Micro-outage (or micro-interruption) - Total loss in the supply of power for 10 ms.
Polarity - In electricity, the condition of being positive or negative.
Rechargeable (or "Secondary") Battery - A galvanic battery which, after discharge, may be restored to the fully charged state by the passage of an electrical current through the cell in the opposite direction to that of discharge.
Load power - Apparent power Pu that the UPS inverter supplies under given load conditions. It is less than or equal to the rated output Pn. The ratio Pu/Pn defines the % load of the inverter.
Frequency - The repetition of cycles measured in Hz. 60 Hz is the standard frequency in the U.S. 50 Hz is the standard frequency in other parts of the world. 60 Hz = 60 cycles per second.
MTBF (Mean Time Between Failures) - Mathematical calculation of the duration of normal operation of a repairable device between failures. The product, expressed in hours, is an indication on the reliability of the device.
Voltage-Keyed - A system which incorporates a mechanical identifier on batteries and devices to ensure only batteries of the correct voltage are connected to the device.