Quote Originally Posted by EddyCurrent View Post
Assuming the OP still wants -10 to +10.
With the method proposed previously by Jonathan there exists a problem, if the reference wire to the servo driver goes open circuit, the drive would go to full speed reverse.
My intention was to expand on the circuit design when if it turned out to be necessary. There's a much easier way to solve that problem, but I don't think it's worth discussing the circuit here.