US1288098A - Automatic telephone system. - Google Patents

Description

IPUCATION FILED FEBMS. 1916.

Patente Dee. 17", 1918.

4 SHEETSH'EET 1.

mwa/E655@ l y LG. MARTIN. AUI'QIMATIC TELEPHONE SYSTEM. APPLICATION FILI-:D FEB. 5, Isis.. 1,288,098. rammed De@ 17,1918.

4 SHEETS-SHEE 2.

TTOR/KEYH T. G. MARTIN.

AUTOMATIC TELEPHONE SYSTEM.

APPLlcATloN FILED FEB. 5, 1916.

1,288,098, T Patented De@.'17,1918.

TTOPNEX 1. e. 111/1111111.` AUTOMANC TLPHONE SYSTEM.

APPLICATION FILED FEB. 5.1916.

4 SHEETS-SHEET 4- TTORNE'Y vzoA as a selector to pick out contacts which N UNITED sTATEs PATENT oEEIcE.

TALBOT e. MARTIN, or cHIcaee, ILLINoIs, AssIGNoR To AUTOMATIC ELEcTRIo COMPANY, 0F CHICAGO,

ILLINOIS, A CORPORATION or ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Dec. 17, 1918.

Application filed February 5, 1916. Serial No. 76,309. y

To ai? 'wLpm t may concern.'

Be it known that I, TALBOT G. MARTIN, a citizen of the United `States 'of America, and resident of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which' the following isa specific-ation.

My invention relates to automatic telephonepsystems and ,in certain of its features has particular' reference to those systems which include automatic private branch exchanges.

In these exchanges it has been customary to .provide so calledconnector and selector switches,l the former for completing local f connections and the latter for selecting an idle one ofthe connectors or for selecting an idle trunk line to the main exchange.

One of the objects of my invention is the provision of a. switch which can perform the functions of both a selector` and a connector.

vMy improved type of switch operates as a connector on the first nine levels, these levels containing contacts which are terminalsl of local lines; but on the tenth level it operates are terminals of an idle trunk line.

A further object is to provide in a switch vof the above character an improved ringing method by virtue of which a called subscriber is enabled to instantly stop the ring by removing his'receiver from the hook.

' In a system of the general character described above the subscribers station equipment may include acoin collecting device by means of which a coin or other token may be collected for each successful originating call.

the relay isenergized, but with no effect other than to place certain of its parts in operative' position. When the called party answers, -however,`the connector reverses the direction of current fiow in the calling line Whereupon the polarized relay operates to close a shunt around the transmitter. The calling subscriber can hear his party answer but cannot talk untilhe has dropped a suitable ;coin in the coincollecting device where by his transmitter is again made operative for talking purposes. f Y,

Howevezg at each main exchange there 'usuallygare certain telephones to which itis the telephonecompanyshould be accessible v to the subscribers without' charge. In the A vpast it has been customary to'provide a separate section of the switchboard for handling the above class of service, the connec tors in this special switchboard 'being ar ranged so'as not to reverse battery tothe calling line. But the use of a special switchboard provides no means byA which one of the regular switchboard numbers may be madetemporarily accessible without charge and, furthermore, the special equipment. is a source of considerable eXtra expense.

In addition to these features already mentioned, my invention provides .simple and efficient means whereby a connector of the regular type, which ordinarily reverses battery to the calling line, is prevented from so doing when the called lineisone to which it is desired to give free access. .I make kno change in the connector switches or inthe general trunking scheme,' but rather employ individual apparatus in connection with each free substation whereby a connector,' upon completing a connection with that substation, is prevented from performing certain of'its functions, thereby enabling the calling subscriber to converse without depositing the usual coin. Trunk lines accessible to the regular connectors yand extending to` operators positions may be equipped in accordance with these specifications whereupon vthey will also be made accessible to all the subscribers without charge.

These and other valuable features ofmy invention are provided for by means which will be hereinafter fully explained, reference being had to the accompanying drawings.

The telephone system illust-rated therein comprises an automatic private branch exers individual switch C, connector switch switch C. i v

F ig. 4 represents apparatus'at the mam exchange which 'may be Used forlvompleting vP and the called subscribers individual y a nce coil 16.

a. connection between a calling substation A., whose line terminates in the said private branch exchange, and a called substation, which may be similar to the substation A', but whose line terminates in the main exchange. The said connection is established by means of the subscribers individual switch C, connector switch P, (which acts as a selector switch on the top level, as will be hereinattermore fully explaineth) repeater I, connector switch H (located in the main exchange) and t-he calledsubscribes individual switch.

In the circuit, connections referred to above, the central otlice equipment, as shown, comprises only the so called line switches, connector switches, and repeater, but it. will be clearly understood by those versed in the art, that so-called selector switches may be inserted before the connector switches, thereby increasing the capacity of the system, without departing from the principles of my invention. Selector switches which may be used are of the type disclosed in British patent to T. G. Martin, No. 1419 ot' 1910.

The automatic telephone or substation A,

as herein represented, comprises the usual receiver 2, transmitter 3, switchhook l, ringer 5, and condenser 6. Beingan automat-ic substation, it is also provided with an automatic calling device. This calling device may be of the same type as that shown in British patentl to S. G. S. Dicker, No..29,651 of 1910. The calling device is shown diagraminatically by pair of impulse springs 7 and S and a ,toothed Vimpulse wheel 9, which latter is controlled by the subscriber through 'the medium of av dial not shown) provided with finger holes for convenience in turning. Thecoin collecting device is also shown diag ammatically: it consists essentially of a polarized electroniagnet. the coils 11 and 12 of which are connected in series with the telephone, and bridged by a condenser 1?. The springs 13, 11 `and 15 are so arranged that when their contacts are closed, the transmitter 3 is short circuited and the receiver 2 is shunted by the resist- The coin connecting device is similar to that described in British'patent specification ilo. 5847 of 1912.

