US2010372A - Telephone system - Google Patents

Description

E. S. PETERSON TELEPHONE SYSTEM Filed June 19, 1953 Aug. 6, 1935.l

l0 Sheets-Sheet 1 Y TTY:

Aug- 6, 1935 E. s. PETERSON 2,010,372

TELEPHONE SYSTEM Filed June 19, 1933` 10 Sheets-Sheet 2 F/s. Z

f/vvE/v me- EDWARD S. PETERSON v TTY.:

Aug- 6, 1935. E. s. PETERSON 2,010,372

TELEPHONE SYSTEM -Filed June 19, 1933 l0 Sheets-Sheet 3 INVENTOR- Eowmo 5. PETERSON,

E. S. PETERSON TELEPHONE SYSTEM Aug. 6, 1935.

Filed June 19, 1935 10 Sheets-Sheet 4 u Ruh N VEN TOR- EDWARD 5. PETERSON A118- 6, 1935. s. PETERSON TELEPHONE SYSTEEM Filed June 19, 193s 10 Sheets-Sheet 5 -A/vE/vToR- Enma/w 5. PETERSON 10 Sheets-Sheet 6 'A TTY.'

Aug. 6, 1935.

E-. s. PETERSONv TELEPHONE SYSTEM Filed June 19, 193s 10 Sheets-Sheet '7 m www Nsu www Sm P

K d@ SQ@ -N VEN Tof?- EDWARD S. PETERSON h AQN l0 Sheets-Sheet 9 s. PETERSON TELEPHONE SYSTEMv Filed June 19, 1933 l Aug. 6, 1935.l

E. S, PETERSON TELEPHONE SYSTEM Aug. 6, 1935.

10 Sheets-Sheet 10 Filed June 1.9, 1953 Patented Aug. 6, 1935 TELEPHONE ASYSTEM Edward S. Peterson, Elmwood Park, Ill., assignor to Associated Electric Laboratories, Inc., Oliicago, Ill., a corporation of Delaware Application June 19, 1933, Serial No. 676,439

26 Claims. (C1. 179,-26)

The present invention relates to telephone systems in general, but is concerned more particularly with semi-automatic telephone systems wherei by connections between manual lines entering an exchange may be set up by automatic switches under the control of an operator at a switchboard in a remote exchange.

The main object of the invention is the producvtion of new and improved circuit arrangements for simplifying and improving the operation in semi-automatic magneto telephone systems of `the type disclosed in U. S. Patents Nos. 1,752,543 and 1,801,368 issued to L. L. Ruggles and E. S.

Peterson et al. on April 1, 1930, and April 21, 1931,

,-, respectively.

In each of the above patents connections are set up between manual magneto lines by automatic switching apparatus responsive to control exercised over a control trunk extending between the manual magneto exchange and a remote operating center. improve service in rural communities by making it possible for a remote operator, instead of a local operator, to control the connections. The design is intended to retain, to as great a degree as possible, the same method of operation as was formerly used in connection with the old manual board. The remote operator can give practically the same service to the subscribers as could the local opera- :m tor and can give the service in very much the same manner, the chief difference being that shev operates a dial instead of plugging up cords.

Thisl equipment is intended to replace manual magneto switchboards which cannot profitably 5 carry the cost of a local operator. i

The general operation of this type of system is as follows: A local subscriber, upon initiating a call by turning his hand generator, causes a finder in the local exchange to find his line and signal the remote operator over a controltrunk extending to the remote operating center or main exchange. The remote operator answersthe call, dials back over the same control trunk thereby establishing the desired connection to the local called line, and then rings the party. The remote operator then retires from the local connection and either the local calling or called party can release the local connection by turning the hand generator. Calls to and from other distant exchanges are handled the same as local subscriber calls because the trunk lines to such exchange terminate in equipment the same as local magneto lines.

1. One of the features'of the invention relates to the circuit arrangements in which the remote This type of system was designed to operator, whenV extending a call for a local calling party, can enter a local completed telephone connection which tests busy in order to determine if the local subscribers have failed to release such connection by ringing down at the close of con- 5 versation and wherein the calling partyY cannot hear the conversation on the completed connection in case the connection is still in use.

2. Another feature relates to the means whereby the remote operator can remove the busy tone when she listens in on `a busy line for the purpose of holding the calling party on the line for completing the desired connection.

3. A further feature relates to the circuit arrangements whereby the remote operator can release a busy local connection from the line she has called and then ring the called party to complete the desired Vlocal connection between the local calling and called parties.

4. Another feature relates to means whereby the remote operator can, while completing a connection for the calling party, split the local connection so that she can talk to either the local called or the local calling party without the other hearing such conversation.

5. An additional feature relates to the circuit arrangements for storing calls and for notifying the remote operator by a tone that additional calls are waiting in a system wherein local connections are completed through the medium of a single control trunk extending to the remote op-V erator.

6. Another feature relates to the means whereby a remote operator can originate a call and complete a local connection to local subscribers even though the call has not been initiated by a local party.

7. Another feature relates to the local connector which, when operated to a trunk level, converts its circuits so that the control operator may di- 40 rectively step the connector step by step until she hasfound an idle trunk line in this particular level.

8. A furtherfeature relates to the novel circuit arrangements whereby an audible signal is transmitted over the control trunk from the local exchange` to the remote operator to identify a local calling paystation line.

9. Another feature relates to the means whereby the operators control trunk is automatically connected to either `one of two identical units of equipment when the capacity of aremote controlled exchange (RCX) is greater than one unit.

10. A further feature relates to the circuit arrangements whereby the control trunk extending from the local exchange (RCX) to the operating center may be only a single wire using a ground return.

Other objects and features of the invention will be apparent upon a further perusal of the specification in connection with the detail description of the accompanying drawings in which Fig. li shows the manner in which the various sheets oi drawings are arranged while Figs. l to l0, inclusive, show the detail circuits.

Referring now to Fig. 1: The lower left-hand circuit diagrammatically represents a plurality of well-known magneto substation circuitsin which the ringers thereof may be connected to either line conductor and ground or may be bridged across the line conductors. The center left-hand circle diagrammatically illustrates magneto paystation lines while the upper circle represents a jack and ring down trunk terminating in a distant manual exchange. LC shows theline circuit for 'the regular magneto lines andl LC-l'the line circuit for the paystation magneto extending to the' distant manual exchange and is similar tothe line circuit LC. LC-S is the line circuit ior permitting the remote control operator at the operatingI center to initiate' calls and to test. PST represents the relay group associated with the paystation magneto lines for generating a paystation tone. The finder switch F is of the well-known rotary type in which the wipers move step by step on the deenergization of its motor magnet and in which the wipers remain in the position last used.

Fig. 2 representsl thelocal connector permanently associated with the finder F and the'ringing machine RM. VThe local connector is of the well-knownY Strowger type having vertical and rotary movements. The normal post springs TOLL-'PS5' operate when the connector is operated to the levelinwhich the toll trunks terminate while the vnormal post springs TBK-PS2 operate when'thevconnection is operated to the level in which the trunk lines to distant eX- -changes terminate.

