US1231922A - Telephone-exchange system. - Google Patents

Description

A. E. LUNDELL.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 26, 1915.

1,281,922 Patented July 3, 1917.

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 26, 1915- 1,231,922. Patented July 3, 1917.

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A. E. LUNDELL.

APPLICATION FILED NOV. 26.1915.

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A. E. LUNDELL.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED NOV. 26. 191-5. m mmg Patented. July 3,1917.

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TIN STATES PATENT ALBEN E. LUNIDELL, OF NEW' YORK, N. Y., A

SSIGNC'R TO WESTERN ELECTRIC COMPANY,

INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPI-IGNE-EXCHANGE SYSTEM.

Application filed November 26, 1915.

To all whom it may concern:

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

This invention relates to telephone exchange systems, and more particularly to such systems in which the character of service rendered upon any one of a plurality of telephone lines by the operating forces of telephone exchanges may be observed from a central point.

An object of this invention is to provide improved signaling means for such systems.

A more specific object of this invention is the provision of signaling means through which the number of the telephone line, upon which service is being observed, may be indicated to the observer.

In accordance with this invention there is provided a connecting circuit extending from a central oflice, at which terminate a plurality of telephone lines, to a service observing desk. At the central oflice there is provided apparatus operating, when a call is made on any one of the telephone lines, to seize the connecting circuit, and to connect this particular line to the connecting circuit. At the service observing desk there is provided asignaling device corresponding to each of the telephone lines to which the connecting circuit has access, which are adapted to indicate to the observer the number of the line upon which service is being observed. There is also provided in this system a plurality of electromagneticallycontrolled switching devices, which are operated upon the seizure of or the connection to the connecting circuit to control the selection and operation of the signaling device corresponding to the telephone line which has seized the connecting circuit.

This invention will be more fully understood by reference to the accompanying drawings illustrating one embodiment thereof. To obtain a clear idea of the entire system, the drawings should be arranged from left to right in the following order: Figures 1, 2, 3 and 4.

As shown in the drawings, this invention comprises a service observing trunk ,I made Specification of Letters Patent.

Patented July 3, 1917.. Serial No. 63,531.

up of six wires, A, B, O, D, E and F, extending between central oflices S and T. At the central oflice S a plurality of telephone lines terminate, two of which are shown in Fig. 1. In Fig. l is also shown an ordinary cord circuit R for interconnecting the tele phone lines for conversation. In Figs. 2 and 3 there is shown the end of the service ol serving trunk II which terminates at the central oflice S. In Fig. A is shown the end of the service observing trunk H which terminates at central oifice T. Associated with the service observing trunk H is apparatus for indicating to the observer located at central office T the number of the telephone line upon which service is being observed. The indicating apparatus is shown to the right of the dotted line in Fig. A.

The service observing system embodying this invention is capable of use for observing the service upon any one of twenty-six telephone lines. For convenience, however, only the first and last telephone lines, No. 1 and No. 26, are shown in the drawings. Telephone line N o. 1 is an-ordinary common battery line, while telephone line No. 26 is similar to No. 1, with the addition of a message register located at the central oiiice. Each of the lines, to which the trunk circuit H has access at any one time, is connected to a pair of jacks by means of plugs and cords. Telephone line No. 1 is connected to jacks 32 and 3 t by means of a cord 30 and plugs 31 and and telephone lineNo. 26 to jacks 4&6 and 4&8 by means of a cord 44k and plugs and A7. Associated with the connecting circuit or service observing trunk H at the central oiiice S, shown in Fig. 2, are six relays individual to each telephone line to which service observing trunk II. has access. Five of these rela s are for the purpose of seizing the connecting circuit II where a call is made on one of the telephone lines, and connecting this particular telephone thereto. The sixth relay is for the purpose of releasing the connecting circuit and for preventing the connection of a telephone line to the connecting circuit if the circuit is busy at the time a call is made on a line. If the call is a terminating call, the line upon which it is made is connected to the connecting circuit immediately, while if the call is an originating call, the connecting circuit is merely seized at this time and the line upon which the call is made is completely connected to the connecting circuit, when the call is answered by the regular operator. The relays to the left of the dot ted line in Fig. 2 are individual to telephone line No. 1, while those to the right of the dotted line are individual to telephone line No. 26. The leads from jack 32 and the upper lead from aek 34 terminate in normally open contacts of relay 39, while the lower lead from jack 3-1 extends through the winding of relay 35 to battery. The leads from jack -16 and 43 are similarly as sociatcd with relays 53 and 19. Relays 36 and 37, individual to telephone line No. 1, are equipped with tour leads, K, L, and N, which are shown terminating in arrows. Likewise, relays 50 and 51, individual to telephone line No. 26, have four leads, K, L, M and N, which are shown terminating in arrows. For each pair of similar relays individual to the remaining twentyfour telephone lines (not shown), there would also be leads K, L, M and N. These four leads K, L, M and N, for the various twenty-six pairs of relays, are to be connected to terminals 101 to 112 inclusive, shown in Fig. 3, in the manner indicated in the table of Fig. 5.

