Fully support Asterisk IP PBX. SIP protocol For personal use, SOHO, especially suitable for enterprises with several small branches (with a staff 1 to 4). 1 FXS port, 1 FXO port ATA Ethernet ports: TWO* 10/100 Base-T Ethernet ports, Bridge/Router function Functions: Out route selection(use VoIP or PSTN), Caller ID transfer(VoIP and PSTN),Volume adjust Support features: Call hold/Retrieve, Call waiting, Call transfer, 3-way calling, G.711 fax, MWI, Do Not Disturb, Call forwarding: Busy, No answer, Unconditional Impedance: optional Automatically new version detection and user can upgrade by key in the special number Auto configure download Dimension:108x 72x 26 (L x W x H)