US1257720A

US1257720A - Automatic telephone-exchange system.

Info

Publication number: US1257720A
Application number: US17824217A
Authority: US
Inventors: Alben E Lundell
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1917-07-02
Filing date: 1917-07-02
Publication date: 1918-02-26
Anticipated expiration: 1935-02-26

Description

A. E. I UNDELI..

AUIGMA'HC TELEPHONE EXCHANGE SYSTEM,

APPLICATION FILED JULY 2. ISH?.

5 SHEETS-SHEET I.

WWI Q *Q A. E. LUNDELL. AUTOMATIC TELEPHONE EXCHANGE SYSTEIVI.

APPLICATION FILED ,IULY 2.1917.

Patented FGI 26, 1918..

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A.. UJNUELL.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLlCfXT l 0N FILED JULY 2. l 9 l Patented Feb. 26, NM

4 SHEETS-SHEET 3 -isluHll Wmv@ mmmmmummummul ill A. E. LUNDELL. l AUTOMATIC TELEPHONE EXCHANGVE SYSTEM.

APPLICATION FILED lTULY 2.1917.

Patented Feb. 26, 12H8.,

4 SHEETS-SHEET 4.

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.ALBEN E. JLITNDELL, 0F NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY,

INCORPORATED, OF NEW YORK,l N. Y.,

A CORIORATION 0F NEW YORK.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

i y `Specification of Letters Patent. Pat-@nitrati lFeE-glb, 26, 191%.,

Application filed July 2, 1917. Serial 1110.178342.

To all u-hom t may concern:

Be it known that I, ALBEN E. LUNDELL, a citizen of the lUnited States, residing at New York, in the county of Bronx and State 'of New York, have invented certain-new and useful Improvements in Automatic Telephone-Exchange Systems, of which the following is-a full, clear, concise, and exact description.

This invention relates toA automatic telephone exchange systems, and particularly to impulse con-trolling systems for automatic telephone exchanges.

It is the object of the present invention to provide a new and useful circuit arrangement for controlling the operation of apparatus employed for determining the setting of selectively operable switching devices.

In automatic telephone exchanges in which an impulse sending or controlling apparatus is adjusted in accordance with 'the various digits of the desired line number for controlling the establishment of a connection by setting a plurality of selectlvely operable switching devices, the sending apparatus cannot be used for controlling the establish` mentof another connection until it has successfully completed the control of the first connection. The sending apparatus is set by the subscriber or operator in accordance with all the digits of the called number. 1f, for any reason, for instance, a selector finds all the available trunk outlets busy, the sending apparatus is prevented from sending or receiving the impulses representing all the digits of the called number, it will remain set for controlling the sending of a certain number of impulses, and thus be unavailable for use in the control of the establishment of other connections until the operator or z subscriber restores it to normal. In order to insure in such cases the ,prcmpt restoration of the sending dev1ce, 1n accordance with one feature of the present invention, the sendery may be automatically run down (restored to normal) at certain stages of its operation and independently of the control of the selector switches. Ifone of the selector switches finds all the trunks of a desired group busy, then it connects the sender to an overflow switching arrangement under the control of which the sender is restored to normal in the same manner as under the control of the other selector switches, the setting of which could not be eected.

whereupon the lamp the proper signals to the operators supervis` ing the connection if a selector switch seizes an overflow trunk.

The drawings, when placed together as indicated in Figure 6, represent a semi-rnechanical telephone exchange system embodying the various features of the present invention.

The selector switches employed in the present system are preferably of the type disclosed in a patent to E. B. Craft and J. N. Reynolds, No. 1,123,696, and the sequence switches are of the structure shown in Patent N o. 1,127,808. rl`he sending device is of substantially the same type as the one disclosed in a patent to A. E. Lundell, No. 1,169,819, but in its stead other well-known sending devices, especially those employed in seml-mechanical telephone exchange systems, may be used. i

y Only so much is shown of the circuits and controlling apparatus as is necessary for a clear understanding of the invention.-

The subscriber at station 100 desiring to obtain a Connection with a subscriber at station 800, removes his receiver from the switchhook, closing thus an lenergizing circuit for his line relay 101. The line relay by attracting its armature causes the lighting of a line lamp 102, whereupon an A operator inserts an answering plug 103 in which one end of her cord circuit 101 terminates, into the answering jack 105 of the calling line. A circuit is closed thereupon from grounded battery, through a calling supervisory lamp 106, a resistance 107, the sleeve contacts of plug 103 and jack 105, the winding of a cut-oilI relay 108, to ground. The cut-oil` relay becomes energized and opens the circuit of the

line relay

101, 102 is extinguished. The lamp 106 will not be lighted, because a shunt is closed around it through .the armature and front contact of an answering supervisory relay 109 that was energized in the well-known manner through the calling subscribers line circuit. After the A operator learned from the calling subscriber the number of the desired subscribers line, she communicates with a B operator through a call circuit (not shown). The B operator controls the completion of the connection at the exchange at which the called subscribers lill() line terminates. The B operator instructs the A operator to extend the calling line to an idle trunk 110, 111 and depresses her assignment key 120 for causing the association of an idle sender with,aJ selector 121 by means of which the trunk 110, 111'may be extended. A circuit is closed from ground through the contact of key 120, the

