US1531494A

US1531494A - Nongrounded or metallic circuit system

Info

Publication number: US1531494A
Application number: US369012A
Authority: US
Inventors: Edward A Mellinger
Original assignee: Automatic Electric Co
Current assignee: Automatic Electric Co
Priority date: 1907-04-18
Filing date: 1907-04-18
Publication date: 1925-03-31
Anticipated expiration: 1942-03-31

Description

March 31, 1925. 1,531,494

E. A. MELLINGER NONGROUNDED OR METALLIC CIRCUIT SYSTEM Filed April 18, 1907 2 Sheets-S116 1 CPQK/W 6 a WWW. Affwwa??? March 31, 1925,

E. A. MELLINGER NomouNDED on QE'rALLIc CIRCUIT SYSTEM Filed April 18. 1907 2 Sheets-Sheet 2 Patented Mar. 31, 1925.

UNITED STATES PATENT OFFICE.

EDWARD A. HELLINGm OF CHICAGO, ILLINOIS, ASSIGNOR, BY MERE ASSIGNMENTS, TO AUTOMATIQ ELECTRIC COMPANY, A CORPORATION OF ILLINOIS.

' HONGBOUNDED OR METALLIC CIRCUIT SYSTEM.

Application filed April 18, 1507. Serial No. 889,012.

Metallic Circuit Systems, of w iich the following is a specification.

My invention relates to telephone systems in eneral, but more particu arly to automatlc or semi-automatic telephone exchange systems, and especially to systems in whichno operating grounds are employed at the subscribers substations. Prior to my 1nvention it was proposed to operate switches without employing the ground or earth between the substations and the exchange, for.

both connecting and releasing purposes. In my improved system, however, as herein disclosed, new and improved means are provided by which a series of switches can be successively operated or controlled from a substation at which no ound connection is provided, whereby the ine circuits for controlling the switches all include the two sides of the line in series. Furthermore, with my improved arrangement means are provided by which the calling subscriber can release the diiferent switches by which a connection was extended to the called subscribers line-that is to say, by simply opening the line circuit, when he hangs up his receiver, the calling subscriber may release the switches at any stage of the call, either before or after the called subscribe r answers. In addition, the subscribers individual switches are of such character that they cannot remain ofi normal-that is to say, these switches cannot be retained in an operated position unless their respective telephone lines are closed at the substations. In this way the trouble and annoyance which usually results from off-normal switches is avoided, as an accidental ground on any telephone line will not cause the individual switch thereof to operate, the operation of the switch being dependent upon the closing together of the two sides of the line. With this arrangementI provide improved means for trunking on a percentage basis, and make it possible to automatically trunk a calling telephone line into connection with a called telephone line in a ten-thousand or even larger exchange, without the necessity of employing operating grounds at the substations. As stated, the mere act on the part of a subscriber in hanging up his receiver is sufiicient to immediately release and restore any trunkin connection which may have been establis ed between his line and the line of some other subscriber. Such act, as will hereinafter more fully appear, is also sufiicient to release any switch or switches which may have been 0 rated by the calling subscriber, should he or any reason decide to hang up his receiver before the connection has been fully extended to the line of the called subscriber. These and other advantages will hereinafter more fully appear.

In the accompanying drawings, Figures 1 and-2 taken together re resent diagrammatically a calling substation A connected, by means of central ofiice switching apparatus, with a called substation A, in a system embodying the principles of my invent-ion. The switches through which the stations A and A are shown connected comprise (in Fig. 1) the so-called first-selector C which is allotted to the calling line, and the second-selector D, and (in Fig. 2) a connector E and a first-selector C of the called line. The selector C is individual to the lin of the substation A, while the first-selector C is individual to the line of the substation A. The said selectors C and O are alike. For operating the central oflice switches there. is provided a central source of current or battery B having its positive terminal preferably grounded at G (Fig. 2). It will be understood, of course, that in this system the first-selectors are arranged in groups, as well as the second-selectors and connectors. A somewhat common arrangement is to divide the subscribers and their allotted first-selectors into groups of thousands. Each thousand-group is sub-divided into groups of one-hundred. Then the like hundreds-that is, the one-hundreds, thetwohundreds, etc.-of the various thousands are each arranged in one group, so that in a tenthousand system the one-hundreds of the thousands form one group, the two-hundreds a second group, etc. Furthermore, each bank level of each of these hundred-groups has allotted to it one group of second-selectors allotted to the thousand corresponding to the levelthat is, the second-selectorgroup of the first-selector first bank level is allotted to the first thousand, the second level to the second thousand, etc., thus takof the hundreds; there being in a tenthousand system ten one-thousand-groups of first-selectors; ten one-hundred-groups in each thousand; also ten groups of secondselectors, one for each t ousand and ten ement groups'of connectors in each thousand, one

or each hundred. With this arrang it will be understood that thefirst level of the first hundreds in all thousands in the system is multiplied in a manner well understood likewise the second level, etc. Also,

all like levels of each second-selector-grou one of which, as stated, is alloted to eac -t ousand) are likewise multiplied. In each of the aforesaid connector-groups, and in the same manner, the like levels are, of

course, also multiplied. In this way the individual switches are the same in number as the subscribers, but all other switches are 28 g It will be clear from the drawings that when employed on a percentage basis.

The substations in the system ma be of any suitable or approved type. e substation A, for example, comprises a receiver 2, a'switch-hook 3 for controlling the substation circuits, which controlling o erations are accomplished through the me ium of any suitable means, such as the cam-arms 4 and 5. When the switch-hook is down the cam-arm 4 holds the spring 6 out of engagement with the spring 8 and in enga ement with the spring 7, thereby bridging t e ringer 9 in series with the condensers 10 and 10 across the line. When the switchhook descends the said cam disengages the springs 11 and 12, thus breakin the local circuit which includes in series t e primary winding 13, transmitter 14 and local battery 15. The said substation comprises the usual induction-coil 16 having the primary winding 13 and secondary winding 17. Being an automatic substation it is provided with impulse springs. The springs 18- and 26 are the vertical impulse springs and the springs 19 and 30 are the rotary impulse springs. Said substation is, of course, provided wlth -a dial (not shown) which is secured tothe shaft 20, together with the locking do 21. This dial is ordinarily located on the ack side of the im ulse wheel 23, as also the switch-hook 3, ut for convenience of illustration this .is shown diagrammatically. Furthermore, there is a locking cam 22 that locks the dog 21, while the receiver is on the switch-hook, to prevent rotation of the impulse teeth 24 an .to Keith, Erickson & Erickson.

dial. Foro ra' theim ulse rin 1s and 26 and l the sl fbstati dh is mosecured to the shaft 20, which lse'wheel carries on its periphe the so-ca ed vertical one rotary impulse 'vided with an impulse wheel 23 that is tooth 25. The said im ulse teeth are so arranged that when the 'al is drawn down the im ulse springs are notopera'ted; but as the ial returns, first thevertical impulse teeth operate to close the vertical impulse s rings 18- and 26, and after they have come p ete their work the rotary impulse teeth 25 operates to separate the rotary impulse springs 19 and 30. In this operation the vertical impulse spring 18 is pressed'into contact with the spring 26 a number of times, whereby the vert cal line conductor 27 becomes directly connected with the rotary line conductor 28. Normally, when the receiver is removed, the vertical and rotary line conductors27 and 28 are connected through the high resistance coil 29. After the vertical impulse teeth have operated the vertical impulse springs, the rotary impulse tooth 25 momentarily disengages the springs 19 and 30, whereby the line conductors 27 and 28 become separated, and when the v springs engage, the line conductors 27 and "are again connected through the coil 29.

