PURPOSE: To detect a defect of a leaked coaxial cable and a wiring in a fixed station by coupling a terminal of the leaked coaxial cable of a radio zone of adjacent fixed stations by a repeater to expand the radio area from an adjacent base station.

CONSTITUTION: A signal from a fixed station 1' is detected by a level monitor 6 via a changeover device 5' of a repeater provided at a boundary between the leaked coaxial cable 2' and a zone. When the monitor 6 detects the signal as intermission, a logic circuit 7 changes over changeover devices 5, 5' to the position of a frequency converting circuit 8. Then a signal from the normal fixed station 1 via a cable 2 and the changeover device 5 is converted into a frequency with less transmission loss by the circuit 8 and transmitted to a cable 2' at the fixed station 1' side. The signal from the base station 1 via the cable 2' is selected by a filter 10', this signal is converted into a signal of the fixed station by a frequency converting circuit 11 and fed to a switching device 12'. A monitor circuit 13' actuates the switching device 12' to separate the fixed station 1', the signal from the fixed station 1 is transmitted to the cable 2' from filter 9' and communicated with a mobile station 4.