US1710934A - Automatic telephone system - Google Patents

Description

April 30, 1929. c. E. LOMAX 1,710,934

AUTOMATIC TELEPHONE SYSTEM Filed April 12. 1926 Ii'mTE'F-- Zarsnsa E. Lnmax Patented Apr. 39,

UNITED STATES PATENT our! CE.

CLARENCE E. LOIMAX 0 @AK PARK, ILLINOIS, .AESIGNOR, BY MESNEiASSIGNMENTS,

TO AUTOMATIC ELJZCTIHC ING, 0F GHIOAGQ;

WARE.

ILLINOIS, A CORPORATION "OF "DELA- AUTOMATIG TELEIIiONE SYSTEM.

Application. filed April 12,

This invention relates in general to auto .mutic tr-dephone systems in which connections are established through the medium of sub scriher control ed automatic switches, but is more particularly concerned with such automatic telephtnie systems as include party lines and selective rin in; equipment at the central exchange.

In any telephone system, in order to establish a talking connection with a particular party on a party line, some means must be provided tor sig rnalingr the particular party on the line with which a calling subscriber wishes to coininunioatm and this pitt'erably without actuatiiur the bells at the other substations on the same line. l lui'nerous methods of selectively gnali 11;; a particular party on a party line have been proposed and are in use. The method in common use by the Bell Telephone Company tln-oiuighout the United States one which depends for this selective action on the use o't positive or negative ringing current impulses applied to either one or the other side of the line.

In the patent to Martin No. 1,52%h19d, an adaptation of this method to automatic telephone systems is described. In this system, each pal y line is made accessible to the corn nectors of four different groups, the connectors of each group beingarranged tosupply ringing current impulses ot a certain kind over a re]. iin side of the line to signal a ceu tain one of tour parties on the line. This systemr while satisfactory from an operating point of View, requires the use otmore connector switches per one hundred lines than would be necessary if all the connectors having access to the one hundred lines were in one large group.

The principal object of the present invention is the provision of a new and improved connector switch having an individual means for selectin the kind of ringing current i1npulses and the side of the line to which they are to be applied, for particular use in a full selective tour-party line telephone system in which "full selection is obtained by the application of either positive or negative currentimpulses to one or the other side of theline By the utilization of this new and improred connector switch in the above described systom, the number of connectors needed for a certain number of party lines will be considerably less than are necessary when the party 1826 Serial No. 1013234.

lines are accessible to the connectors ofitour ditterent groups.

The invention, its object and other features a not specifically mentioned, will be desci'ibcd in detail hereinafter, reterenee beingihad :to"

the acc-olnpanyiirg drawing, in which is shown eutlicicnt ot the apparatus in an automatic telephone system to enable the inventionto be explained and understood.

The reference character-A indicates an automatic substation of the usual type, which ot the well knownrotary type whose wipers have no normal position and move in aforward direction only. Asis well knownhthe function of the individual line-switch'is to extend its associated line to anidle selector switch when the receiver is raised at the substation to initiate acall.

One oi the first selector switchcs, to which the line switch C has access in common with other similar line switches, is indicated in the drawing by the rectangle D. Inasmuch as selector switches are well knownin the art, it has not been considered necessary to show the circuits in detail. It may bestated briefly that the selectorD is a St-row ger Vertical and rotary switch ofwell known mechan= ical construction, and operable according: to the two-wire system of control. Then used in setting up a connection in the system as shownin the drawing, the selector responds to the first digit in the called number inorder to select a desired group of connectors, after t which the selector automatically rotates to selectand connect with a trunk line extending to an idle connector in theselected group The above is, of course true only of a one thousand line system; if the capacity ofethe system grcaterthan this, second or third selectors Will be interposed between the first selectors and connectors in the well under- This is in accord with the.

stood manner. usual percentage trunking system, however, and neednot be discussed in detail.

One of the trunk lines to which-theselectm' D has access is shown in the drawing as extending tothe connector E which is also a Strowger vertical and rotary switch having a capacity of one hundred subscribers lines. The connector E is operable according to the two-wire system of cont-roll similar to the selector D, and responds to the next two dig-i ts in :1 called number to complete the connection to the called line.