In Fig. 6 there is a table showing the polarity of current connected to the conductors D, E and A of the connecting circuit when a particular telephone line of the twenty-six to which the connecting circuit has access, is connected thereto.

At the central office T the service observing trunk H terminates at a service observing desk. On this service observing desk there is a lamp, corresponding to each of the twenty-six telephone lines, to which the service observing trunk H has access. For convenience, these indicating lamps are given numbers301 to 326 inclusive, corresponding to the number of the telephone lines1 to 26. Relays 327 to 332 inclusive, shown in Fig. 1, are selectively responsive to currents of different character to control the signal lamps on the service observing desk, which indicate to the observer the number of the line connected to the service observing trunk H. The other relays, shown to the right of the dotted line in Fig. 4:, are controlled by relays 327 to inclusive, and enter into control of the indicating lamps 301 to 326 inclusive. There is also on the service observing desk a key 352, preferably of the locking type, by means of which the observer may render the desk apparatus efifective. Keys 358 and 359 are for the purpose of controlling the character of calls which are to be observed. lVith these two keys in the normal position, as shown in the drawings, the observer may observe the service upon any of the twenty siX different lines whenever a call is made thereon, regardless of whether the ca l is originating or terminating. When the observer wishes to observe the service upon lines on which originating calls are made, and does not wish to observe the service upon the lines upon which terminating calls are made, key 358 is actuated, while to observe terminating calls only, key 359 is actuated. Relays 113 to 118 inclusive, shown in Fig. 3 and located at the central otiices, are for the purpose of determining the character of current sent over the connecting circuit H to select the proper relays at the service observing desk to cause the lighting of the lamp corresponding to telephone line connected to the connecting circuit H. V

The subscriber on telephone line No. 1, initiating a call, causes the operation of line relay 27, which in turn causes the lighting of line lamp 28. The operation of line relay 27 also causes the operation of relay 35 over a circuit from battery, through the lower winding of relay 35, lower engaged contacts of jack 3 1 and plug 33, and the contact of line relay 27 to ground. Relay 35, in operating, causes the operation of relays 36 and 37 over a circuit from battery, through the upper contact of relay 35, right-hand normal contact of relay 40, the windings of relays 36 and 37 in parallel, left-hand normal contact of relay 37 conductor Z and the normal contactof relay 121 to ground. Relay 37, in operating, closes a locking circuit for relays 36 and 37 from battery, through the windings of these two relays in parallel, the middle alternate contact of relay 37, lead'lifli, terminal 107, and the winding of relay 121 to ground, and causes relay 121 to operate. Relay 36, in

operating, causes the operation of relays 113 and 119 over a circuit from battery, through the winding of relay 119, the righthand winding of relay 113, terminal 106, lead L, middle contact of relay 36, the lower engaged contacts of jack 34c and plug 33 and the contact of line relay 27 to ground. Relay 119 in operating, causes tie operation of relay 350 over a circuit from battery, through the contact of relay 119, conductor C and the winding of relay 350 to ground. Relay 350, in operating, causes the lighting of lamp 355, which indicates to the observer that an originating call has been made on a telephone line. The operation of relay 1.21, hereinbeit'ore referred to, causes the actuation of relay 12% over a circuit from battery, through the winding of relay 12 1, and the contact of relay 121 to ground. Relay 121, in operating, causes the operation of relay 126 over a circuit from battery, through the left-hand contact of relay 124, the normal contact of relay 123, and the winding of relay 126 to ground. The operation of relay 113, hereinbetore referred to, has connected a source of positive y to the upper alternate contact of relay 126, so that polarized relay 327 now operates over a circuit from positive battery, through the contact of relay 113, upper alternate contact of relay 126, upper normal contact of relay 127, conductor 1), upper normal contact of relay 318,the windings o1 polarized relays 327 and 328 to ground. Polarized relay 327 is poled to operate on positive battery only, While relay 328 is poled to operate on negatire battery only. The observer, noticing the lighted condition of lamp 355, actuates key 302 to connect the desk apparatus to the service observing trunk. The actuation of key causes the operation of relays 351 and 333 over a circuit from battery, through the winding of relay 2333, contact of polarized relay 327, resistance 360, the winding of relay 351 and lcey to ground. The operation. o't relay 333 causes the operation of relay 3410, whereupon these two relays lock up ore-r a circuit trom battery, through the windings oi relays 333 and E310, middle alternate contact of relay middle normal contact of relay 33-1, normal contact ot relay 336, normal contact of relay 335 and key to ground. The operation of relay 340 causes lamp 301 to be lighted and relay 353 to be operated, the circuit therefor being from battery, through the middle contact of relay 310, lamp 301. normal contact 01"" relay 3&6, normal contact of relay 317, windof relay 353 and key 352 to ground. The lighting of lamp 301 indicates to the observer that the telephone line, which has seized the trunk circuit H, is No. 1. The operation of relay causes the operation of relay 341 which opens conductor 1) and connects the observers telephone 357 to conductors D and E, which are the tip and ring conductors of the service observing trunk H. The opening of conductor D permits polarized relay 327 to release, and relay 351 is thereupon released. Relays and 310, however, remain operated, because the locking circuit for these two relays is independent of the contact of polarized relay 327, is now controlled entirely by the hey The release of relay 351 permits relay 125 to operate over a circuit from battery, through the right-hand contact of relay 121-, winding of relay 125, conductor F, contact of relay 351 and left-hand alternate contact of relay 353 to ground. Relay 125, in operating, causes the operation of relay 123, which completes a locking circuit for relays 36 and 37, this circuit being from battery, through the left-hand alternate contact of relay 123, normal contact of relay 122, conductor X, lower contact of relay 36, the windings of relays 36 and 37 in parof relay Winding These two relays 37, lead M, terminal 107 and the of relay 121 to ground.

