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Marked recorded signals

  • US 5,079,648 A
  • Filed: 04/20/1989
  • Issued: 01/07/1992
  • Est. Priority Date: 04/20/1988
  • Status: Expired due to Fees
First Claim
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1. Apparatus for monitoring marking of a recorded signal including:

  • generating means for generating a plurality of marking signals;

    modulating means for modulating the recorded signal with one of the marking signals;

    monitoring means for monitoring the modulated marked signal, which means includes a demodulator which provides a demodulated signal comprising the recoreded signal and the one marking signal, comparisonmeans for comparing the magnitude of the one marking signal with the plurality of marking signals thereby to produce an output in dependence upon the differences between the magnitudes such that if the difference does not exceed a predetermined margin, the recorded signal is again modulated with the one marking signal.

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