| 摘要 |
PURPOSE:To inhibit the usage of an automobile telephone terminal equipment in an airplane without depending on an artificial operation by incorporating an air pressure detector which converts an air pressure into an analog electric signal, and measuring the absolute value of the air pressure and the changing amounts of the air pressure per unit time. CONSTITUTION:An air pressure detector 1 which converts the air pressure into the analog electric signal is an oscillation circuit in which surface acoustic wave elements having a distortion generating diaphragm are integrated with an amplifier, and an oscillation frequency in inverse proportion to the phase delay time of the transmission of a surface acoustic wave when pressurization is operated is obtained. The oscillation frequency is measured by a frequency counter 5 and an information processing controller 6, the oscillation frequency under a constant air pressure is held by a storage element 7 as an initial value, the oscillation frequency changing due to the air pressure and the stored oscillation frequency are compared and computed, and the present air pressure can be discriminated. Then, the air pressure in the airplane and the air pressure changing amounts per unit time are measured, and a power switch is turned off by an information processor 6 when the air pressure in the air plane is identified. |
