Digital compact disc player security system reproducing method and apparatus
First Claim
1. A device for reading digitally encoded data comprising:
- first and second optical receivers positioned above a nominal track position on a recording medium and receiving optical reflections from the recording medium to produce corresponding signals, respectively; and
a device for comparing the signals received from the first and second optical receivers for identifying a physical offset modulation of a plurality of data bits from the nominal track position.
4 Assignments
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Accused Products
Abstract
A security system for preventing disc players from being used with unauthorized software is disclosed. The security code is stored through modulating an offset of the physical position of a plurality of data bits from a nominal track position. A two part optical read head provides an RF signal corresponding to the presence of a physical offset modulation. The RF signal is present when there is a physical offset of the data bits defining a first logical state and the absence of the RF signal defines a second logical state. A digital security code is encoded and decoded in this manner. A system for encoding a security code through modulating the physical offset of a plurality of data bits from a nominal track position is also disclosed.
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Citations
8 Claims
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1. A device for reading digitally encoded data comprising:
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first and second optical receivers positioned above a nominal track position on a recording medium and receiving optical reflections from the recording medium to produce corresponding signals, respectively; and
a device for comparing the signals received from the first and second optical receivers for identifying a physical offset modulation of a plurality of data bits from the nominal track position. - View Dependent Claims (2, 3, 4)
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5. A method for decoding digital data comprising:
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generating first and second signals based on optical reflections from opposite sides of a nominal track position on a recording medium;
comparing the first and second signals to identify a physical offset modulation of a plurality of data bits from the nominal track position; and
generating a code determined by the offset modulation of a plurality of data bits from the nominal track position. - View Dependent Claims (6, 7, 8)
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Specification