US1289504A

US1289504A - Automatic telephone trunking system.

Info

Publication number: US1289504A
Application number: US6027215A
Authority: US
Inventors: Anders M Malmberg
Original assignee: Automatic Electric Co
Current assignee: Automatic Electric Co
Priority date: 1915-11-08
Filing date: 1915-11-08
Publication date: 1918-12-31
Anticipated expiration: 1935-12-31

Description

' A. M. MALMBERG. AUTOMATIC TELEPHONE TRUNKING SYSTEM.- APPLICATION F| LED NOV. 8. 191's.

Patented Dec.v 31, 1918.

3 SHEETS-SHEET I.

A. M. MALMBERG. AUTOMATIC TELEPHONE TRUNKING SYSTEM.

l APPLICATION men NOV. s, 1915. v 1,289,504. Patented Dec. 31,1918.

3 SHEETS-SHEET 2 r A. M. MALMBERGL' AUTOMATIC TELEPHONE TRUNKING SYSTEM. I -APPL|CATION FILED NOV- 8, 19l5- 1,2 9,504, Patented Dec. 31,1918.

3 SHEETS-SHEET 3- UNITED STATES PATENT OFFICE.

ANDERS M. MALMIBERG. OF CHICAGO, ILLINOIS, ASSIGNOR T0 AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE TRUNKING SYSTEM.

Specification of Letters Patent.

Patented Dec. 31, 1918.

Application filed November 8, 1915. Serial No. 60,272.

I is a specification.

My invention relates to automatic telephone trunkmg systems and more particularly to those automatlc trunking systems in which numerical and non-numerical switches are employed and in which, for example, a. non-numerical switch is used to extend a connection from a subscribers line to a numerical trunking switch.

Among the objects of my invention are the followingz to provide, in a system of the above character, means for extending a connection through the medium of a non-numerical switch to a numerical switch, which latter is then employed in locating the desired line, whereupon another non-numerical switch is brought into use for finding the first non-numerical switch, whereby the connection between the calling and'called lines may be established over a more direct path directly from one non-numerical'switch to another to the exclusion of the numerical switch; thereby providing a connection from a calling to a called line exclusively through non-numerical switches.

Another object of my invention is to provide means for releasing the numerical switch after it has performed its function in establishing a connectiOn, thereby making it accessible to other calling lines.

Another object of my invention is to pro- I ride separate holding circuits for the calling and called non-numerical switches, these holding circuits being under the control of the calling and called subscribers, respeclively, thereby permitting either party to a connection to terminate it at will.

Another object of my invention is the provision of means whereby the non-numerical switch'of the called line may test for and lo cate the nonnumerical switch of the calling line without interference from other lines which may be calling at the same time, such means consisting of an individual battery for each trunk. Another object of my invention is to provide certain details of improvement in a system of the above character tending to intraced through all the drawings in order.-

crease the efficiency and serviceability of an automatic trunking ystem.

To accomplish the foregoing and other useful ends my invention comprises the means hereinafter set forth and claimed.

In the drawings Figures 1 and 2 show a complete connection between a calling substation A and a called sub-station A in an automatic system embodying the principles of my invention, and Fig. 3 shows several of the numerical witches or connectors, one of which has been used temporarily to assist in establishing the connection. To fully com-.

prehend the circuits illustrated herein the drawings should. be placed side by side in order andwith the lines at the sides thereof in alinement.

Referring to Fig. 1, at A and A there are represented two substation to the line conductors of which there are allotted at the central oiiice individual or line switches C and C. At D there is shown a master switch for controlling the switches C and C and similar switches individual to other substations. Referring now to Fig. 2, at E and E are shown non-numerical rotary switches which are accessible to the line switches C and C. In connection with each switch E and E is shown a group of relays whose functions will be described. In Fig. 3, at F and F are shown connector switches each of which contains terminals of all the lines entering theoflice. At B is shown a battery the undergrounded pole of which may be The substation shown herein may be of any suitable or approved type and comprises the usual receiver '2, transmitter 3, ringer 4, and condenser Being an automatic substation, it is also provided .with an .impulse transmitter or calling device which is rcpre-, sented herein by a pair of impulse springs 6 and 7 and an impulse wheel 8, which latter is assumed to be controlled by a finger hole dial (not shown) in such a manner that the impulse springs (i and 7 may be momentarily separated a number of times corresponding to each digit of the called line.

The line switch C which is associated with the particular type Newforth. This line switch comprises among other details a plunger (not shown) attached to the end of a so called plunger arm Hwhich controlled by the magnet 13. The magnet 13 comprises two windings, the pull-in windingl7 and the'holding winding 16. The winding 17 operates both the plunger arm Hand the cut-off armature 15, but the winding 16 is only strong enough to hold the plungerarm and cut-ofl' armature in an operated position after they have been operated by the winding 17.

The circuit of the acting, z'. e., it retains its armature for an instant after the energizing'circuit is broken. When the plunger arm 14 is operated the plunger is forced intoa bank of springs, forcing the

springs

25, 26, 27, 28 into engagement with the

contacts

29, 30, 31, 32 respectively; Although only one set 0 springs and contacts (25 to 32) is shown, it is to be understood that each line switch is provided with a plurality of such sets, each set forming the'terminal of a trunk line extending 'to'arotary switch E. Each trunk line is connected in multiple to the corre- .-sponding springs of all the switches controlled by the master switch D.

The master switch D is of the same general type as that disclosed in British patent to R. \V. James, No. 26,301 of 1906 above referred to; being, however, more nearly of disclosed in British patent to T. G. Martin, No. 1410 of 1910. The function of the master switch, as is well known, is to maintain the plungers of all th idle line switches in position before an idle trunk line.

The rotary switch E may be of any suitable construction in so far as its mechanical details are concerned, it being only required that the wipers 110, 111, 112, 113 and their connections be so constructed as to permit of a forward movement in one direction only. As shown herein diagrammatically, the ratchet wheel 101 is adapted to be actuated by the motor magnet 100 through the medium of its armature 102 and pawl 103. At each ,energization of the motor magnet 100 it interruptsits own circuit a rapid vibrationot' its armature, which results in the rotation .of the ratchetlOl and causes the wipers (110113) mountedthere- .on to traverse the contact sets, such as (114-117) in the bank. The bank contact sets, such as (114-117) shown herein as arranged in a straight line for convenience in drawing, are preferably arranged in a complete circle with the wipers (110113) carried by the ratchet 101 pivotally mounted in the center thereof. The bank contacts of all the rotary switches are in multiple and form terminals of two difierent kinds of trunks. -The contacts (114-417) and simipull-in \i'inding is con- .trolled by the line relay 12 which is slow I it to operate in thereby causing "of Fig. 2 the first set of multiple contacts (11+117 is'shown connected to a trunk leading to a connector F. The next two sets of contacts are similar to contact set (214217) and are multiple terminals of trunk lines, leading to and E. The fourth set of contacts is similar to contact set (111-117) and is the multiple terminal of a trunk line leading to a connector F. While I have shown every third set of contacts as being the multiple terminal of a connector trunk, the rest being multiple terminals of rotary switch trunks, I do not wish to limit myself to any definite proportion between the two kindsof trunks. In actual practice it has been sufficient to make every sixth set of multiple contacts the terminal of a connector trunk.

Since the rotary switch must be capable of testing trunksof-either kind at the proper time two test wipers 110 and 111 are provided. When it is required that an idle connector trunk be selected the test wiper and similar sets arerotary switches E 110 is madeeifective, but while testing for a for an idle connector trunk, the top contact 214 of all rotary switch trunksis permanently connected to the ground.