upper contact of a sequence switch spring 122, and the power magnet of a sequence switch 123, to grounded battery, whereupon the sequence switch is moved out of position 1 and under the control of its master contact 124 into position 2. While the sequence switch 123 is in positions 2 to 18 the sequence switch contact 163 is closed and the lamp 165 lighted. The lighting of lamp 165 indicates to the B operator the busy condition of trunk 110, 111. A circuit is closed from ground through upper right-hand contact of a sequence switch spring 125, a conductor 126, the upper righthand contact of a sequence switch spring 500, and the power magnet of a sequence switch 501 to grounded battery. The sequence switch 501 is moved out of position 1 and under the control of its master contact 502 into position 2. A circuit is then closed from grounded battery, through the winding of a magnet 503, a sequence switch contact 504, and the left-hand back Contact and armature of a relay 505 to ground. rlhe magnet becomes energized and causes the upward movement of a cord finder switch. As soon as the-wipers of the cord finder reach a set of terminals individual to the trunk 110, 111, a circuit is closed from ground through the lower left-hand contact of sequence switch spring 125, a conductor 127, cord finder wiper 506, the lower contact of a sequence switch spring 507, and the winding of relay 505, to grounded battery. The relay 505 becomes energized and closes a locking circuit for itself through the upper contact of a sequence switch spring 507, the outer left-hand front contact and armature of relay 505, a cord finder wiper 508, a conductor 509, and the lower right-hand contact of sequence switch spring 125, to ground, the relay 505 becomes energized and opens at its left-hand back contact ythe circuit of magnet 503, whereupon the cord linder is arrested in its upward travel. At its inner left-hand front contact and armature, the relay 505 closes a circuit through the lower right-hand contact of sequence switch spring 500, for driving the sequence switch 502 out of position 2 and into position 3.

The B operator adjusts the sender (Fig. 4) in accordance with the number of the called line by depressing

keys

510, 511, 512

and 542, representing the thousands, hundreds, tens and units digits, respectively, of the desired number. She then depresses a start key 513 and thus closes a circuit from ground through the contact of this start key, the upper contact of a .sequence switch spring 514, and the power magnet of sequence switch 501, to grounded battery, for moving this sequence switch out of position 3 and into position 4. A fundamental circuit is now closed from ground through the lower contact of a sequence switch spring 128, a conductor 129, a cord finder wiper 517, the outer left-hand armature and back contact of an upper zero counting relay 518, a sequence switch contact 519, the windings of a stepping relay 520, a cord finder wiper 521, a conductor 522, the lower left-hand contact of a sequence switch spring 130, and the winding of a relay 131 to grounded battery. The relays 131 and 520 become energized. Relay 520 closes a circuit from ground through its armature and front contact, the upper left hand contact of a sequence switch spring 516, the Contact of key 510, and the winding of a lower zero counting relay 515, to grounded battery. The relay 515 becomes energized and closes a locking circuit for itself from ground, through a sequence switch contact 525, the armature and front contact of relay 515, and the windings of counting

relays

518 and 515, to grounded battery. The counting relay 518 cannot become energized, because its winding isl shunted through a grounded path closed at the front contact of the stepping relay 520.

lThe relay 131 closes a locking circuit for itself through its right-hand armature and the upper contacts of sequence switch spring 130, and also closes a circuit from ground through its left-hand armature and front contact, the upper right-hand contact of a sequence switch spring 132, and the power magnet of sequence switch 123 to grounded battery, for moving this sequence switch out of position 2 and into position 3. A circuit is then closed from ground through the letthand armature and front contact of relay 131, the lower left-hand and the upper righthand contacts of a sequence switch spring 133, and the winding of a magnet 134 to grounded battery. T he magnet 134 becomes energized and causes wipers 135, 136 and 137, and a commutator brush 138 of selector 121, to move in an upward direction. wWhen the commutator brush 138 engages a conducting segment 139, it connects ground through conductor 140, and the lower righthand and upper left-hand contacts of sesequence switch spring 130, te the winding of relay 131, whereupon the stepping relay 520 is shunted out, and by releasing its armature, permits the energization of the upper counting relay 518. The counting relay 518 opens at its left-hand back contact the fundamental circuit and closes a circuit from ground through its lett-hand armature magnet of Leraren kand front contact the lower contact of sequence switch spring 514, and the power sequence switch 501, to grounded battery, for moving this sequence switch out of position 4 and into position 6. When the sequence switch 501 moves out of position 4, the

relays

515 and 518 become denergized. Due to the opening of the fundamental circuit, the relay 520 becomes deenergized, but'the relay 131 remains energized as long as the brush 138 is in engagement with segment 139. As soon, however, as the brush 138 leaves the segment 139, the relay 131 becomes denergized `and closes a circuit from ground through its leithand armature and back contact, the lower righthand contact of sequence switch spring 132, and the power magnet of sequence switch 123, to grounded battery, for moving this sequence switch out of position 3 and into position 7. When the sequence switch 123 reaches position 7, a circuit is closed from ground through the lower contact of a sequence switch spring 140, and the lefthand winding of a test relay 141 to grounded battery. 'lhe relay 141 becomes energized and closes a circuit from ground through its lett-hand armature and front contact, the upper contact ot a lsequence switch spring 142, and the power magnet of sequence switch 123, to grounded battery, for moving this sequence switch out of position 7 and into position 8. 14s soon as the sequence switch leaves position 7, the lower contact of sequence switch spring 140 is opened, and assumingthat the iirst trunk in the desiredgroup is idle, the relay 141 will not find a locking circuit for its righthand winding and becomes denergized. A circuit is then closed from ground through the left-hand armature and back contact of relay 141, the lower contact of sequence switch spring 142, and the power magnet of sequence switch 123 to grounded battery, for moving this sequence switch out of position 8 and into position 10. Another circuit is closed from ground through the lower letthand and upper contacts or" a sequence switch spring 143, 'wiper 137, a test terminal 144 and multiples thereof, a conductor 200, and the winding o1 a relay 201, to grounded battery. Relay 201 becomes energized and due to the connection ot ground through the lower right-hand contact of sequence switch 143 and the wiper 137 to the multiples or' test terminal 144, this terminal is guarded against seizure by other'seleetors in a manner to be hereinafter set forth.

