US1166645A - Lock-out party-line telephone system. - Google Patents

Description

I B. I). WILLIS. LOCK-OUT PARTYQLLNE TELEPHONE SYSTEM.

191669645. APPLICATION FILED m. 29, 1912. Patented (fan. 4 1916.

2 SHEETS-SHEET I.

Y B. D. WILLIS-I I LOCK-OUT PARTY LINE TELEPHONE SYSTEM.

APPLICATLON FILED FEB.'29I 1912. 1,166,645.

2 SHEETS-SHEET 2.

Patented an. 4, 1916.

I To all whom itmag concern BER-Nani) :5. warns, on CHICAGO, ILLINoIs, AssIs'Non .TO AUTOMATIC ELECTRIC COMPANY, or CHICAGO, ILLINOIS, a oonron-ATIoN or ILLINOIS.

Loon-our" renter-LINE TELEPHONE I sYsrEM.

' Specification of Letters Patent;

racemes Jan. 4, 1916.

Be it known that "I, BERNARD D. WILLIS, a citizen of the United States'of America, and resident of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Lock-Out Party Line Telephone Systems,

of which the following is a specification.

My invention relates .to' party-linetelephone systems, and more particularly to an improved lock-out device by which means are provided scriber from coming in upon ths line when one subscriber upon the line is using the sam e,' iv

invention isparticul'arly adapted tor. use Iii-connection with automatic or semiautomatic "telephone' systems in which 'an automatic calling device is provided at "the subscribers stations.

Among the specific objects of my inventionare to provide a relay'which, upon'ener- Y s z g,

line. This relay is marginal in operation, I

bridges the talking circuit across the and-lwill not energize if the talking circuit of any vother substation isj bridged across the'line. 'Incombination with this relayl provide an' electromagnet which is energized :when the subscriber replaces his re'-.

ceiver upon the hook, which magnet oper= atesto return the operated parts to their normal positions. These and other ob ects -of.my invention will be more readily and' clearly understood by re,ference to the accompanying drawings, inwhich-'- Figures 1 and 2 taken together show a complete connection between a calling substation A and a' called substation A in a telephone system embodying the principles of my invention.

The telephone system v automatic system of the shown herei'n'is an well-known type in which the connections are established between-the calling and called lines through there is shown a the medium of individual preselector or line switches," first and second selector switches and connectors The connection shown" is established through the medium of first selector E, second selector F and the connector H. At D there is shown the usual master switch for controlling the line switch C. At B (Fig, 2) central ofiice battery for supplying current for operating the switches and "for talking purposes.

for preventing a second sub difierent stations on the same line inay be 'trate my invention and as shown at Fl 1 comprise the usual receiver 2, trans- At R a ringing signaled selectively: Very satisfactory results are obtained by the following wellknown arrangement, in which the bells of the difierent substations are tuned or otherwise adapted to respond to only a certain. kind of ringing'curr'ent. oflice means are provided for producing as many different kinds of ringing current as there are substations upon each line. Each line is accessible through as many difie'rent groups of connector switches as there are substations on it, and each group of connectors is supplied with ringing current of a different character. Thus, to-signal any At the central. j

particular substation on a line it is neces-- sary to call this line through the medium,

'ofa connector in a group which is supplied with ringing current of the proper character to operate the bells atthe substation desired. Each of the different groups of connectors which have access to the same linemay be accessible through a difierentlevel of the second selectors, so that the numbers of the different substations on each line may be different, and the proper group of connectors will be automatically selected when the number of any substation is called.

