US1330220A - Assigetob to western electeic - Google Patents

Description

E.H.SMYTHE. TELEPHONE CALL DISTRIBUTING SYSTEM.

Patented Feb. 10,1920.

4 SHEETSSHEET I.

APPLICATION FILED MAR- 27. 1918.

E. HJSMYTHE.

TELEPHONE CALL DISTRIBUTING SYSTEM.

APPLICATION FILED MAR. 2?. 191B.

1 ,330,220. Patented Feb. 10, 1920.

TSHEETSQSHEET 2.

WW/y Frame E. H. SMYTHE.

TELEPHONE CALL DISTRIBUTING SYSTEM.

APPLICATION FILED MAR. 27. I918.

, Patented Feb. 10,1920.

4 SHEETS-SHEET 3.

E. H. SM YTHE. TELEPHONE CALL UISTRIBUTING'SYSTEM.

APPLICATION FILED MAR- 27, I918.

Patented Feb. 10, 1920.

4 SHEETS-SHEET 4. 2*.

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nrrn srarns nr orrren.

EDWIN H. SMYTIIE, F HUBBARD WOODS, ILLINOIS, AifiIGNOR *10 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORIET, N. Y., A CORPORATION OF NEW YQRK.

TELEPHONE-GA3LL-DISTRIBUTING Application. filed March 27, 1918.

To all whom it may concern:

Be it known that I, EDWIN H. SMYTHE, a citizen of the United Eitates, residing at Hubbard WVoods, in the county of Cook and State 6i Illinois, have invented certain new and useful Improvements in Telephone-Call- Distributing Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to a telephone call distributing system of the type in which the calls originated by the telephone lines Of the exchange are automatically distributed to the operators positions that are available for receiving them. In complex systems of this character, abnormal conditions sometimes arise that tend to prevent the proper and prompt extending Off the circuits of calling lines to the operators positions. lit is the principal object oi. this invention to provide an organization in which such abnormal conditions, when they arise, will be taken care of and prevented from interfering with the proper operation of the system.

Generally stated, the present system provides a plurality of operators positions each equipped with a number of plug-terminated connecting circuits for completing connection with called subscribers lines. The connection between these connecting circuits and the calling subscribers lines is effected through the medium of a number of finder circuits each of which has an automatic switch at one end for finding and connecting with any subscribers line that may be calling, and an automatic switch at the other end for selecting an available operators position, and then connecting with an idle connecting circuit at that position. The selection of an available operators position is controlled by operators selecting apparatus common to all of the finder circuits and all of the operators positions.

In the normal operation of the system the potential whichidentifies any of the lines as a calling line is automatically withdrawn when the finder circuit makes connection with that line. I

It through any fault of the apparatus the potential isnot immediately withdrawn, it may result in the rapid tying up oi all of the line finders and cord selectors serving the grou of lines in which the abnormal line terminates.

In accordance with the present invention Specification of Letters l atent.

Patented Feb. 10, 1920.

Serial lilo. 2%,943.

it is proposed to provide an arrangement for preventing the operation of more than one line finder and its corresponding cord selector when such an abnormal condition as that above described exists.

The preferred embodiment of the system of the invention is illustrated in the accompany diagrannnatic drawings in which Figure 1 shows two groups of lines with two line finder switches for making connection therewith, together with the associated circuits and apparatus through the medium of which the lines control the switches; Fig. 2 shows one finder circuit complete, and enough of two other finder circuits to illus irate the relationship between them; Fig. 3 shows two cord selector switches of one frame with their associated selection con trolling apparatus and circuits, together with similar apparatus and circuits for the cord selector switches (not shown) of another i'rame; and Fig. a shows the position apparatus and one of the connecting cord circuits or one operators position and indicates the position apparatus and a connecting cord circuit oi another position, also one of the called lines with which the cord circuit may be connected. The figures taken together, and arranged side by side in the order indicated bythe lines that extend to the margins of the sheets, illustrate as much a complete organization as is necessary to gain an understanding of the construc' tion and mode of operation of the system.

Two telephone lines are indicated in each 7 of the two groups shown in Fig. '1, it being understood that each group may comprise a large number of such lines. .The practice is to give the finder switch brushes access to the terminals of five hundred lines, these lines being arranged in ten groups of fifty lines each. Each of the lines has associated with it at the central oilice a line relay 12,

and cut-ofif-relay 11. Each line is also provided with one or more spring jacks 1d by mea or which connection may be made i with the line when it is called line. The

lines represented as calling lines in Fig. l y and the line shown as a called line in F ig. 4

may be lines of thesame sort, similarly equipped and located at the same exchange; or the lines may be located at different of :fices. lin the present instance, the called line shown in Fig. i is indicatedasbeing pro vided with connections it by means of which it may have control over finder switch mechanism in the manner illustratedm connection with the lines of Fig. 1. Each group of lines, LG and LG, has associated with it certain group apparatus'consisting of two relays l9 and 24;, a common protective relay 250, and a timing sequence switch 100. There is also provided apparatus common to all of the line groups, comprising the relays 22. '23 and 33.

The groups of lines have access to groups of connecting circuits through the medium of finder circuits F, F, and F which terminate upon the brushes of pairs of finder switches of which two sets, LF and CS and LF and CS, are shown. Each of the groups of connectlng circuits is associated with a particular operators position, or

which the apparatus of one is shown at G -ple connections of the connecting circuit with the terminals of the cord selector switches are shown in the case of the connecting circuit that is completely illustrated; and in like manner multiple connections oi the telephone line with the terminals of the line finder switches are shown in the case of the line that extends from station A. The multiple connections that exist between corresponding sets of switch terminals and the other connecting circuits and telephone lines are omitted to avoid confusing the drawing.

A number of groups of cord selector switches like the group illustrated in Fig. 8 may have access'to the same groups of con necting circuits and their corresponding operators positions. This is indicated in Fig. 3. Each of the groups of cord selector switches has associated with it certain selection controlling apparatus, that associated with the cord selector switches shown in Fig. 3 appearing under the caption Frame 2, and that associated with the cord selector switches of the other group that is not shown appearing under the caption Frame 1. The selection controlling apparatus for each frame or group of cord selector switches comprises a set of relays 77 93 and 9% for each operators group, CG, CG, to which the cord selector has access, and group of relays 52, 5e, 55, 61, 63 and 254 common to all of the first mentioned groups.

As the line finder switches LF and LF',

brushes carried at the top of the switch sha and and the cord selector switches CS and CS in themselves are not novel, they are shown merely diagrammatically. These switches may be substantially like the switch illustrated and described in the patent to James L. hlcQuarrie, No. 1,177,0-lrl, issued March 28, 1916. The line finder and cord selector switches are alike in all substantial respects. Each comprises a longitudinally movable shaft 1 carrying as many sets of brushes 2 as there are groups of stationary terminals to be engaged. To more the shaft up, an e tension at the lower end of the shaft is brought into engagement with the constantly rotating power member 3 by means of an idler wheel operated by the up-driie magnet 32; and to move the shaft down, the extension is brought into engagement with the power member by means of an idler wheel operated by the down-drive magnet 62.

