US 6,472,992 B1 · Alarm filter circuit

Abstract

An alarm filter circuit used in telecommunication systems for interconnecting between incoming telephone lines and alarm unit located at a subscriber's premises so as to block DSL data signals to and from the alarm unit for preventing interference is provided. In one preferred embodiment, the alarm filter circuit includes a second-order low-pass filter section for blocking the DSL data signals to and from the alarm unit, a first-order high-pass filter section for bypassing the DSL data signals on the incoming telephone lines to the house wiring, and a first-order low-pass filter section for blocking high-frequency signals between the house wiring and the alarm unit. In a second embodiment, a fourth-order elliptical low-pass filter section replaces the second-order low-pass filter section. In a third embodiment, a third-order high-pass filter section replaces also the first-order high-pass filter section. In fourth through sixth embodiments, the first-order low-pass filter section is replaced by a second-order low-pass filter section. Further, the fourth through sixth embodiments includes surge protection circuitry for protecting the alarm unit from being damaged by transients.

Claims20

Dependent claims

An alarm filter circuit used in telecommunication systems for interconnecting between incoming telephone lines and an alarm unit located at a subscriber's premises so as to block DSL data signals to and from the alarm unit for preventing interference, said alarm filter circuit comprising:

a second-order low-pass filter section formed of a first inductor, a second inductor, and a first capacitor;
the first inductor having a first end and a second end;
the second inductor having a first end and a second end;
the first capacitor having a first end connected to said first end of said first inductor and to a first output terminal pin and having a second end connected to said first end of said second inductor and to a second output terminal pin;
a first-order high-pass filter section formed of second capacitor and a third capacitor;
the second capacitor having a first end connected to said second end of said first inductor and to a first input terminal pin and having a second end connected to a second input terminal pin;
the third capacitor having its first end connected to said second end of said second inductor and to a third input terminal pin and having its second end connected to a fourth input terminal pin;
a second-order low-pass filter section formed of third inductor, a fourth inductor and a fourth capacitor;
the third inductor having a first end connected also to said second end of said second capacitor and having a second end connected to one end of the fourth capacitor and a third output terminal pin;
and
the fourth inductor having a first end connected also to said second end of said third capacitor and having a second end connected to the other end of the fourth capacitor and a fourth output terminal pin.

8 more elements

a fourth-order elliptical low-pass filter section formed of first through fourth inductors and first through fourth capacitors;
the first inductor having a first end and a second end;
the second inductor having a first end and a second end;
the first capacitor having a first end connected to said first end of said first inductor and having a second end connected to said first end of said second inductor;
said third inductor and said second capacitor being connected in parallel and having its one end joined also to said first end of said first inductor and its other end joined to one end of said third capacitor and a first output terminal pin;
said fourth inductor and fourth capacitor being connected in parallel and having its one end joined also to said first end of said second inductor and its other end joined to the other end of said fourth capacitor and a second output terminal pin;
a first-order high-pass filter section formed of fifth capacitor and a sixth capacitor;
the fifth capacitor having a first end connected to said second end of said first inductor and to a first input terminal pin and having a second end connected to a second input terminal pin;
the sixth capacitor having its first end connected to said second end of said second inductor and to a third input terminal pin and having its second end connected to a fourth input terminal pin;
a second-order low-pass filter section formed of fifth inductor, a sixth inductor and a seventh capacitor;
the fifth inductor having a first end connected also to said second end of said fifth capacitor and having a second end connected to one end of the seventh capacitor and a third output terminal pin;
and
the sixth inductor having a first end connected also to said second end of said sixth capacitor and having a second end connected to the other end of the seventh capacitor and a fourth output terminal pin.

10 more elements

a fourth-order elliptical low-pass filter section formed of first through fourth inductors and first through fourth capacitors;
the first inductor having a first end and a second end;
the second inductor having a first end and a second end;
the first capacitor having a first end connected to said first end of said first inductor and having a second end connected to said first end of said second inductor;
said third inductor and said second capacitor being connected in parallel and having its one end joined also to said first end of said first inductor and its other end joined to one end of said third capacitor and a first output terminal pin;
said fourth inductor and fourth capacitor being connected in parallel and having its one end joined also to said first end of said second inductor and its other end joined to the other end of said fourth capacitor and a second output terminal pin;
a third-order high-pass filter section formed of fifth through eighth capacitors and a fifth inductor;
the fifth capacitor having a first end connected to a first input terminal pin and having a second end connected to a first end of said sixth capacitor and to a first end of said fifth inductor;
a second end of said sixth capacitor being connected to a second input terminal pin;
the seventh capacitor having its first end connected to a third input terminal pin and having its second end connected to a first end of said eighth capacitor and to a second end of said fifth inductor;
a second end of said eighth capacitor being connected to a fourth input terminal pin;
a second-order low-pass filter section formed of sixth inductor, a seventh inductor and a ninth capacitor;
the sixth inductor having a first end connected also to said second end of said fifth capacitor and having a second end connected to one end of said ninth capacitor and a third output terminal pin;
and
the seventh inductor having a first end connected also to said second end of said sixth capacitor and having a second end connected to the other end of said ninth capacitor and a fourth output terminal pin.

12 more elements

Dependencies are inferred from the claim text.

Alarm filter circuit

Life of this patent

Alarm filter circuit

Life of this patent

Abstract

Claims20