US1474008A

US1474008A - Machine-switching telephone-exchange system

Info

Publication number: US1474008A
Application number: US428162A
Authority: US
Inventors: Stokely Ray
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1920-12-08
Filing date: 1920-12-08
Publication date: 1923-11-13
Anticipated expiration: 1940-11-13

Description

NM2, 33 y 1R. STOKELY MACHINE swITcHNG TELEPHONE EXCHANGE SYSTEM Filed me@ s snetsgsheei 5 Nm., E3 9 i923 EAM-,mg R. @Tamm l MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed Dec. 8 1925 5 Sheets-5h96?, 4

No 'm ma l-Qmmg R. STOKELY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed Dec. 8 1920 5 Sheets-Sheet 5 BAY BTOXELY, F FLORAL PARK, NEW YORK, ASSIGNGB T@ WESTIBH- 1 COIPANY, INCORPORATED, 0l' NEW YORK, N. Y., .A GQBPQBATEON @E Le HACmSWITCHING TELEPHONE-BGE @Y i M Application lied December l, im. Berta! lo. MAN.

To all whom z't may conm:

Be it known that I, RAY S'mxnnr, a citizen of the United States, residing at Floral Park, in the county of Nassau, State of New I York, have invented certain new and useful IImprovements in Machine-*Switchi Telehone-Exchange Systems, of which t e fol,-

owing is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems employing machine switching and its object is to provide an improved circuit arrangement to take care of toll calls to and from full automatic offices.

This invention is an improvement in the s stem shown anddescribed in m A application filed July 26, 1919, Serial o. 313,521 for telephone exchange system.

In that application a circuit arrangement is disclosed whereby the calling supervisory lamp at the toll operators position is flashed at a certain rate if any selector encounters ay busy trunk group in the process of building up a connection and at another rate if the connector finds the called line busy.

` -In the system disclosed in the above-identified application, however, the lamp will give the busy line flashing si nal to the toll operator not only if the ca led line is ac- :m tually busy, but also if such line is out of order, or 1f for an reason,except encountering a busy trun group building up the connection does not` proceed to the oint where the connector tests the line and) finds it to be idle. Thus, the operator may be given an erroneous signal. p e present invention provides an improved circuit arrangement whereby the busy line flashing signal of the calling supervisory lamp in the c'ord circuit at the toll operators position is only iven when the lclonnector finds the selecte line actually usy.

The invention will be more readily under- 46 stood from a detailed description of the operation of the system.

Referring to the drawings, Fig. 1 shows a toll cord circuit, Fig. 2 shows a trunk circuit outgoing from the toll board to a full 0 mechanical or automatic office, Fig. 3 shows a selector circuit at the full mechanical oflice; Fig. 4 shows a toll transmission selector repeater, and Fig. 5 shows a combination toll and local connector. Referring first to Fig. 1, this drawing the process of L toll supervisory lamp shows a cord circuit at the toll operator@ position. The left hand side of this circuit will be called the toll end and the right hand side will be called the `tell and4 trupk and. The operator answers an incoming call by inserting the 113g T of the toll end in the answering jac in the ordinary manner. If the called subscriber is located in a nearf by exchange, the call is completed by irt.- ing the plug TT of the trunk and' toll end` in a toll switching trunk jack TSJ. operator then actuates the dialing and monitoring key DK which causes the relay B--S to operate, which in operating energizes a monitoring relay (not shown) place the perators telephone set in a. monitoring pesition on the cord. The operatori-"now tu the dial D for the first digit of the Wanted a number. The dial in movin out of its nor# mal position short circuits t e relay B-3t 35 permitting the relay E-7 2 to operate. lR.e' lay E72 in operatin locks itselfto batter f and transfers the tip of the plu 'u x through the impulse springs ofA the l to the battery. The dial, in returnin to nor. mal, interrupts the battery to the tip of the plug causin the impulse relay of the trunk circuit of ig. 2 to operate intermittently, theV number of times dependin upon the digit involved. This impulse re ay, in thus operating. causes the setting of the selector circuit of Fig. 3, which thereupon automatically picks out an idle trunk. in the selected level. When the operator has' operated the dial for all the digits involved which causes the last switch to be set on the desired line she restores the monitoring key DK. M the called line is not busy, the trunk and lights as a ringing v signal, whereupon t e operator by deprcss- @5 ing ringing key RK causes the connect/0 to start the ringing of the called linewhic rinlging continues automatically. unti'l the cal ed party answers, whereupon the current is out oi and the lamp-:.100 is ex mi@ tinguished. When the called subscriber re; places his receiver, this lamp again liglitafaa a disconnect signal.

If the called line is busy or if one of thai! selectors had failed to find an idle trunk, the, W5 lamp 100 will flash, the frequency of theflashes depending upon the busy condition encountered. The toll operator in response to the dashing of the lain removes the plu TT of the t 1. and to end of the cor BHO from the toll switching jack TSJ, but before removing the toll plug T from jack J, the operator by means of her ringing key RK,- rmgs on the toll line terminating at the ]ack J to notify the distant operator that the line is clear. lf the distant operator rings first, however, the toll supervisory lamp 101 lights and when the operator actuates listening key LK, or pulls out the plug T, this lamp 1s extinguished.

If the called subscriber is a distant one reached over a toll line, the toll operator inserts the plug TT of the trunk and toll end in the proper jack similar to jack J and by means of her ringing key R K applies alternating current to such toll line to signal the distant operator. When the operator at the distant end of the toll line applies ringing current to the trunk at the termination of the conversation the toll supervisor lamp 101 lights until the listening ke L is operated or the connection is ta en own. The keys K and K serve, when operated, to disconnect either end of the cord from the operators telephone set when the operator is talkin on the other end. When the plug T of t e toll end is inserted in toll answering jack J, relay itl-156 operates, in turn operating relay B-162. Relay B-162 opens the circult of relay E-162 preventing the toll supervisory lamp 101 from lightin When the plugP TT of the trunk and tol end is inserted in toll switching trunk jack TSJ,'relay E-99 operates in series with relay E-155 and the lower winding of relay E-156. Relay E-99 disconnects the busy test equipment of the operators telephone set from the tip of the cord and connects the tip of the cord through to the ringing key. Relay E--l is marginal and does not operate at this time on account of the high resistance in the sleeve of the trunk circuit.

