US1801368A - Telephone system - Google Patents

Description

April 21, 1931. E. s. PETERSON ET AL 1,801,358

TELEPHONE SYSTEM Filed Aug. 6, 1928 ll Sheets-Sheet l E. s. PETERSON ET Al. 1,801,368

TELEPHONE SYSTEM Filed Aug. 6, 1928 11 Sheets-Sheet 2 iii April 21, 1931.

April 21, 1931- E. s. PETERSON ET AL 1,801,368

TELEPHONE SYSTEM Filed Aug. 6, 1928 1l Sheets-Sheet 3 Inu'en uns Edward EFE EnEnn Lennard L Fulas April 21,.1931.

E. S. PETERSON ET AL TELEPHONE SYSTEM Filed Aug. 6. 1928 11 Sheets-Sheet 4 Edm ard 5. Fe ersnn Leunar'dLFu les g 51TH.'

April 21, 1931. v E. s. PETERSON ET Al. 1,801,368

TELEPHONE- SYSTEM Filed Aug. 6, 1928 11 Sheets-Shec-:l 5

ImfEnm-E Eduard 5F12 @145cm Lennard 14.5711591125 April 21, 1931- E. s. PETERSON ET AL 1,801,368

TELEPHONE SYSTEM Filed Aug. 6, 1928 l1 Sheets-Sheet 6 TTT??? nuen UT'S Eduard 5.12am Lennard L Euggles April 21, 1931- E. S.PETERSON ET A1. 1,801,358

TELEPHONE SYSTEM Filed Aug. s, 1928 11 sheets-sheet 7 [numanar' Edward D. Fslernn Leonard LEufZeS 11 Sheets-Sheet 8 TELEPHONE SYSTEM Filed Aug. 6, 1928 April 21, 1931. E. s, PETERSON ET AL Leonid .L-fugg April 21, 1931.

E. S. PETERSON ET AL TELEPHONE SYSTEM Filed Aug. 6, 1928 11 Sheets-Sheer?, 9

April 21, 1931- E. s. PETERSON ET AL 1,801,368

TELEPHONE SYSTEM Filed Aug. 6, 1928 l1 Sheets-Sheet 10 TRUNK Edward 5'. FIETD-n LeunamLEugleE E..s. PETERS-ON ET AL 1,801,368

`April 21, 1931.

TELEPHONE SYSTEM Filed Aug. 6. 1928 11 Sheets-Sheet ll k .fsk

% i N u mRE les

Imran c1115 Edward EFE EF an LEnnar'dLEu HIT.'

Patented Apr. '21, 1931 UNITED s'rA'rlisl PATENT oFFlcE EDWARD S. PETERSON, 0F ELMWOOD PARK, LEONARD L BUGGLES, OF WHEATON, ILLINOIS, ASSIGNOBS TO RESERVE HOLDING COMPANY, 0F KANSAS (LI'IL'Y2 MISSOURI,

'A CORPORATION OF DELAWARE lfriimrnonn syscrmfc Application mea August e, 192s. serial 1ro. 291,631.

199,917, filed June 20, 1927, now Patent No.'

1,7 52,543, and in his application Serial No. 237,140, filed December 2, 1927.

In each of the above disclosures, connections are set up between manual magneto lines by automatic switching apparatus responsive to control exercised over an operating trunk extending between the manual magneto exchange and a distant operating center.

One object of the invention is to avoid the use of a finder `for connecting the operating trunk with a local connector on which a call v equipment.

A further object is the production of an arrangement for still further simplifying the connectors by omitting the code selecting devices individual to the respective connectors and by arranging a ringing relay controlled over the operating trunk to respond to control from the operating center which may be exercised by an operators key or otherwise to signal the called subscriber.

It is a further object to arrange the com-r mon sequence-control equipment so that it vcan be used interchangeablyiwith diierent types of connectors so that the same operating trunk equipment may be used in any one of four of exchanges as follows: (a) automat1cr1ng1ng,ringo release, (b) automatic-ringlng battery-holding, (c) keyringing ring-01T release, (d) key-ringing, battery-holding.

Another object is the arrangement whereby an alarm or other abnormal condition arising in semiautomatic magneto exchange (abbreviated S. A. M. X.) results in an alarm call being sent to the operating center over the operating trunk and in the alarm call being switched to a. special operators position in the operating center.

Other objects and features will become apparent upon a further perusal of the specification 1n connection with the accompanying drawings.

.Referring now to the drawing comprising F1gs. 1-1 4, they show by means of the usual circult diagrams a suiiicient amount of apparatus in a telephone system embodying the features of the invention toenable the invention to be understood. Figs. 1-10 are circuit diagrams, while Figs. 11-14 show the way in which Figs. 1-10 should be assembled in order to be understood best. Referring now to Figs. 1-10, Fig. 1 shows the operating-center equipment associated with the operating trun r.

Fig. 2 shows thc emergency operatino' set and the alarm and signal relays in the A. M. X. associated with the operating trunk.

Fig. 3 shows the common i sequence control equipment in which the operating trunks terminate in the S. A. M. X.

