Telephone tone detector
CA 1268570 C · Owner: Roberts, Melvin J. · Inventors: Roberts, Melvin J.; Dea, Frank Y.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A tone detector comprising means for detecting multi-frequency dialing (DTMF) signals applied to an input terminal and for generating a "DTMF present" indicating signal, and means for detecting the presence of supervisory signals applied to the input terminal and for generating a "supervisory signal present" indicating signal. The dialing tones are converted to digital value signals and are preferably stored in a shift register. The digital value signals and the supervisory signals are applied in serial form to an output terminal. The "DTMF present" indicating signal is applied to a "DTMF present" terminal. Accordingly the presence of the "DTMF present" indicating signal can be monitored …
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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
- Granted May 1, 1990. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended May 1, 2007.
- 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
Timeline From CIPO dates
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.