"Baby Tesla Coils" use inverter circuits to get the voltage up high enough to drive the primary. "Real" Tesla coils tend to use luminous tube ("neon sign") transformers for their power. A transformer like this puts out 12 to 15KV at around 30ma and it can easily kill you. After running through a spark gap and the Tesla coil primary, the secondary can output over 250KV but at a much lower current. Still, it's nothing to play with. There is little in this electrical world as impressive as a Tesla coil operating in a darkened room and there's little in this electrical world, short of an electric chair, that's as potentially dangerous.

Be very careful when using them and never touch anything while it's under operation. There are photos of Nikola Tesla casually reading a newspaper while sitting near the primary of his huge, factory-sized coils in full operaton. These are double-exposures. For all his genius in the electrical power industry, Tesla was still a bit of a snake oil peddler.

Dean