US1318941A - Planoobaph co - Google Patents

Description

S. B. WILLIAMS 1n.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 27. ms.

Patented 0ct.14,1919.

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. :1. v THE COLUMBIA PLANMRAFH CO WASHINGTON, Il-C.

S. B. WILLIAMS, In.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV 27. 1916- Patented Oct. 14,1919.

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s. B. WILLIAMS, In. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV- 27. 19").

Patented Oct. 14, 1919;

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S. B. WILLIAMS, In.

.TELEPHONE EXCHANGE SYSTEM.

APPLlGATlON FILED NOV. 27. l9l 6.

Patented 00t;14,1919.

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S. B. WILLIAMS, 11'. TELEPHQNE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 27. l9l6- Patented 001. 14,1919.

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UNITED STATES PATENT OFFICE.

SAMUEL B. WILIiIAMS,-J1 0F BROOKLYNJNEW YORK, ASSIGNOR TOWESTERN' ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N; Y., A CQRPOR ATION OF NEW YORK.

. TELEPHONE-EXCHANGE; SYSTEM.

. Patented 0ot.14, 19 19.

Application'filed November 27,1916. seri l ma 133,701.

To all whom it may concern:

Be it known that I, SAMUEL B. WILLIAMS,

J12, 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 Telephone- Exchange Systems, of which the follow ng is a full, clear, concise, and exact descrlption.

This invention relates to emergency apparatus for telephone exchange systems.

The object of the invention is to safeguard the operation of such systems by providing means automatically responsive to any failure of the more important parts of the organization for indicating the nature and location of the trouble and also for operatlng devices to restore the operativeness of the system. r

In the present instance the inventionus illustrated in connection with acall distributing system of the type in which apparatus is automatically operated to dis tribute the calls from a large number of subscribers lines to the connecting c rcuits of a large number of operators positlons.

In thisspecific embodiment'the subscribers" lines may be divided into groups of 500, and the calls that-originate in eachgroup of 500 lines may be-extended to the connecting cord circuits of a number of operators positions by means of a plurality of finder circuits, each of the finder'circuits having a' switch at one end for connecting with any one of the 500 lines and a switch at the other end for connecting withanycord circuit of any of the plurality of operators positions. The controlling circuits over which any calling line of the group appropriates to its own use anyone of the'finder circuits, and over which the appropriated finder circuit gains access to any of the operators positions at the time available, are common to all of the line circuits, finder circuits and operators positions which are thus in operative relation with each other. It "therefore follows that anything which causes a failure of these common controlling circuits and-their associated apparatus may tie up the calls from .500 lines. It is toward the safeguarding of the operation of such a system with respect to the failure of the apparatusand circuits common to a'large number of lines and interconnecting links that the present invention Broadly stated, this"-result}is accomplished by providing devices that respond. to any alteration of the electrical condition of the common controlling circuits,'or to any change in the operative condition of the common controlling apparatus that continues for an interval longer than the interval that such alterat ons or changespersist" in the normal operation of the systemyor that isunaccom panied by such changes as occur in the normal sequence of operation. In the normal operation of the system the various stages of the operation follow each other'at substantially definite time inter'va'lsi Byasso- 'ciating with the controlling circuit s and apparatus emergency devices each of which is set to respond'within a definite'interval after a certainstage of. the operation is reached, this interval being somewhat in excess of the normal intervalrequired for reaching the succeedin'gstage o'ffthe opera tion, and causin the succeeding stage 30f operationtobloc the operation of the de vice, the devlce' operates only in case abnormal conditions arlse. 7 p

A speclfic embodiment of the invention in a' preferred form .is illustrated in the accompanying drawingsfin which Figures 1, 2, 3, 4 and 5, when, arranged' side by side injthe inanner'indicated by the/correspond;

ing lines that extend to the margins of the drawings, show diagrammatically the application of the invention to a telephone system of the call distributingitype.

As illustrated" in the drawing,lthe system is represented as comprising telephonellines extending from stations, as A and A, to stationary terminals upona-il'ine finder" frame,

thesestationary *term'inalsbeing' adapted to be connected with by a plurality of line finder switches or elevators, as LF and LF'." Each line has associated with it a line relay l2 and a cutoff relay 11, and e'achJof the groups of lines-V into a which the"wli ole munher of lines served by theffind'er framear'e divided, has associated withit certain group wapparatus designated"IlG and LG'a The group apparatus is connected through the medium of conductors 57 and "58 with: the starting apparatus, (see '2), which s common to all of the; groups and to the 165 whole number of lines terminating upon the. line finder frame. Thecommon starting ap;

paratus is connected-through the ,medium of V conductors" 25,26,127, 28 and 29.with the apparatus of are group er fiaaa circuits F, F and F associated with the line finder switches or elevators, as LF and LF, which serve the whole group of lines. The finder circuits F F and F terminate in cord selector switches or elevators, as CS and CS, and through the medium of these, operating under the control of the operators selecting apparatus SF, the finder circuits are adapt ed to have their connections extended to any one of the connecting cord circuits which extend in conductors 85, '86, 8 7 and 88 to the various operators positions. The operators selecting apparatus SF common to the entire group of finder circuits is brought into cooperative relation with the apparatus of the finder circuits throu h the medium of the conductors 70, 71, 72, T3, 74, 75 and 76. Each one of the connecting cord circuits oflthe group at each of the operators positions may be equipped generally as indicated in Fig. 5, and may terminate in a plug 170 which in completing the connection, may be inserted in the multiple spring-jack 14. of a line extending to called subscribers station A The connecting cords of the. various operators positions have multiple connection with different cord selector frames like that which includes the cord selectors CS and CS, such multiple connectionsfor a second cord selector frame together with the common operators selecting apparatus for that frame being indicated at SF. I

The apparatus and circuits for safeguarding and indicating failure in the common circuits and apparatus that cofiperatively relate the lines with the finder Y shown in F ig; 2 of the drawing. The apparatus comprising the lamp 250, the relays 251, 252, 253 and 255 and the key 254 (Fig. 2) has to do with the safeguarding of the common conductors which link the line group apparatus with the starting apparatus. The apparatus comprising the lamp 260, the relays 26 1, 262, 255 and the key 263 has to do with safeguarding thepart of the common, starting control circuit which passes through the resting contacts of the relays 22,23 and 'to ground. The apparatus comprising the lamp 240, the relays 241, 242, 24:3, 244 and 245 and the key 246 has todo with the safeguarding of the system with respect to -.the operation of the common starting relay22 and the'coopen ating parts of the finder circuits. The appa ratus comprising the lamps 270 and 271 and the relays 272, 273 and 281 (see Fig. at) has to do with the safeguarding of the common circuitover which the finder circuits are brought into operative relation with the common operators position selectmg apparatus, The apparatus comprising the lamps 280' and 271 and the relays 281, 282, 283, 287 and 285 has to do with the safeguard'ngof the releaseof the common circuits are operators selecting apparatus. The lamps 290 and 291 and the relays 292, 293 and 29a have to do with safeguarding the common circuit over which each operators position has operative relation with the corresponding position-selecting apparatus of the different selector frames.

