US1304641A - Call-distbibuting system - Google Patents

Description

. s. B, WILLIAMS. JR. CALL DISTRIBUTING SYSTEM. APPLICATION FILED lUtY 14.1911

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UNITED STATES PATENT FFICE.

SAMUEL n wILLIAMs, JR, or BROOKLYN, NEW-YORK, ASSIGNQR To WESTERN ELECTRIC COMPANY, INCORPORATED, 013 NEW OF NEW YORK.

YORK, N. Y., A CORPORATION CALL-DISTRIBUTING SYSTEM.

Specification of Letters Patent. Patented May 27, 1919.

Continuation of application Serial No. 107,090, filed July 1, 1916, This application filed Ju1y 14, 1917.

Serial No.

To all whom it may concern:

Be it known that I, SAMUEL B. WILLIAMS,

J r., a citizen of the United States, residing at Brooklyn, in the county of Kings and State of New York, have invented certain new and useful Improvements in Call-Distributing Systems, of which the following is a full, clear, concise, and exact description.- This invention relates to telephone exchange systems, and more particularly 'to The object of this invention is to provide a telephone system in which each calling subscribers lineshall be connected with an operators connecting circuit with the mini- -mum of delay; in which the trafiic shall be distributed in such a way as to keep the operators positions uniformly busy; in which the calls shall be extended to operators po sitions' that are'at the time unengaged, and diverted from thosepositionsthat are busy; in which each calling line'shall be extended to only one of the operators positions that mavat the time be ready to receive a call; in whichtwo ,or more calls that are to be ex tended to operators positions at practically the same instant may be directed to differ- ,ent operators positions and -be prevented from reaching the same operator; in which thedistribution of the calls among the va rious operators positions may be underthe' control of selection 'controlling apparatus common to the various operators positions,

and to the circuits that extend the calls thereto; .in which this common selection controlling apparatus may be in operative relation with only one of the call-extending circuits at a time and may be promptly released for the use of other circuits as-soonas it has performed its function; inwhich the operator may be informed of that fact the instant her'position is selected by an incoming call; in which the selection of a position by an incoming call may temporarily suspend the operativeness of 'certainof the operators position apparatus; in which the condition of the operators position with respect to its ability to handle the traffic that 11S pending upon the position or may be directed to it may determine the accessibility of the position with respect to incoming. calls; in which the operator may be put into communication with the calling'subscribe'r the instant the call reaches a connecting circuit; in which the connecting circuits may be safeguarded against untimely selection, disconnection, application of ringing current and other improper operations; in

which anoverfiow arrangement is provided 7 to return the finder switch to its normal position when it fails to select the terminals of the calling line due to the removal of the test condition from these terminals, but if selection is prevented through fault of the The preferred embodiment of the system of the invention is illustrated in the accom-- p'anying diagrammatic 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 apparatusthrough the medium of which the lines control the switches; Fig. 2 shows .one finder enough of two other finder circuits to illustrate the relationship between them; Fig. 3

shows two cord selector switches of one frame with their associated selection controlling apparatus and circuits together with similar apparatus selector switches (not shown) 'of another "frame; Fig. 4 shows the position apparatus and circuits of one operators position, with enough of the position apparatus of another position to illustrate the inter-relation'ofthe tw.o;'and Fig. 5 shows one connecting. cord circuit complete, together with certain intercircuit complete, andand circuits forthe cord related parts of other cord circuits located on the same operators 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 or der indicated by the lines that extend to the margins of the sheets, illustrate as much of a complete organization as is necessary to gain an understanding of the construction and mode of operation of the system.

Two telephone lines are indicated in each 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 oflice a line relay 12, a cut-off relay 11 and, if it is a message-rate line, a connection register 164. Each line is also provided with one or more spring jacks 14 by means of which connection may be made with the line when it is a called line. The lines represented as calling lines in Fig. 1 and the line shown as a called line in Fig. 5 may be lines of the same sort, similarly equipped and located at the same exchange; or the lines may be located at different ofiices. In the present instance, the called line shown in Fig. 5 is indicated as being provided with connections by means of which it may have control over finder switch mechanism in the manner illustrated in 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 19 and 24, and a timing sequenceswitch 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 GS, are shown. Each of the groups of connecting circuits is associated with a particular operators' position, of

which the apparatus of one is shown at 0 and the apparatus of the other is partially shown at O. In the particular system illustrated, it is the practice to provide each operators position with twenty con necting circuits extending to multipled groups of terminals upon the cord selector switches, and to give the brushes of each cord selector switch access to the terminals of twenty-five such groups of connecting circuits. But one of the connecting circuits is shown complete, the other connecting circuits in the associated group and in the other groups being assumed to be similarly organized and connected. The mul- ,tion Frame 1.

tiple 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 the multiple connections of 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 lection controlling apparatus, that associated with the cord selector switchesshown in Fig. 3 appearing under the caption F rame'2, and that associated with the cord selector switches of the other group that is not shown appearing under the cap The selection controlling apparatus for each frame or group of cord selector switches comprises a set of relays 77, 93 and 9 1 for each group, CG, CG, to which the cord selector has access, and a group of relays 54, 55, 61 and 63, common "to all of the first mentioned groups.

As the line finder switches LF and LF, 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. McQuarrie, No. 1,177 ,044, 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 move the shaft up, an extension at the lower end of the shaft is brought into engagement with the constantly rotating power member 3 vby means of an idler wheel operated by the up-drive magnet 32; and to move the shaft down, the extension is brought into engagement with the power -member 4 by meansof an idler wheel operated by the downdrive magnet 62.

Normally the brushes of each of the sets 2 are held apart so as to clear the associated terminals by means of a separating cam 5 located between the innermost brushes of the set. The cam 5 is rotatably mounted, and when rotated in one direction, releases the brushes and permits them to engage the associated terminals. The tripping or releasing of the brushes is controlled by a numher of trip- magnets 16, 17. Each of these when energized rotates an associated trip rod 6 that extends transversely to the switch shafts 1and 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 of the finder switches is caused to move up has that set of brushes tripped that corresponds with the particular'trip- magnet 16, 17;, that is at the time energized. WVhen the finder switch that has beenin use is returned 'to its normal position, any of'the'as'sociated controlling cams 5 that has been tripped is engaged and rotated in a reverse direction to separate 1ts switch springs again and thus render them inactive.

Each of the line finder and cord selector switches hasassociated with it a commutator 8 which comprises a number of-stationary commutator segments'and a set of movable brushes carried at the top of the switch shaft 1 and cooperating with the stationary segments. This commutator serves to make and break a number of controlling circuits in the various stages of the upward move-. ment of the switch shaft.

