Grandstream GS-GXW4108 8 Port Fxo Gateway VoIP Phone & Device 2 10/100 Mbps network ports Comprehensive codec support, Caller ID, flexible dial plans and security protection Advanced security protection with SRTP Designed and tested for full interoperability with leading ip-pbxs, soft-switches and sip-based environments Failover SIP server feature in case Main SIP server goes down