Nikola Tesla U.S. Patent 725,605 - System of Signaling Patent Wrapper Page 8

622 the receivers necessarily more delicate. Evidently a circuit, however excellently constructed and adjusted to respond exclusively to vibrations of one period, is apt to be affected by higher harmonics, and still more so by fundamental tones, and since, particularly if the circuit is designed for oscillations of a very high frequency, the number of the effective harmonics may be large, the circuit may be easily disturbed by extrane ous influences, so that, when very short waves, as those produced by Hertzian spark apparatus, are used, little benefit, if any, is derived from synchronizing the circuits. It being an imperative requirement in most practical applications of such systems. of signalling or intelligence transmission, that the signals or messages should be exclusive or private, it is highly desirable 1 to do away with the above limitations, all the more so, as it is 1 a fact, which I have actually observed, that the influence of powerful electrical disturbances upon sensitive receivers extends, even on land, to distances of many hundreds of miles and consequently, in accordance with theory, still farther on sea. To overcome these drawbacks and to enable a great number of transmitting and receiving stations to be operated, selectively, and exclusively, without any danger of the signals or messages being disturbed or intercepted, or interfered with pted in any way, is the object of my present improvement. improvement. Sul Spre Broadly stated, my invention involves the use of involves a transmitter capable of generating two or more kinds or series 1 or impulses, differing in their characteristics, each of waves -2