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Environmental indicator device and method

  • US 4,646,066 A
  • Filed: 06/27/1985
  • Issued: 02/24/1987
  • Est. Priority Date: 06/27/1985
  • Status: Expired due to Fees
First Claim
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1. An indicator device comprising a target that has a tuned electrical circuit and that includes an element having an electrical property that, in response to a particular environmental parameter, changes in a predetermined fashion, whereby the response of the target to an electromagnetic interrogation signal, having a frequency in the microwave range or lower, can be related to the exposure of the target to the parameter.

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