US1402905A - Telephone system - Google Patents

Description

F. M. StOUGH. TELEPHONE SYSTEM. APPLICATION FILED ocr. 18, 1913.

1,4029%, Pa tented Jan. 10,1922.

2 SHEETS-SHEET I.

IN VENTOR'.

W 23 I v FRANK M..SLOUGH M his ATT F. M. SLOUGH. TELEPHONE SYSTEM.

APPLICATION FILED OCT, 18, I913.

2 SHEETS-SHEET 2.

INVENTOR. W v FRANK M..SL.OUG/' l H/s' ATT v PatentedJ 111. 10, 1922.

starts" rarest @Fhlfitt.

i FRANK M. SLOUG-H OF ELYRIA, OHIO, ASSIGNOR, BY IvIESNE ASSIGNIVIENTS, TO

EwTROIdBERG-CARLSON TELEPHONE MFG. 00., OFROGHESTER, NEW YORK,

a conrona'rionor new roan.

'rnnnrnonn SYSTEM.

naoasos.

Specification of Letters Patent.

Patented Jan. 16*, 1922.

Ahplicationfilcfl Octoberl 1913: Serial 795323;

To all whom it may concernr I Be it known that I, FRA K M. SLoUGH, a citizen of the United States, residin Elyria, in the county of Lorain and tate of C hio have. invented certain new and useful Improvements in Telephone Systems; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same. 1 p f 1 My invention relates to telephone systems, and more especially to centralenergy sys; tems, in which a plurality of telephone lines lead from subscribers stations to a main station where apparatus is providedto connect such lines. together. In general, cord circuits are employed for connecting the lines together, the lines and the cords bemg provided with complementaryswitching apparatus to connect the ends'of the cords to the lines. After the termination of the conversation, the operator is automatically signalled of the tern'iination but frequently the disconnections are not made immediately, owing either to the inattention or the engagement of the operator. Durmg this period the lines are tied up to the cord, preventing their use for other connections. One of the objects of my invention is to provide means for releasing the lines from the cord employed in a conversation as soon as that conversation has terminated.

Another object is to provide means for accomplishing this firstnamed object and placing such means under the control of the switching apparatus employed for connecting the cord to a line.

Another object is to accomplishthe ab'bve' operators set to the cord Another object of my invention is to providexwhat has come to belmown as secret listening in connection with the automatic disconnecting apparatus, placing the secret listening controlling, apparatus under the control of the automatic disconnecting apparatus so as to: prevent the return of the after the disconnection is made. i i

Another object of my invention is to place the control of theringing current under the called subscriber, and especially to place both the automatic disconnecting apparatus and the ringing apparatus under the control of the callinsubscriber. Other 0 jects of my invention and the inventionitself willgbe better understood from a description of the particular embodiments of my invention illustrated in the'drawings.

"Fig. 2 is a diagram illustrating a more complicated form of circuit.

Referring now to the embodiments of my invention illustrated in the drawing and first tothat illustrated in Fig. 1, at'A I show a telephoneline. B indicates a substation connected on this 'line,the substation set in cluding a tra'nsmitterC, a receiver D and switch E controlled by the weight of the receiver. This form ofapparatus is Well known and needs no particularly description. The line is connected by conductors 1 and 2 to the main station F, Where it terminates in a switch element G, here shown as a jack, consisting ofa plurality of contacts 3, 4 and 5. The line apparatus of the line A is illustrated at Hand consists of a wellknown "form of line and cut-oil relays. This apparatus constitutes no part of my invention and any suitable form may be used. At the station F connecting apparatus is employed for connecting .the lines together,

here shown as 'a cord circuit, the talking strands of Whichare illustrated at I and J. In the 'formshown a third strand is employed and illustrated at K. The strands of the cord circuit terminate inswitching ele ments complementary to the switching elements employed on the line and illustrated, for example," at G on the calling line. In the form shown the switching elements on the cord circuit consist of plugs illustrated at L and M; The plug L consists of a plurality of contacts, shown at 6, 7, and '8 and in the plug M at 9, 10 and 11.

