| 摘要 |
PURPOSE:To enable to detect the abnormal pressure without placing the power supply in the tire of a car, by providing crystal oscillator in the enclosed space and using the attenuating oscillation after the excitation of oscillator. CONSTITUTION:At the enclosed space 6 such as tire of a car, the coil 3 and the pressure response switch 2 are provided in parallel with the crystal oscillator 1. Further, after transmitting electromagnetic waves epual in the frequency of the natural vibration frequency of the oscillator 1 from the external transceiver 4, the transceiver 4 is selected to a receiver. In this case, if the pressure in the space 6 is normal, the switch 2 keeps OFF, and the attenuating oscillation after the excitation of the oscillator 1 is detected with the receiver 4 via the coil 3. On the other hand, if the pressure in the space 6 is abnormal, the attenuating oscillation of the oscillator 1 is shortened with the switch 2 turned on and it is not detected by the receiver 4. |
