Nikola Tesla U.S. Patent 725,605 - System of Signaling Patent Wrapper Page 20

634 syntonegyed 1 2 the liability of its being affected by extraneous disturbances, is carefully synchronized with the transmitter. By a scientific design of the sending and receiving circuits and other apparatus, and skillful adjustment of the same, these objects may be in a measure attained, but in long experience I have found that notwithstanding all constructive advantages and experimental resources, this method is in many cases inadequate. Thus, while I have succeeded in so operating, selectively, under certain favorable conditions, more than one hundred receivers, in most cases it is practicable to work successfully but a few, the number rapidly diminishing as, either owing to great distance or other cause, the energy available in the synchronized circuits is small, and therefore 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 harRub. Spee frequencies i monics, 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 extraneous 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 intelligente transmission, that the signals or messages should be exclusive or private, it is highly desirable to do away with the above limitations, all the more so, as it is a fact, which I have actually observed, that the influence of -2