' Any suitable number of substations may be connected on any of the telephone lines. On the lineN, I have illustrated four substations at O, P, Q and R. Each'substation is provided with a talking and signaling set,"

such as illustrated diagrammatically atO. The line N leads to the central station'and terminates thereat in asuitable switching element, such as a jack S,-here*shown' as con-' receiver D is removed from the switch-hook,

whereupon theswitch E- isclosed and the lamp 15 operated in the usual manner. Seeing-the operatio'n'of the lamp 15, the opera tor at F inserts the plug L into the jack G,

connectingone end of the cordto thejcalling line. A circuit, will be. completed from 16- through 17 1 8- 19 20' relay 21'. 8 57- 22- to groundat 23, completing a circuit and energizing therelays 21. and 22.

The relay 22 cuts oil the line signal and line relay from the .line in the usual manner.

Belay 21 closes the switch 24 -25 and completes the circuit of the supervisory signaling lamp 26 through a conductor. 27 to a back contact28 of the tip supervisory relay 7 29. This relay will be energized, owing'to the fact that the substation circuit at B is closed, a circuit being traced from the battery 30- through the left hand end of the talkingstrands of the cord circuit and over the calling subscribers line, The operator operates the listening springs U, connecting her telephone set V to the talking r in order that the relays 31 and 32 may be de strands and communicates with the subscriber at B, learningthat it, is the subscriber at O that is wanted. After testing the line and assumin that it is found idle, the plug M is inserte' into the jack S, completing a circuit through the relays 31, 32 and 33. Relay 31 cuts off the line signal and line relay from the called line. The relay 32 attracts the armature 734,.closing a switch 3435 and completing the circuit of the supervisory lamp 36, whichburns as long .as

the called line is open. Relay 33 will not be energized at this time, sincethe relay 29 has been energized, completing a shunt 37 through the contacts 3839 around the winding of the relay 33.

I make therelay 33 of higher resistance,

energized when the winding of the relay 33 is connected in the circuit of the relay 31, and also in order that the batteryv potential on the sleeve 12 of the ack may be sufiibecause the higher resistance of'this relay connected unshunted ln'circult with winding 31 and sleeve 12 will reduce the current fiow through this circuit. Y

When the called subscriber responds, the

relay 40 will be energized from the battery cover the right hand end of the cordcircuit and the line of the called subscriber. relay will attract the armature 41, closing a This switch 41.42 and completing a second shunt 43 about the winding of the relay 33. The switch 41- 414 will be opened,.retiring the supervisory signal. 36. The conversation having continued to. a termination, the subscribershang up f their receivers, interrupting the continuity of the lines and deenergizing the relay 29 and 40, interrupting the shunts about the relay 33, whichis-ener gized over a circuit .60- 61- 33 62 32 63- 11- 12-.- .31 64. 'As stated, the introduction of the resistance 33 in this circuit reduced the current to such an extent that the relays 31 and 32 released their conditions. The relay 33, however, was

.armatures, restoring the called line. relay. and line and supervlsory slgnals to normal energized, attractingits armature 65, closing a switch 66 in a circuit including the electromagnets 67 and 68, wh1ch circuit'ls 67 70- 68- 71, and a second circuit through the disconnect lamp 72 to ground 73. The operation of this lamp indicates to the operator that the automatic disconnection has taken place. The relay 67 was energized over this circuit, attracting its armatures 53 and 56 and opening the switches52-53 and 5657, each shown in the talking strand of the cord circuit, and

disconnecting the plug M from the inter: mediate portion of the cord circuit. The relay 68 was also energized, attracting its armatures 51, 5 1 and 20, opening the switches 50'51 and and disconnecting the plug L from the intermediate portion of the cord circuit. The switch 19--2O was also opened in the circuit of the relay 21, whereupon the line relay and signaling apparatus of the calling line was restored to normal. In this condition both lines are released and may be used forother connections and the battery potential of the contact 12 of jack S being greatly reduced bytheinterposition of the high resistance relay 33 in its circuit, the line will not test busy. "Also, as the circuitof the corresponding contact 5 of the jack G is opened at 19-20 the calling line will also indicate a non-busy condition upon being called.

Assuming that the called subscriber at O Wise, the operators set iyon never responds and that the subscriber B for some reason, such as impatience, hangs up his receiver, under these circumstances the automatic disconnecting apparatus will be operated, since the shunt e8 will never have been closed about the relay 33, owing to the failure of the called subscriber to answer and tie shunt 37 completed will be interrupted when the calling lineis opened.

