USRE12943E - Telephone-exchange system - Google Patents

Description

E. LAND.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED we. 9, 1906.

Reissued Apr. 20, 1909. 1 2,943.

AA///I L B. LAND.

TELEPHONE EXGHANGE SYSTEM.

APPLICATION FILED AUG. 9, 1906.

Reissued Apr. 20, 1909.

1-]. LAND. TELEPHONE EXCHANGE SYSTEM. APPLIOATION FILED v5.0, 1900.

Reissued Apr. 20, 1909. 1 2,943

4 BHBBTS-BHEBT 3.

E. LAND. TELEPHONE EXGHANGE SYSTEM. APPLIUATION rum) AUG. 9, 1906.

Reissued Apr. 20, 1909. 1 2,943

4 SHEETS-SHEET 4.

- term UNITED STATES PATEN T OFFICE.

IIMI'ND LAND. OF GRANT) RA PIDS. MICHIGAN, ASSIGhOI-I TO MILO G. KELLOGG. OJ HIUAGO,

ILLINOIS.

TELE PHONE-EXOHANGE SYSTEM.

Specification of Reissued Letters Patent. Reissued April 20, 1909. Original N0. 818.540, dated April 24, 1906, Serial No. 250,933.

Application for reissue filed August 9, 1906.

Serial No. 329,949.

To all whom it may concern.

Be it lmow i that I, EpiuUNn LAND, a citizen ol' the Dominion of (anadzn and a resi' dent of (lrand Rapids, county of Kent, and State. of Michigan, have invented a new and useful lmprm'emcnt in 'lelephone-Exchzn'lge Systems, of which the following is a specification.

My invention pertains to semi-automatic telephone exchange equipment. By the semi-automatic" I indicate those systems in. which automatic selecting equipment is supplen'iented hy the attention of a rent ral-ollicc operator who assists in promoting the connection to the desired station.

I provide a system of keys for automatic 1 selecting. ringing. and supervising with associntcd circuits and automatic selecting witches which will "ive tothe centriil-ofiicc operator facilities lor promoting with the greatest rapidity orders received by telephonic transmission from the calling patron and to enable her to supervise and disconnect such connection with the greatest accuracy and case. No llexihle cords are used. It is believed that the system shown in this (le scription and drawings will afford for the operator facilities for completing a. greater number of connections per unit of time than any known method of manual crating with cords, plugs, and jacks, and W1 l atl'ord for the patron a. system involving the advantage of manual supervision of the connection.

In the d awi11gs, Figure 1 is a. general circuit diagram of my invention, the figure be ing drawn on two sheets designed to he placed end to end to complete the figure. 1g. 2 is a dmgrammatic detail of the switch l'ormmg a. part of the line equi iment 16. Fig. 3 1s a. diagrammatic detail of the autok a mntic switch 3. 1 1g. 4 is on additional detail of the, oil-normal switch of Fig. 3. Fig. 5 is a diagrammatic detail of the automatlc tentpawl.

an armature for magnet 19.

switch 85, and Fig- 6 shows diagrammntically an alternative form of selecting-key device tor the operators equipment 41.

Relays, keys, visunl signals, &c., are

shown in conventional form, as my invention does not in any way involve the me- I .chamcal detail of the respective parts of apparatus used.

At 10 is shown a. connnon battery substation telephone equipment of a wellknown switch.

typo in which circuit through conductor 11 is closed for direct current when the hook up, and circuit through a condenser 12 and high-resistance ringer 13 is closed for alternoting current when the hook is down. This substation telephone is connected hy line. conductm's I4 and IS with an automatic central ol'lice equipment pertaining individually to that line and indicated as a whole The line equipment It) consists of an automatic circnit-selecting switch of any desired. mechanical type, the associated operating-magncts of said switch, relay-armatures, and contacts for said operating-magnets, andan associated relay 1?, not necessarily, mechanically a pant of said automatic In said automatic switch, in is a magnet adapted to propel the moving part of the switch, and I9 is a. magnet adapted. to release said moving part for restoration to its normal position of rest through action of springs or grzn'ity. 2U, 21, .32 are moving contact terminals or wipers attached to the moving port of said automatic switch and adapted to make contact with fixed terminals or waiting contact as those shown a. sociated with conductors 25, 26, ll.

In mechanical design, the automatic switch mechanism of the equipment 16 may he of any desired form, a diagrammatic representation of the conditions required for this switch being shown in Fig. 2. in which the designating numerals given are those of Fig. 1, some further parts being designated by letters.

In Fig. 2, B is a shaft siqiportiug insulated wipers 20, 21, 22. A is a ratchet mounted upon the shaft B. is an armature l'or magnet 18. .l) is a pawl pivoted upon armature C. K is a fixed pin guiding pawl I). H is a pin upon pawl I). .\l is a pivoted de- G is a pin upon pawl M. E

F is a link pivoted upon armature E and having a hook l projection to engage pin G, and a straight arm projection to he engaged by pin H.

In operation successive energizations of magnet 18 will attract armature (I successively, and

thus cause driving-pawl I) to propel ratchet A one tooth for each such cnergization, the ratchet A being held in its determined position by the detent-pawl Following this, the energization ol magnet 19 will attract its armature E, causing link F to pass forward until its hook projection passes over 1 pin G, the ratchet A beingretamed by detent-pawl M during the continuance of the energization of magnet 19. Upon deenergization of magnet 19 and consequent reease of armature E and return of that armature by spring tension to its position of rest, link F retires to its normal position of rest, and in doing so its hook projection engages pin G on detent-pawl M and withdraws said detent-pawl from epgagement with ratchet A. Ratchet A therefore is released and now may return to its normal position of rest by action of springs or gravity. energization o magnet 18 and consequent novement of armature C and )awl D, )in 11 engages link F and lifts it unti its 1100 projection is lifted out of engagement. with pin G, thus releasing detent-pawl M to act as previously mentioned.

Referring again to Fig. 1, the step-by-step movement of the wipers 20, 21 22 causes them to make contact successively with the waiting contacizsjishown adjacent thereto until connection is made with the waiting contacts of a trunk not already in use, when connecting-relay 19 is energized, resulting in the stopping of the motion of the wipers and in the connecting of the line conductors 14, 15 to the wipers 21, 22.

1118,0138 of the automatic switch in equipment 16 are connected to a plurality of trunks,

each trunk being equipped .with keys and signals, as ShOWIl lIl the lower portion of sheet L, and with an automatic selectingswitch, (designated as ,a whole 23 in Sheet R,) the trunk thus terminating in armature parts of relay 56 and being connected through armature-contacts to magnets 54 1 and 55 when the switch 23 is not in use. f

The trunk-conductors are two in number, (including respectively conductor 24, 117, 110, 63 and 25, 118, 111, and they are multiplied through the waiting contacts of a plurality of automatic switches pertaining to 5 inc equipments, as 16, and an auxiliary conductor 26 also is multiplied through. the i waiting contacts of those automatic switches 5 for purposeof busy test. Each trunk thus j is accessible from a plurality of automatic switches, and each automatic switch has accessible a plurality of trunks.

