US878017A - Party-line telephone system. - Google Patents

Description

No. 878,017. PATENTBD FEB. 4, 1908.

A. P. POOLE. PARTY LINE TELEPHONE SYSTEM.

APPLIGATION FILED FEB. 20, 1905.

2 SHEETS-SHEET 1.

VB IIIIP fi/h dr' F. Paula Es WWW BITE-BF for the actuating current flow.

ARTHUR F. POOLE, OF WHEELING, WEST VIRGINIA.

PATENT orrros.

PARTY-LINE TELEPHONE SYSTEM.

Specification of Letters Patent,

Patented Feb. 4, 1908.

Application filed February 20, 1905. Serial No. 246,404,

To (1 whom it m up concern/.-

Be it known that l, An'riufn F. Poona, a citizen of the United States, residing at Vv'heeling, in the county of Ohio and State of 'est Virginia, have invented a certain new and uselul Improvement in Party Line Telephone Systems, of which the following is a full, clear. concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates toy party line telephone systems and particularly to improved 1ocl ing-out means therefor.

My improved system can be applied to party lines to which are connected any number of substations, and the invention consists broadly in providing at each substation a high resistance and a low resistance path tion of apparatus at a calling substation the low resistance path is eventually connected in circuit and the pressure of the system greatly reduced, whereby the current, which would llow through the high resistance path at another substation ol the same party line upon an attempt to listen-in, would be in sullicient to cause actuation ol apparatus controlled by the high resistance circuit whereby the telephonic apparatus at the listening-in substation is maintained in'an in operative condition. More specilically, I employ at each substation a relay provided with a high resistance winding and a low re- The armature ol' this rea short circuit about the telephonic apparatus. Upon removal of the receiver from its hook at a calling substation the relay is primarily energized through a circuit including the high resistance winding, whereupon the armature is attracted to open the short circuit about the telephonic apparatus and to close a short circuit about the high resistance winding, the telephonic apparatus being then connected in a. circuit including the low resistance winding, and the armature willremain attracted. The current supply may'be fed from a central energy battery or from local sources. This low resistance path greatly reduces the strength-ct the current flowing through the party line, and upon an attempt of a second party to use the line the current will be insutl'icient to actuate the relay at the substation through the high resistance winding, and, therefore, the short cir cult about the telephonic apparatus at this sistance winding. lay normally closes Upon actual g l l l second substation will remain unbroken and thus any second subscriber will be locked out.

The calling subscriber on a party line may desire communication with another subscriber connected with the same party line, and each substation, therefore, is provided with switching meansfor rearranging the circuits to allow such connection. The calling subscriber wishing communication with the other subscriber on the same line actuates a switch or presses a button whereby to open the short circuit about the high resistance winding, and the circuits then will be such that the path through the calling substation will include the high and low resistance windings and the telephonic apparatus in series. Thus the second subscriber, after having been signaled by the central operator, removes his receiver from the hook, and, as the current flow over the line is now suflicie'nt, owing to the high resistance path through the calling substation, the relay at the called substation will be actuated to open the short circuit about the telephonic apparatus and conversation can nowbe carried on. I also provide means preferably in the form of a condenser which isbridged about thehigh resistance apparatus at the calling substation to more readily convey voice currents through the telephonic apparatus.

Any number of subscribers may be connected to a single party line, and any selective ringing s fstem maybe used in conjunction with this locking-out arrangenu-ait.

My invention will be better understood by referring to the accompanying drawings, in which Figure 1 shows one arrangement of circuits, and Fig. 2 shows a slightly modified arrangement thereof.

111 both figures l have shown party lines X and Y connected with the central exchange C, each line terminating in a. spring jack 1 and normally connectedv with the central source 2 through an indicating signal 3'. cord circuit D is provided at the central exchange for connecting party lines together and includes well known apparatus such as the operators listening key 4 and ringing keys 5 and 6 suitably connected with the source 7 of ringing current. A supervisory signal 8 is also shown.