lllpon the successful setting et selector 121 in accordance with the thousands digit, a fundamental circuit is closed from ground through the upper contact ot a sequence switch springr 202, a conductor 203, selector wiper 135, a sequence switch contact 145, conductor 522, cord linder wiper 521, the

windings of stepping relay 520, sequence switch contact-519, the outer left-hand back contact and .armature of relay 518, cord linder wiper 517, conductor 129, the upper contact of sequence switch spring 128, se-

right-hand contact of a sequence switch spring 205, and the winding of a relay 206, to grounded battery. The relay 206 becomes energized and locks up through its lefthand armature and the lower letthand contact of sequence switch spring 205. The relay 520 closes a circuit from ground through its armature and front contact, the upper right-hand contact of sequence switch spring 516, the contact of key 511, the armature and back contact of a counting relay 530, and the winding ot a. counting relay 531, to grounded battery. The relay 531 closes a locking circuit from ground through sequence switch contact 525, the left-hand armature and front contact of relay 531, and the windings of relays 530 and 531, to grounded battery.- Due to the shunt closed around the winding of relay 530 through the front contact of relay 520, the former relay cannot become energized. 'llhe relay 206 closes a. circuit from ground 'through its right-hand armature and liront contact, the upper right-hand contact of a sequence switch spring 206", and the power magnet of sequence switch 207, to grounded battery. 'lfhe sequence switch is moved out of position 1 and under the control of its master Contact 208, into position 2. ln this position of the sequence switch 207, a circuit 4is closed from grounded battery, through the winding of a magnet 209, a sequence switch contact 210, and the right hand front contact and armature oit relay 206, to ground. The magnet 209 becomes energized and causes the movement of wipers 210, 211 and 212, and commutator brush 213 oit a selector 214, in an upward direction. its soon as the brush A213 engages a conducting plate 215, it connects ground through conductor 216, and a sequence switch contact 217 to the winding of relay 206, causing thus the shunting out ot' the stepping relay 520, whereupon the counting relay 530 becomes energized and locks up. As'seon as the cominutator brush 213 leaves the conducting plate 215, the relay 520 becomes again energized and connects ground through key 511 and the armature and front contact ot' relay 530, to the winding of relay 515. This relay becomes energized and operates in the above described manner to prepare the energizing circuit et relay 518. .4s soon as the commutator brush 213 again engages the conducting plate 215, the relay 518 becomes energized and opens the fundamental circuit. The relay 206 is maintained energized until the commutator brush 213 leaves the conducting lector wiper 136, a conductor 204, the lower icc' plate 215. Due to the energization of relay 518, the above traced circuit for sequence switch 500 is again closed, and this sequence switch is driven out of position 6 and into position 8, whereupon the counting relays are unlocked. Upon the denergization of relay 206 a circuit is established from ground, through the right-hand armature and back contact of this relay, the upper left-hand contact of sequence switch spring 206', and the power magnet of sequence switch 207, to grounded battery for driving this sequence switch out of position `2 and into position 16. The magnet 209 become de'energized and assuming that the first trunk in the desired group is idle, the selector 214 is arrested with its wipers 212, 211 and 210, on the terminals of

trunks

221, 222 and 306. v

Upon the setting of selector 214 in accordance with the hundreds digit of the desired number, a circuit is closed from ground, through a sequence switch contact 220, test wiper 212, conductor 221, and the winding of a relay 300 to grounded battery. The relay 300 becomes energized. A fundamental circuit is closed from ground, the lower contact of a sequence switch spring 305, conductor 306, wiper 210, the lower contact of sequence switch spring 202, conductor 203, selector wiper 135, sequence switch contact 145, conductor 522, cord finder wiper 521, the windings of relay 520, sequence switch contact 519, outer left-hand back c ontact and armature of relay 518, cord inder wiper 517, conductor 129, the upper contact of sequence switch spring 128, selector wiper 136, conductor 204, the upper contact of sequence switch spring 205,'selector wiperl 211, conductor 222, the lower right-hand contact of a sequence switch spring 307, and the winding of a relay 308, to grounded battery. The relay 308 becomes energized. Relay 308 closes a locking circuit for itself through its left-hand front contact and armature, and the lower left-hand contact of sequence switch spring 307, and a driving circuit for sequence switch 310 from ground through its right-hand armature and `front Contact, the upper right-hand contact of a sequence switch spring 309, and the power magnet of a sequence switch 310, to grounded battery. The'sequence switch 310 is moved out of position 1, and under the control of its master contact 311, into position 2. A circuit is closed thereupon from grounded battery, through the winding of a magnet 312, a sequence switch contact 313, and the right-hand front contact and arma- -`ture of relay 308, to ground. The magnet 312 causes connector 314 with its

wipers

315, 316 and 317 and commutator brushes 318 and 319, to move in an upward direction. The relay 520 closes a circuit from ground through its armature and front contact, the

