| 摘要 |
A theft prevention device includes an optical sensor for detecting a level of ambient light and a vibration sensor for detecting a vibration of a protected article. The theft prevention device further includes an alarm circuit operatively coupled to the optical sensor and the vibration sensor for providing an alarm when the optical sensor detects a change in the level of ambient light from relative brightness to relative darkness and the vibration sensor detects a vibration of the protected article. The theft prevention device may further include a disconnection sensor for detecting a disconnection of a member attached to the protected article, whereby the alarm circuit activates the alarm upon such disconnection. The theft prevention device may further include a microswitch which is automatically activated upon removal of the protected article from an article casing. Still furthermore, the theft prevention device may include devices located at an exit of a place in which the protected article is located for emitting a high frequency light which may be detected by the optical sensor. |
