US1772690A - Telephone system - Google Patents

Description

N. H. SAUNDERS k FQ III Aug. l2, 1930.

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N. H. SAUNDERS TELEPHONE SYS TEM Filed Dec. 10 1926 Y il@ Ullllll llll Q vfll-... OLE i 8 Sheets-Sheet 2 Aug. 12, 1930. N. H. sAUNDERs 1,772,690

TELEYHONE SYSTEM Filed Dec. l0, 1926 8 Sheets-Sheet 3 mfen al" Norman H. Eaunder's HTH:

Aug. l2, 193). N. H. sAuNDERs TELEPHONE SYSTEM 8 sheets-sheet 4 Filed Dec. 10, 1926 Im Norm an H. Saunders MKM@ A Aug. l2, 1930. N. H. sAUNDERs TELEPHONE SYSTEM Filed Deo. 10. 1926 8 Sheets-,Sheet 5 Imran nr' Norman H. Saunders Man-H;

Aug. 12, 1930.

N. H. SAUNDERS TELEPHONE SYSTEM a sheets-sheet s Filed Dec. 10, 1926 1| I||d H .nl rl llll @w11 x urn MT wi m 1 r El# ILFI n Mad Im?? Norman HEam-lder's MAME@ US- 12, 1930. N. H. sAuNDERs 1,772,690

TELEPHONE SYSTEM Filed Dec. 1o, 192s a sheets-sheet 7 'Norman H Saunders Aug. 12, 1930. N. H. sAUNDERs TELEPHONE SYSTEM Filed Dec. 10 1926 8 Sheets-Sheet 8 Inu'en n Norman HEamder's MHH-:

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s. .IM i w3 E n NNN SN N Emma m M l TI w I I 4w-1||lNI| S L@ ma SN m.. .E oo h Patented Aug. 12, 1930 UNITED STATES PATENT-QFFICE NORMAN 1I. SAUNDERB, 0F HOMEWOOD, ILLINOIS, ASSIGNOB TO RESERVE HOLDING COMPANY, OF CHICAGO, ILLINOIS, A COBPOBATIONOF DELAWARE v'rnnrrnorin SYSTEM Application led December 10,1926. Serial No. 153,791.

The present invention relates to telephone systems in general, but is concerned more particularly with the production of a new and improved apparatus for use in tele- 5 phone systems for supplying service to net works of small telephone exchanges, although many of the new features are not confined therto.

One feature of the invention has to do with 1o the production of an arrangement for freeing the central office equipment in an automatic exchange when one subscriber on a local battery party line operates his hand generator to signal another subscriber on the same line.

Other features of the invention have to do with the production of new and improved circuits for connector switches for use in extending connections to party lines of the 2o local-battery simplex-dialing type.

Another feature of the invention is concerned with the provision of a new and imv proved code-generating device for generating the codes necessary -to signal the various party-line subscribers to which connnections are extended.

Another feature is directed to the provi-4 sion of a new and improved trunk circuit for use `on a trunk line seized by an automatic selector switch and extending to an operators position. The trunk circuit automatically projects ringing current out over the trunk line to signal the distant operator and cuts off the ringing current when the operator responds.

The foregoing and other features of the invention may be understood best from a further perusal of the specification in connecticn with the accompanying drawings comprising Figs. 1-9.

Referring now to the drawings, Figs. 1-7 show by means of the usual circuit diagrams a suilicient amount of apparatus in a telephone system embodying the features of the invention to enable the invention to be understood; Fig. 8 is a trunking diagram which shows a telephone net work comprising four exchanges interconnected by trunk lines; and Fig. 9 shows how Figs. 1-7 should be assembled together.

Considering Fig. 8 in detail, the four exchanges shown are A, B, C, and D. Exl changes A and B are automatic exchanges and each has an ultimate capacity approaching a thousand lines, there being a single order of selectors in each oflice. The exchange C is a manual exchange of the common-battery type, and two way trunk lines are provided connecting this exchange with each of the other three exchanges. And ex- 50 change D is an automatic exchange having a capacity approaching 100 lines, this exchange being provided with connectors only.

It is assumed that exchanges A and B are located relatively close to one another, and that telephone service between these two exchanges is charged for at the same rate as telephone service local to either exchange, there being no extra charge for inter-exchange trunking. It is assumed that ex- 7U changes C and D are more or less remotely situated from exchanges A and B and from each other, and that there is an extra charge for service between either of the exchanges C and D and any other exchange. And it is 7" assumed that exchange C is of relatively small size and that the same operator handles calls local to the exchange C and also calls involving the exchange C either as a switching point or as an originating point or ter- 8 n unating point for inter-exchange connections.

Upon reference to exchange A, it will be noted that the line of the telephone T1 ter- .minates at the exchange in the lineswitch LS1 85 and also in the bank of the connector Cl. The selector S1 is one of a number of selectors for handling calls originated by the lines such as the line of substation T1. The bank of the selector S1 -is multiplied with the 90 banksof the incoming selectors S2 and S3. These selectors have access on the fifth level to a group of connectors of which the connector C2 is one, and they have access on the sixth level to a group of connectors represented by the connector C1. It is assumed that the line of substation Tl is accessible through the twenty-first set of contacts in the bank of connector C1, being line number 621.

Referring to exchange B, it will be noted 10 that the layout of this exchange is the same as that of exchange A, the selector S6 being a local selector, and selectors S4 and S5 being incoming selectors. Connector C3 is reached from the fifth level of the selectors, and connector C4 is reached from the sixth level. The line of substation T2 is assumed to be reached through the first set of contacts in the second level of the connector C4, being line number 621.

Re arding connections between exchanges A an B, it will be noted that there is a twoway trunk line TLB extending between the repeaters R1 and R2. This trunk line is one of a roup provided for extending connections etween the two exchanges. This trunk line may be seized at the A-exchange when a selector in the A exchange is operated to the third level, the repeater R1 being interposed to repeat the dialing impulses and to provide a holding circuit for the selector and ineswitch involved in the connection. 1n making a call from exchange A to exchange B, the subscriber dials the same number that would be dialed by a subscriber in exchange B to obtain the same connection, except that the subscriber in exchangeApreiXesthe digit 3 to operate a selector in exchange A to extend connections to an incoming selector in exchange B. In a similar way, calls originated in exchange B and intended for lines terminating in exchange A are handled through a trunk line and an incoming selector such as the trunk line TL3 and the selector It will be noted that the trunk line TLl extends between the trunk circuit TC1 in exchange A and the jack J2 in exchange B. This trunk line is a two way trunk line, and the selector S2 in exchange A may be operated over this trunk line when the operator in exchange C makes connection through the 'ack J2. The trunk line TLl may be seized y a selector in exchange A through the fourth level, whereupon the trunk circuit TC1 applies ringing current to the trunk line to signal the operator in exchange C. Similarly, the trunk line TL2 is a two-way trunk line connecting exchanges C and B, terminating at the exchange C in the jack J4 and passing through the trunk circuit TC2 in exchange B to the fourth level of the selector bank and to selector S5.

