Patent ID: 7106573

Claim:
A protection circuit for a telecommunication device that communicates over a twisted-pair telephone line having a first line and a second line, the protection circuit comprising: a transformer having a primary winding and a secondary winding, the primary winding having a first portion and a second portion, wherein the first portion is coupled to a first line terminal adapted to couple the protection circuit to the first line, and the second portion is coupled to a second line terminal adapted to couple the protection circuit to the second line; a capacitor connected in series between the first portion of the primary winding and the second portion of the primary winding; a first voltage controlled device coupled to the first line terminal and a ground terminal, wherein the first voltage controlled device has a first threshold turn-on voltage at which the first voltage controlled device provides a first current path from the first line terminal to the ground terminal; and a second voltage controlled device coupled across the capacitor, wherein the second voltage controlled device has a second threshold turn-on voltage at which the second voltage controlled device provides a second current path from a first capacitor terminal of the capacitor to a second capacitor terminal of the capacitor; and wherein the second threshold turn-on voltage is lower than the first threshold turn-on voltage.