Railway signalling systems

A railway signalling system for the detection of a train within a defined section of track by means of a track circuit apparatus utilizing the rails within the section as part of an electric circuit and in which system the rails are electrically shunted by the wheels and axles of a railway vehicle of the train within the section, characterized in that a shunt assist circuit is provided on the railway vehicle, said circuit comprising:

• an inductive loop aerial that is closely inductively coupled with the two rails beneath the railway vehicle;
• and
• an alternating power source connected to the loop aerial;
• whereby when the loop aerial is energized by the alternating power source, a current is induced to flow in a circuit formed by a first wheel/axle set of the railway vehicle, through a first rail length underneath the railway vehicle, through a second wheel/axle set of the railway vehicle, and back through a second rail length underneath the railway vehicle to the first wheel/axle set.