F or controlling the circuits of the organization, there are employed a. number of Se' quence switches which are shown at different points and are designated 100, 200, 300,

100 and 500 respectively. These sequence switches may be of the type disclosed in Patent No. 1,127,808 issued February 9, 1915,

to Reynolds and Baldwin. Each consists of an electromagnetically controlled motor or driving mechanism and a number of associated switch cams. The switch cams .associated with each of the squence switches 100 are designated 101 to 103 inclusive; those associated with each of the sequence switches 200 are designated 201 to 222 inclusive; those associated with eath of the sequence switches 300 are designated 301 to 310 inclusive those associated witheach of the sequence switches 100 are designated 401 to 416 inclusive; and

those associated with each of the sequence switches 500 are designated 501 to --521 inclusive. To each of the contacts associated with the various sequence switch cams are applied certain numerals. Those numerals in the case of the cams 101, 201, 301, 401 and 501 indicate the only positions of the associated sequence switch in which theseparticular contacts areopen; 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 associatedcontacts 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 200. l

Scguen ce switch 300.

. Awaiting a call. Positlcn vacant. Position busy.

Sc lichen switch .400. Normal. Listenlng 1n.

Listenmg out.

Sequence switch 500.

. Normal. Awalting I listening key sequence .swltch. 1

Selective ringing operations.

causes the energization of a trip magnet corresponding to the group of lines in which his line is located. The finder switches each have as many sets of brushes as there are groups of, lines. The closing of the starting circuit causes a preselected one of the finder switches to move its brushes, and the energization of the trip magnet makes activethe set of brushes corresponding with the group in which the calllng line 15 located.

The apparatus which brings about the energization of the tr1p magnet operatesto prevent temporarily the trip magnets of other groups of lines from being energized by calls that may at the time be initiated in the other groups.

which the first mentioned calling line is located. That group is deprived of control over the starting circuit until after the finder switch has connected with the termlna-ls of the calling line. The object of this is to prevent the same calling line from starting a second finder switch in theinterval before the calling line is found.

When the finder switch brushes complete connection with the terminals of the calling line, the finder circuit operates certain apparatus that determines to which of a number of operators positions the connection of the calling line shall be extended. The selection is effected through the medium of selection controlling apparatus that is common to the cord selector switches upon which the finder circuits terminate, and to the operators positions to which these cord selector switches are designed to extend calls. lVhen a finder circuit is ready to extend a call, it first causes all of the operators positions that are idle or awaiting a call to indicate their receptive condition by operat ing corresponding switch parts upon the common selection controlling apparatus. The selection controlling apparatus responds by preparing a-path for the energization of a cord selector tripping magnet corresponding with the first opera-tors position in the series that is ready to receive a call. The finder circuit that is extending the call then sends a tripping impulse over the path thus prepared. When the tripping magnet operates, it starts the movement of the cord selector switch. At the outset of the movement the set of brushes is tripped that corresponds with the preselected operators position, and immediately thereafter the common selection controlling apparatus is released and made available for determining the selection of other operators positions by other cord selector switches and finder circuits.

After the set of cord selector brushes has responding trip magnet energized. a tone is produced in the operators telephone receiver which notifies her that her position has been selected and that a call is coming. At the same instant, the listening-in keys isoeeii the terminals of the selected connecting circuit, it lights a lamp associated with that circuit on the operators position and at the same time causes the tone in the operators telephone receiver to cease. It also moves a sequence switch of the selected connecting circuit to bring the operators telephone set, into connection with the selected circuitaand operates a relay that closes the circuit to the operators telephone instantly and in advance of its closure by the sequence switch, thus saving time in establishing communication between the calling subscriber and the operator.

' lVhen the operator has received the calling subscribers instruction, she tests the line that is called for and, if it is free, inserts the calling plug into the line jack. This act automatically disconnects the operators telephone apparatus from the circuit, and the disconnection of the operators telephone apparatus causes the actuation of the calling cord apparatus to apply ringing current to the called subscribers line.

lVhile the calling line and called line are I united, the operator can bring her telephone apparatus into or out of connection with the circuit by pressing the listening-in key individual to the circuit or the listening-out key common to all of the circuits. In pressing a listening-in key to bring hertelephone set into connection with one of the connecting circuits, the telephone set is automatically disconnected from any other connecting circuit with which it may at the time be in connection.

As long as the operators telephone set is in connection. with a cord circuit, the operator may withdraw the calling plug from the spring-jack of the line into which it was first inserted and insert it into another spring-jack without disturbing the connection of the calling line with the circuit,as when the calling subscriber wishes connection with several different lines in succes sion. But if the operator withdraws the calling plug in response to the disconnect signals, without reconnecting her telephone with the cord circuit, the connection is released and all of the switches return to normal. If the calling line is a message-rate line, the operator, before withdrawing the plug, presses a charge key which causesa registration upon a meter associated with the line, and which also makes the calling plug ineffective to bring about the release of the connection while the charge key is depressed. Also at the instant of release, a

relay acts to prevent any possible reener- The operators positions are arranged to receive incoming calls byway 01: several groups of finder circuits with their associ ated cord selector switches, and to prevent interference 3 between; simultaneous calls originating in different groups of finder c1r-' cuits, the arrangement being such that when.

the selecting apparatus of one group acts to select a particular operators position, that position is made inaccessible to the selecting apparatus and finder circuits of! another group. The different operators positions are also so inter-related that the kept equally busy, this being accomplished by rendering each position inaccessible to incoming calls" after it has received a call or after the operator has supervised an existing connection, and restoring its accessibility only when all of the positions have received acall or supervised a connection. The positions are then all restored to accessibility excepting such as may at the time be attending to acall or to a connection, or have all of their cords .in use, or may be out of service by reason of the operator being absent'froin-the position.

The features of'the operation that have been set forth in outline in the foregoing,

together with other features presentin the I system, will be fully explained in the detailed description thatfollows.

It will be assumed that the subscriber at station A initiates a call; l/Vhen the teleswitchhook,- I a circuit is closedthatextends by way of phone receiver is taken from the both windings of the line relay 12 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 attracting its armature, the conductor 18. This causes current toflow from battery through the winding of the relay 19, sequence switch contact 103 185} to 11-. conductor 18 and ground at the contact of the operated line-relay 12. The relay 19 attracts its armature and closes a circuit that extends from battery through the right-hand winding of the associated-relay 24, front contact of relay 19, back con' tact of relay 22 and lower armature and back contact of relay 23 to ground. Relay 24. operates and closes in its left-hand front contact a circuit that extends from battery by way of the winding of the associated group trip magnet 16 and the left-hand lay 22, and the lower back Contact of the 4 relay 23 to ground.

positions are applies ground to 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 7 0. groups. The trip magnet 16 rotates its associated trip rod to bring all of the yokes into position to trip the 7 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 58 to the corresponding relays 24'ofthe succeeding groups of the series.

