Rear panel
Speaker terminals (SPEAKERS)
Used to connect speakers. link
Speaker Optimization switch (SPEAKER OPTIMIZATION)
This switches the Speaker Optimization function on/off. link
Analog audio input terminal (ANALOG IN)
Use a stereo mini plug cable (sold separately) to connect between this terminal and a headphones jack on a portable music player, etc. link
USB digital audio input terminal (USB-DAC 
)
Used to connect to a computer with a USB port. link
Subwoofer terminal (SUB WOOFER OUT)
Used to connect a subwoofer with a built-in amplifier. link
AC inlet (AC IN)
Used to connect the supplied power cord. link