In Fig. 1 each substation is provided with the usual apparatus consistingof the switch hook 9, receiver 10, transmitter 11, and

i niitter to the conductorfii, an

primary and secondary windings 12 and 13 of an induction coil. The switching apparatus, actuated upon removal of the receiver from the hook. is associated with the actuating button 14 extending from the hook I The ac- 26 of the key It is connected to a terminal of each of the relay windings,

while the contact 27 normally engaged by the lever 26 is connected with the armature arm 24:. The transmitter and primary winding are connected to the switch hook and with the armature arm 25, the switch hook 25 being also normally directly connected with the arm 25 through the back contact 28 and conductor 29. The other terminal of the low resistance winding 23 connects with the switch hook through the transmitter and 30 primary winding, and also connects with the inner contact- 19 of the hook switching mechanism. resistance winding connects with the front contact 30 of the armature and with the line limb a, this line limb connecting also with the contact 20 of the hook switching mechanism. The line limb b connects with the switch hook contact 31 and also through the signal bell 32 with the inner contact 18. Thus the con- 46 du ctor 29 normallyshort circuits the telephonic apparatus, while the signal bell 32 is connected from one'line limb through the condenser to ground, and for the purpore of illustration 1 have shown a two party selective system. in accordance with this arrangement and for the purpose of ringing either of thetwo substations selectively the keys 5 and'6, at the central exchange serve to connect ringing current from either line BO'limb to ground, thus causin actuation of the signal bell either at so station A or at substation B as desired.

, The operation of .this arrangement is as 1 follows: Sup Jose the subscri )GI at substation B wlsi I scriber at substation A connected with the line Y. He removes the receiver from the hook, whereupon current will flow from the "line limb a through the switch hook and for Q an instant will flow through the short cir- ,cuiting conductor 29, through contact Z8and armature arm 25, and through conductor 33 t6 conductor 34, but subseiuently will flow through the primary win ing and, transfrom thence The other terminal of the high less to converse with the sub-' even 1*? I seriallyithrough the low and} high resistance lwindings to the line limb b. The relay, l therefore, is actuated and its armature attracted to open the short circuit about the primary winding and transmitter and to l close about the high resistance winding the 1 short circuit path including the contact 30., i arm 24 and the key 70. The line: limbs being thus closed through the substation B, the indicator 3 connected with the line X will be actuated, whereupon the operator connects I the cord circuit with the spring jack 1 and ascertains that communication which is desired with the subscriber at substation A on I the line Y. Upon actuation of the proper the two arms 24 ringing key the bell at the called substatlon is rung, and upon removal of the receiver thereat from the hook, the relay will be energized to open the short circuit about the telephonic apparatus, and conversation can i now be carried on between the substations I B and A.

Owing to the short circuiting pathabout the telephonic apparatus every othersubscriber on the artyfline X will be locked out -unless the re ay be acutaed'to 0 en this i short circuiting ath. Should anot er subscriber remove iiis receiver from the hook current from the line would have to flow serially through the relay windings, but 0wing to the low resistance path between the line limbs at the calling substation B, the current strength will be insufficient to cause suitable actuation of the relay at the listeningin substation, and the short circuiting path 0 at this substation will not be opened and consequently all other parties, with the exce tion of the calling party, are effective y locked out, and this Would'be the case no matter how many substations were con- 5 nected with .the party line. It is desirable, however, in party line systems, thatjone party on a telephone line be able to converse with another party connected to the same line, but unless some means be provided in. this lock-out arrangement just described, such conversation "cannot be accomplished. I provide, however, the switch or he mechanism 7c and this key is included in t e short circuiting' path about. the high resistance. winding. bhould subscriber at substation B desire communication with the substation A on the same line instead of with substation A on another line, central would inform him to acuate'the key 7c thereupon to open the short circuit about thedugh resistance wind ing. lhis, however, again causes serial inclusion in circuit of the high and low resistance windings and the transmitter and priinary winding, the armature of the relay re rushing attracted. Thus the current flow over theline limbs instead of being drained through' the lowrcsistance path is again of sufiicient strength ton hmrc the relay at the substation as en removal of; thereceiver e by the subscriber thereat in response to the si nal sent by the central exchange operator.

