US784498A - Automatic-telephone-exchange system. - Google Patents

Description

PATENTED MAR. '7, 1905. J. K. NORSTROM & H. M. GRAIP.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAY 18, 1903. RENEWED JULY 5. 1904.

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No. 784,498. PATENTED MAR. '7, 1905. J. K. NORSTROM 6/: H. M. GRAIF.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAY 18, 1903. RENEWED JULY 5. 1904.

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AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLIUATIOH FILED MAY 1a, 1903. BEHEWED JULY 5. 1904.

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UNITED STATES Patented March '7', 1905.

PATENT OEETC JOHN K. NORSTROM AND HENRY M. GRAIF, OF CHICAGO, ILLINOIS, ASSIGNORS TO AUTOMATIC TELEPHONE COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF- ILLINOIS.

AUTOMATlC-TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 784,498, dated. March '7, 1905.

Application filed May 18, 1903. Renewed July 5, 1904. Serial No. 215.393.

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Be it known that we, J OHN K. NORSTROM and HENRY M. GRAIF, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Automatic-'lelephone-Exchange Systems; and we hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, which form part of this specification.

Our invention relates to automatic-telephone-exchange systems wherein the various functions of a telephone-exchange incident to the operation of connecting for intercommunication the lines of two subscribers are automatically performed.

One of the objects of our invention is to provide a system wherein for a switchboard accommodatinga given number of subscribers say one hundreda relatively small nmnber of line-selecting switches-say ten-may be employed and to so arrange the switches with reference to auxiliary devices and the lines that any switch may be controlled and actuated from any line.

A further object of our invention is to so arrange the switches and auxiliary devices relative to the lines of the subscribers that at any time any subscriber can control only the first idle or inactive switch and that when any switch is in service for one subscriber said switch is positively removed from the control of any other subscriber, the first then idle switch, however, being automatically brought within the control of the other subscribers.

A further object of our invention is to provide a system wherein the actuating mechanisms of the various devices are placed in circuits auxiliary to the talking-circuit, so that said talking-circuit when established between two subscribers stations contains no local resistances, such as relay-coils or other impeding devices, in series in said circuit within the exchange.

Numerous other desiderata of automatic-exchange telephony are accomplished in the use of our invention which one will not here seek to enumerate, but which will become apparent to those skilled in the art from the disclosure made in the following specification and claims and the accompanying drawings.

In the drawings, wherein we have illus trated our invention as applied to a centralenergy telephone-exchange, Figure 1 is a diagrammatic illustration of the stations of two subscribers, the line-wires of said subscribers being so related that when the intersection-line Y Y of said figure is coincidently superposed on line Y Y of Fig. 2 said wires form connections with the corresponding wires intersected by line Y Y of Fig. 2. Figs. 2 and 3 are continuing views diagrammatically illustrating the central mechanism of an automatiocxchange system, it being understood that the wires intersected by the broken line V V of Fi 2 are continued from the colresponding points intersected by the line V V of Fig. 3. Fig. 4 is an enlarged detail of the switch mechanism diagrammatically illustrated in Fig. 3, the wiring of Fig. 4. being so arranged that it corresponds with that of Fig. 3 wl1en;su pol-posed upon Fig. 3 with the dotted lines XX of the respective ligures coincidentally placed.

Referring now first to Fig. 1, station No. 1 and station No. 2 are illustrated as equipped with apparatus similar in every respect, so that it will be necessary only to describe a single station, it being understood that the equipment is duplicated at every other station. At station No. 1. 5 indicates a receiverhook; 6, a receiver; 7, a transmitter; 8, a polarized bell, and 9, 10, and 11 represent three eircuitchanging keys suitably associated with the subscribers set. These keys we will for convenient reference arbitrarily designate as follows: 9 the primary-impulse key, 10 the switch-operating key, and 11 the connecting-key. The three keys are illustrated as simple circuit-changing keys, each havingaspring-leaf arranged to play between an upper and a lower contact and each normally closing a circuit through its upper contact. In practice of course other mechanism may be employed; but we prefer to herein illustrate our invention in its simplest asconnected to earth, as by taps 9, 10, and 11,

respectively, to a common ground-wire 12. The key 11 is connected to the upper contact of key 9 by wire 11", so that when said key 9 is in normal position the key 11 is connected to the line-wire Z.

The telephone devices are wired as follows: From the upper hook-contact extends the wire 13, including in its circuit the primary p of an induction-coil and the transmitter 7 and terminating in the upper contact-point of the key 11. A tap 14, taken from said wire 13,includes the polarized hell 8 and terminates in the lower hook-contact. The hook is permanently connected by wire 16 with the upper contact of key 10. The receiver 6 is included in a closed circuit 6, also including the secondary j) of the induction-coil inductively associated with the primary of said coil. 15 indicates a tap from wire 13, extending to a second lower contact of key 11 and preferably including in its circuit a resistance 15.

It will be apparent that with the arrangement described when the receiver is upon the hook, as illustrated at station No. 2, the bell is cut into the line-circuit and the transmitter excluded from said circuit and that when the receiver is removed from the hook, as illustrated at station No. 1, the bell is cut out of circuit and the transmitter 7 included there- It will also be apparent that the depression of any one of the three keys 9, 10, or 11 grounds the line on one side or the other and cuts out all of the telephone instruments.

Referring now to Figs. 2 and 3, which illustrate the apparatus employed at the central station for automatically connecting the lines of any two subscribers for communication upon the proper actuation of the devices at the station of the calling subscriber, the incoming pairs of lines are indicated at L L L, &c., to correspond with their respective stations Nos. 1, 2, 3, &c.

WVe have chosen to illustrate our invention as embodied in a switchboard equipped for five subscribers; but it will be apparent that it might be extended to include any desired number of subscribers. The incoming lines are all brought upon the switchboard and are wired in multiple to corresponding pairs of I it is our plan to employ in conjunction with each switch a group of relays to perform functions which will be hereinafter described, one group being provided for each switch, as illustrated in Fig. 3. Further, associated with each switch is a series of relays, (shown in Fig. 2,) which we will arbitrarily designate switch-controlling relays, equal in number to the number of lines accommodated in the exchange, all of the relays in a series being connected in multiple with the common switch and corresponding relays of the several series being connected inmultiple with the corresponding subscribers lines to form what we term subscribers sets of relays, one set for each subscriber. This arrangement may be clearly seen by reference to Fig. 2, wherein the switch-controlling relays S C R in any transverse line form a series associated with one of the line-selecting switches L S of Fig. 3, while thc'vertically-alining relays S C R form sets operatively connected with the corresponding subscribers lines L L &c. Further, associated with each subscribers linecircuit are certain primary relays, each bridged from one side of the line to a grounding group of auxiliary relays and its series of the aforesaid switch controlling relays, is

identical with that of every other switch except in such particulars as may be specifically pointed out. Hence the description of one line with reference to its associated devices will suffice as description of every line, and, similarly, the description of one switch and its associated devices will suffice as a general description of all of the switches.