The relay 24, in its right-hand front contact, also completes a circuitthat extends from battery through the motor magnet of the sequence switch 100, and contact 102 (18$ to 1%) of that switch. Infm'oving out of position 11}, sequence .switch '100 closes its contact 101 and opens its contact 103. As contact 101 is closed in all positions exce ting position 1 of the sequence switch, the

switch'is caused to make one complete rotasuch as to interrupt the group conductor 18, i

and hold it open until after the line relay '12 of the calling line has been released as'a. re sult of the finding of that line.

The relay 22, common to all the groups, in operating, opens in its back contact the circuit of the conductor efiiwhich extends serially through the back' contacts of the relays 19 of the 'various' groups. As this conductor 57 is thefpath over which the re- -lay 19 of. any group serves toefiect the ini 1 tial energization of the associated-relay 24: and the operation of the corresponding trip magnet, the interruptionof this conductor insures the operation of only one trip magnet and the tripping of only one set of U brushes on a started line finder switch.

The common-relay 22,'inits front contact, completes a-circuit that extends from grounded battery through the. left-hand winding of the findercircuit relay 30 (see 1 Fig. 2), contact 206 (2) of the finder-sequence switch 200, conductor '29, front contact of relay 22, through back contact of relay 23, to groundf- The conductor. 29 has branches extending to like sequence switch cams 206 of all of the finder circuits terminating upon "the line finders that have access to the calling line. But,..for reasons which'will hereinafter be explained, the sequenoe switch 2000fon1y one of these finder trip yokes.

circuits is standing in its 2 position. In

the present instance, it is assumed that this is the sequence switch of the finder circuit F. As a result of the closure of the circuit traced above, the relay 30 is energized and and (2 to 7), commutator segment M of the associated cord finder switch CS, and to ground by way of the brush that is inengagement with this commutator segment. Relay 30, in attracting its armatures, also closes a locking circuit for itself that extends from battery by way of the resistance coil 56, sequence switch contacts 217 (2),,

the right-hand winding of the relay 30, sequence switch-contacts 216 (2 to 4) and (2 to 9), 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 of its motor magnet circuit in the right-hand front con tact of the relay 30, the-sequence switch 200 moves out of position 2 and comes to rest in position 3. In position 3 of the switch, a circuit is. closed that extends from battery by way of the up-drive magnet 32 of the corresponding line finder switch LF, sequence switch contact 207 '(3 to 4), front contact and right-hand armature of relay 30, sequence switch contacts 208 (18 to 14) and (2 to 7), and to ground by way of the commutator segment M and associated brush of the corresponding cord finder CS. The energization of the up-drive magnet 32 starts the upward movement of the corresponding elevator rod with its associated sets of brushes. At the outset of the upward move ment of the elevator rod, all of the brush trip levers are moved past the corresponding The only trip magnet that is energized in this case is the magnet 16 which corresponds with the group in which the calling line is located; and consequently, the only trip yoke in position to engage a trip lever on the elevator rod is the one which controls the brushes 40, 41, 42 and 43 that are adapted to engage the terminals of that particular group of lines-.. This set of brushes, therefore, is released and made operative, and the other sets are held clear of their associated'line terminals.

As soon as the set of brushes corresponding with the calling line is tripped, the group apparatus, by means of which the lines control the brush tripping and line finder starting operations, may be returned to its normalcondition. The first step in this restoring operation is effected by the closurcof a circuit which is 'comple ed 'by way of the'K segment of the line finder commutator immediately after the brushes are tripped. This circuit extends from battery in parallel branches through the relays 23 and 33 (see Fig. 1), conductor 26, sequence switch contact 209 (2 to 3), conductor 68, and to ground by way of the K segment of the .line finder commutator and its associated brush. The energization of the relay 23 interrupts, in the lower back con tact ofthat relay, the previously described circuit that has up to this time maintained the energization of the trip magnet 16, the

group relay 24 and the common starting relay 22. Relay 23, in its upper front contact, closes a lockingcircuit for itself and the associated relay 33 that extends by way of conductor 25 and the sequence switch contacts 210 (2 to 1) of all of the finder circuits in series, to ground at a point beyond the last switch of the series. As has already been stated, normally there is only one of the finder circuits with,

its sequence switch in position2 awaiting the receipt of a call. When the callcomes in, this sequence switch is immediately moved to position 3, in the manner described above. Therefore, at this stage of the 019- eration, the sequence switches of all of the finder circuits are in position to close their contacts 210. The locking circuit for the relays 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

eration 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 (4 to 17) of the sequence switch 200 of finder circuit F contacts 211 (3 to 17) and (3 t03};') of the sequence switch 200 offinder circuit F, conductor 28, lower contact and armature of the relay 33 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 F should fail tobe 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 p0- circuit being assumed. to bein use, the opsition 5 at a slightly later stage in the operation. The circuit by which this result would, under these circumstances, be accomplished extends from battery through the motor magnet and contact 203 (1) of the sequence switch of finder circuit F,.contacts '211 (1) of that sequence switch, sequence switch contacts 211 (4 to 17) and (3 to 17) of 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 groundis supplied by way of the 222 cams in series that moves one of .the' switches into position2, and thus places ..the associated finder circuit in its callawaiting condition.

The sequence switch of finder circuit is' moved out of position 3 by the closureof a circuit that extends frornbattery through the motor magnet and contacts 203 (3) of the sequence switch of that circuit, conductor 27 and upper contact and armature of relay 33 to ground.

As soon as the sequence switch of finder circuit F moves into position 2, it opens in its contacts 210 the circuit by way of conductor 25 which has been maintaining re- .lays 23 and 33 energized, and these relays release their armatures. Relay 23, in releasing, reconnects to ground the circult which extends in branches 57 and 58 through the various sets of group relays, thus again giving the groups access to thestarting circuit.