Fig. 4 shows a local connector, which is one of a plurality of connectors to which the apparatus of Figs. 2 and 3 is common. The local connector shown in this drawing has access to the line of substation A2 and to al1 the other lines terminating in the S. A. M. X. and is accessible to line switch LS of the substation A1 and also to the line switches in which the other lines terminate. It is assumed that the lines of substations A1 and A2 are party lines, for which reason the lines are indicated as common to several substations by the conventional common connection symbols associated therewith. Fig. 4

shows also the master switch common to the line switch LS and other line switches. It 5 has been assumed that there are more than ten connectors in the S. A. M. X., in which case one line switch group, being limited to ten trunks, cannot reach all the connectors with the result that two line switch groups, cach having its own master switch, have been provided. About half the line switches belong to one group and remaining ones to the other group. The line switch LS is assumed to be aline switch of group #1, and the master switch shown is the master switch of group 1. No line switch of group :#:2 nor the master switch of group #2 is shown, but the connections of group #2 will become apparent as the description progresses.

there are numerous conductors brought out to numbered terminals. These terminals indicate to where the conductor extends, and all terminals bearing the same reference numeral are assumed to be connected together.

The connector of Fig. 4 is arranged for key-ringing and battery-holding, that is, the ringing current is relayed in response to impulses received over the operating trunk from the operating center and when a connector is once seized it is held in a seized condition as long as current is fiowing over the calling line.

Fig. 5 shows a connector similar to the connector of Fig. 4 except that it is arranged for ring-olf release, that is, the connection is not maintained by the flow of current over a calling line, but is maintained until the calling subscriber replaces his receiver and rings off (makes a momentary application of ringing current by turning his crank in the usual manner).

The connector of Fig. 6 is a battery holding connector as is the connector of Fig. 4, but is arranged for automatic ringing instead of for key-ringing, that is, a party selecting digit is received over the operating trunk to set a code selector individual to the connector after the connector is set and the ringing is accomplished locally in accordance with the position of the code selector.

The connector of Fig. 7 is similar to the connector of Fig. 5 except that it is provided with automatic ringing as mentioned above in connection with Fig. 6 instead of with key-ringing as mentioned in connection with Fig. 5.

Fig. 8 shows a toll connector arranged to be operated over a toll trunk from the operating center to set up connections to and from S. A. M. X. lines.

This toll connector is arranged for key ringing so that it may be used in connection with either Fig. 4 or Fig. 5.,

Fig. 9 is a similar tollA connector, except It will be noted that, in Figs. 2, 3, and 4,

that it is arranged for automatic ringing so that it may be used in connection with Fig. 6 or Fig. 7.

Fig. 10 shows the operating-center end of the toll line and may be used in connection with Fig. 8 or Fig. 9.

Referring now to Figs. 11-14, Fig 11 shows how Figs. 1-4 and Figs. 8-10 assemble together for use in a key-ringing-battery-holding S. A. M. X.; Fig. 12 shows how Figs. 1-3, 5, 8, and 10 assemble together for use in a key-ringing-ring-oi release S. A. M. X.; Fig. 13 shows how Figs. 1-3, 6, 9, and 10 assemble together in an automatic-ringing battery-holding S. A. M. X.; while Fig. 14 shows how Figs. 1-3, '7, 9, and 10 assemble together for use in an automatic-ringing ring-olf release S. A. M. X.

Detailed alesmz'ptz'on The invention having been described generally, a detailed description of the operation of the apparatus shown will now be given. For-this purpose it will be assumed that Figs. 1-4, 8, and 10 are assembled as shown in Fig. 11.

Handling a local connectz'fm It will now be assumed that the subscriber at substation A1 desires to converse with the subscriber at substation A2. The subscriber at substation A1 operates the hand generator at his telephone in the usual manner, project ing ringin current over his line to the line switch L inv the exchange. This ringing current passes through the lower windin of line relay 404 of the line switch LS. pon operating, line relay 404 locks itself at its inner upper contact to ground by way of the line switch `alarm conductor leading to terminal 206. Terminal 206 is grounded in Fig. 2 by way of the line switch alarm relay 236, which rela is provided for a purpose to be explained ereinafter. At its upper armature, rela 404 places ground on private normal con uctor 402 so .as to guard the line against intrusion. At its middle armature, relay 404 closes a circuit for the pull-down winding of magnet 405 by way of the openchain conductor extending from the master switch through contacts of all the line switches in series, at the same time disconnecting the open-chain conductor from all the 'succeeding line switches in the chain. If the chain is clear, as shown, the closing of the circuit through relay 405 results in an operation of the delay relay in the master switch, the current for this purpose liowing through the high resistance winding of the delay relay. Magnet 405 cannot energize until the delay relay operates and shunts its low resistance winding around its high resistance winding. This operation is delayed slightly by the short circuited upper winding of the relay so as to give time for a complete restoration\ and realignment of the plunger of any line switch that ma happen to be restoring and realigning at t is time before any line switch is permitted to operate. As soon as tho delay relay operates, it closes a circuit through its up er Winding in parallel with its lower win Ing, whereupon magnet 405 of the line switch operates and forces the springs 408-411 into engagement with their respective associated contacts of the trunk line extended to the local connector shown in the drawings. This is accomplished by arm 406 which arm also disconnects the locking winding of line relay 404 from the alarm conductor 206 and connects it to the common locking conductor 208, which locking conductor is grounded through relay 332 Fig. 3 as' will be ointed out subseuently. The cut-oil' arm 40? is operated to isconnect the lower winding of relay 404 from in bridge of the calling line. As vthe result of the operation of springs 408 and 411, the talking conductors of the calling line are connected to the corresponding conductors of the connector. At contact spring 409, conductor 402 is extended to the normali -grunded release-trunk conductor 413 of t e connector, which conductor at this time isvgrounded at the contacts of relays 435 and 436. At contact spring 416, a ground potential is extended to hold conductor 414, which is a test conductor of the master switch, causing the usual advance of the master switch responsive to t-he operation of the test relay which advances the master e switch by connecting the grounded chain-in conductor 204 to the winding of the locking relay. The test relay also disconnects ground from the lower terminal of the delay relay so as to prevent any further line switch operation at this time. The open-chain relay is operated from contacts ofthe locking relay and opens Ya further point in the chain circuit extending to the line switches, at the same time placing a shunt around its normallyopen upper winding so as to make the relay slow acting in order to keep the chain open for a slight interval after the master switch.

