| 摘要 |
PCT No. PCT/JP90/00036 Sec. 371 Date Sep. 19, 1990 Sec. 102(e) Date Sep. 19, 1990 PCT Filed Jan. 12, 1990 PCT Pub. No. WO90/08441 PCT Pub. Date Jul. 26, 1990.In a ground fault detector for long distance subscriber lines accommodated in a small capacity digital electronic exchange, a DC/DC converter for power supply is stopped during detection of ground fault. Upon reception of the stop signal, the DC/DC converter converts the power supply voltage for the subscribers to a voltage as the system power supply of the exchange, namely to a low voltage before voltage conversion of the DC/DC converter. The battery feed circuit can maintain the alarm condition, even if a current flows continuously to the battery feed resistor due to a ground fault, until the ground fault is recovered by the maintenance person without breaking the resistor.
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