AN APPARATUS FOR PROTECTING A SUBSCRIBER LINE INTERFACE CIRCUIT AGAINST OVERVOLTAGES

摘要

An apparatus for protecting a subscriber line interface circuit against overvoltages occurring on its two input wires and exceeding the voltage of the supply voltage source of the subscriber line interface circuit. A resistor is connected in series with a respective input wire to respective input terminals of the subscriber line interface circuit. Each input terminal is connected to the anode of a respective first diode, whose cathode is connected to the positive terminal of the supply voltage source, and also to the cathode of a respective second diode. The anodes of the second diodes are connected to the cathode of a thyristor which is common to the second diodes. The anode of the thyristor is connected to the positive terminal of the supply voltage source and the gate of the thyristor is connected to the negative terminal of the supply voltage source.