The line finder switches LF, LF, and the cord selector switches CS, US, may be sub stantiall y like the switch illustrated and described in Patent 1,177,044- to James L. Mc- Quarrie, issued March 28, 1916. The line finder and cord selector switches are alike in all substantial respects. Each comprises a longitudinally movable shaft l-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 by means of an idler wheel operated by the updrive magnet 2; and to move the shaft down, the extension is brought into engagement with the power member 4: by means of an idler wheel operated by the down-drive magnet 62. Normally the brushes of each of the sets 2 are apart so as'to clear the associatedterminals by means of a separating cam 5 lo-' cated 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 number of trip magnets, as 16' and 17. Each of these when energized rotates an associated trip rod 6 that extends transversely to the shafts 1 and carries as many trip yokes 7 as there are finder switches in the group. The trip rod in rotating brings all of its trip yokes 7 into position to operate the brush-controlling cams 5 of the corresponding sets of brushes on. all of the sets, so that whichever of the finder switches iscaused to move up has that set of brushes tripped that corre sponds with the particular trip magnet 16, 17, that is at the time energized. When the finder switch that has been in use is returned to its normal position, any of the associated controlling cams 5 that has 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 comprises a number of stationary commutator segments and a set of movable brushes car ried at the top of the switch shaft 1 and cooperating with the stationary segi'imnts. This commutator serves to make and break a number of the controlling circuits in the various stages of the upwardmovement of the switch shaft. V

For controlling the circuits the organ ization, there areemployed' a number ofse- 1- quence switches which are shown at different points and are designated 100, 200 and-300 V respectively. These sequence switches may be of the-type disclosed in Patent 1,127,808 issued February 9,1916 to Reynolds and Baldwin. Each consists of an electromagnetically controlled motor or driving mechanism and a number of associated (switch cams. The witch 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-222, inclusive; andthose associated with each of the sequence switches 300 are designated 301 to 304, inclusive. To each of the contacts associated with the various sequence switch camsare appliedcertain numerals. These numerals in the case of the cams 101, 201 and'301 :indicatethe only positions of the associated sequence switch in which these particular contacts are open; the numerals applied to all'of the other-con-. tacts of each sequence switch indicate the only positions of the particular sequence switch in which the associated contacts-are closed. 1 w

The sequence switches 100 merely act as timing switches and have only one resting position. The resting positions ottheother sequence switches, andthe stages of operation with which these positions .areassociatedyare asfollows.

Sequence switch .200.

1. Normal.

2.. Awaiting starting circuit.

3. Awaiting starting circuit-release.

+1. Huntingcalling line.

6. Awaiting preceding finder circuit.

7. Awaiting operators selecting circuit. 8. Releasing operators selecting circuit.

a 9. Hunting cord circuit. I

14:. Talking. A

15. Line finder-at tell-'tal 16. Line finder return.

17. lord selector return.

Sequence switch 300.,

1. Awaiting a call. '4. Position vacant. 17. Position busy. 7

The operation cfithe system as illustrated in the accompanying drawings is as follows:

' When a subscriber calls the taking of the telephone receiver from its hook 1 closes a circuit in the usualway that causes the energization ofthc associated lino relay at the central oflice. The line relay in opcrating closes a circuit that extends from battery through the winding of relay 19 of the group in which the calling line. located, contacts 103 (1S+1-to 11..) or seouenc switch 1000f thatgroup. group conductor 18-, and armature and front contact .of line relay 12 to ground. Relay 19 in operating closes a circuit that extends from battery through the right-hand winding of relay 24:, front contact and armature of relay 19, conductor 57, inner back contact and'armature of relay 22,1eft-hand back contact and armature of relay 23, back contact and armatureof relay to ground. Relay 24 in operating closes a-loclgmg circuit for itself in its left-hand front contact and. armature, and in doing so causes the operation of the associated tripping 'magnetylfi, the energizing path for thectri'pping magnet and for the left-hand or looking winding of relay 2 1 being in parallel from battery by way of the left-hand front contact and armature of relay 24, conductor 58, winding of relay 22, left-hand back contact andarmature of contact 102 (18?; 'to 1%), and rightghand front contact andgarmature of" relay 24 to ground. The closure of this. circuit moves 7 sequence switch out. of position 1, whereit completes its cycle andagain comes to rest in position 1. While the sequence switch 100 is rotating it maintains open in sequence switch contact 108 (-18% to 11;) the connection of the relay 19 with the group conductor 18, so that'duringthis period the relay '19 is not'under the'control of the-line relays'12 of-the corresponding group. During this interval the callingfline is found and-the line relay 12 de'energized torelnove the ground from the conductor 18, as here; inafter-to .be described. [1 j Included inithecircuityby'way of con ductor f-58 closed upon theinitiation'of a call, as described above. is the winding of.

the starting relay 22. This relay in operating closes the circuit of the starting conductor-29, andin doing so brings about the movement ofa-v line. finder switch otjone or another of the finder circuits RF or F For reasons that Jwill hereinafterbeen: plainejd only one ot'the,.'sequence switches ass sociated with these findercircuits is in;po. ;-:i-"

tion 2. Assuming-that this is the sequence switch ofifinder circu t F, a circuit is completed that extends. from batterv through the'lett-han'd winding of relay 30. sequence switch contacts 206 (-2) ,conductor 29, inner front. contact and armature of relay 22; left- "from battery through resistance coilf56', so

quence switch contacts :21? (21to .9.) right hand wind ng oji relay 80, sequeuce switch 7 past the corresponding trip yokes.

contacts 216 (2 to 1) and (2 to 9), lefthand front contact and armature of relay 30, and armature and back contact of relay 37 to ground. Relay 30 also closes a circuit that extends from battery through the motor magnet and cam 202 (2) of sequence switch 200, right-hand front contact and armature of relay 30, sequence switch contacts 208 (18 to 14) and to 7) to ground. The closure of this circuit causes sequence switch 200 to move out of position 2 and come 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 3201 the corresponding line finder switch LF, sequence switch contact 207 (3 to 4), front contact and righthand armature of relay 30, and sequence switch contacts 208 (18 to 1 1) and (2 to 7) to ground. The energization of the updrive magnet 32 starts the upward move ment of the corresponding elevator rod with its associated sets of brushes. At the outset of the upward movement of the elevator rod all of the brush trip levers are mo%ed he only trip magnet that is energized in this case is the magnet 16 which corresponds with the group in which the calling line is assumed to be 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, 11, 4:2 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 normal condition. The first step in this restoring operation is effected by the closure of a circuit which is completed 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 33 and 23 (see Fig. 2), conductor 26, sequence switch contact 209 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 left-hand back contact of that relay, the previously described circuit that has up to this time maintained the energization of the trip magnet 16, the group relay 2 1 and the common starting relay 22. Relay 23 in its right-hand front contact closes a locking circuit 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 serles.

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 ing applies a ground to conductor 28 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 condue tor 27 to move the sequence switch of the appropriated finder circuit out of position 3.

