PURPOSE: To detect the abnormality of a satellite station equipment caused by rain water on a central station equipment side by a method wherein, if the penetration of rain water is detected by a rain water penetration detecting part in the satellite station equipment, the penetration information is transmitted to the central station.

CONSTITUTION: If a trouble occurs in the case of a satellite station equipment 1 and rain water penetrates into the equipment, a signal is transmitted to an I/O part 9 by a rain water penetration detecting part 16 and judgement is made by a logic part 12. Normally, the satellite station equipment 1 judges information collected by the I/O part 9 by the logic part 12 in accordance with periodical signals from the central station equipment 15 and the judged information is transmitted to a central station equipment 15 through a transmission part 14 and a communication line 7. Therefore, if rain water penetrates into the satellite station equipment 1, the information of the penetration can be transmitted to the central station immediately. With this constitution, if a trouble occurs in the case of the satellite equipment by an external cause and rain water penetrates into the satellite equipment, the abnormality can be detected by the central station equipment. Therefore, the unexpected response of the satellite station equipment caused by rain water penetration can be avoided and the equipment can be used for a long time free from care.