US1109163A

US1109163A - Telephone-exchange system.

Info

Publication number: US1109163A
Application number: US71441612A
Authority: US
Inventors: Elmer R Corwin
Original assignee: COOK FRANK B CO
Current assignee: FRANK B COOK Co; COOK FRANK B CO
Priority date: 1912-08-10
Filing date: 1912-08-10
Publication date: 1914-09-01
Anticipated expiration: 1931-09-01

Description

a. R. GORWIN. TELEPHONE EXCHANGE SYSTEM.

, APPLICATION FILED A1IG 10,1912. I 1,109,163.. Patented Sept. 1, 1914.

4 $HEETS-SHEET 1.

[NVENTURI I E-LMER RIIORWM ATTORNEY WRTNESSES E. R. 00min. TELEPHQNE. EXCHANGE SYSTEM.

APPLIGATION FILED AUG. 10. 1912.

Patented Sept. 1, 1914.

4 SHEETS-SHEET 2.

.1 INVENTOR E-TLMER R CORWIN AT TORNEY E. R, GORWIN.

' TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED AUG. 10 1912. 1,109,163. v

#i-I I I I I III I III wrr'kns sss q- I INVENTOR I ELMER R.CRW1N ATTORN EY' Patented Sept. 1,1914.

4.SHEETSSEEET 3.

TELEPHONE BXGHANGE SYSTEM. APPLICATION FILED AUG. 10, 1912.

E. R. GORWIN.

Patented Sept. 1, 19M.

4 SHEETS-SHEET 4.

INVENTOR ELMELR R CORVV'IN ATTORNEY UNITED STATES PATENT OFFICE.

ELMER R. CORWIN, OF CHICAGO, ILLINOIS,' ASSIGNOR', BY MESNE ASSIGNMEN'I'S TO FRANK B. COOK COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent. Application filed August 10. 1912. Serial No. 714,416.

Patented Sept. 1, 1914.

To (IZZ whom, it may concern Be it known that I, ELMER R. Conwrx, citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to those telephone exchange systems in which electro-magnetic mechanism is employed for extending telephone lines and while my invcntionhas been specifically embodied in a system in which the operators have control of such electro-magnetic mechanism yet the invention is not to be restricted to such a system.

In accordance .With my invention I provide a telephone exchange system which includes telephone lines, such for example as those which extend from subscribers stations to an exchange though the invention is not to be limited to subscribers"telephone lines, extensions for such telephone lines, a line extending connecting device, controlling circuits associated with different telephone line extensions for governing the association of said connecting device, and operator controlled means for changing the character of the controlling circuits.

My invention, in another of its aspects, may generally be described as a telephone system including telephone lines extending.

from stations to an exchange, extensions for such telephone lines having contacts at the exchange, a line extending connecting device for engagement with the contacts, controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engage ment with the connecting device, the controlling circuits being associated with different telephone line extensions, means for changing the'character' of the controlling circuits associated with desired telephone line extensions, and means for maintaining the connecting device in association with a modified controlling circuit.

In the preferred way of practising my invention each telephone line that is to be extended is connected witha set of contacts which maybe in the form of traveling wipers, the waiting contacts of Whili are character.

divided into sets-each individual to a telephone line extension. Each of these sets of waiting contacts includes a contact that is contained in a controlling circuit individual thereto.. Each of these controlling circuits, as I have embodied my invention in one form. has a manually controlled switching device individual thereto-for controlling its The group of; wipers now individual to the line that is to be extended rotates until one of the wipers of such group engages a contact of a controlling circuit whose character has been temporarily modified for the purpose of causing the arrest of the wipers, this particular waiting contact and the wiper engaging the same establishing or otherwise modifying the altered controlling circuit to arrest the wipers. The wipers of the arrested group that are companion to the wiper engaging the waiting contact of the altered controlling circuit themselves engage contacts that are terminals of the selected talking extension. This particular extension which has been added to a tele phone line may extend directly to a subscribers station if the telephone system is of a sufficiently small number of lines or it may extend to another group of wipers which may be similarly connected with another telephone line extension, and so on,

whereby the system may be adapted to any number of lines.

I will explain my invention more fully by reference to the accompanying drawings showing the preferred embodiment thereof and in which- Figure 1 is a very simple diagram generally outlining important features of the invention; Fig. 2 is a general diagrammatic view drawn along the lines of Fig. l but in whiclrtlie invention is adapted to a larger system; Fig. 3 is a diagram that is intended to be somewhat general but which is more specific than the diagram of Fig 1; Figs. and 5, taken collectively with the conductors at the top margins thereof in alinement, illustrate one embodiment of the invention more in detail; and Fig. 6 shows a detail of construction.

Like parts are indicated by similar characters of reference throughout the different figures.

Referring first to Fig. 1, I have there illustrated

telephone stations

1, 2, 3 and A by meanscfci'rcles. Telephone station A is illus- -tion No. 3.. The controlling circuits contain 55 tion with station No. 1. The operator will tratedas-havin its line manually extended by an operator y-means of a plu and ack at- .4,.the link-connector connecte with the p g '1: terminating in talking-wipers illustrated by the single wiper 5. I have shown the manual extension of the line-from sta-Y tion A to the wiper 5 merely tosimplify the i 1lustration,-thougl; ntcourse such telephone line could be extended the vmanner described as. in toll line service.- The talking wiper 5 has. an; wiper 6 that constitutes a terminal common to a l'urality of.

