The PC1857A is a sound control IC with I2C bus. It has functions to control volume, balance, and tone, and a phase shift matrix surround function. The surround function achieves wide sound expansion using only two front speakers. Three modes can be selected: movie mode that increases the presence of sound with stereo sound input, music mode emphasizing vocal music, and simulated mode that gives expansion and left and right sound depth with monaural sound input. The PC1857A can perform all control (mode switching, volume control and so on) using I2C.