One of the party lines to which connector E has access comprises line conductors lit :uid 1 152 to which the substations A to it; elusive are connected. These substations are of the well. known type used in the above de scribed type of full selective party line systom, the substation A being shown in full and only the ringing circuits of substations A i and A being shown. The line switch C is associated with this party line at the central exchange and is similar to line switch C.

Just below the connector E, the auxiliary switch ll is shown which is individual to the connector E. This switch, comprising; the wipers 122 and 123 and their associated sets o t ljianks, the stepping magnet 120, and the re lease uiagent- I121, constitutes with its controlling circuits the means above referred to which predete 'inines the hind o't ringing current impulses and the side ot the line to which they are to be applied for signalling a particular subscriber on a party line. Switch l? perit'torins this function responsive to the dialinn ot the last digit in the called number.

The common ringing equipment for pro ducing positive pulsating current and negative pulsation current comprises the it. C. genera-tor G, the three additional batteries B B and B, and the interrupter I, the battery ll being the regular exchange battery. With the connections as shown, positive pulsations are inter nittentl'y impressed on conductor 1-432 and negative pulsations are intermittentl v impressed on conductor 14:1. '1." he battery 13' and the exehi'inge ljiuttery l3 serve as trio ping batteries for operating the ring, cut-ott relay in the connector when a subscriber answers a call during the silent period.

With this general description of the system and the apparatus used in mind, a further iniderstanding j of the invention may be gained from a detailed description of the ope. ations which take place when on subscriber another subscriber on a party line. For this purpose it will be assun'ied tl at the subscribe. at substation A desires to establish a connccti on with asubscriber at substation lid. l'Vhen the receiver is removed at the calling station, a ciraiit is completed over the con ductors' ll and 12 for the slow acting line relay 15. Upon energizing, relay 15 closes a circuit at armature 20, which includes the winding of the switching relay let and the stepping magnet 16 in series; and at its armature 21 connects the test wiper 26 to the above circuit at a point midway between the said switching; relay and the magnet. The op eration now depends upon whether the trunk I) are now enernir line with whico the line inviteh wipers are asseciated is busy, or is not bur-w. lt the trunk line is busy, there will be a round potential upon the test contact wit which the test la); i will he she h and the step "I i re short circuit is removed from '.i rel v and the operation ot i toppii 'iiagrnet it; will cease bi ause ot the high resiiaatance ol': the said switching re luv. llhe latter relay however, is energ'ixed and grounds the test wiper at its armature i8, and at it. arnutturrs l? and it disconnects the line ctmdimtors ti and 12 from the winding of the line rela v l5 and 'tl'Olll around. rcspeetivel v, and extends them by: way ot wipers E35 and and haul: contra-ts Q9 and 30 to the line relay (not shown) of the first selector l). The line and release relays ot the selector in the usual manner and the latter rela' ground :the rel use trunk conductor ot the trunl: lii e n order to establish a holding circuit tor the rwsiteliiusi relav ll of the line switch (3. This operation is well understood and need not he explained turther. A

The calling: subscriber nia'v now operate his calli g); diwice in accordance with the first digit in the desired iuunher. lu response to the interruptions in the line thus produced. the Yerlical magnet oi the selector D is on eratetl under control of the line relay to raise the wipers ll) "h inclesivc. to the particular level in. which a c t rininated the trunlt lines extending to the desired group of connec r switches Thereafter the rotary or trunk so lect movement initiated auto:naticallt in the usual manner. and the wipers are retated in search of an idle trunk line. Arsune i n 51' the i the trunk line shown in the drawino; 1st l( l'trSt idle trunk line, then when the vipers arrive t the test wiper i l. will find no ground potential upon the lost contact all, and the rotation of the switch will cease lVhen this occurs. the incoming line coi'idurtors are extended in the usual in oer by way oi the switch wipers l0 and i2 bank contents t?- und 4-5. and contact springs CUl'lil'Olltitl by the revershu relay 50 to toe wind s of the double wound ielajv 51 ot the co: ctor l Vt hen the line i1: extended .2 s above o'escrihed, the line rent} iii is energized over the line circuit to close a circuit tor the slow-acting release relay F llpou energizing. relav prepare-1 a circuit. tor i he vertical lilttt? not 58 at its armature (3'2", and at its armature it bank contacts 413-45 inclusive magnet 58 to battery.

tary magnet 59 to battery.