T e subscriber at B maintains depression of v the key 70 until he gets response from the subclusion of all these windings upon depression of the'key at substation B, there is considerreceiver from the hook, he Wlll becomlectcd able impedance and difliculty may be encountered therefore in receiving the telephonic voice currents. However, the .condenser 21 upon release of the switching hook is bridged about the relay windings through the path including the conductor 35, contact 20, actuating spring 16 through the condenser, spring 15, contact 19 and conductor 34,,the condenser affording an easy path for the voice currents. Normally, however, the condenser is connected in the groundcircuit from a line limb including the signal bell 32, the ground connection, however, being removed upon release of the switch hook.

In Fig. 2 is shown a slight modification of the circuit arrangements. instead of automatically actuating switching mechanism upon movements of the switch hook this switching mechanism is incorporated in the key It, to be manually actuated. This key consists of the actuating springs 36 and 37, the inner springs 38 and 39 normally engaged thereby and the outer alternate contact springs 40 and 41. The spring 36 is connected with the armature24 of the relay, and the inner contact spring 38 'is connected at one terminal of each Windin The condenser 21 is connected to the actuating armature contact spring 40, this condenser circuit being grounded, as shown. The inner contact s ring 39 is connected through the signal bel 32 with one of the line limbs. The condenser, therefore, instead of being continuously connected in circuit upon release of the receiver hook in Fig. 1, is bridged about the relay windings only upon depression of the manual switch or key 7a.. In this modified arran ement also the short circuit conductor 29 bridges the primary winding and transmitter and also the loW resistance winding 23 of the relay. The operation with this circuit arrangement is as follows: The subscriber at B desiring communication,

Y, raises his receiver, whereupon current flows from the line limb a to the receiver hook 9 and instantaneously passes mostly all through the short circuit conductor 29, contact 28, armature 24, through the key It and through the high resistance winding. The relay being encrgized will open the short circuit path about the telephonic apparatus and the low resistance winding, but will close a short circuit path about the high resistance winding, this spring 37 and the v for instance with the substation A on the line path including the front contact 30, armature 24- and springs 36 and 38. The current now flows between the line limbs, from the line limb (I through the primary winding and I transmitter, through the conductorZT, low

resistance winding 23, key springs 36 and 38 .to armature 24 and from contact 30 to the line limb b. -'l he operator receiving the call at the indicator 3 ascertamsthe connection desired and accordingly rings substation A,

and upon the subscriber at A removing his for conversation with the subscriber at B. .In the same manner as 111 Fig. 1, any other subscriber connected with the hue cannot listen-in owing to the inoperative condition of this telephonic a )paratus which remains short circuited until actuation of the relay, but, owing to the low resistance path between the limbs at the substation B, the current strength insuilicient to actuate any other relay on the line. Subscriber B, however, desiring communication with another subscriber on the line X, for instance as A, must actuate the key /c which will open the short circuit about the high resistance winding and will cause the high resistance winding to be included serially in circuit with the low re sistance winding and the transmitter and primary winding. The relay at the called substation A will then receive sullicient current to be actuated upon removal of the receiver from the hook in response to a calling signal sent from the central exchange. Actuation of the lacy at substation B also .will connect the condenser 21 in bridge of the relay windings, and when the subscriber at A answers, the voice currents will readily pass through the condenser and through the telephonic apparatus at B. llaving obtained connection with A, B may release the l ey and conversation may be carried on in the ordinary manner, the only impedance in these circuits being the low resistance winding and the primary winding which is not snllicient to hinder free transmission of the voice currents Although I have shown selective means at the central exchange adapted only for selectively signaling two party subscribers, I need not be so limited, as any selective system may be employed inv connection with the locking-out feature as the bell circuits at the substations are entirely distinct from thelocking-out circuits. This lockingout feature can, therefore, be applied to any style telepl'ione since the sole connection between the lock-out apparatus and the telephone apparatus is an electrical one, and it may readily, tlu refoi'e, be installed in existing systems. The same condenser which is used in the usual manner in the bell circuit, may serve to carry the voice currents about the impedance windings. There are also no additional connections or' apparatus necessary at the central exchange. No additional operations are necessary to be performed the exchange operator, except cases where one subscriber wishes communication with another subscriber on the same ii s, which is comparativel rare and in Whic case this. necessary on y for the exchange operator to notify the calling subscriber to actuate his Having described my invention, I claim as new and desire to secure by Letters Patent:

1'. In a party line telephone system, the combination with a party line, of a plurality of substations connected therewith, telephonic apparatus and a relay at each substation, said telephonic apparatus being inoperative when said relay is inert, a low resistance path and a high resistance path for including said relay, actuation of saidreiay causing the telephonic apparatus to become,o erative, and a source of current for supp ying current fiow through said paths, the current flow from said source when the low resistance path is included in circuit atone substation I eing insuflicient to actuate the relay at any other substation, whereby the telephonic apparatus at any other substation remains inoperative.

