US646675A - Telephone-exchange system. - Google Patents

Description

Nd. 646,675. Patented A ir.-3, I900.

- E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

(Application filed June 16, 1898.)

(No Model.) a Sheets-Sheet I.

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No. 646,675. Patented 'Apr. 3', won. E. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM.

(Application filed June 16, 1898.) (No Model.)

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No. 646,675. Patented Apr. 3, I900. E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

(Application filed June 16, 1898.) (No Model.)

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EDWVARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO THE SUN ELECTRIC MANUFACTURING COMPANY, OF NEW JERSEY.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Fatent No. 646,675, dated April 3, 1900. Application filed June 16, 1898. Serial No. 683,652. (No model.)

To aZZ whom it may concern.-

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States, residing in the city of Washington, in the District of Columbia, have invented a new and useful Improvement in Telephone Exchange Systems, of which the following is a specification.

My invention relates to the connective means employed in telephone-exchange sys- 1o tems and includes of necessity not only the central-office apparatus, but a portion of the apparatus at subscribers stations;

My invention has for its object the simplification of the switchboard apparatus now required in large exchanges and the provision of means whereby all exchange work, regardless of the size of the exchange, may be expedited.

The invention is applicable to exchange systems having any number of subscribers over five hundred. With less than that number it could be used, but would probably not be economical.

The whole end and aim of a telephone cen- 2 5 tral station is to enable any given subscriber to secure connection with any other subscriber with whom he may desire to converse and to disconnect the lines when the conversation has been finished. All the various methods 0 which have been proposed and used from time to time to attain this connection and disconnection at Will are divisible into two main classesviz., manual and autom atic-that is, those in which the operators manually per- 3 5 form the Work incident to connection and disconnection and those in which all the work is done by a machine on machines under the control of the subscribers. Each of these classes has its advantages and disadvantages. The manual systems,speaking generally,have obtained better repute and are in general use because of their certainty of operation and their lower cost in the first instance. Automatic systems, so far as I know, have never 5 been brought to such a state of perfection that they could be entirely relied upon, and in the few instances in which they have been installed it has been found that not only was their first cost high, but that the cost of maintenancc actually approached, if it did not exceed, that of a manual exchange. Manual systems, so far as they are at present developed, are almost as gravely handicapped as the automatic systems, however. The enormous increase in the number of telephone users at the present day, which bids fair to be continuous, renders it necessary to furnish interconnection on a scale, especially in large cities, which positively prohibits reliance being placed upon any single exchange center. This means that the system of today to be successful must be divided in such a way that there will be independent connection centers, each serving the class of people who are most intimately related to each other in their business dealings and all interconnected by common lines, usually designated as trunk-lines, through which subscribers connected to one center or local exchange may secure connection with those of another. Where all the lines of an exchange system not exceeding a few thousand subscribers are centered upon a single board, the so-called multiple switchboard has proved the most economical means for handling the business; but the trunk idea referred to above has been so convenient, particularly in the ease both of its extension and of its adaptability to new conditions, that it is only a question of a short time when the multiple board will give Way entirely to trunking arrangements within the exchange operating-room itself. Theoretically speaking, the trunking system or,

as it is sometimes called, the divided central scheme constitutes a perfect solution of the problem .of interconnection first above stated. Practically, however, there are numerous conditions connected with the operation of any trunking system which must be overcome before its efficiency will be equal to the more limited multipleboard arrangement. Both the scheme and the difficulties in its practical execution are those always inherent in the subdivision method of handling large numbers. In any given case Where a 5 certain unit out of many is to be selected the most logical way to proceed is by a series of subdivisions. The difficulties involved in any case are the indirectness of the process and its consequent lack of speed.

