US1031667A - Telephone switchboard apparatus and circuits therefor. - Google Patents

Description

H. J. ROBERTS. TELEPHONE SWITGHBOAED APPARATUS AND CIRCUITS THEREFOR.

A'PPLIGATION FILED 00113, 1906. RENEWED NOV. 21, 1911.

1,031,667, Patented July 2, 1912.

2 SHEETS-SHEET l.

H. J. ROBERTS. TELEPHONE SWITGHBOARD APPARATUS AND CIRCUITS THEREFOR.

APPLICATION FILED OCT. 13, 1906. RENEWED NOV. 21I 1911.

1,031,667. Patented July 2, 1912.

2 SHEETSSHEET 2.

COLUMBIA PLANOGRAIH cu wAsmNo'ron, I): :4

Original application filed September 5, 1905, Serial No. 276,975.

October 13, 1906, Serial No. 338,384. Renewed November 21, 1911.

UNITED STATES PATENT OEFIQE.

HOMER J. ROBERTS, EVANSTONi ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO HOMER ROBERTS TELEPHONE CO., A CORPORATION OF WEST VIRGINIA.

TELEPHONE SWITCI-IBOARD APPARATUS AND CIRCUITS THEREFOR.

To all whom it may concern:

Be it known that I, HOMER J. ROBERTS, a citizen of the United States, residing at Evanston, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Telephone Switchboard Apparatus and Circuits Therefor, of which the following is a specification.

This invention relates to telephone switchboard apparatus and circuits therefor, and it has for its general object the provision of selective calling apparatus and circuits therefor by means of which all of the cord controlling keys pertaining to a particular group or section are placed under the direct control of a master-key which in turn controls the selective calling apparatus and also effects the conversion or specialization of cords or cord pairs for the time being so that they may be used for making connections with selective party-lines.

Further objects of the invention are to provide a system which is susceptible of being installed in ordinary manual exchange switchboards without to a serious extent necessitating the re-wiring or disturbing of the switchboard connections already installed; to provide a system adapted to act or combine with a special form of automatic counting out mechanism, which latter forms the subject of another application; to provide a system of the character referred to which is so organized as to admit of com bining therewith both a calling-in signaling system and a supervisory signaling system; and in general to provide an improved system of the character referred to.

To the above ends the invention consists in the matters hereinafter described and more particularly pointed out in the appended claims.

The invention will be readily understood from the following description, reference being had to the accompanying drawings forming a part thereof, in which Figures 1 and 1 taken together represent diagrammatically the complete switchboardv circuits and operating mechanism.

In the particular embodiment of the invention illustrated, it is designed for use in a switchboard which has both selective party-line subscribers and individual line subscribers; the selective party-lines being Specification of Letters Patent.

Patented J uly'2, 19121 Divided and this application filed Serial No. 661,633.

of that type in which the selections are per formed by counting out a definite number of impulses of current of one polarity and the ringing of the several parties effected by throwing onto the line pulsating current of a polarity opposite that employed in se lecting. In the present system two sets of signaling apparatus are embodied, one controlling the line drops and operated by common battery, the other controlling self-restoring supervisory signals and also operated by common battery. The supervisory signals are individual to the several pairs of cords so that each signal is in use only as its corresponding cord is in use.

In practice, in adding to an ordinary manual exchange switchboard already installed selective party-lines, the cord keys already installed may be and usually are utilized by simply adding additional pairs of contact strips and additional bus-lines connecting each of the cord keys so converted to the master-key set. Thus ar ranged, the operator desiring to use any given pair of cords for connecting between two party-lines, or between one party-line and an individual line, simply places the key controlling that pair of cords in its selfretaining position and thereafter performs the further work of completing the connections through the master-key, as well as the operation (which is usually necessary in lock-out party-line systems) of clearing, i. e. restoring the line to normal.

Referring now to the diagram, A, A, A designate a plurality of cord keys, and B, B, two somewhat similar keys which latter together constitute the complete master-key set.

C designates diagrammatically a source of usual alternating callmg current, the generator shown being connected by bus-lines 1 and 2 with the several cord keys.

I) designates as a whole diagrammatically a generator so arranged as to afford pulsations of either polarity.