The connector switch F is of the same general type and closed in U. S I grantedMarch 13, 1906.,to Keith, Erickson and Erickson, the circuits and mechanism however, being modified somewhat to enable accordance with my invention. It has the usual magnets for raising and rotating the shaft and for effecting the- The private magnet.

release of the same. 123 controls the movement of the side switch wipers 157 and 158 in the well known manner. A busy test relay 128 is provided for connecting one side of the trunk with the induction coil T and busy machine H at the proper time. The battery B is permanently associated withthe connector 1* and the battery B is permanently associated with the connector- 1 in fact every connector such as F or F has its individual battery such as B or B The bank contacts of all the connectors are in multiple and form terminals of normal wires which extend to the incoming negative line and holding winding of the line switches C, C. etc., and it is understood that each incoming line to the exchange is represented by a set of multiple contacts in the connector banks.

Having given a general description of the apparatus I will now describe in detail the construction as that dis-v Letters Patent No. 815,176,

:b w the subscriber at A, by taking off his reobiver will be automatically connected wa an idle rotary switch E which will operate automatically to connect with an idle connector F. It will furthermore be shown how the subscriber at A, by sendingtwo v as follows: ground at G, contact 22, pull-in -winding 17, contact 23 to battery 13: Upon series of impulses to the connector F, can

place its wipers upon the normal contacts belonging to the line switch C associated with the substationA', upon which the line switch C is operated to make connection with an idle rotary switch E which rotates automatically until its wipers reach the multiple contacts belonging to the rotary switch E, whereupon its movement is arrested and a connection is completed from substation A to substation A through line switch C, rotary switch E, rotary switch E and line switch C. It will furthermore be shown how, on the completion of this connection,

the connector F is released and made accessible to other calling lines. It will further-- more be shown how either party to a connection, such as the subscriber at A or the subscriber at A, can effect the disconnection of his individual line switch and the rotary switch with which it is temporarily connected, independently of the other party.

When the subscriber at A, in making the call, raises the receiver from -the hook, a circuit is completed for the line relay 12 of the line switch C, which circuit extends from ground at G through normally'closed contact springs 21 and 20, and over line 11 to substation A, whence it returns over line 10, through normally closed contact springs 18 and 19, and winding of relay 12 to battery B. Upon the energization of the line relay a circuit for the pull-in winding 17 is closed the energization of the pull-inwinding the plunger arm 14 and the armature 15 are attracted, the former, by means of its plunger, causing the springs (25-28) to make connection, respectively, with thccontacts 29-32; and the latter breaking the connection of the springs 18 and 20 with the springs 19 and 21, respectively. 7

'By the engagement of springs 25 and 28 with contacts 29 and 32, respectively, a circuit is closed for the relay 35 and the line relay 41 of the switch E as follows: ground at G, winding 39 of relay 35, contact springs 66 and 67, contact springs 47 and 48. contact 32, springs 28, previously traced circuit through subscribers loop, spring 25, contact 29, contact springs 51 and 50, contact springs 83 and 84. contact springs 57 and and winding of relay 41 to battery B.

\Vhen relay 35 attracts its armature it closes a circuit for the slow acting relay- 37, which circuit extends from ground at G", through contact springs 87 and 88, and

winding of relay 37' to battery B. -Upon the energization of relay 37'; a holding C11- is established over the following path: ground at G, contact springs 92, 91 and 89, contact 30, spring 26, and holding winding 16 to battery B. lt'is understood that the line relay 12 of the line switch 0 is slow acting in order that the holding circuit just described may be established before it retracts its armature and opens the contact 22. A branch of the holding circuit extends from the junction of the holding winding and spring 26 to the multiple test contact of line switch C in the connector banks where it makes the line busy to incoming calls. As a further result of the energization of relay 37, test wiper 111 isdisconnected (contact springs 90 and 91), test wiper 110 is connected up (contact springs 95 and 96), and

the contact springs 93 and 94 included in a .tact springs 107 and 106, and winding of motor magnet 100 to'battery B. The lat-' ter circuit is as follows; wiper 110, contact springs 95 and 96, and contact springs 74 and 73, to the lower terminal of relay 40, where it joins the previously described circuit of that relay; Now, if the test wiper 110 is resting upon an idle or ungrounded test contact the relay'40 energizes at once from ground at G and the wipers are not rotated because the winding of the relay 40 is of too high resistance to permit the motor magnet 100 to effectually energize in series with'it. If, however, the wiper 110 is resting upon a grounded test contact the relay 4.0 will be short circuitcd and the motor magnet 100, having now a direct circuit from ground, will be energized and attracting its armature, will rotate the wipers 110113 one step. Since the motor magnet interrupts its own circuit at the springs 10.6 and 107, it continues to rotate the wipers until the wiper 110 reaches an nu grounded test contact, when the. rotation necessarily ceases and relay 40 energizes over its previously described circuit. Relay 40, upon attracting its armature, closes a locking circuit for itself at the contactsprings 76 and 77 which circuit is the same as the one already completed by the line relay 41. As a further result ofthe encrgization of relay 40the circuit of the line relay 41 is broken at contact springs 83 and 84, and there is substituted for relay 41 the line relay 130 of the connector'F, the circuit being as follows: ground at G, winding 39 cuit for the winding 16 of the line switch G in the circuit of relay 43, and the closure of contact springs 80 and 81. The latter springs extend the negative pole of battery B to the multiple test contacts of rotary switch E in-the banks of all the rotary switches, the circuit being as follows: negative pole of battery B, contact 116, wiper 112, contact springs 80'and 81, contact springs 60 and 59, contact springs 62 and 61 to test contact 215 and multiple contacts.

The completion of this circuit to the other pole of battery B will be described later. Returning now to the line ,relay 130 of connector F, this relay. upon energizing, completes a circuit for the slow acting relay 129 as follows: ground at G, contactsprings 132 and 133, and winding of relay 129 to battery B. Upon energizing, relay 129 closes contact springs'134 and 135 and thereby places ground potential upon the multiple test contacts of connector F, in the rotary switch banks whereby connector F is made busy to other rotary switches, such as E. Relay 129 also opens its contact springs 137and 133 which are included in the circuit of the release magnet 124, and closes its contact springs 136 and 137 thus preparing a circuit for the vertical magnet 126-.

The foregoing operations have all oc curred in response to the removal of the re ceivcr at the substation A. The subscriber at substation A may now operate his dial in accordance with the first digit of the number he wants, thereby breaking the circuit of the line relay 130 a corresponding number of times. At each dcenergization of the line relay 130 a current impulse is sent through the vertical magnet 126 thereby raising the wipers 160 and 161 until they stand opposite a row of contacts in which are located the normal contacts of the line switch C belonging to the substation A. The circuit of the vertical magnet 126 as follows: ground at (i contact springs 132 and 131. contact springs 137 and 136, contacts springs 142 and 141, winding of slow acting relay 127, side switch wiper .157 in its first position, winding of vertical magnet 126'to battery B. The relay 127 is energized in ser es with the vertical magnet but, being slow acting, it retains itsarmature during a series of in'ipulses. By closing contact springs 143 and 1414, relay 127 completes a circuit for the private magnet 123 which circuit is immediately broken at the end of the series of impulses. The resultant energization and deenergization of the private its second position) sends impulses to the rotary magnet .125. The rotary magnet, by alternately attracting and releasing its armature, rotates the wipers 160 and 161 a number of steps corresponding to the last digit of the number of the desired line until, at the end of the series of impulses, the wipers will be brought to rest upon the

normal contacts

162 and 163 of that line. During the rotary impulses the relay 127 keeps the energizing circuit of the private magnet 123 closed as before. At the end of the series of impulses the private magnet deelnergizes (assuming the called line to be idle) and allows the side switch wipers to. move to their third position.