the subscriber pulls down the dial the rotary impulse tooth 25, upon rotating in a forward direction, meets the angled member shown on the end of the spring '19, pressing as it advances, both s rin 19 and 30 out of the way, but without rea ing connection. However, when the dial returns toward normal position the impulse tooth 25 comes in behind the member on the. end of the sprin 19, flexing the'said -s ring 19 away from t e spering 30, thus brea 'ng the circuit, as descri d. It will be understood, furthermore, that the shaft 20 is provided with a proper tension sprin adapted to restore the dial when once it as beenrotated out of normal position. Furthermore, the switch-hook 3 is also provided with a suitable spring whereby said switch-hook may be caused to rise when theweight' of the receiver is removed. Means wh reby the subscriber may si nal the called ubscriber comprises the pus ,-button 31 which, when pressedfcarries the spring 32 into engage- The first-selector may be of any suitable- I or approved type, for instance of the general type described in United States Letters Patent No. 815,321, granted March 13, 1906,

The firstselector 0 herein shown, however, is characterized by a number of new features. It embodies the following details and circuits: a switch shaft 34 that carries the vertical and rotary wipers 35 and 36, respectively, and the private wiper 37, and aside switch which is well known and which comprises the side switch wipers 38, 40, 41 and 42. The side switch is under the control of the private magnet 43, and when the side switch is in normal or first position the wipers 38, 40, 41 and 42 occupy the contact points 44, 46, 47 and 48, respectively. In the second position they rest on the contact points 49, 51, 52 and 53, respectively, and in the third position the contact points 54, 56, 57 and 58 are engaged by their respective wipers. Through the medium of the vertical line relay 59, and while the side switch is in first position, the subscriber controls the vertical magnet 60, which latter operates to raise the switch shaft 34 and

wipers

35, 36 and 37 vertically. By means of the rotary line relay 61, and after the switch shaft has been raised to close the springs 62 and 63but before the shaft has rotated to disengage said springs-the subscriber controls the private magnet 43 and, therefore, the side switch. While the side switch is in second position the rotary magnet 64, which operates to carry the switch shaft and

wipers

35, 36 and 37 in a rotary direction, is energized. Associated with this rotary magnet and in series therewith there is, as usual, a circuit interrupter, the springs of which are shown at 141. This interrupter may be of any design, but the interrupter disclosed in United States Letters Patent No. 841,004, granted January 8, 1907, to John Erickson, for improvement in interrupter for electro-magnets, discloses one form that is especially adapted to operate with the switch C, or with any other selector disclosed in this system. The relay 65 provides the means whereby the subscriber controls the release magnet 66. The release magnet and mechanism is of the character shown in connection with the release magnet of the connector disclosed in United States Letters Patent No. 815,176, granted March 13, 1906, to Keith, Erickson & Erickson-that is, when the release magnet 66 is energized its armature is at-.

tracted, and the release and restoration of the switch shaft and side switch is brought about immediately, even before the release magnet de-energizes, in the same manner in which the connector is released in the said patent. The bridge-cut-olf relay 68 is provided to open the connection between the line relays 59 and 61 and the battery terminals. It 'will be seen that the vertical line relay 59 is connected to the non-grounded terminal, and that the rotary line relay 61 is connected to ground. This disconnection is for the purpose of preventing the line relays 59 and 61 from chattering when ringing current for signaling the subscriber A is sent over the line. It is also desirable to remove the bridge formed through the said relays from across the line to give the voicecurrents as clear a path as possible. Furthermore, the shaft 34 is provided with the cam 69 which, when'the shaft is in normal position, permits the "springs 62 and 63 to disengage; but on the first vertical step of the shaft 34 the cam 69 presses the said springs into engagement. Now, when the shaft is given a rotary step the cam 69 is carried out of engagement with the spring (53, and the springs 62 and 63 disengage. The switch shaft is provided with a normal arm 70 which, when the shaft is given a vertical impulse, permits the spring 71, which normally engages the spring 72, to pass into contact with the spring 73, and then to carry this latter spring into contact with the spring 74.

The second-selector D is similar to the first-selector C, with the exception that there are no normalconductors such as the normal conductors. and 70. Since there is no1 use for such conductors they are omittet. ond-selector for a bridge-cutoff relay such as the relay 68 of'the selector C, and it is also omitted, and the line relays are connected directly to the battery terminals. The private normal conductor, such as the private normal conductori77 of the selector C, is of no use in connection with the second-selector and is also omitted. This selector is, however, equipped with the verti cal magnet 78 and the rotary magnet 79, the release magnet 80 and the private magnet 8 1. The said private magnet 81, of course, controls the side switch wipers 82, 83, 84 and 85. The vertical movement of the switch shaft 86'and, therefore, of the wipers 87, 88 and 89 is controlled by the vertical magnet 78, and the rotary movement by the rotary magnet 79. the rotary magnet circuit being provided with the usual interrupter springs 90. The operative magnets of the switch are, of course, controlled by the subscriber through the use of the vertical and rotary line relays 91 and 92, as is well known. Said relays have under their control the usual springs 93, 94 and 95. The selector D is also provided with a release relay 96 for controlling the release of the switch. The release magnet 80 and mechanism is of the type described in said connector patentthat is, when the release magnet is energized and the armature attracted, the switch shaft and side switch are restored to normal position. It will be understood that in both the selectors C and D the release magnet mechanism is of the type employed in the connector switch instead of that usually employed in selector switches of the general type disclosed in said selector patent. The cam springs 97 and 98 are controlled by There is also no necessity in the sec- 3;

ion

- known, are very much the same. The connector switch shaft 104, likethe first-selector switch shaft, carries the

line wipers

105 and 106 and the private wiper 107. The connector switch is also controlled by the calling subscriber through the medium of the vertical and rotary line relays 108 and 109. The vertical line relay directly controls the verticalmagnetllO, and also the rotary magnet 111 and the ringer relay 112. The ofiice of the vertical magnet 110 is to give the shaft and shaft wipers their vertical motion, and the rotary magnet 111 imparts to the shaft and shaft wipers a rotary or circular motion. The rotary line relay 109 controls the energizing circuit-of the release relay 113. The release relay 113 is similar to the relay 96 of the second-selector and the relay of the first-selector. The private magnet 114 is controlled by the rotary line relay 109, and under certain conditions controlsthe release magnet 120 and also the side switch wipers 115, 116, 117, 118 and 119. j The side switch of the connector, like the side switch of the first-selector, has a normal or first position, a second position and a third nsition. By the condensers 122 and 123 the talking circuit through the connector is divided into two inductively-connected sections. The central office is equipped with a busy-signaling apparatus of any suitable design, as, for example, the one comprising an interru ter H in series with the primary windmg 121 of the induction-coil 124, whereby a busy-signaling current is induced in the secondary winding 125 of the said coil. The connector switch shaft 104 also carries a normal post arm 126 which, when the connector shaft is oil normal, allows the spring 127 to engage the contact point 128, whereby the busy-signal may be transmitted to the rotary line conductor. Also, when the shaft is given a vertical step the springs 129 and 130 engage, whereby the release magnet 120 is connected to the battery lead. 1 V a The substation A is like the substation A; also, the first-selector switch 0' allotted to the line #2220 is like the first-selector switch C allotted to the line #5000.

