US2021287A - Telephone system - Google Patents

Description

V@oY

E.. D. BUTZ ET AL WKN.

NNN

Nov. 19, 1935.

m ...El

E. o. Burz INVENTUM c. D. KOECHL/NG ATTORNEY Nov. ,19, 1935. E. D. BUTZ Er AL TELEPHONE SYSTEM Filed May 5, 1934 8 Sheets-Sheet 2 .ORN

En EQQS" NN .oNN

. N ...um

E D. BU TZ INVENTORS C KOECHL/NG By 777? 34"?,

ATTORNEY Nov. 19, 1935. E. D. BUTz r AL TELEPHONE SYSTEM Filed May 5, 1934 8 Sheets-Sheet 5 E 0. BUTZ NVENTORSC D. /foEcHL/NG l ATTORNEY Nov. 19, 1935. E, Q BU-rz Er AL 2,021,287

TELEPHONE SYSTEM Filed May 5, 1954 8 Sheets-Sheet 4 E D. BUTZ /NvENroRs 1 a/foEC/-IL/NG A 7` TORNEV Nov. 19, 1935. E. D. BUTZ ET AL v TELEPHONE SYSTEM Filed May 5, 1954 8 Sheets-Sheet 5 @E QW MMP www m5. www l www www TELEPHONE SYSTEM Filed May 5, 1954 8 Sheets-Sheet 6 E D. BUTZ C. D. KOECHL/NG N VE N TORS A T TOR/VE Y Nov. 19, 1935. E D BU-rz E1- AL 2,021,287

TELEPHONE SYSTEM 8 Sheets-Sheet '7 Filed May 5, 1954 /NTERRUP MARC/NAL E 0. @U77 NVENTORSC o. KOECHL//vc ATTORNEY om 19? 1935. E. D. Bu'rz ET AL 2,021,287

TELEPHONE SYSTEM Filed May 5, 1954 n 8 Sheets-Sheet 8 E D. BUTZ NVENTORS c. o. KOECHL/NG @www A 7' TORNEV lil) CTI

Patented Nov. 19, 1935 Unirse spares PATENT QFHCE TELEPHNE SYSTEM Application May 5, 1934, Serial No. 724,074

7 Claims.

This invention relates to telephone systems and more particularly to systems employing automatic switching equipment for completing connections between the subscribers lines.

The object of this invention is to provide an improved arrangement for completing intercepted calls in an automatic telephone system,

In automatic telephone systems it is usual to connect an intercepting trunk to blank terminals in the selector and connector banks and also to provide an intercepting trunk from a pluggingup line for intercepting calls to a subscriber whose line is temporarily removed from service. When the intercepting positions for a plurality oi offices are located at a central A switchboard the intercepting trunks may terminate in the banks of trunk-finder switches each associated with an outgoing trunk circuit to the central A switchboard. The calf. thus forwarded to an intercepting position in a distant oiice may be intercepted over a plugging-up line in which case the call can not be completed, may be from a toll operator in case is no necessity for completion by the intercepting operator. It may, however, be desirable to complete other intercepted calls.

According to the features of this invention, a two-conductor trunk is provided for forwarding intercepted calls to an intercepting operators position at a centralized A switchboard. A completing selector is associated with the outgoing end of the trunk for use in completing intercepted calls, and switching means at the outgoing end ci the trunk, controlled from the intercepting operators position, operatively connects the trunk to the completing selector so that dial impulses may be transmitted over the trunk to establish .a connection with a desired line. Switching means is also provided for closing a talking circuit from the calling to the called station, supervisory means being provided in the completing selector for causing the operation of the last mentioned switching means in response to the answer ci the called subscriber. The talking conductors oi the completing train of switches are freed of all bridging apparatus and extended to a source of talking battery in the switch at which the call was intercepted or in the intercepting trunk connected to the terminals of this switch. A further feature of the invention is the arrangement whereby such a completing selector is held during a connection by ground feo forward over the sleeve conductor of the intercepting trunk.

The drawings which form a part of this specication represent, in schematic form, a telephone system in which the invention is embodied.

The invention is of course not limited in its application to the particular system shown and described herein.

Referring to the drawings:

Fig. l represents a telephone system comprising an automatic oilice O-I and a centralized A switchboard CA;

Figs. 2 to 8, inclusive, show in detail the controlling circuits for the system represented in Fis. 1; 1o

Fig. 9 shows the position in which the various Figures 2 to 8 inclusive are to be placed with respect to each other to form an operative system.

Considering nrst the general arrangement of the system, as shown in Fig. l, ITi, IT2, IT3 and IT4 represent intercepting trunks connected, respectively, to terminals in the banks of a toll selector TS, toll connector TC, local selector LS and local connector LC, all of which switches are in cnice O-l. ITS represents an intercepting trunk connected by a plugging-up line PL to another set of terminals in the lbank of the local connector LC. These intercepting trunks are also connected to terminals in the bank of trunkiinder switch TF and other similar switches. The trunk-iinder switch TF and the associated outgoing trunk equipment OT are permanently associated with the trunk T, the distant end of which is connected to the incoming trunk equipment IT and answering jack J at an intercepting operators position of the centralized A switchboard CA. CC represents one of the intercepting operators cords and PCS represents the operators position and telephone equipment. CS represents a completing selector in office O-l individual to the outgoing trunk equipment OT; IS represents an intermediate selector, C represents a connector switch, and B represents a subscribers station connected to terminals in the bank 0i connector switch C.

The finder, selector and connector switches are all of the two-motion step-by-step type. For a general description of the construction and operation of such switches reference may be had to pages 53 to 65 inclusive of the second edition of Automatic Telephony by Smith and Campbell. rlfne selector and connector switches TS, TC, LS, LC are each represented by a set of brushes and one or two sets of terminals. The intercepting trunks ITI, ITZ, IT3, ITG and ITS and the plugging-up line PL may be similar to correspondingly designated trunks shown and described in detail in the copending application Of E, D. Butz, Serial No. 648,052, filed December 55 1932. The intercepting trunk ITS, trunkinder TF, outgoing trunk equipment OT, completing selector CS, intermediate selector IS, connector C, incoming trunk equipment IT. the operatcrs cord OC and the position equipment POS are shown in detail in Figs. 2 to 8, inclusive. The line-finder LF represented in Fig. 2 by one set ci brushes and a single set of terminals may be similar to the line-iinder disclosed in the patent to H. Hovland No. 1,711,682, granted May '7, 1929.

The operation of the system shown in the drawings will be most readily understood by assuming that a call originated by the subscriber at station A in Fig. 2 is intercepted by Vtrunk I'I, extended by trunk-under TF over trunk T to the interceptin position and that the call is completed under control of the intercepting operator by completing selector CS, intermediate selector IS, and connector C to the called subscribers station B. The intermediate selector IS and connector C are similar to intermediate selectors and connectors employed in completing toll calls.

When the call is originated at station A, a line-lnder LF hunts for and extends the calling line 2li@ to the associated local selector LS. The selector LS is selectively operated under the control oi the impulses created by the dialing of the iirst digit or" the called number to select a corresponding group of terminals and to then automatically hunt for and seize an idle set of terminals in the selected group. Assuming that the first digit represents an unassigned group or" telephone numbers, the selected set of terminals will be connected to an intercepting trunk such as IT3. Since local selectors have no means for signaling over a selected trunk, as do connectors and toll selectors, the trunk ITS is arranged. to initiate the further extension of the connection to the intercepting operator and to hold the selector and line-nder switches in their operated positions.

Upon seizure of trunk IT3, the tip conductor of the calling line 292 is extended through the upper brushes of line-finder LF and selector LS to terminal 2|9, thence through winding 2|2 of repeating ccil RCl, the upper back contact of .relay 2535, windings of relay 204, and through the lamp 2id to ground; and the ring conductor of line 2li@ is extended through the middle brushes Yof line-finder LF selector LS to terminal 220,

thence through winding 2 i3 of repeating coil RC lower back contact of relay 295, windings of relay Ztil, and through the lamp 2H to battery. Relay Rill is operated by the current through its windings and closes an obvious circuit for operating relay 262. Relay Eil, operated, also ccnnects ground through its inner front contact to sleeve conductor 2id to hold the selector and line-nnder switches in their operated position in the usual manner. Relay 202, operated, closes an obvious circuit for energizing relay 253. In operating, relay 2G25 connects ground through its inner lower front Contact to sleeve conductor 2 4; connects battery through the winding of relay and the outer lower front contact of relay and through the inner lower back contact of relay 291 to sleeve terminal 25 in the bank of the trunk-under switch TF; connects ground through its innermost upper front contact, back contact of relay 228, lowerrnost back Contact of relay 227|, over conductor 222 to battery through the winding of group relay 25| which is common to the group of trunks which includes trunk ITS.

