1978-02-27
1979-09-25
Claffy, Kathleen H.
179 81E, H04M 100, H04M 168
Patent
active
041692179
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.
REFERENCES:
patent: 2496642 (1950-02-01), Shann
patent: 3899644 (1975-08-01), Hunt
patent: 3961142 (1976-06-01), Caffine
Carew Edward C.
Hillman Garth D.
Szanto Attila J.
Claffy Kathleen H.
Jelly Sidney T.
Northern Telecom Limited
Popek Joseph A.
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