US1661536A - Telephone-exchange system - Google Patents

Description

March 6, 1928.

- 1,661,536 w. c. JORDAN I TELEPHONE EXCHANGE SYSTEM Filed Feb. 8, 1927 5 Sheets-Sheet 1 11 m; V 2 t k g /mkn/anr W////a/77 C 40/40 by Jmafl Af/omey TELEPHONE EXCHANGE SYSTEM Filed Feb. 8, 1927 5 Sheets-Sheet 2 IHI' IHI-

March 6, 1928.

w. 6. JORDAN TELEPHONE EXCHANGE SYSTEM Filed Feb. 8. 1927 5 Sheets-Sheet 5 A/famey I w. c. JORDAN V.

TELEPHONE EXCHANGE SYSTEM Filed Feb. 8, 1927 5 Sheets-Sheet 4 kWh/0i:- W////'0/7z 6 Jordan March 6, 192s.- 1,661,536

W. C. JORDAN TELEPHONE EXCHANGE SYSTEM Filed Feb. 8. 1927 5 Sheets-Sheet 5 Patented Mar. 6, 1928.

UNITED STATES Letters PATENT ()FFlCl'll \VILLIAM C. JORDAN, OF MADISON, NEVK JERSEY, ASSIGNOR TO BELL TELEPHONE LABORATORIES, INCORFOBATED, 01E NEW YORK, N. Y., A. CORPORATION 013 NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed February 8, 1927.

This invention relates to telephone systoms and has for its object the provision of means for establishing connections with telephone subscribers whose substatiol'i 5 equipment is located at a point remote from the central oflice.

ltzis sometimes desirable for telephone subscribers, whose place of business is located in a small town, to have direct telephonic connection with some larger and better known city; or an urban business subscriber may wish direct telephonic conncction with the suburbs. here the central ofiice is equipped with. automatic switching apparatus and the interconnecting lines are of great length, the establishment of coni'iections may not be satisfactorily accomplished by the automatic apparatus if the lines are of the standard type. A line circuit arrangement of a special type therefore necessary for such subscribers, which will permit the completion of connections thercover under the control of an operator at the central ofiice.

In. accordance with the present invention an intercepting line is provided at the central office, individual to each line extending to a distant subscribers substation. On out going calls the switching apparatus of the central o'llice selects this intercepting line and an operator connects it with the sub scribers line. If a call is initiated over a trunk by the subscriber when the corre-- spouding intercepting line has been seized by the switching apparatus, a distinctive signal is displayed before the operator. The intercepting line also arranged so that when the operator is resignaled thereover, the signal may only be retired by the act of the operator in signalling the called subscriber.

The preferred embodiment of the present invention, specifically stated. consists of a two-way line extending from a jack at an A operators position of a machine switching central otlice to a distant private branch exchange, and a one-way intercepting line which is individual to the first line and which extends from the bank terminals of the automatic switches of the machine switching central office to an intercepting Serial No. 165,637.

jack at the position. The two-way line is provided. with a repeating coil, a line lamp, and equipment controllable over the line by means of ringing current from the branch exchange to operate the line lamp and a disconnect signal in the operators cord circuit, as well as ringing equipment controllable by the operator to signal the branch exchange. The intercepting line has equipment responsive to ringing current supplied by the switching apparatus to control a calling lamp. In addition there is provided a key by means of which the operator may cause the call to be charged. In the case oi? calls incoming from the machine switching equipment, the operator responds to the calling lamp associated with the intercepting line to connect the intercepting jack with the line jack by a cord circuit. She then signals the branch exchange over the two way line. On calls incoming from the branch exchange the operator inserts the answering plug of her cord circuit in the line jack and employs the calling plug to extend the desired connection by means of trunk lines appearing at her position. If a call is originated at the branch exchange after the intercepting line has been siezed by the switching apparatus, the line lamp will be caused to flash whereupon the operator will inform the subscriber that the line has been taken for an incoming call. Where an incoming" call is controlled by a distant operator and that operator rerings over the connection a lamp associated with the cord circuit employed in completing the connection will be lighted until extinguished by the operation of the ringing key to resign'al the branch exchange.

The manner in which the apparatus embodying the invention functions will be more clearly understood from a consideration of the following description in connection with the accompanying drawings in which:

Fig. l shows a calling substation and an operators position at a manual oflice equipped. with key indicator apparatus, indicated by the dotted rectangle at the right Oil the figure;

Fig. 2 shows an incoming selector at a machine switching ofiice adapted for ex;

tending connections from key indicator equipment Fig. 3 shows a final selector;

Fig. 4: shows a cord circuit for use at an A operatofs position in a machine switching otiice';

Fig. 5 shows the line circuit for use bctween-machine switching equipment and a remote ln'anch exchange; and

Fig. 6 shows the i'nethod of arranging Figs. 1 to 5 inclusive.

Connection ("0 Zrrmmlt m nim/i 76.

