US684289A - Signal for telephone switching systems. - Google Patents

Description

No.' 684,289. Patented oct. 8, mol.

, F. R. McBEnTY'.

slaan ron TELEPHonE swncmue svsrems.

(Applica-tion Bled In. 28, 1899.)

(No Modal.)

|nve nto r: '35m/rf, QR 88e@ his A117? Witnesses' 5 nois, have invented a certain new and use- In a former patent, No. 567,404, dated Sep- UNITED 4STATES PATENT OFFICE.

FRANK R. MCBERTY, OF EVANSTON, ILLINOIS, ASSIGNOR TO THEWESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS.

. SIGNAL Fon TELEPHONE swli-CHING SYSTEMS. Y

'sPEcmIcA'rIoN forming pare of Letters Patent No. e4,2s9, dated october e, 1901.`

Application led .Taimry 26. 1899. Serial No. 703,462. (No model.)

To a/ ZZ whom, at may cor'wen: e fone for. each line'liefore each distributing Be it known that I, FRANK R. MCBERTY, a operator. It is to this feature of the call-discitizen ofthe United States, residingat Evans? tributing system that the present invention ton, in the county of. Cook and State of Illi applies. 5S

ful Improvement in Signals for Telephone tember 8, 1896,*(Case 34,) I have described Switching Systems, (Case No. 58,) of which f and claimed a device by which the switching the followingis'a full, clem-,.eoncise, and ex operators act of connecting her telephone act description. with a trunk -line in position to receive oi-, 6o lo My invention concerns the type of switchders from a calling subscriber automatically ing system for telephone-exchanges known as sets the signal associated with the trunk-line the call-distributing system, and has for before the distributing operator to indicate its object to prevent interference between di'f-y that the switching operator is ready to referent call-distributing operators. ceive connections. The even distributionof 65 l5 The system referred to comprises an anwork among the different switching operators nunciator or distributing board wherein are is thus facilitated'by the device for continuloeated call-indicating instruments for all the ously informing the distributing operator of lines entering the central oce and switchthe busy or idle condition of the dilferent boards, preferably of the multiple type, in switching operators. -v zo' each of which are spring-.jacks or terminals The present invention consists in the comof all the lines and trunk or transfer lines bination, 'with this signaling mechanism for from the annunciator-board to each ofthev signalizing to the distributing operator the multiple boards, with means for connecting idle condition of a switchingoperator, of mulone terminal of the trunk-line with any line tiple terminals for the trunkf-line before dif- 75 z5 of the annunciator-board and the other terferent operators, a signal associated with minal of the same trunk-line with any line each of the terminals, and mechanism wherein a section of the multipleboard. A call by the act of connecting either trunk-line from a station is observed at the annunciawith any subscribers line performed bya distor-board, and thereupon the line is extended -tributing operator indicates the use of the 8o 3o by the operator at the annunciator-board trunk-line to the otherdistribnting operators through `the agency of a trunk-line to any opand prevents them from using the line,where erator at the multiple board, who may hapbyin the event of unintentional disregard of pen to be free to make new connections, the the signals or simultaneous action on the part object of that processbeing to 'attain even of distributing operators a signal shall be 85 35 distribution of the work of switching lines displayed before one of the operators, the obinto connection among the dierent operators ject being to prevent two distributing operav at the multiple board. There will of course tors from connecting a single trunk-line sibe as many distributing operators at the anmultaneously with the lines of two calling nunciator-board as may be necessary to transsubscribers. 9o 4o fer the calls to the operators at the multiple The invention is represented diagrammatboards and as many of these latter operators ically in the attached drawing in association as may be necessary to complete and superwith a switchboard provided with means for A vise the connections. automatically operating signals in the switch- When there are several distributing operaboard. Two lines are shown, each connected 95 45'tors, it is essential to the eiicent operation with an instrument controlling a signal in of the system that each of the distributing the annunciator-board, with a socket in the operators have access to trunk-lines to all annunciator-board, and withasocketin each the switching operators. To this end it is deof the three sections of the multiple switchsirable that trunk or transferlines to each of board.` A trunk-line is shown extending roo 5o the switching operators shall appear in the between the annunciator-board and one of multiple terminals at thc distributing-board, the sections of the multiple lboard, the trunlc.

lines appearing intbrice-multipled terminais in the annunciator-board for the use of three distributing operators. he drawing represents also the terminal plugs of another trunk-line multiplcd before the same three distributing operators and extending to adiierent multiple section, together with the signal-lamp of this truuk-line at a multiple section, the ci-rcuits of this trunk-line having been omitted to avoid complication of the drawing.

