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When a mechanical power switch is operated, the power is not available instantly. The switch contacts bounce, giving a series of pulses, as shown in the graph. The circuit may see these as a series of logic pulses and behave incorrectly. The circuit shown prevents this. If we revise the SET/RESET flip-flop, we will recall that once Q has been pulsed high by the SET input, further pulsing produces no change at Q. Therefore Q only recognises the first pulse from the bouncing switch and ignores any others. Similarly, when Q is taken low by taking RESET high, only the first pulse is recognised. |