36 and 3'? are now locked up, independent of the battery furnished by the operation of relay The operation of relay 123, also permits the release of relay 126 to close the tip and ring conductors of the trunk 12..

The regular operator, having noticed the lighted condition of the line lamp 28, answers the call by inserting the answering plug of the cord circuit 1% into the jack as sociated with telephone line No. 1. Cut-off relay 29 and relay 38 thereupon operate over a circuit from battery, through supervisory lamp 60, resistance 61, sleerc contacts of the answering plug and jack, to the point 62 where it branches, one branch going through the winding of cut-oil relay 29 and. the other through upper engaged contacts of the plug 33 and jack 3 1, and the winding of relay 38 to ground. The operation of cut-oil relay 29 releases line relay 27 and extinguisher; line lamp 528. he operation of relay 38 causes the operation ot' relay 39 over a cir cuit from battery, through the contact of relay 38, winding of relay 39 and the upper "winding of relay 35 to ground. The oper ation of relay 39 connects the limbs 01 the telephone line No. 1 to tip and ring conductors of the service observing trunk ll. The operation of relay also causes the opera tion of relay 120 over a circuit from but tcry, through the contact of relay 38, upper alternate contact of relay 36, lead K, terminal 193, left-hand winding otlf' relay 113, and the winding of relay 120 to ground. This circuit through the lefthand winding of relay 113 maintains relay 113 operated to furnish positive battery to conductor D for operating polarized relay 327, if the ob server does not talre up the call before the regular operator answers. Relay 120, in operating, causes the operation of relay 3 19 over a circuit from battery, through the contact of relay 120, conductor B and the Winding of relay 3419 to ground. The operation of relay 319 causes lamp to be lighted to indicate to the observer that the regular operator has answered the call. The release of line relay .27 caused the release of relay 119. Belay 350 does not release and lamp 355 is not extinguished, because battery is furnished to the conductor C through the operation of relay 129, which is operated after the regular operator has answered the call by inserting the answering plug of the cord circuit 13 into the jack of telephone line No. 1, if the subscriber has the receiver removed from the switchhoolr. The circuit over which relay 129 is operated is from battery, through the winding of supervisory relay (33, ring contacts of the answering plug and jack, out over one side of the telephone line, through the substation apparatus, back over the other side of the line, upper engaged contacts of the plug 31 and jack middle contact of relay 39, left-hand winding of til relay 128, the contact thereof and the winding of relay 129 to ground. Relay 128 does not operate, for the left-hand winding thereof is of low resistance while the right-hand winding is of high resistance, and the winding of relay 129 is of low resistance. On a two party line, when the call bell of one party is operated by ringing current projected over the tip side of the line, the call hell would be shunted by the low resistance winding of relay 129, thereby preventing the ope 'ation of the bell, were it not for the relay 128. Relay 12S responds to any current of a higher voltage than the usual central office battery of twenty-four volts, there by substituting the high resistance winding thereof for the low resistance winding'of relay 129. Pi hen the receiver is restored to the switchhook, the switchhook contact is opened, whereupon relay 129 releases, causing the release of relay 350, extinguishing lamp When lamp 355 is extinguished, the observer knows that the subscribers receiver is on the switchhook, while if this lamp is lighted, the observer knows that the receiver is oil the switchhook.

