US2142653A - Telephone system - Google Patents

Description

Jan. 3, 17939. E. s. PETERsc-)N 2,142,653

TELEPHCNE SYSTEM Filed March 16, 195e `14 sheets-sheet` 1 E. S. PETERSON TELEPHONE SYSTEM Jan. 3', 1939;

Filed March 16, 1936 14 sheets-Sheet 2 w .gl

IN VENTOR. EDWARD S. PETERSON qlk qll

ATTORNEY.

Jan. 3, 1939. E. s, PETERSON TELEPHONE SYSTEM Filed Marchie, 193e 14 sheetsfsheet 5 Nimm im@ A y EDWARD 5. PETERSON By 5% ATTORNEY.

E. s. PETERsoN TELEPHONE SYSTEM Jan. 3,. 1939.

Filed March 1e, 195e 14 sheets-sheet 4 INVENT OR EDWARD 5, PETERSON 8% Z ATTORNEY.

Jan- 3, 1939- E. s. PETERSON v TELEPHONE SYSTEM 14 Sheets-Sheet 5 Filed March 16, 1936 Jan. 3, 1939. E. s. PETERSON TELEPHONE SYSTEM Filed March 16, 1936 14 Sheets-Sheet 6 Jan. 3, 19.39. E. s. PETERs'oN j TELEPHONE SYSTEM Filed March 1e, "1956 14 sheets-sheet 7" ATTORNEY.

Jan. 3, 1939, as. PETERSON TELEPHONE SYSTEM 14 Sheets-Sheet 8 Filed March 16, 1936 me" NQ" INVENTOR. EDWARD 5. PETERSON ATTORNEY.

' Jan. 3, 1939. E. s. PETERSON TELEPHONE SYSTEM Filed March 16,' 1956 14 Sheets-Sheet 9 Qmmmzm@ I I I I I I I I I I I I I I INVENTOR. EDWARD 5. PETERSON ATTORNEY.

E. S. PETERSON TELEPHONE SYSTEM Jan, 3, 1939.

File March 1e, 1956 14 Sheets-Sheet 10 n N UFO .NSQQG X259# HOWNFDO .www 4 INVENTOR EDWARD 5. PETERSON BLZM ATTORNEY.

E. s. PETERSON 2,142,653

TELEPHONE SYSTEM A 14 sheets-sheet 11 Filed March 16, 1936 INVENTOR. EDWARD 51 PETERSON ATTORNEY.

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E. s. PETERSON TELEPHONE SYSTEM 14 SheetS-Sheet l2 Filed March 16, 1956 y INVENTOR. EDWARD sfere/:50N-

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Jan. 3,1939.

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14 Sheets-Sheet 14 INVENTOR.

EDWARD 5. PETERSON BY v ATTORNEY.

E. S. PETERSON TELEPHONE SYSTEM Filed Mar-Ch 16, 1936 Jan. 3, 1939.

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e this character. Mount Morris and Leicester designated OTI and handle calls through the same group of autotwo-way local-service trunks are provided as is therewith common-control equipment which may change, the toll line TLI is provided. This toll from one attended exchange, while the toll calls to The Mount Morris and Leicester exchanges are Patented Jan. 3', 1939 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Edward S. Peterson, Elmwood Park, Ill., assignor to Associated Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application March 16, 1936, Serial No. 69,087

