US1689543A - Multioffice telephone system - Google Patents

Description

Oct. 30, 1928. 1,689,543

. J. WICKS MULTIOFFICE TELEPHONE SYSTEM Filed March '7, 1927 7 Sheets-Sheet Z -Inuen [773- Jmhn M15145 HIT y.

0a. so, 1928. 1,689543 J WICKS MULTIOFFICE TELEPHONE SYSTEM Filed March 1927 '7 Sheets-$21604; 3

Irma John M'LCJkE Oct, 30,1928. 1;689,543

J. wicKs IULTIOFFICE TELEPHONE SYSTEM ,Filed March 1927 7 Sheets-Sheet' 4 IIULTIOFFICE TELEPHONE SYSTEM J. WICKS 7 Sheets-Sheet 5 Filed March '7, 1927 N N N L Y N um um umm lam Oct. 30, 1928. 1,689,543

7 J. WICKS MULTIOFFICE TELEPHONE SYSTEM I Filed March '7. 1927 7 Sheets-Sheet 6 ,MMHn- Oct. 30, 1928.

J. WICKS IULTIOFFICE TELEPHONE SYSTEM 7 Sheets-Sheet '7 Filed March '7, 1927 -Im.ran ur- Juhn Jnfwks Patented Oct. 30, 1928.

UNITED STATES PATENTqOFFICE. J

JOHN WICKS, E OAK PARK, ILLINOIS, AssIeNo T0 REsERvE HOLDING coi/IPANY. OF KANSAS CITY, MIssoURI, A coRroR 'rIo 0E DELAWARE.

MULTIOFFICE TELEPHONE SYSTEM.

Application filed March 7, 1927. Serial No. 173,258.

The present invention relates to.'mu1tioffice telephone systems in general, but is concerned more particularly with multiofiice'automatic telephone systems; and the broad general object is the production of new and improved circuit. arrangements for use in inter-oflice connections of' a multi office automatic telephone system wherein automatic switches of a given type are used in one office and wherein automatic switches of a different type fromthe "standpoint of their circuit arrangements are used in another office.

There are other objects and features of the invention whichare, for the most part, more or less incidental to the carrying out I of the main object above stated. These latfor objects and features will be better understood after a general description has been given of the system to whiohthe inventionv has been applied.

Referring now to the accompanying drawings comprising Figs. 1-8, they show by means of the usual circuit diagrams a sufficient amount of equipment in a telephone system embodying thefeatures of the invention to enable the invention to be understood. Fig. 1 is atrunking diagram showing switch trains in two offices of a system, the switches used in the respective switch trains being of different types from acircuit standpoint. Figs. 2-6 are circuit diagrams showing in detail certain circuits to be hereinafter explained; Fig. 7 is a'sheet layoutshowing' how the sheets on which Figs. 26 are drawn should be placed together in. order to be understood best; and Fig. 8 is a circuit diagram showing an alternative method of effecting a certain connection to be hereinafter explained.

Referring now particularly to Fig. 1, the equipment indicated in this drawing is assumed to be located in two offices X and Y of a multi-ofiice automatic telephone system,

- the dotted line down the center of the sheet indicating the dividing line between the two offices. The switches in office X are operated according to the two-wire method of control over thetwo sides of the calling line in series, talking current in local connections being supplied to both parties from the con nector (last switch in the train). In office Y, the'usual two-wire loop control is excrcised over the calling line. The talking current for the called line is supplied from the final switch of the train, but the talkingcur rent for thecalling line is supplied from the first switch in the train, this first switch being a so-called first selector repeater. Accordingly, in office Y, all switches, after the first, operate responsive to impulses repeated from the first selector repeater and not over the calling line loop as in office X. i

Referring now to office X, two subscribers lines are shown entering this oflice. One line is the line of substation Al, and the other line is the line of substation A2. It

is assumed that office X is office No. in I t substation A1 and it completes aconnection whenthe associated line is calling to a first selector such as the selector S1. The selector S1 is the office selector and trunk lines Lextend from the various levels thereofto the various offices of the system. Forexample the. trunk lines extend from the fifth level to. local thousands selectors, one of -w,hich is the thousands selector S2. The

coming from the sixth level of the. selector S1 in office Xand the incoming thousands selector SR3 in office Y. This repeater is used primarily to permit the use of a twoconductor inter-office trunk instead of a three-conductor trunk which would be required if the repeater were-not used. vAt thispoint, it may be mentioned that the circuit details of the switches shown in ofiice X are not shown in the present application and that these circuits may be similar to those shown on pages and 61 (and de scribed on'the adjacent pages) of Automatic Telephony, by Smith and Campbell, first edition, published by McGraw Hill Book Co., Inc. New York City.

In Onc Y, a will be noted that the a;

peater R2 is inserted between the trunk line from the ofiice selector banks and the incoming thousands selector S3 in office X. This repeater has functions similar to those of the repeater R1 in office X, and it has the additional function of translating the control received from the first selector repeaters in office Y into the regular two-wire loop control to operate the switches in office X. The circuits of the repeater R2 are shown in full in Fig. 6 and will be described herein.

It will be noted that there is a toll line shown incoming to the oflice and terminating in the selector repeater SR1, the banks of which are multipled with the banks of the first selector repeater SR2. This toll line is shown more fully in Fig. 5 and it originates in a remote exchange at a toll board and connections thereover through the automatic switches are set up with either of the offices X or' Y or with any of the other ofiices of the exchange.

Reference may now be had to Figs. 2 and 3 which show a certain amount of the details of the circuits of the switches which may be used in setting up a connection from substation A3, Fig. 1, to substation A44. These switches are the lineswitch LS2, the selector repeater SR2, the thousands selector S5, the hundreds selector S6, and the connector C2. Since the circuits of these switches are old and well known, only so much of the circuits as are of utility in understanding the cooperation of these switches with the remaining part of the system have been shown.