The ringing machine RM shown in the lower left-hand cornerv comprises the usual ringing transformer Tand a group .of relays one of which has a vibrating armature.

lilig.V 3 shows the distributor for preselecting idle local 'finder connector links shown in Figs. l and 2. The distributor comprises a well-known step-oy-step rotary switch similar ink construction to the Yiinder F and an associated groupoi relays.

Fig. 4' shows. the common equipment coinprising a group of relays which are common to all the local nnder connector links for controlling functions to be described in' detail hereinafter.

Fig. 5 shows a supervisory switch for enablingV the remote operator at the remoteV operating center to supervise in a manner to be described later. This switch isv also of the well-known rotary step-by-step type. and comprise a switching arrangement whereby when two similar systems, one of which` is shown, are providedthe control trunk coming frornV the operating centercan be switched to either system. An emergency" operating center indicatedV by the vsquare in the center of the drawing is somewhat sirnilar to the remote koperating center shown in the `dottedrectangle in the lower Ylett-hand corner.. The equipment located-attire remote operating center comprisesI LLC- 2 is the line circuit for the trunk K The relays del, 593,

the usual operators head set drop, calling device CD, repeating coil RC2 and the ringing, monitoring and connecting keys.

Fig. 6 is somewhat similar to Fig. i and is to be substituted for Fig. e when a single grounded control wire is used for a control trunk to the remote operating center. This single wire control trunk may be grounded phantom taken from a metallic toll trunk if desired.

Fig. 'l is somewhat similar to Fig. 5 and is to oe substituted for Fig. 5 Whenever Fig. 6 is t0 be used.

Fig. 8 shows a jack ending toll trunk TT terminating in either the remote operating center or another distant exchange. The equipment comprises the usual jack J, drop D, calling device CD, buzzer lila, dry cells DC, repeating coil and the holding, dialling, monitoring and ringing keys. The toll trunk TT is accessible from the local connector banks oy way o conductors ll to i613, inclusive, which terminate in the toll levels of the local connector banks.

Fig. 9 shows the toll connector which is oi` the well-known Strowgertype having vertical and rotary movements. The toll'connector is located in the local remote controlled exchange (RCX) and has its bank contacts rnultipled with the canks of the local connector shown in Fig. 2.

Fig. l0 shows a group or relays for use with the common control equipment shown in Fig. 6 when divided ringingV is to 'ne employed.

This system is primarily a fifty-line unit although two nity-line units can he connected together to torni a one--hundred-line board. Each nity-line unit may, when required, 1ce equipped with ten local lnder-connector links and one or more toll connectors. The two fifty-line units are operated separately and each unit may be switched to the control trunk when required. Each fifty-line unit will have one distributor and one connnon relay control group.

Having given a general description oi the systern and drawings, a detailed description of the circuit operations'will now be explained.

For this purpose it will be assumed that one of the regular magneto subscribers wishes to he connected to another local station. The suoscriber operates the hand generator at his telephone in the'usual manner, projecting ringing current over his line conductors and 23 and through the upper winding ci" relay il. rIhis ringing current passing through the upper winding of line relay il causes the energization of such relay which thereupon at arinature E3 connects negative battery through the winding of cut-on relay. it?. to the fourth bank contact accessible to the iinder wiper 6i. At armature lf2- relay li closes a circuit extending through the lower winding of line relay il, armature i8 and finder start conductor 3S, through the normally closed springs controlled by armature Ell and through the winding of slow-to-operate start relay 28E. Line relay il immediately locks itself over this circuit and after an interval oi= time start relay Ei'becoines operated. At armature iii line relay l i opens a peint in its original energizing circuit. Start relay 223i, upon energizing, at armature 252 completes a circuit for energizing the slow-to-operate relay 252 and at armature 'cornpletes a circuit for energizing slow-tooperaterelay Zlin case the wipers of the distributor are standing on an idle iinder connector link. Since the distributor is of the preselecting type, guard wipe-r 255 should therefore be in engagement with an-idle nder-connector link withY which negative battery is `connected through the guard lead 65 terminating in the first bank contact accessible to guard wiper 255. 4At this time a circuit may now be traced for energizing relay A2113 as follows: from grounded armature 414, conducor 252, varmature 232 and its resting contact, conductor 213, armature 32S, conductor 214, armature 231 and its' Working contact, armature 245, armature 213, through the winding or relay 263, interrupter springs 254 and through the winding of motor magnet 253 to `battery. Re-

lay 2133 after an interval energizes over thek above-traced circuit but the motor magnet 253 on account of the high resistance in the winding of relay 293 is prevented from energizing at this time, SloW-to-operate relay 232, upon energizing, at armature 214 connects ground to` conductor 211; at armature 215 connects battery through resistance 216 to conductor 215; and at armature 218 closes a shunt around the armature 213 to maintain the relay 21.13 in energized position. Relay 293, upon energizing, at arma-` ture 219 connects ground tothe chain conductor.

