Hi Everyone: My friend Dan stopped over Monday. Let me tell you something, it was like Santa coming back! Dan is an Electronic/Electrical Technican at a local mill. He fixes and does alot of prevenative maintance on their automated line. He gets these sensors for nothing and they work! The ones I am using. Uses fiber optics. In one fiber line, there is a transmit and a recieve signal. There are two of these per unit. (There will be a picture of which I am talking about.) I drilled holes between the rails and mount the sensors in the areas in which I want them. The yellow box is the guts of the unit. Here's how that works. The unit it made of "block". These blocks are delays, sensitivy, logic, and power. You "program the unit by placing the "block into a certain position! Once you have that done, there are 4 screws you install. Then you connect a relay up and power. Speaking about power. Depending how you have the power setting, you can use 5vdc -220vdc and 110vac -440vac without any outside electronics! All contained in the "blocks"!!! The other unit is a IR sensor. There is one draw back, placing it acoss the tracks can leave gaps for trains and signal function is poor. The delay on it is very poor. I tried to use relays and capasitors to no avail. The big question is, can you buy them. The answer is yes. But the price is costly. If you want the company's name. Contact me. This has made my layout so much more impressive! Andy Dan is giving me some logic controls and software to run my next layout by computer!