E designates as a whole an automatic pulsation-counter, which for convenience of description will be herein termed a selector; its function being to count out a definite number of pulsations and in this manner effect selection of the particular party wanted on a party-line.

F designates a main battery, which affords current for various purposes, and G a second battery of a less number of elements which supplies current for both signaling systems.

H, H, H designate a plurality of springjacks forming the terminals of corresponding metallic lines, and I, I, I corresponding line drops. Each cord key is provided on each side wit-h inner pairs of contacts, as 3, 3, 4, 4L and 5, 5 and 6, 6, which, in the intermediate position of the key, are closed. The springs 3, 4, 5 and 6 are respectively connected with the tip and sleeve sides of the cords, as 7 8, 9 and 10, and are shifted into contact with outer springs 11, 12, 13 and 141, respectively, when the key is shifted in one direction or the other. Of these latter springs, 11 and 12 are connected with the bus-lines 1 and 2, respectively, while thesprings 13 and 14. are connected with another pair of bus- lines 15 and 16, respectively. These latter lines lead to the master-key and, as will be seen by tracing the circuit, connect the master-key with the answering cord sides of the several keys A, A, A The additional springs which are added to each key are indicated at 17, 18 and 19, 20, respectively; the moving members 18 and 19 being connected with but insulated from the corresponding springs 13 and 1 1. Springs 18 and 19 are respectively connected with the left and right sidesof another pair of bus- lines 21, 22, while the cooperating springs 17 and 20 are respectively connected with the innermost springs 3, 4 of the opposite side of the key and also with the innermost springs 5, 6 of the same side of the key. A condenser 23 is interposed in the connection leading from spring 17 to spring 5, 2'. e. from the tip side,

to prevent interference with the proper operation of the supervisory signal when a Roberts line is connected .to an ordinary bridged line. The connections of each key A, A, A are precisely similar.

Referring to the master-key set, the key B is so organized that when shifted in one direction (downwardly, as shown) it throws current through the selector E and to the answering cord of whatever cord key is in use and shifted to a self-retaining position. Similarly when key B is shifted in the opposite direction it throws current through the selector E to the connecting cord of the same cord key. In either of the shifted positions of key B the current sent to line may be pulsating positive or pulsating nega tive, depending upon the position of the selector E. That is to say, the selector E when rotating sends current of one polarity to line but as it reaches its normal or zero position it reverses the connections and sends current of opposite polarity to line. i It will be seen from the foregoing that key B is utilized for calling the subscribers. Connected with key B so as to move positively in both directions with the latter is a subsidiary key B which is so constructed as to shift the springs controlled thereby whenever it moves in either direction. This key performs various functions as will hereinafter appear, chief among which being the control of the battery connections. Key B is so organized as to place the main battery E which is of relatively large capacity directly to the left-hand side of the line and at the same time to ground at the opposite side of the battery; the shifting of the key in one direction (downwardly, as shown) serving to throw the main battery direct to the answering cord and the shifting of the key in the opposite direction sending the current to the connecting cord. Connected with key B is a subsidiary key B similar to the subsidiary key B but so connected that it moves with key B in one direction only, namely when the latter key is shifted upwardly. The mechanical connection whereby'this is effected is indicated at 24 wherein the stem of key B telescopes within a sleeve connected with key B; the end of the stem of key B terminating in proximity to the body of key B. Key B is provided with a stem and push button whereby it may be depressed and when so depressed it obviously forces with it key B.

The functions of key B are in general similar to those of key B. An auxiliary push button J is provided which is mounted on one side of a lever pivoted at 25, the opposite end of the lever being operatively connected with the stem of key member B The push button J controls a group of conparticular party-line system for which the present invention is in this instance specifically adapted, any subscriber who calls in is located and connection given him by looking out all stations between his set and central, and this looking out is effected by operating the relays at the several stations one after another'by a series of pulsations thrown to line through push button J. Since this operation is in effect running down the line until the station is reached from which the subscriber has called, the push button J will be designated the running key. A call for connection coming in over a subscribers party-line would throw the line drop, as for example at I, whereupon the operator would insert a plug of any available answering cord and secure talking connections and take the order from the calling subscriber as follows: Observing that the call was on a party-line she would shift the cord key to its self-retaining position, thus extending the circuits from the g. a

spring jack over conductors 9, 5 and 13 to bus-line 15 and over conductors 10, 6 and 14 to bus-line 16, thereby extending the connections to the master-key set. Buslines 15 and 16 are connected with the master-key set through conductors 26 and 27 and the circuit closed by the running key in responding to the subscribers call may be traced as follows: over line 26 to intermediate spring 28 of key B, inner spring 29, conductor 30 to intermediate spring 31 of running key, to back spring 32, thence over conductor 33 to conductor 34, from the.

