US831819A - Telephone system. - Google Patents

Description

PATENTED SEPT. 25, 1906.

1?. G. BELL. TELEPHONE SYSTEM.

APPLIOATION FILED 001.9, 1905.

6 SHEETS-SHEET 1.

Jam. wwwm- 1n: "anal: Psrnu 0a., wnsmnamrv. a c.

PATENTED SEPT, 25, 1906.

F. G. BELL. TELEPHONE SYSTEM.

APPLICATION FILED 0GT.9,1905.

6 SHEETS-SHEET 2.

fer

PATENTED SEPT. 25, .1906.

F. G. BELL.

TELEPHONE SYSTEM.

APPLICATION FILED OCT.9, 1905.

6 SHEETS-SHEET 3.

0., WASNINUYON. one.

No. 831,819. PATENTED SEPT. 25, 1906. PG. BELL.

TELEPHONE SYSTEM. APPLICATION FILED 0019, 1905.

6 SHEETS-SHEET 4.

flame t No. 831,819. I PATENTED SEPT. 25, 1906. P. G. BELL.

TELEPHONE SYSTEM.

APPLIGATION FILED 002m, 1905.

8 SHEETS-SHBET 5.

No. 831,819. PATENTED SEPT. 25, 1906.

P. G. BELL. TELEPHONE SYSTEM.

APPLICATION FILED OGT.9, 1905.

6 SHEBTS-SHEET 6.

UNITED STATES PATENT EEroE.

FRANCIS GEORGE BELL, OF LONDON, ENGLAND, ASSIGNOR OF ONE-HALF TO ISIDORE BERNARD BIRNBAUM, OF LONDON, ENGLAND.

TELEPHONE SYSTEM.

No. s31,e19.

Specification of Letters Patent.

Patented Sept. 25, 1906.

Application filed October 9 1905. Serial No. 281,974.

To all whom it may concern:

Be it known that LFRANGIS GEORGE BELL, electrical engineer, a subject of the King of Great Britain, residing at 200 Upper Thames street, in the city and county of London, England, have invented new and useful Improvements in or Relating to Telephone Systems, of which the following is a specifica tion.

This invention relates to telephone-exchange systems working with a common battery; and it has for its object to simplify and improve the indicating and switchboard arrangements and the calling and connecting apparatus of such systems.

According to this invention the line-indicator is made simultaneously to serve as a clearing-out indicator and impedance-coil and in some cases also as a translator and as a self-inductor for a special calling apparatus.

Further, the arrangement of the operators set is improved and a novel method of constructing and wiring the through communication-plugs is introduced, whereby a telephone system well balanced and arranged as a whole is secured.

In the accompanying drawings, Figure 1 shows two subscribers stations and the connections therefor at the switchboard in one arrangement in accordance with the invention. Fig. 2 shows the operators set for use with the switchboard shown in Fig. 1. Fig. 3 shows the through connecting-plugs. Fig. 4 is a diagram illustrating the connections when the operator is speaking with a subscriber. Fig. 5 shows the connections when two subscribers are in conversation. Fig. 6 shows a modified arrangement at the subscribers station for calling with earth-return or common-return connection. Fig. 7 shows the arrangement of the operators set for use when the subscribers set is as in Fig. 6. Fig. 8 shows a modified arrangement at the switchboard. Fig. 9 shows the operators set as modified for use with the switchboard arranged as in Fig. 8. Fig. 10 is a diagram of the connection when two subscribers are talking with this modified arrangement of the switchboard. Fig. 11 is a diagram of the operators set with "simple impedance and with the special calling apparatus applied thereto. Fig. 12 illustrates the connections for the board shown in Fig. 1 when the operator is calling a subscriber by the arrangement shown in Fig. 11. Fig. 13 is a diagram of the operators set with split impedance y" j and with the special calling apparatus applied thereto. Fig. 14 similarly illustrates the connections for the apparatus as in Fig. 8 when the operator is calling a subscriber with the apparatus shown in Fig. 13. Fig. 15 shows the special calling apparatus applied in a somewhat difl'erent way in the operators set.

