US1567122A

US1567122A - Automatic telephone-exchange system

Info

Publication number: US1567122A
Application number: US227287A
Authority: US
Inventors: Bert G Dunham
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1904-10-05
Filing date: 1904-10-05
Publication date: 1925-12-29
Anticipated expiration: 1942-12-29

Description

Dec. 29, 1925 1,567,122

' B. G. DUNHAM AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed Oct. 5, 1904 7 shets-Sheet l Zgc V) fuif m76, /zp

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Dec. 29,1925. 1,567,122 B. G. DUNHAM AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed Oct. ,5, 190g '7 Sheets-Sheet 2 d, u s l xm B. G. Du nham, WTNESSES. Q' [Nl/ENTO.

Dec. l 29 1925- 1,557,122

- B. G. DUNHAM AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed oct. 5, 1904' '7 sheets-sheet \B. .Dunha WITNESSS: by N a NVENTUR.

m l ATTORNEK- Dec. 29, 1925- 1,567,122

B. G. DUNHAM AuTom'rIc TELEBHONE EXCHANGE SYSTEM Filedoct. 5, 1904 7 sheets-sheet 4 Y B54. Dunham 2\ D WHW/isms: L; 3 m IN1/zwom dm! 508V, e5( 7AM .ffm/aver.

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Dec. 29, 1925 1,567,122

B. G. DUNHAM AUTOMATIC TELEPHONE EXCHANGE SY\SIEM Filed Oct. 5, 1904 '7 Sheets-Sheet 5 Q f? Q Q {Qx Q QL" Q Q. B S n l .(Dunhmfn, WIT/vgsw; zg t INVENTOR.

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Dec. 29, 1925- 1,567,122 B. G. DUNHAM AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed Oct. 5, 1904' 7 Sheets-Sheet 7 WIEEEEEE: 'Inval-lfm :Ei-Emblem' switch involved in the connection are, or are adapted to be, connected in abridged path across the circuit of the respective subscribers lines, and trunk lines, instead of being connected in series in the talking circuit, as has been the case in most systems of the prior art. Furthermore instead of these bridges being all closed across the talking circuit of an established connection, a part ofthe bridges are open after the corresponding selecting switches have performed their selecting functions and established the con iiection. Thus it will be seen from Fig. 1 that the controlling magnets, VR and RR, of the first selector of the calling line, and VR and RR', of the second selector, are disconnected from the talking circuitv built up between the two subscribers lines shown, although these magnets were present in bridges across the circuit long enough to enable them to control their corresponding selectors in selecting and connecting with the proper trunk lines. In this way the disadvantage in the old system of having the series magnets in the talking circuit is eliminated, and while the bridge system is adhered to, the disadvantage of having too many sets of magnets bridged across the talking circuit is eliminated.

An understanding of the circuits of the snbscribers station adapted for use with my invention may be had by reference to Fig. 2. The talking apparatus, consisting of a receiver, transmitter and induction coil, may be connectedrbetween the vertical and rotary limbs of the lines, V and R, respectively, by the action of the hook switch, 3, in a manner well understood. Under normal conditions, that is, when the receiver is upon the hook, the bell or ringer, 4. is connected between the two sides of the line, thisV connection eX- tcnding through the spring, 5, and the arm, (i, of the hook when the telephone is not in use. vVhen the receiver is removed from the hook this connection is broken, and the talking contacts completed in an obvious manner. All ground connections at the sub` scribers station are primarily controlled at the pair of contacts, .7, these contacts being held open as long as the receiver is on its hook, and after the receiver has been removed, until the impulse transmitting device has been put into operation.

The impulse transmitting device acts by causing the springs, 3 or 9, to engage the ground spring, 10, according to whether impuises are to be sent over the vertical or rotary sides of the line. That is, if six impuises are to be transmitted, the spring 8, will be pressed against the spring, 10, siX times, thus allowing that many impulses to Atow from the central oiiice over the vertical :ei-de of the line to ground. 1t is obvious from the presence of the springs, 7, that no such impulse can take place unless the receiver has been removed from its hook, and

manner an impulse over the rotary side of the line may be secured by pressing the spring, 9, against the spring, 10. It should be remembered that all selecting is done over the vertical side of the linel by sending a series of impulses corresponding to the digits belonging to the number of the subscriber wanted. Each series of impulses over the vertical side of the line caused by the movements 'of the spring, 8, is followed by a single impulse over the rotary side of the line caused by the movement of the spring, 9.

When the hook, 3, is depressed at the close of the conversation, its arm, 11, serves to press the springs, 12, 13 and 14, momentarily into engagement with each other, thereby grounding both the vertical and rotary sides of the line through the spring, 14, and the contact, 7. The mechanical arrangement of parts is such that the springs, 1Q, 1.3, and 14, are not brought into engagement with each other as the hook rises, or while it is either depressed or elevated.

15 is the spring actuated by the ringing lntten, this'spring normally bearing against spring, 16, and serving to hold closed the talking circuit. When, however, the ringing button is depressed, spring, 15, engages sprintf, 17, thereby grounding the vertical side of the line for the operation of the ringing relay in the connector switch.

