US1849087A - Telephone system - Google Patents

Description

March 15, 1932. HQVLAND 1,849,087

TELEPHONE SYSTEM Filed May 14, 1930 2 Sheets-Sheet 1 //v VENTOR H. H0 VLAND A 7' TDRNE Y 2 Sheets-Sheet Filed May 14, 1930 ./Nl/N TOR H. HOVLAND ATTORNEY terminals to signal any one of the five parties on either line conductor. The revertive signal will consist of one short impulse transmitted over either conductor.

A detailed description will now be made of the functioning of this system, first in connection with a call from a party line subscriber on line 20 through the selector 21 and connector 22 to a party line subscriber on another line 23; second, a description will be made of a call from a party line subscriber on line 20 through selector 21 and connector 22 to a subscribcrs station on line 23, and assuming that this line is the same as the one on which the calling subscribers station is located, in other words, a so-called revertive call.

Referring now to the first type of connection, when the subscriber on line 20 has selected through the selector 21 and connector 22, a circuit is completed for the operation of the connector 22 to select a desired subscribers line. This circuit will be completed through the subscribers dial over the tip and ring conductors, the make-before-break contacts of relay 25, the windings of relay 26 to battery and ground. Relay 26 is thereby operated and a circuit is completed for the operation of relay 27 from battery, winding of relay 27 armature and front contact of relay 26 to ground. Relay 27 in operating connects at its upper armatures and front contacts the sleeve lead to the selector 21 to ground, for the purpose of holding the preceding switches used in this connection. This relay also opens a circuit for the release magnet 28 at its lower inner armature and back contact and prepares an operating circuit for the Vertical magnet 30 as well as a number of other circuits which will be described hereinafter. Relay 27 due to its slow-to-release characteristics will remain operated during the pulsing operation of relay 26. The first release of relay 26 in response to the first series of impulses sent out from the calling subscribers station, after the seizure of the circuit of this connector, closes a circuit for the vertical magnet 30 from battery, winding of this magnet, winding of the change-over relay 31, normal contacts of the vertical olfnormal contacts 32, lower inner armature and front contact of relay 27, armature and back contact of relay 26 to ground. Both the vertical magnet and the change-over relay 31 operate on this circuit and relay 31 being slow to release remains operated during the succeeding impluses transmitted to the vertical magnet 30. As soon as the vertical magnet has taken one step, the original circuit for this magnet is changed to pass through the upper inner armature and front contact of relay 31 and the lower closed contacts 32. The succeeding impulses of this series now cause the vertical magnet to advance the brushes 35 to the proper level in the bank of connector 22 in which the desired subscribers line is located.

When the pulses cease relay 31 releases and prepares a circuit for the rotary magnet 36 which will be closed as follows when relay 26 releases in response to the first of the second series of impulses: battery, winding of magnet 36, fourth lower armature and back contact of relay 37, second upper armature and back contact of relay 33, upper inner armature and back contact of relay 31, lower closed contacts 32, inner lower armature and front contact of relay 27 armature and back contact of relay 26 to ground. Relay 39 also operates at the first release of relay 26 over a circuit from battery, winding of relay 39, upper inner armature and backcontact of relay 31 over the circuit traced for the rotary magnet to ground at the armature and back contact of relay 26. Relay 39 is slow-to-release, so that it will remain operated during the sending of the second series of impulses. Relay 39 closes a circuit for the operation of relay 40 from battery, winding of relay a0,

third upper armature and back contact of M relay 38, upper outer armature and back contact of relay 31, lower inner armature and front contact of relay 39 to ground. Relay 40 prepares circuits for making a busy test on the called line terminals as will be here- 3' inafter described.

