According to the property that the capacitor voltage will not change suddenly, the rising edge of Uc 1 will slow down, that is, the level of logic 1 will be moved back. 74HC 14 is an inverter with Schmidt input, and the two-stage series logic remains unchanged.

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The function of the whole circuit is signal delay, and the delay time is determined by the capacitor, so the series resistance cannot be increased, and the logic level when the input signal is low can not be guaranteed if it is too large.