Assuming that the sequence switch of finder circuit F is in position 1, and that the sequence switch of finder circuit F is in some position between sand 17, that finder circuit being assumed to be in use, the operation of the relay 33 completes a circuit from battery through the motor magnet. and cont acts 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 F contacts 212 (3 to 17) and (3 to 33;) of the sequence switch 200 of finder circuit 'F that has just been appropriated, conductor 28, and left-hand front contact and armature of relay 33 to ground. This causes the sequence switch of finder circuit F to move into position 2. Atthe same time the sequence switch of finder circuit F is moved out of position 3 by the closure of a circuit that extends from battery through the motor magnet and contacts 203 (3) of the sequence switch of that circuit, conductor 27, and right-handfront 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 con ductor 25 which up to this moment has maintained relays 23 and 33 energized, and these relays thereupon release their armatures. Relay 23 in releasing reconnects to ground the circuit which extends in branches 57 and 58 through the various sets of line group relays, thus again giving the line 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 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 successively with the sets of terminals corresponding with the different lines of the group. At the instant of engagement of the brush 42 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), con ductor 50, brush 42, line terminal 46, conductor 53, and winding of cutofi relay 11 to ground. In case a line over which the brushes are passing is busy, either as a callingor as a called line, a branch pathfrom battery is closed to conductor 53 which serves to shunt the relay 52 and prevent its operation as the finder brushes pass over the terminals of the corresponding line. In the case of the lines that are not busy, the relay 52 isoperated as the brushes engage the'terminals of such lines. In attractinggits armatures the relay 52 closes'a circuit that extends from battery through the lower winding of the relay 37, front contact and inner armature of relay 52, sequence switch contact 213 (2 to 4), conductor 49, brush 41, line terminal 45, 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), upperarmature and front contact of the relay 52, and upper windingof the relay '37 to ground. The circuit traced above is not completed until the finder switch brushes engage the terminals of the calling line, for the reason that the calling line is the only line that has its telephone receiver off the hook and at the same time is not made busy by being connected with either by some other line finder or by a connecting cord 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 theleft-hand armature and front contact of the'relay 30, sequence switch contacts 216, right-hand winding of relay 30, sequence switch contacts 217 and resistance 56 to battery, which circuit has been holding relay 30 locked up from the moment that the relay was first energized upon the receipt of the call.

Relay 30in releasing its armaturesbreaks 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 magnet 32 of the line finder. Therefore the operation of the relay 37 upon the finding of 30, sequence switch'contacts 208' (18 to 14) and (2 to 7), to ground. The closure of this circuit moves the sequence switch out of p0= sition 4. hen the sequence switch reaches position'l, it closes a path for the fioW of current through the cutoff relay 11 of the calling line by way of resistance coil 64, sequence switch contact 212 (4}to 12%), conductor 5 0, brush 42, line terminal 46 and.

conductor 53. The fiow of current. in this path operates the cutoff relay 11 to disconnect the line relay 12 from the circuit, and that relay in releasing its armature disconnects ground'trom thecommon conductor 18. The disconnection of ground from conductor 18 occurs before the timing sequence switch lOO has completed its cycle of rotation and reconnected conductor 18 with relay 19.

In the foregoing the normal operation of the system has been described up to the time when the line finder switch of an unengaged finder circuit. completes connection'with a calling line. The operation of the part of the system that comes into action when an emergency or abnormal condition arises in the circuits and apparatus controlling the above-described stages of operation will now be explained.

In order thatthe'calling lines may have control over the apparatus that energizes an idle finder circuit when any line calls, it is necessary that there shall be. a normally continuous series circuitby way of the conductors 57 and 58 through the resting. contacts of the group relays 19 and 24 of the various groups. As long as this condition exists circuits are completed which hold the relays 251 and 252 energized. The circuit for the relay 251' extends frombattery through the winding of that relay, thence 'by way of the conductor58 and the left-hand back contact and armature of each of the group relays 24 in series, the winding of the starting re lay 22, left-hand back contact and armature of; relay 23, and right-hand back contact and armature of relay 65 to ground. ,Thenormal energizing circuit .forthe relay 252extends from battery through the 'windingfof that relay and thence-by way of conductor 57 and the back contact and armature 0t each of the group relays 19, inner back contact and armature of starting relay '22, lefthand back contact and armature of relay 23, and right-hand back contact and armature i so of relay to ground. The winding of each of the relays 251 and 252 is of high resistance,the high resistance of the relay 251 preventing the current normally permitted to flow through it from energizing the starting relay 22; but in each case the normal current flow is sufficient to keep the relays 251 and 252 energized and their arinatures attracted. lVhen the energizing circuit of either of these relays is interrupted, the relay is denergized and closes a circuit, subject to certain conditions that will hereinafter be set. forth, which extends from battery through the winding of relay 253, the switch contacts of whichever of the relays 251 and 252 has released its armature, and the right-hand back contact and armature of relay 255 to ground. When this circuit is closed the relay 253 in its upper front contact and armature closes a locking circuit for, itself by way of the release key 254:; and also closesthe circuit that extends from battery through the common relay 134, the lamp 250, righthand front contact and armature of relay 253, left-hand back contact and armature of relay 262 to ground. The closure of this circuit lights the lamp 250 and also energizes the relay 13a which may close a circuit for operating the electromagnet 136 to give an alarm or bring about other appropriate action. When the illumination of the lamp 250 has been noted, or such action as is called for by the arising of the condition has been taken, the release key 254 is pressed to open the locking circuit and permit the release of the relay 253.

The operation as described above wil1 result if either of the group conductors 57 and 58 has its continuity interrupted by the arising of any abnormal condition in the circuit. If, however, the interruption of the conductors 57 and 58 is caused by the operation of any of the sets of group relays 19 and 2% by the initiation of a call in the normal operation of the system, such interruption is accompanied by the actuation of the starting relay 22 as already described. This relay in operating closes a circuit that extends from battery through the winding of relay 151 and the outer front contact and armature of relay 22 to ground. Relay 151 in operating closes a circuit that extends from battery through the winding of relay 255, lefthand front contact and armature of relay 151 to ground. Relay 255 in operatinginterrupts in its right-hand back cone tact and armature the path over which the relay 253 is energized when the switch contacts of either or both of the relays 251 and are closed upon the interruption of the energizing circuits of these relays. The relays 251 and 252 are so constructed as to be slow in releasing their armatures, as by providing the cores of the relays with copper shells, and the relay 253 may similarly be constructed and adjusted so as to be slow in attracting its armatures. The result is that in the normal operation of the system the relay 255 is operated to block or prevent the operation of the lamp controlling relay 253 before the slow-releasing relays 251 and 252 effect the closure of their switch contacts to permit it. But if the interruption of the continuity of conductors 57 and 58 is a continuing accidental interruption, and not incident to the normal operation of the systems, such interruption is not followed by the operation of the relay 22, the relay 255 is not operated to prevent the energization of the relay 253, and that relay oper ates to light the lamp 250.