Relay 203 also closes a circuit through its middle upper front contact for operating relay 206. It is assumed that the trunk ITB and the other trunks in the same groupare connected to`terminals in the second level of the banks of trunknnder TF. Group relay 25| connects ground through its upper front contact, over conductor to the second oir-normal segment of the vertical commutator 2l5 cf nder TF and the corresponding segment oi the commutators of all other truiik-nders having access to this group of trunks. Relay 25| also connects ground to the start lead 252 which is common to the group of trunk-finders having access to trunk ITS.

the trunkmnnder 1F to be the rst idle finder in the grcup, the connection oi ground to the start lead 252 effects the operation of relay Relay 255i closes a circuit from battery through the uppermost back contact oi relay upper winding oi relay back Contact stepping up the two brushes to the rst level oi terminals in the associated banks and stepping up the vertical commutator brush 2li! to make Contact with the lst cir-normal segment or the comniutator 2?'5. The vertical oinormal springs El are ment ci the shaft out oi normal position. operation of magnet also causes the release of relay 255; and the release ci relay 255 in turn causes the release ci magnet Since the trunk for which the trunk-inder I'r is seeking, L

is connected to terminals in the second level, commutator brush 2l@ does not encounter ground potential on the rst off-normal segment of the commutator. With magnet 25"! released, relay reoperates, again closing circuit for operating magnet 25?; and 'the brushes of switch TF are stepped up to 'the second level of the terminal banks. trunk ITIS is connected to terminals in the second level, a circuit is closed for energizing relay 2E! as soon as the commutat brush El@ comes in contact with the second oi'l\no1mal comrnutator segment; this circuit is traced from battery through the uppermost back contact of relay upper winding oi relay 255. back contact ci magnet 256, upper winding of relay commutator brush Zl and second oifnormal segment ci commutator, conductor 253, and through the upper front contact of group relay 25| to ground. This circuit is also effective tc hold relay T255 cperated. Relay 26| is slow in operating to insure proper positioning,r oi the brushes before the first rotary step is taken. The operation oi relay 253| causes the release of magnet Since the intercepting trunk IT;r shown connected to terminals in the with which the brushes 2M 265 and 2 are associated, the description ci the termi al hunting operation of the trunk-under 'I-F will be limited to the case where the calling trunk is encountered by this set of brushes. When relay 2li operates, it closes a circuit from batte` through the winding of rctary-stepping magnet lowermost iront contact oi relay 26|, front contact ci" relay and through the lowermost front contact oi relay 25d to ground. The operation of magnet 253 rotates the two sets of .ctuated by the movey The brushes into contact with the rst set of terminals in the second level of each of the associated banks. The circuit through the upper winding of relays 255 and 25| is opened when magnet 253 operates and is also opened at the commutator due to the rotation of brush 213 out of alignment with the commutator segments. Relay 255 releases but relay 23| is held operated in a circuit from battery through the uppermost back Contact of relay winding of magnet 251, low er winding inner lower front contact of relay 23|, to ground at the lowermost front contact of relay 25d. The current in this circuit is not sulicient to operate the magnet 251. The release of relay 255 causes the release of magnet 256 and, if the first set of terminals in the second level is not the set to which the calling trunk IT3 is connected, relay 255 reoperates and causes the reoperation of magnet 255 to advance the brushes into engagement with the second set of terminals. Relay 255 and magnet 253 continue to cooperate to advance the brushes until test brush 236 encounters the terminal 225 to which the winding or the cut-on" relay 233 ci trunk T3 is connected.

- A circuit is thus closed from battery through the winding of relay 233, lowermost front contact oi relay 233, inner lower back Contact of relay 231, terminal 225, brush 255, lower winding of relay 263, lower back contact of relay 23.2, lower winding of relay 255, and through the inner lower front contact of relay 254 to ground. Relay 238 operates, relay 255 is held operated, and relay 253 operates sufficiently to close at its inner upper iront contact a circuit for completing its own operation; this circuit is traced from battery through the upper winding and inner upper front contact of relay 263, front contact of magnet 253, front contact of relay 255, to ground at the lowerrnost front contact of relay 254. Magnet 253 is held operated under control of relays 26|, 255 and 254. The operation of cut-off relay 233 of the trunk IT3 disconnects the ground at trunk TTS from group conductor 222 and connects the source of ringing current M5 through the lamp 245, iront contact oi relay 238, and condenser 2 l to one of the talking conductors of trunk IT3, thereby transmitting a ringing tone to the calling subscriber'. Group relay 25| releases unless conductor 222 is connected to ground at one of the other trunks in the same group. The complete operation of relay 253 closes a circuit for operating relay 232; this circuit is traced from battery through the lower winding of relay 262, middle upper front contact of relay 263, conductor 214, lower front contact of the vertical off-normal springs 233 to ground. The operation of relay 232 and the release of relay 25| are each eiective to cause the release of relay 254. The operation of relay 262 and release of relay 254 cause the rele-ase ci relays 253 and 2M. With relay 254 released, the lower winding of relay 232 is also connected to conductor 21d by the back contact of relay 253. With relay 252 operated, the upper winding of relay 253 is connected through its inner upper front contact and the inner lower front contact or relay 252, over conductor 213 to sleeve conductor 333 of trunk equipment OT.v

TF, lowermost back contact of relay 253, lowermost front contact of relay 236, conductors 212 and 331, right back contact oi relay 3|2 or trunk equipment OT, right outer back contact of relay 3M, left Winding of relay resistance 33|, and through the back contact of relay 3|3 to ground. Relay 33| operates in this circuit but relay 231 is marginal and does not operate. The operation of relay 30| is a signal to the trunk equipment OT that the call has been intercepted at the banks of a local selector or a toll selector. Had the call extended by trunk-finder TF to trunk equipment OT been intercepted at the bank of a toll or local connector, relay 33| would be operated due to the energization of its right winding by ringing current from the connector or due to the energization of its left winding by direct current during the silent partI of the ringing cycle.

At the time that start relay 253 of trunk-nder TF operated, the connection or ground potential through the inner lower contact of this relay to conductor 213, thence over sleeve conductor 338 of trunk equipment OT, through the back contact of relay 3H to the winding of relay 323, causes the operation of relay 323. The three relays 351, 323 and 323 are provided for the purpose of maintaining the connection of ground potential to conductors 333 and 213 in case relay 254 of the nder TF releases prior to the operation of relay 333 of trunk equipment OT. The operation of relay 323` connects sleeve conductor 333 to the winding oi relay As long as conductor 213 is connected to ground at the inner lower front contact of relay 255i, the winding of relay 323 is short-circuited. But when relay 254 releases, relay 323 is operated by current in a circuit from battery through the upper winding and inner upper front Contact of relay inner lower front contact of relay 252 conductor 213, sleeve conductor 338, front contact of relay 323, and

through the winding of relay 323 to ground; the current in this circuit also holds relay operated. When relay 30| operates as hereinbefore described, it closes an obvious circuit for operating relay 303. Relay 333 connects ground to conductor 339 thereby operatino relay 3l?. 3| 1 connects conductor 33S to the sleeve conductor 333 thereby establishing a holding connection for relay 253 of trunlr--nder TF. The operation of relay 3|1 causes the release of relay 328 and the release of relay 323, if operated. lay 333 closes a locking circuit through its inner left front contact, inner left contact of relay 333, inner right back contact or relay over conductor 33S, to ground at its own outer left front contact. Relay also closes a circuit for operating relay 333; relay closes a circuit for operating relay 335; relay 335 closes a circuit for operating relay 335; relay closes a circuit for operating relay 331; and relay closes circuits for operating relays 363, and The circuit for operating relay 333 is traced from battery through the winding or relay 308, left front contact of relay right back contact of relay 322, over conductor 333 to ground at the outer left front contact ci relay Relay 389 connects ground to conductor 333 to hold relay 3| 1 and from conductor 335 through the front contact of relay 341 over conductor 333 to hold relay 233 of the trunk-lnder TF. Relay closes a circuit for operating relay 3M. Relay 308, in operating, opens the locking path for relay 303 and closes a circuit over conductors and 333 of trunk T to signal an intercepting operator at the distant centralized A switchboard CA. 75

This circuit is traced from battery through the right winding of relay 322, left front contact of relay 308, leit back contact of relay 3I5, winding 334 of repeating coil RC2, right back contact of relay 3m, over conductor 332 of trunk T, through the upper back contact of relay I0I of the incoming trunk equipment IT, winding 602 of repeating coil RC3, upper back contact of relay E33, winding of relay winding of relay 505, lower back contact of relay 503, winding 50E of repeating coil RC3, lower back contact of relay 60E, over conductor 333 of trunk T, left back contact of relay SI5, winding 335 of repeating coil RC2, right back Contact of relay 3I5, right front contact of relay 353, and through the left winding of relay 322 to ground. Relay 505 is operated by the current over trunk T; but relay 322 is marginal and relay 535 is polarized so that neither of these two relays operates. Relay 604 closes a circuit from battery through its front contact, back contacts of relays 351 and 505, through lamp 633 to ground; the lamp lights to signal the operator.

