portant marketing tool for attracting status-conscious customers. All networks require handsets with chips compatible with their air interfaces. The major- ity of carriers in the United States subsidize handsets that they sell to subscribers as an incentive to use their service. A carrier might pay $350 for a handset that it offers customers for $250. The rationale is that ongoing usage revenue will offset the initial handset costs and that customers will gravitate to operators offering newer, more desir- able handsets. Radios in handsets must also match the frequencies used in networks. Multiband Handsets versus Multi-mode Handsets Handsets that operate in more than one frequency band have multiband capability. Those that operate on 800MHz and 1.9GHz frequencies are dual band. Devices that operate on multiple air interfaces-Code-Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), as well as various third-generation (3G) and 4G standards-have multi-mode as well as multiband capabilities. Multi-mode devices are also referred to as multistandard. Because carriers often have networks Mobile and Wi-Fi Networks made up of two or more frequencies and air interfaces, it is important that handsets and data devices operate in more than one set of frequencies and air interfaces. Customers need handheld devices that match both the air interface and the frequency for compat- ibility throughout the carrier's network. Also, when networks are upgraded to next- generation, 3G, or 4G services, they might be deployed in pockets of the network and need to fall back to the lower-generation services for continuity. In addition, people who roam to other networks might need multiband and possibly multi-mode handsets. Multiband Devices Each handset needs to be designed to operate over specific frequencies. As mobile telephony grew in popularity, countries expanded the amount of spectrum available for the service. In doing so, they opened new frequencies for voice and data service. The European Union decreed t