US375543A - Electric-circuit changing and signaling apparatus - Google Patents

Description

(No Model.) 3 Sheets-Sheet 1.

I. H". FARNHAM. ELECTRIC CIRCUIT CHANGING AND SIGNALING APPARATUS- No, 375,543, Patented Dec; 27, 1887., I v

Ind/(970607".

' DMZLLK'MAQ i 2 i s sheets sheet '2.

(No-Model.)

I. H. FARNHAM. .ELEGTRIG 01301111 CHANGING A-ND' SIGNALING APPARATUS.

Patented Dec; 27, 18-87.:

V No.- 375.543.

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no Model.) 3 Sheets-Sheet a.

I. H. FARNHAM.

ELEGTRIG CIRCUIT CHANGING AND SIGNALING APPARATUS. No; 375,543. Paten t'ed Dec. 27, 1887.

72527166565. 7 I Inventor fizz/Ag Ens. PhMvLhhogmphur, wamlngwn, :ui

UNITED STATES PATENT OFFICE.

ISAIAH H. FARNHAM, OF MALDEN, ASSIGNOB TO THE AMERICAN BELL TELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.

ELECTRIC-CIRCUIT CHANGING AND SIGNALING APPARATUS.

SPECIFICATION.forming part of Letters Patent No. 375.543, dated Decemioer 27, 1887.

Application filed March 26, 1887. Serial No. 232,522. (No model.)

To all whom it may concern:

Be it known that I, ISAIAH H. FARNHAM, residing at Malden, in the county of Middlesex and State of Massachusetts, haveinvented certain Improvements in Electric Circuit Changing and Signaling Apparatus, of which the following is a specification.

This invention relates to the construction, arrangement, and operation of automatic circuit-changers and to the circuits and actuating devices therefor. It has been and is now used in connection with the village system of telephone exchange circuits heretofore patented by E. T: Gilliland,.United States Letters Patent Nos. 306, 238,306,239, and 306, 240, all hearing date of October 7, 1885, which show and describe a series of substantially parallel line-circuits, each and all entering all' of a number of telephone sub-stationsin the system. The sub-stations have free access to each circuit, a proper proportion of the total number of the said sub-stations being normally located and provided with a signal-receiving device on each circuit.

Reference may be had to the above patents which I have cited.

The objects of my invention, briefly stated, are to provide convenient and trustworthy means whereby a distant station connecting with the village system by a single trunk-line wire may automatically unite itself with any predetermined circuit of the system, simultaneouslytransferring both trunk and village line from their normal connections or terminals to a connection with one another. accomplish the above with a much greater degree of certainty than has prior to my invention been attainable and to receive at the transmittingstation a response-signal indicating positively that line of the village system which will next, by the action of the circuit changer, be unitedwith the trunk-line, and to provide a novel stopping and starting mechanism at once accurate and efficient. In pursuance of these purposes the automatic circuit-changing apparatus is placed at a station in the village system, at'which all the villagelines terminate, and consists of a rotatable contact-arm which constitutes the terminal of the trunk-line extending from the distant station, a motor to revolve the same adapted tem circuits, such line being thus raised from its earth-contact, although, like the others, it comes to rest on the said earth-contact .when the-arm passes from under it. An electric impulse from the distant station releases the motor and permits the arm to revolve. The rotation of the arm ceases, however, as soon as the next local-line terminal is raised. In other words, the cireuit-changing arm, once released, does not make a complete revolution before it is arrested, but is stopped as soon as it makes contact with the next village-exchange terminal, there being as many stopping-points as there are lines to connect with in the village system. W'henever contact'is Inadebetween any arm and the springterminal of any circuit, the arm raises the said terminal from its normal ground-terminal,and the moving arm, while passing from one circuit to another, is disconnected from any ter-. minal, its circuit being open. The motor by which the circuit-changing arm is impelled may be an ordinary clock-train. I provide, also, means actuated by the same motor to send a specific return or response signal, whereby the next line to be brought into contact with the trunk-line arm is at all times indicated, so that the central-station operator is constantly informed of the position of the said arm with respect to the village-system terminals.

My invention also involves the combination, with these devices, of a novel and essentially useful stopping and starting mechanism, whereby the motor may be stopped With'exactness and accuracy at any one of a number of desired points, while bythe use of this mechanism I am enabled to release the said motor with a very low degree of power and without an objectionable amount of friction or mechanical resistance. This invention involves, likewise, the employment at the distant and controlling station of controlling devices whereby the circuit-changing motor can be started or stopped at will, and of a signalreceiving device of suitable character whereupon the return-signals indicating the line next to be connected may be received.

