Enables PBX connection to VoIP Services SIP protocol For office use 4 FXS ports gateway Ethernet ports: ONE* 100 Base-T Ethernet port Functions: Caller ID transfer, Call forwarding: Busy, No answer, Volume adjust, Ringer selection by caller ID Support features: Call hold/Retrieve, Call waiting, Call transfer, 3-way calling, Split 3-way calling, T.38 fax, Do Not Disturb Support IP inbound relay function(4 port use 1 account for incoming call) Support billing machine and get CDR Size: 236*140*318mm (L*W*H)