Referring now to Fig. 3, the two limbs, V and R, of' the subscribers line may be seen entering at the left of the sheet. These limbs correspond with those shown in Fig. 2, leading from the mechanism at the subscribers station. The bridge cut-olf relay, CO, has one terminal connected to the live pole of the battery, B, of about 50 volts. The other terminal is connected to the contact, la; this is a portion of what is" known as the oil normalswitch, the office of which is to break contact between springs, 1a and 2a, and make contact between 2a and 3a, whenever the shaft of the selector is moved from its normal position; this switch will be actuated at the first vertical motion of the shaft, remaining so actuated until the switch has been wholly released and restored to normal. The relay, CO, will therefore be disconnected from anything except one pole of the battery, B, whenever the switch is or normal. The springs, 4a, 5a and 6a, are controlled by the relay, CO; they are normally in contact with each other, the result being that a connection is made between the live pole of the battery, B, and the relays, VR and RR. The other terminal of the relay, VR, connects with the contact point, 26", of a device known as a side switch. This side switch is a device operated in a manner yet to be described, and which, in my system, has four levers, 25a. 25h, 25e, and 2. d, adapted to move together as a unit, but connected to four distinct parts of the circuit. The side switch mechanism is illustrated in Figure 8 and the sami.l reference characters are used, Where possible, as those used in the other figures. No attempt is made, in this igure, however, to illustrate associated parts which are not directly concerned in the operat-ion of the side-switch- Thus, for example, the private magnet, PM, is shown without the contacts 9a, 10a and 12 which, in fact, are associated with this magnet as shown, for example, in Fig. 3. The rotatably mounted shaft, 201, carries the side-switch levers 25a, 25h, etc. only two of which are shown, however. The associated contacts are shown at 26a, 27, 28a, and at 26h, 27h, and 28". The arm, or lever, 202, having a triangular cross-section is rigidly mounted upon the shaft, 201. The private magnet PM is provided with an arn'iature, 203, pivoted at 204- and having an arm 205, extending toward the lever, 202. A spring, 211, co-operating with a spring arm, 212, tends tocause a rotation of the side-switch shaft and its switch arms in the direction of the arrow, 213. Thus upon the energization of the private magnet PM, the arm, 205, is depressed and this causes the tooth, 206, on the escapement arm to strike the top of the tooth, 210, on the spring, 208, thus forcing the spring out of engagement with the escapement arm, 202. The face of the tooth, 206, is only slightly to the left of the face of the tooth, 210, so that the substitution of the tooth, 206, to retain the escapement arm 202 in its position in place of the teeth 210 does not permit any material rotation of the side-switch shaft due to the tension of the spring, 211. TVhen, however, the de-energization of the private magnet, PM, permits retraction of the armature, 203, due to the influence of the spring, 214, `the face of the tooth, 210, will not engage the front surface of the escapement arm, 202, and this arm and shaft will be permitted to turn to the left under the influence of the spring, 211, until it strikes the vface of the tooth, 209. So, also, a subsequent energization of the private magnet, PM, will `first cause the tooth, 207, to be substituted for the tooth, 209, to retain the sideswitch shaft in its position, and then upon the de-energization of the private magnet the side-switch shaft will be caused to move a step further in advance. The wire, 215, which is connected with the arm, 212, passes through a hole in the rigidly supported `guide, 216, and is provided with an adjustable stop` 217, by means of which the forward rotation of the side-switch shaft limited.

The restoration of the side switches and the shaft upon which they are mounted to their normal position is brought about by the energization and subsequent de-energi- Zation ot' the disconnect-magnet, DM. In addition to the mechanism associated with this magnet for causing restoration of the shaft, 31, to its normal position, the armature, 21S, of the magnet, DM, is provided with a catch. 219. The armature is pivoted at 220 and returned to its normal position by a comparatively stiff spring, 221. The wire, 21:7, which is quite springy, is provided at its end with a very thin, flexible plate. this plate having a suitable opening at 223. The vertical magnet, VM," is equipped with an armature, 224.-, pivoted at 225. and provided at its extremity with a catch. 220. The energization of this magnet, VM, raises the armature, 224, and by means of the catch, 226, it raises also the plate, disengaging it from the restraining influence of the catch, 219, and making the rotation of the side-switch shaft 201, subject only to the operation ofthe escapement associated with the private magnet, PM.

The restoration of the selectorl mechanism upon the energization and de-energization of the disconnect-magnet, DM, restores the plate, 222. to the position shown in Fig. 8. When next this particular mechanism is called into service the first energization `of vertical magnet, VM, immediately releases the plate, 22.2, from the catch, 219, and puts the side-switch under the control of the escapement associated with the private magnet, PM. The normal position of this side switch is that shown in Fig. The described contact of the lever, 25", upon point, 26", operates to connect the vertical rela),v with the 'vertical wire, V; similarly, contact of the lever, 25, upon the point, 26C, connects the rotary relay with the rotary wire, R; ground contacts upon the vertical wire, therefore, as caused by the subscriber instituting a call, will operate the vertical relay by as many impulses as there are digits in the left-hand figure `of the called subscribe1"s number. This will cause as many contacts between the' springs, 7a and 8a; the resultl will be an operation of the vertical magnet, VM, in as many impulses, the circuit being from the live pole of the battery.` B, 'through the vertical magnet, VM, the contact between the springs, 9 and 102L `of the private magnet, PM, and t0 ground bv contact between the springs, 7

and Sn. The shaft, S, will be lifted by this action, as many steps of its ratchet as there lwere ground contacts, and will remain lifted. As a series of vertical impulses is always followed by one rotary limpulse, this latter `will cause a closing of the vcontact of the rotary relay between-springs, 11EL ,and

