In 2009, a European Commission initiative resulted in the specification of a common external power supply (common EPS) for use with data-enabled mobile phones sold in the European Union. The external power supply is the AC electric power adapter that converts household AC electricity voltages to the much lower DC voltages needed to charge a mobile phone's internal battery. Although compliance is voluntary, a majority of the world's largest mobile phone manufacturers agreed to make their applicable mobile phones compatible with Europe's common external power supply specification (EN 62684:2010).