Circuit for detecting unbalance of the traction current in a track circuit

DETAILED DESCRIPTION What I claim is: 1.
A device for detecting unbalance of the traction current in a track circuit of the type comprising a track section which is short-circuited by rolling stock, there being a transmitter for transmitting a track circuit signal current and an associated receiver characterized in that the unbalance detecting device comprises two current sensors for coupling to respective rails of the track section, an unbalance detecting circuit for receiving from the current sensors respective signal currents in the respective rails for transmitting track circuit signal currents to the receiver when the signal currents detected by the current sensors are equal and responsive to any detected unbalanced currents of a given frequency and magnitude of unbalance effective to render the unbalance detecting circuit effective to preclude transmission to the receiver, and a pole change switch for connection between the track circuit current transmitter and the rails associated therewith for alternately changing the direction of the track circuit signal current through the track circuit to render the track circuit signal current balanced.
2.
The unbalance detecting device of claim 1, characterized in that the unbalance detecting circuit is provided with filter means tunable to the actual frequency used for the track circuit signal current.
3.
An arrangement for detecting the presence of rolling stock on a track section, comprising the unbalance detecting device of claim 1 or 2, a transmitter for transmitting a track circuit signal current, and an associated receiver.
4.
The arrangement of claim 3 in combination with a section of track coupled to the arrangement.




Description:
BACKGROUND OF THE INVENTION The present invention relates to a circuit for detecting unbalance of the traction current in a track circuit of the type comprising a track section which is short-circuited by rolling stock in such a manner as to form an independent track circuit, each such section being provided with a transmitter for transmitting a track circuit current and an associated receiver