PG-101 is a well-designed, high performance personal gateway, a VoIP adapter with FXS, FXO interface. It is a device that converts analog voice signals into digital IP packets for transport over an IP network. It also converts digital IP packets in analog voice streams. Connects your phones or PBX via FXS port and connects your POTS (PSTN) line via FXO. The benefit is for transferring traditional PBX to get low cost of VOIP services.