Dual band

Describes a handset that works on both 800 MHz cellular and 1900 MHz PCS frequencies. (Cingular)

A wireless phone that is capable of operating on two frequency bands such as the 900 MHz digital band and the 1800 MHz digital GSM band. The dualband phones can be used in Europe, Africa, and Asia. (Nokia)

Different mobile phone networks in different countries 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 "dual-band" phone operates on two frequency bands, 900Mhz and 1,800Mhz, allowing you to use it in the UK and Continental Europe. (Motorola)

Dual band mobile phones can work on networks that operate on different frequency bands. This is useful if you move between areas covered by different networks. For example GSM 900, GSM 1800. (Ericsson)

In mobile phones, dual band refers to functionality that allows a cellphone to support two frequency bands out of the four major GSM (or TDMA) bands. This is important because different countries peg the allowed transmission frequency at different values. A cellphone with dual band 850/1800 MHz, for example, will work in both the United States (850 MHz) and India (1800 MHz). (Wikipedia)