| 摘要 |
An antenna assembly for vehicle radio transceiver which is detachably mounted on the car body of an automobile, for example. The assembly includes a rod-shaped antenna, a hollow casing which supports the lower end of the antenna, a permanent magnet for securing the casing to the car body by magnetic attraction, a vibration detector which electrically detects any vibration applied to the casing, and an alarm circuit which operates to produce an alarm in response to detection of vibration applied to the casing or the car body. The vibration detector includes a printed circuit board which is placed on the bottomplate of the casing and which is formed with a first and a second electrode each including a plurality of interdigitated fingers and connected across a d.c. power supply circuit. The vibration detector also includes a conductive spherical body which is placed on the printed circuit board in a rollable manner. When the spherical body moves over the printed circuit board in response to vibration applied to the casing, the circuit connection across the power supply is repeatedly turned on and off to produce a pulse signal, which operates the alarm circuit.
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