Cell phone conversations are transmitted through radio waves. Just as there are different frequencies on the radio which allow you to flip between different stations, there are also different frequencies for cell phones used in different geographical locations. The frequencies used in the US are different than those used abroad, so if you want to use your cell phone when traveling internationally, you will need a phone that can provide coverage in all of the areas where you will be traveling.
Frequency Bands
There are four frequency bands used in the GSM digital system: 850 MHz, 900 MHz, 1800 MHz, and 1900MHz. 1900 and sometimes 850 are used in the US and Canada, and the other two are used in most other countries. The US and Canada also use the American Cellphone System, which is not compatible with the GSM digital system.
Dual - Tri - Quad - Band phones
A dual band phone can read two frequencies. For US shoppers, that might mean it gets both the US frequencies and is only good within the US, or it might get one US frequency and one international. A tri-band phone can read three frequencies and is better for international travel. A quad-band phone can read all four bands. For international use, a quad-band phone would be idea,l as it will get all the frequencies, but a tri-band phone is generally cheaper and will work fine for most people.
Different Types of Tri-band Phones
When choosing a tri-band phone, be sure to select a phone with the frequencies that will be most useful to you depending on where you will be traveling. The most common is 900/1800/1900 - which is going to give you fantastic international coverage and also be very good in the US. The 850/1800/1900 option is also available and will give you excellent US coverage but will not give as good coverage internationally.
Service Carriers
If you want your phone to work internationally as well as in the US with the same phone number, be sure to sign up with a GSM service carrier in the US. For example; T-Mobile, AT&T and Cingular. Read the policies carefully, as US GSM accounts can be very expensive overseas and your US account will only work where there are cross-billing services overseas.
Locked and Unlocked Phones
Another way to use your tri-band phone abroad is by using SIM (Subscriber Information Module) cards which are basically removable computer memory chips which store account information, phone numbers, etc. SIM cards are available all over the world and can offer a quick pay-as-you-go option without the hassle of a contract. Each SIM card will give you a new phone number which is local to the area in which you bought it.
However, if you want to use SIM cards, be sure that your phone is "unlocked." This means that it will be possible to use other SIM cards from other service providers. Many phones bought in the US are locked so that the user can not use services provided by other phone companies.
Where to Buy a Tri-Band Phone
You can buy a phone directly through a cell phone company, but be sure to research the plan options carefully. Find out what the fees are if you use your account overseas and make sure that your phone is unlocked so that you have the option of using international SIM cards.
You can also buy your phone directly from the companies that manufacture them, but this tends to be more expensive.
You can buy a phone while overseas, but be sure to do your research ahead of time.
Specialty suppliers can be a good place to buy, but be sure it is a reputable one. In addition, eBay has lots of phones for sale, but be sure you know the risks before using eBay. Be sure to buy only from sellers with a long history of positive feedback.
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