The action of the line equipment 16 in selectin a trunk not already in use is as follows: Tfpon r moval of the receiver from the hook at snbst tion-telephone 10 current flows from batte y 27 through conductors 28, 15, 11, 14, 2 and to ground, energizing relay 17 an attracting its armature.

current from battery through conductors 30,

into (BOiIDQCtlOIl with wait1ng-test contacts Upon the next The waiting conof the trunk conductors 24, 2.3, and wipers 21, 22 into connection with said conductors 24, 25. The attraction of the armature of relay 18 has int rupted the circuit last de- ,'scribed by breaking the connection between i conductors 30 and 31; but this interruption has de'energized relay 18, and upon the re- 1 lease ol" its armature the previously described circuit is completed again as far as wiper 20. i If at this time trunk conductors 24, 25 be already in use, a ground will be found upon 1 test-conductor 26, and circuit will be completed for battery 27 over conductors 30, 31, 32, 33, 20, 26 and to ground, energizing relay 18 and stepping wipers 20, 2 1, 22 forward to l the next trunk. This cycle of operation will .lrepeat automatically, so long as wiper 2O finds aground upon the test-conductor of 1 the trunk connected with, but as soon as a trunk is found whose test-conductor, as 26, l is not grounded, the circuit from the wiper 20 to ground will not exist, and current will 1 36, 35 and to ground. The resistance of rc lay 18 is low, and the number of turns of the conductor 30 upon relay 18 is comparatively small, while the relay 19 is of high resistance, and the number of turns of conductor 36 upon relay 19 is comparatively large. Furthermore, the spring tensions upon the armatures of thiise relays are capable of relative i adjustment. In response to this current through relays 18 and 19 in series, the relay 18 is not sufliciently energized to attract its armatures or to break its armature-contact, while the relay 19 is energized to operate its arniatures. Conductor 33 is removed from conductor 32 and placed in connection with conductor 37, thus placing a ground upon wiper 20 and upon test-conductor 26, and thus upon the multiplied test-contacts of the trunl conductors 24, 25, preventing the connection wlt'h that trunk of any telephoneline through its equipment, such as 16, and reserving that trunk exclusively for the use of telephone-line 14, 15 and the substationtelephone 10. The arniatures of the relay 19 also have connected conductors 29 and 38 to wipers 21, 22, and therefore to conductors 24, 25. Current previously flowing from battery 27 to conductors 28, 15, 11, 14, 29 and to ground now flows through conductors 28, 15, 11, 14, 29, 22, 24, 39 and to ground without such interru )tion in changing as. would affect relay 17. The energization of relays 17 and 19 therefore is continued and calling visual signal 40 is displayed before the operator usin equipment 41, indicating 1 to her that a calling patron has been connected to the trunk served by the signal 40. The energization of relay 17 gives path for The circuit conditions now existing and i which will remain unchanged throughout the further promotion and continuance of the connection give a current from the battery l 27 through the speech transmission device flow from battery 27 over conductors 30, 31,

of the substation 10 in series with the, eonductors forming winding of relay 17, between one side of the line and the ggroundi t r l l l battery and the winding of visual signal 10, i

bet ween the other side of the line andground. 1

The relative resistances and impedances of relay 1? and visual signal 40 shall be such as to maintain proper balance of the line conductors and to supply proper current for speech. transmission from the substation it) without unduly 'detracting from speech transmission to substation 1U. Conductors 42, 43, 44 provide for calls in which substagage pin 205.

213 and armature 206. 73 is an oll'-normal switch. 216isatlangeuponshait2Utl1nem tion 10 is the called station to the connect ion.

Such conditions will be described later in this specification.

A trunk equipment consists of visual signals 40 and i5 and keys 4t), 4T. 48, it), 50, Si,

gy-i ggcment with one of the springs of the pair 73%, holding said pair separated. and extending in such direction an for such distance that such engagement of the flange with one member ol' the pair continues throughout the motion of the wipers in the first or primary 5;, 53, located in. a switch-board accessible 3 visually and manually to the operator using the equipment 41, also autonnztie switch 23, located in the some central otiico with the operator 41. two directions of motion in its wipers, the first motion being controlled by actuatingmagnet 54 and the second motion being controlled by actuating-magnet 55. By the first motion, as in the vertical steps of a Strowger switch, wipers move to a desired position, constituting by the selection of the position the selection of a. group of trunks-- i. (a, a. group of sets of waiting contacts. By the second motion. controlled by nutgnct 55, the wipers are moved, as in the rotary motion of a Strow geiswitch, to select one set of contacts from the group of sets preliminarily selected. Magnet 56 is a connecting and rel'he switch 23 is of a t )ehavin i leasing, magnet, and magnets 55, 56 bear the same relationbetween themselves as do ma;; 1

nets 18, 10, described in connection with switch 16 as will be seen in the detailed description of the operation of switch 23 immediately following.

The automatic switch 23 may be of any prt-d'erred mechanical detail, one possible associationof necessary parts being shown diarrannnatically in Fig. 3. 1

In Fig. 3, 200 is a movable shaftsustaining the wipers St), N1, 82. 201 is a cylindrical pawl 203.

direction oi selection and that the rug-gagemcnt is discontinlu-d when the wipers make their first step in the secondary direction, at which time by the release of such. engagement of the spring with the flange the contact between the two springs oi the pair is per? mitted, and the oil -normal switch 73 is closed. This switch detail is illustrated fur ther in Fig. 4, which. is taken at an angle. of

ninety degrees with Fig. 3, the shut t 200 and flange '31 6 being shown in section.

The operation of the autonuitic snitch. shown diagrammatically in Fig. 3 is as follows: By successive energizations of n'uzgnet .34, armature 206 is attracted successively and driving-pawl 207 acts upon successive teeth of the cylindrical rack, the rack being held in its determined position by detentpawl 203. Then successive encrgizations of magnet 55 attract armature 209 successively, causing drivin -pawl 210 to act upon suecessive teeth 0 cylindrical ratchet 202, turning it step by step in the direction indicated by the arrow, the cylindrical ratchet being held in its determined position by the detent- Thcn cnergization of magnet 56 1 attracts armature 212, thus advancing link rack upon the shaft by which the wipers may be moved in the primary direction of s =lcction. 202 is a cylindrical ratchet upon the shalt bywhieh the wipers may be moved in the secondary direction of selection. 203 is 213 until com 214 passes pin205, which it is perinitted'to do by reason of the slotted con' nection between link .213 and link 215. l"'ocn upon detmergization of magnet 56. armature 212 is returned by spring tension to its position of rest, witlulrawinc link 1213, causing cam 314 to engage pin 205, withdrawing detent-pawl 1203, and releasing shalt .300 and l wipers 8t), 81, 82 to return to the normal poa, detentpawl adapted to engage both the 1 cylindrical rack andthe cylindrical ratchet to hold the wipers in the determined position I pawl 203 for service, as above described.

both in primary and secondary directions and to release the wipers l'roni rcstraintin Ell-l is 306 is an armature for 208 is a lixcd pinactiue sition of rest by spring tension or gravity. Then upon the next energization of lnagnet 54 the movement of ar1nature-2t)6, acting: through link 2J5, lifts link 1213 to disengage cam 214 from pin 205 and release detent- The operation of the trunk equipment, as a. whole, is as follows: By the action of automatic switch 1 G, consequent upon the closing of the circuit at substation 10, trunk conductors, as .24, are selected and the signal 41) of that trunk is caused to be d played by current from battery 27. There is no further Hill ill)

change in the circuit conditions of elements 10, 16, or until the termination of the conversation.

