variety of equipment can be powered from almost any source of power. A "Green Plug" system has been proposed, based on USB technology, by which the consuming device would tell the external power supply what kind of power is needed. Laptop charger In early laptop computers, the power supply units were internal like in desktop computers. To facilitate portability by sparing physical space and reducing the weight, power supply units were externalized. When a laptop computer is operated while recharging, the integrated circuitry which controls the charging makes use of a power supply unit's remaining electrical current capacity. This allows supplying the device's components with power during usage while maintaining an uncompromised constant charging speed. Use of USB The USB connector (and voltage) has emerged as a de facto standard in low-power AC adapters for many portable devices. In addition to serial digital data exchange, the USB standard also provides , up to ( over USB 3.0). Numerous accessory gadgets ("USB decorations") were designed to connect to USB only for DC power and not for data interchange. The USB Implementers Forum in March, 2007 released the USB Battery Charging Specification which defines, "...limits as well as detection, control and reporting mechanisms to permit devices to draw current in excess of the USB 2.0 specification for charging ...". Electric fans, lamps, alarms, coffee warmers, battery chargers, and even toys have been designed to tap power from a USB connector. Plug-in adapters equipped with USB receptacles are widely available to convert or power or automotive power to USB power (see photo at right). The trend towards more-compact electronic devices has driven a shift towards the micro-USB and mini-USB connectors, which are electrically compatible in function to the original USB connector but physically smaller. In 2012, a USB Power Delivery Specification was proposed to standardize delivery of up to 100 watts, suitable for devices such as laptop computers that usually depend on proprietary adapters. Standards The ITU published Recommendation ITU-T L.1000, "Universal power adapter and charger solution for mobile terminals and other hand-held ICT devices", which specifies a charger similar in most respects to that of the GSMA/OMTP proposal and to the European Common external power supply. The ITU recommendation was expanded and updated in June, 2011. The hope is to markedly reduce the profusion of non-interchangeable power adapters. The European Union defined a Common external power supply for "hand-held data-enabled mobile phones"