| 摘要 |
PROBLEM TO BE SOLVED: To provide a protection circuit which can protect circuit patterns on a printed circuit board and circuits without burning out, even when an overcurrent is applied through a communications line. SOLUTION: In a protection circuit, provided between an telephone line and an exchange and having an arrester 21 to protect an exchange by making the overcurrent flow to the ground when an overvoltage is applied to an telephone line, switches 31a, 31b are turned off to cut off to separate the operating arrester 21 and the exchange 13 from the line 12, so as no to form a circuit to the arrester 21, when the arrester 21 exceeds a prescribed temperature. |
