USRE15389E - Poration oe new yore - Google Patents

Description

c. L. GOODRUM. AUTOMATIC mam-one EXCHANGE svsrsm.

' APPLICATION FILED FEB- Za, 1915- Reissued June 20, 1922. 15,389.

5 SHEETS-SHEET 1.

TO MAIN BATTER) //7V/7f0/.' (bar/es L. Good/um.

' Reissued une '20, 1922.

C. L. GOODRUM.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM. nrrucmon FILED FEB-28,1916.

5 swans-sun 2.

Char/e: L Good/um. ,5 j W V C.L.GO0DRUM.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED FEB. 2B. 1915.

1 5,389. 5 SHEETSSHEET 3- Reissued June 20, 1922.

iv ba/rry invenfor: Char/es L. ood um by M C. L. GOODRUM. AUTOMATIC TELEPHUNE EXCHANGE SYSTEM.

APPLICATION FILED FEB- ZB, 1916-" Reissued J line 20, 1922.

5 SHEETSSHEET 4.

/n venfor: Ch ar/es L Goodfl/m C.L.GO0DRUM. AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

I A PPEICATIDN EILED'FEB. 28, I916. Reissued J une 20, 1922.

1 5,389 5 SHEETS-SHEET 5.

//7 v e I? f 0/ Char/es L aqdrum. y

UNITED STATES PATENT OFFICE.

CHARLES LANE GOODRUM, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS,

TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A. COR- PORATION OF NEW YORK.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Specification of Reissued Letters Patent. Reissued I -113 20, 1922.

Original No. 1,156,475, dated October 12, 1915, Serial No. 249,380, filed March 10, 1905. Application for reissue filed February 28, 1916. Serial No. 81,049.

To all w ham it concern.

Be it known that I, CrIARLEs LANE Goon- RUM, a citizen of the United States, residing at. New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Automatic Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to automatic telephone exchange systems, and more particularly to systems of this type adapted for party line service.

One of the objects of this invention is to provide means whereby one only per connection of a plurality of subscriber stations on a line may be selectively called by any other subscriber in the exchange system.

Another object of this invention consists in the provision of means in an automatic telephone system, whereby a selectively operable switching device may be caused to select and seize certain lines irrespective of the busy or idle condition thereof, said switching device being provided with testing means for preventing the seizure of busy lines, if said first mentioned means is not operated.

Another object of this invention resides in the provision of means whereby a subscriber on a'party line is enabled to make a revertive call; that is, to call another subscriber on the same line in spite of the busy test placed on the test conductor of each line when the line is taken for use.

A further object consists in means to prevent a'release of the switches by a party line subscriber as long as the telephone receiver of another subscriber station connected to the line is off the switchhook.

Other features of the invention will become apparent from the following descrip tion and the appended claims.

The invention is directed to a system in which every party line is provided with groups of outgoing multiple terminals equal in number to the number of subscribers on the party line. Each subscriber on a party line is signaled with a characteristic kind of ringing current, and the outgoing terminals,

of the various party line subscribers that:

are signaled by the same kind of current, are gathered or grouped in certain of the switching devices of the system. These switching devices are individual to a particular type of signaling current, which will selectively signal the subscriber station individual to the terminals selected by the switching device.

Any system equipped with party-line service must naturally be provided with means so that a subscriber at one of the subscriber stations of the party line can signal and communicate with a subscriber at another substation on the same line. The o-rdinary busy test in such a case will give a false busy indication, because a test guard has been placed upon the multiple terminals of the line by reasonof the use of that line in calling and not because it is engaged by some other subscriber. This false busy is obviated by momentarily removing the same when the line and test wipers of the connector switch are brought into contact with the line terminals of the-calling subscribers line.

In automatic telephone systems the release of the switches used in setting up a connection is ordinarily accomplished by the subscriber hanging up his receiver. This operation would result in a premature disconnect on a connection involving a party line subscriber in case-one of the subscribers on the party line other than the one engaged in conversation were'to remove his receiver from the switchhook and, finding the line busy, restore. To avoid a premature disconnect of this kind means are provided to prevent the release of the switches by a party-line subscriber as long as any other subscriber station onthe line is taken for use.

The party-line scheme is shown as applied to an automatic system using switches of the Strowger type, and it will be quite obvious that anyone skilled in the art could readily adapt this system to any of the other types of well known automatic switches. The general operation of an automatic system using Strowger switches is 'old in the art and well known, and the description herein will be restricted, therefore, to a brief outline of the general operation of this system, emphasizing the features appertaining to the partyline scheme.

T he invention is illustrated in the accompanying drawings in which- Figure 1 shows the circuit of the calling subscribers line and its'associated first selector switch; Fig. 2,'-the circuit of one Or thesecond selector switches 3, the cire cuit' of a connector switch withfiwhich are associated the called Subscriber terminals; Fig. 4, the circuit of a called'substation and its associated first selector switch and Fig. 5-is'ai diagrammatic showing of "a, party line illustratingwthe method ofgrouping the various party-line signaling'sources with their associated connector switches. a n

The invention may be best described by I first trajcinga call fronjiacalling, to ,aacalled subscriber through the various switches v without any reference to the party-line features associated therewith, after which the:

method {of .incorporating the party-line I scheme in thesystem will "be explained When a calling subscriber desires to make a call he' will remove his receiver from the switchhook andoperate his calling trans-' ing operated his calling transmitter forthe mitter for the thousands digit in the number of the called subscribers line desired. It will be assumed for convenience in description that :thenumber oi the subscriber de sired is4856; The calling subscriber havnumeral will thereby place fiourvsuccessive gmunds cn the verticalside of the line.

These groundswill complete a circuit from,

the ground shown at the impulse transmit I ter at the calling subscriberls station through the resistance 9", contact springs 66*, m oontactspringsc a, wire -to the vertical side ofthe line .3 and thence through the side switch arm f, wire vertical relay D, wire 31, contact springs 70 7:3 and is to the conductor 32-andthe common battery. Com

sequently v-erticalrelay Dwill be operated four successive times and will close the cirsuit of the vertical magnet a like number of times over a circuit which maybe traced I selector switch tov a osition whereits wiper fromthe ground 9., contact spring cl, to contact springs p iand p" of the private magnet P, and through the vertical magnetl)" and the wires 39 and 32 to the common battery. The successive energizations of the vertical magnet D will elevate the shaft of ithe'first contacts in and b W111 be in alinementwith the multiple contacts m and m which are connected to trunksleading to a second se lector innthe four thousands group.