latter over conductor 35 to the pole changer, from the pole changer over conductor 36 to front spring 37 of the selector, thence to the intermediate spring 38, from the latter over conductor 39 to a contact arm 40, thence over conductor 41 to conductor 34 which connects by conductor 42 with the back contact 32 of the running key, which is at this time closed with intermediate spring 31. The latter, as hereinbefore described, is connected with conductor 27. This completes the circuit.

The result of throwing pulsations of one polarity over the circuit described is to lock out the subscribers successively until the subscriber is reached who called for the connection. By operating his switch hook or some other suitable act the subscriber places his set in such condition that succ'eeding impulses, after his instrument has been reached, will fail to pass the same. But although he thus arrests the further selection it is necessary to put one or more impulses of opposite polarity through his set in order to place the same in talking circuit. This reverse polarity impulse is sent over the line by shifting key B clownwardly, which results in transposing the connections between the generator D and the line. This reverse is not made until an ample number of impulses have been sent out to more than reach the sub-station; the excess impulses being ineffectual. That part of the circuit which is reversed may be traced from the generator over the conductor 35 to line 34, thence to outer spring 43 of key B, thence to switch spring 44, over conductor 45 to inner spring 46 of the running key, to switch spring 31, thence over line 27 to bus-line 16, which is connected through the cord key to the sleeve side of the line. From the other side of the generator the circuit is over conductor 36, springs 37 and 38, conductor 39, arm 40, conductor 41 to spring 43 of key B, thence to switch spring 44 and thence to inner spring 46 of the running key over conductor 45. From spring 46 the circuit is through spring 31, thence over conductor 30 to and through springs 29 and 28 of key B and to bus-line 15 over conductor 26.

In the self-retaining position of the cord keys the exchange operators set is in listening connection with both ends of the cord. The listening connections with the answering end of the cord may be traced from bus lines 15 and 16 as follows: over conductor 26, springs 28, 29, conductor 30, springs 31 and 46 of the running key, conductor 45, springs 44 and an inner spring 48 of key B, through a condenser 49, thence over a conductor 50 to the tip side of operators jack 51. The other side is over conduct-or 27, springs 31 and 46 of the running key, conductor 45 to switch spring 44 and inner spring 48, thence through condenser 49 and over conductor 50 to spring 52 of key 13", to spring 53 and back over conductor 54 to the sleeve side of the operators jack.

The listening circuit connections with the calling end of the cord are from bus-line 21 over a conductor 55, to switch spring 56 of key B, to inner spring 57, thence over conductor 58 to switch spring 59 of key B, thence to inner spring 60, and thence over conductor 61 to conductor 50 and to the tip side of the jack. Similarly from bus-line 22 over conductor 62 to switch spring 59, inner spring conductor 50 and thence to the sleeve side of the jack as before traced. The operator, having answered the subscriber, takes his order for a connection. It a party on an individual line were wanted the connection would be made by simply inserting the connecting or calling end of the cord in the proper jack and shifting the cord key into its reversed position, thereby throwing ringing circut from the bus-lines 1 and 2 through the called subscribers bell. If, however, a party-line connection is called for, the next operation will be to insert the connecting end of the cord in the proper jack and select and call the particular party wanted. The first operation, after inserting the plug, will be to set the selector dial to throw upon the line as many impulses (which are automatically counted out by the selector instrument) as will effect the selection of the right party. The selector E is so constructed that the dial and connected ratchet are spring-returned to the Zero position, and the returning movement is con trolled by a magnet K the armature 7c of which constitutes an escapement lever. By means of a suitable handle the dial is manually turned forwardly as many notches as will correspond with the number of the party wanted counting the sub-stations outwardly from central. The magnet escapement permits the dial to return one notch for each impulse, and as the dial reaches the Zero position it is arrested by a stop-pin 63 engaging a suitable stationary stop 64. Cams 65 and 66 are mounted upon the ends of the respective switch springs 38 and 38 of the selector, and these cams in the Zero position of the dial rest in recesses 67,

