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Expired Canadian patentCanada

Control circuit initiating conduction of an opto- isolator unit

CA 1089939 A · Owner: Westinghouse Electric Corporation · Inventors: Fox, David A.; Apfelbeck, Otto L.

CIPO record

Overview

Drawings and full text

Its claims, description and drawings are in the Canadian Patents Database.

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Abstract From the Canadian patent

A control circuit for turning on an optical isolation unit only when an input signal is at least of a given magnitude or threshold level. The circuit exhibits a resistive input below the threshold level and a constant current characteristic above the threshold. An arrangement of transistors is provided to bypass the opto-isolator below the threshold and to drive the opto-isolator with substantially constant current above the threshold.

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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 November 18, 1980. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended November 18, 1997.
  • We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
FiledMay 16, 1977
GrantedNovember 18, 1980
Term endedNovember 18, 1997
Patent numberCA 1089939 A
Classification (IPC)H03K5/08 +2 more

Timeline

Timeline From CIPO dates

1978198019821984198619881990199219941996Application filedMay 16, 1977Patent grantedNov 18, 1980Term endedNov 18, 1997

Sources & verification

Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.