PURPOSE: To contrive discrimination in error not to be generated from a logic discriminating circuit due to the disconnection or the like of a connecting cable or the like, by monitoring the working state of a section switch contact with the exsistence of current flowing through an electromagnetic coil.
CONSTITUTION: When the operating section 7 of a sub station 2 is set to be in an ON-operation state by command from a parent station, then its information is transmitted to a logic discriminating circuit 8. As its result, from the logic discriminating circuit 8, the output of signal for exciting the making coil 10 of a making relay 9 as output for closing a main contact 3 is generated, and a making contact 11 is closed. From a controlling power source 6, current flows to a connecting cable 5 via the making contact 11 and a current detection circuit 13, and an electromagnetic coil 4 is energized, and the main contact 3 is closed. At the same time, by the current detection circuit 13, it is detected that current flows into the connecting cable 5, and its fact is fed back and is reported to the logic discriminating circuit 8. Then, by the logic discriminating circuit 8, it is discriminated that the main contact 3 is closed.
MIYATA TOSHIAKI
TSUKADA MASAO
UEYASU RYUJI
NISHIKAWA TAKATSUGU
KANEDA AKIRA
FUJI ELECTRIC CO LTD
TOSHIBA CORP
MITSUBISHI ELECTRIC CORP
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