The IP-PBX 1 includes a multimedia gateway controller 2 in which a call control data master table stores call control data for all terminals falling under the control of the IP-PBX and protocol handlers which are installed on a system bus 101 or expansion system bus 102 in a sufficient number for serving...http://www.google.com/patents/US7580402?utm_source=gb-gplus-sharePatent US7580402 - Internet protocol compliant private branch electronic exchange and a method expanding the number of controlled terminal ports
