious circuit and'opens the operating circuit for relay 418 to cause its release. Belay 423 lockstoground on the front contact of relay 405 through its inner left front contact.

I The left and right windings of relay 407 are now associated with

conductors

425 and 424 and thence over the tip and ring conductors through the'connector to battery and ground through the windings of relay 306. The locking circuit for relay 408 is closed to ground on the sleeve of jack 413 as previously described.

. It is apparent that since relay 409 is normal the shunt formed by key 416 for the left winding of relay 407 is opened. This prevents rclay 306'i'rom operating and reversing the battery through the, subscribers loop for operating the message register.

'What is claimed is:

1. A'telephone system, comprising a toll operators position, local subscribers stations, an intercepting operators position, a trunk circuit, switches for extending a connection from either said local subscribers stations or said toll op'erators position to said intercepting operators position over said trunk circuit,- a cord circuit at said intercepting operators position, and means in said trunkcn'cuit for enabling said cord circuit to discriminate between a call from said local subscribers stations or said tolloperators position.

2. A telephone system, comprising a toll .operators position, local subscribers"sta- '7 said cord circuit to discriminate between calls from said sources.-

3. A telephone system, comprising a toll operators laoSition, a local subscribers station, an intercepting operators position, a

trunk circuit, selectorswitches and a connectorfor extending a'connection from either said local subscribers station or said toll operators position over-said trunk-circuit to said intercepting operators position, a cord circuit at said intercepting operators position, and means in said connector for controlling theoperation of a relay in said trunk circuit to enable said cord circuit to discriminate between a call from said local subscribers station or said tolloperators osition.

4. A telephone system, comprising a toll operators position, a local subscribers station, a responsive device associated with said subscribcrs station, an intercepting operators position, a trunk circuit, switches for extending a connection from either said local subscribers station or said toll operators positionover said trunk circuit to said intercepting operators position, a cord circuit at said intercepting operators position, and discriminating means in said trunk circuit for maintaining a. high resistance bridge across said cord circuit during a call from a local subscribers station to prevent said device from operating.

5. A telephone system, comprising a toll operators position, a signal at said operators position, a local subscribers station, a trunk circuit, an intercepting operators posit-ion, switches for extendin a connection from either said local subscri ers station or said toll operators position over said trunk circuit to said intercepting operators position, a cord circuit for association with said trunk circuit at said intercepting operators position, means in said trunk circuit for enabling said cord circuit to discriminate be tween a call from said local subscribers station or said toll operators position, a high resistance bridged in said intercepting operators cord circuit, and a key in said intercepting operators cord circuit for changing the resistance of said bridge in accordance with said discriminating means for operating said signal.

6. A telephone system comprising an operators position, local subscribers stations, a second operators position, a trunk circuit, switches for extending a connection from either said local stations or said first operators position to said second operators position over said trunk circuit, a cord circuit at said second operators position, and means in said trunk circuit for enabling said cord circuit to discriminate between a call from a local station and a call from said first operators position.

7. In a telephone system, a toll operators position, a local subscribers station, an intercepting operators position, a trunk circuit, switches for extending a connection from either said local station or said toll operators position to said intercepting operators position over said trunk circuit, a cord circuit at the intercepting operators position, means at the intercepting operators position to discriminate between a call from a local station and a call from the toll operators position, a signal at the toll operators position, and a key at the intercepting operators position cooperating with said discriminating means to flash said signal.

8. In a telephone system, a toll operators position, a local subscribers station, an intercepting operators position, a trunk circuit, switches for extending a connection from either the local station or from said toll operators position to said intercepting operators position over said trunk circuit, a cord circuit at the intercepting operators position having a disconnect signal associated therewith, means in said trunk circuit to discriminate between a call from the local. station and a call from the toll operatofls position, and means controlled by the toll operator for rendering efi'ective said signal.

9. A telephone system comprising a toll operators position, a signal at said toll operators position, a local subscribers station, an intercepting operators position, a trunk circuit, switches for extending a connection from either said local subscribers station or said toll operators position to said intercepting operators position over said trunk circuit, a cord circuit at the intercepting operators position for association with said trunk circuit, means for discrin'iinating be tween calls from toll and local sources at said intercepting operators position, a high resistance bridge in said intercepting operators cord circuit, and means in said cord circuit operable in accordance with said dis criminating means for shunting said high resistance to operate said signal at the toll operators position.

In Witness whereof, I hereunto subscribe my name this 14th day of August, A. D. 1925.

, RAY L. STOKELY.