A security node disposed in the telecommunications network connecting calling and called parties transforms information (which can be voice, data, facsimile, video and other types of calls or messages) encrypted in a first format to (a) encrypted information in a different format or to (b) non-encrypted...http://www.google.com.tw/patents/US5434920?utm_source=gb-gplus-share專利 US5434920 - Secure telecommunications