The operator answers a call by operating key 1I5 and inserting the answering plug 10i of a cord 0C in the answering jack 625 associated with the lighted lamp 528. The operation of key 'H5 closes a circuit for operating relay 13| provided no other key similar to key 'H5 is operated at the same time, this circuit is traced from battery through the winding of relay 135, upper outer front contact of key 1I5, conductor 835 to ground through the upper back contact of relay 831 in parallelV With resistance 855. The operation of relay 13| closes a circuit from battery through the winding of relay 3.3i, resistance 802, lower back contact of relay 853, conductor 50d., inner upper front contact of relay 13|, inner lower back Contact of relay 126, winding 106 of repeating coil RC5, ring conductor of the plug 10! and jack 525, winding B23 of repeating coil RC3, lower winding of relay 6 I 2, to ground. Relay SI2 is not operated by the current through its winding but relay I operates and closes a circuit from ground through its front contact, back contact of relay 838, conductor 800, lowermost front contact of key 1I5, upper back contact and winding of relay 122, and through the lower back contact of relay 123 to battery. Relay 122 operates and closes a locking circuit over the sleeve conductor 'H5 of the answering cord; this circuit is traced from ground through the winding of relay S03 of trunk equipment IT, sleeve conductors of the answering jack and plug 10I conductor 1I9, uppermost front Contact and winding of relay 122, and through the lower back contact of relay 123 to battery. Relay 603 is operated by the current in this circuit thereby causing the release of relay 334. The release of relay 335 extinguishes lamp 608. The operation of relay 503 connects the windings of relay 6I5 to the conductors of trunk T to cause the operation of relay SI5 of trunk equipment IT and the operation of relay 322 of trunk equipment OT, each winding oi relay SI5 being connected in a separate circuit in series with a different one of the windings of relay 322. One of these circuits is traced from ground through the left winding of relay 322, right front contact of relay 3633, right back contact of relay 3I5, winding 335 of repeating coil RC2, left back contact of relay Slt, conductor 333 of trunk T, lower back. contact of relay 50|, winding 606 of repeating coil RC3, lower front Contact of relay E33, lower back contacts of relays 5i@ and 559, uppermost back Contact of relay 3M, through the upper Winding RC3, inner upper front contact of relay 503, upper back contacts of relays 5MB and 503, inner upper back contact of relay @l5 and through the lower winding of relay SI5 to ground. Relay SI5 closes a circuit for operating relay SI I. Relay 6I I closes a circuit for operating relay 651 and closes a circuit from Ll-Volt battery through the upper winding of relay SI2, winding 629 of repeating coil RC3, tip conductor of the answering jack E25 and plug 10i, winding 105 of repeating coil RC3, upper winding of relay 121, lower back contact of key 12), inner upper back contact of relay 123, uppermost back contact of relay 133, and through resistance 'l2-l2 to 2li-volt battery; relay SI2 remains normal but the answering cord supervisory relay 12! operates. in a circuit from battery through the right winding and right front contact, over conductor 339 to ground at the outer left front contact of relay and at the front contact of relay 339. The operation of relay 322 causes the release of relay and the operation or" relay 3I9. The release of relay again closes the locking circuit for relay disconnects the windings of relay 322 from conductors 332 and 333 of trunk T and con-Y nects a dry bridge across these conductors; this bridge, which is effective to hold relay SI5 'of the trunk equipment IT operated, is traced from conductor 332, through the outer right back contact of relay 3i6, winding 334 of repeating coil RC3, left back contact of relay 3 I 5, outer left back contact of relay 308, resistance 344 and left winding of relay 326, left winding of relay 321, right front contact of relay 306, right back contact of relay 338, right back contact of relay 3I5, winding 335 of repeating coil RC3, and through the left back contact of relay 3I6 to conductor 333. Relay 321 operates but relay 326 is polarized and the current through its left winding is not at this time in the operating Relay 322 locks Y direction. The right windings of relays 32B and 321 are short-circuited by the right front contact of relay 305. Relay 321 closes a holding circuit for relay 301. The aforementioned operation of relay 3I0 opens the circuit through the left winding of relay 33I and closes a circuit for operating relay 3M. Relay 3M disconnects the windings of relays 35i and 302 from conductors 336 and 331 causing the release of these relays, if operated. With relay 30I released and relay 3I4 operated, relay 303 releases. The ground at the front contact of relay 309 remains connected to conductor 339 as a holding potential. The release of relay 303 also causes the successive release of relays 305, 305 and 306, relay 331 remains operated under control oi relay 321. Since relays 333, 30d and 335 are slow in releasing, the resistance 339 is temporarily connected through the right front contact of relay 305, left y tact of relay 206, winding 221 of repeating coil RCI, terminal 224 and brush 265 of trunk-lnder TF, lowermost back contact of relay 259, lowermost front contact of relay 260, conductors 212 and 331, right back contact of relay 312, left back Contact of relay 313, left front contact of relay 3l4, and through the right front contact of relay 305 and resistance 339 to ground. Relay 201, operated, locks through its continuity front contact to ground at the lower front contact of relay 203. The operation of relay 201 causes the release of relay 208, thereby disconnecting the ringing source 215 to terminate the audible ringing signal over the calling subscribers line; and ground potential is connected through the lower front Contact of relay 206 and the inner lower front contact of relay 201, to terminal 225 to hold the trunk-iinder TF. With relays 201 and 314 operated, a circuit is closed from battery through resistance 342, left outer back contact of relay 321, winding 343 of repeating coil RC2, inner right front contact of relay 314, right back contact of relay 313, left back contact of relay 312, conductors 338 and 211, uppermost front contact oi relay 260, uppermost back contact of relay 259, brush 254 and terminal 223 of trunk-iinde-r TF, uppermost front contact of relay 201, winding 22B of repeating coil RC1, uppermost front contact of relay 203, through the lower winding of relay 288 to battery. This circuit is without effect, but if the call were one intercepted at the bank of a toll selector or connector, the connec-tion of battery through resistance 342 of trunk equipment OT to brush 284 of trunk-iinder TF and over the tip conductor of an intercepting trunk IT! or IT2, (Fig. l) would be effective to operate a relay in the tolltransmission selector and thereby cause the connection of a tone to the talking conductor to inform the intercepting operator that the intercepted call is a toll call. When relay 385 releases, a circuit is closed from battery through the inner back contact of relay 321, both windings of relay 324, winding 341 of repeating coil RC2, back contact of relay 305, left front contact oi relay 314, left back contact of relay 313, right back contact of relay 312, conductors 331 and 212, lowermost front contact of relay 280, lowermost back contact of relay 259, brush 285 and terminal 224 of trunk-under TF, winding 221 of repeating coil RC1, upper front contact of relay 208, innermost upper front contact or relay 201, and through the upper winding of relay 209 to ground. Relay 324 is operated by the current in this circuit, but relay 209 is marginal and does not operate. Relay 324 operates before relay 308 releases thus maintaining the short circuit around the right windings of relays 326 and 321.

When relay 122 of the cord OC operates, as hereinbefore described, a circuit is closed for operating relay 831 of the position equipment POS; this circuit includes the uppermost front contact of relay 131. The operation of relay 801 disconnects the ground at its back contact from conductor 805 leaving this conductor connected to ground through resistance 80S; this resistance is sufficiently high to prevent the o-peration of a relay similar to relay '131 in any other cord circuit if another cord circuit key similar to key 115 is operated inadvertently. Relay 801 also closes a holding circuit for relay 881 and connects interrupter 811 to the winding o relay 808. As soon thereafter as the brush of interrupter 811 is connected to ground relay 808 operates; and when the connection to ground is again opened ground potential is connected through the upper front contact of relay 801, resistance 802, lower back contact of relay 803, inner upper front contact of relay 131 inner lower back contact of relay 126, and through winding 105 of repeating coil RC4 to the ring conductor of plug 101 for the purpose of operating the ring cut-oir relay on calls incoming directly over intercepting trunks from connectors in the same cnice with the intercepting operators position. Relay 803 closes at its uppermost front contact a circuit through the upper winding of relay 813, and a circuit over conductor 814 through the inner lower front contact of relay 135, lowermost front contact of relay 122, and through the winding of relay 121; relays 813 and 121 both operate. Relay B03 also disconnects at its lower back contact the ground potential connected to the ring conductor of plug 101. Relay 121 locks under control of relay 122. The operation of relay 808 disconnects ground from conductor 800. The operation of relay 813 closes through the talking circuit from the operators telephone set to the tip and ring conductors of the answering plug.

