IP Phone

A VoIP phone or IP Phone uses Voice over IP (Voice over Internet Protocol - VoIP) technologies for placing and transmitting telephone calls over an IP network, such as the Internet, instead of the traditional public switched telephone network (PSTN). Digital IP-based telephone service uses control protocols such as the Session Initiation Protocol (SIP), Skinny Client Control Protocol (SCCP) or various other proprietary protocols. [VoIP phone. Wikipedia]