Chapter 3 Arbitrary Waveform Output    RIGOL 
DG4000 User's Guide 
Tip 
Users can use User to quickly recall the built-in waveforms or waveforms stored 
in the non-volatile memory of the instrument. After you define the waveform to 
be recalled by this key, pressing this key will immediately recall the specified 
waveform. Users can press Utility  UserKey to modify the waveform to be 
recalled by this key (refer to introduction in
"User-defined Waveform Key").