This circuit was found in the April 1971 Radio Electronics magazine. It uses common transistors and can be adapted to use an LED or audible indicator instead of a light bulb.
This circuit, which appears at other points on this site, can be designed with both 4011 and 4001...
We found this circuit in an American documentation from the 90s. The circuit applies to vehicles...
Found in Motorola documentation from 1967, this circuit shows how it is possible to obtain a...