' has inished its operation. The actual movement of the master switch segment takes place at this time in a counter-clockwise direction under the control of the usual U spring (not shown).

When the master switch advances to a new position, the test relay falls back provided the trunk #2 is idle permitting the locking relay to fall back and catch and hold the master switch in this position. The open-chain relay falls back a moment later, placing the master switch in normal condition, the delay relay having fallen back responsive to the opening of the chain occurring upon the operation o the test relay.

n the connector, the connecting relay 437 operates over hold conductor 416 from the ground potential supplied thereto through ,contact spring 410 and through contacte of rela 436. Upon operating, relay 437 operative y associates the associated connector with tFhe cgmmon sequence control equipment of When the locking circuit of line relay 404 is transferred from the alarm conductor 206 to the common locking conductor 208, as above pointed out, the lower windin of relay 332 is operated over the common locin conductor (see terminal 208 Fig. 2) throng contacts of relay 335. Relay 332 at its inner armature disconnects the inner terminals of the associated left-hand repeated coil windings from ground and connects them to battery through the differential relay 333 and the upper winding of impulse relay 334. This ope-ration places battery through relays 333 and 334 on both conductors of the operating trunks with a result to be pointed out subsequently. As a further result of the operation of relay 332, the two chain control relays of the master switches of the two groups are energized at the two lower armatures by ground potential applied to terminals 205 and 214. Terminal 205 is connectedlto the openchain relay of the master switch shown in Fig. 4, while terminal 214 is connected to the corresponding rela in the second group. This operates the bot open-chain relay so as toprevent further line switch operation until the call being handled has taken its regular. course.

At armatures 349 and 350, relay 332 removes ground from the alarm-ground conductor and from the ground-control conductor for a purpose to be hereinafter explained, while at its upper contacts relay 332 connects up the condenser between the inner terminals of the right hand repeating' coil windings, thereby preparing a talking circuit.

As a result of the connecting of the battery potential through relays 333 and 334 to the minus and plus trunk conductors of the operating trunk, a current iows over the two conductors of the operating trunk in parallel to ground over a circuit path to be traced subsequently, bringing about an energization of line relay 334. Differential ringing control relay 332, however, does not operate owing to the fact that the current flow in one winding counterbalances the flow in the other winding. Upon operating, relay 334 closes a circuit for release relay 335 in series with. the series relay 336.

Relay 335 operates and at its inner lower armature closes a "locking circuit for itselr` through the inner lower contacts of relay 340, thereby preparing an operating circuit for series relay 336 and an impulsing circuit through the lower armature, normal, of relay 342 for the vertical magnet of the local connector #1 which is now connected to conductor 303 through contacts of connecting relay 437. Due to the fact that the vertical magnet is now shunted around the series relay 336, this relay does not operate in series with the relatively high resistance release relay 335. At its inner upper armature, relay 335 prepares locking circuits for relays 341 and 342, while at its upper armature it closes a circuit for the slow acting clear-out control relay 334, which relay operates and prepares a circuit for clear-out relay 345. At its lower armature relay 335 -closes a local circuit for relay 332 through resistance 352, opening the initial circuit, whereupon the line relay `404, Fig. 4, falls back. The` circuits in the S. A. M. X. are now prepared for operatin local connector in accordance with the esired number.

In the operating center, line relay 111 is normally connected between ground and the lower conductor of the operating trunk by way of contacts of relays 101, 104, 105, and 113, and is connected with the upper conductor of the operating trunk through contacts of relays 102 and 103 in parallel, the upper winding of differential relay 115 being in series with the upper operating trunk conductor and the lower winding being in series with the lower operating` trunk conductor.

