Patent ID: 6694011
Filing Date: 2004-02-17
Classification: H04M,H04Q

Abstract:
A tone detection system for reliably detecting a signaling tone, wherein said signaling tone comprises one or more frequencies, said tone detection system comprising:a tone detector configurable to a first or second state and for detecting said signaling tone while in said first or second state, a notch-filter for attenuating from near-end audio at least one frequency comprising said signaling tone to prevent said near-end audio from talking-off said tone detector, and a speech energy detector for detecting the presence or absence of near-end audio and switching said tone detector between said first or second state based on the presence or absence of near-end audio, wherein said first state comprises a large signal-to-guard ratio for combating far-end talkoff and wherein said second state comprises a small signal-to-guard ratio for combating near-end talkdown.