A description oi. the operations taking place during the setting up of a connection from the line of substation A3, Fig. 2,-to the line of substation A4, Fig. 3, will now be given.

When the receiver is removed at substation A3, the usual loop control circuit is closed over the two conductors of the calling line, and the lineswitch LS2 starts irom its home position and searches for an idle trunk: in the usual manner. 'VVhen an idle trunk line is encountered, for example, the trunk line comprising conductors 218-22O and extending to the first selector repeater SR2, an operating circuit is closed for the combined switching andcut-otf relay 201 over the test and release trunk conductor 219, through theupper winding 01 relay 211 of SR2 and the ofi-normal contacts 213. Relays 211 and 201 operate in series and relay 201 shuntsits high resistance upper wind ing so as to place a guarding potential on conductor 219 through its low resistance lower winding. The marginally adjusted meter M does not operate at this time in multiple with the lower winding of relay 201. As a result of the operation of relay 201, the wipers 202 and 204 are connected up to the calling line, whereupon line relays 207 and 208 in the selector repeater SR2 operate. Relay 208 closes a circuit for release relay 209, whereupon relay 209 operates and prepares the switch for operation.

lVhen the calling subscriber dials the first digit 6 in the numberof the substation A l,

line relay 203 falls back six times and brings about the operation of the vertical magnetfnot shown) of SR2 in the usual by the vertical movement, are rotated over the bank contacts in the sixth level in search of an idle trunkline. hen an idle trunk line is reached, a circuit is closed over test wiper 215 for the test and switching relay 212 from ground at the upper armature of release relay 209 through the lower winding of the release relay of the switch (the switch for example) to which the idle trunk extends. the rotary movement in the usual manner, shunts its high resistance upper winding, so as to make the seized trunk busy, and connects up the wipers 214tand 216.

In the selector'S5, relay 231' operates and prepares the switch for operation, closing a connection between the test and switching relay 23 1 and the test wiper 236.

When the calling subscriber dials the second digit 1 in the number, line relay 208 falls back once momentarily and grounds the upper talking conductor, thereby operating the impulse relay 232 of the selector S5. Relay 232 causes the operation of the vertical magnet (not shown) of the selector S5 in the usual manner. At the same time, re lay 208 in the switch SR2 operates the slow acting relay 210, whereupon battery is connected through the lower armatures of relays 209 and 210 to the lower talking conductor. As a result, the changeover control relay 233 in the selector S5 operates and prevents the rotary movement of the selector from starting until the vertical movement has been terminated. I

lV hen relay 210 falls back at the end of the digit and opens the circuit of relay 223, the latter relay falls back and initiates the rotary operation in the usual manner. When an idle trunk line is reached, for example the trunk line extending to the selector S6, Fig. 3, relay 23% operates through test wiper 236 and over conductor 1205 Relay 234i shunts its high resistance winding so as to place a busy potential on the seized trunk line and it disconnects the incoming conductors 217 and 219 from relays 232 and 233 and connects them to the wipers 235 and 237. it

Bela 212, in addition to stopping Hill may be pointed out at this time that the function of the off-normal contacts 213 and 230 is to increase the resistance of the associated circuit when the oil-normal movement occurs so as to cut down the holding current.

lVhen the next digit 2 is dialled, relay 302 oi the selector S6, Fig. 3, is operated twice over conductor 419 by the line relay208 of SR2. In the usual manner, relay 203 brings about the vertical operation of S6, with the result that the wipers 305-307 are raised opposite the second level of bank contacts. Relay 303 is operated throughout the vertical movement by relay 210 of the switch SR2, and it falls back at the end of the vertical movement to initiate the usual trunk hunting operation.

lVhenan idle trunk is reached, for example the trunk extending to connector C2, relay 30st operates and makes the seized trunk busy, in addition to extending the incoming conductors 4:19 and 421 to the corresponding conductors 321 and 323 of the connector C2 through wipers 305. and 307.

In the connector C2, there is asequence switch having wipers 329 and 330. In positions 1 and 2 of these wipers, the combined front bridge and back bridge relays 326 and 327 are connected to the incoming conductors 321 and 323, respectively. The side switch arms are moved in the usual manner from position 1 to position 2 at the end of the vertical movement, and are moved from position 2 to position 3 at the end of the rotary movement. If the called line is busy, the arms 329 and 330 remain in position 3 and the usual busy tone is transmitted back to the calling line. However if the line is idle, the busy tone is not placed on the calling line and the side switch arms 329 and 330 advance into position at when the called. subscriber answers.

then the calling subscriber dials the tens digit 3, relay 326 is operated three times over conductor 321, resulting in the usual vertical operation. Vipers 331333 are thereby raised opposite the third level of bank contacts. Relay 327 is operated over conductor during the vertical operation, and when it falls back at the end of the vertical movement it secures the advance of the side switch arms from position 1 to position 2 in the usual manner.

\Vhen the calling subscriber dials the units digit 1, impulse relay 326 of the connector C2 again responds and brings about the rotary movement of the switch in the usual manner. The wipers 331-333 are advanced one step into engagement with the bank con tacts in which the conductors 33l336 of thecalled line terminate. Relay 327 is operated again throughout the rotary movement and it falls back at the end thereof, bringing about the advance or" the side switch through the heavy conductors. Relays 326 and 327 now operate over the called line, and the side switch arms 329 and 330 are caused to advance into position 4.

Conversation may now take place, talking current for the called line being supplied through back brid e relays 326 and 327 of the connector G2, and talking current for the calling ine being supplied through line relays 207 and 208 of. the selector repeater S32, Fig. 2.