A number of circuits are now closed over the normal wires extending to line switch C. The first of these circuits to eratirely effective is a circuit for the line relay 12 of the line switch C. It may be traced as follows: ground at G contact springs 151 and 152, side switch wiper 158 in its third position, wiper 160, contact 162, contact springs 18 and 19, winding of line relay 12 to battery B. Line relay 12 attracts its armature and by closing contact 22 completes the circuit of the pull-in winding- 17 of the line switch C. Upon the energization of the pull-in winding 17, the plunger arm 14 and the cut-off armature 15 are attracted, the former, by means of its plunger, causing the springs 25, 26, 27, and to make connection, respec tively, withcontacts 29, 30, 31, and 32'; and the latter separating the

springs

13 and 26", respectively, from the springs 19 and 21. A holding circuit for the holding winding 16 has already been completed over the other normal wire and may be traced as foilows: ground at G resistance 1, contact springs 1 19 and 118, contact springs 1+6 and 115, wiper 161, contact 163, and holding winding 16' to battery 13.

The engagement of the spring 25 with the contact 29' conuiletcs a circuit for the line relay 41 of the rotary switch E, which circuit may be traced as follows: ground at G contact springs 151 and 152, side switch wiper 158 n its third position, wiper 160, contact 162, spring 25, contact 29, contact springs and 50, cbntact' springs 83 and 84. contact springs 57 and 58, and winding of relay 41 to battery. A branch of the above circuit may be traced from the juncbecome opare cop tion of the contact spring 58 and the Winding of the relay =11 by way of contact springs 97' and 96', to contact spring '71. Upon the energization of the line relay 11 this branch circuit is extended as follows: from contact spring 7-1 to contact spring 73', thence .via contact springs 107' and 106', and winding of motor magnet 100' to battery B.

The line relay 41' also upon energizing, closes a circuit for the relay 40', which may be traced as a branch ofthe previously described holding circuit of winding 16 of line switch C. The branch circuit extends from contact spring 26 by way of contact 30, contact springs 76' and 77, contact springs 70 and 69', winding of relay 40, contact springs 107 and 106, and winding of motor magnet 100 to battery B. Relay 40', being short circuited does not energize at this time. Motor magnet 100, however, is energized and since it interrupts its own circuit at contact springs 106 and 107 it starts rotating the wipers (110"-113) in search of the multiple contacts of rotary switch E.

In connection with the rotary switches E and E it is to be understood that the wipers of these switches have no normal position but rest at all times upon the last trunk used. In the foregoing description it has been assumed that rotation Was-necessary in order to reach the set of contacts of the desired trunk, but it is evident that at times the wipers will already be resting on an idle connector trunk or the desired rotary switch trunk as the case may be, in which event it will be readily understood that no rotation takes place, the test circuit taking ett'cct in'nnediately.

We will now return to the connector F and trace a circuit from the positive pole of battery B. \Ve have already traced a circuit from thenegative pole of battery l3 to the contact 116 of rotary switch I) and thence to contact 215 in the bank of rotary switch 15. It: is evident then that the positive pole of battery 13' must be extended to the test wiper 111 of rotary switch E, this wiper being adapted to engage the multiple test contacts such as contact 215 during its rotation. This extension may be traced as follows: positive pole of battery ll, oft-normal contacts 156 aml 155 (closed at first vertical step of connector 1 wind ing 121 of relay 120, contact springs 145) and l-tti,contact springs HG aml l-l5, wiper 161, contact 1623, contact spring 26, contact 50. contact springs 76 and .75, contact springs 91 and 90, and contact springs 101.

and 105' to test wiper 111'. it follows therefore, that when the wipers of rotary switch It reach the. set of multiple contacts 21-t2l7. and the springs 104' and 105 close upon the return of armature. 102, the circuit ot battery B will be completed by the engagement of the-test wiper 111 with the test contact 215. This circuit includes the 'winding 121 of relay 120 which relay ener- 158 in third position. thence over path already traced via wiper 160 and through winding of line relay 41' to battery. The winding 122 of relay 120 is of suflicient resistance to prevent the effective energization of motor magnet 100. A further result of the separation of the springs 151 and 152 is the removal of the short circuit from relay 40' which thereupon energizes and attracts its armature, causing circuit changes which will be explained hereafter. In addition to separating contact springs 151 and 152 relay 120 closes contact springs 150 and 151 thereby causing the energization of the. release magnet 124 over the following circuit: ground at G contact springs 151 and 150, oft normal springs 153 and .154 (closed at first vertical step of connector F) and windingot release magnet 124 to battery B. The energization of the release magnet results in the withdrawal of the holding pawls from the shaft. allowing it to return to normal; and the return to first position of side switch wipers 157 and 15%, thereby breaking the circuit of line relay 41 and also the holding circuit of line switch The .line relay 11' now retracts its armature but relay 40 and the holding winding 16 of line switch remain energized over a new holding circuit which may be traced as fol lows: ground at (i (switch E), contact springs92. 91 and S9. winding of relay 42, lower winding -16 of relay 36, contact springs 62 and (31. multiple test contact 215, wiper 111'. contact springs 105' and 104'. contact springs 90 and 91 to contact springs 75, To. and 77. where. the-circuit divides. one branch extending by way of contact spring 77. contact springs 70' and 69', winding of relay 10 contact springs 107"and 106. and winding of magnet- 100' to battery B; and the other branch ext uiding by way of contact spring 76. ;onta ct 30.. spring 26', and holding \vindinfi 'l tt. to battery B.

(urrent flowing .in. the. above described holding circuit is sutticieht to energize relays 42 and 36 in series, both relays attracting their a rmatures. Relay 42 opens the circuit of relay 40 which, upon deenergizing. disconnects the wipers 112 and 113 and prepares a circuit for relay 43 by closing contact springs 85 and 86. Relay 36 locks it self over a path extending from ground at G through contact springs 92, 91 and 89, winding of relay 12, windings 46 and 45 of relay 36 in series, and contact springs 54: and

53 to battery B. Relay 36 also causes other.

circuit changes as follows: By opening contact springs 59 and 60, ground through winding of relay-12 and winding 46 of relay 36 is removed from the left hand talking conductor of switch tact springs 57 and 58 the original energizing circuit of relay 11 is broken; and finally by closing contact springs 55 and 56 a circuit through the winding 38 of relay is completedas follows: ground at G, winding 39 of relay 35, contact. springs 66 and 67, contact springs 47 and *8, contact 32, spring 28, subscribers loop, spring 25, contact 29, contact springs 51 and 50, contact springs 56 and 55, contact springs 68 and 64, and winding 38 of relay to battery B. The above circuit serves to supply talking battery to substation A and to maintain relay. 35 in an energized condition during conversation.