Normally the brushes of each of the sets 2 are held apart, so as to clear the associated tern'iinals, by means of a separating cum 5 located between the innermost brushes ot the set. The cam 5 is rotatably mounted, and when rotated in one direction, rclcarcs th brushes and permits them to engage the associated terminals. The tripping or releasing of the brushes is controlled by a number of trip- magnets 16, 17. Each oi: these when energized rotates an associated trip rod 6 that extends transversely to the switch shafts l and carries as many tripping yokes 7 as there are finder switches in the group. The trip rod, in rotating, brings all of its tripping yokes 7 into position to operate the brush controlling cams 5 of the corresponding sets of brushes on all of the switches, so that whichever oil? the finder switches is caused to more up has that set of brushes tripped that corresponds with the pa 'ticular trip magnet l6, 17, that is at the time energized. lJhen the finder switch that has been in use returned to its normal position, any of the associated controlling cams 5 that l as been tripped is engaged and rotated in a reverse direction to separate its switch springs again and thus render them inactive.

Each of the line finder and cord selector switches has associated with it a commutator 8 which compr es a number of stationary commutator segr cuts and a set oi movablb t l L l and cooperating with the stationary ments. This commutator serves to make and break a number of controlling circuits in the various stages oi the upward movement of the switch shaft.

For controlling the circuits of the organization, there are employed a number of quence switches whi'h are shown at dili'crent points and are designated 100, 200, 300 l-OO, respectively. These em nence switches may be of the type disclosed in Patent 1,127,808 issued February 9, 1915, to Reynolds and Baldwin. Each consists of an electro-magnetically controlled motor or driving mechanism and a number of associated switch cams. The switch cams associated with each of the sequence switches 100 are designated. 101 to 103 inclusive; those associated with each of the sequence switches 200 are designated 201 to 22 1 inclusive; those associated with each of the sequence switches 300 are designated 301 to 30% inclusive; and those associated with each of the sequence switches 100 are designated 401 to 413 inclusive. To each of the contacts associated with the various sequence switch cams are applied certain numerals. These numerals in the case of the cams 101, 201, 301 and 101. indicate the only positions of the associated sequence switch in which these particular contacts are open; the numerals applied to all of the other contacts of each sequence switch indicate the only positions of the particular associated switch in which the associated contacts are closed.

The sequence switches 100 merely act as timing switches and have only one resting position. The resting positions of the other sequence switches, and the stages of operation with which these positions are associated, are as follows:

Sequence switch 9200.

Normal. Awaiting starting circuit. Awaiting starting circuit release. Hunting calling line. Awaiting preceding finder circuit. Awaiting operators selecting circuit. Releasing operators selecting circuit.

Hunting cord circuit. Talking; Line finder at tell-tale. Cord selector at tell-tale.

Line finder return. Cord selector return.

Sequence switch 300.

. Awaiting a call. Position vacant. Position busy.

Sequence switch .400.

1. Normal. 7. Listening in. 15. Listening out.

The manner in which the system is organized will appear from the description of its operation which follows. It will be assumed that thesubscriber at station A initiates a call. When the telephone receiver is taken from the switchhook, a circuit is closed that extends by way of both windings of the line relay l2 and both limbs of the telephone line, and is completed in the contacts of the switchhook at the subscribers station. The flow of current in this circuit energizes the line relay 12, which in operating applies a ground to the conductor 18 through righthand front contact and armature of relay 12 and left-handback contact and armature of relay 250. This causes current to flow from battery through the winding of the relay 19, sequence switch contact 103 to 1 1:), conductor 18 and ground through the contacts of the operated line relay 12 and the left-hand back contact of relay 250. The relay 19 attracts its armature and closes a circuit that extends from battery through the right-hand winding of the associated relay iii 1 front contact of relay 19, back contact of relay 22 and lower armature and back contactof relay 23 to ground. Relay 24 opcrates and closes inits left-hand front con tact a circuit that extends from battery by way of the winding of the associated group trip magnet 10 and the lefthand winding of the relay 24:, in parallel, to the front con tact of that relay, and thence by way of conductor 58, the winding of the relay 22, and the lower armature and back contact of the relay 23 to ground.

Current flowing in the circuit traced above operates the trip magnet 16 of the group in which the calling line is located, locks up the relay 24: of the associated group and operates the relay 22 common to all of the groups. The trip magnet 16 rotates its associated trip rod to bring all of the yokes into position to trip the corresponding set of brushes of whichever of the line finder switches is started. The group'relay 24: breaks, in its left-hand back contact, the circuit of the conductor to the corresponding relays 241 of the succeeding groups of the series.

The relay 2%, in its right-hand front contact,'also completes a circuit that extends from battery through the motor magnet of the sequence switch 100, and contact 102 (185;; to 15;) of that switch. Tn moving out of position 1, sequence switch 100 closes its contact 101 and opens its contact'103. As

contact 101 is closed'in all positions excepting position 1 of the sequence switch, the swltch is caused to make one complete rota- .tion; and as contact 103 of the sequence switch is open in all positions excepting positions 18%} to 13;, the condu tor 18 is held open while the sequence switch is maknig its revolution and until it gets back to position 1. The time required by the sequence switch. to make one complete rotationis so regir lated as to be greater than that occupied by the line finder switch in finding the terminals of any calling line. Tlieaction, there in operating opens in its back contact the circuit of the conductor 57, which extends serially through the back contacts oi? the relays l9 oi the. various groups. As this conductor 57 is the path over which the relay 19 of any group serves to eiiect the initial energization of the associated relay 2% and the operation of the corresponding trip magnet, the interruption of this conductor insures the operation of only one trip magnet and the tripping of only one set of brushes on a started line finder switch.

The common relay 22, when it operates, applies ground to the starting conductor 29 to start a finder switch hunting for the calling line. The starting conductor 29 has branches extending to hire sequence switch cares 206 of all of the finder circuits teririnating pon the line finders that have access to the calling line. But, for reasons which will hereinafter be explained, the sequence switch 200 oi only one of these finder circuits is standing in 2 position. Assuming that this is the sequence switch. of finder circuit F, when the relay 22 is actuated by the calling line, as already described. a circuit is completed that extends tron! battery through the leftland winding of relay 30, sequence switch contacts 206 (2,, conductor 29, front contact and armature ol? starting relay 2-2, lower armature and back contact of relay 23 to ground. The righ hand winding of relay 80 is at this time also included in parallel with the left-hand winding of the relay in the energizing circuit, the parallel branch beii'lg from battery through resistance coil 56, sequence switch contact 217 (2 to 9), righ -hand winding o't' rela 30, sequence switch contacts and (1 to 13), thereafter joining; the conductor that extends from the left-hand w' iding' of relay 80, and to-ground over the circuit already traced. The eflect oi this is to giro the relay 80 the benefit or. the energizing action of both windings.

As a result of the closure oi the circuit traced above, the relay 30 is energizcl an. closes a circuit that causes the associated sequence switch 200 to move out of position 9. This circuit extends from battery through the motor magnet of the sequence switch. 900, sequence switch contact 202- right-hand front contact and armature of rails; 30, .equence switch contact 208 (2 7), conductor 79, connnutator seguent M of the associated cord finder switch CS, and to ground by way of the brush in engg'ap'enicnt with this commutator segment. Relay 30, in attracting its ctr-matures, also closes a leching circuit for itself that extends from hattery by way of the resistance coil 56, sequence switch contacts 21.? (2 to a) the right-hand winding of the relay 30, can switch contacts 216 (2 to l) and t front contact and left-hand armature of the relay 30, and armature and back contact of the relay 37 to ground.

