Original poster: "Dr. Resonance by way of Terry Fritz <teslalist-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com> Most of them have a tap selector switch which allows you to change the output potential. Max output is 14.4 kV. Dr. Resonance Resonance Research Corporation E11870 Shadylane Rd. Baraboo WI 53913