clintrollingfciruit's l; 8'an d 9. 1 conductor which is common tothese controlling cirmagnet 10, a batte v cuits', and fjwliichrcoiiductor the wiper 6 is ai' 'termin'ali includes. av wiper arresting llcommon to the contrailing. circuits, an

keys

12, 13 and 14, the --key'14'having a normal contact by which .Qtlie -k ey 13,.is 'connected with the battery 11 *a'n'd the key '13 having a normal contact by which-theikjfim is connected with such battery. The" alternatecontacts of

keys

12, 13 an 1'4 are respectively individual to the controlling circuits 7, 8 and 9. The controlling'circuit 7*pertains to the line extending froin-station'l, the controlling circuit 8-pertains-to "the line extension from the station No. 2, and the controlling circuit 9 pertains to the line extending from the stajele'ctro-magnets 15, 16 and 17 individual to the

lines

1, 2 and 3, these magnets being operatedwhen the lines to which they are ind-ividual are to become connected with teleph'one lines that are to be extended into connection therewith, these magnets serving to arrest the'connecting device 5, 6 in association with contacts 18 that pertain to desired telephone line extensions and the controlling circuits associated therewith. The circuits 7 ,"8 and 9 include waiting contacts thatare individual thereto and which are designed to be engaged by the wiper 6. These waiting contacts are provided each with an asso- 'c iate contact or set of contacts that are individual to the subscribers"telephone lines or telephone line portions, such as trunk lines, that are to become connected with the line which is to be extended. All of these *waiting contacts are designated by the numeral 18 in Fig. 1. Assuming that a calling line (A) has in some way become connected with the wiper 5 and has informed a receiving operator that he desires connecdepress the key 12 so as to charge the waiting contact individual to the circuit 7. The

wiper rotating device 19. which has been set into operation by some suitable means, is caused to turn the wipers until the wiper 6 engages the waiting contact individual to the controlling circuit 7 whereupon circuit through the wiper arresting magnet 10 will be closed to arrest the wiper 6 in engage- -l ine extensions 25 wit ment with its then engaged waiting contact, in which engagement the wiper 5 is connected .with the line leading to station 1. Similarly, if station 2 is to be connected with station A the key 13 will be depressed, whereupon wipers 5 and 6 will become con nected with the middle group of contacts at 18, If station A is to be connected with station 3, the key-14 will be depressed,

whereupon the wipers 5 and 6 will become connected with the third group of waiting contacts at 18. The

keys

12, 13 and 14 in addition to charging the waiting contacts individual thereto also charge the wiper 6 common to the controlling circuits with current of opposite. polarity so that circuit is established when a charg d waiting contact is engaged by the charge wiper. While the line to be extended is shown as being provided with traveling wipers and the line extensions are shown as being provided with waiting stationary contacts, I do not wish to be. limited to terminals for the line to be extended andcoiiperating stationary terminals for the line extensions.

As is understood, the telephone line extension which is to be added to another telephone line may be in the nature of trunk lines or link connectors, or may themselves be telephone lines that extend to subscribers stations. In an exchange larger than that '20 is'provided with traveling wipersindicated at 21, these wipers constituting a, line extending connecting device for connection with one of the--lines ofthe group to which it pertains. vThe sets of wipers 21- pertaining to the different groups of subscribers telephone lines are to be selected according to the group in which the desired line is included, these wipers, being connected by means of telephone line extensions 22 with waiting contacts illustrated at 23, each set of waiting contacts at 23 beingv connected with a set of wipers 21. :Thewaiting con facts at 23 are associated with wipers indicated'at 24, these latter wipers being; em-

ployedfor associatin one of the telephone I a selected telephone line extension 22. There are aplural ty of sets of wipers 24 each in association with.

a difierent group of waiting contacts 23 and these wipers 24 are connected through. the telephone line" extensions ,25. withwaiting' contacts illustrated at 26,:each set of waitin t s a 6 ei emm ted with a ferent set of wipers 24. The waiting contacts 26 are associated with wipers indicated at 27, the wipers 27 being adapted to become connected with a selected one of several telephone line extensions 25 extending to the desired set of'wipers 24. The wipers 27 are connected, for example, with calling station A by way of the cord and plug illustrated at 4, though other means may be employed for associating the wipers 27 with the calling line. Thus by means of my invention the wipers 27 are connected with one of several telephone line extensions 25 that has the wipers 24 that are associated with a particular set of waiting contacts 23 that has the desired telephone line extension 22 which isprovided with wipers 21 that are associated with the waiting contacts 20 among which are included those Waiting contacts that are terminals of the desired'subscribers line. When a subscriber initiates a-connection in any suitable way 'and assuming that the system is presided over by operators, the operator will proceed to extend the calling line into connection with the-desired line by the following operations: The key 28 individual to the desired telephone line extension' and the associate controlling circuit (there being as many keys 28 and controlling circuits to which they pertain as there are such telephone line extensions 25 and each of which keys 28 may be multipled at different operators positions) is depressed partially to establish a circuit including the battery 11, the key 28 and its alternate contact, the closed switch 29, a waiting contact at 26 which is in association with the waiting contacts of the selected telephone line extension 25, the wiper 30, and the wiper arresting magnet 31. lVhen the wiper 30 engages the waiting contact connected with the switch 29, circuit is closed throu h the magnet 31 to arrest the wipers where y the calling telephone line is extended into connection with the desired telephone line extension 25. By equipment to be described in connection with another figure, the motor device 32 is set into operation when the selected telephone line extension 25 has been connected whereby switch 29 is opened to protect the circuit previously established at 28 so that contacts 26 of other switches which are similarly connected with other keys 28 and which contacts of these switches are inmultiple relation with the contacts 26 shown, will not have their circuits partially established. The operator will depress the key 33 individual to the desired telephone line extension 22 and the associate controlling circuit (there being as many keys 33 and controlling circuits to which they-pertainas there are such telephone line extensions 22 and each of which keys 33 may be multipled at different operators positions) to partially establish a circuit including the which is in association with the batter 11,-the key 28 and its normal contact, t e key 33 and its alternate contact, the closed. switch 34, a waiting contact a t 23 walting contacts of the selected telephone line extension 22, the wiper 35, and the wiper arv resting magnet 36. When the wiper 35 engages the waiting contact connected with the switch 34 circuit is closed through the wiper 30, the contact engaged thereby, magnet 31 and the magnet 36 to arrest these wipers whereby the calling telephone line is extended into connection with the desired telephone line extension 22. By equipment to be described in connection with another figure, the motor device 37 is set into operation when the selected telephone line extension 22 has been'connect'ed whereby switch 34 is opened to protect the circuit previously established at 33 so that contacts 23 of other switches which are similarly connected with other keys 33 and which contacts of these switches are in'multiple relation with the contacts 23 shown, will not have their circuits partially established. The operator will also depress one of the