--After the impulse transmitter at the; callting subscribers station has transmitted the.

four grounded impulses to the vertical side oii-the linc, a' single w grounded impulsewill befltransmitted over the rotary S1618 of the line. This circuit may be traced from the ground atthe subscribers station through the resistance r, conta'ct springs a and a contact sprlngs c and a, w1re4, "the vertical: side oit' the line '12, side switch arm f conductor 34, rotary relay E," conductor 33 andz'the contact springs J6, 7c, and wire 32 to \battery. The subsequent operation of the a rotary relayE willv close a circuit-from the ground g byway of relay spring 6 through the p ivate magnet l? and wire 32 to 'battery, This. will cause the operation of the private magnet P which, inthe well known manner, will move the side switch arms f, 7,

f f into'theirsecond position. Inythis po sition of the side switch a circuit is closed from ground through the side switch arm f to the rotary magnet E and over the Com ductors 39 and 32 to battery.

The operation of-the rotarymagnet moves the wiper contacts *0 and 0 over the multiple contacts m and m and likewiseupon each operation interrupts its :own circuit. When the. contact wiper o rests upon a multiple contact m which is busy, that is, one which has been connected to the contact wiper o of some other-selector circuit, this contact will be grounded and a circuitwill be established from the ground on the corn tact mflby way of contact wiper oflthrough the relay J, conductor 53, side switch arm fflconductor 40, private magnet P, andconductor; 32 to battery; This will maintain private magnetP in its energizedposition until anon-grounded "nonbusy contact m is found, "at which time the private magnet P will be deenergized andfltheiside switch will move into its third position extending the lector switch'shown in Fig. 2. i The. calling subscriber will nextoperate his impulse transmitter soas tosend' eight grounded impulses over the vertical side of the line. in order to raise the second selector shaft to the eighth l-evelof the selector contact bank,

whichcontains trunks leading to the connector switchto the contact bank of which is vwired the desired subscribers line, nu1nber 4856. These eight grounded impulses will flow from the subscribers station over thez verticalside of the line to the side switch arm f of the first selector through one winding'of the differential relay 0, the vertical contact wiper 1), contact terminal m, the conductor 13, side switch arm 7 conductor 45, vertical relay D and wire 32 to battery.

These (eight impulses; over the vertical side of. the line will cause a like number of operationsoi the vertical relay D Each operation of the vertical relay D willclose a circuit from the ground spring g to thecontact springs of the private magnet *P the vertical magnet D and conductor 32': tov baxt= tery, The successive energizations of the vertical magnet D will elevate theshaft of the a second selector switch to av -position where'its wiper contacts o and n will be in alinementwith the multiple contacts m and war, which are connectedto trunks vleading to calling subscribersjline to the second sei connector switches in the eight hundreds groupr After-the impulse transmitter-at the calling subscribers station has transmitted the eight grounded impulses to the vertical side of the line, a single grounded impulse will be transmitted over the rotary side of the line. This circuit may be traced from the ground at the subscribers station to the rotary line wire 12, the side switch arm f the second winding of the differential relay 0, contact wiper 0, contact m, side switch arm f conductor 46 and through the rotary relay E and the wire 32 tobattery. The subsequent operation of the rotary relay E will close a circuit for the private magnet which will move the side switch arms of the second selector into their second position, whereupon the rotary magnet will be switched into circuit and the contact wipers of the second selector will automatically huntfor an idle trunk to a connector switch in a manner identical to that described in connection with the first selector. The calling subscriber is now connected through the first and second selectors to a connector switch which contains the number of the desired subscribers line. He will consequently operate his impulse transmitter so as to send five grounded impulses over the vertical side of the line in order to raise the connector shaft to the fifth level of the contact bank which contains the contacts of the desired called subscribers line, number 4856. These five grounded impulses will flow over the vertical side of the line to the first selector switch, through the winding 0 of the differential relay, over the vertical side of the trunk leading to the second se lector switch and thence over the vertical side of the trunk leading to the connector switch, where the circuit may be traced through the vertical relay D conductor 56, contact springs 57, 58 and 59 to conductor 32 to battery. The subsequent five energizations of the vertical relay D will close a circuit from the grounded spring 9 and spring d of the vertical relay D, the contacts p and p of the private magnet P conductor 65, side switch arm f vertical magnet D and conductors 67 and 32 to battery. These impulses will raise the shaft of the connector switch so that the contact wipers c and w will be raised in alinement with the contacts m and m of the fifth .bank of the connector switch, which bank contains the connector terminals of the desired subscribers number 4856.

Immediately after the five grounded impulses have been sent over the vertical side of the line, a single grounded impulse will ond selector switch, side switch arm 7", rotary side 16 of the trunk leading to the connector switch, rotary relay E, contact springs 63 and 62 of the ringing relay W and contact springs 58 and 59 of relay V, to conductor 32 and battery. This will operate the rotary relay E, thereby closing a circuit from the grounded spring 9 through the springs of the rotary relay and the winding of the'private magnet P to battery. The subsequent operation of the private magnet P will move the side switch of the connector into its second position. The calling subscriber will next send impulses equal in number to the units digit of the number of the desired subscribers line. As previously assumed, the number of the desired subscriber is 4856, and consequently the calling subscriber will send six impulses over the vertical side of the line which will cause six operations of the vertical relay D over the circuit just traced. However, since the single grounded impulse which was sent over the rotary side of the line moved the side switch of the connector into its second position, the operation of the vertical relay in this case will close a circuit that may be traced from the grounded spring g by way of the spring (2 of the vertical relay, the springs 39 and p of the private magnet P conductor 65, side switch arm 7, conductor 68 rotary magnet E and conductors 67 and 32 to battery. The rotary magnet will, therefore, be operated six times and connect the contact wipers '0 and 12 to the contacts m and m of the desired subscribers line 4856.

After the six impulses have been sent over the vertical side of the line, a single impulse will be transmitted over the rotary side of the line which will operate the rotary relay E and this in turn will operate the private magnet P in a manner similar to that described in connection with the grounded impulse which was transmitted over the rotary side of the line directly after the first set of impulses transmitted to the connector switch. If the subscribers line is busy the multiple contacts m of this line will be grounded, and a circuit will be closed from this ground through the side switch arm 7, contact springs 79 and p of the private magnet P the release magnet J and conductors 750 and 32 to battery. Consequently, before the private magnet is deenergized the release magnet J 2 is operated, and the vertical shaft and the side switch of the connector will be returned to normal.

