US1323483A - martin - Google Patents

Description

T. G. MARTIN.

SEMI-AUTOMATIC IELEPHONE SYSTEM. APPLICATION FILED MAY 14, I906- RENEWED res. 8, 1919.

Parental Doc. .2, Hi9.

T. G. MARTIN.

SEMI-AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED MAY 14, I905- RENEWED FEB. 8. 1919.

1 .,3%3,%83D I Patented Dec. 2,1919.

6 SHEETS-SHEET 2- s 8% QQ 5%? e as. a. W

v T. G. MARTIN. SEMI-AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED MAYI4, I906- RENEWED FEB. B, 1919.

Tat anted Dec 2, 19191 .6 SHEETSSHEET 4 m hhw J QQ T. G. MARTIN.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAY 14, \906. RENEWED FEB. 8. me.

6 SHEETS-*SHEET 5.

Patented Dec. 2, 1919.

HIIIWIWI R T. G. MARTIN.

SEMI-AUTOMATIC TELEPHQNE SYSTEM. APPLICATION FILED MAY 14. I906- RENEWED FEB. 8. 1919.

Patented Dec. 2, 1919.

6 SHEETSSHEET 6.

"or en TALBOT G. MARTIN, OF CHICAGO, ILLINOIS, ASSIGNOR,

BY MESNE ASSIGNMENTS, TO

AUTOMATIC ELECTRIC COMPANY, A CORPORATION OF ILLINOIS.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

Application filed May 14, 1906, Serial No. 316,742. Renewed February 8, 1909.

that is to say, telephone systems in whichboth manual switchboards and automatic switches are employed for establishing connection between calling and called subscribers lines.

Generally stated the object of my invention is the provision of an improved and highly eliicient telephone exchange system.

Special objects of my invention are the provision of an improved and highly efficient semi-automatic telephone exchange system; the provision of improved means for supervising the system both with respect to service between subscribers lines and certain kinds of trouble, as will hereinafter more fully appear; the provision in a system of this character of improved releasecircuits for releasing or restoring whatever automatic switching means may have been found necessary in establishing connection between any two subscribers lines;'the provision of an improved arrangement for dividing the exchange into a main or central station and a plurality of outlying auxiliary or sub-central stations, whereby greater economy and efiiciency are obtained; the provision of an im roved arrangement by which each subscribers line entering a subcentral station is provided with an improved individual-switch for making connection with an idle trunk-line leading from such sub-central station to the main or central station; the provision of an im proved arrangement whereby the capacity of a telephone system may be increased to any desired extent at a comparatively small cost and expenditure of time and labor; the provision of an improved arrangement for effecting a reduction in the equipment necessary for the manual board. operators; the provision of an improved arrangement involving operators cord-circuits adapted to operate in conjunction with individual- Specification of Letters Patent.

tral station, the operator will Patented Dec. 2, 119119.

Serial No. 275,854.

switches and in connection with improved repeaters, as will hereinafter more fully appear; and the provisionof certain combinations, details and features of improvement tending to increase the general efiiciency and serviceability of a telephone exchange system of this particular character.

In a system characterized by my invention a subscriber whose line terminates at a sub-central station can make a callin the usual mannerthat is, in the manner ordinarily employed in manual exchanges. As soon as he takes down his receiver the socalled individual-switch in which his line terminates automatically selects for him an idle trunk-line leading from the sub-central station to the main or central station. At this main or central station the trunk-line thus automatically selected for the calling subscriber terminates in the manual board and is there provided with a visual line signal. The operator at this board, observing the line signal, picks up the answeringplug of the cord-circuit corresponding to this trunk-line and inserts the same in the jack connected therewith. She can then press her listening-key in the ordinary manner and by means of her talking set converse with the calling subscriber and receive his order for the connection. If the calling subscriber desires connection with the line of a subscriber terminating in the same or some other sub-centra1 station, the operator then employs her calling device or impulsetransmitter for operating a connector at the sub-central station at which the called line terminates. She thus operates the said connector and causes the same to make connection directly with the line'oi the called subscriber. After this, the connector can automatically ring or signal the called subscriber in the ordinary and well-known manner. If, however, the calling subscriberdesires connection with a subscribers line whichterminates directly at the main or centhen simply connect the calling plug of the cord-circuit with a multiple-jack which is connected with the called line and which is located on her board. She then rings or calls the called subscriber. In the other case, namely when the called subscribers line terminated at the sub-central station, the operator inserted the calling plug of the co -o-circuit in the geek oi a trunk-line leading te such sub-central station. In either case, however, the calling subscriber obtains connection with the operator through the medium of his individual-switch, and from this point on the operation is either purely manual or semi-automatic, according to whether the called subscribers line terminates in a multiple-jack on the operators board, or in the multiple-contacts of connectorslocated at a sub-central station. In one case, also, the ringing or signaling of the called subscriber is done by the operator at the manual board; but in the other case the ringing is done by the automatic ringingconnector. With this arrangement the operator re quires but little equipment in order to take care of a large number of subscribers.

To the foregoing and other useful ends, my invention consists in matters hereinafter described and claimed.

In the accompanying drawings,

Figure 1 is a diagram illustrating how my improved system is used in connection with a purely manual exchange; and the said manual exchange is shown to the left, and the trunkin positions allotted to outlying sub centra s and their allotted substations employing individual-switches are indicated to the right; and the said subcentrals are represented by circles.

Figs. 2, 3 and 4 are diagrammatic views that represent an established connection between calling and called subscribers whose lines terminate at a sub-central station; and the substations are designatedas #2050 and #2120, respectively, and the intermediate apparatus for maintaining the said connection consists of an individual-switch A, a battery B for operating-said switch and all other switches, a repeater C, a cord- 'ircuit D with allotted line and multiple jacks, a connector E at the called subcentral, and the individualswitch A of the called line; and for selectively operating the individual-switches each sub central or group of individual-switches is provided with a master-swit h F which, in Fig. 2. is shown with the calling substation #2050, the individual-switch A and the repeater C.

Fig. 3 is a diagram showing the cordcircuit allotted to one of the trunking operators position at the central or main station.

Fig. 4 is a diagram showing the connectorswitch E and the individual-switch A of the called line, together with the calledtelephone. 7 V

Fig. 5 is also a diagrammatic view of the individual-switch A and of the masterswitch F, with circuits appertaining thereto.

Fig. 6 is a diagrammatic perspective view of the connector-switch of the general class described in Patent No. 815,176, issued March 13, 1906, to Keith, Erickson and Erickson showing the automatic ringing and to various parts of the system wherever it ma be necessar Thi arran ement however,-is not essential since, if desired,

