Insulated track circuit

The invention provides an insulated track circuit. Each section of the insulated track circuit comprises a sending side and a receiving side; each of the receiving side and the transmitting side comprises a common mode inductor unit, a lightning protection transformer, a transmission cable, a matching transformer, a tuning unit and a transceiving device; the transmitting-receiving device is connected with the steel rail through the lightning protection transformer, the transmission cable, the common mode inductor unit and the matching transformer in sequence. The tuning unit is arranged between two connection points of the matching transformer and the steel rail; the tuning units are located at two ends of a mechanical insulation joint in the insulation track circuit; the tuning unit is used for generating series resonance for adjacent section signals to form short-circuit impedance approaching zero and generating parallel resonance for the section signals to form high impedance; the transmission cable presen