The advance of side switch arm 330 into position at is for the purpose of preparing a circuit for causing the meter M, individual to the calling line, Fig. 2, to be operated upon the release of the connector. It will be noted that the lower incoming conductor 323 of the connector C is grounded through relay 327 in positions 1 and 2 of the side switch arm 330, and that it is connected to battery in position 3 through the high resistance 337 and relay 325. In position 4: (talking position) the arm 130 is,for the first time connected to battery through the relatively low resistance of relay 325. It will be seen therefore that a distinctive condition placed on the lower incoming talking conductor only in case the called subscriber has responded and caused the side switch to pass into its fourth position.

When the conversation has terminated, the two subscribers replace their receivers. The replacing or the receiver at the called substation merely brings about the cleanergization of relays 326 and 327, but does not produce any other circuit changes as regards the incoming talking conductors.

ll hen the receiver is replaced at the cal.- ing substation, relays 207 and 208 fall back. Relay 20S opens the circuit of relay 209 and closes the circuit of relay 210. Relay 210 accordingly operate Relay 210 places battery on the lower talking conductor as before, but this is of no particular utility at this time. Itelay 210 it will be noted closes multiple holding circuits for relays 211 and 212 at its upper armature and at its inner lower armature. A moment later, relay 209 falls back and disconnects battery from the lower talking conductor at its lower armature, at, the same time connecting the lower talking conductor to ground through the meter operating relay 217. Relay 217 now operates over the lower talking conductor in series with relay 325 of the connector C relay 325 being connected up by the side switch arm 330 in its fourth position. Upon operating, the meter operating relay 217, Fig. 2, connects ground to conductor 219, thereby shunting relay 211 and increasing the current flow over conductor 219 and through relay 201 of the lineswitch to such an extent that the meter M, bridged around the lower winding of relay 201, operates to record the completed connection.

A moment alter relay 209 falls back, relay 210 falls bad because its circuit is opened at inner lower armature of relay 209. At its upper armature, relay 210 removes ground from the lower terminal of relay 212; it removes ground from the lower terminal 01 relay 211 at its inner armature; and at its lower armature it disconnects the lower talking conductor from relay 217. As a result relay 217 also falls back and disconnects ground at another point from coiuluctor 219. As a result of the removal of ground from conductor 219, the lineswitch LS2 is freed and it returns to its home position in the usual manner responsive to the deenergization of relay 201.

As a result of the removal of ground from the lower terminal of relay 212, the trunk line Xtending to the selector S5 is rendered idle and relay 212 falls back, disconnecting the wipers 214s and 216. The selector repeater SR2 is now restored to its normal position by the action of the release magnet (not shown). l fhen the normal position is reached, the off-normal contacts 213 reclose so as to pe nit the switch to be taken for use ago. 11.

Responsive to the freeing of the trunk line extending to the selector S5, release relay 231. falls back and brings about the usual releasing operation, at the same time disconnecting test wiper 286 so as to deenergize relay 23% and to tree the trunk line extending to the selector S6. in the selector S6, release relay 801 now falls back and brings about the release of the switch and the disconnection of the switching relay from the test wiper.

In the connector C2, release relay 32 1 falls back when the test wiper of the selector S6 is disconnected, and the releasing operation occurs in the usual manner.

Mention may be made at this point of the resistances 205 and 206 in the selector repeater wlich are connected between ground and the respective terminals of the condenser associated with the right-hand repeating-coil windings. These resistances are relatively high and their function is to permit a small current flow over the talking conductors of the established. connection during conversation, one reason advanced for this being that a quieter circuit results. The battery connections to the talking conductors at this time are in the connector C2 through the relay 325 and the high re sistance 328.

he establishment and release of a connection local to oiiice Y having een explained hereinbefore and the establishment and release of a connection in the otlice X being as explained in the Smith and Campbell publication hereinbeiiore referred to, the expla- 112 ion of inter-connections between the two ol'lices may now he proceeded with. For this purpose it will be assumed first that the subscriber at substation A1, Fig. 1, in otlice X desires to converse with the sub scriber at substation A l in cities Y The substation A4; it will be noted is shown in 1 and also in Fig. 3.

Referring first to Fig. 1, the lineswitch LS1 extends the calling line to a selector such S1 when the receiver is removed at substation A1. l Vhen the first digit 6 is dialled, the selector S1 operates to raise its wipers (not shown) opposite the sixth level and to rotate them over the bank contacts in search of: an idle trunk line. It will be assumed that the trunk line extending through the repeater R1 to the selector SR3 in cities Y is the one selected. In this case, the repeater R1 responds to its seizure in the'manner pointed out in the above mentioned Smith and Campbell publication and closes a bridge across the associated outgoing trunk conductors. The detailed circuits of the selector SR3 in oilice Y are shown in Fig. 1, to which drawing reference will now be had.

When the bridge is closed across the incoming conductors 4 .01 and 402 by the distant repeater R1 in oiiice X, the line relay 40 1-, which is bridged across these conductors through contacts of the reversing relay 403, operates and closes a circuit for release relay 405. Release relay 105 operates andprepares the switch for operation. I

lVhen the calling subscriber dials the next digit 1 in the desired number the bridge across conductors 401 and 402 in the repeater R1 is opened once momentarily, whereupon relay 10 i falls back momentarily. When it does so, it closes a circuit through the inner lower armature of release relay 105 for series relay 406. Relay L06 operates and opens a point in the circuit of rotary magnet 413. A circuit for vertical magnet 115 exists in parallel with relay 406 through an armature of the test and switching relay 4-10. Accordingly, vertical magnet 4:15 is momenta rily operated to raise the wipers ilo- 118 op posite the first level of bank contacts.