keys

12, 13, 11 belonging to thecontrolling circuit individual to the telephone line extending to the wanted station, 1 2, or 3 (there being as many such keys and controlling circuits to which they pertain as there are such telephone lines having waiting contacts at 20, that is there are as

many keys

12, 13, 14 as there are telephone lines in a group, and each of which

keys

12, 13, 14 may be multipled at different operators positions) partially to establish a circuit including the battery 11, keys 28 and 33 and their normal contacts, the

depressed key

12, 13 or 14 and its alternate contact, the closed switch at 15, 16 or 17 according to'the line selected, the waiting contacts at 20 which are in association with the desired subscribers telephone line,

the wiper 38 and the wiper arresting maghet 39. When the wiper 38 engages the waiting contact connected with the switch at 15, 16 or 17, circuit is closed through the magnet at 15, 16 or 17 (by way 'of

wipers

35 and 30 and magnets 36, 31) to arrest

Wipers

38, 21

whereby the calling telephone line is ex-v tended into connection with the desired subscribers line.

Fig. 3 is furnished to show more of the circuit connections that were omitted from Fig. 2 for the sake of clearness. The system shown in Fig. 3 illustrates how a calling line may secure access to each of the other nine hundred ninety-nine lines of a thousand line system, enough apparatus being suggested in Fi 3 to accomplish this result. However t e equipment suggested in F ig. 3 is not sufiicient to take care of the trafiic in a thousand line exchange and it is therefore understood' that the waiting contacts 26 of one switch are in mult ple rela i n with similar contacts 26 of other

switches having wipers

27, 30 employed by other subscribers lines, there being say one hundred switches having the contacts 26; that the waiting contacts 23 of each selector switch are in multiple relation with similar waiting contacts of say two other selector switches having' wipers 24. and that the waiting contacts 20 of each connector switch are in multiple relation with similar waiting contacts of say nine other connector switches having switch having ten subscribers lines (1, 2,3,

etc.) terminating in the waiting contacts 20 and also having waiting contacts that are in circuit with magnets 15, 16,17, etc. Where there are three connector switches to each group of multiply connected connector switches ten subscribers lines are in connection with the waiting contacts of each such switch. Each of the operators has a set of ten keys 28, the contacts of these keys 28 among the difi'erent operators positions being multipled so that each operator may have access to any of the switches having contacts 20 and to said contacts 26. Each of the operators has a set of ten keys 33, the contacts of these keys 33 among difierent operators positions being multipled so that each operator may have access to any of the switches having contacts 23 and to said contacts 23. Each of the operators has a set of ten

keys

12, 13, 14, etc., the contacts of these

keys

12, 13, 14, among different operators positions being multipled so that each operator may have access to any of the switches having contacts 20 and to said contacts 20. Where the exchange exceeds 1.000 lines, additional connector switches will be required and it will be readily understood by those skilled in the art how an exchange in excess of 1,000 lines maybe equipped by the interposition of other selector switchesin advance of the connector switches, such at dit'ional select'c r switches of course requiring associate buttons having functions similar to the buttons 33. The thousand. line sys tem which has been taken for an exani'pie will be. suflicient to enable my invention to'he understood.

Reference will now be, hadto Figs. 1 and which amplify the time arrangement shown in Fig. Assuming that subscribers station U0. 1 desires communication with subscribers station No. 2, the calling subscriber will rembve his telephone re'ceiver 40'from its switch hook 41 to open the bridge containing the signal bell 42 and condenser 43 and to close the metalic'ally continuous bridge containing the telephone transmitter 44 and the telephone receiver 40. Circuit is thereupon established through the relay 45 which may be traced from the grounded terminal of this relay through its winding, the upper armature switch of ringing relay 46 and its normal contact (this relay being operated only when its line is :1 called line), the sides of the calling line, the lower armature switch of relay 46, and its normal contact, next to the uppermost armature switch of relay l5 and its contact, the relay 47 to the grounded battery 48, the battery 48 also supplying, talking current to the transmitters. The relay 47 may be common to the lines of a group of subscribers lines and when its armature is attracted acircuit is established which is traceable from the grounded battery 48 through the circuit interrupter 49, the armature of relay 47 and its contact, the lowermost armature switch of relay 50 and its normal contact, themotor magnet 51, to ground. .The circuit of the motor magnet 51 is interrupted so that its armature moves the ratchet wheel 52 that carries wipers 53, 54, 55, 56 and 57 that pass over sets of waiting contacts belonging to the group of telephone lines having the relay 4?, there being two sets of such'waiting contacts indicated at 58, 59, 60, 01 and (S2. \Vhen a subscriber initiates a call a circuit connection is established for the waiting contact 62 belonging to his line which circuit connection may be traced from the contact 62 of the calling line, the lowermost armature switch of relay 45 and its then engaged contact, the follow-up contact of the armature switch immediately above the core of relay 15, the upper winding of the relay- 15, to the grounded battery 48. That is potential is laced upon the waiting contact 62 of a callmg line by connecting the grounded battery 48 therewith, the contacts 62 of non- Calling' linesbeing clear of such potential. When the wiper 57 engages the contact 62 having this potential the circuit-connection just traced has a continuation that establ,ishes a closed circuit which continuation includes the, wiper 57, the follow-up normal Contact of the upper armature switch of -relay 50, the windin of relay 50, the upper armature switch 0 relay 63 and one of its contacts, to ground. Thus the magnet 50 becomes energized and its upper armature switch leaves its normal follow-up contact into engagement with its alternate contact core of this relay having left its normal follow-up contact and now engaging its alternate'contact to the circuit initially es-- tablished for this relay 15 at the-lowermost armature switch of the previously energized relay -15), the armature switch imn'iedi'ately above the core of relay 15, the alternate contact of this arn'iature switch, the waiting contact 59 of the operated wipers, the wiper 5i engaging this waiting contact, the upper armature switch of relay 50 and its alternate contact, the winding of this relay 50, the upper armature switch of relay 63 and one of its normal contacts, to

ground. The locking circuit for the upper winding of relay 15 continues through its armature switch immediately above its core, the alternate contact of this armature switch, both sides of the calling subscriber's line, the relay 45, to ground.