When the impulses of the second series have been transmitted, relay 39 releases and opens the circuit for relay 40 and also closes a circuit for making a busy test which takes place before relay 40 releases, as it will be noted that this relay is slow to release. If the terminals of the called line 23 are busy a ground connection will be found on the sleeve conductor and this ground causes the operation of relay 38 before relay 40 releases. This circuit may be traced from battery, winding of relay 38, third lower armature and back contact of relay 42, lower armature and front contact of relay 40, upper armature and back contact of relay 39 to ground on the sleeve conductor of line 23. Relay 38 provides a locking circuit for itself from battery winding of relay 38 and its up- H per inner armature and front contact, lower outer armature and back contact of relay 37 to ground at the upper armatures and front contacts of relay 27., Relay 38 closes a circuit from the busy tone equipment at 43 through its lower outer armature and front contact, third lower armature and back contact of relay 37 to the ring conductor leading to the calling subscribers line 20.

If the called line is idle relay 38 will not operate at this time so that on the release of relays 39 and 10 the sleeve conductor from the called line 23 is connected to ground to make this line busy over a circuit from battery through the usual cut off relay of the called line over this sleeve conductor, upper figs-49 0M armature andback contact of relay 39, lower arma ure and back contact of relayed-upper winding of relay37', fourth upper armature and back contact of relay 38-to ground: at the upper armatures and front contacts of relay 27. T his ground connection serves as a ground potential for the sleeve conductor un til the relay 37 operates, which it doesin this circuit, suliiciently to: close a connection through its lower inner armatureand front contact for the lower winding of this relay. Relay 3? now fully operates through a circ it established from battery through the lower inding and this lower inner armature and front contact to ground at the upper outer armature and front contact of relay.- 27. YVhenrelay 3? operates fully a direct ground, connection is established for the sleeve con ductor at the second lower armature and front contact of relay 87. Relay 37 also closes a connection over the tip and ring conductors to the called line 23 for the purpose of applying ringing signal to call the desired subscriber on'this'line.

It should be noted that the operation of relay 27 a circuit was completed toground at the lower armature and front contactof this relay over lead 45 for the purpose of starting the common control equipment shown in Fig. 3 to supply the ringing signal. This circuit may be traced from battery through the winding of the start relay 100, left armature and back contact of relay 101, lead 425 to ground at the lower outer armature andfront contact of relay 27. In Fig. 3, the switch 102 consists of live terminal banks 103 to 107 and associated brushes driven in a stepby-step manner by a stepping magnet 108 for the purpose of supplying signaling codes for calling the subscribers on party lines as will hereinafter be described. In this case, a single impulse of signaling current will be sup-- plied at intervals for calling a subscriber on line 28 and this signal is supplied when interrupter relay 38 is operated which does-not however occur until relay i6 is operated. The circuit for relay 46 will be closed when the common control equipment is in a normal position, such as is shown in Figure 3 with the brushes of the banks 103 to 10? standing on the zeroterininals or on the 11th terminals. in either case relay 101 will'be in a release condition. This relay 46 will, therefore, not operate to start ringing until a complete series of code signals have been transmitted This is for the purpose of preventing mutilated signals from being transmitted in case the common equipment is in use by some other connector, in which case, the brushes may be traveling between positions 1 and lO'or 11 and 22. If itis assumed that the brushes of the switch 102 are located in the position shown, the circuit for relay 46 will be completed from battery, winding of relay 46, second lower armature and backcontact of relay 4%,. make beforeehnealn contacts of; res lay 4.6, sixth. lowen' armature and. fnontr' com tact of" relay 351,. conductor; 48,-.o1iten'right: handi armature and back: contact of: relay 10L tozground. Relay 4r6. in operatingplosesa' locking circuit. for itself from; battery through the winding? of this relayg. second lower armature and'zbaclc contact; of'nelay lfl, upper armature.- fronticontact ozfiirelaiy to ground; at; the. upper anmatures and fiiont contacts of: relay 2711 On the operation of the start relay 106;. a circuit was completed for locking this; relay from. battery. through!- its inner rightrhand: armature'andi front, contact to the grouindt on lead. 455 independent of: the connection through the left-hand armature and back contact'of relay 1021a. The startrelay liQQrin operating closes at its left=handzarmature and front contact a circuit. for the alternate operation. and release of relay ll0 u=ndercone trol of an interrupter'll'ln Relay 1510 corn-.- trols the pulsing circuit for themagnet 10.8

extending through: the lofts-hand armature and back contact of relay 1 12. Magnet-108.