sub-batteries may be provided at any desired point. p

The individual-switches are of the type described in application Serial No. 258,026, filed April 29, 1905. Each individual switch comprises a release-magnet 2, a tripmagnet 3, a bridge-cut-olf-relay 4, and a bank H with ten jack positions, each position comprising three individual springs 5, 6 and 7 and five multipled springs 8, 9, 10, 11 and 12that is, springs that are multipled in the same bank and to similar springs of all other banks. Each of said bank jacks corresponds to a trunk-line, any one of which trunk-lines may be seized by the individual-switch A. Each of said trunklines comprises two line-conductors and a trunk-release conductor, and in Fig. 5 the trunk-line allotted to the jack there shown terminates in the springs 5 and 6, and the corresponding release trunk conductor in the spring 7. It has been described that the said jack, shown in Fi 5, represents the first jack of the bank Like this jack there are corresponding jacks in every other banli olt the same group. Furthermore, in all "(if said corresponding jacks all similar springs 5 are connected in multiple. The same is true of all similar springs 6 and all similar springs 7. 0f the said bank H only one of the jack positions is shown. Adapted to engage the said bank jacks one at a time there is provided a plunger 13 which is pivotally secured to a plunger-arm It, said plunger arm being held in position by a pin 15 that rises from the base of the individual-switch, which base is not shown. The release-magnet 2 controls an armature 16 that is held in normal position by any suitable spring 17 and that carries on its forward end. the armature 18 of the trip; magnet 3, the said armature 16' being pivoted to the base of the individual-switch by the pin,19. Upon the end of the tri magnet armature 18 there is a hook-1i e projection 20 that normally locks in engagement with the abutment 21 and thereby the individual-switch bank H same group. Said shaft is out of the control of the individual-switch, but is operated altogether by the vmaster-switch F. The said master-switch is provided with the bank I and auxiliary-relay 24 and difierential-relay 25 and a motor-magnet 26. l T he bank I is composed of a number of contacts 27 (one for each trunk-line leading from and a member 28 common to said contacts. Adapted to engage said bank there is a wiper 29 by means of which any one of the said contacts 27 may be placed in electric connection with the common plate 28. The wiper 29 is a part of a wiper-arm formed by the said wiper and a cam 30. The said cam normally rests in engagement with either one of four pins 31, 32, 33 or 34 carried on a vratchet-wheel 35. Said ratchet-wheel normally rotates in the direction of the arrow and is checked against backward rotation 1 by a pawl36. The cam 30 is retained in engagement with the pins upon said ratchetwheel 35 by a suitable spring 37 wherehy the wiper-arm is given a perpetual tendency to rotate the ratchet-wheel 35 in a clockwise direction. lhe mechanism for rotating the said ratchet-wheel 35 and, therefore, for shifting the wiper 29 from one position to another comprises a pawl 38 upon the end or the armature 39 of the motor-magnet 26, whereby whenever the said magnet 26 is energized the ratchetwheel 35 is rotated one step. The wiper 29 and cam 30 are so adjusted that when the pin 31 engages the said cam 30 at a point marked hythe line 40 the wiper 29. engages the contact-point ii; when said pin advances the line marked 42 the wiper 29 passes the contactpoint 43; and when the said pin passes to the end or the cam 30 the wiper 29 reaches the contact id. Having reached the contact 44, if the ratchet-wheel 35 is advanced another step, the cam 30 disengages from said pin 3i and meets the pin 32 at the point 40 and so on. The construction is such that whenever a guarding potential appears at the contact-point of the bank i engaged by the wiper 29 the ditierentiahrelay 25 is energized which latter upon attracting its armature i5 presses the sprin s t6 and 47 into contact and thereby establishes an energizing circuit through the niotonmagnet 26, whereby the ratchetwheel 35 is advanced one step. The common 23 previousiy mentioned, is attached to the cam-arm at the point i8 and it will be evident each time the said cain-arm is operated that the shatt 23 will be rotated correspondingly, carrying with it all idle plungers normally resting in the channel 22. To illustrate: If the wiper 29 is resting upon the contact ti when the individual-switch A. is operated, the plunger-shaft is then in a position to direct the plunger 13 into the first jack the H, shown in Fig. 5. A guarding potential is then established at the said contactthe motor-magnet 26 to be operated so that the wiper 29 and plunger-shaft 23 are advanced to the next position in which. the wiper 29 engages the contact-point 1-3. l t the contact 43 is also provided with a guarding potential-that is, if the second jack of the bank His busy-the differential-relay 25 is still maintained energized so that the motor-magnet 26 may operate once more to carry the wiper 29 and shaft 23 to the next position. A step-'by-step actuation of the shaft-23 and wiper 29 takes place until the shaft 23 carries all idle plunger-s to a point opposite the hank. jacks that are not occuied.- P The substation may he or the ordinary common battery type in which the suh scrihers line-circuit is normally closed through a ringer'49 and the condenser 50 when the switchhoolr 51 is down. llhe receiver 52 is in series with the secondary winding 53 of the induction-coil 54c, and when the switch-hook is up the primary winding '55 of the said induction-coihin serice with the transmitter 5'6, is hridged across the line instead of the ringer The repeater C is Very simple and cont prises a couple of condensers 57 and 50 located respectively on the vertical tary sides of the main-circuit. (in the nt side or said condensers the vertical. relay 59 is bridged between the yertic l side the iine and the non-grounded f the hattery, while the rotary-ii 0 is bridged hetween the side oi l ground.

inc and the laid vertical L" y line-relays, respectively, control e to he described. Upon hack side of aid condensers the vertical-hach h i 31. is normally connecte ound vertical side c through a couple oi" springs cor :.o the rc'tary line-relay "0. A signalr is normally connected between grouiic the trunk-releaseconductor leaf e a s o o v--- ctheindividaul switch hanks. Eiaid relays hi to "C on e-cut-oh lay it v the e-relay 1 ar the usual ype. out." g tr-units termiin multiple inc to each I eas es erator. Of the said jacks, in Fig. 3, two are shown, namely 72 and 73. Said jacks are each provided with a signal-lamp so that if any one of the trunking operators is using a particular trunk the signal-lamp to each trunking operators position will re main lighted as long as the said trunk 1s used by any one of the operators. Alotted to each trunk-line there are a' quick-acting relay 74 and a slow-acting relay 75 for releasing the automatic switches. Between the trunking operatois and the local operators a system of order-wires is provided whereby the local operators may deliver an order to any one of the trunking operators whenever the local subscribers wish to connect with the sub-central subscribers. One

of the local operators signal-buttons is shown at J while the order signal-lamp 76 is shown in connection with the cord-circuit D. 7

It will be evident that the individualswitch A is like the individual-switch A and will, therefore, need no further description. Beneath the said individual-switch A avdifierential-relay 77 is shown that corresponds to the differential-relay 25 of the master-switch F.

In the establishment of a connection between two subscribers the following apparatus and circuits are involved. If the subscriber #2050 (Fig. 2) desires to establish connection with the subscriber #2120 he removes his receiver 52 from the switch-hook 51, thereby closing a circuit between the lineconductors 78 and 79 through the transmitter 56 and primary winding 55 of the induction-coil 54g. Normally the vertical-lineconductor 78 is connected to ground G while the trip-magnet 3 is normally connected between the rotaryline-conductor 79 and the non-grounded terminal of battery B. Therefore, the establishment of connection between the said conductors 78 and 79, as described, causes the trip-magnet 3 to be energized by a flow of current from ground G? through the transmitter 56 to the rotaryline-conductor 79, and thence through the trip-magnet 3, conductor 85, springs. 8 l-and.