65 connects ground. to the release trunk conductor 47, thereby completing a holding circuit for the selector D and the line switch l in the well known manner. The walling subscriber only now operate his calling device in am-ordance with the next digit in the desired number. As a result, the line relay 5.! is deenergineifla plurality of times, andat the first deenernizcation transmits a current impulse to the vertical magnet 53 over the following circuit: grounded armature (it. and its resting contact, armature UT and its working contact, olinormal springs (3i and 63, winding; of the slow to release series relay 53, and the winding of the vertical By the operation of the vertical magnet, the wipers 90-"92, inclusive, are raised step by stop until they stand opposite the level in which is terminated the line to substation A The slow to release series relay is energized in series with the vertical magnet and by means of its armature (3R maintains the circuit of the vertical nougnet intact after the otl' normal springs have been shifted, which occurs on the first vertical step. At the end of the vertical movement of the switch, relay 53 is deenernized and transfers the operating circuit to the rotary magnet 59. r l

The subscriber will now operate his call inn device in accordance with the next digit of the desired number, which is the last digit which has to do with the line selection. ll hen the calling device is operated, the line relay 51 responds as before and sends impulses to the rotary magnet 59 over the fol l()\\'lI1f) circuit: grounded armature (ill and its resting contact, armature 6'7 and its workin contact, off normal springs 61 and G2, armature 68 and its resting contact, resting; contact and armature 75, armature S5 and its resting contact, and the windingof the ro- By the operation oi? the rotary magzjiict, the wipers 90-92, inclusive, are rotated step by step and are finally brought to rest in engagement with the bank contacts in which the line to substation it trrminates, these bank contacts being indica l in the drawing hv the reference chars 93, 9t and 95. The slow to release rclay an is energized in multiple with the rotary magnet and retains its armature attracted throughout the rotary movement of the switch. At its armature 78, relay .56 connects thotest wiper 91 with the test relay and at its armature T9 the said relay 536 ch a a shunt around the contact at armarnre 75 ot the test relay. The latter operat ion is to prevent the test relay from onenin the rotarymznrnet circuit while the test wiper passing over liiusy test contacts.

It be assumed first that the railed line iv; busy Such being the case, when the test wiper 91L arrives at test contact 94, it will lind a gro and potent-ialthereon, the test relay will be energized, and whenithe slmv to release relay 56 dcenergizes at the end (if the rotary movement of the switch, the test relay 5 establishes a locking circuit/for itself at its armature Tel. lelay 55 also opens the rotary magnet circuit at its armature 75, thus rendering the impulse circuit incllective at this time in case the calling subscriber dials the last or ringing current selecting; digit. ltclay also at its armature 77, connects a lead from the bus? signaling machine BM in the lower heavy talking UOIltlllCtOl'. By this latter operation, an audible signal is transmitted to thecalling subscriber, and, being; advised thereby that the called lineis inaccessible for the time-being, he will hang up his receiver.

lllaving explained the operations which take place when the alled line is busy, it will now be assumed that theline is idle when called. Under these circumstances, when the test wiper 91 arrives attest contact 94, it will find no ground potentialand the test relay :35 will not be energized. Then when the slow to rcloaserelay56 deenergizcs at the end of the rotary movement of the switch, a circuit is completed for the slow acting switching relay as .:tollows: From the grounded release trunk conductor l? by way otarniature H and its resting contact, upper winding" of the switehingrelay 57, resting contact and armature 8, test wiper Slytest contact 9%, winding o'l'hthe s-witchi ng'relay ll-l,:l11tl the whaling of the stepping magnet 1th to battery. Relaysfi? and li-luare energized in series over the above circuit,- and the latter relay is operated toclcar the calledlinc of its normal. battery and g round connections in the line switch G It should be noted that the relay ill is not fully operated at this time, due to a Illl0( 3l1:llll-3tll.llltfll'lutiklllg arrangement between the[armature of this reluy andthe armature or the slow acting line. relay (11:5, and the wipers ot' theline switch 0 are not connected. up. 111 the connector E, switching;- relay 5?, in. energizing, establishes. a locking; circuit for itself at its armature til, grounds the test wipertll at armature 83,

transfers the lllllflllbfll'lll' circuit from magnet 59 to the stepping magnet. hill of the ringing current electing switch F at its armature 85. and prepares a circuit at its armature 86 l which provid for transmittingr a tone signal to the calling subscriber during the ringing operation, i