One ide oi each telephone line is permanently connected with the talking wait ing contact 539 and the other side of each si'ibscribers line is connected with the talking waiting contact 58' when the upper armature switch of relay 45 is attracted. Thus the talking waiting contacts 58 and are connectedwith the talking wipers and 54- respectively, whereby the operators telephone conductors 64 are connected with the calling subscribers line to include the operators telephone set 65 in circuit with the calling subscribers line. The operator is now in telephonic communication with the calling subscriber, this feature of the invention being covered by my application Serial No. 503,345, filed June 21, 1909, though it is to be understood that in practising my invention I- do not limit myself to the manner in which communication is established between 'calling subscribers and the operators. lVhen the operator has received the number of the desired line she actuates the buttons orswitches that pertain to the waiting contacts of the desired line, the waiting contacts extending to the

wipers

21, 38 of the connector switch of the desired line, the waiting contacts pertaining to the selected telephone extension 22, and the waiting contacts pertaining to the selected telephone extension 25, these: buttons being illustrated at the right of Fig. and thereafter depresses the button or switch (36.

Two sets of such buttons are shown and two operators telephone sets (35 are shown, these elements being located at two operators positions. When the selected

buttons

28, 33, 12, 13 or l l are initially depressed they are not then immediately effective, the circuits controlled by these buttons being open at the lowermost armature switch of relay 63. The button 66 has a plunger in which there is a notch 67, this notch being normally out of line with the nose of the armature of re lay 68. When the button 66 is depressed its notch 67 is brought into register with the nose of the armature of relay 68 so that this armaturethen engages a grounded contact to establish a circuit which is traceable from this grounded contact through the armature of magnet 68, and the winding of magnet 50 whereby a ground for magnet 50 replaces the ground previously provided for this magnet at the upper arma ture switch of relay 63 and which latter ground is later removed when the ma gnet 63 is energized. pressed it moves .the switch. members (39 and 70 into engagement with their contacts.

the switch 70 closin a circuit which may be traced from the grounded armature switch of relay 63, the contact connected with the switch member 70, the contact engaged by the s vitch member 70, the actuated wiper 56, th waiting contact 61 engaging this wiper, the lowermost armature switch of relay ]5 and its previously engaged contact, the lowermost armature switch of re; lay 71 and its normal contact, the motor magnet .62, the interrupter 49, to the grounded battery 48. The motor magnet 62 due to the interrupter. 49 operates the ratchet wheel 72 to cause the

wipers

74, 75 carried by the ratchet wheel to travel until these wipers engage wa ting contacts 76, 77, 78 that are free for engagement, such contacts being free for engagement' when the contacts 78 thereof are 0011-, nected with the ground at the relay 63, there being one such relay for each operators position and such connection being cffected when a calling subscriber is connected with an operator in a manner previously described. The grounded battery 48 is connected with the wiper 75 by way of the switch 79 which is closed upon the initial movement of the ratchet wheel 72, the wind ing of relay 71, the upper armature switch of this relay, and the normal follow-up contact of this armature switch so that when the wiper 75 engages the contact 78 the magnet 71 is energized to establish a lockingcircuit for itself which continues through its upper armature switch and its alternate contact, the actuated wiper 74,. the contact 77 engaged thereby, one side of the calling line, thecalling substayion, the other side of the calling line, to tie ground at hen the key 66 is dethe relay 45. When batterywas connected with the ,wiper through the normal follow-up contact of the upper armature switch of relay '71, current from battery found passage from the wiper 7 5 through the contact 78, the employed waiting contact 60, the actuated wiper 55, the intermediate armature switch of relay 63 and its normal follow-up contact, the winding of relay 63, to ground. The relay 63 is now energized and establishes a locking circuit for itself which is traceable from the grounded coil of relay 63, the alternate contact of its intermediate armature switch, the switch element 69 and its contact, to the grounded battery 48. removed from the employed contact 78 so that the

wipers

73, 7 k, 75 of any other switch cannot rest upon any waiting contacts in multiple with the contacts 76, 77, 78 of which contact 78 is grounded, it bein understood that the waiting contacts 76, 77, 78 have multipled counterparts in switches having wipers similar to 73, 74 and 75. The removal of ground consequent upon the attraction of the upper armature switch of relay 63 has opened the circuit of the motor magnet 62 so that this motor magnet ceases to work and allows its wipers to remain in engagement with the automatically selected waiting contacts. Only two switches having the wipers 73, etc., are shown and. the lowermost switch is caused to. operate first if the other switch is idle owing to the fact that the motor magnet 62 of the upper switch depends partially for its circuit upon the engage-- ment of the lowermost armature switch of the lower relay 71 with its alternate contact. If there were more switches with motor magnets 62 the switches would be permitted to operate in succession by means of the lowermost armature switches of relays 71 introduced therebetween. The talking wipers 73 and 74- and the additional wiper 75 are respectively connected with the-two talking wipers 27 and the extra wiper 30, which latter wipers are now brought into connection with the waiting contacts 26 as a consequence of the establishment of a circuit which may be tracedfrom the grounded battery 48, the interrupter 49, the motor magnet 79, the lowermost armature switch of relay 31-and its then engaged contact, the waiting contact v76 engaged thereby, to the grounded relay 45 by Way of its upper armature switch. The armature of magnet 79 operates a ratchet wheel 80 that carries