In the drawings the parts are illustrated in the condition assumed when subscriber No. 1 desiring to call subscriber No. 2, has taken the preliminary steps necessary to secure the connection of his line with the line of said subscriber No. 2 and has rung up said subscriber No. 2, the receiver of station No. 1 being illustratedas off its hook and proper relays of the central exchange being illustrated in the closed or active position assumed to secure the connection of station No. 1 with station No. 2.

Referring now to Fig. 2, it will be seen that with each incoming subscribers line is associated a pair of primary relays, respectively indicated as P Rand P'Rand a set of switchcontrolling S C R, the number of switch-con trolling relays corresponding with the number of line-selecting switches employed in the exchange.

In Fig. 2 it will be noted that allof the primary relays upon the board are connected to a common wire g, including in its circuit a common local relay-battery LRB, and thence extending to groundat Ur. Further, it will be noted that one of the contact-points of each primary relay is connected to the central-battery wire 5, which, as shown in Fig. 3, is connected with the central batteryOB. The relay P R of each subscriber has its other contact-point connected with the wire :r, which said wire has certain connections, to be hereinafter described, with each of the switch-eontrolling relays of the particular subscribers set, while the other contact-point of relay P R has a similar connection with the companion wire :11, likewise common to all the relays of a subscribers set. The relays P R and P R are preferably identical in construction, each preferably comprising simply an electromagnet the movement of whose armature serves to bring into contact two normally open or separated contact-springs. In detail the connections of these two relays are as follows: One terminal of the spool ofrelay P R is tapped by wire 17 to line-wire Z, and its other terminal is tapped by wire 18 to the wire 5 One spring of the normally separated contact-springs is directly connected with wire :11, while the other is tapped, as indicated at 19, to the battery-wire 7). The relay P R also has one terminal of its spool tapped by wire 18 to the wire 9, its opposite spool-terminal being connected by wire 20 with the side! of the incoming line. One of the contact-springs of relay P R is tapped by wire 19' to the common battery-wire b,and its other spring has direct connection with the wire :0. Groundreturn circuits may be established through the sides of the lines to include the spools of the respective relays, as will be hereinafter fully described.

Referring now to the wiring of the switchcontrolling relays S O R, it will be noted that all of the relays of a subscribers set have similar contact connections with the sides l andl of the line of the subscriber and with the companion wires of the auxiliary circuitscc and Ir. Further, certain of the contact and spool connections of each relay in a series corresponding with a switch are made to three pairs of wires common to the series and indicated as a a, c c, and (Z d, the connections whereof will be hereinafter traced.

Referring now to the construction of the switch-controlling relays illustrated, it will be seen that each relay comprises an electromagnet whose armature is carried upon the extended leg of a T-shaped pivoted member. Five contact-springs adapted for cooperation with corresponding contact-points are carried by the armature-carrying member, one such spring being carried by the extended leg, and the remaining four springs being arranged one on each side of each end of the cross-head of the armature-carrying member. The armature is so arranged that when in its normal or unattracted position all of its contacts are open.

To simplify the drawings and description, it is believed unnecessary to number each of the contact-springs; but said springs will be referred to by their relative positions, the cross-head springs beingspoken of as upper Ls ht as v and lower, right and leftspr1ngs, and the single springs upon the extended legs of the armature-carriers being referred to as the end springs. The contact-points will be correspondingly designated.

To describe now the wiring of the switchcontrolling relays: One terminal of each spool is tapped at 21 to a wire 22, which is tapped to the auxiliary line a of a subscribers set of relays. The opposite terminal of the spool is tapped by wire 23 to the wire 0, common to a series of the relays. The wire 22 is likewise tapped by wire 2% to the lower right contact-spring of the relay and has a connection to the end contact-point of the relay. The end contact-spring is tapped by wire 25 to the wire 0, common to a series of relays. The lower right contact-pointis tapped by wire 26 to the wire (I of a relay series. The lower left contact-point is similarly tapped by wire 27 to the wire (Z of the relay series. The lower left spring is tapped by wire 28 to the auxiliary wire 0:. The upper right and left contact-springs are tapped by wires 29 and 30, respectively, to the line-wires/and Z, respectively. The coacting contact-points, upper right and left, respectively, are tapped by wires 31 and 32, respectively, to the wires 11. and a, respectively, common to a relay series. These wires (6 a we will hereinafter refer to as "conncctingwires, as, together with another pair on continuing wires, they subserve practically the functions of the cord wires of a manual exchange.

Referring now to Fig. 3, it will be seen that with each line-selecting switch L S is associated a group of three relays, similar in their general construction to the switch-controlling relays and which for purposes of convenient identification we will arbitrarily designate for reference as the circuit-closing relay O O R, the key-controlled relay K O R, and the busy-test relay B T R. Further, each switch has an operating-relay proper, S O R, having a spring on its armature normally contacting with the upper one of two associated contact-points, and a releasing-magnet R M, movement of whose armature actuates a mechanical switch releasing device to be described. Each switch also has in the operative relation thereto (best shown in Fig. 4) a set of three circuit-changing springs, (indicated, respectively, by the numerals s1), s

and spi) a pair of circuit-making spring 579* and 8p, and a pair of circuit-breaking springs 8p and SP A power-driven ringing-generator for the entire exchange is indicated at R, and a busy-test buzzer or vibrator of an ordinary type, likewise for the entire exchange, is illustrated at Z. O B represent a central battery common to the whole exchange, while local batteries, one for each switch, are indicated at S R B and will be hereinafter arbitrarily designated switch-relay batteries.

Referring now to the general plan of wiring, it will be seen that the pairs of wires a a, 0 c, and (Z (Z of the several relay series are led into proper connection with devices of the corresponding switches, such connections being hereinafter fully described. The corresponding relays of the several groups are quite independent of each other; but the several relays of each group are similarly wired relative to each other. Certain common connections for the several groups of relays and switches are, however, provided,the following-named wires being common to all the switches and their associate devices in the exchange.