The calling subscriber may now operate his calling device in accordance with the.itina1 digit in the ninnber, "which is the digit which determines the proper ringing current and the side of line to which it is to be implied for signalling the particular station wanted. The substations A iV, inclusive, have been nnmbe red tor convenience in. accordancewith the digits to which. they correspond, and'since the substation A is the Wanted substation in i the present case, the final digit to be called will be the digit 4. lVhen the calling device is operated for this digit, the line relay 51 transmits four impulses of current to the step ping magnet 120 of the switch over the following circuit: From grounded armature (ll and its resting contact, armature (i7 and its working contact, oft normal springs 61 and (i2, armature (l8 and its resting contact, restin g contact and armature 7 armature 8:) and its working contact, and the windings of the stepping magnet 120 to battery. By the operation of magnet 120, wipers 122 and 123 are given a step by step movement and are finally brought to rest in engagement with the fourth contacts in their respective banks. The slow to release relay 56 is energized in multiple with the magnet 120 and now serves to prevent the energiaation of relay 55 by holding open its energizing circuit at armature 8( which circuit will he explained. hereinafter.

With wipers 122 and 123 in engagement with the fourth contacts of their respective banks, a circuit for the signal control relays 131 and 132 is closed which may be traced from ground by way of armature 66 and the working contact, wiper 122 in engagement with a fourth bank contact, through the winding of relay 131 to battery; and from ground by way of armature 66 and the working contact, wiper 123 in engagement with its fourth hank contact, through the winding of relay l to battery. Both relays 181 and 132 are energized and perform the following circuit changes: At armature 133 and the working contact, the common ringing conductor 142 connected to the upper terminal of the upper winding of the ring cut-oil relay 1. The lower terminal of the upper winding of ring cut-oil relay 54 is connected by way 01' armature 134i and the working contact and armature 136 and the working contact to the ringing conductor 14.4. At armature 135 and the working contact, groundpotential is connected to the conductor 143. These operations prepare the signalling circuit, predeterniining the kind of signalling current and the side of the line to which it is to he applied.

At the end of the series of impulses transmitted to magnet 120, relay 56 is deenergized and completes the circuit for relay 55 as follows: ground by way of springs 124 which close on the first rotary step of the selector switch F, resting contact and armature 80, through the winding of relay 55, which now functions as a ringing circuit control reh y, to battery. Relay 55 now energizes and performs the following circuit changes: At armature 77 a circuit is closed for the ring back tone which may be traced. from conductor 96 connected to the ring back tone source, work ing contact and armature 86, working contact and armature 77, normally closed springs controlled by armature 71, to the lower heavy talking conductor. By this means a ring back tone is transmitted to the calling subscriber to apprise him that the alled subscriber is being signalled. At armature T3 the circuit for the release magnet 121 of the switch F is prepared. At armature 75 the impulsing circuit is opened thereby making any further manipulation of the dial. at the calling substation ineffective. At aruiaturcs T2 and 76 the signalling circuit is con'ipletcd which may be traced as follows: from common ringing conductor 142, to which positive ringing current impulses and positive battery are alternately connected, working contact and armature 183, the upper winding of the ring cutoff relay o1, armature ll-l-l: and the working contact, armature 136 and the working contact, conductor 111-, working contact and armature '76, resting contact and armature 71, armature 87 and the working contact, wiper 92, bank contact 95, line conductor 112 through the winding of the A. C. relay 103 at substation it to ground, and through the winding of the A. C. relay lthl at the substation A to ground. Due to the condensers in series with the A. C. relays at the ruxhstations, alternating currents are set up in the two A. C. relays 103 and st. Responsive thereto, these relays operate andv connect the ringers st and 153 directly across the line conductors. As soon as these ringers are connected across the line, pulsating current will pass through the two ringers over the above traced circuit from conductor 11.2, and by way of the armatu res of the A. (l. relays and their working contacts, line conductor 111, hank contact 93, wiper 90, working contact and armature 81, armature 69 and resting contact, armature 72 and the working contact, ringing conductor 14-3, working contact and armature 135 to ground. The ringers at the substations are biased in the ordinary way. Ringer 155, is adapted to respond only to negative pulsating current, while ringer rat is zulaptcd to respond only to positive pulsating current. It follows therefore that since the ciurront is being supplied from the positive pulsating ringing conductor 1412 only the ringer 15 1 will respond. I