Each substation is provided with the usual telephones and signaling apparatus, the appliances and circuits being arranged toclose theline-circuit as to continuous currents only during the use of the station-telephone. The line conductors from' cach station are connected w'th the line-contacts of a terminal in the annunciator-board A and in other sockets a', a2, and a in the sections A', A2, and As in the 1n ultiple switchboard. Line conductors are extended through the windings of avrelay l1, which controls a local circuit includng a secondary lamp-signal c, associated with the corresponding line-socket in the annunciator-board. This local vcircuit is made up of conductors 3 and 4, the former of which is a ground branch including the resistance-coil and the latter of which is a conductor leading to the free pole of a grounded source d of current and including the lamp c. The lever of the relay is connccted also by a wire 5 with the thimbles of vall terminal sockets (1,0', a2, and a.3 of the line.

The line-circuits, spring-jacks, and line-signals of two telephone-lines are shown.

A number ot tru nk or transfer lines G 7 extend between the aun unciator-board and each section of the multiple switchboard. Each trunk-line terminates .in a plug e at the multiple switchboard and is branched to three plugsf", and f2 at the annunciator-board. These plugs are designed for the use of three different distributing operators, giving each of them access to the switching operator havin'g charge of the corresponding trunk-line. There will of course be a sufficient number ofdistributing operators to distribute all calls received at the annunciator-board to switching operators at the 1n ultiple sections. A distributing operator can thus distribute as many as seven thousand calls pei-day. Hence in anexchange the number ofdistributing operators required at the annunciator-board will be determined by dividing the total number of calls received at the ann'unciatorboard in a day by seven thousand.- Inasmuch as au even distribution of the calls among the switching operators necessitates her receiving calls from each off the distributing operators, the trunk-lines to each of the switching operatorsshould appear before each of the distributing operators. Hence the equipment of plugs for each trunk-line represented inthe drawing is su'ticient for an exchange having something over twenty thousand calls per day.

To transact such an amount of' vbusiness as `this would' require more switching operators than represented in the drawing, but this would merely involve a larger number of trunk-lines. A switching operator can answer three thonsan d calls and make the required connections per day. Hence sevensections of multiple switchboard will be required and seven groups of trunklines extending froln the multiple switchboards to the an nunciator-board, each trunkline appearingin three terminals at the niultiple switchboard.

The tru 11k-line is provided at the switchingoperators station with the usual calling-key (not shown). for connecting a generator of calling-current with the terminals of plug e and with a listening-key h for connecting the operators telephone with the trunk-line.

I will now describe the local circuits involved in signaling between operators al: the

different boards and between subscribers and operators.

Each plug is provided with a contact-piece 'L' in addition toits line-contacts, designed to register with the thimblesor contact-rings k of the spring-jacks. The contact-piece i of plug e forms the terminal of a wire 8, leading to the free pole of battery d. This conductor 8 traverses an incandescent lamp Z, which is associated with the plug e in the switchboard and constitutes a supervisory signal. The mode of operation between the line-signal c and the supervisory signal Z iswell known to those familiar with existing telephone-switchboards,but may be briefly described. The current from battery CZ through wires 3 4 of a local circuit, which may become closed at a line-relay, is suicient tolight one of the signal-lamps used in the system; but whenever conductor 8 becomes connected with wire 4 through the agency of contact-pieces i and 1c ofa pluginserted in a spring-jack lamps c and l are brought into parallel, both being in series with the resistance-coil in wire 3, under ,which condition neither lamp receives suft- `cient current to light it.

If during the existence of these conditions the line-relay become inei t and separate the-conductor 3 from the wire 4, the full current from battery d will be diverted through wires 8 and 3, whereby Ihesupervisory lamp l will become lighted.

