US2140931A

US2140931A - Telephone system

Info

Publication number: US2140931A
Application number: US96924A
Authority: US
Inventors: Esmond P G Wright; George C Hartley; Wyndham Paul Ian
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1935-09-03
Filing date: 1936-08-20
Publication date: 1938-12-20
Anticipated expiration: 1955-12-20
Also published as: DE767712C; GB462180A

Description

Dec. 20, 1938. E. P. G. WRIGHT ET A1. 2,140,931

TELEPHONE SYSTEM Filed Aug. 20, 1956 4 sheets-sneer 1 E. P. a. wR/GHr /NVEA/ToRs.- c. 2. HAR ner n Wmo/MM By @www TTORNE V Dec. 2o, 1938.

E. P, G, WRIGHT ET A1.

TELEPHONE SYSTEM `4 sheets-sheet 2 F'ileclv Aug. 20, 1956 r ma v3/@l w| EFG Tlw THM E PXLNE MRM S A S N3 .l vm TLNLl al. u. v EN oloo oo oooooooa W @E Q .man E .1 v, rm R MN Q m ECO O0000oooooooooooooooooooooooo om! M .H v 1 ooooooooooooooooooo q V w W p h L, Y IA MN HHH JW 4ms: Wmnw Nm d mw E Mmm B N .QNX qliibbk l aww Dec. 2o, 1938;v

E. P. G. WRIGHT ET AL TELEPHONE SYSTEM Filed Aug. 2o, 1936 4 sheets-sheet s QMWW y A TURA/EV Dec. 20, 1938. E. P. G; WRIGHT Er Al.

TELEPHONE SYSTEM Patented Dec. 20, 1938 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Esmond P. G. Wright,

George C. Hartley, and

Application August 20, 1936, Serial No. 96,924 In Great Britain September 3, 1935 17 Claims.

This invention relates to telephone systems and particularly to systems comprising automatic switching equipment for completing desired connections.

It is the object of the invention to increase the flexibility and eiiiciency of automatic switching equipment in telephone systems.

In telephone systems comprising automatic switches for establishing desired connections, it is known to provide digit registering and translating meansv for controlling the operation of switches through which a desired connection may be established.

A feature of the invention is the provision of means in a telephone system comprising automatic selector switches for translating the position to which a selector switch, through which the establishment of a desired connection is attempted, into the code of an alternative route for use in controlling the reoperation of this switch and the operation of such other switches as may be included in the alternative route.

Another feature of the invention is the connection of a register switch to a selector which has encountered an all-trunks busy condition and the advance of the register switch to a position dependent upon the identity of the trunk group in which all trunks were found busy. If the selector is a two-digit switch the register switch is first advanced to a level corresponding to the level of the selector in which the selected trunk group is located; and then the register switch and the selector switch are advanced step by step in synchronism in these levels until the selector switch reaches its ultimate off-normal position,

whereby the position of the register switch indicates the identity of the busy trunk group.

The invention and its features will be better .understood by consid-ering in detail a multiofce telephone system in which the invention is embodied, one such embodiment being represented schematically in Figs. 1, 2 and 3 of the drawings which form a part of this specification and another embodiment being represented schematically in Figs. 4 and 5 of the drawings.

The invention may be applied to the selector and switch controlling devices of other systems by any one skilled in the art. Referring to the drawings: Fig. 1 shows a two-digit two-motion se-A lector OS;

Fig. 2 shows the register switch VR of a special translator and .a nder switch F for connecting the translator to any one of a group of selectors;

Fig. 3 shows a portion of a translating switch designation distinguishes each contact spring of a relay or magnet from the other contact springs of the same element.

The outgoing group selector of Fig. 1 comprises a vertical magnet VM, rotary magnet RM, release magnet ZM, a Vertical commutator VW, a terminal bank and two sets of brushes; one set consisting of brushes -I, -l-I, and Pl and the other set consisting of brushes 2, +2, and P2. This selector is adapted to be selected and seized, if idle, by a rst selector which is set in accordance vwith the rst of three oce code digits transmitted by a register-translator, neither the first selector nor the register-translator being shown in the drawings. After seizure the selector of Fig. 1 is operated under the control of the second digit transmitted by said register-translator to select a level of the terminal bank and by the third digit transmitted by the register-translator to select the desired group of terminals in the selected level. The selector of Fig. 1 thereupon hunts for an idle set of terminals in the selected group and extends the connection over the junction connected to this set of terminals to the called ofce or exchange. If no junction is available, the brushes are stopped on the last set of terminals in the selected group and in certain cases, it is possible to route the call over a different group of junctions to another oiiice and through this other oiiice to the desired exchange. The completion of a call over an alternative tandem route is desirable, of course, only when all of the direct junctions to the called exchange are busy.

The reoperation of a selector switch OS to select an alternative group of junctions is controlled by the special translator shown in Figs. 2 and 3. The finder switch F comprises a magnet FM, a set of brushes fml, fm2, fm3, fmll, fm5 and fm, and a bank of terminals to which are .connected one or more groups of outgoing group selectors OS. The specialtranslator comprises a register switch VR and a translator switch TS. The register switch has a vertical magnet VMZ, a rotary magnet RM?, a vertical commutator, a terminal bank and brushes wml and mm2. The segments of the vertical commutator of the register switch are connected to the corresponding segments of the vertical commutators of all the selectors OS to which the translator is common.

The translator switch TS shown in Fig. 3 is of the kind described in Patent 1,900,969, granted to E. P. G. Wright, March lll, 1933 and in Patent 1,903,019, granted to E. P, G. Wright et al., March 28, 1933. Each level of the translator switch is connected to a position of the register switch of Fig. 2, which position represents the translated characteristics of a group of direct junctions for which there is an alternative route.