I Will now'trace an energizing circuit for the relay 36 of switch E as follows: ground at G contact springs 92, 91'and 89, winding of relay 42, winding -16 of relay 36, contact springs 62. and 61, multiple contact 215, wiper 111', contact springs 105 and 10%, contact springs 90' and 91', contact springs 75 and 76, winding of relay 42, winding 16 of relay 36, contact sprin 59 and 60', contact springs 81' and 80, wiper 112', contact 216, contact springs 68 and 64, and winding 38 of relay 35 to battery B. Upon energizing, relay 36 locks itself overthe following circuit: ground at G, contact springs 92, 91 and 89, winding of relay 42, winding 46 of relay 36, contact springs 62 and 61, multiple contact 215, wiper 111, contact springs 105' and 104 contactsprings 90 and 91', contact springs 75' and 76 windin of rela 42'. windin s 46' and 45 of relay 36 in series, and contact springs 54 and 53', to battery B. Immediately after completing the above locking circuit by closing contact springs 53' and 54, relay 36' breaks its original energizing circuit by separating contact springs 59' and 60'. The flow of'current in the original energizing circuit is but momentary and relay 42', being a sluggish relay. does not have time to attraetits armature before this circuit is broken. Furthermore relay 42 has a marginal adjustment such that it will not attract its armature when in series with winding 45 but will do so when in series with two windings in parallel such as winding of. relay 40 and holding winding 16. It

E; by separating con-' switches E and E are the same. It follows therefore that relay 42 will not be effectively energized at this time.

As a further result of its energization, rela-y 36' closes contact springs 55' and 56, thereby bridging the double wound relay 35' across the called line extending to substation A. This circuit is similar to one which has been described in the case of relay 35 and need not be gone over again. v

Returning nowto relay 40', this relay upon energizing, closes contact springs 82' and 83, and 80' and 81', thereby finally completing the'connection between the calling and called lines, as will be referred to again hereafter. Also, by closing contact springs 78 and 79 a circuit is completed for the ringing relay 44 which may be traced over the following path: ground at G", interrupter I, contact springs 94' and 93. contact springs 78' and 7 9', and winding of ringing relay 44 to battery B. The ringing relay is thereupon energized intermittently and operates to project ringing current from the generator Gen. out over. the called line in order to actuate the bell at the substation A. 'When the subscriber at substation A', in response to the ringing of his bell, removes his receiver from the hook, the ringing relay being temporarily inactive, the circuit of relay 35' is completed and this relay energizes, feeding talking battery to the substation A and closinga circuit for the slow acting relay 37 as follows: ground at (1. contact springs 87' and 88', and winding of relay 37 to battery B. Upon energizing. relay 37 opens the circuit of the ringing relay at contacts 93' and 94 and also opens the holding circuit of relay 40' and holding winding 16' by separating contact springs 90' and 91'. At the same time a new holding circuit is established as follows: ground at G, contacts 92, 91- and 89', contact 30, spring 26', holding winding 16 to battery. A branch of this circuit may be traced from contact spring 89' to one terminal of coil -12, where it divides, one branclr going through winding of relay 42', windings -16 and 45' in series, and contact springs 54' and 53 to batteryl while the other branch may be traced through contact springs 76' and 77 contact springs and 69', and winding of relay 10 contact springs 107 and 106, and winding of magnet 100 to battery B. Referring now to relay 42 in switch E. it is evident that since the holding circuit extending to switch E has been broken by relay 37' the only current now flowing in relay 42 will be the current supplied to the windings 46 and 45 of relay 36 in series. It has been explained in the case ing a circuit for relay 43 as follows: ground at G contact springs 92, 91 and 89, contact springs 72 and 71, contact springs 85 and 86,

Winding of relay 43, contact springs 54L and 53 to battery B. -Upon the energization of 5 relay-l3 the contact springs 61 and 62 are separated thereby permanently breaking the connection between the holding circuits of switches E and E. Also the line extending to substation A is reversed by breaking the connection of springs (S-l and 66, with springs 68 and 67, respectively, and by causing springs (53 and 65 to engage springs 64 and 66 respectively.

A complete talking connection hasnow been established .between substation A and 'substation A. This circuit is indicated by heavy lines in the drawings and is so apparent that further details will be unnecessary,

It will readily be seen also that since the substations A and A, are furnished with talking battery from the relays 35 and 35 respectively, and moreover, since the holding circuits as described are independent of each other, a subscriber at either substation may now disconnect the switches associated with his line at will. For example, should the subscriber at substation A hang his receiver up the circuit of relay 35 will be broken and relay will dei nergizc thereby breaking the circuit of relay 37'.

zation of relay 37 ground will be removed from the holding circuit whereupon all rcla-ys of rotayy switch E will dei ncrgize and 35 also the holding winding 16' of line switch will deenergizc allowing the plunger to be withdrawn from the bank. The substation A" is now ready to be called again or to originate a call.

I will now describe briefly the case where the called line is busy; Referring to connector I the test contact such as contact 163, associated with a busy line will have ground potential upon it as has already been mentioued. When, therefore. at the end of the last series of impulses the wiper 161 is brought torest upon the test contact of a busy line and the relay IQT dei nergizes. a

circuit is established as follows: ground on test contact, wiper Hi1. contact springs 145 and H6. contact springs 143 and 117, winding oi test relay 1'28. and winding of private magnet 1:23 to battery B. As a result of this circuit the private. magnet remains energized thereby preventing the sideswitch wipers from moving to their third position.

Also test relay 128 is energized and connects a winding of the induction coil T with one side ot' the line extending to the substation A. In this way a distinctive tone from the busy machine ll is thrown upon the calling line and indicates to the subscriber at substation that the line called is busy. lle will then hang up his receiverbreaking '65 the circuit of relays 130 and 35. I pon the Upon the deenergide'nergization of relay 130 and consequent deenergization of relay 129 a circuit is closed for the release magnet 124 as follows:

ground at G con-tact springs 132 and. 131,

contact springs 137 and 138, off normal springs 153 and 154,-and winding of release magnet 124 to battery B. The energization of the release magnet serves to withdraw the retaining pawls from the shaft and allow its return to normal and also restores the side switch levers to their first position. The

deenergization of relay 35 and consequent deenergization of relay 3? causes ground to be removed from the holding circuit of relay IO and hotlding winding 16 of line switch C. Relay 40 thereupon deenergizes and also holding winding 16 deenergizes and allows the plunger to be withdrawn'from the bank. 'All the apparatus is now in its original condition and ready for use.

It will be seen from the foregoing that I .have provided an efiicient automatic telephone trunking system in' which, after a connection has been built up between a calling and called line through the medium of automatic switches, a talking circuit is established between the said lines over a more direct path, thereby making it possible to release certain apparatus utilized in the original connection and make it accessible for use in other connections.

'hile I have described in the foregoing a certain specific embodiment of my invention, I do not wish to be held strictly to the form shown herein, for various adaptations will no doubt suggest themselves to persons skilled in the art. I desire, therefore, to include and have protected by Letters Patent all forms and modifications of my invention which may come 'withinthe scope of the appended claims.

What I claim as. my invention is:

1. In a trunking system, a conductor, a first switch and a second switch, said first switch for seizing one end of said conductor and for extending it into association with said second switcln'a third switch associated with said conductor. means for operating said third "switch to find said second switch, and means for then operating said second switch to find said conductor.

2. In a trunking system, a conductor, a first switch and a second switch. said first switch for seizing one end of said conductor aud tor extending it into association with said second switch. a third switch associated with said conductor, means for operating said third switch to find said second, switch, meansfor then operating said second switch to find said conductor, means for es tablishing a circuit over said conductor comprising a battery and a magnet energized thereby; and means controlled by said magnet for controlling said second switch.

In a trunking system, a conductor, a. 130

first switch and a second switch, said first switch for seizing one end of said conductor and for extending it into association with 1 said second switch, a third switch associatedwith said conductor, means for operating said third switch to find said second switch and to extend the other end of said conductor thereto, means for then operating said a second switch to find the first end of said conductor, whereby a circuit is established.

- over said conductor,a battery in said circuit and a magnet energized thereby, means con- I first switch and a second 'switcln'said first trolled by said magnet for controlling said second switch, and means controlled bysaid magnet for controlling; said third switch.

