PURPOSE: To obtain highly reliable checking device prevented from the miss of checking with a simple constitution by using a display element having a storing property and utilizing said property.
CONSTITUTION: Since V1>V2 is formed during the period the voltage of a battery is changed in a range exceeding a prescribed value V0 fixed by the relation of reference voltage V2 and the resistance values of R1, R2, a transistor (TR) Q5 is turned off and an ECD is held at decolored state. When the battery is consumed and the voltage is reduced less than V0 at the time of t0, V1<V2 is formed only for the short moment and the TRQ5 is turned on. Consequently, the ECD is charged and colored. Then the current consumption is turned to the original state and the voltage V of the battery is restored, but the color is left as it is because of the storing property and the time to replace the battery (or charging time) is displayed. If the voltage of the battery is being reduced without restration, the TRQ5 is turned off before the dilution of the colored density, so that the colored state is held.
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