US1343462A - mellinger - Google Patents

Description

E. A. MELLINGER. TELEPHONE 'EXCHANGE AUTOMATIC, WITVCHING SYSTEM. APPtICATIONHLED SEPT-4, 190a. RENEWED us. 16. m9.

' Patented June 15;1920

3 SHEEJS-SHkET I.

mine hm m mm mm m N E. A.MELLINGER. TELERHONE EXCHANGE AUTOMATIC SWITCHINGSYSTEM.

Patented'Jun 15, 1920.

3 SHEETS-SHEET 2.

APPLICATION FILED SEPT-'4. 1908 RENEWED AUG.

E- A. MELLINGER.

TELEPHONE EXCHANGEAUTOMATIC SWITCHING SYSTEM. APPLICATION FILED SEPT-4, 190s. ncmzwsu we. 16.1919.

"1,343,462. PatentedJune 15,1920.

3 SHEETSSHLET 3- efli'ciencv of a telephone system uurrso STATES PATENT OFFICE.

TIIHVAIIEtD A. MELLINGER, OF CHICAGO, ILLINOIS. ASSIGNOR T AUTOMATIC ELECTRIC COMPANY. OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS. t

TELEPHONE-EXCHANGE AUTOMATIC SWITCHING SYSTEM.

Specification of Letters Patent.

Patented June 15. 1920.

Application filed September 4. 1908, Serial No. 451.674. Renewed August 16, 1919. Serial No. 318,040.

no operating grounds at the substations, which are cinnmonly called two-wire sysams.

Objects of my invention are the provision of an improved non-numerical trunking lVltliL-llldt is to say. a switch for automuticully selecting idle trunks without reference to any digit of the called number; the provision of an improved master switch for controlling the operation of a plurality of said non-numerical trunking switches,-

n'hercby the latter select idle trunks ahead of the calls: the provision of an improved selector or numerical trunking switch for a twowire system; the provision. of an im-- proved connector switch for finding the called line: and-the provision of certain details and features of improvement and combinations tending to increase the general w 7 of this par ticlilar character. 1

To the foregoing and other useful ends my invention consists in matters hereinafter set forth and claimed.

In the accompanying drawings Figure 1 shows diagrammatically the calling subscrihers substation A and the central office switching apparatus of a system involving the principles offmy invention. To the line of substation A is allotted the line switch (1 controlled by: the master switcl1 D. At E is represented a first-selector switch; and at F a diagramof a second-selector switch 1S shown. I

In Fig. 2 there is shown digrammatically a connector switch H, at I a central ofiioe ringer generator is shown and at 'J'a busysignaling device. K represents a device for interrupting the ener iz ing circuit of the ringer re1ay-t hat is, y means of the apparatus K the ringer relay may be caused to energize intermittently. To the line of stems, and especially to systems that have the substation A there is allotted the line switch (1" which is like theline switch (7.

Figs. 1 and 2 taken together represent diagrammatically the central ollicc switchinn apparatus involved in establishing a onnection between two substations. In Fig. i a central battery is shown at ll having its positive terminal preferably grounded at G. The central oflicc switching apparatus is of thegcneral type disclosed in Eng lish Patent No. 526.301 of 1906. but with modifications and circuit changes to adapt the same to operate in connection with a twowire syste.m-that is. a system in which there is no ground connection at the subscribcrs telephone. The line switches of which C and C are modified forms are also disclosed. in The llcsfmn Electrician of January 25, 1908, and the American Telephone Journal of June 6,1908. The master switch D is also of the form disclosed in the said llesteru Electrician and the A mcricoin Talc phone Journal. The first-selector E and second-selector F are of the general ty )e shown in United States Letters Patent i 0. 815,321, granted March 13, 1906. to Keith, Erickson and Erickson. while the connector switch H is of the general type shown in United States Letters Patent No. 815,176, granted March 13, 1906, to Keith, Erickson and Erickson.-

Fi 3 is a diagrammatic View showing t 1e line switch, theline switch plunger and the line switch bank, together with the circuitsand parts of the master switch.

The snbscribers substation. it will be. seen, is somewhat dilferent from the usual automatic substation, substation A being arranged and modified to operate in connection with a two-wire system-that is, a system in which no ground connection is used at the subscribers substation. Substation A, for example,'comprises the usual receiver 2, switch-hook 3, induction coil, 4 which consists of the primary winding 5 and secondary winding 6, transmitter 7, condenser '8, ringer 9 and impulse wheel 10, which latter has the usual impulseteeth 11. The impulse wheel 10"is secured to the shaft 12, to' iwhi'ch shaft there is also'secured the dial (not-shown). When the dial is turned the impulse'teeth, 11 are adapted to engage the cam 13 upon the end of the spring 14 and thereby carry the latter out of engagement with the s ring 15. Upon the switch-hook 6 there is t e cam 16 which, when the switchhook is u permits the springs 17 and 18 to engage, t ereby bridging across the subscribers line conductors 19 and 20 the rimary .circuit including the transmitter in series with the primary winding 5; but when the switch-hook is lowered the spring 21 is carried into engagement with the spring 22, whereby the ringer 9 in series with the condenser 8 is bridged across the line conductors 19 and 20 instead.

The connector switch H (Fig. 2) like the line switch (3 and first-selector 1 1, is arranged to operate in a system in which there is no ground connection at the subscribers station.

A clearer understanding of my improved system may be had from an explanation of its operation when a subscriber operates the central oiiice switches to establish-a connection. For example, it will be pointed out how the subscriber at substation A may operate the main office switches to establish connection with substation A (Fig. 2), the number of which is 2220. To call the number 2220 the subscriber at substation A, after removing the receiver from the switch-hook, operates the calling device for each digit in the well-known manner. When the receiver is removed from the switch-hook, and the springs 17 and 18 engage, an energizing circuit is closed through the line relay 23 of the line switch C. When this role energizes, a circuit is closed through t e trip or plunger ma net 24, which then operates toforce the p unger into a bank terminal andextend the calling liiie conductors to a trunk-line leading to a selector s itch. The dial is operated for the first digit, and upon returning to normal position operates the first-selector switch to establish connection with a trunk-line leading to a second-selector switch. The second-selector is thenoperated for the second digit to select a trunk-line leading to a connector switch. The impulses delivered by the dial for the last two digits are directed toward the connector, which operates to place its shaft wipers in connection with the contacts corresponding to the desired number. When the substation primary circuit is bridged across the line conductors 19 and 20 an energizing circuit is established through the line relav 23, said circuit extending from ground G 'hrough the springs 26 and 27 to the line conductor 20, through the transmitter 7 and primary winding 5, impulse springs 14 and 15, springs 17 and 18 to .the line conductor 19, springs 28 and '29, winding of the line relay 23 to the battery lead 25, thence through battery B to ground G. The line relay. upon energizing, ressesthe springs 3H and 31 into contact. 5 shown. the line relay '23 is slow-acting- -that is. when once energized terminal similar gages from the spring and the energizing circuit is then broken the relay does not instantly return to normal position, but remains in its energized position for a short interval. The engagement of the springs 30 and 31 closes an energizing circuit through the trip or plunger magnet 24, \VlllCll magnet operates to attract the plunger arm and thrust the plunger into an idle bank terminal. The inn er magnet circuit extends from groun G t irough the springs 30 and 31, plunger magnet 24 to the battery lead 25, thence through battery B to groundG. When the plunger enters the bank terminal and closes the bank springs 32 and 33 into contact an energizing circuit is closed through the motor magnet relay 34, which in turn operates to close a circuit through the motor magnet 35 of the master switch D. The motor magnet then operates to advance-all idle plun ers that are in locked engagement witht 1e plunger shaft 36 to a position opposite the next idle bank to the one just engaged. The circuit through the motor magnet relay extends fromground G throu h the relay 34to the common segment 0 the master switch bank, wiper 37 ,individual segment 38, through the bank springs 32 and 33 to the battery lead 25, etc. .The relay 34, upon energizing, operates to place the sprin s 39 and 40 in contact, whereby a circuit is c osed throu h the motor magnet 35, said circuit exten ing from ground G through the motor magnet 35, interrupter springs 41 and 42, motor ma net relay springs 39 and 40 to the battery ead 25, etc. The motor magnet, upon energizing, attracts its armature 43, and the pawl 44 engages a tooth of the ratchet wheel 45 andmoves the latter one step. iVhen this occursthe spring 46 engages the spring 47 (hearing in mind that the spring 46, rior to this 0 oration, engaged a notch o the toothed w ieel 48), and