I am well aware that a circuit-changing device capable ofperforming the line-connecting functions which I have described is not broadly new, since such a device has heretofore been patented to E. T. Gilliland, January 12, 1886, No. 334,014. The said patented device has, however, developed certain inherent defects in its construction,which by this invention I aim to overcome. In its use it was necessary to operate two like instruments running synchronously with one another, and it was difficult to maintain such synchronism. An enormous amount of battery-power was required. The machine was, moreover, very susceptible to circuit troubles, and in the event of a cross with a line carrying a battery-current would continue in motion until it was run down. No device was embodied therein whereby the distant operator could be informed asto whether the instruments were running in synchronism with one another, and it was therefore a matter of frequent occurrence to connect with an undesired line. These difficulties are all overcome by my invention, it being perfectly independent in action, not being required to run in synchronism with any other instrument. It cannot run down in the event of a cross, since it requires the circuit to be both closed and opened before more than a single revolution can be performed. Moreover, I employ in connection with the starting device a delicate polarized needle in the main line as a relay, (this being irresponsive to rapid alternations or to battery-currents except when of proper direction,) whereby the actual operating-magnet, which is placed in a local circuit, can be vitalized without necessitating the use of a large amount of battery, and by the adoption of this needle-relay all danger of the accidental starting of the mechanism by rapidly-alternating magneto-electriccall currents is averted.

In the drawings which illustrate and form a part ofthis specification, Figure l is 3. diagram of the entire systemas ordinarily operated. Fig.2 is a detailed diagram of the trunkline and the auxiliary connecting-station, showing the working parts of the circuit-changing mechanism and its actuating apparatus. Fig. 2 is a diagram showing the principle of operation exemplifying its simplest embodiment. Fig. 3 is a front view of the central-station actuating device and indicator. Fig. 4 is a detail section on lineof Fig. 3, showing the retaining-snap of the actuating-button. Fig. 5 represents a side elevation of the motorstarting magnet. Fig. 5 is a modification in the response or return signal apparatus whereby the starting-relay is cut out during the period when the return-si nal is being sent.

Fig.6 is a section on the line y y, Fig. 2, looking toward the electro-magnet. Fig. 7 is an illustration of the stop movement, and Fi 7 a side view of a detail thereof. Fig. 8 shows the circuit-changer and its actuating devices in their application to a series of sub station circuits which are not parallel to one another, but which radiate from the convergent point in different directions.

In Fig. 1 a general plan is shown of the village system operated by means of my circuitehanger in connection with a trunk-lineleading to a distant central station at which are located the actuating devices of the said circuit-changer. A series of substantially parallel telephone-circuits, 1 2 3, having each a series of telephone sub-stations, GD E, arranged as described in the patents hereinbefore cited, converge to a common terminal station,B, where each of the said circuits terminates in contact- springs 8,9,and 10,all of which extend over earth-contacts 27, upon which they rest when not raised therefrom, as hereinafter described. At each sub station loops from all the circuits enter and are represented by spring-jacks 1 2 3, into which the telephone T may be looped by the double conductor plug or wedge 14. From the station B, at which these lines terminate, extends another line, 5, leading to a distant central station,A, where, through the instrumentality ofaswitchboard, 11, the said line 5, and consequently any one of the lines 1, 2, or 3, may be united for through communication with the lines entering the central station. The central station, A, is of course provided with telephones 12.

At the connecting-station B is an automatic circuit-changer, H, consisting of a conductingarm, 7, which is capable of rotation on its axis, and which is in permanent electrical connection with the trunk-line 5. This arm is adapted to be rotated by a suitable motor, and I use a clock-train actuated by a weight or spring, but for convenience preferably a spring. Normally the end of the arm 7 rests under the spring-terminal of one of the converging lines, raising the same from the earthcontact, which it would otherwise rest upon. For convenience it is customary always to have the same line (say No. 1) normally resting upon the arm, and thus normally extended over the trunk-line 5 to the main central station. \Vhen the motor is in operation and the arm 7 is in revolution, thc'lattcr raises the several line springs successively from their earth-contacts and substitutes a contact with itself, and the arm when once started will advance only from one of the auxiliary line-terminals to the next,and will then stop. At the central station, A, is also an apparatus, 4,, in the main circuit, which, when operated as described hereinafter, serves to control the distant motor and to receive return-signals therefrom, this apparatus being connected with the switch board by wire 13 and with a suitable battery by wire 15.