8a; the private magnet, PM, of which one terminal is connected to the live pole of the battery will t-hus be energized. The armature ot this ',iagnet, by drawing up and falling hack again, will operate the side switch, as Yit is this forward and back motion of the armature of' this magnet which controls the side switch through an escapement associating these parts together; but the move ment of the side switch forward one step, acts to move all four of its levers; the movement of the lever, 25a, connects to ground one of the terminals of the rotary magnet, Rlvl; the other terminal of' that magnet is connected through its own armature contact to the live pole of the battery. rit the point, 30, associated with the rotary magnet, RM, is a contact which is broken just at the close of each stroke of the armature of this magnet, somewhat after the manner of the Vfamiliar vibrating electric bell. The operation oit the side switch in making this rst step, therefore, will, so far as this feature concerned, cause the rotary magnet to make a series of strokes, and these will rotate the shaft through the agency of the rotary advancing pawl. As each impulse of therotary magnet causes the wipers upon the rotary shaft to make successive connections with the contact pieces in the bank, the wiper, 33, will connect with the contacts of the private wires of' trunk lines, which are or are not busy. lf the trunk lines are busy, the private contacts made by the wiper, 33,

'I will be grounded, in which case the private magnet will form a circuit from the battery, B, through its winding, through the contact, 27d, of the side switch to the lever, 25d, through the winding of the disconnect relay, DR, the wiper, 33, to the contact which is grounded on the private wire of the busy trunk line. This will Cause the armature of the private magnet to be retained and will thus prevent a movement of the side switch from its middle to its last position. The disconnect relay, DR, will not, however, 4be operated because it is of so iew turns that the current it may receive while in series with the private magnet, will not be sufficient to actuate it. When the wiper. 33, makes connection with the contact piece of the private wire of a trunk line which is not in use, no ground will be found upon that contact, the private magnet will be released instead of being held as last described, and this operation will permit a second motion of the side switch, thus carrying the levers on to the extreme position. This final motion of the side switch accomplishes four results: First, because of the removal of' the ground from the lever, 25a, the rotation of the shaft will be stopped because lof the opening of the circuit of the rotary magnet, RM; second, the two line conductors, V and R, which until this time had been connected to their respective relays'ffliJ and Rit, are now disconnected from those relays, and third, they are eXtendedthrough the wipers. 3l and 32 to the conductors, and 36; and it is to be noted that these line conduc tors are now free of any bridge or any series magnet windings; fourth, by the movement of `the lever, 25, upon the point, 28d, a ground is placed upon the private wiper, 33, through the winding of the disconnect relay, Dit. This serves to hold the selected trunk line busy against the stoppage of other selector switches upon it, because it is the presence of' ground which prevents such a selection of the trunk.

Reference has been made to the off nor-- mal switch, and to the 'fact that its operau tion disconnects the cut-ofi relay, CO, from the circuits. lts further operation is bv cont-act between the spring, 2a, and the point, 3a, to ground, through the private conductor of' the individual line of the selector in question. Such a ground serves to prevent a connector from completing a connection with the line, and this needs to be so because a line should become busy as soon as its first selector a tempts a connection with another line.

But the trunk line composed of the conductors, 35 and 36, is one which extends to a second selector. Referring to Fig. 4, it will be seen that these conductors enter the mechanism of the switch quite as was true in the case of the first selector. W' ith the side switch in the normal position, vertical impulses over the wire, 35, will operate the vertical relay, and in turn the vertical magnet, the connections and sequences being exactly as described ior these operations with reference to the first selecfor. rlhe first vertical. motion of the shaft in response to impulses from the vertical magnet, operates to close the contact in the off normal switch, 37, allowin(Y current to flow from the battery, B, through the lamp, 38; this lamp simply signied that this selector, or one of a group if the lamp be made common to a number of other contacts in parallel with the parts 37, has 0perated, and has no function in setting up the connection between lines. As the series of' vertical impulses ceases, and is followed by an impulse through the rotary relay, its closure of the spring, 39, upon the ground contact, 40, causes current to flow from the battery, B, through the winding of the private magnet, PM', drawing up the armature thereof. Consequent circuit changesv of the springs, 42, 43 and 44, resulting from this armature action, need not be here considered. The important thing which happens is that the drawing up and falling back of the armature ofthe magnet, PM', allows the associated escapement to advance the side switch one step. This brings the rotary magnet, RM', into action by allowing current to flow from the battery, B, through the windings to the ground on the point, 47a. iiiinultaneously, the levers, if", 45@ and 45d, move to their respective contacts, t7", 47C and 4:.71. Dueto the presence of the contact, 5%?. associated ivith the rotary magnet, Rld, the circuit of this magnet will be opened by the stroke of its own armature as described with reference to Fig. 3, and a series of impulses will advance the contact wipers, 49, 5t) and 5l, step by step over the contact pieces of that row of the bank. As soon as the contact wiper, 5l, engages a con tact of the private wire, 53, which is not grounded, the private magnet, PM, will release its armature, although it had been held since the beginning of the described rotation of the wipers. This release accomplishes through the escapenient, the second step of the side switch, advancing the arms, Li5 lto 45d, to the last position, breaking the ground contact between 4.5 and 47a, stopj ping further rotation of the shaft, as caused by the rotary magnet, RM. The actions of this last described movement of the side switch, are to .stop the rotation as indicated, to extend the line conductors to the wipers, 49 and 50, and to place a ground through the contact of the lever, 45d, with point. 48d, through the winding of the disconnect relay, DR, and the wiper, 5l, upon the conductor, and the various contact pieces of the private wire, It will be noted that the operations, and the `conditions in which `the selector is left, are quite identical with relation `to the first selector illustrated in Fig. 3.

