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 Title: |
US4038596:
Method and apparatus for authenticating a record medium consisting of applying two different strength magnetizing fields and monitoring the remanent fields
[ Derwent Title ]
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| Country: |
US United States of America
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| Inventor: |
Lee, Cyril Arthur; Maidenhead, United Kingdom
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| Assignee: |
E M I Limited, Hayes, United Kingdom
other patents from EMI LIMITED (172440) (approx. 349)
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| Published / Filed: |
1977-07-26
/ 1975-07-02
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| Application Number: |
US1975000592669
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| IPC Code: |
Advanced:
G06K 7/08;
G07D 7/04;
G07D 7/20;
G07F 7/08;
Core:
G07D 7/00;
more...
IPC-7:
G01R 33/12;
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| ECLA Code: |
G06K7/08+IDT; G07D7/04; G07D7/20; G07F7/08B;
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| U.S. Class: |
Current:
324/210;
235/449;
324/226;
340/005.8;
340/540;
Original:
324/034.R;
235/061.7B;
235/061.11D;
235/061.12M;
340/149.A;
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| Field of Search: |
324/34 R,34 H
340/149 A
235/61.11 D,61.12 M,61.7 B
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| Priority Number: |
| 1974-07-04 |
GB1974000029663 |
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| Abstract: |
Apparatus to examine a magnetic storage layer expected to contain a magnetic watermark includes means to magnetize the layer with a unidirectional field of a selected strength without saturating it and means to detect any distinct region of magnetic remanence. The apparatus may further include means to record the resultant remanence levels (or their ratio) for such a region and another part of the layer, means to magnetize the layer with a unidirectional field of a different selected strength, means to detect any then-existing such distinct region or regions, means to measure the remanence levels (or their ratio) for the then-existing such region and another part of the layer, and means to compare the measured and recorded levels (or their ratios) and indicate from the result of the comparison whether or not this represents a layer having a magnetic watermark of regions of distinctly aligned anisotropic magnetic particles. The use of different amounts of magnetization will produce different ratios of remanence in a layer having such a watermark but not in an homogenous layer.
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| Attorney, Agent or Firm: |
Fleit & Jacobson ;
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| Primary / Asst. Examiners: |
Corcoran, Robert J.;
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| INPADOC Legal Status: |
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| Family: |
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First Claim:
Show all 11 claims |
What I claim is:
1. A system for examining a record medium expected to include a magnetic material storage layer exhibiting an inherent pattern of magnetic remanence difference between a part of the layer and another part of the layer when both parts are subjected to a uniform magnetising field including
- means for applying to the layer in turn at least two different strength magnetising fields along the same direction,
- means for measuring the relative remanent magnetisation in said part and said another part for each said magnetising field, and
- means responsive to the measurements to assess the authenticity status of the medium, the relative remanent magnetisations differing for said different strength magnetising fields for an authentic medium.
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| Background / Summary: |
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| Drawing Descriptions: |
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| Description: |
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| Forward References: |
Show 42 U.S. patent(s) that reference this one
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