lower right-hand contacts of sequence switch spring 516, a contact of key 512, the armature and back contact of counting relay 540, and the winding of counting relay 541, to grounded battery. The relay 541 becomes energized and locks up through the winding of relay 540, the latter being prevented `from energizing as long as the stepping relay 520 keeps its armature attracted. As soon as the commutator brush 318 engages a conducting plate 320, a ground is connected through brush 318, plate 320, the lower contact of a sequence switch spring 321, and the lefthand armature and front Contact of relay 308, to the winding of this relay. The stepping relay 520 becomes denergized thereupon, and permits the energization of relay 540, whereupon relay 540 locks up and causes the energization of relay 531 in the above explained manner. Relay 531 becomes energized and prepares a locking circuit for itself through the winding of relay 530. In view of the fact, however, that in the meantime the commutator brush 318 has left the conducting segment 320 and the stepping relay 520 became energized. the relay 530 cannot become energized. When the commutator brush 318 renga ges the conducting plate 320, the relay 520, by releasing its armature, permits the energization of relay 530 and the latter causes the energization of relay 515. Relay 515 locks up and prepares the energizing circuit of relay 518, and as soon as the commutator brush 318 engages for the third time the conducting segment 320, the relay 518 becomes energized, opens the fundamentall circuit and causes the movement of sequence switch 501 out of position 8 and into position 10. Upon the opening of the fundamental circuit, relay 308 becomes denergized. The setting of the connector in accordance with the tens digit of the called number is now completed. In response to the denergization of relay 308, the magnet 312 becomes denergized and the connector 314 is arrested in its upward travel. Relay 308 closes a circuit from ground through its right-hand armature and back contact. the upper left-hand Contact of sequence switch spring 309` and the power magnet'of sequence switch 310, to grounded battery, whereupon the sequence switch is driven out of position 2 and into position 3. Upon the reclosure of the fundamental circuit, the relay 308 becomes again energized. The relay 308 locks up in the above described manner and closes a circuit from ground through its right-hand armature and front contact, the upper right-hand contact of sequence switch spring 309, and the power magnet of sequence switch 310, for driving this sequence switch out of position 3 and into position 4. The circuit of the driving magnet 312 is now again closed and the connector caused to further travel in an upmarmo ward direction; Upon ehergization, the stepping relay 520 closes a circuit for the counting relay 511 in the same manner as described in connection with the tens selection, the circuit leading through sequence switch contact 516 and the contact of key 542. The step-by-step actuation of the counting relays is accomplished now, the energization and denergization of the stepping relay 520 being controlled by the commutator brush 319 engaging and disengaging a commutator plate 322. Upon the energization ot the upper zero counting relay 518, the units selection is completed and the fundamental circuit is opened. 'llhe relays 520 and 308 become denergized. 'lfhe relay 518 causes the movement` of sequence switch 501 out of position 10 and into position 16, whereupon the counting relays are unlocked. The relay 308 closes through its right-hand back contact a circuit for moving the sequence switch 310 out of position 4 and into position 16. While the sequence switch 310 is moving from position 4 to 16, the ringing of the called party is accomplished in the wellfknown manner, the ringing circuit being closed in position 12 of the sequence switch from a ringing current source 323, through the lower contacts of sequence switch springs 321 and 325.

lWhile the sequence switch 501 is moving from position 11 to position 13 the circuit of magnets 570 is closed and these magnets cause the restoration to normal of the

deressed keys

510, 511, 512, 513 and 512. IWhen the sequence switch 501 reaches position 16, a circuit is closed from ground through the lower contact, sequence switch spring 550, cord nder wiper 551, conductor 552, the lower left-hand contact of sequence switch spring 132, andthe power magnet of sequence switch 123 to grounded battery.v The sequence switch 123 is moved out of position 10 and into position 16. Ats soon as the sequence switch 123 leaves position 10 and opens the lower right-hand con-- tact of sequence switch spring 125, the loclring circuit of relay 505 is opened and this relay by denergizing closes a circuit from ground through its inner left-hand armature and back contact, the lower left-hand contact of sequence switch spring 500, and the power magnet of sequence switch 501, to grounded battery, for moving this sequence switch out of position 16 and into position 17. A circuit is then closed from ground through a sequence switch Contact 553, and the winding of a magnet 551, to grounded battery. The magnet 554 becomes energized and causes the downward movement of the cord finder. As soon as the cord finder reaches its normalposition and a commutator brush 555 carried by the cord finder engages a conducting plate 550, a ground is connected through the upper left-hand contact of sequence switch spring 500, and the power magnet of sequence switch 501, to grounded battery, for moving this sequence switch out of position 17 and into position 1.

lln the meantime the A operator has inserted a plug 112 into a jack 113 in which the assigned trunk 110, 111 terminates. A

circuit is then closed from grounded battery, through a calling supervisory lamp 114,v a resistance 115, the sleeve contacts of plug 112 and jack 113, the left-hand winding of a relay 150 and the armature and back contact of a polarized relay 151, to ground.` rlhe relay 150 becomes energized and the lamp 114 lights up. The relay 151 operates only when the positive (grounded)- pole of battery is connected to its lower terminal and the negative pole to its upper terminal. For this reason, if the A operator inserts the plug 112 into the jack 113 while the sequence switch 123 is standing in some position between 1 and 14; that is to say, prior to the complete setting up of the connection, a circuit is closed from the (negative) pole of battery, through the upper contact of a sequence switch spring 152, the lower winding of a relay 153, trunk conductor 111, the armature and front contact of relay 150, the winding of relay 151, trunk conductor 110, the upper winding of relay 153, and the lower contact of a sequence switch spring 155, to the (positive) pole of battery. Relay 151 does not become energized, but relay 153 becomes energized. When the connection is cut through, z'. e., when sequence switches 123, 207 and 310 reach position 1G, a circuit is `closed from the (positive) pole ot' battery, through the left-hand winding of relay 301, contact 302 ot' relay 303, the primary winding of repeating coil 304:, the upper contact of sequence switch spring 305, conductor 306, selector wiper 210, the lower contact ofsequence switch spring 202, conductor 203, selector wiper 135, the upper contact of sequence switch spring 155, the winding of relay 153, the winding of relay 151, the front contact and armature ot' relay 150, the lower winding of relay 153, the lower contact of sequence switch spring 152, selector wiper 136, conductor 201, the upper contact ot sequence switch spring 205, selector Wiper 211, conductor 222, the upper contact of sequence switch spring 307, the primary winding of repeating coi'l 301, contact 330 of relay 303, and the right-hand winding of relay 301, to the negative pole of battery. Relay 301 becomes energized, but relay 151 remains dcnergized. As soon as the called subscriber removes his receiver from the switchliook, a supervisory relay 332 becomes energized in the wellknown manner. The relay 332 closes a ciicuit from ground through the armature and front contact of relay 301, the front contact iio and armature of relay 332, and the winding of relay 303, to groundedF battery. Relay 303 becomes energized, opens in its back contacts the above traced circuit of

relays

301 and 151, and closes a new circuit for these relays through its Jfront contacts In this new circuit the connection to battery is reversed and the relay 151 becomes energized. By opening its back contact, the relay 151 disconnectsthe lamp 114 from the low resistance path that was closed through the lefthand winding of relay 150 and causes thus the eXtinguishment of lamp 114.