A signal-lamp is associated with each of the plugs f, f', and f2, which form the terminals ofi the trunk-line at the annunciatorboard. These lamps are designated m, m', and lm2, respectively. These lamp-signals are included in a local circuit associated with the corresponding trunk-line whose continuity is normally controlled by switch-contacts on 'the lopenators listening-key, these contacts being adapted to close the local cir- `cuit to livht the lam s m, m and 'm2 when e p a the operator connects her telephone with the trunk-line. The circuit is also controlled by plug-seat switches of plugs f, f', andfz. The switch-levers of they listening-key h are pro- IIO vided with an auxiliary switch-contact h', which plays between two contact-pieces h2 and h5, being thrust against the contact h2 when the key is putin position to connect the operators telephone in a bridge of the trunkline 6 7. Contact-piece h2 is connected by wire 9 with the free pole of battery d. The lever h is connected by wire 10 with the switch-lever of a plu g-seat switch n of plug f. The normal resting contact of this switch is connected with the switch-lever of a similar switch n of plugf by wire 11. The resting contact of the last-mentioned switch is connected with the lever of switch n2 of plug f2 by wire 12. The resting contact of the switch fn,2 is connected to earth through wire 13, which includes serially the signal-lamps m2 Im m, associated with plugs f2 f f. Thus while the listening-key is in position to connect the operators telephone with the trunkcircuit and plugs f, j", and f2 are in their resting-sockets a circuit will be complete from battery d through wires 9, 10, 1l, 12, and 13 to light the lamps m, m', and m2. The sleeve 1l of each' of the plugs f, f', and]c2 is connected with the wire extending from wire 10 to the plug-seat switch of the same plug- Aso namely, the sleeve of plug f is connected with wire 10, the sleeve of plug f with wire' 11, and the sleeve of plug f2 with wire 12.

The alternate contact-piece h3 of the lever h on the listening-key forms the terminal of a conductor 14, which is connected with wire 9, and thus is completed to the free pole of battery d, which includes a supervisory signal-lamp p, also associated with plug e in the switchboard, and which is controlled by a plug-seat switch ofplug e.

Clearing-'out lamps q, q, and q2 are associated with the plugsf, f', and frespectively, in the switchboard. These lamps are located in multiple earth branches of the conduct-or 16, which terminates in a contact-piece of a plug-seat switch of the plug e. Each of the earth branches is controlled by switch-contacts of the plug-seat switch of the plug n, n", or n2, with which the lamp q, q', or q2 in question is associated, these switch-contacts being arranged to open the ground branch including the vlamp when the plug is not in use. The plug-seat switch rr' of plug e is ar- -ranged to connect the wire 16 with the wire 15,

leading by way of wire 9 to battery d, when yplug e rests in its socket. Hence the general circuit, including the clearing-out lamps q, q', and q2 of a trunk-line, is established when the terminal plug e of the trunk-line is replaced in its socket, and the branch, including the clearing-out lamp of the particular terminal plug at the distributing-board which may be in use, is closed during the use of that plug.

I will first briefly trace the general mode of operation of the system. Any switching operator who may be free to receive calls and make connections indicates this vfact to the distributing operators by connecting her telephone with a trunk-line by means of her listening-key, whereby the lamp-signals associated with the trunk-line at the distributingboard become lighted. A subscriber at one station wishing to obtain connection with a'nother station takes his telephone from its hook, which act causes the illumination of a lamp in the annunciator-board associated with his line. The distributing operator observing this signal makes connection With a spring-jack of the calling-line by means of some trunk-plug of which the associated lamp had been lighted, whereby the calling-line is, in effect, extended to a switching operator who is free to attend to the subscribers wants and who already has her listening-telephone connected with the trunk-line, such connection of the telephone with the trunk-line being the cause of the lighted condition of the signals fm/m m2. The waiting operator immediately demands the number of the line with which connection is required and after receiving it makes the usual test and establishes connection with the required line at the multiple switchboard. Thereafter this operator supervises the connection by means of signal-lamps associated with the trunkline through which the required connection has been established.

Any of the several distributing operators may observe the subscribers call and attempt to trunk the call to some switching operator. It two distributing operators should attempt to make connection with lines of two calling subscribers by means of plugs of the same trunk-line, only one of the connections would be effective. The lighted signal-lamp of that subscriber would become extinguished, while the line-lamp of the other subscriber would remain lighted, its illumination being an indication to the distributing operator that another operator had obtained the useof the trunk-line. Thus the mechanism prevents confusion which might arise through the accessibility of every trunk-line to each of several distributingoperators. When theswitching operator removes the connection with the called line, the distributing operator who made the connection between the same trunkline and the calling-line is apprised ot'- this fact by meansof a signal-lamp and withdraws the other terminal of the trunk-line from the spring-jack of the calling-line.

