HT881. Supports 3 SIP profiles through 8 FXO ports; Built-in performance NAT router; Lifeline support to protect against power outages (FXS port is hard-relayed to the FXO port); 3-way voice conferencing per port; Automated and secure provisioning options using TR069; Supports T.38 Fax for reliable fax-over-IP; Failover SIP server automatically switches to the secondary server if the main server loses connection; AES encryption with unique security certificate per unit provides powerful security protection.