SP5052A VoIP FXO Gateway, 2 FXO, SIP, G,711A/µ-law, G,723,1, and G,729 codecs, Call Hold, Call Forward, Call Transfer, Dial plan, Hunting group, Phone book, Hotline, T,38 fax, Power current drop, Polarity reversal detection, QoS. Key Features * Compliant with ITU-T H.323 or IETF SIP standards * Provide 2 RJ-11 FXO ports for PSTN or PBX's extension * Provide 2 10/100M RJ-45 ports * Support G.711A/µ-law, G.723.1, and G.729 codecs * Transmit T.38 fax * Support VAD, CNG and EC * Support detection of power denial, polarity reversal and disconnect tone * Support caller ID * Support outbound proxy and STUN for NAT traversal (Only SP5052A/S support ) * Support advanced IVR for PSTN subscriber to dial in * Support static IP, DHCP and PPPoE * Support QoS by setting ToS (Type of Service) parameters of VoIP packets