The substations may be of any suitable common battery twowire automatic type. The ones with which I have elected to illus- P) mitter 3, switch hook 4:, ringer 5 and con denser 6. Being an automatic substation it must alsobe provided with an. automatic calling device. This calling device'may be of the type shown in .British patent to S. G. Dicker, No. 29,654: of 1910, but is herein represented diagrammatically by a.

pair of impulse springs 7 and'8 and the toothed impulse wheel 9, wh1chlatter may be controlled by the-subscriber through the medium of a dial (not shown), which dial is provided with finger holes in such a manner that it may be operated to cause the springs 7 and 8 to be separated momentarily a number of times, corresponding to the respective digits of the number to be called. WVith each substation there are also associated two relays 10 and 11. These. relays are interlockingthat is, they are so arranged that when the relay 11 becomes energized its contact springs become locked in their operated positions and cannot return to normal position until the relay 10 has been energized. Any suitable interlocking means may be used in connection with these relays. As shown herein, this means comprises a U-shaped lever 12 which, when the relay 11 is energized, drops down behind the armature 13 and will not permit said armature to restore to its normal position until after the relay 10 is energized to lift the lower end of the lever 12 above the armature 13. It will be understood, of course, that the representation of the relay 11 is only diagrammatic and that the armatures 14 and 15 remained locked in their energized positions along with the armature 13. The switch hook springs 16, 17 and 18 are so arranged that as the switch hook rises upon the removal of the receiver the spring 18, after disengaging the spring 19, engages the spring 16 and then 'forces the spring 16 out of engagement with the spring 17. It will thus be seen that during the time the switch hook is rising, there is an instant whoa the springs. 16, 17 and 18 are all in conqactat the same time. The substation A (Fig. 2) is in all respects the same as the substation A except, that its switch hook con trols a simple make-andbreak contact. The relays 20 and 21 are similar to the relays 10 and 11 shown in Fig. 1, the circuit connections being somewhat different, as will be pointed out hereinafter. If desired, the relay 21 may be made sluggish to pull up in anyone of a: number of known manners.

The line switches C and C and the master switch are of the general type of line and master switches disclosed in British patent to R. W. James, No. 26,301 of 1906, but of the particular form described in British patent to T. G. Martin, No. 1319 of 1910.

The selectors E and F are ofthe general type of selector-switches shown in United States Letters Patent No. 815,321, granted March 13, 1906, to Keith, Erickson and Erickson, the circuits being modified, however, as shown in said British patent No.

1,419 of 1910, in order to operate in a twowire system.

The connector H is of the general type of connector switches disclosed in United States Letters Patent No. 815,176, granted 'March 13, 1906, to Keith, Erickson and Erickson, but, like the selectors, is also modilied in order to operate in a two-wire system and being especially adapted to a partyline system.

In, order to give a complete understanding of my invention it will be explained in general how a complete connection is established between the calling substation A and the called substation A, the number of which latter will be assumed to be 2220. Since the apparatus shown herein is in gen eral well known in the art and is fully described in the publications hereinabove referred to, it is not thought necessary to describe its construction and operation in detail herein. W hen the receiver is removed from the switch hook at the substation A preparatory to making a call, the switch hook 4i rises in the usual manner, and at the instant-the spring18 engages the spring 16 and before the spring 16 disengages the spring 17, the relay 11 is bridged across the line conductors 22 and 22 whereby'a circuit is closed extending from ground G at the central office through the springs 23 and 24, line 22 springs 18,16 and 17, relay 1]., line 22, springs 25 and 26 and the line winding 27 of the line switch C to the battery lead 28, thence through battery B to ground G. 'The relay 11, upon energizing, attracts its armatures 13, 14 and 15, which thereupon become locked in their operated positions, as previously explained. The armature 13, in its operated position, completes "a conned tion from the line conductor 22 through the relay 10 to the hook switch spring 19. The armature 15, in. its operated position, bridges the talking circuit across the line conductors 2 2 and 22. This bridge extends from the line conductor 22 through the hook springs18 and 1G, transmitter 3, re ceiver 2, impulse springs 7 and 8, armature 15 and push button springs 29 to the conductor 22. When the transmitter and receiver are thus bridged across the line, the current through the line'winding' of the switch C 'is' increased sufiiciently to cause said winding to attract its armature 30, ii it was not already so energized in series with the relay 11, which has considerable resistance. The armature 30, upon being attracted, 'closes the circuitvof the operating winding 31, which causes the line switch C to operate in the usual manner to extend the line connection through the springs 32 and 33 and 31 and 35 to the first selector E, and the switch 0 is disconnected from the line by its cut-off armature 36. When connection is extended to the first selector E,-the line relay 37 becomes energized by reason of the bridge across the line through the talking circuit of the substation A and, upon energizing, closes the circuit-of the relay 38. The relay 38. upon energizing closes a holding circuit for the winding 39 of the line switch C.

