World phones are cell phones that are designed to be used anywhere in the world and therefore operate on international frequencies. Typically such phones support between three and four frequency bands to enable roaming between different countries. As a result, world phones are sometimes referred to as tri-band or quad-band phones.
International travelers require such world phones because the cell phones that are designed for use within one country often do not work outside that country or region. For example, in the U.S. several major carriers such as Verizon Wireless, Sprint and U.S. Cellular operate what are known as Code Division Multiple Access (CDMA) networks.
Cell phones operating on CDMA networks do not work on Global System for Mobile Communications (GSM) networks, which is the standard across Europe, Latin America and Asia. Several carriers in the U.S including AT&T and T-Mobile do operate GSM networks. But phones operating on these networks may not work on GSM networks outside the country because of different radio frequencies. In the U.S. all GSM networks operate at 850 and 1900 radio frequencies, while those in Europe use the 900 and 1800 frequencies while some parts of Asia operate on the 1800 frequency.
So in order for a world phone to be able to operate in as many countries as possible it needs to be either a tri-band GSM phone supporting the 900, 1800 and 1900 radio frequencies, or it has to be a quad-band phone supporting all four GSM frequencies–850,900, 1800 and 1900.
Several options exist today for individuals in the U.S. looking to purchase or rent a world phone when travelling outside the country. Some examples of tri-band phones include the Sony Ericsson W508, the LG KS360 and the Samsung F480. Examples of the relatively more expensive quad-band GSM phones include the Samsung T539 model, Sony Ericsson’s C905 and the Blackberry Curve quad-band.
All of these phones are designed for use internationally. However, if they are currently being used on a U.S. network, the service provider may have to “unlock” the phones in order for them to be used overseas.
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