If you're taking along a computer, cell phone, hair dryer or other plug-in electrical appliance on vacation overseas, you probably will have to deal with different electrical voltages and some unusual-looking plugs.
Adapting to a foreign electrical system is usually no problem--adapters and other devices are widely available to smooth the conversion. The trick is to be prepared so that you don't find yourself desperately needing an electrical device at a time when you can't easily get access to a converter, like 6 a.m. on a bad hair day.
A couple of Web sites help you choose the appropriate conversion equipment. One of the best is the "World Electric Guide" at http://kropla.com/electric.htm, which also provides links to equipment suppliers. Other good sites for general information are http://www.howstuffworks.com/question430.htm and http://www.magellans.com/guides/world-guide.html.
Ironically, one of the most complex electronic carry-ons--the portable computer--causes relatively few problems. Most of the more recent laptops are designed to work both in the Western hemisphere, where most countries use an electrical system operating at 110 to 120 volts, and in much of the rest of the world where 220 to 240 volts is the norm.
To make sure your computer goes both ways, check to see that it has a label that says something on the order of "Input: AC 100V-240V" or is described as "dual voltage." Warning: A computer or any other device can get fried quickly if it's plugged into a foreign system it's not set up to handle.
Even if the device is dual voltage, you still might need an adapter for the plug. In Britain, for example, the plug prongs are round or they could be horizontal instead of our usual vertical configuration. In Australia, the plugs are diagonal.
Adapters that slip over U.S. plugs are cheap and can be found at travel shops and on the Web.
Unless a device can handle various voltages, a converter or transformer also might be necessary. A converter will work with non-electronic devices, such as hair dryers, that are used for a fairly short amount of time. But if you are recharging a computer or a cell phone that does not adapt automatically to a foreign system, you'll need a transformer.
Another warning: Most of the world uses alternating current (AC) systems, but a handful of countries use direct current (DC), including India, Brazil and South Africa. In those places, you will need special conversion equipment.
So, is all this conversion and adaptation worth it? It probably depends on how long you will be staying in a country and how reliant you are on plug-in devices. If you are going to be visiting or working there for an extended period, the easiest route is to simply buy appliances that were made for that country's system. The handy exceptions are portable computers, most of which just need a plug adapter to make them feel at home in much of the world.
Times staff writer David Colker covers personal technology.