brations being emitted simultaneously or in rapid succession, as may be desired, at each closure of the circuit. The two receiving circuits at the distant station, each tuned to 235respond to the vibrations produced by one of the elements of the transmitter, affect the sensitive devices a1 and a2 and cause the relays R1 and R2 to be operated and contacts c1 and c2 to be closed, thus actuating the 240receiver or relay R3, which in turn establishes a contact c3 and brings into action a device a by means of a battery d4, included in a local circuit, as shown. But evidently if through any extraneous disturbance only one 245of the circuits at the receiving-station is affected the relay R3 will fail to respond. In this way a communication may be carried on with greatly-increased safety against interference and privacy of the messages may be 250secured. The receiving-station shown in Fig. 2 is supposed 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 255known means, which it is not thought necessary to illustrate 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, 260as R3, may be made dependent instead of upon two upon more than two such transmitting systems or circuits, and thus any desired degree of exclusiveness or privacy and safety against extraneous disturbances may 265be attained. The apparatus as illustrated in Figs. 1 and 2 permits, however, special results to be secured by the adjustment of the order of succession of the discharges of the primary circuits P1 and P2 or of the time 270intervals between such discharges. To illustrate: The action of the relays R1 R2 may be regulated either by adjusting the weights of the levers l1 l2, or the strength of the batteries b1 b2, or the resistances r1 r2, or in other 275well-known ways, so that when a certain order of succession or time 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 280instant, and thus operate the relay R3, but will fail to produce 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 285additional safety against disturbances from other sources may be 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 290circuits. Instead of closing and opening the circuit of the source S1, 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, 295as by varying the inductance of the primaries.
Obviously 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 an instrument300 having but one such circuit. A few of 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 system e s3 d3 is partly shunted305 by a rotating wheel or disk D3, which may be similar to that illustrated in Fig. 1 and which cuts out periodically a portion of the coil or conductors s3, or, if desired, bridges it by an adjustable condenser C3, thus altering the310 vibration of the system e s3 d3 at suitable 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 315periodically short-circuiting, through an induction-coil Land 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 caused320 to be emitted by a system e s5 d5, this result being produced by inserting periodically a 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 p5325 and three rods or brushes in, 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. 1330 or in any other convenient way. 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,335 that the different vibrations 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. 340Evidently, however, it is not necessary 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.345 3, 4, and 5, in which case the corresponding disks, as D3 D4 D5, at the sending will be driven in synchonism with those at the receiving stations as far as may be necessary to secure the desired result; but whatever the 350nature of the specific devices 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 to355 waves, impulses, or vibrations of a certain kind or class produced either simultaneously or successively by a suitable transmitter.
It 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 transmis-