An AC adapter is a power supply built into an AC mains power plug. Electric burr grinders are powered by electricity from a battery or mains supply. Voltage regulators or stabilizers are used to compensate for voltage fluctuations in mains power. Mains voltage LED strips are also available. The AC voltage is the line frequency of the mains. The filaments use a rather high voltage, allowing them to work efficiently with mains voltages. Usage on battery in case of AC Mains power failure. Electric fans used for ventilation may be powered by solar panels instead of mains current. Ideal designs had the potential to reduce demand on mains water supply by half. Hollowed wooden logs wrapped in steel banding were used for plumbing pipes, particularly water mains. The first mobile computers were heavy and ran from mains power. There were shared privies that were not connected to mains drainage. I is for measurements performed on circuits not directly connected to mains. V countries was a circular tube ballasted by an under-run regular mains filament lamp. The quake cut most of the water mains.