X-Axis reference switch

Hi guys,
I am currently trying to convert an engraving machine to Linuxcnc but I have a problem with the X-Axis. Linuxcnc is looking for my switch in a wrong direction. No matter what I enter, the X-axis always travel from left to right but my switch is on the left. How do I configure LinuxCNC so that the X-axis searches for the switch on the left?
My Z-Axis work fine and travel from zero to -170mm

Niko

Home_search_velocity
In the ini file, if it has a - remove it, or add it if it doea not have.

Thanks Tommy.
never thought it could be negative.