33 claims. (c1. 17e- 26) This invention relates to telephone systems, but lines and are designated aS Mount MOII'S, is concerned more particularly with telephone Leicestenend GeneseoJ respectively. The Leicessystems wherein automatic. switching apparatus ter exchange is the remotely eentlelled eXChange; in a telephone exchange is remotely controlled Mount Morris is located relatively near the by a switchboard operator in a distant exchange, Leicester exchange, for which reason the remote 5 the control being exercised over what is cominoncontrol over the local switching operations in 1y known as an operating trunk. Leicester is exercised from the Mount Morris The broad general' object may be stated to be exchange; and Geneseo is the exchange from the provision of new and improved circuit arwhich tool calls originating in or intended for rangements with facilities for enabling the calls the remotely controlled Leicester exchange are l0 originated in a remotely controlled automatic handled, unless such calls are to be directed exchange to be handled more expeditiously, as thrOugh the Mount MOTIS eXChenge because 0f well as to provide a more flexible service than the destination or origin of the call. has heretofore been possible with exchanges of Two operating trunks are provided between A specific object of the invention is the pro- 0T2, respectively. The fact that there are only vision of a novel arrangement whereby two oper two of these trunks is indicated by the digit-2, ating trunks may be employed alternatively to located adjacent the operating trunks. Four matic switches, whereby simultaneous calls in the indicated by the local-Service trunk LST and 20 remotely controlled exchange may be disposed of the adjacent digit 4. FOI the handling 0f t011 more rapidly. The foregoing arrangement decalls which may be trunked through the Mount pends for its novelty upon the further provision Morris exchange from other nearby exchanges that each of the operating trunks has associated (not shown) and intended for the Leicester exbe used to supplement any automatic switch with line may also be used for extending calls from which the operating trunk becomes connected. Leicester by way of Mount Morris to such other It is believed that this is the rst time two or exchanges as may be reached more conveniently more common-control equipment units have been through the Mount Morris exchange than provided for the common use of the same group through the Geneseo exchange. 30 of automatic switches. The toll line TL2 is one of four similar two- GENERAL DESCRIPTION way toll lines provided for handling toll trafficV between Leicester and Geneseo, as well as between It has been chosen to illustrate the invention Leicester and any other exchanges reached by as applied in meeting the requirements of a spewey 0f Genesee; end the tell line T113 iS One 0f e 35 cinc installation wherein the remotely controlled suitable number which may be provided between exchange is so located with respect to two attend- Mount Morris and Geneseo for the purpose of ed exchanges that it is convenient to provide the enabling diieet 13011 @Onneetiens t0 be made beremote control for the setting up of local calls tween these exchanges.

and from the remotely controlled exchange are located suiciently close together that service is handled largely through the other. rendered between these exchanges onthe same Of the eighteen gures of accompanying drawcharge basis as service is rendered between subings, Fig. l is a map showing the remotely conscribers local to either exchange. This is the trolled exchange and the relative locations of the reason for providing the local-service trunks such two nearby exchanges; as LST' for handling this inter-exchange trai-lic Fig. 2 is a trunking diagram showing the interseparate from the handling of toll traino which relation between the groups of equipment in the may be directed from either exchange through remotely controlled exchange; the other.

Figs. 3 to 17 are circuit diagrams; and 50 Fig, 13 shows the way in which the sheets of Local layout drawings should be arranged in order that they Referring now particularly to Fig. 2, the arbe understood best. rangement of the equipment in the remotely con- Referring now particularly to Fig. 1, the three trolled Leicester exchange will be explained: exchanges are shown interconnected by trunk The local traiic is handled through nderp connector links, one of which includes the nder F and the interlinked local connector LOC. Each of these switches is denoted by a rectangle having ten short horizontal lines placed beneath it. These short horizontal lines are indicative respectively of the ten levels of bank contacts, as the finder and connector switches are of the usual Strowger, vertical-and-rotary type. The link shown is one of seven similar links as is indicated by the encircled digit 'I placed above the finder F.

The finder F has access to the calling terminals of the local lines by way of line circuits such as LCI to LCS, while the local connector LOC has access to the called terminals of the lines in common with the toll connectors such as TCI and TC2.

A feature of the system disclosed is that the same group of connectors serves both four-party full-selective lines and ten-party code-ringing lines. The four-party line FPL is representative of the four-party full-selective lines, and the line TPL is representative of the ten-party code-ringing line. These two lines terminate at the exchange in the line circuits LCI and LC2, respectively. Service, of course, may be given to singlestation lines, preferably by equipping a line with only a single substation with a bridged ringer and using a single one of the ten codes to signal this substation when it is called.

The local-service trunk LST (Figs. 1 and 2) is representative of the four local-service trunks extending between Leicester and Mount Morris. This trunk terminates at the Leicester exchange in the line circuit LCS, which line circuit is similar to the line circuits LCI and LC2. The localservice calls between Mount Morris and Leicester are therefore handled through the local finderconnector links in Leicester on the same basis as` local calls to and from subscriber lines in Leicester.

