US1504275A - Automatic telephone-exchange system - Google Patents

Description

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F. J. SCUDDER AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed June 23 1921 4 Sheets-Sheet 2 Aug., l2 1924, 1,504,275

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FREDERICK J. SCUDDER, 0F LONG ISLAND, NEW A ELECTRIC COMPANY, INCORPORATED, OF NEW YO'RK, N. Y.,.A CORPORATION OFl NEW YORK.

minoritario TELEPHONE-encarnada sYs'rnr/n Application ined .nine as, 192i. semi n0.,47e,`73o.

To @ZZ whom t may concern.'

Be it known that l, FREnnnroK J. Soonh DER, a citizen of the United States, residing at Long Island, in the county of Queens, State of 'New York, have invented certain new and useful lmprovements in Automatic Telephone-Exchange Systems, of which the following is va full, clear, concise, and eX-V actdescription. y

This invention relates to automatic telephone exchange systems, and more particularly to automatic systems in which the selective movements of the various switches' are controlled by a central oiice sending device.

lt is the object of this invention to provide an improved method of controlling the release of the selector1 switches, and the associated sending device. f

lt is moreA definitely the object of the invention to provide means, such that release of the connection will take place properly in case the call' is abandoned before the called subscriber has responded, and regardless of the stage of operation to which the connection` has progressed at the time of such abandonment.

lt is a further object of the invention to reduce the time interval before a calling subscriber may initiate a second call after abandoning a previous call.

ln systems employing` a central office sender various problems arise under the variousconditions of premature abandonment of calls. lf a call is abandoned before the first numerical switch has been positioned, it is possible to immediately restore the sending device. If the rst numerical switch has been positioned it is usually necessary to operate all the succeeding switches in the train before release takes place, since otherwise the progression switch in the sender might be left in a position from which it could notbe advanced, which would put the sender out of service until the condition was elimin ated. Under certain conditions, diihcuL ties would also beencountered in releasing succeeding switches in the train.

A feature of the invention is the provision of means such that the release of the connection is controlled by the condition of the sending device, that is, if connection has not proceeded far enough to prevent proper restoration lof thel sender, this fact will Vbe-v .indlcated and allow disconnection to pro-V ceed. If connection has advanced to a point where it will be necessary to fully actuate the sender, the abandonment of the call is made ineffective to cause release until all the .switches have been operated whereupon relt is thought that the invention will best.

be understood from the following detailed description, reference being had to the ac companying drawings.

In the drawings, Figi shows the circuit of an individual line switch for extending a calling line to an idle district selector; Fig.'

Q shows thecircuits of a district selector switch anda sender selector"switch, Fig. 3

shows Vcircuits for the sender controlling sequence switches and a step-by-st`ep progression switch. tacts above and, to the right of the broken' line in this ligure are controlled by sequence switch 400, while the sequence switch con tacts below and to the left of the broken line arecontrolled by sequence switch 301; Fig. 4 shows the registering devices which control the action of the counting relays of Fig. 3.

The circuits have been simplilied as far as possible in order to eliminate matter which is not necessary to an understanding of the invention. The invention has been applied to a system of the type shown and described in an application Serial No. 487,520, filed July Q5, 1921, in the name of Alben E. Lundell. The application just mentioned shows in detail the complete circuits and describes the complete operation of a sending device similar to the one shown in Figs. 3 and 4 of the present application.

'lhe translator switch shown in Fig. 4 is a step-by-step two-motiony switch and re.- sponds directly to the irst two series of im- Yonn, assrenon rro WESTERN' The sequence switch con-V sor pulses. This translator switch therefore, cor- Y responds to the lirst two registers and translator switch of the above'mentioned Lundell application taken in combination.

The detailed operation of the system is as follows: When a subscriber at substa tion 1 removes his receiver from the switchhook a circuit is completed :from grounded battery, right-hand winding of line relay 2, inner lower armature and back contact of cut-ott relay 3, through the loop of the calling substation line, upper armature and.

back contact of relay 3 to ground. Line relay 2 is energized in this circuit and attracts its armatures. Test brush 5 is at this time in engagement with its normal contact, not shown, and since its normal contact is connected to ground, the energization of line relay 2 completes a circuit from grounded battery, winding, armature and baclr conn tact oflstepping magnet 4, lower armature and back contact of cut-oil relay 3, righthand armature and front contact of line relayV 2, conductor 15, test brush 5, normal terminal to ground. Magnet 4 is energized and interrupts its own circuit to release its armature and advance the line switch Vinto its rst olia normal position. As soon as the line switch makes its first step, olf-normal contact 13 closes and o-normal spring 14 releases its upper contact and engages its lower contact. One-normal contact 14 removes the control of the cut-oftl relay from any line which may be calling and supplies battery to test terminal 16, to render the calling line busy to other calling subscribers.

Test terminals of trunks extending to busy district circuits will be characterized by the presence of ground potential on such test terminals as will be evident from the following description. As long as test brush 5 engages contacts associated with busy trunks, ground will be supplied to conductor 15, and stepping magnet 4 will continue to interrupt its own circuit to cause the advance of the line switch. As soon as test brush 5 engages a terminal on which there is no ground potential the circuit for magnet 4 is opened and the switch is brought to rest with its brushes resting on the terminal set of an idle trunk leading to Van available district selector.

It should be noted that during the o eration of the line switch a circuit for cut-off relay 3 is in existence. This circuit extends from ground, upper and lower windings of cut-ott relay 3, left-hand winding of line relay 2, left-hand armature and front contact of relay 2, and thence to grounded battery, through the winding of magnet 4. Cut-ofin relay 3 cannot however, be energized in this circuit, since its windings are short-circuited by the direct ground supplied to conductor 15 by way of test termiswitch spring 198, armature and back contact of relay 102, conductor 10G, terminal 9, test brush 5, conductor 15, left-hand winding, armature and :trent contact oi relay 2, through the windings of cut-oil' relay 3 to ground. The presence of battery potential at terminal 9 short-circuits magnet 4 and allows cut-oli relay 3 to operate. The operation of cut-olf relay 3 causes the deenergization of line relay 2.

A circuit is now completed trom grounded battery, (Fig. 2), right-hand winding of relay 102, armature and back contact ot' re lay 139, lower right-hand contact of sequence switch spring 103, sleeve conductor 104, terminal 11, brush 7, winding of message register magnet 17, lower middle armature and front contact of relay 3, lower winding of relay 3 to ground. Relay 102 is energized, and at its inner left-hand armature and front contact supplies ground by way of conductor to test conductor 106 and its associated test contacts, to render the trunk non-selectable to other limiting line switches. The energization of relay 102 also completes a circuit from grounded battery, righthand winding of relay 107, upper left-hand contact of sequence switch spring 108, lower contacts ot sequence switch spring 109, right-hand armature and 'front contact of relay 102 to ground. Relay 107 is energized in this circuit.