wipers

27, 30 and this ratchet wheel continues to rotate until the rotating wiper 3O enga es a waiting contact at 26 'complemental t ereto and which complemental waiting contact at 26' has battery placed thereupon by a path traceable from the lower pole of the-bat? to the wiper-30. Circuit is closed when the Ground is now terminates in talking wipers 24: and an ex:

removing the bell crank lever from this tery 11, the winding-of trip magnet; comniou'to'button's 28 at' an ope'ratorfs'jposition, the serially related switches that" iii-- clude the bell "crank contact lcvers i82 p'iy oted'at'their lower ends 'to"the-'pa'rticu lar 70 Switch 28, in this inst'ance'j'the uppermost switch,- the contacts 8 3 of, the depressed switch 28, the switch '29 and its normal; contact, to the waiting conta'ct26 co nplementali 75 employed wipergw 'engages the contact 26 thus connectecl with battery 11 owingto the fact that the wiper 30 is connectediwith the upper terminal of tlie battery 11 by apath.

.minal jof't hisbattery, the lowermost actu-i ated; armature switch of relay 63 and its"-- contact, theactuated wiper 55, the waiting contact '60 engaging the same, the employed waiting contact 78 and the actuated wiper 85 75 engaging'the same, the switch 8 4 closed upon the initial operation of the ratchet 80, the upper windin' relay 31, to the aforesaid wiper The up er coil of re-' lay 31 thus becomes energized to a'rrest the' wipers by opening the circuit of the motor magnet 7-9 at the lowermost armature switch of relay 31. The relay 31 is provided with; a lower winding that serves to maintain the energization of the relay core, the cir'-'95 cuit bein traced from the grounded batter'y 48, t e lower'windin of relay 31, the." upper armature switch'o relay 31 and its previously engaged contact, the actuated wiper 74% and the waiting contact 77 era-.1 gaged thereby, both sides of the calling line,

to the grounded relay 45. 'The 'talking wipers 27 are now connected with a'selected line extension 25. This line extension 25 tra wiper 35, such line extension being prevented from selection by any other wipers 27, 3O owing to the fact that batteryllf. is disconnected from the waiting contact 26 engaged by the arrested wiper 30 at the previously engaged contacts 83 which are separated by the circuit established through-- the restoring magnet 81 and the battery 11, the bell crank element 82 of the actuated key having previously entered a normally unalined notch 86when this notch is'bro'ught into alinement with the upper branch of the bell crank lever upon the depression of the key having the notch, the magnet '81.

notch'when this magnet is energized so as to restore. the key and permit the contacts 83 to separate. The armature of the magnet j v 81 is shown as being common to the keys; 28 for this purpose. The selection ,pf a bus line extension 25 is furtherjgiia' v 1? against by the separation ofthe'swit'chw from its normal contact upon 'the initial operation of the motor magnet 87. (in

cuit forthe motormagnetfif is traceable 130 from the grounded battery 48, the interrupter 49, the winding of said motor magthe wiper 73, the waiting contact-76, to the grounded relay (by way of its upper armature switch) of the calling line. lhe connection of the wipers 24 and with the selected waiting contacts 23 is had by operations similar to those employed for connecting

wipers

27, 30 with the waiting contacts 26 and the magnet 36 operates similarly to magnet 31 for arresting these wipers. The buttons 33 have an associa tion with the ratchet 37 and associating mechanism similar to the association of buttons 28 with the mechanism of ratchet 32 and the wipers 21, 38are brought into engagement with selected wipers 20 in a manner similar to that employed for connecting the wipers 27 30 with the contacts 26. The structural mechanism of the keys- 28, 33, 12, 13. 14 are similar and similar parts of these keys are given similar characters of reference.

I will now describe the results of the operation of the final key, in this instance key No. 13, as line No. 2 isthe called line. From Fig. 5 it will be seen that all the keys employed in extending a telephone line may be depressed simultaneously but that a depressed key 33 cannot come into service until the operations set up by the depressed key 28 have occurred and a

depressed key

12, 13, etc., cannot come into serviceiuntil the operations set up by the depressed key 33 have occurred. It will also be observed that .7- the keys are automatically successively brought into effect, each succeeding key as it is brought into effect being preceded by the restoration of the preceding key. When the depressed key 13 is automatically reached to enable it to take part in the line extending operation the circuit previously partially established at 83 is completed, this of relay 31 and its now engaged contact, the.

actuated wiper 30 and ,the contact 26 engaging the same, the switch 29 and its alternatev contact, the intermediate armature switch of relay 36 and its engaged contact, the

and its engaged contact, the wiper 38 and the contact 20 engaged thereby, the arznature switch of relay 16 immediately beneath the core of this relay and the normal follow-up contact of this armature switch, the lower winding of relay 16, the previously closed contact 83 of the key 13, the employed magnet 81, the relay 68, the series of switches 82 of keys 33, all of which are now in normal position, the magnet 81 pertaining to the keys 33, the seriesof switches 82 of keys 28, the magnet 81 pertaining to the keys 28, to the lower pole of the battery 11. The relay 16 belonging to the called line is now energized, and a locking circuit for itself is established traceable from the grounded battery 48, theupper winding of relay 16, the armature immediately above the core of relay 16 and its alternate contact, the lower of the two wipers 21 and the waiting contact 20 engaged thereby, the lower of the two wipers 24- and the waiting contact 23 engaged thereby, the lowermost of 85 the two wipers 27 and the waiting contact 26 engaged thereby, the wiper 74 and the contact 77 engaged thereby, both sides of the calling subscribers line, the calling subscribers relay 45, to ground. A circuit was previously traced through the relay 68 and this circuit caused this relay to be energized to withdraw its armature and thereby remove ground at this armature from the magnet '50 of the operator selector switch which was actuated-as a consequence of the mature of relay 68 was attracted its nose was disengaged from the notch 67 of the pre- 10.; viously depressed key 66 so that the key 66 was automatically restored to normal and I in being so restored the switchlevers 69 and 70 were separated from their contacts. The associate magnet 63 then has its circuit open .at 69 and this magnet 63 is restored to normal and ground connection with the wiper 55 is broken at 70 so that the previously employed operator selector switch may again be employed when another call is initiated. 11;; Thus the operator is freed for further selection and the apparatus of keys 28, 33,

