The Turn Of The Century Electrotherapy Museum http://www.electrotherapymuseum.com  4" Capacity Induction Apparatus 2.375 x 10" Secondary Coil - 34 AWG, approx 1500T Primary 8 turns of Copper Ribbon Core 1.5" Square x 13" Long Acetate sheets used for interleave material.  120-240V HID Ballast, 7.5 mfd Motor Run Cap, Spark Gap Current-limiting inductors are small electromagnets of various shapes and sizes.  They effect the electrical discharges seen. Hot ribbon Hot hissing ribbons Hot discharge Hissing Sparks Single Sparks Crackles - Hissing Sparks Crackles Click here for a movie!