relay 2515; and at armature 223 closes a pointA in the nder testing circuit. The circuit for energizing the motor magnet 54 of the iinder may. be traced as follows: from grounded armaturev 22B, armature 228 and its resting contact, armature 221, wiper 251 in engagement with its irst bankcontact, conductor 61, and through the Winding of motor magnet S4 to battery. Magnet E4 energizes over the above-traced circuit and at springs 63 grounds the conductor 63 engaged by wiper 256 for ,energizing the stepping' relay 2135. Stepping relay 2136, upon energizing, at armature 221 opens the circuit extending to the motor magnet 54, whereupon the magnet 64 deenergizes and advances the wipers of the iinder F one step in engagement with the next set of contacts terminating the next magneto subscribers line. Magnet 64 in addition to operating the wipers of the finder one step also interrupts the circuit extending `through the upper winding of stepping relay 206 with the result that the stepping relay 235 again deenergizes and at armature 221 reestab-V lishes the circuit for energizing the motor magnet 611. This interaction between stepping magnet 54, and stepping relay 282 continues until such time as the 4test wiper 51 encounters a bank contact marked with negative battery thereon throughl the winding of the associated cut-oir relay in the line circuit. As soon as test wiper Si encounters the marked bank contact, or in case the wiper S1 has been sitting on the fourthlbank contact, a circuit is completed for energizing the cut-off relay 12, the test relay 221, and the stepping relay 265 in a series circuit as follows: from grounded armature 115 (Fig. 5), conductor armature 223, through the lower winding of stepping relay wipers have been rotated to this bank contact the operation of armature 221 prevents the energization of motor magnet 64. Cut-off relay 12 energizes over the above-traced circuit and at armature 16 opens a further point inthe original energizing circuit of line relay 11; at armature 13 opens the locking circuit of relay 1 1 extending to start conductor 39 whereupon line relay 1| and start relay 281 deenergize; and at armature 11 closes a locking circuit for itself by way of conductor 24, test wiper 61, to the grounded hold conductor `SS. Test relay 291, upon energizing over the above-traced circuit, completes a circuit for energizing motor magnet 253 by Way of armature 220 and armature 228 and its working Contact, while at its resting contact opens a further'point in the energizing circuit of the finder magnetV 64. At armature 231i grounds the guard conductor 65 by way of grounded armature 230, working contact of armature 221 and saidarmature, armature 225, Wiper 255, start conductor 65, and thence by way of spring 123 and its resting contact in the local connector, spring 125 and its resting contact, throughthe winding of hold relay 163 to battery, and through the normally closed springs controlled by armature 14B of relay through the Winding of .connecting relay 164 to battery. yThe hold relay 183 and the connecting relay 4G11 are energized over this circuit to prepare the connector for operation as will be described hereinafter. At armature 231 relay 231 completes a locking circuit for itself extending from grounded armature 325 and its restingA c'ontact, and conductor 254 through the lower winding of relay 201 to battery. Armature 231 also grounds conductor 261 to energize relay 401 to` prevent a call on the second fifty-line unit from switching the control trunk, comprising conductors 1153 to G54, into the second unit. This is accomplished by relay 13521 energizing and disconnecting ground irorn conductors 269 and 282 by the operation of armatures 111 and 1112; it being understood that the conductors 265', 26|', and 252 are connected to the second unit in the same mannerA as conductors 259, 251, and 262 in the iirst unit are connected. At armature 232 relay 201 opens the energizing circuit of relay 2113 at its resting contact and at its working Contact l `connects the grounded conductor to conductoi` 223 for energizing slow-to-release Vrelay Fig. 5, by way of the normally closed springs controlled by armature 431. Relay 4311 energizes over the above-traced circuit and at armature 533 closes a circuit for energizing the slow-tooperate relay 43 1 At armature relay 439 con Vnects ground to conductor i and at armature 481 connects negative battery through a resistance to conductor 452. A circuit may non7 be traced over the two trunk conductors 453 and 54 extending to the remote operating center for causing the energization of the drop to signal the operator. This circuit may be traced as follows: grounded armature 432, conductor 451, resting contact of armature 425i and said armature, trunk conductor (154, through the upper right- Vhand winding of the repeating coil RC2, spring A161 and its resting contact, through the winding Vof the drop, through the lower right-hand wind# ing of repeating coil RC2, trunk conduct-or 453,

armature 419 and Vits resting contact, conductor through the resistance to battery. :A short 1nterval thereafter slow-to-operate reiay 23| energizes and completes a locking circuit for itself Y from grounded conductor 254 by Way of armatureV Ymagnet 253 to battery.

438. At armatures 434, 435, and 43S relay 43H. disconnects the supervisory switch wipers s, M5, and 45E from the control trunk and at armature i531!k opens the energizing circuit of slow-to-release relay F53!) which after an interval of time deenergizes and connects the left-hand windings of the repeating coil RCI to the trunk conductors 453 and 356 by way of armatures 532 and A8L Returning now to the point in the circuit description where the distributor magnet 253 energized as a result of the energization of test relay 2ST, said magnet at springs 2M also opens a point in the circuit of relay 2% which accordingly deenergizes after an interval. At armature 2li) relay 293 disconnects ground from4 the all-trunkbusy relay ZJ but this relay is still maintained energized over the chain conductor 69 extending from all of the idle finder connector links. At armature 225i relay 2% opens the circuit of magnet 253 whereupon the magnet deenergizes and advances the wipers of the distributor one step. At armature 2! relay 2M closes a self-interrupting circuit for the stepping magnet 253 to the guard conductor 55. n case the wiper 255 should be in engagement with a guard conductor such as 55 extending to a busy nnder connector link, then ground will be on this guard conductor with the result that a circuit may be traced from the grounded guard conductor, wiper 255, armature 225, armature 22B and its resting contact, interrupter springs 256i, and through the winding of Magnet 253 energizes and at the end of its stroke opens the spring 256i to interrupt its own circuit whereupon the magnet deenergizes and advances the wipers of the distributor switch another step. This interruptor action of the motor magnet 253 continues until the guard wiper Z55 no longer encounters a grounded bank contact. All finder connector links which are busy will have ground connected to their guard conductors 65 while the idle nder connector links will have negative battery connected to their guard conductors. The distributor is therefore operated to preseleot an idle iinder connector link. At armature 222 relay 263 opens the circuit of relay 265 with the result that relay 295 deenergizes and at the Vibrating spring 226 opens the circuit of slow-to-operate relay 294 before relay 2G@ has had sufficient time to energize. It should probably be mentioned at this time that the armature Eilvibrates for a predetermined length oi'time before it permanently closes the circuit to relay 295i and since relay 264 is a slow-to-operate relay said relay will not energize as long as the armature 22E is vibrating. At armature 223 relay 203 opens the circuit of stepping relay 2F35 and test relay 267 with the result that the stepping relay 25B@ deenergizes while the test relay is held locked over its lower Winding as previously described.

Referring now to the local connector shown in Fig. 2 and at a time when relays 63 and lilll were energized as a resultv of the energization of the distributor test relay 2t?, relay H33, upon energizing, at arma-tures M5 and H9 prepares a circuit for connecting the calling subscriber to the right-hand windings of the repeating coil RC. This circuit may be traced from the magneto telephone line shown in Fig. l extending by Way of conductors 22 and 23, wipers @il and 62 of the finder S, conductors 'i2 and i3, armatures l l5 and l l to .armatures U33 and lil. At armature H6 relay 593 connects ground to hold conductor 58 to maintain the cut-oli relay l2 in the subscribers line circuit LC in energized position and to mark the calling line busy to the iinders and connectors having access thereto. At armature lll' relay iElB opens one of the grounded connections extending from the local connectors in normal position from the chain conductor 69. The all-trunks-busy relay 208, however, is maintained energized as long as there is an idle finder connector link. At armature ii relay E53 completes a locking circuit for itself extending from grounded armature H2 and this ground also maintains the connecting relay i065 in energized position. Armature H8 also maintains this ground on guard conductor 65 to maintain this finder connector link busy and inaccessible to the distributor shown in Fig. 3. At armature i2@ relay |93 opens a point in the circuit extending to the release magnet M39.

