This circuit is valid for other comparators of the same series. In this case, a lamp is excited, but an LED can be used in series with a resistor or other load. The transistor admits equivalent.
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....