The term dual band phones means that a cellular telephone supports two frequencies. You will see the phrase often enough, so it's worth understanding. That said, if you don't know what technology and what frequencies are referred to, however, the distinction is meaningless. The place to start is with the technology of the phone.

Understanding Mobile Phone Technology: Frequencies

Wireless technology today is almost exclusively digital, and has been since the late 1980s. Before then, it was analog. Analog works very much as a radio does--both transmitter and receiver are tuned to the same frequency. The technology allows for only a limited number of users. This inefficiency led to digital wireless technology, which converts analog voice signals to binary codes. It means that far more users can use the same frequency, or band, at the same time.

There are three digital technologies--TDMA (time division multiple access), CDMA (code division multiple access), and GSM (global system mobile communications). Each of these operates on specific frequencies. Dual band phones working on TDMA and CDMA technology, in the United States, take 800/850 MHz (analog and digital) and 1900 MHz (digital). Dual band phones working on GSM technology, which is digital, work on 850/1900 MHz, but only in America.

In Europe, where GSM technology developed several years earlier than in the United States, digital mobile telecommunications standards were planned carefully. They were set, as far as frequencies are concerned, at 900 MHz and 1800 MHz. This standard spread to Africa, Asia, and the Pacific Rim. Dual band phones in Europe then, will not work in America, and those in America will not work elsewhere, a few South American countries excepted. Dual band refers to a GSM phone being enabled for two of the four frequencies.