Assuming that the sender, on the terininais of which the brushes of the sender selector are resting, is busy, and that this busy condition is indicated by presence of ground on the test terminal of' such sender, a locking circuit for relay 107 is completed from grounded battery, left-hand winding and left-hand armature and front contact of relay 107, conductors 110 and 111, upper left-hand contact of sequence switch spring 112, lower left-hand contact of sequence switch spring 113, conductor 114, test brush and its associated test terminal to ground. Relay 107 completes a circuit trom grounded battery, power magnet of sequence switch 100, lower rigln'z-hand contact ot sequence switch spring 11G, inner rightshand armature and front contact ot relay 107, lower left-hand contact of sequence switch spring 117 to ground for moving this se quence switch out oi position 1 and into position 2, under the control or" its master spring contact 101.

In position 2 of' sequence switch 100 a. circuit is completed for causing the selection of an idle sender. The circuit for the sender selector stepping magnet 118 extends trom grounded battery, armature and back contact of magnet 118, winding ot magnet 118, conductor 119, lower contact ot sequence switch spring 120, inner right-hand armature and front contact of relay 107, and the lower contact of sequence switch spring lit) 117 to ground.` VStepping magnet 118 interrupts its own circuit and causes the advance oi" the sender selector brushes until an idle sender is tound. 1N hen an idle sender is found the absence of `ground on the test terminal of such sender breaks the locking circuit of relay 107 and this relay deenergizes, and opens the circuit of steli ping magnet 118, thus bringing the sender selector to rest. Relay 107 upon deeuergization also completes a circuit from grounded battery, power magnet of sequence switch 100, upper right-hand contact of sequence switch 116, inner right-hand armature and back Contact or" relay 107, lower contact ot' sequence switch spring 117 toA ground, for moving this sequence switchout of position 2 and into position 3.

During the limiting movement of the sender selector a circuit is in existence from grounded battery, armature and back contact of stepping magnet 118, winding of magnet 118, winding of relay7 121, lower right contact of sequence switch spring 122 to ground. 'llhe presence of direct ground on conductor 119 shunts relay 121 at this time, to prevent its operation. However, as soon as relay 107 is deenergized this shunt is removed and relay 121 is energized to` connect the controlling leads to the selected sender. Relay 121 at its inner lett-hand armature supplies ground to the terminal associated with test brush 115 to render the sender non-selectable iby other sender selectors. y

'its soon as the sender has been seized and relay 121 has operated, a circuit is completed from grounded battery, winding of line re lay 215 (Fig. 3), conductor 216, brush 1255, outer lei'tshand armature and front contact ont relay 121, upper left-hand contact ot sequence switch spring 125, trunk conductor 126, terminal 12, brush 8, inner lower armature of cut-oit relay .3, through the substation apparatus including` the sending device, the upper armature `and :trout contact ot relay 3, brush 6, terminal 10, trunk con ductor 127q upper left-hand contact of sequence switch spring 128, conductor 129, brush 130 and its associated contact, conductor 131 and the rightdiand winding' or' an induction coil 213. Relay 215 is energzed in this circuit and completes a circuit for slow-release relay 217. With. relay l" enerjized, dialing tone is induced into the line circuit just traced, since alternating current now supplied to the lefthand 4.ing ot coil 213, and thence through the control switch brush 314iand its normal contact to ground. VVhen the calling subscriber hears this tone he understands that he now tree to` dial and therefore he may b nv to transmit series ot impulses to set 'thiA various registers. A slow-release relay 399 is energized `in parallel with relay 217.

ylhe function, ot relay 399 will be kdesrribed hereinafter.

lt should be noted that upon the energiza4 tion or relay 121 a circuit is completed Lfrom grounded battery, winding ol relay 302 (Fig. 3), upper contacts of sequence switch spring 302i, sender selector brush 115, conductor 114tto ground at the inner left-hand armature and front contact ci relay 121. ltelay 302 is energized in this circuit and locks up through its inner righthand armature, while at its outer right-hand ture it supplies ground to sequence switch 301 by way ot the upper leftehund contact oi' sequence switch spring 308 to advance this sequence switch ont of position 1 and into position 3.

lt will be asumed that the line to bei selec-ted is one which terminates in a full inechanical exchange which may be selected directly by mea-ns oi a district selector and an office selector. ln this case the registers and class: register. switch will have to be. set in such positions as to control brush and group selection at the district, oliice, and incoming switches, and brush, group and line selection at the tinal switch.

ln order to prevent confusion as to which switches the various brushes and contact arms shown in Figs. 3 and L1- are related, the brushes belonging to the progression or side switch have been indicated by the letters SS; the arms ot the register switch vwhich is set in response to the two` series oit impulses ot the oliice code, have been designated by the letter C; the brushes ot the thousands register are indentilied by the letters ,ll'l, and those oit the hundreds, tens .and units registers have been designated `by the letters El, T, and U respectively.

It will be assumed that when the subscriber operates his dial to transmit the first letter oil the otlice code, three impulses will be The irst interruption caused bv the return of the dial causes the deenergization ot relay 215.

Before proceeding with the operation ot setting the Various register switches it should be noted that the energization ot' relay 217 completes a circuit troni grounded battery, winding ot relay 500, vertical oil-normal contact 531, `conductor 325, outer' lett-hand armature and front contact oit relay 217 to ground, for energizing' the relay 1100.

The deeneroization oi relay 215 complet-es a circuit 'troni ground through its armature and back contact, iight-hand armature and front contact of relay 217, winding of slowto-release relay 305, brush 312, conductor 32st, right-h and armature and frontl contactA oit relay 500, winding of vertical stepping magnet 504; to batt-ery and ground. The retraction of the armature of relay 215 also completes a circuit from grounded battery,

through the winding of relay 306, brush 313, conductor 322, outer left-hand armature and front contact of relay 500, contact and armature of magnet' 504, and thence to ground at the armature and back contact of relay 215. Relay 306 becomes energized and completes a circuit from ground through its outer armature and contact, winding of relay 305, brush 312, conductor 324, and thence as above traced, through the winding of magnet 504 to batte-ry and ground. Relay 306 is therefore energized in a circuit which depends upon the arma ure and contact ot' the verticalV stepping magnet 504, and as long as it remains energized a circuit for suc-h magnet Ais maintained independently oi the armature and bac-lz contact of relay 215. Should the opening period et the line. circuit be abnormally short due to an imperfect dial or for any other reason, the consequent attraction of the armature of relay 215 will not canse the premature opening of the circuit of magnet 504. The magnet 504 remains energized due to the continued energization ot the relay 306, until it has had time to advance the brushes of the switch a full step to position them opposite the iirst level ot terminals. When the full ste-p has been completed the armature and contact of magnet 504 are opened and t-he circuit of relay 306 Vis interrupted. Relay 306 thereupon releases its armatures and opens the circuit of magnet 504, which in turn becomes deenergized. Relay 306 furthermore maintains a circuit at its inner armature and contact for the slow-to-release relay 217. Relay 217 is designed to remain operated during the normal periods in which this circuit is opened by the armature of relay 21.5. If, however, relay 215 remains deenergized for an abnormally long period, relay 217 cannot become deenergized, due to the Jfact that relay 306 provides a substitute holding circuit therefor. As the translator switch, by which term the switch which receives the irst two series of impulses to register the office code will be hereinafter designated, takes its first step the cont-act 531 is opened to interrupt the original energizing circuit of relay 500. Relay 500 however, remains energized in the circuit as follows: grounded battery, through the winding, front contact, and inner lett-hand armature of relay 500, conductor 323, contact and armature of slow-torelease relay 305 to ground. Relay 305 does not retract its armature during the brief interruptions of its circuit at the armature and back contact of stepping relay 215. On each of the remaining interruptions ot the line circuit in the transmission of the lirst digit, the brushes 511, 512, 513, 514,515 and 516 of the translator are advanced one step until they are linally positioned opposite the third level of terminals in their respective banks. Following the third impulse the stepping relay 215 remains energized for a. comparatively ,long period, during which interval the slow-torelease relay 305 is permitted to release .its armature. Relay 305 opens the .holding circuit of relay 500, which becomes deenergized.

