5 , 6, 
17
selecting a different track 5 , 6
press 5 / 6 to select the desired track.
fast searching within a track
during playback, press and hold 5 / 6 briefly.
psa plays track at high speed until the button is released.
using the button lock 
deactivates the other buttons so they are not activated accidentally.
to activate / deactivate the button lock, press and
hold 
2 seconds.
display: 
appears if button lock active.