Hence, when the calling subscriber attempts to ring the desired subscriber by depressing his ringing key and closing the contacts a, a, he will complete a circuit which maybe traced from the ground at the subscribers station through resistance r, by way of contact springs (L -a a on, a, and

When the vertical shaft oii'the connector ate-a5 to'the verticalside o'flthe line 11, side switclrarm f, contact wiper 1), multiple contact m, side switch arm .75, contact. wipenm multiplewcont'act m conductor 15,

, vertical .relay D coi'iductor 56 and .the con tactsprings 57, 58uand of .rel'ayVtof battery. This willoperate the vertical reA lay D, and as theconnectorfswitch has" been returned to normal the operation of this nelay, as previously described, will energize thewyertical-magnet I) and elevate thever' tical'sha'ft. of theconnector switch one step.

switch has beenthus displaced fromnormal, acircuitewill be completed from ground through :one winding :of the busy-back transformer, condenser 101, oil-normal springs 1.02; and 108, side switch. arm f,

25. switch arm f wiper, o contact m and spring 7:1, "rotary side of the trunk 16, contact m wiper"ofi sicleswitch arIn f?,concluctor 14, contact on, wiper a), side switch arm f rotaryfiside of the line .12 through the subscribers .loop and back. to the -ver-; tical side'of the line 11, side switch arm f, wiper o, contactm, conductor '13, side i thence through the vertical relay D con.-

, ductorf56 and contacts 57,58 and 591 to wire 32fandubattery- The completion of this circuit will. send the busy. tone back to the callingqsubscriber, informing him thatthe party desired is busy, and he will hang up his receiver. When hanging up his receiver the calling subscriber willmomentarily ground both sides. of the line which will simultaneously energize the, vertical relay 1) and the rotary relay E and this will release the switches as hereinafter described.

. In case the desired party is not busy the .40

last impulse on the rotary side; of the line,

as previously' explained, will operate the rota-ry relay E4, which in turn will operate the private magnet P and this will move the side'switch into its third position- The calling subscriber will then be connected through the .first and second selector switches and the connector switch direct to. the desired subseribers line, number 4856.

The calling subscriber mua next send signaling current over the rotary side of: the

desired subscribers line so as to operate the ringerQ. This is accomplished. by closing qthe circuit at the ringingkey springs 64 and a which, as previously described, will operate the vertical relay D5- The opera-- tion of this relay will close a circuit from the grounded springg by wayo'f conductor 64:to the contacts 79 and 79'. of the private magnet Pflside switch arm-1f the ringing 560 relay W'andconductor '32 to battery. The subsequent operation olf the ringing: relay will DOIIHBCtwtllI-J ringing generator by means of springs 61 and 71 'to-the. rotary sideof.; the"]ine audit-hence through the side switch arm f ,'contact wiper o contactm",

to condenser and ground, ,This willgsigllal the called subscriber in the regular way,

and when he removes.his-receiver. from the switch hook he wlll close a circuit from battery,through-relayVstothe rotaryside p of the line and thencexby;.,way of spring 71 ofthe IringingrelaylV, side switch arm f flwviper '0 contact wa through the subscribers loop. to the vertical sideotthe line,

contact 072 contact wiper. o sideswitch 22mm ft, the verticall-ine springsof the]ring I and the winding 7 ing relay W, conductor 15 of relay V to ground.

A Relays V and V 'are constructed so as to. have the same electrical characteristics;

However, relay V is equipped: with set of springs which make contact when the relay is energized, whereas the springs of relay 1V serve to break contact when it is energized. Consequently, if these relays are simultaneously energized, the springs controlled by the armatures of the respective I relays will afiect their-operation in such a manner that the springs of relay Vwwill breakcontact before the springs. ofrelay V make contact. Conversely, when the relays are simultaneously deenerg'ized-their respective spring combinations will affect the relay operation so that thesprings of relay V" will break contact before thesprin-gsoff relay V make contact. Therefore, the springs 57, 5.8 and 59 of relay V are ,separated and the connections of .relays*D* and E are broken before :therelays X and Y and the common battery are bridged across thecalling line circuit. In practiceiit might be difficult to obtain relays of like electrical characteristics. However, notwithstanding this :fact and assuming that relay V -,might close its contacts before the relay V opens its contacts, the: time interval during which the contacts of relay V. and V are :both closed would be of such short duration that a relaywor elec-tromagnet included in such circuit would not receive sufiicient current for its operation. Obviously if such a condition; should arise it couldgbe readily overto pull up and release.

It willlbe noted that the circuit '1' ust traced, containingv relays V and V, is connected to theline wires of theuconnector circuit on the called side of the condenser C. This circuit consequently supplies talking cur rent to the called subscriber. Theoperw tion of relay V disconnects the-battery which isconnected tothe vertical and rotary relays D-and E? respectively, whereas the come by making the relay V. slightly slow.

operation of V completes acircuit from the subscribers loop back to the vertical side of thelinew and thence by way of conductor 76 through springs 77 and 78and relay X to ground. Talking current is, therefore, fed to the calling subscriber over a circuit which includes relays X and Y, and the supply of this talking current is controlled by the called subscriber by means of relays V.

Relays X and Y like relays V and V are designed with like electrical characteristics and control respectively a break and a make contact. These two relays function exactly the same as relays V and V, and obviously relay Y could also be made slightly slow to pull up and release. Therefore, when these relays are simultaneously energized, the break contact of relay X will open before the contact of relay Y closes, and thus the release circuit, which is controlled by the simultaneous closing of the contacts of these two relays, will. not become operative at this time.

The connection has now been traced to the point where the subscribers are talking. WVhen the subscribers have completed their conversation and hang up their receivers, the switching apparatus will be returned to normal. If the calling subscriber hangs up his receiver before the called party does, the subscribers loop will be opened at the calling partys station and thus will open the circuit containing the relays X and Y which, therefore, will be deenergized. How ever, as the subscriber momentarily grounds both sides of the line directly after the sub scribers loop isopened, the relay Y, which is connected from battery to the rotary side of the line, will be momentarily energized and again close its contact. Consequently, as relay X is deenergized and relay Y momentarily energized, a release circuit is closed which may be traced from the ground connected to the side switch arm 7" (Fig. 2), through. the release relay J, to the contact wiper o thence by way of contact m, the armature and contact spring of relay X, and the armature and contact spring of relay Y by way of conductor 70, the release magnet J and the conductors 750 and 32 to battery. Thus the release magnet J of the connector switch will be operated, and the switching apparatus associated with the connector switch will be restored to normal.