. when theratchet wheel 45' is given one step the sprin 46 slides of from the toprofthe notch an engages the spring 47. be engagement of these two springs provides a energizing circuit for the motor magnet 35, said circuit extending, through the springs 46 and 47 to the battery lead 25 instead of through the springs 39 rind 40. Furthermore, the motor magnet. when encrnew ' gized, separates the interrupter springs 41 and-L2. thereby breaking its own circuit like a buzzer. The motor magnet 35 continues to operate in this manner as long as the siring's 46 and 47 remain in engagement. llhen the next succeeding tooth on the wheel 48 advances far enough the spring 47 disen- 46. thereby opening the energizing circuit for the motor magnet. By the time the last notch disengugcsthc springs 46 and 41' the master switch wiper 37 has passed from the first contact 38 to the second ontact 49. suppose. however, that when the wiper 37 engages the individual cuit, retains the plunger arm in an attracted segment 49 there then is a guarding potenposition and the plunger in the bank termitial present. In that event an energizing nal. Thus it will be seen that the line switch, circuit is closed through the motor magnet after being operated from the subscribers 5 relay 34, said circuit extending from the constation, is maintained in its operated posi- 7o tart through the wiper 37, common segment tion by a ground connection at the firstof the master switch bank, through the selector switch E. Furthermore, the superwinding of the rela 34 to ground G, as visory relay 70 also energizes and places the previously traced. he motor magnet relay springs 72 and 73 in contact, thereby closing 10 again energizes and closes the circuit for a circuit throu h the supervisory lamp 74 the motor magnet. The motor magnet operwhich extends from ground G through the ates as before, and the wiper 37 [5 carried side switch wiper 75,springs 72 and 73, lamp to the next contact, and the next tooth of 74 to the battery lead 25, thence through the wheel 48 separates the sprin s 46 and 4?. battery B to ground (i. The slow-actin re- 15 This operation continues as ong as the lease relay 6? also carries the spring 76 rom so wiper 37 continues to find contacts with prothe spring 77 and into contact with the teeting potential. It will he understood, of spring 78. course. that when the motor magnet 35 thus The foregoing is the condition of the operates, the plunger shaft 36 and all luncentral office switches after the calling subgers that are in locking engagement wit the scriber removes his receiver andbefore the 85 said shaft are moved to a new position oppodial .is turned. When the dial returns to site an idle-bank terminal similar to the one normal position for the first digit 2 the engaged by the line switch C, and at the firsbselector switch E is operated. The same time the bridge-cut-ofi' springs 26 and first digit being 2, the impulse spring 14 is 29 are separated from the springs 27 and twice carried out of engagement with the 90 28, respectively, to disconnect the line conimpulse spring 15. As a result the energizductors from the line switch C. At the in- -ing circuit through the line relay 58 isstant that the plunger enters the bank the broken twice, and the spring 63 comes into following springs are pressed intocontact: contact with the spring 64 twice. After the 80 and 51,, 52 and 53, 5.4 and 55, and 32 and two "impulses "are thus delivered the line'flb 33. The enga ement ofthe springs 50 and relay' 58 again energizes and carries the i 51 and 54 an 55 extends the-ca ing subs ring 63 into contact with the spring 65. scribers' line conductors 19"and 20 to the previously explained, the relay 67 is a trunk-line conductors56 311(1'57'Whi6h terslow-acting relay-that IS, slow to deener- 86 minate in the first-selector E. This exten-' gize; and; when his energizing circuit is sion of-the -line provides an energizing cir: momentaril brokendur ng the yertienlimcnit' for the line'rela 58 of the first-selector. just elivered, the said relay'does 'not Thecircuit extends rom ground Gthrongh enor'gize but remains in an operated po the winding 59, side switchwiper 60, trunk sition with the springs68 and 76 in contact 40 conductor 57, bank springs 55 and 54, line .with the- springs 69 and 78. Then whenfthe 106 conductor-20, transmitter Lprimarywind spring (SS-engages the spring '65 two uning 5, impulse springs 14 an 15-, s'pringsl'i' pulses'aretransnpttedto the vertical and. 18, line conductor 19, bank springs 50 net479,-' extend1ng from ground G' throng and 51, trunk conductor'56, side sw tch wiper the springs 63 and to the springs 76 and 45 61, through-winding 62'to-the battery lead 78," t rou h the l rivate" magnetrelaygfio, 25, thence through attery B t'of'ground G. through t e-wmd g of the'yertlcal magnet Theline relay 58 thereupon energims and -79, contact'po1n t 81 side switch w1per82to operates ,to .earrythe sp'rln 63 out of enthe battery lead thence thrbn battery gagement with the spring and into-en B ground 4G. jflho twoimpu 60 gal ement with the spring 65,'thereby r0 dehvered,'the vertical magnet 19-1sthere'by-115 vid ingan energizing circuit for the s ow energized twice, and the shaft w1 rs are acting release relay 67, whichlatter ih t urn "given two' vert cal steps in the we known operates to provide-an energizing circuit for ma,nner. It will seen that the private the bridge-cnt-ofi' relay 66 oftheline switch-; magnet relay 80 is ncluded inthe ener 56 C. This circuit extends irom ground G eircnltof thevertical'rnagnet 79. V 13120 through the prin' 68 and 69, winding of re ay also energ zes, but b'olilg a slow actmg the supcrviso refii y 70 conductor -71, bani; relay it energrzeson the first impulse and springs 53 and 52, bridge-.cut-ofi relay 66, remams'so until all the impulses are'trunstrip or. plunger magnet 24 to the'battery mitbed. ThlS relay, upon ener zing, oper- 60 lead 25, thence throu h battery B to ground ates to close the springs 83 an 84 1n eon- G. Since the cut-o springs 26 and 27 are tact, whereby an energizing circuit 18 estabalread in an operated position the energizalished. through the private magnet 85. This tion 0 the relay 66 at this time is without circuit extends from ground G through the particular function. The trip or longer springs 83 and 84, pr vate magnet 85.120 the 66 magnet 24, being also included in wt is cirbattery lead 25, thence through battery B m to ground G. The private magnet relay deener 'izes after the last vertical impulse,

since his energizing circuit is no lon er maintained after the springs 63 and (it c isengage. Hence, the said relay again de'e'nergizes, permitting the springs 83 and 84 to disengage, whereby the energizing circuit through the private magnet 85 is in turn broken. which private magnet now deenergizes and permits the side switch to pass f m first to second position, permitting the de switch wipers S6 and 82 to engage the contact points 87 and 88, respectively. The closure of contact between the side switch wiper 82 and the contact point 88 sets up an energizing circuit for the rotary magnet 89. As shown at L in Fig. 1, a pair ot relays is provided for producing the intermittent energization of the rotary magnet 89. The energizing circuit extends from ground Gr through the springs 90 and 91, relay 92, winding of the rotary magnet 89, contact point 88, side switch wiper 82 to the battery lead 25, thence through battery B to ground G, the rotary magnet and relay 92 energizin in series. The rotary magnet moves the shaft wipers one step, and the relay 92-, upon energizing, places the springs 93 and 91 in contact, whereby a circuit is closed from ground G through the said springs a d relay 95. The relay then operates to separate the springs 90 and 91, therebv breaking'the circuit for the relay 92 and the rotary magnet 89, which restore to normal. When the relay springs 93 and 9-1 disenga the circuit for the relay 95 is broken an it returns to normal, permitting the springs 90 and 91 to engage, thereby closing the circuit through the relay 92 and the rotary magnet 89 as before, as long as l the side switch wi an 82 remains in second position. From tie foregoing it will be seen that one relay, upon energizing, ro-. vides a circuit -'0r :1 second relay, w ich latter, upon energizing, breaks the circuit for the first relay, which then restores to normal, breaking the energizing circuit for the second relay. the relays L may be allotted to a group of first-selector switches and used in common to produce the intermittent energizing of vthe rotary magnets. At M there is shown a like pair of re ays for producing the interinittent energization of a group of secondselector switches. The said rotary magnet then operates to rotate the shaft wipers 97, 9S and 99 of the selector E into en agement with the first contact of the secon level of the selector banks, from which contact it is assumed that the trunk-line conductors 100. 101 and 102 lead to the second-selector switch F. If the first trunk-line is busy, however. and the wipers have to pass over busy trunk-lines, then as soon as the private wiper 99 engages the first private bank con- -third position. busy trunk-lines the private magnet 85 reand 10.1 which,

