uninterruptible power supply (UPS)

Definition of uninterruptible power supply (UPS) in The Network Encyclopedia.

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What is Uninterruptible Power Supply (UPS)?

Uninterruptible Power Supply, or UPS, is a device that can temporarily provide power to key components of a network if a general power failure happens.

Uninterruptible power supply (UPS) devices generally use rechargeable batteries and perform operations such as the following:

  • Notifying users that a shutdown is imminent and that they should save their work
  • Pausing services on servers to prevent new connections from being established
  • Providing enough power to perform a soft shutdown of servers and other key network components
  • Performing other actions as specified in a batch file that runs automatically
  • Providing power line conditioning and smoothing out spikes and dips in the power flow

UPS units for computer networking equipment are available in both stand-alone and rack-mountable versions. UPS devices are generally rated according to two values:

  • Volt-amperes (VA) or kilovolt-amperes (kVA), which represents the overall ability of the UPS unit to support connected equipment. The larger the kVA value, the greater the number and power requirements of the connected equipment it can support. UPS units range from 1 or 2 kVA units for computer network server rooms to cabinet-sized 500-kVA units for hospitals. UPS units can also be rated in watts (W): 1 VA = 1 W, and 1 kVA = 1 kW.
  • The amount of time that the unit can sustain maximum power generation. Typical times for network UPS units are 5 to 15 minutes. You can use additional battery packs with some devices to extend available uptime.

To configure a UPS to work with Microsoft Windows NT 4, use the UPS utility in Control Panel. (To configure a UPS to work with Microsoft Windows 2000, use the Power Options utility in Control Panel.) A serial cable with special pinouts is usually required to connect servers running Windows NT or Windows 2000 to the UPS devices.


Always test your UPS after installing it. Otherwise, you might be sorry when a power failure happens in your neighborhood!


The larger the load attached to a UPS unit, the shorter the time interval the unit can continue powering attached devices during a power outage. Be sure that your UPS unit can support your power needs for the time needed to properly shut down your system.