The release relay J of the second selector in operating closes a contact which completes a circuit from the ground connected to the side switch arm f (Fig. 1) by way of'the release relay J, conductor 52, contactwiper V contact MP, the contact springs of relay J and the release magnet I of the second selector to battery. The operation of the release magnet I restores the apparatus of the second selector switch to normal, while the operation of the release magnet J closes a circuit from ground through the contact subscriber-b station.

springs of relay J, the release magnetI and conductors 4.2 and 32 to battery. The subsequent operation of the release magnet I restores the switching apparatus of the first selector.

Should the calling subscriber restore his receiver before the desired called subscriber answers, he will simultaneously energize relays D and E by the momentary grounding of both sides of the line. The simultaneous operation of these two relays will complete a circuit from battery by way of conductors 32 and 7 50 through the release magnet J and thence through the contact springs and d to the'test contact m, the contact wiper 0 the release relay J and the side switch arm f to ground. The subsequent operation of the release magnet J will restore the connector switch to normal, and the first and second selector switches will be thereafter restored to normal in a manner similar to that previously described.

In case the. called subscriber hangs up his receiver before the calling subscriber, the subscribers loop will be opened at the called This will open the circuit containing the relays V and V which, therefore, will be deenergized.v However, when the callingv subscriber simultaneously grounds both sides of the line in hanging up, the relay V" will be momentarily oper-- ated and this will close a circuit from battery by way of conductors 32 and 7 50 through the release magnet J springs 743 and 742 of relay V, and springs 74:1 and 740 of relay V to multiple contact m and thence by way ofv contact wiper o, the 're lease relay J and the side switch arm 7" to ground. The completing of this circuit will operate the release magnet J and restore the connector switch to normal. The subsequent release of the first and second selector switches will be effected in a manner similar to that previously described.

The manner in which a call is initiated by the calling subscriber and is set up by the switches and extended to the called subscriber has been described in the foregoing description of the operation of the system. A more detailed consideration of. the partyline features of this system will now be undertaken. I j 1 Referring to Fig. 1, it will be noted that four subscribers stations arev connected to the subscribers line, one of which is illustratedin detail, whereas the other three are shown diagrammatically. Associated with the line wires connected to the first selector switch in Fig.1 are shown four sets of contacts representing'the line and test contacts of the party line at four different groups of connector switches. Each one of these In other scriber A number 1211, subscriber A number'1311, and subscriber A number 1411. Then as the subscribers party-line multiple is grouped in the connector switches, in accordance with the signaling source with which the connector switches are associated, a calling subscriber will automatically select the particular selective signaling current required to call the particular subscriber as a result of the number which has been allotted to the particular subscriber. Thus, whenever an exchange subscriber calls the partyline subscriber No. 1111, the second selector will be directively set by the calling subscriber so as to hunt and select an idle trunk in the first level of the selector contact bank.

The contacts of this bank are wired to a group of connectors associated with a 20- cycle ringing generator and, therefore, the calling subscriber will automatically select the signaling current required to ring partyline subscriber No. 1111, as a result of the regular operation in setting up a call through the switches to complete a connection. Likewise, when partyline subscriber No. 1211 is desired, the second level of contacts will be selected, which cont-acts are Wired to a group of connectors associated with the LO-cycle ringing generator. To

call subscriber 1311 the third level will be selected, the contacts of which are wired to a group of connectors associated with the 60-cycle ringing generator, whereas the multiple connector terminals of party-line subscriber 1411 are located in the banks of the, connector switches which are wired to the fourth level of contacts in the second selector switches, etc.

The manner in which a party-line subscriber calls and signals another subscriber on. his own line will now be described in connection with Fig. 5. Suppose that subscriber A initiates a call, has set up the connection through the first selector switch and has been connected, as shown, to the connector switch, with which is associated a signaling current of 20 cycles. It will be assumed, for example, that the signaling device at the subscribers station A who originated the call, responds to a ringing current of 80 cycles, and that he desires to call the subscriber at station A whose signaling device responds to a signaling current of 20 cycles. Y Vhen the calling subscriber transmits the grounded impulses for setting up the switches,-they pass over either side of the line through one winding only of the differential relay 0, and thence through the various vertical and rotary relays associated. with the switches used in setting up the connection. Each impulse over either side'of the line will, therefore, momentarily operate the differential relay 0. The relay will not be operated by a current flowing 6 serially in the line circuit. As soon as the first selector switch associated with the calling subscriber has been displaced one step from normal, a busy potential is placed on the test lead of all the multiple contacts associated with that line over a circuit, which may be traced from ground by way of springs a and 14, contacts 0' and 0 and the various multiple test contacts m m, m and m.

When the calling subscriber sends the final impulse over the vertical side of the line to the vertical relay D of the connector switch, thereby connecting the wipers of the connector switch with the contact terminals of the desired line, an impulse is sent through the winding of the differential relay 0 connected seriallyin the vertical side of the line. This will energize the differential relay 0, thereby breaking the contact between 0 and 0, and this will momentarily remove the busy potential which has been placed on the multiple test contacts of-the line. This momentary removal of this busy potential will permit the seizure by contact wipers '0 of the connector of the multiple connector terminals of the line of the calling party-line subscriber.

As has been assumed and as shown in the circuit drawing, Fig. 5, the party desired is A whose signaling device responds to a ringing current of -cycle frequency. Consequently, when the calling subscriber operates his ringing key, he will momentarily energize the vertical relay D asso-- ciated with this connector switch, thereby placing ground on the spring cl, and as the side switch is in its third position it will close a circuit through the ringing relay W which will therefore be operated. The operation of this relay will connect the QO-cycle generator to the spring, 71,-and thus this signaling current will be transmitted over the side switch arm f the rotary wiperof the connector switch and contact m to the rotary side of the line, and through the signaling devices of all of the party-line subscribers in parallel. As the subscriber A is the only one equipped with a signaling device which will respond to a ringing current of 20 cycles, this subscriber will be the only one signaled. When he removes his receiver the two subscribers A 'and A of the party line will be connected for conversation.