As a result of the closure o'l its motor magnet circuit in 1; 1c right-hand trout contact of the relay 30, the sequence switch E200 moves out of position 2 and comes to rest in position 3. In position 3 of the switch, a circuit is closed hat extends from battery by way of the llp-ClllYG magnet oi the corresponding line finder switch Ll, conciated sets ot' brushes. lit the outset oi: the

upward movement oi the elevator rod. all oi? the brush trip lovers are moved past the Corresponding trip yohcs. The only trip ot that is energized in th s case is the 16 which correspond with the group ch tho callinoline if; locrtc consequently, the on trip yoke in po to engage. a trip lever on the elevator rod is the one which controls the brushes 40. "ll. 42 and that are adapted to engage thetcu niinals oi that iarticular group o'l lines. This set of brushes, therefore. is released and made operative, and the other sets are held clear of their associated lino terminals.

As soon as the 1 cl? brushes corresponding with the calling; line is tripped, the .np apparatus, by means 0'? which the lines control the brush tripping and line finder starting; ope tions, may be returned to its normal condition. The first step in this restoring operation is elfectcd by the closure of a circuit which is completed by way of the K segment of the line finder connnutator immediately after the brushes are tripped. lhis circuit extends from buttery in. parallel branches through the relays and 33 (see l) ,condnctor 26, sequen e switch contact 209 (2%} to conductor 68 and to ground by way of the K segment or the line finder commutator and its associated brush. The enerc'zaticn of the role interrupts, at the lower back contact of that relay, the previously described circuit that has up to this time maintained the eucr su: tion of the trip magnet 16, the .q'roun relay 2% and the common surrting; relay 22. A llclai' 23, at its upper front contact, closes a lot-liing circuit for itself and the associated. relay 3o extends by wily ot conductor tlo sequence switch contacts QlO (9 l of the finder circuits in series, ound at a point beyond the la t sr-ritch As has already been stated, normally there is only one of the finder circuits with its sequence switch in position 2 awaiting the receipt of a call.

When the call comes in, this sequence switch is immediately moved to position 3, in the manner described above. Therefore, at this stage 01' the operation, the sequence switches of all of the finder circuits are in position to close their contacts 210. The locking circuit for the r t lays 23 and 33 is, therefore, held closed until another one of the finder circuits has its sequence switch moved into position 2. This is accomplished by relay 33, which, in operating, applies a ground to conductor 23 to move the sequence switch of another finder circuit out of position 1 and into position 2, and which also applies a ground to the conductor 27 to move the sequence switch of the appropriated finder circuit out of position 3.

Assuming that the sequence switch 01 finder circuit 1 is in position 1 and that the sequence switch of finder circuit F is in some position between 1 and 17, that finder circuit being assumed to be in use, the opera tion of the relay 33 completes, the following circuit; from battery, through the motor magnet and contacts 203 (1) of the sequence switch of finder circuit F, contacts 211 (1) of the same sequence switch, contacts 211 (3 to 17) and (1 to 17) of the sequence switch 200 of finder circuit 1*, contacts 211 (3 to 17) and (3 to 3%) of the sequence switch 200 ol finder circuit 1 conductor 28, lower contact and armature of the relay to ground. This causes the sequence switch of finder circuit F to move into position 2. If by any chance the sequence switch of finder circuit 1*" should fail to be moved into the call-awaiting position 2 when the relay 33 operates, it will be moved into that position when the sequence switch of the appropriated finder circuit F moves into position 5 at a slightly later stage in the operation. he circuit by which this result would, under the circumstances, be accomplished ex tends from battery through the motor 7 ne and contact 203 (1) oi the sequence switch or"- finder circuit'F, contacts 211 ('1) of that sequence switch, sequence switch contacts 211 (3 to 1'?) and 1 to 17) 0t finder circuit F (assumed to be in use), and

thence by way of contacts 222 (5 to 1) of all of the finder circuit sequence switches in series to ground, In other words, at any time that the finder circuit sequence switches are all standing in position 1 or in position 5 and beyond, a ground is applied by way of the 222 cams in series that moves one of the switches into position 2, and thus places the associated finder circuit in its call-aimitcondition. The sequence switch of finder circuit F is moved out 01 position 3 by the closure of a circuit that extends from battery through the motor magnet and contacts 203. (3) oi the sequence switch of that circuit, conduetcr .27 and upp r con ac nd armature 01 relay 33 to ground. As soon as the sequence switch of finder circuit F moves into position 2, it opens at its contact, 210 the circuit by way of conductor which has been maintaining relays 23 and 33 energized, and these relays release their armatures. Relay 23, inreleasing, reconnects to ground the circuit which eX- tends in branches 5? and 58 through its various sets of group relays, thus again giving the groups access to the starting circuit.

At this stage of the operation of the system, the sequence switch of the appropriated finder circuit F is in position 4, and the elevator rod of the associated line-finder LF is moving up with the set of brushes tripped that corresponds with the group in which the calling line is located. Asthe tripped brushes rise, they come into engagement successively with the sets of contacts corre sponding with the different lines of the group. At the instant of engagement of the brush 43 with the terminal 17 of each line, the test relay 37 of the finder circuit is connected with local conductor 253 of that line. This local conductor has two branches, one or the other of which is closed, depending upon the condition of the line relay 12 of the associated line. If the line relay is inert, as it is when the line is not calling, or when the line has been connected with and its cut-oil relay operated, the local conductor 253 oi the line is connected with ground by way of an identifying device 252 and a relatively low potential battery. If the line relay 12 is energized, as it is when the line is calling andis not connected with, the local conductor 253 of the line isconnected with ground by way of the left-hand armature and front contact of relay 12, right-hand back contact and armature of the protective relay 250 common to a group of lines, the energizing winding of this relay, and a relatively high potential battery 251. Therefore, as the elevator rises and the brush 43 engages the corresponding terminal 47 of each of the lines of the group in which the calling line is located, a circuit is completed as each line terminal is engaged that extends, either by way of the low potential battery, the device 252, and the leithand back contact and armature of relay 12 to the local conductor 253 of the line; or by way of the high potential battery, the winding of common relay 250, the right-hand.

armature and back contact of that relay,

and the left-hand frontcontact and arma and not to that produced by the low potential battery. As the line relay 12 of the cal1 ing line is energized, thus connecting the highpotential battery to the associated local conductor 253, the test relay 37 responds when the brush l3 engages the terminal e7 of the calling line. The response of the relay 37 causes that relay to interrupt in its back contact the previously traced circuit by way of the left-hand armature and front contact of the relay 30, sequence switch con tacts 216, and right-hand winding of relay 30, which circuit had been holding the relay 30 locked up from the moment that the relay was first energized upon the receipt of the call. Relay 30 in releasing its armatures breaks its own locking circuit, and also breaks the previously-traced path including sequence switch contacts 208, right-hand armature and front contactof the relay 30, and sequence switch-contact 207, over which current has been flowing to energize the up drive magnet 32 of the line finder. There-- fore, the operation of the relay 37 upon the finding of the calling line acts to efiiect the instant deenergization oi the up-drive 1nagnet 32, and thus to stop the brushes upon the terminals of the calling line.