The subscribers vindividual switch C is of the general type of lsubscribe1"'s switch shown in British patent to R."W. James, No. 26,301 of 1900. being however, of the particular type disclosed in British patent to T. G. Martin No. 1419 of 1910. This line switch comprises among other details, a. plunger (not shown) attached to the end of a so-called plunger .arm 1S which is controlled by the magnet. 19. The magnet 19 comprises four windings, namely a pull down winding 20, cut-oit or holding winding 21, line winding 22 and an auxiliary Winding 23. The core of the magnet 19 is so constructed that themagnetic circuit. ot the windings 20 and 21 is separate from that of the windin'gs 22 and 22:3. The winding 20 operates botlithe plunger arm 1S and the cut-ott armature 2-1, while the winding 21 is strong enough only t0 operate the cut-ott" armature 21 and to hold the plunger arm 1S in its operated position. when the plunger arm 18 is operated, the plunger is forced into a bank of contactA springs, forcing the springs 25, 26, 27 and 2S into engagement with the contacts 29, 30, 31 and 32, respectively. Although only one set of springs and contacts (25 and 32 inclusive) is shown, each line switch is provided with a plurality of such sets, each set forming the terminals of a trunk line leading to a connector P. Each trunk line is connected in multiple with the corresponding springs of all the line switches of the group which is controlled by the master switch D. The switch C is controlled b v the subscriber, throughthe medium of the line winding 22, as will be hereinafter more fully explained.

The master switch D is of the general type disclosed in British Patent No. 26,301 of 1906, referred to above, being, however, of the particular type disclosed in said British Patent No. 1119 of 1910. The function of the master switch, as is well known. is to maintain the plungers of all the idleline switches in position to engage the terminal of an idle trunk line.

The' connector switch T is ot' the same general type of connector switch disclosed in United States Letters Patent No. 815.170, granted iwlarch 13, 1900, to Keith, Erickson and Erickson, the circuits. however. being modified to enable the switch to operate in a system in which the central otlice appaatus is controlled by impulses delivered over the two sides of the line in series. The connector is provided with a shaft (not shown) carrying the wipers 35. 30, :5T and 3S and controlled by the vertical magnet 39 and the rctary magnet 40. The connector switch is also provided with banks of contacts, which-are divided into rows or levels,

generally ten in number. The bank contactsin the lirst nine rows or leveds are used t'or local connections, while the bank contacts in the tenth level are connected to trunk lines leading to the main exchange. The springs 47, e18, 49 and 50 are controlled .b v the switch shaft-that is, they are operated whenever the switch shaft is raised to the tenth row or level of bank contacts. The function of thesaid springs is to change the operation otl the connector switch from that of a connector to that of a selector.v The bank contacts accessible to the wipers 3T. 23S and 35 are multiplied between the banks of the switches on all ten levels while the bank contacts accessible to the wiper 30 are only multiplied 'between banks on the tenth level and are left disconnected on all other levels. The usual side switch lcomprising the switch wipers 41, 42 and 43 is controlled by the private. magnet 44 in the wellknown manner. The magnet 45 is the usual release magnet, The line relay 46 is the means for controlling the various operations of the connector switch. The ringing relay 51 is the means by which ringing current is applied tothe called line from the ringing current generatorR. At Q-there is shown a busy vsignaling mac-hine which provides a busy signal; said busy signal being applied to the calling line when the called line is 'in use.

, -The substation A" switch C are' similar in all respects tothe substationA, and the line switch C.

The repeater I comprises aline relay 52, slow acting relays 53 and54, battery reversing relay 55 and an impedance coil 56. The line relay 52 i's normally Abridged across-the trunk conductors 57 and 58 in series with the battery, through the reversing springs of the battery' reversing relay 55,.,and is arranged so that when its armature operates in accordance with. the impulse'sfrom the subscribers substation A, it opens andcloses the bridge across the trunk extending to the connectorfH a correspond-ing number of times. Another function of the repeater I is to supply talking current to the calling line and maintain a holding circuit for the connector P and line switch C, thus obviating the necessity of having three conductor trunks between exchanges.

-The connector H is of the same general type as connector. P, but is provided with only three shaftwipers' and operates as a straightconnector on all levels. By means of wipers 168, 169 and 170, connector H has access to the' group of relays K, to the special substation U', and to a number of substations similar to the substation A in Fig. B.

The group of relays K may be loca-ted in a manual board *and 1s for the purpose of allowing an operator to answer an informa- ',tion call or the like without necessitating the calhng subscriber droppmg a. com 1n his' coin collecting device. In the event that a subscriber has had his telephone removed or .taken out of service for any-reason, his line is disconnected from the/central oice apparatus, and-the connector bank normals are connected to what. is known as a tratti-c trunk, as shown at K, said trunk being. designated by the reference numerals 60 and 61. Therefore, when the subscriber at substation A attempts to call a subscriber whose telephone hias been disconnected (and the connector banknormals connected tosaid traiiio trunk) hewill signal an operator who will immediately give himthe required information.= 'Itis desirabletas hereinbefore -stated) e I Y and-128 `,with the contacts 29 and 32, respecto pay? for .such a callifthereforej,

thatathe calling subscriber should nothav'e and the i individual i ments are provided in the group of relays K for obviatlng the necessity of the callingl -v tus and for talking purposes` there is`A shown throughout the drawings, a plurality of bat# teries B and B', each having one of its terminals grounded at G and G respectively. In practice there need be only one such battery, or preferably one battery for each er1 change.

