US1347069A - Automatic telephone system - Google Patents

Description

G. A. YANo'cHowsKl. AUTOMATIC TELEPHONE SYSTEM.

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TTO/P/VF Y G. A. YANOCHOWSKI.

AUTOMATIC TELEPHONE SYSTEM.

l APPLICATION FILED APR.10, |916. 1,847,069. wanted July 2o, 1920.

2 SHEETS-SHEET 2.

MTA/55555 w/E/VTQR:

FQ MATITA?? UNITED STATES PATENT OFFICE.

YGfEOItGrnI/i, YANoCIioWs-KI, or CHICAGO,v ILLInoIs, nssIGivOR` To AUTOMATIC ELECTRIC CQMPANY, or CHICAGO, TLLIIOIs, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE sYsTn'M.

Application filed April 10, 1916.

To @Zlio/0m 1i/map' Concern! y 'Y leit known that I, Gro-non AQ YANooI-Iowsin, a citizen oit the United States of America, and a resident oi Chicago,` county ,of Cook, and State ot Illinois, have invented certain new and useful improvements in Automatic rtelephone Systems, ot' Vwhich the following is a speciica'tion..

VMy invention relates to automaticV telephone systemsand more particularly to those automatic systems which are commonly rinown as, two-wire, systems, so called by reason of the iact that the' automatic switches are Controlled over the two sides oi the line in series, exclusive of ground at the subscribefs station.

ln systems or' the above general character it has been the common practice to control the release and the switching of the' local circuits of the automatic switches through the medium of a combination ot' quick and slow acting relays. More specificallyfa slow acting relay may be provided responsive to a prolonged interruption of the line circuit to control the release, while a'. second slow acting relay may be provided responsive to a ltime interval between series ot impulses to control the switching.

The object of my invention'is to provide an automatic system in which the control ot 'the releasing'and switching functions does not depend exclusively upon a time element, thereby avoiding to a considerable extent the use of slow acting' relays.

The particular means employed in attaining the foregoing ends and the operation thereoi will be fully described hereinafter, reiference being had to the accompanying drawings, in which Figures l and 2, when alten' in order with the lines at the ends thereoiQ in alinement, represent.,diagram` .f'cally a complete circuit connection be'- n a cfing substation ri. anda called tion` It in a system embodying the ciples oit my invention. The said connection has been established vthrough the,

medium ot the idividual line switch C, selector switch E, and connector H.Y Fig. 3 is a detail oi" a portion ofthe dial mechanisni.

Referring now toFig. l, the subscribers substation .et be or" any suitable type and comprises the usual receiver 2, transmitter Sfringe'r and' condenser 5. Being an automatic substationit is also provided with suitable impulse sending device somei. Specification of Letters Patent.

Patented July 20, 1920 serial No. 90,047.

what similar to that shown in British Patent No, 29,654- ot 1910 to S. G. S. Dicker, except that two extra impulse Vsprings are added, together' with means for controlling the same. The impulse sending` device comprises a pair of impulse springs G and 7, and an auxiliary pair of impulse springs 9 and l0, which are assumed to be controlled through the medium of a finger hole dial (not shown) in suoli a manner that the impulse springs G and 7 may be momentarily separated a number of times corresponding to the digit called, followed by a group ot high speed impulses or interruptions transmitted bythe impulse springs 9 and ll). These highspeed impulses are similar to the impulses transmitted by the impulse springs 6 and l but are at a much greater speed, or in other words, they consist ot one or more interruptions or impulses at a high frequency, as lcompared to the impulses transmitted by the impulse springs (l and 7. Referring to Fig. 5, it will be seen that to the rotatable portion ll of the dial, there is secured a pawl l2, one end oi2 which is held in normal position against the pin 13 by a spring le'. lllhen the dial is rotated in a clockwise direction (which is in a counter clockwise direction as seen in Fig. 3),the pawl l2 strikes the spring 9 in such a inan- `ner as to tilt the said pawl downward, thus allowing it to pass the spring 9 without causing it to break contact with the spring l0. But when the dial is released and the rotatable portion ll rotates back to normal, one or more impulses are transmitted over the line conductors by means ot impulse springs 6 and T, then, just before the dial has returned to normal position, the pawl l2 engages the spring` 9 and bends itdowne ward until the pawl 1Q, has passcdbeyond the said spring. Then the pawl l2 releases the spring 9, the said spring v'ibrates for a instant and br alrs Contact several times with spring l0, sending one or more quick or high frequency impulses'.