The operation of selector OS and the operation of the special translator, in consequence of of the selector OS nding all junctions in a desired group busy, will be described in detail. When a subscriber makes an `outgoing call, the digits dialed are received by a register-translator which transmits three code digits, the rst of which sets a iirst code selector, and the second and third of which set a two-digit outgoing selector OS of Fig. l. When the outgoing group selector OS is seized by a rst selector (not shown), relay A is operated in a circuit from battery through its right winding, back contacts of springs hs, hb2, haZ and cl3 over the conductor incoming from the first selector, through the controlling register-translator (not shown), back over the conductor, back contacts of springs el, hat, M33, hs, and left winding of relay A to ground. Relay A closes a circuit at the front contact of spring al for operating relay B; and relay B closes a circuit for operating relay C from the winding of relay C, vertical olfnormal contact n2, rotary off-normal contact 1112, contacts b3, ha and hb5rto ground. Relay A is alternately released and reoperated in response to the impulses of the second code digit when transmitted by the register-translator. Each release of relay A closes at the back contact of spring al a circuit for energizing the left winding of relay C and the winding of vertical magnet VM, thereby raising the brushes of the switch up to the level corresponding to the digit transmitted. Being slow in releasing, relay B remains operated during the response of relay A to each digit received. The circuit for operating relay C is opened at contact 112 when the switch moves out of normal position but relay C is held by its left winding until all of the impulses of the second code digit have been received by relay A. The release of relay C closes a circuit through the winding of relay E, contact nl, back contact of spring c4, rotary off-normal contact m2, contacts b3, ha5 and hb to ground. Relay E operates, transferring at spring e5 the left winding of relay C from magnet VM to magnet RM and closing at contact c3 a circuit for reoperating relay C. At spring c, relay C opens the operating circuit and closes a locking circuit for relay E. Relay A then responds to the impulses of the third code digit when transmitted from the register-translator, each release of relay A closing the circuit for operating magnet RM, the brushes being thereby advanced by magnet RM into engagement with the first set of terminals in the desired group of the selected level. When the brushes are advanced out of the normal rotary position opposite the selected level, the rotary oli-normal springs are actuated, contact n12 being eiective to hold open the operating circuit for relay E. When all of the impulses for the third code digit have been received, relays C and E are released in succession. While relay E is releasing, the first two sets of terminals in the selected group are tested. If the set engaged by the upper set of brushes is idle, relay I-IA is operated by the current in a circuit from ground through contact bl, vertical offnormal contact n3, back contact of spring hbi, winding of relay HA, rotary off-normal contact nrl, contact cl, front contact of spring e4, contact hsl and through the right winding of relay G to battery. Relay G is marginal and does not operate at this time. Relay HA closes a locking circuit through its contact hal; and, at its front Contact had, connects ground from contact bi to the test brush Pi to guard the selected junction from seizure by any other hunting selector. The operation of relay HA extends the connection from the first selector through the iront contacts'of springs mi2 and m3, and through brushes l and -2 to the junction connected to the terminals with which these brushes are in engagement. The opening of contact ha prevents the reoperation of magnet RM after relay E releases.

If the set of terminals engaged by the upper set of brushes is busy, but the set of terminals engaged by the lower set of brushes is idle, the busy ground potential encountered on the test terminal with which brush Pl is in engagement is effective by its connection through the back contact of spring hall and contact b4 to shortcircuit the winding of relay HA so that relay HA does not operate and relay G operates. Relay G closes a locking circuit from battery through contact gil, left winding of relay G, contact g2, front Contact of spring b5, Vertical off-normal contact c5, and contacts ha and M15 to ground. With relay HA normal and relay G operated, a circuit is closed for operating relay HB; this circuit is traced from battery through the winding of relay HB, back contact of the eleventh step spring sl, conta-cts g5, n3 and bl to ground. Relay HB locks through the front contact of its spring kbl; and the opening of the back contact of this spring prevents the operation of relay HA when relay E releases. Relay G releases when relay HB opcrates. V/ith relay HA normal and relay HB operated, the connection from the iirst selector is extended through the back contacts of springs haZ and hat and the front contacts of springs hb2 and hb, and through the brushes 2 and +2 to the junction connected to the terminals with which these brushes are engaged. The operation of either of relays HA or HB causes the release of relay A and the release of relay A causes the release of relay B, the ground potential for holding whichever one of relays HA or HB is operated being supplied from the seized junction through the brush PI or 1LT-'Zas the case may be. The register-translator controls the operation of the remaining switches required for completing the ydesired connection. When the connection is released, the disconnection of the holding ground potential from the test conductor P causes the release of relay HA or HB and operation of release magnet ZM in a circuit through the back contact of spring b5, Vertical oil-normal contact p5, and back contacts ha and hb. When the switch reaches normal the circuit for operating magnet ZM is opened at contact fc5.

If both sets of contacts, with which the upper and lower sets of brushes are in engagement, are busy when relay C releases at the end of the group selecting operation of magnet RM, the ground potential encountered A'by brush P2 is connected through the back contact of spring hb4 and contact g4 to short-circuit the Winding and thereby prevent the operation of relay HB. The operating circuit through the right winding of relay G having been opened by the release of relay E and the left winding of relay G- being short-circuited by the busy ground potential encountered by brush P2, relay G releases closing a circuit for operating the rotary magnet RM; this circuit is traced through contact el, the back contact of spring hs'l, contact gl, rotary oil"- normal contact M2, and contacts b3, ha5 and hb to ground. The operation of magnet RM steps the brushes to the next sets of terminals in the group which are tested in the manner hereinbefore described,'except that the test circuit through the right winding of relay G is closed through the contact rml while magnet RM is releasing instead of through the front contact of spring c4. The selector' is provided with an additional brush D and associated terminals for use in determining Whenever the brushes are advanced to the last terminal of a group without iinding any line in the group idle. To this end the contact g3 ci relay G is connected to each of the terminals in the selected level with which brush D engages when advanced to the last position of a group; so that, if all of the junctions in a selected group are busy, a circuit is closed from the busy ground potential encountered by brush P2, through the back contact of spring hbd, contact g3, terminal and brush D, contact c2, and lower winding of relay HS. Relay ES operates and closes at its contact hsli a locking circuit through its upper winding, the front contact of spring b5, contacts p5, hai and hb to ground. Relay G releases but the circuit through contact gly for reoperating magnet RM is held open at the back contact of spring hs'l. At contacts-7135 and het the connection of the incoming conductors and -lto the windings of relay A is'interchanged so as to reverse the current over these conductors and through the register-translator which in known manner thereupon stops the transmission of digit impulses until the normal direction oi current is restored.

