US444108A - Signaling apparatus - Google Patents

Description

UNITED STATES PATENT FFICE.

ISAIAH H. FARNHAM, OF VVELLESLE Y, ASSIGNOR TO THE NEW ENGLAND TELEPHONE AND TELEGRAPH COMPANY, OF BOSTON, MASSACHUSETTS.

SIGNALING APPARATUS.

SPECIFICATION forming part of Letters Patent No. 444,108, dated January 6, 1891. Application filed August 20, 1890. Serial No. 362,4=70. (No model.)

To all whom it may concern: ber of stations. If, however, it be desired to Be it known that I, ISAIAH H. FARNHAM, reapply the same principles in connection with siding atVVellesley, in the county of Norfolk a single-wire or earth-completed circuit, the and State of Massachusetts, have invented several closed and discontinuous bridges, or

certain Improvements in Signaling Apparaderived or branch circuits,including,respecttus, of which the following is a specification. 'ively, the call-bell magnets, the generating- This invention concerns telephone-circuits, armature, and the telephone or telephones, and is an improvement in that class of such will necessarily be connected at each station circuits wherein a numberof stations are conin parallelism with the single line-wire, and

:0 nected with the same main line. It is espewill extend-therefrom to earth. In the above cially applicable to metallic'circuits. but can arrangement it is intended when the callalso be applied to single-wire or earth-comsending generator at any station is operated pleted lines involving the same principles. that the bells at all of the other stations of The most approved modern practice of t-elthe circuit, including the bell at its own sta- 15 ephone-circuit construction and arrangement tion, shall ring, the current developed by where a number of stations are to be consaid generator being divided among the elecnected with the same circuit is to construct tro-magnets of the said bells. A distinctive a metallic circuit between the two terminal signal is assigned for each stat1on,and though stations,causingbothwires thereofto loop-also all stations h ar every ring that one onl5 20 into all of the intermediate stations. The whose signal is given will respond. All of electric call-bell at each station is placed in the bell electro-magnets used in connection a closed bridge or branch extending from one with systems of the character indicated are of the main wires of the metallic circuit to of high resistance and self-induction, they the other. The call-sending generator canbeing often wound up. to a resistance of five 25 not be efficiently included serially in circuit hundred and sometimes to one thousand with the said bell, because if it were the reohms. sistance of the said bell would form virtually It is evident from what has been stated that a portion of the internal resistance of the genin the above class of circuits when any staerator, and make the latter so high that the tion-operator actuates his generator to call 0 system would not be self-regulating. Thereanother station the said generator will, dur- 8o fore the call-generator is included in a secing the said call, be connected in multiple 0nd but norinally-discontinuous bridge-cirare or in parallel with the ringing part or cuit between the two wires of the main cir call-bell magnets of said instrument. I have cuit, which bridge is closed only by and in ascertained that with this arrangement the 35 the act of sendinga call-signal, and this'closclosed bridge of the call-bell magnet of the ure may be effected either manually, as a disstation sending the call becomes a very continct action, or automatically, in a manner 'siderable obstacle to the strong and clear well understood and extensively employed ringing of the other call-bells connected with in the operation of such generators. The telthe same line at distant stations-that is, it

4o'ephone at'eacli station also is included in a being by far the nearest call-bell bridge to normally-discontinuous bridge between the the particular generator at this time in Opera main wires, which is held open by the prestion,will divert from themain linealargerpro once of the receiving-telephone on its supportion of current than will any other onesta port, but which is closed when the said retion or bell. While this disadvantage is not 5 ceiver is removed for u e, so that the genserious on a short line, it becomes of considerator and telephone-bridge circuits are both erable moment in long ones, and is likely to shunted by the bell-bridge. This arrangebe very detrimental to their satisfactory opi'n'ent has, for reasons unnecessary here to eration. It might be supposed that the easistate, been found extremely satisfactory in est way to overcome or avoid this'disadvan- 50 the operation of circuits connecting a numtage would be to so arrange the ringingap- 10o pliances as to disconnect the call-bell at the ringingestation altogether from the circuit during the operation of sendinga call. It is, however, not practicable to do this, for the reason that the subscriber must hear his own bell ring or he would not know or would not be satisfied that his generator was doingany work at all.

In View of the forcgoingconsiderations the object of my present invention is to prevent; a disproportionate amount of the calling-current from being short-circuited at the calling- 5 station, and to arrange the appliances and circuits at each station in such a way that outgoing signals shall be enabled to manifest themselves at the station where they are prot duced without depreciating their effect upon the call-bells at other stations. In carrying out these objects I provide means for increasing the resistance of the closed bell-bridgc or branch circuit at the home or ringing station at the moment of sendingthe call from thence.