In order that the brushes may always be stopped inregistration with the line terminals, the locking circuit 01 the relay 80 has an alternative path to ground by way of sequence switch contact 215 (2 to a), con ductor 66, the C segment of the line finder commutator and the corresponding brush to ground. The C segment of the commutator is so formed and related to its brush that the connection between the two is interrupted only when the corresponding line brushes on the elevator rod are in engagement with corresponding sets of line terminals. The unlocking of the relay 30 and the consequent stopping or the upward movement of the elevator rod, can therefore occur only when the line brushes are in proper relation to the terminals of the calling line.

When the relay 30 is deenergized, as a result of finding the calling line, it also coinpletes a circuit that extends from battery through the motor magnet and cortact 202 (3 to 4:) of the finder sequence switch, ii

1. gh thand back contact and armature or" the rela 30, sequence switchcontact 208 (2 to 7) conductor 7 9, and M segment and corresponding brush or the cord selector CS to ground. The closure of this circuit moves the sequence switch outof position ii:-

VVhen the finder sequence switch reaches position 4'5} it closes a path for the flow of current through the cutoff relay 11 of the calling 7 line by way of resistance coil 64, sequence v switch contact 212 (4% to 12%),conductor '50, brush42', line terminal 46 and conductor flow of current in this circuit, operates" the cut-elf relay 11 to disconnect the relay 12 from the circuit, and that relay in releasing its armatures disconuects the high potential test battery from the local conductor 253 and disconnects ground from the common conductor 18. The disconnection of ground from conductor 18 occurs before the timing sequence switch 100 has com pleted its cycle of rotation and reconnected conductor 18 with relay 19.

The brushes of the line finder switch are now at rest in engagement with the terminals of the calling line, the sequence switch 200 of finder circuit F is at position (5, the group starting circuit represented by the conductors 57 and 58 and the associated relays 22, 23 and has been released and is in readiness to respond to another calling line, and the sequence switch oi another finder circuit has been moved into position 2, and thus brought into operative relation with the starting conductor 29.

When the sequence switch of the finder circuit over which the call is being extended has reached position (3, the finder circuit is brought into operative relation with the operators selecting circuit. \Vhcn the finder sequence switch reaches position (3, it awaits the closing of a circuit, the completion of which is dependent upon the condition of the other finder circuits of the associated group. This circuit extends from battery through the leit-hand winding 01" the relay 30, contact 219 oi: the appropriated circuit sequence switch, contacts 219 (9 to a) of the sequence switches of the associated finder circuits preceding it in the series, conductor 76, outer armature and back contact of relay 541-, and right-hand back contact and armature of relay (31 to ground. A branch path for the energization of relay 30 also exists at this time, this branch path extending from battery through resistance 56, sequence switch contacts 217 to 9), righthand winding of relay 30, sequence switch contacts 220 (6) and (1 to 13), and contact 1 219 of the ZIPPI'OPliZIlLQCl finder circuit sequence switch, from which point it extends to ground a the right-hand bacl; contact and armature of the relay (31 over the path already traced. energization of relay 30 is open either in the (am 219 of a preceding finder sequence switch in the series, or in contacts of the relay 5% or 61 as long as any sequence switch of the series is in positions a to 9. That is, it is open from the time the line finder switch of any associated finder circuit finds a. calling line until the cord finder switch of that circuit has moved far enough. to trip the brushes corresponding with the selected i operators position, as will be described. Not until this has occurred will the above traced circuit of the awaiting finder circuit be closed. When the circuit is closed, the

relay 30 attracts its armatures and com- This circuit for the in its 1 position.

pletes a circuit that extends from battery through the motor magnet and sequence switch contact 202 (6 to 7) of the sequence switch 200, righthand front contact and armature oi relayBO, sequence switch con tact 208 (2 to 7), conductor 79, and segment M and corresponding brush oi": the cord selector commutator to ground. The completion of this circuit moves tinder sequence switch out of position 6.

When the sequence switch 200 reaches position 6 it closes a circuit that extends from battery by way of the winding of relay 55 (Fig. 3), conductor 71, sequence switch contact 218 (6% to 8), conductor 67,

and segment M and corresponding brush of the line finder commutator to ground. The operation of the relay 55 applies ground to the conductors 81 extending; to all of the operators positions. fit each of the positions where the operator is at her station and is in readiness to receive a call, the as sociated relay 91 (Fig. 1) is inert, and the operators telephone sequence switch 300 is Consequently at each of such positions, a circuit is closed that eX- tends from battery, through the winding of the associated relay 92, left-hand armature and baclc contact of relay 91, sequence switch contact 303 (1), conductor 81, armature and front contact oi relay 55 to lid ground, The relay 92 of each awaiting position therefore attracts its armature and closes a circuit that extends from battery, through the front contact and armature of the relay 92 to the conductor 82, and thence to ground by way of the windinp's of the relays 77 corresponding to tha, operators position at the various cord selector frames.

When the finder sequence switch. 200 rea chposition 7, in which position it comes to rest, it closes a circuit that extends from battery through the winding of relay 5%, left-hand baclr contact and armature oi relay 61, conductor 73, finder sequence switch contact 218 ('7 to 8), conductor 67, and

segment M" and corresponding brush of the line finder commutator to ground. ,ftielay 54L attracts its armatures and completes a branch of the circuit traced above, which branch extends from conductor 78 way oi the armature and back contact of the relay 63, front contact and left-hand armature of relay 541, right-hand armature and back contact olt' relay (i2, armature and front contact of relay 77, (which relay is energized, as previously described, as a result of the corresponding operators position being in readiness to receive a call), right-hand back contact and switch spring of relay oithe corresponding group,

. windins; of associated relay 94;, winding; of

relay 93, left-hand switch. spring andrcstme; contact of relay 93, conductor 83, lefthand back contact and armature of relay at the O operators position to battery. Upon the closure of the above-traced branch circuit, group relays 93 and 9%. are enersized in parallel with the relay 54:. Relay 93 in operating disconnects its own ener: gizing winding and that 01"- relay 94 from the previously traced path to battery by way of the left-hand back contact and armature of relay 95, and connects them in a path which extends to battery by way of conductor 84: and the winding oi the relay 9-3. This causes the relay 95 also to be en ergized and to interrupt in its left-hand armature and back contact the'path by way of conductor 83 over which the the relays 98 and 9 1- were initially energized.

