PowerWalker VFI (Voltage and Frequency Independent / voltage and frequency independent) Series always provides a result of the on-line (double conversion) technology a clean uninterrupted power supply. In the double conversion technology in the first step of the incoming AC power is converted into direct current and cached. In the second step, the stored direct current is converted into alternating current and and asked for the consumer. In this way, a complete separation between the network of electricity supplier with all possible power fluctuations and the generated by the UPS stable and clean load-side power grid is achieved. Another advantage of this technology is that in case of power failure no switching times which can occur at critical loads may lead to failure or damage. Optional plug-in cards (SNMP, AS / 400) extend this connectivity.