PO+PRE OUT (default position): front headphone out+rear audio out (volume adjustable)
PO: audio output only from the front headphone jack (volume adjustable)
PRE OUT: audio output only from the rear connectors (volume adjustable)
LO: audio output only from the rear connectors (fixed level output)
COAXIAL: standard RCA connectors, digital output
OPTICAL: standard toslink connectors, digital output