, upon to the number of the next one.

So far I have described the general system, which I do not claim; but I will now proceed to describe the peculiar and special circuitchanger, motor, and operating appliances and their modes of arrangement, referringto Figs. 2, 3, 4, 5, and 6. These devices. enable the operator at the central station, A, to disconnect his trunk-line 5 from any one of the village lines to which it may be united and to connect it with any other desired line of the series, and also to receive a signal upon a bell, to denote the line which next will be connected. By this means the operatoris enabled to know with absolute certainty which of the village-system lines has already been in connection with his trunk-line, and also which one will neXt be connected therewith. Fig. 3

is a front elevation of the central-station apparatus 4, which may be made in the form of a rectangular box. In this view is shown the bell 54, upon which the return-signal is received, a dial, 52, whereupon the numbers of the village-lines are indicated, a pointer, 53, mechanically actuated to revolve round the said dial to indieate the line which at the j unction-station may at any distinctive period he in electrical union with the trunk-line 5, and a circuit-closing key or switch,'51, which when at rest normally stands in a vertical plane, being held in place by the snap 52. (See also Fig. 4.) The pointer 53 also normally standsin a-verticalplane, pointing to No. l on the dial, thus indicating that the trunk-line 5 is in contact with its normal eX- tension-line No. 1. The instrument is also fitted with bindingserews 55, 56, and 57, to which wires leading, respectively, to switchboard,battery, and line are attached, as clearly indicated in Fig. 2.

By reference to that portion of Fig. 2 which represents the central station, A, the operation of the apparatus at may readily be understood. The switchor key 51 is mounted on an axis, and when turned operates, through spurgear 62, 63, and 65, to turn also at aslower rate the arbor 66 of the larger spurwheel. and with it the pointer 53, which is affixed thereto.

The dial 52 is divided into spaces equaling in number the lines converging to the junction-station of the village system, (in the present case three,) and the gears are so ,speeded that the key or switchand the first wheel, 62, can be turned a complete revolution during the time that the pointer53 advances upon the dial from the number of the line it last rested Thus, supposing that theswitch 51 be turned from its vertical position completely round to the same position once more, the pointer 53 will in the same time advance to the figure 2 on the dial. This system is of course not restricted Y to three lines, this number being adopted herein simply as being sufficient to illustrate the system. 7

From the binding-screw 57 a wire, 58, runs in the box of the instrument to the cam-contact, 59, whichis mounted on the arbor 60 and in electrical connection therewith. This is normally in contact with a metal spring, 67, from which a wire, 71, leads to binding'serew 55, and thence by wire 13 to the switchboard. A second spring, 68, is mounted in close proximity to the spring 67, both being fixed to a non-conducting support, and from the second spring a wire, 69, leads to one terminal of thc not make contact therewith on account of the Y cut portion thereof being presented at that time. The battery and bell circuit is therefore normally open at the spring 68, and the line 5 is normally closed'through the spring 67 and cam 59 to the switchboard. When, however, the switch 51 is moved round a portion of a revolution to the right, the cam is withdrawn from the spring 67, and the switchboard connection is thereby broken, and the corner of the ,disk 61 comes round and makes contact with the spring 68, thus transferring the line 5 from its switch-board connection to a connection with the battery through the bell 54, thus sending a battery-current to the line. It is not absolutely essential to employ this form of apparatus at the central station, nor,

in fact,to employan indicatingdialand pointer; but I prefer such an arrangement in practice,

it being a convenient means of informing the operator at the central station of the line which was last connected, and being conducive to accuracy in operation.

Fig. 2 shows a simple arrangement of circuits and appliances which, if desired, can be made to serve all necessary purposes.

An ordinary doublecontact key, 7., has its stem permanently united to the trunk-line 5. Its back and normal contact-stop connects by wire 13 to the switchboard, and its front contact, to which it maybe pressed, leads by wire 15 to bell b and battery and thence to earth, this plan thus being electrically the equivalent of the .former.

In Fig. 2, B represents thejunction or connecting station where the trunk-line 5 may be united with any of the village-system lines 1- 2 3, &c. At this point the several lines end, as shown, in contact springs, lines 1 2 3 being provided, respectively, with springs 8, 9, and 10, the springs each being fixed at one end to some suitable support.

