Re: OK I'm biting..
Very few UPS systems can handle prolonged outages (multiple hours). The battery backup in the analogue phone adapter can handle up to 1 hour, however the problem is what happens if there is a power cut that happens at night when people are asleep. In the morning there would be no electricity and no way to call for help. With the analogue PSTN system phones would work for over a day in the absence of mains electricity (and much longer if the exchange has a backup generator).