The termination availability database (TADB) of the instant invention performs routing decisions in response to call requests received from data access points (DAPs). The TADB takes each of the requests, which relate to a special service call of a subscriber, and determines the particular termination...http://www.google.com.tw/patents/US5787163?utm_source=gb-gplus-share專利 US5787163 - Intelligent load balancing of special service calls based on availability of terminations 
