US1294498A - Telephone-exchange system. - Google Patents

Description

A. E. LUNDELL 6L F. A. SEARN.

TELEPHONE EXCHANGE SYSTEM.

APPLxcATIoN F1110 nov.2s,1917.

1,294,498. Patented Feb.18,1919.

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A. E. LUNDELL & F. A. STEARN.

TELEPHONE EXCHANGE SYSTEM.

APPucATmN man Nov. 2e, 1911.

pQQQS. Patented Feb. 18, 1919.

4 SHEETS-SHEET 2.

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A. E. LUNDELL & F. A. STEARN.

TELEPHONE EXCHANGE SYSTEM.

APPucATloN man Nov. 2s. |911;

1,29A98, y Patented Feb.1s,1919.

4 SHEETS-SHEET 3.

A. E. LUNDELL 6L F. A. STEARN.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV.26. 1917.

ALBEN E. LUNDELL, or NEW YORK, N, Y., AND FRANKLIN A. s'rE'AEN, 0E PATENSCN, NEW JERSEY, .assreNons To WESTERN ELECTRIC COMPANY, INCORPORATED, CE NEW Yoan, N. Y., s CORPORATION or NEW Yom. l

TELEPHONE-EXCHANGE SYSTEM.

To all whom t may concern:

Be it known that we, ALBEN E. LUNDELL and FRANKLIN A. STEARN, citizens of the United States, residing at New York, in the county of Bronx and State of New York, and at Paterson, in the county of Passaic and State of New Jersey, respectively, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to automatic telephone systems, and has for its object the provision of improved means for controlling the disconnection of various switching devices thereof which are used for interconnecting telephone lines for conversation.

lt is the object of this invention to provide improved means for controlling the operation of the automatic switch mechanism or selector switches to cause their release after starting, but before completing their operation to interconnect subscribers telephone lines.

The invention readily be adapted to various types of telephone exchanges but the present embodiment is especially designed for use in semi-auton'latic systems wherein the sending apparatus is located at the central oiice and arranged for actuation by an operator in accordance with instructions recei ved from a calling subscriber. In the system disclosed the initial connection between the operator and the calling line is made by the operator by inserting a plug, at the answering end of a cord circuit, into the jack of the calling line. The outgoing end ot' each cord terminates in a selector switch` and sending mechanism is temporarily associated with the cord circuit while connection is being established, for the purpose of controlling the operation of this and other switches by means of which the connection between subscribers lines is established. These switches are of the type disclosed in Patent 1,123,696, issued Jan. 5, 1915, to E. B. Craft and J. N. Reynolds. Associated with each cord circuit and under the control of the operator, an arrangement is provided whereby under certain conditions the switches which are used in establishing a connection may be returned to their normal position before a complete connection is established.

Specification of Letters Patent.

A feature ofthe invention is an arrangement whereby this restoring means may be operated during a period in which the selector switches are being selectively operated.

This feature is accomplished by holding ythe fundamental `circuit closed upon the depression of a key by the operator, thereby causing the switch, which is being operated, to move to its uppermost position, which positlon 1s known as tell-tale. The sequence switch associated with said switch will then be rotated into talking` position. The switch which is being operated, is then returned to normal by the disconnection of the district selector, which is released when the tell-tale position of the switch under selection is reached.

The movement of the selector mechanism may thus, be checked before it has completed the desired connection and be caused immediately to return to normal. Thus in casev the operator has made a mistake in manipulation of the sending apparatus, she is enabled to start a new connection immediately. Hereto-fore, after the first selector' switch had been selectively operated, the connection could not be released until after the last series of impulses had been sent from the sending apparatus.

ln the drawing, Figure l shows circuits and apparatus which are directly associated with a cord circuit terminating in a selector switch, this beingxlrnown as the district switch; Fig. 2 shows the circuits associated with an incoming selector switch; Fig. 3 shows the circuits associated with a final selector switch; and Fig. 4 shows the circuits associated with a sender controlling mechanism and a cord nder.

The operation of the system will now be described. First, a call will be traced from a calling to a called subscriber and then the means for wiping out a call will be de scribed. This last description will only refer to the operation of the system after one of a train of switches has been operated and is in a position to allow the operation of the remaining switches of the train, since this invention relates only to the release of the switches at this particular period of the operation of the system.

Then the subscriber at substation A removes his receiver from the hook, a circuit is completedfrom grounded battery, lett-v,

Patented Feb.' 18, 1919.

Application filed November 26, 1917. Serial No. 204,081. i

hand winding of relay 101, outer armature and back contact of relay 102, apparatus of substation A, back contact and inner armature of relay 102, right-hand winding of relay 101, to ground. Relay 1011 becomes energized and closes a circuit for lamp 108.

rEhe operator seeing the lighted lamp inserts the plug 104 lintoV the jack 105 associated with the calling line. A circuit is then completed from grounded battery, Winding of cutoill relay 102, sleeve of jack 105, sleeve of plug 104, winding of relay 106, to ground. Relay 102 is energized and causes the de'e'nergization of relay 10'1 in a well-known manner. Relay 106 becomes energized and closes a circuit from grounded battery, power magnet of sequence switch 100, upper lett-hand contact of sequence switch spring 107, front contact and arma* ture of relay 106, to ground, for moving the sequence switch 100 out ot position 1 and into position 2.

1n position 2, a circuit is closed from grounded battery, winding of relay 401, lower contact of sequence switch spring 402, conductor 403, lett-hand contact of sequence switch spring 108, to ground. Relay 401 by attracting its lett-hand armature closes a circuit from grounded battery, power magnet ot1 sequence switch 400, upper right-hand contact of sequence switch sprin g 404, left-hand armature and front contact of relay 401, to ground, for moving the sequence switch 400 out of position 1 and into position 2. as soon as the sequence swiich 400 reaches position 1-1/2 a locking circuit for relay 401 maintains this relay energized, this circuit being traced from grounded battery-winding of relay 401, right-hand armature and front Contact of relay 401, up-

er contacts or sequence switch spring 402` hack contact ad right-hand armature of relay 405, to ground.