A general description of the apparatus having been given, it will now be. explained how a connection is extended from a calling' substation A to a called substation A", whose lines terminate in the same private branch exchange. We will assume the number of the called substation to be 20. Since part of the automatic switching apparatus disclosed herein is in general fwell known in the art, and is described in the publications here- 2, transmit-ter 3, and polarized relays l1 and 12 are bridged across the line conductors G4 and causing an energizing circuit to be closed through the line winding 22 of the individual switch C. thereb v attracting t'he line arma-ture 34. At this time the current flowing through the coils 11 and 12 is in such a direction as to attrict the armature to the coil 11, thereby moving the arm y66 behind the lugGT on the arm 68.' The arma'- tu-re 34. when attracted. closes a circuit through the pull down coil 20. in series with the auxiliary winding 23. vThepull-down coil, uponenergizing. attracts the plunger arm 18 to force the plunger into the bank of springs thereby 'forcing springs to 28 into engagement ,with contacts 29 to 32,113,- spectively. rllhe cut-ofic armature 24 is, also` attracted, thereby disconnecting the`- two Sides of the line from ground and from the l-ine winding 22. The armature 34 does not fall back immediately.'however, being -held `by the vwinding 23 which is ,still in series with the pull down winding20. Asthe plunger enters the bank, lthe springslv and for a 'holding circuit to be closed in", the

switch ahead for the cut-olf or holding winding. 21. The engagement of thel springs 25 tively, @Xtends' the subscribers line to the line relay 16 ot the connector l). The circuit thus established extends from ground G0 through lower winding ot line relay 46, ontact springs 711, conductor S9, bank contact 32, spring 28, conductor 65, to and through substation A, conductor 6l, spring 25, -bank contact 29, conductor 8S, contact springs 71 and upper winding of line relay 16 to the battery B. The line relay 16 ot' the connector sv'itch P is thereupon energized, closing a circuit extending from ground Gra through contact springs 7l, springs 73 and 7l and the relay G9 to battery B. The relay 69, upon energizing. closes the albove-mentioned holding circuit through the cut-off winding 21 of the line switch C. This circuit extends vfrom ground G23 through the. Contact. springs 75, conductor 90, bank conA tact 30, spring 26, and cut-ott' winding 21 to the battery B. The winding 21. upon energizing, holds the armature 2l and the plunger arm 18 in their operated positions after the circuit of the pull down winding is broken b v the falling back of the line armature 3l. .5r guardin,f r ground potential is supplied to the connector private bank contacts ot' the calling line as soon as the relay 69 is energized. This circuit extends over the circuit just traced to the bank spring "26, thence over the conductor 33 to said private bank contacts. The energzation of the relay 69 also prepares a circuit for the vertical magnet by bringing into engagen'ient the springs 76 and 77 and opens the circuit of t-he release magnet at the springs 77 and 78.

The .calling subscriber now operates his calling device for the first digit 2 of the desired number, whereby the subst-ation impulse springs 7 and 8 are separated twice momentarily, each time .breaking the circuit of the connector line relay yat-G. The relay 69 of the connector being slow acting, it

does not denergize during the momentary interruptions of its circuits by the line relay 46 and, consequently, each. time the latter relay denergizes, an impulse is transmitted over the circuit extending from groundGr3 through the contact springs 71, springs 73 and 7 2, springs 77 and 76, relay 79, vertical magnet 39, and side switch wiper 43 (in first position) to battery B. The vertical magnet 39 receives two impulses over this circuit and operates to raise the switch wipers 35, 30, 37 and 38 to a position opposite the second level of'bank contacts. The relay 79, which is included in series with the vertical magnet, is slow acting and remains in its energized position during the entire time that impulses are being transmitted through it and operates to close the circuitof the private magnet 44. This circuit extends from ground G* through con-` tact springs S1 and 83 and the left hand winding of relav 4.4 to battery B. 'After the last impulse is delivered, the relay 7S) opens the circuit of the private magnet tst, which, upon denergizing. permits the side switch to advance from tirst to second position. The movement ot the side switch wiper 13 from tirst to second position transt'ers the battery connections from the vertical magnet 39 to the rotary magnet 10. rl`he calling -subscriber now operates his calling devicefor the last digit 0, in response to which the connector line relay 46 `operates to transmit ten impulses through the 'rotary magnet 40 in series with the relay 79, whereby the shaft wipers gare rotated onto the contacts of the desired line. The. circuit for the rotarv magnet extends from ground Gr3 through contact springs 71, springs 73 and 72, springs 77 and 76, relay 79, springs 50 and 4 9, rotarymiagnet l0, and the side switch wiper 43 (in second Yposition) to battery B. Each time the rotary magnet emergizes, a circuit is closed througl the relav 85, however, the operation of '.said relay is funetionless at this time. T hef relay 79 operates In response to this digit in the same manner for the previous digit to cause the private magnet 4l to advance the side switch one more step, that is, from second to third position-after the last im-.

pulse for the digit has been transmitted. By the energization of the relay 86 and the bridge cut-off winding S7 ot the called subscribers individual switch C' the line connection is completed with the called substation, as shown by the heavy conductors. The energizing circuit for the said bridge cut-oftl coil extends from ground G6 through the'side switch wiper 41 (in third position) wiper 37, conductor 91 and the said bridge cut-ofi` windingi' to battery B. The connection of ground Gr6 with the connector private bank contact 9:2 of the called line prevents the called line from being seized by some other connector switch. The energizing circuit for said relay 86 extends from ground G23 by way of contact springs 75, conductor 90, side switch wiper 42 in third position. winding of relay 86 and side switch wiper 43 in third position to battery.

