UPS

Uninterruptible power supply

An uninterruptible power supply (UPS), also known as a continuous power supply (CPS) or a battery backup is a device which maintains a continuous supply of electric power to connected equipment by supplying power from a separate source when utility power is not available. It differs from an auxiliary power supply or standby generator, which does not provide instant protection from a momentary power interruption, however could be used to provide uninterrupted power to equipment for 1 - 20 minutes until a generator can be turned on. Integrated systems that have UPS and standby generator components are often referred to as emergency power systems.