At this stage of the oper'ationof the sys-- tem, thesequence switch of the appropriated finder circuit F is in positiohfl, and the ele- 1 vator 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. As the tripped brushes rise, they come into engagement con-' secutively with the sets of terminals corre sponding with the different lines of the group. At the instant of engagement of the brush 12 with the corresponding'line terminal 46 of each line, a circuit is closed that extends from battery by way of the relay 52, sequence switch contacts 212 (2 .to 4-), conductor 50, brush 42, line terminal. 46,-',con- 1 ductor 53 and winding of cut-ofl relay '11 to ground, If a line is busy as a calling line, a

branchqpath is in existence for the flow of current through the cut-ofi relay 11 by way of contacts 212 of another finder circuit sequence switch, and associated resistance 64' if the switch. is in positions 4*}; to 12%;, or windings of associated relays 30 of the finder circuit and 155 of the connecting cord circuit if the switch is in positions 12% to 14. If the line is busy as a called line, a branch path is in existence by way of the windings of relays 119 and 175 associated with the conof the calling line.

' 4.), conductor 49,,brush 41, line terminal 45, j conductor 39 to one limb of the telephone line, thence by way of the path controlled in contacts of. the substation switchhook, to the other limb of the line, conductor 38, terminal 44', brush. 40, conductor 48, sequence switch contact 214 (2 to 4), upper armature and front contact ofthe relay 52, upper winding of the relay 37 to ground. The circuit traced above is not completed until the finder switch brushes engage the terminals of the cal-ling line, as the calling line is the only line that has its telephone receiver off the hook, and at the same time is not connected with either by some'other line finder or by a connecting circuit calling plug. The completion of this circuit energizes the relay '37 and causes that'relay to interrupt in its back contact the circuit by way of the lefthand armature and front contact of the relay 30, sequence switch contacts 216,-rigl1thand winding of relay 30, sequence switch contacts. 217, and resistance 56 to battery, which had been holding relay 30 locked up from the moment that relay was first energized upon thereceipt of the call.

Relay 30, in releasing its armatures,

. breaks its-own locking circuit traced above,

and also breaks the previously traced path including sequence switch contacts 208, right-hand front contacts of the relay 30 and sequence switch contacts 207, over which current has been flowing to energize the up-drive operation of the relay 37, upon the finding of the calling line, acts to effect the instant de- 'energizationof the up-drive magnet 32 and thus to stop the brushes upon the terminals In order that. the brushes may always be stopped in registration with the line terminals, the locking circuit of the relay 3O has an alternative path to ground by way of sequence switch contact-215 (2 to l) conductor 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.

'magnet 32 of the line finder. Therefore, the

stopping of 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.

lVhen the relay 30 is deenergized, as a result of finding the calling line, it also completes a circuit that extends from battery through the motor magnet and contacts 202 (3 to 4) of the sequence switch 200, righthand back contact and armature of the relay 30, sequence switch contacts 208 (18 to 14) and (2 to 7), conductor 79, segment M of the cord finder commutator and its correspond ing brush to ground. The closure of this circuit moves the sequence switch out of position 4.

When the sequence switch reaches 'position 4%}, it closes a path'for the flow of current through the cut-off relay 11 of the calling line by way of resistance coil 64, sequence switch contact 212 (45} to 12%), conductor 50,'brush 42, line terminal 46 and conductor 53. The flow of current in this path operates the cut-ofi relay 11 to'disconnect the line relay 12 from the circuit, and that relay, in releasing its armature, disconnects ground from the common conductor 18. The times. of operation of the various parts are so related that the line relay 12 is deenergized, in the manner described above, before the timing sequence switch 100 of the associated line group has completed its rotation and closed the circuit of conductor 18 in sequence switch contacts 103. The current which previously flowed through the cut-off relay 11 by way of the winding of relay 52 of the finder circuit had been insufiicient to operate the cut-off relay "by reason of the winding of relay 52 being of relatively high resistance.

The brushes of the line finder switch are now at rest in engagement with the terminals of the calling line, the group starting circuit represented by the conductors 57 and 58 and the associated common relay 22 has 1 been released and is in readinessto respond to another calling line, and the sequence switch of another finder circuit has been moved into position 2, and thus brought into operative relation with the starting conductor 29. The stages of the operation that are next to be described have to do with the selection by the appropriated finder circuit of an idle operators position and the selection of an idle connecting cord on that position.

When the finder sequence switch 200 reaches position 5, it closes a circuit that extends from battery by way of the winding of relay 55, (Fig. 3), conductor 71, sequence switch contact 218 (5 to 8), conductor 67,

operators positions to the connecting circuit terminals of which the cord finder switch of the finder circuit has access. At each of the positions where the operator is at her station and is in readiness to receive a call, the associated relay91, (Fig. 4) is inert, and the operators telephone sequencethe front contact and armature of the relay 92 to the conductor 82, and thence to ground by way of the windings. of a number of relays 77 of which one is provided for-each cord finder frame that has access to this particular operators position. The'particular nature of this connection of the difi'erent operators circuits to a plurality of finder frames will be explained later. present, the operation will be' described merely in its relation to the particular finder frame that serves the finder circuit that has been assumed to have been appropriated by the calling line. For the present it will also further be assumed that the operators position 0 is in readiness to receive a call. The finder circuit sequence switch 200 does not stop in position 5, but continues its movement and comes to rest in position 6.

Here 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 lefthand winding of the relay 30, contact 219 (6) of the appropriated finder circuit sequence switch, con tacts 219 (9 to 4) of the sequence switches of the associated finder circuits preceding it in the series, conductor 76, outer armature and back contact of relay 54 and right-hand back contact and armature ofrelay 61 to ground. This circuit is open either in cam 219 of a preceding finder sequence switch 200 in the series, or in contacts of the relays 54 or 61 as long as any other sequence switch of the series is in same position between positions 4 and 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 group. Not until this has occurred will the above-traced circuit of the awaiting finder circuit be closed.

The closure of this circuit causes relay 30 to attract its armatures and complete a circuit that extends from battery through the,

motor magnet and sequence switch contact For the 202 (6) of the sequence switch 200, front contact and right-hand armature of relay 30, sequence switch contacts 208- (18 to 14) and (2 to 7), conductor 79, commutator segment M of the cord finder and corresponding brush to ground.- The completion of this circuit moves the finder sequence switch out of position 6.

\Vhen the finder sequence switch reaches position 651-, it closes a circuit that extends from battery through the winding of relay 54, (Fig. 3), left-hand back contact and armature of relay 61, conductor 73, finder sequence switch contact 218 (6% to 8), conductor 67, commutator segment M of the line finder switchand corresponding brush to ground. Relay 54 attracts its armature and completes a branch of the circuit traced above which extends from conductor 73 by way of the armature and back contact of the relay 63, front contact and inner armature of relay 54, 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 93 of the corresponding group, winding of associated relay 94, winding of relay 93, lefthand switch spring and resting contact of relay 93, conductor 83, left-hand back contact and armature of relay '95 at the corrcsponding operators position to battery. Upon the closure of the abovetraced branch circuit, the group relays 93 and 94 are energized in parallel with the relay 54. Relay 93, in operating, disconnects its own energizing winding and that of relay-94 from the previously-traced path to battery by way of the left-hand bank contact and armature of the relay 95, and connec-ts them in a path which extends from battery by way of the winding of the relay 95 and conductor 84.