A further result of the engagement of side switch wiper 43 with its third position contact point is the closure of a circuit through the ringing relay 51. This circuit extends from ground G7 through the interrupter 93, springs 94. springs 95, ringing relay 51 and the side switch wiper 43 (in third position) to battery B. The ringing relay is energized intermittently through the mediuni of the interrupter 93. The path of the ringing current extends from ground Gr8 through the contact of springs 98 and 99, springs 101 of' relay 86, Wiper 38, conductor 10'2, ringer at Vsubstation A', contact springs 400 .of line switch C. return conductor 103,' wiper 35, springs 104,'springs 105 and 106, the right hand winding of relay 97, generator B, to and through the battery B to ground G. 'gllie relay 97 is so constructed and so ad- ]usted that it will not respond to ringing current from the generator B. when the substation bells and condenser are bridged across the line, butA the instant that the receiver is removed at the called substation,

' thereby bridging the transmitter and renector release magnet ceiver across the line, sutiicient-current is permitted to iiow 'troniy the battery B,

through the generator R, and through the said relay 97, for it to become operatively energized. Should the called subscriber answer during the ringing period-that is during the time the ringing relay 51 is energiZed, the relay 97 will immediately energize and upon energizing. opens the circuit of the ringing relay 51 at the springs 95 and closes a locking circuit toi itself through the springs 108. The said locking circuit extends trom ground G6 through the side switch wipe-i' 41 (in third posit-ion), springsy108, the left hand winding of relay 97 and the side switch wiper i3 (in third position) to battery B. The called subscriber is provided with talking battery through the windings of the back bridge relay 109. if the calling subscriber should answer during thetime that the ringing relay 51 is deenergized, the back bridge relay 109, being bridged across thecalled line in series with battery'B, will immediately energize. The relay 109, upon energizing, closes a circuit through the ring cut-oli' relay 97. The saidV circuitextends from ground Gr@` through the said side switch wiper 1.1 (in third. position), contact of springs 111, the said relay 97, and the side switch wiper 43 in third position) to battery B. The relay 97. upon energizing, forms a locking circuit for itself over a hereinbefore traced circuit. The subscribers may now carry on an interrupted conversation over the shown.

After the conversation is completed, the connection is released in the following manner: When the receiver at the substation A "is restored to the switch hook, the separation of the hook switch springs Opens the tion and its own circuit is-broken'. at the springs 112 when the shaft reaches its lowheavy conductors' est position. The winding 21 of the line switch (l, upon denergizing, allows the plunger arm loto return to normal position.

It now having been explained how one subscriber establishes a "connection and re leases the.` saine, it will be explained how a connection is prevented from being' made with a busy line, and how the calling subscriber receives a busy signal when calling av busy number. If the called number is busv, there will be a guarding potential upon the connector private bank contact, just as explained in connection with lthe line switch C. The connector private wiper 37, upon engaging this contact before the private magnet 44 has denergized to allow the side switch to pass to third position, completes locking circuit through the said private magnet, thus retaining the side switch in second' position. This circuit. extends from ground upon the private bank contact 99), through the wiper 37, side switchwiper il' (in second position), Contact springs 82 and 83 (when relay 79 denergizes), and the left hand winding of said private magnet` 44. to battery B. The private magnet thus locks the side switch in second position, and transmits a busy signal Ato the calling subscriber over the following path: battery B, secondary winding of the induction-coil, contact spriiigs'll, springs 99 and lli, heavy cou-l ductor 89, to and through the substation A, return conductor 88, springs 7lal of relay 117, and through the-upper winding of relay 46 to battery B. A tone induced in the ,secondary winding of the induction coil is pei'- ceived bythe calling subscriber who, upon replacing his receiver, releases'the apparatus in a hereinbeto're mentioned manner.

It having been explained how a local connection is established and released, it` will now be explained how a connection may be extended from the calling substation A to a called substation in the main exchange,

'whose number, we will assume to be OQO. `The calling subscriber upon removing his receiver preparatory to making a call, opera-tes his individual switch C in the same manner as liereinbefore described to effect connection with the connector switch P. The calling'subscriber now operates his calling device `for the firstdigit 0 in response to which the switch shaft and wipers of. the

connector P are raised opposite thetenth row rlhe switch shatt,

or'level of bank contacts. upon being raised to the tenth level, operates to switchl the springs 47, 48,49 and 50 in a hereinbefore mentioned manner. lThe, private magnet 44', operates in the same manner as hereinbcforedescribed tostep the side switch from first toisecond position. The side switch Wiper 43, upon passingto second position operates to closeacircuit through 'the rotary magnet 40 andthe pri vate magnet l-l.. The said circuit extends from ground G23 through contact springs 75, right hand winding ot' magnet il, springs 115. springs 18 and 1S), rotary magnet 10, and the side switch 13 (in second position) to battery B. The rotary magnet #10, upon energizing, operates to rotate the shaft. and