If upon answering the call the intercepting operator hears a tone indicating that the call has been intercepted at the bank of a toll selector or toll connector, operation of the tone-removal key 825 causes the operation of relay 133 of cord OC. Relay 133 locks through its lower iront contact under control of relay 121. Relay 133 short-circuits, at its upper front contacts the lower winding of the answering supervisory relay 121 thereby disconnecting the tip and ring conductors of the answering cord from resistances 132 and 134 and bridging the upper winding of the answering supervisory relay 121 across these conductors to cause the operation of relay 612 of trunk equipment IT. Relay 612 closes a circuit for operating relay 509; and relay 609 interchanges the connections between the windings of relay 515 and the conductors of trunk T, thereby reversing the current tmough the left windings of relays 328 and 321 to cause the release of relay 321 and the operation of relay 328. Relay 321 is not polarized and reoperates immediately. Relay 326 closes a circuit for operating relay 325; and relay 325 closes a circuit for operating relay 321. The release oi relay 321 opens the operating circuit of relay 301. Relay 321 closes a holding circuit for relay 310, thereby maintaining relays 311 and 309 operated. With relays 325 and 321 operated the circuit from battery through resistance 342 over conductor 336 and the circuit from battery through the windings of relay 324 over conductor 331 are both opened and the left winding of relay 324 is bridged across conductors 333 and 331 to cause the operation of a supervisory relay in the toll transmission selector (not shown) and thereby cause the disconnection of the toll indicating tone from the connection. Ii the ilashing key 128 of cord OC is now operated, the bridge through the upper winding of relay 121 is opened and relay 612 releases each time the dashing key is operated. Each release of relay SI2 causes a corresponding release of relay 339 and the reversal of current over trunk T. Relays 326 and 321 of trunk equipment OT are thereby alternately released. and operated to cause the alternate opening and closing of the bridge across conductors 336 and 331 and a resulting flashing of a supervisory signal at the toll operators position.

If a call originated by a local operator is intercepted at the bank of a local selector or connector, it may be found necessary to signal this operator. In such a case repeated operation of the flashing key 12@ intermittently bridges the upper winding of the answering supervisory relay 'IZI across the conductors of the answering cord to cause the alternate operation and release of relays GIZ and S69 of trunk equipment IT, the alternate operation and release oi relay 325i, the alternate release and reoperation of relay 32? and the alternate operation and release of relays 335 and 32| as hereinbefore described. The intermittent bridging of the left winding ci relay across conductors and 331 is effective to cause the alternateY operation and release of relay 2&9 of trunk IT3.

Relay 239 causes the intermittent operation of relay 235 thereby interchanging the connections between the incoming line conductors of trunk ITS with respect to battery and ground to cause the flashing ofthe local operators supervisory lamp (not shown).

If the call has been intercepted at a local selector or at a local connector but not from a 'plugging-up line, and ii the information received from the calling subscriber indicates that it is desirable to coinplete the connection, the operator inserts the calling plug 13.2 into the dialing jack S21 associated with the trunk over which the intercepted call was received. The windings of relays 1II and 1|2 of the cord OC are thereby connected in series with the winding of relay 323 of the trunk equipment IT; relays 1|2 and 323 operate but relay "iii is marginal and does not operate. Relay 'H2 closes a circuit for operating relay 155. Relay i323 closes a circuit through the windings of relays 622 and tgl in series. Re-

:wen

lay GZI operates but relay eea is marginal and does not operate until the plug is fully seated in jack E21 unless the tip and ring springs of jack 321 are short-circuited while the plug is being inserted; in which case ground at the inner lower back contact or relay 323 is connected to the winding of relay causing the release of relay 62| and the premature operation or" relay 622, The release of relay 32| is then eiective to prevent the premature operation of relay 23. With relay il@ operated,` the operators busy-testconductor 125 is disconnected from the tip conductor of plug 832; and with plug 132 fully seated, a circuit is closedrfrom battery through the windingof relay 522 of trunk equipment IT, inner upper front contact of relay 623, lowermost back contact of relay 62e, inner upper back contact of relay 324, tip conductors or" dialing jack E21 and plug 132, upper back Contact of relay III, uppermost front contact of relay 1 IS, winding 'ie'i of repeating coil RC3, upper back contact of relay 1I I, upper V:front contact of relay "l i2, winding or" relay 154, lower back contact of relay 'I I I, winding of repeating coil RCl, lowermost front contact of relay 1 I6, lower back contact of relay |I1, ring conductors of plug 132 and jack 621,to ground atthe inner lower back contact of relay 62s. The current in this circuit is effective to operate relay 322 but Vis, ineiective toV operate polarized relay 15:2. With relay 62| operated, the operation of relay 622 causes the operation of relay E20; and relay 626 closes a circuit for operating relay 6M. Relay 6M Vdisconnects the windings of relay SI5 from the conductors of trunk T, closes a holding circuit for relay 6I I= and closes an operating cir- 5 cuit for relay 69|. Relay Sel bridges the high resistance winding of relay BIS across the conductors of trunk T. The disconnection of the windings of relay 6 5 from the trunk and the connection of winding of relay 3I3 across the con- 101 ductors 332 and 333 causes the release of relay 321 of trunk equipment OT. The release of relay 321 causes the release of relay 331. The release of relay 301 closes a circuit for operating relay 3I6;

this circuit is traced from ground through the 15,

back contact of relay 321, back contact of relay 331, outer left front contact of relay 3| I, right front contact of relay 324, and through the winding of relay 3l@ to battery. Relay 3l?) locks under control of relays 324 and 3| I; the locking circuit 20;

is traced from battery through the winding of relay 356, right front contact of relay 324, inner right front contact of relay 3 It, to ground at the outer right front contact of relay 3| I. The operation of relay 3I6 disconnects the tip and ring 25A conductors 332 and 333 of trunk T from the windings or" repeating coil RC2 and connects these conductors through the outer back contacts of relay 329, over conductors 345 and 346, through the armatures 423 and 4I'I and back contacts of 30 relay 4GB of the completing selector CS, back contacts of relay 461, resistances 435 and 356, back contacts of relay 4M, through the windings of line relay 33| to ground and battery, respectively.

The line relay 49| of selector CS and bridge relay 35 |5|3 of trunk` equipment IT are, therefore, operated in series. Relay GIS closes a circuit for operating relay 624; this circuit is traced from ground at the front contact of relay f5 I 3, inner upper front contact of relay 53|, uppermost front 40 contact of relay B23, and through the uppermost back contact and'winding of relay i324 to battery. Relay |524 locks through its uppermost front contact to ground at the lower front contact of relay 623. The operation of relay 324 causes the release 45 of relays 32| and 622 and extends the incoming conductors oi trunk T through the tip and ring conductors of dialing jack E21 to the cord OC, the winding of relay Ell of trunk equipment IT and winding of relay 14 of vcord OC, being 50 thereby connected in parallel with the winding of relay 6I3 and in series with the windings of line relay 40| of completing selector CS. The polarized relay 1I4 remains normal but relay SI1 operates, closing a circuit for operating relay 55 6I8; and relay 6|8 closes a circuit for operating relay 6I9. Relay SIS opens the circuit through the winding of relay 6I3 and closes a holding circuit for relay E23. The purpose of relays 6I1,