rlfhe calling subscriber next operates thc sending dial to transmit the second series ot impulses representing the second digit ot the oiiice code. lit will be assumed that seven impulses are sent. On the first opening of the impulse circuit relay 215 becomes; deenergized and completes a circuit to ground through its armature and back contact, right-hand armature and 'front contact or relay 217, winding oi relay 305, brush 312 and its normal Contact, conductor 324, right-hand armature and back contact of relay 500, winding ot the rotary stepping magnet 503 to battery and ground. A circuit is also completed 'tor the energization of relay 306 as follows: grounded battery, winding said relay, brush 31.3 and its normal contact, conductor 322, left-hand normal contact of relay 500, contact and a1'- mature of ystepping magnet 503 and thence to ground as above traced, at the back contact and armature of relay 215. Relay 300 in a manner similar to that previously de scribed closes a circuit for the rotary stepping magnet 503 to insure that said magnet takes a full step before its circuit is opened. For each of the seven impulses of the second digit the brushes of the translator switch are advanced one step over the third level of terminals, and are finally brought to rest in engagement with the seventh set ot terminals in such level. The slow-to-releasc rclay 305, which became energized during the transmission of the second series ol impulses, completes a circuit from ground, through its armature and Contact, conductor 323, inner left-hand armature and back contact of relay 500, conductor 327, winding` ot progression switch magnet 316, to battery and ground. Magnet 316 energizcs prepara tory to advancing the brushes oi the con* trol switch when its circuit is opened. After the last impulse has been transmitted relay 215 remains energized tor u period oi time sutiicient to permit the release ot slow relay 305. Relay 305 opens the circuit ol stepping magnet 316 which in turn dcencrgizes and advances the brushes 311, 312, 313, 314, and 315 into engagement with their second position terminals. The two movement step-by-step translator switch has thus been positioned in accordance with the oiiice code to determine the operation ot the district and office yswitches to route the call in the proper direction. The calling subscriber now continues to manipulate his dial to transmit the digits corresponding to the numerical designation of the wanted line. 1n a ten thousand line oiiice the subscriberls line number consists of tour digits and consequently, four mimerical registers 540, 545, 550 and are provided to take a record oi these digits. When the dial is operated to transmit the rst digit of the wanted number, relay 215 becomes decnergized and compietes a circuit from ground, through its armature and back contact, right-hand armature and front Contact of relay 217, brush 312, and its second terminal, conductor 329, winding of stepping magnet 541, to battery and ground, li/Iagnet 541 energizes and when its circuit is broken at the end of the i'irst impulse advances the brushes 543 etc., into engagement with .the second position. terminals. 1n a similar manner for each succeeding impulse the brushes oi register 540 are advanced step-by-step until a position corresponding to the lirst digit is reached. 4Relay 305 completes the circuit above traced for stepping magnet 316 and at the end of the series of impulses this relay releases to permit the deenergization of such magnet. The brushes of the control switch are thereupon advanced into engagement with vtheir third position terminals.

The `first deenergization of relay 215 in response to the transmission oi'f the second series of impulses of the wanted line number causes a circuit to be closed from ground throughthe armature and front contact of relay 217 winding of relay 305, brush 312 and its third terminal, conductor 330, winding of stepping magnet 546 ot' the hundreds register, to battery and ground. The register is thereupon moved forward stepby-step in response to the second series ot impulses. Relay 305 closes the above traced circuit for the stepping magnet 316 and at the end of the series opens its circuit to advance the control switch to its fourth posi tion.

In a similar manner the remaining series of impulses are directed to the stepping magnets 551 and 556, of the registers 550 and respectively, and these registers are advanced into their proper positions. Following the transmission of the last series of impulses the control switch isadvanced to its sixth position.

The circuits of the system are arranged to start the district and office selections immediately after the setting of the translator switch` or in other words, as soon as the record of the called oiiice has been received. lli-Thile the district and oitice switches are being positioned the subscriber may contin'ue the dialing operation to register the number of the called line.

y Immediately after the translator switch has been positioned the control switch is moved to .its second position terminal as eX pla/ined.. A. circuit is then completed from grounded rbattery,winding of relay 307, brush 314 and its associatedterminal to ground. Relay 307 becomes energized and locks `up in a circuit extending through its left-hand armature and front contact. toV ground by way of the sequence switch spring 398. Relay 307 at-its inner armature completes a circuit from grounded battery, power magnet of sequence switch 301, lower rightsliand Contact of sequence switch springv 303, left-hand armature and back lcontact of relay 371 to ground for causing the advance of class sequence switch 301 into a position to properly route the call. The position taken 'by sequence switch 301 is determined in accordance with the position which hasv been assumed by the translator switch. Class sequence switch 301 continues in motion until relay 371 is energized. The control of the energizing circuit of relay 3.71 is successively shifted to the various terminals in the translator bank served by translator brush 511 by way of the contacts of sequence switch springs 372 and 373. When sequence switch`301 reaches position 9g a circuit is completed from grounded battery, windingof relay 371, upper righthand contact of sequence switch spring 372, conductor 376, terminal 522, translator brush 511 to ground. Relay 371 is energized and opens at its left-hand armature, the driving circuit of sequence switch 301 which advances into position 10 under the control of its master Contact and comes to rest in this position. Relay 371 upon energization locks by way of its rightdiand ar mature, and the lower contact of sequence switch spring 398. Relay 371 at its lefthand armature completes a circuit from `grounded battery, power magnet of sequence switch 400, upper contact of sequence switch spring 439, leftehand armature and front contact of relayv 371, inner armature and front Contact of relay 307. to ground for moving this sequence switch out of position 1 and into position 2.

As soon as sequence switch 400 reaches position 2 a circuit is completed from grounded battery, left-hand winding of relay 107 (Fig. 2), lower left-hand and upper right-hand contacts of sequence switch spring 112, inner right-hand armature and front contact of relay 121. sender selector brush 132 and its associated contact, conductor 133, Contact of sequence switch spring 347, contact of sequence switch spring443, winding of stepping relay 445, `armature and back contact of relay 446, contact of sequence switch spring 444 to ground. Relays 107 andV 445 are energized in this circuit.

