"The greatest discoveries and developments connected with the great names in the alternating current and related systems were dated already in early nineteenth century, see review [1.1]. However, an important basic invention was the battery, a source of electricity, disclosed by the Italian scientist Alessandro Volta in 1799. This simple source of a direct current (DC) allowed many important experiments with the electricity. In 1820 Danish physicist Hans Christian Ørsted discovered an effect of electricity on the magnetic field and his findings were confirmed by experiments of French physicists Andre-Marie Ampere and Francoise Arago. The parallel wires with DC current visibly attracted or repelled each other according to the mutual current directions. However, an ability to generate electricity by the moving magnets and the corresponding principle of the electric induction was discovered in 1830 by English scientist Michael Faraday. These new effects based on the electric induction inspired Serbian-American electrical and mechanical engineer Nikola Tesla and led to his inventions of an alternating current (AC) generator used rotating magnetic field, his Tesla coil, the transformation of AC voltages to very high voltages or vice-versa, as well as other inventions patented at the end of 1887. Besides of his fundamental inventions Tesla is considered as a pioneer also in the radar technology, X-ray technology and remote control.