It should be stated that I from the spring tact the private magnet 85 again energizes, locking the side switch in second position. '1 he energizing circuit for said private magnet extends from the grouiided terminal G of the batter B through an occupying switch (not s own), through the private wiper 99, thence through the conductor 103 to the side switch wiper 80, contact point 87, through the winding of the private magnet 85 to the battery lead 25, thence through battery B to ground G. The private magnet 85, upon thus becoming energized, locks the side switch wiper 82 in engagement with the contact point 88, whereby the rotary magnet 89 will be energized step by step until the wipers are carried beyond the last busy trunk-line. At the instant that the private wiper leaves the last busy contact point the energizing circuit through the private magnet 85 is destroyed, and as a result the selector side switch passes to If, however, there are no leases the side switch to third position as soon as the wipers are carried into' engagement with the first trunk-line. As soon as the side switch passes to third position, as stated, the subscribers line conductors 19 and 20 are extended to the conductors in this case, it is assumed lead to the second-selector switch F. The extending of the line occurs, of course, as soon as the side switch wipers 61 and 60 engage the contact points 104 and 105, respectively. hen the subscribers line is thus extended to the selector switch F an energizing circuit is established through the line relay 106 in the same manner in which the energizing circuit was established through the line relay 58 of the selector E when the subscribers line conductors 19 and 20 were extended through the line switch. bank to the trunk conductors 56 and 57. The relay 106, upon energizing, operates to shift the sprin 107 from the spring 108 to the spring 109; Vhen the springs 107 and 109 engage, an energizing circuit is established through the slow-actin release relay 110. This circuit extends rom ground G through the springs 10? and 109, through the relay 110 to the battery lead 25, thence through butt-ery B to ground G. ergizing, operates to shift the spring 111 1'12 to the sp'ring 113, and the springs 114 and 115 are also closed in contact. his operation of the second-selvtor switch F occurs at the instant that the side switch wipers 61 and 60 of the selector switch E pass to third position and extend the subscribers line conductors 19 and 20 to the second-selector switch F. When the second-selector switch, therefore, operates, a guarding potential is established at the private wiper 99 for protecting the se zed trunk-line conductors 100 and 101 against The relay, upon en-' said circuit extending from ground thencethrough battery B to ground G.

seizure by another calling first -selector. This guarding potential extends from ground 6' to the contact point 116, side switch wiper 11?. through the springs 11:: and 114. comlnctor in. to the contact engaged by the private wiper 99. Furthermore. when the first-selector switch l'l operates and the side switch passes to third position, a new energizing circuit is established through the release relay 6?. This energizing circuit extends from ground (i at the selector switch i" through the springs 11.3 and 114. conductor -3. shaft wiper 99. conductor 103. through the side switch wiper 86. contact point 118. relay 6?. thence through battery B to ground G. The relay 6? thus remains in an operated position with the spring 68 in engagement with the spring 69. but the line relav 58 returns to normal position when the side switch wipers 60 and 61 engage the contact-points and 104, respectively. The energizing circuit through the l ne relay 106 extends from ground G through the winding 119 to the side switch viper 1'20. thence through the conductor 101. conductor 5 and line conductor 26. through the primary circuit of the substation. through the line conductor 19. thence through the trunk conductor 56, conductor 100. side switch wiper 121. through the winding 12? of the relay 106 to the battery lead 35. thence through hattery B to ground 6.. .When the dial returns to normal position totthe second digit '2. this circuit through the, line, relay 106 is interrupted twice when the impulse spring 14 is carried out of engagement with the spring 15 by'theiimpulse teeth on .the wheel 10. Thelcircuit being interrupted'twice. the said relay 106 momentarily 'dee'nergizes. thus permitting he swing 197 to engage the spring 108, where y an energizing circuit is completed ..hrough the vertical magnet 122, G" to thesprings 10? and 108, springs 111 and 113. through the windingof the private magnet rela'v 123, through the winding of the vertical magnet 1122. contact point 124. side switch wiper to the battery lead 25, The

private.=magnet'rela v 123. being included in this circuit. energizes and, since it is a slow-acting relay. remains in an operated position untilthe last vertical impulse is delivered. and the relay 1G6 remains energized with the spring 107 in contact with the spring 109. whereby the circuit through the private magnet relay and the vertical magnet 122 remains open. When the relay 123 energizes. the springs 126 and 127 are pressed into contact. thcrehy causing an energizing current to How through the private magnet 12%. the circuit extending from ground G" through the springs 10? and 108, through the winding of the private magnet 128 to the hattery lead 25, thence through hattery B to ground G. When the relay 123 deenergizes and breaks the energizing circuit through the private magnet 128, the private magnet also dei nergizes and permits the side switch to pass from first. to second position. \l'hen the side switch wiper 125 passes to second position and into engagement with the contact point 129 an energizing circuit is established through the rotary magnet 130 which now operates. as explained in connection with the rotary magnet 89 of the seicctor switch ii. to select an idle trunk-line leading to the connector switch. After the switch comes to rest with the side switch in third position. the shaft wipers 131. 132 and 1321 are in engagement with the trunk conductors 134. 121. and 136, respectively. which lead to the connector switch H (Fig. 2). .\t the instant that the side switch wipers 121 and 12 pass to third position into engagement with the contact points 131 and 138. the suhscrihcfis line conductors are extended to the connector switch H. and an energizing circuit is established through the line relay 139 in the same manner in which the energizing circuit was estahlished through the line relay 106 of the selector switch 1" when the side switch wipers of the first-selector passed to third position. The energizing circuit through the line relay 139 extends from ground G through the winding 14". trunk conductors 13 i. 161 and 57 to the line conductor 20, thence through the substation to the line conductor 19. trunk conductors 56, 100 and 134. thence through the winding 141 to the battery lead 25. and through battery B to ground G. The line relay' 139, upon energizing. operates to sl 'ft the spring 142 from the spring 143 tothe spring 144, whereby an energizing circuit is established through the release relay 145 extending from groan G through the springs 142 and 144, springs 146 and 147, rela 145 to the battery lead 25. thence throng battery 13 to ground 'hen the relay 145 energizes, the spring 148 is shifted out of contact with the spring 149 and into contact with the spring 150, and the spring 152' is shifted into engagemerit with the spring 151. This primary o'ieration of the connector relays 139 and 1 5 occurs at the instant that the side switch wipers 120 and 121 of the selector F pass to third osition and" extend the subscribers line con. uc rs to the connector H. e enga "ment of the springs 151 an tablis es a guarding potential for protecting the trunk-line conductors 1:34, and 136 against seizure by another line and second-selector. This potontial'extends from ground G through the winding 153 of the busy-signaling device to the side switch wiper 154 (in second position), springs 152 and 151, conductor 136 to the private bank contact engaged by the shaft wiper 133. Furthermore, when the side switch of the second-selector F passes to third position a new energizing circuit is established through the release relay 110, said circuit extendin from ground Gr at the connector. switch (F in. '2) through the springs 152 and 151, conductor 136, side switch wiper 15:), conductor 156, from which one branch passes through the relay 110 to battery, while another branch extends through the contact point 157, side switch wiper 117, springs 115 and 114, conductor 102 to the bank contact engaged by the private wiper 99 of the selector switch E, thence to and through the relay 6?, as previously traced. The 0 eration of the dial for the last two cigits afl'ects the connector switch, and when the dial is operated for the third di it 2 the impulse spring 14 is twice carried out of engagement with the sprin 15, thereby momentarily deener izing t e line relay 139 twice, whereby t e spring 142 twice enga es the spring 143, thus sending two impu ses to the vertical magnet 158 from ground (i through the springs 142 and 143, springs 148 and 150, private magnet relay 159, through the vertical magnet 158, contact point 161, side switch wiper 162 to the battery lead 25, thence through battery B to ground G The private magnet relay 159 energizes when the first impulse is delivered, and since the said relay is slowacting it remains in an operated position until all the vertical impulses'are sent. The vertical magnet, upon being energized. operates one step at a time to carry the shaft wipers 163, 16-1 and 165 two steps to a point opposite the second level. The relay 159.

lupon ener izing, shifts'the springs 166 and 167 out o engagement, and the spring 169 is shifted into engagement with t 1e spring 168. \Vhen the springs 168 and 169 engage, an energizing circuit is established throu h the private magnet 170 from ground 1 through the springs 168 and 169. private magnet 170 to the battery lead 25. thence through batterv B to ground G. The relay 159,being a s ow-acting relay. remains in an operated position while the vertical impulses are being sent: but after all the impulses are delivered. and the line relay 139 returns to its operated position. the circuit through the relay 159 becomes broken. thus permitting the springs 16? and 169 to return to. normal position. 'hen the springs 169 and 168 disengage. the circuit through the private magnet 1T0 becomes broken. whereby the said magnet dei nergizcs. permitting the side switch to pass from first to second position. The calling Sllll.('1'lllll' now operates the calling device for the last digit thereby transmitting ten impulscs and operating the line rc'lay 139 ten times. Each tin'ie that the line relay springs 142 and 143 cugage, an energizing circuit is established through the rotary magnet 161 from ground G through the said springs 1-12 and 143 and the springs 148 and 150, through the private magnet relay 159, through the rotary magnet 171 to the contact point 172, thence through the side switch \viJer 162 to the battery lead 25, and througi battery B to ground G. Again the private magnet relay energizes, as in the previous case, remaining so until all the impulses are transmittal. thereby retaining the private magnet encrgized also. The rotarv magnet 1T1 thcn operates to rotate the shaft wipers into cngagement with the desired line #2226. if this line is busy at the time, the connector will be given the busy-release in the ma nucr to be described, and the calling subscriber is given the busy-signal. thus making it impossible to extend the calling line into connection with the called line.