In the arrangement shown in Fig. 1 the subscribers stations I II are connected by pairs of line-wires with pairs of terminals a b on the switchboard. It will be convenient to refer to the lines as the a, line and 1) line, respectively, which are connected to the a and 1) terminals in each case and to letter all terminals connected to said lines as a and b, respectively. Each subscribors set includes a receiver 1', transmitter 25, hook-switch it, (operated by hanging up and taking down the receiver,) and a hell i, bridged across the a and b lines by a condenser It, so that said bell can answer to alternating or pulsating but not to continuous currents.

There is a spring-jack 0n the switchboard for each subscriber, each jack having two movable springs c and f and three fixed springs or contacts (Z, 6, and g. In front of each jack also is a collar Z in direct electrical connection with the terminal of the a line. An indicator m is connected between the fixed spring f in each jack and the a line, while the movable spring 0 in each jack is directly connected to the b-line terminal. Each indicator is of the type in which the dropplate is directly operated by the armature 9 and which therefore continues to indicate so long as a current passes through the indicator-coils. The drop does not return to its non-indicating position until the flow of current through the coil ceases and the armature is released. The armature 9 preferably touches a back contact 10 at all times when said armature is not attractedby the electromagnet m. The object of this is explained below.

The indicators have their coils wound on cores, so that said indicators will serve also as impedance-coils for the battery-circuits. No other impedance-coils are necessary in the speaking-circuits. 0 is the common battery of a suitable number of cells according to the size of the telephone-exchange which'itoperare a and 5 terminals connected, respectively, -with the sleeves s and tip p of the operators' plug. 'When this plug is inserted in ajaClg-the-sleeve 8 contacts with collar Z and is thus-connectedwiththe subscribers a lineywhile the tip p presses back the spring a, connected to the subscribers Z) line. The operators a terminal is connected, on the one hand, through the receiver 1", key q, transmitter t,--an'd impedance-coil with the terminal 2, connected to the (zinc) terminal of the common battery 0. It is also connected by wire 3 with the calling-generator u, the switch '2) of which is normally connecting the b terminal to the impedance-coil j, but which "automatioa'llyconnects said terminal I) to the generator it during calling in well-known manner.

The-pair of'through connecting-plugs 1 2 .(shown -inFig."3)are'used to connect two subscribers. One plug differs from the other inthat' one, -1, hasa sleeve sand tip p only, while the other, '2, hasasleeve s, a ring w, and a" tip p. These parts in each plug are of course-insulated,*and the tip p of-plug 1 is connected to the sleeve 8 of plug 2, as shown,

i whilethesleevesof plug 1 is connected to the ringw of plug 2. The tip of plug 2 has no electric connections, as it serves only-as a mechanical device to operate the inner springfof one jack in any pair placed in connection. The-sleeves-s always enter the collars Z,'while' the tip of plug 1 (and of the oper- -atorsplug)--and the ring w of plug 2 always press against the spring 0 of any jack in which they are inserted.

In operationwith this system the battery '0isnOrmallyconnected, as will be seen, on the side through the springs e f of the jacks withthe w lines of all subscribers stations and on the side through the relay n and springs "d c with the 5 lines; but owing to 'theuse -of a condenser k at each station no current can'pass in" any of the circuits. As soon, howevergas-a subscriber'e. g.,"at station- Ireinoves his telephone from the hookswitch-Zr or otherwise closes his line-circuit the current of the common batteryo passes over'his a and b'lines through his station by the contacts between springs cf and d c of the j'acks,'--as above mentioned, and thus the relay or -audible signaling device eat the centralstation is-operated. The operator hearing the "relay signal and seeing the particular drop-signal of the indicator m of the station (I) which is calling, inserts her plug into the jack of the said calling-station; but as said ator presses the key q, connecting her tele-,

phone set between her a and .2 terminals, and the speaking-circuits are then, as follows: from the terminal of battery 0 through the springs e f in jack I and through the indicatorcoil m of the station I which has called. From this point there are two paths'open. The first is through the subscribers line-wire a and his telephone set back byline b to'the jack, through the spring 0 therein, the tip 19 of the operators plug, operators terminal b, the spring contact-switch '0 of the generator in the operators set, the impedance-coil j, and back tothe terminal of" the battery 0. The second path is from the indicator-coil m through the collar Z of the jack, the sleeve 8 of the plug, operators a terminal, through opertors telephone set, the key (1 of which is closed, and'the impedance-coil 7' back to the battery terminal. Fig. 4 shows diagrammatically the circuits whichare now closed, and it will be seen that the impedance-coil j balances the indicator mat the side of thecircuit next to the battery terminal, and asa perfect balance'is thus obtained speaking can be effectually carried on between the operator and a subscriber. As will be seen later, (see Fig. 5,) the indicator-coil m of a second subscriber serves'the purpose of the impedance-coil 7' when two subscribers'are connected through to one another.

