This switch controls the full range of the current in the magnet.
If the setting is at 100%, the range is larger but coarser
(212 possible settings regardless of the range), and on the
20% setting the range is smaller but finer which may be required
in some cases.
In the summer 1999 run, all the magnets were operating in
100% mode. If that is changed to "20%", the new DAC value(s)
should be set.