The energization of relay 107 completes a circuit from grounded battery, power magnet of sequence switch 100, lower righthand contact of sequence switch springt' 116',

654until the third shunting down of the stepinner right-hand armature and front contact of relay 107, lower contact of sequence switch spring 11.7 to ground for moving sequence'switch 100 out of position 3 and into position 4. Relay 107 remains energized in position 4 of sequence switch 100 due to the closure of a locking circuit extending from grounded battery, left-hand winding, armature and front contact of relay 107. conduc-` tors 110, 111, upper left-hand contact of sequence switch spring 112 to ground over the path described.

In position 4 of sequence switch 100 a circuit is completed for up-drive magnet 124.V This circuit extends from grounded battery, winding of magnet 124, upper righthand contact of sequence switch spring 120, inner right-hand armature and front cointact of relay 1.07, lower contact of sequence switch spring 117 to ground. The energization of magnet 124 causes the district selector to advance its brush shaft in a brush selecting movement.

Referring now toiFig. 3 it will be observed that the energization of stepping relay 445 completes a circuit from ground. armature and front contact of relay 445, upper contact of sequence switch spring 465, conductor 469. translator brush 512, termina-l 523, 'and thence to the armature and back contact of the No. 2 counting relay (Fig. and the winding of the No. 2 counting relay to grounded battery. The No. 2 counting relay is energized in this circuit and prepares in the well-known manner the circuit for the No. 2 counting relay, The winding of the No. 2 counting relay is however, shunted by the ground controlled at the armature and front contact of relay 445, and does not energize at this time.

As soon as the district brush shaft is advanced a sufficient distance to allow the commutator brush 135 to engage the first conducting segment of commutator 136, stepping relay 445 is shunted down, since the locking circuit of relay 107 now extends from grounded battery, left-hand winding of relay 107, left-hand armature and front contact of relav 107, conductors 110, 111, upper left-hand contact of sequence switch spring 112.y upper right-hand contact of sequence switch spring 113, commutator 136, and commutator brush 135 to ground. The shunting of stepping relay 445 causes it to deenergize and allow the No. 2 counting relay to be energized. The energization of the No. 2 counting relay prepares a circuit for the No. 1 counting relay in the wellknown manner. When brush 135 leaves the conducting segment of commutator 136, the shunt'is removed from lstepping relay 445, and-this relay again energizes, and causes the energization of the No. 1 counting relay. Thej counting relays are successively actuated switch 400, upper Contact of sequence switch spring 441, armature and front contact of the No. 0 counting relay to ground for moving this sequence switch ont of position 2 and into position 4.

rlhe energization of relay 446 opens the lower branch of the locking circuit ot relay 107 and when, a moment later. brush 135 engages an insulating segment ot romlnutator 136, the circuit of relay 107 is broken and this relay deenergizes, completing a circuit from grounded battery, power magnet. of sequence switch 100, upper right-hand contact of sequence switch spring 116. inner right-hand armature and back Contact of relay 107. lower contact of sequence switch spring 117 to ground` for moving sequence switch out of position 4 and into position 5. The deenergization of relay 107 also opens the circuit of up-drive magnet 124 and brings the selector to rest in a` position to trip the third set of brushes. As soon as sequence switch 400 leaves position 2 the locking circuits of the counting relays are broken at the upper and lower right-hand contacts of sequence switch spring 463 and the counting relays are restored.

In position 5 of sequence switch 100 the fundamental circuit is again completed, from grounded battery. left-hand winding of line relay 107. lowei` left-hand and upper right-hand contacts of sequence switch spring` 112, inner right-hand armature and front contact of relay 121, brush 132 and its associated contact. conductor 133. contacts of sequence switch springs 347 and 443. winding of stepping magnet 445. armature and back contact of relay 446. contact of sequence switch spring 444 to ground. Relays 107 and 445 are energized in this eircuit. relay 107 completing a locking circuit for itself by way of its left-hand armature and front contact. conductors 110 and 111` and the upper left-hand contact of sequence switch spring 112 to ground over the path described. Relay 107 also completes a circuit from grounded battery, power magnet of sequence switch 100. lower right-hand contact of sequence switch spring 116, inner right-hand armature and front contact of relay 107, lower contact of sequence switch spring 117 to ground, for moving sequence switch 100 out of position 5 and into position 6.

In position 5 of sequence switch 100 a circuit was completed from grounded battery,

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winding of trip magnet 137, upper righthand contact of sequence switch spring 122 to ground. The trip magnet was energized in this circuit to operate the trip rod so that on subsequent upward movement of the brush shaft the third set of brushes will be released into engagement with the section of the contact bank served by it.

rlhe above mentioned energization of stepping relay 445 completes a circuit from ground, armature and front contact of relay 445, lower Contact of sequence switch spring 465, conductor 470, translator brush 513, terminal 524, and thence through the armature and back contact of the No. 9 counting relay (Fig. 3), and the winding of the No. 9 counting relay to grounded battery. The No. 9 counting relay is energized and prepares a circuit for the No. 9 counting relay.

In position 6 of sequence switch 100 a circuit is again completed for Lip-drive magnet- 124, extending from grounded battery, winding of magnet 124, upper right-hand contact of sequence switch spring 120, inner righthand armature and front contact of relay 107, lower contact of sequence switch spring 117 to ground. Under the control of magnet 124, the selector brush shaft is moved upwardly to select the desired group. As soon as commutator brush 137 engages a conduct-- ing portionl of commutator 138, stepping relay 445 is shunted down and deenergizes to allow the energization of counting relay No. 9.

On the tenth shuntng down of stepping relay 445, counting` relay No. 0 is energized in parallel with relay 446 in a manner similar to that previously described. The energization of relay 446 opens the lower branch of the locking circuit of relay 107 and when, a moment later, brush 137 engages an insulating segment of commutator 138, the locking circ-uit of relay 107 is broken and this relay deenergizes. The deenergization of relay 107 completes a cir cuit from grounded battery, power magnet of sequence switch 100, upper right-hand contact of sequence switch spring 116', inner right-hand armature and back contact of relay 107, lower contact of sequence switch spring 117 t-o ground for moving sequence switch 100 out of position 6 and into position 7. The deenergization of relay 107 also opens the circuit of up-drive magnetl 124 and brings the selector to rest rllhe energization of the No. 0 counting relay completes a circuit to advance the sender sequence switch 400 out of position 4 and into position 6, in a manner identical with that previously described..

lilith sequence'switch 100 in position 7 a circuit is completed from grounded battery, right-hand winding of relay 107, upper lefthand contact ofl sequence switch spring 10S, lower contacts of sequence switch spring 109, right-hand armature and front contact of relay 102I to ground. Relay 107 is energized in this circuit.

It should be observed at this point that when sequence switch 100 reached position 2, a circuit was completed from grounded battery, left-hand winding of relay 139, upper left-hand Contact of sequence switch spring 122 to ground at spring 166. Relay 189 was energized in this circuit and at its left-hand armature transferred the holding circuit of relay 102 from the lower righthand contact oi' sequence switch spring 103 to the upper right-hand contact of such sequence switch spring. Relay 139 remains energized over this circuit until sequence switch 100 leaves position 11 except in the case of an abandoned call, which condition will be described in detail hereinafter.

