This circuit was published in a 90s Radio Electronics. The circuit uses the well-known LM386 that appears in a large number of projects on this site.
In the figure we have the way to obtain an adjustable 1 to 10 mAconstant current source. The...
We found this circuit in an old General Electric documentation. In fact, PUTs are not common...
This alarm uses several sensors that directly trigger a sensitive relay. A larger relay can be...