The establishment of a connection from :1. subscriber in a manual oilicc to the remote branch exchange will first be described. When the subscriber at manual substation 100 removes his receiver from the switch hodk, he closes a circuit from battery through the left winding of line relay 101, outer hack contact of relay 102, over his line and substation equipment to the inner back contact of relay 102, right winding of relay 101 to ground. Relay 101 operates. lighting line lamp 103 which is located before an operator at the central otficc. The operator, observing lamp 103, inserts pug 104; of cord circuit 105 in answering jack 106. A circuit is thereupon closed from battery through cord "lamp 107, resistance 108, sleeves ot pflu'g 101*and jack 106, winding of cut-oil relay 1021to ground. Relay 102 operates in this circuit, opening the circuit of relay 101 and extinguishing lamp 103. At the same time a circuit is closed from battery, lower left winding of repeating coil 109, winding of supervisory relay 110, rings of plug 104 and jack 10, over the =subscribc1"s line. tips of jack 106 and plug 101, upper left winding of repeating edit 100 to ground. The operation of relay 110 connects battery through resistance 111 to the circuitof relay 102 "inishu'nt of lamp 107, thereby preventing the lighting of lamp 107. The operator will then operate talking key 112, connecting hcr headset 113 to the cord. circuit 105 so that She'may talk with the-calling subscriber.

Having learned from the subscriber that the wanted line is located in the machine switching exchange. portions oi which are shown in Figs. 2 to 5 inclusive, she will operate a key, individual to the oflicc at which the wanted line terminates and forming a part 01 the key indicator equipment rcpresented by the rectangle at the right of Fig. '1. The operation of this key will cause the selection of an idle trunk outgoing to the distant ofiice and the indication of the number of the selected trunk on an indicator before the operator. Assuming that trunk 11 1 is selected, which trunk terminates in jack 115, the operator inserts the calling plug 116 in jack 115 as soon as she receives the indication. A circuit is thereupon closed from battery, through lamp 117, resistance the called subscriber 124., sleeves of plug 116 and jack 115, winding of relay 118 to ground. Relay 118 in operating prepares an operating circuit and a holding circuit for relay 119, which is operated from the key indicator equipment when the selection of the called line has been completed. A circuit for supervisory relay 122 similar to that for relay 110 is prepared when plug 116 is inserted in jack 115 but is not completed until relay 119 is operated and answers. Therefore lamp 117 remains lighted as an indication that the connection has not been completed.

The key indicator equipment includes numerical keys at the operators position and a sender under the control of which the wanted line is selected. After recording the number of the wanted line and inserting plug 116 in jack 115 the operator may attend to other calls. For a complete description of the operation of the -key indicator equipment. reference is made to U. S. Patent 1,518,362, granted to L. M. Allen, October as, 1924.

When the first digit of the wanted number has been registered on the key indicator sender, a fundamental circuit is established between the incoming selector at the machine switching oflice and the key indicator sender. This circuit may be'traced in part from battery, through the leftwinding of relay 201, lower left contact of sequence switch cam 202, upper left contact of cam 203 over conductor "204 of the interofiice trunk 114 to the key indicator equipment, Where it extends through the stepping relay oi. the associated sender, back to conductor 205 of the trunk, lower contacts-of cam 206 to ground. Relay 201 operates, closing a locking circuit for itself extending from bat- V tery through its left winding, right contact of cam "207, left front contact of relay 201, upper left contact of cam 202, to the fundamental circuit as above traced. Relay 201 also closes a circuit from ground at its right front contact. upper left contact of cam 208, winding ot sequence switch magnet- 200 to battery. The sequence switch is advanced to position 2 in this circuit.

in position 2 the energizing circuit of relay 201 is opened but the locking circuit remains closed. A circuit therefore closed from battery, through up-(lrive magnet 200. lower right contact of cam 210, upper right contact of cam 211, to ground at the right front contact of relay 201. The incoming selector is moved upward under the con trol of magnet 209 in its brush selecting operation. During this upward movement a circuit is closed intermittently from ground over the lower left and upper right contacts of cam 212, commutator brush 213, conducting segments of commutator strip 214:, upper right contact of cam 202 to the fundamental circuit. This ground holds (ill : llill'll-l'liy lie eoiulitiou not up h ihe relay $30!. operated and shunts the stopping relay of the seiufler in the well l uowu manner. When tl e ste )piug relay has been released a s1 llcieut iliifl'lljfll of times to seiuleig the jlj'ulu alueiilial circuit is uruuul in the sender aiul relay 1301 releasec. ,'.llie relcaso o1" relay Llll closes a circuit from lmttery through the uiiuliug of iua uet 5201), 1 ppm: right m'urlacl' ol. 1 11211 2W, if groiuul :1 right hacli contact of relay 530i. quencc switch advanced to position El in this c'rcuit.

I11 positions 53 aiul hruch tripping 11mguet Ell-5 operated over the lower contacts of cam 216. in these positions likewise, relay 201 operates causing the :--:elecl'or to make group selection. and advancing the sequence switch to positions l; arul 5 in the manner clescrihecl for brush s l cti1u The shunting circuit for the slop j relay ea teucls at this time from sniouurl to hrush 2i? as previously traced and tl'ruce over conducting segments oi? sltrig' 521.2 and lhe upper right contact of cum. 1303 lo the luiulameutal circuit In position 5 a. test is uuule ol' the trunk eutcucliug to the first l ual selector of the group selected, on the terminals oi. which the incoming selector rosls at this time. lle lay 201 is oj ieratcrl. in. a. local circuit exteiu'llug from battery, through the right Wiru'liue; of relay 201, upper contact of cum 219, right .iori'ua-l Contact of relay upper left and lower right contacts of ca 1 2521 to grouul. Relay 201 in ()Pfiilhlillg advances sequence switch 200 to position 6. it also prepares a locking circuit for itseli? which may be traced from both 1 through the left Wiurling of relay 20L. right COlllJMIl) otcam 20?, lel' rout contact of relay Qlll, upper coul'actri oi cam fl'lll t1 slrevo brush $2 224. if the.

