Century Accessory 110V/120V to 220V/240V Step-Up & Down Voltage Converter 100W Transformer A: Switch to AC117V, input voltage must be AC110/120V, voltage converter (output) AC220/240V B: Switch to AC230V, input voltage must be AC220/240V, And change the voltage into (output) AC110/120V Attention: It will be broken with wrong operation, and we will not responsible for the wrong operation. If you are not use it please plug it out!