83 to the battery-lead 80 and through battery B to ground G. The trip-magnet 3- -Will then attract its armature 18 and thereplunger 13 and a number of relays and magnets are energized as follows When the: springs 8 and 10 come into contact they establish a guarding potential by way of theprivate-normal-conductor 82 at the connector-banks that are allotted to the group of subscribers of the twentieth hundred, so that no calling subscriber may be able to connect with the calling line #2050 by way of the conductors 82 and 82 after the plunger 13 has once been tripped. The closure of contact between the springs 9 and 7 sets up a circuit between the non-grounded terminal of battery 15 and contact 41' of the master-switch I as follows: from the battery B through the battery-lead 80 and release-magnet 2 to the said springs 9 and 7 and conductor 86 to the contact-point 4:1. The establishment of said guarding potential at that point energizes the difierentialrelay 25, which latter then causes the motormagnet 26 to operate to carry the Wiper 29 and the shaft 23 to the next non-guarded position, as previously described. Also, the closure of contact between the springs '12 and 6 extends the subscribers vertical-lineconductor 78 to the repeater C, and since the said conductor is grounded at G.

through the springs 87 and 88 the verticaltary-line-conductor 79 through the said 100 springs 11 and 5 to the said rotary-line-relay 60, thence to ground G Therefore, the said rotary-line-relay 60 is short-circuited between the ground terminals G and G.

into contact not only is there a guarding potential established at the connector banks by way of the private-normal-conductor 82, but an energizing circuit is established through the cut-oii-magnet i from ground 110 G throughthe said springs 8 and 10. conductor 92, cut-od-relay i to the battery-lead 80 and through battery B to ground G. The aforesaid relay 4:, upon becoming energized,

forces the springs 88 and 93 away from the 115 springs 87 and 94, thereby breaking the circuit between ground G and the verticalline-conductor 78, and between the tripmagnet 3 and the spring 93. At the instant that the springs 87 and 88 are pressed apart 12 by the relay 4 the connection to ground for maintaining the vertical-line-relav 59 energized is furnished by the ground G through the rotary-line-relay 60 and through the line-conductor 78. At once the said rotaryline-relay 60 pulls up so that the said vertical and rotary line-relays 59 and 60 are energized in series, the current in which circuit passes from the saidground G through we When the aforesaid springs 10 and 8 come substation transmitter 56 to the vertical- 1% the primary Winding 55 at the substation,

transmitter 56, vertical-line-relay 59 to the battery-lead 80 and through battery B to theground terminal Gr. \Vhen the springs 9 and 7 close contact, as described, not only is there a guarding potential established at the contact 11, but an energizing circuit is set up through the signal-relay 62 from ground G through the said relay and through the springs 7 and 9, release-magnet 2 to the battery-lead 80, thence through battery B to ground G. Said signal-relay 62 is wound to a very high resistance, about four thousand ohms, more or less. Said relay remains energized from the time that the individual-switch A operates until the subscriber releases the switching apparatus, in a manner to be described. Normally the said relay plays no part in the establishment of connections, as it is nothing more than a trouble supervisory relay for transmitting signals to the operator at the main exchange, in a manner to be described. The vertical and rotary line-relays 59 and 60, however, are only wound to about three hundred and fifty ohms each, and the vertical -back-' bridge-relay 61 to about five hundred ohms. After the subscriber has established connection with the repeater C, and upon energizing the rotary-line-relay 60, as described, the springs 95 and 96 are separated, and the springs 97 and 98 are also separated, but the springs 95 and 97 are brought into contact. As a result the vertical-backbridge-relay 61 is bridged across the incoming trunk-conductors 99 and 100, whereby the said relay is connected in series with the line-signal-relay 71, and whereby both of said relays are energized. The magnetizing current flows from ground G through the contact 101, armature 102 of the line-cutoff-relay 70, vertical-trunk-conductor- 99, vertical-back-bridge-relay 61, springs 95 and 97 of the rotary-line-relay 60 to the rotarytrunk-conductor 100, thence through the armature 103 of the line-cut-off-relay 70, contact-point 104, line-relay 71 to the battery-lead 80, and through battery B to the ground terminal G. The vertical backbridge-relay 61 of the repeater C upon at tracting its armature forces the springs 91 and 105 into contact, whereby the said spring 91 and, therefore, the spring 89 of the vertical-line-relay 59 is connected with ground G for future use. Not only are the springs 91 and 105 in contact, but since the signal-relay 62 is energized the spring 106 is also in contact with spring 105; and since the rotary-line-relay 60 is energized the connection between said springs 105 and 106 has no consequence at this time. The linerelay 71, at the central station, upon energizing draws the armature 107 onto the contact-point 108, whereby theline signal-lamp 109 is bridged between ground G and the battery-le'ad 80. The said lamp, upon being thus connected, is lighted and gives a signal to the trunking operator, indicating that some one is calllng. Said operator then inserts the answering end of the cord-circuit 99 and the rotary-trunk-conductor 100 are placed in connection, respectivelv, with the tip-spring 112 and the sleeve 111. as shown. As a result the previously described energizing circuit for the "ertical-back-bridgerelay 61 is transferred from ground G at the line-cut-ofi-relay to the ground terminal G and through the tip supervisory relay 63, whereby not only the said relay 61 is retained energized, but the relay 63 is'also energized. The transfer or change of circuit occurs so quickly that the relay 61 has no time to deener ize. The current in this last circuit, it Wlll be seen, passes from ground G through the relay 63, tip-spring 112, vertiv cal-trunk-conductor 99, relay 61, rotarytrunk-conductor 100 to the sleeve 111, thence through the supervisory relay 64 to the battery-lead 80 and through the battery B to ground G. When the armature 103 leaves the contact-point 104, at the time when the line-cut-ofi'aelay 70 is energized, the linesignal-relay 71 de'nergizes and releases the armature 107, whereby the line-signal-lamp 109 is extinguished. As soon as the sleeve supervisory relay 61 attracts its armature 113 the energizing circuit is closed through the back supervisory lamp 111 from ground G through the armature 115 of the tip back supervisory relay 65, thence through the con tact-point 116, armature 117 of the sleeve back supervisory relay 66, through the contact-point 118, lamp 114. contact-point 119, and armature 113 to the battery-lead 80 and through battery B to ground G. It will be noticed that for the purpose of preventing the front supervisory lamp 120 from lighting up when the operatorinserts her plug in the jack 110 the armature'121 of the relay 63 is attracted and thereby separated from the contact-point 122. Having plugged into the calling line the operator presses the key a and thereby. throws her talking set across- 132. The transmitter 56 of the substation #2050 being provided with talking battery that flows through the said transmitter in series with the line-relay 59 and 60 of the repeater C, the subscriber, by talking into said transmitter, .will cause the resistance of said circuit to be varied. By varying the resistance of the circuit comprising said transmitter, in the usual and well-known manner, the impressed potential between the condensers 57 and 58 is caused to vary in accordance with the vibrations of the transmitter 56, so that talking currents are sent from the condenser 57, thence over the trunk-conductor 99 to the tip-spring 112, thence through the condenser 133. conductor 123, spring 125,'contact-point 127, secondary winding of the induction-coil 131, receiver 129,- condenser 132, contact-point 128, spring 126, conductor 124, condenser 134, sleeve 111 to the rotary-trunk-conductor 100, thence to the condenser 58.- The transmitter of the operators talking set being bridged across the battery B through the impedance-coil 136 is also provided with talking battery current. Said transmitter, like the transmitter 56, will vary the potential between points on either side of said transmitter and thereby cause voice-currents likewise to be sent through the prlmary winding 137 of the induction-coil 131 and through the condenser 135. In a wellknown manner said currents affect the secondary winding130 of the said inductioncoil 131,.which pass to the substation #2050 through the transmitter 56 and primary winding 55 of the induction-coil 54. The secondary windin 53 of the said inductioncoil is thus afiecte whereby the voice-waves are reproduced in the receiver 52. The subscriber being asked the number desired Wlll call for the number 2120 and the operator will release the key 0. She then inserts the calling terminal of hercord into one of the jacks of the outgoing trunk-lines. The 130k 72 being one of such jacks, then as soon as the plug is driven home the quick-acting relay 74 1S magnetized as soon as the spr ngs 138 and 139 are pressed into contact, and

