SURGE PROTECTION UNIT AND PROTECTOR

PROBLEM TO BE SOLVED: To provide a surge protection unit which can block a lightning surge. SOLUTION: This surge protection unit is provided behind a protector or in a protector. A balance/unbalance converter 14 is connected to an apparatus terminal 11 of the surge protection unit 10 and a balance/unbalance converter 13 is connected to the circuit terminal 12 of the surge protection unit 10. A high-pass filter 15 having capacitors 17a and 17b is provided between the balance/unbalance converters 13 and 14. With such a constitution, a surge does not flow into a protector earth via a customer terminal apparatus. The customer terminal apparatus is, therefore, protected from the surge. As the capacitors 17a and 17b are provided between two lines of a balanced line, they do not need high dielectric strengths. COPYRIGHT: (C)2003,JPO