The Turn Of The Century Electrotherapy Museum http://www.electrotherapymuseum.com From Diathermy Machine to Tesla Magnifying Transmitter Adding an "Extra" Coil to a Diathermy Machine can make some nice sparks without destroying a historical machine in the process! Various coil forms were tried - this one is space-wound 28 AWG DSC  - 4.5" diameter. Two "Violet Ray" hard rubber handles wound with 30 AWG SSC wire. The windings are 2" x 7.875".  A metal rod (electrode) is connecting the two coils in series... (It is curious to note that these dimensions [5 cm x 20 cm] were given for two Tesla Coils under coil used for his "Light And Other High Frequency Phenomenon" lecture.) Sparks are long as if from a Oudin resonator, but still hot and able to cause bad RF burns on the higher power levels! Click here for a movie! I'm surprised HG Fischer didn't manufacture something like this! Wiring Diagram of a typical Diathermy Machine The secondary winding  of the Tesla/Oudin Coil has only 90 turns of 20 AWG Cotton Covered Wire! (C) Jeff Behary, 2007, 2008