also the tell-tale lamp 140 isat the same time lighted, as well as all other tell-tale lamps 141 connected in multiple across the conduc tors 142 and 143, for notifying all trunk operators that have multiples to the outgoing trunk-conductors 144 and 145. The energizing current for the quick-acting relay 74 passes from ground Gr through the s rlngs 138 and139 and through the said re ay 74 to the battery-lead 80 and through the battery B to ground G. In like manner the current that lights the tell-tale lamps flows from ground G to the conductor 143, thence through all of said lamps to the conduct'or 142, and to the battery-lead 80, thence through battery B to ground G. As soon as the relay 74 is energized the armatures 146, 147 and 148 are attracted and when the said armature 147 engages the contact 149 the slow-acting relay 75 is in turn energized. The current for this last relav flows from 70 ground G to the said relay 75, thence through the contactpoint 149, armature 147 to the battery-lead 80 and through the battery B to ground G. Said relay, upon energlzing, attracts its armatures 150 and 151 75 and establishes a ground connection to the contact-points 152 and 153 for future use. The operator will, of course, know that the trunk-line-conductors 144 and 145 that she has selected lead to the twenty-one hundred 80 sub-central and will proceed to operate the connector-switch at said sub-central to connect with the subscriber 20 in the said twenty-first hundred. She then proceeds by pressing the key 2), whereby the springs 154 35 and -155 are withdrawn from the contactpoints 156 and 157, respectively, and pressed lnto contact with the points 158 and 159*, thereby placing the said spring 15.4 and 155 indirect connection with the springs 67 and 90 68 of the calling device. The operator then presses the vertical-button 159. twice and thereby grounds the vertical-trunk-conductor 144 twice. As a result the well-known vertical-line-relay 160 of the connector is 95 energized. Current through said relay flows from ground G through the springs 69 and 67 contact-point158, spring 154, contactpoint 161, spring 162, tip-spring 163 to the vertical-trunk-conductor 144, thence through the vertical-line-relay 1'60 and winding 164 of the diflerential-relay 165 to the batterylead 80, thence through battery B to ground G. Both the verticaldine-relay 160 and differential-relay 165 are energized, but the energization of the latter has no significance at present. The vertical-line-relay by pressing the spring 166' and 167 into contact in turn energizes the vertical-magnet 168. The current through this last magnet flows from no ground G through the springs 167 and 166 and through the rivate-magnet- springs 169 and 170 to the si e-switch-wiperr171, thence through the contact-point 172, vertical-magv net 168 to the battery-lead 80 and through 115 battery B .to ground G. V The said verticalmagnet bein energized twice through the medium of t e verticaharmature 173 raises the shaft 174 two steps and the switch-shaftwi ers 175, 17 6 and 177 are raised to the sec-v me on level of their respective banks 178 and 179. Having raised the connector-shaft 174 two steps the operator presses the rotarybutton 180 once and thereby grounds the rotary-trunk-conductor 145 once, sult the rotaryline-relay 181 of the connector is energized. The current for energizing said relay flows from ground G through thesprings 69 and 68, through the contactpoint 159*, thence through the spring 155, 1130 As a re- 125 contact-point 182, spring 183, sleeve" 184 to the rotary trunk conductor 115, thence through the said rotary-line-relay 181, winding 185 of the differential-relay 165, verticalback-bridge-relay springs 186 and 187 to the battery-lead 80, through battery B to ground The rotary line relay 181 presses the springs 187 and 167 into contact and thereby energizes the private-magnet 188. The current through said private-magnet flows from ground G through the springs 167 and 187, and through the said private-magnet 188 and vertical-back-bridge-relay springs 186 and 187 to the battery-lead 80 and through the battery 13 to ground G. The privatemagnet, upon being energized and deenergized, permits the side-switch retractingspring 189 to draw the side SWItCh to second position and thereby shift the sideswitch-wiper 171 onto the contact-point 190.

The operator then again presses the vertical-button 159 ten times corresponding to the digit 0, thereby energizing the verticalline-relay 160 ten times in the same manner previously described. As a result, since the side-switch wiper 171 and contact-point 190 are in engagement, each time the springs 166-and 167 come into contact the rotarymagnet 191 is energized. The said relay 160 being operated ten times the rotor magnet is energized ten times and the switch-shaft 174:, through the medium of the rotary-armature 192, IS rotated ten steps. The energizing current for the said rotaryrnagnet 191 flows from ground G and through the private- springs 169 and 170 to the side-switch-wiper 171, thence through the contact-point 190 and throughthe rotarymagnet 191 to the battery-lead 80 and through the battery B to ground G. The switch-shaft-wipers 175, 176 and 177 are, therefore, carried into engagement with the tenth contact of the second level of their respective banks, from which contacts the normal-conductors 193, 19 1and 195 lead to the individual-switch A of the called line, and from thence the norinal-line-conductors 193 and 19% extend to the subscribers station #2120. The operator then for the lastthe contact- points 198 and 199, respectively.

The said wipers 196 and 197 being thus shifted the trunk-conductors 11 1 and 1 15 also.

But heretofore the energization of said differential-relay has been of no importance. At the same time that the sideswitch-wipeis 196 and 197 engage the contact- points 198 and 199 the side-switchwiper 202 finds the grounded contact-point 203 and establishes an energizing circuit through the ringer-relay 20st, whereby ringing current from the ringergenerator 205 may be sent over the called subscribers line for ringing said subscribers bell. The ringing, as described in my said prior application, occurs intermittently, since the ringerrelay 204 is energized intermittently by means of a circuit-breaker 206 that may be located upon the armature of the ringergencrator 205, but which may, in any desired manner, bekept in perpetual:.- rotation. The said circuit-breaker, as shown, is built like a commutator with alternate conducting and non-conducting sections, but which construction is not absolutely essential. Diametrically opposite conducting segments of said circuit are connected together and the wipers 207 and 208 are so adjusted that when one of the metallic segments on one side is in contact with one of the said wipers, the corresponding segment on the opposite side is in engagement with the other wiper. Each time that the conditions recited occur an energizing current flows through the ringer-relay 204:, the path of which current may be traced fromiground G to the contac -point 203, thence through the side switch wiper 202, conductor 209, rotary-back-bridge-relay springs 210 and 211, vertical-back-bridge-relay springs 212 and 213, conductor 211, ringer relay 2041 and through the circuit-interrupter 206 to the battery-lead 80 and through battery B to ground .G. Each time that the said ringerrelay is. energized the ringer-relay-springs 215 and 216 are withdrawn from thesprings 217 and 218, respectively, and carried into engagement with the springs 219 and 220, whereby the called line is disconnected from the calling line and a circuit established from the ringer-generator 205 through the ringer or hell of the called substation. The

path may be traced from the said generator through the ringer-relay-springs 220 and 216, side switch wiper 196, contact point 198, vertical line wiper 175 and vertical normal-conductor 198 to the vertical-lineconductor 221, thence through the condenser 222, ringer 223 to the rotary line-conductor 224, rotary normal conductor 194-, rotaryllne-wiper' 176, contact-point 199, sideswitch-wiper 197 and ringer-relay-springs 215 and 219 to the ringer-generator 205. In this way the called subscribers bell continues to ring at intervals until the said subscriber answers, or until the calling subscriber hangs up his receiver. To prevent any other subscriber from calling upon the cailed line second level of the private-bank 179, which while the connection described is maintained, the side-switch-wiper 202 is connected with the private-wiper 177, whereby a guardin potential from ground G is es tablishe at the tenth contact of the sec- 0nd level of the private-bank 179.

same time to the cut-off-rela 231 of the individual-switch A (Fig. 4 whereby the said relay is energized. The current passes froir'ground G to the private-wiper 177,

thence over the private normal conductor 195, through the said relay 231 to the battery-lead 80 and through battery B to ground G. For well-known reasons it is desirable to operate the said relay 231 to destroy the connection between the verticalnormal-conductor 193 and the ground G by separating the springs 232 and 233, and to separate the springs 234 and 235, whereby the trip-magnet 236 is disconnected from contact, of course, is allotted to the called line. That being the case when the rotaryline-rela 181. of the connector is energized for the ast time by the operator, as stated, and, of course, while the side-switch is in second position an energizing circuit for the rotary-back-bridge-relay 225, which is normally open between the private-springs 170 and 226 at the instant of groundin the rotary line is closed. The said rotaryinerelay 181, upon being energized, causes the private-magnet 188 to be energized and close the said s rings 170 and 226 in contact in the wel -known and usual manner..

