A power supply provides current to an electric load. Batteries, and some power supplies, especially those that have solar or renewable power as the input energy, generate direct current (DC), where current flows only in one direction. In alternating current (AC), the charge changes direction at intervals, and there is generally a higher voltage. Most digital equipment, including cell phones and electric cars, uses DC, but most homes, offices and industries are wired for AC. The high voltage of AC results in less energy loss during transmission. Some power supplies generating DC transform the input current to AC with higher or lower voltage, as required, using a transformer or a rectifier. An AC power supply usually takes its input from the main supply, and lowers the voltage to the required level. AC to DC converters are available as simple linear devices, or complex switching devices. AC and DC power supplies come in various modes, such as switched mode, open frame, enclosed, and cased. Power supplies may also be categorised as industrial or conventional, depending on application and capacity. AC/DC converters are in widespread use, owing to the popularity of renewable energy. Such converters and accessories are used to power homes using solar energy, among other uses.