When the slow acting series relay 106 falls back after the vertical movement has been eilected, it completes at its inner lower armature a circuit'lor rotary magnet 113 which has been prepared at the oil-normal contacts 1 This circuit includes the lower armature of the auxiliary release relay L00 and the its circuit is closed,magnet 413 operates and advances the wipers 416-418 into engage ment with the first set of bank contacts in the level opposite which they have been raised, Near the end of its stroke, magnet 413 closes a locking circuit for itself through the armature of stepping relay 408 and it closes a circuit for the lower winding of the said stepping relay. Relay 408 operates and opens the circuit of the rotary magnet, whereupon the rotary magnet falls back and opens the circuit of the stepping relay. In

case the trunk line termining in the first set of bank contacts is idle,'the test and switching relay 410 now operates through both of its windings .in series, stopping the rotary movement. If the first trunk line: is busy however the rotary magnet circuit is not opened and the rotary magnet operates again advancing the wipers another step. This alternate operation of the rotary magnet and the stepping relay continues as described until an idle trunk lineis reached, which trunk line, it will be assumed, is the one comprising conductors419-421 and extending to the hundreds selector S6, Fig. 3. When said idle'trunk'is reached, relay 410 operates through test wiper 417 and over conductor 420, both windings being .connected in series between the test wiper and ground at the inner lower armature of the auxiliary release relay 409. Upon operating, relay 410 disconnects the vertical magnet 415 at its middle lower armature; opens the rotary magnet circuit and shunts its high resistance upperwinding' at its inner lowerv armature; and at its upper and lower arma tures connects up the line wipers 416 and 418.

In the seized selector S6, Fig. 3, relay 301 operates over release trunk conductor 420 and prepares the switch for operation in the usual manner.

WVhen the calling subscriber dialsthe hundredsdigit 2 in. the desired number, line relay 404 of the switch SR3,-Fig. 4, falls back twice momentarily. Each time it falls back, it grounds the upper talking conductor at its upper armature, with the result that impulse relay 302 of the selector S6, Fig. 3, is operated twice over conductor 419. In addition, the line relay 404 of the switch SR3 closes a circuit for series relay 406 each time it falls, back, with the result that relay 406 operates and remains operated throughout the digit. At its lower armature, relay 406 connects battery through the lower talking conductor through wiper 418 so as to operate the change over relay 303 in the selector S6, Fig. 3.

At the end of the hundreds digit 2, line relay 404 comes to rest in an'energized condition and relay 406 shortly falls back and removes battery from the lower talking conductor.

. -Responsive to the digit transmitted to it the selector S6, Fig. 3,-operates in the-usual manner and extends the connection to a'connector, such as connector C2. 7

' WVhen the neXttwo digits 3fl-and 1 are diallechthey are repeated by the selector repeater SR3, Fig. 4, in the above manner with the result-"that the connector C2 is caused to bring its wipers 331-333 into engagement with the bank contacts of the called line. Assuming that the called line is idle and that the subscriber at substation A4 responds, the side switch arms 329 and 330 are caused to move into their fourth position;

It. may be pointed out that the supervisory relay407 is normally connected between ground and the lowerv line wiper 418 of the selector repeater SR3. This relaydoesnot operate while the side switch arm 330' of the connector C2 is in third position owing to the high resistance of the resistance element 337, this element being provided for a purpose with which we need not be-cons cerned in the present. case. 3 However, when the side switch arm 330 reaches position 4 when the called subscriber responds, supervisory relay 407 inthe selector repeater SR3 operates in series with relay 325.013 theconnector G2 and closes a circuittor'the revers ing relay 403. The reversing relay 403' re.-

verses the connection between the conductors 401 and 402 and the line relay 404 so .as to bring. about a reversal in the direction of current flow in the said conductors 401 and 402. v This causes the usual reversal of current flow in thecalling line to be made at. the repeater R1 in the calling ofiice,-Fig. 1.

This latter reversalinay be made use of to operate a meter it'so desired, or to give supervision in those cases where thecallxis coming "from an operator in a private branch exchange, or the ike. I v f The conversation may now take place, and, when it has been terminated, the two subscribers replace their receivers. .When the receiver is replaced at the called substation, the battery teed relays 326 and 327 merely fall back, but the remaining circuits shown remain in the same condition.

When the receiver is replaced at the calling substation A1, Fig. 1,'the repeaterRl permits the release of the selector S1 andthe lineswitch LS1 and opens the bridge across the conductors 401 and 402 of the selector repeater SR3, Fig. 4. When the bridge across these conductors in the repeater is opened, line relay 404 of the selector repeater falls back and opens the circuit of release relay 405, at the same time operating relay 406 which opens a point inthe talking circuit at its'lower armature, therebypermitr ting relay 407 to fall back. This operation is more or less incidental at this time,;but it results in the deenergization of the reversing relay 403, without however any particu- 1511 efiiect being produced. A moment later release relay 405 falls back and opens the circuit of relay 406, at the same time opening the circuit of the auxiliary release relay 409., Relay 409 falls back and opens the connection between test wiper 117 and ground, resulting in the release of relay 110 and in the freeing of the trunk line extending to the hundreds selector S6, Fig. 3. As a further result of the deenergization of relay' l05, the usual release magnet circuit is closed through oft-normal contacts 312. Magnet 311 now operates and restores the switch to normal in the usual manner. The switches S6 and C2 release in the usual manner.

i The manner in which connections are completed from ofiice Y to ofiice X will now be explained. For thispurpose it will be assumed that the subscriber at substation A3, Figs. 1 and 2 desires to converse with the subscriber at substation A2, Fig. 1. It will be assumed further that the lineswitch' LS2, Fig. 2, seizes the selector repeater SR2 when the receiver is removed and that the selector repeater SR2 finds the trunk line comprising conductors 220222 and extending to the repeater R2, Fig. 6, idle when it rotates over the bank contacts in the fifth level responsive to the dialling of the first digit 5. That 7 being the case, relay 212 of the switch SR2 operates over the test conductor 221 in series with release relay 601 of the repeater R2 when the idle trunk is reached. Relay 212 short circuits its upper winding so as to make the seized trunk busy in the usual manner.