Further, to prevent the lamp 250 from being lighted in the normal operation of the system, the blocking relay 255 is also energized by the operation of the relay 23. When the relay 23 operates as a result of the starting of the finder switch, as already described, it opens in its left-hand back contact and armature the path to ground of the conductors 57 and 58. This releases the starting relay 22, and that relay in releasing opens the energizing circuit of the relay 151, which in turn opens the path over which the relay 255 had theretofore been energized. But relay 23 in operating closes an alternative energizing path for the relay 255 which extends by way of the left-hand front contact and armature of the relay 23 and the right-hand back contact and armature of relay 65 to ground. Therefore the relay is held operated to prevent the closure of the energizing path for the relay 253, which energizing path would otherwise be closed on account of the de'c'nergization of the relays 251 and 252, due to the interruption of conductors 57 and 58.

Another condition that results in the release of the relays 251 and 252 in the normal operation of the system is that in which a call is initiated when all of the finder cir-- cuits that serve the group of lines in question are in use. Then this condition arises, a circuit is completed that extends from battery through the winding of relay 135, conductor 80, and sequence switch contacts (st to 17 of all of the busy finder circuits in series, to; ground at the end of the series. Relay 135 in operating closes the energizing c' suit of the relay 133, the relay 133 in op eratingcloses the energizing circuit of the relay 138, the last mentioned relay in operating closes the energizing circuit of the relay 139, and that relay in operating closes the energizing circuit of the relay 65. The relays of this train perform other functions with which the present invention is not concerned and which functions, therefore, are not here described.

When the relay 65 operates, it opens in its right-hand armature and back contact the normal connection with ground of the group conductors 57 and 58, this being for the purposeof preventing calling lines from energizing the starting relay 22 and therelay 24 and tri magnet 16 of the associated group, whennone of the finder circuits is incondition to be used. The opening of the path to ground of the conductors 57 and 58 permits the deenergization of the slow acting relays 251 and 252; but inasmuch as the opening'of the conductors 57 and 58 is one that is incident to the normal operation of the system,the relay 255 is operated to open the circuit of the relay 253 controlled by the relays 251 and 2 52, and thus prevent the lighting of the emergency lamp 250. The energizing circuit of the relay 255 is from battery, through the winding of that relay, andto ground byway ofthe front contact and left-hand armature of the relay 65. Thus the relay 65, in preventing the operation of the starting apparatus, when all of the'finder circuits are busy, also blocks and prevents the display of the emergency lamp 250.

The emergency lamp 260 and its associated controlling relays are for the purpose of indicating any accidental or improper opening in that part of the series group circuit that extends to ground by way of resting contacts of the relays 22, 23 and 65. The path by way of these relay contacts to ground normally short-circuits the winding of the high resistance relay261, When this short circuit is interrupted, the relay 261 is energized by means of current that flows to its winding from battery by way of the winding of the relay 252, conductor 57, and the resting contacts-of the relays 19 of the various groups. The relay 261 in operating closes, subject to the control of relay 2 in a manner hereinafter to be described, a circuit that extends from battery, through the winding of relay 262, armature and front contact of relay 261, and left-hand back contact and armature of relay 255 to ground. Relay 262 in operating closes, by Way of its right-hand armature and front contact, a locking circuit for itself that includes the normally closed contacts of'the release key 263. It also, closes a circuit that extends from battery, through the winding of common relay 134, lamp 260, and upper front contact and armature of relay 262 to ground. The closure of this last mentioned circuit causes the illumination, of theeinergency lamp 260; and when appropriate action has beentaken in response to the lighting of the lamp, the. relay'262 may be released by operating the'release key 263. In order that the emergency lampy260 may not be lighted when the, short circuit is removed from relay 261 asa'result of the normal operation of the system, the circuit is. so arranged that either of the relays 22,

23 and 65, in operating to break this normal short-eircuiting path, also closes an energiz ing path for the relay 2'55, and the last mentioned relay in operating opens in its lefthand armature and back contact the ground connection of the lamp controlling relay 262. Thus, when the starting relay is energized, it closes in its outer armature and front contact the energizing circuit of the relay 151,-and that relay closes in its lefthand armature and front contact the energizing circuit of the relay 255, which operates, as described, to prevent the relay 261 from causing the energization of the relay 262. Again, when relay 23 in operating opens the normal short circuit of the relay 261-, it closes in its left-hand armature and front contact the energizing circuit of the relay 255. Again, when the relay in operating breaks the short-circuiting path of the relay 261, it closes in its left-hand armature and front contact the energizing circuit for the relay 255. But ifthe ground connection of the group conductors-57 and 58 is broken accidentally or abnormally, the relay 255 is not operated, and the actuation of the relay 261 causes the lighting of the emergency lamp 260.

' It will be noted that the left-hand armature of the relay 262 controls in its back contact the energizing circuit of the emergency lamp 250,-and con'trolsin its front contact the energizing circuit of the emergency lamp 260; Therefore, if the interruption of the series group circuit including the conductors 57 and 58 is in that part of the circuit that extends through the resting contact of the relays 22, 23 and 65, the energization of the relay 262 tolight the emergency lamp 260. prevents the lighting of the emergency lamp 250 which would otherwise result from this same interruption; But ifthe break in the series group circuit is in that part which extends through the con tacts of the group relays 19 and 21, the

relay 262 is not operated, and the emergency lamp 250;is therefore lighted. Thus, one

or. the other of .thelamps 250 and 260 is lighted to indicate in which part of the com- 'mon series group circuit the accidental interruption exists. v r

As has hereinbefore' been described, the starting relay 22 is actuated by a calling line to appropriatea finder circuit, and is released when the passing of the K segment, at the outset of the upward movement of. the 1inefincler.,sWitcl1, energizes-the relay 23. .As soon as the starting relay 22 is operated, it closes a circuit thatextends from battery, through the winding of relay 241, right-hand back contact and armature of relay and outer front contact and a1 mature of'relay 22 to ground. Relay 211 in operating closes a branch from battery of this same circuit that includes the Winding of relay 2&2. Relay 242 in operating closes another branch from battery of this same circuit that includes the winding of relay Relay 243 in operating closes a looking circuit for itself by way of it righthand front conta'ctand armature, and also, in the back contact of its right-hand armature, opens the energizing circuit of the relay 24:1. Relay 241, in releasing its armature, opens the energizing path through the winding of the relay 24:2; and relay 242, in releasing, closes a path that extends from battery through the Winding of relay 24:1, left-hand armature and front contact of relay 2&3 (which is now locked up), back contact and armature of relay 212, and to ground by way of the outer front contact and armature or starting relay 22. The relays 211, and are so constructed and adj usted as to be slow in pulling up and slow in releasing. Consequently a considerable time interval el-apses after the actuation of the star-ting relay 22 before the energizing path of the relay 244: is completed by the pulling up of the relays 2-ll, 212, and 24:3 in series and the falling 'back of the relays 2 11 and 242. This interval is such that in the normal operation of the system, the starting relay is released by the passing of the K segment and the energization of relay 23 before the slow-acting train of relays have acted to bring about the closure of the energizing circuit of relay 244. But it the release of the starting relay 22 is unduly delayed, the relay 24% operates and closes in its left-hand armature and front contact the energizing circuit of the relay This relay in operating closes a locking circuit for itself by way of its armature and the release key 246, and also closes a circuit that extends from battery, through the winding of common relay 134C, emer gency lamp 210, switch spring and armature of relay 215, and normally closed contacts of release key 216 to ground. The closure of this circuit'lights the emergency lamp, and when appropriate action has been taken the lamp may be extinguished and the relay 215 released by pressing the release key 246. V

The relay 244 in operating as a result of an unduly delayed release of the starting relay 22, also closes a circuit'that'maycause apparatus to act automatically to remedy the condition responsible for the delayed release of the starting relay. This result is obtained by causing relay 244:, when it operates, to apply aground to the conductor 28 to move out of position 1 the sequence switch of another finder circuit in the same manner as relay 33 acts to bring about this result in the normal operation of the system, as hereinbefore described. Thus, if the de lay in the release of the starting relay 22 has been due to the failure of the line finder elevator, as LF, of the appropriated finder circuit to move up, the relay 244 responds to the abnormal condition and grounds conductor 28 to prepare another finder circuit for the use of the calling line.

