22WIRE*44WIRE CONVERTING CIRCUIT

摘要

PURPOSE:To ensure the high-quality talking for the analog signal 2-wire/digital signal 4-wire converting circuit, by offsetting through the arithmetic circuit the echo signal produced at the A/D converting circuit and the digital output of the A/D converting circuit by means of part of the output of the D/A converting circuit. CONSTITUTION:The digital signal arrived is converted into the analog signal through D/A converting circuit DAC and then sent out to 2-wire transmission line 2W via hybrid circuit H. In this case, part of the converted analog signal enters A/D converting circuit ADC to be turned into the echo signal. This echo signal is applied along with the analog signal arrived via line 2W to circuit ADC and then converted into the digital signal to be applied to arithmetic circuit ALU. Thus the arithmetic process is given the digital signal applied to circuit ADC and the digital signal arrived at terminal Rin in order to give the offset to the echo component. As a result, the high-quality talking is ensured.