This circuit was found in an Australian publication from 1991. It is a transmitter that transmits a signal when it detects moisture. The range is on the order of a few tens of meters.
We found this circuit in a 1979 documentation, but it can be changed to use more modern...
This balance control for the channels of a stereo system was found in a 1969 Mullard...
This circuit is based on the 3 A LM350. The circuit is from Popular Electronics having a...