US1733568A - Telephone system - Google Patents

Description

Oct. 29, 1929. R. s. WILBUR TELEPHONE SYSTEM 3 Sheets- Sheet 1 Filed March 31, 1927 m R m 0 7 mm 4 mm w o h v, M V i 9. %m T R I IIHIIIJ). |\N De 3 -l iv kw Oct. 29, 1929. R. s. WILBUR TELEPHONE SYSTEM Filed March 51, 1927 3 Sheets-Sheet 2 Oct. 29, 1929. R. s. WILBUR 1,733,568

TELEPHONE SYSTEM Filed Marc 51, 192'! s Sheets-Sheet 5 Patented Get. 29, 1929 was STATES (PATENT FicE RAY s. wrLBUn, or LYNDHURS'I, inn-w JERSEYQASS'IGNOB T BELL TELEPHONE LAB- oRA'roRI'Es, moonronarnn, or new YORK, n. Y., A CORPORATION OF NEW YORK TELEPHONE sYs'rnM Application'filed March 31 1927. Serial No. 179,827.

versation that may be in progress between the calling subscriber and the operator over said trunln A feature of this'invention is an arrangement wliereby'the dialing impulses are transmitted over the trunk as a simplex circuit.

According to another feature means are provided whereby the toll operator may call an automatic subscriber through the automatic exchange over said trunk.

Another feature is an arrangement whereby the calling line may be either a regular automatic subscribei"s line or a line leading to a private branch exchange and whereby connections initiated by the toll operator may be established to either ot-theso two types of lines.

to systems for checking the numbers of calling lines'bytoll switchingoperators. If the calling fline is'a regularautomatic subscribt ers line the arrangement is such that the checking connection will ,be established through the usual automatic switches at the automatic exchange regardless oi -the fact that this subscribers line is busy and it the line is a P. B. X. line the arrangement is I such that the checking connection will be established to this particular busy P. B. X. line.

This inventionhas been illustrated inthe accompanying drawing in which; F 1

' shows partly in detail and partlyin diagrammatic form the automatic circuit equipments at an automatic exchange which may be em ployed in the establishing of connections between an automatic subscr befis line or The invention is particularly "applicable P. B. X. lineto two-way trunks leading to toll operators positions at a distant manual exchange. i I

Fig. 2 shows the equipment at the automatic exchange which is required for a twoway trunk connection between the automatic exchange and a toll operators position at the manual exchange I Fig 3 shows the equipment required at the terminating end of a two-way trunk at the toll operators position in the manual ex- Y change. A toll operators cord circuit has also been shown in diagrammatic form in this figure for extending toll connections from the twoway trunk.

In general the apparatus required and the operations of the arrangement as shown in the drawings for establishing connections of these types may be outlined as follows WVhen the subscribenof a line such as 1, or the operator at the distant end of a P. B. X. line, such as 2, dials to establish a connec; tion'to a toll operators position, such as 300, at the manual exchange B, the automatic switches at the automatic exchange A, such as the line finders 4: or 5 and districtswitch 6, shown diagrammatically, are operated to connect the calling line to a two-way trunk T, terminating through the circuits shown in Fig. 2 in terminals 7 at the bank ofthe district switch Gor at the multiple banks of other district switches. lVhenthis connection is completed the line lamp 301 at the ack 302 of the trunk T lights and indicates to the toll operator'that a connection is desired over this trunk.

When the toll operator answers the call by connecting her telephone set to the cord 300 and inserting plug 318 into jack 302, the battery supplied to the calling line from the trunk T is reversed so that battery is present on the'tip and ground on the ring at the calling line, whichis opposite to the condition occurring when a connection is established over the automatic switchesbetween the calling subscribens line and an ordinary called subscribers line. The toll operator now asks the calling subscriberfor the number of his line and for the information relating" to the toll connection. As soon as the through toll operator receives the numberof the calling subscribers line she connects her dial 331 through key 327 to the cord and dials this number. The dial impulses are transmitted back over the trunk T arranged as a simplex circuit. Thatis, the impulses are transmitted I over the two conductors of the trunk in parallel. r r

The arrangement is such that the line finder 10 and its associated apparatus were prepared during the establishing of the connection to the toll operator to cause the selection of an idle sender and switching equipment for extending the checking connection to the calling subscriber. Therefore, when the dialing impulses are received through this line finder they are registered on the sender 12, and when the sender is satisfied it will control the establishment of a connection to the calling subscribe-rs line over the ordinary switching equipments at the automatic exchange such as 14 and a final switch such as 15. If the calling subscriber gave the correct number the final switch will find on the multiple terminals of this line the above mentioned reversal of battery, and through suitable means hereinafterdescribed the final switch will thereby be actuated to stop with its brushes on these terminals, even though these terminals are in the ordinary sense made busy. s