"he observer, after having made the desired observations upon telephone line No. 1, may disconnect the service observing desk apparatus from the service observing trunk, and in so doing, release the trunk circuit. To accomplish this, the observer restores key 352 to its normal position, whereupon relays 353, 333 and 310 release and lamp 301 is extinguished. he release of relay 353 per mits the release of relay 34S, thereby disconnecting the observers telephone 357 from the tip and ring conductors of the service observing trunk. Relay 318, in releasing, causes the operation of relay 122 over a circuit from battery, through the left-hand contact of relay 121, right-hand alternate contact of relay 123, winding of relay 122, lower normal contact of relay 126, conductor [1, lower normal contact of relay 3&8 and the windings of polarized relays 331 and 332 to ground. Relay 122, in operating, causes the operation of relay 40 over a circuit from battery, through the lower contact of relay 35, winding of relay 10, lefthand normal contact thereof, the right-hand alternate contact of relay 37, conductor P and the contact of relay 122 to ground. Relay 10, in operating, completes a locking circuit for itself through its alternate contact to ground. The release of relay 353 also releases relay 125, which in turn releases relay 123. The operation of relay 122 opens the locking circuit of relays 36 and 37 which thereupon release. The operation of relay 1'10 occurs before the release of relays 36 and 37. These two relays cannot again be energized until after the subscriber has restored the receiver to the switchhook and the regular operator has withdrawn the answering plug from, the jack of telephone line No. 1. The release of relay 3G closes a short circuit about the winding of relay 39 causing the release thereof, which disconnects the limbs of telephone line No. 1 from the tip and ring conductors, of the service observing trunk, and permits relay 113 to release. The release of relay 37 permits relay 121 to release. VVhen the regular operator disconnects, relays and 38 are released, whereupon relay l0 releases, restoring all apparatus associated with the service observing system to normal position.

Relay 10, individual to telephone line lilo. 1, and the relays corresponding thereto, 111- dividual to the other telephone lines to which the service observing trunk has access, have several important functions. The first is to permit the observer to release the trunk circuit. This is accomplished by the operation and the locking up of relay 40 when the ob server restores key 352 to its normal position. Relay 10, in operating, opens its normal right-hand contact which is in the energizing circuit of relays 3G and 37. which relays serve to lock the line, upon which a call has been made, on to the trunk. The second function is to prevent the connection of a telephone line, upon which a call is made, to the service observing trunk, if the trunk is already connected to a telephone line, when a call is made on a second telephone line to which the trunk has access. If the trunk is busy, relay 121 will be operated, so that when a call is made on a second line, assuming this to be No. 1, the operation of relay 35, will cause the operation of relay e10 over a circuit from battery, through the lower contact of relay 35, winding of relay 40, normal left-hand contact thereof, righthand normal contact of relay 37 conductor Y, and alternate contact of relay 121 to ground. Relay 40 operates and locks up through its alternate contact to ground, thereby preventing the connection of the telephone line to the busy trunk. This telephone line cannot under any circumstances be connected to the trunk circuit until after the receiver has been restored to the switchhook and the regular operator has disconnected. The third function of relay 10 is to lock off a telephone line upon which an originating call is made if the observer has actuated key 359 so as to be able to observe only those lines upon which terminating calls are made. The actuation of key 359 places relay 354: in parallel with lamp 355 so that when an originating call is made on a telephone line, for example, No. 1, the chain of operations hereinbefore described, up to and including the operation of relay 350, takes place, thereby completing a circuit from battery, through lamp 355 and relay 354: in parallel, and the contact of relay 350 to ground. Lamp 355 lights but is extinguished almost immediately thereafter, as will be more fully explained. Relay 354 operates, thereby causing the operation of relay 125 over a circuit from battery, through the right-hand contact of relay 124, Winding of relay 125, conductor F, contact of relay 354 and normal contact of relay 353 to ground. The operation of relay 125 causes the operation of relay 123. Relay 23 in operating, causes the operation of relay 122 which completes the operating circuit of relay 40, which is from battery, through the lower contact of relay 35, winding of relay 40, left-hand normal contact thereof, right-hand alternate contact of relay 37, conductor P and the contact of relay 122 to ground. Relay 40 operates and locks up as before described. Relays 36 and 37 release, for the locking circuit therefor from battery through the contact of relay is open at the right-hand normal contact of relay 40, and the locking circuit therefor from battery through the left-hand alternate contact of relay 123 is open at the normal contact of relay 122. The release of relay is, as before described, controlled by the subscriber of line No. 1 and the regular operator. The fourth function of relay 40 is to lock off a telephone line upon which a terminating call is being made, if the observer has actuated key 358 to arrange the system so that service may be observed only upon lines upon which originating calls are made. The operation of key 358 places relay 354 in parallel with lamp 356, whereupon, when the call is made, lamp 356 lights momentarily and relay 354 operates. The other appara tus functions in the same manner as under the conditions assumed in connection with the third function for this relay.

If a terminating instead of an originating call is made upon telephone line N o. 1, relay 38 operates, causing the operation of relay 35 over a circuit from battery, through the contact of relay 38, normal contact of relay 36, and the upper winding of relay 35 to ground. The operation of relay 35 causes the operation of relays 36 and 37, which in operating, lock up over a circuit including the winding of relay 121. The operation of relay 36 removes the short circuit from about the winding of relay 39, permitting relay 39 to operate to connect the limbs of the telephone line to the tip and ring conductors of the trunk H. The manner in which the observer takes up the call and the manner in which the circuit of inclicating lamp 301 is completed is similar to that described above in connection with the operation of this apparatus when an originating call is made on telephone line N o. 1.