In order to provide for paystation service, separate paystation lines such as the line PSL of the paystation |600 are provided. This line extends to the line circuit LCd, which is diierent from the line circuits LCI to LCS in that it is not accessible to the local nders, but is equipped with the lineswitch LS which has hunting access to the four local service trunks such as LST. The result is that an originated paystation call is extended over a local-service trunk to the Mount Morris exchange, on the theory that the most paystation calls will be directed to Mount Morris o1` to some other outside exchange. In the somewhat rare event that a paystation subscriber calls a subscriber of the Leicester exchange, the Mount Morris operator may extend the call back to the Leicester exchange over another of the localservice trunks such as LST. On the other hand, when a paystation subscriber makes a toll call, the Mount Morris operator extends the connection over a toll line such as the toll line TLS, Fig. 1, to the Geneseo toll operator, which operator records the desired call and later calls back over a Leicester-Geneseo toll line such as TL2, Figs. 1 and 2, to recall the paystation when the connection is ready.

In order to control the nders such as F the pre-selecting distributor D, Fig. 2, has hunting access to all of the finders. Start wires extend from the line circuits such as LCI-L03 to the distributor D so as to cause the distributor to control a pre-selected finder to search for the calling line when a call is originated.

The operating trunks OTI and 0T2 terminate in the common equipment units CEI and CE2, respectively. Control conductors associated with these two units are multipled into each of the local connectors such as LOC so as to enable any local connector to become associated with either common-equipment unit and the connected operating trunk. The arrangement (to be later described in detail) is such that the operating trunk OTI is normally taken for use when both are idle, and the operating trunk 0T2 is taken for use in the event that a second call arrives while the operating trunk OTI is in use. By this arrangement, calling subscribers do not need to wait so long in order to secure service when calls are being originated in rapid succession.

Each of the toll lines such as TLI and TL2, Figs. 1 and 2, terminates in a toll connector, such as the toll connector TCI and TC2, Fig. 2, each toll line passing by way of contacts of a transfer relay in the respective one of the outgoing trunk circuits such as OTCI and OTCZ. These outgoing trunk circuits are interposed between the connector bank terminals assigned to the toll lines for outgoing service and the toll line for the purpose of controlling supervision and signalling operations.

It is customary in connection with a remotely controlled exchange of this general character to provide arrangements whereby a trunk line ordinarily used for other service may be used as an operating trunk during an emergency, such as, for example, following a wind storm or sleet storm which may break down the operating trunk. Since two operating trunks are provided in the system disclosed herein, all of the calls may be handled temporarily over one of the operating trunks in the event that the other becomes temporarily defective. For this purpose, connections are made between the common equipment units and conductors leading from designated contact members of the connector banks so that an operator either in Mount Morris or in Geneseo may dial a pre-assigned number on any connector and cause either of the common equipment units and associated operating trunks to be marked busy, so that no further calls are directed to the defective operating trunk. Subsequently, a different predetermined number may be dialled so as to unbusy the operating trunk after suitable repairs have been made.

In the event that both operating trunks become defective, the transfer relay 855, Fig. 2, may be caused to operate and transfer the control ordinarily exercised over operating trunk OTI to the toll line TL2 extending between Leicester and Geneseo, following which calls originating in Leicester may be handled in Geneseo, using the toll line TL2 temporarily as an operating trunk. The reason for placing the operation of the remotely controlled exchange under the control of the Leicester exchange, instead of transferring to an alternative trunk leading to the Mount Morris exchange during the time of the failure of both the operating trunks, is that, in the event oi the failure of both operating trunks, there is a strong possibility that the failure is general and that any other pre-assigned trunk line between Leicester and Mount Morris is probably defective. This may occur when a pole has fallen, for example. The transfer relay 856 is caused to operate to make the above-mentioned transfer responsive to the dialling of a predetermined number on any one of the connectors in the Leicester exchange, as is indicated by the disclosed association between this relay and conductors leading from the connector banks. The transfer relay may be subsequently caused to restore responsive to the dialling of a second predetermined number on any of the connectors.

Provisions are made inV the disclosed system for an authorized person to temporarily operate the remotely controlled exchange locally by means of the local control set LCS, as for instance, during an emergency when none of the provided remote operating channels is serviceable.

The circuit drawings The local arrangement as shown in Fig. 2. having been described, further attention will now be directed to the general aspects of the circuit drawings, Figs. 3 to 17, wherein the circuits of the apparatus of Fig. 2 and the circuits of certain apparatus in the Mount Morris and Geneseo exchanges are shown in detail. As previously mentioned, Figs. 3 to 16 should be arranged as indicated in Fig. 18. The equipment shown in Figs.