. operation of-rel'ay: l'lllz" a circuit. is completed from battery, winding' of; relay 38,. lower outer armature and front contact of rel-46:, the fourth brush of connector 20K and thejcorresponding terminal; of line'23i, le-adoll, armature and front contact. of relay; L14- to. ground. This cau-sesthe operation oftrelay 38-each time relay114is operated It. should,

however, benoted that. the-brushofbank 103 will bridge two.-v adjacent terminals and relay 114 will therefore remain operated during the: third and fourth, the seventh and eighth, the fourteenth and fifteenth andthe; eight,- eenth and nineteenth steps. so; that; relay 38 due to these operations of: relay 114; will be operated four times while. the brush travels from positions 1 to. 22?. In this manner: two periods of operation of; relay 38' will take placefor each half operation ofthe switch 102;. These operations of switch: 102 will therefore cause the application of ringing signals to; the line 23;- conxprising a: code of two impulses: repeated. at intervals. It. will be later explained how different eocle'signals will be selected when other subscribers: lo- 7 source 51, second lower armature and front contact of relay 46, inner lower armature and front contact of relay 38, inner upper armature and back contact of relay 40, upper 5 Winding of relay 47, second upper armature and back contact of relay 40, inner upper armature and back contact of relay 47 the ring conductor of connector 22 and upper inner armature and front contact of relay 37 to the ring brush and ring conductor of line 23 to the bell of the called subscribers station.

These signals will be repeated until the called subscriber answers, when the ringing trip relay 47 will operate, Relay 47 operates sufficiently to close a circuit from battery, lower winding of relay 47 and its lower inner armature and front contact to ground at the upper outer armature and front contact of relay 27. This circuit will then cause the relay 47 to become fully operated, to c0-m plete the connection at its upper armatures and front contacts over the tip and ring conductors of connector 22 between the two subscribers. Talking battery for the called subscriber is supplied from battery and ground through the windings of relay 25. Relay 25 is now operated and the operation of relay 47 opens the holding circuit of relay 46 which releases and opens the circuit for relay 38 to prevent it from being further controlled by relay 114 and to discontinue the ringing. Relay 25 in operating also reverses the battery and ground connection through. the windings of relay 26 at its left-hand armatures and front contacts for supervisory purposes or metering services which are of no importance in connection with this invention.

The following description relates to the selection of a signaling code for calling a subscriber on a party line, when an idle connector is found, it will be actuated by impulses to select one of the ten sets of terminals of the desired party line representing the desired subscribers number and thereby causing the common equipment shown in Fig. 3 to be actuated to control through the connection for the fourth terminal relay 38 in a manner to transmit the proper code signal. In the connector 22 the fourth terminal has been connected through lead 50 for control by relay 114. This will cause as hereinbefore explained a code comprising two impulses to be'repeated at fixed intervals. If the connector had selected a set of terminals in which the fourth terminal had been connected to conductor 120 a code of three impulses would have been transmitted at fixed intervals, or if conductor 121 had been connected to the fourth terminal a series of four impulses would have been transmitted or if conductor 122 had been connected to the fourth terminal a series of impulses comprising one long impulse followed by one short impulse would have been transmitted, or if conductor 123 had been connected to the fourth terminal a code comprising one long impulse and two short impulses would have been transmitted. It is therefore evident that the five subscribers having their ringers connected to one conductor may be rung by five distinguishing codes and that the five subscribers having their ringers connected to the other conductor may be rung by the same five distinguishing codes. The selection of the set of terminals will determine the conductor over which the code is to be transmitted and the connection for the fourth terminal in the selected set will determine the code itself.

