Impedance blocking filter circuit

Abstract

An impedance blocking filter circuit is provided for use in telecommunication systems for interconnecting between incoming telephone lines and customer's terminal equipment so as to unconditionally block impedances above 20 KHz due to the customer's terminal equipment from an ADSL network unit and / or home networking interface unit. The filter circuit includes first, second, and third inductors connected in series between a first input terminal and a first common point. A first resistor has its one end connected also to the first common point and its other end connected to a first output terminal. Fourth, fifth and sixth inductors are connected in series between a second input terminal and a second common point. A second resistor has its one end also connected to the second common point and its other end connected to a second output terminal. A capacitor has its ends connected across the first and second common points. In another aspect, the filter circuit also includes current limiting protection circuitry for reducing ring trip, dial pulse and off-hook transient current spikes.

Description

PRIORITY AND RELATED APPLICATIONS[0001]The present reissue application is a continuation application of prior application Ser. No. 10 / 366,656 filed Feb. 12, 2003 of the same title, now U.S. Pat. No. Re. 41,145, which is a reissue of application Ser. No. 09 / 195,522 filed Nov. 19, 1998, now U.S. Pat. No. 6,188,750 issued Feb. 13, 2001 of the same title, each of the foregoing incorporated by reference herein in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates generally to telecommunication systems and more particularly, it relates to an impedance blocking filter circuit used in telecommunication systems for interconnecting between incoming telephone lines from a telephone company's central office (C.O.) and subscriber or customer telephone equipment such as a telephone set located at a subscriber's premises so as to unconditionally block telephone impedance above 20 KHz.[0004]2. Description of the Prior Art[0005]The prior art appears t...

AI Technical Summary

Benefits of technology

[0012]Accordingly, it is a general object of the present invention to provide an impedance blocking filter circuit which effectively and efficiently eliminates ADSL interference caused by telephone terminal equipment.

[0015]It is still another object of the present invention to provide an impedance blocking filter circuit which is of a modular design so as to be easily connected in series with the offending telephone terminal equipment.

Problems solved by technology

However, since one or more telephone subscriber terminal equipment such as telephone sets, facsimile machines and / or answering devices are also connected to the same incoming telephone lines via internal house wiring, ADSL interference problems may be caused by the terminal equipment which can significantly limit or reduce the data rate.

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