US1233893A - Telephone-exchange system. - Google Patents

Description

A. E. LUNDELL.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILEDJAN.5,1916- Patented July 17, 1,917.

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A. E. LUNDELL.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED IAN-5,1916- Patented July 17 1917.

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A.E.LUNDELL. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED lAN.5,'\916- Patented July 17, 1917.

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Affjy.

ALBEN E. LUNDELL, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Fatent.

Patented July 17, 1917.

Application filed January 5, 1916. Serial No. 70,459.

, 1 0 all whom, it may concern:

Be it known that I, ALBnN E. LUNDELL, a citizen of the United States, residing at New York, in the county of Bronx and State of New York, 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 telephone exchange systems and more particularly to semi-automatic telephone systems in which connections may be established through a plurality of manual and automatic oflices between two subscribers stations.

It is the object of this invention to provide an arrangement whereby a line extended through a connecting circuit may be rendered idle'under the control of an operator supervising the establishment of a connection thereto.

According to the main feature of this invention, means, such as an interrupting mechanism, are provided for temporarily rendering idle a calling line, if an operator engaged in extending this calling line to a called line desires to again seize the former, whereby this engaged line will test idle. It is desirable to establish such revertive calls, in order to permit the calling subscriber to hang up his receiver while the toll connection is being established, and also to enable the operator to verify the calling line number.

The drawings represent a semi-automatic telephone exchange system. Figures 1, 2 and 3 should be placed side by side in the named order, and Fig. 4 below Fig. 2.

In general terms, the operation of the system is as follows: Upon the removal of the receiver at a sub-station 100, a connecting operator, located at an office in which this line terminates, inserts her plug 101 into jack 102. A characteristic potential. is thus placed on the calling line for rendering it inaccessible to incoming calls, and said line is extended to a connecting circuit 108. The connecting operator, after having learned from the calling subscriber the number of his line and the num ber of the line wanted, extends the connecting circuit by any well-known means to a trunk 104 leading to another office and there terminating in a jack 105.

A toll operator, located at the other oflice,

station 100, an interrupting mechanism 201 being provided to remove the busy test potential from this line. The interrupting mechanism is adjusted to cause the removal of the busy test potential, under the control of the connecting and incoming operators. The busy test .will not be removed unless the connecting operator caused the actuation of a relay 1412 and the incoming operator the actuation of a relay 260. the calling line has been seized, the toll operator removes her plug 108 from jack 105 and inserts it in the multiple jack connected to the called subscribers line (not shown), causing thereby, in the well-known ,manner, the displaying of a clearing-out signal at the connecting operators position. The connecting operator then removes plug 101 from jack 102, and the calling subscriber may converse with the called subscriber through connector 300, selector 200 and the toll operators cord circuit 106.

A clearer understanding of this invention may be had from the following detailed description and the appended claims.

The subscriber at station 100, desiring to obtain a connection to a station associated with a distant exchange, removes his receiver from the switchhook, causing thereby in the well-known manner the energization of a line relay 120, which in turn closes the circuit of a lamp signal 121. The connecting operator, noticing lamp 121 lighted, inserts her plug 101 into answering jack 102 forming the answering terminal of the calling line. A test circuit is closed thereupon from ground, through the left-hand armature and'back contact of a relay 122, the winding of a relay 123, the sleeve contacts of plug 101 and jack 102, and the winding of a slow-acting cutofi' relay 124 to grounded battery.

Due to the closure of this test circuit, the potential on the test conductor of this line is reduced to make the line unaccessi-bleto in- After 126, the connecting contacts 129 and coming lines. Relay 124 becomes energized and opens the circuit of relay 120, whereupon lamp 121 is extinguished.

Relay 123 closes a circuit from the plus pole of battery, through its left-hand armature and front contact, contact 125 and the power magnet of a sequence switch 126 to grounded battery, for moving sequence switch 126, under the control of a normal spring 127, out of its first into its seventh position. In position 7 of sequence switch operators telephone set 128 is connected through sequence switch to the cord circuit, and the connecting operatormay thus converse with the calling subscriber. A circuit is now closed from plus battery, through contact 131 of sequence switch 126, conductor 132, contact 133 and the power magnet ofsequence switch 134, to the minus pole of the battery, and this sequence switch is moved, under the control of a normal spring 135, out of position 1 into position 12.