The trunk line TL4 extending between exchanges C and D terminates at exchange C in the jack J3, and, when it is seized through this jack, the line switch LS3 in exchange D is operated to extend the connection to an idle connector, such as the connector C5. When this trunk line is seized in exchange D by a connector, ringing current is projected out over the trunk line by the connector to signal the operator at exchange C.

Referrin now to Figs. 1-3, it will be noted that these rawings show the circuits of the equipment necessar to set u `the connections between the telephone su station T1 of exchange A and substation' T2 of exchange B. This equipment comprises the lineswitch LS1 and the selector S1, Fig. 1, the repeater R1, trunk line TL3, the-repeater R2 and the selector S4, Fig. 2, andthe connector C4, Fig. 3. Since the circuits of the selector S4 may be the same as the circuits of the selector S1 the selector S4 has -been indicated by a dotted rectangle.

It will be noted that Figs. 1, 2, 5, 6, and 7, show apparatus for extending a connection from the substation T1 of exchange A to the substation T4, of-exchange D. This apparatus includes the lineswitch LS1 and the selector S1, Fig. 1, the trunk circuit TCl and the trunk line TL1, Fig. 2, the trunk circuit TC3 and the cord circuit CC, Fig. 5, the trunk circuit TC5, the trunk line TIA, and the lineswitch LSB, Fig. 6, and the connector C5, Fig. 7.

The apparatus shown in Fig. 4 is the relay device for generating the ringing codes for operating the ringing relays 1n the connectors to signal the party line subscribers. Although only the code-generating device in exchange B has been shown, it will be understood that a similar device is provided for exchan e A and another device is provided for exc an e D. It will be noted that the ringing-co e conductors shown in Fig. 4 extend to the right-hand edge of the sheet and terminate there in circles labeled 1-10. These circles indicate terminals that are to be connected to the corresponding bank terminals of the Various code-selecting switches of the connectors in exchange B, such as the code-selecting switch CS4 of the connector C4, Fig.- 3, the bank wires of the switch CS4 being provided with similar circles to indicate the connection between the code-selector bank and the ringing-code conductors. The circles numbered 1-10 associated with the code-selecting switch CS5 of the connector C5, Fig. 7, indicate that the bank wires of CS5 are connected in the same way to the ringing-code conductors of the associated code-generating device (not shown).

Gall from substation T1 to substation T2 A detailed description of the operation of the apparatus shown will now be given. For this purpose it will be assumed first that the subscriber at substation T1, Fig. 1, desires to converse with the subscriber at substation T2, Fig. 3. The called line number is 621, and the station number on the called line is 5. Consequently the number, if called from another tele hone in exchange B, is 621-5, the dash being used ahead of the 5 to separate the line number from the stations digit. Since, however, the calling subscriber is in exchange A, he must prefix a 3 to the number, which then becomes 3-621-5. It is assinned that the numbers of subscribers to the two exchanges are listed in separate portions of the'directory, and that general instructions are issued to the subscribers to prefix the digit 3 when calling from one exchange to the other.

When the subscriber at substation T1, Fig. 1, removes his receiver, the usual receiver and transmitter circuits are completed at the switchhook contacts, and, in addition, a circuit is closed at contacts 108 through the springs 106 of the calling device 105 to the junction of the coils of the bridged ringer 104. lVhen this occurs, current from the exchange battery through the winding of line relay 113 flows through the associated cutoff-relay spring combination through both line conductors 101 and 102 in parallel, being afforded a path to ground at the calling substation through the two windingsof the ringer 104 in parallel. Line relay 113 closes a circuit for the pull-down winding 114 through the usual so-called open-main conductor 122 to battery. The pull-down Winding operates the plunger 4117 and the bridge-cut-of armature 116. The bridgecut-ofi armature 116 op'ens the shunt across the talking conductors and disconnects relay 113. Relay 113 is slow releasing and remains operated for an interval. The pull-down armature 117 o erates the springs 118-121,

Aextending the ine conductors 101 and 102 and the private normal conductor 127 to the corresponding conductors 124, 126, and`125 of selector S1. Line relay 131 of the selector S1 now energizes through the two windings of the impedance 130 and over the two conductors of the calling line in parallel. Line relay 131 closes a circuit orrelay 132 and vertical magnet 137, at the same time disconnecting series relay 133 from in shunt of relay 132. Magnet 137 is not operated at this time owing to the relatively high resistance of relay 132. Series relay 133 is of relatively low resistance and magnet 137 will operate when connected in series with relay 133. The circuit of magnet 137 is closed momentarily through relay 133 after the armature of relay 131 has engaged its front contact and before relay 133 has been removed from its shunt of relay 132. This interval, however, is of such a short duration that neither relay 133 nor magnet 137 have time to operate. Relay 132, upon operating, closes a locking circuit for itself at armature 144 including magnet 137, and at armature 145 places ground on release trunk conductor 125. This closes a circuit through the bridge-cutofl' and holding winding 115 of the lineswitch. The current flow through this winding is sufficient to maintain the bridge-cutofl and pull-down armatures operated after relay 113 falls back and opens the circuit through the pull-down winding 114. The advance of the master switch to another idle trunk takes place responsive-.to the placin of ground on conductor 125 and is controlle over the branch conductor 123 extending to the master switch bank.

The calling subscriber may now dial the first digit 3 in the desired number, whereupon line relay 131 falls back three times due to the three interruptions produced in its circuit at springs 106 of the calling device 105 upon the return of the calling device to its normal position. It will be noted that off-normal springs 107 of the calling device 105 shunt the coils of the ringer 104 so as to afford a better impulsing circuit for line relay 131 ofthe selector S1. Each time it falls back, relay 131 places relay 133 in multiple with relay 132. When thls occurs the first time, relay 133 operates in series with magnet 137, and magnet 137 operates to raise the wipers of the switch one step. Although'the resistance of relay 133 is so low, relatively, that relay 132l will eventually fall back, when shunted by relay 133, it does not have time to do so during dialing. When the armature is again attracted magnet 137 falls back, but the slow-acting relay 133 remains operated until the end of the digit. Magnet 137 is operated two more times, raising the wipers of the switch three steps in all. Upon the operation of relay 133, a circuit is prepared for stepping relay 134. This circuit is completed through the interrupter springsof the rotary magnet 140 and the off-normal contacts 141 as soon as the first step of the switch has been taken. Relay 134 thereupon operates and locks itself to release trunk conductor 125 at armature 147, and at armature 148 prepares a circuit for rotary magnet 140. When relay 133 falls back at the end of the digit, it shifts thecircuit of relay 134 to the test wiper 154 preparatory to the usual testing operation, and at the same time completes the circuit of rotary magnet 140. Rotary magnet 140 thereupon operates and advances the wipers 153-155 one step into engagement with the first set of bank contacts in the third level. Near the end of its stroke, magnet 140 opens the circuit of relay 134, whereupon relay 134 falls back and opens the rotary magnet circuit. The rotary magnet falls back and again closes its interrupter contacts.