1n position 2 of sequence switch 400, a circuit is closed from grounded battery, winding of updrive magnet 406, contact oiI sequence switch spring 407, front contact and left-hand armature of relay 401, to ground. Under the control of the updrive magnet 406, the brushes of the cord tinder are moved upward. As soon as the brush 408 engages terminal 409, a circuit is closed from grounded battery, winding of relay 405, left-hand Contact of sequence switch spring 411, brush 408, terminal 409, conductor 410, lower right-hand contact of sequence switch spring 108, to ground. -Relay 405 becomes energized and closes a locking circuit for itself from grounded battery, winding ot relay 405, right-hand Contact of sequence switch spring 411, left-hand armature and front contact of relay 405, brush 412, terminal 413, conductor 414, upper contact oit sequence switch spring 108, to ground, Relay 405 by attracting its right-hand ar- Langues mature opens a branch ot the energizing circuit of relay 401, but this relay is held energized until the brushes are accurately centered due to a circuit being closed from grounded battery, windingof relay 401, righthand armature and front contact of relay 401, conductor 415, conducting segment of commutator 416, commutator brush 417, to ground. As soon as the brushes are accurately centered en the terminals, the brush 417 engages an insulated segment of the commutator 416, thus causing the relay 401 to be denergized and open the energizing circuit of the updrive magnet 406. The denergization of relay 401 also closes a circuit from grounded battery, power inagnet of sequence switch 400, upper left-hand contact of sequence switch spring 404, back Contact and left-hand armature of relay 401, to ground, for moving the sequence switch 400 out of position 2 and into position 3. 1n position 3, a circuit is closed from grounded battery, power magnet of sequence switch 490, lower contact of sequence switch spring 492, contact of sequence switch spring 418, to ground, for moving the sequence switch 400 out of position 1 and into position 3.

At the time relay 106 is energized, by the insertion of the plug 104 into the jack 105, a circuit is also completed from grounded battery, power magnet of listening key sequence switch 175, contact of sequence switch spring 176, front contact and armature of relay 106, to ground` for moving the listening key sequence switch out of position 1 and into position 5. As Isoon as the listening key sequence switch reaches position 4, the operators telephone sct is connected to the cord associated with the plug 104, thereby enabling the operator to ascertain the desired number from the calling subscriber. 14s soon as she obtains this number', she sets it up upon her key board. As is well known in the art, the operator has one row of oiiice keys and four rows or' digit keys, and by pressing one key ot each row. six sets of impulses are transmitted due to translation. 1n order, however, to simplify the disclosure and description in the present invention. a key for each set of impulses is shown, it being assumed that there are two oihce keys instead of one.

1t will be assumed that the operator depresses the No. 1 key in the oflice tens row- No. 2 key in the oliice units row, No, 0 key in the thousands row, No. 2 key in the hundreds row, No. 1 key in the tens row, and the No. 2 key in the units row. As soon as she has set up this number she depresses the start key 491` thereby completing a circuit from grounded battery, power magnet of sequence switch 400, lower lefthand contact of sequence switch spring 404. key 491, to ground, for moving .sequence switch 40G-out of position 3 and into position 8. A circuit is also completed at this time from grounded battery, power magnet ot' sequence switch 490, upper right-hand contact of sequence switch spring 492, key 491 to ground, for moving the sequence switch 490 out of position 3 and into position 6.

As soon as the sequence switch 490 reaches position 6, the fundamental circuit is closed :t'rom grounded battery, winding of relay 109, lower right-hand contact of sequence switch spring 110, conductor 111, terminal 419, brush 420, right-hand armature and back contact of relay 421, contact of sequence switch spring 493, outer armature and back contact of counting'. relay 0, winding of stepping relay 494, brush 422, terminal 423, conductor 424, upper left-hand contact of sequence switch spring 112, to ground.

The relay 494 becomes energized, and by attracting its armature, completes a Circuit from grounded battery, winding of counting relay 1, armature and back contact of counting relay l', conductor 497, No. 1 key of the oiiice tens row, lower contact of sequence switch spring 496, armature and front contact of relay 494, to ground. Counting relay No. 1 by attracting its armature closes a circuit from grounded battery, windings of counting relays 1 and 1, armature and front contact of counting relay 1, upper right-hand contact of sequence switch spring 485, to ground. Counting relay 1', however, does not become energized at this time, due to the shunt around its winding which is closed at the armature and front contact of the stepping relay 194.

Relay 109 also becomes energized at the time the fundamental circuit is closed and closes a circuit from grounded battery, power magnet of sequence switch 100, lower contact of sequence switch spring 113, right` hand armature and front Contact of relay 109, to ground, for moving the sequence switch 100 out of position 2 and into position 3. While the sequence switch is mov-` ing from position 2 into position 3, relay 109 is held energized over a locking circuit extending through its left-hand armature and front contact and the lower left-hand contact of sequence switch spring 110, to

ground over the circuit previously described. In position 3 a circuit is closed from grounded battery, winding of updrive magnet 114, upper contact of sequence switch spring 115, front contact and righthand karmature of relay 109, to ground. Under the control of the updrive magnet 114, the brush rod 116, carrying the line brushes 117, 118 and 119 and commutator brushes 120 and 121` is moved upward. As soon as the commutator brush 120 engages the first conducting segment of the commutator 122, a shunt circuit is closed around the stepping relay 494, this circuit being traced from grounded battery, winding of relay 109, lett-hand armature and front contact of relay 109, lower left-hand and upper right-hand contacts of sequence switch spring 110, conducting segment of commutator 122, commutator brush 120, to ground. Stepping relay 494 denergizes and opens the shunt around the counting relay 1 which becomes energized. As soon as the commutator brush 120 engages the rst insulated segment of the commutator 122, the stepping relay 494 is again energized and a circuit for the 0 counting relay is completed through the armature and front contact of the No. 1 counting relay. The 0 counting relay becomes energized and closes a circuit for the 0 counting relay which, however, does not become energized on account of the shunt around its winding which is closed by the armature and front contact of the stepping relay 494. As soon as the commutator brush 120 engages the second conducting segment of the commutator 122, the stepping relay 494 is again deenergized thereby causing the -energization of the 0 counting relay. The 0 counting relay by attracting its inner armature closes a circuit from grounded battery, power magnet of sequence switch 490, inner armature and front contact of the 0 counting relay, left-hand contact of sequence switch spring 485, to ground, for moving the sequence switch 490 out of'position 6 and into position 8. The relay 0 by attracting its outer armature opens the fundamental circuit, but the relay 109 is held energized until the eommutator brush 120 engages the second insulated segment of the coinmutator 102, due to the shunt circuit previously described. As soon as the commutator brush engages this insulated segment, relay 109 denergizes and opens the circuit of the 11p-- drive magnet 114. Brushes 117, 118 and 119 are now accurately centered upon the first set of terminals of the second group in the district terminal bank. The de nergization of relay 109 also closes a circuit from grounded battery, power magnet of sequence switch 100, upper left-hand contact of sequence switch spring 113, right-hand armature and back contact of relay 109, to ground, for moving the sequence switch 10'0 out of position 3 and into position 6.

