The circuit shown indicates voltages from 10 to 14 V used to monitor automotive voltage. One or two LEDs light up depending on the voltage.
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...