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.
It is a simple blinker that simulates the action of an alarm when installed on the dashboard of a...
The circuit is from a 1978 publication and the transistor may be the BC558. The transformer is...
This simple unregulated circuit was found in a Radio Electronics from June 1964. Note that the...