M8 and GIS is to hold relays S23, tile, GII and 12| 60 operated during dialing and thereby prevent the lighting of the answering supervisory lamp 133. During the transmission of dial impulses, as hereinafter described, relay G I1 is alternately released and reoperated but relay 6I8 is slow in releasing 65V AVlay V3| I, and connects ground through the inner upper back contact of relay 'iII to the alarm equipment 4m. When the intercepting operator moves the dial Gm oif-normal to dial the first 75 digit cf the number' of the station with which the calling subscriber desires connection, relay @I5 operates in an obvious circuit. Relay 325 closes a circuit for operating relay lil of cord OC; this circuit is traced from battery through the inner lower front contact of relay liti, lower Winding of relay il, middle lower front Contact of hey H5, conductor '527, inner lower iront contact of relay 855 to ground at the back contact of relay 816. Relay lll locks in a circuit from battery through the lower front contact of relay H2, upper Winding and inner upper front contact of relay lil, conductor 128, back contacts of relays all and 858, to ground through the Winding of relay Siti. Relay 8l 6, operated by the current in this circuit, disconnects ground from conductor lill so that no other relay similar to relay 'lill in any other cord will be operated in Case the key corresponding to key H5 should be operated inadvertently. Relay 1H, operated, bridges the interrupter contacts of dial 8| 9 in series with the uppermost front contact of relay il across the tip and ring conductors of plug lil?, in place of the Winding of relay H4. During its return movement, the circuit through the Winding of relay fill of trunk equipment IT, over the conductors of trunk T and through the windings of line relay lill of selector CS are alternately opened and closed, by the interrupter contacts of dial Bid, as many times as there are units in the digit dialed. Relay lill is released by each opening of the circuit and reoperated by each succeeding closing of the circuit. lThe rst release of relay lle! closes a circuit from ground through its upper back contact, outer left front contact of relay de?, lowermost back contact of relay :il i, Winding of relay and through the Winding of the verticalu stepping magnet it to battery. Relay 433 and magnet tl@ both operate. The operation of magnet 553 steps the shaft and brushes of selector CS up to the irst level of the terminal bank. When relay del reoperates magnet H3 releases. Each succeeding release and reoperation of relay 49! causes a corresponding operation and release of magnet 553, thereby stepping the brushes of selector CS to the level corresponding to the digit dialed. The oil-normal contacts fi/l are actuated as soon as the shaft leaves normal position. The circuit through the Winding of relay flte is opened each time relay lli releases, but relay is slow in releasing and remains operated during receipt of dial irnpulses. Relay 63 is also slow in releasing and remains operated until all of the impulses in the train have been received. Relay 593 closes a circuit, for operating relay M8, from ground through the outer right front Contact of relay 13532, conductor inner front contact of relay 493, to battery through the Winding of relay M8. Relay 'lid closes a locking circuit through its Winding and inner leit front contact, upermost back contact of relay Ml, over conductor to ground at the outer ight front contact of relay 92. The operation of relay d3 and actuation of the oi-normal springs itil closes a circuit for operating relay 459; this circuit is traced from battery through the back Contact of release magnet des, uppermost front Contact of off-normal springs M4, Winding of relay M9, out r front contact oi. relay G63, over conductor 41 ground at the outer right front contact of relay Relay M9 closes a locking circuit from ground at its left front contact, through the back contact of rotarystepping magnet 42|, winding of relay MQ, uppern most front Contact of vertical oinoimal springs 444, to battery through the back contact of release magnet 4de. The reoperatio-n of relay 4M, after receiving the last impulse the rst digit from the dial, causes the release of relay 493; and the release of relay 483 closes a circuit from battery through the winding of rotary-stepping magnet 42E, right front contact of relay Gill, back contact of relay over conductor @2G to ground at relay 482. The operation of magnet 42| rotates the one step so that the brushes 514, Il i 5, 4 it, and Ml engage the first set of terminaisI in the selected level. ln operating magnet 425 opens the circuit through the Winding of relay die. Relay iid releases in turn opening the circuit through the Winding or" magnet dal. If the trunk connected to the rst set of terminals is idle, the brushes are not further advanced; but if this trunk is busy, the test brush elfi encounters ground potential thereby causing the reoperation of relay H9 and the further advance of the brushes. Assuming that the trunk connected to the rst set or" terminals is busy, the circuit for reoperating relay el@ is traced from ground through brush Md, inner lower hack contact of relay di l, back Contact of magnet 421, winding of relay lle, uppermost iront contact of oir-non mal springs 444, to battery through the back contact of release magnet lille. locks through its left front contact and closes the operating circuit for magnet 5.42; and the brushes are advanced another step into contact with the second set of terminals in the selected level. Relay dit is released when brush l breaks Contact with the test terminal of the rst trunk; the release of relay fili! causes the r-elease of magnet 42E. Relay i9 and magnet d2! con tinue to repeat this cycle of operation to advance the brushes until an idle set of terminals is encountered. Such a set or terminals is represented by terminals f'i22, 23, 62e and fiile. Brush dit encounters no ground potential on terminal 421i and relay :lll is thereupon operated by the current in a circuit from ground at the outer right front Contact of relay 555i?, conductor 42e, Winding of relay dil, back Contact of magnet 42H, Winding or" relay MQ, uppermost front corn tact of oli-normal springs to cattery through the back contact of release magnet des. Relay 419, being marginal, does not operate in this circuit. Relay di l disconnects ground from the alarm equipment flic and connects ground potential from conductor 525 through its inner lower front contact and through test brush to terminal 32A tol guard against seizure of the trunk connected to terminals 423, 42d and 425 by any other hunting selector having access thereto. Relay iii completes a bridge across the tip and ring brushes die and @it of selector CS to repeat succeeding trains of dial impulses received by relay lili thereby selectively operate the intermediate selector iS connected to terminals i522, 23, iid the connector switch seized by sW"ch This bridge is traced from brush didi, through the uppermost front contact of relay dii, middle lower back contact of relay dell, right front contact of relay 418, resistance 434, lower front contact of relay del, lovvermost iront contact or relay dll, to brush vlll ii. Upon operation of relay l l the circuit for holding relay M8 is traced from the winding and left front contact of relay e358, through the inner upper front contact of relay 4| I, through brush lil and terminal 525 of selec- Relay I9 again Q rupter Vto sv ec tor CS, over control conductor 535 and through a back contact of cut-through relay (not shown) of selector IS, back over sleeve conductor 533, terminal 555 and test brush l inner lower front Contact of relay fil l, over conductor to ground at relay 552. Y

Should all the trunks in the level selected by switch CS be busy, the rotary-stepping magnet will advance the brushes to the eleventh rotary position in which position the brushes will be beyond the and not in enga ornent with any or its terminals. In this condition relay 5l! operates hereinbefore described but there is no circuit for holding relay llo operated. The release ci relay lll@ loses a circuit for operating relay @ill i ound through the upper front contact oi relay ell, outer left baci: contact oi relay winding of relay lower iront contact o the oli-normal springs llil, to battery at the baci: contact oi rel-ease magnet Relay o is short circuits across the windings 53? and o the repeating coil and bridges condenser die across the inner ends or these windings. M" also connects ground Relay through its upper front contact over conductor 535 to operate relay oi the trunk equipment OT. In the eleventh rotary-step position the springs are actuated and connect the interover conductor through the leit back contact oi relay 53.3, outer right back conF tact of relay lill?, and lowerinost back contact of relay fiile to the winding ci relay lilll and through condenser F555 and windings 55| and of the repeating coll to ground. The interu mitteilt connection of ground to conductor 53 by interruptor 552 causes the intermittent operation of relay fllll. VThe alternate operation and release oi relay 555 interchanges the connection between the windings of relay 155 and the incoming line conductors 355 and 355 to intermittently reverse the current over trunk l as a sigto the interce g operator all the trunks are busy. A. ci. y tone is also transmitted through tae iront contacts of relay and condenser Eel and or" trunkL equipment OT to the calling subscribers station.

Assuming the connection to have been extended, by the operation of relay il I, through brushes fi, M5, 555 and ill and terminals 522, 523, 525 and ill/25, the alternate release and reoperation of line relay in response to the impulses created by the dialing of the second digit of the number or^ 4ie called station is effective to repeat these impulses to the line relay (not shown) of the intermediate selector IS. The intermediate selector is thereby selectively operated the level corresponding to the second of the number dialed and is then autome ically operated to select a set oi terminals in that level and to extend the connection through brushes 5M, 553Y and 555 and the selected set of terminals, to an idle connector switch C. The line relay 55i ci" connector C is now operated Vby the current in a circuit trom battery through the upper winding of relay 55|, lowermost back contact of relay 559, terminal and brush 542 or" switch IS, conductor terminal 523 and brush 'M5 oi switch CS, lowermost front Contact of relay li, lower front contact of relay fllt, resistance inner right front contact of relay middle lower back Contact of relay 455, uppermost front contact oi relay 4H, brush 4M and terminal 422 of switch CS, conductor 53|, brush 54| and terminal of switch IS, uppermost back contact of relay 559 to ground through ner lower back contact of relay 559, conductor terminal and brush 553 of switch IS, conductor 533, terminal 424 and brush 4|6 of switch CS, through the inner lower front contact of relay il l, over conductor 425, to the busy and holding ground potential at the outer right front Contact of relay 452. With the connection extended through the intermediate selector IS to the connector C, the holding circuit for relay 4l8 of selector CS is traced through the inner upper front contact ci relay 5H, brush 4|'| and ter-Y minal 525 of selector CS, conductor 534, brush 555 and terminal of selector IS, control conductor 554, inner lower back contact of relay 559 or" connector C, sleeve conductor 553, terminal and brush 553 oi selector IS, conductor 533, terminal 42d and brush 4|6 of selector CS, inner lower front Contact of relay dll, over conductor to ground at relay 452.

