RS flip-flop

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The RS flip-flop made of two NAND logic gates is an asynchronous circuit. The flip-flop has two outputs: a simple Q and a negated nQ. Its S (Set) and R (Reset) inputs can be fed logical states 0 (LOW) or 1 (HIGH). The S input sets the outputs to the active state, the R input resets the flip-flop's outputs. The state in which both inputs are high is a forbidden state.

Switch S            Switch R

LOW (green) = 0,    HIGH red) = 1.
Clicking on the S/R input wheel also toggles the input state of the flip-flop.