The stages of the operation that are next to be described have to do with the selection by the a propriated 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, which it does as a result of being moved out of position 4: by the finding of the calling line as hereinbeforle described, it closes a circuit that extends from battery by way of the winding of relay 55 (see Fig. 41), conductor 71, and sequence switch contact 218 (5 to 8) to ground. The operation of the relay 55 applies ground tothe conductors 81 ex tending to all of the operators positions to the connecting circuit terminals of which the cord selector 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 relay 91 (see Fig. 5) is inert and the operators telephone sequence switch 300 is in its 1 position.

If the operator is listening in on a cord, the switch 415 associated with that cord circuit is closed, in any suitable manner, and an energizing circuit completed for relay 91. Likewise, if all of the connecting cords of a particular operators position are in use, the entire series of switches 416, one of which is associated with each connecting cord-circuit, are closed and the relay 191 energized to complete an energizing circuit for the relay 91. In either case, the energization of the relay '91 renders the operators position unselectable. Furthermore, when the operator is away from. her station, the switch 122 is operated, in any usual or convenient manner, to complete a circuit that extends from battery, through the motor magnet and contact 303 (1 or 17) of the sequence switch 300, to ground by way of the resting contact and left-hand switch spring of the switch 122. The closure of this circuit moves the sequence switch to position 4:, in which position sequence switch contact'30 l (1) is open, and the position is consequently .unselectable. When the operator takes her station, the levers of switch 122 are moved to the right, and a circuit is completed for the motor magnetof sequence switch 300 by way of contact 303 (4) and the alternate contact and right-hand switch lever of switch 122, which causes the sequence switch to move to position 1, its next resting position. In this position oit'the sequence switch the operators position, sub

ject to the control of relay 91, is rendered selectable by the closure of sequence switch contact 304 (1). At each position where neit er the relay 91is'inert and the sequenceswitch 300 is in position 1, as described, a circuit is closed that extends from battery, through the winding of associated relay 92, armature and back contact of relay 91, sequence switch contact 304 (1), conductor 81, armature and left-hand front contact of relay 55, toground. The relay 92 of'each awaiting available position, therefore attracts its armature and closes a circuit that extends from battery, through the front contact and armature of. relay 92, to the conductor 82', and thence to ground by way of the windings of the relays77 at the various cord selector frames as SF'and SF.

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 fthe closing of a circuit the completion of which is dependent upon the condition of the other finder circuits of thea'ssociated group. This circuit extends from battery, through the left-hand winding of the relay 30, contact 219 (6)7of the appropriated finder circuit sequence switch, contacts 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 arma ture of relay 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 positions 4 to'9. That is, it is open from the time the line finder switch of any associated finder circuits 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 thus completing the operators selection; Not until this has occurred, will the above traced clrcuit of the awaiting finder circuit be closed.

When this circuit is closed relay 30 attracts its armatures and completes a circuit that extends from battery, through the motor magnet and sequence switch contact 202 (6) of the sequenceswitch 200, front contact and right-hand armature of relay 30, and sequenceswitch contacts 208 (18 to 14) and (2 to 7) to ground. The completion of thiscircuit moves the finder sequence switch out of position 6. r v I When the finder sequence switch reaches position 6%, it closes a circuit that extends from battery, through the winding'of relay '54 (see Fig. 4), left-hand back contact and armature of relay 61, conductor: 73, and finder sequence switch contact 218 (6 to 8) to ground. V I 7 Relay 54 attracts its armatures'and completes a branch of the circuit just traced, which extends from conductor 7 3 by way of the armature and back contact of the relay 63, front contact and left-hand armature'of gized in parallel with the relay Relay 93 in operating disconnects its own energizing winding and that of associated relay 94 from the previously traced path to battery by way of the left-hand back contact and armature of the relay 95, and connects them in a path which extends from battery by way conductor 84. This causes the relay 95 also of the Winding of the relay and to beenergized and' to interrupt in its lefthand armature and back contact the path by way of conductor 83 over which the relays 93 and 94 were initially energized, and also to close a circuit that extends from battery by wa of the motor magnet and contact 303 (1) o the operators sequence switch, right hand front contact and armature of relay '95 and right-hand contact and lever of switch 122 to ground. The closure of this circuit moves the operators sequence switch through position 4, and to position 17, where it remains until its motor magnet is energized by the operation of switch 192 or of switch 122.

Relay 94 inoperating 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 94. This relay also closes a circuit that'extends from 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 contact 218 (6% to 8) of the line finder sequence switch), through *the armature andfront contact of relay 63, condu'ctor 72, sequence switch contact 220 (7), I

and left-hand winding of relay 30 to battery. Relay 3O attracts its armatures and 12'0' closes a circuit that extends frombattery,

, anism oi the 1..

switch contacts 217 (2 to 9), right-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 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 selector switch, this circuitextending from battery, through the up-drive magnet 3 1 of the cord selector, conductor 89, sequence switch Contact 207 (8 to 9), right hand front contact and armature of relay 30, sequence switch contact 218 (8 to 9), and thence to ground. At the outset of the upward movement or" the cord selector brush rod, the tripping levers of the various sets of brushes are brought simultaneously into operative position with respect to the corresponding trip yokes, and that set of brushes is tripped and made operative whose trip magnet is at the time energized. In the present instance, it may be assumed that this is the trip magnet 20 associated with the terminals of the group or' connection cord circuits extending to the Ooperators position.

Innnediately after the set of brushes is tripped, the common operators selecting circuit is restored so as to be available for the use of other cord finder switches. This is eiiected through the medium ot' a circuit that is completed by the grounding of the K segment of the cord finder commutator, this segment being so located as to be engaged by its brush immediately after the tripping levers or the sets of brushes pass the associated tripping yokes. The circuit referred to extends from battery, through the winding of the relay 61, conductor 7&, sequence switch contact 221 (7% to 8), conductor 180, cord finder commutator segment K and its corresponding brushto ground. Relay 61 in 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 0 operators position and the relays 93 and 91 corresponding to this position on the cord finder frame. The release of the rela 9i deenergizes the corresponding trip magnet 20 and the common relay 63. The deenergi- Zation of the relay 93 re-stablishes, subject to the relee of relay 61, the control of other finder circuits er the brush-tripping mechcociated cord finder frame. Relay 61 in operating closes a locking circuit for itself by way of conductor 7 sequence switch contact 218 (6%; to 8), and

thence to ground. It also completes a circuit that extends from battery through the motor in net and contact 205 (8) of the sequence stch 200, conductor 75, right hand nt contact and armature of relay 61 to ground; The closure of this circuit moves sequence 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 dcenergizing relay 61 and again extending conductor 73 to the relay 54 and the conductors over which the operators selection is effected. In closing its righthand back contact upon release, relay 61 also restores the continuity of conductor 7 6 and makes it availabl 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.

