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How To Buy
In North America, only about 7 percent of PC buyers purchase an uninterruptible power supply (UPS) to safeguard their systems. That means most PC owners are gambling that their systems won't be affected by a power problem-but the odds aren't in their favor.
Experts estimate that a typical computer is subject to about 120 power problems each month if you count brownouts and sags (short-term voltage decreases), blackouts (total power losses), spikes and impulses (dramatic voltage increases), surges (minor short-term voltage increases) and noise (electromagnetic interference and radio frequency interference). Power failures and surges are the biggest problems, accounting for more than 45 percent of all data loss.
In addition to data loss, power fluctuations can cause a wide range of problems, from system lockups or performance degradation to physical damage of system components such as hard drives or modems. Other potential hazards include destroyed cache information, jumbled passwords or lost file allocation tables (which could prevent access to hard disk files). Windows 95 is particularly prone to problems if a power surge or failure takes a computer down before it can go through the complete shutdown procedure.
Most UPS units include external auditory alarms and visual displays (such as LED indicators) to let you know what's going on with your system. Ask if the battery is user replaceable and whether the UPS meets Underwriters Laboratories (UL) standards.
For less than $100, you can get a basic standby or offline uninterruptible power supply (UPS) that provides little more than surge protection and a few minutes of runtime so you can shut down during a blackout. Higher-end systems use line-interactive technology to regulate voltage during spikes, surges and dips, and to provide power during a failure. Prices for these units range from about $150 to $350.
UPS units use sound and LED alarms to tell you what's going on with your system.
More sophisticated UPS units provide software that automatically shuts down an unattended system, logs power difficulties and monitors the system during short-term power difficulties. See sidebar "Safety Net for PCs Left Home Alone."
Runtime is the length of time a UPS' battery can keep your system running. Many manufacturers will list the estimated runtime for an "average" system. The exact runtime for your system will depend on system configuration and the size of the battery in a given UPS. Look for a UPS with at least 5 to 10 minutes of runtime so you can go through an orderly shutdown.
Data Line Protection
You'll need data and phone line protection if you plan to connect to outside data sources via a modem or a LAN. More UPS models now include this as standard.