Referring now to Fig. 2, l have illustrated at a. a diil'ercntial relay controlling the connection of the operatorsset to the cord circuit and the disconnection of the same therefrom. This apparatus is pre viously known and is not a portion of my invention. ll hen the plug insertedinto the jack of the calling line, a circuit is completed through the winding 2') of the relay and the battery 0, energizing the niac net and attracting the arrnatures 100 and 101 and connecting the operators set Z to the cord circuit-x1 place the a under the control. or" the automaticdisconneet o; apparatus, for example, by -ilacinp; a suit-11 103 under control of relay 102, so that the switch 103 in the circuit of the winding 3) Will be interrupted when the automatic dis connecting apparatus is ooeratocl; other a e re; onnected to the calling line agsoon as he called subscriber hung up. At X l have illustrated sources of energy for supnlyinQ one. operate the suhstationsi apparatus. Such apparatus 13 connected to theline over suitable conductors, such as 106, 107 and'l08.

ing a switch 109-110 under centre relay 11L This is especiallya in systems employing automatic 1 cause when calling subscribe which he sometimes does Withofor the called subscriber to ZUISFFEE' niatic ringing current is automatically To moved from the line. This will be accomplished in the system illustrated in as follows:

W hen the relay 33 is eneroized in the Way described in Fig. l. a circ it will be completed as follows: 112l18-11i 115 11c- 117 11.1- 118* 102-; 119,, energizing the relays 111 and 102, disconnecting the plug '32 and g from the in'terniedjc' tion or" the cord circuit, disconnectn source 01" ringing current X from the p g at 109 and 110 and interrupting the cuit of the Winding 7) of the magnet (a 108-12O.

l do not WlSll to be limited to the details of the embodiments of my invention illustrated, these being shown simply for the purpose of describing the invention.

I claim 1.. In a telephone system the combination of a main station, a plurality of substations .7 Alt? 21. 34

telephone lines connecting the substations to the main station. and terminating in jacks at the main station, a cord circuit at the main station terminating in plugs adapted to be inserted in said jacks for connecting the lines together a low resistance relay associated with one of the lines, a high resistance relay associated with the cord circuit, a source of current, means including a pit and jack switch for connecting said relays i C1ICu1tWl l'1 said source fcurrent,

e when said -one system the combination ion and a rality oi sub nc lines for connecting the he inain station, a cord circuit tion torcoi ectingtelephone means controlled by the subautomatically isolating the s or? the cordcircuit from the ry apparatus in the 1 p- Alt; $3185.

corn circutc rolled by the called subscriber and means operative independently of said apparatus controll ng said interrupti means. i

u, in telephone system, the conioination 01 a 119,111 station and a plurality of subfor connecting the connecting teleler, supervisory signaling L ctedto the strands of the control ed by the called subscriber and s operative independently of said suyisory apparatus for automatically disconnecting he plugs of the cords "from the terniediate portion thereof W enthe subibers Whose substation sets have been connected to the cord have been restored to normal.

i one system the combination 1 S'illllcll and a plurality oi subons telephone lines for connecting the substations to the main station, a cord circuit the-main station for connecting telephone linestogether supervisory signaling apparatus connected, to the stranos of the i l controlled t e calling subscriber 1 means open" I "risory apparatus for automatically disthe plugs of the-cores from the thereof W en the subtion sets have been con been, restored to enendently of said 5. In a telephone system, the combination o-t-a main station and a plurality of substations, telephone lines connecting the subscriber for effectively eliminating said elec tromagnetic means from said circuit and means controlled by the called subscriber for effectively eliminating said means from said circuit, each of said eliminating means being inoperative t eliminate said electromagnetic means from said circuit when the talking bridge at the substations is interrupted.

