Nikola Tesla U.S. Patent 725,605 - System of Signaling Patent Wrapper Page 9

kind or series being capable of producing a specific effect upon a distant receiving apparatus, but adapted to co-operate in causing the receiver to be actuated. By employing merely two kinds of impulses or vibrations instead of one, as heretofore, to operate the 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 messages between two stations quite 1 reliable and exclusive, but in exceptional instances, a greater number may be used 7 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 impulses, but also by a judicious choice of the same and mode in which they are made to act upon the receiver. Janelled for heel spee 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-operate 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. -3623