Mobile device that supports voice and data communications conforming to one bearer technology, such as GSM, but on four different sets of frequencies. For example, many European and Asia/Pacific countries/markets have licensed deployment of GSM networks on 900MHz and 1,800MHz spectrums, and in North America GSM has been deployed on 800MHz and 1,900MHz. A quad-band phone allows the user to roam automatically among networks on any of these frequencies in any of these countries, providing that the “home” operator has roaming agreements with local mobile network operators. See also dual-band, dual-mode and tri-band.