ll. he seliual selector ou the teru'iiuals; oil whu-h the brushes are resting, is busy,

the ahore traced. loo. 3 g circuit .hc tour plot Therein ill ll. will .1e held and will operate magector to hunt for an 5301 is helll o ratcfl heal: c r .t, extend operaicil in position not 2209 to cause the Relay irllc truuir. tween trunk llllill 1. i1 .iug l'rou'i. liatlery through its right Winding, contacts ol cam 225, commutator strip 2%, brush 9:27, right contacts of 1:1 to illl, right :lroul: coolant oi. relay Zlll to ground. This circuit also ensures the of the l'uushes oi? the trunk lieru 1 ls. l vhefu an idle trunk is found aurl this circuit is opened. relay F301 releases, opening tho circait of magllil Hui hriuggi g the selector to rest. t lso urlvauces oucucc switcl'i 260 to posil l heu relay E201. releases, a circuit i from. luush upper contacts of cam 216, left back Contact of relay 201., lower l 1 winding oi relay 5201, left mtacls ol" can]. 202, lelt contacts of (11 111 216 1'4 to grouiul. :lu opera-"lug, relay 201, closes 1v locking circuit for elf extending from mll'ery thrmigh its lot "winding, right c0ntact of cam 207, left trout contact of relay 20h llpllfil contact of 221111 228, brush 223, coiu'luctor 301 of the lina selector trunk, resistance 302, left Contact of (21-111 303 to ground. Rel-11y 5201 also a l *auces sequence switch. 200 to position 8, in which position relay 201 remains locked to the final selector, l'f equuu-e switch Q00 remains in this position throughout final selections.

llith sequence switcl 300 in position 8, the il'ululzuoeutal circuit zleiuis from hattori, over the lower letlt 1 ml upper right eo11- lacis of. ram 301-, right winding it relay SW5. lower lelit contact o'li cam 2M6, lowor contact oi (21111. I307, eourfhu'toi' 805%. brush right contact of cam 22:). conductor 20 1, and thence through tho key indicator sender hack to conductor 205. left coi'ltact of cam E210, upper right contact of ram 211 to round at the right front contact of relay V l 150i. Relay operates in this circuit and loses a locking circuit for itself from hatcontact 01 relay .505, upper left contact of cam 306 to the f111ulzu11ental circuit as traced.

Relay 305 in operating closes circuit from battery through the left Wiiuliue o'l. relay 3.1.0. right conl'act of ram. 311, left front contact of relay 505 to ground at the ri ht contact of 21111 312. Relay 2-310 operates in llliH circuit, closing; :1 locking circuit lior itsell irom battery through its left Winding. lower contact of cam 311, back contact of relay 313, right contact of 11111 Elli. outer front contact of relay 310, sleeve conductor Elli), brush 22%, upper right and lower left contacts oil cam 216 to ground. This circuit is effective until sequence switch 301) leaves position 10, but is, oi course, dependent on relay 313. Relay also closes a circuit from battery through tie Winding of sequence switch magnet 300, right contacts cam 316, inner tl'ront couta -t of relay 310 to ground. advancing the sequence switch to position 2. 1

L: position a circuit is closed from haw cry throi'igh the winding of high speed up rive magnet 31?, lower right and upper .ifl contacts of cam 318, li' cnt Contact 1 1 of relay to ground at the -ight Contact of cam 3112. At the same time a circuit is prepared from ground, overthe lower contact of ram 303, connnutator brush 319, commutator strip 320, upper right contact of ram 307 to the fundamental circuit. As the final selector is moved upward under the control of magnet- 31'7, this circuit is intermittently completed to release the sender stepping relay in the well known manner. When the selector is in position to trip the proper set of brushes, relay 305 releases, releasing magnet 31? and bringing the se lector to rest. A circuit is thereupon closed from battery, through the winding of sequence switch magnet 300, lower contact of cam 321, left back contact of relay 305 to ground at the right contact of cam 312, advancing the sequence switch to position 3.

In positions 3 to 5 inclusive, the trip magnet 322 is operated over the upper right contact of cam 303. In position 3 relay 305 is reoperated and flocked, advancing the sequence switch 300 to position at in a circuit from battery, through magnet 300, upper left contact of cum 323, upper left contact of cum 318, left front contact of relay 305, to ground at the right contact of cam 312.

In position 4-, magnet 317 is again 0perated, to control the groin selecting operation of the selector. The intermittent shunt for the stepping relay extends at this time from ground over the lower contact of cam 303, brush 32 1, commutator strip and the upper right contact of cam 306. Relay 305 releases when the fundamental circuit is opened by the completion of the selection, releasing magnet 317. As before itadrances sequence switch 300, this time to position 5.

In position 5, relay 305 is again operated and locked, advancing sequence switch 300 to position 6. In position 6 the low speed up-drive magnet 326 is operated, the circuit extending over the lower right contact of cam 323 and from thence over the same-circuit as traced for high speed magnet 317. The final selector is now elevated more slow- 1 y to select the line designated by the wanted number. The shunting circuit for the stepping magnet in position (3 is the same as traced in position 2.

Since the wanted number represents a private branch exchange, the selector will be brought to rest, following units selection, on the first of a group of trunks leading to the exchange. The release of relay 305 advances the sequence switch to position 8. when sequence switch 300 leaves position 7 the holding circuit of relay 201 is openrd, initiating certain operations which will is described hereinafter.

