Superposition of resonance
Open loop system
Regulation of instantaneous power output of the system
The input and output power ratio is determined by the intensity of energy potential the system deals with. There are few types of easily accessible potential energy in nature: gravity, inertia generated by motion of mass of matter, electric force, magnetic force.
The first prototype kit cost of Free Energy device should be under $100 which includes an electronic controller, Bill of Materials, assembly manual, a book of alternative theory in physics that explains the impossible device by mainstream science . The kit should be released under Free and Open Source license so that it removes any legal trouble of the maker.