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 interesting automotive alarm was found in a 90's Popular Electronics. The circuit uses...
Using the 4001 integrated circuit, this latching relay can employ any general-purpose transistor. The...
The PA222 integrated circuit used in this project from an American 1967 documentation is not...