Belay 94t in operating closes a. circuit from battery through the winding of the trip magnet 20 corresponding to the selected operators position, and to ground by way of the right-hand armature and front contact of the relay 9 1-. This relay also closes a circuit that extends from battery through the winding of the relay (i3 and the left-hand armature and front contact of the relay 91 to ground. The relay63 in operating closes a branch that extends from the conductor 73 (grounded by way of contact 218 (T to 8) of the. line finder sequence switch) through the armature and front contact of relay 63,

back contact and armature of relay 25 i, onductor 7 2, sequence switch contacts 220 (7) and (l to 13), and lett-hand winding; of relay 30 to battery. A branch energizing path for relay 30 also extends from conductor 72 by way of sequence switch contacts 220 (7), ring-hand winding 01'? relay 30, sequence switch contacts 217 (2'to 9) and resistance 56 to battery. Relay 30 attracts its armatures and closes a circuit that extends from battery through the motor magnet and sequence switch contact 202 (6 to 7), front contact and righthand armature of relay 30, sequence switch contact 208 (2 to 7), conductor 79, and segment M and correspond ing brush of the cord selector commutator to ground. The closure of this circuit moves sequence switch 200 out of position 7. Furthermore, relay 30 in operating is locked up over a circuit that extends "from battery through resistance 56. sequence switch contacts 217 (2 to 9), rioht-hand winding of relay 30, sequence switch contacts 216 (7 to 9) and (2 to 9), front contact and left-hand armature of relay 30 and armature and back contact of relay 3? to ground.

When the sequence switch reaches position 8 it closes a circuit that starts the 1113- ward movement of the brushrarryingt rod ductor 67, commutator segment M of the line line finder and corresponding brush to ground. 7

In order to prevent the upward movement '01 the cord selector switch from being started before the selection of a particular one oi the trip magnets 21, has been definitely effected, the circuit of conductor 72, over which the relay 30 is energized wien relay 63 operates, is placed under the control of slow releasing relay 25a. The energizing winding of the slow releasing relay is in parallel with the energizing winding of the relay 5st, and the relay 254 is consequently energized by way of conductor 78 and earn 218 of the finder sequence switch wnen the sequence switch reaches position 7. The energizing path of the relay 254: is by way of:

the back contact and armature of relay 63,

and the armature and back contact of relay controls the path to relay 30 by way of the conductor 72, holding this path open as long as the relay 25 i is energized. When therefore the actuation of one of the relays 9i operates the relay 63, the operation of the relay 63 does not instantly close conductor 7 2 to energize relay 30 and move the finder sequence switch to position 8 where the upward movement of the cord selector. brushes is started. Instead, the closure of this energizing path for relay 30 is delayed until 1 ciated with two operators positions on the same cord selector frame, or for two trip finagnets associated with same operators potripping yokes, and that set of brushes is tripped and made operative whose trip magnet is at the time energized, In the present instance, it is assumed that this is the trip magnet 20 associated with the terminals of the group or" connecting cord circuits extending to'the O operators position.

Immediately after the set of brushes is tripped, the common" operators selecting circult 1s restored so as to be available for the use of other cord finder switches. This is effected through the .iuediiun of a circuit that is completed by the grounding of the K segment of the cord iinder couuuutator, this segment being so located as to be engaged its brush immediately after the tripping levers of the sets of brushes pass the associat tripping yolzes. The circuit re'l'err l to extends from battery through the winding of relay ($1, conductor 74:, sequcnce switch contact 221 (75,; to S), conductor 80, cord finder commutator segment and corrcspoinling brush to ground. leiay 61 in operating opens, at its loft-hand back contact, the pro*iously-traced circuit by way of conductor 72-} which, up to this time, has been holding energized the relay at the O operators position and the relays and 9% corresponding to this position on the cord finder frame. The release of the relay J-Il deenergizcs the corresponding trip mag and the con'nnon relay The dccucrgization oi? the relay 93 reestablishes, subject to the l'clcusc of relay 61, the control or" other finder circuits over the brush tripping mechanism of he associated cord finder frame.

Relay 61, in operating, closes a locking circuit for itself by way of coiuluctor 73, sequence switch contact 218 (Y to 8), con ductor (l7, commutator segment M of the line finder and corresponding brush to ground. It also completes a circuit that extends from battery through the motor magnet and contact 204 (S) of the sequence switch 200. conductor 75, righthund front contact ant. armature of relay U1 to ground. The closure of this circuit mores sequence witch 200 out of position 8. in moving out of position 8.. the scouoncc switch opens its contact 218 (T to 9), thus dci ncrgizing relay 61 and again extent ling conductor 73 to the relay- 5%- and the c nductors over which the operatows selection is cil'cctcd. in closing its right-hand hack contact upon release relay ()1 also restores the continuity of conductor to and makes it available for moving out of position (i the sequence switch of some other finder circuit which may be waiting for access to the operators selecting circuit.

After the cord selector switch CS passes the brush-tripping position, it continues its upward movement until the brushes are stopped by engaging the terminals of one of the connecting circuits that is not in use. The idle or busy condition of the connecting circuit is indicated by the presence or absence of higlrpotential battery on the test terminal 118 of each connecting circuit. When the brushes engage the terminals of an idle connecting circuit, a path for the flow of current is completed from high potential battery 251 (see Fig. l), through the winding of common protective lUS .i ill relay 258, armature and back contact of that relay, lower back contact and armature of relay 259, conductor 128, armature and back contact of relay 429, contact 406 of the listening key sequence switch, conduc tor 88, test terminal 118 and brush 114 of the cord selector, conductor 99, tinder sequence switch contacts 206 (8 to 9) and the winding 01 relay 37 to ground. Relay 87 thereupon attracts its armature and opens the previously traced locking circuit that has been holding relay 30 energized. Relay 30, in releasing its armatures, opens at its rigl1t-hand front contact and armature the energizing circuit for the up-drive mag net 34, thus stopping the brushes of the cord selector switch in engagement with the terminals 01' the selected connecting circuit. in engaging its back contact, the right-hand armature of relay 30 closes an energizing circuit for the motor magnet of the finder sequence switch which extends by way of cam 202 (8 to 9), back contact and righthand armature of relay 30, earn 218 (8 to 9), conductor 67, and the M segment and corresponding brush of the line-finder COlH mutator to ground. The closure 01' this circuit moves sequence switch 200 out of position 9, whereupon the switch continues to move until it reaches position 14, where the talking circuit is completed at cams 213 and 214.

An instant after the finder sequence switch leaves position 9, it closes a circuit that extends from battery through the windings of relays 421 and 423 (see 4) in parallel, listening key sequence switch contacts 407 (1), left-hand back contact and armature of relay 422, conductor 87, cord selector switch terminal 117 and corresponding brush 113, conductor 98, and findersequence switch contacts 217 (9-2; to 14) and (9%} to 11) to ground. Relay 421 in operating closes a locking circuit for itself and relay 428 that extends by way of its upper front contact and armature, and sequence switch contact 405 (1 to 6) to ground. lielay 421 also closes a circuit that extends from battery through the motor magnet and earn 408 (1) of the listening key sequence switch and lower front contact and armature of relay 421 to ground. The closure of this circuit causes the listening key se quence switch to move out of position 1, and, in doing so, to open the test conductor 88 at sequence switch contact 406 (1), and also to open at sequence switch contact 407 (1) the path over which the relays 421 and 42?) were first energized,

ielay 423, associated with relay 421, in operating closes a c rcuit that extends i'rom battery through the windingof relay and upper front contact and armature of relay 423 to ground. As result relay 422, prior to the moving of the listening key sequence switch out of position 1, has disconnected conductor 87 from connection with battery by way of sequence switch contact 407 (1) and the windings oi relays 421 and 423, and has connected it with an alternative path to battery by way of the left-hand iront contact 01? relay 422 and resistance olevice 424. When the listening key sequence switch reaches position 2, an additional path to ground for holding the relay 422 energized, is closed by way of sequence switch contact 412 (2 to '4').