From this point the operation depends upon whether the trunk line terminating in the first set of bank contacts is busy or idle. If this trunk line is idle, relay 135 operates at this time seizing the trunk. If the trunk line is busy, the ground potential encountered by test wiper 154 on the busy test contact'short circuits relay 135 and closes a new circuit through the armature of relay 133, normal, the rotary magnet interrupter contacts, and the off-normal contacts 141 for stepping relay 134. Stepping relay 134 operates again, and again closes the rotary maglos llO

,grounded release net circuit, whereupon the wipers are advanced another step. l

This alternate operation of relay 134 and magnet 140 continues until an idle trunk line is reached, which trunk line, it will be assumed, is the one comprising conductors 156-158 and extending to the repeater R1, Fig. 2. When this trunk line is reached, no ground otential is encountered by test wiper 154, an relay 135, being no longer short circuited, energizes in a circuit including the trunk conductor 125, eleventh-rotary-step contacts 142, the rotarymagnet interrupter contacts, off-normal contacts 141, and relay 134. Relay 134 does not operate in this circuit on account of the relatively high resistance of relay 135. Upon operating, relay 135 at armature 151 opens n. further point in the test circuit and connects wiper 154 to the grounded release trunk couductor 125, thereby making the seized trunk busy immediately to the other selectors having access to it. At armature 150, relay 135 opens the locking branch of the release relay circuit so as to prevent a further operation of magnet 137 and relay 133 and to prevent a premature release magnet operation, and at armatures 149 and 152 disconnects conductors 124 and 126 from the windings of impedance 130 and line relay 131 and extends them through wipers 153 and 155 to conductors 156 and 158 leading to the repeater Rl.

Line relay 201 of the repeater R1 now operates over the calling line and through the two lefthand repeating-coil windings in parallel. At armature 206, relay 201 closes a circuit for release relay 202. Relay `202 operates and closes atl armature 208 a circuit :for relay 203. At armature 207, relay 202 places ground on release trunk conductor 157, so as to maintain the lineswitch LS1 and the selector S1 operated after the release relay 132 of the selector S1 falls back responsive to being shunted and open-circuited by the line relay 131 when the latter falls back responsive to the operation of switching relay- As a result of the closure of the circuit of relay 203 at armature 208, relay 203, at armatures 209 and 210, disconnects the conductors of the trunk line TL3 from the corresponding conductors leading tothe selector S3 and connects them to the right-hand repeating-coil windings. A ground potential is thereby placed on conductors of the trunk line TL3 through the right-hand repeatingcoil windings, closing a circuit over the conductors of the trunk line TL3 and through armatures 209 and 210', normal for the line relay (not shown) of the selector S4. This line rela now operates and prepares the selector 4 for operation in the manner described in connection with the selector S1. When the calling subscriber dials the secextending to the connector C4, Fig. 3. It

will4 be noted that each time relay 201 falls back it opens the circuit of relay 202, but

.relay .202 remains operated throughout the digit on account of the fact that it is placed 1n a clod circuit each time before its energizing circuit is opened.

In the connector C4, relay 305 operates responsive to the grounding of conductor 302 by the selector S4 when the latter seizes the trunk line, its circuit including off normal contacts 321. At armature 326, relay 305 prepares a locking circuit for itself, and at armature 328 it connects vertical magnet 325 to the operating conductor 313, at the same time disconnecting rotary magnet 360. Line relay 306 operates vover conductors 301 and 303 from the ground potential supplied to the trunk line TL3 through armature 204 of the repeater R1, and it closes a circuit for release relay 307 through vertical magnet 325. Upon operating, release relay 307 places ground on locking conductor 314 at armature 333; grounds release trunk conductor 302 at armature 332; and at armature 334 closes a locking circuit for itself including operating conductor 313, armature 328, and vertical magnet 325. i

When the calling subscriber dials the third digit 2 in the desired number, two interruptions are produced in the circuit of line relay 306 of the connector C4 at the line relay 201 of the repeater Rl, with the result that relay 306 falls back twice. Each time it falls back, relay 306 shunts relay 307 with the series relay 311, bringing about the operation of vertical magnet 325. By the operation of the vertical magnet, the, wipers 357--359 are raised o posite the second level of bank contacts. Series relay 311 energizes upon the first impulse of current and remains energized until the digit is over. At armature 348, relay 311 completes the locking circuit for relay 305 through armature 326. The initial circuit of relay 305 is opened at ofi'- normal contacts 321 as soon as the switch moves olf normal. At the end of the vertical movement of the switch, relay 311 falls back and opens the locking circuit of relay 305 at armature 348, whereupon relay 305 falls back and shifts the operating conductor 313 from in connection with vertical magnet 325 into connection with rotary magnet 360. At armature 329, relay 305 closes a circuit including off-normal contacts 335 and the start conductor 375 for operating the code generator, Fig. 4, in a manner to be hereinafter explained.

When the subscriber dials the next digit 1 in the desired. number, one interruption is produced in the circuit of line relay 306 of the connector C4, and this relay falls back momentarily, momentarily shunting relay 307 with series relay 311. This operation transmits an impulse of current through armature 334, operated, and over the operating conductor 313 to rotary magnet 360, through the normally closed contacts controlled by armatures 328 and 355. Rotary magnet 360 responds to thisimpulse of current and rotates the wipers 357-359 one step into engagement with the terminals of the called line. Relay 311 is `energized in series with the rotary magnet. At armature 347, relay 311 disconnects test wiper 358 from the upper winding of relay 312 and connects it instead through armature 350 to busy relay 310, and at armature 348 disconnects ground trom armature 344 so as to prevent the premature shunting of relay 311 in case relay 310 energizes during the rotary movement due to the passing of wiper 358 over busy test contacts.

The operation taking place at the end of the rotary movement depends u on whether the called line is busy or idle. f the called line is busy, relay 310 is energized through test wiper 358 when the wipers come to rest on the contacts of the called line, and, when relay 311 falls back at the end of the rotary movement, a locking circuit is completed for busy relay 310 from the grounded releasetrunk conductor 302 through armature 342, operated, normally closed contacts controlled by arma-ture 347, and armature 350. Relay 311 is shunted at armature 348, normal, through armature 344, so as to prevent it from operating subsequently and interfering with the circuit of busy relay 310 in case the walling subscriber should again turn his calling device before hanging up his receiver.