With relays 107 and 139 energized in position 7 of sequence switch 100, a circuit is completed from grounded battery power magnet of sequence switch 100, lower righthand contact of sequence switch spring 116, inner right-hand armature and front contact of relay 107, right-hand contact of sequence switch spring 117, right-hand armature and front contact of relay 139 to ground for moving` sequence switch 100 out of position .7 and into position 8. As soon. as sequence switch 100 reaches position 7?,- a locking circuit for relay 107 is completed, extending from grounded battery, left-han d winding of relay 107, left-hand armature and front contact of relay 107, conductor 110, lower left-hand and upper right-hand contacts of sequence switch spring 145 to test brush 146 and its associated Contact, and thence to ground, provided the associated trunk is busy. It will be assumed that the first trunk in the group is busy. vRelay 107 therefore, remains energized and completes a circuit from grounded battery, winding of up-drive magnet 124, upper right-hand contact of sequence switch spring 120, inner right-hand armature and front contact of relay 107, lower leftnhand contact of sequence switch spring 117 to ground. The selector brush set is now moved upwardly over the terminals in the selected group and when an idle trunk is encountered, rground will no longer be found on the terminal associated with test brush 146. This branch of the locking circuit of relay 107 is therefore, opened, but the relay is held energized an instant longer in order to properly center the brush set due to` the closure of a circuit extending from grounded battery, right-hand winding of relay 107, upper right-hand contact of sequence switch spring' 108, a conducting portion of commutator 149, commutator brush 180 to ground. As soon as commutator brush 180 engages an insulating segment of commutator 149, at which time the brushes will be accurately centered on the selected terminal set, all branches of the holding circuits ot relay 107 are opened, and this relay deenergizes, causing in turn the f deenercization et ira-drive magnet 124. and

:n l z;

bringing the selector to test. The district select-or has now been actuated to seize a trunk leading to an idle ofliee selector switch. The dee-nergization of relay 107 also completes a circuit from grounded battery, power magnet ot sequence switch 100, upper right-hand contact oit sequence switch spring 116, inner right-hand armature and back contact ot relay 107, lower left-hand contact of sequence switch spring 117 to ground, Vfor moving' this sequence switch out of position 8'and into position 9.

When sequence switch 100 reached position 4, and with sequence switch 400 in position 4 or Some position beyond, a circuit was completed from grounded battery, winding of charge relay 152, lower contact oi sequence switch spring 140, conductor 141, outer right-hand armature and front contact ot' relay 121, lower right-hand contact ot sequence switch spring 142, brush 148 and its associated contact, conductor 144, resistance 223, contact of sequence switch springr 499, armature and back contact ot relay 498 to ground. Relay 152 was energized in this circuit and remains energized until sequence switch 100 leaves position 10.

As soon therefore, as sequence switch 100 reaches position 9 a circuit is completed trom grounded battery, right-hand winding of relay 10,7, upper lett-hand contact ot sequence switch spring 108, lower right-hand and upper lett-hand contacts ot sequence switch spring 109, right-hand armature and 'front contact of relay 152 to ground. Relay 107 is energized and completes a circuit from grounded battery, power magnet of sequence switch 100, lower right-hand contact etsevquence switch spring 116, inner right-hand -arinature and front contact oitl relay Y107,

lower lett-hand contact ot sequence switch spring 117 to ground for moving sequence switch 100 out ot position 9 and into position 10. In position 10, relay 107 remains energized over the circuit previously described. It is to be observed that the trunk leading to the selected otiice selector switch is made busy against other limiting dist-riet selector switches as soon as sequence switch 100 reaches position 84,-, since ground is supplied to test terminal 158 by way ot the upper contacts ot' sequence switch spring` 145.

In position 10 of` sequence switch 100, the Jfundamental circuit is extended to the otlice selector switch (not shown) by way ot the lower contacts ot sequence switch spring 151 and the upper lett-hand and lower righthand cont-acts of sequence switch spring 155 6. by wayotbrushes 154 and 157 and their associated terminals 159 and 158. The tundamental circuit is entirely metallic to the oiiice selector and the switches beyond, and extends trom the stepping relay 445 by way ot the contact of sequence switch spring 466, conductor 343, sender selector brush and its associated contact to the ring conductor ot the trunk as described. lit has not been considered necessary to disclose the circuits oi' the oilice, incoming. and linal selector switches, since they are fully disclosed in the previously mentioned Lun-.dell application, Serial No. 487,520. ln case the call was to have been extended directly to an incoming switch the class sequence switch would have been in a position to cause the advance ot the sender sequence switch 400 through positions 6 and 8.

The necessary selecting operations are performed at the succeeding switches in the well-known manner, under the control of the counting relays and the registers shown in Fig. 4. At the conclusion ot each selective operation, the cnergization oiI the 0 counting relay operates to advance sequence switch 400 into position to control the next selection, and during such advance oi" the sequence switch the counting relays are rcstored. It has been assumed in order to simplify the disclosure, that oilice brush selection takes place in position G of sequence switch 400, oliiee group selection in position 8, incoming brush selection in position 10. incoming group selection in position v12, tinal brush selection in position 14, final group selection in position 16, and inal line selection in position 17. At the conclusion ot the selective operations, the sender selector switch 400 is, therefore. in position 18.

Then sequence switch 400 reaches position 18 a circuit for relay 498 is completed, by way of the contact of sequence switch spring 497. The energization ot relay 498 opens 'the circuit which has been holding relay 152 (Fig. 2), energized, and relay 152 is decnergized. Relay 152 opens the holding circuit through the right-hand winding ot relay 107. and relay 107 is deenergized and completes a circuit from grounded battery, power magnet of sequence switch 100, upper righthand contact of sequence switch spring` 116, inner right-hand armature and back contact ot relay 107, and the lower contact ot sequence switch spring 117 to ground, for moving this sequence switch out ot position 10 and into position 13, which is the talking 1` position.

As soon as sequence switch 100 leaves position 109,- the impulse circuit into the sender is opened at the upper left-hand contacts Vof sequence switch springs 128 and 125, respectively. As a result of the opening of' the impulse circuit, relay 215 is deenergized, causing in turn the deenergization ot slowto-release relays 217 and 399.

A circuit is now completed from grounded battery', winding et control switch stepping magnet 316, armature and back contact oit such magnet, brush 311 and .its sixth contact, and the right-hand armatures ind back contacts ot relays 217 and 215 to ground. ltlagnet 316 interrupts its own circuit and advances the control switch into its tenth position, in which position its circuit is opened by the advance ot brush 311.

llVith the control switch in its'tenth position, circuits are completed tor restoring the inimerical registers. The circuit of the stepping magnet ot the thousands register extents 'trom grounded. battery, winding ot the magnet 541, armature and back contact of such magnet, register brush 542, and an oit-normal contact, conductor 579, brush 314 and its tenth contact to ground. ln parallel with this circuit, circuits are completed torstepping magnets 546, 551. and 556, by way ot the hundreds,`tens and units regis ter brushes 547, 552, and 557 respectively. lThe numerical registers are resto-red to their normal positions, and when they reach their normal positions, a circuit is completed from grounded battery, winding oit control switch steppingI magnet 316, armature and back contact ot such magnet, control switch arm 315 and tenth terminal, and thence through brushes 543, 548, 553, and 553 and their normal contacts. to ground. Magnet 316 is energized in this circuit and interrupts its circuit to advance the control switch into its normal position.

rlhe step-by-step otlice code register switch is restored as soon as relays 215 and 217 are deenergized. This is accomplished due to the closure ot a circuit trom grounded battery. 'winding of release magnet 502, vcrtical ott-normal conta-ct 532. and thence to ground at the baclr Contact of relay 215. The operation of release magnet 502 restores the two-movement step-by-step registei1 switch in the well-known manner.

