Nikola Tesla U.S. Patent 723,188 - Method of Signaling Patent Wrapper Page 7

564 distinctive character with respect to their effect upon a receiving apparatus, and operating thereby a distant receiver, which comprises two or more elements, severally re1 sponsive to the different disturbances or impulses, and which is dependent for operation upon the conjoint or resultant action of two or more of such elements. By employing only two kinds of disturbances or series. of impulses instead of one, as has heretofore been done, to operate a receiver, 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 mes7 sages between two stations quite reliable and exclusive, / but in exceptional instances, a greater number may be used, and a degree of safety against 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 co-operative disturbances or series of impulses, but also by a judicicus choice of the the same and mode in which they are made to act upon the re1 ceiver. Evidently there are a great many ways of generating impulses or disturbances of any wave-length, wave-form, number or order of succession, or of any desired special character, such as will be capable of fulfilling the requirements above stated, and there are also many ways in which such impulses or disturbances may be made to co-oper-3