Telephone line overvoltage protection method and apparatus

摘要

A telephone line overvoltage protection method and device are provided. An overvoltage protection apparatus used with a pair of telephone lines includes first voltage clamping circuitry for clamping voltage signals on the lines at a first predetermined voltage potential; second voltage clamping circuitry for clamping voltage signals on the lines at a second predetermined voltage potential. The second voltage clamping circuitry includes filter circuitry for filtering the voltage signals when the voltage signals exceed the second predetermined voltage signals. The first voltage clamping circuitry is formed by a solid state protective device and a failure mode mechanism adapted for connecting the lines to ground responsive to increased temperature of the solid state protective device.