In this manner the :uibscriher at substation A is selectively sigiiialed until he answers the call or until the calling subscriber replacrs his receiver. It may be mentioned at this time that the ring cut-oft relay 51 adjusted that it will not operate responsive to the ringing current impulses or to the current supplied from the tripping battery B during the silent period, the current in both instances being limited by the comparatively high resistances at the substations.

lVhcn the subscribers at substation A removes his receiver to answer the call, howc ver, a low resistance bridge placed across the line conductors including the transmitter and the primary winding of the induction coil at the called substation. The flow of current lltl it t) in the circuit including the two line conductors in series is thereby sulliciently increased to cause the instant operation of the ring cut-oil relay 54, this current being either from the battery it in. series with generator durii'igthe silent period. Upon energizing, why olcloses the locking circuit for itself at.

armature To, and atarmatures 69 and 71 and their working contacts the talking connection. :tronrthe substation A to the substation A is finally completed, the signaling circuit being-opened at the resting contacts of these arinatures. The ring back tone circuit is also o pvned by the separation oi the normally closed springs controlled by armature 71. As soon as the talking connection is completed to the called line, the back bridge relay 50 operates over the called line loop andperioruis the usual operation": of reversing the battery connections to the calling line. This latter operation is of no utility in connection withlhe apparatus shown, but is the standard operation for use in controlling measured service equipment when such equipment is supplied and is therefore included.

Uoni'ersation may now proceed as desired, and when the subscribers are through they willboth replace their receivers. Replacing the receiver at the called substation merely causes the deenergization oi. the back bridge relay 50 which thereupon restores its arnialures to normal. In response to the replacenuuit ol the receiver at the calling substation, the line relay 51 deenergizes after which the release relay 52 is deenergized. In deenergiaing, relay V 2 initiates the release of the entire conncctionin the usual manner. By the restoration ol' armature 65 ground is removed :l'roni the release conductor 4:7, thereby permitting the selector D and line switch to restore to normal in the usual manner. In addition thereto, the circuit tor the release relay 121 of the switch F is closed which may be traced from ground by way of armature U and resting contact, armature 73 and the working contact, through the winding of the release magnet 121 to battery. Release magnet 121 operates and restores the wipers 122 and 123 of the switch F to normal. The release of armature 66 opens the circuit of relays 131 and 132, and switching relay 57, which. likewiserestor-c to normal. By the releaseaoi armature 64: and armature 67, the

usual circuit for the release magnet is glass: and restores its arinatures to normal.

All the apparatus used in the establishment of the connection is thus freed and may be used in the establishmentot' another connec tion.

an explanation will now be givenof the nlannerin which a connection with the other three stations on the party line may be establishcd. The substations A A, and A may be reached by dialing the same party line numberand by dialing the digits 1,2 and 3, respectively, as final digits. Theoperations performed in establishing a connection with any one of the other three substations are exactly the same as when establishing a connection to the substation A, with the exception of the operations of relays 131 and 132 which controls the polarity of the pulsatingsignals ing current and the line conductor to which it is applied, which in turn predeterniines which ot the tour ringers is to operate. Should a callingsubscriber desire to converse with the subscriber at substation Aihe will dialthe same line number and thendial the digit 3 as the linal digit; In response toudialingthe line number, the selector D and the connector lfi, assuming thatthese switches are again taken for use, operate in the manner described above. In response to the dialing of the linal digit 3, wipers 122 and 123 01 the switch F are positioned on the third set of contacts-in their respective banks. In this case no circuit is closed for the rela' 131 but a circuit is a ain,

