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.
This simple continuity tester consists of an oscillator found in the 1983 Electronics Experimenter Special...
This circuit was found in Radio Electronics magazine from October 1964. The circuit uses two...
This single integrated circuit receiver was found in the 1992 edition of the Electronics...