PowerBright 300 Watts Japanese Voltage Transformers, Step Up and Down Japan Converter, can be Used in 120 Volt and 100V Countries, Convert from 120V to 100V and 100V to 120V, Universal Outlet Socket

The power cord is a standard 3-prong 110 V cord that can be plugged into a 110 V source or into a 220 V source using an adapter that comes with the unit. You adjust a jumper in the back to set the box correctly for the input voltage level you are plugging into. There are a couple of other jumper positions that allow other common international input voltages in the 200 V range. Then in front, you have 110 V output power on the standard 3-prong outlet and 220 V on the universal multi-plug outlet. If you "actually" use 120 V or 240 V as the input voltage rather than 110 or 220 V, the outputs will be 120 V and 240 V respectively, since the big autotransformer will maintain the 1:1 and 2:1 or 1:2 voltage ratios between inputs and outputs. This is an auto transformer, so essentially it is a single center-tapped winding. Thus, it provides no "isolation" between input and output power (common neutral). For common appliances this should work fine. If you are doing some exotic electronics experiment, you need to know that detail to determine if this unit will do what you want it to. "Isolation" type step up/down transformers are commonly available, but are typicall twice the price. The unit is fused and has a power switch that lights up. It comes in a strudy steel box. Being all steel and copper, it is heavier than most rocks its size, but not a great deal more complicated than said rock. That is good -- not much can go wrong with something like this..