Digitally synthesized touch-tone audio signal generator
CA 1106088 A · Owner: Fairchild Camera Anmd Instrument Corporation · Inventors: Lake, Don W.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A solid state signal generator for producing frequency combinations such as used in telephone touch-tone systems. The output of a crystal oscillator is divided to obtain binary signals proportional to the selected pairs of the seven touch-tone frequencies. These signals are scaled with selected binary output signals generated by a free-running pattern generator and representing slopes at various points on a sine wave to produce a binary signal stream that is applied to a controlled charge digital-to-analog conversion circuit that partially charges or discharges a capacitor in accordance with the binary 1's and 0's to produce an output waveform across the capacitor that corresponds to the …
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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 July 28, 1981. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended July 28, 1998.
- 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.