VoIP Cookbook: Linksys SPA9000
An example of IP PBX being used as an example is Linksys SPA9000, a device consisting only two LAN (RJ-45) ports and two telephone (RJ-11) ports. SPA9000 is actually a router or proxy server, with port connectivity to WAN and LAN. The RJ-45 enabling connectivity to WAN is labeled “Internet”, while the RJ-45 connection to LAN is labeled “Ethernet”. The default IP address for the LAN connectivity is 192.168.1.1. Meanwhile, the two RJ-11 telephone ports are part of PBX port that can be connected to two conventional phones, including fax machine. Despite this simplicity, SPA9000 is a PBX that is capable of being connected to up to four PSTN lines or to a large VoIP infrastructure. Internally, SPA 9000 could accommodate 16 extension lines. When compared to a small conventional PBX, SPA9000 has only four ports compared to a small PBX that uses 20 telephone calbles. So all connections will be established through the internet infrastructure.