PURPOSE: To function effectively and correctly even under strong electromagnetic noise environment by utilizing spread spectrum correspondence.

CONSTITUTION: A leakage cable 16 is provided along the running track 12 of moving bodies 10-1, 10-2. A center fixed station 14 is provided with a transmitting part to transmit a burst signal of spread spectrum to the leakage cable at every decided period, a receiving part to demodulate a signal shifted from the received signal through the leakage cable by assigned natural frequency to every moving body in the station frequency, a correlation computing part to compute correlation between a demodulation series from the receiving part and a reference series, and a distance computing part to compute the distance up to the moving body based on a propagated time from completion of transmission to getting correlation maximum value at receiving. Mobile stations 18-1, 18-2 are respectively provided with receiving parts to receive the burst signal transmitted from the fixed station through the leakage cable, frequency converting parts to mix assigned natural frequency with the received burst signal and convert in frequency, and transmitting parts to transmit the burst signal from the frequency converting part to the fixed station through the leakage cable.