| 摘要 |
<p>There are first and second transmission lines equipped with line repeaters, selective filter circuits (1H) and a test signal transmission means (34). A common fault localisation line (32) is connected to a signal output of each of the frequency selective filter circuits. Each of the frequency selective filter circuits may select the output of one or another of the line repeater pairs which are connected in response to the supply voltage polarity connected to the common fault localisation line. The filter circuits each has a means of control (12L) for actuating the circuits of a group only when the supply voltage is less than a selected value, and to actuate the circuits of the other group only when supply voltage is greater than the selected value.</p> |