If indicates a battery-wire connected to the terminal of central battery C B opposite that to which the battery-wire b is connected. 6 indicates another battery-wire tapped to wire 5 while 6 indicates a battery-wire common to relays of the several groups tapped to wire 5.

r and 0" represent wires connected with opposite terminals of the ringing-generator R and having taps to like contacts of corresponding relays of the several groups, while .2 and 2 indicate wires connected with the terminals of the buzzer Z and likewise tapped to contacts of corresponding relays of the several groups.

To take up now in detail the wiring of a single group of relays associated with a switch and the other mechanism of such switch, we will first trace the six wires (0 a, c 0', and (Zd. The wire a is connected by a suitable split tap 39 to both the upper and lower left springs of the circuit-closing relay C C R and is also tapped by wire 40 to the upper right spring of the busy-test relay B T R. The wire a is tapped by wire 41 to a common connection 41 between the right upper and lower springs of the circuit-closing relay O C R and from the point of said tap extends through an impedance-coil l C to tap the wire I), connected to the battery, as heretofore specified. The wire 0 is tapped by wire 42 to the busy-test relay B T R, the tap being split and one branch, 43, connected with the lower right spring of said relay, while the other branch, 44, terminates in the end contact-point 45 of the busytest relay. It will be noted, however, that the end contact-point 45 is so disposed relative to its spring that it contacts with said spring when the relay is deenergized. In this point alone the busy-test relay differs in mechanical construction from the switch-controlling relays. From the point where the tap 42 is taken the wire 0 extends to and terminates in the circuit-closing spring 8p. The wire 0 is tapped at 46 to one terminal of the spool of the circuit-closing relay G C R. Again, it is tapped by wire 47 to the lower left spring of the busy-test relay B TR. From the last-mentioned tap it extends to and is connected with the wire 48, which forms the connection between one terminal of the switchrelay battery S R B and the lower circuitchanging spring 512 The wire l is directconnected to the lower spring 579" of the pair of circuit-making springs. The wire d is direct-connected with one terminal of the spool of switch-operating relay S O R.

Referring now to the circuit-closing relay 0 C R, the upper pair of contact-points are connected by wiper-wires w and on, which in operation are complementary to the connecting-wires a a, to the two wipers or contactsprings of the operating-arm 101 of the lineselecting switch L S. The lower left and right contact-points are connected, respectively, by wires 50 and 51 with the left lower and upper springs of the key-controlled relay K C R. The spool-terminal of the circuitclosing relay opposite that connected by wire 46 with line 0 is connected to wire 52, from which taps 53 and 54 respectively extend to the end contact-points of the circuit-closing and key-controlled relays. The end contactsprings of the three relays C C R, K C R, and B T R are all connected together, being respectively tapped by wires 55, 56, and 57 to a common connecting-wire 58.

Examining now the connections of the key controlled relay K O R, not heretofore stated, the right upper spring is tapped by wire 59 to the ringer-wirefl. The lower right spring forms a terminal for wire 60, which extends thence to one terminal of the spool of the busytest relay B T R and is tapped at 61 to the lower right contact-point of said relay. The upper right point of relay K C R forms a terminal of wire 62, connected with the other terminal of the spool of busy-test relay B T R, said wire being tapped by wire 63 to the lower left contact-point of said busy -test relay. The two usual lower contacts for thelower right and left springs of the key-controlled relay K G R are connected together by wire 64. In addition to these usual contact-points an additional contact-point 65, arranged for contact with the lower left' spring when the relay is denergized, is provided. A wire 66, terminating at one end in said contact-point 65, includes an impedance-coil I G and is tapped to the battery-wire 6 One terminal of the spool of the key'controlled relay K C R is tapped at 67 to the'battery-wire b, and its other terminal is connected by wire 68 with the upper contact-point associated with the spring carried by the armature of switch-operating relay S O R.

Referring now to the busy-test relay B T R, its upper left spring is connected by wire 69 with the battery-wire 71 Its upper right spring is tapped by wire 10 to the connectingwire a, as heretofore described. The coacting contact-points are tapped by wires and 71, respectively, to buzzer-wires .2 and of the buzzer Z. The remaining connections of the busy-test relay have been heretofore described.

Referring now to the connections of the switch mechanism proper, which may be-best seen in Fig. 1, the terminal of the operatingspool opposite that connected to wire (1 is tapped by wire 72 to the battery-wire if. which, as heretofore stated, extends to the circuit-changing spring .91 ()ne side of the spool of the releasing-magnet R M is tapped by wire 7 3 to the aforesaid battery-wire b and the other spool-terminal is wired, as indicated at '74:, to the lower contact-point of the armature-carrying lever of the switch-operating relay. The contact-spring of said switchoperating relay S O R is connected by wire 75 to the circuit-closing spring sp". The terminal of the switch-relay battery S R B opposite that to which wire 18 is connected, as heretofore described, is connected with the lower circuitbreaking spring s7) by wire 76. The upper circuit-changing spring s3) is connected by wire it with the middle spring $1.2 of the circuit-changing group of the next succeeding switch, while the upper spring s1) of said second group is similarly connected by wire it with the middle spring 512 of the circuitchanging group of the third switch, and so on, it being understood that a battery-wire b is connected to the central movable spring sp of a circuit-changing set for one switch and the upper spring 81) of said group for each switch being wired to the spring .9) of the group of the next succeeding switch throughout the entire exchange. I

For purposes of illustration we have herein shown a simple form of switch which might be used in the practice of our invention, and the mechanical arrangement of said switch we will now describe.

Referring particularly to Fig. 1, 101 indicates a rotary switch-arm mounted upon a rotatable shaft 102. Said shaft likewise carries a ratchet 103 and is connected with a spring 101, arranged to exert a pressure upon the shaft, tending to hold it in the inactive position illustrated in Fig. 1. The switcharm 101 is provided with two contact-springs or wipers 105 and 105, adapted when the arm is moved to sweep over the corresponding pairs of contact-points s s &c., into which the incoming subscribers lines are led, as heretofore described. The switch-arm is also provided with two insulated projections 106 and 107, adapted when the switch is in inactive position to respectively engage the springs s2) and A7). The spring .571 is held its projection 106 in contact with the lower spring sp of the circuit-changing set, but is so arranged that when released by the movement of the switch-arm it springs into contact with the uppermost spring .572 of the circuit-changing set. The insulated projection 107 serves to hold the spring *7) out of contact with the spring sp",,such contact being made as soon as the switch-arm is moved. 108 indicates the armature of the switch-operating relay S O R, mounted upon one end of a pivoted lever 109, the opposite end of which extends into proximity to the ratchet 103. 110 indicates a pawl pivoted on the free extremity of the lever 109 and normally held by aspringlll in engagement with the ratchet 103. 112 indicates a pin or linger projecting from the pawl 110, so that when struck upward it will throw the pawl out of engagement with theratchet 103. It will be apparent now that whenever the spool of the switch-operating relay is energized to attract its armature the ratchet-and-pawl connection -will serve to rotate the shaft forward a distance corresponding with one tooth of the ratchet. The parts are so proportioned that this movement also just sutlices to bring the wipers 105 and 105 into contact with the corresponding terminals of the next preceding line, one movement of the lever serving to make connection between the wipers and the contacts s, two movements to move the wipers into contact with termini s &c.

