Cutoff Voltage (also see End Voltage) - The battery voltage at which the discharge is terminated. The cutoff voltage is specified by the battery manufacturer and is generally a function of discharge rate.
MTTR (Mean Time To Repair) - Mathematical calculation (or statistical average if available) of the time required to repair a device.
Static bypass switch - Power-electronics device that can be used to switch from one source to another without interruption in the supply of power. In a UPS, transfer is from Mains 1 to Mains 2 and back. Transfer without interruption is possible due to the fact that there are no mechanical parts and the ultra-fast switching capabilities of the electronic components.
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.
Inverter (on-line) - UPS configuration in which the inverter is in series mounted between the mains and the load. All power drawn by the load passes via the inverter. This is the only configuration used for high outputs.
Midpoint Voltage - The voltage of a battery midway in the discharge between the start of the discharge and the end voltage.
Redundancy (active) - Parallel UPS configuration in which several UPS units with equal outputs are parallel connected and share the load. In the event one UPS unit fails, the other units pick up its share without any interruption in the supply of power to the load. (back)