In response to -the display of signal 40, operator at 41 presses key 46, which is adapted to remain in its depressed position until released by the hand of the operator. This places the operator at 4,1 in tele honic communication with the patron at t e telephone 10. She asks for and receives his order. In the execution of the order she depresses key 47, which remains in its operated position untillreleased by her hand, then depresses key 51, which remains in its operated position until released manually by key or electromagnetieally by magnet 57, then depresses key. 49, which remains in its operated position until released manually by key 48 or electromagnetically by magnet 58, then controls and operates automatic selectingswitch 23 by the use of keys 52, 53.

By the operation of key 5], battery 59 has been connected by conductors 60, 61, 62 with trunk conductor 63, to which conductor battery 64 also is connected by conductors 65, 66, the latter containing the winding of magnet 54; but magnet 54 is not energized as the two batteries are equal in potential and opposing in polarity. of key 53, path is formed [or current from grounded battery 64 over conductors 66, 63, 62, 67 and to ground, energizing magnet 54 successively for each operation of the key 53,

thus accomplishing the first selective movement of the automatic. switch 23 and select- By the operation circuit will be closed for current from hattery 64 over conductors 65, 68, 74, 75, 79, 80, 83, 84 and to ground, resultin in the refiner gization of magnet 55 upon t e releasin of its vibrating armature, and thus the vi 1' tion will continue until a waiting contact not grounded is engaged by wiper 80, at which time, conductor 79 being open, current will flow from battery 64 over conductors 65, 68, 74, 75, 76, 73, 77, 78 and-to ground.

As mentioned, the relation of relay 56 to magnet 55 corresponds to that of relay 19 to magnet 18, and therefore relay 56 isenergized and magnet 55 is not energized. Consequent upon the energization of relay 56,-conductor 79 is removed from conductor 75 and connected with conductor 35, thus ounding conductor 84 and its multiplied waltin contacts and placing busy test upon the se ected trunk or line. Also by the energization of relay 56. conductor 63 is removed from conductor 66 and connected to wiper 82, and conductor 70 is removed from conductor 69 and connected to wiper 81. Conductors 69, 66 are thus isolated, and further operation of magnets 54, 55 is impossible so long as the energization of relay 56 continues by current through key 47. Conductors 63, 70 now are connected through wipers 82, 81 to trunk conductors 37, S6, and thus to the modified Strowgcr switch (indicated as a whole as 88.) The mechanical construction of this switch is well known in the art and is diagrammaticall shown in Fig. 5,- wherein 300 is the she t ing the desired group of trunks or sets of waiting contacts.

Having thus selected the 1 group, key 52 is depressed once by the operator, giving path ior current from grounded battery 64 over conductors 65, 68, 69, 70, 71, 72 and to ground, energizing magnet 55 and moving the wipers one step in their second direction.

Switch 73 now becomes effective, its con strui-tion being suchthat the two parts have a normal tendency to close together, but one part being engaged with'a projection of the reference to the first motion of selection, as

heretofore explained in connection with Figs. 3 and'4. Switches of'this nature are well known in the art both in function and construetion, and the name off-normal is applied to them.

The cnergization of magnet 55 has stopped the wipers forward int o engagement with the first set of the waiting contacts of the selected group, and if wiper 80 finds a ground bearing the insulated wipers 100, 101, 102. 301 is the cylindrical rack for vertical or iimaiyscleetion. 302 is the cylindrical ratc st for rotary or secondary selection. 303 is the detent pawl for operatin upon both the cylindrical rack and cylin rical ratchet. 804 is the pivot of detent-pawl 303. 305 is a pinu on detent-pawl 303, by which pawl 303 is wit idrawn from engagement with the rack and ratchet for disconnection of the wipers and restoration of the shaft 300. 306 is the armature of the vertical magnet 92. 307 is the driving-pawl, pivoted upon the armature 306. 308 is a fixed pin acting as a guide for the driving-pawl 307. 309 is the armature of horizontal magnet 125. 310 is the driving-pawl, pivoted upon the armature 309. 311 is a fixed pin acting as guide to the driving-pawl 310. 312 is the armature of the release magnet 108. 313 is a link ivoted upon the armature 312 and adapts by its hook fornrto engage pin 305 and withdraw pawl 303 .'hcn,1nagnct 103 is energized. 121 is an oil-normal switch closed by the first vertical movement of the shaft 300. 317 is a side switch or auxiliary switch or pilotswitch designed to he propelled by-control of private magnet 04. 318 is the armature of the private magnet 94-. 319 is a driving-pawl pivoted upon the armature 318. 320 is a upon the waiting contact connect-ed with, I fixed pin acting as a guide to driving-pawl 319. Driving-pawl 130 is adapted to pass l actuation of key 52 subsequent to the last one tooth of the part 317 when the armature selective group of actuations of key 53 will 318 is attracted and to move the part 317 by 1 energize and. release private magnet 94, and pulling the tooth thus passed when armature I thus step the side switch- wipers 95, 96, 97

' 318 returns to its position of rest by spring tension after being released magnetically.

05, 00, 07 are insulated wipers upon the side switch part 317. The private magnet also actuates an armature-centsct 04. It is seen that by the first action of the private magnet 04, the wipers 05, 06, 97 will be advanced to their middle positions, while by the second action of the private magnet they will be advanced to their third or last positions, after which no further advancement is possible. 316 is a collar upon the shaft 300, adapted to operate the oil-normal switch 121 and also to restore the side switch pawl 31? to its normal position of rest upon the return of the shaft 300 to its normal position of rest upon disconnection when released by the do 1 tent-pawl 303. Wipers 95, 06, 07 are so spaced upon the side switch that wiper 97 lags behind the other two wipers both in leaving the contact-points immcdiatelv after the starting of the side switch under the pull oi pawl 310 and in making connection with the next contact-pomt just bctore the slde switch reaches the limit of its step.

By another series of actuations, key 53 1 controls switch 88 over the circuit from grounded battery 89 over conductors 90, 91, S7, 82, 03, 62, 67 and to ground, thus energizing the vertical magnet 92 successively and selecting the desired level of waiting contacts. Then by the operation of key 52,

current is taken from battery 80 over conductors .30, 03, S6, 81., T0, 71, 72 and to magnet 04 and stepping the side switchwipers 05, 96, 07 forward one step in the well-known manner.

By another series of operations of the key forward into their right-hand position. In the motion of the side-switch wipers from the middle to the right-hand osition, the se quence of the breakings an makings of connections is as follows: First, wipers, 95, 96 break from conductors 98, 03, respectively; second, wiper 07 breaks from conductor 104; third, wipers 0.5,96 make contact with conductors leading to wipers 101, 100, respec tively, and thus circuit is completed for current from grounded battery 59 over conductors e0, e1, 62, 63, s2, s7, 95, 101, 43', 29 and to ground, energizing magnet 57 and releasing key 51. The release of the key 51 in'm'iediatelv succeeding the last actuation of the key 52 indicates to the operator that the line selected. has been connected with. Fourth, wiper 97 makes contact with conductor 109, thus connecting the ground of 100 through 97, 102, 1.06 to 107 and its multiplied waiting contacts, placing busy test conditions upon the selected line. By contact of wiper 97 with conductor 109, path is formed for current from grounded battery 27' over conductors 31 36, 42, 106,

102, 105, 97, 100 and to ground, energizing relay 19, but not energizing relay 18'. The energization of relay 19 removes the ground from conductor 29' and connects conductors 20, 38' to wipers 22, 21', these wipers being out of connection with an 1 waiting contacts.