12; etc., are restored to normal. The ringing magnet 46 of the called line is consequently energized over a circuit. tracealiilc 126 from the grounded battery 48 through the ringing interrupter 88, the uppermost armature switch of the called subscribers relay 16, and its then engaged contact, the middle switch of called subscribers relay 45 and its contact, the winding of the called subscribers ringin relay 46, to ground. This ringing relay 1s consequently intermittently energized intermittently to include 'theringing generator 89 in bridge of the 130 called line by way of the armature switches of the ringing relay 46 and the alternate contact of these armature switches that constitute terminals of said generator. When the called subscriber responds the generator 89 is automatically cut out of circuit during one of the periods in which the actuated ringing relay 46 is denergized and in which period the called subscribers telephone is removed from its hook whereby the called subscribers relay 45 is then energized to open the circuit of the ringing relay 46 to maintain this ringing relay permanently in open circuit duringthe established'connection. The circuit of relay 45 of the called line is traceable from the grounded terminal of this relay 45, both sidesof the calling line by way of the released armature switches of ringing relay 46 and their normal contacts, the armature switchof called subscribers relay 16 immediately above the core of this relay and the alternate contact of'this armature switch, the upper coil of this relay 16, to the'grounded battery 48, the circuit for the ringing relay 46 being kept open at the middle armature switch of the now energized relay 45. The attracted upper armature switch of relay 45 extends the called line into connection with the con- (luctors leading to the waiting contacts 20 engaged by the Wipers 21 so that connection between the calling and called lines is now completed. WVhen the parties are through conversation their relays 45 are denergized on the restoration of the telephone receivers upon their switch hooks whereby the

relays

15, 16, 39, 36, 31' and 71 are included in open circuit so that the armatures of these relays are restored to normal. When the armatures of

relays

39, 36, 31 and 71 are restored to normal they disengage the actuating pawls' ofthe associate motor magnets from the ratchet Wheels previously operated by these pawls so that these ratchet wheels are restored to normal, as shown in Fig. 6.

Any suitable test feature may be employed. As the system is employed failure of the

depressed buttons

12, 13, etc., to restore the normal will indicate to the operator that the desired line is busy and inasmuch as the operator is not released until this button is restored the operator may'inform the calling subscriber that the desired line is busy. a

Fig. 6 indicates a. delaying device by which the ratchet wheel is permitted to re store to normal prior to the return of the actuating pawl of the motor magnet to the position in which it may actuate the ratchet wheel. The delaying detent a is pivoted at b and is pulled upon by a spring 0 so as to have a position to engage the pawl d of the motor magnet when this pawl is raised by the finger e operated by the holding magnet when energized. When the holding magnet" 'is denergized the finger f fixed upon the ratchet wheel strikes the holding pawl a, when the ratchet wheel has reached normal, and releases the holding pawl from engagement with the actuated pawl operated by the motor magnet so that this actuated pawl may be restored to its relationship with the ratchet wheel.

In my co-pending application Serial No.

714,417, filed August 10, 1912, I have claimed the

key mechanism

28, 33, 12, 13, etc, and I do not limit my present invention to the employment of this key mechanism. -It is desired to make cross reference to my following copending applications: Serial No. 709,405, filed July 15, 1912, Serial No. 709,406, filed July 15, 1912, and Serial No. 709,407, filed July 15, 1912, in which are broadly claimed operator controlled electromagnetic switches for establishing connection between calling lines and calling line extensions or other telephone lines. By means of one of the systems disclosed in these co-pending applications calling line terminals are moved into connection with contacts of link connectors; in another sys tem direct connection is effected between contacts belonging to calling lines and contacts belonging to called lines; and in the remaining system contacts belonging to link connectors are moved into connection with contacts belonging to the calling lines.

While I have herein shown and particularly described the preferred embodiment of my invention, I do not wish to be limited to the precise details of construction and circuit arrangement shown as change may readily be made without departing from the spirit of my invention.

' Having thus described my invention I claim as new and desire to secure by Letters Patent the following I 1. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting device, the controlling circuits being associated with difierent telephone line extensions; means for changing the character of the controlling circuits; electro-magnetic mechanism in the controlling circuits for maintaining the connecting device in association with a modified controlling circuit; and electro-magnetic switches individual to the controlling circuits for restoring such circuits when their associate line extensions have become connected with telephone lines:

2. A telephone system including telephone lines extendin from stations to an exchange; extensions for such telephone lines -means individual to the controlling circuits for restoring such circuits when their associate line extensions have become connected with telephone lines.

3. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange;a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting de- 1 vice the controlling circuits'being associated with different telephone line extensions; means for changing the character of the controlling circuits; elec'tro-magnetic mechanism in the controlling circuits for maintaining the connecting device in association with a modified controlling circuit; and electromagnetic switching mechanism for restoring such circuits when their associate line extensions have become connected with telephone lines.

fl. A telephone'system including telephone lines extending from stations to an exchange: extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for gi' verning the association of said connecting device, each controlling circuit having a contact for engagement with the connecting device the controlling circuits being associated with different telephone line extensions; means for changing the character of the controlling circuits; electro magnetic -mecha nism in the controlling circuits for maintaining the connecting device in association with a modified controlling circuit; and means for restoring such circuits when their associate line extensions have become connected with telephone lines.

