Do you know what dual-voltage means? If an electronic device is dual-voltage, it means that it accepts both 110v and 220v electrical current. It will indicate this by showing a 110v-220v voltage rating on its indication panel. North America, and most of Central and South america use 110v. So what is the point of having dual-voltage appliances?
Well, if you want to travel somewhere outside of the Americas, to a country in Asia or Europe, you will not be able to use your electronics unless they are designed for 220v electrical current. Most countries outside of the Americas use 220v. But a few places, like the island of Azores , a remote territory of Portugal, use both 110v and 220v. If you are going to Azores , be prepared for 220v by bringing dual-voltage appliances. But if you do not own any dual-voltage appliances, and don’t want to buy any, you can buy voltage converter s for your single-volt appliances.
voltage converter s attach to your electrical devices and regulate the electrical current coming out of outlets that use 220v. Without a voltage converter , your single-volt appliances are a safety hazard. They will not work, and may cause a fire. If you want to buy voltage converter s for the single-volt appliances you are bringing with you to Azores , find the wattage rating on the appliances. If it isn’t listed, just multiply the voltage by the amp. When you have this wattage number, buy a voltage converter that is 25% higher in wattage than the appliance you intend to use it with.
Azores also uses two different types of electrical plugs. One of them is the American style plug that you are probably used to. However, another type of plug is also used in Azores , with three cylindrical prongs. Bring a plug adapter designed to fit these outlets in case you do not come across any American-style ones.

Azores plug adapter
Azores voltage converter