rapid succession, as may be desired, at each closure of the circuit. The two receiving-circuits at the distant station, each tuned to respond to the vibrations produced by one of 235the elements of the transmitter, affect the sensitive devices a1 and a2 and cause the relays R1 and R2 to be operated and contacts c2 and c2 to be closed, thus actuating the receiver or relay R3, which in turn establishes 240a contact c3 and brings into action a device a3 by means of a battery d4, included in a local circuit, as shown; but evidently if through any extraneous disturbance only one of the circuits at the receiving-station is affected the 245relay R3 will fail to respond. In this way communication may be carried on with greatly increased safety against interference and privacy of the messages may be secured. The receiving-station (shown in Fig. 2 is 250supposed to be one requiring no return message; but if the use of the system is such that this is necessary then the two stations will be similarly equipped and any well-known means, which it is not thought necessary to 255illustrate here, may be resorted to for enabling the apparatus at each station to be used in turn as transmitter and receiver. In like manner the operation of a receiver, as R3, may be made dependent, instead of 260upon two, upon more than two such transmitting system or circuits, and thus any desired degree of extraneous disturbances may be attained. The apparatus as illustrated in Figs. 1 and 2652 permits, however, special results to be secured by the adjustment of the order of succession of the discharge of the primary circuits P1 and P2 or of the time interval between such discharges. To illustrate, the action of the 270relays R1 and R2 may be regulated either by adjusting the weights of the levers l1 and l2, or the strength of the batteries b1 b2, or the resistances r1 r2, or in other well-known ways, so that when a certain order of succession or 275time interval between the discharges of the primary circuits P1 and P2 exists at the sending-station the levers l1 and l2 will close the contacts c1 and c2 at the same instant, and thus operate the relay R3; but it will fail to 280produce this result when the order of succession of or the time interval between the discharges in the primary circuits is another one. By these or similar means additional safety against disturbances from other sources may 285be attained and, on the other hand, the possibility afforded of effecting the operation of signaling by varying the order of succession of the discharges of the two circuits. Instead of closing and opening the circuit of the 290source S, as before indicated, for the purpose of sending distinct signals it may be convenient to merely alter the period of either of the transmitting-circuits arbitrarily, as by varying the inductance of the primaries.
295Obviously there is no necessity for using transmitters with two or more distinct elements or circuits, as S1 and S2, since a succession of waves or impulses of different characteristics may be produced by and instrument having but one such circuit. A few of300 the many ways which will readily suggest themselves to the expert who applies my invention are illustrated in Figs 3, 4, and 5. In Fig. 3 a transmitting systems e s3 d3 is partly shunted by a rotating wheel or disk D3, which305 may be similar to that illustrated in Fig. 1 and which cuts out periodically a portion of the coil or conductor s3 or, if desired, bridges it by an adjustable condenser C3, thus altering the vibration of the system e s3 d3 at suitable310 intervals and causing two distinct kinds or classes of impulses to be emitted in rapid succession by the sender. In Fig. 4 a similar result is produced in the system e s4 d4 by periodically short-circuiting, through an 315induction-coil L3 and a rotating disk D4 with insulating and conducting segments, a circuit p4 in inductive relation to said system. Again, in Fig. 5 three distinct vibrations are caused to be emitted by a system e s5 d5, this320 result being produced by inserting periodically suitable number of turns of an induction-coil L4 in series with the oscillating system by means of a rotating disk B5 with two projections p5 p5 and three rods or brushes n5,325 placed at an angle of one hundred and twenty degrees relatively to each other. The three transmitting systems or circuits thus produced may be energized in the same manner as those of Fig. 1 or in any other convenient 330way. Corresponding to each of these cases the receiving-station may be provided with two or three circuits in an analogous manner to that illustrated in Fig. 2, it being understood, of course, that the different vibrations335 or disturbances emitted by the sender follow in such rapid succession upon each other that they are practically simultaneous, so far as the operation of such relays as R1 and R2 is concerned. Evidently, however, it is not 340necessary to employ two or more receiving-circuits; but a single circuit may be used also at the receiving-station constructed and arranged like the transmitting circuits or systems illustrated in Figs. 3, 4, and 5, in 345which case the corresponding disks, as D3 D4 D5, at the sending will be driven in synchronism with those at the receiving stations as far as may be necessary to secure the desired result; but whatever the nature of the specific 350devices employed it will be seen that the fundamental idea in my invention is the operation of a receiver by the conjoint or resultant effect of two or more circuits each tuned to respond exclusively to waves, impulses, or 355vibrations of a certain kind or class produced either simultaneously or successively by a suitable transmitter.
I will be seen from a consideration of the nature of the method hereinbefore described360 that the invention is applicable not only in the special manner described, in which the transmission of the impulses is effected through natural media, but for the tranmis-