In mobile phones, dual band (also known as dual-band or dualband) refers to functionality that allows a cellphone to support two frequency bands. Having more than one frequency in one device is useful to enable roaming between different countries that peg the allowed transmission frequency at different values or to allow a better coverage in the same country.
A designation indicating that a phone supports two different frequency bands. Not meaningful without knowing which two bands and which technologies the phone will work with.
For North American TDMA and CDMA phones, dual-band indicates that the phone will work in both the 800/850 MHz band and the 1900 MHz band. Most current TDMA phones in the U.S. are tri-mode, meaning they can use both analog and digital in the 800/850 band. Dual-band CDMA phones can be dual-mode or tri-mode. Dual-mode phones only support analog or digital on the 800/850 band, while tri-mode phones support both. The 1900 MHz band is always digital.
A dual-band GSM phone supports two of the four major GSM bands. Depending on which bands, the phone may only work in certain parts of the world. A GSM 850/1900 phone will only in the Americas. A GSM 900/1800 phone will only work in Europe, Africa, Asia, and Brazil. A GSM 900/1900 phone will work on at least one network in most countries around the world.
