Nikola Tesla U.S. Patent 725,605 - System of Signaling Patent Wrapper Page 40

654 Shab. Ofec 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 esl dl and e s2 d2, arranged and connected in the same manner and tuned with the systems at the sending station so that each responds exclusively to of the two vibrat: ons produced by mitting apparatus. The same rules of adjustment are observed with respect to the receiving circuits, care being furthermore taken that the tuning is effected 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 sl and s2 is shinted by a local circuit containing, respectively, sensitive devices al a², batteries b1 b2, adjustable resistances r1 r2 and sensitive relays R1 R2, all joined in series, as shown. The precise connections and arrangements of the various instruments are largely immaterial, and may be varied in many ways. The sensitive devices al 22 may be any of the well known devices of this kind, as for example, two conducting terminals separated by 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 circuit after each operation, or otherwise. The relays Rl R2 have armature 11 12, which are connected by a wire w, and when attracted, establish electrical contacts at cland 2, thus closing a circuit containing a battery b3 an ad-6ns