Railway track circuit

A railway track circuit for separating first and second successive trains having a front shunt axle at the front and a rear shunt axle at the rear and travelling in the same direction on a track comprising a plurality of track circuits, each said track circuit being switchable between an initial state in the absence of a shunt axle on said track circuit and a complementary state upon passage of a front shunt axle out of said track circuit and comprising:

• a pair of rail segments, said rail segments having a downstream end, towards which the trains are travelling, and an upstream end, away from which the trains are travelling,
• downstream impedance means electrically connecting said rails at a downstream point and defining the downstream end of said track circuit,
• upstream impedance means electrically connecting said rails at an upstream point and defining the upstream end of said track circuit,
• a transmitting member electrically connected to said downstream impedance means when said track circuit is in said initial state and to said upstream impedance means when said track circuit is in said complementary state,
• a first track circuit receiving member electrically connected to said upstream impedance means when said track circuit is in said initial state and to said downstream impedance means when said track circuit is in said complementary state,
• at least one track circuit electromagnetic sensor located between said upstream and said downstream impedance means in the vicinity of one of said rails for detecting passage of the front and rear shunt axles of the trains over said rails,
• a second track circuit receiving member in electromagnetic communication with said at least one track circuit electromagnetic sensor, switchable between energized and de-energized states, and adapted to be switched to said de-energized state upon detection of the passage of the front shunt axle of the first train by said at least one track circuit electromagnetic sensor, and
• switching means electrically connected to said transmitting member and said first track circuit receiving member for reversing the electrical connections between said first track circuit receiving member, said transmitting member, and said upstream and downstream impedance means.