When disconnection is desired the .subscribers restore their receivers to the switchhooks. Upon the restoration of the receiver at the called station 300, the relay 332 becomes dele'nergized and causes in turn the dee'ne'rgization of relay 303. The relay 303 re closes at its

contacts

302 and 330, the originally traced energizing circuit including the

relays

301 and 151, whereupon the relay 151 becomes denergized and permitsthe lamp 114 to light up. Upon the restoration of the receiver at the calling station 100, the relay 109 becomes denergized and opens the shunt yaround the lamp 106,\whereupon. this lamp lights up. The A operator, noticing the lamps 106 and 114 lighted, removes plugs 103 and 112 from jacks 105 and 113, respectively. Relays 108 and 150 become deenergized and lamps 106 and 114 become extinguished. Upon. the denergization of relay 150, relay 153 becomes denergized and closes a circuit from ground through its'armature and back contact, a sequence switch contact 160, and a disconnect lamp 161, to grounded battery. The lamp 161 lights up, whereupon the B operator depresses her disconnnect key 162. A circuit is no w closed from ground through sequence switch contact 163, the contact of key 162, and the winding of a relay 164, to grounded battery. The relay 164 locks up through its lefthand front contact and armature and c loses a circuit from ground through its righthand armature and front contact, the lower contact of sequenceswitch spring 122, and the power magnet of sequenceswitch 123, to grounded battery, forl driving this. sequence switchout of position 16 and into position 18. A circuit is now closed from grounded battery, through the winding of a magnet 166, and a sequence switch contact 167, to ground. The magnet ,166 becomes energized and causes the downward travel of the selector switch 121. When the selector 121 reaches its normal position and the commutator brush 138 engages a normal segment 168, a ground is connected through the upper left-hand contact of sequence switch spring 132, and the power magnet of sequence switch 123, to grounded battery, for driving this sequence switch outof position 18 and into position 1. Magnet 166 and relay 164 become denergized, and the

lamps

161 and 165 become extinguished.

As soon as the test wiper 137 disengages the terminal 144, the relay 201 becomes deenergized and closes a circuit from ground through its armature and back contact, the lower left-hand contact of sequence switch spring 206', and the power magnet of sequence switch 207 to grounded battery, for driving this sequence switch out of position 16 and into position 18. A circuit is now closed from ground through a sequence switch contact 240, and the winding ofa magnet 241, to grounded battery. The magnet 241 becomes energized and causes the restoration of selector 214. When the selector 214 reaches its normal position, and the commutator brush 213 engages a normal conducting segment 242, a ground is con nected through the lower right-hand contact of sequence switch spring 206', and the power magnet of sequence switch 207, to grounded batter whereupon the sequence switch 207 is driven out of position 18 and into position 1, whereupon the magnet 241 becomes denergized.

Assoon as the wiper 212 of selector 214 leaves the terminal of test conductor 221, the relay 300 becomes denergized and closes a circuit from ground, through its armature and back contact, the lower left-hand contact of sequence switch spring 309, and the power magnet of sequence switch 310, to grounded battery, for moving this sequence switch out of position 16 and into position 18. A circuit is now closed from ground through a sequence switch contact 340 and the winding of a magnet 341, to grounded battery. Magnet 341 becomes energized and causes the downward travel of the connector 314. When the connector reaches its normal position, a circuit is closed from ground through commutator brush 318, a normal conducting 'segment 342, the lower right-hand contact of sequence switch spring 309, and the power magnet of sequence switch 310, to grounded battery. The scquence switch moves into position 1. The magnet 341 and the relay 301 become deenergized.

As above stated, the busy condition of trunks terminating in stationary contacts of vselector 121 is indicated by a ground connected through the lower right-hand contact and upper contact of a sequence switch spring 143, and a test wiper 137 to test terminals 144 and multiples thereof. For this reason, after the sending of the thousands impulses from selector 121 to the sender; that is to say, after the completion of the group selecting operation ofthe selector 121, a locking circuit is established for the test relay 141 from grounded battery, through the right-hand winding, front contact and armature of this relay, lower left-hand contactand the upper right-hand contagtof s equence switch spring 143, selector wiper 137, test terminal 144, and thence through the test wiperv137-of another selector and the lower right-hand contact of spring 143 of another sequence switch 123 to round. Due to the :tact that in position 8 o the sequence switch 123 the relay 141 is energized, the sequence switch `.123 will not be moved out of position 8 and for this reason a circuit 1s closed from ground, through theleft-hand armature and front contact ofrelay 141, the upper contacts of sequence switch spring 133 .and the winding ofinagnet 134 to grounded battery. Undenthe control of magnet 1.34 the selector 121 is caused to continue its upward travel. As long as the test wiper 137 engages test terminals that are thus grounded through test wipers of other selector switches, the relay -141 remains locked up and maintains the circuit of magnet-134 closed. As soon as an idle test terniinal is engaged by the test wiper, the loching circuit of relay 141 is opened and this relay opens at its left-hand front contact the driving circuit of magnet 134, and closesat its left-hand back contact a circuit for driving the sequence switch 123 out of position 8 and into position 10, whereupon the establishment: of the connection is completed in the above described manner.

