use in voip-software: download Xlite here
install it, then setting it :
display name:voipdoup cardnumber
user name:voipdoup cardnumber
password:voipdoup password
authorization user name:voipdoup cardnumber
Domain:sip.voipdoup.com
then talkig freedom
use in ip phone. ip phone is is a kind of voice communication terminal which is based on wide band and independent of PC .can support sip and iax2 protocol.