Choosing the right UPS topology for your application will depend
on your power requirements (i.e. whether you need to back up an
editing deck or a transmitter) and the level of reliability you
require (you will not want to spare any margin when backing up
equipment critical to the final game of the playoffs). The most
common types of UPSs are offline, line interactive and online
double conversion.  The most basic (but effective) UPS type is
“offline” topology. Under normal conditions, when utility power
is satisfactory, the UPS will be offline to let the stable power
flow through the UPS to the critical load. If the power voltage
drops due to a brownout or blackout condition, the UPS will
immediately switch online and begin to produce power from its
battery. The transfer time between utility power failure and
stable UPS battery power production is typically less than four
milliseconds — quick enough to avoid interrupting power to
sensitive devices. Better-quality offline UPSs also provide a
level of surge pro