In order to inform the calling subscriber of the busy condition of the line, busy relay 310 at armature 346 connects the busy lead, coming from the busy tone transformer 377, to the lower talking conductor throu h arma ture 356. When the calling subscri er hears the tone produced by the busy tone machine, he is expected to hang up his receiver and bring about the release of 4the operated switches.

Assuming now that the desired line is idle of the lineswitch LS2 to battery. This cutolf relay of the lineswitch LS2 operates over this circuit and disconnects the associated line relay from the conductors of the called line. The cut-off relay of the lineswitch on the called line corresponds to the bridgecut-off armature 116 of the lineswitch LS1 and the winding 115. The cut-off armature of the called lineswitch is operated, but thel pull down armature is not operated owing to the relatively weak pull of the bridgecut-off winding.

In the connector C4, relay 312 operates in series with the cut-off winding of the called lineswitch and closes a locking circuit for its lower windin at armature 352 including a branch of the ocking conductor 314. At armature 354, rela 313 prepares a new locking circuit for re ay 305; at armature 353 it prepares a circuitfor pick-up relay 308; at armature 350 `it opens a point in the previously traced circuit of busy relay 310 so as to prevent this relay from o erating over a similar circuit when the last dlgit is dialed; at armature 351, it places a ground potential on test wiper 358 independent of the ground potential previously placed on this Wiper through the test winding of the relay; at armature 355 it connects the operating magnet 373 of the code selector C84 to the operating conductor, at the same time disconnecting rotary magnet 360; and at armatures 349 and 356 it connects up the Wipers 3 57 and 359.

When the next and last digit, the code selecting digit 5, is dialed, line relay 306 falls back five times, and shunts relay 307 with relay 311 five times, thereby transmitting tive impulses of current over conductor 313 to operating magnet 373 of the code selector CS4. Magnet 373 responds to the five impulses of current and advances the wiper 374 into engagement with the fifth associated bank contact. Relay 311 is energized throughout this series of impulses also, and, when it falls back at the end ofthe series, it closes at armature 348 a circuit for busy relay 310 through ofi-normal contacts 372 of the code selector CS4. Relay 310 operates at this time and, in effect, locks itself energized at armature 344 by closingl a shunt around relay 311'including armature 348, normal. It will be noted that the busy tone circuit is not closed at this time owing to the fact that arnature 356 of switching relay 312 is operate The connection has now been extended to the desired line and the code selector CS4 has been set on the ringing-code conductor corresponding to the code necessary to signal the subscriber at the called substation. In order to insure that the ringing of the called subscriber will begin only at the beginning of a code, the pick-up relay 308 has been provided to close the circuit of the ringing relay 309 onl after a pick-up impulse has been receive over pic -up conductor 376 and through the operated armatures 343 and 353.' The code generating device shown in Fig. 4 grounds the pick-up conductor and the rin 'ng-code conductors at the proper time as wil be exlained hereinafter. At this point it will su ce to say that a pick-up impulse is shortly received over impulse conductor 376, whereupon pick-up relay 308 operates and locks itself to conductor 314 at armature 337, at the same time opening its initial energizing circuit. At armature 338, relay' 308 completes a connection from ringing relay 309 to the wiper 374 through armature 327. Accordingly, ringing relay 309 operates each time an impulse is placed on ringing code conductor 5, in a manner to be subsequently explained. Eachtime it operates, it laces ground on the lower wiper 359 and 1t places ringing current on the upper wiper 357, operating the bridged ringers at the party-line substations. The ringing code sent out is, of course, that of the substation T2 and the subscribers at the other substation do not respond.

When the subscriber at substation T2 responds to the ringin of his bell by removing his receiver, a circuit is closed through the two coils of the ringer in parallel for the supervisory relay 304. This circuit, it will be noted, includes wipers 357 and 359, armatures 349 and 356, armatures 339 and 340, and the right-hand repeating-coil windings. Relay 304 operates when its circuit is closed and closes at armature 322 a circuit for reoperating relay 305. Relay 305 closes a locking circuit for itself at armature 326 including armature 354; it disconnects ringing relay 309 at armature 327; and at armature 329 it renizoves ground from the starting conductor 3 5.

It will be noted that the resistance 324 is inserted into the circuit of line relay 306 at armature 323 of relay 304. This operation is of no particular utilityat this time, but is performed in order to ive a calling operator supervision in case tie connection is set u through an operators switchboard, as will Ee explained hereinafter.

The two subscribers may now converse with each other, the heavy lines being used to outline the talkin circuit. It is understood, of course, that a ocal source of talking current supply is used in both cases.

Release of connection from T1 to T2 ance 324 so as to give the calling operator disconnect supervision in case lan operator is handling the connection.

When the subscriber at substation T1 han up his receiver `relay 201 of the repeater l falls back and opens at armature 204 the circuit of rela 306 of the connector C4. Relay 306 falls ack and shunts relay 307 with series relay 311, but relay 311 does not operate at this time because 1t is shunted in turn through armature 348, normal, and armature 344. At this time, the circuit ofrelease relay 307 includes armature 334, operated, armature 328, and the vertical magnet 325. As a -result, vertical magnet 325 operates when the release relay 307 is shunted, but the shaft and wipers are not disturbed due to the usual mechanical construction'of the switch which prevents further elevation of the shaft and wipers after they have been rotated. Shortly afterit is shunted relay 307 falls back and opens the circuit of vertical magnet 325 at armature 334, at the same time closing a circuit through off-normal contacts 336 for release magnet 330 and a branch circuit through the armature 341 for release magnet 371 of the code selector. Release magnets 330 and 371 now operate to start the restoration of their respective switches to their normal positions. In addition, relay 307 removes ground from release trunk conductor 302 at armature 332 and at armature 333 it removes ground from the locking conductor 314. Responsive to the removal of ground from release trunk conductor 302 the selector S4, Fig. 2, releases in the usual manner. When ground is removed from the locking conductor 314, relays 308 and 312 fall back. The falling back of relay 312 is retarded sli htly by the. cop er on its armature end. When relay 312 alls back it replaces the ground potential on conductor 302 after a sucient time has ela sed to permit the release of the selector S4 ig. 2, to be started by the falling back of the switching relay (not shown) of the selector. The circiut path through which the ground potential is replaced includes armature 348, normal, oil-normal contacts 372 of the code switch, amature 350, normally closed contacts controlled by armaturev 347, and armature 342. This path between ground and the release trunk conductor 302 is established so as to render the connector and the code switch busy while they are releasing.