In position 6 a circuit is closed from grounded battery, left-hand winding of relay 123, upper right-hand and lower left'hand contacts of sequence switch spring 124, to ground. Relay 123 by attracting its outer right-hand armature completes a circuit from grounded battery, power magnet of sequence switch 100, lower right-hand contact ot sequence switch spring 125, outer right hand armature and Jfront contact of relay L recati-ee 123, to ground, for moving the sequence switch 100 out ot' position 6 and into position 7. It the trunk with which the brushes 117, 113 and 119 are in engagement, is busy, ground will be connected directly to the test terminal thereof, so that when relay 123 becomes energized it closes a locking circuit for itselt' from grounded battery, right-hand winding of relay 123, inner right-hand armature and front contact of relay 123, conductor 126, test brush 119, test terminal 127, to ground. The relay 123 will then be energized when the sequence switch 100 reaches position 7 and a circuit will be closed from grounded battery, winding ot' updrive magnet 114, lower contact of sequence switch spring 115, outer rightfhand armature and front contact of relay 123, to ground. Under the control oit the updrive magnet 114, the brushes 117, 118 and 119 are moved upward until the test brush 119 engages the test terminal 127 of an idle trunk, at which time the circuit through the right-hand winding ot re lay 123 will not receive suiicient current to hold its armatures, due to the ground being connected to the test terminal through a high resistance, this circuit being traced from the test terminal 127, conductor 273, resistance 274, to ground. A. circuit, however, will be closed for maintaining the relay 123 energized until the brushes are accurately centered upon the terminals ot this idle trunk, this circuit being traced from grounded battery, lett-hand winding ot' relay 123, upper contacts of sequence switch spring 124, front Contact and left-hand armature ot relay 123, conductor 128, conducting segment of commutator 129, commutator brush 121, to ground. As soon as the brushes are accurately centered the commutator brush 121 will engage an insulated segment of the commutator 129, thereby causing the retraction of the armatures ot' relay 123. Relay 123 by retract-ing its outer right-hand armature opens the circuit ot the updrire magnet 114 and closes a circuit from grounded battery, power magnet of sequence switch 100, lower left-hand contact of sequence switch spring 125, outer right-hand armature and back Contact of relay 123, to ground. for moving the sequence switch 100 out ot position 7 and int-o position 11. When the sequence switch 100 reaches position 6-1/'2 and relay 123 is denergized, `ground is connected directly to the test terminal 127, to cause the selected trunk to test busy at the multipley test terminals thereof. this circuit being traced from ground. upper right contact ot sequence switch spring 112, inner right-hand armature and back Contact ot' relay 123 and brush 119 to test terminal 127.

As soon as the sequence switch 100 reaches position 11 and the sequence switch 490 reaches position 8, the fundamental circuit is again closed, this circuit now being traced from grounded battery, upper contacts of sequence switch spring 201, Contact 227 winding of relay 202, lower and upper lefthand contacts of sequence switch spring 203, conductor 229, resistance 228, conductor 205, terminal 131, brush 117, lower Contact of sequence switch spring 132, conductor 111, terminal 419, brush 420, right-hand armature and back contact ot relay 421, contact of sequence switch spring 493, outer aru'iature and back contact of counting relay 0, winding of stepping relay 494, brush 422, terminal 423, conductor 424, upper contact of sequence switch spring 133, brush 118, terminal 130, conductor 206, resistance 207, upper left-hand Contact of sequence switch spring 208, winding ot' relay 209, lower contact of sequence switch spring 210, to ground. Relays 202 and 209 are energized and close a circuit from grounded battery, power magnet of sequence switch 200, lower Contact of sequence switch spring 211, armature and front contact of relay 209, upper contact ot sequence switch spring 212, front contact and right-hand armature of relay 202, to ground, for moving the sequence switch 200 out of position l and into position 2.

1n position 2, relay 202 is still maintained energized due to a circuit being closed from grounded battery, upper contacts ot sequence switch spring 201, contact 227, winding of relay 202, lower right-hand contact of sequence switch spring 230, left-hand armature and front contact of relay 202, upper contacts of sequence switch spring 203, to ground, over the fundamental circuit previously described. A circuitl is now completed from grounded battery, winding of updrive magnet 217, lower contact of sequencev switch spring 213, right-hand armature and front, contact otl relay 202 to ground. Under the control of the updrive magnet 217, the line brush sets and the commutator brushes 231, 232, 233 and 234 are moved upward. When the fundamental circuit is closed in the manner just described, the stepping relay 494 is energized and completes a circuit from grounded battery, winding of counting relay 2, armature and back contact of counting relay 2, conductor 498, No. 2 key of the office units row, upper right-hand contact of sequence switch spring 496, armature and front contact ot stepping relay 494, to ground. As the commutator brush 231 moves upward, it engages the conducting segments of the commutator 235. Each time the commutator brush 231 engages one of these segments, a circuit is closed from grounded battery, upper contactsot sequence switch spring 201, Contact 227, winding of relay 202, lower righthand Contact of sequence switch spring 230, lett-hand armature and front contact of relay 202, conductor 246, upper contacts ot sequence switch spring 214, conducting segments of commutator 235, commutator rush 231, lower right-hand contact of sequence switch spring 220, to ground. This circuit places a shunt around the relay 494 which denergizes and operates the countm'g relays in thesame manner as above described. The commutator brush y231 continues to move upward until it engages the third conducting segment, at which time the 0 counting relay will be energized. This relay by-l attracting its inner armature completes a circuit from grounded battery, power magnet of sequence switch 490, inner armature and front Contact of counting relay 0', upper left-hand contact of sequence switch spring 485, to ground, for moving the sequence switch 490 out of position 8 and into position 10. As soon as the sequence switch 490 leaves positionl 8 the counting relays are deenergized, due to the 'opening of their locking circuits at the upper right-hand contact of sequence switch spring 485. Counting relay 0 by attracting its outer armature opens the fundamental circuit and opens the original energizing circuit of relay 202. As soon as the commutator brush 231 engages the third insulated segment of the commutat-or 235, relay 202 becomes denergized and by retracting its right-hand armature opens the circuit of the updrive magnet 217, and closes a circuit from grounded battery, power magnet of sequence switch 200, upper right-hand contact of sequence switch spring 211, righthand armature and back contact of relay 202, to ground, for moving the sequence switch 200 out of position 2 and into position 3.

As soon as the sequence switch 200 reaches position 3 and sequence switch 490 reaches position 10, the fundamental circuit is again established, causing the energization of the relays 202 and 494. Relay 494 by attracting its armature completes a circuit from grounded battery, winding of counting relay 0, conductor 499, No. 0 key ofthe thousands row, upper left-hand contact of sequence switch spring 496, to ground. Relay 202 by attracting its right-hand armature closes a circuit from grounded battery, power magnet of sequence switch 200, upper left-hand contact of sequence switch spring 211, front contact and right-hand armature of relay 202, to ground. for moving the sequence switch 200 out of position 3 andinto position 4. Relay 202 by attracting. its lefthand armature closes a locking circuit for itself as previously described.