Ringing current applied by a distant operator operates the rela A--196 which releases rela B162. he latter relay in releasing liglits the toll supervisory lamp 101 and operates rela lil-162 in parallel with the lamp. Relay dl-162 locks u under the control of the llstening key L and relay E--156 so that the lamp remains lighted after the ringing ceases and the relay B-162 is re-operated through the back Contact of relay A--196. The lamp 101 may be extinguished by operating the listening key which releases relay E--lti or by' taking down the connection which releases relays E-156 and E-162- Relay lil- 162 is made slow in operating to guard against the possibility of lam 101 being lighted by Morse impulses. Re ay A-196 may be operated for a short time by Morse impulses but will not remain operated long enough to cause the 0 ration of rela lil- 162. In case relay +162 should re ease momentarily, the

Slow operatin feature of the relay E-162 will give the ormer time to re-operate before the relay E--162 operates and locks. When both ends of the cord are inserted in toll line jacks the marginal relay E-155 disconnects the rela B-43 from the cord circuit. If, on a tiirough toll connection, the splitting key K is operated to disconnect the trunk and toll end from the operators telephone set, relay B-43 is bridged across the trunk and toil end so that it will operate when ringing current is received from the distant operators position connected with the called toll line, the trunk and toll end and flash the lamp 100. When the splittin the circuit or relay B-43 is opened.

Referringlnow to Fig. 2 which represents a toll switc ing trunk over which a connection is extended to a nearby exchange, relay 0 2 operates over its right hand wlnding when t e operator inserts the plug TT into jack TSJ and by attracting its armature closes a looo circuit leading to the impulse relay A-3, Fig. 3, of the first selector at such excha which in operating energizes slow rela -3 to prepare the im ulse circuit. W en the dialing key DK 1s thrown and the dial is operated, relay A-2 o rates, connecting relay I--2 across the 00p leadin to the impulse relay A-3, 3. Relay -2 in operating causes rela -2 to o erate, which relay shunts the le t hand win ing of relay C-2 whereupon the latter relay releases, the circuit through its ri ht hand winding being opened when re ay E-72, Fig. 1, operates as the dial is moved out of its normal position. Relay D-2 in operating operates relay E-Q which locks up to the ground at the inner left contact of relay 13 2, now energized. Relay E--2 at its outer left contact locks up relay D-2, independently of its original energizing circuit Which lead over the front contact of rela I2. The dial in restorin intermittent y operates relays A-Q and 2, relay A-Q intermittently openin the loo circuit to the relay A-B to set ie lirst se ector and relay 1 2 alternately openin and closing a shunt path around relay 2. If, during the operation of building up a connection, one of the selectors fails to find an idle trunk in the selected group, it opens the loop circuit including relays A--3 and I-2. Relay I--Q in closing its back contact permanently shunts out relay D-2. Relay D-2 in closing its right hand back contact operates relay H2. Relay H-Q locks 11p and connects interrupted battery of 60 impulses per minute to the winding of relay C-2 in shunt of the resistance 200. Relay B-43 in the cord (Fig. 1) follows these impulses and ashes the supervisory lamplOO to indicate to the operator the failure to find an idle trunk.

key K is in its normal position lll) arm ature 204,

ramena In case the called line is busy, the polarized rela F-2 operates as in the case ,of a successful call but. in this case a. different interrupter is connected in circuit .to flash the lamp 100 at a different rate to mdxcate to the o rator thebusy condition of the selected e.

In case the called subscribers line is found to be idle by the connector (Fig. 5) this condition causes the polarized relay7 F 2 to operate and cause lam 100 to ight as a r1 ing si al when el operator restores the ey D Relay 'F 2 1n operating also energizes relay G 2 which cuts the trunk throu h, thus disconnecting the relays C .2 and *5 2 from the circuit leading back to the toll operators tion.

Having describe in a general manner the operation of the system, a call will-now be traced in detail.

The toll operator, having been informed of the number of the wanted line and assuming this line to be in a nearby exchange,

tests for an idle trunk by touching the tip of her lug TT to the sleeve of the jack TSJ of tllie toll switching trunk in the well known manner, and if she does not receive a click in her receiver she inserts the rplug TT into the toll switching trunk jack SJ. The following circuit is thereupon 'closed to operate relays E 99, (Fig. 1) and B 2 'g. 2) free pole of battery, relays E 99, E 155, lowei` Winding of relay E 156, sleeves of the plu kand jack, relay B 2 to ground. Relays 155 and E 156 do not operate in the circuit.

Relay E 99 in operating disconnects the operators busy test circuit from the tip of the cord. Relay B 2 (Fig. 2 in operating prepares certain circuits w ich will be traced later. This trunk will now test busy at the other operators positions due ,to battery ap lied to the sleeve multiples by the sleeve o? the plug TT. The insertion of the plug also closes .the following circuit to en ergize relay C 2: free (pole of battery, resistance 200, right han winding of relay C 2, conductor 201, armature 202 of relay G 2, conductor 203, ring of the jack TSJ, ring of the plug TT, conductor 120, lower normal contact of ringing key RK, right hand winding of retardation coil 121, relay B 43 armature and back contact of relay l3l55 which is not operated when the plug TT is inserted in the toll trunk switching jack, but only when it is in` serted in a toll line leading to a distant office, left hand winding of retardation coil 121 upper normal contact of ringing key R', armature and front contact of relay E-99, conductor 102, right hand normal contact of relay E 72, conductor 103, tip of the plu TT, tip of the jack TSJ,

' ack contact of relay G 2, and relay A 2 to ground. Relay A 2 is marginal and does not operate in this circuit. Relay C 2 in attracting its armature closes the following circuitto 'operate relay A 3, Fig. 3, which is the impulserelay of the first selector, shown in Fig. 3; A'free pole of battery, lower winding of relay A B (Fig. 3), conductor 300, back contact'and armature 301 of relay D 3, conductor 302,

