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A VoIP phone or IP Phone uses voice over IP (VoIP)
technologies for placing and transmitting telephone calls over
an IP network instead of the traditional public switched
telephone network (PSTN). IP-based telephone service uses
control protocols such as the Session Initiation Protocol (SIP).
Currently most SIP phones in the US market are based on
embedded chips, e.g. SiTel and DSPG – their functionality is
confined by the feature set of the chip vendor. Telefield can
develop new features in software while developing the OS
and hardware architectural layers independently and in
parallel.