Connecting relay itil, upon energizing, at armatures ll and i3? connects the calling subscribers line to the operators control trunk over the following circuit: from the subscribers line as previously traced to armatures 53 and Ml, armatures lZl and 37, conductors M5 and i313, resting contacts of armatures 329 and 33t and said armatures, conductors 262 and 262i, through the right-hand windings of the repeatingl coil RCI, and from thence by way of the left-hand winding of the repeating coil RCI, resting contacts or" armatures 432 and l'li, conductors 5l and F252, resting contacts or" armatures M9 and Mii, conductors 153 and 35d extending from the local remote controlled exchange to the distant operating center, and thence through the rightu hand windings of the repeating coil RC2 in the distant or remote operating center. At armature t28 relay mii prepares a point in the circuit whereby the operator may transmit ringing current over wiper ll toring all of the magneto subscribers substations having their ringers connected to the negative side or" the line to ground. In a similar manner armature i316 prepares a point in the positive ringing circuit whereby the operator may ring the magneto lines over the positive wiper E54 on the subscribers lines havlng their iingers connected to the positive side of line and ground. At armature i2@ relay i015 prepares a point in the circuit extending to the test relay 3l@ in the common equipment in Fig. 4; at armature lll prepares a point in the circuit extending to the vertical magnet lll; at armature i3d prepares a point in the circuit for energizing cut-through relay ilii; at armature 32 prepares a point in the circuit for energizing relay itt; at armature 33 prepares a point in the circuit for directively rotating the connector in search of an idle trunk; at armature H3llprepares a point in the circuit extending to the rotary magnet MG; and at armature E35 prepares a point in the circuit for energizing sloW-tc-operate relay it?.

When the operator observes the operation of the drop` at her position indicating a call, she will operate the key K which at springs and connects her telephone set to the left-hand windings of the repeating coil RC2 to complete the talking circuit to the calling subscriber over the path previously traced. At spring lol and its resting Contact the circuit for operating the drop is opened and at the make springs on springs 66E, 352, and 53 ground through the impulse springs of the calling device CD is connected to both trunk conductors Vi553 and 5!! through the right hand windings of repeating coil RC2. A circuit may now be traced for energizing relays 3D3 and 3M in the common equipment, Fig. 4, as follows: from ground through the impulse springs of the calling device CD, springs 463, springsof the monitor key MK, springs of the positive ring key, springs 402, lower right-hand winding of repeating coil RC2, conductor 453, armature4 I 9 and its resting Contact, conductor 452, armature 48| and its resting contact, lower left-handwindingof repeating coil RC I, conductor 21 I, through the lower winding of dierential relay 301, and through the windings of relay 303 and 304 in series to battery. At the same time another circuit maytbe traced for energizing line relay302 in the commn equipment as follows: from ground through the impulse springs of the calling device CD, springs 463, normally closed springs controlled by the negative ring key, working contact of springRCZ, conductor 454, armature 420 and its resting contact, 'con-y ductor 45| armature 432 and its resting contact, upper lett-hand winding of repeating coil RCI, conductor 210, through the upper winding of differential relay 30|, and throughthe winding of line relay 302 to battery. Differential relay 30| does not energize over the above-traced circuit because both windings oppose each other. Line relay 302, upon energizing, at armature 3I8 and its working contact completes a circuitfor energizing slow-to-rclease relay 305 which ,relay thereupon energizes and at armature 322 and its resting contact disconnects ground from conductor 238 and at its working contact grounds conductor 261 to maintain relay 4.3i in energized position and to maintain the conductor 254 grounded byl Way of armature 439. At armature 323 relay 305 closes an obvious circuit for energizing relay 30S and connects ground to conductor 10 to energize the vibrating relay 8| in the paystation tone relay group shown in Fig. 1. At armature 324 relay 305 prepares the impulsing circuit. `Relay =303, upon energizing, at armature 3| 0 andits Working Contact closes an auxiliary circuit for maintaining the slow-torelease relay 305 in energized position and at its resting contact opens a point in the circuit to the positive ring relay 300;`and at armature 320 prepares a point in the circuit to the monitor relay 301. Marginal relay 304, upon energizing over the above-traced circuit, at armature 32| opens a point in the circuit to the monitor relay 331, Slow-to-release relay 300, upon energizing, at armature 325 prepares apoint in the cir--r cuit to the cut-through relay |05 or release relay |02 dependent upon the position of the test relay 3 l 0 at armature 326 andits resting contact disconnects ground from conductor 204, which conduc# station tone relay group in Fig. 1, whereupon the dilerential relay energizes and at armature 40 completes a circuit through its upper differential winding to deenergize suchrrelay whereupon the, armature 40 is opened, with the result that the relay is again energized over its `lower winding. Differential relay 45 therefore energizesV and deenergizes in the manner of a buzzerto generate a tone which is connected to all of the paystation lines by the operation ofthe paystation relay 43.

A predetermined time after the relay 8| is ener- A armature continues to vibrate for a considerable time the slow-to-operate relay` 45 will not be operated until a certain period of time has elapsed since the energization of the vibrating relay 8|. Relayl45 opens the locking circuit of relay 43 at armature 48 with the result that ,relay 43 now deenergizesvtodisoonnect the paystation tone. It may be mentioned at this time that whenever a paystation line originates a call the relay 43 is en- Iergized in parallelwith the locking winding of the subscribers line relay, such as relay 3|, and at armature`45 connects the tone created by the differential relay 45j to the negative line conductor to inform the control operator that a paystation sub scriber is calling.

When relay |10 energizes and closes its armature springs |15, a circuit is kclosed for relays I1I and |13 in parallel. Relay I1I being a slow-toe' operate relay is not immediately energized but relay |13 is energized by way of armature |11 to' start .the pendulum |82 vibrating. After a short interval of `time slow-to-operate relay I1| vener# gizes and at armature |16 completes a circuit through the lower winding of relay |12 which is rendered slow to operate because of the normal short circuit through its Lipper winding at arma#` ture |19, and at armature |11 and its working contact closes a short circuit around relay |13 from the vibrating armature |82 and springs |84. At armature |11 and its resting contact relay I1I includes the resistance |80 in the energizing circuit of relay |13. Due to the short circuit around relay |13 said relay deenergies and causes the pendulum to vibrate. After a time which is sufficient to allow the pendulum to pick up speed and vibrate at its full amplitude the slow-to-energize relay |12 energizes and connects the vibrating springs I8I and |83 to the right-hand windings of the ringing transformer T by way of armatures |18 and |19. After this is done, each'backward swing of the pendulum results in a circuit being closed for the upper section of the primary winding of the transformer T and each forward swing results in a circuit being closed for the lower sec-v tion of the primary winding and, consequently, an alternating current is driven through the secondary winding of the transformer T. Returning now to the time in which the calling subscriber originated the call by operating the relays 20| and 202m the distributor in Fig. 3, a description will be given of the operation of these relays to transmit a tone tothe calling subscriber until such time as the nder finds the calling' line. When relay 20| energizes over the start conductor 30, as previously described, said relay at armature 2 I2 completes a circuit for enrelays interact in this manner and generate a,

tick` tone through the normally closed spring controlledl by armature 2| 1 by the ,connection of directv ground to conductor 30 and the inductive kick from the winding of relay 20|. This tick tone circuit extends kback over the nder start conductor 30 through armature I8, armature I4,

and the lower winding of line relay II to battery. This tone is thereby induced from the lower winding into the upper winding and is thereby transmitted to the calling subscriber by way 'of armature I6 and the'negative talking conductor 22. In addition at armatures 2M and 2|5 ground and negative battery'is connected to conductors 2TH and 276 in order to transmit a waiting tone tothe control operator at a time she is extending a prior connection and which tone is transmitted to the control operator over the control trunl; extending to the operating center at a time when the test4 relay 3 i! in the common equipment, Fig. 4, is operated during such prior call. This waiting tone is connected to the conductors 268 and 26S by the operation of test relay 3M) atarmatures 35| and 353 and extends by way oi the repeating coil RCL the talking conductors 45|, 452, 453, and 454 to the repeating coil RC2 at the remote operating center.