2. In a telephone system,'the combination with a party line, of a plurality of sub I stations connected therewith, a relay and telephonic apparatus at each substation," said telephonic apparatus when said relay is inertbeing rendered ino erative, a low resistance winding for sai relay included in the substation circuits, t

therelay circuit a high resistance also 111- cluded in the relay circuit, energization of said relay at one substation causing the telephonic apparatus therea't to be rendered operative and the high resistance in the relay circuit to be removed from circuit and a source of current for su" plying said inc and he current flow upon energization of the relay at the one substation being insu'liicient to cause actuation of relays at other substations connected with the line, whereby the telephonic apparatus at the other substations is maintained in an inoperative condition. 'l 3. In a telephone system, the combination witha party line, of a plurality of substations connected therewith, tele honic apparatus at each substation. a re ay at each substation provided with a low resistance winding and a high resistance winding, said tele.-

"phonic apparatus when said relay is inert -e'ing rendered inoperative,- and a source .for'supplylng current to thehne, current flow through said relay upon actuation of with a party line, of a plur connected therewith, telephonic apparatus fifi at each substation, a relay at eaghsubsta zf evepir switching apparatus at one SUbSlZEtiOIiGaUS a "ing" energization of said relay to short circuit the high resistance winding from circuit, the

', ,entlflovv from said source being them upon of'insufiicient strength to cause acme-i tion of relays at other substations through the hi -h resistance'winding. 4. n a-te-lephoneisystem the combination tion provided with a low resistance winding,

and high resistance winding, said telephonic apparatus; when said relay inert bemgij rendered inoperative, a source for sup lyin fcurrent to the line, current flow throng sai relay upon actuation of switching apparatus at one substation causin 'energization of said relay to short circuit t e high resistance winding irorncircuia'the current flow from said source being thereupon oi" insufficient strength to cause actuation'of relays at other substations through the high resistance wind ing, and means at the first substation for.

causing reinelusion in circuit of the high 99 resistance winding whereby the relays at,

other substations may be actuated,

'5. In a telephone system the combinationof substationaj connected therewith, a relay and telephomc 9a with a party line, ofa plurality apparatus at each substation, said telephonic apparatus when said relay is inert beingrendered inoperative, a low resistance winding for said relay included in the relay circuit, a high resistance also included in the relay cir-- 0c cuit, cnergization of said relay at one sub 7 station causing the telephonic apparatus thereat to be rendered operative and-the.-

high resistance in the relay circuit to be removed from circuit, a source of current formssupplying said line and the substation circults, the current flow upon energization of the relay at the one substation being insufii cient to cause actuation of relays at other'substations 'connected with the line, whereby 11s the telephonic apparatus at the othen substations is maintained in an inoperative condition, and means at the one substation for causing reinclusion in circuit of the high resistance, whereby the current flow will be rendered sufllcient to actuate other relays connected with the liner 6. In a telephone system, the combination with a party line, of a plurality of substations connected substation, switching apparatus at each sub-f station for closing circuits through said relay, 1 telephonic apparatus at each substation,

means for rendering said tele. honic appa--j ratus inoperative when said re ayis nert, a 125 current ior the relay source for providing circuits upon. actuat on of the switching n1echanism,and a highresistance and a low resistance path for said'rclay, actuation of.

the switching apparatus at one substation 13C 'lity oi substations 5.

therewith, a relay at each l causing current flow to energize the relay, whereby the telephomc apparatus is rendered operative and whereby the high resistance path is removed from circuit and the low resistance path maintained to cause energization of the relay, the current flow from said source beinginsuflicient to cause actuation of other relays upon actuation'oi the switching mechanism at other substations.