guarding potential which is transmitted to" the private magnet 11 over the following path; ground on test. cont-act, wiper 3T, side switch wiper 11 (in second position), springs S2 and 83, and theleft hand inding of the magnet ll to battery B. The rotary magn'et, however, denergizes when the springs 115 disengage, regardless of whether the magnet 11 remains energized or not. The rotary magnet, upon denergizing opens the circuit or" the relay at the springs 116. and the relay 85, upon de'e'nergizing, again closes a circuit through the rotary magnet lO'at the springs 115. The rotary magnet will, therefore, operate in the manner of a buzzer to advance the wipers' step by step lover the contacts until a non-grounded contact of an idle trunk line is reached by the wiper 37, whereupon the private magnet lt denergizes and permits the side switch to advance one more step, or 'from second to third position. Y The side switch wiper 42, upon engaging its third position contactl point, closes a circuit through the relays 117 and SG. The circuit tor relay 86 extends from ground G23 by way of springs 75, conductor 90, side switch wiper -12 (in third position), relayV 86, andthe side switch wiper -13 (in third position) to battery B. Therelay 86, upon energizing, connects the line wipers and 3S to the conductors 119 and 120 respectively. The energizing circuit for relay 11T extends from ground G23 over the above traced circuit to side switch Wiper 12 in third position), thence through the springs 47 and the said relay 117 to battery B. The relay 117, upon energizing, disconnects the line, relay 1G from the conductors 88 and S9 and also disconnects the back-bridge relay 109` from the conductors 119 and 120. Ar the same time it short circuits the coudensers 121 and 122 and cuts the calling line through to the line relay of the repeater 1. This circuit extends from ground G1o through the 4lower winding .of relay 52, springs 123 and 124, conductor 58, wiper 3,8 (now resting on bank'conta'ct. of .Q level), conductor 120, to and through the calling substation A, re-

Leashes turn conductor 119, wiper 35 (now resting'ou bank contact ot 0" level), conductor 5T. springs 125 and 126, and the upper winding ot' relay to battery B. The relay 52, upon energizing, closes a circuit through the relay 53, which upon energizing, closes a holding circuit for the relays 8G and 11i of connector P and holding winding 21013 line switch C, the former holding. circuit being broken an instant later when relay 69 denergizes. The circuit energizing relay extends from ground G13, through contact springs 1110 and a and said relay 53 to batteryv B. yl`he said holding circuits for relays 86 and 11T extend from ground G12 through the springs 13T by way of conductor 138, wiper 3G (now resting on bank 'contact O level). side switch wiper l2 (in third position). and over the hereinbefore traced circuits through the said relays to battery B. The holding circuit for holding winding 21 of line switch C may be traced as a branch of the above circuit from wiper l2 (in third position). over conductor 9() and through the said holding winding to battery B. Another branch of the above holding circ-uit extends from eo'nductor'lBS through the right'hand windingvof relay 55 to battery. The right hand winding ot' relay is a polarizing winding` only, being made of German silverA wire, and does not energize the core of relay sufficient to enable it to attract its armature.

.A further result of the energization of line relay 52 of repeater I is the closure of a circuit vacross the conductors 12T and 128 leading tothe connector H-in the main exchange, thus energizing the relay 129 ot' said connector. The energizing circuit Jor said relay extends from ground G1", through the lower winding ot relay 129, springs 130 and 131, trunk conductor 128, springs 132, impedance coil 56, lett hand winding ot'irelay 55, conductor 12T, springs 133 and 131. and the upper winding ot relay 129 to battery B. The relay 12.9,upon energizing. closes a circuit through the slow acting relay 135. This circuit extends vt'rom `ground .Gm through springs 103 and 1G? n, relay 1535i to battery- B. Aalthough both windings ot'the relay 55 are carrying current at this time. the said relay is not operatively energized as the'windings are working in opposition to each other. l

The central oliice apparatus is now in eondition for the transmission ot the second series of impulses, whereupon the dial is operated in the usual manner, opening the circuit ofthe line relay in the repeater I twice momentarily. The slow relay 5?, does not deenergize during the transmission of the impulses. Therefore the holdingr ground G12 is not removed from the conductor 138. Each time the line relay 52 devenergizes, a circuit is closed extending trom ground G13 through contact springs 140 and 139, springs 141, and the relay 54vto battery li. The-result is that the first time the relay 52 deenergizes, the relay 54 closes a direct bridge across the trunk conductors'127 and 128; and, since the said relay 54 is slow acting. it remains energized during the interruptions of its circuit by the line relay 52. A further result ot the deenergif/.ation of line relay 52 the. opening of the bridge across the trunk conductors 127 and 128, therefore each time the said relay denergizes, an impulse is repeated to the line relay 129 of connector H. The line relay 129, re-

sponding to the impulses transmitted' to it by the repeater I, operates to transmit two impulses through the vertical magnet 142 [for this purpose.

in series with the relay 143. The vertical magnet operates to raise ,the switch shaft and wipers to a 'position opposite the second rowor level of bank contacts. The slow relay 143 which is included in series with the vertical magnet, remains in its energized position while impulses are being transmitted through it and operates to close the circuit of the private magnet 145. After the last impulse is delivered, the relay 143"dener gizesand opens thecircuit of the private Ymagnet 145, which upon denergizing, per` mits the side'switch to advance from first toHsecond position. The movement of the side switch'wiper`146 from first to second position, transfers the battery Yconnection from the yertical magnet 142 to the rotary magnet 144. The calling Subscriber now operates his calling devicefor the last digit 0 rin response to which theiepeater relay 52 repeats 10 impulses to the connector line ,relay 129, whereuponthe said connector line relay transmits ten impulses through the rotary magnet 144 in series with the relay 143, whereby the shaft wipers are rotated onto the contact of the desired line. The relay 143,operates-in response to this digit inthe same manner as for the previousdigit .to cause the private magnet 145'to advance the side switch one more step, that is, from second to third position.