6. In a telephone system, the combination of a main station, a plurality of substations, telephone lines connecting the substations to the main station, a cord circuit at the main station for connecting said lines together, means for automatically interrupting the talking strands of the cord circuit,

electromagnetic means controlling said interrupting means, a circuitfor said electromagnetic means, means controlled by the called subscriber for effectively eliminating rupted.

saidelectrom'agnetic means from said circuit, said eliminating means being inoperative to eliminate said electromagnetic means from said circuit when the talking bridge at the calling subscribers station is inter- 7. In a telephonesystem, the combination of a main station, a pluralityj'of sub-' stations, telephone lines connecting the substations to the main station, a cord circuit at the main station for connecting said lines together, means for automatically interrupting the talking strands of the cordcircuit, electromagnetic means controlling said interrupting means, a circuit for said electromagnetic means, means controlled by the calling subscriber for effectively eliminating said electromagnetic means from said circuit, said eliminating means being inoperative toeliminate said electromagnetic means from said circuit when the talking bridge at the called subscribers station is interrupted 8. In a telephone system, the combination of a main station, a plurality of substations, telephone lines connecting the substations to the main station terminating in switch elements at the main station, a cord circuit at the main station for connecting telephone lines together terminating in switch ele-.

1 ments adapted to co-operate with the switch 7 elements in which the subscribers lines terminate, means for disconnecting the switch elements of the cord from the intermediate portion of the .cord, a device controlling said means, a circuit for said device and means forefiectively eliminating said device from'said circuit controlled by a subscribers substation apparatus. 7

9. In a telephone system, the combination of a main station and a. plurality of substations, telephone lines connecting the sub stations to the main station, a cord circuit for connecting'said telephone lines together, means for automatically interrupting the talking strands oi the cord circuit, electromagnetic means controlling said interrupting means, a circuit for said electromagnetic means and a shunt about said electromagnetic means controlled by a subscriber.

10. In a telephone system, the combina- 'for connectin said tele hone linesto ether b c a means for automatically interrupting the talking strands or' the cord circuit, electro magnetic means controlling said interrupting means, a circuit for said electromagnetic means, a plurality 01' shunts about sa d electromagnetic means each under the control of the subscribers.

12. In a telephone system, the combination of a main station and a plurality of substations, telephone lines connecting the substations to the main station, a cord cir- 'cuit'at the main station for connecting the telephone lines together, supervisory'apparatus connected to the strands of the cord circuit controlled by a subscriber, means for interrupting the talking strands of the cord circuit, electromagnetic means controlling said interrupting means, a circuit for said electromagnetic means, a shunt about said electromagnetic means, and a switch including contacts in said shunt controlled by the supervisory apparatus,

13. In a telephone system, the combination of amain station and a plurality of substations, telephone lines connecting the sul stations to the main station, a cord circuit at'the main station for connecting telephone lines together, means for automatically interrupting the talking strands of the cord circuit when the subscriber whose talking apparatus has been connected to the cord circuit has disconnected his talking apparatus therefrom, a talking set at the main station and means controlled by said interrupting means controlling the connection of the operators set to the talking circuit.

14. In a telephone system, the combination oi a main station and a plurality of substations, telephone lines connecting the substations to the main station, a cord circuit at the main station for connecting telephone lines together, means tor automatically interrupting the talking strands of the cord circuitwhen the subscriber whose talking apparatus has been connected to the cord circuit has disconnected his talking apparatus therefrom, a talking set at the main station, and means for automatically connecting the operators set to the telephone line controlled by said interrupting means.

15. In a telephone system, the combination of a main station, a calling and a called line terminating at said station, a subscriber on each of said lines, a cord circuit having separate talking and operating strands at the main station, plug and jack switching means for connecting said talking and operating strands to each of the lines, supervisory means in the answering end of the cord, in cluding a supervisory relay, automatic means for opcratively disconnecting all of the strands of the cord from the calling line when the calling subscribers station apparatus is retired, said automatic disconnect means being initially controlled by the supervisory relay and subsequently maintained by switching means for connecting one of the strands of cord to the called line.

16. In a telephone system, the combination of a main station, a calling line termihating at the main station in a switchboard jack, a calling subscribers substation set upon the calling line, a called line terminating at the substation in a switchboard jack, a called substation set upon the called line, a cord circuit at the main station including separate talking and operating strands, plugs at the main station in which the cord circuit terminates and which are adapted to be inserted into the jacks of the calling and the called line to establish communication between the calling and the called subscriber over the lines and the talking strands of the cord circuit, relay mechanism at the main station having contacts in the talking and. operating strands associated with the calling line. supervisory means in the an swering end of the cord circuit including a supervisory relay, a circuit for the first named relay controlled by said supervisory relay, a third relay in the operating strand of the calling end of the cord also controlling the circuit oi said first named relay, a circuit for the third named relay localto the main station and including contacts of the jack of the called line and thecalling plug.