In the case where the fourth terminal is connected to conductor 120 relay 38 will be actuated and release to cause three impulses to be transmitted from the source 51. In this case the brush of the bank 104 will, as shown, close a circuit for relay 126 from battery through the right-hand winding of relay 127, winding of relay 126, to the second, fourth and sixth, and then after a short interval to the thirteenth, fifteenth and seventeenth terminals of bank 104 to the brush thereof to ground. In the case where four impulses are to be transmitted, relay 127 will control lead 121 to cause relay 38 to be actuated four times with a short interval between the sets of impulses. In this case relay 127 will be operated when the brush of bank 103 makes contact with the second, fourth, sixth, and eighth, and then after a short interval with the thirteenth, fifteenth, seventeenth and nineteenth terminals. For the first three terminals in each group of impulses the circuit will be closed through the right-hand winding of relay 127 and for the fourth impulse the circuit will be closed through the left-hand winding of this relay as shown. In the case where one long impulse, followed by one short impulse, are to be transmitted, relay 128 will be operated from the bank 105 over a circuit from battery through the winding of relay 128 and left-hand winding of relay 129 to ground at the brush of bank 105 at terminals one to four and 6 and again after a short interval at terminals 11 to 14 and 16. Relay 128 will remain operated to cause the long impulses while the brush travels over the first three terminals in each group. In the case where a long impulse followed by two short impulses are to be transmitted, relay 129 controls the operation of relay 38. In this case, in addition to the circuit com- .pleted through bank 105 for the first long t ins? vis not located. on the same conductor as his own ringer but on the-other conductor. .In case the called subscribers iringer is located on the same conductor as his own'he will,-of course, recognize theca-llingsignal code when it is transmitted to actuate the called .subscriber s ringer, as his own ringer would also be operated by :the same code.

The operations of :the circuits are as 01.

lows. Then the callingsu'bscriber"hangs up his .-receiver after having received the busy signal, relay 26 is released. Belay .26 in releasing closes :a circuit for the operation of relay T39 before relay 27 releases as follows: battery, winding of this relay, :u-pper inner armature and :back contact of :r.elay 31,'-vertical oil-normal contact'32, inner lower armature and .itront contact of :relay27 to ground at :the armature and ::back contact of (relay 26. This operation of relay 239. takes place beforezrelay 27 hastime it!) release dueto the slow release characteristics of 'fthis latter relay. ltelay'39in operating'applies a ground to the sleeve conductor of connectori221over a circuit as followszsground, lower "inner armature and fI'OIlhLGOIltdCt o-trelayr39, upper outer armature and back contact of relayBl, third upper armature and front oontactiofrela -y '38, sleeve terminals of .line 2-3. Fllhis groundconnection-makes theline busy from the sleeve terminal of "connector 22. When relay 27 now releases the original holding ground "forthe :preceding'switches is removed from the sleeve conductor rto seleotor2l at the'upper armaturesidf'ithisielay. .However,

the substitute aground drone :the lower inner arlnature and "fI'OIItfCOIItBJCfG: d'fmelay :39:is .no-w extended over the sleeve terminal of line .23, which is the same as the (calling .line, to :the sleeve circuits of the intermediate switches and selector 1'21-to hold them and for other purposes as "will presently Zbecome apparent. Relay'27 :also in.releasing removes the-shunt circuit "for 'the lower 'winding 1032' relay 42 from battery through "resistance E54 and the upper z armature H IIdXEIZOHl'A'COIitaOlZ of relay 38 to ground at the 'upper armature and front contact of relayz2-7'. :Relay 421mm 'nowtherefore operate from battery through resistance 54:, lower winding 0i :relaly 42, lower :outer armature and front contact .of :relay -39, fourth upper armature ;and contact of relay 38 :to .the above mentionedesuhstitute ground on the sleeve conductor from the selector 121.

