| 摘要 |
PURPOSE:To decrease power consumption, to extend battery life, to increase the reliability of a counter, etc., and to facilitate maintenance by enlarging the resistance value of a pull-up resistance when a digital filter detects the electrification. CONSTITUTION:When a ground signal is inputted from an input terminal, this is successively shifted to respective flip-flops of a shift register circuit 19 by the generation timing of a clock signal. When the ground condition continues while the prescribed number of the clock signals is generated. A first logical gate 21 sets a flip-flop 23 for output and generates the deciding output of the ground detection. On the other hand, when the flip-flop 23 for output comes to a set condition, a resetting output is eliminated, the resistance value of a pull-up resistance circuit 17 is increased, and as the result, the current supplied through an input terminal to an external contact is decreased. Since the condition to detect the high impedance of the input terminal is entered at the conducting condition of a small current pulse, a battery exhaustion can be significantly decreased.
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