I also do this by the same act which is ncces sary in order to send the call, and thus impose no additional work, operation, or thought upon the station-operator.

A practical means of embodying this invention is to place a suitable resistance (which may conveniently be formed of a coil or coils of insulated wire) in such relation to the pressbutton or automatic circuit-closer orchanger which brings the generator into action that by the act of operating the said button, key, or circuit-changer (whether actuated manually or automatically) the said resistance shall be automatically or without preconcerted action interposed in the circuit of the homebell magnets, whereby the said bell-bridge when a call 15 being sent by the generator at the same station shall have its resistance so raised or conversely have its conductivity so impaired that, though much nearer to the said generator than are the bell-bridges at the other stations, it shall present no greater facility for the passage of the current than is presented by the bell-bridges at the other stations, respectively. In other words, the said bell-bridge, though physically in close proximity to the generator at its own station, is electrically and for all practical purposes in the same relation with it and with the main circuit as if it were remote therefrom. The interposed resistance may,it is evident, be regulated or adjustable but I prefer a fixed resistance on the ground of simplicity. I find it useful, however, in some cases to provide not simply a resistance-coil, but an electromagnetic coil, and in that event it becomes an inductive resistance and involves the utilization of self-induction. I am thus enabled to use a much smaller amount of wire coils or number of convolutions than otherwise would be necessary, and consequently a less-measured resistance.

In the drawings which accompany this specification, Figure 1 is a diagram showing aportion of a multiplestation telephone'circult, in which my invention is disclosed. Fig. 2 is an enlarged diagram of a smaller part of said circuit, showing two stations only, with the electrical appliances and circuitconneetions fully drawn out at one of the said stations. Fig. 3 shows the embodiment of the invention in a concrete apparatus, the several station applianccsbeingelectrically combined in accordance with said invention; and Fig. -l shows a modified detail of the call-transmitting appliances, illustrating automatic means for bringing the generator into action.

The principle of my invention is fully disclosed in the diagram Fig. 1. A metallic circuit C is there indicated as extending bctween a number of stations, these being designated, respectively, by the numerals l to 6. One of these may, if desired, beacentral station, as 1, or all may be subscribers stations, as would be the case if C were a private line. The electrical apparatus and its connections are alike at all subscribers stations. At each is a call-receiving electro-magnctic bell B, having its electro-'1nagnets connected in a bridge orcross-wirecond uetor, forming a permanent connection between the two main-line wires L and L of the main circuit (3. This bridge-connection is permanently closed at all stations, and the bells being respectively included therein are all connected with the main circuit, and all will respond to signals sent from any station. At each station there is likewise a call-sending magneto-generator (i, also included in a bridge-conductor between the two main wires, whichbridge,however, is normally discontinuous, and only closed while a call isactually being sent. A key or circuit-closer 7a is also provided, and it will be seen that by means of its back or resting contact the said key is in connection with the closed bell-bridge, but that when pressed itisd isassociated therewith and caused to form a new connection with the gcneratorbridge,which thereupon is closed, and by turning the handle the said generator can be actuated to send an outgoing-call signal. Supposing that these appliances only were provided, as has heretofore been the case, if the line be long and if that one of the stations signaling be far from the others, it is obvious that much of the current generated would be shunted through the bell at the signaling-station, and thatthe other station-bells, deprived of theirproper share of current, would be liable to ring imperfectly. Let it furthermore be supposed that station under these conditlons is sending a signal. It is clear that bell B at said station, being much nearer to its own generator than are any of the bells at other stations, will rob the said others of their due proportion of current, and that the major part of said current developed, leaving the generator G, say, by wire 12, will reach the other pole thereof by way of point g, section 1t of main wire L, point 11, bell B, point 8, and key 7c. The home-bell only will ring loudly, the others faintly. To remedy this fault I provide a suitable resistance R and connect it in the bell-bridge serially with the bell B between the point 11 on line-wireL and 10 on line-wire L but it is desirable that this resistance shall only be brought into action at the station from which call-signals are being sent, and that at all other stations it shall be temporarily functionless. Therefore from a point 7 on the bell-bridge wire between the bell-magnet B and the resistance R, I run a wire 6 to the back stop or contact a of the key It, the stem of the said key being connected at 8 with the line-wire L Thus the normal bell-bridge extends from point 11 on line-wire L to point 8 on line-wire L through the key and its back contact, the resistance R being short-circuited or shunted out. This condition is maintained at all stations where signals are being received, so that the ringing-current coming into the several stations is not weakened by the presence of the extra resistance in circuit, but can exert its full force on the bell to give a good ringing efiect; but in sending a signal the crank or handle c of the magneto-generator is revolved and at the same time the key is pressed. This, as already explained, closes the generator-bridge from the point you linewire L to the point 8 on line-wire L the key 7.: having now become a part of the latter bridge. It is to be observed, however, that the movement of the key has not broken the circuit of the bell-bridge, which is still closed or continuous, but that it has removed the short circuit or shunt from the resistance R, which during the signal-sending operation is thus introduced into the bell-circuit, raising the resistance thereof and preventing the currents generated in G from being short-circuited therethrough.

