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Simultaneous transmission of data and audio signals by means of perceptual coding

  • US 5,404,377 A
  • Filed: 04/08/1994
  • Issued: 04/04/1995
  • Est. Priority Date: 04/08/1994
  • Status: Expired due to Term
First Claim
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1. Apparatus for encoding a data signal to be transmitted simultaneously with an audio signal such that said encoded data signal is masked by said audio signal, the apparatus comprising:

  • means for monitoring said audio signal to determine a perceptual entropy envelope thereof, said monitoring means generating control signals indicative of said determined perceptual entropy envelope;

    means responsive to said control signals for encoding said data signal as an frequency shift key (FSK) modulated signal and for outputting said FSK modulated signal at times, frequencies and levels falling within said determined perceptual entropy envelope of said audio signal such that when combined with said audio signal, said FSK modulated signal is masked by said audio signal; and

    means for combining said audio signal with said FSK modulated signal to form a composite signal.

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