It will be seen that when the receiver is removed from the switch ing'station the talking circuit is not bridged across the line by the simple operation of-the hook switch springs, as is usually the case, but is dependent upon the energization'of the relay 11. The relav 11 is momentarily bridged across goes up. This relay 11 has a high resistcuit of the telephone. If no talking circuits are bridged across the line at the time this relay is bridged across it, this relay energizes as described. If, however, the line had been 15 in use by some other substation at the time the receiver. hook at the substation A. the relay 11, when it became bridged across the line, would:

have been shunted by the talking circuit at the first substation, and this would have shunted sufiicient current away from the relay 11 to prevent it from being opera- .tively energized and the talking circuit at the substation A would not have been bridged across the-line.

that while the line is in use at one station no subscriber at any of the-other stations can get in on the line. l

The connection having been extended to the first selector E by the removal'of the re ceiver at the calling substation, I subscriber now operates his calling device for the first digit 2 of the called number,

whereby the substation impulse springs 7 Each time the impulse springs are separated, the line relay 37 of the selector E deeneir nizes. Each deenergization of the relay 37' transmits an impulse of current through the vertical magnet 40 of the selector. Since the digit called. is 2, the vertical magnet operates twice to raise the switch shaft and its wipers two steps, after which the side switch passes to second position and causes the rotary magnet 41 to operate in the usual'manner to rotate the wipers on to the contacts of anidle trunk line leading to a second selector F. The side switch thereupon passes to third position and, throughfthe medium of its wipers 43 and 44, disconnects the line relay 37 from the line circuit and extends the line connection throughthe shaft wipers 45 and 46 and the contacts upon which they have been rotated to the second selector F. The line relay 48 of the second selector thereupon becomes energized in the samemanner in whichthe line relay of the first selector was energized when connection was first extended to it.

When the substation calling device is opnumber, the selector F operates in the same manner] as explained for the selector E in connection'with-the previous digit to extend the connection over the trunk conductors 49 hook at the call-- the line as the switch'hook ance compared with that of the talking ciris again opened twice,

was removed from the .switch' It will thus be seen wipers two steps.

the calling and 8 are separated twice momentarily.

erated for the'second digit 2 of the called and 50 to. an idle connector H which has access to the group of lines to which that of the substation A belongs and which is supplied with ringing current of the proper character; to operate'the ringer at thesub station A. When the connection is thus extended to the connector H, its line relays 52. and 53 become energized. Each of these relays, upon energizing, closes an energizing v circuit' for the relay 54. a 5

When the calling subscriber operates his calling device for the third digit2, theline each time breaking the circuit of the" connector relays 52 and 53. The relay 54, being a slow acting relay, 30 does not have time to deenergize during the momentary interruption of its circuit by I the momentary denergization of the relays.

'.tact, relay 57, vertical magnet 58 and theside switchwiper 59 to the battery lead 28;] Since the digit called is-2, the-vertical mag-- net receives two impulses over this circuit. and operates to. raise the switch shaft and The relay 57, which is in- I eluded in circuit in .serieswith thever tical magnet 58, is a slow acting relay and is en- '95 ergized the first impulse through it and remains energized until after the last impulse for the digit is delivered. .By: ener gizing and denergizing, therela'y 57 transmits an impulse of current through the private magnet 60, which in turn, upon enerv gizing and deenergizmg, causes the side switch to pass from first to' second position. The side switch wiper 59, in passing from first to second position, tery connection from the -vertical magnet .58 to the rotary magnet 61. Thecalling subscriber now operates his calling device for the last digit 0, whereby the connector line' relay '52 is denergized ten times. Each110.