Before describing the results that follow when the connector finds a busy line. the description of how a connection is established will be completed. As soonas the line relay 139 ceases to operate for thc last digit theprivate magnet relay 159 deenergizes. as heretofore.explained. permitting. in this instance. the side switch to trip to third position. The result is that the side switch wipers respectively engage their contact points of the third position. When the side switch wiper 173 engages the contact point 174 a guarding potential is completed at the private wiper for protecting the seized line from outside interference while the connection is established. This guarding potential extends from ground G to the contact point lT-l. thcncc by way of the side switch wiper 173 to the private wiper 165. Not only does this guarding potential prevent other connectors from calling-in on the same line over multiples of the normal conductors 175, 176 and 177. but it also provides means for cuergizingthe cut-off relay 176 of the line switch whereby the said switch C is prevented from :operating when the called subscriber removes hisrecciver 179 from the switch-hook 180. It will also he seen that when the Side switch passed to third position the trunk-release -conductor 1116 that runs'betwccn thc swoml-sclcctor and g ance winding 153 and the side switch wiper 154. The reason for. this is that the guarding potential from ground G is inter- ,rupted while the line relay 139 is operating,

and there is a possibility of some other selector similar to the selector F stopping on the same trunk-line. After the side switch passes to third. position, however,

there is no such danger, and the potential is provided from ground G through the line relay springs, as stated. Of course, when the side switch wipers 182 and 183 engage their third-position contact points 181 and185 the calling subscribers line is placed in connection with the called subscriber's line over the heavy conductors shown, passing through the ringer relay springs 186 and 187 on one side, and 188 and 189 on the other side. As soon as connection is thus established the ringer relay 190 is energizedover the circuit established 7 when the side switch wiper 162 engages the contact point 191, the energizing current flowing from ground G at the ringer interrupter, through the windin 192 of the relay 196, through the back-bridge relay springs 193 and 191, ringer relay 190, mnductor 195," contact point 191, side switch wiper 162 to the battery lead 25,.thence through battery B to ground (1. The relay 196 thereupon energizes, while the ringer relay 190, which is of lower resistance, remains in normalv position. -The relay 196,

'upon energizing, closes the springs 197 and '"maintains the springs 201 and 202 in contact. It will be seen that as the ratchet wheel 200 revolves, the energizing circuit of the ringer relay 190 will be broken periodically so as not to ring the called subscriber continuously. Furthermore, it will be seen that. each time that the ringci'u relay is energ zed the springs 186 and 18.? are separi'lri-d from the ringer relay springs 187 and 15:, thereby breaking the calling line from the called line, and pressed into engagcmcnt with the springs 204 and 205 which are the terminals of the ringer gen-= orator I.- As a result ringing current is sent over the called line for energizing the bell 206 while the springs 207 and 208 are in contact. However, as soon as the called subscriber answers, the baclcbridge relay 209 is energized bya flow of current from rvnrnifir] (117 nnnl-unlnninf 17A. eirln exvlfnl'i relay to energize as 1011 relay 209, ringer relay springs 189 and 188, side switch wiper 183, contact point- 185, line wiper164, normal conductor 176, conductor 211-, transmitter 212, primary winding'213, impulse springs 21 4, switchhook sprin'gs 215 and 216, line conductor 217, normal conductor 175, line wiper 1118, contact point 181, side switch wiper 182, ringer relay springs.186,and 187, winding 218 of the back-bridge iela 209.thence to the batterylead 25 and .tirtlmgh battery B to ground G. When-once the back-bridge relay 209 is energized the energizing circuit for the ringer relay 190 is interrupted at a point between the springs 193 and 194, thus making it imposslble for the ringer as the called subscriber is on the line. the relay 209 energizes, the springs 146 and 147 also disengage, thereby interrupting .the circuit which provided a guarding potential to the conductor 136. lVhen the springs 146 and 147 thus disengage, the relay 221, being included in series instead of in multiple as before, energizes, but at this time produces no effect. The subscribers being thus connected may communicate over the main talking conductors indicated by the heavy lines in Figs. 1 and 2 and including on'one side the condenser 219 at the connector H and on the other side the condenser 220. After the, subscribers are through talking, if the calling subscriber hangs up his receiver he opens the line circuit -at a point between the springs 17 and'18, thereby initiating the release of all the switches. This release is brought about as follows: At the instant that the circuit is broken between the said springs 17 and 18 the double-wound line relay 139 and the release relay 145 of the connector H de-nergize. At the instant that the slow-acting relay 14 5 and the line relay 139 deenergize, the energizing'circuit for the release magnet 222 is closedat a point between the springs 148- and 149 and at another point between the springs 142 and 113; 1 flow ofcurrent is, therefore, set up from ground G through the springs 142 and. 143, through the springs 148 and 149 to the off-normal spring 223, to the contact point 224, to the release ma et 222. thence through said magnet to the attery lead 25, and through battery B to ground G. The release magnet instantly releases the connector switch shaft; and side switch, thereby breaking the energizing circuit through the back-bridge relay 209 (if the called subscriber has not in the meantime restored his receiver), and also the energizing circuit through the bridgecut-otl' relay 178 of the called line switch urthermore, when' rating the oil-normal spring 22:52 by sepa- 2-33 from the contact point 2%. at which instant the re lease magnet of the connector is also restored. The operation of the line relay 1 39 and of the slow-acting relay 145 not only causes the release of the connector. as la-- scribed. but also the release of the precedin; switches. because the ground connection from ground G to the tl'tllllbiclifilSc. conductor 136 is interrupted by both of these. relays. Since the release relays (37 and are dependent upon this ground for their energized condition, as already eX- plained. it follows that they will fall back with the following results: As soon as the release relay 11) of the seoond selector F de't nergizcs. the spring 111 falls back into normal engagement h the spring .112, thereby closing an cmrgizing circuit for the release mania t 22. from ground (i through the springs HJT and 108, through the springs 111 and 112 to the release magnet .225. thence to the contact point 226. oll normal spring 2;? to the battery lead thence through battery I) to ground G. As soon as the release magnet L33 energizes. the secondselector side switch and switch shat't are restored. which shaft, upon reaching its lowest position. opens a release circuit at a point between the oil-normal spring .227 and the contact point 226. whcreliiz the release magnet 2;? is restored also. ll hen the release relay (3? of the selector E deenergizes. the springs T6 anl T7 are brought into contact. and as a result the energizing circuit for the release magnet 228 is closed. The energizing current for this release magnet 228 then flows from ground Gr through the springs 63 and G4 and through the said springs 76 and T circuit for the release magnet.

t to the release magnetZiZS, thence through said magnet to the contact point .229. off-nornial spring 230 to the battery lead 25. thence through battery B to ground G. The release magnet. upon encrgizing, then restore. the first-selector side switch and switch shaft. which shaft. upon reaching its lowest position. opens the en ergizingi circuit for the release magnet 228 at a point between the off-normal spring :ZSI) and the contact point Q29. I urtherniore. when the release relay 6'?- dei nergizes and separates the springs 6S and (if). the energizing circuit of the hridge-cut-oll.rela in series with the phinger magnet 2+ becomes broken. and as a result the lu-idgc-cut-oll' relay and plunger magnet Ll restore to normal position. onscqucntlv the bank springs 52 and 52%. as well as the other bank springs oil the line switch are separated. thus preventing any further action from the trunk. After the switches are thus restored the calling subscriber can. of course, then proceed to make nother call.

Returnin now to thal stane of the call called the line this guarding potential would "i:

be supplied throuizh the connector switch from a ground terminal similar to the ground terminal G in the connector witch H. as already explained; but it the line switch C is calling. a guariiling potential is 8( established from the trunk-line relay ground as in Fig. 1 and thence to the private bank contact. In a similar manner the line switch protects the calling line it when the hank springs 52 and 53 come into contact from SE ground G. from which ground connection is established through the said bank springs to the private nornial conductor 231. Then fore. when the subscriber sends in the last impulse the private wiper ltifi is carried 9( onto the grounded contact. and when the slow--acting relay tilt) of the connector dcenergizes. instead of the side switch tripping to third position. as in the case where the line is not busy. the connector is given the 9f.

luisya'elease as follows: When the private magnet rela 159 (lci ncrgims and the springs 1611i and 167 engage. an energizing circuit. is completed through the release magnet said circuit extending from the busy or ll grounded private hank contact. private wiper 165. side switch wiper H3. contact point 232 (bearing in mind that the side switch in second position). springs 1m;

and 16?. normal spring 22 3. contact point 1( 224. through the release magnet to the battery lead 2.). thence through battery B to ground G. The release magnet thereupon energizes and operates to restore the side switch and shaft wipers to normal position. 11

hen the side switch restores to first positiou. the calling subscriber is given thc bus vsignal. The path of the liusv-sigl'naliiig current extends from ground ll through the windintr 153 of the induction coil 223 i. 1'

through the side switch wiper 154 which is now in lirst position. conductor ri il. side switch wiper i5 3. ringer rcla) springs 1H8 and 15th through the condenser 2;" to the trunk conductor l lo. thence through the suli- 1i scribcfs station to the line conductor 19 and trunk conductor 134. through the winding: ill of the line rclzrv to the battery lcad 2 then e through haticry ll to ground 1;.