When the sequence switch 200 is moved out of position 8, it moves into position ,9 and there awaits the finding of an idle connecting cord circuit upon the operators position that has been selected. 'As the brush carrying rod moves up, the brushes 111, 112, 113 and 11 1 of the set that has been trippedcome into engagement with sets of terminals 115, 116, 117 and 118 corresponding with the difi'erent'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 path-is completed that extends from battery, through the lower winding of relay 87, sequence switch contacts 206 (8 to 9), conductor 99, brush 114, terminal 118, conductor S8 of the cord circuit, contact 161, which is closed when the associated cord is not in use, and back contact and armature of relay 119 to ground. Current flowing in this circuit causes the relay 37 to attract its armature and break the previously traced circuit by way of sequence switch contacts 216 and 217 and the right-hand winding of relay 30, which, up to this time, has been holding relay 30 energized. Then the relay 30 is released, it opens, in its right-hand front contact, the previously traced circuit including the up-drive magnet 31, and thus causes the brushes of the cord finder switch to come to rest on the terminals of the se-' lected cord circuit. The relay 30 in releasing also closes a circuit that extends from battery through the motor magnet and con tact 202 (9) of the sequence switch 200, back contact and right hand armature of relay 50, and sequence switch contact 218 (8 to 9) ing which each of the finder circuits has operative relation with this common opera tors selecting circuit is represented by the time that is occupied by the finder sequence switch in moving from position l to posia tion 9. In the normal operation of the system, this interval is short, bein merely the space of timerequired by the 1 nder circuit to test and obtain access to the'common selecting circuit, select an idle operators position, operate the brush trip magnet corre sponding with that position, and cause the upward movement of the brush-carrying elevator far enough to trip the corresponding brushes. If for any reason this interval should be unduly protracted, thus delaying the access of other finder circuits to the operators selecting circuit, or if the operators selecting circuit should accidentally become inoperative, apparatus is provided for giving prompt notification of such a operators selecting apparatus. Included in the normally closed circuit is a relay 273 which is kept energized by the normal current flow in this circuit. When the test circuit by way of the sequence switch contacts 219 (9 to 4:) is opened, this relay is denergized, releases its armature and permits the closure of the associated contacts. But the relay 273 is made slow-releasing, .asby pro viding its core with a copper sheath, so that the closure of the associated contacts occurs a certain interval after the energizing circuit is broken. When'the contacts of the relay 273 close, a circuit is' completed that extends'from' battery, through the lamp 27 0 and the lefthand winding of the relay 272 in parallel, andthence to ground by way of the switch contacts of therelay 273. The

completion of this circuit lights'the lamp 270 and also energizes the relay 272, which V attracts its armature and lights the lamp 271'.

In the normal operation of the system, the opening of the test circuit in the finder sequence switch contacts 219, when the sequence switch moves out of'position at, is fol lowed promptly by the grounding of conductor 73 byway of contacts 218 (6%; to 8) of the finder sequence switch when the sequence switch moves out of position 6 and connects the corresponding finder circuit with the common operators selecting circuit. The grounding of conductor 73 completes a circuit that extends from battery, through the I ground.

winding of relay 281, conductor 73, and sequence switch contacts 218 to- 8*) to Relay 281 thereupon, attracts its arn'iatures and closes a circuit that extends from battery, through'the winding of relay 273, left hand armature and front contact of relay281, and right-hand armature and front contact of relay 55, thelast mentioned 'made a little longer than the interval required in the normal operation of the system for the sequence switch to move to position 6% and energize relay 281. As a result,

the relay 281 normally acts to close the alternative energizing circuit for the relay 273 before the relay 273 has had time to respond to the opening of its normal energizing circuit by way of conductor 70 and the seriesy I of sequence switch contacts 219. But if the opening of the circuit by way of conductor 7.0 is not followed Within this definite interval by the closure of the alternative the finder se uence switch moves into osi-.

tion-6 and operates relay 281, the relay 55 for any reason isnot energized, then the alternative energizing circuit for relayr27 3 will not be completed and the lamps 270 and 271 will be lighted to indicate trouble in the circuit.

In the. normal operation of the system,

each finder circuit should have connection with the common operators selecting'circuit only for a sufficiently long interval to permit the selecting of an operators position,

the starting of the brush-carrying elevator and the tripping of the brushes. The lamp 280 and its associated apparatus are vprovided to indicate when this normal interval is exceeded. At the moment any finder circuitis connected with the common operatorsselectmg apparatus through the medium of and 285. 1 As a result, the relay 282 operates and closes-the energizing circuit for therelay 283, the relay 283 operates and closes the'energizing circuit-for'the relay 284, the

relay 284 operates and closes the energizing, v

circuit for the relay 285, the relay 285lo'cks up and also opens the energizing circuit of the relay 282, that relay releases slowly and opens the energizing circuit of the relay 283, the relay 283 releases slowly and opens the energizing circuit of the relay 284, the relay 28% releases slowly and closes a circuit that extends from battery through the lamp 280 and from battery through the upper winding of relay 272 in parallel, left-hand,

armature and front contact of relay 285, back contact and armature of relay 28 1, and right-hand front contact and armature of relay 281 to ground, thus lighting lamp 280, and operating relay 272 to light lamp 271. The relays of the slow-acting train are organized and operate in the manner disclosed in Patent 1,163,896 to Darrah, issued December 14, 1915. The time intervals involved in the operation of this train of relays in order finally to close the circuit for the lamp 280 are, in the aggregate, greater than the interval required for the finder sequence switch to move from position 6% to position 8 in the normal operation of the system. Therefore, if the system is operating normally, the relay 281 is deenergized and releases its armatures before the circuit closed by way of its right-hand armature and front contact has existed long enough to effect the closure of the branch including the lamp 280 and the right-hand winding of the relay 27 2. But if, for any reason, any finder circuit holds the common operators selecting circuit for an unduly long interval, then the lamp 280, and the lamp 271, controlled by relay 272, are lighted to indicate the improper operation of the system.

The conductors 83 and 84, which lead to relay at each operators position, are the paths over which is completed the selection of the corresponding operators position by the common selecting apparatus of the different frames having access to that position. The operativeness of these paths and of the associated common apparatus is safeguarded by the emergency apparatus involving the lamps 290 and 291 and the relays 292, 293 and 294:. In the normal condition of the system, current flows from battery by way of the winding of relay 95 at the operators position,.conductor 84:, the left-hand armatures and back contacts of the relays 93 of the various frames in series, and the winding of slow-releasing relay 292 to ground.

