After a brown-out cost me a couple of hours of work, I bought a 1000VA UPS. The PC, monitor, broadband router and NAS are connected to this UPS, with the printers connected directly to the mains. In the event of power failure, with the PC and monitor switched off, the router (and NAS) should run for several hours at least, thus permitting calls to be made, provided the phone handset is also powered from the UPS. As the phone is only drawing around 10W, this should not adversely affect the time the UPS is able to maintain power. It's a pity you can't shut off the beep every 5 seconds that the UPS emits when mains power fails!