when the calling sub criber receives thc 1 lHlFl' S-ltllltll he undcratands that the line is busy and hangs up his receiver. The line circuit is opened. as already explained. with the result that the line and slow-actin; 1e

lays 139 and of the connector ll deC-ncr- 1 When the line #2220 is calling, or it releases theconnector) he energizin 'tery H is provided with a back-release relay.-.

that is. a release relay which so controls a circuit ofthe release magnet that when the called subscriber restores-his receiver-to the switch-hook (before the calling subscriber circuit for the release ma at 222 is c o'secl:

-:This back-release is initiated as follows:

\Vhen-the called subscriber answersflhe relay 209 energizes and separates .the springs 146 and 147, which removes a shunt from the relay 221, thus permitting the latter to energize and lace the springs 235 and 236 in contact. ow, when the called subscriber restores liis receirer the. relay 209 deenergizes and permits thesprings 23T and 238 to en a'ge, thereby closing an energizing (II- cuit or the release magnet 222'. This circuit extends from ground G through'the springs 237 and 238 springs'235 and .236, normal .s rin 223, contact point- 224, throu h t 1e re ease magnet 222 to the batead 25, thence through battery B to ground G. .The connector release magnet then enemizes and restores the connector side switli and shaft wi ers to normal po. sition. The release 1. the remain ng switches used in establislnng the connection "is brought about when the callin subscriber desired line. '23 of the line switch to V t a o crating,

restores his receiver to the switc -hook.

I In the foregoing it has beenpointed out how the subscriber at A may establish con- 'nection with the substation A. Any other: subscriber of the entire system may operate the -central ofiice switching mechanism in a similar manner to extend connection to any Itwill be seen that the relay C- is normally om nected with the battery lead 25 through the v 'sp'rings 239 and 240:of the -so-called open main ,r lay 241 which energizes in multiple ,1; with the motor. magnet 35. jzThe ibi thus puttin relay 2 3 un the energizing circuit in the er the control of the relay 241 is'to'. prevent any. subscriber from operating hishneswitch. While the" master switch 18 to eliminate any possibility of a line switch tripping onto a trunk that is already .in use... It will be seen that when the relay 241 energizes, the sp'rin 239- s separated from the spr1ng240an carried into enga ment with the spring 242,- through latter a busy-Si al may be trans' mitted to. the subscriber 5 station in case-htshould attempt to make a call while the master switch is rotating. It is obvious that if all of the trunks are made busy the master switch will not stop until some oneaof the.

trunks becomes idle, so that the subscriber not only gets a busyto operate his line switc while it is passing 'olf relay in series, said magnet with an armature-harm a finger a apted toal if he attempts from one point to another, butalso if he tries to call'while all of the trunks are busy.

It will be seen that the line switch 0 diagrammatically shown in Fig. 1 is more fully represented in Fig. 3. In the said Fig. 3 the plun er arm 18 more fully shown, controlling by its left terminal the spring 26 and carrying on the right end the plunger which operates the bank springs, such as the bank springs 50, 5t, 52, 53, 54, 55, 32 and 33.

From the foregoing it will be seen that I provide an improve. and highly efficient tw'o-wire systemfor automatically trunking calling lines into connection with called lines.

What I claim as my invention is 1. In a telephone system, a line, a plurality of trunks,'a plunger for traversing the trunks and connecting the line with an idle one thereof, a magnet for drawing the pluner into position to close the connection, a line relay bridged on the line and controlhng said magnet, a bridge-cut-ofl' relay, and a circuit for energizing said magnet and cut-oil relay in series.

2. In a telephone system, a line, a plurality of trunks, a plunger for traversing. the

trunks and connecting the line with an idle one thereof, a magnet for drawing the plunr into positionto close the connectiom-a ine relay bridged on the line and, controlling said magnet, a bridge-cut-ofi. relay a circuit for energizing said magnet rovided open thesprin of sai' cut-off relay.

3. In a telep' one system,- a line, a pluraltrunks and connecting the .line with an idle one thereof, a magnet for drawing the'plunr into position to close the connectiomfa. ine relay bridged on the line and controland and cutity of trunks, .a. plungerfor traversing the llt Ill

ling said magnet, abridge-cut-oflz" relay ,=and j a circuit for energizing 'said magnet and cutofi relay in series, said. circuit including a third or non-talking conductor of any one of said trunks. 5. In a telephone system, a line, a plurality of trunks, a plunger for traversing the trunks and connecting the line with an idle one thereof, a magnet for drawing the plunr into position to. close the connection, a ine rela bridged on the line and controlling sai magnet, a bridg -cut-ofi' relay, a circuit for energizing saic magnet and cutoil relay in series, and. a third relay, said circuit including normal] open contacts of said third relay, said re s rovided with an energizing circuit close uring convercation;

6. In a telephone system, a line, a plural ity of trunks, a plunger for traversing the trunks and connecting'the line with an idle one thereof, a magnet for drawing the pluniger into 'sition to close the connection, a his relay ridged on the line and controllin said magnet, and a bridge-cut-ofi' relay, sair magnet provided with anarmature having a fingr adapted to open the springs of col relay. y

7. In a telephone system, a line, a plurality of trunks, a plunger for traversing the.

trunks and connecting the line with an idle one thereof, a magnet for drawing the plun- 1 into position to closethe connection, a dim relay bridged on the line and controlling said magnet, a bridge-cutoff relay, a circuit for energizing said magnet and cut-ofi' relay in series, said magnet rovidcd with an annature having a finger a opted to 0 en the springs of said cut-off relay, an a third relay, and said circuit including a third or non-talking conductor of any one of said trunks, depending on which one is in use, and inclu ing normall open contacts of said third relay, said dy provided with an energizing circuit closed uring conversation. I

8. In a tale hone-system, a. plurahg of automatic swi ches, trunks to be sciz by said switches, and a master switch common to" said automatic switches said master switch provided with a notched wheel and a motor magnet and ratchet for operating the same, contacts operated by the notches on said wheel, a circuit for said magnet normally open at said contacts, an mterru ter fOfSttid circuit operated b .the said nuignet, and-a relay rovided uu normally 'open contacts conneo ed in parallel with said first-mentioned contacts.

9. In a telephone system, a plurallt sf 3' said switches, and a master switch common to said automatic switches, said master switch provided with a notched wheel and a motor magnet and ratchet for operating the same, contacts operated by the notches on said wheel, a circuit for said magnet normallyopen at said contacts, an interrupter for said cireuitecgierated by the said magnet, a relay provid with normall open contacts connected in parallel wi said firstmcntioned contacts, and a wiper operated by said magnet and provided with a bank of contacts each representing a different trunk and controlling circuit through the windeaidreley. V

10. In a telephone sgstem, a pair of line conductors, athird con nctor, a selector provided with a lamp signal, a supervisory relay controllin said amp, and a slow-acting relay contro lin said supervisory relay over said third con uctor.

11'. In a telephone system a called line a connector honing two selecting motions or seizing said line and for setting up a tall:- ing circuit from the calling to the called line, a busy test circuit for the called line separate from the talking circuit, means for a Jplymg a has potential to the said circuit w ion the caller line is busy, automatic means responsive to said bus potential for releasmg the connector if tie called line is busy, and means for controlling said connector over two sides of the talking circuit in series by means of a varying number of impulses ilependent upon the digit of the called numver.

12. In a telephone system, calling. and called lines, a connector res cousin to the calling subscriber to seize tie called line, and for setting up a talking circuit from the calling to the called line, a busy test circuit for the called line, means for up )lymg a bus potential to said circuit w ion the called inc is busy; automatic means opcrative to release the connector if the called subscriber hangs u) his telephone ahead of: the calling subsori r, and means for controlling the connector over two sides of the talki circuit in series.

13. n a telephone system, subscribers sta. tions including calling mechanism, a plurality of trunk lines, two switches, one switch for selecting an idle trunk line indepeuden tl of any operation of said calling mechanism. and thus extend a connection over said solected trimk to the second switch. a mac'- net for maintainin It said first switch in contact with said trun t, means including a circuit extending from said second switch for controlling saul magnet, and means for controlling said switches over two sides of a line circuit in series.

14. In a. telephone system, a line. a plurality of trunks, an automatic switch, a pluner for traversing the trunks and connecting t to line with an idle one thereof to extend connection to said automatic switch, a map;- net for drawing the plunger into position to close connection. and means including a circuit extending from said switch for controlling aid magnet.

12;. In a telephone system. a line, a plurality of trunks, an automatic switch. a plungerfor traversing the trunks and connecting the line with an idle one thereof to extend connection to said automatic switch. a mug!- net for drawing the plunger into position to close connection, means including a circuit extending from said switch for controlliuu said magnet. and menus for controlling said switch over two sides of the line in series.

