Nikola Tesla U.S. Patent 723,188 - Method of Signaling Patent Wrapper Page 20

T 13 13 13 1 al action. By employing only two kinds of disturbances or series of impulses instead of one, as has heretofore 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 1 signals or messages reliable and exlusive, but in exceptional instances, a greater number 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 disturhances or series of inpulses, but also by a judicious choice of the same and the order in which they are made to act upon the receiver. Evidently there are a great many ways of generating impulses or disturbances of any ave length, wave form, number or order of succession, or of any 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 cooperate and to cause the receiver to be actuated and, inasmuch as the skill and practical knowledge in these novel fields can only be acquired by long experience, the degree of safety and perfection attained will necessarily depend upon the ability and resource of the expert who applies my invention, but in order to enable the same to be successfully practiced by any -3577