I2S is a serial interface which transfers audio data. The following way is utilized to play music using recorded data in storage media such as an audio CD or a USB memory. At first, digital data are read from the storage media. And the data are transferred to a decoder IC which extracts music data. The music data is sent to a DA converter IC and converted to analog signals to play the music. I2S interface is adopted to transfer the music data from the decoder IC to the DA converter IC.