Tri-band

Tri-band

A network infrastructure or wireless phone designed to operate in three frequency bands: 800 MHz, 900 MHz and 800MHz. (Cingular)

Different mobile phone networks operate at different frequencies, which means that if you wish to use your mobile phone outside your home country, you generally need a handset that supports multiple frequency bands. A tri-band phone operates on three frequency bands, GSM900, GSM1800, and GSM1900, allowing you to use it in Europe, Africa, Asia, and nearly all of North America and Australia. (Nokia)

Triband phones (also known as tri-band or tri-mode) are mobile phones that support the GSM 900/1800/1900 MHz bands (commonly sold in Europe, Asia, and Africa), or alternatively the 850/1800/1900 bands (commonly sold in the Americas). Various countries use different frequency bands for their mobile networks, and a tri-band phone can be used on three of these bands, generally speaking, chosen to favor two of the home country's bands, and one for roaming in other countries. A quad band phone will offer more coverage. (Wikipedia)