A clearer understanding of my improved system may be had b following the operation of the centralo ce switches when one subscriber calls another. Suppose, for an example, that the subscriber at substation A desires to communicate with thesubscriber at substation A on the line #2220. The operation of the central oflice switches to bring about this connection is as follows: When the subscriber at substation A removes the receiver 2 from the switch-hook 3 the cam-arm 4 permits the springs 6 and 8 to engage, whereby a series circuit including the vertical line relay 59 of the selector resistance coil 29 of the substation A and the rotary line relay .61 of the selector G, is closed. This circuit extends from ground G at the selector 0 through the springs 131 and 132, throu h the rotary'line relay 61, rotary line COINfilCtOI 28, through the sprin 30 and 19, springs 6 and 8, secondary win .ing 17, receiver 2, through the resistance coil- 29 to the vertical line conductor 27, side switch wiper 38, vertical line relay 59, springs 133 and 134 to the battery lead 135, thence through battery Band to ground G. The rotary l1ne relay 61 is so arranged that the current-flow is sufiicient to operatively energize the said relay, while the vertical line relay 59 is so arranged that the currentflow in this circuit is not sufficient to operatively energize it. The rotary line relay, upon energizing, laces the springs 136 and 137 in contact. is closes a circuit through the release controlling relay 65. The circuit through the release controlling relay extends from ground G. through the springs 136 and 137, throughthe relay 65 to the battery lead 135, thence through battery and to ground G. This relay, upon ener izing, separates the springs 138 and 139, w ich disconnects the battery lead 135 from the releasemagnet 66. When the dial is rotated for the first digit 2 the spring 18 is twice pressed into contact with the s ring 26. By this operation the line con uctors 27 and 28 are directly connected, shunting or short-circuiting' the resistance coil 29; thus a new circuit w ich does not include the resistance coil 29 is established through the vertical and rotaig line relays 59 and 61 of the selector C. uflicient current now flows in the cir cuit to operatively energize the vertical line relay 59, which latter, upon energizing, presses the springs 140 and 136 into contact, which closes an energizing. circuit through the vertical magnet 60. This circuit extends from ground G through the springs 136 and 140, through the vertical magnet 60 to the battery lead 135, thence through batter B and to ground G. The springs 18 an 26 being pressed into contact twice for the first digit, the vertical line relay 59 is operatively energized twice, and in turn the vertical, magnet is energized and operated twice. By this operation of the vertical magnet the shaft 34 and the

shaft wipers

35, 36 and 37 are raised two steps and brought opposite the second bank level. It should be borne in mind that at the first vertical step of the switch shaft the cam 69 o eratcs to close thenornially open shaft springs 62 and 63 in contact. As soon as the said springs 62 and 63 come into contact an energizing circuit is established through the private magnet 43 from ground G at the selector C, through the springs 136 and 137, through the cam springs 62 and 63 to the private magnet 43, thence through said magnet to the battery lead 135, and through battery B to ground G. Furthermore, at the same first vertical ste the normal postarm 70 disengages from t e spring 71, permitting the latter to leave the spring 72 and to engage the spring 73, and to carry the said 5 ring 73 into enga ement with the groun ed spring 74, where y the springs 71, 73 and 74 are maintained in contact while the shaft is off normal. This operation disconnects the privan-v normal conductor 77 from the bridge-cut-oif relay 68, and places a guarding potential on said private normal conductor from ground G to prevent any calling subscriber from calling-in upon the line #5000 after the switch C has been operated. When the rotary impulse tooth 25 operates to separate the springs 19 and 30, and to thus open the line, the circuit including the vertical and rotary line relays and resistance coil 29 is broken. line relay 61 is, therefore, deprived of its energizing current and de-energizes, permitting the springs 136 and 137 to separate,

whereby in turn the energizing circuit of the private magnet 43 is broken and the side switch is permitted to pass to second position. It Wlll be understood that when the vertical impulse teeth 24 close the circuit between the springs 18 and 26, the vertical line relay 59 remains operatively energized only as long as the said springs are maintained in contact. As soon as the impulse tooth 25 disengages from the spring 19 the springs 19 and 30 again come into contact, and again the energizing circuit through the rotary line relay is established. Although, in the meantime, the circuit through the release controlling relay is broken,'said rela being slow-acting retains suifici'ent residua magnetism to maintain its armature in an operated position until this energizing circuit is again established, when the rotary line relay energizes. When the side switch passes to second position an energizing circuit is established through the rotary magnet '64. This circuit extends from the grounded contact point 53 through the side switch wiper 42, interrupter springs 141, rotary magnet 64 to the battery lead 135, thence through battery B to ground G. The rotary magnet, upon energizing, oper- The rotary ates to carry the shaft wipers in a rotary or circular direction. The rotaryv magnet being ener ized one step, the shaft wipers 35, 36 and 3 are carried into engagement with the first set of bank contacts, which contacts, it is assumed, constitute the terminals of the trunk line leading to the selector switch 1); but if the first trunk line is busy some other selector (similar to the selector C) in the exchange will be resting in engagement with said trunk line, and the first private bank contact of the second level will be found connected to ground, as is the case in systems of this general character. Therefore, when the selector shaft is rotated one step an energizing circuit is established through the private magnet 43 when the private wiper 37 strikes the grounded rivate bank contact, thereby retaining the side switch in second position and maintaining an energizing clrcuit through the rotary magnet 64. The rotary magnet, by intermittent energization, causes the shaft. to rotate step by step and carry the wipers past the last busy trunk line. However, as soon as the private magnet is de-energized the side switch is tripped into third position; but if there are no busy contacts to be passed over, as assumed in the first instance, the rotary magnet 64, as is well known, trips the side switch to third position, with the result that the side switch Wipers engage their respective contact points in third position. When the side switch wipers 38 and 40. pass to third position the subscribers line conductors 27 and 28 are extended to the conductor leading to the selector switch D. Also, since the side switch wiper 41 engages a grounded contact oint 57 a guarding potential is -establishe at the private wiper 37 for protecting the seized trunk line from being molested or disturbed by any other switch. It will be seen thatwhen the shaft is given the first rotary step the cam 69 passes out of engagement with the spring 63 and permits the springs 62 and 63 to disengage. This disengagement breaks the energizing circuit formed by the rotary line relay 61 through the private magnet 43. The private magnet 1s, however, still subject to the control of the private wiper 37, when the side switch wiper 41 is in second position, as already described. It will also be seen that the selectors are of the bridging type, inasmuch as the vertical and rotary line relays are permanently connected to the line conductors. As a result of this construction, the energizing circuit through the rotary line relay 61 is maintained and, consequently, the energizingcircuit of the release relay 65. The second di it is called after the subscriber has establlshed connection with the selector D by way of the trunk conductors 142 and 143. When the trunk conductors 142 and 143 are seized an, energizing circuit is established through the vertical and rotary line .relays 91 and 92 of the selector D, in the 94 and 95, through the relay 96 to the battery lead 135, thence through'battery B to ground G. The relay 96 energizes and disengages the springs 144 and 145, whereby the release magnet 80 is disconnected from the battery lead. The subscriber then rotates the dial, as described, for the second digit 2, thereby shunting or short-circulting the resistance coil 29 when the springs 18 and 26 engage. The vertical line relay 91 now operatively energizes and places the springs 93 and 94 in contact, whereby a C11- cuit is closed through the vertical magnet 78,.said circuit extending from ground G through the springs 94 and 93, through the magnet 78 to the battery lead 135, thence through battery B and to ground G. Each time that the vertical magnet 1s energlzed it operates to raise the shaft and shaft wipers one step at a time, unt1l the said wipers are carried two steps and-brought opposite the level in which are located the terminals of the trunk conductors 144 and 145 leading to the connector switch E. In the same manner described in connection with the selector C, when the switch shaft 86 of the selector D rises for the first step the cam 99 presses the cam springs 97 and 98 into contact, whereby an energizlng circuit is set up through the private magnet 81. This energizing circuit extends from ground Gr through the line relay springs 94 and 95, through the cam springs 97 and 98 to the private magnet 81, thence to the battery lead 135, and through battery B to ground G. When the rotary impulse tooth 25 separates the springs 19 and 30 the energizing circuit through the rotary line relay 92 is interrupted, and the said relay restores the springs 94 and. 95 to normal position, which breaks the energizing circuit through the private magnet 81 and the release relay 96. The private magnet upon de-energizing, permits the side switch to pass from first to second position. The release relay 96 being slow-acting, however, does not have time to fall back. When the side switch wiper 85. engages the grounded contact point 146 an energizing circuit is established through the rotary magment 79.

