Broken rail detection system and method

DETAILED DESCRIPTION What is claimed is: 1.
In a track circuit comprising two or more electrically isolated rails, a method for detecting breaks in the rails comprising the steps of: (a) electrically interrupting the first of said rails along its length to form plural blocks; (b) applying a source of voltage having a first polarity at a first end of one of said blocks; (c) applying a source of voltage having a second polarity at the other end of said one block; (d) applying a voltage reference to the second of said rails; and, (e) measuring the current in said first rail.
2.
The method of claim 1, further comprising the steps of: (a) comparing said measured current against a predetermined current value; and, (b) providing a warning signal when said measured current is less than said predetermined current value.
3.
The method of claim 1, further comprising the steps of: (a) maintaining a historical indication of said measured current; (b) providing a warning signal when said measured current is less that the historical indication.
4.
The method of claim 1, further comprising the step of: (a) testing the circuit formed in said first rail by disconnecting one of said sources of voltage from said first rail.
5.
The method of claim 1, further comprising the steps of: (a) providing a mobile short circuit between said first and second rails; (b) moving the mobile short circuit along said first and second rails from the first end of said block to the other end of said block; (c) determining the location of a break along the rails by the location of the mobile short circuit when a change in the measured current is detected.
6.
A method of determining the presence of a rail vehicle along a track circuit comprising two or more electrically isolated rails, comprising the steps of: (a) electrically interrupting the first of said rails along its length to form plural blocks; (b) applying a source of voltage having a first polarity at a first end of one of said blocks; (c) applying a source of voltage having a second polarity at the other end of said one block; (d) applying a voltage reference to the second of said rails; (e) measuring the current in said first rail at said first ends of said block; (f) removing the source of voltage at the other of said ends of said block; and, (g) measuring the current in said first rail at said first end of said block after the source of voltage has been removed at said other end of said block