As soon as the control switch reaches its normal position, a circuit is completed trom grounded battery. winding ot the power magnet et sequence switch 400, left-hand contact ot sequence switch springl 439, control switch arm 311, and its normal contact, and the ri ghohand armatures and back contacts of relays 2.17 and 215 to ground. Sequence switch 400 is advanced into position 1.

1When sequence switch 400 reaches position 1.. a circuit is completed tor restoring the class sequence switch 301 to its normal position. This circuit' extends 'from grounded battery,power magnet ot sequence switch 301, upper right-hand contact ot sequence switch spring 308, contact oit se quence switch spring 442. control switch brush 311 and its normal contact, and thence to ground as described.

The advance of sequence switch 100 into position 13 causes circuit changes at the succeeding switches in the train to cause ringing current to be applied to the called line, and to cause the sequence switches associated with the remaining switches in the train to be advanced into their various talking positions. rthe manner in which this is accomplished is well understood in the art. When the called subscriber answers, polarized relay 160 is energized due to the application @t a source ot battery of suitable polarity tothe tip and ring conductors. The energization ot relay 160 completes a circuit from grounded battery, winding of charge relay 152, right-hand contacts of sequence switch spring 109, the armature and front contact ot relay 160, and the upper right-hand Contact of sequence. switch spring 166 to ground. Relay 152 upon energization locks up by way of the upper lefthand contact of sequence switch spring 109, and the right-hand armature and front contact ot said relay. In position 13 of sequence switch 100, talking battery is supplied to the calling subscriber through the lett-hand windings ot repeating coil 162 and a relay 167, by way of the lower right-hand contacts of sequence switch springs 125 and 128, respectively.

It would be well to observe at this point that relay 139 is a differentially wound relay, and is maintained energized in positions 2 to 11 of sequence switch 100 by a circuit from grounded battery, left-hand winding of relay 139, upper lett-hand contact ot sequence switch spring 122 to ground. 1n positions 1 to 10 of sequence switch 100 a circuit is in existence through the right-hand winding ot relay 139, upper lett-hand contact of sequence switch spring 140, outer right-hand armature and front contact of relay 121, lower contact of sequence switch spring 142, brush 143 and its associated contact, conductor 144, resistance 223, contact ot sequence switch spring 499, and the armature and back contact of relay 493, to ground. Since this circuit includes a resistance 223 (Fig. 3), the magnetic flux set up by the right-hand winding of relay 139 is not sutlicient to overcome the oppositely poled flux set up in the left-hand winding, and therefore, relay 139 remains energized. When sequence switch 100 reaches position 1035 supervisory relay 167 is energized, and the holding circuit of relay 139 now extends through its left-hand winding, armature and front contact of relay 167, and right-hand armature and front contact of relay 139 to ground. VAs soon as sequence switch 100 leaves position 11 the control of relay 139 is entirely dependent on relay l167.

l/Vhen conversation is completed and connection is no longer desired, the calling subscriber will replace his receiver causing the deenergization of relay 167, which causes in vturn fthe deenergiz'ation of relay 139. circuit is thereupon completed from grounded battery, power magnet ot sequence switch 100,v conductor 168, lower right-hand and upperleft-hand contacts ot sequence switch spring 169, right-hand armature and back contact of relay 139 to ground, for moving sequence switch 100 out of position 12 and into position 17. The deenergization of relay 139 does not allow relay 102 to deenergize since this relay is maintained energized in a holding circuit through its right-hand winding by way ot conductor 170, left-hand armature and front contact of relay 152, conductor 171.v upper lett-hand Contact of sequence switch spring 103 to ground through Ythe cut-od relay and message register of.y the callingsubscribers line.

In position 17 of sequence switch 100, due to the energized condition of charge rela-y 152, a circuit is completed from grounded battery, right-hand contacts of sequence switch spring- 172, outer lett-hand armature and front contact of relay 102, lett-hand non-inductive winding' of relay 102, conductor 170 to ground, over the path described. The battery now supplied throughrthe two windings of relay 102 in parallel-raises the potential on conductor 171 sutliciently to allow the message register magnet 17 to operate to record a call against the calling Subscriber. It is obvious that it the called Subscriber had not answered. charge relay 152 would not have operated and no charge would have been made against the callingsubscriber. In this case, relay 102 would have deenergized as soon as'relay 139 released, thus causing the imvmediate release lof the calling` subscribers individual line switch as will be described. In position 17 of sequence switch 100, a time interval is provided by means of in- `terrupter's indicated at 173 and 174, to insure the allowance ot. enough tiine tor the proper operation of the register operating magnet.vr As soon as a circuit is completed through the conducting segments oi' interru-pter 173, a circuit is completed from grounded battery. right-hand winding of reay 107, lower lett-hand contact of sequence switch spring 108, conducting segments of Y interruptor 173 to ground. Relay 107 is en- ,ergized in this circuit and locks up through its lett-handv armature to ground by way of'conductors 110, and 111, and the lefthandcontacts of, sequenceV switch spring V145;V -VVlien`, shortly thereafter` interruptor 1774:.closesits" contacts, a circ-uit is completed from'grounde'd battery, left-hand winding of relay 139, conductor 175, upper contacts of sequence switch spring 142,'outer right-hand armature andfront ycontact o't relay 107,

iconductorxr176, right-hand; contacts of sequence switch spring 177. contacts of interrupter 174.- to ground. Relay 139 is energized in this circuit and completes a circuit from grounded battery, power magnet ot sequence switch 100, lower right-hand Contact of sequence switch spring 11G, inner rightdiand armature and front contacts of relay 107.` upper right-hand Contact of seuence switch spring 117, right-hand armature and 4iront contact ol relay 139 to Tf ftound, for moving sequence switch out position 17 and into position 18. incase the call has been unsuccessful and the callingv subscriber had received no answer, charge. relay 152 would not ha vc been operated. 'llheretortu when th(` calling subscribei.' replaced his receiver on the hook relay 139 would have been deenergized and caused sequence switch 100 to inove into position 17 as previously described. ln this ii" case however, the deencrg'izaticn ol' relay 139 would have caused the decuergrization ot relay 102 as soon as relay 139 decnerg'izcd since with charge relay 152 deenergized no holding' circ-uit for relay 102 is in eriiistence. Sequence. switch 100 would therefore, have been immediately nioved out of position 17 and into posit-ion 1S, due to the closure ot acircuit trom `grounded battery, power mag net oi sequence switch 100. conductor 10S. lower contacts ot sequence switch spring 109. rightehand arn'lature and bach contact ot relay 102 to `ground. The release oft relay 102 would also have caused the innnediate release of the calling subscriber-s individual line sivitch in a manner to be hcreiua tier de scribed,

in position 1S oit sequence switch 100 a circuit is completed troni grounded battery. windingl oi" down drive magnet 173, upper contacts ot sequence switch spring 169, right-hand armature and back conta t ot' relay 139 to ground. Under the control o l' magnet 17S the district brush shaft is restored to its normal position, and when its normal position is reached a circuit is coni pleted 'troni grounded battery` power mag-- net ot sequence switch 100. lower lc''tdland contact ot sequence switch spring 110, normal coinniutator segment 179, connnutator l brush 180, to ground, Jfor moving- .sequence switch 100 out o't position 13 and into position 1.