In order to I06 appreciate the importance of these points, it is only necessary to remember that the numberof calls per day possible to be handled directly determines the earning capacity of an exchange, and consequently the size to which it can profitably be extended-ahat is, when the expenses of operation increase in a greater ratio than the receipts that can be expected to accrue the limit of size has been reached. The present invention relates entirely to divided central systems, and the leading assumption upon which it depends is that with any call received by the proper operator at any central station the subsequent amount of work in subdividing will be constant, depending only upon the number of subdivisions. Changes in apparatus at central can have but little effect upon the time required for the subdivisions, for the number of selections must always remain constant as long as those selections are performed entirely within the exchange. The leading feature of my invention is the provision of means whereby a subscriber performs his part of the necessary subdivision without inconvenience to himself, and that when a call is received upon the proper switchboard-section of the central ofiice to which said subscriber is connected exercise of a mental process is required of one operator only who is called on to perform the last step in the subdivision. The invention even contemplates the removal of the necessity for this last mental act on the operators part; but for reasons which will appear when the invention is fully disclosed such a development is problematic in its value.

I attain the objects and satisfy the require ments enumerated above by using a system which is part manual and part automatic, striving so far as may be to combine the speed and high theoretical eificiency of the automatic system with the certainty and low cost of maintenance of the manual system.

In all automatic systems, so far as I know, there is more or less selective apparatus connected directly to each subscribers line and belonging exclusively thereto in the central office. In addition there must be, even in the best systems of the kind, a large amount of apparatus common to allthe lines. It may be safely assumed that the main objection to which such a system is liable is not on account of the nature of the apparatus itself, but because of the quantity thereof and the ratio between anyincrease of such apparatus and the corresponding increase in the number of subscribers. There must be a m ultitude of contacts every one of which is liable to derangement, consequently requiring attention. Every subscribers terminal selector must have a certain number of contacts and movable parts, dependent upon the number of subscribers which he is enabled to reach therewith. The number of these terminal selectors of course increases with the number of subscribers. Thus the increase in component elements or of selectors is as the square of the increase in the number of subscribers, for that same factor enters into the problem twice. This state of facts prohibits the use, in a successful system, of individual selective apparatus.

In manual systems requiring subdivisionsthat is, the selection, through trunk-lines, of a particular group of subscribers or other trunklines and then the selection ofaparticular one of those subscribers or trunk lines, and so onone of two things is necessary. Either the operators conducting the successive steps in the subdivision and selection must communicate through the trunk-lines or over separate instruction-circuits or the subscriber must repeat to each successive operator with whom he is connected, as the selection proceeds, the instructions he originally gave to the answering operator. Both of these are objectionable. The first because it takes time which the operators could profitably employ in the active work of making and breaking connections for passing orders from one to another, and, moreover, an element of uncertainty is involved, because of the liability of a message or a number which is repeated several times to be erroneously changed. The second course is out of the question. In a system having many thousand subscribers where perhaps three steps would be required for the selection of a particular subscriber three repetitions by the calling subscriber would be necessary. No system could hope to give even the smallest degree of satisfaction to its users which involved such inconvenience.

In designing my system I have succeeded in arranging automatic selecting mechanism which is independent of the subscribers lines which onlyincreases in direct ratio to the increase in subscribers. In other words, I pro vide connective means in number bearing a percentage relation to the number of: lines connected to the exchange that experience has shown to be necessary, and connected with each connective means, as a plug-andcord circuit or trunk-line, I provide a selective device which performs automatically a part or all of the subdivision required. At each subscribers station I provide a transmitter which is adapted to affect the said selective device when the latter has been brought into operative relation to the particular line with which the former is connected. I believe that I am the first to do this. I am aware that in the early days of the telephone art schemes were proposed whereby subscribers could select the particular switchboard upon which they desired connection; but, so far as I know, all such schemes required selective means for each line, which rendered them manifestly impracticable. I am not aware that it has ever been proposed to place such selective means within the cord-circuits or trunk-line circuits in exchanges themselves and only connect them to the lines in answering calls, and that man u- IIO ally. It will be seen at a glance that this not only enormously reduces the amount of selective apparatus and the attention it will require, but also permits the alternative oldfashioned manual work to go on side by side with the automatic, thereby afiording an instant substitute for the latter in case of its' failure to operate satisfactorily.

My invention is described and illustrated in connection with certain apparatus in the present application. Various other forms of apparatus embodying the same broad idea form the subject-matter of other applications filed and to be filed in the Patent Office. See the following: Serial No. 683,654, for a telephone-exchange system, filed J une16, 1898, and Serial No. 713,833, for a telephone-exchange system, filed April 21, 1899.

