Tone blocking using variable delay buffer

摘要

A tone blocking system for use preferably in conferencing systems in order to prevent control tones from being transmitted to other conferees is disclosed. The buffer length used to process the signal and detect tones is varied, being increased when a tone is suspected to allow for sophisticated tone detection algorithms, and being decreased when silence is present by trimming the silence away. The technique minimizes delay, and its degrading effect on echo, but nonetheless provides for a lengthy buffer required to do reliable tone detection. The invention is applicable to any signal other than tone as well.