conductor 205, conductor 206, outer left4 hand armature and back contact of relay H 2, conductor 207, armature and front contact of relay C 2, left hand winding of relay @-2, conductors 299 and 209. inner right armature and front contact of relay B 2, conductor 210, polarized relay F 2, conductor 211, conductor 212, conductor 303, armature 304 and back contact of relay D 3, conductor 305, upper winding of relay A 3, conductor 306, normally closed contact of switch 307, operated on the eleventh rotary step of the selector, to ground. The operator now throws the dialing and monitoring key DK, the listening key LK which was operated in order to connect the operators set with the calling line having been restored, whereupon a circuit is closed tracting its armature closes a circuit to conneet the operators head set across the cord for monitoringpurposes. She now rotates the dial D for the first digit of the wanted number. The closure ofthe contact 1011 of the dial as the dial moves oil' normal shunts the rela B 34, which permits the marginal relay 72 to operate and releases relay B 34. Relay E 72 in attracting its left hand armature locks itself to ground at a contact of the dialing key DK which when actuated remains in its operated position until manually released by the operator. Relay E 72 in closing its right hand contact opens the bridge containing relay B 43 and connects free pole of battery through the impulse Contact 108 of the dial to the 'tip of the plug. The opening of the said bridge opens the circuit heretofore traced through the right hand winding of relay (1 2. Marginal relay A 2 now operates in series with the impulse Contact of the dial, the circuit being as follows: free pole of battery, resistance 109, impulse contact 108, right hand' armature and front contact of relay E 72, conductor 103, tip of the plug TT, tip of the jack TSJ, armature 204 and back contact of relay G 2, conductor 213 and relay A 2 to ground. Relay A 2 in attracting its left hand armature bridges relay I 2 across the tip and ring of the cord in parallel with the left hand winding of relay C 2. Relay 1 2 in attracting its armature closes a circuit to operate relay D 2 as follows: free pole ot battery, resistance 215, relay D 2, conductor 216, right armature and front contact ot relay 1 2, conductor 217, contact 218 of all G2 to ground. Relay D--2 in attracting its left armature short circuits the left hand winding of relay C-2 which thereupon releases, thus opening one of the bridges to the impulse relay A-3 and leaving bridged across the circuit only relay I-2. This circuit may be traced as follows: free pole of battery, lower winding of relay A--3, conductor 300, armature 301 and back Contact of relay D-3, conductorA 302,

conductors

205 and 206, outer left hand armature and back contact of relay lI--2, conductor 207, conductor 208, relay I2, left hand armature and front contact of relay A-2, conductor 211, conductor 212, conductor 303, armature 304 and back contact of relay D-3, conductor 305, upper winding of relay A-3 and upper normal contacts of switch 307 to ground. Relay D2 at its right armature and front contact closes the followin circuit to operate relay E2: free pole of attery, relay E-2, conductor 220, right armature and front contact of relay D--2, conductor 221,

conductors

222 and 228, inner left armature and front contact of relay B2 to ground. Relay E-2 in attracting its inner right armature locks itself to grounded conductor 222. The fune tion of this relay will be later described. Dial D, Fig. 1, in returning to normal, interrupts at. its impulse contact 108 the circuit of the impulse relay A-2, Fig. 2, which at its left armature interrupts the circuit of the impulse relay A-3, Fig. 3, the number of times corresponding to the first digit of the wanted number. Upon each retraction of the armature of relay A-3, the following circuit is closed for the vertical magnet 310 of the first selector: grounded armature 311, and back contact ofrelay D3, conductor 312, armature and back contact of relay A-B, lower armature and front contact of relay B-3, slow relay C-3, ver-- tical magnet 310, and free pole of battery On the first step of the selector off normal springs 313 close the following circuit for relay 314: free pole of battery, relay 314, conductor 315, ofi1 normal springs 313, conductors 316, 317, armature and front contact of relay C--3 to ground at the armature and front contact of relaynB-3. Relay 314 in attractin its upper -'armature locks itself over the following circuit: free pole of battery, relay 314, conductor 315, oil' normal contact 313, conductor 316, armature andvback contact of rotary magnet 318, conductor 319, conductor 320, upper armature andlffront contact of relay 314, conductor 3211Y toground at the armature 311 and back contactofgrelay D-3. Upon the cessation of "thefirnpulses, relay A-3 remains energized and consequently relay C-3 which is slow to release, after an interval releases, whereupon the following circuit is closed to energize the rotary magnet 318 of the serelay lector to step the selector brushes on to the first trunk in the selected level: free pole of battery, magnet 318, conductor 322, lower armature and front Contact of relay 314, upper normal contact of relay C3, upper armature and front contact of relay B-3 to ground. At the end of its stroke, the rotary magnet 318 opens the locking circuit traced for relay 314. Relay 314 in retracting its lower armature opens the circuit of the rotary magnet. If the first trunk is busy, ground is )resent on the test multiple 323 thereof, whereby the following circuit is closed to energize relay 314: grounded muitiple 323, test brush 324, conductor 325, armature 326 and back contact of. relay D-3, conductors 327, 319, back contact ano armature of magnet 318, conductor 316, contact 313, conductor 315, relay 314 to free pole of battery. Relay 314 in attracting its upper armature again locks itself through the back contact of the rotary magnet and in attracting its lower armature again closes the circuit of the rotary magnet whereupon the selector brushes are lstepped to the next trunk. This interaction of the rela 314 and rotary magnet is continued unti an idle trunk is found which is indicated by the absence of round on the test multiple 323 thereof. hen the rotary magnet at the end of its stroke. potions the brushes on to this idle trunk no ground being present, relay 314 does not energize but switching relay D-3 energizes over the following circuit: free pole of battery, rela 314, conductor 315, contact 313, con uctor 316, armature and back contact of rotary magnet 318, conductor 319, conductor 327, conductor 328, relay D-3, conductor 329, lower normal contact of switch 307, conduc-v tor 330, to ground at the upper armature and front contact of relay B-3. Relay 314 is marginal and does not operate in this circuit. D-3 in attracting its armatures 304 and 301 extends the talking conductors through to the selector brushes and cuts oi impulse relay A3.

