Instead of going with a microcontroller he built the circuit around a 555 timer. What he really needed in this case is a flip-flop but lacking a chip for that he went with the 555 because it has ...
The JK flip-flop is an improvement on the SR flip-flop where S=R=1 is not a problem. JK Flip Flop Circuit The input condition of J=K=1 gives an output inverting the output state. However, the outputs ...