IP PBX Feature: 1. Up to 80 concurrent calls and above 100 registers; 2.Codec: G.711-Ulaw, G.711-Alaw, G.726, G.729, GSM, SPEEX ZX50-G4 GSM IP PBX Configuration by WebBuilt-in SIP/IAX ServerBuild in Voice Mail ServerCodec: G.711-Ulaw, G.711-Alaw, G.726, G.729, GSM, SPEEXSIP/IAX Extensions(connect with IP Phone)Zap Extensions(connect with Analog Phone)Support SKYPESupport USB Disk RecordingCall ...