Most countries outside North America use 220-volt electricity. Unless your appliance is dual voltage, you’ll need to use a “converter” or a “transformer.“
If your appliance is dual voltage, you can switch it to work on 220-volts, without a transformer or converter. To see if your destination country uses 110-volt or 220-volt, check the Worldwide Electricity Guide
The plugs on the appliances that you use in the U.S. won’t fit into the outlets in most foreign countries. Therefore, you will need a plug adapter.
Computers must be used with a transformer (not a converter) unless they are dual voltage. Fortunately, most laptop battery chargers and AC adapters are dual voltage and can be used with only a plug adapter. In addition, it is advisable to use a 220-volt surge protector in 220 volt countries. Simply plug your dual voltage charger or AC adapter into the 220-volt surge protector, then plug the surge protector into the electrical outlet (using the appropriate plug adapter).
Modem Adapters – If you want to use your modem abroad, you should make sure that you also have the appropriate tele-plug adapter.