I will now trace the operation in greater detail,fo1lowing the circuits through the various changes involved in making and breaking IOO IIO

When the switching operator at the switchboard;A', for example, is ready to make connections, she brings her telephone intoconnection.withthetrunk-line G 7 by meansof key h. This act connectsV contact-piecesV h and hthus completing'acircuit 9 l0 1l l2 13 through the lamps m, mr', and. m?. The lamps mentioned therefore become lighted, indicating to the different switching operators that the trunk-line to which they refer is free for use and that. the operator havingj charge ot' it is ready to receive calls. A sub scriber calling closes his line-circuitfas to the central source of calling-current when he raises his telephone from its switch, exciting the relay b and closing the circuit` 3 4. Linelamp c is thuslighted, which constitutes a callfto the distributing operators. A. distributing operatorfor example, the one having access to plugf-seeingt-he lamp m lighted: beside the plug f raises this plug from its socket and inserts `itintov the spring-jack ctof the calling-line. A circuit through 'wires 9 and 10 is thus brought into shunt about wire 4, including the line-lamp, and in'series` with the wire 3, whereby the line-lamp isshort-circuited and extinguished. The act. of raising the plugffrom its socket permitted the plug-seat switch n. to break connection` between Wires 10 and 11, whereby theV circuit through lamps m, m', and m2 is broken and permits these lamps to become dark. The same switchcloses the circuit throughclearing-out lamp q, associated Withplugf, which becomes lighted, but its signal is ignored until the operator at switchboard A shall have had suiicient time tomake the required connection. The extinction of line-lamp c indicates to the distributing operatory who, inserted plugf that the connection has been. properly made.l If: the operator before whom plug f is stationed, having seen the lighted lamp m' and wishing to use atrunk-line, had employed plugf'to make connection with the line of a calling subscriber, the shunt-circuit 9 10 would be found disconnected from the sleeve 'i of plug f, so that the lamp c of the calling-subscribers line would remain light-V ed. This would indicate to the operator who had made the connection that another operator had obtained the same trunk-line at nearly the same moment, and the operator would withdraw plug f of that trunk-line from the spring-jack of the calling-line and insert a plug of another trunk-line which was ready for use in place of it. If the plug f' should be used in making a connection, the use of the plugf a moment later would practically leave the connection with the plug f, ordering outplug f-that is, the plugfwould` bring about the extinction ofthe lamp of the line with which it was connected, while the lamp of the line with which plug f' was connected would become lighted and would call for the disconnection of that plug. The oper.- ator at switchboard A, to whom the call has thus been transferred, receives the callingsubscriber-s order for the required connec# tion, tests the. line calledifor` in thek multiple sw,itchboard,and makes connection therewith (assuming that she has found it free for use) in the usual Way, after which she disconnects her telephone. The raising of plug e from, its seat breaks connection between wires 15 and 16, depriving the-clearing-out lamp q of current, and also permits the contacts fr r2 to close the break in wire 14. disconnection ofY the operators telephone by. means of thelistening-key closesconnection between wires 10 and 14, thus completinga-V circuit, through the supervisory signal-lamp Itgwill be observed that this lamplpis now in parallel with the line-lamp c. The current, through conductorv 3 isidividedibetween these twov lamps, so that. both-remain dark. The insertion of, plug e into aspringjack of the line called for brings the lampi into parallel with the line-lampY otl the,l line The subsequent called for; but inasmuch-as the circuit through,

that lamp is broken at the line-relay, the subs.-

scriber called having not yet: responded, the lampvl is lighted by cur-rent fromrbatteryd throughwires 8 and 3. The response ofthe called party is indicatedpby the extinctionbfi lamp Z. Supervisory lampsp and Z thus serve as automatic indicators before theswitching operator ofthe positions-of the telephones at` the calling and called stations.` When` the calling subscriber 'replaces histelephone on its switch, his relay b is deprived of currentv and breaks the conductor 4, whereby the cur-Y rent of battery d is diverted throughfconducf. torsv9, 14, and 10, lighting the lamp p., Simi@ larly the replacement of the telephone onts switch at the calledV stat-ion will divert, theV 'current which previouslyllowed through the line-lamp of that station into the supervir. sory lampl,\vhereby thislamp will be lighted. Thesimultaneous illumination oflampsl and p may be accepted by the switching-operator as a signal for disconnection, after which she will remove the plug e'from the spring-jack` and replace it in its resting-socket. breaks the circuit through lamp Zfat the sepa.- rated contacts i and. k of4 the spring-jack and plug, respectively, andv severs theV circuit through supervisory lamp p atthecontacts fr" r3 of the plug-seat switch fr., The same actv IOO IIO

This ,act

closes together the contact-pieces r' fr* ofi this switch, completing a circuit through Wires Y 15 and 16 to the plug-seat switch n, Where currv rent finds circuit through clearing-outlamp q and the registering contacts of plug-seat switch n to earth. Clearing-out lamp q is thus lighted. removal ofY plugf from the spring-jack of; the calling-line. 1f plug f orf hadv been em.- ployed in making connection with the calls `ing-line the corresponding clearing-out sig.

nal q or q2 would become lighted.