All of the junctions in the selected group having been found busy and relay HS operated, a start circuit is closed for initiating the operation of the finders of all idle special translators in order that one of these translators be associated with the selector OS in question. This start circuit J's traced from Ibattery through contact hs3 and over conductors S, through the off-normal contact nl and contact b of relay B2 of each idle translator, to the upper Winding of the start relay ST of each such translator. Relay ST closes a circuit from battery through the winding of finder magnet FM, contact st2, back contact of spring p2 and back contact of spring d2 to ground. The brushes of the iinder of each idle translator are thereby advanced to hunt for the selector OS which has found all junctions in a selected group busy. When the terminals, to which this selector is connected, are found by one of the hunting switches, relay P2y of the iinder switch in question is operated by the current in a circuit from ground through contact stl, lower winding of relay P2, brush fml and terminal, over conductor T and through contact hs3 of the selector in question to battery. At contact pl, ground is connected through the upper winding of relay P2 to the terminal with which brush fml is in engagement, the potential of this terminal being reduced sufficiently to prevent the operation of the relay P2 of any other hunting nder switch. At the back contact of spring p2, the circuit for operating magnet FM is opened to stop the finder switch and at the iront contact of spring p2 a circuit is closed through the lower winding oi relay T and resistor BSP. This resistor is common to all of the translators so that the current through the' lower winding of relay T will be insufficient to cause the operation of this relay if there is any other translator in the same group then connected to one of the selectors OS and making use of the common marking multiple between the ybanks of the selectors and the banks of the register switches VR. This marking multiple need not necessarily be a straight multiple. Assuming the multiple to be free, relay T operates and at its contact tl connects its upper winding in parallel with its operating winding thereby increasing the drop in potential through resistor BSP to prevent the operation of the T relay of any other translator in the group. At contact t3 a circuit is closed through the lower winding of relay B2 to ground at contact d3, but this winding is sho-rt-circuited as long as contacts MS are closed. The interruptor contacts MS are opened and closed 10 times per second; and the next opening of these contacts, after relay T operates, causes the operation of relay B2. Relay B2 opens the operating circuit for relay ST at contact h6; but it also closes a locking circuit through the lower winding and Contact stt of relay ST, back contact of spring ci, to ground at contact b3. The actuation of contact spring b2 transfers the interrupter contacts MS through the front contact of spring std to the winding of vertical stepping magnet VM2; and theoperation of this magnet each time contacts MS are closed raises the brushes of switch VR one step. When the level corresponding to that on which the brushes of switch OS are standing is reached, a circuit is closed from ground at contact t4 through the Winding of relay C2, vertical comrnutator brush or and segment, through the corresponding segment and the brush VW of the vertical commutator of selector OS in Fig- 1, back contact of spring eli, conductor L, terminal and brush fm2 of the finder F, and through contact t2 to battery. Relay C2 is operated by the current in this circuit. At its back contact spring cl opens the circuit through the lower winding of relay ST and at its front contact connects this winding through the front contact of spring b2, interrupter contacts MS, contact t3, and the back contact of spring d3 to ground; and the next opening of the interrupter contacts MS causes the release of relay ST. The opening of the front contact of spring stfl prevents the further operation of magnet VM2 and the closing of the back contact of spring stil connects the winding of relay A2 to the interruptor contacts MS. Relay A is then alternately operated and released under the control of contacts MS. Each operation of relay A closes, at the front contact of spring a3, a circuit for energizing magnet RME and., at its contact al, a circuit from ground on the terminal with which brush fmt is engaged, through contact g2, brush jmd, over conductor R tothe selector OS, front contact of spring hs'l, contact el and through the winding of rotary magnet RM to battery. Thus the rotary magnet RM2 of the register switch VR of the translator and rotary magnet RM of the selector OS are simultaneously alternately operated and released, under the control of relay A and interrupter conl tacts MS, to advance the brushes of each of these switches step-by-step. When the brushes of selector OS reach their eleventh rotary position, the contact springs si, s2 and s3 are actuated. At the back contact of spring s2, the short circuit around the left winding of relay EL is opened and, the contact i152 being closed, relay EL operates. The operation of relay EL causes the release of relay C2, disconnects the and conductors incoming from the first selector from the windings of relay A, and closes a circuit from battery through contact t2 of relay T in the translator, brush fm2, conductor L, front contact of spring el l, conductor to the first selector and register translator, back over the conductor, through contact elfi and the right winding of relay EL to ground. Relay EL is thus held operated and the register-translator is thus maintained inert. At the front contacts of springs cl3 and elfi the windings of relay A are connected over conductors and -l-, through brushes fm and fm, and contacts a2 and b4 of relays A2 and B2, in series with the upper winding of relay D2, the contact a2 being closed as soon as springs MS are opened and relay A2 releases. Relay D2 is operated by the current through Yits upper winding, and locks through its lower winding and contact d5 to ground at contact b3. The opening of contact d3 prevents the further operation of relay A2 and magnets RM2 and RM, the brushes of switch VR having been advanced to a position complementary to that of the junction group in which all junctions were found to be busy. After relay D2 operates, relay B2 is held operated by its upper winding in a circuit through its contact bi, back contact of spring gl and through the front contact of spring d2. At contact cl2, relay EL closes a circuit for operating the release magnet ZM of switch OS; this circuit is traced through contacts cl2, hsll, front contact of spring b5 of relay B, and through contacts p5, ha and hb to ground. When the selector switch reaches normal, the opening of contacts n causes the release of relay HS and magnet ZM. Relay A of the selector is held operated over the and -lconductors, through brushes fm and fmS, and through contacts c2 and dit in the translator, the upper winding of relay D2 being short-circuited iby Contact dd. The register switch VR having been set to a position indicative of the group in which the selector OS found all junctions busy, the marking multiple between the vertical commutators of the translators and selectors may be released for use by other translators and selectors; to this end the circuit through the winding of relay T is opened at the back contact of spring d2, and relay T releases.

