| 摘要 |
An ultrasonic security system for personal computer comprises a touch-panel section, a lock section, and a key section. The touch-panel section comprises a nonpiezoelectric plate, at least one transducer-unit, and a signal analyzer. The transducer-unit consists of at least one input IDT Ti (i=1, 2, . . . , m), at least one output IDT Ri (i=1, 2, . . . , m), a first input piezoelectric substrate, and a first output piezoelectric substrate. The lock section comprises a second piezoelectric substrate, a coding IDT consisting of interdigital electrode pairs and having a coded pattern, and a terminal IDT having the electrode-finger direction parallel to that of the coding IDT. The key section comprises a third piezoelectric substrate, an initial IDT, and a decoding IDT having the same construction pattern as the coding IDT. If touching a position on the nonpiezoelectric plate, an electric signal appears at the output IDT Ri. The electric signal is applied to the coding IDT, and is detected as a coded burst-signal at the terminal IDT. The coded burst-signal arrives at the initial IDT. And then, a pulse is detected at the decoding IDT, if the coded burst-signal correlates to the coded pattern. As a result, the touch position is sensed by means of the phase of the pulse at the signal analyzer. In other words, no key section or a key section with a decoding IDT having the different construction pattern from the coding IDT causes no pulse. Consequently, far from sensing the touch position, it is not possible to operate the PC preparing such the ultrasonic security system for personal computer.
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