l-issuming that an originating call is made on telephone line N o. 26, the operation of. line relay 41 causes the operation of relay 49, which in operating, causes the operation of relays and 51. Relays 50 and 51, in operating, are locked up over a circuit from battery, through the upper contact of relay 49, right-hand normal contact of relay 54, the windings of relays 50 and 51 in parallel, middle alternate contact of relay 51, lead M, terminal 108, windings of relays 118 and 121 to ground. Relays 118 and 121 operate, the former connecting negative battery to the lower alternate contact of relay 126, and the latter opening the energizing circuit of all relays similar to 50 and 51, associated with the telephone lines to which the service observing trunk has access. One such circuit, opened by the operation of relay 121, may be traced from the left-hand normal contact of relay 37 (a common point in the energizing circuit of relays 36 and 37) through conductor Z, normal contact (now open) of relay 121, to ground. The operation of relay 50 causes the operation of relays 119 and 114 over a circuit from battery, through the winding of relay 119, right-hand winding of relay 114, terminal 105, lead L, middle alternate contact of relay 50, lower engaged contacts of the jack 48 and plug 47, and the contact of line relay 41 to ground. Relay 114, in operating, connects negative battery to the upper alternate contact of relay 126, and relay 119 in operating causes the operation of relay 350, which in operating, causes lamp 355 to be lighted, indicating to the observer that an originating call has been made on a telephone line. The operation of relay 121 also causes the operation of relay 124, which in turn causes the operation of relay 126, whereupon negative battery is sent. over conductors D and A of the service observing trunk, causing the operation of polarized relays 332 and 328, the circuit for the former being from negative battery, through the contact of relay 118, lower alternate contact of relay 126, conductor A, lower normal contact of relay 348, windings of polarized relay 331 and 332 to ground, and the circuit of the latter being from negative battery through the contact of relay 114, upper alternate contact of relay 126, upper normal contact of relay 127, conductor 1), upper normal contact of relay 348, and the windings of polarized relays 327 and 328 to ground. Relay 331 is poled so that it operates upon positive battery only, while relay 332 is poled so that it operates on negative battery only. The observer may now take up the call by actuating key 352. The actuation of this key causes the operation of relays 347 and 351 battery, through the winding of relay 34 7, contact of relay 332, winding of relay 351 and key 352 to ground. Relay 347, in operating, locks up over a circuit from battery through the Winding thereof, alternate rightover a circuit from hand contact thereof and key 352 to ground. The actuation of key 352 also causes the operation of relay 334 over a circuit from battery, through the winding of relay 334, contact of relay 328, resistance 360, winding of relay 351 and key 352 to ground. Relay 334, in operating, causes the operation of relay 342 from battery, through the winding of relay 334, winding of relay 342, middle alternate contact of relay 334, normal contacts of relays 336 and 335, and key 352 to ground. Relays 334, 342 and 347 are now locked up independent of the contacts of the polarized relays 332 and 328, and remain operated as long as key 352 is actuated. The operation of relay 342 causes the lighting of lamp 326 over a circuit from battery, through upper contact of relay 342, lamp 326, alternate left-hand contact of relay 347, the winding of relay 353 and the key 352 to ground. Lamp 326 remains lighted as long as key 352 is actuated. Relay 353, in operating, causes the operation of relay 348, which causes the release of relays 328, 332 and 351, and connects the observers telephone 357 to the tip and ring conductors of the service observing trunk. Relay 353, in operating, also causes the operation of relay 125, which in turn causes the operation of relay 123, which furnishes battery to lock up relays 50 and 51 to place the release of the trunk circuit under the control of the observer, instead of leaving it under the control of the subscriber and the regular operator. Relay 123, in operating, also permits relay 126 to release to close the tip and ring conductors of the trunk H.

The regular operator, in answering, inserts the answering plug into the jack of line 26, whereupon relay 52 operates, the operation of which causes the operation of relay 53. Relay 53 in operating, connects the limbs of the telephone line 26 to tip and ring conductors of the service obseiv ing trunk. Relay 52, in operating, also causes the operation of relay 120 over a circuit from battery, through the contact of relay 52, upper alternate contact of relay 50, lead K, terminal 102, left-hand winding of relay 114 and winding of relay 120 to ground. Relay 120, in operating, causes the operation of relay 349, whereupon lamp 356 lights, indicating to the observer that the regular operator has answered a call.