After having learned the number of the called subscriber, the connecting operator proceeds to extend connecting circuit 103 to a trunk 104, terminating in a jack 105 at a recording operators position. The extension of the connecting circuit is preferably performed by means of selector switches controllable by an impulse sender (not shown). Selector switches'of this type and impulse senders for controlling the same are wellknown in the art, and a complete description of the preferred form of such devices may be had from my Patent No. 1,168,319, issued January 18, 1916. There is shown in Fig. 4, diagrammatically, an impulse sending arrangement which is of 7 this same general typ If the connecting operator adjusts her sender to control the selection of a trunk leading to a recording operators position, a sequence switch (the power magnet of which is not shown), associated with the sender, is moved into position 11 and causes the clo sure of a circuit from the plus pole of battery through its contact springs and 141, the winding'of a relay 142 to the minus pole of battery. Relay 142 becomes energized and, by attracting 'its lower armature, closes a locking circuit for itself and prevents the establishment of a' driving circuit through sequence switch contacts 143 and l 144 of sequence switch 124, whereby this seuence. switch will stay in its twelfth positlon,

Upon the seizure of trunk-104,a circuit is closed from ground, through the armature and back contact of relay 110 and the winding of relay 111 to grounded battery, and this relay causes the lighting of lamp 112 in front of the recording operator. The recording operator inserts plug 108 into jack '105, closing thereby a circuit from ground ed battery through the sleeve contacts of plug 108 and jack 105 and the winding of relay 110 to ground, and this relay opens the circuit of relay 111 and extinguishes lamp 112. A circuit is also closed from grounded battery through the winding of a repeating coil 145, the winding of a supervisory relay 146, the ring contacts of jack 105 and plug 108, retardation coil 147, the tip contacts of plug 108 and jack 105, and the secondary winding of repeating coil 145 to ground. Relay 146 closes a circuit from the plus pole of battery, through conductor 148, contact 149, and the power magnet of sequence switch 134 to the minus pole of battery, for moving this sequence switch out of position 12 into position 13.

The connecting operator having performed her duties depresses a listening-out key 150 for closing a circuit from ground, through this key, contact 151, and the power magnet of sequence switch 126 to grounded battery, and moves the sequence switch out of the listening-in position 7 into the listening-out position 11.

In position 13 of sequence switch 134, a circuit is closed from grounded battery through sequence switch contact 152, the upper armature and front contact of relay 142, sequence switch contact 153, the winding of relay 122, conductor 154, a segment 250, conductor 251 and a disk 252 of interrupter 201 to ground. Segments 250, 253, 254 and 252 of interrupter 201 are carried on a common shaft 255 and are driven by a motor mechanism 256 in the direction indicated by the arrows. One interrupter 201 is provided for a plurality of trunk circuits. The conducting segments of plates 250, and 254 are angularly displaced with respect to each other for reasons to be hereinafter set forth.

Whenever the conducting segment of plate 250 engages the brush in which conductor 154 terminates, relay 122 becomes energized and opens at its lefthand back contact the circuit of relays 123 and 124, causing, thus, the removal of the busy test potential from the test conductor of the calling line. These relays, being slow to release, will not fall off upon these short interruptions of the test circuit, whereby the occurrence of clicks in the calling subscribers receiver and the premature restoration of sequence switch 126 is prevented. The toll operator connects her telephone set (not shown) to cord circuit 106 and inquires the number of the desired subscriber from the connecting operator. Having learned the number of the subscriber wanted, the toll operator confers, by means of an order wire (not shown), with an incoming operator located at the oliice in which the calling line terminates. The incoming operator assigns for use a trunk, such as trunk 202, 203, terminating in jack 107 at the toll operators position. The toll operator 1 jack 107 and plug signed by the incoming inserts then plug 113 into this jack, establishing a circuit from the plus pole of battery through the sleeve contacts of jack 107 and plug 113, the Winding of a relay 111, to the minus pole of battery. A circuit is also closed from grounded battery through the upper winding of a relay 201, contact 205 of relay 206, winding 207 of repeating coil 208, conductor 202, the tip contacts of 113, the winding of a relay 115, ring contacts of plug 113 and jack 107, conductor 203, winding 209 of repeating coil 208, contact 210 of relay 206, and the lower winding of relay 201 to ground. Relay 201 closes a circuit from ground through its armature, conductor 211, and the winding of relay 212, to grounded battery for energizing this relay.

