The principle used in this electronic head or tail circuit is simple: a multivibrator controls a flip flop. The multivibrator oscillates as long as the buton S1 is pressed and the flip flop switches on and off with a frequency of several kilohertz. When the button is released, a +5 volts is set at one of the two gates that makes up th multivibrator. The flip flop latches on at one of the two possible states: “head” or “tail”.
The state of the flip flop is dependent on the exact time when the button S1 was released. because the speed of the flip flop’s switch overs and the relative inertia of the human reaction, the state at which the flip flop latch is random.
The entire circuit is made up of a single 7400 IC. It is important to decouple the circuit and the display bulbs very well to avoid reverse voltages and currents that appear during the switching off of the display bulbs.
The capacitor C5 (not shown in the schematic diagram) is a 250 uF electrolytic capacitor rated at 10 volts.