1)Protocol support:SIP（RFC2543,RFC3261） 2)64 groups incoming or outgoing calls memory displayed,stored 3)Phone Book with 140 groups memory 4)Hand-free dialing function, calculate conversation time automatically 5)PPPoE,IP address dynamic and static dual system compatible 6)Refused to answer call function;Roaming function;Local number check;Pre-dial function;Date and time display;Music hold function 7)At the same time register to 3 groups different SIP number.Three-way conversation;Call transferring function,Call waiting function 8)Transfer calls function;DDNS function;Remote software updates/upgrades;H-F conversation functio