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Photo lock system

  • US 3,896,345 A
  • Filed: 09/03/1974
  • Issued: 07/22/1975
  • Est. Priority Date: 09/03/1974
  • Status: Expired due to Term
First Claim
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1. In an access control system, the combination of:

  • a receptacle having a first station and a second station and including means defining a slot for receiving a key member for movement past said first station to said second station;

    a first radiation sensor mounted at said first station;

    a second radiation sensor mounted at said second station;

    means for directing radiation across said slot to each of said sensors;

    a first transparency mounted at said first station; and

    a key member having a second transparency which is the complement of said first transparency, with said second transparency positioned on said key member to move past said second station to said first station as said key member is inserted into said slot, and with at least the portions of said key member which are at said second station during insertion having an average radiation transmission characteristic substantially the same as that of said second transparency.

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