AS a result, of course, the said rotary-backbridge-relay 225 is energized by a flow of current from the ground terminal G of battery B to the tenth contact of the second level of the private-bank 179, over circuits for providing said guarding potential at the private-wiper 177 and rotary-back-bridge-relay springs 210 and 211 to the said rotary-back bridge relay 225, thence to the side-switch contact-point 22 8, idle switch wiper 249, private-springs 226 and 17 0, side-switch-wiper 171 and contact-point 190, thence. through the rotarymagnet 191 and through battery B to ground G. Of course, it will be understood thatlthe called line may be busy either by being called or by calling. In the former case a connector will be set on said line and a side-switch-wiper, similar to side-switchwiper 202, will be in third position whereby Said guarding potential provides current at the thence by conductor 227 the private-wiper of said connector, similar to the private-wiper 177, will be connected to ground, and, therefore, the private-contact allotted to the said line is connected to a ground terminal similar to the round G in a .way that has already been welt upon.

If the called line has been put in use by the called subscriber himself the individualswitch A! will be found operated so that the bank jack springs 237 and 238 are .pressed into contact and a connection thereby established directly between ground G and the tenth contact of the second'level of the private-bank 179, by way of the private-normal-conductor 195.

-At the instant that the rotary-back-bridgerelay 225 is energized and thereby forces the springs 211, 239 and 240 into cont-act, the rotary-line-relay spring 187 is also connected to ground G13 by way of the springs 240 and 239, side-switch contact-point 203 to the said ground terminal G whereby even ifthe rotary-line-relay 181 deenergizes and, therefore, even if the line-relay- springs 167 and 187 separate, the energizing circuit for the private-magnet 188 may remain established until the rotary-backbridge-relay 225 is denergized. It is evident, therefore, that since the private-magnet 188, whenthe private-wiper'177 is on a' bus contact, controls the energizing circuit for the rotary-back-bridge-relay 225- and since the said rotary-back-bridge-relay, in turn, when energized provides an energizing circuit for the private-magnet 188 until the calling subscriber decides to release-thc said private-magnet and backbridge-relay will, so to speak, be locked in an energized condition. It will be evident, also, that as ion as the private-magnet is energized the si e-switch will be locked in second position, since the escapement-finger 243 IS retained between the escapementteeth 244 and 245, because of the attracted condition of the private-armature 246. The busy signaling circuit whereby a busy signal may be transmitted to the calling subscriber, whenhe calls a busy line, is completed whenever the connector is thus locked; which current also is provided by the ringer-generator 205. An energizing circuit for the ringer-relay 204 is established as; before, but over a slightly different circuit, since the side-switch is in this instance in second position. The energizing circuit for the ringer-relay 204 may be traced from ground G at the side-switch to the contact-point 203,.thence by conductor 242 and springs 239 and 211, and 'sErings 212 and 213 to the conductor 214, t ence to the ringer-relay 204 and to the circuit-interru ter 206 and to the batterylead 80 and t rough battery B to ground G. Each time that the ringer-relay is so energized that the springs 215 and 219 are asaese brought into contact a busy signaling current from the ringer-generator 205 of an interrupted character. corresponding to the interruption of the said ringer-relay, passes to the calling substation from said ringergcncrator through the springs 219 and 215, side-switeh-wiper 197, contact-point 247, private-springs 248 and 226 (since the privats-magnet is energized), conductor 229,

side-s\vitch-\vip:r 249, contact-point 228, condenser 201, rotary-tmink-conductor 145, sleeve 18.4 of the jack 72, spring 183 to the condenser 134 of the cord-circuit D, jacksleevc 111, rotary-trunk-conductor 100, condenser 58, springs 5 and 11 of the individual-switch A and through the primary winding of the induction-coil 54, springs 12 and 6 of the individual-switch A, to the condenser 57 of the repeater C, thence over the \'ertical-trunk-conductor 99, tip-spring 112, and through the tip supervisory relay 63 to ground G, thence to ground G at the ringer 205, through the condenser 250 to the said ringsr-generator 205. But if the called subscribers line is not busy and the calling subscriber has established connection in a manner described, the bell 223 is rung until the subscriber answers. The first move is to take the receiver 251 fr m oil the switch-hook 252, which switch-hook is raised by a spring not shown, and thereby breaks connection with the contact-point 253 and closes connection instead with the contact-point 254. As a result an energizing circuit is established through the rotary and vertical back-bridge-relays 225 and 255' at the connector. The energizing current for magnetizing said relays flows from ground G to the contact-point 203, sideswitch-wiper 202, thence over the conductor 209, rotary-back-bridge-relay springs 210 and 211, rotary-back-bridge-relay 225, con

'd'uctor 256, ringer-relay-springs 217 and 215, side-switch-wiper 197, contact-point 199, conductor 257,- rotary-line-wiper 176, rotary trunk conductor 194, rotary lineconductor -224, primary winding 258 of the induction-coil 259, transmitter 260, contactpoint 254, switch-hook 252, vertical-lineconductor 221, vertical-normal-conductor 193, vertical-line-wiper 175, conductor 261,

contact-point 198, side-switch-wiper 196, ringer-relay-springs 216 and 218,conductor 262, vertical-back-bridge-relay 255, difierential-relay springs 263 and 264 to the battery-lead 80, and through the battery B toground G. The springs 210, 211 and 239 of the rotary-back-bridge-relay 225 are so adjusted that when the said relay is energized the said springs comeinto contact before the spring 211 leaves the spring 210. The object in this construction is to maintain the energizing circuit, just described, over the said relays 2 and 225 unbroken While a section. of the said circuit described is substituted by a new section-that is, the connection between the spring 211 and the ground G after the said relay 225 is energized is established by connection with the spring 239 instead of with the spring 210 and a new connection to ground is as follows: from the said spring 211 to the spring 239, thence over the conductor 242 to the contact-point 203 and to ground G As soon as the back-bridge-relay 255 is energized, as described, the energizing circuit for the ringer-relay 204 is destroyed at a polnt between the vertical-back-bridge-relay springs 213 and 212 over which former the said ringer-relay is directly connected. Also, the spring 186 which is normally connected with the non-grounded terminal of battery .13 through the spring 187 is shifted into connection with the grounded terminal of battery B through the spring 212. The effect of shifting these springs is to establish an energizing circuit through the back supervisory coil 66 at the cord-circuit D. The current is established from ground Gr to the rotary-back-bridge-relay,spring 239, thence through the spring 211 to the vertical backbridge relay spring 212 and through the spring 186 and through the winding 185 of the differential-relay 165 and the rotary-line-relay 181 to the rotarytrunk-conductor 145, thence to the sleeve 184 through the said relay 66, springs 265 and 266 to the conductor 123, thence to the tip spring 163 and to the vertical-trunkconductor 144, through the vertical-line-relay 160 and winding 164 of the difi'erentia-lrelay 165 to the batteryslead .80 and through battery B to ground G. When the rotaryback-bridge-relay 225 is energized the spring 210 is disconnected from the spring 211 to cut oil all connection from the private-wiper 177 during the busy lock-out. The spring 240 in turn is provided so that the private-magnet 188 may be energized during the busy lock-out, and the springs 211 and 239 are provided as a means whereby the energizing circuit through the vertical and rotary back-bridge-relays 255 and 225 may be shifted as described. Returning to the supervisory relay 66 at the cord circuit D, through which an energizing current has been established, it maybe stated that when the said relay becomes energized it attracts its armature 117, whereby the circuit for lighting the lamp 114 is broken. The operator upon noticing that the said light is extinguished will understand that the called subscriber has answered. The said called subscriber having answered, in