Assuming now that the selector has failed to find an i-dle trunk. In that event on the eleventh rotary step, switch 307 is operated by the shaft of the selector and opens the circuit of the impulse relay 'A-3 which causes the selector (Fig. 3) to restore. The opening of the loop circuit also causes relay I-2 (Fig. 2) to be permanently deenergized. When the operator transmits all the digits, relay A-2 in remaining attracted and the' relay I--2 being inert, the following short circuit is closed about the slow relay D-2 to cause the same to release: free pole of battery, resistance 215, right hand armature an front contact of relay A--2, armature and back contact of relay 1 2, conductor 217, contact 218, to ground. It will be understood that relay D-2 is slow to release as shown and holds up during the impulses. Relay D 2 in retracting its right armature operates relay H-2 over the following circuit: free pole of battery, relay H2, conductor 290, right armature and back contact of relay DV-2, conductor 220, inner right hand armature and front contact of relay E-2 to ground on conductor 222. Relay H-2 in attracting its inner left armature locks itself up to grounded conductor 222 and in attracting its inner right armature connects interrupter 223 to the inner left hand armature and front co'n tact of relay E-2 to shunt the resistance 200 t'o cause supervisory relay B-43 in the cord circuit to flash the trunk and toll supervisory lamp at the rate of 60 flashes per minute when the operator restores the key DK which she does after transmitting all the sets of impulses. This rate of flashing will indicate to the operator that one of the switches has encountered a busy trunk group whereupon she will pull out the plug and will then wait and set up the connection later. Although the interrupting machine 223 is connected to the front contact of relay E-2 as soon as relay D--2 releases and relay H-2 operates this is not effective to flash the lamp until the operator, after having turned the dial for the last time, releases her dialing key DK, Fig. 1. The opening of the lowermost contact of this key releases relay E-72 which in retracting its right armature again closes the loop circuit includin the right hand winding of relay (1 2, 2, and the relay A 2, Fi 2 and B-'43 (Fig. 1). It will, of course, a understood if no idle trunk is found relay D-3 is not energized. attracting its outer left armature interposes a break 1n the loop circuit leading to the selector (Fig. 3) thus preventing the subsequent impulses from selector circuit.

Assuming, however, that an idle trunk was found, the seizure of the toll transmis` sion selector repeater Fig. 4, in which such trunk terminates, causes the closure of the following circuit for impulse relay A-4 thereat, Fig. 4: free pole of battery, left hand winding of relay A-4, conductor 400, contact 401 of relay B-4, conductor 402, contact 403 of relay F-4, conductor 409, lower left hand winding of repeating coil 404, conductor 408, multiple terminal 334, brush 333, conductor 332, armature 301 and front contact of relay D-3, conductors 302, 205, 206, left armature and back contact of relay H-2, conductors 207, 208, relay I,-2, left hand armature and front contact of relay A--2, conductor 211, 212, 303, armature 304 and front contact of relay D-3, conductor 352, brush 350, multiple terminal 351, conductor 407, upper left hand winding of repeating coil 404, conductor 405, contact relay inV attracting its outer The relay H-2 inl passing to the l 406 of relay F-4, conductor .410, contact 411 of relay B--4, conductor 412-, through; the right winding of relay A-4 to groundV at the lower normal, contact of the switch' 413 which is only operated on the eleventh 70 rotary step of the selector re ater. The impulse relay A-4 in attracting its ri ht. armature energizes slow rela 414. is

left armature closes a circuit for relay 336 which in. `at-l tracting its armature supplies a local ground to-the test multi le 323 to cause this.: l trunk to test busy. Vhen the. relay 414 operates it closes at its right hand armature the following circuit for relay D-4: ground right armature and `front contact of relay 414,

conductors

415 and 416, contact 417 of relay (lr-4, conductor 418, outer. right hand armature and back contact of. relay F-4. conductor 419, relay D-4 tol free pole of battery.

The second operation of the dial by the operator transmits the corresponding digit of the called line causing relay A-2, F1g.- 2, to open and close the loop circuit for the relay A-4, which in vibrating its right hand armature transmits impulses over the following circuit to the vertical magnet 420 ofthe selector repeater: ground, right armature and back contact of relay A 4, inner left armature and front contact of relayV 414, conductor 421, armature 422 and back. contact of relay (3i- 4, conductor 423, slow relay 424, magnet 420 to free pole of battery. The brushes of the selector are thus elevated to the desired level. When the dial returns to normal and maintains the relay A-2 (Fig. 2) energized, relay A-4 remains energized and, after a slight interval, slow relay 424 releases. When the relay 424 operated on the first impulse. and the selector took its first step, relay 425 corresponding to relay 314 (Fig. 3).. operated over the following circuit: free pole of battery, relay 425, upper contact of off normal switch 426, conductor 427, armature and front contact of relay 424, conductor 432, armature 429 and back contact of relay 430 to ground. In attracting its inner armature, relay 425 locks itself to its inner armature, this circuit includico ing the armature and back contact of rotaryv magnet 431. These circuits are similar to those of the selector of Fig. 3. U on the cessation of the impulses and the re ease of 12 the slow relay 424, the circuit of the rotary magnet is closed as follows: free pole of battery, magnet 431, outer armature and front contact of relay 425, normal oontact of relay 424, conductor 432, to ground at the armature 429 of slow relay 430. The rotary magnet advances the brushes on to the terminals of the first trunk and at the end of its stroke opens the locking circuit of the relay 42,5 which releases opeg the 330 circuit of the rotary magnet. If the trunk is busy, relay 425 again energizes over the following circuit: free pole of battery, relay 425, upper contact of switch 426, conductor 427, armature and back contact of rotary magnet 431, conductor 433, back contact and armature 434 of relay G4, concircuit of relay 425 which in retracting its armature opens the circuit of the rotary magnet-431. The switch 413 corresponds to the switch 307 of the selector circuit, Fig. 3. Its function is to open the circuit of the impulse relay A-4 on the eleventh rota stop of the selector, that is to say, if al the trunks in the group are busy. The opening of this circuit releases the switch and causes relay 1 2, Fig. 2, to become permanently inert which causes the release of slow relay D-2 and prepares a circuit for the interrupter 223 which results in the flashing of the trunk and toll supervisor lamp 100 when the operator restores her ialing ke as described in detail in connection withv Fig. 3. If, however, an idle trunk is found, relay G-4, which corresponds to relay D--3, Fig. 3, operates over the following circuit: free pole of battery, relay 425, upper contact of switch 426, conductor 427, amature and back contact of magnet 431, conductor 433, relay G4, conductor 440, upper contact of switch 413, conductors 441, 415, toground at the right amature and front contact of relay 414. Relay 425 is marginal and does not operate in .this circuit in series with the relay G-4. Relay G-4 operates and in attracting its armatures 442 and 443 extends the talkingconductors through to the talking brushes444 and 445. The attraction of the armature 434 of relay G-4 grounds the test brush 438 and cons uently test multiple 439 of the selected trun causing the same to test busy to other selectors. The contact 446 is made before the contact 417 is broken b the armature 447 of the relay G-4.

onsequently relay D4 is maintained energized over the following circuit: free pole of battery, relay D-4, conductor 419,