In a party-line system in which the sub-. scribers ringers are bridged from either side of the line to ground, special provision must be made for the actuation of the ringers tapped from the vertical side of the line. The resistance r at the subscribers station is used for this purpose. It will be evident that if there was no resistance in the circuit to ground, the subscriber upon depressing his ringing button would put a shunt circuit to ground on the vertical side of the line.

Thisshunt circuit'would rob the ringers of the necessary currentrequired, for their operation; The resistance r is, therefore, made high: enough to prevent the shunting of the major portion of the ringing current, which will seek a, path through the desired subscribers ringeror signaling device. The resistancer at the subscribers station is further useful in preventing a premature d1sconnect onv a party-line connection. Thus this resistance. r prevents a premature release-1 asubscriber on a party line who cuts in on a connection which had been pre viously established with another subscriber on the-Jsame part line. It will beevident P that-ifs connectlon with a1party-line sub Jscriber has been established; that a second party on: theparty line, upon'removing his receiver? andicuttin'gj in on the-connectionv and then restoring, momentarily. ground both sides ofkthe line; Therefore, if the resistance r were notincluded'in the grouncl tap-at the subscribers station, both sides of the line would obtaina momentary connection direct. to ground. This direct ground tap tOvthB vertical side of the line. would shunt out the relay of the connector circuit, and the deenergization of this relay [would close the release circuit and restore the: switches to normal, as previously described. However, when thefground tapat the; subscribers station iswired through the resistance r, the relayX is connected to ground in parallel with the resistance r, and in thisinstance sufiicient current will flow through the relay X tomaintain'it in its operative position and thereby prevent the premature disconnect.

Obviously, this invention is not limited to the specific arrangement herein shown and described, but is, capable of many variations 7 and applications without departing from its spiritand scope; Y

:I claim. Y a I 1. In an: automatic telephone system, a

central exchange -including-a connector switch, subscribers lines extending therei from, a, plurality of subscribers stations, a

[plurality of sour'cesof characteristic signal- 5 0 ing current, each connector switch being associatedlwith but one of saidisources, a sig-l nailiri'gdevice individual a each-subscribers station responsive; to t a characteristic signaling current, and a plurality of salddev ces "eonnectedte oneof said knee, and means wherebysubscribers connected to otherlines may select and call one of thesaid plurality of subscribers; U v 2;"In a telephone system, a central ex,

change including a connector switch, subscribers lines extending therefrom, a plurali ty of subscribers stations, a plurality of sources of; characteristic signaling current, oneofsaidsources bemg associated wlth each connector switch, a. signaling device indi individual subscriber desired.

vidualv to each station responsive to acharacteristic signaling current, a plurality of said devices connectedtonone of said lines, 1

and means at the central station controlled by the subscriber for automatically selecting and calling any one ofsa-id plurality of sub scribers. o

3. Ina telephone exchange system, a sub scribers line and a plurality ofsubscribers? stations connectedv thereto, automatic connective means for saidline common to all of said'subscribers whereby the line may be connected with other lines as determined by any one of: saidsubscribers,andsother'autov matic; connective means associated with the firstmeans butindividua-l to theseveral sub scribers on theline whereby any one sub scriber can be selected called to thecex I clusion of the others.- H e I 4. In a telephone-exchange system, a, central ,oflice' and subscribers lines leading therefrom, a plurality! of subscribers" 'sta tions on one line, automatic switching ap paratus at the central oifice for interconnectmg the lines, a portion of said apparatus being individual to the lines whereby calls lncom ngfrom the subscriber to the central oflice may result in connection with other subscribersas required, and another portion oi said apparatusv common to. the subscribers,

'togetherwith means whereby the selection of a subscriberstcommonswitching apparatus-will automatically select suitable current to send over the proper path to call the .5. In a telephone exchange system, a central office and subscribers? lines leading therefrom, one or more of said lineshaving a plurallty of stations connected thereto, au-

tomatic switching aparatus for each line nection terminalsindividual to" the line, each brought nto servlce in responseto-a call over itsline'ior connectionwith. other lines,and otherconnectionterminals indi-" vidual to the subscribers forcalling said subscribers in completing connections originating at other stations, each adapted for" call ng its own qsubscr-iber. only, rrespective of other :connections.

* 6. In a. telephonesystem,a; plurality of, it it lines eachliaving a plurality of stations, said stations, being provided with selectivesig naling devices, aplurality oi switchesfor said. lines to, which i said lines are connected in multiple, said switchesibeing arrangedin l groups, each grouphavmg a different selecy tive signaling means,each;stationot each, line being repre'sentedln the group; having;

selective signaling meansficorresponding in character to the selectivesignaling devices of saidstation. I '7. Ina telephone system, a plurality of l nes each havil lg a-qplurality. of. stations,

rec

105 wherebythe lines may-be interconnected, -1 csaid switching apparatus comprising con each station on each line having a ringer of differentcharacter, a plurality of switches for each line to which said lines are connected in multiple, said switches being arranged in groups, each group having a source of ringing current of different character, each station of each line being represented in a group having ringing current corresponding to the ringer of said station.

8. In a telephone system, the combination of two telephone lines, a plurality of substations on one line and a plurality of terminals for said line corresponding to each of the substations thereon, each of said terminals being arranged in a different switch having different selective signaling means, selective signaling devices at the said substations corresponding to the signaling means of its switch, and means for connecting the other line with one of said switches.

9. In a telephone system, the combination with two telephone lines, a plurality of substations on one of said lines and a plurality of terminals for said line corresponding to each of said substations, of a plurality of devices for providing signaling currents of different cycles, a signaling instrument adapted to respond only to one of said cur rents arranged at each substation, a plurality of switches common to the other line and adapted to connect it with one of the terminals of the first mentioned line, and means for applying the proper signaling current to the connected line.

10. In a telephone system, the combination with two telephone lines, a plurality of sub stations on one of said lines, and a plurality of terminals for said line corresponding to each of said substations, of a plurality of devices for providing signaling currents of different cycles, harmonic signaling instruments each responding to one of said currents arranged at the substations, and mechanism for connecting the other line with terminals of the first mentioned. line corresponding to a particular substation thereon and applying to the connected line the proper current for operating the signaling apparatus corresponding to the selected terminals.