When the intercepting operator dials the next to the last digit of the number of the station being called, relay 55| of selector CS responds as hereinbefore described, the alternate opening and closing'of its lower iront contact being effective to repeat the dial impulses to line relay 55l of connector C. The release of relay 55|, upon receipt of the first impulse, closes a circuit trom ground through 'the inner upper back contact of relay 559, back contact of relay 55|, inner lower front contact of relay 552, normally closed contacts of the vertical oil-normal springs 561, winding of relay 553, and through the winding of the vertical-stepping magnet 554 to battery. Magnet 555 and relay 553 both operate, the operation oi magnet 554 being eiiective to step the shaft and brushes of switch C up to the first level of the terminal bank. As soon as the switch moves out of its normal position the circuit for energizing the windings of magnet 554 and relay 553 is traced through the front contact of relay 553 and the upper front contact of the vertical oif-normal springs 551 instead of the path previously described. The reoperation of relay 55| causes the release of magnet 554. Each succeeding release and reoperation of relay 55| causes a corresponding operation and release of magnet 554, thereby'stepping the brushes of switch C up to the level corresponding to the digit dialed. During the response of relay 55| to the repeated dial impulses, relay 552 is held over Y" conductor Y553 to ground on conductor 420 of switch CS; and relay is slow in releasing and remains operated until all oi the impulses created by the dialing of this digit have been received.

When the last digit ofthe called number is dialed, the dial impulses are again repeated by relay 40| to relay 55|. The rst release of relay 55| closes a circuit from ground through the inner upper back Contact of relay 559, back contact of relay 55|, inner lower front contact of relay k552, upper front Contact of the vertical off-normal springs 561, back contact of relay 553, Winding of relay 555, land through the Winding of the rotary-stepping magnet 555 to battery. Relay 555 and magnet 556 both operate; and when relay 55| releases, magnet 556 releases. Each release and reoperation of relay 55| causes a corresponding operation and release of magnet 556; but relay 555 1s slow in releasing and remains operated until all of the dial impulses have been received. Each operation of magnet 556 rotates the shaft and brushes of switch C one step to engage successively the sets of terminals in the selected level. Whenthe last step has been taken, the brushes 51|, 512 and 513 are in engagement with the set of terminals to which the called subscribers line is connected. With relay 555 operated, the winding of test relay 551 is connected through the front Contact of relay 555 to the test brush 513 of switch C. Relay 551 is somewhat slow in operating and does not operate if brush 513 engages a grounded test terminal during the advance of the brushes; but as soon as the brushes come to rest on the selected set of terminals, relay 551 operates if the called line is busy as indicated by the presence of a ground potential on the engaged test terminal. If relay 551 operates, a -locking circuit for this relay is closed as soon as relay 555 releases; this circuit is traced from battery through the winding of relay 551, inner back contact of relay 555, inner lower front contact of relay 551, middle upper back contact of relay 559, middle upper front contact of relay 552, upper winding of relay 559, to the sleeve conductor 563, and thence to ground at relay 402 of selector CS as hereinbefore described. Relay 551 is held operated by the current in this circuit and relay 559 is operated sufciently to close its inner lower front contact and thereby energize its lower winding in a circuit from battery through this winding and contact over conductor 563 to ground at relay 402 of switch CS. Relay 559 disconnects the sleeve conductor 563 from control conductor 563 thereby causing the release of relay 4 I8 of selector CS. The release of relay 4|8 causes the operation of relay 401 and establishes a connection from interrupter 558 of connector C, through the lowermost front Contact of relays 551, 552 and 559, conductor 562, terminal and brush 542 of selector IS, conductor 532, terminal 423 and brush 4|5 of selector CS, lowermost front contact of relay 4|I, left back contact of relay 433, outer right back contact of relay 4|8, and through the lowermost back contact of relay 408 to the winding of relay 404. Relay 404 is thus intermittently operated under control of interrupter 558 to reverse the current over trunk T as a busy signal to the intercepting operator. After relay 551 operates, the locking circuit for relay 552 includes the upper front contact of relay 551 instead of the inner upper back Contact of relay 551 and the inner lower back contact of relay 559.

Assuming that the called line is the line 599 connecting station B to the terminals adjacent brushes 51|, 512 and 513, and that this line is idle when selected, the release of relay 555 closes a circuit from battery through the winding of the cut-off relay 598 of line 599, through brush 513, outer back contact of relay 534, inner lower back contact of relay 551, middle upper back contact of relay 559, middle upper front contact of relay 552, upper winding of relay 559 to sleeve conductor 563 and thence to ground at relay 402 of selector CS as hereinbefore described. Relay 559 operates sufficiently to close the circuit for energizing its lower winding. Complete operation of relay 559 causes the release of relays 55| and 552. The operation of relay 559 also disconnects control conductor 564 from sleeve conductor 563 thereby causing the release of relay 4|8 and the operation of relay 401 of selector CS as hereinbefore described. The release of relay 4|8 connects the windings of relays 404 and grounded conductor 420 through the inner left .l

back contact of this relay and the inner upper front contact of relay 4| to the control brush 4|1 and thence over conductor 534 of selector IS and .through brush 544 to control conductor 564 of connector C. Since relay 4| 8 is slow in releasing, relay 552 releases before ground is thus reconnected to conductor 564. Ihe release of relay 552 applies ringing current to the called line; the ringing circuit is traced from the ringing current supply 560, through the middle lower front contact of relay 559, lower winding and lowermost back contact of relay 552, lowermost back contact of relay 551, brush 512 over line 599 and through the ringer at station B, back through brush 51|, uppermost back contact of relay 551, uppermost back contact of relay 552, middle upper front contact of relay 559 to ground. Ringing tone is transmitted through condenser 566, lowermost front contact of relay 559, terminal and brush 542 of selector IS, conductor 532, terminal 423 and brush 4| 5 of selector CS, lowermost front contact of relay 4| I, left back contact of relay 433, outer right back contact of relay 4 I8, lowermost back contact of relay 408, through condenser 440 and windings 44| and 442 of the repeating coil of selector CS, to ground. The induced current in windings 431 and 438 of the repeating coil gives an audible ringing-tone signal to the intercepting operator. With relay 401 of selector CS operated as hereinbefore described, ground is connected to conductor 430 to cause the operation of relay 320 of trunk equipment OT; audible ringing-tone is thereby transmitted through condensers 341 and 348 to the calling subscriber.

When the called subscriber answers, relay 552 is operated by the current through its lower winding and again locked through its upper winding and inner upper front Contact over the control conductor 564, through the terminal and brush 544 of selector IS, conductor 534, terminal 425 and brush 4 1 of selector CS, middle upper front contact of relay 4| inner left back contact of relay 4|8, over conductor 420 to ground at the outer right front contact of relay 402. With relay 552 operated, a circuit is closed from battery through the winding of relay 404, lowermost back contact of relay 408, outer right back contact of relay 4 8, left back contact of relay 433,1owermost front contact of relay 4| brush 4|5 and terminal 423 of switch CS, conductor 532, brush 542 and terminal of switch IS, conductor 562,1owermost front contacts of relays 559 and 552, lowermost back contact of relay 551, brush 512 of switch C, over line 599 and through the subscribers station B, back through brush 51| uppermost back contact of relay 551, uppermost front contacts of relays 552 and 559, conductor 56|, terminal and brush 54| of switch IS, conductor 53|, terminal 422 and brush 4|4 of switch CS, uppermost front contact of relay 4| middle lower back contact of relay 468, inner right back contact of relay 4|8 and through the winding of relay 428 to ground. Relays 428 and 404 operate in this circuit. Relay 404,

.front contact of relay 404.

operated, interchanges the connections between the windings of relay 40| and conductors 345 and 346 of trunk equipment OT thereby reversing the current over trunk T to operate the polarized relay SI1 of the operators position circuit.