The incoming operator proceeds now to extend the connection back to the calling subscribers line. First, she depresses her assignment key 213 and'closes a circuit from ground through this key, contact 211, and the power magnet of a sequence switch 215, to grounded battery. Sequence switch 215 leaves its first position and moves under the control of a normal spring 216 into position 13. In position 2 of sequence switch 215, a circuit is closed from ground through sequence switch contact 217 conductor 100, contact 101 of sequence switch 102, and the winding of a relay 103 to grounded battery. Relay 103 upon energization closes a circuit through its armature and front contact, and contact 101 and the power magnet of sequence switch 102, to grounded battery. This sequence switch is under the control of its normal spring 105 moved into position 13. After sequence switch 102 leaves its first position, relay 103 is maintained energized by a circuit closed through sequence switch contact 106, conductor 107, and contact 218 of sequence switch 215 to ground. While sequence switch 102 is moving from position 1 to 13, circuits are established for causing a cord finder to hunt with its wipers 108 and 109 for conductors 110 and 111 asoperator, and after the cord finder brushes have been set,'the incoming operator sends out the first set of numerical impulses designating the calling line and causes, in the well-known manner, selector switch 200 to engage with its wipers 219, 220 and 221, the contacts in which terminates trunk 301, 302 and 303 leading to the final selector or connector 300. The setting of selector switch 200 is-accomplished before sequence switch 215 reaches position 13.

In position 12 of sequence switch 215 and position 13 of sequence switch 102, a circuit is closed from grounded battery through the coil of a relay 222, sequence switch contacts 223 and 221, conductor 111, cord finder 6 brush 109, sequenceswitch contacts 112 and row.

113, resistance 111, the winding of a stepping magnet 115 and the back contact and armature of a relay 116 to ground. Relay 222 by attracting its right-hand armature prepares a locking circuit for itself, and when sequence switch 215 reaches its 13th position, this locking circuit is completed through sequence switch contacts 225 and 230.

When the wipers of selector switch 200 are set, a circuit is closed from ground through the left-hand armature and front contact of relay 222, sequence switch contacts 226 and 227, wiper 219, conductor 301, contacts 301 and 305 of a sequence switch 310, conductor 306, and the winding of relay 307 to grounded battery. Relay 307 becomes energized and closes a circuit from ground through its left-hand armature and front contact, contacts 308 and 309 of sequence switch 310, and the winding of relay 311, to grounded battery; Relay 311 upon energization causes sequence switch 310 to move from position 1 to 6, by closing a circuit from ground through its left-hand armature and front contact, contact 312, and the power magnet of sequence switch 310 to grounded battery. Relay 311 does not become denergized when the sequence switch leaves its first position, a locking circuit being closed from, grounded battery through the winding, front contact and right-hand armature of this relay, a resistance 313, test conductor 303, wiper 221, a resistance 228 and sequence switch contact 229 to ground. Due to the closure of this circuit, the potential on the terminal of conductor 303 is reduced to guard the trunks selected by selector switch 200 against seizure by other selector switches. Relay 307 I remains also energized when sequence switch 310 leaves its first position, a circuit being closed from grounded battery through the winding of this relay, conductor 306, sequence switch contact 311, front contact and righthand armature of relay 307, sequence switch contacts 315 and 301, conductor 301, wiper 219, contacts 227 and 226 of sequence switch 215, and the front contact and left armature of relay 222 to ground.

In position 6 of sequence switch 310, a circuit is closed for an elevating-magnet 316 of connector 300 from grounded battery through the winding of this magnet, conductor 317, sequence switch contact 318, the front contact and right armature of relay 307, sequence switch contacts 315 and 301, conductor 301., wiper 219, sequence switch contacts 227 and 226, and the front contact and left armature of relay 222, to ground. The elevating magnet 316 attracts its armature 319, and presses thus a brush rod 320 against a roller 321, which is constantly rotating in the direction indicated by the ar- Line wipers 322 and 323, test wiper V quence switch 215 324, and brushes 325, 326 and 327 carried by rod 320 are, under the control of roller 321, moved in an upward direction. The wipers are adapted to engage calling terminals of subscribers lines provided in a terminal bank 328, and the brushes are adapted to engage segmentsof a commutator plate 329. The calling line terminals, through which subscribers lines may be seized, are multiplied to similar terminals provided in the banks of other connector switches.