67, respectively formed in an insulated hub 68 carried on the shaft of the selector and rotating with the ratchet of the latter. As soon as the dial is moved away from the zero position these cams are forced out 'of the V shaped recesses and thereafter ride upon the periphery of the hub, thus moving the switch springs 38 and 38 outwardly into bearing with back contact springs 69 and 70, respectively. The shifting of the switch springs in this manner reverses the connections with the pole changer D, so that while selecting impulses are sent to line during the return of the selector to zero, when' the selector reaches zero impulses of opposite polarity or ringing current is sent to line. Pressing the key B upwardly shifts its switch springs 59 and 59 outwardly into contact with outer springs 71 and 71, and these springs are connected with conductors 34 and 34, respectively, so that impulses are sent to line in substantially the same manner as when operating the running key.

A local circuit is closed through and operates the magnet K when the key B is closed in either direction, (provided the selector has been set) which current may be traced as follows: from the generator through conductor 36 and spring 38 to back contact 70, thence over a conductor 72 to and through the magnet K, thence to a switch spring 73 pertaining to key B, from the latter to cooperating spring 74, which spring is connected with conductors 34 and 35, which lead back to the opposite side of the pole changer.

In the present invention a system of supervisory signals is provided which notifies the exchange operator whenever either party has ceased talking and hung up his receiver, thus indicating that the lineshould be cleared. The subscribers set is so organized that hanging up the receiver closes a full metallic bridge at his station; it beingunderstood that the talking circuit at the subscribers station is through a condenser so that battery cannot flow. Describing this supervisory system, 75 designates a bus-line, and between this bus-line and the answering end of each cord is interposed a self-restoring signal 76; the conductors 77 in which these signals are interposed being connected with the sleeve side of the respective answering ends of the cords. Line 75 extends to and is connected with switch spring 78 of key 13. This spring normally engages inner spring 79 which is connected by conductor 80 with the innermost spring 81 of key B. This is normally closed wit-h an opposed spring 82 which is connected by conductor 83 with signal battery G. The opposite side of the battery is connected to a conductor 84 which forms a bus-line com mon to all of the line drops I, I, I, etc.,

line 84 and the tip springs of the corresponding jacks. It follows that whenever the subscriber connected with the answering end of the cord hangs up his receiver, the self-restoring signal 76, pertaining to the cord in use, is energized and indicates the line should be clear. At this point it may be explained that the line drops are operated by the battery G at central and that said operation is effected by grounding the line at the subscribers station. Ordinarily a flash-ground effected during the upward movement of the switch hook is employed to throw the line drop. The connection from line 84 through the battery G to ground is over conductor 83, spring 82, switch spring 73, a conductor 85 to an inner spring 86 cont-rolled by key B", from the latter to switch spring 78, thence by conductor 87 to a conductor 88 which connects the two switch springs 56 and 28 of key B with each other and to ground at 89 over a conductor 90. Inasmuch as those subscribers between central and the party selected are locked out in the act of selecting the latter, it follows that means must be provided for clearing or restoring the look-out instruments to normal. As much of the subscribers circuit as is necessary to understand this operation is shown at L and M at the foot of Fig. 1; the party-line being shown connected with the spring jack H.

The clearing of the lines is effected by closing a ground-to-ground circuit from central at one end through the main battery at central, over the left or tip side of the subscribers line through the several clearing relays which-are in series with said left line and to ground at the last subscribers set. At the remote end of the left-hand line is located a circuit-catching instrument N comprising a condenser,100,amagnet 101 in series with the condenser and connected to ground at 102, and a shunt conduct-or 103 which leads around the condenser to an armature 104 which, when in closed position, engages a contact 105 connected with a few of the coils of the main magnet in such manner as to form a self-retaining circuit.