4'outer right armature and back contact ofrelay F--4, conductor 418, contact 446. armature 447, conductor 448, brush 449, multiple 450, control conductor 451, conductor 500 (Fig. 5), conductor 501, armature 502 and back contact of relay K--5, conductor 503, sleeve conductor 550, conductor 452, multiple 439, brush 438, conductor 437, armature and back contact 436 of relay1430, conductor 435, armature 434 and front contact of relay G-4, conductor 415,to `ground at the right armature and frontcontact of slow relay 414. Thus,

ing up their own connections. The seizure of the connector causes the closing of the following circuit for the impulse relay A-5z free p'ole of battery, upper winding of relay A-5, conductor 504, contact 575 of rela D'-5. conductor 505, left winding of s ow relay J-5, conductor 507, lowermost armature and back contact of relay K-5, ring conductor 546, conductor 453, multiple 454, brush 445, conductor 455, armature 443 and front contact of relay G4, left armature and front contact of relay A-4, ring conductor 457, armature 456 and back contact of rela H--4, conductor 458, lower right han winding of the repeating coil 404, resistance 459, conductor 460, inner left armature and front contact of relay D-4, left winding of relay 461, conductors 462, 463, resistance 464, upper right hand winding of repeating coil 404, conductor 465, upper armature and back contact of relay H-4, conductor 466, uppermost armature and front contact of relay G-4. brush 444, multiple 467, tip conductor 510, upper armature and back Contact lof relay K--5, conductor 576, back Contact 577 of relay D-5, lower winding of relay A-5 to ground. When relay G-4 operates a circuit is also closed through the 'right hand winding .of relay 461 which leads over 476, 477, 470, armature 434 and front contact of (ir-f4, conductor 415, to ground at the armature and front contact of relay 414. The current in the circuit just traced is opposite in direction to that in the left hand winding of this relay. Consequently this relay does not operate at this time. Relays J5 and A-5 operate in the circuit previously traced therefor, the former at its innermost right armature closing a locking circuit for itself as follows: free pole of battery, right-winding and right lnnermost armature and front contact of J--5, conductor 531, conductor 515, to ground at the armature 516, and front contact of slow relay B--5 which is energized upon the energization of the impulse relay A-5. Relay B-5 unds the sleeve wire 517, leading ,to t e test multiples in the local selectors, this circuit leading from grounded armature 516, conductor 515, to conductor 517- The return of the dial to normal in transmitting the tens digitiof the wanted number interrupts the circuit of relay A-2, Fig. l2 which in turn interrupts the circuit of the impulse relay A-4, Fig. 4 which in vibrating its armatures causes the impulse relay A-5 of the connector to transmit impulses to the vertical magnet 518 of the connector. vThe circuit for the first impulse is as follows: free pole of battery, magnet 518, slow relay 519, right contact .of olf normal switch 520 conductor 521., lower armature and front contact of relay B-5 to ground at the armature and back contact of the impulse relay A-5. At the first step of the connector, the off normal s rings 520 are shifted and the succeeding impulses are transmitted by way of the upper armature and front contact of relay 519 and the contact 522 now closed of the off normal springs 520. Relay F5 is operated by its lower Windin when relay 519 operates, this circuit inc uding the innermost right armature of relay J- and grounded armature 516 of relay B--5. Relay F5 locks up to the control lead 500. The connector brushes are thus lifted to the desired level and upon the cessation of the impulses, im ulse relay A5 remains energized and re ay 519 in series with the 'vertical magnet releases preparing the circuit of the rotary magnet 523. The units impulses pass through the back contact of the impulse relay A-5, lower armature and front contact of relay l3-5, conductor 521, oi normal contact 522 back contact of slow relay 519, conductor 524, innermost left armature and back contact of relay (ir-5, conductor 525, uppermost armature and back contact of relay H-, rbtary magnet 523 to free pole of battery. The connector is thus stepped around into engagement with the desired If this line is idle, full potential is present on its test multiple 526 through the cut off winding of the line switch, and the following circuit is closed to operate relay H5: multiple 526, brush 527, conductor 528, armature 540 and back Contact of relay E-5, conductor 529, upper winding of relay H-5, conductor 530, right hand armature and back contact of relay G-5, conductor 531, conductor 515, armature 516 of relay B-5 to ground. Relay H-5 in attracting its armature 532 locks itself to the e grounded sleeve wire 550 and extends this grounded conductor over conductor 533, middle right armature and front contact of relay J5, conductor 534 t0 the relay K-5. Relay K-5 in attracting its armature 502 disconnects the grounded sleeve wire 550 from the control lead 500 leading back to the. relay D-4, Fig. 4 of the selector repeater. Relay D-4 in retracting its outer left hand armature operates relay F-4, to reverse the' current flow in the circuit leading back to the operators cord to light the lamp as a 'ringing signal, Fig. 4, over the following circuit: free pole of battery, relay F-4, conductor 469, outer left armature and back Contact of relay D-4, conductor 470, armature 434 and front contact of relay (3i-'4, conductor 415 to ground at the right armature and front contact of relay 414. llelay F-4 in attracting its outer right armature applies the following substitute ground to hold up the relay F--5 to prevent ringin from occurring at this time: ground. le t hand armature and back contact of relay 471, conductor 472, outer left armature and back contact of relay B-4outer ri ht armature and front contact of relay -4, control conductor 418, contactv446 and armature 447 of relay G--4, conductor 448, brush 449, multiple 450, conductor 451, conductor 500, front Contact and armature 535 and lower winding of rela F-5 to free pole of battery. The operatlon of relay K- by releasing D-4 and operating relay F-4 which caused the reversal of direction of the current flow in the loop leading back to the toll operators position opens the locking circuit relay F-5 'and unless a substitute circuit is provided .for holding up relay F-5` after rela K-5 operates the ringingv operation wo d' automatically take place. This is prevented by applying round to the control conductor 500 over t e circuit traced to hold the relay F- until the operator, by depressing a key as will be explained, releases relay F-5 to start the automatic ringing operation. The release of the relay D-4 and the consequent energizat'ion of relay F-4 as described reverses the direction of current flow in the talking conductors leading back to the operators position. After the operator has turned the dial for the last time, shev restores her dialing key DK which releases relay E 72 which disconnects the vdial from the tip of the plug causing the release of the relay A--2, Fig. 2, and causes the closure of an energizing circuit for the right hand winding of relay Cf-2, relay B-43 and relay A 2. Relay A-2, it will be remembered, releases under this condition and in retracting its left armature deenergizes relay I-2, which in releasing causes the release of relay D-2. The polarized relay -1-2 is now bridged across the following circuit: upper talking conductor 212, Fig. v2, conductor 211, polarized relay F -2, conductor 210, inner right armature and front contact of relay B2, conductor 209, conductor 299, left hand winding of relay C-2, armature and front contact of relay C-2, conductor 207, outer left armature and back contact of relay H-2, conductor 206 to lower talking conductor 205. The reversal of the directlon of current vin these talking sgi conductors due to the operation of Irelay 1"-4 causes the rela F-2 to operate closing the following c1rcuit for relay G-2: free pole of battery, relay G-2, conductor 224, contact 225 of relay F-2,

conductors

226, 227, 228, inner left armature and front contact of relay B-2 to ground. Relay G-2 locks itself up over the following circuit: free pole of battery, relay G-2,

conductors

224, 229, front contact and armature 230 of relay G-2, conductor 231,

conductors

227, 228 to ground at the inner left hand armature of relay B-2. Relay G--2.