their third position Contact points, the-line connection is completed with the conductors 403 ,and 402- which, with the conductor 391, are connected with the individual line switch of the desired substation which is similar to the one shown in Fig. 3, it being'assumed that'the wiresl403, 391 and 402 are joined to the wires'103r91 and 102. respectively,

A guarding ground poli tential is supplied to the connector private tsome other connector switch, and also serves to energize the vcut-off relay ofl the calledv s ubstations line switch. By the engagebank contactsof the called line, which preyents the called line from being seized by mentof theside switch wiper 146,' with its thi-rd position contact point, thev circuit of By' the engage-- vment of side Switch wipers 147 and 148 withthe ringing relay 150 is closed. This circuit extends Ifrom ground (im. through the intei'i'upter 151. ringing relay 150. springs 152. and the side switch wiper 14h (in third position) to battery B. The ringing relay` -upon energit/zing. disconnects the calling line position). by. way of contact springs 156l and the said relay 154 to battery B. The relay 154, upon energizing. opensy the circuit ot' the ringing relay 150 at the springs 152 and closes a locking circuit'for itselttlirough the .springs 157 independent of' the springs 156. The j circuit thus formed extends from .ground G15 through Side switch wiper 155 '(in third position), springs 15T. and the Said relay 154 to battery B. of the energization of the back bridge relay 153 upon the response of the called subscriber is the transposition of the battery connections of the windings ot the liiierclay 129 with regard to the battery B. -where- A further result by the direction of the current in the trunk. l

lines 127 and 128 is reversed.. The reversin(r of the currentover the trunk conductors 124 and 12S reverses the direction ot' the current iow inthe le't't hand winding ot' .relay ot' repeater l, whereupon the said 'relay energizes. The relay upon energizing. reverses the flow of current over the calling line, whereupon the change ot' direction ot' current through the coils 11 and 12 `oi" the substation 'A causes the armature `160 to be tilted in the opposite direction. The lever 66, by its eng/agement with the'lug ,37 ot' thev arm G8. operates to carry said arm into the slot `of 'the .coin chute (notsliown) and to llO close the contacts of springs 13.14 and 15. 'A

which, has been stated previously. short circuit the transmitter 3 and vshunt the receiver 2. thereby rendering tliesubstation A inoperative for talking purposes. This condition is maintained until the calling party drops` a coin into the chute. the weight of which coin will knock tlielug 6T out ot' engagement with the lever ft and restore the transmitter and receiver `to their normal condition.. i

After the conversationis completed. the connection is released in the following manner: When the receiver at the substation A is restored to the switch hoolothe separa tion of the hook springs'opens the energizing circuit of the line 1clay'52 of vrepeater y The magnet 162, upon energizing, restores reaches its lowest position.

the switch shaft and sideswitch wipers to normal position after which its own circuit 1s broken at the springs167 when the shaft r1`he relay 53, of repeater I, upon denergizing, removes the ground G12 from the conductor 138 allowing the connector P and the line switch (.l to release in the hereinbefore described If the number called is busy, there will be a guarding potential upon the connector private bank contact, just as explained in connection with the line switch C. )Vlien l.t-,hie slow-acting relay 14S denergizes at the 'fendi of l'thelast series of impulses, the connectorprivate wiper'168, by its engagement with' this guarding Contact, completes an energizingcircuit through the busy relay 173. This circuit. extends from the ground at the private bank contact, )rivate wiper, side switch wiper 155, (in second position), springs 176 and 177, relay 173, springs 179 -and 180, and the private magnet 145 to battery B. The private magnet. thus holds the side switch in second position and holds the line circuit open to the called line. The relay 173, upon energizing, opens the circuit of the rotary magnet at the springs 178 and forms a locking circuit for itself and private magnet 145 through springs 175 and 177 and off normal springs 167fL independent of the ground upon the said private bank con tact. Also, by closing contact springs 174,

the busy relay connectsa tone from the busy machine Q with one side of the calling line (side switch lever 148 being in its second position) whereby the calling subscriber is informed that the called line is busy. The calling subscriber upon receiving` the busy signal, hangs 'the receiver upon the hook, thereby releasing the connection in the manner above described.

lVhenever a telephone is removed from service. or temporarily disconnected for any reason, the lines leading to the central exchange are disconnected and the connector bankcontacts are connected to the conduc tors 461 and 60 (as the connector bank contacts 171 and 172 are shown connected in Fig. 4). The conductors 61 and 60 terminate in a key K3 situated at an information desk or manual l"operatos board. 1t will now be explained how7 the subscriber at substation A, in attempting to call a substation lreasons whose telephone has been disconnected, will effect connection with the operator at `4the said manual board and receive the necessary information, without having to deposit a coin in the coin collecting device.

