Nikola Tesla U.S. Patent 723,188 - Method of Signaling Patent Wrapper Page 50

47 bration and oscillate freely, each at its proper rate for a certain period of time at every discharge. The two vibrations are impressed upon the ground through the plate E and spread to a distance, reaching the receiving station, which has two similar circuits or systems esande, arranged and connected in the same manner and tuned to the systems at the sending station so that each responds exclusively to one of the two vibrations produced by the transmitting apparatus. The same rules of adjustment are observed with respect to the receiving circuits, care being furthermore taken that the tuning is affected when all the apparatus is connected to the circuits and placed in position, as any change may more or less modify the vibration. Each of the receiving coils s is shunted by a local circuit containing, respectively, sensitive devices al a2, batteries bl b2, adjustable resistances r¹ r2 and sensitive relays R¹ R2, all joined in series, as shown. The precise connections and arrangements of the receiving a. A various instruments are largely immaterial, and may be varied in many ways. The sensitive devices al a2 may be any of the well devices of this kind, as for example, two conducting terminals separated by a minute air gap or thin film of dielectric, which is strained or weakened by a battery or other means to the point of breaking down, and gives way to the slightest disturbing influence. Its return to the normal sensitive state may be secured by momentarily interrupting the battery circuits after each operation, or otherwise. The relays R1 R2 have armatures 11 12 which are connected by a wire 7, and when attracted, establish electrical contacts at cl and c², thus closing a circuit containing a battery b3, an adjustable resistance r3, and a relay R3. From the above description it and 607