ADPCM VOCODER FOR HIGH SPEED DATA TRANSMISSION AND FAX SIGNAL DETECTION METHOD THEREOF

摘要

PURPOSE: An ADPCM vocoder for high speed data transmission and fax signal detection method thereof are to have the continuous detection capability and include a modem/fax tone detection unit allowing to divide the 2.1kHz signals, thereby allowing the high speed data transmission. CONSTITUTION: An ADPCM vocoder comprises a modem/fax detection unit allowing to detect the fax tone. A fax signal detection method of the ADPCM vocoder for high speed data transmission comprises the steps of: starting the time measure after storing 1 in the tone detection state when being detected the sinusoidal wave upon storing 0 in count; increasing 1 in count when A1, A2 and the quantization coefficients are all matched with the critical values; decreasing 1 in count when A2 and the quantization coefficient conditions are matched and decreasing 2 in count when all are mismatched; adjusting the tone detection state to 0 when the count value is below the lowest critical value and returning to the initial state; and detecting the tone when the count value is above the highest value.