English: Nikola Teslas high voltage laboratory in Colorado Springs, Colo, at which he performed experiments in wireless power transmission from 1899-1900. The copper ball at the top of the telescoping tower is the terminal of his huge magnifying transmitter. Essentially an enormous Tesla coil, it could produce radio frequency potentials of the order of 20 million volts at a frequency of 150 kHz, producing huge arcs hundreds of feet long.