A power redundant system and its protection circuit is configured to have a second circuit unit receiving electricity from a first circuit unit through a power loop. An isolation switch is connected in series with the power loop. An electrical detection un...

An input means inputs, at intervals of a unit time, a current which is supplied from a substation. A first calculation means calculates a current variation amount per the unit time, based on the current which is input at the intervals of the unit time. A h...

The present invention concern a method and an apparatus for stabilizing power supply to a connection device, such as an ONU. The power is supplied via wires, such as telephone wires, using DC voltage and the wires having a first conductor, such as a ring c...

A temperature sensor (50) detects temperature on a zero-phase current transformer or ambient temperature in the vicinity of the zero-phase current transformer. A microcomputer (17) corrects the current difference output from the zero-phase current transfor...