In the case the calling line is a P. B. X. line the final switch starts to hunt for a P. B. X. line in the ordinary manner but will, due to reversal of battery, stop with its brushes on the particular P. B. X; line used in the original connection, even through this P. B. X. line would in the ordinary sense be busy. To make this particular P. B. X. line busy to'other final switches the battery is reversed to its normal condition as soon as it has been found and the busy sleeve condition restored so that it. will test busy to other final switches hunting for an idle P. B. X. line. When the final switch has connected .with the calling line the circuit arrangement is such that the original connectionover line finders i or 5 and districtswitch 6 to the trunk is opened and the trunk connected to. the connection established through line finder 10 and, switches 14 and 15. In this manner calls, from subscribers lines or P. B. X. lines terminating in an automatic exchange, intended fortoll connections 7 may We checked asrto their identity by the toll'operator at the distant manual exchange B by having the toll operator dial the calling line number to set up a separate automatic connection. r r

The trunk line T is also arranged so that the toll operator can establish'a connection to a subscriber in an automatic exchange or to a P. B. X. line on incoming toll calls. In

these cases the'sleeve terminals at the district switches such as 6 are made busyand connection to the desired line is extended over the trunk in the same manner as the checking connection.

Detailed descriptions will now be made of calls from an automatic subscribers line and from a P. B. X. line to a toll operators position and the checking of the number of the calling line followed by a description of a call from a toll operators position to an automatic subscribers line and a P. B. X. line. If the, subscriber of an automatic line 1 desires to make a toll connection he will dial a certain code number which will connect him with an idle trunk line T through the linefinder & and a district switch 6. As such selectionsthrough switches of an automatic exchange are now well known in the art and form no part of this invention the automatic equipment has been shown merely in diagrammatic form. When the brushes of the district switch 6 land on the terminals 7, relays 200 and 201 are operated, due to the closure of the tip and ring conductors in the district switch circuits, as is also well known in the art. The operation of these relays closes a circuit for the operation of relay 203 from battery, through the winding of relay 203, inner lett-handarmature and back contact of relay 204, through the right-hand armatures and front contacts of relays 201 and 200 in series to ground. The operation of relay 203 causes an obvious circuit to be closed for relay 205 and this relay in turn closes a circuit through the left-hand winding of relay 200 for the locking of this relay under control of relay 205 and at the same time relay 205 short-circuits the righthand winding of relay 200. Ground is also connected to the sleeve conductor terminating at the district switch 6. This ground is connected through the right-hand winding of relay 207 for the purpose of making trunk T busy to other district switches. Relay .207 is operated through this sleeve circuit'and locks through its left-hand winding under control of relay 203. The operation of relay 203 also closes an obvious circuit for the operation of relay 209.

Relay 209 in operating suppliesat its armatures and front contacts battery and ground to the trunk T through the, windings of the marginal relay 210, makebef orebreak contactsof relay 211, windings of the dill'erentially wound relay 212, right-handwindings ofrepeating coil 214:, the conductors of trunk Thinner armatures and-back contacts of relay 305, left-hand windings of repeating coil 306, left-hand armature and inner right-hand armature andback contacts of relay 308,

windings of relay '309, armatures and back contacts ofrelay 310, through the loop including resistance 311. Relay 210 is marginal in character and relay 212 isdifi erentially wound and neither of theserelays will operate in thiscircuit as arranged at this time. Be lay 309,'however operates to close a circuit Relay 315 also operated due to the'operation 'ture and back cont of relay 309 from battery, through the left hand winding of relay 31 5 inner right-hand armature and back contact of relay 313, armature and front contact of relay 309 to ground. The operation of relay 315 prevents the operation of relay 310 during this call on the subsequent "operation of relay 313, as will hereinafter be described.