if, however, all the trunks in the selected group are busy, then the selector 121 1s caused to move with its wipers into engagement with terminals of an

overflow trunk

400, 401, 402 (Fig. 4). rllhe relay 141 becomes denergized thereupon and causes 1n the above described manner the arresting vte ping relay 520, sequence switch contact of the Selector 121 and the movement of sequence switch 123 out of positlon 8 and into position 10. A circuit 1s now closed from ground through the winding of marginal relay 403., the lower winding of a relay 404, the lower contact of a sequence switch spring 405, conductor 400, wiper 135, sequence switch Contact 145, conductor 522, cord linder wiper 521, the winding of step)- 51 the outer lett-hand back contact and arinature of countingl relay 518, cord finder wiper 517, conductor 129, the upper vcontact of sequence switch spring 128, selector wiper 136, conductor 401, the lower contact of a sequence switch spring 406, and the upper winding of relay 404 to grounded batter r. The

relays

403, 404 and 520 become energized. rl`he relay 520 closes the above traced circuit through the contact of key 511 and the winding of counting relay 531, whereupon the latter becomes energized, closes a locking circuit for itself and prepares the circuit for the upper counting relay 530. The counting lrelay 530 is prevented from energizing as long as the stepping relay 520 is energized. The relay 404 closes a circuit from ground through its armature and front contact, a sequence switch contact 407, and the power magnet of a sequence switch 408, to grounded battery. `The sequence switch 408 is moved out of position 1 and under the control of its normal contact 409, is moved toward position 18.

When the sequence switch 408 reaches position 1-3/4 the marginal relay 403 locks up through a circuit traceable from ground through the winding of relay 403, the lower contact of a sequence switch spring 430, front contact and armature of relay 403, and the winding of a, relay 422 to grounded battery. The relay 422 becomes energized and by opening its back contacts prevents the closure of circuit paths in which current flows in a direction opposite to that normally used for causing the energization of the stepping relay 520. But for this relay 422, the adjustment of relay 520 might be destroyed by a reversal inthe direction of the current-How.

When the sequence switch 408 reaches position 2, a circuit is closed from grounded battery, through the winding of a magnet 420, sequence switch contact 421, conductor 402, selector wiper 137, and the upper righthand and lower right-liand contacts of sequence switch spring 143, to ground. 'The ,magnet 420 becomes energized, locks up through its front contact, and operates'a well-known message register for indicating the number of the overflow spective group.

When the sequence switch 408 leaves position 2, and until it reaches position 3, the above-traced circuit for

relays

520 and 404 is opened in the lower left-hand contact of sequence switch spring 406. The denergization of relay 404 does not aiect the operation of sequence switch 408. Upon the denergization of relay 520 the counting relay 530 is permitted to become energized, and as soon as the sequence switch 408 reaches position 3 and recloses the circuit at the lower left-hand contact of sequence switch spring 406, the relay 520 again becomes energized and causes the closure of a circuit through the front contact of? relayV 530 for energizing relay 515. The relay 518 will be energized by current flowing through a circuit prepared by relay 515 as soon as the sequence switch 408 moves out of position 3 and causes tlie'de'e'nergizatioii of stepping relay 520 by reopening the circuit in the lower left hand contact of sequence switch spring 406. lThe relay 518 operates in the same manner as described in the establishment of the telephonie connection.

As soon as the sequence switch 501 reaches position 8 and the sequence switch 408 recloses the above-traced controlling or fundamental circuit at the lower left-hand contact of sequence switch spring 406, the relays 404 calls in the reand 520 become denergized. Assuming that this happens when the sequence switch 408 is in position 7, it will be seen that the stepping relay 520 causes the operation of the counting relay 540, while the sequence switch 408 is moving from position 7 to position 8; the operation of counting relay 530 while the sequence switch 408 is moving from position 8 to position 9; and the operation of the counting relay 518 while the sequence switch 408 is moving from position 9 to position 12.- Upon the actuation of the counting relay 518 the sequence switch 501 is moved out of position 8 and into position 10, and the counting relays are unlocked.

While the sequence switch 408 is moving from position 9 to position 18-1/2, the lower lefty-hand AContact of sequence switch spring 406 is opened, but as soon as the sequence switch reaches position 12 and until it moves out of position 17 a sequence switch contact 431 is closed, whereupon the fundamental circuit is again established, but extends now from grounded battery, through the upper winding of relay 404, the right-hand armature and front contact of relay 422, sequence switch contact 431, conductor 401, and then through the above-traced path and back through conductor 400, the upper right-hand contact of sequence switch spring 405, the left-hand front contact and armature of relay 422, the lower winding of. relay 404 and the winding of relay 403 to ground. The stepping relay 520 becomes energized, and causes through the agency of key 542 the energization of counting relay 541. Upon the opening of this circuit at sequence switch contact 431, the relay 520 becomes energized and permits the energization of counting relay 540.

When the sequence switch 408 reaches position 18-1/2 the fundamental circuit traced through the lower right-hand contact of sequence switch spring 405 and lower lefthand contact of sequence switch spring 406 is again closed. The relay 520 becomes energized and causes in turn the en'ergization of counting relay 531. Relay 404 being energized, when the sequence switch 408 reaches position 1, it will be caused to perform another revolution. `When it leaves position 2, the fundamental circuit is opened at the lower left-hand contact of sequence switch spring 406. The stepping relay 520 becomes denergized and permits the energization of counting relay 530. When the sequence switch 408 reaches positiony 3 the relay 520 is again energized and causes the energization of counting relay 515, and when the sequence switch 408 moves out of p osition 3, the Vrelay 520 becomes denergized and causes in turn the energization of the counting relay 518. The counting relay 518 opens the fundamental circuit and causes the movement of sequence'switch 501 into position 16, whereupon the sequence switch 123 is moved into position 16 and the cord nder is released in the above described manner.

