The Codec function of AS3502 uses Sigma-Delta () modulation conversion techniques with 2nd order modulators and an over sampling rate of 128 for excellent signal to noise performance. The AS3502 exceeds all CCITT G712 recommendations and the European ETSI prETS 300085 recommendations. Digital gain setting stages for transmit and receive allow to compensate for transducer tolerances and to set up a handsfree function under software control. A programmable tone generator allows to generate DTMF/Call-Progress Tones and alert sounds required in digital terminals. All programmable functions of AS3502 are controlled by a 4-wire serial control port that easily interfaces to any popular micro controller. The interface to the digital world is accomplished by a serial PCM interface that supports 16-bit linear format or 8-bit A-Law format for both non-delayed and delayed frame synchronzation modes.