At the operation of relay 203 as hereinbefore described a circuit was also closed for the operation of relay 215. Thisrelay is used to prepare a connection for the checking circuit so that it will be ready'for use by the toll operator when she desires to dial the subscribers number. The results produced by the operation of relay 215 may be outlined as follows RelayslOl and 102 are op-- erated in series over an obvious circuit closed to ground through the armature and "front contact of relay 215. The operation of these two relays closes an obvious'circuit for the operation of relay103. Relay 103 in operating closes a circuit for relay 105as follows: battery, winding of relay 105. outer armature and back contact of relay 106yarmature and back contact oil relay107, left-hand armature and front contact o'r'relay 103-110 ground. Belay 105 in operating closes an obvious cir, cuit for the step-by step magnet 109 and this magnet in operating causesthe brushes of the switch 10 to be advancedto find anidle sender 12 and a connection having access to switches 1%. An idle connection of this type will be identified through a battery connection on the terminals of switch bank 110. When such a connection has been reacheda circuit will therefore be established for the operation of relay 112 as follows: battery, se quence switch "contact 17, (position 1) armaact of relay 18, terminal bank 110, outer r ght-handarmature and front contact oi rel 103, both windings of lay 112 in series, winding of marginalre- 107 to ground. The high resistance of the e -hand winding of relay 112 prevents the immediate operation of relay 107 but onthe operation of relay 112 this left-hand winding short-circuit d so that relay 107 will then operate. The ey in the operation of relay 107 pern'ii rela 05 to remain operated lon dcl r 1 enough to allow the magnet 109 to complete the lastthat centers the brushes oi' finder 10 squarely on the terminals of the idle sender circuit. it should be noted that when relay 107 operates the circuit for relay 105 is broken at the armature and back contact of relay 107, so that relay 105 may release and stop the operation of the stepping magnet 109.

Another circuit is closed by the operation of relay 107 from ground at the left-hand armature and front contactot relay 103, through "the armature and tront'contactof relay 107 and winding of relay 106 to battery so that relay 1001 will now operate. Relay 106 in operatingopens the'circuit from relay 105 at another point and prepares anuniber oi other circuits hereinafter described. I 1

One circuit is'closed by relay 106 to lock this relay inoperated position under control of relay 103. 'Another circuit is closed for the operation of relay 18 through the con-. tactsof terminal bank of 113. Relay 18 in operating opens the circuit from battery at se, quence switch 17 to the test bank 110 thereby making the sender nonscloctable. he operation'ot relay 18 also opens the circuit through relays 112 and 107 WJlCll release but as relay 106 is now operated the circuit for relay 105 remains open. Another circuit closed by relay 106 is a connection between the ring conductor terminating at bank 115 through the outer right-hand armature and back contact of relay 116 to lead 117. This lead is the, so-called dialing lead over which dialing impulscs from the toll operators position are. transmitted to the sender 12 for the selection of the calling subscribers line through the checking circuit. This lead 117 terminates at the front contact tor the armature of relay 212 which is the pulsing relay responsive to dialing impulses from the toll ope'rators position as will hereinafter bedcscribed. Another, circuit is closed by relay 106 through the bank 118 to the sequence switch 191501 the subsequent operationof relay 116, as will hereinafter be described.

The. sender12 is now ready to receive dialing impulses. line-finder and sender circuit of the type diagrammatically shown in Fig. 1 may be had by referring to Patent No. 1395977 to Steam] and Scudder, issued November 1, 1921and since this apparatus forms no part of this invention, no complete description otitsoperation has been made here but only such as is necessary for the proper understanding of the invention. I i

' As previously mentioned lamp 301. is lighted to indicat-eto the toll operator that a connection is desired. The toll operator will now insertthe plug 318 into jack 302 of trunk T and connect her telephone set to the cord by operating talking key 3-17. This causes the operation of relay 319. over the sleeve circuit but due to the high. resistance of the winding of relay 319, lamp 320 is not lighted at this time. 'The operation of relay 319 closes an obviouscircuit for the operation of relay 313 and this relay in operating opens the previously mentioned circuit for lamp 301 which is now extinguished. Relay 315 is locked through its right-hand winding by the operationof relay 319 as the original ener- A complete description of a I i this time.

at this time. Another circuit closed by the.

operation of relay 322 to include a resistance 324 toground for the sleeve circuit may be traced as follows: From the sleeve circuit at jack 302, resistance 324, right-hand armature and front contact of relay 322, lower outer armature and back contact of relay 305, armature and a front contact of relay 309 to ground. This resistance is lower than the resistance of winding of relay 319 so that lamp 320 isnow lighted. i

. Relay 313 in operating closes a connection through its outer right-hand armature and front contact to short-circuit resistance 311 so that the loop through ,trunk T. previously mentioned will now cause the operation of marginal relay 210. The operation of this relay closes an obvious circuit for the operaion of relay 204 and at the same time closes a circuit for holding relays 203 and 215 operated after relay 204 becomes operated to open the original energizing circuit for these re lays. The operation of relay 204 closes an obvious circuit for the operation of relay 216. This relay'in operating reverses the current, supplied from the battery and ground connected through the left-hand windings of repeating coil 214, for the tip and ring conductors terminating at the district switch 6. This causes the operation of the polarized relay of the district switch which now connects the calling subscribers line through to the repeating coil 214. The operation of relay 216 connects battery to the tip conductor and ground to the ring conductor. This, as is well known 1n the art, 1s a reversal of the usual talkmg battery connections from a subscribers lines through automatic switches.