In Fig. 5, illustrating the third selector, the trunk conductors, 57 and 58, may be considered to be extensions of the conductors.I 54 and 55, shown in Fig. 4, as leaving the second selectors. Similarly, the private conductors, 59, may be considered as an extension of 'the private conductor, 53, shown iii-Fig. 4, as leaving the second selector. The third selector differs from the first and second selectors in that the vertical and rotary relays are permanently bridged upon the trunk conductors, 57 and 58. In a normal condition the conductors, 57 and 58, are open at their respective levers, 60c and 60d of the side switch. Upon the actuation of the mechanism at the subscribers station in a manner corresponding with the third digit of the called number. ground contacts upon the vert-ical wire will cause current to flow from the battery, B, through the vertical rela-y, to the line, in as many impulses as the digit requires. This, in a manner similar to that previously described, will make contact between the spring, 64, and the ground contact, 65. This will cause current to flow from the battery, B, lever50b, contact. 6l",

through the vertical magnet, VM2, and the closed Contact between springs, 66 and 67, of the private magnet, PM2, to ground. The shaft of the third selector will thus be lifted by impulses until it is opposite the proper horizontal row. The ground impulse upon the rotary wire, which as usual succeeds the vertical series, will cause one movement of the rotary relay, RR2; this, as before, by virtue of current flowing from the battery, B, through the private magnet, PM2, to the ground contact of the spring, 68, with the ground Contact, G5, will cause an at traction and release of the armature of the magnet, PH? The breaking and making of contacts by the action of this armature, need not be here considered,- the important thing is that the forward and back motion of the armature in question acts, through the escapement, to advance the side switch one step, causing the contacts between the arms, 60a to 60e, to be placed upon the points, 62 to 62e respectively. As the contact, G2, is grounded, current will flow from the battery, through the rotary magnet, BH2, and its own interrupting Contact, to the lever, 60a, and to ground. This will cause a rotation of the shaft quite as described with reference to other switches, which will continue until the private wiper, 72, makes contact with a contact piece of the private wire, 73, of a trunk line which is not in use. As the contact of the pr' "ate wire of a trunk which is not in use has no ground upon it, the rotary movement of the shaft will cease because of the release of the armature of the private magnet, which armature is held attracted as long as the private wiper, 72, shall make connections with contact pieces connected with the grounded private wires of busy trunks. This arrest of the rotation of the shaft is due to the fact that current from the battery, B, through the private magnet, PM2, the Contact (S29, lever, 60e, to the private wiper, 7:2, may flow when a ground is encountered by that wiper, and may not otherwise; so that when a ground is not found, thc armature previously attracted falls away, advances the side switch to its third position, removing the connection between 62 and 60a, which has set the rotary magnet, RM2 in action. This third posit-ion of the side switch in addition to stopping the rotation of the shaft, extends the trunk. conductors, 57 and 58, through to the wipers, 7 O and 7l. Further, it acts to place a ground upon the lever, 60e, by contact with the point, 63e, and this grounds the private trunk conductor, 73. The elfect of this is to guard this trunk against being selected by any other third selector attempting to establish another connection.

It is to be noted that the condition of the extended connection is at this time that of having but one bridge upon it, this being that provided by the bridge of the vertical and rotary relays, VB2 and RRZ, in this described third selector.

