The Cisco SPA8800 IP Telephony Gateway is a multipurpose solution that small businesses can use to connect an on-premise IP private branch exchange (PBX) system to the public switched telephone network (PSTN), or connect a legacy time-division multiplexing (TDM) PBX or key system to voice-over-IP (VoIP) services. The Cisco SPA8800 provides a combination of four Foreign eXchange Office (FXO) and four Foreign eXchange Subscriber (FXS) ports to connect to existing analog phones, which helps protect and extend your existing communications equipment investments.