Method and apparatus for periodic signal detection
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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Abstract
An apparatus and method for detecting the presence of ringer signals in a telephone which samples the incoming telephone signals within a prescribed time interval, windows the signals, and computes a set of auto-correlation coefficients. These coefficients are normalized, and their absolute values are calculated and summed and compared with an empirically-derived threshold. If the coefficient sum exceeds the threshold, a high degree of correlation within incoming signals is indicated, distinguishing the incoming signal as containing ringer signal constituents.
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Citations
14 Claims
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1. A method for detecting the presence of periodic signals in an incoming telephone signal, the method comprising the steps:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus for detecting the presence of periodic signals in an incoming telephone signal, the apparatus comprising:
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analysis means connected to the incoming telephone signal for receiving the telephone signal and generating a set of auto-correlation coefficients, including a fundamental coefficient and a set of higher order coefficient; computing means connected to the analysis means for receiving and summing the coefficient values, wherein the sum of the coefficient values represents the correlation between frequency components of the incoming telephone signal; and comparing means connected to the computing means for receiving and comparing the sum produced in the computing means to a pre-stored threshold value and for producing an output signal indicating the relative correlation between frequency components within the incoming telephone signal. - View Dependent Claims (13, 14)
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Specification