With metal poles and ladders, these scale signals will look great along your right-of-way. The 3-position flag has a realistic slow motion. The base has optical sensors built-in with a sensitivity adjustment. Just apply power and put them next to the track. These signals do the rest. They have separate inputs and outputs so they can be daisy chained. The down track signal will hold the up track signal on yellow until the down track signal goes off red.Click here to see the instructions.THIS ITEM IS CURRENTLY BACKORDERED BY THE MANUFACTURER. Your credit card NOT be charged until until it ships to you.