Protective device and communication device

摘要

An apparatus to indicate a state where a communication device connected to a communication wire and a power line is protected from a surge current. A toroidal coil picks up a rapid increase of current caused by a rapid increase of voltage that occurs in the communication wire and/or the power line. The toroidal coil is connected to the current detecting unit. The current detecting unit converts the current from the toroidal coil into a voltage and supplies it to a switching circuit. The switching circuit turns on an indicator light circuit to light up an LED of the indicator light circuit.