lhe common ringing closed for relay 132. conductor 141 then remains connected to the lower terminal of the upper windingof relay 5st. Ground is again connectedto the ring-. ing. conductor 1&4: at armature 135 and the working contact, and the upper terminal of. the. upper winding ct relay 5a is connected to ringing conductor 14i4 by way of armature 133 and the resting contact and armature 136 and the working contact. The signalingcircuit is identical to thattraced for signaling the subscriber at substation At, except that negative pulsating current fromthe common ringing current conductor 141 instead of positive pul eating. current from conductor 142 is used. Both relays 10 l and 103at the substations 2 1V and A operate as before. Ringerlfid will not respondto negative pulsations. Ringer is adapted to respond to negative current impulses and therefore operates whenever it IS br dged across the line by operation of relay 103, thereby signalingithesubscriber at sub station A To signal the subscriber at substation A, the

final digit to be dialed is the digit In this spective banks. In this case, relay131 open ates and relay. 13. remains deenergized. Ground is now connected to conductor 144 by way of armature =and the restingcontacta andpositivecurrent impulsesare supplied from.conductor3'1l2 by way ofthe Working contact and lllilfitltllil-l 133 through the upper winding of relay 54:, armature 134; and the working contact, armature 136 and the resting contact, conductor 1-1 3, from where the circuit extends by way of working contact and armature 72, resting contact and armature (it), armature 81 and the working contact, wiper 90, bank contact 93, line conductor 111, through the A. C. relay 102 at substation A and the A. C. relay 101 at substation A in parallel to ground. Relays 102 and 101 operate responsive to the signaling current impulses in the same manner as did relay 10a and 103. The ringer 152 is biased the same as ringer 15%, and ringer 151 is biased the same asringer 152- Ringer 152 therefore operates responsive to the positive current impulses when connected across the line coi'iductors to signal the subscriber at sulistation A.

To signal the subscriber at substation A the final digit to be dialed is the digit 1. in response to the dialing of the digit 1, tlfftfil the line number is dialed, the wipers 12:2 and 1225 are positioned on the hrst contiwt in their respective banks. Neither relay 1251 nor relay 132 is operated in this case. 'lhe signaling circuit is the same as that for si ding the si'ibscriber at sulistation A except tiat negative current impulses are now supplied from the conunon conductor 1 5-1, to which the ringer 152 is not responsive, and to which the ri uger 151 responds to signal the subscriber at uhstation A it is evident from the drawing and the above description that relay 131 performs the function oi selecting the source of ringing current and. that relay 132 ,)erforn1s the tune tion of dcterniining to Which side of the line the selected source of ringing current is to be Connected. Relay 131 also reverses the coni'iections to the upper winding of relay 54 when the ringing current from conductor i i-i3 is selected. Inso doing, the current flow through the upper winding of relay 5 1 is made to flow in one direction regardless of whether positive current impulses or nega tive current impulses are used, this being the same as the direction of current flow in the lower winding of relay F4: when the circuitot the lower winding is closed at armature "70. Such a provision is obviously necessary for the satisfactory operation of the cut-oil relay 54. i

This completes the description of the operation of the new and improved connector switch and its features. What is considered new and desired to have protected by Letters Patent will be specifically stated in the appended claims.

\Vhat is claimed is:

1. In a party line system, a connector switch for extending calls from a calling line to a called party line, sources oi positive and negath signalling current, a signalling cincuit, aria-oil relay in said switch adapted tor said cut-0113' relay in said signalling circuit so that the direction oi current through the winding oit said cut-oll' relay is the same re;

gardless ot the source selected.

