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.
This service allows called party to listen to the audio or video announcements of callers before connection. The caller can choose a message that will be played and conditions by which the message will be plaid over. For example, before the subscriber answers the call, they will hear audio message with the name of the person who is calling.