My invention is fully described in the following specification and the accompanying drawings, wherein the same letters and figures refer to the same parts throughout.

Referring to said drawings, Figure 1 is a diagram of an arrangement of switchboardsections and plug-circuits ata central office embodying my invention. Fig. 2 is a more specific diagram showing all of the apparatus at two subrcribers stations and throughout one cord or trunk circuit. Fig. 3 is a face View of one form of subscribers apparatus constructed in accordance with my invention; Fig. 4 is a side view, and Fig. 5 is a face view, parts being in section in both views, of one form of a subscribers impulse-transmitter. Fig. 6 is a front view of a modification thereof. Fig. 7 is a diagram of a modification.

Referring to Fig. 1, A, B, O, D, E, and F are sections of a switchboard in the central stat-ion. Upon each section a certain number of subscribers lines terminate and are there provided with spring-jacks and annunciators. The spacing of the line-terminals is roughly represented by squares upon these sections. For the purposes of description I will assume that there is but one operator at each of these sections and that the board contains, say, one hundred drops. In practice the arrangement will be different, as it is possible with my apparatus to greatly increase the number of lines which one operator can care for and at the same time place more operators at one board, thus reducing the number of board-sections for any given number of subscribers. Proceeding, then, upon this assumption, it will be observed that each operator has upon her right hand an answeringplug a and at her left hand a number of connecting-plugs b b, & c. Leading from the plug a in each case is a cord-circuit 9. Connected to this cord-circuit is a selective device S, to be hereinafter described. When it is operated, the circuit 9 may be connected to any one of the circuits 2, 3, 4:, 5, or 6, leading, as shown, each to a plug b upon one of the other board-seetions-that is to say, the answering-plug d ateach board-section is represented by a connecting-plug b at each section. Each plug, whether a. or b,is provided with asignal. The operation of the construc tion thus far described is as follows: When a subscriber calls, his line-annunciator exhibits its signal. The operator at the particular section upon which his line terminates inserts the answering-plug a in his jack. A series of changes are then caused in the circuit by the subscriber, which aifect the selective device S in such a way as to cause it connect the circuit 9 of the answering-plug with the circuit 2, 3, 4, 5, or 6, leading to the particular section upon which the line-terminal of the subscriber with whom he wishes to communicate is located. A complete circuit then exists between the a plug and the calling-subscribers line and a certain I) plug. The signal of the I) plug is thereupon displayed, and the operator upon that section commuicates with the subscriber and ascertains the number of the subscriber wanted.

Having obtained this, she finishes the connection by inserting the I) plug in the proper jack. It will be observed that the operator who answers the call does nothing but insert an answering-plug in the jack of the line calling. She pays no further attention to the matter until she sees the signal pertaining to that plug exhibited, which indicates to herthat the conversation on that line is finished. She thereupon withdraws the plug. In the meantime, upon the insertion of the I) plug in the called subscribers jack, the signal pertaining to that plug became extinguished, and upon the completion of the conversation it relights, indicating to the operator at that section also that the conversation is finished, whereupon she withdraws the I) plug.

Fig. 2 shows, diagrammatically, the elements of the apparatus required for the operation outlined above. A is a subscribers station whose line terminates in connective means located on the A section of the switchboard. ]3' is another subscribers station whose line terminates in connective means located upon the B section. A, B, and 0 represent three sections with a plug-circuittherebetween. At each subscribers station I 10- cate the usual. transmitter T, receiver R, polarized bell P, and induction-coil1. Their arrangement is a matter not germane to the present invention, but varying with the nature and requirements of the service. The bell P in Fig. 2 is represented as connected when the receiver is on the hook from one of the line-wires to ground, while the talking set when the receiver is off the hook is supposed to be bridged across the metallic circuit.