The holding and releasing means may be arranged as follows: 113 indicates a dog pivoted at 11% and provided, as at 115, with a tooth adapted to engage the ratchet to prevent its return to inactive position under the tension of its spring 10-1. A spring 110 serves to maintain the dog in operative or holding position. 117- indicates a lug projecting from the dog 113 and normally lying immediately below the projection 112 from a pawl 110. 118 indicates a pin projecting from the dog on the. same side of the pivot as the tooth 115. 119 indicates a pivoted lever at one end carrying the armature of the release-magnet R M and at its other end carrying a pivoted releasing-arm 120. The arm 120 extends up beside and overlies the dog 113, its front edge normally resting in contact with the pin 118, carried by said dog, and a linger 125, projecting from the switch-arm. A spring 121, connected to a hook 122 of the arm 120, projecting on one side of its pivot-point, serves to both hold the arm normally down in contact with the stop122 and to maintain its bearing with a constant pressure against the stud 113. Notches 123 and 121 are provided on the side of the arm 120, said notches being so arranged that when said arm 120 is elevated and moved inward the pin 118 of the dog and the end,of the circuit-breaking spring .s}) respectively rest therein.

The operation of the release mechanism so ITO arranged will be as follows: When the spool of the magnet R M is energized to attract the armature carried by lever 119, the arm 120 will be raised. If now the switch-arm 101 be in advanced position, so that the finger 125 is removed from the path of the arm 120, the last said arm will be moved inward by the tension of its spring 121, so that its notches 123 and 124 respectively engage the pin 118 and the end of the spring 571 WVhen now the magnet is deenergized, the spring 121 pulls down the arm 120, holding it constantly, however, toward the engaged stud and spring and pulling with it the said instrumentalities. Consequently any circuit established through springs .92 and .59) will be broken, and the dog 113 will be moved so that its tooth 115 is dis engaged from the ratchet 103. At the same time projection 117 of the dog strikes the projection 112 of the pawl 110, throwing the pawl out of connection with the ratchet. The ratchet being now entirely freed, the shaft rotates to return the arm 101 to its normal position under tension of the spring 104. When the arm 101 reaches its normal or inactive position, its linger 125 strikes the arm 120 of the release mechanism and moves it to the right against the tension of its spring, thereby releasing the stud 118 of the dog 113 and spring .592 from the engaging notches in the arm 120 of the release mechanism. At the same time the projection 117 of the dog is removed from the path of the projection 112 of the pawl, allowing the pawl to return under tension of its spring 111 into engagement with the ratchet. The parts are now restored to their initial position, as illustrated in Fig. 4

Having thus described minutely the present illustrative embodiment of our invention, we will now describe the operation of the system. Assuming that the subscriber at station No. 1 is desirous of calling subscriber No. 2, his actions and their results will be as follows: The removal of the receiver 6 from the hook 5, as indicated at station'No. 1 in Fig. 1, cuts the bell 8 out of the line and the telephone instruments into operative connection with the two line-wires, the circuits therethrough being traced in through line-wire Z, key 9, wire 11 to key 11, thence by wire 13 to the transmitter 7, through the primary 7) of the induction-coil to the receiver-hook 5, and thence by wire 16 and key 10 back to the line-wire Z. Now the primary impulse-key 9 is depressed by the calling-subscriber, grounding the side of the line Z through the wire 12. A circuit is thereby completed, which we may trace from the ground in Fig. 1 through the primary impulse-key 9 to the wire Z, thence, in Fig. 2, by wire 17 to the spool of primary relay P R, back from the spool of said relay by wire 18 to the wire 9, and by said wire through the local battery L R B to ground. It will be noted that the above circuit includes the spool of the primary relay P R, the armature of which is accordingly attracted, closing its associated contact-springs. This establishes a circuit which may be traced from the lower spring of primary relay P B through wire 19 to the battery-wire Z), which, it will be remembered, connects with left end of the central battery C B (shown in Fig. 3) and, on

the other hand, extending from the upper spring of the relay P R by wire in and wires 22 and 21 to the spool of the first switch-controlling relay S C R of the first subscribers set, thence from the other terminal of the spool by tap 23 to wire a, continuing, on Fig. 3, past taps 46 and 47 to the wire 48, thence upward to the lower spring 8[)3 of the circuitchanging set, which (it being assumed that the uppermost switch L S is not in use) contacts with spring s7) and from the latter spring by battery-wire Z) to the right terminal of the central battery C B. Thus it will be seen that a closed circuit is established which includes the central battery C B and the spool of the first switch-controlling relay S C R. The armature of said relay S C R-is accordingly attracted to the position illustrated in Fig. 2, and a local circuit, including the spool, is established to hold the armature indefinitely in closed or active position. The local circuit is traced as follows: from the end contact-point of the relay by wires 22 and 21 to the spool, thence by wire 23 to the series wire 0, thence continuing on, in Fig. 3, to the wire 48, connected to the left side of the local switclrrelay battery S B B. On the other hand, the circuit extends from the end spring of the relay by wire 25 to series wire 0, thence, in Fig. 3, alongto the spring sy), which is closed upon spring 72 and thence by wire 76 to the right terminal of the switch-relay battery S R B, completing the closed local circuit. It will be noted that as long as the subscriber maintains the primary impulse-key 9 in closed position the spool of the switch-controlling relay S G R will be energized both by the central battery C B and the local battery S B B. It is necessary, therefore, that the wires 48 and b be connected to like terminals of the two batteries to prevent the occurrence of a short circuit. It will beunderstood, however, that the primary impulse-key 9 need be closed only momentarily to send a single impulse through the primary relay PR and may be then released. The switch-operating key 10 is now depressed by the calling subscriber a number of times corresponding with the number of the subscriber whom he desires to call, in the present instance two movements of the key being necessary to call subscriber No. 2. Upon each depression of the key 10 a circuit is established through the primary relay P R as follows: from the ground, in

Fig. 1, by wire 12 and tap 10 to key 10,

thence to the line-wire Z, continuing on, Fig. 2, by the tap 20 to the one side of .the spool of'relay P R, thence by wire 18 to wire r through the local battery L R B, and to ground again. Consequently the armature of relay P R will be now attracted to close its contact-springs as many times as the switch-operating key 10 is depressed. ith each movement of the armature of said relay P R a circuit is closed through the spool of the switchoperating relay S O R as follows: beginning at the upper spring of the contact pair of the relay P R by wire a" and tap 28 to the lower left spring of the switch-controlling relay S ,C R, (which, it will be remembered, is being maintained in active position,) thence by tap 27 to wire (7, which continuing (in Fig. 3) extends direct to the spool of the relay S O R, thence back by wire 72 and battery-wire b to the right side of central battery C B, and, on the other hand, from the lower contactspring of the primary relay P R by tap 19 to the battery-wire 7), connecting with the opposite terminal of central battery C B. It will thus be apparent that the spool of the switch-operating relay SD R will be energized and deenergized as many times as the switch-operating key 10 of the subscribers station may be depressed.