2. In a party line system, a connector switch for extendin calls ironi a calling line to a called party e sources (it positive and negative si 5 current, a signalling circuit, a cut-oli relay in said. switch adapted for inclusion in so id circuit and operative res ponsive to the answering ot a call by a called subscribcr to interrupt said signalling circuit, means in said. switch 'i'or controlling the solect-ion oil? the source elf signalling current and or controlling the cinincctions of said cutoil relay in said :--i' na.lling circuit so that the direction oi curre .t through the winding of said cut-oli re iy is the same regardless oi. the source selei u, and means in said switch for determining the side 01 the line to which the selected source is connected.

pin y line system, a connector ing calls from a calling line l. pa. ty line, sources o'l positive and negative signalling current, a signalling circuit, a cut-oil relay in said switch adapted for inclusion in said. circuit and operative rcsponsive lo the answering of a call by a called subscriber to interrupt said signallingcircuit, means in said switch for cinitrolling the sclection ot the source oil signalling current and for controlling the connections oi. said cutoil relay in said signalling circuitso that the direc ion oi our out through the winding o'l" said cut-oil relay is he same regardless oi" the source selected, means for determining the side or the line to which. the selei'ited source is connected, and means individual to said connector tor controlling both said first and said second means.

i. in a telephone gsleui, a party line, sources oi positive and negative signalling current, a connector -awitch, means for operating said connector to connect with said line, means in said connector directively controlled. over a calling line for connecting either of said sources to said line to selectively signal stations on said line, a cut-oil relay in said connector having a winding adapted for inclusion in the signalling circuit and having a locking winding, and circuit arrangements such that both windings of said cut-oil relay cooperate wl'icn said relay is operated regardless oi the source of signalling current used. 7

5. In a telephone system, a party line, sources 01' positive andnegative signalling current, a connector switch, means for operating said connector to connect with said line, means in said connector for connecting either of said sources to either side of said line to selectively signal stations on said line, .a cut-oil relay in said connector having a wind- :ing adapted for inclusion in the signalling circuit and having a locking winding, and circuit arrangements such that both windings of said cut-oil relay cooperate when said relay is operated regardless of the source of signalling current used.

6. In a party line connector, means for operating the connector in accordance with a digit of a desired telephone number to select a desired line, a ring cut-oflrelay, a source of positive ringing current, a source o'l negative ringing current, means operative in accordance with a dillerent digit of the telephone number to select one or the other of the sources of ringing current and connect it to the selected line in series with the ring cutoff relay, and commutating means for maintaining the direction of flow oi current tl'irough the relay the same regardless of the source used.

7. In a party line connector having a pair of line wipers, means for operating the connector in accordance with a dig ot a desired telephone nun'ilier to select a desired. line, a ring cut-oil relay, a source of positive ringing current, a source of negative ringing current, means operative in accordance with a different digit of the telephone number to select one or the other of the sources o'l. ringing current and connect it to one or the other of the line wipers in series with the ring cutoff relay, and commutating means for maintaining the direction of flow of current through the relay the same riigardless oi" the source used.

8. In a party line COIHIQCtOl, means for operating the connector in accordance with a digit of a desired telephone numher to select a desired line, a ring cut-oil" relay having an operating winding and a holding winding, a source of positive ringing current, a source of negative ringing current, means operative in accordance with a different digit of the telephone number to select one or the other of the sources of ringing current and connect it to the selected line in series with the operating winding of the ring cut-oil relay, and cominutating means for maintaining the direction of flow of current through both windings of the cut-off relay the same regardless of the source of ringing current used.

9. An automatic telephone system wherein a connector is operative in accordance with value of certain digits in a party line telephone nulnher to select the line and wherein means is operative in accordance with a diflierent digit of the number to select a source of ringing current to ring the desiredstation on the line, and wherein a cut-off relay having two windings has one of its windings included in the ringing circuit and is operated over that winding when the called party answers and 1s locked in its operated pos1- tion over the second Winding, characterized in this, that the ringing current to be select ed is either positive or negative current, and connnutating means is provided for main taining the relative direction of the current flow inthe two windings the same regardless oi the source of ringing current used. I

1.0. An automatictelephone system where-' in a connector having two line wipers is op: crative in accordance with the value of certaindigits in a party line to select the line and wherein there is means operative in accordance with the value of a different digit in the number to select one of two sources ()fl' ringing current and to connect the ring locked in its operated position over the sect 011d winding, characterized in this, that the r1ng1ng current to be selected is either posithe or negative current, and connnutating.

means is provided for inaintainingthe relative direction of the current flow in the two windings the same regardless ot'the source oiiringing current used. a

In witness whereof, I hereunto subscribe 7.

my name this 8th day of April, A. 1)., 1926.

CLARENCE n. LOMAX.

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