| 摘要 |
PROBLEM TO BE SOLVED: To detect change in tire pressure after tire pressure abnormality occurs on the receiving device side while reducing power consumption. SOLUTION: A transmission device 10 detects it tire pressure abnormality exists or not based on an output signal of a tire pressure sensor 16. The transmitting device 10 transmits a tire pressure abnormality signal when it detects tire pressure abnormality, and after that, it transmits a tire pressure abnormality signal and a tire pressure normal signal only when change exceeding a specified value is generated at tire pressure and when tire pressure restores to be normal. In addition, the transmitting device 10 transmits a tire pressure normal signal at a constant time interval when tire pressure is normal. A receiving device 10 lights a first alarm lamp 30 when it receives a tire pressure abnormality signal, and lights a second alarm lamp 32 when the signal is not received for above constant time or over.
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