GOIP-8 GSM VoIP Gateway with External Antenna 8 GSM Channels, up to 8 SIM Cards 8 channels GSM VOIP gateway/GOIP gateway/sip voip gateway, 850/900/18001900mhz 1.Dynamic selection of codec 2.Advanced jitter buffer 3.VLAN / Qos 4.Router Open Standard VOIP Products(ITU H.323 V4 and IETF SIP V2) Single or Multiple Server Registrations, GSM module for making GSM calls Two 10/100 Ethernet circuits connect to the LAN and an additional deivice