In addition to the ordinary apparatus at each snbscribers station I provide an impulse-transmitter or circuit-changer D, provided with apen (1, connected to one line-wire, a setting-hand d, a detent d controlled by a magnet (1 included in the other line-wire, and a restoring-spring d. The arrangement of this circuit-changer, as shown in Fig. 2, is such that when the setting-hand d is at zero-- IIO that is, unset-the pen cZ rests upon a break in the wheel, which may be, as is well understood in connection with transmitting-wheels of this character, a portion of insulation or an indentation in the wheel. Further, the relation between the insulating or cut-away portion of the wheel and the teeth which cooperate with the detent (Z is such that when the pen is upon a conductingtooth of the wheel the detent is in position to engage with a stop-tooth; but when the pen (Z is over the insulating or cut-away portion of the wheel the detent is not in position to stop the mechanism. This is to prevent the magnet from stopping the wheel when it is running down. The same end maybe attained by making the armature of the magnet very sluggish in its action. The subscribers station A is connected by line-wires 21 31 to an annunciator and spring-jack D upon the switchboardsection A. Current is constantly supplied through the spring-jack and an nunciator D to the line-wires 21 31, and, in fact, to all the line-wires in the exchange bya common generator G. Normally this current has effeet to operate the annunciators, because while there is a difference of potential between the sides of the line they are'normally open at the telephone hook-switch and at the transmitter. When, however, a subscriber has set his impulse-transmitter to select a particular switchboard-section, a circuit is closed across the line-wires through the said impulse-transmitter. Under these circumstances the annunciator D exhibits its signal 5 but the subscribers transmitter remains set for the reason that the magnet (Z is of very low resistance in comparison with the annunciatormagnet, and consequently insufficient current is allowed to pass to actuate the former. \Vhen the operator perceives the signal, she lifts the plug a from its seat and inserts it in the jack at D. The jacksprings are thereupon raised oft" their anvils and the resistance of the annunciator removed from the circuit, leaving the magnet d free to retract the armature 0Z and release the impulse-transmitter D. The impulses sent over the line directly affect certain apparatus in the plug-cord circuit, which I will now describe.

S is a step-by-step mechanism consisting of an insulating-disk .9, upon which are located a number of terminal contacts, one for each section of the switchboard, including the one at which it is placed. Pivoted at the center of the disk and adapted to be moved around over these contacts successively is a traveling arm .9, actuated through a toothed wheel 8 by a magnet s acting upon an armature and connecting pawl-carrying link 5 In order to return the traveling arm to zero at the close of an operation, I provide a spiral spring 3, attached at one end to the arm of the device and at the other to the shaft of the toothed wheel, this shaft being fixed and the toothed wheel being loosely journaled thereon. In