Mounted upon the center arbor or shaft, e, of any suitable motor (and for this. work a train of clock-work actuated by a spring or weight answers well) is a revolving contact-arm, 7. This is in permanent electrical connection with the trunk-wire 5 and rests normally under one of the spring-terminals of the radiating lines, and for convenience it is, when at rest, maintained always in connection with the same one, No. 1. The trunk-line 5 is therefore normally connected, through the rotating arm 7 and the spring 8, with the line 1, the said spring 8 being thereby elevated from its contact with the earth-plate 27. The remaining line-springs 9, and 10, rest upon this earthplate except when the end of the arm 7 in its rotation passes under them, or when the said arm is caused or permitted to come to rest immediately under either of them. The plate 27 is connected permanently to earth by the wire 26 and earth-wire 25. The motor and arm 7 are normally quiescent, being controlled as to starting and stopping by an electro-magnet, 39, with its armature and detents, hereinafter to be described.

To the end that the action of the starting and stopping magnet 39 may be as powerful as possible, as well as to render it less liable to be started by alternating or other transient and undesired currents passing in the main line, I place itin the local circuit of a battery, L B, adapted to be closed by a polarized relay, 6, the magnet of which is included in the main line 5. This relay has for an armature a pivoted needle weighted at its lower end to maintain its vertical position when at rest. It is adapted to be operated by an electric current of given and constant direction, and of such direction to deflect the needle to one side only, any vibration of the needle in the opposite direction being furthermore prevented by the limit-stop p. The local circuit controlled by the said relay passes from one pole of the local battery L B by wire 38 directto one wire ofthe starting-magnet 39. The other wire of the said magnet is united to a wire, 35, which bifurcates at the point m, one branch, 32, leading directly to the needle 31, which forms its terminal at the point 34, and the other branch, 33, leading to a contactpoint, 36. A fixed contact, 60, is mounted on 1 a suitable spring, 35, between the points 3i and 36. By this arrangement I provide a double circuit-closing device and a more secure c011- tact for the local circuit, since the needle-armature in its deflection closes the local circuit, first, by the pressure of the point 3L against the point 60, and, secondly, by the pressure of the contact 60 against the point 36, each of these contacts being perfectly independent of the other. I

By using two I add to the certainty of the operation and forestall the possibility ofa poor contact. The disk 72 is fixed upon and revolves with the centerarbor, c, and is furnished with stop-points 21, 22, and 23, and the mo tor after being once started and released from any one stop-point continues in motion only till the next one of these points reaches the detents of the stop mechanism,when it again stops. Vhen at rest, it is started from the central station by sending a battery-current over the line from the said station, and for the information of the operator at such station I provide a return or response signal which operates automatically to indicate to said operator the number of the line which is about to be connected with the trunk-line. This signal is provided for as follows: I place also on the center arbor, e, a multiple signal-wheel, l7,which wheel is adapted to make and break the circuit a predetermined number of times between each two stop-points. This provides for sending from the junction-station to the central station after the disconnection of any line and before the connection of any other line a signal indicating the number of the line next to be connected. A flat contact-spring, 24, is mounted upon the frame of the instrument and is united to an earth-wire, 25. This is so placed that the several signatteeth 18, 19, and

20 will strike its end, and thereby close the circuit a number of times equal to the number of teeth in each signal, this circuit being otherwise open between any two stop-points, because the arm 7 while traveling is disconnected from all contacts. Supposing the motor to have been started, the arm leaves spring 8 and the circuit is opened. The battery is, however, left in connection'with the line at the central station, and before the arm reaches spring 9 the two teeth of the signal 19 will have passed under the earth-contact spring 24, thus closing the circuit of the said battery twice, and consequently striking two on the bell at the central station. This informs the operator that the apparatus is working properly, that the trunk-line when at rest was in contact with No. 1, and that the next line to be connected will be No. 2. Again, supposing No. 2 was the line last in connection with the trunk-line, the signal given will be three, thus indicating that No. 3 is the line next to be connected with the trunk line. By this return-signal the operator can thus at all times know the exact condition or position of his automatic circuit-changer, and all chance of accidentally connecting the wrong line is prevented.