connects the talking conductors of Fig: 2 through to the talking conductors of ig. 1 whereupon the trunk and toll relay B-43 operates in series with the relay A-4 Fig. 4 and lights the supervisory lamp 100 as a ringing signal to the toll operator. Relay (ir- 2, Fig. 2, cuts oil' the bridge including theright winding of relay C-2 and relay A-2. The operator now operates her ringing key R K which impresses alternatingcurrent upon the talking conductors which operates the alternating current relay C-4 which in attracting its armature operates the relay 471. This relay in attracting its left armature opens the circuit heretofore traced, which has been holding relay F-5, Fig. 5, energized. This relay in retracting its. armature 537 connects ringing current to the called .line through its upper winding. This ringing -current is automatically applied until the called party removes his receiver, resulting in an increase in the current through the upper winding of relay F--5 causing the same to operate removing the ringing current. The attraction of the armature 535 of this relay closes a locking circuit for the same over grounded control conductor 500. The extension of the tip and ring conductors by relay F-5 to the called line operates relay 473 over which'talking current is fed to the called line. Relay 473 in operating energizes relay B-4 which in attracting its outer left hand armature applies ground to the conductor 474, and outer right armature of relay F-4, conductor 418, contact 446, armature 447 of relay (ir- 4, conductor 448, brush 449, multiple 450,

conductors

451, 500, front contact and armature 535 of relay F-5, lower winding of relay F-5 to battery, to hold up rela F--5 independently of relay 471. Relay l34 in opening its

contacts

411, 401 opens the connection of battery through the windings of relay A-4 to the talking

conductors

407, 408, leading back to the operators position which causes the deenergization of supervisory relay B-43. This relay in retracting its armature extinguishes the supervisory lamp 100 which notifies the operator that the subscriber has responded. Talking current is fed to the Called line over the wind-ing of relay 473 and the repeating coil 404. This i talking circuit is -a standard repeating coil transmission-circuit used in long distance connections. Talkin current is fed to the calling line from te calling dista-nt exchange. During conversation the trunk leading from the left hand windin s of rev peating coil 404 through the rig t hand winding of the repeating coil (not shown) at the distant oiiice, is dry, in accordance with standard practice. y

Assuming now that the desired line when selected by the connector is busy. In that event the test multiple 526, Fig. 5, is grounded. When test wiper 527 is set on the bus multiple 526, ground is extended over brus 527, conductor 528, contact 544 of relay E-5, conductor 541 armature 542 and back contact of relay Il-5, conductor 543, relay G-5 to free ole of battery. 'Relay G-5 energizes and when E--5 releases as the impulses terminate, locks itself up over the following circuit: free pole of battery, relay G5, conductor 543, armature 542 and back contact of relay H-5, conductor 541, make before break contact of relay E-e5, right armature and front contact of relay G-5, conductor 531, conductor 515 to ground at the armature 516 and front contact of relay B5. Relay G-5 inthe case of a local call connects busy tone from the source 545 to the calling line. this busy tone is not used, a flashing signal being given to the operator instead. Relay G-5 in operating due to the line being busy revents test relay H-5 from operating w en E-5 releases. When busy test relay G--5 operates a circuit is closed for rela D--5 from free pole of battery, upper winding vof D-5, conductor 578, conductor 579, contact 5,80 of K--5, conductor 581, resistance 599, armature 582 and back contact of relay E5, outer left armature and front contact of G-5, inner right armature of relay J-5 and front Contact, conductor 531, 515 to ground at armature 516 ,and front contactlo'f` B--5. Relay D--5 reverses the direction of current flow I through the left winding of relay 461 (Fig. 4) which results in this relay operating. The left armature and front contact of relay 461 closes a circuit for operating relay F-4 as follows: battery, relay F-4, conductors. 469, 475, left armature and front contact of relay 461, conductor 476, .477, 470, armature 434 and front contact ofrelay G-4, conductor 415gto ground on the right armature and front contact of relay 414. Relay F-4 reverses the direction of current ilow in the circuit leading back to the operators cord as in the case of an idle line to operate polarized relay F-2 which in turn operates relay G-2 to connect the talking conductors of the cord through to the connector. The right armature ofnrelay 461connects interrupter 479 to relay 471which in operating intermittently applies ground to con-- ductor 400 in shunt of the circuit leading over tip conductor 407 back to the operators cord. The circuit of relay 471 leads over the outer right front contact of relay D-4 to ground at the right armature of relay A-4. When the operator restores her dialing key, relay G-2 being operated, the intermittent ground applied to conductor 400 by relay 471 shunts out the relay 1%.-43 intermittently which causes the flashing of the lamp 100 at aV rate different from that in the case where a selector found all the trunks busy, for example, 120 flashes per minute. v

When the operator pulls out the plug TT from the trunk switching jack TSJ this causes the release of all switches and the return to normal condition of all the apparatus including' the various locked up relays.

During the conversation the called subscriber by moving his hook down and up causes the supervisory lamp 100 at the toll operators position to flash as in manual ractice without releasing the switches.

his `is apparent from the preceding description inasmuch as relay 473 is in circuit with the called line so that it is energized while the hook'occupies its upper position and each time it attracts its armature operates the relay B-4 which removes battery and ground from the trunk conductors lead.- ing back tothe supervisory relay B-43 and puts a bridge across the relay A-4 to hold 1t operated to prevent release as long as the subscriber has his receiver off the hook. When the called subscriber replaces his receiver this lights the' lamp 100 at the toll operators position, Fig. 1;

The operator may rering'the subscriber if she desires to recall him by actuating her ringing key RK which operates relay C-4 to operate relay 471 which in attracting its left hand Iarmature again releases relay F-5 which initiates the automatic ringing operation at the connector. The control of this relay F-5 was removed from the relay 471 by the attraction of the outer left armature of relay B-4 when the called subscriber responded and is restored to the relay 471 and consequently to the operator when the called subscriber replaces the receiver and deenergizes relay B-4.