The energization of relay 423 at the instant the cord is seized also brings about the closure of a circuit that extends from battery through the winding of the common relay 259, conductor 129, and lower front contact and armature of relay 423 to ground. Relay 259 in operating opens at its lower armature and back contact the circuit over which the potential of the high voltage test battery 251 is supplied to the test conductors 128 of all of the connecting cords oi the position. Thus the electrical condition which permits a connecting cord to be seized by a cord selector is withdrawn from the selected cord and also from its assoclated cords at the instant of seizure, and is not reapplied to such of the cords as'inay be in condition to be selected until the common relay259 is de'e'nergized. The deenergization of relay 259 occurs when the relays 421 and 423 are released by the opening of their locking circuit at a 405 when the listening key sequence switch moves beyond position 6.

When the listening key sequeme switch 400 is moved out of position 1, in the manner described above, it continues its movement until it reaches position 7. In position 7 the cams 408, 409, 410 and 411 of the listening key sequence switch interrupt the talking strands of the connecting circuit and include between their severed ends a loop that has connection by way of conductors 135 and 136 with. the operators telephone set 147. This puts the operator in communication with the calling subscriber. at the same time the operator is informed of the identity of the connecting cord over which the call is being extended by the flashing of the lamp 161 associated with that cord, the circuit for illuminating this lamp extending from battery through the outer back contact and armature of relay 500, iamp 161, sequence switch contact 413 (7), and inter upter 162 to ground.

At this particular time the operators se quence switchEOO is in position 17, or moving to that position. W hen the position was. seleited the operators sequence switch was standing in position 1 and the relay 91 was inert, thus providing apath for the energination of the relay 92, the. operationwoi which relay when anoperatorfisposition .i

.to be selected serving to marketerp r ne lar position as being unengaged or selectable.

When the position is selected, the relay 95 is operated inthe manner previously described; In operating, the relay 95 closes a circuit that extends from battery through the motor magnet and earn 302 (1) of the operators sequence switch, right-hand front contactand armature of relay 95, and lefthand' front contact and armature of relay- 125 to ground. The relay 125 at this time is operated, as its energizing path is completec by way of local contacts 127 of the operators telephone jack 126, which contacts are closed when the operator is at her position and has her telephone plug inserted in'the telephone jack- As a result of the closure of the circuit traced above, the operators sequence switch 300 is moved out of position 1, thus opening the energizing path oi relay 92 in sequence switch contact 808 (1) and making .the position unselectable. The next resting position of the operators telephone equence switch 300 is position l; but as relay 125 is energized, the motor magnet has an ener gizing circuit in this position by way of sequence switch contact 302 (4:) and the right-hand front contact and armature of relay 125 to ground, and consequently the sequence switch moves on to its next resting position 17. The sequence switch remains in position 17, keeping the operators position unselectable', until at a later stage in the operation the switch 192 is operated in any suitable manner to close its contacts. Switch 192 corresponds to the upper armature of relay 192 of application to S. B. Williams, Jr, Serial No. 180,63 l filed July 14, 1917. At this timea circuit is closed that extends from. battery through the mo tor magnet and cam 302 (17) of the operators telephone sequence switch and closed contacts of switch 192 to ground. The closure of this circuit permits the sequence switch to move from position 17 to position 1, thus rendering the operators position again available for receiving calls.

The operators position is also rendered unselectable when the operators telephone set is connected with one of the connecting circuits This iseifected through the medium of the relay 91. When the listening key sequence switch 400 of any of the connecting circuits of the operators position is moved to position 7 to bring the operators telephone set into connection withthe corresponding circuit, an energizing path is completed that extends from battery through the'winding of relay'91, conductor 137, and listenin' key switch contact l0-l 2 to 9 to. grounca The completion of this circuft causesthe relay 91 to'attract its armature and interrupt the path over which the relay '92 s adapted to be energized, thus preventing the operation or the associated selection controlling relays 77; r

The removal of the telephone plug from the operators telephone jack 126 when the operator leaves her position, also renders the position unselectablc. lVhen the plug is removed, the breaking of the circuit at the local contact 127 causes relay 125 to hecome inert and release its armaturcs. This closes a circuit that extends from battery through the motor magnet and earn 302 (1) oi the operators telephone sequence switch, and to ground by way of the right-hand back contact and armature of relay 125. In moving out of position 1 as the result of the closure of this circuit, the sequence switch interrupts the energizing path for the relay 92 in sequence switch contact 303 (1), thus preventing the operation of the corresponding sel ction controlling relays 77 when a connection is to be extended.

Reference has heretofore been made to the operation oi"- the common relay 259 which is energized to remove the test condition from the selected connecting cord and all of its ass ciated connecting cords at the instant the cord is seized. This relay when it operates, also acts to complete a circuit that extends from battery through the winding of relay 91 and the winding oi. relay 193 in parallel, and thence to ground by way of the upper front contact and armature of relay Relay 1: 3 in operating, closes a circuit from battery through the motor magnet and contact 30: (1) of the operators telephone sequence switch, and front cont ct and armature o'l relay 193 to ground. The cio; e or" this circuit safeguards the operators telephone quencc switch from standing or stopping in position 1 from the instant the cord circuit is seized. Relay 91. in operating insures the inaccessibility oi the operators position at this time by opening the path over which relay 92 must be energized.

When the operator has been put into communication the calling subscriber by the. movement of listening key sequence switch 400 to position 7, as already described. and when the operator has learned the number of the line that is wanted, the connection may be com Jlet-ed by inserting calling plug in which, in the present instance, the

in position. 7 as a result of the closure of tcalled su'loscribers station D. As all of' these parts may have them usual iunctmns' and may operate 1n the usual way, a description of them and oi the exact manner in which the cord circuit is organized is thought to be unnecessary.

