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Local-field type article removal alarm

  • US 4,975,680 A
  • Filed: 01/16/1990
  • Issued: 12/04/1990
  • Est. Priority Date: 01/16/1990
  • Status: Expired due to Term
First Claim
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1. An anti-theft device for providing an alarm in response to unauthorized movement of an article of property through a localized field comprising an alarm device adapted to be affixed to the article, the alarm device comprising:

  • motion detection means;

    field detection means; and

    means responsive to the motion detection means and the field detection means, for triggering the alarm if, and only if (a) the field detection means detects the localized field and thereafter ceases to detect the localized field, and (b) the motion detection means detects motion of the article during a predetermined delay interval following the time at which the field detection means ceases to detect the localized field.

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