5. A telephone system including telephone lines extending from stations to an exchange: extensions for such telephone lines having contacts at the exchange; a line .ex-

tending connecting device for engagement with the contacts; controlling c1rcu1ts for governing the association of said connecting device, each controlling circuit having conmet o e g g ent with the connecting device, the controlling circuits being associated\ with different telephone line extensions; Qmeans indivldual to the controlling circuits for changing the character of the controlling circuits; electro-magnetic mechanlsm 1n the controlling circuits for maintainingthe connecting device in association with a modified controlling circuit; and means for restoring such circuits when their associate line extensions have become connected with telephone lines.

(3. A telephone system including telephone lines extending from stations to an exchange; extensions forsuch telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting device, the controlling circuits being associated with difierent telephone line extensions; means for changing the character of the con trolling circuits; and electromagnetic mechanism in the controlling circuits for maintaining the connecting device in association with a modified controlling circuit.

7. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line ex tendin connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a con tact for engagement with the connecting dewith different telephone line extensions;

'means, for changing the character of the controlling clrcults; means for main-taming the connecting device in association with a moditied controlling circuit; and electromagnetic switches individual to the controlling circuits for restoring such circuits when their associate line extensions have become connected with telephone lines.

8. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement withvthe connecting derice. the controlling circuits being associated with difi'crent telephone line extensions; means for changing the character of the controlling circuits; means for maintaining the connecting device in association with a modified control-ling circuit; and means individual to the controlling circuits for r.estoringsuch circuits when their associate line extensions have become connected with teleph ne lines.

9. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting de-- 'vice, the controlling circuits bemgassociated with the contacts; controlling circuits for governing the association of said connecting.

device, each controlling circuit having a contact for engagement with the connecting device, the controlling circuits being associated with different telephone line extensions; means for changing the character of the controlling circifits; means for maintaining the connecting device in association with a modified controlling circuit; and means for restoring such circuits when their associate line extensions have become connected with telephone lines.

11. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a con tact for engagement with the connecting device, the controlling circuits being associated with diflerent telephone line extensions; means individual to the controlling circuits for changing thechara-cter of the controlling circuits; means for maintaining the connecting device in association with a modified controlling circuit; and means for restoring such circuits when their associate line extensions have become connected with telephone lines.

12. A telephone system including telephone linc extending from stations to an exchange: extensims for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device in determining the extensions of telephone lines, each controlllng circuit having a contact for engagement with the connecting device, the controlling circuits being associated with different telephone line extensions; means for changing the.,character of the controlling circuits; means for maintaining the connecting device in association with a modified controlling circuit; and means for restoring such circuits when their associate line extensions have become connected with telephone lines.

18. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a

line extending connecting device for en.

gagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having acontact for engagement with the connecting device, the controlling circuits being associated with difierent telephone line extensions; operator controlled means for changing the character of the controlling circuits; electro-magnetic mechanism in the controlling circuits for .maintaining the connecting device in association with a modified controlling circuit; and electromagnetic switches individual to the controlling circuit s for restoring such circuits when their associate line extensions have become connected with telephone lines.

14:. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting device, the controlling circuits being associated .with different telephone line extensions; operator controlled means for changing the character of the controlling circuits; electro-magnetic mechanism in the' controlling circuits for maintaining the connecting device in association with a modified controlling circuit; and means individual to the cpntrolling circuits for re storing such circuits when their associate line extensions have become connected with telephone lines.

15. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting device, the controlling circuits being associated with different telephone line extensions; operator controlled means for changing the character of the controlling circuits; electro-magnetic mechanism in the controlling circuits for maintaining the connecting device in association with a modified controlling circuit; and electromagnetic switching mechanism for restor ing such circuits when their associate line extensions have become connected With telephone lines.

16. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting device, the controlling circuits being associated with ditferent telephone line extensions; operator controlled means for changing the character of the control ling circuits; electro-magnetic mechanism in the.controlling circuits for maintaining the connecting device in association with a modified controlling circuit; and means for restoring such circuits when their associate line extensions have become connected with telephone lines.

11A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association otsaid connecting device, each controlling circuit having a contact for engagement with the connecting device, the controlling circuits heing associated with different telephone line extensions; operator controlled means individual to the controlling circuits for changing the character of the controlling circuits; elcctro-magnetic mechanism in the coi'itrolling circuits for maintaining the connecting device in association with a modified controlling circuit; and means for restoring such circuits when their associate line extensions have become connected with telephone lines.

18. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting device the controlling circuits being associated with different telephone line extensions; operator controlled means for changing the character of the controlling circuits; and electromagnetic mechanism in the controlling circuits for maintaining the connecting device in association with a modified controllingcircuit.

19. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts controlling circuits for governing the association of said connecting phone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits ffor governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting device, the controlling circuits being associated. with different telephone line extensions; operator controlled means for changing the character of the controlling circuits; means for maintaining the connecting device in association with a modified controlling circuit; and means individual to the controlling circuits for restoring such circuits when their associate line extensions have become connected with telephone lines.

21. A telephone system including tclephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device. each controlling circuit having a contact for engagement with the connecting device, the controlling circuits being associated with different telephone line extensions; operator controlled means for cl'ianging-the character of the controlling circuits; means for maintaining the connect ing device in association with a modified controlling circuit; and electro-magnetic switching mechanism for restoring such circuits when their associate line extensions have become connected with telephone lines.

22. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting device, the controlling circuits being associated with diiierent telephone line extensions; operator controlled means for changing the chanactcr of the controlling circuits; means for maintaining the con necting device in association with a modified controlling circuit; and means for restoring such circuits when their associate line extensions have become connected with telephone lines.

23. A telephone system including telephone lines extending from stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with the contacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with theconnecting device, the controlling circuits being associated with different telephone line extensions; operator controlled means individual to the controlling circuits for changing the character of the controlling circuit-s;

means for maintaining the connecting device in association with a modified controlling circuit; and means-for restoring such circuits when their associate line extensions have become connected with telephone lines.