'lie hoolt switch 16 in addition vto controlling the usual hook switch springs 1T, 18 and i9. also controls the springs 20, 2l,

. TO and 7l.l The springs 2() and 2l are constructed similar to the springs 9 and l0, that is, when the receiver is removed from the switch hook, the pawl 72 `on arm 22 attached to the hook switch lever i6 operates to tilt downward an nisses the sprh 2O and 2l without separ ating their Contact, v

but whenpthe receiver is placed upon the hook switch, the arm 22, invlowering, bends the spring 2O downward, after which and as soon as the spring 2O slides off the arm 22, a number of high speed impulses Yare the said impulse springs, then the springs 20 qand 21 operate as herein described and lastly the springs 17 and 18 separate to` open the line circuit. The subscribers'individual switch C is of the general type of lineswitch shown in British patent to R. lV. James ;l;t26,301 of` 1906, and similar to the type 'of switch shown Vin British Vpatent to T. Gr.v Martin #1419 `oi 1910, the circuits being slightly modified,

however.l This line switch comprises, among other details, a plunger (not shown) Vattached to the end of a so-called plunger arm 23, which is controlled by the magnet 24.: The magnet 24 comprises two windings, namely, the pull-in winding 25 and the holding or cut-ofi' winding 26. The winding 25 operates both the plunger arm v23 and theV cut-ori1 armature 27 while the windv ing V26 is only strong enough to-operate the armature 27 and toV hold the plunger arm 23 in an operated position after it hasV once been operated bythe pull-in winding 25. 'l'he circuit of the pull-in winding 25r is controlled by the line relay 2S andthe auxiliary'V relay 29, 'both of which preferably, make slow acting, that is, they are slow to denergize after their energizing circuit has been broken. Vhen the plunger n arm 23 is operated, theplunger is forced into a bank of contact springs, forcing the springs 30, 31, 32 and 33 into engagement with springs 34, 35, 36 and 37, respectively. Although only one set of springs (30-37) is shown, each line switch is provided with a plurality of such sets, each set forming the terminal of a trunk line 'leading to a selector switch E. Ylach trunk line is connected Vin multiple to. the lcorresponding springs of all the switches of the 'group which is controlled by the master switch D.

The master switch i) 'is of the same gen- Y eral type as that disclosed in British Patent #26,301 above referred to; being, however,

of the'particular type disclosed in saidBritish Patent .#1419 of 1910. The function Y of the'inaster switch, as is wellknown, is

Vto maintain the plungers of all the idle line switches in position to engage the terminal of an idle trunk line.

The irst selector E 1s of theV same general type oi' selector switch disclosed -in the United VStates Letters VPatent jr-,5815,331, granted `March 13, 1906 to Keith, Erickson, and Erickson except that the so-called side switch is dispensed with and the circuits are modified inaccordance with my invention to adaptV the switch to operate in a system in whichcontrolling impulsesare delivered over the two sides of the lineY in series. Among other details, the selector E comprises a bank Vof contacts arranged in horizontal rows or levels, which lcontacts are adapted to be engaged by a set of wipers 38, 39 andf40 carried upon a shaft (not shown) which has a verticalmovement con- 80 trolled ,by the vertical magnet 41 and a Y rotary movement controlled bythe rotaryV magnet 42'. The operations or various parts of the switchv are controlledV through the medium of the double wound line relay 43. Means vfor permitting'the switch to be restored to normal position is provided in the release magnet 44, which, uponenergizing, vwithdraws `the retaining double-dog from the shaft thereby allowingthev shaft and wipers tobe-restored to their normal position.. The contacts 45and 46 close only when the switch-shattlias been raised one or more steps from its lowest position. Thev Y contact spring 47 (controlled by the arma- -95 ture 48 of line relay 43) is so constructed and adjusted as to follow up the spring 49 when thenrelay43 is energized. Should one ork more impulses vbetransmitted..through the line relay 43, as ordinarily produced byV the operation of the impulse springs 6 and 7, the springs 47 and 49 will operate in unison and fremainl in contact, but should high speed impulses be transmitted to the line relay by means ofthe impulse springs 105 v9 andlO or the releasesprings 20 and 21, the