I have found in practice that the ordinary apparatus for electrically starting and stop ping motors or clock mechanism is defective, because the entire power of the prime mover is exerted against the stopping and starting power in either case, and thus there is considerable friction between the detent and stop pins. Consequently it has not been possible to control any but a very low-power motor electrically, except by the use of a very large battery or by complicated systems of leverage. \Vhere heretofore this difficulty has been partially met it has been by effecting the stop through arresting the fan or fly, and under those circumstances ithas not been possible to stop exactly at the point desired. I attach a stop and starting mechanism whereby the light friction of the fly only is exerted against the starting power,and yet whereby the motor can be stopped with great exactness and accuracy at the required point. This I accomplish by causing the stop-point of the disk in any electric circuit and has an armaturelever, 40, provided with a front stop, 44, back stop, 43, and retracting-spring 8.

On the free end of the armature-lever 40 a stop-lever, h, is pivoted at i, and when not engaged is held by spring 3' against a back stop, 49, which is held in a vertical standard, 50, mounted on the armature-lever. The pivotedlever h has at one end a rod projecting therefrom at an angle and adapted to engage the fan a when the other end of the said pivoted lever is pressed. There are two stop-pins,

a 25 fand g, on the disk 72, f being the stop which is engaged by the inwardly-projecting foot h of the pivoted lever when the circuit is closed and the armature attracted, and 9 that which is engaged when the circuit is broken and the armature retracted.

If the motor is in action it will stopafter a single revolution on the point 9, the foot h beingthen in its elevated position, owing to the retraction of the armature. The power of the motor will then, for an instant only, be exerted upon the stop-lever at h. The first effect of this power, however, is to press the foot h of said lever forward against the pull of the spring 8, and the projecting piece 47 is thus brought intothe path of the fly a. Thus the piece 47 now is caused to arrest the motor at a point where there is scarcely any power or friction, and only sufficient power is exerted on the foot h to keep the spring 8 tense and the piece 47 in position to engage the fan. When, now, it is required to start the motor, this is accomplished'with ease and with a moderate amount of battery-power by closing the circuit. The foot h of the lever" drops. away from the pin 9, slacking the strain on the spring 8 and withdrawing the stop 47 from the fan. It then almost immediately engages the lower pin, f, thepin g meanwhile having, with the disk, advanced a short distance. The same efi'ect takes place as before. The pressure of the stop-pin f against the foot h once more stretches the spring 8, and the pivoted lever brings the arm 47 into the path of the fan. Upon again breaking the circuit the disk now completes its revolution, stopping at the completion thereof on stop gonce more.

It would not be necessary in every form of apparatus to show a stop both for the opening and closing of the circuit; but as I use this form in myapparatus I have thought it advisable to describe it here. Inapplying this stop mechanism to my circuit-changer I adopt the obvious equivalenta forked lever end instead of using two pins on the revolving disk. h

The position of the fork with respect to the stop-pin 23 is shown in Fig. 6,which is a view on the line 3 y in Fig. 2, looking toward the magnet 39. In Fig. 2 the motor is supposed to be stopped and the circuit open. The pin 23 thus engages the tine 48, which is a short distance in front of the tine 47, and also a lit- .tle distance in advance of it in the direction of rotation of the disk.

As in Fig. 7 the magnet 39 is provided with armature-lever 40, a swinging lever, h, at-

tached thereto and pivoted at i, this having a fork attached to one end, held in the path of the stop-pin 23 by the spring 8', and a projecting arm, 47, to stop the fan a. The swinging lever has limit- stops 49 and 51. The operation of this device is the same in principle and function as that explained in connection with Fig. 7. I arrange it to stop first on 47 when the circuit closes, and again on 48 when it opens, so that, requiring both an opening and closing of the circuit to fully start the motor after it is first checked, it will be less likely to start from crosses of the line with batteryeircuits.

In Fig. 5 I show a modified arrangement of circuits whereby the polarized relay 6 is cut out of circuit during the time that the arm 7 It is is passing from one circuit'to another. thus not liable to be operated by the moment ary closures of the circuit caused by the grounding of the line when the return-signal is being sent. The only difference is that a branch, 61, is led from the main trunk-line 5 at a point external to the polarized relay and brought into connection with a spring, 24, mounted near to another spring, y, but insulated from it by a non-conducting block, w. The signal-wheel acts by its teeth to mechanically close the circuit, instead of forming part of the said circuit, as in Fig. 2.