The purposeof this reversal of the battery and ground connections will be explained later in connection with the seizing of the subscribers line by the checking connection.

The operation of relay 204 also causes the operation of relay 211 over a circuit as follows: Battery, winding of relay 211, inner left-hand armature and back contact of relay 1 204, armatures and back contacts of relays contacts the circuit from the two windings of relay 212, througl'ra loop established through the' left-hand armature and inner right-hand armature and back contacts ofrelay 220. This loop is now connected to This relay connects through ground at the inner right-hand armature and front contact of relay 203 so that the simplex circuit for dialing is established at this end of the trunk Tfrom the two conductors of trunk T through ,the windings of differential relay 212 to ground. The operation of relay 211 does not cause the release of relay 210 but maintains this relay operated through circuits established from the two windings of relay 210 to ground and battery at its lefthand armature and the inner right-hand armature and front contacts.

The connection to ground through the windings of relay 212 for the conductors of trunk T causes the release of relay 309. This relay in releasing causes lamp 320 to be extinguished, due to the opening of the circuit to ground for resistance 324 through the an mature and front contact of this relay. The extinguishing of lamp 320 indicates to the toll operator that the trunk connection is completed from the calling automatic subscriber and that the circuits are ready for dialing as soon as the toll operator has obtained the number of the calling automatic subscriber. As dialing is done over a simplex circuit comprising the two conductors of the trunk T the toll operator may begin to dial the calling subscribers number as soon as she has received it and simultaneously maintain a conversation with this subscriber in regard to receiving the information required forthe extension of the toll connection. The toll connection may be extended by inserting plug 325 of the cord circuit 300 into jack 326 associated with a toll line.

To dial the calling subscribers number the toll operator will actuate her dialing key 32. A connection is thereby established from battery through the dial contacts of dial 331 to a central point of the secondary windings of repeating coil 328. The tipand ring conductors of the cord are now, therefore, connected in simplex from this battery, through the dialing contacts towards trunk T, while the trunk itself is connected in simplex through the windings of difierentially wound relay 212to the ground at the inner right-hand armature and front contact of relay 203. However, the talking conncction from cord 300 to trunk T which originally extended through repeating coil 306' is not suitable for simplex operation due to the presence of this coil and the condensers 330 in the circuit. To initiate the establishing of a complete metallic connection, it will be notedthat when the dialing key is operated a connection ofbattery is completed through the dial contacts and relays 332 and 334 are thereby operated. The circuit for'relay 332 extends through the tip conductor and upper right-hand winding of repeating cord 306, while the circuit for relay 334 extends through the ring conductor and the lower'right-hand' winding of repeating coil306. The operation of these relays closes a circuit for the operation of. relays 305 and 335 as follows Battery, windings of these relays in seriesthrough the inner right-hand armaturesand front contacts of relays 332 i and 33 1 in series to ground. The operation of these latter relays connect the tip and ring conductors of trunk T through the inner upper and lowerarniatures and front contacts of the two relays directly to the tip and ring conductors of cord 300 and opens the connection through repeating coil 306 and condensers 330. \Vhen relay 335 operates the circuit for relays 332 and 334i is opened so that these relays will now release but relays I 305 and are locked inopcrated position through the ground at the armature and front contact of relay 337, thlsrelay having been operated. overan obvious circuit on the operation of relay 332. As relay 337 isslow-torelease, it will beheld operated for a short period afterthe release of relay 332 sufficient to maintain it operated until relay 339 operates to hold it in operated condition. It will be noted that relay 339. has its left-hand winding included in the connection through the tip conductors of trunk T and cord 300 and its right-hand windingincluded in the connection through thering conductorsso that relay 339 will operateas soon as the simplex circuit is established and thus maintain relays 337, 305 and 335 operated.