When the operators position is selected and this circuit broken by the operation of the relay 93, as previously described, the relay 292 is deenergized. As relay 292 is slow releasing, an interval elapses from the time it is deenergized until it permits the closure of its associated contacts. When these contacts .are closed, if the relay95 in the meantime has not been energized, a circuit is completed that extends from battery by way of the left-hand armature and back contact of relay 95, conductor 83, switch contacts of relay 292 and winding of relay 293 to ground. This causes relay 293 to attract its armature and close a circuit that extends from battery, through the winding of relay 294;, lamp 291 and front contact and armature of relay 293 to ground. He lay 294; in attracting its armature closes an energizing circuit forlamp 290. A set of relays 292 and 293 and a lamp 291 are pro vided in connection with the conductors 83 and 84 associated with each operators position. Only one set is shown in the drawing, the presence of the others being understood. The relay 294; is of low resistance and is common to all of the lamps 291. The lamp 290 is a common lamp and lights Whenever any of the lamps 291 is lighted.

The lighting of the lamp 291 occurs only when the circuit conditions are abnormal. In the normal operation of the system, the breaking of the energizing circuit of the relay 292 is accompanied by the energizing of the operators position relay 95, and the last mentioned relay in operating breaks the con tinuity of conductor 83 over which current must flow to energize relay 293. Therefore, before the slow-releasing relay 292 can re lease its armature far enough to close the associated switch contacts, the circuit for relay 293 is broken at contacts of the relay 9'5.

The relays involved in the emergency circuit part of the organization may be given such resistance values as are convenient, or as readily suggest themselves to those skilled in the art. It may be stated, however, that the following have been found to be suitable resistance values for certain of the relaysz'relays 251 and 252, 1500 ohms; relay 261, 3200 ohms; relay 22, 23.; ohms; relay 273, 1000 ohms; relay 281, 2000 ohms; relay 292, 1500 ohms; relay 95, 23!; ohms; relay 293, 2000 ohms; relay 29 1, 0. 15 ohms. The foregoing values are with a 8-volt current supply for the parts of the circuit organization in which these relays are included.

It has been found desirable to provide switches, preferably in association with the emergency signal lamps, for cutting out apparatus that the lamps indicate is operating improperly, and for substituting therefor duplicate groups of apparatus in order to restore service. The switch 310, comprising switch contacts 3101 to 3106, inclusive, and the switch 311, comprising switch contacts 3111 to 31111, inclusive, are such switches. One of the switches 310 is associated with the group apparatus of each group of lines terminating upon a line finder frame, anda switch 311 is associated with the apparatus common to each line finder frame. fW-hen the lighting of a lamp 250 indicates an improper condition of the series group circuits, the switch 310, associated with the group in which the trouble has occurred, may be operated, and in being operated disconnect-s the group apparatus consisting of the relays 19 and 24 and the timing sequence switch 100 of thatiparticular group and substitutes for it in the circuit a duplicate set of apparatus. Only one duplicate or emergency set of group apparatus is provided for the line finder frame, this set being connected 'with the alternate contacts of all of the switches 810 in the same manner in which the regularly used setis connected with the resting switch contacts, and being substituted by the throwing of'the associated switch 310,

-thrownf Similar switches for disconnecting the various groups of apparatus in the operators selecting c1rcu1t may be provided to be operated in response to the lighting of the cal the

lamps 271 and 280. Where desired, such vcorrective action may be efiected automaticallv. asin the operation of the relay 244 to render another finder ,circuit available in case the selected finder circuit fails to start its line finder switch, as previously described.

In order to complete the disclosure of the system connection with which the invention in its preferred form is here shown, the circuits and operations involved in completing connection with the called line and in disestablishing connection at the end of the conversation will now be described.

The connecting circuit to which'the finder circuit is extended in the manner hereinbetore described, is illustrated in thepresent instance as being a cord-circuit terminating in a connecting plug 170 and including in its talking conductors 85 and 86 the windings of a repeating'coil 169 with a bridged battery, and the usual signal controlling relays 171 and 187. The connectingcircuit also includes a ringing key 120 by means 0: which current from the ringing generator 181 may be applied to the circuit of the called line, and a listening key 130'by means 01 which the connection oft-he operators telephone set-14? with the called line may be controlled. 7 V

The extension of the finder circuit to the connecting cordbriiurs about, in a manner which need not be described, the actuation of a signal onthe associated operators position which informs the operator that a call iswaiting. Th'eoperators telephone is connected with the circuit by means of the listening key 130; and when the operator has learned the number of theline with which "pletes the connectionby inserting the plug into the spring-jaclr14 t line. Before the plu'g'is'iniserted, a busy test may be made in the usual way over the path that is shownextending from the tip of tee plug by way ofthe arn'ia-ture andiback contactof the relay 175, When the plug is inserted, a circuit is closedthat extends from battery through the winding of the relay 119, winding of the relay 175, the cotiperating sleeve contacts of the calling plug 170 and spring-Jack 14, and the wind ng of the cut-off relay 11 to ground. The completion of this circuit causes all three relays to; at-

tract their armatures, the relay 119 opening the path to ground of conductor 88, thus renderlng the connectlng. cord clrcuit un-' selectable, relay 175 disconnecting the tip of the plug'170irom the test conductor and completing the talking circuit of the tip strand, and the cutoif relay 11 disconnecting I the line relay 12 of the called subscribers" line. Ringing current from the ringing generator 181 may ,then be appliedto the called subscribers'line by closing the. contacts of the ringing key 120. q

By means of appropriate, mechanism, which is disclosed in the patent to S. B.

Williams, Jr., No. 1,304,641, issued VMay 27,

1919, (application Serial No. 180,634, filed July'14, 1917), and which it is unnecessary to describe as it forms no part of the present invention, the extension of the finder circuit to the connecting cord circuit brings about the opening of the cont-acts of the switch 161 and the closing of the contacts of the switch 152. The switch 152corresponds to the left-hand armature and'front contact ofrelay 152 of the above mentioned \Villiams patent, and theswitch 161 corresponds to cam 404 of sequence switch 400 of the Williams patent.) The switch 161 in opening its contacts renders the associated cord-circuit unselectable immediatelyand in advance of the opening of the contacts controlled by the relay, 119. The'closing of the contacts of switch 152 completes a: circuit that extends from battery throughthewinding of relay 155, switch contacts 152, conductor 87 contact 117 and cooperating brush 118 of thecord selector, conductor 98, contacts 217 (9% to 14) and, (12 to 14) of the finder sequence switch, right-handwinding of relay 30, sequence switch contact 212 (12% to 14), conductor50, brush 42 and contact 46 of the line finder, conductor 53 and winding of cutofi relay 11 of the calling subscribers line to ground. The currentthat flows in this circuit keeps the relays 155, 30 and 11 energized during the time that the connection is established. The relay 155 closes a normal break in the ring strand 86 of the talking circuit. The relay 30, as long as it is energized, prevents the finder sequence switch 200 from movingout of its talking positionv 14. The cutoff relay keeps the nected' from t e calling line.

