Maintenance termination unit for isdn
CA 2077992 C · Owner: American Telephone And Telegraph Company · Inventors: Debalko, George Andrew
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
Disclosed is a Maintenance Termination Unit (MTU) for an Integrated Services Digital Network (ISDN). A tone ringer is provided at the end of the customer loop to generate an AC signal. The signal is applied through a transformer and rectifier to charge a capacitor. The resulting voltage across the capacitor causes a normally closed MOS switch to open and disconnect the customer until the capacitor discharges.
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 September 10, 1992 and granted April 21, 1998. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended September 10, 2012.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by September 10, 2014.
- 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.