The Grandstream HT881 FXO Gateway is a hybrid VoIP solution featuring 8 FXO ports and 1 FXS port, designed to connect PSTN lines and analog devices to SIP-based networks. With a built-in Gigabit NAT router, SIP failover, T.38 fax support, and advanced security, it is ideal for businesses integrating traditional telephony with modern VoIP systems.