A neon sign transformer is the electrical transformer needed to supply neon sign. Neon signs need high voltages in order to energize the gases inside them. Typical voltages are in the region of 4000 to 15000 volts. Around 6000 is needed at a minimum for a Tesla coil to work. Mine give 7500 volts at 30mA and I have two of them so I get 7500 volts at 60mA.