RIGOL DS1000D - Manual (Page 47)

Command Systems RIGOL
Programming Guide for DS1000E, DS1000D Series
2-35
The query returns the setting value of level in V.
Note: Level A (upper boundary) can not be less than the maximum of Level B
(lower boundary).
Example:
:TRIG:SLOP:LEVB -1.5 Setup the lower boundary of trigger level as -1.5V.
:TRIG:SLOP:LEVB?
The query returns -1.500e+00.