There is a move to allow the operation of personal unlicensed wideband digital devices using the UHF television spectrum in the United States. These 'white space' devices (WSDs) would be required to have GPS and access to a location database to avoid interfering with other users of the band. Initial tests performed by the FCC showed that, in some cases, prototypes of these devices were unable to correctly identify frequencies that were in use, and might therefore accidentally transmit on top of these users.