PURPOSE: To announce that disconnection is caused even after connection of a coil is restored by judging the disconnection of a relay coil by an operating voltage detecting result and a coil current breaking result, and continuously lighting a judged result on an indicating lamp.

CONSTITUTION: Contact points 11 and 12 are opened through operation of a sequence circuit, and when a coil of a U relay 13 is normally connected, an exciting current flows to an X relay 5, and it is energized, and the exciting current also flows to a Y realy 7, and it is energized. Then, since an (a) contact point Ya of the relay 7 is closed and an (a) contact point Xb of a relay 9 is opened, the Z relay 9 is not energized, and an indicating lamp 10 is not lighted. Here, when disconnection is caused in the coil of the relay 13, the relay 5 is deenergized, but the exciting current continuously flows to the relay 7 through the contact points 11 and 12, and the indicating lamp 10 is lighted. Next, when the contact points 11 and 12 are opened, the relay 7 is opened, but since the relay 9 self holds by closing of an (a) contact point Za, the indicating lamp 10 is lighted as it is. Therefore, the fact that the disconnection is restored is announced by lighting of the indicating lamp 10.