After receiving and answering a call the operator rings up the desired stationsay IIby inserting her plug into theja'ck II of said station'and operating the calling-generator u. The alternating current generated then passes from the generator u and a terminal of the operatorsset through the collar Z of the ack II directly through the'lines a, and Z) of station II' and itscondenser Zr and call-bell i and through the spring a of the jack, tip p of plug, operators terminal b, and automatic switch 1) back to the generator u.

The call having been given and answered the operator connects the two stations'by the through"connecting-plugs 1-and'2. "The plug 2, having asleeve 8, ring w,-and tip 10, makes contact with thecollar Z and spring 0 of its jacksay Iwhile simultaneously its tip 29 presses over the'spring f from spring 6 to make contact with spring g,-so that the indicatorm of station I is disconnected from the terminal of the common battery and is connected'instead with the terminal. At the other jack II the plug 1 having only a sleeve 8 and a tip the spring f, connected with the indicator m, remains in contact with spring 6 and is thus in connection with the battery terminal, while the sleeve 8 takes contact with the collar Z, connected to line a, and the tip p with the spring 0 in the jack connected to the line 1), this latter spring being thus pressed back away from spring (Z. The speakingcircuits (indicated diagrammatically in Fig. 5) are now as follows: from the terminal of battery 0 through springs e and f of jack II, indicator m, after which the circuit is branched. The one branch goes over the a line to station II, through the instruments at that station back by the 1) line to spring 0 in the II jack, tip 1) of plug 1, and through the connecting-lead to sleeve 5 of plug 2, thence from collar 1 of jack I through indicator m of station I, springs f and g, (pressed together by the tip of plug 2,) and so back to the battery terminal. The other branch is from the indicator m of station II through the collar Z of jack II, sleeve 8 of plug 1, and by the connecting-lead to ring to of plug 2, spring 0 of jack I, the 1) line of station I to that station and back by the a line through indicator m of station I to springs f and g, as before, to the battery terminal. It will be seen particularly clearly in Fig. 5 how exactly balanced the whole speaking system is with these connectionsthe two stations are connected in parallel between the terminals of the two indicators m m thus brought into action, and the highfrequency speaking-currents of course pass through the two stations as if they were directly connected in series. The indicators m, as before mentioned, have drops which only remain raised or visible so long as a current is passing, so that said indicators will return to their normal position when the current ceases to flow through them. It will be seen that this will not occur when the subscriber at one station only has hung up his receiver or otherwise broken his circuit, because, as seen in Fig. 5, the battery-current will continue to flow through both indicators m and one station even after the other is cut off. It, therefore, no special clearingsignal were giveni. e., if the back contacts 10, explained below, were omitted-the indicators would serve to give the clearing-out signal, showing when both subscribers had finished their conversation, because the two indicator-drops would simultaneously return to their non-indicating position as soon as both subscribers had hung up their telephones; but the indicators are preferably arranged to give a clearing-out signal, as follows: The back contacts 10 of armatures 9 are connected to the 7) terminals in each case, and the armatures 9 themselves are all in electrical connection through the relay n with the battery terminal. The armatures normally rest against the contacts 10, as before explained but there can be no circuit through these contacts unless the through connecting-plugs 1 and 2 are in two jacks and the subscribers thus connected are not communicating. This is easily seen, for as long as a subscribers telephone is on the hook it there is no circuit through his station, and the parts of the switchboard connected to the battery terminal i. 6., jacksprings c and f, indicator-eoils m, a lines, and collars Z-are insulated from all the other parts which are connected with the terminal. As soon as the operator closes a circuit through his station his indicator operates, breaking the contact at 10. Further, if the through connecting-plugs are in two jacks the indicators of both jacks remain operative, and the contacts at 10 are broken until both subscribers hang up their telephones. Then, however, the following oc curs: The armature of the jack in which the plug 2 is inserted falls, because the spring f in that jack is pressed away from the spring a and there in no longer a connection through the other station and the collar Z with the battery terminal. Hence the contact 10 is closed by armature 9 of the indicator m in this jack. The same would happen in the other jack were it not that a circuit is now closed through the spring a and spring f in this jack (in which plug 1 is inserted) through the indicator m of this jack, collar Z, plug-lines to spring 0 in the first-mentioned jack, (in which plug 2 still is,) and thence through contact 10 and armature 9 to relay n and the battery terminal. Hence the relay n will give a clearingout signal calling the operators attention to the fact that the conversation is finished and the relaysignale. 9., sounding ot a buzzer will continue to be given until the operator pulls out the through connecting-plugs, and thus breaks the circuit.