With the register switch VR set in a position indicative of the character of the group in which selector OS found all junctions busy, the winding of relay F2 is connected through contact d, brush Uml and terminal, over the S conductor by which this terminal is connected to relay TA of the translating switch in Fig. 3, through the winding of relay TA, to the normal terminal of the group with which brush tmf! engages. If the translator is then idle, the brush tm is in engagement with its normal terminal and relays` F2 and TA are operated. Relay F2 closes a circuit through the front contact of its spring f3 and the front contact of spring b5 for operating relay G2. Relay TA closes a circuit at contact tal for operating relay TC and as soon as the interrupter contacts MS of the translating switch are next opened relay TC operates. Contact spring tcl transfers the interrupter contacts MS to the winding of the translating switch magnet TM and contact tc3 closes a locking circuit for relay TC. If desired, metering relays D3 may be connected to the S conductors from the bank of switch VR in series with relay TA. The particular D3 relay, which is included in this circuit for operating relay TA, operates; and the aforementioned operation of relay TC closes a circuit through contact dl for operating that one of a plurality of overflow meters OM, which is individual to the junction group in which all junctions were found busy. The interrupter contacts IS and MS operate in synchronism, the contacts MS being effective to alternately operate and release the translator stepping magnet TM. The contacts iS are connected to all of the translator switch brushes tml, tm2, tm3, the banks of which are multipled to impulse conductors P, leading to the terminals of the bank of switch VR with which brush mm2 engages. Translated codes are thus obtained for the groups of junctions connected to the bank of switch OS, which codes control the switching operations required for reaching the same offices over alternative routes. For a more complete description of the interconnection of the terminals of the bank of switch VR over conductors P to the terminals of switch TS to give the desired translated codes, reference may be had to the aforementioned Wright Patent No. 1,900,969. The operation of magnet TM under the control of contacts MS advances the brushes of switch TS to transmit the particular alternative route code identified by the setting of switch VR. Relays TA and F2 are released when brush tmll leaves the home position. Relay G2 is held operated through the back contact of spring f3, contacts g5, d5 and the front contact of spring g4. YRelay B2 releases when contact f4 is opened. Each time one o-f the translator brushes tml, tm2 or fm2 encounters a terminal to which the conductor P (from the terminal in the bank of switch VR with which the brush mm2 is in engagement and which identies the junction group in which all junctions were found busy) is multipled, the winding of relay A2 is connected through the front contact of spring g3, contact fl, brush mm2 and terminal, over a conductor P, terminal and brush tml, tmZ or tm3, to the interrupter contacts IS. As soon thereafter as these contacts are again closed, relay A2 is operated, the opening of its contact a2 causing the release of relay A of the selector OS. Switch TS steps on the back stroke of magnet TM so that the stepping does not affect the control of relay A2 by contacts IS. The impulses corresponding to the first and second digits of the alternative route code are thus transmitted to relay A2 and through it to relay A of selector OS to operate the vertical magnet VM and rotary magnet RM and thereby again advance the brushes of switch OS to the rst set of terminals in the alternative route group in the manner hereinbefore described. When an idle tandem junction in this group is found, relay HA or relay HB operates extending the connection to the selected junction. The remaining code digits are then sent from the special translator by the contacts a2 of relay A of the translator to control the operation of one or more selectors in the tandem or intermediate exchange or exchanges. When all of the code digits, necessary to reach the desired exchange, have been transmitted, re-

lay TB is energized in a circuit through one of the translator brushes and an engaged terminal, which terminal marks the end of a translated code, and through contacts IS to ground. At contact tb2 the winding of magnet TM is connected in parallel with the winding of relay TB. I'he opening of the back contact of spring tbl causes the release of relay TC. After relay TC releases, relay TB is held through contact to2 and through the ofi-normal terminals with which brush tmll engages until the switch TS is restored to normal. The stepping magnet TM operates through its own interrupting contacts, and through contacts tbZ and to2 to the ground on brush im@ When the switch reaches the home position relay TB releases and magnet TM.can not reoperate. While relay TB is operated, ground is connected through the front contact of spring tbl over conductor S to the terminal with which brush crm! is in engagement, thence through brush wml and contact dii to the winding of relay F2 causing the reoperation of relay F2. The operation of relay F2 causes the release of relay G2. The release of relay G2 causes the release of relay D2 and the release of relay D2 causes the release of relay F2. With relays B2, F2 and G2 released the release magnet ZM2 is operated and the register switch VR is restored to normal in usual manner. The release magnet ZM releases when the switch reaches normal and contacts n2 are opened.

'I'he aforementioned release of relay D2 opens at its contact dl the above-mentioned circuit through the register-translator and right winding of relay EL of the selector OS. The release of relay EL completes at the `back contacts of springs cl3 and cls the connection from the iirst selector and register translator, through the brushes of selector OS to the seized junction and through the tandem ofce to the desired office. The register-translator thereupon controls the completion of the desired connection in usual manner.

It may be desirable to connect more than one group of selectors OS, to the nder switches of argroup of translators in which case it is then desirable that there be no interference between the two groups in controlling the setting of the register switch VR. To this end the relay E2 may be provided in which case ground is directly connected to the terminals engaged by brush fm3 and which are associated with the selectors of one group; but the terminals with which brush fm3 engages and associated with the other selector group are not connected directly to ground. When a selector of the second group calls in an alternative route translator the rst operation of relay A2, while effective to operate magnet RM2 and advance switch VR one step, is ineiTective to operate magnet RM of the selector because the terminal with which brush fmS is in engagement is not connected to ground. When relay A2 releases after switch VR takes the lirst rotary step, the closing of the rotary oi-normal springs arl causes the operation of relay E2; the circuit for relay E2 is traced through the back contact of spring c2, contact ml, and back contacts of springs a3 and gl. Relay E2 locks through contacts e2 and b3. At contact el, ground is connected to Contact al so that each succeeding operation of relay A2 causes the operation of magnet RM of the selector as well as the operation of magnet RME of switch VR. The switch VR is thus given one more step when the associated selector is in one group than when it is in the other for the same position of the selectors and the possibility of interference between the two -groups is thereby minimized.

On certain routes, such as a group of long distance lines of a character which provides high grade transmission, it is undesirable to provide alternative trunking. In such a case, the selector is redirected und-er the control of the special translator to a level in which the brushes will be automatically advanced eleven steps to the eleventh rotary position in which position contact springs Si, S2 and S3 are again actuated. The special translator is released and the selector reconnected to the register-translator to indicate the busy condition, whereupon release again takes place as hereinbefore described.

