Telephonic communications – Transmission line conditioning – Interference suppression
Patent
1995-03-03
1997-06-24
Zele, Krista M.
Telephonic communications
Transmission line conditioning
Interference suppression
379399, 379414, 379412, 379429, 455296, H04M 174, H04B 110
Patent
active
056424167
ABSTRACT:
An electromagnetic interference by-pass filtering mechanism suppresses RF noise currents conducted over the tip and ring leads of a telephone line-powered telephone instrument. Such RF noise currents may result from amplitude modulated radio broadcast signals emanating in the vicinity of the telephone instrument. The filtering mechanism comprises a conductive material coated on the interior surface of the housing of the telephone instrument, so as to surround the printed circuit board containing the telephone circuitry of the instrument. The conductive material is coupled to earth. First and second capacitors are coupled between the tip and ring leads and the conductive material, and first and second inductors are coupled in series with the tip and ring conductors and connections of the tip and ring conductors to the printed circuit board containing the telephone circuitry.
REFERENCES:
patent: 1949996 (1934-03-01), Fleming
patent: 2136659 (1938-11-01), Wood
patent: 4738638 (1988-04-01), Bogese, II
patent: 4876713 (1989-10-01), Crosby et al.
patent: 5073924 (1991-12-01), Frisby
patent: 5271056 (1993-12-01), Pesola et al.
patent: 5490030 (1996-02-01), Taylor et al.
patent: 5557653 (1996-09-01), Paterson et al.
Hill Ralph Leon
Pratt Noel C.
Harris Corporation
Kumar Devendra T.
Wands Charles E.
Zele Krista M.
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