The system can be equally'well arranged for working with a common return in the calling-circuits, each station then having a third terminal connecting the bell with such commen-return line or earth, while one generatorterminal is connected to said return line or earth, as the case may be.

Figs. 6 and 7 show the modifications in the subscribers stations and the operators set, respectively, for this purpose. At the subseribers stations the switches h have contacts at, which they rest against when the receivers are on the hooks, and the bells i are connected to these contacts, on the one hand, and to earth or a common return 1 on the other hand. In the operators set the wire 3 is similarly connected to a common return or earth 1 instead of being connected with the wire from the a terminal. The ringing in this case is effected by the generator at over the 1) terminal of operators set, operators plug-tip p, subscribers jack-spring c, b terminal, 1) line to hook-switch h at subscribers 'paratus, as explained below.

set, and (as the receiver is on the hook) by contact x through the bell i to the common return or earth 1 The speaking-circuits remain as before.

Where it is required to have translators in order to obtain induced speaking-currents capable of operating over long distances, the

indicators m may be arranged to work as translators. In such case the indicator-coils are split, so that the current going to one station passes through one part of the coil and the current to the other station through the other part. Each portion then serves as a translator for the other. This is shown in Figs. 8, 9, and 10, which correspond with Figs. 1, 2., and 5, above explained, for the simple type of indicator. The arrangement of Fig. 8 differs from that of Fig. 1 only in that the indicators have split windings m m connected, respectively, with the a terminal and the collar Z. In the operators set, Fig. 9, the arrangement differs from that of Fig. 2 only in that the impedance-coil is split into two parts j P, with the connection to the terminal 2 between them, while the part 3" is connected to the speaking instruments t and r and the part 3' to the generator-switch v. The calling and speaking circuits with this modified arrangement are substantially the same as with the first-described arrangement, the only difference being that each of the parallel battery-circuits during speaking contains the parts m of one indicator and m of the other, or one of the impedance-coil parts 9" 3' in place of one of the indicator parts. The diagram Fig. 10 will make this clear. In speaking, the high-frequency current in one part'of the indicator-coil serves to induce corresponding current impulsesin the other part, and these impulses will operate effectively in the receivers of stations at considerable distances. In this case, therefore, the calling-indicators serve also as impedance-coils, clearing-out in dicators, and translators. They may further serve as self-inductors in a special calling ap- If there are no back contacts 10 to armatures 9, the clearingout signal is only a visible one given by both drops oftwo communicating stations falling back simultaneously when the second subscriber hangs up his telephone, as before explained with reference to Fig. 1. If, however, the contacts 10 are provided, the relay n is caused to give an audible or other suitable clearing-out signal, as already explained.

With the special calling apparatus about to be described a magneto-generator becomes unnecessary in the operators set. Fig. 11 shows one arrangement for the purpose. The talking instruments 7" t and the key g are in lines normally connected between the operators a and 6 terminals, with a connection through the impedance y tothe 2 terminal, and a key 4 is provided for cutting out the speaking set and connecting a vibrator across the lines. This vibrator is similar to that used in an electric bell L. 6., it has an electromagnet 5 and an armature 6, adapted to alternately make and break the circuit of the magnet. With this device after the operator has plugged in to the line to be called she has only to press the key 4. Current from the common battery 0 then passes through the springs e and f of the jack of the station to be called, the indicator m, the collar Z, sleeve 8 of operators plug to the a terminal of the operators set, thence through the contact of armature 6, the coils of electromagnet 5, the key 4, and impedance-coil j to the 2 terminal of the operators set and so to the terminal battery. -The armature 6 is thus attracted by the magnet 5 breaking the circuit above mentioned and stopping the flow of batterycurrent. The magnet is thus denergized, the armature makes'contact again, and a vibrating action is thus set up just as in an electric bell. At every break of the circuit during the vibration a very powerful self-induced current will be set up in the indicator and impedance-coils, and this current passes through the a and 1) lines of the subscriber to be called and acts through the condenser is to ring a polarized bell t at the subscribers station.

