The TWL1110 provides extended gain and attenuation flexibility for transmit, receive, and sidetone paths. A differential earphone output is capable of driving speaker loads as low as 8 for use in speaker phone applications. The single tone function on the TWL1110 generates a single tone output of up to 8 kHz. The resolution of the DTMF tone is also selectable to 7.8125 Hz, 15.625 Hz, or 31.250 Hz through the interface control. The analog switch provides more control capabilities for voice-band audio processor (VBAP). The VBAP is an analog-digital interface for voice band signals designed with a combination of coders and decoders (codecs) and filters. It is a low-power device with companding options and programming features, and it meets the requirements for communication systems, including the cellular phone. The device operates in either the 15-bit linear or 8-bit companded (-law or A-Law) mode, which is selectable through the I2C interface. A coder, an analog-to-digital converter or ADC, digitizes the analog voice signal, and a decoder, an digital-to-analog converter or DAC, analogs the digital-voice signal. VBAP provides a companding option to overcome the bandwidth limitations of telephone networks without degradation in sound quality. The human auditory system is a logarithmic system in which high amplitude signals require less resolution than low amplitude signals. Therefore, an 8-bit code word with nonuniform quantization (-law or A-law) has the same quality as 13-bit linear coding. VBAP provides better digital code words by generating a 15-bit linear coding option.