The official DICOM rule, if the specific character set (0008,0005) is absent
is to use ISO_IR 6 - i.e. just 7 bit US ASCII. This however commonly causes problems
since many modality equipment suppliers (especially in Europe & Japan) use extension
characters in the range 128-255 but don't bother to include 0008,0005 in their data.
This property allows the default to be changed, and the initial value is "ISO_IR 100",
which permits and assumes use of European accented characters in the upper range. Fortunately,
the lower raneg (0-127) of this character set is identical to US ASCII (ISO_IR 6), so this value
does not break compatibility for valid ASCII-only data.