SIPphone

Depending upon the Session Initiated Protocol (SIP) a SIPphone is the SIP utility which provides a free SIP-based VoIP network.

In order to use the SIPphone, you may need either the SIPphone adapter or softphone software in addition to a broadband Internet Connection.

To make free SIP to SIP (in-network) calls, there must be a SIPphone adapter or software on the both sides i.e. caller/recipient.  In order to make lower cost calls to non-SIPphones (PSTN) we need the SIP minutes.