In the figure we have the way to control a flip-flop with the 4069 from positive pulses. The circuit can be used as a shield, if powered by 5 V.
This polarity test or indicator indicates the polarity of a power line by LEDs. The circuit is...
This is the circuit of a digital clock published in the January 1975 issue of Radio Electronics magazine....
Found in an Elektor from the 90s, this circuit can be powered directly by the power grid. The...