Telephone intercom device
CA 1307602 C · Owner: Pami Enterprises · Inventors: Kirby, William Albert
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A telephone intercom device utilises a pair of conductors connected between telephones but not to an external line. The intercom device connects the telephone to either the external line or the other telephones by a mode selection switch that is operated by a relay. The relay is energised by a manual switch connected in parallel to the telephone to attain the intercom mode and held in the intercom mode by a holding circuit that includes the switch associated with the telephone handset. Replacement of the handset. opens the holding circuit and causes the mode selection switch to revert to the external lines. The holding circuit is not functional until the mode selection switch is once again …
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
- Granted September 15, 1992. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended September 15, 2009.
- 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.