After the talking circuit between telephone line No. 26 and the line called has beenestablished, the regular operator registers a call on line register 65 associated with the telephone line No. 26. This is accomplished by actuating key 64, upon the actuation of which the electromagnets of the line register 65 and the position register 66 are energized, the circuit therefor being from battery 67, through the winding of the electromagnet of the position register 66, contact 68 of key 64, sleeve contacts of the answering plug and jack, and both windings of the electromagnet of the line register 65 to ground. Battery 67 is of higher voltage than the ordinary common battery at the central office, and is preferably of 36 volts. The electromagnet of. the line register 65, in attracting its armature, shortcircuits one winding, so that after the release of key 64, the line register will remain actuated due to a flow of current from the common battery at the central office. The electromagnet of the line register 65 will not attract its armature when both windings are included in circuit with a 24-volt battery, which is the usual central oflice bat tery, but does operate when both windings are included in circuit with the 36-volt battery. The actuation of key 64 causes the operation of relay 127 over a circuit from 36-volt battery 67, through the winding of the electromagnet of the position register 66, contact 68 of key 64, sleeve contacts of the answering plug and jack, upper engaged contacts of plug 47 and jack 48, upper contact of relay 53, winding of relay 127 to ground. The operation of relay 127 connects a tone in circuit with the observers receiver 357 which has been connected to the tip and ring conductors of the service observing trunk through the operation of relay 348. Relay 127 is marginal, so that it does not operate when in circuit with a 24-volt battery but does operate when in circuit when a 36-volt battery. This tone in the receiver 357 indicates to the observer that the regular operator has registered a call on the line register associated with telephone line No. 26. The release of key 64 permits relay 127 to release to close the tip and ring conductors of the trunk 11., The switchhook signals from telephone line No. 26 are obtained in the same manner as the same signals from telephone line No. 1 are obtained.

In order that the operation of the indicating portion of the service observing system may be more clearly understood, it will be assumed that telephone line No. 10, instead of No. 1, is connected by means of a cord and plugs to the jacks 32 and 34, and that an originating call has been made upon this telephone line. Relays 35, 36 and 37 are operated in the manner hereinbefore described, and relays 36 and 37 are locked up over a circuit including the windings of these re lays in parallel, the middle alternate contact of relay 37, lead M, terminal 108, the windings of relays 118 and 121 to ground. The operation of relay 36 causes the operation of relays 113 and 119 over a circuit from battery, through the winding of relay 119, right-hand winding of relay 113, terminal 106, lead L, middle contact of relay 36, lower engaged contacts of jack 34 and plug inserted therein, and the contact of the line relay or" line 10 to ground. Relay 119 controls the lighting of lamp 355. Relay 113, in operating, connects positive battery to the upper alternate contact of relay 128. The operation of relay 118 connects negative battery to the lower alternate contact of relay 126, and the operation of relay 121 opens the energizing circuit of all other relays similar to relays 36 and 37. The operation of relay 37 causes the operation of relay 115 over a circuit from battery, through the winding of relay 115, terminal 111, lead N, lower left-hand alternate contact of relay 37, lead N, terminal 108, and the windings of relays 118 and 121 to ground. Relay 115, in operating, connects positive battery to the middle alternate contact of relay 126.

The operation of relay 121 also causes the operation of relay 12 1., which, in operating, causes the operation of relay 126. When the regular operator answers the call, relay 38 operates, causing the operation of relay to connect the limbs of the telephone line to the tip and ring conductors of the service observing trunk. Relay 38, in operating, also causes the operation of relay 120 over a cir cuit from battery, through the contact of relay 38, upper alternate contact of relay 36, lead K, terminal 103, left-hand winding of relay 113 and the winding of relay 120 to ground. The circuit through the left-hand winding of relay 113 maintains this relay in operative condition to connect positive bat tery to conductor D for operating polarized relay 327, if the observer does not take up the call until after the regular operator has answered. When relay 126 operates, in the manner hereinbefore describec polarized relays 329 and operate. Polarized relay 327 operates over a circuit from positive battery, through the contact of relay 113, upper alternate contact of relay 126, upper normal contact of relay 127, conductor D, upper normal contact of relay 34 3, and the windings of polarized relays and 328 to ground. Polarized relay 329 operates over a circuit from positive battery, through the contact of relay 115, middle alternate contact of relay 126, lower normal contact of relay 12. conductor l), middle normal contact of relay 348, and the windings of polarized relays 329 and 330 to ground. Polarized relay operates over a circuit from negative battery, through a contact of relay 11S, lower alternate contact of relay 126, conductor A, lower normal contact of relay 318 and the windings of relays 331 and 332 to ground. Relay is poled to operate on positive battery only, and relay 330 is poled to operate on negative battery only. The observer in tal'ing up the call, actuates key whereupon relay operates over a circuit from battery, through the winding oi relay 34:7, contact of relay 332, winding of relay 351 and hey to ground. Relay 3-H, in operating, locks up over a circuit from battery, through the winding and right-lured alternatc contact thereof and key to ground. ltelay 351 also operates. The actuation ot' key 352 also causes the operation of relay 333 over a circuit from battery, through the winding of relay 333, contact of relay 327, r sistance 3G0, winding oi relay 351 and key 352 to ground. The operation of relay 333 causes the operation of relay 337 over a cin cuit from battery through the winding of relay 333, the winding of lay 33?, lower alternate contact of lblztf? 3 lower normal contact of relay 33d, winding oi relay 335, contact of relay 329, the winding of relay and key 352 to ground. Relay 335 also operates, whereupon a locking circuit is completed for relays 333, 33'? and ii'rom battery, through the windings oit relays and 337, lower alternate contact of relay 333, lower normal contact of relay winding of relay 335, alter ate contact thereof and key 352 to ground. These three relays are now locked up, independent oi the con-- tacts of the polarized relays. The operation of relay 337 causes lamp 311) to be lighted over a circuit from battery, through the up per contact of relay 33?, lamp 310, leit-hand alternate contact of relay 347, the winding of relay 353 and key 352 to ground.