Relay 111 energizes when the battery potential is applied to the operating trunk in the S. A. M. X. as above pointed out, but the differential relay 115 does not operate at this time. Upon operating, relay 111 grounds the locking conductor 131 at its upper armature; closes at itslower armature a circuit for relay 112 from ground .through armature 119 of relay 102, and contacts of relays 115 and 114. This circuit is completed to battery through the inner upper contacts of relay 114 and the operating magnet of the sender selector. At its inner upper contacts, relay 111 connects the test wiper of the sender selector tothe junction of the winding of the operating magnet and winding of relay 112, with the result that the operating magnet is operated directly from the test wiper in case the sender on which the sender selector is standing is busy, the switching relay 112 being short circuited in this event. The self-interrupting operating magnet operates in a buzzer-like manner and advances the wipers of the sender selector until an idle sender is reached. Assuming that the sender yshown in the drawings is the first idle one reached, the wipers of the sender selector stop thereon owing to the absence of ground potential on the test contact thereof, whereupon relay 112 operates in series with the operating magnet, but the operating magnet does not o rate at this time owing to the relatively high resistance of relay 112. Upon operating, relay 112 disconnects the test wiper from the junction of its own winding and that of the operating magnet connects it to ground instead, thereby grounding the test wiper of the sender selector so as to make the seized sender busy to the other sender selectors. At its remaining armatures, relay 112 connects up ,the corresponding wipers of the sender selector.

The impulsing wiper is now grounded at the impulse contacts of the sender, with the result' that a circuit is now closed from the grounded impulse contacts through the impulse wiper of the sender selector, armature 120, relay 110, contacts of relays 109 and 108, and contacts of relay 105' to battery through winding of relay 105. Relays 105 and 111 operate in this circuit and relay 105 closes a locking circuit for itself at its inner upper armature to the locking conductor 131 through contacts of relay 104. At its lower armature, relay 105 opens a point in the circuit of the release magnet of the code switch, at the same time preparing a circuit for relay 106. At two upper armatures, relay 105 disconnects the simplex leg ofthe operating trunk from relay 111 and connects it instead to ground by way of repeating relay 110, closing a local holding circuit for relay 111 through resistance 116. Relay 110 now remains energized over the operating trunk.

As a result of the ,grounding of the test conductor of the sender through the test wiper of the sender selector, circuit arrangements with which this invention is not concerned are brought into play to cause the operator to be signalled and to cause the contacts in the sender to close the connection through to the operators headset.

The operator now converses with the calling subscriber in the usual manner and ascer tains the desired number. Under the assumption that the subscriber desired `is the subscriber at substation A2Fig. 4,'the operator receives the number of this subscriber, which number may be, for example, 115, the final digit indicating the particular party on the line. The operator is provided with a key set (not shown) for controlling the sender. Upon learing the number the operator manipulates her key-set in accordance therewith and pushes the start key thereof, whereupon her headset and keyset are automatically disconnected from the sender and the transmission of impulses begins.

When the first digit 1 is retransmitted by the sender at the impulse-sending contacts thereof, relays 110 and 334 respond, and re lay 110. closes a circuit for series relay 106 through the lower armature of relay 105. Relay 106 operates and closes a circuit for the upper winding of the two-step relay 107, whereupon relay 107 operates its first step locking contacts to lock itself to a branch of the grounded locking conductor 131 through the lower contacts of stop relay 104. No current flows in this locking-circuit as long as the initial circuit remains closed at the contacts of relay 106. However, when relay 106 falls back at the end of the first digit and opens the initial circuit of relay 107 bothy windings energize in series, operating the relay through its second step to transfer the operating circuit, at the upper contacts of the relay, to relay 108.

As a result, relay 108 operates through its hrst ste at the beginning of the second digit Al and w en relay 106 again falls back at the end ot the second digit 1, relay 108 operates through its second step. At its lower contacts, relay 108 connects the rotary magnet of the code switch in parallel with series relay 106 so as to enable the code switch to respond to the stations-selecting digits. At its inner upper armature, relay 108 transfers the relay operating circuit to relay 109, while at its two upper armatures it shifts the upper terminal of relay 110 to battery through the resistance 117 and applies a holding ground to the operating trunk conductor so as to maintain the established circuit conditions in the S. A. lli/l., X.

W hen the station digit 5 is retransmitted, it is repeated hy relay 110 to the rotary'inagnet of the code switch in parallel with relay 106, with the result that the code switch is advanced live steps and its wiper contesto rest on the tth code conductor. Relay 103 responds to the first of the series ot impulses and, being slow acting, remains operated 1throughout the digit. When relay 106 operates it closes an operating circuit :for the upper winding of the two-step relay l0@ which operates through its lirst step, and, when relay falls back, it operates through its second step. At its lower contacts, relay 109 connects the pick-up conductor of the code machine to piclrfup relay 102; at its middle lower armature' it disconnects the rotary magnet of the code switch from in multiple with the series relay 103; and at its upper armature it opens the circuit et relay which 4falls back and again operates through relay 106 but without any particular result at this time.

Before proceeding further with the description of the operation in the operating center, it will be well to take up the operation in the S. A. M. Y..

