Reads out the response value of the marker.
If the reference marker is turned ON, the values of the markers
from 1 to 15 are read out as relative values to the reference
marker.
The data include 2 elements:
<numeric 1> real number in rectangular format, real part in
polar and Smith chart formats;
<numeric 2> 0 in rectangular format, imaginary part in polar
and Smith chart formats.
(query only)