. In Fig. 6, are shown the conditions of the connector. It is to a switch of this type that theY connection now is led, the trunk conductors entering the switch on the wires, 76 and 77; the vertical relay, VRS, and the rotary relay, BB3, forming a permanent bridge across the trunk co-nductors. In respense, therefore, to the impulses sent by the subscribers instrument for selection relative to the fourth digit of the called number, the vertical relay will be energized by current from the battery, B, through its winding to the wire, 76. At the same time the relay, VR2, in the third selector, will be operated, but, due to the fact that the side switch shown in Fig. 5, has completed its cycle. of connecting operations, these vertical impulses will produce no effect in that switch. In the connector as shown in Fig. 6, however, the vertical relay movements will cause steps on the part of the vertical magnet, VMS, by virtue of current from the battery, B, through the vertical magnet, the co-ntact, 81, to the lever, 80, of the side switch, the springs, 84 and 85 of the magnet, Pil/13. the spring, 86, to the ground contact, 87. These vertical impulses will cause the shaft of the switch to be lifted by successive steps. As usual, the series of vertical ground contacts at the substation will be followed by one rotary ground contact, the result being, through the agency of the magnet, PMS, to advance the side switch one step exactly as described with reference to the other switches. The results, however, of moving the sideJ switch levers to their second positions, are not eX- actly as before described. The movement of the lever, a, to the contact, 82a. puts the rotary magnet RM3, in the relation to the vertical relay, VB3, previously occupied by the vertical magnet, VMS. This being so, the next series of contacts at the substation between the gro-und and the vertical wire, causes as before, successive contacts between the springs of the vertical relay, VRS, and the rotary magnet, RMS, which is now actuated, stepping the shaft through as many horizontal steps as are required by the units in the fifth and last digit of the called number. The wipers, 88 and 89 thus make conu tact with two terminals of the line of the called subscriber, although the lines of the calling and called subscribers are not as yet connected together. The succeeding rotary impulse which always accompanies the series belonging to any digit, actuates the relay, BB3, to make one contact upon its spring, 91, and the ground contact, 87. Bv virtue of `current flowingq from the battery, B, through the magnet, PMS, and this contact between 91 and YV87, the armature o-f PM-3 is attracted and then released. This operates the side switch through the escapement, advancing all the levers to the third position. The results are three:

First, that the line conductors, 7 6 and 77, which have in series with them the condensers, 96 and 97, are extended by contact respectively of the levers, 80b with 88h, and 80c with 83e, tothe contacts o-f the spring, 92 with 102, and 94E with 95 respectively, of the ringing or calling relay, GR, and thence to the wipers, 88 and 89, respectively. This establishes a connection of the line of the calling subscriber with that of the called subscriber, as in this instance the conductors, 100 and 101, leading from the contacts, 98 and 99, are not a trunk line, but are a line to the called subscriber, via his first selector, yet to be described.

The second result of the side switch mo tion is that the lever, 80a, in moving upon the contact, 83a, entends the conductor which it carries to one terminal of the winding of the calling relay, Clt; the other terminal of that winding is connected to the battery, B. At this juncture, the calling` subscriber presses the ringing button of his telephone, which, vas before described, places a ground upon the vertical wire, this being in Fig. 6 designated as 76. Current from the battery, B, through the relay, VRS, to this ground at the substation, will actuate the relay, VB3, operating the winding of the calling relay, Clt, the path for current being from the battery, B, through the winding of the relay CR, by the side switch contact of 88 with 80a, and the contact of the private magnet springs, 84 witl1r85, the spring, 86, the contact, 87 of the relay, VRS, and thus to ground. The operation of the mechanism of the relay, CR, is to disconnect the springs, 102 and 95 from theirrespective contacts, 92 and 91, bringing them into contact with the springs, 103 and .93, these being the terminals of a ringing generator, 104, or other convenient source of ringing current. As the called subscribers line is immediately connected to the springs thus moved, calling current will be sent over his line. Upon his response, conversation may ensue.

The wires, 100 and 101, in the consideration of Fig. 6, have been spoken of as extending directly to the station of the called subscriber. By reference to Fig. 7, in which 127 and 128 are the extensions of the conductors, 100 and 101, the lines, 129 and 130. are to bev considered as leading directly to the station of the called subscriber. lOtherwise Fig. 7, is a duplicate representation of a first selector, and is similar to Fig. 3. ln the case of a selector of a called line, however, it is evident that it will not contain at the time of the connection, conditions which result from thecontrol of its station as no call has been made from that instrument;

nor has'the shaft of the switch been moved from a normal position. As this is so, the conductor, 131, which is anV extension ofthe private conductor, 132, of Fig. 6, leads through the closed ofi normal switch in the contact of springs-,142, 143 and 144, to the cut-off relay, CO. Upon the completion, therefore, through the act of the connector shown in Fig. 6, of a connection With a called line having the mechanism of Fig'. i", ground which is thus applied to the private Wires, 131 and 132, by the Wiper, 90, will establish a circuit from the battery, B, in Fig. 7, to and through the cut-off relay Winding, CO', through the contacts, 142 and 143, operating the cut-ofi relay, and removing the circuits of the relays` VR and RR, from thev line. This will eectuaily prevent any operation of the mechanism of the selector, and will keep that bridge off the line as is indicated inthe schematic arrangement of the circuit shown in Fig. 1.

The third result of the motion of the side switch is to effect contact between the lever, d, and the grounded point, 83d. This places a ground through the medium of the Wiper, 90, uponthe private contacts associated ivith the line of the called subscriber, thus preventing another connector from stopping With its Wipers upon the line of the called subscriber.