for the previous digit to cause the private 2 ma gnetto 'step the side switch front second to'thlrd position after, the last impulse for the last digit 1s delivered, to the rotary magnet, 1 y 'The side switch wipers 62 and 63, upon. 125.

reaching third position, complete the connection between the calling. and the called line, as indicated by the heavy'conductorsin the drawing. The .side switchiyvipe'r 64, upon reaching third position, provides se transfers the bat through the private bank contacts ofv the called line. and an energizing circuit for the c'ut-ofl" winding 65 of the line'switch C. This guarding potential and circuit-extends from ground G wiper 66, thence to alltheconnector private bank contacts of the called line and also through the winding 65 to the battery lead 28. The winding 65, upon energizing, at-

tracts the armature 67, whereby the line switch C is disconnected from the line and the contact 68 in' the talking circuit is closed. The side switch wiper 59 of the connector, upon reaching third position, circuitfor the ringing relay 69, which circuit extends from ground G through the interrupter '70, springs 71, relay 69and the side switch wiper 59 'to the battery lead. The relay 9, upon energizing, disconnects the calling line from the called line and bridges the subscriber. Since the circuit of the ringing relay 69 includes the interrupter 70, this relay is energized only intermittently, so as not to ring the called subscriber continuously. When, the called subscriber removes his receiver. from the switch hook, the relay 21 is bridged across the line by the closure of the hookswitch sp'rings'72 and 73. It Will be seen that normally the transmitter and the receiver at thecalled station are short-circuited through the armature 74 of the relay 21 and its back contact. As soon as the relay 21 isthus bridged across the line, itis energized. The relay 21, upon energizing, bridges the talking circuit across the line through the armature 74: and its front contact and becomes locked in its operated" position, as explained in connection with the relays 10 and 11 at the calling substation A. As soon as the talking circuit at the called substation is bridged across the line, or as soon thereafter as the ringing relay 69.at theconnector denergizes, if it happens to be energized at the time, the

' called substation is provided with talking current over a circuit extending from ground G through the side switch wiper 64, lower winding of the back-bridge relay 75, thence over the heavy conductors, through the springs of the ringing relay, side switch wiper 63, shaft wiper 76, substation hook switch springs, 73 and 72, impulse springs 77, receiver 78, transmitter 79, armature 74 and its front contact,'push button 80, contact 68, wipers 81 and 62, and the ringing relay springs, and through the upper winding of the back-bridge relay 7 5 to the battery lead 28. The back-br1dge relay is energized by this current, and by separating the springs 71 cuts off the ringing relay 69.

After the conversation is completed the entire connectionis automatically released side switch wiper 64, shaft completes a ringing current generator R across the called line to signal the called .wiper,v thence through the side by the hanging up of the receiver at the calling substation in the following manner: During the time the connection is bein maintained the release relays 38 and 82 of the selectors E and F, as Well as the relay 54: of the connector, are maintained energized througlr the springs of the connector line relays 52 and 53. When the calling subscriber hangs up his receiver, these relays 52 and 53 deenergize and break the circuits of the relays 54:, 82 and 38 of the switches H, F and E,-respectively. The relays 54', 82 and .38, upon deenergizing, close the circuits of their respective release magnets 83, 84 and 85, which, upon energizing, release their respective switches. The relay 38 of the selector E, upon deenergizing, also-destroys the holding circuit of the Winding 39 of the line switch C and allows said switch to berestored to normal position. When the receiver at the calling substation is first hung up and the springs 18 and 19 come into contact, the -relay 10 is bridged across the line conductors 21 and 22 through the armature l3 and its front contact. The relay 10 energizes and by lifting the lever 12 unlocks the armature of the relay 11 and allows it to resume its normal position. As soon as the armature 13 disengages its front contact, the bridge across the line through the relay 10 is broken. At the called substation the relay 20 is energized by the hanging up of the receiver and unlocks the relay 21in the same manner as explainedfor the relay 10 at the calling substation.