11. In a telephone system, the combination with an exchange, telephone lines extending therefrom each having a plurality of terminals arranged in groups, switching mechanism cooperating with said groups of terminals for'connecting the lines, devices for supplying different signaling currents, of a plurality of substations on each line, harmonic signaling instruments each responsive to one of said currents one of which is located at each substation on each line, and means for applying the different signaling currents to the different groups of terminals.

12. In a telephone system, the combination with an exchange, telephone llnes extending therefrom each having a plurality of substations and a plurality of terminals, the terminals of each line corresponding to the re spective stations thereon, those of similar stations on the several lines being arranged in groups, of devices for supplying different signaling currents to the different groups of terminals, harmonic signaling instruments located at the various stations, and switching mechanism cooperating with the terminals to connect different telephone lines.

13. In a telephone system, the combination with an exchange, party telephone lines extending therefrom provided with a selective terminal for incoming calls and with as many terminals for outgoing calls as there are telephone and signaling instruments on the line, the corresponding outgoing terminals of the several lines being arranged in groups, of means for supplying to each of said groups of terminals different signaling currents adapted to call stations of the class only to which the corresponding party-line instruments belong, and means for connecting the incoming terminal of one line with one of the outgoing terminals of another.

let. In a telephone system, the combination with a plurality of party lines each connected to a plurality of subscribers tele phone and harmonic signalinginstruments, said signaling instruments on the several lines being divided into classes each of which is adapted to be operated by a different signaling current, multiple contacts for each line corresponding to the several telephone instruments thereon which are arranged in groups corresponding to said classes of subscribers instruments, of a separate source of signaling current for each of said classes of instruments, means for applying said current to the corresponding groups of terminals, and switching devices cooperating with the latter for connecting one telephone line with another.

15. In a telephone system a central exchange including a connector switch provided with movable and stationary terminals, a plurality of sources of characteristic signaling current, a plurality of sub scribers lines, a plurality of subscribers stations connected to said lines, a signaling device individual to each station responsive to a characteristic signaling current, and means at the central exchange controlled by the calling subscriber for automatically connecting one of said sources to said terminals to call any one of said plurality of subscribers.

16. In an automatic telephone system, the combination with subscribers party lines, of a plurality of sources, of characteristic signaling current, a signaling device at each substation responsive to one only of said sources, connector switches each associated with one only of said sources, and means to group the subscribers line terminals at the r ti'vely, called: 15w

connector switches so that-jar subscriber on a partly; line can be selectively called.

17: Inan automatictelephone system,"thecombin ation with subscribers party-line circuits, of a pluralitysof sources oi. characteristic signaling current, signaling devices at the substations responsive to one s only of said sources, connector switches, one of said sourcesbcing individual, to a group' of said switches, saidparty line being multipled to a plurality of saidgroups; and; means to select aXparticular switch in a group whereby a1subscribeno11 party. line-can be selec- 18. In an automatic telephone systennjthe combination; withparty-line circu1ts, of av plurality of sources of characteristic signalingqcurrents, signaling devices at the substations; responsive to one only ,i of said sources, groups of; subscribers lines,ja plurality-lof connectors each" provided ,;to serve dilferent: group of lines, andmeanswhereby a signaling sourcei individual, to said group will selectively ring a, subscriber on a partyline. r, r I

19. In an automiatic telephone system, the combination; with party; lines, groups of switches automatically controlled by the subscriber to establish a connectionila plu ra-lity of sources ofcharacteristic signaling current, eachof said: sourcesbeingindiyidual to a roupiofxsaidswitches,andmeans for selectmg a particular source of said signaling-current, at oneoranother group of said, switches to selectively signal oneonly of the subscribers on .a'party line.

20. In a telephone exchange system, a

- telephone line a plurality of substations on said. line, means adapted to place atest guardon said hne when taken for use, and

. means-for} momenta-rily removing said test guard the instant. connection is completed when the calling and called subscriber Sta tions are both connected to thesame line.

21. Ina telephone system, a telephone line, a; plurality of subscriber stations on said line, means adaptedto.,place test guardon saidline when it istalten for use,

and means actuated when" one of the sub- ,scribcrs{on saidlineis, calling to momentarily; remove said test guard the instant disconnection iscompleted with another subscriber station on said linea 22. In an automatic telephone system, the combination 'with subscribers lines, aplurality of substationsconnected to some of sa d lines,v automatic switching devices controlled by the subscriber torestablish: connection between two of sa1d lines, of means at the subscriber stationito automatically release said devices and means to prevent the. release ofjsaid-dev-ices by a 'subscribertoua r part line when another subscriber station Ilsationa party lineisl connected, for'conver- I minals. r 7

23. In an automatic telephone system, the combmatloirlwith subscribers llnes, a plur ality of subscribers stations connectedto some of said lines, automaticswitching devices, controlled by the subscribers to estabt lish a connection between two of said sub-v scriber stations, of means to release said devices when one of said connected Sill)? scribers hangsup his receiver, and means to prevent the: release of said devices by 1 subscriber on a party line when the receiver of anothersubscriber on the party line is oil the switchhook.v v

24. Ina telephone exchange: system, a line, answering and callingterminals for saidline, a connecting circuit, means: for extending said circuit to one of saidtermin'als,

means operative upon extending, said (circuit to one of said terminals for causing said line to test busy at the other terminal, and means for removing the busy test from the last mentioned terminal while the connect of said tering circuit is extended to, one

25. In a'telephone exchange system, a'line, answering and calling tcrmlnals for said line, acOnnectmgcu-cult, means for extend- ,ing said circuit to said answeringterminal,

means operative upon extending s aid circuit "to said answering terminal for causing said line to test busy at saidcalling terminal, and meansforremovmg the ,busy test fromsaid 26. In a telephone exchange system, a line, answering terminals and multiple calling terminals; for said line, a connecting circult, means'for extendingsa d circuit-to said answering terminal, means; operative upon extending said circuit to said answering ter minal for causing said line to testbus'y at said multiple calling terminals, and means operative while said connecting circuitis extendedto said answeringterminal for causcalling terminals I,

27. In a telephone exchange system, a pluing said line to test idle at said multiple ralityof' lines, asclector switch for selecting a line, means associated with said selector for preventing the seizure of busy lines, and electromagnetically operated means for per.- mitting said ,selcctor to seizealine while it isbusy. j v a y 28-. Inatelephcne exchangesystcm, aplurality, of lines, a selector-switch for selecting one of said lines, test means associated witl'rsaid selector switch normally tending to prevent the seizure} of a busy l1ne, and electromagnetically operated. means for; controllingfisaid test means to permit said selector switch to seizea line; while itis busy.