order to hold the arm in any position to which it may be stepped, I provide a detent .9", carried upon a lever 8 pivoted at and normally forced upward by a springs. The lever 3 is normally depressed by the weight of the plug a, beneath whose seat it extends. Connected at one end to the lever 5 and at the other end to one pole of a grounded generator G is a circuit containing a lamp or other signal Z. Leading from the terminal contacts on the periphery of the disk 3 are wires 1 2 3, &c., each of which forms one side of the circuit of a plug 1) at one of the board-sections. The very first terminal contact on the disk, however, is not connected to any operators board-section, but is connected to a trouble or complaint operator, who thus has a direct connection with all of the cordcircuits in the exchange. The second terminal contact is connected by wire 1 with the plug b on the A board-section, the third terminal contact is connected by wire 2 to the plug Z) on the 13 section and the fourth terminal contact by the wire 3 to the plug h on the C section, and so on. A common return is provided which goes to all these plugs and the common plug a. The apparatus at each of these connecting-plugs b is the same. It consists of listening-in and calling means of any ordinary type. I have shown the listening-in means as a contact-arm b and contact b and the ringing means as a key b adapted to complete connection from the individual line to the circuit of a grounded alternating-current generator G Each plug is provided with a lamp or other signal Z, one side of whose circuit is permanently connected to individual wire 1, 2, or 3 and the other side to a spring I), which extends into the plugseat and is adapted to be engaged by the plug while in its seat and forced into contact with the anvil b. When the I) plug is removed from its seat, spring Z2 which is already under tension, moves over, leaving the anvil b and making connection with the anvil N, which is connected to the circuit of agrounded direct current generator G. The further operation after the insertion of the plug a into a calling subscribers jack will now be understood. Current from the generator G passes through the wire 8, the cord-circuit 9, the tip of the a plug, the spring-jack at D, line-wire 21, magnet cZ impulse-transmitterD, pen (Z, line-wire 31, spring jack and sleeve of the a plug, cordcircuit 10, wire 11, magnetsfiwire 12, and back to the generator G. The magnets s and cZ being approximately of the same resistance,both being low, will both operate, the latter to release the impulse-transmitter D and start it revolving and the former to step around the wheel 8 in consonance with the makes and breaks in the circuit. If the setting-hand d has been set to the letter B, there will be a sufl'lcient number of makes and breaks to move the traveling arm 8 around until it rests upon the contact-terminal connected to plug 7) on the B board. Then this has been accomplished, the impulse-transmitter will have again reached zero and the pen (Z will rest upon the spot of insulation. A new circuit will have been formed from the generator G through the wire 8, traveling arm 5, contact-terminal, and wire 2, the lam p-circuit on board B, to and through the lamp Z to the spring b to the contact bflwire 13, and back to the generator. This will cause the lamp Z to become incandescent, and the operator at the 13 board is made aware that some one is calling upon the trunk-line connected with that plug. She thereupon depresses the plug,which brings the spring-arm b into contact with the anvil b and bridges her telephone set across the trunk-line. Having ascertained the number required, she lifts the plug from its seat and inserts it in the proper jack, immediately afterward depressing the ringing-key N, by which a current passes from the grounded alternating-current generator G2 to and through the ringing-key b at board-section B to the circuit-wire 2, to the tip of the plug 1), to the spring-jack of the subscriber wanted, to his line-wire 5, to and through his telephone hookswitch and the bell to ground. When the plug b was removed from its seat, the spring 6 was allowed to move away from the anvil b and engage with the anvil b thereby changing the circuit of the lamp Z, so that in order to complete that circuit it is now necessary that there should be a ground upon the wire U", which, it will be perceived, will not again occur until the subscriber hangs up his telephone and cuts in his bell. The subscribers are now enabled to converse over a complete metallic circuit consisting of their line-wires, plug a, the wire 2, the common return 7, the plug 1), and line-wires 4: 5. When the subscribers have finished their conversation,they hang up their receivers. This completes the ground-circuits through both lamps Z l, the

former of which was put into condition to receive this signal when the plug a was lifted from its seat by contact of the detent s with the wheel 5 The operators thereupon withdraw the plugs. The plug a by its weight forces the detent away from the toothed wheel 8 allowing the spring 3 to return it to zero,

and the plug 1) presses the spring 17 awayfrom the anvil b and again in contact with the anvilb the entire cord-circuit being thus restored to its normal condition of disuse.

One form of apparatus at the subscribers station which will serve to accomplish the results hereinbefore set forth is shown in Figs. 3 to 6, inclusive.

In Fig. 3 it will be perceived that although a telephone set of ordinary appearance is employed (shown, for the purpose of illustration, as having a backboard, bell-box, and a Blake transmitter) no hand-generator isprovided; but instead thereof the setting-hand d is provided upon the face of the bell-box, said setting -hand being adapted to sweep around and indicate letters or numbers corresponding to those designating the diiferent board-sections at central.

Figs. 4 and 5 show the interior of the bell box. Mounted upon the top of the box is a magnet (1 in position to lift the armature d attached to the detent-lever d Pivoted upon the lever d is a pawl d normally resting against a stop-pin d upon which it is held, if required, bya spring. Projecting through the side of the box is a resetting-button d carried on a rod 01 surrounded by a spring, which normally tends to force the button outward, and provided upon its inner end with a cam-surface d The end of the armaturelever d is provided with an inclined face which normally rests upon this cam-face in such a position that the pawl (1 will properly engage the teeth of the wheel D. The wheel D is provided with a stop arm or projection (1 1, which normally engages with a stop-pin c1 and when in such position the contact-spring cl is adjusted to rest upon an insulated spot on the .wheel. In the position shown, however, in Fig. 5 the wheel has been set a single step, the pen resting between two insulated portions and the pawl engaging one of the teeth. It will be observed that the teeth upon the wheel D in this figure are provided with flattened crowns, the relation between these crowns and the insulated spots being such that the pawl (1 will always be right upon a flattenedtooth-crown when the pen (:1 is passing over an insulated spot. When, however, the pawl reaches-the face of a tooth and would, if not otherwise withheld, engage therewith, the pen is always upon the conducting-face of the wheel, and the magnet, having its circuit closed thereby, is energized to hold the armature up.

