This is a variable voltage, universal, AC to DC power supply with DC voltage selectable from 3 to 12V DC. This unit accepts an input voltage of 100V to 240V and includes snap-in adapters for US, UK, Europe and Australia (see image above for plug types). Utilizing the variable output voltage feature provides manual speed control for all of our products. Speed is adjusted by varying the voltage and the normal operating range of the cooling and ventilation products is 7 to 9V for most applications or 12V for more demanding and aggressive situations. However, operating our products between 7 and 9V provides for quieter operation of the fans while at 12V most of our products will be audible. The advantage to this feature is that it provides the option to run the cooling products quietly when components are within close proximity of sitting areas or more aggressively when components are tucked away in cabinetry and closets. This is when components require more airflow and noise is not as big of a factor.The DC end of the power supply utilizes a 2-pin female receptacle on the end of a 6' cord. The receptacle plugs directly into most of our products but on the remaining products (mainly the metal, cooling units), a 2.1mm Coax plug is used. The power supplies come with several DC plugs that are color coded but due to inconsistencies in the color coding, find the plug that fits the best; the correct plug will simply fit snuggly into connector. You can also check the packaging as coding should be indicated correctly on the actual package that you receive. Again, you will use the 2.1mm plug.