Inside the VTS is a bunch of reed switches and when the shaft goes in and out, a magnet on the shaft switches them. Some are for the gauge, and the end ones are for the limits. So the switch goes to your relay and turns off the travel in that direction and if you wire it right, will only allow travel in the opposite direction. But the reeds are all part of the VTS module, so you will have to rig your own. Or some other kind of switch.