I'Vhen sequence switch 300 reaches position 7%, relay 305 is operated in a circuit from battery, through the left winding of relay 305, left contact of cam 327, inner a ,ee 1 ,eee

l ron't contact of relay 310 to ground. When the sequence switch reaches position 8 with relay I305 operated, the condition of the line is tested by means of a circuit extending from ground, lower left contact of cam 328, winding o f relay 313, winding of relay 329, upper contacts :of earn 330, right front contact of relay 305, left contacts of cam 309 over sleeve conductor 33-1, brush 332, to the sleeve terminal of the first trunk of the group. Assuming thatthis trunk is busy, battery will be connected to the sleeve terminal as will be described hereinafter. Likewise, due to the low resistance marking the sleeve of P. B. X. trunks other than the last, the potential on the sleeve terminal will cause the operation of relay 329 "but not of relay 313. Relay 329 closes a holding circuit for relay 305 extending from battery, lower left and upper right contacts of cam 30 1, right winding of relay 305, lower left contact of earn 306, upper left contact of earn 307, to ground at the front contact of relay 329. Relay 305 advances the sequence switch to position '9, where the holding cirrelay 305 and magnet 326 to bring the selec'tor to rest. Relay 305 is maintained energized between trunk terminals and the brushes are properly centered 'by means of a circuit extending from battery through the left winding of relay 305, right contact of cam 335, right winding of relay '310, commutator strip 336, brush. 337, upper right contact of cam 323, upper left contact of cam 318, left front contact of relay 305, upper contact of cam 312, inner front contact of relay 310 to ground.

As soon as relay 305 releases,a circuit is closed from battery, left contacts of cam 304, resistance 338, upper left contact of cam 339, right back contact of relay 305, left contacts of cam 309, sleeve conductor 331, brush 332, conductor 501, right back contact, of relay 502, windings of relay 503 to ground. Relay 503 operates, closing an obvious circuit for relay 504. Relay 504 connects shunted battery to the sleeve of calling jack 505 to mark the intercepting line terminating in that jack as busy. Relays 503 and 504 also prepare circuits which will be traced as they become effective.

The release of relay 305 also closes a circuit from battery, through the Winding of sequence switch magnet 300, lower contact of cam 321, left back contact of relay 305, upper contact of cam 312, inner front contact of relay 310 to ground. Sequence switch 300 advances to position 12 in this circuit. As the sequence switch passes through position 10, the holding circuit of relay 310 is extended over the upper le f't'contact-o-fcam 311 directly to the outer front contact of that relay, rendering the continued energization of the relay independent of relay 313. The sequence switch is thenadvanced to position 13 by means of a circuit over the right contacts of cam 310 to ground at the inner front contact of relay 310, and to posit-ion 11 in a circuit over the lower contact of am 321, left back contact of relay 305 to ground at the right contact of cam 312. In position 14-, tip conductor 308 is connected over the lower contacts of earn 307 to brush 33 1 and comluctor 500 of the intercepting line circuit, while ring conductor 301 is connected over the upper contacts of cam 310 to brush 333 and conductor 507 of the intercepting line circuit.

It will, be remembered that when sequence switch 300 left position 7 relay 201 was released. The release of relay 201 advances sequence switch 200 to position 9. In posi tion battery tln'ough the left winding of relay 201 is connected over the upper left contact of earn 211, and the left c n1tact of cam 210 to tip conductor 205, and gl'filllld is connected over the left contacts of earn 216, upper left contact of earn 202 and the'upper left contact of cam 203 to ring conductor 2041. This reverses the direction of current flow over the fuinlaniental circuit to the sender, advancing the sender to a position where it connects grolilnd to conductor 120, operating relay 111) which thereupon locks through both windii gs to ground at the outer contact of relay 118. The sender then releases.

.llelay 201 operates in this circuit, advancing &'-:e p1ence switch 200. In position 10 the right winding of relay 201 is connected to the tip conductor, in parallel with the left winding, over the upper contact of cam 219, upper right and lower left contacts of cam 230, upper left winding of repeating coil 231., and the upper right and lower left contacts of cam 206. When sequence switch 200 leaves position 10, relay 201 releases, stopping the sequence switch in position 11.

Assuming that the operator has inserted plug 110 in not: 115, a circuit is now closed from battery, lower right winding of repeating coil 100, winding of relay 122, lower normal contact of ringing key 121, rings of plug 110 and :aclc 115, inner contact of relay 119, ring coiuluctor 204: of trunk 114, upper left and lower right contacts of cam 203, lower left winding of repeating coil 231, both windi ,,s of relay 232, upper left winding of repealnig coil 231, upper right and lower left contacts of earn 206, tip conductor 205, outer (mutant of relay 119, tips of jack 115 and plug 111", upper normal contact of ringing hey upper right winding of repeating coil 109 to grouno. Relay 232 operates closing an obvious circuit for relay 233 which locks over its left contact to cam 23%. Relay 233 closes a circuit from ground at its p pears,