This causes the relay 95 also to be energized and to interrupt, in its left-hand armature and back contact, the path by way of conductor 83 over which the relays 93 and 94 battery through the winding of the relay 63 and the left-hand armature and front contact of the relay 94 to ground. The relay 63, in operating, closes a branch that extends from the conductor 73 (grounded at commutator segment M of the line finder switch) through the armature and front contact of relay 63, conductor 72, sequence switch contact220 (7-), and left-hand Wind'- ing or relay 30 to battery. Relay 30-atuse of other cord finder switches.

tracts its armatures and'closes a circuit that extends from battery through the motor magnet and sequence switch contact 202 (7),

by way of the M commutator segment of the cord finder switch. The closure of this circuit moves sequenceswitch 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), right-hand winding of relay 30, sequence switch contacts 216 (7 to 9) and (2 to 9), front contactand' left-hand armature of relay 30 and armature and back contact of relay 37 to ground.

When the sequence switch reaches position 8, it closes a circuit that starts the upward movement of the brush-carrying rod of the cord finder switch, this circuit extending from battery through the up-drive magnet 34 of the cord finder, conductor 89, sequence switch contact 207 (8 to 9), right- At the outset of the upward movement of,

the cord finder brush rod, the tripping levers hand front co'ntactand'armature of relay of the various sets of brushes are brought simultaneously into operative position with respect to the corresponding tripping 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 22 associated with the terminals of the group of connecting cord circuits extending to the .O operators position.

Immediately after the set 'of tripped, the common operators selecting circuit is restored so as to be available for the effected through the medium of a circuit that is completed by thegroundinjg of'the This "is brushes is K-segment of the cord finder commutator,

this segment being so located as to be engaged by its brush immediately after the tripping levers of the'sets of brushes pass the associated tripping yokes. The circuit referred to extends from battery through the winding of relay 61, conductor 74, sequence switch contact 221 (7% to S), conductor 80, cord finder'commutator segment K and its corresponding brush to ground. Relay 61, 111 operating, opens, in its-left-hand back contact, the previously-traced circuit by way of conductor 73 which, up to this time, has

been holding energized the relay 95 at the Ooperators position and the relays 93 and 94 corresponding to this position on the cord finder frame. The release of the relay CILQ 94 deenergizes the corresponding trip magnet 22 and the common relay 63. The deenergization of the relay- 93 recstablishes, subject to the release of relay 61, the control of other finder circuits over the brush tripping mechanism of the associated cord finder frame. It also restores the corresponding operators position to operative relation wit-h the common. selecting apparatus of other finder frames, in a manner which will hereinafter be explained.

Relay 61, in operating, closes a locking circuit for itself by way of conductor 73, sequence switch contact 218 (6gto 8), conductor 67, 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 205 (8) of the sequence switch 200, conductor 75, right-hand front contact and armature of relay 61 to ground. The closure of this circuit movessequence switch 200 out of position 8. In moving out of position 8, the sequence switch opens its contacts 218 to 8) and 221 (7% to 8), thus deenergizing relay 61 and again extending conductor 7 3 to the relay 5 and the conductors over which the operators selection is eflected. In closing its right-hand back contact upon release relay 61 also restores the continuity of conductor 76 and makes .it available for moving out of position 6 the sequence switch of some other finder circuit which may be waiting for access to the operators selecting circuit. lVhen the sequence switch 200 is moved out of position 8, it moves into position9 and there awaits the finding of an idle connecting cord circuit upon the operators position that has been assigned. as the brushcarrying rod moyes up, the brushes 111, 112",

113 and 114 of .the set that has been tripped come into engagement successively with sets of terminals 115, 116,117-and 118 correspondingwith the different connecting cord circuits located .at that operators position. When a cord circuit is not in use, its corresponding terminal 118 is connected directly to ground; and when the terminals of such a connecting circuit are encountered, a circuit is completed'that extends from battery through the lower winding of relay 37,- sequence switch contacts 206 (8 to .9), conductor 99, brush 11%, terminal 118, conductor 88, sequence switch contact 404 (1), righthand back contact and armature of relay 119 to ground. Current flowing in this cir-,

cuit causes the relay 37 to attract its armature and break the previously traced circuit by way of sequence switch contacts 216 and 21.7 and the right-hand winding of relay 3Q,

Twhich, up to this time, has been holding relay 30 energized. It may here be noted that the locking'c ircuit of relay 30 has a branch to ground in parallel with the branch conof the line finder commutator; that is, it prevents the relay 37 from causing the deenergization of the relay 30 excepting when the brushes ofthe cord finder switch are centered upon their successively engaged sets of terminals.

When the relay 30 is released, as a result of the brushes engaging the terminals of a connecting circuit that is not in use, it opens, in its right-hand front contact, the previously traced circuit including the up-drive magnet 33%, and thus causes the brushes of the cord finder switch to come to rest. The relay 30, in releasing, -also closes a circuit that extends from battery through the motormagnet and contact202 (9) of the sequence switch 200, baek c0ntact and righthand armature of relay 30, sequence switch contact .218 (8 to 9), conductor 67, M segment of the line finder commutator and corresponding brush to ground. The closure of this. circuit moves the sequence switch 200 out of position 9.

It has previously been explained how,

when the sequence switch of an-appropriated finder circuit reaches position 65}, itoperatcs a particular strip magnet on the cord finder frame that corresponds with. a waiting operators position, and at the same time operates the relay associated with the apparatus at that operators position. When the relay 95 at the operators osition attracts its ar1natures,'it closes a circuit which extends from battery through the motor mag- "net and contact 303 (1) of the operators se 1 quenceswitch 300, conductor 121, right-hand front contact and armature of relay 95, conductor 123, right-hand front contact and armature of relay 125 to ground. The closure of this circuit causes the operators sequence. switch 300 to moye outof position 1.