It will be observed that of1 thek series off plugsf, f,and f2 the plugf wouldalways, in effect, cut 0R the other plugs in the series, so that the distributing operator using plug f Its illumination calls'for the` would always deprive the other distributing i plug fat different positions at the annunci ator-board. These plugs in each position in the circuit should be located before each of the distributing operators, so that all distributing operators would find trunk-lines busy an approximately equal number of times-that is, assuming, for' example, that three trunk lines terminated in multiple plugs before the three distributing operators I would arrange plugfof one line, plugf' of another line, and plug jl2 of a third line before one of the operators; plug f' of the rst line, plugf2 of the second line, and plug f of the third line before another operator, and plugf2 of the first line, plug fof the second line, and plug f of the third line before the third distributing operator, carrying out a similaiarrangement for a larger n mnber of plugs.

The invention is defined in the following claims:

1. In a call-distributing system comprising telephon e-lines,each having a terminal socket and a signaling instrument in an annunciator-board, and a terminal socket in each of several sections in a multiple board, a trunkline extending from the annunciator-board to each section of the switching-board, of multiple terminal plugs for each of the said trunk-lines at the annunciator-board,where by several distributing operators have access to the same trunk -lines to equitably distribute the calls to the switching operators, as described.

2. The combination with a call-distributing system comprising telephone-lines, each having a terminal socket and a line-signal in an annunciator-board, and a terminal socket in each of several sections of a multiple switchboard, and a trunk-line extending from the annnnciator-board to a section'of the multiple switchboard, of multiple terminals for the said trunk-lines at the annunciator-board, a signal associated with each terminal, and a local circuit including the said signals, said local circuit being controlled by a switch associated with the trunk-line at the section of multiple switchboard; whereby all distributing operators are apprised of the readiness of a switching operator to receive calls, as described.

3. In combination with a call-distributing system comprising telephone-lines, each having a line-signal and a terminal socket in an annunciator-board, and a terminal socket in each section of a multiple switchboard, and a trunk-line extending from each section of the multiple switchboard to the annunciator-board, of multiple terminals for the said trunk-line at the annunciator-board, a signal associated with each of said terminals, a local circuit including said signals, and a switch at the multiple section controlling the said circuit and a switch connected with each of said multiple terminals to be actuated in the use thereof also controlling all of said signals; whereby a switching operator may apprise all the distributing operators of her readiness to receive calls, and the act of any distributingA operator in making use of the trunk-line may be signaled to the other distributing operators, as described.

4. The combination with tween switchboards, of multiple terminal plugs therefor at one switchboard, a signal associated with each of said multiple terminals, a circuit for operating the signal, a switch controlling the circuit at the distant terminal of the trunk-line, and a switch associated with each of said multiple terminals controlling all said signals, as described.

'5. The combination with a trunk-line between switchboards, of multiple terminals at one extremity of the trunk-line, a signal associated with each of said multiple terminals, a circuit for operating the said signals simultaneously, a switch at the distant terminal of the trunk-line controlling the said circuit, and a switch connected with each of said multiple terminals to be actuated in the use thereof adapted to render all of said signals inoperative when one of the multiple terminals is used, as described.

6. The combination with a trunk-line having a terminal at one station and multiple connection appliances at the other station accessible to diierent operators, of signals c c with which the several connection appliances are adapted to be temporarily associated, a circuit-changing device operated by each connection appliance when in use, and circuits associated with the several connection appliances adapted to be brought thereby into temporary association with the several signals c c, said circuits being controlled by the aforesaid circuit-changing device, whereby the use ot one of said connection appliances is caused to effect the operation of the several signals c c and so to indicate the busy condition of the trunk-line, as described.-

7. The combination with a telephone-line and the connection-socket thereof, of a signal near the socket, a link conductor having multiple terminals, each adapted for connection with the socket of a line, switches associated with each of said terminals to be made operative in the use of the terminal, and circuit connections of the said signal controlled by the said switches adapted to vcause the display of the signal near one of said terminals in a socket when either of said terminals is brought into use; whereby one operator in making connection with a telephone-line is warned that another operator has made connection with a difereut line by means of the same link conductor, as described.