In the repeater R2, the slow-to-pull-up relay 601 operates shortly after its circuit is closed and after a sutlicient time has been allowed for the test relay of the selector repeater SR2 to operate. Upon operating, relay 601 removes the shunt from around its upper winding so as to decrease the holding current, and it prepares a circuit for relay 603 and closes a circuit through the lower winding of the electro-polarized relay 60%. This lower winding is the high resistance polarizing winding and the current flow through it is not of a sufficient value to operate the relay. As a further result of the operation of relay 601, a bridge is closed across the outgoing trunk conductors eX- tending to the incoming selector S3, 1,-

in office X. This bridge includes, in addition to the lower armature of relay 601, the lower armature o'f'impulse relay 602, impedance coil 605, and the upper winding of-electro-polarized relay 604. Responsive to the establishment of this bridge, the distant selector S3 is prepared for operation in the usual manner, the upper outgoing trunk conductor extending to battery through the upper winding of the line relay of the selector and the lower outgoing conductor ex- 7 sistance is inserted tending to ground through the lower winding ofthe said line relay Although cur.- rent is now flowing through both windings of the electropolarized relay, the relay is not operated owing to the fact that the current .is flowing in opposite directionsin the two windings. When the calling subscriber dials the second digit 1 in the desired number, the upper talking conductor extending from the switch SR1 to the repeater R2 is grounded once momentarily by line relay 208., Fig. 2, with the result that relay 602 in the repeater operates once momentarily, 1 opening the bridge across the outgoing conductors at its lower armature. Change-over relay 606 is operated at the the same time over conductor 222 by series relay 210, Fig. 2. Relay 606 disconnects the upper talking conductor from the associated talking condenser and connects it instead to the lower talking conductor by a more direct path, excluding the impedance coil 605 and the upper winding of the electro-polarizedrelay 604-, so as to reduce the impedance of the bridge during impulsing. After the digit has been trans mitted, relay 606 falls back. The distant selector S3 in oilice X, Fig. 1, responds to the digit 1 and selects an idle hundreds selector, for example the selector S4.

When the neXt digit 2 is dialled, the selec tor See, Fig. 1, responds to the impulses re peated to it by the repeater R2, Fig. 6, and raises its wipers opposite the second level, selecting an idle connector, for example the connector C1.

When the last two digits 3 and 0 are "dialled, the connector G1, responds to the impulses repeated to it from the repeater R2, Fig. 6, and completes the connection to the line of substation A2. Ringing current is applied in the usual manner when the connection is completed.

When the called subscriber responds by removing his receiver, the current flowin the conductors incoming to the connector is reversed in the usual manner by the connector, whereupon the electro-polarized relay 604-, Fig. 6, responds as the current flow in its two windings is in the same direction. Upon operating, relay 604 closes a circuit for supervisory relay 603, whereupon relay 603 locks itself independent of relay 604. At its upper cuits, as regards the incoming conductors, into a condition to simulate the condition placed 011 the incoming conductors of the connector, Fig. 3. Specifically, a high rein series with impulse relay 602 atthe upper armature of relay 603, and the upper terminal of change-over rela 606 is shifted from ground to battery at t ie inner upper armature of relay 603 so as to place the necessary battery potential armatures, relay 603 places the cir on conductor 222 to permit the meter M of the calling subscrlber to operate when the conneet10n 1s released.

The conversation may now take place over the established connection. When the conversation has terminated, the subscribers replace their receivers. Then the receiver is replaced at the called substation, the current flow in the conductors outgoing from the-repeater R2, Fig. 6, is reversed back to normal, whereupon the electro-polarized relay 604 restores. Relay 603 however remains operated because of. its loclring'circuit.

When the receiver is replaced at the calling substation, the meter M of the calling line is operated in the hereinbefore described manner after which'the selector SR2 frees the trunk line extending to the repeater R2 and restores to normal, in addition to freeing the lineswitch LS2.

hen the trunk lineextending to the repeater R2 is freed, release relay 601. falls back and opens the bridge across the outgoing trunk conductors at its lower armature, at the same time opening the holding circuit ofrelay (S03 and the polarizing cir cult of relay 604 at its inner lower armature.

Responsive to the opening of the bridgeacross the outgoing conductors, the switches in oflice X release in the usual manner.

It will now be explained how connections are completed over the incoming toll line Figs. 1 and 5 to the exchange containing the oflices shown in Fig 1. It may be. pointed out here that the exchange containing the toll board through which the connections set up over the incoming toll lines are completed is a manual exchange and that a 24r-volt battery is used therefore at the toll board instead of the iS-volt battery ordinarily provided in automatic exchanges. That being the case, it is desired to impulse over the incoming toll lines with the 48-volt battery at the automatic'exchange rather than with the 24-volt battery at the manual exchange, as the higher voltage gives better operation, especially in view of varying ground potentials that may be encountered between the ground connections at the two exchanges. In view of the foregoing and in view of the fact that the so-called dry trunk supervision is desired, certain special circuit provisions are necessary in connection with the impulsing and supervision over the toll line as will be pointed out hereinafter.

Assuming now that the toll operator at the cord circuit CC desires to set up a connection through the cord circuit CC and over the toll line to the exchange including offices X and Y, to thc'subscriber at substation A l, the upper spring contacts of the jack J close a circuit for the release relay 553 when the plug is inserted into the jack. Relay 553 operates and closes a circuit for the slow acting relay 552. Relay 552operates and prepares a circuit for releasing'the distant connection after it is setup, this circuit being prepared at its upper, armature, and it closes a locking circuit for itself through the armature of relay 551. As a further result of the operation of relay 558, the impulse conductor terminating in the upper. armature of this relay is connected toground through contacts of the key K and the supervisory relay 55%. When this occurs, relay 554 oper ates over the aboveinipulse conductor and over the two sides of 'thctoll' line in parallel. Upon operating, relay 554 places ground on the sleeve of the aclr J, lighting the supervisory lamp L in the cord circuit (1C.