Referring now to Fig. 4, it will be apparent 1% of the line L coming in from the station of subscriber No. 2. In Fig. 3 the wiper-arm is illustrated in such position. The movement of the arm 101, as heretofore stated, releases the spring 6P2, which leaves its lower spring 5]) and contacts with spring for a purpose to be described. It will be noted now that the line-wires of subscriber No. 1 are connected, respectively, by taps 29 and 30 to connecting-wires a and H, which, as shown in Fig; 3, are led in by taps 11 and 39, respectively, to the right upper and lower and left upper and lower springs of the circuit-closing relay 0 U R. It will also be noted that the wipers of a switch arm are connected by wiper-wires and w to the upper left and right contact-points of said circuit-closing relayU C R. As no circuit has yet been established through the spool of said relayG O R, however, the lines of the subscribers 1 and 2 are not yet connected, but are open at that point. A single operation upon the part of subscriber No. 1 now secures for him the connection of the two lines and either rings subscriber No. 2 or, if the latter subscribers' line be busy, gives the calling subscriber No. 1 the busy slgnal and disconnects h1s line from the line already busy. The results enumerated follow the depression of the connectn'ig-key 11, which closes a local circuit through the primary relay P R as follows: from the ground by wire 12 through the connecting-key 11, wirell, and key 9, to thelinewire 1, thence by tap 17 to the coil of relay PR, back by tap 18 to the ground-wire g, and thence through the local battery L R B to ground at G. As long as the said connectingkey 11 is maintained closed the armature of the primary relay P R maintains connection between the springs of said relay, establishing the following circuit: from the lower contactspring of relay P R by wire 19 to the batterywire I), connected to the left-hand side of the central battery C B, and. on the other hand,,extending from the upper spring of the pair of relay 1 R by wire a and taps 22 and 24 to the lower right spring of the switch-controlling relay, thence by tap 26 to wire (Z, thence direct to spring x79 on to the upper spring x7), thence by wire 75 to the spring of the switchoperating relay S O R, (which is now deenergizcd,) and from said spring by wire 68, through the spool of key-controlled relay K C R; thence by tap 67 to the battery-wire 7/, which connects with the right terminal of the central battery C B. Accordingly the relay K C R is energized, attracting its armature and closing its various contacts. It will be apparent, however, that the relayK C R remains energized only while the keyll is held depressed. The closing of the key-controlled relay K C R primarily serves to close a circuit through the spool of circuit-closing relay C (1 R, such circuit being traced as follows: on the one hand, from the end spring of the relay K C R by wires 56 and 58 to end spring of relay B T R, end spring-contact 45, wire 14, and tap 12 to the wire 0, through the springs s and .sp? and wire 76 to the right end of the battery S R B, and, on the other hand, from the end contact-point of relay K C R, tap 54K, wire 52, to the spool of relay 0 C R, thence from the other side of the spool by tap 46, wire 0, and wire 18 to the left end of battery S R B. The armature of relay C C R is accordingly attracted and is held in such position irrespective of the key controlled relay by the closing of the end spring of the relay C C R upon its point, giving a connection (through wires and 53) between wires 58 and 52 of the circuit last traced parallel with the connection between such circuit- wires 58 and 52 established by the keycontrolled relay through wires 5st and 56. The closing of the circuit-closing relay serves, primarily, to establish a direct connection between the lines of the calling and called subscribers, including no local resistances, such as relay-coils or like impedanccs', within the line-circuit in the exchange. Further, the closing of said relay serves to bridge the a ringer, buzzer, and central-battery wires onto the connected lines, so that upon the closing of circuit through any one of said instrumentalities it is enabled to perform its functions. The ringing and busy-signal ing devices are first brought into operation only if both the key-controlled relay K (J R and circuit-closing relay are simultaneously closed, while the central battery is bridged onto the connected lines only when the relay K C R is denergized. WVe will first trace the line-circuit through from station to station, presuming that the station instruments are in the conditions illustrated in Fig. 1 of the drawings. Commencing now with the hook 5 at station 1: by wire 13, including primary 7) of the induction-coil, and transmitter 7 to the upper contact of the connecting-key 11, thence through the key 11, wire 11, and key 9 to the line-wire Z, continuing, Fig. 2, to the energized switch-controlling relay by tap 30 to the upper left spring thereof, thence by tap 32 to connecting-wire a, continuing, Fig. 3, to the circuit-closing relay 0 U B, through tap 39 and upper left spring, thence by complementary connecting-wire .w to the wiper, and on to the terminal of line L, corresponding with line-wire Z, thence (returning) through wire Z of pair L in Fig. 2 up to station 2 in Fig. 1, in through the key 9, wire 11", key 11, wire 13, and tap 1 1, including the bell 8, to the receiver-hook 5, out over wire 16 and key 10 to line Z, returning to the corresponding terminal of the central switch, through the wiper to wire 20, onto upper right spring of the relay C C R, thence by taps 4:1 and 11 to the connecting-wire a, back to the upper right spring of the energized switch-controlling relay S C R, and by tap 29 to line-wire Zof line L and in through key 10 and wire 16 of station No. 1 to the receiver-hook 5. Assuming now that the key 11 is, when depressed to energize the key-controlled relay K CR, as heretofore described, maintained in such position for a suitable time, the ringing-generator R is bridged upon the connected'lines of subscribers 1 and 2 to ring the bell of subscriber 2 and energizing the primary 7) of the induction-coil and the transmitter of subscriber No.

