Patent ID: 6472992
Filing Date: 2002-10-29
Classification: H04L,H04M

Abstract:
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.