The circuit has a fairly simple explanation. U1 is a counter. Figure 1 A Flip ON Flop OFF circuit for DC voltages. The gadget is connected to the output terminals of the PB. With an adequate heat sink ...

Impulse relay turns on with an electrical impulse at the control input and turns off again with another impulse.

Figure 1 F1a regeneratively debounces S1 so F1b can flip ON and flop OFF reliably. An (almost) universal truth about mechanical switches, unless they’re the (rare) mercury-wetted type, is contact ...