.circuit causes relay A2 to operate: suflicientl y to close an energizing circuit. for itself from battery through the upper winding and upper inner armature rand front .contact of relay 42, third .lower armature .and "back contact of relay 4B7, :middle made-contacts or the verticaleofi normalcontact 321:0 ground. l -his circuit fullyenergizes relay 42 :to .close the remaining connections controlled thereby. Relay 4:2.inoperating closes a circuitior theoperation ofrelay 31 as follows battery, winding of magnet 30, winding of relay .81, resistance 56, lower outer armature and :front contact :of relay 42... seventh lower armature and back contactzo-f relay d? to ,ground' at the lower inner armature andtront contactaot relay .39.. Due-ltozthe resistance 56in-this circnit the vertical .magnet will .not operate. Relay 31. in operating-opens. at its upper outer armature and back [contact the ground connection supplied from the lower armature and tront contact of relay 39 as hereinbefore traced through the sleeve terminal .of connector 22, :the intermediate switches .and the selector :21. :Fll-lSrEeDIOVal of the .groundconnection from the sleeve causes the release of .all the preceding switches including selector "Connector 22 will not be released as the circu-itzforthe:release magnet is maintained open .at the second upper armature and baok cont-acteofrelayfiL-even though this circuit will'rbe closed on .the, release of relay 38 at the second lower armature and .back contact. It should be noted that relay 38 doesnotmelease until the ground is removedlirom the sleeize to open its docking circuit over its upper .inner armature. and iront contact.

Relay 39-.al so releases-due -.to the operation of relay 31 as the circuit therefor is (opened at the upper :inner armature and back contact of relay 3'1. Relay 39 is slow in releasing so as :to permit the above P operations to take place ;as described. When relay 39 is released the circuit for the sleeve conductor :0": line .28 is.--again-'closed-to ground toj-make the line busy. Thisground extends from the lowerinner armature and .back contact of relay 39.=upper outer armature and'front contact oflrel-ay42, fourth upper armature and back contact of relay 38, upper winding 7 of relay 37., lower armature and back contact of relay '40, upper :armature .and back contact :of :relay 39 to the sleeve. As battery :is

now 'present on-this conductor through -the,

winding ofthe :usual cut-ofi :relay'not shown rel-e3 3? :will-operate suiiiciently in thiscircult to close acircuit "hereinbefore traced "for the lower windingto cause the relay to fully operate. The release of relay-39 also allows relay 81 to release but this relay is slow in releasing and, therefore, remains operated long enough to permit the partial operation ofrelay37. V

llelay ii'' in operating -.cl oses a connection for the tip and ring conductors through to the ring tripping relay 47 for the application of ringing current and relay 46 is now operated over a circuit as hereinbefore traced for this relay, completed over lead 48 while the common control equipment is in normal position or in position 11. The operation of relay 38 will now be controlled by the switch 113 to transmit the proper ringing current to the desired called subscriber. It should also be noted that on bank 102, the brush thereof will when it connects with the terminals 5, 10, 15 and 20, close an obvious circuit for the operation of relay 131. This relay in operating at these periods will close a circuit for the momentary operation of relay 40 from battery winding of relay 40, second lower armature and front contact of relay 42, lower inner armature and front contact of relay 46 to ground at the armature and front contact of relay 131. Relay 40 in operating causes an impulse from source 51 to be transmitted over the tip or ring conductor to ring the calling subscribers bell provided it is on the opposite conductor from that on which the called subscribers bell is located. This circuit may be traced from source 51, second lower armature and front contact of relay 46, upper inner armature and front contact of relay 40, upper winding of relay 47, second upper armature and front contact of relay 40, upper outer armature and back contact of relay 47, tip conductor of connector 22, upper armature and front contact of relay 37 over the tip brush to the called party line. This is for the purpose of notifying the calling subscriber under these circumstances that the called subscribers station has been run. In case the calling subscribers bell is on the same conductor as the called subscribers bell the calling subscribers bell will of course receive the same code as the called subscribers bell. When the subscriber at the called station answers, relay 47 is operated as hereinbefore described and talking battery is supplied to the line through the windings of relay 25. On the operation of relay 47 the holding circuit for the upper winding of relay 42 is opened at the third lower armature and back contact of relay 47 but relay 42 is slow in releasing so that it will be held operated from the connection completed to ground for this holding circuit on the second outer armature and front contact of relay 53 which operates when the call-ed subscriber answers. If the called station does not answer, the calling subscriber must remove his receiver from the hook to trip the ringing to release the connection.