Assuming that the code selector CS4 reaches its normal position before the connector C4 reaches its normal position, as will usually be the case, the circuit of relay 310 and the path throughwhich ground is supplied to release trunk conductor 302 is opened at off-normal contacts 372 when the code selector reaches its normal position. Relay 310 thereupon fallsback and opens the circuit of magnet 371 at armature 341, and at armature 344 removes the shunt from around the Winding of series relay 311, whereupon relay 311 o erates in series with release magnet 330 an at armature 348 applies ground to release trunk conductor 302 through armature 326, normal. This second guarding circuit is established to guard the connector from seizure during its release.

When the shaft of the connector C4 reaches its normal position, off-normal contacts 335 and 336 o en, and olf-normal contacts 321 close. Tie circuit of the release magnet and the series relay is opened at s rings 336, and the circuit of relay 305 iuc uding conductor 302, now grounded by series relay 311, is reestablished, .and relay 305 operates. Relay 311, however, falls bacl: an instant later and removes ground from conductor 302, rendering the connector idle again and releasing relay 305 In the repeater R1, Fig. 2, when line relay 201 falls back, as above-mentioned, it o ens the circuit of the release relay 202 and p aces the said relay 202 in a closed circuit with the result that relay 202 falls back after a slight interval, removing ground from release trunk conductor 157 and opening the circuit of relay 203. The switching relay 135 of the selector S1 and the magnet of the lineswitch LS1 both deenergize, and relay 135 at armature 150 closes a circuit for release magnet 146 at armature 150 and through armature 144 and off-normal contacts 143. This circuit includes series relay 133. Relay 133 and magnet 146 both operate, and relay 133 closes a circuit for stepping relay 134 through the rotary-magnet interrupter contacts and olf-normal contacts 141. Relay 134 now operates and applies ground potential again to release trunk conductor 125 so as to prevent the master switch from again stopping opposite this selector until it is fully released. When the normal position is reached, the release magnet and series relay circuit is opened at contacts 143; and the circuit of relay 134 is opened at contacts 141. Relay 134 thereupon falls back and removes ground from the release trunk conductor, and relay 133 falls back shortly thereafter.

All trunks busy at selector S1 Consider now the case when the selector S1 is operated, but is unable to find an idle trunk. The rotary movement takes place in the hereinbei'ore described manner and continues until the wipers 153--155k pass oi the last bank contact upon the eleventh rotary set. When this occurs, springs 136 and 142 are operated by the usual cam arrangement. The circuit of relay 135 is opened at springs 142 to prevent this relay from operating at this time. At spring 136, the common busy tone lead is connected to the lower talking conductor 126, so as to give the calling subscriber a busy tone. Upon hearing this tone,`

the calling subscriber is expected to hang up hls receiver and bring about the release of `.the connection.

Operation of code-generating device ate the impulses to operate the other relays.

The remaining relays, especiall relays 405- 410, operate to count the impu ses generated by relays 403 and 404, and the device as a whole ls'eapable of assuming any one of nineteen posltlons, successively, the operation be- 1ng repeated in cycles. The positions of the devlce 1n which the various relays are operated have been noted on the drawings. Also, the pos1tions of the device in which the principal conductors are grounded have been note 1n order that the disclosure may be understood better.

When start conductor 37 5 is grounded, ground 1s extended through the lower armature of relay 402 to conductor 416, closing a c1rcu1t for relays 403 and 404, in series, through the resistance element 422. Relay 404 belng short circuited, rela Y403 is the only one that responds immediatelly. When relay 403 operates, it places ground on conductor 417 at lts upper armature, and removes the shunt from around relay 404 at its lower armature. Relay 404 operates and prepares to place ground on conductor 419, and at the same time shunts relay 403. Relay 403 falls back, and the device may be said to be in its second position. Inthe second position of the device, a circuit is closed through the upper armatures of relays 403 and 404 for the upper winding of relay 406, including conductor 419 and the upper armature, normal, of relay 406. Relay 405 operates and closes a locking circuit for itself at its upper armature including the upper windingof relay 405, the lower armature of the said relay, and the grounded conductor 416.

With the device in position two, relay 404 is short circuited at the lower armature of relay 403, and relay 404 shortly falls back, the device thereupon passing into position three. When relay 404 falls back, it removes ground from conductor 419, whereupon relay 405 operates in the locking circuit of relay 406, and at its upper armature prepares a circuit for shunting relay 406. It will be noted now that a new locking circuit is completed for relays 405 and 406 in series, and that the circuit of the upper windings of these relays is opened. The new circuit includes the lower windings of the relays in series and the inner lower armatures of the two relays.

When relay 404 alls back it removes the shunt from around relay 403 with the result that relay 403 operates again and removes the shunt from around relay 404. Relay 404 now reoperates and shunts relay 403. This o eration of relays 403 and 404 continues, 1n t e manner described, until it is terminated bv the action of relay 402, as will be desdribed hereinafter.

It will be noted, that relay 403 is labeled 1, 3, 5, etc. while relay 404 is labeled 1-2, 3-4, etc. These labels indicate that relay 403 is operated in positions 1, 3, 5, etc., and that relay 404 is operated in positions 1 and 2, is released momentarily, is operated again in positions 3 and 4, etc.

Vith the device in position 4, ground is again placed on conductor 419, short circuitin lower winding of relay 406. Relay 406 fa ls back when this takes place and opens the previously established locking circuit at its inner lower armature. Relay 405 remains operated over conductor 419.

When the device arrives in position 5, ground is removed from conductor 419, whereupon, relay 405 falls back.

The above described operation of relays 405 and 406 is repeated, begininng with position 6.

While rela 406 is operated in positions 2 and 3, groun from conductor 416 is held on impulse conductor 420, extendingto the similar relays 407 and 408. The result is an operation of relays 407 and 408 similar to the above described operation of relays 405 and 406, but the time required for a complete operation is twice as long as that of relays 405 and 406, on account of the fact that only half as many impulses are delivered over conductor 420 as are delivered over conductor 419. It may be seen, therefore, that relay 408 is operated in positions 2 5, 10-13, and 18, and that relay 407 is operatedI in positions 4-7, and 12-15.

It will be noted, that round from conductor 416 is placed on contgluctor 421 as long as relay 407 is operated. The result is that conductor 421 is grounded in the positions of the device in which relay 407 is operated, conductor 421 being the impulse conductor extendin to the third pair of counting relays 409 ancgl 410. Itmay be seen, therefore, that relay 410 is operated in positions 4--11, and that relay 409 is operated in positions 8-15.

When 418 is rounded in position V2, a circuit is closed t rough the lower armature of relay 412 for relay 413. Relay 413 operates and locks itself through the middle lower y armature of relay 412 to conductor 416, and remains operated until relay 412 o erates in position 13, as will be pointed out ereinafter.