29. 111 atelephone system; anautomatic ",connector, telephone lines I divided into groups, amanually operable switchingdevice, and meansfor controlling saidconcalling terminal while the connecting, cir- 611113 is extended to the answering terminal.

nector from said switching device to connect with either a busy or an idle line, said connector having one motion to select groups and a second motion to find the called line in any selected group.

30. In a telephone exchange system, a plurality of lines, selector switches for selecting a line, means for preventing the seizure of busy lines, a connecting circuit, automatic switching mechanism for extending the same towards one of the selectors, and means controlled by said mechanism for rendering a busy line selectable.

31. In a telephone exchange system, a plurality of lines, automatic selector switches for selecting a desired line, means associated with said selector switches for preventing the seizure of busy lines, and means automatically operative under certain conditions for permitting one of said selector switches to seize a desired line while it is busy.

32. In a telephone exchange system, a plurality of lines, connector switches for selecting a desired line, means for preventing the seizure of busy lines, a connecting circuit, automatic switching mechanism for extending the same towards one of said connectors, and means controlled by said mechanism for causin a busy desired line to test idle.

33. n a telephone exchange system, a plurality of lines, connector switches for selecting the desired line, test means at said connector switches normally operative to prevent the seizure of busy lines, a connecting circuit, automatic switching mechanism for extending the same towards on of the said connectors, a switch for controlling the operation of said switching mechanism, and means controlled by said switching mechanism for causing said connector to seize certain of said lines whether busy or idle.

34. In a telephone exchange system, a selector switch, movable and stationary contacts for said switch, connecting circuits terminating in said movable contacts, lines terminating in said stationary contacts, a busy test condition for said lines, and automatic means operative upon the extension of said connecting circuit to one of said lines for removing the busy test condition from said line.

35. In a telephone exchange system, a plurality of lines, a connecting circuit, automatic switching mechanism for extending a calling line through said connecting circuit, a test circuit for said calling line closed upon the extension of said line, a relay for controlling said test circuit, a connector adapted to extend said connecting circuit to said calling line, automatic testing means associated with said connector, and means operative upon the building up of said connecting circuit for actuating said relay to permit the seizure of the calling llne by said connector.

36. In a telephone exchange system, a selector switch, stationary and movable contacts for said selector switch, lines terminat ing in said stationary contacts and connecting circuitsin said movable contacts, means for extending a calling line to a connecting circuit, means including said selector switch for extending said connecting circuit through said movable and stationary contacts to the calling line, means for rendering extended lines unselectable, and automatic means for rendering said calling line selectable while it is extended to said connecting circuit.

37. In a telephone exchange system, a plurality of lines, a connecting circuit, means for extending desired line to one and means for extending it to the other end of said circuit, means for placing a characteristic potential on busy lines, and means for removing the characteristic potential from the desired line while it is connected to said circuit.

38. In a telephone exchange system, a plurality of lines, a connecting circuit, means for extending desired line to one and means for extending it to the other end of said circuit, means for placing a characteristic potential on busy lines, and automatic means controlled during the extension of said circuit for removing the characteristic potential from the desired line while it is connected to said circuit.

\ 39. In a telephone exchange system, a plurality of lines, a connecting circuit, means for extending one end of said circuit to a 100 calling line, means for extending the other end of said circuit to said calling line, means for placing a characteristic potential on lines to which one end of said circuit is extended, and means operative during theex- 105 tension of the other end of said circuit for removing said potential from said line.

40. In a telephone exchange system, a plurality of lines, a connecting circuit, means for extending the same in both directions, 110 means operative upon the extension of said circuit in one direction for placing a characteristic potential on a calling line, and means actuated upon the extension of said circuit in the other direction for removing said potential from the line.

41. In a telephone system, telephone lines divided into groups, an automatic connector having one motion to select groups and a second motion to find a line in a selected group, a manually operable switching device, and means for controlling said connector from said switching device by means of its two operating motions to connect with and test either a busy or an idle line.

42. A telephone exchange system including a line connecting a plurality of party telephone stations with an exchange, said telephone stations having signal receivers responsive to currents of difi'erent character; 130

selecting liiGCliflIliSiiT, at'the exhange tor ex- "tending the line t-her 'ea't; a-plniality o'f son-trees ofs ig'naling current" fol supply'i fr said signal" receivers" are responsi c and means governed eta party hne'station for causing said selecting mecha'nisin' selectively to connect a soui' ceof signaling current Wl'tlil said line tosuit tlie signal ,I'GUGILVGTF at a n l other party line station to "be sele tively i signaled;

said connector? 43;.Ini telephone" exchange system; the combination of telephone line, a plurality of subs substation; and -"cential iaed means controllahle from any oneof sa d substations for rojecting alternating" cui'ients of different frequency" onto said line to selectivel opei'ate'said ringers. F

44,111 telephone exchan e system; the combinatio'n of t'ele'phone line; a plinality of substations on said line, a ringer at each si'i'bstati'onyand centnized -means cont 'ol ].able. from any: 0" e. of d substations for projecting ringing "currents of cl1ar'actei'istics onto said line to selectively operate saidr'inger's.

Ina telephone sy's' em, a line, a pli fa'L ity, of:'substationsio'ii sa line; aconnce tor switch, s id switch being provided with a terminal of; said line means for engag ng said terminal when one subscriber call-lsanotheronthcsani'e line, a test'cir'cuit forsaid line, means for applyingan electrical gnaifd mg cond itionf to said test' circnit, a'ndf'or tem rarily o nging said earing condition to erm iesa'idconnectorn te connect wit-l the line.

