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Method and apparatus for periodic signal detection

  • US 5,390,244 A
  • Filed: 09/10/1993
  • Issued: 02/14/1995
  • Est. Priority Date: 09/10/1993
  • Status: Expired due to Term
First Claim
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1. A method for detecting the presence of periodic signals in an incoming telephone signal, the method comprising the steps:

  • generating a series of auto-correlation coefficients from the incoming telephone signal, the coefficients comprising a fundamental coefficient and a series of higher-order coefficients;

    computing the sum of the auto-correlation coefficients which represents the correlation between frequency components comprising the incoming signal; and

    comparing the sum of auto-correlation coefficients to a predetermined threshold value in order to determine whether the incoming signal contains periodic signals.

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