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.
This is a circuit that should not be used for readers interested in a fair game. The circuit...
This circuit has a general-purpose transistor to compensate for the non-linearity of the generated...
This circuit was found the Optoelectronics Sourcebook by Texas Instruments. Any phototransistor...