As soon as the sequence switch 408 moves out of position 14 and opens its contact 430, the locking circuit includin relays 403 and 422 is opened and these rays become deenergized. As soon as the sequence switch 123 reaches position 14-3/4 and while sequence switch 408 is in positions 1-3/4 t0 18-3/4, a circuit is closed from ground through the primary winding of an induetion coil 418, a condenser 419, the upper lefthand contact of sequence switch spring 405, conductor 400, selector wiper 135, sequence switch contact 155, trunk conductor 110, the tip contacts of jack 113 and plug 112, and the secondary winding of a repeating coil 154 to ground. A tone is induced into this circuit by a device 417 that is connected in circuit through a sequence switch contact 415, and thus the A operator receives an audible signal indicating that the selector 121 seized the overflow trunk.

Another circuit is closed from the negative pole of grounded battery, through the upper windin of relay 404, the right-hand armature and ack contact of relay 422, the upper right-hand contact of sequence switch spring 405, conductor 400, selector wiper 135, upper contact of sequence switch spring 155, the upper winding of relay 153, the winding of the polarized relay 151, the front contact and armature of relay 150, the lower winding of relay 153, lower contact of sequence switch spring 152, selector wiper 136, conductor 401, the upper right-hand contact of sequence switch spring 406, the left-hand back contact and armature of relay 422, the lower Winding of relay 404, and the winding of the marginal relay 403 to the positive pole of battery.

Relays

404 and 153 become energized, but due to the relatively high resistance of the windings of relay 153, the Inarginal relay 403 cannot pull up its armature, and leaves the relay 422 denergized. The current flowing in this circuit is of the proper direction to cause the energization of relay 151 which, in the above-described manner, causes the extinguishing of lamp 114.

As soon as the sequence switch 408 moves out of position 17-3/4 the above-traced circuit is opened and the relays included therein become denergized. The disconnect lamp 161 and the supervisory lamp 114 light up. When the sequence switch 408 reaches position 18-1/2, a circuit is closed from the negative pole of grounded battery, through the upper winding of relay 404, the lower Contact of sequence switch spring 406, conductor 401, and then through

relays

153 and 151, and back through conductor 400, the lower contact of sequence switch spring 405, the lower winding of relay 404 and the winding of relay 403 to the positive pole of batlill tery.. The

relays

404 and 153 hecome energized, hut due to therelatively high resistance of the circuit, the relay 403, and due to the direction of the current, the relay 151 remains denergized. The lamp 161 is extinguished and the relay404 causes the sequence switch 408 to perform another revolution. Byinterrupting this circuit at the -lower lett-hand contact ot spring 406, the

sequence switch 408 causes through the agency of relay 153, the llashingot lamp 161.

When the sequence switch 408 reaches position 11, the above-traced circuit through the upper contact of sequence switch springs 405 and 406 is again closed, whereupon the relay 151 becomes energized andlcauses the extinguishing of lamp 114.

The above described operation continues until the A and B operators perceive the overow signals and sever the connection in the already explained manne-r.

y lt will loe seen` that as long as the sender is connected with the overflow trunlr, the marginal relay' 403 is energized hy current llowing through the circuit including the windings of relay 404, or the loclring circuit including the winding of relay 4122. lhe relay 422 loeing energized, the polarized relay 151 cannot loecome energized, and further more, as alcove stated, a reversal in thedirection ot the current dowing through the windings ot the sender stepping relay 520, is prevented. lt in positions 14 to 18 ot the sequence switch 408 vthe sender is connected with the overflow trunk, the relay 422 is supplied with ground through. a resistance 440, the upper contact or sequence switch spring 430, and the 'front contact and armature ot relay 403.

What is claimed isf:

1. lln a telephone exchange system, a caill-n ing and a called line, a plurality ol selec-- tively operalole switching devices tor interconnecting said lines, a varialoly adjustable sender, means lor operating said sender in accordance with its adjustment to control the successive setting ot said switching devices, and other :tor controlling the operation oit said sender in accordance with its adjustment and irrespective ot the setting oi3 said switching devices.

i?. l'n a telephone exchange system, a variahly adjustable sender, a plurality o'l.E selectively operal'ole switching devices, means tor adjusting" said sender to peritorin certain operations :tor controlling the setting ofi said switching devices, means controlled hy said devices for causing said sender to coinplete sai-d certain operations, and means separate lrorn said devices tor causing said sender to perform said certain operations.

'3. 1n a telephone exchange system, a series of selectively operalole switching de vices, a sender, means tor adjusting said sender to successively control the setting oil said devices, and means operable-upon the setting of the lirst device in the series and independent of the other devices for controlling said sender to complete its operation.

4. In a telephone exchange system, a series of selectively operable switching devices, `a sender, means for. adjusting said sender in accordance .with the desired setting of all of said switching devices, means operative thereupon and successively controlled by said devices for restoring said sender to normal, and means operable upon the setting ot' the rst device oit' said series for controlling the restoration of said sender independent of the operation of said switching devices.

5. ln a telephone exchange system, two lines, means including a series oi selector switches for establishing a connection hetweensaid lines, a set ci counting relays, means successively controlled by each of said selectors in their selecting operation lor operating said counting relays ina certain predetermined manner, and automatic means operalole upon the initiation ol said connection tor operating said counting relays in said predetermined manner.