the above manner, may thereby establish 1 himself in connection with the calling subscriber by means for conversing. The transmitters 56 and 260 being energized, as described, and the receivers 52 and 251 being connected in series with. the second ary windings 53 and 268, respectively, of the induction-coils 54 and. 259 the two subscribers may communicate with each other over the following main talking circuit, in a manner well understood by those skilled in the art: from the transmitter 56 at the substation #2050 to the vertical-line-conductor 78, individual-bank springs 12 and 6, condenser 57, trunkconductor 99, tip spring 112, condenser 133, .tip spring 163, vertical-trunk-conductor 144, condenser 200, ringer-relay-springs 218 and 216, side-switch-wiper 196, contact-point 198, vertical-line-Wiper 175, vertical-nor- 15 mal-conductor 193, vertical-line-conductor 221, switch-hook 252, contact-point 254, transmitter 260, primary-winding 258 of the induction coil 259, rotary line conductor 224, rotary-normal-conductor 194, ,rotaryline-wiper 176, contact-point 199, sideswitch-wiper 197, ringer-relay-springs 215 and 217, condenser 201, rota1*y-trunkcon-' ductor 145, sleeve 184, condenser 134, sleeve 111, rotary-trunk-conductor 100, condenser 58, individual-switch springs 5 and 11, 1'0- tary-line-conductor 79, primary winding 55 of the induction-coil 54 and back again to -the transmitter 56. After the subscribers have communicated, if the subscriber at the substation #2050 then restores his receiver to the switch-hook he thereby destroys the energizing circuit through his transmitter 56 and also through the relays 5.9 and 60 of the repeater C, and as a result said relays 59 and 60 are deenergized. When the linerelay 60" deenergizes, the springs 95 and 97 separate and the vertical-back-bridge-relay 61 denergizes as a result, but the construc- -tion is such that the line-relay-springs 89 4 0 and 90 of the vertical-line-relay 59 come into contact before the springs 91 and 105 separate. Closure of contact between said springs 89 and 90 While the springs 91 and 105 are in contact establishes a circuit through the release-magnet 2 of the individual-switch A. The current for energiz- 'ing said magnet flows from ground Gr through the springs 105 and 91 and through the springs 89 and 90, individual-bank springs 7 and 9 to the release-magnet 2, thence to the battery-lead 80 and through battery B to ground G. When the releasemagnet 2 attracts its armature 16 the catch 20 is raised above the abutment 21 of the plunger arm 14, whereby the said catch is carried. into position to engage the plunger.

arm 14 by the spring 269 when the release-' magnet deenergizes. The said release-magnet 2 deenergizes as soon as the relay 61 permits the springs 91 and 105 to separate, as described, at which time the spring 17 restores the release-armature 16 and causes the plunger-arm 14 to move the plunger 13 from the b ank jack which the latter engages, and into normal position against the at the connector private-banks is removed.

It will be evident that when the cut-off-relay 4 is restored the ground terminal G is reconnected with the vertical-line-conductor 78, and the'trip-magnet 3 is reconnected with the rotary-line-conductor 79. When the rotary-line-relay 60 of the repeater C permits the springs 95 and 97 to separate not only is the relay 61 deenergized, as described, but the supervisory relay 63 is denergized also.

Upon such denergization said relay 63 permits the armature 121 to engage the contact 122 and at once the supervisory lamp 120 flashes up. The energizing circuit for said lamp is from ground G through the armature 121 and contact-point 122 to the lamp 120, thence to the'contact-point 270 and armature 113 to the non-grounded terminal of battery B. The operator at the cord-circuit .1) upon seeing the light will understand that the calling subscriber has disconnected. The called subscriber upon restoring his receiver destroys the energizing circuit through the vertical and rotary-back-bridge-relays 255 and 225 previously described. When the said back-bridge-relays deenergize they, of course,restore the springs they control to normal positiomso that the vertical-back-bridgerelay 255 restores the spring 186 to connection with the non-grounded terminal of battery B, at the same time destroying the connection between said spring and the ground terminal of said battery. As a result the 11 energizing circuit through the vertical and rotary line-relays 160 and 181 and through the back supervisory relay 66 at the cordcircuit D is broken and said relays return to normal condition. The armature 117 of 11 the supervisory relay 66 upon being released engages the contact-point 118 and a circuit is established through the back su ervisory lamp 114 for lighting said lamp. e opera.