1 On the operation of relay 339 relay 323 releases, but as;it is slow-to-release lamp 320 will be momentarily lighted due to the fact that-relay 305 is now operated. The circuit may be traced as follows: Battery, lamp 320,

ential relay 212 to ground, this relay was operated. Relay 212 inoperating causes relay 218 to operateover thec'ircuit frombattery, winding'ofrelay 218, inner right-hand armature and front contact of relay 20 1 to ground as it will-be "noted that this circuit for 218 is normally shorted by a circuit completed to ground through the outer right hand armature and front contact of relay 20st and the armature and back contact of relay 212, this latter circuit being opened on the operation of relay212. Relay 218 is sufficiently slow-to-release to hold it operated during the dialing impulses, that is, when relay 212 is subsequently released, due to the dialing, as will'behe'reinafter described. Relay 218 in operating closes a holding circuit for relay 211completed at its inner righthandarmature and front contact. The operation of relay 218'will'also closean obvious circuit for, relay. 219 and relay 219in operating willprovide alocking circuit for itself to the ground at the inner left-hand armature and front contact of relay 210. :The purpose ofthe operation of relay 219will be explained hereinafter; I t I i I i When now the operator actuates thefdial 331 n accordance with the number of the through the dial contacts is alternately broken, and relay 212 will, therefore, befalternately released andoperated in accordance .with the impulses transmitted over the sirn- I It will be noted that theffirst operationof relay 212 closedthe pulsing plex circuit.

lead 117 to: ground. A circuit is now completed through thewinding of pulsing relay 24 in the sender 12, sequence switch 22, bank 115 of line-finder 10, an armatureand front contact of relay 106, outer right-hand arinature and back contact of relay 116, lead 117 to ground atthe armatureandfront contact of relay 212. .The succeedingimpi lses will,

lay 24- so that the sender 12 ,will'be set in accordance with the numberof the wanted subscriber. 3 t J I V/hen' the toll operatorfinishes dialing the calling subscriber, the connection to battery therefore, alternately operate and release 'resender will control switches la toselect a final switch 1.5 and the final switch 15 will he operated to connectwith the 'termin als'26 of the calling line, if the number given'by the calling subscriber isjthe correct number. vAtthis time the sequence switch 19 will close acounectionto ground for bank 118 and a, circuit hand armature and'back contac'tof this relay, the second outer left-hand armature and back contact of relay 106throu-gh bank 118,

willbeconipletedforrelay 116 as follows: 3 'Battery, winding of'relay 116, inner rightsequence switch 19 'to ground, Relay 116 in operating provides a locking circuit for, it- 1 self, to ground at the inner left-hand'armature and front contact of relay 106, and opens the connection through its outer left-hand armature and bac'lecontact for the pulsing lead 117 which will thereby be disabled. This relay also by closing a connectionto battery at its middle right-hand armature and back contactcauses relay 101 to be re- 215. i t t .When the contacts 26 are reached by the brushes of the finalswitch 15 the circuit changes in switch 15 would ordinarily take place to send a busy tone back over the connectionto the tolloperator, as these terminals wouldtest busy. However, due to the fact that the (battery connections for the tip and 7 ring conductor through the line-finders and the district switch 6 have been reversed, this 15 to advance to the position where it would cause the busy tone to be sent back over the hue, but Wlll remain infa position where "changes will take place to cause the switch to be malntained with lts brushes connected to the terminals 26. It is unnecessary to show and describe in detail how the usual busy tone signal is produced, and how the final switch acts under the usual condition as it forms no part of this invention. For a complete disclosure of an arrangement of this kind in a final switch reference may be had to the above mentioned patent to Stearn et al. To produce this effect, to wit, to cause the switch to stop with its brushes on terminals 26, sequence switch cams 30 and 31, relay 28 and associate circuits have been added to the usual equipment for the final switch 15. It should be understood that the usual functions of the switch 15 are not disturbed, except in this respect, that the switch circuits act to perform the additional functions as hereinafter'set forth. These functions are as follows: NVhen the brushes of switch 15' are brought in contact with the terminals 26, the

' sequence switch will be driven from position 9 to position'12. In positions 10+ 12 the sequence switch cam 30 will close a connection from relay 28 to the ring conductor leading back through switches 14, and the sequence switch cam 31 will in these postions (10+ 12) close a connection through for the tip conduct-or of the switch 15 from the tip brush of the. switch 15 to the tip conductor of the switches 14. A circuit is, therefore, first completed for actuating relay sea the moment the brushes of switch 15 come in contact with terminals 26 as follows: battery, winding of relay 201, lower left-hand winding of repeating coil 214, left-hand make-before-break contacts of relay 221, lower armature and front contact of relay 216, tip conductor of the connection through the district switch 6 Y and line-finder 1, tip conductor of line 1, tip

brush of final switch 15, sequence switch cam V 31, positions 10+12, tip conductor of the switches 14, upper armature and back contact of relay .33, sequence switch cam 3%,bank