Fig. 12 shows a diagram ofthe connections when simple'indicator-coils m and impedancecoils j are used. The'battery-current when it flo WS passes through the indicator and .impedancc coils in the reverse direction to that of the self-induced current, and consequently the self-induced current of the indicator-coil is assisted and increased by the self-induced current in the impedance-coil, and vice versa. Fig. 18 shows the operators set for calling with the special apparatus when split impedances j y' are used, and Fig. 14 gives a diagram corresponding with Fig. 12, but showing the operators split impedance-coil and the subscriber s split indicato coil m" m The action in this case is similar to that of Fig. 12.; but the current impulses inv the subscribers calling'circuit on break in the operators battery-circuit are due to a large extent to actual induction from indicator-coil m to coil m and impedance-coil y" to coil The advantage of this method of calling lies partly in the saving of the cost of an expensive generator and partly in the con- IIO venience which results from the giving of the call by simply pressing a key insteadof by turning a generator-handle.

' The self-inducing effect would be obtained. in the calling apparatus if the impedance-coil of the operator s set were omitted or if a simple impedance 1, as in Fig. 1 1, were used with double indicator-coils m m and I do not, therefore,zlimit myself to the use of such a coil or any one type of coil with this special calling device; but said device is applicable to all common-battery telephone installations in which there are impedances of suitable I3 the key (1 untouched, and the vibrating type in connection with the line-circuits, either in the to rm of the indicators or as separate impedance-coils.

I desire to make it clear that I do not limit myself to any particular mechanical devices for effecting most of the operations hereinbefore mentioned.

The system is applicable to subscribers sets of any type now usual. The relay or other commonsignaling apparatus at the central station may also of course take a number of forms and may give a visible or other signal, as is desired, and although I prefer the well-balanced arrangement wherein the two indicators are on opposite sides of the battery both indicators may be in some cases arranged on one side of the battery, while the other features of my invention and the calling arrangement which are applicable in such cases are retained. The device illustrated in Fig. 15, for example, is .claimed to be within the scope of this invention. Fig. 15 shows one or two small modifications of the special calling apparatus. In this case an additional battery 7 is provided in the operators set for increasing the strength of the callingcurrent, and in place o1 a separate switch 4 for operating the calling apparatus a back contact is provided at 8, against which the operators hand-key q rests in its normal position. The calling-circuits are the same as above described, the only difference being that the battery 7 provides more current, if required, while the back contact 8 makes it possible for the one key (1 to be used for both calling and speaking purposes. The operator with this device has only to plug into the jack of the subscriber to be called, leaving apparatus 5 6 will give the required call. By pressing the key (1 the operator will bring herself into speaking communication with the called station while simultaneously cutting out the calling apparatus 5 6. Similar arrangements are obviously applicable with split impedance-coils, as in Fig. 13; but it is needless to go further into such details.

hat I claim is 1. In a common-battery telephone system, the combination of the battery, the sub scribers stations and c'onnectinglines, a switching apparatus and an indicator at the central station in connection with each subscribers station, and means for connecting the switching devices to bring two subscribers into communication, the switching apparatus, connecting means and indicators all being such that the two indicators of two communicating subscribers will be connected between the battery and the subscribers stations one indicator at each terminal of the battery and that the two indicators will both remain on the lines when a conversation is proceeding, will serve together to give the line indications, the clearing-out signals and will also serve as impedance-coils in the system.