3 to 9 and in Figs. 14 to 17 is located in the Leicester exchange; the equipment shown in Figs. 10 and 11 is located in the Mount Morris exchange; and the equipment shown in Figs. 12 and 13 is located in the Geneseo exchange.

Figs. 3, 4, and 5 show the line circuits LCI. LC2, and LCS, respectively, which are associated respectively with the four-party line FPL, the ten-party line TPL, and the local-service trunk LST. These line circuits are similar to each other. Figs. 3, .4, and 5 show also the finder terminals 35|, 45|, and 55|. Through these terminals and multiples thereof, the finders make connection with the calling lines. Figs. 3, 4, and 5 show also the connector terminals 350, 45D, and 555. Through these terminals and their multiples, the connectors make connections with the illustrated line when they are called. It is to be noted that the conductors of the local-service trunk LST are reversed at the negative and positive terminals in group 550 and the multiples thereof. This reversal has to do with giving supervision in the Mount Morris exchange, as will be explained hereinafter.

The start conductors 36|, 46|, and` 56| extend to appropriate ones of the level start leads associated with start relay 80|, Fig. 8. Each of the start conductors 36|, 46|, and 56| (as well as each of the other seven start conductors associated with groups of line circuits not illustrated) is multipled to the ten line circuits reached by way of a given bank level of the finders, in accordance with the usual practice.

Figs. 6 and 7 show the finder F| and the associated local connector LOC, which are linked together by trunk conductors 62|626. The bank of the finder FI is not illustrated except for the terminals 35|, 45|, and 55| connected to the line circuits of Figs. 3, 4, and 5. It will be understood, of course, that there are one hundred such sets of terminals in the bank of the finder FI, and that these terminals are connected in multiple with the corresponding terminals of the other nders.

The bank of the connector LOC, Fig. 7, is not illustrated except for a showing of terminals such as 350, 450, and 550, associated with the line circuits of Figs. 3, 4, and 5. It will be understood, of course, that the bank of the connector LOC is a. 40B terminal bank having |00 sets of terminals such as those illustrated in Figs. 3, 4, and 5, which terminals are connected in multiple relationship to the bank terminals of the other connectors in the usual and well known manner.

It is to be noted that the wipers '|00 of the local connector LOC are marked C, and EC, respectively. A similar `designation of the terminals of Figs. 3, 4, and 5 is made. From this it is to be noted that no connection is closed by way of the EC wiper of the local connector LOC when a line illustrated in Figs. 3 to 5 is called, as the EC terminal is left unwired at such lines. The EC terminal, it may be mentioned, is used only in the event that a toll line is called, by way of terminals such as |450, Fig. 14, the EC terminal of which is connected to the circuit by way of the forced-release conductor |422.

The connector LOC, Fig. 7, is provided with a party selector PSI, used to effect party selection when a party line is called. This party selector has wipers 74| and 142, each of which has a double bank of contacts so disposed as to be bridged in pairs according to the position which the wiper is caused to assume. The wipers are operated in their directive setting by operating magnet 143, and they are restored to the illustrated normal position by the release magnet 144.

Fig. 8 illustrates the distributor D which is composed of a group of relays and therotary switch mechanism comprising wipers 82|-825, driven by the operating magnet 809. Fig. 8 shows also the miscellaneous relay group MG, which includes relays Nil-356. The relays in this group are used for miscellaneous purposes which will be hereinafter brought out.

Fig. 9 illustrates the common equipment units CE| and CE2. 'Ihe common equipment unit CE| is illustrated in detail, while of the commonequipment unit CE2 only certain terminals are illustrated, and the conductors which connect thereto. Certain terminals in group B00, appearing at the left-hand edge of Fig. 9, part l, are not used in the common-equipment unit CE2, and are consequently not shown in group 950' associated with the common equipment CE2. Those terminals peculiar to CE| have been identified by a line drawn around them, as for example, the ve terminals in group 905 associated with the supervisory switch SS. It is preferred,fhowever, for the sake of uniformity in manufacturing procedure that the two common equipment units be made exactly alike. In this way, the commonequipment units are interchangeable, although certain parts of the common equipment CE2 are not needed unless this common equipment should be interchanged with the common equipment CE|.