It is necessary to clear both the calling and called subscribers if both are partylines, and the key B is so constituted as to effect clearing of the answering end of the cord when shifted downwardly, and the connecting or calling end when shifted in the reverse direction. Assuming the calling subscribers line is to be cleared, the circuit will be from ground at.89 to switch spring 28, back spring 91, conductors 92 and 93 to battery F, thence by conductors 94 and 95 to back spring 91 and switch spring 28, which latter is connected by conductor 26 with the bus-line 15. Line 15 is connected with the tip side of the answering end of the cord through springs 13, 5, and conductor 9. In case the called subscribers line is to be cleared, the circuit will be from ground at central through the battery over conductors 90 and 88, to switch spring 56, thence to back spring 96, to conductors 92 and 93 to battery, from battery over convductor 94 to 95, and to back spring 96,

thence to switch spring 56 and from the latter to bus-line 21 over conductor 55. Bus-line 21 is connected with spring 18 and engages spring 17 which is connected by a conductor 3 with the inner spring 8 of the cord key. Spring 3 is at this time closed with spring 3 which is connected by conductor 7 with the tip side of the plug.

In the operation of the master-key set, it is necessary that ground he cut off at central when ringing impulses are sent to line; it is necessary that the supervisory signal and line drop circuit-s be protected against the main battery and generator D when clearing and ringing and it is desirable that the exchange operators set be either short circuited or opened before either the main battery or pole changer circuits are thrown upon the line, in order to prevent reports in the operators ear. It is the function of the supervisory keys B and B to effect these results. In case the running key J is depressed, the ground at 89 is opened between the springs 7 8 and 86 of key 13, and in case the key B be shifted in either direction those same contact springs cut off the main battery F from the conductor 85 which is a part of the line drop circuit. In a similar manner movement of key 13 opens the circuit between springs 78 and 79, which form part of the supervisory circuit. For the same reasons and in the same manner springs 73 and 82 open the line drop circuit at key B, and springs 81 and 82 at the same key open the supervisory circuit. Movement of key B opens the operators listening circuit betweenthe springs 52 and 53, while movement of key B effects the same result of preventing a report in the operators receiver by short circuiting the operators jack through the springs 97 and 98 and the conductors connected therewith.

In the practical operation of telephone systems difliculty is experienced in many instances on account of residual magnetism remaining in magnets after they have been energized with current of a given polarity, such residual magnetism tending to make the armature stick to the pole pieces unless cushioned away from the latter by stops which prevent very close approach of the armature of the pole piece. Inasmuch as the working power of a magnet increases proportionately as the square of'the distance decreases between armature and pole piece it is obvious that the employment of a stop which prevents the armature from approaching closely to the pole piece, greatly impairs the eificiency of the magnet. In any system where the magnet is required to do an amount of mechanical work approaching the whole strength of the magnet it is obvious that the handicap of large cushioning stops is serious. I have invented an expedient which obviates these objections by effectually clearing out the troublesome residual magnetism, thus leaving the magnet substantially neutral when deenergized and avoiding any tendency of the armature to stick. I accomplish this result by so arranging the circuits and source of current that following each Working or main impulse sent through the magnet or magnets there is sent a very weak impulse through the magnet or magnets opposite polarity, which while so weak as to fall far below the current necessary to operate the magnet or magnets, is nevertheless effectual in neutralizing the residual magnetism. In the present instance I effect this result by placing a bridge conductor 106 across the two limbs of the circuit which are connected with the repective poles of the generator D and in this conductor interpose a resistance 107 which is so high as to permit but a very slight leakage across from the limb which is receiving the main impulse to the opposite limb. It follows that while the pole changer D is sending each impulse through the local circuit including the magnet K there occurs a divided flow or slight leakage across from line 36, through high resistance 107 to the line which connects to the external circuit, and this weak impulse is of opposite polarity to that of the full or unrestricted impulse sent over the external circuit.

I claim as my invention:

1. In a manual telephone switchboard system, the combination with a plurality of subscribers lines and suitable terminals located at said switchboard, of a connecting cord circuit, a key arranged to control the circuits through said cord, an impulsecounting selector connected with said cord circuit in a normally open key-controlled circuit and comprising a magnet-controlled actuating mechanism, a source of pulsating current connected in circuit with said magnet-controlled actuating mechanism, and means for manually setting said selector to count out a predetermined number of impulses.

