Apparatus and robust method for detecting tones
CA 2089593 C · Owner: American Telephone And Telegraph Company · Inventors: Dighe, Rajiv S.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A robust tone detector is realized by applying a single taper which, provides a relatively narrow bandwidth filter to a received signal and, then, performing a Discrete Fourier Transform of the tapered signal. The result of theFourier transform is used to obtain an estimate of energy in the frequency domain of the expected tone. A prescribed selection algorithm based on the relationship of the received signal energy in the time domain and the energy estimate in the frequency domain is used to determine whether a valid tone has been received. Robustness of the tone detector is improved by performing a plurality of Discrete Fourier Transforms of the single tapered version of the received …
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Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Filed February 16, 1993 and granted August 12, 1997. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended February 16, 2013.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by February 16, 2015.
- We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
Timeline
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Sources & verification
Official CIPO records
Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.