I This circuit extends from the grounded conbattery B and to ground G. The rotary magnet, by intermittent magnetization, operates to rotate the shaft and shaft wipers step by step and carry the wipers past the last busy trunk line, if any such are found, and as described in connection with the selector C. 1191141118 wiper 89 disengages from the last busy trunk line the energizing circuit (extending from the grounded pri-- vate contact to the private wiper 89, side switch wiper 84, contact point 147,-throughthe private magnet 81 to the battery lead 135, thence through battery B and to ground G) is broken, and thecside switch passes to third position, thus extending the subscribers line conductors 27 and'28to the conductors 144 and 145 which-lead to the connector switch E. Or. if the first trunk is idle, the rotary magnet trips the side switch to third position. as already explained. When the side switch passes to third position the side switch wiper 84 engages the grounded contact point 148, and a guarding potential is established at the private wiper 89 for protecting the seized trunk line from being molested by any other switch. In this selector, as in the'selector C, the energizing circuit through the rotary line relay '92 is maintained even after the side switch passes to third position; consequently, the circuit through the release relay 96 remains unlnterrupted. Since the subscribers line conductors 27 and 28 are new extended to the connector E. a circuit is established through the vertical line relay 108,, resistance coil 29 at the substation A, rotary line relay 109 of the connector E. It will be seen that in each instance when the'subscribers vertical and rotary line conductors 27 and-28 are extended to the next switch, a new energizing circuit is established through the line relays of the new'switch in multiple with the line relays of the old swltches, and through the substation reslstance coil 29. The subscribers conduc tors 27 and'28 having been extended to the connector E, the'rotary line relay 109 operates and places the springs 149 and 150 in contact. which closes a circuit through the releasing relay 113. This circuit ex: tends from ground G through the springs 149 and 150, through the winding'of the relay 113 to the battery lead 135, thence through battery B and to ground G. The relay 113 now operates to disengage the springs 151 and 152. The subscriber then operates the dial for the third digit 2, thereby energizing the vertical line relay 108 twice and de-energizing the rotary line re-' lay 109 once. The current for energizing the vertical line relay flows from ground G through the rotary line relay 109 to the trunk conductor 145. shaft wiper 88, side switch wiper 83, conductor 143, shaft wiper 36, rotary line conductor 28, springs 26 an d 18 to the vertical line conductor 27, side switch wiper 38, shaft wiper 35, conductor thence to the battery lead .135, and through battery B to ground G. Each time that the vertical. line relay is energized the line relay springs 153 and 149 are pressed into contact, thereby closing an energizing circuit through the vertical magnet 110. The circuit through the vertical magnet extends from ground G through the springs 149 and 153, side switch wiper 117, through the vertical magnet110 to the battery lead 135, thence through battery B and to ground G. Each time that the vertical magnet is energized it operates to raise the shaft and shaft wipers one step at a time, until the said wipers are carried two steps and brought opposite the level in which are located the terminals of the line #2220. When the rotary line relay 109 de-energizes, owing to the break or rotary impulse, the circuit through the private magnet 114 is broken. The private magnet now de-energizes and permits the side switch to pass to second position, thus placing the side switch wipers 115, 116, 117, 118 and 119 in connection with their respective contact points in second position. During the instant at which the rotary line relay 109 is de-energized, the releasing relay 113 is maintained in its operated position by the residual magnetism, in the same manner in which the relays and 96 of the selectors C and D are retained in their operated position during the rotary impulse. The last digit being naught the subscriber energizes the vertical line relay 108 ten times and the rotary line relay 109 onoe. However, when the line relay springs 149 and 153 engage, a circuit is closed through the rotary magnet 111 instead of through-the vertical mag-' net 110. -This energizing circuit extends from ground G through the springs 149 and 153. side switch wiper 117 to the rotary magnet 111. thence to the battery lead 135, and through battery B to ground G. Each time that the rotary magnet is energized rupted. The private magnet de-energizes and one of two results occurs, namely the release of the side switch from second to third position, or the so-called busy-release of the connector, which will be disclosed hereinafter. Suppose the former result to occur and the side switch to pass 'to third position, thus placing the side switch wipers 115, 116, 117, 118 and 119 in contact with their respective contact points in third position. Then when the-side switch passes to third position. the side switch wiper 119 engages the third-position contact point, which is grounded, and as a result a guarding potential is established at the private wiper 107 for protecting the called line. This potential extends from ground Gr through the side switch wiper 119 and to the private wiper 107 which engages the private contact of the called line. The engagement of the side switch wiper 119 and the third-position contact point also closes an energizing circuit through the cut-off relay 157 of thefirst-selector C, thereby removing the bridge/formed by the rotary and vertical line relays ,158 and 159 of the selector C across the called line. i The energizing circuit for the relay 157 may be traced from ground G to the private wiper 107, thence through the private normal conductor 156, switch shaft springs 158" and 159 to the bridge-cut-ofi'relay 157, thence to the battery lead 135, and through battery B to ground G. .Of course. when the relay 157 energizes it separates the springs-160 and 161 from the springs 162 and 163, thereby disconnecting the

relays

158 and 159 from the battery terminals.