The operating trunk OT| is shown extending from the common-equipment unit CE| of Fig. 9 across the top of Fig. 8 to the operating equipment of Fig. 10, located in the Mount Morris exchange. The operating trunk 0T2, associated with CE2, is similary equipped.

Fig. 11 shows the jack and trunk equipment in the Mount Morris exchange associated with the local-service trunk LST. Each of the other three local-service trunks hereinbefore discussed is similarly equipped.

Fig. 12 shows the jack and trunk equipment at the toll board in the Geneseo exchange and associated with the two-way toll line TL2. Fig. 12 shows also the transfer key K3, used to transfer the toll line TL2 from the trunk and jack equipment of Fig. l2 to the control equipment of Fig. 13 when the toll line TL2 is to be used temporarily as an operating trunk.

Fig. 13 indicates the control equipment brought into play when the toll line TL2 is used as an operating trunk, which control equipment is similar to that illustrated in Fig. lA and usedI in the Mount Morris exchange to exercise the control over the operating trunk OT|.

Fig. 14 shows the outgoing trunk circuit OTC, associated with the toll line TL2, through which outgoing calls to toll line TL2 are made. This outgoing trunk circuit is accessible to the local connectors by way of bank terminals |450 and multiples thereof, and to the toll connectors by way of terminals |45| and multiples thereof. This trunk circuit includes the transfer relay |4|| which substitutes the outgoing trunk circuit OTC for the toll connector TG2 when the outgoing trunk circuit OTC is taken for use.

The toll connector TC2 of Fig. 13 is used to complete calls incoming to the Leicester exchange from Geneseo. This toll connector, like the local connector of Fig. '1, is provided with a party selector, the party selector of Fig. being designated PS2.

DETAILED DESCRIPTION The disclosure having been described generally, a detailed description of the operation of the system will now be given.

Local call toi a ten-party line It will rst be described how a local call is extended to a ten-party, code-ringing line. For this purpose, it will be assumed that the Subscriber at substation 300 on the four-party line FPL desires to converse with the subscriber at substation 400 on the ten-party line TPL. In order to obtain the desired connection, the subscriber at substation 300 removes his receiver and waits for the operator to reply, whereupon he informs the operator of the desired number, following which the operator causes the desired connection to be completed and the desired subscriber to be signalled.

When the receiver (not shown) is removed at substation 300, the closure of the usual directcurrent bridge across the conductors of the line FPL results in the energization of line relay 38|, bridged across the conductors of the line in series with the usual exchange battery and contacts of cut-off relay 30|. When` line relay 30| energizes, it places a ground potential at its lower armature on the start conductor 36|; it disconnects the associated C terminal in group 350 from the cut-off relay 302 and connects it to ground, so as to guard the calling line immediately against seizure by way of one of the connectors, and it connects the winding of cutoff relay 302 through contacts of lock-out relay 303 to the C terminal in group 35| so as tomark this group of terminals as calling in the bank of nder Fl and the other nders.

It will be assumed that the call is originated at a time when the common equipment units CEI and CE2 are both idle, and at a time when the wipers 82|-825 of the distributor D, Fig. 8, are standing on the terminals of conductors 83|-835, extending to the finder Fl, Fig. 6. As a result of the idle condition of the common equipment units CEI and CE2, Fig. 9, a battery potential is maintained on the lower terminal of start relay 80|.