17, I a telephone system, the combination of a main station and a plurality of substations, telephone, lines leading from said substations to the main station, a cord circuit having separatetalking and operating strands at the main station for connecting two telephone lines together, co-operating switching means for connecting the cord circuit to the telephone lines, means for operatively disconnecting all of the strands leading to the answering switching means from the corresponding strands of the cord circuit, said means maintained under the sole control of the switchingmeans at the'other end of the cord and a disconnect signal operated at the time of disconnection, likewise maintained.

18. In a telephone exchange system, subscribers lines having switching terminals, operators connecting circuits having co-opcrating switching terminals, said opera-tors connecting circuits including two talking strands and a third strand, and means controlled by the subscribers through said circuits for disconnecting both talking strands from both subscribers and disconnecting said third strand from one of said subscribers without disconnecting it from the other. i y

19. In a telephone system, the combination of a main station, a plurality of substations, telephone lines for connecting the substations to the main station, a cord circuit at the main station for connecting telephone lines together, plug and ack switching means for connecting the cord circuit to the telephone lines, a source of current, a cut-off relay in a line circuit, a high resistance relay in the cord circuit, current conductors including a plug and ack connecting the high resistance relay and the cut-off relay in circuit with said source of current and means to prevent the energization of one of said relays while the other is energized.

:20. In a telephone system, the combination of a main station, aplurality of substations, telephone lines for connecting the substations. to the main station, a cord circuit at. the mainstation for connecting telephone lines together, plug and jack switching means for connecting the cord circuit to the telephone lines, a cut-off relay in the line circuit, a high resistance relay in the cord circuit in circuit With said cut-oil relay and means to prevent the actuation of one of said relays While the other is actuated.

21. In a telephonesystem, the combination of a main station, a plurality of substations, telephone lines for connecting the substations to the main station, a cord circuit at the main station for connecting telephone lines together, plug and jack switching means for connecting the cord circuit to the telephone lines, line signal apparatus normally connected to the line, a'cut-olf relay controlling said, line signal apparatus, a high resistance relay associated with the cordccircuit, means for supplying energy to said relays and subscriber controlled apparatus for causing thede-energization of the cut-off relay and the energization of the high resistance relay.

22. In a telephone system, the combination of a main station, a calling line leading to the main station, a called line leading to the main station, substation apparatus on said lines, a source of current associated with said system, a cord circuit at the main station having separate talking and operating strands, plug and jack switching means for connecting each end of the cord to a telephone line, apparatus for automatically disconnecting all of the talking strands of the cord circuit from one ofthe connected lines, means including a calling subscribers set controlling said automatic disconnecting ap- V paratus, said automatic interrupting apparatus being inoperative until the calling subscriber retires, and mechanism under the control of the plug and jack switching means associated with the other connected line for maintaining said automatic interrupting apparatus until the plug of the last mentioned plug and jack switching means is withdrawn from the corresponding jack.

In a telephone system, the combination of a main station, a calling and a called line terminating at said station, a subscriber on each of said lines, a cord circuit having separate talking and operating strands at the main station, plug and jack switching means for connecting said talking and operating strands to each of the lines, supervisory means in the answering end of the cord, including a supervisory relay, automatic means for operatively disconnecting all of the strands of the cord from the calling line when the calling subsoribers station apparatus is retired, said automatic disconnect means being initially controlled by the supervisory relay and subsequently maintained by switching means for connecting an operating strand of the cord to the called line;

'24-. A telephone system comprising subscribers lines having switching terminals, link conductors having co-operating switching terminals, line signals for said lines, cut-' cit relays for said line signals, a local circuit associated with each end of said link conductors, each local circuit including a cooperating pair of switching terminals, one of said cut-off relays and a source of current, and means controlled by one of the subscribers for decreasing the flow of current to a predetermined positive value in one of said local circuits to release one of said outoff relays, whereby the subscribers may regain contlOl'of their line signals.