In the foregoing it has been explained how the connector H completed connection with an idle line. In case the called line is busy the connector H will not complete connection therewith, and the calling subscriber will be given a busy signal in the following manner: 1V henever a line is in use, either on account of having made a call or on account of having been called, there is a guarding ground potential upon its connector private bank contacts. Therefore, when the private Wiper 66 of the connector engages the contact of a busy line, a ground potential is extended from said contact through said switch wiper 64 (which is then in second position) and through the relay springs 86 and 87 and the relay 88 to the spring 89 of the private magnet relay 57. Therefore, when the private magnet relay deenergizesafter the last in1- pulse for the last digit is delivered, it does not break the circuit of the private magnet 60, but forms a new holding circuit for said magnet by "'ay of the relay 88 and the pri vate wiper 66. The private magnet, therefore, does not deenergize topermit the side switch to pass to third position and the connection with the called'line is maintained open at the side switch wipers 62 and 63. The relay 38, which is included in the locktends from ground renelgllmgnshl'itsthe holding ground of itfilf and the'irivate'magnet from the gua'rdprivatebankeontact tothegrouncl G by 51.1Way;;,0f:"the-springs-87, 90 andx9l and the sidezsWitchfwi-per The private magnet ..remaining:senergizedtand the side switch- -rei' mainlng locked,;in"second pos1t1on,- the busy =signalingrmachinegcS isconnected'with the -calling-, line .through the. springs 93 of the :private magnet through the side switch i'wiper. 63;:1 (in {second position) thence I C It'having been shown how the connector is prevented from completing connection witha busy line; since a calling line is provided wlth a guarding potential upon its connector private-bank contacts as soon as the call 1s 1nitiated,'"some special means must he provided in order to permit a calling subscriber to call baclg upon his own line to. signal another subscriber thereon. This 15 "accomplished in th'e'following manner: The guarding potential which is placed upon the private bank contacts of the calling line ex- H G at the selector E (Fig. 1)f. through-the springs 96, thence through the: springs 97 of a. slow acting relay',' line 'switch'bank springs 98 and 99 and 'the' conductor 100 to the connector pri- 'v'atebank contacts. "The springs 97 are controlled byf'a slow acting relay 101, which in turn is controlled by a. relay 102 which is inserted inoneside' of the trunk .line leading from theline switch to the first selector.

' It will thus'be seen'gthat all the impulses .i'or 40 operating the switches E, F and must pa'ssthiougli' the relay 102. Each time this relay deen'ergiz'es response to theseim pul e -n closesthe' circuit of the relay 101, this circuit extending from ground G 445 through the springs 96- and 103' and the relay lml to the batt ery lead 28. The relay 1 01; upon energizing'. separates the springs 97,' '",,thereby" removing the short-circuit around-[the resistance 105, whereby said resi's'tance inc ludedlin the ground'conrlectr ats the connector private bank contacts of the calling line; The rela 'y 101 is a slow i acting relay .and, ;therefore remains ener- "gized'continuouslv while the impulses are being transmitted hrough the relav102 for anvdigit. and also]remains energized for a short time after-the last impulse for each digit islcompleted.. Thus it will be seen that when a calling subscriber is calling I l the time when the backonhisown line. at