Consider now the embodiment of the invention illustrated in Figs. 4 and 5. In this system two digits determine the exchange in which a wanted subscriber is located. A calling subscribers line is connected to a i'irst selector which in response to the first digit dialed selects an idle second selector. The second selector is a onedigit selector and, in response to the second digit dialed, selected a group of junctions outgoing to the wanted exchange and selects an idle junction in this group. One of these second selectors OS is represented in Fig. 4, only the apparatus required for a disclosure of the invention being shown. With each group of 25 second selectors, there is associated a group of three link circuits one of which is shown in Fig. 4. Each link comprises a selector finder switch SF having access to 25 second selectors and a register finder RF having access to a group of 5 or 6 register-translators RC, the translators being common to all of the links in the exchange. When a second selector findsY all junctions busy in a selected group it calls into service a link and a translator which thereupon assumes control of the rerouting of the call and which also receives and registers the numerical digits dialed by the calling subscriber. The second selector is released from its set position and is selectively reoperated to seize an idle junction to a tandem exchange. This translator then controls switching operations in the tandem vexchange to select an idle junction leading to the called exchange and the numerical selections in the called exchange.

When a second selector is seized and, in response to the second digit dialed by the calling subscriber, is moved out of normal, the off-normal contact n2 closes and relay X operates in series with the release magnet ZMl. The release magnet is marginal and does not operate in series with relay X. At contact :rl a circuit is closed for operating the common start relay SA. At contact sa, relay SA closes circuits for operating relay ST4 of each free link in the group associated with the group of second selectors to which relay SA is common. In each suchlink relay ST4 closes, at Contact StZ, a circuit for operating the selector-iinder magnet SEM. When the brushes of a nder engage the terminals to which the selector OSA is connected, a circuit is closed through brush sfml and both windings of relay P4 to 4ground at contact sti.` Relay P4 operates and at its contact p2 short-circuits its right winding, thereby decreasing the potential of the terminal with which brush sfml is en gaged to cause the release of relay SA and thereby stop the hunting of the other links. In the successful link, the operation of relay P4 opens the operating circuit of magnet SFM and at the front contact of spring pl closes a circuit for operating relay PP. At contact m05, relay PP opens the operating circuit of relay ST4. At the front contact of spring ppll, relay PP closes a circuit for operating the finder magnet RFM; this circuit includes the back contact of spring t2, brush rfmi of the register-lnder switch and the back contact on! of any register-translator with the terminals of which the brushes of switch RF are then in engagement. If this translator is busy, the ON relay is not operated and the magnet RFM is energized to step the brushes to the next set of terminals. When the brushes encounter a set oi terminals to Which an idle translator is connected, the ON relay of this translator being operated, contact oni is open and magnet RFM cannot reoperate; and the hunting operation is ended.

If the second selector OS@ finds an idle junction in the selected group, the operation of the usual switching relay H, the winding of which is not shown in the drawings, opens at contact hl the operating circuit of relay X. The release of relay X causes the release of relay Pl!- of the associated link and the translator is not brought into action.

If. however, the selector finds all of the junctions in the selected group busy and the level of this group is one arranged for alternative routing, the eleventh step springs are actuated when the brushes reach the eleventh rotary position. The operating circuit for relay X is opened at contacts s2, and a circuit is closed from ground at contact bl, through the oir-normal springs nl, eleventh rotary step spring sl, winding of relay K, and through brush sfm and contact ppl of relay PP of the associated link. Relay K operates in this circuit; locks through its contact k2; and closes, at its contact kl, a circuit through brush sfmZ, contact ppl of relay PP of the link, winding of relay Til, front contact of spring ppl and winding of magnet RFM. Being marginal magnet RFM does not reoperate, but relay T4 operates. Relay T4 closes a holding circuit for relay PP through contacts mit and il, and through brush rfm to ground at the back contact Tl of relay R of the associated translator. Relay P4 of the link releases when relay X of the selector is released. Since relays P4 and PP of the link are slow in releasing, the above traced holding circuit for relay PP is closed soon enough to prevent the release of this relay. The aforementioned operation of relay K opens vat contacts 7c3 and 74:4 the normal connection between the incoming and conductors and relay A4 of the selector OSG; but relay All remains connected tothe calling loop through brushes sfm and sfm'i, contacts mi2 and m23, back contacts of springs t3 and t4 and brushes smil and sfm' until relay T5 operates. Relay Til interconnects the selector and register-translator, the calling subscribers loop being disconnected from the windings of relay All and connected through the front contacts of springs t3 and t4 and brushes rfm and Tfn/:3 to the windings of relay RA in the register-translator. Relay A6 is held operated through contacts t5 and t5, brushes rfml and #m5, back contact of spring T2 of relay R in the register-translator, contact 80.2 and through contacts mf and m95 in parallel. Relay RA operates over the calling subscribers loop, closing at the front contact Vof spring ral a circuit for operating relay RB; and relay RB closes at contact Th2 a circuit for operating relay BB. The opening of contact T123 causes the release of relay ON. The closing o contact on! connects ground to the terminal with which brush 'rfml is in engagement, through the front contact of spring t2 in the link, to the winding of relay T4 to hold relay T4 operated independent of the ground potential on the sleeve conductor P of selector OS. Relay BB of the translator completes a circuit for operating relay MG from the common resistor BS in the link, through Contact t9 and brush rfm, contact bbS of relay BB, contact mja and through both windings of relay MG in series. Relay MG operates if the MG relay of none of the other translators is operated when relay BB of the translator in question operates. At contact mgl, the high resistance right winding is short-circuited to increase the drop in potential through resistor BS and thereby prevent the operation of the MG relay of any other translator while the common marking multiple between the vertical commutators of the selectors and the banks of register switches BS of the translators is in use by the translator whose operation is being described. Relay MG closes the operating circuit of the selfinterrupting stepping magnet BSM of switch BS through contact m93, back contact of springs mi and mf to ground at the front contact of spring bbl. Each of the groups of terminals with which brush bsml of switch BS engages, is connected by a common marking multiple to the commutators of the selectors in a different group of second selectors; and when brush bsml engages the terminal which is connected to the commutator segment with which brush-es vm of the second selector in question are in engagement, relay M of the translator operates, the opening of the back contact of spring ml'preventing the further advance of switch BS; the circuit for operating relay M is traced through contact myZ, brush bsml, common' marking multiple conductor, commutator wipers um of selector OS4, brush smil of switch SF, contact t8 of link relay T, brush Tfm of switch RF, to ground at contact mg of relay MG of the translator. At the front contact of spring m! relay M closes a circuit for operating relay MF; and relay MF locks through the front contact of its spring mfG, to ground at contact bbl. Both of contacts mf2 and m95 having been opened, relay A4 of selector OS4 releases, causing the release of relay B (winding not shown). The release magnet ZM4 is thereupon operated through contacts n2, b2, al and hl, the brushes of selector OS4 being thereby restored to normal. Relay M of the translator releases when the selector is restored. Relay MF having been operated and relay M released, both of contacts mf3 and m2 are open and relay MG releases. The common marking multiple between the second selectors and switches BS of the translators is thereby released.

