Train Detection. This is my train detection track piece. Under the black 1x4 tile is a reed contact hidden. The wires are bent and lead trough holes from 1mm diameter and bent on the underside. There i soldered the wires that can go either to a RCX, NXT or custom controller module. Wires are fixed with UV glue. I guess you can use hot glue too. Applications are: - Railroad crossing control. - start a waiting train in the station. - loop counter. You can use a LEGO magnet, but with the new fully encapsulated magnets, I use Viessmann magnets. Catalog number: 6841 Size: 10 x 5 x 1,5 mm Wire: bought in a Märklin model train shop, used to wire up point motors. Remark: Test the distance from the magnet to the reed contact. If to close, you get 2 impulses (one by entering the reed contact & one by leaving the reed contact) If to large, the reed contact doesn't close at all. Be verry carefull with reed contacts, they break ferry fast where the solid wire leaves the glass tube where the contact is placed! You can use pliers to hold the solid wire between the glass tube and where you want to bent the wire, preventing stress on the glass tube while bending. Enjoy it. Regards, Ludo