In the distant excl iange, the line relay 505, whose lower terminal is connect-ed to the 418- volt exchange battery, operates through the associated impulseconductor and over the two sides of the toll line inparallel, in series with the calling supervisory relay at the toll board. Upon operating, relay 505 closes a circuit for the associated release relay 506, whereupon relay 506 operates and prepares the switch for operation, the auxiliaryree lease time.

The calling toll operator now throws her calling device hey K, thereby disconnecting the impulse conductor from supervisory relay 55 i and connecting it to ground through the calling device Gil Belay 554 falls back and the lamp L becomes extinguished. i

lVhen the operator turns the callingdevice CDin accordance with the first digit 6 in the number, six interruptions are produced in the circuit of the line relay 505 in the oiiice- Y, whereupon relay 505 falls back momen-' tarily six times.

507 operates. and remains operated through out the series of impulses. Vertical magnet 51.7 is operated in multiple with relay 507 each time an impulse is delivered to the d relay. Theresult is that the wipers 518 520 are r ised step-by-step opposite the sixth level on bank contacts.

When relay 507 falls back at the end of the vertical movement, it closes at its inner lower armature 'acircuit for rotary magnet 515 that has been prepared at oii normal contracts 510. When the circuit of the rotary magnet is closed, therotary magnet operates and advances the wipers into engagement with the first set of bank contacts, at the same time locking itself inclependent of the test relay contacts and closa circuit for the stepping relay 510. The stepping. action is similar to that described in connection with the selector repeater SR3,

Fig. 4. It will suffice to say then that when an ldle trunk is reached, for example the trunk line including conductors 217-'-219,

relay 511 being operatedat the same Each time itfalls back,. relay 505 closes a circuit for the'slow actmg series relay 507, with the result that relay the rotary movement stops due to the energization of the test and switching relay 512 over the test conductor 218. Relay 512, it will be noted, at its middle lower armature disconnects vertical magnet 517 at its inner lower armature opens the rotary magnet cir cuit and shunts its upper winding so as to make the seized trunk busy; and at its upper and lower armatures connects up the wipers 518 and 520.

As a result of the seizure of the trunk line comprising conductors 2l72l9, the selector S5, Fig. 2, is prepared for operation in the usual manner.

l i heu the calling operator dials the next digit 1 in the number, line relay 505 of the selector repeater SP2 falls back once momentarily, sending one impulse over the upper talking wiper to the impulse relay of the selector S5. At the same time, slow acting relay 507 places battery on the lower talking conductor of the trunk line through the wiper 520 so as to operate the change over-control relay in the selector lhe result is that the selector S5 operates in the hercinbefore described manner to extend the connection to a hundreds selector such as the selector S6, Fig. 3.

lVhen the next digit 2 is dialled, the selector S6 operates in the usual manner to extend the connection to a connector, for example the connector C2.

lVhen the last two digits are dialled, the connector C2 operates in the usual mannerto extend a connection to the line of sul station A l. Assuming that this line is idle, the connection is completed and the side switch passes into position 4 when the called subscriber responds. l Vhen this take place, the supervisory control relay 508 in the selector repeater SR3 operates in series with r y 325 in connector C2 and closes a circ .i for relay 504. Belay 504 closes a local holding circuit for relay 505 through the upper armature of relay 503, at the same time disconnecting relay 505 from the incoming impulse conductor and connecting the said conductor to ground through the so-called forced-release relay 503. Since he impulse circuit is now grounded at both ends, the circuit having been restored to ground through the supervisory relay 55% upon the restoration of the calling device lrey K upon the completion of the dialing operatiou, with the result that the relay 55a reoperates at this time, relay 556i falls back and extinguishes the supervisory lamp L so as to inform the operator that the called subscriber has responded. The conversation may now take place in case the operator has completed the connection to the other subscriber through the other plug of the cord circuit CC.

When the conversation has been com pleted, the two subscribers replace their receivers. The replacement of the receiver at substation A4 does not result in the relighting of the lamp L as a disconnect signal owing to the fact that the side switch arms of the connector do not move upon the replacement of the receiver at the called station. However, the operator obtains disconnect supervision in the usual manner from the local subscriber when he replaces his receiver. The operator thereupon pulls down the connection.

When the plug P is removed from the jack J, the'circuit of relay 553 is opened. Relay 553 falls back and opens the circuit of the slow acting relay 552, at the same time connecting the impulse conductor through the upper armature of relay 552 and through the winding of relay 551 to the 24e-volt battery. When this occurs, current from the 24-volt battery flows over the toll line and operates relay 503. Relay opens the circuit of line relay 505 at its upper armature and at its lo T61 air-mature it closes a multiple holding circuit for the supervisory control relay 508 so as to main- .tain relay 508 operated for the time being.

Relay 505 falls back when its circuit is opened and it opens the circuit of release relay 506 and reoperates relay 507 through the lower armature of relay 506. Relay 50? operates and disconnects supervisory relay 508 from the lower talking wiper 520, but

relay 508 remains operated through the lower armature of relay 503.

At this point it may be mentioned, that, although the final result would be the same in either case, it is to be assumed that the releaseimpulse is terminated at the toll hoard prior to the release of the slow acting release relay 506. lhe termination of the releasing impulse is brought about as follows: Relay 551 operates in series with the forced-release relay 503 of the switch SR3 and opens the locking circuit o-l 'rclease relay 5 2. Release relay 552 falls back after a slight interval and opens another point in its locking circuit, at the same time opening the forced release circuit at its upper armature.