When brush 325 engages a conducting segment, thereby in response to each step taken by the brush, magnet 415 is shortci'rcuited and causes upon its deenergization the stepbystep release of the impulse sending arrangement set by the inconr ing operator. This short-circuit may be traced from ground, through the armature and back contact of relay 416, windings" of magnet 415, resistance 414, sequence switch contacts 413 and 412, cord finder brush 409, conductor 411, sequence switch contacts 224 and 230, wiper 220, trunk conductor 302, sequence switch contacts 330 and 331,} conductor 332, conducting segment'333, brushes 325 and 327 conducting'plate 334, conductor 335, sequence switch contact 336, conductor 33?, and the front contact and left-hand armature of relay 307 to ground. After the impulse sending mechanism has returned to normal, and thus the wipers of connector 300 have been moved a number of steps determined by the set position of the impulse sending mechanism, a circuit (not shown) is closed for relay416. Relay 416 attracts its armature and causessequence switch 402 to move out of position 13 into position 16, the circuit being closed from ground through the front contact and armatureof this relay, contact 420 and the power magnet of sequence switch 402 to grounded circuit is now closed from battery. A ground through sequence switch contact 421, cord finder brush 408, conductor 410,-

contact 231 and the power magnet of se to grounded battery, and thissequence is moved into its fourteenth position. Contact 218 being open now, relay 403 becomes deenergized and closes a circuitf'from ground through its armature and back contact, contact 440 and the power magnet of sequence switch 402 to grounded battery, for driving th s sequence switch out of 16'into'position 1. The sendingapparatusmay now be used to control the extension of another connection,

In view of the fact that the desired (in this case the calling) subscribers line is busy, the incoming operator, when setting up the line number on her keyboard, depresses. also a key 430, closing thereby, a circuitfrom ground through this key, conduct0r43l, the winding of relay 260, and contact. 26.1' of sequence switch 215 to,-

grounded battery. Relay 260 upon energization closed a locking circuit for itself through its right-hand armature and front contact. When sequence switch 215 leaves position '13, the tcircuit of relay 222 is opened, the sender being restored to normal, and sequence switch contacts 224 and 225 being open. In position 14 of sequence switch 215 a circuit is closed from ground through plate 252, conductor 251, plate 254, conductor 262, the left-hand front contact and armature of relay 260, contact 263 of sequence switch 215, conductor 264, the armature and front contact of relay 212, and the winding of relay 222 to grounded battery. As soon as the conducting segment of plate 254 engages the brush in which conductor 262 terminates, relay 222 becomes energized and closes a circuit from ground through its left-hand armature and front contact, contact 205 and the power magnet of sequence switch 215 to grounded battery, for driving this sequence switch out of 14 into position 15. The conducting segments of plates 253 and 250 are so cut that ground will be connected first to conductor 262 and then to conductor 154. During the time elapsing between the sending of an impulse through these conductors, the calling line is seized in the following manner:

hen relay 222 becomes deenergized after sequence switch 215 moves out of position 13, the energizing circuit of the elevating magnet is opened. Due to the opening of contact 226 of sequence switch 215, relay 307 also becomes deenergized and closes a circuit from ground through its left-hand armature and back contact, contacts 340 and 341 and the power magnet of sequence switch 310 to grounded battery, and this sequence switch is moved into position 7. In position 7 of sequence switch 310, when sequence switch 215 reaches position 15, relay 307 is again energized by a circuit closed from the minus pole of battery through the winding of this relay, conductor 306, sequence switch contacts 305 and 3,04, conductor 301, wiper 219, sequence switch contacts 227 and 270, the upper back contact of relay 271 and the secondary winding of repeating coil 208 to the plus pole of battery. The energization of relay 30 causes sequence switch 310 to move into position 8, the circuit being closed through the left-hand armature and front contact of relay 307 and sequence switch contacts 308 and 341.