To signal the called subscriber, the calling subscriber presses the signaling button 31, whereby the spring 32 is placed in contact with the contact point 33, as a result placing in direct connection the vertical and rotary line conductors 27 and 28. This now causes an increase of-current-fiowdhrough the vertical line relay 108 of the connector E. It will be remembered that the connector side switch has passed from second to third position, and that the side switch wiper 117 is in engagement with the contact point 164, thereby placing the verticalline relav 108 in control of the ringer relay 112, in the same manner in which the rotary magnet 111 came under the control of the vertical line relay 108 when the side switch passed from first to second position. Therefore, when the vertical line relay 108 presses the springs 149 and 153 into contact, the ringer relay 112 is energized by a flow of current from ground G through the springs 149 and 153, side switch wiper'117, contact point 164, ringer relay 112 to the batterv lead 135, and through battery B to ground G. The ringer relay, upon energizing, shifts the springs 165 and 166 from the springs 167 and 168 to the springs 169 and 170. This results in separating the calling subscribers line from the called subscribers line and bridging across the line of the latter, m

the terminals of the ringer generator I. The signaling current is, therefore, sent from the ringer generator I to the ringer generator sprin s 169 and 165, side switch wiper 115, sha t wiper 105, normal conductor 154, vertical line conductor 171,'condenser 172, rin or 173, condenser 172, s rings 174 and 1 5, rotary impulse springs 176 and 177 to the'rotary line conductor 178, normal conductor 155, shaft'wiper 106, side switch wiper 116, ringer relay springs 166 and 170, back to the generator I. As soon as the calling subscriber ceases to press the signaling button 31 the ringer relay 112 becomes de-energized and the sprlngs 165 and 166 resume-their normal position in contact with the springs 167 and 168. The subscriber A, in response to the signal, removes the receiver 179 from the switch-hook 180, thereby removing the ringer 173 from across his line and bridging instead the secondary circuit which includes the receiver 179, the

' secondarywinding 181 of the induction-coil 182, secondary springs 183 and 175, and rotary impulse springs 176 and 177. The 10- cal transmitter circuit is closed as soon as the

springs

185 and 186 engage in contact. The two substations #5000 and #2220 are now connected over the circuit shown by heavy lines in Figs. 1 and 2.

The release of the central oflice switching apparatus occurs when the calling subscriber restores the receiver 2 to the switch-hook 3,

thereby breaking the connectionbetween the springs 6 and 8 at the substation, whereby the energizing circuits through the rotar line relays 61, 81 and 109 of the switches are broken-that is, the line conductors 27 and 28 are disconnected. The rotary line relay 109 of the connector E, upon de-energization, permits the springs 149 and 150 to disengage, thereby breaking the circuit through the releasing relay 113. The releasing relay 113 in turn de-energizes and places in contact the springs 151 and 152, thereby closing an energizing circuit through the release magnet 120. This circuit extends from ground Gthrough the springs 151 and 152, release magnet 120, normal springs 129 and 130 to the batter lead 135, and through battery B to ground The release magnet 120 being thus supplied with current energizes and operates in the well known manner to restore the connector shaft and shaft wipers to their normal position's; and when the normal arm 126 presses the springs 129 and 130 out of contact the energizing circuit through the release magnet 120 is broken. When the energizingcir-v cuit through the rotary line relay 92 of the selector D is broken the springs 94 and 95 disengage, thereby breaking the energizing circuit through the release relayiw96. The release relay 96 of the selector D also deenergizes and places'the springs 144 and and 102, release ma 145 in contact, whereby a circuit is completed through the release magnet 80 ofthe selector D. This circuit extends from ground G through the normal springs 101 et 80, release relay sprin s 145 and 144 to the battery lead 135, and tirough battery B to ground G. The release magnet 80 in turn operates to release the second-selector D in the same manner in which the connector release ma et operated to release the connector E. en the shaft 86 returns to normal position, the normal armlOO carries the springs 101 and 1.02

out of engagement, whereby the circuit through the release magnet 80 is. broken, thus permitting the armature to return to normal position. In a similar manner, when the rotary line relay 61 of the selector C deenergizes the sprin s 136 and 137 disengage,

thereby breaking t e circuit through the release relay 65. The release rela selector C also (is-energizes an laces the springs 138 and 139 in contact, w ereby an energizing circuit is closed through the release magnet 66 of the selector C. This circuit extends from ground G" through the normal springs 74 and'73, release magnet 66, through the relay springs 139 and 138 to the battery lead 135, and through battery B to ground G. The release magnet 66 operates the same as the release magnet 80 of the selector D to restore the first-selector shaft 34 and side switch to normal position. When the normal arm 70 permits the normal springs 73, 74 and 71 to return to normal position the. energizing circuit through the release magnet 66 is broken.

The busy-release of," the connector E follows as a result of the de-energization of the rotary line relay 109 if the called line is busy. 4 If, when the private magnet 114 65 of the de-energizes for the last digit, the called line .subscriber (Fig. 1) presses the signaling button 31 and energizes the vertical line relay 108, the latter then operates the vertical magnet 110. The vertical magnet in turn raises the switch shaft so that the normal post 126 permits the switch shaft sprin 127 to engage the contact point 128, and a usysignaling current is sent to the calling subscribers station. The calling subscriber upon hearing the busy-signal will under-' stand that the desired line is in service and will release the switching apparatus over the been operated and established connection with the selector D,'and that it is desired to release the selector C and make a new call. In that event, when the subscriber restores the receiver 2 to the switch-hook 3 and separates the line conductors 27 and 28, the ener gizing circuit through the rotary line relays 61 and 92 is broken, and in turn the energizing circuit through the release relays 65 and 96 is broken. Similarly, the selector D and the connector E may be released before the switch has been fully operatedthat is, during the operation of the switches in establishing a connection, the central ofiice switches may, at the option of the calling subscriber, be released and fully, restored.

The vertical and rotary line relays of the selector switches and connector may be wound to any suitable resistance, but good results have been obtained when the coils were wound to a resistance of five hundred ohms. While I have shown the vertical line relays as consisting of heavier wire, therefore implying lower resistance, in order to illustrate the fact that they are not as sensitive as the rotary line relays, it is to be understood that I do not wish to be limited to this specific construction, but may use any suitable means for obtaining such operation of these relays. The release relays 65, 96 and 113 may be wound to a resistance of one thousand ohms, and the substation resistance coil 29 to a resistance of three-thousand ohms.

From the foregoing it will be seen that I provide a full automatic trunking system inwhich automatic trunking is accomplished on a percentage basis, and without the necessity of employing operating grounds at the subscribers substations. Furthermore, it will be seen that I provide means by which complete metallic line circuits are universally employed for controlling both the connecting and releasing operations of any series of automatic switches which may be found necessary for extending connection to it called subscribers line. The calling subscriber can, of course, release at any time, either before or after the called subscriber answers, and he thus has direct control over the release at any stage of the call by the mere act of hanging up his receiver. In other words, the mere act of opening the calling telephone line is sufiicient to release any switch or switches which may have been brought into service in extending connection to the called subscribers line. The retaining of a subscribers individual switch in an off-normal position is absolutely contingent upon the closure of the line circuit, and if the line be not thus closed the individual switch thereof cannot remain in an off-normal position. In

this way the liability of constant trouble and annoyance from off-normal switches is reduced considerably, and the work of supervising the exchange is materially simplified.

The transmitting of the call-signal" to thecalled subscriber is'initiated by simply shortcircuiting the calling telephone line, so that no ground circuitsare employed outside of the exchange for signaling purposes.

