We found this circuit in an American documentation from the 80s. The integrated circuits are operational amplifiers of the time. We can test modern comparators like the LM339.
This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
The LEDs act as diodes, so if good they will show the same characteristic curve. Arrangment shown...
We found this circuit in an ancient American documentation. It can be adapted to operate in other...