The reversal of current over trunk T,'by the operation of relay 404, due to an all-trunks-busy condition having been encountered by selector CS or selector IS, due to a line busy condition having been encounteredby connector C, or due to the answer of the called subscriber, is in any case effective to cause the operation of relay 811 at the intercepting operators position unless the dial release key has been operated prior to the reversal of current. The operation of the dial release key 820 before relay 8I1 is operated by the reversal of, current over trunk T, closes .a circuit for operating relay BIB. If the dial has not reached. normal position when relay 3|8 operates, relay 8|8 locks to ground at the'front contact of relay 8I5 until the dial reaches normal position, at which time relays SI5 and 8l8 release. The operation of relay 8I1 and the operation oi relay 6|8 are each effective to cause the release of relays 8 I E and 1I1. The releaseof relay 1|1 disconnects the tip and ring conductors of plug 102 from the dial and connects these conductors to the winding of relay 1|4 so that the reversal of current over trunk T is now eiective to cause the operation of polarized relay 1I4. The operation of relay H4 causesy the operation or relay 125. Relay shunts lamp 104, the deenergization of this lamp indicating to the operator that the called subscriber has answered or that a busy condition has been encountered. Relay 125 closes a circuit from battery through the winding of pick-up relay 123, inner lower iront contact of relay 122, lower front contact of relay 125, through the back contact of relay 123 to the pick-up conductor 131 of interrupter 140. As soon thereafter as ground is connected by the interruptor 140 to conductor 131 the pick-up relay 123 operates thereby connecting ground fromthe lowermost back contact of relay 1216 through the inner upper front contact of relay 12,3 over conductor to the interrupter 140. After an interval of .from 2 to 5 seconds, the interrupter connects ground over conductor 139 through the outer upper front contact of relay 123 and the uppermost back contact of. relay 126, to the winding of relay 126. Relay 126 then operates and locks through its upper front contact to ground at the lowermost front contact of relay 121. Relay E25 disconnects the battery through resistances 132 and 134 from the tip and ring conductors of plug 10| and bridges the low resistance upon winding of supervisory relay 12| across these conductors. The bridge is effective, on a call intercepted at the Vbank of a switch in theV same oflice as that in which the intercepting operators position is located, to operate the supervisory relay of the connector switch and thereby establishthe charge condition for the calling subscriber. However, since the call here being described is one intercepted at the bank of a switch ina distant office, the bridging of the low resistance winding of relay 112i across the tip and ring conductors of plug 10| is without effect.

The aforementioned operation of relays 428 and 4,04 closes a circuit for operating relay 433; this ,circuit is traced rorn battery through the winding and outer right back contact of relay 433, front contact of relay-428, to ground at the inner left Relay 433 locks through its inner right front contact to ground at the outer right front contact of relay 402 and closes .a circuit for operating relay 408; this circuit is traced from ground at the inner left front contact of relay 404, front contact of relay 428, outer right front contact of relay 433 and through the upper winding Aof relay 408 to battery. Relay 408 locks through its lower winding and inner lower front contact over conductor435 to ground at the front contact of relay-309. Relay 408 disconnects the windings of relays 404 and 428 from the called line and extends the connection from the called line through the front contacts of springs 426 and 4I1, to conductors 345 and 346 of trunk equipment OT. Relays 404 and 428 then release. Relay 408 also disconnects the windings of relay 40| from conductors 345 and 346 but relay 40I is held operated by the closing of a circuit from battery through the contact of release magnet 409, lower winding of relay 40 I, left back contact of relay 404, resistance 406, winding 431 of the repeating coil, middle upper front contact of 400, resistance 433, winding 438 of the repeating coil, resistance 405, right back contact of relay A404, to ground through the upper winding of relay 40 I. Relay 400 also closes at its uppermost front contact a circuit for operating relay 329 of trunk equipment OT; and relay 329 closes a circuit for operating relay 3 I2. With relays 3 I 2 and 329 operated, conductors 336 and 331 of trunk equipment OT are connected to conductors 345 and 346 thereby completing a circuit from battery through the lower winding of relay 209 of the intercepting trunk IT3, uppermost front contact of relay winding 226 of repeating coil RCI, uppermost front contact of relay 201, terminal and brush 254 of trunk-finder TF, uppermost back contact of relay 259, uppermost front con- `tact oi? relay 250, conductors 21| and k336, left front contactof relay 3 I 2 or trunk equipment OT, outer left iront contact of relay 329 over conductor 345, inner upper front contact of relay 408, v

uppermost iront contact of relay 4I I, brush 404 and terminal 422 of switch CS, conductor 53|,

.brush 54| and terminal of switch IS, conductor brush 'M5 of selector CS, lowermost front contact of relay 4I I, lower front contact of relay 40 I, lowermost front contact of relay 403, over conductor 346, right front contact of relay 329, right front Acontact of relay 3 I 2, over conductor `331, conductor 212,1owermost iront contact of relay 260, lowermost back contact of relay 259, brush 265 and terminal 224 of trunk-finder TF, through winding 221 of repeating coil RCI, upper front contact of relay 255, inner upper front contact of relay 201, and through the upper winding of relay 209 to ground. The marginal relay '209 is operated in this circuit thereby closing a circuit for operating relay 205 of the trunk IT3. changes the connections between the windings of relays 20| and v204 and the windings 2I2 and 2 I3 of repeating coil RCI thereby reversing the current over the calling line to indicate that the called subscriber has answered.

The aforementioned operation of relay 329 of trunk equipment OT also opens the holding circuit of relay 3H; and the release of relay 3II causes the release of relay 309. With relay 309 Relay 205 interconductor 338 solely under control of the originating subscriber. That is, the ground at the lower front contact of relay 205 is extended through the lower front contact of relay 201, terminal 225 and brush 206 of trunk-finder TF to hold relay 260 of trunk-finder TF operated, thence through the inner lower front contact of relay 260, inner lower back contact of relay 259, lowermost front contact of relay 252, over conductors 213 and 338, through the front contact of relay 3H to hold relay 3I1 operated, thence over conductor 435 to hold relay 408 operated. The aforementioned operation of relay 3|2 also causes the release of relays 324 and 3|6. A talking connection is thus established between stations A and B, and all bridging apparatus which was used in intercepting and answering the call is disconnected at the contacts of relays 329 and 3 I 2 and restored to normal as hereinafter described. Talking battery for the calling subscriber is furnished through the windings of relays 20| and 204; and talking battery for the called subscriber is furnished through the windings of relay 209.

When the windings of relay 40| are disconnected from conductors 345 and 346, by the operation of relay 408 as hereinbeiore described, relay 6|1 of the trunk equipment IT and relay 1 I4 of cord OC release. The release of relay 5|1 causes the successive release of relays 6i3, 5|9, 620, 0M, 60| and 6| I. The release of relay 53| reoonnects the conductors 33| and 332 of trunk T to the windings 602 and 506 of the repeating coil RC3. The release of relay 6| I disconnects the upper winding of relay 6|2 from the tip conductor of jack 525 thereby causing the release of relay 12| of cord OC. The release of relay 12| causes the operation of relay 128 in a circuit from battery through the winding of relay 123, back contact of relay 12|, upper normally closed contact of key 120, lowermost back contact of relay 133, to ground at the lowermost front contact of relay 121. The operation of relay 128 closes a circuit for lighting lamp 103 as a signal to the operator to remove rthe plugs 10| and 102 from the jacks 325 and 621.

With key 1|5 normal the cord and the position equipment is fully restored to normal. The release of sleeve relays 303 and 523 of trunk equipment IT when the plugs 10| and 102 are removed, completes the restoration of trunk equipment IT to normal.

When the connection is released by the subscriber .at station A, relay 20E releases thereby causing the successive release or" relays 202, 203, 206, 201 and 209. The release of relay 203 disconnects ground from the sleeve conductor 2| 4 allowing the selector LS and line-nder LF to return to normal-in the usual manner. The release of relay 205 disconnects the holding ground from the sleeve terminal 225 to cause the release of relay 260 of trunk-lnder TF, the release of relay 3 1 of trunk equipment OT, and the release of relay 408 of completing selector CS. The release of relay 260 closes a circuit from battery through the release magnet 258, upper front contact of oilnormal springs 216, inner upper back contact of relay 26|, upper back contact of relay 250, back contact of relay 254, over conductor 214 to ground at the lower front Contact or oir-normal springs 216. Release magnet 258 operates in this circuit and returns the shaft and brushes to their normal position. When the shaft reaches normal the springs 216 open the circuits of the release magnet 258 and relay 262,

The release of relay 438 of selector CS causes the successive release of relays 329 and 3|2. The

outgoing trunk equipment OT is now normal. The release of relay 408 also causes the release of relays 40| and 402. The release of relay 402 disconnects holding ground potential from conductor 420 causing the release of relay 4| The release of relay 402 also closes a circuit from ground through the upper back Contact of relay 40|, back contact of relay 402, Winding of release magnet 409, and through the middle front contact of oir-normal springs 444 to battery. Release magnet 409 operates in this circuit and returns the selector CS to normal, in which position the circuit through the winding of release magnet 409 is opened at the off-normal springs.

