Patent ID: 8406417

Claim:
A line card, comprising: a subscriber line interface circuit having a first input terminal operable to receive power at a first reference voltage; an interface line coupled to the subscriber line interface circuit for interfacing with a subscriber line external to the line card; a first overvoltage protector coupled to the interface line and referenced to the first reference voltage to provide overvoltage protection responsive to a voltage on the interface line exceeding the first reference voltage by a first predetermined threshold; and a power sink coupled to the interface line and arranged to provide a bypass path to ground for current up to a predetermined current limit responsive to a voltage on the interface line exceeding the first reference voltage prior to exceeding the first predetermined threshold, said power sink comprising; a power transistor coupled between the interface line and ground; a limiting resistor in series with the power transistor; and a bias circuit coupled to a sate of the power transistor, wherein said predetermined current limit is a function of the value of said limiting resistor.