121, winding of relay 224 to ground. Relay 224 is polarized and operates in this circuit. A circuit is thereupon closed by the operation I of relay 224- for the operation of relay 28 as follows:

battery, winding of relay 28, se quence switch cam 30, positions 10+12, ring conductors of switches 14:, lower armature and back contact of relay 33, sequence, switch cam 22, bank 115, outer armature and back contact of relay 222, armature and front contact of relay 224 to ground. Relay 28, by attracting itsleft hand armature may cause the switch 15 to remain with its brushes on termito complete the talking connection as described in the above mentioned patent to Stearnet al., that is, relay 28 would open at its left-hand armature and back contact the connection to the sleeve brush causing the advance of the normal. This causes the release of relays 339 and 212. The release of relay 339 causes the release of relay 337 and this relay in releasing opens the holding circuit for relays 335 and 305 which are now also released. By the release of the two last mentioned relays the tip and ring conductors of the trunk will now be reconnect-ed through the repeating coil 306. The release of relay 212 causes relay 218 to release and this relay in releasing closes an obvious circuit for the operation of relay 220. Relay 220 in operating opens the loop to ground for the simplex circuit through the windings of relay 212. Relay 218 also by releasing closes an obvious circuit for the operation of relay 221. The operation of this relay opens the connection from trunk T to the district switch 6 at the make-before-break contacts of this relay so that the talking connection between the calling subscriber and the toll operator will now extend through the checking circuit by way of the inner left and right hand armatures and front contacts of relay 221. Relay 228 is also released by relay 218. It will be noted that this relay was operated when relays 218 and 219 were operated. The operation of relay 221 opens at its outer left-hand armature and back contact the sleeve circuit for the district switch 6 to cause the release of the original connection through this switch. Sufficient time to allow this disconnection to be completed is provided as relay 228 is slow-to-release. That is, relay 228 does not again'close the sleeve circuit until a short period after the operation of relay 221 to give sufficient timefor the district switch and the connection to the line 1 to release. The release of relay 228thus re-establishes the busy condition on the sleeve terminal of the district switches, and this busy condition remains until relay 205 is released, as will hereinafter be described. The circuits are now in condition for conversation between the calling subscriber at 1 and the toll operator at 300 through the checking circuit while the originally established circuit through linefinder 4 and district switch 6 is released. It will be noted that the release of the dialing key to establish this new talking connection does not in any way interfere with the conversation between the subscriber and the toll perator, which may not be finished when the transfer takes place.

The connection may now be extended by the toll operator by releasing the talking key and by inserting plug 325 into jack 326 pleted in the standard manner to the wanted subscriber. I I j To rel this connection the calling subscriber on lincl hangs up his receiver and thus causes the release of relay 201. Relay 201 in releasing opens the circuit fo'r'relay 211 and th' "clay in releasing causes theoperation of relay 309. The operation ot relay 309 closes a circuitiorthe lighting oflainp by establishing a connection to ground from the resistance "224 hereinbefore described. 'lhetoll operator noting the lighting of lamp 320 removes plug 318 from jack 302, thus causing the release of relay 319, and relay 319 in releasingcauses the release of relays and 315. Relay 313 in releasing 041) causes the release of relays 321 and 322. As relay 321 is slow-'to-release, a circuit will be momentarily closed for the operation of relay 308 through the armature and front con tact of relay 321 from the ground at the inner left-hand armature and backcontact'o'f relay313. The operation of relay 308 prevents the momentary lighting of lamp 301 on the release of relay 313 and also causes the release of relay 309. I I r The momentary operation of relay 308 opens the circuit to the conductors of trunk T so that relay 210 will now release. Relay 210 in releasing causes the release of relays,

204;, 203,215 and 219.. The release of relay 20 1* causes LlIlG release of relay 216. 1 The release ofv relay 203 causes the releaseofirelays 209,205 and204'." Relay 205 in releasing causes the. release of relay 200 and opens the busy connection to ground for the "sleeve con- ,"ductor at the, terminals 7. ,The release of-relay 219 causes therelease of relay. 220, while the release of relay 215 causesthe rele'aseof the checking connection through the lineiinder 10 and the switches 1 1" and of the of relay 103 and the release of relay l03causes the release of relays 106 and1116." 106 in'releasingcausesthe release of relay'18 and'the line-finder 10 and the succeeding switches are therefore restored to normal condition in a manner WGlllUJOWnJD the art.