When the irst digit 1 is transmitted hy the sender, line relay 334 ot the common sequence-control equipment, Fig. 3, falls back and delivers an impulse to the vertical inagnet of local connector #1, Fig. 4, over a circuit path which starts from ground through the inner lower contacts of relay 340 and includes the inner lower armature of release relay 335, normally closed contacts controlled by the armature of line relay 354, lower armature, normal, of relay 342, vertical operating conductor' 303, and contacts of connecting relay 437 to the vertical magnet. The vertical magnet responds by raising the associated wipers opposite the first level of bank contacts. When this occurs, the off-normal contacts associated with the release magnet of the connector operate to prepare a circuit for the release magnet, which circuit is now open owing to the factthat relay 434 is energized from the'contacts of line relay 432 which is energized over the calling line in series with battery feed impedance 431. At the off-normal contacts associated with conductor 415, an additional guarding otential is placed on the trunk line as regar s to the master switch, by way oithe lower test bank of the master switch.

In the common sequence-control equipment,.the series relay 336 is operated in parallel with the vertical magnet of the connector, being so designed with respect to the vertical magnet and release relay 335 that it will operate and remain operated through out a series of impulses. "Upon operatin series relay 336 closes a circuit 'for the auxi iary relay 337 at its upper armature, whereupon relay 337 operates and closes at its upper armature a circuit for relay 342 which operates and locks itml to the call-lamp Vconductor at itsv .upper armature, preparing a circuit "lor relay 342 at its lower armature. lt will he noted that the release relay 335' is short circuited each time an impulse is deliyered to the magnet operating circuit and to series relay 336. v This does not result in a deenergization of the release relay during a series of impulses because a short circuitecl relay is slow to fall back as is well lmown.

`EWhen the rst digit is terminated, relay 333 falls hack, followed hy the deenergization of relay 337. At its upper armature, relay 337 completes the circuit oie relay 342 through the lower contacts ora relay 343. Relay 342 operates and locks itself to ground through the inner upper armature of release relay 335, opening its initial circuit. At its upper armature, relay 342 opens the locking circuit of relay 343, which relay talle back. At its lower armature, relay 342 shifts the impulse conductor from the vertical magnet to the rotary magnet.

When the second digit 1 fis-received over the operating trunk from the sender in the operating center, line relay 334 again alls hack momentarily, delivering another impulse to series relay 336 and over the operating conductor to the connector. Since relay 342 is operated at this time, the impulse is delivered through the lower armature, operated of relay 342, armature 355, normal, lower armature of relay 388 rotary operating conductor 304, and contacts of connecting relay 437 to the rotary magnet. The rotary magnet responds and rotates the wipers of the connector into engagement with the contacts in which the line of substation A terminates. i

It will be noted that the test wiper of the connector is now connected through contacts of relay 437 and by way of test conductor 311 to the lower armature of series relay 336. With series relay 336operated during the rotary movement of the connector, the test conductor is extended to the winding of the busy test relay 340. In case the line is busy, relay 340 is energized from ground on the busy test contact when the wipers come to rest upon the bank contacts of the called line, with the result thatv when series relay 336 falls bac-k it closes a locking circuit for the busy relay from the grounded call-lamp conductor throu h the inner upper armature, normal, of re ay 338, inner upper armature operated, of busy relay 340 normally closed contacts controlled by the lower armature of relay 336, and the middle lower amature of relay 338.

When the auxiliary relay 337 falls back, responsive to the energization of series relay 336, with busy relay 340 operated, the busytone source is connected through contacts of rela s 341, 340 and 337 to the lower talking con uctor, the upper talking conductor being grounded at this time' by contacts of relay 340, giving a busy tone to the calling subscriber to inform him that the called line is busy. Upon hearing the busy tone, the. callin subscriber is expected to replace his receiver and allow the equipment to clear out.-

Assumin now that the desired line is idle when calle there is no ground potential encountered upon the test contact of the line by the test wiper of the connector when it lands thereon, and busy relay 340 does not operate. In this case, when series relay 336 falls back it connects the test conductor of the connector at its lower armature to ground by way of the upper winding of test relay 341, this upper winding being grounded at this time by way of contacts of relays 340 and 338 to the call-lamp conductor.V

As a result, relay 341 energizes over the test conductor of the connector and through the -private normal conductor of tliecalled line in series with the bridge-cut-oif winding of the called line switch corresponding to the brid e-cut-oii windin the lower winding, of tie line switch L The bridge-cutoil winding energizes and clears the called line. Relay 341, upon operating, closes a locking circuit for itselr1 at its inner lower armature through the inner upper armature of release relay 335; extends the ground potential on the called lamp conductor through contacts of relay 338 to the test wi per at its arm'ature 353 so as to place a more direct ground potential on the test conductor of the called line; disconnects the operating conductor from the rotary magnet at armature 355 and connects it to the code-selector operating conductor 312; and prepares the ringing circuit at armature 356.

From the foregoing it will be seen that the connector has now been positioned on' the contacts of the desired line, that the line has been seized, and that the ringing circuit has been pre ared and is now under the control of the di erential relay 332.