4. In a trunking system, a cond'uctor, a

switch for seizing one end of said conductor and for extending it into association with said second switch, a third switch associated with said conductor, means for operating said third switch to find saidsecond switch and to extend the other end of said c0nductorthereto, means for then operating said second switch to find the first end of said conductor, whereby a, circuit is established oyer said conductor,ta battery in said'circuit and a magnet energized thereby, means" controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said'third switch,- and means controlled by said magnet for rendering said circuit inoperative.

In a trunking system,a conductor, a

means controlled by saidmagnet for con-, trolling said second swltch, means controlled by said magnet for controlling saad third i switch, means controlled by said magnet for rendering said circuit inoperative, and release mechanism for said third switch, said mechanism controlled by said magnet.

6. In a trunking system, a plurality of conductors, a switch and a second switch,

said first switch for seizing one end of any one of said conductors and for extendmg 1t.

into association with said second switch, a

third switch associated with the seized conductor, means for operating said third switch to find said second switch, and means for then operating said second switch to find the seized 'conductor.

7. In a trunking system, a pluralityof conductors, a switch and a second switch,

said first switch for seizing one end of any one of said conductors and for extending it into association with said second switch, athird switch associated with the seized conductor, 'ineans for operating said third switch to find said second switch and to extend the other end of said conductor .thereto, means fol then operating'said second switch to find the first end of the seized conductor, whereby a circuit is established over the seizedcbnductor, a battery insaid circuit and a magnet energized thereby, and means control-led by said magnet for controlling said second switch.

8, In trunking system, a plurality of conductors, a switch and a second switch, said first switch for seizing one end of any one of said conductors and for extending it into -association with said second switch, a third switch associated with the seized conductor, means for operating said third switch to find said second switch and to extend the other end of said conductor thereto, means for then operating said second switch to find the first end of the seized conductor, whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, and means controlled by said magnet for controlling said third switch. 1

9. In a trunking system, a plurality of conductors, a switch and a second'switch,

said first switch for seizing one end of any one of said conductors. and for extending it into association with said second switch, a third switch associated with the seized conductor, means for operating said third switch to find said second switch and to extend the other end of said conductor thereto, means for then operating said second switch to find the first end of the seized conductor, whereby a circuit is established over.

the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said magnet for controllingsaid third switch, and means controlled by said magnet for rendering said circuit inoperative.

10. In a trunking system, a plurality of conductors, a switch and a second switch, said first switch for seizing one end of any one of said conductors and for extending it into association with said secondswitch,

a third switch associated with the seized conductor, means for operating said third switch to find said second switch and to extend the other end of said conductor thereto,

means for then operating said second switch to find the first end of the seized conductor, whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch, means ontrolled by said magnet for tendering said circuit inoperative, and release mecl'ianism for said third switch, said mechanism tontrolled by said magnet. I

11. In a trunking system, a plurality of conductors, a first swit h and a plurality of second switches, said first switch for seizing one end of any one of said conductors and for extending it into association with one of said second switches, a third switch asso; ciated with the seized conductor, means for operating said third swit h to find any one of said second switches, and means for then operating said second switch to find the Seized conductor. 12. In'a trunking system, a plurality of conductors, a first switch, and a plurality of second switches, said first switch for seizing one end of any One of said conductors and forextending it into association with one of said second switches, a third switch associated with the seized conductor, means for operating said third switch to find any one of said second switches and to extend the other end of said conductor thereto, means for then operating said second switch to find the first end of the se zed conductor, whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, and means con trolled by said magnet for controlling said seco d switch.

13. In a trunking system, a plurality of conductors, a first switch and a plurality of second switches, said first switch for seizing one end of anyone of said conductors and for extending it into association with one of said second switches, a third switch asso ciated with the seized conductor, means for operating said third switch to find any one of said second switches and to extend the other end of said conductor thereto, means for then operating said second switch to find the first end of the s ized conductor, where by a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, and means controlled by said magnet for controlling said third switch.

14. In a trunking system, a plurality of conductors, a first. switch and a plurality of second switches, said first switch for seizing one end of any one of said conductors and for extending it into association with one of said second switches, a third switch associated with the seized conductor. means for operating said third switch to find any one of said second switches and to extend the other end of said conductor thereto, means for then operatingsaid second switch to find the first end of the seized conductor, whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch, and means controlled by said magnet for rendering said circuit inoperative.

15. In a trunking system, a plurality ct conductors, a first switch and a plurality of second switches, said firstswitch for seizing one end .of any one of said conductors and for extending it into association with one of said second switches, a third switch associated with thesei'zed conductor, means for operating said third switch to find any one of said second switches and to extend the other end of said conductor thereto, and means for then operating said second switch to find the first end of the seized conductor, whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch,

means controlled by said magnet for renden,

ing said circuit inoperative, and release mechanism for said third switch, said mechanism controlled by said magnet.

16. In a trunking system, a conductor, a,

17 In a trunking system. a conductor, a

first switch and 'a plurality of second switches, said first switch for seizing one end of said conductorand for extending it into association with one of said second switches,

a third switch associated with said conductor, means for operating said third switch to find any one of said second switches and to extend the other end of said conductor there'- to, means for then operating said second switchto find the first end of said conductor. whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, and means controlled by said magnet for controlling said second switch.

18. In a trunking sys em. a conductor, a first switch and a li lurality of sec nd switches, said first switch r'or seizing on"- end of said conductor and for extending it into association withone of said second switches, a third switch associated with said conductor, means for operatingsaid third first switch and a plurality of second switches, said first switch for seizing one end of said conductor and for extending it into association with one of said second switches, a third switch associated with said conductor, means for operating said third switch to find any one of said second switches and to extend the other end of said conductor thereto, means for then operating said second switch to find the first end of said conductor, whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second,sivitch,\ means controlled by said magnet for controlling said third switch, an means controlled by said magnet for rendering said circuit inoperative.

20. In a trunking system, a conductor, a

first switch and a. plurality of second switches, said first switch for seizing one end of said conductor and for extending it into association with one of said second switches, a third switch associated with said conductor, means for operating said thirdv switch to find any one of said second switches and to extend the other end of said conductor thereto, means for then operating said second switch to find the first end of said conductor. whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling sa'id secondswitch, means controlled by said magnet for controlling said third switch. means controlled by said magnet for rendering said circuit inoperative, and release mechanism ifor said third switch, said mechanism controlled by said magnet 21. In a trunking-system, a conductor, a first switch and a second switch, said-first switch for seizing one end of said conductor and for extending it into association with said second switch, a line. a third switch associated with said condnctonaneans for operating said third switch tofind said line and to extend the other end of said conductor thereto, a switch for said line andmeans for then operating said line switch to connect the line and'the second switch and for further extending said other end thereto, and means for then operating said second switch to find the fiist end of said conductor.

, sociated with said conductor, means 22. In a trunking system, a conductor, a first switch and a second switch, said first switch for seizing one end of said conductor and 'for extending it into association with tor thereto, a switch for said line and means for then operating said line switch to connect the lineand the second switch and for further extending said other end thereto, means for then operating said second switch to find the first end of said conductor, whereby a circuit is establishedover said conduc- ,tor, a battery in said circuit. and a magnet energized thereby, and means controlled by said magnet for controlling said second switch.

23. In a trunking system, a conductor, .a first switch and a switch for seizing one end of said conductor and for extending-it into association with said second switch, a line, a third switch associated with said conductor, means. for op erating said third switch to find. said line and to extend the other end of said conducsecond switch, said first tor thereto, a switch for said line and means I for then operating said line switch to connect the line and the second switch and to extend said other end thereto. means for then operating said second switch to find said conductor, whereby a circuit is established over said conductor. a battery in said circuit and a magnet energizedthereby. means controlled by said magnet for controlling said second switch, and means controlled by said magnet for controlling said third switch.