If in setting the signal the subscriber moves the hand too far, it is only necessary to press the button at to lift the lever d and the pawl d whereby the wheel is released and may be reset.

It is understood, of course, that the wheel D is carried upon an arbor adapted to be rotated by the hand d in the setting direction and to be returned when released bya proper spring-motor,wl1ich forms no part of the present invention.

In the modification of the transmitter shown in Fig. 6, on a somewhat-enlarged scale, no magnet is employed to release the signal. In this case the lever d is the hook-switch lever AVhlCh opens and closes the bell and talking circuits and being actuated by the receiver R. The pawl d is pivoted and normally rests upon a stop-pin d in the proper position to engage with the teeth of the wheel D; but the signal is retained until the subscriber removes his telephone-receiver from the hook, which he does only upon hearing a single stroke on his bell, which results from the operator having plugged into his line jack, thereby connecting a grounded direct-current generator G thereto. If he desires to reset his signal, he momentarily lifts the receiver and then allows itagain to hang upon the hook.

I wish it to be distinctly understood that my invention is not limited to the use of the apparatus herein described, but contemplates many forms of such apparatus, some of which, together with valuable modifications and developments of the system itself, are illustrated and described in other applications of mine now pending or to be filed. It should also be understood that while I have described the invention as applied to connections in a system where the subscribers have terminals located upon divided boards, it may be used upon single boards for the purpose of enabling any given subscriber, when a plug has been inserted in his spring-jack, to connect himself with any subscriber upon the board. In this case the only change that would be required in the circuits shown in Fig. 2 would be the connection of the lines 1, 2, 53, &c., to subscribers line-wires direct instead of to the plugs I). This is indicated in diagram in Fig. 7, wherein a is an answering-plug, S is the switch controlled by magnet s and the switch-contacts are shown connected to the lines back of the spring-jacks.

Having described my invention, what I claim, and desire to secure by Letters Patent of the United States, is

1. In atelephone-exchange system,aswitch board carrying line-terminals, subscribers lines connected thereto, and provided with selecti ve apparatus at the subscribers stations, operators connective means, adapted to cooperate with said line-terminals, and a selective device connected with each operators connective means, and adapted to continue the circuit to anyone of a number of given points, as previously determined by the subscribers instrument, substantially as described.

2. In atelephone-exchange system,aswitchboard, line-terminals thereon, subscribers lines connected thereto, and provided at the subscribers stations, with selective transmitters; answering-plugs and cord-circuits at the switchboard, and mechanism connected with said cord-circuits adapted, when the said plugs are inserted in the line-terminals, to respond to the subscribers transmitter, and connect the answering-plug with any desired one of a series of circuits, substantially as described.

3. Ina telephone-exchange system,a switchboard, subscribers line-terminals thereon, an answering-plug, calling-plugs, and circuits between said plugs, the calling-plugs being disposed upon different parts of the switchboard; and a selective mechanism connected with the answering-plug and adapted to be controlled by a subscriber, to connect answering-plug with any of the calling-plugs, substantially as described.

4. In a telephone-exchange system,a switchboard divided into sections, subscriberslines having terminals grouped upon said sections,

answering-plugs and calling-plugs at each section, and circuits leading therebetween, magnetic selective apparatus adapted, when actuated, to automatically connect an answering-plug with any desired calling-plug, and means whereby said selective apparatus is placed under the control of a subscriber in answering a call, substantially as described.

5. In a telephone-exchange system, a series of subscribers lines, provided with connective terminals and signals, and means whereby a connection in response to a signal, is mannally initiated by an operator, and thereafter, automatically controlled from the subscribers station, substantially as described.