tor will, therefore, receive the signal that the called subscriber has disconnected also. She will then withdraw her plug from the jack with the following result. The energizing circuit through the line-cut-off-relay 70 and through the supervisor relay 64 is de- 1 stroyed. The latter relay tien permits the armature 113 to leave the contact-points 27 0 and 119, whereby the current for the lamps and 114 is cut oil and the said lamps are thus retired or put out. When the cut-otf- 15 relay dee'nergizes, the armatures 102 and 103 then leave the contact-points 271 and 272 and return to normal engagement With the contact-points 101 and 104, respectively. The operator then Withdraws the other plug from the jack 72 and thereby permits the springs 138 and 139 to separate. The energizing current through the quick-acting relay 74 and through the lamps 140 and 141 is destroyed, causing the said lamps to go out, and relay 74 is then denergized. As a result of the deenergization of said relay 74 the armatures 146 and 148 return to normal engagement with the contact-points 152 and 153, respectively, and the armature 147 leaves the contact-point 149. As soon as said armature 147 and contact 149 separate theenergizing'current for the slow-acting relay 75 is cut off, but before the armatures 150 and 151 leave the contact-points 273 and 274, with which said armatures engage when the relay 75 is energized, the armatures 146 and 148 engage the contacts 152 and 153, as described. As a result electric impulses are sent simultaneously to the vertical and retary trunk-conductors 144 and from the groundterminal G". In the former conductor the impulsepasses from ground G to the contact-point 273, thence through the are mature to the contact-point 152, armature 146 and to the conductor 144. In the rotary-line-conductor 145 the impulse passes i'romground G to the contact-point 274 through the armature 151, contact-point 153 and armature 148 to the said conductor 145. The effect of simultaneously grounding the conductors 144 and 145 that lead to the connector is Well known. The line-relays and 181 become energized simultaneously, as Well as the difierential-relay 165, the current from the conductor 144'passing through the vertical-line-relay 160 and Winding 164 of the difierential-relay 165 to the batterylead 80 and through battery B to ground G. item the rotary-line-conductor 145 the current passes through the rotary-linerelay 181, Winding of the difl'erential-relay 185, vertical-backebridge-relay springs 1'86 and 187 to the batteryuead 80, and through battery B to ground G. Upon being energized simultaneously the line-relays 160 and 181 press the trunk-release-springs 275 and 27 8 into contact at the same time that the springs 264 and 277 of the difierentiahrelaiy 65 are retained in contact by said relay. The concurrence of operations of said line-relays and said diile'rential-relay, as described, sets up an energizing circuit through the connector release-magnet 278, and the current in said circuit flows from ground G through the springs 275 and 276 to the release-magnet 278, thence through the difierentiahrelay springs 277 and 264 to the battery-lead 8 0 and through battery B'to ground G. As soon as the release-magnet 278 attracts its TLZIL armature 27 9 the double-dog 280 is struck to the right of the pivot 281, whereby the locking dogs 282 and 283 are Withdrawn from the switch-shaft 174 and the side-switch K is restored to normal position, swinging about the pivots 285 in the Well-known manner. ,When the rotary locking-dog 283 leaves the longitudinal teeth 286 the coiled spring 287 at the top of the shaft 174 then returns the. shaft to normal rotary position, the movement continuing until the normalpost-arm 288 strikes the normal-post 289, at which time the shaft-support 290 finds the longitudinal-slot 291, thus permitting the shaft to fall of its own Weight to normal vertical position. ()f course, as soon as the private-Wiper 177 leaves the tenth contact of the second level of the private-bank 179 the energizing circuit for the cut-ofi-relay 231 of the individual-switch A is broken, w ereby the said relay restores the springs ii controls to normal condition, thus restoring the individual-switch A to the direct control of the subscriber #2120 to Whom said switch is allotted. Immediately after the impulses are sent to the trunk-conductors 14-4 and 145 by the operation of the quick-acting relay 74 the armatures 150 and 151 of the slowacting relay 75 Withdraw from the contactpoints 273 and 274, whereby the said impulses are cut ofl. As a result the energized connector relays are denergized and the release-magnet 27 8 is restored to normal condition, whereby the armature 279 resumes its normalposition. Therefore, as described, When the calling subscriber hangs up his receiver he. releases his individualswitch A, restores the energized relays of the repeater C, and causes the disconnect-lamp 120 to be lighted at the cord-circuit When the called subscriber hangs up subsequently he causes the disconnect-lamp 114 to flash up as described. When the oper ator notices thatboth subscribers have sent in the disconnect-signal she removes her plugs from the answering and calling jacks and by the latter operation causes releasing impulses to be sent to the automatic switching apparatus at the sub-central to which the subscriber #2120 belongs. The combined act of the calling and called subscribers and of the central operator restores the originally involved apparatus to normal condition.

in the case previously assumed, in which the calling subscriber finds the called line busy and receives a busy-signal as a result, the said subscriber, of course, restores his reieiver and Waits until the connection can be obtained. Upon restoring his receiver, I

give the usual si nal. The operator upon noticing that bot lamps 120 and 114 are lighted will withdraw her plugs from the jacks, thereby causing release impulses to be sent to the automatic switches as before, whereby the release-magnet 278 of the connector may be energized with well-known results. It will be noticed that'heretofore the use for the signal-relay 62 at the repeater C does not appear. Said relay in fact is nothing more than a trouble supervisory relay and only comes into use in the event of certain kinds of trouble. For instance, if

- for some cause the subscribers rotary-lineconductor 79 receives a momentary ground impulse in any manner the trip-magnet 3 will. be energized and the plunger 13 will drop into the bank and, if opposite, into the bank jack. H. As a result the springs 7 and 9 will be forced into contact and the said relay 62 will,'therefore, be energized, as before b current flowing, from ground Gr throug said springs and through the release-magnet 2 to the battery-lead 80. Of course, the springs 8 and 10 will also come into contact and the cut-ofi-relay 4 will be energized also, but this is of no significance. When the relay 62 pulls up a ground connection is established from ground Gr through the springs 98 and 97 to the rotarytrunk-conductor 100, so that the "line-signalrelay 71 will be pulled up and the line-lamp 109 will'be lighted. The operator will notice the signal and think, of course, that some subscriber is trying to call. However, on receiving no answer she will know that the line is in trouble and will insert the callingplug (1 instead of the answering plug (5 into the jack 110, and will then press the ringingkey 0 so that the springs 162 and 183. are forced onto the contact-points 292 and 293. Ringing current will then be projected from the generator 294 to the trunkconductors 99 and 100 and through the vertical-back-bridge-relay 61. The current will pass from the conductor'99 through the said relay 61 and through the rotary-line-relay springs 95 and 96 to the ground terminal G", thence to ground G and through the springs 105 and 106 of the relay 62 to the springs 98 and 97 of the rotary-line-relay 60, thence to the rotary-trunk-conductor 100, sleeve 111, calling plug sleeve to the spring 183, thence to the contact-point 293 to the generator 294.. The pulsations from the generator 294 will cause the relay 61 to be energized, which latter will then close a circuit from ground G through the springs 89. and 90 to the release-magnet 2, thence to the battery-lead 80 and through battery B to ground G. It is well known that when the release-magnet 2 becomes'energizcd and deenergized the individual-switch A is then restored to normal condition. Un being restored the individual-switch A will permit the springs 7 and 9 to separate and thereby cause the relay 62 to be again deenergized. If the rotary-line-conductor 79 instead of receiving one ground. impulse is grounded permanently, then as fast as the switch A is released by the operator it will again energize and the line-signal-lamp 109 will continue to burn. She will then report the matter to the switchboard attendant who will look further into the trouble.

Referring to Fig. 4, the following should be borne in mind. When any subscriber calls the subscriber #2120 the connection is established directly between the connector and the called line by means of the normalconductors 193 and 194; but when the subscriber #2120 proceeds to make a call, and upon operating his individual-switch A he connects the bank jack springs 295 and 296 with the springs 297 and 298, respectively, or other similar springs, which latter springs lead to a repeater similar to the repeater C. This is plainly indicated in Fig. 1. For example: When the subscriber #2050 calls the subscriber #2120 he comes in through one of the .repeaters 0 among which isiincluded the repeater C and over .the cable 299 which comprises the trunkconductors 99 and 100 at the trunking operators board L which contains the cordcircuit D, thence through the plugs e and (Z and over the cable 300 which comprises the trunk-conductors 144 and 145 to the connectors M among which is included the connector E, thence to the substation #2120. But when. the subscriber #2120 calls he comes in and operates one of the individualswitches N'among which: is included the individual-switch A and uses one of the repeaters f among which will be found a repeater with which the springs 297 and 298 of the individual-switch A are connected. If the additional sub-oentrals are too many to be taken care of by one'trunkingoperator or a combination of" trunking operators in one board another board 0 may be added, said board being a duplicate, of course, of the board L. In that case multiple jacks P will be added, so that the operator at the board L will be able to connect any of the subscribers thereof with the subscribers of 'the twenty-five hundreds and twenty-six hundreds sub-oentrals, as indicated, and so that the operator at the board Q may connect the subscribers thereof with the subscribers of the twenty and twentyone hundreds sub-centrals. llf any of the subscribers allotted to the sub-centrals desire connection-with any of the subscribers.