24. In a trunking system. a conductor, a first switch and a switch for seizing one end of said conductor and for extending it into association with said second switch, a line, a third switch associated with said condnctor,.means for operating said third switch to find said line and to extend the other end of said conductor thereto, a switchfor said line and means for then operating said line switch to connect the line and the second switch and to extend said other end thereto, means for then operating said second switch to find the first end of said conduct-or, whereby acircuit is established over said conductor, a battery in said circuit and a magnet energized thereby,

means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch. and means controlled by said magnet for rendering said circuit inoperative.

25. In a trunking system, a conductor. a first switch and a second switch, said first switch for seizing one end of-said conductor and for. extending it into association with said seconthswitch, a line, a third switch. as-

second switch, said first for opcrating said third switch to find said line and to extend the other end of said conductor thereto, a switch for said line and means for then operating said line switch to connect the line and the second switch and to t d id other end thereto, means for then operating said second switch to find the first end of said conductor, whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said lntlgliGUfOr' controlling said third switch, means controlled by said magnet for rendering said circuit inoperative, and release mechanism for said third switch, said mechanism controlled by said magnet.

26. In a trunking system, a plurality of conductors, a. first switch and a second switch, said first switch for seizing one end of any one of said conductors and for ex tending the seized conductor into association with said second switch, a line, a third switch associated with the seized conductor, means for operating said third switch to find said line and to extend the other end of said conductor thereto, a switch for said line and means for then operating said line switch to connect the line and the second'switch and to extend said other end thereto, and means for then operating said second switch to find the first end of the seized conductor.

27. In a trunking. system, a plurality of conductors, a first switch and a second switch, said first switch for seizing one end oi any one of said conductors and for extending the seized conductor into association with said second switch, a line, a third switch associated with the seized conductor, means for operating said third switch to find said line dd to extend the other end of said conductor thereto, a switch for said line and means for then operating said line switch to connect the line and the second switch and to extend the said other end thereto, means for then operating said second switch to find the first end of the seized conductor, where by a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, and means controlled by said magnet tor controlling said second switch.

28. in a trunking system, a plurality of conductors, a first switch and a second switch, said first switch for' seizing one end oi. any one of said conductors and for extending the seized conductor into ilSt-JOClH- tion with said second switch, a line, 11 third switch associated with the seized comluctor, means for operating said third switch to find said line and to extend the other end of said conductor thereto, a switch for said line and means tor then operating said line switch to connect the line and the second switch and to extend said other end thereto, means for then operating said second switch to find the first end of the seized conductor, whereby a circuit is established ,oyer the seized conductor, a battery insai'd circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, and means controlled by said magnet for controlling said third switch.

29. In a trunking system, a plurality of conductors, a first switch and a second switch, said first switch for seizing one end of any one of said conductors and for extending the seized conductor into association with said second switch, a line, a third switch associated with the seized conductor, means for operating said third switch to find said line and to extend the other end of said conductor thereto, a switch for said line and means for then-operating said line switch to connect the line and the second switch and to extend said other end thereto, means for then operating said second switch to find. the first end of the seized conductor, whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch. means controlled by said magnet for controlling said third switch, and means controlled .by said magnet for rendering said circuit inoperative.

30. In a trunking system, a plurality of condu tors, a first switch and a second switch, said first swit h for seizing one end of any one of said COIldll"tOIS and for eX- tending the seized conductor into as o-iati on with said se ond switch, a line, a third switch associated with the seized eoudwtor, means for operating said third swit h to find said line and to extend the other end (i' said conductor thereto, a switch for said line and meaus'for then operat ng said line switch to connect the line and the second switch and to extend said other end thereto, means for then operating said se"ond switch to find the first end of the seized conductor, wherebya circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said se'ond switch, means controlled by said magnet for controlling said third switch, means controlled by said magnet for rendering said circuit inopcrative. and release mechanism for said third switch, said mechanism con-- trolled by said magnet. 4

31. In a trunking system. a plurality of association with one of said se ond switches,

a line, a third switch associated with the seized conductor, means for operating said third switch to find said line and to extend the other end of said conductor thereto, a switch for said line and means for then operating said line switch to connect the line and any one of said secondswitches and to extend said other end thereto, and means for then operating the connected second switch to find the first end of the seized conductor.

32. In a trunking system, a plurality of conductors, a first swit h and a plurality of second switches, said first switch for seizing one end of any one of said conductors and for extending the seized conductor into association with one of said second switches, a line, a third switch associatedwith the seized conductor, means'for operating said third switch to find said line and to extend the other end of said conductor thereto, a switch for said line and means for then operatingsaid line swit h to connect the line and any one of said second switches and to extend said other end thereto, means for then operating the conne ted se ond swit'h to find the first end of the seized conductor, whereby a circuit is established over the seized conductorya battery in said circuit and a magnet energized thereby, and means controlled by said magnet for controlling said se ond switch.

33. In a trunking system, a plurality of conductors a firstswitch and a plurality of second swit hes, said first swit h for seizing one end of any one of said condu tors and for extending the seized conductor into assoclation wlth one of said second sw tches, a line. a third swltchassoclated with the seized conductor, means for operating said third switch to find said line and to extend the other end of said conductor thereto, a switch for sa d line and means for then operating saidline switch to connect the line and any one of sald second switches and to extend said other end thereto, means for then operating the' connected second switch to find the first end of the seized conductor,-whereby acircuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, and means controlled by said magnet for controlling said third switch.

34. In a trunking system, a plurality of plurality of. second switches, said first switch for seizcondu tors. a first switch and a ing one'end of any one of said onductors and for extending the seized conductor into association with one of said second switches, i a line, a third switch as ociated with the seized conductor, means for third switch to find said line and-to extend the other end of said conductor theret'o,i swltch for said line and means for the operating said line, switch to connect the:

tor. v r

In-fia trunking, system, a conductor, a

operating said I 1 line and any one of said second switches and to extend said other end thereto, means for then operating. the connected second switch to find the first end of the seized conductor, whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for'con trolling said second switch, means controlled by said magnet forcontrolling said third switch, and means controlled by said magnet for rendering said circuit inoperative.

85. In a trunking system, a plurality of conductors, a first switch and a plurality of second switches, said first switch for seizing one end ofv any one of said conductors and for extending the seized conductor into association with one of said second switches, .a line, a third .switch associated with the seized conductor, means for operating said third switch to find said line and to extend the other end of the conductor thereto, a switch for said line and means for then operating said line switch to connect the line and any ne of said second switches and to extend said other end thereto, means for then operating the connected second switch to find the first end of the seized conductor, whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means con trolled by said magnet forcontrolling said second switch, means controlled by said magnet for controlling said third switch, means controlled by said magnet for rendering said circuit inoperative, and release mechanism for said third switch, said mechanism controlled by said magnet.

36. In a trunking system, a conductor, a

first switch and a plurality of second switches, said first switch for seizing one :end of sa d conductor and for extending it line and any one of said second switches and to extend said other end theret and nieans for then operating the connecte'd' se'c'ond switch to find the first, end of [said conduc switc plurality of second 'idffi 't s'witch for seizing one end diito'rand for extending it into l one of said second switches, ":switch associated with said ,m'ea'fis for operating said third find said line and to extend the other endqf said conductor thereto, a switch forxsaidline and means for then operating switch to connect the line and any first said magnet said other end thereto,

hiagnet energized thereby,

one of said second switches and to extend means for then oper-' ating the connected second switch to find the first end of said conductor, whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, and means controlled by for controlling said second switch.

