A type of backup system, usually battery-powered, used to insure continuous availability of power in the event of an interruption of service. These are most commonly used with PCs to provide emergency backup energy in the event of an unplanned outage or brief interruption of power. In the case of momentary power outages, UPS' allow operators to work through the outage by preventing the rebooting that would otherwise occur with even a split-second of interrupted power. In the case of longer outages, the UPS should provide enough energy to allow equipment operators (usually computer operators) sufficient time to properly save their data and shut down their equipment, and perhaps even continue working through the outage for several minutes to several hours. (The length of time a UPS can keep a PC functioning depends on the storage capacity of the UPS and the energy consumption of the PC.) Perhaps most importantly, UPS' protect operators against the loss of data that commonly occurs when a PC reboots or shuts off without warning.

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