It may be well at this 'point to explain that p acircuit is closed that extends from battery through the motor magnet and contact 303 (1) of theoperators sequence switch and the left-hand front contact and armature of relay 125 to ground. Therefore, while the operator is at her station it is impossible for the operators sequence switch to rest in 190- sition 4. iVhen the operator leaves her station the deenergization of relay 125, as a result of the withdrawal of the operators telephone plug from the jack 126, closes a circuit that entends from battery through the- '17, and can rest only in position 4.

lVhen the operators sequence switch moves out of position 1 as a result of the selection of theoperators position and the actuation of relay 95, a circuit is closed that extends fromhattery through the winding of relay 145, upper back contactand armature of relay 153, sequence switch contacts 304 (2 to 16), outer backcontact and armature of relay 142, sequence switch contact '305 (1 to 16) and right-hand front contact and armature of relay 125 to ground. As a result of the flow of current in this circuit, the relay 145 attracts its armature and closes a circuit that extends from the device 143 for producing a characteristic tone, through a condenser 144, right-hand front contact and armature of relay 145 and winding 146 of the induction coil of the operators telephone set 147 to ground. The "result, therefore, is that an instant after the ope'rators sequence switch ismoved out .of position 1, as a result of the selection of that particular operators position by the seeking finder circuit, a call tone is applied to the operators telephone receiver which warns the operator that her position has been selected and that a call is coming. I

' The manner in which the, selection of an idle cordcircuit is accomplished by the seeking cord finder switch, and the manner in which such selection moves the finder se quence switch 200 out of position 9, whence it moves into position 14, have already been described. As long as the finder sequence switch 200 is in position 9, the conductor eX- tendingfrom the third 'or sleeve brush 42 of the line finder is connected with battery by way of sequence switch cam 212 and resistance coil 64, to holdthe cut-off relay 11 of the calling line energized; and the conductor 98 extending from the third or sleeve brush 113 of the cord finder switch is open at sequence switch cam' 217. )Vhenthe finder sequence switch reaches position 9%, it closes a circuit, which will be traced hereinafter, for the energization of relays 151, 154 and 157 of the connecting cord circuit. This last-mentioned circuit is maintained until the finder sequence switch 200 moves out of position 11, when it is interrupted in contacts of Cam 217. An instant later, in position 12 of the sequence switch, the'cam 217 'acts to extend the sleeve conductor. 98

through the right-hand winding of the relay 30 to contacts of the cam 212, which are closed a moment later in'position 12% of the sequence switch. In moving from position 12jto position 12%, the sequence switch 200, by. the action of cam 212, substitutes the path last referred to by way'of the right hand winding of the relay 30 for the path by way of the resistance coil 64, over which, up to this moment, the cut-off relay 11 of the calling line had been maintained energized.

From the moment the'finder sequence switch 200 reaches position 12 therefore, the cutoff relayfll nd the relay 30 of the finder circuitare included serially 'in a circuit that maintains their energization, and as long as the continuity of the circuit is maintained, the findericircuit is held in its talking condition.

As was stated in the foregoing, when the finder sequence switch 200 reaches position 9%, after the ibrushes of the cord finder switch have come to rest upon the terminalsof the-idle connecting cord circuit, a circuit is completed for the energizationfof relays 151, 154 and 157 of the connecting cord circuit. This circuit may be traced from battery through the windings of relays 151,154 and 157 in parallel (the branch through the winding of relay 157 also passing through contacts 509 (1) of the calling cord sequence switch 500) to sequence switch contacts 505 (1), and thence by way of listening-key sequence switch contacts 405 (1), left-hand back contact and armature of relay 152, conductor 87, contact 117 and brush 113 of the cord finder switch, conductor 98, sequence switch contacts 217 (9% to 14) and (9% to and resistance coil 36 to ground. Therefore, an instant after the idle connecting cord circuit has been appropriated and the finder sequence switch 200 moved out of position 9, the three relays 1'51, 154 and 157 of the connecting cord circuit are operated. Relay 154, in operating, closes, in its armature and front contact, a locking circuit for all three of the relays, which circuit-extends byway of calling cord sequence switch contacts 506 (1), and listening key sequence switch contacts 406 (1 to 6) to ground. The

three relays are thus held lockedup while the listening-key sequence switch 400 is moving from its normal posit-ion 1 to its listen-' ing-in position 7. This movement of the listeningkey sequence switch is effected by a circuit that eXtends from battery through the motor magnet. and contacts 403 of I the sequence switch 400, sequence switch concompleted a circuit that extends from bat' tery through the winding of relay 152 and outer front contact and armature of relay 151 to ground. is a result, relay 152 is energized and in its left-hand armature and front contact has disconnected the conductor 87 from the branch extending by way of sequence switch contacts 405 (1), and has connected it instead with battery by way of the left-hand switch spring and resting contact of relay 150 and the winding of relay 155. i The relay 155 thereupon operates to close the circuit of the talking conductor 86 hich is normally maintained open for a reason which will hereinafter be explained.

After relay 152 is initially energized by the operation of the relay 151, it is maintained operated by a path to ground that is closed by way of cam 407, as soon asthe listening-key sequence switch reaches position 2 and thereafter until it moves out of its listening-in position 7. f

\Vhen the relays 151 and 157 operate at the moment the idle connecting cord circuit is seized, they effect certain changes in the condition of the operators telephone circuit, which will now be described. When relay 151 operates, it closes a circuit that extends from battery through the winding of relay 153 of the operators circuit (see Fig. 4), conductor 129, calling cord sequence switch contact 502 (1), and inner front contact. and armature of relay 151 to ground.

Relay 153 operates, and in its upper armatures and back contact opens the circuit over which, up to this moment, the relay 145 had been maintained energized. Relay 145 thereupon releases its armature, and 1 opens the circuit, previously traced, over which the calling tone from the device 143 had there tofore been supplied to the operators telephone apparatus. The ceasing of this .tone inher telephone notifies the operator that the incoming call has been extended to one of her. connecting cord circuits. the connecting cord circuits at her position has been appropriated is indicated to'the operator by the flashing of the lamp 161 associated with that cord. The circuit by.

rupter 162 to ground. The lamp is thus caused to flash as soon as the listening-key sequence switch moves into position 1%.

Relay 157, in operating, at the instant the cord circuit is seized, connects the operators telephone set with the telephone of the calling subscriber. This circuit may be tracedfrom the operators'telephone apparatus by way of conductors 135 and 136, conductors Which of,

nacaeer tacts510 (1) and 511' (1), conductors 16.9

and 170, back contacts and armatures of re.- lay 158, conductors 851 and 86, terminals 115 and 116 and corresponding brushes 111 and 112 of the cord finder switch, cord finder conductors 96 and 97, finder sequence switch contacts 214 (9% to 14) and 213' (9%} to'14),

line finder conductors 48 and 49, line finder brushes 40 and 41 and corresponding line termlnals 44 and 45, and line conductors 38 and 39 to the telephone apparatus at the calling station.