Returning now to the circuits in the operating center, the operation therein has been described to the point where the pick-up conductor from the common code machine has been connected through contacts of relay 109 to pick-u relay 102. The code machine is shown on y diagrammatically, but it will be understood that the contact springs shown are operated in the proper sequence so that the pick-up conductor is grounded first, following which the various other contacts are operated in accordance with codes assigned to the positions of the code switch, after which the stop conductor is grounded.

Now, when the pick-up conductor is grounded after relay 109 has operated, a circuit is closed for pick-up relay 102, which thereupon operates and locks itself throu h the lower armature of stop relay 104 to t e grounded locking conductor 131. As a further result of its operation, relay 102 prepares a circuit for stop relay 104 at its lower armature; removes a shunt from the upper con-v tacts of ringing' relay 103 at its upper armature; closes a circuit for relay 101 at its inner upper armature; and at armature 119 opens the circuitof switching rela 112 associated with the sender selector, w ereupon relay 112 falls back and frees the sender selector. As the result of the closure of the circuit for relay 101, this relay operates and opens the circuit of relay 111 at its upper contacts. Relay 111 falls back after a short interval and removes ground at its upper armature locking conductor 131, but this conductor is now maintained grounded through contacts of the relays 102 and 101. The lower winding of ringing relay 103 is now connected through the. inner lower contacts of relay 102 to the wiper of the code switch which is standing on the #5 code conductor and therefore receives the impulses corresponding to the #5 code. Each time one oi these impulses is delivered, relay 103 operates and opens the circuit through the upper winding of the differential relay 115 and over the upper conductor of the operating trunk, permitting the differential relay 115 to operate, but without any particular result at this time since its armature is ungrounded at armature 119 of relay 102.

In the S. A. M. X., differential relay 333 operates each time the line is unbalanced as above pointed out. Each time it does so, it applies ringing current at its lower armature and through armature 356 to the minus ringing conductor which is now connected through contacts of connecting relay 357 to the minus wiper of the connector, and at its inner armature it applies ground to plus ringing conductor 308 which is now connected through contacts of connecting relay 437 to the plus Wiper of the connector. The di'erential rela restores each time a ringing impulse is en ed. As the result,ringin current isy placed on the called line by the di erential ringing relay 333 in accordance with the code placed on the #5' code conductor by the code machine shown in Fig. 1.

When the stop conductor of the code machine is grounded at the end of the code period, stop relay 304 is energized over the stop conductor through contacts of pick-up relay 102. Upon operating, relay 104 locks itself energized through contacts of ringing relay 103 at its inner lower armature; unlocks piola-up relay 102 and counting relays 107-109 at its lower armature; unlocks relay 105 at its inner upper armature; and at its upper armature it extends a connection from the upper winding of relay 103 throu h the normally closed contacts controlled gy the middle upper armature ot relay 105 and through normally closed contacts controlled by the upper armature relay 113 to the lower operating-trunk conductor, a parallel con'- nection being extended to the upper operating-trunk conductor through contacts oi relays 102 and 103. y

.hs a result of thisapplication of battery potential to the operating trunk, instead of the ground potential previously applied thereto, through the middle upper armature oia relay 108 and the middle upper armature of relay 105, line relay 334 in the S. A. M. X. Fig. 3 i'alls back and relay 103 in the operating center does not operate at this time. Upon falling back, line relay 334 places a shunt around release relay 335, incidentally operating series relay 336.

locks relays 341 and 342 at its inner upper armature; removes ground at its upper armature from the call lamp conductor opening the circuit ot the clear-out control relay 344, but this relay, beingv slow-acting, does not fallback immediately. As a result, the upper armature of relay 335 closes a circuit through the inner upper armature of relay 344 :tor clear-out relay 345. switchin relay 341 has been energized, relay 346 has een energized by the upper armature of the switching relay through the'inner armature of relay 347, and, being slowacting, is still operated at this time. That being the case, when relay 345 operates through contacts ot relay 344 it extends a momentary impulse to the switch-through conductor 307, operating the switch-through relay 436 through contacts ofthe connecting relay 437. Relay 436 locks itself to the grounded conductor 414, at the same timel opening the circuit of connecting relay 437. Connecting relay 437 thereupon falls back and disassociates the local connector #l from thecommon sequence-control equipment. At its inner upperarmature, relay 436 Release relay.` 335 falls back after a slight interval and un? Sincel opens the normal ground connection to condoctor 413, but this ground connection has been replaced previously by a connection through the upper armature of the operated relay 434. At another of its upper armatures, relay 436 opens a pointin the circuit of the release magnet; at another upper armature i-t removes ground at one point from the alltrunks-busy conductor, and applies ground directly to the test wiper of the connector to replace the ground potential removed therefrom upon the deenergization of relay 437; and at its upper and lower armatures it connects the incoming minus and plus conductors 412 and 416 to the borresponding Wipers of the connector, thereby completing the talking connection between the calling liney and tle called line.

