Vital railway signal link with photo-emission means
CA 2094227 C · Owner: Union Switch & Signal Inc. · Inventors: Capan, Ronald R.; Mokkapati, Chinnarao
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A vital railway signal link for passing DC signals between a first terminal location and a second terminal location. A transmitter at the first terminal location receives a DC input signal and responsively produces a light signal modulated at a preselected frequency. The light signal is conducted through an optical fiber to the second terminal location. There, a receiver detects the light signal and produces a DC output signal. The receiver contains discriminator circuitry preferably including a bandpass filter to prevent light signals other than those modulated at the preselected frequency from giving an output signal.
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 April 16, 1993 and granted March 4, 1997. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended April 16, 2013.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by April 16, 2015.
- 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.