An uninterruptible power supply is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails. A UPS differs from an auxiliary or emergency power system or standby generator in that it will provide near-instantaneous protection from input power interruptions, by supplying energy stored in batteries, supercapacitors, or flywheels. On-line (VFI) UPS systems are regarded as 'high-end' and employ more sophisticated technology which uses a rectifier and inverter, hence "double-conversion". This effectively isolates the load from virtually all types of power supply problems. We provide ups of three different companies.