When the device arrives in position 6, relay 414 is operated from the grounded conductor 416 through the inner lower armature of rela-y 407, lower armature .of relay 406, and the lower armature of relay 413. Relay 414 operates and locks itself through the locking conductor of relay 413, with the result inner lower armature of relay 405, inner lower armature, normal, of relay 406, middle upper amature of relay 408, and the middle upper armature of relay 409. At its lower armature relay 411 locks itself and relay 401 to conductor 416. Relay 401 prepares a lockin circuit for relay 402 at its inner amature.

hen the device arrives. in-position 13, relay 405 falls back and closes at its lower armature a circuit through the inner up r armature of rela 411 for relay 412. Re ay 412 operates an locks itself to conductor 416 until conductor 416 is ungrounded in position 18. At its middle lower armature, relay 412 opens the locking circuit of relays 13kand 414, whereupon these relays fall When the device arrives in position 18, relay 408 is operated again, and it completes at its upper armature a circuit for relay 402 including the upper armature of relay 412'and the middle lower armature of relay 409. Relay 402, thereu on operates and locks itself to conductor 3I75 through the inner armature of relay 401, at the same time opening its initial circuit. At its lower armature, relay 402 removes ground from conductor 416 and y laces ground on pick-up conductor 376. he removal of ground from conductor 416 stops the operatlon of relays 403 and 404 and permits the operated relay 404 to fall back, and it opens the locking circuits of the relays 405-414, permitting such of these relays as are operated to fall back. Relay 401, which is in series with relay 411, is slow-acting and does not fall back right away when its circuit is opened upon the removal of ground from conductor 416.

When relay 401 falls back it opens'the locking circuit of relay 402, the device is in osition 19. A moment later relay 402 falls ack,

and removes ground from pick-up conductor 376, reapplying it to conductor 416; then the device is 1n position 1 again.

The above described operation is repeated over and over as lon as the ound potential remains on start con uctor 375.

Considering now how the codes are placed on the various conductors, the conductor extending to terminal 1 is grounded through the lower armatures of relays 401 and 408 while the device is in positions 2-5; this code corresponds to one long ring.

The conductor extending to terminal 2 i's grounded through the upper armatures of rea s 403 and 411, and the middle armature of re ay 410 while the device is in positions 1 rand 3; t is code corresponds to two short rings.

Thel conductor extending to terminal 3 is grounded in positions 3, 5, and 7 of the device through l.the upper armatures of relays411, 413, and 409; this code corresponds to three short rings.

The conductor extending to terminal 4 is connected to the impulse conductor 417 through the upper armature of relay 411 and the middle upper armature of relay 410, and is grounded in positions 5, 7, 9, and 11; this code corresponds to four short rings.

In a similar way the rcm'ainin code conductors are grounded in the positions indicated. The code laced on the conductor extending to termmal 5 corresponds to five short rings; the code placed on conductor `6 corresponds to two long rings; the code placed on conductor 7 correspondsl to three ong rings; the code placed on conductor 8 corresponds to a short ring and a long ring; the code placed on conductor 9 corresponds to a short ring and two long rings; and the code laced on` conductor 10 corresponds to two siiort rings and two long rings.

@all from substation T1 to substation T4 It will now be assumed that the subscriber at substation T1, Fig. 1, desires to converse with the subscriber at substation T4, Fig. 7. In order to complete the connection, the subscriber at substation T1 dials the number assigned to the manual exchange C (the digit 4). It will be assumed, that when the subscriber removes his receiver the lineswitch LS1 seizes the selector S1, and that when the'digit 4 is dialed the selector S1, uponI raising its Wipers to the fourth level, rotates Ithem and finds the trunk line comprising conductors 159-161, extending to the trunk circuit TG1, as the iirst idle trunk line. When this occurs, `line relay 223 of the trunk circuit TCl operates over the calling line and places ground on the release trunk conducnection including armature 225 between the ringing relay 222 and the 1 ringing code conductor of the code enerating device in exchange A. The code aced on this conductor 'corresponds to one ong ring, and it 1s, of course, repeated at' intervals. At armature 230, ground is placed on conductox 375 through armature 224 so as to start the asso- 'ciated code-generating device.

Each time ground is placed on the'rin 'ingvcode 'conductor -connected to termina 1,` ringing'relay 222 operatesand pro]ects ringingfc'rrent outE "over the trunk line TL1.

This ringing current passes through the lefthand windings of the repeating coil associated with the trunk circuit TG3, Fig. 5, to the upper windin of the ring-u relay 501. Relay 501 respon s and closes a llocking circuit for itself through'its lower winding at armature `506, including armature 514 of sleeve relay'505. At armature 507, relay 501 closes a circuit for the line lamp 515.

When the operator notes the lighted condition of the lamp 515, she inserts the answering plu'g of an idle cord circuit, such as the cord circuit CC, into the jack J2. When the plug has been fully inserted, a circuit is closed from the exchange battery through 'the two left-hand windings of the cord circuit CC for the relay 504 in the trunk circuit TG3 including the right-hand windings of the repeating coil in the trunk circuit TG3, and armatures 508 and 510. At armature 511, relay 504 places ground on the lowei` terminal of the sleeve relay' 505, whereupon sleeve relay 505 operates over the sleeve conductor of the left-handjplug of the cord circuit and'closes a lockingv circuit for itself at armature 514, at the sa'me time opening the locking circuit of relay 501. Relay 501 falls back and extinguishes the lamp 515. At

armature 512, relay 505 shunts the condenser "95 in the left-hand windings of the repeating coil so as to improve the talking conditions, and at armature 513, it connects ground throu h relay 502 to both inner terminals of the le -hand repeating coil windings, thereby closing a circuit over the two conductors lof the trunk line TL1, and the ri ht-hand windings of the repeating coil at t e trunk circuit TG1 for relay 221. Relay 221 operates over this circuit and closes a locking circuit for itself at armature 224, at the same time removing ground from conductor ,375 and disconnecting the code conductor I2 from'the ringing relay 222. The closure of the locking circuit for relay 221 shunts the current away from supervisory relay 502 in the trunk circuit TO3, permitting this relay to remain non-operated. i

In the cord circuit CC, supervisory relay 516 operates in series with relay 504 of TG3,

and shunts the associated supervisory lamp so as to keep it A:from lighting in the sleeve circuit. p

The operator now throws her key K2 into listening A osition and converses with the calling su scriber. Upon learning that the calling subscriber desires connection with the subscriber at substation T4, Fig. 7, the operator makes a note of the number of the calling substation and the number of the called substation. She then inserts the right-hand plug of the cord circuit CC into the jack 'of an idle trunk line, such as the trunk line TL4,-extending toexchange D. When the l plug-is to .the jack J3, a circuit is windings of the repeating coil in the ltrunk circuit and at armature 608 and 610. Relay 604 operates and grounds the lower terminal of relay 605, whereupon relay 605 operates over the sleeve circuit and closes a locking circuit for itself at armature 614. At

armature 612, relay 605 shunts the condenser associated with the right-hand repeating coil windings of the trunk circuit, and at armature 613 it connects ground to the two inner terminals of the associated ri ght-hand repeating coil windings, closing a circuit including re ay 602, the two conductors of the trunk line TL4 in multiple, and the line relay of the lineswitch LSB. Relay 602 o erates in this circuit and opens the circuit o relay 604 at armature 608. Relay 504 falls back and relay 517 of the cord circuit CC remains nonoperated, permitting the associated superv isory lamp to become lighted in the sleeve circuit. l p

The lineswitch LS3 now operates and extends the connection to the connector C5.