From what has already been said. will be seen that in the first selector the locking means for preventing the first selector G. from being released comprises a slow-acting relay which is adapted to energize as soon as the line relay 61 is energized. This rela 61, it will be seen, is energized as soon as t e subscriber closes his line circuit, with the result that the springs 136 and 137 are pressed into contact, therebv closing the said circuit through the magnet 65. The magnet.. 65, upon energizing, separates the springs" 138'and 139 in order to prevent the release magnet 66 from energizing as soon as the switch shaft 70 is raised from normal, at which time the s rings 74 and 7 3 come into. contact. The re ay 65 is made slow-acting so that it will not fall back when'the relay 61 de-energizes to permit the side switch to pass from one position to another.. With this arrangement it will be seen that the switch C is prevented from releasing until the line conductors 27 and 28 are separated for a sufiicient length of time to enable the relay 65 to de-energize. As soon as the relay 65 de-ener'gizes, the energizing circuit for the release magnet 66 is closed from ground Gr through the springs 74 'and 73, through the said magnet 66 and through the springs 139 and 138 to battery lead 135, and thence to battery. As soon as the release magnet 66 energizes, the shaft is left free to return to normal. and as 'soon. as it reaches normal the energizing circuit for the release magnet 66 is opened by that portion of the switch shaft marked 70 which, it will be seen, is adapted to separate the-springs 73 and 74;. With this arrangement it is obviousithat the switch is provided with an automatic releasethat is, a release which follows automatically if the switch is ofi'normal and if the line circuit is open. The locking means and automatic release at the selector D is exactly the same, the magnets'92, 96 and 80 corresponding to the magnets 61, 65 and 66. In the connector switch a similar arrangement is employed, the magnets 109, 113 and 120 being similar to the magnets 61, 6 5 and 66 of the selector 0. 7

What I claim as my invention is 1. An automatic telephone exchange systalking circuit and the 2. A telephone exchange system comprising a second-selector and a battery having one pole grounded, said selector provided with a vertical line relay permanently connected to non-grounded battery, and with a rotary line relay permanently connected to grounded "battery.

3. A telephone system comprising a battery having'one pole grounded, and a connector provided with a rotary line relay having one terminal thereof permanently connected to ground, and a vertical line relay having one terminal thereof, permanently connected to the non-grounded terminal of the battery.

4. A telephone system comprising a connector switch, a vertical relay permanently connected between one side of the talking circuit and the non-grounded terminal of a battery, and a rotary line relay permanently connected between one side of the grounded terminal of the battery.

5. A telephone system comprising a second-selector switch provided with a rotary line relay bridged permanently between ground and the main-talking circuit,

and a side-switch operating magnet controlled by said relay, substantially as set forth.

6. A telephone system comprising a second-selector, and vertical and rotary line relays for said selector, the vertical line relay being bridged between the nongrounded terminal of a battery and one side of the main talking circuit and the rotary line relay being bridged between ground and the other side of the main talking circuit.

7. An automatic telephone exchange system comprising a second-selector having a side switch, said .selector provided with means having vertical motion to select different operative levels depending on the number called, and rotary motion to connect with a line in the selected level, and a rotary line relay having one terminal thereof permanently connected to ground and the other to movable arm of the side switch.

8. A telephone exchange system comprising a second-selector provided with means having vertical motion to select different operative levels depending on the number called, and rotary motion to connect with a'line in the selected level, and a battery having one pole grounded, said selector also provided with a vertical line relay permanently. connected to non-grounded battery, and with a rotary line relay permanently connected to grounded battery.

9. A telephone system comprising a bat tery having one pole grounded, and a connector provided with means having vertical motion to select different operative levels depending on the number called, and rotary motion to connect with a line in'the selected level, and-provided also with a rotary linle relay'ha-ving one terminal thereof permanently connected to ground, and a vertical line relay having one terminal thereof permanently connected to the nongrounded terminal of the battery. I

-1 A telephone 1 exchange system comprising a switch shaft, a rotary line relay,

a private magnet, an energizing circuit for said private magnet controlled by said switch shaft and rotary line relay, said shaft provided with means by which it is raised and rotated, and means operated by the said shaft and relay for setting up the said circuit while the said rotary line relay is energized and the switch shaft out of normal vertical position but in normal rotary position, said energizing circuit when established adapted to be broken either by the rotation of the shaft, by the de-energizing of the rotary line relay, or by both.

11. A telephone system comprising a second-selector, a side switch for saidselector, a private magnet for controlling the side switch, a shaft, and a plurality of energizing circuits for the private magnet, one of said circuits controlled by the switch shaft and the other controlled by the side switch.'

112. A telephone system comprising a second-selector, a private magnet for said selector, a switch shaft, a private wiper, a side switch, the private magnet adapted to control the side switch, and a plurality of energizing circuits for said private magnet, one of said circuits controlled by the switch shaft, and another of said circuits said selector, a switch shaft, a private wiper, a side switch, the private magnet adapted'to control the side switch, and a plurality of energizingcircuits for the said private magnet, one of said, circuits controlled by the switch shaft, and another of said circuits controlled by the side switch and private wiper, substantially as set forth. 15. A telephone system comprising a bridging first-selector, a private magnet a private wiper, a

therein, a. switch shaft, side switch, the private magnet adapted to control the side switch, and a plurality of energizing circuits for the said private magnet, one of said circuits controlled by the switch shaft, and another of said circuits controlled by the private wiper, substantially as set forth.

16. A telephone system compr sing a se lector, a vertical line relay therein brldged between one sideof the main talking line and the non-grounded terminal of a battery, a rotary line relay bridged between the grounded terminal of the battery and the other side of the main talking line, and a bridge-cut-off relay adapted to disconnect the said vertical and rotary relays from the 1 battery.

17. A telephone system comprising a selector, a line terminating in said selector, a release magnet and a bridge-cut-ofl' relay in said selector, said relay having contacts for disconnecting both sides of said line from the battery, a switch shaft, and energizing circuits for said release magnet and said bridge-cut-ofi' relay under the control of the switch shaft, substantially as set forth.

18. An automatic telephone exchange system comprising a second-selector provided with a rotary line relay having a normally open energizing circuit, means for extending connection to the said selector, and means for closing said circuit at the instant that connection is completed to the said selector, said energizing circuit comprising the calling subscribers' line conductors, a substation high resistance coil, and a vertical line relay at the selector.

l9. A telephone system comprising a subscribers line, a subscribers station, a switch allotted to said line, means at the substation for controlling said switch over a metallic line circuit, a plurality of relays in series with said line for operating said switch, one of said relays connected to the nongrounded pole of battery, and the other connected to ground, and a resistance-com trolling means at the substation for operat ing said line relays.

20. A telephone system-comprising a subscribers telephone, a line for said telephone comprising two parallel metallic conductors, a switch for .said line, line relays for operating said switch in series with the line, and means whereby one or both of said relays may be energized over the two sides of the line in series.

21. A telephone system comprising a subscribers telephone line, a series of automatic switches, and means whereby the said switches are operated. to select other lines by varying the resistance of the line and by breaking the line.

22. A telephone system comprising a subscribers telephone, a series of automatic switches, and means whereby the said switches are selectively operated by varying the resistance of the line suddenly from a given normal resistance to a lower resistance.