1, the circuit being as follows: from one'terminal of the generator by wire r and tap 19 to the upper-left spring of the key-controlled relay K C R, thence by wire 51 to the lower right spring of the circuit-closing,relay C C R, which, it will be remembered, forms part of the connection of one side of the line of subscribers 1 and 2. From the other terminal the circuit is traced from the ringing-generator B, through 'wire '1", wire 59, to upper right spring of the key-controlled relay K C R, thence by wire 62 to the spool of the busy-test relay B T R, returning by wire to the lower right spring of the key-controlled relay, thence by the connection 64 to the lower left spring, and

' thence by wire 50 to the lower left contactwill be seen that the ringer is bridged on the two lines, so that it transmits its impulses both ways. In tracing the foregoing circuit it will have been noticed that the spool of the busy-test relay B T R was included therein. It will be understood, however, that the said spool is so wound that its armature is not responsive to the current supplied by the ringing-generator, which for purposes of illustration we will say-is designed to develop about one-tenth ampere, but that said armature is responsive to a heavier current of, say. onefifth ampere. designed to furnish a tenth ampere of current with the working resistance (which may by proper balancing of the lines be made uniform for all subscribers lines) it will be apparent that if a circuit be established to con- 'neet both the battery and the ringing-generator to jointly supply current to the spool of the busy-test relay the latter will be energized to attract its armature when the directions of current from both sources coincide. Assuming now that line calledthat is to say, the line of subscriber No. 2-is already busy, it is obvious that any circuit closed across the wiper-lines w and 10 will receive the batterycurrentfromthe busyline. If now the key-controlled relay is actuated to bridge the ringinggenerator across the connected lines of the subscribers by the circuit including the spool of the relay, as above described, it will be apparent that current from both the central battery and the generator will pass through the spool of the busy-test relay. Consequently the battery-current of, say, one-tenth ampere is alternately reinforced and opposed by the impulses generated by the ringing-generator, so that a pulsating current of one-fifth ampere is developed in the relay-spool. Consequently with the first such impulses the armature of said relay is attracted, breaking the circuiteontrolling relay-circuit as the end contactspring of the relay leaves its point 45, and so by the restoration of the circuit-controlling relay to inactive position breaking the ringing-circuit. The busy-test relay is now maintained closed by a local circuit, which may be traced from the spool of the relay B T R by wire 60 and tap 61 to lower right contactspring, thence by wire 43 and tap 12 to wire 0, thence through the circuit-making springs .93) and .571 to the right side of the local relaybattery S R B, returning by wire 18, wire 0, tap 4E7, lower left spring of relay B T R, tap 63, and down by wire 62 to the opposite side of the spool of relay B T R. It is well known that when an electromagnet is once energized to attract its armature but little current is required to retain the armature in attracted position, and the local battery need not be of great strength to accomplish this result. The actuation-of the busy-test relay B T R in breaking the ringing-circuit by moving its end contact-spring from contact-point 45 also de- If the central battery be also Ioo IIO

stroys the connection between the two subscribers connecting-lines, as it will be recalled that the local circuit maintaining the circuitclosing relay C U R in energized condition included therein said spring and point of the busy-test relay, so that said local circuit is broken by the actuation of the said busy-test relay. In addition to its circuit-breaking functions the busy-test relay also serves to bridge upon the line of the calling subscriber the busy vibrator or buzzerZ. The buzzer-circuit, it will be seen, is made direct through wire son the one side to upper right spring of the busy-testrelayBTR and thence by tap 4:0 to the wire a, while on the other side it includes line 2, upper left spring of the busy-test relay, tap 69, battery-wire 6 which is tapped to the battery-wire I), and thence through the central battery (J B, returning by the opposing battery-wire 6 up to the point where said wire is tapped by wire it, thence through the im pedance-coil l G, and returning along the wire a; It will be remembered that the connecting-wires 1 and a are connected at the switchcontrolling relay S C R by taps 32 30 and 31 29, respectively, with the subscribers linewires and Z, and it will there fore be apparent that a circuit including the central battery C B and the vibrator Z will be bridged upon the calling-subscribe1"s line. It may here be noted that when once the busy signal is start ed it continues indefinitely, irrespective of whether the line desired remains busy or not, until the calling subscriber takes proper steps to restore the whole system to normal condition, and the contact at point 45 of relay B T R remaining broken the calling subscriber is unable to actuate the circuit-closing relay C C R for any purpose.

Referring now for a moment to the ringing operation heretofore described, when the ringing-generator is bridged upon the connected lines of two subscribers it will be obvious that an arrangement whereby the calling subscriber is apprised of the fact that the called subscriber is being rung may be advantageously employed. We provide, therefore, a closed circuit through the calling-subseribefis line and the primary winding of his induction-coil in order that the alternating generator-current flowing therethrough may inductively occasion the magnet in his receiver to assume alternately opposite polarities, causing its diaphragm to vibrate with a series of clicks, assuring him that his line is working properly and the desired party is being called. It will be remembered that in ringing the connecting-key 11 is depressed, and With such understanding the circuit may be traced from the line Z, through the key 9, wire 11", to connecting-key 11, thence to the second contact-point of said connecting-key, and by tap 15 through the resistance 15 (if included) and wire 13 to the transmitter and primary of the induction-coil to the upper hook-contact,

and key 10 to the line Z. It is essential that in this circuit just traced there be considerable resistance, for reasons to be hereinafter stated, and the inclusion of the resistance 15 will only be necessary when the resistance of the transmitter 7 is insuflicient for the purpose to be disclosed. Assuming now that the called subscriber is not busy, but that the ringing operation has been concluded and the key 11 released by subscriber No. 1, the system is in the condition illustrated in the drawings, the circuit-closing relay C U R being'closed and the key-controlling relay K C R being open. Now it will be apparent that the central battery C B is bridged upon the connected-subscribers lines, as in an ordinary central-energy exchange. The circuit in detail is as follows: starting from the left side of central battery C B, by battery-wire I) and wire 6 tapped thereto. through taps 66, including the impedance-coil l C, to lower left spring of relay K C R, thence by wire 50 to the lower left spring of relay U U R, and by tap 39 onto the side (0 of the pair of connectingwires. On the other hand, starting from the right side of the battery, the circuit is traced by battery-wire I) direct to wire a, the latter wire including the impedance-coil l C and forming part of the remaining side of the connecting pair of wires. Now to complete the talking-circuit it only remains for the subscriber at station No; 2 to remove his receiver from the hook, cutting his transmitter and induction-coil primary into circuit, as heretofore described.