If it is desired to raring the calling subscriber o f line, 1, ringing key 341 is operated to connect battery to the tip conductor of the cord 300. This battery connection causes the operation of relay 33 1 and, this relay in operating closes a circuit for the operation of relay 305 and also connects ringing battery and ground atits left-hand armature and outer righthand armatures and front contacts to the ring and tip conductors and lower inner armatures and front con- This ringing current and relay'230 in operating closes a circuit for the *OPGI'iLblOIlOf relay 33; from battery, winding ofrelay 33, sequence switch contact contacts to the tip and ring conductors of the connectionto the 'calling subscriber 1.

The flashing of the ringing key 3 11 causes correspondlng impulses of current to be transmitted to the calling subscribers line.

If the calling line is a P. X line such I as line 2, theconditions relating to the estab- I hshing 01' a connection to this hue and the busy condition for the line 2 will be similar to the conditions when a connection is,

made with an ordinary subscribersline; In

this case the brushes of the final switch will be stop'ped'on the terminals 39 by the operation' of relay 28 in the same manner as i theyare stoppedon terminals 26. Theswitch "15 will, of course, first be directed to the point'whereit will begin to hunt for the P. B.

line 2; The normal busy condition of a 1 B. X. line is, as is well known, such that battery is connected to the ring terminail and ground to the t1p term1nal, while theterminals 39' of line 2have batter-yon the tip terminal and ground on the ring terminal. Hence, when thesw1tch has passed by the terminals of busy P. B. X. lines in the usual manner and lands with its brushes on theterminals' 39, the circuits previously men? tioned will be closedas follows: first to ac relay 28. The actuation of relay 28 causing the switch 15' to remain with its brushes on terminals 39 and cause the sequence switch to advance to the talklng position in the same manner as hereinbefore described and 1n accordance Wltll. the arrangement shown in the above mentioned patent to Stearn et al. i It is evident that the final switch in hunt-j ing forterminals '39 might encounter the terminalsof idleP. B. X. 'linesand in this case the switch would naturally stop with 1 its brushes on the terminals of the first idle line encountered." Theoperation or the circuits would in this case be identical wi h the operationwhen theswitch stops onterminals 39. It should be understood that it is only necessary to avoid having the switch stop with its brushes on any other busy terminals except terminals 39 as it is the P. B. X. that it is desired to check but not necessarily the particular P. B. X. line employed in the first instance. The completionof the con nection'is identical with that for the automatic subscriber of line 1 and will, therefore,

not be further described. respectively of trunk T at the upper inner It is now assumed that the toll operator tact of relay thus cause the operation of relay 319. Re-

lay 319 in operating causes the operation of relay 313 and relay 313 causes the operatlon otrelays 321, .322 and .310. Relay 322 in operating closes a circuit for the operation of relay 323 which relay performs no function in this connection but relay 322 in operating brings the resistance 32% under control of relay 309 for the purpose of actuating lamp 230 for supervisory purposes as will hereinafter appear. Relay 310 in operatin connects battery and ground at its armatures and front contacts through the windings of relay 309. and armatures and back contacts of relay 308 over trunk T, repeating coil 218, windings of relay 212, make-beforebreak contacts of relay 211, windings ofrelay 210 and through the loop established through the armature and back contacts of relay 209. lay 309 and causes lamp 320 to be lighted over a circuit as hereinbetore mentioned to indicate to the operator that the connection is now being prepared for dialing. The

connection of battery and ground to the armatures and front contacts of relay 310 causes also the operation of the marginal relay 210. Relay 210 inoperating causes the operation in succession ofv relays 20%, 205 and 200 for. purposeshereinafter to be described. Relay 215 is also operated by relay 210 to prepare the line-finder 10 for establishing .a connection through switches 14: and final switch 15 to the wanted subscribers line. He-

lay 233 is also operated by the operation of I relay 210 over a circuit as follows: battery,

winding of relay 233, outer right-hand armature and back contact of relay 220, outer right-hand armatureand back contact of relay 203 to the inner armature and front con- 210. The operation of relay 233 connects ground to the mid-point of the simplex circuit connected from the trunk through the windings of relay 212, makebei'ore-break contacts of, relay 211, windings of relay 210, armatures and backicontacts of relay 209. Relay 210 although marginal will not release in this circuit.

' will be extinguished to indicate that the-dialing may begin. The operator now actuates her dial-331 to call the wanted subscriber and V causes the alternateoperation and release of relay 212. The first operation of relay 212 on the actuation of relays 305 and 335 caused the operation of relay 218 which remains op- This causes the operation of reerated during the pulsing. Relay 219 is also operated and maintained locked in operated position under control of relay 210. 'Relay 211 is operated by the operation of relay 218 and connects the simplex circuit through the windings of relay 212, the outer right-hand The dialing may now proceed and the wanted line selected as hereinbefore described in connectionwith the establishing of a checking circuit.