24. A telephone system including telephone lines extending from-stations to an exchange; extensions for such telephone lines having contacts at the exchange; a line extending connecting device for engagement with thecontacts; controlling circuits for governing the association of said connecting device, each controlling circuit having a contact for engagement with the connecting device, the controlling circuits being associated with different telephone line extensions; operator controlled means for changing the character of the controlling circuits; and means for maintaining the connecting device in association with a modified controlling circuit.

A telephone system including telephone lines; extensions for such telephone lines; a line extending connecting device for associating a selected telephone line extension with the telephone line having the connecting device; controlling circuits associated with different telephone line ex ten sions for governing the association of said connecting device in determining the extensions of telephone lines; means for changing the character of the controlling circuits; and

means for restoring. such circuits when their associate lineextensions have become connected with telephone lines.

26. A telephone system including telephone lines extending to an exchange: extensions for such telephone lines; a line ex tending connecting'device; controlling cir' ocales cuits associated with difi'erent telephone line extensions for governing the association of said connecting device; and operator controlled means tor changing the character of the controlling circuits.

27. A telephone system including telephone lines; extensions for such telephone lines; a'line extending connecting device; controlling circuits associated with different telephone line extensions for governing the association of said connecting device; and operator controlled means for changing the character of the controlling circuits.

28. A teiephonesystem including tele phone lines; extensions for 'such telephone lines; a line extending connecting device; controlling circuits associated with different telephone line extensions for governing the association of said connecting'device in determining'the extensions of telephone lines; means for changing the character of the controlling circuits; means governed by the controlling circuits, when modified, for maintaining the extensions associated therewith in connection with the line extending connecting device; and means. for restoring such circuits when their associate lineextensions have become connected" with telephone lines. 7

29. A telephone system including telephone lines extelnding to an exchange; extensions for such telephone lines; a line extending connecting device; controlling cireuits associated with difl'erent telephone line extensions for governing the association of said connecting device; operator controlled means for changing the character of the controlling circuits; and means governed by the controlling circuits, when modified, for maintaining the extensions associated therewith in connection with the line extending connecting device.

30. A telephone system including telephone lines; extensions for such telephone lines; a line extending connecting device; controlling circuits associated with diflerent telephone line extensions for governing the association of said connecting device; operator controlled means for changing the char actor of the controlling circuits; and means governed by the controlling circuits, when modified, for maintaining the extensions associated therewith in connection with the line extending connecting device.

BLL'A telephone system including tele phone lines; extensions for suchtelephone lines: a line extending connecting device; controlling circuits associated with different telephone line extensions for governing the association of said connecting device in determining the extensions of telephone lines and individual to the line extensions pertaining to the line extending connecting device: means for changing the eharacterof the controlling circuits; and means 50! re storing such circuits when their associate line extensions have become connected with telephone lines,

32. A telephone system including telephone lines extending to an exchange; ex-

. tensions for such telephone lines; a line ter of the controlling circuits.

A telephone system including telephone lines; extensions for such telephone lines; a line extending connecting device; controlling circuits associated with different telephone line extensions for governing the association of said connecting device and individual to the line extensions pertaining to the line extending connecting device; and operator controlled means for changing the character of the controlling'circuits.

34. A. telephone system including telephone lines; extensions for such telephone lines; a line extending connecting device; controlling circuits associated with different telephone line extensions for governing the association of said connecting device in determining the extensions of telephone lines and individual to the line extensions perraining to the line extending connecting detl'ce; means for changing the character of the controlling circuits; means governed by the controlling circuits, when modified for maintaining the extensions associated therewith in connection with the line extending connecting device; and means for restoring such circuits when their associate line extensions have become connected with telephone'lines. i I

35; A telephone system including telephone lines extending to an exchange; extensions for such telephone lines; a line extending connectin device; controlling circuits associated wlth different telephone line extensions for governing the association of said connecting device and individual to the line extensions pertaining -to the line extending connecting device; operator controlled means for changing the character of the controlling circuits; and.

means governed by the controlling circuits, when modified for maintaining the extensions associated therewith in connection with the line extending connecting device.

36. A telephone system including tele phone lines; extensions for such telephone line.-.1 a line extending connecting device;

taining to the line extending connecting device; operator controlled means for changmg the character of the controlling cir cuits; and means governed by the controlling circuits, when modified, for maintaining the extensions associated therewith in connection with the line extending connecting device.

'37. A telephone exchange system including telephone lines extending from stations to an exchange; extensions for such telephone lines; an electromagnetic line extending switch having a number of sets of waiting contacts pertaining to different telephone line extensions, and a set of Wipers for interchangeable connection with said sets of waiting contacts; electro-magnetic mechanism for holding the wipers in connection with the waiting contacts; and operator governed controlling circuits pertaining to the different telephone line extensions for controlling said electro-magnetic mechanism and having waiting contacts in the sets of waiting contacts to enable the operator to determine the set of waiting contacts to be engaged by the set of Wipers.

38. A telephone system including telephone lines; extensions for such telephone lines; an electro-magnetic line extending connecting device; switching mechanism for setting said connecting device into operation: and manually modified controlling circuits individual to the difierent telephone line extensions and each serving, when modified, to stop the moving connecting device in connection with the corresponding telephone line extension.

39. A telephone system including telephone lines; extensions for such telephone lines; an electro-magnetic line extending connecting device; switching mechanism for setting said connecting device into operation; and controlling circuits having opera. tors means for modifying the same and which are individual to the different telephone line extensions and each serving, when modified, to stop the moving connecting device in connection with the corresponding telephone line extension.

In witness whereof, I hereunto subscribe my name this sixth day of August A. D., 115

ILMER R. CORVVIN. \Vitnesses G. L. CRAGG, E. L. WHITE.

Copiers this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, 3.3.0.