This simple rain, leak or moisture detector circuit appears in other places on this site with slight variations. This was obtained in an English documentation from the 70s.
We found this amplifier for automotive use in the Philips integrated circuit manual from 1990. The...
This interesting circuit records a few seconds of audio signals, reproducing them in a small...
Settings like this can be found at various points on this site. The trigger door can be a 4093...