23. In a telephone system, the combination with a telephone circuit extending between distant stations, ofan automatic selector switch at one of said stations and a sending device at the other of said stations adapted to control said switch over said circuit, said sending device comprising a resistance included in said circuit when the device is in normal position, and means governed'by said sending device in the op-. eration thereof for intermittently short circuiting said resistance.

24. In a telephone system, the combination with a telephone circuit extending between distant stations. of an automatic selector switch at one of said stations and a sending device at the other of said stations adapted to control said switch over said cir-- cuit, said sending device comprising a re sistance included in said circuit, and a switch independent of said sending device for intermittently short-circuiting said resistance. 1

25. In a telephone system, the combination with a telephone circuit, an automatic selector switch controlled over said circuit and a sending device for controlling said switch, said device comprising a resistance bridged across said circuit, and means independent of said sending device for intermittently short-circuiting said resistance.

26. In a telephone system, an automatic directively controlled selecting switch for use in connecting calling and called lines, a control circuit for said switch, a device for varying the resistance of said circuit between fixed limits to produce a series of current impulses in said circuit, and operating mechanism for said switch non-responsive to the closure of said circuit but responsive'to said impulses to advance said switch a variable amount depending on the number of impulses received.

27. In a telephone system, an automatic directively controlled selecting switch for use in connecting calling and called lines, a control circuit for said switch including the station on a calling line and two metallic conductors each extending from said station to said switch, said circuit having two different resistance values, a device for rapidly and intermittently changing the resistance from one value to the other a plurality of times, and step by step operat ing mechanism for said switch responsive to the resulting current changes in said circuit. i

28. In a telephone system, an automatic directively controlled selecting switch for use in connecting a calling and a called line, a control circuit for said switch established by the calling subscriber, said circuit having two different resistance values, a calling device at the station on the calling line operable to change the control circuit resistarice a plurality of times in accordance with a digit in the called number, thereby producing alike plurality of substantially equal momentary current impulses in said circuit and operating mechanism in said switch responsive to the said impulses.

29. ,In a telephone system,'a subscribers line comprising two metallic conductors extending from the substation to the exchange, a series of automatic switches, means at the station on said line for closing a switch control circuit including said two conductors, means for then operating said switches successively by intermittently varying the normal resistance of said circuit, and means in each switch except the last effective after the switch is operated for transferring the control circuit to the next switch in the series.

30. In a telephone system, a calling subscribers line, a series of automatic switches, a calling device at the station on the calling line operable after the receiver is removed to lower the normal resistance of the line a pluralityof times and then increase the same, and means for operating said switches responsive to resistance variations to connect said line with a called line.

31. In a telephone system, a calling subscribers line, an automatic switch for connecting said line with a called line, a calling device at the station on said line comprising a resistance normally included in the line circuit when the same is closed, said device also including means for producing directive series of impulses by cutting said resistance out of the line circuit a plurality of times, and operating means for said switch responsive to said impulses.

32. In a telephone system, a subscribers line, an automatic switch, a control circuit for said switch established when the receiver is removed at the station on said line, said.

switch being irresponsi ve to normal current in said circuit, and a calling device at the said station for intermittently decreasing the resistance of said circuit in accordance with a digit in a called number to operate said switch.

33. In a telephone system, a calling subscribers line, an automatic directively controlled switch, a closed control circuit for said switch including the said subscribers line, a calling device at the station on said line for producing a variable series of impulses in said circuit by decreasing the'normal resistance thereof a variable number of times, and relay mechanism in said switch for controlling its operation in accordance with the series of impulses produced.

34. In a telephone system, a calling sub- 'scribers line, an automatic directively controlled step bystep switch, a closed con trol circuit for said switch including said subscribers line, a calling device at the Sta tion on said line for producing: impulses of increased current in said'circuit, and a step: ping relay in said switchirresponsive to normal current in said circuit but responsive to said increased current impulses to operate said switch.

35. In a telephone'system, an automatic directively controlled switch, a closed control circuit for said switch including a source of current, a calling device for producing a variable series of increased current impulses in said circuit, and a relay in said switch irresponsive to normal current in said circuit but responsive to said increased current impulses to operate .said switch to an extent determined by the number of impulses received.

36. In a telephone system, an automatic switch having directive primary and automatic secondary movements, a closed control circuit for said switch, means for intermittently changing the resistance of said circuit, means for opening the circuit, means for operating said switch in its primary movement responsive to the resistance changes, and means for accomplishing'the change over from primary to secondary movement responsive to the opening of the circuit.

37. In a telephone system, an automatic switch having directive primary and second ary movements, a closed control circuit for said switch, means for intermittently altering the resistance of said circuit to produce variable series of impulses therein, means for opening the said circuit, means for operating said switch in its two movements responsive to two series of said impulses, and

means for accomplishing the change over from primary to secondary movement responsive to the opening of the said circuit.

38. In a telephone system, an automatic switch having directive primary and second ary movements for selecting a called line, a closed control circuit for-said switch, means for intermittently altering the resistance of said circuit to produce variableseries of impulses therein, means for opening the said circuit, means for operatin said switch in its two movements responsive to two series of said impulses, means for accomplishing the change over from primary to secondary movement responsive to the opening of the said circuit, and means for completing the connection to the. called line responsive. to another opening of the said circuit.

39. In a telephone system. the combination with a series of variably adjustable switching devices, of a circuit for controlling said devices, means for producing resistance changes in said circuit and means for o ening the same, means for adjusting said c evices responsive to resistance changes in the circuit, and means for switching said circuit to successive devices responsive to the opening of the circuit.

40. In a telephone system, the combination with two variably adjustable switching devices, of a control circuit including a resistance, means for closing a shunt around said resistance, means for opening said circuit, and two relays included in said circuit, one of said relaysbeing responsive each time the said shunt is closed to adjust the first of said devices, and the other relay being responsive when the circuit is opened to switch the circuit into association with the second of said devices.

41. In a telephone system, an automatic directively controlled selecting switch for use in connecting calling and called lines, a control circuit for said switch including two metallic conductors ea'ch extending from the station on a calling line to said switch, said circuit having two different resistance values, a device for changing the resistance from one value to the other a plurality of times, operating mechanism for said switch responsive to the resulting current changes in said circuit, means for changing the control circuit resistance to a still different value by opening the circuit, and releasing mechanism for said switch responsive when the circuit is opened.

42. In a telephone system, a subscribers line, a series of automatic switches, means at the station on said line for closing a switch control circuit, means for then operating said switches by intermittently decreasing the normal resistance of said circuit, means for opening said control circuit after the switches have been operated, and releasing mechanism for said switches responsive when the control circuit is opened.

43. In a telephone system, a calling subscribers line, an automatic switch for connecting said line with a called line, a calling device at the station on said line comprising a resistance normally included in the line circuit when the same is closed, said calling device also including means for producing directive series of impulses by cutting said resistance out of the line circuit a plurality of times, operating means for said switch responsive to said impulses, means for opening the line circuit after the said switch has been operated, and releasing mechanism in said switch responsive when the line circuit is opened.

