Poptronics recommends this circuit for use in the car when the headlights are left on. The circuit uses a sensitive relay with contact current according to the headlights.
This transistorized circuit is powered by a voltage of 6 to 12 V providing high voltage for a neon...
This circuit is from an Electronics World of 1968. The transistors are of the time and the power...
This circuit is from a 1972 German magazine Funkshau. The circuit can use BC548 transistors...