| 摘要 |
<p>PURPOSE:To surely discriminate the existence of a passport and to previously prevent the generation of an accident such as the loss or robbery of the passport by driving an alarm tone generator based upon an output from a sensor for detecting the intensity of a magnetic field from a permanent magnet. CONSTITUTION:A magnetic sensor 6 for detecting a magnetic field M applied from a permanent magnet 3, an amplifier/comparator 7, an alarm tone generator 8, a battery 9 to be a power supply for driving these members, etc., are integrated in a body device 5. The device 5 and a passport 1 provided with the magnet 3 are respectively stored in different pockets of a suit or the like and the magnetic field of the magnet 3 is weakened in accordance with the increment of a distance between the device 5 and the passport 1. The intensity of the magnetic field to be changed in accordance with the distance is detected by a pickup coil 6 and converted into an electric signal. The electric signal is amplified by the amplifier/comparator 7, the amplified signal is compared with a prescribed reference value, and when the detected value is less than the reference one, a buzzer 8 is driven and a prescribed alarm tone is generated, so that the passport can be prevented from being lost or robbed.</p> |