6. In a telephone system, acentral office or exchange, a series of subscribers lines terminating therein, each provided at the subscribers station with automatic controlling means, and a number of automatic line connectors at the central oifice less than the number of subscribers lines, each adapted to be manually connected to any subscribers line, and thereafter controlled by the subscriber, substantially as described.

7. In a telephone-exchangc system,aswitchboard, subscribers lines provided with terminals upon said switchboard, and a normallydisconnected selective device at the subscribers station, means, whereby the setting of the subscribers selective device, displays a signal upon the switchboard, and automatic connecting means adapted to be placed, by the operator, under control of the subscriber in response to said signal, substantially as described.

8. In a telephone system, a central office, subscribers lines radiating therefrom, each provided, at the subscribers station, with a normally open selective transmitting circuit, and a normally-closed signal-receiving circuit, and at the central ofiice with a normally-closed signal-circuit; means whereby the subscriber may close his selective signalcircuit, and thereby operate the central-office signal, and automatic connecting devices at the central office adapted to be connected to the subscribers line while disconnecting the central-office signal therefrom, substantially as described.

9. In atelephone system,two or more switchboards or board-sections, each provided with line-terminals, and lines leading from said terminals to different localities; connective means at each one of said boards, and circuits therebetween, and automatic selective means connected with certain of the connective means, and adapted, when the same are placed in connection with line-terminals, to be controlled through the lines, to complete connection through the boards, substantially as described.

10. In a telephone system, a subscribers line, provided at the subscribers station, with telephonic apparatus normally disconnected therefrom, a signal normally connected thereto, an impulse-transmitter and a magnet controlling the same, in a circuit normally connected to the line, but broken at said transmitter, a signal for the line at the central office, a magnet for controlling the same, and a generator, both normally connected to the line, the generator-current being of a proper character to operate the signal-magnet, but not the transmitter-magnet at the subscribers station, when said transmitter is set thereby closing its own circuit, operators connective means at the central office, adapted to be connected to the line-wires while disconnecting the signal-magnet therefrom, a responsive circuit-controlling device in the circuit of said connective means, and suitable connections whereby the character of the current upon the line is so changed in the act of makin g connection therewith,that the subscribers transmitter-magnet is operated, and the circuit-controlling device afiected in response thereto, substantially as described.

11-. In a telephone-exchange system, a series of boards or board-sections, subscribers lineterminals grouped thereon, answering and calling plugs at each board, circuits leading from each answering-plug at one board to calling-plugs at two or moreboards, and automatic means in the answering-plug circuit,

adapted to be controlled by any subscriber with whose line it is connected, to complete a circuit from said plug to any one of its associated calling plugs, substantially as described.

12. In a telephone system, a subscribers circuit containing telephonic instruments in a normally-open bridge, and an impulse-transmitter or circuit -changer in another normally-open bridge, containing also a low-resistance transmitter controlling magnet, a signal at the central office, and a magnet therefor, of high resistance, normally connected to the line and to a suitable generator of electricity, together with plugs and cordcircuits and automatic selectors connected thereto,whereby-, when the subscribers transmitter is set, the signal at the central office alone is operated, and when a plug is connected with the line-circuit, the signal-magnet is disconnected therefrom and the automatic selector connected in its place, to respond to the subscribers transmitter, substantially as described.

13. In a telephone-exchange system, a series of switchboards or board-sections, subscribers lines connected to terminals grouped thereon, answering-and connecting plugs at each section, one terminal of each answeringplug beingconnectedbyacontinuousline with the corresponding side of a number of connecting-plugs, the other terminalof the answering-plug being connected to a selecting device consisting of a movable conducting-arm, adapted to cooperate With a series of terminals, from each of which, a Wire leads to the corresponding terminal of each of' the connecting-plugs before mentioned, anda magnet for said selecting device connected to the plug-circuit, and adapted to be brought under the control of a subscriber when connection is made with his line, substantially as described.