right contact, upper contact of earn 210, up per left contact of cam 211, left winding of relay 201 to battery. Relay 201 operates, advancing sequence switch 200 to position 12. Relay 201 is held operated. in a circuit from battery through its left winding, right contact of cam 2/. left front contact of relay 201, left contacts of earn 210 to ground, until the sequence switch leaves position 11% to prevent the premature operation of relay 220. When sequence switch 200 reaches position 12, a circuit closed from battery, through the winding of relay 220, right contact of earn 235, left normal contact of relay 220, upper left and lower right contacts of earn 230, left back contact of relay 201, lower contacts of earn 213 to ground. Relay 220 ol'leratcs closing a holding circuit for itself over the right contact of earn 235, left altern ate contact of relay 220, left contact of cam 230, haclr contact of relay 237, to ground at the right contact of relay 233. Relay 220' also closes a circuit from battery through the winding of magnet 200, lower contact of cam 21% n alternate contact of relay 220, left contact of earn 213 to ground, advancing the sequence switch to position 13. In position 13 ringing current is applied to the called line. The circuit for it may be traced rom ringing source 238, contact of cam 239, winding of relay 237', outer right front contact of relay 220, right contact of cam 228, ln'ush 223, conductor 301, upper contacts of cani 3-10, brush 333, conductor lower winding of alternating current relay 503, condenser 509, conductor 506, brush 331, lower contacts of cam 30?, conductor 308, brush 222, lower contact of cam 229 to ground.

Relay 508 operates, locking in a circuit from battery through its upper winding and inner front contact to ground at the outer front contact of relay 504i. Relay 508 also closes a circuit from ground at its upper front contact, through the winding of relay 510 to battery and, in parallel therewith, through the lower winding of relay 511 to battery. Relays 510 and 511 operate. Relay .111 closes a circuit from battery, over the bacl-z contact of relay 512, lower front contact of relay 511, through lamp 513 to ground. The lighting of lamp informs the A operator at whose position this line that a call has been extended thereto.

The operator thereupon inserts answering plug 400 of a cord circuit at her position into the intercepting aclr 5141 of this line. A circuit is closed from battery through the winding of relay 101, sleeves of plug 100 and ack 514, winding of relay 512 to ground. Relays 401 and 512 operate in this ClI'CItlt. The operation of relay e01 closes an ObVlOllS circuit for lighting the answering cord lamp 105, but lamp 105 is shunted as subsequently described. Relay 512 in operating disconnects battery from lamp 513 and connectsit over the lower front contact of relay 512 and the lower back contact of relay 515 to lamp 516 and: ground. Relay 512 also closes an obvious circuit for relay 502. Relay 502 o Jens the circuit of relay 503 and therefore of relay 504. It also opens the locking circuit of relay 508 which releases relays 510 and 511. Relay 502 connects a shunted battery over its inner front contacts to sleeve conductor 501 as a busy condition. It also connects battery through resistance 517, to ring conductor 507 during the releasing time of relay 510. When relay 511 closes its back contact, it completes a circuit from battery through the lower left winding of repeating coil 406, winding of supervisory relay 407, lower normal contact of ring-back key 408, ring conductor 409, rings of plug 400 and jack 514, back contact of relay 511, upper back contact of relay 515, retard coil 519, tips of jack 514 and. plug 400, tip conductor 41 0, upper normal contact of key 408, front contact of'relay 401, upper left winding of repeating coil406 to ground. Relay 407 in operating closes a. circuit from battery through the left winding of relay 411, normal contact of relay 412, right normal contact of relay 413, front contact of relay 407, left normal contact of relay 413, resistances 414 and 415 to ground at the right contact of relay 401. This circuit shunts lamp 405 preventing its lighting. Relay 411 operates but is immediately released by the operation of the listening key.

The connection. of battery to conductor 507 as above described causes the operation of relay 237 which opens the holding circuit of relay 220, disconnecting ringing current from the line. With relay 220 released, a circuit is closed from battery through the right winding of relay 201, upper contact of earn 219, right normal contact of relay 220, upper left and lower right contacts of earn 221 to ground. Relay 201 energizes and. ad- Vances sequence switch 220 to position 14 whereupon it releases to advance the sequence switch to position 15. In position 15 relay 201 is reoperated in a. circuit from battery through its left winding, left contacts of cam 211 to ground, advancing sequence switch 200 to. position 16 which isthe talking position. sitions 15 to 17 inclusive under the control ofthe operator at the calling office, the circuit extending from battery through its left winding, upper left contact of cam 21]., upper contact of cam 210, to ground at the right contact of relay 233.

As soon as the operator at the called officc has inserted plug 400 in jack 514 she will. operate listening key 416 and insert plug 402 in jack 505. The operation of the key 416 connects her telephone circuit with the cord circuit and also closes a circuit from ground Relay 201 is held operated in poover its lower contact, right winding of releft alternate contact and left winding of relay 413, resistance 415 to ground at theright front contact of relay 401. The operation of relay 413. disconnects relay 411 but maintains the shunt around la1np405.

The insertion of plug 402 in jack 505 com pletes a circuit from. battery, through the windings of relays 403 and 404, sleeves of plug 402 andv jack. 505, left back contact of relay 504,, winding of. relay 518 to ground. Relays 403, 404 and 518 operate- The operation of relay 403 disconnects relay 417 fromand connects relay 418 to the repeating coil 406. Relay 404 in operating closes a-n obvious circuit for relay 419 which opens the busy test circuit and completes the circuit of relay 418. This circuit extends from battery through the left winding of relay 418, outer front contact of relay 403, lower right winding of repeating coil 406, lower normal. contact of ringing key 420,. lower normal. contact of dialing key 421,. rings of plug, 402. and jack 505, lower left winding of repeating coil. 520, back contacts ofv relay 521', through direct current relay 522 in parallel: with alternating current relay 523 and condenser 524, upper left winding of repeating coil 520, tips of jack 505 and plug 402, outer front contact of relay 419, upper normal con.-

tacts of keys 421 and 420, upper right winding of repeating coil 406, inner front contact of relay 403,. right winding of relay 418 to ground. Relays 418 and 522 operate, relay 418 opening thecircuit of lamp 422 and relay 522 opening. the locking circuit of relay 525.