As soon as sequence switch 100 leaves posit-ion 17 the battery supply on the sleeve terminal oi the line` switch is cut oil'. and the cut-oli' relay of the calling` line is deenergized to allow the 'calling subscribers line switch to be restored to its normal position. The deenergization ot relay 102 also reino ves the busy ground condition Ytroni the test ter ininal ot the line switch to render the switch selectable by other hunting' line switches.

The restoration ot the district switch shown in F 2 causes the restoration ot the 1550 dll succeeding switches in the train in the man ner fully described in the hereinbefore nien` tioned Lundell application, Serial No. 487,520.

Referring now to Fig. 1 the: release of the calling subscribers individual line switch will be described. As soon as cut-off relay 3 is deenergized, stepping magnet 4 is energized in self-interrupting circuit extend ing from grounded battery, winding, armature and back contact of magnet 4, lowermost armature and back contact ot cut-oil' relay 3, right-hand armature and back con tact of line relay 2, olf-normal contact 13 to ground. The operation of magnet 4 causes the line switch to be advanced into its normal position, at which time contact 13 is opened to bring the switch to rest.

The manner in which the apparatus is restored to its normal condition in case the calling subscriber prematurely abandons his call, tha-t is, replaces his receiver before the connection. is completed, will now be described.

The replacing of the receiver by the calling subscriber will in every oase, result in the deenergization of differential relay 139 and the consequent deenergization of rela-y 102 and cut-od relay 3, as just described, so that the line switch is immediately restored in every case. This immediate release of the line switch is a novel feature and will be claimed hereinafter.

It will first be assumed that the district switch has been completely positioned at the time the calling subscriber replaces his receiver. ln this case the district sequence switch is in position 10.

lt the sequence switch 100 had been in some position beforethat in which trunkhunting takes place, the deenergization ot' relay 139 will complete circuits for restoring the district switch immediately, However, with the district switch positioned, in order to prevent the possibilit-y of Yfailure to release the succeeding switches in the train and to completely operate the sender, it is` necessary to wait until all the switches have beenset before the dist-riet switch can be released. Sequence switch 100 does not move out of position 10 since itrcanno-t advance until relay 107 is deener'gized, and this relay is maintained energized by means of a cire cuit completed at the right-hand armature and front contact of relay 152,l which it will be remembered lis at this time, held energized by means of ground supplied to conductor 144.

ln case the subscriber had dialed his complete code at the time of replacing his receiver, all of the switches'are set as previously described.l and sequence switch 100 is moved out of position 10 and into position 13 as previously described. However, since the subscriber hasnow abandoned the call a circuit is completed as soon as sequence switch 100 reaches position. 12, this circuit extending from grounded battery, power magnet 100, conductor 168, lower right-hand and upper lett-hand contacts of sequence switch spring 169, right-hand armature and back contact of relay 139, to ground, for advancing sequence switch 100 out ol" position. 12 and into posi-tion 17.

Since relay 102 is deenergized as soon as relay 139 is deenergized, because charge relay 152 cannot reoperate under these condi tions, sequence switch 100 is immediately moved out of position 17 and into position 18, due to the completion of a circuit extending from grounded battery, winding of power magnet of sequence switch 100, conductor 168, lower contacts of sequence switch spring 169, right-*hand armature and back contact olf relay 102, to ground. The completion of this circuit causes the advance of sequence switch 100 out of position 17 and into position 18. The district selector is then restored to its normal position as pre* viously described.

In case the calling subscriber abandons the call without having fully dialed the digits of the wanted number, and assuming that the district switch has been positioned at the time such abandonment takes place, the release of the apparatus is accomplished in a. manner substantially like that described. As before, relay 139 is deenergized, due to the dilerential action of its right-hand winding when direct ground is supplied to such winding to cause the deenergization of relay. llhen the calling subscriber abandons the call under the conditions under discussion, the'opening of the impulse circuit causes the dee-nergization of line relay 215 and the subsequent deenergization of slowrelease relay 217. An energizing circuit for relay 220 is thereupon completedlby way of the right-hand armatures and bach contacts of relays 217` and 215. Relay 220 supplies ground through noresistance to conductor 144 by way oit' its armature and front contact and the contact of sequence switch spring 397, thus short circuiting resistance. 223, and allowing sufficient current to iiow ythrough the right-hand winding of relay V139, to cause the release of this relay, due to the dilerential actionof its windings. The deenergization o'l relay 139 causes the deenergization of relay 102 and cut-otlrelay 103,

with the subsequent restoration of the line switch. The succeeding switches in the train are operated in turn, but since certain ones of the registers have not been positioned, the switches controlled by them will be caused to take 0 settings, since in the normal positions of the registers they will control the counting relays to send one pulse only in each case. Then the sender sequence switch reaches position 18 the advance of the sender circuits-and the release of the district switch take place as previously described.

It the calling subscriber abandons the call before the district switch has been positioned the release of the district switch may be accomplished in one ot several ways, depending upon the particular position in which sequence switch 100 is resting at the time of the-'abandonment of the call. In each case'the replacing ct' the receiver causes the de'energization ot' relays 215 and 217. Vith vrelays 215 and 217 deenergized, relay 220 is energized as described by means of a circuit extending through the right-hand armatures and back contacts of relays 215 and 217. The energization of relay 220 causes direct ground to be supplied to conductor 144, and consequently causes the deenelgization ot differential relay 139. The deenelrgization of relay 139 causes the deenergization of relays 102 and 3 as previously described.

It sequence switch 100 has not reached position 7 `at the time of the abandonmentof the call, the deenergization of relay 102 comple-tes a circuit from grounded battery, winding of power magnet of sequence switch 100,

Vconduct-or 168, lower contacts ot' sequence ceeding switches in the train are not operswitch spring 169, right-hand arma-ture and back contact of relay 102 to ground for moving sequence switch 100 out of whatever position it is in and into position 7; In position 7 with relay 102 deenergized, a circuit is completed :trom grounded battery, winding of down-drive magnet 178, upper right-hand and lower left-hand contacts ot sequence switch spring 169, right-hand armature and back contact of relay 102, to ground. The district selector brush shaft is then restored to its normal position, and when it reaches its-'normal position, a circuit is completed from grounded battery, power magnet of sequence switch 100, lower left-hand contact of sequence switch spring 116, normal commutator segment 179 and commutator brush 180, to ground, for moving sequence switch 100 out of position 7 and into position 1.