rThe release of relay MG closes, at contact m95, the above described circuit through brushes rfmd and Tfr/"L5 for operating relay All of selector OS4. The release of relay MG also closes a circuit through the winding of relay CC and Contact r3, myd, se'and mfd; and, as soon after this circuit is closed as the interrupter contacts MS are opened, relay CC' operates. At the front contact o spring cci, the winding of stepping magnet SSM of switch SS is connected to the interrupter contacts MS, which contacts are opened and closed ten times per second. Each operation of magnet SSM advances the brushes ssml, ssmZ and ssm3. When brush ssm3 engages 'terminal 4, a circuit is closed through this brush and contacts mf and sa for operating relay SA. Relay SA is held in this circuit until relay SZ operates during the next 11 additional steps of switch SS. At contact sa2, relay SA opens the short circuit around impulse springs. IS, which springs are also opened and closed ten times per second. Each opening of springs IS, after contact 8d2 is opened, causes the release of relay A4 of selector OS4, the brushes of this selector being raised onev step by each operation of relay A4 in usual and well-known manner. Assume that the tandem office junctions, which constitute the route alternative to the group in which the selector OS4 found all junctions busy,

are located in the sixth level of the bank, so that the brushes are to be raised to the sixth level by the operation of relay A4 under the control of springs IS. In this case the terminal, with which brush scm3 of switch SC is in engagement when in normal position, is connected to the terminal with which brush sSmZ of switch SS is in engagement in the tenth off-normal position. Six impulses having at that time been sent to relay A4, a circuit is closed from ground at the front contact of spring mfl, through brush scm3 and normal terminal, terminal Ill and brush ssmi, contact sal, and lower winding of relay SZ. Relay SZ locks through contact S24 and brush ssml; and contact S22 of relay SZ shortcircuits the impulse springs IS to prevent the transmission of another impulse to relay A4.

'Ihe selector OS4 thereupon hunts in the sixth 'contact S25, the magnet SSM is connected to brush ssml and the brushes of switch SS are thus advanced to normal; and at contact S21 a circuit for operating stepping magnet SCM of switch SC is closed. When switch SS reaches normal, relay SZ releases and opens the operating circuit of magnet SCM; the release of magnet SCM advances the brushes scml, scm2 and scm3 to the rst off-normal position. Relay CC reoperates when relay SZ releases and the contacts MS are next opened; and thestepping magnet SSM is energized each time contacts MS are closed to again advance the brushes of switch SS. Relay SA reoperates when position 4 is reached and is held until relay SZ operates during the next 11 additional steps. The selections to be controlled in the tandem oiiice determine the digits transmitted by contacts IS to the tandem oiiice, an impulse being transmitted by each closure of these contacts after contact sal is opened by the reoperation of relay SA. The rst off-normal terminal, with which terminal brush scm3 is in engagement is connected to brush bsmZ and through cross connecting conductors CCF to the desired one of terminals 4 to I3, inclusive, with which brush ssm2 engages; and, when brush ss'mZ encounters the particular terminal which is connected to the terminal with which brush bsmZ is in engagement, relay SZ is reoperated to end 'the first train of digit impulses being transmitted to the tandem ofce. Relay SZ causes switch SC to be advanced to the second off-normal position and a second digit is sent to the tandem oflice in the same manner, the circuit for operating relay SZ a third time to end the second digit transmitted to the tandem olice being traced through brush scm3 and second oir-normal terminal, brush bsm3 and terminal with which it is in engagement, over one of cross connecting conductors CCF to the terminal with which brush ssm2 is then in engagement and through contact sal, to the lower winding of relay SZ.

When all selections necessary to reach the wanted exchange have been transmitted from the translator, the further progress of the call depends upon the numerical digits dialed by the calling subscriber; and during the transmission of the oiiice code digits and wholly independent thereof, these numerical digits have been received by relay RA and registered by switches MS, HS, TS and US. Each release of relay RA in response to the impulses of the thousands digit closes a circuit from ground through the back contact of spring ral, contacts rb'l andr4, winding of relay C5, brush d`d`3 in normal position, to stepping magnet MSM of the thousands register switch. Relay C5 operates in sc ries with the stepping magnet and being slow in releasing remains operated until all of the impulses in the train created by the dialing of the thousands digit have been received by relay RA. Relay C5 closes a circuit at contact cI for operating stepping magnet DDM of switch DD. When relay C5 releases at the end of the digit, magnet DDM releases thereby advancing the brushes ddl, dd2 and dd3 to the iirst off-normal set of terminals. In response to the hundreds digit, relay RA is effective to operate the stepping magnet HSM of the hundreds register through brush dd3 and terminal I; in response to the tens digit, relay RA is effective to operate the stepping magnet TSM of the tens register through brush dd3 and terminal 2; and in response to the units digit, relay RA is effective to operate the stepping magnet USM of the units register through brush dd3 and terminal 3. At the end of the units digit, the release of relay C5 again causes the release of magnet DDM and the brushes of switch DD are advanced to the fourth off-normal position and no additional impulses will be registered. The numerical digits may be sent out as soon as they are registered and the preceding digit has been sent. that the thousands digit will not be sent until completely received, relay SZ is held operated, after the second digit has been transmitted to the tandem ofce, until switch DD has advanced out of normal position; the circuit for holding In order` relay SZ Vis traced through its upper winding and contact sal, brush scmZ in second oi-normal position, brush' ddmZ in normal position to ground at the front contact of spring bb. In like manner relay SZ is held through brush scm2 in ofi-

normal positions

3, 4 and 5 and brush dd2 in off-normal positions I, 2 and 3 so that each of the hundreds, tens and units digits must have been completely received before it can be transmitted -to the called exchange. The sending switch SS is reoperated, as hereinbefore described to send each one of the numerical digits, the circuitl for operating relay SZ to end the thousands digit being traced through contact sal, brush ssm2, the cross-connecting multiple se, terminal with'which brush msm? is in engagement, vand brush scm3 lin third oit-normal position; Yto endv the sending ofthe hundreds digit, the circuitI for operating relay SZ includes brush scm3 in fourth off-normal position and the terminal with which brush hsm2 is in engagement; to end the sending of the tens digit, the circuit for operating relay SZ includes brush scm3 in fifth off-normal position and the terminal with which brush tsm2 is in engagement; and to end the sending of the units digit, the c'puit for operating relay SZ includes brush scm in sixth off-normal position and the terminal with which brush usmZ is in engagement.

