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US 5,349,254 AGranted
Call progress detection circuit
AssigneeMatsushita Electric Corporation of America
InventorDursun Sakarya
Life of this patent
Estimating the term…
Abstract
A call progress detection circuit filters the audio input along parallel bandpass and band reject paths. The relevant band of frequencies is defined by the range of 350-620 Hz, within which band all of the call progress tones are found. The energy output from the bandpass path is compared to the energy output from the band reject path to determine if the audio input is generated by a call progress tone or by vocal input.
Claims38
A signal detection system comprising:
- at least one first filter means for allowing transmission of signals having energy in a first range of frequencies;
- at least one second filter means for allowing transmission of signals having energy which is not is said first range of frequencies;
- means for converting the output of said at least one first and said at least one second filter means from alternating current to direct current;
- and
- at least one first means for comparing the output of said at least one first filter means to the output of said at least one second filter means.
2 more elements
A method for determining if an input signal is within a range of frequencies comprising:
- providing said signal to at least one first filter means having at least one pass band in said range of frequencies;
- providing said signal to at least one second filter means having at least one reject band in said range of frequencies;
- converting the outputs of said filters to direct current;
- and
- comparing the converted outputs of said at least one first filter means to the converted outputs of said at least one second filter means.
2 more elements
Dependencies are inferred from the claim text.