In the common sequence control equipment in Fig. 3, relays 344 and 346 fall bach aiter an interval but produce no further result. As a further result of the deenergization of the release relay 335 of the common sequence control equipment, the locking circuit of relay 332 through resistance 352 is opened, whereupon relay 332 falls back and replaces ground' on both conductors of the operating trunk, at the same time removing ground from both cham control conductors at its lower armatures so as to permit the open chain relay of each of the two master switches to tall back and allow calls to be made.

It may be pointed out that in case the clear-out condition is performed :following a busy condition of the called line or in case of a false call, the switching relay 341 is not operated, in which case relay 346 is not operated through the upper armature of relay 341, and the clear-out impulse is passed to the release conductor 306 instead of to the switch-through conductor. In this case, the release impulse comes in and locks up the connecting relay 437 by means ot its left hand winding, at the same time closing a circuit for the slow-acting release relay 435. Relay 435 in this case removes ground from conductor 413 and brings about the release of line switch and connector in a manner to be pointed out hereinafter. When the release pulse ends, the circuit of relay 435 is opened and relay 437 falls back to disconnect the connector from the common equipment.

In the operating center, relay 103,- Fig. 1 now energizes over the operating trunk because ground potential is now applied to both operating trunk conductors and it removes ground potential from the locking circuit of stop relay 104, permitting the stop relay to fall back and restore the simplex leg of the operating trunk to its normal path to ground by way of line relay 111 in readiness for the next call over the operating trunk.

When the conversation is completed, the

calling subscriber replaces his receiver, whereupon current flow over conductors 401 and 403 and through impedance 431 and relay 432 ceases, permitting relay 432 to fall back and open the circuit of relay 434. Relay 434 falls back after ashort interval and removes ground potential from conductor 413, relay 436 being operated at this time. When the ground potential is removed from conductor 413, magnet 405 of the line switch is deenergized and the line switch restores to normal. When the contact spring 410 breaks engagement with the associated contact, it removes ground from the hold conductor 414, opening the circuit of cut-through relay 436 of the connector, which relay thereupon restores and completes the release magnet circuit through contacts of relay 434 and the offnormal contacts associated with the release magnet. The release magnet nowenergizes from the battery potential supplied thereto over the release signal conductor 201 through the release relay 231, Fig. 2. When the nor mal position of the switch is reached the release magnet circuit is opened and the release magnet deenergizes. The operation of the release signal relay 231, Fig. 2, will be explained hereinafter.

Han-(lling an outgoing toll call It will now be assumed that the subscriber at substation A desires to set up a connection to a line outside of the S. A. M. X., which connections are handled by the toll operator.

In order to do this, the subscriber removes his receiver and causes his line switch LS to operate and seize a connector in the hereinbefore described manner, the local connector .#1, Fig. 4, for example, whereupon the local connector is associated with the common sequence control equipment by the operation of relay 437 as hereinbefore described and the operating trunk is placed in calling condition as before.

lVhen the operator is signalled by the operation of the sender selector of Fig. 1 seizing a sender, she converses with the calling subscriber and learns the destination of the call. The call subscribers are usually instructed to ask for long distance. The operator now sets up the digit 0 on her key-set whereupon the sender retransmits the digit and switches through by means of its switchthrough contacts. lfVhen the switch-through operation is performed under this condition, counting relay 109 has not been operated anda circuit is closed immediately through contacts of the operated relay 112 and the nonoperated relay 109 for the stop relay 104. Relay 104 operates to clear-out the equipment in the manner described hereinbefore.

In the S. A. M. X., the single digit 0 is conductor 303 as described hereinbefore.

This operates the local connection #l of Fi 4 until its wipers stand opposite the tent level of bank contacts. When the tenth level is reached, the 0level springs of the connector close and extend ground through contacts of connecting relay 437 to the 0level conductor 310, operating the 0level relay 338 so as to alter the circuits of the common sequence control equi ment to ermit a hunting action on the tent level. his operation of relay 338 occurs upon the receipt of the tenth impulse by the connector and while series relay 336 and the series axiliary relay 337 are still operated. With relays 337 and 338, operated, a circuit is closed from the call lamp conductor, which is grounded at the up per contacts of relay 335, through the innerupper armature operated of relay 338, inner upper armature of relay 337, and the inner lower armature of relay 338 for stepping relay 339. Upon operating, relay 339 prepares a circuit for the rotary magnet of the connector over the rotary conductor 304 at its lower armature, and at its inner lower armature it locks itself energizedby grounding the test wiper of the connector by way of the test conductor 311. This locking circuit includes the interrupter contacts of the rotary magnet of the connector, contacts of relay 437, interrupter conductor 305, and the inner lower armature of 0level relay 338.

0level relay 338 closes at its upper contacts a holding circuit for line relay 334 through contact of relay 341 so as to hold up the clear-out operation until an idle trunk is selected.

