Nikola Tesla Books
TECHNICAL APPENDIX without sensible distortion and attenuation...The earth's diameter passing through the pole should be an odd multiple of the quarter wave length - that is, of the ratio between the velocity of light - and four times the frequency of current... It is necessary to employ oscillations in which the rate of radiation of energy in the form of hertzian or electromagnetic wave is very small.' After returning from Colorado Springs he began to build a center for intelligence transmission named 'World Telegraphy'. In this system he proposed to use multicarrier transmitter with a special receiver tuned to all carriers. In his own words the method of 'individualization and isolation' is as cited below: 'this invention consists of generating two or more kinds or classes of disturbances or impulses of distinctive character with respect to their effect upon a receiving circuit and operating thereby a distant receiver which comprises two or more circuits, each of which is tuned to respond exclusively to the disturbances or impulses of one kind or class and so arranged that the operation of the receiver is dependent upon these conjoint or resultant action'. Tesla double circuit system is a predecessor of the modern spread spectrum system which is intended to protect the transmission from message intruders and at the same time decrease disturbing effect of noise. Even when developing a system for intelligence transmission, he did not neglect the transmission of energy on an industrial scale. He had an offer from The Canadian Niagara Power Company for developing such a system and he proposed 'to distribute ten thousand horsepower under a tension of one hundred million volts', which he claimed to be able to produce and handle with safety'. The transmitted power was intended to be used for illumination of isolated homes with vacuum tubes as well as for driving clocks! Tesla spent next forty years of his life trying to persuade the world that it would be possible to use the energy of a waterfall for supplying light, heat or motive power, anywhere - on sea, or land, or high in the air. But, without electrical laboratory and experimental verifications, his own theories and visions could not be developed so his future inventions were not anything as dramaticv as his poliphase system or Tesla coil. His practical 158
