The Turn Of The Century Electrotherapy Museum http://www.electrotherapymuseum.com New design for an Induction Coil based on a Radio Inductance Coil 15 Turn Primary Coil, 750 Turn Radio Inductance Coil (Tuning Coil from De Forrest and similar sets) Core is 1.375" x 5.500" long Whole assembly tossed in wax for insulation Produces 12,000V in the circuit below Sparks 1/2" - 3/4", believed to be around 25kHz Tesla Coil Circuit, yet unusual values for low frequencies