This is a variable voltage, universal, AC to DC power supply with DC voltage selectable from 3 to 12 V DC. This unit plugs into a standard US 110/120V AC receptacle and 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 when noise is not as big of a factor.The DC end of the power supply utilizies a 2-pin female receptacle on the end of a 4' cord. The receptacle plugs directly into most of our products but on the other products (mainly the metal, cooling units), a 2.1mm Coax plug is used. The power supplies come with several 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 the DC jack on the fan product.