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 simple robot circuit was found in a Radio Electronics from the 90s. The components are...
In the figure we have the basic application of an LM3900 transconductance amplifier, as suggested by...
A fine adjustment of the output voltage of a power source is achieved with this circuit, which...