44. In a telephone system, an automatic directively controlled switch, a closed control circuit for said switch including a source of current, a calling device for producing a. variable series of increased current impulses in said circuit, a relay in said switch irresponsive to normal current in said circuit the substation,

a second relay in said switch responsive to normal current in said circuit but irresponsiye to impulses therein for preventing the release of said switch while the same is in use.

45. In a telephone system, a subscribers line, an automatic directively movable switch for connecting Said line with a called line, two line relays for controlling the operation and release of said switch, one of said relays being a marginal relay and the other a nonmarginal relay, a control circuit including said line and the two relays in series, and a resistance at the stat-ion on said line for controlling the marginal relay.

46. In a telephone system, an automatic switch having a motor magnet and a release magnet, a control circuit for said switch, two relays and a battery included in said circuit in series, means controlled by one relay for actuating said motor magnet, and means controlled by the other relay for actuating said release magnet. I

47..In a telephone system, a subscribers line, an automatic directively movable switch for connecting said line with a called line, a control circuit for said switch, means at the station on said line for closing said circuit and for then transmitting impulses over said circuit, a relay in said circuit non-responsive to the closure of said circuit but responsive to said increased current imto said impulses to control the operation of said switch, a second relay in said circuit irresponsive to said impulses, and release mechanism said second relay.

48. In a telephone system, an automatic directively movable switch for use in connecting a calling and called line, a control circuit for said switch, means for producing a series of impulses in said circuit, a relay in said circuit responsive to impulses to control the operation of said switch, another relay in said circuit irresponsive to said impulses. a slow acting relay controlled by said second relay, and a release magnet for said switch controlled by said slow acting relay.

49. In a telephone system, atwo-conductor subscribers line insulated from ground at an automatic directively controllable switch, a line relay in said switch energized over the two sides of said line in series, means for controlling the operation of said switch over the subscribers line while maintaining said relay energized, and a release magnet in said switch controlled by said relay.

50. In a telephone system, a subscribers line. an automatic directively controllable switch, a line relay in said switch energized over the two sides of said line in series, means for said switch controlled by for controlling'the operation of said switch over the subscribers line while maintaining said relay energized, releasing mechanism for said switch, and a slow acting relay controlled by said line relay for controlling said release mechanism.

51. In a. telephone system, a subscribers line, an automatic directively controllable switch, a line relay in said switch energized over the two sides of said line. in series, means for controlling the operation of said switch over the subscribers line while maintaining said relay energized,means for opening the line to deenergize said relay, a release magnet, and means for energizing said release magnet a definite time interval after said relay has fallen back.

52. In a telephone system, an automatic switch having primary and secondary movement for connecting subscribers lines, a closed control circuit for said switch, means for operating said switch over said circuit without interrupting the same, means for producing long and short interruptions in said circuit, means in said switch for accomplishing the change over from primary to secondary movement responsive to a short interruption in said circuit, and means for releasing said switch responsive to a long interruption in said circuit.

53. la a telephone system, an automatic switch having primary and secondary movement for connecting subscribers lines, a closed control circuit for said switch, means for producing resistance changes in said circuit to operate said switch in its primary movement, means for producing long and short interruptions in said circuit, means in said switch for accomplishing the change over from primary to secondary movement responsive to a short interrupt-ion in said circuit,-and means for releasing said switch responsive to a long interruption in said circuit.

54. In a telephone system, a series of auto matic directively controlled switches for connecting a calling and a called line, a relay in each switch maintained energized throughout the duration of the connection to prevent its associated switch from releasing, parallel energizing circuits for said relays grounded only at the exchange and each including the two sides of the calling line in series, and release mechanism in each switch responsive whenever the associated relay is deenergized.

55. In a telephone system, a series of automatic directively controlled switches for establishing a two conductor metallic talking circuit, a relay in each switch maintained energized after thetalking circuit is established to prevent the release of its associated switch, an energizing circuit for each relay including. a portion of the talking circuit, and release mechanism in each switch contfolled solely by the associated relay and independent of the relays in any of the other switches.

slow acting relay controlling the release of said switch, another relay controlling the change over from primary to secondary movement, and a circuit for energizing said relays in parallel.

57. In a telephone system, an automatic switch having directive primary and auto matic secondary movements, a line relay for controlling said switch, a slow acting relay controlling the' release of said switch, a quick acting relay controlling the changeover from primary to secondary movement, and a circuit controlled by said line relay including said quick and slow relays in parallel. 7

58. In a telephone system, a calling subscribers line, a connector switch, a line relay in said switch energized over the two'sides of said line in series, means 'for operating said switch over the calling line to connect with a called line while maintaining said relay energized, a second relay energized by said first relay, a test wiper, means for deenergizing said relays after the called line is connected with, a release magnet, and a circuit for said release magnet closed in case the called line is busy, said circuit including said wiper and contacts of the said second relay.

59. In a telephone system, an automatic connector switch, means for controlling the said switch over the'two sides of a calling line in series to connect with and signal a called line, and means whereby the calling subscriber can control the duration of the signalling operation while maintaining'the connection established.

6O.v In a telephone system, an automatic connector switch, means for controlling the said switch over the two sides of a calling line in series to connect with and signal acalled line, a ringing relay foretiecting the signalling operation by projecting ringing current out over the called line, and subscriber operated means at the station onthe calling line for controlling said relay while the connection is maintained.

61. In a telephone system, an automatic nector including the two sides of the calling line in series, a resistance associated with said circuit, a push button operable by the calling subscriber to determine whethersaid resistance is included in said circuit or not, and a ringing relay in said connector re sponsive when the said push button is actu ated to signal the called subscriber.

63. In a telephone system, a subscribers line, an automatic step by step rotary trunking switch individual to said line, two controlling line relays for said switch normally connected to opposite poles of the exchange battery, a circuit for energizing said relays over the two sides of said line in series when the subscriber makes a call, and a cut-oil? relay for disconnecting said relays from the battery when the line is called.

64. In a telephone system, a subscribers line, an automatic step by step rotary trunking switch individual to said line, two controlling line relays for said switch, a circuit for said relays including the two relays in series and the two sides of said line in series, and means at the station on said line for energizing both of said relays or only one of said relays over said circuit at the option of the subscriber.

($5. In a telephone system, a subscribers line, an automatic step by step rotary trunking switch individual to said line, two controlling line relays for said switch, a circuit for said relays including the two relays in series and the two sides of said line in series, means at the station on said line for energizing both of said relays or only one of said relays over said circuit at the option of the subscriber, and a-cut-ofi relay for disconnecting 'said relays when the line is called.

66. In a telephone system, an automatic switch having primary and secondary movement, a switch control circuit, means vfor controlling the operation and release of said switch over said circuit, and relay mechanism operated through contact springs closed by the switch shaft at the beginning of the primary movement of said switch to permit the initiation of the secondary movement after the primary movement is completed.-

67. In a telephone system, an automatic switch having primary and secondary movement, a control circuit for said switch includ-- ing the two sides of a subscribers line in series, a line relay in said circuit and controlled thereover ,for controlling the primary movement, another relay for controlling the secondary movement, oil normal springs closed at the beginning of'the primary movement, and a circuit for said second relay including said off normal springs. Signed by meat Chicago, Cook County, Illinois, this 12th day of April, 1907.

EDWARD A. MELLINGER. lVitnesses EDWARD D. FALES, ARTHUR B. SPERRY.