Preparing the distributor The placing of the ground potential on start conductor 36| closes a circuit through the corresponding one of the ten-levell start leads of Fig. 8 and through the associated isolating resistor for start relay 80|. When relay 80| operates it closes a circuit for switching relay 802 fromV the normally grounded busy-common conductor 86|. Switching relay 802 operates in series with operating magnet 800, but magnet 800 is not operatively energized owing to the relatively high resistance of relay 802. Relay 802 closes a locking circuit for itself at its lower armature, independent of contacts of start relay 80 I, in additionto starting the nder FI into operation, as will be pointed out. Switching relay 802 also closes a circuit at its lower armature through contacts of pulse-cut-of relay 808 for hold relay 808 of the relay group including relays 806-808, comprising a restart timer. These three relays cooperate to time the finding operation and to cause a second nder to be taken for use if the rst nder fails to iind the calling line within a short interval, three seconds, for example. Relay 806 is now operated by its upper winding to open the initial circuit of the now-locked switching relay 802, to prepare locking circuits for the lower windings of relays 804 and 805, and to operate pendulum relay 801 in multiple with its lower winding. Pendulum relay 801 closes an operating circuit for cut-off relay 808 and a holding circuit for the lower winding of relay 808. Cutoff relay 808 now operates and locks itself through the lower contacts of relay 802, breaking the circuit of the upper winding of relay 806 and the circuit of pendulum relay 801. Relay 801 immediately deenergizes and permits its weighted contact member to oscillate. The circuit of the lower winding of relay 806 is broken momentarily on each swing, but the slow-acting relay 808 remainsy operated until the oscillations have attenuated greatly, at the end of several seconds, for example, which time is sucient for a normal finder cycle to be completed.

Returning now to the operation of switching relay 802, relay 802 at its inner upper armature prepares a change-over circuit through the upper winding of changeover relay 804 and over control wiper 823'; it prepares a circuit for the upper winding of Ender-pilot relay 805; it prepares a restart stepping. circuit for the operating magnet 800 through contacts of the restart timing relays 806 and 808; it disconnects test wiper 82| from one side of the interrupter contacts associated with operating magnet 800 and connects it directly to the magnet; it extends ground potential at its upper armature through contacts of relays 803, 806, and 804, wiper 824, and vertical conductor 834 to vertical magnet 603 of the finder Fi, and it places a ground potential through contacts of finder pilot relay 805 and through wiper 825 on start conductor 835.

Starting the finder Start relay 802 now operates over grounded start conductor 835 and connects the common rotary conductor 838 through contacts of switching relay 80| to rotary magnet 604; it connects the common selecting conductors 96| and 982 with the individual selecting conductors 625 and 828; it removes ground potential at one point from the busy-common conductor 88|; it disconnectstest conductor 832 from off-normal contacts 601 and prepares an automatic return circuit through overflowcontacts 608; and at its upper contacts it applies ground potential to the junction of the two windings of electro-polarized switching relay 80|', causing current to flow in thev lower or polarizing winding of this relay and preparing a test circuit through the upper windingof the relay by way of theC wiper to enable the finder to test for the calling condition of the marked terminal set.

Vertical magnet 603 operates responsive to the closure of its circuit over conductor 834 upon the operation of switching relay 802 and raises wipers 000 and 600 one step. It also applies ground potential to stepping conductor 832, closing a. circuit through wiper 823 for stepping relay 803. Relay 803 thereupon operates and interrupts the circuit of vertical magnet 603, whereupon the vertical magnet 003 restores and opens the circuit of the stepping relay. The stepping relay thereupon restores and again closes the circuit of the vertical magnet. This operation continues until the wipers 600 and 609 have been raised opposite the level of bank contacts containing the calling line.

Finding the calling level When the level of bank contacts containing the calling line is reached, test wiper 600 encounters ground potential over the contact then encountered and through a multiple of the corresponding one of the level start leads indicated in Fig. 8 to the left of the distributor. This encountered ground potential results in an opera-` tion (over control conductor 833 and through wiper 823) of changeover relay 804, the operation being brought about b-y an energization of the upper winding of changeover relay 804 in series with the winding of stepping relay 803, by way of the inner upper contacts of switching relay 802. This operation occurs only after stepping relay 803 has operated and broken the circuit of vertical magnet 603 upon the calling level being reached, and after vertical magnet 603 has restored and removed ground potential from conductor 832 to thereby open the direct stepping circuit of relay 803. It is at this point that the upper winding of changeover relay 804 is energized in series with stepping relay 803. Relay 803 remains operated in series with changeover relay 804 until the changeover relay has operated. Upon operating, relay 804 (whose operation is delayed somewhat by the copper collar on the armature end thereof, as indicated by the solid black upper portion of the relay), locks itself at its inner lower armature through contacts of hold relay 806; it disconnectscontrol wiper 823 from its own upper winding and extends it through contacts of switching relay 802 to the upper winding of finder-pilot relay 805. Relay 805 is not operated at this time, even though the upper terminal of the upper winding thereof is grounded through contacts of switching relay 302, because ground potential is applied to both terminals of the upper winding. At its upper armature, changeover relay 804 transfers the stepping circuit from vertical magnet 603 to the common rotary conductor 836 now extended through contacts of the individual start relay of finder Fi, and contacts of switching relay 60|, to rotary magnet 604 of the finder. Therefore, when stepping relay 603 now restores responsive to the operation of changeover relay 804, a circuit is closed for rotary magnet 604.