25. A telephone exchange vsystem including telephone lines extending from substations to an exchange, a cord circuit to connect said substations and comprising separate talking and operating strand circuits individ ual to the respective cord circuit for calling andcalled lines, a disconnect signal circuit associated with said cord circuit during an established connection therewith and closed by the opening of said talking and operating strand circuits under the combined control of both calling and called substations.

26. In a telephone system comprising subscribers lines terminating at a central ohice, link conductors thereat having cooperating switching terminals, line signals for said lines, cut-cit relays for said line signals, a local circuit associated with each end of said link conductors, each including a co-operating pair of said switching ters minals, one of said cut-off relays, a source of current and another relay and apparatus controlled by the subscribers in the operation of their switch hooks for increasing and decreasing the flow of current through said local circuits, said cut-off relays restor ing the line signals to the control of the subscribers when said apparatus is operated to decrease the current in the local circuits.

27. A telephone system comprising subscribers lines terminating in. a central oflice, line signals thereat for said lines, link conductors at said oflice for interconnecting said lines, a pair of relay windings associated with the one end of said link conductors, one of which is normally short-circuited when said link conductors are associated with one of said lines, a cut-off relay for the line signal of the said line energized over a circuit including the non-shortcircuited winding of said pair of relay windings, and electromagnetic means controlled by the subscriber in the operation of his switch-hook for removing the short circuit of the short-circuited windingof said pair of relay windings for releasing said cut-off relay, whereby said subscriber may regain control of his line signal.

28. In a telephone system, the combinationoi a main station, a plurality of telephone lines leading thereto, a cord circuit including a third strand for connecting said telephone lines together, switching mechanism for connecting the cord to a line and electromagnetic means without the talking circuit for automatically disconnecting such switching mechanism from the cord circuit when a connected subscriber retired his substation talking set, said last named meanscontrolling the third strand of the cord.

29. A telephone exchange system, including telephone lines extending from sub-stations to an exchange, link connectors to connect said sub-stations and comprising separate talking and operating strand circuits individual to the respective link connectors for calling and called lines, means under the control of apparatus at the callingand called substations to open the talking and operating strand circuits of said link connectors connected to their lines, a high resistance circuit including the magnetic winding of a disconnect relay, and a disconnect signal operated by said relay when said link connector strand circuits of both calling and called sub-stations are so opened.

30. In a telephone system, a main station, a plurality of substations, telephone lines leading "from said main station to said substations, line signal apparatus associated with each of said telephone lines at the main station, a cut-off relay associated witheach line and adapted to remove said line signal apparatus from the telephone line, a cord circuit at the main station containing separate talking and operating strands, a plug and jack switch for associating the talking strands of the cord circuit with the talking strands of the calling line and for associating the cut-off relay of the line circuit with an operating strand of the cord circuit, a plug and jack switch for associating the talking strands oi the cord circuit with the talking strands oi the called line circuit and also to associate the cut-cit relay of the called line with an operating strand of the cord circuit, a relay in the cord circuit under the control or one of the connected substations, a disconnect relay at each end of the cord circuit adapted to operatively disconnect each of the connected line circuits and each of the cutoff relays from the talking strands and operating strands of the'cord circuit, and a high resistance relay in the operating strand leading to one of the plug and jack switches, said high resistance relay being operated when the cut-off relay con nected in the same operating strand is operatively disconnected, said high resistance relay controlling a disconnect signal.

31. A telephone system, comprising subscribers lines having switching terminals, link conductors thereat having co-operating switching terminals, line signals for said lines, cut-oil relays for said line signals, an operators telephone associated with said link conductors, a relay for connecting said operators telephone to said link conductors, a local circuit associated with each. end of said link conductors, each local circuit ineluding a co-operating pair of switching terminals, one of said cut-oft relays, a source of current and a. winding of said operators connecting relay and apparatus controlled by the subscribers in the operation of their switch-hooks :tor increasing the resistance of said local circuit associated with one end of said link conductors, said decreased flow of current permitting the release of said cutoff relays to restore to the Subscribers the control of said line signals and simultaneously disassociating said operators connecting relay from said cut-oil relays.

32. A telephone system comprising sublink conductors and means controlled by the operation of. a subscribers switch-hook for removing the short circuit from said high resistance relay winding to release said outoff relay and said second relay, whereby the subscriber may regain control of his line signal and the operators set is prevented from being connected by said second relay to the link conductors.