In position 4 of sequence switch 200, a circuit is completed from grounded battery, winding of updrive magnet 217, lower contact of sequence switch spring 213, righthand armature and front contact of relay 202, to ground. Under the control of the updrive magnet the line and commutator brushes are again moved upward. As the brush rod 236 moves upward the third set of brushes is tripped due to the energization of the trip magnet 216, this energizing circuit being traced from grounded battery, winding of trip magnet 216, upper contact of sequence switch spring 215. to ground. As soon as the commutator brush 232 e11- gages the first conducting segment of the commutator 237, a circuit is closed from grounded battery, upper contacts of sequence switch spring 201, contact 227, winding of relay 202. lower right-hand contact of sequence switch spring 230, left-hand armature and front Contact of relay 202, upper and lower right-hand contacts of sequence switch spring 203, conductor 238, conducting segment of commutator 237, brush 232, lower right-hand contact of sequence switch spring 220, to ground. This circuit shunts out the stepping relay 494, which in turn causes the energization of the 0 counting relay in the same manner as previously described. The 0 counting relay by attracting its inner armature completes a circuit from grounded battery, power magnet of sequence switch 490, inner armature and front contact of 0 counting relay, left-hand contact of sequence switch spring 485, to ground, for moving sequence switch 490 out of position 10 and into position 12. The 0 counting relay by attracting its outer armature opens the fundamental circuit, thereby allowing the relay 202 to denergize as soon as the commutator brush 232 engages an insulated Segment of the commutator 237. Relay 202 by retracting its right-hand armature opens the energizing circuit of the updrive magnet 2.17 and closes a circuit from grounded battery, power magnet of sequence switch 200, upper right-hand contact of sequence switch spring 211, back contact and right-hand armature of relay 202, to ground, for moving the sequence switch 200 out of position 4 and into position The brushes 223, 224 and 225 are now in engagement with the tirstset of terminals in the selected group.

In position 5 of sequence switch 200 a circuit is closed from grounded battery. lower contact of sequence switch spring 218, lefthand winding of relay 219, upper and lower right-hand contacts of sequence switch spring 220, to ground. Relay 219 by attracting its lett-hand armature closes a circuit from grounded battery, power magnet of sequence switch 200, upper contact of sequence switch spring 239. left-hand armature and front contact of relay 219, to ground, for moving the sequence switch 200 out of position 5 and into position 6- If the brush 223 is in engagement with the terminal of a busy trunk. a circuit is now closed from grounded battery, right-hand winding of relay 219, lower contact of sequencevswitch spring 221, right-hand armature and front contact of relayr 219, resistance 222, brush 223, to ground, through the test terminal 241 of the busy trunk. Relay 219 is thereby held energized in position 6 and completes a circuit from grounded battery, winding of updrive magnet 217, 4upper contact of sequence switch spring 213, left-hand armature and front contact of relay 219 to ground. Under f the control of the updrive magnet 217, the

brushes are moved upward over the contacts of the selected group of trunks until the test brush 223 engages the test terminal of an idle trunk, at which time the relay 219 denergizes, duc to the absence of ground on the test terminal. Relay 219 is held energized, however, until the brushes are accurately centered on the terminals of the idle trunk, due to a circuit being closed from grounded battery, lower contact of sequence switch spring 218, left-hand winding of relay 219, conducting segment of commutator 240, commutator brush 234, lower left-hand contact of sequence switch spring 220, leftlia-ud armature and front contact of relay 219, to ground, As soon as the brushes are accurately centered on the terminals of the idle trunk, the conimutator brush 234 engages an insulated segment of the commutator 240, thus causing the denergization of relay 219. Relay 219 by retracting its lefthand armature opens the circuit of the updrive magnet 217 and closes a circuit from grounded battery, power magnet of sequence switch 200, lower contacts of sequence switch spring 214, left-hand armature and back Contact of relay 219 to ground, for moving the sequence switch 200 out of position G and into position 7. As soon as the sequence switch reaches lposition 6-3/4, ground is connected to the test terminal 241 of the selected trunk and causes this trunk to test busy, this circuit being traced from test terminal 241, brush 223, resistance 222, lower contact of sequence switch spring 244, to ground.

1n position 7, a circuit is closed from grounded battery, upper cont-acts of sequence switch spring 201, contact 227, winding of relay 202, left-hand Contact of sequence switch spring 230 to ground. Relay 202 by attracting its right-hand armature completes a circuit from grounded battery, power magnet of sequence switch 200, upper left-hand contact of sequence switch spring 211, right-hand armature and front contact of relay 202, to ground, for moving sequence switch 200 out of position 7 and into position 9. Relay 202 by attracting its lefthand armature completes a locking circuit for itself, this circuit being traced from grounded battery, upper contacts of sequence switch spring 201, contact 227, winding of relay 202` right-hand contact of sequence switch spring 230` left-hand armature and front contact of relay 202, conreeaaes ductor 246, right-hand contact of sequence switch spring 247, conductor 248, brush 2247 fterminal 242, conductor 301, lower left-hand and upper right-hand contacts of sequence switch spring 302, resistance 303, yto ground. Relay 202 is lleld energized over this circuit until the sequence switch 300 leaves position (i.

As soon as the sequence switch 200 reaches position 9 and the sequence switch 490 rear-.lies position 12, a circuit is completed from grounded battery, winding of relay 304, lower left-hand Contact of sequence switch spring 305, conductor 306,'terminal 243, brush 225, conductor 249, upper lefthand contact. of sequence switch spring 250, resistance 228, over the fundamental circuit previously' described, -to ground, through the resistance 207 and the contact of sequence switch spring 251. Relays 304 and 494 become energized. Relay 494 completes a circuit from grounded battery, winding of counting relay No. 2,l armature and back contact of counting relay No. 2f, conductor 439, No. 2 key of the hundreds row, lower left-hand contact of sequence switch spring 495, armature and front contact of relay 494, to ground. Counting relay No. 2 becomes energized and closes a circuit for counting relay No. 2 in the same manner as above described.

Relay 304 by attracting its right-hand armature closes a locking circuit for itself from grounded battery, winding` of relay 304. right-hand armature and front contact of relay 304, lower right-hand Contact of sequence switch spring 305, to ground, over the fundamental circuit. Relay 304 by attracting its left-hand armature completes a circuit from grounded battery, winding of relay 307, lower left-hand and upper right-hand contacts of sequence switch spring 303, left-hand armature and front Contact of relay 304 to ground. Relay 307 by attract-ing its right-hand armature completes a locking circuit for itself from groundedbattery, winding of relay 307, right-hand armature and front contact of relay 307, resistance 309, conductor 310, terminal 241, brush 223, resistance 222, lower 115 contact of sequence switch 244, to ground. Relay 307 by attracting its left-hand armature closes a circuit from grounded battery, power magnet of sequence switch 300, upper right-hand Contact of sequence switch spring 12o 311, left-hand armature and front Contact of relay 307, to ground, for moving the sequence switch 300 out of position l and into position 2.