Disconnecting ground from the conductor 420 also causes the return of the intermediate selector IS t normal and causes the release of relays 552 and 559 of connector C. A circuit is now closed from battery through the winding of release magnet 565, lower front contact of off-normal springs 561, inner lower back contact of relay 552, back contact of relay 55|, inner upper back contact of relay 559 to ground. Release magnet 565 operates in this circuit and returns the shaft and brushes of connector C to normal position. Magnet 565 releases when the shaft reaches normal. The release of relay 559 also causes the release of the cut-off relay 590 of the called line 599. All of the equipment units involved in completing the connection from the intercepting trunk IT3 to the intercepting operator and thence to a called subscribers station B have now been restored to normal.

Referring now to the intercepting trunk IT of Fig. 2, reference may be had to the aforementioned copending application of E. D. Butz Serial No. 648,052 for a description of the plugging-up line PL and the extension of an incoming call to the intercepting trunk. Upon seizure of line PL relay 234 or relay 232 of trunk IT5 is operated by ringing current from the connector LC. If the called line is a party line the ringing current source in the connector may be connected either to conductor 223 or conductor 230 of the plugging-up line PL depending upon which of the stations is the called station. If the ringing current circuit includes conductor 229, it is traced from this conductor through the uppermost back contact of relay 235, the inner upper back contact of relay 230, condenser 233 and the upper winding ol relay 234; if the ringing circuit includes conductor 230, it is traced from this conductor through the uppermost back contact of relay 236, condenser 23|, and upper winding of relay 232 to ground. If relay 234 is operated by the ringing current it closes a circuit for directly operating relay 231. If relay 232 is operated, it closes a circuit for operating relay 235; and relay 235 then closes a circuit for operating relay 231. Relay 235 also interchanges the connections between the conductors 229 and 230 of plugging-up line PL and the outgoing conductors 239 and 240 of trunk ITS; so that the ringing current circuit from connector LC will in either case be further extended over the tip conductor 239 and not over the ring conductor 240. The operation of relay 231 connects the winding of cut-off relay 236 over the sleeve cOnductor 24| to test terminal 228 in the bank of trunk-finder TF. Relay 231 also connects the upper winding of relay 238 in parellel with the upper Winding of relay 232, if relay 232 has responded to the ringing current, or in parallel with the upper winding of relay 234, if relay 234 has responded to ringing current. 'I'he upper Winding of relay 238 is not energized sunlciently to cause its operation. Relay 238 locks in a circuit from battery through its lower winding and lowerrnost front contact, to ground at the lowermost front contact of relay 231. Whichever of relays 232 and 230 responded to ringing current is held operated by the energization of its lower winding in parallel with the lower winding of relay 233. Relay 238 also connects ground from the inner lower back contact of relay 236, to the group conductor it being assumed that terminals 226, 221 and 226 are in the same group as are terminals 224 and 225; the group relay 25| is thus operated to cause the operation of trunk-lnder TF- or some other idle trunk-finder in the same group to hunt for the terminals 226, 221 and 226. When the trunk-finder nds these terminals the cut-off relay 236 is energized in series with the lower winding of relays 260 and 255; the operation of relay 260 or" the trunknder extends the connection from conductors 240 and 2M of trunk IT5, to conductors 336 and 331 of the trunk equipment OT. The operation of cut-off relay 236 disconnects ground from the conductor 222 and causes the release of relay 231. The release of relay 231 causes the release of relay 233 and the release of relay 232 or relay 234. Relay 235, ii operated, is locked through its inner upper front contact to ground at the lower front contact of relay 235. After relay 262 of trunk-finder TF operates, as hereinbefore described, the cut-off relay is held operated by the circuit from battery through its winding and inner upper front Contact, sleeve conductor 24|, terminal 228 and brush 266 of trunk-iinder TF, inner lower front contact of relay 230, inner lower back contact of relay 25e, lowerrnost front contact oi relay 262, over conductor 213 to sleeve conductor 338 of trunk equipment OT, thence through the front Contact of relay 323 and winding of relay 323 to ground or through the iront contact of relay SI1 over conductor 339 to ground as hereinafter described. The impedance o'f the windings of relays 232, 235;- and 230 is suiicient to prevent the operation of the tripping relay, (not shown) in the connector LC so that relay 302 of trunk equipment OT operates due to the energization of its right winding by the ringing current from connector LC or due to the energization of its left winding by direct current during the silent part of the ringing cycle. Relay 302 closes a circuit for operating relay 3IB; and relay 3|8 closes circuits for operating relays 3I3 and 3I5. Relays 3 i 3 and 3 I 8 close a circuit for operating relay 303; this circuit is traced from battery through the winding of relay 303, inner left front contact of relay 3I3, inner right back contact of relay 3M, conductor 330, right front Contact of relay 3I8 to ground at the iront contact of relay 302. The ground connection at the front Contact of relay 302 extended through the right front contact of relay 3|8 to conductor is also effective to operate relay SI1 so that the cut-oir relay 2136 of trunk IT5 and relay 266 of trunk-finder TF are now held over conductors 213 and 330 through the front contact or" relay 3 I1, to the ground potential connected to conductor 330. The operation of relay 303 is followed by the operation of relays 304, 305, 306, 301, 308, 303, 3M! and 3II as hereinbefore described. The operation of relay 3I3 interchanges the connections between conductors 336 and 331 and the windings 300 and 30| of repeating coil RC2. The operation of relay SI5 interchanges the connections between conductors 332 and 333 of trunk T and the outer armature springs of relay 303, so that the operation of relay 368 causes the current through the windings of relay 322 over trunk T and through the windings of relays 604 and 605 of the incoming trunk equipment IT to be in the direction in which it is effective to operate polarized relay 605 in addition to operating relay 604. With both of relays 664 and 605 operated a circuit is closed for operating relay 6|6; and relay 6I6 closes a circuit for lighting lamp 632 thereby indicating to the intercepting operator that the incoming call has been intercepted at a plugging-up line. Relay 6I6 also closes a circuit for operating relay 6 I 0. Relay 6I0 also closes a locking circuit for operating relay 6 I 0. Relay 6I@ interchanges the connections between the conductors of trunk T and the windings of relay 6 I 5. When the call is answered by insertion of plug 10| in jack 626, associated with lamp 632, relay 603 operates in series with relay 122 of the cord OC. The operation of relay 603 disconnects the windings of relays 604 and 605 from the conductors of trunk T and extends these conductors to the windings of relay 6I5. Relays 604 and 605 release thereby releasing relay 6I6 to deenergize lamp 632. After relay 6I6 releases relay 6I0 is held operated through its own inner upper front contact under control of relay v603. With relays 6I0 Aand 603 both operated, the connections between the conductors of trunk T and the windings of relay 6I5 are interchanged from that existing on the call intercepted by trunk ITS; since the connections between the conductors of trunk T and the windings of relay 322 were also interchanged, by the operation of relay 3 I 5, from that existing on the call intercepted by trunk ITS, the windings of relays SI5 and 322 are connected in the same relation to each other on the call intercepted by trunk ITE as that described on the call intercepted by trunk IT3. The operation of relay 6|5 causes the operation of relay 6I I; and the operation of relay 322 causes the operation of relay 3I9 and the release of relay 308. Relay 322 is held Operated, after relay 300 releases, by the energization of its right winding in a circuit through its right front contact, over conductor 339 to ground at relay 303. The operation of relay 3I9 causes the operation of relay 3I4 and closes a holding circuit for relay 3I3. The operation of relay 3|4 causes the release of relay 303 and connects the incoming conductors 336 and 331, through the windings 340 and 34| of repeating coil RC2 to battery potential at the back contacts of relay 342 as hereinbefore described. The release of relay 303 is followed by the release of relays 304, 305 and 306, the tripping resistance 399 being temporarily connected through the right front contact of relay 305, left front contact of relay 3|4, and outer left front contact of relay 3I3 over conductors 336, 21|, 239 and 229 to operate the tripping relay (not shown) of the connector LC. The aforementioned operation of relay BII closes a circuit for operating relay 601 and connects the upper winding of relay 6I2 to the tip conductor of jack 626, relay 12| of cord OC being thereupon operated as hereinbefore described. The aforementioned release of relay 308 bridges the left windings of relays 326 and 321 across the conductors of trunk T, the operation of relay 321 being effective to hold relay 301 operated after relay 306 releases.

The talking connection between the intercepting operator and the calling subscriber having been completed as a result of the insertion of plug 10| in jack 626 in the same manner as that hereinbefore described for the call intercepted by trunk IT3, the interceptng operator informs the

Images