Method and apparatus for detecting underground utility conveyances
CA 2205544 C · Owner: At&T Corp. · Inventors: Huffman, John Sinclair; Eslambolchi, Hossein
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
An underground utility conveyance may be precisely located by impressing both a locating signal and a confirmation tone on the conveyance. The locating signal, comprises an RF signal that produces a first field that radiates above the earth that is, sensed by a first, above-ground signal detector to establish the general location of the, conveyance. The confirmation tone comprises a near-DC signal that produces a second, field having a relatively limited radiation path. A second detector is inserted into the, earth at successive places in the region where the conveyance is located to establish its, precise location.
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 23, 1996 and granted December 12, 2000. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended September 23, 2016.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by September 23, 2018.
- 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.