If in a connection that is not a revertive call, the subscriber at the called station disconnects before the subscriber at the calling station disconnects, relay 25 is released, causing the release of relays 47, 37 and 42, and

then when the subscriber at the calling station disconnects, relay 26 releases, causing the release of relay 27. Thecircuit is then closed for the operation of the release magnet 28 as follows: from battery, winding of this magnet, upper made contacts of the vertical off-normal contacts 32, fourth lower armature and back contacts of relay 3?, outer right-hand armature and back contacts of relay 25, middle upper armature and back contact of relay 31, middle lower armature and back contact of relay 33, inner lower armature and back contact of relay 3?, armature and back contact of relay 26 to ground. This circuit is opened at the vertical off-normal contacts 32 when the switch has returned to normal.

If the subscriber at the calling station disconnects before the subscriber at the called station relay 25 remains operated and holds relays 47 37 and 42 operated through its inner right-hand armature and front cont-act, third lower armature and front contact of re lay 47, middle made contacts of vertical olfnormal contacts 32 to ground. Relays 26 and 27 release when the subscriber at the calling station disconnects and a momentary circuit is closed'for the operation of relay 39 before relay 2? releases as follows: battery, winding of relay 39, inner upper armature and back contact of relay 31, lower made contacts of vertical off-normal contacts 32, inner lower armature and front contact of relay 27 to ground at the armature and back contact of relay 26. Relay 39 operating, removes the ground connection for the sleeve conductor to the preceding switches which are thereby released. Then when relay 39 releases, the ground potential is again applied to the sleeve conductor to prevent the connector from being seized until it is released by the called subscriber hanging up his receiver when relay 25 releases and causes the release of the other relays as hereinbefore described.

In case of a revertive call relay 25 remains operated until both subscribers on the party line have replaced their receivers. The release of relay 25 causes the release of the remaining relays in the circuit and restores the connector to normal.

In releasing the circuits of the common control equipment shown in Fig. 3 it should be noted that relay 101 was operated as soon as the brush of bank 106 left a normal position. The operation of this relay will then partially close a self-interrupting circuit for the operating magnet 108 which is fully completed when relay releases due to the removal of the ground connection from lead 45 when the connector is restored to normal due to the release of relay 27 and the opening of the rotary ofl-normal contact 60. This circuit may be traced from battery through the winding of magnet 108 and its self-interrupting armature and back contact, inner right-hand genesis? armature and front contact ofrelay 101, outer right-hand armature and back "contact of relay 1100 to ground. Ontthe release of relay 100 the pulsing circuit controlled by interrupter 111 is also'opened. It should be noted that on theeleventh'step ofthe switch 113 the brush of bank 210 6 opens the circuit :for relay 101, so thattheiswitch 1113 may either stand'with its brushes in the'n'ormalposition shown :in Fig. '3 'orwith their brushes in the normal eleventh position.

In order to provide a pause between the series of signaling :impulses as determined by the .first half and 'the second half ofithe banks 'of :the switch 113,:relays 112, 133 and 1341are provided. .Assuming'then, for example, that the "eleventh position :has been reached in the operation of the switch 113, the 'brushofbank 107 'will close in this position an obvious circuit :for the operation of .relay112. illlii-srelay in operating'transfers the pulsing circuit for magnet 1108 to close a circuit for relay :134- when relay 1'1O'isoperatedas follows battery, winding ofzrelay .134, iarmaturean'dEback contact of relay 1133,

