This is a device allowing a user to make VoIP calls using session initiation protocol (SIP). SIP is a telecommunication technology developed as a fast, easy standard for delivering IP-based data, voice, and video communications.
In order to make phone calls via the Internet one’s device has to be compatible with Softphone software. In example in order to call from a PDA using VoIP technology one has to install Softphone software, in order for it to work properly, PDA has to have Softphone compatibility.