Check the listing for details. Coil and Rotary Tattoo Machine Linear Power Supply With LED Display. Color: Gray, Condition: New. Listed at 150.00 USD. Coil and Rotary Tattoo Machine Linear Power Supply With LED Display. THis is engineered to be connected to a 12 volt battery for true, constant power! As you know, coil and rotary machines run best on constant voltage supplies. Pure, constant power can only be achieved from a battery, the old school way. Newer power supplies utilize rectifiers to transform AC power into something similar to constant voltage. But that method of voltage conversion is fine for standard electronics, but for the veteran tattooer a huge difference can be seen and felt with the move to a linear power source, powered by a battery. This linear power supply comes with a battery clamp that plugs into the power supply. Battery not included. Please message me with any questions. Happy tattooing!