Fig. 8 is a diagram indicating a modified arrangement of sub-station circuits, showing that it is not necessary to arrange them parallel to one another and to enter every station, as in Figs. 1 and-2,"as they may be caused to pursue divergent directions, in which case the application of my invention is equally pertinent.

In the operation of this invention, if the operator at the central station wishes to connect the trunk-line with, say, No. 2, he turns the key 51 partly round. This disconnects the trunk-line from the-switch-board continuation through the cam 59 and transfers it to a connection with the main battery. The batterycurrent flows over the line and energizes the magnet 39 at the junction-station. The circuit-changer is thus started. The operator regarded, and the bell can be so adjusted that as long as the resistance of the original subscribers line he added to that of the trunkline such single extra stroke may be prevented. As soon as he has heard the said signal two he brings his key 51 completely round to its normal position, and in the meantime the pointer 53 has advanced to 2 on the dial and serves as a reminder to the operator that he has transferred the trunk-line to No. 2. During the same time the circuit-changing arm at the junction-station has stopped in contact with. the spring-terminal of line No. 2. He then sends a call-signal to the required station on line 2, and, receiving an acknowledgment, connects the trunk-line with any central-station line through the switch-board. The call-signal will not alfect the startingmagnet, this not being responsive to alternating currents.

It will be obvious that my invention is not restricted to telephonic circuits, but is equally applicable to any system of electrical communication.

I do not herein broadly claim the special stop mechanism described herein, as I propose to file for such mechanism a separate application for Letters Patent.

1. Aseries of local substation circuits, each extending to a number ofsub-stations, a trunkline extending from a distant central station to a junction-station, to which the lines of said series converge, a motordriven arm constituting the terminal of the trunk-line normally at rest, but adapted to engage successively the terminals of the'several lines of the said series, an electro-magnet operated over the said trunk-line circuit to control the said motor, means, as described, located at the central station to operate the said magnet, and a return-signal-sending device moving with the said movable or revolving arm to indicate the position thereof to the central station, substantially as described herein.

2. A main line, a series of sub station lines, a central station, an auxiliary station to which the sub-station lines converge and connected with the central station by the said mainline, an automatic circuit-changer at the said auxiliary station adapted to unite any predetermined one of the sub-station lines with the main line at the will of the centralstation operator, means, as indicated,at the central station for actuating the said circuit-changer and for indicating its position with relation to the sub-station lines, a signal-bell, also located at the central station in the circuit of the main line, and an automatic multiple-signal-transmitting device located at the auxiliary station and operating in association with the circuitchanger during the time occupied by said circuit-changer in passing from one line to another to strike on the central-station signalbell the number of the line'next to be connected with the main line, substantially as described.

3. An automatic circuit-changer adapted to connect a main-line electric circuit with any predetermined one of a series of other circuits, comprising an arm normally at rest, in connection with one of the said series, but adapted to be disconnected therefrom and connected successively with the other lines of the said series, a clock or other motor for actuating the said arm, an electro-magnet operated by a polarized needle-relay in the main circuit to control the said motor, a return or response signal operated by the said motor and comprising a brake-wheel adapted to give definite signals and an earth-contact spring, and a circuit-closer and alarm-bellat a distant central station, whereby the circuit-changer may be actuated and its operations indicated at the said central station.

4. In combination with an automatic circuitehanger constructed and connected substantially as described herein, and its main and subsidiary electric circuits, the circuit-closing and signal-reeeiving devices at a distant station, and the hereindescribed return indicating-signal-transmitting device adapted to be automatically operated by the motion of the circuit-changer, whereby the number of the line next to be connected is automatically reported upon the said distant signal-receiving device, for the purposes specified.

5. An automatic connecting apparatus located at ajunction-point between a trunk or main circuit and a series of substation circuits, comprising a CIOCk IllOVGlIlBllF, a circuitchanging arm constituting the terminal of said main circuit and adapted to be actuated by the said clock-movement and to be brought into connection with and tobreak the normal ground-connections of the sub-station lines successively, means for sending a definite automatic return-signal to a distant central station located 011 the said main line, a polarized relay located in the main-line circuit, and a stop-magnetlocated in alocal circuit controlled by said polarized relay, as and for the purposes specified.

6. The combination, substantially as hereinbefore described, of a circuit-closer comprising the cam-wheel 59, connected permanently with the main line, and the contact-spring 68, the main battery, the signal-bell included in circuit between the said contactspring and battery, the key orswitch 51, for operating the said eircuit-closer, and the mechanical pointer and dial-indicator, the pointer being geared with the circuit-closing wheel in such a manner as to pass a given division of its dial while the key or switch makes a complete revolution, as specified.

