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POSTAL TRACKING SYSTEM

  • US 3,750,167 A
  • Filed: 07/22/1971
  • Issued: 07/31/1973
  • Est. Priority Date: 07/22/1971
  • Status: Expired due to Term
First Claim
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1. A tracking system comprising a. a passive transponder having 1. a Receiving antenna lying in a plane and responsive principally to radiation polarized in said plane, and 2. means for transmitting signals when activated by the radiation received by said antenna, b. means for activating said transponder when it is located in a region including a transmitting antenna array for radiating signals in three planes orthogonal to each other to provide a radiation pattern in said region in said receiving antenna plane, and c. means for receiving signals transmitted from said transponder so as to track said transponder when it is located in said region.

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