All of the foregoing operations have occurred as the result of a subscriber initiating a call and in response tothe control operator operating her dial and answer key K. The operator now challenges the call and receives the number of the line to be called. After receiving the number of the desired called subscriber the operator will operate the calling device CD in accordance with the first digit of the called number. In response to the operation of the calling device the impulse springs interrupt the circuit of relays 332, 333, and 384 with the result that these relays deenergize each time the impulse springs of the calling device CD are opened over the circuit previously traced for said relays; rThe operation of relays 363 and 364 at this time is Without eiect. At armature 3|8 and its resting contact line relay 302, upon each deenergization, completes a circuit for energizing the series relay 3|5 and vertical magnet as follows: from ground by Way of armature 3|8 and its resting contact, armature 3|ll and its resting contact, armature 324, armature 35i, armature 36|, through the Winding of series relay 3I5 in parallel to battery, and thence by way of armature 364 and its resting Contact, conductor |90, armature |36, and through the winding of vertical magnet to battery. The slow-to-release series Vrelay 3|5 is energized in response to the first received impulse and maintains its armatures in attracted position throughout the impulse series. At armature 320 relay 3&5 closes a shunt around armature 36| and at armature 369 and its Working contact completes a circuit for energizing relay 3 I4. Relay 3 4, upon energizing, at armature 361 completes a circuit for energizing relay 3|2 by way of armature 365 and at armature 368 and its resting contact opens a point in the circuit to test relay 3H] and at its Working contact prepares a point in the circuit for the busy relay 3| Relay 3|2, upon energizing, at armature 363 and its working contact completes a. short circuity around relay 3|3 to prevent its operation during the dialling period. This circuit maybe traced as follows: ground by way of armature 321, armature 363 and its working contact, through the winding of relay 3|3, armature 365, to grounded armature 36?.

In the local connector the vertical magnet is operated by each impulse to step the Wipers of the local connector in a vertical direction. l The Wipers of the local connector are therefore operated step by step and stop opposite the level in which the desired called line terminates. Upon the first vertical step of the wiper shaft the off.- normal springs |2|, |22, and |25 are operated. Oinormal springs |2| prepare a circuit for the release magnet |09 which, however, is opened at armature |26 at this time; off-normal springs |22 disconnect one of the ground connections eX- tending from the chain conductor 69; and oir-normal springs |25 disconnect the guard conductor 65 from relays |33 and 62, which relays, however, are maintained in operated position at this time from grounded armature H2 While at the working contact of off-normal springs |25 the guard conductor 65 is grounded to maintain this finder connector link busy.

At the termination of the first series of impulses transmitted relays 392, 303, and 364 are maintained in their operated position. Relay 365, due to its slow-releasing characteristic, does not deenergize during the transmission of impulses. Shortly after the rst series of impulses series relay 3|5 deenergizes and'at armature 363 opens the circuit of relay 3M which thereupon deenergizes. Relay 3M, upon deenergizing, at armature 367 removes the short circuit from around relay 3 3 with the result that this relay now energizes in series with relay l3i2 over the following circuit: from ground by way of armature 322, armature 363 and its working contact, and through the windings of relays 3i3 and 3| 2 in series to battery. Change-over relay 3 l 3, upon energizing, at armature 36:3 and its resting contact opens the impulsing circuit extending to the vertical magnet and at its Working contact prepares the impulsing circuit to the rotary magnet i6; at armature 365 opens a point in the previously traced short circuit for said relay, and at armature 336 prepares a circuit for directively operating the rotary magnet in case the connector is operated to trunk or toll levels.

The control operator now dials the second digit of the called number with the result that the line relay 3,62 and relays 333 and 331i follow the impulses as previously described. Relay 335, due tok its slow-releasing characteristic, is maintained energized during the impulsing period by the intermittent operation or armature 353. Each time line relay 362 deenergizes a circuit may be traced for operating the rotary magnet i6 as follows: from ground by way of armature 3|8 and its resting contact, armature 3H and its resting contact, armature 322, armature 357, armature 36|, through the winding of slow-to-re lease series relay to battery and also by way of armature 3613 and its Working contact, conductor |95, armature |34, and through the rotary magnet lill to battery. Rotary magnet H3, upon operating, rotates the Wipers of the local connector into engagement with the bank contacts terminating the called line. Series relay 3i5 energizes as previously described and at armature 3`|0 closes a shunt around armature 36| to prevent the operation of the busy relay from opening the rotary impulsing circuit and at armature 369 again completes the circuit for relay 3|4. Relay 3M, upon energizing, at armature 362 disconnects the busy tone; and at armature 368 opens a point in the circuit to the test relay 3|!) and at its working contact prepares a circuit for the busy test relay 3| l.

The operation is now dependent upon whether the called line is busy or idle. In case the called line is idle no circuit vis completed for the busy test relay 3|| during the time relays 36 and 314 are in energized position. Shortly after the rotary impulses relay 3|5 deenergizes and in turn deenergizes relay 3M. The deenergization of relay 314 at armature 368 and its resting contact completes a circuit for the test relay 3|@ which now energizes over the following circuit: from .ground by way of armature 321, through the upper winding of test relay 3|0, resting contact of armature 368 and said armature, conductor |89, armature |29, wiper |52 in engagement with the test contact terminating the called line, and through the winding of the cut-oli relay, similar t relay 92 in Fig. l, to battery. The cut-off relay individual to the called subscribers line and the test relay 3| 8 venergize over the abovetraced circuit. yThe cut-oir relay, such as relay I2, upon energizing, at armature IB disconnects the line relay, such as line relay from the line conductors of the called line and at armature I8` opens a point in the circuit` extending to `the nder start conductor 33. At the armature `corresponding to armature v| 1 the cut-off relay completes a circuit for busying the called line in the banks kof the nder F. Test relay 3| 8, upon energizing in series with the cut-offrelay of the called `subscribers line, at armatures 35| and 353 prepares a circuit for transmitting a waiting tone to the control operator in case a second calling subscriber may be calling Vat this time. As previously described, it will be remembered that relays 28| and 292 intermittently operate when a subscriber initiates arcall and therefore relay 202 at armatures 2 4 and 2| 5 intermittently connects ground and battery through resistance 2|6 to conductors 211 and 216. A circuit may now be traced through the armatures 35| and 353 to the heavy talking conductors 268 and 299 and thence through the right-hand windings of the repeating coil RCI which includes a tone in the left-hand winding of such repeating coil and thence overthe conductors 45| and 452, trunk conductors 53 and 454, to the right-hand winding of the repeating coil RC2 and thence over the heavy talking conductors from the left-hand winding to the operators telephone set. The operator, upon hearing this tone, is advised of the fact that a second calling subscriber is waiting tobe served. Relay 3|0, at armatures 352 and 354, prepares a point in the bridged talking an-d listening circuit as will be more fully explained hereinafter, at armature 355 and its resting Contact opens a point in the release circuit extending to the local connector over conductor |95 and at its Working contact prepares a point in the circuit to the cut-through relay |85 also in the local connector. At armature 356 relay 3| 0 closes a locking circuit through its lower winding from grounded armature 321. and at armature 351 opens a point in the impulsing cir-v cuit. 'The called line is temporarily marked busy through the upper winding of relay 3|9 over the previously tracedcircuit for energizing the cutoff relay and test relay 3 8 from ground at armature 321.

