Everyone is asking what kind of GSM phone to get: Dual, Tri, or Quad band? Since there are two frequency bands that are used by GSM services in the United States, and also two different frequency bands are used in the rest of the world, ideally, one would want a quad- band phoneone that works on all four bands. This should be your first choice when seeking a phone. However, since some of the best phones can still be expensive and hard to find, many gravitate toward the second best choice, the tri band phone. When doing this, be mindful which three bands your phone has, as some bands are more useful than others.

The United States originally only used 1900 MHz for its GSM service, but more recently, there has been a growing amount of GSM service on the 850 MHz band. When choosing a phone, it's important to know how you will be using it. For example, if you are in the United States and operate with in the major metropolitan areas, you won't really miss the 850 MHz bank. On the other hand, if you regularly travel to secondary areas, you will benefit from the extra coverage that the 850 MHz band provides. Basically, if you travel outside of the big cities, you'll want a phone that supports 850 MHZ and 1900 MHz.

Internationally, things are a little different. In the beginning, all countries with GSM service used the 900 MHz band, but due to congestion, service providers have been adding 1800 MHz coverage. When GSM became available in the United States, a few other countries chose to used the same frequencies the U.S. used1900 MHz, and in some cases, 850 MHz. Most international countries that use the non U.S. international frequency banks have 900 MHZ service. Many also have 1800 MHz service. All international countries that have the U.S. frequency bands have 1900 MHz service. A few may also have 850 MHz service. So, which frequencies do you need when traveling internationally? That depends on where you're going. Generally, 900 MHz is the most common band used internationally. 1800 MHz will give you expanded coverage in countries that also use 900MHz.

Ideally, your phone should support all four bands. In the real world, not everyone is going to have a quad band phone, so here are some guidelines:

If you're only using your phone in the United States, and you get a dual band phone, make sure it has both 850 MHz and 1900 MHz. If you must get a single band phone, one with 1900 MHz only will give about the same amount of coverage.

If you're going international, and your countries have international frequencies, get a dual band phone with 900 and 1800 MHz. If you must go single band, one with 900MHz will be almost as good. If your countries have U.S, frequencies, get a tri band phone with 900, 1800, and 1900 MHz. This type of phone is excellent internationally, and very good in the United States. Another type of tri band is 850-1800-1900. This one is great for the United States, but not very good internationally.

For more detailed information, or to view coverage maps, visit the official GSM association website.