Telephonic communications – Emergency or alarm communications – Personal monitoring
Reexamination Certificate
1998-11-19
2001-02-13
Kuntz, Curtis A. (Department: 2743)
Telephonic communications
Emergency or alarm communications
Personal monitoring
C379S090010, C379S412000, C333S167000, C333S177000, C375S219000, C375S220000
Reexamination Certificate
active
06188750
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
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.
2. Description of the Prior Art
The prior art appears to be best exemplified in the following U.S. Letters Patent which were developed in a search directed to the subject matter in this application:
4,613,732
4,823,383
4,742,541
5,642,416
4,743,999
5,802,170
In U.S. Pat. No. 4,823,383 issued to Cardot et al. on Apr. 18, 1989, there is disclosed a protection device for terminal equipment on telephone subscriber premises which includes a voltage surge protection circuit and/or a filter for providing protection against radio frequencies and interference. The filter is comprised of series inductors L1, L2, L3 and L5 interconnected between terminals E1 and S1 and series inductors L′1, L′2, L4 and L′5 interconnected between terminals E2 and S2. A capacitor C5 is connected between the junctions of the inductors L2, L3 and the inductors L′2, L4. The surge protection circuit includes thermistors TH1, TH2 and voltage limiters D1-D3.
In U.S. Pat. No. 5,802,170 issued to Smith et al. on Sep. 1, 1998, there is disclosed a customer bridge module for connecting telephone company wiring and subscriber telephone wiring in a telephone network interface apparatus. In one embodiment, the customer bridge module includes overcurrent protection and an RFI filter. The overcurrent protection is formed by positive temperature coefficient resistors 220, 222 and inductors. The RFI filter is formed by inductors 224
a-
224
c,
226
a-
226
c
and capacitors 236
a-
236
c.
The inductors and capacitors are used to form a multi-pole low pass filter.
In U.S. Pat. No. 5,642,416 issued to Hill et al. on Jun. 24, 1997, there is disclosed an electromagnetic interference by-pass filter which suppresses RF noise currents conducted over the tip and ring leads of a telephone line-powered instrument. The filter includes first and second inductors 51, 53 and first and second capacitors 41, 43.
It is generally well-known these days that many telephone subscribers or customers also have a personal computer located on their premises. At times, the computer user receives ADSL (an acronym for Asymmetric Digital Subscriber Line) signals from the Internet over the same telephone lines via an Internet Server Provider (ISP). In order to increase the speed of downloading of information from the Internet, an ADSL network interface is typically purchased and installed between the incoming telephone lines and the user's computer. 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. In one situation, it has been experienced that the change of state from “on-hook” to “off-hook” of the telephone equipment and sometimes the telephone terminal equipment even being “on-hook” can create a resonance effect to occur so as to drop the impedance value to less than 10 &OHgr;(Ohms) at a frequency as high as 500 KHz.
Accordingly, it would be desirable to provide an impedance blocking filter circuit for connection to the telephone terminal equipment causing the erratic input impedances. The impedance blocking filter circuit of the present invention is of a modular design so as to be easily connected in series with the offending telephone terminal equipment. The impedance blocking filter circuit blocks unconditionally any telephone impedances (e.g., open, short, capacitive, inductive, resonant, or any combination thereof) above the frequency of 20 KHz.
SUMMARY OF THE INVENTION
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.
It is an object of the present invention to provide an impedance blocking filter circuit for connection to telephone terminal equipment causing the erratic input impedances.
It is another object of the present invention to provide an impedance blocking filter circuit used in telecommunication systems for interconnecting between incoming telephone line and customer's terminal equipment so as to unconditionally block impedance above 20 KHz due to the customer's terminal equipment from an ADSL network interface unit and/or home networking interface unit.
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.
It is still yet another object of the present invention to provide an impedance blocking filter circuit which is comprised of six inductors, two resistors, and a capacitor.
In accordance with a preferred embodiment of the present invention, there is provided an impedance blocking filter circuit used 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 interface 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. The first inductor has its one end connected to the first input terminal and its other end connected to one end of the second inductor. The second inductor has its other end connected to one end of the third inductor. The third inductor has its other end connected to the first common point. A first resistor has its one end also connected to the first common point and its other end connected to a first output terminal.
The filter circuit further includes fourth, fifth and sixth inductors connected in series between a second input terminal and a second common point. The fourth inductor has its one end connected to the second input terminal and its other end connected to one end of the fifth inductor. The fifth inductor has its other end connected to one end of the sixth inductor. The sixth inductor has its other end connected to the 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 one end connected to the first common point and its other end connected to the second common point.
REFERENCES:
patent: 4667173 (1987-05-01), Okochi
patent: 4761623 (1988-08-01), Schneider
patent: 4823383 (1989-04-01), Cardot et al.
patent: 5077630 (1991-12-01), Bina
patent: 5623543 (1997-04-01), Cook
Chin Davis
Excelsus Technologies, Inc.
Kuntz Curtis A.
Tran Quoc D.
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