Patent ID: 6088446
Filing Date: 2000-07-11
Classification: H04M

Abstract:
Protection circuitry for use in a telephone device having line interface circuitry including DC-holding circuitry adapted to be coupled to a telephone line, the protection circuitry comprising:a hook switch that selectively places the telephone device in an on-hook state or an off-hook state, the protection circuitry and DC-holding circuitry being inactive when the telephone device is in the on-hook state;voltage sensing circuitry coupled across the telephone line and connected to the DC-holding circuitry, the voltage sensing circuitry indicating an over-voltage condition on the telephone line when the telephone device is in the off-hook state and the voltage on the telephone line exceeds a predetermined voltage level; andswitching circuitry coupled to the voltage sensing circuitry, the switching circuitry switching from an OFF state to an active state when the over-voltage condition is indicated, wherein current is directed away from the DC-holding circuitry when the switching circuitry is in the active state.