In practice of course there are but two main-line station-terminals or points of attachment for the apparatus. This is made clear by Fig. 2, which also shows the telephone connections. The normal circuit through the station 3 is, as in all cases, by way of the permanently-closed bell-bridge, from point 11 on line L, by wire 15, bell B, point '7, wire 2, back contact a, key it, point 10, wire 16, automatic switch 3, lower contactspring 1; thereof, and wire 18, to point 8 on line-wire L This represents the station apparatus at rest, the bell included in the only closed conductor through the station, the generator and telephone bridges open, and the resistance short-circuited or shunted. The key 70 being depressed, the bell-circuit by way of e is broken; but the point 10 is'reaehed through the resistance R. The generator bridge is also closed, and follows the following route: from point 11, by way of wire 12, magn eto-generator G, wire 22, key-anvil f, key 70, wire 23, to point 10, and thence on the same path as the bell-bridge to point 8 on line-wire L Only during the operation of the generator, therefore, is the resistance R introduced to the'bell-bridge circuit.

the telephones while thelatter are being used.

At station 2, Fig. 2, the bell-magnets B and resistance R are indicated in dotted lines.

Fig. 3 shows that the several station appliances hereinbefore described are all, as usual, inclosed in a single box, which is indicated by broken lines. The several instrumentalities and their electrical connections are substantially identical with those described, as shown in Fig. 2, and are similarly distinguished by letters and figures of reference, and it would therefore be useless to describe them again. The figure, however, is useful as indicating a suitable mechanical arrangement. The two upper binding-screw terminals represent, respectively, the line connections 11 and 8, and of the six shown below, g and h are for the attachment of the receivingtelephone, '5 and j are for the purpose of leading the local battery and primary coil-wires into the bell-box, so that the primary circuit will be operated when the switch 3. is depressed, and on and 'n are for connection of the transmitter main-line helix.

Fig. 4 shows a simple mode of applying this invention to a bell whose generator-circuit is to be automaticallyclosed. Many magnetobell apparatuses are at the present time made which dispense with the manually-operated key It and have in lieu thereof a circuit-changer, which the movement. of the bell-crank actuates as a secondary function.

The essential features of the apparatus as described herein are unchanged, as are also the principal electrical connections. The key is, however, superseded by a flat contactspring 16*, which, as shown, is permanently connected with the telephone-hook s, and which is capable under certain conditions of making contact at its free end with the endz of the generator-armature axis, (representing one end of the generating-coils,) but which is normally held away therefrom and in contact with the point a, and thereby shunts the resistance R. The action of turningthe crank c by means of the notch device V, and in a manner well understood, gives the crankshaft q alateral motion against the coil-sprin g r, and its receding from the spring k permits the latter to break contact with its back point a, and to close the generator-circuitat z, the resistance R being by the first part of the operation introduced into the bell-circuit.

The resistance R, as stated, may be formed in Variousv ways. Ordinarily, diiferentiallywound helices of wire are the most conven ient. Frequently, however, as already explained, the electromagnetic coils may with advantage be employed, and I regard their employment as being distinctively a feature of my invention.

The resistance required for the attainment of the best results may of course vary with the length of the circuit, the resistance of the bell-magnets, and the distance between any special station and the others; but a very good average resistance, if it be simply made of coiled wire, is the same as that of the associated bellmagnet. If an inductive resistance be employed, a much lower resistance will be required.

Although I have throughout this specification referred to the-call-receiving device as a call-bell, it is evident that any other similar device-such, for example, as a sounder or buzzer-is to be considered as involving the spirit of my invention.

