Calling circuit
CA 1088683 A · Owner: Nippon Tsu Shin Kogyo K.K. · Inventors: Kerman, Stephen E.; Tanaka, Yuji; Hamatani, Fumikazu
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
The diclosure is directed to a calling circuit which controls the connection of two different audio signal sources to a single audio signal transmission path for broadcasting the audio signals over a telephone set loudspeaker as well as controlling the illumination of indicators in the telephone set and at the main control circuit. Only four conductors are used to connect the telephone set with the main control circuit two of which are, power supply conductors which may supply other circuits as well.
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 October 28, 1980. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended October 28, 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.
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.