In the selector repeater SR2, relay 503 now falls back and recloses the line relay circuit at its upper armature, at the same time opening the circuit of relay 508 at its lower armature. 'l'lelayi508 falls back and relay 505 reoperates. "Relay 508 however opens the circuit of relay 50d, whereupon relay 50-fl falls back and reconnects line relay 505 to the uugrouneed impulse. conductor,

t the same time disconnecting relay 503. Belay 505 new falls back again and the release or the switch takes place when the circuit of release magnet 513 is closed through oil-normal contacts 514 upon the deenergization of release relay 506. 7

Considering now the release of the selector tion disclosed therein will be explained.

repeater SR2 in case the operator pulls down the connection after an unsuccessful attempt has been made to set up a connection to a desired line, it may be pointed out that relay 50a is not operated in this case because the supervisory control relay 508 is not operated unless a called subscriber has responded. Therefore, when the impulse conductor the trunk circuit TC is switched over from ground through the supervisory relay 554C to the 2-t-volt battery tln'ouglrrelay 550 upon the deenergization of release relay 553, relay 550 operatesas before, but line relay 505 remains operated due to the difi'erence in potential between the t8-volt battery at the automatic exchange and the 24;volt battery at the toll board. Then, when the slow acting release relay 552' in the trunk circuit TC opens the forcedrelease circuit, relay 505 falls back and the release takes place as before.

Considering now the case when relay 552 is adjusted so as to release slower than the release relay 506, this will not have any effect different than that described herein before except when a release takes place after a called subscriber has responded. In this-case it will be remembered that relay 508 and relay 504 are operated when the forced released circuit is closed. Relays 551 and 503 operate in series with each other as before, and relay 551 opens the circuit of the slow acting relay 552. Relay 503 opens the circuit of line relay 505, and the latter relay in turn opens the circuit o'f'the slow acting release relay506. \Vhen relay .506 falls back, the release of the switch takes place in the usual manner, but relay 503 remains operated and maintains relay 508 o'p erated, which in turn maintains relay 504C ope ated until the forced release circuit is subsequently opened by relay 552. Vhen this circuit is opened upon the deenergization of relay 552, the said relays 603, 508, and 60 i fall back, and the circuits remain in this position until the toll line is again taken for use at .the toll board.

Referring now to Fig. 8, the modifica- 1n explanation of the utility of .thismodified arrangement, it may be pointed out that it may sometimes happen that a considerable number of first selector repeaters such as selector repeater SR2, Fig. 2, are on hand when the toll lines such as the one shown in Fig. 5 are installed between the toll board and the automatic exchange. .3115 such is the.

case, it may be more economical to use these switches and provide a repeater R3, Fig. 8, between each toll line and a selector repeater such as the selector repeater SR2, instead of providing entirely new switches such as the selector repeater SR3, Fig; 5. In this case, the selector repeaters are left un-' changed, except that two extra conductors are'brought out fromthe terminals of the condenser in series with the right hand repeating coil winding, Fig. 8. The regular taken for use by a lineswitch such as LS2.

Line relay 801 also closes a bridge across conductors 1-18 and 420 including the right hand repeating coil windings between the toll line and the repeater, and the current limiting resistance 806. It may be pointed out that the resistance 806 and the associated condenser are used to avoid a saturation'of the core of the repeating coil as might take place if the two windings were connected directly together. Responsive to the closure oi. the bridge across conductors 418 and 420, the line relays of the selector, repeater SR2 operates as explained in connection with the selector repeater SR2, preparing the switch for operation.

lVhen the calling operator manipulates her calling device, relay 801 responds and opens the bridge across conductors 4:18 and 120, whereupon the selector repeater SR2" responds just as though a local calling subscriber we're using the said selector repeater.

The supervisory control relay 804 has been provided to give supervision to the calling operator when the calling subscriber responds, this relay being operated in multiple with the resistance 206 when battery through a sufiicieutly low resistance is placed on the lower talking conductor bythe connector when the called subscriber answers.

This maybe seen upon're'ference to the con-,

nector C2, Fig. 3. The impedance 805 is added so as to maintain the talking circuit in a balanced condition. lVhen relay 804 operates, it connects line relay 801 in alocal holding circuit through contacts of relay 802, atthe same time disconnecting the said line relay 801 tlrom the impulseconductor and connecting the impulse conductor to the :t'oreed-release relay 802/ This gives the hereinbetore-described supervision to the calling toll operator.

When the toll operator pulls down the connection, the impulse conductor is connected to the 2 l-voltbatteryat the switchboard in the above described manner whereupon relay 802'operates and opens thelcir cuit vofline relay 801. Relay 802 also closesa local holding circuit for relay 804.

Inc

at the manual switchboard, relay 802 falls back and opens the circuit of relay i at the same time reclosinp; the circuit of line relay S01. Relay 804 falls back and opens the local holding circuit of the line relay, at the same time transferring it back to the impulse conductor. Linc relay 801 thereupon again falls back. The release of the selector repeater SR2, Which was temporarily halted. upon the momentary reoperation ot linerelay 801, now takes place due to the continued deenergization of relay 801.

ll hat is claimed is:

1. In amulti-ofiicc automatic telephone system, an automatic oilice in which talking current in local connections is supplied to both subscribers lines from the last. switch o'lt' thetrain, an automatic oilice in which talking current in all connections supplied to the calling line from the first switch of the train and in which talking current in local connections is supplied to the called line lrom the last switch. oi the train, and suitable circuit connections "for enabling talking connections to be set up from lines oli' either oilice to lilies of the other oiiice, said talking connectionsincluding switching mechanism in the called oilice which is also used to-set up connections local to lines of such oliice.

2. In a multi-ofiice automatic telephoi'ie-sy tom, an automatic otiice in which talking current in local connections is supplied to both. subscribers lines from the last switch of the train, an. automatic office in which Milking current in all connections is supplied to the calling line from the first switch of the train and in which talking current in local connections is supplied to the called line from the last switch of the train, and suitable circuit connections for enabling talking connections to be set up from calling lines in the first oflice to called lines in the second oiiice through the medium of switching mechanism which isalso used in setting up connections local to the lines of such oiiicc.