lit will he observed that the observer may delay taking up the call until after the regular operator has answered, when the apparatus at the service observing desk will tune tion in the same manner as if the call were taken up before the regular operator answers. It will also be observed that the observer, when not observing upon a line, may actuate key 352, whereupon when a telephone line is connected to the service observing trunk, the indicating lamp corresponding to the connected line will be lighted. automatically.

lVhat is claimed is:

1. In a telephone exchange system, a central ollice, a plurality of telephone lines terminating thereat; a circuit changing switch for each line, a second central oliice, a connecting circuit extending between said central ollices, means for connecting a telephone line with the connecting circuit, a signaling device corresponding to each telephone line, and a plurality of electromagnetically-controlled switching devices adapted upon connection of said line with the connecting circuit to cause the operation of the signaling device corresponding to the connected line, independent of the position of the circuit changing switch.

2. In a telephone exchange system, a central office, a plurality of telephone lines terminating thereat, a second central ofiice, a connecting circuit extending between said central ofiices, means for connecting a telephone line with the connecting circuit, a signaling device corresponding to each telephone line, a selectively controlled circuit for each signaling device, a plurality of electromagnetically-controlled switching devices selectively responsive to currents of different characters for com iileting the circuit of the signaling device corresponding to the connected line, and electromagnetic means operating upon connection of said line with the connecting circuit to determine the character of current for selecting the switching devices.

3. In a telephone exchange system, a central ofiice, a plurality of telephone lines terminating thereat, a second central ofiice, a connecting circuit extending between said central oliices, means for connecting a telephone line with the connecting circuit, a signaling device corresponding to each telephone line, a selectively controlled circuit for each signaling device, and a plurality of electromagnetically-controlled switching devices selectively responsive to current of dit ferent polarity for completing the circuit of the signaling device corresponding to the connected line, and electromagnetic means operating upon connection of said line with the connecting circuit to determine the polarity of current for selecting the switching devices.

4. In a telephone exchange system, a central office, a plurality of telephone lines terminating thereat, a service observing desk, a connecting circuit extending from said central office to said desk, means for connecting a telephone line, upon which a call has been made, with the connecting circuit, a signaling device at the service observing desk corresponding to each telephone line, a selectively controlled circuit for each signaling device, a plurality of electromagneticallycontrolled switching devices at the service observing desk selectively responsive to currents of different characters for completing the circuit of the signaling device corresponding to the connected telephone line, and electromagnetic means at the central otlice operating upon connection of said line with the connecting circuit to determine the character of current for selecting the switching devices.

5. In a telephone exchange system, a central o'tlice, a plurality of telephone lines terminating thereat, a service observing desk, a connecting circuit extending from said central otlice to said d sk, means for connecting a telephone line, upon which a call has been made, with the connecting circuit, a signaling device at the service observing desk corresponding to each telephone line, a selectively controlled circuit for each signaling device, a plurality of electromagnetically-controlled switching devices selectively responsive to currents of dili'erent characters, electromagnetic means at the central o'l'lice operating upon connection of said line with the connecting circuit to determine the character of current for selecting the switching devices, a key at the service observing desk, and relays operating upon the actuation of the key to complete the circuit of the signaling device corresponding to the connected telephone line.

(3. In a telephone exchange system, a central oflice, a plurality of telephone lines terminating thereat, a service observing desk, a connecting circuit extending from said central otlice to said desk, means for connecting a telephone line, upon which a call has been made, with the connecting circuit, a signaling device at the service observing desk corresponding to each telephone line, a selectively controlled circuit for each signaling device, a plurality of electromagnetically-controlled switching devices selectively responsive to currents of difierent characters, electromagnetic means at the central oftice operating upon connections of said line with the connecting circuit to determine the character of current for selecting the switching devices, a key at the' service observing desk, and relays conditioned for operation upon the operation of the selected switching devices and operating upon the actuation of the key to complete the circuit of the signaling device corresponding to the connected telephone line.

7. In a telephone exchange system, a cen tral otlice, a plurality of telephone lines terminating thereat, a service observing desk, a connecting circuit eXtending from the central oflice to said desk, means for connecting a telephone line, upon which a call has been made, with the connecting circuit, a signaling device at the service observing desk corresponding to each telephone line, a selectively controlled circuit for each signaling device, a plurality of electromagneticallycontrolled switching devices at the service observing desk selectively responsive to currents or" different polarity for completing the circuit of the signaling device corresponding to the connected telephone line, and electromagnetic means at the central o'llice operating upon connection of said line with the connecting circuit to determine the polarity of current for selecting the switching devices.