When the calling; plug 4:25 is inserted in the called line spring jack, an energizing circuit is completed that includes serially the windings oi the connecting cord relays 120 and 4:31 and the cut-oil relay 11 or the called line. The cut-oil relay 11 may have its usual function of disconnect i'ng-the line relay 12 thus depriving the line of control over the calling apparatus. The relay 4-20 in operating interrupts at another point the path oi the test conductor 88, thus keepingthe cord circuit unselectable while the plug 125 is in the spring jack oi the calledlline. lhe relay l31 at its upper back contact breaks the connection of the tip of the plug with the conductor 138, which may extend to the test winding of the operators telephone set, and at its upper front contact closes the tip strand of the connecting cord to complete the talking circuit. T he relay car in operating also closes a circuit that extends from battery through the winding of the relay 500 and the lower front contact and armature of relay l31 to ground. The relay 500 at its right-hand armature and back contact interrupts the circuit or the flashing call lamp 161 and extinguishers the lamp. At its inner left-hand armature and l ront contact, the relay 500 closesa locking circuit "for the holding relay 122 that extends by way of the rightdiand :tront contact and armature of that relay. ;he relay 500 also closes a circuit that extends from battery throun'h the motor magnet and contact 402 (7) or thelistening key sequence switch, outer left-hand front contact and armature of relay V500, and lower back contact and armature of relay 4:21 to ground, the relays 421 ands/18 having been released by the opening of their locking circuit at cam 4-05 when the listening key sequence switch moved beyond position 6. The listening key sequence switchinoves out oit'listeniug- 1S tin last-mentioned circuit, and comes to re, position 15. a

l The termination of the conversation between the subscribers in indicated in the usual way by signals displayed when the supervisory relays 4:27 and become inert, and disconnection is effected by witlr drawing the calling plug 425 from the spring iaclr 14 The withdrawal of the calling plug 225 interrupts the energizing circuit of the relays 431 and 120, and these relays release their armatures. The relay 131 in releasing breaks the energizing circuit of therelay 500, and that relay in releasing closes a circuit that extends from battery throughthe motor-magnet and cam s02 (15) of the listening key sequence switch, outer left-hand back contact and an mature oi relay 500, and lower back contact and armature of relay 4121 to ground. llhe listening rey sequence switch 7 thereupon moves out of position 15, and comes to rest in position 1. Relay 500 in releasing also opens at its inner left-hand front contact and armature, the locking circuit of the holding relay 49 2, and that relay, in releasing, breaks the connection of conductor 87 with battery by way or the device 424:. l Vhen current ceases to flow through conductor 87, the relay 30 of the finder circuit, which has been included in the path of current flow by way of conductors 87, 98, 50 and 53, and the finer sequence switch cams E217 and 212, releases its armatures.

This closes the circuit from battery through motor lllitgll t and cam 209; (14) or the finder sequence switch, left-hand back contact and armature oi? relay 30, and armature and ba: l: contact of relay-37 to ground. This moves the iindcr sequence switch out of the talking position 1.4.

When the finder sequence switch reaches position 15 a circuit is closed for the energlZulJlUli oi? the relay 50 that includes in par allel branches both windings of that relay. Gee branch of this circuit extends from hatthrough resistance 56, sequence switch re contacts 217 (15 to 16) and (12 to 16) rightiand winding oi relay 30, sequence switch contacts (l5) and (11 to 16) to conit'ront contact and armature of relay 30, and

armature and baclr contact of relay 3? to ground. Relay 30 in operating also closes a circuit that extends from battery, through motor magnet and contact 202 (15) oi the finder sequence switch, right-hand frontcontact and armature oi relay 30, sequence switch contact 218 (15), conductorhl, and

M segment and correspoiu'ling brush oi the line-linder commutator to around completion of this'circuit energizes th y cquence switch 200 and causes it to nio eits cams to position 16. ii

in moving out of positioirlfithefsequence switch opens at its 5320 calm, the branch of the energiai Pa thqthfit includes the letthandwinding of relay 30, and also opens the path to ground by way of conductor 67 and the M segment of the line-finder commutator; the energization of the relay being maintained in position 16 ot the sequence switch by way of the branch that in- 7 eludes its right-hand winding, cam 216, lefthand contacts 01 relay 80, and resting contacts of relay'37. This circuit is held closed and relay is kept energized until the cord circuit through which the call was extended has returned to its normal position. lVhen this occurs a circuit is closed that extends from higlrpotential battery 251, through the winding and contacts of common relay 258 (see Fig. l), armature and back contact of relay 259, conductor 128, armature and bacl; contact of relay e20, sequence switch contacts 106 (1),closed when the cord circuit returns to normal, conductor 88, cord selector contact 118 and corresponding brush 114, conductor 99, sequence switch contact 208 (16), right-hand armature and front contact 01": relay 30, sequence switch contacts 224- (9 to 17) and (16), and winding of relay 37 to ground. The closure of this circuit energizes relay 37, which attracts its armature and opens the previously-traced holding circuit of the relay 30. Relay 30 in releasing its armatures closes a circuit that extends from hattery through the winding of down-drive magnet 62 of the line-finder switch, conduc tor 60, sequence switch contacts (16 to 7) and (16 to 16-1), left-hand back contact and armature of relay 30, and armature and back contact o1"- relay 3'? to ground (the energizing circuit of relay 8? 'liaying been interrupted atthe right-hand front contact and armature of relay 80 when that relay released). As a. result of the closure of this circuit, the brushes oi" the line-finder switch are returned to normal.

As the line-finder brushes reach normal, a circuit is closed that extends from battery through the motor magnet and contact (16) 01 the finder sequence switch, conductor 69, and Y segment and corresponding brush of the line-finder commutator to ground. lVhen the finder sequence switch moves to position 17, as a result of the closure. of the above traced circuit, a circuit is completed that extends from battery through the winding of the down-drive magnet or" the cord selector, conductor 90, finder sequence switch contact 218 (17), conductor 67, and hi segment and corre sponding brush or the line finder commutater to ground. The closure of this circuit returns the cord selector switch to normal; and as the brushes reach. normal a circuit is closed that'extends "from battery through the winding and contact 20% (17 of the finder sequence switch, conductor 31.

and segment Y and corresponding brush'ot' the cord selector coun'mwator to ground. lhe closure of this circuit causes the finder sequence switch 200 return to its normal or lposition.

1t will be remembered that when the finder switch makes connection with the calling line the sequence switch 200 is moved out of position l, and that when the sequence switch reaches position 4:}, a circuit is closed by way of cam 212 and conductors and 53 for energizing the cutcii relay 11 of the calling line and bringing about the release of the associated line relay 12. It may occasionally happen in the operation of the system that the line relay 12 will fail to release when the calling line is connected with, either on account of the sticking of the line relay itself, or on account of the failure of the cut-ofi relay to operate and open the energizing circuit of the line relay. The result of this ordinarily would be to cause the starting of a plurality of finder switches, for the reason that as long :is the line relay 12 has its armature attracted the circuit for the energization of the group relay 19 will be closed by waj, oi the timing sequence switch contact 103 (18 to 1]) as often as the timing sequence switch completes its cycle of rotation and the group relay 19, in turn, causes the closing oi the starting circuit and the starting of another finder switch. Each of these started finder switches, under the conditions assumed, would have its brushes stopped upon the terminals of the line whose line relay had failed to release, as the continued attraction of the line relay armature would main 'tain the calling test potential on the test conductor of the associated line.

In order to prevent such improper operation, the present system is so organized that when the test potential continues on a calling line at a time when it should be withdrawn, the inn roperly operated relay is deprived of control over the starting circuit, and a signal is given the switchboard attendant to inform him of the abnormal condition that Xists, the calling test potential at the same time being removed from the test conductor of the line.