1n position 2 a circuit is completed from 12e grounded battery, winding of updrive magnet 312, lower contact of sequence switch spring 313, conductor 314, left-hand arma- =ture and front contact of relay 304, to ground. Under the control of the updrive 130 magnet 312 the line brush sets 315, 316 and 317, the commutator brushes 318, 319 and 320 are moved i-ipward.v As soon as the commutator brush 319 engages the first conducting segment of the commutator 321, a circuit is completed from grounded battery,

winding of relay304, right-hand armature tinue 'to move upward until the countingl relay 0 is energized, at which time the fundamental circuit is opened. Relay 304 then becomes denergized as soon as the commutator 319 engages an insulated segment ot' the commutator 321. Relay 304 by retracting its left-hand armature opens the circuit ot' the updrive magnet 312 and completes a circuit from grounded battery, power magnet of sequence switch 300, lower right-hand and upper left-hand contacts of sequence switch spring 308, left-hand armature and back contact of relay 304, to ground, for moving the sequence switch 300 out of position 2 ergization of counting relay 0 also completes a circuit from grounded battery, power magnet of sequence switch 490, inner armature and front contact of counting rela)r 0. lett-hand contact of Sequence switch spring 485, to ground, for moving the sequence switch 490 out of position `12 and into position 14.

As soon as the sequence switch 300 reaches position .3 and the sequence switch 490 reaches position 14, the fundamental circuit is again established, causing the energization of relays 304 and 494. Relay 494 by attracting its armature completes a circuit from grounded battery, winding of counting relay 1, armature and back contact ot counting relay 1', conductor 48T, No. 1 lrey of thc tens row, lower right-hand contact of scquence switch spring 495, armature and front contact otl relay 494, to ground. Counting relay No. 1. by attracting its armature. closes a circuit through counting relay No. 1, in the same manner as above described. lelay 304 b v attracting itsI right-hand armature closes the locking circuit for itself as previously described. and by attraiting its left-hand armature closes a circuit from grounded battery. sequence switch 300. lower and upper right-hand contacts of sequence switch 308, lett-hand armature and front contact of relay 304. to ground, for moving` the sequence switch 300 out of position 3 and into position 4, and as soon as sequence and into position 3. The enswitch 300 leaves position 4, the circuit of the updrive magnet 312 is closed, as previously described. Under the control of the updrive magnet 312, the brushes are again moved upward. The third set of brushes is tripped at this time, since the trip magnet 324 is energized due to a circuit closed from grounded battery, winding of trip magnet 324, contact of sequence switch spring 4325, to ground. As soon as the commutator brush 320 engages the first conducting segment of commutator 327, a circuit is closed from grounded battery, winding of relay 304, right-hand armature Iand front cont-act of relay A304, lower right-hand contact of sequence switch spring 305, lower contact of sequence switch spring 322, conducting segment of comn'uitator 327, commutator brush 320, lower contact of sequence switch spring 323, to ground. This circuit closes a shunt around the stepping relay 494, which deenergizes and allows the counting relay 1 to energize. As the brushes move upward the counting relays are actuated in the same manner as above described, and until thc counting relay 0 is again energized. Counting relay 0 by attracting its inner armature completes a circuit from grounded battery, power magnet of sequence switch 490, inner armature and front contact of counting relay 0, left-hand contact of sequence switch spring 485, to ground, for moving the sequence switch 490 out of position 14 and into position 16. Counting relay 0 by attracting its outer armature again opens the fundamental circuit, thereby causing the de'e'nergization of relay 304. as soon as the commutator brush 320 engaUes an insulated segmentof comlnutator 32. Relay 304 by retracting its left-hand armature opens the circuit of the updrive magnet 312, and closesa circuit from grounded battery, power magnet of sequence switch 300, lower right-hand and upper left-hand contacts of sequence switch spring 308, lett-hand armature and back contact of relay 304. to ground. tor moving the sequence switch 300 out of position 4 and into position 5.

As soon as they sequence switch 300 reaches position 5 and the sequence switch 490 reaches position 16, the fundamental circuit is again established, causing the energization of relays 304 and 494. Relay 494 b v attracting its armature completes a circuit from grounded battery, winding of counting relay 2, armature and back contact of counting relay 2, conductor 486, No. E2 key of the units row, upper contact ot' sequence switch spring 495, armature and Yl'ront contact of relay 494, to ground. Counting relay No. 2 lby attracting its armature closes a circuit for counting rela-y No. 2. in the same manner as above described. Relay 304 by attracting its right-hand armature closes the locking circuit for itself, previousl described, and by attracting its lefthan armature completes a circuit for moving the sequence switch 300 out of position 5 and into position 6, and as soon as the sequence switch reaches position 6 a circuit is closed from grounded battery, winding ot' slow-speed updrive magnet 328, upper contact of sequence switch spring 313, left-hand armature and t'ront contact of relay 304, to ground. Under the control ot magnet 328, the selected brush set is moved upward. As the brushes move upward, the brush 319 by engaging the commutator 321. actuates the counting relays in the same manner as above described. As soon as the counting relay 0 is energized, a circuit is completed from grounded battery, power magnet of sequence switch 490. inner armature and front contact otl counting relay 0', left-hand cont-act ofsequence switch spring 485, to ground. for moving the sequence switch 490 out of position 16 and into position 1. As soon as the sequence switch 490 reaches position 1, a circuit is closed from grounded battery, power magnet of sequence switch 100, lower Contact ot sequence switch spring 107, conductor 134, terminal 4.31, brush 432, contact of sequence switch spring 433, upper Contact ot sequence switch spring 484, to ground, for moving the sequence switch 100 out of position 11 and into position 16` In position 1 of sequence switch 490, a circuit is also closed :trom grounded battery, winding of downdrive magnet 428 of the cord finder, contact of sequence switch spring 429, contact of sequence switch spring 483, to ground. Under the control of the downdrive magnet 428, the brushes of the cord finder are returned to their normal position. As soon as the commutator brush 417 reaches its normal position, a circuit is closed from grounded battery, power magnet of sequence switch 400, lower right-hand contact of se` quence switch spring 404, conductor 430, conducting segment 451, commutator brush 417, to ground, for moving the sequence switch 400 out ot position 8 and into position 1.

`When the fundamental circuit was opened by the energization ot counting relay 0, relay 304 became denergized as soon as the commutator brush 319 engaged an insulated segment of the commutator 321. Relay 304 by retracting its lett-hand armature opens the circuit of the updrive magnet 328 and closes a circuit from grounded battery, power magnet of sequence switch 300, lower righthand and upper lett-hand contacts of sequence switch spring 308. lett-hand armature and back contact of relay 304, to ground, for moving the sequence switch 300 out of position 0 and into position 7. The brushes 315, 316 and 317 are now in engagement with the terminals ot the desired line.