left'hand armature and front contact'of relay 112to'ground atth'e armature and front contact :of relay 1110. Then when relay 110 :is released a circuit'is closed for the operation of relay 133 in series "with relay 134 as r01- lows: :frombattery through :the winding of relays 134 and 113 in series, and front contact of relay 134, right-hand armature a and front contact of relay 1112 to ground 'on lead :45. -Relay:13.3:in'operating open-sithe original for energizing relay '134:and closes a-circuit 'for the winding'of the magnet 108 :so that on the next operation of relay 110 magnet 10? operates over sa circuit .as follower-battery, winding of this magnet,- armature and front contact ofirelay 1 33, :left-handarmature and :front contact ofrelay 1 12 to :ground .Elt'itllfi armature :and front contact of relay 110. lvlagnet 107*now moves thebrushes ofswitch i 13 intoithetwelfthzposition and'the switch will then continue tobe operated under contrOlofthe interrupter "lll-asshereinbefore described. Itelay EIIQ'DOW releases aCO CiLllSOillB release of'relays 133-and 134. .Anzalarmcir- .cuit arrangement has-been provided to indicate irregularitiesrin the performance: ofzthese circuits, in 'onecase vi-f-za =false ground connection should for some :reasonor other, he applied onaconductor .48 and in'another case, if :the start relay 110 should fail to start the switch .113 in 1 operation. In the first :instance,ithe false ground connection on-lead :48 would, =while relay 101 is operated, close circuitithrough the-outer armature and front contact from thisground-tl1rough the winding of relay 136 to batteryand thus cause'this relay to be operated and remain locked throughiits left-handarmature and. front contactas long as this ground remains. A cir- 5 icuit -will 110W 'be completed ifrorn battery lamp and for thesounding of an alarm signal.

if the switch :1 131for any reason failsto operate when the start relay is operated, .a circuit is prepared for the operation ofzrelay 1&2. Wh'en the interrupter v 143 closes .azcircuit'to battery this circuit may be traced from battery, interrupter 143, vleft hand winding and makebeforc-brealr contacts of'relay 11412, lamp 144, armatureand back contactof relay 150,- outer-right-hand' armature and front contacto'frelay :100 to ground. 1RelayI142 locks itself through its right-hand winding :and when the interrupter 146 applies ground "to the'left-hand armatureof'relay142a circuitis completed for relay 1&7. This relay in operating-locksitself in series withttheilamprlela tojthe groundat the outer right-hand armature and front contactofrelay I100. Relay 147 also closes an obvious circuit for .relay 137 which in operating'oloses the alarrn'circuits at 140. If for any reasohtheswitc'h-HS fails to continue to step after having=once started relay 101 closes circuits for theaoperationof relays-142, 1 17, 137 ,andifor ltheilamp ll' l as abovedescribed. *Relay 150'=isnormal ly operated when relay 101 is operated to open the circuit 'for relay 142 'c'losed by the operation of relay 100 topreventthe-alarm circuits fromvfunctioning-under*normalconditions. Relay 137 willalso be operated'to close analarmcircuit'if an accidental ground is applied on conductor 50 or onathe-other' conductors leadingito=other partyslineterminals. The *circuits ;in these instances will *extend over'the right-hand armatures andiback contacts of relays 11 1, 126, 127, 128, 129 and 131 respectively andtheassociatedlamps 151, 152, 15-3, 1154, 155,-and156 will be lightedrespectively *to indicate on what [lead the .false groundconnectionhas been made, whilerelay 137 will be operated :to sound the :alarm.

It should be understood-that whilethe invention has onlybeen disclosedrin-connection With-one-circuit arrangement it could rreadily be applied-.to anumber of. other systems without departing from the spirit thereof.

Whatis claimed is: 1. In a telephone system, a line, .a;p"1urality of switches, means for establishing 'a'connec tion from oneof saidswitches to said'lin'e, a signal source, .means associated with each switch including a relay variably operable to produce codes of signals from said source for transmission to said line, a common device for actuating said 'relay to produce various code signals, and means for selectively determining the' type of code signals :tobe produced and transmitted. l

...2. In atelephone system, a line,a2switch,

a source of signaling current, means associated with each switch including a current interrupting device variably operable to produce codes of signals from said source'for transmission over said line, and means responsive to the establishment of a connection between said switch and line for operating said device in a particular manner depending on the terminal point to which the connection is established to produce and transmit a corresponding signaling current code over the line.

3. In a telephone system, a line, a plurality of switches, means for establishing connections from one of said switches to said line, a signal current source, means associated with each switch including a relay variably operable to produce codes of signals from said source for transmission to said line, a common device for actuating said relay to produce various code signals, means for selectively determining the type of code signals to be produced and transmitted, and means for preventing the production and transmission of a selective code signal except at the beginning of a code.

