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.