Grandstream Networks HandyTone 503 FXS FXO VoIP Adapter 1 FXS telephone port (RJ11), 1 FXO PSTN line port (RJ11) with power-outage life line support Up to 2 SIP account profiles, SIP over TCP/TLS, SRTP Dual 10/100 Mbps network ports (RJ45) with integrated high performance NAT router Status LED for power, telephone, PSTN line, network and message waiting indication Advanced telephony features