4. In a telephone system, subscribers lmes including party lines, switching means responsive to one subscriber calling another on the same party line for connecting the line with terminal points of said line identifying the desired subscriber, and means responsive to the calling subscriber thereafter hang ing up his receiver for signaling the desired subscriber with a code signal identifying said subscriber and for signaling the calling subscriber with a code signal assigned as a notifying signal that the desired subscriber has been called and for partially releasing the connection between the line and said terminal points established by said switching means.

5. In a telephone system, subscribers lines including party lines, switching means responsive to one subscriber calling another on the same line, for selecting a terminal point on said line identifying the desired subscriber, means operative after said terminal point has been selected for signaling the desired subscriber with a code signal identifying said subscriber and for signaling the calling subscriber with a code signal assigned as a notifying signal that the desired subscriber has been called.

6. In a telephone system, subscribers lines including party lines, switching means responsive to one subscriber calling another on the same party line, for selecting a terminal point on said line identifying the desired subscriber, means operative after said terminal point has been selected for alternately signaling the desired subscriber with a code signal identifying said subscriber and for signaling the calling subscriber with another code signal assigned as an identifying signal that the desired subscriber has been called.

7. In a telephone system, subscribers lines including party lines, switching means responsive to one subscriber calling another on the same line, for selecting aterminal point on said line identifying the desired subscriber, means operative after said terminal point has been selected for signaling the desired subscriber with a code signal identifying said subscriber and for signaling the calling subscriber with a code signal assigned as a notifying signal that the desired subscriber has been called, said code signals being transmitted through the selected terminal point.

8. In a telephone system, subscribers lines including party lines, switching means responsive to one subscriber calling another on the same line for selecting terminal points on said line identifying the desired subscriber, a relay responsive to said selection and to the calling subscriber hanging up his receiver, means including another relay responsive to the operation of said first relay for transmitting through said terminal points a code signal to call the desired subscriber, means including a third relay responsive to the operation of said first relay for transmitting through said terminal points another code signal to notify the calling subscriber that the desired subscriber has been called.

9. In a telephone system, subscribers lines including party lines, means including a connector responsive to one subscriber calling another on the same line for selecting a terminal point identifying the desired subscriber, a source of signaling current, a current interrupting device associated with said connector, another current interrupting device associated with said connector, and means for cont-rolling said first device to transmit a signal current code to the'calling subscribers station and for controlling said second device to transmit a signal current code to the called subscribers stations.

10. In a telephone system, subscribers lines including party lines, switching means responsive to one subscriber calling another on the same line for selecting a terminal point on the same line identifying the desired subscriber, a relay responsive to said selection and to the calling subscriber hanging up his receiver, and means responsive to the operation of said relay for transmitting over said line a signal to call the desired subscriber and another signal to notify the calling subscriber that the desired subscriber has been called.

11. In a telephone system, subscribers lines including party lines, switching means responsive to one subscriber calling another on the same line for selecting a terminal point on the same line identifying the desired subscriber, a relay responsive to said selection and to the calling subscriber hanging up his receiver, and means responsive to the operation of said relay for transmitting over said line a signal to call the desired subscriber, another signal to notify the calling subscriber that the desired subscriber has been called and for partially releasing the connection established by said switching means.

12. In a telephone system, subscribers lines including party lines, a connector, means for extending a connection from a party line to said connector, meansin said connector for completing said connection to a desired line, a relay operated when the calling subscriber hangs up his receiver, and means responsive to the operation of said relay only when the calling and called subscribers are on the same party line for releasing said con-- nection extending means but maintaining, said connector in connection with said party no line during conversation. I

13. In a telephone system, subscribers lines including party lines, a connector, means 7 for extending a connection "from a party line to said connector, means in said connector for completing said'connection to a desired line, a relay operatedwhen the calling subscriber hangs up his receiver, means responsive only when the calling and called subscribers are Y on the same party line to the operation of my said relay for releasing said connecting extending means but maintaining said connector in connection with said party line, and for transmitting signals to call the desired subscriber and for notifying the callingsub scriber that the desired subscriber has been called. p 1

In witness whereof, I hereunto subscribe my name this 8th dayvof May, 1930.

HENRY HOVLAND.

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