The present invention provides a universal host-to-switch application program interface (API) utilizing a generic message format for performing call control processing and capable of being customized to meet telecommunications application and network signalling protocol requirements....http://www.google.com.hk/patents/US5826030?utm_source=gb-gplus-share專利 US5826030 - Telecommunication switch having a universal API with a single call processing message including user-definable data and response message each having a generic format 