Finding the calling line C terminals with which it comes into contact, but the C terminals of the line circuits encountered by the C wiper of the nder are normally disconnected in the line circuit.

When the line circuit LCi is reached, however, a call-indicating potential is found by the c wiper 600 of the finder F| through cut-off relay 302, the upper contacts at the energized line relay 30| and contacts of lockout relay 303. As a result, current now flows from the upper contacts of the energized start relay 602, through the upper or test winding of the electropolarized switching relay 00|, in series with the cut-ofi relay of the line circuit LCI. When it operates, switching relay 60| opens the rotary magnet circuit; opens an additional point in the circuit of release magnet 605; it closes the talking leads 62| and 622; and it connects the C wiper of the finder, the junction of its own winding, and holding conductor 623 together so as to provide a holding circuit for itself and to place ground potential i directly on the C lead extending to the line circuit LCI. The holding conductor 623, it may be pointed out, is normally grounded in local connector LOC, Fig. '7, by way of contacts of the forced-release relay 108 and contacts of the cutolf relays '102' and 102. As a result, switching relay 00| is enabled to remain operated through its lower polarizing and holding winding after start relay 602 has fallen back, as it shortly does.

When the line circuit LCI is found, and cut-off relay 302 operates in series with switching relay 60| of the lnder, relay 302 locks itself directly to the associated nder C lead at its inner upper contacts; at irl-s connects line relay 30| and ground potential from the conductors of the calling line FPL; and at its lower armature it closes a circuit for lockout relay 303 so as to operate relay 303 preparatory to locking the line FPL out of service in the event that it becomes defective, which operation will be covered in a subsequent part of the description. With line relay 30| restored and lockout relay 303 operated, ground potential is now removed from start conductor 36|, permitting start relay 80| to restore unless another call has been initiated in the meantime. It is to be noted that `the restoration of start relay 80| has no immediate affect on the sequential operation of the distributor D, as the switching relay 802 has become locked in the meantime at its inner lower armature as previously pointed out and for the further reason that ground potential has been removed at relays 804 and 806 from the armature of start relay 80|.

In the local connector LOC, line relay 6is now operated over the calling line to operate release relay 101. Relay '|01 additionally grounds holding conductor 623.

Delivering the seizing pulse In the nder FI switching relay 60| vat its lower armature transfers rotary magnet 604 from the rotary operating conductor 830 to control conductor 832, thereby extending a negative potential over control conductor 833, wiper 823, through contacts of the operated changeover relay 804, and contacts of the operated switching relay 802 to the finder-pilot relay 805. Finder-pilot relay 805 now operates and locks itself at its inner lower contacts Vto ground potential at the lower contacts of the energized hold relay 806. At a separate contact, lnder-pilot relay 805 breaks the circuit previously existing over conductor 835 .for start relay 602, while at its inner upper armature it closes a circuit through con- `tacts of seizing-control relay 80| of common equipment CEI and over conductor 95| (associated with common equipment CEl) to cause the local connector LOC, linked with the nder FI of Fig. 6, to seize the common equipment CEI. This circuit passes through contacts of the start relay 602. Although the circuit of start relay 602 is broken by relay 885 at the same time that the seizing circuit is closed, the seizing circuit remains closed long enough to permit the seizing operation to take place, as relay 602 is rendered slow acting by the indicated conducting sleeve around its core. It is to be noted that the seizing potential is placed upon the No. 1 seizing or selecting conductor 96| because seizing control relay 86|r of the common equipment CEI is deenergized, indicative of an idle condition of this control equipment, whereas if this relay were in an energized condition and the control common equipment CE2' were idle, then the seizing impulse would be transmitted over the No. 2 seizing or selecting conductor 962, associated with common equipment CE2.