7. The combination of an auxiliary telephone-station, a series of substation lines converging thereto and ending thereat in con tact-springs normally resting upon a groundplate, a central station, a main or trunk line extending from the central station to the auxiliary station and ending thereat in a motordriven arm adapted to rotate and to connect successively and alternately with the springterminals of the sub-station lines and to 'disconnect the said lines from their normal earthterminals, an electro-magnet in a local ,circuit controlled by a relay in the mainline, and a stopping and starting mechanism actuated thereby, a battery-circuit closer, and a signalbell at the central station, and a return-signal mechanism operated by the motor of the rotating arm to indicate upon the central-station signal-bell the line next to be connected, all substantially as specified.

8. In combination with the hereinbeforedescribed rotary circuit-changer and its actuat ing-motor, aeontrolling electro-magnet, alocal circuit in which thesaid magnet is included,

and the polarized needlerelay shown and described, governing thesaid local circuit, and provided with the double local contacts, whereby imperfect contacts are forestalled, the said relay being itself controlled by the presence or absence of a current of definite direction in the main line, but being irresponsive to currents of opposite direction or to currents of rapidly-alternating direction.

9. The combination, at a connecting telephone-station, of a rotary connecting-arm constituting the terminal of a main electric circuit, a clock-motor to rotate the same, a series of sub-station line-terminals normally in contact with an earth-plate arranged in a circle round the said connecting-arm, and each adapted'to be raised thereby from its earthplate contact and to be connected to the. said arm, a polarized relay included in the main trolled by an electro-magnet, an earth-plate,

two or more auxiliary circuit-terminals normally connected with the said earth-plate and located in the path of the movable main-circuit terminal, which in its movement simul-- taneously makes connection with and breaks the earth-connection of the said auxiliary cir cuits, an automatic stop for the said movable terminal, adapted to arrest the motion of the same at the moment when connection is made with any one of the auxiliary circuit-terminals and to throw a detent in the path of the clock-train fan, a releasing mechanism controlled by the electro-magnet and adapted, as described herein, to become operative only after the circuit of said magnet has been broken and again closed, a local circuit, including said magnet and governed by a polarized needle-relay, included in the circuit represented .by the movable main terminal, and a definite signal-transmitting device comprising other, its circuit being temporarily open and operating to send a signal over such line indicating the line next to be connected with, for the purposes specified.

11. In a system ofautomaticintercommunication, the clock-operated circuit-changer, together with its electrical starting and stopping mechanism and its return signal devices, as indicated herein, combined with an electric circuit and a mechanical circuit-closer, a signal-bell, a battery, and a visual indicator, all at a distant station upon the said electric circuit, substantially as hereinbefore described;

12. In combination with a clock-motor and a circuit-changing arm driven thereby, a starting and stopping mechanism therefor and an electro-magnet controlling the same, the said magnet being in a local circuit and governed by a polarized relay of the character indicated herein in the mainline, together with the return-signal transmitting devices described herein, comprising a branch from the main line at a point external to the polarized relay, a terminal contact-spring therefor, a complementary contact-spring in connection with the earth, and a signal-wheel driven by the said clock -motor and adapted to press the said springs into contact with one another and thereupon to close the main circuit in correspondence with the signals represented upon the said wheel, the said polarized relay being meanwhile cut out of circuit, substantially as described.

13. In combination with an automatic circuit-changer constructed and connected substantially as hereinbefore described, the return-signal-reporting devices, comprising the signal-wheel and earth-contact spring included in a branch of a main circuit, and the starting and stopping mechanism therefor, consisting of an electro-magnet and armature and armaturelever, a pivoted lever mounted on the said armature-lever, a forked arm extending from one end of the said lever into the path of stop-pins arranged upon the periphery of a disk mounted on the center arbor and held in place by a spring, and an arm projectingfrom the other end of the said pivoted lever into proximity to the fan or fly of the circuitchanger and adapted to be forced into the path thereof when the forked arm is struck by the disk-pins, substantially as and for the purposes described.

In testimony whereofI have signed my name to this specification, in the presence of two sub scribing witnesses, this 19th day of March, v

Witnesses: V

- GEo. WILLIS PIERCE,

V. M. BERTHOLDE.

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