33. A telephone exchange system including telephone lines extending from substations to an exchange, link conductors to con nect said substations and comprising separate talking and operating strand circuits individual to the respective link conductors for calling and called lines, a disconnect signal. circuit associated with said link conductors during an established connection therewith and closed by the opening of said talking and operating strand circuits under the combined control of both calling and called substations.

84. A telephone exchangesystem, including telephone lines extending from substations to an exchange, link conductors to connect said substations andcomprising sepa= rate talking and operating strand circuits individual to the respective link conductors for calling and called lines, means under the control of the calling and called substations to open the talking and operating strand circuits of said link conductors connected to their lines, a disconnect signal circuit associated with said link conductors during an established connection therewith, said disconnect circuit including a high resistance and closed when said line conductor strand circuits of both calling and called lines are opened, and relays in series with said circuit rendered inoperative by said resistance when said link conductor strand circuits of both calling and called lines are so opened.

35. A telephone exchange system, including telephone lines extending from substations to an exchange, link conductors to connect said substations and comprising sepa rate talking and operating strand circuits individual to the respective link conductors 7 to their lines a disconnect si nal circuit asa g sociated with said link conductors during an established connection therewith, said disconnectcircuit including a high resistance and closed when said link conductor strand circuits of both calling and called lines are opened, and the winding of a ringing relay individual to each link conductor and the winding of a cut-out relay individual to each called line, said relays being rendered inoperative by said resistance when said link conductor strand circuits of both calling and called lines are so opened.

36. A telephone exchange system, including telephone lines extending from substations to an exchange, link conductors to connect said substations and comprising separate talking and operating strand circuits individual to the respective link conductors for calling and called lines, means'under the control of apparatus at the calling anl called substations to open the talking and operating strand circuits of link conductors connected to their lines, a disconnect signal circuit associated with said link conductors during an established connection therewith, said disconnect circuit includinga high resistance and closed when said link conductor strand circuits of both calling and called lines are opened, a disconnect relay, the winding of a ringing relay individual to each link conductor and the winding of a cut-out relay individual to each called line,

' said ringing and cut-out relays being rendered inoperative by said resistance when said link conductor strand circuits of both calling and called lines are so opened, and said disconnect relay being rendered operative when said link conductor strand circuits of both calling and called lines are so opened.

37. In a telephone exchange system, including telephone lines extending from substations to an exchange, a cord circuit to connect said substations and comprising separate talking and operating strand circuits individual to said cord circuit for calling and called lines, means under the control of the calling and called substations to open the talking and operating strand circuits of said cord circuit connected to their lines, a disconnect circuit associated with said cord circuit during an established connection therewith, said disconnect circuit including a high resistance and closed when said line conductor strand circuits of both calling and called lines are opened and relays in series with said circuit rendered inoperative by said resistance when said cord strand circuits of both calling and called lines are so opened.

88. A telephone system comprising a tele-' phone line terminating at a central ofiice, a line signal for the line, a link circuit, a cut-off relay associated with the line for controlling the line signal and actuated upon connection of the link circuit with the line, a resistance coil, and means controlled over the telephone line for including'the rein series with the relays, the inclusion of the coil serving to disable the relay asso ciated with the line. 7

40. In a telephone exchange system, the combination of a called subscribers line having an associated jack and relay, of a cord circuit for interconnecting with said jack, a relay and resistance coil associated with said cord circuit, the windings of the relays being adapted to be placed in series when the cord circuit interconnects with said jack, and means controlled by the called subscriber for including the winding of the resistance coil in series with said relays, the inclusion of said coil serving to disable the relay associated with the line.

41. A telephone system comprising telephone line terminating at a central office, a line signal for the line, a link circuit, a cutoii relay associated with the line for controlling the line signal and actuated upon connection of the link circuit with the line, a supervisory relay in the link circuit responsive to the opening of the telephone line, and a resistance coil included in circuit with the cut-oit relay upon the response of the supervisory relay to cause the release of the cut-ott relay.

In witness whereof, I have affixed my signature in the presence of two witnesses this 15th day of October, 1913.

FRANK M. SLOUGH.

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