Found in a 1968 Novel Electronics Circuit, this circuit compares two light intensities using common LDRs as sensors. Transistors can be modern PNP equivalents.
I found this circuit in a 1980 documentation, but it can be easily assembled with BC548...
We found this alarm in an English publication from 1978. Although the original power supply is 3...
Found in old documentation, this circuit can use modern equivalent components. The signal has good...