I claim as my invention 1. In an electrical signaling systen1,an electric circuit, an elcctro-magnetic signal-bell or equivalent electro-magnetic signaling device in a permanently-closed branch of the said circuit, a signal-sending magneto-generator in a normally-open branch of the said circuit, and means for increasing the resistance of the said bell-branch circuit while the said gene M01 is being operated to send outgoing signals.

2. The combination, substantially as hereinbefo re described, with an electric circuit extending between two or more stations, an electro-magnetic call-receivin g device located at each station in a permanen tly-closed bridge or branch of said circuit, and a call sending generator at each station in a normally-open bridge or branch of the said circuit parallel to the said closed branch, of means for closing the said generator-circuit to send an outgoing signal and for simultaneously increasing the resistance of the parallel bell branch at the same station.

The combination of a metallic main-line circuit extending between and connecting two or more stations, an electro-magn etic callbcll at each station in a permanently-continuous bridge between the two wires of said circuit, a call-sending generator at each station in a normally-open bridge, said bridge being when closed parallel with the bellbridge, a resistance, as described, in a shunt of the said bell-bridge, and means, as indicated, for breaking the said shunt and for introducing the said resistance into the bellbridge circuit when the generator is being operated, and for withdrawing the same therefrom and for reinstating the said shunt when the generator becomes quiescent.

i. The combination of a metallic main-line circuit extending between and connecting a number of stations, an electro-magnetic callbell at each station in a permanent bridge between the two wires of said circuit, a reae moe sistancc adapted to be included with said call-bell in said bridge, but normally shunted therefrom, a call-sending generator at each station in a parallel bridge of said circuit normally open, but adapted to be closed in the act of sending signals, and a circuitchanging device controlling the generatorbridge and the resistance-shunt and adapted to close the one and open the other, and vice versa, according to its position.

5. In an electric signaling system, an elec tric main circuit extending between two or more stations, a normally and permanently closed bridge or derived circuit at each station connected with said main circuit and including an elect ro-magnetic call-receiving device, a normally-open bridge or derived circuit at each station, also connected with said main circuit in multiple arc with the said bell branch and including a signal-sending generator, an inductive resistance, substantially as described, connected with the said permanently-closed bell branch, but normally shunted therefrom, and a circuit-changer controlling the said resistance-shunt and normally maintaining the continuity thereof, but capable of assuming a second position, in which the generator branch is closed and the said resistance included in the bell-circuit, for the purposes specified.

(3. A station apparatus for a multiple-station metallic circuit combining two mainline terminals, one for each wire of the said metallic circuit, a permanently-continuous conductor uniting the said terminals and forming a bridge between them, an electro magnetic call-bell, and a resistance included in said bridge, combined with a n0rinally-discontinuous independent bridge also extending between said terminals parallel to the first, a call-sending magneto-generator in the circuit of the said normally-open bridge, a shunt-circuit normally closed round the bellbridge resistance, and a circuit-changing key or switch normally forming, together with its back contact, a portion of said shunt-circuit and maintaining the continuity thereof, but adapted when operated to form, together with its front contact, a portion of the generatorbridge and to complete the same,whcreby the act; of sending the signal is caused to add resistance to the bell-bridge.

7. The combination, substantially as described herein, of an electric call-bell and a call-sending magneto-generator connected, respectively, in a permanently-closed and a normally-open bridge between the line-terminals of a telephone-station apparatus, with a suitable resistance and a circuit-changer controlling the same and adapted to connect the said resistance in the call-bell circuit during the operation of the said generator in sending outgoing signals, but to withdraw the same therefrom when said operation is intermitted, substantially as and for the purposes set forth.

8. The combination, in a tclephone'signaling system, of a metallic main circuit, a number of telephone-stations interconnected thereby, a permanently-eontinuousbridge or cross-conductor at each station, including the call-bell magnets, a resistance-coil at each station, also included in the said bell-bridge, but normally shunted or short-circuited, a normally-discontinuous independent bridge or cross-conductor at each station, a call-sending magneto-generator connected with the same and arranged to be included therein when the said cross-wire is closed, and a circuit-changer constructed to close the said open cross-Wire during the operation of said generator and to simultaneously and automatically break the resistance-shunt,whereby the said extra resistance may remain shunted at all stations except that sending a call and shall at said call-sending station be introduced into the bell branch, substantially as described.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 6th day of August, A. D. 1890.

ISAIAH I-l. FARNHAM. Witnesses:

GEO. WILLIS PIERCE, FRANK C. LOOKWOOD.

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