The protected section of track can be as long or as short as desired and does not have to be the same length on both sides of the crossing. The circuit works in both directions and can be connected to other grade crossing circuits to provide fully automatic protection for multiple track crossings.
The Grade Crossing circuit provides prototypical operation of the signals at level railway crossings and can supply up to 100 milliamps for LED flashers, small incandescent lights or other circuits such as crossing gates or sound units.
The circuitboard has been designed to be easy to build and install. Widely available and inexpensive components are used in its construction. None of the parts are static sensitive.
An upgraded version of the 2004 circuit is at this link - 2008 - Automatic Railway Grade Crossing Circuit. The new circuit designed to prototypically control crossing gates.
One Track Crossing - Circuitboard Connection Diagram
The following diagrams show how the circuit is connected for a crossing with 1 track. A diagram of the circuit board showing the terminal block positions is used.
The next diagram shows how the phototransistor sensors are placed along the track and the actions that occur as each is covered by the train. The sensors that start the flashers can be placed any distance from crossing desired.