If the power goes out you`ll most likely not be able to use any phone, unless it`s an old corded model with no features. We use Vonage and it works great.
I completely agree with the outage. If DSL is the service and the both the modem, VoIP adapter, router, and phone are protected by UPS then this does not only protect the equipment but does increase the chances of it continuing to run. Power over Ethernet even brings more positive results.
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