The calling subscriber operates the con nector H to cause the line wipers 170 and 169 to make connection with the bank contacts 171 and 172.l The upper winding of relay 185" is normally bridged across ithe conductors 61 and 60, therefore as soon as the connectorwipcrs land on the contacts 171 and 172 the said relay energizes in series with the back bridge relay 153. rllhe relay 153 reverses the battery upon the calling line in thesame manner as hereinbefore described but .the calling subscriberdoes not deposit his coin because he has not yet heard the called subscriber answer by giving hisl name or number. The relay 185, upon energizing, closes a. circuit through the signal lamp 186` This circuit extends from ground G, through contactA 187,A contact 188 andl armature 189 and the said lamp to battery B. The operator immediately answers by throwing key K3 which bridges her head set (not shown) across the conductors 61 and 6'() in series with the condenser 193 and closes a circuit through the relay 191.` This latter circuit extends from ground G1S through the Springs 194 vand the rsaid relay to battery B'. The relay .191 upon energizing, closes a locking circuit for itself and removes the shunt from around the lower winding of relay 185l atA the, springs 192. The two windings of relay 185a are now connected in series across the trunk conductors 61 and 60. The lower winding of relay 1,85a is of suiiiciently high resistance to cause the back bridge relay 153 to denergize and reverse the battery upon the calling line back to normal, whereby the substation A is again rendered operative for talking purposes without the necessity of depositing a coin. The operator now gives the calling subscriber the necessary information, where upon the connection is lreleased as hereinbefore described by the calling subscriber replacing his receiver upon his receiver hook.'

If the calling substation A desired to call the individual substation U, which' substa tion is intended to be accessible without charge to all subscribers, the apparatus is operated in the saine manner as hereinbefore explained. The connector H, 4upon complet ing connection to the substation U through the medium of bank contacts 501 and 502 and conductors 220 and 221, signalsthe subscriber at substation U, who upon answering, causes the'switch hook to close springs 224 for a long enough period of time to cause the back-bridge relay 153 to ull upland energize the ring cut-olf relay 154. The said springs then separate and the resistance 225 is cut in series with the backbridge relay 153, thereby causing it to fall back and reverse the flow of current back to normal on the calling line. It follows that the subscribers at substation and snhstation U may now converse without requiring the subscriber atv sustation L to deposit a coin.

While I have shown and explained in the .skilled in the art. I desire, therefore, to include and have protected by Letters Patent t all niodiiications of my invention which may lcome within the scope of the appended claims.

rWhat I claim as my invention isz' 1. In a telephone system, a subscribers station and a line therefor, a device for rendering said station inoperative for talking purposes, a trunk line, means for connecting said line and said trunk line, means included in said connecting means for operating said device, means included in said trunk line whereby said operating means is renderedeffective, means for completing a talkingconnection over said trunk line, and means included in said trunk line, whereby said operating means is rendered ineffective without destroying said talking connection.

2. In a telephone system, a subscribers station and a line therefor, a device for rendering said station inoperative foi' talking purposes, `an automatic lswitch accessible to said line, means included in said switch for operating said device, a? trunk line accessible tosaid switch, means whereby said operating means is rendered effective upon the connection of said switch with said trunk line, means'for completing a talking connection over said trunk line, and means whereby said operating'means is rendered ineffective without destroying said talking connection.

3. Inv a telephone system, a subscribers station and a line therefor, a device for rendering Vsaid station inoperative for talking purposes, a trunk line extending .to an operators position, means for connecting said line and said trunk line., meansI included in said connecting means (for operating said device, means included in said trunk line whereby said operating means is rendered effective,"

means for completing a talking connection `over said trunk line, and manually controlled means included in said. trunk line whereby said operating means is rendered ineffective without destroying said talking connection.

4. In a telephone system, a subscribers station and a line therefor, a device for ren:- dering said station inoperative for talking purposes, an automatic switcheccessible to said line, means included in said sWitch'fo'r operating said device, a trunk line accessible by said switch, ine-ans included in said" switch for reversing the direction of current flow in said line, a trunk line accessible to said switch, means whereby said reversing means is rendered effective upon the connection ofv said switch with said trunk line, means for completing a talking connection over said trunk line, and means whereby said reversing means is rendei'ed ineffective without destroying said talking connection.

6. In a telephone system, a subscribers station and a line therefor, areverse cur rent controlled device for rendering said station inoperative for talking purposes, an automatic switch accessible to said line,l a source of current for said line controlled by said switch, means included in said switch for reversing the direction of current flow in said line, a trunk line accessible to said switch extending to an operators positioin' means whereby said reversing means is rendered effective upon the connection of said switch with said trunk line, means for completing a talking connection over said trunk line, and manually controlled means whereby said reversing means is rendered inelfective without destroying said talking connection.

7. In a telephone system, a subscribers station and a line therefor, a reverse current controlled device for rendering said station inoperative for talking purposes, an automatic switch accessible to said line, a sourceof current for said line controlled by said s itch, a back bridge relay in said switch for reversing the direction of current flow in said line, a trunk line accessible to said switch, means whereby upon the connection of said switch with said trunk line, a circuit including said trunk line is established for said relay, and means associated with said trunk' line for increasing the resistance of said trunk line to make said relay inoperative.

1StIn a telephone system, asubscribers station inoperative for talking purposes, an automatic switch accessible to'said line and and a line therefor,

extending to an operators position, a source of urrent for said line controlled by said switch, a back bridge relay in said switch for reversing the direction of current flow in said line, a trunk line accessible to said switch, means whereby, upon the connection of said switch with said trunk line, a circuit. including said trunk line is established for said relay, and manually controlled means associated with said trunk line for increasing the resistance of said trunkline to make said relay inoperative.'