Clearing out the distributor When the slow-acting start relay 602 restores responsive to the breaking of its circuit by finder pilot relay 805, it disconnects common conductors 83'6, 96|, and 962 from the associated individual conductors, it prepares a circuit for release magnet 605 (which is now maintained open by switching relay 60|) through the shifted off normal contact 606; and it places ground potential on `test conductor 83|, through the shifted offnormal contact 601, to cause finder FI to test busy to the distributor DI and thereby guard the nder from further seizure until it is again freed.

In the distributor D, when ground potential is placed on test conductor 83| a circuit is closed through wiper 82| vand contacts of the operated switching relay 802 of the distributor for operating magnet 800. Magnet 800 operates when this circuit is closed, but as is well known the wipers 82|-825 do not advance until the magnet restores. The magnet does not restore until switching relay 802 restores responsive to being rst short circuited by the closing of the circuit for operating magnet 800 and then disconnected when magnet 800 operates and opens its interrupter contacts.

Upon the restoration of switching relay 802, the grounded test wiper 82| is transferred from its direct connection with operating magnet 800 to its normal connection therewith through the interrupter contacts of the magnet. Magnet 800 thereupon restores and advances the wipers 82 825 one step, at the same time closing its interrupter contacts so as to permit a further automatic hunting advance of the wipers until wiper 82| encounters an ungrounded test contact indicative of an idle iinder.

When switching relay 802 is restored, the holding circuit of the lower Winding of holding relay 806 is broken. Relay 808 restores after a very slight interval, permitting changeover relay 804 and finder pilot relay 805 to restore when their locking circuit is opened at the inner lower contacts of holding relay 806. Also, cut-01T relay 808 is unlocked at the lower contacts of relay .802. With the restoration of these relays, the distributor D has passed through its complete cycle of normal operations and is in readiness to be started to control the operation of the next selected finder, as ground potential is again extended from the busy-common conductor 86| through contacts of relays 808, 806, and 804 to the armature of start relay 80|, so that the start relay may now again control switching relay 802 when the next occasion arises.

The restart timer It may happen occasionally that a finder becomes defective, either mechanically or electrically, to such an extent that it fails to operate properly to find the calling line. In this event the restart timer composed of relays 806-808 cooperate to cause the distributor D to select another finder and start it into operation in search of the calling line. This operation will now be explained It will be recalled that relays 806, 801, and 808 operate successively responsive to the operation of switching relay 802; that relay 808 locks itself energized; and that relay 80T deenergizes and permits its weighted pendulum to vibrate and keep relay 806 operated. While the pendulum of relay 801 is vibrating vigorously, the circuit of the lower winding of relay 806 remains closed almost continuously, and relay 806 remains operated because it is a slow-releasing relay. However, when the vibration of the pendulum attenuates considerably, and assuming that the finder has not found the calling line and permitted the distributor to clear out, relay 806 restores. At its inner lower armature relay 806 removes ground ypotential from the pendulum contacts, at the same time opening the locking circuit of relays 804| and 805 (assuming that these relays have operated). Also, relay 606 closes a circuit at its middle upper armature from ground at contacts of switching relay 802, through contacts of the operated pulse-cut-off relay 808 for operating magnet 800. The closure of this circuit short circuits relay 002. Magnet 800 now operates preparatory tc advancing the wipers 82|-825, at the same time disconnecting the short circuited switching relay .802 at its inner upper contacts. Relay 802 now restores and at its lower armature opens the circuit of the locked pulse cut-oil relay 808, at the same time opening the circuit of operating magnet 800. Magnet 800 then restores and advances the wipers 82|-825 one step. Since switching relay 802 is now restored, wiper 82| is reconnecter), in the usual hunting circuit with magnet 800, causing this magnet to operate in a buzzer-like manner in search of an idle nder and causing switching relay 802 to remain restored until an idle finder is reached.

Upon the restoration of pulse-cut-oi relay 808, ground potential is reconnected to the armature of start relay 80|, with the result that switching relay 802 may reoperate as soon as wipers 82|- 825 have been advanced into association with another idle. iinder.

It is to be noted that restart timer is effective to re-cycle the distributor D and cause it to advance at any time when switching relay 802 does not become restored in the usual way responsive to the restoration of a start relay (such as 602 of the nder FI) and the consequent application of `guarding ground potential to the test conductor (such as 83|) within the time allowed for the restart timer to function. In this way, the reliability of the system is greatly improved and the advance of the distributor D following the completion of each connection through a nder is more positively assured.

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