IP PBX

http://www.ggutc.com.tw/NEWS/news_ippbx_upg.htm
http://www.netcom.com.tw/Mosa/index.htm
http://eservice.seed.net.tw/class/class147.html
http://www.3cx.com/pbx/ip-pbx-faq/
http://www.3cx.com/pbx/ip-pbx-overview/

過去企業的語音通訊需要接一條PBX交換機線路，而數據通訊則需要透過路由器接上一條網路線路，另外如果企業的語音通訊要達到VOIP功能，則必須再在PBX上面再接上一台Gateway，
但是，使用了IP PBX設備之後，就不用再接那麼多元而複雜的線路，只要透過一台IP PBX就可以達到全部的功能。
另外，IP PBX所具備的電話隨身功能，則又讓VOIP跨入行動化的門檻，這也是PBX與Gateway整合應用所辦不到的



A VoIP Phone System / IP PBX system consists of one or more SIP phones / VoIP phones, an IP PBX server and optionally includes a VoIP Gateway.

The IP PBX server is similar to a proxy server: SIP clients, being either soft phones or hardware based phones, register with the IP PBX server, and when they wish to make a call they ask the IP PBX to establish the connection. The IP PBX has a directory of all phones/users and their corresponding SIP address and thus is able to connect an internal call or route an external call via either a VoIP gateway or a VoIP service provider to the desired destination.