ABSTRACT:   A tone detector circuit for detecting the presence of a certain tone or tones in an input signal. An estimate is calculated for each of the following three parameters of the band limited spectrum of the input signal: total power, power mean frequency, and mean square power bandwidth. Each of the three input spectrum parameters is compared to the same parameter of the tone or tones desired to be detected. If a match within certain bounds occurs on all three parameters, the desired signal has been detected.

U.S. REFERENCES:

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Patent No. Inventor Issued Title 3652805 Wisner 3 /1972 BINARY FREQUENCY IDENTIFICATION SYSTEM 3882283 Proudfoot 5 /1975 Method and apparatus for detecting the presence of signal components of predetermined frequency in a multi-frequency signal EXEMPLARY CLAIM(s): Show all 9 claims What is claimed is: 1. A tone detector comprising: an input terminal for receiving an input signal; a plurality of estimating means each comprising: an input connected to said input terminal; an output; and means for generating at said estimating means output an estimate of a parameter of the frequency spectrum of said input signal; one or more decision circuits, each decision circuit comprising: a plurality of inputs each connected to a respective one of said plurality of estimating means outputs; an output; and a plurality of comparison circuits, each comparison circuit corresponding to one of said plurality of estimating means and comprising: an input connected to the one of said decision circuit inputs connected to the corresponding estimating means; an output; and means for generating at said comparison circuit output a first signal if the signal present on said input of said comparison means is essentially equal to the value of the corresponding parameter of a tone to be detected and a second signal in the absence of equality; and means for generating at said decision circuit output a third signal if all of said outputs of said plurality of comparison circuits have a first signal present and a fourth signal if one or more of said outputs of said plurality of comparison circuits has a second signal present; and one or more output terminals, each connected to a corresponding decision circuit output for indicating the presence or absence of a predetermined tone whose presence is to be detected. RELATED U.S. APPLICATIONS: none FOREIGN APPLICATION PRIORITY DATA: none FOREIGN REFERENCES: none OTHER REFERENCES: J. N. Denenberg and L. G. Peach, "Estimation of Spectral Moments", Proceedings Ninth Annual Allerton Conference on Circuit & System Theory, Oct. 6-8, 1971, p. 1085. PRIMARY/ASSISTANT EXAMINERS: Cooper; William C.; Popek; Joseph ADDED TO DATABASE: Aug. 21, 1996