It will be noted from the foregoing statement of operation that the line of the calling subscriber is not directly connected to the wipers of the switch until the operation of actuating the switch-arnito advance it to the terminal contact-points of the line of the subscriber desired to be called has been accomplished and the lines prepared for the final step of ringing the called subscriber or notifying" the calling subscriber that the line desired is busy. Further, it will be noted that the operation of connecting the line of the calling subscriber with the wiper is performed by an instrumentality distinct from that employed in operating the switch. This arrangement results in many distinct advantages, as it is apparent that entire secrecy is insured any two subscribers engaged in conversation, as the now calling subscriber cannot have his line bridged upon the connected lines before he operates the connecting-key and as soon as his connecting-key is depressed he will get the busy-signal and the momentary connection of his connecting-wires with the wiper-wires will be broken. Further, such an arrangement obviates the possibility of calling subscriber by any improper manipulation of his actuating devices from bridging the ringing generator upon the wiper-line and then in acthencereturning through the hook 5, Wire 16,

tuating the switch, momentarily connecting said ringer with each of the lines over which its wiper-contacts travel.

When the connected subscribers have finished their conversation and it is desired to restore the switch and the other instrumentalities to their normal or inactive positions, the keys9 and 11 are simultaneously depressed and both maintained closed for an instant. As a result circuits are established as follows: Both line-wires land Z being grounded by the depression of the keys a ground return-circuitis established through each of the primary relays PR and P R, as heretofore described. Consequently the contact-springs of relay P R are brought together, establishing a circuit, which has heretofore been traced, through the central battery C B,the spool of the switchoperating relay S OR, and back by way of the lower left spring of the switch-controlling relay S CR and the auxiliary line as. The armature of the switch-operating relay being attracted, its end spring is brought down into contact with the lower contact-point, and .(the relay P R being energized and its contactsprings accordingly connected) the attraction of the armature of the switch-operating relay establishes a circuit which may be traced from the upper spring of the relay P Rby the line 00, through the lower right spring of the switchcontrolling relay S C R by tap 26 to wire cl, thence up to the lower spring 819 of the circuit-closing pair of the line-selecting switch, by wire to the end spring of the switchoperating relay, lower contact, and wire 7 1, to the spool of the release-magnet, returning by tap 7 3 to the battery-wire b thence to the right end of the battery, and from the left terminal of the battery, by wire 5 and tap 19, to the lower spring of the primary relay PR. The release-magnet is accordingly energized, and the releasing-arm 120 is raised to operatively engage the stud 118 of the switch-armretaining dog 113 and the contact-making spring .519 as heretofore described. When now the keys 9 and 10 are released, the releasemagnet is deenergized and, as heretofore described, frees the switch-arm 101, sothat it is enabled to return under tension of its spring 104 to inactive position while the circuitbreaking springs s1) and 810 are parted, so destroying the continuity of the. local circuits serving to maintain the switch-controlling relay S C R and the circuit-closing relay COR energized. Consequently all of the operating-circuits being now broken the parts are all restored .to their normalor inactive positions, the return of the switch-arm serving, as heretofore described, to disengage the releasingarm 120 from the dog and the springand permitting the return of these mechanical instrumentalities to their normal position.

Reverting now to the description of the wiring of the stations whereby the calling subscriber is apprised of the fact that the ringof line L is actuated.

ing operation is being successfully consummated, it will be noted that the connections are such that ground-circuitsfor both primary relay P R and P R are established. The path from line-wire Z (with which relay P R is connected) to ground through key 11 has been fully traced; but it will be noted that during the time the connecting-key 11 is depressed the'line-wire Z (connected with relay P R) is grounded through key 10, wire 16, hook 5, line 13, (including coil 1) and trans mitter 7,) wire 15, (with resistance 15, if present,) key 11, wires 11 and 12 to ground. The last-described restoring operation does not follow from this connection, however, on account of the high resistance interposed between relay P R and ground. The circuit just traced contains the transmitter 7 and coil 1), which in most cases sufiice to prevent the flow of sufficient current through relay P R to attract the armature to said relay. Obviousl y, however, enough resistance may be included at 15 to prevent the possibility of the relay P" R becoming operatively energized, and so inopportunely working simultaneously with relay P R to restore the devices to inactive position.

The foregoing statement of operation is predicated on the assumption that the call is made and connection established on a switchboard whereon no lines are busy; but let us now assume that with lines L and L connected subscriberNo. 3 desires to call subscriber No. 5. Of course the personal operations of subscriber 3 are just as described in connection with subscriber No. 1 and the relay P R The relay S O R of the first or upper series cannot, however, respond, as the primary actuating-circuit of all of the relays in said series, it will be remembered, included a path across the springs .912 and s3] dependent upon the closed condition of the latter. The springs .319 and .939 of the first switch being parted when the switch is in use, as heretofore described, prevents positively the completion of an actuating-circuit for any relay of the first series. A corresponding primary actuating-circuit traced.

through the second series, however, shows the lower spring cp to be closed on the middle spring .539 which is connected through wire h, springs .91) and .912 of the first or upper switch with the battery-wire 6 Any one of the switch-controlling relays of a series, it will be remembered, controls both the ener- ICO gizing-circuit of the switch-operating relay of such switch and the connection of the calling subscribers line with the connectingwires (0 a of the series. Thus every subscriber when using a switch is protected against interference, the switch-controlling relays of the corresponding series being absolutely removed from the control of any other subscriber, while the series of switchcontrolling relays corresponding with the first then idle switch are automatically brought within the control of any other subscriber.

For purposes of a full disclosure of our invention we have illustrated and described in some detail an embodiment thereof which we deem suitable for illustration; but we do not desire to be understood as limiting ourselves to such disclosure in detail, as our invention contemplates a broad system susceptible of many variations in specific embodiment without departing from the spirit and scope of our invention.

Having thus described our invention, what we claim as new, and desire to secure by Lettcrs Patent of the United States, is

1. In an automatic-telephone-exchange system, the combination with the lines of the subscribers, of a central group of line-selecting switches adapted and arranged to be instrumental in connecting for communication the lines of any two subscribers, switch-actuating means operatively associated with each switch, such means, for each switch, including a series of devices each adapted and arranged to control the corresponding switch, one of such devices in each series being operatively associated with each subscribers line for control by the subscriber.

2. In an automatic-telephone-exchange system, the combination with the lines of the subscribers, of a central group of line-selecting switches, each adapted and arranged to be instrumental in connecting for communication the lines of any two subscribers, switch-actuating means, including a switch-circuit, and a series of switch-oircuit-controlling devices, operatively associated with each switch, one of such circuit-controlling devices of each series being provided for and operatively associated with each subscribers line, and means within the control of each subscriber for operating the switch-circuit-controlling devices associated with his line.

