Abstract: The present invention provides a track circuit for AC electrified railways, formed by the two rails (R.sub.1,R.sub.2) of a railway section and comprising a transmitter (E) connected to one end of the track circuit for generating therein an alternating signal of given frequency and a receiver (R) connected to the other end for controlling the operation of a track relay (RV). A number of capacitive impedances (Z.sub.1,Z.sub.2, . . . Z.sub.n) with parallel inductance and capacitor (each having a middle point (3) connected to the ground) are connected between the rails (R.sub.1,R.sub.2) while being spaced apart over the whole length of the track circuit with a given pitch (P), depending on the values of the impedances, so that the transmission attenuation of the circuit at the operating frequency is always less than the transmission attenuation of a circuit having the same length formed by a rail with ground return.

Abstract: A sensor arrangement is disclosed for detecting the presence of an axle of a rail vehicle in a short length of a track. The arrangement includes a bridge coupled to and including resistances of the rail upon which the vehicle travels. This bridge is unbalanced by wheels of an axle shunting resistance of the bridge with the bridge unbalance producing an output indicative of the presence of the axle. Two such arrangements displaced relative to each other will enable detecting the direction of movement of the vehicle. This sensor arrangement contains no electric components on the rail and is insensitive to interference from rail currents and electromagnetic rail brakes.

Abstract: Coded energy applied to the track circuit rails for cab signal control when a train occupies the section is also applied over a line circuit to the local input of the solid state track relay unit and to a code reset module in which it drives a code following relay and charges a timing capacitor during a predetermined number of code pulses. When the section becomes unoccupied, the track relay unit produces a coded output, from the combined rail and local inputs, to which the track registry relay is non-responsive. An analog storage circuit in the reset module receives and stores this coded output energy during each timing period. During each code off-time, the timing capacitor is connected to a switching relay circuit controlled by a DIAC unit.