An apparatus and method for an alert and signal management device for an already engaged telephone line is described. The device can interface to either a modem of FAX or answering machine, and to a telephone and is triggered by conventional call waiting or distinctive call waiting SAS tones. It will...http://www.google.com.tw/patents/US6628771?utm_source=gb-gplus-share專利 US6628771 - Distinctive call waiting alert and management device