Due to the deenergization of magnet 316, the wipers of connector 300 are arrested on the contacts in which the calling subscribers line terminates. The brush rod 320 with the wipers is maintained in its advanced position by a spring pressed pawl 342 adapted to engage openings in rod 320.

A circuit is not. closed from grounded battery through the winding ofcutofi' relay 124, test conductor 155, test terminal 343, wiper 324, sequence switch contact 345, the low resistance Winding of marginal test relay 344, sequence switch contacts 346 and the high resistance winding of relay 344 to ground.

Simultaneously, with the closure of this test circuit a ground impulse is sent through plate 250 and conductor 154 to relay 122, and this relay removes the busy test potential from the calling line by opening the circuit including relays 124 and 123 as above described.

lthe electrical condition of the calling line being normal, relay 344 becomes energized and closes a locking circuit for itself from ground through its upper armature, front contact and low resistance winding, sequence switch contact 345 and then through relay 124 to grounded battery, the high resistance winding of relay 344 being short-circuited upon the closure of this circuit. The closure of this locking circuit reduces the potential on the multiples of test terminal 343 so as to prevent another test relay 344 from becoming energized when the connector with which it is associated engages the calling terminals of this calling line, and thereby causing this line to test busy at its multiple answering and calling terminals.

Relay 344 being energized, a circuit is closed from ground through the lower armature and front contact of this relay, conductor 347, contact 348 and the power magnet of sequence switch 310 to grounded battery. Sequence switch 310 moves out of position 8 into position 16.

When sequence switch 215 comes into position 16, a circuit is closed from grounded battery, through sequence switch contact 272, the windings of relays 273 and 271, sequence switch contact 274, conductor 211 to the front contact and armature of relay 204 to ground. Relay 271 becomes energized, relay 273 however, remains deenergized, its winding being shunted through its armature and back contacts, and the armature and back contact of a ringing relay 27 5. When sequence switch 310 moves into position 16, ringing current is applied to the calling line from ground through the upper armature and front contact of relay 271, sequence switch contacts 270 and 227, the talking conductors (indicated in heavy lines), the bell at station 100, sequence switch contacts 370, 330 and 276, the bottom armature and front contact of relay 271, sequence switch contact 277, the winding of ringing relay 275, and a ringing current generator 278 to ground. If the receiver at substation is removed or as soon as the calling subscriber removes it in response to the ringing current, relay 275 becomes energized and removes the shunt from relay 273; this relay becomes energized and closes a shunt around relay 271.

' Upon the restoration of the armatures of relay 271, the talking conductors are closed at the back contacts of this relay and the circuit of relay 27 5 is opened. Relay 273 is maintained energized by a circuit from grounded battery, through sequence switch contact 272, the winding, armature and front contact of relay 273, sequence switch contact 274, conductor 211, and the armature and front contact of relay 204 to ground. Supervisory relay 280 became also energized upon the closure of the talking circuit at the called station, after relay 271 released its armatures. A circuit is closed from ground through the armature and front contact of relay 204, the front contact and armature of relay 280 and the winding of relay 206 to grounded battery. Upon the energization of relay 206, the circuit of relays 115 and 204 is opened, but relay 204 is maintained energized due to the closure of a circuit through contact 281 of relay 206. Upon the deenergization of relay 115, a signal 170 (which was lighted upon the energization of this relay) will be extinguished, indicating to the toll operator that the calling line is ready for extension to the desired distant station. She will pull plug 108 out of jack 105, causing thereby, in the well-known manner, the release of the mechanism employed in the extension of the connecting circuit 103, and will establish the connection by inserting plug 108 into a jack (not shown) in which the called line terminates. In the well-known manner, a clearing-out signal will be conveyed to the connecting operator, whereupon she will pull a plug 101 out of jack 102.