, Line relay 803 of the connector C5, now operates over conductors 616 and 618 in multiple and closes a circuit for release relay 804. The circuit of release relay 804 includes, at this time, the normally closed contacts controlled by armatures 819 and 857, and rotary magnet 855. Relay 804 upon operating, locks itself to the operating conductor 822 at armature 826; grounds the locking conduc` tor 701 at armature 825; and at armature 824 placesground on release trunk conductor 617 to maintain the connector busy to the lineswitches having access to it, and to hold the lineswitch LS3 operated. When ground is placed on conductor 617, relay 802 operates through off-normal contacts 812 and prepares a locking circuit for itself at armature 817.

p At armature 819 it substitutes vertical magnet 816 for rotary magnet 855.

After inserting the right-hand lug of the cord circuit CC into the j ackJ 3, the operator inserts the plug of the dial cord DC into the dlal. jack DJ 2. When the operator turns the calling device CD, in accordance with the first digit 3 in the number of the called substation, the off-normal springs of the 'calling device CD close a circuit for relay 603, whereupon relay 603 opens at armature 610 a further point in the circuit of supervisory` relay 604, and at armature 609 it disconnects relay 602 and substitutes the impulse springs of t e calling device CD. Upon the return of the dial to its normal position, three interruptions are produced inthe circuit of line relay 803, Fig. 7, and when the normal position is reached, the off-normal springs bring about the deener ization of relay 603, whereupon relay 602 1s brought into the circuit again.

Each time line relay 803 of the connector C5 falls back it shunts release relay 804,

thereby operating vertical magnet 816 three times. Series relay 809, inc uded in the shunt circuit around relay 804, operates upon the first impulse and, being slow-acting, remains operated throughout the series of impulses. At armature 843, relay 809 completes the locking circuit of relay 802 so as to maintain the relay o erated after its initial circuit is opened at o -normal contacts 812.

At the end of the vertical movement of the connector, relay 809 falls back and permits relay 802 to deenergize and transfer the operating conductor 822 to the rotary magnet 855.

When the calling o erator dials the next digit 0, line relay 803 alls back and operates rotary magnet 855 ten times. Relay 809 is again operated throughout the series of impulses and it closes at armature 842 a circuit for relay 810. Relay 810 operates and at armature 845 connects test wiper 857 to bus relay 808 through the normally-closed o normal contacts of the code selector US5. In case the called line is busy, relay 808 is o rated at the end of the rotary movement, w en the wipers 856-859 are on the cont-acts of the called line, and the busy tone is transmitted back to the operator at armature 841, in the usual manner. If the line is idle, a circuit for the upper winding of the switching relay 811 is completed upon the falling back of relays 809 and 810, which circuit includes the grounded release trunk conductor 617, armature 836, upper winding of relay 811, armature 845, armature 847, test wiper 857, test contact of the called line, and the bridgecutoff windin (not shown) of the lineswitch LS4. elay 811, upon operating, locks itself to conductor 701 at armature 848; at armature 847 shifts the test wiper 857 from the upper winding of relay 811 to ground; connects up the wipers and opens a point in the busy signalling circuit at armatures 846 and 853; shifts the operating circuit to the operating magnet of the code selector at ar armature 851; and at armature 850 prepares a circuit for pick-up relay 805.

When the calling operator dials the next and lastf digit 5, five impulses of current are transmitted to the operating magnet of the code selector, whereupon the wiper of the code selector is driven into engagement with the fifth associated bank contact. Relays 809 and 810 are energized throughout this digit, and the circuit of relay 808 is maintained open at armature 845. When relay 809 falls back, a circuit is closed at armature 842 through the normally-open off-normal contacts of the switch CS5 and for the busy relay 808. Relay 808 operates at this time and, at armature 837, shunts the series relay 809 so as to prevent any further operation of this relay; at armature 839, it shifts the operating conductor back to vertical magnet 816; it prepares the release circuit at armature 835; and at armature 838V it completes the connection between the pickup conductor and pick-up relay 805. The start conductor 375 havingbeen grounded through contacts 823 and armature 820, the associated code generating device is operating, and, when the pick-up conductor is grounded, pick-up relay 805 operates and locks itself to conductor 701. At armature 829, it completes a connection through armature 818 between ringing relay 806 and the wiper of the code selector. The ringin current is now projected out over the cal ed line b rela 806 in 'xccordance with the code of t e su tation When the subscriber at substation T4 responds a circuit is closed over the two sides of the called line in parallel for relay 801. At armature 813, relay 801 closes a circuit for relay 802. Relay 802 operates and at armature 817 closes a locking circuit for itself including armature 849; it disconnects the ringing relay atarmature 818; and at armature 820 it removes ground from start conduct'or 375. Relay 801,. at armature 814, inserts the resistance 815 into the circuit of line relay 803,'whereupon the marginall supervisory relay 602, Fig. 6, falls back-and again completes a circuit through relay 604, whereupon the right-hand supervisory relay 517 of thc cord circuit CC operates and extinguishes the associated supervisory 1am so as to give the operator answered supervlsion.

The two subscribers may now converse with each other in any desired manner, and when the conversation is terminated they both replace their receivers.

When the receiver is replaced at the calling substation, line relay 223. of the trunk circuit TCl, Fig. 2, falls'back and removes ground at armature 229 from release trunk conductor 160, permitting the line-switch and selector, Fig. 1, to release. At armatures 228 and 232 the conductors of the trunk line TL1 are switched back to the selector S2, and

at armature 230 the lockin circuit of relay 221 is opened, whereupon re ay 221 falls back.

The supervisory relay 502, Fig. 5, now operates over the trunk line TL1 in series with the line relay (not shown) of the selector S2, and at armature 508 opens the circuit of supervisory relay 516, whereupon supervisory relay 516 falls back and permits the associated lamp to become lighted as a disconnect signal.

