Photoelectric alarm (CB23798E)

This simple passage alarm is powered by the power grid using an LDR as a sensor. The circuit is from a February 1962 Radio Electronics magazine.

PH meter (CB5324E)
This circuit is from an 80's documentation. The circuit makes use of a component of the era, the...
1-and-a-half-minute delay (CB13951E)
This circuit is from an old 1974 documentation. The circuit can be used to obtain longer...
Negative voltage converter (CB20669E)
We found this circuit in a Maxim documentation from the 90s. This circuit provides a negative...