16. In a telephone system, a plurality of ating said motor magnet,

, "lines, an automatic switch to a extend a connection over sa d saidzautomatic F.

.said motor magnet,-an comp'nsmg'a air of springs automatic switches, trunks to be seized h said switches, said automatic switches, a pair oihormally opencontarts, a short-circuit adaptcd to be closed around said contacts, means [or initially closing said short-circuit to operate said master switch, and means for continuing the operation of said master switch through the medium of said contacts.

1?. in a telephone system, a plurality of automatic switches, trunks to be seized by said switches, a master switch common to said automatic switches, a pair of normally open contacts, a shorl-dircuit adapted to be closed around said contacts, means for initially closing said short-circuit to operate said master-switch, means for continuing the operation of said master switch through the medium of said contacts, and means for controlling said switches over two sides of a line circuit in series.

18. In a telephone system, a plurality of automatic switches, trunks to be seized .by said switches, a master switch common to saidautomatic switches, a motor magnet for operating said master switch, means comprising a pair of springs for initially 03erand indepen ent means comprising a pair of circuiting 'said first pair for continuing said operation after the initial operation.

19. Ina. telephone sys a pluriailg of automatic switches, trun smt be se' by said switches, a-master switch common to switches, am'otor magnet for operating sald master switch, ,a pa'1r of springs 'and a relay for" initially operating d independent-means for short circuitmg -said rst "r for-continuing said operation after the initial operation.

an. Ina.' telephone system, a p

bpmatically means signal Tfor seizing said switch, a supervisory for said switch, means signal when said switch is serz for cont lling said switch over I of a line circuit in series.

21. In a telephone-system, a plurality of lines divided. into groups, an automatic switch to automatically extend a'connection over said lines, means for seizing said a h,

' a supervisory signal for said switch, m'eans {-for displaying said signal when said. switch is seized, and means for controlling said switch over twosides of a line circuit in series. said switch having motion in one plane to select groups and motion in an intersecting planeto find a line in a selected .group.

22. In a telephone system. a line. a plurality of trunks, a plunger for traversing the trunks and connecting the line with an idle one thereof a magnet for drawing the planger into position to close the connection. a

line relay bridged on the line and control a master switch common to springs for short idle one thereof, ajnagnet for drawing lurahty of.

'trun and connecting for zg 3am .one' thereof, a mag et and-means two sides ling said magnet, a hridge-cut-ofl' relay, a circuit for energizing said magnet and cutoll' relay in series, and means for controlling said line relay m'rr two sides of the line in series.

23. In a telephone system, a line, a plurality of trunks, a plunger for'travcrsing the trunks and connecting the line with an idle one thereof. a magnet for drawing the plunger into position to close the connection, a line relay bridged on the line and controlling said magnet. a hridge-cut-oll' relay, a circuit for energizing said magnet and cutof! relay in series. said magnet provided with an armature ha \ing a finger adapted to open the springs of said cut-oil relay, and means for controlling said line relay over two sides otthe line in series.

24. In a telephone system, a line, a plural ity of trunks. a plunger for traversing the .trunks and connecting the line with an idle one thereof, a magnet for drawing. the plunger into position to close the connection, a line relay bridged on the line and controlling said magnet, a bridge-cut-ofl' relay, a circuit for energizing said magnet and cut-oil relay in series, said circuit including a trunk condoctor, and meansfor controlling said line relay over two sides'of the line in series.

25. In a telephone system, a line, a phirality of trunks, a plunger for traversing the trunks and connecting the line with in t a [0D to close the-conneczidged on the-line. and cut-0E relay, acircnit for energizing sai r'nagn'etand cut-0E relay in rice, sai circuit including a third or non-trlkingconductor of any one of said trunks, and means for controlling saidline relay over two s des of the line in plungerj into posit 26. In a-telephone system, ralit of trunks, a-plunger fortraversing the the. line with an idle for'drawing the pluner into pos'tion to close the connection, a rela bridged on the line and control sai 'magnet, a bridge-carrot! relay, a circuit for'energizing sai magnet and cut-- oil relay inseries, a third relay, said circuit includin normally open contacts of' said third -re ay, said lay provided with an energiaing circu't closed during conversation, and means, for controlling said line relay over two sides of the linein series.

27. In a telephone a line, a plurality of trunks, -a plunger for traversing the trunks and conhecting the line with an idle one thereof, a magnet for drawing the plunger into position to close the connection, a line relay bridged on the line and controlling said to et, a bridge-cnt-ofi relay, said magnet provided with an armature having I finger adapted to open the springB of said a line; a plus cutofi' relay, and means for controlling said line relay over two sides of the line in series. 28. In a telephone system, a line, a plurality of trunks, a plunger .for traversing '5 the trunks and connecting the line with an idle one thereof, a magnet for drawing the plunger into ,position to close the connection, a line relay bridged on the line and-controlling said magnet, a brid e-cut-ofl' relay, :1 circuit for energizing sai magnet and cutoi! relay in series, said magnet rovided with an armature h aving'a fin er apted to open the springs of said cut-o relay, a third relay, said circuit including a third or nontalkin conductor of any one of said trunks, depending on which one isin use, and including normally open contacts of said third relay, said relay provided with an energizing circuit closed during conversation, and :0 means for controlling said line relay over two sides of the line in series.

29. In atelephone system, a pluralit of 'automatic switches, trunks to be'seize by.

said switches. and a master switch common into, said automatic 7 switches, said master "switch provided with a notched wheel and a }motor magnet and ratchet for operating the same, contacts operated by the notches on said wheel, a circuit for said magnet norso finally open at said contacts, an interrupter for said circuit operated by the said magnet, ii relay provided with normally'open' contactsvconnected in parallel with said first- Imentioned contacts, and means for controlling said automatic 'switches over two sides of a llnecircuit in ser es.

1 '30. In a. telephone system, a plurality lof :antomatic switches,- trunks to be seize said-switches, and a master switch common.

said automatic switches, said master a motor magnet and ratchet for operating the same, contacts operated the notches onisaid wheel, alcijrcuit for sai magnetjnor- '45 --mally open at said contacts, an interrupter provided with a notched wheel and ."ifor said circuit operated by the said magnet,

- 'farelay provided with normall open contacts connected in parallel wit said firstmentioned contacts, a wiper operatedby'said 50...inagn'et and provided with a bank .0 contacts each representing a difl'erenttrunk and controlling cirr-uitthrough the winding of said relay, and means for controllingsaid automatic switches over-two of a lme at circuit in series.

531. -In a telephone system, a' line circuit,

repair of line conductors, a third conductor,

' f'a'selector provided'with a lamp silgnlzl, a anmp, a

.jwrvisory relay controlling sai no slow-acting relay controlling said supervisory relay over said third conductor, and

means for controlling said selector over two sides of said line circuit in series, j

4,3,2. In a called subscriber hangs up his telephone .magnet, and'means for energizing said re- "of said release magnet and a apted to re- 3 '36. In a telephone-system, a called line means for controllin telephqne n, i

called lines divided into groups, a connector 06 responsive to the calling subscriber to seize the called line to establish'a talking circuit between two subscribers, automatic means operative to release the connector if the 10 ahead of the calling subscriber, and means for controlling the connector over two sides of the talking circuit in series, said connector having motion in one plane to select groups and motion in a planeat right-angles thereto to fihd a line in a selected groups 33. In a telephone system, subscribers lines, a connector switch, means controlled from any one of said'lines for seizing said connector switch and for operating said switch to extend a talking circuit to any other one of said lines, a line'relay for said connector switch energized over the two sides of the talking circuit in series to control the operation of said switch, a release magnet for said connector, and means for energizing said ma et when connection is made with a busy ine to release said confor establishing a talklng'circuit with the called line, a connector for seizing said line, means for controlling said connector over two sides of.the talklngcircuit in series, a release magnet for said connector, an energizing circuit for saidmagnet, a side switch or saidconnector, a relay for controlling the operation of said side switch and likewise controlling the circuit of said release 10. lease magnet when connection is made witha ,busy line in order to release said connector.

35. In a telephone system, a. called line,-'a connector for seizing said line, a release magnet for said connector, a rotarymagnet for controllingthe-operation of and switch, a slow acting relay controllin the circuit main energized while said rotarymagnet is operating, and means for energizing said 11a release magnet whenfconnection is made 1 with a busy line in order to release said connector.

for establishing a talking. circuit with the ;Illi called line, a connector. for seizing said line,

said connector over two sides of the tal ing circuit in series, it

-.a release magnet, a side switch having a plurality of positions, a relay for controlling 12 said side switch, a private wiper, and means i for closingacircuit for said release magnet through said. private wiper and said. side switch while msecond position, whereby said connector may be releasedawhencon- 126 nection is made within; busy'linel 37.;In a telephone system, a called line, e a" release magnet for said connector. a side switch, a

"slow acting relay controlling the operation at when in second position, to thereby release I said connector when connection is made with a busy line. v i

38. In a telephone system, a called line, a connector for seizing said line, a release ma et for said connector, a relay for controfi i ng a. circuit for said magnet, and means whereby said relay is normally short-circuited.