springs 47 and 49 willbe separated for anV instantbecause the spring 47, by V'reason of the inertia of theweight at its extremity, isY unable to'follow. '.1 11( The connector switch H' (Fig.l 2) is of the l generalztype vof connector switch disclosed in United States Letters Patent #815,17 6 granted March 13, 1906, to Keith, Erickson,

vand Erickson; the circuits, however, being modified in vaccordance with the same principles followed in the design of the selector Like. the selector, the connector is provided with a' shaft `(not shown) carrying the l wipers 55, 56, and,57,'and controlled by the 12( vertical magnet'53 Vand the rotary magnet 54. The usual sideY switch comprising the wipers 50, 51, 52, vand 59 is controlled 'by the private magnet 58 in the usual andV well `known. manner. The Vmagnet 60 is the usual 12:

release magnet. -The relay 62 is the back bridge Yrelay whichfurnishes talking batteryto the called subscriber. The springs 63 and 64 controlled by the line relay 61 operate in Y the same manner as hereinbet'ore 13( described in the case of the springs 47 and 49 of the selector E. The contacts 65, 66, and 67 close only when the shaft has been raised one or more steps from its lowest position, while the contact 68 closes only when the shaft has been rotated one or more steps from its normal position. AThe relay 69 is the means through which ringing current isV applied to the called line. y The substation shown at A and the line switch C are similar in all respects to the line switch C and the substation A.

F or the purpose of supplying battery current ior operating the apparatus at the central exchange and for talking purposes, thereis shown the battery B having its positive terminal grounded. At Q there is shown a busy signaling machine which provides a busy signal for application to the calling line when the called line is in use.

Havingl given a general description of the vapparatus and in order to give a clear understanding of the operation of the system, it will now be described in detail how the calling subscriber at substation A may obtain connection with the subscriber a't the called substation A. 7e will assume that the number of the called substation is 229. Upon the removal of the receiver at the substation A, a circuit is closed through the line relay 28 of line switch C. This V.circuit extends from ground G2 through contact springs 73, conductor 75, to and through the substation A, conductor 76, springs 74 and the line relay 28 to battery B. The line relay 28, upon energizing, operates to close the circuit' or the pull-in winding 25. This circuit extends from ground G through the springs 66, springs 67 and 68, pull-in winding 25 and the springs 69 to battery B. The pull-in winding 25 operates to disconnect the line relay 28k from the line through the medium of cut-oli armature 27, and to force the plunger into thev bank of contacts (B0- 37). The line relay 28 being slow acting, does not fall back immediately, however, but holds the plunger arm in an operated position until aV Vholding ground is supplied to the holding winding 26 from the selector E. The engagement of' springs 30 and 33 with the springs 34 and 37, respectively, extends the subscribers line to the Vline relay43 of the selectorrlil. The line lrelay 43 of the selector :switch E is thereupon energized, thereby closing a circuit through the relay 78, it beingnoted, that spring 47 follows spring 49 all the way so that springs and 77 come into electrical connection atthe same time. The circuit for relay 78 extends from ground G3 through contact springs 77, 49, and 47 springs 7 9 and the relay'7 8 to the battery B. The relay 78, upon energizing, closes the above mentioned holding circuit through the cut-oil1 winding 26 Ofiline switch C. This circuit extends from ground G4' through the springs 80, bank contact 35 and spring 31 and the said cut-oil winding 26 to battery B. A guarding potential is supplied to the connector private bank contacts of the calling line by the energization of relay 29. The energizing circuit for the relay 29 may be traced as a branch of the holding circuit from spring 31, through springs 81 and the relay 29 to battery B.