8. The combination with a trunk-line having multiple terminal plugs at one station, of a plug-seat switch for each plug, a signaling a trunk-line be- IOO instrument adapted for association with any plug, and circuit connections of said signal changed in the simultaneous use of two plugs adapted to operate the warning-signal at one of the plugs, whereby one of two operators attempting to make use ot` different terminal plugs of the trunk-line willV be warned of the use of the line, as described.

9. The combination with subscribers lines and the terminal sockets and line-signals of each ot' said lines in a switchboard, of a link conductor having multiple terminals adapted for connection with such sockets, and circuit connections comprising a conductor including` one of said line-signals, and switch-contacts operated in the simultaneous use of two of said terminals completing the said circuit connections to cause the display of saidV signal; whereby one of two operators simultaneously using` the trunk-line is warned of such use by the line-signal, asdescribed.

10. The combination with aYtrunk-line extending between two stations having a single terminal plug at one station and multiple terminal plugs at the other station, of a signal associated with each of said multiple terminalsa local circuit including saidk signals, and` a switch at said single terminal controlling the local circuit, a switch for each of said multiple terminals actuated in the use of the terminal, a signal associated with one of said multiple terminals, and circuit connections of said signal controlled by the switch associated with another of said terminals adapt-y ed to cause the excitement of said signal; whereby an operator atthe said single terminal may-call to all the operators having aclcessfto said multiple terminals, but the simultaneous use of said multiple terminals by two operators will bel indicated to one of said operators.

1.1. The combination with a link conductor for, uniting telephone-lines having multiple connectiony terminals at one end thereof, of a clearing-out or equivalent signal associated with each of the saidV multiple terminals, al

device associated with each of the multiple terminals adapted to make the signal associ'ated with the same terminal operative when theter-minal is'in use, the condition of the remainingl signals remaining unchanged, and meansfor controlling the circuits ot' said-signalgas described.

12. The combination with a link conductor fou uniting telephone-lines having lnultiple terminals at one end, of a clearing-out signal associated with each. ot'l the terminals, a circuit common to said terminals, and means associated with the other end of the trunk-line for controlling the operation of said clearingout signals, and adevice associated with each of saidmultiple terminals operated in the use ofsaid terminal adapted to make the clearing-out signal associated with the terminal operative during the use of the terminal, the conditionot'Y the other clearing-out signals remaining unchanged, substantially as den connecting-switch for the line', and a circuit of said line-signal formed temporarily through the connecting-switch, and a conductor associated with the trunk-line to the distant terminal thereof, and means at the distantterminal for controlling the circuit thus formed; whereby the subscribers line-signal may be controlled through the trunk-line, as described.

14. The combination with a telephone-line, a relay connected therewith to respond to currentin the line during its use, and asecondary signal controlled; by the-relay, anda spring-jack for the line, of a, link conductor having multiple terminal plugs, a, circuit having multiple branches to each plug adapted to be brought into shunt of the signal-lamp .of a line through registering contacts of the plug and spring-jack, and a plug-seat switch of each ot' said multiple terminal plugs, havingV switch-contacts controlling the circuit of said branches to all plugs but` its own, as described.A

15. In combination with a trunk-line, multiple terminal plugs thereof, and switches, one for each of said multiple plugs, aI signal and a circuit thereof traversingsaid switches in series, and an independentY switch at the distant terminal station ofi said trunk-line controlling the said signaling-circuit, substantially as described.

, 16. In combination with a trunk-line and vrmultiple terminal plugs thereof, al clearingout signal for each of the plugs and adswritch yfory each plug controlled thereby, each, of

said clearing-outv signals beingV together withV .said switch of the same plug in a multiple branch of the signaling-circuit, and independent means at the distant station of thez trunk-line, common to the different si,f. 'na.ls,

for controlling the signaling-circuit; whereby the clearing-out signal of any plug which is'in use is made operative tcp receive the isignal for disconnection, substantially as d escribed.