39. Ina telephone system, a called line, a connector for se1z1ng sald line, a release ma et for said connector, a: relay for com trofii ng a circuit for said magnet, means whereby said relay is normally short-circuited, and means for removing said shortcircuit when the calledsubscriber answers.

' 40. In a telephone system, a called line, a connector for seizing said line, a release magnet for said connector, an energizing circuit for said release magnet, said circuit including normally open and normally,

closed contacts, means for closing said nori -mally.open contacts and opening said norm'ally closed contacts when the called sub- SCI'lbEPflIlSWOIS, and means for again closing i said normally closed contacts when the called subscriber replaces his receiver upon the hook to thereby release said connector.

41. In a telephone system, a called line. a connector for seizing said line, a release magnet for said connector, anenergizing circuit for said magnet, said circuit including normally open and normally closed contacts,'a slowacting relay controlling said normall open contacts, a second relay for controlling said normally closed contacts.

means for energizing said second relay upon the response of the calledsubscriber to thereby open said normally closed contacts, and to energize said slow acting relay to thereby close said normally open contacts, and means for deenergizing said second relay when said subscriber replaces his receiver upon the hook to thereby again close said normally closed contacts, whereby the c1rcuit for the release magnet is closed and the connector released. a

42. In a telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, means for supplying ringing current to the called line, said means including a ringing relay,

an energizing circuit for said ringing relay including a second relay, means for closing said circuit to energize said second relay but not said ringing relay, andmeans for thereafter increasing the How of current in said circuit to thereby energize said ringing relay to apply ringing current to the called line.

43. In a telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, a ringer relay, a circuit for said relay including a second relay having suliicient resist: ance to prevent energization of said ringer relay, ineans for intermittently operating said second relay to thereb increase the flow of current through sail ringer relay,

and meanscontrolled bysaid ringer relay for supplying ringing current to-the called 44. Ina telephone system, a calling line, a called line, a progressively movable trunking connector switch for connecting the two over a talking circuit, a busy test circuit for the called line separate from the talking circuit, means for operating said connector over two sides of the talkingcircuitin series to, find the called line, means for supplying a busy test potential to said test circuit whenever the'called line-is-busy, and means responsive to said potential for releasing said connector.

45;In a telephone system, a calling line, a called line, a progressively movable trunking connector switch for connecting the two over, a talking circuit, a busy test circuit for the called line, means -for operating said connector over two sides of the talking circuit in series to find the called line, means for applying a busy test potential to said test circuit whenever the called line is busy, means responsive to said potential for releasing said connector, and a busy signaling circuit for indicating to the calling line that the called line is busy.

46. In a telephone system, a calling line,

a called line, a progressively movable trunking connector switch for connecting the two over a talkingcircuit, a busy test circuit for the called line, means for operating said connectorover two sides of the talking circuit in series to find the called line, means for applying a busy test potential to said test circuit whenever the called line is busy,

means responsive to said potential for recuit, means for voperating said connector over two sides of the talking circuit in series to find the called line, means for applying a busy test potential to said test clrcuit whenever the called line is busy, means responsive to said potential for releasing said connector, said last means comprising a release magnet, and an energizing circuit for said release magnet, said circuit comprising in turn a busy test circuit individual to the connector switch, said energizing circuit controlled by the release of the connector.

48. In a telephone system, a group of second selector switches, each operative in accordance with the second di it of the called number, trunks to beselected by said second selectors, a pair of relays common to said second selectors, operating to intermittently interrupt the flow of current through any selector until an idle trunk is found, each relay controlling the circuit of the other, a talking circuit, line relays for said selectors connected to said talking circuit, and means for controlling said relays over two sides of the talking circuit in series.

49. In a telephone system, a plurality of second selector switches, each operative in accordance with the second digit of the called number, a plurality of controlling relays common to all of said second selector switches, local circuits controlled by said relays, a'talking circuit, line relays for said selectors connected to said talking circuit, and means for controlling said relays over two sides of the talking circuit in series.

50. In a telephone system, a switch having vertical and rotary motions, an operating magnet controlling the rotary motion of said switch, an energizing circuit for said magnet, a pair of relays controlling said energizing circuit, means for energizing one of said relays in order to energize the second of said relays, and means for opening said energizing circuit for said operating magnet by the energizing of said second relay while said first relay is energizedf 51. In a telephone system, a vertical and rotary motion switch, a vertical operating ma not, a rotary operating magnet, a slow acting relay connected in series with said vertical operating magnet, 21 second relay controlled by said slow acting relay. and

means for closing the energizing circuit for said rotary operating magnet by first energizing said relays and then dei nergizing said slow acting relay.

. 52. Ina telephone system, a switch having vertical and rotary motions, an operating magnet controlling the rotary motion of said switch, an energizing circuit for said magnet, a pair of relays controlling said energizing circuit, means for energizing one of said relays in order to energize the second of said relays, means for opening said energizing circuit for said operating mag net by the energizing of said second relay while said first relay is'en'ergized, and m for controlling the operation of said switclfi over two sides of the line. 53. ,In a telephone system, a vertical and rotary motion switch, a vertical operating magnet, a rotary operating magnet, a slow acting relay connected in series with said vertical operatin magnet, a second relay controlled by sai slow acting relay, means for closing the energizing circuit for said rotary operating magnet by first energizing said relays and then denergizing said slow acting relay, and meansfor controlling the operation of said switch over two sides of the line circuit in series.

54. A telephone exchange system com prising telephone lines, automatic connectors less in number than said telephone lines, selectors less in number than the telephone lines, subscribers individual switches correspondin in number to the telephone lines, subscri ers devices for closing .the lines to control said individual switches and selectors and connectors by a varying number of impulses, line circuits by which the said individual switches and selectors and connectors are controlled, each line circuit including the two sides of a calling telephone line in series, said devices having provisions for determining'the number of impulses necessary for each di it of the called number, and means for releasing saidindividual switches and selectors and connectors by the opening of the calling line.

55. A telephone system comprising telephone lines, a plurality of step by step connector switches less in number than said telephone lines, locking means dependent upon the use of said connector switches for connecting purposes to hold the same in an oil-normal position, and automatic means for restoring said connector switches when thrown into an oil-normal position while idle.

56. A telephone system comprising trunk lines, a step by step first selector switch adapted to select idle trunk lines. locking means dependent upon the use of said selector switch for connecting purposes to hold lines, a subscribers step-by-step in-ividual normal position while idle.

59. A telephone exchange system coniprising telephone lines, automatic connec- 'tors less in number than said telephone lines. selectors less in number than the telephone lines. provided with means having vertical step-by-step motion to select different operative levels, depending on the number called, and rotary step-by-step motion to connect with a line in the selected level, subscribers individual switches corresponding in number to the telephone lines, subscribers devices for closing thelines to control said individual switches and selectors and connector line circuits by-which the said individual switches and selectors and connectorsla-re controlled, each line circuit including the two sides of a calling telephone line in series, and means for releasing said individual switches and selec' tors and connectors by-the opening of the calling line. Y

60. A telephone system comprising telephone lines, a p urality of connector switches less in number than said telephone lines. provided with means having vertical motion to select different operative levels depending on the number called, and rotary step-by-step motion to connect with a line in theselected level, locking means dependent upon the use of said connector switches for connecting purposes to in. an off-normal position, and automatic means for restoring said'connector switches when thrown into an off-normal positron .while idle. v

61. A telephone system comprising trunk lines. a first-selector switch adapted to select idle trunk lines. provided with means having vertical step-by-step motion to select differ ent operative levels depending on the number called. and rotary step-by=step motion to connect with a line in-the selected level..locking means dependent upon the use of said selector switch for connectingpurposes to .hold the same in an oft-normal position, and

automatic means for restoring .said first selector when thrown into sition while idle. a

'62; A telephone system comprising trunk lines. a second-selector switch adapted to select idle trunk lines provided with means having vertical stcp-by-stcp motion to select different operative levels depending on the number called. and rotary motion to connect with a ine in the selected lcvcl. locking means dependent upon the use of said sch-c tor switch for connecting purposes to hold hold the same calling line.-

a-n off-normal po the same in an oil-normal position, and automatic means for restoring said second-selector when thrown into an ofi-normal position while idle.

63. A telephone exchange system comprising a calling telephone linc.a called telephone line. means including a plurality of selectors and a cmmector for extending connection from the calling line to the called line, calling mechanism requiring a separate manual operation thereof for each digit of the called number. operative to transmit suitable controlling current for one digit before the said mechanism is manually operated for the next digit. line circuits for controlling the selec tors. and a line circuit for controlling the connector. each line circuit including saidmechanism and the two sides of the calling. line in series.