7. In a telephone system, the combination with a party line, of a plurality of substations connected therewith, a relay at each substation, switching apparatus at each sub- "path is removed from circuit and the low resistance path maintained. to cause energization of the relay, the current flow from said source being insu'llicient to cause actuation of other relays upon actuation of the switching mechanism at other substations, and means at the one substation for causing etl'ectiveness of the high resistance path, whereby the current How will be suificient to actuate the relays at the other substations 8. In a telephone system, the combination with a party line, of" a plurality of substations connected therewith, a relay and telephonic apparatus at each substation, a source for supplying current to the line and substations, switching mechanism at each substat on for connecting said source with said relay, a comparatively low resistance winding for said relay, and a high resistance initially included in the relay circuit upon actuation otthe switching mechanism, said telephonic apparatus being short circuited when the relay is inert, energization of the relay causing opening oi said short circuit to render the telephonic apparatus operative and causing said resistance to be rendered inefl ective, the current itow from said source when a relay at one substation is energized being insu'llicicnt to cause actuation of a relay at any other substation through the high rcsistanee initially included in circuit therewith.

Q. In a telephone system, the combination with a party line, of a plurality of substations connected therewith, a relay and tolephonic apparatus at each substation, a source for supplying current to the line and substalions, switching mechanism at each substation for connecting said source with said relay, a comparatively lowresistance winding for said relay, a high resistance initially included in the relay circuit upon actuation of the switching mechanism said telephonic l apparatus being short cilcuited. when the relay is inert, energization of the relay causing opening of said short circuit to render the telephonic apparatus operative and causing said high resistance to be rendered inetl ective, the current flow from said source when a relay at one substation is energized being insutl'icient to cause actuation of a relay at sistance initially included in circuit therewith, and independent means at each substation for causing rcinclusion of said resistance in circuit whereby there will be sufficient current flow to actuate the'relay at another substation.

'10. In a telephone system, the combination with a party line, of a plurality of substations connected therewith, a source of cur,- rent for-supplying the line and the substations, telephonic apparatus and switching apparatus at each substation, and a relay at each substation provided with a low resistance and a high resistance winding, said relay when inert causing closure of a short circuit path about the telephonic apparatus, said relay upon actuation of the switching mechanism being initially energized through both windings, actuation thereupon of the relay causing opening of said short circuit and the closure of a short circuit about said high resistance winding, whereby the relay is maintained in an energized condition through the low resistance winding and the telephonic apparatus maintained in an operative condition, the current from said source when the relay at the one substation is thus energized being insutlicient to cause actuation of the relay at any other substation through the high resistance winding thereof, whereby the telephonic apparatus at all other substations is maintained inoperative. I

11. In a telephone system, the combination with a party line, of a plurality of substations connected therowith, a source of current for supplying the line and the substations, telephonic apparatus and switching apparatus at each substation, a relay at each substation provided with a low resistance and a high resistance winding, said relay Wlien inert causing closure of a short cir cuit path about the telephonic apparatus, said relay upon actuation of the switching mechanism being initially elicrgized through both windings, actua ion thereupon of the relay causing opening of said short circuit and the closure of a short circuit about said high resistance winding, whereby the relay is maintained 1n an energized condition through the lowv resistance winding and the l telcphomc apparatus maintained in an oplerative condition, the current from said any other substation through the high r'e station whereby said liigl'i resistance windi windings upon actuation of the circuit ch angp by virtue of the low resistance winding.

- by'yirtue of the low resistance winding, the

. stations, and an armature for said, relay relay thereupon causing attraction of the artelephonic apparatus is opened and whereby 14.111 a telephone system, the "combine tion with a: partyi line, of a pluralit of sub source when the relay at the one substation is I thus energized being insuflicient to cause actuation of the relay at any other substation through the high resistance winding thereof,

whereby the telephonic apparatus at all other substations vis maintained inoperative, and additional switching means at the one subiiig may be reincluded in circuit whereby suilicient current may flow to energize the relay at any other substation to render the telephonic ap aratus thereat operative.