14. In a telephone exchange system a switchboard divided into sections, subscribers lines connected to terminals grouped thereon, answering and calling plugs at each section, each answering-plug adapted to be connected to any one of a series of callingplugs upon different sections, automatic means connected With the plug-circuit and adapted to be controlled by the subscriber, for effecting such a connection, and a signal for each calling-plug connected to its circuit, and a suitable generator, substantially as described.

15. In a selecting device for telephoneswitchboards, a series of terminals connected to the various sections of a switchboard, a movable conducting-arm adapted to cooperate with said terminals, a connecting-plug connected to said movable arm, a detent adapted to retain said arm in contact with any given terminal, and means controlled by the movement of the plug for operating said detent, substantially as described.

16. In a selecting device for telephoneswitchboards, a series of terminals connected to calling-plugs, a movable partadapted to make contact with any of said terminals, and, itself, connected to an answering-plug, and a controllingdetent for said movable part, adapted to be operated by the removal of the answering-plug from, and its replacement in, its seat, substantially as described.

17. Connecting means for telephone-switchboards, each consisting of an answering-plug and a series of calling-plugs, a selective device comprising a series of terminals connected with the calling-plugs, a common terminal adapted to make contact with any of said terminals and connected to the answering-plug, and a magnet for effecting the movement of said common terminal, connected to the answering-plug circuit, and adapted to be placed under the control of a subscriber when connection is made with his line in answer to a call, substantially as described.

18. Connective means for switchboards, each comprising an answering-plug and a number of calling-plugs, a series of adjacent terminals, each connected to a calling-plug, a movable terminal connected to the answering-plug and normally resting in an idle position, a magnet connected with the answering-plug circuit, and adapted to cause the movable terminal to make contact with any one of the calling-plug terminals, and means controlled by the movement of the answering-plug, in making or breaking the line connection, to return said movable terminal to its normal idle position, substantially as described.

19. In connective means for telephoneswitchboards, a series of plugs and circuitcontrollers therefor, supervisory signals connected to said circuit-controllers, and operative only while the circuit-controllers are set, means actuated by the movement of the plugs in disconnecting through-circuits,and returning the plugs to their seats, to restore said circuit controllers and simultaneously eiface said signals, substantially as described.

20. In switchboard apparatus for telephone systems, answering and callingplugs, circuits for interconnecting the same, and circuitcontrollers therefor, each circuit-controller consisting of fixed and movable terminals, a magnet or magnets connected with the answeringplug circuit and controlling the engagement of thefixed and movable terminals, a detent for each circuit-controller, a supervisory-signal circuit, and means whereby said detent is controlled by the movement of the answering-plug, and itself controls the supervisorysignal circuit, substantially as described.

21. In a telephone-exchange system, a series of switchboards or board-sections, answering and calling plugs at each board, means placed under control of a calling subscriber in answering his call, for connecting the answering-plug with the circuit of any one of a number of calling-plugs at the different boards, and a signal for each callingplug, connected to the circuit of that plug, and to a suitable generator, substantially as described.

22. In a telephone-exchange system, a series of trunk-lines interconnecting board-sections, each trunk-line having a common answcringterminal and normallyincomplete circuits leading therefrom toanumberof calling-terminals, means for completing any one of said circuits at will, a signal connected to the circuit of each calling-terminal, and serving, in its normal position, as an advance signal for that terminal of the trunk-line, and means whereby, duringthe use of the callingterminal in completing a connection, the said signal is switched into position to serve as a clearing-outsignal,substantiallyas described.

23. In switchboard apparatus for telephoneexchanges,atrunk-line,aterminal-plug therefor, a signal associated with said plug, and connected upon one side to the plug-circuit, and upon the other to a spring-contact in the plug-seat, fixed terminals between which, said springcontact is adapted to move, and connected to separate generators in such manner that, when the plug is in its seat, the signal serves as an advance signal for the trunkline, and at all other times as a supervisory or clearing-out signal, substantially as described.

In testimony whereof I have hereunto set my hand, this 15th day of June, A. D. 1898, in the presence of two witnesses.

EDIVD. E. CLEMENT.

Witnesses:

MORTIMER A. J ONES, JNo. W. SCOTT.

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