Relay 123 (its circuit being opened for a sufiiciently long period) becomes deenergized and closes a circuit from the plus pole of battery, through its right-hand back contact, contacts 171., 172 and the power magnet of sequence switch 126 to the minus pole of the battery, and this sequence switch is driven out of 11 into position 1. A circuit is closed thereupon from the minus pole of battery, through the winding of a relay 173, contact 174 of sequence switch 134, contacts 175 and 171 of sequence switch 126, and the right-hand back contact and armature of relay 123 to the plus pole of the battery. Relay 17 3 closes a locking circuit for itself through its left-hand armature and front contact, and a driving circuit from the plus pole of battery, through its right-hand armature and front contact, conductor 176 and contact 177, and the power magnet of sequence switch 134 to the minus pole of the battery. Sequence switch 134 is moved to its first position, and relays 173 and 142 be come deenergized.

After the conversation is finished and the segment 334,

calling subscriber hangs up his receiver, re lay 280 becomes deenergized and deenergizes in turn relay 206. Upon the release of the armature of relay 206, the-windings of relay 204 are again included in the original energizing circuit, and relay 115 causes again the actuation of the supervisory sig nal 170. .The operator controlling the cord circuit 106 pulls plug 113 outof jack 107, causing thereby relays 114, 115 and 204 to release. Relay 204 upondeenergization, opens the circuit of relay 212, which, by retracting its armature, closes a circuit from ground, through sequence switch contact 285, t-he armature and back contact of relay 212,'and the winding of a slow-to-energ'ize relay 286 to grounded battery. Relay286 closes then a circuit from ground, through its front contact and armature, and contact 287 and the power magnet of sequence switch 215' to grounded battery, and this sequence switch is moved over its eighteenth into its first position. In positions 17 and 18 of the sequence switch, selector 200 is restored to normal'in the well-known manher. When the selector 200 reaches its normal position and closes a contact ON, a circuit is closed through sequence switch contact 265 for driving the sequence switch 215 out of position 18 and into position 1.

When the brush 221 of selector 200 disengages the terminal of conductor 303, relay 311 becomes deenergized and closes a circuit from ground, over its armature and back contact, contact 350 and the power magnet of sequence switch 310 to grounded battery, and this sequence switch is moved into its eighteenth position. When sequence switch 310 leaves position 16, the circuit of test relay 344 is opened at 345, and this relay becomes deenergized. Further, a circuit is closed from grounded battery, through the wind- 'ing "of a release magnet 351, conductor 352 and sequence switch contacts 353, 354 to ground. H Magnet 351 attracts its armature 355-, causing thereby pawl 342 to disengage brush rod320, and presses the brush rod against a roller 356 constantly rotating in a counter-clockwise direction. The roller 356 moves the brush 'rod in a downward diree' lion -and when the rod reaches its normal position, a circuitis closed from grounded battery, through the power magnet and contact 357 of sequence switch 310, conductor 358, conducting segment 359 of commutator 329-, brushes 326 and 327, conducting conductor 335, and sequence switch contact 354 to ground. Sequence switch 310 moves out of position 18 into position 1, and opens the energizing circuit of magnet 351-.

t The apparatus is now and ready for use in the other connection. 7 V

If the subscriber at station 100 desires to released to normal building up of an- 7 reaches position 14, and the conducting obtain a connection to a substation asso-' ciated with a local exchange, the setting up of the call would be accomplished generally in the same way as above described, except for the following:

The connecting operator extends the trunk 103 direct to the incoming operator rather than through the toll operators cord circuit. By thus extending the line, she sets the sender sequence switch to another position than to 11. o circuit is established for relay 142, and when sequence switch 134 reaches its twelfth position, it will be innncdiately driven into position 14 due to the closure of a circuit from the plus pole of battery, through contact 143, the lower armature and back contact of relay 142-, contact 144 and the power magnet of this sequence switch to grounded battery. Contact 1530f sequence switch 134 being open, relay 122 will not receive impulses from in terrupter 201 througl'i conductor 154-, and therefore the calling line will stay busy.

The incoming operator will not depress key 430, and relay 260 remains thus deenergized. hen sequence switch 215 segment 0 plate 253 engages the brush in which conductor 290 terminates, a circuit is closed from ground, through 252, 251, 253, 290, the left-hand back contact and armature of relay 260-, sequence switch contact 263, the armature and front contact of relay 212 and the winding of relay 222 to grounded battery.

