I also notice that the Belkin 4-port ADSL/VoIP modem and the wireless version both have...
"a fail safe port, so if your ADSL line goes down or if you lose power to the modem through a power failure, the phones automatically routes calls through your standard telephone line. In essence, if you subscribe to a VoIP service, you can use this modem and have one telephone line manage three phone accounts with three separate numbers - your standard phone line plus two voice over internet accounts with a VoIP provider."
This is potentially very useful. If the power is off, or if your ADSL connection is down, you can still make emergency calls.
-josh <http://tinyurl.com/dx4jn>
