| 摘要 |
PURPOSE:To accurately display the clogging of a filter by providing a power source holding means made up from a diode and a condenser in a counter circuit and holding the circuit in a state where counting is stopped when the power source is down. CONSTITUTION:After a counter IC9 counts a predetermined frequency by receiving a pulse from a pulse oscillating circuit 1 at a CLK terminal, the counter IC9 puts an output terminal Q into a high level. A power source holding circuit 2 consisting of a diode 10 and condenser 11 is connected to a power source terminal VD. The display circuit 3 makes a transistor 14 conductive by the putput voltage of the counter IC9 and lights a liminous diode 13 to display the lapse of a predetermined time of the operation of the blower. When the power source is down while counting, a discharge current is supplied from the condenser 11 to the counter IC9, and the counter IC9 is held in a state where the counting is stopped. The counting is continued again by the recovery of the power source. Hence, counting of time is accurately performed.
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