When the operator desires to break down the connection after the called subscriber has replaced his receiver, she removes the plug TT from the toll switching jack TSJ. sThis releases relay A 4, Fig. 4 which causes the restoration of all the switches. If, however, the operator pulls out the plug while thecalled subscriber still has his receiver ofi the switch hook, the switches are not released since relay A-4 which controls the release is maintained energized over the .following circuit: battery, left hand winding of relay A4, conductor 400, armature 480 and -front contact o f relay B-4, resistance 481, conductor 412, right hand winding of relayl A-4 to ground at the lower normalcontact of contacts 413, it being noted that the relay B4 which controls this loop circuit is itself controlled by relay 473 in circuit With the called line and controlled at the switch hook of said line.

Assuming, however, that the called subscriber has replaced his receiver, when the operator removes the plug, relay A-'4 in releasing deenergizes relay 414. Relay 414 in retracting its outer left armature removes ground from the sleeve conductor 482 leading over the sleeve conductor to the relay 336 which in releasing its'armature removes ground from the sleeve wire 325. The removal 'of this ground releases relay D-3 whereupon the release magnet 340 operates as follows: free pole of battery, magnet 340, off normal switch contact 341, lower armatures and back contacts of relays B-3 and A3 to ground at the armature 311 and back contact of relay D-3. Thus the first selector is restored and upon reaching its normal position opens the off normal springs 313 and 341. The removal of ound from conductor 415, by the retraction of right hand armature of relay 414 releases relay (ir-4 and the retraction of the right hand armature of relay A-4 and inner left armature of relay 414 closes a circuit for the release magnet 483 at the selector repeater.

gli

The slow relay 430'is energized in parallel v with the release magnet and opens the circuit to the test brush 438 during restoration at its armature 436. At its armature 484 it short circuits the right hand winding of relay A4. At its upper armature it closes a locking circuit for itself which is opened when t-he off normal switch aumes its normal position. The opening of the circuit of the tip and ring conductors 510. 546 causes the release of relays A-5, B-5, J-5, Fig. 5, which results in the closure of `.the following circuit for connector release magnet 540: free pole of battery, magnet 540, left hand contact of off normal switch 520, back contact and lowermost armature 583 of relay D-5. lower armatures and back contacts of relay B-5 and A-y to ground. The connector uponreaching normal position restores the ofi normal switch 520.

What is claimed is:

1. In a telephone exchange system, the combination with telephone lines, automatic switches, groups of trunks terminating therein, an operators position, a. signal thereat, means controlled from said position for setting said switches to interconnect said lines over said trunks, means controlled solely lby the' busy condition of the selected line for operating Said signal in one Inanner, means controlledby the idle condition of the selector line for operating said signal in a second manner and means controlledl by thebusy condition of a selected trunk group for operating said signal in a third manner. 2. In a telephone exchange system, the combination with telephone lines, automatic selector switches, groups of trunks terminating therein, an operators position. a lamp thereat, an impulse sender which restores to normal after each set of impulses for setting said switches to interconnect said lines over said trunks, means'controlled solely by the busy condition of the selected line for flashing said lamp in one manner and means controlled by the busy condition of a selected trunk group for flashing said signal in a different manner.

3. In a tele hone exchange system, the combination with an oflice including automatic switches, subscribers lines terminating therein, another oflice, a toll operators position thereat including a cord circuit having a supervisory lamp therein, an impulse sender which restores to normal after each set of impulses associated with said position and controlling said switches, means actuated in case one of said switches fails to find an idle trunk for flashing said lamp in a certain manner, and means actuated only in case the connector finds the selected line busy for flashing said lamp in a different manner.

4. In a telephone exchange system, the combination with a. telephoneline. automatic switches, groups of trunks terminating therein, anv operators position, a lamp there-at, means at said position for controlling said switches to interconnect said lines over said trunks, means controlled by the idle condition of said line for lighting said lamp as a ringing signal, means controlled by the operator for causing ringing current to be applied to the selected line, means controlled by the response of the called party for cutting off the ringing current, means controlled by the busy condition of a selected trunk group for flashing said Vlamp at a certain rate, and means controlled solely by the busy condition of the called line for flashing said lamp at a different rate.

5. In a telephone exchange system, the combination with telephone lines, automatic switches, groups of trunks terminating therein, an operators position, means at said position for controlling said switches to interconnect said lines over said trunks, a supervisory lamp at said position, a supervisory relay controlling the same, a polarized relay bridged across one of said trunks, means controlled by the idle condition of the selected line for operating said polarized relay for causing the energization of said supervisory relay, means controlled solely by the busy condition of said line for closing an interrupted circuit through said supervisory relay to flash said lamp at a certain rate, and' means controlled by the busy condition of a selectedtrunk group for closing an interrupted circuit tov intermlttently energize said supervisory relay for flashing said lamp at a different rate.

6. In a telephone exchange system, telephone lincs, automatic switches, a trunk circuit, an operators position, a cord circuit thereat having means for controlling said switches to buildup a condition over said trunk lines'to a selected line, a supervisory lamp in said cord, a supervisory relay, a polarized relay in one-of said trunks, means controlled by the idle condition of the se lected line for operating said polarized relay to close the circuit of said supervisory relay, means controlled lsolely by the busy condition of the selected line for preventing the operation of said polarized relay and for closing an interrupted circuit to said supervisory relay to flash said lamp at a certain rate, and means controlled by the busy condition of a selected trunk group for closing an interrupted circuit to said supervisory relay to flash said lamp at a different rate.

7. In a telephone system, the combination withtelephone lines, groups of trunks including automatic switches, an operators position, means at said position for building up a connection to a called line over said trunks and switches, a supervisory lamp at said position. a key at said position, a supervisory relay therefor. a circuit for said supervisory relay controlled by contacts of said key, means including a relay energized when the selected line is found busyto interrupt said circuit to flash said lamp at a given rate when said key is restored and a'relay actuated by the busy condition of a selected trunk group for closing an interrupted circuit when said key is restored to flash said lamp at a different rate.

