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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.
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