The circuit between the operators telephone and the telephone at the calling subscribers station is completed the instant the connecting cord is seized. At the same instant, as previously described, the relay 154 operates to close the circuit for moving the listening-key sequence switch 400 out of its 1 position.

where it comes to rest. Just before the sequence switch reaches position 7, it opens the circuit, by way of sequence 'switchcontact 406 (1 to 6), and left-hand armature and frontcontact of relay 154-, over which the relay 157, and its associated relays 151 and 154, had been held energized; and at the same moment, it completes an alternative path for the connection of the =operators telephone with the calling subscribers telephone. This alternative path extends from the operator-s telephone apparatus 147 by way of conductors 135 and 136, resting con tacts of the ring-back key 160, and the coinreturn key 159, listening-key sequence switch contacts 408 (6 to 8) and 409 (6 to 8), and resting contacts and armatures of relay 158 to the conductors 85 and 86, Whence the circuit as previously traced -to the calling subscribers line and telephone apparatus.

The connection between conductor 136 and conductor 86 also includes contacts of the relay 155 which are closed at this time, the

relay 155 being energized over a path previously' traced.

When the listening-key sequence switch reaches position 7, therefore, the bypath .to

the operators telephone by Way of the contacts of relay 157 is opened, and the main path by way of the sequence switch contacts 40.8 (6 to 8) and 409 (6 to 8-) is closed. The

object of providing the bypath closed instantly by the relay 157 upon the seizure of the connecting cord circuit, is to save the time, required for the sequence switch 400 to close the direct path by way of its cams 408 and 409, and thus place the operator in communication with the calling subscriber a little sooner than would be the case if the Sequence switch 400 con-1, tmues to move until it reaches position 7,

establishment of the circuit waited upon the ing subscriber, although slight, is of practical importance.

At the stage of the operation that has now been reached, the operators telephone sequence switch 300 is'resting'in position 17, 'and' the listening-key sequence switch 400 is resting in position 7. In position 7 of the lis tening-key sequence switch, each of the talklistening-key sequence switch, the supervi-' station. This relay controls the illumination ing conductors 85 and 86 of the circuit is severed, and is connected in a'loop which may be traced through the operators circuit by way of listening-key sequence switch contacts 408 (6 to 8) and 409 (6 to 8), conductors 135 and 136, including the resting contacts of the coin-return key 159 and the ring-back key 160, conductors 165 and 166, and listening-key sequence switch contacts 410 (6 to 8) and 411 (6 to'8). From this point, the circuit of the talking conductors extends to opposite poles of the battery by way of two windings of the cord circuit repeating co-il 169, the other two windings of the repeating coil being included in conductors that extend from the poles of the battery to the tip and ring contacts respectively, of the calling plug 17 0, when certain apparatus hereinafter to be described is operated.

The extension of the talking conductor 86 to the free pole of the battery by way of its corresponding repeating coil winding,, includes the 'winding of the answering supervisory relay 171, so that in position 7 of the sory relay 171 is included in the circuit that extends to the calling subscribers line and of the answering supervisory lamp 172 by controlling a shunt about the lamp including the resistance 173. When the listening-key sequence switch moves out of position 1, upon the seizure of the cord circuit, it closes a circuit that extendsfrom battery through resistance 174, answering supervisory lamp 17 2 and sequence switch contacts 407 (1% to 181-) to ground. The current flowing in this circuit tends to light the lamp: 17 2; but the illumination of the lamp is prevented by the act that the answering supervisory relay 171 is energized over the circuit which at this time is'closed at the calling subscribers station. The answering supervisory. lamp 172 is thus shunted and prevented from lighting.

When the operatoris informed, by the cessation of a call tone in her telephone receiver and by the lighting of thecall lamp 161 that she is connected with the calling line, she speaks to the calling subscriber and ascertains the number of the line with which he desires connection. She then lifts the call-v ing plug 170 of the connecting cord identi fied by the flashing call lamp 161, and tests the line with which connection is desired by touching the tip of the plug to the sleeve of the corresponding spring-jack 14. As-

sume that the called line is similar in its line is busy, by reason of the brushes of a finder switch being in engagement with these terminals, batteryis applied to the finder switch terminal 46 of that line and by way of conductor 53, and its multiple connections, to the sleeve of the corresponding springack 14. When the sequence switch of the finder circuit is standing in position.

4% to 12:}, battery is applied by way of the resistance coil 64 and'sequence switch cam 212. When the sequence switch 200 is standing in positions 12% to 14, battery is applied either by way of the windings of the relays 151, 154 and 157 of the connecting cord circuit, if the listening-key sequence switch 400 has not yet moved out of position 1, or by way of the winding of relay 1-55 of the connecting cord circuit if the holding relay 152 of the connecting cord circuit has'operated. In case the line with'which connection is desired is busy as a. called line, battery is applied to the sleeveof the tested springja-ck by way of the windings of relays 1l9 and 175, the sleeve of the calling plug 170 of the cord circuit that is already connected .with the line, andithe multiple connectlon between the sleeve of the spring-jack that is connected with and the sleeve of,the springjack that is being tested.

When the tip of the calling plug 170 is touched to the sleeve of the spring-jack of such a line, current flows by way of the tip of the plug, right-hand armature and back contact of relay 17 5, conductor 133 and winding of theoperators test relay 184 to ground. This relay, in attracting its armature, closes a circuit that extends from battery through a retardation coil 185, front contact and armature of relay 184 and winding 146 of the induction coil of the operators telephone set 147 to ground. The closure of this circuit causes a click in the operators telephone receiver, which notifies her that the line is busy. The operator may then tell the calling subscriber that the called line is busy, and release the connection by pressing her master listening-out key 186. The manner in which this effects the release will be described hereinafter.

If the called line is not in use, there will be no battery connection with the sleeve of the tested jack, and no click will be produced in the operators telephone receiver. Conseof position 2.