8. In a telephone exchange system, a central office, a. plurality of telephone lines terminating thereat, a service observing desk, a connecting circuit extending from the central office to said desk, means for connecting a telephone line, upon which a call has been made, with the connecting circuit, a signaling device at the service observing desk corresponding to each telephone line, a selectively controlled circuit for each signaling device, a plurality of electromagneticallycontrolled switching devices selectively responsive to currents of difl erent polarities, electromagnetic means at the central oflice operating upon connection of said line with the. connecting circuit to determine the polarity of current for selecting the switching devices, a key at the service observing desk, and relays operating upon the actuation of the key to complete the circuit of the signaling device corresponding to the connected telephone line.

9. In a telephone exchange system, a central oilice, a plurality of telephone lines terminating thereat, a service observing desk, a connecting circuit extending from the central otlice to said desk, means for connecting a telephone line, upon which a call has been made, with the connecting circuit, a signaling device at the. service observing desk corresponding to each telephone line, a selectively controlled circuit for each signaling device, a plurality of electromagneticallycontrolled switching devices selectively responsive to currents of different polarities, electromagnetic means at the central office operating upon connection of said line with the connecting circuit to determine the polarity of current for selecting the switching devices, a key at the service observing desk, and relays conditioned for operation upon the ope 'ation of the selected switching devices and operating upon the actuation of the key to complete the circuit of the signaling devices corresponding to the connected telephone line.

10. In a telephone exchange system, a central ofiice, a plurality of telephone lines terminating thereat, a service observing desk, a connecting circuit extending from said central otlice to said desk, means for connecting a telephone line, upon which a call has been made, with the connecting circuit, a signaling device at the service observing desk corresponding to each telephone line, a selectively controlled circuit for each signaling device, and a plurality of polarized relays, one or more of said relays oper ating upon connection of said line with the connecting circuit to complete the circuit of the signaling device corresponding to the connected line.

11. In a telephone exchange system, acentral oilice, a plurality of telephone lines terminating thereat, a service observing desk, a connecting circuit extending from said central oiiice to said desk, means for connecting a. telephone line, upon which a call has been made, with the connecting circuit, a signaling device at the service observing desk corresponding to each telephone line, a selectively controlled circuit for each signaling device, a plurality of polarized relays at the service observing desk selectively responsive to currents of diflierent polarity, electromagnetic means at the central oilice operating upon connection of said line with the connecting circuit to determine the polarity of current for selecting one or more or" said polarized relays, a key at the service observing desk, and relays conditioned for operation upon the operation of the selected polarized relay or relays and operating upon the actuation of the key to complete the circuit of the signaling devicecorresponding to the connected telephone line.

12. In a telephone exchange system, a central otlice, a plurality of telephone lines terminating thereat, a service observing desk, a connecting circuit extending from the central ol'lice to the desk, a plurality of relays individual to each line for connecting a particular line with the connecting circuit, a signaling device at the desk corresponding to each line, a plurality of relays at the central otlice common to the telephone lines and selectively controlling the operation of the signaling devices, and a plurality of conductors, individual to each line, joining the relays, individual to each line, and the common. relays, the conductors for the diiierent lines being connected to the common relays in different combinations, and one or more of the common relays operating upon con nection of a telephone line with the connecting circuit to cause the selection and operation of the signaling device corresponding to the connected line.

13. In a telephone exchange system, a central otlice, a plurality of telephone lines terminating thereat, a signaling device corresponding to each telephone line, a plurality of electromagnetically controlled switching devices selectively responsive to currents of difl'erent character to select and cause the operation of any one of said signaling devices, electromagnetic means for determining the character of current for selecting the switching devices, and means for operatively associating a telephone line and. said electromagnetic means to cause the selection and operation of the signaling device corresponding to the associated line.

4. In a telephone exchange system, a plurality of telephone lines, electromagnetically-controlled signal controlling mechanism selectively responsive to currents of different electrical characteristics, electromagnetic means for determining th char acter of current for selecting the signal controlling mechanism, and means for oper atively associating a telephone line and said electromagnetic means.

15. In a telephone exchange system, a plurality of telephone lines, a plu ality of signaling devices therefor, electromagneticallycontrolled signal controlling mechanism selectively responsive to currents of different characters, electromagnetic means for determining the character of current for selecting the signal controlling mechanism and means for operatively associating a telephone line and said electromagnetic means.

16. In a telephone exchange system, a central oiiice, a plurality of telephone lines terminating thereat, a signaling device individual to each line, electromagnetic means selectively responsive to currents of different characters for actuating the signaling devices, means for associating any line with said electromagnetic means, and means operating thereupon to furnish characteristic current for operating said electromagnetic means.

17. In a telephone exchange system, aplurality of telephone lines, a signaling device individual to each line, electromagnetically controlled means responsive to currents of varying character for operating the signaling devices, electromagnetic switching means to determine the character of the current for setting the controlled means, and means for associating any line with said controlled and switching means Whereupon they are automatically connected to cause the operation of the signaling device individual to the associated line.

In witness whereof, I hereunto subscribe my name this 24th day of November, A. D., 1915.

ALBEN E. LUNDELL.

Goaies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G.

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