The connection of con uctor 33' also is changed from conductor 32 to conductor 37 By the automatic release of key 51, path is ground, energizing and releasing the private 1 53, switch 88 is controlled by a circuit from i grounded battery 80 oven conductors 00, 08,

05, 87, S2, 63, 62, 67 and to ground, stepping the wipers 100, 101 102 forward into contact 1 with the selected telephone-line by energize tiou ol' rotary-magnet 125.

If the line thus selected be busy, it will have the condition of busy test namely, a ground upon the terminal connected with by private wiper 102. Then the actuation of key 52, subsequent to the last selective group oi actuations of key 23, will energize private iii-agnet 04. will be provided from battery 89 over eonductors .90, J9, 103, 104, 94", H7, 105, 102, 106, 1.07 and to ground, energizing release magnet 103 and restoring the wi er-curriage to its normal position ol rest. T his restoration will occur without the magnetic release of key 51, which is provided for in the next paragraph If the line selected be not busy, then the Thereupon, a path for current given for ringing current from ringing-generator 115 over conductors 113, 111, 70, 81, so, 06, 100, 44', 116, 15, 43', 101, 95, 87,82, 63, 110, 112 and to ground. From junctionpoint 116 a branch circuit exists over eonductor 28 and through battery 27' to ground. The current flowing over this branch path is not designed to actuate the armature of relay 17', since relay 17' is of considerable impedance and is designed to be energized by continuous current; but such actuation would not in any way afl'ect the operation of the circuits shown, since the armature would but place ground upon conductors and 34, both of which are already grounded, the former through 42, 106, 102, 105, 97, 109 and the letter through 20, 33, 37'. Owing to the high resistance of element 1 13 in the main ringing-circuit traced above,

magnet 58 does not receive suflicient current to energize it to the degree required to attract its armature. The signal-bell 13 is actuated by the current flowing through it. In response to this signal, the patron at substation 10' lifts the receiver from the hook, and thus substitutes the low resistance of conductor 11 for the high resistance of eleparty had been rung ments 12 and 18,

ductors 15 and 14. This reduction of the resistance of. the main ringin -circuit traced 5 above results in an increase 0 the volume of current flowing through that circuit, and

- therefore results in a greater energization of to the telephone operator that the called station has answere and also connecting the called line through to the calling-line by connection between conductors 110, 111 and,

conductors 117, 118. Path is furnished also for current from grounded battery 27 over conductor 28', 15', 11', 14', 43', 101, 95, 87,

82, 63, 110, 117, 119 and to ground, energizing relay 17 without consequent effect and energizing visual signal 45. Current will continue to flow through this path without change throughout the duration of the conversation, furnish energy for speech transmission from station 10 and cause signal 45 to remain dis layed before the operator.

. Ifkey 51 ad not released automatically immediately upon the last actuation of selective key 52, the 0 rator would understand that the linese ected had been found busy and would so report by telephone to the calling patron. If within a reasonable time the ringing-key 49 had not been released antomatically and signal 45 had not been displayed the operator would understand that the called party had not answered and would report to the calling atron that the called or a reasonable length of time without response. In the case of the failure of the release'automatically of either or both of the keys 49, 51, the operator is provided with means, such as 50 and 48, to release those keys.

Signals 40 and 45 associated together and both displayed indicate to the operator that the conversation is in satisfactory progress.

Before proceeding with a consideration of the conditions of disconnection, it will be noted that in the selection of the trunk 83, 86,-87 by the switch 23 and the consequent energization of relay 56' the grounded condue or 85 was connected to trunk conductor 83 nd furnished path for current from batteriy 9 over conductors 90, 99, 83, 80, 79, 85 an t ground, energizing relay 120, the winding of which forms a portion of conductor 83. This relay during its energizetion breaks connection between conductors 122 and 123.

Electric switch 121 is an off-normal switch similar in all respects to the 0ffnormal switch 73 of automatic switch 23, but closed by the first vertical step of the modified Strowger switch 88, as previously explained.

The release-magnet 108 differs from the switching and release magnet 56 in its mechanical relation to the switch 88. The reformerly connecting conlease-magnet 108 is adapted to restore switch 88 upon cnergization and not consequent upon denergization.

We now will pass to the consideration of the disruption of the connection set up and the consequent restoration to normal of all parts used By hanging the receiver upon the hook at substation 10, direct current previously flowing through conductors 11 and 119 is in terrupted "and signal 45 is released. By hanging receiver upon the hook at substation 10, current flowing through conductors 11 and 39 is interrupted and signal 40 is released.

The breaking of circuit for direct current through substation 10 has deenergized relay 17 and, by release of the armature of that relay, has interrupted current through relay 19, by the deencrgization of which the mechanisms associated with its armature have effected the restoration of switch 16 as a whole to its position of rest. the signals 40 and 45, the operator will manually release the key 47, disconnecting conductor 77 from conductor 78 and interrupt ing the current previously flowing to ground at 78 from battery 64 over conductors 65, 68, 74, 75, 76. 73, 77, 78, and which has maintained the energization of rela 56. By the interruption of that circuit an the release of the armatures of relay 56, the mechanisms associated with thosearrnatures have ef-- fected the restoration to normal of the switch 23 as a whole.

By the restoration of the switch 23 round conductor 85 has been disconnecte from conductor 83 and the circuit through relay 120 is interrupted, thus releasing its armature and closing its circuit for current from battery 89 over conductors 90, 99, 103, 121, 122, 123 and to ground, energizing release magnet 108 and restoring connector 88 as a whole to its normal position of rest, including in such restoration the interruption .of said restoring-circuit by the opening of this switch 121.

The restoration of the switch 88 to norn1al has disconnected ground conductor 109 from conductor 106, and the breaking of the circuit through conductor 11 had previously conductor :28 and de'e'nergized relay 17, releasing its armature. Thus all grounds are removed from conductor 42- and circuit is interrupted formerl giving current through conductor 36. Re ay 19, thereforejis denergized and switch 16 as a whole is restored to its normal position of rest.

The hanging up of the two receivers at the substation-telephones in connection thus automatically has signaled the operator at 41, who by release of her key 47 in con junction with the hanging up of the re- Upon the release of' interrupted the circuit through of my invention.

88, and 16.

ceivers has restored all parts to a normal spects in the interpretation of my invention to the particular devices or circuits herein shown, as many variations may be made without departing from the spirit or scope For instance; no indication is given, either in the drawings or in this written description, indicating the relative locations of the equipments 16, 23, Thus the figures shown are a plicable to an installation in which all of t iese parts are placed in the same central office or to one in wl'iich the different parts" are distributed in any desired manner among a plurality of ce tral ollices, the length of the connecting trunk conductors, as 24 25, e3 70 77, 83 so 87, 42' 43' ii, not being a limiting factor in the operationof the sys tem as applied to exchange areas of present commercial size.

