A communications system is designed to allow an end-user device that is coupled to a telephone set to receive activation codes that are transmitted thereto by a switch of such communications system when the telephone set is in an on-hook position. The communications system may initiate the transmission...http://www.google.com.tw/patents/US6396914?utm_source=gb-gplus-share專利 US6396914 - Method and system for transmitting activation codes to a communication device
