Electrical apparatus developed by Nikola Tesla. It is a type of transformer. In this, a current is raised in voltage and lowered in amperage. It has two coils, primary at the bottom and secondary at the top. At the top of the secondary coil, there may be a discharge of lightning. It has some use in radio, but during the period after Tesla's death was mostly used for demonstrations and decoration. Tesla had been using a giant version as a key component of his proposed universal energy transmission system during experiments at Wardencliffe and Colorado Springs.