The ringing operation performed by the control operator is now dependent upon whether the called subscriber has his ringer connected to the negative line conductor and ground, whether the ringer is connected to the positive line conductor and ground, or whether the ringer is bridged across the two line conductors. Ifv the called subative ring key, ground extending from the impulse.`

springs of the calling device CD is disconnected from trunk conductor 454 thereby causing the deenergization of line relay 392 and the energization of dierential relay 38|. A circuit may now be traced for energizing the negative ring relay 308 as follows: from ground at armature 3|8 and its resting contact, armature 3|1 and its working contact, and through the winding of negative ring relay 308 to battery. Relay 388, upon energizing, closes .armature 335 without effect atthis ,time and at armatures 338 and 34| completes the circuit for ringing the called subscriber as follows: from direct generator lead extending from the transformer T in Fig. 2, Working contact of armature 338 and said armature, negative Vring conductor |81, armature |28, wiper |5| in engagement with the bank contacts terminating the negative line conductor of the called subscriber, and thence over the negative line conductor through the substation ringer `to ground. In case the subscribers ringer should be bridged across both line conductors then the return circuit extends by way of -the positive line conductor, the connector bank contacts and wiper |54, armature |38, conductor |88, armature 34| and its working contact to generator return conductor 1S which is connected to the other terminal ofthe transmitter T shown in Fig. 2. At armature 336 and 838 the ring-back condensers 331i and 348 are connected to the conductors 288 and 269 in order to transmit a ring-back tone to inform the operator that the actual ringing is taking place. At armature 342 relay 388 also connects ground to the lower winding of test relay 3|9 to ensure the energization of the latter and operates armature 343 to ground conductor 212 which is without effect at this time.

In case the called subscribers number indicates that the called subscribers` ringer is connected to the positive line conductor and ground, then the control operator will operate the positive ring key in accordance with the code of the called subscriber. Responsive tothe operation of the positive ring key the positive side of the trunk conductor is opened a corresponding number of times to deenergize relays 383 and 394 and to energize differential relay 39|. A circuit may now be` traced for energizing the positive ring relay 339 as follows: from grounded armature 3|9 and its resting Contact, armature SHG, and through the winding of positive ring relay 398 to battery. Relay 309, upon energizing, at armature 348 connects direct generatorto the positive ring conductor V|88 and thence by Way of armature |35, wiper |54 in engagement with the bank contact terminating the positive line conductor of the called subscribers line and thence through the called subscribers ringer to ground, `r if the ringer is bridged, to the negative line conductor and from thence to the negative bank contact terminating the negative line conductor, wiper |5|, armature |28, conductor |81, armature 346, to the generator return conductor 18, At armatures 345 and 341 and their working contacts the ring-back condenser- s 331 and 349 are connected across the trunk conductors 268 and 269 for transmitting a ring-back tone to the control operator as previously described. AtV armature 349 relay 339 connects ground through the lower winding of test relay 3|!) and operates armatures 344 and 350 without effect at this time.

After the operator has operated the proper ringing key in accordance with the code of the called subscriber the operator may either Aoperate her monitoring key or she may, without operating her monitoring key, take care of some of her other duties. monitor key MK the resistance R is inserted in In case the operator operates her result that the marginal relay @ii-S deenergizes while relay is maintained in energized posiu tion. The differential relay Sill may or may not energize in response to the inclusion of the resistance R in the positive trunk conductor but the energization of such relay at this time is without effect. Since the marginal relay .'iill is now deenergized and the elay tilt is maintained in energized position a circuit may now be traced for the monitor relay @ill as follows: from grounded armature 36e and its resting contact, armature 32E', armature 3%, and through the winding of monitor relay ill to battery. Monitor relay Bill, upon energizing, at armatures 32e and 325i and their resting contacts disconnects the negative and positive talk conductors extending back to the calling subscriber from the operators trunk conductors 268 and 2&3 and connects the operators trunk conductors and to the line conductors of the called subscriber as follows: from negative trunk conductor 26B, armature 32e and its working contact, negative ring conductor ll, armature t28, wiper E56 in engagement with the bank contacts terminating the negative line conductor of the called subscribers line, and trunk conductor 26d by way of armature @3l and its working contact, positive ring conductor ist, armature 636, and wiper 651i in engagement with the bank contacts terminating the positive line conductor of the called subscribers line. Monitor relay 3S? at armature opens a point in the circuit of busy relay l to deenergize the same in case it should be energized at this time and operates armature 335 without effect at this time. By the operation of the monitor relay Sill' the calling subscriber has therefore been disconnected and cannot listen in on the conversation between the control operator and the called subscriber when the called subscriber answers. When the called subscriber answers the control operator will disconnect from the connection by restoring first the monitor key MK and the answer and dial key In case the operator has other duties to perform she will not immediately operate her monitor key after having rung the code of the called subscriber and in this case a temporary talking and listening circuit is provided for enabling the calling and called subscribers to talk together over the following circuit: from the magneto. telephone circuit indicated by the lower c' cle in Fig. 1, talking conductors 22 and 23 and armature l5, the .associated bank Contact and wipers 6G and 52 of the nder F, conductors 'l2 and '53, armatures H and M9, armatures M3 and bill and their resting contacts, armatures itil' and i3?, talking conductors lee and HB5, resting contacts of armatures 329 and 33t and said armatures, armatures 3435 and @lll and their resting. contacts, over the dotted Y connection provided for bridge listening, armatures S52 and 354i, resting contacts of armatures 338 and 3M, conductors i8? and |88, armatures t28 and 13S, wipers itl and E54, and thence over the called subscribers line. The calling and called subscribers may converse over this temporary talking connection and when the operator comes in on the connection she will be advised of the fact that the called subscriber has answered due yto their conversation since the trunk conductors 26S and 269 are connected to the conductors E85 to 83, inclusive, at armatures 325 and 33. lThe operator may now disconnect by restoring the key K or if she desires to talk to the called subscriber to the exclusion the positive trunk line conductor 5553 with the of the'calling subscriber, she will operate the monitor key MK with the result that the talking connection extending to the calling subcriber is disconnected at armatures 329 and as previously described. ln case the bridged listening circuit is not required the dotted Y connection may be omitted and in such cases the operator will have to restore the monitor key MK in order to connect the calling and called subscribers together. When the control operator restores the monitor key MK and the answer and dial key K, ground through the impulse springs of the calling device CD is disconnected from both conductors of the control-trunk with the result that relays 392 393, and 3M now deenergize. At armatures Bill and 3l9 relays 302 and 393 open the circuit of the slow-to-release relay 3&5 which after an interval deenergizes and at armature disconnects ground from conductor 257i with the result that relay 2G? in the distributor and relays lul and 453i in Fig. 5 also deenergize. At armature'SES and its working contact relay upon deenergizing, disconnects ground from unlock conductor lfb to open the circuit to the vibrating relay 8l and also opens the circuit extending to the slow-to-release relay StB. Relay at armature i323 transmits a ground impulse before the slow-release relay SBS deenergizes for energizing the cut-through relay we in the local connector as follows: from ground by way of armature and its resting contact, armature armature 355 and its working contact, cut-through conductor lei, armature ISI, and through the winding of cut-through relay it to battery. Relay liti', in Fig. 5, upon deenergizing, at armatures fili and SI2 grounds conductcrs 2553 and ESE to enable the second iiftyline unit to be connected with the trunk conductors Q53 and fli in a manner described for the system shown in the drawings. Relay 43H, upon deenergizing, at armatures 1331i to e36 connects up the supervisory switch and at armature 43? prepares the original energizing circuit for the signailing relay fitti. Relay 2M in the distributor, upon deenergizing, prepares a point in the circuit extending to the motor magnet of the preselected nnder; at armature 22g prepares a point in the circuit to the motor magnet lill of the supervisory switch, at armature 232 opens the energizing circuit extending to signal relay li'l before relay Si fully deenergizes and at the resting contact of armature 232 prepares a point in the energizing circuit of relay 203.

