@VoltageConverter
Most single phase AC power supplies in the world are powered at 100-120V (Japan, USA, Canada, etc.) or 220-240V (UK, Australia, China, New Zealand, Netherlands, etc.). One common use of voltage converter (step up & step down transformer) is to allow electrical appliances manufactured in one region voltage to operate in an area with different voltage. Buying a reliable step-up/step-down voltage converter, the appliances you buy in Europe can work well on the US power grid (and vice versa), also suitable for travel between different countries. But please note that the voltage converter can only convert the voltage, not the frequency.