12. in a te ephone-systen'i, the combination with a party line, ot a plurality of substations connected therewith, telephonic apparatus and circuit changing switching means at each substation, a relay at each substation provided with a low resistance and a high resistance winding, a source of current for supplying the line and the subadapted when inert to close a short circuit path'about the telephonic apparatus, both ing apparatus being initially eiiective toward energizing said relay, actuation of said relay thereupon causing attraction. of the armature, whereby the short circuit about the telephonic apparatus is opened and whereby the high resistance winding is rendered ineffective and the relay maintained energized mature, whereby'the short circuit about the the high resistance winding. is rendered ineffective and the relay maintained energized current flow from said source when the low resistance path at a substationis active be. ing insufficient to cause actuatioirof the l elay at any other substation throughth high resistance winding thereof, whereby the telephonic apparatus at anyotliet'silbstation is maintained inoperative.

stations connected thcrew'ith telep onic apparatus and circuit changing means at each substation, a relayat each,

substation provided: a .low resistancpj and a high resistance winding, a source of current for supplying the line and the substations, an armature for said relay ada ted when inert to close a short circuit path a out the telephonic apparatus, both winding upon being initially effective toward energizing said relay, actuation of said relay thereupon causing attraction of the armature, whereby the short circuit about the telephonic'appaactuation of the circuit changing apparatus ratus is o ened and whereby the high resistance win ing is rendered ineifec-tive and the relay maintained energized by virtue of the low resistance winding, the current flow from said source when the low resistaiice path at a substation is active being insuiiicient to cause actuation of the relay at any other substation through the hi h resistance winding thereof, whereby the to ephonic apparatus ta any other substation is maintained inoperative, and additional switching means for again rendering the high resistance winding effective whereby the current becomes of sui-.

fieient strength to actuate other relay's.

15. In a-telephone system, the combination with a party line, of a plurality of substations c'onnected therewith, a source of current for. supplying the line and substations, telephonic-and switching apparatus at each substation, a relay at each substation provided with a low resistanceand a high resistance winding, an armature for said relay adapted when inert to close'a short circuit path about said telephonic apparatus, actuation of said switching apparatus causing an initial current flow throu h a path including the high resistance win ing, energization thereupon of the relay causing attraction of the armature, whereby the short circuit path about the telephonic apparatus,

is open. and whereb is closed about the gh resistance Win in the relay being maintained energized sole y through. the low resistance wiruilinjg, and an additional switch included in the short circuit path about the high resistance winding, actuation of said additional switch causing reinclusion in windin a telephone system, the c'oinbina-- circuit of the high resistance Y tion with a party line, of a plurality ofsiihstations. connected therewith, a source of current for supplying the line and substa tions, telephonic and switching apparatus'at each substation, a relay at each substation."

provided with a low resistancec nd fli high resistance winding, an armature forsaid re lay adapted when inert-to close Zia-short cuit path about said telcphonichppa actuation of said switching a paratiis ngiai initial current; flow t rou h a lncludmgftne high resistancawinding,

gization thereupon of the relayqgausing at tra slet the ar atu e, wh reby t e c sitsatl ahain tte...iel rho aeap a a short circuit ath is open and whereby a short circuit path is closed about the high resistance winding, the relay being maintained energized solely hrough the low resistance winding, the resistance of the low resistance Winding being ,sufliciently low to prevent sufficient current clusion in circuit of the liigh resistance Windipg, whereby sufficient current may flow to actuate other relays connected in circuit at other substations.

17. In a telephone system, the combination with a party line, of a plurality of substations connecte'd therewith, telephonic aparatus and switching mechanism at each i substation, a relay at each substation having the relay causin a low resistance and a high resistance winding, a source of current for supplying the line and substations, means for normally rendering the telephonic apparatus at each substation inoperative, thecurrent flow upon a c-.

tuation of the switching; mechanism at only one substation being sufficient to cause active energization of the relay through the high resistance winding, means upon energization for maintaining actuation of the relay solely through the low resistance windin independent means for rendering the hig resistance winding effective, and a condenser adapted to be shunted about the relay wind in s.