- tending to the operators busy test relay 164,

and connects it instead with the tip conductor of the talking circuit. Relay 175 also closes a circuit that extends from battery through the motor magnet and contacts 503 (1) of the calling cord sequence switch, contacts 413 (7) of the listeningkey sequence switch,'left-hand front contact and armature of relay 175 and normally closed contacts of the charge key 176 to ground, The closure of this circuit energizes the motor magnet and moves the calling cord sequence switch .out of position 1. l/Vhen the calling cord sequence switch reaches position 2,it comes to rest and completes a circuit that extends from battery through the motor magnet and contact 403 (7) of the listening-key sequence switch, contact 515 (2) of the calling cord sequence switch, and right-hand back contact and armature of relay 154 to ground. When the listening-key sequence switch 400 moves out of position 7 as a re'sultof the closure of this circuit, it completes a circuit that extends from battery through the motor magnet and contact 504 (2) of the calling cord sequence switch, contact 413 (8 to 15) of the listeningkey sequence switch, lefthand front contactand armature of relay 175, and resting contact of the charge key 176 to ground. The closure of this circuit moves the calling cord sequenceswitch out A the listening-key sequence switch 400 moves out of position 8, it operates its cams 408, 409, 410 and 411 to disconnect from the connecting cord-circuit the loop that extends to the operators telephone circuit by way oi the conductors 135, 136 and 165, 166, and connects the talking conductors 85 and 86 of the connecting cord circuit directly through to the left-hand windings of the repeating coil 169. Furthermore, it inter rupts the branch of the energizing circuit of the cord circuit holding relay 152 that had been completed to ground by way of listening-key sequence switch contacts 407 (2 to -7), andleaves the continued energizationof the holding relay dependent upon a path to ground that extends by way of'the right-hand front contact and armature of magnet of that switch.

is moved out of position 2 by the movement of the listening-key sequence switch out of position 7 as described above, it moves through its various stages until it reaches The closure of this circuit energizes relay 180 and causes it to open in its right-hand armature and back contact a circuit by way of contact. 504 (4 to 13) of the calling cord sequence switch, which theretofore had maintained the energization of the motor A's the cam 501 of the calling cord sequence switch is cut so as to keep the energizing circuit of the mo switch ringing current is applied to the connecting cord circuit to ring the bell at the called subscribers station. This is eflected through the medium of a circuit which has two branches alternately closed in the rotation of the commutator 182, one of. the branches including the batteryand the other including a source of ringing current 181. From the commutator 182, the circuit extends by way of sequence switch contact 517 (13), winding of relay 177, left-handarmature and front contact of relay 180, sequence switch contact 519 (13), ring contact of the calling plug 170, ring spring of the spring-jack 14, and thence over the corresponding side of the line to the called sub scribers station, whereit is connected to ground by way of the substation condenser and bell. At the same time, the other side of the called subscribers line is connected directly to ground'by Way of sequence switch contacts 518 (13). r

The closure ofv this circuit causes the bell at the substation to ring intermittently, and also, by the diversion of a small partpf the alternating current byway of the condenser '85 tor magnet closed in position 12 of-the 'se- 183 and the-upper right-hand winding of limbs of the line causesanincrease in the Y current flow over the circuit just traced and brings about the energizationi of the relay 177. This relay is preferably so constructed and adjusted, in any well-known way, asto make it insensitive tot-he alternating current flow that passes through it during the ringing of the bell, but responsive to'the current liow that takes place when the telephone receiver is taken from its hook.

. Then the relay 177 operates, it opens the.

short circuit that normally exists about the winding of the relay 178, which relay is included in the path previously traced through the relay 180 and cams 507'and 518 of the calling cord sequence switch. The removal of the short circuit causes relay 178 to at: tract its armatures. The opening of the left-handarmature and back contact of the relay 178 prevents there'establishment of the short circuit about the winding of relay 178 when the armature of relay 177 falls back after a momentary attraction. The engagement of the right-hand armature of relay 178 with its front contact closes a path from battery including a resistance coil 179, which is in parallel with the path from battery including the relay 180. The resistances of the coil 179 and the winding of the relay 180 are so proportioned that the relay180 is shunted and releases its annature's. The left-hand armature of relay 180, in falling back, opens the previously traced path over which ringing current was applied to. the connecting cord circuit. armature of relay 180, in releasing and closing its back contact, closes a circuit that extends from battery through the motor ma,.,-'

net and contact 504 (4 to 13) of the calling cord sequence switch. This causes the sequence switch to move out ofpositi'on 13.

The calling cord sequence switch..500 is indicated as being adapted, after leaving position 2, to come to rest in positions 4-, 5, 7, 8, 10 and 11, as well as in position 13 as described above. These positions of the se quence switch may be employed for the purpose of effecting the application to the connecting circuit of ringing currents of different characteristicsfor the purpose of selectively ringing the bells of party lines. The movement of the sequence switch in and through these positions may be under the control of a branch of the energizing circuit of the relay 180 which extends to a cam 520 of the calling cord sequence switch, and may be further controlled by a branch of the energizing circuit of the motor magnet of sequence switch 500 which is adapted to be closed in positions 4, 7 and 10 of the sequence switch cam 504. The application of party line ringing current to the connecting cord circuit may be effected through the medium of contacts of the calling cord sequence switch cams 518 and 519, closed in positions 5, 8 and 11. The particular method in which this is accomplished is disclosed and claimed in my Patent No. 1,251,604 of January .1, 1918; but inasmuch as this is a feature with which the present invention is not concerned, it is not herein shown.

When the calling cord sequence switch The right-hand thecal-l first came in, has been burning steadleaves position 13, it moves to position 16. In this position, a circuitis completed that extends from battery through the lower right-hand winding ofthe repeating coil 169, calling supervisory relay 187, sequence switch contact 519 (16 to 17), engaging ring contact surfaces of the calling plug 170 and called line spring-jack l4, thence to the called subscribers station, over one limb of the line, through the substation apparatus and backover the other limbo f the line to the engaging tip contact surfaces of the spring-jack l l'and calling plug'170, righthand armature and front contact of relay 1.75, sequence switch contact 518 (14: to 17)v and upper right-hand winding of the repeating coil 169 to ground. [The current flowing in this circuit energizes the calling supervisory relay 187 and causes it to close a circuit .that extends from battery through the motor magnet and contact 503 (16) of the calling cord sequence switch, and armature and front contact or relay 187 to ground. This moves the sequence switch out of position 16, whereupon it moves to position 1.7, which is .the talking position. a

Up until this moment, the lamp 161, which, as described, was caused to flash when ily as a ringing lamp, the circuit for its illumination being to ground by way of contact 516 V (3 to 16) of the calling cord sequence switch. When the sequence switch moves out of position 16, this circuit is interrupted and lamp 161 is extinguished. At the same time, a circuit is closed from battery through resistance co-il 188, and thence by way of two branches, one of which extends through the calling supervisory lamp 189, left-hand front contact and armature of relay 119 and sequence switch contact 521 (17) to ground and the other one of which ex- 'tends' by way of resistance coil 190, sequence the connecting cord sequence switch 500 is inposition 17 and the listening-key sequence switch is in position 15,-the listening-out position. In this condition of the circuit,

the calling subscriber has control over the answering supervisory lamp 172 through the medium of the answering. supervisory relay 171, and the called subscriber has con trol over the calling supervisory lamp 189 through the mediumof the calling supervisory relay! 187. As long as both sub-.130

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