The conducting segment of plate 253 makes contact with the brush in which conductor 290 terminates, after the conducting segment of plate 250 has engaged the brush of conductor 154-. If a connecting and an incoming operator are engaged in the extension of a local call to substation 100 while this station is being connected to a toll line, sequence switch 134 being in position 18, the line leading to station 100 will test busy due to the fact that relay 122 is actuated before relay 222 (in position 14 of sequence switch 215); Thus, another connector tests this line after relay 122 became deenergized and again closed the test circuit.

Supposing that the called subscribers line is busy, the potential on its multiple test terminal, 6-. g. 375, is reduced so as to prevent the energization of test relaj 344 in position 8 of sequence switch 310. A circuit is therefore closed from grounded battery, through the winding of relay 307, conductor 306, sequence switch contacts 376 and 377, and the lower armature and back contact of relay 344 to ground. Relay 307 becomes energized and closes a circuit from ground, through its left-hand armature and front contact, contacts 308 and 341 and the power magnet of sequence switch 310 to grounded battery, for moving this sequence switch into position 14. Release magnet 351 is now energized, a circuit being closed from grounded battery, through the winding of this magnet, conductor 352, sequence switch contact 380 and the back contact and lower armature of relay 34:4: to ground. Under the control of magnet 351, connector switch 300 is returned to its normal position, whereupon a circuit is closed from grounded battery, through the power magnet of sequence switch 310, sequence switch contact 357, conductor 358, conducting segment 359, brushes 326 and 327, conducting plate 334:, conductor 335, and sequence switch contact 354 to ground. Sequence switch 310 moves into position 17 and a busy tone is applied to the calling subscribers line from 381 through sequence switch contacts382.

What is claimed is:

1. In a telephone exchange system, a line having answering and calling terminals, a connector switch arranged to engage said calling terminals, a plurality of selector switches, means for operating one of said selector switches for extending the line through its answering terminals to said connector switch, means operative thereupon for rendering the calling terminals of said line unselectable, testing means associated with said connector switch, and means permanently associated with said selector switches and common thereto for rendering said line selectable at its calling terminals while it is extended through its answering terminals.

2. In a telephone exchange system, a line having answering and calling terminals, a connector switch arranged to engage said calling terminals, a plurality of selector switches, means for operating one of said selector switches for extending the line through its answering terminals to said connector switch, means operative thereupon for rendering the calling terminals of said line unselectable, testing means associated with said connector switch, a constantly operating interrupter permanently associated with said selector switches and common thereto for rendering said line selectable at its calling terminals while it is extended through its answering terminals, and means operative upon the completed operation of said selector switch for rendering said interrupter effective.

3. In a telephone exchange system, a line, a connecting circuit, means for extending one end of said circuit to said line, means operative thereupon for applying an electrical busy potential to the terminals of said line, means including a selectively operable switching device for extending the other end of said circuit to said line, a constantly rotating shaft carrying a plurality of interrupters, means for controlling the e'li'ectiveness of said busy potential controlled in turn by one of said interrupter-s, and means for operating said switching device under the control of another interrupter.

at. I11 a telephone exchange system, a line, a connecting circuit, means for extending one end of said circuit to said line, means operative thereupon for rendering the line busy, a selective switching device for ex tending the other end of said circuit to said line, a constantly operating interrupting device adapted to control the operation of said device, and means controlled by said interrupting device for rendering said line idle, when said switching device is being operated.

5. In a telephone exchange system, a line, a connecting circuit, means for extending one end of said circuit to said line, means operative thereupon for rendering the line busy, a selector switch for extending the other end of said circuit to the line, a plurality of constantly operating switching devices; one controlling said second mentioned means, and another one said selector, and means for actuating said other switching device prior to said one switching device.

6. In a telephone exchange system, a plurality of lines, means including a selector switch for extending a connection between a calling and a called line, means including said selector switch for extending a connection from a line back to the same line, means operative upon the extension of a line for rendering the same busy, a device for controlling the operation of said selector, a second device for controlling said last mentioned means, a third device for performing the functions of the first device, said devices being constantly operated in the named order, means for rendering efiective only the first and second devices, if connection is desired back to the calling line, and means for rendering effective only the second and third devices, it connection is desired between a calling and a called line.

In witness whereof, I hereunto sub scribe my name this lth day of January A. D. 1916.

ALBEN E. LUNDELL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

' Washington, D. C.

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