Method and system for delivering a message over a telecommunications network to a recipient comprising transmitting a message over the telecommunications network to the recipient when a predetermined energy/silence condition is detected, performing echo cancellation on a signal communicated from the...http://www.google.com.hk/patents/US6782358?utm_source=gb-gplus-share專利 US6782358 - Method and system for delivering messages to both live recipients and recording systems
