Dial tone detector
CA 1259146 A · Owner: Nortel Networks Corporation · Inventors: Brown, Anthony K.D.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
Abstract of the Disclosure A dial tone detector of improved performance is provided by precise definition of a passband. In one example virtually infinite roll off is achieved in less than 5 hertz. An incoming analog signal of at least a predetermined amplitude is limited to produce square wave pulses which are counted in a first counter over a period of time determined by a periodic RESET signal. A READ signal occuring just before the RESET signal causes either a valid count state or an invalid count state to be stored depending upon the value of the count in the first counter. When a valid count state is in storage, a second counter counts timing pulses while the valid count state …
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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 September 5, 1989. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended September 5, 2006.
- 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.