A further result of the energizing of line relay 43 is the closure of a circuit through the relay 82. This circuit extends from ground G3 through the springs 77 and 49, the upper winding of said relay 82 and the springs 83 to battery B. The relay 82, upon energizing, forms a locking circuit for itself,

extending from ground G5 through the springs 85, the lower winding of relay 82 and the springs 83 to battery A further result oiE the energizing of ,relay 82 is to close a circuit through the relay 86. This circuit extends from ground G5 through the springs 88 and 87 and the said relay 86 to battery B. Further results of the energizing of relay 82 a-re the preparation of a circuit or the vertical magnet 41 by closing lthe springs 89 and 90, and the opening oi the circuit of the release magnet 44 at the springs 90 and 91. The apparatus is now 'in readiness to receive impulses for the first digit. f

- 1f the calling subscriber should now replace his receiver upon the receiver hook the switch hook upon descending would cause the springs 20 and 21 to operate in a hereinbefore mentioned manner to ytransmit one or more high speed interruptions or impulses. lThe relay 48 will vibrate its armature in response to the said impulses, with the resul-t that the springs 47 and 49 are separated for an instant at this time because the spring 47 has a slower natural period of vibration Vthan the spring 49. It may vbe mentioned here that the rapid vibrations of the line relay 43 do not `affect the vertical magnet to any extent, for the closure of vsprings 97 is extremely short. The separa- .lay' 82 at springs 83, thus allowingV the said relay 82 to denergize; and as soon as the switch hook has separated the switch hook springs 17 and 18 the line relay 43 denergizes and opens the circuit oit the relays 94 and 78. The relay 78, upon dener,g'izing,

opens the circuit of the holding winding 26 of line switch C at the springs-80. The hold` ing winding, upondenergizing, permits the plunger arm of lineswitch C to return to normal;

- responding tothe two impulsessentv by the impulse springs 6 and 7 operates to transmit two impulses of current through the vertical magnet 41. This circuit extends from ground GG through contact springs 97, springs 98, springs and 89 and the vertical magnet 41 to battery B. The y,vertical magnet receiving two impulses over this circuit operates to raise the shaft and wipers .of selector E two steps to a positionopposite the second row or level of bank contacts. AThe closureof the off-normal contact 46, which occurs when the selector shaft is raised, operates to close a locking circuit for the relay 36 over a path extending from ground G4 through the contact springs S0,

springs V99, off-normal contact46, springs 103'.and 104 and the said relay S6 to battery B. The ,high speed interruptions at` the springs 9 Aand 10 that follow thetwo impulses just transmitted by the impulse springs 6 and 7, cause the'line relay 43 to Vvibrate quickly.- Asheieinbefore stated the result is that the springs 47 and 49 are se 5 varated for an instant thusrallowingthe relay 94 to energize overa previously-traced circuit. The relay 94, upon energizing, opens the circuit of the relay 82 at the springs 33 and permanently removes the shunt from around itself at springs 79. The de'nergizing of relay4 82 closesV a circuit through the rotary magnet 42over the tollowing path: ground G4, contact springs 8 0,