17. The trunk-line circuit 6 7, provided at;

one end withmultiple plugs ff f2, switches. 'n n n2 for said plugs, respectively, a1 signalY and a signaling-circuit'thereof travel-singen: rial contacts of said switches, and independent means at the distant terminal off the trunk-line, for controlling said circui t,sul'pY stantially as described.

18., The combination withka trunk-line andi multiple terminal plugs thereof, of plug-seat switches n n n2, one for each plug, :ay-signal;- ing-circuit connected through said switches, clearing-ont signals associated with the dif.-` ferent plugs, and an individual. circuit of:

, each of said clearing-outsignals controlletlojyY IOO IIO

the plug-seat switch of the corresponding plug, a switch at the distant terminal of the trunk-line for controlling said signaling-circuit, and a clearing-out switch r controlling the general circuit of said clearing-out signals, substantially as described.

19. The combination with a telephoneline, a relay therein responsive to current in the line, a line-signal and a local circuit of the signal controlled by the relay, a plug and spring-jack for making connection with the line, and a conductor terminating in the plug, adapted to form a shunt about said line-signal when the plug is in the jack, and a switch adapted to break the circuit of said conductor and prevent the shunting of the line-signal thereof, substantially as described.

20. The combination with a telephone-line, a relay in the line responsive to current therein, a trunk-line for making connection with the telephone-line, and a supervisory signal at the distant terminal of said trunkline, a circuit of said supervisory signal completed through registering contacts of the terminal plug of the trunk-line and the spring-jack of the subscribers line, said cir cuit being controlled by said relay in the subscribers line, and an operators listening-key also controlling said circuit, as described.

21. The combination substantially as herein set forth, of a telephone-line and a relay therein, a trunk-line and means for making connection from each terminal thereof to a subscribers line, a supervisory signal associated with the distant terminal of the trunk-line, and a circuit of said signal closed at one point in making connection from said trunk-line to said subscribers line,said circuit being controlled by the relay in the subscribers line, and a switch actuated in mak- [SEAL] Countersigned F. I. ALLEN,

ing connection with said distant terminal of the trunk-line, controlling said circuit ot the signal.

22. The combination with a telephone-line, a terminal spring-jack thereof and a line-signal associated with the spring-jack, a trunkline for uniting telephone-lines, and a circuit of said line-signal closed through said springjack and a plug ot' the trunk-line when insel-ted therein, a conductor of the trunk-line, and a switch at the distant terminal of said trunk-line, actuated in making connection with said distant terminal, controlling the circuit formed through said conductor, including said line-signal; whereby the subscriber-s line-signal indicates the formation of connection with the distant terminal of the trunk-line, as described.

23. In a telephone-exchange system, the combination with trunk-lines, each provided with multiple terminal connections, any of said multiple plugs of a trunk-line being adapted to be connected with the spring-jack of a subscribers line, and cach being provided at its distant terminal With a supervising-signal and having a circuit divided into multiple branches terminating in the difterent multiple terminal connections thereof, a relay in each subscribers line, and a circuit controlled thereby adapted to be brought into connection with the circuit of said supervising signals of the trunk-line through the spring-jack of the line and one of said terminal plugs of the trunk-line, as described.

In Witness whereof I hereunto subscribe my 7 5 name this 30th day of December, A. D. 1898.

FRANK. R. MCBERTY. Vitnesses:

ELLA EDLER, D. E. WILLETT.

F. L. CAMPBELL,

Assistant Secretary of the Interior.

Commissioner of Patents It is hereby certified that in Letters Patent No. 684,289, granted October 8, 1901, upon the application of Frank B.. McBerty, of Evanston, Illinois, for an improvement in Signals for Telephone Switching Systems, an error appears in the printed specication requiring correction, as follows: In line 66, page 4, the reference letter A should read A and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Qce.

Signed, countersigned, and sealed this 22d day of October, A. D., 1901.

It` is hereby certified that in Letters Patent No. 684,289, granted October 8, 1901, upon the application of Frank R. McBerty, of Evanston, Illinois, for an improvement in Signals for Telephone Switching Systems, an error appears in the printed specification requiring correction, as follows: In line 66, page 4, the reference letter A should read A' and that the said Letters Patent Should be read with this correction therein that the same may conform to the record of the case in the Patent Qiice.

Signed, countersigned, and sealed this 22d day of October, A. D., 1901.

[SEAL] F. L. CAMPBELL,

Assistant Secretary of the Interior. Conntersigned:

F. I. ALLEN,

Commissioner of Patents.

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