Oudin coil
An Oudin coil, also called an Oudin oscillator or Oudin resonator, is a resonant transformer circuit that generates very high tension, high frequency alternating current (AC) electricity at low current levels, used in the obsolete forms of electrotherapy around the turn of the 20th century. It is very similar to the Tesla coil, with the difference being that the Oudin coil was connected as an autotransformer. It was invented in 1893 by French physician Paul Marie Oudin as a modification of physician Jacques Arsene d'Arsonval's electrotherapy equipment and used in medical diathermy therapy as well as quack medicine until perhaps 1940. The high voltage output terminal of the coil was connected to an insulated handheld electrode which produced luminous brush discharges, which were applied to the patient's body to treat various medical conditions in electrotherapy. (Wikipedia).