46. I""a telephone system, a' line," a plurality 30f substations on said-dine; a c nnectoi switch; said-SW1 ch being provided with a terminal of said line, means] for'placing an electrical guarding"Condition on said terminal When-a party at one'of said'snh stations originates a call, asendei' at said sub tationfor: settl. (I said connector to se- 'le'ct: another substation on? said line and 11116111119 operated thereby "to temporarily changing said guardingcondition to perm it connect with said line];

4C7. In an automatic exchange system'for party line telephones,- exchan e mechanism forconnecti nisnifor each-party line'snfbscrihers circuit, i'ingin and nieansflfoi' causing 1 a1 definite elctiiczil condition thereof whereby norm lly a oncnitTWhe-n 1n usewnl ap eaflbus t0any other circuit! attempting connection there,

" With, and prevent such connection; and

switching means associated with said ex change mechamsm; to suspend the operation lon'sbion saidiline, a" finger" at each different g' sub criberslinesmultiple line contactspi-oiudedx lngsal'd" exchange mechamechanism, electromagnetic inecha- ,nism foi' assoclating ng'mg'mechamsm with said multiple line contacts, switch contacts 15sec of saidbusy switch contacts when a cailing par'tydine s'llbsci'ibeirs apparatus calls party-line subsciibei s"apparatus on the sani'eline.= 1 w 4:8. In an automatic parity line-te1ephones, {exchange mechanism for connecting subsc1'ihe1'slines multiple line termii'ials provided in" said exchange" mechanism for each party line subscribers circuit, ringing*mechanisin, electfomagnetic mechanism for associating ringing media?- nisfn with said multiple line terminals; switch contacts and means-foe causing adef inite electiical' conditionthereof whereby normally a circuit when in use will a pear busy to any other circuit attempting connection therewith, and prevent such connection, and automatic means associated with said exchangemecha'nism, tosuspend theope-ration o-fsaid bus switch coi'itacts when a calling party line snhscri calls a patty line siihsciihefis a paratus on 'thesameline.

4L9. Inan automatic exchange system for party line telephones, exchange mechanism for connecting subscribers lines, multiple line terminals provided in said exchange mechanism itoi each party line siihsci'ibei' s circuit, ringing mechanism for furnishing currents of" different electrical character,- e1e'ctli o'i'i'iagnetic mechanism foi'j associating ringing mechanism;selectively witlisaid multiple line contacts, thus to send selective signaling'cm-rents over said party lin'e subsc'tibei s circuit; I v

50. In an automaticexchangesystem for party line telephones, exchange mechanism incluc'ling wipers for connecting subscribers lines; line terminalsTpi ovidd in exchange mechanism for each party line subscribe rs circninringing mechanism for furn1 shing currents of different fiqnency, electromagnetic mechanism and circuit connections for conliectnig rlng ng mechanism sclectivelytlirough said Wipers to .theQhne' terminalsof a party line snloscriberis Gll cuit,- thus to send selective signaling currentsovei: saidi arty line snbscribefis circuit, 5 and means at the telephon -fol'-f'operating said electromagnetic mechanism i 51. Inan antomatic exchange system for party line telephones, exchange mechanism for" connecting subscribers lines, line tennin als provided in said exchange, exchange operating mechanism "for each party linesnbs'cribefis clrcnlt; calling mechanism; el'ectfo magnetic Inechamsm' for associating,callingmechanism with said-line terminalgantomatic means *wher'eb'y normally circuit when innseWvill appe'anhusy to any other circuit attempting connection therewith, and

prevent such connection, and "additional automatic means associated with" said exchange mechanism to suspend the operation of said first aforesaid automatic means when acallexchange system for apparatus. a

ing party line subscribers apparatus calls a party line subsoribers apparatus on the same line.

52. A telephone system comprising party telephone lines, automatic switch mechanism having contact makers for interconnecting said lines, signaling currents, and means for connecting said currents through certain of the contact makers for operating the substation call bells of the party lines selectively.

53. A telephone system comprising party telephone lines, signaling bells at the substations of said lines responsive to different frequencies of ringing current, automatic switches for interconnecting said lines, signaling apparatus including call generators of different frequencies corresponding to the substations, and means for connecting such generators to ring the substation call bells selectively.

54;. A telephone system comprising party telephone lines, a call bell included in a circuit of each substation on each line, said bells being responsive to different predetermined frequencies of signaling current, automatic switch mechanisms for interconnecting said lines, signaling currents of dif ferent frequencies corresponding to the substations, and means for applying said currents for operating said call bells selectively.

55. A telephone system including a calling telephone line and a called polystation telephone line, a directively controlled stepby-step selector switch and a directively controlled connector switch for use in connecting said lines in a conversational circuit, a pair of talking wipers for said connector switch through which said conversational circuit extends, a test wiper for said connector switch for testing called lines, and means responsive to interruptions of the calling subscribers line circuit to operate said switches to extend a connection to the called subscribersiline and to selectively signal the desired substation upon the called line.

56. A telephone system including a calling polystation telephone line provided with calling and called contacts, directively controlled automatic switches for use in extending a connection from the calling contacts of said line to the called contacts thereof, means responsive to interruptions of the calling subscribers line circuit to operate said switches, a pair of talking wipers and a test wiper for the directively controlled switch that connects to the called contacts of said line, means for making said subscribers line test busy when a call is initiated thereover, means for removing said busy condition when said test wiper tests said called contacts, and means for selectively signaling the desired substation upon said line.

57. A telephone system including a calling polystation telephone line provided with calling and called contacts, directively controlled automatic switches for use in extending a connection from the calling contacts of said line to the called contacts thereof, means responsive to interruptions of the calling subscriber s line circuit to operate said switches, a pair of talking wipers and a test wiper for the directively controlled switch that connects to the called contacts of said line, means for placing a busy potential upon the called contacts of said line when a call is initiated thereover, and means for removing said busy potential when said test wiper tests said called contacts.

58. A telephone system including a calling telephone line and a called polystation telephone line, a directively controlled stepby-step selector switch and a directively controlled connector switch for use in connecting said lines in a conversational circuit, a pair of talking wipers for said con nector switch through which said conversational circuit extends, a test wiper for said connector switch for testing called lines, and means responsive to impulses created in the calling subscribers line circuit by grounding and interrupting said calling subscribers line circuit to operate said switches to extend a connection to the called subscribers line and to selectively signal the desired substation upon the called line.

59. A telephone system including a calling polystation telephone line provided with calling and called contacts, directively controlled automatic switches for use in extending a connection from the calling contacts of said line to the called contacts thereof, means responsive to impulses created in said calling subscribers line circuitto operate said switches, a pair of talking wipers and a test wiper for the directively controlled switch that connects to the called contacts of said line, means for making said subscribers line test busy when a call is initiated thereover, means for removing said busy condition when said test wiper tests said called contacts, and means for selectively signaling the desired substation upon said line.

CHARLES LANE GO ODRUM.

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