As soon as the sequence switch 300 leaves recense position 6, the holding circuit of relay 202 is opened at the upper right-hand contact of sequence switch spring 302. The deenergization of relay 202 closes a circuit from grounded battery, power magnet of sequence switch 200, upper right-hand contact of sequence switch spring 211, righthand armature and back Contact of relay 202, to ground, for moving the sequence switch 200 out of position 9 and into position 10. A circuit is now closed from grounded battery, lower lett-hand Contact of sequence switch spring 252, winding of relay 253, upper left-hand winding of repeating coil 254, conductor 205, terminal 131, brush 117, upper contact of-sequence switch spring 132, upper right-hand winding-ot repeating coil 135, to ground. Relay 253 closes a locking circuit for itself from grounded battery, left-hand contact of sequence switch spring 252, winding of relay 253, lower contact of sequence switch spring 255, armature and front contact of relay 253, conductor 256, upper contact of sequence switch spring 218, lefthand winding of relay 219, upper and lower right-hand contacts of sequence switch spring 220, to ground. Relay 219 becomes energized and closes a locking circuit for itself from grounded battery, right-hand winding of relay 219, lower contact of sequence switch spring 221, right-hand armature and front contact of relay 219, lower contact of sequence switch spring 244 to ground. Relay 219 also closes a circuit from grounded battery, lower contact of sequence switch spring 258, winding of relay 259, right-hand armature and front contact of relay 219, lower contact of sequence switch spring 244, to ground. Relay 259 completes a circuit from grounded battery, resistance 262. left-hand armature and front contact of relay 259, winding of relay 202, lower lett-hand contact of sequence switch spring 230, to ground. Relay 202 becomes energized and completes a circuit from grounded battery, power magnet of sequence switch 200, upper left-hand contact ot1 sequence switch spring 211, right-hand armature and front contact of relay 202,'to ground, :tor moving the sequence switch 200 out of position 10 and into position 12.

As soon as sequence switches 200 and 300 reach positions 11 and 7, respectively, a. circuit is closed from grounded battery, winding ot relay 304, lower left-hand contact ot sequence switch spring 305, conductor 306, terminal 243. brush 225, conductor 249, lower contact of sequence switch spring 250, upper armature and back contact of relay 260, upper right-hand winding of repeating coil 254. to ground. Relay 304 by attracting its lett-hand armature completes a circuit for moving the sequence switch 300 out of position 7 and into position 8, this circuit being traced from grounded battery, power magnet of sequence switch 300, lower and upper fight-hand contacts of sequence switch spring 308, left-hand armature and front contact of relay 304, to ground.

It will first be assumed that the called line is idle and a high battery potential will then be found upon the test terminal 328. As soon as the sequence switch 300 reaches position 8, a circuit is closed from grounded battery, winding of cutoi relay 331, terminal 328, brush 315, contact ot' sequence switch spring 332, left-hand low resistance winding of relay 333, lower contacts of sequence switch spring 334, righthand` high resistance winding of relay 333, to ground. Relay 333 becomes energized and completes a. locking circuit for itself, this circuit being traced through its lefthand low resistance winding and its lefthand armature and front contact, to ground. T his circuit shunts out the high resistance of winding of relay 333 and so reduces the potential on the terminal 328 as to cause the line to test busy. The energization of relay 333 also closes `a circuit from grounded battery, power magnet of sequence switch 300, lower left-hand contact of sequence switch spring 311, right-hand armature and front contact of relay 333, to ground, for moving the sequence switch 300 out of position 8 and into position 10. As soon as the sequence switch 300 leaves position 7-1/4, the relay 304 denergizes so that the sequence switch 300 is immediately moved out of position 10 and into position 14, due to a circuit being closed from grounded battery, power magnet of sequence switch 300, lower right-hand and upper lett-hand contacts of sequence switch spring 308, lefthand armature and back contact of relay 304, to ground. Sequence switch 300 is moved out of position 14 and into position 16, due to the circuit previously described, for moving it out of position 8. In position 16, the line conductors 306 and 301 are extended through to the called line.

As soon as the sequence switch 200 reaches position 11 when moving from position 10 to position 12 in the manner above described, the relay 253 is held energized over a circuit traceable from grounded battery, upper contact of sequence switch spring 261, lett-hand armature and front contact of relay 202, lower right-hand contact of sequence switch spring 252, winding of relay 253, upper left-hand winding of repeating coil 254, conductor 205, terminal 131, brush 117, upper contact of sequence switch spring 132, upper right-hand winding of repeating coil 135 to ground. In position 11, the relay 253l completes a circuit from grounded battery, upper contact ot sequence switch spring 255, armature and front contact of relay 253, upper contact of sequence switch spring 258, winding of relay 259, upper left-hand contact of sequence switch spring 244, to ground. This circuit is maintained energized until the sequence switch 200 leaves position 14. Relay 259, by holding its lett-hand armature attracted, still maintains the circuit for relay 202 closed.

It will be assumed that the commutator brush 233 is in engagement with an insulated segment. ot' the commutator 263, when the sequence switch 200 reaches position 12. A circuit will then be closed from` grounded battery, upper contact of sequence switch spring 255, armature and front contact of relay 253, upper contacts of sequence switch spring 258, winding of relay 260, armature and back Contact of relay 264, armature and back contact of relay 265, left-hand armature and back Contact of relay 219, to ground. Relay 260 becomes energized and connects ringing current to the called line over a circuit from grounded sourcev of ringing current, left-hand winding of relay 265, lefthand Contact of sequence switch spring 266, lower armature and front contact of relay 260, left-hand contact of sequence switch Spring 247, conductor 248, brush 224, terminal 242, conductor 301, lower contacts of sequence switch spring 302, brush 316, terminal 329, apparatus of substation B, terminal 330, lbrush 317, upper contact of sen quence switch spring 305, conductor 306, terminal 243, brushf 225, conductor 249, lower contact of sequence switch spring 250, upper armature and front contact of relay 260, to ground.

Relay '265 does not become energized at this time due to the high resistance in the circuit at the substation B. Ringing current is rthus applied to the called line until the called party answers, at which time relay 265 receives suiiicient current and attracts the armature. A circuit is then closed rthrough the winding of relay 264,v which had previously been shunted out by the circuit through the armature and back contact of relay 265 and the armature and back Contact of the relay 264. Relay 264 by attracting its armature closes a locking circuit for itself and places a shunt around relry 260. Relay 260 denergizes and connects the subscribers lines together for conversa-tion.

The operator now depresses the listening out key 179, provided she has not previously done so, which completes a circuit from grounded battery, power magnet of sequence switch 175, upper contact of sequence switch spring 177, key 179 to ground, for moving the sequence switch 175 into position 8, which is the listening out position.

