Tone calling with single sideband radio equipment
CA 1049616 A · Owner: Hindson, William D. · Inventors: Hindson, William D.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
Tone calling equipment for radio telephones employing a single sideband radio frequency transmitter to transmit a double tone signal comprising two precisely spaced side tones. These side tones are at frequencies fc + f1 and fc - f1, produced by modulating an audio tone f1 on a subcarrier audio signal at fc. The two side tones are modulated by a single sideband transmitter onto a radio frequency (RF) signal and are then both transmitted. At a single sideband RF receiver the two side, tones are received as an RF signal. The absolute value of this signal may vary, but the two side tones are separated by precisely 2f1. The difference 2f1 between the two side tones is detected thus eliminating, …
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 February 27, 1979. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended February 27, 1996.
- 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.