Nikola Tesla U.S. Patent 723,188 - Method of Signaling Patent Wrapper Page 47

604 도사 of transmitting and receiving stations to be operated, selectively, and exclusively, and without any danger of the signals or messages being disturbed, intercepted or interfered with in any way, is the object of my present invention. T Broadly stated, this invention consists in generating two or more kinds or classes of disturbances or impulses of distinctive character with respect to their effect upon a receiving circuit, and operating neareby a distant receiver which comprises two or more circuits, each of which is tuned to respond exclusively to the disturbances or impulses of one kind or class, and so arranged that the operation of the receiver is dependent upon their conjoint or resultant action. By employing only two kinds of disturbances or series of impulses instead of one, as has here tofore been done to operate a receiver of this kind, I have found that safety against the disturbing influences of other sources is increased to. such an extent, that I believe this number to be amply sufficient in most cases for rendering the exchange of signals or messages reliable and exclusive, but in exceptional instances, a greater numer may be used and a degree of safety against mutual and extraneous interference attained such as is comparable to that afforded by a combination lock. The liability of a receiver being affected by disturbances emanating from other sources as well as that of the signals or messages being received by instruments for which they are not intended may, however, be reduced not only by an increased number of the cooperative disturbances or series of impulses, but also by judicious choice of the same and order in which they are made to act upon the receiver. P Evidently there are a great many ways of generating in-3