Cut-through relay SBS in the local connector, upon energizing, at armature lill) completes a locking circuit for itself extending from grounded armat re El? and at the normally closed springs controlled by armature i453 opens the locking circuit of' connecting relay its with the result that the latter relay now deenergizes. At

armature iSS relay M connects the upper leftv hand winding of the repeating coil RC to the negative talking conductor of the called subscribers line; at armature i352 connects direct ground to the test wiper 52 to maintain the called subscribers line busy to other connectors having access thereto; at armature Mi prepares a point in the circuit to slow-to-operate relay E62; and at armature lll? connects the positive talking conductor extending to the calling subscribers line to the lower right-hand winding of the repeating coil RC thereby 'completing a talking connection between the calling and called subscribers exclusive of the common operating equipment shown in Fig. 4. The calling subscriber is now bridged directly across the righthand winding of the repeating coil RC while the called subscriber is bridged across the left-hand Winding of the repeating coil RC. The deenergization of relay |04 at armatures |21 to |31, in-

clusive, disconnects the common equipment from the local connector and from the operators conn trol trunk. l

In the common control equipment shown in Fig. 4 the slow-to-release relay 305 deenergizes after interval and at armature 325 opens a point in the original energizing circuit to relay which, however, is locked up at this tiile from grounded armature H2; at armature 326 and its working contact opens a point in the circuit extending to the start relay lle-of the ringing machine, and at its resting contact again grounds conductor 264. At armature 323 relay 305 prepares the original energizing circuit for relay 2&3 of the distributor and at armature 32? opens the locking circuits of relays 3H), 3|2, and 3|3 which thereupon deenergize. By the deenergization of relays Bill, SI2, and SiS the common control equipment is completely released and may be used on a subsequent call.

After disconnecting, either subscriber may release the connection by turning the hand generator at his station. ln case the calling subscri ser, upon the termination of the conversation, operates his magneto, ringing current is transmitted over the `previously traced talking circuit and through the right-hand winding of the repeating coil RC and through the winding of the alternating current relay it. In a similar manner the operation of the magneto at the called substation will extend ringing current over the left-hand winding oi the repeating coil RC and through the winding of the alternating current relay lill. The operation of alternating current relay |57 at armature |48 completes a circuit for energizing slow-to-operate relay U32 as follows: from ground by way of armature IM, armature |58, and through the winding of relay N32 to battery. The operation or" alternating current relay Hill in a similar manner `at armature |55 closes a circuit for relay m2. Relay |02 is made slow to operate to ensure that the 4relay will not operate 'from momentary surges of current on the line due to outside influences. Relay |62, upon energizing, at armature ||3 closes a circuit for maintaining the hold relay 93 and the cut-through relay |05 in energized position and at armature ||ll completes a circuit for grounding the supervisory release conductor 'l and for energizing slow-to-release relay Iiii, When the subscribers have finished ringing down the connection the alternating current relay il or Bilt will deenergize and open the circuit of relay 02 and the latter relay after an interval of time will also deenergize and open the locking circuit of the hold relay |53 and the cut-through relay iEiii as well as opening the circuit of relay lill. Since relay lili is a slow-to-release relay ground is not connected to armature ||2 until after the hold relay |53 and the cut-through relay |ii5 have fully restored. Hold relay |03, upon deenergiaing, at armatures IIE and H9 opens the talking circuit, at armature lit` disconnects ground from the hold conduct-or 68 to remove the busy condition and to, deenergize the cut-oir` relay I2 of the calling subscribers line which thereupon deenergizes. At armature 'l I1 slow relay |93 prepares a circuit for again grounding the chain conductor E9 as soon as the local connector restoresits switch Shaft and wipers to armatures such as armatures at the remote operating center.

normal position; and at armature |20 completes the circuit for energizing the release magnet |09. By the operation of the release magnet |09 the switch shaft and wipers are restored to their normal position in the well-known manner and' guard conductor G5 and'at the working contact thereof prepares lthe circuit for again energizing the hold relay E53 and the connecting relay 04. The deenergization of cut-through relay [Q5 opens the talking circuit at armatures |38 and |42 and at armature |39 removes ground from the trunk wiper |52 to remove the busy condition from the called line to enable other connector switches to connect thereto. All of the relays in the local connector are now in their normal position or the position shown in the drawings and may therefore be used in subsequent calls.

