This circuit was found in a 1985 documentation. It provides an audiovisual indication of the presence of moisture or water in the sensor. The circuit can be powered by voltages from 6 to 9 V.
We found this circuit in the October 1991 issue of Radio Electronics magazine. The circuit uses...
This sinusoidal oscillator was found in the 1993 Linear Interface ICs by Motorola. Other series...
We found this circuit in a Motorola documentation from 1978. The circuit is based on the LM324...