belonging to the manual board Q, connection would then be established through the messes the key 0 and signal the Subscriber desired. Assuming that the jack g, shown in Figs. 1 and 3, is the ack that is allotted to the desired line, the plug (1 is inserted therein. The operator then depresses the key- 301 and locks the key in the depressed condition until she is ready to destroy the connection. Upon depressing said key the bridge-cut-oifrelay 302 allotted to the line-jack h is energized, which latter then, in the usual and well-known manner, attracts the armatures 303 and 304 for well-known purposes. The current for energizing said relay 302 flows from ground Gr through the coil 302 to the jack sleeve 305, thence to the sleeve of the plug a, spring 306 of the key 301, contactpoint 307 and impedance-coil 136 to the battery B, thence through said battery to ground G. The operator then presses the ringing-key c and sends current from the ringer-generator 294 through the springs 162 and 183 and through the plug d to the called subscribers station. When said subscriber answers he removes his receiver from the switch-hook, thereby disconnecting the ringer from across the circuit and substituting the transmitter and primary winding of the induction-coil in series with the line. As a result the supervisory relay 65 is energized by a flow of current through the following circuit. From the ground terminal G of battery B through the said relay 65, thence through the contact-point 308, spring 309 of the key 301 to the tip of the plug 03, thence through the transmitter and primary winding of the called subscribers telephone and back again to the sleeve of the plug d, through the springs 306 and 307 of the key 301, through the im-' pedance-coil 136 to the battery B and through said battery to ground G. Said relay 65 upon attractin its armature 115 breaks the energizing circuit for the back supervisory lamp 114 and when said lamp goes out the operator understands that the called subscriber has answered. When the connectedsubscribers are through talking and when they both restore their receivers to their switch-hooks the front and back supervisory lamps are connected up as previously described, the calling subscriber at the same time releasing his individualswitch and restoring his repeater C. The operator then withdraws the plugs from the jacks into which they have been inserted. If one of the manual subscribers connected with the board Q desires to connect with one of the sub-central subscribers he removes his receiver from his hook and thereby, in a manner well known to those skilled in the art, operates his line signal. The operator upon answering will ascertain the number of the subscriber desired. She will then press an order-key J to signal the proper trunking operator by causing the order.

lamp 76 to flash up. It is assumed that the manual subscriber has called for the subscriber #2120. The operator will at once know that. said called subscribers line is controlled by the trunking operator at the board L, and will operate the proper button J. lVhen the button J is pressed the springs 3ll-gan d 312 come into contact and the current is-established through the lamp 76 that flows from ground G through the lamp 76, springs 313 and 314, conductor 315,

i-"springs 311 and 312 to battery. B, thence through said battery to ground- Gr. The operator will press the key 316 and thereby throw her talking set into connection with the talking set S of the operator giving the The circuit connecting the two operators sets-is as'follows: From'the receiver 129 to the. condenser 132, thence through the springs 317 and 318, conductor 319, springs 320 and 321 to the talking set S back to the springs 322 and323, conductor 324 to the springs 325 and326 to the secondary winding 130 of the induction-coil 131, and back to the receiver 129. When the operator at the board L answers the operator at the board Q will report to her that subscriber #1050, for example, wants to connect with the subscriber #2120. The operator at the board L will then release the button 316 and the other operator will release the key J. Furthermore,'the operator at the board L will insert her answering plug 6 into the multiple jack R of the sub-- scriber #1050, and with the calling plug d will call up the desired subscriber #2120, in a manner that has been previously described, and thus establish the desired connection. Evidently, when the answering plug 6 is inserted into the multiple jack of the calling subscriber the supervisory relays 63 and 64 will be energized or pulled up simultaneously, since the calling subscriber s receiver is oil the hook. The back supervisory lamp 114, of course, will flash up and stay thus lighted until the subscribed #2120 answers, as before described. As long as both subscribers are connected the lamps 120 and 114 will not be lighted, but when they both han up their receivers the-said lamp will brig ten up and signal the operator that the line is out of use. She will then withdraw the plugs from their jacks with the usual and well-known result.

ll thus provide an improved telephone system comprising numerous new features as set forth. I provide means by which a manual system that has reached a reasonable limit may be still further enlarged. I provide trunking boards for said manual exchange in which trunk-line terminate that connect sub-centrals with the main-central and means whereby subscribers in these subcentrals may communicate with each other and with the subscribers of the main manual exchange and vice versa. I provide an improved cord-circuit for the trunking boards that facilitates the establishment of any of the aforesaid connections, and with apparatus for working the automatic switches that must be operated in establishing a connection. I provide separate means also in connection with the outgoing trunk-lines whereby the automatic switches may be antomatically released without any special effort on the part of the operator. I also provide a highly eflicient repeater for the purpose set forth. I provide means at the trunking boards whereby if one operator at one board occupies one of the outgoing 1 trunks a signal is established at all other multiple boards to notify all other operators that said trunk is busy, as clearly illustrated.

The resistance of the various coils in this system may be varied, but good results are obtained when they are wound as follows: coil 62, 4000 ohms; coil 4, 1800 ohms; coil 71, 200 ohms; coils 24, 61, 70, 74, 7 5 and 204, 500 ohms each; coils 59, 60 and 188, 350 ohms each; coils 2, 3, 26, 191, 168 and 278, 60 ohms each; coils 63, 64, 65, 66 and 136, 100 ohms each; coils 160 and 181, 150 ohms each; coils 225 and 255, 375 ohms each; windings of the difierential-relay 25, 500 ohms each; windings 164 and 185 of the difierential-relay 165, 350 ohms each. The battery may be of Volts.

With my improved arrangement it will be seen that I- make it possible for a manual board operator to receive calls through automatic trunk-selecting switching machinery, and to then establish connection with the called subscribers line either manually or semi-automatically, according to whether the called subscribers line terminates directly at her board or in the multiple-jacks of the connecter-banks at a sub-central station. Thus, if the connection with the called subscribers line must be made through the medium of a connector, it is evident that the number-impulses for operating the connector are transmitted by the switchboard operator. Thus, in any case all a calling subscriber does is to simply take down his receiver and give his order in the usual manner. The taking down, of his receiver constitutes the expedient by which he automatically operates his individual-switch to obtain trunk-line connection with the main or central station, providing, of course,

thathis line terminates at a sub-central station. Calling subscribers whose lines termi- .nate directly in answering-jacks on the manual boards will make their calls in the are concerned, but in such case there is, of course, no automatic trunk-selecting operation to obtain connection with the switchboard operator. The calling subscriber recurrent supply B. Thus, the common battery is used for feeding talking current through the repeater-relays and through the individual-switch to the calling line, and through the connector-relays and the connector-switch to thecalled line. The battery is bridged across the cord-circuit, but the circuits for charging the subscribers microphone transmitters do not include any portion of the cord-circuit.

With the individual-switch mechanism shown and described, it will be seen that each calling subscriber gets connection with the first idle trunk-line next in order after the trunk-line last put in use. For example, if the fifth trunk-line was the one last used by the calling subscriber, the subscriber who 'makes the next call will then obtain connection with the sixth trunk-line. In each case therefore, a calling subscriber takes a pie-selected trunk-line, and at the same time automatically selects the next idle trunkline for use by the subscriber making the next call. In other words, a subscriber does not select his own trunk-line, but simply takes the one already selected for him, and

in each case the calling subscriber merely takes the trunk-line ready and waiting for him andselects another for the next calling subscriber.

What I claim as my invention is 1. A telephone exchange system comprising a repeater, 'a' calling subscribers line, a subscribers telephone, a switch individual to said line and controllable from the subscribers telephone, a release-circuit for conducting current to restore the said individual-sw1tch, provided with a normally-closed switch-point, the said switch adapted for connectingthe subscribers line with the repeater and said repeater provided with a relay for controlling said switch-point in the release-circuit, said relay being connected to supply talking current to said calling line during conversation.

. 2. A telephone exchange system comprismg a calling subscribers line, a subscribers120 to trouble on the line and operate said line signal.

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