* AC Utility
The electric power furnished by an electric power plant.

* AH
The unit of battery capacity.

* Ampere (Amp or A)
The unit of for electric current.

* Backup Time
The time provided by battery in a UPS system when AC utility loss.

* Battery Charging Current
The current to charging the battery that is regulated from the AC utility by the circuit inside the UPS.

* Blackout
A complete loss of the AC utility

* Buck and Boost
A function to adjust the output of UPS. When the voltage is under normal condition then the UPS will boost the voltage higher. When the voltage is over normal condition then the UPS will buck the voltage lower.

* CE
A safety standard for Europe

* DC Voltage
Normally, it is used for the battery voltage.

* Efficiency
A. AC Efficiency: The ratio of the output power from the UPS to the input power from the AC utility in Line mode. 
B. DC Efficiency: The ratio of the output power from the UPS to the input power from the batteries in Battery Mode.

* Frequency
The number of completed cycles in one second. It is defined as Hertz (Hz). It exists 50 or 60 Hz power system in the world.

* Hot-swappable Batteries.
Allow the user to easily exchange UPS batteries without power interruption.

* Input Power Cord
The cord for the AC input of UPS. Normally, there are three wires of Line-Neutral-Ground in it

* LED
Light Emitting Diodes located on the front panel of the UPS that inform users the condition of UPS.

* Manual Bypass Switch
A manually operated transfer switch used to bypass the major electronics in the UPS. When it is enabled then the service engineer can have the repair service without power interruption.

* Outlet
The output socket that is located on the rear panel of UPS.

* Power Factor (PF)
The ratio of total real power, (W) to the total apparent power in volt-amperes (VA); W/VA.

* Rack-Mount UPS
UPS that can be mounted in a rack case.

* Start-On-Battery
The UPS can be started from battery directly without AC utility. Some people also name it as DC start.

* User-Replaceable Batteries
User replaceable batteries allow the user to easily exchange UPS batteries. Normally, the battery lifetime is close to 2~3 years.

* Volt (V)
The unit of measure for voltage.

* Volt-Ampere (VA)
Voltage (V) multiplied by the current (ampere); apparent power.

* Watt (W)
The unit of measure for true power. Watts = VA x Power Factor