The A operator now. operates ringing key 420- which applies ringing current to relay 52.3 over a portion: of the circuit above traced. Relay 52.3 operates closing an obvious circuit for relay 52.6. Relay 526 causes the application of ringing current to the trunk 534 leading to the private branch exchange fromv source 527 ,through lamp 528,

outer lower contact of relay 526 to thebranch. exchange and back: over the upper front contact of relay 526' to ground. At, the same time, ringing tone is returned to the calling subscriber. over the inner lower contact. of relay 526, condenser 529 and the ring conductor 507.

When the operator at the branch exchange answers which she does orally during an interval between ringing, the A operator may reply. She will then. operate key 537.

The operation of this. key closes an obvious circuit for relay 515 which then looks over its outer upper front contact to ground at the outer upper contact of relay 512. lVith relay 51:5-operated, lamp. 516. is extinguished,

the circuit of supervisory relay 240 is closed and a new circuit closed for relay 407. The new circuit of relay 407 may be traced from ground through the upper right winding of repeating coil 231, upper left contact of cam 229, brush 222, conductor 308, lower contacts of cam 307, brush 334, conductor 506, inner upper front contact of relay 515, resistance 539, lower back contact of relay 511., rings of jack 514 and plug 400, conductor 409, lower normal contact of key 408, winding of relay 407, lower left Winding of repeating coil 406 to battery. The circuit of relay 240 may be traced from battery, through the lower right winding of repeating coil 231, winding of relay 240,

lower right contact of cam 228, brush 223, conductor 301, upper contacts of cam 340,

brush 333, conductor 507, back contact of relay 510, resistance 538, lower front contact of relay 515, tips of jack 514 and plug 400, conductor 410, upper normal contact of key 408, left front contact of relay 401, upper left winding of repez'itil'ig coil 406 to ground. Relay 240 operates in this circuit, closing at its front contact a shunt around the high resistance winding of relay 232. This reduces the resistance in the circuit of relay 122 sutliciently to permit that relay to operate. The operation of relay 122 connects battery through resistance 123 in shunt of lamp 117, extinguishing that lamp to inform the key indicator operator that the connection has been extended to the distant exchange. Conversation may now proceed between the subscriber at substation 100 and the operator at the branch exchange, who will complete the connection to the wanted. person.

It may be noted that a talking circuit exists between the A operator and the calling subscriber, before key 537 is operated, which extends through condensers 540 and 541 by means of which the operator may talk with the calling subscriber if necessary, without charging the call.

Owing to the length of the line between the central o'fiice and the branch exchange, ringing current is transmitted from the branch office as a disconnect signal. This current operates relay 530, which closes a circuit from battery through the winding of relay 531, front contact of relay 530 to ground at the inner upper back contact of relay 526. Relay 531 closes a circuit from battery through the winding of relay 532, back contact of relay 533, front contact of rclay531 to ground at the inner upper back contact of relay 526. The operation of relay closes a circuit from battery through the winding of relay 533, front contact of relay front contact of relay 531 to ground at the inner upper back contact of relay 526. Relay 533 is slow to operate. but on completely attracting its armature it opens the circuit of relay 532, which, being slow to release, closes its back contact after an interval. A circuit is now closed from battery, through the winding of relay 521, inner right front contact of relay 518, back contact of relay 532, front contact of relay 533, front contact of relay 531 to ground at the inner upper back contact of relay 526.

Relay 521 locks over its front contact, inner left contact of relay 518 to ground at the inner upper back contact of relay 526. The operation of relay 521 opens the circuit of relay 418, thereby closing a circuit from battery through lamp 422, resistance 423, back contact of relays 418 and 417, inner front contact of relay 419 to ground, lighting lamp 422 as a disconnect signal to the A. operator. It is apparent from the foregoing that the ringing current must be applied for a definite interval in order that the A operator may receive a disconnect signal. This delay prevents the premature display of such a signal from momentary disturbances of the line.

When the A operator sees lamp 422, she withdraws plugs 402 and 400 from jacks 505 and 514 respectively. The removal of plug 402 releases relays 410 and 518 extinguishing lamp With relay 518 released. relay also releases. The removal of plug 400 releases relay 512, opening the circuits of relays 502 and Relay 502 removes the busy condition from conductor 501 and reconnects relay 503 thereto, reoperating relay 504 to mark the sleeve of jack 505 busy. The removal of plug 400 also releases relays 401, 407 and 413 restoring the A operators cord to normal.

The release of relay 515 opens the circuit of supervisory relay 240, which relem opening the shunt around the high resi. ance wii'lding of relay 232. This increase in resistance releases relay 122 which opens the shunt around lamp 117, permitting it to relight. The key indicator operator will thereupon remove plugs 110 and 104 from. the jacks 115 and 106, restoring her cord circuit to normal.

The removal of plug 116 opens the circuit of relay 232 which releases in turn releasing relays 233 and 201. Relay 201 on releasing advances sequence switch 200 to position 18. As the sequence switch leaves position 16% ground is disconnected from sleeve brush 224. When the sequence switch arrives in position 18, the down drive magnet is energized in a circuit extending from battery tl'irough the winding of magnet 241, lower right and upper left contacts of cam 202, left contacts of cam 216 to ground. The, selector is restored to normal. under the con-- trol of magnet 241. l Vhen it reaches normal, a circuit is closed from battery through the winding of sequence switch magnet 200, lower left contact of cam 208, normal commutator segment 242, brush 217, upper right ill) and lower left contacts of cam 21:2 to ground. Sequence switch 200' advances to position 1 in this circuit restoring the incoming selector circuit completely to normal.