springs 99, contact 46, springs 103 and 104,

springs S7 and 105, springs 101 and the rotary magnet'42 to battery B. Trie rotary Vmagnet, upon energizing, rotates thewipei's `one step'and, by separating the springs 99 and the springs 101, opens its own circuit and also the circuit of relay 86. Tf therst trunk line of the second level is idle, the relay 86 denergizes immediately, but if this trunk line is busy, the private wiper 39 finds the contact with which it engages provided with a guarding groundV potential, which is transmitted to the relay 86 .through the springs 103 and 104, thereby preventing itY from denergizing. The rotary magnet, however, denergizes .when the springs 101 separate, regardless oi' whether therelay 86 lremains energized or not. lf the relay 86 Vremains energized, the circuit of the rotary magnet will be again closed as soonV as the armature drops back far enough to close the springs 101. The rotary magnet will, therefore, operate in a Vinanneisimilar to that of af buzzer to advance the wipers step by step over the contacts until the non-guarded con-'f tact of an idle trunk line is reached by the f wiper 39whereupon the relay SGrle'energiz'es. YThe relay V86, upon dene'rgizing, whether aiter one or several operations of the rotary magnet,permanentlybrealrs the circuit of the'magnet42 andcloses the cir-V cuit of the switching relay 106. VThe circuit through said relay 106 extends from ground Gr4 through the contactspringsSO, springs 99, contact 46, springs 103and 102 and the switching relay 106 to battery B. The re'- v'lay106, upon energizing, extends the line connection throughthe wipers 3S and 40 to the line relay 61 oit connector H anddis- 'connects the line'relay 43 from the said call- The line relay 61, upon energizing, closes i a circuitthrough the relay 110. This circuitpextends from ground GS through theY springs 111 and 64, lower windingI otrelay 110, springs 112, springs 114,V springs 115,

Yand the side switch wiper 59 first posi,

tion)` to battery B. The relay 110, upon energizing, closes a locking circuit'tor itself through the springs '116, and prepares acircuit for the vertical magnet by bringing the springs 118 r and 119V intoengagement. A further result of the energization of Ythe line vrelay 61 is' theclosure of a circuit vthrough vthe relay 120. This circuit extends from ground GS throughfthey springs 111, 64, and 63, springs 113 andthe 'relayv 120 to battery B. The relay 120,` upon energizing, sup-V plies a holdinggroundtothetrunk release conductor 103i to hold the relay 106 of Ase lector E and winding 26 of line Vswitch .0, energized. f This circuit extends from ground VG9 through Athe ,springsV 121, springs 122,

124, where theV circuit divides, onebraneh extending through the springs 103 and 102 and vthe relay 106 toi battery B, andthe other branch extending lfrom' point 124 through the oi'-`iiormal contact,;46, springs 99,`banlr contact 35 springs31and the holding winding 26 to battery B.

place hisreceiver upon the receiver hook the switch hook upon descending would cause the springs 20 and 2 1 to'operate` in a hereinbefore `mentioned manner to transmit one or more l high speed interruptions or impulses. VThe V'line relay 61 will respond to the said impulses Y' and as hereinbeto're lstatedthe result is that the springs 63 and 64 are separatedtor an instant at this time because thespring 63A Vconductor 10S, wiper 39V to wire junction f .ll4 Tt the callingsubscriber should nowrehas al slower natural periodV ot Vvibration thantlie spring-64. The separation of the springs 63 and 64 for an instant allows the relay to energizeby removing the shunt VJfrom around the said relay. The .energia h ing circuit for relay 125 extends from ground GS through the springs 111 and 6.4, relay 1.25, and the. relay 120 to battery B.. The relay 125, upon energizing, opens the shunt from. around itselrat' the springs 113, opens the circuit of relay 110 at springs 11,2, and closes a circuit through the. private magnet 58 overa circuit extending from ground G11 through the contact springs. 127, 12.8, and 129, magnet 58 and the side switch wiper 59 (in lirst position) to,` battery B. As soonv as the receiver hook has descended far enough to open the circuit of line relay 6l, thesaid relay willr denergize. The line relay, upon denergizing, opens the circuit of relays 125 and 120 at springs 64 and 111. The relay 125, upon denergizing, opens the circuit of the private magnet 5S, at the springs 127, 128 and 129; but the private magnet, upon denergizing, does not trip the side switch to second position'as the side switch cannot advance to second position until the switch shaft has been raised one or moreV steps from. its lowest position as shown in the patents abovereferred to. The re lay 120, upon denergizing, removes the ground: from the trunk release conductor 1:08 at the springs 121, thus. allowing the relay 106 of selector E and holding coil 26 of line switch C to denergize. The line switch (l releases in the hereinbefore mentioned: manner. The relay 106, upon deenergizing, closes a circuit through the release magnet 44. This circuit extends from ground Gr6 through the springs 97, springs 98, springs 90 and. 91, release magnet 44 and the oflnormal contact 45 to. battery B.. The release magnet, upon energizing, withdraws the retaining double-dog from the shaft and the switch releases in a well known manner.

