This simple circuit, found in American documentation, uses only one relay that locks when any of the sensors is activated. To reset, simply turn off the power for a moment.
I got this circuit from an English magazine from 1977. It can still be easily assembled, as the...
This simple lie detector was found in Popular Electronics. Transistors are commonly used. The...
Found in a 1980 documentation, this circuit drives a transducer (X1) when the car battery has its...