In the description herein given, an exchange district is considered involuing directory numbers of three digits and in which one digit is cared for by switch 23 and the remaining two by switch In an exchange district involving directory numbers of but two digits, switch 23 may be dispensed with. In. an exchange district involvin directory numbers of four digits, an ad itioiial switch 23 would be required intervening between the switch 23 shown and the switch 88, and in larger exchange would be required, and these might be all in one central ollice or distributed through many central oliices.

A single automatic calling" device may be substituted for keys 53 and :52. As key 51 connects those selecting keys to the trunk under actuation and disconnects them upon release, but one such automatic device would be necessary for each operator. This modification is shown in Fig. 6, the mechanism ol' the well-known Strowger device beingindicated in connection electrically with the key 51 and associated circuits of Fig. l, the necessary circuits of the Strowgcr callingalevice itself being shown in dotted lines.

Any l'orm ol' inductive link may be substituted for the condensers 124.

In the drawings, l have shown grounded batteries .27, 59, 64, 89, 27, all of which are of the same potential and polarity. As many. of these batteries as are placed in the same central olliccmay be combined, or, in other words, one battery may be used in each central ollice and all conductors taken to it.

Many other variations are possible without departing from the spirit of my invcntion.

v5 cnt, is I do not wish to limitinyseli' in all re- E a i l What I claim, therefore, and what I desire to secure by United States Letters Pat 1.. In a telephone system, the combination of a substation-telephone, a central office, a trunk-selecting switch in said central otlicc, a line connecting said substation-telephm1e with said trunk-conne ting switch, speechtransmitting elements forming a part of said substation-telephone and adapted to receive electrical-energy for speech transmission from said connecting telephone-line, a source of electrical potential in said central office, a relay in said central ofiice and connected to said line, a trunk in said central oliice, a visual signal, and a circuit including said source ol' potential, said relay, said line, said speech-trailsmitting elements, a conductor in said trunk and said visual signal, substantially asdescribed.

.2. In a telephone system, the combination of a substation-telephone, a central ol'lice, an automatic switch in said central oilice, a grounded source of electric energy in said central office, a relay in said central office, a tele hone-line extending between said substation-telephone and said central office; a switch-controlling circuitextending from ground through said source of energy, said relay, a limb of said line, the speech-transmitting elements of said substation-telephone, the remaining limb of said line and to ground; a trunk; a visual si al; and a supervisory circuit extending rorn ground through said source of energy, said relay, districts a greater number of switches 23 the limbs of said line, the speech-transmitting elements of said substation-telephone, a conductiiirof said trunksaid visual signal and to ground; said first-mentioned circuit and said second-inentioncd circuit being effective ,alternatively, substantially as described.

, mitting elements at said substation connected between the limbs of said line, a trunk, a signal device associated with said trunk and having an inductive wmdm balancing nductively the inductive windin of said. relay; means for connecting sai line and said trunk, and a circuit includin said source 5 said Y signa of potential, said relay, the two limbsof said line, said s eech-transmitting elements and l device, substantially as described. 4. .Iiiatelephone system, the combination of an automatic switch adapted to connect a telephonc-linc'to a selected trunk, a telephone-substation, a telephone-line connectmg said substation-telephone with said automatic switch, a relay associated with till said automatic switch, a source of electrical potentiaLa circuit extending from ground through said source ol' clectrical potential and the windings of said'relay to one of the limbs of said line, a selected trunk, a signal device associated with said trunk, a circuit extending from ground through the winding of said signal device and a conductor of said trunk, and through the selecting contacts of said automatic switch to the other limb of said telephone-line and speech-transmitting elements forming a part ofsaid substationtelephone and connected between the two limbs of said line, substantially as described.

5. In a telephone system, the combination of a substation-telephone, a central oilice, a relay having an'inductive winding in said central ofl'ice and associated with said line, L source of electrical potential in said central oilice, a plurality of trunks in said central T office, means for connecting said telephone lnie with a selected one of said trunks, a

visual signal having an inductive winding adapted to transmit speech by energy re-' and associated with said selected trunk, and

a circuit comprising said source of potential, 1'

said inductive winding of said relay, said telephone line, the speech-transmittin elements of said telephone, a conductor 0 said trunk, and said inductive winding of said signal device, substantially as described.

6. In a telephone system, the combination of a substation 10, a line 14--15 connecting said substation to a central office, an autoinatic switch 16 in said central oflice, a trunk 24*25 leading from said automatic switch to an operator, an operators equipment 41 adapted to be associated with said trunk, an

automatic switch 88 adapted to be associated with. said trunk, keys "forming a part of said operators equipment and adapted to control said automatic switch 88 when it is associated with said trunk, and a plurality of lines twi l '15 selectively accessible to Said automatic switch 88, substantially as described.

7. Ina telephone system, the combination of a substation 10, a line 1415 connecting, said substation with a central ollice, a trunk in said central office, an automatic switch 16 adapted to connect said line withsaid trunk. an operators equipment, keys forming a part of said operators equipment and associated with said trunk, an automatic switch .Zl associated with said trunk and adapted to be controlled by said keys, anautomatic switch 88 ada ted to be associated with said trunk and a apted to be controlled by said keys when so associated, and a plurality of lines as 14'*l5" selectively accessible to said autoniatic switch 88, substantially asdcscribed.

S. In a telephone system, the combination of a substationrtelephone 10, ii line 14-l5 connecting said substation-telephone to an automatic switch 16, an automatic switch 16 adapted to connect said telephone-line to a "trunk, U.- trunk, a lirsi circuit including source of electric potential, the speech-trans niitting elements of said substation-tale phone, said line, said automatic switch 16, and a portion of said trunk; an automatic switch 88 controlled manually by a central oliice operator, at selected telcphone line l4'l5, a substation-teleplionc 10 on said selected telephone-line, a second circuit in cluding a source of electric potcntiahthe ductive link connecting together said first circuit and said second circuit for speech transmission between the two said substation-telephones, substantially as described. l 9. In a telephone system, the combination of a sulistation-telephone, a central ollice, a 1 line connecting said substation with said central oi'lice, speech transmitting elements forming a part of said substation-telephone r 'ceived over said telephone-line, an automaticswitcb in said central ollice connected to said line and adapted to connect said line i with a trunk leading to an operators equipment, the trunk, an automatic switch conl nccted with said trunk and adapted to said" operatofls control and adapted to connect said trunk to a selected line, a substation on lsaid selected line, speech-transihitting elel ments in said latter substation adapted to transinit'speech by energy received over said i selected line, a circuit ineludin a centraloflice source of elcctricalpotential and said speech-trainsmitting elements of said lirst substation, an independent circuit including a source of electrical potential in said central oil'iee and the speech-transniitting elements of said latter substation-telephone, and an inductive link connecting said circuits adapted to transmit alternating currents between said circuits, substantially as described.

10. In a telephone system, the combination of a substation-tclcphone, a central oflice, a line connecting, said telephone and said central oliice, trunk-lines wholly within said central ollicc and adapted at one end to be selected by a telephone-line and at the 5 other end to select a telephone-line, an automatic switch coniicctmi to said telepiibneline for selecting an idle one of said trunks, keys connected with said selc'ctcd trunk for controlling its selecting end, and visual signals connected to said selected trunk and adapted to be controlled by substation-telephones connected to said trunk, substan- 5 tially as described.