3. In an automatic-telephone-exchange system, the combination with the lines of the subscribers, of a central group of line-selecting switches each having terminal contact connections with allof the lines and each having also a movable member adapted to be brought into contact with the contact-terminals of any line, and adapted and arranged to be instrumental in connecting for communication the lines of any two subscribers, means, for each switch, for actuating the movable member thereof, and a series of devices associated with each switch adapted and arranged to control such actuating means, one such controlling device of each series being operatively associated with each subscribers line for control from the subscribers station.

4. In an automatic-telephone-exchange system, the combination with the lines of the subscribers, of a central group of line-selecting switches, each having terminal contact connections with all of the lines and each havingalso a movable member adapted to be brought into contact with the contact-terminals of any line, means associated with each switch for actuating the movable member thereof including a circuit and a series of circuit-controlling devices, one device in the series for each switch being operative] y associated with each subscribers line for control from the subscribers station and each device comprising circuitclosing means, and normally open circuit connections between the line of each subscriber and the movable contact member of eachlineselecting switch, each of said open circuits being adapted and arranged to be closed by the circuit-closing means of the switch-controlling device of the corresponding subscribers line included in the actuating means of the corresponding switch upon the actuation thereof,

,to connect any subscribers line to the movable contact member of any switch.

5. In an automatic-telephone-exchange system, the combination with the lines of the subscribers, of a central group of line-selecting switches, each switch having a set of terminals to which all of the lines are respectively connected, and a contact member adapted to make contact with the terminals of any line, means for establishing connection between any two lines through said switch-contact member including series of switch-controlling relays, one series being operatively associated with each switch and each series having a relay operatively associated with each subscribers line for control from the subscribers station, and suitable circuits for the relays.

6. In an automatic-telephone-exchange system, the combination with the lines of the subscribers, of a central set of line-selecting switches, each switch having contact-terminals connected with each line and a movable contact member adapted to contact with the terminals of any line, and adapted and arranged to be instrumental in connecting for communication the lines of any two subscribers, means associated with each switch for actuating the moving contact member thereof, such means for each switch comprising a series of relays each adapted to control the corresponding switch, one of such relays in each series being associated with each subscribers line for control by the subscriber, means for placing the relays of one switch normally within the control of all subscribers, and means for automatically removing the relays of each actuated switch from the control of any other than the actuating subscriber, and placing the relays of the first then idle switch within the control of such other subscribers.

7. In an automatic-telephone-exchange system, the combination with the lines of the subscribers, of a central set of line-selecting switches, each having a series of contact-points forming terminals of all the subscribers lines, and a movable contact member, means for actuating said contact member including an electric circuit, a series of switch-controlling relays for each switch, each relay being arranged and adapted to control the circuit of the actuating means of its switch, means Within the control of each subscriber for actuating a switch-controlling relay of each series, and means forautomatically removing the relays of the first-actuated switch from the control of any other than the actuating subscriber and placing within the control of such other subscribers the relays of the first then idle switch.

8. In an automatic-telephone-exchange system, the combination of the lines of the subscribers, a plurality of switches each adapted and arranged to be instrumental in connecting the lines of any two subscribers, means for actuating each switch, a series of relays for each switch, each relay being adapted and arranged to control the actuating means for its switch, one relay of each series being provided for and operatively associated with the line of each subscriber, a normally open circuit normally including one series of relays, means within the control of each subscriber for closing said circuit to render operable the switch-actuating means of the switch corresponding with said series, and means controlled by the switch, for cutting out of the normally open circuit the series of relays of the first-actuated switch, and cutting into said normally open circuit the relays of the first then idle switch.

9. In an automatic-telephone-exchange system, the combination with the lines of the subscribers, of a plurality of line-selecting switches, each adapted and arranged to be instrumental in connecting for communication the lines of any two subscribers, actuating means for each switch including a normally open circuit, a series of switch-controlling relays associated with each switch, each relay being adapted to close said actuating-circuit, and a relay of each series being provided for the line of each subscriber, and an auxiliary circuit including means within the control of each subscriber for energizing the subscribers switch-controlling relay of the series of relays associated with any switch whereby the actuation of the corresponding switch is brought within the control of the subscriber.

10. In a telephone-exchange system, the combination with the lines of the subscribers, of a line-selecting switch having a series of contact-terminals to which the subscribers lines are respectively connected, and a contact member adapted to make contact with any of said terminals, actuating means for said contact member including a normally open circuit having therein devices within the control of any subscriber, adapted and arranged when the circuit is closed to actuate the switch, a series of relays for said switch, one relay being provided for the line of each subscriber, circuit connections for the lines of the respective subscribers and the contact member of the switch open at the respective relays and adapted to be closed by the energizing of any relay to bring the switch within the control of the corresponding subscriber, a normally open relay-energizing circuit, and means within the control of each subscriber for closing said circuit through his corresponding relay.

11. Incombination,apluralityoftelephonelines, a switch having contacts arranged to form the termini of the lines, and a contact member adapted to sweep over said termini, electromagnetic devices for operating said switch, a circuit for the electromagnetic devices, a series of relays, one for each subscribers line, arranged to control the circuit of the switch-actuating electromagnet, connectingwires arranged and adapted to be connected to any line by the actuation of its relay, complementary connecting-wires terminating in the contact member of the switch, a relay adapted when energized to connectsaid complementary wires, and means associated with the switch arranged to be brought into operation by the movement of the latter for bringing the circuit-closing relay within the control of the subscriber, whereby the talkingcircuit may be established by the subscriber.

12. In combination,a plurality of telephonelines a line-selecting switch provided with a contact member adapted and arranged to be instrumental in connecting for communication the lines of any two subscribers, means for operating said switch-contact member arranged for control by any subscriber, and means for connecting the line of the calling subscriber with the switch-contact member arranged to be operated subsequently to the switch-operating means. I

13. In an automatictelephone exchange system, the combination with the subscribers lines adapted to be connected, and means for supplying energy to said lines when'connected for conversation, of means within the control of each subscriber for connecting any two subscribers lines, a ringing-circuit includinga ringing-generator adapted to be connected to the connected lines of the subscrib-- ers, whereby when the called line is busy and already energized current from the energized line is received in the ringing-circuit, a busytest circuit including a signaling device and means for connecting said device with the line of the calling subscriber, comprising a relay having its coil arranged to receive current from the ringing-circuit, said relay being inoperable by the ringing-generator current, and operable by the current transmitted thereto when said ringing-circuit isconnected to a busy line.

In testimony that we claim the foregoing as our own We aflix our signatures in presence of two witnesses.

JOHN K. NORSTROM. HENRY M. GRAIF. In presence of GEO. T. MAY, Jr., MARY F. ALLEN.

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