Leak Detector (CB22456E)

We found this circuit in a Popular Electronics from 1992. The transistor is general purpose, assuming equivalent.

Self-biasing JFET stage (CB25566E)
This circuit was found in Electronics Now magazine and can be applied to any JFET. The circuit has high...
Low Power Alarm (CB538E)
When this alarm is off current drained is very low, only about 60 µA. The circuit can be powered...
VU-Meter (CB10589E)
This circuit was published in an English magazine from 1977, but it can be easily assembled since...