The iPower wireless power supply has inputs for two tattoo machines and a foot-switch, The 4 ampere power supply works with any device and can be powered by a USB cable. The iPower is compatible with both iPhone 4S or newer and Android 4.3 or newer devices, meaning you can use the device with most smartphones or tablets. The iPower is a double-output power supply controlled by USB connection. The power supplys double output allows connecting two coil or rotary tattoo machines at the same time, and using the control application its possible to choose which one to use and change its output voltage. Simply turn on Bluetooth and connect to your phone, then select the operating mode. You can then control the voltage and switch between your 2 machines at will. There are 5 quick-recall memory buttons, and then another area for infinite custom setups.Alex De Pase: "The iPower Tattoo is absolutely amazing! It's so helpful. This new type of power supply will change my work life."Bill Murran: Words can't express how impressed I have been with iPower Tattoo. The app is user friendly, intuitive and easy to use use.Mojo Tattoo: This Rocks! Something has changed!