The removal of ground from brush 224 opens the holding circuit of relay 310 which releases. The release of relay 310 closes a. circuit from battery, through the winding oi sequence switch magnet 300, lower right and upper left contacts of earn 316, inner back contact 01. relay 310 to ground, advancing the sequence switch to position 15. Relay 310 is reoperated in position 15 in a circuit from battery, upper contact of interrupt-er 341, upper contact of cam 335,. right windin of relay 310, left contacts of cam 314 to ground. The operation of relay 310 closes the same circuit for magnet 30.0 as was traced in position 1, advancing the sequence switch toposition 16 Relay 310 is again operated in position 16 over the lower contact of interrupter 341 and the lower left contact of earn 335 to advance sequence switch 300 to. position 17. Sequence switch 300 is moved to positioni 1:3 in a circuit over the lowi-ir right and upper left contacts of cam 316 to ground at the inner back contact ogl relay 310, which released as soon as the switel'i leil't position 16. In" position 18 the linal selector is restored to normal under the control of down drive magnet 342-. which is energized in a. circuit from battery through its winding. lower left contact of cam 318,upper right contact of cam 323, loweu contact 0t cam 303 to ground. When the selector switch reaches normal, a circuit is closed from battery through the winding of magnet 300;.

Connect/Ton initiated at branch ewe/marge.

V hen a subscriber at the branch exchange wishes to talk to a subscriber at the main exchange or at some other exchange, an impulse of ringing current will be transmitted from the branch over the trunk 534 of the necessary duration. In consequence relays 530, 531, and 533 will be successively operated and relay 532 released asabove described. hen relay 532- closesits back contact, a circuit is completed from battery. through the winding of relay 525, back contacts ot' relays 518 and tront contacts of relays 533 and 531,. to ground at the inner upper back contact 01? relay 526. Relay operates and locks over its inner right contact to ground at the back contact of; relay Lees-nae 522. It closes circuit from battery over the back. contact of relay 503, leftcontaet of relay 525,. line lamp 535 to ground, lighting the lam y. Relay 525 also closes a circuit from battery through the winding of relay 502, outer right contact of relay 525 to ground at the right back contact of relay 504. Relay 502 connects the busy condition to sleeve conductor 501 to mark the line busy to final selectors. The operator now inserts answering plus 1100 of a cord circuit in ack 505. A; circuit is completed from ground: through relay 518, left back contact ot relay 504, sleeves of jack 505 and plug 400, Wind ing of relay 401 to battery. Relay 401 con.- nects ground to lamp 405 and completes the tipconductor oi 'the cord circuit. However, a circuit is at once closed from battery,

through the lower left winding of repeating coil 400,v winding of relay 40?, lower normal: contact of key 408, conductor 409, rings of plug 400 and jack 505, lower left winding of. repeating coil 520, back contacts. of relay 521 through relay and relay 523 in parallel, upper left winding of coil 520, tips of jack 505 and plug 400, upper normal con tact 01' key' 408, left contact of relay 40.1., upper left winding of coil 406 to ground, operating relays and 407. Relay 40? closes the circuit previously traced ii'or relay 411, but as the operator immediately. operates talking key 416, relay 413 is operated and looked as before, holding lamp 405 extinguished.

The operation of relay 518opens the energizing circuit for relay 525, and closes a new circuit for relay 502. The operation 0t relay 522 opens the locking circuit of: relay 525, extinguishing line lamp 535.

The operator now ascertains from the alling subscriber the number of the wanted subscriber and extends a connection thereto by the use 01. calling plug 402, and in the case 013 a local subscriber by the use of dial 424. If the subscriber at the branch exchange wishes to recall the A. operator, she will cause the reapplication of ringing current to. the trunk 534, operating relays 530, 531, 532 and 533 as before. Relay 518 being operated at this time, relay 521 will. be operated as in the ease ot the disconnect signal. However, since plug 400 is inserted in. jack 505, the operation of relay 521' releases relay 407 in turn releasing relay 413 and lighting lamp 405. The release of relay 413. permits relay 411 to operate. When interrupter 425 closes its contact a circuitis completed thereover from ground over the front contact of relay 41]., winding of relay 412: and. battery. .Vhilc relay 412 is operated, relay 411 is held operated through its two windings in series by way of the right front contact of relay 412. Relay 412 also closes a circuit. from battery over its left contact through buzzer 426 to; ground giving the operator audible signal. As soon as the operator responds to this signal by operating listening lrey 4-16, relay 413 operates to open the circuit oil relay 411, silencinej the buzzer. In order J reoperate relay 2 and extinguish lamp the it qoerator may either opera e her rir 'ng key 420 or withdraw and rein-sort plug 400 in jack 505. ing current will oper te relays 523 and 52., openii g illil; of relay 521 at the contact 01" lay e26, whil withdrawing plug 400, relecsrs relay 518 momentarily to unloclr relay 521 at the contact of relay 518.