At the termination of the conversation, the replacing of the telephone receivers on their switchhooks at the calling and called subscribers stations brings about the display of supervisory signals (not shown) which may be controlled by the cord-circuit relays 171 and 187 in the usual way, and the op erator in response to this indication withdraws the calling plug 170 from the spring iack of the called subscribers line. The withdrawal of the plug is accompanied by the opening of the contacts of switch 152. This opens the circuit traced in the preceding paragraph including the relays 155, 30 and 11, and these relays release their armatures. When relay 30 of the finder circuit releases, it closes a circuit that extends from battery through the motor magnet and contact 202 (8 to 14) of the finder sequence switch, left-hand back contact and armature of relay 30, and armature and back contact of relay 37 to ground. This moves the finder sequence switch out of the talking position 14. IVhen the finder sequence switch reaches position 15, it is moved through that position by means of a circuit that is completed from battery, through its motor magnet and contact 202 (15), right-hand back contact and armature of relay 30, sequence switch contacts 218 (15) to ground. (hen the line finder sequence switch reaches position 16, a circuit is completed that extends from battery through the down-drive magnet 62 of the line finder switch, and sequence switch contacts 208 (16) to ground. As a result, the brushes of the line finder switch are returned to normal.

When the brushes reach their normal position, a circuit is closed that extends from battery, through the motor magnet and contact 205 (16) of the finder sequence switch, conductor 69, segment Y of the line finder commutator and its corresponding brush to ground. This moves the finder sequence switch out of position 16. In the next resting position 17 of the finder sequence switch, a circuit is closed that extends from battery through the down-drive magnet 35 of the cord selector switch, conductor 90, and sequence switch contact 218 (17) to ground. The closure of this circuit energizes the down-drive magnet 35 and causes the cord selector brushes to return to their normal position. At the end of the downward movement of the brushes, a circuit is closed that extends from battery through the motor magnet and contact 205 (17) of the finder sequence switch, conductor 31, Y segment of the cord selector commutator and corresponding brush to ground. The completion of this circuit moves the finder sequence switch 200 out of position 17 after which it returns to position 1 under the control of its cam 201.

In order that the features to which this invention is directed may be fully and clearly disclosed, it has been necessary to describe them in connection with other features that are the subject of co-pending applications assigned to the same assignee, such applications including the application of S. B. Williams, Jr., Serial No. 75,328, filed J anuary 31, 1916; application of S. B. Williams,

J12, Serial No. 75,329, filed January 31, 1916; application of S. B. Williams, Jr., Serial No. 107,090, filed July 1, 1916; joint application of S. B. Williams, Jr., and R. L. Quass, Serial No. 131,089, filed November 13, 1916; and application of F. A. Stearn, Serial No. 107 ,5 10, filed July 5, 1916. Such other features are the subject of claims in the applications mentioned above, and are not claimed in the present application.

What is claimed is:

1. In a call distributing system, the combination with a plurality of lines and a plurality of finder switches for making connection therewith, of a starting relay for starting the movement of a finder switch to connect with a calling line, a controlling circuit for said starting relay, means responsive to the initiation of a call for altering the electrical condition of said controlling circuit to operate said starting relay, an electrical emergency device, a timing device for operating the same a predetermined interval after the electrical condition of said controlling circuit is altered, and means for preventing the operation of said emergency device made active in the operation of said starting relay.

2. In a call distributing system, the combination with a plurality of lines and a finder switch for making connection therewith, of a starting relay for said finder switch, an electrical emergency device, a controlling circuit for said starting relay and said emergency device, means responsive to the initiation of a call for altering the electrical conditions of said controlling circuit to operate said starting relay first and said emergency device a predetermined interval thereafter, and means for preventing the operating of said emergency device made operative in the actuation of said starting relay.

3. In a telephone system, the combination with a plurality of lines and a finder switch for making connection therewith, of a starting relay for said finder switch, a controlling circuit for said starting relay, said controlling circuit being normally continuous, an electrical emergency device responsive to an interruption in the continuity of said controlling circuit a predetermined interval after said interruption occurs, means responsive to the initiation of a call for altering the normal continuity of said controlling circuit and operating said starting re- 7 lay, and means for preventing the operation ing said emergency device, and means for preventing the operation of said emergency device made active, inv the starting of said finder switch.

5. In a telephone system, the combination with a plurality of lines and a plurality of finder switchesformaking connection there,- with, of an electrical emergency device, means made active in initiating a call for first starting a finder switch and then after a predetermined interval operating said emergency device, and means for preventing the operation of said emergency device made active when all of said finder switches are in use.

6. In a telephone system, theconrbination with 'a plurality of lines and a finder switch for making connection therewith, of a starting relay for said finder switch, .an electrical emergency device, means actuated in the initiation of a call for operating said starting relay and then after a predetermined interval operating said emergency device, and means for preventing the operation of said emergency device made active in the starting of said finder switch.

7. In a switching system, the combination with a plurality of controlling relays, ot a normally continuous controlling circuit extending serially through normally closed contacts of said relays, an emergency device, a controlling magnet therefor having its winding included in a shunt of said contacts and adapted to be operated when the portion of said controlling circuit including said contacts is opened, an electromagnet forpreventing the operation of said emergency de vice, and means for energizing said electroinagnet made operatlve inthe operation of any of said controlling relays, whereby said emergency device is responsive to abnormal opening of said controlling circuit but irresponsive to an opening efiected by the operation of said controlling relays.

8. *In a telephone switching system, the combination with switching apparatus, of a normally continuous controlling circuit therefor, normally closed contacts in one part of said circuit adapted to be opened in the switching I operations by group appa-- ratus, normally closed contacts included in another part of said controlling cirijuit adaptedto be opened in the switching operations by common apparatus, two electrical emergency devices, means responsive to the opening or said controlling c1rcu1t associated wlth the group apparatus for operating one of said devices, means responsive to the opening of the part of the circuit associated with the common apparatus for operating the other device, means responsive to the switching operations controlled by the group apparatus for preventing the operation of the first-mentioned emergency device, and b means responsive to the switching operations controlled by the common apparatus torpreventing the operation of the last-mentioned emergency device, whereby an I abnormal opening of any part of said controlling circuit is indicated by the operation of one or the other of said emergency devices. 7

9. In a telephone system, the combination with a plurality of lines and aplurality of finder switches for making connection therewith,fof a switchrfor controlling theoperative relation of said lines with said finder switches, an electrical emergency device, means made active by any line 1n calling 'for first operating said controlling switch for making connection therewith, of a starting relay for said finder switch, means made active by any line in calling for operating said starting relay, a slow-acting electrical emergency devlce, means made active during the operation of the starting relay for energizing said emergency device, and means made active in the starting of a finder switch for releasing said starting relay be- -tore the expiration of the interval required for the operation ofsaid emergency device.

11. In a telephone system thecombination with asplurality of lines and a finder switch for making connection therewith, of a starting relay for said switch actuated ,by a line in calling, means] made operative .in, the starting of said switch for releasing said starting relay, an emergency device, and

means for operating the same made effective by the energ zatlon of said startmg relay for longer than the normal interval required 'forstartmg said finder swltch.

'12-. In a telephone system, the combination with a plurality of lines and a plurality of finder. switches for making connection therewitlnof a starting circuit for said finder switches, a starting. relay under the

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