| 摘要 |
PROBLEM TO BE SOLVED: To enable a train approach alarm receiver carried by a guard of a work area of a train track to detect the failure of transmitter sending out train approach alarms by transmit waves of constant intervals, by alarm sound. SOLUTION: A receiver is provided with a carrier SQ circuit 11, a switch 12, a rectifier 14, cycle judging circuits 13, 15, an alarm sound oscillator 16 and an alarm control part 17. Since modulated radio waves are sent as tone signals at the time of no train and as message signals at the time of the presence of a train at constant intervals from a transmitter, output of the SQ circuit 11 is inputted to the timer 13 to check the interval of intermittent transmission, and when the switch 12 is on, wave detection output is rectified by the rectifier 14, and whether the tone signals or message signals are at constant intervals is checked by the cycle judging circuit 15. The alarm control part 17 judges the failure of the transmitter if a receive level is low or the interval changes from the checked result, and outputs failure alarm sound from a speaker 84.
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