8. In a telephone system, telephone lines, automatic switches. trunk groups, an operators position, a lamp thereat. a dial at said position for building up a, connection to a called line over said trunks and switches, a dialing key, and means controlled bythe busy condition of a selected group for flashing said lamp at a certain rate upon the restoration of said dialing key, and means controlled solely by the busv condition of the selected line for flashing said lamp ata different rate upon the restoration of the dialing key.

9. In a telephone system, the combination with telephone lines, automatic switches. groups of trunks. an operators position, a supervisory lamp thereat, a dial at said position for building up a connection to a called line over said trunks and switches,

a dialing key -for connecting said dial to said circuit and for disconnecting said supervisory relay therefrom, means controlled by the busy conditionl of a selected group for flashing said lamp at a certain rate upon the restoration of said dialing key,.and means controlled solely bythe billy condition of the selected line for flashing said lamp at a different rate upon restoration of said dialing key.

10. In a telephone system, the combination with telephone lines, automatic switches and grou s of trunks, an operators position, a dial thereat for vbuilding up connection over said trunks and switches, a dialing key for connecting said dial to said trunks, a su rvisory rel'a thereat, a lamp controlled t ercby, said ialing key when actuated disconnecting said supervisory relay, means controlled by the idle conditions of the selected line and the restoration of said key for lighting said lamp, meansl controlled by the busy condition of a selected group and the restoration of said key for dashing said lamp at a certain rate, and means controlled solely by the busy condition of the selected line andrestoration of said key for flashing said lamp at a different rate.

11. In a telephone system, telephone lines, automatic switches, groups of trunks, lan operators osition, a supervisory lamp thereat, a dial, a dialing key for connecting said dial to said circuit to build up a connection to a called line over said trunks and switches and to simultaneously open the circuit of said supervisory relay, a cir cuit prepared by the finding of a selected group busy and closed upon the restoration of said dialing key -for dashing said lamp at a certa-in rate, a second circuit prepared solely due to the busy condition of the selected line and closed by the restoration of the key for flashing said lamp at a different rate, and means controlled by the idle condition of the selected line for preventing the closure of either of said circuits.

12. In a telephone system, the combination with telephone hnes terminating in different oflices, automatic switches, groups of trunks, an operators position, a supervisory relay and lamp thereat, a dial for controlling said switches to build up a connection from one oflice to a called line in another oiiice over said trunks, means controlled by the idle condition of the called line for applying current to said trunk to operate said supervisory relay to light said lamp, means controlled by the response of the called party for removing battery from the trunk to deenergize said relay to extinguish said lamp, means controlled by the busy condition of a selected trunk group to {iash said lamp in one manner, and means controlled solely by the busy condition of trolled by the idle condition of the called line for applying current to said trunk to operate Vsaid superviso relay to light said lamp, means controlle by the response of the called partyv for removing battery from the trunkto deenergize said relay to extinguish said lamp, means controlled by the replacing of the receiver by the called party for again applying current to said trunk to operate said supervisory relay to light said lamp, means'V controlled by the busy condition of a selected trunkl group to flash said lamp at a given rate, and means controlled solely by the busy condition of a selected line for flashing said lamp at a different rate, i

14. In a telephone system, the combination with telephone lines, a connecting circuit including automatic switches, an operators position, a sender thereat for controlling said switches to select the calledline, a supervisory lamp at said position, a polarized relay in said connecting circuit, means for reversing the `current in said connecting circuit if the selected line is either idle or busy to operate said polarized relay to cause said lamp to light, and means actuated by the busy condition of the called line for causing said lamp to flash.

15'. In a telephone system, the combination with telephone lines terminating in different oiices, an operators position at the originating oilice, a lamp at said position, a two-Wire trunk extending from said position to an automatic oiice, automatic switches thereat, a sender at said position for setting said switches to connect with the called line, a polarized relay in said trunk at the originating oilice, means for reversing the current flow in said trunk if the selected line is idle or busy to operate said polarized relay to cause said lamp to light, and means actuated by the busy condition of the called line for causing said lamp to fiash.

16. Ina telephone system, the combination with telepllone lines terminating in different oiiices, an operators position at the originating office, a lamp at said position, a two-wire trunk extending from said position to an automatic oflice, automatic switches thereat, a sender at said position for setting said switches to connect with the called line, a polarized relay in said trunk at the originating oce, a relay at said automatic oirice for reversing the current How in v a circuit for said relay, two rela s severally controlling said reversing re ay circuit, means for operating one of said relays .to operate said reversing relay when the called .l'ne is foundA idle, means for operating said other relay to operate said reversln relay if the called line is found busy, an additional means controlled by said other relay for causing the subsequent flashing of said lam 17E.) In a telephone system, the combination with telephone lines terminating in different oflices, an operators position at the originating oice, a lamp at said position, a two-wire trunk extending from said poisition to an automatic oice, -automatic switches thereat, afsender at said position for setting said switches to connect with the called line a'polarized relay in said trunk at the originating oilice, a relay at said automatic oilice for reversing the flow in said trunk to cause the lighting of said lamp, a circuit for said relay, two relays severally controllin said reversing relay circuit, one of said re ays being polarized and included in the trunk circuit to the connector, means actuated by the connector in finding the line idle for releasing one of said relays to operate said reversing relay, means actuated by the connector finding the line busy for reversing the current in said last named trunk to operate said last mentioned polarized relay to cause the operation of said reversing relay, and additional means controlled by said last mentioned polarized relay when operated for causing the flashing of said lamp.

18. In a telephone system, the combination with telephone lines terminating in different oiices, an operators position at the originating olice, a lamp' at said position, a circuit therefor, a two-wire trunk extending from said position to an automatic office, automatic switches thereat, asender at said position for setting said switches to connect with the called line, a polarized relay in said trunk at the originating office, a relay at said automatic office for reversing the flow in said trunk to cause the closure of said lamp circuit, two relays severally controllin said reversing relay circuit, one of said re ays being polarized and included in the trunk circuit of the connector, means actuated by the connector in finding the line idle for releasing one of said relays to operate saidV reversing relay, means actuated by the connector finding the-line busy for reversing the current in said last named trunk to operate said last-mentioned polarized relay to ca use the operation of said reversing relay, and a shunt circuit intermittently closed about said supervisory relay by said polarized relay to causethe same to flash said lamp.

In witness whereof, I hereunto subscribe my name this 1st day of December, A. D., 1920.

RAY STOKELY.