0. ln a telephone exchange system, a calling and a called line, a selector switch, means for extending the calling line thereto, a plurality oi trunlt lines arranged tor seizure by said selector switch, another selector switch arranged to entend one ot said trunk lines toward the called line, a sender adjustable to control the setting of said selector switches, means successively operable hy said switches during their selecting operations ior operating said sender in accordance 'with its adjustment, and means separate from said second selector switch lier operating in conjunction with said lirst mentioned selector switch said sender in accordance with its adjustment.

hln' a telephone exchange system, two

lines, means including selector switches and trunk lines i'or establishing a connection loetween said lines, a supervisory signal associated with one of said trnnh lines, a polar-Y ized relay adjusted tor operation in response to current ciE a certain direction lor controlling said supervisory signal, means operable during the estahlishnient ont said connection for sending current 'through said supervisory' relay in the opposite direction, means oper ahle through said called line ior sending current through said relay said certain direction, an overdow trunk, and means operable through said overllow trunh tor causing the sending ot current in a certain direction through said polarized relay.,

8. ln a telephone exchange system, two' lines, means including selector switches and trunk lines tor establishing a connection hetween said lines, a supervisory signal asso vcalled line for sending current in a certain vce ciated with one of said trunk lines, a polarized relay adjusted for operation in response to current of a certain direction controlling said supervisory signal, means operable during the establishment of said connection for sending current' through said supervisory relay in the opposite direction, means operable through said called line for sending current through said relay in said certain direction, an overflow trunk, and means controllable through said overflow trunk for intermittently changing the direc-- tion of current sent through said polarized relay.

9. In a telephone exchange system, a calling and called line, means including a plurality of selector switches and trunk lines for establishing a connection between said calling and called lines, a variably adjustable sender for controlling the operation of said selector switches, means successively controlled by said selector switches during their setting for causing the restoration of said sender, a supervisory signal, means for operating said signal upon the successful establishment of said connection, an overow trunk, means including one of said se' lector switches for connecting said sender to said overflow trunk, means controllable through said overflow trunk for causing the restoration of said sender, and other means controllable through said overflow trunk upon the restoration of said sender for operating said supervisory signal.

10. In a telephone exchange system, a calling and called line, means including selector switches and trunk lines for interconnecting said calling and called lines, a varably adjustable sender forcontrolling the setting of said selector switches, means successively operable in response to the setting of said selector switches for restoring said sender to normal, a supervisory signal associated with one of said trunk lines, a polarized relay adjusted for operation in response to current of a certain direction controlling said signal, means operative during the establishment of'said connection for sending current in the opposite direction through said relays, means controllable through the direction through said relay, an overflow trunk` means including one of said selector switches for associating said sender therewith, means operable through said overflow trunk for causing the restoration of said sender, and means operable upon the restoration of said sender and controlled through said overflow trunk for causing the sending of current in a certain direction through said relay.

1l. ln a telephone exchange system, a calling and called line, means including a pluralty of selector switches and trunk lines for establishing a connection between said calling and called lines, a variably adjustable sender for controlling the operation of said selector switches, means successively controlled by said selector switches during their setting for causing the restoration of said sender, a supervisory signal, means for operating said signal upon the successful establishment of said connection, an overflow trunk, means including one of said selector switches for associating said sender with said overflow trunk, a sequence switch associated with saidfoverflow trunk, means operable upon the association of said sender with said overflow trunk for causing said sequence switch to perform a plurality of revolutions, means operable during one of said revolutions for causing the restoration of said sender, and meansoperable during another revolution of said sequence switch for operating said signal.

12. In a telephone exchange system, a calling and a called line, a plurality of groups of trunk lines, means for rendering said trunk lines busy, a selector switch, means for extending the callingl line thereto, a sender, means for adjusting it to determine the setting of said selector switch, means for operating said selector switch to select a group of said trunk lines, means operable during the selective movement of said switch for causing the operation of said sender in acccrdance with its adjustment, means operable thereupon for causing said switch to select and seize an idle trunk line in the selected group, a second selector switch, means for adjusting said sender to determine the setting of said second selector switch, means for operating said second selector switch to extend the seized trunk line toward the called line, means operable by said second selector switch during its operation for causing said sender to operate in accordance with its last mentioned adjustment, and means for causing said sender to operate in accordance with its second adjustment if all the trunk lines in said selected group are busy.

13. 1n a telephone exchange system, a calling and a called line, means including a plu- -rality of selector switches and trunk lines for establishing a connection between said calling and called lines. a variably adjustable sender for controlling the setting of said selector switches, a relay associated with said sender for controlling its restoration, a circuit for said relay, means for extending said circuit successively to said selector switches, an overflow trunk, means including one of said selector switches for extending said circuit to said overflow trunk, means arranged to control the sending of current through said trunk in both directions, and means operable while said circuit is connected to said overflow trunk for preventing the sending of current in a certain direction.

14. lin a telephone exchange system, a calling and a called line, means including a plurality of selector switches and trunk lines for establishing a connection between said calling and called lines, a variably adjustable sender for controlling the setting of said selector switches, a relay associated with said sender for controlling its restoration, a circuit for said relay, means for extending said circuit successively to said selector switches, a supervisory signal associated ,with one of said trunk lines, a polarized relay for controlling said supervisory signal, means operable upon the completion of said connection for sending current in the proper direction through said polarized relay, an overtlow trunk, means including one ot said selector switches for extending the circuit of said relays to said overow trunk, a switch at said overow trunk arranged to control the sending of current through said trunk in both directions, means operable while the circuit of said first mentioned relay is connected to said overiow trunk for preventing the sending of current in a certain direction, and means operable upon the restoration o1" said sender for permitting said switch to send currents of both directions through said circuit to intermittently operate said polarized relay.

In 'witness whereof, l hereunto subscribe my name this 29th day of June, A. D. 1917.

ALBEN E. LUNDELL.