Template:Convert/to(-)/AonSoff
< Template:Convert | to(-)
{{{1}}}–{{{2}}} {{{u}}}
The Template:Convert/to(-)/AonSoff formats a range where the 2 amounts are separated by "to" when non-abbreviated, but by "–" when showing the unit symbols. If the 2nd amount is negative, then the dash will be surrounded by spaces to separate from the &minus sign.
For unit-codes where the unit symbol is undefined (or blank), then the template also checks for literal "{{{u}}}" with leading curly brace "{" and then the unit name (depending on amount singular or plural) will be displayed instead.