UPS Backup Power Distribution Units
UPS is an acronym for Uninterruptible Power Supply. A UPS is defined as a back-up power system used to ensure uninterrupted power for various electronic devices
The three basic types of UPS Systems:

• Standby Power System (SPS):
  Most Commonly used to protect POS equipment and single work stations. Monitors the power line. When a problem is detected, the SPS switches to battery power.

• Line Interactive:
  Most commonly used UPS system for network environments. Used for small networks up to enterprise applications.  The inverter (a battery-to-AC power converter)  is always connected to the the UPS output. The inverter operates in reverse during times when the input AC power is normal to provide battery charging.

• Double Conversion On-line UPS:
  Most commonly used for mission critical applications: server farms, hospitals, etc. Avoids momentary power lapses by continuously providing power from its own inverter. The double conversion on-line UPS provides power from its own inverter even with proper power line functioning.

Why use a UPS Power System for your Server Room or Data Center?
A UPS has it's own rechargeable battery which provides emergency power for your system immediately when the main supply is cut, thereby preventing data loss.  In the event of a sustained power failure, the UPS will provide sufficient battery power for your files to be saved and for the whole system to be shut down in an orderly manner.  If an alternative power source such as a generator is available, the battery will provide sufficient power to keep your system running until the secondary supply is brought online.  UPS's also filter the power supply entering your computer system, limiting the detrimental effect of "spikes", "noise" and other electrical disturbances.