2. In a manual telephone switchboard system, the combination with a plurality of subscribers lines and suitable terminals located at said switchboard, of a connecting cord circuit, a key arranged to control the circuits through said cord, an impulse-counting selector connected with said cord circuit in a normally open key-controlled circuit and comprising a magnet-controlled actuating mechanism, a source of pulsating current connected in circuitwith said magnet controlled actuating mechanism, means for manually setting said selector to count out a predetermined number of current impulses,

' subscribers lines and suitable terminals 10- cated at said switchboard, of a connecting cord circuit, a key arranged to control the circuits through said cord, an impulsecounting selector connected with said cord circuit in a normally open key-controlled circuit and comprising a magnet-controlled actuating mechanism, a source of pulsating current connected in circuit with said magnet-controlled actuating mechanism, means for manually setting said selector to count out a predetermined number of current impulses, and contact devices actuated by said selector and operating to automatically reverse the line circuit connections so as to reverse the impulses sent to line after a predetermined number have been counted out.

4. In a manual telephone switchboard system, the combination with a plurality of subscribers lines terminating at said switchboard, of a cord circuit adapted for connection with said terminals, a key controlling said cord circuit, a source of constantly re-. curring uni-directional pulsating current, a selector having a ratchet-controlled stepping mechanism, a magnet controlling said ratchet mechanism, means for manually set ting said selector to perform a predetermined number of steps, suitable circuit connections for sending current through said ratchet-controlling magnet mechanism, suitable circuit connections for synchronously sending impulses to line and contact-s actuated by said selector operating to automatically interrupt the sending to line of impulses of a given polarity upon the completion of the counting out of the number of impulses for which the selector is set.

5. In a manual telephone switchboard system, the combination with a plurality of subscribers lines terminating at said switchboard, of a cord circuit adapted for connection with said terminals, a key controlling said cord circuit, a source of constantly recurring uni-directional pulsating current, a selector having a ratchet-controlled stepping mechanism, a magnet controlling said ratchet mechanism, means for manually setting said selector to perform a predetermined number of steps, suit-able circuit connections for sending current through said ratchet-controlling magnet mechanism, suitable circuit connections for synchronously sending impulses to line and contacts actuated by said selector operating to automatically reverse the circuit connections with said source of pulsating current so as to interrupt the sending to line of impulses of a given polarity upon completion of the counting out of a definite number of im-' pulses and efiect the sending to line of impulses of opposite polarity.

6. In an electric system, the combination of an electric circuit, means for sending alternate impulses of opposite polarity over said circuit, a magnet in said circuit, and a shunt connected'with one limb of said circuit between the source of energy and magnet and operating to reduce the amount of current of one potential sent through the magnet to a fraction of the amount of opposite potential current sent there through.

7 In an electric system, the combination of an electric circuit, a magnet in said circuit, and means for sending alternate impulses of opposite polarity and difi'erentiated strength over said circuit, the impulses of one polarity being of a strength sufiicient to actuate the magnet and those of the opposite polarity being less than sufficient to operate the magnet but acting to neutralize residual magnetism in said magnet.

8. In an electric system, the combination of a source of energy, a constantly shifting commutator connected with one pole of 100 said source of electric energy, a pair of brushes with which said commutator alternately contacts, a magnet, a conductor connected with one of said brushes, including the windings of said magnet, and connected 105 at its opposite end with that pole of said source of energy opposite the pole with which said commutator is connected, a second conductor connected with the second brush and with the first conductor so as to 110 form a shunt between said brushes, and a resistance interposed in said shunt high enough to prevent operation of the magnet under normal working conditions.

9. In an electric system, the combination of a source of electric energy, a constantly shifting commutator connected with one pole of said source of energy, a pair of brushes with which said commutator alternately contacts, a plurality of magnets, a conductor connected with one of said brushes, including the windings of the several magnets and connected at its opposite end with the opposite pole of said source of energy, a second conductor connected with the second brush and with the first conductor so as to form a shunt between said brushes, a resistance interposes in said shunt high enough to prevent operation of V the magnets under normal working condi-' tions, an electrically-controlled impulsepredetermined number have been counted counter connected 1n clrcuit W1th sald source out.

of energ means for manuall settin said counter 0 0 count out a defini t e numl er of HOMER ROBERTS impulses, and means operating automati- \Vitnesses:

cally to arrest the sending to line of Work- ALBERT H. GRAVES,

ing impulses of a definite polarity when the EMILIE RosE.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). G.

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