2. In a common-battery telephone system, the combination of the battery, the subscribers stations and connecting lines, a switching apparatus, and an indicator at the central station in connection with each subscribers station, an operators set including an impedance-coil and calling apparatus, and means for connecting the switching devices to bring the operator and a subscriber, or two subscribers into communication, said switching apparatus, connecting means and indicators being such that the indicators, or one indicator and the operators impedancecoil, will become connected to opposite terminals of the common battery with the two telephone sets in parallel between the terminals of the indicators, or the indicator and impedance-coils, and that the indicators will serve to give the line indications, the clearingout signals, and will also serve as impedancecoils.

3. In a common-battery telephone system, the combination of the common battery, the subscribers stations and connecting-lines, indicators at the central station each in connection with one subscribers lines, switching devices each in connection with one subscribers station and with the indicator there- 9 5 for and adapted to normally connect said in dicator with one terminal of the common battery, and meansfor connecting any two stations through their switching devices, said means such that the indicator-of one connected station has its connection changed from one terminal of the common battery to the other when the connection between two stations is made. 4. In a common-battery telephone system, the combination of the common battery, the subscribers stations and connecting-lines, indicators at the central station each in connection with one subscribers lines, acks each having springs respectively in connection with the common-battery terminals, the indicator and the lines of one subscribers station, and a pair of plugs with connectingwires, said plugs adapted to be inserted in the jacks to connect two stations, and one of said plugs adapted to change the connection of the indicator through its jack from one terminal of the common battery to the other. 5. In a common-battery telephone system, the combination of the common battery, the subscribers stations and connecting-lines, indicators at the central station each in connection with one subscribers line, jacks each having springs respectively in connection with the common-battery terminals, the indicator and the lines of one subscribers station, and a pair of plugs with connectingwires, said plugs adapted to be inserted in. the acks to connect two stations, said plugs and connecting-wires such that they connect one terminal of thecommon battery through i the coils of one subscribers indicator to the subscribers stations in parallel, and through said stations to the other subscribers indicator,'through the coils of said indicator back to the other terminal of the common battery, whereby'a balanced communicating system is produced.

'6. Ina common-battery telephone system, the combination of the battery, the subscribers stations and connecting lines, a switching apparatus andan indicator at the central station in connection with eachsubscribe'rs station, a signaling-relay and means connecting'it with the battery and switching devices, 'mea'ns'for connecting the switching devices, to bring any two subscribers stations into communication, and connections adapted to'be made by the indicators when not indicat ing such that a battery-circuit is established through the switching devices and means connecting s'am'e,and through'the signalingrelay when both subscribers have broken their speaking lines, whereby a clearing-out signalcontrolled by the indicator is' given by the signaling rel'ay until the connection between'the'switching devices-is broken.

'7. In a common-battery telephone system, the combination of the common battery, the subscribers stations and connecting-lines, indicators at the centralstation each in connection with one subscribers lines, jacks ea'ch'h'aving'springs respectively in connec tion withthe common-battery terminals, the indicator and the lines of one subscribers station, "a pair of plugs with connecting-wires, said plugs adapted to be inserted in the jacks to connect two stations, a signaling-relay and means for connecting it to the battery and to a part in each jack, and connections adapted to be'madeby'the indicators when not indicating such that a circuit is established from one battery-terminal through part of one jac-k,'the through connecting-plugs, part of the other jack,'and'through the signalingrelay back to the other battery-terminal when both connected subscribers break their speaking-circuits, whereby, 'a clearing-out signal controlled by the indicator is given which persists until the through connectingplugs'are withdrawn.

8. In a common-battery telephone system, the combination of the common battery, the subscribersstations and connecting-lines, indicators eachincluding two coils wound on the core, one'of said indicators connected to the-line of eachsubscriber, switching devices one in connection with each subs'eribers station and the indicator thereof, and means for connectingthe-switching devices of'any two stations, said means and switching devices such that th'e'stations'are connected to the commonbatter'y in parallel circuits each with one coil of one indicator and one coil of the 5 other included therein, whereby the indicaswitching devices of any two stations, said connecting means such that two stations, or the operators set and one station, may'be connected thereby to the commonbattery in parallel circuits each circuit including one coil of one indicator and one coil ofthe other or of the split impedance, whereby balanced speaking-circuits are produced.