private magnet. rela .57 deenergizes after a thellast di it iscalled. the resistance1-05 T wi-l-l b zinclucled in thecirciuti whlchqtencls 1 to lock the private magnet 60. This resistance is high enough to. prevent saldmagnet I racemes e 60, I upon enabled in this manner talking circuit at the called from being locked andthe side switch passes to third position in the 'usual fmanner and connection is therefore completed. A moment later the relay i 1 01 "deenergizes and short-circuits the resistance 105, thereby restoring the guarding potential of the lineto "its normal condition to "prevent. any'fother con'iiector from obtaining connection therevvit When a calling subscriber calls back on his own line, a circuit will be closed through the back-bridge relay" of the connector 1 through the talking circuit of the calling substation. This will energize the backbridge relay and prevent the ringing relay 69 from operating to signal the called subscriber. In order scriberin this case, the subscriber at the calling substation depresses the push button 29. This depressing, of the push button opens a short-circuit around the relay 11 and includes said relay in the bridge across the calling line. This increases the resistance of the bridge sufiiciently to cause the connector back-bridge relay to allow its armature to drop back and close the circuit of the ringing relay. The insertion of the resistance of the relay 11 in the bridge across the line at the calling substation also increases its resistance sufiiciently so that when the called subscriber removes his receiver there will not be enough current shunted away from his relay 11 to prevent it from operating to complete his talking circuit. and. therefore, two subscribers are to come in on the line at the same time. Of course, when; the substation be comes bridged across the line, the connector back-bridge relay 75 energizes again and cuts ofi the ringing current. The calling subscriber then releases his push button and the two subscribers carry on their conversation in the usual manner.

- It will be seen that the connector H has two line relays 52 and 53, and that after the connection is completed either one or both of these relays must be maintained energized in order to prevent the connection from being released. The obiect in providing two relays is that the relay 52 must be adjusted so as to respond to the impulses for operating the switch. When it is thus adjusted it may possibly deenergize when the push button at a calling station is depressed .to signal a called subscriber on the same line. The relay 53, however, spend toany impulses. may

be adjusted so that it will not be thus de'energized when the to signal the called sub 1 not having to rethat I do not wish such system for use With matic system, vantageously manual.

What I claim as my invention'is v 1. In a telephone system, a party-line, a plurality of telephone stations thereon, a relay at each of said stations, means for energizing said relay When said line is taken for use at any station, means controlled by said relay for preventing any other subscriber from coming in on said line when said line is busy, an electromagnet, and means controlled by said electromagnet for returning said relay to normal position.

2. In a telephone system, a party-line, a plurality of substations thereon, a relay at each of said substations, means for energizing the corresponding relay When a receiver is removed from the hook at a substation, means for locking said relay in an energized position, means controlled by the energize- .tionof said relay for preventing any other subscriber from coming in on said line While to limit my invention to as it is equally as Well adapted any automatic or semi-autoor could even be employed adin a system -Which is entirely the same is in use, an electromagnet, and

meanscontrolled thereby for unlocking said rela 3. In a telephone system, a party line, a plurality ofsubstations thereon, a relay at each of said substations, means for energizing the corresponding relay when a receiver is removed from the hook at a substation, means for locking said relay in an energized position, means controlled by the energizarelays upon the removal of tion of said relay for preventing any. other subscriber from coming in on said line While the same is in use, an electromagnet, means controlled thereby for unlocking said relay, and means for energizing said electromagnet when the receiver is replaced upon the hook.

4:. In a telephone system, a party-line'having a plurality of substations thereon, a re lay bridged across the line at each of said stations, means for energizing one of said 4 the correspondmg receiver from its book, means controlledby said relay for closing the talking circuit, means for preventing said relay from energizing when a receiver is removed'from the hook and said lineis busy, means for locking said relay in an energized positiomand anelectromagnet for unlocking said relay.

- 5. In a telephone system, a party-line having a plurality of substations thereon, a relay bridged across the line at each of said stations, means for energizing one of said relays-upon the removal of the corresponding receiver from its hook, means controlled by said relay for closing the talking circuit, means for preventing said relay from energizing when a receiver is removed from the hook and said line is busy, meansfor look ing said relay in an energized position, an

line, upon removing a receiver from its hooiz,

' plurality line While the same --net, means controlled therebyfor unlocking electromagnet' forunlocking said relay, and means for energizing said electromagnet When the receiver is replaced upon the book.