18. In a telephone system, tion with a party line,

the combinacurrent for supplying the line and substations, telephonic apparatus and switching ap aratus at each substation, a'relay at each su station having a low resistance and a hi h resistance winding, actuation of the switc ing apparatus atone substation causing current flow through the high resistance winding whereby said winding is initially effective in causing actuation of the relay, actuation of the high resistance winding to become ine ective and the relay maintained in an energized condition solely the low resistance winding, the tele honic apparatus at each substation being e only upon energization of the corresponding relay, the current flow, however, from said source being insul'licient upon energization of one relay through the low resistance path to su'fiiciently energize any other relay connected with the line, whereby the telephonic aparatus at other substations is maintained inoperative, means at the one substation for reincluding the high resistance winding in circuit whereby su'llicient current flow may pass through another relay to render the remove the im edance effect of the windings necting a plurality of stations,

mechanism causing reinof a plurality of sub- K stations connected therewith, a source of,

electromagnet the energizing circuit of ective telephonic apparatus controlled thereby operative, and whereby ,two subscribers connected with the same line may converse, and

a condenser at the substations connected to V onic'rircuit.

a telephone line cona source of current connected betweenthe two sides of the telephone line, telephonic apparatus at each station, an electromagnet at each station, a high resistance energizing circuit for said electromagnet, an energizing circuit-of decreased resistance for said electromagnet, mechanism controlled by each electromagnet serving normally to render inoperative the associated telephonic apparatus and when actuated by the energization of the'associated electromagnet to render o jerative said telephonic apparatus, a manna switch at each substation serving when actuated to close the high resistance energizing circuit' through said electromagnet'in brid e of the telephone line, and means controlle by each electromagnet and serving when actuated through its high resistance energizingcircuit to close the energizing circuit of decreased resistance through said electromagnet in bridge of the telephone line said circuit including the telephonicapparatus. 9.5 20. In combination, a telephone line connecting a plurality of stations, a source'of current connected between the two sides of the telephone line, telephonic apparatus at each station, an electromagnet at each station, a high resistance energizing circuit for the electromagnet, an energizing circuit of decreased resistance for the electromagnet, switching means controlled by each electromagnet to govern the operative connection of the associated telephonic apparatus with the line, a switch at each substation serving when actuated to close the high resistance energizing circuit through the winding of the associated electromagnet, and switching I10 mechanism controlled by each electromagnet and adapted when actuated by the associ ated electromagnet to establish through said e L including the telefrom the tele 19. In com ination,

creased resistance and phonic apparatus.

21. In combination, a telephone line connecting aplurality-of stations, a source of current connected between the two sides of the telephone line, telegraphic apparatus ineluding a transmitter at each station, an electromagnetat each station, a high resist-. ance energizing circuit for the electromagnet, an energizing gircuit of decreased resistance for the electromagnet, mechanism controlled by each electromagnet serving normally to render inoperative the associated telephonic apparatus and when actuated by the energization of the associate electromagnet to render operative saidtelephonic apparatus, a manual switch at each substation serving when actuated to close the hi h resistance energizing circuit through said elhctromagnet in bridge of' the telephone s line, means controlled by each electromagnet and serving when actuated through its highre'sistance energizing circuit to close the energizing circuit oi decreased resistance ,through said electromagnet inbrid e of the tele'ghone'line, and means for inc uding a ing of the electromagnet at any station in a circuit sniiplying current to the associated transmitter. "22. in. combination a telephone line con- .necting a plurality ostations, a source of cnrrentconnected between, the two sides of' thectelephone line, telephonic apparatus ineluding a transmitterat each, station, an

electrornagnet ateach station, a high resistanceenergizmg cn'cuit for the eleetrornagnct,

by each eleetroniagnetfand adapted w-hen actuated by the associated electromagnet to establish through said electromagnet the enscam? ergizin circuit of decreased resi ce, and means ocated at each stationfor u drug a winding of the electr'ornagnet at that station ,tWo energizing coils normally in series, and

means for cutting out one of the coils when the relay is operated, substantially as and for the purpose specified.

24. In a look-out for party-line telephone system, a mainswitch, a relay adapted by the operation of said main switch to be bridged across the line, and a talkingcircuit adaptedby the operation of said relay to be also bridged across the line, energizing coils in series on said relay, and means for cutting out one of said coils when. the relay is oper ated to connect the talking outfit, substantially as specified. y

In witness whereof, I hereunto subscribe my name this fifteenth day of February A. D., 1905. i

ARTHUR F. POOLE.

Witnesses:

'JAsoN C. STAMP, G50. Bnownn.

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