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 circuit was found in a 1975 documentation. Current general-purpose transistors can be used,...
We found this circuit in a publication for radio amateurs in 1974. The bipolar transistors can be...
This conventional humidity or water alarm circuit was found in an English documentation from 1974....