11. In a telephone system, the combinaliec, at line connecting said telephone and said central ollice, trunks within said central oilicc, an automatic switch associated with said speech-transniittiilg elements of said sub;' station telephone 10', said selected teleQf-i phone-line, said automatic switch 88, and the. remaining portion of said trunkyand an -1ntion of a subslirtion-lele ihonc, a central olkey for connecting said operators tcle hone) with said trunk, means associated wit 1 said trunk for connecting with a selected one of a plurality of telephone-lines, a key associated with said trunk having electro-magnetic release and adapted to be released consequent upon connection with a selected telev honeline, another key associated with said trunk adapted to connect a source of ringing energy to said selected line and having electromagnetic release adapted to release said key upon the answering of a substation-telephone upon said selected telephone-line, and a visual signal associated with said trunk adapted to be displayed while the receiver is off the hook at a substation-telephone upon said selected telephone-line, conse uent to the release of said keys, substantial y as described.

' 12. In a telephone system, the co1nbina- .tion of a substation-telephone, a central ofi free, a line connecting said telephone and said central ofiice, trunks within said central oflice, an automatic switch associated with said line, and ada ted to connect selectively with 1 an idle one 0 said trunks, a visual signal associated with said selected trunk, and adapted to be displayed when said trunk is connected with, an operators telephone equipment, a key for connecting said operators ments in said substation-telephone adapted telephone with said trunk, means associated with said trunk for connecting with a selected one of a plurality of telephone-lines, a key I 13. In a telephone system, the eombination of a substatiointelephone, a central office, a line connecting said telephone and said central office, trunks in said central office, an automatic switch associated with said line and adapted to connect said line selectively with an idle one of said trunks, a relay con- 5 trolling said automatic switch, a source of F electric potential in said central ofli ce, speechtransmitting elements in said substation adapted to transmit speech by energy received over said line, a visual signal assoically applying the same to the called line if ciated with said selected trunk, a circuit ineluding said source of potential, said relay, said line, said speech-transimtting elements,

idle, and a signal whereby a selected telephone-line, a substation-tale phone upon said selected line, speech-transmitting elements in said latter substationtelephone adapted to transmit speech b energy received over said line, keys associated with said trunk for controllingsaid latter automatic switch, a key associated with said trunk for impressing ringing: energy upon said selected telephone-line, a key associated with said trunk, for maintaining connection between saidtrunk and a selected telephoneline and for disrupting said connection, another visual signal associated with said trunk,

a second circuit including said source of po-' tential, said selected line, the speech-transmitting elements of said latter substationtelephone and said other visual signal, and an inductive link connecting said first circuit with said second circuit, substantially as described.

14. In a telephone system, the combination of a suhstation-tele hone, a central ofllce, a line connecting said telephone with said central oifice, a relay in said central office, a visual signal in said central office, automatic switch in said central office, and a circuit including a central office source of electrical potential, said relay, said line, said tele )hone, circuit-conductors passing through saic automatic switch, and said visual signal, substantially as described.

15. In a telephone system, the combination of a substation tele hone, a central office, a line connecting said telephone with said central office, speech-transmitting eleto transmit speech by energy received over said line, a relay in said central office, a visual signal in said central office, automatic switch in said central oiiice, and a circuit including a central-office source of electrical potential, said relay, said line, said speechtransi'nitting elements of said tele hone, circuit-conductors assing through sai automatic switch, and said visual signal, substantially as described.

16. A: telephone exchange system comprising a plurality of telephone lines and means for mterconncctin calling and called lines for conversation inc uding a trunk line extending through an operators position, electromagnetically actuated selecting and connecting switch mechanism for connectin said trunk line in circuit with a desired called line, means under the control of the operator for transmitting directive currents to actuate said mechanism, a source of ringing current with connections for automatthe operator may be advised of such application automatically and said signal, an operators telephone, key" controlled thereby.

for connecting said operators telephone wit 1 said trunk, an automatic switch associated prising a a telephone-line, l means for interconnecting calling and called with said trunk for selecting 17. A telephone exchange system com- ]urality of telephone lines and lines for conversation including a trunk line c prising a extending throu h an operators position, electromagnetica ly actuated selecting and connecting switch mechanism for connecting said trunk line in oircuit with a desired called line and means under the control of the operator for transmitting directive currents to actuate said mechan sm.

18. A telephone exchange system comprising a plurality of telephone lines, call signals at the exchange, means under the control of a calling subscriber for causing the display of the associated call signal, and means for connecting calling and called lines for conversation including a trunk line extending through an operators position and automatic S= ti.g2tl[l" and connecting switch mechanism under the control of the operator for connecting said trunk line in circuit with a desired called line.

19. A telephone exchange system comprising a plurality of telephone lines, call signals at the exchange, means under the .control of a calling subscriber for causmg the display of the associated call signal and means for connectin calling and called lines for conversation including a trunk line extending throu h an operators position,

electromagnetica ly actuated selecting and connecting switch mechanism for connecting said trunk in circuit with a desired called line and means under the control of the operator for transmitting directive currents to actuate said mechanism.

20. A telephone exchange system comprising a plurality of telephone lines and means for HIlZBICOHIIGCtiII calling and called lines for conversation including a trunk line extending through an operators position, automatic selecting and connecting switch mechanism under the control of a calling party for connecting his line to one end of said trunk line, and automatic selecting and connectin switch mechanism under the control 0 the operator for connecting the other end of said trunk line to a desired called line.

21. A telephone exchange system comlurality of telephone lines and means for terconnectin calling and called lines for conversation including a trunk line extending through an operators position, automatic selectmg and connecting switch mechanism under the control of a calling party for connecting his line to one end of said trunk line, electroniagnetically actuated selecting and connecting switch mechanism for connecting the other end of said trunk line to a desired called line and means under the control of the operator for transmitting directive currents to actuate said electromagneticall actuated mechanism.

22. A te ephone exchange system comprising a plurality of telephone lines and means for interconnecting calling and called i l i lines for conversation including a trunk line extending through an operator's position at the exchange, automatic selecting and connecting switch mechanism under the control of a calling party for connecting his line to one end of such trunk line, a call signal displayed upon the establishment of such connection, and automatic selecting and connecting switch mechanism under the control of the operator for connecting the other end of such trunk line to a desired called line.

2?. A telephone exchange system com 1 prising a plurality of telephone lines and l means for interconnecting calling and called lines for conversation including a trunk line i extending through an operator's position at the exchange, automatic selecting and connecting switch mechanism under the control of a calling party for connectin his line to one end of such trunk line, a ca 1 signal displayed upon the establishment of such connection, electromagnetically actuated selecting and connecting switch mechanism for connecting the other end of such trunk line to a desired called line and means under the control of the operator for transmitting directive currents to actuate such mechanism.