When the units digit has been received and transmitted, the operation of relay SZ closes at contact ssl the' circuit for operating magnet SCM whereby switch SC is stepped to the seventh oil-normal position, in which position relay R is operated by the energization of its lower winding, through brush scmB in the seventh oiT-normal position to ground at the front contact of spring mfl. The operation of relay R causes the release of relay PP of the link; and the release of relay PP causes the release of relay K of the selector OS4 and the release of relay T4 of the link. Relay K releases quickly and relay T4 releases slowly. When relay K releases, the calling subscribers loop is connected through contacts k3 and 104 to the brushes (not shown) of the selector OS4 thus completing the connection between the calling and called lines. When relay T4 releases, the opening of contacts t3 and t4 disconnects the calling line from relay RA. After relay PP releases and before relay T releases, the resistor which is normally short-circuted by contact r2 of relay R is connected in the loop across contacts t5 and t6 so that the release of relay K will not cause excessive noise at the calling station. The release of relay RA causes the release of relays RB, BB and MF in succession. Switches MS, HS, TS, US, SS, SC and DD are thereupon advanced to normal by operation of their stepping magnets through brushes msml hsml, tsml, usml, ssml, scm! and ddl respectively. Switch BS is a non-restoring switch. When all of the numerical register switches are normal, relay ON reoperates and opens at contact o'rLZ a holding circuit for relay R. Contact o'fLl disconnects ground from the terminal with which brush Tfml of nder RF is in engagement, thereby causing this register-translator to test idle.

If a selector OS4 is advanced into the eleventh rotary position on a level for which there is no alternative route, the link is seized while the selector is being stepped up to this level and the register-translator is seized when the eleventh rotary stop springs are actuated as hereinbefore described. Relay MG operates and switch BS hunts for the level to which the brushes of switch OS4 have been set. 'Ihe vertical commutator segments of all levels for which alternative routes are not provided are connected to one terminal of the bank with which brush bsml engages. When brush bsml encounters this terminal, relays M and MF are operated as hereinbefore described. No alternative route translation being required, relay R is immediately operated, when relay MF operates, in a circuit through brush bsmd in normal position to ground at contact mfl. The operation o f relay CC is thus prevented by the opening of contact T3 so that no digits can be transmitted. Relays PP and T4 of the link and relay K of the selector are released as hereinbefore described. Upon release of relay K, a busy tone circuit (not shown) is closed to transmit a busy tone to the calling station. Contact S2 prevents the operation of relay X after relay K releases. Y

A forced release of the register-translator may occur at any stage of its use in case an interval of from 18 to 27 seconds has elapsed after the operation of relay BB. At contact 17118, the upper winding of relay ZA is connected to an impulse conductor to which ground impulses of .'75 second duration are connected at intervals of 9 seconds. The rst ground impulse after relay BB operates causes the operation relay ZA suciently to actuate only its contact sal, at the end of the impulse relay ZA is completely operated by its windings in series. The next impulse, 9 seconds later, energizes the upper winding of relay ZB suiiciently to actuate only its contact zbl and at the end of the impulse relay ZB is completely operated by its windings in series. At the front contact of spring zb2, the upper winding of relay R is then connected to the 9 second impulse conductor; and, after 9 seconds more, the next impulse causes the operation of relay R. The release of the register-translator is thereby forced by the operation of relay R irrespective of the stage of the call. In such a case, if the selector OS4 has seized an idle outgoing junction, the calling subscriber could obtain completion of the call by dialing whatever digits remained to be dialed.

If the calling subscriber releases the connection at any time after the line is connected to relay RA of the register-translator, relays RA, RB and BB release. Relay R is then operated through contact onZ and bbl to cause the release of the link and the return of all switches to normal as hereinbefore described.

What is claimed is:

l. In a telephone system, a selector switch for use in establishing desired connections, groups of lines connected to the bank of said switch, means for advancing the brushes of said switch to select any desired one of said groups of lines, means for hunting for an idle line in a selected group, a register switch, and means effective if no idle line is found in a selected groupv for operatively associating said register switch with said selector switch..

2. In a telephone system, a selector switch for use in establishing desired connections, groups of lines connected to the bank of said switch, means for advancing the brushes of said switch to select any desired one of said groups, means for hunting for an idle line in a selected group, a register-translator comprising a register switch and a translator switch, and means eective if no idle line is found in a selected group for operatively associating said register-translator with said selector switch.

3. In a telephone system, according to claim l, means for advancing said register switch and selector switch simultaneously one step at a time.

4. In a telephone system, according to claim l,

Vmeans comprising vertical commutatore of said selector and register switches ior identifying the group in which no idle line was found.

5. In a telephone system, a two-motion selector switch for use in establishing desired connections, groups of lines connected to the bank of said switch, means for advancing the brushes of said switch to select any desired one of said groups of lines, means for hunting for an idle line in a selected group, a register switch, means eiective if no idle line is found in a selected group for operatively associating said register switch with said selector switch, means comprising vertical commutatore of said selector and register switches for identifying the terminal level in which said selected group is located, and means for advancing said register switch and selector switch simultaneously one step at a time to complete the identificationof said group.

6. In a telephone system according to claim 1, means for advancing said register switch to identify the group in which no idle line was found, and means comprising a translator switch for determining the identity of another one of said groups which other group constitutes an alternative route to the group in which no idle line was found.

7. In a telephone system according to claim 1, means for advancing said register switch to identify the group in which no idle line was found, and means effective upon completion of the identication of said group for returning said selector to normal.