VJhen the dialing key is released relay 339 is released to cause the release of relay 337.

Relay 337 causes the release of relays 305 and 335 to establish the connection from the toll operator to trunk T through the repeating coil 306. Relay 212 is released and causes the release of relay 218. Relay 218 causes the release of relay 211 and relay 228 and the operation of relays 220 and 221. The operation of relay 221 connects the trunk T through to the tip and ring conductors of the established connection through line-finder 10, while the operation of relay 220 opens the circuit for relay 233 which is released to re move the connections for the simplex circuit. Relay 211 in releasing reestablishes the connection through the windings of relay 210 from the toll operators cord. On ringing the Wanted subscribers line the operation of ringing key 341 will operate relays 334 and 305 to establish a circuit for the operation of relay 230, this relay in turn operating relay 33 to transmit ringing current to the called line. lVhen the called subscriber answers relay 201 is operated. A circuit is thereby established for the reoperation of relay 211 so as to'remove the battery and ground from the trunk T and cause the release of relay 309. This relay in releasing causes lamp 320 to be extinguished. If the called subscriber actuates his hook he may thereby cause lamp 320 to flash for supervisory purposes. The release of the connec tion is the same as hereinbefore described in relation to the release of'a checking circuit.

While the invention has been shown as applied to a given toll switching arrangement it is not so limited, but may be applied to systems of other types.

What is claimed is:

1. In a telephone system, an exchange, a line incomin to said exchange, a trunk outgoing from said exchange, an operators position at which said trunk terminates, switching means at said exchange for connecting said line and trunk, and other switching means at said exchange controllable from said operators position over said trunk for establishing a diilerent connection between said line and trunk and for breaking said first connection. 1

2. In a telephone system, an exchange, a line incoming to said exchange, a trunk outgoing from said exchange, an operators position at which said trunk terminates, switching means at said exchange for connecting said line and trunk, other switching means at said exchange controllable from said operators position over said trunk for establish.- ing a different connection between said line and trunk, and means operatively conditioned by the establishing of said second mentioned connection and controllable from said operators position for releasing the first mentioned connection.

3. In a telephone system, an exchange, a line incoming to said exchange, a two-cons ductor trunk outgoingfrom said exchange, an operators position at which said trunk terminates, switching means at said'exchange -tor connecting said line and trunk, another switching means at said exchange controllable from said operators position over a circuit established through the two conductors of said trunk inparallel for establishing a different connection between said line and trunk, and for breaking down said first mentioned connection. I i

4. In a telephone system, an exchange, a line incoming to said'exchange, a trunk outgoing from said exchange,an operators position at which said trunk terminates, switch ing means at said exchange for connecting said line and trunk, and another switching means at said exchange controllable from said operators position over said trunk for establishing a different connection between said line and trunk and for breaking said first mentioned connection without interrupting a conversation that may be in progress over said trunk. a

5. In a telephone system, a plurality of lines, an operators position, a trunk terminating at said operators position, means for establishing a, communicative connection from any one of said lines to said operators position over said trunk, means for automatically establishing a separate communicative connection from said operators position to any one of said lines oversaid trunk, and means for releasing said first mentioned connection from said oper'ators position.

6. In a telephone system, a line, a means at one end of said trunk for'auto matically connecting said line to the trunk and for automatically extending the trunk to the line, manual extension means at the opposite end of said trunk, meansfor dialing over said trunk from said manual extension means for controlling said automatic extension means to select said line, and means for trunk, o

establishing a busy condition on the trunk for the automatic connecting means from said line to said trunk. a

7. In a telephone system, a plurality of lines, a trunk, meansat one end ofsaid trunk for automatically connectinganyone of said lines to said trunk, means for automatically extending said trunk to any one of said lines, a manual extension means at the opposite end of said trunk, means for dialing over said trunk from said manual extension means for: controlling said automatic extension means to' select any one o'tsaid lines, and means op erative if a linehas been selected for'releasing a connection from one of said lines tothe trunk if it has been established and if no such connection is established to prevent such a'connection from being established 8. In a telephone system, an exchange, lines of diiierent characteristics incoming to said exchange, a trunk outgoing from said exchange, an operators position at which said trunk terminates, switching means exchange for connecting any one of saidlines *ith said trunk, and other switching means at said exchange controllable from said op erators position over said trunk for estab-' lishing .a different connection with any one of said lines and for breaking down the first mentioned connection. s

In witness whereof, I hereunto subscribe I my name this 24 day of March, A. D. 1927.

RAY S. WVILBURQ at said

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