The pushbutton or toggle switch is a simple form of data entry into a
digital system.
However, a problem occurs since the normal human reaction time is about
s and digital electronics responds to times of the order of
s.
Thus any unnoticed mechanical contact bounce of a few milliseconds
will be seen as several distinct switch closures by a digital system.
We may de-bounce the mechanical switch by using an RC circuit and
Schmitt trigger logic or a flip-flop latch.
The latter design requires a break-before-make action, which means
that during the throw there is a time when the common is connected to
neither terminal.