As soo-n as the subscribers are through talking and have replaced their receivers, the operator receives a disconnect signal in the well-known manner. She then removes plug 104 from jack 105. Relay 106 denergizes and completes a circuit from grounded battery, power magnet of sequence switch 175, lower contact of sequence switch sprlng 177, armature and back contact of relay 106 to ground, for moving the sequence switch 175 out of position 8 and into position 1. Y

-The denergization of relay 106 also closes a circuit from grounded battery, power magnet of sequence switch 100, upper right-hand contact of sequence switch spring 107, armature and back Contact of relay 106 to ground, for Ind-ving the sequence switch 100 out of position 16 and into position 18. 1n position 18, a circuit is completed from grounded battery, winding of downdrive magnet 138,-lower contact of sequence switch spring 112 to' ground. Under the control of the downdrive magnet 138, the brush Upd 116 is returnedto its normal position. As soon as the commutator brush 120 reaches its normal position, a circuit is completed from grounded battery, power magnet of sequence switch 100, upper right-hand contact of sequence switch spring 113, conducting segment 139, commutator brush 120 to ground, for moving the sequence switch 100 lout of position 18 and into position 1.

As soon as the sequence switch 100 leaves position 16, the holding' circuit of relay 253 is opened at the upper left-hand contact of sequence switch spring 132. Relay 253 by retracting its armature opens the circuit of relay 259, which denergizes, and opens the circuit of relay 202. Relay 202 by retracting its rightlhand armature closes a circuit from grounded battery, power magnet of sequence switch 200, upper right-hand contact of sequence switch spring 211, righthand armature and back contact of rela-y 202 to ground, moving the sequence switch out of position 12 through position 14 and into position 18. ln position 18, a circuit is completed from grounded battery, winding of downdrive magnet 271, lower contact of sequence switch spring 215 to ground. 'Under the control of the dowvndrive magnet 217, the brush rod 236 is returned to its normal position. As soon as the commutator brush 234 'reaches its normal position, a Circuit is completed from grounded battery, power magnet of sequence switch 200, lower contact of sequence switch spring 275, conducting segment 276, commutator brush 234,

lower contact of sequence switch spring 220 to ground, for moving the sequence switch 200 out of position 18 and into position 1.

As soon as the sequence switch 200 leaves position 16, the holding circuit of relay 307 is opened at the lower contact of the sequence switch spring 244. Relay 307 by retracting its left-hand armature completes. a circuit from grounded battery, power magnet of sequence switch 300, upper left-hand contact inea-,aes

of sequence switch 311, left-hand armature and back contact of relay 307 to ground, for moving the sequence switch'out of position 16, through position 17 and into position 1'8. A circuit is then closed from grounded battery, winding of downdrive magnet 340, lower contact of sequence switch spring 341 .to ground. Under control of the downdrive contact of sequence switch spring 323 to ground, for moving the sequence switch-300 out of position 18 and into position 1.

1f the called line is busy when the sequence switch 300 reaches position 8, the test relay 333 does not receive suiiicient current to attract its armatures, due to the low potential on the test terminal 328. Relay 304, however, is energized in thisrcase in position 8, due to a circuit being closed (from grounded battery, winding of relay 304, lower contacts of sequence switch spring 337, left-hand armature and back contact or' relay 338, right-hand armature and back contact of relay 333 to ground. Relay 304 by attracting its left-hand armature completes a circuit from grounded battery, power magnet of sequence switch 300, lower and upper righthand contacts of sequence switch spring 308, left-hand armature and front contact of relay 304 to ground, for moving the sequence switch 300 out of position 8 and into position 10. As soon as the sequence switch reaches position 9, a circuit `is closed from grounded battery, winding of relay 338, upper contacts of sequence switch Spring 339 to ground. The energization oi? relay 338 opens the circuit of relay 304, whichvdenergizes and completes a circuit for moving the sequence switch 300 out of position 10 and into position 14, this circuit being traced from grounded battery, power magnet of sequence switch 300, lower right-V hand and upper left-hand contacts of sequence switch spring 308,1eft-hand armature and back contact of relay 304 to ground'. In position 14, a circuit is completed for the downdrive magnet 340, from grounded battery, winding of downdrive magnet 340, upper contact of sequence switch spring 341, right-hand armature and back Contact of relay 333 to ground. Under the control of the downdrive magnet 340, the brush shaft 342 isreturned to its normal position. As soon as the commutator brush 320 engages the normal conducting segment 343, a circuit is closed from grounded battery, power magnet of sequence switch 300, lower righthand contact of sequence switch spring 311, conductor 344, conducting segment 343, brush 320, lower contact of sequence switch spring 323 to ground, for moving the sequence switch 300 out of position 14 and into position 17 A busy tone is now connected to the lower line conductor 301 through the upper contacts of sequence switch spring 334. The operator receives a characteristic flash of the so-called supervisory lamp (not shown) in a well-knownnianner and removes plug 104 from the jack 105, thereby causing the denergization of relay 106. The switches are then returned to their normal positions in the same manner as above described. 1

We will nowconsider the wipe-out operation which may take place in position 11 of sequence switch 100. It will be remembered that the sequence switch 400 is in position 8 at this time. It will also be observed that the wipe-out operation can only take place while the sequence switch 175 is in position 5. When the wipe-out key 173 is operated, a circuit is completed from grounded battery, winding of relay 140, upper contact of sequence switch spring 174, Wipe-out key 173 to ground. In position 11 of the sequence switch 100, relay 140 completes a vcircuit from grounded battery, winding of relay 421, brush 440, terminal 441, conductor 442, contact of sequence switch spring 144, armature and front contact of relay 140 to ground. Relay 421 by attracting its left-hand armature completes a locking circuit for itself from grounded battery, winding of relay 421, left-hand armature and front contact of relay 421, upper contact of sequence switch spring 435, lower contact of sequence switch spring 484 to round. Relay 421 by attracting its rightand armature opens the fundamental circuit through the stepping relay 494 and closes it through the right-hand winding of the relay 436. In this manner the switch being operated is removed from thc control of the counting relays. Assuming that the brushes 117, 118 and 119 have just engaged the terminals 131, 130 and 127, respectively, at the time the wipe-out key 173 is operated. Sequence switch 200 will move into position 2 in the same manner as above described, causing the fundamental circuit to be closed in the same manner as above described except that it will be completed through the right-hand winding of relay 436 instead of through the winding of stepping relay 494 and the outer armature and back contact of the counting relay 0. Relay 436 will not, however, be energized at this time due to the high resistance of the winding 202. In position 2 of the sequence switch 200, the above traced circuit of the updrivc magnet 217 will be completed. Under the control of this updrive magnet, the brush rod 236 'tion 7, due to a circuit being closed from grounded battery, power magnet o-f sequence switch 200, lower contacts'of sequence switch spring 214, left-hand armature and back contact of relay 219 to ground. The sequence switch 200 is moved out of position 7 through positions 8 and 9 and into position 10, due to the circuit above described for movlng it out of position 2. In position 10, a circuit is completed from grounded battery, lower contact of sequence switch spring 208, winding of relay 209, upper contact of sequence switch spring 210, over-How contact 277, commutator brush 234, lower contact of sequence switch spring 220 to ground. Relay 209 completes a circuit from grounded battery, left-hand contact of sequence switch 4,spring 252, winding of relay 253, upper lefthand winding of repeating. coil 254, conductor 205, terminal 131, brush 117, lower contact of sequence switch spring 132, conductor 111, terminal 419, brush 420, righthand armature and front contact of relay 421, right-hand winding of relay 436, brush 422, terminal 423, conductor 424, upper contact of sequence switch spring 133, brush' 118, terminal 130, conductor 206, upper contact of sequence switch spring 279, armature and front contact of relay 209, lowercontact of sequence switch spring 212 to ground. Relay 436 now receives sufficient current to attract its armatures and completes a locking circuit for itself from grounded battery, left-hand winding of relay 436, left-hand armature and front contact of relay 436, lower contact of sequence switch spring 435, lower contact of sequence switch spring 484 to ground. Relay 436 also completes a circuit from grounded battery, power magnet of sequence switch 490, upper left-hand contact of sequence switch spring 492, righthand armature and front contact of relay 436 to ground, .for moving the sequence switch 490 into its normal position. As soon as the sequence switch 490 reaches position 1, the cord finder is released and the sequence switch 100 moved into position 16 in the same manner as above described.

