The Omega 1000 USD,DSD, and Access limit switches are no longer manufactured. I believe the switches are hall effect sensors, with +24volts to the red wire and the black and white wires which are n/o go to the input circuit, black to ground and white to appropriate terminal. You can put a n/o mechanical switch in its place, just cap off the red wire which goes to the +24 volt supply. also make sure the switch stays activated from anywhere past the slowdown point. you can probably use an LS type switch, or one of the eeco flat switches with a little modification. I tried to find an exact replacement but have had no luck so far, if anyone knows of an exact replacement please post here thanks. also to get the car running i have taken the access limit switch and put in its place, the car just wont access down from hall, until you replace or modify.