Assuming that the calling subscriber did not replace his receiver at this time, but that he operates his dial for the second digit 2 of the called number, the substation impulse springs. 6 and 7 are separated twice, tollowed by high speed impulses transmitted by. the impulse springs 9 Yandv 10. The line relay 61 responding to the two. impulses sent by the impulse springs 6 `and 7 operates to transmit two impulses through the vertical magnet 53. This circuit extends from ground G13 through the springs 130, springs 118 and 119, the vertical 1nagnet53, and the side switch wiper 51 (in rst position) to battery B. The vertical magnet, upon receiving the two impulses over this circuit, opcrates to raise the shaft and wipers two steps to a position opposite the second row or level of bank contacts. The high speed interruptions that tollow'the two impulses just transmitted by the impulses springs 6 and 7 cause the line rel-ay 61 to vibrate quickly. As hereinbefore stated the result is that the springs 63 and 64 are separated for an instant, thus allowing the relay 125 to energize over a hereinbeiiore traced circuit. rlhe relay 125, upon energizing, closes aY circuit through the private magnet 58 and opens the circuit of the relay 110. The relay 110, upon denergizing, shunts out the relay 125 over a circuit extending from ground (is through the springs 111, 64 and 63, off-normal contact 65, and springs 1.3.1 to one terminal of relay 125, the other terminal being connected to ground G8 over a hereinbefore traced circuit. rlhe relay 125, upon denergizing, causes the private magnet 53 to advance the side switch to second position and again closes the circuit of relay 110 at the springs 112, The springs 113 and 112 ot relay 125 are so adjusted that the relay 125, upon denergizing, again places a shunt around itself before the circuit of relay 110 is closed. The side switch wiper 51 moving' from lirst to second position transfersthe battery connection from the vertical magnet 53 to the rotary magnet 54. i

The apparatus is now in readiness to receive impulses for the third digit 0. If the calling subscriber should now replace his receiver hook, the springs 2O and 21 will operate in a hereinbefore described manner to transmit one or more high speed impulses which cause the line relay 61 to respond to said impulses and to operate relays 125 and 110, as hereinbefore described. TheA relay 125 operates to close a circuit through the private magnet and the release magnet 60.

vThe private magnet is unable to advance the side switch from second to third position, because, as is well known, the side switch is mechanically locked in second position until the switclrshatt has been rotated one or more steps from normal. The circuit through the release magnet extends from ground G1V1 through the springs 127 and 128, side switch wiper 50 in second position, rotary olf-normal Contact 68, release magnet 60 and the vertical off-normal Contact 67 to battery B. The release magnet, upon energizing, closes a locking circuit for itseliCv through the springs 134, and oil'- normal contact 66 to G16 and, restores the switch shaft and side switch wipers to normal position and its own circuit is broken at the contacts 67 and 66 when the switch shaft reaches its lowest position. The relay 120, being slow acting, will dcnergize a short time after its` energizing circuit is broken by the line relay 61. The relay 120, upon denergizing, removes the ground from the trunk release conductor 108, allowing the selector E and line switch C to release as hereinbefore described.