10. In a common-battery telephone s'ys-.

tem, the combination of the common battery, the subscribers stations and connecting-lines, indicators each includingtwo coils wound on the core,'one of saidindicatorsconnectedto the line of each subscriber, switching devices one in connection with each subscribers station and the indicator thereof, a signaling-re lay andmeans connecting it with the battery and switching devices, means for connecting the switching devices of any two stations, said means and switching devices such as to connect the subscribers sets and halv'es of'the indicators in parallel balanced circuits on the terminals of the common battery, and connections adapted tobe'm'ade by'the indica-- tors when not indicating such that a batterycircuit is established through the switching devices and means connecting *them and through the relay when both subscribers havebroken their speaking-lines, whereby a clearing-out signal isgiven by the relayuntil the connections between the-switching devices are broken.

11. In a telephone system the combination of a common "battery, the subscribers stations each including telephone instruments and an audible signaling apparatus, connecting-lines for the subscribers stations, an operators set including a vibrator "and key therefor, adapted to connect said vibrator directly across the operator s telephone-wires, an'impedance, and means for connecting the operators set and asubscribers lines in parallel to the terminals of the common battery through the impedance, whereby the pulsations of current allowed to passthrough the battery and im edance by the vibra-torare enabled to pro uc'ecurrent impulses inthe subscriberslines which impulses in turn operate the subscribers signaling'apparatus.

12. In a telephone system the combination of a common battery, the subscribers stal in communication in such a way that the pultions each including telephone instruments and an audible signaling apparatus, connectinglines for the subscribers stations, an operators set including a vibrator and a key therefor adapted to connect said vibrator directly across the operators telephone-wires, indicators the coils of which are adapted to act as impedances in connection with each subscribers lines, and means for connecting the battery and one indicator-coil in parallel to the operators and one subscribers sets, whereby the pulsations of current allowed to pass through the battery and coil by the vibrator are enabled to produce current im pulses in the subscribers lines which impulses in turn operate the subscribers signaling apparatus.

13. In a telephonesystem the combination of a common battery, the subscribers stations each including telephone instruments and an audible signaling apparatus, connecting-lines for the subscribers stations; an operators set including a vibrator and key therefor, means for connecting the operators set to a subscribers lines, an impedance-coil in the operators set, indicator-coils in connection with the lines of each subscribers station, and means for connecting the battery between the impedance-coil and indicator of the operators set and subscribers station respectively which are in communication, whereby the pulsations of current allowed to pass by the vibrator are enabled to produce current impulses in the lines which impulses in turn operate the subscribers signaling apparatus.

14. In a telephone system the combination of a common battery, the subscribers stations each including telephone instruments and an audible signaling apparatus, connecting-lines for the subscribers stations, an operators set including a vibrator and key therefor, means for connecting the operators set to a subscribers lines, a split impedancecoil in the operators set, split indicator-coils in connection with each subscribers lines, and means for connecting the battery between the impedance and indicator coils of the operators and subscribers sets which are sations of current allowed to pass by the vibrator through one circuit are able to produce, in the impedance and indicator coils, induced current impulses in the other circuit capable of operating the subscribers signaling apparatus.

15. In a telephone system the combination of a central battery, subscribers stations each including telephone instruments and audible signaling apparatus, indicators with split coils, one indicator for each subscribers set, an operators set including a vibrator and key therefor, means for connecting the operators set and a subscribers station in balanced parallel circuits on the centralbattery terminals, means for connecting two subscribers stations in balanced parallel cir cuits on the central-battery terminals, a sig naling-relay at the central station, and means controlled by the indicators and station-connecting means for closing the circuit of the relay when two communicating subscribers break their speaking-circuits.

16. In a telephone system the combination of a common battery, the subscribers stations each including telephone instruments and an audible signaling apparatus, connecting-lines for the subscribers stations, an operators set including telephone instruments, a vibrator, a two-way key adapted to connect either the telephone instruments or the vibrator to the line-wires of the operators set, an impedance, and means for connecting the battery and impedance in parallel to the operators and one subscribers sets, whereby the pulsations of current allowed to pass through the battery and impedance by the vibrator are enabled to produce current impulses in the subscribers lines which impulses in turn operate the subscribers signaling apparatus.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

FRANCIS GEORGE BELL.

IVitnesses IIUBERT A. GILL, LEON E. IIAYNES.

Images