The energization of relay 253 ciuses the sequence switch 200 to move into position 12 in the same manner as above described. As

soon as theroperator removes the'plug 104e rom'the jaclr 105, the sequence switches 100 and 200 are moved into their normal positions in the same manner as above described.

It the wipe-out key is operated while the sequence switch 200 is in position 3, it conleading to Aa iinal selector is seized in the same manner as above described and the ifundamental circuit is completed, causing the energization of relay 304i which moves the sequence switch 300 into position 2. IThe relay 4.36 does not attract its armatures at this time, due to the high resistances of the winding of relay 304, and of the resistance 303. Due to the energization of relay 304, the circuit for the updrive magnet 312 will be closed, thereby causing the brushes to move upward until the commutator brush 320 engages the overow contact 350. A circuit is then completed trom grounded battery, power ymagnet of sequence switch 300, lower right-hand contact of sequence switch spring 351, overow contact 350, commuy tator brush 320, lower contact of sequence switch spring 323 to ground, for moving the sequence switch out oi position 2 and into position 10. As soon as the sequence switch 300 leaves position 6, the sequencevswitch 200 is moved out of position 9 and into position 10 in the manner above described. Relay 304 is denergized in position 10 in the saine manner las above described, so that the sequence switch 300'is immediately moved out of position l0 and into position 14, due to a circuit from grounded battery, power magnet of sequence switch 300, lower right and upper lett-hand contacts of sequence switch spring 308, left-hand armature and back contact of relay 304 to ground. Sequence switch 300 is immediately moved out of position lei and into position 16, due to the circuit which moved it out of position 2. As soon as the sequence switch 300 reaches fposition 16, a. circuit is closed or the relay 209, from grounded battery, lower contact ot sequence switch spring 208, winding of relay 209, upper contact of sequence switch spring 210, upper righthand Contact of sequence switch spring 250, conductor 249,

Y f brush 225,ter1ninal 243, conductor 30S, lower right-hand contact'of sequence switch springl 305, lower left-hand contact oi sequence nosas-ce switch spring 351, overow contact 350, o3

leased in the manner above described. It V the wipe-out key is depressed while the sequence switch 300 is in position between 2 and 7,'it is obvious that the brushes ofthe final selector will be moved upward until the overflow contact is reached, whereupon the connection will be released in the manner similar to that -just described.

vWhat isclaimed is: Y v I 1. ln aV telephone exchange system, a switch, sending apparatus, means to operate said switch in a motion controlled by said sending apparatus, means operative during said motion to render-said sender control inedective and to allow said motion to continue until a limiting position is reached, and means made operative lwhen said limiting position is reached for releasing said switch.

2. ln a telephone exchange system, a train of switches, sending apparatus, means to operate each of said switches in a motion controlled by said sending apparatus, means operative during any one of said motions to render said sender control inedective and to allow the motion ofA the switch being operated to continue until a limiting position is reached, and means made operative when said limiting'position is reached for releasing said switch and the switches previously controlled by said sending apparatus.

3. In a telephone exchange' system, a train of switches, sending apparatus, means to operate each of said switches in a motion controlled by said sending apparatus, a wipeout key, means controlled Aby said key when operated during any one of said motions for rendering said sender control ine'ective and to allow the motion of the switch being operated to continue until a limiting position is reached, and means made operative when said limiting position is reached for releasing said switch and the switches previously controlled by said sending apparatus.

4. In a telephone exchange system, a train of switches, a control circuit therefor, sending apparatus arranged to be included in said control circuit, means controlled by said circuit for operating each of said switches in a motion controlled by said sending apparatus, means operative during any one of said motions to disconnect said sending ap.

paratus from lsaid circuit and to maintain said circuit closed to allow the motionof the. switch being operated to continue until a limiting position is reached, and mea-ns made operative when said limiting position is reached for releasing said switch and the rool switches previously controlled by said Sending apparatus.

5. In a telephone exchange system, a train of switches, a control circuit therefor, sending apparatus arranged to be included in said control circuit, means controlled by said circuit for operating each of said switches in a motion controlled by said sending apparatus, a marginal relay, a {wipe-out key, a relay operative by the depression of said key during any one of said motions todisconnect said Sending apparatus from said circuit and to maintain said control circuit closed to allow the motion of the switch being controlled to continue until a limiting position is reached, an energizing circuit for said marginal relay completed when said limiting position is reached, and means operative by said marginal relay energizing for releasing said switch and the switches previously controlled by said sending apparatus.

6. In a telephone system, a switch, a control circuit therefor, sendin apparatus arranged to be included in saic control circuit, means controlled by said circuit for operating said switch ina motion controlled by said sending apparatus, means operative during said motion for disconnecting said sending apparatus from said circuit and for maintaining said circuit closed to allow said motion to continue untila limiting position is reached, and means made operative when said limiting position is reached for releasing said switch.

7. In a telephone exchange system, a calling line, a connecting circuit terminating in a selector switch, means for connecting said calling line to said lconnecting circuit, a called line, a plurality of switches, sending apparatus, means for operating each of =said plurality of switches successively in a motion controlled by said sending apparatus to extend a connection from said selector switch to said called line, means operative during any one of said movements to render said sender control ineffective and to allow ALBEN E. LUNDELL. FRANKLIN A. STEARN.

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