| 摘要 |
The apparatus for separating the desired line like a control or communication line for testing the line state includes a nonlinear element (3) which is turned on by certain voltage level being higher than the normal one, a relay (2) of which contacts (C1,C2) are connected to contacts (a1,a2) in normal state. For testing the line, the master station provides higher voltage than normal one between line (l2) and earth (E) termals. Then the device (3) is turned on and the relay is switched to contacts (b1,b2) to check the line-line or line-earth resistance.
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