Query
:SYSTem:SERVice?
This command reads whether the E4991B is in the service mode or not.
{1|0}<newline><^END>
Dim Var as Long
Ana.WriteString ":SYST:SERV?", True
Var=Ana.ReadNumber
Displayed on the instrument status bar (at the bottom of the LCD display).
SCPI.SYSTEM.SERVICE