| 摘要 |
PROBLEM TO BE SOLVED: To securely detect a receiver unit trouble with a simple structure by comparing the frequency of the demodulating signal with the modulated frequency output from a modulating signal generating unit and different per each cycle. SOLUTION: The train detecting signal received by a receiver unit 3 is sent to a demodulating unit 14. The demodulating unit 14 demodulates the train detecting signal and output it to a signal determining unit 4 and a level determining unit 5. The signal determining unit 4 compares the demodulating signal input from the demodulating unit 14 with the modulated frequency output from a frequency generating unit per a constant cycle, and determines whether the frequency of the demodulating signal and the modulated frequency coincide with each other or not. In the case where the frequency of the demodulating signal and the demodulated frequency coincide with each other or the frequency of the demodulating signal and the modulated frequency coincide with each other, the signal determining unit 4 determines the normal operation of the receiver unit 3, and outputs the normality determining signal. In the case where the frequency of the demodulating signal and the modulated frequency are different from each other, the signal determining unit 4 determines the generation of trouble in the receiver unit 3, and outputs the trouble determining signal.
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