A signalling protocol that is used to set up and control real-time traffic calls, such as voice and video, over a data network. In digital telecare SIP is used in three main ways: SIP-based digital telephone lines are replacing traditional copper phone lines, such as ISDN; SIP is used by digital telecare protocols to carry signalling between the alarm device and the ARC; and SIP is also used by digital alarm devices configured to use VoIP to set up and control the voice call to the ARC.