En the operation of this connector switch, as has been described, it was assumed that at the moment the Wipers, 88 and 89, are carried into connection With the contacts, 98 and 99, of the desiredline, that that line was not busy. lVhen it is remembered that at the moment of the making of this contact, the side switch was in its middle position, and that the rotary impulse, about to succeed the series of vertical inipulses, had not yet been given, the operations which succeed that impulse, in case the called line is busy, will be understood: In such a condition of connecting with a busy line, the contact Wiper, 90, will be in engagement with the grounded contact of the private Wire belonging to that line. In these circumstances` a circuit'involving the disconnect magnet. DMS, is established as follows: From the battery, B, through the Winding of the magnet, DMS, to the contact between the springs, 105 and 106, at the relay, RR3 to the contact, 82d, upon which at this moment rests the lever, 80d, to the private Wiper, and thence to ground. This will permit the energization of the magnet, DMS, and its action upon the vertical and rotary pawls will permit the shaftv to return to normal position, through the agency of its springs and gravity. It is thus seen that the rotary impulse following the series of vertical impulses which established final connection, acts to disconnect the connect-or switch if the line is busy, or to close the line through for con versation if the called line is not busy. In the care of the disconnection by virtue of the line being'busy, the side switch will be restored to its normal position. The subscriber will not know Whether he has connected with the called line or not, and uill, as a natural sequence, press his ringing button. This acts to ground the vertical wire` but instead of the resulting operation of the relay, VB3, being, as described, to operate the calling relay, CR, it will be to lift the Vshaft vertically one step, the means by which this is done being, as frequently described hereinbefore, the result of a period of ground upon the vertical wire, as 70 in Fig. G. It may be that the pressure of the ringing button may be in one impulse or in several, but the effect is only to lift the vertical shaft one step or several as the case may be. If it be lifted even one step` the oii normal switch, formed of the springs, 10T and 108, will close together; and in so doing Will establish a circuit from one pole of the auxiliary battery, B, through the high speed interrupter, 109, which is shunted by the condenser, 110, through the lamp resistance. 111, contacts 107 and 108, to the contact Si of the side switch, through the condenser, 96, over the conductor, 76, to the subscribens instrument, through his telephone, back to the central oliice and through the rotary line conductor, ultimately reaching through the conductor, 77, the relay, FR3, and through its Winding to the other pole of the battery, B. As the current in question is an interrupted one, it will find` a path through the circuit described, giving in the subscribers receiver a tone understood by him to mean that the called line is busy. In response to this signal he will hang up his receiver, causing disconnection of the other switches used in the previous operations, of which disconnection the sequence of events is as fol/lows:

By reference to Fig. 1, it Will be seen that in afcompleted connection there are only tivo permanent relay bridges upon the builtup line, so` far as any control ofthe calling station is concerned'. These are at the third selector and at the connector. It is evident that if disconnection is to take place through the agency of the bridged relays.` it cannot be instituted by the use of the relays at thi` first and second selectors concerned in the connection, nor at the first selector of the line which is called, but must be instituted by functions of the connector or the third selector, or of both. So far as the connector is concerned, as it has its vertical and rotary relays, VB3 and BB3, permanently in bridge and connected to the batterj, B, the act of hanging up the telephone receiver and connecting together and to ground the tivo sides ofthe line Will energize both of these relays, as has been described in the processes of connection. The rotary relay will, as usual, operate the magnet, PM3, because of current from the live pole of the battery, B, through the magnet, PMS, and to ground by Contact of the springs, 91 and 87. The magnet, PMP', will effect contact between its spring, 85, and contact, 112, establishing a circuit from the battery, B, through the disconnect magnet, DMS, to the spring, 86, and thence, through the simultaneous operation of the relay, VRS, toground by contact with the spring, 87. This current will energize the disconnect magnet, Dl 3, and witl draw the vertical and rotary pawl-s, allowing the shaft to return to its normal position by action of its spring and gravity.

lith respect to the disconnect actions in the third selector, reference to Fig. 5 will show that in this switch also, the vertical and rotary relays, VR2 and RRZ, are in permanent connection with two sides of the line, and with the battery. At the same instant when the ground was applied at the substation to the two sides of the line, releasing the connector, the relays, RRZ, and VR2, operate in precisely the same manner, energizing the disconnect magnet, DM2, Fig. 5, withdrawing the pawls from the shaft and allowing it to return to normal position. At the moment of the energization of the disconnect magnet marked DM2 in Fig. 5, 'a contact was made by that magnet between the springs, 113 and 114. This is by way of being a relay function of the disconnect magnet, DM2, and is the-only feature wherein the disconnect portions of the mechanism shown in Fig. 5, differ from those which have been described with reference to Fig. 6. The closure of the contact between springs, 113 and 114, establishes a circuit bacl: over the private conductor, 59, to the second selector. Current results, flowing from the live pole of the battery, B, through the resistance, 115, of about 100 ohms, over the private wire, 59, in Fig. 5, over the private wire, 53, in Fig. 4, to the contact which is in connection with the private wiper, 51, through the disconnect relay, DR', to the lever, 45d; and as this is in its final position, to the ground at contact, 48d. The winding of the disconnect relay, DR', is of low resistance and few turns, and therefore did not develop sutlicient energy within itself to be actuated in the circuit in which it was previously placed in series with the magnet, PM', of its own switch. It will, however, be actuated by being placed in the circuit which I have just described. and will close its contacts, 116 and 117. I find a convenient resistance to which to wind the relay, DR', to be about 8 ohms. The effect of closing together the springs, 116 and 117, willbe to establish a circuit from the battery, B, in Fig. 4, through the disconnect magnet, DM', springs, .116 and 117, to