The selector S2, see Fig. 8, is incidentally prepared for operation when its line relay operates over the trunk line in series with the supervisory relay 502, Fig. 5,

When the receiver is replaced at the called substation, relay 801 falls back and at armature 814 shunts the resistance 815, whereupon relay 602, Fig. 6, operates again over the trunk line TL4 and gives the operator a vflufther disconnect signal by opening the circuit I of supervisory relay 517 at armature 608.

Upon perceiving the two disconnect signals, the operator pulls down the connection.

lVhen the plug is removed from the jack J2,

the associated supervisory lamp becomes ex- J3, sleeve relay 605,*falls back and removes ground from the'inner terminals .of the associated right-hand repeating coil windin s, whereupon line relay 803 of the connector falls back and shunts release relay 804, causing an incidental operation of vertical magnet 816. After a slight interval, relay 804 falls back and, at armature 824, removes ground fromv conductor 617 so as to permit the lineswitch LSB to release. At armature 825 `it removes ground from conductor 701,

permitting relays 805 and 811 to fallback. The relay 811 releases the bridge-cut-o winding of the lineswitch LS4 at armature 847, and at armature 849 opens the locking circuit of relay 802,I whereupon relay 802 falls back. Release magnet 821 operates through oil-normal contacts 827, and the release magnet of the code selector operates through off-normal contacts 835.' It is to be noted, that no reapplication of ground application of ground potential to conductor 617 occurs at this time, as it is not desired to busy the connector C5 during the release. When the code selector CS5 reaches its normal position, the circuit of relay 808 is o ened, and relay 808- falls back, opening the re ease magnet circuit of thecode selector at armature 835. At armature 837, relay 808 removes the shunt from around the winding of relay 809, whereupon relays 809 and 810 operate agaln. However, the reapplicaticn of ground to the release trunk conductor, described in connection with the similar relay 311 of the connector C4, does not occur at this time, owing to the elimination of the connection at armature 817 corresponding to the connection between the resting contact of armature 326, Fig. 3, and the release trunk conductor 302.

`When the connector C5 reaches its normal position, the circuit of magnet 821 and relay 809 is opened at off-normal contacts 827. Relay 809 now falls back and opens the circuit of relay 810 at armature 842, with the result that .relay 810 falls back also.

The entire connection is now released, and the apparatus involved therein may be used in setting up other connections.

Regarding the reason for the elimination of the busy-during-release feature from the connector C5, it may be pointed out that, in case the' connector Q5 er the code Selector US5 lool should become mechanically defective so that no release would occur, the ground potential would remain applied to conductor 617, with the result that, in case the lineswitch used to 4make the original call should be reo rated right away to make a new call be ore the master switch has picked-up the line' they are releasing. On the other-hand, theV busy-during-release feature has been applied to the connector C4, Fig. 3, because this connector is preceded by a selector and as soon as the release starts the selector is freed and thereis no danger of a line being locked out of commission upon the reapplication of the ground potential to the release trunk. However, notwithstanding the danger of lines bcing locked out of commission, the guard-durfing-release feature has been applied to the selector S1, as it is assumed that an vattendant is present most of the time in exchange A, and that he will be ready to take care of such situations as they occur. to exchange B.

@all from substation T4 to substation T3 In order that the automatic rota-ry operation of the connector C5, Fig. 7, be understood, this operation will be ex lained in connection with a call from the su scriber at substation T4 in exchange D, to the sub- A scriber at substation T3 in exchange C.

It will be assumed that, when the subscriber at substation T4 removes his receiver, the lineswitch LS4, Fi 8, seizes the connector C5 at a multiple o the conductor 616-618, see Figs. 6 and 7. When this occurs, the connector C5 is prepared for operation in the manner hereinbefore explained, and a holding circuit for the calling lineswitch is closed over conductor 617.

The calling subscriber now dials the number 211 assigned to the exchange C for the use of subscribers in exchange D. When the digit 2 is dialed, the connector C5 responds by raising its Wipers opposite the second level of bank contacts.

When the second digit, the digit 1, is dialed, the wipers of the connector C5 are rotated one step in the hereinbefore described manner. It Will be recalled that the series relay 809 is operated in series with the operating conductor 822 when the rotary movement of the connector takes place, and that relay 810 is operated by relay 809 at armature 842. The operation taking place at the lend, of the- The same applies directed rotary movement of the connector, depends u on whether the trunk line '1`Llis busy or id e, itibeing assumed that the trunk 'l`L4 is the one terminating in the first set of bank contacts in the second level. Assuming that the trunk line is busy, there is a groundpotentialon the test contact thereof, nowencountered by test wiper 857, and a circuit is therefore closed through armatures 847and 845, and oil-normal contacts of the code selector CS5 for busy relay 808. Busy relay 808, at armature 840, prepares a circuit for stepping relay 807, including the rotary test wiper 858. When series relay 809 falls back and opens the circuit of the slowacting relay 810 at armature 842, it completes at armature 844 a connection between relay 807 and the test wiper 858, this connection including the interrupter contacts 854 and armature 852. Relay 807 now` operates from the ground potential on the test conductor of the trunk line, which ground potential is carried to the rotary test contact through th'e associated jumper connection. Upon operating, relay 807, at armature 833, closes a holding circuit for slow-acting relay 810, so as to prevent it from falling back at this time. At armature 834, relay 807 locks itself to the release trunk conductor 617 by placing ground therefrom on the test wiper 858, and at armature 832 it closes a circuit over the operating conductor 822 for rotary magnet 855. Rotary magnet 855 now ,responds and ad vances the wi ers another step. Near the end of its stro e, magnet 855 opens the circuit of relay 807 at contacts 854, whereupon relay 807 falls back and o ens the rotary magnet circuitresulting in t e deenergization of the rotary magnet. If the test contact of the second trunk line is busy, the stepping relay operates again and the rotary movelnent continues. Vhen an idle trunk line is reached, relay 807 ceases to operate and the busy relay 808 falls back. As an alternative, the wipers may be driven to the last trunk line of the group, and, if this trunk line is busy. the busy relay remains operated, but no `further operation of the stepping relay 807 takes place on account of the ommission of the corresponding umper connection between the rcgular test contact and the rotary test contact of the last trunk line. The busy signal is transmitted back in the latter instance, and the calling subscriber replaces his receiver, bring ing about'the release of the connection.

For the purpose of the present description it will be assumed that the trunk lineTL4 is idle when tested, With the result that relay 807 does not operate,and busy relay 808 remains normal when the directed rotary movement is completed.

Responsive to the deenergization of relay 810, which takes place when its circuit is opened by relay 809, the switching relay 811 operates in series with the bridge-Cutoff

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