Patent · US Expired

Line status apparatus for telephones

US4169217A · kind A · utility

20Cited by

3References

10Claims

0Family size

Assignee

Nortel Networks Limited · CA

Inventors

Attila J. Szanto · Ottawa, CA
Garth D. Hillman · Lakeway, US
Edward C. Carew · Carleton Place, CA

Key dates

Filing date	Feb 27, 1978
Grant date	Sep 25, 1979
Priority date	—
Expiry date	Feb 27, 1998

Classification

Technology area (CPC H)Electricity
CPC primaryH04Q5/00
WIPO fieldTelecommunications
WIPO sectorElectrical engineering

Abstract

In a telephone installation in which more than one telephone terminal is connected to one pair of conductors--Tip and Ring--a line status apparatus is provided for each telephone terminal, the apparatus sensing a change in line characteristics resulting from an "off-hook" condition at any telephone and producing an output which is used to provide an indication. Little or no current is drawn from the telephone lines. Typical examples are sensing variations in AC characteristics, as resulting from voice transmission, ringing tones and the like; sensing DC variations, such as voltage drop when a telephone is "off-hook". Indication is generally visual.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.