ground, operating the magnet, DM', the release of its armature, acting to withdraw the vertical and rotary pawls from the shaft, permitting it to return to its normal position by the action of its spring and gravity. But the magnet, DM', similarly to the magnet, DM2, is provided with a con* tact so that it acts not only as a disconnect magnet, but as a disconnect relay, as well. Its contact, composed of the springs, 118 and 119, assists in establishing a circuit from the live pole of the battery, B, through the resistance, 120, conveniently of 100 ohms, over the private wire, 121, to the private wire, 56, shown in Fig. 3, as associated with the first selector. The sid-e switch of this lirst selector, being upon its third contacts, the circuit from the private wire, 56, will be extended through the wiper, 38, and-the disconnected relay, DR, to ground, via the lever, 25d, and the contact, 28d. The relay, DR, being energized will close contact between its springs, 122 and 123, establishing a circuit from the live pole of the battery, B, through the disconnect magnet, DM, to ground. The disconnect magnet will thus attract its armature, not shown in the drawing, and its subsequent release will withdraw the vertical and rotary pawls from the shaft, allowing it to return to normal position, through the agency of its spring and gravity. The disconnect relay, DR, of this switch, is provided with a winding of few turns, and low resistance, the latter being practical if about 8 ohms, adapted as described with reference to the second selector, to operate in series with the battery and a resistance of about 100 ohms, but not to operate in the previous condition of being in series with the winding of the private magnet, PM.

It will be observed that all of the switches have been released, and that the condition is now normal and ready for the setting up of a new connection.

For the purposes of giving service between toll or interurban lines, and local lines of an automatic exchange, it is sometimes necessary to establish trunk lines between a toll board and the automatic system. A satisfactory method of doing this is to terminate such trunk lines in spring jacks upon the toll board, and in lirst selector switches in the automatic apparatus. The toll operator may thus, by means of suitable lreys or switches, send impulses to the selector, which will cause it, and others with which it. will associate itself, to set up any desired connection with a called subscribers line. A subscriber so called by the toll opera'tor may desire to release his line from a toll connection, or may desire to 'signal the toll operator. Fig. 6 illustrates how this may be done. Assuming that it is desired by the called -subscriber to disconnect his line from the toll board, and knowing that at such a time of the connection the side switch will be upon its third position, the operations are these: The called subscriber moves the dial ot his instrument as if to cal'l adigit ot a desired number, and then hangs up hisreceiver. The movement ot the dial first mentioned serves to establish ground connection between the springs, 7, in Fig. 2, and the hanging up ot' the receiver, the connect-ion between the springs, 12, 13 and 14, grounding both sides ofthe line. This will ac'tua'te both the relays, BS and BR, in Fig. 6, the circuit in both cases being traced from the battery,B, through the relay in question, over the side of 'the line with which it is associated, and to the ground at the substation. These relays being i operated, the springs, 124, 125 and 126 will be closed togather. The spring, 126, being grounded by 'this joint action of the relays, which would not have been true if relay,fBR, `alone had been actuated, a circuit will be established trom the battery, B, through the magnet, DMS, 'to ground, attracting the armature of this disconnect magnet, withdrawing the vertical and rot-ary Apawls trom theshait, allowing it to returnto its normal iposition through the agency ot its spring and gravity. Y

i Itwill be seen that the described actions on the part of the subscriber would have secured release ot his line on the part ofthe connector, however the connection had been setup. f' i v tIt it should be desired by the subscriberfto give ay signal tothe toll board for the `purpose of indicating further instructions on his part while his line was being held by the toll operator, his manipulation `would he to press his ringing button, which `would ground `the conductor, 100, and establisha circuit as follows: From the batter B. through the relay, BS, lever, .80", an the contact, 83 of the side switch, the springs,

92 :and 102, of the relay, CR, the wiper, 88, and contact, 98, of the connector switch. The relay, BS, will operate, establishing a circuit as follows: From the battery, B, through conductor 150 to 4:aurelay or' other signal 151 on the toll board T, through conductor 152 tothe spring, 125, and the con-' tact, 12st, to ground. This will energize the relayer' signal upon the toll board during' the `pressure oi' the button at the subscribens stat-ion, indicating that he desires attention on the part of the toll operator.

