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 ...

If you need a circuit that converts a momentary push button to a latching switch with low standby current, this design might suit your needs.

Even today, for some applications it is hard to beat the ubiquitous 555 timer IC. It is cheap ... one or two transistors, a flip flop and an inverter. The idea is you use a capacitor to charge ...

Turn power on and off with a minimal switch or even no switch at all by adding a flip-flop to a SPST for a classic push-on, push-off Continue Reading ...

Figure 4 and 5 represent the transistor level schematic that show how a typical asynchronous RESET type flip-flop can be converted into the proposed circuit which can function as either RESET or SET ...