BC ..It depends if you are using a software VOIP solution like
X-Lyte or a hardware phone ATA which you plug a normal phone into. The hardware can be built in to the Router or be a standalone ATA. All you need is an always on broadband connection ..ADSL/Cable/Unwired/Iburst ...
I use an Iburst modem in the hotel and call out thru X-Lyte or Skype from my laptop ...beats paying $1.00 for a local call and I won't even think about long distance
Max