A track circuit for railway systems or the like includes a track segment of predetermined length electrically insulated from an adjacent track segment by an electric joint, which includes a conductor and forms two loops arranged in a longitudinal S-shape within the space between the rails. Units are provided that transmit and receive electric signals and that are operatively coupled with the electric joints. The transmitting/receiving units include a unit transmitting and receiving a high-frequency signal to detect a train on the a track segment, and a unit transmitting and receiving a low-frequency signal which provides the carrier encoded with information to be transmitted to a train-based receiving unit. Units are further provided that enable/disable the high-frequency signal transmitting/receiving units, and units that enable/disable the low-frequency signal transmitting/receiving units, which are alternately actuated. The electric joint includes an internal impedance disposed between the two loops.