8. In a telephone system according to claim 1, means for advancing said register switch to identify the group in which no idle line was found, means effective upon completion of the identification of said group for returning said selector to normal, and means comprising a translator p switch for controlling the reoperation of said selector to select another one of sai-d groups which other group constitutes .an alternative route to the group in which no idle line was found.

9. In a telephone system, a selector switch having groups of lines connected to its terminal bank, each group leading to a different exchange, means for advancing the brushes of said switch to select the one of said groups which leads to a called one of said exchangesv and for advancing the. brushes to hunt for an idle line in the selected group, a register switch, means effective if no idle line is found in the selected group for operatively associating said register switch and selector switch, means for advancing said register switch to identify the group in which no idle line was found, and translator means for determining the code for controlling the completion of the desired connection over an alternative one of said groups and through another one of said exchanges to said called exchange.

10. In a telephone system, a selector switch having groups of lines connected to its terminal bank, each group leading to a different exchange, means for advancing the brushes of said switch to select any desired one of said groups and for advancing the brushes to hunt for an idle line in a selected group, a register-translator comprising a register switch and a translator switch, means effective if no idle line is found in a selected group for operatively associating said selector switch with said register-translator, means for advancing said register switch to identify the group in which no idle line was found, and means comprising said translator switch for determining the code of an alternative route over which the desired connection can be established.

11. In a telephone system, a selector switch having groups of lines connected to its terminal bank, each group leading to a different exchange, means for advancing the brushes of said switch to select any desired one of said groups and for advancing the brushes to hunt for an idle line in a selected group, a register switch, means effective if no idle line is found in a selected group for operatively associating said register switch and selector switch, means for advancing said register switch to identify the group in which no idle line was found, means effective upon completion of the identification for returning said selector switch to normal position, and translating means for controlling the reoperation of said selector switch to select an alternative group of trunks over which the desired connection can be completed.

12. In a telephone system, a selector switch having groups of lines connected to its terminal bank, each group leading to a different exchange, means for advancing the brushes of said switch to select any desired one of said groups and for advancing the brushes to hunt for an idle line in a selected group, a register switch, means effective if no idle line is found in a selected group for operatively associating said register switch and selector switch, means for advancing said register switch to identify the group in which no idle line was found, means effective upon completion of' the'identincation for returning said selector switch to normal position, and translating means for determining the codev of an alternative route.

18. In a telephone system, a selector switch having groups of lines'connected to its terminal bank, each group leading to a different exchange, means for advancing the brushes of said switch to select any desired one of said groups and for advancing the brushes to hunt for an idle line in a selected group, a register switch, means effective if no idle line is found in a selected group for operatively associating said register switch and selector switch, means for advancing said register switch to identify the group in which no idle line was found, means effective upon completion of the identification for returning said selector switch to normal position, and translating means for determining the code of an alternative route, for transmitting the first digit of said code to control the reoperation of said selector switch and selection of a group leading to a tandem office, and for transmitting the remaining digits of said code to control the extension of the con,- nection through the tandem oflice to the wanted office.

14. In a telephone system, groups of selector switches for use in completing desired connections, groups of lines multipled to the terminal banks of a group of said selectors, each of said groups leading to a different exchange, means in each of the selectors for advancing its brushes to select any desired one of said groups of lines and for advancing its brushes to hunt for an idle line in a selected group, translators, links for connecting the translators to the selectors, means effective upon one of said selectors finding no idle line in a selected group for starting the operation of a link to operatively associate one of said translators with` said selector, register means in said associated translator for determining the group in which no idle line was found, means effective upon completion of the identification of said group for causing they return of said selector to normal, and means in said translator for sending the code digits of an alternative route for controlling the reoperation of said selector to select a group of lines to a tandem exchange and for controlling the extension of the connection through said tandem exchange to the called exchange.

15. In a telephone system, a two-digit selector switch having groups of lines connected toits terminal bank, each group leading to a different exchange, means for receiving digit impulses for controlling the operation of the switch, means responsive to a first one of two digits for advancing the brushes of the switch to a corresponding level of the terminal bank, means responsive to .the second one of said digits for advancing the brushes to select a desired group in a selected level, means for advancing the brushes to hunt for an idle set of terminals in said desired group, translators, means effective if the brushes of said selector switch are advanced to the last set of terminals in the desired group without nding an idle line for operatively associating an idle one of said translators with said selector, a register switch in said translator, means for advancing the brushes of said register switch to a level corresponding to said selected level of said selector switch, means for advancing the brushes of said register switch one step at a time and for simultaneously advancing the brushes of said selector switch one step at a time until the brushes of said selector switch reach the eleventh rotary position, the terminal with which the brushes of said register switch are then in engagement being indicative of the digit code by which said desired group of lines is selected.

16. In a telephone system, a group of two-digit, selector switches for use in establishing desired connections, another group of such switches, groups of lines connected to the banks of the switches in one group of selectors, other groups of lines connected to the banks of the switches in the other group of selectors, each group of lines leading to a diierent exchange, means in each selector for advancing its brushes to select a desired level, a desired group of terminals in said level and an idle line in said group, translators, means eiective upon` the brushes of one of said selectors being advanced to the last set of terminals in` a desired group without nding an idle line for operatively associating said selector with an idle one of said translators, a register switch in said translator, means for advancing the brushes of said register switch to a level corresponding to the level selected by the brushes of said selector switch, means for simultaneously advancing the brushes of said register switch and the brushes of said selector switch step-bystep until the brushes of said selector reach the eleventh rotary position in the level, and means eiiective only if said selector is in one of said groups for advancing the brushes of said register one step without at the same time advancing the brushes of said selector switch before said simultaneous stepping of said switches begins.

17. In a telephone system, groups of selector switches used in completing desired connections, different groups of lines multipled to the banks of each group of selectors, each group of lines leading to a dii'erent exchange, means in each selector for advancing its brushes to select a desired level and an idle line in the desired group, a translator, link means effective upon all of the lines in a desired group being found busy by one of said selectors for operatively associating said translator and selector, group identifying terminals for said selectors, a register switch in said translator, groups of terminals in the bank of said register switch, the terminals in each group being multipled to the group identifying terminals of the selectors in a different one of said groups of selectors, and means including said group identifying terminals for advancing the brushes of the register switch to the terminal corresponding to groups in which the selector found all lines busy.

ESMOND P. G. WRIGHT.

GEORGE C. HARTLEY.

PAUL IAN WYNDHAM.