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 current monitor can operate on 500V circuits. The circuit is suggested by a 2005 Linear...
This circuit was found in a Popular Electronics of the 90s. The output amplitude will be between...
This circuit uses two transistors, the low noise BC549. Its quality is very good and it has a...