The 9 volt converts AC "wall" current into DC (direct current). This type of electricity is essential for most digital equipment, as it prevents interference and allows clear transmission of signals. So than 100 Hz. The 9V ADAPTER FEATURES: Light weight, small in size with high efficiency. It's your best compact power supply no matter what. This adapter for electronic equipment LIEN has ten US advantages over traditional power supplies including being safe and reliable. It contains no mount that can collect dust, corrosion or oxidation which will make the output voltage unstable; its exported electricity meets international standards so there is less risk in using hazardous goods with your equipment etc... By above said reasons, not only will customers' fewer expenses be offset by this product's higher price but the products can still bring greatest good to human society. Nine components produced in Taiwan, Mainland China and elsewhere : no need for assembly; internally circulated production links combined with vertical industry integration create remarkable efficiencies. Additionally, one control center eliminates duplicity or redundancy. No Maintenance:The product is designed with silicon junction transistors which ensures that the whole machine will not refuse to work, when you most need it. As for the microwave it emits pure and good sound. If something goes wrong, one of its chips will disable the whole thing; in normal circumstances though, every Integrated Circuit behaves well and prolongs life. The 9-volt adapter is your best choice wherever you are for charging units, capable of being dragged wherever you go in its suitcase/tiny tie holder or plugged into any wall socket plugged directly. Besides this, it doesn't use harmful material either; so it's cleaner than the ordinary power supply. For all these reasons and more, citing several technological advances. The company has won 14 international and national patents. No other similar device can compete in its power-saving effect of up to 91%.