3. In a multi-oiiicc automatic telcphoncsystom, an automatic ofiico in which talking current in local connections is supplied to both subs; ibe'rs lines from the last switch of the train an automatic oiiicc in which talking current in all connections s supplied to the calling line from the first switch of the trainand in which talking current in local '(OilllCPilODFl is supplied to the called line from the last switch oi the train, and suitable circuit connections for enabling talking); connect-ions to be set up between ca ling lines of the second ollice and called lines of the first oflice through the medium o'fswitching mechanism which is also used in setting; up connections localto the lines of such oliice.

site end when the called subscriber responds so as to give supervision over the trunk line, and means at the opposite end of the trunk line for momentarily connecting the associated end of the impulse circuit to a di'l terent potential source so as to bring about the release of the connection.

5. In a telephone system, a trunk line extending from a given point to a distant point, means at the said given point for closing a control circuit over said trunk line and for subsequently interrupting said control circuit to said digit impulses, automatic switching mechanism controlled over said trunk line from the distant end thereof to set up a telephone connection, loching means at the distant end of said-trunk line for stopping the current flow thereover when the call is answered and for maintaining the connection intact, and means t the said given point for terminating the locked up condition of the connection and for bringing about its release by momentarily reestablishing a current flow over said control circuit.

6. In a telephone system, means including a repeater, a trunk line, and a train of auto-- matic switches for setting up a connection to a called line, connections in the last switch of the train for supplying talking current to the called line, two talking conductors incoming to said repeater, repeating means in said repeater controlled over said incoming talking conductors in series for repeating impulses to the switches of said train to secure their operation, said impulses being repeated over one talking conductor of said trunk line and a return path independent of the other talking condctor there-of, a supervisory relay'in said trunk line counectedto the other talking conductor, means in the final switch of the train responsive. to the answering of the called subscriber for operating said supervisory relay over a 0i"- cuit path including said other talking (.Hlll" ductor and excluding; said one talkiiur-conductor, and circuit connections in said re peater responsiveto the operation oi said supervisory relay to place a distinctive supiwvisory condition on "said incoming talking conductors. r

7. In a telephone systen'i, means inchuling a trun l: line and a train of automatic switches iiQl SGlflilfl up a connection to a called line... said automatic switches being operated responsive to impulsestransmit ,d over one conductor of said-trunkline and. a return Fill lit)

over one conductor of said trunk line and areturn circuit independent of the other talking conductor, a supervisory relay connected. to said other talking conductor, means in said trunk line for controlling the changeover operation of the switches in said train over the other talking conductor 01 the trunk line without operating said supervisory relay, and circuit connections in the last switch of the train for bringing about the operation of said supervisory relay when the called subscriber responds.

9. In a telephone system wherein a train of automatic switches is operated over one talking conductor independent of the other and the change over operation of the switches is controlled over the other talking conductor independent of the first, means for transmitting hack a supervisory signal over the established connection to set up an answered supervision state at the originating end thereof when the called subscriber answers.

10. In a telephone system, a trunk line, two trains oi automatic switches, one train oi? switches being of the type arranged to respond to impulses over one talking conductor independent of the other and to respond to a changeover control over the other talking conductor independent of the first, the switches in the other train being of the type arranged to respond to setting impulses over both talking conductors in series, a repeating device associated with said trunk line and arranged to control the switches in the first mentioned train, and a second repeating device between said trunk line and the second mentioned train arranged to suitably translate the control so that the second train of switches may be operated responsive to the said control exercised over the trunk line.

1].. In a telephone system, an impulse repeater having two incoming talking conductors and two outgoing talking conductors, means in said repeater responsive to impulses received over an incoming talking conductor for repeating impulses over an outgoing talking conductor, means for transmitting asupervisory signal back to said repeater over both outgoing talking conductors in series, and means in said repeater responsive to said supervisory signal for transmitting'a supervisory signal back over only one incoming talking conductor. x

12. In a telephone system, a repeater hav ing two incoming and two outgoing talking conductors, means in said repeater for repeating impulses received over only one incoming talking conductor into a circuit including both outgoing conductors in series,

and means in said repeater controlled over an outgoing talking conductor for placing a distinct supervisory condition on one of said incoming talking conductors and for maintaining said distinct condition on such conductor independent of further control over such outgoing conductor.

13. In a telephone system, a repeater having two incoming and two outgoing talking conductors, means in said repeater for repeating impulses received over only one in comingtalking conductor into a circuit including both outgoing conductors in series, and means in said repeater responsive to a current reversal effected outside of saidrepeater over said outgoing conductors for ing two talking conductors and having two-- outgoing talking conductors, means responsive to a selzure of said repeater over the incoming conductors for closing a bridge across said outgoing conductors, means 1n said repeater responsive to impulses received over the first lncommg talking conductor for sending impulses over the outgoing talking conductors by interrupting the bridge thereacross, means in said repeater responsive to a prolongedimpulse received over the second incoming talking conductor for reducing the impedanceof the bridge across the outgoing conductors during impulsing, a polarized relay in said repeater responsive to a current reversal in the outgoing conductors, and contracts controlled by said relay for placing a distinctive supervisory condition on the second incoming talking conductor. 7

15. In a multi-otiice automatic telephone system, an automatic oiiice in which talking current in local connections is supplied to both subscribers lines from the last switch of the train, an automatic oliice in which talking current in all connections originating therein is supplied to the calling line from the first switch of the train and in which talking current in local connections is supplied to the calling line from the last switch of the train, and suitable circuit connections for enabling talking connectionsvto be set up from lines of either office to lines of the other oflice, saidcircuit connections including supervisory means controlled from the called office to give supervision in the calling oflice.

Ill)

switch of the train, and suitable circuit connections for enabling talking COHDOCJLIODS to be set up from lines of either office to hncs of the other oliice, said circuit connect-inns including means for indicating in the callinn o'lfice When'the calling subscriber in the called office responds.

Tn Witness whereof, I hereunto subscribe my name this 5th day of March, A. D.. 1592? JOHN WICKS.

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