Having described the detailed operations which take place when the called line is found 'to be idle, a description will now be given of the operations which take place when the control operator encounters a busy called line. For this purpose it will be remembered that the energization of relay Siti at armature 36S prepared a circuit to the busy relay 3l| during the transmission of the second digit. In case the called lin-e is busy then test wiper |52 in the local connector will encounter a grounded bank Contact applied thereto by another connector either from H6 or |39 dependent upon Whether the called subscriber originated the call or wasV called in the previous connection. A circuit may now be traced for the busy relay 3|i` as follows: from the grounded bank contact encountered by test wiper |52, armature !29, conductor |85, armature 368 and its working contact, armature 3,32, and through the winding of busy relay 3l! Vto battery. At armature 355 busy relay 35| prepares a point in its own locking circuit and at armature 35| opens a point in the impulsing circuit. At armatures 358 and 3,55 busy relay 3| connects the busy tone to conductors |85 and |85 and from thence over the heavy talking conductors extending to both the calling subscriber and the control operator The busy tone circuit extends from the busy tone conductor, armature S532, armature 353, conductor |85, over the heavy talking conductors to the calling subscriber and over the conductors 2GB and 269, through therepeating coils RC! and RC2 to the control operator, while the busy tone return circuit returns to grounded arinatur 35S. Shortly after the impulsing period the series relay 3 5 and relay deenergize as previously described and the latter relay at the normally closed springs controlled by armature 338 complete a locking circuit for the busy relay as follows: from grounded armature 32'l, armature 360, normally closed springs controlled by armature 388, armature 332, and through the winding of busy relay 3|| to battery. When the operator hears the busy tone she will operate her monitor key MK to monitor the connection to determine if the called line is actually in use or if in a previous connection the subscribers have failed 'to ring 2do-wn the'connection. Responsive to the operation of the monitor key MBI, the resistance R is included in series with the positive trunk conductor with the result that the marginal relay 386 deenergizes as previously described. The deenergization of the marginal relay 304 completes the -circuit vfor energizing the montior relay 3S? from grounded armature 359 by way of armatures 324 and 32e. Monitor relay Sel, upon energizing, at armature 332 opens the locking circuit of the busy relay 3l! with the result that the busy relay at armatues 35d and 3555 disconnect the busy tone from both the control operator and calling subscriber. At armatures 329 and 33E vmonitor relay del connects the trunk conductors lo l and li. The operators headset is now bridged Yacross the previously established connection and in case the called line is actually in use the operator will hear the conversation and may inform the called subscriber that `he is desired on a new vconnection if the call is urgent. If the call Jis not urgent the control operator will release the monitor key with the result that .the monitor relay deenergizes and again connects the operator to the calling subscriber so that the operator .may inform the calling subscriber that thecalled lline is busy. rlhe calling subscriber will now hang up and the control operator now releases her answering and dial lkey K with the result that relays 363, and 3M deenergize in the manner previously described. Relay 355 in the manner as previously described ldeenergizes after an interval and transmits a release impulse for energizing relay HB2 in the .local connector over the following circuit: from .grounded armature 323i and its resting contact, armature 325,.armature 355 and its resting contact, .conductor 5%, armature i735, and through the `winding of relay e2 to battery. The energization of relay it causes the energization of :relay -lSi :after which the slow-torelease relay .3% deenergizes and opens the cir- .cuit of relay 52 with the lresult that Athe latter relay .now dcenergizes and opens the circuit of hold relay le@ and connecting relay l Q4. The deenergization of hold relay S33-causes the release of .the localconnector in the same manner as previously described. The deenergization of slow-torelease .relaye also returns all the operated relays in the common-equipment to their normal position ready for use in extending another call.

It will now be assumed that the called line is not actually .in use .but is vmarked busydue to the callingandcalled.subscribers kfailing to ring down the v.local :connection and therefore when the operator operates her ymonitor key and does not hearany conversation the operator vill therefore challenge and in receiving no response will operateeither one .of her ring keys after restoring the monitor .key in order to release the locked-up local connector. Responsive to the operation of either .ringing key `the negative ring relayo the fpositive .ring relay Sile will energize in the samernanner as .previously .described to connect ringing .current to either-of the wipers ll or i563. This ringing current .will be extended from wipers l5`l or llll of the local connector now in use from thence over the engaged bank-contacts terminating .the .called lineand frointhence through the wipers corresponding to wipers l5! or 55e of the .other called local connector and from thence through .armatures corresponding to armatures .M4 and 38, the upper left-hand winding of the repeating coil corresponding to RC, through the winding of the alternating current relay corre- .spondingto relay till', through the lower lefthand winding of the repeating coil, through cori responding armature lfl to the wiper corresponding to wiper lt, and thence back over the multiple bank contacts to wiper H54 of the local connector now in use. The alternating current relay in the held connector is thereupon energized by the ringing current and at the cor-responding armature E48 completes a circuit by way of. the corresponding grounded armature lll for energizing the corresponding release relay ld? in the held connector. In the held connector relay lo? energizes the relay 95 and after termination of the ringing current the alternating curr-ent relay lill and release relay m2 deenergize to unlock the hold relay such as relay E83 and the cut-through relay such as relay H35 in the held connecte.: The deenergization of the hold relay m3 in the held connector closes the circuit to the release magnet such as release magnet its whereupon the heldconnector is released in the same manner as previously described. The held connector is therefore released and removes the busy condition from both thecalling and called subscribers at armatures such as armatures i i6 and 139. In the common equipment shown in Fig. 4 the operation of negative ring vrelay Sie@ or positive ring relay 399 in addition to ringing down the held local connector establishes a'circuit for energizing the test relay 3l@ through its lower winding at armatures Sfl vor 3139. Relay 35o, upon energizing, at armature 35% establishes the previously traced locking circuit therefor. The local connector and the-common equipment are now inthe same condition as if the vlocal connector had Vencountered an idle line instead of a busy line and therefore the operation from this point on is just the same as ,previously described in connection with the local connector encountering an idle called line. The operator will therefore operate the proper vringing key in accordance with the code of the called subscriber and when thecalled subscriber answers the operator will restore her answer and .dial key K in order to directly connect the calling and called subscribers together and in-order to release the common control equipment in Fig. 4 to permit the control equipment and the control trunk to 4be used establishing a new connection.

In case the calling subscriber has asked to be connected with a toll operator, then the inst digit dialled by the control operator raises the wipers of the toll connector to a tolllevel whereupon the toll normal post springs PS3 are operated. The operations performed by both the calling subscriber and the control operator are the same as those previously described. The operation of the normal post springs PSE at springs .IE5 prepares a point in the circuit for directively operating the rotary magnet l i8 in a manner to be .more fully described hereinafter. The eperation vof springs l 5l prepares a point in the circuit for relay |65. The operator now dials the second .digit assigned to the toll trunk whereupon the local connector rotates its wipers in the same manner as previously described. The Wipers of the local connector have now been rotated into engagement with the bank contacts terminating the rst toll trunk in the group 'and in case this first toll trunk is busy test wiper |52 will engage a grounded bank Contact with the result that the busy relay 3H will energize

Images