6; In a telephone system, a party-line having a plurality of substations thereon, a re lay at each substation bridged across said means for energizing one of said relays means for locking said relay in an energized position, means operated by said relay for closing a low resistance talking bridge across said line in shunt of said relay, said shunt preventing-any other relay being energized upon the removal of any other subscribers receiver from the hook, an' electromagnet, means controlled thereby for unlocking said relay, and means for energizing said electromagn'et upon replacing said receiverupon its hook. 1

7. In a telephone system, a party-line having a plurality of substations thereon, electricallysoperated means at each of said substations forbridging the talking circuit at its substation across the line provided the talking circuit is not bridged across the line at any other substation, and electrically-op erated means for returning said relay to normal position.

8. In a telephone system, a party-line, a plurality of telephone stations thereon, a relay at each Of'Sitld stations, means for energizing said relay when said useat any station;

from coming in on said line when said line is busy, an electromagnet, means controlled by said electromagnet for returning said relay to normal position, automatic impulsetransmitting means on said line, and automatic switches controlled. thereby.

9, In a telephone system, a party-line, a of substations thereon, a relay at each ofsaidsubstations, means for energizing the corresponding'relay When a re ceive'r is removed from thehook at a substation, means for locking said relayin an energized position, means controlled by the energization ofSaid relay for preventing any other subscriber from coming in on said is in use, an electromag said relay, automatic means on said line, controlled thereby. v

10. In a telephone system, a party-line, a plurality of substations thereon, a relay at each of said substations, means "for energizing the corresponding relay when a receiver is removed from thehook at a subimpulse-transmitting and automatic switches line is taken for, means controlled 'by said relay for preventing, any other subscriber station, means for locking said relay in an M energized position, means controlled by the energizatlon of sald relay for preventing any other subscriber from coming in on said line While the same isin use, an electromagnet, means controlled thereby for unlocking said relay, means for energizing said electromagnet when the receiver is replaced upon the hook, automatic impulse-transmitting means on said line, and automatic means controlled thereby.

11. In a telephone system, aparty-line having a plurality-of substations thereon, a relay bridged across the line at each of said stations, means for energizing one of said relays upon the removal of the corresponding receiver from its hook. means controlled by said relay for closing the talking circuit, means for preventing said relay from energizing when areceiver is removed from the hook and said line is busy, means for locking said relay in an energized position, an electromagnet for unlocking said relay, automatic impulse-transmitting means on said line, and automatic switches controlled thereby.

12. In a telephone system, a party-line having a plurality of substations thereon, a relay bridged across the line at each of said stations, means for energizing one of said relays upon the removal of the corresponding receiver from its hook. means controlled by said relay for closing the talking circuit, means'for preventing said relay from energizing when a receiver is removed from the hook and said line is busy, means for locking'said relay in an energized position. an

electromagnetfor unlocking said relay,

. means for energizing said electromagnet when the receiver is replaced upon the hook, automatic impulse-transmitting means on said line, and automatic switches controlled thereby.

13. In a telephone system, a partyvline having a plurality of substations thereon, a

relay at each substation bridged across said line, means for energizing one of said relays upon removing a receiver from its hook, means. for locking said relay in an. energized position, means operated by said relay for closing a low resistance talking bridge across said line in shunt of said. re-- lay, said shunt preventing any other. relay being energized upon the removal of any other subscribers receiver from the hook, an electromagnet,means controlled thereby for unlocking said relay, means for energizingsaid electromagnet upon-replacing said receiver upon its hook, automatic impulsetransmitting means on said line, and auto-' matic switches controlled thereby.

.14. In a telephone system, a party-line having a plurality of. substations thereon,

-electrically-operated means at each of said electrically-operative means individual to each substation for preventing interference between two subscribers, and electricallyoperat-ive means at the calling substation for restoring said first-mentioned means to normal position.

Si ed by me at Chicago, Cook county, Illinois, this 24th day of February, 1912'.

BERNARD D. WILLIS. Witnesses:

ARTHUR'J: RAY, ALBERT ANDERSEN.

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