(H. A telephone ing telephone lines, less in number than said telephone lines. selectors less in number thanithe teleph 'nc lines, subscribers individual switches c rresponding in number to the tplephone lines,

exchange system cpmpifisautomatic coiinectiirs 8 control said individual switches and selectors and connectors, comprising a. calling mechanism requiring a separate manual opnumber, operative to transmit suitable com trolling current for one digit before the saii'. mechanism is manually operated for the new digit, line circuits by which the said individ nal switches and selectors and connectors ar controlled, each line circuit mechanism and the two sides of a calling telephone line in series, and means for r leasing said individual switches and seleci tors and connectors by' the opening of the} eration thereof for each digit of the called] 65. A telephone exchan e system oompris ing a calling telephone line, a called tel];- phone line. calling mechanism requiring a separate manual operation thereof for each digit of the called number, operative to 110 transmit suitable controlling current for one digit before the said mechanism is manually operated for the next digit. means including a plu 'alit-y of selectors and a connector for extending connection from the call ilig line-to 135 the calledline. provided with means having vertical motion to select dill'crent operative levels. depending on the number called. and rotary motion to connect with a line in the selected level. line circuits selectors. and a lbw-circuit for controlling tlnwonncctor. each line circuit including said mechanism and the two sides of the calling line in series.

66. A telcphonc exchange system compris- 125 ing a selector switch. another selector switch provided with a side switch. a hnc rclay for said other switch. and means for energizing inchiding'saii for controlling the said line relay after said first switch extends connection to said other switch, ada )ted to maintain said line relay energized as ong as the side switch of said other switch remains infirst or second position.

67. In a telephone system, a connector switch, a side switch, a release magnet, and another clectromagnet therefor; an energizing circuit for the said release magnet controlled by said other electromagnet while the side switch is in second position, the said other electromagnet retaining its armature attracted while the side switch is in second position to prevent the release of said connector switc 68. In a telephone system, a connector switch; a side switch, a test wiper, a release magnet, and another electromagnet therefor; an energizing circuit for said release magnet controlled by said other electromagnet while the side switch is in second position, the said other electromagnet retaining its armature attracted while said test wiper is passin over busy contacts to prevent the release 0 said connector switch.

69. In a telephone system, a connector switch; a side switch, a release magnet and another electromagnet therefor; an ener izing circuit for said release magnet contro led by said other electromagnet while the side switch is in second position, said circuit established by deenergizing said other electromagnet.

, 70. A tale hone system comprising a connector switc ii. line relay therefor, av release magnet, means whereby if the line relay is deiinergizedmomentarily the release magnet is prevented from energizing, and means whereby if the line relay deiinergizes for a greater length of time the release magnet energizes and releases the said connector switch.

71. -A tale hone system comprising a connector switc ,a release magnet therefor a slow acti relay, a line relay, and a shaft or said swit fi, an energizing circuit for said slow acting relay controlled by said line relay, and an energizing circuit for said re lease magnet controlled by said slow acting relay and by said shaft, means whereby if said line relay denergizes said slow acting relay deiinergizes and sets up an energizing circuit through said release magnet to re lease said shaft to in turn destroy the ener gizing circuit for the said release magnet.

72. A telephone system comprising a series of switches each provided with a release. relay, a subscribers telephone and line, 'h first switch of said series being allotted to the line, means whereby when a subscriber removes his receiver the release relay of the first switch energizes and remains energized until the subscriber hangs up, means whereby the first switch me be made to connect with the second switc of said series, and

whereby the release relay of said second switch energizes as soon as connevti i made with said second switch, which second release relay remains energized until the subscriber hangs up, and means whcrchv said second switch may be inade to HIIHICL t with the third switch of said series. and whereby the release relay of said third switch thcn encw'izcs and remains cncrgizcd until the subscriber hangs up his receiver.

73. .1 telephone exchange system com prising a selector switch, another selector switch having a side switch, said other switch provided with means having vertical motion to select different operative levels depending upon the number called, and rotary motion to connect with a line in the selected level, a line relay for said other switch. and means for energizing said line relay after the first-switch extends connection to said other switch adaptcd to maintain said line relay energized as long as the side switch of said other selector remains in first or second position.

74. In a telephone system, a connector 5 switch for completing connection to a desired subscribers line; a test wiper, a release magnet and another electromagnet therefor; an energizing circuit for said release magnet controlled by said other electromagnet. said 1 other electromagnet retaining its armature attracted while said test wiper is passing over busy contacts to prevent the release of said switch.

75. In a telephone system, subscribers 7 lines arranged in groups, a connector switch for electing a group of saidlines and picking out thedesired line in that group, a release magnet, another electromagnet and an energizin circuit for said release ma ct controlle by said other electromagnet w ile said switch is picking out the desired line. said circuit established by deiinergizing said other clectromagnet.

76. In an automatic telephone system, an automatic progressively movable switch, a plurality of lines accessible to said switch, said lines divided into groups, means for operating said switch to elect a group and means for thereafter operating the switch to 7 establish connection with a line in the elected 4 group: means for releasing said switch after it has been operated, said means including-a release magnet, a circuit for said release magnet, said switch comprising a magnet auxiliary to said release magnet, said circuit controlled by said auxiliary magnet to mamtain the circuit of the release magnet open while the switch is being operated in the elected group to find any particular line in a the elected group.

77. The combination of an automatic switch and a plurality of lines, said lines divided into groups, said having means whereby it may be operated automatic switch to elect a group and whereby it may thereafter be operated to pick out a line in the elected group, said switch having a release magnet and an auxiliary magnet, a circuit for the release magnet, said auxiliary magnet having control overthe circuit of the release magnet to maintain the same open while the switch is operating. to pick out a line in the elected group.

'78,. In an automatic telephone system, an

automatic progressively movable switch, a

plurality of lines accessible to said switch, said lines divided into groups, means for operating said switch to elect agroup and means for thereafter operating the switch to establish connection with a line in the elected group: means for releasing said switch after it has been operated, said means including a release magnet, a circuit for to elect a group and whereby it v.may there-.

after be operated to pick out a line in the elected group, said switch having a release magnet and an auxiliary magnet, a circuit for the release magnet, saidauxiliary magnet having control over the circuit of the a release magnet to maintain the same open while the switch is operating to pick out a line in the elected group, and means for energizing said auxiliary magnet during the interval that it is holding the release circuit open. r

80. In a telephone system, a lurality of selectors, a connector,. release re ays in each ofsaid selectors, and means in said connector for maintaining all of said relays energized. f i

81. In an automatic telephone exchange trunking system, a calling subscribers line and a walled saibscrihers line, a plurality of switches for establishing connection between solid lines, a slow-acting relay in each of said switches, one of said switchesadapted to supply the talking circuit with talking currenn'the said talking current supplying switch comprising means for maintaining all the said slow-acting relays energized.

82. In an automatic exchange trunking switch, a calling line and a called line, a

plurality of switches for establishing connection between said lines, releasing apparates ,for each of said switches, a release switches for'teunking the calling relay for controlling each releasing apparatus, one of said switches comprising means for supplying the talkin'gcircuit with talk ing current, said one switch also comprising means for maintaining all of said release relays energized.

83. In an automatic telephone exchange trunking system, a callin suhscribers line and a called subscribers l ne, means including a plurality, of selector switches and a connector switch for connecting the two lines, a releasing mechanism for each switch and a releasing relay for'controllingeach releasing machanism, parallel circuits for said release relays, and a, line relay for the connector switch, said line rela adapted to control the parallel circuits 0t? all of said release relays after the two lines are con-' nected.

84; In an automatic telephone exchange trunking system, a calling subscribers line and a called subscribers line, means includ-' connection between the two lines in a step by-step, manner, a release mechanism for each switch,-a slow-acting release relay forcontrolling each releasing mechanism, the slow-acting releasing relay of the last switch brought into the connection being adapted to control the circuit ofthe slow-acting release relays of all the preceding switches, the releasing relay of each switch adapted to become energized from the instant that this switch is brought into use until it is released.

85. In an automatic telephone exchange trunking system, a calling subscribers line and a called subscribers line, means including a plurality of selector switches and a connector switch for connecting the two lines, a releasing mechanism for each switch and a releasing relay for controlling each re leasing mechanism, parallel circuits for said release relays, and a line relay for the connector switch, said line 'relay adapted to control the parallel circuits of all of said release relays after the two lines are connected, the releasing relay of'each switch adapted to become. energized from the instant that this switch is brought into use until it is released.

86. In an automatic telephone exchange trunking system, a calling line and a called line, a plurality of switches'for connecting the calling linewith the called line, including a switch individual to the calling line, line bank springs for-the said individual line switch included in the connectin line circuit, and automatic means where y 1f said springs are separated all of thGSWltChGS are released.

mg a plurality of switches for extending 87. In an automatic telephone exchange,

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