| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress excessive stacks of a DSU 15 without being burnt out even if various surges intrude. <P>SOLUTION: A triac Tr comprising a T1 terminal, a T2 terminal and G (gate) terminal is provided, the T1 terminal and the G terminal are connected to a communication line L, and in a communication line between the T1 terminal and the G terminal, protection units 11, 12 each comprising a resistor R for converting a current flowing in the communication line into a voltage are provided, and T2 terminals of triacs Tr1, Tr2 of the protection units 11, 12 are connected. If a surge current intruding via a communication line L1 or L2 is a predetermined current value smaller than a limit current value of an overcurrent limiter 14, the triacs Tr1, Tr2 are turned on by voltages generated by resistors R1, R2, and the surge current flows from the communication line L1 to the communication line L2. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