24. A telephone exchange system comprising a lurality of telephone lines and means for mterconnecting calling and called lines for conversation including a plurality of trunk lines extending through an operator's position at the exchange; automatic selecting and connecting switch mechanism under the control of a calling party for selecting and establishing connection between a callin line and one end of an idle one of said trun lines, and automatic selecting and connecting switch mechanism under the control of the operator for connecting the other end of fhe selectgd trunk line to a desired called 25. A telephone exchange system comprising a lurality of telephone lines and means for interconnecting calling and called lines for conversation including a plurality of trunk lines extending through an operator's position at the exchange, automatic selecting and connecting switch mechanism under the control of a calling party for selecting and establishing connection between the calling line and one end of an idle one of said trunk lines, electromagnetically actuated selecting and connecting switch mechanisni for connecting the other end of the selected trunk line to the desired called line and means under the control of the operator for transmitting directive currents to actuate said electromagnetically actuated mechanposition a! the exchange, automatic select- 1 mg and connecting switch mechanism under the control of a calling party for selecting and establishing connection between the calling line and one end of an idle one of said trunk lines, a call signal displayed upon the establishment of such connection and automatic selecting and connecting; su itch niechanism under the control of the operator 1 or 5 connecting the other end of the selected trunk line to a desired called line.

27. A telephone exchange system comprising a plurality of tclcplrone lines and; means for interconnecting, calling and called lines for conversation including a plural-lit; oi trunk lines extending through an operatofs position at the exchange, automatic selectmg and connecting switch me hanism under the control of a calling" party for selecting and establishing connection between ii e calling line and one end of an idle one of said trunk lines, a call signal disphqz'ed upon the i establishment of such connection, elcctro-l magnetically actuated selecting and c0nnrct- 1 ing switch mechanism for connecting: the l other end of the selected trunk line to a dej sired line and means under the control of the l operator for iransmittin; directive currents to actuate such electromagneticalljf actuated r mechanism.

28. A telephone exchange s; stem comprising a plurality of telephone lines and means for intcrconnectin calling, and called lines for conversation inc uding a trunk lino extending through an operatofls position, electron'iagnetically actuated selecting and connecting switch mechanism for connecting said trunk line in circuit with a desired called line, means under the control of the operator for transmitting directive currents to actuate said mechanism, and means for indicating to the operator the busy condition of a selected line.

29. A telepione exchange s cm comprising a plurality of telcplone lines and means for interconnecting calling and called lines for conversation including a trunk line extending through an operator's-position, electromagnetically actuated. selecting and, con

neeting switch mechanism for connecting f said trunk line in circuit with a desired called 1 line, means under the control of the omrator for transmitting directive currents to actu- 1 ate said mechanism, and means under the control of the operator for restoring said 3 mechanism to normal.

30. A telephone (XClEttl'lgP sYstem compriring a plurality of telep one lines and means for interconnecting, calling and called linrs i for conversation includine' a trunk line e.\- tending through an operators position, clertromagneticall r uctuated selecting and eon-' net-tins; switch mechanism for connecting said trunk line in circuit with a desired called line, means under the control of the operator for transmitting directive currents to actuate said mechanism, and means for indicatin to the operator the response of the called partj 25 i. A telephone exchange system comprising a plurality of telephone lines and means For intercmim-cting calling and called lines for conversation including a trunk line extending through an. operator's position, electromagnctieall; actuated selecting and connecting switch mechanism for connecting said trunk line in circuit uith a desired called line, means under the control of the operator for transmitting directive currents to actuate said mechanism, and means for signaling the operator at the end of conversation.

32. A telephone exchange system comprising; a plurality of telephone lines and means for interconnecting calling and called lines for conversation including a trunk line extendingthrough an operators position, automatic selecting and connecting switch mechanism under the control of the calling part? for connecting liis line to oneendof said trunk line, electromagneticalljy' actuated selecting and connecting switch mechanism for connecting the other end of said trunk line to a desired called line, means under the control of the operator for transmitting dircctive currents to actuate said electromag neticallj; actuated mechanism, and means for indicating; to the operator the bus: condition of a selected called line.

33. A telephone exchange sj'steni comprising a plurality of telephone lines and means for interconnecting calling and called lines for conversation including a trunk line extending through an operators position, automatic selecting and connecting switch mechanism in der the control of the calling part3 for connecting his line to one end of said trunk line, electron]agnetically actuated selecting and connecting switch mechanism for connecting the other end of said trunk line to a desired called line, means under the control of the operator'l'or transmitting directive currents to actuate said electromagneticalljr actuated mechanism, and means under the control of t;;e operator for restoring said electromagnetically actuated mechanism to normal.

34. A telephone exchange system comprising a plurality of telephone lines and means for interconnectine calling and called lines for conversation including a trunk line extending through an operators position,

automatic seleclims and connecting switch mechanism under the control of the calling selecting and connecting switch mechanism for connectim: the other end of said trunk' line to a desired called line, means under the control of the operator for transmitting directive currents to actuate said electromagnetically actuated mechanism, and means for indicating to the operator the response of 9. called party.

35. A telephone exchange system comprising a plurality of telephone lines and means for interconnecting calling and called lines for conversation including a trunk line 'extendin throu h an o erato1"s )osition,

automatic selecting and connecting switch mechanism under the control of the calling party for connecting his line to one end of said trunk line, electromagnetically actuated selecting I and connecting switch mechanism for connecting the other end of said trunk line to adesired ealled'line, means under the controlof the operator for transmitting directive urrents to actuate said electromag neticali actuated mechanism, and means for signalingthe operator at the end of the conversation. v

36. A telephone exchange s 'stcm comrising a-plurality of telephone ines, means or establishing connection for conversation between calling and called lines consisting of rising a plurality of telephone lines, mean or establishing connection for conversation between calling and called lines consisting of interconnecting trunks and electromagnetically actuated switches for linking said trunks and lines together without manually established connections, means under the control of a calling party for transmitting current to interconnecting trunks and electromagnetically actuated switches for linking said trunks and lines together without manually estab- I lished connections, means whereby a party F desiring connection with another may communicate his order to an operator, and means under the control of the operator for transmitting directive currents to operate one or more of said switches.

37. A. telephone exchange system comrising aplurality of telephone lines, means For establishing connection for conversation between calling and called lines consisting of selective operative relation therewith, and

an operator's switching station on said linkcircuit located intermediate of said terminal and said selective switching mechanism and provided with mechanism for exercising directive electromagnetic control over mech' anism at said other end of said link-circuit.

41. A telephone system including telephone lines, a link-circuit at' the exchange normally terminating in a contact ada ted' for interchangeable connection with ca ling l 1 l l interconnecting trunks and electromagnetic- 1 allyactuated switches for linking said trunks j and lines together without manually established connect ons, means whereby a party desiring connection" with another may communicate hisorder to anoperator, means under the control of the operator for transmitting directive currents to operate one or more of said switches, and means under the control of the operator for restoring the parts to normal at the end of conversation.

rising aplurality of telephone lines, means or establishing connection for conversation between calling and called lilies consisting of interconnecting trunks and electroniagnetically actuated switches for linking said trunks telephone exchange system comand lines together without manually established connections, means under the control of a calling party for transmitting current to l actuate certain of said switches, means whereby the calling party may comnmnicate his order tofan operator, and means under the control of the operator for transmitting directive currents to the remaining switches necessary to establish the desired connection.