9. In a telephone system a subscribers station and a line therefor, a device for rendering'said station inoperative for talk ing purposes, a second subscribers station means for completing a connection between said lines, means in eluded in said connecting means for operating said device, means associated with said second station whereby said operating means made effective, means for completing a talking circuitnthrough said second station, and means included in said talking circuit whereby said operating means' is rendered ineffective without destroying said circuit.

10. In a telephone system, a subscribe1"s station and al linetherefor, a device for rendering said station inoperative for talking purposes, a second stationand a line therefor` an automatic switch for connecting said lines, means included in said switch for operating said device, means associated with said second station whereby said operating means is made effective. 'means for completing a talking circuit through said second station, and means included in said talking circuit whereby said operating means is rendered ineffective without destroying said circuit.

11. In a telephone system, a subscriber-s station and a line therefor, a reverse current controlled device for rendering" said station inoperative for talking purposes, a second subscribers station-and a line therefor, a source of current for said lines, means for completing` a connection between said lines, means included in said connecting means for reversing the direction of current flow in said first line, means associated with said second station whereby said reversing means is made effective, means for completing a talking circuit through said second station, and means included in said talking circuit whereby said reversing means is renderedl ineffective without destroying said circuit.

12. In a telephone system, a subscribc1"s station and a line therefor, a reverse current controlled device for rendering said station inoperative for talking purposes, a second station and a line therefor,- a source of current forsaid lines. an automaticv switch for connecting said lines, means included in said switch for reversing the direction of cur rent flow in said first line; means associated with saidA second station whereby said reversing means is made effective, means for completing a talking circuit through said second station and fmeans included in said talking circuit whereby said reversing means is rendered ineffective without destroying said circuit.

13. In `a telephone system, ay subscribers station and a line therefor, a reverse current controlled device for rendering said station inoperative for talking purposes, a second station and a line therefor, a source of current for said lines, an automatic switch for connecting said lines, a back-bridge relay in said switch for reversing the direction of current iow in said first line, means associated with said second station whereby, after the completion of said connection. an operating circuit may be momentarily established for said relay, and means included in said second station for completing a talking circuit therethrough without operating said relay.

14. In a telephone system, a subscribers station and a line therefor, a reverse current controlled device for rendering said station inoperative for talking purposes, an. automatic switch accessible to said line. a source of current for said line controlled b v said switch,'a back bridge relay in said switch for reversing the direction of current iiow in said line, signaling apparatus in said switch controlled by said relay, a trunk line accessible to" saidswitch. means whereby upon the connection of said switch with said trunk line, a circuit including said trunk line is established for said relay to disconnect said signaling apparatus, and means associated with said trunk line for increasing the resistance of said trunk line to make said relay inoperative.

15. In a telephone s vstem. the combination of a first circuit. a source of current therefor, a device electrically rclatedto said circuit. a first switch, a First magnet in said first circuit for controlling said first switch, `a second switch, a second circuit. a second magnet in Said second circuit for controlling said second switch, a third switch for clos ing said second circuit for energizing said second magnet to operate said second switch to change the character of the current in the .first circuit to operate said first switch through the medium of its controlling magnetto change the electrical relation of said device to said first circuit. and means for (.'ontrolling` said second circuit without interrupting the same to restore the current in the first circuit to its original character thereafter, whereby the first magnet is operated to restore the Original electrical relation of said device to said first circuit.

16. In a telephone system, the combination of a first circuit, a source of current ina meshes therefor, a device electrically related to said circuit, a` first switch, a first magnet in said first circuit tor controlling said first switch, a second switch, a second circuit, a second magnet in said second circuit for controlling said second switch, a third switch for closing said second circuit for energizing said second magnet to opel ate said second switch to change the character of the current in the first circuit to operate said ,first switch through the medium of its controlling magnet to change the electrical relation of said device to said first circuit, a device electrically related to said second circuit andmeans for controlling said second circuit.

without interrupting theysame to restore the current in the first -circuit to its original character thereafter, whereby the first magnet is operated to restore the original electrical relation of said device to said first circuit Wherebv communication may be had between the two devices.

v v17'. In a telephone system', the combina- `'tion with a first circuit, a telephone instrument electrically related thereto,l and a niagnet in said first circuit for changing said electrical relation, of a second circuit, a

source of currentl for said circuits, a secondv net in said first circuit for changing said electrical relation, of a second circuit inductively related to said first circuit, a, source of current for said circuits, a second magnet in said second circuit for altering the cha acter of current flow in said first circuit to operate the magnet included -therein, means for closing said second circuit to operate the said second magnet, a second telephoneinstrument and means for associating said instrument with said second circuit, and means for controlling said second circuit wit-hout interrupting the same to render the said second`magnet`inoperative, whereby the electrical relationbetween the first circuit and said telephone instrument is rst changed and the-n restored toits original condition to enable conversation to be held between said telephone instruments.

19. In a telephone system, a pair of subscribers stations and lines therefor, means for connecting said lines, condensers normally in series with said stations, a source of signaling current, a source of direct current, means for intermittently completing a signaling circuit including said current sources and the called one of said lines all in series, a controlling relay for said last means in.-

cluded in saidcircuit, said relay being irresponsive to said signaling current, a second relay for initially controlling said controlling relay, said second relay being in series with the called one of said lines and said direct current source between signals, and means for completing a path for direct current throughsaid called substation for operating said controlling relay during signals and for operating Vsaid second-relay between signals.

Signed by me at Chicago, Cook county, Illinois, this 31st day of January, 1915.

- TALBOTKG. MARTIN.

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