Assuming that the calling subscriber did not replace his receiver upon the receiver hook, but that he operates his dial for the last digit 0, the substation impulse springs 6 and 7 are separated ten times followed by high speed impulses transmitted by the imi Y pulse springs 9 and 10. The line relay 61 responding to the ten impulses sent by the impulse springs 6 and 7 operates to trans-A Y the relay 125 to operate toclose a circuit Vline.

through the piivatemagnet 58 and to open i the circuit ofV the relay 110 at the springsV 112. The relay 110, upon denergizing, again places a shunt around the relay'125, thus causing the relay 125 to denergize, which causes` the private magnet to deiinergize and advance the side switch to third position. IThe circuit of the relay 110 is again closed at the springs 112 when the relay 125 denergizes but the said relay does not energize at vthis time as its circuit was opened at the side switch wiper 59 when it passed from second to third position. The opening of the rotary off-normal springs 68 Vprevents the release magnet 60 from be-A ingenergized4 when the relay 125 is energized at this time. The side switch wiper 52,'upon passing to third position closesa circuit through the cut-oit winding 186 or" line switch C, and the relay 138 ofconnector HL A further result of the Vpassing otside switch wiper' 52 to third position. is the placing oit a guarding potential upon the multiple bank contacts ot the called The eneigization of the relay 13S completes the line connection troni the call ing to the called subscribersline. VThe side 'switch wiper 51 upon passing from second to third position closesV a circuit through the ringer relay 69. This circuit extends from ground G15 through the interrupter 139, ringer relay `69, springs 140 and the side switch wiper 51 (in third position) to battery B. The ringer relay 69, upon energizing, disconnects the calling line from the called line and bridges the ringing current generator R across the called line. The ringer relay 69 is energized intermittently through the medium ot' the interrupter 139. Upon the response of the called subscriber his line is providedrwith talking battery through the windings of the back bridge relay 62, ,which relay, upon energizing, closes-a circuit through the ringer cut-oit y relay 142. This circuit extends from ground G16 through off-normal contact 66, springs V143, (relay 142 and the side switch wiper 51 (in third position) to battery B. The

The highY Ysignal from his own individual line switch.

' converse without lfurther eort. The transmitter at the calling substation issupplied with' talking current through the windings of the double-wound relay V61, "while the transmitter at the called'substation is supplied with talking current through the 'windings of the double-wound relay The path for Vvoice currents hasbeen drawn in heavy lines and Ywill Abe apparent without further explanatiom f v After the .conversation isV completed, the connection is released by the `hanging up or the receiver at the calling substation in the tollowingcmanner: The connector is released by theopening of the switch hookY springs 17 and 18, which opens the circuit ot' the connector line relay 6l.y The line relay 61', upon denergizing, closes a circuit through the release magnet 60 and opens the circuit of the relay 120 at springs 111 and 64. The circuit for the release magnet extends from ground Glthrough the springs 130, springs 118 and 117,7release'magnet 60 and the oitnormalcontact 67V to battery B. Upon the closure ot the above circuit, the connector releases in the manner previously described. The relay 120, iipon denergizing, removes the holding ground G9- rom the release conductor 10S, allowing the selector E and line switch C to release ashereinbetore described.

It havingbeen explained how one sub seriber establishes Connection with another subscriber and releases the saine, it will new be explained how a. connection is prevented from being made with a-busy line, how the calling automatic switches are released, and

how the calling subscriber receives a busy T the called number is busy there will be a guarding potential uponthe connector private bank contact, justas explained in cen nection with line switch C. The connector private wiper 56, upon engaging this guarding contact and when the privatemagnet' energizes, a circult is closed through the busy relay 145. This circuit extends trom ground upon the private Vbank contact through the wiper. 56, side switch wiper 52 .(in 'second position), busy relay 145, and the springs 146 ot private magnet 5S, to battery B. The relay 145, upon energizing, closes a locking circuit for itself through thercontacts 147 independent of the private magnet 5S, re-