In the case just described, that is, when the district switch is not positionedV at the time the call has been abandoned, the sucated, and the sender is restored to its normal condition.

It should be observed that while stepping relay 215 is'energized a slow-to-release relay 399 is energized in parallel with slow release relay 217.V It abandonment of the call takes place after sequence switch 100 has reached position 715/4 the sender sequence Vswitch will not be restored due to the tact that relay 496 (Fig. 3) is energized over a circuit extending from grounded battery, winding otrelay 496, lett-hand armature and back Contact of relay 399, conductor 221', sender-selector brush 181 and its associated bank contact, sequence switch spring 182, to ground. In the present case since the district sequence switch had not yet reached position 7 at the time the call was abandoned, relay Ll96 does not lind an energizing circuit upon the release of relay 399, since the circuit ot relay 1-96 is held open at sequence switch spring 182. The release ot relay 399 therefore, completes a circuit from grounded battery, power magnet ot sequence switch 400, lower contact ot sequence switch spring tl-1 right-hand armature and back contact oi' relay 399, armature and back contact ot relay l96, to ground, tor moving the sender sequence switch out ot whatever position it is in, and into position 1. T he release ot the register switches and the class sequence switch takes place as previously described.

It sequence switch 100 is standing in position 7 at the time the subscriber abandons the call the deenergization ot relay 102 will complete the above traced circuits for causing the restoration of the switch by energizing down drive magnet 178. Sequence switch 100 is advanced into position 1, by means ot the normal commutator segment, as just described. The release ot the sender taires place as justdescribed.

It the calling subscriber abandons the call. after sequence switch 100 has lett position 7 but before it reaches position 10, the remaining switches in the train are operated. since in this case relay 496 will be energized to prevent the release ot the sender sequence switch as soon as its circuit is closed at sequence switch spring` 182. It the district sequence switch is in position 8 trunk hunting is completed and the setting ot the succeeding switches is then completed as previously described. It all the switches have been set release takes place in the usual manner.

From the foregoing it will be apparent that it abandonment of a call takes place before the directive operations ot the dis-- trict switch have been completed, the district switch and the sender will be immediately restored. It the call is abandoned at any time thereafter the selective operations of the entire train of switches talre place before the apparatus is restored. It should also be noted that the. release ot the calling subscrib'ers line switch is started as soon as the call is abandoned, except in the case ot a completed connection to which the called subscriber has responded, in which case the, release of the calling subscribei"s line switch is delayed until onlv the message register magnet has had an opportunity to operate to register the call.

It should also be noted that relay 139 which controls the release. is at certain times caused to deenergize under the control rof circuits set up in the sender, and at llu lli

other times is caused to release under the control of circuits associated with the district selector switch;

What is claimed is:

l. lln a telephone exchange system, an incoming line, an outgoing line, an automatic switch for interconnecting said lines, a sending device, means to operate said sending device, means to selectively control said switch during a portion of the operation oit said sending device, a diderential relay controlled in accordance with the electrical condition of said incoming line, release circuits effective upon the operation of said relay at certain times to cause the immediate restoration of said switch and said sending device, and means eiilcctive upon the operation of said relay at other times to cause the release oit said switch and said sending device only after the `complete operation oli' said sending device.

2. 1n a controlling system, a line, a differentially wound relay, means to complete an energizing circuit through one winding of said relay, a resistance, means to complete a circuit through another winding of said relay and said resistance without releasing said relay, means to short-circuit said resistance to cause the release of said relay, said short-circuiting means being controlled in accordance with the condition of said line, and means to subsequently come plete a locking circuit for said relay controlled in accordance with the condition of said line independently of said. other winding.

8. lu a telephone exchange system, an automatic switch, a release relay therefor, an impulse relay, a supervisory relay, means operative at certain times to control said release relay in accordance with the condition ot' said impulse relay, and means operative at other times to control said release relay at contacts of said supervisory relay.

ln a telephone exchange system, an incoming line, an outgoing line, `an automatic switch for interconnecting said lines, an impulse relay, registering devices. means to position said registering devices under the control of said impulse relay, a sending device, means to operate said sending de vice in accordance with the setting of said regi ste "ing devices, means to selectively control said switch during a portion ot the operation ot said sending device, a supervisory relay, release relay for said automatic switch, means operative at certain times t0 control said release relay in accordance with the condition oli said impulse relay to cause the release of said automatic switch, and means operative at other times to control said release relay at contacts ot said supervisory relay.

ln a telephone exchange syst-em, an incoming line, an outgoing line, an automatic switch for interconnecting said lines, a plurali-ty of sending' devices, means to associate an idle sending device with said automatic switch, an impulse relay and a set o registering devices individual toi each ol'n said sending devices, means to position said registering devices under the control of said impulse relay by means oiI impulses transmitted over incoming line, means to operate said sending device, means to selecn tively control said switch during a portion of the operation of said sending device, a supervisory relay associated with said switch, a release relaytor said automatic switch, nier-,ns operative at certain times t0 control said release relay in accordance with the condition of said impulse relay, and means operative at other times to control said release relay at contacts of said supervisory relay.

6. ln a telephone exchange system, an incoming line, an outgoing line, an auto matic switch for interconnecting said lines, a plurality of sending devices, means to associate an idle sending device with said automatic switch, an impulse relay and a set of registering devices individual to each ot said sending devices, means to position said registering devices under the control of said impulse relay 'by means of impulses transmitted over said incoming line, means to operate said sending device, means to selectively control said switch during a portion of the operation of said sending device, a supervisory relay associated with said automatic switch, a release relay for said automatic switch, means operative at certain times to control said release relay in accordance with the condition of said impulse relay, means operative 4at other times to con trol said release relay at contacts of said supervisory relay, release circuits controlled by said release relay effective when said relay is operated at certain times to cause the immediate restoration of said switch and said sending device, and release circuits effective upon the operation of said release relay at other times to cause the release of said switch and said sending device only after the complete operation. of said sending device.

7. 1n a. telephone exchange system, a calling subscribers line, a plurality of selector switches, a trunking switch, means to operate said trunk'ing switch t0 establish connection between said calling subscribers line and an idle one of said selector switches, release means for said trunling switch, an electromagnetic device associated with said calling subscribers line, means operat-ive under certain conditions to actuate said device, means to delay the operation of said release means when a calling subscriber abandons a call under said certain conditions, and means operative lygflien a calling subscriber abandons a call lectors-witches, a trunling switch, means to operate said trunling switch to establish connection between said calling subscribers line and an idle one of said Selector switches, release Ineans for said "orunkingl switch, a release relay for said selector switch to control Yalso the release of said trunking switch an electromagnetic de viee associated with said calling snbscribers line, means operative under certain conditions to actuate said device, means to delay the operation of said release means when a calling subscriber abandons a all-under said certain conditions, and means operative when che calling subscriber abandons the call under other conditions to render said release ine-ans innnedia'ely effective.

In Witness whereof, l hereunto subscribe my naine this 20th day of June, A. D. 192i.

FREDERICK J. SCUDDER.

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