The manner in which this result is accomplished is as follows: Let it be assumed that the movement of the finder sequence switch 200 to position G when the calling line is found, fails to br'g about the release oi the associated lino relay 12. lVheu the finder sequence switch moves out of pos ion 6 upon the finder circuit gaining to the operators selecting circuit. a circuit is closed that extends from the high potential test battery 251, the winding of the common protective relay 250. the back contact and armature of that relay. lefthand front contact and armature of line reins-once lay 12, test conductor253, test terminal 4:? and corresponding test brush 43 of the line finder, conductor 51, contacts 22 l- (l to 8) "and to 8) oi the finder sequence switch,

conductor 260, and winding of relay 52 of the operators selecting circuit to ground by way of the relatively lower potential but tery. The completion of this circuit causes the energization of the relay ti llelay in operating closes a locking circuit toritself that extends from battery through the winding o'l' relay 5E2, left-hand tront contact and armature of that relay, conductor 71, finder sequence switch contact 218 to 8), conductor 67, and the. M segment and corresponding brush of the line finder commutator to ground.

The protective relay is so wound and adjusted that it is unresponsive to the current which normally lows through it in connection with the testing and seizing of a calling line, but responds to the increased current flow which occurs when a direct path to ground is established. The operation or the relay 52 referred to establ'shes such a path, the circuit extending from high potential battery 251, right-hand inductive winding of protective relay 250, right-hand back contact and armature of that relay, lefthand front contact and armature oi the sticking line relay l2, conductor 253, terminal Mand its corresponding brush 4-3, conductor 51, sequenceswitch contact (l. to 8) and (6-2- to 8), conductor 260, left-hand front contact and armatureof relay 52, condnctor 71, contact 218 (lll to 8), conductor 67 and the M segment and corresponding brush of the line finder commutator to ground. The protective relay 250 attracts its armatures, and at its right hand armature and front contact completes a locking circuit for itself that extends to ground by way of normally closed contacts of key 501, and which also includes the left-hand noninductive winding of relay 259 in series with the right-hand or inductive winding, the left-hand winding being a protective winding which is normally short-circuited in the right hand armature and back contact of the relay. The closure of this locking path directly to ground from the windings of the relay 250 also serves to remove the high potential calling test condition from the test conductor or" the associated line.

At the left-hand front contact and arms-- ture of relay 250 a circuit is closed including the lamp 502 and the winding of the relay 503. The lamp is-there'fcre lighted, and the relay 503by attracting its armature completes a circuit for actuating an alarm signal of any suitable sort. Furthermore, relay 250 in operating opens, at its left-hand arma ture and back contact, the path to ground by way of which the line relays 12 are able to exercise control over their associated group relay 1. llheretorenvhen the timing sequence'switch 100 completes its cycle and closes its contact 103 (l8-l: to 11-), the path to ground tor the energisation or the relay 19, which otherwise would be completed at the right-hand armature and front contact arthe sticking line relay, open. at the left hand baclr contact and arn'iature of the protective relay i250, and the sticking relay is thus prevented from operating relay l9 and energizing the starting circuit to cause the starting oil other tinder switches. l hen the attendant, responding to the alarm signal, removes tl e abnormal condition and de presses the key 501, relay 256 released, thus opening the alarm signal circuit and closing the common lead to again give the line relays 12 or the associated group control over the starting circuit.

The system herein (1 sclosed is also so arranged that when the test relay 52 (see Fig, 3) responds as a result of the failure ot the line relay to release, it opens at its righthand baclr contact and armature the path over which the finder circuit operates to sclect an available operatofs position, and to close at its right-hand armature and front contact a circuit for moving the tinder sequence switch 200 into position to cause the upward nioveniient oi"- the cord selector. its the opening of the path at the right-hand armat-u e and back contact of relay 52 has *reven the tripping of any of the magnets 20, '21, the cord selector elevator rises with its hrusl'ies out of engagement with the connecting circuit terminals, and at the end of its up vard movement grounds the segment off the cord selector commutator.

The circuit completed by the grounding of this segmentcauses the sequence switch 900. to move to position 15 and then to position 16 where the relay 255 (see Fig. 2) is operated to light the trouble lamp 257. lit the associated switch is open at this time, the cord selector switch remains at its top or tell-tale position. If the switch 256 is closed, the apparatus operates to return the line finder switch and the cord selector switch to normal. This organization has been disclosed in the drawings, and is here referred to briefly because it supplements the present invention in taking care of the situation which arises when a line relay fails to release; but it has not been described in detail since it forms no part of the present invention. A detailed description of the operation of this portion o'tthe system is fully given in the copending application of S. B. Williams, Jr, Serial No. 180,633, filed lisc'losed, they have been described in connection with certain features that are the subject of other copending applications assigned to the same assignce, such applications including the applications of S. B. lVilliams, J12, Serial No. 75,328, filed January 51, 1916; Serial No. 75,329, filed (lair uary -l, 1916'; Serial No; 180,63i, filed July 1%, 1917, and the application F. A. Stearn finerial No. 107,5e0,filed July 5, 1916. These features are the subject of claims in the applications mentioned. above, and are not claimed in the present application.

lVhat is claimed is:

1; Thecombination with a plurality of telephone lines, of means for altering the electrical condition of each line in calling, a

plurality of finder, switches, means actuated b y the altered electrical condition of'a calling line for starting one of said finder switches to make connection therewith and for bri'nging'another finder switch into operative relation with said lines, means actuatcd by the establishment of connection be tween a finder switch and a calling line for restoring the calling line to its normal electrical condition, a test magnet associated with said finder switch, said test magnet being responsive to the altered electrical con dition of the associated telephone line, and means controlled by said test magnet for preventing said calling line from starting other finder switches.

2. The combination with a telephone line, vmeans actuated by said line in calling for altering the normal electrical condition thereof, a plurality of finder switches, means actuated by the altered electrical condition of a calling line for starting one of said finder switches and'placing another of said switches in readiness to be started, means actuated in establishing a connection between said started finder switch and said calling line for restoring said calling line to its normal electrical condition, atest magnet associated with said finder switch, said test magnet being responsive to the failure of the calling line to be restored to normal condition when connection is established therewith, and means controlled by said test magnet for preventing the altered electrical condition of said calling line from starting other finder switches.

3. The combination with a telephone line, a plurality of finder switches responsive to the altered electrical condition of the line in calling for making connection with said line, means actuated by the establishment of connection with said line for restoring the normal electrical condition thereof, other finder switches actuated by a continuation of the altered electrical condition of the calling line after connection is made therewith, and means responsive to a continuation of said altered electrical condition after the est-ab lishment of connection for restoring the normal condition of said line and preventing the starting of other finder switches.

i. The combination with a telephone line, a plurality of finder switches, means actuated by said line in calling for causing one of said finder switches to make connection tierewith, means actuated in making connection for altering the calling condition of said calling line, a test magnet associated with said finder switch responsive to a continuation of said calling condition after connection is made with the line, and auxiliary means controlled by said test magnet for n'eventing said continued calling condition from causing the starting of another of said finder switches.

5. The combination with a telephone line, a plurality of finder switches. means actuated by said line in calling for starting a finder switch and producing a test condition on said line to which said finder switch is responsive. means actuated bv a finder switch in making connection with said line for restoring the test condition and finderstarting condition to normal, a test magnet associated with said finder circuit responsive to a continuation of said test condition after connection is made with the line, and auxiliary means actuated in the response of said test magnet for changing the test and finder-starting condition of said line.

In witness whereof, I hereunto subscribe my name this 15th dnv of March A. D. 1918.

EDWIN H. SMYTHE.

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