moves the ground from the release conductor 108 at springs 122, and opens the circuit or relay 110 at springs 114. The removal et' the ground from the said conductor 108 causes the plunger of the line switch C to be withere drawn from its bank of contacts and the selector .E to be released as hereinbefore described. The cut-off arm 27 and plunger' arm 23 dropping back allow the circuit of the line relay 28 to be closed. The relay 28, upon energizing, closes a locking circuit through the relay 29, which being slow acting has not denergized. The relay 29 maintains the circuit of the pullin Yinding open at the springs 68 and (3.7. A further result of the energization of the line rela-y 28 is the supplying of a busy tone from the machine Q, to the calling line through the contact of its springs 14S. The opening of the line circuit of the connector I-I at the bank spr'n gs 30, and 33 causes the line relay 61 to deenergize. The line relay 61, upon deenergizing, causes the connector II to release as hereinbefore described. The calling subscriber upon receiving the busy signal replaces his receiver upon the receiver hook and releases relays 28 and 29 of the line switch C, whereupon all the apparatus will `have been returned to normal.

t will be seen from the foregoing that my invention provides an automatic telephone system, in which the local, switching, at the various automatic switches is accomplished entirely through the medium of a device responsive to high frequency impulses while irresponsive to the preceding operating impulses; and it will be seen, furthermore, that at certain times the release of the automatic switches is brought about directly or indirectly in response to similar righ frequency impulses transmitted -by the subscribers switch hook.

lllhile I have illustrated and described herein a certain particular embodiment of my invention, I do not wish to be held to the exact form shown, for modifications will no doubt be devised by persons skilled in the art. I desire, therefore, to include and have protected by Letters Patent all forms and modifications of my invention which may come within the scope of the appended claims.

W'hat I claim as my invention is:

l. In a telephone system, an automatic progressively movable switch, a controlling circuit for said switch including the two sides of a calling line in series, an operating magnet and a release magnet for said switch, means for transmitting a plurality of impulses of one character over said controlling circuit to control said operating magnet, and means for transmitting a plurality of impulses of a dierent character over said controlling circuit to control said release magnet.

2. In a telephone system, an automatic progressively movable switch, a controlling circuit for said switch, an operating magnet and a release magnet for said switch,

means for transmitting impulses of low and high frequency over said circuit, a relay in said switch responsive to said low frequency impulses for controlling said operating 1 L. `ne anc a re a in sait swi ci res onmag t, l l l tl sive to said high frequency impulses for controlling said release magnet.

E3. In a telephone system, an automatic progressively movable switch, a controlling circuit for said switch, an operating magnet and a release magnet for said switch, means for transmitting low and high frequency impulses over said circuit, a relay in said switch for controlling said release magnet, and a line relay in said switch responsive to said low frequency impulses for controlling said operating magnet and responsive to said high frequency impulses for operating said first relay to release said switch.

4L. In a telephone system, a line terminating in an automatic progressively movable switch, means at the substation on said line for transmitting groups of operating impulses of one frequency and a group of releasing impulses of a different frequency to said switch over said line, said switch provided with operating means responsive to said group of operating impulses, and releasing means responsive to said group of releasing impulses.

5. In a telephone system, a substation telephone instrument and a linel therefor eX- tending to a central Xchange, an automatic switch, means at the exchange for making said switch accessible to said line, means in said instrument for sending directive impulses over said line to operate said switch, means controlled by the receiver hook of said telephone instrument for sending a group of high frequency impulses over said line, and means responsive to said last impulses for releasing said switch.

(5. In a telephone system, an automatic progressively movable switch provided with operating means and releasing means, and a common controlling circuit therefor, said means separately responsive to impulses of different frequency transmitted over said controlling circuit.

7. vIn a telephone system, a calling subscribers line, means including an automatic switch for extending said line into connection with a called line, means at the substation on the callingline for producing long and short interruptions of the line circuit for controlling said switch, operating mechanism in said switch responsive to said long interruptions, and release mechanism in said switch responsive to said short interruptions.

Signed by me at Chicago, Cook county, State of Illinois, this th day of April, 1916.

GEGRGE A. YANOCHOVSKI.

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