SIP to Skype
To make free calls to a Skype contact from a SIP account, you must first open a free account with ippi here, and follow the instructions below.
To call from ippi to Skype, dial "firstname.lastname@example.org" then start the call
Skype to SIP
To receive a call from a Skype contact, follow the instructions below.
To call from Skype to ippi, call "skype2ippi" (add the contact), and when you receive a chat message, enter the ippi username or ippi number in the chat window and send the message to start the call.