Compaq Presario 3000 Series Operation And Reference Manual page 55

Nominal
Figure 4-6. Utility voltage fluctuation indicating a possible need for
extended range setting
To match the utility voltage, the UPS operating range can be modified in two
ways:
If the utility voltage differs from the currently configured nominal
voltage, but stays within a ±20% band (see Fig 4-5), consider shifting
the nominal voltage parameter selection to match the measured utility
voltage range.
If the utility voltage frequently varies outside the UPS operating range
(see Fig 4-6), consider changing from normal to extended range
(+20% to –35%). This provides more tolerance to brief utility voltage
fluctuations.
To update the nominal voltage and operating range parameters:
1. Have a qualified electrician monitor utility voltage.
2. Use the following tables to identify the operating range that most closely
matches requirements:
Operating Range
+20%
- 20%
-35%
Utility Voltage
Time
Configuration 4-9
Extended
Range