Telephone line interface circuit
CA 2016258 C · Owner: Kabushiki Kaisha Toshiba · Inventors: Kimura, Setsuo; Tsurusaki, Masayuki
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A telephone line interface circuit for connecting telephone equipment provided with internal speech lines having predetermined DC impedance to external telephone lines, comprising a rectifying circuit connected with the telephone lines for rectifying the DC voltage coming from the telephone lines; a dial pulse sending circuit which makes connection and disconnection between the output terminals of the rectifying circuit and the internal speech lines for sending dial pulses to the telephone lines; and a polarity inversion detecting circuit which discriminates the voltage relationship between the telephone lines and the internal speech lines for detecting the polarity inversion of the DC …
Read the whole patent
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 May 8, 1990 and granted July 12, 1994. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended May 8, 2010.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by May 8, 2012.
- 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.