39. A telephone exchange system comlines, selective switch mechanism responsive to substation control to establish such connection, selective switch mechanism associated with the distant end of said link-circult and in normal selective operative relation with said link-circuit, and an operators switching station connecting with said linkcircuit at a point intermediate of said terminal and said selective switching mechanism and provided with mechanism for exercising directive electromagnetic control over mechanism at said distant end to connect said link-circuit with it called line.

42. A telephone system including telephone lines, a link-circuit connected at its answering end with a calling line, selective switching mechanism at the other end or said link-circuit in normal selective relation therewith, a switching: station at an inter mediate point of said link-circuit with operator's mechanism for exercising directive electrical control over said selective mechanism to extend the calling line to it called line, and means including a switch at the calling substation for disconnecting said link-circuit and calling line at the will of the subscriber.

43. A telephone system comprisin tele hone lines, a link-circuit at the exdhange aving selective switching mechanism normally in operative selective relation with its two ends, a switch at a calling substation,

iso

means responsive thereto to operate the} mechanism at one end to estabhsh connectionbetween said fink-circuit and'thecalling tun-ted, apparatus for automatically disconnecting said device from a connected trunk,

him, and a switching station on said Iinkcircuit including 0 erator s means to elec- 44. A telephone'system com rising telephone lines, a linkqzircuit at t e exchange v-mg selectlve swltchmg. mechanism normadly in operative selective relation with its two ends, a switch at a callingsubstation, means responsive thereto to operate the mechanism at one end to establish connection between said link-circuit and the calling line, a switching station on said link-circuit including operators vmeans to electrically adjust mechanism at the other end of said circuit to complete a connection to a called line, means controlled by a'subscriber for releasing one line included in a connection, and means controlled by the operator for releasing the other line.

v 45. A telephone system com 'risin telehene lines, a link-circuit at t e exc ange aving selective switching mechanism normally in operativeselective relation with its two-ends, a switch at a calling substationfi means responsive thereto to operate themechanism at one end to'estabhsh connec between said linlccircuit and the calling line, a switching station on said link-circuit includin operators meansto electricali adjust met: anism at the other end of sai circuit to complete a connection to a called line, and releasemechanism for disrupting an established connection controlled in part by a ective switches associated with the calling subscri r and in part by the operator.

46. telephone. system including telehone lines, a plurality of link-circuits seends of said circuits, an operators switching station on said link-circuits including a manually actuated device for exercising directive electrical control over said switches to extend said circuits to connections with articular lines an o erators switch for each J k-circuit servin when actuated to con- 50 nect said device with its circuit, and means automat1cally effective on connection made with the called line to disconnect said device and si al the operator.

47. n a telephone system, the combina- 'tion with a plurality of trunk lines, of a calling device, manually operated means for interchangeably connecting said device with trunk lines to he actuated, and apparatus for automatically freeing said device from a connected trunk effective on completed operation of the device.

48. Ina telephone system, the combination with a plurality of trunk lines, of a call- -ing device, means for interchangeably connecting said device with trunk lines to be acand means for notifving the operator of such phone lines, link-circuits at the exchange aving' automatically controlled selective switch mechanisms at both their ends and in normal selective relation'with said circuits, means responsive to a substation switch of a calling line serving to actuate mechanism at one end of a' circuit to establish connection between such line and an idle link-circuit, an

and for transmitting directive currents to the mechanism at the distant end of the connected link to complete the wanted connection.

"51. A telephone system comprisin telephone lines, link-circuits at the axe ange avin automatically controlled selective switch mechanisms at boththe'ir ends and in normal selective relation with said circuits, means responsive to a substation switch of a calling line serving to actuate mechanism at one end of a circuit to establish connection between such line and an idle link-circuit, an operators switchingstation comprising means for learning the want of the calling subscriber and for transmitting directive currents to the mechanism at the distant and of the connected link to complete the wanted connection, a calling device for transmitting said currents, and manual]. actuated operators keys for interchangeab y connecting said device with link-circuits in connection with calling lines. l

52. A telephone system comprising telephone lines, link-circuits at the exchange having automatically controlled selective switch mechanisms at both their ends and in normal selective relation with said circuits, means responsive to a substation switch of a callingline serving to actuate mechanism at one end of a circuitto establish connection between such line and an idle link-circuit, an operators switching station comprising means for learning the want of the calling subscriber and for transmitting directive curconnection, a calling device for transmitting said currents, manually actuated operators keys for interchangeably connecting said device with link-circuits in connection with rents to the mechanism at the distant end of r the connected link to complete the wanted operator s switchingstation comprisin means for learning the want of the calling su scriber calling lines, and means automatically actuated on completion of a wanted connection to free said device from a connected trunk.

5.3. A tale hone exchange system comprising a suscribers telephoneline, substation equipment including a receiver and switch hook, a trunk line, automatic selecting and. connecting switch mechanism responsive to the removal of the receiver from its hook to connect said line to one end of said trunk line, other telephone lines, and

automatic selecting and connecting switch mechanism under the control of the operator constitutingthc sole means for connecting the other end of said trunk line to a desired other telephone line.

54. A telephone exchange system comprising a suhscribers telephone line, substation andthe callingfline, an operators switching station, and means for operativelv associatmg sald statlon with said link-circuit for electrically adjusting the mechanism of said circuit tocomplete a connection to a called line.

56. A telephone system com rising telephone lines, a link-circuit at tie exchange, raving selecting and connecting switch mechanism normally in operative relation with its two ends, a switch at a calling substation, means responsive thereto to operate the mechanism at one end to establish connection between said link-circuit and the calling line, and operator's calling device mechanism adapted to elcctricalh adjust mechanism at the other end of said circuit to 1 complete connection to a called line.

equipment including a receiver and swit ehj hook, a phiralityof trunk lines, automatic selecting and connecting switch mechanism responsive "to the removal of the receiver from its hook to connect said line to one end of an idle one of said trunk lines, other telephone lines, eleotroniagiieticallyl actuated selecting andconnecting switch i nechanisin constituting, the sole ancans ior connecting the other end ofitheselectedftrtnik line to a desired other telephone line, and meansiin der the control of the operator for transmitting directive currents to actuate said electromagnetically actuated mechanism.

55. A telephone system com risin telephone lines, a link-circuit at t 1e exc ange aving selecting and connecting switch mechanism normally in operative selective relation with its two ends, a switch at'the calling substation, means responsive thereto to o erate the mechanism at one end to estabhsh connection between said link-circuit i i i 57. A telephone exclanige sjxstem comprising a subscribers telephone line. a plurality EDMUND LAND.

Witnesses H.' H. Inn, M. IRENE'G. GRADY til) It is hereby certified that in Reissue Letters Patent No. 12,943, granted April 20, 1909, upon the application of Edmund Land, of Grand Rapids, Michigan, for an improvement in Telephone-Exchange Systems, errors appear in the printed specification requiring correction, as follows: In lines 45, 48, and 106, page 2, line 83, page 4, and lines 89-90, page 5, the word multiplied should read multipled; line 1, page 5, the reference-numeral 139 should read 819; line 55, same page, the referencenumeral 23" should read 58; line 110, page 6, the word this should read the; and in line 25, page 7, the word involuing should read involving; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 25th day of May, A. D., 1909.

[mm o. o. BILLINGS, Acting Commissioner of Patents.

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