Developed for small businesses, the Cisco SPA8800 IP Telephony Gateway adapts to the needs of businesses that maintain their own on-premise IP private branch exchange (PBX) or that want to add voice over IP (VoIP) to their legacy time-division multiplexing (TDM) PBX or key system. The SPA8800 can be configured to be a FXO gateway for an asterisk open source PBX, providing a versatile solution when conditions favor an external device.