If the subscriber at the branch 'Xcliange should attempt a connection over a trunlr after it has been seized by a calling iinal selector a special. signal is given to the A operator. It will be remembered that the seizure oi the line by the final selector operates relays 503 a d 504, while the application of ringing current from the incoming selector operates relays 508, 510 and 511, lighting lamp 513. The application o'l ringing current to trunlr 534 will operate relays 530, 52731, 532 and 533, and release relay 532 previously described. Since relay 518 has not been operated the release of relay 532 causes the operation of relay 525. With relays 503 and operated, a circuit is closed from battery, over interrupter 535, right o of relay 503, left front cony 525 to ground through lamp causing this lamp to dash, giving a disyc signal to the A operator. The erator will then insert plug 400 of one of her cords into jack 505. This causes the operation of relay 522, releasing relay 525 nguishing lamp 535. She will then the subscriber that the trunk has be i or for an incoming call, after which the will withdraw plug 4.00 and complete the incoming connection in the manner described.

the lrey indicator operator wishes to recall the A operator she may operate the rine'in key 121 of her cord circuit. Relays 232 and 233 being slow to release do not release the incoming circuit during brief interruptions of the trunlr. The ringing current is repeated through coil 231 to relay 508 which operates. It key 537 has not yet been operated, relays 510 and 511 will operate, relay 511 locking in a circuit from bat-- tery, through its upper winding and contact, inner upper contact of relay 512, outer lettcontact of relay 518 to ground at the inner upper back contact of relay 526. Relay 511 will open the bridge through retard coil 538, thereby releasing relay 407., permitting lamp 405 to light. Relays 508 and 510 release when ringing ceases' When the A operator rings the branch exchange, relays and 526 will be operated as described and relay 511 will be released, reoperat relay 4:0? to inguish lamp 405. She t then reope ate her listening lrey until the branch ope itor answers, ll relay 515 has been operated at the time of the raring, the talking circuit will have been completed, so that the operation of relay 511 disconnects the ring (it jack 514 from conductor 505, thus opening the circuit oi relay 407 to light lamp 405.

l 'i 'hat is claimed is:

1. in a telephone exchange system, a machine switching oilice, an operators position there-at, a two-Way line extending from a remote point and terminating at said operators position, intercepting terminals indiridual to said line appearing in the banks of selector switches, means tor extending a connection to said line comprising means for causing a selector switch to connect with said switch terminals, and means at said operators position for connecting said terminals with said line.

2 lo a. telephone exchange system, a machine switching ollice, an operators position thereat, a two-way line extending from a remote po' t and terminating in a jack at said operacors pocm on, an intercepting line individual to said first line extending from selector switch b l its and terminating in a "@Cli at said operators position, and means 101 extending the connection to said line comprising means for causing a selector switch to connect with said intercepting line and cord circuit at said operators position for connecting said jacks together.

in a telephone exchange system, an ollice, two-way line extending from a remote point and terminating; in said office, a signal at said oilice associated with said line, intercepting terminals for said line, means for extending a connection to said intercepting terminals, means at said ollice for connecting said intercepting terminals to said line, mans to operate said signal in one when a call is initiated at said remanner mote point and said terminals are free, and means for operating said signal in a distinctive manner when a call is initiated at said remote point it, at the time, said intercepting terminals have been seized by said connect-ion extending means.

4. lln a telephone exchange system, a. machine switching oll'ice, an operators position thereat, a two-way line extending from a remote point and terminating at said operators position, a signal at said position associated with said line, intercepting terminals for said line appearing in the banks of selector switches, means at said operators position for connecting said terminals to said line, means to operate said signal in one manner when a call is initiated at said remote point and said terminals are free, I? l means for operating said signal in a manner when a call is initiated time, said ha tereepting terminals have been seized by a selector switch.

5. In a telephone exchange system, a machine switching ofiice, an operators position thereat, a two-way line extending from a remote point and terminating in a jack at said operators position, a lamp signal associated with said jack, an intercepting line individual to said first line extending from selector banks and terminating in a jack at said operators position, a cord circuit at said operators position for connecting said lines, means to operate said signal in one manner when a call is initiated at said remote point and said intercepting line is free, and means for operating said signal in a distinctive manner when a call is initiated at said remote point it, at the time, said intercepting line has been seized at said selector bank.

6. In a telephone exchange system, an office, an operators position thereat, a twoway line extending from a remote point and terminating at said operators position, intercepting terminals for said line, means for extending a connection to said terminals, a link circuit'at said position for connecting said terminals to said line, a signal in said link circuit responsive to ringing current applied over said connection extending means, and means for maintaining said sig nal until ringing current is applied to said line.

7. In a telephone exchange system, an

otiiee, an operators position thereat, a two way line extending from a remote point and terminating at said operators position, intercepting terminals for said line, means for extending a connection to'said terminals, link circuit at said position for connecting said terminals to said line, a signal in said linli circuit responsive to ringing current applied over said connection extending means, a ringing key for applying ringing current to said line, and means for maintaining said signal until said key has been operated.

8. In a telephone exchange system, an otlicev an operators position thereat, a twoway line extending from a remote point and terminating at said operators position, in tercepting terminals for said line, means or e tending a connection to said terminals, lini: circuit at said position for connecting said intercepting terminals to said line, a relay associated with said terminals responsive to ringing eirrent applied over said connecting means, a ringing signal in said link circuit responsive to said relay, a ringing relay said line, a ringing key in said link circuit for controlling said ringing relay and a locking circuit for said first relay under the control of said ringing relay.

In witness whereof, I hereunto subscribe my name this 3rd day of February, A; 1).,

WILLIAM 0. JORDAN.

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