We find this circuit in an old documentation, but it can be made using modern transistors. The circuit trips, producing a continuous sound when the sensor is wet. The 1 mOhm resistor is actually 1 Mohm.
Found in a Popular Electronics from the 90s, this circuit uses components that are still current....
This circuit uses an operational that is not currently common. We found it in an old American...
This circuit was obtained from an Electronics World of 1968. The transistor may be general purpose and...