When series relay 336 falls back at the end of the digit, it opens the circuit of relay 337, whereupon relay 337 falls back and starts the rotary movement by closing at the normally closed contacts controlled by its inner upper armature a circuit from the grounded call-lamp conductor through the inner upper armature, operated, of relay 338 for the rotary magnet through the lower contacts of stepping relay 339 and over conductor 304. The rotary magnet of the connector shown in Fig. 4 operates and advances the wipers into engagement with the first Set of bank contacts in the tenth level and, near the end of its stroke, opens its interrupter contacts, deenergizing stepping relay 339. Relay 339, on falling back, opens the circuit of the rotary magnet, whereupon the rotary magnet falls back again and closes its interrupter contacts.

The further operation depends u on If the trunk line extending from this set of bank contacts is busy, a ground potential is encountered on test contact thereof by the test wiper of the connector, furnishing a reoperating circuit for the stepping relay 338 through the interrupter contacts and the inwhether the trunk line terminating in the rst set of bank contacts is busy or idle.

continuos until an idle trunk line is reached,l

which trunk line may be assumed is the one comprising conductors 804-807 and extending the toll connector shown in Fig. 9. When this trunk line is reached, no ground potential is encountered by the test wiper of the connector and the stepping relay 339 does not again operate. As the result, switching relay 341, whose upper windingyhas been short circuited by the ground potential encountered on busy test contacts, now operates in series with stepping relay 339 over the interrupter and test conductors in series and through the interrupter contacts of the relay magnet. Upon operating, relay 341 causes the switch-through operation before described and opens at its upper armature the holding circuit of line relay 334, permitting the equipment to clear-out as before.

Responsive to the seizure ot the trunk line comprising conductors 304-807, ringing relay 821, Fig. 3, responds to the ground potential extended thereto over conductor 805 through the test wiper of the connector shown in Fig. 4 and through contacts of relay 828 and 824 and applies ringing current to the toll trunk. Relay 821 also closes a circuit lor the vibrating-type relay 823 which operates and vibrates yits contacts 'for awhile after which the contacts come firmly into engagement allowing the slcw-to-operate relay 824 to pull-up and shift the energizing ground potential from relay 821 and lock relay 824 energized. Relays 821 and 823 now fall back and the application of ringing current is ended.

ln Fig. 10, the ring-up relay 1003, which is shunted around the condenser associated with the lett-hand repeating coil winding and connected in series with another condenser of similar capacity, responds to the-ringing current and locks itself mechanically subject to the operation oi cut-oil relay 1002, byk the standard interlocking arrangement used in connection with ring-up and cut-od relays. Upon operating, relay 1003 closes a circuit for the busy lamp at the toll board and the busy lamp at the special position and also closes a circuit for the call-lamp at the toll board.

Upon perceiving the lighted condition of the call-lamp, the toll operator inserts the plug of an idle cord circuit into the jack J2, whereupon the marginal sleeve relay 1001 opcrates over the sleeve of the plug and jack, and the cut-od relay 1002 is operated from the upper jack. contacts to extinguish the ca ll lamp and close an alternate circuit for the busy lamp to replace the circuit opened when relay 1003 falls back responsive tobeing unlocked mechanically by relay 1002. 'Ihe cord circuit used by the toll operator is such that no difference of potential is now brought about across the talking conductors so that relay 1005 does not operate at this time.

Incidentally, relay 1002 at its inner lower armature connects the left hand repeating coil inner terminals directly together and at its lower armature grounds the tied-together inner terminals of the repeating coil, operating line relay 827 of the connector of Fig. 8 over the two conductors of toll trunk in parallel, and through the twowindings of the diierential relay 826. Release 827 is operated by line relay 826, and at its upper armature applies ground to release trunk conductor 805 so as to maintain this toll trunk guarded as long as the operator has her plug in the' jack at the toll board. Incidentally, relay 824 falls back at this time.

The toll operator now converses with the calling subscriber and completes the toll connection immediately in ease it is to a near-by line. lin case the call is to a line that cannot be reached immediately, the toll operator request the calling subscriber to replace his receiver and he is recalled when the connection is ready to the distant line and the recall is handled in the same manner as an incoming toll call, which will be described in detail hereinafter.

When the calling subscriber at substation A1 replaces his receiver, the local connector of llig. 4 releases in the manner hereinbetore pointed out.

"When the operator at the toll board shown in Fig. 10 removes her plug from the jack J2, the relays associated with the jack fall back and the simplen7 circuit over the toll line is opened, permitting line relay 826 and release relay 827 ot the toll connector to fall baclr and remove the guarding potential from conductor 805. There is an incidental operation of the vertical and release magnets of the toll connector at this time as may be observed from an inspection.

Handling an fn/coming oZZ call lt will now be assumed that the operator at the toll board shown in Fig. 10 receives a call intended 'for the line of substation A2, Fig. 4. ln order to complete this call to the line of substation A2, the operator inserts the calling plug of a cord into the jack J2, assuming that the toll trunk shown is idle as indicated by the unlighted condition ci' the associated busy lamp, whereupon relays 1001 and 1002 operate through the sleeve of the plug and j ack and through the upper contacts of the jack, respectively. Relay 1002 lights the busy lamp as before and closes the simplex circuit by shunting the condenser associated to the right-hand repeating coil windings at its inner lower armature and by ill

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