38. In a trunking system. a, conductor, a first switch and a plurality of second switches, said first switch for seizing-one end of said conductor and for extending it into association with one of said second switches, a line, a third switch associated with said conductor, means for operating said third switch to find said line and to extend the other end of said conductor 'thereto, a switch for said line and means for then operating said line switch to connect the line and any one of said second switches and to extend said other end thereto, means for then operatingthe connected second switch to find the first end of said conductor, whereby a circuit is established over said conductor, a battery in said circuit and a means controlled by said magnet for controlling said second switch, and means controlled by said magnet forcontrolling said third switch.

39. In a trunking system, a conductor, a first switch and a plurality of second witches, said first switch for seizing one end of said conductor and for extending it into association with ne of said second switches, a line, a third switch associated with said conductor, means for operating said third switch to find said line and to extend the other end of said conductor thereto, a switch for said line and means for then operating said line switch to connect the line and any one of said second switches and to extend said other end thereto, means for then opcrsecond switch to find the first end oisaid conductor. whereby a circuit is established over said conductor, a battcryin said circuit aml a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch, and means controlled by said magnet for rendering said circuit inoperative.

40. In a trunking first switch and a plurality of second switches, said first switch for seizing one end of said conductor and for ating the connected system, a conductor, a

extending it into association with one of said second switches, a line, a third switch associated with said conductor, means foroperaling said. third switch to find said line and to extend the other end of said conductor thereto, a switch for said line and means for then operating said line switch to connect the line and any one of said second switches and to extend said mating said extension whereby switch finds the extension said extension is other end thereto, means for then operating the connected second switch to find the first end of said conductor, whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby. means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch, means controlled by said magnet t'or rendering said circuit inoperative, and release mechanism for said third switch, said mechanism controlled by said magnet.

41-. In a trunking system, a conductor, a first switch and a second switch, said first switch for seizing'one end of said conduc tor and for extending it into association with said second switch, a third switch associated with said conductor, means for operating said third switch to find said second switch, means for then operating said second switch to find said conductor, and means for controlling said extension whereby when said second switch finds the extension said extension is cut ofi.

42. In a trunking system, a conductor, a first switch and a second switch, said first switch for seizing one end of said conductor and for extendin it into association with said second switc a third switch associated with said conductor, means foroperating said third switch to find said second switch and toextend the other end of said conductor thereto, means for then operating said second switch to find the first end of said conductor, means for controlling said extension whereby when said second switch finds the extension said extension is cut off, whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, and means controlled by said magnet for controlling said second switch.

43. In a trunking system, a conductor, a first switch and a second switch, said first third switch associated with said conductor, means for operating said third switch to find said second switch and to extend the other end of said conductor thereto, means for then opsaid second switch to find the first end of said conductor, means for controlling when said second a circuit is established over battery in said circuit and a magnet. energized thereby, means controlled by said magnet for controlling said second switch, and means controlled by said magnet for controlling said third switch.

it. in a trunking system, a conductor, a first switch and a second switch, said first switch for seizing one end ofsaid 'conduc tor and for extending it into association cut ofi'. whereby said conductor, a

. with said second switch, a third switch associated with said conductor, means for operating said third switch to find said second switch and to extend the other end of said conductorthereto, means for then op erating said second switch to find the first end of said conductor, means for controlling said extension whereby when said second Switch finds the extension said extension is cutotl, whereby a circuit is established over said conductor, a battery'in said circuit and a magnet energized thereby, means con trolled by said magnet for controlling said second switch, means controlled by said mag net for controlling said third switch, and

means controlled by said magnet for rendering said circuit inoperative.

45. In a trunking system, a conductor, a

first switch and a second switch, said first switch for seizing one end of said conductor and for extending 1t into association 'with said second switch, a third switch associated with said conductor, means for operating said third switch to find said second switch and to extend the other end of said conductor thereto, means for then operating said second switch to find the first end of said conductor, means for controlling said extension whereby when said second switch finds the extension said extension is cut oil, whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch, means controlled by said magnet for rendering said circuit inoperative, and release mechanism for said third switch, said mechanism controlled by said magnet.

46. In a trunking system, a plurality of conductors, a first switch and a second switch, said first switch for seizing one end of any one of said conductors and for ex-. tending it into association with said second switch, a third switch associated with the seized conductor, means for operating said third switch to find said second switch and to extend the other end of said conductor thereto, means for then operating said seeond switch to find the first end of the seized conductor, and means for controlling said ond switch to find the first end of the seized conductor, means for controlling said ex tension whereby when said second switch finds the extension, said extension is cut 011',

whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, and means controlled by said magnet for controlling said second switch.

48. In a trunking system, a plurality of conductors, a. first switch and asecond switch, said first switch for seizing one end of any one of said conductors and for extending it into association with said second switch, a third switch associated with the seized conductor, means for operating said third switch to find said second switch,

and to extend .the other end of said conductor thereto, means for then operating said second switch to find the first end-of the seized conductor, means for controlling said extension whereby when said second switch finds the extension, said extensionis cut oil, whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, and means controlled by said magnet for controlling said third switch.

ail-In a trunking system,a plurality of conductors, a. first switzh and a second switch, said first switch for seizing one end of any one of said conductors and forextending it into association with said second switch, a third switch associated with 'the seized conductor, means for operating said third switch to find said second switch, and to extend the other end of said conductor thereto, means for then operating said second switch to find the first end of the seized conductor. means for controlling said extension whereby when said second switch finds the extension, said extension is cut off, whereby a circuit is established over the seized conductor, a. battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch. means controlled by said magnet for controlling said third switch.

and means controlled by said magnet for "rendering said circuit. inoperative.

50. In a trunking system, a plurality of conductors. a first switch and a second switch. said firstswitch for seizing one end of any one of said conductors and for extending it into association with said second switch, athird switch associated with-the. seized conductor. meansitor operating said third switch to find said second switch and to extend the other end of said conductor thereto, means for then operating said second switch to find the first end of the seized conductor, means tor controlling said extension whereby when said second switch finds the extension, said extension is out otf, whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch. means controlled by said magnet for rendering said circuit inoperative, and release mechanism for said third switch, said mechanism controlled by said magnet.

51. In a trunking system, a plurality of conductors, a first switch and a plurality of second swit;hes, said first switch for seizing one end of any one of said conductors and for extending it into association with one of said second switches, a third switch associated with the seized conductor. means for operating said third switch to find any one of said second switches and to extend the other end of said conductor thereto, means for then operating the found second switch to find the first end of the seized conductor, and means for controlling said extension whereby when said second switch finds the extension, said extension is cut off.

52. In a trunking system, a plurality of conductors, a first switch and a plurality of se:ond switches, said one end of any one of said conductors and for extending it into association with one first switch for seizingof said second switches, a third switch associated with the seized conductor, means for operating said third switch to find any one of said second switches and to extend the other end of said conductor thereto,-

meansfor then operating the found second switch to find the first end of the seized conductor, means for controlling said extension whereby when said second switch finds the extension, said extension is cut ofl, whereby a circuit is established over the seized conductor, a battery in said ci'cuit and a magnet energized thereby, and means controlled by said magnet for controlling said se'ond switch.