Referring to Fig. 1, it will be seen that in addition to showing the relation of the vertical and rotary relays to coiuluctorsotithc line proper of each ot' lthe iive switches involved in a completed connection, the 4portions ottheprivate wire, P, are indicated to extend troni each switch group to the succeeding one, The result of this arrangement is that three conductors are required in each trunk which entends 'from switch group to switch group, and my invention contemplates such an arrangement, which is not a disadaf'antage ot economic importance in an exchange which has all of the lines ot its subscribers centering in one oilice, vor in a p'mrality of ofiiccs which are located very near to each other. The private wire which forms this third conductor in the sections .from switch group to switch group, serves, as has been described, to establish busy test conditions for t-he prevention or" connection with trunk lines which are in use, and in addition serves `t-he purpose oi' enabling one switch at which a bridge is present, to secure the operation of the release magnet at another switch at which no bridge is present.

lt will be seen from a consideration of the foregoing description and the illustrations to which it rcicrs, that each of the `line relays, such as VR and RR, VR and RR', etc., are means at the central oil'ice by which the subscriber controls the operation ot the various selectors and connectors. The magnets ot these controlling relays may, therefore, be termed controlling magnets, and it will be seen that in all cases they are normally bridged across the circuit of the subscriber-s line or of the trunk line to which 4the corresponding selecting switch belongs. ln the case, however, of some of the selecting switches, and more particularly of those connected with Athe subscribers lines for selecting trunks, and those of the `trunks selected by said subscribers selectors, these controllingmagncts are cut oit by the action oi the side switch so as to be ineiifective for further use after the selecting switches to which they belong have yperformed their' functions ot selecting and connecting with the succeeding trunk lines. By this means the combined circuit between two subscribers 4is relieved of some ot the bridges that would be' placed across it were the controlling magnets of all the selecting switches involved in making the connection le'lit permanently bridged. Unless other means are provided these selecting switches would be left without means tor releasing them at the close ot the conversation, since the two controlling magnets have in the past formed the only means tor bringing about such release. My system herein described, provides against this diiliculty, and makes pos sible the releasing of those switches which are deprived ot their normal bridges by means of a separate wire associated with each ot the various trunk lines, over which wire an electrical impulse is sent which, either directly or indirectly, energize's the release magnet of 4the switch or switches in vo'lved in the connection from which the normal bridges havebeen removed. lnother words, 'I provide uiieans `whereby one select Cil Cri

ing switch at which a bridge is present is adapted to bring about the operation of the release magnet of one or more other switches involved in the same connection, at which no bridge is present, this being accomplished over the third or p rivate wire.

I do not wish to limit myself in all respects tothe exact details and circuit connections here shown. For inst-ance, while I- have described a system in this applicationY with particular reference to an eli-- change wherein the subscribens numbers are composed oi' five digits, it is obviously applicable to apparatus and mechanisms re, quired by systems having a greater or a less. number of digits. Neither do I wish to limit Vmyself as to the number of selector switches involved in a connectio-n that shall have their normally bridged ycontri'illing magnets removed from connection with the line dur-v ing a connection. It is obvious that there will be conditions where only one of said pairs of controlling magnets need be'removed, and in other cases it may be desirable to remove an even `greater number than in the system of this application. It is also obvious that many other changes may be made without departing trom the spirit oi my invention.

Having thus described my invention, what I claimV as new and desire to secure by Iictters Patent, is:

l. In a telephone system, a metallic circuit line, a substation there-for, a selector for said line, selecting contacts in said selector, a pair of controlling `magnets ing the second of said magnets to cause the movement of said selecting contacts in another direction, a side switch adapted to disconnect botli ot said magnets and said line, and meanscontrolled by said second magnet for operatino` said side switch to disconnect both of saiy magnets from said line, substantially as described.

2. In an automatic telephone system, a metallic circuit line, a substation therefor, a selector at the central oliice for said line, selecting contacts in said selector, a pair of controlling relays for said selector bridged across said line, a source of current adapted to energize said relays overV the limbs of said line, means at the substation for. closing the circuit of one of said relays 'for causing said selecting contacts to move in one direction, means at the central of- Ytice for moving said selecting contacts 'in rent, a pair of controlling relays normally` connected between the limbs of said line and said source of current, means under the control of one of said relays for causing said selecting contacts to be moved in a longitudinal direction, a side switch, means under the control Aof said side switch for causing said selecting contacts to rotate, contacts on said side switch adapted to disconnect said pair of relays Yitrom the limbs of said line, and means under the control of said second relay to cause the operation of said side switch, substantially as described.

4. An automatic telephone system comprising a temporarily established circuit, a pair of switches having contacts serially included in said circuit, an electromagnet controlling the release of. one lof said switches, a third conductor independent ot the talking circuit extending between said switches, a iesistance coil in the other switch, and means at the latter switch for connecting said elect-romagnet and said resistance coil in series with said third conductor or causing the release of the iirst switch.

5. An automatic telephone system coniprising a temporarily established talking circuit, a selector relay bridge temporarily disconnected or cut oiit from said circuit, a selectorwiper controlled by said bridge, a connector relay bridge retained across said circuit for releasing purposes, together with selector and connector releasing means, a resistance coil associated with the connector and included in a release circuit through said wiper controlled by the connector relay bridge.

6.- An automatic telephone system coinprising a temporarily established talking circuit, a selector relay bridge temporarily ,disconnected or cut off from said circuit, a y,selector wiper controlled by said bridge, a .connector relay bridge retained across said circuit for releasing purposes, together with selector and connector releasing means, a

resistance coil associated with the connector State of Illinois.

BERT @UNI-IMEI,