This train detector makes use of hand held laser pointer devices that are widely available to detect trains over long distances.
WARNING Laser Pointers must be used with great caution as they may cause eye damage. Follow the directions that are supplied with these devices carefully or permanent injury could result.
The following diagram shows the basic laser pointer circuit. It is identical to the infrared circuit except that the infrared LED's have been replaced by the laser pointer unit.
Due to the long range of these devices this detector method can easily span great distances and could be used to detect trains in a long section of straight track such as in a lader yard or across the throat of a very wide yard.
http://home.cogeco.ca/~rpaisley4/ATLaser.html