53. In a trunking system, a plurality of conductors, a first switch and a plurality of second swit-i hes, saidfirst switch for seizing one end of any one of said conductors and for extcnding it into association with one of said second switches, a third switch associated with the seized conductor, means for operating said third switch to find any one or" said second switches and to extend the other end of said conductor thereto, means for then operating the found second switch to find the first end of the seized conductor, means for controlling said extension whereby when said second switch finds the extension, said extension is cut oil. whereby a circuit is established over the seized conductor. a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, and means controlled by said magnet for controlling said third switch.

.54. In a trunking system, a plurality of conductors, a first switch and a plurality of second switches, said first swit1h for seizing one end of any one of said conductors and for extending it into association with one of said second switches, a third switch associated with the seized conductor, means for operating said third switch to find any one of said second switches and to extend the. other end of saidconductor thereto, means for then operating the found second switch to find the first end of the seized conductor, means for controlling said extension whereby when said second switch finds the extension, said extension is cut ofi", whereby a circuit is established over the seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said n'iagnet for controlling said third switch, and means controlled by said magnetfor renderihg said circuit inoperative.

55. In a tibhnking system, a plurality of conductors, a first switch and a plurality of second switches, said first switchfor seizing one end of any one of said conductors and for extending it into asso'iation with one of said se ond switches, a third swit'h associated with the seized conductor, means for operating said third switch to find any one of said second switches and to extend the other end of said conductor thereto. means for then operating the found second switch to find the first end of the seized conductor, means for controlling said extension whereby when said second switch finds the extension, said extension is cut oil", whereby a circuit is established over the. seized conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnetfor controlling said second switch, means controlled by said magnet for controllingsaid third switch, means controlled by said magnet or rendering said circuit, inoperative, and release mechanism for said third switch, said mechanism .(ontrolled by said magnet.

56. In a trunking system. a conductor, a first switch and a plurality of second switches, raid first switch for seizing one end of said conductor and for extending it. into association with one at said second switches, a third switch associated with said conductor, means for operating said. third switch to find any .one of said se-ond switches and teextcnd the other, cade said conductor thereto, means for thenopcrating the found second switch to find the first end of said cont luctor, and nieansfor controlling said extension whereby when said second switch finds the extension, said extenslon is cut ofi.

57; In a trunking system, a conductor, a

, conductor thereto, means for then operating the found second switch to find the first end of said conductor, means for controlling said extension whereby when said second switch finds the extenslon, said extension is cut ofi, whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, and means controlled by said-magnet for controlling said second switch.

58. In a trunking system, a conductor, a first switch and a plurality of second switches said first switch for seizing one end of saidvconductor and for extending it into association with one of said second switches, a third switch associated with said inductor, means for operating said th'rd switch to find any one of said second switches and to extend the other end of said conductor thereto, means for then operating the found second switch to find the ifirst end of said conductor, means for controlling said extension whereby when said second, switch finds the extension, said extension is cut off, whereby a circuit is established over said conductorga battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, and means controlledv by said magnet for controlling said third switch.

59. In a trunking system, a conductor, a first switch and a plurality of; second switches, said first switch for seizing one end of said conductor and for extending it into association with one of said second switches, a third switch associatedwith said conductor, means for operating said third switch to find any one of said second switches and to extend the other end of said conductor thereto, means for then operating the found second switch to find the first end of said conductor, means for controlling said extension whereby when said-second switch finds the extensiomsaid extension is cut off, whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch, and means controlled by said magnet for rendering said, circuit inoperative.

switches and to extend the other end of said,

conductor thereto, means for the operating the found second switch to find the first end of said conductor, means for controlling said extension whereby when said second switch finds the extension, said extension is cut off, whereby a circuit is established over said conductor,,a batter in said circuit and a magnet energized tereby, means controlled by said magnet for controlling said second switch, means controlled. by said magnet for controlling said third switch, means controlled by said magnet for rendering said circuit lnoperative, and release mechanism for said third switch, said mechanism controlled by said magnet.

61. In a trunking system, a conductor, a first switch and a second switch, said first switch for seizing one end of said conductor and for extendin it into association with said second switc a third switch associated with said conductor, means including said third switch for extendin the other end of said conductor into association with saidsecond switch, and means for then operating said second switch to unite the extended ends of said conductor.

62. In a trunking system, a conductor, a first switch and a second switch, said first switch for seizing one end of said conductor and for extending it into association with said second switch, a third switch associated with said conductor, means including said third switch for extending the other end of said conductor into association with said second. switch, means for then operating said second switch, to unite-the extended ends of said conductor, whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, and means controlled by said magnet for controllin said second switch.

63. n a trunking system,|a conductor, a first switch and a second switch, said first switch for seizing one end of said conductor and for 'extending it into association with said second switch, a third switch associated with said conductor, means including said third switch for extending the other end of said conductor into association with said second switch, means for then operating said second switch to unite the extended ends of said conductor. whereby a circuit is established over said conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, and means controlled by said magnet for controlling said third switch.

64. In a trunking system, a conductor, a first switch and a second switch, said first switch for seizing one 'end of said conductor and for extending it into association with said second switch, a third switch associated with said conductor, means including said third switch for extendingthe other end of said conductor into association with said second switch, means for then operating said second switch to unite the extended ends of said conductor, whereby a circuit is established over said conductor, a battery insaid circuit and a magnet energized thereby,

- means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch, and means controlled by said mag-- net for rendering said circuit inoperative.

' 65. In a trunking system, a conductor, a first switch and a second switch, said first switch for seizing one end of said conductor and for extending it into association with said second switch, a third switch associated with said conductor, means including said third switch for extending the other end of said conductor into association with said second switch, means for then operating said second switch to unite the extended ends oi said conductor, whereby a circuit is estab.

lished over said conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, means controlled by said magnet for controlling said third switch, means controlled by said magnet for rendering said circuit inoperative, and release mechanism for said third switch, said mechanism controlled by said magnet.

66. In a trunking system, a plurality of conductors, a first switch and a second switch, said first switch for seizing one end of any one of said conductors and for extending the conductor s0 selected into asso ciation with said second switch, a third switch associated with the selected conductor, means including said third switch for extending the other end of said selected conductor into association with said second switch, and means for then operating said I tending the conductor 50 selected into association with said second switch, a third switch associated with the selected conductor, means including said third switch for extending the other end of said selected conductor into association with said second switch,

means for then operating said second switch to unite the extended ends of said selected conductor, whereby a circuit is established over the selected conductor, a battery invsaid circuitand a magnet energized thereby, and means controlled by said magnet for controlling said second switch.

68. In a trunking system, a plurality of conductors, a first switch and a second switch, said first switch for seizing one end of any one of said conductors and for extending the conductor so selected into association with said second switch, a third switch associated with the selected conductor, means including said third switch for extending the other end of said selected conductor into association with said second switch, means for then operating said second switch to unite the extended ends-of said selected conductor, whereby a circuit is established over the selected conductor, a battery in said circuit and a magnet energized thereby, means controlled by said magnet for controlling said second switch, and means controlled by said magnet for controlling said third switch.

69. In a trunking system, a plurality of conductors, 'a first switch and a second switch, said first switch for seizing one end of any one of said conductors and for extending the conductor so selected into association with said second switch, a third switch associated with the selected c0nduc tor, means including said third switch for extending the other end of said selected conductor into association with said second conductors, a first switch and a sec nd swltch, said first switch for selzing one em of any one of said conductors and for ex-' tending the conductor so selected into as; sociation with said second switch, a third switch associated with the selected conductor, means including said third switch for extending the other end of said selected conductor into association with said second switch, means for then operating said second switch to unite the extended endsof said selected conductor, whereby a circuit is established over the selected conductor, a battery in said circuitand a magnet energized thereby, means controlled by said magnet for controlling said second switch,